Effect of Additive Ti3SiC2 Content on Mechanical Properties of B4C–TiB2 Composites Ceramics Sintered by Spark Plasma Sintering

Effect of Additive Ti3SiC2 Content on Mechanical Properties of B4C–TiB2 Composites Ceramics Sintered by Spark Plasma Sintering | 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 Effect of Additive Ti 3 SiC 2 Content on Mechanical Properties of B 4 C–TiB 2 Composites Ceramics Sintered by Spark Plasma Sintering Xingheng Yan, Xingui Zhou, Honglei Wang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-78483/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 16 Oct, 2020 Read the published version in Materials → Version 1 posted You are reading this latest preprint version Abstract B 4 C-TiB 2 composite ceramics with ultra-high fracture toughness were successfully prepared via spark plasma sintering at 1900℃ using B 4 C and Ti 3 SiC 2 as raw materials. The results show that compared with pure B 4 C ceramics sintered by SPS, the hardness of B 4 C-TiB 2 composite ceramics is decreased, but the flexural strength and fracture toughness are significantly improved, especially the fracture toughness has been improved by leaps and bounds. When the content of Ti 3 SiC 2 is 30vol.%, the B 4 C-TiB 2 composite ceramic has the best comprehensive mechanical properties: hardness, bending strength and fracture toughness are 27.28 GPa, 405.11 MPa and 18.94 MPa·m 1/2 , respectively. The fracture mode of the B 4 C-TiB 2 composite ceramics is a mixture of transgranular fracture and intergranular fracture. Two main two reasons for the ultra-high fracture toughness are the existence of lamellar graphite at the grain boundary, and the formation of a three-dimensional interpenetrating network covering the whole composite. Ceramics Spark plasma sintering Boron carbide Ti3SiC2 Fracture toughness Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Boron carbide is an attractive engineering material with a high melting point, low density, high hardness, high thermal conductivity and large neutron absorption surface, which makes it a candidate material for wear-resistant parts, cutting tools, light armor products and neutron radiation shielding [ 1 , 2 ] . However, the low sintering property (due to the strong B-C covalent bond and B 2 O 3 oxide layer) and poor fracture toughness limit its excellent performance. Spark plasma sintering is a kind of electric current assisted sintering technology, which can enhance the bonding and densification of particles through the combination of mechanical pressure, electric field and thermal field [ 3 , 4 ] . SPS adopts the same stamping/die system concept as hot pressing, and the difference between them is that the heating methods are fundamentally different. Hot pressing sintering is heated by heating body radiation, while the SPS heat source is Joule heat generated by the current of mold or sample [ 5 , 6 ] . The heating rate of up to 1000 ℃/min can be obtained by SPS, and the heating up time is greatly shortened, which is beneficial to limit the grain growth [ 7 ] . In addition, current can also enhance powder sintering by activating one or more parallel mechanisms, such as surface oxide removal, electromigration and electroplasticity [ 8 ] . Reasonable use of additives can make boron carbide densification without deterioration of mechanical properties. Some additives can react with boron carbide in situ to form nonvolatile second phases, which is helpful for densification and can enhance properties. Ti 3 SiC 2 can react with B 4 C to form TiB 2 with high hardness and high melting point, which can be used as an ideal toughening phase for B 4 C ceramics [ 9 ] . In this study, B 4 C-TiB 2 composite ceramics with ultra-high toughness were prepared by the SPS process with different contents of Ti 3 SiC 2 as additives, and the influence mechanism of Ti 3 SiC 2 content on the microstructure and properties of B 4 C-TiB 2 composite ceramics was studied. 2. Experimental Procedure Commercially available B 4 C powders (purity 99.9%, 1 µm, 4.53 g/cm 3 , Nangong Naiyate Alloy Welding Material Co., Ltd), Ti 3 SiC 2 powders (purity 99.9%, < 74 µm, 4.53 g/cm 3 ,Nanjing Mingchang New Material Co., Ltd) were used as raw materials. Ti 3 SiC 2 -B 4 C powders containing 20 vol.%, 25 vol.%, 30 vol.% and 35 vol.% Ti 3 SiC 2 respectively were mixed for 24 h through a small vertical mixer at 80 r/min without adding solvent. The simples were prepared by SPS equipment (HP D 25/4-SD, FCT Systeme GmbH, Germany) in a vacuum with 35 MPa mechanical pressure at 1900 ℃ for 5 min. The heating rate was 100 ℃/min and the cooling rate was 50 ℃/min. The absolute density of B 4 C-TiB 2 composite ceramics was determined using the Archimedes method. Hardness was measured by a Vickers-indentation tester (Shimadzu, HMV-2TADW E, Japan) at 9.81 N load with a holding time of 15 s on the polished surface. Flexural strength was determined by a three-point bending test with a span of 30 mm and the loading speed of 0.5 mm/min, and the specimens used in the test were 3 × 4 × 35 mm bars. SENB method was used to determine the fracture toughness of the specimens, with dimensions of 2 × 4 × 20 mm (with 2 mm high notch). The microstructures of the composite ceramics were characterized by X-Ray powder diffraction (XRD, X′ Pert PRO-MPD, Holland Panalytical, Netherlands), scanning electron microscope (SEM, S-4800N, Hitachi, Japan), transmission electron microscope (TEM, JEM-2100, JEOL, Japan) and energy dispersive spectrometer (EDS, INCA, OXFORD INSTRUMENTS, England). 3. Results And Discussion The scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns of the as-received powders of B 4 C and Ti 3 SiC 2 are shown in Fig. 1 . The SEM images show that B 4 C particles have ladder-like surface undulation, which is a typical transgranular fracture appearance during the particle crushing process; Ti 3 SiC 2 particles have obvious lamellar structure. It can be seen from the XRD images that the two kinds of powders are relatively pure and almost no oxide exists (the content of oxide is too small to be detected in XRD). Figure 2 shows the phase composition of B 4 C-TiB 2 ceramic composites prepared at 1900℃ with different content of additive Ti 3 SiC 2 . There is no diffraction peak of Ti 3 SiC 2 in all XRD images, which indicates that Ti 3 SiC 2 has completely reacted with B 4 C. The overall reaction in the system can be described as the following reaction [ 10 ] : (1) TiC appears as an intermediate product in the whole reaction process but does not exist in the final product. According to the XRD test results, the content of each phase is shown in Table 1 . TiB 2 and B 4 C are the main phase composition of the composites, and a small amount of SiC and C exist. With the increase of Ti 3 SiC 2 content, the proportion of TiB 2 , B 4 C and C in the composite increases, while the content of B 4 C decreases. Table 1 contents of different phases in B 4 C-TiB 2 composite ceramics sintered at different temperatures Sample name Content of Ti 3 SiC 2 (vol.