Magnetorheological nanofinishing of BK7 glass for lens manufacturing

BK7 is a high-quality crown glass which is used where additional benefits such as temperature sensitive applications of fused silica glass are not required. Due to very low inclusion content with extremely low bubbles, BK7 glass can find its application in lens manufacturing. The present work focuses on nanofinishing of the BK7 glass specimen for ratifying its utility in practical application. A programmable logic controlled 3-axis motions are fed to the magnetorheological (MR) rotating tool for finishing the glass specimen. MR polishing fluid used for nanofinishing consists of deionized water, magnetic iron particles, and cerium oxide powder. Under the influence of magnetic field, the stiffened MR polishing fluid is assisted in reducing the surface roughness of glass up to nanolevel range. Optical properties such as transmittance, absorbance, and reflectance of finished BK7 glass are analyzed and found suitable for lens manufacturing. Results of higher surface quality with excellent finishing are obtained by the present MR finishing process. After 90?min of finishing, the surface roughness values R_a and R_q are reduced to 17 and 27?nm from the initial values of 41 and 57?nm, respectively. To study the surface morphology, scanning electron microscopy is performed on BK7 glass.     

Thermophysical Parameters of Optical Glass BK 7 Measured by the Pulse Transient Method

This paper is focused on the pulse transient method. The theory of the method and the measuring regime (time window) are analyzed. The results of the analysis are verified on borosilicate crown glass BK7, which is a candidate for a standard for thermal conductivity. Thermal contact and surface effects affect the length of the time window in which the evaluation procedure is applied. The one-point evaluation technique is compared with the results of the fitting procedure that uses the time window found by difference analysis. The values of the thermal conductivity, thermal diffusivity, and specific heat were found to be 1.05 W· m^–1 · K^–1, 0.548 × 10^–6m ^{– 2} · s^–1, and 767 J· kg^–1 · K^–1, respectively, using the one-point evaluation technique.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1–4, 2002, London, United Kingdom.     

石英和BK7玻璃的离子束刻蚀特性研究

石英和BK7玻璃是常用的光学材料和微系统材料.用Ar作为工作气体对石英和BK7玻璃及其掩模材料AZ1350的离子束刻蚀特性进行了研究,分析了离子能量、离子束流密度和离子束入射角等几种因素对刻蚀速率和选择比的影响,结合相关理论得到了相应的刻蚀速率拟合方程.AFM测量结果表明刻蚀工艺对材料的低损伤.由于与光刻胶的刻蚀选择比较低,随着石英和BK7玻璃刻蚀深度的增加,图形转移精度下降.因此提高刻蚀选择比是获得高分辨率图形的前提.     

飞秒激光照射银离子掺杂的 BK7光学玻璃的显微结构变化

使用聚焦的800nm,120fs,1kHz的超短脉冲激光在掺Ag^＋的BK7玻璃内部空间选择性地写入了光栅结构,然后将样品在不同温度下进行热处理.吸收光谱表明,BK7玻璃在飞秒激光照射后产生了氧空位色心,在575℃热处理后析出了银纳米颗粒.光栅的衍射效率随热处理温度的升高而减小,在575℃后又开始升高.用光学显微镜观察了光栅的结构变化并对现象产生的机制进行了分析.     

碲锌镉晶片机械研磨和机械抛光工艺研究

研究了碲锌镉(CZT)晶片表面的机械研磨和机械抛光工艺.采用不同粒度的Al2O3磨料对CZT晶体表面进行机械研磨和机械抛光,并研究了工艺参数变化对CZT晶体表面质量、粗糙度、研磨速度和抛光速度的影响.结果表明,机械研磨采用粒度2.5μm的Al2O3磨料,最佳的研磨压力和研磨盘转速分别为120g/cm.和75r/min,...     

In-process monitoring of shape accuracy of flat surfaces of optical and microelectronic components in polishing

The in-process monitoring of surface shape of optical surfaces directly in the course of polishing is demonstrated to be accomplished through the confocal chromatic imaging technology. A linear relationship has been found between the deviation from square waveform and the variation of the workpiece surface shape.     

New Measurements of the Thermal Conductivity of PMMA,BK7, and Pyrex 7740 up to 450K

New measurements of the thermal conductivity of polymethyl methacrylate (PMMA), BK7, and Pyrex 7740 are presented. The technique employed is a refined transient hot-wire technique, based on a full theoretical model with equations solved by finite elements for the exact geometry. At the 95 % confidence level, the standard deviations of the thermal conductivity measurements of PMMA, BK7, and Pyrex 7740 are 0.47 %, 1.0 %, and 0.8 %, respectively. The technique is absolute and is characterized by an uncertainty of <1 %.     

