Controlling ceramic composition using precursor chemistry: A study on borosiloxane derived SiBOC ceramics

Controlling ceramic composition using precursor chemistry: A study on borosiloxane derived SiBOC ceramics | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Controlling ceramic composition using precursor chemistry: A study on borosiloxane derived SiBOC ceramics Sreejith K. J., Deepa Devapal, Packirisamy S. This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8468563/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract This paper reports the solventless synthesis and characterization of borosiloxane oligomers from boric acid and mixtures of vinyltriethoxysilane and phenyltriethoxysilane, using different monomer feed ratios. The oligomers were characterized by gel permeation chromatography and infrared spectral analysis. Microstructure of the oligomers was studied using 1 H-, 13 C- and 29 Si-NMR spectra. Ceramic conversion of the borosiloxane oligomers were carried out at 900°C. The ceramics obtained at 900°C were further heat treated at 1500 and 1650°C. The ceramic powders were characterized by FT-IR and XRD. The effect of monomer feed ratio on the oligomer structure and on its ceramic conversion process is discussed. polymer derived ceramics borosiloxanes boric acid phenyltriethoxysilane vinyltriethoxysilane SiBOC ceramics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. INTRODUCTION Among the various preceramic polymers being evaluated as precursors for advanced ceramic materials, borosiloxanes find their place as one of the cheapest and easily synthesizable resins. High ceramic residue of these oligomers (> 50%) combined with the amorphous nature of siliconboronoxyrbide (SiBOC) ceramics formed on heat treatment above 1000°C has resulted in enormous research interests in these precursors 1 , 23 – 5 , 5 – 7 . Borosiloxanes have been reported as precursor for ceramic matrix composites 8 – 13 , 14 ceramic foams 15 , as ink for ceramic 3D printing 16 , metamaterials 17 . Novel metal containing borosiloxane variants are also being explored 18 – 21 . Apart from its use as a preceramic polymer, borosiloxanes are also reported as binders 22 , self-healing materials 23 adhesion promoters 24 , flame retardant materials 25 , 26 , shock-wave dissipators 27 , 28 , impact-resistant composites 29 , 30 , flexible conductors 31 . fireproofing 32 solid electrolyte interphases 33 . One of the key requirement for its use as precursor of CMC fabrication, is the presence of a crosslinkable group in the precursor backbone 14 . The crosslinkable groups can be effectively utlized during the green composite fabrication stage, to prevent resin ooze out and to ensure shape retention. Borosiloxanes have been synthesized via both aqueous sol-gel 5 , 34 method and non-aqueous methods 4 , 35 , 36 . Solvent less synthesis method 37 , a variant of the non-aqueous method has been particularly very useful for preparing functionalized borosiloxanes 6 , 38 . In this method 37 , boric acid and alkoxysilanes are reacted directly without using solvent and catalyst. As the synthesis is carried out at relatively low temperatures, the polymerization of the functional groups during the synthesis is prevented/minimized. The borosiloxane is obtained as solution in a low boiling alkyl alcohol, which is formed as reaction byproduct. By regulating the removal of alkyl alcohol, the viscosity of the borosiloxane solution can be easily varied, enabling its use as an effective infiltrating resin for CMCs 37 . Vinyl borosiloxanes give better ceramic residue at 900°C compared to phenyl borosiloxanes 4 , 6 , 9 , 36 . One of the major disadvantage of vinylborosiloxane is its lower processability, as it undergoes gelation on flash evaporation to remove the alky alcohol byproduct. On the other hand alkyl/aryl group containing borosiloxanes such as phenyl and methyl – borosiloxanes are having excellent processability 9 , 15 . A borosiloxane containing both vinyl and alkyl/aryl group can have a balance of the cross linkability and porcessabily. More than that, by varying the vinyl and alkyl/aryl alkoxysilane monomer feed ratios, the polymer microstructure and its ceramic conversion can be controlled. Such borosiloxanes can produce novel ceramic systems with varying content of amorphous and crystalline phases. In these lines, it would be advantageous to combine the processability of pheny/methyllborosiloxanes and high ceramic residue of vinylborosiloxanes in a single system. In view of this, the present study focuses on the synthesis and characterization of novel borosiloxane oligomers from mixture of vinyltriethoxysilane with phenyltriethoxysilane, using different monomer feed ratios in an attempt to understand the effect of monomer feed ratio and the type of alkoxysilanes used for the synthesis on the microstructure and thermal stability of the oligomers. The effect of monomer feed ratio on the oligomer properties and ceramic residue is also investigated. It is expected that the monomer feed ratio will play an important role in controlling the microstructure, thermal stability and ceramic residue of the oligomers which in turn would influence the ceramization process. 2. EXERIMENTAL Materials Boric acid (H 3 BO 3 , Mol. wt. = 61.83, assay ≥ 99.5%, Merck Specialities, Mumbai), phenyltriethoxysilane [PTEOS] (C 12 H 20 O 3 Si, Mol. wt. = 240.38, assay ≥ 98%, Spectrochem Research Laboratories, Mumbai, India), and vinyltriethoxysilane [VTEOS] (C 8 H 18 O 3 Si, Mol. wt. = 190.32, assay ≥ 97%, Nabond, Shenzhen, China), were used as received. Synthesis : In a typical experiment, a mixture containing 6.18 g (0.1 mol) of boric acid, 24.04 g (0.1 mol) of PTEOS and 19.03 g (0.1 mol) VTEOS was taken in a three-necked round bottom flask equipped with a mechanical stirrer, water condenser and a set-up for purging argon. The contents of the flask were heated under the flow of argon in an oil bath and the bath temperature was maintained at 150–160°C. Stirring and heating of the reaction mixture was continued for 5 h after which the contents of the flask were allowed to cool to room temperature. Phenylvinyl borosiloxane was obtained as a solution in ethanol, which was formed as the byproduct and the oligomer was labeled BPV 12 . Following a similar procedure, oligomers were also synthesized in 1:0.5:0.5, 1:0.5:1.5, 1:1.5:0.5 and 1:1.5:1.5. Characterization The oligomers were characterized by gel permeation chromatography (Waters Alliance), viscosity measurement (HBDT Visco II +), FT-IR spectral analysis (Perkin Elmer Spectrum GX), NMR spectral analysis (Brucker Avance 300) and TG analysis (Mettler TA 3000). XRD patterns of ceramic samples were recorded on an Xpert Pro MPD model Rontgen diffractometer (40 KW and 30 µ amps) with Cu Kα (1.54 Å). CHN analysis was carried out in Perkin Elmer Elemental Analyzer (Model PE 2400). Si and B contents were estimated by wet-analysis. The ceramic powders were also characterized by SEM/EDX analysis. Carl Zeiss EVO 50 series in Extended Pressure (EP) imaging mode was used for SEM analysis. For EDX analysis, an OXFORD INCA system was used. 3. RESULTS AND DISCUSSION 3.1 Synthesis and Characterization: The reaction scheme for the synthesis and GPC curves of these oligomers is given in Fig. 1 . the molecular weight (for the elution range 15.3–18.8 min) and viscosity data are presented in Table 1 . Table 1 GPC and viscosity data of borosiloxane oligomers from PTEOS and VTEOS Oligomer Monomer feed ratio (Boric acid : PTEOS:VTEOS) Mw Mp Mn PDI Viscosity at 30°C (cps) BPV 11 1:0.5:0.5 1440 1040 950 1.32 15.0 BPV 12a 1:1:1 1560 1260 1040 1.24 19.0 BPV 12b 1:0.5:1.5 2290 1230 1010 1.97 8.0 BPV 12c 1:1.5:0.5 1250 1260 920 1.23 17.0 BPV 13 1:1.5:1.5 1250 1300 980 1.28 9.0 Comparison of molecular weight data of the oligomers, BPV 11 , BPV 12a and BPV 13, which were synthesized using PTEOS: VTEOS molar ratio of 1:1 suggests that maximum molecular weight is obtained for BPV 12a . Comparison of molecular weight data of BPV 12a , BPV 12b and BPV 12c indicates that maximum Mw is obtained for BPV 12b suggesting that higher concentration of VTEOS in the monomer feed favors the formation of oligomers with higher molecular weight. It is noticed that the tendency for polymodal molecular weight distribution increases with the increase in alkoxysilane concentration in the monomer feed. Unlike the other oligomers, BPV 13 synthesized using boric acid: PTEOS: VTEOS molar ratio of 1:1.5:1.5 shows a prominent broad peak in the elution range 17.8 to 18.5 min which is attributed to the presence of unreacted alkoxysilane monomers/low molecular weight products. This conclusion is supported by 29 Si-NMR spectral data, which will be discussed later. Possible reactions in the system are given in Scheme 1 . IR spectra of the oligomers are shown in Fig. 2 and the peak assignments are given below: 3400 (ν SiO-H ), 3224 (ν BO-H ), 2983 (ν C-H(asym.) of Ph group), 1603 (ν C=C of Ph group), 1432 (ν Si-Ph ), 1195 (δ B-OH ), 884 (ν SiOB ), 775 (ρ SiOSi ), 675 (δ SiOB ), 486 (ν Si-Ph ). The peaks at 884 cm - 1 (ν Si-O-B ) and 675 cm - 1 (δ Si-O-B ) support the formation of Si-O-B linkages. BPV 12b oligomer having a higher VTEOS concentration in the monomer feed shows a peak at 1412 cm - 1 , attributed to -CH 2 scissoring vibration of vinyl group. Similarly, Si-Ph stretching (1432 cm - 1 ) is shown by BPV 12c oligomer having a higher concentration of PTEOS. Peaks corresponding to unreacted Si-OEt (1133 cm - 1 ) and B-OH (3224 cm - 1 ) groups were also present in the FT-IR spectra. 1 H-NMR spectra of the oligomers are given in Fig. 3 . The signal observed from 1.18 ppm to 1.26 ppm for the oligomers is assigned to CH 3 protons of unreacted SiOEt, ethanol and ethyl borate. The signal observed at 3.54–3.66 ppm is attributed to CH 2 protons of ethanol and ethyl borate. The signal at 3.73–3.88 ppm is due to CH 2 protons of unreacted SiOEt groups. It is worth noting that the ratio of the intensity of the peaks at 3.54–3.66 ppm and 3.73–3.88 ppm decreases in the following order: BPV 11 (0.82) > BPV 12c (0.64) > BPV 12b (0.61) > BPV 12a (0.59) > BPV 13 (0.24) The above trend suggests that, with the increase in alkoxysilane or in other words decrease in boric acid concentration, the amount of ethanol and ethyl borate formed decreases. The signal observed at 4.4 ppm is due to Si-OH group. The two broad signals observed at 5.3 and 6.0 ppm are attributed to -CH and -CH 2 protons of vinyl group respectively. The signals centered at 7.3 and 7.7 ppm are due to aromatic protons. 