Prep. of preparing fiber reinforced silica-base composite material

Abstract

The present invention is the making process of wave-permeating fiber reinforced silica-base composite material. With oxide fiber fabric as prefabricated matter, organosilicon alkoxide as precursor and high-purity argon and oxygen as carrier gas and carbon eliminating gas, part with complicated shape, thin wall and relatively precise sizes may be produced in chemical vapor permeating furnace as making equipment, and its dielectric performance can meet the requirement as antenna hood and other astronautic wave-permeating material.

Description

Technical field [0001] The present invention relates to a chemical vapor infiltration (Chemical Vapor Infiltration, CVI method for short) method for manufacturing continuous oxide fiber reinforced silica ceramic matrix composite material for wave transmission. It is suitable for the manufacture of silica ceramic matrix composites reinforced by continuous oxide fibers (quartz fibers, alumina fibers and various alumina-silica composite fibers) and various special-shaped parts with complex shapes and precise dimensions. Background technique [0002] Aerospace wave-transmitting material is a multi-functional dielectric material that protects the normal operation of communication, telemetry, guidance, and detonation of aerospace vehicles under harsh environmental conditions. be widely used. Oxide fiber reinforced silica ceramic matrix composites such as continuous quartz fiber and high silica fiber are the best wave-transmitting materials for high Mach number (M>6.5) aircraft...

AI Technical Summary

Problems solved by technology

The disadvantages are: ①When the hot pressing temperature is above 1300°C, quartz is easy to crystallize to form α-cristobalite, and its high thermal expansion coefficient makes the composite material lose its thermal shock resistance. At the same time, the oxide fiber has low shear resistance. Severe damage to the fiber; ②The large difference between the size after winding and the final size, and the uneven distribution of the matrix in the fiber bundle and between the bundles lead to a great difference in the performance of the flat material and the special-shaped material prepared by this method, and the material has strong directionality and shear resistance between layers. Poor cutting ability

The disadvantages are: ①During the impregnation process, obvious dialysis phenomenon occurs, which reduces the impregnation density. In addition, the heat treatment temperature is low, and the matrix is ​​not completely sintered, so the density and mechanical properties of the composite material are low.

②The composite material has a porous structure, and a large amount of hydroxyl groups may remain on the surface of the silica particles. The aircraft is easy to absorb moisture during storage and flight. Through capillary action, water vapor diffuses along the pores to the inside of the material, which seriously affects the stability of the high-temperature dielectric properties of the material. Therefore, it is necessary to use fluoride for surface passivation treatment or to prepare a hydrophobic protective film, which increases the process and cost

③ When the alkali metal in the silica sol causes the warhead to re-enter the atmosphere, the electron density in the high-temperature plasma sheath due to aerodynamic heating increases sharply, which not only interrupts the communication between the aircraft and the ground, but also increases the radar reflection cross section due to free electrons entering the wake , is extremely detrimental to penetration

The cyclic impregnation method of silica sol cannot solve the contradiction between the relative density requirements of the composite material and the contradiction between the demand for low cost and the high scrap rate.

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