热分解对镍化合物粉末粒度与形貌的影响

对尿素均匀沉淀、碳酸铵沉淀和草酸盐沉淀所得镍的化合物粉末及其热处理样品,采用SEM、XRD、激光粒度分析仪和氮吸附仪进行表征。结果表明：不同沉淀体系形成的粉末粒度和形貌等各不相同,且在热分解过程中的变化行为也不同。较低温度下（如400℃）的热分解产物较好地继承了沉淀粉末的原有特征;温度过高时（如900℃）则易导致显著的烧结团聚。     

不同粒度褐铁矿对高钛型烧结矿指标的影响

在实验室进行了不同粒度及比例的褐铁粉矿对高钛型烧结矿指标影响的研究,结果表明,将褐铁粉细磨至平均粒度0.082～0.123 mm后,在烧结矿产质量基本不变的情况下,可将高钛型烧结中的褐铁矿配比提高至9％,以达到利用廉价资源的目的.     

煅烧温度对锐钛型钛白颜料性能及粒径的影响

研究了煅烧温度对锐钛型钛白消色力、白度、形貌及粒径的影响规律,并通过拉曼光谱、颜料性能检测、SEM对煅烧样品进行表征。结果表明:随着煅烧温度从915℃增加至970℃,消色力逐渐增加,蓝相逐渐降低;较高煅烧温度下钛白粒子将发生烧结,平均粒径增大至310 nm,且不均匀。935~945℃为最佳煅烧温度,得到的钛白粒径为260 nm,粒度分布较窄,消色力大于1 500,蓝相大于4.0。     

粉末粒径对真空等离子体喷涂钛涂层的影响

粉末粒径是影响等离子体喷涂涂层结构和性能的主要因素之一。本文采用四种不同粒径分布的钛粉,通过真空等离子体喷涂（VPS）工艺在不锈钢基体上制备了粗糙多孔的钛涂层,研究了粉末粒径与钛涂层表面粗糙度、气孔率和结合强度间的关系。结果表明：在粉末熔融状况良好的情况下,不同粒径分布的钛粉制备的涂层结构均较均匀;钛涂层的表面粗糙度和气孔率随粉末粒径的增大而增大,涂层结合强度随粉末粒径增大而减小。     

超细草酸镍粒子的制备及其形状和粒度控制

研究了以氨镍络合－草酸沉淀法制备均匀细小纤维状和球形颗粒，溶液初始pH值和草酸加入方式对沉淀粉末颗粒的形貌具有显著影响，草酸以液体形式加入到氨镍溶液中，当氨镍溶液初始pH值小于8．0时，得到球形或类球形团聚体颗粒，当氨镍溶液初始pH值大于8．0时则得到纤维状颗粒，而草酸以固体形式加入时只能得到球形或类球形的颗粒，温度升高，有利于颗粒长大，分散剂的加入，有利于颗粒分散性能的改善，分析认为，溶液中氨的含量是影响颗粒形状的根本原因，固体草酸对沉淀物质的生长具有诱导效应，利于球形颗粒的生成。     

The Influence of the Composition and Particle Size of Starting Titanium Hydride Powders on the Consolidation of Titanium Under Sintering

Powder Metallurgy and Metal Ceramics - The influence of the starting powder composition, grinding conditions, and sintering temperature on the compaction mechanism under sintering and the porosity...     

渗硼剂粒径对钛合金渗硼层组织和性能的影响

采用不同粒径的碳化硼作为硼源,以氧化铈作为催渗剂,在非惰性气氛保护下对TC4钛合金表面进行固体渗硼。利用场发射扫描电镜(FESEM)、背散射电子成像(EBSD)、X射线衍射(XRD)、UMT摩擦磨损试验机对渗硼层的微观组织结构和摩擦学性能进行研究。结果表明,TC4钛合金表面渗硼层为双相硼化物;随着碳化硼粒径的增加,Ti B层厚度与渗层总厚度减少,渗层硬度约为60(HR30N),硼化物层摩擦系数约为0.2,碳化硼的杂质组成对渗层有较大影响。     

钛粉粒度对Ti-Mo吸气剂性能的影响

以3种不同粒度的活性Ti粉制备Ti-Mo吸气剂. 研究了Ti粉粒度及烧结温度对吸气剂性能的影响. 对样品进行了表面形貌的观察和比表面积、孔隙度的测试, 分析了粒度影响Ti-Mo吸气剂性能的原因. 结果表明, 活性Ti粉的粒度影响吸气剂的比表面积和孔隙度, 从而影响Ti-Mo吸气剂的吸气性能. Ti粉粒度过大或过小, 制备的Ti-Mo吸气剂的孔隙度和比表面积均较低, 吸气性能较差;平均粒度适中的Ti粉制备的吸气剂孔隙度和比表面积均较高, 吸气性能最佳.     

