Preparation method of SiC powder particles with exposed high-activity surfaces

Abstract

The invention discloses a preparation method of SiC powder particles with exposed high-activity surfaces. The preparation method comprises the following steps: step 1, purifying raw materials; 2, mixing the raw materials; 3, melting the raw materials; step 4, cooling and crystallizing; step 5, cooling to obtain SiC powder particles; the raw materials are purified, adverse effects of impurities on growth of the crystals are avoided, SiC powder particles are prepared through a liquid phase method so as to control the particle size of the SiC crystals and avoid reduction of the specific surface area caused by overgrowth of the crystals, specific crystal face directional exposure growth under control of impurity elements can be achieved through the liquid phase method, and the preparation method is suitable for large-scale industrial production. According to the preparation method disclosed by the invention, the growth of an inactive crystal face is inhibited and the growth of an active crystal face is enhanced by utilizing the synergistic effect of a plurality of crystal face control agents, and the growth direction and crystal face orientation of the crystal are influenced by applying a magnetic field, so that the growth of the active crystal face is further enhanced, and the SiC powder particles with the exposed high-activity face are obtained.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a method for preparing SiC powder particles with high active surface exposure. Background Art

[0002] Silicon carbide is one of the typical representatives of the third generation of semiconductors. It has excellent properties such as stable chemical properties, high thermal conductivity, high electron mobility, high mechanical strength, high hardness, low price, and environmental friendliness. It has been widely used in industry in recent years. As an excellent semiconductor material, it is also widely used in photoinduced reaction systems, such as photoelectrocatalytic electrode materials, photocatalytic decomposition of water to produce hydrogen, etc. As a photocatalyst with industrial application prospects in the future, the surface of silicon carbide semiconductors is basically passivated, which is also one of the main reasons for the relatively stable chemical properties of silicon carbide. However, this passivation is not conducive to the catalytic reaction on its surface, which seriously restricts its catalytic performance when used as a catalyst. It is generally believed that a catalyst has a good reaction active surface, which is a prerequisite and necessary condition to ensure its excellent catalytic performance. Therefore, improving the exposure rate of the active surface of silicon carbide is a key technical problem to be solved as an excellent photocatalyst.

[0003] However, in the existing silicon carbide production method, the exposure rate of the active surface of silicon carbide is low due to the following defects, specifically: 1. The existing technology lacks an effective crystal surface control mechanism, and the growth of the crystal mainly depends on thermodynamic and kinetic factors, which are difficult to accurately control, resulting in the inability to effectively expose the highly active crystal surface; 2. The particle size of the silicon carbide crystal cannot be accurately controlled, and excessive crystal growth leads to a decrease in specific surface area, which easily causes a relative reduction in active surfaces; 3. Impurities in the raw materials will have an adverse effect on the growth of the crystal, thereby reducing or covering up the active surface. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing SiC powder particles with high active surface exposure, so as to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing SiC powder particles with high active surface exposure, comprising the following steps: step 1, purifying raw materials; step 2, mixing raw materials; step 3, melting raw materials; step 4, cooling and crystallizing; step 5, cooling to obtain SiC powder particles;

[0006] In the above step 1, the C powder and Si powder are purified to remove surface impurities;

[0007] In the above step 2, the C powder and Si powder pretreated in step 1 are surface modified, and then a crystal plane control agent is added and fully mixed, and then dried to remove the solvent and placed in a crucible;

[0008] In the above step 3, the crucible in step 2 is placed in a high temperature reaction furnace for heating until the C powder and the Si powder reach a molten state;

[0009] In the above step 4, the molten liquid obtained in step 3 is subjected to programmed cooling to perform a crystallization process until the crystal particle size reaches the required requirement, and the crystallization process is terminated;

[0010] In the above step 5, the high temperature reaction furnace in which the crystallization process is terminated in step 4 is rapidly cooled to room temperature to obtain SiC powder particles with exposed highly active surfaces.

[0011] Preferably, in step 1, the purification treatment is specifically as follows: placing the C powder and the Si powder respectively in an argon atmosphere, heating the temperature to 700°C-900°C at a heating rate of 5°C / min-10°C / min and maintaining the temperature for 2 hours.

[0012] Preferably, in step 2, the surface modification is specifically as follows: dispersing the pretreated C powder and Si powder in ethanol, and then adding 2%-3% of the total mass of C powder and Si powder γ-aminopropyltriethoxysilane, and reacting for 1h-3h; wherein, C powder and Si powder are mixed in a stoichiometric ratio of 1:1.

