DE112021007872T5 - THE SEED-INDUCED MICROWAVE SYNTHETIZED SiC CRYSTAL AND THE PRODUCTION METHOD - Google Patents

Abstract

The invention discloses a SiC crystal synthesized by microwave nucleus induced and the production method, and it relates to the technical field of inorganic non-metallic materials, it includes the following steps: after uniformly mixing silica fume, nano carbon black and SiC nuclei, mixed powder is obtained, and then the mixed powder is pressed into preform, which is then heated by microwave and kept at 800~1100°C for 15~30min to synthesize SiC crystal, that is, the SiC crystal synthesized by microwave nucleus induced is obtained, compared with the nucleus induced technology currently used in the industry, the method provided by the present invention will greatly reduce the difficulty and process conditions of SiC crystal synthesis, and for the synthesis of SiC, the microwave and composite nucleus induction have good application prospects.

Description

Field of invention

The invention relates to the technical field of inorganic non-metallic materials, in particular to a SiC crystal synthesized by crystal seed-induced microwaves and the production method.

Background of the invention

SiC has the advantages of high strength, high hardness, high elastic modulus and excellent chemical stability, and is widely used in abrasives, refractories, metallurgy, machining and other fields. SiC has a large band gap, high electron mobility and excellent high-temperature electrical and thermal conductivity. It occupies a very important position in the application in semiconductors for electronic devices and heat exchangers.

At present, the process for industrial production of SiC crystal still mainly uses the traditional Acheson process.

Currently, the traditional Acheson method is still mainly used in the industrial production of SiC crystals. The production of SiC crystals using the Acheson method is characterized by cheap raw materials, simple processes and easy industrial production. However, the thermal efficiency is low, the synthesis temperature is high, the energy consumption is high, the cycle is long, the pollution is severe, and it has serious impacts on the atmospheric environment; and the crystal shape is complex and the particle size is large that cannot meet the application requirements of high-end areas. In recent years, there have been more and more new methods for producing SiC crystals, such as the sol-gel method, the chemical vapor synthesis method and the solvothermal method. However, these processes have disadvantages such as complex synthesis steps, high energy consumption and high manufacturing costs.

Summary of the invention

The purpose of the present invention is to solve the above-mentioned deficiencies in the background technology and provide the preparation method of seed crystal induced microwave synthesized SiC crystal, this method uses SiC as a good microwave absorber material in the process of seed crystal induction of microwave synthesis of SiC, the SiC seed crystal couples with microwave to form heat, which promotes the reaction of raw materials at low temperature, SiC seed crystal can be used as a crystallization platform at high temperature to promote seed crystal nucleation and growth, SiC seed crystal not only can become a local hot spot to promote raw material reaction, but also can be used as a crystal growth hot stage to induce synthetic SiC nucleation and in situ growth. Compared with the seed crystal induction technology currently used in the industry, the method in this work will greatly reduce the difficulty and process conditions of SiC crystal synthesis. Microwave and seed compound induction synthesis of SiC has good application prospects.

• nach gleichmäßigem Mischen von Silikastaub, Nanoruß und SiC-Kristallkeime wird Mischpulver erhalten, und dann wird das Mischpulver in Vorform gepresst, die dann durch Mikrowelle erhitzt und bei 800~1100°C für 15~30min gehalten wird, um SiC-Kristall zu synthetisieren, das heißt, der durch kristallkeiminduzierte mikrowellensynthetisierte SiC-Kristall wird erhalten.

The first object of the present invention is to provide a manufacturing method of the seed-induced microwave-synthesized SiC crystal, comprising the following steps:

• after uniformly mixing silica fume, nano carbon black and SiC crystal nuclei, mixed powder is obtained, and then the mixed powder is pressed into preform, which is then heated by microwave and kept at 800~1100°C for 15~30min to synthesize SiC crystal, that is, the crystal nucleus-induced microwave-synthesized SiC crystal is obtained.

Preferably, the power consumption during the microwave heating process is 200~600W/min.

Preferably, the particle size of the SiC crystal seed is 0.5-5 μm, and the amount added is 1-20% by weight of the total mass of the raw material.

