微米孔径多孔铝的制备及性能

为获得高强度的微米孔径多孔铝,通过真空压力烧结溶解工艺制备微米孔径多孔铝,对制备过程、微米孔径多孔铝的强度及渗透性能进行研究。结果表明:真空环境下的压力烧结可明显促进铝粉烧结,提高微米孔径多孔铝的抗弯强度;在压制压力500 MPa、烧结温度650℃、烧结时间2 h以及烧结压力150~200 MPa条件下可获得孔隙率44%~61%、平均孔径55~230μm的多孔铝;随着孔隙率和平均孔径的提高,微米孔径多孔铝的相对渗透系数增大;与尺寸相同、孔结构相似的多孔不锈钢相比,微米孔径多孔铝具有较好的渗透性能和较高的耐压破坏比强度。     

泡沫铝的新型渗流法制备及其压缩性能

在热传计算的基础上,采用锌粒子为前驱体、铝熔体为渗流体,通过氩气渗流制备通孔泡沫铝;对泡沫铝的制备、压缩性能及锌残余量进行研究。结果表明:滑石粉隔热层厚度与渗流时间之间的关系为x2=7.35×10-8τ;优化的渗流工艺如下:渗流温度740℃、锌粒子预热温度220℃、锌粒子直径3 mm;平均孔径为3 mm的泡沫铝的屈服强度随孔隙率的增加而减小;孔隙率为63%和67%的泡沫铝的屈服强度都随孔径的增大而提高;泡沫铝孔隙率从60%提高到71%,锌残余量从11.3%降低到4.5%。     

多孔NiTi形状记忆合金的制备工艺

以NH_4HCO_3为造孔剂,利用元素粉末混合烧结法制备了多孔NiTi形状记忆合金。研究了压制压力、烧结温度和烧结时间对多孔NiTi合金孔结构的影响,并分析了其物相组成。结果表明:随压制压力的增加,平均孔径和孔隙率逐渐减小;随烧结温度提高,多孔NiTi合金的平均孔径减小、孔隙率先增加后减少,孔隙分布趋于均匀;随烧结时间延长,多孔NiTi合金的平均孔径及孔隙率先增加后减少。在造孔剂添加量50%,压制压力250 MPa,烧结温度1000℃,烧结时间6 h条件下可制备出孔结构均匀(平均孔径为314μm,孔隙率56.3%)的多孔NiTi合金,其基体相为B2(NiTi)相。     

凝胶辅助发泡法制备三维互联多孔SiC陶瓷

通过机械搅拌发泡结合冷冻-凝胶法制备了三维互联多孔SiC陶瓷材料,所获得的多孔陶瓷材料孔径分布均匀、孔结构可调并具有双级孔结构。研究了PVA含量与搅拌速度对多孔陶瓷孔结构及性能的影响。结果表明,随着PVA含量的增加,孔结构均匀程度和联通性提高、一级孔孔径尺寸逐渐减小且孔壁变薄。当ω(PVA)/ω(SiC)质量比为1.5时,样品孔径分布最均匀;并且随着搅拌速度的增大,孔隙率增加、联通性增强、一级孔孔径尺寸减小。当转速为1600 r/min时,SiC多孔陶瓷的孔隙率和抗压强度分别为88.42%和4.36 MPa。     

