bluuebunny/crossref_metadata_2025 huggingface dataset:
A Thermodynamical Model for Analysis of Isothermal Phase Transformations under High Pressure
Authors: Grigorova Veneta , Roussev Dimitar
Published: March 2009

In the present study we elaborated a thermodynamical model for analysis of isothermal
phase transformations under high pressure. Our study was provoked by the necessity to characterise
the behaviour of MTe2 chemical compounds (M = Pd, Pt) while subjected isothermally to high
pressure. As known [1] MTe2 powders are representatives of the CdI2 structure type. This structure
type is a bi-dimensional one and as such is atypical for the big family of lamellar MQ2-type
dichalcogenides (M = Pd, Pt; Q = S, Se, Te). Specific of lamellar structure is the strong ionicity of
the bonds. One of the most interesting points stands on the possibility for realising interactions
between the layers of different types of ions. That could be done under high pressure by any of the
following transformation processes: (i) phase transition to the typical pyrite structure; (ii) phase
rearrangement changing the parameters of the crystal cell but keeping the 2D-type structure. In this
framework our aim was to elaborate a thermodynamical model for analysis of such isothermal
phase transformations under high pressure. Our analysis model is designed to answer the following
questions: (i) if the treated compound undergoes a classical phase transition or a phase
rearrangement; (ii) which is the order of the phase transition or the phase rearrangement,
respectively; and (iii) what is the degree-of-stability of the treated compound under high pressure.
To detect if the transformation process is a phase transition or a rearrangement, we compute both
volumetric and longitudinal Gibbs free energies and their partial derivatives. We recognise the
transformation to be: (i) a phase transition when it affects the volumetric Gibbs free energy and its
partial derivatives; (ii) a phase rearrangement if it affects the longitudinal Gibbs free energy and its
partial derivatives. The order of the transformation process (phase transition or rearrangement,
respectively) is determined by the order of the partial derivative of the Gibbs free energy
(volumetric or longitudinal, respectively), which is discontinuous in the transformation point.
Hence, we compute the two first partial derivatives (i.e., the first one and the second one) of the
Gibbs free energy (both volumetric and longitudinal). For characterising the degree of stability of
the treated compound under high pressure we calculate its entropy generation (volumetric and
longitudinal, respectively) during the treatment process. The established model was further applied
to PdTe2 and to PtTe2 while subjected isothermally to high pressure.
Structural Characterization of Titanium Nitride Coatings on AISI M2 Steel
Authors: Deniz G. , Şen Şaduman , Şen Uğur
Published: March 2009

In this work, some surface properties of AISI M2 steel were improved by a thermoreactive
deposition process. Gas nitriding was realized on AISI M2 steel at 550°C for 2 h in an
ammoniac atmosphere and then, titanizing treatment performed on pre-nitrided steel in the powder
mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 1-4 h.
Structural characterization of titanium nitride layer formed on the surface of AISI M2 steel was
carried out by using optical microscopy, scanning electron microscopy, electron microprobe and Xray
diffraction (XRD) analysis. The hardness measurements of titanium nitride layer were
conducted under 10 g loads by using Vickers microhardness indenter. Structural analysis studies
showed that titanium nitride layers formed on the AISI M2 steel samples were smooth, compact and
homogeneous. XRD analysis show that the coating layer formed on the steel samples includes TiN,
Fe6Mo7N2, C0.7N0.3Ti, C0.3N0.7Ti and V2N phases. The hardness of titanium nitride layers formed on
the steel samples is between 2040±186 and 2418±291 HV0.01. The thickness of titanium nitride
layer formed on the steel samples ranged from 3.86±0.43 9m to 6.13±0.47 9m, depending on
treatment time.
Local Structures of Si2(O,N)7 Ditetrahedra in J-Phase
Authors: Takahashi Junichi , Shimada M. , Yamane H.
Published: March 2009

Oxygen/nitrogen (O/N) configuration in RE-J-phase, RE4Si2O7N2 (RE = rare earth element), was simulated by the Monte Carlo method applied to O/N distribution models. Proportion of local structures of Si2(O,N)7 ditetrahedra and Si(O,N)4 tetrahedra in the J-phase was quantitatively assessed. For the Lu-J-phase model with the bridging site between two Si atoms being occupied by nitrogen atom, the Si2(O,N)7 ditetrahedra composed of O3≡Si–N–Si≡O2N (> 40 %), O3≡Si–N–Si≡O3 (c.a. 30 %), and O2N≡Si–N–Si≡O2N(c.a. 15 %). Tetrahedra of SiO3N and SiO2N2 were dominant and small amount of SiON3 tetrahedra coexisted. For La-J-phase model with the O/N occupancy of 0.1/0.9 at the bridging site, configurations of O3≡Si–O–Si≡O2N (c.a. 5%), O3≡Si–O–Si≡O3 (c.a. 3%), and O2N≡Si–O–Si≡O2N (c.a. 2%) were demonstrated in addition to the three configurations of ditretrahedra recognized in the Lu-J-phase. In La-J-phase coexistence of SiO4 tetrahedra was presented.
Ecomaterials in the Global Eco-Society: Present Situation and Future Prospects
Authors: Umezawa Osamu , Halada Kohmei , Shinohara Yoshikazu
Published: March 2009

