What is ceramic fiber? What are the uses of ceramic fiber?

Refractory ceramic fiber is a protective coating for refractories used in ceramic industrial kilns.

The surface of refractories in sections of ceramic industrial kilns that are subjected to high-temperature atmospheres is often coated with a refractory coating mainly composed of mullite and alumina particles, with clay or water glass as binders, to prevent the surface of the refractories from fusing with the fired materials inside the kiln and to protect the surface of the refractories from damage. However, when the above-mentioned coating is applied to the surface of the refractory, the water glass binder in the coating will vitrify, creating a thermal expansion difference with the refractory matrix, resulting in cracks and coating peeling, which prevents the coating from fully protecting the refractory substrate. Furthermore, the insulation is reduced, the resistance to thermal shock is weakened, and the service life of the refractory is shortened, requiring frequent maintenance and repair, which undoubtedly increases the cost of refractory materials and construction. To overcome these shortcomings, a refractory protective coating that is non-peeling, oxidation-resistant, and resistant to thermal shock, and can effectively protect refractories, has been successfully developed.

I. Refractory Protective Coating

This protective coating is mainly composed of ceramic fibers with a size of 60-300 mesh and silica sol (silicon dioxide content 5-70%, particle size 5-30 μm), with an appropriate amount of organic binder.

1. Ceramic Fiber

The ceramic fiber used depends on the operating temperature. For operating temperatures of 800-1600°C, alumina-based aluminum fiber is recommended. During use, the fiber is pulverized, de-ironed, and sieved into short fibers with a size of 60-300 mesh. If the ceramic fiber size is less than 60 mesh, the thermal shock resistance is reduced; if it exceeds 300 mesh, the adhesion is reduced. The fiber content is 30-50% (by weight).

2. Silica Sol

Silica sol is used as an inorganic binder. The silicon dioxide content is in the range of 5-70%, with the optimum being 10-15%. If the silicon dioxide content is not within this range, either the bonding strength is reduced and peeling occurs, or silicon dioxide easily melts on the surface of the coating, weakening the effect of preventing fusion with the fired material. In addition, to improve the uniformity of the silicon dioxide particle size and prevent the bonding strength from decreasing due to reduced inter-particle bonding force, the silicon dioxide particle size should be maintained within the range of 5-30 μm. The silica sol content is 50-65% (by weight).

3. Organic Binder