bluuebunny/crossref_metadata_2025 huggingface dataset:
Densification Behaviour of Nano-Size CeO2
Authors: Djurović D. , Zinkevich Matvei , Bošković Snezana , Srot V. , Aldinger Fritz
Published: March 2009

A nano-sized CeO2 powder was synthesized by a modified glycine nitrate process
(MGNP). The synthesized powder was characterized by X-ray diffraction (XRD), the Brunauer
Emmett Teller (BET) method, and transmission electron microscopy (TEM). The lattice parameter
and crystallite size were determined by the Rietveld refinement of X-ray diffraction patterns. The
shrinkage kinetics of the green body was continuously monitored in air and in oxygen atmospheres
using a high temperature dilatometer up to 1500°C. During the high temperature sintering in air a
redox reaction occurred (Ce4+ was partially reduced to Ce3+, and oxygen gas was released). The
redox reaction influenced the sintering behaviour of CeO2, resulting in a decrease in density. On the
basis of shrinkage kinetics data in oxygen atmosphere a master sintering curve for CeO2 was
constructed. Using the concept of the master sintering curve, the densification behaviour in oxygen
atmosphere was successfully predicted from early to final stages of sintering. During sintering of
CeO2 at lower temperature in air atmosphere a significant contribution of the surface diffusion was
observed.
Investigation of (PO4)/(WO6)3 - Lattice Components of Keggin`s Anion Interaction with Cations in Alkaline-Earth Salts of 12-Tungstophosphoric Acid
Authors: Uskoković-Marković S. , Colomban Philippe , Mioč U.B. , Todorović M.R.
Published: March 2009

On the basis of previously recorded Raman and IR spectral data on different
crystallohydrates of alkaline-earth 12-tungstophosphoric acid salts (obtained from mother solution
and those kept under constant relative humidity (RH) of 35%), an effort was made to determine the
position of cations in the Keggin unit. Shifts or band splitting in vibrational spectra of the salts, as
well as the changes in band intensities were found to be connected to the cation properties. The
spectral data also demonstrated a great influence of cation properties on the secondary structure of
Keggin anions and dynamics of protonic species.
Dielectric and Ferroelectric Properties of BaTi1-xSnxO3 Multilayered Ceramics
Authors: Marković S. , Mitrić M. , Jovalekić Č. , Miljković M.
Published: March 2009

Multilayered BaTi1-xSnxO3 (BTS) ceramics with different Ti/Sn ratios were produced by
pressing and sintering at 1420 oC for 2 hours. X-ray diffractometry, scanning electron microscopy and
energy dispersive spectroscopy were used for structural, microstructural and elemental analysis,
respectively. The dielectric and ferroelectric behavior of sintered samples was studied, too. It is found
that in ingredient materials, with increasing Sn content, the tetragonality decreases; Curie
temperature moves towards room temperature, while the maximum of the dielectric constant
increases, and also, they becomes less hysteretic. It is noticed that multilayered BTS ceramics with
different Ti/Sn contents have a broad transition temperature and show a relatively high dielectric
constant in a wide temperature range. It is shown that dielectric properties of these materials may be
modified by a combination of different BTS powders as well as layers number.
Polystyrene-Polymethylmethacrylate Block Copolymers for Lithographically Assisted Bottom-Up Assembly of Nanostructures
Authors: Borsetto F. , Kosmala B. , Fitzgerald T.G. , Shaw Matthew T. , Patterson J. , Rapposelli P. , O´Callaghan J.M. , Holmes J.D. , Morris Michael A.
Published: March 2009

Polystyrene-polymethylmethacrylate (PS-PMMA) block copolymers are well known to
exhibit microphase separation to form a series of regular structures with local periodic arrangements
of the blocks. By developing films of PS-PMMA within topographically patterned silicon (100)
substrates (with photolithographically defined rectangular channels of depth 60 nm and widths 166
– 433 nm) these irregular arrangements form highly periodic structures where the features are
parallel to the side walls of the channels. However, the use of silicon substrates leads to problems in
processing of these films. PS-PMMA does not wet the surface, and this results in island formation
on flat substrates. On channel etched substrates this phenomena ensures that the thickness of the
films is irregular and poorly defined alignment is seen. Detailed considerations of this polymer
system suggest that feature sizes below 25 nm are not realisable. The results suggest other
copolymer systems should be studied.
Nano-Structured TiN Thin Films Deposited by Single Ion Beam Reactive Sputtering
Authors: Bogdanov Ž. , Popović N. , Zlatanović M. , Goncić B. , Rakočević Z. , Zec S.
Published: March 2009

The reactive sputter deposition of TiN thin films onto glass substrate at the ambient
temperature using a homemade broad beam argon ion source was investigated in order to deposit
the films with nanostructural characteristics. While constant Ar beam energy of 2 keV was used, the
N2 partial pressure and the substrate current, adjusted by different accelerator grid potentials (Vacc)
were varied. A negative substrate bias voltage (100 V) was additionally applied. The TiN film
structure was investigated by XRD and STM methods. All deposited films exhibited (220) preferred
orientation, and the change in normalized peak intensity (I220/d), lattice spacing (d220) and full-with
at half-maximum (FWHM) were investigated. As a result of higher energy bombardment with 100
V negative substrate bias, compared to the substrate current change with Vacc, nearly constant (220)
peak broadening with the increase of N2 partial pressure was obtained. The measured grain diameter
(STM and XRD) confirms that the grain size is less than 12 nm, and the (220) preferred orientation
was disturbed but not destructed.
Microstructural Properties of PZT Thin Films Deposited on LaNiO3-Coated Substrates
Authors: Branković Z. , Branković G. , Vojisavljević K. , Počuča M. , Srećković Tatjana , Vasiljević-Radović Dana
Published: March 2009

