bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Secondary Phases on Hydroxyapatite Powders for Bone Regeneration: Effect of Water Source
Authors: Lourenço Vera , Dias Susana , Nogueira Carlos A. , Oliveira Fernando A. Costa
Published: March 2009

This study focus on the synthesis of Ca-deficient apatites (CDA) by using the wet
chemical precipitation method in demineralised water solutions at pH=7 and synthesis temperature
of 90 °C. Upon calcination at 1000°C, the resulting HAP powders decomposed leading to the
formation of small amounts of β-TCP. Surprisingly, under some conditions, minor amounts of α-
TCP were also formed at 1000°C together with β-TCP. The appearance of α-TCP is favoured by the
absence of mineral ions in the precipitation medium, which in turn depends on the purity of the
water used. Factors affecting the formation of both β-TCP and α-TCP are discussed.
Metallic Powders Amorphization by Mechanical Alloying and Subsequent Electrical Sintering
Authors: Urban Petr , Cuevas Francicso Gomez , Martos Juan Manuel Montes , Gallardo José M.
Published: March 2009

Al-base and Fe-base powders have been amorphized by a high energy milling process in
an Attritor miller. Microstructural evolution in powder particles has been analyzed by XRD, DSC,
SEM and TEM. The conventional route of cold pressing and sintering applied to these powders
does not result adequate to preserve their amorphous or nanometric character. An additional
disadvantage of this route appears during the cold pressing stage, as a consequence of the
insufficient green strength of the compacts, due to the high hardness of the milled powders. In order
to avoid these difficulties a new consolidation technique, electrical resistance sintering (ERS), has
been successfully employed. ERS consolidated compacts have been microstructurally characterized
by optical microscopy and XRD, showing that compacts preserve their amorphous and/or
nanometric character.
Intermetallic Effects on the Ductility of Sintered Aluminium
Authors: Cintas Físico Jesus , Rodríguez José A. , Cuevas Francicso Gomez , Gallardo José M.
Published: March 2009

Mechanically alloyed aluminium powder was prepared by attrition-milling for 10 hours
in the presence of a wax. Milled powders were annealed in vacuum at different temperatures (500,
575, 600, 625 and 650°C). Compacts were consolidated starting from unannealed and from 600°Cannealed
powders. Studies by SEM microfractography and quantitative metallography, to
investigate the influence of Fe-Al intermetallics on compacts fracture, have been carried out. It is
concluded that fracture takes place at regions where the area occupied by the intermetallics is high
and intermetallics particles are big. Intermetallic particle size can be controlled by an appropriated
heat treatment.
Effect of Gravity/ Vibration/ Centrifugal Process on Mechanical Properties of an Al-Si Alloy
Authors: Chirita G. , Stefanescu I. , Soares Delfim , Silva F.S.
Published: March 2009

On this paper, a study that evaluates the influence of some variables on the mechanical
properties of the vertical centrifugal casting is made. It is emphasized the fact that the centrifugal
effect from vertical centrifugal casting brings special features on mechanical properties. It has been
observed that the centrifugal effect may substantially increase, in some alloys, the rupture strength,
rupture strain, and Young modulus, as compared to the gravity casting technique. When compared
to gravity casting, the centrifugal casting process, besides the centrifugal force (pressure effect),
always has an inherent associated vibration during the casting. In this study, as an attempt to isolate
the vibration effect from the overall centrifugal effect, tests on castings obtained by vibrating
gravity casting process are made. A comparison between castings obtained by centrifugal casting
technique, vibrating casting technique and gravity casting technique is made in order to fully
understand the features that allow the improvement on mechanical properties during the vertical
centrifugal casting technique. An analysis of the most important effects, on both mechanical
properties and on some metallurgical features is made.
KrF Excimer Laser Ablation of Human Enamel
Authors: Sivakumar M. , Oliveira Vitor , Vilar Rui , Botelho do Rego A.M.
Published: March 2009

Laser treatment is a promising technique for dental applications such as caries prevention,
dental hypersensitivity reduction and improvement of bond strength of restoration materials. In this
study the morphological, structural and chemical changes of enamel surface due to treatment with
KrF excimer laser radiation were evaluated using scanning electron microscopy, X-ray diffraction,
and X-ray photoelectron spectroscopy. For radiation fluences near 1 J/cm², laser processing
originates a relatively porous surface due to preferential removal of material in the enamel prism
sheaths. Increasing the fluence leads to a relatively flat surface with clear evidence of surface
melting. The X-ray diffractograms of both treated and untreated enamel are similar and correspond
to hydroxyapatite. The only modification due to the laser treatment is a slight shift of the peaks,
probably, due to a loss of the structural water of hydroxyapatite. X-ray photoelectron spectroscopy
confirmed that organic matter is removed from the irradiated surface but no significant changes in
the mineral phase occur.
Strain Path Change Effect on Deformation Behaviour of Materials with Low-to-Moderate Stacking Fault Energy
Authors: Sakharova Nataliya A. , Vieira Milena M. , Fernandes José Valdemar , Vieira Manuel F.
Published: March 2009