The concept of environmental conscious materials, ecomaterials, is reviewed. It has
dispersed and recognized in the world as contributing to a sustainable society. Advanced models for
secondary materials utilization, environmental benign processes and new material recycling systems
are introduced.
Plasma Etching for the Application to Low-K Dielectrics Devices
Authors: Lee Jong Woo , Kim Hyoun Woo , Han Jeong Whan , Kim Mok Soon , Yoo Byung Don , Kim M.H. , Lee C.H. , Lee C.H. , Lim Cheol Ho , Hwang Sun Keun , Lee C. , Chung D.J. , Park S.G. , Lee S.G. , O B.H. , Kim J. , Chang S.P. , Lee S.H. , Chai Seung Yong , Lee Wan In , Park S.E. , Kim K. , Choi D.K. , Chung C.W.
Published: March 2009

We present a study of the photoresist (PR) etching and the low-k materials damage using a
ferrite-core inductively coupled plasma (ICP) etcher, in order to develop an etching process for the
low-k dielectric devices. We reveal that the N2/O2 flow ratio and bias power affected the PR etching
rate. By Fourier transform infrared spectroscopy and HF dipping test, we investigated the effect of the
gas flow ratio and bias power on the amount of etching damage to the low-k material.
A Model of Gamma-Ray Irradiation Effects in Silicon Dioxide Films and on Silicon Dioxide - Silicon Interface
Authors: Odalović M. , Petković D.
Published: March 2009

The gamma-ray irradiation causes positive charge traps formation in silicon dioxide films
and at silicon dioxide - silicon interface of MOS devices, and the threshold voltage shift in MOS
transistors. Here, the Monte Carlo model was used to develop an approach for estimating gammaray
induced traps spatially distributed in silicon dioxide films. This is combined with the model of
energy distributed traps at silicon dioxide - silicon interface. The developed model enables gammaray
induced charge and threshold voltage shift determination as a function of gamma-ray doses. The
threshold voltage measurements at a single specified current, both of radiation sensitive and
radiation hardened MOS transistors irradiated with different doses of gamma-ray are compared with
the developed model and good agreement are obtained.
A New Aspect in Computational Nanomaterial Science: Odd Electrons in Molecular Chemistry, Surface Science, and Solid State Magnetism
Authors: Sheka E.F.
Published: March 2009

A unified theoretical and/or computational odd-electrons approach is suggested
for molecules, surfaces and magnetic solids making possible their consideration on the same
conceptual basis as well as on the same computational footing. The current paper presents the
approach application to the chemistry of fullerenes, carboneous nanotubes, surface science of
silicon crystal, as well as to the molecular magnetism of both solid polymerized fullerenes and
molecular crystals composed of transitional metal complexes.
The Activity of Iron-Containing Zeolitic Materials for the Catalytic Oxidation in Aqueous Solutions
Authors: Milojević Maja , Dondur V. , Damjanović Lj. , Rakić Vesna , Rajić Nena , Ristić Alenka
Published: March 2009

In this work, a series of iron-containing zeolitic materials has been tested as
heterogeneous catalysts for decomposition of H2O2 and for oxidation of the cationic dye Methylene
Blue with H2O2 in aqueous solutions. FeAPO and FeBEA zeolites, synthesized through
hydrothermal crystallization of basic hydrogels, and FeY and FeZSM-5 zeolites, prepared by ionexchange
procedures, have been studied. The ion exchange with Fe(III) cations was performed from
different salt solutions. Fe-exchange procedure carried out in Fe-citrate solution has been identified
as an attractive option for the preparation of highly effective FeZSM-5 catalysts in wet oxidation
processes. It has been shown that both tetrahedral, framework Fe, and octahedral, extra-framework
Fe species incorporated into zeolite structure are catalytically active in wet oxidation reactions.
Raman Spectra of Bismuth Titanate Ceramics
Authors: Lazarević Z.Ž. , Romčević N.Ž , Romčević M.J. , Stojanović B.D.
Published: March 2009

Bismuth titanate is a typical layer-structured ferroelectric material and belongs to the
Aurivilius type-structure compounds family. A bismuth titanate ceramic material could be obtained
by mechanically activated synthesis after thermal treatment at a temperature slightly lower than in
conventional solid-state reaction. In this case bismuth titanate was prepared through
mechanochemical synthesis starting from bismuth oxide and titanium oxide in rutile form. The
mixture of oxides was milled in a zirconium oxide jar in a planetary ball-mill in intervals from 1 to
12 hours. The ratio of powders to zirconium oxide balls during milling was 1:20. Bismuth titanate
was formed after 1 h. The Raman spectroscopy analysis was performed.
Reduction of Nanometric Magnetite Powder
Authors: Vulićević Lj. , Ivanović N. , Popović N. , Kusigerski V. , Srećković Milesa , Tomić Ž. , Vardić S.
Published: March 2009

The investigated nanometric magnetite powders were synthesized electrochemically, and
examined by XRD and SEM techniques. Their reduction was conducted through the isothermal
heating in hydrogen in the temperature range from 600 to 860 K. Kinetics of the hydrogen recovery
process during oxidation of freshly formed Fe powders in a water vapor stream was also studied. It
was assumed that the solid-gas reaction is diffusion controlled, and Jander’s model was applied to
describe it. The experimental data suggest that the reoxidation process proceeds in two stages, at
various activation energies. By changing the conditions of the electrochemical (EC) process we
were able to produce the iron oxide powders with optimal particle size and activity, for pure
hydrogen production through appropriate reduction/oxidation processes.
Catalyst-Free Growth of Tin Oxide One-Dimensional Nanostructures on Silicon Nitride Substrates
Authors: Shim S.H. , Kim Hyoun Woo , Lee C. , Chung D.J. , Park S.G. , Lee S.G. , O B.H. , Kim J. , Chang S.P. , Lee S.H.
Published: March 2009

