高孔隙率、小孔径泡沫铝的制备及压缩性能

以纯铝为基体材料、钙为增黏剂、TiH2为发泡剂制备了高孔隙率(80%)不同孔径的泡沫铝;研究了对发泡剂进行表面氧化处理、增黏搅拌时间、发泡剂加入量和发泡时间对泡沫铝孔结构的影响,并对不同孔径的泡沫铝进行了压缩试验。结果表明:对发泡剂进行氧化处理可以减缓其释放氢的速度,经过相同时间发泡后可获得孔径更小的泡沫铝,但要获得相同孔隙率的泡沫铝,则经氧化处理发泡剂的加入量应比未经氧化处理的大;延长增黏搅拌时间有利于获得小孔径泡沫铝;其他条件相同时,泡沫铝的孔径和孔隙率随着发泡时间的延长而增大;孔隙率相近时,孔径小的泡沫铝,单向压缩应力应变屈服平台较高,吸能能力也较大。     

无需增黏熔体发泡法制备泡沫铝及其压缩性能

以CaCO3为发泡剂,加入基体质量1.0%~3.0%的镁,在不使用增黏剂的情况下采用熔体发泡法制备出了孔结构均匀、孔隙率在62.4%~84.0%的泡沫铝,研究了镁的添加对铝熔体发泡效果的影响,最后考察了泡沫铝的压缩性能。结果表明:在铝熔体中添加适量的镁有利于形成孔结构均匀的泡沫铝,CaCO3与熔体发生产气反应后,产生的金属氧化物颗粒对铝熔体有增黏作用,可以提高熔体黏度,并可以存在于胞壁中,有利于小孔径胞孔的形成;但泡沫铝胞壁中存在的大量微孔会导致泡沫铝压缩性能降低。     

球形孔泡沫铝及其合金的拉伸性能

采用熔体发泡法制备了球形孔泡沫铝及其合金,对它们进行了拉伸试验,研究了孔隙率对拉伸性能的影响。结果表明:球形孔泡沫铝及其合金的拉伸应力-应变曲线相似,均呈现线弹性变形、平台、塑性上升、破坏四个阶段;它们的抗拉强度远低于它们的抗压强度;随孔隙率的增大它们的抗拉强度逐渐减小。     

过氧化苯甲酰对偶氮二甲酰胺在硅橡胶中发泡行为的影响

以偶氮二甲酰胺(AC)为发泡剂、尿素为发泡助剂、过氧化苯甲酰(BPO)为硫化剂,通过化学发泡方法制备了硅橡胶泡沫材料;使用发泡流变仪研究了发泡剂AC在硅橡胶中的发泡性能,使用SEM、电子万能材料试验机分析了泡沫材料的泡孔结构和拉伸性能。结果表明:在一定温度下,发泡速率与硫化速率可较好地匹配,得到不同泡孔结构的硅橡胶泡沫材料;增加发泡剂AC用量,可提高胶料的发泡率,当其用量为8份时(100份硅橡胶),泡沫材料具有较好的拉伸性能。     

原料配比对石英质孔梯度陶瓷性能的影响

以低品位石英砂为主要原料,通过制浆、成型、干燥和烧结等工序制备得到不同原料配比的石英质孔梯度陶瓷,研究了石英砂含量、水料质量比和发泡剂含量对该陶瓷气孔率、抗压强度和显微结构的影响,得到了较佳的原料配比.结果表明:随着石英砂含量的增加,试样的气孔率增大,宏观上呈现出一定的孔梯度结构;随着水料质量比的增加,试样的气孔率先增后降,气孔变得均匀,裂纹减少;随着发泡剂含量的增加,气孔率增大;抗压强度与气孔率呈现相反的变化规律;较佳原料配比为石英砂质量分数为70%,水料质量比为1.0,发泡剂质量分数为0.8%,制备得到石英质孔梯度陶瓷的抗压强度为6.18MPa,气孔率为63.5%,孔形较好.     

中空玻璃微珠改性PP泡沫复合材料的发泡效果和力学性能

先用硅烷偶联剂(KH550)对中空玻璃微珠(HGB)进行表面预处理,然后采用型内二次发泡工艺制备了中空玻璃微珠(HGB)改性聚丙烯(PP)泡沫复合材料,研究了HGB质量分数对泡沫复合材料发泡效果、界面结合性能及力学性能的影响。结果表明:HGB的加入能显著改善发泡效果,当HGB质量分数为15%时,能够获得泡孔分布均匀、泡孔直径细小的闭孔结构,泡沫复合材料的力学性能最佳,冲击韧度、抗弯强度和压缩强度分别为25.6kJ·m-2,11.2 MPa和17.6MPa;KH550表面预处理增强了HGB与PP基体之间的界面结合性能,且对泡壁强度起到了显著增强效果。     