Thermal Conductivity of Polymethyl Methacrylate (PMMA) and Borosilicate Crown Glass BK7

The thermal conductivity of polymethyl methacrylate (PMMA) and borosilicate crown glass BK7 has been studied. The transient hot-wire technique has been employed, and measurements cover a temperature range from room temperature up to 350 K for PMMA and up to 500 K for BK7. The technique is applied here in a novel way that minimizes all remaining thermal-contact resistances. This allows the apparatus to operate in an absolute way and with very low uncertainty. The method makes use of a soft silicone paste material between the hot wires and the solid under test. Measurements of the transient temperature rise of the wires in response to an electrical heating step over a period of 20 μs up to 5 s allow an absolute determination of the thermal conductivity of the solid, as well as of the silicone paste. The method is based on a full theoretical model with equations solved by a two-dimensional finite-element method applied to the exact geometry. At the 95% confidence level, the standard deviations of the thermal conductivity measurements are 0.09% for PMMA and 0.16% for BK7, whereas the standard uncertainty of the technique is less than 1.5%.     

Controllable hybrid side-polishing method (CHPM) for optical fibers by combination of polishing and etching

We introduce the controllable hybrid polishing method (CHPM), which is a combination of enhanced side-polishing and etching methods, leading to a more controllable and precise clad polishing process for optical fibers. The two key advantages of CHPM are enabling of real-time monitoring of the etching process with a resolution of ~100 nm and fabrication of a 34% smoother polished surface than that of traditional polishing methods. Bearing in mind that these two factors are very important for the fabrication of any polished fiber devices, such as plasmonic sensors, the CHPM should prove highly useful in related industrial and scientific applications.     

Preparation of porous alumina abrasives and their chemical mechanical polishing behavior

Porous alumina abrasives with different pore sizes were prepared using hydrothermal synthesis method by different hydrothermal temperatures. The pore structure, pore size and pore volume of the products were characterized by transmission electron microscopy and nitrogen adsorption desorption isotherm measurement. The chemical mechanical polishing (CMP) performances of porous alumina abrasives in hard disk substrate CMP were investigated. The results show that, the polished surface average roughness (Ra) decreases when the pore diameter of porous alumina abrasive increases. By comparison with solid alumina abrasive, the prepared porous alumina abrasives give lower Ra, and the porous alumina abrasive with 8.61 nm pore diameter has higher material removal rate under the same polishing conditions.     

CF4/CHF3反应刻蚀石英和BK7玻璃

用CF4/CHF3作为工作气体对石英和BK7玻璃进行了研究,分析了气体组分、气体流量和射频偏压等几种因素对刻蚀速率的影响,结果表明刻蚀速率与射频偏压的均方根成正比.在1 CF4∶1CHF3的等离子体中由于与光刻胶良好的刻蚀选择比,在石英基片上获得了侧壁陡直的槽形.用光学表面轮廓仪观测的结果表明偏压的增加和过高的气体流量易使基片表面质量下降.     

Optimization of Polishing Parameters with Taguchi Method for LBO Crystal in CMP

Chemical mechanical polishing(CMP)was used to polish Lithium triborate(LiB3O5 or LBO)crystal.Taguchi method was applied for optimization of the polishing parameters.Material removal rate(MRR)and surface roughness are considered as criteria for the optimization.The polishing pressure,the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal.Experiment results indicate that for MRR the polishing pressure is the most significant p...     

Silica particles settling characteristics and removal performances of oxide chemical mechanical polishing wastewater treated by electrocoagulation technology

The purpose of this study was to explore the feasibility of removing silica particles and reducing turbidity from oxide chemical mechanical polishing (oxide-CMP) wastewater. Based on the dynamic characteristics of batch electrocoagulation, three operating stages (lag, reactive, and stabilizing) are proposed to identify the relationships among the zeta potential of the silica particles, solution turbidity, and the corresponding mean particle size of the silica. Experimental results show that the silica particles were destabilized and settled at the critical mean particle size, which was estimated to be above 520 nm after 10 min, and the corresponding turbidity removal mostly occurred during the reactive stage. Furthermore, the corresponding mean particle size varied from 520 to 1900 nm as the treatment time progressed from 10 to 20 min, which also occurred during the reactive stage. Several parameters, including different electrode pairs, electrolyte concentration, applied voltage, and the optimum condition of power input were investigated. Experimental results indicate that a Fe/Al electrode pair is the most efficient choice of the four electrode pair combinations in terms of energy consumption. The optimum electrolyte concentration and applied voltage were found to be 200 ppm NaCl and 30 V, respectively.     

超细氧化铝抛光液的制备及其抛光特性研究

化学机械抛光（CMP）技术广泛用于表面的超精加工,抛光液是CMP技术中的关键要素。本文制备了一种超细Al2O3抛光液,采用激光粒度杖、扫描电镜等对其进行了表征,进而研究了其在镍磷敷镀的硬盘基片CMP中的抛光特性,结果表明抛光液中Al2O3粒子用量、氧化剂用量均直接影响抛光后的表面质量及材料去除速率。借助时抛光后表面的原子力显微镜（AFM）、俄歇能谱以及X射线光电子能谱分析,对其CMP机理进行了推断。     

Removal of acid orange 7 by guava seed carbon: A four parameter optimization study

The preparation of carbon from waste materials is a recent and economic alternative for the removal of dyes. In this study four samples of carbon were obtained by thermal treatment at 1000 °C using as precursor the guava seed with different particle sizes. The Taguchi method was applied as an experimental design to establish the optimum conditions for the removal of acid orange 7 in batch experiments. The chosen experimental factors and their ranges were: pH (2–12), temperature (15–35 °C), specific surface area (50–600 m² g⁻¹) and adsorbent dosage (16–50 mg ml⁻¹). The orthogonal array L₉ and the larger the better response category were selected to determine the optimum removal conditions: pH 2, temperature 15 °C, S_esp 600 m² g⁻¹ and dosage 30 mg ml⁻¹. Under these conditions a total removal of acid orange 7 was achieved. Moreover, the most significant factors were the carbon specific surface area and the pH. The influence of the different factors on the adsorption of acid orange 7 from solution is explained in terms of electrostatic interactions by considering the dye species and the character of the surface.     