The modified polymeric precursor method (Pechini method) was successfully used for
the preparation of epitaxial and polycrystalline ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films.
Films were deposited on LaNiO3 (LNO) – coated silicium (1 0 0) and platinum substrates
(Pt (1 1 1)/Ti/SiO2/Si) by spin coating technique. LNO electrodes were also prepared by the Pechini
method and treated under different thermal treatment conditions to obtain films with different
structural and microstructural properties. Investigation of PZT microstructure was performed as a
function of orientation and morphology of the bottom electrode, as well as of thermal treatment
conditions. Grain size and morphology were analyzed by AFM, while the quality and orientation of
PZT films were determined by GIXRD analysis. It has been found that the proposed thermal
treatment on a hot plate, with slow heating rate and long annealing time, can result in the formation
of epitaxial PZT films on Si and LNO-coated Si substrates.
Hydrogen in Metallic Nanostructures
Authors: Andrievski R.A.
Published: March 2009

Features of hydrogen nanostructure synthesis are described as applied to metals (Mg and
Pd) and intermetallics (Mg2Ni, FeTi and LaNi5). Attention is focused on the high-energy ball
milling as a universal method for hydrogen nanostructure preparation. The effect of crystallite size,
absorption/desorption properties of Pd - H2, Mg2Ni - H2, TiFe - H2 and Mg - H2 systems are
characterized in detail. Structural features and some physical properties of nanohydrides studied by
different independent characterization methods are considered.
Photophysics of Fullerene-Doped Nanostructures: Optical Limiting, Hologram Recording and Switching of Laser Beam
Authors: Kamanina Natalie V.
Published: March 2009

The fullerene-doping effect on spectral, nonlinear optical properties, and dynamic
parameters of conjugated organic systems based on pyridine, polyimide, polyaniline, polyvinyl
alcohol, liquid crystal, etc. has been studied. Introduction of fullerenes into these materials has been
made due to their high electron affinity that allows intermolecular donor-acceptor interaction to be
reinforced. The new charge transfer complex provokes new nanostructures potentials such as
nonlinear transmission, laser-induced change in the refractive index, self-organization. The
application of studied nanostructures in laser and display techniques, and medicine has been
discussed.
Structural Characterization of Erbium doped LAS Glass Ceramic Obtained by Glass Melting Technique
Authors: Krsmanović R. , Bertoni Giovanni , Van Tendeloo Gustaaf
Published: March 2009

Samples of transparent glass-ceramics in the ternary system Li2O-Al2O3-SiO2 (LAS),
with Er2O3 as a luminescent dopant, are investigated. The initial glass is obtained by the classical
melting technique. In order to induce ceramization of the glass, TiO2 and ZrO2 are added in small
amount as nucleating agents. The thermal treatments at 730 and 770°C are carried out to promote
formation of titanium zirconate solid solution precipitates. The spatial distribution of the
precipitates in the material, their morphology, and their composition are investigated with TEM,
HRTEM, HAADF-STEM, EELS and EFTEM. The results demonstrate that with the glass-melting
preparation technique it is possible to achieve small nanoparticles with uniform distribution and
higher number density than with the sol-gel glass preparation.
Design Considerations for Nonmagnetic Semiconductor-Based Spin Filters
Authors: Radovanović J. , Milanović V. , Ikonić Z. , Indjin D.
Published: March 2009

In this paper we have analyzed the possibility of enhancing spin-polarization
performance of conventional nonmagnetic semiconductor heterostructures which rely on the
resonant tunneling mechanism. Both the bulk inversion asymmetry (BIA) and the structural
inversion asymmetry (SIA) effects are taken into account in the presented model. The aim is to
engineer nanostructures with maximal degree of spin separation in the electron tunneling current,
which might be useful in studying various spin-related phenomena in semiconductor materials.
Spin-polarization status of the current, in the devices under consideration, should be controllable by
moderate emitter-collector voltages. Additionally, the spin orbit-interactions affect the dwell times
of electrons in spin-up and spin-down states, therefore the prospects of spin-filtering in the time
domain may be considered as well.
Algal Biophysics: Euglena Gracilis Investigated by Atomic Force Microscopy
Authors: Gruenberger C. , Ritter R. , Aumayr Fritz , Stachelberger Herbert , Gebeshuber Ille C.
Published: March 2009

Matter produced by organisms is remarkable. Evolutionary optimized properties, e.g.
regarding hydrodynamic, aerodynamic, wetting and adhesive behavior, can already be found in the
“simplest” forms of organisms. Euglena gracilis, a single-celled algal species, performs tasks as
diverse as sensing the environment and reacting to it, converting and storing energy and
metabolizing nutrients, living as a plant or an animal, depending on the environmental constraints.
We developed a preparation method for atomic force microscopy investigation of dried whole
Euglena cells in air and obtained data on whole cells as well as cell parts. Our studies corroborate
TEM, SEM and optical microscopy results. Furthermore, we found new features on the pellicle, and
set the ground for AFM force spectroscopy and viscoelastic studies on the nanoscale.
A Cu2+ Probe over Nizatidine and Ranitidine, or In Silico Vs. Experimentally Obtained Complexation of Drugs
Authors: Drakulić B.J. , Sovilj S.P.
Published: March 2009

