Relation between Electrical Mobility,Mass, and Size for Nanodrops 1–6.5 nm in Diameter in Air

A large number of data on mobility and mass have been newly obtained or reanalyzed for clusters of a diversity of materials, with the aim of determining the relation between electrical mobility (Z) and mass diameter d _m = (6m/ π ρ ) ^1/3 (m is the particle mass and ρ the bulk density of the material forming the cluster) for nanoparticles with d _m ranging from 1 nm to 6.5 nm. The clusters were generated by electrospraying solutions of ionic liquids, tetra-alkyl ammonium salts, cyclodextrin, bradykinin, etc., in acetonitrile, ethanol, water, or formamide. Their electrical mobilities Z in air were measured directly by a differential mobility analyzer (DMA) of high resolution. Their masses m were determined either directly via mass spectrometry, or assigned indirectly by first distinguishing singly (z = 1) and doubly (z = 2) charged clusters, and then identifying monomers, dimers, … n-mers, etc., from their ordering in the mobility spectrum. Provided that d _m > 1.3 nm, data of the form d _m vs. [z(1+m _g /m) ^1/2 /Z)] ^1/2 fall in a single curve for nanodrops of ionic liquids (ILs) for which ρ is known (m _g is the mass of the molecules of suspending gas). Using an effective particle diameter d _p = d _m + d _g and a gas molecule diameter d _g = 0.300 nm, this curve is also in excellent agreement with the Stokes-Millikan law for spheres. Particles of solid materials fit similarly well the same Stokes-Millikan law when their (unknown) bulk density is assigned appropriately.     

Characterization of a Vortex Shaking Method for Aerosolizing Fibers

Generation of well-dispersed, well-characterized fibers is important in toxicology studies. A vortex-tube shaking method is investigated using glass fibers to characterize the generated aerosol. Controlling parameters that were studied included initial batch amounts of glass fibers, preparation of the powder (e.g., preshaking), humidity, and airflow rate. Total fiber number concentrations and aerodynamic size distributions were typically measured. The aerosol concentration is only stable for short times (t < 10 min) and then falls precipitously, with concomitant changes in the aerosol aerodynamic size distribution; the plateau concentration and its duration both increase with batch size. Preshaking enhances the initial aerosol concentration and enables the aerosolization of longer fibers. Higher humidity strongly affects the particle size distribution and the number concentration, resulting in a smaller modal diameter and a higher number concentration. Running the vortex shaker at higher flow rates (Q > 0.3 lpm), yields an aerosol with a particle size distribution representative of the batch powder; running the vortex shaker at a lower aerosol flow rate (Q ～ 0.1 lpm) only aerosolizes the shorter fibers. These results have implications for the use of the vortex shaker as a standard aerosol generator.

Copyright 2013 American Association for Aerosol Research     

Fluorine‐Free Synthesis of Well‐Dispersed Hollow TiO2 Spheres via Ostwald Ripening: Process,Mechanism, and Photocatalytic Performance

Well‐dispersed hollow TiO₂ spheres were synthesized via Ostwald ripening through a fluorine‐free solvothermal process in a n‐PrOH/H₂O mixed solvent. Several commonly used acids, such as HNO₃, HCl, and H₂SO₄, were found to be effective as the ripening‐directing agent to replace the highly corrosive HF, and the hollow TiO₂ sphere size could be modulated by varying the reactant concentrations. The effects of the solvents and reactants were explored in details, which demonstrated that four important criteria existed in this fluorine‐free process to create well‐dispersed hollow TiO₂ spheres, including the utilization of n‐PrOH/H₂O mixed solvent, certain degree of acidity, coexistence of different acids, and the existence of SO₄^2? in the reaction solution. After calcination for a better crystallization, these hollow TiO₂ spheres were composed of pure anatase phase, and had a good photocatalytic degradation performance on RhB under UV illumination.     

