An apparatus for producing an ultra-long directional alpha-phase silicon nitride fiber array and a method of manufacturing the same

Abstract

The application discloses a production device of an ultra-long directional alpha-phase silicon nitride fiber array and a preparation method thereof. The device comprises a reaction kiln and a high-temperature synthesis furnace. The reaction kiln is composed of a silicon nitride substrate, a ceramic baffle and a ceramic cover plate. The high-temperature synthesis furnace is a vacuum high-temperature furnace, and the chamber of the high-temperature synthesis furnace is arranged with a vacuum extraction port, an air inlet, an air outlet, an emergency pressure relief port and a vacuum pressure gauge. The ultra-long directional alpha-phase silicon nitride fiber array is prepared by using the device under the condition that there is no any metal or metal catalytic salt, by taking ammonia and silicon tetrahalide as source gas and by reacting at high temperature. The preparation device of the application is simple. The kiln composed of the silicon nitride substrate, the ceramic baffle and the ceramic cover plate with a circular hole in the center provides a growth substrate for the silicon nitride fiber. By stacking the kiln, the large-scale preparation of the silicon nitride fiber array can be realized. The ultra-long alpha-phase silicon nitride fiber array can be prepared without any metal and metal salt catalyst, and there is no metal impurity.

Description

Technical Field

[0001] This invention relates to the field of non-oxide ceramic powder material preparation technology, and in particular to a production apparatus and preparation method for an ultra-long oriented α-phase silicon nitride fiber array. Background Technology

[0002] Silicon nitride possesses advantages such as high strength, high hardness, good chemical stability, heat and wear resistance, wide bandgap, and high theoretical thermal conductivity. Therefore, silicon nitride powder has significant application potential in industries such as semiconductors, metallurgy, aerospace, machinery, photovoltaics, medical devices, and precision grinding. Silicon nitride fibers, due to their unique microstructure, surpass the physicochemical properties of bulk silicon nitride materials. The microstructure characteristics of the fibers endow silicon nitride fibers with wide bandgap semiconductor properties and mechanical properties such as high elastic modulus. These properties of silicon nitride fibers demonstrate their immense application value in the fields of micro / nano semiconductors and modified and reinforced materials based on metals, ceramics, and polymers.

[0003] Current methods for preparing silicon nitride fibers mainly include thermal evaporation, metal-assisted chemical vapor deposition (MACVD), heat treatment dry gelation, and template methods. These methods generally suffer from drawbacks such as complex processes, high equipment requirements, metal impurity contamination, and difficulty in large-scale production. In MACVD, a common procedure involves using graphite soaked in a solution containing Ni or Co metal ions as a substrate, followed by heating silicon powder under a nitrogen atmosphere. Guided by metal ions, silicon nitride grows directionally from the graphite substrate into silicon nitride fibers. This method introduces metal impurities, affecting the high-temperature mechanical properties and creep resistance of the silicon nitride fibers. Therefore, it is necessary to design a device with a simple structure and process to meet the needs of silicon nitride fiber production. Summary of the Invention

[0004] The purpose of this invention is to provide a production apparatus and preparation method for ultralong oriented α-phase silicon nitride fiber arrays. Using this apparatus, ultralong oriented α-phase silicon nitride fiber arrays are prepared by reacting ammonia and silicon tetrahalide as source gases at high temperature without any metal or metal catalyst salt. This is achieved through the following technical solutions:

[0005] This invention provides a production apparatus for ultra-long oriented α-phase silicon nitride fiber arrays, comprising a reaction sagger and a matching high-temperature synthesis furnace. The reaction sagger consists of a silicon nitride substrate, a ceramic baffle, and a ceramic cover plate; the high-temperature synthesis furnace is a vacuum high-temperature furnace, with a vacuum port, an air inlet, an air outlet, an emergency pressure relief port, and a vacuum pressure gauge arranged in its chambers.

[0006] Furthermore, the ceramic baffle and ceramic cover plate of the present invention are made of one of the following non-silicon nitride materials: corundum, zirconium oxide, mullite, and silicon carbide.

[0007] Furthermore, the ceramic cover plate of the present invention has a central circular hole with a diameter of 5 to 10 cm;

[0008] Furthermore, the silicon nitride substrate described in this invention is an unpolished reactive sintered silicon nitride ceramic substrate.

[0009] Another aspect of the present invention provides a method for preparing ultralong oriented α-phase silicon nitride fiber arrays using a silicon nitride fiber array production apparatus, comprising the following steps:

[0010] (1) Place the reaction sagger in the homogenization zone of the high-temperature synthesis furnace.

