bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of High Energies Radiations to Characterise Solid-Liquid Systems
Authors: Arouca Fábio de Oliveira , Damasceno João Jorge Ribeiro
Published: March 2009

The behavior of an isothermal and non-reaction solid-liquid system can be model using a mathematical model based on the Mixtures’ Theory of Continuum Mechanics. The knowledge of the constitutive equations of this phenomenon, as pressure on the solids and medium permeability, is very important in the design and performance evaluation of the continuous thickeners or filters. In this work the batch sedimentation phenomena of a kaolin aqueous suspensions was investigated. The technique consists on measuring of the gamma rays attenuation when they cross the physical media as a function of the local concentration at several vertical positions in a reservoir. Using the experimental data and local concentration as a function of the attenuation curve, it is possible to determine the constitutive equations. The results were satisfactory, allowing simulations of this phenomenon for steady and transient regimes in future papers.
A Study of Settling Techniques for Measurement of the Size Distribution of Solid Particles
Authors: Arouca Fábio de Oliveira , Barrozo Marcos A.S. , Damasceno João Jorge Ribeiro
Published: March 2009

The determination of the grade distribution of solid particles is fundamental for the performance analysis of several pieces of equipment promoting the solid-fluid separation. The main objective of this work is to compare the results obtained for two traditional methodologies for determination of the sized grade distribution of powdery solids: the gamma rays attenuation technique (GRAT) and LADEQ test tube technique. The influence of draining of suspension in the two used techniques was also analyzed. The gamma rays attenuation technique can supply the grade distribution of solids through the monitoring of solid concentration in experiments of batch settling of diluted suspensions. The results show that the usage of the peristaltic pump in GRAT and LADEQ methodologies presented a significant difference among the values obtained for the parameters of the particles size model.
Synthesis and Characterization of 0.9PMN-0.1PT Powders by the Use of a Modified Columbite Precursor
Authors: Bruno Juliana C. , Cavalheiro A.A. , Zaghete M.A. , Cilense M. , Varela José Arana
Published: March 2009

The complex perovskite compound 0.9PbMg1/3Nb2/3O3-0.1PbTiO3 is one of the most promising relaxor ceramic because the addition of lead titanate increases Tm by about 5°C/mol% from intrinsic Tm value for pure PMN (near –7 to -15°C). A Ti-modified columbite precursor was used to prepare PMN-PT powders containing single perovskite phase. This variation on columbite route includes Ti insertion in MgNb2O6 orthorhombic structure so that individual PT synthesis becomes unnecessary. Furthermore, effects of Li additive on columbite and PMN-PT structures were studied by XRD to verify the phase formation at each processing step. XRD data were also used for the structural refinement by Rietveld method. The additive acts increasing columbite powders crystallinity, and the amount of perovskite phase was insignificantly decreased by lithium addition. By SEM micrographs it was observed that Li presence in PMN-PT powders leads to the formation of rounded primary particles and for 1mol% of additive, the grain size is not changed, different from when this concentration is enhanced to 2mol%.
Synthesis of WC Powders by Reactive Milling
Authors: Passador F.R. , Maestrelli S.C. , Pallone Elíria Maria Jesus Agnolon , Esposto R.F. , Tomasi Roberto
Published: March 2009

One possible route for the production of nanometric powders is the reactive high-energy milling. For a variety of systems of highly exothermic reactions, the milling can lead to self-sustaining reactions, with the reaction being observed after an induction or ignition time, which produces a temperature increase in the reactants. In this work, WC powder was obtained by reactive high energy-milling, performed in a SPEX 8000 shaker/mill. During milling the highly exothermic displacement reaction of reduction of the WO3 by Mg was performed in presence of carbon to produce WC and MgO. The material to ball mass ratio was fixed in 4:1 and the ignition time of the reaction was determined. In order to characterize the transformations from reactant powders to reaction products, the milling was stopped at given times before, immediately after and after the reaction; the powders obtained were characterized by X-ray diffraction, scanning electron microscopy and specific surface area. Depending on the amount of carbon, W and the W2C were also observed as reaction products. The complete formation of WC was achieved with addition of an excess of carbon.
Effect of Grain Size on Reaction between Pb-Free Solder and Plated Iron
Authors: Nishikawa Hiroshi , Takemoto Tadashi , Uetani Takashi , Sekimori Norihisa
Published: March 2009

Recently the soldering iron tip has been severely damaged by molten Pb-free solders during operation due to the high reaction rate of metals in molten lead-free solder. The tip is usually protected by plated iron to prevent the direct contact of copper with molten solders. However, the plated iron tip is heavily dissolved into molten Pb-free solders and the life time of the iron tip is reduced. In this study the simple reaction test between Sn-3.0Ag-0.5Cu (mass%) solder and plated iron was carried out to estimate the dissolution of plated iron in molten Pb-free solder and the effect of the grain size of plated surface on the reaction between Pb-free solder and plated iron. An iron-plated copper was used as the test piece. The Pb-free solder was placed on the test piece and it was put into an oven held at 673, 703 and 733K for 3.6, 10.8 and 32.4ks. After heating, the dissolution thickness of plated iron was measured and the intermetallic compound between Pb-free solder and plated iron was analyzed by XRD. As a result, it has been made clear that the dissolution thickness of plated iron decreases with the decrease of the grain size and then the dissolution of plated iron in molten Pb-free solder is attributable to the grain size of plated iron.
Estimation of Mechanical Properties of Al/Cu Compound Layer Formed by Impact Welding
Authors: Date Hidefumi , Futakawa Masatoshi , Naka Masaaki
Published: March 2009

