In situ reaction synthesis, electrical and thermal, and mechanical properties of Nb4AlC3

In this work, a bulk Nb(4)AlC(3) ceramic was prepared by an in situ reaction/hot pressing method using Nb, Al, and C as the starting materials. The reaction path, microstructure, physical, and mechanical properties of Nb(4)AlC(3) were systematically investigated. The thermal expansion coefficient was determined as 7.2 x 10(-6) K(-1) in the temperature range of 200 degrees-1100 degrees C. The thermal conductivity of Nb(4)AlC(3) increased from 13.5 W.(m.K)(-1) at room temperature to 21.2 W.(m.K)(-1) at 1227 degrees C, and the electrical conductivity decreased from 3.35 x 10(6) to 1.13 x 10(6) Omega(-1).m(-1) in a temperature range of 5-300 K. Nb(4)AlC(3) possessed a low hardness of 2.6 GPa, high flexural strength of 346 MPa, and high fracture toughness of 7.1 MPa.m(1/2). Most significantly, Nb(4)AlC(3) could retain high modulus and strength up to very high temperatures. The Young's modulus at 1580 degrees C was 241 GPa (79% of that at room temperature), and the flexural strength could retain the ambient strength value without any degradation up to the maximum measured temperature of 1400 degrees C.