[0011] (2) Evacuate the high-temperature synthesis furnace until the gas pressure inside the furnace is less than 50 Pa; then raise the temperature to 900-1000℃ at a rate of 5-10℃ / min and hold for 0.5-2 hours to make the reaction box reach a uniform temperature.

[0012] (3) The mixture of argon and silicon tetrahalide is introduced into the reaction vessel through the inlet corresponding to the central hole of the ceramic cover plate at a flow rate of 1 to 30 L / min to -80 to -60 kPa; then the argon and silicon tetrahalide valves are closed to stop the introduction; then the temperature is increased to 1250 to 1350℃ at a heating rate of 0.1 to 2℃ / min and held for 0.5 to 2 hours to make the reaction vessel reach a uniform temperature.

[0013] (4) Open the ammonia valve connected to the gas inlet on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrahalide valve connected to the gas inlet corresponding to the center hole of the ceramic cover plate of the reaction sagger. Adjust the gas flow rate to 1-50 L / min and charge the furnace to a pressure of 50 kPa; then close the ammonia, argon, and silicon tetrahalide valves to stop charging; when the pressure inside the furnace expands to 80 kPa, open the gas outlet valve to release the gas to 20 kPa. During this process, keep the furnace temperature constant at 1250-1350 °C.

[0014] (5) Keep the furnace temperature constant at 1250-1350℃ for 1-5 hours. Repeat step (4) 2-5 times to adjust the gas pressure until the reaction is complete.

[0015] (6) After the reaction is completed, the furnace is cooled to room temperature to obtain a large number of ultra-long oriented α-phase silicon nitride fiber arrays from the silicon nitride substrate.

[0016] Furthermore, in the preparation method, silicon tetrahalide is any one or a combination of silicon tetrachloride and silicon tetrafluoride.

[0017] Furthermore, in the preparation method, the purity of ammonia, argon, and silicon tetrahalide gas is 99.99-99.999%.

[0018] Furthermore, in the preparation method, step (2) involves evacuating the high-temperature synthesis furnace to a vacuum level of less than 50 Pa, preferably less than or equal to 20 Pa;

[0019] Furthermore, in the preparation method, the volume ratio of argon gas and silicon tetrahalide mixed gas in step (3) is (85-95):(5-15).

[0020] Furthermore, in the preparation method, the volume ratio of ammonia, argon and silicon tetrahalide gas in step (4) is (50-70):(25-40):(5-10).

[0021] This invention is based on the inventors' extensive systematic experimental research on ultralong oriented α-phase silicon nitride fiber arrays. Through the design of a simple apparatus, without metal assistance, silicon nitride substrates are used as substrates, and ammonia and silicon tetrahalide are used as reactant gases. Silicon tetrahalide gas with argon as the carrier gas is introduced first, and then ammonia is introduced after reaching the target temperature. The silicon nitride fibers are synthesized statically using an intermittent gas-filling method. The resulting silicon nitride fibers exhibit an oriented array, all being α-phase.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) The silicon nitride fiber preparation device of the present invention is simple. The sagger composed of silicon nitride substrate, ceramic baffle and ceramic cover plate with round hole in the center provides growth substrate for silicon nitride fiber. By stacking saggers, the large-scale preparation of silicon nitride fiber array can be realized.

[0024] (2) The present invention can prepare ultra-long α-phase silicon nitride fiber arrays without any metal or metal salt catalysts, and there are no metal impurities present.

[0025] (3) The silicon nitride fibers prepared by the present invention have a single length of more than centimeters, are arranged in an array, and can be separated, which has great practical value.

[0026] (4) In the process of preparing silicon nitride fibers, the present invention adopts an intermittent gas filling method. During the preparation process, the synthesis gas is in a static mode for most of the time. This method is conducive to the directional growth of silicon nitride fibers and can greatly improve the utilization rate of synthesis gas and reduce the waste of synthesis gas. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the device of the present invention.

[0028] Figure 2 This is a cross-sectional view of the reaction sagger in the apparatus of the present invention.

[0029] Figure 3 This is a top view of the reaction sagger in the apparatus of the present invention.

[0030] Figure 4 This is a physical image of the ultra-long oriented α-phase silicon nitride fiber array of Embodiment 1 of the present invention.

[0031] Figure 5 The image shows the XRD pattern of the ultra-long oriented α-phase silicon nitride fiber array of Embodiment 1 of the present invention.

