On the fabrication of ZrC x N y from ZrO 2 via two-step carbothermic reduction–nitridation

Abstract

This study examined the processing parameters of a two-step carbothermal reduction-nitridation of ZrO 2 as a UO 2 /PuO 2 simulant to fabricate ZrN. Variables studied were the reaction time, reaction temperature and the starting powder composition Higher temperatures, longer reaction times and higher initial amounts of carbon in the starting material lead to increased nitridation similar to previous work with uranium oxide but that reaction rate decreases with time. SEM and TEM of the reacted powders reveal regions of ZrC with ledges indicative of crystal defects with small particles of ZrN growing on the ZrC bulk material suggesting a reaction that occurs via Zr transport to the reaction site either through mass diffusion or evaporation-condensation of Zr (g) and with N 2(g) forming the nitride. Annealing experiments on these mixed phases shows formation of a solid solution is rapid compared to the nitridation, where there is no formation of a mixed phase.

Chemical reactivity of hot-pressed Si3N4–ZrB2 ceramics at 1500–1700 °C

“…This might be because the carbon from graphite-rich sintering environment at 1700 • C could diffuse into ZrN to form ZrC x N y and thus lead to the slight peaks shift toward lower angles. Previous study has shown that the peaks of ZrC x N y shifted slightly to lower angles with the increase of carbon content [18].…”

О Возможности Синтеза Карбонитрида Циркония При Температуре 1200 °С

“…В работах [8,9] возможность образования карбонитрида Zr в ходе карботермического восстановления-азотирования оксида ZrO2 изучали по смещению угла дифракции и уширения линий в интервале 2θ от 55 до 75°. На рисунке 3 показана дифрактограмма синтезированных в настоящей работе порошков в сравнении с литературными данными.…”

“…Рисунок 3 -Дифрактограмма азотированных порошков: а)настоящая работа;б) литературные данные(в скобочках указан режим азотирования в токе азота) [8,9] …”

Deconvolution of Mass Gain and Mass Loss Mechanisms During Carbothermic Reduction to Nitridation of Zirconia

“…The carbothermic reduction to nitridation (CTR‐N) process has been used experimentally to produce zirconium oxynitrides as well as high purity zirconium nitride . Although CTR‐N is utilized both in the laboratory and industrially to produce numerous mononitride and mixed nitride materials (e.g., uranium mononitride, aluminum mononitride), zirconium provides a simplified reference case in that a single stoichiometric phase exists for the oxide (ZrO 2 ), carbide (ZrC), and nitride (ZrN).…”

“…. This final step results in the removal of carbon through the formation of gaseous HCN, producing a carbon‐free product …”