Selective oxidation of HMF to DFF using Ru/γ-alumina catalyst in moderate boiling solvents toward industrial production

Selective oxidation of 5-hydroxymethyl-2-furfural (HMF) to 2,5-diformylfuran (DFF) toward industrial production was studied over Ru supported γ-alumina catalyst using molecular oxygen as an oxidant. From the solvents screening, considering recyclability after reaction, toluene was found to be the best solvent and gave maximum conversion of 99% with 97% DFF selectivity at 130 °C and 40 psi O₂ pressure. Catalyst was washed with NaOH solution of pH = 12 to remove the adsorbed polymer impurities and then reused up to 5 cycles. The product could be purified by simple evaporation of the solvent, which could add advantage for industrial process.     

以钙色素线性扫描极谱法测定血清白蛋白的研究及分析应用

在pH4．0的Britton-Robinson(B—R)缓冲溶液中钙色素与蛋白质能够发生相互作用,生成一种非电活性的超分子复合物,使钙色素在溶液中的游离浓度降低,从而造成钙色素于-0．31V处产生的二阶导数极谱还原峰电流下降而峰电位不变。在优化的结合反应条件和电化学测定条件下,峰电流的下降值同人血清白蛋白(HSA)的浓度在4．0—70．0mg／L范围内呈线性关系,其线性回归方程为△Ip““／nA=69．93c(mg／L)-192．90,(r=0．992)。将该方法应用于实际人血清样品的测定,结果与经典的考马斯亮蓝G-250光度法一致,回收率令人满意。此方法还可应用于牛血红蛋白、卵清白蛋白等蛋白质的测定。     

淹没深度对三自由度波能浮子获能的影响

为明确浮子淹没深度对三自由度浮子装置获能的影响,提出漂浮式与淹没式两种浮子模型,计算并比较在不同淹没深度和波浪条件下浮子的获能特性。浮子模型具有纵荡、垂荡与纵摇3个运动自由度。浮子选用直立圆柱体浮子。淹没深度分别设置为其高度的0.5、1.0、1.5与2.0倍,质量相同。漂浮式浮子模型作为对照,基于线性势流理论与边界元方法,建立浮子水动力学模型,计算浮子水动力学参数及运动响应,并采用线性能量转换(power take-off, PTO)系统阻尼,计算并对比浮子在最优PTO阻尼下的平均输出功率,分析淹没深度对浮子获能的影响。研究结果表明,增大淹没深度可以减小浮子的波浪激励力和平均输出功率。对于三自由度浮子,漂浮浮子在低频波浪下获能特性较好,而具有较小淹没深度的浮子在高频波浪下性能更优。     

废印刷线路板回收处理技术研究

全面详实的介绍了废印刷线路板的污染现状、对人体及环境的危害。总结了废印刷线路板脱漆、拆解、破碎及各种传统和新型的回收处理技术。文章为回收利用废印刷线路板提供了广阔的思路。需要利用各种技术,互相结合,才能最终实现废印刷线路板的资源化处理。     

SBA-15 mesoporous silica modified with rhodium by MDD method and its catalytic role for N<Subscript>2</Subscript>O decomposition reaction

SBA-15 mesoporous silicas modified with rhodium were studied as catalysts for the N₂O decomposition reaction. Rhodium was deposited on SBA-15 by the Molecular Designed Dispersion (MDD) method using Rh(acac)₃ as a precursor of active phase. The same method was used for the deposition of Cu, Fe, Al and Ti. The SBA-15 support modified with metals were characterized with respect to metal loading (EPMA), structure (XRD), texture (BET), morphology (SEM), Rh dispersion (oxygen chemisorption), surface acidity (pyridine adsorption) and chemical nature of introduced copper and iron species (UV–vis-DRS). The rhodium-containing SBA-15 samples were found to be active catalysts for the N₂O decomposition reaction. Deposition of Al on the Rh-loaded catalyst increased its activity. An opposite effect was observed for the samples modified with Cu and Fe.