[0032] Figure 6 This is a SEM microstructure image (10,000x magnification) of the ultralong oriented α-phase silicon nitride fiber array of Embodiment 1 of the present invention.

[0033] Illustration: 101-Silicon nitride substrate; 102-Ceramic baffle; 103-Ceramic cover plate with a central hole; 201-Vacuum pressure gauge; 202-Emergency pressure relief port; 203-Outlet; 204-Vacuum port; 205-Inlet I; 206-Inlet II. Detailed Implementation

[0034] This invention will be further described with reference to the accompanying drawings and the following embodiments. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention and therefore only showing the components relevant to the invention. Furthermore, the technical solution for synthesizing ultralong α-phase silicon nitride fiber arrays using the apparatus of this invention and its scope of protection include, but are not limited to, the following embodiments.

[0035] like Figure 1-3 As shown, Figure 1 This is a schematic diagram of the device of the present invention. Figure 2 This is a cross-sectional view of the reaction sagger in the apparatus of the present invention. Figure 3 This is a top view of the reaction sagger in the apparatus of the present invention. The reaction sagger consists of a silicon nitride substrate 101, a ceramic baffle 102, and a ceramic cover plate 103 with a central circular hole. The reaction sagger, as the chamber for silicon nitride fiber growth, restricts the diffusion range of halide gases, increasing the probability of gas-phase reaction between ammonia and halide gases. Simultaneously, the unpolished sintered silicon nitride substrate, serving as the substrate for silicon nitride fiber growth, is beneficial for the nucleation and growth of silicon nitride fibers. The reaction saggers are arranged as follows... Figure 1 In the homogenization zone of the high-temperature synthesis furnace shown, the furnace chamber pressure is first evacuated to less than 50 Pa through vacuum port 204. Then, a mixture of argon and silicon tetrahalide gas is introduced through inlet II 206, followed by ammonia gas through inlet I 205. Based on the pressure reading on vacuum pressure gauge 201, the gas is discharged from outlet 203 when the pressure reaches 80 kPa. Emergency pressure relief port 202 acts as an emergency pressure relief valve, automatically releasing pressure when the furnace chamber pressure exceeds 100 kPa. Following the provided synthesis method, ultralong oriented α-phase silicon nitride fiber arrays can be fabricated, further illustrated by the following specific implementation example.

[0036] Example 1.

[0037] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to an internal pressure of 20 Pa; then raise the temperature to 900 °C at a rate of 5 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrachloride (85:15 by volume) at a flow rate of 30 L / min through inlet II 206, corresponding to the central hole of the ceramic cover plate, to -60 kPa; then close the argon and silicon tetrachloride valves to stop the inflator; then raise the temperature to 1250 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I 205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrachloride valve connected to inlet II 206, corresponding to the central hole of the ceramic cover plate. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrachloride = 70:25:5, and the mixed gas was charged at 50 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrachloride valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated three times, maintaining the furnace temperature at 1250 °C for 3 hours. After the reaction, the furnace was cooled to room temperature, yielding a large array of ultralong oriented α-phase silicon nitride fibers on the silicon nitride substrate. Figure 4 This is a physical image of the ultra-long oriented α-phase silicon nitride fiber array of Embodiment 1 of the present invention. Figure 5 The image shows the XRD pattern of the ultra-long oriented α-phase silicon nitride fiber array of Embodiment 1 of the present invention. Figure 6 This is a SEM microstructure image (10000x magnification) of the ultralong oriented α-phase silicon nitride fiber array of Example 1 of the present invention. As can be seen from the physical image and SEM image, the prepared silicon nitride fibers exhibit an array-like structure with good size uniformity, and a diameter of approximately 2 μm. The XRD pattern shows that the prepared silicon nitride fibers are all α-phase, with no β-phase present.

[0038] Example 2.

[0039] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to an internal pressure of 20 Pa; then raise the temperature to 900 °C at a rate of 10 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrafluoride (85:15 by volume) at a flow rate of 30 L / min through inlet II 206, corresponding to the central hole of the ceramic cover plate, to -60 kPa; then close the argon and silicon tetrafluoride valves to stop the inflator; then raise the temperature to 1250 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I 205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrafluoride valve connected to inlet II 206, corresponding to the central hole of the ceramic cover plate. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrafluoride = 70:25:5, and the mixed gas was charged at 50 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrafluoride gas valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated three times, maintaining the furnace temperature at 1250 °C for 3 hours. After the reaction, the furnace was cooled to room temperature, yielding a large array of ultralong oriented α-phase silicon nitride fibers on the silicon nitride substrate.