Stacking fault energy (SFE) plays an important role in face centred cubic (f.c.c.) metals
and alloys in determining the prevailing mechanisms of plastic deformation. Low SFE metals and
alloys have a tendency to develop mechanical twinning, besides dislocation slip, during plastic
deformations. Deformation behaviour and microstructure evolution under simple and complex
strain paths were studied in 70/30 brass, with small and intermediate grain sizes, which corresponds
to a f.c.c. material with low SFE. Simple (rolling and tension) and complex (tension normal to
previous rolling) strain paths were performed. The macroscopic deformation behaviour of materials
studied is discussed in terms of equivalent true stress vs. equivalent true strain responses and strain
hardening rates normalized by shear modulus (dσ/dε)/G as vs. (σ – σ0)/G (σ0 is the initial yield
stress of the material and G is the shear modulus). The mechanical behaviour is discussed with
respect to dislocation and twin microstructure evolution developed in both, simple and complex
strain paths.
Bulk Copper-Nanodiamond Nanocomposites; Processing and Properties
Authors: Correia Jose Brito , Livramento Vanessa , Shohoji Nobumitsu , Tresso Elena , Yamamoto Kazunori , Taguchi Tomitsugu , Hanada Kotaro , Osawa Eiji
Published: March 2009

Copper has widespread use as engineering material, because of its structural and
functional properties, notably high thermal and electrical conductivity. A major drawback of this
base metal and its alloys is a relatively low hardness. This precludes its utilization in applications in
which both high conductivity and high strength/hardness are needed, e.g. in injection moulds for
plastics. Nanostructured metals and nanocomposites are ways to address the low hardness problem,
provided the nanostructured material is thermally stable during processing and service. In the
present research, composite powders, with 5 to 30 at % nanodiamond, were consolidated into bulk
samples. The copper-nanodiamond composite powders were vacuum encapsulated and extruded at
600°C. A significant proportion of the initial hardness in the powders is retained after extrusion.
Transmission electron microscopy (TEM) of the extruded material indicates good bonding between
the nanodiamond particles and the copper matrix. Raman spectroscopy on the consolidated samples
evidences the presence of graphite, possibly due to partial disintegration of ultradisperse
nanodiamond agglomerates.
Iron and Chromium Removal from Binary Solutions of Fe(III)/Cr(III) and Fe(III)/Cr(VI) by Biosorbents Supported on Zeolites
Authors: Silva B. , Figueiredo Hugo , Quintelas Cristina , Neves I.C. , Tavares T.
Published: March 2009

The removal of metallic ions from binary aqueous solutions of Fe(III)/Cr(III) and
Fe(III)/Cr(VI) by an Arthrobacter viscosus biofilm supported on NaY zeolite was investigated.
Experiments were repeated with suspended biomass for comparison purposes. Batch assays were
performed using different concentrations (10, 25 and 40 mg/L), for both metals in solution. Results
indicated that Arthrobacter viscosus is able to retain the metallic ions, although not totally. The
removal efficiencies were improved when the biofilm was supported on the zeolite, for all the initial
concentrations of Cr(III), for the intermediate and higher concentration of Cr(VI) and for all range
of initial concentrations of Fe(III), in the presence of Cr(III). The bacteria reduce Cr(VI) to Cr(III)
and, only then, this cation may be entrapped in the framework zeolite by ion exchange. Suspended
bacteria had higher affinity for Fe(III), than for Cr(VI) or Cr(III), while the conjugated system was
selective to Fe(III) when in the presence of Cr(VI). For solutions of Fe(III)/Cr(III), very high
removals were achieved by the supported system, ranging from 94 to 100 % for Cr(III) and from 98
to 100 % for Fe(III). The conjugated system also reached the highest removal ratio of Cr(VI), 36 %,
for the initial concentration of 40 mg/L. The materials in study were characterized by techniques
such as FTIR, SEM and chemical analyses.
Changes in Particle Size and Crystallinity in Ground Nickel Powder
Authors: González J.M. , Rodríguez José A. , Herrera Enrique J.
Published: March 2009

Nickel powder was dry-milled using a high-energy disc-oscillating mill. The average
particle size increases and the specific surface area diminishes with milling time. Crystallite size
decreases and microstrains increase, under the same conditions, as shown by X-ray analysis. At
120 min milling time, the crystallite size has a value of 17 nm, i.e., a nanostructured powder, with a
perturbed lattice, is obtained. The above results have been compared with published data about the
effects of milling on a ceramic powder. There is, in both cases, a general agreement concerning the
changes produced in crystallite size. Nevertheless, opposite results are reached regarding particle
size and specific surface area.
Approach to Fabricate CuO Nanoparticles from Low Cost Raw Materials
Authors: Baharvandi H.R. , Abdizadeh Hossein , Ehsani N. , Tadjrishi M.M. Mir Mohammad Ali , Nami H.
Published: March 2009

Nanostructured CuO powders have been synthesized using chemical methods in the
current study. Ammonium oxalate and copper nitrate were used as the precursor materials. The
weight ratios of the raw materials (ammonium oxalate/copper nitrate) were 1.1, 1.2, 1.3, and 1.4. As
a result of chemical reaction (between them), copper oxalate was synthesized. Produced samples
were analyzed by XRD and SEM. The results show that the best ratio (for ammonium
oxalate/copper nitrate) is 1.2. Produced copper oxalate powder was heated at 600, 700 and 800oC.
The final product was CuO nanopowder. XRD studies indicate that the highest ratio of Cu2O to
CuO was observed in the specimen heated at 700oC.
Production of Calcium Phosphate Particles from Marine Wastes by Gas Jet Assisted Laser Heating
Authors: Lusquiños F. , Boutinguiza M. , Comesaña R. , Riveiro A. , Quintero F. , Pou Juan
Published: March 2009

