泡沫镁制备技术研究现状及其在航空航天领域的应用前景

泡沫镁作为一种新型功能材料,近年来逐渐受到了国内外的广泛关注,但由于镁过于活泼,易引起爆炸,难以在生产中被大量使用,故关于泡沫镁的研究较少。主要综述了泡沫镁阻尼性能、吸声性能、吸能性能、散热性能、生物医学性能和电磁屏蔽性能等几种主要的性能特点,进而综述了粉末冶金法、熔体发泡法、渗流铸造法等几种常见的泡沫镁材料制备工艺的研究进展,并结合笔者的研究理解对几种制备工艺进行了对比,分析了各种制备方法的优缺点。在此基础上对泡沫镁材料在航空航天领域上的应用进行了分析,表明了其在航空航天领域有着广阔的应用前景。     

多孔泡沫镁合金的研究进展

多孔泡沫镁是用特殊方法制成的具有多孔结构的新型金属材料,由于其特殊的结构和性能,在能源、建筑、交通、航空等领域有着广泛的应用前景。本文就多孔泡沫镁合金制备工艺的研究进展进行了介绍,同时对它的发展前景进行了分析。     

泡沫玻璃生产技术的研究进展

概述了泡沫玻璃的发展及研究现状,介绍了利用废玻璃、粉煤灰、脱镁硼泥、油页岩渣、废阴极射线管、珍珠岩尾矿和浮石等固体废弃物制备泡沫玻璃的工艺方法,以及制备泡沫玻璃的典型工艺流程.辅助添加剂对泡沫玻璃的烧成反应和性能有重要影响,按照作用机理的不同,将添加剂划分为发泡剂、稳泡剂、促进剂、表面活性剂、着色剂、脱模剂等几类进行分析讨论,并展望了泡沫玻璃的发展前景.     

碱式硼酸镁改性聚氨酯泡沫阻燃特性研究

为了研究碱式硼酸镁改性聚氨酯泡沫的阻燃性能,该文先采用水发泡“一步法”制作多种含量碱式硼酸镁改性聚氨酯泡沫,再采用锥形量热（CONE）和极限氧指数（LOI）方法对制备所得的聚氨酯泡沫材料的阻燃性能进行表征。试验结果表明,当添加整体质量为1%的碱式硼酸镁时,其LOI由17.2提升至17.8;当添加整体质量为10%的碱式硼酸镁时,其LOI上升至24.1。此外,随着增加碱式硼酸镁的添量,可以有效降低聚氨酯泡沫的热释放速率峰值和总热释放量,添加10%碱式硼酸镁改性的聚氨酯泡沫的阻燃效果最好。目前的工作对今后聚氨酯泡沫阻燃改性的研究具有参考意义。     

泡沫镁的制备及其性能和应用

论述了渗流铸造法、定向凝固法、熔模铸造法、粉末冶金法、整体铸造法、熔体直接发泡法、真空发泡法和中空球铸造法等几种主要的泡沫镁制备方法,从泡沫镁合金的仿生性能和力学性能两方面突出泡沫镁合金在将来的汽车、航天航空、船舶、生医材料等领域的巨大应用潜力。在综述分析泡沫镁材料研究现状的基础上,针对存在的问题和不足,提出了泡沫镁合金今后研究发展的方向。     

双氧水对镁系无机泡沫材料性能和孔结构的影响

以镁系胶凝材料为基体,双氧水为发泡剂,采用化学发泡工艺制备了内部含有大量密闭气孔的镁系无机泡沫材料。研究了双氧水添加量对泡沫材料发泡倍率、体积密度、压缩强度、弯曲强度、孔结构参数以及导热系数的影响。研究结果表明:双氧水添加量增加,导致胶凝体中的气泡核增加以及气泡生长的内动力增大,气孔孔径变大,体积密度和力学强度减小;随着双氧水添加量增加,材料的导热系数不断减小,在双氧水添加量大于16‰时增大。镁系无机泡沫材料的压缩强度和弯曲强度与体积密度的回归方程分别为y=-6.06+24.19x,y=-0.64+3.82x,均为密切线性相关关系。且在双氧水添加量为8‰时泡沫材料取得最大力学强度,此时气孔孔径最小,孔结构参数较优,导热系数为0.071 W/(m·K),体积密度仅为0.54g/cm3。     

