3,5-二羟基-2,4,6-三硝基苯酚氨基脲铵盐半水合物的合成、晶体结构和热分解特性

A new compound, semicarbazidium 3,5-dihydroxy-2,4,6-trinitrophenolate hemihydrate （SCDHTNP·0.5H2P）, was synthesized by the reaction of the aqueous solutions of semicarbazide with trinitrophloroglucinol. Its structure was determined by single-crystal X-ray diffraction analysis and characterized by elemental analysis, FTIR, DSC and TG-DTG techniques. The crystal is monoclinic with space group P21/n and the empirical formula C7H9N6O10.50. The unit cell parameters are： a= 1.3791（3） nm, b=0.9256（2） nm, c=2.0468（4） nm,β= 106.93（3）°, V=2.4995（9）nm^3, Z=8, Dc= 1.835 g/cm^3, Mr=345.20, F（000）= 1416, s=0.945,μ（Mo Ka）=0.174 mm^-1. The final R and wR are 0.0401 and 0.0896. Its structure consists of two semicarbazidium cations, two 3,5-dihydroxy-2,4,6-trinitrophenolate anions and one crystal water molecule, which are interconnected by electrostatic forces and hydrogen bonds into layer structure, making the title compound very stable. Under a linear heating rate, the thermal decomposition processes of SCDHTNP·0.5H2O have one endothermal dehydration stage and two intensive exothermic decomposition stages at 178-241℃ to evolve abundant gas products.     

Pr3+掺杂的TiO2纳米粉体的表面特性和光催化活性

利用酸催化的溶胶-凝胶法制备了纯的和不同Pr³⁺掺杂量的TiO₂纳米粉体.以亚甲基蓝(MB)溶液的光催化降解为探针反应,评价了它们的光催化活性.利用XRD和BET技术研究了Pr³⁺掺杂量和焙烧温度对TiO₂纳米粉体的相结构、晶粒尺寸和表面织构特性的影响,并用XPS和SPS技术研究了Pr³⁺掺杂的TiO₂纳米粉体的表面组成和表面光伏特性,探讨了Pr³⁺掺杂提高纳米TiO₂的光催化活性的机制.结果表明:适量Pr³⁺掺杂能显著提高纳米TiO₂的光催化活性.当Pr³⁺掺杂量为1.25%(以Pr³⁺/TiO₂质量比计),焙烧温度为600℃时,制得粉体的光催化活性最佳.Pr³⁺掺杂强烈地抑制TiO₂由锐钛矿相向金红石相的转变,减小晶粒尺寸,增大比表面积,增加表面羟基和吸附氧的含量,提高光生电子和空穴的分离效率,改善粉体表面的光吸收性能,上述因素均有利于光催化活性的提高.