硬脂酸修饰LaPO4和Ce/LaPO4纳米微粒的制备及其摩擦学性能

采用共沉淀表面修饰法,制备了硬脂酸修饰LaPO4和Ce/LaPO4纳米微粒,用红外光谱仪、X射线衍射和透射电子显微镜对表面修饰纳米微粒的结构、形貌进行了表征,考察了表面修饰纳米微粒在溶剂中的分散性,利用四球试验机考察了表面修饰纳米微粒的摩擦学性能,并用扫描电镜对钢球磨斑表面形貌进行了分析.结果表明,硬脂酸修饰LaPO4...     

有机表面修饰温度对纳米二氧化钛微结构的影响

首先制备出纳米二氧化钛水分散液, 然后通过蒸馏的方法, 把纳米二氧化钛粒子由水分散液转移到溶有硬脂酸的甲苯溶液中, 以确保纳米二氧化钛在有机相中进行表面修饰. 然后升温到不同的温度, 利用硬脂酸对纳米二氧化钛进行有机表面修饰, 研究了有机表面修饰温度对纳米二氧化钛微结构的影响. 采用红外光谱(FT IR)、X 射线光电子能谱（XPS）、热分析(TG DTG)、X 射线粉末衍射（XRD）和透射电镜(TEM)等对有机表面修饰前后的纳米二氧化钛进行分析表征. 结果表明, 硬脂酸与纳米二氧化钛表面之间存在双齿配位方式的化学键作用, 硬脂酸在纳米二氧化钛表面形成了均匀的单分子化学修饰层. 随着表面修饰温度的升高, 纳米二氧化钛的晶粒逐渐长大, 硬脂酸在纳米二氧化钛表面的化学包覆量逐渐下降, 硬脂酸分子间排列更加紧密, 硬脂酸包覆层由1nm变为2～3nm. 表面修饰温度对硬脂酸与纳米二氧化钛表面的结合方式影响不大.     

纳米燃油助燃剂的节能性能评定

用脂肪酸对3种纳米微粒进行了有效的修饰，并对修饰后的纳米微粒进行了结构表征及油溶性实验，结果表明纳米微粒经表面修饰后油溶性得到显著提高。采用氧弹测热值对比法对所研制的纳米添加剂进行了实验室评价，结果表明几种修饰纳米微粒均能在不同程度上改善燃油燃烧性能。     

纳米微粒表面修饰的研究进展

本文综述了近年来纳米微粒表面修饰的研究进展情况 ,并对纳米微粒表面改性的各种方法及其特点、修饰机理进行了归纳和分析。     

硬脂酸对CeO2纳米粒子的表面修饰研究

利用表面修饰法合成了硬脂酸修饰的 CeO2 纳米粒子,采用透射电子显微镜(TEM)观察了经表面修饰的CeO2 纳米粒子的形貌及分散性,并采用红外光谱(IR)、紫外可见分光光度计等对修饰的CeO2 纳米粒子进行了表征。结果表明:表面修饰剂硬脂酸与 CeO2 纳米粒子表面之间发生了化学键合作用;修饰后的CeO2 纳米粒子表面存在疏水有机基团,阻隔了 CeO2 纳米粒子的团聚,起到了分散作用;同时,修饰后的CeO2 纳米粒子在苯乙烯中的稳定性得到了提高。并且获得了硬脂酸的修饰量与CeO2 纳米粒子的最佳配比。     

纳米材料表面修饰的研究进展

通过材料的表面修饰与包覆以改善材料的表面性质乃至改变材料的相结构和性质,已经成为纳米材料制备和应用的关键技术.综述了近年来纳米微粒表面修饰的研究进展,并对纳米微粒表面改性的各种方法原理及其特点进行了归纳和分析.     

