High purity tungsten silicide and method for producing the same

Abstract

The application belongs to the technical field of tungsten silicide preparation, and particularly relates to high-purity tungsten silicide and a preparation method thereof, the preparation method comprising the following steps: S1, obtaining silicon powder and nano tungsten oxide, mixing the silicon powder and the nano tungsten oxide, then performing wet grinding, washing and centrifugal separation to obtain a mixed slurry, and the medium for the wet grinding is cyclohexane; S2, placing the mixed slurry in an alumina boat with a cover to perform drying, reduction, calcination and natural cooling to obtain high-purity tungsten silicide. The application uses multiple methods to prevent the oxidation of Si and avoid the generation of silicon oxide; the high-activity tungsten powder obtained by reduction of nano tungsten oxide is used to shorten the calcination time; the sintering of the sample inside and outside is ensured; the high-temperature short-time rapid calcination makes the WSi2 powder loose and not hardened.

Description

Technical Field

[0001] This application relates to the field of tungsten silicide preparation technology, specifically, this application relates to a high-purity tungsten silicide and its preparation method. Background Technology

[0002] With the rapid development of high-end fields such as aerospace, microelectronics semiconductors, high-temperature metallurgy, and hard cutting tools, extreme high temperatures, strong oxidation, high loads, and low electrical resistance conditions place stringent demands on high-temperature structural and functional materials. Refractory metal silicides, due to their high melting point, low resistivity, excellent thermal stability, and high-temperature oxidation resistance, have become a hot research topic, with tungsten disilicide (WSi2) showing the greatest application potential. WSi2 has a melting point exceeding 2160℃ and possesses good electrical and thermal conductivity, wear resistance, and high-temperature chemical stability. It can be used as a polycrystalline silicon replacement material in integrated circuits, serving as gate electrodes, interconnect wiring, and diffusion barrier layers; it can also be used as a protective coating for tungsten-based alloys and high-temperature alloys, providing high-temperature oxidation protection in hot-end components of aero-engines and heat-resistant rocket components. Furthermore, it can be used as a cemented carbide additive to enhance the high-temperature wear resistance and oxidation resistance of cutting tools and high-temperature molds. Currently, the mainstream preparation methods for WSi2 mainly include high-temperature solid-state heat treatment, CVD deposition, magnetron sputtering, and mechanical alloying. However, significant technical bottlenecks remain: the synthesis temperature window is narrow, impurities such as W5Si3 are easily generated, and the controllable synthesis of pure phases is difficult; traditional processes are energy-intensive, time-consuming, and require stringent preparation conditions; the crystal form is difficult to control, and stable and metastable phases are prone to coexistence; during large-scale production, phase homogeneity and batch stability are poor, and novel predicted crystal structures are difficult to experimentally prepare. Therefore, conducting research on the controllable synthesis, crystal form regulation, and performance optimization of WSi2 is of great practical significance for promoting its industrial application in microelectronics, aerospace, and high-temperature engineering.

[0003] Currently, the mainstream method for synthesizing WSi2 is the high-temperature solid-state method. Although WSi2 possesses good oxidation resistance and excellent thermal stability at high temperatures, the special properties of Si, one of its raw materials, lead to a dilemma in its high-temperature solid-state synthesis. When using fine-particle Si for synthesis, the Si oxidizes upon exposure to air, forming silica that is difficult to remove. When using coarse-particle Si powder as a raw material, insufficient temperature or short holding time results in unreacted silicon within the Si powder particles. Excessively high temperature or excessively long holding time causes the WSi2 powder to easily clump together, requiring intensive crushing. Therefore, it is necessary to find a preparation method that can ensure sufficient sintering of WSi2 samples, low oxygen content, and high WSi2 content. Summary of the Invention

[0004] To solve the above-mentioned technical problems, this application provides a method for preparing high-purity tungsten silicide, comprising the following steps: S1, obtaining silicon powder and nano-tungsten oxide, mixing the silicon powder and the nano-tungsten oxide, and then wet-milling, washing, and centrifuging to obtain a mixed slurry, wherein the medium for wet milling is cyclohexane; S2, placing the mixed slurry in a covered alumina boat for drying, reduction, calcination, and natural cooling to obtain high-purity tungsten silicide.

