Electrodeposition and characterization of Ni-Co/SiC nanocomposite coatings

Ni-Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni-Co alloy and Ni-Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.% SiC in the Ni-Co matrix increased hardness more than 60%. The average depth of scratch in the mentioned composite coating was about 15% less than that of the Ni-Co alloy coating. The corrosion penetration rate (CPR) of the Ni-Co alloy coating in a 3.5 wt.% NaCl solution was more than 17 times greater than that of the Ni-Co/SiC coating with 30.5 vol.% SiC.     

EFFECT OF TH ETHICKNESS OF SPECIMENS ON THERMAL RESIDUAL STRESSES IN SiCw/Al COMPOSITES

１．ＩｎｔｒｏｄｕｃｔｉｏｎＷｈｅｎＳｉＣｗ／Ａｌｃｏｍｐｏｓｉｔｅｓｗｅｒｅｃｏｏｌｅｄｄｏｗｎｔｏｒｏｏｍｔｅｍｐｅｒａｔｕｒｅｆｒｏｍｔｈｅｆａｂｒｉｃａｔｉｏｎｏｒｑｕｅｎｃｈｔｅｍｐｅｒａｔｕｒｅ,ｔｈｅｒｍａｌｒｅｓｉｄｕａｌｓｔｒｅｓｓｅｓｓｕｃｈａｓｔｒａｄｉｔｉｏｎａｌｍａｃｒｏｓｔｒｅｓｓａｎｄｍｉｃｒｏｓｔｒｅｓｓａｓｗｅｌｌａｓｔｈｅｒｍａｌｍｉｓｍａｔｃｈｓｔｒｅｓｓｗｅｒｅｉｎｄｕｃｅｄｉｎｔｈｅｍ．Ｍａｎｙｐｒｏｐｅｒｔｉｅｓｏｆｃｏｍｐｏｓｉｔｅｓｉｎｃｌｕｄｉｎ…     

Synthesis and characterization of cuprous oxide dendrites: New simplified green hydrothermal route

Cuprous oxide (Cu₂O) dendrites were prepared by simple hydrothermal route at two different temperatures using starch as reducing and stabilizing agent. Scanning Electron Microscopy (SEM) revealed the alterations in morphology with reaction temperature and time. The spherical nanoparticles obtained at lower reaction temperature self-assembled into distinct dendritic nanostructures at high temperature. The mechanism of formation of dendrite over the polysaccharide template has been discussed. Transmission Electron Microscopy (TEM) revealed that the crystalline size of these dendrites in one dimension is about 50 nm. The nanoparticles were characterized by UV-vis and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), FT-IR and Thermal Gravimetry Analyzer (TGA). Impedance analysis of the nanostructures showed conductivity to be a function of temperature.     

Synthesis and studies of properties of graphite oxide and thermally expanded graphite

Graphite oxide is synthesized using various reaction parameters. Stagewise evaluation of graphite oxidation dynamics in the course of synthesis is carried out using the method of sample collection and thermogravimetric analysis. Thermally expanded graphite with high texture characteristics was obtained from graphite oxide. Properties of graphite oxide and thermally expanded graphite were determined using scanning electron microscopy, X-ray diffraction, thermogravimetry, differential scanning calorimetry, energy dispersive spectroscopy, and low-temperature adsorption of nitrogen. The values of capacity of supercapacitors based on graphite oxide and expanded graphite are found.     

Crystal Structure and X-ray Powder Diffraction Data for Rare Earth Compound PrNiSn

１ＩｎｔｒｏｄｕｃｔｉｏｎＴｅｒｎａｒｙｉｎｔｅｒｍｅｔａｌｉｃｃｏｍｐｏｕｎｄｓｃｏｎｔａｉｎｉｎｇｒａｒｅｅａｒｔｈｍｅｔａｌｓｈａｖｅｖａｒｉｏｕｓｃｒｙｓｔａｌｓｔｒｕｃｔｕｒｅｓａｎｄｍａｎｉｆｅｓｔｓｅｖｅｒａｌｉｎｔｅｒｅｓｔｉｎ...     