In silico model of title drugs mode of interaction with Cu2+ ion was proposed. A hundred
conformations of each drug are used in this study. Examination of drugs interactions with Cu2+ ion
were conducted using GRID package. The Cu2+ probe was used. The two favorable regions of
interactions were detected: a) the nitro group and terminal imino nitrogen in a γ position from it, as
proposed from the experimental data, b) the region of heterocyclic ring (tiazoline and furan from
Nizatidine and Ranitidine, respectively) as the most favorable one. Therefore, the present study
identifies the second region of the molecule that is able to strongly interact with the Cu2+ ion. The
position and energies of obtained molecular interaction fields (MIF) are discussed. The results
support the fact that the properties, which express recognition forces of the molecules, are strongly
dependent on 3D geometry.
Release and Diffusion Studies of Hydrogels Based on Itaconic Acid
Authors: Mićić M.M. , Tomić S.Lj. , Filipović J.M. , Suljovrujić E.
Published: March 2009

Controlled release studies of drugs (theophylline (TH), fenethylline hydrochloride (FE)
and gentamicin sulphate (GS)) from pH sensitive poly(2-hydroxyethyl methacrylate/itaconic acid)
(P(HEMA/IA)) hydrogels obtained by gamma irradiation were carried out to investigate transport
phenomena. Drug behavior and release profiles were analyzed using the restriction coefficient
combining the influence of network structure and the size of the drug on release and transport
properties. The results demonstrated that the ratio of drug radius to polymer pore size and drugpolymer
interactions were dominant factors in hindering the diffusion process. The diffusivity of a
drug through the hydrogels decreases with the size of the drug molecules and with the decrease in
gel pore size. The diffusion equations for used drugs explain drug transport in hydrogels.
Kinetics of the Formation of Poly(Methyldecylsiloxane) by Hydrosilylation of Poly(Methylhydrosiloxane) and 1-Decene
Authors: Antić V.V. , Antić M.P. , Govedarica M.N. , Dvornić P.R.
Published: March 2009

Poly(methylhydrosiloxane) [PMHS], prepared by siloxane equilibration reaction, was
used for the hydrosilylation with 1-decene to obtain poly(methyldecylsiloxane) [PMDS]. Pt(0)-1,3-
divinyltetramethyldisiloxane complex was used as a catalyst for hydrosilylation reaction. In order to
investigate the kinetics of the formation of PMDS, a series of experiments was performed at
different reaction temperatures (from 48 to 64 °C) with catalyst concentrations of 7.0 · 10-7 mol of
Pt per mol of CH=CH2. All reactions were carried out in bulk, with equimolar amounts of the
reacting Si-H and CH=CH2 groups. The course of the reactions was monitored by following the
disappearance of the Si-H bands by quantitative infrared spectroscopy. The obtained results show
that an induction period occurs at lower reaction temperatures and that the rate of Si-H conversion
follows the first-order kinetics.
Changes in Structure and Properties of Oligophenylenes under Selected External Influences
Authors: Radisavljević I. , Marjanović D. , Novaković N. , Ivanović N.
Published: March 2009

Effects induced by uniaxial compression and external electric field in P2P to P6P
oligophenylene molecules are investigated by versatile calculations. In this way some useful
relations between particular values of compression or field directions and intensities to specific
changes in molecular structure and properties have been established, enabling estimation of
possibilities for tuning the materials characteristics and their spectroscopic analyses. The results are
compared to the existing experimental data and similar calculations, and some consequences for
applications of oligophenylenes-based materials are discussed.
Phase Composition and Magnetic Properties of Multiphase Melt-Spun Nd4.3Fe76.2B19.5 Alloy
Authors: Ćosović V. , Grujić A. , Stajić-Trošić J. , Spasojević V. , Talijan N.
Published: March 2009

Phase transformations and magnetic properties of multiphase Nd4.3Fe76.2B19.5 alloy were
investigated in the temperature range of heat treatment 600-700°C. The influence of different heat
treatment regimes was observed by correlation of phase composition and measured magnetic
properties. The heat treatment regime, which provided the microstructure that improves exchange
interactions between grains of soft and hard magnetic phases and consequently enhances magnetic
properties, was defined and discussed. For optimized magnetic alloy grain size of the present phases
Fe3B, Nd2Fe14B and α-Fe was calculated by size-strain analysis of X-ray powder diffraction data.
Calculated mean grain size was on a nanoscale, below 30 nm.
Influence of Charging on SiO2 Etching Profile Evolution Etched by Fluorocarbon Plasmas
Authors: Radjenović B. , Radmilović-Radjenović M. , Petrović Z.Lj.
Published: March 2009

A comprehensive simulation of etching profile evolution requires knowledge of the
etching rates at all points of the profile surface during the etching process. Electrons do not
contribute directly to the material removal, but they are the source, together with positive ions, of
the profile charging that has many negative consequences on the final outcome of the process
especially in the case of insulating material etching. The ability to simulate feature charging was
added to the 3D level set profile evolution simulator described earlier. The ion and electron fluxes
were computed along the feature using the Monte Carlo method. The surface potential profiles and
electric field for the entire feature were generated by solving the Laplace equation using finite
elements method. Calculations were performed in the case of a simplified model of Ar+/CF4 nonequilibrium
plasma etching of SiO2.
Magnetoimpedance Effect in Fe89.8Ni1.5Si5.2B3C0.5 Metallic Glass Ribbons
Authors: Kalezić-Glišović Aleksandra , Mitrović N. , Maričić A. , Simeunović R.
Published: March 2009