胞状AlCu5Mn合金泡沫的压缩性能和能量吸收特性

用熔体发泡法制备孔隙率为51.5%～90.5%、孔结构均匀的胞状铝合金(AlCu5Mn),研究其孔结构、压缩性能、能量吸收能力、能量吸收效率和吸能性能.结果表明:胞状铝合金孔结构由高孔隙率(88.8%)时的大孔径、多边形孔向低孔隙率(62.5%)时的小孔径、球形孔孔结构过渡,其压缩应力(σ)-应变(ε)曲线具有线性变形阶段、屈服平台阶段和致密化阶段三个部分,由线性变形阶段进入屈服平台阶段所对应的ε_s值介于2%～9%之间;屈服强度σ_s~*随着孔隙率的增大而下降,在孔隙率相同的条件下,胞状铝合金的力学性能优于胞状铝和多孔铝合金,其比刚度高于钢;当应变为定值时,胞状铝合金单位体积和单位质量的压缩吸能能力(C和C_m)都随着孔隙率的升高而降低,但是孔隙率在73.5%～82.1%范围内时,其C_m与ε的关系几乎不随孔隙率的改变而改变;对于孔隙率为51.5%～90.5%的胞状铝合金,它们的吸能效率的峰值都大于80%.胞状铝合金的C-σ和C_m-σ关系可以表征其吸能性能,从而可以根据实际工况选择作为减振吸能材料的胞状铝合金的最佳孔结构.     

半固态法泡沫铝材料制备工艺研究

采用半固态法制备泡沫铝,并对制备工艺进行了初步探索。研究了熔体浇注温度、发泡剂TiH_2添加量对Al-Si合金熔体发泡孔隙率和平均孔径的影响。研究表明,利用Al-Si合金在半固态区的自增粘作用,可以得到孔隙率为20%~50%、孔径为2~4 mm的泡沫铝;浇注温度在650~670℃时,随浇注温度的升高,Al-Si合金泡沫铝试样孔隙率增加,更高的浇注温度使孔隙率减少;发泡剂TiH_2添加量在1%~3%时,随发泡剂添加量的增加,孔隙率和孔径均增加,发泡剂过多反而使孔隙率和孔径减小。浇注温度为670℃、TiH_2添加量3%时,Al-Si熔体发泡效果最优,孔隙率可达48%。     

多孔蒙乃尔合金的制备及其结构特性

为了制备蒙乃尔合金多孔材料,本文以蒙乃尔粉为原料,以K2CO3为造孔剂,采用烧结-溶解法制备了不同孔隙率的蒙乃尔合金多孔试样。研究了造孔剂体积分数、压坯压力和烧结温度对试样孔隙率、孔径和透气度的影响。实验结果表明,当造孔剂的体积分数在20%~ 40%之间时,制备的样品孔隙率为31%~46%。当压坯压力在200~400MPa范围时,随压力的增大试样的孔隙率、孔径和透气度均减小;当烧结温度在850~1000℃范围时,随烧结温度升高,孔径和透气度先增大后缓慢降低,在950℃达到峰值。当造孔剂体积分数为30%,压制压力为200MPa,烧结温度950℃时,所制备的蒙乃尔多孔材料孔隙率为37%,最大孔径为21.5μm,透气度为76.77 m3/(h?kPa?m2)。     

小孔径泡沫铝的制备及压缩性能研究

在常规熔体发泡法基础上,采用添加0.5%Mg(质量分数,下同)以降低表面张力;发泡剂400 ℃,6 h+500℃,1 h氧化预处理以协调发泡剂分散均匀性与发泡过程关系;发泡搅拌60s以破碎初始气泡等措施,成功制备出了平均孔径1.3 mm、孔隙率70.5%、结构均匀的小孔径泡沫铝.泡沫铝及Al-9Si泡沫的压缩性能分析表明,随平均孔径减小,泡沫铝的屈服强度、致密化应变和能量吸收能力均明显提高,泡沫铝压缩性能随孔径减小而提高,与泡沫铝的孔结构因素及孔结构均匀性有关.     

复合碳酸盐作发泡剂制备泡沫铝的工艺研究

采用熔体发泡法制取泡沫铝,利用DSC和DTG两种方法,分析了CaMg(CO3)2的热分解特性,同时系统地研究了发泡剂含量、温度及搅拌时间对泡沫铝孔结构的影响.结果表明,发泡剂加入质量分数为2%～3%,搅拌时间1 min～2 min,发泡温度为660℃～710℃的条件下,可以制取孔结构均匀、孔隙率高的泡沫铝合金.     