X-ray elastic constant determination and residual stress of two phase TiAl-based intermetallic alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｉＡｌｉｎｔｅｒｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｈａｓｌｏｗｅｒｄｅｎｓｉｔｙ ,ｈｉｇｈｅｒｔｅｍｐｅｒａｔｕｒｅｓｔｒｅｎｇｔｈ ,ｈｉｇｈｅｒｓｔｉｆｆｎｅｓｓａｎｄｂｅｔ ｔｅｒｏｘｉｄａｔｉｏｎｒｅｓｉｓｔａｎｃｅｃｏｍｐａｒｅｄｔｏｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｈｉｇｈ ｔｅｍｐｅｒａｔｕｒｅａｌｌｏｙｓ[1 ] ,ｔｈｅｒｅｆｏｒｅ,ｉｔｉｓｅｘｐｅｃｔｅｄｔｏｂｅａｐｏｔｅｎｔｉａｌｌｉｇｈｔｍａｓｓｈｅａｔ ｒｅｓｉｓｔａｎｔｍａｔｅｒｉａｌ.Ｅｘｔｅｎｓｉｖｅｓ…     

Synthesis,characterization and spectroscopic studies of CdS/polyaniline core/shell nanocomposite

In this work, CdS/polyaniline (PANI) nanocomposite was synthesized by a novel method. Transmission electron microscope (TEM) images showed that the CdS/PANI nanocomposite had a core/shell structure. The crystal structure was studied using X-ray diffraction (XRD) and the obtained results showed that CdS had cubic structure. Fourier transform infrared (FTIR) spectroscopic measurements confirmed the formation of PANI at the surface of CdS nanoparticle. The prepared samples were further characterized using UV–visible (UV–vis) and fluorescence spectroscopy.     

Interfacial reaction between zirconium alloy and graphite mold/yttrium oxide ceramic mold

Zirconium alloys are active in the molten state and tend to react with the mold during casting. The casting technology of zirconium is not yet well established; especially in selecting the mold materials, which are difficult to determine. In the present work, the interfacial reactions between zirconium casting and casting mold were studied. The zirconium alloy was melted in a vacuum arc skull furnace and then cast into the graphite mold and ceramic mold, respectively. The zirconium casting samples were characterized using SEM, EDS and XRD with an emphasis on the chemical diffusion of elements. A reaction layer was observed at the casting surface. Chemical analysis shows that chemical elements C, O and Y from the mold are diffused into the molten zirconium, and new phases, such as ZrC, Zr30, YO1.335 and Y6ZrO11, are formed at the surface. In addition, an end product of zirconium valve cast in a yttria mold has a compact structure and good surface quality.     

Synthesis and characterization of metal oxide multilayers obtained via MOCVD as protective coatings of graphite against oxidation

Zirconia (ZrO₂) titania (TiO₂) and alumina (Al₂O₃) thin films were deposited on a graphite substrate both in mono- and in multi-layer systems, using the metal organic chemical vapor deposition technique, to test their practical qualities as protective coatings against oxidation at high temperatures. The depositions were performed using a hot wall reactor at reduced pressure (0.6 Torr) in the temperature range 350–500 °C, using, as precursors, (η⁵-C₅H₅)₂Zr(CH₂C(CH₃)₃)₂, Ti(OCH(CH₃)₂)₄, and (CH₃CH₂)₂Al(OCCH₃CHCCH₃O), respectively. Surface and topographical analysis of the deposits using X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy techniques as well as thermogravimetric measurements (TG and DTA) in an oxygen flux of mono- and multi-layer systems are reported and examined.     

Synthesis, characterization and densification of WCu nanocomposite powders

In the present investigation, W20-40wt.% Cu nanocomposite powders with average sizes ranging between 25 and 30 nm were synthesized by a soft chemical approach using tungsten hexacarbonyl [W(CO)₆] and copper acetonyl acetonate [Cu(acac)₂] as metal precursors. Particle size, morphology and distribution were measured using transmission electron microscope (TEM) and small angle X-ray scattering (SAXS). Surfactant coating on WCu composite powders was removed on heat treatment of powders at 450 °C in hydrogen atmosphere for 1 h. Elemental analyses of as-synthesized and annealed (at 450 °C) WCu nanocomposite powders were carried out using inductively coupled plasma-optical emission spectrometer (ICP-OES) and Leco gas analyzers. X-ray diffraction studies showed that the tungsten phase is amorphous while the crystal structure of copper phase is fcc in as-synthesized WCu nanocomposite powders. After annealing at 700 °C peaks corresponding to bcc tungsten are observed and peaks corresponding to fcc copper become sharper. Relative densities of 98.2%, 98.8% and 99.2% were achieved for W20wt.% Cu, W30wt.% Cu, and W40wt.% Cu composite powders respectively when sintered at 1000 °C.     

