Study on the evolution feature and formation mechanism of Cu layer on the surface of copper-iron composite powder

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It focused on how various process parameters, such as the amount of additives in the copper sulfate solution, the wet powder stacking time after coating, and the reduction temperature, impact the surface morphology, composition, and structure of the copper coating layer. The surface morphology and composition of the copper-iron composite powder were characterized using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), the cross-sectional thickness of the copper coating layer was characterized using a metallurgical microscope, and the crystal phase structure of the copper-iron composite powder was detected using an X-ray diffractometer (XRD). It indicated that when the amount of additives in the copper salt solution was ≥ 5 times (calculated as 1 time based on 0.5% of the iron powder amount), noticeable accumulation of copper coating layer and grooves appeared on the surface, leading to a decrease in surface smoothness. Additionally, if the stacking time of the wet powder exceeded 0.5 hours, the surface copper content decreased and the volume of the deposited material increased, resulting in the formation of CuO and Cu 2 O phases. Furthermore, when the reduction temperature was between 600 and 650℃, the surface copper coating layer remained smooth and continuous, with oxygen content measured below 4000ppm. Physical sciences/Chemistry Physical sciences/Engineering copper-iron composite powder additive accumulation time reduction temperature copper coating layer Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 1 Introduction Copper-based metal powder mainly consists of copper powder and copper alloy powder, which is an important component in the field of metal powder and one of the non-ferrous metal powder varieties with the highest production and consumption in China. Copper-iron composite powder is a key component of copper-based metal powder. It is one of the primary products in the cladding powder industry, and has a high market application value. Copper-iron composite powder is the ideal material for the production of oil bearings, compared to cobalt-based and copper-based diamond tool bonding agents, copper-iron composite powder bonding agent is less expensive. Its corrosion resistance is stronger, and performance is more stable compared to iron-based diamond bonding agent. In the field of friction materials, they are mainly used in cassettes, brake blocks and brake pads of high-speed trains. When compared to the preparation of friction parts with copper-iron hybrid powder, copper-iron composite powder reduces the porosity of the products, improves the strength and coefficient of friction [1] . In addition, copper and iron composite powder can enhance the thermal conductivity, thermal stability, wear resistance and high temperature impact resistance of friction materials. A type of copper-iron composite powder, which has iron as the "core" and copper as the "shell", can be used to partially replace copper powder as the sintered metal cladding powder because of its good pressing performance, low sintering temperature, and high strength of the iron base, as well as its excellent corrosion resistance and high thermal conductivity. It offers a wide range of potential applications and can partially replace copper powder as the best raw material for sintered oil bearings [2][3] . The preparation methods of metal-coated composite powder mainly include mechanical ball-mill coating [4] , replacement plating [5] , chemical plating [6] , sol-gel [7] , physical vapor deposition [8] , and chemical vapor deposition [9] , etc. It has been demonstrated that the mechanical ball-mill coating, replacement copper plating, and chemical copper plating are the main techniques now used to prepare copper-iron composite powders. which overcomes the drawbacks of uneven color and luster, unstable mechanical properties, and low product qualification rate that are frequently present in the production of other powders while offering the benefits of lead-free, corrosion-resistant, low cost, good iron and copper metal bonding, and excellent overall product performance. Liu [10] found that the replacement plating method of copper involves an electron transfer between the two metal ions, as a plated body in the substrate of the outermost electron of the metal atoms are drawn to the powerful other metal ions within the double electric layer of the empty track. While the other metal ions that acquire electrons are reduced to atoms and deposited on the surface of the metal substrate to form the conversion plating layer, some of the atoms on the substrate's surface lose electrons to become metal ions and exit the substrate to enter the solution. The electrons in the matrix atoms also leap in quantum states into the empty orbitals of the reduced metal ions. However, this process is directly related to the potential difference between the reduced metal and the matrix metal. That is, the negative potential matrix can provide electrons to the positive potential metal ion to be reduced. At this time, the outer electrons of the matrix metal atoms leap into the outer orbitals of the reduced metal ions, reducing them to metal atoms and crystallizing them into a metal coating. This process is disordered when it occurs naturally, and continues until the original metal on the surface of the matrix metal is oxidized to a metal salt, and the original crystallization sites are replaced by the reduced metal. For example, the displacement reaction of iron in an acidic copper solution usually consists of the following two half-reactions: anode reaction: Fe→Fe 2+ + 2e φ°= -0.441V cathode reaction: Cu 2+ +2e→Cu φ°= +0.337 V Typically, iron dissolves rapidly in acidic solutions, causing a large accumulation of electrons on the electrode surface, resulting in a strong negative shift of the electrode potential. Thus generating a high crystallization overpotential, which leads to a large number of two-dimensional nuclei precipitating and growing up near the electrode surface, and ultimately forming a loose replacement copper layer that has a poor bonding force with the substrate. It is well known that the matrix surface state has an important influence on the binding force of chemical plating. Wang and Ding [11] used the replacement copper plating method to modify the surface of the iron powder, founding that the degree of the supersaturation in the solution is the key parameter that affects the morphology of the coating material when combined with the critical nucleation theory. Due to the competition of heterogeneous and homogeneous nucleation during crystal nucleation, the precipitation of Cu 2+ in the solution cannot be completely coated on the surface of the iron powder, part of the copper will spontaneously form copper powder in the copper solution through homogeneous nucleation. Figure 1 shows the surface microstructure of the copper-iron composite powder. Heterogeneous nucleation occurs under a lower degree of supersaturation, so that part of the copper particles deposited on the surface of the iron particles, as shown in Fig. 1 (a). Homogeneous nucleation occurs under a higher degree of supersaturation, forming copper particles in the solution, and the surface roughness increases significantly, as shown in Fig. 1 (b). A large number of studies have shown that in the process of copper replacing coating, the coating solution without introducing special additives cannot produce uniform and dense copper coating layers no matter how the pretreatment process is strengthened. Wang [12] showed that the reaction speed of Fe replacement Cu 2+ is very fast during the replacement of copper-iron composite powder, if not using additives in the coating, so that the Cu nucleated on the surface of Fe particles would grow and thicken rapidly, resulting in a large consumption of Cu 2+ . Subsequently, it was difficult to continue thickening due to insufficient Cu 2+ nucleation sites, and some sites will not be able to form the plating layer due to the lack of contact with Cu 2+ . At the same time, the side reaction of hydrogen evolution will be accompanied in an acidic environment [13] , resulting in a very rough and discontinuous surface of the prepared coating layer. Instead, the introduction of additives in the plating solution uniformly compacted the coating layer. This is because the additive molecules contain large functional groups, strong adsorption, easy to form complexes. So that the cathode potential negative shift, increasing the cathode polarization, restricting the reduction of copper ions, inhibiting the growth of copper grains, thus improving the density of copper coating, reducing the coating roughness [14][15] . However, when additives were introduced in excess, a large number of stable chelates would be formed, which would severely hinder the reduction of copper ions, and were easily adsorbed in the coating layer, making them difficult to resolve. This ultimately leads to a significant decrease in the adhesion of the coating layer [16][17] . Wu Shixue [18] found that precise control of the deposition rate of Cu was the key to obtain a good replacement coating by metallographic section analysis. By comparing the the experiments with and without additives, it was found that the addition of additives