基于二维微管模型的多孔铝渗流浇注过程研究

通过建立多孔铝合金的二维微管渗流数学模型,对铝熔体浇注过程中的渗流时间与渗流压力关系及其对孔隙率的影响进行了研究,同时分析了静压力与孔隙率的关系。结果表明:采用二维微管渗流模型可以较准确反映实际浇注渗流过程。孔隙率受到填料颗粒背压区气体和静压力变化的影响。     

Thermal properties of pressureless melt infiltrated AlN–Si–Al composites

Thermal properties of AlN-Si-Al composites produced by pressureless melt infiltration of Al/Al alloys into porous α-Si₃N₄ preforms were investigated in a temperature range of 50-300 °C. SEM and TEM investigations revealed that the grain size of AlN particles was less than 1 μm. In spite of sub-micron grain size, composites showed relatively high thermal conductivity (TC), 55-107 W/(m.K). The thermal expansion coefficient (CTE) of the composite produced with commercial Al source, which has the highest TC of 107 W/(m.K), was 6.5×10^?6 K^?1. Despite the high CTE of Al (23.6×10^?6 K^?1), composites revealed significantly low CTE through the formation of Si and AlN phases during the infiltration process.     

Properties of Al/TiNi composite using porous TiNi fabricated by a self-propagating high temperature synthesis method

In the present study, equi-atomic porous TiNi shape-memory alloys have been successfully prepared by self-propagating high-temperature synthesis (SHS) using elemental titanium and nickel powders. The porous TiNi alloys thus obtained have an open porous structure with about 64 vol.% porosity, and the pore size is about 1.8 mm. The effect of preheating temperature on the microstructure has been investigated. It was found that the pore size increased with increasing preheating temperature. Moreover, the preheating temperature was shown to have a significant effect on the microstructure of the SHS-synthesized porous TiNi shape memory alloys. Aluminum was infiltrated into porous TiNi shape-memory alloys and the damping property of Al/TiNi was measured by a vibration analyzer (FFT analyzer). The specific damping capacity of Al/TiNi composites is 70% that of a pure TiNi ingot.     

基于包混和复合添加工艺的多孔碳化硅陶瓷的制备和性能

采用包混工艺合成核-壳结构的硅-树脂先驱体粉体,引入Al2O3-SiO2-Y2O3复合添加剂,通过成型、炭化和烧结工艺制备多孔碳化硅陶瓷。分析多孔碳化硅陶瓷样品的物相、形貌、孔隙率、热导率、热膨胀系数和抗热震性能。结果表明：复合添加能够在较低的温度下制得多孔碳化硅陶瓷;陶瓷样品的晶粒较小,明显增强了多孔碳化硅陶瓷的导热性能;复合添加提高了碳化硅陶瓷的抗热震性能,添加Al2O3-SiO2-Y2O3并且在1650℃下烧结制备的多孔碳化硅陶瓷经过30次热震后的抗弯强度损失率为6.5%;陶瓷样品的孔壁更加光滑,孔分布更均匀;复合添加对多孔碳化硅陶瓷热膨胀系数的影响较小。     

Preparation and Pore Structure Stability at High Temperature of Porous Fe-Al Intermetallics

Porous Fe-Al intermetallics with different nominal compositions (from Fe-8 wt.% Al to Fe-50 wt.% Al) were fabricated by Fe and Al elemental powders through reaction synthesis. The effects of the Al content on the pore structure properties, and the comparison of pore structure stabilities at high-temperatures among the porous Fe-Al intermetallics and porous Ti, Ni, 316L stainless steel samples, were systematically studied. Results showed that the open porosity, maximum pore size, and permeability vary with the Al content. Porous Fe-(25-30 wt.%) Al intermetallics show good shape controllability and excellent pore structure stability at 1073 K in air, which suggests that these porous Fe-Al intermetallics could be used for filtration at high temperatures.     