Synthesis and characterization of Ag@PPy yolk–shell nanocomposite

Ag@SiO₂@polypyrrole (PPy) nanocomposites were fabricated by a simple method. Ag@PPy yolk–shell nanocomposite was obtained after the removal of the midlayer SiO₂. TEM confirmed that the movable Ag cores were encapsulated in the interior of the hollow PPy nanoparticles. The structure of the resultant product was characterized by the Raman spectrum and X-ray diffraction technologies. Thermogravimetric analysis (TGA) revealed that the thermal stability of the nanocomposites was improved as compared with the pure PPy.     

用Kroner模型计算取向薄膜的弹性矩阵与X射线弹性常数

首先用Kroner模型计算了具有丝织构的TiN薄膜的弹性矩阵,当材料具有较强的丝织构时,材料弹性矩阵的对称关系将发生变化,得到的弹性矩阵与各向同性同种材料的弹性矩阵相差很大,相同分量的值一般相差在13-20GPa之间,然后计算了TiN薄膜的弹性常数曲线随φ角的分布,当应力测试方向不同时,即使是同一晶面,弹性常数也会产生差异,而且弹性常数随φ角的分布在低φ角区发生了弯曲,计算了TiN薄膜X射线弹性常数曲线的弯曲情况与实测的PVDTiN薄膜应力测试曲线相似。     

Synthesis and structural characterization of undoped and Co doped zinc oxide thin films obtained by aerosol assisted chemical vapour deposition

Dilute magnetic oxides are transparent, wide-bandgap materials that behave ferromagnetically when doped with a few percent of a magnetic 3d cation. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material, that is a prerequisite for successful fabrication of useful devices for the emerging technologies of spintronics. Here we report a study of growth characteristics and microstructural properties of undoped and Co doped ZnO films grown onto borosilicate glass substrates, using aerosol assisted chemical vapour deposition method. The obtained films are single phase, of Wurtzite type, some of them with a strong c-axis orientation, i.e. with the c-axis normal to the substrate surface.     

Thermal contraction phenomenon of cluster structure of indium melt

1　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｍｏｄｅｒｎｓｃｉｅｎｃｅａｎｄｔｅｃｈｎｏｌｏｇｙ ,ｔｈｅｓｔｒｕｃｔｕｒｅａｎｄｐｒｏｐｅｒｔｉｅｓｏｆｓｏｌｉｄｓｔａｔｅｈａｖｅｂｅｅｎｄｅｅｐｌｙｕｎｄｅｒｓｔｏｏｄ .Ｈｏｗｅｖ     

Synthesis and characteristics of poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe3O4 nanocomposite

Poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe₃O₄ nanocomposite was successfully synthesized by an in situ polymerization of 1-(2-carboxyethyl) pyrrole in the presence of synthesized Fe₃O₄ nanoparticles. Evaluation of structural, morphological, electrical and magnetic properties of the nanocomposite was performed by XRD, FT-IR, TEM, TGA, magnetization and conductivity measurements, respectively. XRD analysis reveals the inorganic phase as Fe₃O₄ and TGA shows about 90 wt% loading of Fe₃O₄ in the nanocomposite. FT-IR analysis indicates a successful conjugation of Fe₃O₄ particles with polypyrrole acetic acid. Magnetization measurements show that polypyrrole acetic acid coating decreases the saturation magnetization of Fe₃O₄ significantly. This reduction has been explained by the pinning of the surface spins by the possible adsorption of non-magnetic ions during the polymerization process. The conductivity and dielectric permittivity measurements strongly depend on the thermally activated polarization mechanism and thermal transition of PPyAA in the nanocomposite structure. Large value of dielectric permittivity (?′) of the nanocomposite at lower frequency is attributed to the predominance of species like Fe²⁺ ions and grain boundary defects (interfacial polarization).     