纳米氧化锌的表面修饰及其机理的研究

采用改进的直接沉淀法制备了Φ10nm氧化锌. 分别用油酸(OA), 山梨醇酐单硬脂酸酯(Span-60), 月桂酸钠(SL)三种表面活性剂修饰纳米氧化锌颗粒. 宏观沉降实验分析了修饰后的纳米氧化锌在液体石蜡中的稳定性, 发现油酸修饰的纳米氧化锌能在液体石蜡有机相中长时间分散而不沉淀, 具有优异的修饰效果, 而山梨醇酐单硬脂酸酯和月桂酸钠则无法长期稳定存在于有机相中; 微观红外光谱分析表明, 油酸与纳米氧化锌以共价键和氢键两种形式结合, 在无机纳米颗粒表面形成单分子膜; 而山梨醇酐单硬脂酸酯和月桂酸钠的修饰则不牢固.     

超音速微粒轰击金属表面纳米化新技术

对金属材料表面纳米化作了扼要阐述，着重介绍一种适合于大面积与复杂形状金属构件自身表面纳米化的新技术－超音速微粒轰击技术，并介绍了金属在超音速微粒轰击下晶粒纳米化的原理和装置结构以及应用前景。     

无团聚纳米氧化锆的制备及应用

采用高分子表面修饰－共沸蒸馏工艺成功地制备了纳米氧化锆微粒;合成过程中高 分子的空间位阻作用阻碍了前驱体颗粒的长大,通过与正丁醇的共沸蒸馏有效地脱除了前驱体 内的水分,在颗粒表面形成了正丁醇分子的包裹结构,在随后的干燥过程中避免了颗粒间形成 强化学键,获得了平均粒径在２０ｎｍ的无团聚的纳米微粒．纳米氧化锆微粒加入到润滑脂中能 明显改善后者的耐磨性能．     

表面态对纳米晶BaTiO3介电性能的影响

采用硬脂酸凝胶法制备了粒度均匀的纳米晶BaTiO3，用X射线衍射分析、红外光谱分析、透射电子显微镜对产物进行了表征，研究了表面态与介电性能。结果表明，BaTiO3纳米材料表面的不完整性主要是氧空位造成的，暴露在粒子表面的是一些金属离子，随着晶粒尺寸的减小，氧空位缺陷的浓度增加，极化增强，纳米材料的这种表面状态对其介电性能有重要影响，使其静态介电常数远比常规材料的大。     

镧系硬脂酸盐及聚乙烯蜡对HDPE流变性能的影响

利用恒速型、恒压型毛细管流变仪分别考察了镧系硬脂酸盐以及硬脂酸镧与聚乙烯蜡(PE-X)混合物对高密度聚乙烯(HDPE5000S)流变性能的影响。试验结果表明,HDPE加入一定份数的镧系硬脂酸盐以及硬脂酸镧和聚乙烯蜡共混后,熔体的表观黏度降低,产生压力振荡时的滑移长度减少以及信号强度明显减弱。其中以硬脂酸镧及聚乙烯蜡复合体系可以较好地改善聚乙烯的加工流变性。     

Size-tunable near-infrared PbS nanoparticles synthesized from lead carboxylate and sulfur with oleylamine as stabilizer

High quality PbS nanocrystals are synthesized reproducibly through lead stearate and sulfur stabilized by oleylamine in a non-coordinating solvent. The morphology, crystalline form and phase composition of PbS nanocrystals are examined by transmission electron microscopy (TEM), high-resolution TEM, x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS). The as-synthesized PbS nanocrystals have strong absorption and photoluminescence emissions in the near-infrared region. The size of PbS nanocrystals from 5 to 13?nm can be adjusted through the optimization of the synthesis conditions. The smaller PbS nanoparticles are obtained at the lower reaction temperature, lower precursor concentration, larger oleylamine quantity and larger lead precursor/sulfur ratio. The basic oleylamine enhances the reactivity of both lead stearate precursor and sulfur precursor in the reaction.     