%) TiB 2 (wt.%) B 4 C (wt.%) SiC (wt.%) C (wt.%) BT20 20 9.4 87.4 1.6 1.7 BT25 25 19.7 73.2 3.3 3.8 BT30 30 29.6 61.9 4.2 4.4 BT35 35 40.6 47.7 6.1 5.6 Table 2 shows the properties of the samples prepared with different content of Ti 3 SiC 2 . BT0 is the reference sample without Ti 3 SiC 2 , and its hardness, bending strength and fracture toughness are 33.5GPa, 224.43 MPa and 5.96MPa·M 1/2 , respectively. Compared with BT0, all samples with Ti 3 SiC 2 have higher relative density. Figure 3 shows the BSE images of BT0 and BT30 after polishing. There are some closed pores in BT0, but not in BT30. This is because the B 4 C particles have sharp edges and corners, and its hardness (55GPa) is very high. Thus, they can not be extruded and deformed under pressure, leaving a non-contact space inside, and forming pores. The hardness of Ti 3 SiC 2 (4GPa) is much smaller than that of B 4 C, it can be extruded and deformed without leaving voids between particles under external load. After reaction sintering, TiB 2 , B 4 C, SiC and C (exist in the form of graphite) in the composites have different thermal expansion coefficients, which make the ceramics more compact after cooling. Table 2 Properties of ceramics prepared with different content of additive Ti 3 SiC 2 Simple name Content of Ti 3 SiC 2 (vol.%) Density (g/cm 3 ) Relative Density (%) Hardness (GPa) Flexural Strengh (MPa) Fracture Toughness (MPa·m 1/2 ) BT0 0 2.50 99.20 33.50 224.43 5.96 BT20 20 3.12 101.16 31.14 317.55 17.68 BT25 25 3.13 101.51 28.70 383.25 18.37 BT30 30 3.17 101.54 27.28 405.11 18.94 BT35 35 3.17 102.28 26.71 343.95 19.00 Because the hardness of the second phase particles produced by the reaction is lower than that of B 4 C, especially the graphite phase, it is inevitable that the hardness of the composite ceramics is lower than that of the pure B 4 C ceramics. Compared with BT0, the flexural strength and fracture toughness of BT20-BT35 are improved except for the decrease of hardness. Figure 4 shows the fracture morphology of BT0 and BT30. It can be seen that the fracture surface of BT0 is flat, which is a typical transgranular fracture morphology. While the fracture surface of sample BT30 is rough, which is a typically mixed fracture morphology of transgranular fracture and intergranular fracture. In Fig. 4 (b), the dark gray flat area is the B 4 C matrix, and the light gray rough area is TiB 2 particles, which indicates that the fracture modes of the B 4 C phase and the TiB 2 phase are transgranular fracture and intergranular fracture respectively. In addition, there is a dark gray lamellar phase around the TiB 2 grain, which can be inferred ad graphite phase by energy spectrum analysis. Due to the mismatch of thermal expansion coefficients between B 4 C, TiB 2 and graphite (B 4 C: 4.5 × 10 − 6 k − 1 ; TiB 2 : 8.1 × 10 − 6 k − 1 ; Graphite: 1 × 10 − 6 k − 1 in the parallel direction, 29 × 10 − 6 k − 1 in c direction) [ 11 ] , there will be large residual stress at the interface of the phases, which will induce crack deflection along the grain boundary and extend the crack propagation path to improve the strength and toughness of the material. The nano TiB 2 particles embedded in the B 4 C matrix will introduce internal stress, which will strengthen the B 4 C matrix by lattice distortion effect, and can also nail the dislocations and hinder their movement, so as to enhance the strength of the material. It should be noted that the fracture toughness of the composites has a leap forward improvement by adding more than 20vol.% Ti 3 SiC 2 . The fracture toughness of BT30 is 18.94 MPa·m 1/2 , which is more than 3 times of that of BT0 (5.80 MPa·m 1/2 ) and is more than 2 times higher than the highest fracture toughness cited in Table 3 . Wen Q et al [ 9 ] adopted the same ratio of raw materials as ours to sinter the ceramics. They used 0.5 µm B 4 C powders and 0.5 ~ 10 µm Ti 3 SiC 2 powders as raw materials, and their process was 1850 ℃ hot pressing sintering for 30 min. Compared with their work, the particle size of the raw powders we used has more difference in size (B 4 C: 1 µm; Ti 3 SiC 2 : <74 µm), making it easier to form aggregates, which are beneficial for toughness but unfavorable for strength [ 16 ] . Besides, our ceramics has a higher relative density and graphite content, which may be due to the evaporation of Si at higher sintering temperature and electric field [ 17 ] . Graphite phase exists at the grain boundaries of TiB 2 and B 4 C, which reduces the bonding strength of the interface and has an adverse effect on the hardness and strength of the composite ceramics. This is the reason why the flexural strength of BT30 is at a low level in Table 3 . But at the same time, the existence of graphite can limit the grain growth. In the cooling process, microcracks are produced under the effect of interfacial stress produced by different thermal expansion coefficients, and the cracks propagate along the interlayer of graphite during fracture, resulting in lamellar pull-out. It can be seen from Fig. 4 (b) that there are traces of particle pull-out and lamellar graphite pull-out in the fracture surface of BT30, which is one of the important reasons for the toughening of the composite. Table 3 Comparison of the properties of the B 4 C-TiB 2 composite ceramics reported in recent years Serial no. Starting powder Relative Density (%) K IC , (MPa·m 1/2 ) Flexural strength (MPa) Ref.(year) 1 B 4 C + 5 wt% (Ti 3 SiC 2 + Si) —— 5.61 457.6 [ 12 ] (2019) 2 B 4 C + 30 wt% (TiB 2 + Si) 99.6 5.77 531.2 [ 13 ] (2018) 3 B 4 C + 20 mol%TiB 2 97.9 3.7 —— [ 14 ] (2020) 4 B 4 C + 15 wt%SiC + 20 mol%TiB 2 98.6 4.2 343.8 [ 15 ] (2020) 5 B 4 C + 6.45vol.%SiC + 7.78vol.%TiB 2 99.62 6.38 632 [ 16 ] (2019) 6 B 4 C + 30vol.% Ti 3 SiC 2 98.72 8.0 492.3 [ 9 ] (2017) BT30 B 4 C + 30vol.% Ti 3 SiC 2 101.54 18.94 405.11 This work Figure 5 shows the variation of relative density and hardness of B 4 C-TiB 2 composite ceramics with the content of Ti 3 SiC 2 . Due to the slight evaporation of silicon [ 17 ] , the density of composites is slightly higher than the theoretical density. The evaporation capacity of Si increases with the increase of Ti 3 SiC 2 content, resulting in an increase of the relative density. The hardness decreases with the increase of Ti 3 SiC 2 content because of the proportion of the second phase with lower hardness, especially graphite, increases. Figure 6 shows the variation of flexural strength and fracture toughness of B 4 C-TiB 2 composite ceramics with additive Ti 3 SiC 2 content. When the content of Ti 3 SiC 2 is in the range of 20vol.