Preparation and Application of Polymers for Production and Application of Structural Ceramics Yu Kangtai Zhang Shuhua (Wuhan University of Technology, Wuhan University, Wuhan 430070) The actuators can be used to manufacture structural ceramics safely and efficiently. In addition, the manufacturer made some minor improvements to it, pioneering newer application areas.

1 With the development of modern science and technology, industry, energy, transportation, and space technology have set high demands on materials, such as good wear resistance, high temperature resistance, corrosion resistance, and sufficient machinery. Strength, etc., and can be used under a variety of harsh conditions. For example, as a key material for magnetic fluid power generation of new energy technologies, a channel material requires high temperature resistance, high temperature, high velocity airflow, and various chemical substances (such as K2C3, 2S4, etc.), and other harsh environments. Metal or alloy materials are difficult to handle, and non-structural ceramic materials are the only ones.

Structural ceramics such as silicon carbide and boron carbide are all compounds based on covalent bonds, which are difficult to sinter. The sintering temperature is high. The preparation process starts with the raw material powder, and it is formed and fired. The process flow is complex, and the parameters to be controlled are many. It is costly.

Is there a new preparation process that partially replaces the above process? The answer is yes.

Among them, SiC and C organic polymer precursors are prepared first, and precursors are then used to prepare SiC, C or their composites with fibers, whiskers, and the like. The advantage of this process is that the process flow is simplified, and both a single ceramic material and a composite ceramic material can be prepared, and the overall manufacturing cost is reduced.

The core of the process is to prepare a single-component new thermosetting SiC polymer, which is a fluid, and uses it as a raw material to prepare SiC ceramics and SiC composite ceramics.

2 Basic properties that the polymer must possess (1) Good fluidity is required to facilitate molding or to be easily combined and compounded with other materials such as ceramic fibers.

(5) The use of polymer precursors for the production of corresponding ceramic products facilitates the processing and production with higher efficiency than conventional production methods.

3 The new SiC organic polymer developed by the long-term research of SiC polymer precursor has a chemical composition with a fractional ratio of carbon to silicon-benzene that is close to 1:1. It can minimize the amount of free carbon after heat treatment, and can effectively avoid excess in SiC. The carbon causes a decrease in the thermal stability of the product.

This SiC polymer is non-toxic, can change its viscosity and other properties at the molecular level, and it can be used as a matrix and high-temperature adhesive for coating composites. It is a kind of low-cost and reusable steel mold that is fired in a protective atmosphere. It is a kind of organic polymer that can produce high-purity SiC ceramic precursors with high efficiency.

圄1 is the relative mass of the ceramic precursor at different temperatures (with 0!

When compared to). There is no need to add another solvent throughout the process, and there is no chloride, acid or other corrosive gases generated throughout the sintering process, thus meeting the environmental protection and manufacturer's interests. Non-toxic hydrogen gas is the exhaust gas of thermal decomposition, and the production rate of SiC ceramics produced by using SiC polymer precursors can be increased by 80% to 85%. The higher the firing temperature, the lower the yield. The use of ceramic polymers facilitates the molding of precursors of various shapes. After sintering, the amount of cold work is very small.

In addition, there is almost no pollution to the environment throughout the preparation process.

4 New Uses for Ceramic Polymers In addition to using the above-mentioned standard ceramic polymer precursors to safely and efficiently manufacture structural ceramics, manufacturers have also made some small improvements to open up more new applications.

For dense sintered ceramic materials with small shrinkage, forming binders and sintering aids are indispensable. Another purpose of the development of SiC organic polymer variants is to use as a structural ceramic additive. It can make the ceramic body after the extrusion or cold press forming can press the foot under pressureless sintering under normal pressure, so that the sintering process is greatly simplified. These polymers and certain powders, such as SiC, are used together to facilitate the molding of the product, so as to fully exert the binding effect of the polymer binder. Manufacturers can no longer add sintering aids and solvents like they used to make structural ceramics. In the molding process, the adhesive is cured in the range of 200 to 400 ", resulting in high strength and easy finishing of the finished product. The resulting semi-finished product can reach high precision after being fired. The amount of cold work is very small, even Can not be processed to greatly reduce the cost of production.

5 Composite materials and coating materials for the preparation of ultra-high temperature stability Ceramic manufacturers strive to obtain ceramic matrix composites and coatings with excellent high temperature stability. They combined the precursor of SiC polymer with some advanced refractory materials and metal powders to have good thermal insulation and to prevent oxygen diffusion. They were used as adhesives in the products and then sintered. This technique is different from the traditional method of chemical vapor deposition coating. It is a method of heating the SiC precursor to an overall sintering process of 1100 in an atmospheric gas atmosphere furnace. Ceramic composites made using this method are below 2800". Using 10 minutes of radiation damage from the MAPP Oxygen Photocell is minimal. In contrast, a sintered SiC plate with the same thickness of 3 mm made by the conventional method is damaged within 30 seconds.

The new SiC ceramic polymer precursor has a wide range of applications, it overcomes some of the deficiencies and difficulties of the previous structural ceramic manufacturing process, and thus has been widely adopted in the production of structural ceramics has produced significant technical and economic benefits.

Main properties of SiC precursor polymers Film type (Grade) Flexural strength (MPa) Tensile strength (MPa) Carbon injection film coating before thickening.

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