湿化学法合成单分散陶瓷超微粉体的基本原理

通过综述分析超微粒子的形核与长大过程及团聚的成因，介绍了湿化学合成单分散陶瓷超微粉体的基本原理；给出了粒径分布，颗粒形状和团聚的影响因素及相应的控制措施。     

平均粒径大小及磁性能不同的Fe3O4超微粉的制取

本文研究了以共沉淀法和沉淀氧化法获得平均粒径大小及磁性能不同的Fe_3O_4超微粉的可能性。实验表明:以不同的共沉淀反应条件所制取的Fe_3O_4超微粉平均粒径及磁性能变化不大,而由改变沉淀氧化反应条件则可制取平均粒径及磁性能显著不同的各种Fe_3O_4超微粉。     

硅溶胶性能指标的分析与测试

本文分析了与硅溶胶性能密切相关的粘度、粒径、稳定性和PH值等几个重要性能指标的影响因素，并汇总了这几个指标的现有测定方法。     

ZrO2基纳米超微粉生产技术与粉体特性

介绍了化学共沉淀一凝胶法制备ＺｒＯ２基纳米超微粉新技术，该法利用廉价原料和简单工艺过程可工业化生产杂质总量低于０．１ｗｔ％平均粒径为１０ｎｍ，分散性良好，粒度分布极窄的高纯ＺｒＯ２或ＺｒＯ２基纳米超微粉，对所制粉体的相结构和烧结特性也进行了研究。     

Y2O3添加剂对ZrO2超微粉体性质的影响

添加0-6mol%Y2O3的ZrO2超微粉体由化学共沉淀法制备，系统地研究了添加剂对粉体粒子粒径，表面性质和团聚状态的影响，结果表明，添加Y2O3组元，使制备的ZrO2粉体粒子粒径减小，对粒子的长大趋势可起到抑制作用，但加剧了粉体粒子的团聚，团聚体颗粒变大，团聚强度升高，随着组元添加量的增多，作用加剧。     

表面活性剂对相反转法制备金属颗粒的影响

采用相反转悬浮液体系中不同表面活性剂同步修饰的方法制备超细低熔点金属颗粒,研究阳离子和阴离子表面活性剂对金属颗粒的影响。通过沉降实验观察不同表面活性剂修饰的金属颗粒在水中的分散及稳定性,并采用激光粒度仪、扫描电镜对低熔点金属颗粒的粒径和形貌进行表征分析。结果表明:表面活性剂的种类对制备低熔点金属颗粒有重要的影响,其中阴离子表面活性剂的效果最好。对几种阴离子表面活性剂的研究表明:油酸钠的作用最明显,其浓度大小对低熔点金属颗粒的粒径、形貌和分散效果有显著的作用。采用质量分数为1%的油酸钠水溶液可制备出分散稳定、粒径分布窄和球状的超细低熔点金属颗粒,平均粒径为0.343μm。     

影响粉体粒度测定准确性的研究

讨论了用NSKC - 1A离心式光透射粒度测定仪进行粉体材料粒径测定影响测定结果的几个因素 :在预分散时 ,要根据粉体的硬度和大致粒径范围 ,合理确定分散设备或设备组合 ;分散剂的种类和离心开始区段的设置对粒径分布影响很大 ;在充分分散的基础上 ,分散剂的量和分散时间对粒径影响不大     

溶胶凝胶快速热解法制务ZrO2超细粉体

采用溶胶凝胶快速热解法制备了ＺｒＯ２超微粉体，详细考究了各种制备参数对胶凝时间以及样品性质的影响规律。结果表明：胶凝时间受溶液中脲含量及胶凝温度影响显著；而热解温度、胶溶剂用量、胶凝温度和溶液组成对样品的性状，比表面积、孔分及粒径均有不同程度的影响。     

金属注射成形过程中的粉末堆积问题

本文综述了金属注射成形中颗粒及粉末堆积的研究状况，对双组元球形颗粒的数学模型的理论基础、基本概念和方法作了比较详细的介绍和分析，并扼要介绍了连续粒径分布的颗粒堆积和影响粉末—粘结剂的装载量大小的因素。     

粉末粒度对FeAl金属间化合物多孔材料孔结构的影响

研究了粉末粒度对FeAl金属间化合物多孔材料孔结构的影响.研究表明,当粉末粒径在60μm以上时,随着粉末粒径的增加,FeAl金属间化合物多孔材料的总孔隙度和开孔隙度变化不大,即粉末粒度不是决定FeAl多孔材料孔隙度的主要因素;粉末粒度是决定FeAl金属间化合物多孔材料最大孔径的主要因素,在18～125μm的粒度范围内,多孔体最大孔径与粉末粒径之间严格遵循dm=0.4·d.的直线变化规律.     