13 C-NMR of the oligomers are shown in Fig. 4 . The signal at 17.2 ppm is due to CH 3 carbon of ethanol and ethyl borate. The signal at 18.5 ppm is attributed to CH 3 carbon of SiOEt. As observed for phenylborosiloxane system, the ratio of the intensity of these two signals decreases with the increase in alkoxysilane concentration in the monomer feed. This indicates that the extent of formation of the byproduct ethanol decreases and the concentration of unreacted SiOEt group increases with the increase in alkoxysilane to boric acid ratio. The signals at 57.8 ppm, 59.1 ppm and 59.4 ppm are due to CH 2 carbon of ethanol, unreacted Si-OEt groups and ethyl borate respectively. It is noticed that the ratio of intensity of the signals at 57.8 ppm and 59.1 ppm decreases with the increase in alkoxysilane concentration in the monomer feed which supports the conclusion drawn above. Signals observed in the region 130.6 to 136.1 ppm correspond to vinylic and aromatic carbons. The signal at 127.7 ppm is assigned to C 1 , C 3 and C 5 carbon of phenyl group. The signal at 130.6 ppm is attributed to both phenyl-C 4 carbon and vinyl-CH carbon. The signal at 134.4 ppm is due to C 2 and C 6 carbons. The signal at 136.1 ppm is assigned to CH 2 carbon of vinyl group. 29 Si-NMR spectra of the BPV oligomers are given in Fig. 5 . Soraru et al. 5,39 studied in detail the 29 Si-NMR spectra of borosiloxane oligomers prepared by sol-gel process of boric acid and organic substituted alkoxysilanes and assigned the chemical shifts to the structural units, T 1 , T 2 and T 3 , where T i indicates the unit with ‘i’ siloxane (-O-Si) bonds attached to the central silicon atom (Fig. 5 ). In the present study, classical T n R notation is used for representing different phenyl substituted Si species, where the superscript ‘n’, represents the number of oxo-bridges and the subscript R, represents the substituents (-OH and/or -OEt) and their numbers. The observed signals are attributed to two types of structural units, viz., T n OEt and T n OH on the basis of whether the ethoxy group remains as such in the Si moiety or it has hydrolyzed to -OH group. It is reported that the Si-O-Si and the Si-O-B bonds do not differ in their 29 Si-NMR chemical shifts 34 . This implies that the chemical shift values of T i structures are not influenced by whether they contain Si-O-Si or Si-O-B bonds. The 29 Si-NMR spectra of borosiloxane oligomers are interpreted based on the chemical shift assignments reported for the sol-gels synthesized from phenyltrialkoxysilanes 40 , 41 and the assignments of chemical shifts are given in Table 2 . Table 2 29 Si-NMR chemical shift assignments for borosiloxane oligomers from PTEOS and VTEOS BPV 11 BPV 12a BPV 12b BPV 12c BPV 13 Vi-T 3 -79.9 -82.0, -80.9, -81.0, -79.2 -80.3, -79.5, -78.9 -82.2, -81.6, -80.9, -79.1, -76.3 Ph-T 3 -77.43, -78.11 -78.1 -78.5 -78.6, -78.2, -77.6 * Vi-T 2 OEt * -73.3 -74.1, -72.7 -73.0 -74.2, -73.5, -72.5 Vi-T 2 OH * -71.7, -72.5 -71.8 -71.2 -71.7 Ph-T 2 OEt * -71.0 * -70.9, -70.2 -71.1 Ph-T 2 OH -70.9, -70.6, -69.2,-68.2 -68.0,-69.0 -69.2, -68.2 -69.7, -68.7 -68.6 Vi-T 1 (OEt)2 * * * * -66.1 Ph-T 1 (OEt)2 * * -65.4 -65.4, -65.1 65.3, -65.4 Vi-T 1 (OH)(OEt) * * -64.3 * -64.2 Ph-T 1 (OH)(OEt) * * -63.0 -63.3 -63.4 Vi-T 0 (OEt)3 * * * * -58.3 Ph-T 0 (OEt)3 * * * -57.7 -57.7 BPV oligomers show two major peaks centered around − 72 and − 79 ppm, though the peaks are much broader compared to that of BP oligomers. In BPV oligomers, the number of microstructures is expected to be more due to the presence of phenylsiloxy and vinylsiloxy units and this is responsible for the broadening of signals. The major peaks observed around − 72 and − 79 ppm are attributed to T 2 and T 3 structures respectively. Apart from these major peaks, BPV 12b , BPV 12c and BPV 13 show a peak in the range − 60 to -68 ppm attributed to T 1 structure. BPV 13 , like BP 13 clearly shows the presence of unreacted monomer at -57.7 and − 58.4 ppm corresponding to PTEOS and VTEOS respectively. This observation is in line with that made by GPC analysis. The T 3 : (T 2 + T 1 ) ratio follows the trend BPV 11 (3.36) > BPV 12a (1.94) > BPV 12b (1.56) > BPV 12c (1.28) > BPV 13 (1.06) respectively. This observation suggests that boric acid plays an important role in the formation of T 3 structure. No T 1 peaks were observed for BPV 12a system and no splitting is observed. However, for BPV 12b and BPV 12c the peak multiplicity is observed which may be due to two different types of T 2 structures (Ph-T 0 and Vi-T 2 ) and also due to difference in the monomer feed ratios of PTEOS and VTEOS. BPV 13 which was synthesized using excess of alkoxysilanes (boric acid: alkoxysilanes ratio 1:3) shows the presence of Vi-T 0 and Ph-T 0 and the concentration of Ph-T 0 is more than that of Vi-T 0 . This observation suggests that VTEOS is more reactive than PTEOS. TG and DTG curves of BPV oligomers are given in Fig. 6 . The TG data are summarized in Table 3 . Based on the DTG curves, the TG curves can be divided into four regions: room temperature to 200°C, 200 to 430°C, 430 to 650°C and 650 to 900°C. The mass loss up to 200°C is attributed to the loss of mainly water and ethanol formed from the reaction of residual -OH and/or -OEt moieties 42 . The weight loss observed up to 200°C follows the trend, BPV 11 > BPV 12a = BPV 12b > BPV 12c > BPV 13 , clearly indicating that the weight loss depends upon the boric acid:alkoxysilane ratio. As per the possible reactions shown in Scheme 1 , boric acid is required for the condensation reactions forming water and ethanol byproducts. In the absence of sufficient quantity of B-OH groups, these reactions are affected. This effect of boric acid concentration is an important aspect of borosiloxane pyrolysis, as the mass loss upto 200°C is the second largest mass loss during the pyrolysis. The gradual mass loss observed from 200 to 430°C is attributed to the loss of low molecular weight oligomers and cyclic or cage polysiloxanes 43 . The weight loss in the region 200 to 430°C is about 2–3%, which is due to the loss of oligomeric products and cyclic/cage structures. This implies that under the experimental conditions, the formation of such products is very minimum. The weight loss in the region 430–650°C is 5.1 to 13.1% which is attributed to the ceramization process, i.e., cleavage of pendant vinyl and phenyl moieties 44 , 45 . The weight loss in this region follows the trend, BPV 12c > BPV 13 > BPV 12a > BPV 11 > BPV 12b . The maximum weight loss noticed for BPV 12c is due to the higher concentration of Si-Ph units in the system. The least weight loss observed for BPV 12b is understood in view of the lowest concentration of Si-Ph units. Between BPV 11 and BPV 13 which were synthesized using the same alkoxysilane monomer feed ratio (PTEOS:VTEOS ratio 1:1), the weight loss is less for BPV 11 and this is due to the higher concentration of T 3 structures and higher boron content in BPV 11 . The weight loss in the region 650–900°C is 1–2%, which is probably due to the loss of hydrogen. BPV system shows an improvement in overall thermal stability compared to that of phenyl borosiloxanes 46 . This is attributed to: i) high reactivity of VTEOS which increases the relative concentration of T 3 units and ii) reduction in mass loss in the 430–650°C due to the lower relative concentration of phenylsiloxane units compared to phenylborosiloxanes. 3.2 Ceramic conversion and characteriazaton: As described in the previous Section, BPV 11 , BPV 12a , BPV 12b ,BPV 12c and BPV 13 were synthesized using the monomer feed ratios (boric acid:PTEOS:VTEOS) 1:0.5:0.5, 1:1:1, 1:0.5:1.5, 1:1.5:0.5 and 1:1.5:1.5 respectively. For initial pyrolysis of the oligomers, the samples obtained at 175°C were powdered and pyrolyzed at 900°C under the flow of argon. The 900°C pyrolyzed samples were used for ceramic conversion studies at 1500 and 1650°C in separate experiments. All the ceramic conversions were carried out under argon flow. The details of the procedure are given in Section 2.4. XRD patterns and FT-IR spectra of the ceramic residue obtained at 900°C are given in Figs. 7 and 8 respectively. At 900°C, the ceramic powder consists mainly of SiBOC glassy phase as evidenced by a diffraction halo centered around 2θ = 21.25°. The diffraction line observed at 2θ = 28.13° for BPV 11 and BPV 12a is due to boric acid. The FT-IR analysis supports the inferences drawn from XRD studies. The presence of SiOB bond is evident from the absorption at 884 and 648 cm - 1 corresponding to Si-O-B stretching and bending vibrations respectively. The higher concentration and higher extinction coefficients of Si-O masks these peaks, particularly at higher alkoxysilane concentrations. The absorptions at 1080 and 458 cm - 1 are caused by Si-O-Si stretching and bending vibrations respectively. The relative intensity of Si-O-Si stretching with respect to that of B-O stretching (1440 cm - 1 ) increases with the increase in alkoxysilane concentration in the monomer feed. The absorption at 1614 cm - 1 is attributed to –C = C– stretching vibration of carbidic carbon 47 . These absorptions get prominent with increase in phenylsiloxy and vinylsiloxy units in the starting precursor and this is more pronounced with the increase in phenylsiloxy units. This peak is associated with absorptions at 2854 and 2925 cm - 1 due to C-H stretching of hydrogen attached to carbidic carbon. The ceramic residues obtained at 900°C from BPV oligomers are further heat treated at 1500°C. XRD patterns of BPV-1500 are given in Fig. 7 . Comparison of XRD patterns of BP-1500 and BPV-1500 systems indicates that the extent of formation of β-SiC crystallites from SiBOC glass is more for BP-1500 than for BPV-1500. This observation suggests that the presence of vinylsiloxy units in the oligomer backbone brings down the formation of β-SiC crystallites from SiBOC glass. Among the five different samples of BPV-1500 system, it is noticed that the extent of formation of β-SiC follows the trend, BPV 11 -1500 > BPV 12a -1500 > BPV 12c -1500 > BPV 13 -1500. The crystallite size of β-SiC follows the trend BPV 11 -1500 (46 nm) > BPV 12a -1500 (14 nm) = BPV 12c -1500 (14 nm) > BPV 12b -1500(7 nm). The observed trend can be explained taking into consideration the following factors: i) boric acid concentration in the monomer feed and ii) the type and the relative concentration of siloxy units. As discussed earlier, the redistribution of Si-C and Si-O bonds is quite local and can account for the nucleation of small β-SiC crystals 48 . The growth rate of SiC in SiOC glasses is very low because of the extremely high viscosity of SiOC glass. As discussed earlier, the incorporation of boron in SiOC glass brings down the viscosity. The high boron content of BPV 11 is responsible for higher crystallite size as the crystallization kinetics, which is a diffusion controlled process, is enhanced with the lowering of viscosity 48 . Ceramics