Preferably, the molar ratio of silica fume to nano carbon black is 1:1~3.

Preferably, the mixed powder is prepared by mixing silica fume, nanoblack and SiC crystal seeds with absolute ethanol as a dispersing medium by the ball milling method, the rotation speed is set to 100 rpm, the ball milling is carried out for 12 hours and then it is at a temperature of 80 ° C, vacuum dried for 12 hours and obtained.

The particle size of the mixed powder is preferably ≥60 mesh.

Preferably, when heating the preform, the preform is placed in the aluminum oxide crucible and covered with quartz sand powder, then Finally, the crucible is placed in a thermal protection structure composed of the alumina incubator and the mullite thermal insulation fiber cotton, and it is heated by microwave.

The second object of the present invention is to provide a seed-induced microwave synthesized SiC crystal.

The third object of the present invention is to provide an application of a SiC crystal in semiconductors for electronic devices and heat exchangers.

• Diese Erfindung verwendet SiC als gutes Mikrowellen-Absorbermaterial im Prozess der Impfkristallinduktion der Mikrowellensynthese von SiC, der SiC-Kristallkeim koppelt mit Mikrowellen zu Wärme, die die Reaktion der Rohstoffe bei niedrigen Temperaturen fördert, SiC-Kristallkeim kann als Kristallisationsplattform bei hoher Temperatur verwendet werden, um Kristallkeimbildung und -wachstum zu fördern, also im Mikrowellen-Erwärmungsprozess, kann SiC-Kristallkeim nicht nur ein lokaler Hot-Spot werden, um die Rohstoffreaktion zu fördern, sondern kann auch als Kristallwachstums-Heißstufe verwendet werden, um synthetische SiC-Keimbildung und in-situ-Wachstum zu induzieren. Verglichen mit der derzeit in der Industrie verwendeten Kristallkeim-Induktionstechnologie wird das Verfahren in dieser Arbeit die Schwierigkeit und die Prozessbedingungen der SiC-Kristallsynthese erheblich reduzieren. Die Mikrowellen- und Kristallkeim-Verbindungsinduktionssynthese von SiC hat gute Anwendungsaussichten.

Compared with the prior art, the advantageous effects of the present invention are:

• This invention uses SiC as a good microwave absorber material in the process of seed crystal induction of microwave synthesis of SiC, the SiC crystal seed couples with microwave to form heat, which promotes the reaction of raw materials at low temperature, SiC crystal seed can be used as a crystallization platform at high temperature to promote crystal seed formation and growth, so in the microwave heating process, SiC crystal seed not only can become a local hot spot to promote raw material reaction, but also can be used as a crystal growth hot stage to induce synthetic SiC seed formation and in situ growth. Compared with the seed crystal induction technology currently used in the industry, the method in this work will greatly reduce the difficulty and process conditions of SiC crystal synthesis. Microwave and seed crystal compound induction synthesis of SiC has good application prospects.

Short description of the drawings

• is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 1~4.
• is the scanning electron microscope (SEM) photos of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 1~4.
• is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 4~6.
• is the scanning electron microscope (SEM) photos of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 4~6.
• is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 4, 7, 8.
• is the scanning electron microscope (SEM) photos of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in embodiments 4, 7, 8.

Detailed description of some embodiments

In order to enable those skilled in the art to better understand that the technical solutions of the present invention can be implemented, the present invention will be further described below in connection with specific embodiments and figures, but the cited embodiments are not intended to limit the present invention.

It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise stated; the reagents and materials used can be purchased on the market unless otherwise stated.

The type of SiC crystal seeds used in the following embodiments was α-SiC particles with a purity of 99.9% manufactured by Baofeng Hengrui New Material Co., Ltd. were obtained.

The silica fume was purchased from Shanghai Chaowei Nano Technology Co., Ltd.; the nano carbon black was purchased from Hebei Xintie Metal Material Co., Ltd.;

The technical solution of the present invention is further described below in connection with specific embodiments.

