Pressureless sintering of ZrC with variable stoichiometry

This paper presents the experiments on the synthesis of zirconium carbide (ZrC) using carbothermal reduction of zirconia (ZrO2). The ratio of ZrO2:C is used to adapt ZrCxOy with x < 1 or ZrC + C. The modification of ZrCxOy and the total carbon amount allows the use of pressureless sintering method in combination with sintering temperatures <= 2000 degrees C. Fully densified ZrC products are obtained. The relevant details of ZrC formation are investigated by X-ray diffraction (XRD). The sintered products are characterized by XRD, field emission scanning electron microscopy (FESEM), as well as mechanical and electrical methods. XRD and FESEM investigations show that ZrCxOy is formed during the manufacturing process. The grain size and additional zirconia or carbon are related to the ZrO2: C ratio of the starting powder mixture. Bending strength up to 300 MPa, Young's modulus up to 400 GPa, fracture toughness up to 4.1 MPa.m(1/2), and electrical resistance at room temperature around 10(-4) Omega.cm are reached by the pressureless sintered ZrC.