纳米ZnO制备工艺中电位与分散性的关系

本工作采用化学工艺制备10nm左右的ZnO粉体,并对工艺过程中碱式碳酸锌前驱体分散性和表面电位之间的关系进行了研究.专门对洗涤后粉体表面电位进行了分析.发现采用蒸馏水洗涤后粉体的ζ电位明显降低,接近其等电点,并导致粉体团聚.因此,在洗涤过程中,使用0.1M氨水取代蒸馏水来控制pH值,提高ζ电位,改善粉体的分散性.     

纳米ZnO制备工艺中ζ电位与分散性的关系

本工作采用化学工艺制备１０ｎｍ左右的ＺｎＯ粉体,并对工艺过程中碱式碳酸锌前驱体分散性和表面电位之间的关系进行了研究．专门对洗涤后粉体表面电位进行了分析．发现采用蒸馏水洗涤后粉体的ζ电位明显降低,接近其等电点,并导致粉体团聚．因此,在洗涤过程中,使用０．１Ｍ氨水取代蒸馏水来控制ｐＨ值,提高电位,改善粉体的分散性．     

利用声波粒度仪研究Mg2+在Al2O3表面的特性吸附

利用声波粒度仪、Zeta电位仪详细研究了金属镁离子在氧化铝粉体表面的特性吸附行为。发现Mg^2 浓度、体系pH以及浆料的固体含量对氧化铝颗粒表面的Zeta电位有显著影响,在不同的实验条件下引起粉体颗粒表面电荷的反转或等电点的位移。不同pH条件下的粒度测量结果所反映的体系稳定性与Zeta电位较好的吻合。首次用AFM证实了特性吸附条件下,氧化物表面水化层的存在。     

半导体用高纯超细SiC粉体的表面改性

通过偶联剂预处理、接枝聚合丙烯酸钠两步法对SiC粉体进行表面改性,制备聚丙烯酸钠接枝改性SiC粉体,并对改性粉体进行表征,测试SiC粉体的zeta电位,讨论改性对SiC粉体料浆分散稳定性和流动性的影响。结果表明:SiC微粉经表面改性后并未改变原始SiC微粉的物相结构,只是改变其在水中的胶体性质;微粉团聚现象减少,分散性得到改善;改性SiC微粉与原始SiC微粉相比,表面特性发生很大变化,zeta电位值显著提高,悬浮液的分散稳定性得到明显改善,且黏度降低。     

有机包覆改性SiC粉体表面结构与性质的表征

本研究中的有机包覆改性SiC微粉通过硅烷偶联剂处理以及有机单体在其表面上的接枝聚合而获得。通过X-射线衍射分析改性前后粉体的主要物相成分;以粉体悬浮液离心清液的离子电导率和粉体胶粒的Zeta电位曲线来表征粉体表面的吸附离子浓度及表面电性;通过TEM、FTIR等测试手段表征粉体有机包覆层的形貌和化学组成结构。研究表明:以提高SiC粉体水基分散固含量为目的的有机包覆改性工艺在未改变粉体基本成分的基础上,有效降低了粉体表面吸附离子的浓度,提高了表面电荷;其完整的表面有机包覆层体现包覆物质的结构和性质,有效地掩蔽了SiC粉体原有的表面,使有机包覆改性成为SiC粉体水基分散性能提高的有效方法。     

利用声波粒度仪研究Mg~(2 )在Al_2O_3表面的特性吸附

利用声波粒度仪、Ｚｅｔａ电位仪详细研究了金属镁离子在氧化铝粉体表面的特性吸附行为．发现Ｍｇ２＋浓度、体系ｐＨ以及浆料的固体含量都对氧化铝颗粒表面的Ｚｅｔａ电位有显著影响,在不同的实验条件下引起粉体颗粒表面电荷的反转或等电点的位移．不同ｐＨ条件下的粒度测量结果所反映的体系稳定性与Ｚｅｔａ电位较好的吻合．首次用ＡＦＭ证实了特性吸附条件下,氧化物表面水化层的存在．     

氧化铝包覆石墨复合粉体的制备及性能研究

通过无机铝盐的水解,利用异相成核的方法在天然鳞片石墨表面包覆氧化铝制备了氧化铝包覆石墨复合粉体.对复合粉体进行了形貌观察、结构分析、热分析、表面电位及与水的润湿性测定.研究结果表明,在石墨表面形成了较为均匀的氧化铝包覆层,所包覆的氧化铝为无定形,其与石墨表面结合良好,包覆层厚度约1μm;氧化铝包覆石墨复合粉体与水具有良好的润湿性,其表面特性与氧化铝相似,并且抗氧化性能得到较大的改善.     

