CN110963812A

CN110963812A - Preparation method of carbon nano tube toughened silicon carbide ceramic

Info

Publication number: CN110963812A
Application number: CN201911305927.5A
Authority: CN
Inventors: 刘媛; 王金娥; 董明
Original assignee: Saifu Nano Technology Xuzhou Co ltd
Current assignee: Saifu Nano Technology Xuzhou Co ltd
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2020-04-07

Abstract

A preparation method of carbon nano tube toughened silicon carbide ceramic belongs to the technical field of composite ceramic materials. The preparation method of the carbon nano tube toughened silicon carbide ceramic comprises the following steps: s1, uniformly mixing silicon carbide, carbon black, silicon nitride coated carbon nanotubes, water-soluble phenolic resin and pure water to obtain uniformly dispersed slurry with solid content of 48-52%; s2, heating the slurry obtained in the step S1, evaporating to remove water to obtain a block material, dry-pressing the block material, and forming at one time to obtain a green body; s3, covering the surface of the green body with simple substance silicon, placing the green body into a vacuum high-pressure sintering furnace, heating to 1300 ℃ and 1400 ℃, and preserving the temperature for a certain time to convert the amorphous silicon nitride on the surface of the carbon nano tube into hexagonal silicon nitride; and then heating to 1450-1500 ℃ for a certain time to obtain the carbon nano tube toughened silicon carbide ceramic.

Description

Preparation method of carbon nano tube toughened silicon carbide ceramic

Technical Field

The invention relates to a technology in the field of composite ceramic materials, in particular to a preparation method of carbon nano tube toughened silicon carbide ceramic.

Background

Silicon carbide is a crystalline substance with a diamond structure formed by bonding carbon and silicon elements through covalent bonds, has many excellent properties such as high hardness, high temperature resistance, corrosion resistance, high thermal conductivity and the like, and has very excellent properties under extreme conditions such as corrosion, high temperature, aerospace and the like, so that the silicon carbide has become a widely-used non-oxide ceramic material.

Reactive sintering is the most common method for the preparation of silicon carbide ceramics. Silicon permeates into the blank body containing the silicon carbide and the carbon black at high temperature and reacts with the carbon to generate the silicon carbide, and the newly generated silicon carbide is combined with the original silicon carbide particles in the blank body to obtain the silicon carbide ceramic material. The silicon carbide ceramic prepared by the reaction sintering process has high hardness, good wear resistance and corrosion resistance, high-temperature strength and good oxidation resistance. However, reaction-sintered silicon carbide ceramics contain a certain amount of free silicon, resulting in increased brittleness of the silicon carbide ceramics. In order to overcome the defects, theoretically, carbon fibers can be added into the raw materials, but finally, the fact that the toughness of the silicon carbide ceramic can be improved by adding the carbon fibers is not found because the carbon fibers react with liquid-phase silicon to generate silicon carbide in the reaction sintering process.

The present invention has been made to solve the above-mentioned problems occurring in the prior art.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a preparation method of carbon nanotube toughened silicon carbide ceramic, which can retain the fiber structure of carbon nanotubes in reaction sintering, fully play the toughening role of carbon fibers and enhance the performance of composite ceramic materials.

The invention comprises the following steps:

s1, uniformly mixing silicon carbide, carbon black, silicon nitride coated carbon nanotubes, water-soluble phenolic resin and pure water to obtain uniformly dispersed slurry with solid content of 48-52%;

s2, heating the slurry obtained in the step S1, evaporating to remove water to obtain a block material, dry-pressing the block material, and forming at one time to obtain a green body;

s3, covering the surface of the green body with simple substance silicon, placing the green body in a vacuum high-pressure sintering furnace, heating to 1300 ℃ and 1400 ℃, preferably keeping the temperature for 0.5-1h, and converting amorphous silicon nitride on the surface of the carbon nano tube into hexagonal silicon nitride; then the temperature is raised to 1450-1500 ℃, and the temperature is preferably kept for 0.5-1h, so as to obtain the carbon nano tube toughened silicon carbide ceramic.

In the step S1, at least one of ball milling, sand milling and stirring is used for mixing.

The carbon nano tube is coated by the silicon nitride, wherein the diameter of the carbon nano tube is 80-150 nanometers, the length of the carbon nano tube is 5-10 micrometers, and the silicon nitride is amorphous silicon nitride and has the thickness of 10-20 nanometers.

The weight ratio of the silicon carbide, the carbon black and the silicon nitride coated carbon nano tube is 10 (0.5-1) to 0.5-1.

