bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Friction Materials Reinforced by Porous Mullite
Authors: Cho Bum Rae , Lee Han Young
Published: March 2009

Mullite reinforced composites were produced by the injection molding technique to
develop environmentally friendly friction materials for automotive applications. In order to examine the effect of mullite content on the friction and wear properties, two different specimens containing 10wt% and 30wt% of mullite were respectively fabricated and wear-tested by using the plate-on-disc type sliding friction and wear test machine. The sliding friction and wear test demonstrated that both
specimens show similar tendencies at different sliding speeds under a low load of 2.9N. In comparison with common glass fiber reinforced composites, both of the mullite reinforced composites exhibited a lower wear rate at room temperature.
Effects of Annealing Atmosphere on the Optoelectrical Properties of ZnO Thin Films Grown by Atomic Layer Deposition
Authors: Lee Chong Mu , Park Yeon Kyu , Park Anna , Kim Choong Mo
Published: March 2009

This paper investigated the effects of annealing atmosphere on the carrier concentration, carrier mobility, electrical resistivity, and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD). X-ray diffraction (XRD) and photoluminescence (PL) analyses, and Hall measurement were performed to investigate the
crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. According to the XRD analysis results, the crystallinity of the ZnO film annealed in an oxygen atmosphere is better than that of the ZnO film annealed in a nitrogen atmosphere. It was found that annealing undoped ZnO films grown by ALD at a high temperature above 600°C improves the crystallinity and enhances UV emission.
Energy Efficiency Alloy Design in PSN-PMN-PZT Ceramic System for Piezoelectric Transformer Application
Authors: Choi Y.G. , Son Y.-J. , Kwon Joon Chul , Cho K.W. , Kweon Soon Young , Hong Tae Whan , Lee Young Geun , Ryu Sung Lim , Kim Il Ho , Yoon Man Soon , Ur Soon Chul
Published: March 2009

To enhance high power characteristics for piezoelectric transformer, an alloy design approach in PZT base ceramic system was considered. Various Zr/Ti ratio compositions in 0.03Pb(Sb0.5Nb0.5)O3- 0.03Pb(Mn1/3Nb2/3)O3-(0.94-x)PbTiO3-xPbZrO3 (0.445x0.475 mol)[PSN - PMN - PZT] system were
synthesized by the conventional bulk ceramic processing technique. To improve high power characteristics at their morphotropic phase boundary (MPB) composition of PSN-PMN-PZT system, various spectra of Zr/Ti ratio were systematically experimented, and their effects on the subsequent piezoelectric properties and dielectric properties for high power piezoelectric transformer application were investigated using an impedance analyzer and a laser vibrometer. Microstructure and phase information were characterized using X-ray diffractometer (XRD) and a scanning electron microscope (SEM). When the Zr/Ti ratios were
0.475/0.465, the mechanical quality factor and electromechanical coupling factor were shown to reach the maximum, indicating that this alloy design can be a feasible composition for high power transformer.
Vibration-Damping Capacity of Lotus-Type Porous Magnesium at Room Temperature
Authors: Xie Zhen Kai , Banno Takumi , Yamada Yasuo , Tane Masakazu , Hyun Soong Keun , Okuda Yosiyuki , Nakajima Hideo
Published: March 2009

Lotus-type porous magnesium with a large number of unidirectional cylindrical pores
was fabricated by unidirectional solidification of melt dissolving hydrogen in a pressurized hydrogen atmosphere. The vibration-damping capacity of the lotus-type porous magnesium plate which has many open pores was measured in this work.
The attenuation coefficients of the free vibration of lotus-type porous magnesium were measured by hammering-vibration-damping test, which revealed that the attenuation coefficients increase with increase in porosity; the damping capacity of lotus magnesium is higher than that of non-porous magnesium. The mechanism for high damping capacity was analyzed on the basis of the Fourier transform technique, which indicates that various vibration modes of high frequency are
observed. The excited vibrations of high frequency enhance the damping capacity of lotus-type porous magnesium.
Preparation of Nickel Powders by the Reduction of Hydrazine of Ni(OH)2 Reactant Slurries from Nonaqueous Media
Authors: Kim Yang Do , Choi Eun Young , Lee Yoon Bok , Kim Young Seok , Kim Hyong Kuk , Kim Kwang Ho
Published: March 2009

Nickel powders were prepared by the reduction of hydrazine of Ni(OH)2 reactant slurries from non-aqueous media. The morphological characteristics of nickel powders were investigated under various processing conditions. Nickel powders were characterized by using scanning electron microscope (SEM), X-ray diffractometer (XRD), thermal gravitational analysis (TGA) and X-ray
photoelectron spectroscopy (XPS). The size of nickel powders was increased as the reaction temperature and time increased because of the thermal agglomeration of nuclei and/or increased growth rate. The surface of nickel powders composed of both Ni and Ni(OH)2 was oxidized in the temperature range of 400-600°C.
Synthesis of Nickel Powders by the Reduction of Hydrazine from Diethanolamine Solution
Authors: Kim Yang Do , Choi Eun Young , Lee Yoon Bok , Kim Young Seok , Kim Hyong Kuk , Kim Kwang Ho
Published: March 2009