The impact welding of aluminum onto copper was carried out using a gas gun and the mechanical properties of Al/Cu joint were investigated by tensile tests and micro hardness indentation tests. The strength measured by tensile test decreased with increasing of the impact velocity. The results of the tensile test suggested that it was necessary to make a microscopic survey of the joint interface. Then, the inverse analysis with FEM analysis was applied to the load and depth curves measured by the indentation technique to identify the material constants in the constitutive equations of aluminum, copper and the compound layer. In addition, the numerical simulation for the tensile test was carried out using the identified material constants of aluminum, copper and the compound layer. The nominal stress-strain curve of the compound layer obtained by the numerical simulation showed the typical feature of brittle material. The ultimate tensile stress of the compound layer was about 1.2 GPa and ten times larger than that of aluminum. It was concluded that the bonding strength of Al/Cu joint was dependent on the integrity of the compound layer.
Interpretation of Hardness in Pseudobinary Nitrides by Bulk Modulus Estimated from Interatomic Distance
Authors: Makino Yukio
Published: March 2009

Hardness of the pseudobinary transition metal aluminum nitride (T-Al-N) films is improved with increasing the AlN content as far as the B1structure is maintained. A drastic change in the compositional dependence of the hardness corresponds to the phase change of the pseudobinary nitride from B1(NaCl) to B4(wurtzite) structure. Predicted value of AlN content for the drastic change agrees with the AlN content determined experimentally. Hardness of various T-Al-N films was closely correlated with the bulk modulus calculated from interatomic distance based on the power functional formula. The improvement of hardness is attributed to the inherent increase of bulk modulus due to dissolution of AlN into transition metal nitride.
An Investigation on the Application of Cryogenic Ball Milling to Ibuprofen Particle and Its Characteristics
Authors: Rhee Kyong Yop , Cho Hyun Kab , Hong Jai Sung
Published: March 2009

For a present study, a cryogenic ball milling process was applied to reduce the Ibuprofen particles to submicron in order to enlarge their dissolution rate. The cryogenic ball milling was performed using 6 mm zirconia balls at a temperature of -180 °C or lower. The effects of milling time, the weight ratio of ball to Ibuprofen, and milling speed on the particle size were investigated. SEM and particle size analyzer were used to analyze the shape and size of particles before and after ball
milling. The chemical changes before and after the cryogenic ball milling process were examined through XRD (x-ray diffraction) analysis. The results show that the size of Ibuprofen particles was reduced to about 1/20 of its initial size and the particle size showed negligible change after six hours of ball milling. The effect of weight ratio and the milling speed on the particle size was almost negligible. The results also show that cryogenic ball milling yielded no chemical changes in the
particle.
Influence of Forced Convection on Columnar Microstructure during Directional Solidification of Al - Ni Alloys
Authors: Nguyen-Thi Henri , Zhou Bing Hong , Reinhart Guillaume , Billia Bernard , Liu Q.S. , Lan C.W. , Lyubimova Tatyana , Roux B.
Published: March 2009

This paper presents a summary of cellular and dendritic morphologies resulting from the upward directional solidification of Al – Ni alloys in a cylindrical crucible. We analysed the coupling of solid-liquid interface morphology with natural and forced convection. The influence of natural convection was first analyzed as a function of growth parameters (solute concentration, growth rate and thermal gradient). In a second step, the influence of axial vibrations on solidification microstructure was investigated by varying vibration parameters (amplitude and frequency). Experimental results were compared to preliminary numerical simulations and a good
agreement is found for natural convection. In this study, the critical role of the mushy zone in the interaction between fluid flow and solidification microstructure is pointed out.
Macrosegregation in CC Slabs
Authors: Réger Mihály , Verő Balázs , Csepeli Zsolt , Szélig Árpád
Published: March 2009

In continuously cast semi-finished products, fluid flow results in macrosegregation
patterns. There are two reasons for fluid flow during solidification: density differences in the liquid phase and outer forces or constraints, which mix, suck or squeeze the liquid inside. The calculation method described in this paper can be used to analyze the effects of fluid flow caused by outer constraints and to estimate the expected macrosegregation level.
Study of the Eutectoid Transformation in the As-Cast Spheroidal Graphite Cast Iron with 'in Situ' Dilatation Analysis – Method for Quality Control
Authors: Mrvar Primož , Tribžan Milan , Medved Jožef , Križman Alojz
Published: March 2009

The eutectoid transformation of the spheroidal graphite cast iron (S.G.I.) has been
investigated with “in situ” dilatometer, which was made for the investigation of the cast iron alloys. The investigation of the eutectoid transformation has been taking place by evaluation of the “insitu” dilatation curves in connection with metallographic examinations, chemical analyses and thermodynamic calculations of the phase equilibriums. By dilatometric curves it is possible to follow the exact eutectoid transformation of austenite. On a basis of numerous quantitative relations, as the relation between the ferrite and pearlite fractions in the as-cast SGI, which was determined by the analysis of the dilatometric curves and the composition, the ratio between ferrite and pearlite in the microstructure could be determined in a very short time. From the kinetics of austenite transformation and temperature dependence of the ferrite or pearlite growth the following characteristic temperatures of the eutectoid transformation have been established: the ferrite nucleation o Tα , the beginning of the ferrite growth Tα , and pearlite growth Tp , respectively. Kinetic curves, which show the fraction of the single microstructure constituents in the microstructure in dependence of the transformation time for mainly ferrite SGI, are good represented by the physical sigmoidal Boltzmann model.
High Temperature Chemical Interaction Between SSiC Substrates and Ag-Cu Based Liquid Alloys in Vacuo
Authors: López-Cuevas Jorge , Rendón-Angeles Juan Carlos , Rodríguez-Galicia J.L. , Herrera-Trejo M. , Méndez-Nonell J.
Published: March 2009

