金刚石膜超高速抛光温度场的有限元模拟

金刚石膜超高速抛光是一种新的抛光方法,抛光区域温度场分布直接影响金刚石膜的抛光质量.本文采用三维热-力耦合有限元法分析了抛光盘超高速旋转时,不同直径的金刚石厚膜与抛光盘之间由于摩擦生热形成的温度场.结果表明:随着金刚石膜直径的增大,其内、外边缘温度差明显增大.只有当金刚石膜与抛光盘作同向相对运动时,金刚石膜的内、外边缘温度才趋于均匀.文中得出的结论可以为金刚石膜超高速抛光机的设计和实际操作提供可靠的理论依据.     

Structure and chemical composition of LiB3O5 surfaces

The electronic and structural properties of LiB₃O₅ (LBO) surfaces have been studied by X‐ray photoemission spectroscopy (XPS) and reflectance high‐energy electron diffraction (RHEED). The as‐grown (110) crystal face and mechanically polished (001) surfaces have been investigated comparatively. Electronic structure of LBO has been determined on as‐grown (110) crystal face previously cleaned by chemical etching with RHEED control. The correlation of valence band structure and measured binding energies with earlier reported results has been discussed. Core‐level spectroscopy reveals strong enriching of mechanically polished LBO surface with carbon, when nanodiamond powder is used as an abrasive. So high carbon level as C:B = 0.7 has been observed at the surface while the ratio Li:B:O remains according to LBO chemical composition. The association of LBO Kikuchi‐lines with strong background has been shown by RHEED analysis of the surface. Thus, the polished LBO surface constitutes a high structure quality LBO with the inclusions of some amorphous carbon compound. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of the topography of silver films on the structure of surface ensembles of 11-mercaptoundecanol

The effect of the topography of the silver surface on the formation of self-assembling monolayers of 11-mercaptoundecanol was examined. The metal surface was modified by nitric acid in the presence of hydrogen peroxide (deep etching (DE)) or aqueous malononitrile (chemical polishing (PE)). The adsorption properties of the monolayers differ significantly for the DE and PE surfaces and are a function of the ratio of functional hydroxyl groups available for reaction with analyte and hydrophobic segments of the hydrocarbon chain of the molecule. A correlation between the amount of adsorption and the analyte acidity was demonstrated. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 2, pp. 98-103, March-April, 2009.     

Wine Faults: State of Knowledge in Reductive Aromas,Oxidation and Atypical Aging,Prevention, and Correction Methods

The review summarizes the latest scientific findings and recommendations for the prevention of three very common wine faults of non-microbial origin. The first group, presented by the reductive aromas, is caused mainly by excessive H₂S and other volatile sulfur compounds with a negative impact on wine quality. The most efficient prevention of undesirable reductive aromas in wine lies in creating optimal conditions for yeast and controlling the chemistry of sulfur compounds, and the pros and cons of correction methods are discussed. The second is browning which is associated especially with the enzymatic and non-enzymatic reaction of polyphenols and the prevention of this fault is connected with decreasing the polyphenol content in must, lowering oxygen access during handling, the use of antioxidants, and correction stands for the use of fining agents. The third fault, atypical aging, mostly occurs in the agrotechnics of the entire green land cover in the vineyard and the associated stress from lack of nutrients and moisture. Typical fox tones, naphthalene, or wet towel off-odors, especially in white wines are possible to prevent by proper moisture and grassland cover and alternating greenery combined with harmonious nutrition, while the correction is possible only partially with an application of fresh yeast. With the current knowledge, the mistakes in wines of non-microbial origin can be reliably prevented. Prevention is essential because corrective solutions for the faults are difficult and never perfect.     

铌酸锂单晶薄膜材料

铌酸锂晶体集电光、声光和非线性光学等物理特性于一身,且透光范围宽,作为一种重要的光学材料被广泛应用于通信、传感等领域.通过离子注入与直接键合的方式制备出的铌酸锂单晶薄膜材料,保留了铌酸锂体材料的优秀物理特性,并且具有高折射率对比度的优点,使光子器件在集成度和性能上都得到了很大程度的提升.本文介绍了铌酸锂薄膜的制备及应用...     

