Reactive Hot Pressing and Properties of Nb2AlC

Dense Nb2AlC ceramic was synthesized from NbC, Nb, and Al powder mixture at 1650 degrees C and a pressure of 30 MPa for 90 min using an in situ reaction/hot-pressing method. The reaction kinetics, microstructure, physical, and mechanical properties of the fabricated material were investigated. A thermal expansion coefficient of similar to 8.1 x 10(-6) K-1 was measured in the temperature range of 30 degrees-1050 degrees C. At room temperature a thermal conductivity of similar to 20 W. (m. K)(-1) and a Vickers hardness of similar to 4.5 GPa were determined. The material attained Young's modulus, four-point bending strength and fracture toughness of similar to 294 GPa, similar to 443 MPa, and similar to 5.9 MPa. m(1/2), respectively. The nanolayered grains with a mean grain size of 17 mu m contributed to the damage tolerance of this ceramic. Quenching from 600 degrees, 800 degrees, and 1000 degrees C into water at room temperature resulted in decrease in bending strength from 443 MPa for the as-synthesized Nb2AlC to 391, 156, and 149 MPa, respectively.