Sol-gel prepared Ni-alumina composite materials

The microstructure of sol-gel prepared Ni-alumina ceramic-metal composites containing up to 50% Ni has been studied with X-ray diffraction, the scanning electron microscope and the transmission electron microscope. The influence of processing temperature upon the size distribution of Ni was established. It was found that increasing the total amount of Ni increases only the number of micrometre-size Ni inclusions in the alumina, whereas the hot-pressing temperature determines the size distribution of Ni. When temperatures much higher than the melting temperature of Ni are used, a large number of Ni inclusions of the order of 10 nm can be found mainly within alumina grains; only a few are formed in grain boundaries and in triple points. When a temperature close to the melting point is used, there are fewer nanometre-size Ni inclusions and a larger number of Ni inclusions of the order of 100 nm to 1 m. In this case, the large ( 100 nm) and small ( 10 nm) Ni inclusions are found in grain boundaries and triple points.     

Properties and microstructure of Ni-alumina composite materials prepared by the sol/gel method

Sol-gel techniques have been used to make mm-size pieces of Ni-alumina gels for abrasive use. The microstructure was studied extensively by electron microscopy methods and by electron and x-ray diffraction. The hardness, stiffness, and toughness were measured by indentation methods. Seeding of the gel with small additions of nm-size α-Al₂O₃ grains resulted in enhanced α-Al₂O₃ crystallization, a denser structure and better mechanical properties. The best Ni-alumina gel specimens had hardnesses and stiffnesses comparable to successful abrasive products and even better fracture toughnesses.     

电场激活压力辅助SHS法合成TiC-Ni-Fe复合材料

采用电场激活压力辅助SHS法制备了TiC 15%Ni 20?物相体系金属间化合物基复合材料.分析表明TiC 15%Ni 20?物相体系生成物中主要相为TiC,基体成分为NiTi2与FeNi金属间化合物;随着压力增加,生成物成分更均匀,密度增大,表面硬度和显微硬度值也显著提高.     

Sol-gel synthesis of hybrid materials

Sol-gel chemistry allows the synthesis of hybrid organic-inorganic materials. Organic molecules can be used as complexing ligands to provide a chemical control over hydrolysis and condensation reactions, leading to the formation of stable suspensions of nanoparticles. They can also be trapped within the sol-gel matrix in order to provide some optical properties such as photochromism. When chemically bound to the oxide network via Si-C bonds they lead to hybrid nanocomposites that offer new possibilities in the field of materials science. Even biospecies, such as enzymes or antibodies, can be trapped within sol-gel matrices in order to make bio-sensors or bio-catalysts.     

Sol-gel prepared β-TCP/FHA biphasic coatings

β-tricalcium phosphate/fluoridated hydroxyapatite (β-TCP/FHA) biphasic coatings were prepared on titanium alloy substrate by means of sol-gel method. The coatings combine the initial dissolution of β-TCP with the long-term stability of FHA to create a high quality bioactive coating. Ca(NO₃)₂, P₂O₅ and HPF₆ were dissolved in ethanol respectively and mixed in designed sequence and Ca : P : F ratios to form a sol. After the sol was refluxed for 24 h, the as-refluxed sol was used for FHA coating. β-TCP powders were dispersed into the sols to form colloidal sols for β-TCP/FHA biphasic coatings. The as-refluxed sols with different Ca : P : F ratios only resulted in apatite coatings with low F content. Biphasic coatings were prepared with the colloidal sols. The β-TCP contents of the coatings could be tailored by varying the amount of the powders in the colloidal sols. The surface morphology of the coatings becomes rougher with increasing amount of the powders, which favors cell attachment. However, excessive amount of powders results in powder agglomeration, leading to more cracks in the coatings. Fine powders and good dispersion are essential factors for good biphasic coatings.     