陶瓷颗粒增强泡沫铝基复合材料的制备与性能

陶瓷颗粒增强泡沫铝基复合材料是近年来开发的一种新材料。本文介绍了各种陶瓷颗粒增强泡沫铝基复合材料的制备方法及组织性能研究现状。认为今后一段时期应着重研究以下几方面问题：对泡沫铝基复合材料制备工艺做进一步的研究，优化工艺参数，使工艺更稳定可靠；分析陶瓷颗粒对泡沫铝基复合材料发泡工艺、气泡尺寸及形状的影响．深入探讨其机理，进一步解决气孔结构和均匀性问题；系统研究泡沫铝基复合材料微观组织及界面结合形态；系统研究泡沫铝基复合材料的机械性能、物理性能及其影响因素，为该类材料的应用奠定理论基础；广泛开展泡沫铝基复合材料的推广应用研究，使之尽快为工农业生产的发展做出贡献。     

SiCp增强泡沫铝制备工艺研究

对熔体发泡法制备SiCp增强泡沫铝基复合材料的制备工艺进行了探索，通过正交试验研究了SiC的粒度、发泡剂TiH2的加入量、发泡温度、保温时间等工艺参数对泡沫铝孔隙率及孔结构的影响，确定了制备SiCp增强泡沫铝基复合材料的最佳工艺参数：掺入10％（质量分数）1000目的SiC颗粒增粘，在发泡剂TiH2加入量为2％（质量分数），搅拌时间2min，保温温度700℃以及保温时间3min的工艺条件下，制得的泡沫铝的孔隙率达到80％，平均密度达到了0．5g／cm^3，且基本没有无泡层。最后对泡沫铝的产业化生产的可行性作了讨论。     

镁铝复合阻燃剂热分解过程简析

适当改变镁铝摩尔比等工艺条件，所制得的镁铝复俣阻燃人有不同的热分解温度，其ＤＳＣ吸热值也各异。文章对镁铝复合阻燃剂的热分解过程加以分析，提出了不同制备工艺对所制成的样品热分解行为的影响，认为镁铝复合阻燃剂的热分解温度可根据实际需要，人为地加以控制。     

空心微珠/金属基复合泡沫制备方法与吸能性能的研究进展

金属基复合泡沫是由空心微珠和金属基体复合而成的一种新型结构功能多孔复合材料。它具有许多优异的性能,如轻质、高比强度、高比刚度、高吸能能力、隔热、吸声隔音及电磁屏蔽等,高吸能能力是金属基复合泡沫的突出特点,在防撞、减振、缓冲及防爆抗振的汽车、航空航天、军事装备及船舶等领域具有广阔的应用前景。本文对金属基复合泡沫的基体材料、空心微珠填充材料、影响金属基复合泡沫压缩吸能性能的因素及压缩吸能机制进行了概述,重点报道了金属基复合泡沫常用的制备工艺及近年来铝基、镁基、锌基及钢基复合泡沫吸能性能的研究进展,分析了当前研究中存在的一些问题,并对金属基复合泡沫的应用现状作了阐述,最后展望了金属基复合泡沫的研究发展趋势。      

Behaviour of foam concrete under sulphate environments

This paper reports the effects of variation in density, concentration and type of cation associated with sulphate on the expansion, mass and strength loss of foam concrete produced with two synthetic surfactants. Comparisons are made between behaviour of foam concrete of different densities and that of corresponding base mixes of mortar without foam. The investigations indicated that the expansion in sodium sulphate environment was up to 28% higher than that of magnesium sulphate environment which can be attributed to greater quantum of ettringite formation in sodium sulphate environment. The major deterioration mechanism in magnesium sulphate environment is disintegration of cementing material and this contributed to loss in mass of 1% and higher sulphate deterioration factor of 0.4 for specimens under very severe magnesium sulphate environment. Irrespective of the type of sulphate environment, the deterioration of foam concrete was lower than that of base mix.     

