bluuebunny/crossref_metadata_2025 huggingface dataset:
A CAD Idea of Braided Composite and Establishment of Its Relation Model
Authors: Jiao Zong Xia , Wang Xiao Dong , Huang Guo Ping
Published: March 2009

A CAD/CAM idea with its relation model including the analyses of braid process, yarns internal geometry and mechanical properties is proposed. An infrastructure of CAD/CAM system with platform and criterions which endure expandability is introduced. Based on the platform, some subsystems are built to accomplish various tasks such as 3D modeling, finite element analysis and braided process simulation. In order to implement the platform, parameter transferring is analyzed and an example is given. Based on the braiding process of composite, the axis direction stiffness/flexibility matrix, cell stiffness and engineering constants is acquired by the analysis of yarns and cell. At last, a proper and feasible collaborative environment and the tasks assignment is proposed. Based on the platform, an analysis instance is finished and the results are exhibited.
Development of Pressure Technique of Brake Nanofluids from an Arc Spray Nanoparticles Synthesis System
Authors: Kao Mu Jung , Lo Chih Hung , Tsung Tsing Tshih , Lin Hong Ming
Published: March 2009

The low-pressure control methods for an arc-submerged nanoparicle synthesis system (ASNSS) was proposed and developed for brake nanofluids. In the process, a copper bar is melted and vaporized in insulating liquid for core formation with crystallization suppressed to derive nanofluid that contains nanometer copper particles in DOT3 brake fluid. Two technical advances associated with nanoparticle synthesis were achieved. One is the novel pressure control technique developed for nanoparticle fabrication. The other is the verification that the constant low-operating pressure. Pressure operating plays important role in determining the characteristics of the prepared nanoparticles in brake fluids. From the experimental processes, pressure control of the ASNSS was identified as crucial to success of nanoparticles synthesis. To achieve the desired pressure control, a vacuum chamber was developed as a nanoparticle accumulator and low-pressure reservoir. The chamber was controlled by the proposed flow –valve feedback control system and integrated with the ASNSS. The pressure control equipment of the ASNSS was effectively developed to prepare desired copper-oxide brake nanofluids with well-controlled size.
Effect of Travelling Magnetic Field on the Directional Solidification of Refined Al-3.5 wt%Ni Alloys
Authors: Zaïdat K. , Ouled-Khachroum T. , Mangelinck-Noël Nathalie , Reinhart Guillaume , Dupouy M.D. , Moreau R.
Published: March 2009

The specific objective of the paper is to investigate the effect of fluid flow on the development of a dendritic microstructure and more particularly on the columnar and equiaxed solidification regimes. A gradient furnace (BATMAF) with a possibility of applying a travelling magnetic field was designed for the solidification of aluminium-based alloys. The travelling magnetic field (TMF) drives a forced flow in the liquid above the solidifying interface. Some experiments are achieved in this furnace on an Al-Ni3.5wt% refined alloy. As a result, a significant change of the microstructure due to the transversal melt flow is observed. This work is performed in the framework of the CETSOL/MICAST Microgravity Application Projects of the European Space Agency (ESA).
Microsegregation in Steels during Dendritic Columnar Growth and Peritectic Reaction Part I: Experimental Investigation of Fe-Ni-C Alloys
Authors: Addad A. , Bourgraff C. , Combeau H. , Lesoult Gérard
Published: March 2009

The aim of this study is to investigate the effect of the chemical composition, the nature of the primary solidification and peritectic reaction on microsegregation in cast steels. For this purpose, binary and ternary alloys in the Fe-Ni-C system have been selected. This study was carried out in parallel with a modelling work [1] in order to improve the prediction of macrosegregation of cast steels products.
Segregation Profiles in Diffusion Soldered Ni/Al/Ni Interconnections
Authors: Wołczyński Waldemar , Kloch J. , Janczak-Rusch Jolanta , Kurzydlowski Krzysztof Jan , Okane T.
Published: March 2009

