Deposition of Charged Aerosol Particles on a Substrate by Collimating Through an Electric Field Assisted Coaxial Flow Nozzle

Electroaerodynamic (EAD) jet printing, where aerodynamic force is coupled with electrostatic force in order to obtain a wide range of controlled pattern sizes, is introduced. Charged and sheathed aerosol particles yield a high deposition rate even at low velocity owing to the force of their electrostatic attraction to the substrate. In this study, two coaxial nozzles (inner diameters of 6 mm and 100 μm) were designed and tested theoretically and experimentally in order to observe the effects of electrostatic force, particle size, and air flow rate on particle trajectory and dot pattern size. A higher sheath air flow rate (higher Stokes number) caused the aerosol jet stream to be focused. For Stokes numbers higher than 1, the effect of applied voltage on pattern size was less than that of the sheath air flow rate. However, for Stokes number lower than 1, the pattern size was affected by both the applied voltage and the sheath air flow rate. After incorporating all data, the diameter of the particle deposition area (W_p) was expressed as a function of nozzle diameter (W), sheath air flow rate (Q_sheath), aerosol flow rate (Q_aerosol), Stokes number (Stk), and Electrostatic number (Es). Three different equations were obtained for Stk < 1, for 1 ≤ Stk < 5, and for Stk ≥ 5, respectively. These equations would be used to predict pattern width for given conditions of aerosol and sheath flow rates, particle size, electric field, and nozzle size.

Copyright 2013 American Association for Aerosol Research     

磁场对细菌浸出尾矿中铜、锌的影响

针对尾矿中重金属对矿区的污染,考虑尾矿中部分金属的回收利用,利用环境友好,反应温和,流程短,能耗低的细菌浸出的方法来处理尾矿,浸提重金属Cu和Zn。在浸矿前,用磁场磁化半小时的无铁培养基做浸矿基液,用嗜酸氧化亚铁硫杆菌浸出27 d。实验结果显示,在浸矿浓度为5%,接种量为10%,温度为30℃,p H值为2的条件下,在磁场强度分别为2、5、8、11 m T的情况下,Cu的浸出率受磁场的影响较小,而对Zn的浸出率有较大影响,Zn的浸出率最大提高了13%左右。磁感应强度的大小对锌的浸出率也有影响,锌的最佳浸出磁感应强度是2 m T。     

SiC颗粒对镀铁层表面形貌和结构的影响

采用自制的不对称交直流电镀电源,在氯化亚铁镀铁液中加入S iC颗粒制备了Fe-S iC复合镀层。研究了S iC颗粒对镀铁层表面形貌和镀铁层结构的影响,并对复合镀层的硬度和耐磨性进行了评定。研究结果表明,加入S iC颗粒可以减少镀铁层中的微裂纹,提高镀铁层的硬度和耐磨性。     

Determination of External and Internal Mixing of Organic and Inorganic Aerosol Components from Hygroscopic Properties of Submicrometer Particles During a Field Study in the Lower Fraser Valley

A tandem differential mobility analyzer (TDMA) system was developed to measure particle growth factors over a range of relative humidities from 50–85%. This system was deployed in the Lower Fraser Valley, and data was collected at Golden Ears Provincial Park and Eagle Ridge Mountain during the Pacific 2001 field study. Following humidification, particles either had a single hygroscopic mode or a bimodal distribution with more hygroscopic and less hygroscopic modes. Growth factors for the less hygroscopic mode were found to be consistent throughout the study. Monomodal distributions were the more common result. Their growth factor ranged between that of the less and the more hygroscopic modes. Using observed and calculated growth factors, relative organic and inorganic fractions were estimated. Particles at these sites were largely organic. Organic fractions near unity were found at Golden Ears forest and during rainy days at Eagle Ridge.     