Nickel powders were synthesized by the reduction of hydrazine of nickel salts from
diethanolamine (DEA) solution, and the morphological characteristics of nickel powders were investigated with various process conditions such as the addition of hydrazine, reaction temperature, the composition of mixed solvents. The addition of hydrazine in DEA solution largely affected the size control of nickel powders. Under N2H4/Ni2+molar ratio= 1.5 and 2.0 conditions, spherical nickel powders in the submicron range were obtained owing to higher the reduction rate. An
increase of temperature increased the size of nickel particles. At 220°C for 40min, the nickel powders were composed of polyhedral particles with a high crystalline in the submicron range. The mixed volume ratio of TEA to DEA solvent improved the inhibition of agglomerate between particles.
Preparation and Antibacterial Activity of Silver Ions-Substituted Hydroxyapatite/Titania
Authors: Lv Guo Yu , Li Yu Bao , Yang Ai Ping , Zhang Xiang , Yang Wei Hu , Li Ji Dong
Published: March 2009

In this paper a series of silver ions-substituted hydroxyapatites (HA) were prepared. The antibacterial activities of these materials on textiles against bacteria have been investigated. Titania (TiO2) was selectively added into the materials to decrease the silver-ions concentration to get the same active antimicrobial effects. The microstructure, the shape and size, concentration of silver, and the groups of the composite materials were characterized using transmission electron
microscopy (TEM), infrared spectroscopy (IR), Atomic absorption spectroscopy (AAS), and X-ray diffraction (XRD). The results showed that there was a dose dependent-effect of silver-ions concentration from the disk diffusion test. The higher the silver-ions concentration, the better the
antibacterial activity of the composite materials was. Keeping silver-ions concentration constant, the antibacterial activity of the materials for adding Titania was better than that of without Titania. Moreover, the addition of Titania would inhibit the discolouration of the composite materials. The antibacterial activities of the composite materials differentiate to some extent with the bacterial strains.
Fabrication and Microstructure of ZnO-TiO2 Composite Membranes by a Reverse Micelle and Sol-Gel Processing
Authors: Bae Dong Sik , Kim Byung Ik , Han Kyong Sop
Published: March 2009

ZnO-TiO2 nanoparticles were synthesized by a reverse micelle and sol-gel process.
The average particle size of the colloid was below 30 nm and well dispersed in the solution. ZnOTiO2 composite membranes were fabricated by using the dip-coating method on a porous alumina support. ZnO-TiO2 composite membranes showed a crack-free microstructure and narrow particle size distribution even after the heat treatment up to 600°C. The average particle size of the membrane was 30-40nm, and the pore size of ZnO-TiO2 composite membrane was below 10 nm.
Comparison of Hydroxyapatite Synthesized under Different Conditions
Authors: Mo Li Rong , Li Yu Bao , Lv Guo Yu , Li Ji Dong , Zhang Li
Published: March 2009

In this paper, using sodium phosphate and calcium nitrate as reagents,
nano-hydroxyapatite (n-HA) was synthesised under 8 conditions. The morphology and crystallinity of these prepared HA were investigated by Transmission Electron Microscope (TEM) and X-ray diffraction pattern (XRD). The Ca/P molar ratio of n-HA was tested by chemical method. In order to find a better way to obtain purer nano-hydroxyapatite, the phases transition and purification of these 8 samples before and after sintering at 1000°C were compared. The results indicated that all these samples showed similar, poorly crystallized apatite structures before sintering. The adding order between calcium and phosphate would affect the crystallinity, structure and Ca/P molar ratio
of hydoxyapatite significantly. XRD analysis showed that adding sodium phosphate into calcium nitrate could gain more HA phase after sintering at 1000°C. The pH of reaction system had obvious effects on the structure of hydroxyapatite. Besides the pH of reactants also affected the structure of hydoxyapatite.
Design for Environment (DfE) of Ultralight Aluminum Camshaft Development
Authors: Kim Shae K.
Published: March 2009

In order to solve problems modular type camshafts have, that is, reducing weight,
increasing oil filling time and designing multi-valve system, research was initiated about feasibility for DfE (Desing for Environmrnt) about ultralight camshaft . Through LCA (Life Cycle Assessment) and properties and process evaluation, an attempt has been made to develop cost-effectvie process for ultiralight aluminum camshaft without the problems modular type camshaft have. The results clearly
show 50% weight reduction achieved and better environmental impact of the ultralight aluminum camshaft compared with that of modular camshafts.
Preparation and Characterization of a New Type of Sr-Contained Hydroxyapatite Bone Cement
Authors: Guo Da Gang , Yong Han , Xu Ke Wei
Published: March 2009

A novel route is developed to prepare a new type of Sr-contained hydroxyapatite bone cement. Tetracalcium phosphate, strontium hydrogen phosphate or anhydrous strontium chlorite, dicalcium phosphate, phosphoric and water are used as precursors. XRD, FTIR and EDXS are used to characterize the incorporation of 5% or 10% Sr2+ into the crystal lattice of hydroxyapatite. Results indicate that the Sr-contained CPC system of TTCP/DCPA/DSPA can set in 0.5M diluted phosphate
acid with a final product of non-stoichiometric Sr-contained hydroxyapatite.
Use of Bauxite Minerals to Control Pollutant Outflow in Urban Areas
Authors: Kim Ree Ho , Jeong Jinwoo , Lee Sang Ho , Gee Chae Sung
Published: March 2009

