Effect of n-alkanes and n-alcohols on quartz surface hydration

The results are presented of investigations to determine the effect of the presence of two different liquids (polar and nonpolar) on the properties of hydration layers of a quartz surface. The thickness of the water layers and energy changes related to water adsorption are determined on the basis of the experimental results. The water structure type and the formation mechanism of these layers are suggested.     

Influence of wettability on bubble formation in liquid

This paper presents experimental results of the surface phenomena effect on bubble formation from a single orifice in water and at nozzle in liquid aluminium with gas blowing at small flow rates. The usage of coated orifice in water and nozzles of different materials in the melt realized wide range of contact angles. The meaningful stages, termed (1) nucleation period, (2) under critical growth, (3) critical growth and (4) necking, were identified during bubble formation in a regime referring to simultaneous forced flow and surface tension control. It was revealed that bubble formation is substantially dominated by hysteresis of contact angle. Evolution of interface equilibrium and force balance conditions distinctive for bubble formation is clarified. X-ray fluoroscope was used to carry out in-situ observation of bubble formation in the melt. It was shown that bubble volume increased with wettability worsening both for aqueous and metallic systems. A further insight into the mechanism of the bubble formation was obtained by comparison of the bubble behaviour at the tip of the injection devices in liquid aluminium and at the orifice in water.     

Electroosmotic capillary flow with nonuniform zeta potential

The present work is an analytical and experimental study of electroosmotic flow (EOF) in cylindrical capillaries with nonuniform wall surface charge (zeta-potential) distributions. In particular, this study investigates perturbations of electroosmotic flow in open capillaries that are due to induced pressure gradients resulting from axial variations in the wall zeta-potential. The experimental inquiry focuses on electroosmotic flow under a uniform applied field in capillaries with an EOF-suppressing polymer adsorbed onto various fractions of the total capillary length. This fractional EOF suppression was achieved by coupling capillaries with substantially different zeta-potentials. The resulting flow fields were imaged with a nonintrusive, caged-fluorescence imaging technique. Simple analytical models for the velocity field and rate of sample dispersion in capillaries with axial zeta-potential variations are presented. The resulting induced pressure gradients and the associated band-broadening effects are of particular importance to the performance of chemical and biochemical analysis systems such as capillary electrokinetic chromatography and capillary zone electrophoresis.     

Zeta电位测量中电场对颗粒粒径的影响

为确定电泳光散射法测量纳米颗粒zeta电位过程中电场对颗粒系统性质的影响,实验研究210、360 nm 2种标准颗粒的单分散溶液在通电前、后颗粒粒度的变化;通过测量90°散射角的动态光散射信号,采用自相关技术进行信号分析,用累积法反演计算颗粒的粒径。结果表明,颗粒在小电压的情况下,粒径几乎没有变化;随着电压的增大,平均粒径逐渐增大,说明样品发生团聚;电压越大,颗粒团聚越快。     

添加剂对Ag/陶瓷复合触点材料浸润性及电性能的影响

采用固相反应法制备了LaFe0.25Ni0.75O3陶瓷并加入少量添加物作为改性剂,对其与Ag的浸润性,材料的电阻率以及Ag/陶瓷复合电接触材料的电性能分别进行了研究,结果显示,改性剂使陶瓷材料与Ag之间的浸润性发生明显的变化,且作用效果与改性剂的加入方式有关,添加剂的加入使材料的电阻率增大,同时一定程度上改变了陶瓷在银基体中的分布状态,从而对电接触材料的使用性能产生较大的影响.     

Influence of N-alkanes on contact angle and flotability of quartz

Measurements of time dependence of the contact angle were carried out for water drops on a quartz surface in the presence of saturated hydrocarbon vapour as well as on a quartz surface previously wetted with a hydrocarbon. The results obtained were compared with theoretically calculated values on the basis of the modified Young equation and the literature data for the surface free energy components of quartz covered with a monolayer water film. On the basis of the measurements and calculations it was found that the values of the contact angle in the studied systems depend on the kind and thickness of hydrocarbon film present on the quartz surface, as well as on the thickness of water film present on this surface. Changes of the contact angle with the hydrocarbon film thickness are characterized by the maximum and minimum values. This allows previously obtained results of the quartz flotation activity changes in the presence of the aliphatic hydrocarbon films to be explained.     

Influence of quartz anisotropy on shock propagation and spall damage

Stress wave propagation and shock-induced damage in quartz are issues of key interest for many applications. Here, we present original observations in laser shock-loaded single-crystal quartz, showing the strong influence on spall damage of the direction of shock application versus crystal orientation. Indeed, due to the anisotropy of the quartz atomic structure, a compressive pulse applied onto a circular spot may propagate in an oblique direction, or change shape during its propagation through the target, so that its reflection on the opposite free surface may produce specific damage, in unexpected locations. Such anisotropic effects have been investigated experimentally by applying laser shocks on thick samples of single-crystal quartz along the three particular crystallographic axis. Preliminary three-dimensional computer simulations based on the rigidity matrix of quartz have confirmed those effects, and a good overall consistency has been obtained between observed and computed damage in all three cases.     

Influence of surface wettability on the cathodic electroluminescence of porous silicon

It is shown that the wettability of porous silicon influences the efficiency of its cathodic electroluminescence in electrolytes. A model is proposed to explain the nature of the electroluminescence in a system consisting of porous silicon and an oxidizing electrolyte. Pis’ma Zh. Tekh. Fiz. 23, 58–63 (January 12, 1997)     

非晶碳膜的表面润湿性对生物相容性的影响

采用等离子体注入沉积方法(PⅢ-D),混合通入C2H2、Ar或N2,制备了具有不同表面润湿性的非晶碳薄膜a-CH和掺N非晶碳薄膜a-CNH.采用Raman及XPS方法对薄膜的结构进行了分析,采用血小板黏附实验评价薄膜的抗凝血性能,采用材料表面的内皮细胞培养,对材料的细胞毒性以及生物相容性进行评价.结果表明非晶碳膜的生物相容性的提高与其表面的润湿性的变化密切相关,可通过掺杂特定的元素,增加a-CH薄膜表面张力的极性倾向,提高非晶碳膜的亲水性,来进一步改进a-CH薄膜的生物相容性,特别是血液相容性.     

