Physicochemical properties and tensile properties of boron filaments, perspectives of their application for reinforcing of composite materials

Results of investigating structure, characteristics, tensile properties of boron filaments and materials reinforced by them are reviewed from 1966 to 1977. High tensile properties of boron filaments are defined by fine-crystal structure of boron layer. Boron crystallites have the size of 15-30 A. The filament core consists of big crystal tungsten borides of the WBsub(6.25) composition (mixture of WB4 and W2B5 borides) Physico-chemical properties of boron filaments are determined by boron and tungsten properties and their interaction. Low density ensures high specific tensile characteristics. High melting temperature determines filament thermostability and high surface energy. At room temperature thermal conductivity of filaments comes near to thermal conductivity of stainless steels and decreases with temperature increase (5 times at 1000 deg C). High stability at abrasive effects is due to high hardness. Considered are specific electrical resistance, durability at bending, tension, torsion and compression, level and distribution of residual tension. The data presented in the review show that boron filaments permit to create details of flying vehicles with record technical indexes thanks to high tensile properties