from BPV 13 will have the highest viscosity due to low boron content and for this reason, the redistribution reaction is expected to be quite local. As a result, BPV 13 -1500 shows the least tendency for SiC crystallization. Among BPV 12a -1500, BPV 12b -1500 and BPV 12c -1500 samples obtained from the precursors synthesized using boric acid: alkoxysilanes monomer feed ratio of 1:2, lowest crystallite size is obtained for BPV 12b -1500. This is understood in view of higher content of vinylsiloxy units in the starting precursor compared to the other two samples. Higher amount of vinylsiloxy units means lower pyrolytic/carbidic carbon content present in the glassy matrix which in turn is responsible for localizing the redistribution reaction. XRD pattern of BP 11 -1500 also shows diffraction lines corresponding to B 2 O 3 (2θ = 28.13°). A hump observed in the amorphous region is attributed to silica phase (2θ = 26.14°). The formation of silica in BPV 11 -1500 is similar to the observation made in BP 11 -1500. The higher boron content in the ceramic brings down the viscosity of SiBOC glass and speeds up the formation of SiC and SiO 2 phases. It is to be noted that the intensity of diffraction plane of β-SiC also shows an increase in BPV 11 -1500 along with silica formation, thereby supporting the above fact. FT-IR spectra of the BPV-1500 samples are given in Fig. 8 . In line with the observations based on XRD patterns, BPV 11 -1500, BPV 12a -1500 and BPV 12c -1500 show absorptions at 815 cm - 1 corresponding to Si-C stretching of SiC. The absorptions at 1404, 1092 and 906 cm - 1 are assigned to stretching vibrations of B-O, Si-O-Si and Si-O-B respectively. It is seen that the relative intensity of B-O and Si-O-B stretching with respect to Si-O-Si stretching is the least for BPV 12b -1500 when compared to that of BPV 12a -1500 and BPV 12c -1500. This observation suggests that increase in VTEOS concentration in the monomer feed results in less incorporation of Si-O-B bonds in the precursor. As the temperature of heat treatment is further increased to 1650°C, the samples show a color change from black to grey and surface of the sample was covered with off-white fluffy materials. The sample along with the fluffy material was powdered and analyzed by XRD and FT-IR. In the 1500–1650°C temperature range, the major reaction possible is the carbothermal reduction resulting in the formation of β-SiC with a corresponding reduction in the SiBOC phase. This is clearly observed in the XRD patterns of the samples shown in Fig. 7 . All the major diffractions correspond to β-SiC, and the left-side hump in the 2θ = 35.59° diffraction line corresponds to B 4 C and/or structural anomalies in the β-SiC unit cell. It is worth noting that compared to BP system, in BPV, all the samples give similar SiC diffraction lines irrespective of the alkoxysilane content. Crystallite size of β-SiC was calculated using Scherrer equation and the values are80, 90, 98, 65 and 83 nm for BPV 11 -1650, BPV 12a -1650, BPV 12b -1650, BPV 12c -1650 and BPV 13 -1650 respectively. It is worth comparing the crystallite size of BPV-1650 samples with that of BP-1650 samples in order to understand more about the mechanism of formation of β-SiC. BP-1650 samples have crystallite size in the range 40–62 nm whereas BPV-1650 samples have crystallite size of 65–98 nm. In BP system, the presence of residual carbon incorporated into the borosilicate matrix or the free carbon can act as a diffusion barrier for the mobility of silicon and carbon atoms, thereby reducing the crystal growth 49 . FT-IR spectra of all the samples after heat treatment at 1650°C are given in Fig. 8 . Though the XRD patterns of samples heat treated at 1650°C look alike, differences are seen in the IR spectra of these samples. Si-C stretching vibration at 819 cm - 1 is seen for all the samples. Absorption due to Si-O-Si stretching vibration at 1020 cm - 1 is seen in the IR spectra of BPV 11 -1650 and BPV 12b -1650 samples and the relative intensity of this peak with respect to Si-C stretching vibration at 819 cm - 1 follows the trend, BPV 12b -1650 > BPV 13 -1650 > BPV 11 -1650. This observation suggests that the increase in vinylsiloxy units in the precursor or the increase in boric acid concentration in the monomer feed, would bring down the presence of carbon domains in the ceramic and hence, all the SiO 4 units could not get converted to SiC 4 through carbothermal reduction. It is worth noting that absorption around 1400 cm - 1 corresponding to B-O stretching vibration is not seen in the IR spectra. However, it is seen that the peak at 819 cm - 1 is broad except for of BPV 12a -1650. This may be due to merging of Si-O-B stretching vibration of residual SiBOC glass with Si-C stretching vibration of β-SiC. 4. CONCLUSIONS Borosiloxane oligomers were synthesized from boric acid and mixtures of alkoxysilanes (PTEOS + VTEOS) via solventless synthesis. The oligomer was obtained as either low or high viscous resins in ethanol which formed as the byproduct. FT-IR analysis of the oligomers confirmed the presence of Si-O-B bonding (884 cm - 1 ) in the oligomer backbone along with unreacted Si-OEt (1133 cm - 1 ) and B-OH (3224 cm - 1 ) groups. In all the different borosiloxanes, the oligomer synthesized in 1:1 (boric acid: alkoxysilanes) ratio showed precipitation of unreacted boric acid on standing. BPV oligomers synthesized from mixture of PTEOS and VTEOS showed higher molecular weight and viscosity values than that of phenyl borosiloxanes. 13 C-NMR and IR spectra shows that vinyl group is intact in the oligomer. 29 Si-NMR of the oligomer-ethanol solutions shows that the microstructure of the as-synthesized borosiloxane consists of three major structural units. The relative concentration of the highest cross-linked unit viz., T 3 structure indicate that its formation is enhanced by the increase in boric acid concentration in the monomer feed. 29 Si-NMR analysis also supports the fact that VTEOS is more reactive than PTEOS towards condensation with boric acid under solventless reaction condition. Along with the NMR analysis results, the thermal analysis results clearly support the role of vinyl group in increasing the thermal stability and ceramic residue of phenyl borosiloxanes. Detailed ceramic conversion study of the borosiloxane oligomers shows that the nature of ceramic obtained is greatly influenced by the boron and carbon content of the borosiloxane oligomer. All the oligomers give an amorphous SiBOC phase at 900°C. Nano sized β-SiC crystallizes out from the glassy SiBOC matrix at higher temperature. Two independent and overlapping mechanisms are proposed for the formation of β-SiC, viz., the nucleation and crystal growth mechanism and carbothermal reduction mechanism. In the first one, redistribution reactions between Si-O and Si-C bonds in the SiBOC matrix leads to the formation of SiC 4 tetrahedra, which acts as nucleating centers for further crystal growth. Compared to siloxanes, borosiloxanes show an increased β-SiC crystallization at 1500°C. This is attributed to the presence of boron in the matrix which brings down the viscosity of SiBOC glass. As the viscosity of the glass is reduced, the mobility of Si and C in the matrix is enhanced resulting in faster crystallization. Carbothermal reduction is the reaction between the free carbon phase and Si-O rich phase forming SiC and CO. The reaction results in mass loss of SiBOC ceramic. Though the carbothermal reduction takes place in the temperature range close to 1500°C, itis predominant at temperatures above 1500°C. Thus, the crystallite growthof β-SiC is controlled by carbothermal reduction predominantly in the temperature range 1500–1650°C and depends mainly on the carbon content of the ceramics. Declarations Author Contribution Sreejith has carried out the experimental work and interpreted the data, Deepa has carried out the initial works on the topic and Packirisamy has guided the work. Acknowledgements The authors thank the authorities of Vikram Sarabhai Space Centre for the permission to publish this work. 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Formation of B-O-Si and Si-O-Si linkages Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 05 Feb, 2026 Reviews received at journal 29 Jan, 2026 Reviews received at journal 24 Jan, 2026 Reviewers agreed at journal 10 Jan, 2026 Reviewers agreed at journal 09 Jan, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers invited by journal 08 Jan, 2026 Editor assigned by journal 30 Dec, 2025 Submission checks completed at journal 28 Dec, 2025 First submitted to journal 28 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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15:13:41","extension":"png","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":41582,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/c9865409b5a3460a21ca1567.png"},{"id":100363400,"identity":"38f2e530-691f-435a-af1f-26c968f43859","added_by":"auto","created_at":"2026-01-16 07:49:39","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":11012,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/2c8fe8aa01e45699f4a0ab42.png"},{"id":100064135,"identity":"c71db1b0-baae-4371-91b9-9fcfc4f410a2","added_by":"auto","created_at":"2026-01-12 15:13:41","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":41440,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/74ada08f4cea9cf1f0194280.png"},{"id":100363987,"identity":"7b46816e-495e-4fc2-9d3d-072cd17d0e6a","added_by":"auto","created_at":"2026-01-16 07:52:18","extension":"png","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":21520,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/a9056be35d104ac4ab4edd7d.png"},{"id":100064127,"identity":"fb7ee203-baa9-4814-9216-9ae08219b38b","added_by":"auto","created_at":"2026-01-12 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15:13:41","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":46013,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/6c9109e4882d1719b76e7584.png"},{"id":100364168,"identity":"b01aac49-2379-46fe-901c-a756d33b8a34","added_by":"auto","created_at":"2026-01-16 07:52:45","extension":"png","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":138911,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/e699a07641db5ad2c5293d8f.png"},{"id":100364156,"identity":"d3c21f2a-5438-452c-b5df-2021a6f201f9","added_by":"auto","created_at":"2026-01-16 07:52:41","extension":"png","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":72706,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/7bc0dba78ebea78f6991d8d1.png"},{"id":100064137,"identity":"66081753-5c41-4e21-9450-ec3c7f2d448f","added_by":"auto","created_at":"2026-01-12 