effectively reduced the displacement reaction rate, and the bonding force between the coating layer and the matrix was stronger. In addition, Chen [19] added additives to the plating solution, and found that the density of the coating layer was significantly improved, and the porosity between the coating layer and the matrix was reduced. In the process of industrial production, due to the large production of copper and iron composite powder, the wet powder before powder is inevitably stored and accumulated. Due to its large specific surface area and activity, it is easy to absorb moisture and be oxidized, and the finer the powder, the more serious the tendency of oxidation. The inevitable high temperature and high humidity environment is easy to produce electrochemical corrosion, the influence of trace impure gas and subsidence in the atmosphere and the production process leads to the discoloration and corrosion of powder [20] , and the change of copper structure on the surface of the powder. Ding et al [21] . found that the oxidation of pure copper is a spontaneous reaction by analyzing the thermodynamics, kinetics and oxidation behavior of pure copper. However, the spontaneous trend would gradually decrease and the trend of forming Cu 2 O is the largest with the increase of temperature. Cu 2 O is a thermodynamically stable oxidation product. The growth of pure copper oxide film is firstly the adsorption of oxygen on the copper substrate to form the Cu 2 O film, and then the formation and growth of CuO particles on the Cu 2 O film. Firstly the absorbed oxygen on the copper matrix formed a massive oxide film, and then the white particles appeared and accumulated on the massive oxide film. In this process, temperature, tissue and purity were all important factors affecting the oxidation of pure copper. The higher the temperature, the higher the oxidation rate of pure copper, and the higher the purity, the smaller the oxidation rate. In recent years, Zhang [22] have summarized the application, the preparation method and the problems in the preparation process of copper-iron composite powder. Among them, how to effectively balance the uniformity of coating layer and coating rate is the key problem in the preparation of copper -iron composite powder. On this basis, how to further optimize the preparation process parameters to develop better copper-iron composite powder is an important direction to be broken through. Above all, this paper mainly explored the influence of process parameters such as additive dosage, wet powder accumulation time and reduction temperature on the surface morphology, composition and microstructure of copper-iron composite powder. The effects on the oxygen content of copper-iron composite powder and the coating uniformity of the surface copper layer were investigated. On the basis of the above studies, the optimal process parameters were selected, and the copper-iron composite powder with better coating performance was prepared. 2 Materials and Methods 2.1 material The raw materials used in the study, including iron powder and copper sulfate (CuSO4 5H 2 O), were commercially available. The iron powder was 200 mesh reduced iron powder provided by Baowu Huanke Metal Co., with a purity of 98%, and copper sulfate was provided by Chongqing Guangsheng Nonferrous Metal Material Co., Ltd., with a purity of > 95%. 2.2 technology roadmap The specific preparation process for copper-iron composite powder was as follows: (1) Pretreatment of the iron powder; (2) The amount of additives was calculate according to the amount of 0.5% of the amount of iron powder. On this basis, 5 times, 8 times, 10 times and 15 times of additives were added to the copper sulfate solution respectively, and the mixture was evenly mixed. (3) The copper-iron composite powder containing 15% copper was coated and wet powder was post-treated. Among them, Step (3) is divided into two situations: one is to simulate the wet powder accumulation environment with a constant temperature and humidity box, and to explore the influence of the accumulation time of coated copper-iron composite powder on the structure of powder coated layer. The time range was 0.5-3h, and then dried. The specific accumulation time of the coated wet powder was 0.5h, 1h, 1.5h, 2h and 3h, respectively ; secondly, the wet powder was placed in a hydrogen atmosphere, and different reduction temperatures were set to explore the effect of reduction temperature on the surface structure and morphology of copper-iron composite powder. The reduction temperature range was 300–800℃, with specific reduction temperatures set at 300℃, 400℃, 500℃, 550℃, 600℃, 650℃, 700℃ and 800℃, respectively. The dried powder was crushed and sieved after cooling. Figure 2 is the process flowchart for the preparation of copper-iron composite powder. 2.3 Characterizations The surface morphology and composition of copper-iron composite powder were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The section thickness of copper cladding layer was characterized by metallographic microscope. The phase structure of copper-iron composite powder was characterized by X-ray diffraction instrument (XRD); and the oxygen content was detected by a steel research oxygen analyzer. 3 Results and discussion 3.1 Effect of the additive dosage on the micromorphology of the powder Following the formation of a complex with the additive, the concentration of free Cu 2+ was decreased, reduceing the probability of collision between Cu 2+ and Fe molecules, and impeding the approach of copper ions to the iron powder matrix, thus effectively slowing the rate of Cu reduction and plating speed. Meanwhile, the complex formation of copper reduced the electrode potential of copper, which is more difficult to be reduced than Cu 2+ , thus also reducing the growth rate of copper. The plating solution's high temperature aging stability and coating performance can sustain an outstanding or good state over an extended period of time, respectively, with increasing mass concentration. Figure 3 showed the SEM pictures of the copper-iron composite powder produced with different amounts of additives. As can be seen from Fig. 3 (a), when the additive dosage was 5 times, the prepared powder was well combined with the matrix, and the surface was smooth, continuous and complete; when the additive dosage was 8 times, as shown in Fig. 3 (b), the powder surface was incomplete, with a small gap or incomplete; and when the additive dosage was 10 times or more, as shown in Fig. 3 (c) and (d), the copper layer was uneven, and there were a large number of gullies on the surface. When the amount of additive was 10 times, the concentration of additive was too high to make the reaction speed too slow, the copper layer formed on the surface was discontinuous, and there was a pore between the iron powder particles. Cu 2+ in the solution entered the copper layer via the pore, and continued to react on the surface of the iron powder, forming a new discontinuous copper layer. Because the Fe surface has been partially coated with copper, the resistance to Cu 2+ reentry drove Cu 2+ to react with the surface of the unreacted Fe powder, thickening the copper layer by layer. In conclusion, the copper-iron composite powder with smooth and continuous copper layer and good combination with the matrix could be obtained when the additive (based on the 0.5% iron powder ) was added to the copper sulfate plating solution for 5 times. 3.2 Wet powder accumulation time test 3.2.1 SEM analysis of the metallography and microsection Figure 4 was the metallographic section of copper-iron composite powder, and Fig. 5 was the microscopic section SEM diagram of wet powder accumulation at different times. As can be seen in the images, the surface of the iron powder was coated with a relatively uniform layer of copper, and there were pores between the copper layer and the surface of the iron particles. With the increase in the accumulation time of the wet powder, the surface copper layer showed a trend of growth. When copper was exposed to air, it reacted with oxygen to form a layer of copper oxide film. As the accumulation time increased, the temperature of the powder rose, and the oxide film absorbed oxygen to form a blocky oxide film. Subsequently, white particles appeared on the blocky oxide film and accumulated and grew, gradually thickening the oxide layer. When the accumulation time is ≥ 1 hour, the thickness of the surface copper layer increased significantly. In conclusion, after the coating of copper-iron composite powder was completed, the accumulation time of wet powder should not exceed 1h. 3.2.2 EDS complexity analysis Figure 6 showed the EDS scanning (surface scan) curves of elemental content changes in powder particles after different durations of wet powder accumulation. As can be seen from the figure, the iron content increased with the increase of stacking time, whereas the copper content decreased. When the powder was not placed in a constant temperature and humidity chamber, the EDS scannig spectrum indicated that the copper content was 93.6%, with a dense coating of copper on the surface. However, when the powder was placed in a constant temperature and humidity chamber and accumulated for various durations before drying, as shown in Fig. 6 , the surface copper content was below 90% for all samples. Using a nitrogen-oxygen analyzer to detect the directly dried copper-iron composite powder, the results showed that the oxygen content was below 6000ppm; however, after the powder was piled up for 0.5 hours and then dried, the oxygen content exceeded 10000ppm; and after piling up for 1 hour and then drying, the oxygen content exceeded 20000ppm. It was evidented that the surface copper layer of the copper-iron composite powder was oxidized rapidly after washing, centrifuging, and piling up for a period of time, and the degree of oxidation deepens with the increase of piling-up time. In summary, the stacking time of wet copper-iron composite powder should not exceed 0.5 hours. If it exceeded 0.5 hours, the iron and oxygen content of the powder particles increased rapidly, and the surface copper content decreased. 