The magnetoimpedance (MI) effect in magnetically soft Fe89.8Ni1.5Si5.2B3C0.5 metallic
glass ribbons is studied in this paper. As soft magnetic properties were determined by field induced
anisotropy (and therefore by magnetic domain structure), ribbon samples were annealed under
tensile stress in order to enhance induction of transverse anisotropy and to improve
magnetoimpedance effect. Stress-annealing (SA) technique up to 420 0C/475 MPa/30 min. was used
for tailoring electrical resistivity (ρ) and magnetic permeability (μ), i.e. two material properties that
in classical skin effect determine the penetration depth δm and therefore have influence on MIeffect.
The critical frequency of about 600 kHz was observed as the point with the initial increase of
MI. Significant improvement of MI-response reaching the value Z/Z ≈ 25 %, after annealing at
420 0C, was recorded at driving frequency 4 MHz. The highest MI-element sensitivity was found for
low magnetic field intensity where values of about 12 % / kA/m were attained.
The Effect of Thermo-Mechanical Processing on the Properties of some Al-Fe-Si Alloys with High Fe/Si Ratio
Authors: Delijić Kemal , Asanović V. , Radonjić Dragan
Published: March 2009

The paper deals with the effects of thermo-mechanical processing parameters on the
properties of two Al-Fe-Si foil alloys. Two twin roll cast alloys with high Fe/Si ratios (Fe/Si≈6)
were processed under different combinations of homogenization, deformation and annealing
treatments. The influence of small additions of manganese on the mechanical behavior and plastic
anisotropy of sheets in hardening and annealing conditions are described. The corrosion resistance
of tested sheets in chloride ambience is also presented, because this type of Al foils is dominantly
used in the packaging (food) industry and heat exchangers.
Structural and Magnetic Properties of the Zn-Mn-O System
Authors: Milivojević D. , Blanuša Jovan , Spasojević V. , Kusigerski V. , Babić-Stojić B.
Published: March 2009

Zn-Mn-O semiconductor crystallites with nominal manganese concentration x = 0.01,
0.02, 0.04 and 0.10 were synthesized by a solid state reaction route using oxalate precursors.
Thermal treatment procedure was carried out in air at different temperatures in the range 400 -
900°C. The samples were investigated by X-ray diffraction, magnetization measurements and
electron paramagnetic resonance. X-ray analysis reveals that dominant crystal phase in the
Zn-Mn-O system corresponds to the wurtzite structure of ZnO. Room temperature ferromagnetism
is observed in the Zn-Mn-O samples with lower manganese concentration, x ≤ 0.04, thermally
treated at low temperature (500°C). Saturation magnetization in the sample with x = 0.01 is found
to be 0.05 μB/Mn. The ferromagnetic phase seems to be developed by Zn diffusion into Mn-oxide
grains.
Comparison between Schottky Diodes with Oxide Ramp Termination on Silicon Carbide and Diamond
Authors: Brezeanu Gheorghe , Brezeanu M. , Udrea F. , Amaratunga G. , Boianceanu C. , Badila M. , Zekentes Konstantinos , Visoreanu Adi
Published: March 2009

A classical implementation of the field plate technique is the oxide ramp termination. This paper presents for the first time a comparison between SiC and diamond Schottky barrier diodes (SBD) using this termination. The influences of the ramp angle and oxide thickness on the diodes electrical performance are investigated for both punch-through (PT) and non punch-through (nPT) structures. The efficiency of the termination is also evaluated.
Recrystallization and Mechanical Properties of Hot Rolled Seamless Steel Tubes
Authors: Kvačkaj Tibor , Zemko Michal
Published: March 2009

The article deals with FEM analysis, with mathematical modeling of structure evolution
and with prediction of mechanical properties during hot rolling of seamless steel tubes. With use of
DEFORM 3D software the present state of stretch-reducing mill of Železiarne Podbrezová, Inc was
described. The next part of article presents mathematical model describing the tube production for
low carbon steels grade St52 on analyzed calibration sequence. Values of temperature, strain and
strain rate from FEM simulation were substituted into the mathematical models of recrystallization,
grain growth, transformation and prediction of mechanical properties. The calculated values were
compared with experimental ones resulting from mechanical tests of industry rolled tubes of various
chemical compositions. Good correlation of structural and mechanical properties was achieved for
all chemical compositions and treatment conditions.
Three Dimensional Monte Carlo Simulation of Isotropic Coarsening of Particles in Liquid Phase
Authors: Lee Suk Bin , Rollett Anthony D.
Published: March 2009

Coarsening of particles during liquid phase sintering is known to be an example of Ostwald ripening. This coarsening process, in a fully wetting system, is simulated in three dimensions with a kinetic Monte Carlo model. The results from the simulation for microstructures, kinetics and particle size distributions are compared to available experimental findings. It is found that the average particle volume increases linearly with time and that the particle size distributions are consistent with those obtained experimentally, as in the W-Ni-Fe and Sn-Pb systems.
A New Approach to Model Heterogonous Recrystallization Kinetics Based on the Natural Inhomogeneity of Deformation
Authors: Luo Hai Wen , An Lian Zi , Ni Hong Wei
Published: March 2009