15:13:41","extension":"xml","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":145540,"visible":true,"origin":"","legend":"","description":"","filename":"f079bb8ecde84314ad52cc8af954ca8f1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/4455fe9b1bde38f341a247df.xml"},{"id":100363695,"identity":"9e136285-4a28-404b-a187-e869bc6fc54f","added_by":"auto","created_at":"2026-01-16 07:51:15","extension":"html","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":154818,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/018afd3cab5c6bf364904d62.html"},{"id":100064106,"identity":"f1547fab-b845-4052-8180-4c990811a638","added_by":"auto","created_at":"2026-01-12 15:13:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":114585,"visible":true,"origin":"","legend":"\u003cp\u003eScheme of synthesis and GPC/viscosity data of of borosiloxane oligomers from PTEOS and VTEOS\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/9f66d80d73fa1ed65b7c26a8.png"},{"id":100363940,"identity":"00163b0b-46f3-421e-8e21-d4e6e11b4e14","added_by":"auto","created_at":"2026-01-16 07:52:10","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":178274,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectra of the borosiloxane oligomers from PTEOS and VTEOS\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/474896c58a69966a20423a24.png"},{"id":100364388,"identity":"1d653d80-8566-4315-ad68-a203b5208abb","added_by":"auto","created_at":"2026-01-16 07:53:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":82468,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e1\u003c/sup\u003eH-NMR spectra of borosiloxane oligomers\u0026nbsp;\u0026nbsp;from PTEOS and VTEOS\\\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/d90a3d63af00064dade9d899.png"},{"id":100064113,"identity":"2b9e7fca-4c63-4fcd-84ef-6a59c5d351d1","added_by":"auto","created_at":"2026-01-12 15:13:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":115609,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e13\u003c/sup\u003eC-NMR spectra of borosiloxane oligomers\u0026nbsp;from PTEOS and VTEOS\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/0eb49fbebd18be64a852e2b0.png"},{"id":100364395,"identity":"95620cff-3612-4b49-9bb2-44249b633e3d","added_by":"auto","created_at":"2026-01-16 07:53:36","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":93630,"visible":true,"origin":"","legend":"\u003cp\u003e\u003csup\u003e29\u003c/sup\u003eSi-NMR spectra of borosiloxane oligomers from PTEOS and VTEOS\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/e8421aebbafad6d14968f2eb.png"},{"id":100064110,"identity":"546a0e5d-bc5b-4835-b52c-8ccb0abecfe2","added_by":"auto","created_at":"2026-01-12 15:13:40","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":142872,"visible":true,"origin":"","legend":"\u003cp\u003e(a) TG and (b) DTG curves of borosiloxane oligomers from PTEOS and VTEOS\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/341499324bc91d7f1a7f1517.png"},{"id":100064116,"identity":"5851ac82-29b5-4198-8db2-796fdbc02014","added_by":"auto","created_at":"2026-01-12 15:13:40","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":212923,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of ceramic residues obtained at 900°C, 1500 and 1650°C from BPV oligomers\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/58f520d85affb533c6caad50.png"},{"id":100364698,"identity":"62c29c48-61f1-468c-9f00-602015ce4d2d","added_by":"auto","created_at":"2026-01-16 07:54:11","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":221020,"visible":true,"origin":"","legend":"\u003cp\u003eIR spectra of ceramic residues obtained at 900°C, 1500 and 1650°C from BPV oligomers\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/f4de63f34a2fc0c41e996624.png"},{"id":100381966,"identity":"c6651e50-859a-4670-9118-cb2752ad72b5","added_by":"auto","created_at":"2026-01-16 10:40:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1789049,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/ffa5c2b6-eecc-473f-ba69-7d56175022fb.pdf"},{"id":100364773,"identity":"0814e64f-4981-43d7-8284-589dc464d256","added_by":"auto","created_at":"2026-01-16 07:54:18","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":152343,"visible":true,"origin":"","legend":"\u003cp\u003eScheme 1. Formation of B-O-Si and Si-O-Si linkages\u003c/p\u003e","description":"","filename":"Scheme1.png","url":"https://assets-eu.researchsquare.com/files/rs-8468563/v1/d0e8facfc822064efe22167f.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Controlling ceramic composition using precursor chemistry: A study on borosiloxane derived SiBOC ceramics","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eAmong the various preceramic polymers being evaluated as precursors for advanced ceramic materials, borosiloxanes find their place as one of the cheapest and easily synthesizable resins. High ceramic residue of these oligomers (\u0026gt;\u0026thinsp;50%) combined with the amorphous nature of siliconboronoxyrbide (SiBOC) ceramics formed on heat treatment above 1000\u0026deg;C has resulted in enormous research interests in these precursors \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Borosiloxanes have been reported as precursor for ceramic matrix composites \u003csup\u003e\u003cspan additionalcitationids=\"CR9 CR10 CR11 CR12\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e,\u003csup\u003e14\u003c/sup\u003e ceramic foams\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e, as ink for ceramic 3D printing\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, metamaterials\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Novel metal containing borosiloxane variants are also being explored\u003csup\u003e\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Apart from its use as a preceramic polymer, borosiloxanes are also reported as binders \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e, self-healing materials\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e adhesion promoters \u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, flame retardant materials\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, shock-wave dissipators\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, impact-resistant composites\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, flexible conductors \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. fireproofing\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e solid electrolyte interphases\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOne of the key requirement for its use as precursor of CMC fabrication, is the presence of a crosslinkable group in the precursor backbone\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. The crosslinkable groups can be effectively utlized during the green composite fabrication stage, to prevent resin ooze out and to ensure shape retention. Borosiloxanes have been synthesized via both aqueous sol-gel \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e method and non-aqueous methods \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. Solvent less synthesis method\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e, a variant of the non-aqueous method has been particularly very useful for preparing functionalized borosiloxanes \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. In this method \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e, boric acid and alkoxysilanes are reacted directly without using solvent and catalyst. As the synthesis is carried out at relatively low temperatures, the polymerization of the functional groups during the synthesis is prevented/minimized. The borosiloxane is obtained as solution in a low boiling alkyl alcohol, which is formed as reaction byproduct. By regulating the removal of alkyl alcohol, the viscosity of the borosiloxane solution can be easily varied, enabling its use as an effective infiltrating resin for CMCs \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eVinyl borosiloxanes give better ceramic residue at 900\u0026deg;C compared to phenyl borosiloxanes \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. One of the major disadvantage of vinylborosiloxane is its lower processability, as it undergoes gelation on flash evaporation to remove the alky alcohol byproduct. On the other hand alkyl/aryl group containing borosiloxanes such as phenyl and methyl \u0026ndash; borosiloxanes are having excellent processability \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. A borosiloxane containing both vinyl and alkyl/aryl group can have a balance of the cross linkability and porcessabily. More than that, by varying the vinyl and alkyl/aryl alkoxysilane monomer feed ratios, the polymer microstructure and its ceramic conversion can be controlled. Such borosiloxanes can produce novel ceramic systems with varying content of amorphous and crystalline phases.\u003c/p\u003e \u003cp\u003eIn these lines, it would be advantageous to combine the processability of pheny/methyllborosiloxanes and high ceramic residue of vinylborosiloxanes in a single system. In view of this, the present study focuses on the synthesis and characterization of novel borosiloxane oligomers from mixture of vinyltriethoxysilane with phenyltriethoxysilane, using different monomer feed ratios in an attempt to understand the effect of monomer feed ratio and the type of alkoxysilanes used for the synthesis on the microstructure and thermal stability of the oligomers. The effect of monomer feed ratio on the oligomer properties and ceramic residue is also investigated. It is expected that the monomer feed ratio will play an important role in controlling the microstructure, thermal stability and ceramic residue of the oligomers which in turn would influence the ceramization process.\u003c/p\u003e"},{"header":"2. EXERIMENTAL","content":"\u003cp\u003e \u003cstrong\u003eMaterials\u003c/strong\u003e \u003cp\u003eBoric acid (H\u003csub\u003e3\u003c/sub\u003eBO\u003csub\u003e3\u003c/sub\u003e, Mol. wt. = 61.83, assay\u0026thinsp;\u0026ge;\u0026thinsp;99.5%, Merck Specialities, Mumbai), phenyltriethoxysilane [PTEOS] (C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003eSi, Mol. wt. = 240.38, assay\u0026thinsp;\u0026ge;\u0026thinsp;98%, Spectrochem Research Laboratories, Mumbai, India), and vinyltriethoxysilane [VTEOS] (C\u003csub\u003e8\u003c/sub\u003eH\u003csub\u003e18\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003eSi, Mol. wt. = 190.32, assay\u0026thinsp;\u0026ge;\u0026thinsp;97%, Nabond, Shenzhen, China), were used as received.