We have obtained one-dimensional (1D) nanomaterials of tin oxide (SnO2) on silicon
nitride (Si3N4)-coated Si substrates by carrying out the thermal evaporation of solid Sn powders and
varying the substrate temperature in an Ar/O2 ambient gas. We analyzed the samples with scanning
electron microscopy, X-ray diffraction, transmission electron microscopy and photoluminescence
(PL). Reactions at a lower substrate temperature gave rise to thinner 1D structures. The obtained 1D
nanomaterials were single crystalline with a tetragonal rutile structure. We proposed a vapor-solid
process as the growth mechanism for SnO2 nanorods. The PL spectrum exhibited visible light
emission.
Infrared and Photoluminescence Study of Rapidly Thermally Annealed SiOx Thin Films
Authors: Milutinović A. , Dohčević-Mitrović Z. , Nesheva Diana , Šćepanović M. , Grujić-Brojčin M. , Popović Zoran V.
Published: March 2009

Silicon suboxide, SiOx thin films with different oxygen contents (1.15≤x≤1.70) were
prepared by thermal evaporation of silicon monoxide at a residual oxygen pressure of 1·10-3 Pa and
deposition rates of 0.2, 1.0, 3.0 and 6.0 nm/s. Rapid thermal annealing (RTA) of films was carried
out at 1100°C in vacuum for 15 and 30 s and the films were analyzed by infrared (FTIR) and
photoluminescence (PL) spectroscopy. In the FTIR spectra of SiOx annealed samples, a blue-shift of
the stretching band with initial oxygen content, x, is observed. This band is shifted to a much lower
frequency with prolonged RTA time. This behavior can be interpreted in terms of the partial
decrease of oxygen content and film density upon annealing in vacuum. With annealing time
increase a new band at 1106 cm-1 appears. Therefore, infrared spectra of SiOx films are significantly
affected by the oxygen content. PL spectra of these films also change drastically with increasing
annealing time. In the PL spectra of films annealed for 15 s two bands are easily visible: broad redorange
band at 2.2 eV and a green band at 2.4 eV, while for 30 s annealing only low-energy band
exists. Green band is connected with the defects in the SiOx matrix while red-orange band can be
deconvoluted into several bands at 2.0, 2.3 and 2.5 eV. Two types of defects can be responsible for
the PL band at about 2 eV: defects in a-Si (amorphous silicon) nanoparticles separated during RTA,
and nonbridging oxygen hole recombination centers (NBOHC) formed by loosing of oxygen during
RTA. The PL band at 2.3 eV is associated with the defects formed at a-Si/SiOx interfaces while a
hardly visible band at 2.5 eV is related to the defects connected with the oxygen deficiency formed
in the SiOx matrix during RTA.
High Surface and High Nanoporosity Boron Nitride Adapted to Hydrogen Sequestration
Authors: Laversenne L. , Miljanić Š. , Miele Philippe , Goutaudier Christelle , Bonnetot B.
Published: March 2009

High surface area nanoporous powders of hexagonal boron nitride (h-BN) have been
prepared from molecular precursors to be used for hydrogen sequestration. The more promising
samples were obtained using a precursor derived from trichloroborazine (TCB). The precursor was
first reacted with ammonia at room temperature leading to the molecular complex Cl3B3N3H3, 6
NH3 which was heated up to 650 °C under ammonia and then up to 1000 °C under nitrogen, giving
rise to a high reactive h-BN powder. This crude powder was stabilised by an annealing up to 1800
°C under nitrogen atmosphere leading to a very stable compound exhibiting a specific area of more
than 300 m2·g-1 and presenting a very specific nanometric spherical texture. Some samples were
doped with platinum (about 1 wt.%) to enhance the activity of pure h-BN using an original one step
synthesis route starting from a mixture of BN and Pt precursors. Attempts to sequester hydrogen
into these powders were made successfully at -196 °C under 10 MPa, but the stored amount was
only about 0.3 wt.% and the platinum added BN powders did not lead to an enhancement of the
storage capacity.
Low Temperature Aerosol Synthesis of YAG:Ce3+ Nanostructures: Comparative Study of the XRPD Micro Structural Parameters
Authors: Kandić Ljiljana , Marinković K. , Mančić Lydia , del Rosario G. , Milošević O.
Published: March 2009

The objective of this work is to present the results of the comparative analysis of
YAG:Ce3+ microstructural parameters obtained from x-ray powder diffraction (XRPD) data using
Rietveld based Koalariet and Fullprof programs. YAG:Ce3+ powder is obtained via low
temperature aerosol route at 3200C followed by post annealing treatment. The chosen technique of
synthesis, i.e. ultrasonic spray pyrolysis, provides the generation of spherically shaped and
submicronically sized particles having composite nanostructure. Since the targeting garnet phase
represents a very promising host phosphor material being doped with rare-earth ions, the most
important criteria determining its applicability in various optical devices is the uniform distribution
of the luminescent center in the host lattice as well as the cubic YAG phase crystallinity.
Comparison of the data obtained for the same samples by the above mentioned XRPD analyses
gives us an insight into the validity of the refined parameters.
A Unified Decoherence-Based Model of Microparticles in a Solution
Authors: Jeknić J. , Dugić M. , Raković D.
Published: March 2009

