The Removal of Submicron Particles in Liquid-Based Cleaning

Megasonic cleaning is one of the most widely used wet-cleaning processes in the semiconductor, hard disk and flat panel display industries. Presented results involve different and new techniques for introducing the high frequency ultrasonic energy in the cleaning bath. The effects of power, temperature and time on the removal efficiency of Si₃N₄ particles in the size range from 0.1 μm to 1.0 μm from silicon wafers are presented. Results show that removal efficiencies near 100% for silicon nitride particles using deionized water could be achieved under the right conditions. The megasonic input power has a greater effect on the removal efficiency than does temperature.     

Liquid Explosive Evaporative Removal of Submicron Particles from Hydrophilic Oxidized Silicon Surfaces

A pulsed CO₂ laser-based system, operating at a wavelength of 10.6 μm, was used as a cleaning tool to remove particles as small as 0.1 μm from hydrophilic, oxidized silicon surfaces. The laser beam served as a fast heating source to induce the explosive evaporation of a water film deposited on the particle-contaminated surface. The resulting explosive forces were high enough to expel particles from the surface efficiently. The contaminant particles used were 0.1 μm alumina, 0.1–0.2 μm silica, and 0.1 μm polystyrene latex.

For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm², at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent.

The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface.     

Liquid Explosive Evaporative Removal of Submicron Particles from Hydrophilic Oxidized Silicon Surfaces

A pulsed CO₂ laser-based system, operating at a wavelength of 10.6 μm, was used as a cleaning tool to remove particles as small as 0.1 μm from hydrophilic, oxidized silicon surfaces. The laser beam served as a fast heating source to induce the explosive evaporation of a water film deposited on the particle-contaminated surface. The resulting explosive forces were high enough to expel particles from the surface efficiently. The contaminant particles used were 0.1 μm alumina, 0.1-0.2 μm silica, and 0.1 μm polystyrene latex.

For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm², at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent.

The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface.     

旋转填充床除尘技术的研究

采用新型传质分离设备——旋转填充床研究其对发电厂燃煤飞灰的除尘性能。作为一种湿式除尘器,在气量200m^3/h,液量0．5～2．0m^3/h,转速900～l500r／min的条件下,旋转填充床显示出良好的颗粒捕集性能,总效率达99％以上,切割粒径范围在0．02～0．3μm,设备的气体压降较低。讨论了旋转填充床的除尘性能和压降行为,并解释了一些实验现象。     

Modeling and Experimental Study of CO2 Removal by Alkanolamines in a Packed Bed

Absorption of CO₂ by monoethanolamine, diethanolamine, and triethanolamine solutions in a lab–scale packed bed tower was investigated. A model for analyzing the heat and mass transfer mechanism in the presence of reaction was developed and validated using the measured data for MEA and TEA solutions and the results were compared with the others' experimental data. The well-known correlations for determining Henry's constant, as a critical parameter in the presented model, were evaluated and it was shown that the available correlations are often limited to a narrow range of operating conditions which could limit the applicability of the available models.     

Separation of Submicron Particles in Packed Columns – Optimization and Scale-up of the Process

Particle enlargement by heterogeneous condensation and – based on it – separation of submicron particles in packed columns of technical scale are investigated. The activation of submicron particles and droplet growth by heterogeneous condensation is briefly described. Calculations of the droplet growth are performed and compared with experimental results. The enlargement and the separation of submicron particles by cascading packed columns trickled with water which is alternately colder or warmer than the gas is experimentally studied in a technical scale pilot plant consisting of three packed columns with a diameter of 300 mm. Droplet size distributions are measured by means of an optical particle sizer at the outlet of the columns. In order to optimize the separation process, the influence of different parameters on the separation of the submicron particles is investigated. These are the gas and the water temperature, the gas and the water flow rate, and the particle concentration. Moreover, the supersaturation of the air stream in the column is calculated by means of a rate-based nonequilibrium process model as a function of different parameters.     

Dielectric Behavior of Silica/Polyacrylamide Nanocomposites

Polyacrylamide (PAAM) nano silica inclusions composites were prepared having different ratios of nano silica. The silica inclusions were either modified or unmodified. The nanocomposite films were characterized by transmission electron microscope (TEM) and infrared spectroscopy (IR). The dielectric behavior of the composites had been investigated as a function of the concentration of the nano silica inclusions.

