酸碱度对磁流变抛光去除作用的调节机制

随着磁流变抛光技术在超精密加工领域的应用需求不断增长,提高该技术的抛光效率成为一种必然趋势。本文从研究磁流变抛光液料浆的性质出发,建立了以pH值调节为手段改善抛光液性能的实验方法。采用透射电镜、粒度分析,黏度测试和Zeta电位测试等实验分析表征了抛光颗粒的分散行为及料浆的流变特性,并对抛光料浆特性进行了研究和优化。结果表明:当pH值为12时,抛光料浆具有绝对值最大的Zeta电位(33.28 mV)和最小的颗粒粒径(260nm),获得了抛光颗粒分散均匀、悬浮性能稳定的料浆。使用该料浆抛光液与初始抛光液在相同工艺条件下对熔石英进行抛光。实验结果表明,在未明显恶化表面粗糙度的前提下,该抛光液的峰去除效率和体去除效率分别提升87%和66%,获得了良好、高效的去除效果。     

络合剂对蓝宝石晶片化学机械抛光的影响

利用自制的抛光液对蓝宝石晶片进行化学机械抛光,研究化学机械抛光过程中抛光压力、抛光液pH值、SiO2浓度、络合剂种类及其浓度等参数对抛光速率的影响,采用MicroNano D-5A扫描探针显微镜观察抛光前后蓝宝石晶片的表面形貌。结果表明:在抛光条件为压力7psi、转速为50 r/min、抛光液流量为60 mL/min,抛光液组成为pH值12、SiO2浓度5%、络合剂Ⅰ及其浓度为1.25%时,得到最大抛光速率为35.30 nm/min,蓝宝石晶片表面质量较好,表面粗糙度Ra达到0.1 nm。     

硅衬底的化学机械抛光工艺研究

在分析硅衬底CMP的动力学过程基础上,提出了在机械抛光去除产物过程中,适当增强化学作用可显著改善产物的质量传输过程,从而提高抛光效率.在对不同粒径分散度的氧化铈抛光液进行比较后提出了参与机械研磨的有效粒子数才是机械抛光过程的重要因素,而不是单纯受粒径大小的影响.分析和讨论了CMP工艺中的几个影响因素,如粒径大小与分散度、pH值、温度、流量和浓度等.抛光后清洗,抛光雾得到了有效控制.     

铜抛光液中缓蚀剂5-氨基四唑(ATA)的作用机制研究

采用静态腐蚀实验、接触角测试、XPS等手段,比较在不同pH值下抛光液中缓蚀剂(5-氨基四唑(ATA),苯并三唑(BTA))对铜表面化学机械抛光(CMP)的影响,并探讨ATA在铜表面的作用机制。结果表明,BTA和ATA是优良的铜缓蚀剂,当pH值为3～10时,两者可在铜表面成膜,保护铜表面不受腐蚀,从而降低铜片的静态腐蚀速率和去除率,其中当pH=4时,2种缓蚀剂表现出最佳的缓蚀性能。当pH值为3～5时,ATA的缓蚀性能优于BTA。ATA通过四唑环上的N原子和氨基上的N原子吸附在铜表面,形成保护膜,从而抑制了H2O2对铜表面的腐蚀,改善了表面质量,是一种优良的适用于酸性铜抛光液的缓蚀剂。     

不同氧化剂对6H-SiC化学机械抛光的影响

选用胶体SiO₂纳米颗粒为磨粒,研究不同pH值条件下高锰酸钾和双氧水两种氧化剂对6H-SiC晶片化学机械抛光的影响,并使用原子力显微镜观察抛光后表面质量。采用Zeta电位分析仪分析溶液中胶体SiO₂颗粒的Zeta电位,采用X射线光电子能谱分析SiC抛光表面元素及其化学状态。结果表明：SiC晶片的材料去除率随pH值变化而变化,采用高猛酸钾抛光液抛光时,材料去除率在pH 6时达到峰值185 nm/h,R_a为0.25 nm;采用双氧水抛光液抛光时,材料去除率在pH 8时达到峰值110 nm/h,R_a为0.32 nm。pH值低于5时,电负性的SiO₂颗粒会通过静电作用吸附在带正电的SiC表面,抑制SiC晶片表面原子的氧化及去除,降低材料去除率;pH值高于5时,SiO₂颗粒在双氧水抛光液中的静电排斥力弱于高锰酸钾抛光液中静电排斥力,从而影响了SiO₂颗粒的分散性能,降低了抛光效果。采用高锰酸钾抛光液抛光后,SiC晶片表面的Si-C氧化产物含量（Si-C-O、Si₄C_4-xO₂和Si₄C₄O₄）较高,高锰酸钾抛光液的氧化能力较强。     