Embodiment 1

• Nanoruß und Silikastaub wurden nach dem Molverhältnis 2:1 mol abgewogen, die zugegebene Menge an 5 µm SiC-Kristallkeime betrug 20 (Gew.)% der Gesamtmasse. Unter Verwendung von absolutem Ethanol als Dispergiermedium wurden Nanoruß, Silikastaub und SiC-Kristallkeime mit einer Partikelgröße von 5 µm in einen Kugelfräsbehälter gegeben, kugelgemahlen und 12 Stunden gemischt und die Rotationsgeschwindigkeit wurde auf 100 U/min eingestellt. Nach dem Kugelmahlen wurden sie 12 Stunden bei 80°C in einen Blastrockenofen gegeben und dann zur Verwendung gesiebt. Unter Verwendung des Vorform-Formdrucks von 2MPa wurde das Mischpulver mit einer Masse von 8g uniaxial zu Vorform von 25×35×10 mm gepresst. Um eine Oxidation während des Mikrowellensyntheseprozesses zu verhindern, wurde die Vorform in Tiegel aus Aluminiumoxid gelegt und mit Quarzsandpulver bedeckt. Der Tiegel wurde in eine Wärmeschutzkonstruktion aus Aluminiumoxid-Inkubator und Mullit-Wärmedämmfaser-Baumwolle eingebracht und in einem Mikrowellenofen im TE666-Resonanzmodus erhitzt ((WXD20S-07, Nanjing Sanle Microwave Equipment Co., Ltd.). Die Mikrowellenfrequenz betrug 2,45 GHz und die maximale Eingangsleistung betrug 10 KW. Die Temperatur wurde mit einem Infrarot-Pyrometer gemessen, die anfängliche Anzeige begann bei 600°C, das Experiment passte die einfallende Leistung mit einer Rate von 400W/min auf den maximalen Wert von 6400W an, um die Heiztemperatur zu steuern, die Heiztemperatur betrug 800°C , und die Haltezeit betrug 20min, damit der durch kristallkeiminduzierte mikrowellensynthetisierte SiC-Kristall erhalten wurde.

A preparation method of the crystal nucleation-induced microwave synthesized SiC crystal that comprises the following steps:

• Nano carbon black and silica fume were weighed according to the molar ratio of 2:1 mol, the added amount of 5 μm SiC crystal nuclei was 20 (wt)% of the total mass. Using absolute ethanol as a dispersing medium, nano carbon black, silica fume and SiC crystal nuclei with a particle size of 5 μm were put into a ball milling container, ball milled and mixed for 12 hours, and the rotation speed was adjusted to 100 rpm. After ball milling, they were put into a blast drying furnace at 80°C for 12 hours and then sieved for use. Using the preform molding pressure of 2MPa, the mixed powder with a mass of 8g was uniaxially pressed into preform of 25×35×10 mm. To prevent oxidation during the microwave synthesis process, the preform was placed in alumina crucibles and covered with quartz sand powder. The crucible was placed in a thermal protection structure made of alumina incubator and mullite thermal insulation fiber cotton, and heated in a microwave furnace in TE666 resonance mode (WXD20S-07, Nanjing Sanle Microwave Equipment Co., Ltd.). The microwave frequency was 2.45 GHz and the maximum input power was 10 KW. The temperature was measured by an infrared pyrometer, the initial display started at 600°C, the experiment adjusted the incident power at a rate of 400W/min to the maximum value of 6400W to control the heating temperature, the heating temperature was 800°C, and the holding time was 20min, so that the crystal nucleation-induced microwave-synthesized SiC crystal was obtained.

Embodiment 2

Same as Embodiment 1 except that the heating temperature was 900°C.

Embodiment 3

Same as Embodiment 1 except that the heating temperature was 1000°C.

Embodiment 4

Same as Embodiment 1 except that the heating temperature was 1100°C.