[0005] In a preferred embodiment of the method for preparing high-purity tungsten silicide according to this application, in step S1, the particle size of the silicon powder is 10-20 μm, and the specific surface area of ​​the nano-tungsten oxide is 11-13 m². 2 / g, wherein the molar ratio of the silicon powder to the nano-tungsten oxide is 2:1.

[0006] As a preferred embodiment of the method for preparing high-purity tungsten silicide according to this application, in step S1, the wet milling is carried out in a planetary ball mill. The grinding balls and the inner wall of the grinding jar used in the wet milling are made of cemented carbide. The wet milling is carried out intermittently, with a stop time of 5-10 minutes after every 10-20 minutes of operation. The rotation speed of the wet milling is 200-240 r / min, the total time of the wet milling is 3-4 hours, and the atmosphere of the wet milling is argon.

[0007] In a preferred embodiment of the method for preparing high-purity tungsten silicide as described in this application, in step S1, cyclohexane is used as the washing agent, and the mixed slurry contains cyclohexane covering all solids.

[0008] As a preferred embodiment of the method for preparing high-purity tungsten silicide according to this application, in step S2, the heating rate of the drying process is 8-12℃ / min, the holding temperature of the drying process is 60-85℃, the holding time of the drying process is 40-90min, the drying atmosphere is argon, and the flow rate of the argon is ≥4L / min.

[0009] In a preferred embodiment of the method for preparing high-purity tungsten silicide according to this application, in step S2, the heating rate of the reduction is 8-12℃ / min, the holding temperature of the reduction is 880-920℃, the holding time of the reduction is 1-2h, the atmosphere of the reduction is hydrogen, and the flow rate of the hydrogen is 0.8-1.2L / min.

[0010] As a preferred embodiment of the method for preparing high-purity tungsten silicide according to this application, in step S2, the heating rate of calcination is 3-6℃ / min, the holding temperature of calcination is 1380-1450℃, the holding time of calcination is 20-40min, the atmosphere of calcination is argon, and the flow rate of argon is 1-3L / min.

[0011] This application also provides a high-purity tungsten silicide, which is prepared using the above-described method for preparing high-purity tungsten silicide.

[0012] As a preferred embodiment of the high-purity tungsten silicide described in this application, the microstructure of the high-purity tungsten silicide comprises more than 96.0 wt% WSi2 and less than 4 wt% W5Si3, wherein the WSi2 crystal form is a body-centered tetragonal structure under standard conditions.

[0013] As a preferred embodiment of the high-purity tungsten silicide described in this application, the oxygen content of the high-purity tungsten silicide is ≤0.05%.

[0014] The beneficial effects of this application are as follows: This application proposes a method for preparing high-purity tungsten silicide. By using Si with suitable particle size as the silicon source, the amount of silicon oxide that is difficult to remove from the raw materials can be reduced. Coarse silicon powder and tungsten oxide are wet-milled together under the dual protection of cyclohexane and argon. The silicon powder is crushed and mixed while minimizing oxidation, ensuring that fully sintered WSi2 with low oxygen content can still be obtained even when using coarse silicon powder. The raw materials are dried, reduced, and sintered directly in a tube furnace after mixing, further ensuring low oxygen content. Nanoscale tungsten oxide, which is uniformly mixed with crushed silicon powder, is used as the tungsten source. After reduction, highly active tungsten powder is generated on the surface of the silicon powder, which greatly reduces the temperature and time required for sintering. Therefore, fully sintered tungsten disilicide with no silicon residue can be obtained by short sintering at a lower temperature, solving the problems of incomplete sintering, low WSi2 content, and high oxygen content in tungsten silicide.

[0015] In this application, when the particle size of Si powder is too small, it can react quickly with oxygen to form silicon dioxide when exposed to air. Silicon dioxide is extremely difficult to process in the subsequent process, which increases the oxygen content of WSi2 material. When the particle size of Si powder is too large, it is difficult to sinter it fully inside, and Si elemental will remain. After nano-tungsten oxide is reduced in hydrogen, it generates highly active W powder, which can shorten the sintering time of Si.