[0040] Example 3.

[0041] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to a pressure of 15 Pa; then raise the temperature to 1000 °C at a rate of 5 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrafluoride (95:5 volume ratio) at a flow rate of 20 L / min through inlet II 206, corresponding to the central hole of the ceramic cover plate, to -80 kPa; then close the argon and silicon tetrafluoride valves to stop the inflator; then raise the temperature to 1300 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I 205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrafluoride valve connected to inlet II 206, corresponding to the central hole of the ceramic cover plate. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrafluoride = 60:30:10, and the mixed gas was charged at 50 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrafluoride gas valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated four times, maintaining the furnace temperature at 1300 °C for 4 hours. After the reaction, the furnace was cooled to room temperature, yielding a large array of ultralong oriented α-phase silicon nitride fibers on the silicon nitride substrate.

[0042] Example 4.

[0043] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to an internal pressure of 20 Pa; then raise the temperature to 900 °C at a rate of 5 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrachloride (volume ratio 95:5) at a flow rate of 20 L / min through inlet II 206 corresponding to the central hole of the ceramic cover plate to -80 kPa; then close the argon and silicon tetrachloride valves to stop the inflator; then raise the temperature to 1350 °C at a rate of 2 °C / min and hold for 1 hour to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrachloride valve connected to inlet II 206 corresponding to the central hole of the ceramic cover plate of the reaction crucible. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrachloride = 60:30:10, and the mixed gas was charged at 30 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrachloride valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated three times, maintaining the furnace temperature at 1350 °C for 3 hours. After the reaction, the furnace was cooled to room temperature, yielding a large array of ultralong oriented α-phase silicon nitride fibers on the silicon nitride substrate.

[0044] Example 5.

[0045] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to a pressure of 15 Pa; then raise the temperature to 1000 °C at a rate of 5 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrafluoride (95:5 volume ratio) at a flow rate of 25 L / min through inlet II 206, corresponding to the central hole of the ceramic cover plate, to -60 kPa; then close the argon and silicon tetrafluoride valves to stop the inflator; then raise the temperature to 1280 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I 205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrafluoride valve connected to inlet II 206, corresponding to the central hole of the ceramic cover plate. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrafluoride = 70:25:5, and the mixed gas was charged at 40 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrafluoride gas valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated three times, maintaining the furnace temperature at 1280 °C for 4 hours. After the reaction, the furnace was cooled to room temperature, yielding a large array of ultralong oriented α-phase silicon nitride fibers on the silicon nitride substrate.

[0046] Example 6.

[0047] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to an internal pressure of 20 Pa; then raise the temperature to 950 °C at a rate of 10 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrachloride (volume ratio 90:10) at a flow rate of 20 L / min through inlet II 206 corresponding to the central hole of the ceramic cover plate to -70 kPa; then close the argon and silicon tetrachloride valves to stop the inflator; then raise the temperature to 1300 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I 205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrachloride valve connected to inlet II 206 corresponding to the central hole of the ceramic cover plate of the reaction crucible. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrachloride = 50:40:10, and the mixed gas was charged at 45 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrachloride valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated four times, maintaining the furnace temperature at 1300 °C for 5 hours. After the reaction, the furnace was cooled to room temperature, yielding a large array of ultralong oriented α-phase silicon nitride fibers on the silicon nitride substrate.

[0048] Comparative Example 1.

[0049] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to an internal pressure of 20 Pa; then raise the temperature to 900 °C at a rate of 5 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrachloride (volume ratio 95:5) at a flow rate of 30 L / min through inlet II 206 corresponding to the central hole of the ceramic cover plate to -80 kPa; then close the argon and silicon tetrachloride valves to stop the inflator; then raise the temperature to 1250 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the nitrogen valve connected to inlet I205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrachloride valve connected to inlet II 206 corresponding to the central hole of the ceramic cover plate of the reaction crucible. The gas flow rate ratio was adjusted to nitrogen:argon:silicon tetrachloride = 50:40:10, and the mixed gas was charged at 50 L / min until the furnace pressure reached 50 kPa. Then, the nitrogen, argon, and silicon tetrachloride valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas to 20 kPa. This intermittent charging and releasing process was repeated four times, maintaining the furnace temperature at 1250 °C for 5 hours. After the reaction, the furnace was cooled to room temperature. No ultralong oriented α-phase silicon nitride fiber array was obtained on the silicon nitride substrate.

[0050] Comparative Example 2.