Effect of Nucleant Particle Agglomeration on Grain Size

Metallurgical and Materials Transactions A - Solute accumulation/depletion in the liquid around a growing solid particle during the solidification of metallic melts creates a constitutionally...     

Effect of Particle Size on Thermal Conductivity of Nanofluid

Nanofluids, containing nanometric metallic or oxide particles, exhibit extraordinarily high thermal conductivity. It is reported that the identity (composition), amount (volume percent), size, and shape of nanoparticles largely determine the extent of this enhancement. In the present study, we have experimentally investigated the impact of Al₂Cu and Ag₂Al nanoparticle size and volume fraction on the effective thermal conductivity of water and ethylene glycol based nanofluid prepared by a two-stage process comprising mechanical alloying of appropriate Al-Cu and Al-Ag elemental powder blend followed by dispersing these nanoparticles (1 to 2 vol pct) in water and ethylene glycol with different particle sizes. The thermal conductivity ratio of nanofluid, measured using an indigenously developed thermal comparator device, shows a significant increase of up to 100 pct with only 1.5 vol pct nanoparticles of 30- to 40-nm average diameter. Furthermore, an analytical model shows that the interfacial layer significantly influences the effective thermal conductivity ratio of nanofluid for the comparable amount of nanoparticles. This article is based on a presentation given in the symposium entitled “Materials Behavior: Far from Equilibrium” as part of the Golden Jubilee Celebration of Bhabha Atomic Research Centre, which occurred December 15–16, 2006 in Mumbai, India.     

The Effect of Bubble Size on Fine Particle Flotation

Abstract

Expressions for the probability of collision (P_c) and adhesion (P_a) have been derived for fine particle flotation by calculating the trajectory of particles as they flow past a bubble in streamline How. Three different flow regimes have been considered in the present work, i.e., Stokes, potential and intermediate. For the intermediate flow conditions in which most flotation operations are carried out, the particle trajectories have been determined using an empirical stream function derived in the present work. For the case of a very hydrophobic coal sample, the values of the probability of collection (P) determined experimentally have been found to be in close agreement with the theoretically predicted P_c values over a range of bubble and particle sizes

The expression for P_a has been derived by determining the time it takes for a particle to slide along the surface of a bubble after collision. It has been assumed that the bubble-particte adhesion occurs when the sliding time is equal to or exceeds the induction time, which varies with the particle hydrophobicity. P_a is shown to be a function of particle size, bubble size and induction time. The values of P_a predicted in the present work are in good agreement with the results of microflotation tests conducted on a coal sample.     

Effect of Particle Size on the Contact Angle of Molybdenite Powders

In this work, the contact angles of molybdenite powders in various size fractions (+150 μm, ?150 + 75 μm, ?53 + 38 μm, ?38 + 20 μm, and ?5 μm) were determined with the Washburn method by measuring the mass of capillary rise liquids in molybdenite powder beds as the function of time. It was shown that molybdenite powders had a smaller contact angle in superfine size range (?5 μm) than the common size range (+20 μm), which might be attributed to the large decrease of the face/edge ratio on molybdenite surfaces. Also, it has been found that the contact angle of molybdenite particles did not change as the decrease of particle size in the range of +20 μm.     