% ~ 30vol.%, the flexural strength and fracture toughness are positively correlated with the content of Ti 3 SiC 2 . Compared Fig. 7 (a)-(c), it can be seen that the region as shown in Fig. 7 (e) becomes larger and more numerous with the increase of Ti 3 SiC 2 content. In this region, TiB 2 , graphite and B 4 C intersect each other to form a three-dimensional interpenetrating network. During the crack propagation process, multiple two-phase interfaces must be bypassed to disperse into more small cracks and a large number of changes in the propagation direction. The pull-out mechanism of graphite also plays an important role in this agglomeration area. Besides, this area does not exist in isolation. Every small network links to each other, forming a large network structure covering the whole composite. At the same time, the network divides the B 4 C concentration area into small parts and surrounds them, so that there is no large area of continuous B 4 C phase in the composites, which is very unfavorable to the toughness of the composite. With the increase of interlacing degree of TiB 2 , graphite and B 4 C, the cracks need to bypass more two-phase interfaces, change more directions and disperse into more small cracks. Therefore, the fracture toughness of B 4 C-TiB 2 composite ceramics is greatly improved by the overall three-dimensional interpenetrating network structure. However, when the content of Ti 3 SiC 2 is 35 vol.%, as shown in Fig. 6 (d), a large TiB 2 -SiC agglomerated area appears in the BT35 (among which the dark gray, medium gray and light gray phases are B 4 C, SiC and TiB 2 respectively). There is a bad stress effect in the multiphase mixing region with more SiC. At higher magnification Fig. 7 (f), many microcracks due to mismatch of thermal expansion coefficient can be found in this region, which is conducive to the toughening of the material. Nevertheless, it has a bad effect on the bending strength, resulting in a significant decrease in the bending strength. 4. Conclusions Ultra-high toughness B 4 C-TiB 2 composite ceramics were prepared by the SPS method at 1900℃. The content of additive Ti 3 SiC 2 has a great influence on the microstructure and mechanical properties. With the increase of Ti 3 SiC 2 content, the relative density and fracture toughness of the material increase, while the hardness decreases, and the flexural strength first increases and then decreases. When the content of Ti 3 SiC 2 is 30 vol.%, B 4 C-TiB 2 composite ceramics have the highest bending strength and the best comprehensive mechanical properties: hardness 27.28 GPa, bending strength 405.11 MPa, fracture toughness 18.94 MPa·m 1/2 . The fracture mode of the material is a mixture of transgranular fracture and intergranular fracture. The main reason for obtaining high fracture toughness is the existence of the graphite phase and the formation of a three-dimensional interpenetrating network covering the whole composite. The existence of the graphite phase has an effect on the hardness and fracture toughness of B 4 C-TiB 2 composite ceramics, but they still remain at a high level. References Suri AK, Subramanian C, Sonber JK, et al. 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Synthesis mechanism and mechanical properties of TiB2–SiC composites fabricated with the B4C–TiC–Si system by reactive hot pressing. Journal of Alloys and Compounds 2015; 619:26-30. Cite Share Download PDF Status: Published Journal Publication published 16 Oct, 2020 Read the published version in Materials → Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-78483","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":2435626,"identity":"52e94ca2-9566-4f70-9a00-fcdb036b5c41","order_by":0,"name":"Xingheng Yan","email":"","orcid":"","institution":"Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Xingheng","middleName":"","lastName":"Yan","suffix":""},{"id":2435627,"identity":"ece18873-a66b-46d3-b488-c4b263f4944f","order_by":1,"name":"Xingui Zhou","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIiWNgGAWjYBACNvnHBw4kGEjIsbE3H3yQUFFDWAsfQ1rigwcVFsZ8PMeSDR6cOUZYixxDjrHhgzMViXISPmaSD1uYiXAYw7E0icQ2iQQ2Cba0isQGNgb+9u4E/FoYm4+BtOSxSTcfu5G4Q4ZB4szZDfi1MLOBbSlmkzmWdiPxDBuDgUQuAS1sPGYgLUCUY1aQ2MZMhBYeHmODhDMQLQzEaZFgSwRGh4QxGzCQJRLOHOMh6Bf5GcwHDv4wqJOTb28++PFHRY0cf3svfi0YgIc05aNgFIyCUTAKsAIAmF9H0S0bBjkAAAAASUVORK5CYII=","orcid":"","institution":"Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Xingui","middleName":"","lastName":"Zhou","suffix":""},{"id":2435628,"identity":"241ba6b3-a2fc-4bb9-9103-9cca92f379e0","order_by":2,"name":"Honglei Wang","email":"","orcid":"","institution":"Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Honglei","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2020-09-16 00:07:46","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-78483/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-78483/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.3390/ma13204616","type":"published","date":"2020-10-16T21:06:19+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":2541937,"identity":"1d5d38e7-cd18-4f99-8e6d-42e1f471e190","added_by":"auto","created_at":"2020-09-22 18:53:28","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2148145,"visible":true,"origin":"","legend":"SEM images and XRD patterns of raw powders","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/Fig.1.jpg"},{"id":2541938,"identity":"aee425b0-e59b-4671-820c-ee878307b145","added_by":"auto","created_at":"2020-09-22 18:53:28","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":3560430,"visible":true,"origin":"","legend":"XRD patterns of B4C-TiB2 ceramic composites sintered at 1900℃ with different content of additive Ti3SiC2","description":"","filename":"Fig.