The interfaces formed at 850 °C under vacuum between polished or oxidized substrates of pressureless sintered α-SiC (SSiC) and Cusil, Cusil-ABA and Incusil-ABA brazing alloys have been characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. No chemical interaction is observed for Cusil on both SSiC substrates. In contrast, the Ti contained in the Cusil-ABA and Incusil-ABA alloys promotes the occurrence of chemical reactions at the metal/ceramic interface with both SSiC substrates. The formation of TiC and Ti5Si3 is observed for Cusil-ABA and Incusil-ABA on untreated SSiC, following the sequence SiC → TiC → Ti5Si3 at the metal/ceramic interface. The formation of Ti5Si3 and Cu3Ti3O, following the sequence SiC → Ti5Si3 → Cu3Ti3O, is observed for both Ti-containing alloys on pre-oxidized SSiC. During the wetting experiments, Ti5Si3 and Cu3Ti3O detach from the ceramic surface, floating away from the ceramic/metal interface into the liquid alloy, where the latter phase partially dissolves. It is concluded that for both Ti-containing alloys in contact with pre-oxidized SSiC, the Ti remaining after the reaction with the silica film is insufficient to decrease the contact angle to the values observed for untreated SSiC or to produce a strong metal/ceramic joint.
Mechanical Properties of Ultra Clean Low C/Cr Stabilized Annealed Sheets
Authors: Molina A. , Campillo B. , Mendoza R. , Guardián R. , González-Rivera Carlos , Juárez-Islas J.A.
Published: March 2009

The microstructural and mechanical properties of an ultra-clean low carbon steel sheet with 0.035% Cr have been evaluated. The isothermal recrystallization kinetics at 800 oC is analyzed by using the Kolomogorov-Johnson-Mehl-Avrami (KJMA) equation. The obtained results indicate that Cr retards the recrystallization kinetics owing to the presence of fine particles of chromium carbides. The annealing process produces a fully recrystallized microstructure. The main texture components in the specimens are: {111}<112>, {112}<110> and {111}<110>. These are related with the Lankford value and the elongation. The obtained results suggest that the formability of this steel is excellent.
Microstructures and Wear Properties of Al Matrix Composites Fabricated by Two Different Processes
Authors: Kim Yeong Sik , Kim Kyun Tak , Kim Seon Jin , Kim Jae Dong
Published: March 2009

SiC particulates reinforced metal matrix composites (MMCs) were fabricated by two different processes, pressureless infiltration and thermal spray. 10, 20, 30, 40 and 50 vol% SiC reinforced Al matrix composites (AMCs) were fabricated by these two processes. For these AMCs, dry sliding wear tests were performed under a normal load of 3 N, a constant sliding speed of 0.2 m/s and sliding distance of 1000 m against an AISI 52100 ball. Microstructures and wear behavior were studied by means of scanning electron microscope (SEM) and electron probe micro-analysis
(EPMA).
Self-Propagating High-Temperature Synthesis for Aluminum Oxynitride (AlON)
Authors: Lee Jae Ryeong , Lee Ikkyu , Chung Hun Saeng , Ahn Jong Gwan , Kim Dong Jin , Kim Byoung Gyu
Published: March 2009

As the result of combustion reaction in Al-Al2O3-N2 system, AlON phase can be
synthesized in the range of initial nitrogen pressure, from 1 to 5 MPa. On the occasion of rm = 0.3, the unreacted Al was detected in the case of 1 MPa of PN2. Its intensity decreases with an increase of nitrogen pressure. Ultimately, no peak of Al was observed in the product at nitrogen pressure of 5 MPa. In addition, the peak intensity of AlON in the products increases proportionally with the nitrogen pressure, while the intensities of AlN and Al2O3 decrease slightly with an increase of
nitrogen pressure. The formation of AlON may be induced by successive two reactions. The former is the formation of AlN, and the latter is the reaction between AlN and Al2O3 in the after-burning period sustaining high temperature.
Novel Method to Fabricate Porous n-HA/PVA Hydrogel Scaffolds
Authors: Mu Yuan Hua , Li Yu Bao , Wang Ming Bo , Xu Feng Lan , Zhang Xiang , Tian Zhi Yue
Published: March 2009

Porous n-HA/PVA hydrogel composite was prepared through in-situ hydrothermal
treatment under normal pressure and emulsion foam freeze-drying method, which was used to fabricate porous hydrogel. The pores exhibited interconnection-pore structure owing to the injection of air bubbles and the removal of emulsifier (OP). The porous hydrogels were investigated by using IR, XRD, TEM and SEM. The results indicated that n-HA in the composite could disperse uniformly, and there were chemical bonding with PVA. In addition, nano-hydroxyapatite existed
in the composite in the shape of short-rod. The pores were interconnection with narrowly pore size and highly porosity. And the pore size and size distribution were influenced by the weight of OP. The emulsion foam freeze-drying method can be used to prepare porous hydrogel scaffold for tissue engineering, or to contain proteins scaffold, because of operating at a low temperature. The method
displayed a vast potential of applied foreground.
Effect of Paraffin Oil Used as a Lubricant in Tensile Tests of Carbon Fibre Bundles
Authors: Rosa Luis Guerra , Colella Alberto , Anjinho Carlos A.
Published: March 2009