3.2.3 Micromorphology analysis Figure 7 shows the scanning electron microscope images of the wet powder at low magnification after different periods of time. Figure 7 (a) showed the powder before being placed in the constant temperature and humidity chamber, where the surface of the powder appears relatively smooth with fewer adhering small particles; Figs. 7 (b-f) represent the powder after being placed in the chamber for 0.5h, 1h, 1.5h, 2h, and 3h, respectively. It was observed that the surfaces of the powders had a considerable number of fine particles, and there was a clear trend of increasing particle numbers with longer placement times. Figure 8 showed the SEM pictures at high multiple. Except for Fig. 8 (a), there were obvious deposits on the surface of the powder., most of which were granular, and a few were irregular. Figure 9 showed the enlarged SEM images of stacked particles, which were mostly long sheets and stacked particles. Copper-iron composite powder was accumulated in the air, the longer the accumulation time, the higher the temperature, the newly formed copper on the surface was easily oxidized to form copper oxide and brown copper oxide deposits on the powder; the longer the accumulation time, the copper and iron in the inner layer of the powder particles were oxidized, which was difficult to reduce, and the coating quality and bonding force were poor. In summary, the stacking time of wet copper-iron composite powder should not exceed 0.5 hours. 3.2.4 XRD Figure 10 showed the XRD diffraction pattern of the dry powder after wet powder accumulation at different times. After analysis, it was found that there were other impurity phases in the copper-iron composite powder, which were composed of Fe, Cu and copper oxides. The diffraction peaks of powder samples with different stacking times were basically consistent, but the oxide diffraction peaks of copper were different. The XRD map showed that when the wet powder accumulation time exceeds 0.5h after drying, the more obvious CuO phase and Cu 2 O phase would appear in the diffraction pattern. Therefore, it could be inferred that the surface layer of the powder was oxidized to a certain extent. Combined with the SEM morphology characterization analysis in Fig. 9 , it could be seen that large-sized long sheets were CuO, and small-sized accumulated particles were Cu 2 O. If the copper-iron composite wet powder was piled up for a long time without drying, most of the surface copper layer would exist in the form of CuO, and a small part exist in the form of Cu 2 O, resulting in the color of the powder darkened. 3.3 Reduction temperature test Figure 11 was a phase diagram for the Fe-Cu binary system, from which it can be seen that the solubility of copper in iron varied significantly with temperature. The solubility in α 2 Fe, was approximately 1.4% at total temperature(835℃) while decreased dramatically to 0.3% at 700℃ and to 0.2% at room temperature. The solubility of Cu in γ 2 Fe, was about 7.5–8.5% at 1094℃, still decreased sharply with the decrease of temperature. Therefore, when the content of Cu added to iron was high, due to the insolubility of Fe and Cu, the weak interaction of partial false alloy (pseudo-alloy) can only be formed, so that the copper-iron composite powder could present a specific combination of the intrinsic properties of the two elements [23] . Because copper and iron cannot be completely alloyed, the oxides of Cu and Fe were mainly reduced in the reduction process. Figure 12 showed the change curve of the oxygen content of copper and iron composite powder under different reduction temperatures. The oxygen content in the powder will significantly decrease with the increase of the reduction temperature. When the reduction temperature rose to 500℃, the oxygen content decreased significantly below 4000 ppm; when the reduction temperature reached 600℃, the powder oxygen content was basically stable at about 3000ppm. Thus, the lower the reduction temperature, the higher the powder oxygen content, the surface appeared to be black. However, when the reduction temperature was higher than 700℃, the reduced powder was massive, and it was difficult to be broken. Therefore, the optimum reduction temperature of copper-iron composite powder should be controlled at 500–700℃. 3.3.1 Micromorphology analysis Figure 13 showed the SEM plot of copper-iron composite powder at different reduction temperatures under low magnification. As shown in Fig. 13 , the powder particle surface was not smooth when the reduction temperature was lower than 600℃. When the reduction temperature was 600–650℃ (Fig. 13 (e) and (f)), the powder copper layer was well connected with the substrate, and the surface was continuous and smooth. When the reduction temperature was 700℃ (Fig. 13 (g)), narrow pores appeared in the surface copper layer. When the reduction temperature reached 800℃ (Fig. 13 (h)), the powder surface showed obvious bulges and more gullies. Figure 14 showed the SEM plot of high ratios of copper-iron composite powder at different reduction temperatures. When the reduction temperature was below 600℃, the powder surface was bran-shaped, as shown in Fig. 14 (a-d). When the reduction temperature was 600–650℃ (Fig. 14 (e) and (f)), the surface was a continuous flat copper layer. At the reduction temperature of 700℃, shown in Fig. 14 (g), the surface copper layer began to split. When the reduction temperature reached 800℃, as shown in Fig. 14 (h), the copper layer on the powder surface shrinked to the formation of copper accumulation, the surface was uneven, and deep gullies appeared around the bulge. According to the phase diagram of copper and iron, the solid solution of copper and iron was very low, and the copper and iron cannot be alloyed. With the increase of the reduction temperature, the copper layer (the thickness was about 1µm) on the surface of iron diffused between each other, melted and shrinked, and then the position was reconstructed. In the process, it gradually accumulated, the surface was convex, and the gully was formed around the convex part. In conclusion, the copper-coated layer of iron powder should be prepared at 600–650℃. 3.3.2 XRD Figure 15 showed the XRD diffraction profiles of eight kinds of copper-iron composite powder at different reduction temperatures. After analysis, it was found that the diffraction patterns of several powder were basically consistent. There were no other impurity phases in the reduced copper-iron composite powder, which were composed of Fe and Cu phases, and no copper or iron impurities such as copper or iron oxide was observed. 4 Conclusions When preparing copper-iron composite powder, the additive dosage of copper salt solution should be 5 times, the accumulation time of wet powder should not exceed 0.5h, and the reduction temperature should be 600–650℃. Under this condition, the resulting powder surface has a continuous and smooth and smooth copper layer, which is well connected with the matrix. Declarations Author Contribution Zhang Jingguo. Conceptualization and design; Writing and editing; Data analysis and interpretation; Literature review. Tang Jianying. Experimental operations and data processing; Chart making; Writing and editing; Literature review. Zhou Ming. Writing and Editing. He Huijun. Conceptualization and Design; Management and Coordination. Li Zhanrong. Conceptualization and Design; Management and Coordination. Wang Chengjun. Writing and Revision. Zhang Yubo.Date collection and analysis; Experimental operation; Writing and Revision. Qu Yalong. Writing and editing; data processing. Han Shangyu. Writing and editing; data processing. Ren Li.Analytical detection. Zhao Yuning. Analytical detection. Li Xiaoyao. Experimental operation. Zhou Yaoyao. Experimental operation. Data availability All data generated or analysed during this study are included in this published article. Acknowledgments This study was supported by the National Key R&D Program (2023YFB3812102) and Chongqing Municipal Technology Innovation and Application Development Special Key Project (CSTB2022TIAD-KPX0027). GRIPM Advanced Materials Co. Ltd.,.Innovation Fund (2024500001000867) References T Peng, Q Yan, G Li, et al. The influence of Cu/Fe ratio on the tribological behavior of brake friction materials[J]. Tribology Letters, 2018, 66: 1–12. 