Embodiment 5

• Nanoruß und Silikastaub wurden nach dem Molverhältnis 2:1 mol abgewogen, die zugegebene Menge an 5 µm SiC-Kristallkeime betrug 20 (Gew.)% der Gesamtmasse. Unter Verwendung von absolutem Ethanol als Dispergiermedium wurden Nanoruß, Silikastaub und SiC-Kristallkeime mit einer Partikelgröße von 5 µm in einen Kugelfräsbehälter gegeben, kugelgemahlen und 12 Stunden gemischt und die Rotationsgeschwindigkeit wurde auf 100 U/min eingestellt. Nach dem Kugelmahlen wurden sie 12 Stunden bei 80°C in einen Blastrockenofen gegeben und dann zur Verwendung gesiebt. Unter Verwendung des Vorform-Formdrucks von 2MPa wurde das Mischpulver mit einer Masse von 8g uniaxial zu Vorform von 25×35×10 mm gepresst. Um eine Oxidation während des Mikrowellensyntheseprozesses zu verhindern, wurde die Vorform in Tiegel aus Aluminiumoxid gelegt und mit Quarzsandpulver bedeckt. Der Tiegel wurde in eine Wärmeschutzkonstruktion aus Aluminiumoxid-Inkubator und Mullit-Wärmedämmfaser-Baumwolle eingebracht und in einem Mikrowellenofen im TE666-Resonanzmodus erhitzt ((WXD20S-07, Nanjing Sanle Microwave Equipment Co., Ltd.). Die Mikrowellenfrequenz betrug 2,45 GHz und die maximale Eingangsleistung betrug 10 KW. Die Temperatur wurde mit einem Infrarot-Pyrometer gemessen, die anfängliche Anzeige begann bei 600°C, das Experiment passte die einfallende Leistung mit einer Rate von 200W/min auf den maximalen Wert von 6400W an, um die Heiztemperatur zu steuern, die Heiztemperatur betrug 1100°C , und die Haltezeit betrug 20min, damit der durch kristallkeiminduzierte mikrowellensynthetisierte SiC-Kristall erhalten wurde.

A preparation method of the crystal nucleation-induced microwave synthesized SiC crystal that comprises the following steps:

• Nano carbon black and silica fume were weighed according to the molar ratio of 2:1 mol, the added amount of 5 μm SiC crystal nuclei was 20 (wt)% of the total mass. Using absolute ethanol as a dispersing medium, nano carbon black, silica fume and SiC crystal nuclei with a particle size of 5 μm were put into a ball milling container, ball milled and mixed for 12 hours, and the rotation speed was adjusted to 100 rpm. After ball milling, they were put into a blast drying furnace at 80°C for 12 hours and then sieved for use. Using the preform molding pressure of 2MPa, the mixed powder with a mass of 8g was uniaxially pressed into preform of 25×35×10 mm. To prevent oxidation during the microwave synthesis process, the preform was placed in alumina crucibles and covered with quartz sand powder. The crucible was placed in a thermal protection structure made of alumina incubator and mullite thermal insulation fiber cotton, and heated in a microwave furnace in TE666 resonance mode (WXD20S-07, Nanjing Sanle Microwave Equipment Co., Ltd.). The microwave frequency was 2.45 GHz and the maximum input power was 10 KW. The temperature was measured by an infrared pyrometer, the initial display started at 600°C, the experiment adjusted the incident power at a rate of 200W/min to the maximum value of 6400W to control the heating temperature, the heating temperature was 1100°C, and the holding time was 20min, so that the crystal nucleation-induced microwave-synthesized SiC crystal was obtained.

Embodiment 6

As in Embodiment 5, except that the incident power was set to the maximum value of 6400 W at a rate of 600 W/min to control the heating rate.