The failure of carbon fibre bundles of Tenax 5131 HTA with 6000 filaments is
characterised using the European Standard EN 1007-5. It is shown that the addition of liquid paraffin to the bundle causes a global change of the load-displacement curve and the effects of the presence of a liquid lubricant are discussed.
Design of DBR Mirrors for GaN Vertical Cavity Surface Emitting Laser
Authors: Mahmoud Ahmed Naser , Hashim M. Roslan , Zainuriah Hassan
Published: March 2009

In the fabrication of nitride-based laser, the cavity plays a vital role in order to enhance the fundamental modes while suppressing the higher order modes. The critical problem faced between the designer and the grower is the idealistic approach in the design laboratory, which more often cannot be met in the fabrication lines. This is because the design does not take into account the limitation in the growth chamber in achieving the targeted mirror thickness and material composition. This paper discusses methods of designing DBR mirrors for vertical cavity surface emitting GaN based lasers. Our design considers variance in the thickness and material composition of the mirrors. The simulation results are given for the investigation of several properties of DBR mirror, as well as a comparison of same types of symmetric DBR mirror.
Growth of Diamond-Like Carbon Thin Film Using Microwave Chemical Vapor Deposition
Authors: Ooi H.T. , Ibrahim Kamarulazizi
Published: March 2009

This paper presents an analysis of diamond-like carbon thin film deposited using homebuilt microwave chemical vapor deposition. Two different deposition conditions were investigated, namely, with and without microwave power. Post deposition analysis included Raman spectroscopy, scanning electron microscope (SEM), energy dispersed X-ray (EDX), four-pointprobe resistivity measurements and refractive spectroscopy. Substrate with pretreatment was observed to have thin film formation. Samples with diamond paste pretreatment show better quality compared to SiC treated samples as suggested by Raman spectral. The presences of sp3 and sp2 peaks were identified in the Raman spectral. The overall resistivity is low due to the graphite content.
Effects of Confinement, Strain and Nonstoichiometry on Raman Spectra of Anatase TiO2 Nanopowders
Authors: Šćepanović M. , Grujić-Brojčin M. , Dohčević-Mitrović Z. , Popović Zoran V.
Published: March 2009

Nanosized titanium dioxide (TiO2) powders in anatase phase were prepared by laserinduced
pyrolysis. Specific surface area of as-grown powders measured by BET method was
between 77 and 110 m2/g. The particle sizes (14.4-20.6 nm) estimated from these data coincide well
with the crystallite sizes (12.3-17.4 nm) determined by XRD measurements. The mean particle sizes
(35-41 nm) obtained from the subsequent SEM measurements refer to considerable agglomeration
of nanoparticles. Raman spectroscopy has been used to investigate the structural properties as well
as the changes under laser irradiation of TiO2 nanopowders. The blueshift and broadening of the
lowest frequency Eg Raman mode were analyzed using a phonon-confinement model which
includes strain effect and broadening associated with the size distribution. Influence of the
nonstoichiometry and anharmonic effects on this mode have been also investigated. Besides,
different changes in Raman spectra after the laser irradiation in vacuum were observed for the
nanopowders with different strain values.
Thermal Contraction during Solidification of Aluminium Alloys
Authors: Eskin Dmitry G. , Katgerman Laurens
Published: March 2009

Aluminium alloys during solidification change their density. This process can be conditionally divided into two stages: solidification shrinkage due to the density difference between liquid and solid phases and thermal contraction due to the temperature dependence of the solid density. Solidification shrinkage is the main cause of porosity in castings and also plays an essential role in the development of macrosegregation, whereas thermal contraction is important for the development of hot and cold cracks and is responsible for shape distortions during casting. An experimental technique has been developed and applied to binary Al–Cu alloys in order to quantify the thermal contraction in the solidification range and at subsolidus temperatures. It is shown that thermal contraction of aluminium alloys starts at rather high fractions of solid, between 80 and 95%. The experimentally determined temperature of contraction onset agrees well with the temperature at which the mushy material acquires the ability to transfer stresses. The magnitude of contraction accumulated in the solidification range corresponds well to hot tearing susceptibility of the alloy. Factors that decrease the temperature of contraction onset and the magnitude of contraction, e.g. grain refinement, are also known to decrease hot tearing. The data on the temperature at which the thermal contraction starts, on the magnitude of the contraction, and on the thermal contraction coefficient are used to model hot tearing and shape distortions during casting.
Trace Element Effects on Microstructure and Mechanical Properties in Al-Cu-Li Alloy after Thermal Exposure
Authors: Zheng Zi Qiao , Chen X.Z. , Chen Zhi Guo , Li S.C. , Wei Xiu Yu
Published: March 2009

The effects of trace Ce, Ag on the microstructure and mechanical properties of Al-Cu-Li
alloy after thermal exposure have been investigated. It’s found that the addition of Ce may lead to a
slight increase in mechanical properties after thermal exposure at 107

. The stability of T1 phase is
enhanced by independent Ag addition and the combined additions of Ag and Ce,which results in
higher strength compared with Ag-free alloy at 150

thermal exposure. However, at 200

exposure,
a great number of q¢ precipitates at the expense of T1 may be responsible for higher tensile strength in
the Ag-free alloy than that of the independent addition of Ag and combined additions of Ag and Ce
alloys.
Precipitation Behaviour of Mg and Si at RT in Pre-Aged Al-Mg-Si Alloys
Authors: Takata Ken , Ushioda Kohsaku , Kikuchi Masao
Published: March 2009