[0016] Common wet grinding media such as alcohol contain oxygen, which leads to an increase in oxygen content during ball milling. This application uses cyclohexane as the ball milling medium, and cyclohexane evaporates rapidly at low temperatures, significantly reducing the overall experimental time. High-purity argon gas mainly serves to remove air and prevent Si from reacting with oxygen in the air to form silicon oxide. During ball milling, the material accumulates heat, which can cause some material to caking and ultimately result in incomplete calcination. Therefore, this application employs intermittent operation.

[0017] This application uses a centrifuge at low speed to separate the solid and liquid phases, retaining a portion of the cyclohexane liquid within the solid (enough to cover the material). Retaining the cyclohexane portion primarily prevents the high surface energy powder from being oxidized by direct contact with air after ball milling. The material containing the cyclohexane portion is placed in a covered alumina boat, and the drying process uses 80℃ and a high flow rate to quickly remove the cyclohexane vapor. Nano-tungsten oxide is reduced to highly active tungsten powder at a reduction temperature of 900℃, facilitating the subsequent solid-phase reaction between W and Si. The calcination holding temperature is 1380-1450℃, and the holding time is 20-40 minutes; excessively high temperatures and holding times will cause WSi2 to clump together, while excessively low temperatures and holding times will result in uncalcined Si particles remaining in the material.

[0018] This application employs multiple methods to prevent the oxidation of Si and avoid the formation of silicon oxide; it uses highly active tungsten powder obtained by reducing nano-tungsten oxide to shorten the calcination time; it ensures sufficient sintering inside and outside the sample; and it uses rapid calcination at high temperature for a short time to make the WSi2 powder loose and prevent it from caking. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a SEM image of the surface of the high-purity tungsten silicide prepared in Example 1 of this application; Figure 2 This is a SEM image of the cross-section of the high-purity tungsten silicide prepared in Example 1 of this application; Figure 3 The XRD pattern of the high-purity tungsten silicide prepared in Example 1 of this application; Figure 4 This is a SEM image of the cross-section of the high-purity tungsten silicide prepared in Example 2 of this application; Figure 5 This is a SEM image of the cross-section of the high-purity tungsten silicide prepared in Example 3 of this application; Figure 6 SEM image of the surface of high-purity tungsten silicide prepared in Comparative Example 2 of this application; Figure 7 This is a SEM image of the cross-section of the high-purity tungsten silicide prepared in Comparative Example 2 of this application; Figure 8 SEM image of the surface of high-purity tungsten silicide prepared in Comparative Example 6 of this application; Figure 9SEM image of the cross section of high-purity tungsten silicide prepared in Comparative Example 6 of this application; Figure 10 The image shows the XRD pattern of the high-purity tungsten silicide prepared in Comparative Example 6 of this application.

[0021] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] This application provides a method for preparing high-purity tungsten silicide, comprising the following steps: S1. Obtain silicon powder and nano-tungsten oxide. Mix the silicon powder and nano-tungsten oxide and then perform wet milling, washing, and centrifugation to obtain a mixed slurry. The medium for wet milling is cyclohexane. The silicon powder has a particle size of 10-20 μm, and the nano-tungsten oxide has a specific surface area of ​​11-13 m². 2 / g, the molar ratio of the silicon powder and the nano-tungsten oxide is 2:1; the wet milling is carried out in a planetary ball mill, the grinding balls and the inner wall of the grinding jar are made of cemented carbide, the wet milling is carried out intermittently, every 10-20 minutes, the machine is stopped and waited for 5-10 minutes before restarting, the rotation speed of the wet milling is 200-240 r / min, the total time of the wet milling is 3-4 hours, the atmosphere of the wet milling is argon; the washing uses cyclohexane as the washing agent, and the mixed slurry contains cyclohexane covering all solids.

[0024] S2. The mixed slurry is placed in a covered alumina boat for drying, reduction, calcination, and natural cooling to obtain high-purity tungsten silicide. The drying process involves a heating rate of 8-12℃ / min, a holding temperature of 60-85℃, a holding time of 40-90min, and an argon atmosphere with a flow rate ≥4L / min. The reduction process involves a heating rate of 8-12℃ / min, a holding temperature of 880-920℃, a holding time of 1-2h, and a hydrogen atmosphere with a flow rate of 0.8-1.2L / min. The calcination process involves a heating rate of 3-6℃ / min, a holding temperature of 1380-1450℃, a holding time of 20-40min, and an argon atmosphere with a flow rate of 1-3L / min. Specifically, the calcination holding temperature is any one or any two of 1380℃, 1390℃, 1400℃, 1410℃, 1420℃, 1430℃, 1440℃, and 1450℃, and the calcination holding time is any one or any two of 20min, 25min, 30min, 35min, and 40min.