超细CeO2粉体在醇水混合介质中的超声分散行为

通过测定20nm、200nm、500nm和5μmCeO2粉体在醇水混合介质中的粒度分布、表面电性及分散稳定性,研究了不同粒径级别超细CeO2粉体在体积比为1∶1的醇水系悬浮液中的超声分散行为。实验结果表明:在一定超声功率和超声频率下,不同粒径级别醇水系CeO2悬浮液均存在最佳超声时间。不同粒径级别醇水系CeO2悬浮液的表面电性各不相同;纳米级和亚微米级CeO2在醇水中所带Zeta电位为正值,微米级CeO2的Zeta电位为负值,悬浮液中CeO2粉体的平均粒度越大,其电位绝对值越小。不同粒径级别醇水系CeO2悬浮液的分散稳定性能各不相同;从超声结束后的分散效果来看,亚微米CeO2粉体在醇水混合介质中的分散性能最好;从多个沉降时间段内的稳定性来看,纳米CeO2粉体在醇水混合介质中的稳定性能最好。     

氮化硅粉体的水基流延研究

本文采用国产的α-氮化硅粉(d50=1μm),测定了粉体的zeta电位.根据粉体的表面性质,选用聚丙烯酸钠作为分散剂,分析了pH值、分散剂对氮化硅粉体zeta电位以及浆料粘度的影响,确定了良好分散的Si3N4浆料的pH值和分散剂含量分别为10和1wt%.选用PVA为粘结剂,PEG为塑性剂,二者在浆料中的含量分别为5wt%和2.5wt%.最后,制备了氮化硅水基流延膜,并用SEM对得到的流延膜进行了表征.     

碳纳米管／石英复合粉体的制备

采用表面活性剂和超声辅助的混酸处理工艺对碳纳米管进行了表面修饰，均获得了分散均匀的碳纳米管悬浮水溶液，利用傅立叶红外吸收光谱及Zeta电位等手段对其分散机理进行了分析；采用快速溶胶一凝胶法，制备了多种碳纳米管含量的石英基复合粉体，透射电镜观察显示两种修饰碳纳米管表面的方法都有效提高了碳纳米管在石英基体的分散性，制备出了均匀的碳纳米管／石英复合粉体。     

Controlled adhesion of human lymphocytes on electrically charged polymer surface having phosphorylcholine moiety

The human lymphocytes were interacted with polymer surfaces whose surface potential was controlled by the formation of a polyion complex (PIC) having a phosphorylcholine moiety. 3-(Methacryloyloxypropyl)-trimethyl ammonium iodide as the cationic unit or potassium 3-methacryloyloxypropyl sulfonate as the anionic unit was copolymerized with 2-methacryloyloxyethylphosphorylcholine (MPC) and _n-butyl methacrylate. PIC was made at the solid-liquid interface, that is, an aqueous solution containing an anionic polymer with different concentrations was contacted with a cationic polymer coated polymer membrane. The formation process of PIC was followed using a quartz crystal microbalance, and the PIC surfaces were analyzed by ζ potential and X-ray photoelectron spectroscopy. The surface potential on the PIC was controllable from +20 to -16 mV, which increased in the amount of adsorbed anionic copolymer as the ζ potential decreased toward the negative charge. The PIC surface in contact with human lymphocyte for 5 h was observed using ascanning electron microscopy and the density of the adherent human lymphocyte was determined by the lactate dehydrogenase method. The lymphocyte adhesion on the surface was gradually reduced with an increase in the negative value of the ζ potential. The morphological change in the adherent lymphocytes was not observed on the polymer surfaces with MPC units.The adherent lymphocytes were not activated on the PIC surface. The lymphocyte adhesion with reduced activation could be controlled by changing the surface potential on the polymer with the MPC unit.     