The complex behavior of microparticles in a solution calls for different theoretical
backgrounds. Here, we follow the line of two, recently developed theories on individuality, on the
one hand, and conformational transitions of macromolecules in a solution, on the other. Given as
separate theories, the two models may raise certain controversy in respect to their mutual
consistency. Needless to say, their mutual consistency is necessary for the validity of the theories
both in a general context as well as in search for a unified physico/chemical picture concerning the
microparticles in a solution dynamics. We point out the consistency of these theories based on the
definition of a molecule through its constituent subsystems (e.g. the center-of-mass and the
“conformation” subsystems).
Investigation of Antimicrobial Activity of Encapsulated Essential Oils
Authors: Rakin Marko , Mojović Lj. , Dimitrijević Suzana , Mihajlovski K. , Siler Marinković S.
Published: March 2009

Antimicrobial activity of essential oils obtained from many plants has been known for a
long time. However, the use of essential oils as active components of biomedical textile have
recently gained popularity and aroused scientific interest. The antimicrobial activity of two essential
oils, Rosmarinus officinalis and Abies sibirica, respectively, was detected using two indicator
strains: Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, respectively.
To achieve a controlled release of antimicrobial activity and to enable utilization of higher
concentrations of active ingredient, the essential oils were first encapsulated in beads based on
alginate, gelatin and yeast cells, and then bounded to medical textile. The maximum oil content
(85.4%) was achieved in alginate capsules. The release of essential oils was followed by
determination of viable bacterial cells during a seven-day incubation of beads in saline. Rosmarinus
officinalis and Abies sibirica immobilized in the beads showed a significantly prolonged activity,
with some gel-dependent variation.
The Stabilizer Influence on Morphological Characteristics of Poly-(DL-Lactide-Co-Glycolide) Nanospheres
Authors: Stevanović Magdalena , Jordović Branka , Nedić Zoran , Miličević Dejan
Published: March 2009

Copolymer poly(D,L-lactide-co-glycolide) is used for obtaining the systems for
controlled delivery of medicaments. Its specific characteristics make it suitable for various
researches where its synthesis is performed in different ways. Using the system for controlled
delivery of medicaments, an equal concentration of the medicament is achieved in the body
throughout an extended period of time and it has advantages over the conventional methods. In this
paper we present a new solvent/non-solvent chemical method for obtaining DLPLG nanospheres. In
the experiment various stabilizers were used in order to examine their influence on morphological
characteristics of DLPLG particles. The samples were characterized by Infrared Spectroscopy (IR),
Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Stereological
analysis.
The Effect of Processing Parameters on Characteristics of Poly-L-Lactide Microspheres
Authors: Jovanović Ivana , Stevanović Magdalena , Nedeljković B. , Ignjatović N.
Published: March 2009

Biodegradable micro- and nanospheres made of poly-l-lactide (PLLA) are very potent
drug or antigen delivery systems with inherent potential for drug and antigen targeting. The
objective of this study is to formulate modified PLLA microparticles with defined size and shape
that can efficiently bind bioactive component. The effects of some process variables on the size
distribution of particles prepared by precipitation method are examined. The main focus is to study
the effect of co-solvent selection and poly(vinyl alcohol) PVA concentration on the shape and size
of the particles. Chlorophorm is used as a solvent. Methanol (MeOH) and ethanol (EtOH) are
selected as co-solvents. Motivation for replacing MeOH with EtOH in pharmaceutical applications
is explained by less harmful nature of EtOH. Scanning electron microscopy (SEM) and X-ray
diffraction (XRD) are used to characterize the particles. Optimal particles are achieved in ethanol
and at higher PVA concentration
Micromechanical Analysis of Constraint Effect on Fracture Initiation in Strength Mismatched Welded Joints
Authors: Dobrojević M. , Rakin Marko , Gubeljak Nenad , Cvijović Ivana , Zrilić Misa , Krunich N. , Sedmak Aleksandar
Published: March 2009

In this paper the micromechanical approach to ductile fracture was applied in a study of
constraint effect on crack growth initiation in mismatched welded joints. The single-edged notched
bend specimens (precrack length a0/W=0.32) were experimentally and numerically analyzed. The
coupled micromechanical model proposed by Gurson, Tvergaard and Needleman was used.
Constraint effect was tested by varying widths of the welded joints (6, 12 and 18mm). Highstrength
low-alloyed (HSLA) steel was used as the base metal in a quenched and tempered
condition. The flux-cored arc-welding process in shielding gas was used. Two different fillers were
selected to obtain over- and undermatched weld metal. The micromechanical parameters used in
prediction of the crack growth initiation on precracked specimen were calibrated on a round smooth
specimen. The difference in fracture behavior between over- and undermatched welded joints
obtained in experimental results was followed by numerical computations of void volume fraction
in front of the crack tip.
Numerical Modeling of RF Magnetron Sputtering with Metallic or Dielectric Target
Authors: Makabe T. , Yagisawa T.
Published: March 2009

