低氯缓蚀石棉橡胶板中痕量氯的间接原子吸收法测定

根据胶体的性质，本文提出了一种测定痕量氯的新方法，即在未知样溶液中定量加入过量的硝酸银标准溶液，使氯离子沉淀完全，然后再加入少量电解质，破坏氯化银胶体使之聚沉，过量银离子的吸收强度与其浓度成正比。间接计算出待测溶液中氯离子的含量。方法准确、可靠。     

基于静电学讨论蛋白质分子的聚沉现象

日常生活中,将食盐加入到胶体蛋白质溶液中会出现聚沉现象.本文基于球形胶粒模型,运用静电学的泊松方程以及玻尔兹曼分布定律讨论蛋白分子的聚沉现象.通过挖掘生活现象中的物理思想,不仅加深学生对物理学定律的理解,培养解决实际问题的能力,而且提升教学的效果.     

阴离子对银胶光谱学性质的影响

借助紫外-可见吸收光谱和共振散射光谱技术, 研究了几种阴离子的加入对“化学纯”银胶的光谱学性质的影响。研究发现, 阴离子的加入会发生离子在银胶表面的吸附和胶体的聚沉作用, 造成等离子体共振吸收的下降和长波区新峰的出现; 同时, 其共振散射峰也发生了规律的变化。比较这些实验现象, 再接合相应的理论分析, 解释了不同的阴离子和胶体间不同的作用方式和造成这些差别的可能原因。     

摄影光学 感光材料与性能测试

TB84 2006043405超声场下不同形貌银胶体的制备与表征=Preparation andcharacterization of different morphological silver colloids byultrasonic field[刊,中]/程敬泉(天津大学化工学院.天津(300072)) ,姚素薇…∥天津大学学报.—2006 ,39(1) .—34-38为了研究制备工艺条件对不同形貌银胶体稳定性的影响,在超声场作用下,以AgNO3为前驱物,聚乙烯吡咯烷酮为保护剂,KBH4和N2H4·H2O分别为还原剂,制备了稳定的银胶体,并利用透射电镜和分光光度技术对制备的银胶体进行了表征。结果表明,超声场分布、超声作用时间、超声功率和还原剂种类…     

剪应力作用下流体力学关联对胶体聚团的影响

用计算机模拟的方法，探讨了剪应力下流体力学关联对胶体聚团特性的影响，并与无流体力学关联时的结果作了比较，研究表明，流体力学关联因素对胶体簇团的分形维数和栩位数没有明显的影响，但却使聚团的机理发生改变，从无流体力学关联时的颗粒－颗粒型向簇团－簇团型过渡。这个结果都很好地解释了有关的实验现象。     

二氧化钛胶体及其自组装薄膜的光谱分析

水解钛酸四丁酯制备了二氧化钛胶体;采用静电自组装技术制备了聚电解质与二氧化钛胶体的复合薄膜;采用吸收光谱和荧光光谱对二氧化钛胶体及其复合薄膜进行了表征。吸收光谱显示,胶体的吸收带边蓝移,显示出量子尺寸效应,胶体的荧光光谱出现了多个发光带,最短发光波长位于371nm,发光主要集中在蓝光区域内;在252nm光源激发下。复合薄膜的发射谱带具有二氧化钛水溶胶的发射谱带的特征,荧光发射主要来源于二氧化钛,聚电解质的引入对复合薄膜的光致发光特性有一定影响。     

光纤表面自组装胶体晶体微结构的实验研究

利用自组装方法在普通单模光纤裸纤表面生长胶体晶体,采用自组装方法制备了一种新型的三维光子晶体微结构光纤。将单分散度小于2％的二氧化硅胶体微球超声分散于乙醇溶液,通过垂直沉积法在表面经湿法腐蚀处理的裸光纤表面组装胶体晶体。采用SEM对样品进行表征,胶体样品表面为六角密排列,晶体呈FCC结构,其（111）晶面平行于光纤表面。当微球直径远小于光纤直径时,在60℃温度下制备的胶体样品有较好的质量。     