HCl-（NH4）2S2O8体系抛光液中钌的化学机械抛光研究

金属钌(Ru)有可能作为集成电路中铜互连阻挡层材料,作为阻挡层必须具有低的表面粗糙度。化学机械抛光技术已经成为集成电路制造中实现局部平面化和全局平面化的关键技术,因此对钌的化学机械抛光研究具有重要意义。利用自制抛光液,研究了在HCl-(NH4)2S2O8体系抛光液中盐(KCl)的浓度、络合剂浓度、pH值和抑制剂(BTA)等对钌的去除速率的影响。实验发现,在HCl-(NH4)2S2O8体系抛光液中,金属钌在1wt.%SiO2、1wt.%过硫酸铵、1wt.%酒石酸、1mmol/L BTA和10mmol/L KCl,pH值为9.0的抛光液中,抛光速率为10.8nm/min。电化学实验发现,在1wt.%SiO2、1wt.%过硫酸铵、1wt.%酒石酸、1mmol/L BTA和1mmol/L KCl,pH值为4.0的抛光液中,金属钌表面化学反应受抑制;在1wt.%SiO2、1wt.%过硫酸铵、1wt.%酒石酸、1mmol/L BTA和1 mmol/L KCl,pH值为9.0的抛光液中,金属钌表面钝化膜较致密、较厚。     

光助芬顿反应对6H-SiC化学机械抛光的影响

为提高6H-SiC晶片化学机械抛光的材料去除率(MRR)并改善其表面质量,采用光助芬顿反应体系对6H-SiC晶片进行化学机械抛光,研究紫外光功率、抛光液pH值、H2O2质量分数和Fe2+浓度对6H-SiC晶片抛光效果的影响。使用原子力显微镜观察6H-SiC晶片表面质量,采用纳米粒度电位仪测量抛光液中SiO2磨粒的粒径分布及Zeta电位,利用可见分光光度法检测溶液中羟基自由基(·OH)的浓度并通过紫外-可见光谱分析紫外光的作用机制。结果表明:引入紫外光提高了6H-SiC的MRR,增大紫外光功率,MRR也随之增加;随pH值、H2O2质量分数和Fe2+浓度的升高,MRR先增大后减小;pH值影响磨粒间的静电排斥力及磨粒的分散稳定性,从而影响6H-SiC的MRR;与采用芬顿反应体系的抛光液相比,采用光助芬顿反应体系的抛光液中产生的·OH数量较多,说明紫外光能够增加反应体系中·OH的数量,从而促进6H-SiC晶片的表面氧化,提高6H-SiC晶片的MRR,并改善其表面质量。     

抛光液pH值对玻璃超光滑表面完整性影响

为研究抛光液的pH值在精密抛光加工过程中对表面完整性的影响,选取K9玻璃为试件材料,用浮法抛光加工成超光滑表面,使用相同浓度的氢氟酸和氢氧化钠溶液对2个试件进行腐蚀,用原子力显微镜、扫描电镜和纳米硬度计测量作用不同时间段的表面质量,通过对比分析各作用时间段2个试件的表面粗糙度、表面形貌和表层硬度的相似和差异,研究了pH值对超光滑表面完整性的影响,得出在玻璃工件抛光加工中,抛光液为微碱环境有利于提高加工效率和得到高质量的超光滑表面.     

单晶SiC化学机械抛光液化学反应参数研究

选择影响化学机械抛光化学反应速率的参数:催化剂浓度、氧化剂浓度、抛光液的pH值、抛光液温度等进行了试验,研究了它们对基于芬顿反应的单晶SiC化学机械抛光效果的影响规律。发现只有当H_2O_2浓度高于20%、Fe_3O_4浓度高于1.25%时,增大H_2O_2、Fe_3O_4浓度,材料去除率才会显著越高,此时材料去除速率由化学液腐蚀速度与磨料机械去除速度共同决定;低于此范围时由磨料的机械作用决定。温度升高会加速H_2O_2分解,抑制羟基自由基·OH的生成,减缓化学腐蚀,降低材料去除率。当Fe_3O_4浓度、H_2O_2浓度、pH值、抛光液温度分别为1.25%、15%、7、41℃时,化学腐蚀与机械去除的协调性及磨料的分散性较好,表面粗糙度最低;当它们分别为5%、25%、9.3、15℃时,材料去除率最高。     