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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-6125845","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":441499105,"identity":"c81e4f47-0d2a-4e72-be5b-a9588292e86d","order_by":0,"name":"Jingguo Zhang","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Jingguo","middleName":"","lastName":"Zhang","suffix":""},{"id":441499106,"identity":"db997ef0-5e10-43c8-bbef-f2286de911fd","order_by":1,"name":"Jianying Tang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAApElEQVRIiWNgGAWjYFCCA4wPGBgkSNDAw3CA2YBULQxspKgHAnvGM2aVX/dY5Om2H97A8KNiGzG2nDG7LfNMotjsTFoBY8+Z20RqkTggkbjtBo8BM2MbkVqKSdfC+IE0LQeOFUszHID45SBRfmGfcXjjxx8H6vLMjh/e+OBHBRFaGCROGDADIycByDQ4QIR6IOBvf8D4A6qFOB2jYBSMglEw4gAAdik+llfq6IEAAAAASUVORK5CYII=","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":true,"prefix":"","firstName":"Jianying","middleName":"","lastName":"Tang","suffix":""},{"id":441499108,"identity":"f538f461-060f-4cb2-ab02-ff3f9b9d8749","order_by":2,"name":"Ming Zhou","email":"","orcid":"","institution":"Chongqing University","correspondingAuthor":false,"prefix":"","firstName":"Ming","middleName":"","lastName":"Zhou","suffix":""},{"id":441499110,"identity":"d6c4570b-7da6-4f20-8d2c-2a041fbadf97","order_by":3,"name":"Huijun He","email":"","orcid":"","institution":"Metal Powder Meterials Industral Technology Research Institute of CHINA GRINM","correspondingAuthor":false,"prefix":"","firstName":"Huijun","middleName":"","lastName":"He","suffix":""},{"id":441499111,"identity":"27927f81-e18d-4213-8892-1894fa93a03a","order_by":4,"name":"Zhanrong Li","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Zhanrong","middleName":"","lastName":"Li","suffix":""},{"id":441499112,"identity":"d5fdf7dc-245d-4c44-a9be-8f925ad6aceb","order_by":5,"name":"Chengjun Wang","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Chengjun","middleName":"","lastName":"Wang","suffix":""},{"id":441499113,"identity":"7b962f9c-c526-4736-9e7c-e091bdc59604","order_by":6,"name":"Yubo Zhang","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Yubo","middleName":"","lastName":"Zhang","suffix":""},{"id":441499117,"identity":"918c969b-7842-4dee-819f-71ddb3a993ee","order_by":7,"name":"Yalong Qu","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Yalong","middleName":"","lastName":"Qu","suffix":""},{"id":441499118,"identity":"ac0ee0b8-10e1-4201-aa02-288fd9de427f","order_by":8,"name":"Shanyu Han","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Shanyu","middleName":"","lastName":"Han","suffix":""},{"id":441499122,"identity":"70db1d79-6c19-4ce0-bd5b-f7fa7a3173f5","order_by":9,"name":"Li Ren","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Ren","suffix":""},{"id":441499125,"identity":"0acc79d0-a50f-4c8e-be2b-f58e9b74b606","order_by":10,"name":"Yuning Zhao","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Yuning","middleName":"","lastName":"Zhao","suffix":""},{"id":441499128,"identity":"3134b9d3-3ada-4635-9261-21874392a56c","order_by":11,"name":"Xiaoyao Li","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Xiaoyao","middleName":"","lastName":"Li","suffix":""},{"id":441499129,"identity":"c4b44c81-efbd-420f-8b60-cf86a89605f7","order_by":12,"name":"Yaoyao Zhou","email":"","orcid":"","institution":"Gricy Advanced Materials Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Yaoyao","middleName":"","lastName":"Zhou","suffix":""}],"badges":[],"createdAt":"2025-02-28 06:38:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6125845/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6125845/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81102465,"identity":"f4c638ec-58d4-44b2-bae7-cc202eec6e3a","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2374829,"visible":true,"origin":"","legend":"\u003cp\u003eScanning EM map of copper-iron composite powder prepared by replacement copper plating\u003csup\u003e[11]\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e(a)Non-homogeneous nucleation, (b)homogeneous nucleation\u003c/p\u003e","description":"","filename":"Figure1ScanningEMmapofcopperironcompositepowderpreparedbyreplacementcopperplating111.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/398d4c56ea5d395b4ba6dfa4.png"},{"id":81102517,"identity":"06f5f658-91d7-4272-af33-10991787571d","added_by":"auto","created_at":"2025-04-22 09:04:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":677427,"visible":true,"origin":"","legend":"\u003cp\u003eProcess flow chart\u003c/p\u003e","description":"","filename":"Figure2.Processflowchart.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/3b37dead0fe7b8945c30029a.png"},{"id":81103938,"identity":"6642afb2-be43-4c7c-ad9f-c8d6130632a6","added_by":"auto","created_at":"2025-04-22 09:20:06","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3640177,"visible":true,"origin":"","legend":"\u003cp\u003eScanning EM map of copper-iron composite powder with different additives\u003c/p\u003e\n\u003cp\u003e(a) 5 times additive, (b) 8 times additive, (c) 10 times additive, (d) 15 times additive\u003c/p\u003e","description":"","filename":"Figure3ScanningEMmapofcopperironcompositepowderwithdifferentadditives1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/e79c39193cc96860d2d296cf.jpg"},{"id":81102456,"identity":"f4396a35-8447-4e3c-973a-0d2ad9be6ac1","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":955431,"visible":true,"origin":"","legend":"\u003cp\u003eThe metallographic profile of wet powder accumulation at different times\u003c/p\u003e\n\u003cp\u003e(a) No accumulation, (b) for 0.5h, (c) for 1h, (d) for 1.5h, (e) for 2h, (f) for 3h\u003c/p\u003e","description":"","filename":"Figure4Themetallographicprofileofwetpowderaccumulationatdifferenttimes.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/022f78b2be565cf8886fff40.png"},{"id":81102460,"identity":"82619929-3ae0-4c65-a44f-16a6d4445164","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":655024,"visible":true,"origin":"","legend":"\u003cp\u003eMicroscopic profiles of wet powder accumulation at different times at magnification\u003c/p\u003e\n\u003cp\u003e(a) No accumulation, (b) for 0.5h, (c) for 1h, (d) for 1.5h, (e) for 2h, (f) for 3h\u003c/p\u003e","description":"","filename":"Figure5Microscopicprofilesofwetpowderaccumulationatdifferenttimesatmagnification.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/0f186cad13120f02eb21ca16.png"},{"id":81102455,"identity":"695f17e1-e858-4b12-bc1d-fa32c9185216","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":559105,"visible":true,"origin":"","legend":"\u003cp\u003eChange curve of copper and iron composition scanned by EDS scan at different accumulation times of wet powder\u003c/p\u003e","description":"","filename":"Figure6ChangecurveofcopperandironcompositionscannedbyEDSscanatdifferentaccumulationtimesofwetpowder1.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/3edd89009564402ba3af39db.png"},{"id":81102471,"identity":"cbbb1008-5985-4f58-80f3-bdbb53862d2f","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1374286,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of wet powder accumulation at different times (1 kX)\u003c/p\u003e\n\u003cp\u003e(a) No accumulation, (b) for 0.5h, (c) for 1h, (d) for 1.5h, (e) for 2h, (f) for 3h\u003c/p\u003e","description":"","filename":"Figure7SEMimagesofwetpowderaccumulationatdifferenttimes1kX.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/f3eaaf69b48a922f75b5813b.png"},{"id":81103633,"identity":"d3aa3a41-89d5-46f6-bb28-cec6a87e3a3a","added_by":"auto","created_at":"2025-04-22 09:12:06","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":2328826,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of wet powder accumulation at different times (5 kX)\u003c/p\u003e\n\u003cp\u003e(a) No accumulation, (b) for 0.5h, (c) for 1h, (d) for 1.5h, (e) for 2h, (f) for 3h\u003c/p\u003e","description":"","filename":"Figure8SEMimagesofwetpowderaccumulationatdifferenttimes5kX.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/70a251abd638be4bec32d9de.png"},{"id":81102468,"identity":"c9585e42-b92e-43d3-8d4a-a29d2351e3c1","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":1227908,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscope image of the surface particles of the wet powder of non-stacked copper-iron composite powder at high magnification\u003c/p\u003e","description":"","filename":"Figure9Scanningelectronmicroscopeimageofthesurfaceparticlesofthewetpowderofnonstacked1.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/780e0b5d496c580dea631ec9.png"},{"id":81102457,"identity":"d3fcf44d-055e-4a03-af69-e02465021aeb","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":714021,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of the dried powder after different times of accumulation of copper-iron composite powder\u003c/p\u003e","description":"","filename":"Figure10XRDpatternsofthedriedpowderafterdifferenttimesofaccumulationofcopperironcompositepowder.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/fcdc80b4098a2e187014caec.png"},{"id":81103937,"identity":"551d7887-35f8-4dc8-9dc4-15418fbfc93e","added_by":"auto","created_at":"2025-04-22 09:20:06","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":677153,"visible":true,"origin":"","legend":"\u003cp\u003eCopper-Iron Binary Phase Diagram\u003c/p\u003e","description":"","filename":"Figure11CopperIronBinaryPhaseDiagram1.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/a0548382e1bc40d3d08c370a.png"},{"id":81102458,"identity":"58c3bdc3-d733-48bb-a2db-449410eb46a8","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":575524,"visible":true,"origin":"","legend":"\u003cp\u003eThe oxygen content change curve of copper-iron composite powder\u003c/p\u003e","description":"","filename":"Figure12Theoxygencontentchangecurveofcopperironcompositepowder1.