The classical JMAK equation was modified by combination with distribution density of the rate parameter k, which was deduced from a normal distribution of local strain. The modified equation is able to calculate the JMAK plots and the average Avrami exponent to characterize the entire heterogeneous recrystallization process. This new extension can successfully describe the relevant experimental observations, such as a smaller exponent than the basic JMAK theory predicts, and a decreasing slope of JMAK plots with the proceeding recrystallization. Moreover, it reveals that the Avrami exponent observed experimentally should significantly decrease with the increasing standard deviation of local strain distribution. In addition, it has a great potential to explain why most of experimentally observed values of Avrami exponents are less than 2 and why the Avrami exponent is insensitive to temperature and deformation conditions when the real standard deviation of local strain distribution in deformed metals is known.
Modeling the Evolution of Orientation Distribution Functions during Grain Growth of some Ti and Zr Alloys
Authors: Sawina Grzegorz , Gerspach Francois , Bozzolo Nathalie , Sztwiertnia Krzystof , Rollett Anthony D. , Wagner Francis
Published: March 2009

A 2D cellular automaton model developed for the simulation of grain growth in hexagonal metals is presented here. It allows the direct use of experimental measurement as input data. Texture evolution of a titanium alloy and a zirconium alloy are simulated on the basis of simple hypothesis and compared with experimental evolution as well as the results from a 3D Monte Carlo model. Results from both models are discussed with regards to their characteristics.
Modeling Recrystallization for 3D Multi-Pass Forming Processes
Authors: Teodorescu Mihaela , Lasne Patrice , Logé Roland E.
Published: March 2009

The present work concerns the simulation of metallurgical evolutions in 3D multi-pass
forming processes. In this context, the analyzed problem is twofold. One point refers to the
management of the microstructure evolution during each pass or each inter-pass period and the
other point concerns the management of the multi-pass aspects (different grain categories, data
structure). In this framework, a model is developed and deals with both aspects. The model
considers the microstructure as a composite made of a given (discretized) number of phases which
have their own specific properties. The grain size distribution and the recrystallized volume fraction
distribution of the different phases evolve continuously during a pass or inter-pass period. With this
approach it is possible to deal with the heterogeneity of the microstructure and its evolution in
multi-pass conditions. Both dynamic and static recrystallization phenomena are taken into account,
with typical Avrami-type equations. The present model is implemented in the Finite Element code
FORGE2005®. 3D numerical simulation results for a multi-pass process are presented.
Lattice Relaxation in Ni-P Amorphous Alloy Accompanied with Growth of Ni3P Nanocrystals
Authors: Tanaka Shunichiro , Takioto Jun , Kwon Sang Koo , Shinoda Kozo , Suzuki Shigeru
Published: March 2009

Studies on lattice change of a nickel-phosphorus amorphous alloy were carried out using
not only high temperature X-ray diffraction but also extended X-ray absorption fine structure
(EXAFS) analysis. Their thermal properties were characterized by differential scanning calorimetry
(DSC). Since the results suggested that lattice relaxation occurred in the amorphous state by
annealing, EXAFS measurements were carefully performed for characterizing the local structure of
the amorphous alloys. The EXAFS analysis showed that the local structures around Ni atoms,
which may be the Ni-Ni and Ni-P correlation, were changed by annealing. High temperature X-ray
diffraction showed that small amount of crystal phase appeared by annealing up to 820 K, while
clear diffraction peaks of Ni3P were observed above 1100 K. These micro/nanoscale structural
changes did not correspond to that obtained by DSC which showed an exothermic reaction of
atomistic reordering at 630 K. We need analysis of the nanostructures by small angle X-ray
scattering or a high resolution transmission electron microscope.
Effect of Initial Texture on the Deformed Microstructure of IF Steel
Authors: Kang Jun Yun , Bacroix Brigitte , Oh Kyu Hwan , Lee Hu Chul
Published: March 2009

The development of deformation texture and microstructure was examined for four different initial textures. IF steel sheets with a majority of α-, ε-, and γ-fiber and near random texture were prepared and cold rolled. The specimens exhibited characteristic behaviors in rolling texture evolution and deformation-induced misorientation development, according to their initial textures, especially at small strain levels. Due to the orientation dependence of intra-granular misorientation accumulation, the different texture evolutions affected the induced misorientation distribution. A larger fraction of γ-fiber orientations was related to more prominent misorientation development, while the initial texture stability simultaneously affected the misorientation development. The unstable, initial ε-fiber texture showed a stronger tendency of misorientation accumulation than the stable α-fiber during the subsequent cold rolling.
The Effect of Dislocations in Grains on Texture Formation in Strain Induced Boundary Migration
Authors: Murakami Kenichi , Kubota T. , Grégori Fabienne , Bacroix Brigitte
Published: March 2009

In order to elucidate the predominance of Goss grains after SIBM in electrical steel sheets, Goss, D-Cube and {111}<112> grains after temper rolling of 5 and 9% reduction were observed by TEM. In 5% strain the amount of dislocations in Goss grains was the smallest of the three orientations. In 9% strain dislocations in Goss grains were distributed more heterogeneously than the other two types of grains. It is considered that {111}<112> grains have large amounts of dislocations owing to high Taylor factors and the differences of microstructures between Goss and D-Cube grains are due to orientation stabilities. Goss grains are speculated to be easy to recover and therefore they are predominant after SIBM.
Nucleation of Recrystallization in Cu-8%at. Al Alloy Studied by Orientation Mapping in TEM
Authors: Paul Henryk , Morawiec Adam , Bouzy Emmanuel , Darrieulat M.
Published: March 2009