Enormous use of ground for various purposes in urban areas has led to disappearance of green-planted surfaces. Considering space constraints, planted roofs become one promising and stabilizing choice to improve amenity and reduce the thermal loads on the building’s shell. However, a critical issue for rooftop garden is the release of pollutants in urban runoff. Not only particles but
also dissolved pollutants should be removed from building drainage because of their potential impact on water environment. To add functions for the control of pollutant outflow, bauxsite minerals made of red waste from alumina refineries were incorporated in the rooftop garden as a special soil. The minerals have high trapping capacities for trace metals and other soluble species. Moreover, they are
easy to integrate with rooftop garden systems. Based on their equilibrium capacity for removing pollutants, an optimum amount of bauxsite minerals is suggested. The characteristics of rainwater runoff and pollutants release were compared for normal and modified rooftop garden in laboratory scale. As expected, the green roof system with the bauxsite layer reduces the concentration of heavy metals. The technique used in this study is also likely to be implemented in other green surfaces in housing complexes.
Preparation of SiC Nanoporous Membrane for Hydrogen Separation at High Temperature
Authors: Kim Y. , Kim Soo Ryong , Cho Kun Hang , Bae Seong Youl , Kwon Woo Teck
Published: March 2009

Nanoporous SiC membrane was developed on the porous alumina plate for the hydrogen separation using preceramic polymers such as polyphenylcarbosilane. The prepared preceramic polymers were characterized with FT-IR, TGA, GPC and XRD. Nanoporous SiC membrane was derived from the preceramic polymer using a spin coating method. The SiC membrane spin coated using 20 wt.% of polyphenylcarbosilane solution in cyclohexane does not show any cracks on the
surface after heat treatment at 800oC. The average thickness of the SiC membrane is about 1µm. SiC coated porous alumina possesses asymmetric pore size distribution. There are micropores that originated from porous alumina substrate, and nanopores that derived from amorphous state of SiC membranes. The pore size distribution measurement showed that the sample contains 1-3 nm sized nano pores.
Effect of Nano-Structures on the Optical Features of Hydrogenated Amorphous Si Films
Authors: Park Myung Beom , Shim Jae Hyun , Cho Nam Hee
Published: March 2009

Hydrogenated amorphous Si (a-Si:H) films were prepared by plasma enhanced chemical vapor deposition (PECVD) techniques, and the effect of nano-structure on the photoluminescence (PL) phenomena of the films was investigated. The films, which were prepared at R.T., contain both amorphous and crystalline phases of 1 ~ 3 nm size nano-crystallites with {100} orientation preference while the films prepared at 500°C are composed of about 6 nm and 150 nm size crystallites. The former exhibit a strong PL intensity near blue light region, while the latter exhibiting
little PL phenomena; also, the optical band gap of the former was calculated at 4.2 eV.
Nanostructural and Optical Features of nc-Si:H Thin Films Prepared by Plasma Enhanced Chemical Vapor Deposition Techniques
Authors: Shim Jae Hyun , Cho Nam Hee , Kim Y.J. , Whang Chin Myung , Cho Won Seung , Yoo Yeon Chul , Kim J.G. , Kwon Young Jae
Published: March 2009

The nanostructural and optical features of hydrogenated nanocrystalline silicon (nc-Si:H) thin films, which were prepared by plasma enhanced chemical vapor deposition (PECVD), were investigated as a function of deposition conditions. It was found that the crystallite size varied with the relative fraction of Si-H3 bonds in the films, [ ] eger n n
n H Si H Si int 3 1 3 / ] [ = = ∑ − − , which was sensitively related with the flow rate of SiH4 reaction gas. The silicon nanocrystallites in the films enlarged from ~2.0 to ~8.0 nm in their size with increasing gas flow rate, while the PL emission energy varied from 2.5 to 1.8 eV; the relative fractions of the Si-H3, Si-H2, and Si-H bonds in the amorphous matrix were
also varied sensitively with the SiH4 flow rate. A model for the nanostructure of the nc-Si:H films was suggested to discribe the variations in the size and chemical bonds of the nanocrystallites as well as the amorphous matrix depending on the deposition conditions.
Nanocrystalline CuOx-CeO2 Systems: FTIR Analyses of Catalytic Reactions
Authors: Saitzek S. , Villain Sylvie , Gavarri Jean R.
Published: March 2009

In the general framework of studies on nanomaterials for micro-sensors, cerium dioxide nanopowders (CeO2-z) and nanocomposites systems of copper doped ceria (CuOx-CeO2-z) were prepared and characterized. The aim of this specific study is to try to connect catalytic activity of such nanopowders with microstructure, additional phases and/or doping effect. The nanopowders of pure and doped cerium oxide were elaborated from various “Sol-Gel” chemical routes. Microstructural analysis was first carried out by X-ray diffraction (XRD). The specific areas were determined from BET adsorption techniques and the results were correlated to the size determinations obtained from XRD. The catalytic activity of such nanopowders in presence of methane gas CH4 was analyzed making use of FTIR spectrometry and a homemade device. For a better understanding of such catalytic responses, we proposed a modeling approach of solid gas interactions that takes into account a typical temperature dependent Avrami's model.
Surface Heat Treatment Design Methodology of Large-Scale Castings
Authors: Kula P. , Liskiewicz T. , Pacyniak T.
Published: March 2009

The process of induction heating followed by forced cooling of large-scale castings is
considered. The main goal of this study is to develop a reliable design methodology of surface heat treatment process to provide high quality of the treated component. It is assured by determination of the material constants and convection coefficient during heating and cooling experiments carried out on the specimens made of material adequate to the considered large-scale casting. The main part
of the investigations was preceded by wide analyses of the mechanical and chemical properties of the tested specimens. The presented global design methodology of large-scale castings gives a possibility to predict the temperature distribution on the hardened surface during induction heating and forced cooling. This allows to select the most adequate parameters and apply them in a real
specific process. The obtained results have been analyzed and discussed.
Effect of Processing Conditions on the Microstructure and Electrical Resistance of Nanocrystalline ITO Thin Films Made by Laser Ablation
Authors: Savu Raluca , Joanni Ednan
Published: March 2009

