聚甲基丙烯酸甲酯微球表面镀银的研究

用分散聚合法制备聚甲基丙烯酸甲酯(PMMA)微球,以聚乙烯吡咯烷酮(PVP)为分散剂,依次用葡萄糖和硼氢化钠还原银氨溶液,在微球表面化学镀银,得到表面覆银的PMMA-Ag微球,对其进行了表征和分析。结果表明,微球分散性好,银层光滑致密,粒径较均匀,直径约2μm;XRD图谱显示无银以外的其它物相存在;红外光谱显示银与PMMA微球的表面可能存在相互作用,是银还原沉积的影响因素;热重分析表明,PMMA-Ag耐热性有所提高(26℃);制备使用的硝酸银占PMMA微球质量分数为55%时,样品的导电率最大(330 S/cm)。     

Synthesis and structure-directing effect of piperazinium hydroxides derived from piperazines for the formation of porous zeolites

A series of organic structure-directing agents (SDAs) derived from N-methyl piperazine are synthesized and first used in the zeolite synthesis. When the hydrothermal synthesis route is applied, SDA1, SDA3 and SDA4 are beneficial to the formation of ZSM-12 lattice, but SDA2 and SDA5 readily induce the nucleation and crystallization of ZSM-5 phase. When using the dry gel conversion route, only SDA5 yields a porous material similar to the ZSM-11 topology. Thus, synthesized zeolites have been confirmed by XRD and IR characterizations to possess characteristics of MFI, MEL and MTW lattices, respectively. The crystal size (1.0 × 9.3 μm) of ZSM-5 synthesized is measured to be much larger than those of ZSM-11 (0.10∼0.50 μm) and ZSM-12 (0.80∼2.0 μm). The TG curve of ZSM-12 shows a two-stage weight loss in the flow of air, while those of ZSM-5 and ZSM-11 contain three-stage weight losses in air. ¹³C CP MAS NMR spectra confirm the encapsulation of SDAs in the pore channels of as-synthesized ZSM-5, ZSM-11 and ZSM-12.     

二氧化硅表面化学镀银研究

通过二氧化硅(SiO2)表面硅烷偶联剂改性,继续以聚甲基吡咯烷酮(PVP)为稳定剂,银氨溶液为银源,葡萄糖与甲醛为二元还原剂,对SiO2表面化学镀银工艺进行了研究。最佳镀银工艺条件为:当AgNO3/SiO2质量比为1:1,葡萄糖浓度为0.1 g/mL,反应温度为30℃,反应溶液pH值为13.5,能够获得较高导电率的SiO2镀银(SiO2-Ag)复合粒子,最高导电率为2564 S/cm。使用红外光谱、X射线衍射、热重分析和偏光显微镜等表征产物的物化性能,结果表明:PVP参与化学镀银反应,使SiO2-Ag的热失重变大。基于实验结果探讨了二氧化硅化学镀银的反应机理。