The nucleation of new grains during annealing in high purity single crystals of Cu-8%wt. Al alloy with initial (112)[111] orientation has been characterized by detailed transmission electron microscopy (TEM) orientation measurements. The samples were channel-die deformed and then recrystallized to form a substructure composed of a mixture of deformation twins, shear bands (SBs) and the recrystallized grains. Substantial progress in understanding the mechanism of texture transformations at the early stages of recrystallization was possible thanks to orientation mapping using TEM. Microtexture analysis of partly recrystallized samples indicates a simple 25-40o (<111> or <112>) relation, most frequently observed during the early stages of recrystallization between single nuclei and one of the two as-deformed groups of components (twins or matrix). As recrystallization proceeds, recrystallization twinning develops strongly and facilitates rapid growth of the recrystallized phase. The first and higher generations of twins systematically tend to obscure the initial crystallographic relation between the deformed state and the recrystallization nuclei.
In Situ EBSP Analysis of Grain Boundary Migration during Recrystallization in Pure Aluminum Foils
Authors: Takata Naoki , Ikeda Kenichi , Nakashima Hideharu , Tsuji Nobuhiro
Published: March 2009

Grain boundary mobility in preferential growth of cube grains ({100}<001>) was evaluated by in-situ electron back scattering diffraction pattern (EBSP) analysis in order to clarify the fundamental mechanism of primary recrystallization in pure aluminum foils of 99.9% purity thermo-mechanically processed in the industrial production route for aluminum foils for electrolytic capacitors. We have carried out the continuous EBSP measurements during recrystallization of the aluminum foils heated to various temperatures in the chamber of scanning electron microscopy (SEM). We have succeeded in dynamic observation of the preferential growth of cube grains by the in-situ EBSP analysis. The in-situ EBSP analysis could reveal the migration rate of grain boundaries surrounding the cube grains. It was clarified that the proportional relation between migration rate and annealing time was satisfied. The stored energy providing the driving force for the grain boundary migration during primary recrystallization could be estimated from the misorientation within the deformed grains. The mobility of the grain boundary could be evaluated using the measured grain boundary migration rate and stored energy. Then the activation energy could be estimated by the in-situ EBSP analysis at various temperatures ranging from 270°C to 310°C. The obtained activation energy was 124 kJ/mol, which approximately corresponded to that for the diffusion of impurity such as iron or silicon in aluminum. This suggested that the rate-determining process of the grain boundary migration of cube grains was impurity diffusion in the pure aluminum foils.
Effect of Initial Lamellar Structure on Globularization of Hot Multi-Forged ELI Grade Ti-6Al-4V Alloy
Authors: Kim Jin Young , Shim In Ok , Hong Soon Hyung
Published: March 2009

The effect of initial lamellar structure of β heat treated Ti-6Al-4V alloy on the globularization behavior during the multi-step forging was investigated. Specimens of different lamellar thicknesses were upsetted and stretched by side pressing repeatedly, i.e. multi-step forging, at the sub-transus temperature to break down the lamellar structure. The microstructural changes after multi-step forging were analyzed in the light of globularization behavior. The results showed that the thick lamellar structure was more difficult to be transformed to homogeneous equiaxed structure than thin lamellar structure.
Microstructural Evolution in a Commercial Al-Mg-Sc Alloy during ECAP at 300°C
Authors: Sitdikov Oleg , Sakai Taku , Avtokratova Elena , Kaibyshev Rustam , Tsuzaki Kaneaki , Watanabe Yoshimi
Published: March 2009

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy at a temperature of 300oC (~0.6Tm). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. ECAP at moderate-to-high strains leads to the formation of a bimodal grain structure with grain sizes of around 1 and 8 μm and volume fractions of 0.3 and 0.6, respectively. The development of new-grained regions has been shown to result from a concurrent operation of continuous dynamic recrystallization that occurs during deformation and static recrystallization that occurs during each ECAP cycle by the exposure of the as-deformed material in the die kept at 300oC for around 1.5 minutes. The microstructural development during warm-to-hot ECAP is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to the localization of plastic flow and inhibition of recovery in the present alloy.
Effect of Carbon Addition on Ultrafine Grained Microstructure Formation by Warm Compression for Fe-18Ni Alloys
Authors: Xu Ping Guang , Li J.H. , Tomota Yo , Adachi Yoshitaka
Published: March 2009

The warm-compression microstructures of two nickel-containing tempered martensite steels with and without carbon were investigated. The EBSD measurement and TEM observation/Kikuchi pattern analysis confirm that the ultrafine microstructures contain ferriteaustenite dual phases with more than 18% austenite. The difference in the austenite amount before and after warm compression proves that the dynamic austenite precipitation occurs during warm deformation and the carbon addition is beneficial to the austenite precipitation. It is also found that the ultrafine austenite grains as a hard phase promote the dynamic recrystallization of ferrite during warm deformation.
Ferrite Grain Refinement during Hot Rolling of Seamless Tubes
Authors: Barbosa Ronaldo , Santos Dagoberto Brandão , Ferreira Marcelo A.C. , Nolasco R.N.
Published: March 2009

Hot rolling of seamless tubes is performed in two stages: one at high temperature, ie,
above 1000oC and a second part at low temperature range, namely below 900oC. Above 1000oC,
dynamic, metadynamic and static recrystallization may happen leading to full softening and grain
refinement. Below 900oC, however, some pancaking may occur and ferrite is thus refined during
transformation. Nonetheless, in order to refine ferrite grains further, cooling to room temperature
and re-austenitization at an intermediate reheating furnace can be a viable alternative to be
explored. The present paper examines the implications of re-austenitization followed by phase
transformation plus low temperature deformation on ferrite grain refinement. Phase transformation
on re-heating and cooling as well as recrystallization play important roles in the process of ferrite
grain refinement. These mechanisms are analyzed and discussed. Results indicate that ferrite grain
refinement is most effective in the case of processing using a re-austenitization cycle in the
intermediate furnace followed by rapid cooling after deformation in the stretch reducing mill.
The Effects of Hot Band Annealing Temperature on the Texture of 1% an 2%Si Nonoriented Electrical Steels
Authors: Choi Jae Young , Park Jong Tae , Bae Byung Keun , Kim Jae Kwan
Published: March 2009