Embodiment 7

• Nanoruß und Silikastaub wurden nach dem Molverhältnis 2:1 mol abgewogen, die zugegebene Menge an 5 µm SiC-Kristallkeime betrug 20 (Gew.)% der Gesamtmasse. Unter Verwendung von absolutem Ethanol als Dispergiermedium wurden Nanoruß, Silikastaub und SiC-Kristallkeime mit einer Partikelgröße von 5 µm in einen Kugelfräsbehälter gegeben, kugelgemahlen und 12 Stunden gemischt und die Rotationsgeschwindigkeit wurde auf 100 U/min eingestellt. Nach dem Kugelmahlen wurden sie 12 Stunden bei 80°C in einen Blastrockenofen gegeben und dann zur Verwendung gesiebt. Unter Verwendung des Vorform-Formdrucks von 2MPa wurde das Mischpulver mit einer Masse von 8g uniaxial zu Vorform von 25×35×10 mm gepresst. Um eine Oxidation während des Mikrowellensyntheseprozesses zu verhindern, wurde die Vorform in Tiegel aus Aluminiumoxid gelegt und mit Quarzsandpulver bedeckt. Der Tiegel wurde in eine Wärmeschutzkonstruktion aus Aluminiumoxid-Inkubator und Mullit-Wärmedämmfaser-Baumwolle eingebracht und in einem Mikrowellenofen im TE666-Resonanzmodus erhitzt ((WXD20S-07, Nanjing Sanle Microwave Equipment Co., Ltd.). Die Mikrowellenfrequenz betrug 2,45 GHz und die maximale Eingangsleistung betrug 10 KW. Die Temperatur wurde mit einem Infrarot-Pyrometer gemessen, die anfängliche Anzeige begann bei 600°C, das Experiment passte die einfallende Leistung mit einer Rate von 400W/min auf den maximalen Wert von 6400W an, um die Heiztemperatur zu steuern, die Heiztemperatur betrug 1100°C , und die Haltezeit betrug 20min, damit der durch kristallkeiminduzierte mikrowellensynthetisierte SiC-Kristall erhalten wurde.

A preparation method of the crystal nucleus-induced
microwave synthesized SiC crystal that it includes the following steps:

• Nano carbon black and silica fume were weighed according to the molar ratio of 2:1 mol, the added amount of 5 µm SiC crystal seeds was 20 (wt.)% of the total mass. Using absolute ethanol as a dispersing medium, nano carbon black, silica fume and SiC crystal seeds with a particle size of 5 µm were placed in a ball milling container, ball milled len and mixed for 12 hours and the rotation speed was set at 100 rpm. After ball milling, they were put into a blast drying furnace at 80°C for 12 hours and then sieved for use. Using the preform molding pressure of 2MPa, the mixed powder with a mass of 8g was uniaxially pressed into preform of 25×35×10 mm. To prevent oxidation during the microwave synthesis process, the preform was placed in alumina crucibles and covered with quartz sand powder. The crucible was placed in a thermal protection structure made of alumina incubator and mullite thermal insulation fiber cotton, and heated in a microwave furnace in TE666 resonance mode (WXD20S-07, Nanjing Sanle Microwave Equipment Co., Ltd.). The microwave frequency was 2.45 GHz and the maximum input power was 10 KW. The temperature was measured by an infrared pyrometer, the initial display started at 600°C, the experiment adjusted the incident power at a rate of 400W/min to the maximum value of 6400W to control the heating temperature, the heating temperature was 1100°C, and the holding time was 20min, so that the crystal nucleation-induced microwave-synthesized SiC crystal was obtained.

Embodiment 8

Same as Embodiment 7, except that the particle size of the SiC crystal seed was about 1 µm.

In order to illustrate the relevant performance of the SiC crystals produced by the production method provided by the present invention, the relevant performance tests of the SiC crystals provided in Embodiments 1 ~ 8 were conducted as shown in ~ 6 shown for details.

X-ray diffractometer (XRD, SmartLab Japan Science Co., Ltd.) and scanning electron microscope (SEM, JSM 7001F Japan Electronics Co., Ltd.) were used to characterize the phase composition and microscopic morphology of the products.

