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Composites of titanium carbide with scandium matrix
Brožek, Vlastimil ; Pala, Zdeněk ; Vilémová, Monika ; Kubatík, Tomáš František ; Mušálek, Radek ; Nevrlá, Barbara ; Mastný, L.
First reference about existence of ultrahard composite in the TiC-ScCx system was made by G.V. Samsonov in the year 1962. Further research performed on ICT Prague and University of Vienna proved a discrepancy in the structure and stoichiometry of scandium carbide. Analogously to cubic carbides and nitrides of 3rd period metals, Scandium was also expected to have extreme hardness, high chemical stability and to enable solid solution formation (Vegard rule) with controlled regulation of physical parameters. Higher hardness of the cubic carbides is related to the decrease of lattice parameter, thus is was expected that smaller atomic radius of Sc in TixSc1-xC solid solution will lead to increase in hardness. However it was discovered that scandium carbide differs chemically as well as structurally, e.g. Sc15C19 is hydrolyzed and the product of the reaction is hydrogen, allylen and other hydrocarbons. Due to high price of Sc compounds, CVD and PVD layers of TiAlN or TiScAlN on sintered
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Preparation of multiphase materials with spark plasma sintering
Mušálek, Radek ; Dlabáček, Zdeněk ; Vilémová, Monika ; Pala, Zdeněk ; Matějíček, Jiří ; Chráska, Tomáš
Spark plasma sintering (SPS), also called Field Assisted Sintering Technique (FAST), represents a novel method of preparation of sintered materials from powders. The main advantage of the SPS method is a high achievable heat rate (>200 °C/min) and high sintering temperatures (up to 2200 °C in our laboratory). Combination of high heating rate, rather high pressures (up to 80 MPa) and electric field fluctuations leads to an effective sintering and significant reduction of sintering time for both coarse-grained and nanocrystalline powders. Composite materials may be easily obtained by mixing or layering of different powders. The paper will introduce several examples of multiphase materials sintered by SPS at our institute and the establishment of procedures for routine testing of sub-sized specimens.
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