Nano-(Ta, Zr)C Precipitates at Multigrain Conjunctions in TaC Ceramic with 10 mol% ZrC and 5 mol% Cu as Sintering Aid

Lianbing Zhong,Limeng Liu,Feng Ye,Guihong Geng,Yujin Wang

doi:10.1155/2018/1634814

Abstract

A fully dense TaC ceramic was prepared by hot pressing using 10 mol% ZrC plus 5 mol% Cu as a sintering aid. Formation of (Ta, Zr)C solid solution (ss) by reaction between TaC and ZrC facilitated densification. Addition of Cu refined the microstructure and consequently improved flexural strength of the TaC ceramics. TEM investigation found ubiquitous precipitation of nanocrystallites at multigrain conjunctions. The nanocrystallites were (Ta, Zr)C solid solution with uniform dispersion in an oxygen-rich glassy matrix. Although formation of nanoprecipitates may not much affect the mechanical properties of the TaC ceramic, the structure suggested a new type of nanoceramic worth further research.

Highlights

Tantalum carbide (TaC) is one of the ultrahigh temperature ceramics (UHTC) [1] as it has high melting point (∼3983∘C), good electrical and thermal conductivity, and relatively good mechanical properties
Secondary phases in the TaC ceramics were detailed by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) to show precipitation of nanocrystallites in a continuous glassy phase at multigrain conjunctions
The dominant XRD peaks from the consolidated ceramic were indexed by TaC with significant broadening and shift towards lower 2θ positions, indicating formation of a (Ta, Zr)C ss [18, 19]

Summary

Introduction

Tantalum carbide (TaC) is one of the ultrahigh temperature ceramics (UHTC) [1] as it has high melting point (∼3983∘C), good electrical and thermal conductivity, and relatively good mechanical properties. TaC ceramics were hot pressed with ZrC plus Cu as sintering aids [18]. Secondary phases in the TaC ceramics were detailed by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) to show precipitation of nanocrystallites in a continuous glassy phase at multigrain conjunctions. Considering the good physiomechanical properties of the TaC and the ZrC compound, the intergranular composition of the TaC ceramics may suggest a new type of nano-(Ta, Zr)C ceramic of good electrical and thermal conductivities

Results

Discussion

Conclusion