Measurements of ultrafine particle concentrations and size distribution in an iron foundry

The number and surface area concentration of ultrafine particles in an iron foundry is of interest as freshly generated ultrafine particles are produced by metal melting, pouring and molding processes. This study measured the number and surface area concentrations of ultrafine particles and their size distributions in an iron foundry using a scanning mobility particle sizer (SMPS). The 10-100 nm ultrafine particle number concentrations (NC(0.01-0.1)) and surface area concentrations (SC(0.01-0.1)) measured at the iron foundry were 2.07 x 10(4) to 2.82 x 10(5)particles cm(-3) and 67.56 to 2.13 x 10(3)microm(2)cm(-3), respectively. The concentrations changed dramatically depending on on-site manufacturing conditions. The NC(0.01-0.1) levels in the iron foundry were approximately 4.5 times higher on average compared with those in the outdoor ambient environment. These measurement results indicate that the presence of extra particles in the workplace air is within the ultrafine range. Additionally, the analytical results suggest that the number mode diameter can be used to estimate the SC(0.01-0.1) levels using the NC(0.01-0.1) levels. Moreover, the ultrafine particle number mode diameter was found to be about 46.1 nm in the iron foundry.     

三七超微粉体与细粉、不同目数范围粉体的粒度分布和显微形貌特征的比较

通过比较三七超微粉体、细粉(三七常规饮片)以及不同目数范围粉体(三七细粉经多次筛分得到的粉体)在粒度分布、显微形貌特征方面的差异,探讨了超微粉碎技术应用于中药三七加工的优势。应用激光粒度分析仪对三七超微粉体与细粉、不同目数范围粉体的粒度及其分布进行表征,观察其显微形貌特征。粒度分布测试和显微形貌观察的结果表明,超微粉粒度分布在0.30～24μm,大部分粉体达到了10μm以下,呈对称的单峰分布,引起团聚的作用力为各种表面力,说明超微粉体均匀度高质量易控。三七细粉及不同目数范围的粉体粒度分布范围在2～190μm,分布不对称,引起团聚的作用力为重力的等质量力,说明其均匀度差,质量难以控制。     

Detection of negative ions from individual ultrafine particles

Aerosol mass spectrometers can be used to classify individual airborne particles on the basis of chemical composition. While positive ion mass spectra are normally used to characterize ultrafine particles (defined here as particles smaller than 200 nm in diameter), negative ion mass spectra can provide complementary information. To effectively utilize the negative ion mass spectra of ultrafine particles, it is important to understand biases in the formation and detection of negative ions. It is found that the intensity of negative ions is generally less than that of positive ions, due to the creation of electrons in the ablation process that must react to form negative ions. The ablation efficiency, defined as the probability that an ablated particle produces a detectable ion signal, exhibits both size and composition dependencies. The ablation efficiency for detection of negative ions follows the same trends as the ablation efficiency for the detection of positive ions: sodium chloride and ammonium nitrate have higher ablation efficiencies than oleic acid, and the ablation efficiency decreases with the particle diameter. The ablation efficiency of negative ions is less than or equal to the ablation efficiency of positive ions, and the relative difference increases as the particle diameter decreases. Pure ammonium sulfate particles exhibit an ablation efficiency too low to be measured in the present experiments. However, trace amounts of sulfate in mixed-composition particles can be readily detected in the negative ion mass spectra.     

Preparation of Pt-Ru-Ni ternary nanoparticles by microemulsion and electrocatalytic activity for methanol oxidation

Ternary platinum-ruthenium-nickel nanoparticles are prepared by water-in-oil reverse microemulsions of water/Triton X-100/propanol-2/cyclohexane. Nanoparticles formed in the microemulsions are characterized by transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffractometry (XRD), energy dispersive X-ray analysis (EDX). These resulting materials showed a homogenous alloy structure, the mono-dispersion and an average diameter of 2.6 ± 0.3 nm with a narrow particle size distribution. The composition and particle size of ternary Pt-Ru-Ni nanoparticles can be controlled by adjusting the initial metal salt solution and preparation conditions. Pt-Ru-Ni ternary metallic nanoparticles showed an enhanced catalytic activity towards methanol oxidation compared to Pt-Ru bimetallic nanoparticles.     