A self-consistent modeling of two-dimensional and temporal (2D-t) structures of RF
magnetron plasma with a metallic (copper) and a dielectric (SiO2) target is performed at 5 mTorr in
argon by using plasma hybrid model consisting of a particle-in-cell/Monte Carlo (PIC/MC)
simulation for electrons and the relaxation continuum (RCT) model for ions. The erosion profiles of
both targets are numerically predicted through the flux velocity distribution of ions incident on the
surface. The mechanism of plasma maintenance in a dielectric target is quite different from that in a
metallic one. Two major differences exist in an erosion profile between both targets. One is the
presence of dual peaks in the erosion profile of the dielectric target. The other is the discrepancy in
the position of the maxima between incident ion flux and erosion depth on the dielectric target.
These are direct influences of the radially localized structure in an interfacial sheath based on the
charge accumulation on a dielectric surface.
Simulation of Recrystallization Using Molecular Dynamics; Effects of the Interatomic Potential
Authors: Godiksen Rasmus B. , Trautt Zachary T. , Upmanyu Moneesh , Schmidt Søren , Juul Jensen Dorte
Published: March 2009

Recrystallization is governed by the migration of high angle grain boundaries traveling through a deformed material driven by the excess energy located primarily in dislocation structures. A method for investigating the interaction between a migrating grain boundary and dislocation boundaries using molecular dynamics (MD) was recently developed. During simulations migrating high angle grain boundaries interact with dislocation boundaries, and individual dislocations from the dislocation boundaries are absorbed into the grain boundaries. Results obtained previously, using a simple Lennard-Jones (LJ) potential, showed surprisingly irregular grain boundary migration compared to simulations of grain boundary migration applying other types of driving forces. Inhomogeneous boundary-dislocation interactions were also observed in which the grain boundaries locally acquired significant cusps during dislocation absorption events. The study presented here makes comparisons between simulations performed using a LJ- and an embedded atom method (EAM) aluminum potential. The results show similarities which indicate that it is the crystallographic features rather than the atomic interactions that determine the details of the migration process.
On Strain-Induced Grain Growth Using Modified Monte Carlo Method and Digital Image Correlation Technique
Authors: Lin Wei Ling , Kuo Jui Chao
Published: March 2009

In this study the strain-induced grain growth was simulated on an aluminum bicrystal by using channel-die compression. After compression of the bicrystal up to 5% deformation the strain mapping were characterized by using digital image correlation (DIC) technique and the 2D strain filed provided data to simulate grain growth using a modified Monte Carlo method. The strain-induced grain growth on grain boundary was simulated and compared with experiment after annealing at 450°C for 4 hours. The relation between the deformation heterogeneity and the grain growth was discussed in this work.
Stored Energy and Recrystallisation in Cold Rolled Steel
Authors: Wierzbanowski Krzysztof , Baczmanski Andrzej , Tarasiuk Jacek , Lipiński Paul , Bacroix Brigitte , Lodini Alain
Published: March 2009

Plastic deformation induces the dislocation and residual stress fields, which rest in a
material after releasing of applied external forces. One can distinguish the stored energy connected
with dislocation density and that with residual stresses. The stored energy distributions can be
determined experimentally by diffraction experiments and also can be predicted by deformation
models. The so obtained distributions of the stored energy versus crystal orientation were correlated
with deformation and recrystallization textures of low carbon steel.
Monte Carlo Potts Model Simulation and Statistical Theory of 3D Grain Growth
Authors: Zöllner Dana , Streitenberger Peter
Published: March 2009

An improved Monte Carlo (MC) Potts model algorithm has been implemented allowing an extensive simulation of three-dimensional (3D) normal grain growth. It is shown that the simulated microstructure reaches a quasi-stationary state, where the growth of grains can be described by an average self-similar volumetric rate of change, which depends only on the relative grain size. Based on a quadratic approximation of the volumetric rate of change a generalized analytic mean-field theory yields a scaled grain size distribution function that is in excellent agreement with the simulation results.
Crystallization Behavior and Mechanical Property of Cu Based Metallic Glass Powders
Authors: Kim Hye Sung , Lee J.K. , Shin Seung Y. , Kim Taek Soo
Published: March 2009

Crystallization behavior of gas atomized and spark plasma sintered (SPS) Cu54Ni6Zr22Ti18 amorphous powders were studied using X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and transmission electron microscope (TEM). By heating to the temperatures of 837K and 909K, the amorphous phases in the powders formed particles such as Cu10Zr7 and Cu51Zr14. The size of crystals devitrified is about 20nm and 50nm, respectively. In order to identify the sintering ability of SPS, the compressive strength was measured with the initial powder size and SPS pressure.
Effect of O2 Partial Pressure on Magnetic Properties of Alloys CoFe-Rich Nanocrystalline Thin Films
Authors: Tho L.V. , Lee K.E. , Kim Cheol Gi , Kim Chong Oh , Cho W.S.
Published: March 2009

Alloys of CoFe-rich magnetic films are well known as typical soft magnetic alloys. They are used for many kinds of electric and electronic parts such as magnetic recording heads, transformers and inductors. In order to get superior soft magnetic properties of the CoFe-based nanocrystalline thin films, the effect of O2 partial pressure on magnetic properties of Co-Fe-Hf-O nanocrystalline thin films have been investigated. It is found that the soft magnetic properties and electrical property of these films show a dependence on the partial pressure of reactive gases, which presumably changes the microstructure of the films and related magnetic anisotropy. With optimal conditions, thin film exhibit excellent soft magnetic properties: saturation magnetization (4πMs) of 21 kG, magnetic coercivity (Hc) of 0.18 Oe, anisotropy field (Hk) of 49 Oe, and an electrical property is also shown to be as high as 300 μcm. The combination of high 4πMs and relatively high Hk in these films are believed to be partly responsible for the excellent ultra-high-frequency behavior
Effects of Initial Texture on Drawing and Recrystallization Characteristics of Gold Bonding Wire
Authors: Kim Han Sol , Kim Won Yong
Published: March 2009