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cem\u003eSynthesis\u003c/em\u003e: In a typical experiment, a mixture containing 6.18 g (0.1 mol) of boric acid, 24.04 g (0.1 mol) of PTEOS and 19.03 g (0.1 mol) VTEOS was taken in a three-necked round bottom flask equipped with a mechanical stirrer, water condenser and a set-up for purging argon. The contents of the flask were heated under the flow of argon in an oil bath and the bath temperature was maintained at 150\u0026ndash;160\u0026deg;C. Stirring and heating of the reaction mixture was continued for 5 h after which the contents of the flask were allowed to cool to room temperature. Phenylvinyl borosiloxane was obtained as a solution in ethanol, which was formed as the byproduct and the oligomer was labeled BPV\u003csub\u003e12\u003c/sub\u003e. Following a similar procedure, oligomers were also synthesized in 1:0.5:0.5, 1:0.5:1.5, 1:1.5:0.5 and 1:1.5:1.5.\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCharacterization\u003c/strong\u003e \u003cp\u003eThe oligomers were characterized by gel permeation chromatography (Waters Alliance), viscosity measurement (HBDT Visco II +), FT-IR spectral analysis (Perkin Elmer Spectrum GX), NMR spectral analysis (Brucker Avance 300) and TG analysis (Mettler TA 3000). XRD patterns of ceramic samples were recorded on an Xpert Pro MPD model Rontgen diffractometer (40 KW and 30 \u0026micro; amps) with Cu Kα (1.54 \u0026Aring;). CHN analysis was carried out in Perkin Elmer Elemental Analyzer (Model PE 2400). Si and B contents were estimated by wet-analysis. The ceramic powders were also characterized by SEM/EDX analysis. Carl Zeiss EVO 50 series in Extended Pressure (EP) imaging mode was used for SEM analysis. For EDX analysis, an OXFORD INCA system was used.\u003c/p\u003e \u003c/p\u003e"},{"header":"3. RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Synthesis and Characterization:\u003c/h2\u003e \u003cp\u003eThe reaction scheme for the synthesis and GPC curves of these oligomers is given in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. the molecular weight (for the elution range 15.3\u0026ndash;18.8 min) and viscosity data are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eGPC and viscosity data of borosiloxane oligomers from PTEOS and VTEOS\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOligomer\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMonomer feed ratio (Boric acid : PTEOS:VTEOS)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMw\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMp\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePDI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eViscosity at 30\u0026deg;C (cps)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBPV\u003csub\u003e11\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1:0.5:0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1440\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1040\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e950\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e15.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBPV\u003csub\u003e12a\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1:1:1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1560\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1040\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e19.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBPV\u003csub\u003e12b\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1:0.5:1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1230\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e8.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBPV\u003csub\u003e12c\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1:1.5:0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e920\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e17.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBPV\u003csub\u003e13\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1:1.5:1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e980\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e9.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eComparison of molecular weight data of the oligomers, BPV\u003csub\u003e11\u003c/sub\u003e, BPV\u003csub\u003e12a\u003c/sub\u003e and BPV\u003csub\u003e13,\u003c/sub\u003e which were synthesized using PTEOS: VTEOS molar ratio of 1:1 suggests that maximum molecular weight is obtained for BPV\u003csub\u003e12a\u003c/sub\u003e. Comparison of molecular weight data of BPV\u003csub\u003e12a\u003c/sub\u003e, BPV\u003csub\u003e12b\u003c/sub\u003e and BPV\u003csub\u003e12c\u003c/sub\u003e indicates that maximum Mw is obtained for BPV\u003csub\u003e12b\u003c/sub\u003e suggesting that higher concentration of VTEOS in the monomer feed favors the formation of oligomers with higher molecular weight. It is noticed that the tendency for polymodal molecular weight distribution increases with the increase in alkoxysilane concentration in the monomer feed. Unlike the other oligomers, BPV\u003csub\u003e13\u003c/sub\u003e synthesized using boric acid: PTEOS: VTEOS molar ratio of 1:1.5:1.5 shows a prominent broad peak in the elution range 17.8 to 18.5 min which is attributed to the presence of unreacted alkoxysilane monomers/low molecular weight products. This conclusion is supported by \u003csup\u003e29\u003c/sup\u003eSi-NMR spectral data, which will be discussed later. Possible reactions in the system are given in Scheme \u003cspan refid=\"Sch1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIR spectra of the oligomers are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and the peak assignments are given below: 3400 (ν\u003csub\u003eSiO-H\u003c/sub\u003e), 3224 (ν\u003csub\u003eBO-H\u003c/sub\u003e), 2983 (ν\u003csub\u003eC-H(asym.)\u003c/sub\u003eof Ph group), 1603 (ν\u003csub\u003eC=C\u003c/sub\u003e of Ph group), 1432 (ν\u003csub\u003eSi-Ph\u003c/sub\u003e), 1195 (δ\u003csub\u003eB-OH\u003c/sub\u003e), 884 (ν\u003csub\u003eSiOB\u003c/sub\u003e), 775 (ρ\u003csub\u003eSiOSi\u003c/sub\u003e), 675 (δ\u003csub\u003eSiOB\u003c/sub\u003e), 486 (ν\u003csub\u003eSi-Ph\u003c/sub\u003e). The peaks at 884 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e (ν\u003csub\u003eSi-O-B\u003c/sub\u003e) and 675 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e (δ\u003csub\u003eSi-O-B\u003c/sub\u003e) support the formation of Si-O-B linkages.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBPV\u003csub\u003e12b\u003c/sub\u003e oligomer having a higher VTEOS concentration in the monomer feed shows a peak at 1412 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, attributed to -CH\u003csub\u003e2\u003c/sub\u003e scissoring vibration of vinyl group. Similarly, Si-Ph stretching (1432 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) is shown by BPV\u003csub\u003e12c\u003c/sub\u003e oligomer having a higher concentration of PTEOS. Peaks corresponding to unreacted Si-OEt (1133 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) and B-OH (3224 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) groups were also present in the FT-IR spectra.\u003c/p\u003e \u003cp\u003e \u003csup\u003e1\u003c/sup\u003eH-NMR spectra of the oligomers are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The signal observed from 1.18 ppm to 1.26 ppm for the oligomers is assigned to CH\u003csub\u003e3\u003c/sub\u003e protons of unreacted SiOEt, ethanol and ethyl borate. The signal observed at 3.54\u0026ndash;3.66 ppm is attributed to CH\u003csub\u003e2\u003c/sub\u003e protons of ethanol and ethyl borate. The signal at 3.73\u0026ndash;3.88 ppm is due to CH\u003csub\u003e2\u003c/sub\u003e protons of unreacted SiOEt groups.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIt is worth noting that the ratio of the intensity of the peaks at 3.54\u0026ndash;3.66 ppm and 3.73\u0026ndash;3.88 ppm decreases in the following order:\u003c/p\u003e \u003cp\u003eBPV\u003csub\u003e11\u003c/sub\u003e (0.82)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12c\u003c/sub\u003e (0.64)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12b\u003c/sub\u003e (0.61)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12a\u003c/sub\u003e (0.59)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e13\u003c/sub\u003e (0.24)\u003c/p\u003e \u003cp\u003eThe above trend suggests that, with the increase in alkoxysilane or in other words decrease in boric acid concentration, the amount of ethanol and ethyl borate formed decreases. The signal observed at 4.4 ppm is due to Si-OH group. The two broad signals observed at 5.3 and 6.0 ppm are attributed to -CH and -CH\u003csub\u003e2\u003c/sub\u003e protons of vinyl group respectively. The signals centered at 7.3 and 7.7 ppm are due to aromatic protons.\u003c/p\u003e \u003cp\u003e \u003csup\u003e13\u003c/sup\u003eC-NMR of the oligomers are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The signal at 17.2 ppm is due to CH\u003csub\u003e3\u003c/sub\u003e carbon of ethanol and ethyl borate. The signal at 18.5 ppm is attributed to CH\u003csub\u003e3\u003c/sub\u003e carbon of SiOEt. As observed for phenylborosiloxane system, the ratio of the intensity of these two signals decreases with the increase in alkoxysilane concentration in the monomer feed. This indicates that the extent of formation of the byproduct ethanol decreases and the concentration of unreacted SiOEt group increases with the increase in alkoxysilane to boric acid ratio.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe signals at 57.8 ppm, 59.1 ppm and 59.4 ppm are due to CH\u003csub\u003e2\u003c/sub\u003e carbon of ethanol, unreacted Si-OEt groups and ethyl borate respectively. It is noticed that the ratio of intensity of the signals at 57.8 ppm and 59.1 ppm decreases with the increase in alkoxysilane concentration in the monomer feed which supports the conclusion drawn above. Signals observed in the region 130.6 to 136.1 ppm correspond to vinylic and aromatic carbons. The signal at 127.7 ppm is assigned to C\u003csub\u003e1\u003c/sub\u003e, C\u003csub\u003e3\u003c/sub\u003e and C\u003csub\u003e5\u003c/sub\u003e carbon of phenyl group. The signal at 130.6 ppm is attributed to both phenyl-C\u003csub\u003e4\u003c/sub\u003e carbon and vinyl-CH carbon. The signal at 134.4 ppm is due to C\u003csub\u003e2\u003c/sub\u003e and C\u003csub\u003e6\u003c/sub\u003e carbons. The signal at 136.1 ppm is assigned to CH\u003csub\u003e2\u003c/sub\u003e carbon of vinyl group.