一种高效过滤亚微米级细颗粒的新液固过滤技术——表层过滤

论述一种新的可高效过滤液体中亚微米级细颗粒的表层过滤技术,分析了表层过滤技术的特点、过滤模式、表层过滤基本条件和设计计算中所必需的数学模型。介绍了表层过滤技术在我国工业生产上推广应用的概况。     

Influence of interactions between NOM and particles on UF fouling mechanisms

This study focused on the mechanistic effects of molecular interactions between inorganic particles (kaolinite) and the two main NOM fouling fractions of polysaccharides (alginate) and humics (humic acids) in ultrafiltration. Fouling effects were studied during the dead-end filtration of individual and mixed compounds as well as during the subsequent filtration of individual compounds. SEM analyses were performed to further study the fouling-layer structure. A significant synergistic effect was observed during combined particle-NOM fouling, which was considerably greater than the sum of particle and organic fouling alone. Synergistic fouling could be explained by NOM-particle interactions in the feed solution and during the fouling process. Kaolinite alone formed a fouling layer of particle aggregates, whereas humic acid adsorption onto kaolinite resulted in a fouling layer of stabilized colloids of humic acid and kaolinite. In the case of alginate, simultaneous pore-blocking and cake-layer formation of NOM and kaolinite dominated the fouling. In both cases, incorporation of the organics in the kaolinite fouling layer resulted in a fouling cake of significantly reduced porosity compared to individual particle filtration. Irreversible fouling by NOM could not be prevented by kaolinite. SEM images showed patches of the particle-fouling layer remaining on the membrane surface after backwashing, which can be linked to particle-membrane associations by NOM bridging.     

无机刚性粒子增韧PVC／CPE合金体系的加工流变性能（二）

研究了无机刚性粒子（超细CaCO3，轻质CaCO3）对PVC／CPE体系加工流变性能的影响，分别探讨了CPE用量、超细CaCO3粒子用量和粒径大小对PVC／CPE共混体的影响。实验表明：超细CaCO3增韧PVC／CPE体系，能有效地改善体系的塑化行为，缩短塑化时间；在保证最佳的综合力学性能的同时，超细CaCO3的加入对加工流变性能影响不大；并且，随其粒径的减小，体系的塑化时间明显减小。     

剪切稀化流体中微粒子聚集行为研究

在化工过程、生物工程等领域中,实现颗粒分离至关重要。通过整合微流控技术、高速显微图像采集技术和数字图像处理技术,探究微粒尺寸、通道流量和液相流变特性对微粒聚集的影响规律。结果表明,在剪切稀化流体羧甲基纤维素钠(CMC)水溶液中,随着通道流量和颗粒粒径增大,微颗粒聚集位置逐渐向剪切速率较高的一侧偏移;随着CMC质量分数增加,聚集位置不断向剪切速率较低的一侧偏移。利用求解的幂律型剪切稀化流体速度和剪切速率方程,结合对微颗粒的受力分析,证明稠度系数越大,聚集位置越偏向剪切速率较低处;剪切稀化特性越强,聚集位置越偏向剪切速率较高处,说明在幂律型剪切稀化流体中的黏度变化是微颗粒发生特殊迁移聚集行为的一个重要原因。     

高速微粒轰击对微弧氧化铝合金疲劳性能的影响

以获取高性能微弧氧化陶瓷膜,且不降低基体铝合金的抗疲劳性能为目标,采用高速微粒轰击处理工艺和微弧氧化处理工艺制备了未处理、高速微粒轰击处理、微弧氧化处理、高速微粒轰击+微弧氧化处理复合处理4种状态的试样,通过疲劳试验机对其疲劳寿命进行了测试;同时,采用TEM和XRD残余应力测试仪等分析方法对试样的表层微观组织结构和残余应力进行了观察与测试。结果表明:加载载荷较高时,4种试样疲劳寿命基本相同,寿命较短;加载载荷较低时,微弧氧化处理铝合金的疲劳寿命明显低于未处理试样,高速微粒轰击处理导致的微观组织结构细化和形成的残余压应力可以有效抑制疲劳裂纹的萌生和扩展,使未处理和微弧氧化铝合金的疲劳寿命均得到有效提高,这2种高速颗粒轰击处理过的试样的疲劳寿命均高于未处理试样,这表明高速颗粒轰击强化处理可有效提高低应力水平时微弧氧化铝合金的疲劳寿命。     

