Dispersion stabilization of antimony-doped tin oxide（ATO）nanoparticles used for energy-efficient glass coating

Nano-antimony-doped tin oxide（ATO） was synthesized using the sol-gel method.A colloidal dispersion of ATO nanoparticles in distilled water was achieved using a milling process in which different dispersants were studied.In this paper,different factors that affect the stability of ATO nanoparticles were discussed,such as zeta potential,dispersant,and pH value.Sodium polyphosphate was a suitable dispersant for stabilizing ATO nanoparticles in distilled water.A stable dispersion of ATO nanoparticles in distilled water was prepared.The stable dispersion of ATO nanoparticles was used to prepare nano-thermal insulation glass paint to block near-infrared rays of sunlight.     

Dispersion stabilization of antimony-doped tin oxide (ATO) nanoparticles used for energy-efficient glass coating

Nano-antimony-doped tin oxide (ATO) was synthesized using the sol–gel method. A colloidal dispersion of ATO nanoparticles in distilled water was achieved using a milling process in which different dispersants were studied. In this paper, different factors that affect the stability of ATO nanoparticles were discussed, such as zeta potential, dispersant, and pH value. Sodium polyphosphate was a suitable dispersant for stabilizing ATO nanoparticles in distilled water. A stable dispersion of ATO nanoparticles in distilled water was prepared. The stable dispersion of ATO nanoparticles was used to prepare nano-thermal insulation glass paint to block near-infrared rays of sunlight.     

Synthesis of Fe3O4 nanoparticles by wet milling iron powder in a planetary ball mill

Fe3O4 nanoparticles with sizes ranging from 30 to 80 nm were synthesized by wet milling iron powders in a planetary ball mill. The phase composition and the morphologies of the as-synthesized products were measured by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Nanosized Fe3O4 particles were prepared by wet milling metallic iron powder （-200 mesh, 99%） in a planetary ball mill equipped with stainless steel vials using iron balls under distilled water with a ball-to-powder mass ratio of 50：1 and at a rotation speed of 300 rpm. The use of the iron balls in this method played a key role in Fe3O4 formation. The present technique is simple and the process is easy to carry out.     

How rotational speed of planetary ball mill and polymer load influence the performance and water vapor sorption in solid dispersions composed of tadalafil and soluplus

The presence of residual water may deteriorate the performance of amorphous solid dispersions prepared by ball milling, affecting molecular mobility, crystallinity, particle size and finally, the drug dissolution rate. As the stability of these metastable systems depend on both formulation and process variables, the aim of this study was to assess for the first time, the impact that the polymer load and the rotational speed applied upon high energy ball milling could have on the performance of binary co-milled solid dispersions composed of tadalafil (a hydrophobic crystalline drug) and Soluplus (an amphiphilic, hygroscopic amorphous polymer). Each of these variables was tested at three levels. Scanning electron microscopy, laser diffraction and X-ray powder diffraction were used to analyze morphology, particle size distribution and crystallinity of ball milled formulations respectively. Dissolution studies were also carried out. Advanced tools of applied physics, namely solid state ¹H NMR and relaxometry were used to assess the structure and water mobility upon gaseous phase hydration on storage. It was shown that both tested variables determined the particle size of the formulation. When the rotational speed of 400 rpm was used, all solid dispersion were XRD-amorphous, but to ensure the immediate release of tadalafil its micellar solubilization in Soluplus was necessary. While the formulation was exposed to water vapor, the hydration level increased with an increasing polymer load as well. Hence, the rotational speed governed the space available for the adsorption of water molecules and their organization in a monolayer or multilayers. Such behavior may have impact on the kinetics of the amorphous drug recrystallization, and finally deteriorate its dissolution.     

高能球磨时间对碳质中间相结构及其高温摩擦磨损特性的影响

采用高能球磨法对煤焦油沥青碳质中间相进行非平衡处理,利用X射线衍射仪和激光Raman光谱仪研究中间相高能球磨前后的结构变化,用差示扫描量热仪测试不同状态下碳质中间相的结构稳定性,在SRV高温摩擦磨损试验机上采用阶梯升温方式考察了碳质中间相作为润滑油添加剂的摩擦磨损性能.结果表明,高能球磨处理导致中间相的结晶有序度下降,微晶石墨平面尺寸减小,层间间距增加,说明高能球磨处理促使中间相向无定形结构转变.高能球磨时间越长,中间相的无定形结构特征越明显.高能球磨处理降低了碳质中间相的稳定性,随着球磨时间增加,碳质中间相的稳定性变差.球磨态碳质中间相具有高温减摩抗磨效应,球磨时间越长,其减摩抗磨效果越明显.高能球磨处理在一定程度上促进摩擦机械诱发碳质中间相的石墨化转变,从而对其高温减摩抗磨效应有一定促进作用,球磨时间越长,其促进作用越大.     