The results show that the dielectric constant and dielectric loss of the nanocomposites are smaller than those obtained for the neat polymer. As the concentration of the surface-modified nano silica inclusions increases, the dielectric constant decreases. This behavior may be attributed to the successful interaction between the polymer and the surface of the nano silica inclusions. As would be expected, the results thus obtained are a clear manifestation of the role of surface treatment of the filler inclusions and subsequently the role played by the interface on the properties of the composites.     

聚碳酸酯/硫酸钡核壳复合粒子的制备

采用溶析结晶法制备亚微米聚碳酸酸(PC)-硫酸钡(BaSO_4)核壳复合粒子,PC 为连续相,BaSO_4为分散相。运用扫描电镜、能量散射仪、X 衍射仪、红外光谱、激光粒度分析仪等分析方法对粒子的粒径、粒度分布、形貌、结构和晶相进行表征。结果表明溶析结晶法成功地使 PC 对 BaSO_4进行包覆,制备得到平均粒径300～650nm、粒度分布均匀、形貌均一的聚碳酸酯-硫酸钡核壳结构亚微米复合粒子。     

Removal of Silica from Geothermal Brine

The problem of removing silica from geothermal brine is considered. The colloidal and chemical properties of the brine are studied. Silica precipitation by electrocoagulation is described, and the process parameters are optimized. Factors in the profitability of the multipurpose utilization of the hydrothermal heat carrier are discussed.     

采用板框过滤工艺去除木薯酒精废水CSTR厌氧反应器出水悬浮物的研究

针对出水CODCr和SS浓度超标等问题,某酒精废水处理站在CSTR高温厌氧反应器出水去除悬浮物的斜筛/气浮/沉淀工艺基础上进行了提标改造试验研究,出水执行《水污染物排放限值》(DB 44/26-2001).结果表明,通过将板框过滤工艺作为CSTR厌氧反应器出水去除悬浮物的工艺,SS从改造前的8～15 g/L下降到改造后的3 g/L以下,保障了进入后续二级厌氧及A/O生化池的稳定运行,最终实现出水水质达标排放.     

基于矩法和时间域分析法研究稠密CO2中甲苯和对氯苯在硅胶固定床系统中的吸附和传递性质

Based on chromatographic theory, the moment method and the time-domain fitting analysis were applied to measure and evaluate the adsorption equilibrium constant and mass transfer properties (axial dispersion coefficient and effective intra-particle diffusivity) for toluene and p-dichlorobenzene on silica gel adsorbent in the subcritical and supercritical CO2. An apparatus based on supercritical fluid chromatography was established and the experiments were performed at temperatures of 298.15-318.15 K and pressures of 7.5-17.8 MPa. The two methods have been compared. The results show that for the systems studied here the moment method can give reasonable values for both adsorption equilibrium constant and mass transfer properties, but the time-domain analysis only can obtain the adsorption equilibrium constant. The dependence of adsorption equilibrium constant and mass transfer properties on temperature and pressure was investigated.     

Separation Characteristics of Submicron Particles in an Electrostatic Precipitator with Alternating Electric Field Corona Charger

Experiments were carried out to investigate filtration characteristics of an electrostatic precipitator (ESP) with alternating and direct electric field corona charger. Potassium Sodium Tartrate Tetrahydrate as the material was used to generate polydisperse submicron aerosols by using Constant Output Atomizer. The results indicated that the aerosol penetration through the ESP decreased as applied voltage increased. The maximum collection efficiency of either alternating or direct electric field was more than 98%, though the applied voltage of alternating electric field was higher than that of direct electric field. However, from the viewpoint of power consumption, the direct electric field had higher power consumption rate than alternating electric field at similar collection efficiency. For example, when the 0.2 μm particle penetration was about 4%, the power consumptions of alternating and direct electric field were 16 watt and 18 watt, respectively. Hence the separation quality of alternating electric field was better than that of direct electric field. Moreover, considerably lower ozone concentration was found in alternating electric field ESP, compared to direct electric field.     