Synthesis and growth mechanism of ThO2–W–Mo alloy nanocomposite powder

Nanocomposite ultrafine powders of thorium oxide and tungsten molybdenum alloy were prepared by arcing between a pure molybdenum cathode and a thoriated tungsten anode under an argon–hydrogen atmosphere. The microstructure, morphology and chemical analyses of the ultrafine powders were examined by X-ray diffraction, transmission electron microscopy and associated techniques. The powders are composed of thorium oxide single-crystalline nano-grains decorated by tungsten molybdenum alloy particles which are crystallized in a metastable A15 structure. Two morphologies were observed: octahedra and needle-like particles. Every octahedral particle bigger than 15 nm had on each corner a metallic grain generally less than 8 nm in size. The needles had a length below 600 nm and their width to length ratio ranged from 1/3–1/15. They all presented on one of their ends a metallic particle which was comparable in size to the needle width. Other smaller particles (<10 nm) may be encountered along the edges. The metallic particles were found to be epitaxial on the thorium oxide grains according to the relation: (100) [011]_ThO2∥(100) [011]_A15. The extensive study of the microstructural and morphological properties of the powders leads us to suggest a growth mechanism of the nanocomposite particles. This revised version was published online in November 2006 with corrections to the Cover Date.     

超细钨粉的制取及其氧化钨原料和钨粉的粒度测量

选取相成分单一的氢钨青铜（H0.33WO3）、铵钨青铜（NH4）0.5WO3）和紫钨（WO2.72）作为原料，研究钨原料对制取超细钨粉的影响，对氧化钨原料和超细钨粉的粒度测量方法作了比较，研究结果表明，紫钨由于有着特殊的结构，其制得的钨粉细而均匀，分散性好，可适合于做微晶硬质合金的原料。氧化钨原料的粒度（伪同晶颗粒尺寸，即二次颗粒）测量，推荐使用激光衍射法，超细钨粉粒度（一次颗粒）的炉前测量，BET法测球形当量径相当理想。     

岛津离心粒度分析仪测量模式的比较

分别对沉降式离心粒度分析仪的自然沉降与混合沉降以及混合沉降与离心沉降进行了比较试验,结果表明,当最大粒径值达到混合沉降测量模式的上限,即临界粒径值时,应对两种测量模式进行比较试验,才能从中选出最佳测量模式;对超细粉体而言,4μm以下的颗粒才适合选用离心沉降模式,最大粒径大于4μm时,应用混合沉降模式测量。     

Development of electric virtual impactor with variable sampling particle size range

An electric virtual impactor with a capability of sampling fine and ultrafine particles was developed and its performance was evaluated both numerically and experimentally. The electric virtual impactor was provided with metallic electrodes, to which electric voltage in the range of 75–9000 V was applied for creating an electric field within the virtual impactor. Particle electric mobility was utilized to sample ultrafine particles at the major outflow section, while particle inertia was employed to collect fine particles at the minor outflow section. Silver nanoparticles with known charge level and Arizona test dust were used to experimentally validate the performance of the electric virtual impactor. Numerical and experimental outcomes agreed well with each other. The upper cutoff size of the electric virtual impactor was fixed at about 2.6 μm, while the lower cutoff size varied from 7 nm to 110 nm depending on the applied electric voltage. As a result, the proposed electric virtual impactor was able to sample both fine and ultrafine particles of a desired particle size range.     

Research on ultrafine particle size measurement using small amounts of data

The paper puts forward a new method of ultrafine particle size measurement using small amounts of data of a dynamic light-scattering signal, and establishes an arithmetic model of the measurement by wavelet package transform. First, through the wavelet package transform, the ultrafine particle dynamic light-scattering signals were decomposed into multifrequency bands. Then, the noise of signals of different frequency bands were removed and the power spectrum of the wavelet packet coefficients of each frequency band was calculated. Finally, the ultrafine particle size distribution information could be deduced from inversing the power spectrum. The standard polystyrene particles of 100, 300, and 400 nm were measured using this method, and the inversion results indicated that this method can effectively remove noise and improve the accuracy of particle size measurement using small amounts of data.