Yang Chen,Chengji Deng,Chao Yu,Jun Ding,Hongxi Zhu
ZrN nanopowders were obtained by using ZrO 2 and Mg as the main raw materials in a molten salt environment and a high-purity nitrogen atmosphere. The effects of ZrO 2 / Mg mole ratio, nitriding temperature , and holding time on the synthesis of ZrN were investigated. ZrN was formed at 700 °C for 3 h. When the nitriding temperature increased to 1000 °C, pure phase ZrN was formed. The specific surface area of ZrN was 20.92 m 2 /g. When the temperature rose to 1100 °C, the resulting ZrN particles were finer; the average size of ZrN decreased from 71.60 to 49.65 nm. Further, an excessively long holding time led to evaporation of the molten salt, ZrO 2 , which was not fully nitrided. Finally, a possible formation mechanism of ZrN is proposed.
Xia Hua,Zhihong Gao,Qianqian Wang,Wenming Hao,Xiaoliang Yan,Ruifeng Li
The accumulation of heavy metal on catalysts during petrochemical process produces deactivated catalysts that cannot be directly disposed in nature, due to the high toxicity. The elimination of the detrimental effect of heavy metal ions can be achieved by immobilizing these ions in the form of spinel structure, yet this requires high-temperature calcination . Herein, Ni 2+ ions are stabilized and confined within the surface NiAl 2 O 4 on Al 2 O 3 through hydrothermal process and subsequent low-temperature thermal treatment. The formation of nickel aluminum layered double hydroxide (NiAl-LDH) as intermediate favors the generation of surface aluminate spinel at the temperature as low as 450 °C. The formation of surface spinel is beneficial to restricting the mobility of Ni 2+ ions. The growth and immobilization mechanisms of the surface spinel structure were proposed, which contributes to alternative and promising route for the low-temperature approach of the retention of the heavy metal ions mobility.
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