阅读说明：本技术 多孔碳化硅陶瓷材料及其制备方法 (Porous silicon carbide ceramic material and preparation method thereof ) 是由 张景德 李子禾 温家强 韩桂芳 于 2020-07-07 设计创作，主要内容包括：本公开提供了一种多孔碳化硅陶瓷材料及其制备方法。所述多孔碳化硅陶瓷为蜂窝状结构,多孔碳化硅陶瓷的孔隙呈立体网格状无序联通,孔隙分布均匀,孔隙的尺寸为20μm～30μm。所述多孔碳化硅陶瓷材料的制备方法包含：a.将基体原料碳化硅粉体、氢氧化铝粉体、氧化钇粉体加入容器中,然后再加入分散剂、去离子水,首次球磨,之后再加入粘结剂,二次球磨,得到均匀的浆料；b.将步骤a所制得的浆料倒入容器中真空除泡,之后将除泡后的浆料注入到冷冻模具中冷冻,得到冷冻生胚；c.将步骤b所制得的冷冻生胚在真空条件下干燥,得到多孔SiC胚体；d.将步骤c所制得的胚体放入保温箱干燥；e.将步骤d所得到的胚体烧结。本公开的制备工艺简单高效,操作易于控制。(The present disclosure provides a porous silicon carbide ceramic material and a preparation method thereof. The porous silicon carbide ceramic is of a honeycomb structure, the pores of the porous silicon carbide ceramic are in three-dimensional grid-shaped disordered communication, the pores are uniformly distributed, and the size of each pore is 20-30 micrometers. The preparation method of the porous silicon carbide ceramic material comprises the following steps: a. adding matrix raw materials of silicon carbide powder, aluminum hydroxide powder and yttrium oxide powder into a container, then adding a dispersing agent and deionized water, carrying out primary ball milling, then adding a binder, and carrying out secondary ball milling to obtain uniform slurry; b. pouring the slurry prepared in the step a into a container for vacuum defoaming, and then injecting the defoamed slurry into a freezing mould for freezing to obtain a frozen green blank; c. drying the frozen green blank prepared in the step b under a vacuum condition to obtain a porous SiC green body; d. c, placing the blank prepared in the step c into an incubator for drying; e. and d, sintering the blank obtained in the step d. The preparation process disclosed by the invention is simple and efficient, and the operation is easy to control.)

1. The porous silicon carbide ceramic material is characterized in that the porous silicon carbide ceramic material is of a honeycomb structure, the pores of the porous silicon carbide ceramic material are in three-dimensional meshed disordered communication, the pores are uniformly distributed, and the size of the pores is 20-30 micrometers.

2. The porous silicon carbide ceramic material according to claim 1, wherein the porosity of the porous silicon carbide ceramic is 50-80%.

3. The porous silicon carbide ceramic material of claim 1, wherein the compressive strength of the porous silicon carbide ceramic is between 4MPa and 25 MPa.

4. The porous silicon carbide ceramic material according to claim 1, having a specific surface area of 4m²/g～18m²/g。

5. A method for preparing a porous silicon carbide ceramic material according to any one of claims 1-4, comprising the steps of:

a. adding matrix raw materials of silicon carbide powder, aluminum hydroxide powder and yttrium oxide powder into a container; then adding a dispersing agent and deionized water, carrying out primary ball milling, then adding a binder, and carrying out secondary ball milling to obtain uniform slurry;

b. pouring the slurry prepared in the step a into a container for vacuum defoaming, and then injecting the defoamed slurry into a freezing mould for freezing to obtain a frozen green blank;

c. drying the frozen green blank prepared in the step b under a vacuum condition to obtain a porous SiC green body;

d. c, placing the blank prepared in the step c into an insulation can, and drying;

e. and d, sintering the blank obtained in the step d to obtain the porous silicon carbide ceramic material with the honeycomb structure.

6. The method for preparing a porous silicon carbide ceramic material according to claim 5,

in the step a, the dispersing agent is at least one of tetramethylammonium hydroxide, sodium silicate and polyacrylamide, and the addition amount of the dispersing agent is 0.5-1.5% of the mass of the base raw material; and/or

In the step a, the binder is selected from at least one of polyethylene glycol, polyvinyl alcohol and sodium carboxymethyl cellulose, and the addition amount of the binder is 0.5-1.5% of the mass of the matrix raw material.