[0025] This application also provides a high-purity tungsten silicide, comprising: the microstructure of the high-purity tungsten silicide comprises more than 96.0 wt% WSi2 and less than 4 wt% W5Si3, wherein the WSi2 crystal form is a body-centered tetragonal structure under standard conditions; the oxygen content of the high-purity tungsten silicide is ≤0.05%.

[0026] The technical solution of this application will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] This application provides a method for preparing high-purity tungsten silicide, comprising the following steps: S1. Obtain silicon powder and nano-tungsten oxide. Mix the silicon powder and nano-tungsten oxide, then wet-mill, wash, and centrifuge to obtain a mixed slurry. The medium for wet milling is cyclohexane. The silicon powder has a particle size of 15 μm, and the specific surface area of ​​the nano-tungsten oxide is 12 m². 2 / g, the molar ratio of silicon powder and nano-tungsten oxide is 2:1; wet milling is carried out in a planetary ball mill, the grinding balls and the inner wall of the grinding jar are made of cemented carbide, the wet milling is intermittently operated, every 15 minutes of operation, stop for 8 minutes and then restart, the speed of wet milling is 220 r / min, the total time of wet milling is 3.5h, the atmosphere of wet milling is argon; cyclohexane is used as the washing agent, the mixed slurry contains cyclohexane covering all solids.

[0029] S2. The mixed slurry is placed in a covered alumina boat for drying, reduction, calcination, and natural cooling to obtain high-purity tungsten silicide; The drying process involves a heating rate of 10℃ / min, a holding temperature of 75℃, a holding time of 60min, and an argon atmosphere with a flow rate ≥4L / min. The reduction process involves a heating rate of 10℃ / min, a holding temperature of 900℃, a holding time of 1.5h, and a hydrogen atmosphere with a flow rate of 1.0L / min. The calcination process involves a heating rate of 4℃ / min, a holding temperature of 1400℃, a holding time of 30min, and an argon atmosphere with a flow rate of 2L / min.

[0030] For testing of the prepared high-purity tungsten silicide, please refer to [link / reference]. Figure 1 , Figure 2 , Figure 3 , Figure 1 This is a SEM image of the surface of the high-purity tungsten silicide prepared in Example 1 of this application; Figure 2 This is a SEM image of the cross-section of the high-purity tungsten silicide prepared in Example 1 of this application; Figure 3 The image shows the XRD pattern of the high-purity tungsten silicide prepared in Example 1 of this application. The results show that the microstructure of the high-purity tungsten silicide includes 96.7 wt% WSi2 and 3.1 wt% W5Si3, wherein the WSi2 crystal form is a body-centered tetragonal structure under standard conditions. The oxygen content of the high-purity tungsten silicide is 0.038%. The XRD image shows that the main phase of the obtained powder is WSi2, with only a small amount of W5Si3. The cross-sectional SEM image of the powder shows that the powder is fully sintered inside, and W and Si elements are uniformly distributed.

[0031] Example 2

[0032] This application provides a method for preparing high-purity tungsten silicide, comprising the following steps: S1. Obtain silicon powder and nano-tungsten oxide. Mix the silicon powder and nano-tungsten oxide, then wet-mill, wash, and centrifuge to obtain a mixed slurry. The medium for wet milling is cyclohexane. The silicon powder has a particle size of 10 μm, and the specific surface area of ​​the nano-tungsten oxide is 13 m². 2 / g, the molar ratio of silicon powder and nano-tungsten oxide is 2:1; wet milling is carried out in a planetary ball mill, the grinding balls and the inner wall of the grinding jar are made of cemented carbide, the wet milling is intermittent, every 10 minutes of operation, stop for 5 minutes and then restart, the speed of wet milling is 200 r / min, the total time of wet milling is 3 hours, the atmosphere of wet milling is argon; cyclohexane is used as the washing agent, the mixed slurry contains cyclohexane covering all solids.