Effect of an Iron Catalyst and Process Parameters on Si-Based Ceramic Materials Synthesized From Rice Husks

Silica and carbon are naturally occurring in rice husks (RH) and these were used for the production of ceramic materials made of Si, C, N and O as the main constituents. The various “silicon-based” ceramics were produced from the thermal decomposition of rice husks and posterior heat treatment at temperatures varying from 1200–1450 °C under a pure nitrogen atmosphere. FeSO₄ in various concentrations was introduced to the decomposed rice husk prior to the heat treatment. The formation of various Si/C/N/O ceramics in general and silicon nitride in particular, were studied with respect to the concentration of FeSO₄ (4–10%) as well as temperature (1200–1450 °C). The formation of different phases were confirmed by XRD and FT-IR analysis. Morphology and surface properties of the products have been studied using SEM. The maximization of whiskers of the ceramic products was also studied through microstructural analysis. Elemental analysis of the whiskers product was analyzed through EDX. The chemical analysis of raw rice husk was also carried out.     

Optimal Recovery of Iron Values from a Low Grade Iron Ore using Reduction Roasting and Magnetic Separation

A low grade iron ore containing 51.6% Fe, 17.6% SiO₂, 4.3% Al₂O₃, and 3.8% LOI was subjected to reduction roasting followed by low intensity magnetic separation studies. The phase transformation of hematite into magnetite and fayalite due to reduction roasting was investigated using reflected microscope and X-ray diffraction (XRD) techniques. The effects of reduction variables such as reduction time (40?175 min), temperature (750?1000°C), and reductant dosage (3?11%) using activated charcoal were studied. The process was optimized by using central composite rotatable design (CCRD) and response surface methodology. Iron grade from 59?66% with recovery of 9.5?87% was achieved using CCRD experiments. Model equations were developed both for Fe grade and recovery and then optimized within the bounds of experimental conditions. The program predicted 63.3% Fe with 79% recovery with the following optimum conditions: temperature: 950°C, time: 53.04 min, and reductant: 3%.     

氟啶虫胺腈与乙基多杀菌素混用防治水稻迁飞性害虫田间药效试验

为探索防治水稻迁飞性害虫的有效药剂,开展了田间药效试验。结果表明:22%氟啶虫胺腈悬浮剂与60 g/L乙基多杀菌素悬浮剂混用防治稻飞虱、稻纵卷叶螟具有速效性好、持效期长的特点,可起到防治多种害虫的作用,其适宜剂量为22%氟啶虫胺腈悬浮剂375 mL/hm2+60 g/L乙基多杀菌素悬浮剂500 mL/hm2,对水稻生长无任何不良影响,且对稻田害虫天敌如蜘蛛、黑肩绿盲蝽等杀伤作用小。     

Effect of Cobalt and Nickel Doping on Structural and Magnetic Properties of Iron Oxide Nanoparticles

Two series samples of Iron Oxide nanoparticles doped with nickel and cobalt with different doping values (x?=?0.01; 0.03; 0.05 and 0.07), were successfully synthesized by using sol–gel method, and then they were characterized by X-ray diffraction, scanning electron and vibrating sample magnetometer (VSM). X-ray diffraction analysis of two series samples showed the formation α-Fe₂O₃ nanoparticles, accompanied by two phases iron spinels, CoFe₂O₄ and NiFe₂O₄. In addition, the variations in grain size were observed for both two series. The observation by scanning electron microscopy reveals a change in the morphology of the grains of all the samples doped, which confirm the cobalt and nickel effect on the morphology of iron oxide nanoparticles. Magnetic measurements which were measured by VSM showed significant magnetic parameters such as coercivity and magnetization besides the ferromagnetic behavior of both two series doped with Cobalt and Nickel.

     

Combined Effect of Magnetic Field and Rotation on Thermosolutal Instability of a Compressible Fluid in Porous Medium

The combined effect of magnetic field and rotation on thermosolutal instability of a compressible fluid in porous medium is considered. The system is found to be stable for (C_p/g)β < 1 where C_p, β, and g stand for specific heat at constant pressure, uniform adverse temperature gradient, and acceleration due to gravity, respectively. The stable solute gradient, magnetic field, and rotation introduce oscillatory modes in the system for (C_p/g)β > 1, which were nonexistent in their absence. For stationary convection, the stable solute gradient and rotation have a stabilizing effect on the system for (C_p/g)β > 1. In the presence of rotation, the magnetic field has a stabilizing (or destabilizing) effect, and the medium permeability has a destabilizing (or stabilizing) effect under certain condition, whereas in the absence of rotation, the magnetic field and rotation have stabilizing and destabilizing effects for (C_p/g)β > 1, respectively, on the system. The sufficient conditions for the existence of overs-lability are obtained.     