复合结构泡沫铝隔声性能的研究

采用自制的试验装置对泡沫铝与实体铝复合结构的隔声性能作了研究。结果表明：泡沫铝与实体铝的复合结构在声频范围内均具有较好的隔声作用且对频率敏感，在500-1000Hz内隔声效果最佳，综合降噪率为40％；隔声效果受两者复合方式的影响不大，但随泡沫铝孔结构的不同而异；孔径为1．0mm、孔隙率为60％的泡沫铝试样，隔声效果最优，可在实体铝隔声的基础上再降噪16％-23％。     

泡状铝合金发泡工艺的探讨

在综合分析泡状铝合金各种制备工艺的基础上，选用廉价的漂珠作发泡剂和增稠剂，对五种不同的发泡工艺进行了对比实验研究。结果表明：在液固两相区采用喷吹漂珠机械搅拌和重熔多级发泡的方法，适当控制处理温度、搅拌速度和时间，可以制备出空隙率达６０％左右、孔隙均匀的泡状铝合金材料。     

塑料泡沫自动覆膜机的开发

针对目前塑料泡沫制品易燃的现象,利用某些化学成分的阻燃特性,设计开发了塑料泡沫自动覆膜机。在发泡后的塑料泡沫颗粒中加入多种化学产品,并进行搅拌,发泡后的塑料泡沫颗粒表面均匀涂上一层特殊的化学覆膜液,然后再成型,使塑料泡沫保温制品达到阻燃的效果。该机具有自动进料、自动计量、自动出料、故障报警等功能,自动化程度高。     

变压器隔声降噪用Al_2O_3泡沫陶瓷的制备及其吸声性能

采用凝胶发泡法制备了变压器隔声降噪用Al_2O_3泡沫陶瓷,通过试验得到了胶凝剂和发泡剂的最佳加入量,研究了在该最佳加入量下制备试样的厚度及其背后空腔尺寸对吸声性能的影响。结果表明:当发泡剂和胶凝剂的质量分数均为1.00%时,制备的泡沫陶瓷的孔隙率为75.2%,平均孔径为150μm,抗弯强度和抗压强度分别为8.13 MPa和5.41 MPa;当试样厚度为15mm、背后空腔厚度为20mm时,Al_2O_3泡沫陶瓷的峰值吸声系数可达0.8,其在100~500 Hz低频范围的吸声系数为0.12~0.65。     

金属铝粉/无机多孔粉末改性PP基复合材料的性能研究

本文以聚丙烯(PP)为基础材料,通过添加一定量的金属铝粉和多孔粉体对其进行共混改性,并研究了复合材料的拉伸强度、冲击强度、球压痕硬度和耐热性.结果表明:当金属铝粉含量为2wt％,多孔粉体含量为7wt％时,复合材料的耐热性最好;当金属铝粉含量为2wt％,多孔粉体含量为9wt％时,复合材料的拉伸强度达到21.14MPa,冲...     

硅渣和玻璃粉直接烧结制备多孔材料的气孔结构与力学性能

以硅渣和玻璃粉为原料,采用粉体直接烧结法制备多孔材料,研究了烧结温度(700~900℃)、烧结时间(15~120min)和升温速率(10~100℃·min^-1)对多孔材料表观密度、气孔率、物相组成、抗压强度的影响。结果表明:气孔结构均匀性随烧结温度的升高而降低;表观密度随烧结温度的升高先减小后增大,随保温时间的延长而增大,随升温速率的增大而减小,气孔率的变化趋势与表观密度的相反;多孔材料的主要物相为玻璃相和硅、SiC、SiO2、Ca2Al2SiO7等结晶相,且结晶度随烧结温度的升高而降低;抗压强度随烧结温度的升高呈先增大后减小的趋势;当烧结温度为750℃,升温速率为30℃·min^-1,烧结时间为30 min时,多孔材料的主晶相为硅和Ca2Al2SiO7,抗压强度最大(1.60MPa),表观密度为0.43g·cm^-3,气孔率为80%。     

稀土对泡沫铝及泡沫铝合金耐腐蚀性能的影响

研究了稀土对泡沫铝及泡沫铝合金泡沫化和压缩性能的影响,讨论了稀土加入量和泡沫铝及泡沫铝合金耐腐蚀性能的关系。结果表明：稀土对铝合金泡沫化无异常影响;在泡沫铝和泡沫铝合金中添加适量稀土元素,可以提高泡沫铝和泡沫铝合金的耐腐蚀性能;相同腐蚀介质中,孔隙率高的泡沫铝合金腐蚀更严重;稀土对泡沫铝及其合金的力学性能影响不大。     

