Ti/SiO2 composite fabricated by powder metallurgy for orthopedic implant

Titanium/silica (Ti/SiO₂) composites are fabricated using powder metallurgy (P/M). Nanoscale biocompatible SiO₂ particles are selected as reinforcement for the Ti/SiO₂ composite to enhance its biocompatibility and strength, especially when with high porosity. Effects of the SiO₂ particle addition and sintering temperature on mechanical properties of the Ti/SiO₂ composites are investigated. The results indicate that the mechanical property of Ti/SiO₂ composites sintered at 1100 °C are better than those at 900 and 1000 °C. The strength of the Ti/SiO₂ composites is significantly higher than that of pure titanium. The composite with the SiO₂ content of 2 wt% sintered at 1100 °C for 4 h shows an appropriate mechanical property with a relative density of 96.5%, a compressive strength of 1566 MPa and good plasticity (an ultimate strain of 15.96%). In vitro results reveal that the Ti/SiO₂ composite possesses excellent biocompatibility and cell adhesion. Osteoblast-like cells grow and spread well on the surfaces of the Ti/SiO₂ composites. The Ti/SiO₂ composite is a promising material for great potential used as an orthopedic implant material.     

Osteoblast and stem cell response to nanoscale topographies: a review

To understand how cells respond to the nanoscale extracellular environment in vivo, cells from various sources have been cultured on nanoscale patterns fabricated using bottom-up and top-down techniques. Human fetal osteoblasts (hFOBs) and stem cells are some of them and they are known to be overtly responsive to nanoscale topographies – allowing us to investigate the hows and whys of the response in vitro. Information gathered from these in vitro studies could be used to control the cells, i.e. make the stem cells differentiate or retain their characteristics without the use of medium supplements. In this review, hFOB and stem cell responses to nanotopographies are summarized and discussed to shed some light on the influence of patterns on the reactions. Although both types of cells are responsive to nanoscale topographies, the responses are found to be unique to topographical dimension, shape, orientation and the types of cells used. This implies that cellular responses are influenced by multitude of factors and that if done right, cheaper self-assembled nanotopographies can be tailored to control the cells. A new self-assembly, powder-based technique is also included to provide an insight into the future of nanofabrication.     

Fabrication and microstructure of ZrO2-Ni functional gradient material by powder metallurgy

Functional gradient material (FGM) of the ZrO₂-Ni system was developed by a powder metallurgical process, and investigated for its microstructure by means of X-ray diffractometry (XRD), electron probe microanalysis (EPMA), transmission electron microscopy (TEM) and optical microscopy. It was shown that the sintered body of ZrO₂-Ni FGM is almost fully densified, and its chemical composition and microstructure have the expected gradient distribution. With composition variation, the microstructure changes gradually from zirconia particles dispersed in a nickel matrix to the converse with nickel particles dispersed in a zirconia matrix, with network structures in the intermediate composition range. Therefore, no distinct interfaces appear in the FGM due to the gradient change of components, that is, both zirconia and nickel are present everywhere in the microstructure. In phase composition, the sintered ZrO₂-Ni FGM consists of nickel, tetragonal zirconia and a little monoclinic zirconia. No reaction between nickel and zirconia has been detected. The substructure of nickel and monoclinic zirconia are twins, and strain fringes can also be found in zirconia.     

Fabrication of TiB2 particulate reinforced magnesium matrix composites by powder metallurgy

Magnesium metal matrix composites (MMCs) reinforced with 10, 20 and 30 vol.% TiB₂ particulates, respectively, were fabricated by powder metallurgy. The microstructure, porosity, hardness and abrasive wear behavior of the composites were evaluated. Microstructural characterization of Mg MMCs showed generally uniform reinforcement distribution. As compared with pure Mg, the hardness (HB) values of Mg MMCs reinforced with 10, 20 and 30 vol.% TiB₂ particulates were increased by 41%, 106% and 181%, respectively. The abrasive wear tests showed that the wear resistance of Mg MMCs is increased with the increasing of the reinforcement volume fraction. This was due to the strong particulate-matrix bonding and high hardness of the TiB₂ particulate.     

烧结多孔钛的显微组织和孔隙特征

采用粉末冶金方法，添加聚甲基丙烯酸甲酯作为造孔剂，经1300℃烧结2h获得孔隙度为25％～70％（体积分数），孔隙尺寸为10～10001am的多孔钛。多孔钛具有三维连通的孔隙结构，其孔可以分为两种：一种是分布均匀、而且相互连通的宏观孔隙；另一种是分布在开放贯通的大孔壁上，孤立的近似球形的微孔。其孔隙度、孔隙尺寸及孔隙的连通程度随着造孔剂体积分数和粒度的增大而增大。     

