Structure and oil retaining capacity of gasar copper fabricated by radial solidification with a combined crystallizer

Porous copper with elongated pores was fabricated by a radial solidification method. The process was carried out in a combined crystallizer under high pressure of a mixture of hydrogen and argon. Pore size, pore length, pore density and porosity of the porous copper were characterized. Furthermore, the oil retaining capacity including oil content and oil efficiency was also evaluated. It is found that porous copper solidified with water-circulated chiller through a thick graphite jacket possesses a gradient structure with increasing pore size, and thus pore density decreases. Also pore length and pore aspect ratio decrease from lateral inwardly, while its porosity is almost uniform. The results show that the porous copper with radial pores has a good oil retaining capacity.     

Pore structure analysis of directionally solidified porous copper

Directionally solidified porous copper is considered as a potential candidate in the field of microchannel heat sinks.By the Bridgman-type directional solidification method,a porous copper ingot was fabricated.Evolution of the porosity,pore number density,average pore diameter and average interpore spacing at different ingot heights was investigated.The results show that with the increase of ingot height,the porosity firstly increases and then basically remains unchanged from the ignot height of 65 mm;the pore number density rapidly decreases at first,and the decreasing speed becomes slower when the ignot height higher than 85 mm;the average pore diameter increases and then remains unchanged from the ingot height of 85 mm;the average interpore spacing increases,and the increasing speed of average interpore spacing becomes slower with the increase of height to higher than 85 mm.In order to study the evolution of diameter and spatial distribution of pores,the distribution ranges of pore diameter,nearest-neighbor distance and radial cumulative pore number were analyzed.As the ingot height increases,the distribution ranges of pore diameter and nearest-neighbor distance firstly increase and then tend to be stable.There are no pore clusters and for long distance,the spatial distribution of pores is uniform at different ingot heights.Pore structure and 3D pore morphology of porous copper were observed with the help of light illumination and X-ray tomography.Pore nucleation,pore interruption,pore coalescence,diameter change of pores and lateral displacement of pores were found to exist in the pore structure.     

藕状多孔铜的连铸法制备工艺研究

连铸法是一种制备具有均匀孔洞分布的大尺寸藕状多孔材料的新工艺.利用自行开发的GASAR连铸装置,成功拉制出了15 mm的藕状多孔Cu连铸试样,并研究了下拉速率对孔隙率及气孔直径的影响.结果表明:随着下拉速率的增加,连铸试样中气孔尺寸分布逐渐变均匀;下拉速率对孔隙率的影响不大,而气孔直径随下拉速率的增加而降低.     

多孔铜的阻尼行为研究

为了研究宏观孔的引入对铜的阻尼性能的影响,运用气压渗流法制备了多孔铜,并利用多功能内耗仪对材料的阻尼行为进行了研究.研究发现,材料的阻尼性能得到提高,提高的幅度随孔隙率的增大或孔径的减小进一步增加,并对应变振幅有明显的依赖性.通过透射电镜微观分析,发现多孔铜中存在大量位错.试验结果表明,宏观孔和位错是材料阻尼性能提高的两大影响因素.     

Effect of transference velocity and hydrogen pressure on porosity and pore morphology of lotus-type porous copper fabricated by a continuous casting technique

A continuous casting technique was developed to fabricate, in a pressurized hydrogen atmosphere, lotus-type porous copper with long cylindrical pores aligned parallel to the solidification direction. The molten copper dissolving the hydrogen was pulled downward to be solidified through a cooled mould at a given transference velocity. This technique has the benefit of producing long-sized lotus-type porous metal slabs as long as 700 mm. The effects of the hydrogen gas pressure and the transference velocity on the porosity and the pore morphology were investigated. The porosity was independent of the transference velocity but dependent on the hydrogen gas pressure. The average pore diameter and pore length were affected by the changes of both the transference velocity and hydrogen gas pressure. The change of transference velocity affected the pore formation position near the slab surface. The porosity and pore size were therefore well controlled by the transference velocity and hydrogen gas pressure. It is concluded that the continuous casting technique is a promising method for the mass production of lotus-type porous metals.     

Gasar工艺下藕状多孔银的气孔结构研究

金属-气体共晶定向凝固（Gasar)是制备藕状多孔金属的新工艺,利用自行研制的Gasar装置,成功地制备了不同纯氧分压下的藕状多孔银试样,研究了氧气分压对藕状多孔银气孔形貌（气孔率、气孔尺寸和分布、气泡形核）的影响。结果表明：氧气分压对气孔形貌影响十分显著。随着氧气压力的增加,气孔率增大而平均气孔直径减小。     

气压对定向凝固藕状多孔镁的气孔分布影响

采用统计分析方法,通过孔径分布、气孔最邻近距离和局部气孔率定量分析定向凝固藕状多孔镁横截面上的气孔分布特征,并在此基础上分析气压对藕状多孔镁气孔分布的作用规律。结果表明:纯氢条件下气压越高,孔尺寸分布越趋于一致、孔位置和气孔结构单元分布越均匀;氢气分压一定,选择合适的氩气分压可使熔体共晶凝固时,孔尺寸、孔位置和气孔结构单元的分布最均匀。     