[0013] Preferably, in step 2, the crystal plane control agent is one or more of boron oxide, magnesium oxide, aluminum oxide, lanthanum oxide, and carbon nanotubes, and the amount of the crystal plane control agent added is 1%-5% of the total mass of the C powder and the Si powder.

[0014] Preferably, in step three, the heating treatment is specifically as follows: in a high-purity argon atmosphere, the high-temperature reaction furnace is heated to 1600°C-2200°C at a heating rate of 10°C / min-20°C / min.

[0015] Preferably, in step 4, the programmed cooling is as follows: firstly, the temperature is lowered to 1500°C at a cooling rate of 50°C / min, then the cooling rate is reduced to 30°C / min and the temperature is further lowered to 1000°C.

[0016] Preferably, in step 4, during the crystallization process, an external magnetic field is applied to assist crystallization, and the direction of the magnetic field is parallel to the normal direction of the crystal plane whose growth needs to be promoted.

[0017] Preferably, in step 4, the particle size of the crystal particles is required to be 500nm-5μm.

[0018] Preferably, in step 5, rapidly cooling to room temperature specifically comprises: cooling to room temperature at a cooling rate of 50°C / min-100°C / min.

[0019] Preferably, in step five, the exposed active surfaces of the SiC powder particles include the (0001) crystal plane, the (000-1) crystal plane, the (10-10) crystal plane and the (11-20) crystal plane.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention purifies the raw materials to avoid the adverse effects of impurities on the growth of crystals, prepares SiC powder particles by a liquid phase method to control the particle size of SiC crystals and avoid excessive crystal growth leading to a reduction in specific surface area, the liquid phase method can achieve directional exposure growth of specific crystal faces under the control of impurity elements, thereby achieving high explosive exposure of highly active faces, the present invention utilizes the synergistic effect of multiple crystal face control agents to inhibit the growth of inactive crystal faces and enhance the growth of active crystal faces, and affects the growth direction and crystal face orientation of the crystal by applying a magnetic field, further enhancing the growth of active crystal faces, thereby obtaining SiC powder particles with highly active face exposure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Please see attached Figure 1 , an embodiment provided by the present invention: a method for preparing SiC powder particles with high active surface exposure, comprising the following steps: step 1, purifying raw materials; step 2, mixing raw materials; step 3, melting raw materials; step 4, cooling and crystallizing; step 5, cooling to obtain SiC powder particles;

[0024] In the above step 1, the C powder and the Si powder are purified to remove surface impurities. The purification process is as follows: the C powder and the Si powder are placed in an argon atmosphere, heated to 700°C-900°C at a heating rate of 5°C / min-10°C / min and maintained for 2 hours;

[0025] In the above step 2, the C powder and Si powder pretreated in step 1 are taken for surface modification, specifically: the pretreated C powder and Si powder are dispersed in ethanol, and then 2%-3% of the total mass of the C powder and Si powder are added with γ-aminopropyltriethoxysilane, and the reaction is carried out for 1h-3h; wherein the C powder and Si powder are mixed according to a stoichiometric ratio of 1:1; then a crystal surface control agent is added and fully mixed, and the mixture is dried to remove the solvent and placed in a crucible; wherein the crystal surface control agent is a combination of one or more of boron oxide, magnesium oxide, aluminum oxide, lanthanum oxide, and carbon nanotubes, and the amount of the crystal surface control agent added is 1%-5% of the total mass of the C powder and Si powder;

[0026] In the above step 3, the crucible in step 2 is placed in a high-temperature reaction furnace for heating treatment until the C powder and the Si powder reach a molten state; wherein the heating treatment is specifically: in a high-purity argon atmosphere, the high-temperature reaction furnace is heated to 1600°C-2200°C at a heating rate of 10°C / min-20°C / min;

[0027] In the above step 4, the molten liquid obtained in step 3 is subjected to programmed cooling and a crystallization process is performed until the particle size of the crystal particles reaches 500nm-5μm, and the crystallization process is terminated; wherein the programmed cooling is specifically as follows: firstly, the temperature is lowered to 1500°C at a cooling rate of 50°C / min, and then the cooling rate is reduced to 30°C / min and the temperature is further lowered to 1000°C; during the crystallization process, an external magnetic field is applied to assist crystallization, and the direction of the magnetic field is parallel to the normal direction of the crystal face whose growth needs to be promoted;

[0028] In the above step five, the high-temperature reaction furnace that terminates the crystallization process in step four is cooled to room temperature at a cooling rate of 50°C / min-100°C / min to obtain SiC powder particles with highly active surfaces exposed; the exposed active surfaces of the SiC powder particles include (0001) crystal plane, (000-1) crystal plane, (10-10) crystal plane and (11-20) crystal plane.

