Adsorption of cationic polyelectrolyte at the solid/liquid interface and dispersion of nanosized silica in water

Adsorption of cationic polyelectrolyte, a homopolymer of maleimide propyl trimethylammonium chloride (MPTMAC), on silica nanoparticles from aqueous solution was studied. The adsorbed amount of MPTMAC and the adsorption layer thickness from solutions of different pH, polyelectrolyte concentration, salt type, and salt concentration were measured. The adsorbed amount exhibited a maximum as a function of the electrolyte concentration. The onset of the decline in the adsorbed amount depended on the type of counterions. The thickness of the adsorption layer increased gradually with increased of electrolyte concentration and leveled off at high electrolyte concentration. The enhanced adsorption in the presence of Na2SO4 can be explained by the bivalent SO4(2-) causing a better shielding effect. With increasing pH the adsorbed amount of MPTMAC increased, whereas the thickness of an adsorbed layer of MPTMAC decreased. At low polyelectrolyte concentrations unstable silica suspensions were observed from a stability test. At high polyelectrolyte concentrations the higher particle coverage caused electrosteric stabilization of the dispersion. However, further increase in MPTMAC concentration after saturated adsorption would flocculate the dispersed system. At low pH, MPTMAC tending to create a loops or tails conformation stabilized the suspension.     

VBA编程模拟惠斯登电桥

VBA编程是对PowerPoint软件的二次扩展,本文利用VBA编程制作了一个模拟惠斯登电桥的PowerPoint课件,可以实现虚拟操作、虚拟测量。     

TiO2在水及丙二醇介质中表面电性质的研究

0引言 固体颗粒在液相介质中的分散是基础研究领域和工业技术部门普遍遇到的问题 ?在化学工业领域,如涂料 ? 染料 ? 油墨 ? 化妆品等,固体颗粒的分散及分散稳定性直接影响着产品的质量和性能 ?TiO 2 颗粒的水基分散体系广泛应用于涂料 ? 油墨以及化妆品中,也是陶瓷制备过程中重     

Bismuth sulfide thin films with low resistivity on self-assembled monolayers

Using self-assembled monolayers (SAMs), highly crystalline bismuth sulfide thin films with low electrical resistivity have been prepared from aqueous solution at low temperature (40-70 degrees C). The nucleation and growth process of Bi2S3 thin films was investigated in detail by XPS, AES, SEM, XRD, SAED, and HRTEM. Solution conditions have marked effects on the microstructure, growth rate, and mechanism of Bi2S3 films. Increased solution temperature resulted in a higher growth rate and a shorter induction time due to a higher supersaturation degree. In the solution of pH 1.12, homogeneous nucleation and the attachment process dominated the formation of Bi2S3 films. In contrast, at pH 0.47 Bi2S3 thin films were formed via heterogeneous nucleation and growth. The c-axial orientation of bismuthinite films was enhanced with the increase of reaction time. By controlling the solution supersaturation and reaction duration, highly crystalline Bi2S3 films composed of closely packed and coalescent crystallites could be realized, whose dark electrical resistivity could reach as low as 0.014 Omega cm without any post-treatment.     

聚丙烯酸在纳米TiO2表面吸附行为的研究

讨论了聚丙烯酸在纳米TiO₂水悬浮体系中的吸附行为.红外光谱分析和吸附实验结果表明,纳米TiO₂通过氢键吸附PAA.PAA吸附量随着浓度的升高而增大直至饱和吸附量,且分子量越大,饱和吸附量越大.pH值增大,则饱和吸附量减小.在相同条件下,表面吸附层的厚度随PAA分子量、浓度和pH值增大而增大.这是由PAA在颗粒表面构型的变化所致.吸附PAA后的纳米TiO₂的表面电荷密度和ζ电位发生变化,pHiep值向低值方向移动.表面吸附自由能的计算结果说明,PAA在纳米TiO₂表面的吸附是自发过程.