[0033] S2. The mixed slurry is placed in a covered alumina boat for drying, reduction, calcination, and natural cooling to obtain high-purity tungsten silicide; The drying process involves a heating rate of 8℃ / min, a holding temperature of 60℃, a holding time of 40min, and an argon atmosphere with a flow rate ≥4L / min. The reduction process involves a heating rate of 8℃ / min, a holding temperature of 880℃, a holding time of 1h, and a hydrogen atmosphere with a flow rate of 0.8L / min. The calcination process involves a heating rate of 3℃ / min, a holding temperature of 1380℃, a holding time of 20min, and an argon atmosphere with a flow rate of 1L / min.

[0034] For testing of the prepared high-purity tungsten silicide, please refer to [link / reference]. Figure 4 , Figure 4 The image shows a SEM image of the cross-section of the high-purity tungsten silicide prepared in Example 2 of this application. The results show that the microstructure of the high-purity tungsten silicide includes 97.2 wt% WSi2 and 2.4 wt% W5Si3, wherein the WSi2 crystal form is a body-centered tetragonal structure under standard conditions. The oxygen content of the high-purity tungsten silicide is 0.040%. The SEM image of the powder cross-section shows that the powder is fully sintered and the W and Si elements are uniformly distributed.

[0035] Example 3

[0036] This application provides a method for preparing high-purity tungsten silicide, comprising the following steps: S1. Obtain silicon powder and nano-tungsten oxide. Mix the silicon powder and nano-tungsten oxide, then wet-mill, wash, and centrifuge to obtain a mixed slurry. The medium for wet milling is cyclohexane. The silicon powder has a particle size of 20 μm, and the specific surface area of ​​the nano-tungsten oxide is 11 m². 2 / g, the molar ratio of silicon powder and nano-tungsten oxide is 2:1; wet milling is carried out in a planetary ball mill, the grinding balls and the inner wall of the grinding jar are made of cemented carbide, the wet milling is intermittently operated, every 20 minutes of operation, stop for 10 minutes and then restart, the speed of wet milling is 240 r / min, the total time of wet milling is 4 hours, the atmosphere of wet milling is argon; cyclohexane is used as the washing agent, the mixed slurry contains cyclohexane covering all solids.

[0037] S2. The mixed slurry is placed in a covered alumina boat for drying, reduction, calcination, and natural cooling to obtain high-purity tungsten silicide; The drying process involves a heating rate of 12℃ / min, a holding temperature of 85℃, a holding time of 90min, and an argon atmosphere with a flow rate ≥4L / min. The reduction process involves a heating rate of 12℃ / min, a holding temperature of 920℃, a holding time of 2h, and a hydrogen atmosphere with a flow rate of 1.2L / min. The calcination process involves a heating rate of 6℃ / min, a holding temperature of 1450℃, a holding time of 40min, and an argon atmosphere with a flow rate of 3L / min.

[0038] For testing of the prepared high-purity tungsten silicide, please refer to [link / reference]. Figure 5 , Figure 5 The image shows a SEM image of the cross-section of the high-purity tungsten silicide prepared in Example 3 of this application. The results show that the microstructure of the high-purity tungsten silicide includes 96.1 wt% WSi2 and 3.1 wt% W5Si3, wherein the WSi2 crystal form is a body-centered tetragonal structure under standard conditions. The oxygen content of the high-purity tungsten silicide is 0.043%. The SEM image of the powder cross-section shows that the powder is fully sintered and the W and Si elements are uniformly distributed.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the particle size of the silicon powder in step S1 is 5 μm, while the other steps are the same as in Example 1.

[0040] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide consisted of 95.3 wt% WSi2 and 3.2 wt% W5Si3, and the oxygen content of the high-purity tungsten silicide was 1.140%.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the particle size of the silicon powder in step S1 is 40 μm, while the other steps are the same as in Example 1.