旋转填充床中O_3/Fenton工艺处理聚丙烯酰胺污水的研究

在旋转填充床(RPB)中,研究了O_3/Fenton工艺处理模拟聚丙烯酰胺(PAM)污水的效果。考察了溶液p H值,Fe~(2+)浓度,H2O2浓度,O_3浓度,反应温度与RPB转速对PAM氧化降解率以及化学需氧量(COD)去除率的影响。结果表明,在pH值为4,Fe~(2+)浓度为0.25 mmol/L,H_2O_2浓度为0.8 mmol/L,O_3浓度为50 mg/L,反应温度为25℃,以及RPB转速为800 r/min的条件下,PAM氧化降解率和COD去除率可以达到96.82%与89.96%,表明采用RPB强化O_3/Fenton工艺处理PAM污水具有良好的效果。     

超重力辅助溶剂-反溶剂重结晶法制备亚微米级RDX

为了获得粒径分布均匀的细化RDX,在超重力反应器中,以丙酮-水作为溶剂-反溶剂重结晶体系,添加聚乙烯吡咯烷酮(PVP)作为表面活性剂,制备了亚微米级RDX。研究了RDX溶液浓度、PVP含量以及超重力反应器转速对RDX形貌和尺寸的影响,获得最优工艺条件,利用SEM、XRD和FT-IR对其形貌、晶体结构和分子结构进行了表征,并采用DSC研究了RDX的热分解过程。结果表明,在RDX溶液浓度为0.04g/mL、PVP浓度为0.2g/L、超重力反应器转速为1500r/min时,制备了平均粒径为0.54μm的亚微米级RDX,细化处理未改变RDX的晶型;与原料RDX相比,亚微米级RDX的分解峰温提前了1.2℃,热分解活化能从180~250kJ/mol降至约150kJ/mol。     

原位乳液聚合制备丙烯腈聚合物/纳米氧化硅复合粒子

利用2,2'-偶氮(2-脒基丙烷)二氯化氢(AIBA)引发剂与纳米氧化硅粒子的静电作用而使AIBA吸附在纳米氧化硅表面,进而引发丙烯腈-甲基丙烯酸甲酯(AN-MMA)原位乳液聚合.考察了AIBA浓度和反应温度对AN-MMA原位乳液聚合动力学的影响以及氧化硅含量对AN-MMA共聚物/纳米氧化硅复合乳胶粒径分布和形态的影响.结果表明:聚合速率随AIBA浓度和聚合温度的升高而增大; AIBA浓度相同时,原位乳液聚合速率小于普通乳液聚合;AN-MMA共聚物/纳米氧化硅复合粒子粒径随纳米氧化硅含量增加而增大;原位乳液聚合得到的复合胶粒表面粗糙,当纳米氧化硅质量分数为10%时,纳米氧化硅与聚合物乳胶粒子复合良好;当纳米氧化硅质量分数为20%和30%时,有部分纳米氧化硅粒子与乳胶粒子分离而分散在连续相中.     

用旋转填料床治理火炸药厂的氮氧化物尾气

为解决火炸药行业高浓度氮氧化物尾气治理困难的现状,采用新型吸收设备——旋转填料床进行治理,利用旋转填料床的优良特性,达到提高吸收剂的利用效率、降低治理成本和治理后尾气达标排放的目的.在初期试验中,以清水为吸收剂,研究了进气量、液气比、超重力因子等操作参数对吸收率的影响,得出了最佳操作参数范围.采用吸收剂强化吸收,并对吸收机理进行了初步探讨.试验结果表明,在进气量2 m3/h、液气比20 L/m3和超重力因子为90的条件下,吸收率达到85.3%,采用两级串联吸收后,氮氧化物尾气达到了国家排放标准.试验证明旋转填料床用于治理火炸药行业氮氧化物尾气的可行性,具有良好的工业应用前景.     

旋转填料床生产纳米粉体材料的研究进展

本文介绍以旋转填料床为强制混合反应器进行化学液相沉淀反应,实验生产碳酸钙、氢氧化铝、硫酸钡、氧化锌、拟薄水铝石等纳米粉体材料的工艺及实验结果,考察旋转填料床转速、溶液的过饱和程度、分散剂等因素对平均粒径的影响,提出还需要完善的方面,建议用错流型旋转填料床解决气相压降过大的难题。     

可生物降解药物载体--纳米/亚微米壳聚糖微球的制备及性能

利用聚电解质的离子凝胶反应,在溶液中壳聚糖为聚阳离子电解质与带反相电荷的聚阴离子三聚磷酸钠(TPP)发生离子凝胶反应,在合适的浓度和适当的搅拌速度下,得到亚微米级的壳聚糖微球。利用环己烷作为油相,以壳聚糖溶液为水相,配制澄清透明的W/O反相微乳清液,滴加质量浓度为5mg/mL的TPP溶液于已配制好的微乳清液中,制得纳米级壳聚糖微球。采用上述两种方法制得的纳米/亚微米壳聚糖微球用作生物降解药物载体,载药实验结果表明,释放初期无明显暴释现象,具有良好的药物缓释作用。