非传统粉末冶金制备生物医用多孔钛及其性能

以生物医用球形雾化钛粉为原料,碳酸氢铵做造孔剂,采用放电等离子烧结(SPS)技术制备了生物医用多孔钛块体材料。采用XRD、SEM分别对所制备的多孔钛的物相组成、微观形貌进行分析,并研究了多孔钛的力学性能及成骨细胞在其表面的粘附生长情况。结果表明:通过调节造孔剂添加量、控制烧结工艺可制备孔隙率为50.3%～70.5%、孔径为100～300μm的多孔钛,其力学性能(抗压强度为24.40～68.96MPa、弹性模量为1.010～1.287GPa)与人体松质骨相匹配。与SD大鼠成骨细胞的联合培养结果表明,该材料的粗糙表面和多孔结构可粘附生长成骨细胞,具有良好的生物相容性。     

ZrO2、SiO2改性对Al2O3薄膜的影响

Al2O3薄膜的应用近年受到很大的关注，它在过滤和分离等领域内具有极大的应用前景，但就其本身而言，仍存在一些不足之处。本文用Sol-Gel法制备了掺杂ZrO2、SiO2的改性Al2O3薄膜，并通过SEM、XRD等方法进行了表征。实验表明，掺杂后能提高Al2O3薄膜的化学稳定性和延缓烧结过程中的相变，使薄膜的性能得到提高。     

ZrO2/hydroxyapatite coating on titanium by electrolytic deposition

In this study, hydroxyapatite (HA) was coated on a titanium (Ti) substrate over a ZrO(2) layer by the electrolytic deposition method, this double layer coating was then compared with a single layer coating of HA. The HA layer was used to increase the bioactivity and osteoconductivity of the Ti substrate, and the ZrO(2) layer was intended to improve the bonding strength between the HA layer and Ti substrate, and to prevent the corrosion of the Ti substrate. The electrolytic deposition formed an HA layer with a thicknesses of approximately 20 mum, which adhered tightly to the Ti substrate. The bonding strength of the HA/ZrO(2) double layer coating on Ti was markedly improved when compared to that of the HA single coating on Ti. The improvement in bonding strength with the use of a ZrO(2) base layer was attributed to the resulting increase in chemical affinity of the ZrO(2) to the HA layer and to the Ti substrate. The osteoblast-like cells cultured on the HA/ZrO(2) coating surface, proliferated in a similar manner to those on the HA single coating and on the pure Ti surfaces. At the same time, the corrosion resistance of Ti was improved by the presence of the ZrO(2) coating, as shown by a potentiodynamic polarization test.     

Interfacial design of Cu/SiC composites prepared by powder metallurgy for heat sink applications

In order to dissipate the heat generated in electronic packages, suitable materials must be developed as heat spreaders or heat sinks. Metal matrix composites (MMCs) offer the possibility to tailor the properties of a metal (Cu) by adding an appropriate reinforcement phase (SiC) to meet the demands for high thermal conductivities in thermal management applications. Copper/SiC composites have been produced by powder metallurgy. Silicon carbide is not stable in copper at the temperature needed for the fabrication of Cu/SiC. The major challenge in development of Cu/SiC is the suppression of this reaction between copper and SiC. Improvements in bonding strength and thermo-physical properties of the composites have been achieved by a vapour deposited molybdenum coating on SiC powders to control the detrimental interfacial reactions.     

Improvement in physical and mechanical properties of aluminum/zircon composites fabricated by powder metallurgy method

Metal–matrix composites (MMCs) are known as the most useful and high-tech composites in our world as well as aluminum (Al) as the best metal for producing these composites. Combining aluminum and zircon (ZrSiO₄) will yield a material with the best corrosive resistance and mechanical properties like strength at high temperatures. Also, the abrasive wear behavior of these composites will be improved. In the present investigation, a study on aluminum/zircon composites has been carried out. Micro-structures of these composites in powder metallurgy conditions show different size distribution of zircon with different proportions in the composite. Also, there is a case-study about density and compressive strength and hardness of aluminum/zircon composites. The green specimens prepared by isostatic pressing of prepared powders with different zircon percentages, were sintered at two temperatures. These specimens were then investigated by different physical and mechanical testing methods to observe in which conditions the best properties would be obtained. The most improved compression strength was obtained with the specimen including 5% of zircon sintered at 650 °C.     

Control of microstructure and component shape in rapidly solidified/powder metallurgy titanium alloys

Extensive use of titanium rapidly solidified/powder metallurgy (RS/PM) components requires not only careful control of the microstructure for optimum mechanical properties but also cost-effective processing. A new direct reduction process for production of titanium alloy powder will be presented. Control of the microstructure in conventional alloys such as Ti-6Al-4V and in non-conventional dispersion strengthened terminal and intermetallic alloys will be discussed. It will be shown that RS/PM processing allows production of a fine grain size and useful dispersions of rare earth and metalloid phases; phases which normally form as gross undesirable particles. The use of hydrogen as a temporary alloying element, thermochemical processing, will be discussed and it will be demonstrated how this treatment can lead to refined microstructures with enhanced mechanical behaviour. Cost-effective processing using near-net shape techniques such as the ceramic mold process, rapid omnidirectional compaction (ROC), and the use of RS/PM preforms for subsequent isothermal forging will be presented. Microstructural control and shape-making used in unison should lead to increased use of titanium components in advanced aerospace systems. work done as a consultant to Metcut-Materials Research Group     

SiO2f/SiO2-BN复合材料的制备及其性能

以石英纤维预制件和硅溶胶为原料,采用溶胶-凝胶法制备了SiO2f/SiO2复合材料,在此基础上用尿素法制备了SiO2f/SiO2-BN复合材料,并对其力学性能和介电性能进行了测试.结果表明,随着工艺循环次数的不断增加,复合材料的密度随之提高,但增长速度逐渐减慢.三次循环后,SiO2f/SiO2-BN复合材料密度达1.8...     

