Experimental Study of Alumina Particle Removal From a Plane surface

Micron and submicron alumina particles are often used for the mechanical polishing of the GaAs wafers processed in the microelectronic industry. A better understanding of the adhesion mechanisms is the key factor for the particle removal and for the optimisation of the industrial chemical cleaning. However, the nature and the strength of the complex interactions occurring between asymmetrical alumina particles and the surface remain unclear. Thus, an experimental study of the detachment of asymmetrical alumina particles in adhesive contact with a glass plate was done using a specially designed shear stress flow chamber. A series of experiments was performed to measure the shear stress necessary to remove individual alumina particles (of 3 and 0.3 µm nominal size) under various chemical solutions (diluted ammonia, surfactant and glycerol). Then the effects of the particle size, the resting time, the pH and the nature of the chemical solutions used for the removal of the alumina particles was characterised in terms of percentage of alumina particles detached. Results have shown that the longer the resting time, the more adherent the particles are. Moreover, it was found that the ammonia solution gives the best particle removal rate (80%) because of the strong repulsive electrostatic interactions between the alumina particles and the glass surface, both being charged negatively in a basic solution.     

Experimental Study on the Fluorene Removal From Fluorene-Acenaphthene-Dibenzofuran Mixtures of Wash Oil

The azeotrope mixtures in wash oil usually could not use conventional distillation to separate. The objective of this work is to separate and obtain fluorenone from fluorene-acenaphthene-dibenzofuran mixtures which were extracted from wash oil via chemical transformation and azeotropic distillation. We prepared fluorenone-acenaphthene-dibenzofuran mixtures from fluorene-acenaphthene-dibenzofuran mixtures by liquid-phase catalytic oxidation employing air. The effects of catalyst loading, type, and amount of solvent have been investigated. The result showed that fluorene was transformated into fluorenone while other substances were not oxidized. Then we used azeotropic distillation to isolate fluorenone from fluorenone-acenaphthene-dibenzofuran mixtures. And ethylene glycol was found to be the better entrainer than diethylene glycol. The purity and recovery rate of fluorenone was more than 96% and 95%, respectively.     

钛合金平面磁粒研磨轨迹的均匀性实验研究

为了获得更好的研磨加工质量和高效、高均匀度的加工效果,采用磁力研磨法,利用AD-AMS模拟单颗磨粒运动轨迹,并运用数值计算对运动轨迹的均匀性作出评判.通过搭建实验平台,在不同条件下,对钛合金平面进行研磨抛光,获取其表面粗糙度的变化与加工时间的关系,并在加工区域取3点测量其表面粗糙度,探讨研磨轨迹的均匀性对加工平面粗糙度...     

Experimental Investigation of Particle Removal from Surfaces by Pulsed Air Jets

This work presents an experimental study of particle removal from surfaces by means of a pulsed air jet directed toward the particle-laden surface. During the experiments, solid particles were dispersed over the surface, forming a layer of particles that did not touch each other. Under these conditions, resuspension of an individual particle was independent of the number of particles and their location. We attempt to explain the observed phenomena by analogy to heat transfer enhancement by pulsed jets. It is expected that since pulsed jets are effective in surface cooling, their application to improved surface cleaning should be promising. For a pulsed jet, we investigated the effect of pulse frequency on particle removal. It was found that particle removal efficiency could be significantly affected by the frequency of the jet. In particular, for a fixed jet velocity, the efficiency increases with frequency, reaches a maximum, and then decreases.     

氧化铝陶瓷热压铸压成型与颗粒尺寸分布关系的研究

研究了石蜡加入量及烧成收缩率与颗粒尺寸分布的关系 ,发现蜡浆含蜡量及烧成收缩率与理论计算的准积气孔率密切相关。     

Sol-Gel法制备氧化铝负载铜基超细粒子影响因素的研究

通过对Sol-Gel法制备氧化铝负载铜基超细粒子的研究,表明PEG分散剂对粒度分布有重要影响;采用XRD对制得的催化剂表面组成进行了研究,指出了发生固相反应生成活性较低的CuAl2O4的影响因素。     

Electrostatic Force on a Moist Particle Near a Ground Plane

The effect of surface moisture on the electrostatic force of attraction between an uncharged particle and a ground plane is investigated. Describing a moist sphere with an effective complex permittivity allows the image force to be calculated using complex linear multipoles. The number of multipoles needed for an accurate image force calculation is determined as a function of particle-plane separation. Adsorbed moisture introduces a relaxation in the electrostatic image force. For particles exposed to a range of relative humidities, the model predicts relaxation times that vary by several orders of magnitude. In addition, at small particle-plane separations adsorbed moisture can increase the image force by several orders of magnitude. Finally, multipolar moments are used to calculate the electric field in the gap separating the particle and ground plane to determine the onset of breakdown or field emission.     