7. The preparation method of the porous silicon carbide ceramic material according to claim 5, wherein in the step a, the addition amount of deionized water is 0.5 to 2.5 times of the mass of the matrix raw material, the time of the first ball milling is 2 to 12 hours, and the time of the second ball milling is 1 to 6 hours.

8. The method as claimed in claim 5, wherein in step b, the bottom material of the freezing mold is a metal with a thermal conductivity of 100-250W/mK, and the peripheral material of the freezing mold is a polymer with a thermal conductivity of less than 0.05W/mK; for example, the bottom material is at least one of aluminum, beryllium, or an aluminum-beryllium alloy; for example, the peripheral material is at least one of polystyrene, polytetrafluoroethylene and silicon rubber.

9. The method for preparing a porous silicon carbide ceramic material according to claim 5, wherein the freezing temperature in step b is-10 ℃ to-20 ℃.

10. The method for preparing a porous silicon carbide ceramic material according to claim 5, wherein the sintering temperature in step e is 1400-1500 ℃.

Technical Field

The disclosure relates to the field of ceramic materials, in particular to a porous silicon carbide ceramic material and a preparation method thereof.

Background

The porous silicon carbide prepared by the freeze-drying method has the properties of high porosity, high specific surface area, excellent mechanical property, stable chemical property, higher thermal conductivity, lower thermal expansion coefficient and the like, and has great application value in the aspect of catalyst carrier materials.

At present, porous silicon carbide ceramics prepared by a freeze drying method mostly have a layered or dendritic pore structure with high orientation.

In the reports of preparing the porous silicon carbide material by freeze drying at home and abroad, the freezing process of the slurry is not accompanied with the occurrence of phagocytosis generally, and the prepared pore structure is generally in a high-orientation lamellar or dendritic shape. For example, chinese patent application publication No. CN108101544A, published in 6/1 of 2018, discloses a lamellar gradient porous silicon carbide ceramic and a method for preparing the same, in which a lamellar pore structure having a high orientation is prepared by using silicon carbide powder as a raw material and water as a freezing medium. For example, chinese patent application publication No. CN102260092 published on 11/30/2011 discloses a method for preparing a porous silicon carbide ceramic material, wherein samples with different layer thicknesses and layer spacings are prepared by controlling the addition amount of a binder, and the pore structure of the samples is highly oriented layer-like or dendritic.

However, the pore channels in the lamellar and dendritic structures are relatively straight, and when reactants enter the pores, sufficient residence time cannot be obtained to perform sufficient catalytic reaction, so that the application of the porous silicon carbide ceramic prepared by a freeze-drying method in the aspect of catalyst carriers is limited to a certain extent.

The above description is merely provided as background and is not an admission that the above "background" constitutes prior art to the present disclosure.

Disclosure of Invention

In view of the problems in the background art, the present disclosure is directed to a porous silicon carbide ceramic material and a method for preparing the same.

In some embodiments, the porous silicon carbide ceramic material of the present disclosure is a honeycomb structure, pores of the porous silicon carbide ceramic material are in disordered communication in a three-dimensional grid shape, the pores are uniformly distributed, and the size of the pores is 20 μm to 30 μm.

In some embodiments, the present disclosure provides a method for preparing a porous silicon carbide ceramic material for preparing a honeycomb porous silicon carbide ceramic material of the present disclosure, comprising the steps of:

a. adding matrix raw materials of silicon carbide powder, aluminum hydroxide powder and yttrium oxide powder into a container; then adding a dispersing agent and deionized water, carrying out primary ball milling, then adding a binder, and carrying out secondary ball milling to obtain uniform slurry;

b. pouring the slurry prepared in the step a into a container for vacuum defoaming, and then injecting the defoamed slurry into a freezing mould for freezing to obtain a frozen green blank;

c. drying the frozen green blank prepared in the step b under a vacuum condition to obtain a porous SiC green body;

d. c, placing the blank prepared in the step c into an insulation can, and drying;

e. and d, sintering the blank obtained in the step d to obtain the porous silicon carbide ceramic material with the honeycomb structure.

The beneficial effects of this disclosure are as follows:

the porous silicon carbide ceramic material prepared by the method has a honeycomb-shaped pore structure, and has the characteristics of high porosity, high pore distribution disorder, concentrated pore size distribution, high compressive strength, high specific surface area and the like. The preparation process disclosed by the invention is simple and efficient, and the operation is easy to control.

Drawings

Fig. 1 is an electron micrograph of the porous silicon carbide ceramic according to example 1 of the present disclosure;

fig. 2 is another scanning electron micrograph of the porous silicon carbide ceramic of example 1 of the present disclosure.