2014 and 6061 aluminium alloy-based powder metallurgy composites containing silicon carbide particles/fibres

The present investigation covers the processing and mechanical properties of 2014 and 6061 Al alloy-based power metallurgy composites containing up to 8 vol% of SiC in either particle or continuous fibre form. For consolidation of the green compacts, liquid phase sintering under vaccum at 635°C was adopted. The addition of reinforcement imparted improved densification such that particulate composites were better densified than the fibrous ones. Relatively higher work hardening rates were observed in fibrous composites than in the particulate ones. The ductility values of obtained porous particulate composites were similar to those of the fully dense ones reported in the literature.     

Preparation and properties of lead-free FeS/Cu-Bi composites by flake powder metallurgy via shift-speed ball milling

Lead-free FeS/Cu-Bi (FCB) self-lubricating composites were prepared via shift-speed ball milling (SSBM) and powder metallurgy. The microstructure and evolution of mixed powders were studied, and the mechanical and tribological properties of the FCB composites were tested. SSBM includes long-term low-speed ball milling (LSBM) and short-term high-speed ball milling (HSBM). In the early LSBM, the matrix phase CuSn10 powder was flattened into flakes, and the lubricating phases FeS and Bi were refined and gradually dispersed on the CuSn10 flakes. After short-term HSBM, FeS and Bi were further trapped on the CuSn10 flakes, which not only improved the bonding performance between the lubricating phase and copper alloy but also protected the continuity of the copper alloy matrix from additional damage. 6 + 1 h SSBM (6 h LSBM + 1 h HSBM) improved the mechanical properties, antifriction and wear resistance of FCB composites. Compared with traditional HSBM, SSBM provides a new way to prepare FCB self-lubricating composites with better comprehensive properties.     

溶胶-凝胶法制备SiO2/ZrO2无机复合膜的研究

以硅酸乙酯和氧氯化锆为先驱体,用乙醇为溶剂,采用溶胶--凝胶法于室温下在Al2O3基体上制备了ZrO2/SiO2无机复合膜.重点考察了涂膜温度、ZrOCl2摩尔百分含量、溶胶浓度及添加剂对膜性能的影响.结果表明:在较高的温度下涂膜可以提高膜的性能;ZrOCl2的存在对渗透比的影响不大,但能够提高溶胶的交联度,从而提高制膜效率,同时也有利于渗透通量的提高;采用浓溶胶和稀溶胶结合的方式涂膜不但可以提高制膜效率,还可以提高膜的性能.添加剂TEABr能够均化膜孔径,提高膜的性能.     

TiB2/ZrO2复合材料介电及力学性能研究

以热压烧结制备了TiB2/ZrO2复合材料,研究了其在8.2～12.4GHz的介电特性和力学性能,探讨了材料极化和损耗机理.结果表明,Ib2降低了复合材料的烧结性能;纯ZrO2无明显损耗,Ro2内部价电子随电场移动使基体发生极化,Ib2在材料中形成的导电网络使复合材料复介电常数实部和损耗增加.复合材料的硬度随TiB2体积分数增加而下降,抗弯强度和断裂韧性随TiB2体积分数增加先上升后下降,这是由复合材料相对密度、基体晶粒尺寸以及TiB2的韧化作用等因素共同决定的.     

Fabrication,microstructures, and tensile properties of magnesium alloy AZ91/SiCp composites produced by powder metallurgy

Abstract

The tensile properties and microstructural evolution of hot extruded AZ91 magnesium alloy with and without reinforcement of SiC particles have been investigated in terms of extrusion parameters, such as extrusion ratio and extrusion temperature. Also, the effect of SiC particles on the grain size of the matrix in the composites was evaluated using the Hall-Petch equation. The AZ91 magnesium alloy powders prepared by wet attrition milling from magnesium machined chips were hot pressed with and without SiC particles, hot extruded, and then solution treated. Microstructural observation revealed that both the composites and the magnesium alloy have fine equiaxed grains due to the dynamic recrystallisation during hot extrusion. The tensile strength of both materials increased with increasing extrusion ratio, and the strengths of the composites were higher than that of the magnesium alloy without reinforcement. It was found that the tensile strength of both the materials decreased after solution treatment, and the decrease in tensile strength of the composites was considerably smaller than that of the magnesium alloy. From analyses of the microstructures and the mechanical properties, combined with examination of the H all–Petch relationship, the refinement of the matrix was primarily responsible for the improvement in the yield strength of the composites. The grain growth of the matrix was inhibited by the introduction of the SiC particles.