There are many manufacturing techniques to form metallic particles with certain size and
properties. The laser heating method has been successfully applied to generate metallic particles
when a supersonic gas flow is assisting this process. The metallic target is heated, melted and
vaporised and micro-particles are carried away by a gas flow stream. The high-velocity gas is used
to solidificate molten particles and to condensate the metallic vapour resulting in the formation of
fine particles. Several attempts were carried out for the production of metallic particles by laser
supersonic heating method, obtaining spherical micro-particles (1- 50 "m) of copper, steel, or
aluminium. This work presents the application of this method to generate particles from fish bone,
in order to obtain a material with a composition close to the inorganic part of the bones. A pulsed
Nd:YAG laser has been used to obtain calcium phosphate micro- and nanoparticles. Microparticles
size ranges from 10 to 100"m, whereas the nanoparticles have diameters as small as 2 nm. High
resolution transmission electron microscopy (HRTEM) allowed us to identify the nanoparticles as
whitlockite.
Acrylic Adhesives in the Polyolefins Joining
Authors: Pinto A.M.G. , Magalhães A.G. , Gomes da Silva F. , Baptista A.P.M.
Published: March 2009

The mechanical behaviour of single lap adhesive joints was characterized, using two
commercial acrylic adhesives. For this purpose the surfaces were cleaned and abraded using fine
grit abrasives. The effect of temperature and moisture in the mechanical strength was, also,
evaluated. For this characterization, mechanical tests were carried out according procedure and
geometry foreseen by ASTM D3163-01 [1] and ASTM D4501-01 [2] standards. The results show
that it is possible to get good strengths without great surface preparation. The temperature and
moisture effect observed don’t seem to be relevant for the mechanical behaviour.
Synthesis of Urea-Nitryle-Urethanes with Aid of Microwaves
Authors: Ryszkowska Joanna , Wasniewski Bartlomiej
Published: March 2009

Polymerisation of urea-nitryle-urethanes performed in electric heating devices. It was
suggested to manufacture these materials using microwave radiation as the heat source. As a part of
this research project urea urethanes were fabricated using various strength of microwave radiation.
The structure and properties of manufactured materials were investigated.
Mechanical Behaviour of Ausformed and Marformed Ti-Rich Ni-Ti Shape Memory Alloys
Authors: Paula Andersan S. , Mahesh Karimbi Koosappa , Santos C.M.L. , Braz Fernandes Francisco Manuel , Viana C.S.C.
Published: March 2009

Shape memory effect (SME) in Nickel-Titanium (Ni-Ti) alloys is ascribed to the
thermoelastic reversible martensite phase transformation. Phase transformation is established to be
affected by the pre- thermal and mechanical history of the alloy. The present work deals with the
effect of mechanical working, known as ‘marforming’ and ‘ausforming’, on the phase
transformation characteristics and mechanical behaviour of Ti-rich Ni-Ti alloy. Tensile study and
measurement of the hardness data were carried out at room temperature. Mere heat treatment or
heat treatment at 773 K after the marforming shows similar characteristics, whereas, the as-received
and the ausformed samples exhibit different behaviours. Hardness numbers of the heat treated
samples are found to be smaller than those of the as-received and mechanically worked samples.
Development of Co-Ni-Ga Ferromagnetic Shape Memory Alloys with Enhanced Properties
Authors: Sarma Sidananda , Srinivasan A.
Published: March 2009

Polycrystalline ingots of Co70-xNixGa30 (22 ≤ x ≤ 25) alloys were prepared by a sequence
of arc melting high purity Co, Ni and Ga in argon atmosphere, followed by homogenization at
1150°C under a pressure of 10-3 Pa, and quenching in ice water. Structural characterisation of the
quenched alloys was carried out to verify the presence of the martensite phase at room temperature.
The martensite start (Ms), martensite finish (Mf), austenite start (As) and austenite finish (Af)
temperatures for the alloys were determined using a differential scanning calorimeter. The
ferromagnetic to paramagnetic phase transition temperature (TC) of the alloys was determined using
an indigenously developed ac susceptometer. All the alloys are FSMAs with Ms, Af and TC above
room temperature. The composition dependence of the properties of these alloys could be
understood on the basis of the e/a (electrons to atom) ratio and the Co/Ni ratio. Presence of γ-phase
precipitates along with the β-phase in these alloys enhances the ductility as well as influences the
physical properties of these alloys.
Novel Bioadhesives for Restorative Dentistry
Authors: Pereira S.G. , Telo J.P. , Osorio R. , Toledano M. , Nunes Teresa G.
Published: March 2009

The objective of this study was to develop new adhesive formulations based on 2,2-bis[4-(2-
methacryloxyprop-1-oxy) phenyl] propane (CH3-BisGMA) aiming to obtain high double bond conversion
(DC) even in the presence of radical scavengers and monomers with acidic groups. NMR, EPR spectroscopy
and spatially-resolved 1H Stray-Field MRI observations enabled to study the influence of the composition
in DC, free radical concentration, reactivity of the monomers and volumetric contraction.
In vitro Formation of Apatites and other Biologically Related Calcium Phosphates: Influence of Temperature and pH on the Nature of the Mineral Phases
Authors: Leite Ferreira B.J.M. , Magalhães M.C.F. , Correia Rui N.
Published: March 2009

We investigated the in vitro formation of apatites and other biologically relevant calcium
phosphates, in particular the influence of temperature and pH in the nature of the mineral phases.
With this purpose several calcium phosphates were synthesized under controlled conditions, in
presence of atmospheric CO2. The results obtained suggest that both factors under study,
temperature and pH, have major influence in the nature of the mineral phases obtained.
β-PVDF Membranes Induce Cellular Proliferation and Differentiation in Static and Dynamic Conditions
Authors: Rodrigues M.T. , Gomes Manuela E. , Mano João F. , Reis Rui L.
Published: March 2009