壳聚糖脱乙酰度对海藻酸钠/壳聚糖微胶囊的表面性质及蛋白吸附的影响

采用流动电势技术、 接触角技术及表面轮廓技术分别考察了由不同脱乙酰度壳聚糖制备的海藻酸钠/壳聚糖(ACA)膜的表面电荷分布、 表面亲疏水性、 表面粗糙度, 并以纤维蛋白原为模型, 采用静态吸附实验技术考察了表面性质对蛋白在ACA微胶囊表面的吸附量及吸附构象的影响。结果表明, ACA微胶囊表面净电荷为负, 表面正电荷随脱乙酰度的降低而减少。由脱乙酰度60%~90%壳聚糖制备的ACA膜的表面接触角均为70°左右, 且无显著性差异。ACA微胶囊表面呈颗粒状结构, 表面粗糙度随壳聚糖脱乙酰度的降低而减小。蛋白吸附分析表明, "棒状"的纤维蛋白原分子以"侧向"和"直立" 2种形式吸附于ACA微胶囊表面。当壳聚糖脱乙酰度较低时, 蛋白吸附量较小, 且此时蛋白多以"直立"形式吸附。以上结果表明, 由壳聚糖脱乙酰度带来的ACA微胶囊表面性质差异不仅影响了蛋白吸附量, 而且影响了蛋白吸附方式。      

苯乙烯/甲基丙烯酸共聚微球的制备及其性能表征

以苯乙烯(St)为单体,甲基丙烯酸(MAA)为功能单体,采用无皂乳液聚合方法制备了聚(苯乙烯-甲基丙烯酸)共聚微球。运用傅立叶红外光谱(FT-IR)、透射电子显微镜(TEM)、场发射扫描电镜(FE-SEM)、电势与纳米粒径分析仪等手段,对微球的组成成分、表面形貌、粒径及其分布、表面电势进行了表征。结果表明,微球粒径均匀,在100～200nm之间,球形度良好且呈单分散性,poly(St-MAA)共聚微球zeta电势为-37.2mV,MAA的亲水性基团和引发剂KPS的残基共同作用提高了共聚微球乳液的稳定性。     

Measurement of the depth of surface cracks using the Direct Current Potential Drop Method

The direct current potential drop method is used to determine the depth of surface cracks in laboratory crack growth experiments. In the present paper calibration tests are described which were done on tensile loaded flat plates containing centrally located surface cracks. The cracks were propagated by fatigue loads and the load shedding technique was used to obtain beach marks on the fracture surface which were needed to calibrate the potential drop readings. Since the resolution of the direct current potential drop method is very low in the case of surface cracks the experimental parameters were optimized such that the accuracy of the crack depth determination can be about ± 1 per cent of the specimen thickness.     

Development and in vitro evaluation of surface modified poly(lactide-co-glycolide) nanoparticles with chitosan-4-thiobutylamidine

The objective of this study was to develop a nanoparticulate drug delivery system based on the surface modification of poly(lactide-co-glycolide) (PLGA) nanoparticles with a thiolated chitosan. PLGA nanoparticles were prepared by the emulsification-solvent evaporation method. Immobilization of chitosan to the surface of PLGA nanoparticles via amide bonds was mediated by a carbodiimide. Thiol groups were covalently bound to the chitosan surface of particles by reaction with 2-iminothiolane. Obtained nanoparticles were characterized in vitro regarding size, zeta potential, thiol group content, stability at different pH values, mucoadhesion, and drug release. Results demonstrated that the surface modification of PLGA nanoparticles with thiolated chitosan (chitosan-TBA) leads to nanoparticles of a mean diameter of 889.5 ± 72 nm and positive zeta potential of + 24.74 mV. The modified nanoparticles contained 7.32 ± 0.24 μmol thiol groups per gram nanoparticles. The size of nanoparticles was strongly influenced by the pH of the surrounding medium, being 925.0 ± 76.3 nm at pH 2 and 577.8 ± 66.7 nm at pH 7.4. Thiolated nanoparticles showed a 3.3-fold prolonged residence time on the mucosa and an unchanged release profile in comparison to unmodified PLGA nanoparticles. These data suggest that surface modified chitosan-TBA conjugate PLGA nanoparticles have the potential to be used as mucoadhesive drug delivery system.     