混合邻间对甲酚制备化工中间体的工艺研究

以介孔分子筛为催化剂,催化烷基化混合邻间对甲酚制备6-叔丁基邻甲酚、6-叔丁基间甲酚、2-叔丁基对甲酚混合液,并精馏获得三种叔丁基甲酚纯品。考查了催化剂用量、异丁烯用量、反应温度等反应条件对烷基化反应的影响,确定了最佳工艺条件。结果表明,催化剂为三混甲酚用量的2.0%(质量),异丁烯用量与三混甲酚用量之比为1.05∶1(摩尔比),最佳反应温度为95℃的反应条件下,三混甲酚的总转化率达到96.25%以上,反应液中目标产品含量达94.67%,产品选择性可达98.36%。精馏后,6-叔丁基邻甲酚、6-叔丁基间甲酚、2-叔丁基对甲酚三种产品的质量含量分别为99.75%、99.57%、99.54%。整个工艺过程安全环保,成本低,能耗低,收益高。     

磁场环境下不同质子酸掺杂对聚苯胺结构和电导率的影响

在磁场环境下,采用微乳液合成法,研究了质子酸种类、氧化剂和乳化剂种类等因素对苯胺聚合反应及产物性能的影响,并通过红外光谱、粒径分析、腐蚀电位等表征了PAn性能与结构。实验结果表明：磁场对苯胺聚合的影响是正向的。     

Triaxial Crystalline Orientation of MgTi2O5 Achieved Using a Strong Magnetic Field and Geometric Effect

Tailoring the crystallographic orientation in ceramics is very useful for improving their properties. We reported that the colloidal processing in a strong magnetic field was able to control the crystallographic orientation even in diamagnetic ceramics. In this process, a strong magnetic field is applied to the particles in a stable suspension. The orientation of the crystal depends on the axis having easy magnetization and one‐dimensional orientation can be controlled. In this study, our concept is that control of multiaxial crystalline orientation in ceramics by using both anisometric particles and a magnetic field. The control of the triaxial orientation was achieved by tape casting of rod‐like MgTi₂O₅ particle in a magnetic field. The b‐axis was aligned by the magnetic field, and the a‐axis was aligned by the geometric effect and shear stress during tape casting.     

Effect of Chemical Work on the Flame Temperature and Burning Rate of an H2/O2Mixture

Combustion, Explosion, and Shock Waves - A general model describing the combustion of mixed gases is proposed, which accounts for the chemical work and assumes a single chemical reaction. An energy...     

Effect of Coal Type and Residence Time on the Submicron Aerosol Distribution from Pulverized Coal Combustion

Three types of pulverized coal were burned in a laboratory furnace under various combustion configurations. Pulverized samples of Utah bituminous, Beulah (North Dakota) lignite, and Texas lignite coals were burned at a rate of 2.5 kg/hr in a laboratory furnace. Aerosol size distributions were measured at various positions within the convection section, and temperature and gas compositions were measured throughout. The evolution of the submicron particle size distribution within the convection section for the three coals was similar, although the location of the initial particle mode at the convection section inlet varied with coal type. While staged combustion of Utah bituminous coal had a variable effect on the volume of submicron aerosol produced, staged combustion of the lignites caused a definite increase in the submicron aerosol volume. Vapor enhancement due to a localized reducing atmosphere, which would effect coals of higher ash volatility, is thought to explain this behavior.     

羟基乙叉二膦酸与磁场对碳酸钙协同阻垢作用研究

通过静态和动态实验研究了单独使用羟基乙叉二膦酸(HEDP)及其与磁场的协同阻垢性能.利用扫描电子显微镜表征了水垢试样中的碳酸钙晶型.静态实验结果表明:磁场与HEDP的协同作用可提高对Ca2+的螯合作用.在HEDP的浓度为0.5 mg·L-1,磁场与HEDP协同作用时,静态阻垢率比HEDP单独作用时可提高28%.动态实验结果表明:磁场与HEDP具有较好的协同增效作用.在HEDP的浓度为2.0 mg·L-1,磁场与HEDP协同作用时,动态阻垢率比HEDP单独作用时提高10%以上.SEM分析结果表明:HEDP可使碳酸钙晶型完全扭曲,磁场与HEDP协同可使晶体更加细小分散、扭曲现象更加明显.     