球形金属表面球磨制备石墨烯薄膜摩擦特性研究

采用球磨的方法实现了在钢球表面制备大面积连续的石墨烯薄膜,考察其随球磨时间变化,石墨烯薄膜在钢球表面的包裹程度、形貌变化、结构演变过程、结合性能及摩擦学性能. 研究表明:随着球磨时间的增加,石墨烯在钢球表面团聚减少,包裹更加均一,结构趋于有序;当球磨时间达到50 h时,在钢球表面形成分布均匀且大面积连续的石墨烯薄膜,使与含氢类金刚石碳薄膜组成配伍的平均摩擦系数从裸钢球的0.043降至0.022,磨痕深度和宽度都显著降低. 经胶带粘取100次或乙醇中超声清洗30 min后球磨制备石墨烯薄膜仍然粘附于钢球表面,在氩气环境下石墨烯薄膜表现出优于钢球的摩擦磨损性能.      

等离子体辅助球磨制备表面修饰纳米TiO2的摩擦学性能分析

以季铵盐和月桂酸钠为过程处理剂,利用等离子体辅助球磨制备表面修饰纳米TiO_2粉体,并测试其摩擦学性能.结果表明:在等离子体的热爆效应及脉冲电子轰击效应的协同作用下,辅助球磨11 h制备的表面修饰纳米TiO_2粉体粒径在20 nm左右,晶型发生由锐钛矿型向金红石型的转变.等离子体辅助球磨使得纳米TiO_2获得了良好的亲油疏水表面特性,在40CA船用润滑油中表现出稳定的分散性.由于纳米TiO_2粉体的"微轴承"作用,复合润滑油的摩擦系数降低,摩擦副的磨损失重量减少.纳米TiO_2粉体在摩擦过程中容易吸附沉积在摩擦副表面并修补磨痕,使得复合润滑油具备良好的减摩及自修复性能.     

Discontinuous shear thickening in the presence of polymers adsorbed on the surface of calcium carbonate particles

In the presence of dispersant molecules currently used in cement industry and based on polyethylene oxide (PEO), we found a strong discontinuous shear thickening (DST) at high volume fraction in suspensions of calcium carbonate particles. The transition was reversible and the critical shear rate and shear stress for which this instability appears are reported versus the volume fraction of particles. A model of repulsive forces between polymers, taking into account the thickness of the polymer layer and the density of adsorption on the surface of the particles, can explain the differences of critical stresses observed between these three dispersant molecules. In particular, it explains why a small polymer densely adsorbed can be more efficient to repel the transition at higher stress than a larger molecule less densely adsorbed. Above the transition, we find that the suspension presents a special kind of stick-slip instability with even the presence of a negative shear rate under constant applied stress. A model is proposed which well predicts this regime by taking into account both the inertia of the apparatus and the viscoelasticity of the suspension.     

纳米Cu在聚乙二醇溶液中的摩擦磨损性能研究

采用原位合成法以聚乙二醇400作为反应介质,以氢氧化钠和氨基配体作为分散剂,用乙二醇还原六水合乙酸铜制备出纳米Cu粉和纳米Cu聚乙二醇溶液,用X射线衍射仪和透射电子显微镜表征其结构,在四球摩擦磨损试验机上评价了含不同质量分数纳米铜粉的聚乙二醇溶液的摩擦磨损性能,并与分散剂进行对比.结果表明:所制备的纳米铜粒径约5 nm且分布均匀;纳米Cu粉可以显著提高聚乙二醇的抗磨和减摩性能.这是由于纳米铜在钢球磨斑表面形成了铜沉积膜和微量的一价氧化铜.     

氟化石墨烯的制备及其作为润滑油添加剂的摩擦学性能研究

采用球磨的方法制备了少层氟化石墨烯薄片,利用原子力显微镜、透射电子显微镜、X射线衍射仪对其微观形貌和组成结构进行了表征分析,使用SRV-Ⅳ高温摩擦磨损试验机考察了氟化石墨烯片作为润滑油添加剂的摩擦学性能.结果表明:氟化石墨烯可以明显提高润滑油的承载能力和抗磨损性能,当添加浓度为0.30 mg/ml时,润滑油的抗磨损性能最佳.     