[0042] For testing of the prepared high-purity tungsten silicide, please refer to [link / reference]. Figure 6 , Figure 7 , Figure 6 SEM image of the surface of high-purity tungsten silicide prepared in Comparative Example 2 of this application; Figure 7 The image shows a SEM image of the cross-section of the high-purity tungsten silicide prepared in Comparative Example 2 of this application. The results show that the microstructure of the high-purity tungsten silicide includes 89.4 wt% WSi2 and 10.2 wt% W5Si3 and residual elemental Si, and the oxygen content of the high-purity tungsten silicide is 0.026%.

[0043] Comparative Example 3 The difference between this comparative example and Example 1 is that the wet grinding medium in step S1 is anhydrous ethanol, while the other steps are the same as in Example 1.

[0044] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide consisted of 90.1 wt% WSi2 and 7.9 wt% W5Si3, and the oxygen content of the high-purity tungsten silicide was 1.570%.

[0045] Comparative Example 4 The difference between this comparative example and Example 1 is that the wet grinding in step S1 is carried out continuously, and the total wet grinding time is 3 hours. The other steps are the same as in Example 1.

[0046] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide consisted of 93.7 wt% WSi2 and 4.2 wt% W5Si3, the oxygen content of the high-purity tungsten silicide was 1.361%, and the high-purity tungsten silicide exhibited agglomeration.

[0047] Comparative Example 5 The difference between this comparative example and Example 1 is that the calcination holding temperature in step S2 is 1550°C, while the other steps are the same as in Example 1.

[0048] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide consisted of 97.3 wt% WSi2 and 2.5 wt% W5Si3, the oxygen content of the high-purity tungsten silicide was 0.041%, and the high-purity tungsten silicide exhibited agglomeration.

[0049] Comparative Example 6 The difference between this comparative example and Example 1 is that the calcination holding temperature in step S2 is 1300℃, while the other steps are the same as in Example 1.

[0050] For testing of the prepared high-purity tungsten silicide, please refer to [link / reference]. Figure 8 , Figure 9 , Figure 10 , Figure 8 SEM image of the surface of high-purity tungsten silicide prepared in Comparative Example 6 of this application; Figure 9 SEM image of the cross section of high-purity tungsten silicide prepared in Comparative Example 6 of this application; Figure 10 The image shows the XRD pattern of the high-purity tungsten silicide prepared in Comparative Example 6 of this application. The results show that the microstructure of the high-purity tungsten silicide includes 89.9 wt% WSi2 and 9.8 wt% W5Si3 and residual elemental Si. The oxygen content of the high-purity tungsten silicide is 0.033%. The XRD image shows that the main phase of the obtained powder is WSi2, and in addition to a small amount of W5Si3, there is also residual elemental Si.

[0051] Comparative Example 7 The difference between this comparative example and Example 1 is that the calcination holding time in step S2 is 1 hour, while the other steps are the same as in Example 1.

[0052] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide consisted of 96.4 wt% WSi2 and 3.5 wt% W5Si3, the oxygen content of the high-purity tungsten silicide was 0.049%, and the high-purity tungsten silicide exhibited agglomeration.

[0053] Comparative Example 8 The difference between this comparative example and Example 1 is that the holding time for calcination in step S2 is 10 minutes, while the other steps are the same as in Example 1.

[0054] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide included 92.3 wt% WSi2, 7.3 wt% W5Si3 and residual elemental Si, and the oxygen content of the high-purity tungsten silicide was 0.046%.

[0055] Comparative Example 9 The difference between this comparative example and Example 1 is that micron-sized tungsten oxide is used in step S1, while the other steps are the same as in Example 1.

[0056] The high-purity tungsten silicide prepared was tested, and the results showed that the microstructure of the high-purity tungsten silicide included 91.0 wt% WSi2, 8.8 wt% W5Si3 and residual elemental W, and the oxygen content of the high-purity tungsten silicide was 0.027%.

[0057] As can be seen from the above embodiments and comparative examples: Example 1, in conjunction with Comparative Example 1, shows that Si powder raw materials with excessively small particle size have a high oxygen content, and the oxygen in silicon oxides cannot be reduced and removed by hydrogen, ultimately resulting in a high oxygen content in the product.

[0058] Example 1, combined with Comparative Example 2, shows that when the silicon powder particle size is too large, the particle size remains too large after ball milling, resulting in incomplete sintering. The SEM image of the particle cross-section shows that elemental Si still exists in the central part of the product particles.