The precipitation behavior of Mg and Si during storage at RT in Al-Mg-Si alloys
pre-aged at 90°C was studied using a tensile test and differential scanning calorimetry (DSC)
measurement. Specimens were solutionized at 530°C, water-quenched and then pre-aged for 2, 6
and 12 hours at 90°C during which small precipitates were formed. In the pre-aged alloy, the
strengthening rate at RT has two stages. In the initial stage, the yield strength increases slowly with
the aging time and in the final stage, it increases rapidly. In the initial stage, the strength in the
pre-aged alloy is smaller than that in the non pre-aged alloy, while in the final stage, the strength in
the pre-aged alloy is larger than that in the non pre-aged alloy. Furthermore, the period of the initial
stage is dependent on the pre-aging period at 90°C. The DSC curves of alloys in the initial stage do
not show the presence of clusters, while those in the final stage do. It seems that in the initial stage
Mg and Si atoms accumulate around the small precipitates that have been formed in pre-aging at
90°C while in the final stage, the clusters of these atoms are formed.
The Effect of Heat Treatment and Mn, Cu and Cr Additions on the Structure of Ingots of Al-Mg-Si-Fe Alloys
Authors: Bryantsev P.Yu. , Zolotorevskiy V.S. , Portnoy V.K.
Published: March 2009

Phase transformations in 6XXX alloys with Mn, Cu and Cr additions have been studied in the process of homogenization annealing at different temperatures. The continuous cooling transformation diagrams of decomposition of solid solution during the cooling of ingots from the homogenization temperature have been plotted. The effect of the cooling rate after homogenization on the properties of ingots during extrusion has been studied.
The Effect of Grain Refiners for Aluminium Alloy Containing Mn-Ti-Sr Dispersoid
Authors: Vacariu V.T. , Buzaianu Aurelian , Vasile Eugeniu , Trusca R. , Moldovan Petru
Published: March 2009

The new structural applications of aluminum materials are determined by
intelligent lightweight design: the demand of safety, ecology, recycling and by
economics. Al-Si alloys allow complex shapes to be cast. Metallurgical a high volume
fraction of fine dispersoid which are less about 0.1 microns in size are useful for
retaining a fine grain. In the 6061 series of alloys, iron combines with aluminium and
silicon to form two types of commune inter-metallic, (beta AlFeSi and alpha
AlFeSi).The type of inter-metallic that is present these alloys will have an important
bearing on the homogenization time, workability and quality of the surface finish.
The microstructure of the as-cast samples was evaluated by electronic microscopy
and the morphology of inter-metallic compounds related to the efficiently modification.
Mn-Ti-Sr modification of Al-alloys is normally accompanied by an increase in porosity
in the casting.
Protection of Aluminium Alloys via Hybrid Sol-Gel Coatings with Encapsulated Organic Corrosion Inhibitors
Authors: Khramov A.N. , Balbyshev V.N. , Mantz R.A.
Published: March 2009

Several heterocyclic organic corrosion inhibitors that contain ionazible functional group
were encapsulated into nano-structural hybrid organo-silicate coating to improve its corrosion
protection performance on aluminum alloy 2024-T3 substrate. When the coating is formed on the
substrate surface, it serves simultaneously as protective barrier and as a reservoir for leachable
corrosion inhibitor that is stored and released through the mechanism of reversible ionic interaction
with the matrix material. The efficiency of active corrosion protection for these coating systems
was examined by electrochemical methods including potentiodynamic polarization (PDS) and
electrochemical impedance spectroscopy (EIS). The effects of chemical structure and the loading
concentration of the inhibitor within the coating were determined.
Damage-Based Finite Element Modeling of Stretch Flange Forming of Aluminium-Magnesium Alloy
Authors: Chen Zeng Tao , Worswick Michael J. , Lloyd David J.
Published: March 2009

The numerical simulation of the stretch flange forming operation of Al-Mg sheet
AA5182 was conducted with an explicit finite element code, LS-DYNA. A Gurson-Tvergaard-
Needleman (GTN)-based material model was used in the finite element calculation. A strain
controlled void nucleation rule was adopted with void nucleating particle fraction measured directly
from the as-received Al-Mg sheet. Parametric study was performed to examine the effect of void
nucleation strain on the predicted onset of ductile fracture. Critical porosity levels determined
through quantitative metallurgical analysis were adopted to predict the commencement of void
coalescence in the GTN model. The numerical results were compared to the experimental ones and
an applicable void nucleation strain was suggested.
Exfoliation and Fracture Behavior of Oxide Films Formed on Titanium and Its Alloy in High Temperature Environments
Authors: Oka Yoshinori Isomoto , Yamabe Takahiro , Tsumura Toshinori
Published: March 2009

It is very difficult to obtain mechanical properties of oxide films formed on a
material in high temperature environments despite its importance of estimating material
degradation caused by such as thermal stress. Corrosion/oxidation tests were conducted for
pure titanium and titanium alloy in high temperature corrosive environments of wet air and
water vapor with hydrogen chloride at temperatures from 673 K to 973 K to look into basic
behavior of degradation and the growth of titanium oxide films. It was found that oxide films
were usually formed on the specimen surface and the growth was accelerated by the
corrosiveness of the environment. In order to examine mechanical properties and exfoliation of
corrosion products or oxide films formed on titanium and its alloy, tests of single particle
impact on the specimen surface with a glass bead were performed in high temperature
corrosive environments. The piling-up surfaces around impact craters were formed and
plastically strained. The oxide film formed on the metal surface was detached in a wide range
of the circumference and fractured a little far from the rim of the crater. Then fracture and
exfoliation stress of the oxide film were estimated by the calculation of impact energy and
fractured and detached areas. It was found that both the fracture and exfoliation stress of the
oxide films were different depending on the corrosive environment and chemical composition
of titanium alloy.
Deformation and Fracture Behavior of Surface Oxide Scale on Fe-13Cr Alloy in Hot-Rolling Process
Authors: Hidaka Y. , Anraku T. , Otsuka Nobuo
Published: March 2009