[0051] Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace. Evacuate the high-temperature synthesis furnace to an internal pressure of 20 Pa; then raise the temperature to 100 °C at a rate of 5 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Inflate the reaction crucible with a mixture of argon and silicon tetrachloride (volume ratio 95:5) at a flow rate of 30 L / min through inlet II 206 corresponding to the central hole of the ceramic cover plate to -80 kPa; then close the argon and silicon tetrachloride valves to stop the inflator; then raise the temperature to 1350 °C at a rate of 2 °C / min and hold for 2 hours to achieve homogenization throughout the reaction crucible. Open the ammonia valve connected to inlet I205 on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrachloride valve connected to inlet II 206 corresponding to the central hole of the ceramic cover plate of the reaction crucible. The gas flow rate ratio was adjusted to ammonia:argon:silicon tetrachloride = 40:50:10, and the mixed gas was charged at 50 L / min until the furnace pressure reached 50 kPa. Then, the ammonia, argon, and silicon tetrachloride valves were closed to stop the charging. When the furnace pressure expanded to 80 kPa, the outlet valve was opened to release gas down to 20 kPa. This intermittent charging and releasing process was repeated four times, maintaining the furnace temperature at 1350 °C for 5 hours. After the reaction, the furnace was cooled to room temperature, yielding a trace amount of ultralong oriented α-phase silicon nitride fiber array on the silicon nitride substrate.

Claims

1. A method for fabricating an ultralong oriented α-phase silicon nitride fiber array, characterized in that, The preparation method utilizes a production apparatus including a reaction crucible and a high-temperature synthesis furnace; the reaction crucible consists of a silicon nitride substrate, a ceramic baffle, and a ceramic cover plate; the high-temperature synthesis furnace is a vacuum high-temperature furnace, its chambers are arranged with a vacuum port, an air inlet, an air outlet, an emergency pressure relief port, and a vacuum pressure gauge; the preparation method includes the following steps: Step 1: Place the reaction crucible in the homogenization zone of the high-temperature synthesis furnace; Step 2: Evacuate the high-temperature synthesis furnace until the internal pressure is less than 50 Pa; then raise the temperature to 900-1000℃ at a rate of 5-10℃ / min and hold for 0.5-2 hours to ensure that all parts of the reaction vessel reach a uniform temperature. Step 3: Inflate the mixture of argon and silicon tetrahalide gas through the inlet corresponding to the central hole of the ceramic cover plate of the reaction vessel at a flow rate of 1~30L / min to -80~-60Kpa; then close the argon and silicon tetrahalide gas valves to stop the inflation; then heat the mixture to 1250~1350℃ at a heating rate of 0.1~2℃ / min and hold it at that temperature for 0.5~2h to make the reaction vessel reach a uniform temperature. Step 4: Open the ammonia valve connected to the gas inlet on the side wall of the high-temperature synthesis furnace, and open the argon valve and silicon tetrahalide valve connected to the gas inlet corresponding to the central hole of the ceramic cover plate of the reaction sagger. Adjust the gas flow rate to 1~50L / min and charge the furnace to a pressure of 50Kpa; then close the ammonia, argon and silicon tetrahalide gas valves and stop charging; when the pressure inside the furnace expands to 80Kpa, open the gas outlet valve and release the gas to 20Kpa; during this process, keep the furnace temperature constant at 1250~1350℃. Step 5: Maintain the furnace temperature at 1250~1350℃ for 1~5 hours; repeat the gas pressure adjustment process in step 4 2~5 times until the reaction is complete. Step 6: After the reaction is complete, the furnace is cooled to room temperature to obtain a large number of ultra-long oriented α-phase silicon nitride fiber arrays from the silicon nitride substrate.

2. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The silicon tetrahalide is any one or a combination of silicon tetrachloride and silicon tetrafluoride.

3. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The purity of the ammonia, argon, and silicon tetrahalide gases is 99.99-99.999%.

4. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The volume ratio of the argon gas and silicon tetrahalide mixed gas in step 3 is (85~95):(5~15).

5. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The volume ratio of ammonia, argon and silicon tetrahalide gas in step 4 is (50~70):(25~40):(5~10).

6. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The ceramic baffle and ceramic cover are made of one of the following non-silicon nitride materials: corundum, zirconium oxide, mullite, and silicon carbide.

7. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The ceramic cover plate has a central circular hole with a diameter of 5-10 cm.

8. The method for fabricating an ultralong oriented α-phase silicon nitride fiber array according to claim 1, characterized in that, The silicon nitride substrate is an unpolished reactive sintered silicon nitride ceramic substrate.

Images