多孔材料孔径及孔径分布的测定方法

孔径及其分布显著影响着多孔体的透过性、渗透速率、过滤性等一系列性能。本文介绍多孔材料孔径及其分布的常用测定方法，包括断面直接观测法、气泡法、透过法、压汞法、气体吸附法、液．液法、悬浮液过滤法、X射线小角度散射法等，并对几种测量方法进行了比较。     

喷射成形Al10.8Zn2.9Mg1.9Cu合金的显微组织演变规律研究

主要采用金相、X射线衍射和透射电镜等测试手段，对M10．8Zn2．9Mg1．9Cu合金在沉积、挤压和热处理3种状态的显微组织演变规律进行研究。结果表明：合金在沉积和挤压前预热两种状态中基体都由等轴晶粒组成，晶粒的平均尺寸分别约为23和24μm，热挤压之后．晶粒平行挤压方向被拉长。在沉积和挤压两种状态中一次析出相主要为MgZn2，Al2Cu和Al2CuMg3种，没有发生变化；热处理之后，一次析出相大部分回溶，少量的Al2CuMg相没有回溶。Al10．8Zn2．9Mg1．9Cu合金经过热处理之后，晶内分布大量弥散的尺寸约为6～15nm的η’，晶界上分布不连续、尺寸在10～20nm左右的η相，不存在明显的晶间无析出带。     

Aluminium Foam Sandwich (AFS) Ready for Market Introduction

A novel production process for aluminium foam sandwich panels (AFS) is described. As an example for a serial application of AFS a support for a mobile telescope arm on a small lorry is presented and discussed.     

Process Stability in Serial Production of Aluminium Foam Panels and 3D Parts

Powder Metallurgy (PM) technology is emerging as one of the most promising techniques for the manufacture of net shape components and panels of aluminium foam. Control of the stability of the aluminium foaming process is one of the key issues in a serial production. Since there are many different parameters to be controlled in the raw material, the precursor and the finished foam part, the best solution is to keep all these factors in one centre of competence to exclude external influences and transporting problems. The latest material for the foaming tools plays also a decisive role concerning a high surface quality and a constant heat generation within the foam. New developments such as a precursor testing equipment or a foaming optimized furnace construction guarantees constant production conditions to be equipped for a more and more demanding market.     

The Role of Oxidation in Blowing Particle‐Stabilised Aluminium Foams

Metal foams were produced by blowing gas into aluminium alloy melts. The effect of oxygen content of the blowing gas on composition and structure of the inner surface of the foam cells is studied by varying gas composition from argon, nitrogen and air to pure oxygen. Scanning Electron Microscopy, Auger Electron Spectroscopy and Transmission Electron Microscopy are used to analyse the surfaces. Initially particle‐free melts are pre‐treated by bubbling air through them after which a certain degree of foam stability is achieved. The oxidation products are characterised by microscopy on such foams.     

Endogenous Particle Stabilization During Magnesium Integral Foam Production

The production of magnesium integral foam components with a dense shell and a porous core is investigated. High pressure casting methods are used where liquid magnesium mixed with a blowing agent is injected into a permanent steel mould. A compact shell develops due to fast cooling at the walls. Larger cooling times in the core allow the decomposition of the blowing agent and the evolution of a foam structure. The resulting integral foams show a high weight‐specific stiffness combined with high energy absorption capability. For the first time, foam stabilizing without additives is realized. Stabilization is by foaming during solidification with the primary α‐phase particles acting as obstacles slowing down cell wall thinning.     

Influence of Powder Morphology and Chemical Composition on Metallic Foams produced by SlipReactionFoamSintering (SRFS)‐ Process

The SlipReactionFoamSintering (SRFS)‐ process is a metallurgical method to produce open‐cell metallic foams of iron based materials, steels and nickel based materials. In this process several chemical reactions take place. Through the most influential parameter, the morphology of the metallic powder, different properties of the foam can be adjusted, such as the viscosity of the slip, the cell structure and the mechanical properties. Several examples are presented in this paper. Moreover, the thermal conductivity of three foams is measured with the transient‐heat‐source‐technique.     

Mastering the structure of PLA foams made with extrusion assisted by supercritical CO2

In this study, the outcome of operating conditions of extrusion assisted by supercritical CO₂ for the manufacture of poly(lactic acid) foams was investigated. It was found that the temperature before and inside the die was the most prominent parameter to tune the foam properties. Foam porosity as high as 96% could be obtained (for die temperature between 109 and 112 °C), representing a total expansion exceeding 30. In this temperature range, low crystallinity (≈6%) was induced giving foams with high radial expansion i.e., large diameters and open porosity. At 112 °C, the CO₂ was able to greatly expand the foams, providing 73% of its potential blowing effect. On the other hand, a low die temperature (below a die temperature of 107 °C) induces a significantly higher level of crystallinity resulting in foams with closed‐porosity and a large longitudinal expansion due to higher strength of the polymer melt. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45067.     

The influence of the stabilizing agent SDS on porosity development in alkali-activated fly-ash based foams

Alkali activated foams (known also as “geopolymer foams”) are formed by the adding of a foaming agent, such as Al powder or H₂O₂, to an alkali activated matrix which can be based on, for example, fly ash, slag or meta-kaolin. The foaming agent decomposes and reacts inside the matrix, resulting in the release of gasses which form pores within the structure. Such pores have to be created before the alkali activated foams harden. In order to prevent the escape of these gasses from the foam, a stabilizing agent can be added to the foam mixture. This paper presents the results of tests involving the pore-foaming process in the case of highly porous, alkali activated, fly-ash based foams. Between 0.5 and 1.5 mass % of H₂O₂ was added to the fly ash precursor as a foaming agent, as well as different amounts (varying from 0.1 to 4.0 mass %) of the selected stabilizing agent, which is known as SDS - sodium dodecyl sulfate. The physical, mechanical, and microstructural properties of the hardened alkali-activated foams were determined. Their pore structures were characterised by SEM, as well as by a three-dimensional (3D) technique, X-ray computed micro-tomography. The advantage of the latter method is that a better insight can be obtained into the characteristics of the hardened pore structure, including information about its homogeneity and the pore size distribution. The influence of the amount of the added foaming agent, as well as that of the amount of the stabilization agent, was evaluated, and optimal addition mass percentages were determined. In the case of the best mixtures, the investigated hardened pore structures showed relatively good mechanical properties, and could therefore be used for various applications in the building industry.