The Effect of Orientation on the Mobility and Dynamic Shape Factor of Charged Axially Symmetric Particles in an Electric Field

The mobility of a nonspherical particle is a function of both particle shape and orientation. Thus, unlike spherical particles, the mobility, through its orientation, depends on the magnitude of the electric field. In this work, we develop a general theory, based on an extension of the work of Happel and Brenner (1965), for the orientation-averaged mobility applicable to any axially symmetric particle for which the friction tensor and the polarization energy are known. By using a Boltzmann probability distribution for the orientation, we employ a tensor formulation for computing the orientation-averaged mobility rather than a scalar analysis previously employed by Kim et al. (2007) for nanowires. The resulting equation for the average electrical mobility is much simpler than the expression based on the scalar approach, and can be applied to any axially symmetric structures such as rods, ellipsoids, and touching spheres. The theory is applied to the specific case of nanowires and the experimental results on the mobility of carbon nanotubes (CNT). A set of working formulas of additional mobility expressions for nanorods and prolate spheroids in the free molecular, continuum, and transition regimes are also presented. Finally, we examine the expression of dynamic shape factor common in the literature, and propose a clearer definition based on the tensor approach. Mathematica codes for the electrical mobility evaluations for five cases are provided in the Supplemental Information.

Copyright 2012 American Association for Aerosol Research     

Particle Size Effect on the Crystal Structure of Y2O3 Particles Formed in a Flame Aerosol Process

Y₂O₃ is a material with wide applications. Its cubic and monoclinic polymorphs have significantly different mechanical and optical properties. The flame aerosol technique offers unique advantages in the synthesis of Y₂O₃ particles, but it also faces the challenge of phase control for Y₂O₃. One possible strategy for Y₂O₃ phase control is to utilize the particle size effect that causes the formation of the monoclinic phase at atmospheric pressure. In this study, the particle size effect on crystal structure was experimentally investigated for Y₂O₃ particles synthesized in a high-temperature flame aerosol process. A critical particle diameter of approximately 1.5 μm was found by single-particle electron diffraction. At the critical diameter, the probability is 50% for a particle to be either cubic or monoclinic. Particles significantly smaller than the critical diameter were all monoclinic, while those significantly larger were all cubic. The critical diameter was interpreted using an analysis that involves the free energy of a particle, which includes the bulk Gibbs free energy and the surface energy.     

磁场影响铝的阳极氧化膜的形成与封闭的研究

用浸酸失重法研究了磁场对铝的阳极氧化膜的形成及其封闭处理的影响,磁场可以增大膜胞,减小氧化膜的空隙率,提高氧化膜常温封闭和水解盐封闭的封孔度,改善氧化膜的封闭质量。     

11%氧乐·酮乳油防治麦蚜、小麦白粉病试验

田间试验结果表明，１１％氧乐·酮乳油防治麦蚜、小麦白粉病，优于氧乐果对麦蚜的防效，对白粉病的防效与三唑酮相当，并且具有用药成本低，劳动强度小，一次施药兼治病虫害的优点，是防治麦田病虫的较好药剂     

Effect of Release of Combustible Volatile Components from the Disperse Phase on Self-Ignition of a Gas–Particle Mixture

The paper presents a physicomathematical model for self-ignition of a gas-particle mixture whose disperse phase reacts heterogeneously with the gas-phase oxidizer and releases volatile components, which also react with the gas-phase oxidizer. The model takes into account the effect of Stefan flow of the volatiles and gaseous products of the heterogeneous reaction on the heat and mass transfer between the particles and the gas phase. Four regimes of self-ignition of the gas-particle mixture were established: ignition of individual particles (without interaction) ignition due to the heterogeneous reaction during self-ignition of a particle aggregate; self-ignition due to heat release from the gas-phase reaction of the volatiles released; self-ignition under the mutual effect of the gas-phase and heterogeneous reactions. The paper proposes a method for determining the parameter of the disperse phase in which different self-ignition regimes are observed. Analytical formulas for the self-ignition delay period of the gas-particle mixture are derived for each regime and compared with numerical results. The effect of Stefan flow on the self-ignition of the gas-particle mixture is analyzed. Key words: gas–particle mixture, volatiles, Stefan flow, self-ignition.