Preparation of Al_1.6Sc_0.4Mo₃O₁₂ nanofibers and their negative thermal expansion properties

One-dimensional negative thermal expansion material has important applications in thermal expansion control and fiber toughened composite. Orthorhombic Al_1.6Sc_0.4Mo₃O₁₂ nanofibers have been prepared by electrospinning. The phase composition, microstructure, morphology, and thermal expansion performance of the samples prepared at various temperatures were investigated. Results show that as-prepared Al_1.6Sc_0.4Mo₃O₁₂ nanofibers are smooth and homogeneous with a fiber diameter of about 370.00 nm, but they show an amorphous structure. Orthorhombic Al_1.6Sc_0.4Mo₃O₁₂ nanofibers can be obtained at 550 ℃ with a diameter of around 140.00 nm. With the increase of post-annealing temperatures, the crystallization of the samples was improved. However, higher post-annealing temperatures will destroy the nanofiber structure of the samples. HTXRD reveals that orthorhombic Al_1.6Sc_0.4Mo₃O₁₂ nanofibers show anisotropic NTE in 25–700 °C. The expansion coefficients α_a, α_b, and α_c of Al_1.6Sc_0.4Mo₃O₁₂ nanofibers are −5.05 × 10^–6 °C⁻¹, 4.41 × 10^–6 °C⁻¹, and −3.18 × 10^–6 °C⁻¹, respectively. The α_v is −3.83 × 10^–6 °C⁻¹, and the corresponding α_l is −1.28 × 10^–6 °C⁻¹.