Preparation of Zirconium Carbide-Zirconium Silicide Composite Powders by Solid Reaction of Zr and SiC Powders

In the present work, zirconium carbide-zirconium silicide composite powders were prepared by solid reaction using Zr and SiC powders as reactants. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results showed that, after treatment at 800 ºC, the produced zirconium carbide-zirconium silicide diffusion layer was very thin and mainly consisted of ZrC and ZrSi2. After treatment above 900 ºC, the produced phases were mainly consisted of ZrC and ZrSi2, plus less ZrSi.

Effects of Zirconium Silicide on the Vulcanization, Mechanical and Ablation Resistance Properties of Ceramifiable Silicone Rubber Composites

Ceramifiable silicone rubber composites play important roles in the field of thermal protection systems (TPS) for rocket motor cases due to their advantages. Ceramifiable silicone rubber composites filled with different contents of ZrSi2 were prepared in this paper. The fffects of ZrSi2 on the vulcanization, mechanical and ablation resistance properties of the composites were also investigated. The results showed that the introduction of ZrSi2 decreased the vulcanization time of silicone rubber. FTIR spectra showed that ZrSi2 did not participate in reactions of the functional groups of silicone rubber. With the increasing content of ZrSi2, the tensile strength increased first and then decreased. The elongation at break decreased and the permanent deformation increased gradually. The thermal conductivity of the composite increased from 0.553 W/(m·K) to 0.694 W/(m·K) as the content of the ZrSi2 increased from 0 to 40 phr. In addition, the thermal conductivity of the composite decreased with the increase of temperature. Moreover, thermal analysis showed that the addition of ZrSi2 increased the initial decomposition temperature of the composite, but had little effect on the peak decomposition temperature in nitrogen. However, the thermal decomposition temperature of the composite in air was lower than that in nitrogen. The addition of ZrSi2 decreased the linear and mass ablation rate, which improved the ablative resistance of the composite. With the ZrSi2 content of 30 phr, the linear and mass ablation rate were 0.041 mm/s and 0.029 g/s, decreasing by 57.5% and 46.3% compared with the composite without ZrSi2, respectively. Consequently, the ceramifiable silicone rubber composite filled with ZrSi2 is very promising for TPS.

Studies on magnetron-sputtered zirconium-silicide coatings deposited on zirconium alloy for the enhancement of their high-temperature oxidation resistance

Zirconium alloys used widely in nuclear industry as fuel claddings are prone to violent oxidation in water steam atmosphere in the case of loss of coolant accident (LOCA). Accompanying generation of large quantities of heat and explosive gaseous hydrogen may lead to destruction of nuclear core. As the safety of nuclear installations is of primary importance, intensive research works are conducted on the development of so-called accident tolerant fuels much less prone to oxidation. In this paper, the application of external zirconium-silicide coatings deposited by magnetron sputtering is proposed. The preliminary results of their synthesis and studies of air oxidation properties at elevated temperatures are presented.