Effect of carbon on the growth of TaC crystal derived from organometallic precursors
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ORIGINAL ARTICLE
Effect of carbon on the growth of TaC crystal derived from organometallic precursors Yoonjoo Lee1 · Philjae Kang2 · Sooyong Jung2 · Seonggun Bae3 · Joungil Kim4 · Manyoung Lee5 · Dong‑Geun Shin3 Received: 21 February 2020 / Revised: 26 June 2020 / Accepted: 10 August 2020 © The Korean Ceramic Society 2020
Abstract TaC, which is an ultra-high-temperature structural material, was derived from two types of organometallic precursors: Me3CCH = Ta(CH2CMe3)3 and Cp*-TaMe4. Both compounds are kinds of single-source precursors composed only of tantalum, carbon, and hydrogen, which should be converted into carbide material without oxygen contamination. The carbide material was formed through several processes such as pyrolysis, nucleation, and crystal growth, which are dependent on heat treatment temperature. However, organometallic precursor usually leaves residual carbon, and the crystallization of carbide is affected by the carbon. In this study, two types of organometallic precursors containing different amounts of carbon in the organic part were used to prepare TaC, and the crystallization behavior of TaC in rich carbon was investigated. The amount of residual carbon was estimated by thermogravimetry (TG) analysis, and the TaC crystals were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nano-sized TaC particles were obtained by heat treatment without any by-products but with excess carbon. The TaC crystal was formed starting from 1300 °C, but the crystals grew better with less carbon, while the carbon barrier prevented agglomeration of the atoms. Keywords TaC · Tantalium carbide · Residual carbon · Crystal growth
1 Introduction TaC is a rock-salt-structured compound used in ultra-hightemperature ceramics (UHTCs) because of its extremely high melting point (3880 °C), high hardness (15–19 GPa), and elastic modulus (537 GPa). TaC can be synthesized by several methods, such as carbothermal reduction, solvothermal synthesis methods, and gas-phase condensation [1–3]. Chemical vapor deposition (CVD) process is a typical gasphase reaction method in which chloride compounds such
* Dong‑Geun Shin [email protected] 1
Energy and Environment Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Korea
2
Department of Chemistry and Molecular Structure Laboratory, Yonsei University, Seoul 03722, Korea
3
Convergence R&D Division, Korea Institute of Ceramic Engineering and Technology, Jinju 52851, Korea
4
R&D Center, DACC Carbon Co. Ltd., Jeonju 54853, Korea
5
4th Directorate, Agency for Defense Development, Daejeon 34186, Korea
as TaCl5 are commonly used as a starting material with hydrocarbon gas [4–6]. However, a multi-source process is not easy even for setting proper conditions for CVD, and it also accompanied by an issue caused by chlorine gas. Thus, organometallic compounds have been suggested as singlesource precursors to replace the chloride compound. Organometallic compound is a kind of metal complex in which metalli
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