Preparation, mechanical properties, and diffuse reflectance of YAG continuous fibers and nanofibers

Abstract

Yttrium-aluminum-garnet (YAG) ceramic fibers not only have good flexibility, a large aspect ratio, good continuity, light weight, and high strength but also a high melting point, stable physical and chemical properties, high-temperature creep resistance, and excellent optical properties of YAG itself. These properties allow YAG fibers to be used as structural reinforcement and as basic optical materials. In this study, a YAG precursor was selected by comprehensive analysis of the spinning properties of solutions synthesized from aluminum powder, AlCl3·6H2O, and Y(CH3COO)3·4H2O. YAG precursor continuous fibers and nanofibers were spun by extrusion-forming and electrospinning, respectively. The decomposition, crystallization, and microstructure of the fibers were analyzed by thermogravimetry-differential thermal analysis (TG-TDA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The mechanical properties and diffuse reflectance of the YAG ceramic fibers were also determined. The results showed that the YAG precursor synthesized with an AlCl3·6H2O/Al powder molar ratio of 1:4 and Al/Y ratio of 3:5 had the best spinnability. The bundle of continuous fibers was 50 × 40 μm, and the length of the individual fibers was greater than 50 cm. The diameter of as-obtained YAG continuous fibers was approximately 23 μm. Both YAG continuous fibers and nanofibers showed good flexibility, uniform diameters, and high crystallinity. During the heat treatment process, loss of free water and crystalline water, decomposition and carbonization of organic matter, and crystallization and densification of the fibers occurred. YAG was directly crystallized from an amorphous material at 750 °C with a ceramic yield of 32.5%. The tensile stress and Young's modulus of the as-obtained YAG continuous ceramic fibers reached 851 MPa and 150 GPa, respectively. The average diffuse reflectance of the YAG nanofibers in the wavelength range of 700–2500 nm reached 92.7%.