多孔TiC/NiAl复合材料的孔洞形貌及抗压强度

通过控制Ti、C、Ni、Al粉末之间的反应,利用自蔓延技术原位合成多孔TiC/NiAl复合材料,研究Ti-C(摩尔比1∶1)含量对多孔材料孔洞形貌和抗压强度的影响。结果表明:多孔材料孔洞形貌主要受反应物吸附气体挥发和液相流动的影响,Ti-C含量增加,孔隙率和孔径增大。当Ti-C含量为0～25%时,孔洞分布均匀,形貌以近球形为主,孔径大小在20～70 μm之间;多孔材料抗压强度随Ti-C含量增加逐渐增大。当Ti-C含量为30%时,除近球形孔洞外,还出现了一些尺寸大于100 μm的形状不规则孔洞和狭长形孔洞,抗压强度下降。     

FRICTION PROPERTIES OF OIL-INFILTRATED POROUS AAO FILM ON AN ALUMINUM SUBSTRATE

1. IntroductionA lum inum and its alloys are used in m any engineering applications because of their highstrength-to-w eightratio and high therm alconductivities.H ow ever,high friction coefficient,poorw earresistance and low seizure load ofalum inum allo…     

多孔金属结合剂CBN砂轮孔隙结构对磨料层胎体力学性能的影响

为解决多孔金属结合剂CBN砂轮在高孔隙率下的强度下降问题,采用球形尿素颗粒为造孔剂,制作孔径、孔形和孔隙可控的多孔金属结合剂砂轮磨料层胎体,研究不同载荷情况下的孔隙率和孔隙排布等孔隙结构因素,对多孔金属结合剂磨料层胎体力学性能的影响规律。结果表明:孔隙有序排布时的胎体弹性模量要小于孔隙无序排布的;胎体材料的屈服强度随孔隙率增大而下降;在相同孔隙率下,孔隙有序排布的胎体,在纵向受压、孔隙正向排布的情况下屈服强度更高。      

Influence of Structural Parameters on Tensile Property of Gasar Porous Copper

采用金属-气体共晶定向凝固工艺,制备了不同结构参数的Gasar多孔铜,并研究了结构参数对单向拉伸下多孔铜性能的影响。利用扫描电镜观察拉伸试样的断面形貌,通过建立数学模型和计算机模拟的方法来表征其拉伸强度,并用实验数据加以验证。结果表明,多孔铜的拉伸性能主要取决于气孔率和拉伸方向;多孔铜在平行气孔轴向拉伸时比垂直气孔轴向拉伸时具有更优异的抗拉强度;平行气孔轴向拉伸时,抗拉强度随着气孔率的增加线性下降,气孔对基体的应力集中作用微小,抗拉强度的数学模型数值和模拟数值与试验数值拟合良好;垂直气孔轴向拉伸时,抗拉强度随气孔率的增大而明显下降,气孔对基体的应力集中作用显著,抗拉强度的试验数值与模型数值以及模拟数值基本符合     

The effect of porosity on the elasticity of pure titanium: An atomistic simulation

The effects of the porosity, size, shape and mutual connectivity of pores on the elastic property of pure titanium were investigated using an atomistic simulation (molecular statics). The study concluded that the elasticity of porous Ti is mainly governed by its porosity. The results showed that the size and shape of the pores do not have a significant effect as long as the pores are separated from each other. The interconnection of the pores contributes to further decrease the elasticity than expected from the porosity of samples with isolated pores, and can be thought to be an important factor to further reduce the elasticity of porous load-bearing implant metals. In addition, the atomistic calculation proved to be a successful approach to use with experiments testing the effect of porosity on elastic property, and could be further developed to deal with Ti alloys that have more complex distribution and pore shapes.     

定向凝固多孔Cu热沉传热性能的实验研究

利用定向凝固多孔Cu制备了气孔呈定向规则排布的多孔Cu热沉,对沿孔长方向长度20 mm热沉的传热性能进行了实验研究.实验结果表明,定向凝固多孔Cu热沉具有优异的传热性能,当气孔率为29%,平均孔径为400μm时,热沉的换热系数可以达到5 W/(cm~2·K),沿孔长垂直方向将定向凝固多孔Cu切割成沿孔长方向排列的2段后,其换热系数可以提高到6.5 W/(cm~2·K).这说明当定向凝固多孔Cu沿孔长方向的长度较大时,通孔率降低限制了热沉的传热性能.     