分散介质和温度对纳米二氧化硅胶体剪切增稠行为的影响

对分散介质和温度对纳米二氧化硅胶体剪切增稠行为的影响进行了系统研究. 用四种液体分散介质(乙二醇, 聚乙二醇400, 丙二醇, 聚丙二醇400)制备的纳米二氧化硅胶体表现出不同的连续剪切增稠或者跳变剪切增稠行为. 温度上升降低了分散介质的黏度, 进而降低了胶体的表观黏度. 剪切增稠的临界黏度与温度的关系符合“Arrhenius”公式的描述. 胶体黏度与分散介质黏度的比值用来归一化不同温度下的稳态剪切流变曲线. 在低剪切速率的剪切变稀阶段, 剪切变稀现象与分散介质黏度没有明显相关性, 而与分散介质的化学性质密切相关. 在高剪切速率的剪切增稠阶段, 分散介质黏度越高, 胶体剪切增稠现象越强烈.     

胶体晶体和基于胶体晶体的纳米结构

胶体晶体及基于胶体晶体的各种纳米结构的制备和物理性质是近来物理学和材料科学共同关注的一个热点，文章简要阐述了胶体颗粒间的基本相互作用，着重介绍了各种胶体晶体的制备方法；结合我们近期的工作，综合评述了胶体晶体在二维纳米颗粒阵列、二维有序孔单层膜及三维光子晶体等纳米结构材料研究中的应用，并对未来的发展进行了展望。     

SiO2溶胶及其静电自组装薄膜的制备

采用HCl催化、NH3 ·H2 O催化、HCl与NH3 ·H2 O分步催化三种途径制备了SiO2 胶体 ,用透射电镜观察了胶体粒子的形貌 .用静电自组装 (ESAM)法制备了聚电解质PDDA与SiO2 胶体粒子的有机 /无机复合光学薄膜 .实验结果表明 ,用HCl催化制备的SiO2 透明溶胶不适合于用ESAM法制备薄膜 ,用HCl与NH3 ·H2 O分步催化以及用NH3 ·H2 O单独催化制备的SiO2 胶体适合于用ESAM法制备光学薄膜 .薄膜的透射电镜微观察结果表明 ,以HCl与NH3 ·H2 O分步催化的SiO2 胶体制备的PDDA/SiO2 薄膜为连续结构 ,NH3 ·H2 O单独催化的为颗粒堆积 .研究了薄膜透光率与薄膜层数的关系 ,考察了薄膜的机械强度 .结果显示 ,以NH3 ·H2 O单独催化的SiO2 胶体制备的光学薄膜的增透效果较好 ,但耐机械擦伤强度较弱     

A new way to apply ultrasound in cross-flow ultrafiltration: Application to colloidal suspensions

A new coupling of ultrasound device with membrane process has been developed in order to enhance cross-flow ultrafiltration of colloidal suspensions usually involved in several industrial applications included bio and agro industries, water and sludge treatment. In order to reduce mass transfer resistances induced by fouling and concentration polarization, which both are main limitations in membrane separation process continuous ultrasound is applied with the help of a vibrating blade (20 kHz) located in the feed channel all over the membrane surface (8 mm between membrane surface and the blade). Hydrodynamic aspects were also taking into account by the control of the rectangular geometry of the feed channel.Three colloidal suspensions with different kinds of colloidal interaction (attractive, repulsive) were chosen to evaluate the effect of their physico-chemical properties on the filtration.For a 90 W power (20.5 W cm⁻²) and a continuous flow rate, permeation fluxes are increased for each studied colloidal suspension, without damaging the membrane. The results show that the flux increase depends on the initial structural properties of filtered dispersion in terms of colloidal interaction and spatial organizations.For instance, a Montmorillonite Wyoming–Na clay suspension was filtered at 1.5 × 10⁵ Pa transmembrane pressure. Its permeation flux is increased by a factor 7.1, from 13.6 L m⁻² h⁻¹ without ultrasound to 97 L m⁻² h⁻¹ with ultrasound.     