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/Fig.2.jpg"},{"id":2541939,"identity":"c12e0f08-ff0a-432d-a1bf-cf4824193109","added_by":"auto","created_at":"2020-09-22 18:53:28","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":4455778,"visible":true,"origin":"","legend":"(a) BSE image of BT0; (b) BSE image of BT30","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/Fig.3.jpg"},{"id":2626921,"identity":"01e10429-eb0a-44cb-86e7-01fe1c92b844","added_by":"acdc","created_at":"2020-09-25 21:03:17","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3894667,"visible":true,"origin":"acdc-manuscripts-figure","legend":"(a) SEM image of fracture surface of BT0; (b) SEM image of fracture surface of BT30","description":"{\"primaryId\":\"undefined\",\"secondaryId\":\"JACE-D-20-00490\",\"acdcId\":\"undefined\",\"revision\":\"undefined\",\"timestamp\":\"2020-09-16T23:53:48\",\"document\":\"manuscripts\",\"linkRel\":\"figure\"}","filename":"figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/figure_4.jpg"},{"id":2626918,"identity":"f366ff9c-479a-4a5f-838b-91491ef870cf","added_by":"acdc","created_at":"2020-09-25 21:03:17","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1236949,"visible":true,"origin":"acdc-manuscripts-figure","legend":"Relative density and hardness of the B4C-TiB2 composite ceramics sintered with different content of Ti3SiC2","description":"{\"primaryId\":\"undefined\",\"secondaryId\":\"JACE-D-20-00490\",\"acdcId\":\"undefined\",\"revision\":\"undefined\",\"timestamp\":\"2020-09-16T23:53:48\",\"document\":\"manuscripts\",\"linkRel\":\"figure\"}","filename":"figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/figure_5.jpg"},{"id":2626916,"identity":"fe93498e-bff5-4ae0-962c-0e9f18acfe0a","added_by":"acdc","created_at":"2020-09-25 21:03:17","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1384856,"visible":true,"origin":"acdc-manuscripts-figure","legend":"Flexural strength and fracture toughness of the B4C-TiB2 composite ceramics sintered with different content of Ti3SiC2","description":"{\"primaryId\":\"undefined\",\"secondaryId\":\"JACE-D-20-00490\",\"acdcId\":\"undefined\",\"revision\":\"undefined\",\"timestamp\":\"2020-09-16T23:53:48\",\"document\":\"manuscripts\",\"linkRel\":\"figure\"}","filename":"figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/figure_6.jpg"},{"id":2626920,"identity":"1fc8d41c-47c4-468b-b04f-8ee1acbd1a62","added_by":"acdc","created_at":"2020-09-25 21:03:17","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":13496875,"visible":true,"origin":"acdc-manuscripts-figure","legend":"BSE images of B4C-TiB2 composite ceramics sintered with different content of Ti3SiC2 ","description":"{\"primaryId\":\"undefined\",\"secondaryId\":\"JACE-D-20-00490\",\"acdcId\":\"undefined\",\"revision\":\"undefined\",\"timestamp\":\"2020-09-16T23:53:48\",\"document\":\"manuscripts\",\"linkRel\":\"figure\"}","filename":"figure7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/figure_7.jpg"},{"id":15668961,"identity":"ca1589bd-6f12-4661-aa58-d379b5ae6950","added_by":"auto","created_at":"2021-11-18 13:51:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1441247,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-78483/v1/f776bbe9-152d-4060-87eb-8c54bb444906.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eEffect of Additive Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e Content on Mechanical Properties of B\u003csub\u003e4\u003c/sub\u003eC–TiB\u003csub\u003e2\u003c/sub\u003e Composites Ceramics Sintered by Spark Plasma Sintering\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":" \u003cp\u003eBoron carbide is an attractive engineering material with a high melting point, low density, high hardness, high thermal conductivity and large neutron absorption surface, which makes it a candidate material for wear-resistant parts, cutting tools, light armor products and neutron radiation shielding\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. However, the low sintering property (due to the strong B-C covalent bond and B\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e oxide layer) and poor fracture toughness limit its excellent performance. Spark plasma sintering is a kind of electric current assisted sintering technology, which can enhance the bonding and densification of particles through the combination of mechanical pressure, electric field and thermal field\u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. SPS adopts the same stamping/die system concept as hot pressing, and the difference between them is that the heating methods are fundamentally different. Hot pressing sintering is heated by heating body radiation, while the SPS heat source is Joule heat generated by the current of mold or sample\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. The heating rate of up to 1000 ℃/min can be obtained by SPS, and the heating up time is greatly shortened, which is beneficial to limit the grain growth\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. In addition, current can also enhance powder sintering by activating one or more parallel mechanisms, such as surface oxide removal, electromigration and electroplasticity\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eReasonable use of additives can make boron carbide densification without deterioration of mechanical properties. Some additives can react with boron carbide in situ to form nonvolatile second phases, which is helpful for densification and can enhance properties. Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e can react with B\u003csub\u003e4\u003c/sub\u003eC to form TiB\u003csub\u003e2\u003c/sub\u003e with high hardness and high melting point, which can be used as an ideal toughening phase for B\u003csub\u003e4\u003c/sub\u003eC ceramics\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. In this study, B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics with ultra-high toughness were prepared by the SPS process with different contents of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e as additives, and the influence mechanism of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content on the microstructure and properties of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics was studied.\u003c/p\u003e "},{"header":"2. Experimental Procedure","content":" \u003cp\u003eCommercially available B\u003csub\u003e4\u003c/sub\u003eC powders (purity 99.9%, 1\u0026nbsp;\u0026micro;m, 4.53\u0026nbsp;g/cm\u003csup\u003e3\u003c/sup\u003e, Nangong Naiyate Alloy Welding Material Co., Ltd), Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e powders (purity 99.9%, \u0026lt;\u0026thinsp;74\u0026nbsp;\u0026micro;m, 4.53\u0026nbsp;g/cm\u003csup\u003e3\u003c/sup\u003e,Nanjing Mingchang New Material Co., Ltd) were used as raw materials. Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e-B\u003csub\u003e4\u003c/sub\u003eC powders containing 20 vol.%, 25 vol.%, 30 vol.% and 35 vol.% Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e respectively were mixed for 24\u0026nbsp;h through a small vertical mixer at 80 r/min without adding solvent. The simples were prepared by SPS equipment (HP D 25/4-SD, FCT Systeme GmbH, Germany) in a vacuum with 35\u0026nbsp;MPa mechanical pressure at 1900 ℃ for 5\u0026nbsp;min. The heating rate was 100 ℃/min and the cooling rate was 50 ℃/min.