Detailed Description

It is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various forms, and that specific details of the disclosure are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure.

In the description of the present disclosure, terms and terms not specifically described are common general knowledge of those skilled in the art, and methods not specifically described are conventional methods known to those skilled in the art.

[ porous silicon carbide ceramic Material ]

The porous silicon carbide ceramic disclosed by the invention is of a honeycomb structure, the pores of the porous silicon carbide ceramic are in three-dimensional meshed disordered communication, the pores are uniformly distributed, and the size of the pores is 20-30 micrometers.

In some embodiments, the feedstock of the porous silicon carbide ceramic material of the present disclosure comprises silicon carbide, aluminum hydroxide, and yttrium oxide. In some embodiments, the mass ratio of the silicon carbide, the aluminum hydroxide and the yttrium oxide is (65-85): (10-30): 5-25).

In some embodiments, the porous silicon carbide ceramic of the present disclosure has a porosity of 50% to 80%.

In some embodiments, the porous silicon carbide ceramic of the present disclosure has a compressive strength of 4 to 25 MPa.

In some embodiments, the porous silicon carbide ceramic of the present disclosure has a specific surface area of 4m²/g～18m²/g。

[ preparation method of porous silicon carbide ceramic Material ]

The present disclosure utilizes freeze-drying techniques to prepare the porous silicon carbide ceramics of the present disclosure. In some embodiments, the present disclosure prepares porous silicon carbide ceramics of the present disclosure by control of freezing temperature. In some embodiments, the present disclosure prepares the porous silicon carbide ceramic of the present disclosure by defining the material of the freezing mold and/or the freezing container.

In some embodiments, the method of making the porous silicon carbide ceramic of the present disclosure comprises the steps of:

a. adding matrix raw materials of silicon carbide powder, aluminum hydroxide powder and yttrium oxide powder into a container; then adding a dispersing agent and deionized water, carrying out primary ball milling, then adding a binder, and carrying out secondary ball milling to obtain uniform slurry;

b. pouring the slurry prepared in the step a into a container for vacuum defoaming, and then injecting the defoamed slurry into a freezing mould for freezing to obtain a frozen green blank;

c. drying the frozen green blank prepared in the step b under a vacuum condition to obtain a porous SiC green body;

d. c, placing the blank prepared in the step c into an insulation can, and drying;

e. and d, sintering the blank obtained in the step d to obtain the porous silicon carbide ceramic material with the honeycomb structure.

In step a: in some embodiments, the mass ratio of the silicon carbide, the aluminum hydroxide and the yttrium oxide is (65-85): (10-30): 5-25); in some embodiments, the dispersant is selected from at least one of tetramethylammonium hydroxide, sodium silicate, and polyacrylamide; in some embodiments, the addition amount of the dispersing agent is 0.5-1.5% of the mass of the base raw material; in some embodiments, the binder is selected from at least one of polyethylene glycol, polyvinyl alcohol, and sodium carboxymethyl cellulose; in some embodiments, the addition amount of the binder is 0.5-1.5% of the mass of the base raw material; in some embodiments, the amount of deionized water added is 0.5 to 2.5 times the mass of the base material; in some embodiments, the time for the first ball milling is 2h to 12h, and the time for the second ball milling is 1h to 6 h.

In step b: the bottom material of the freezing mold is a metal with the thermal conductivity of 100-250W/mK, and in some embodiments, the bottom material is at least one of aluminum, beryllium or aluminum-beryllium alloy; the peripheral material of the freezing mould is a polymer with the thermal conductivity of less than 0.05W/mK, and in some embodiments, the peripheral material is at least one of polystyrene, polytetrafluoroethylene and silicon rubber; in some embodiments, the freezing temperature is between-10 ℃ and-20 ℃.

In step c: in some embodiments, the vacuum condition is a temperature of-5 ℃ to-60 ℃, a vacuum degree of 4Pa to 20Pa, and the drying treatment time is 20h to 40 h.

In step d: in some embodiments, the drying temperature is 70 ℃ to 120 ℃, and the drying time is 2h to 36 h.

In step e: in some embodiments, the temperature of sintering is 1400 ℃ to 1500 ℃.

The disclosure is further illustrated with reference to the following examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure.

In the following examples and comparative examples, reagents, materials and instruments used were commercially available or prepared by methods known in the art, unless otherwise specified.