Nanocrystalline indium tin oxide (ITO) thin films were deposited on Si/SiO2 substrates by laser ablation from a ceramic target with a composition of 0.9 In2O3 . 0.1 SnO2. Samples were prepared in the pressure range from 10-1 to 5mbar, either in-situ at 500°C or at room temperature and heat-treated in air at 500°C. X-ray diffraction results show that the films are not oriented, except the ones made at high temperature which exhibit strong (400) orientation. AFM pictures show that
the grains are round shaped and the sizes are in the range between 50 and 200nm, except for films made in-situ at 10-1mbar which are elongated and faceted. For higher pressures the grains tend to be small and to form agglomerates. The porosity of the films increases with the deposition pressure and the thicknesses reach a maximum of 2.8µm at 1mbar for the films made at room temperature and of 1.2µm at 2mbar for the ones made in-situ; for higher pressures the growth rate drop
drastically, as revealed from SEM observations of cross-sections. The electrical resistance increases with the deposition pressure due to the increase in porosity, changing from 3.3k to 38.9M for films deposited at room temperature and from 20 to 265k for the ones made in-situ.
Luminescence and Absorption of Hybrid Xerogels Doped with PbS Nanoparticles Prepared by Gas Diffusion Method
Authors: Gonçalves Julia T. , Boev Victor I. , Solovyev Alexey , Silva Carlos J.R. , Gomes M.J.M.
Published: March 2009

Transparent hybrid organic-inorganic ureasil xerogels with embedded PbS nanoparticles
were prepared by exposing the xerogels doped with lead (II) nitrate to hydrogen sulphide
atmosphere. Absorbance spectrum of the nonocomposites showed well defined peaks at 560 nm and
370 nm attributed to 1s(v) - 1s(c) and 1s(v) - 2p(c) exciton transitions, respectively. After four days
of thermal treatment at 50 °C under argon atmosphere the obtained materials showed enhanced
photoluminescence response in the near infra-red region.
Thermoelectric Properties of Bi2Te3/Sb2Te3 Thin Films
Authors: Gonçalves Luís M. , Couto Carlos , Alpuim Pedro , Rowe D. Michael , Correia J. Higino
Published: March 2009

The deposition and characterization of n-type Bi2Te3 and p-type Sb2Te3 semiconductor films are reported. The films were deposited by thermal co-evaporation on a 25 µm thick polyimide (kapton) substrate. The co-evaporation method is inexpensive, simple, and reliable, when compared to other techniques that need longer time periods to prepare the starting material or require more complicated and expensive deposition equipment. Seebeck coefficients of -189 µVK-1 and +140
µVK-1 and electrical resistivities of 7.7 µ0m and 15.1 µ0m were measured at room temperature on n-type and p-type films, respectively. These values are better than those reported for films deposited by co-sputtering or electrochemical deposition, and are close to those reported for films deposited by metal-organic chemical vapour deposition or flash evaporation. Because of their high figures of merit, these films will be used for the fabrication of a micro-Peltier element, useful in temperature
control and laser-cooling for telecommunications.
Optical Properties of 3,4,9,10-Perylenetetracarboxylic Dianhydride and 8-Hydroxyquinoline Aluminum Salt Films Prepared by Vacuum Deposition
Authors: Stanculescu Anca , Stanculescu Florin , Tugulea Laura , Socol Marcela
Published: March 2009

The main purpose of this paper is to investigate the optical properties of PTCDA and
Alq3 films, prepared by two steps, vacuum evaporation and deposition processes on platelets of glass, quartz, and indium-tin-oxide (ITO) coated glass. We have emphasised the bands structure of the absorption spectra with peaks situated at 358 nm, 374 nm, 475 nm and 552 nm in PTCDA, respectively 232 nm, 261 nm and 380 nm in Alq3 that confirms the dominant presence of Alq3 meridianal molecular isomer. For PTCDA films deposited on glass coated with ITO, the structure of
the weak double peak at low wavelength is partially modified, but the positions of the two important absorption peaks situated at 2.25 eV and 2.61 eV are unchanged. The two different luminescence emission peaks obtained in Alq3 for different excitation wavelengths (λ=360 nm and λ=520 nm) suggest the existence of the facial isomer beside the meridianal one. We have evidenced a significant Stocks shift in the spectra (EPTCDA=0.40 eV; EAlq3=0.9 eV) and a large Frank-
Condon shift (0.40-2.3 eV), suggesting important effect associated respectively with the solid state structure and important conformational differences between the ground and excited state.
Synthesis and Properties of SnO2 One-Dimensional Nanomaterials on Pt-Coated Substrates
Authors: Kim Hyoun Woo , Shim S.H.
Published: March 2009

We have synthesized the belt-like structures of tin oxide (SnO2) by carrying out the thermal evaporation of solid Sn powders. We have analyzed the samples with scanning electron microscopy, X-ray diffraction, transmission electron microscopy and photoluminescence (PL). The obtained nanobelts were single crystalline with a tetragonal rutile structure. PL spectrum exhibited the visible light emission. We have discussed the possible growth mechanisms.
Fabrication and Characterization of Uniform Quantum Size Porous Silicon
Authors: Ali N.K. , Hashim M. Roslan , Aziz Azlan Abdul
Published: March 2009