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.     

Processing of magnesium foams by weakly corrosive and highly flexible space holder materials

High-quality magnesium foams were fabricated by an infiltration technology using tailor-made salt–flour mixture space holders. The pore structures and mechanical properties of space holder particles as well as the resultant foam production with spherical pores were characterized in the present study. The particles after high-temperature sintering dissolved rapidly in water due to their porous structures, guaranteeing the weak corrosion and high-purity of magnesium foams. The spherical pores foams exhibited usual stress–strain behaviors and nearly isotropic properties. The yield strengths of the foams increased with the decrease of sample porosity, and the relative mechanical properties of foams were mostly dependent on their relative densities, which obeyed a power law relation. Moreover, porous magnesium materials with tunable pore structures could be fabricated owing to the flexible forming features of salt–flour mixture, showing great application prospects in bone implant material field.     

Aluminum integral foam castings with microcellular cores by nano-functionalization

The goal of the present work is the refinement of the pore morphology of aluminum integral foam castings. Integral foam molding, a modified high pressure die casting process, is used where a mixture of melt and blowing agent particles (magnesium hydride, MgH₂) is injected at high velocity into a permanent steel mold. At the mold surface, decomposition of the blowing agent and pore formation is suppressed due to the high solidification rate whereas solidification of the core is much slower allowing blowing agent decomposition, pore nucleation, and growth. Blowing agent particles not only act as gas suppliers but also represent pore nuclei. Thus, microcellular foam cores can be attained by increasing the number of MgH₂ particles. But increasing the number of powder particles by powder milling strongly decreases the flowability and strong particle agglomeration as a result of the increasing cohesive forces leads to inhomogeneous foams. Flowability of the powder can be restored by coating it with SiO₂-nano-particles resulting in a homogeneous microcellular foam morphology.     

Thermal stability and fire behaviour of flame retardant high density rigid foams based on hydromagnesite-filled polypropylene composites

The present work deals with the development of new rigid polypropylene composite foams filled with high amounts of flame-retardant systems based on synthetic hydromagnesite, a basic magnesium carbonate obtained from an industrial by-product. A partially-interconnected cellular structure with a cell size around 100 μm was obtained for the hydromagnesite-filled PP foams. A 40% reduction of this cell size was observed when a small amount of a combination of montmorillonite and graphene layered nanoparticles was added to the hydromagnesite. The combination of hydromagnesite with an intumescent additive (ammonium polyphosphate) and layered nanoparticles led to improved thermal stability. In particular, the intumescent additive delayed the beginning of the thermal decomposition temperature and the layered nanoparticles split the second step of thermal decomposition in a third peak observed at higher temperatures. Improved flame retardancy, measured by means of cone calorimetry, was observed in the samples containing the intumescent additive. A novel normalized parameter, called foam efficiency ratio (FER), which takes into account the expansion ratio of the foam and the relation of its fire properties with that of the base solid, was also analyzed.     

Quasistatic and dynamic crushability of polymeric foams in rigid confinement

An approach was developed for investigating the crushability behavior of epoxy-based, low-density structural polymeric foam (initial bulk density 0.81 g/cm³ was used for test illustration) under quasistatic and high strain rate conditions in rigid confinement. Quasistatic crushability tests were conducted in a steel confinement cell using an MTS material testing system and the high strain rate (dynamic) crushability behavior was investigated by placing a foam specimen in a steel confinement tube and then loading the specimen using two different split Hopkinson pressure bar systems, namely, a magnesium bar and steel bar. The dynamic deformation characteristics were obtained using a multi-step incremental loading procedure. It was found that these foams exhibited large uniform inelastic deformation during the confined loading. It is verified that multi-step incremental loading can be used to construct the complete stress–strain response curve for the specimens under both quasistatic and dynamic loading conditions. A phenomenological constitutive model was then applied to parametrically describe the crushability response and to determine the rate sensitivity of the foams. The rate sensitivity of yield stress was found to be around three under rigid confinement.