氧化钨原料对钨粉粒度的影响

不同的氧化钨原料明显地影响到钨粉的粒度。因此，正确地选择和生产氧化钨原料在钨粉生产中是非常重要的。用氢还原紫色氧化钨可高效地获得细钨粉。     

激光粒度分布仪检测细碳化钨粉方法

随着微细、超细甚至纳米级钨粉、碳化钨粉的生产,粉末粒度分布的检测方法也随之发生重大变革,从传统的沉降法、显微镜法等逐步演化成了现代的激光粒度分布仪检测方法,然而现在的激光粒度分布仪检测方法仍然存在一些问题,尤其是检测不稳定,检测出较多的粗大颗粒或团聚问题。笔者对激光粒度分布仪的检测方法进行了摸索,找到其检测不稳定的原因,并提出了检测稳定的方法。     

AH法制备钨粉过程中钨粉粒度的控制研究

研究了AH法制备钨粉中氢还原过程的工艺参数与钨粉平均粒径之间的关系。结果表明还原温度、装舟量和保温时间与钨粉平均粒径呈一定的函数关系。实验数据经线性回归处理,获得预测和控制钨粉平均粒径的回归方程。     

WC粉末粒度与形貌对硬质合金中WC晶粒度、晶粒形貌与合金性能的影响

探讨了粗颗粒与特粗颗粒两种粒度级别以及平面化表面与球化表面两种形貌特征的WC原料对WC-Co硬质合金中WC晶粒度、晶粒形貌以及合金性能的影响。结果表明,分别采用费氏粒度为11.4￣13.4μm,与22.0￣28.3μm两种粒度级别的WC粉末为原料制备合金,尽管两种合金硬度之间存在明显差别,但是两种合金的晶粒度相差很小,在4.0￣4.3μm之间,同属一种粒度级别。WC原料的原始形貌对合金中WC晶粒形貌与合金性能影响很小,碱金属掺杂原料制备的合金中WC晶粒结晶完整性相对较差。因此,高纯原料是制备高性能硬质合金的基础。     

提高钨制品粉末平均粒度准确性的实践

采用WLP-205平均粒度测定仪,通过增重、减重及烘干的方法,提高钨制品粉末平均粒度测定结果的准确性。     

Wavelet Analysis of Soil Mass Images for Particle Size Determination

A method for determination of average grain size from images of fairly uniform particle size soil masses is presented. The procedure utilizes two-dimensional wavelet decomposition of gray scale images. Earlier attempts to quantify grain sizes based on the statistics of co-occurrence matrices suffered from dependence on the illumination intensity and soil color. By normalizing the energy distribution from wavelet decomposition the effects of these previously problematic factors have been eliminated. A general relationship between the center of area beneath the normalized energy distribution and the perceived particle size in pixels per diameter (PPD) is established. A sample problem demonstrates that the proposed wavelet decomposition method provides accurate grain sizes for a wide range of magnification levels as long as the resulting PPD is between approximately 1 and 50.     

稀土草酸盐的溶解度与稀土氧化物粒度之间的关系及粒度控制

通过稀土草酸盐溶液度与粒度的关系。探索控制稀土氧化物粒度的途径。实验测定了几种稀土草酸盐在草酸沉淀母液中的溶解度，并对不同草酸沉淀条件下获得的单一稀土氧化物的粒度进行比较。得到了其氧化物粒度与草酸盐溶解度之间的关系，通过对Y2O3，Eu2O3,Gd2O3,Dy2O3的粒度数据进行分析对照，提出了控制其粒度的途径。     

Particle Size Distribution in Highway Runoff

Particles in highway runoff contain various sorbed pollutants, and many best management practices (BMPs) are selected for particle removal efficiency, which makes particle size distribution a crucial BMP design parameter. Particles between 2 and 1,000?μm in diameter were quantified for three rainfall events during the 2002–2003 rainy season at three highway sites in west Los Angeles. Rainfall, runoff flow rate, and a large suite of water quality parameters were also measured. An experimental protocol was developed for bottle cleaning, sample storage, and mixing that provided repeatable results. Particle aggregation occurred which required samples to be analyzed in less than 6?h; the concentration of small particles decreased with a corresponding increase in the concentration of larger particles in stored samples. The particle concentration decreased as the storm progressed and the number of large particles decreased more rapidly than the total number of particles. Particles demonstrated a strong first flush. On average, 40% of the particles were discharged in the first 20% of the runoff volume.     

库尔特激光粒度分布仪在测定钽铌复合物粒度分布中的应用

文章介绍了应用库尔特激光粒度分布仪测定钽铌复合物粒度分布的方法。钽铌复合物颗粒均匀分散在二次去离子水中,以一定的流速通过激光束。衍射光经透镜被光电探测器接收转化为电信号,由此测出颗粒的粒度分布,并讨论了应用中的经验。该方法容易建立,精密度高,能够给出多种粒度分布结果以及参数,非常适合生产过程中的应用。     

氧化铝种分过程的粒度分析

用粒数衡算的方法对氧化铝生产种分过程氢氧化铝粒度分布进行了分析,通过计算得到各种分槽产品氢氧化铝的晶体生长速率和净粒子生成数,由此推测了氧化铝实际生产过程中成核、生长、附聚过程发生的位置及生产条件。并分析了晶体生长速率与种分进行时间之间的关系。     