Effect of Degassing Temperature on the Specific Surface Area and Other Physical Properties of Magnesium Stearate

Abstract

The effect of degassing temperature on the magnitude of the BET specific surface area and other physical properties of magnesium stearate was investigated. Magnesium stearate samples from two manufacturers were degassed using helium at 23°, 30°, 40°, 50° and 60°C. The specific surface area of the degassed samples was measured using both single- and multi-point BET methods. The moisture content and thermal properties of the degassed magnesium stearate samples were also examined. The specific surface area values decreased with an increase in the degassing temperature. The Karl Fischer and thermogravimetric analysis results also showed a decrease in the moisture content with an increase in the degassing temperature. The differential scanning calorimetry thermograms of the degassed samples showed changes in the endotherm characteristics along with changes in the melting point and heat of fusion values. It is hypothesized that the lower specific surface area values obtained after degassing at higher temperatures may be due to a partial conversion of the magnesium stearate dihydrate crystals into a monohydrate, an anhydrate or a mixture of the two forms. These results suggest that magnesium stearate samples should be degassed only at room temperature prior to the BET surface area analysis. The results of this study also show that it is important to consider the degassing conditions used when comparing specific surface area data from different sources.     

Mixing Action and Evaluation of Tablet Lubricants in Direct Compression

The effect of a series of modern lubricants during mixing on both lubricating action and binding properties of a direct compressible tablet formulation has bean investigated and compared with the effect of magnesium stearate. Lubricants which gave the best lubricating action (magnesium stearate, hydrogenated vegetable oils and glycerides) caused the largest reduction in tablet strength with an increase in. mixing time. When used in concentrations of It. the hydrogenated vegetable oils and glycerides tested gave about the same reduction of the ejection force as 0.5% magnesiun stearate, but their effect on tablet hardness during mixing was much smaller. This result was conflrmed for three direct compressible tablet formulations, composed with different excipients, where magnesium stearate could be replaced advantageously by Boeson VP or sterotex.     

The Tensile Strength of Tablets of Binary Mixtures Lubricated with Magnesium Stearate

Abstract

The influence of magnesium stearate on the tensile strength of tablets prepared from binary mixtures of materials lubricated with magnesium stearate have been studied. Mixtures of which both components (lactose and Emcompress) compact by fragmentation are largely unaffected. For a mixture of materials with dissimilar compaction mechanisms, (lactose and sodium chloride) magnesium stearate has a significant effect in that the originally high tensile strength of the sodium chloride is reduced to the level of lactose and the strengths of the mixtures and independent of the proportion of the components.     

Adhesion of Tablets in a Rotary Tablet Press II. Effects of Blending Time, Running Time, and Lubricant Concentration

Of the three essential functions of tablet lubricants, only the true lubricant and glidant properties have been studied in detail by objective means. Only recently has instrumentation which permits the objective measurement of the antiadhesion activity in a rotary tablet press been developed. Using a rotary press instrumented to measure the adhesion of tablets to the lower punch face, this study focuses on the adhesion of tablets in two direct compression systems. At any given compression force, adhesion of microcrystalline cellulose tablets lubricated with magnesium stearate appeared to decrease with increases in blending time or intensity of blending. Over a three-hour running time, adhesion force was found to increase to peak values and then to decline with both microcrystalline cellulose and hydrous lactose lubricated with magnesium stearate. However, ejection forces decreased gradually to apparently limiting values in each case. The adhesion of tablets to the lower punch face appeared to be affected partly by the condition of the tablet - die wall interface. Studies comparing lubricated and unlubricated microcrystalline cellulose suggest two opposing effects on tablet adhesion: (1) enhancing adhesion due to an increased reaction at the lower punch resulting from reduced die wall friction; and, (2) reducing the adhesion of tablets via the “antiadherent” effect. At the lubricant levels studied, stearic acid generally appeared to be less efficient than magnesium stearate in reducing both the adhesion and ejection forces in microcrystalline cellulose blends. However, with hydrous lactose blends, the true lubricant and antiadherent activities of stearic acid appeared to be greater than those of magnesium stearate at the 1.00% level of addition.     