\u003c/p\u003e \u003cp\u003e \u003csup\u003e29\u003c/sup\u003eSi-NMR spectra of the BPV oligomers are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Soraru et al. \u003csup\u003e5,39\u003c/sup\u003e studied in detail the \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003eSi-NMR spectra of borosiloxane oligomers prepared by sol-gel process of boric acid and organic substituted alkoxysilanes and assigned the chemical shifts to the structural units, T\u003csup\u003e1\u003c/sup\u003e, T\u003csup\u003e2\u003c/sup\u003e and T\u003csup\u003e3\u003c/sup\u003e, where T\u003csup\u003ei\u003c/sup\u003e indicates the unit with \u0026lsquo;i\u0026rsquo; siloxane (-O-Si) bonds attached to the central silicon atom (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the present study, classical T\u003csup\u003en\u003c/sup\u003e\u003csub\u003eR\u003c/sub\u003e notation is used for representing different phenyl substituted Si species, where the superscript \u0026lsquo;n\u0026rsquo;, represents the number of oxo-bridges and the subscript R, represents the substituents (-OH and/or -OEt) and their numbers. The observed signals are attributed to two types of structural units, viz., T\u003csup\u003en\u003c/sup\u003e\u003csub\u003eOEt\u003c/sub\u003e and T\u003csup\u003en\u003c/sup\u003e\u003csub\u003eOH\u003c/sub\u003e on the basis of whether the ethoxy group remains as such in the Si moiety or it has hydrolyzed to -OH group. It is reported that the Si-O-Si and the Si-O-B bonds do not differ in their \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003eSi-NMR chemical shifts \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. This implies that the chemical shift values of T\u003csup\u003ei\u003c/sup\u003e structures are not influenced by whether they contain Si-O-Si or Si-O-B bonds. The \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003eSi-NMR spectra of borosiloxane oligomers are interpreted based on the chemical shift assignments reported for the sol-gels synthesized from phenyltrialkoxysilanes \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e and the assignments of chemical shifts are given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003csup\u003e29\u003c/sup\u003eSi-NMR chemical shift assignments for borosiloxane oligomers from PTEOS and VTEOS\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBPV\u003csub\u003e11\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBPV\u003csub\u003e12a\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBPV\u003csub\u003e12b\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBPV\u003csub\u003e12c\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eBPV\u003csub\u003e13\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVi-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-79.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-82.0, -80.9,\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-81.0, -79.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-80.3, -79.5, -78.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-82.2, -81.6, -80.9, -79.1, -76.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePh-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-77.43, -78.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-78.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-78.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-78.6, -78.2, -77.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVi-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eOEt\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-73.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-74.1, -72.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-73.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-74.2, -73.5, -72.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVi-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eOH\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-71.7, -72.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-71.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-71.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-71.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePh-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eOEt\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-71.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-70.9, -70.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-71.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePh-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003eOH\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-70.9, -70.6, -69.2,-68.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-68.0,-69.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-69.2, -68.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-69.7, -68.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-68.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVi-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003e(OEt)2\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-66.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePh-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003e(OEt)2\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-65.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-65.4, -65.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e65.3, -65.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVi-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003e(OH)(OEt)\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-64.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-64.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePh-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003e(OH)(OEt)\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-63.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-63.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-63.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVi-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e0\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003e(OEt)3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-58.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePh-T\u003c/b\u003e\u003csup\u003e\u003cb\u003e0\u003c/b\u003e\u003c/sup\u003e\u003csub\u003e\u003cb\u003e(OEt)3\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-57.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-57.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eBPV oligomers show two major peaks centered around \u0026minus;\u0026thinsp;72 and \u0026minus;\u0026thinsp;79 ppm, though the peaks are much broader compared to that of BP oligomers. In BPV oligomers, the number of microstructures is expected to be more due to the presence of phenylsiloxy and vinylsiloxy units and this is responsible for the broadening of signals. The major peaks observed around \u0026minus;\u0026thinsp;72 and \u0026minus;\u0026thinsp;79 ppm are attributed to T\u003csup\u003e2\u003c/sup\u003e and T\u003csup\u003e3\u003c/sup\u003e structures respectively. Apart from these major peaks, BPV\u003csub\u003e12b\u003c/sub\u003e, BPV\u003csub\u003e12c\u003c/sub\u003e and BPV\u003csub\u003e13\u003c/sub\u003e show a peak in the range \u0026minus;\u0026thinsp;60 to -68 ppm attributed to T\u003csup\u003e1\u003c/sup\u003e structure. BPV\u003csub\u003e13\u003c/sub\u003e, like BP\u003csub\u003e13\u003c/sub\u003e clearly shows the presence of unreacted monomer at -57.7 and \u0026minus;\u0026thinsp;58.4 ppm corresponding to PTEOS and VTEOS respectively. This observation is in line with that made by GPC analysis.\u003c/p\u003e \u003cp\u003eThe T\u003csup\u003e3\u003c/sup\u003e: (T\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;+\u0026thinsp;T\u003csup\u003e1\u003c/sup\u003e) ratio follows the trend BPV\u003csub\u003e11\u003c/sub\u003e (3.36)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12a\u003c/sub\u003e (1.94)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12b\u003c/sub\u003e (1.56)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12c\u003c/sub\u003e (1.28)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e13\u003c/sub\u003e (1.06) respectively. This observation suggests that boric acid plays an important role in the formation of T\u003csup\u003e3\u003c/sup\u003e structure. No T\u003csup\u003e1\u003c/sup\u003e peaks were observed for BPV\u003csub\u003e12a\u003c/sub\u003e system and no splitting is observed. However, for BPV\u003csub\u003e12b\u003c/sub\u003e and BPV\u003csub\u003e12c\u003c/sub\u003e the peak multiplicity is observed which may be due to two different types of T\u003csup\u003e2\u003c/sup\u003e structures (Ph-T\u003csup\u003e0\u003c/sup\u003e and Vi-T\u003csup\u003e2\u003c/sup\u003e) and also due to difference in the monomer feed ratios of PTEOS and VTEOS. BPV\u003csub\u003e13\u003c/sub\u003e which was synthesized using excess of alkoxysilanes (boric acid: alkoxysilanes ratio 1:3) shows the presence of Vi-T\u003csup\u003e0\u003c/sup\u003e and Ph-T\u003csup\u003e0\u003c/sup\u003e and the concentration of Ph-T\u003csup\u003e0\u003c/sup\u003e is more than that of Vi-T\u003csup\u003e0\u003c/sup\u003e. This observation suggests that VTEOS is more reactive than PTEOS.\u003c/p\u003e \u003cp\u003eTG and DTG curves of BPV oligomers are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The TG data are summarized in \u003cb\u003eTable\u0026nbsp;3\u003c/b\u003e. Based on the DTG curves, the TG curves can be divided into four regions: room temperature to 200\u0026deg;C, 200 to 430\u0026deg;C, 430 to 650\u0026deg;C and 650 to 900\u0026deg;C. The mass loss up to 200\u0026deg;C is attributed to the loss of mainly water and ethanol formed from the reaction of residual -OH and/or -OEt moieties \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. The weight loss observed up to 200\u0026deg;C follows the trend, BPV\u003csub\u003e11\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12a\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;BPV\u003csub\u003e12b\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12c\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e13\u003c/sub\u003e, clearly indicating that the weight loss depends upon the boric acid:alkoxysilane ratio. As per the possible reactions shown in Scheme \u003cspan refid=\"Sch1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, boric acid is required for the condensation reactions forming water and ethanol byproducts. In the absence of sufficient quantity of B-OH groups, these reactions are affected. This effect of boric acid concentration is an important aspect of borosiloxane pyrolysis, as the mass loss upto 200\u0026deg;C is the second largest mass loss during the pyrolysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe gradual mass loss observed from 200 to 430\u0026deg;C is attributed to the loss of low molecular weight oligomers and cyclic or cage polysiloxanes \u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. The weight loss in the region 200 to 430\u0026deg;C is about 2\u0026ndash;3%, which is due to the loss of oligomeric products and cyclic/cage structures. This implies that under the experimental conditions, the formation of such products is very minimum. The weight loss in the region 430\u0026ndash;650\u0026deg;C is 5.1 to 13.1% which is attributed to the ceramization process, i.e., cleavage of pendant vinyl and phenyl moieties \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. The weight loss in this region follows the trend, BPV\u003csub\u003e12c\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e13\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12a\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e11\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12b\u003c/sub\u003e. The maximum weight loss noticed for BPV\u003csub\u003e12c\u003c/sub\u003e is due to the higher concentration of Si-Ph units in the system. The least weight loss observed for BPV\u003csub\u003e12b\u003c/sub\u003e is understood in view of the lowest concentration of Si-Ph units. Between BPV\u003csub\u003e11\u003c/sub\u003e and BPV\u003csub\u003e13\u003c/sub\u003e which were synthesized using the same alkoxysilane monomer feed ratio (PTEOS:VTEOS ratio 1:1), the weight loss is less for BPV\u003csub\u003e11\u003c/sub\u003e and this is due to the higher concentration of T\u003csup\u003e3\u003c/sup\u003e structures and higher boron content in BPV\u003csub\u003e11\u003c/sub\u003e. The weight loss in the region 650\u0026ndash;900\u0026deg;C is 1\u0026ndash;2%, which is probably due to the loss of hydrogen.