Porous silicon layer microstructure is sensitive to many parameters which need to be controlled during etching. These include not only anodization time, current density and applied potential but also electrolyte composition. Careful control these parameters will yield excellent reproducibility from run to run. In this paper we outline the advances in porous silicon surface quality and uniformity by recent techniques that have made the production of uniformly sized silicon nanocrystallites possible. In this work we used the oxidant H2O2 in the wet etching bath, with a high etching current. The resulting technique greatly improves the uniformity of the porous surface, producing a very thin layer of porous silicon. This is a significant improvement to the previous method. The result of a combined study of FTIR spectra and photoluminescence show that both quantum confinement and surface passivation are responsible of blue shift of the luminescence peak.
Gelification Effects on the Structure and Birefringence of Charge Transfer Complex Terthiophene Bisililated – TCNQ Hybrid Materials
Authors: Kancono N. , Senin H.B.
Published: March 2009

Charge transfer complexes (CTC) can be readily introduced into materials by cohydrolysis-copolymerisation of bis-silylated ter-thiophenes as precursors with TMOS and TEOS in the presence of TCNQ. CTC formation is shown in the visible spectrum of the xerogel by the band at 850 nm characteristic of the TCNQ·- radical anion. Vibrational spectra have shown that strong vibration of C≡N bond at 2184, 2120 and 1595 cm-1 as peaks characteristics of CTC. The CTC bands are weak and the complex is easily destroyed by washing with acetone, which removes the TCNQ. The gelification effect of the charge transfer complexes on the hybrid materials of 2,5’’- bis(trime thoxysilyl)terthiophene/TCNQ/ TMOS showed that the peak with distance of more than 11.68 Å, formed by precursors and matrices, as a lamellar structure. The birefringence of xerogel BTS3T in presence of alkoxysilane showed that the value is near the detection limit of 0.1 – 0.4 x 10-3, which is weaker than BTS3T / THF with the birefringence value of 4.5 x 10-3.
Characterization of Plasticized Hexanoyl Chitosan-Based Polymer Electrolytes and Application in LiCoO2/MCMB Cells
Authors: Winie Tan , Majid S.R. , Hassan M.F. , Arof A.K.
Published: March 2009

Hexanoyl chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. The effect of plasticizers on the electrical properties of hexanoyl chitosan: LiCF3SO3 electrolytes have been investigated. The plasticizers used were EC, PC and a mixture of EC and PC. The highest room temperature conductivity of about 1.1 x 10-4 S cm-1 was achieved for electrolyte with composition of 50:50 (wt.%) mixture of PC: EC. The variations in conductivity have been explained using the Rice and Roth model from which the numbers of free ions per unit volume, mobility and diffusion coefficient of free ions were obtained. Electrochemical cells based on LiCoO2/MCMB couple were assembled using the electrolyte that exhibited the highest ionic conductivity. The performance of the cells have been studied and discussed in this paper.
Nanoscale Topography of GC/Pt-C and GC/Pt-Ru-C Electrodes Studied by Means of STM, AFM and XRD Methods
Authors: Kowal A. , Olszewski P. , Tripković D.V. , Stevanović R.
Published: March 2009

Electrodes, assigned as GC/Pt-C and GC/Pt-Ru-C, were formed by deposition of Ptbased
catalysts (47.5 wt % Pt + high surface area carbon) and (54 wt. % Pt-Ru alloy + high surface
area carbon) on glassy carbon (GC) discs. X-ray diffraction measurements were used for the
determination of the average crystallite size and phase composition of both catalysts. Crystallite size
for Pt-C catalyst was 2.9 nm for Pt-fcc. In the diffraction pattern of the Pt-Ru-C catalyst two phases,
e.g. Pt-Ru-fcc and Ru-hcp were refined using the Rietveld method. Crystallite sizes were 3.9 nm for
Pt-Ru-fcc and 2.8 nm for Ru-hcp. STM observations of the surface of GC/Pt-C and GC/Pt-Ru-C
electrodes revealed the presence of metal particles of the size in the range 2-6 nm and Pt-C or Pt-
Ru-C agglomerates in the range of several tenth of nm. The thickness of the Nafion covering layer
determined by AFM is ca. 100 nm. A simplified scheme of the investigated electrodes was created.
Comparative Analysis of λ≈9µm GaAs/AlGaAs Quantum Cascade Lasers with Different Injector Doping
Authors: Indjin D. , Höfling S. , Mirčetić A. , Jovanović V.D. , Radovanović J. , Ikonić Z. , Vukmirović N. , Harrison P. , Milanović V. , Reithmaier Johann Peter , Forchel A.
Published: March 2009