The weight ratio of the water-soluble phenolic resin to the silicon carbide is (0.05-0.06): 1.

Technical effects

Compared with the prior art, the invention has the following technical effects:

1) silicon nitride is adopted to coat the carbon nano tube, so that the carbon nano tube is prevented from being consumed by liquid phase silicon in the sintering process, the fiber structure of the carbon nano tube is reserved, and the toughening effect of the carbon fiber is fully exerted; and the amorphous silicon nitride on the surface of the carbon nano tube is converted into the hexagonal silicon nitride in the sintering process, so that the performance of the composite material is further improved;

2) the carbon nano tube is coated by the silicon nitride, so that the affinity of the carbon nano tube and a ceramic material is improved, and the problem of uniform dispersion of the carbon nano tube in the ceramic is effectively solved;

3) the method has the advantages of simple process, high efficiency, energy conservation and environmental protection, and is suitable for batch production.

Drawings

FIG. 1 is an SEM photograph of silicon nitride coated carbon nanotubes of example 1;

FIG. 2 is an SEM photograph of the slurry of example 1;

FIG. 3 is an SEM photograph of the carbon nanotube-toughened silicon carbide ceramic of example 1.

Detailed Description

The invention is described in detail below with reference to the drawings and the detailed description.

Example 1

The embodiment comprises the following steps:

s1, uniformly mixing 1kg of silicon carbide, 0.1kg of carbon black, 0.1kg of silicon nitride-coated carbon nano tube, 0.06kg of water-soluble phenolic resin and 1.2kg of pure water to obtain uniformly dispersed slurry with 50% of solid content, wherein an SEM photograph of the slurry is shown in FIG. 2;

s3, covering the surface of the green body with simple substance silicon, then placing the green body into a vacuum high-pressure sintering furnace, heating to 1400 ℃, and preserving the temperature for 30min to convert the amorphous silicon nitride on the surface of the carbon nano tube into hexagonal silicon nitride; and then heating to 1500 ℃ and preserving the temperature for 1h to obtain the carbon nano tube toughened silicon carbide ceramic, wherein an SEM photo of the carbon nano tube toughened silicon carbide ceramic is shown in figure 3.

The carbon nano tube coated by the silicon nitride is manufactured by adopting the method in the Chinese patent application with the application number of CN201910753109.5, the diameter of the carbon nano tube is 80-150nm, the length of the carbon nano tube is 5-10 mu m, the thickness of the silicon nitride is 10-20nm, and the SEM photo is shown in figure 1.

According to the carbon nanotube toughened silicon carbide ceramic prepared by the embodiment, the relative density of the ceramic is more than 99.0 percent TD, the volume of free silicon is less than 5 percent, and the fracture toughness is more than 5.6 MPa.m^1/2(ii) a The performances are superior to those of the silicon carbide ceramic only adopting mechanical mixing to add the carbon nano tube.

It is to be emphasized that: the above embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and all simple modifications, equivalent changes and modifications made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A preparation method of carbon nano tube toughened silicon carbide ceramic is characterized by comprising the following steps:

s3, uniformly paving a layer of simple substance silicon on the surface of the green body, then placing the green body into a vacuum high-pressure sintering furnace, heating to 1300 ℃ and 1400 ℃, and preserving the temperature for a certain time to convert amorphous silicon nitride on the surface of the carbon nano tube into hexagonal silicon nitride; then heating to 1450-1500 ℃, and preserving the temperature for a certain time to obtain the carbon nano tube toughened silicon carbide ceramic.

2. The method of claim 1, wherein the step S1 is performed by at least one of ball milling, sand milling, and stirring.

3. The method for preparing carbon nanotube-toughened silicon carbide ceramic according to claim 1, wherein the silicon nitride coats the carbon nanotubes, wherein the carbon nanotubes have a diameter of 80 to 150nm and a length of 5 to 10 μm, and the silicon nitride is amorphous silicon nitride and has a thickness of 10 to 20 nm.

4. The method for preparing carbon nanotube-toughened silicon carbide ceramic as claimed in claim 1, wherein the weight ratio of the silicon carbide, the carbon black and the silicon nitride coated carbon nanotube is 10 (0.5-1) to (0.5-1).

5. The method for preparing the carbon nanotube-toughened silicon carbide ceramic according to claim 1, wherein the weight ratio of the water-soluble phenolic resin to the silicon carbide is (0.05-0.06): 1.

6. The method as claimed in claim 1, wherein the step S3 comprises maintaining the temperature at 1300-1400 ℃ for 0.5-1h, and maintaining the temperature at 1450-1500 ℃ for 0.5-1 h.