\u003c/p\u003e \u003cp\u003eBPV system shows an improvement in overall thermal stability compared to that of phenyl borosiloxanes \u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. This is attributed to: i) high reactivity of VTEOS which increases the relative concentration of T\u003csup\u003e3\u003c/sup\u003e units and ii) reduction in mass loss in the 430\u0026ndash;650\u0026deg;C due to the lower relative concentration of phenylsiloxane units compared to phenylborosiloxanes.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Ceramic conversion and characteriazaton:\u003c/h2\u003e \u003cp\u003eAs described in the previous Section, BPV\u003csub\u003e11\u003c/sub\u003e, BPV\u003csub\u003e12a\u003c/sub\u003e, BPV\u003csub\u003e12b\u003c/sub\u003e,BPV\u003csub\u003e12c\u003c/sub\u003e and BPV\u003csub\u003e13\u003c/sub\u003e were synthesized using the monomer feed ratios (boric acid:PTEOS:VTEOS) 1:0.5:0.5, 1:1:1, 1:0.5:1.5, 1:1.5:0.5 and 1:1.5:1.5 respectively. For initial pyrolysis of the oligomers, the samples obtained at 175\u0026deg;C were powdered and pyrolyzed at 900\u0026deg;C under the flow of argon. The 900\u0026deg;C pyrolyzed samples were used for ceramic conversion studies at 1500 and 1650\u0026deg;C in separate experiments. All the ceramic conversions were carried out under argon flow. The details of the procedure are given in Section 2.4. XRD patterns and FT-IR spectra of the ceramic residue obtained at 900\u0026deg;C are given in Figs.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e respectively.\u003c/p\u003e \u003cp\u003eAt 900\u0026deg;C, the ceramic powder consists mainly of SiBOC glassy phase as evidenced by a diffraction halo centered around 2θ\u0026thinsp;=\u0026thinsp;21.25\u0026deg;. The diffraction line observed at 2θ\u0026thinsp;=\u0026thinsp;28.13\u0026deg; for BPV\u003csub\u003e11\u003c/sub\u003e and BPV\u003csub\u003e12a\u003c/sub\u003eis due to boric acid.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe FT-IR analysis supports the inferences drawn from XRD studies. The presence of SiOB bond is evident from the absorption at 884 and 648 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003ecorresponding to Si-O-B stretching and bending vibrations respectively. The higher concentration and higher extinction coefficients of Si-O masks these peaks, particularly at higher alkoxysilane concentrations. The absorptions at 1080 and 458 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e are caused by Si-O-Si stretching and bending vibrations respectively. The relative intensity of Si-O-Si stretching with respect to that of B-O stretching (1440 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) increases with the increase in alkoxysilane concentration in the monomer feed.\u003c/p\u003e \u003cp\u003eThe absorption at 1614 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e is attributed to \u0026ndash;C\u0026thinsp;=\u0026thinsp;C\u0026ndash; stretching vibration of carbidic carbon \u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. These absorptions get prominent with increase in phenylsiloxy and vinylsiloxy units in the starting precursor and this is more pronounced with the increase in phenylsiloxy units. This peak is associated with absorptions at 2854 and 2925 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e due to C-H stretching of hydrogen attached to carbidic carbon.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe ceramic residues obtained at 900\u0026deg;C from BPV oligomers are further heat treated at 1500\u0026deg;C. XRD patterns of BPV-1500 are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Comparison of XRD patterns of BP-1500 and BPV-1500 systems indicates that the extent of formation of β-SiC crystallites from SiBOC glass is more for BP-1500 than for BPV-1500. This observation suggests that the presence of vinylsiloxy units in the oligomer backbone brings down the formation of β-SiC crystallites from SiBOC glass.\u003c/p\u003e \u003cp\u003eAmong the five different samples of BPV-1500 system, it is noticed that the extent of formation of β-SiC follows the trend, BPV\u003csub\u003e11\u003c/sub\u003e-1500\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12a\u003c/sub\u003e-1500\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12c\u003c/sub\u003e-1500\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e13\u003c/sub\u003e-1500. The crystallite size of β-SiC follows the trend BPV\u003csub\u003e11\u003c/sub\u003e-1500 (46 nm)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12a\u003c/sub\u003e-1500 (14 nm)\u0026thinsp;=\u0026thinsp;BPV\u003csub\u003e12c\u003c/sub\u003e-1500 (14 nm)\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e12b\u003c/sub\u003e-1500(7 nm). The observed trend can be explained taking into consideration the following factors: i) boric acid concentration in the monomer feed and ii) the type and the relative concentration of siloxy units. As discussed earlier, the redistribution of Si-C and Si-O bonds is quite local and can account for the nucleation of small β-SiC crystals \u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. The growth rate of SiC in SiOC glasses is very low because of the extremely high viscosity of SiOC glass. As discussed earlier, the incorporation of boron in SiOC glass brings down the viscosity. The high boron content of BPV\u003csub\u003e11\u003c/sub\u003eis responsible for higher crystallite size as the crystallization kinetics, which is a diffusion controlled process, is enhanced with the lowering of viscosity \u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. Ceramics from BPV\u003csub\u003e13\u003c/sub\u003e will have the highest viscosity due to low boron content and for this reason, the redistribution reaction is expected to be quite local. As a result, BPV\u003csub\u003e13\u003c/sub\u003e-1500 shows the least tendency for SiC crystallization. Among BPV\u003csub\u003e12a\u003c/sub\u003e-1500, BPV\u003csub\u003e12b\u003c/sub\u003e-1500 and BPV\u003csub\u003e12c\u003c/sub\u003e-1500 samples obtained from the precursors synthesized using boric acid: alkoxysilanes monomer feed ratio of 1:2, lowest crystallite size is obtained for BPV\u003csub\u003e12b\u003c/sub\u003e-1500. This is understood in view of higher content of vinylsiloxy units in the starting precursor compared to the other two samples. Higher amount of vinylsiloxy units means lower pyrolytic/carbidic carbon content present in the glassy matrix which in turn is responsible for localizing the redistribution reaction.\u003c/p\u003e \u003cp\u003eXRD pattern of BP\u003csub\u003e11\u003c/sub\u003e-1500 also shows diffraction lines corresponding to B\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (2θ\u0026thinsp;=\u0026thinsp;28.13\u0026deg;). A hump observed in the amorphous region is attributed to silica phase (2θ\u0026thinsp;=\u0026thinsp;26.14\u0026deg;). The formation of silica in BPV\u003csub\u003e11\u003c/sub\u003e-1500 is similar to the observation made in BP\u003csub\u003e11\u003c/sub\u003e-1500. The higher boron content in the ceramic brings down the viscosity of SiBOC glass and speeds up the formation of SiC and SiO\u003csub\u003e2\u003c/sub\u003e phases. It is to be noted that the intensity of \u0026lt;\u0026thinsp;111\u0026thinsp;\u0026gt;\u0026thinsp;diffraction plane of β-SiC also shows an increase in BPV\u003csub\u003e11\u003c/sub\u003e-1500 along with silica formation, thereby supporting the above fact.\u003c/p\u003e \u003cp\u003eFT-IR spectra of the BPV-1500 samples are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. In line with the observations based on XRD patterns, BPV\u003csub\u003e11\u003c/sub\u003e-1500, BPV\u003csub\u003e12a\u003c/sub\u003e-1500 and BPV\u003csub\u003e12c\u003c/sub\u003e-1500 show absorptions at 815 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e corresponding to Si-C stretching of SiC. The absorptions at 1404, 1092 and 906 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e are assigned to stretching vibrations of B-O, Si-O-Si and Si-O-B respectively. It is seen that the relative intensity of B-O and Si-O-B stretching with respect to Si-O-Si stretching is the least for BPV\u003csub\u003e12b\u003c/sub\u003e-1500 when compared to that of BPV\u003csub\u003e12a\u003c/sub\u003e-1500 and BPV\u003csub\u003e12c\u003c/sub\u003e-1500. This observation suggests that increase in VTEOS concentration in the monomer feed results in less incorporation of Si-O-B bonds in the precursor.