High-resolution imaging of molecular and nanoparticles assemblies with Kelvin force microscopy

High-resolution studies of self-assemblies of semifluorinated alkanes molecules F12H8 and F14H20 [FnHm = CF3(CF2)n(CH2)mCH3], and CdTe particles were performed with single-pass Kelvin force microscopy. Surface potential contrast, which is related to the strength and orientation of molecular dipoles, empowers the characterization of self-organized structures. Lamellar structures, ribbons and toroids of F14H20 and F12H8 were observed on graphite and the differences of surface potential were interpreted in terms orientation of -CH2-CF2- dipoles. A gradual sublimation of F12H8 molecules allowed a visualization of top and bottom molecular layers on the substrate. Prior to the sublimation a part of lamellae of the bottom layers was transformed into the ribbons. The surface potential data suggest that this transition proceeds with the reorientation of the molecular chains from the horizontal to vertical direction. Self-assembly of CdTe nanoparticles into nanowires was monitored upon drying on mica. The process is accompanied by drastic changes of surface potential. The formed nanowires exhibit strong positive surface potential that assumes a structural transition with a formation of strong dipole moment in these self-assemblies.     

自组装白蛋白共负载光敏剂及基因纳米递送系统的构建及初步评价

通过小分子十二烷基硫酸钠(SDS)调节牛血清白蛋白(BSA)疏水区域暴露,使白蛋白分子在不借助额外催化剂和交联剂的相对温和条件下自组装,合成了一种可共载光敏剂二氢卟吩e6(Ce6)及基因(CpG寡脱氧核苷酸)的白蛋白纳米载体。在其成功负载光敏剂Ce6后,用聚醚酰亚胺(PEI)对BSA纳米颗粒(BSA NP)表面进行了修饰,并通过调节合适的修饰比例得到高效负载基因的纳米体系。随后对纳米颗粒体系的形貌、尺寸分布、表面电荷、稳定性以及基因负载能力、产生活性氧能力进行了初步评估。结果表明合成得到的PEI修饰的白蛋白共负载Ce6及CpG(BSA-Ce6-PEI-CpG)的纳米颗粒尺寸分布均匀,微观形貌呈现光滑规整的圆球形,对CpG基因有较好的负载能力,并在光照下高效产生活性氧,且纳米体系能够在表面活性剂处理后依然保持结构稳定,可作为良好的光敏剂和基因递送载体。     

表面活性剂对金刚石在树脂中悬浮性及与树脂结合性的影响

用KH550硅烷偶联剂和聚电解质型表面活性剂聚乙烯亚胺(PEI)分别对金刚石进行表面改性,研究了KH550和PEI对金刚石表面电性、金刚石在聚酰胺酰亚胺树脂液中的悬浮性及与树脂结合性的影响.结果表明:改性后金刚石表面的电性能发生显著变化,在酸性条件下,zeta电位绝对值明显提高,颗粒间的静电斥力增强,改善了金刚石在树脂液中的悬浮稳定性;改善了树脂对金刚石表面润湿性及其界面结合性,提高了线锯的切割性能;KH550对金刚石的改性效果优于PEI的改性效果.     

无皂乳液聚合法制备单分散聚苯乙烯微球

以苯乙烯(St)为单体,过硫酸钾(KPS)为引发剂,采用无皂乳液聚合法制备了聚苯乙烯微球。研究了单体、引发剂的浓度,引发剂加入方式,聚合温度对制备PS微球粒径的影响。运用傅立叶红外光谱(FT-IR)、透射电子显微镜(TEM)、场发射扫描电镜(FE-SEM)、电势与纳米粒径分析仪等手段,对微球的组成成分、表面形态、粒径及其分布、表面电势进行了表征。结果表明微球粒径均匀,在100～200nm范围内,球形度良好且呈单分散性。     

TiNi合金化学抛光工艺及其对耐蚀性的影响

对ＴiNi合金化学抛光液的组成和抛光工艺进行了研究和优化发现,化学抛光的质量不仅与抛光液配和抛光工艺直接相关,还与ＴiNi合金的处理状态有关,冷轧态固溶及退火态易获得低的表面粗糙度,用电化学方法测试了化学抛光与机械抛光试样的阳极极化曲线,结果表明,化学抛光能提高ＴiNi合金的点蚀电位（Ｅb) ,降低再钝化电位（Ｅrp)从而显著提高其耐蚀性,使化学抛光的表面达到镜面状态。