阅读说明：本技术 一种ZrC-SiC混合纳米粉体的制备方法 (Preparation method of ZrC-SiC mixed nano powder ) 是由 张明瑜 曾晨 黄启忠 于 2019-10-25 设计创作，主要内容包括：本发明涉及一种超细ZrC-SiC混合粉体的制备方法,利用溶胶-凝胶法,将八水氧氯化锆、正硅酸乙酯和酚醛树脂依次溶解到酒精中形成含Zr、Si和C的溶胶,通过自发进行聚合反应形成凝胶,接着室温下陈腐24h后干燥处理得到干凝胶,再将干凝胶球磨成粉,最后将其在氩气气氛保护下,进行1500～1700℃热处理,过筛后得到超细ZrC-SiC混合粉体。本发明制得的超细ZrC-SiC混合粉体为多角形颗粒结构,主要由ZrC、SiC和少量的C组成,实现了亚微米级甚至纳米级的ZrC-SiC混合粉体的制备,其平均粒径约为200nm。(The invention relates to a preparation method of superfine ZrC-SiC mixed powder, which comprises the steps of sequentially dissolving zirconium oxychloride octahydrate, tetraethoxysilane and phenolic resin into alcohol by a sol-gel method to form sol containing Zr, Si and C, carrying out polymerization reaction spontaneously to form gel, ageing at room temperature for 24 hours, drying to obtain dry gel, ball-milling the dry gel into powder, carrying out heat treatment at 1500-1700 ℃ under the protection of argon atmosphere, and sieving to obtain the superfine ZrC-SiC mixed powder. The superfine ZrC-SiC mixed powder prepared by the method is of a polygonal particle structure and mainly comprises ZrC, SiC and a small amount of C, the preparation of submicron or even nanoscale ZrC-SiC mixed powder is realized, and the average particle size of the ZrC-SiC mixed powder is about 200 nm.)

1. The preparation method of the superfine ZrC-SiC mixed powder is characterized by comprising the following steps: dissolving zirconium oxychloride octahydrate, ethyl orthosilicate and phenolic resin into alcohol in sequence by using a sol-gel method to form sol containing Zr, Si and C, wherein the molar ratio of C (Zr + Si) is 3-5: 1, and the molar ratio of Zr to Si is 0.5-5: 1; then the sol volatilizes at room temperature and spontaneously carries out polymerization reaction to form gel containing Zr, Si and C, and then the gel is aged for 24 hours at room temperature and is subjected to freeze-drying treatment to remove all water to obtain xerogel; ball-milling the dry gel into powder to obtain a ZrC-SiC mixed powder precursor, wherein the rotating speed in the ball-milling process is 100-300 rpm, and the ball-milling is carried out for 10-60 min; and finally, carrying out 1500-1700 ℃ heat treatment on the precursor powder under the protection of argon atmosphere, preserving the heat for 0.5-3 h, and sieving to obtain the superfine ZrC-SiC mixed powder.

2. The method for preparing ultrafine ZrC-SiC mixed powder according to claim 1, wherein the method comprises the following steps: the mol ratio of Zr to Si to C in the sol is 3.5-4.5: 1 (Zr + Si) and 1-3: 1 (Zr: Si).

3. The method for preparing ultrafine ZrC-SiC mixed powder according to claim 1, wherein the method comprises the following steps: the drying process adopts freeze-drying, and the temperature of the freeze-drying process is-60 to-20 ℃.

4. The method for preparing ultrafine ZrC-SiC mixed powder according to claim 1, wherein the method comprises the following steps: the rotating speed in the ball milling process is 150-250 rpm, and the ball milling is carried out for 30-50 min.

5. The method for preparing ultrafine ZrC-SiC mixed powder according to claim 1, wherein the method comprises the following steps: and (3) carrying out heat treatment on the ZrC-SiC mixed powder precursor for 1-2 h at 1550-1660 ℃ under the protection of argon.

6. The method for preparing ultrafine ZrC-SiC mixed powder according to claim 1, wherein the method comprises the following steps: the grain diameter of the superfine ZrC-SiC mixed powder is 0.178 mu m.

Technical Field

The invention relates to the field of ZrC-SiC composite material preparation, in particular to a preparation method for ZrC-SiC mixed nano powder.

Background

Zirconium carbide-silicon carbide (ZrC-SiC) composites incorporating ZrC and SiCSuch as extremely high melting point, hardness and elastic modulus, stable thermochemical properties and excellent corrosion resistance. In addition, the existence of SiC provides self-healing capability for the ZrC-SiC composite material, and SiC is firstly oxidized to generate liquid SiO in a high-temperature aerobic environment₂Filling up micropores and microcracks on the surface of the ZrC-SiC composite material and preventing further oxidation, thus having excellent oxidation resistance.

