共查询到20条相似文献,搜索用时 140 毫秒
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以玉米淀粉为基体,辅以相应的增塑剂和发泡剂,利用挤出发泡法制备了淀粉基复合发泡材料。运用双料筒毛细管流变仪研究了甘油增塑剂、NaHCO3发泡剂含量对淀粉基复合发泡材料流变行为的影响。采用扫描电镜(SEM)研究了不同熔体黏度对泡孔形态的影响。结果表明:淀粉基复合发泡材料的熔体流动特性表现为假塑性;随着甘油含量的增加,熔体黏度逐渐下降;随着NaHCO3含量的增加,熔体黏度先下降后提升;随着熔体黏度的降低,熔体内泡孔数量减少,孔径增大,当熔体黏度为1 200 Pa·s时,泡孔大小适中且分布均匀。 相似文献
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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。 相似文献
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根据制备过程中金属的状态,从液相法、固相法、金属沉积法三方面介绍了多孔金属材料的制备工艺。液态金属的发泡可以通过直接吹气法发泡法、金属氢化物分解发泡法来实现;固态金属可以通过粉末冶金法、粉末发泡法、金属空心球法和金属粉末纤维烧结法来实现;与前两种不同的是,金属沉积法是采用化学或物理的方法来实现的。最后,讨论了多孔金属材料在结构材料和功能材料两方面的应用。 相似文献
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国外可降解淀粉发泡材料最新研究进展 总被引:2,自引:0,他引:2
主要综述了国外可降解环保型淀粉发泡材料的研究现状,阐述了淀粉挤出发泡和烘焙发泡以及淀粉基聚氨酯泡沫塑料的最新研究进展.同时也概述了超临界熔体挤出法应用于淀粉发泡的最新研究成果和淀粉发泡过程的模型建立,为淀粉发泡材料的进一步工业化应用提供了一定的参考. 相似文献
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The effects of melt viscosity on the foaming process and the structures of foamed aluminum have been examined. Methods for measuring the melt viscosity, pore structure, and foaming process are introduced. To increase the stability of the foaming melt and get the sample with a uniform pore distribution, a proper viscosity is needed. Further, the structure of foamed aluminum can be controlled by adjusting the Ca addition and other process parameters. 相似文献
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《Composites Science and Technology》2006,66(11-12):1606-1614
Three methods to mix ceramic fillers, hydroxyapatite or β-tricalcium phosphate, with a polymer matrix, a poly l-lactic acid, are investigated as a first step prior to supercritical foaming to prepare porous composite structures for biomedical applications. First the dry process consists in mixing ceramic powder and polymer pellets before a compression molding step. The second technique is based on the dispersion of ceramic fillers into a polymer–solvent solution. The third method is a melt extrusion of a ceramic/polymer powder mixture. Each technique is first optimized by defining the processing parameters suitable for the bioresorbable materials considered. Then comparison of the three methods shows that solvent or melt processing results in a more homogeneous filler distribution than the dry technique. Extrusion leads to composites with a higher modulus than solvent prepared compounds and is a solvent-free approach. The former technique is therefore selected to prepare ceramic/polymer blends before supercritical CO2 foaming. 相似文献
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研究了高熔体强度聚丙烯为发泡树脂的挤出发泡行为,分别采用聚合物流变工作站、偏光显微镜、扫描电镜等考察了挤出配方和工艺对发泡体系流变性能及发泡性能的影响。研究发现,高熔体聚丙烯的熔体黏度随发泡剂用量、螺杆温度、螺杆转速的提高而降低,聚丙烯发泡制品的泡孔形态、泡孔密度和尺寸在螺杆温度为(185±3)℃,模头温度为(153±1)℃,螺杆转速为(19±2)r/min,自制发泡剂体系用量为4%时最佳,泡孔尺寸均匀且泡孔密度可以达到每立方厘米2.65×1013个以上,此时发泡倍率为9.6倍。 相似文献
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采用新型发泡剂制备了泡沫铝,研究了包覆改性和混合改性两种改性方式对新型发泡剂在铝熔体中分散性的影响。结果表明,采用Al溶胶和Si溶胶对新型发泡剂进行包覆改性处理,发泡剂分散性差,所制备的泡沫铝存在较多大孔和裂纹;采用TiB2粉末和AlSi合金粉末混合改性处理新型发泡剂时,发泡剂分散性良好,并且随着TiB2和AlSi含量的增加得到的泡沫铝样品裂纹明显减少、泡体趋于均匀,但孔隙率逐渐降低。相比较而言,合金粉末混合改性法比溶胶包覆改性法使发泡剂的分散更均匀,制备的泡沫铝裂纹较少,且泡体结构较均匀。 相似文献
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Yubo Zuo Jianzhong Cui Zhihao Zhao Haitao Zhang Lei Li Qingfeng Zhu 《Journal of Materials Science》2012,47(14):5501-5508
Low-frequency electromagnetic casting (LFEC) process had been developed and is being used for the past several years with
the application of an induction coil placed outside the conventional direct chill (DC) casting mould. It has been demonstrated
that the LFEC process has a significant grain refining effect on aluminium alloys. In the present study, temperature measurement
and direct quenching from liquid and/or semi-solid were carried out to study the temperature field during casting process
