Hafnium (pronounced h-fun-ny) is a metallic element with atomic number 72, which belongs to the Group 4 (IVb) of the periodic table. It has a lustrous silvery appearance, and is dispersed to the extent of 3 parts per million in Earth’s crust. It is found in minerals of the zirconium group, including altered and native zr-silicates such as alvite and cyrtolite and is also present in commercial sources of rhombohedral and tetragonal zircons.
Among refractory materials, tantalum carbide (TaC) and hafnium carbide (HfC) possess very high melting points which are the highest in the class of inorganic compounds. They are also very resistant to oxidation at oxygen deficient and rich environments.
A new method for forming nanocrystalline TaC and HfC fibers was developed by the ForcespinningTM technique via a nonhalide-based sol-gel process. A systemic study was performed using neat polyacrylonitrile/dimethylformamide (PAN/DMF) to determine an optimal solution viscosity range and the parameters of a spinneret-to-collecting rod distance required for ideal fiber formation.
This synthesis is the first step in a series of large-scale selective synthesis of coatings made of ternary HfTaC systems with predefined stoichiometry and properties, using a unique plasma dynamic experimental setup. The results reveal that this system is a good candidate for the preparation of coatings with a wide range of properties.
Tantalum and hafnium carbides are versatile materials that are often used in aerospace applications. Moreover, they have the potential to provide thermal protection systems for spacecraft that could resist temperatures of nearly 4000degC!