Oil retaining capability and sliding friction behaviour of porous copper with elongated cylindrical pores

Porous copper with elongated cylindrical pores aligned either axially or radially was fabricated under a high pressure of mixture gas of hydrogen and argon. Structure characterization indicated that pore size increased, pore density decreased, pore size distribution became wider with an increase in porosity for the porous copper. The dependence of oil retaining capability and sliding friction coefficient on porosity and pore size of the porous copper were investigated. It was found that the oil content of the porous copper depended mainly on the porosity, and reached 27.6% on the specimen with a porosity of 47.1%. On the other hand, the oil efficiency was not satisfactory, and became worse when the porosity increased, which was attributed to the increase in pore size and the wider pore size distribution for the porous copper. It was proven that the impregnated oil in the pores played an important role in improving the sliding friction behaviour of the porous copper.     

高强度多孔氮化硅陶瓷的制备及性能研究

以氮化硅为原料,以叔丁醇为溶剂,采用凝胶注模成型工艺和无压烧结工艺,制备出具有高强度和高气孔率的多孔氮化硅陶瓷。在浆料中初始固相含量固定为10vol%的基础上,研究烧结温度和保温时间对多孔氮化硅陶瓷材料的气孔率、孔径尺寸分布、物相组成及显微结构的影响,分析抗弯强度与结构之间的关系。结果表明,通过改变烧结温度和保温时间,可制备气孔率63.3%~68.1%的多孔氮化硅陶瓷;气孔尺寸呈单峰分布,平均孔径为0.97~1.42μm;抗弯强度随烧结温度提高或保温时间延长单调增大,在1750℃保温1.5h下达到最大值(74.2±8.8)MPa。     

注射成形制备多孔钛及其性能

以氯化钠作为造孔剂,利用金属注射成形(MIM)工艺制备多孔钛。研究烧结温度、造孔剂粒度和含量对多孔钛孔隙度、微观形貌和力学性能的影响。结果表明,随着烧结温度的升高,多孔钛的孔隙度逐渐下降而抗压强度和弹性模量逐渐升高;随着造孔剂粒度的减小,多孔钛的孔径也随之减小;随着造孔剂含量的增多,多孔钛的孔隙度逐渐增大;MIM多孔钛植入体的最佳烧结温度为1100～1200℃,NaCl的最优粒度为150～250μm。     

高温过滤支撑体用SiC基多孔陶瓷的制备与表征

通过以平均粒径300 μm的SiC为骨架材料,特定配比的高岭土、长石和二氧化硅的混合物为粘结剂,制备了可用于高温过滤膜管支撑体的SiC基多孔陶瓷.将粘结剂在1300 ℃烧结并保温1 h,X射线衍射(XRD)分析表明粘结剂中主要为石英相和玻璃相.多孔陶瓷的气孔率随着粘结剂含量从3%增加到15%(质量分数,下同)先升高后降低,其抗弯强度随着粘结剂含量的增加而增加.在粘结剂含量为10%时,多孔陶瓷的气孔率和抗弯强度都取得了较高的值,分别是34.3%和36.6 MPa.压汞法测得其平均孔径为24 μm,孔径分布较窄.用X射线能谱(EDS)测得不同SiC颗粒粘结处的粘结剂的元素组成,并与粘结剂设计组成对比,结果显示粘结剂各组分在多孔陶瓷中分布较均匀.利用扫描电子显微镜(SEM)观察了多孔陶瓷试样条断面的形貌.研究表明此多孔陶瓷可用作高温煤气过滤管的支撑体材料.     

Preparation of big size open-cell aluminum foam board using infiltration casting

This paper presents an infiltration casting technique for manufacturing big size open-cell aluminum foam boards. The principle and key technologies of infiltration casting are also analyzed. Based on the previous practice of the small size aluminum foam production, the die for preparing big size aluminum foam boards is designed and manufactured. The experiments on aluminum boards of 300 mm × 300 mm × （20-75） mm, with the pore size ranging from 1.0 to 3.2 mm and average porosity of 60%, have been performed. The experimental results show that a reliable infiltration process depends critically on the pouring temperature of the molten AI-alloy, the preheated temperature of the mould and salt particles and vacuum. Current research explores the possibility of large-scale manufacturing and application of the aluminum foams.