永磁磁浮叶轮在心脏泵内的偏心距及振幅测量

研制成一种永磁磁浮心脏泵,无需转子位置测量和控制反馈装置,报道了其转子的偏心距及振幅的测量,从而探明转子究竟是否已经悬浮,和影响转子磁浮性能的各种因素及其影响情况。试验结果表明转子转速和输出流量越高,对转子悬浮越有利;转子与定子之间的气隙和输送介质的粘度对转子的悬浮性能也有影响,且气隙越小、粘度越大对转子的悬浮越有利。     

Properties of Dispersion of Multiwalled Carbon Nanotubes as Cutting Fluid

This article presents the results of experiments performed to evaluate properties of dispersion of multiwalled carbon nanotubes (MWCNT) in water with sodium dodecyl sulfate (SDS) as a dispersant. Different samples of varying concentrations of MWCNTs were prepared for the analysis and properties including thermal conductivity, pH value, viscosity, wettability, etc., were evaluated. These properties were compared with the properties of conventional cutting fluid, which was taken as a mix of water and mineral oil. It was found that the thermal conductivity of the MWCNT dispersion was higher than the conventional cutting fluid by about 42%. There was a decrease in contact angle by about 70%. Thus, dispersing MWCNTs in water with SDS increases the thermal conductivity and wettability of fluid. The pH value of fluid with 0.2 vol% MWCNTs was found to be 8.4. It thus reduced the corrosive nature of water. Nanoparticles of MWCNTs did not have much influence on the viscosity of the base fluid. Thus, the use of MWCNTs in water with SDS appeared to result in a better cutting fluid for machining than conventional cutting fluid.     

阴离子表面活性剂及复配对阻挡层抛光液性能的影响

为提高铜互连化学机械抛光(CMP)后表面质量，在抛光液中需引入适当的表面活性剂以改善磨料的稳定性以及CMP后铜的表面粗糙度。研究了十二烷基硫酸铵(ADSA)、脂肪醇聚氧乙烯醚硫酸铵(AESA)、直链烷基苯磺酸(LABSA)3种不同阴离子表面活性剂，以及非离子表面活性剂脂肪醇聚氧乙烯醚(AEO-9)和LABSA复配表面活性剂对钽阻挡层抛光液润湿性、分散性以及对材料去除速率的影响。通过接触角测量仪、纳米粒度仪、扫描电镜和原子力显微镜测试表面张力、接触角、大颗粒数、粒径分布以及CMP后铜的表面粗糙度，并分析复配表面活性剂的作用机制。结果表明：抛光液中加入LABSA后，因其具有直链型结构，抛光液的润湿性和分散性效果最好，抛光后铜表面的粗糙度最低；AEO-9和LABSA进行复配，相较于单一的LABSA,抛光液的润湿性、分散性、稳定性和抛光后铜表面粗糙度均有所改善，体积分数0.1%LABSA+0.1%AEO-9的复配表面活性剂性能最优，CMP后铜表面粗糙度降至0.7 nm。     

微磨料浆体射流的浆体配制及钻孔性能研究

微磨料浆体射流技术是在微磨料水射流加工技术基础上发展起来的一种新技术。通过添加分散剂和悬浮剂来提高浆体的沉降稳定性;为了配制出优质钻孔浆体,研究了磨料质量浓度、磨料种类、分散剂体积分数和悬浮剂体积分数对钻孔加工的影响,并研究了分散剂体积分数和悬浮剂体积分数对浆体沉降稳定性的影响。研究结果表明：磨料质量浓度存在最佳取值;分散剂并非一定能改善颗粒的沉降稳定性,这与磨料种类、磨料质量浓度和分散剂体积分数等有关;悬浮剂能够改善浆体的悬浮性,其体积分数影响浆体的沉降稳定性和钻孔效果。     

基于神经网络的火电厂脱硫控制系统研究

以某火电厂 ２×３００MW 机组为研究对象,设计了以石灰石 石膏湿法为工艺基础的烟气脱硫控制系统.对脱硫控制系统中吸收塔的浆液pH值的控制进行了改进,设计了基于神经网络自适应控制器.该控制器能有效提高浆液pH值的控制精度与稳定性.     