石墨烯纳米片对多孔PI复合材料含油性能及摩擦学性能的影响∗

多孔聚酰亚胺(PI)应用广泛,但其摩擦磨损特性有待进一步提升。 采用石墨烯纳米片(GNS)为改性剂,制备多孔 PI 复合材料,系统研究 GNS 填充剂对多孔 PI 材料的冲击性能、含油性能和摩擦学性能的影响,探究 GNS、PI 和润滑油三者的协调润滑机制。 结果表明:添加一定量的 GNS 可以提高多孔 PI 材料的含油率和含油保持率。 加入 GNS 填料后,复合材料的孔径和孔隙率均有所增大,使复合材料对油液的吸附力更强,提高了其贮油能力。 复合材料的冲击强度随着 GNS 含量的变化为先升高后降低,少量的 GNS 分散在基体中,可以起到增韧的结果,而大量的 GNS 削弱了 PI 颗粒之间的结合性,且容易团聚导致界面结合性变差。 添加 0. 5% GNS 时,多孔 PI 复合材料表现出最佳的摩擦学性能,相比纯 PI,摩擦因数降低了 37. 2%,磨痕宽度减小了 26. 5%。 适量的 GNS 可以进一步提高材料的含油性能和摩擦性能。     

Pore size scaling for enhanced fracture resistance of nanoporous polymer thin films

Poly(arylene) ether (PAE) polymer films containing controlled nanometer-sized pores are shown to exhibit increasing fracture resistance with porosity. Such surprising behavior is in stark contrast to widely reported behavior for the fracture toughness of porous solids, which decreases markedly with porosity. A ductile nano-void growth and coalescence fracture mechanics-based model is presented to rationalize the increase in fracture resistance of the voided polymer film. The model is shown to explain the behavior in terms of a specific scaling of the size of the pores with pore volume fraction. It is demonstrated that the pore size must increase with close to a linear dependence on the volume fraction in order to increase rather than decrease the fracture energy. Independent characterization of the pore size as a function of volume fraction is shown to confirm predictions made by the model. Implications for the optimum void size and volume fraction are considered for superior fracture resistance of the nanoporous films.     

藕状多孔金属Mg的Gasar工艺制备

金属／气体共晶定向凝固(Gasar)是一种制备规则多孔金属的新工艺．本文利用自行开发的Gasar装置，成功制备了具有规则气孔分布的藕状多孔金属Mg，并研究了气体压力对气泡形核、气孔率、气孔大小和分布的影响。     

Study on Micron Porous Copper Prepared by Physical Vacuum Dealloying

Porous copper was prepared successfully by physical vacuum dealloying method using the Cu Zn alloy precursors(Cu30Zn70, Cu40Zn60 and Cu50Zn50 alloys). The micron porous copper showed a three-dimensional continuous porous structure with 1–5 μm pore size. With the increase of the Zn content in the CuZn alloy, the pore structure of the porous copper was more uniform and ordered. Temperature was the key factor for physical dealloying, and the optimized temperature was 500 °C for the CuZn alloy. The pores would fuse and disappear when the temperature was over 500 °C.Physical vacuum dealloying was an effective preparation method for porous copper, which can be used to prepare other porous metals based on the sublimation and the Kirkendall effect.     

新型超轻TiAl多孔材料的制备及其力学性能

基于化学反应造孔和物理占位造孔的联合作用,发展了一种新型Ti Al金属间化合物多孔材料的制备工艺,具体可用均混、压制、脱溶、烧结4个阶段来描述。该工艺实现了毫/微米双孔结构Ti Al多孔材料的制备,其中微米孔由Kirkendall效应产生,毫米孔由物理占位造孔颗粒实现。材料具有完全的通孔结构,孔洞分布均匀,且孔隙率、孔径、孔型、孔结构可控,最高孔隙率可达90%。准静态压缩力学性能测试表明,Ti Al多孔材料属于脆性多孔材料,具有典型的脆性破坏断裂机制,其屈服强度与相对密度的关系可通过Gibson-Ashby正六面体单胞模型来解释。     

孔隙对NiTi形状记忆合金中B2-R相变影响的相场模拟

建立了适用于含孔隙NiTi合金中B2-R相变的相场模型,并用该相场模型研究了多孔NiTi合金中B2-R转变的微观组织演化过程以及孔隙率和孔尺寸对R相变体生长动力学行为的影响.多孔NiTi合金中R相变体以相互协调的方式形成"带状"的三维结构和"鱼骨"状的二维组织,变体之间形成的孪晶面包括{101}B2和{001}B2 2...     

Effect of fly ash cenosphere pore formers on the microstructure and mechanical properties of vitrified diamond grinding wheels

This paper focuses on the influence of fly ash cenosphere (as a pore former) content and particle size on the porosity, microstructure and mechanical properties of vitrified bond diamond tools. The sintered specimens were examined using comprehensive thermal analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, three point bending tests and porosity measurements. The porous morphological parameters (volume, size and distribution of pores) of the sample correlated with the content and size of the fly ash cenosphere, and diffusion layers were formed between the pore former and the vitrified matrix. The bending strength of the porous vitrified matrix varied between 27.28 and 35.92 MPa as the porosity changed from 40.66–43.97%. Based on response surface methodology (RSM) studies, two second-order response models for the open porosity and bending strength were established, and the utilization of the response surface model was evaluated with regards to the content and size of fly ash cenosphere present.