Permeability of porous materials from refractory compounds

Summary A study was made of porous materials from spheroidized powders of refractory compounds. A relationship is established linking permeability with porosity and the particle size of the powder from which the materials were prepared. An empirical formula is proposed for determining the dependence of the coefficient of permeability on powder particle size and component porosity under linear filtration conditions. The integral and differential pore radius distribution curves obtained show that such materials are relatively homoporous and exhibit little scatter in pore radius size.Translated from Poroshkovaya Metallurgiya, No. 1(49), pp. 27–30, January, 1967.     

合金成分和奥氏体变形对粒状贝氏体和粒状组织转变的影响

在Gleeble热模拟试验机上研究了低碳Mn-B系贝氏体钢的组织转变,分析了合金成分和奥氏体变形对粒状贝氏体及粒状组织转变的影响。结果表明,在相同冷却条件下,添加铬、铌元素后更利于粒状贝氏体组织的转变;在奥氏体未再结晶区,变形对粒状贝氏体及粒状组织的转变有明显的影响,随奥氏体变形温度的降低以及变形程度的增加,组织由粒状贝氏体向粒状组织变化。     

Laws of vibrational compaction of difficultly deformable powder materials: 1. Theory of dynamical behavior of unbonded granular media

A model is proposed to describe the behavior of an arbitrarily loaded granular medium. The model is based on known results of the theory of irreversible deformation of self-poured media, and the kinetic theory of dense gases. The model is used to describe the process of vibrational compaction.Institute for the Problems of Materials Science, Ukrainian Academy of Sciences, Kiev. Institute of Impulsive Processes in Technology, Ukrainian Academy of Sciences, Nikolaev. Translated from Poroshkovaya Metallurgiya, Nos. 1/2(383), pp. 22–27, January–February, 1996. Original article submitted April 25, 1994.     

颗粒物质的堵塞行为

在无序状态体系中形成了屈服应力或者是当应力的驰豫时间超过实验时间尺度时就会形成堵塞（jamming）。近年来,堵塞行为已成为颗粒物质研究中的一个热点和难点问题。文内概述了颗粒物质堵塞的基本概念和临近堵塞的行为特征（如颗粒间应力的形成和分布特征、颗粒构形和密度）,以及相关实验和数值模拟研究得出的重要结论。有关颗粒物质堵塞行为的研究,对探明颗粒物质的本质特征,非晶相变机制,以及人流、物流、交通流、信息流中的瓶颈效应等重大问题的解决将产生积极的推动作用。     

钝化颗粒镁的试验研究及应用

用化学反应法对镁粒进行钝化处理,研究了钝化液浓度,用量,反应温度,反应时间,干燥处理对产品质量的影响,在SEM下观察发现,钝化处理后镁粒表面生成了致密的钝化层,且包裹均匀。实验中采用的钝化剂具有对环境污染小,成本低,活性镁损失小,钝化液可循环使用等特点,经工业批量生产,用于铁水溶脱硫取得良好效果。     

Permeability of microporous carbon preforms

The permeability of microporous amorphous carbon preforms with varying pore size and pore distributions has been experimentally examined. The porous structures have been characterized by mercury porosimetry and by quantitative metallography of pressure-infiltration-cast metal matrix composites based on the carbon preforms. The permeability shows a linear correlation with the fraction porosity and the square of the pore diameter.     

Oxygen Permeability of Fiber-Reinforced Polymers

Several independent studies have confirmed that fiber-reinforced polymers (FRP) used for repairing corrosion-damaged concrete structures slow down the corrosion rate. This suggests that in this application, FRP serves as a barrier to the ingress of moisture and oxygen that are critically important for sustaining electrochemical corrosion of steel in concrete. Because oxygen molecules are smaller than both water and chloride molecules, they diffuse faster. Therefore, their permeation through FRP is more critical. This paper presents results from an experimental study that determined the oxygen permeability of FRP laminates. Four different commercially available carbon-fiber-reinforced polymer (CFRP) and glass-fiber-reinforced polymer (GFRP) systems were investigated, and four different fiber orientations were evaluated for one-layer and two-layer configurations. The results showed that the oxygen permeability of FRP was somewhat poorer than the epoxy used for its fabrication. Single-layer FRP laminates were less permeable than two-layer laminates, a finding that had previously been reported but considered anomalous. Scanning electron micrographs indicated that this could be attributed to voids between the layers. The nonzero oxygen permeability of FRP explains why it can slow down but cannot completely stop chloride-induced corrosion of concrete.