The behavior of the surface oxide scale on steel products during hot rolling process influences the surface properties of final products. To investigate the deformation and the fracture behavior of surface oxide scale of Fe-13Cr alloy, a hot rolling test was carried out. The oxide scale rolled out was observed in detail by using TEM. The specimen was hot-rolled after oxidation at 1100 for 90 minutes in air. The hot rolling tests with two conditions (. The hot rolling test of the outer scale {=whole layer scale} , . The hot rolling test of the inner scale that removed the outer scale) were carried out. The rolling reduction rate was 25, 44, 58, and 68%. The outer scale was composed of Fe2O3 and F3O4, and the inner scale was composed of Fe3O4, FeCr2O4, and a small amount of Fe2SiO4. Fe2SiO4 formed along the grain boundaries of the other oxides (Fe3O4, FeCr2O4) was observed by TEM. In the test , Fe2O3 of the outer scale was pulverized to fine particle that looks like red powder, and Fe3O4 of the outer scale was cracked by hot rolling. A ductility-like behavior was observed in the inner scale (Test ). That is, it was found by the SEM observation that porosity and micro cracks of the surface oxide disappeared gradually according to the increase in the rolling reduction. It was thought that the porosity and the micro cracks eased the compression stress caused by hot rolling. In the case of high reduction rate, FeSi2O4 ,which is a low melting point oxide, formed on grain boundary caused grain boundary slipping. When the rolling reduction is very high, plastic deformation by dislocation occurred in Fe3O4 and FeCr2O4. However, these oxides were broken, when their plasticity would not be able to accept considerably high rolling reduction.
Corrosivity of KCl(g) at Temperatures above Its Dew Point - Initial Stages of the High Temperature Corrosion of Alloy Sanicro 28 at 600°C
Authors: Pettersson C. , Svensson Jan Erik , Johansson Lars Gunnar
Published: March 2009

The influence of gaseous KCl on the high temperature oxidation of alloy Sanicro 28 (27Cr31Ni) at 600°C in 5% O2 (N2 in balance) is reported. The samples were exposed isothermally in flowing gas, the dew point of KCl being 590°C corresponding to a partial pressure of KCl of about 2·10-6 atm. The exposure time was 24, 72 and 168 hours. The samples were investigated by gravimetry, grazing incidence XRD, SEM/EDX and AES. The results show that the oxidation of Sanicro 28 at 600°C is accelerated by KCl(g) at metal temperatures above the dew point of the salt. KCl(g) reacts with the protective chromium rich oxide ((Fe1-xCrx)2O3) forming K2CrO4. The resulting chromium depletion of the oxide gives an increasing oxidation rate but does not trigger “breakaway” corrosion. The distribution of potassium chromate on the sample surface is strongly flow-dependent, showing that the rate of formation of potassium chromate is limited by the rate of transport of KCl(g) to the surface. No evidence for chlorine was found on the corroded samples by AES profiling or EDX.
TEM Observation of the Initial Stage Oxidation of TiAl Based Alloys in a Simulated Combustion Atmosphere
Authors: Yoshihara Michiko , Taniguchi Shigeji , Li X.Y.
Published: March 2009

The oxidation behavior of Ti-48Al-2Cr-2Nb, Ti-48Al-2Cr-2W and Ti-48Al-2Cr-2Fe was
studied in a simulated combustion gas, 10O2-7CO2-6H2O-bal.N2 (vol%), at 1173 K and TEM
observation was performed for understanding the initial stage of oxidation behavior.
Ti-48Al-2Cr-2Nb and Ti-48Al-2Cr-2W show excellent oxidation resistance in the test gas by
forming thin and protective Al2O3-rich scales, while Ti-48Al-2Cr-2Fe shows poor oxidation
resistance. The superior oxidation resistance of W-containing alloy is explained in terms of the
formation of a bcc phase with low Al content in the alloy which was confirmed by TEM
observation and also possible enhanced Al diffusion from the substrate to the scale in this phase.
The oxidation resistance of the former two alloys in the test gas is better than in laboratory air, due
to the lower O2 content in the test gas. The presence of H2O and CO2 in the test gas enhances the
oxidation of Ti-50Al, while it has almost no influence on the oxidation behavior of these two alloys,
indicating that these gases are influential to a TiO2-rich scale but not to Al2O3-rich scales.
Residual Stress Gradients in PVD-Coated Carbide Cutting Tools
Authors: Denkena Berend , Breidenstein Bernd
Published: March 2009

PVD-coated cutting tools show a typical kind of failure in use: cohesive damage, which
is believed to be a result of the residual stress state of substrate and coating. As the sin2ψ-technique
does not give satisfactory information on near surface residual stress trends of coated tools the
scattering vector method was applied to determine residual stress depth distributions of coating and
substrate. The results are presented and an attempt for an interpretation is given.
Evolution of Residual Strains in Metastable Austenitic Stainless Steels and the Accompanying Strain Induced Martensitic Transformation
Authors: Hedström Peter , Almer Jonathan , Lienert Ulrich , Odén Magnus
Published: March 2009

