What Is Silica Fiber?

Fiber made of high-purity silica and natural quartz crystals. With heat resistance, corrosion resistance and softness. High strength retention at high temperature, dimensional stability, thermal shock resistance, chemical stability, light transmission and electrical insulation.

Quartz fiber is an inorganic fiber made from high-purity quartz or natural crystal. Its diameter is generally several microns to several tens of microns.

It maintains some of the characteristics and properties of solid quartz, is an excellent high temperature resistant material, and can be used as a reinforcing phase for advanced composite materials. 9% SiO ₂ mass fraction of quartz glass fiber is as high as 99.9%. The high temperature resistance is higher than that of high-silica fiber. The long-term use temperature can reach 1200 ° C and the softening point temperature can reach 1700 ° C. At the same time, it has high electrical insulation performance, ablation resistance, thermal shock resistance, excellent dielectric properties and good chemistry Stability, etc. Therefore, quartz fiber has important applications in the military, national defense, aviation, and aerospace industries, and can be used to manufacture rocket fire vents, aerospace thermal protection devices, and the like.

The manufacturing methods of quartz fiber are:

(1) The quartz rod or tube is melted and drawn with an oxyhydrogen flame, and then sprayed with an oxyhydrogen flame torch to make a quartz wool with a diameter of 0.7-1 m;

(2) Quartz is melted by flame to form short fibers and felts with high-speed airflow;

(3) Pass the quartz wire or rod through a hydrogen or oxygen flame or a gas flame at a constant speed, and then soften it into a high-speed wire.

Thermal damage mechanism of quartz fiber

Quartz fibers are often exposed to high-temperature working environments. Under the action of high temperature, quartz fiber has the tendency of thermal degradation, which affects its high temperature performance. At present, there are many researches on high-temperature phase changes of quartz materials, but there are few reports on the thermal damage mechanism of quartz fibers.

Some scholars have studied the phase transition, surface microstructure change and its influence on mechanical properties of quartz glass fiber under high temperature conditions, and provided a theoretical basis for exploring and improving the service life of quartz glass fiber and broadening its application field.

The research results show that the decline of the strength of quartz fiber can be divided into two stages ^[1] .

(1) In the heat treatment temperature range below 600 ° C, due to the volatilization of the surface treatment agent of quartz fiber, the diameter of the quartz fiber gradually decreases, and the defects such as cracks, stripe protrusions and scars on the original surface are gradually exposed, resulting in quartz fibers. The tensile strength decreases slowly;

(2) In the heat treatment temperature range of 600 1000 , the surface treatment agent of quartz fiber has already been volatilized. During the heating and cooling process, due to the effect of thermal stress, the strip-like protrusions and scars on the surface began to peel off, causing a certain number of new surface cracks and crack defects. The higher the temperature, the more pronounced the strip-like protrusions and scars on the surface of the quartz fiber. This is the main factor that causes the strength of the quartz fiber to decrease at this temperature, resulting in a significant decrease in the strength of the treated quartz fiber at 600 to 1000 ° C.

Surface treatment of quartz fiber

Quartz fiber is a kind of glass fiber with high SiO ₂ content. It has excellent properties and is widely used in areas with special requirements on materials, such as biological conduits and exhaust gas treatment. In recent years, due to its outstanding mechanical properties and dielectric properties, it has been increasingly used in the aerospace and aviation fields, especially in high temperature resistant radome systems. At present, the research on quartz fiber mainly focuses on its crystallization performance, surface coating modification and so on. The ceramic matrix composites for ultra-high Mach number radomes often use continuous quartz fiber reinforcements. In this way, the quartz fibers must be woven to obtain the initial shape. In order to maintain the bunching properties of the quartz fibers and facilitate weaving, they must be added during the fiber production process. Sizing agent. The main component of the sizing agent is organic matter. Ceramic-based radomes generally require high-temperature treatment under vacuum or a protective atmosphere to obtain the final product. In this way, organic matter will be carbonized, and the presence of free carbon will seriously affect the dielectric properties of the radome. Therefore, in the preparation of the quartz fiber reinforced ceramic-based radome material, the fiber surface wetting agent must be removed first, and the damage to the quartz fiber must be reduced at the same time. However, there are no reports on how to remove the sizing agent, the surface morphology, composition changes, and performance changes of the quartz fiber before and after the sizing agent is removed.

Some scholars ^[2] studied the method of removing the sizing agent on the surface of quartz fiber, and performed SEM and XPS analysis on the quartz fiber treated by different methods, and compared the changes in the tensile strength of the quartz fiber before and after treatment. The results show that the high temperature heat treatment can completely remove the surface wetting agent of the quartz fiber, and the strength of the quartz fiber is more sensitive to the heat treatment temperature.