[0059] Example 1, in conjunction with Comparative Example 3, shows that wet milling using a water-absorbing solvent, even under an argon atmosphere, will increase the oxygen content after ball milling.

[0060] Example 1, in conjunction with Comparative Example 4, shows that without intermittent wet milling, the surface energy of the material after ball milling is too high, leading to caking.

[0061] Example 1, in conjunction with Comparative Example 5, shows that the raw material after wet milling already possesses high activity. Excessive calcination temperature will cause the product to overheat and caking.

[0062] Example 1, in conjunction with Comparative Example 6, shows that excessively low calcination temperatures lead to incomplete sintering, with elemental silicon still present in the central region.

[0063] Example 1, in conjunction with Comparative Example 7, shows that excessive calcination time leads to product caking.

[0064] Example 1, in conjunction with Comparative Example 8, shows that insufficient holding time during calcination leads to incomplete sintering and the presence of a significant amount of elemental Si.

[0065] Example 1, in conjunction with Comparative Example 9, shows that using micron-sized tungsten oxide as a tungsten source, a shorter time is insufficient to complete the sintering process.

[0066] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for preparing high-purity tungsten silicide, characterized in that, Includes the following steps: S1. Obtain silicon powder and nano-tungsten oxide. Mix the silicon powder and nano-tungsten oxide and then perform wet milling, washing, and centrifugation to obtain a mixed slurry. The medium for wet milling is cyclohexane. S2. The mixed slurry is placed in a covered alumina boat for drying, reduction, calcination, and natural cooling to obtain high-purity tungsten silicide.

2. The method for preparing high-purity tungsten silicide according to claim 1, characterized in that, In step S1, the silicon powder has a particle size of 10-20 μm, and the nano-tungsten oxide has a specific surface area of ​​11-13 m². 2 / g, wherein the molar ratio of the silicon powder and the nano-tungsten oxide is 2:

1.

3. The method for preparing high-purity tungsten silicide according to claim 1, characterized in that, In step S1, the wet grinding is carried out in a planetary ball mill. The grinding balls and the inner wall of the grinding jar are made of cemented carbide. The wet grinding is carried out intermittently, with a stop time of 5-10 minutes after every 10-20 minutes of operation. The rotation speed of the wet grinding is 200-240 r / min. The total time of the wet grinding is 3-4 hours. The atmosphere for the wet grinding is argon.

4. The method for preparing high-purity tungsten silicide according to claim 1, characterized in that, In step S1, cyclohexane is used as the washing agent, and the mixed slurry contains cyclohexane that covers all solids.

5. The method for preparing high-purity tungsten silicide according to claim 1, characterized in that, In step S2, the heating rate of the drying process is 8-12℃ / min, the holding temperature of the drying process is 60-85℃, the holding time of the drying process is 40-90min, the drying atmosphere is argon, and the flow rate of the argon is ≥4L / min.

6. The method for preparing high-purity tungsten silicide according to claim 1, characterized in that, In step S2, the heating rate of the reduction is 8-12℃ / min, the holding temperature of the reduction is 880-920℃, the holding time of the reduction is 1-2h, the atmosphere of the reduction is hydrogen, and the flow rate of the hydrogen is 0.8-1.2L / min.

7. The method for preparing high-purity tungsten silicide according to claim 1, characterized in that, In step S2, the heating rate of calcination is 3-6℃ / min, the holding temperature of calcination is 1380-1450℃, the holding time of calcination is 20-40min, the atmosphere of calcination is argon, and the flow rate of argon is 1-3L / min.

8. A high-purity tungsten silicide, characterized in that, It is prepared by the method for preparing high-purity tungsten silicide according to any one of claims 1-7.

9. The high-purity tungsten silicide according to claim 8, characterized in that, The high-purity tungsten silicide has a microstructure comprising more than 96.0 wt% WSi2 and less than 4 wt% W5Si3, wherein the WSi2 crystal form is a body-centered tetragonal structure under standard conditions.

10. The high-purity tungsten silicide according to claim 8, characterized in that, The oxygen content of the high-purity tungsten silicide is ≤0.05%.

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