氧化铝载体的水合、烧结实验研究

氧化铝催化剂载体在高温下会发生烧结,并且在有含水或生成水的条件下还会发生再水合,从而导致比表面积减少甚至使催化剂失活。考察了MgO改性氧化铝载体的高温热稳定性和抗水合性能,实验结果表明,引入MgO能够增加氧化铝载体的热稳定性,并能抑制其烧结,当MgO质量分数为0.5%时,γ-Al2O3改性载体的抗水合性能最佳。     

Particle Removal in Linear Shear Flow: Model Prediction and Experimental Validation

In many industrial processes, particle contamination is becoming a major issue. Particle detachment from surfaces can be detrimental, e.g., during lithographic processing. During cleaning, however, detachment of particles is aimed for. However, until recently, only little was known on the mechanism of particle detachment due to flowing gasses. In high throughput applications, large gas velocities are likely to occur at certain locations in the system. It is important to test particle behavior experimentally under all conditions that may arise. Therefore, the aim of this study is to be able to predict the risk of particle detachment by modeling. For this purpose, particle–surface interaction is studied for micrometer-sized particles. Based on the particle Reynolds number, critical particle diameters were determined for which the flow-induced forces on the particles (drag and lift forces) are larger than the attractive forces between the particle and the surface (van der Waals force). Among the different possible particle motions (lift, sliding and rotation), particle rotation turns out to be the mechanism responsible for particle removal. A critical particle diameter was defined for which attractive and flow-induced forces are equal. Calculated values of the critical particle diameter agree with the experimental results within a few micrometers. This removal mechanism model can thus be used to calculate the cleaning efficiency of a flow, and for determining the probability of unwanted detachment of particles from surfaces in ultra-clean production or processing environments.     

新型旋风管内颗粒浓度分布的实验研究

在Shell型旋风管基础上进行了结构与尺寸的优化匹配,得到一种新型高效旋风管. 采用等动采样方法,对新型旋风管内的颗粒浓度场进行了测试与分析. 实验结果表明,新型旋风管开有排尘槽的锥形排尘结构有较好的分离效果,并在一定程度上可以降低颗粒的返混;加设导流锥结构可显著减少短路流,并能使细小颗粒受到较强的惯性作用而得到分离. 灰斗上方区域,沿轴向向上颗粒浓度呈下降的趋势,表明内旋流对颗粒具有较强的二次分离作用. 对粒级效率的估算结果表明,新型旋风管可将粒径大于7 mm的颗粒全部除净,3~7 mm的细小颗粒的粒级分离效率可达86%以上,而相同操作条件下Shell型旋风单管仅能将10 mm以上的颗粒除净. 本工作为旋风管的结构改进、尺寸优化乃至工业推广应用提供了必要的基础.     

城市污泥中重金属去除技术研究

重金属污染是目前城市污水处理厂污泥农用的主要障碍之一。综述了城市污泥中重金属去除的常用四种技术：化学浸提、生物淋滤、动电技术和固化-稳定化,同时分析了污泥中重金属去除技术的发展方向。     

Experimental Study of Particle Collection by Small Cyclones

A new set of experimental data on the particle collection characteristics of small cyclones is reported. The collection efficiency for particles ranging from 2 to 10 μm in diameter was measured systematically for nine cyclones at flow rates ranging from 8.8 to 18.4 L/min. Special emphasis was given to the effects of the exit tube size and of the cyclone body size on the particle collection efficiency. The size ratio of the exit tube to the cyclone body was varied from 0.24 to 0.80. The experimental results show that the stiffness of the particle collection cutoff with size does not change noticeably with a change in the cyclone body size while operation of a cyclone at a low flow rate can cause the particle collection characteristics to become less stiff. It was also found that the exit tube diameter influences the particle collection efficiency substantially, with results showing that as the exit tube size is decreased, the collection efficiency increases. A large cyclone body size increases the efficiency. However, when the cyclone body is increased excessively, the collection efficiency appears to decrease somewhat. The experimental data were compared with existing cyclone theories and Barth's (1956) theory was found to be in good agreement. Finally, the exit tube was found to affect substantially the pressure drop of cyclones. As the exit tube size increased, the pressure drop decreased. However, when the exit tube size was further increased until it approached the body size, the pressure drop increased again.     