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/120c9dc23d3c3dd16adeb550.png"},{"id":81103630,"identity":"fc697133-b58e-438c-9855-8ac89eca29ba","added_by":"auto","created_at":"2025-04-22 09:12:06","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":1307249,"visible":true,"origin":"","legend":"\u003cp\u003eSEM of copper-iron composite powder at different reduction temperatures (1 KX)\u003c/p\u003e\n\u003cp\u003e(a) 300℃, (b) 400℃, (c) 500℃, (d) 550℃, (e) 600℃, (f) 650℃, (g) 700℃, (h) 800℃\u003c/p\u003e","description":"","filename":"Figure13SEMofcopperironcompositepowderatdifferentreductiontemperatures1KX.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/9e74e46d8c57819981ce6eb5.png"},{"id":81102461,"identity":"f1a386d4-2efe-42aa-8aad-25ee7251f4ba","added_by":"auto","created_at":"2025-04-22 09:04:06","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":1090198,"visible":true,"origin":"","legend":"\u003cp\u003eSEM map of copper and iron composite powder at different reduction temperatures (5 KX)\u003c/p\u003e\n\u003cp\u003e(a) 300℃, (b) 400℃, (c) 500℃, (d) 550℃, (e) 600℃, (f) 650℃, (g) 700℃, (h) 800℃\u003c/p\u003e","description":"","filename":"Figure14SEMmapofcopperandironcompositepowderatdifferentreductiontemperatures5KX.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/d038d11e86b213360c7fe484.png"},{"id":81103632,"identity":"a2ad7903-9db6-464b-a06c-3d336fa59f61","added_by":"auto","created_at":"2025-04-22 09:12:06","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":758245,"visible":true,"origin":"","legend":"\u003cp\u003eXRD profiles of copper-iron composite powder at different reduction temperatures\u003c/p\u003e","description":"","filename":"Figure15XRDprofilesofcopperironcompositepowderatdifferentreductiontemperatures.png","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/8622e9d936801c6d7f6af865.png"},{"id":84482019,"identity":"c928e8c0-6238-4135-b4fa-b5748c5a3eef","added_by":"auto","created_at":"2025-06-12 12:47:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":20493467,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6125845/v1/70d33ef6-a582-43c1-b75f-ca8940160281.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study on the evolution feature and formation mechanism of Cu layer on the surface of copper-iron composite powder","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eCopper-based metal powder mainly consists of copper powder and copper alloy powder, which is an important component in the field of metal powder and one of the non-ferrous metal powder varieties with the highest production and consumption in China. Copper-iron composite powder is a key component of copper-based metal powder. It is one of the primary products in the cladding powder industry, and has a high market application value. Copper-iron composite powder is the ideal material for the production of oil bearings, compared to cobalt-based and copper-based diamond tool bonding agents, copper-iron composite powder bonding agent is less expensive. Its corrosion resistance is stronger, and performance is more stable compared to iron-based diamond bonding agent. In the field of friction materials, they are mainly used in cassettes, brake blocks and brake pads of high-speed trains. When compared to the preparation of friction parts with copper-iron hybrid powder, copper-iron composite powder reduces the porosity of the products, improves the strength and coefficient of friction\u003csup\u003e[1]\u003c/sup\u003e. In addition, copper and iron composite powder can enhance the thermal conductivity, thermal stability, wear resistance and high temperature impact resistance of friction materials.\u003c/p\u003e \u003cp\u003eA type of copper-iron composite powder, which has iron as the \"core\" and copper as the \"shell\", can be used to partially replace copper powder as the sintered metal cladding powder because of its good pressing performance, low sintering temperature, and high strength of the iron base, as well as its excellent corrosion resistance and high thermal conductivity. It offers a wide range of potential applications and can partially replace copper powder as the best raw material for sintered oil bearings\u003csup\u003e[2][3]\u003c/sup\u003e. The preparation methods of metal-coated composite powder mainly include mechanical ball-mill coating\u003csup\u003e[4]\u003c/sup\u003e, replacement plating\u003csup\u003e[5]\u003c/sup\u003e, chemical plating\u003csup\u003e[6]\u003c/sup\u003e, sol-gel\u003csup\u003e[7]\u003c/sup\u003e, physical vapor deposition\u003csup\u003e[8]\u003c/sup\u003e, and chemical vapor deposition\u003csup\u003e[9]\u003c/sup\u003e, etc. It has been demonstrated that the mechanical ball-mill coating, replacement copper plating, and chemical copper plating are the main techniques now used to prepare copper-iron composite powders. which overcomes the drawbacks of uneven color and luster, unstable mechanical properties, and low product qualification rate that are frequently present in the production of other powders while offering the benefits of lead-free, corrosion-resistant, low cost, good iron and copper metal bonding, and excellent overall product performance.\u003c/p\u003e \u003cp\u003eLiu\u003csup\u003e[10]\u003c/sup\u003e found that the replacement plating method of copper involves an electron transfer between the two metal ions, as a plated body in the substrate of the outermost electron of the metal atoms are drawn to the powerful other metal ions within the double electric layer of the empty track. While the other metal ions that acquire electrons are reduced to atoms and deposited on the surface of the metal substrate to form the conversion plating layer, some of the atoms on the substrate's surface lose electrons to become metal ions and exit the substrate to enter the solution. The electrons in the matrix atoms also leap in quantum states into the empty orbitals of the reduced metal ions. However, this process is directly related to the potential difference between the reduced metal and the matrix metal. That is, the negative potential matrix can provide electrons to the positive potential metal ion to be reduced. At this time, the outer electrons of the matrix metal atoms leap into the outer orbitals of the reduced metal ions, reducing them to metal atoms and crystallizing them into a metal coating. This process is disordered when it occurs naturally, and continues until the original metal on the surface of the matrix metal is oxidized to a metal salt, and the original crystallization sites are replaced by the reduced metal.\u003c/p\u003e \u003cp\u003eFor example, the displacement reaction of iron in an acidic copper solution usually consists of the following two half-reactions:\u003c/p\u003e \u003cp\u003eanode reaction: Fe\u0026rarr;Fe\u003csup\u003e2+\u003c/sup\u003e + 2e φ\u0026deg;= -0.441V\u003c/p\u003e \u003cp\u003ecathode reaction: Cu\u003csup\u003e2+\u003c/sup\u003e +2e\u0026rarr;Cu φ\u0026deg;= +0.337 V\u003c/p\u003e \u003cp\u003eTypically, iron dissolves rapidly in acidic solutions, causing a large accumulation of electrons on the electrode surface, resulting in a strong negative shift of the electrode potential. Thus generating a high crystallization overpotential, which leads to a large number of two-dimensional nuclei precipitating and growing up near the electrode surface, and ultimately forming a loose replacement copper layer that has a poor bonding force with the substrate.\u003c/p\u003e \u003cp\u003eIt is well known that the matrix surface state has an important influence on the binding force of chemical plating. Wang and Ding\u003csup\u003e[11]\u003c/sup\u003e used the replacement copper plating method to modify the surface of the iron powder, founding that the degree of the supersaturation in the solution is the key parameter that affects the morphology of the coating material when combined with the critical nucleation theory. Due to the competition of heterogeneous and homogeneous nucleation during crystal nucleation, the precipitation of Cu\u003csup\u003e2+\u003c/sup\u003e in the solution cannot be completely coated on the surface of the iron powder, part of the copper will spontaneously form copper powder in the copper solution through homogeneous nucleation. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the surface microstructure of the copper-iron composite powder. Heterogeneous nucleation occurs under a lower degree of supersaturation, so that part of the copper particles deposited on the surface of the iron particles, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a). Homogeneous nucleation occurs under a higher degree of supersaturation, forming copper particles in the solution, and the surface roughness increases significantly, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA large number of studies have shown that in the process of copper replacing coating, the coating solution without introducing special additives cannot produce uniform and dense copper coating layers no matter how the pretreatment process is strengthened. Wang\u003csup\u003e[12]\u003c/sup\u003e showed that the reaction speed of Fe replacement Cu\u003csup\u003e2+\u003c/sup\u003e is very fast during the replacement of copper-iron composite powder, if not using additives in the coating, so that the Cu nucleated on the surface of Fe particles would grow and thicken rapidly, resulting in a large consumption of Cu\u003csup\u003e2+\u003c/sup\u003e. Subsequently, it was difficult to continue thickening due to insufficient Cu\u003csup\u003e2+\u003c/sup\u003e nucleation sites, and some sites will not be able to form the plating layer due to the lack of contact with Cu\u003csup\u003e2+\u003c/sup\u003e. At the same time, the side reaction of hydrogen evolution will be accompanied in an acidic environment\u003csup\u003e[13]\u003c/sup\u003e, resulting in a very rough and discontinuous surface of the prepared coating layer. Instead, the introduction of additives in the plating solution uniformly compacted the coating layer. This is because the additive molecules contain large functional groups, strong adsorption, easy to form complexes. So that the cathode potential negative shift, increasing the cathode polarization, restricting the reduction of copper ions, inhibiting the growth of copper grains, thus improving the density of copper coating, reducing the coating roughness\u003csup\u003e[14][15]\u003c/sup\u003e. However, when additives were introduced in excess, a large number of stable chelates would be formed, which would severely hinder the reduction of copper ions, and were easily adsorbed in the coating layer, making them difficult to resolve. This ultimately leads to a significant decrease in the adhesion of the coating layer\u003csup\u003e[16][17]\u003c/sup\u003e. Wu Shixue\u003csup\u003e[18]\u003c/sup\u003e found that precise control of the deposition rate of Cu was the key to obtain a good replacement coating by metallographic section analysis. By comparing the the experiments with and without additives, it was found that the addition of additives effectively reduced the displacement reaction rate, and the bonding force between the coating layer and the matrix was stronger. In addition, Chen\u003csup\u003e[19]\u003c/sup\u003e added additives to the plating solution, and found that the density of the coating layer was significantly improved, and the porosity between the coating layer and the matrix was reduced.\u003c/p\u003e \u003cp\u003eIn the process of industrial production, due to the large production of copper and iron composite powder, the wet powder before powder is inevitably stored and accumulated. Due to its large specific surface area and activity, it is easy to absorb moisture and be oxidized, and the finer the powder, the more serious the tendency of oxidation. The inevitable high temperature and high humidity environment is easy to produce electrochemical corrosion, the influence of trace impure gas and subsidence in the atmosphere and the production process leads to the discoloration and corrosion of powder\u003csup\u003e[20]\u003c/sup\u003e, and the change of copper structure on the surface of the powder.\u003c/p\u003e \u003cp\u003eDing et al\u003csup\u003e[21]\u003c/sup\u003e. found that the oxidation of pure copper is a spontaneous reaction by analyzing the thermodynamics, kinetics and oxidation behavior of pure copper. However, the spontaneous trend would gradually decrease and the trend of forming Cu\u003csub\u003e2\u003c/sub\u003eO is the largest with the increase of temperature. Cu\u003csub\u003e2\u003c/sub\u003eO is a thermodynamically stable oxidation product. The growth of pure copper oxide film is firstly the adsorption of oxygen on the copper substrate to form the Cu\u003csub\u003e2\u003c/sub\u003eO film, and then the formation and growth of CuO particles on the Cu\u003csub\u003e2\u003c/sub\u003eO film. Firstly the absorbed oxygen on the copper matrix formed a massive oxide film, and then the white particles appeared and accumulated on the massive oxide film. In this process, temperature, tissue and purity were all important factors affecting the oxidation of pure copper. The higher the temperature, the higher the oxidation rate of pure copper, and the higher the purity, the smaller the oxidation rate.\u003c/p\u003e \u003cp\u003eIn recent years, Zhang\u003csup\u003e[22]\u003c/sup\u003e have summarized the application, the preparation method and the problems in the preparation process of copper-iron composite powder. Among them, how to effectively balance the uniformity of coating layer and coating rate is the key problem in the preparation of copper -iron composite powder. On this basis, how to further optimize the preparation process parameters to develop better copper-iron composite powder is an important direction to be broken through.\u003c/p\u003e \u003cp\u003eAbove all, this paper mainly explored the influence of process parameters such as additive dosage, wet powder accumulation time and reduction temperature on the surface morphology, composition and microstructure of copper-iron composite powder. The effects on the oxygen content of copper-iron composite powder and the coating uniformity of the surface copper layer were investigated. On the basis of the above studies, the optimal process parameters were selected, and the copper-iron composite powder with better coating performance was prepared.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 material\u003c/h2\u003e \u003cp\u003eThe raw materials used in the study, including iron powder and copper sulfate (CuSO4 5H\u003csub\u003e2\u003c/sub\u003eO), were commercially available. The iron powder was 200 mesh reduced iron powder provided by Baowu Huanke Metal Co., with a purity of 98%, and copper sulfate was provided by Chongqing Guangsheng Nonferrous Metal Material Co., Ltd., with a purity of \u0026gt;\u0026thinsp;95%.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 technology roadmap\u003c/h2\u003e \u003cp\u003eThe specific preparation process for copper-iron composite powder was as follows: (1) Pretreatment of the iron powder; (2) The amount of additives was calculate according to the amount of 0.5% of the amount of iron powder. On this basis, 5 times, 8 times, 10 times and 15 times of additives were added to the copper sulfate solution respectively, and the mixture was evenly mixed. (3) The copper-iron composite powder containing 15% copper was coated and wet powder was post-treated. Among them, Step (3) is divided into two situations: one is to simulate the wet powder accumulation environment with a constant temperature and humidity box, and to explore the influence of the accumulation time of coated copper-iron composite powder on the structure of powder coated layer. The time range was 0.5-3h, and then dried. The specific accumulation time of the coated wet powder was 0.5h, 1h, 1.5h, 2h and 3h, respectively ; secondly, the wet powder was placed in a hydrogen atmosphere, and different reduction temperatures were set to explore the effect of reduction temperature on the surface structure and morphology of copper-iron composite powder. The reduction temperature range was 300\u0026ndash;800℃, with specific reduction temperatures set at 300℃, 400℃, 500℃, 550℃, 600℃, 650℃, 700℃ and 800℃, respectively. The dried powder was crushed and sieved after cooling. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e is the process flowchart for the preparation of copper-iron composite powder.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Characterizations\u003c/h2\u003e \u003cp\u003eThe surface morphology and composition of copper-iron composite powder were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The section thickness of copper cladding layer was characterized by metallographic microscope. The phase structure of copper-iron composite powder was characterized by X-ray diffraction instrument (XRD); and the oxygen content was detected by a steel research oxygen analyzer.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n\u003ch2\u003e3.1 Effect of the additive dosage on the micromorphology of the powder\u003c/h2\u003e\n\u003cp\u003eFollowing the formation of a complex with the additive, the concentration of free Cu\u003csup\u003e2+\u003c/sup\u003e was decreased, reduceing the probability of collision between Cu\u003csup\u003e2+\u003c/sup\u003e and Fe molecules, and impeding the approach of copper ions to the iron powder matrix, thus effectively slowing the rate of Cu reduction and plating speed. Meanwhile, the complex formation of copper reduced the electrode potential of copper, which is more difficult to be reduced than Cu\u003csup\u003e2+\u003c/sup\u003e, thus also reducing the growth rate of copper. The plating solution's high temperature aging stability and coating performance can sustain an outstanding or good state over an extended period of time, respectively, with increasing mass concentration.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e showed the SEM pictures of the copper-iron composite powder produced with different amounts of additives. As can be seen from Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(a), when the additive dosage was 5 times, the prepared powder was well combined with the matrix, and the surface was smooth, continuous and complete; when the additive dosage was 8 times, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(b), the powder surface was incomplete, with a small gap or incomplete; and when the additive dosage was 10 times or more, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(c) and (d), the copper layer was uneven, and there were a large number of gullies on the surface.