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Preparation of Zirconium Boride Ultra-High Temperature Ceramic Matrix Composite

wallpapers Industry 2020-07-21

At present, the commonly used preparation methods of carbide and  Zirconium Boride ultra-high temperature ceramic matrix composites include pressureless sintering, hot pressing sintering, and reactive hot pressing sintering.

Pressureless sintering (PS): Pressureless sintering is to heat and form raw materials under normal pressure. It is the simplest sintering method. It is suitable for the preparation of components of different shapes and sizes. The temperature is easy to control, but the resulting Material is dense. Lower, the raw material particle size and sintering aid have a significant influence on Material density.

Hot-pressing sintering: hot-pressing sintering is a sintering method in which raw material powder is filled into a mold and pressurized and heated from a uniaxial direction at the same time. The process cost of this method is high, and the size of the prepared Material is limited, so its application is affected by certain restrictions.

Reactive hot pressing sintering: Reactive hot pressing sintering is a sintering process formed by using chemical reactions between raw materials and combined with a hot pressing sintering process. This method has lower sintering temperature, high density of stuff, no need for powder preparation, and cost relatively little.

Spark plasma sintering: Spark plasma sintering is to pass a high-energy pulse current into a powder-containing mold, and generate plasma discharge between the powder particles for heating and sintering. It is a kind of low sintering temperature, high speed, and a high degree of densification. Sintering processes, but the uneven distribution of sintering temperature for large-size samples in practical applications restrict this technology application.

At present, the preparation methods of fiber-reinforced ceramic matrix composites include precursor immersion cracking method (PIP), reactive melt infiltration method (RMI), chemical vapor infiltration method (CVI), mud method (SI) and so on.

Precursor impregnated pyrolysis method (PIP): The precursor impregnated pyrolysis method is also called a polymer impregnated pyrolysis method or precursor conversion method. The general process is: fiber preforms are used as the skeleton, polymer impregnated as the precursor, and inert gas. Under the protection, it is cross-linked and cured and then subjected to high-temperature pyrolysis in a particular atmosphere, thereby obtaining a ceramic matrix composite material. The advantages of this method are: pioneer molecules can be designed to control the composition, structure, and performance of the final composite ceramic matrix; the preparation temperature is low, and the equipment requirements are simple; large and complex-shaped structural parts can be prepared, and net shaping can be achieved. But there are also disadvantages such as high porosity and long preparation cycle.

Reactive melt impregnation method (RMI): The responsive melt impregnation method is to infiltrate molten metal into a porous preform (usually a C/C preform) under high-temperature conditions and then react with C in the preform to form a ceramic matrix. The general process is partial densification of the fiber preform. Finally, with molten metal infiltration, the molten metal reacts with the matrix carbon to obtain a highly dense carbide matrix. This method has a short preparation period, low cost, high material density, and adjustable matrix composition; however, due to the high immersion temperature, the fibers are easily damaged.

Chemical vapor infiltration method (CVI): The chemical vapor infiltration method is to put the fiber preform into an individual furnace, and the vapor precursor diffuses around the preform with the pressure difference and diffuses into the interior through the pores, and the reaction product is deposited in the pores Methods. The method has the following advantages: it can prepare ceramic matrix composite materials with a higher melting point at a lower temperature; it can be used to make ceramic matrix composite components with larger size and complex structure; the pressure during the preparation process is more economical, and the fiber is mechanically damaged. Small, various ceramic substrates can be prepared with a wide range of applications.

Slurry method (SI): The slurry method is to make the required ceramic powder into a slurry and then introduce it into the fiber preform, and then sinter it at a high temperature to obtain a continuous fiber-reinforced ceramic matrix composite material, which can be divided into slurry according to the way the mud is introduced Material dipping method and slurry brushing method. The slurry dipping method can promote the dispersion of ceramic powder and improve composite materials' overall performance. Still, the power distribution in the slurry is difficult to homogenize, resulting in uneven mechanical properties of the Material, weak oxidation resistance, and easy phase separation.

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Tag: Zirconium Boride