Ag-Sb composite prepared by chemical reduction method as new anode materials for lithium-ion batteries

Ag-Sb composite anode was prepared by chemical reductive method. The structure, morphology, chemical composition and electrochemical properties of synthesized Ag-Sb composite anode were evaluated by XRD, FE-SEM, EDS and galvanostatical charge-discharge tests. The results indicated that the changes of structure and volume were alleviated effectively by using metal phase instead of intermetallic phase and restraining the lithiation reaction of Ag at high current density (0.2 mA cm⁻²). The electrochemical reactions took place in a stable and highly conductive Ag framework, which ensured the good cyclability of the Ag-Sb composite electrode.     

MWNTs/PANI composite materials prepared by in-situ chemical oxidative polymerization for supercapacitor electrode

Multi-walled carbon nanotubes (MWNTs)/polyaniline (PANI) composite materials were prepared by in-situ chemical oxidative polymerization of an aniline solution containing well-dispersed MWNTs. The supercapacitive behaviors of these composite materials were investigated with cyclic voltammetry (CV), charge–discharge tests, and ac impedance spectroscopy, respectively. The composites based on the charge-transfer complex between well-dispersed MWNTs and PANI matrixes show much higher specific capacitance, better thermal stability, lower resistance, and were more promising for applications in supercapacitors than a pure PANI electrode. The highest specific capacitance value of 224 Fg⁻¹ was obtained for the MWNTs/PANI composite materials containing MWNTs of 0.8 wt%. The improvement mechanisms of the capacitance of the composite materials were also discussed in detail.     

Sol-gel法制备耐蚀涂层的技术及应用

Sol-gel法制备耐蚀涂层对提高基材的化学耐久性、防止氧化、控制腐蚀有显著的效果,有望完全替代传统材料表面腐蚀控制处理使用的毒性物质铬酸盐处理工艺,可以减轻对环境的污染,是一项可持续发展的表面处理技术.为了阐述该项技术的工艺方法及特点,综述了Sol-gel法制备技术在不同的金属基体--不锈钢、铝合金和铜合金表面中的应用现状和最新研究进展.分析了采用Sol-gel法制备耐蚀涂层可以有效地阻止腐蚀介质对基体金属材料的破坏,延长材料在实际应用环境中的使用寿命等方面的作用原理,从理论上对Sol-gel耐蚀涂层的形成机制和耐蚀机理进行了初步讨论,并对Sol-gel技术的应用前景作一简要展望.     

锂离子电池用Sn-MCMB复合材料碳热还原合成的研究

用碳热还原法制备了Sn-MCMB复合材料，通过XRD、SEM、恒流充放电循环和慢速扫描循环伏安（CV）等方法对其电化学嵌脱锂性能做了研究。结果表明：SnO2被MCMB还原成金属Sn圆球颗粒，吸附在McMB上的球径平均尺寸为500nm，而未吸附的为15μm，均匀分散在MCMB微球之间。该材料的首次嵌脱锂比容量分别可以达到892和657mAh／g，库仑效率为73％，循环14周以后的脱锂比容量为366mAh／g。     

Local elastic moduli of particle-filled B83 babbitt-based composite materials prepared by powder metallurgy techniques

We have measured local elastic moduli of particle-filled B83 babbitt-matrix composite materials produced by powder metallurgy techniques and containing silicon carbide (SiC) ceramic and modified shungite rock particles as fillers. The measurements were made by an optoacoustic laser method, whose basic principle is to determine the phase velocities of thermo-optically excited longitudinal and shear ultrasonic waves. The addition of 3 wt % of high-modulus SiC particles tends to increase the Young’s and shear moduli (by 10–12%) and decrease Poisson’s ratio (by 5%) relative to a hot-pressed B83 babbitt sample without fillers.     

