Niklas Ahlen

On the carbothermal vapour–liquid–solid (VLS) mechanism for TaC, TiC, and TaxTi1–xC whisker growth

The growth of TaC, TiC and TaxTi1-xC whiskers has been studied in some detail. The whiskers were synthesised via a vapour-liquid-solid (VLS) growth mechanism in the temperature range 1220-1400 degr ...

Synthesis and characterisation of TaxTi1 − xC and TaxTi1 − xCyN1 − y whiskers

Abstract Ta x Ti 1 − x C and Ta x Ti 1 − x C y N 1 − y whiskers have been synthesised via a carbothermal vapour-liquid-solid (VLS) growth mechanism in the temperature region 1250–1400 °C, in argon and nitrogen atmospheres, respectively. The starting materials consisted of Ta 2 O 5 , TiO 2 , C, Ni and NaCl. Carbon was added to reduce the oxides, and nickel to catalyse the whisker growth. NaCl was used as a source of Cl for vapour phase transportation of Ta-oxochlorides and Ti-chlorides to the catalyst. The yield of whiskers was about 80 vol%, with a length of 10–30 μm and a diameter varying from about 0.25 μm for TaC to about 0.55 μm for TiC. The whiskers were straight and had smooth surfaces. TEM studies showed that they were monocrystalline. The average x -value of the formed whiskers could be controlled by varying the weighed-in ratio of Ta 2 O 5 to TiO 2 and the synthesis temperature. The maximum nitrogen content decreased with increasing x value in Ta x Ti 1 − x C y N 1 − y . The residual oxygen content in the whiskers decreased with increasing synthesis temperature and increasing x -value.