Refractory ceramic fiber

Aluminosilicate Fibers. Vitreous alurninosihcate fibers, more commonly known as refractory ceramic fibers (RCF), belong to a class of materials known as synthetic vitreous fibers. Fiber glass and mineral wool are also classified as synthetic vitreous fibers, and together represent 98% of this product group. RCFs were discovered in 1942 (18) but were not used commercially until 1953. Typical chemical and physical properties of these materials are shown in Table 3. 

Table 3. Typical Physical and Chemical Properties of Refractory Ceramic Fibers...

Sihca and aluminosihcate fibers that have been exposed to temperatures above 1100°C undergo partial conversion to mullite and cristobaUte (1). Cristobahte is a form of crystalline siUca that can cause siUcosis, a form of pneumoconiosis. lARC has deterrnined that cristobaUte should be classified as 2A, a probable carcinogen. The amount of cristobahte formed, the size of the crystals, and the nature of the vitreous matrix in which they are embedded are time- and temperature-dependent. Under normal use conditions, refractory ceramic fibers are exposed to a temperature gradient, thus only the hottest surfaces of the material may contain appreciable cristobahte. Manufacturers Material Safety Data Sheets (MSDS) should be consulted prior to handling RCF materials. 

Stone, R. Oxford University Press, Inc., New York, NY. 2000. 

Brown DM, Fisher C, Donaldson K. 1998. Free radical activity of s mthetic vitreous fibers Iron chelation inhibits hydroxy radical generation by refractory ceramic fiber. J Toxicol Environ Health 53 545-561. 

Mast RW, Hesterberg TW, Glass LR, et al. 1994. Chronic inhalation and biopersistence of refractory ceramic fiber in rats and hamsters. Environ Health Perspect Suppl 102 207-209. 

Mast RW, McConnell EE, Anderson R, et al. 1995. Studies on the chronic toxicity (inhalation) of four types of refractory ceramic fiber in male Fischer 344 rats. Inhal Toxicol 7 425-467. 

Yu CP, Zhang L, Oberdorster G et al. 1995. Deposition of refractory ceramic fibers (RCF) in the human respiratory tract and comparison with rodent studies. Aerosol Sci Technol 23 291-300. 

Yu CP, Ding YJ, Zhang L et al. 1996. A clearance model of refractory ceramic fibers (RCF) in the rat lung including fiber dissolution and breakage. J Aerosol Sci 27 151-160. 

Mineral fibers for the production of insulating materials are named after their. starting materials as glass or rock fibers and as refractory ceramic fibers. The names mineral, glass or rock wool are usually used, since they, in contrast to textile glass fibers, are produced as short, randomly oriented fibers. The end products are therefore known as mineral wool insulation materials. 

The economic importance of mineral wool is considerable. In 1995 the worldwide production was just under 5-10 t/a, shared equally by the USA, Western Europe and the rest of the World. The share of refractory ceramic fibers is small and in 1995 accounted with 190 10 t/a for ca. 1 - 2% of the total production of synthetic mineral fibers. 

Raw materials for refractory ceramic fibers kaolin and cyanite in addition to alumina, quartz, zircon... 

Electric arc resistance heated furnaces and electrical melting units are mainly used for refractory ceramic fibers, due to the high melting temperatures of the raw materials. In ovens with resistance heating the melt itself acts as the electrical resistance, since silicate melts generally become sufficiently conductive with increasing temperature to transport sufficient current, due to ionic conduction. 

---