The deformation behavior of metastable austenitic stainless steel AISI 301, suffering different
initial cold rolling reduction, has been investigated during uniaxial tensile loading. In situ highenergy
x-ray diffraction was employed to characterize the residual strain evolution and the strain
induced martensitic transformation. Moreover, the 3DXRD technique was employed to characterize
the deformation behavior of individual austenite grains during elastic and early plastic deformation.
The cold rolling reduction was found to induce compressive residual strains in the austenite along
rolling direction and balancing tensile residual strains in the ά-martensite. The opposite residual
strain state was found in the transverse direction. The residual strain states of five individual
austenite grains in the bulk of a sample suffering 2% cold rolling reduction was found to be
divergent. The difference among the grains, considering both the residual strains and the evolution
of these, could not be solely explained by elastic and plastic anisotropy. The strain states of the five
austenite grains are also a consequence of the local neighborhood.
A Parametric Model for the Straightness Deviation in the Cutting Processes of Aluminum Alloys
Authors: Sánchez J.M. , Sebastián M.A. , Rubio E. , Sánchez-Carrilero Manuel , Sevilla L. , Marcos Bárcena Mariano
Published: March 2009

Light alloys are increasingly applied in different industrial sectors, mainly aerospace.
Because of this, it is needed to analyze their behavior in the different processing procedures and,
specially, machining. On the other hand, up to a few years, cutting fluids were successfully
employed in these processes since their coolant and lubricant properties. Notwithstanding,
environmental necessities have promoted researches focused on the development of cleaner
processes avoiding cutting fluids, in particular, dry machining. However, this process can change
tool geometry and affect to the material giving rise to changes in the design specifications. In this
work, geometrical deviations, particularly straightness deviations, in the dry turning of UNS
A92024 (Al-Cu) alloy are studied as a function of feed and cutting speed through a parametric
model.
Effect of Tool Electrode Material on the Spark Erosion of Micro Grooves
Authors: Yeo S.H. , Murali M. , Balakrishnan S.
Published: March 2009

Micro electro discharge machining is an important unconventional metal micromachining
technology. The performance of micro EDM depends on the combination of the tool and work
materials used. In the absence of a comprehensive theoretical model to predict the effect of
electrode materials on the performance of EDM, experimental investigations as described in this
paper become useful. The work materials studied include ferrous, non-ferrous and exotic material
(XW42, Ti6Al4V, WC) and the tool electrode materials include the commonly used EDM tool
materials namely tungsten, copper and graphite. It is found that in the microgroove machining by
micro EDM using foil electrodes, graphite consistently provides higher material removal rate than
tungsten and copper tool electrodes and hence it is useful for the rough machining. On the other
hand tungsten tool electrode is preferable for finish machining as it provides the least surface
roughness.
Optimization of a SiC Super-SBD Based on Scaling Properties of Power Devices
Authors: Hatakeyama Tetsuo , Ota Chiharu , Nishio Johji , Shinohe Takashi
Published: March 2009

Scaling theory is applied in the design of power devices. The scaling law for power devices
is presented. A new figure of merit (HFOM) is derived as an invariant of scale transformation, which
is a function of avalanche breakdown field and regarded as a measure of the performance of a power
device. The optimization of a SiC Schottky barrier diode with the floating junction structure
(Super-SBD) has been performed using the HFOM as a measure of the performance. The
performance of the optimized Super-SBD surpasses the performance limit of 4H-SiC devices with the
conventional structure.
Development of Ultra High Sensitivity UV Silicon Carbide Detectors
Authors: Yan Feng , Xin Xiao Bin , Alexandrov Peter , Stahle Carl M , Guan Bing , Zhao Jian Hui
Published: March 2009

A variety of silicon carbide (SiC) detectors have been developed to study their sensitivity,
including Schottky photodiodes, p-i-n photodiodes, avalanche photodiodes (APDs), and single
photon-counting APDs. Due to the very wide bandgap and thus extremely low leakage current, SiC
photo-detectors show excellent sensitivity. The specific detectivity, D*, of SiC photodiodes are
many orders of magnitude higher than the D* of other solid state detectors, and for the first time,
comparable to that of photomultiplier tubes (PMTs). SiC APDs have also been fabricated to pursue
the ultimate sensitivity. By operating the SiC APDs at a linear mode gain over 106, single photoncounting
avalanche photodiodes (SPADs) in UV have been demonstrated.
Minimum Ionizing Particle Detector Based on p+n Junction SiC Diode
Authors: Moscatelli Francesco , Scorzoni Andrea , Poggi Antonella , Bruzzi Mara , Lagomarsino Stefano , Sciortino Silvio , Wagner Günter , Nipoti Roberta
Published: March 2009

In this work ion-implanted p+/n diodes have been used as minimum ionizing particle
(MIP) detectors. The diode structure is based on a 0.45 $m deep, NA = 4×1019 cm-3 doped p+ anode,
ion implanted in an n-type epilayer with thickness equal to 55 $m and nominal donor doping ND
= 2×1014 cm-3. The diode breakdown voltages were above 1000V. At 1000V reverse bias the diode
leakage current was of the order of 1 nA. The punch through depletion voltage was nearing the
range 220-250 V. The charge collection efficiency to minimum ionizing particle was investigated by
a 90Sr β source. The pulse height spectrum was measured as a function of the reverse voltage in the
range 0-605 V. At each bias point the signal was stable and reproducible, showing the absence of
polarization effects. At 220 V the collected charge was 2970 e- and saturated at 3150 e- near 350 V.
At the moment, this is the highest collected charge for SiC detectors. At bias voltages over 100V
the spectrum was found to consist of two peaks clearly separated. Around 250 V the signal
saturates, in agreement with CV results.
Structural Properties and Electrical Characteristics of Homoepitaxial GaN PiN Diodes
Authors: Cao X.A. , Larsen M. , Lu H. , Arthur Steve
Published: March 2009