The results of the invention are as follows:

1.The influence of temperature on the seed-induced microwave-synthesized SiC crystal

is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 1~4. shows the X-ray diffraction (XRD) pattern of the raw materials, which are mixture of nano carbon black, silica fume and SiC crystal nuclei by ball milling. It can be seen that the power consumption is 400W/min and the particle size of the SiC crystal nucleus is 5µm. It can be seen that the complete conversion of the raw materials can be achieved by keeping the temperature at 800°C for 20 minutes and SiC crystals can be synthesized, since the crystallinity becomes better with increasing temperature.

is the scanning electron microscope (SEM) photos of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 1~4.

shows the scanning electron microscope (SEM) photos of the raw materials, which are a mixture of nanosoot, silica fume and SiC crystal seeds by ball milling It can be seen that at a temperature of 800 ° C, small particles of nano-SiC are attached to the silicon carbide crystal nuclei, with increasing temperature, the newly synthesized silicon carbide crystals gradually nucleate and grow on the silicon carbide crystal nuclei, and growth steps appear. It shows that the silicon carbide crystal nuclei promote the reaction of raw materials to induce nucleation at low temperature, and becomes a hot stage for silicon carbide crystal growth at high temperature.

2.The influence of heating rate on the crystal seed-induced microwave synthesized SiC crystal

is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 4~6. Figure 1 shows the X-ray diffraction (XRD) pattern of the raw material mixture of nanocarbon black, silica fume and SiC crystal seeds obtained by ball milling, and the phase of the SiC crystal synthesized by crystal seed-induced microwave changes at power consumption rates of 200 W/min, 400 W/min and 600 W/min. is the X-ray diffraction (XRD) pattern of the raw material mixture of nanocarbon black, silica fume and SiC crystal seeds obtained by ball milling; is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystal provided in Embodiment 5; is the X-ray diffraction (XRD) pattern of the seed-induced microwave-synthesized SiC crystal provided in Embodiment 4; is the X-ray diffraction (XRD) pattern of the crystal seed-induced micro row wave synthesized SiC crystal provided in Embodiment 6.

Out of It can be seen that at power input rates of 200 W/min, 400 W/min and 600 W/min, heating at 1100 °C for 20 minutes can achieve complete reaction of the raw materials and synthesize SiC crystals. And with increasing heating rate, the crystallinity becomes better and better.

is the scanning electron microscope (SEM) photos of the seed-induced microwave-synthesized SiC crystals provided in raw materials and in Embodiments 4~6. shows the changes in micromorphology of the seed-induced microwave-synthesized SiC crystals at power input rates of 200W/min, 400W/min, and 600W/min. is the scanning electron microscope (SEM) photograph of the seed-induced microwave-synthesized SiC crystal provided in Embodiment 5; is the scanning electron microscope (SEM) photograph of the seed-induced microwave-synthesized SiC crystal provided in Embodiment 4; is the scanning electron microscope (SEM) photograph of the seed-induced microwave-synthesized SiC crystal provided in Embodiment 6.

Out of It can be seen that the temperature is raised to 1100 °C at a heating rate of 200 W/min for 20 minutes, the heating rate is slow, and the synthesized silicon carbide crystal has a smaller particle size. With the increase of input power, the synthesized silicon carbide crystal at a heating rate of 400 W/min and 600 W/min has a larger particle size, clear outline, and better crystal morphology and structure.

3.The influence of the particle size of the SiC crystal nuclei on the crystal nucleus-induced microwave-synthesized SiC crystal

is the X-ray diffraction (XRD) pattern of the seed-induced microwave synthesized SiC crystals provided in raw materials and in embodiments 4, 7, 8. shows that the phases of the seed-induced microwave-synthesized SiC crystals change under the conditions of adding 0.5 µm, 1 µm, and 5 µm seed crystals, respectively. is the X-ray diffraction (XRD) pattern of the SiC crystal provided in Embodiment 7; is the X-ray diffraction (XRD) pattern of the SiC crystal provided in Embodiment 8; is the X-ray diffraction (XRD) pattern of the SiC crystal provided in Embodiment 7.

Out of It can be seen that under the conditions of adding 0.5µm, 1µm and 5µm SiC crystal seeds, heating to 1100 °C at a heating rate of 400W/min for 20 minutes can achieve the complete reaction and synthesize SiC crystals. And as the size of the SiC crystal seeds increases, the crystallinity improves.

is the scanning electron microscope (SEM) photos of the seed-induced microwave synthesized SiC crystals provided in raw materials and in embodiments 4, 7, 8. shows the changes in the microscopic morphology of the seed-induced microwave-synthesized SiC crystals under the conditions of adding 0.5 µm, 1 µm and 5 µm SiC seeds, respectively. is the scanning electron microscope (SEM) photo of the SiC crystal provided in Embodiment 7; is the scanning electron microscope (SEM) photograph of the SiC crystal provided in Embodiment 8; and is the scanning electron microscope (SEM) photo of the SiC crystal provided in Embodiment 4.