Adhesion of Tablets in a Rotary Tablet Press II. Effects of Blending Time,Running Time,and Lubricant Concentration

Abstract

Of the three essential functions of tablet lubricants, only the true lubricant and glidant properties have been studied in detail by objective means. Only recently has instrumentation which permits the objective measurement of the antiadhesion activity in a rotary tablet press been developed. Using a rotary press instrumented to measure the adhesion of tablets to the lower punch face, this study focuses on the adhesion of tablets in two direct compression systems. At any given compression force, adhesion of microcrystalline cellulose tablets lubricated with magnesium stearate appeared to decrease with increases in blending time or intensity of blending. Over a three-hour running time, adhesion force was found to increase to peak values and then to decline with both microcrystalline cellulose and hydrous lactose lubricated with magnesium stearate. However, ejection forces decreased gradually to apparently limiting values in each case. The adhesion of tablets to the lower punch face appeared to be affected partly by the condition of the tablet - die wall interface. Studies comparing lubricated and unlubricated microcrystalline cellulose suggest two opposing effects on tablet adhesion: (1) enhancing adhesion due to an increased reaction at the lower punch resulting from reduced die wall friction; and, (2) reducing the adhesion of tablets via the “antiadherent” effect. At the lubricant levels studied, stearic acid generally appeared to be less efficient than magnesium stearate in reducing both the adhesion and ejection forces in microcrystalline cellulose blends. However, with hydrous lactose blends, the true lubricant and antiadherent activities of stearic acid appeared to be greater than those of magnesium stearate at the 1.00% level of addition.     

An investigation into the impact of magnesium stearate on powder feeding during roller compaction

A systematic evaluation on the effect of magnesium stearate on the transmission of a placebo formulation from the hopper to the rolls during screw fed roller compaction has been carried out. It is demonstrated that, for a system with two 'knurled' rollers, addition of 0.5% w/w magnesium stearate can lead to a significant increase in ribbon mass throughput, with a consequential increase in roll gap, compared to an unlubricated formulation (manufactured at equivalent process conditions). However, this effect is reduced if one of the rollers is smooth. Roller compaction of a lubricated formulation using two smooth rollers was found to be ineffective due to a reduction in friction at the powder/roll interface, i.e. powder was not drawn through the rollers leading to a blockage in the feeding system. An increase in ribbon mass throughput could also be achieved if the equipment surfaces were pre-lubricated. However this increase was found to be temporary suggesting that the residual magnesium stearate layer was removed from the equipment surfaces. Powder sticking to the equipment surfaces, which is common during pharmaceutical manufacturing, was prevented if magnesium stearate was present either in the blend, or at the roll surface. It is further demonstrated that the influence of the hopper stirrer, which is primarily used to prevent bridge formation in the hopper and help draw powder more evenly into the auger chamber, can lead to further mixing of the formulation, and could therefore affect a change in the lubricity of the carefully blended input material.     

微胶囊相变材料的储能特性分析

以硬脂酸丁酯为囊芯,密胺树脂(MF)和聚酯树脂(PET)为囊壁,合成了两种具有相变储热功能的胶囊.采用扫描电子显微镜(SEM)观察胶囊的形貌,差示扫描量热仪(DSC)研究胶囊的储热性能,发现MF/硬脂酸丁酯微胶囊表面粗糙,储能效果明显,稳定性好.利用MF/硬脂酸丁酯微胶囊制备了具有相变储能功能的建筑材料,微胶囊在水泥和...     

Batch Variation of Magnesium Stearate and its Effect on the Dissolution Rate of Salicylic Acid from Solid Dosage Forms

The effects of different batches of magnesium stearate on the release of salicylic acid from capsules and from a compacted formulation have been investigated. The results indicate that retardation of salicylic acid release becomes independent of the particle size of magnesium stearate when the blending of the two substances prior to encapsulation or compaction is prolonged for a sufficient time.

Variation in the release rates observed after prolonged blending times have been shown to exhibit a rank order correlation with the different hydrophobicities of the batches of magnesium stearate as indicated by the results of contact angle measurements on drops of dissolution medium on compacts of this lubricant.

Determination of the surface tension of an aqueous extract of each batch of lubricant has indicated that water-soluble, surface-active impurities may be responsible for this apparent variation in the degree of hydrophobicity and hence for the change in the release rate of salicylic acid from solid dosage forms when they are manufactured with different batches of magnesium stearate.