Bone marrow cells are a potential source to induce different lineage cells which can be
used to rebuild or replace damaged tissues using a Tissue Engineering (TE) approach. However, TE
strategies usually require the use of a material to support the development of a biological tissue.
Beta-polyvinylidene fluoride (β-PVDF) is a biocompatible, thermoplastic with piezo-electrical
properties that has been shown to provide a good cellular attachment and therefore might present
advantageous properties as a scaffold material for cell seeding/culturing. The present study
describes the characterization of β-PVDF membranes as a support material for growth and
differentiation of goat marrow cells (GMCs) into osteoblasts, leading to the formation of substitutes
for tissue regeneration.
The obtained results suggest that β-PVDF piezoelectric properties influence cellular behavior. β-
PVDF membranes not only enhance GMCs adherence and proliferation but also improve
differentiation towards the osteogenic phenotype both in static and dynamic culture conditions.
Furthermore, β-PVDF membranes exhibit very promising properties, suggesting that this material
provides adequate support for the seeding and the development of undifferentiated cells towards a
desired phenotype.
Mineralization of Chitosan Membrane Using a Double Diffusion System for Bone Related Applications
Authors: Gomes Silvia , Boulon Marie Emmanuelle , Oliveira A.L. , Leonor Isabel B. , Mano João F. , Reis Rui L.
Published: March 2009

Chitosan membranes were subjected to a pre-treatment in a double diffusion system, with
a calcium solution in one chamber and a phosphate solution in the other chamber. Both chambers
were separated by the chitosan membrane and subject to three mineralization periods (5, 10 and 15
minutes). After this pre-treatment the bioactivity of the different calcium phosphate coatings formed
was tested for different periods of immersion time, 7, 14 and 21 days at room temperature and 37°C,
in acellular simulated body fluid (1.0x). The results obtained demonstrated that the calcium
phosphate coatings formed during the pre-treatment process are bioactive. It was found that the
calcification is effective just in the side of the membrane exposed to the calcium solution chamber.
This enabled to develop membranes with asymmetric osteoinductive properties that can be useful in
different orthopedic applications.
Pre-Tensioned Geogrids Reinforced Soil Structures with Face Panels in Fiber Glass
Authors: Mendonça Agostinho , Lopes M. Lurdes
Published: March 2009

This paper presents an innovative technology for soil reinforced structures. The
technology is based on the use of pre-tensioned geogrids reinforcements and face panels reinforced
with fiber glass. Main technology advantages are: i) the very light face with great variety of
geometries, size, color and surface textures; ii) either the face and the reinforcements are corrosion
free; iii) the good behavior under seismic actions; iv) reduction of structure horizontal strains due to
the pre-tension. First, the state of art on reinforced soil structures is done and then the constituents
of the new technology are presented followed by the reference to the main theoretical principles
considered in its conception. Secondly, numerical data from the behavior, in static conditions, of
geogrid reinforced soil structures with and without pre-tensioned reinforcements are presented. In
the numerical study the FLAC program, based on the differences finites method, will be used. The
construction of the structures will be modeled considering the sequential placement of soil layers
and reinforcements, enhancing the deformation behavior of the structures. Thirdly, the advantages
of the new technology against the traditional ones are quantified, based on the results of the
numerical studies. Special relevance will be given to face horizontal deformations and
reinforcements strains. Finally, the main conclusions about the new technology will be put forward
and its main advantages towards traditional technologies will be listed. Application fields where the
technology is competitiveness will be identified.
Procedural Aspects of the Wedge Splitting Method to Measure the Fracture Energy of Ceramic Materials
Authors: Ribeiro S. , Vieira J.S.C. , Exposito C.C.D. , Rodrigues J.A.
Published: March 2009

To study the fracture energy of materials, the stable crack propagation must be observed
during the test. To this end, an appropriate method, particularly in the case of large samples, is the
wedge splitting method. By this method, the test machine stores less elastic energy, facilitating
stable propagation. The materials tested in this study were mortars with sand:cement ratios of 2:1
and 3:1. Two types of samples were prepared: one with a notch and grooves produced with a
diamond disk and the other with notch and grooves produced directly during molding of the mortar.
The crack moved easily along an imaginary vertical plane defined by the grooves. The methodology
proved sensitive to the material’s microstructure, modified here by varying its formulation. High
sensitivity was also found in relation to the shape of the tip of the notch, whether V-shaped or
square. In the material studied here, the values of fracture energy varied from 23 to 56 J.m-2.
Mechanosynthesis of La0.95Sr0.05Ga0.90Mg0.10O3-δ
Authors: Gonçalves Priscila , Figueiredo Filipe M.
Published: March 2009

The production of La0.95Sr0.05Ga0.90Mg0.10O3-δ powders was achieved at room temperature
by a mechanosynthesis route in a high energy planetary ball mill starting from a mixture of
lanthanum, strontium, gallium and magnesium oxides. The milling was carried out in nylon
containers, using zirconia balls and a balls:powder mass ratio of 10:1. The planetary rotation was
kept constant at 650 rotations per minute (rpm), and the container at 1300 rpm, in the opposite
direction. The formation of the perovskite phase was detected from the early milling stages and
nearly completed after milling for 360 min, as shown by powder X-ray diffraction. Transmission
electron microscopy results revealed that powders consist of agglomerates of homogeneous,
crystalline particles with an average equivalent diameter of about 16-17 nm, in excellent agreement
with average crystallite size estimates obtained from X-ray diffraction.
Welding Technologies for Repairing Plastic Injection Moulds
Authors: Silva B. , Pires I. , Quintino L.
Published: March 2009