\u003c/p\u003e \u003cp\u003eThe absolute density of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics was determined using the Archimedes method. Hardness was measured by a Vickers-indentation tester (Shimadzu, HMV-2TADW E, Japan) at 9.81\u0026nbsp;N load with a holding time of 15\u0026nbsp;s on the polished surface. Flexural strength was determined by a three-point bending test with a span of 30\u0026nbsp;mm and the loading speed of 0.5\u0026nbsp;mm/min, and the specimens used in the test were 3\u0026thinsp;\u0026times;\u0026thinsp;4\u0026thinsp;\u0026times;\u0026thinsp;35\u0026nbsp;mm bars. SENB method was used to determine the fracture toughness of the specimens, with dimensions of 2\u0026thinsp;\u0026times;\u0026thinsp;4\u0026thinsp;\u0026times;\u0026thinsp;20\u0026nbsp;mm (with 2\u0026nbsp;mm high notch). The microstructures of the composite ceramics were characterized by X-Ray powder diffraction (XRD, X\u0026prime; Pert PRO-MPD, Holland Panalytical, Netherlands), scanning electron microscope (SEM, S-4800N, Hitachi, Japan), transmission electron microscope (TEM, JEM-2100, JEOL, Japan) and energy dispersive spectrometer (EDS, INCA, OXFORD INSTRUMENTS, England).\u003c/p\u003e "},{"header":"3. Results And Discussion","content":"\u003cp\u003eThe scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns of the as-received powders of B\u003csub\u003e4\u003c/sub\u003eC and Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e are shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The SEM images show that B\u003csub\u003e4\u003c/sub\u003eC particles have ladder-like surface undulation, which is a typical transgranular fracture appearance during the particle crushing process; Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e particles have obvious lamellar structure. It can be seen from the XRD images that the two kinds of powders are relatively pure and almost no oxide exists (the content of oxide is too small to be detected in XRD). Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the phase composition of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e ceramic composites prepared at 1900℃ with different content of additive Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e. There is no diffraction peak of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e in all XRD images, which indicates that Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e has completely reacted with B\u003csub\u003e4\u003c/sub\u003eC. The overall reaction in the system can be described as the following reaction\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e:\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/58893_b39df98f09c4a4bb/58893_custom_files/img1600773508.png\" alt=\"\" /\u003e\u0026nbsp; \u0026nbsp; (1)\u003c/p\u003e\n\u003cp\u003eTiC appears as an intermediate product in the whole reaction process but does not exist in the final product. According to the XRD test results, the content of each phase is shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. TiB\u003csub\u003e2\u003c/sub\u003e and B\u003csub\u003e4\u003c/sub\u003eC are the main phase composition of the composites, and a small amount of SiC and C exist. With the increase of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content, the proportion of TiB\u003csub\u003e2\u003c/sub\u003e, B\u003csub\u003e4\u003c/sub\u003eC and C in the composite increases, while the content of B\u003csub\u003e4\u003c/sub\u003eC decreases.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003econtents of different phases in B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics sintered at different temperatures\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSample name\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eContent of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e (vol.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTiB\u003csub\u003e2\u003c/sub\u003e (wt.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC (wt.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSiC (wt.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eC (wt.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e9.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e87.4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1.7\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e19.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e73.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.8\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e29.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e61.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e4.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e4.4\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e40.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e47.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e6.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5.6\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the properties of the samples prepared with different content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e. BT0 is the reference sample without Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e, and its hardness, bending strength and fracture toughness are 33.5GPa, 224.43\u0026nbsp;MPa and 5.96MPa\u0026middot;M\u003csup\u003e1/2\u003c/sup\u003e, respectively. Compared with BT0, all samples with Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e have higher relative density. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows the BSE images of BT0 and BT30 after polishing. There are some closed pores in BT0, but not in BT30. This is because the B\u003csub\u003e4\u003c/sub\u003eC particles have sharp edges and corners, and its hardness (55GPa) is very high. Thus, they can not be extruded and deformed under pressure, leaving a non-contact space inside, and forming pores. The hardness of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e (4GPa) is much smaller than that of B\u003csub\u003e4\u003c/sub\u003eC, it can be extruded and deformed without leaving voids between particles under external load. After reaction sintering, TiB\u003csub\u003e2\u003c/sub\u003e, B\u003csub\u003e4\u003c/sub\u003eC, SiC and C (exist in the form of graphite) in the composites have different thermal expansion coefficients, which make the ceramics more compact after cooling.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eProperties of ceramics prepared with different content of additive Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSimple name\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eContent of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e (vol.