Effect of Surface Roughness on the Strength of Sapphire Fibers

The study examines the strength of sapphire fibers produced using the modified Stepanov/edge-defined film-fed growth (EFG) method. Investigation of the surface shows that the roughness of the sapphire fibers obtained from the melt is primarily due to their oscillation in ascending gas streams during growth. The effect of the surface roughness of the fiber on its strength is studied. Using a fiber-diameter stabilization system brings the roughness parameters to a few tens of nanometers. Reducing the surface roughness of the fiber increases its strength, and the strength of the fibers decreases with length in a power-law dependence.