GaN PiN diodes with a 4 μm Si-doped n--GaN drift layer (n~7×1016 cm-3) were grown on
free-standing GaN using metalorganic chemical vapor deposition. Atomic force microscopy showed
smooth surfaces with a step structure indicating good 2D growth. The dislocation density and
impurity incorporation in the drift layer were remarkably reduced compared to a similar diode
structure grown on sapphire. The full width at half maximum of the (0002) rocking curve was 79
arcsec, much smaller than 230 arcsec for the heteroepitaxial structure. The diodes on GaN
demonstrated rectification up to –265 V, corresponding to a critical electric field ~2.7×106 V/cm.
The maximum value of the figure of merit is ~2.4 MW cm-2, which represents a 2.2× improvement
over the diodes on sapphire.
Atomic Layer Epitaxy of (Si1-xC1-y)Gex+y Layers on 4H-SiC
Authors: Pezoldt Joerg , Kups Thomas , Weih Petia , Stauden Thomas , Ambacher Oliver
Published: March 2009

3C-(Si1-xC1-y)Gex+y ternary alloys were grown on 8.5° off axis 4H-SiC substrates by solid
source molecular beam epitaxy in a temperature range between 750°C and 950°C. Energy dispersive
X-ray (EDX) analysis revealed a decrease of the Ge incorporation versus substrate temperature. This
effect is due to the fixed Si/Ge ratio during the epitaxial growth. The Ge distribution within the
grown epitaxial layers was found to be nearly homogeneous. The investigations by atomic location
by channeling enhanced microanalysis allowed the conclusion that Ge is located mainly at Si lattice
sites.
Effect of the Crystallization Conditions on the Epitaxial Relationship of Si Deposited on 3C-SiC(100)
Authors: Ferro Gabriel , Polychroniadis Efstathios K. , Panknin D. , Skorupa Wolfgang , Stoemenos J. , Monteil Yves
Published: March 2009

The epitaxial relationship of Si deposited on 3C-SiC was studied using both free standing
3C-SiC(100) material from Hoya and 3C-SiC thin layers deposited on Si(100) as substrates. The
conditions of Si growth were varied depending on the substrate. When Si is deposited at 1000°C on
(001) 3C-SiC, it is in perfect epitaxial relation with the SiC layer [100]Si//[100]SiC and
[001]Si//[001]SiC. After a 20 ms flash lamp pulse on the same sample, which has the effect of fast
melting of the Si top layer only, the defects in the Si are eliminated. Using free standing 3C-SiC, the
deposition temperature was not limited by the Si melting point so that it was fixed at 1500°C in
order to form a set of Si liquid droplets on the surface with diameters ranging from 5 to 20 μm.
Surprisingly more than 60% of the Si droplets exhibit the epitaxial relation [110]Si//[001]SiC and
[111]Si//[110]SiC after crystallization. The occurrence of this epitaxial relationship can be understood
in terms of lattice mismatch reduction from 20% to 18.3%. The conditions of crystallization, most
probably the cooling rate, seem to have a strong effect on Si orientation.
Post-Implantation Annealing in a Silane Ambient Using Hot-Wall CVD
Authors: Rao Shailaja P. , Bergamini Fabio , Nipoti Roberta , Hoff A.M. , Oborina E. , Saddow Stephen E.
Published: March 2009

Post-implant annealing of Al implanted 4H-SiC has been performed in the temperature
range from 1600°C to 1750°C. Annealing was conducted in a hot-wall CVD reactor using a silanerich
ambient. Ar was used as the carrier gas to deliver the silane to the annealing zone where the
sample was heated via RF induction. The resulting annealed surfaces exhibited a step-bunch free,
smooth morphology when viewed on SEM and AFM. The maximum surface roughness as
measured via AFM was 0.65 nm RMS for the sample annealed at 1750°C.
Reduction-Diffusion Preparation of Nd15Fe77B8, NdFe11Ti, NdFe10.5Mo1.5 and NdFe10.75Mo1.25 Alloys for Magnets
Authors: Guilherme Eneida da G. , Hechenberg H.R. , Pascoal José Octavio A.
Published: March 2009

The calciothermic reduction-diffusion (CRD) process is a alternative preparation route for Nd15Fe77B8, NdFe11Ti, NdFe10.5Mo1.5 and NdFe10.75Mo1.25 alloys, which eliminates the need for long homogenizing heat treatment; in addition, the resulting alloy is already in powder form. We have examined the effect of various processing variables in the preparation of mother alloys. Compacts made of NdCl3, Fe, Ti, Mo and Fe-B powders and Ca granules were heated under argon for different times and temperatures. The alloys as-prepared contained mostly the hard magnetic phase. The NdFe11Ti, NdFe10.75Mo1.25 and NdFe10.5Mo1.5 alloys have been successfully nitrogenated by heating a mixture of powdered alloys with sodium azide (NaN3) at temperatures between 330 and 450 oC.
The Use of Granite and Kaolin Residues as Raw Materials to Obtain Ceramic Tile
Authors: Ramalho M.A.F. , Almeida R.R. , de Lima Santana Lisiane Navarro , Lira Hélio Lucena , Ferreira H.C. , Neves Gelmires Araújo
Published: March 2009

Recycling of residues from different industrial process as new raw materials has been
studied by several institutions to be applied in the production of ceramic bricks, roof tile. The
aim of this work is to study the potentiality of the residues from granite and kaolin industries
as raw materials to obtain ceramic tile. The raw materials were fired at temperatures of
1100oC, 1120oC and 1150oC. After fired the specimens were submitted to a physical and
mechanical tests, such as, linear shrinkage, mechanical resistance, water absorption and
apparent density. The results show that the residues can be used in the composition of the
paste to produce ceramic tiles.