Due to these excellent properties, ZrC-SiC composites are widely used as ultra-high temperature structural materials in the fields of Thermal Protection Systems (TPS), rocket motors, and supersonic aircrafts. It is worth noting that the sinterability of the ZrC-SiC composite ceramic material is closely related to the initial mixed powder particle size and homogeneity. Therefore, from the ceramic industry to military applications, the superfine ZrC-SiC mixed powder is a raw material for producing ZrC-SiC composite ceramic materials, and low-cost and large-scale manufacturing techniques thereof are receiving global attention. To this end, the present invention seeks to provide a process technology using inexpensive zirconium oxychloride (ZrOCl)₂·8H₂O), Tetraethoxysilane (TEOS) and phenolic resin are respectively used as initial raw materials of a zirconium source, a silicon source and a carbon source, and the superfine ZrC-SiC mixed powder can be synthesized by combining a sol-gel technology and a freeze drying method through carbon thermal reduction.

Disclosure of Invention

The technical problem is as follows: the invention provides polygonal granular ZrC-SiC mixed powder with ZrC and SiC phases mixed uniformly and small and uniform grain size and a method for preparing the mixed powder.

The invention provides a method for preparing ZrC-SiC mixed powder, which comprises the following steps:

1) preparation of Mixed sols

Mixing a zirconium source (ZrOCl)₂·8H₂Adding O, a silicon source (TEOS) and a carbon source (phenolic resin) into a proper amount of alcohol in sequence, stirring and mixing uniformly to obtain sol containing Zr, Si and C, wherein the molar ratio of C (Zr + Si) is 3-5: 1, and the molar ratio of Zr to Si is 0.5-5: 1;

2) preparation of Mixed gels

Volatilizing the sol prepared in the step 1) at room temperature, spontaneously carrying out polymerization reaction to condense the sol into gel, and ageing the gel for 24 hours at room temperature;

3) drying treatment

Freeze-drying the gel prepared in the step 2) until the water is completely removed to obtain dry gel;

4) ball milling treatment

Performing ball milling treatment on the xerogel prepared in the step 3) to obtain precursor powder of ZrC-SiC mixed powder, wherein the rotating speed in the ball milling process is 100-300 rpm, and the ball milling is performed for 10-60 min;

5) carbothermic reduction

Carrying out heat treatment on the precursor powder obtained in the step 4) at 1500-1700 ℃ for 0.5-3 h under the protection of argon;

6) and after the reaction is finished, taking out the product, and carrying out treatment such as crushing, grinding, sieving and the like to obtain ZrC-SiC mixed powder.

On the basis of the technical scheme, the invention can be further improved as follows.

Preferably, the mol ratio of C (Zr + Si) to C (3.5-4.5: 1) and the mol ratio of Zr to Si is 1-3: 1 in the sol containing Zr, Si and C in the step 1)

Preferably, the lyophilization temperature in step 3) is set to-60 to-20 ℃.

Preferably, the ball milling rotation speed in the step 4) is set to be 150-250 rpm, and the ball milling time is 30-50 min.

Preferably, the heat treatment temperature in the step 5) is set to 1550-1650 ℃, and the heat preservation time is 1-2 h.

Through the innovation and optimization of the aspects of the ingredients, the drying mode, the preparation process and the like, the invention realizes the preparation of the low-cost large-scale superfine ZrC-SiC mixed powder, and has the following specific beneficial effects:

1) compared with other methods (such as solid-solid reaction synthesis methods) except the sol-gel method, the method provided by the invention fully utilizes the sol-gel method to realize the mixing of reactants at a molecular level, so that phenolic resin molecules can be inserted between silicon and zirconium colloidal particles, the direct contact of the colloidal particles is reduced, and the hard agglomeration and the particle growth are further inhibited.

2) Compared with the prior technology for synthesizing ZrC-SiC mixed powder by sol-gel, the method provided by the invention combines a freeze-drying method, and removes water by sublimation directly. In the conventional drying process, water is volatilized and removed in a liquid state, and excessive water can form hydrogen bonds with hydroxyl groups on the surfaces of the colloidal particles in the process, so that the agglomeration among the particles is promoted. Therefore, the invention can avoid the formation of hydrogen bonds by using freeze-drying and drying, effectively reduces hard agglomeration and soft agglomeration among particles, and further realizes the refinement of the particles.

3) The method of the invention can really push the technology of preparing ZrC-SiC mixed powder by a sol-gel method to large-scale industrial production, shows obvious competitive advantages in comprehensive comparison with other production methods, and finally provides a brand-new and low-cost production technology for the important chemical raw material of high-quality superfine ZrC-SiC mixed powder.

Drawings

FIG. 1 is an X-ray diffraction pattern of a ZrC-SiC mixed powder obtained in example 1;

FIG. 2 is a photograph of a transmission electron microscope showing a ZrC-SiC mixed powder obtained in example 1;

FIG. 3 is a particle size distribution diagram of a ZrC-SiC mixed powder obtained in example 2;

Detailed Description

The principles and features of this invention are described in connection with the drawings and the detailed description of the invention, which are set forth below as examples to illustrate the invention and not to limit the scope of the invention.