Basalt fibers are mainly composed of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra connected by sharing oxygen corner tops to form a continuous linear structure.
Basalt fibers are non-flammable, they are highly chemically stable and have good resistance to weathering, alkalinity and acid. Depending on the thermal stability of the composition of the raw material and the presence of a large number of micropores that prevent air convection and thermal radiation, it is a reason to consider the use of basalt fiber fabrics in thermal insulation and passive fire protection applications.
The main factor determining the thermothermal stability of basalt fibers is their crystallization behavior. The crystallization ability depends mainly on the chemical composition of the fiber as well as the heat treatment conditions. In particular, due to its high content of iron oxides, crystallization in basalt fibers begins with the oxidation of ferrous cations and the formation of spinel structural phases on the surface of the fibers: that is, divalent cations diffuse from the inside to the surface, where they form nanocrystalline layers CaO, MgO, (Mg, Fe)3O4 with ambient oxygen.
The mechanical strength of basalt fibers is thought to be closely related to the presence of surface heterogeneity such as surface defects, structural defects, and impurities. Another characteristic of basalt fibers is that they have good compatibility with matrix materials, and there are some studies that focus on the surface treatment of these fibers to change their surface morphology and improve their wettability with matrix materials.