Out of It can be seen that under the condition of heating at 1100 °C at a heating rate of 400 W/min for 20 minutes, the SiC crystal size synthesized by adding a 0.5 μm SiC crystal seed with the small particle size is smaller, and as the size of the crystal seed increases, the particle size of the synthesized silicon carbide powder also increases, and the outline becomes clear and the crystal morphology and structure are better.

In summary, this invention uses SiC as a good microwave absorber material in the process of seed crystal induction of microwave synthesis of SiC, the SiC crystal seed couples with microwave to form heat, which promotes the reaction of raw materials at low temperature, SiC crystal seed can be used as a crystallization platform at high temperature to promote crystal seed formation and growth, so in the microwave heating process, SiC crystal seed not only can become a local hot spot to promote raw material reaction, but also can be used as a crystal growth hot stage to induce synthetic SiC seed formation and in situ growth. Compared with the seed crystal induction technology currently used in the industry, the method in this work will greatly reduce the difficulty and process conditions of SiC crystal synthesis. Microwave and seed crystal compound induction synthesis of SiC has good application prospects.

The present invention describes preferred embodiments and their effects. However, once a professional does the basics ative concept, he can make additional changes and modifications to these embodiments. Therefore, the appended claims are to be interpreted to cover the preferred embodiments and all changes and modifications that come within the scope of the present invention.

Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. Without prejudice to the foregoing, the scope of the present invention is defined by the appended claims and their equivalents.
(The chemical element symbol SiC used in the present invention is silicon carbide.)

Claims (9)

A production method of crystal seed-induced microwave synthesized SiC crystal, which is characterized by comprising the following steps: after uniformly mixing silica fume, nanoblack and SiC crystal seeds, mixed powder is obtained, and then the mixed powder is pressed into preform, which is then heated by microwave and kept at 800~1100°C for 15~30min to synthesize SiC crystal, that is, the SiC crystal synthesized by crystal seed-induced microwave is obtained. The preparation method of the crystal nucleus-induced microwave-synthesized SiC crystal according to Claim 1 , characterized in that during the microwave heating process the power consumption is 200~600W/min. The production method of the crystal seed-induced microwave-synthesized SiC crystal Claim 1 , wherein it is characterized in that the particle size of the SiC crystal seed is 0.5-5 μm, and the addition amount is 1-20% by weight of the total mass of the raw material. The preparation method of the crystal nucleus-induced microwave-synthesized SiC crystal according to Claim 1 , characterized in that the molar ratio of silica fume to nano carbon black is 1:1∼3. The production method of the crystal seed-induced microwave-synthesized SiC crystal Claim 1 , wherein it is characterized in that the mixed powder is prepared by mixing silica fume, nanoblack and SiC crystal seeds with absolute ethanol as a dispersing medium by the ball milling method, the rotation speed is set to 100rpm, the ball milling is carried out for 12 hours and then vacuum dried it at a temperature of 80 ° C for 12 hours and obtained. The preparation method of the crystal nucleus-induced microwave-synthesized SiC crystal according to Claim 5 , characterized in that the particle size of the mixed powder is ≥60 mesh. The preparation method of the crystal nucleus-induced microwave-synthesized SiC crystal according to Claim 1 characterized in that when heating the preform, the preform is placed in the alumina crucible and covered with quartz sand powder, then the crucible is placed in a heat-insulating structure composed of the alumina incubator and the mullite heat-insulating fiber cotton, and it is heated by microwave. A crystal seed-induced microwave-synthesized SiC crystal using the manufacturing method according to one of the Claims 1 until 7 will be produced. The application of the SiC crystal after Claim 8 in semiconductors for electronic devices and heat exchangers.