Microstructure and texture formation behavior of a gold rod and fine wire which were produced by continuous casting process and drawing, respectively were investigated by means of optical micrographs, TEM images and X-ray pole figure. Well-developed unidirectional structure aligned to casting direction was found in 7 mm gold rod. Higher casting speed was found to be favor in developing the directional microstructure. In the sample with unidirectional microstructure developed in partial it is found that dislocation substructure with nano-size appeared to display a characteristic feature, while no dislocation substructure is seen in the sample with complete unidirectional microstructure. Interface stability between solid and liquid may be responsible for this difference in dislocation substructure. <100> fiber component was observed to be well developed over the whole microstructure in unidirectional sample. With decreasing casting speed <100> fiber component became weak. Two texture components consisting of <111> fiber and <100> fiber were seen in as-drawn samples. For the development of <111> fiber texture component initial texture component plays a more significant role than subsequent annealing process. Annealing heat treatment would be effective way to control the formation of <100> fiber component. On the basis of results obtained it is suggested that both the initial texture and final annealing are important in controlling the texture of gold bonding wire.
Effect of Crystallization on High-Temperature Plastic Flow and Ductility in Pre-Annealed Zr-Al-Ni-Cu Bulk Metallic Glass
Authors: Takigawa Yorinobu , Kobata J. , Tsuda Hiroshi , Higashi Kenji
Published: March 2009

High-temperature plastic flow and tensile ductility in pre-annealed Zr65Al10Ni10Cu15 bulk
metallic glass are examined in a supercooled liquid region. The specimen annealed at 673K for
1.8ks before the tensile test exhibits uniform deformation, and large elongation of 1100% is
obtained in the tensile test at 673K and in a constant true strain rate of 1×10-2s-1. In the specimen,
initial stress decreases in comparison with that of the specimen without annealing, but apparent
strain hardening arise during deformation. SEM analysis after the deformation reveals that the
cavitation is very limited even at the fracture tip. XRD and TEM analyses reveal that icosahedral
phase is observed only in gage section but not in grip section after the deformation. The limited
cavitation due to the accommodation of stress concentration through the grain boundary amorphous
phase possibly makes a positive contribution to the large elongation in the annealed specimen, as
well as the neck stability due to the strain hardening by the interaction between the icosahedral
phase particles increasingly crystallized by the local strain.
Distribution of the Precipitates on the Grain Boundaries in Fe-3%Si Steel during Secondary Recrystallization Annealing
Authors: Yim Jung Ryoul , Min Ah Ri , Park Jong Tae , Joo Young Chang
Published: March 2009

The distribution of the precipitates on the grain boundaries in Fe-3%Si steel during
secondary recrystallization annealing were studied using high-angle annular dark filed (HAADF)
scanning transmission electron microscopy (STEM). Because HAADF image can show both grain
boundaries and precipitates clearly, the change of precipitate distribution on grain boundaries can be
quantitatively analyzed. It was observed that the total area of the precipitates on grain boundaries
increased in the order of non-annealed, 600°C, and 900°C sample and the total area of precipitates on
grain boundaries in the 1000 °C sample was much lower than that in the 900 °C sample. The
compositions of the precipitates were also analyzed using X-ray energy-dispersive spectrometer
(XEDS). The most precipitates were multi-phase ones, mainly composed of AlN and MnS. Our
analysis results suggest that such a precipitate behavior is responsible for the abnormal grain growth
of Fe-3%Si steel occurring under the temperature above 900 °C.
Activated Slip Systems and Nucleation of Recrystallized Grains in Aluminium Deformed in Channel-Die
Authors: Paul Henryk , Driver Julian H.
Published: March 2009

The relations between the active slip systems within the deformed state and the orientations of the first formed nuclei of recrystallized grains have been studied in strongly deformed samples of high purity aluminium single crystal and polycrystalline aggregates. The new grain orientations and misorientations were followed by systematic local orientation measurements using SEM-FEG/EBSD and semi-automatic measurements in TEM. Investigations of the direction of growth indicate the privileged role of {111} planes in the initial stages of recrystallization. The grain boundary migration and ‘consumption’ of the as-deformed areas was always favoured along directions parallel to the traces of the most active {111} slip planes as shown clearly in the stable and structurally homogeneous Goss{110}<001> oriented crystallite. In the case of polycrystalline material the influence of grain boundaries and their triple junctions on the crystallographic aspects of nucleation is discussed.
Formation of Ferrite-Cementite Ultrafine Grained Microstructure by Warm Compression for SM490 Martensite Steel
Authors: Li J.H. , Xu Ping Guang , Tomota Yo , Adachi Yoshitaka
Published: March 2009

The low carbon steel, SM490 was austenized at different temperatures followed by quenching into water to obtain martensite microstructures with different grain sizes. Then specimens were heated up to 600°C followed by warm-compression at έ=1.7x10-3 s-1 (strain rate) to investigate the dynamic recrystallization behavior. The influence of pre-tempering before compression was also investigated. The microstructure observations were performed with FE-SEM and orientation imaging analysis with EBSD. It is confirmed that the dynamic recrystallization occurred in the tempered martensite as well as the as-quenched marteniste, resulting in fine grained ferrite microstructure with about 2μm. The dynamic recrystallization grain size is hardly dependent on the block size of initial martensite.
An Investigation of Microstructure Inhomogeneity in Waspaloy Subjected to Plane Strain Compression Testing
Authors: Thomas M.J. , Wynne Bradley P. , Palmiere Eric J. , Mingard Ken P. , Roebuck Bryan
Published: March 2009

