通过共沉淀法合成了CuCr_(2)O_(4)黑色颜料。研究了沉淀剂(即尿素、氨水、氢氧化钠)对相组成和颜色性能的影响。同时,计算了以氨水和氢氧化钠为沉淀剂时CuCr_(2)O_(4)的结晶动力学和结晶机制。结果表明,由于两种离子(Cu^(2+)和Cr^(3+))...通过共沉淀法合成了CuCr_(2)O_(4)黑色颜料。研究了沉淀剂(即尿素、氨水、氢氧化钠)对相组成和颜色性能的影响。同时,计算了以氨水和氢氧化钠为沉淀剂时CuCr_(2)O_(4)的结晶动力学和结晶机制。结果表明,由于两种离子(Cu^(2+)和Cr^(3+))的溶解度不同,沉淀过程的最佳pH值为7.5;由于产物中存在Cr2O3,尿素不适合作为沉淀剂。氨水作为沉淀剂时,CuCr_(2)O_(4)结晶的活化能为120.2 k J/mol,氢氧化钠作为沉淀剂时为141.3 k J/mol。CuCr_(2)O_(4)的结晶过程涉及成核和三维生长。较小的结晶活化能得到的CuCr_(2)O_(4)颗粒细小,分散均匀,呈色性能更优异。展开更多
Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD,...Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD, surface area, pore volume and average pore diameter and the results were compared. The activity and stability of the close-coupled catalysts supported by aluminas prepared by different precipitating agent were compated. The alumina formed by ammonium carbonate showed larger surface area, pore volume, average pore diameter, higher thermal stability and better support property than that formed by ammonium hydroxide. The precusor of NH4Al(OH)2CO3 in the ammonium cabonate process was responsible for the difference.展开更多
文摘通过共沉淀法合成了CuCr_(2)O_(4)黑色颜料。研究了沉淀剂(即尿素、氨水、氢氧化钠)对相组成和颜色性能的影响。同时,计算了以氨水和氢氧化钠为沉淀剂时CuCr_(2)O_(4)的结晶动力学和结晶机制。结果表明,由于两种离子(Cu^(2+)和Cr^(3+))的溶解度不同,沉淀过程的最佳pH值为7.5;由于产物中存在Cr2O3,尿素不适合作为沉淀剂。氨水作为沉淀剂时,CuCr_(2)O_(4)结晶的活化能为120.2 k J/mol,氢氧化钠作为沉淀剂时为141.3 k J/mol。CuCr_(2)O_(4)的结晶过程涉及成核和三维生长。较小的结晶活化能得到的CuCr_(2)O_(4)颗粒细小,分散均匀,呈色性能更优异。
文摘Aluminas were prepared by precipitation of aqueous aluminum nitrate solution using ammonium carbonate and ammonium hydroxide as precipitation agent respectively. The prepared samples were characterized by TG/DTA, XRD, surface area, pore volume and average pore diameter and the results were compared. The activity and stability of the close-coupled catalysts supported by aluminas prepared by different precipitating agent were compated. The alumina formed by ammonium carbonate showed larger surface area, pore volume, average pore diameter, higher thermal stability and better support property than that formed by ammonium hydroxide. The precusor of NH4Al(OH)2CO3 in the ammonium cabonate process was responsible for the difference.