Sol-gel processing of drug delivery materials and release kinetics

Silica, calcium (5 mol%) silicate and silica/polycaprolactone hybrid inorganic/organic amorphous materials, all mixed with sodium ampicillin, a broad-spectrum antibiotic, have been synthesized by sol-gel method. The amorphous nature of the gels was ascertained by X-ray diffraction analysis. Release kinetics in a simulate body fluid (SBF) have been subsequently investigated. The amount of sodium ampicillin released has been detected by UV-Vis spectroscopy and SEM. The release kinetics seems to occur in more than one stage. Finally FTIR measurements and SEM micrograph showed the formation of a hydroxyapatite layer on the surface of the samples soaked in SBF. All data showed that these materials could be used as drug delivery bioactive systems.     

Polyimide-matrix-based composite materials

A polycondensation solid-state-reaction-based polyimide (PI) matrix has been used for composite material formation. Two types of PI matrix have been employed – a bulk PI system prepared by pressing a mixture of the powdered precursors (4, 4′-oxidianiline (ODA) and pyromellitic dianhydride (PMDA)) and a thin-film matrix formed by vapor co-deposition of the same precursors, PI monomers. A variety of different “guests” (trimethylaminalan, phthalocyanine, carbon) and the methods for their incorporation into the PI matrix are presented. The influence of the “guest” concentration and the thermal-treatment conditions on the surface morphology are shown and discussed.     

Electroformed composite materials

Electroforming has been used as a method of incorporating fibres in a metal matrix. Studies on both conducting and non-conducting fibres formed the basis of a critical assessment of the potentialities of this technique for making composite materials. Examples of the application of the method to the forming of various materials are given.originally submitted to Applied Materials Research 7 November 1966     

Sol-gel processing of materials for electronic and related applications

Various techniques of sol-gel processing for the preparation of electronic and related materials are described and reviewed. Typical examples are chosen from thin films and coatings of gels, crystalline materials and glasses as also bulk glasses to illustrate the variations in processing parameters and material properties.     

热压扩散焊接法制备Ti-Al复合电极材料及性能

采用热压扩散法制备Ti-Al复合电极材料, 并通过SEM、 四探针法、 EDS、 电化学工作站等测试手段 对样品的结构与性能进行表征。结果表明: 热压扩散焊接在压力6 MPa、 焊接温度550℃、 氩气中保温时间≥90 min 的条件下, 可以实现Ti和Al的冶金结合, 而且扩散反应层产物的变化过程是: TiAl→TiAl₂→TiAl₃; 复合材料的电化学性能较纯Ti的有所提高, 制备工艺条件对电化学性能的影响与对电阻率的影响一致; 在同等条件下, 复合材料的极化电位较纯钛下降37~54 mV, 其电流密度至少可提高59.29%, 电阻率仅为纯钛的1/10。     

Alumina composite membranes prepared by MOCVD

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Polypropylene-clay composite prepared from Indian bentonite

In the present work, a set of experimental polypropylene (PP) clay composites containing pristine bentonite clay of Indian origin has been prepared and then characterized. The polymer clay composites are processed by solution mixing of polypropylene with bentonite clay using a solvent xylene and high speed electric stirrer at a temperature around 130°C and then by compression molding at 170°C. The mechanical properties of PP-clay composites like tensile strength, hardness and impact resistance have been investigated. Microstructural studies were carried out using scanning electron microscope and transmission electron microscope and the thermal properties were studied using differential scanning calorimeter. Mechanical properties of the prepared composites showed highest reinforcing and toughening effects of the clay filler at a loading of only 5 mass % in PP matrix. Tensile strength was observed to be highest in case of 5 mass % of clay loading and it was more than 14% of that of the neat PP, while toughness increased by more than 80%. Bentonite clay-PP composite (5 mass %) also showed 60% increase in impact energy value. However, no significant change was observed in case of hardness and tensile modulus. Higher percentages of bentonite clay did not further improve the properties with respect to pristine polypropylene. The study of the microstructure of the prepared polymer layered silicate clay composites showed a mixed morphology with multiple stacks of clay layers and tactoids of different thicknesses.