An experimental and theoretical comparative analysis of the output characteristics of λ ≈
9m GaAs/Al0.45Ga0.55As quantum cascade lasers based on single and double phonon resonance
depopulation mechanisms were presented. The layer structures were grown with solid source
molecular beam epitaxy and consist of 48 or 36 active stages embedded in a symmetrical plasmon
enhanced waveguide. From the wafers, ridge waveguide lasers were fabricated by optical
lithography and dry etching. The theoretical model is based on a fully non-equilibrium Schrödinger-
Poisson self-consistent analysis of the coupled scattering rate and single-temperature energy
balance equations, taking all relevant electron-LO phonon, electron-electron and electron-ionised
impurity scattering processes into account. Single phonon resonance devices exhibit clear current
saturation, simultaneously with a decrease of the optical power. In the moderate doping regime, a
quasi-linear dependence of both the threshold and saturation current densities on injector doping,
were measured, in a very good agreement with theoretical predictions. Double phonon resonance
lasers exhibit ‘saturation’ mechanism evident from their decrease in optical power, but without
pronounced current saturation. Previously reported saturation of the ‘maximal’ current under higher
injector doping in single phonon resonance lasers, is also observed in the double phonon resonance
structure for injector sheet doping above 8x1011cm-2.
Influence of the DC Current Annealing Treatment on Magnetotransport Properties of Soft-Magnetic Alloys with Amorphous Precursors
Authors: Mitrović N. , Roth Stefan , Kane S.
Published: March 2009

Multistep current annealing (CA) treatments were performed on amorphous FINEMETtype Fe-Cu-V-Si-B, as well as on a novel Fe-Al-Ga-P-C-B alloy with a large supercooled liquid region, in order to optimize their magnetotransport properties. On-line and post-annealing electrical resistivity measurements, DSC, XRD and Mössbauer spectroscopy were used for characterization of structural changes evolved during CA treatments. Results on magnetoresistance (MR) and magnetoimpedance (MI) effects after CA in ribbon samples with relaxed amorphous as well as precipitated nanocrystalline structure are presented. Significant improvement in MI-response after CA up to Z/Z ≈ 50% was recorded at frequencies 2-3 MHz. The highest MI-element sensitivity was found for low magnetic field intensity where values of about 6 %/kA/m for samples of Fe-Al- Ga-P-C-B alloy were attained.
Electrical and Optical Signal Analysis of Pulse Powered Glow Discharge System
Authors: Popović I. , Zlatanović M.
Published: March 2009

The electrical and optical signal waveforms of nitrogen/hydrogen glow discharges used
for plasma nitriding process were recorded and analyzed. The shape of the discharge voltage and
current signals is dependent on the process parameters, pulse plasma generator properties and
cathode geometry. It has been found that the dynamic parameters of the electrical signal waveforms
contain information related to the charged particles generation, which is relevant to the
homogeneity of different gas discharge surface treatment processes. On the other hand, information
related to the active species generation responsible for thermochemical processes at the cathode
surface is stored in the optical emission waveforms. The generation and quenching of the active
ingredients during the voltage pulses switch on and off influence the shape of the emitted light
signals. From the optical signal analysis it was found that the thermochemical processes are
influenced by the plasma generator properties such as pulse duty cycle, frequency, applied
discharge voltage level and process parameters like working gas composition, operating
temperature and pressure.
Downstream Processing of Some Al-Fe-Mn-Si and Al-Fe-Si TRC Alloys and Its Influence on Sheet/Foil Properties
Authors: Delijić Kemal , Asanović V. , Radonjić Dragan
Published: March 2009

This paper describes the general trends correlating mechanical and corrosion properties with chemical composition of some Al-Fe-Si and Al-Fe-Mn-Si alloys for foils. These Al-rich eutectic alloys based on Al-Fe-Si and Al-Fe-Mn, when roll cast and appropriately processed to give fine and regular dispersion of intemetallic particles, can provide good combinations of strength and ductility. These characteristics have been responsible for the alloy success in replacing commercially pure (CP) aluminum for applications in thin sheet and foil gauges. The objective was to obtain an opinion about the possible role of alloying elements in corrosion behavior and mechanical properties of these commercial materials produced by cold rolling of twin roll cast strips.
Microstructural Analysis of Fatigue Initiation in Al-Si Casting Alloys
Authors: Moffat Andrew J. , Mellor B.G. , Chen C.L. , Thomson Rachel C. , Reed P.A.S.
Published: March 2009

Fatigue initiation behaviour in three multi-component Al-Si casting alloys with varying Si content is compared using a range of microscopy and analytical techniques. A higher proportion of stiffer secondary phases leads to load transfer effects reducing particle cracking and particle/matrix debonding. Si appears stronger than the Al9FeNi phase, which cracks and debonds to form initiation sites preferentially over Si. Reducing Si content results in clusters of intermetallics forming, and increased porosity. The effect of porosity, combined with mesoscopic load transfer effects to the high volume fraction intermetallic regions make these potent crack initiation sites in low silicon alloys.
Modelling Precipitate Evolution during Friction Stir Welding of Aerospace Aluminium Alloys
Authors: Robson Joseph D. , Kamp Nicolas , Sullivan A. , Shercliff Hugh R.
Published: March 2009

Two models to predict the microstructural evolution and post-weld properties of friction stir welds in aerospace aluminium alloys are presented. The first model is a develop- ment of an existing semi-empirical method for the prediction of hardness profiles after welding, calibrated using isothermal hardness data. Post-weld natural ageing is accounted for, and a new method that predicts natural ageing kinetics is introduced. Once calibrated, the model is shown to accurately predict weld hardness profiles. However, this model does not explicitly predict the microstructure and therefore cannot readily be extended to model other properties. It can also only be applied to alloys welded in peak or overaged conditions. The second model aims to explicitly predict the heterogeneous precipitate distributions obtained after welding for any initial condition. It is based on classical kinetic theory and the numerical framework of Kampmann and Wagner. Multiple nucleation sites and multiple phases are accounted for. This model provides detailed microstructural information required for prediction of complex properties.
Optimisation of the Strength of Aluminium Foam Sandwich (AFS) Panels by Different Heat Treatments
Authors: Shabestari S.G. , Wanderka N. , Seeliger W. , Banhart John
Published: March 2009