and to understand the mechanism of the grain-refining effect of the LFEC process. The experimental results showed that in
contrast to the conventional DC casting process, the liquid melt from the launder, during the LFEC process, is cooled with
very high cooling rate directly to 3–6 °C below the liquidus, and the temperature field of the entire melt in the mould, and
the hot top is quite uniform, which results in the enhanced heterogeneous nucleation and improved survival rate of the nuclei.
This is believed to be the main reason why the LFEC process can significantly refine the grain size of aluminium alloys. 相似文献
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《Materials Science & Technology》2013,29(5):560-566
AbstractInfluence of combined electromagnetic field application on horizontal direct chill casting of 7050 aluminium alloy is investigated. Temperature measurement and structure observation are carried out to analyse the casting process under different electromagnetic fields. Combined electromagnetic field can reduce the harmful gravitational thermal effect in the horizontal direct chill casting process and improve the ingot properties. With application of combined electromagnetic field, temperature distribution in the melt is more uniform, sump of the ingot becomes flat and symmetric, surface quality of ingot improves markedly, grain morphology changes from feathery grains to equiaxed grains and grain size decreases. Distribution of copper and zinc in the transverse section of the ingot becomes more uniform. 相似文献
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《Materials Science & Technology》2013,29(1):101-107
AbstractMelt conditioning by advanced shear technology (MCAST) is a new process for microstructural refinement of both cast and wrought magnesium alloys. Melt conditioned direct chill (MCDC) casting combines the MCAST process with conventional direct chill (DC) casting. In the present work, melt conditioning has been combined with permanent mould casting to simulate the production of DC cast AZ91D billets and slabs. The results show that the MCDC process can achieve significantly finer grain size and more uniform microstructure than conventional DC process for both billets and slabs. Grain refinement in the MCDC process is due to the fine and well dispersed oxide particles produced after processing in the MCAST unit. 相似文献
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Using a new temperature programmed decomposition (TPD) theory and related experimental technique, a set of thermal decomposition kinetics equations of titanium hydride can be acquired by separating and simulating its TPD spectrum. According to these equations, the relation curve of decomposition quantity and time for titanium hydride at temperature of 940 K is obtained and the result coincides well with the Al alloy melt foaming process, which provides a scientific basis for controlling the Al alloy melt foam and then the Al alloy foams with different pore structure are successfully prepared. 相似文献
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Two kinds of equipments were designed for casting composite ingots, and three‐layer ingots of 4045/3004/4045 aluminum alloys were prepared by direct‐chill (DC) semi‐continuous casting process, macro‐morphology, microstructure, temperature distribution near the interface, elements distributions and tensile strength of the interface were investigated. The equipment suitable for casting composite ingots was determined, and results show that solid supporting layer with uniform temperature distribution forms near the interface, which ensures the stable casting process. The two different aluminum alloys are well bonded. The criterion for temperature control of solid supporting layer is founded based on the relationship between the interface bonding strength and the temperature of solid supporting layer when contacted by 4045 alloy melt. 相似文献