The aim of the present paper is to investigate the metallurgical behaviour of AISI P20
tool steel frequently used in injection moulds, after welding. For this purpose Tig and Laser welding
tests were conducted to determine the influence of the welding parameters, materials and preheating.
The welding quality was assessed through the microstructural properties and microhardness
evolution. The results achieved with the different processes were compared. This work allows to
obtain a deeper knowledge concerning tool steels behaviour after welding.
Microstructural Changes due to Secondary Precipitation Hardening of Martensitic Creep Resistant Steel X20CrMoWV 12 1 (AISI 422)
Authors: Elarbi Y. , Palotás Béla
Published: March 2009

After development of the well-known T/P91 steel grade in the early 80’s and its long
industrial experience since early 90’s, it has been necessary to develop new martensitic creep
resistant steels to answer the demand of the power generation industry. New USC (ultra-super
critical) boilers require materials with advanced creep properties to reach severe steam parameters.
Addition of W to the steel has been found by many researches to be effective to increase creep
rupture strength at high temperatures and already used in some developed steel grades such as
T/P92, T/P122 and AISI 422 for the USC boilers. Recently, long-term creep strength of the
advanced high Cr ferritic steels has been argued regarding the instability of their microstructures at
high temperatures over 600 °C. This microstructural instability seems to be enhanced with
increasing Cr content or with substitution of Mo by W in the steels. The aim of this paper is
concentrated on the investigation of the microstructural development of the studied steel using the
Jominy end-face quench test. Different hardness profiles from this test were introduced.
Tribological Behaviour of C-Derived Si3N4 Nanocomposites
Authors: Koncsik Zsuzsanna , Maros Maria Berkes , Kuzsella László
Published: March 2009

The main topic of the current work consists in analysing the tribological behaviour of
graphite reinforced Si3N4 nanocomposites. The basic aim was to investigate the influence of
microstructural features, i.e. amount and grain size of the added reinforcing graphite, as well as the
effect of applied load on the wearing characteristics like wearing profile, wear rate, friction
coefficient or mechanism of the wear damage process. Tribological tests were performed on a pinon-
disc tribometer with on-line measurement of friction coefficient and the wear profile. Wear tests
were completed with traditional micro-hardness and instrumented hardness tests, furthermore
fractographical analyses of the wear tracks using scanning electron microscopy.
Perspective on the Development of III-Nitrides for Optical Emitters
Authors: Monemar Bo
Published: March 2009

This chapter serves as an introduction to the chapters on III-nitrides in this book. It gives
a brief review of the development of relevant III-nitride materials for light emitters since the late
1960´s, when single crystalline GaN layers grown on sapphire were first demonstrated. The first
wave of scientific work died out in the late 1970´s, since low-ohmic p-GaN could not be made at
the time. After another 10 years several important breakthroughs were made, using the technology
of metal organic vapor phase epitaxy (MOVPE). Smooth thin epilayers could be made, and ways to
dope the materials n-type as well as p-type were invented. In the period 1986-1997 high brightness
violet and blue double heterostructure (DH) LEDs, narrow quantum well (QW) LEDs, and QW
based violet laser diodes with a long operating lifetime of 10000 hours were demonstrated, mainly
by Japanese groups. Since then the development efforts have spread worldwide, and a large
spectrum of novel applications based on nitride emitters are already in practical use. Perhaps the
most important one is the future possibility of using nitride LEDs for general lighting purposes.
AlN and AlGaN by MOVPE for UV Light Emitting Devices
Authors: Amano Hiroshi , Imura Masataka , Iwaya Motoaki , Kamiyama Satoshi , Akasaki Isamu
Published: March 2009

The fundamental growth issues of AlN and AlGaN on sapphire and SiC using metalorganic vapor phase epitaxy, particularly the growth of AlN and AlGaN on a groove-patterned template are reviewed. In addition, the conductivity control of AlGaN is shown. The conductivity control of p-type AlGaN, particularly the realization of a high hole concentration, is essential for realizing high-efficiency UV and DUV LEDs and LDs.
Assessment and Modification of Recombination Dynamics in InxGa1-xN-Based Quantum Wells
Authors: Kawakami Yoichi , Kaneta Akio , Funato Mitsuru
Published: March 2009

Nanoscopic optical characterization using scanning near-field optical microscopy was
performed on both InxGa1-xN/GaN single quantum wells (SQWs) grown on polar (0001) orientation
and a semipolar (1122) microfacet SQW fabricated by a re-growth technique. The
photoluminescence intensity of a conventional (0001) SQW emitting in the blue was completely
independent of the threading dislocations (TDs) due to the small diffusion length less than 100 nm. In
contrast, the photoluminescence intensity was well correlated with the TDs in the sample emitting in
the green due to the association of In-rich clusters with dislocations, and the effect was enhanced by
the larger diffusion length contribution from the longer radiative recombination lifetime. It was found
that in a (1122) SQW, the suppression of the piezoelectric field leads to orders-of-magnitude faster
radiative lifetime and consequently, a shorter diffusion length. In addition, the highest internal
quantum efficiency was approximately 50% at 520 nm, which is about 50 nm longer than in (0001)
QWs, suggesting that (1122) QWs are suitable for green emitters.
Mechanical Activation of Nb75Al Powder Mixtures with Different Process Control Agents
Authors: Gonçalves Valéria S. , da Rocha Cláudio José , Neto Ricardo Mendes Leal
Published: March 2009