Aluminium foam sandwich panels (AFS) made of a low-density aluminium alloy
AlSi6Cu6 foam core and two dense 6082 alloy face sheets were fabricated, after which the panels
were subjected to two different heat treatments. First, the AFS panels were aged to increase their
strength without further solution heat treatment and fast quenching, a process which resembles a T5
treatment. Second, to define a reference point the face sheets of AFS samples were cut off the foam
and subjected to a full T6 treatment. Hardness profiles were measured across the thickness of the
face sheets after the two different treatments and the microstructure was investigated. The main
conclusion is that mechanical performance of AFS panels can be considerably increased by heat
treatment without full solution heat treatment (T5), but without reaching the level of a full T6
treatment. The potential use of an easy to apply T5 treatment is an important cost reducing factor.
Evaluation of AA 2050-T87 Al-Li Alloy Crack Turning Behaviour
Authors: Crill Matthew J. , Chellman David J. , Balmuth Ed S. , Philbrook Mike , Smith K. Paul , Cho Alex , Niedzinski Michael , Muzzolini Raphael , Feiger Jim
Published: March 2009

Crack turning or delamination behavior of AA 2050-T87 and AA 7050-T7451 ESE(T)
and hourglass coupons under cyclic fatigue conditions is presented. Fatigue crack growth rate
curves, fracture surface examinations, and the preferred manner of crack growth for each alloy are
discussed in an effort to better understand fatigue crack growth behavior of aluminum-lithium
alloys in structural components under service conditions.
Through Process Modelling
Authors: Hirsch Jürgen
Published: March 2009

A new approach to improve existing and develop new simulation models and apply them in a sequence to simulate the complete production processes of Aluminium semi-finished products is described. The development has been a joint effort of academic and industrial partners developed in the frame of the VIR* European projects. It integrated advanced material models with industrial fabrication process models to predict the microstructures and properties in the complete production chain processes of Al sheet and profiles, i.e. by DC ingot casting, rolling and extrusion and analyze complex interactions of critical process parameters with the corresponding metallurgical mechanisms and predict the related material response and properties. The principles are discussed and examples are given for their successful application to simulate industrial fabrication processes.
Solidification Structure and Casting Defect in a High-Speed Twin-Roll Cast A6022 Aluminium Alloy with Various Fe Contents
Authors: Suzuki Kenta , Kumai Shinji , Tokuda Kenji , Miyazaki Takeshi , Ishihara Akiko , Nagata Yusuke , Nakamura Ryoji
Published: March 2009

Closed-loop recycling should be promoted for wrought aluminum alloy scraps including impurity iron in order to use natural resources effectively. Fabrication of the alloy strip using a high rate of cooling is a promising method for reducing the detrimental effects of impurity iron. In the present study, strips of A6022 aluminum alloy with various Fe contents of up to 1.5 mass% were fabricated by a vertical-type, high-speed, twin-roll caster. The caster used in the study was equipped with a pair of water-cooled, pure copper rolls, and a cooling slope upstream of the rolls. The strips exhibited a common microstructural feature. Columnar grains grew from both surfaces of the strip, and they were gradually replaced by equiaxed grains. In the mid-central region, a band of fine grains was observed. Such fine grains seemed to originate from the crystallized α-Al dendrites on the cooling slope or the roll surfaces. Internal cracks were observed in the A6022 alloy strip that was subjected to the highest cooling rate. The cracks were located between equiaxed grains and fine grains at the mid-central region. The cracks were reduced with increasing Fe content. No cracks were observed for the alloy strips with 1.0 mass% Fe or greater. It was found that both a slight reduction in the cooling rate and addition of Fe were effective for obtaining sound A6022 strips.
Effect of Solution Treatment and Artificial Aging on the Work Hardening Characteristics of D357 Alloy Castings
Authors: Tiryakioğlu Murat
Published: March 2009

The effects of solution treatment time and artificial aging on the work hardening characteristics on Al-7%Si-0.6%Mg (D357) alloy castings were investigated. Four different solution treatment times at 540°C (1, 4, 16 and 64 hours) and six different artificial aging times at 160°C (0, 2.5, 5, 10, 20 and 40 hours) were used. Work hardening characteristics were investigated by Kocks-Mecking plots for each specimen. The effects of Si particle morphology (solution treatment) and matrix strength (aging) on Kocks-Mecking (Stage III) work hardening model parameters are discussed in the paper.
3DAP Characterization and Thermal Stability of Nano-Scale Clusters in Al-Mg-Si Alloys
Authors: Serizawa Ai , Hirosawa Shoichi , Sato Tatsuo
Published: March 2009

The formation of nano-scale clusters (nanoclusters) prior to the precipitation of the
strengthening β" phase significantly influences the two-step aging behavior of Al-Mg-Si alloys. In
this work, two types of nanoclusters are found to be formed at different temperatures. The
characterization of these two nanoclusters has been performed from the viewpoints of composition
and thermal stability using a three-dimensional atom probe (3DAP) and differential scanning
calorimetry (DSC). Mg-Si co-clusters formed at room temperature (RT), Cluster(1), play a
deleterious role in the subsequent formation of the β" phase because of the high thermal stability even
at the bake-hardening (BH) temperature of 443K. In contrast, the nanoclusters formed by pre-aging
at 373K, Cluster(2), are effective in the formation of the refined β", suggesting that Cluster(2)
transforms more easily into the β" phase than Cluster(1). The quantitative estimation of the chemical
compositions of the two nanoclusters suggests that the Mg/Si ratio is one of the key factors in
addition to the internal structures consisting of Si, Mg and probably vacancies. The detailed two-step
aging mechanism in Al-Mg-Si alloys is proposed based on the characteristics of the two types of
nanoclusters.
Coherency Loss of Al3Sc Precipitates during Ageing of Dilute Al-Sc Alloys
Authors: Tsivoulas Dimitrios , Robson Joseph D.
Published: March 2009