An assessment of the inhomogeneity of microstructure generated within plane strain
compression test specimens has been performed using the nickel based superalloy, Waspaloy. Two
variables were investigated: the effect of strain rate and the effect of friction at the tool/specimen
interface. Tests were performed at 1040°C at nominal strain rates of 0.01 and 1 s-1 with and without
a glass based lubricant. At the low strain rate the microstructure was relatively homogeneous
regardless of the friction conditions. At the high strain rate there was significant microstructure
variation from surface to mid plane which was further exaggerated by increased friction.
Quantification of the inhomogeneity, however, is non-trivial in this alloy due to the complicated
recrystallisation behaviour it exhibits and difficulty in differentiating between recrystallised and
non-recrystallised grains.
Dynamic Recrystallization of Ferrite in Low Carbon Steels
Authors: Sun Zu Qing , Li Long Fei , Yang Wang Yue
Published: March 2009

Dynamic recrystallization(DRX) of ferrite in low carbon steels was investigated by hot
compression tests at temperatures of 550 to 700oC at strain rates of 0.001 to 10s-1. The results indicate
that DRX of ferrite can occur in low carbon steels and lead to grain refinement. With increasing
Zener-Hollomon parameter Z, its mechanism changes from discontinuous dynamic recrystallization
to continuous dynamic recrystallization, the turning point is approximately at Z=1×1016s-1 for a low
carbon steel with 0.171wt% C. The results also indicate that changing the minor constituents of the
low carbon steel from pearlite colonies to fine cementite particles has an effect on promoting DRX of
ferrite, and the increase of Mn content and the presence of tiny Nb precipitates have opposite effects
respectively. However, all these changes are of benefit to the refinement of recrystallized grains.
Recrystallisation, Grain Growth and Texture Evolution in Nonoriented Electrical Steels
Authors: Park Jong Tae , Kim Jae Kwan , Szpunar Jerzy A.
Published: March 2009

The magnetic properties of nonoriented electrical steels are influenced by grain size and texture of final products. The key technology in the commercial production of nonoriented electrical steels is to grow grains with {hk0}<001> texture up to the optimum size in the final annealing process. The problems related to grain size control have been extensively investigated, while texture control has received much less attention. Therefore, there is enough room to improve the magnetic properties through the control of texture. In this study, systematic investigations on the texture evolution during both recrystallization and grain growth have been made. The formation of recrystallization texture is explained by oriented nucleation. This is supported by the fact that the area fraction of nuclei or recrystallized grains with specific orientation to all new grains remains almost constant during the progress of recrystallization. Most nuclei have a high misorientation angle of 25∼55° with the surrounding deformed matrices. During the progress of grain growth, the Goss texture component continues to decrease because the Goss grains have a high percentage of low angle, low mobility grain boundaries. The grains of Goss orientation have a smaller grain size than those of random orientation.
Topological Approach to Abnormal Grain Growth in three Dimensions
Authors: Rios Paulo Rangel , Glicksman Martin E.
Published: March 2009

Theories of abnormal grain growth (AGG) in three dimensions usually approximate an
abnormal grain by a sphere. The abnormal grain is then represented by its spherical equivalent grain
radius. This study, by contrast, treats AGG in terms of concepts that include both the boundary
curvature and the number of faces of the abnormal grain. We treat AGG for the case of pinned
matrices, including the phenomena of initiation and growth kinetics. The influence of interfacial
energy and mobility of the abnormal grain boundary are also discussed.
Statistical Aspects of Grain Coarsening in a Fine Grained Al-Sc Alloy
Authors: Ferry Michael , Burhan N.
Published: March 2009

A supersaturated Al-0.3 wt.% Sc alloy was cold deformed by ECAP to an equivalent von Mises strain of 9.2 then pre-aged at 350 °C to generate a fine-grained alloy with an average grain size of 1 μm. The microstructure was highly resistant to grain coarsening at temperatures up to 500 °C with a detailed statistical analysis showing that the initial grain size distribution was very close to lognormal and, throughout annealing, remained lognormal and the normalized frequency distribution was time/temperature invariant despite a moderate broadening of the size distribution. This behaviour is largely similar to subgrain coarsening during recovery and grain growth after recrystallization. The homogeneous evolution of the microstructure during annealing, coupled with no appreciable change in texture, is also consistent with the advanced stages of continuous recrystallization.
Evolution of the Texture on Primary Recrystallization and Grain Growth in Fe-3%Si Steels
Authors: Han Kyu Seok , Park Jong Tae , Kim Jae Kwan , Szpunar Jerzy A.
Published: March 2009

Recrystallization texture in grain oriented silicon steel at different annealing temperature is investigated. Normalized x-ray intensities of various orientation components observed in Orientation Distribution Function are used for comparison. The computed CSL boundary distributions about Goss component with annealing condition were calculated. The misorientation angle distribution is also measured in order to find the importance of high-energy boundary with misorientation 20~45° range for the secondary recrystallization of Goss grain. From the analysis of CSL boundary distribution and misorienation angle distribution, the distribution of CSL boundaries does not evidently show any preferred difference between Goss and other texture components. Whereas, the misorientation angle analysis shows that the number of 20°~45° misoriented boundaries is higher around the Goss grains than around other texture components.
Microstructure of Friction Stir Processed Mg-Y-Zn Alloy
Authors: Morishige Taiki , Tsujikawa Masato , Chung Sung Wook , Oki Sachio , Higashi Kenji
Published: March 2009