The behavior of different process control agents (PCAs) during mechanical activation of
Nb75Al powder mixtures was investigated. Mechanical activation by high-energy ball milling was
carried out on a shaker mill (SPEX®8000) for 1 hour. Each PCA (Stearic acid, ethanol and
methanol) was added to the powder charge in two proportions (1 and 2 wt%). Shape and
microstructure of activated powders (aggregates) were analyzed by scanning electron microscopy.
Milled powder mixtures were uniaxially pressed in cylindrical compacts that were further vacuum
reacted at a constant heating rate (30°C/min) in order to produce NbAl3 intermetallic compound.
The temperature of the samples was monitored by an S-type thermocouple. The results show that
the shape and the microstructure of the milled powders were strongly affected by the type and
quantity of PCAs, therefore changing the reaction behavior and the densification of the produced
pellets. Although ethanol was more effective to control aggregate size, best densification results
were attained with 2 wt% of stearic acid.
Corrosion Resistance and Cytotoxicity Study of 17-4PH Steels Produced by Conventional Metallurgy and Powder Injection Molding
Authors: Costa Isolda , Rogero Sizue Ota , Saiki Mitiko , Marques Rogério Albuquerque , Rogero José Roberto
Published: March 2009

The corrosion resistance of 17-4PH stainless steel obtained by powder injection
molding (PIM) was investigated in a phosphate buffer solution (PBS) that simulates
physiological solution and compared with that of 17-4PH steel obtained by conventional
metallurgy. The corrosion resistance was investigated by electrochemical techniques for
different immersion times. The cytotoxicity of both types of 17-4PH steel was also
investigated using a minimum Eagle’s medium (MEM). The MEM solution is a type of cell
culture medium, which simulates physiological fluids. The cytotoxicity assay was carried out
by neutral red uptake methodology utilizing NCTC L929 cell line from ATCC bank and none
of the steels showed cytotoxic effects. The resulting extracts obtained by immersion of the
steel samples in MEM were analyzed by neutron activation analysis and the results indicated
liberation of chromium and cobalt as corrosion products but in very low amounts. The
electrochemical evaluation of both steels indicated that they are passive in PBS but presented
susceptibility to pitting. The 17-4PH PIM steel was slightly more susceptible to pitting than
that fabricated by conventional metallurgy due to its inherent porosity.
Study of the Debinding Rate on MIM Parts Using Plasma Assisted Debinding
Authors: da Silveira W. , Wendhausen Paulo A.P. , Klein Aloísio Nelmo
Published: March 2009

Binders based on mixtures of polymers and waxes are suitable both for solvent
combined with thermal extraction, as well as for pure thermal debinding. The recently developed
plasma-assisted debinding and sintering (PADS) process has been targeted, for historical reasons,
on a wax-polymer system, appropriated for solvent combined with thermal extraction processes.
This paper shows experimental results related to the debinding rate of parts produced by metal
powder injection molding using the recently developed Plasma Assisted Debinding process.
Influence of temperature and the ratio of cathodic area on the mass loss were studied.
Troubleshooting and Preventive Maintenance of Furnace Atmospheres
Authors: Corrêa Silva Gian Ricardo
Published: March 2009

Protetive atmospheres are used in powder metallurgy to prevent oxidation and to reduce
oxides, to control carbon contents of iron and iron alloys, and to flush volatilized lubrificants from
the furnace. Another important function of the atmosphere during sintering is to burn and remove
the hydrocarbon lubrificants used to compact the powdered metal. However, one of the most
important services that the Air Products "industrial gas company" can provide to its heat treat
customers is assistance in troubleshooting their furnace(s) when there are problems.
To be able to troubleshoot a furnace, it is important to know what the typical problems are that
arise, what causes them and how to fix or minimize to problem.
This work should aid in finding the source of the problem with analysis equipment, and, by using
your knowledge of the furnace and the process, solve the problem.
Summarizing, (1) ensure system integrity, (2) Know the required safety interlocks, and (3) Verify
their operation.
Effect of the Temperature in the Antimicrobial Action of the Bactericide Wood Polymer Composite - BWPC
Authors: Fiori M.A. , da Silva Paula Marcos Marques , Angioletto Elidio , Santos M.F. , Riella Humberto Gracher , Quadri M.G.N.
Published: March 2009

These work present studies about influence of the high temperature at the antimicrobial
properties of the Bactericide Wood Polymer Composites (BWPC) after exposition during different
times at 110 oC. The composite was formulated containing Polypropylene (PP) as matrix polymeric,
wood powder of the species Pinus and Triclosan additive as bactericide agent. The BWPC was
exposited during different times in the ambient and submitted to microbiological tests. The Agar
Diffusion tests were applied with two kind bacteria, the Echerichia coli (EC - Gram Positive) and
Staphylococcus aureos (SA - Gram Negative). The FT-IR and TGA techniques were utilized to
available of the temperature effect in the chemical structure of the composites BWPC. The studies
showed a strong dependence of the bactericide action of the composites with exposition time at 110
oC and a constant bactericide action after 100 hours of exposition.
Transport of Solids through Rotary Dryers with Flights of Two and Three Segments
Authors: Arruda E.B. , Façanha J.M.F. , Pires L.N. , Assis A.J. , Barrozo Marcos A.S.
Published: March 2009

Rotary dryers are commonly used to dry particulate in a range of food and mineral
processing industries. The purpose of this work was to study the design and performance of a rotary
dryer. It was evaluated the number of flights and operational conditions that corresponding to the
optimal performance for the equipment. A set of equations to predict the solids holdup in flights
with three and two segments was also evaluated. Their predictions were compared to measurements
performed with a pilot plant rotary dryer. The equation generated very accurate estimations.
Study of ZrO2-TiO2 Ceramics with SnO2, SrO2 and Nb2O5 Additives for Dielectric Resonator Application
Authors: Souza José Vitor C. , Castro Pedro José , Nono Maria do Carmo de Andrade , Siqueira A.R.
Published: March 2009