%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eDensity (g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eRelative Density (%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eHardness (GPa)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFlexural Strengh (MPa)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFracture Toughness (MPa\u0026middot;m\u003csup\u003e1/2\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e2.50\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e99.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e33.50\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e224.43\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5.96\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.12\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e101.16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e31.14\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e317.55\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e17.68\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.13\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e101.51\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e28.70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e383.25\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e18.37\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e101.54\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e27.28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e405.11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e18.94\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e35\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e102.28\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e26.71\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e343.95\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e19.00\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBecause the hardness of the second phase particles produced by the reaction is lower than that of B\u003csub\u003e4\u003c/sub\u003eC, especially the graphite phase, it is inevitable that the hardness of the composite ceramics is lower than that of the pure B\u003csub\u003e4\u003c/sub\u003eC ceramics. Compared with BT0, the flexural strength and fracture toughness of BT20-BT35 are improved except for the decrease of hardness. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the fracture morphology of BT0 and BT30. It can be seen that the fracture surface of BT0 is flat, which is a typical transgranular fracture morphology. While the fracture surface of sample BT30 is rough, which is a typically mixed fracture morphology of transgranular fracture and intergranular fracture. In Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b), the dark gray flat area is the B\u003csub\u003e4\u003c/sub\u003eC matrix, and the light gray rough area is TiB\u003csub\u003e2\u003c/sub\u003e particles, which indicates that the fracture modes of the B\u003csub\u003e4\u003c/sub\u003eC phase and the TiB\u003csub\u003e2\u003c/sub\u003e phase are transgranular fracture and intergranular fracture respectively. In addition, there is a dark gray lamellar phase around the TiB\u003csub\u003e2\u003c/sub\u003e grain, which can be inferred ad graphite phase by energy spectrum analysis. Due to the mismatch of thermal expansion coefficients between B\u003csub\u003e4\u003c/sub\u003eC, TiB\u003csub\u003e2\u003c/sub\u003e and graphite (B\u003csub\u003e4\u003c/sub\u003eC: 4.5\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u0026nbsp;k\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; TiB\u003csub\u003e2\u003c/sub\u003e: 8.1\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u0026nbsp;k\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Graphite: 1\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u0026nbsp;k\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the parallel direction, 29\u0026thinsp;\u0026times;\u0026thinsp;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e\u0026nbsp;k\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in c direction) \u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e, there will be large residual stress at the interface of the phases, which will induce crack deflection along the grain boundary and extend the crack propagation path to improve the strength and toughness of the material. The nano TiB\u003csub\u003e2\u003c/sub\u003e particles embedded in the B\u003csub\u003e4\u003c/sub\u003eC matrix will introduce internal stress, which will strengthen the B\u003csub\u003e4\u003c/sub\u003eC matrix by lattice distortion effect, and can also nail the dislocations and hinder their movement, so as to enhance the strength of the material.\u003c/p\u003e\n\u003cp\u003eIt should be noted that the fracture toughness of the composites has a leap forward improvement by adding more than 20vol.% Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e. The fracture toughness of BT30 is 18.94 MPa\u0026middot;m\u003csup\u003e1/2\u003c/sup\u003e, which is more than 3 times of that of BT0 (5.80 MPa\u0026middot;m\u003csup\u003e1/2\u003c/sup\u003e) and is more than 2 times higher than the highest fracture toughness cited in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. Wen Q et al\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e adopted the same ratio of raw materials as ours to sinter the ceramics. They used 0.5\u0026nbsp;\u0026micro;m B\u003csub\u003e4\u003c/sub\u003eC powders and 0.5\u0026thinsp;~\u0026thinsp;10\u0026nbsp;\u0026micro;m Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e powders as raw materials, and their process was 1850 ℃ hot pressing sintering for 30\u0026nbsp;min. Compared with their work, the particle size of the raw powders we used has more difference in size (B\u003csub\u003e4\u003c/sub\u003eC: 1\u0026nbsp;\u0026micro;m; Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e: \u0026lt;74\u0026nbsp;\u0026micro;m), making it easier to form aggregates, which are beneficial for toughness but unfavorable for strength\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. Besides, our ceramics has a higher relative density and graphite content, which may be due to the evaporation of Si at higher sintering temperature and electric field\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Graphite phase exists at the grain boundaries of TiB\u003csub\u003e2\u003c/sub\u003e and B\u003csub\u003e4\u003c/sub\u003eC, which reduces the bonding strength of the interface and has an adverse effect on the hardness and strength of the composite ceramics. This is the reason why the flexural strength of BT30 is at a low level in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. But at the same time, the existence of graphite can limit the grain growth. In the cooling process, microcracks are produced under the effect of interfacial stress produced by different thermal expansion coefficients, and the cracks propagate along the interlayer of graphite during fracture, resulting in lamellar pull-out. It can be seen from Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b) that there are traces of particle pull-out and lamellar graphite pull-out in the fracture surface of BT30, which is one of the important reasons for the toughening of the composite.