纳米Fe/C复合材料的原位合成

在石油渣油中加入二茂铁，通过热缩聚反的位合成纳米级铁粒子均匀分散于炭基体中的新型复合材料，研究了在420℃热缩聚时停时间和二茂铁添加量对Fe/C形成的影响，并用TEM和XRD观测和分析了Fe/C的形态和结构，结果表明，在基体中铁粒子的粒径为25－50nm，在一定条件下，二茂铁添加量的增加和停留时间的延长均使Fe/C产率提高，停留时间对热缩聚反应的影响遵循一级反应动力学，二茂铁的添加能显著提高反应速率常数k值。     

Mechanical and thermal properties of HVOF sprayed Ni based alloys with carbide

The objective of the present study is to develop multi-functioned coating to the components, which are made of copper with electroplated Ni and are widely used for steel making industry. In this paper, we report the mechanical and thermal properties of Ni based superalloys with carbide sprayed by high velocity oxygen fuel (HVOF), and the detailed effects of sprayed material, spraying conditions, and initial powder structure on these properties. It was found that, among commercial Ni self-fluxing alloys (without fusing treatment), coating with a carbon content of 0.58 mass% had the most preferable properties, with a good balance of the hardness, strength, and thermal shock resistance. The thermal shock resistance depended not only on the strength of the coating but also on the volume contraction when tested at high temperatures. For the several developed Ni based superalloys with carbide, Ni20Cr8Mo5Fe–WC and Ni16Cr15Mo3–WC demonstrated the prominent adhesion strength and thermal shock resistance with high Galvanic corrosion resistance through optimized spraying condition. Also, 20 mass% NiCr–Cr₃C₂ coating sprayed by using employed relatively small primary particle succeeded in achieving the multi-superior properties; high adhesion strength, high corrosion resistance and thermal shock resistance.     

Recent developments of high-performance NEOMAX magnets

For further improvement in achieving extremely high magnetic properties of Nd- Fe- B sintered magnets, extensive investigation has been done to densify the magnet up to the theoretical value, to increase the volume fraction of the Nd ₂Fe₁₄B matrix phase, and to achieve a high degree of alignment. By controlling chemical composition and the amount of constituent phases,improving particle size distribution, and adopting the isostatic pressing method to get better alignment of fine particles, we have succeeded in obtaining a high-performance magnet having residual flux density (B_r) of 1.495 T (14.95 kG), maximum energy product [(BH)_max] of 431 kj/m³ (54.2 MGOe), and intrinsic coercivity (iH_c) of 845 kA/m (10.62 kOe).     

Influence of melt superheat on breakup process of close-coupled gas atomization

In close-coupled gas atomization（CCGA）, the influences of melt superheat on breakup process are fundamental to obtain desired or finer powder. Based on a series of Cu atomization experiment under different superheating conditions, the influences of melt superheat on breakup process were studied. Experimental results indicate that as the melt superheat is increased to 150, 200, 250 and 300 K, the mean particle size （D50） decreases consequently to 34.9, 32.3, 30.9 and 19.7 μm. Theoretical analysis reveals that the primary breakup and secondary breakup processes are close coupled, and the melt superheat radically influences the melt properties, and plays a crucial role on governing the filming process of primary breakup and the atomization modes of secondary breakup. There exists a strong nonlinear decrease of contact angle of melt to nozzle orifice wall when the superheat is increased fi＇om 250 K to 300 K, leading to a marked fall of the film thickness formed in primary breakup, and D50 of copper powders is therefore sharply reduced. However, the log-normal distribution feature of particle size has not been substantially improved.     

THE RELATIONSHIP BETWEEN HAZE AND THE SIZE OF PARTICLES IN BEER

Haze measurements have been obtained for suspensions of polystyrenelatex particles of known diameter using two light scattering instruments which measure at angles of 90° and 13° respectively. The results agree well with the theory of light scattering and demonstrate the significant effects of particle size and angle of detection upon the instrumental values for haze. This information has been used to correlate the particle size distributions of a number of beers, as measured by Coulter Counter, with the corresponding, measured haze values.     

减少激光粒度仪系数矩阵数目的方法

通过分析激光粒度仪的系数矩阵的计算公式．指出不同焦距下的各个系数矩阵之间存在着简单的比例关系，即可由一个焦距对应的系数矩阵推得另一个焦距的系数矩阵，从而可减少仪器测量所需的系数矩阵数目。这一关系式已由数值计算及对标准颗粒的实测得到证实。     

压力对Fe－29wt％Ni合金超细微粒特性的影响

利用蒸发冷凝法，制备了不同平均粒径的Ｆｅ－２９ｗｔ％Ｎｉ合金超细微粒。在不同压强下，将超细微粒压制成片。随压强增大，马氏体体积分数和比饱和磁化强度σｓ明显增大，而矫顽力Ｈｃ呈线性下降。压力效应与平均粒径ｄ大小密切相关     

Effect of Particle Size on Monometallic and Bimetallic (Au,Pd)/C on the Liquid Phase Oxidation of Glycerol

The influence of metal particle size of monometallic and bimetallic supported catalysts (Au, Pd, Au–Pd)/C was studied using as a model reaction the liquid phase oxidation of glycerol. By tuning the metal particle size from 2 to 16 nm a progressive decrease of activity and simultaneously an increase in the selectivity to sodium glycerate was observed. Moreover, the influence of the temperature was studied and it was found that by increasing the temperature, only with a large particle size the formed glycerate was retained and not over-oxidized to tartronate.     

Energy Dissipation at the Slug Nose and the Modeling of Solids Transport in Intermittent Flow

It is shown, by means of Lagrangian momentum and power balances across the slug nose in slug flow, that the power dissipated due to sudden expansion of the fluid in the film immediately downstream of the slug nose is greater than the power lost due to viscous action at the pipe wall but that it may not be large enough to materially aid particle transport. This has the implication that sand transport in intermittent flow may be considered as transport in a hybrid flow of hydraulic conveying and stratified flow when the length of the mixing section at the slug nose is short compared to the length of the slug body.     

水平管气力输送数值模拟

本文采用粒子追踪理论对水平管中粒子流动状态进行了数值模拟.文中提出了一种新的粒子碰撞模型,并忽略粒子的旋转和扬力,仅考虑气流阻力和重力对粒子的影响,在输送量为9.13×10~3kg/s,混合比约0.3的条件下,通过数值计算得知:由于粒子间的碰撞,使得异径粒子的速度趋向平均化;粒子间的碰撞是粒子悬浮的原因之一;粒子的浓度沿管轴向是随时间而发生变化的.