\u003c/p\u003e \u003cp\u003eAs the temperature of heat treatment is further increased to 1650\u0026deg;C, the samples show a color change from black to grey and surface of the sample was covered with off-white fluffy materials. The sample along with the fluffy material was powdered and analyzed by XRD and FT-IR. In the 1500\u0026ndash;1650\u0026deg;C temperature range, the major reaction possible is the carbothermal reduction resulting in the formation of β-SiC with a corresponding reduction in the SiBOC phase. This is clearly observed in the XRD patterns of the samples shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eAll the major diffractions correspond to β-SiC, and the left-side hump in the 2θ\u0026thinsp;=\u0026thinsp;35.59\u0026deg; diffraction line corresponds to B\u003csub\u003e4\u003c/sub\u003eC and/or structural anomalies in the β-SiC unit cell. It is worth noting that compared to BP system, in BPV, all the samples give similar SiC diffraction lines irrespective of the alkoxysilane content. Crystallite size of β-SiC was calculated using Scherrer equation and the values are80, 90, 98, 65 and 83 nm for BPV\u003csub\u003e11\u003c/sub\u003e-1650, BPV\u003csub\u003e12a\u003c/sub\u003e-1650, BPV\u003csub\u003e12b\u003c/sub\u003e-1650, BPV\u003csub\u003e12c\u003c/sub\u003e-1650 and BPV\u003csub\u003e13\u003c/sub\u003e-1650 respectively. It is worth comparing the crystallite size of BPV-1650 samples with that of BP-1650 samples in order to understand more about the mechanism of formation of β-SiC. BP-1650 samples have crystallite size in the range 40\u0026ndash;62 nm whereas BPV-1650 samples have crystallite size of 65\u0026ndash;98 nm. In BP system, the presence of residual carbon incorporated into the borosilicate matrix or the free carbon can act as a diffusion barrier for the mobility of silicon and carbon atoms, thereby reducing the crystal growth \u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFT-IR spectra of all the samples after heat treatment at 1650\u0026deg;C are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. Though the XRD patterns of samples heat treated at 1650\u0026deg;C look alike, differences are seen in the IR spectra of these samples. Si-C stretching vibration at 819 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e is seen for all the samples. Absorption due to Si-O-Si stretching vibration at 1020 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e is seen in the IR spectra of BPV\u003csub\u003e11\u003c/sub\u003e-1650 and BPV\u003csub\u003e12b\u003c/sub\u003e-1650 samples and the relative intensity of this peak with respect to Si-C stretching vibration at 819 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e follows the trend, BPV\u003csub\u003e12b\u003c/sub\u003e-1650\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e13\u003c/sub\u003e-1650\u0026thinsp;\u0026gt;\u0026thinsp;BPV\u003csub\u003e11\u003c/sub\u003e-1650. This observation suggests that the increase in vinylsiloxy units in the precursor or the increase in boric acid concentration in the monomer feed, would bring down the presence of carbon domains in the ceramic and hence, all the SiO\u003csub\u003e4\u003c/sub\u003e units could not get converted to SiC\u003csub\u003e4\u003c/sub\u003e through carbothermal reduction. It is worth noting that absorption around 1400 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e corresponding to B-O stretching vibration is not seen in the IR spectra. However, it is seen that the peak at 819 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e is broad except for of BPV\u003csub\u003e12a\u003c/sub\u003e-1650. This may be due to merging of Si-O-B stretching vibration of residual SiBOC glass with Si-C stretching vibration of β-SiC.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. CONCLUSIONS","content":"\u003cp\u003eBorosiloxane oligomers were synthesized from boric acid and mixtures of alkoxysilanes (PTEOS\u0026thinsp;+\u0026thinsp;VTEOS) via solventless synthesis. The oligomer was obtained as either low or high viscous resins in ethanol which formed as the byproduct. FT-IR analysis of the oligomers confirmed the presence of Si-O-B bonding (884 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) in the oligomer backbone along with unreacted Si-OEt (1133 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) and B-OH (3224 cm\u003csup\u003e-\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e) groups. In all the different borosiloxanes, the oligomer synthesized in 1:1 (boric acid: alkoxysilanes) ratio showed precipitation of unreacted boric acid on standing. BPV oligomers synthesized from mixture of PTEOS and VTEOS showed higher molecular weight and viscosity values than that of phenyl borosiloxanes. \u003csup\u003e13\u003c/sup\u003eC-NMR and IR spectra shows that vinyl group is intact in the oligomer.\u003c/p\u003e \u003cp\u003e \u003csup\u003e29\u003c/sup\u003eSi-NMR of the oligomer-ethanol solutions shows that the microstructure of the as-synthesized borosiloxane consists of three major structural units. The relative concentration of the highest cross-linked unit viz., T\u003csup\u003e3\u003c/sup\u003e structure indicate that its formation is enhanced by the increase in boric acid concentration in the monomer feed. \u003csup\u003e29\u003c/sup\u003eSi-NMR analysis also supports the fact that VTEOS is more reactive than PTEOS towards condensation with boric acid under solventless reaction condition. Along with the NMR analysis results, the thermal analysis results clearly support the role of vinyl group in increasing the thermal stability and ceramic residue of phenyl borosiloxanes.\u003c/p\u003e \u003cp\u003eDetailed ceramic conversion study of the borosiloxane oligomers shows that the nature of ceramic obtained is greatly influenced by the boron and carbon content of the borosiloxane oligomer. All the oligomers give an amorphous SiBOC phase at 900\u0026deg;C. Nano sized β-SiC crystallizes out from the glassy SiBOC matrix at higher temperature.\u003c/p\u003e \u003cp\u003eTwo independent and overlapping mechanisms are proposed for the formation of β-SiC, viz., the nucleation and crystal growth mechanism and carbothermal reduction mechanism. In the first one, redistribution reactions between Si-O and Si-C bonds in the SiBOC matrix leads to the formation of SiC\u003csub\u003e4\u003c/sub\u003e tetrahedra, which acts as nucleating centers for further crystal growth. Compared to siloxanes, borosiloxanes show an increased β-SiC crystallization at 1500\u0026deg;C. This is attributed to the presence of boron in the matrix which brings down the viscosity of SiBOC glass. As the viscosity of the glass is reduced, the mobility of Si and C in the matrix is enhanced resulting in faster crystallization.\u003c/p\u003e \u003cp\u003eCarbothermal reduction is the reaction between the free carbon phase and Si-O rich phase forming SiC and CO. The reaction results in mass loss of SiBOC ceramic. Though the carbothermal reduction takes place in the temperature range close to 1500\u0026deg;C, itis predominant at temperatures above 1500\u0026deg;C. Thus, the crystallite growthof β-SiC is controlled by carbothermal reduction predominantly in the temperature range 1500\u0026ndash;1650\u0026deg;C and depends mainly on the carbon content of the ceramics.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eSreejith has carried out the experimental work and interpreted the data, Deepa has carried out the initial works on the topic and Packirisamy has guided the work.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors thank the authorities of Vikram Sarabhai Space Centre for the permission to publish this work. Help rendered by the members of Analytical and Spectroscopic Division and Material Characterization Division is also acknowledged.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eA.W. Knights, Synthesis and Modification of Polyphosphinoboranes and Polyborosiloxanes. 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Soc. \u003cb\u003e16\u003c/b\u003e(7), 721\u0026ndash;737 (1996). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0955-2219(95)00186-7\u003c/span\u003e\u003cspan address=\"10.1016/0955-2219(95)00186-7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Schemes","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-inorganic-and-organometallic-polymers-and-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"joip","sideBox":"Learn more about [Journal of Inorganic and Organometallic Polymers and Materials](https://www.springer.com/journal/10904)","snPcode":"10904","submissionUrl":"https://submission.nature.com/new-submission/10904/3","title":"Journal of Inorganic and Organometallic Polymers and Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"polymer derived ceramics, borosiloxanes, boric acid, phenyltriethoxysilane, vinyltriethoxysilane, SiBOC ceramics","lastPublishedDoi":"10.21203/rs.3.rs-8468563/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8468563/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper reports the solventless synthesis and characterization of borosiloxane oligomers from boric acid and mixtures of vinyltriethoxysilane and phenyltriethoxysilane, using different monomer feed ratios. The oligomers were characterized by gel permeation chromatography and infrared spectral analysis. Microstructure of the oligomers was studied using \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003eH-, \u003csup\u003e13\u003c/sup\u003eC- and \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003eSi-NMR spectra. Ceramic conversion of the borosiloxane oligomers were carried out at 900\u0026deg;C. The ceramics obtained at 900\u0026deg;C were further heat treated at 1500 and 1650\u0026deg;C. The ceramic powders were characterized by FT-IR and XRD. The effect of monomer feed ratio on the oligomer structure and on its ceramic conversion process is discussed.\u003c/p\u003e","manuscriptTitle":"Controlling ceramic composition using precursor chemistry: A study on borosiloxane derived SiBOC ceramics","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 15:13:31","doi":"10.21203/rs.3.rs-8468563/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-02-06T01:42:18+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-29T10:01:11+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-24T15:44:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"332744040064989822262828811840247164520","date":"2026-01-10T12:03:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"201647421689395796113426154832093066577","date":"2026-01-09T08:00:43+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"164155958489653328457047927924918077418","date":"2026-01-09T02:34:02+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-08T11:52:48+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-30T13:15:08+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-29T04:22:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Inorganic and Organometallic Polymers and Materials","date":"2025-12-29T02:35:45+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-inorganic-and-organometallic-polymers-and-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"joip","sideBox":"Learn more about [Journal of Inorganic and Organometallic Polymers and Materials](https://www.springer.com/journal/10904)","snPcode":"10904","submissionUrl":"https://submission.nature.com/new-submission/10904/3","title":"Journal of Inorganic and Organometallic Polymers and Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"61747501-c608-4c11-b7b5-5cd9db4c60bb","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-03T12:09:20+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 15:13:31","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8468563","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8468563","identity":"rs-8468563","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}