The effects of hot band annealing temperature on the texture of the 1% and 2%Si nonoriented electrical steel were investigated. Slab was hot rolled and then hot band annealed in the temperature range of 900°C~1100°C. The magnetic flux density and the core loss were improved by the hot band annealing because of the texture improvement. As the hot band annealing temperature was increased, the magnetic properties were improved. The microstructure of the hot band was composed of a recrystallized structure at the surface and a deformed structure near the middle plane. These hot bands were completely recrystallized after annealing above 1000°C. The main texture of the hot band was rotated cube and gamma-fibre. After hot band annealing, rotated cube changed to cube texture and gamma-fibre intensity gradually decreased. In the case of specimen without hot band annealing, rotated cube in the middle plane was changed to near {111}<112>texture and Goss texture in the surface to gamma fibre after final annealing. In the case of the hot band annealed at 900°C, Goss texture and cube texture were developed. After final annealing, the {111} and {112} texture was dramatically decreased as the hot band annealing temperature was increased. Although the total {100} texture intensity was not changed, Cube texture, {100}<001>, was strengthened and rotated cube texture, {100}<011>, weakened for 2% Si steel. However, 1% Si steel was opposed to 2% Si steel. The {110} texture was strengthened irrespective of hot band annealing temperature. As the hot band annealing temperature was increased, the Goss texture was strengthened, and this makes the anisotropy of the magnetic flux density bigger.
Influence of Localized Primary Recrystallization Texture on Secondary Recrystallized Grains in Fe-3%Si
Authors: Morishige N. , Murakami Kenichi , Homma Hotaka
Published: March 2009

The local-area analyses of the primary recrystallization sheets were carried out in
Fe-3%Si to explain the reason why only Goss appears during the secondary recrystallization. It was
found in the present study that Goss grains have the higher Σ9 frequency in their nearest neighbors
than {311}<011> grains, both of which were attached to the neighbors having the texture with high
Σ9 frequency to the texture of the matrix. Another analysis showed that Σ1 and Σ3 frequencies were
higher around {311}<011> grains than around Goss. It is concluded that Goss grains possess the
satisfactory criteria to be the secondary recrystallization nuclei from the following viewpoints of
high Σ9 frequency and low Σ1 and Σ3 frequencies.
Misorientation Aspects of Growth during Recrystallization
Authors: Juul Jensen Dorte , Rowenhorst David J. , Schmidt Søren
Published: March 2009

Effects of the crystallographic misorientation across boundaries between recrystallising grains and the neighbouring deformed matrices are discussed and exemplified by recrystallisation investigations of fcc metals. Classic misorientation observations are reviewed in the introduction, whereas the main parts of the paper focuses on two special boundary migration phenomena observed by in-situ recrystallisation experiments; namely protrusions and facets.
Mechanically Driven Migration of <100> Tilt Grain Boundaries in Al-Bicrystals
Authors: Molodov Dmitri A. , Gorkaya Tatiana , Gottstein Günter
Published: March 2009

The stress induced migration of planar grain boundaries in aluminium bicrystals was
measured. Symmetrical <100> tilt grain boundaries with misorientation angles in the range between
5.7° and 17.8° were examined. Boundary migration under a shear stress was observed to be ideally
coupled to the lateral translation of grains. The measured ratios of the normal boundary motion to
the lateral displacement of grains are in an excellent agreement with the respective boundary geometry.
The temperature dependence of grain boundary mobility was measured, and the corresponding
activation parameters were determined. The activation enthalpy of boundary migration was
found to be independent of misorientation angle in the investigated misorientation range and
amounts to H=1.44 eV.
Faceting of Σ3 Grain Boundaries in Al
Authors: Protasova Svetlana , Kogtenkova Olga A. , Straumal Boris B.
Published: March 2009

The temperature dependence of the energy of various facets of twin GBs has been measured. For the investigation of GB faceting the Al bicrystals of 99.999% wt. purity were grown by the modified Bridgman technique. One grain in these bicrystals is semi-surrounded by another one. Bicrystals were coated with a layer of Sn–Al alloy and annealed at various temperatures. Contact angles at the junction of a GB and two solid/liquid interfaces have been measured. The ratios of GB energy to solid/liquid interface energy have been calculated. Using these data, the Wulff-Herring plots and GB phase diagrams were constructed. Three different crystallographic facets were observed for the coincidence GB. Two of them are stable at all studied temperatures, the third one becomes metastable below ~ 800K. In GBs with θ = 3° only one facet (symmetric twin GB) is stable.
Atomic-Scale Processes of Grain-Boundary Faceting in a Zirconia Bicrystal
Authors: Shibata Naoya , Oba Fumiyasu , Yamamoto Takahisa , Ikuhara Yuichi
Published: March 2009

In this paper, we characterized atomic structure of a Σ = 3, [110]/{112} grain boundary in a yttria-stabilized cubic zirconia bicrystal. High-resolution transmission electron microscopy (HRTEM) clearly revealed that the grain boundary migrated to form {111}/{115} periodical facets, although the bicrystal was initially joined so as to have the symmetric straight boundary plane of {112}. Atomic-scale process for the facet growth could be modeled by the continuous flippings of atoms at the boundary core.
Synthesis of Si3N4 from Na2SiF6 as a Solid Precursor: Microstructural Evolution
Authors: Leal-Cruz Ana Lilia , Pech-Canul Martin I.
Published: March 2009