[0029] Based on the above, the advantage of the present invention is that when the invention is used, the C powder and Si powder are first purified to remove surface impurities to avoid the adverse effects of impurities on crystal growth, and then the C powder and Si powder are surface modified, and then a crystal plane control agent is added so that the crystal plane control agent can be better adsorbed on the powder surface, and then the SiC powder particles are prepared by a liquid phase method, that is, the C powder and Si powder are converted into a molten state by heating, and crystal precipitation is achieved by programmed cooling. During the crystal precipitation process, a variety of crystal plane control agents are used to act synergistically to inhibit the growth of inactive crystal planes and enhance the growth of active crystal planes, and the growth direction and crystal plane orientation of the crystal are affected by applying a magnetic field to further enhance the growth of active crystal planes, thereby obtaining SiC powder particles with exposed high-activity surfaces. The liquid phase method can control the SiC crystal particle size by controlling the temperature conditions, and can achieve directional exposure growth of specific crystal planes under the control of impurity elements, thereby achieving high explosive exposure of high-activity surfaces.

[0030] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing SiC powder particles with high active surface exposure, comprising the following steps: Step 1, purifying raw materials; Step 2, mixing raw materials; Step 3, melting raw materials; Step 4, cooling and crystallizing; Step 5, cooling to obtain SiC powder particles; characterized in that: In the above step 1, the C powder and Si powder are purified to remove surface impurities; In the above step 2, the C powder and Si powder pretreated in step 1 are surface modified, and then a crystal plane control agent is added and fully mixed, and then dried to remove the solvent and placed in a crucible; In the above step 3, the crucible in step 2 is placed in a high temperature reaction furnace for heating until the C powder and the Si powder reach a molten state; In the above step 4, the molten liquid obtained in step 3 is subjected to programmed cooling to perform a crystallization process until the crystal particle size reaches the required requirement, and the crystallization process is terminated; In the above step 5, the high temperature reaction furnace in which the crystallization process is terminated in step 4 is rapidly cooled to room temperature to obtain SiC powder particles with exposed highly active surfaces.

2. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 1, the purification treatment is specifically as follows: placing the C powder and the Si powder respectively in an argon atmosphere, heating the temperature to 700°C-900°C at a heating rate of 5°C / min-10°C / min and maintaining the temperature for 2 hours.

3. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 2, the surface modification is specifically as follows: the pretreated C powder and Si powder are dispersed in ethanol, and then 2%-3% of the total mass of the C powder and Si powder is added with γ-aminopropyltriethoxysilane, and the reaction is carried out for 1h-3h; wherein the C powder and Si powder are mixed in a stoichiometric ratio of 1:

1.

4. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 2, the crystal plane control agent is one or more of boron oxide, magnesium oxide, aluminum oxide, lanthanum oxide, and carbon nanotubes, and the amount of the crystal plane control agent added is 1%-5% of the total mass of the C powder and the Si powder.

5. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step three, the heating treatment is specifically as follows: in a high-purity argon atmosphere, the high-temperature reaction furnace is heated to 1600° C.-2200° C. at a heating rate of 10° C. / min-20° C. / min.

6. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 4, the programmed cooling is specifically as follows: firstly, the temperature is lowered to 1500°C at a cooling rate of 50°C / min, and then the cooling rate is reduced to 30°C / min and the temperature is further lowered to 1000°C.

7. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 4, during the crystallization process, an external magnetic field is applied to assist crystallization, and the direction of the magnetic field is parallel to the normal direction of the crystal plane whose growth needs to be promoted.

8. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 4, the crystal particle size is required to be 500nm-5μm.

9. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 5, rapidly cooling to room temperature specifically includes cooling to room temperature at a cooling rate of 50°C / min-100°C / min.

10. The method for preparing SiC powder particles with high active surface exposure according to claim 1, characterized in that: In the step 5, the exposed active surfaces of the SiC powder particles include the (0001) crystal plane, the (000-1) crystal plane, the (10-10) crystal plane and the (11-20) crystal plane.

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