Removal of colloidal precipitation plugging with high-power ultrasound

Petroleum is a continuous and dynamically stable colloidal system. In the process of oil extraction, transportation, and post-treatment, the stability of the petroleum sol system is easily destroyed, resulting in asphaltenes precipitation that can make pore throat, oil wells, and pipelines blocked, thereby damaging the reservoir and reducing oil recovery. In this paper, removing near-well plugging caused by asphaltene deposition with high-power ultrasound is investigated. Six PZT transducers with different parameters were used to carry out the experimental study. Results show that ultrasonic frequency is one important factor for removing colloidal precipitation plugging in cores, it could not be too high nor too low. The optimum ultrasonic frequency is 25 kHz; Selecting transducers with a higher power is an effective way to improve the removal efficiency. The optimum ultrasonic power is 1000 W. With the increase of ultrasonic treatment time, the recovery rate reaches the maximum and tends to be stable. ultrasonic processing time should be controlled within 120 min. Besides, three methods — ultrasonic treatment alone, chemical injection alone, and ultrasound-chemical method — for removing colloidal precipitation plugging are compared. Results indicate that the ultrasound-assisted chemical method is better than chemical injection alone or ultrasonic treatment alone to remove colloidal sediment in the core. Finally, the mechanism of the ultrasonic deplugging technique is analyzed from three aspects: cavitation effect, the thermal effect, and mechanical vibration.     

Ultrasound attenuation in ferrofluids

The absorption of acoustic energy by internal degrees of freedom of short chains is proposed as a new viable mechanism of ultrasound attenuation in ferrofluids. It is demonstrated that even though the volume fraction of the chains may be quite small, such an effect may reach the order of magnitude of viscous damping. In addition, by investigating the statistical properties of dimers in ferrofluids, it is shown that an applied magnetic field modifies the sound attenuation in a highly anisotropic manner. The proposed mechanism provides new insight into the fundamental issue of colloidal response, and, in particular, may lead to its utilization in novel experimental concepts.     

The photoacoustic effect from particles and bubbles

Irradiation of colloidal suspensions with the output of a high power, pulsed laser can give rise to chemical reactions and phase transitions that are linked to the production of ultrasound. Transient grating experiments, which record both photoacoustic and photothermal processes, show the effects of the concentration of heat at the sites of colloidal particles, chemical reactions leading to the formation of stable gaseous species, and the production of steam bubbles. The efficiency of sound by these processes is, in general, determined by the rapidity of the density change that follows the absorption of the laser radiation.     

Low-frequency and high-power ultrasound-assisted production of natural blue colorant from the milk and unripe Genipa americana L.

This study presents the production of a novel natural blue colorant obtained from the cross-linking between milk proteins and genipin assisted by low-frequency and high-power ultrasound technology. Genipin was extracted from unripe Genipa americana L. using milk as a solvent. Also, milk colloidal system was used as a reaction medium and carrier for the blue color compounds. The effects of ultrasound nominal power (100, 200, 300, and 400 W) on the blue color formation kinetics in milk samples were evaluated at 2, 24, and 48 h of cold storage in relation to their free-genipin content and color parameters. In addition, Fourier transform infrared (FTIR) spectrum, droplet size distribution, microstructure, and kinetic stability of the blue colorant-loaded milk samples were assessed. Our results have demonstrated that the ultrasound technology was a promising and efficient technique to obtain blue colorant-loaded milk samples. One-step acoustic cavitation assisted the genipin extraction and its diffusion into the milk colloidal system favoring its cross-linking with milk proteins. Ultrasound process intensification by increasing the nominal power promoted higher genipin recovery resulting in bluer milk samples. However, the application of high temperatures associated with intensified acoustic cavitation processing favored the occurrence of non-enzymatic browning due to the formation of complex melanin substances from the Maillard reaction. Also, the blue milk samples were chemically stable since their functional groups were not modified after ultrasound processing. Likewise, all blue colorant-loaded milk samples were kinetically stable during their cold storage. Therefore, a novel natural blue colorant with high-potential application in food products like ice creams, dairy beverages, bakery products, and candies was produced.     

