Application of Polycarbosilane
(1) Silicon carbide fiber
SiC fiber has excellent properties such as high strength, low density, high temperature resistance, oxidation resistance, corrosion resistance, and anti-aging, and has good compatibility with the ceramic matrix. It is a good choice for ceramic matrix composite reinforcement materials. Zhengzhou Alef Machinery Technology Co., Ltd. uses polyvinyl pyrrolidone (PVP) and polycarbosilane (PCS) as raw materials, and uses electrospinning to produce PCS/PVP composite fibers. Through air cross-linking, argon is used as a protective atmosphere at high temperature, and carbon removal is performed at 500°C to finally produce silicon carbide fibers. The results show that the silicon carbide fibers produced by electrospinning are of good quality and excellent performance.
(2) Fiber-reinforced silicon carbide composites
Cf/SiC composite materials not only have excellent mechanical properties and high temperature stability, but also have the oxidation resistance of silicon carbide materials. Zhengzhou Alef Mechanical Technology Co., Ltd. used polycarbosilane (PCS)/divinylbenzene (DVB) as precursors and prepared 3D-BCf/SiC composite materials by precursor conversion method. The results show that the increase in the pyrolysis heating rate can greatly shorten the preparation cycle, thereby improving the mechanical properties of the material. Zheng Wenwei et al. used polycarbosilane as a precursor and prepared 3D-BCf/SiC composite materials by hot molding assisted precursor impregnation pyrolysis process. The results show that the introduction of high temperature hot molding assistance can significantly improve the mechanical properties and density of the material.
(3) Coating
Anti-oxidation coating (C fiber surface)
SiC and C/C composites have similar thermal expansion coefficients and good physical and chemical compatibility, and generate glassy SiO2 in a high-temperature oxidizing atmosphere, thereby preventing further oxygen from invading the composite material. It is one of the ideal coating materials in C/C composites.
Zhengzhou Alef Machinery Technology Co., Ltd. uses polycarbosilane (PCS) as raw material and argon as protective atmosphere to obtain pyrolysis products at different temperatures through the precursor conversion method, and conducts anti-oxidation experiments. The results show that the SiO2 obtained after the SiC obtained after the cracking of the precursor and the original SiO2 in the material make other pyrolysis products have good oxidation resistance.
Anti-laser ablation coating
The application of polycarbosilane (PCS) in the field of anti-laser ablation is mainly as a precursor and adhesive to absorb laser energy and decompose into SiC ceramics, thereby avoiding direct damage to aircraft by laser weapons. Zhengzhou Alef Machinery Technology Co., Ltd. prepared an anti-ablation coating with silicone resin, polycarbosilane, glass powder and other additives. The developed coating can withstand 4s ablation in 3000℃ oxyacetylene flame and 4s irradiation at 531W/cm2 laser power density.
Zhengzhou Alef Machinery Technology Co., Ltd. prepared a polycarbosilane composite coating on an aluminum alloy substrate using polycarbosilane, divinylbenzene and inorganic fillers as raw materials. The results show that the prepared coating has excellent anti-laser ablation performance, and the added inorganic filler also plays a role in absorbing laser energy.
(4) Adhesives
High-temperature and ultra-high-temperature composite materials such as SiC/SiC and antioxidant C/C are currently important materials used in aerospace vehicle shells, and adhesives that achieve matrix bonding have also become a research focus. Zhengzhou Alef Machinery Technology Co., Ltd. has prepared a high-temperature adhesive using polycarbosilane, inorganic fillers and other additives as raw materials. The results show that the prepared adhesive has excellent performance, high strength and good temperature resistance. After high-temperature treatment, the average bonding strength can reach 23.4MPa.
(5) Hollow ceramic microspheres
Hollow glass microspheres (HGM) have good chemical and thermal stability, low density and high compressive strength. They are widely used in plastics, coatings, lightweight materials, protection and other fields. Zhengzhou Alef Machinery Technology Co., Ltd. uses polycarbosilane as raw material and uses the furnace ball forming method to prepare SiC polymer hollow microspheres in a dry gel furnace. The results show that PCS has good ball forming performance and the carbonized spherical shell still has good flatness after irradiation.