Role of sub stochiometric carbon content on the structural thermal and electrochemical properties of TaCx

Abstract

Interstitial transition metal carbides (ITMCs) display unique mechanical, thermal (high melting point) and electromagnetic properties. ITMCs of group IV and V metals show strong non-stoichiometric character i.e. the composition of the carbide can vary over a wide range without any change in the crystal structure. The change in composition of strongly nonstoichiometric compounds is a very important parameter in determining the properties of these materials. These materials are extremely hard, have the highest known melting points and are also radiation resistant. Out of the entire group V ITMCs Tantalum Carbide (TaC) finds its industrial applications because of its high temperature stability. Synthesis of nano sized powders of TaC with large specific surface area and their complete characterization is of paramount importance for ultra- high temperature (UHT) as well as catalytic applications. Apart from the precursors, the synthesis method and processing parameters like temperature, time, pressure, and catalyst etc. play very important role in determining the properties of the final powders and hence their performance. The stoichiometry of TaC plays an important role in determining its properties in UHT as well as electro catalytic applications. The present work deals with the synthesis and characterization of nano sized cubic TaC by single step chemical reaction synthesis route. Further, the prepared materials have been tested as electrocatalyst for HER in acidic media. The entire work of the thesis is divided into eight chapters. Chapter 1 deals with the interstitial transition metal carbides (ITMCs). Properties and industrial applications of ITMCs are discussed taking into consideration their crystal structure and bonding. Non stoichiometric nature of the group IV and V ITMCs and its influence on property determination is described. Among the ITMCs, the significance of TaC, its industrial applications, especially as ultra-high temperature material (UHTM), are discussed. The tantalum-carbon binary system with