Determination of the zeta potential for highly charged colloidal suspensions

We compute the electrostatic potential at the surface, or zeta potential ζ, of a charged particle embedded in a colloidal suspension using a hybrid mesoscopic model. We show that, for weakly perturbing electric fields, the value of ζ obtained at steady state during electrophoresis is statistically indistinguishable from ζ in thermodynamic equilibrium. We quantify the effect of counter-ion concentration on ζ. We also evaluate the relevance of the lattice resolution for the calculation of ζ and discuss how to identify the effective electrostatic radius.     

Influence of a magnetic field on quartz crystal resonators

The magnetic sensitivity of quartz crystal resonators is a consequence of the ferromagnetic properties of the metal used as support for the vibrating plate. Various magneto-mechanic interactions can contribute to the overall sensitivity, the most important of which is shown to be the change in Young's modulus of the spring material submitted to a magnetic field, which in turn modifies the stress in the quartz plate and then induces a change in the crystal resonant frequency. The experimental setup and procedure are described and a large number of experimental results obtained with resonators of different technologies are presented and discussed. A comparison between the magnetic behavior of identical resonators mounted with different materials definitely proves the responsibility of the supports in the magnetic sensitivity of resonators and gives interesting information on its reduction     

Structural analysis of Si-substituted hydroxyapatite: zeta potential and X-ray photoelectron spectroscopy

The aim of this study was to determine the effect of the incorporation of silicon on the surface charge of hydroxyapatite (HA) and to assess surface structural changes of HA and Si–HA induced by dissolution in both static and dynamic systems. X-ray photoelectron spectroscopy (XPS) analysis showed that SiO₄ ^4– groups were substituted for PO₄ ^3– groups in the silicon-hydroxyapatite (Si–HA) lattice according to a previously proposed substitution mechanism without the formation of other crystalline phases, such as tricalcium phosphate or calcium oxide. The substituted silicon induced a decrease in the net surface charge and the isoelectric point of HA as determined by zeta potential (ZP) measurements. At physiological pH=7.4 the surface charge of Si–HA was significantly lowered compared to unmodified HA, i.e. –50±5 to –71±5 eV, caused by the presence of silicate groups in the HA lattice, which may account for a faster in vitro apatite formation using SBF testing. XPS results indicated that silicon seems to be preferentially leached out from Si–HA surface compared to other ionic species after dissolution studies in tris-buffer using a dynamic system.     

Influence of hydrophobic characteristic of organo-modified precursor on wettability of silica film

The objective of this study is to design new hybrid silica materials as templates with hydrophobic properties, prepared at room temperature by a base catalyzed sol–gel process. As silica sources, organoalkoxysilanes functionalized with short hydrophobic chains were used: tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), octyltriethoxysilane (OTES) and isobutyltriethoxysilane (iTES). It was shown that hydrophobicity of the functionalized silica nanoparticles increased as a function of length of the aliphatic chains (MTES < iTES < OTES) or when, instead of a hydrophobic alkyl chains (substituting group of silica precursors), a monounsaturated group was used (VTES). It was observed that the samples responded in a specific way to each type (hydrophilic or hydrophobic) of the dropped liquid. Even though the experiments were limited to short hydrocarbon chains, they showed that there is a threshold to reach high hydrophobicity of the hybrid surface.     

Influence of Cu powders on the wettability and mechanical properties of solderable epoxy composites

Journal of Materials Science: Materials in Electronics - A Cu powder-filled solderable epoxy composite (Cu-SEC), in which Cu powders were applied as reinforcement materials, was developed to...     

Influence of electrodes arrangement on the quartz resonator equivalent circuit

The strip electrodes deposited on the main surfaces of the rotated Y-cut quartz plate in the Z' direction and overlapping only in the central part of the plate excite a non-negligible electric field parallel to the surface of the plate. The influence of this field on the parameters of the electrical equivalent circuit and frequency-temperature characteristic of the AT-cut quartz plates is examined. The influence of this electric field parallel to the surface depends on the orientation of electrodes in the rectangular coordinate system of quartz.     

Study of the zeta potential of Fe(O)OH colloids

Zeta potentials of colloidal particles were used to study the influence of anions on the formation of ferric oxide hydroxides [Fe(O)OH]. This anion effect, complexation with ferric ions and adsorption on the resulting particle surface, correlated well with the determined zeta potentials. The greater anion effect in ferric ion solution decreased the measured zeta potential of colloidal particles. This effect increased with increasing size, charge and complexation of anions. The results indicated that the composition and morphology of Fe(O)OH precipitates were affected by the presence of anions in solution.     

Structural,thermal, zeta potential and electrical properties of disaccharide reduced silver nanoparticles

Silver nanoparticles (AgNPs) have been synthesized using maltose as reducing agent and microwave heating as reaction initiator. The nanoparticles are studied for their optical, structural, thermal, zeta potential and electrical properties. The synthesis protocol used is fast and resulted in the formation of multi-shaped AgNPs as indicated by their optical response and TEM. The crystallite size of nanoparticles and strain of the sample was found to be around 39 nm, and 2.3 × 10^?1, respectively, as calculated from XRD data. Zeta potential and electrical response both showed almost threefold increase for multi-shaped as compared to isotropic nanoparticles.