Synthesis of FeCu Nanopowder by Levitational Gas Condensation Process

Condensation from the vapor state is an important technique for the preparation of nanopowders. Levitational gas condensation is one such technique that has a unique ability of attaining steady state. Here, we present the results of applying this technique to an iron-copper alloy (96Fe-4Cu). A qualitative model of the process is proposed to understand the process and the characteristics of resultant powder. A phase diagram of the alloy system in the liquid–vapor region was calculated to help understand the course of condensation, especially partitioning and coring during processing. The phase diagram could not explain coring in view of the simultaneous occurrence of solidification and the fast homogenization through diffusion in the nanoparticles; however, it could predict the very low levels of copper observed in the levitated drop. The enrichment of copper observed near the surface of the powder was considered to be a manifestation of the lower surface energy of copper compared with that of iron. Heat transfer calculations indicated that most condensed particles can undergo solidification even when they are still in the proximity of the levitated drop. It helped us to predict the temperature and the cooling rate of the powder particles as they move away from the levitated drop. The particles formed by the process seem to be single domain, single crystals that are magnetic in nature. They, thus, can agglomerate by forming a chain-like structure, which manifests as a three-dimensional network enclosing a large unoccupied space, as noticed in scanning electron microscopy and transmission electron microscopy studies. This also explains the observed low packing density of the nanopowders.     

不同粒度高比容钽粉性能分析

为了了解不同粒度钽粉的性能变化,以便更好地指导生产,使用拍打式打击筛将120 000μFV/g钽粉分成不同粒度范围的产品进行化学杂质含量、物理性能、电气性能各项分析。不同粒度范围的钽粉的化学性能、电气性能相当,因为物理性能的不同,压制性能不同。     

表面改性剂在溶胶-凝胶法制备纳米氧化锌中的应用

以草酸与二水合醋酸锌为原料,采用溶胶-凝胶法制备纳米氧化锌。探讨了不同表面改性剂及其用量对氧化锌粉体的粒度、形貌及分散性的影响。利用SEM、TG、IR、XRD对氧化锌粉体进行了表征。结果表明十二烷基硫酸钠和聚乙二醇6000能有效地分散颗粒和控制颗粒的团聚。制得粒径在80 nm左右、纯度高、晶型良好、分散性好的纳米氧化锌。     

Particle Size Distribution of Lunar Soil

Meteorite impact on the lunar surface produces a consistent, broadly graded soil. In this note, the geotechnical and geological systems are compared to characterize lunar soil. In geotechnical terms, the lunar soil particle size distribution is described as sandy silt/silty sand, well-graded. In geologic terms, it is described as very fine sand, very poorly sorted, nearly symmetrical, and mesokurtic. Because of its broad particle size distribution, lunar soil may be internally erodible.     

Magnetite Particle Size Distribution and Pellet Oxidation

Oxidation of magnetite pellets is commonly performed to prepare strong pellets for ironmaking. This article presents a contribution to quantitative understanding of fundamental pellet oxidation kinetics, based on measured oxidation kinetics of magnetite particles and pellets. The commonly observed “plateau” oxidation behavior is confirmed to be consistent with the effect of very large differences in magnetite particle sizes in the concentrate from which pellets are produced. The magnetite particles range in size from less than a micron to several tens of a microns; changing the size distribution by inert sintering of pellets decreases both the plateau level of oxidation and the specific surface area, in ways that are compatible with an assumed Rosin-Rammler magnetite particle size distribution.     

颗粒粉碎能耗与粒度的关系

基于弹性力学和断裂力学理论,探讨了颗粒粉碎的机理,认为颗粒粉碎是原生裂纹失稳扩展的结果,得出粉碎能耗与原生裂纹长度成反比的结论,并认为原生裂纹长度随粒度减小而减小.最后导出了普遍适用的粉碎能耗与粒度关系式.     

Particle Size Distribution and Metal Content in Street Sediments

Sediments that had accumulated during the winter season, and which were left at the surface when the snow had melted, were studied with regard to physical and chemical characteristics. The investigation was carried out in the city of Lule?, which is located in northern Sweden. Sediment samples were collected in the city center and in a housing area at streets with different traffic loads. The results showed that the amount of the sediments at a street surface was evidently affected by the presence of a sidewalk. The street with a sidewalk accumulated much more sediment than the street without a sidewalk did. Both of these streets had approximately the same traffic load. The sidewalk also affected the particle size distribution. The content of heavy metals in the sediments varied with the traffic load and the area type. The highest concentration of cadmium, lead, and zinc was found in the street with the highest traffic load.     

Synthesis of ZnO：Dy Nanopowder and Photoluminescence of Dy^3＋ in ZnO

A type of dysprosium-doped ZnO （ZnO：Dy） nanopowder was synthesized by high temperature calcinations. XRD was used to analyze the structure. Photoluminescence spectra were used to study the optical characteristic. PL of ZnO：Dy shows two different spectra which are broad band resulted from the defect of Dy in ZnO and sharp lines from the 4f→4f transition of isolated Dy^3 ＋ luminescence center. The emission and excitation spectra depend on the excitation wavelength and the concentration of Dy^3＋ . The broad bands with peaks at 600 and 760 nm are attributed to the recombination from an electron of the defect Dy in ZnO to a hole in VB.