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [(m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.
Grain-Growth Phenomena in ZnO-Based Ceramics
Authors: Bernik Slavko , Podlogar Mateja , Daneu Nina , Rečnik Aleksander
Published: March 2009

Grain growth in ZnO ceramics doped with 0.01 and 0.02 mol.% Bi2O3 and Sb2O3 in amounts appropriate for Sb2O3/Bi2O3 ratios of 0.8, 1.0 and 1.2, sintered at 1200oC for 2 and 10 hours, was investigated. Grain growth is promoted by a sufficient amount of the Bi2O3 liquid phase at the grain boundaries and also by the presence of IBs in the ZnO grains. While the doping of ZnO with such small amounts of Bi2O3 caused the exaggerated growth of some grains, the addition of Sb2O3 resulted, via the IBs-induced grain-growth mechanism, in uniform grain growth and the presence of IBs in most of the ZnO grains. The formation of the pyrochlore phase bounds the Bi2O3 and Sb2O3, which affects, depending on the Sb2O3/Bi2O3 ratio, the occurrence of the Bi2O3 liquid phase and also the amount of available Sb2O3 for the nucleation of IBs in the ZnO grains during the early stages of sintering. As a result, it influences the grain growth.
Microband-To-Microshear Band Transition near Grain Boundaries in BCC Steel
Authors: Dorner Dorothée , Adachi Yoshitaka , Tsuzaki Kaneaki
Published: March 2009

Compression tests were performed on Fe-3%Si specimens with few grains. The deformation
microstructure and microtexture were investigated by electron backscatter diffraction (EBSD)
and related to the initial crystal orientation and grain boundary characteristics. Groups of microbands
were found that are characterised by a periodic change in crystal orientation, shear at the
grain boundary, and the formation of new grains. It is supposed that these microband groups represent
an early stage of microshear band development.
Recovery of HPT-Processed Iron Studied by Orientation Imaging Microscopy
Authors: Ivanisenko Julia , Minkow Alexander , Valiev Ruslan , Fecht Hans Jorg
Published: March 2009

A comprehensive investigation of microstructure evolution upon annealing in the
temperature range between 100°C and 450°C in SPD-processed nanocrystalline iron had been
conducted using transmission and orientation imaging microscopy, and XRD analysis. The asprocessed
microstructure was typical of severely deformed metals consisting of grains with a mean
size of 110 nm, each subdivided by a network of subgrain boundaries. Additionally, measurements
of microstrains using XRD found a very high microstrain level of 0.003 in this material. After
annealing at 200°C a drastic decrease of microstrains was observed; whereas no notable changes in
the size of grains and subgrains as well in misorientation spectra have been revealed. Thus we relate
this decrease of microstrains with recovery of non-equilibrium grain boundaries. Annealing at
higher temperatures hadn’t led to further decrease of microstrains, but resulted in slight subgrain
growth from 65 to 78 nm accompanied by increase of mean misorientation angle from 5° to 6.3°at
450°C. This indicates the occurrence of coalescence of subgrains as additional recovery mechanism.
Faceting and Migration of Low Angle <100> Tilt Grain Boundaries in Pure Aluminum
Authors: Kirch Dirk M. , Zhao Bing Bing , Molodov Dmitri A. , Gottstein Günter
Published: March 2009

The kinetic and structural behavior of symmetrical <100> tilt grain boundaries with rotation
angles 8.4°, 12.0°, 14.3° and 16.0° were investigated in-situ in a hot stage SEM in the
temperature range between 380°C and 640°C. The results revealed that depending on the rotation
angle the boundary either remained straight, became faceted or curved under the driving force provided
by the boundary surface tension during high temperature annealing. The transition “facetedcurved
boundary” was also found to depend on temperature. The observed behavior is attributed to
the anisotropy of grain boundary energy with respect to boundary inclination.
Grain Boundary Engineering by Application of Mechanical Stresses
Authors: Winning Myrjam
Published: March 2009

It is shown that an externally applied mechanical stress field can change the kinetics of individual grain boundaries. Moreover, such mechanical stresses also have influence on grain growth and recrystallization kinetics and can strongly affect the microstructure evolution, so that the application of mechanical stresses during annealing can be used as a new approach in the field of grain boundary engineering.
High-Entropy Alloys – A New Era of Exploitation
Authors: Yeh Jien Wei , Chen Yu Liang , Lin Su Jien , Chen Swe Kai
Published: March 2009

A high-entropy alloy (HEA) has been defined by us to have at least five principal elements, each of which has an atomic concentration between 5% and 35%. In the exploration on this new alloy field, we find that HEAs are quite simple to analyze and control, and they might be processed as traditional alloys. There exist many opportunities to create novel alloys, better than traditional ones in a wide range of applications. In this paper, we review the basic microstructural features of HEAs and discuss the mechanisms of formation. Instead of multiple intermetallic phases, the HEAs tend to form simple solid solution phases mainly of cubic crystal structure, especially at elevated temperatures. This tendency is explained by the high entropy effect based on the simple relation: (Gmix = (Hmix – T(Smix, and the second law of thermodynamics. Moreover, nanostructures and amorphous phases are easily formed in HEAs. This tendency is explained by kinetics theory as due to slow atomic diffusion.