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eComparison of the properties of the B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics reported in recent years\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSerial no.\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eStarting powder\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eRelative Density\u003c/p\u003e\n\u003cp\u003e(%)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eK\u003csub\u003eIC\u003c/sub\u003e,\u003c/p\u003e\n\u003cp\u003e(MPa\u0026middot;m\u003csup\u003e1/2\u003c/sup\u003e)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFlexural strength\u003c/p\u003e\n\u003cp\u003e(MPa)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eRef.(year)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;5\u0026nbsp;wt% (Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;Si)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026mdash;\u0026mdash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5.61\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e457.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e(2019)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;30\u0026nbsp;wt% (TiB\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;Si)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e99.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e5.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e531.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e(2018)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;20\u0026nbsp;mol%TiB\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e97.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e3.7\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u0026mdash;\u0026mdash;\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e(2020)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;15\u0026nbsp;wt%SiC\u0026thinsp;+\u0026thinsp;20\u0026nbsp;mol%TiB\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e98.6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e4.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e343.8\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e(2020)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;6.45vol.%SiC\u0026thinsp;+\u0026thinsp;7.78vol.%TiB\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e99.62\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e6.38\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e632\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e(2019)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;30vol.% Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e98.72\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e8.0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e492.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e(2017)\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eBT30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;30vol.% Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e101.54\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e18.94\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e405.11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eThis work\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e shows the variation of relative density and hardness of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics with the content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e. Due to the slight evaporation of silicon\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e, the density of composites is slightly higher than the theoretical density. The evaporation capacity of Si increases with the increase of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content, resulting in an increase of the relative density. The hardness decreases with the increase of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content because of the proportion of the second phase with lower hardness, especially graphite, increases.\u003c/p\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e shows the variation of flexural strength and fracture toughness of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics with additive Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content. When the content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e is in the range of 20vol.% ~ 30vol.%, the flexural strength and fracture toughness are positively correlated with the content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e. Compared Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(a)-(c), it can be seen that the region as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(e) becomes larger and more numerous with the increase of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content. In this region, TiB\u003csub\u003e2\u003c/sub\u003e, graphite and B\u003csub\u003e4\u003c/sub\u003eC intersect each other to form a three-dimensional interpenetrating network. During the crack propagation process, multiple two-phase interfaces must be bypassed to disperse into more small cracks and a large number of changes in the propagation direction. The pull-out mechanism of graphite also plays an important role in this agglomeration area. Besides, this area does not exist in isolation. Every small network links to each other, forming a large network structure covering the whole composite. At the same time, the network divides the B\u003csub\u003e4\u003c/sub\u003eC concentration area into small parts and surrounds them, so that there is no large area of continuous B\u003csub\u003e4\u003c/sub\u003eC phase in the composites, which is very unfavorable to the toughness of the composite. With the increase of interlacing degree of TiB\u003csub\u003e2\u003c/sub\u003e, graphite and B\u003csub\u003e4\u003c/sub\u003eC, the cracks need to bypass more two-phase interfaces, change more directions and disperse into more small cracks. Therefore, the fracture toughness of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics is greatly improved by the overall three-dimensional interpenetrating network structure.\u003c/p\u003e\n\u003cp\u003eHowever, when the content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e is 35 vol.%, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e (d), a large TiB\u003csub\u003e2\u003c/sub\u003e-SiC agglomerated area appears in the BT35 (among which the dark gray, medium gray and light gray phases are B\u003csub\u003e4\u003c/sub\u003eC, SiC and TiB\u003csub\u003e2\u003c/sub\u003e respectively). There is a bad stress effect in the multiphase mixing region with more SiC. At higher magnification Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(f), many microcracks due to mismatch of thermal expansion coefficient can be found in this region, which is conducive to the toughening of the material. Nevertheless, it has a bad effect on the bending strength, resulting in a significant decrease in the bending strength.\u003c/p\u003e"},{"header":"4. Conclusions","content":" \u003cp\u003eUltra-high toughness B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics were prepared by the SPS method at 1900℃. The content of additive Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e has a great influence on the microstructure and mechanical properties. With the increase of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e content, the relative density and fracture toughness of the material increase, while the hardness decreases, and the flexural strength first increases and then decreases. When the content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e is 30 vol.%, B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics have the highest bending strength and the best comprehensive mechanical properties: hardness 27.28 GPa, bending strength 405.11\u0026nbsp;MPa, fracture toughness 18.94 MPa\u0026middot;m\u003csup\u003e1/2\u003c/sup\u003e. The fracture mode of the material is a mixture of transgranular fracture and intergranular fracture. The main reason for obtaining high fracture toughness is the existence of the graphite phase and the formation of a three-dimensional interpenetrating network covering the whole composite. The existence of the graphite phase has an effect on the hardness and fracture toughness of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics, but they still remain at a high level.\u003c/p\u003e "},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSuri AK, Subramanian C, Sonber JK, et al. Synthesis and consolidation of boron carbide: a review. International Materials Reviews 2013; 55(1):4-40.\u003c/li\u003e\n\u003cli\u003eDomnich, Vladislav, Reynaud, et al. Boron Carbide: Structure, Properties, and Stability under Stress. 2011; 94(11):3605-3628.\u003c/li\u003e\n\u003cli\u003eGhosh S, Chokshi AH, Lee P, et al. A Huge Effect of Weak dc Electrical Fields on Grain Growth in Zirconia. 92(8):1856-1859.\u003c/li\u003e\n\u003cli\u003eZhang ZH, Liu ZF, Lu JF, et al. 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Ceramics International 2019; 45(7):8790-8797.\u003c/li\u003e\n\u003cli\u003eYin S-P, Zhang Z-H, Cheng X-W, et al. Spark plasma sintering of B4C-TiB2-SiC composite ceramics using B4C, Ti3SiC2 and Si as starting materials. Ceramics International 2018; 44(17):21626-21632.\u003c/li\u003e\n\u003cli\u003eLiu Y, Wu X, Liu M, Huang Y, et al. Microstructure and mechanical properties of B4C\u0026ndash;TiB2\u0026ndash;SiC composites fabricated by spark plasma sintering. Ceramics International 2020; 46(3):3793-3800.\u003c/li\u003e\n\u003cli\u003eLiu Y, Li Z, Peng Y, et al. Effect of sintering temperature and TiB2 content on the grain size of B4C-TiB2 composites. Materials Today Communications 2020; 23.\u003c/li\u003e\n\u003cli\u003eZhang X, Zhang Z, Liu Y, et al. High-performance B4C\u0026ndash;TiB2\u0026ndash;SiC composites with tuneable properties fabricated by reactive hot pressing. Journal of the European Ceramic Society 2019; 39(10):2995-3002.\u003c/li\u003e\n\u003cli\u003eZhang Z, Xu C, Du X, et al. Synthesis mechanism and mechanical properties of TiB2\u0026ndash;SiC composites fabricated with the B4C\u0026ndash;TiC\u0026ndash;Si system by reactive hot pressing. Journal of Alloys and Compounds 2015; 619:26-30.\u003c/li\u003e\n\u003c/ol\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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Spark plasma sintering, Boron carbide, Ti3SiC2, Fracture toughness","lastPublishedDoi":"10.21203/rs.3.rs-78483/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-78483/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eB\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics with ultra-high fracture toughness were successfully prepared via spark plasma sintering at 1900℃ using B\u003csub\u003e4\u003c/sub\u003eC and Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e as raw materials. The results show that compared with pure B\u003csub\u003e4\u003c/sub\u003eC ceramics sintered by SPS, the hardness of B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics is decreased, but the flexural strength and fracture toughness are significantly improved, especially the fracture toughness has been improved by leaps and bounds. When the content of Ti\u003csub\u003e3\u003c/sub\u003eSiC\u003csub\u003e2\u003c/sub\u003e is 30vol.%, the B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramic has the best comprehensive mechanical properties: hardness, bending strength and fracture toughness are 27.28 GPa, 405.11\u0026nbsp;MPa and 18.94 MPa\u0026middot;m\u003csup\u003e1/2\u003c/sup\u003e, respectively. The fracture mode of the B\u003csub\u003e4\u003c/sub\u003eC-TiB\u003csub\u003e2\u003c/sub\u003e composite ceramics is a mixture of transgranular fracture and intergranular fracture. Two main two reasons for the ultra-high fracture toughness are the existence of lamellar graphite at the grain boundary, and the formation of a three-dimensional interpenetrating network covering the whole composite.\u003c/p\u003e","manuscriptTitle":"Effect of Additive Ti3SiC2 Content on Mechanical Properties of B4C–TiB2 Composites Ceramics Sintered by Spark Plasma Sintering","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2020-09-22 18:53:26","doi":"10.21203/rs.3.rs-78483/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"95dd6da0-e8bb-455c-b92b-e456d0d92f2a","owner":[],"postedDate":"September 22nd, 2020","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":578948,"name":"Ceramics"}],"tags":[],"updatedAt":"2021-07-22T21:06:19+00:00","versionOfRecord":{"articleIdentity":"rs-78483","link":"https://doi.org/10.3390/ma13204616","journal":{"identity":"materials","isVorOnly":true,"title":"Materials"},"publishedOn":"2020-10-16 21:06:19","publishedOnDateReadable":"October 16th, 2020"},"versionCreatedAt":"2020-09-22 18:53:26","video":"","vorDoi":"10.3390/ma13204616","vorDoiUrl":"https://doi.org/10.3390/ma13204616","workflowStages":[]},"version":"v1","identity":"rs-78483","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-78483","identity":"rs-78483","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}