Experimental Study of Particle Deposition on Semiconductor Wafers

A sensitive method for detecting particle deposition on semiconductor wafers has been developed. The method consisted of generating a monodisperse fluorescent aerosol, depositing the known-size monodisperse aerosol on a wafer in a laminar flow chamber, and analyzing the deposited particles using a fluorometric technique. For aerosol particles in the size range of 0.1–1.0 μm, the mobility classification-inertial impaction technique developed by Romay-Novas and Pui (1988) was used to generate the monodisperse test aerosols. Above a particle diameter of 1.0 μm, monodisperse uranine-tagged oleic acid aerosols were generated by a vibrating-orifice generator. The test wafer was a 3.8-cm diameter silicon wafer placed horizontally in a vertical laminar flow chamber which was maintained at a free stream velocity of 20 cm/s. A condensation nucleus counter and an optical particle counter were used to obtain the particle concentration profile in the test cross section and to monitor the stability of aerosol concentration during the experiment. The results show that the measured particle deposition velocities on the wafers agree well with the theory of Liu and Ahn (1987) in the particle size range between 0.15 and 8.0 μm. The deposition velocity shows a minimum around 0.25 μm in particle diameter and increases with both smaller and larger particle size owing to diffusional deposition and gravitational settling, respectively.     

垂直立管中颗粒移动床蠕动流动特性的实验研究

在无负压差的环境下,采用PV6D型颗粒速度测量仪,考察了垂直立管中FCC催化剂颗粒移动床的蠕动流动特性. 结果表明,颗粒质量流率较小时立管中颗粒流动具有明显的蠕动流动特性,可划分为两种流态,拟气固雷诺数Re<500时为间歇式蠕动流动,5004000时颗粒的蠕动流动转变为密相流化流动. 立管中颗粒的蠕动流动主要是出口区颗粒成拱与崩塌交替进行产生的,其次为颗粒与器壁滑动摩擦力的不稳定性变化起作用. 微观上颗粒流动的蠕动行为是颗粒之间力链作用变化的结果.     

Thermophysical Properties of Alumina Particle Reinforced Glass Matrix Composites

Alumina particles incorporated glass matrix composites, which showed good prospect to be used as coating materials for high‐temperature corrosion protection on intermetallics or titanium alloys, were prepared via pressureless sintering. With increasing alumina content, the Young's modulus, fracture strength, Vickers hardness, indentation toughness, softening point, and thermal shock resistance of the composites increased monotonically. A similar increasing trend could be found for the thermal expansion coefficient of the composites, except for an abnormal drop at small amount of incorporation, which closely correlated with the Al³⁺ dissolution into the glass matrix.     

Effect of Particle Size Distribution on the Sintering of Alumina

The effect of particle size distribution on the sintering of Al₂O₃ was investigated. Samples could be sintered to high relative density (∼99%), small average grain size (1 μm), and no growth of exaggerated grains using powders with either broad or narrow particle size distribution. However, the broad particle size distribution provided the advantage that powder compacts could be prepared with higher green density and, therefore, samples could be densified with less total shrinkage.     

染色废水脱色实验研究

研究用化学混凝法处理活性染料F3B废水的脱色效果 ,探讨混凝剂种类、加入量和体系pH值对脱色效果的影响 .实验结果表明 ,FeSO4·7H2 O对F3B染色废水脱色效果优于PFS ,FeCl3 ·6H2 O ,AlCl3 ,在pH值 10 - 11条件下 ,脱色率可以达到 90 %左右     

单颗粒橡胶球撞击破碎的实验研究

对天然橡胶球进行单颗粒、低温撞击破碎实验,通过分析破碎产物的粒度分布,考察颗粒的撞击速度、破碎温度、板靶撞击角度和橡胶球初始粒径对破碎过程的影响规律。结果表明:颗粒撞击速度和破碎温度对天然橡胶球破碎产物粒度分布的影响最大;撞击角度在0~45°之间变化时,撞击角度对破碎产物的粒径分布影响不显著;颗粒的初始粒径越小,破碎产物中细颗粒所占的百分比越大。     

钒厂废水中去除硫代硫酸钠实验研究

采用化学法去除钒厂废水中残留的海波。通过实验考察了去除硫代硫酸钠的六个影响因素：氧化剂、氧化剂的加入量、反应温度、反应时间、pH值、搅拌强度。实验结果表明：次氯酸钠做氧化剂时,次氯酸钠的加入量为15mL,反应时间为25min,pH值为7,室温时,使处理后废水达到排放标准。     

湿法磷酸脱除铝离子研究

采用离子交换法对湿法磷酸进行了脱除铝离子的实验研究,考察了树脂用量、温度、时间等因素对铝离子净化率的影响,优化了工艺条件。实验结果表明：当搅拌速度为250rpm、树脂用量为100g、温度为25℃、时间为15min时,湿法磷酸中铝净化率可达到92．35％。