粘结法制备磁性磨料及其对轴承钢外圆表面的光整加工研究

采用粘结法制备磁性磨料,对磁性磨料制备工艺进行了优化,确定了最终的工艺方案。研究了在磁性磨料粒度及配比不变的情况下,结合剂的种类、结合剂中粘结剂与固化剂的质量比以及混料与结合剂的质量比对轴承钢外圆表面粗糙度的影响。试验结果表明,使用粘结剂为环氧树脂B制备的磁性磨料具有较好的研磨效果,并且当粘结剂与固化剂的质量比为3∶1,以及混料与结合剂的质量比为6∶1时,研磨效果最佳。磁性磨料光整加工技术为轴承钢的表面加工提供了一种新方法。     

Enhancing High-Temperature Strength and Thermal Stability of Al_2O_3/Al Composites by High-Temperature Pre-treatment of Ultrafine Al Powders

Amorphous Al_2 O_3-reinforced Al composite(am-Al_2 O_3/Al) compacted from ultrafine Al powders for high-temperature usages confronts with drawbacks because crystallization of am-Al_2 O_3 at high temperatures will result in serious strength loss.Aiming at this unsolved problem,in this study,high-temperature Al materials with enhanced thermal stability were developed through introducing more thermally stable nano-sized particles via high-temperature pre-treatment of ultrafine A1 powders.It was found that the pre-treatment at ≤550℃ could introduce a few Al_2 O_3 in the Al matrix and increase the strength of the composites,but the strength was still below that of am-Al_2 O_3/Al because without being pinned firmly,grain boundaries(GBs) were softened at high temperature and intergranular fracture happened.When the pre-treatment was carried out at 600℃,nitridation and oxidation processes happened simultaneously,producing large numbers of intergranular(AlN+γ-Al_2 O_3) particles.GB sliding and intergranular fracture were suppressed;therefore,higher strength than that of am-Al_2 O_3/Al was realized.Furthermore,the(AIN+γ-Al_2 O_3)/Al exhibited more superior thermal stability compared to amAl_2 O_3/Al for annealing treatment at 580℃ for 8 h.Therefore,an effective way to fabricate high-temperature Al composite with enhanced thermal stability was developed in this study.     

Particle filtration and distribution during the liquid composite molding process for manufacturing particles containing composite materials

The effects of major process parameters on particle filtration and distribution were investigated by using newly developed microscopic methodology using an electron probe micro-analyzer and numerical simulation. The mapping results indicated that well-dispersed particles were distributed uniformly in the inter-tow and intra-tow regions. Agglomerates were likely to be filtered at the boundary or inside of the fiber bundle. The results of quantitative analyses showed particle concentrations in the inter-tow region to be uniform throughout the composite part, whereas the intra-tow concentrations varied according to particle size and fiber orientation. The poor dispersion state of the CNT-Ag particles resulted in quite irregular distributions. A high volume fraction of the fiber preform resulted in a lower particle concentration inside the fiber tow. Numerical analysis of the filtration of large clusters of particles indicated that filtration occurred in the initial stage of the injection process at the tow boundaries.     

Simulation of granular packing of particles with different size distributions

The study of granular matter composed of spherical particles is of interest in manufacturing, material, and metallurgy. The viscoelastic and frictional contacts between the particles are the cause of forming the agglomeration. We present a numerical simulation for particles packing with three different kinds of size distributions: monosize, bimodal, and Gaussian, using distinct element method (DEM). The particles are initially put randomly but without any overlap, and then fall down due to the gravity force and collide with neighbor particles. Because of the dissipative factors of viscoelastic collision and frictional force, all the particles finally come together to form an agglomeration. Coordination number, porosity, radial distribution function, and force distribution are calculated for different size distributions. It is demonstrated that particle size distribution does affect the granular packing structure.     

Efficient recovery of nano-sized iron oxide particles from synthetic acid-mine drainage (AMD) water using fuel cell technologies

Acid mine drainage (AMD) is an important contributor to surface water pollution due to the release of acid and metals. Fe(II) in AMD reacts with dissolved oxygen to produce iron oxide precipitates, resulting in further acidification, discoloration of stream beds, and sludge deposits in receiving waters. It has recently been shown that new fuel cell technologies, based on microbial fuel cells, can be used to treat AMD and generate electricity. Here we show that this approach can also be used as a technique to generate spherical nano-particles of iron oxide that, upon drying, are transformed to goethite (α-FeOOH). This approach therefore provides a relatively straightforward way to generate a product that has commercial value. Particle diameters ranged from 120 to 700 nm, with sizes that could be controlled by varying the conditions in the fuel cell, especially current density (0.04-0.12 mA/cm²), pH (4-7.5), and initial Fe(II) concentration (50-1000 mg/L). The most efficient production of goethite and power occurred with pH = 6.3 and Fe(II) concentrations above 200 mg/L. These results show that fuel cell technologies can not only be used for simultaneous AMD treatment and power generation, but that they can generate useful products such as iron oxide particles having sizes appropriate for used as pigments and other applications.