Facile Fabrication of Anisotropic Colloidal Particles with Controlled Shapes and Shape Dependence of Their Elastic Properties

A facile technique with only one step for fabrication of anisotropic colloidal particles at the air/water interface is demonstrated. Anisotropic colloidal particles with controlled shapes can be easily obtained by tuning the incubation time in solvent vapor at room temperature. The formation of separate anisotropic particles is attributed to the lateral stretch on the particles by the interfacial forces and repulsion among the neighboring particles by the generation of the polymer solution flows. To further explain the proposed formation mechanism of the colloidal particles with shape anisotropy, an in situ experiment is designed for direct observation of the arrangement change of the colloidal particles. This fabrication technique is general and applicable to polymer colloidal particles with various initial sizes ranging from microscale to nanoscale. Moreover, the elastic properties of the anisotropic colloidal particles are measured which exhibit a prominent change with different shapes and the change trend of the elastic moduli is similar for particles with different original sizes. This work provides a versatile approach for fabrication of anisotropic colloidal particles with tunable shapes and sizes and establishes the interplay between particle shape and elastic property, which is much valuable for further research on the effect of particle parameters on drug delivery process.     

Diffusion of a chemically active colloidal particle in composite channels

Diffusion of colloidal particles in microchannels has been extensively investigated, where the channel wall is either a no-slip or a slip-passive boundary. However, in the context of active fluids, driving boundary walls are ubiquitous and are expected to have a substantial effect on the particle dynamics. By mesoscale simulations, we study the diffusion of a chemically active colloidal particle in composite channels, which are constructed by alternately arranging the no-slip and diffusio-osmotic boundary walls. In this case, the chemical reaction catalyzed by the active colloidal particle creates a local chemical gradient along the channel wall, which drives a diffusio-osmotic flow parallel to the wall. We show that the diffusio-osmotic flow can significantly change the spatial distribution and diffusion dynamics of the colloidal particle in the composite channels. By modulating the surface properties of the channel wall, we can achieve different patterns of colloidal position distribution. The findings thus propose a novel possibility to manipulate colloidal diffusion in microfluidics, and highlight the importance of driving boundary walls in dynamics of colloidal particles in microchannels.     

基于光纤的三维可调胶体光子晶体

用改进的垂直沉积法在光纤端面制备了高质量的SiO₂胶体光子晶体,经过烧结、固化构成胶体光子晶体-光纤结构. 用扫描电子显微镜确定了样品为面心立方密排结构,其密排面平行于光纤基底表面. 利用全光纤传感网络测试了该胶体光子晶体,反射峰中心位于845 nm处,与Bragg理论计算值符合很好. 将该样品浸入不同折射率的液体中,反射光谱的峰值位置随着液体折射率的改变而发生偏移,近似呈线性关系,实现了峰位可调. 对于不同浓度引起的液体折射率的变化,基于光纤的胶体光子晶体结构也能够很好地分辨出来. 关键词： 可调胶体光子晶体 2微球')" href="#">SiO₂微球 Bragg反射 光纤     

Photoinduced Degradation of the Optical Properties of Colloidal Ag<Subscript>2</Subscript>S and CdS Quantum Dots Passivated by Thioglycolic Acid

The results of studying degradation of the optical properties of colloidal Ag₂S and CdS quantum dots (QDs) 2.6–3.2 nm in size passivated by thioglycolic acid (TGA) are presented. The photoluminescence intensity of colloidal Ag₂S QDs has been found to decrease under laser irradiation at a wavelength of 445 nm, beginning with the effective power of 10 mW. The observed effect is interpreted as a photochemical reaction of formation of new nonradiative-recombination channels in Ag₂S QDs upon excitation. It is established for colloidal CdS QDs passivated by TGA that a decrease in the optical density in the entire absorption spectrum and the luminescence intensity is accompanied by precipitation of the colloidal particles in a cell and related to photodegradation of the passivating shell.     

Dispersions and mixtures of particles with complex architectures in shear flow

We review the effect of shear flow on the phase behavior and structure of colloidal dispersions with increasing degree of complexity. We discuss dispersions of colloidal rods, stiff living polymers like wormlike micelles, and colloidal platelets. In addition, a review is presented on sheared binary dispersions. For all cases we discuss the interplay between thermodynamic instabilities and hydrodynamic instabilities.