The effect of dissolved polymers on the rheological properties of coating colours

Coating colours used for the coating of paper and board consist mainly of a mineral pigment, which is very often clay, a synthetic binder such as a styrenebutadiene latex, dispersion agents and water retention aids. The latter are often water soluble polymers. These polymers have a very strong influence on the rheological properties of the coating colours, both on the strain rate dependence of the apparent viscosity and on the viscoelasticity. The effects of two different grades of carboxymethylcellulose (CMC) and one grade of hydroxyethylcellulose (HEC), on the rheological properties at room temperature of a clay-based coating colour at pH 8, have been investigated. It is concluded that the high values of the dynamic modulus of the colours are due to interactions between the cellulose derivatives and the solid particles, i.e. mainly the clay particles. For HEC this interaction is associated with adsorption of the polymeric molecules on the clay particles. In the case of CMC, the adsorption is strongly retarded by the presence of the dispersant (a polyacrylate salt). It is suggested that the marked elasticity of the CMC-containing colour in addition to a possible polymer adsorption may be due to charge interactions and/or depletion flocculation. The effect of CMC and HEC on the water-retention properties of the colour is also discussed.     

Effect of polymer bridging on rheological properties of dispersions of charged silica particles in the presence of low-molecular-weight physically adsorbed poly(ethylene oxide)

 The effect of a low-molecular-weight physically adsorbed poly(ethylene oxide) on the rheological behavior of aqueous dispersions of silica particles (as a model system) has been investigated. Particular attention is given to the evolution of the rheological behavior with increasing polymer concentration in the system at different volume fractions of the particles. Experiments were performed in the absence of salt and just the pH of the dispersion was adjusted to 9.5, a condition at which the system is electrostatically stable and electrostatic repulsive forces are long range in nature. It was observed that the shear viscosity and the linear viscoelastic functions of the dispersion at 55 vol% increase initially through the addition of polymer, reach a maximum, and then decrease to a minimum with further addition of polymer to the system. At higher polymer concentrations, there may be an increase in the viscosity of the dispersion owing to an increase in the concentration of free polymer chains in the medium causing depletion flocculation in the system. The increase in the rheological behavior of the dispersion at low polymer coverage is attributed to polymer bridging flocculation caused by a low-molecular-weight poly(ethylene oxide) in the system. Comparison of the data given here with the results of earlier studies on the viscosity behavior of the system in the presence of salt (0.01 M) indicates that the range of the electrostatic repulsion has a significant role in the rheological behavior of the system. Received: 7 February 2001 Accepted: 18 October 2001     

油酸表面修饰PbO纳米微粒作为润滑油添加剂的摩擦学性能研究

利用四球摩擦磨损试验机考察了油酸修饰PbO纳米微粒作为润滑油添加剂的摩擦学行为,并用X射线光电子能谱仪（XPS）、扫描电子显微镜（SEM）和能量散射谱仪（EDS）等现代分析工具对钢球磨损表面进行了分析,摩擦磨损试验结果表明,油酸修饰PbO纳米微粒作为润滑油添加剂能够明显提高基础油的减摩抗磨能力,当添加质量分数为0.30%时,与基础油相比可以使摩擦系数和钢球磨厂主 直径降低30%左右。XPS、SEM及EDS分析结果表明,钢球表面在摩擦过程中形成了一层富含PbO的边界润滑膜,这使得油酸修饰PbO纳米微粒作为润滑油添加剂表现出良好的摩擦学性能。     

Study of milling stability with Hertz contact stiffness of ball bearings

This present work examines the stability and nonlinear responses of a spindle milling system supported by ball bearings. A shaft finite element based on Timoshenko beam theory is employed to model the spindle, and modal reduction method is therefore adopted for saving the numerical calculating time. The issues of evaluating the effects of the ball bearing Hertz contact stiffness are consequently addressed. It is found that suitable constant bearing stiffness can be adopted to replace the nonlinear nonsmooth Hertz stiffness in prediction of the critical cutting depth of the milling system in certain bearing configuration conditions. For the constant bearing stiffness can be obtained by experiment, this replacement will undoubtedly simplify the spindle-bearing milling system. But with the increase in the bearing clearance, the spindle milling system will present obvious nonlinear behaviors, and the nonlinear Hertz contact bearing stiffness will take over. Isolated islands of chatter vibration, which are induced by the nonlinear nonsmooth bearing Hertz stiffness, can be found exist in milling processes in large bearing clearance conditions.     

Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO4 nanoparticles were synthesized in the presence of sodium polyacrylate （PAAS） by a simple precipitation method, with BaCl2 and （NH4）2SO4 as reactants. The different roles performed by PAAS in the synthesis of BaSO4 nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the assynthesized BaSO4 nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl2 to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO4 nuclei. During formation of the BaSO4 nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO4 seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO4 nanoparticles.     

SYNTHESIS OF NiO NANOPARTICLES IN ETHYLENE GLYCOL

NiO nanoparticles with well-dispersed property were prepared via a wet chemical method in ethylene glycol (EG) without soluble polymer as a protective agent. The mechanism of chemical process was proposed based on color change during the experiment. The dispersion function of EG was discussed.     

Roles of polyacrylate dispersant in the synthesis of well-dispersed BaSO4 nanoparticles by simple precipitation

Well-dispersed BaSO₄ nanoparticles were synthesized in the presence of sodium polyacrylate (PAAS) by a simple precipitation method, with BaCl₂ and (NH₄)₂SO₄ as reactants. The different roles performed by PAAS in the synthesis of BaSO₄ nanoparticles were investigated using X-ray diffractometry, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicate that the as-synthesized BaSO₄ nanoparticles were spheres with an average diameter of 30 nm and that their surfaces were affected by the PAAS. Under a typical procedure employed, PAAS reacted with BaCl₂ to yield an intermediate, serving as a control releasing agent and separating the nucleation and crystal growth processes of the BaSO₄ nuclei. During formation of the BaSO₄ nanospheres, the intermediate slowly dissolved and released barium and polyacrylate ions, inhibiting the growth and aggregation of newly formed BaSO₄ seeds and resulting in particles of narrow diameter distribution and improved dispersibility. Moreover, these polyacrylate ions further modified the surfaces of the BaSO₄ nanoparticles.     

Influence of suspension stability on wet grinding for production of mineral nanoparticles

Grinding behavior of nanoparticles in an attritor mill and the minimum achievable particle size are strongly influenced by the suspension stability. In the present work, suspension stability （i.e. ξ-potential） of nanoparticles was studied by measuring pH as a function of grinding time in the wet milling process. It was found that after a certain time in an attritor mill, there is no further size reduction and the average product particle size increases monotonically. One of the reasons is that the production of submicron particles leads to more particle-particle interactions and consequently pH of the suspension decreases with grinding time. Usually pH value is related to suspension stability and it can be enhanced by addition of NaOH solution. The maximum negative ξ-potential of -51.2 mV was obtained at pH of 12 for silica. The higher the ξ-potential with the same polarity, higher will be the electrostatic repulsion between the particles. Hence, the maximum electrostatic repulsion force was maintained by the adjustment ofpH value in wet milling. The experiments were conducted at different pH conditions which were maintained constant throughout the experiments and nanosized particles were obtained consequently.     

Influence of suspension stability on wet grinding for production of mineral nanoparticles

Grinding behavior of nanoparticles in an attritor mill and the minimum achievable particle size are strongly influenced by the suspension stability. In the present work, suspension stability (i.e. (-potential) of nanoparticles was studied by measuring pH as a function of grinding time in the wet milling process. It was found that after a certain time in an attritor mill, there is no further size reduction and the average product particle size increases monotonically. One of the reasons is that the production of submicron particles leads to more particle-particle interactions and consequently pH of the suspension decreases with grinding time. Usually pH value is related to suspension stability and it can be enhanced by addition of NaOH solution. The maximum negative (-potential of -51.2 mV was obtained at pH of 12 for silica. The higher the (-potential with the same polarity, higher will be the electrostatic repulsion between the particles. Hence, the maximum electrostatic repulsion force was maintained by the adjustment of pH value in wet milling. The experiments were conducted at different pH conditions which were maintained constant throughout the experiments and nanosized particles were obtained consequently.     

片状纳米石墨的制备及其作为润滑油添加剂的摩擦磨损性能

采用搅拌球磨法制备了平均直径1 μm、厚度10～20 nm的片状纳米石墨;利用扫描电子显微镜、透射电子显微镜和X射线衍射仪分析了片状纳米石墨的微观形貌和组织结构;利用四球和销-盘式摩擦磨损试验机考察了片状纳米石墨作为液体石蜡添加剂的摩擦磨损性能.结果表明,片状纳米石墨能够显著提高润滑油的抗磨性能及承载能力,降低摩擦系数,其最佳添加量约为50 ppm.