液体喷射抛光材料去除机理的研究

从实验出发,研究了液体喷射抛光中抛光区的特征及材料的去除机理。得到了垂直喷射时在材料的去除区域呈W型的环状分布现象,并运用射流与冲击理论对这一现象做了详细地分析。实验结果表明,磨料粒子碰撞时的剪切作用对材料的去除来说占主导地位,而直接冲击作用占次要地位。     

具有公自转运动模式的高效轮式抛光工具设计

为了提高光学加工效率,缩短大口径光学元件制造周期,本文提出了一种具有公自转运动模式的新型高效抛光方式,对其结构、工作原理以及去除特性进行了研究。首先,介绍了公自转抛光装置机械结构及工作原理。接着,根据Hertz接触理论和Preston方程进行了去除函数建模,讨论了不同转速比情况下的去除函数形状。然后,根据理论模型进行了去除函数实验、工艺参数实验以及稳定性实验,研究了压入深度、转速等工艺参数对去除结果的影响。最后,进行了200 mm口径SiC工件的仿真加工。实验结果表明:在2 mm压入深度、200 rpm转速情况下,去除区域直径为19.23 mm,体去除率达到0.197 mm~3/min,去除效率高于同等去除区域大小的传统小磨头加工方式;仿真加工结果表明:SiC仿真镜经过3.7 h加工,面形从3.008λPV,0.553λRMS提高到0.065λPV,0.005λRMS,收敛效率为达到98.18%。     

高强度凝胶树脂的合成及其在电厂凝结水精处理系统中的应用

介绍了采用一次聚合工艺合成适用于电厂凝结水精处理混床的凝胶型强酸、强碱离子交换树脂的过程,对树脂的抗渗透冲击强度、氧化稳定性等进行了对比测试,并就该树脂与普通树脂相比较的差异进行阐述。     

Challenges and strategies of surface modification of electrogalvanized coatings for electron microscopy analysis

Despite wide usage of electrogalvanized coatings in various applications, characterization studies on their micro/crystal structure, and the understanding of how they correspondingly affect the properties, such as corrosion, are rather limited. This is mainly attributed to some difficulties in preparing and examining the zinc coating layers, owing to their intrinsically low corrosion resistance and refined nano-scaled crystallite size. This study aims to examine such challenges systematically and propose some mitigation strategies. Particularly, sample preparation processes, including surface finishing for metallography and sample thinning processes are explored. Furthermore, a range of electron microscopy techniques, including scanning electron microscopy (SEM), electron back scattered diffractometry (EBSD), and transmission electron microscopy (TEM) are investigated in relation to the achievable clarity of microstructural details of electrogalvanized coatings.     

Flow field-flow fractionation-inductively coupled plasma mass spectrometry of chemical mechanical polishing slurries

Alumina- and silica-based chemical mechanical polishing slurries were analyzed to demonstrate the feasibility of field-flow fractionation-inductively coupled plasma mass spectrometry (FFF-ICP-MS). After FFF separation ²⁷Al and ²⁹Si were measured by ICP-MS to obtain size distributions, mean particle size, number average-, mass average-, Z average- diameters, minimum and maximum particle sizes, dominant particle size, and particle size ranges (breadth of size distribution, and polydispersity) characteristics. Five commercial alumina and 13 silica slurry samples were characterized. Broad distributions were detected and two polydispersity calculations were compared. Most silica samples and one alumina sample show monomodal normal distributions. Asymmetric distributions were observed for a few silica and most alumina slurries. The degree of deviation from normal distribution was assessed. Mean particle sizes of alumina slurries varied between 150 and 350 nm with the maximum detected particle of less than 680 nm. Silica slurries exhibited maximum particle sizes of less than approximately 400 nm with the mean particle sizes ranging from 110 to 220 nm. Trace metals (Fe, Ti and Zr) coeluted with Al, Si; whereas, Pb appeared to be present as colloidal fractions.