Classification of Inorganic Fibers: Types, Properties, and Applications

Inorganic fibers, both metal and non-metal, are more resistant, rigid, have higher melting points, and exhibit greater heat resistance than traditional fibers. They are also completely uninflammable, but except for the metal fibers, they tend to be fragile. Their textile applications are limited, though they are widely used as reinforcement in composite materials. Inorganic fibers are especially useful in high temperatures and corrosive environments.

Inorganic fibers are made from inorganic materials and can be classified into the following categories:

1. Glass Fiber
2. Amorphous Fiber (e.g., Rock Wool)
3. Carbon Fiber
4. Polycrystal Fiber (e.g., Alumina Fiber)
5. Monocrystal Fiber (e.g., Wollastonite, Potassium Titanate Fiber)

Each category has distinct characteristics:

• Amorphous Fibers have high strength but low modulus elasticity due to the absence of grain boundaries.
• Polycrystalline Fibers have superior heat resistance because of small crystals.
• Monocrystalline Fibers are extremely strong due to their fine, whisker-like fibers.

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Types of Inorganic Fibers

1. Glass Fiber

   • Properties: Glass fibers, primarily used for papermaking, have a fiber diameter of 6-20 µm and a length of 3-25 mm. They are known for their superior heat resistance and dimensional stability.
   • Applications: Used in building materials, floor insulation, and construction due to their heat resistance and stability.

2. Micro Glass

   • Properties: Micro glass is a wool-like glass fiber with a fiber diameter of 0.1-3 µm.
   • Applications: Commonly used in filters, analytical-grade filter paper, and insulating materials.

3. Carbon Fiber

   • Types: Carbon fibers can be divided into two main categories:
     • PAN-based (Polyacrylonitrile)
     • Pitch-based (Petroleum oil and coal)
   • Properties: Carbon fibers have superior mechanical strength, modulus of elasticity, heat resistance, and chemical resistance. Their electric resistance and heat conductivity are similar to metals.
   • Applications: Used in electromagnetic shields, electrodes, and heat-resistant structures, thanks to their low thermal expansion coefficient.

4. Activated Carbon Fiber

   • Properties: Characterized by an excellent absorption rate, which cannot be achieved by granules or powders. The fibrous form offers a low-pressure loss in filtration.
   • Applications: Primarily used in filtration applications.

5. Meerschaum (Hydrated Magnesium Silicate)

   • Properties: Meerschaum is a form of magnesium silicate, similar to talc, but with a distinct molecular structure and micro-level fine pores. It has superior adsorptive properties and is effective as an inorganic binder.
   • Applications: Used in the adsorption and deodorization of substances like water, ammonia, and hydrogen sulfide.

6. Potassium Titanate Fiber

   • Properties: Potassium titanate fibers have needle-like crystals and exhibit varying physical and chemical properties depending on the manufacturing process. Fibers with submicron diameters have significantly higher strength.
   • Applications: Known for low heat conductivity and high electrical insulation, these fibers are used in heat and electrical insulation materials as well as in filters.

7. Ceramic Fiber

   • Properties: Composed primarily of alumina and silica, ceramic fibers are lightweight, flexible, and have superior heat insulation properties, withstanding temperatures of 1000°C and higher.
   • Applications: Used in sealing, packing, heat insulation, and filters.

8. Wollastonite (Calcium Silicate Fiber)

   • Properties: Wollastonite is a natural mineral with needle-like crystalline structures. It has superior heat resistance and electrical insulation properties.
   • Applications: Considered an alternative to asbestos and widely used for heat resistance and electrical insulation.

9. Rock Wool

   • Properties: Created by combining iron-making blast furnace slag with silicate rock, basalt rock, and lime rock, rock wool has excellent flame resistance, sound-absorbing, and insulating properties.
   • Applications: Primarily used in heat retention, heat insulation, and sound-absorbing materials.