Experimental and Numerical Studies on Self-Propagating High-Temperature Synthesis of Ta5Si3 Intermetallics

Chun-Liang Yeh,Po-Wen Hwang,Chi-Chian Chou

doi:10.3390/met5031580

Abstract

Formation of Ta5Si3 by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion wave velocity and reaction temperature. The apparent activation energy, Ea ≈ 108 kJ/mol, was determined for the synthesis reaction. Based upon numerical simulation, the Arrhenius factor of the rate function, K0 = 2.5 × 107 s−1, was obtained for the 5Ta + 3Si combustion system. In addition, the influence of sample density on combustion wave kinetics was correlated with the effective thermal conductivity (keff) of the powder compact. By adopting 0.005 ≤ keff/kbulk ≤ 0.016 in the computation model, the calculated combustion velocity and temperature were in good agreement with experimental data of the samples with compaction densities between 35% and 45% theoretical maximum density (TMD).

Highlights

Transition metal silicides are of great interest as high-temperature materials, due to their specific properties such as high melting point, good thermal stability, excellent oxidation resistance, good creepMetals 2015, 5 tolerance, and high mechanical strength at elevated temperatures [1,2,3]
The objective of this study is to perform a thorough investigation on combustion synthesis of Ta5Si3 from elemental powder compacts of Ta:Si = 5:3
A typical sequence of combustion images recorded from a powder compact of Ta:Si = 5:3 is illustrated in Figure 1, showing that a steady and nearly parallel combustion wave traveling in a self-sustaining fashion

Summary

Introduction

Transition metal silicides are of great interest as high-temperature materials, due to their specific properties such as high melting point, good thermal stability, excellent oxidation resistance, good creepMetals 2015, 5 tolerance, and high mechanical strength at elevated temperatures [1,2,3]. Transition metal silicides are of great interest as high-temperature materials, due to their specific properties such as high melting point, good thermal stability, excellent oxidation resistance, good creep. The compounds of the Ta–Si system are among the most refractory silicides with melting points in the range of 2200 to 2500 °C [4]. Preparation of transition metal silicides has been conducted by a variety of fabrication routes, often combining two or more of them, like hot pressing, hot isostatic pressing, reactive sintering, combustion synthesis, mechanical alloying, thermal or plasma spraying, and vapor infiltration [5]. The SHS method has been applied for the preparation of many advanced materials, including borides, carbides, nitrides, carbonitrides, aluminides, silicides, and complex oxides [6,7,8]

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Conclusion