\u003c/p\u003e\n\u003cp\u003eWhen the amount of additive was 10 times, the concentration of additive was too high to make the reaction speed too slow, the copper layer formed on the surface was discontinuous, and there was a pore between the iron powder particles. Cu\u003csup\u003e2+\u003c/sup\u003e in the solution entered the copper layer via the pore, and continued to react on the surface of the iron powder, forming a new discontinuous copper layer. Because the Fe surface has been partially coated with copper, the resistance to Cu\u003csup\u003e2+\u003c/sup\u003e reentry drove Cu\u003csup\u003e2+\u003c/sup\u003e to react with the surface of the unreacted Fe powder, thickening the copper layer by layer.\u003c/p\u003e\n\u003cp\u003eIn conclusion, the copper-iron composite powder with smooth and continuous copper layer and good combination with the matrix could be obtained when the additive (based on the 0.5% iron powder ) was added to the copper sulfate plating solution for 5 times.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2 Wet powder accumulation time test\u003c/h2\u003e\n\u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.1 SEM analysis of the metallography and microsection\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e was the metallographic section of copper-iron composite powder, and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e was the microscopic section SEM diagram of wet powder accumulation at different times. As can be seen in the images, the surface of the iron powder was coated with a relatively uniform layer of copper, and there were pores between the copper layer and the surface of the iron particles. With the increase in the accumulation time of the wet powder, the surface copper layer showed a trend of growth. When copper was exposed to air, it reacted with oxygen to form a layer of copper oxide film. As the accumulation time increased, the temperature of the powder rose, and the oxide film absorbed oxygen to form a blocky oxide film. Subsequently, white particles appeared on the blocky oxide film and accumulated and grew, gradually thickening the oxide layer. When the accumulation time is \u0026ge;\u0026thinsp;1 hour, the thickness of the surface copper layer increased significantly.\u003c/p\u003e\n\u003cp\u003eIn conclusion, after the coating of copper-iron composite powder was completed, the accumulation time of wet powder should not exceed 1h.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.2 EDS complexity analysis\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e showed the EDS scanning (surface scan) curves of elemental content changes in powder particles after different durations of wet powder accumulation. As can be seen from the figure, the iron content increased with the increase of stacking time, whereas the copper content decreased.\u003c/p\u003e\n\u003cp\u003eWhen the powder was not placed in a constant temperature and humidity chamber, the EDS scannig spectrum indicated that the copper content was 93.6%, with a dense coating of copper on the surface. However, when the powder was placed in a constant temperature and humidity chamber and accumulated for various durations before drying, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e, the surface copper content was below 90% for all samples.\u003c/p\u003e\n\u003cp\u003eUsing a nitrogen-oxygen analyzer to detect the directly dried copper-iron composite powder, the results showed that the oxygen content was below 6000ppm; however, after the powder was piled up for 0.5 hours and then dried, the oxygen content exceeded 10000ppm; and after piling up for 1 hour and then drying, the oxygen content exceeded 20000ppm. It was evidented that the surface copper layer of the copper-iron composite powder was oxidized rapidly after washing, centrifuging, and piling up for a period of time, and the degree of oxidation deepens with the increase of piling-up time.\u003c/p\u003e\n\u003cp\u003eIn summary, the stacking time of wet copper-iron composite powder should not exceed 0.5 hours. If it exceeded 0.5 hours, the iron and oxygen content of the powder particles increased rapidly, and the surface copper content decreased.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.3 Micromorphology analysis\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows the scanning electron microscope images of the wet powder at low magnification after different periods of time. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(a) showed the powder before being placed in the constant temperature and humidity chamber, where the surface of the powder appears relatively smooth with fewer adhering small particles; Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(b-f) represent the powder after being placed in the chamber for 0.5h, 1h, 1.5h, 2h, and 3h, respectively. It was observed that the surfaces of the powders had a considerable number of fine particles, and there was a clear trend of increasing particle numbers with longer placement times.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e showed the SEM pictures at high multiple. Except for Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(a), there were obvious deposits on the surface of the powder., most of which were granular, and a few were irregular.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e showed the enlarged SEM images of stacked particles, which were mostly long sheets and stacked particles. Copper-iron composite powder was accumulated in the air, the longer the accumulation time, the higher the temperature, the newly formed copper on the surface was easily oxidized to form copper oxide and brown copper oxide deposits on the powder; the longer the accumulation time, the copper and iron in the inner layer of the powder particles were oxidized, which was difficult to reduce, and the coating quality and bonding force were poor.\u003c/p\u003e\n\u003cp\u003eIn summary, the stacking time of wet copper-iron composite powder should not exceed 0.5 hours.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n\u003ch2\u003e3.2.4 XRD\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e showed the XRD diffraction pattern of the dry powder after wet powder accumulation at different times. After analysis, it was found that there were other impurity phases in the copper-iron composite powder, which were composed of Fe, Cu and copper oxides. The diffraction peaks of powder samples with different stacking times were basically consistent, but the oxide diffraction peaks of copper were different. The XRD map showed that when the wet powder accumulation time exceeds 0.5h after drying, the more obvious CuO phase and Cu\u003csub\u003e2\u003c/sub\u003eO phase would appear in the diffraction pattern. Therefore, it could be inferred that the surface layer of the powder was oxidized to a certain extent.\u003c/p\u003e\n\u003cp\u003eCombined with the SEM morphology characterization analysis in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e, it could be seen that large-sized long sheets were CuO, and small-sized accumulated particles were Cu\u003csub\u003e2\u003c/sub\u003eO. If the copper-iron composite wet powder was piled up for a long time without drying, most of the surface copper layer would exist in the form of CuO, and a small part exist in the form of Cu\u003csub\u003e2\u003c/sub\u003eO, resulting in the color of the powder darkened.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n\u003ch2\u003e3.3 Reduction temperature test\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e was a phase diagram for the Fe-Cu binary system, from which it can be seen that the solubility of copper in iron varied significantly with temperature. The solubility in \u0026alpha;\u003csub\u003e2\u003c/sub\u003eFe, was approximately 1.4% at total temperature(835℃) while decreased dramatically to 0.3% at 700℃ and to 0.2% at room temperature. The solubility of Cu in \u0026gamma;\u003csub\u003e2\u003c/sub\u003eFe, was about 7.5\u0026ndash;8.5% at 1094℃, still decreased sharply with the decrease of temperature. Therefore, when the content of Cu added to iron was high, due to the insolubility of Fe and Cu, the weak interaction of partial false alloy (pseudo-alloy) can only be formed, so that the copper-iron composite powder could present a specific combination of the intrinsic properties of the two elements\u003csup\u003e[23]\u003c/sup\u003e. Because copper and iron cannot be completely alloyed, the oxides of Cu and Fe were mainly reduced in the reduction process.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e showed the change curve of the oxygen content of copper and iron composite powder under different reduction temperatures. The oxygen content in the powder will significantly decrease with the increase of the reduction temperature. When the reduction temperature rose to 500℃, the oxygen content decreased significantly below 4000 ppm; when the reduction temperature reached 600℃, the powder oxygen content was basically stable at about 3000ppm.\u003c/p\u003e\n\u003cp\u003eThus, the lower the reduction temperature, the higher the powder oxygen content, the surface appeared to be black. However, when the reduction temperature was higher than 700℃, the reduced powder was massive, and it was difficult to be broken. Therefore, the optimum reduction temperature of copper-iron composite powder should be controlled at 500\u0026ndash;700℃.\u003c/p\u003e\n\u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n\u003ch2\u003e3.3.1 Micromorphology analysis\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e showed the SEM plot of copper-iron composite powder at different reduction temperatures under low magnification. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e, the powder particle surface was not smooth when the reduction temperature was lower than 600℃. When the reduction temperature was 600\u0026ndash;650℃ (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e(e) and (f)), the powder copper layer was well connected with the substrate, and the surface was continuous and smooth. When the reduction temperature was 700℃ (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e(g)), narrow pores appeared in the surface copper layer. When the reduction temperature reached 800℃ (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e(h)), the powder surface showed obvious bulges and more gullies.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e showed the SEM plot of high ratios of copper-iron composite powder at different reduction temperatures. When the reduction temperature was below 600℃, the powder surface was bran-shaped, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e(a-d). When the reduction temperature was 600\u0026ndash;650℃ (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e(e) and (f)), the surface was a continuous flat copper layer. At the reduction temperature of 700℃, shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e(g), the surface copper layer began to split. When the reduction temperature reached 800℃, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e(h), the copper layer on the powder surface shrinked to the formation of copper accumulation, the surface was uneven, and deep gullies appeared around the bulge.\u003c/p\u003e\n\u003cp\u003eAccording to the phase diagram of copper and iron, the solid solution of copper and iron was very low, and the copper and iron cannot be alloyed. With the increase of the reduction temperature, the copper layer (the thickness was about 1\u0026micro;m) on the surface of iron diffused between each other, melted and shrinked, and then the position was reconstructed. In the process, it gradually accumulated, the surface was convex, and the gully was formed around the convex part.\u003c/p\u003e\n\u003cp\u003eIn conclusion, the copper-coated layer of iron powder should be prepared at 600\u0026ndash;650℃.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\n\u003ch2\u003e3.3.2 XRD\u003c/h2\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e showed the XRD diffraction profiles of eight kinds of copper-iron composite powder at different reduction temperatures. After analysis, it was found that the diffraction patterns of several powder were basically consistent. There were no other impurity phases in the reduced copper-iron composite powder, which were composed of Fe and Cu phases, and no copper or iron impurities such as copper or iron oxide was observed.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e"},{"header":"4 Conclusions","content":"\u003cp\u003eWhen preparing copper-iron composite powder, the additive dosage of copper salt solution should be 5 times, the accumulation time of wet powder should not exceed 0.5h, and the reduction temperature should be 600\u0026ndash;650℃. Under this condition, the resulting powder surface has a continuous and smooth and smooth copper layer, which is well connected with the matrix.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eZhang Jingguo. Conceptualization and design; Writing and editing; Data analysis and interpretation; Literature review. Tang Jianying. Experimental operations and data processing; Chart making; Writing and editing; Literature review. Zhou Ming. Writing and Editing. He Huijun. Conceptualization and Design; Management and Coordination. Li Zhanrong. Conceptualization and Design; Management and Coordination. Wang Chengjun. Writing and Revision. Zhang Yubo.Date collection and analysis; Experimental operation; Writing and Revision. Qu Yalong. Writing and editing; data processing. Han Shangyu. Writing and editing; data processing. Ren Li.Analytical detection. Zhao Yuning. Analytical detection. Li Xiaoyao. Experimental operation. Zhou Yaoyao. Experimental operation.\u003c/p\u003e\n\u003ch2\u003eData availability\u003c/h2\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article.\u003c/p\u003e\n\u003ch2\u003eAcknowledgments\u003c/h2\u003e\n\u003cp\u003eThis study was supported by the National Key R\u0026amp;D Program (2023YFB3812102) and Chongqing Municipal Technology Innovation\u003cbr\u003e\u0026nbsp;and Application Development Special Key Project (CSTB2022TIAD-KPX0027). GRIPM Advanced Materials Co. Ltd.,.Innovation Fund (2024500001000867)\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eT Peng, Q Yan, G Li, et al. The influence of Cu/Fe ratio on the tribological behavior of brake friction materials[J]. Tribology Letters, 2018, 66: 1\u0026ndash;12.\u003c/li\u003e\n\u003cli\u003eL J Chen, S L Li, Y J Yang, et al. Preparation and structural characterization of copper-coated nanoscale iron powder[J]. 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Shanghai: Shanghai Institute of Electronics Electroplating Professional Committee, 2007: 289\u0026ndash;290.\u003c/li\u003e\n\u003cli\u003eQ Zhu. Introduction to Theoretical Electrochemistry[M]. Changsha: Central South University of Technology Press, 1988: 422\u0026ndash;427.\u003c/li\u003e\n\u003cli\u003eX Xiao, Y Q Long. Study on rapid chemical immersion copper plating process for steel parts[J]. Corrosion and Protection, 2003, 24(3): 115\u0026ndash;118.\u003c/li\u003e\n\u003cli\u003eJ J Sun, R J Tian, R Lu, et al. Overview of the mechanism of copper plating from copper sulfate solution[J]. Printed Circuit Information, 2012(3): 40\u0026ndash;44.\u003c/li\u003e\n\u003cli\u003eS X Wu. Study on process and mechanics of surface trauspositioual coating of copper on iron powder dissertation[D]. Chongqing: Chongqing University, 2006.\u003c/li\u003e\n\u003cli\u003eY Y Chen, R X Wang, S Chen,et al. Investigation on chemical replacement copper plating[J]. Plat Finish, 2001, 23(4): 1.\u003c/li\u003e\n\u003cli\u003eR H Yao, J Yang. Surface passivation treatment of copper materials(I)-Research on the evaluation method of discoloration and its inhibition effect of copper materials[J]. Southern Metallurgy Science and Technology, 1997(1): 16\u0026ndash;21.\u003c/li\u003e\n\u003cli\u003eY T Ding, Z H Lu, Y Hu, et al. Oxidation behavior and influencing factors of pure copper[J]. Journal of Lanzhou University of Technology, 2010, 36(02): 1\u0026ndash;4.\u003c/li\u003e\n\u003cli\u003eS S Zhang, C Y Li, Y W Pan, et al.. Application and preparation of copper-iron powder[J]. Powder Metallurgy Technology, 2020, 38(06): 465\u0026ndash;474.\u003c/li\u003e\n\u003cli\u003eH B Li, A X He, L Cao, et al. Research on the properties and applications of Cu/Fe composite powder[J]. Sichuan Nonferrous Metals, 2005(01): 18\u0026ndash;21.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"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":"copper-iron composite powder, additive, accumulation time, reduction temperature, copper coating layer","lastPublishedDoi":"10.21203/rs.3.rs-6125845/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6125845/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis article examined the preparation process of copper-iron composite powder using a chemical displacement method. It focused on how various process parameters, such as the amount of additives in the copper sulfate solution, the wet powder stacking time after coating, and the reduction temperature, impact the surface morphology, composition, and structure of the copper coating layer. The surface morphology and composition of the copper-iron composite powder were characterized using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), the cross-sectional thickness of the copper coating layer was characterized using a metallurgical microscope, and the crystal phase structure of the copper-iron composite powder was detected using an X-ray diffractometer (XRD). It indicated that when the amount of additives in the copper salt solution was \u0026ge;\u0026thinsp;5 times (calculated as 1 time based on 0.5% of the iron powder amount), noticeable accumulation of copper coating layer and grooves appeared on the surface, leading to a decrease in surface smoothness. Additionally, if the stacking time of the wet powder exceeded 0.5 hours, the surface copper content decreased and the volume of the deposited material increased, resulting in the formation of CuO and Cu\u003csub\u003e2\u003c/sub\u003eO phases. Furthermore, when the reduction temperature was between 600 and 650℃, the surface copper coating layer remained smooth and continuous, with oxygen content measured below 4000ppm.\u003c/p\u003e","manuscriptTitle":"Study on the evolution feature and formation mechanism of Cu layer on the surface of copper-iron composite powder","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-22 09:04:01","doi":"10.21203/rs.3.rs-6125845/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":"bf60ec1c-69dd-4203-9185-0e38708e75d1","owner":[],"postedDate":"April 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":47010099,"name":"Physical sciences/Chemistry"},{"id":47010100,"name":"Physical sciences/Engineering"}],"tags":[],"updatedAt":"2025-06-12T12:39:00+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-22 09:04:01","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6125845","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6125845","identity":"rs-6125845","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}