原位反应法制备Al2O3/Cu复合材料的工艺研究

将自蔓延和传统铸造方法相结合,制备原位Al2O3颗粒增强铜基复合材料。研究原料配比、反应温度、预制片成型压力以及混粉时间等参数对复合材料组织的影响。结果表明,最佳的工艺参数为:铝粉与氧化铜粉的质量比为2∶1,铜粉加入量为5%(质量分数);预制片成型压力为12 MPa;浇注温度为1 120℃,混粉时间为30 min。     

Processing and properties of Al2O3/SiC nanocomposites

Alumina/SiC nanocomposites were produced by mechanical mixture of commercial powders. The preparation steps involved the vigorous mixing of the powders and drying under conditions where the homogeneous mixture was kept stable. Pressureless sintering of die-pressed powders achieved reasonable densities (～97% theoretical density) for 2·5wt% of SiC on sintering at 2073 K. Higher SiC contents strongly reduced the sintered density. The use of a more reactive alumina (finer matrix powder) gave similar results. Hot pressing at 1973 K/1 h/25 MPa produced high-density materials for SiC contents as high as 20 wt%. Transmission and scanning electron microscopy analysis showed that the SiC particles were well distributed and were situated both inside the grains and on the grain boundaries of the alumina matrix. The SiC strongly inhibited grain growth in the matrix in keeping with the Zener model. The bend strength increased as the SiC content increased, a result partly explained by the grain size refinement. The strength improvement of 20% over monolithic was explained in terms of the change to an intergranular fracture mode.     

A novel approach to manufacturing and experimental investigation of closed-cell Al foams

This investigation proposes a modified technique for manufacturing closed-cell aluminum foams to reduce the cost of production of foaming agents during the casting and foaming process. The addition of foaming agents promotes the uniformity of cell sizes and controls the viscosity of the melting aluminum alloy. Moreover, this work elucidates the mechanical characteristics of closed-cell aluminum foams under compressive loading. Discussions cover the compressive stress-strain curve, densification strain and energy absorption effects of various specimens with various porosities. Furthermore, the thermal conductivity of the aluminum foams is determined, and the results compared with some theoretical predictions. The optimum parameters for meeting some tendentious and practical design requirements, such as those of impact absorption and thermal insulation design applications, are discussed. Finally, an empirical correlation between normalized yield strength and relative densities is obtained .     

A novel approach to the manufacturing and experimental investigation of closed-cell Al foams

This investigation proposes a modified technique for manufacturing closed-cell aluminum (Al) foams to reduce the cost of the foaming agents during the casting and foaming processes. The addition of foaming agents promotes the uniformity of cell sizes and controls the viscosity of the melting aluminum alloy. This work elucidates the mechanical characteristics of closed-cell aluminum foams under compressive loading. The discussions in this paper cover the compressive stress–strain curve and the densification strain and energy absorption effects of various specimens with various porosities. The thermal conductivity of the aluminum foams is determined, and the results are compared with some theoretical predictions. The optimum parameters for meeting some practical design requirements, such as impact absorption and thermal insulation design applications, are discussed. Finally, an empirical correlation between the normalized yield strength and the relative densities is obtained.     

橡胶模成型和真空烧结制备碳化硼锆合金

以碳化硼、氢化锆-2粉为原料,用橡胶模成型和真空烧结的方法制备了碳化硼锆合金,用浸渍法测定烧结体的相对密度与开孔率,用扫描电镜分析了烧结体的微观结构,研究了碳化硼含量、成型压力、烧结温度、保温时间、助烧剂加入量对碳化硼锆合金相对密度的影响。结果表明:碳化硼对烧结有阻碍作用,烧结体的相对密度随碳化硼含量的增加而降低;坯体的成型压力越高,烧结温度越高,保温时间越长,烧结体的相对密度越高;锡粉有较好的助烧作用,但锡粉的质量分数不宜超过0.5%,如果添加量过高,烧结体的相对密度反而下降。     

Fabrication and characterization of three-dimensional poly(ether- ether- ketone)/-hydroxyapatite biocomposite scaffolds using laser sintering

The ability to have precise control over porosity, scaffold shape, and internal pore architecture is critical in tissue engineering. For anchorage-dependent cells, the presence of three-dimensional scaffolds with interconnected pore networks is crucial to aid in the proliferation and reorganization of cells. This research explored the potential of rapid prototyping techniques such as selective laser sintering to fabricate solvent-free porous composite polymeric scaffolds comprising of different blends of poly(ether-ether-ketone) (PEEK) and hydroxyapatite (HA). The architecture of the scaffolds was created with a scaffold library of cellular units and a corresponding algorithm to generate the structure. Test specimens were produced and characterized by varying the weight percentage, starting with 10 wt% HA to 40 wt% HA, of physically mixed PEEK-HA powder blends. Characterization analyses including porosity, microstructure, composition of the scaffolds, bioactivity, and in vitro cell viability of the scaffolds were conducted. The results obtained showed a promising approach in fabricating scaffolds which can produce controlled microarchitecture and higher consistency.