The effect of processing parameters on the weight loss of the silicon solid precursor
(Na2SiF6) and the deposition characteristics and morphology of Si3N4 formed onto SiCp/Si porous
substrates by CVD has been investigated. The results show that the weight loss of Na2SiF6 is most
significantly affected by the processing temperature, followed by the processing time and the type
of nitrogen precursor. Formation of Si3N4 is mostly influenced by the substrate temperature,
followed by the type of nitrogen precursor and processing time. An increase in processing time and
temperature from 60 to 120 min and from 900 to 1300 oC, respectively, favors dissociation of
Na2SiF6 and formation of Si3N4. Moreover, N2 enhances Na2SiF6 dissociation and hampers Si3N4
formation, while the N2-NH3 mixture hinders the solid precursor dissociation and favors Si3N4
formation. With regard to microstructure evolution, it is found that in N2 the amount of Si3N4
increases with temperature and the morphology changes from wool-like and light fibers to thicker
and compact fibers. When N2-NH3 is used and the processing temperature is increased, the
morphology of Si3N4 is modified from deposits with wool-like and compact appearance to whiskers
and spheres and finally to thick and compact fibers.
Study on Susceptibility of Hydrogen Embrittlement in a Tool Steel
Authors: Wang X.T. , Siwecki Tadeusz
Published: March 2009

Susceptibility of hydrogen embrittlement of a super grade AISI 420 tool steel was studied.
Tensile samples were cathodically charged to different hydrogen level. Hydrogen induced mechanical
property degradation was measured by tensile tests at a low strain rate. Fractography of broken
surfaces was observed using SEM. Relationship between hydrogen content and tensile strength and
elongation were studied. Critical hydrogen contents were obtained for different heat treatment states.
It was found that for annealed materials could stand for a 3.5ppm hydrogen for keeping 80% of
original ductility, and the effect of hydrogen on strength was unobvious. However, for material
quenched and tempered at 250°C, only 0.3ppm hydrogen could lead the ductility drop to 80% of
original. The material quenched and tempered at 500°C was more sensitive on hydrogen, less than
1ppm hydrogen could lead the strength drop to 80% of original.
Rheological Transitions at Low Solid Fraction in Solidifying Magnesium Alloy AZ91
Authors: Gourlay Christopher M. , Meylan B. , Dahle Arne K.
Published: March 2009

Transitions in the mechanical behaviour of solidifying alloys influence feeding mechanisms and
defect formation during many casting processes. This paper explores dendrite coherency and the
cracking transition during the equiaxed dendritic solidification of Mg alloy AZ91 using the
continuous-torque technique and vane rheometry. The two techniques yielded similar dendrite
coherency values of ~17% solid, and the cracking transition occurred at 40% solid in vane
rheometry tests. These transition values are similar to those reported for Al alloys with equiaxed
dendritic morphology and a similar grain size.
High Speed Deformation of Ultrafine Grained TWIP Steel
Authors: Ueji Rintaro , Harada Kenji , Tsuchida Noriyuki , Kunishige Kazutoshi
Published: March 2009

Tensile properties of twinning induced plasticity (TWIP) steels (31%Mn-3%Al-3%Si-Fe)
with various mean grain sizes ranging from ultrafine grain size (1.1μm) to conventional one (35.5μm)
at a wide range of strain rates from 10-3sec-1 to 103sec-1 were studied. The ultrafine grained TWIP
steel exhibits a large work hardening and keeps an adequate elongation at any strain rate. The strength
held to the Hall-Petch relationship at each strain rate and the Hall-Petch slopes do not change largely.
Spray Forming of Al-Fe-Cr-Ti and Al-Si-Li Alloys
Authors: Banjongprasert Chaiyasit , Hogg S.C. , Palmer I.G. , Grennan-Heaven N. , Stone I.C. , Grant Patrick S.
Published: March 2009

This work presents an investigation of the spray forming and downstream processing of
Al alloys that are difficult to produce in bulk by conventional solidification processing: Al-Fe-Cr-Ti
alloys for intermediate temperature applications and Al-Si-Li alloys for high stiffness, low density
applications in fast moving machinery. For the Al-Fe-Cr-Ti alloys, spray forming is being
investigated to allow the scale-up of alloy compositions previously explored only as ribbons or
powders in traditional rapid solidification routes. For Al-Si-Li alloys, spray forming is used to
provide globular primary AlLiSi in a fully divorced AlLiSi/α-Al eutectic structure. For both alloys,
the as spray formed and downstream processed microstructure of 20kg billets has been investigated
by scanning electron microscopy, electron probe microanalysis, and X-ray diffractometry.
Preliminary mechanical properties have also been investigated.
Enhancement of Magnetocaloric Effects in Single Phase La1-zNdz(Fe0.88S 0.12)13
Authors: Fujieda S. , Fujita A. , Fukamichi Kazuaki
Published: March 2009

The single phase of a cubic NaZn13-type La1-zNdz(Fe0.88Si0.12)13 is obtained in the region
z ≤ 0.2. The field-induced first-order transition from the paramagnetic to ferromagnetic state, that
is, the itinerant-electron metamagnetic (IEM) transition is kept after the substitution of Nd. In
addition, a discontinuous change of magnetization at the Cure temperature becomes larger with
increasing z. As a result, the isothermal magnetic entropy change and the relative cooling power
in the magnetic field change from 0 to 5 T increase to –27 J/kg K and 518 J/kg, respectively, by the
partial substitution of z = 0.2.