In situ Measurement of Journal Bearing Lubricant Viscosity by Means of a Novel Ultrasonic Measurement Technique Using Matching Layer

An ultrasonic viscometer was used to measure the circumferential viscosity variation in a journal bearing noninvasively. This sensing technique is based on the reflection of a shear wave at a solid–liquid boundary that depends on the viscosity of the liquid and the acoustic properties of the solid. Very little ultrasonic energy can propagate into the oil at a metal–oil interface because the acoustic mismatch is significant. Interleaving a matching layer between the metal and the lubricant enables accurate ultrasonic viscosity measurements (M. Schirru, et al., Tribology Leters, Vol. 60, No. 3, 2015). This technique has been used to build a miniaturized ultrasonic viscometer that is accommodated inside a journal to obtain the circumferential viscosity profile. Four viscosity regions are identified due to the variations in the localized temperatures and loads. The results are compared with the isothermal solution of the Reynolds equations for hydrodynamic lubricated bearings. The ultrasonic viscometer locates the angle at which the maximum load occurs and the length of the loaded contact with good accuracy. Finally, the viscosity results are used to estimate the frictional power losses. It is shown that over 70% of the total losses in the journal bearing occur in the region where the load is maximum.     

Erosion of steels in coal-solvent slurries

The erosion of several commercial piping steels by coal-solvent slurries was investigated at room and elevated temperatures. The liquid solvents used (kerosene, creosote oil and anthracene oil) had different viscosities that resulted in marked differences in the erosivity of the slurries. The effects of the mechanical properties and compositions of the steel alloys were related to their erosion behavior. The effect on the erosion of steel alloys of the impingement angle of the slurry was determined and related to the viscosity and boundary lubrication of the slurry carrier liquids. The effect of heat treatment of low alloy steels on their erosion behavior was determined.     

Study on Changes in the Rheologic Properties of EHL Film Using Fluorescence Measurements

This article describes a fundamental study using the fluorescence measurement method to understand the rheologic properties (such as viscosity and solidification) of elasto-hydrodynamic lubrication (EHL) film. The measurement principle is based upon the excimer emission of a pyrene fluorescence agent, which depends on the viscosity. To investigate the relationship between the excimer emission and viscosity, the measurements were taken under low temperature, with the results showing that the excimer emission decreased with decreasing temperature because of increasing of viscosity. No remarkable peak was observed below the temperature at which the state changed from liquid into a viscoelastic or elastic–plastic solid. The fluorescence was clearly observed in EHL film, and its spectrum revealed that the intensity of excimer emission decreases along the flow direction, with a contact area having the same behavior as that of the elastic–plastic solid at 243 K. These results suggest that the viscosity increased at the inlet of contact because of increasing hydrodynamic pressure under the wedge action and that the state in the contact region changes to solid because of high contact pressure. This study also proposes that this measurement method can be used to understand the viscosity change and solidification in the lubrication film.     

Research on the physicochemical and tribological properties of nano-TiO2 in the aqueous rolling liquid

Aqueous rolling liquids with different concentrations of TiO₂ nano-particles are prepared. The dispersing mechanism of nano-TiO₂ in the rolling liquid is studied by FTIR and TEM. Wettability and viscosity of these rolling liquids is evaluated based on Dataphysics OCA50 contact angle measuring device and SYD-265C viscometer, respectively. New viscosity empirical formula that suitable for nano-TiO₂ aqueous rolling liquid is proposed. The tribological property is also investigated by the MM-WIA universal tribological tester. The results indicate that with the increase in the nano-particle’s addition, the contact angle gradually decreases, whereas the viscosity rises, which would contribute to ameliorating the frictional behaviour of aqueous suspensions. The aqueous suspension with 0.7 wt% TiO₂ possesses excellent friction reduction and anti-wear properties.     

考虑软三体接触的粗糙界面混合润滑模型研究

软三体颗粒润滑是利用大量松散的固体软颗粒在界面中的承载和剪切行为实现特殊环境下界面的减摩,因此研究软颗粒介质摩擦界面在剪切过程中的受力情况,对软三体颗粒润滑机理的分析以及润滑装置的设计都具有重要意义。研究中将第三体颗粒类比为流体,基于雷诺方程、黏度方程、Greenwood和Williamson接触模型（G-W模型）等建立了含大颗粒粗糙界面的混合润滑模型。该模型中摩擦副的总载荷及总摩擦力由流体、微凸体和大颗粒三部分共同构成。通过采用有限差分法对上述物理模型进行求解分析,探究膜厚比、第三体大颗粒的质量浓度、粒径以及试件的表面形貌、弹性模量对三体接触界面的承载和摩擦力的影响情况,进而分析大颗粒粒径和接触表面粗糙度耦合时软三体接触界面的力学性能。基于对所构建的软三体接触界面混合润滑模型的研究可知：合理选择大颗粒质量浓度、粒径以及试件的表面形貌、弹性模量有助于提高承载、减小摩擦力,使得软三体颗粒流具有更好的减摩润滑性能。