This paper presents a systematic study about ceramics made of zirconium oxide and
titanium oxide (ZrO2-TiO2) doped with tin oxide (SnO2), strontium oxide (SrO2) and niobium oxide
(Nb2O5). These ceramics can be applied as dielectric resonators in microwave systems for
telecommunications. For a good microwave performance, these ceramics must reach some
parameter values as high dielectric constant and high quality factor due to the dielectric losses. The
ceramics were manufactured using suitable powder mixtures of ZrO2-TiO2 with additions of 1 % of
SnO2, SrO2 and Nb2O5, resulting in four different kinds of samples for analysis. The samples were
compacted by an uniaxial (190 MPa) and an isostatic (300 MPa) pressing, sintered at 1200 °C for 3
hours, characterized in the chemical compound formation using X-ray Diffraction (XRD) and
scanned for microstructure densification degree and grain distribution analysis in Scanning Electron
Microscopy (SEM). The dielectric parameters were measured using a microwave system. The main
goal of present procedure is manufacture ceramic materials for promising application as dielectric
resonators.
Portland Cement Polyurethane Composites for Cementing Oilwell
Authors: Nascimento José Heriberto O. , Martinelli Antonio Eduardo , Melo D.M.A. , Nóbrega A.C.V. , Martinelli D.M.H. , Pinto Erica N.M.G.
Published: March 2009

The presence of fissures in the cement material of an oil well due to thermo-mechanic
conditions caused by steam injection and acidizing operations, tends to commit the mechanical
integrity of the annular space, resulting in the environmental contamination of the phreatic sheets
and oil producing zones. However, the development of new materials for oil wells cementing has
lead to several researches to achieve the optimization of this process. This work proposes the
formulation of portland/polyurethane nonionic composites as a new material for oil wells
cementing. The results prove the ability of the formulated composite to improve the mechanical
properties when compared with portland/water cement slurry. Also, were obtained significant
improvements in mass losses when acids were present.
High Density Ba2AlWO5.5 Ceramic Compacts Produced through Liquid Phase Sintering Route for Temperature Sensores
Authors: Yadava Yogendra Prasad , Ferreira Ricardo Arthur Sanguinetti
Published: March 2009

Structural and functional characteristics of ceramic components highly depend on their
microstructure and mechanical properties. In the production of such ceramics sintering plays
extremely important role. Recently, we are working on the development and fabrication of
temperature sensors for the petroleum wells. In this connection, we have developed a new alumina
based ordered complex cubic peroviskite oxide ceramic Ba2AlWO5.5. During our study, we found
that Ba2AlWO5.5ceramics compacts could not be densified by normal sintering route. To overcome
this hurdle, we have utilized the liquid phase sintering process, using CuO additives. By addition of
1 to 2 wt% CuO, we succeeded to sinter this ceramic in the temperature range 1200 to 14000 C.
Sintered Ba2AlWO5.5 ceramics were examined by X-diffraction and scanning electron microscopy
to verify the presence of any extra phase due to CuO addition in the Ba2AlWO5.5 matrix. Our
studies revealed that CuO addition did not affect the structural characteristics, but considerably
modified the densification process, microstrutural characteristics and consequently mechanical
properties of the Ba2AlWO5.5 ceramics.
Turning of Compacted Graphite Iron Using Commercial TiN Coated Si3N4 under Dry Machining Conditions
Authors: Souza José Vitor C. , Nono Maria do Carmo de Andrade , Ribeiro M.V. , Silva Olivério Moreira Macedo , Lanna M.A.
Published: March 2009

Due to their high hardness and wear resistance Si3N4 based ceramics are one of the most
suitable cutting tool materials for machining hardened materials. Therefore, their high degree of
brittleness usually leads to inconsistent results and sudden catastrophic failures. Improvement of the
functional properties these tools and reduction of the ecological threats may be accomplished by
employing the technology of putting down hard coatings on tools in the state-of-the-art PVD
processes, mostly by improvement of the tribological contact conditions in the cutting zone and by
eliminating the cutting fluids. However in this paper was used a Si3N4 based cutting tool
commercial with a layer TiN coating. In this investigation, the performance of TiN coating was
assessed on turning used to machine an automotive grade compacted graphite iron. As part of the
study were used to characterise the performance of cutting tool, flank wear, temperature and
roughness. The results showed that the layer TiN coating failed to dry compacted graphite iron
under aggressive machining conditions. However, using the measurement of flank wear technique,
the average tool life of was increased by Vc=160 m/min.The latter was also observed using a
toolmakers microscope and scanning electron microscopy (SEM).
Using Flow Properties to Solve Flow Problems with Hard-to-Handle Powders in the Ceramics Industry
Authors: Purutyan Herman , del Campo Alfredo , Barnum Roger A.
Published: March 2009

Many processes in ceramic manufacturing require handling of fine powders with particle
sizes down to sub-micron range. Problems that are often experienced with these powders, such as
stoppages and/or surges, can be predicted and prevented by first measuring relevant flow properties
of these powders, and then using these properties to design a handling system. In this paper we will
review common problems with handling such powders and the relevant flow properties tests, such
as permeability, compressibility, cohesive strength and friction, as well as how these properties can
be used to prevent and solve problems. Issues related to handling titanium dioxide (TiO2) will be
used as an illustration.
Sintering of Commercial Leucite-Based Dental Porcelains
Authors: Fredericci Cátia , Yoshimura H.N. , Molisani André Luiz , Bellinati C.E. , Alcântara R.Q.E. , Cesar Paulo Francisco
Published: March 2009