Analysis of Particle and Crystallite Size in Tungsten Nanopowder Synthesis

Tungsten nanopowders were synthesized by a low-temperature technique and then heat treated in a gaseous reductive atmosphere in order to study the phase evolution, crystallite size, and particle size of the powders as the heat treatment temperature was modified. Synthesis of the powders was carried out in aqueous media using NaBH₄ as a reducing agent using careful control of the pH of the solutions. The XRD patterns of the as-synthesized powders showed an amorphous phase. After washing, energy dispersive spectroscopy showed that the powders had peaks for oxygen and tungsten. In order to promote crystallization and eliminate the oxygen, the powders were heat treated at 773 K, 923 K, and 1073 K (500 °C, 650 °C, and 800 °C) in a H₂/CH₄ reducing atmosphere for 2 hours. XRD after heat treatment showed α-W peaks for the powders treated at 1073 K and 923 K (800 °C and 650 °C) and a mixture of β-W and α-W for the powders treated at 773 K (500 °C). The crystallite sizes determined from X-ray peak broadening were 12, 16, and 20 nm, whereas the average particle sizes from dynamic light scattering were 260, 450, and 750 nm, for heat treatment temperatures of 773 K, 923 K, and 1073 K (500 °C, 650 °C, and 800 °C), respectively. The average crystallite size and particle sizes increased proportionally with the treatment temperature, in contrast to what has been found for some ceramics, in which as the heat treatment temperature is increased, the crystallite size increases, but the particle size stays constant.     

脱硫剂粒度对铁水脱硫的影响试验

 通过不同粒度脱硫剂的铁水脱硫试验,结合实际生产中脱硫渣微观结构的分析,探讨了脱硫剂粒度对铁水脱硫的影响。结果表明,随着脱硫剂粒度的减小,铁水脱硫量、脱硫率和脱硫速率常数均随之增大。脱硫渣结构分为3层：外层主要为脱硫产物CaS,厚度为10~50μm;中间层主要为2CaO·SiO2;内核为未反应的CaO。粒度越小,石灰颗粒利用率越高。为保证较好的脱硫效果和提高利用率,建议将脱硫剂粒度控制为0.5~1.5mm。     

Effect of Texture and Grain Size on Bio-Corrosion Response of Ultrafine-Grained Titanium

The bio-corrosion response of ultrafine-grained commercially pure titanium processed by different routes of equal-channel angular pressing has been studied in simulated body fluid. The results indicate that the samples processed through route B_c that involved rotation of the workpiece by 90 deg in the same sense between each pass exhibited higher corrosion resistance compared to the ones processed by other routes of equal-channel angular pressing, as well as the coarse-grained sample. For a similar grain size, the higher corrosion resistance of the samples exhibiting off-basal texture compared to shear texture indicates the major role of texture in corrosion behavior. It is postulated that an optimum combination of microstructure and crystallographic texture can lead to high strength and excellent corrosion resistance.     

粒度对高硫铝土矿焙烧脱硫的影响

在不同矿石粒度下,探究焙烧预处理对矿石宏观形貌、粒度分布、硫含量、物相结构及矿物微观形貌的影响。结果表明,较粗粒径的盘磨矿的焙烧效果优于较细粒径的球磨矿;焙烧后矿石粒度有细化的趋势,其中盘磨矿中的黄铁矿被氧化成赤铁矿,颗粒变得较为疏松,球磨矿中含有微量的磁铁矿;在700℃、30min的焙烧条件下,矿石的硫含量从2.3%降低至0.48%,满足工业生产要求。     

关于人炉焦炭质量及其粒度大小对鼓风炉炉况的影响分析

统计分析澜沧公司鼓风炉某生产时段部分焦丁人炉的比例及其数量,并结合焦炭质量论述了其对铅鼓风炉作业的重要性,提出了对焦丁有效使用的建设性意见。     

碳化钒对超细WC粒度和物相的影响

为了研究在超细WC粉的制备过程中,碳化钒(VC)添加对超细碳化钨(WC)粉末粒度和相形成的影响,对不同VC添加量和不同碳化温度下制备的超细WC粉末的粒度、相成分和微观形貌进行了分析。研究结果表明:在1 400℃碳化时,当碳化钒的添加量由0%增加到10%时,WC的BET粒度由0.274μm降到0.159μm,WC粉末单颗粒粒度在逐渐减小,WC粉末颗粒的聚集程度增加。随着碳化钒的添加量的增加,碳化钒相衍射峰强度增大,WC的衍射强度降低。此外,碳化温度提高到1 600℃时,WC粉末的BET粒度增大,VC晶粒结晶更完整。