电解质等离子抛光液中硫酸铵含量的检测方法

电解质等离子抛光过程中受抛光产生的金属微粒的干扰,无法使用电导法对抛光液中硫酸铵的含量进行检测,为了解决这一问题,基于实验提出了两种确定硫酸铵含量(质量分数)的方法.一种方法是利用抛光液中硫酸铵的含量低于2.5%以后抛光的电流密度会明显下降的现象,定时检测抛光过程中电流值和抛光液温度,以确定是否需要补充硫酸铵.另一种方法是通过实验得到一定抛光液温度下抛光量与硫酸铵消耗量的关系,再在抛光过程中记录抛光量计算抛光液中硫酸铵含量的方法.研究发现,前一种方法应用更为简便,适用于一般工业生产;后一种方法适用于对抛光效果要求更高的加工.经实验验证两种方法均具有可行性.     

静电自组装制备复合磨粒及其 对铜的抛光特性研究

研究苯代三聚氰胺甲醛（BGF）微球与阳离子型聚电解质聚二烯丙基二甲基氯化铵（PDADMAC）、阴离子型聚电解质聚4－苯乙烯璜酸钠（PSS）之间的吸附特性,利用静电自组装技术改变和控制BGF微球的荷电特性,制备出不同形式的PEi BGF/SiO2复合磨粒,以Zeta电位、透射电子显微镜（TEM）和热重分析（TG）等手段对复合磨粒进行了表征,并利用这些复合磨粒制备了铜片抛光用的复合磨粒抛光液。抛光试验表明,吸附在聚合物微球表面和游离于抛光液中的SiO2磨粒在抛光中均起到材料去除作用。传统单一SiO2磨粒抛光液的铜材料去除率为264 nm/min,PE0 BGF/SiO2混合磨粒抛光液的铜材料去除率为348 nm/min,PE3 BGF/SiO2复合磨粒抛光液的铜材料去除率为476 nm/min。经上述3种抛光液抛光后的铜表面,在5 μm×5 μm范围内,表面粗糙度Ra从0.166 μm分别降至3.7 nm、2.6 nm和1.5 nm,峰谷值Rpv分别小于20 nm、14 nm和10 nm,复合磨粒抛光液对铜片有良好的抛光性能。     

电力通信光传输网络优化的分析与应用

当前电力通信光传输网络技术的优化对于整个电力系统的建设和发展来讲均有着重大的意义,故应加强对问题的重视,加强对技术的分析。文章针对这一方面的内容展开论述,详细的分析了电力通讯光传输网络技术的发展和现状,同时对相关技术的优化措施和技术的整改路线进行了细致的研究,旨在不断促进相关技术的发展,保证光传输网络技术可以得到不断的创新改良。     

液晶光学相控阵的改进型口径拓展方法及远场特性分析

天线通光口径是液晶光学相控阵的重要技术指标,本文在多子阵并行驱动和两级器件级联方法(PAPA)的基础上,提出改进型的i-PAPA方法,通过对COM电极进行分区域驱动,在单个相控阵天线上实现大口径相控光束控制,具备单器件工作、插损低等优点。通过数值仿真分析,结果表明：相控阵天线后的近场相位分布连续;当指向角度在0°到+6°范围内,远场衍射效率和指向角度的数值关系呈现平滑单调下降,衍射效率均大于48%;当指向角度在0°到+3°范围内,衍射效率均大于80%。     

A study on the effect of polishing fluid volume in ball end magnetorheological finishing process

Ball end magnetorheological finishing is a unique process that utilizes a magnetically controlled ball of polishing fluid at the tip of the rotating tool to finish workpiece of different materials and shapes. The aim of this research is to study the effect of polishing fluid volume on finishing spot size and the surface finish associated with it. A magnetostatic simulation is done to find the variation of flux density in the working gap and on the workpiece surface. The maximum limit of the polishing fluid volume is selected on the basis of area of threshold magnetic flux density (minimum value required for finishing) region on the workpiece surface. The surface characteristics and the diameter of the finished spot are analyzed by varying the fluid volume. The surface obtained with high fluid volume is poorly finished and has scratch marks as the excess fluid flows out from the working gap and forms a thick ring at the periphery of the tool tip. Contrary to this, if the fluid volume is too less, then it merely rotates over the workpiece surface without causing any finishing action. An optimum range of fluid volume produces a good quality surface finish with constant finished spot size.