The aim of this work was to study the effect of temperature and heating rate on the
densification of two leucite-based dental porcelains: one low-fusion and one high-fusion
commercial leucite porcelains (Dentsply-Ceramco). Porcelain powders were characterized by
differential thermal analysis (DTA), X-ray diffraction (XRD), particle size distribution, and helium
picnometry. Bar samples were sintered from 650 to 1050oC, using heating rate of 55oC and
10oC/min. Sintered samples were characterized in terms of bulk density, measured by the
Archimedes method in water, and fractured surface microstructure by scanning electron microscopy
(SEM). The results show that densification increases with increasing temperature and the increase in
heating rate has no effect on the densification of the porcelains studied.
Ni/α-Al2O3 Catalysts Modified with ZnO and Fe2O3 for Steam Reforming of the Natural Gas
Authors: Neiva Laédna Souto , Gama Lucianna , de Freitas Normanda Lino , Andrade Heloysa Martins Carvalho , Mascarenhas Artur Jose S. , de Melo Costa Ana Cristina Figueiredo
Published: March 2009

This work has as objective the synthesis for the method by combustion reaction of
catalytic supports of α-Al2O3 modified with ZnO and Fe2O3 with and without impregnation of the
species it activates (Ni) and your structural and morphologic characterization. The catalytic supports
were obtained by method of the synthesis da combustion reaction. The catalytic supports were
characterized by XRD, adsorption of nitrogen by BET method and infrared. The results of XRD
showed the formation of powders with high cristalinity, characteristic picks of difraction of the
phase α-Al2O3 indicating that there was the partial substitution of the ions of Al3+ for Zn2+ and Fe3+
in the hexagonal net of the alumina. The impregnation of the nickel promoted an increasing in the
size of the particles, this carried to reduction of the superficial area of the same, of the volume and
of the diameter of the pores of the structure of the material. Were accomplished catalytics tests in
row of seats scale. The result of catalytic tests showed that the developed catalysts in this work were
efficient in the methane conversion process.
Morphological and Structural Analysis of Alfa-Al2O3 Modified with Zr Prepared by Combustion Reaction
Authors: Ramalho M.A.F. , de Freitas Normanda Lino , de Melo Costa Ana Cristina Figueiredo , Lira Hélio Lucena , Andrade Heloysa Martins Carvalho , Gama Lucianna
Published: March 2009

The addition of zirconia to alumina can improve the chemical properties, mechanical
stability, acidity and surface area of alumina. The aim of this work is to evaluate the influence of
0.005 moles of zirconia addition to the structure and morphology of alumina powders by
combustion reaction. The compositions were called AP (alpha-Al2O3) and AZ (Zr0.005Al1.995O3) and
were prepared by using a silica container with direct heating on a hot plate at 480oC until selfignition.
The powders were characterized by X-ray diffraction and nitrogen adsorption by BET
analysis. The composition AZ showed high surface area (47 m2/g) and small crystallite size (60
nm). The alpha-alumina AP showed a wide agglomerates distribution with small agglomerates size
when compared with AZ composition.
Obtained of Diamond Nanometric Powders Using High Energy Milling for the Production of Alumina-Diamond Nanocomposites
Authors: Silva K.L. , Bernardi L.O. , Yokoyama Makoto , Trombini Vania , Cairo Carlos Alberto Alves , Pallone Elíria Maria Jesus Agnolon
Published: March 2009

The addition of nanometric particles of a second phase into ceramics matrix is one of the
most recent alternatives in the development of materials with high mechanical properties and wear
resistance. These nanostructured materials can be defined as systems that have at least one
microstructural characteristic of nanometric dimensions (less 100nm). In this work aluminadiamond
nanocomposites were produced using diamond nanometric powders obtained by high
energy milling. Diamond powder was produced in the SPEX shaker/mill during 6h, with a ball-tomass
ratio of 4:1. The crystallite size was 30nm. After the elimination of the Fe deriving of the
contamination during the milling, and desaglomeration, this nanometric powder was added in the
alumina matrix in the ratio of 5wt%. The powder densification was performed by hot pressing
sintering. The obtained nanocomposites were characterized by X-ray diffraction (XRD), scanning
electron microscopy (SEM) and microhardness, and they have promising characteristics regarding
abrasion and wear resistance.
The Coercivity Mechanisms in Sm(CoFeCuZr)z Nanocrystalline Magnets: Nucleation x Pinning
Authors: de Campos Marcos Flavio
Published: March 2009

It is discussed the difference between the magnetic reversal mechanisms: i) coherent
rotation, ii) nucleation, iii) unpinning of domain walls. The main argument to suggest pinning as the
coercivity mechanism of Sm(CoFeCuZr)z magnets is the low initial susceptibility of magnetization
curves of thermally demagnetized magnets. However, coherent rotation also implies in low initial
susceptibility, since the grain size of the magnets is near the single domain particle size. It is
unlikely that pinning could be the coercivity mechanism in this case, since the anisotropy field of
Sm2Co17 phase is 65 kOe, whereas the coercivity of magnets can be higher than 40 kOe. Such
coercive field of 60% of the anisotropy field indicates coherent rotation as mechanism. A model for
describing the abnormal coercivity behavior in Sm(CoFeCuZr)z magnets is proposed.