Oxidation of tungstate‐containing green rust (Cl–) in aqueous solution

The influence of tungstate on the oxidation of green rust [GR(Cl^–)], which contains both Fe(II) and Fe(III), was investigated by synthesizing suspensions of GR(Cl^–) containing tungstate and oxidizing them via injection of N₂ gas containing O₂. XRD and TEM analyses were used for characterizing the solid particles formed during synthesis and oxidation. The results showed that the formation of fine α‐FeOOH was enhanced by the addition of tungstate to the GR(Cl^–) suspensions, while GR(Cl^–) without tungstate was transformed primarily into γ‐FeOOH. The pH, oxidation‐reduction potential (ORP), and dissolved oxygen (DO) values of the aqueous solution were measured during oxidation of GR(Cl^–) with and without tungstate. The results showed that whereas the pH value of the solution was decreased and the ORP value was increased monotonically by oxidation of GR(Cl^–), the pH and ORP values during oxidation the GR(Cl^–) suspension containing tungstate revealed characteristic changes with time. XAS was also used for characterizing the chemical state and local structure of tungstate in the oxidized particles. The results indicated that the local structure of WO was essentially retained in the particles precipitated from GR(Cl^–) suspensions.     

Relaxation of residual stresses in 20%SiC_w/6061Al composite as-extruded at high temperature

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｌｕｍｉｎｕｍｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｒｅｉｎｆｏｒｃｅｄｗｉｔｈｓｉｌｉ ｃｏｎｃａｒｂｉｄｅｗｈｉｓｋｅｒ (ＳｉＣｗ/Ａｌ)ａｓａｎｅｗｔｙｐｅｏｆｓｔｒｕｃｔｕｒａｌｍａｔｅｒｉａｌｎｏｔｏｎｌｙｈａｓｃｅｒｔａｉｎａｄｖａｎｔａｇｅｓｓｕｃｈａｓｈｉｇｈｓｐｅｃｉｆｉｃｓｔｒｅｎｇｔｈ ,ｈｉｇｈｓｐｅｃｉｆｉｃｍｏｄｕｌｕｓ ,ｌｏｗｃｏｅｆｆｉｃｉｅｎｔｏｆｔｈｅｒｍａｌｅｘｐａｎｓｉｏｎ (ＣＴＥ)ａｎｄｓｏｏｎ ,ｂｕｔａｌｓｏｃａｎｂｅｓｅｃｏｎｄａｒｉ…     

Isothermal Section of the Cu-rich Cu-Be-Ag Ternary System

ＩｓｏｔｈｅｒｍａｌＳｅｃｔｉｏｎｏｆｔｈｅＣｕｒｉｃｈＣｕＢｅＡｇＴｅｒｎａｒｙＳｙｓｔｅｍＺｈａｎｇＬｉｐｉｎｇ，ＺｈｏｕＫａｉｗｅｎａｎｄＺｈｕａｎｇＹｉｎｇｈｏｎｇ（张丽萍）（周开文）（庄应烘）ＩｎｓｔｉｔｕｔｅｏｆＭａｔｅｒｉａｌｓ...     

Synthesis and characterization of mechanical-alloyed Ti–xMg alloys

The synthesis and characterization of Ti–xMg (x=4, 9, 12, 15, 21, 24 at%) alloys using mechanical alloying was investigated. A nanometer-sized Ti–24Mg alloy was produced. During mechanical alloying, the height of the XRD peaks of the Mg in the Ti–9Mg alloy decreased, and then disappeared, whereas the Ti XRD peaks broadened, and the grain size decreased with increasing milling time. The Mg firstly dissolved in the grain boundaries of the Ti, and then diffused into the Ti grain interiors. The grain boundaries played an important role in enhancing the solid solubility of Mg in Ti. With increasing Mg content the volume fraction of grain boundaries increased, and a decrease in grain size occurred after mechanical alloying for 48 h.