Scandium additions are known to offer a number of benefits to aluminium alloy performance. Many of these benefits can be attributed to the precipitation of fine Al3Sc particles. These particles are fully coherent with the aluminium matrix when they are small, but can lose coherency as they grow or coarsen. In this work, the change in coherency has been studied in an Al- 0.12 wt%Sc alloy over the temperature range 300-425oC. Three coherency regimes were identified, consistent with previous observations. The time and temperature range over which coherency changes occur have been measured for a range of conditions and correlated with the precipitation kinetics and the predictions of a model for Al3Sc precipitation. The effect of the coherency change on the particle morphology has also been investigated.
Characterization of Ageing Products in AA6111 Using Dynamic Dislocation-Defect Analysis
Authors: Saimoto Shigeo , Subbaiyan S. , Gabryel C.
Published: March 2009

In dynamic dislocation-defect analysis, the thermodynamic deformation-mode signatures are examined as the ageing proceeds. In this method, the activation volume (ν) and the mean slip distance (λ) is simultaneously determined with the flow stress (τ) such that the inverse workhardening slope (1/θ) can be plotted versus b2λ/ν where b is the Burgers vector. The slope of this almost linear locus is directly proportional to the activation distance (d). Calibration with a model alumina-dispersed high conductivity copper reveals that punched-out loops are produced up to failure and is represented by a linear locus from 0.1 to 11 % strain. Artificial ageing of AA6111 at 180°C follows this pattern but the naturally-aged specimen manifest a distinctly different signature which shows a transition as the GP zone-type precipitates are sheared. Furthermore by selecting a suitable tensile-test temperature below 250K, the particle size and volume fraction can be determined if particle shearing does not take place. The optimum size and volume fraction necessary for sufficient strength and ductility can be assessed using this method.
Influence of Scandium Addition on the High Temperature Compressive Strength of Aluminium Alloy 7010
Authors: Mukhopadhyay A.K. , Prasad K. Satya , Dutta A.
Published: March 2009

The influence of Sc addition on the high temperature compressive strength of a commercial
alloy 7010 (hereafter termed base alloy) has been examined. The base alloy, and the base alloy with 0.23
wt% Sc were cast, homogenized and subjected to compression tests at temperatures ranging from 300 to
450oC and strain rates of 10-3, 10-2, 10-1 and 1 sec-1. It is shown that Sc addition to the base alloy increases
the compressive flow stress under these deformation conditions. The increase in peak flow stress is nearly
3-6 times the peak flow stress of the base alloy at temperatures 300-350oC over the strain rate range
investigated. Whilst, at temperatures ³ 400oC, the flow stresses decrease significantly irrespective of the
strain rate used. Transmission electron microscopy (TEM) revealed that a combination of (1) increased
nucleation frequency of dispersoids, (2) evolution of smaller subgrain size, and (3) refinement of alloy
phases in the Al-Zn-Mg-Cu system contribute to superior strengthening in the alloy containing Sc. Whilst,
it is primarily a combination of coarsening and instability of the alloy phases in the Al-Zn-Mg-Cu system
that dramatically reduces the flow stresses in both the alloys at temperatures ³ 400oC.
The Bauschinger Effect in AA 6111
Authors: Proudhon Henry , Poole Warren J.
Published: March 2009

In this paper, tension compression tests are carried out on AA6111 specimens in order to
characterize the internal stress. The impact of the microstructure is investigated by applying a variety
of ageing conditions to the specimens prior testing. It is shown that the Bauschinger effect depends
strongly on the precipitation state. More precisely, when the precipitates are still shearable by the
dislocations, no significant internal stress is found, although when the precipitates are large enough,
a large internal stress, up to 30% of the yield stress, is observed.
Steam Oxidation of TP 347H FG in Power Plants
Authors: Hansson A.N. , Montgomery Melanie
Published: March 2009

The long term oxidation behaviour of TP 347H FG at ultra supercritical steam
conditions was assessed by exposing the steel in test superheater loops in a Danish coal-fired
power plant. The steamside oxide layer was investigated with scanning electron microscopy
and energy dispersive X-ray diffraction in order to reveal the effect of oxidation time and
temperature on the microstructure.
A double layered oxide formed during steam oxidation. The morphology of the inner
Cr-containing layer was influenced by the oxidation temperature. At temperatures below
approx. 585oC, it consisted of regions of Fe-Ni-Cr spinel surrounded by Fe-Cr oxide. At
higher temperatures almost the entire inner oxide layer was composed of Fe-Cr oxide.
Possible mechanisms for the oxide growth are discussed and it is suggested that faster Cr
transport within the alloy at higher temperatures explains the change in morphology. This
hypothesis is supported by thermodynamic calculations and kinetic data.
The thickness of the inner oxide layer did not change significantly with oxidation time
and temperature for exposures less than 30000 h; however after 57554 h the thickness had
increased significantly at the lowest temperatures.