An Al foil of 25 µm thickness was used to produce a Ni/Al/Ni interconnection under
isothermal conditions at 680°C. After dissolution of the Al filler metal in the Ni substrate, and Ni from the substrate in the Al liquid foil, a solidification process occurred. First of all, the solidification was stopped just at the disappearance of the Al liquid metal, but also at different steps of the progress of solidification. Sub-layers of the two phases Al3Ni2 and Al3Ni were revealed within the frozen joints. A solidification - segregation model was developed to describe the formation of the sub-layers of both mentioned phases. The model is able to predict solute segregation profiles across the sub-layers of the Ni/Al/Ni interconnection, taking into account a superposition of some phenomena like partitioning, back-diffusion into the solid and peritectic reactions. The value of the diffusion coefficient into the solid for the Al3Ni2 phase formation in the presence of the liquid is also estimated.
Solidification of Co-Cu Alloys in the Metastable Miscibility Gap under Low Gravity Conditions
Authors: Kolbe Matthias , Gao J.R. , Reutzel S.
Published: March 2009

Liquid Cu-Co shows a metastable miscibility gap where the homogeneous melt separates into the Co-rich L1-liquid and the Cu-rich L2-liquid. The required undercooling of the melt of > 120 K can be achieved by containerless methods as electromagnetic levitation, laser melting or drop tube processing. Due to the large undercooling, rapid solidification of the melt is favoured and preserves microstructure features of the metastable (liquid) phases. In Co-84.0 at% Cu alloy the L1- phase nucleates in the Cu-rich majority phase L2 as a dispersion of spherical droplets. Convective flow in the liquid influences largely the time evolution and the nature of the droplet dispersion and makes a theoretical description of the droplet growth extremely difficult. In the present work droplet dispersions are compared which formed under processing methods with different levels of convection: (i) (Terrestrial) electromagnetic levitation (EML), (ii) processing in the TEMPUS facility under parabolic flight conditions and (iii) processing in an 8 m drop tube. The distributions of droplet radii of the L1-phase has been measured in the solidified samples. EML processing leads to significant convection in the melt which causes coagulation of droplets. Reduced gravity conditions in the TEMPUS facility during parabolic flight or in a drop tube can decrease convection, but effects of the convective flow on the dispersion of droplets are still present. The need for experiments under micro-gravity conditions is evident from the results.
Simulation of High Pressure Die Casting Solidification
Authors: Molnár Dániel , Dúl Jenő , Szabó Richárd
Published: March 2009

By the help of simulation software it is possible to follow and predict the high pressure die casting process. In the Department of Foundry Engineering at the University of Miskolc, Hungary we use both Finite Element- and Finite Difference programs for simulation. In this paper we examine a special specimen, a plate with knobs, witch has point symmetric hot spots and cored parts which
effect the characteristic of flow and solidification. We examined the solidification process and the temperature distribution. We determined that the
finite element method, because of the meshing and the calculation mode, is more suitable for the simulation of thermal processes.
Free Surface Flow Control and Electromagnetically-Driven Stirring by a Double-Permanent-Magnet-Driver
Authors: Wang Xiao Dong , Fautrelle Yves , Dupouy M.D. , Li Ting Jie , Jin J.Z.
Published: March 2009

This paper presents a method aimed at controlling free surface flow and stirring melt via a magnetic field induced by the permanent magnets. The rotating magnetic field (RMF) can realize the free surface shape control and the melt stirring simultaneously. Numerical model was built to analyse the magnetic field distribution. Two drivers that have the same structure were analysed and optimised. Quasi-steady-state free surface was obtained by regulating the rotating velocity of the magnetic drivers, which is proportional to the magnetic force. Solidification experiment was preformed on a platform of a mini-continuous caster. The solidifying front was observed via addition of a small quantity of Sn-wt.43%Pb into the continuous casting alloy Sn-wt.3.5%Pb, it was found that the solidifying shell grows uniformly under the condition of a proper imposition of the double-permanent-magnet-driver.
Grain Refinement during Superplastic Deformation of Coarse-Grained Al-Mg-Cu Alloys
Authors: Cruz-Palacios M.I. , Hernández-Silva D. , Barrales-Mora L.A. , García-Bernal M.A.
Published: March 2009

In the present study the superplastic behavior of Al-6%Mg–0.5%Cu and Al–8%Mg– 0.5%Cu in a coarse grain size condition has been studied. The alloys are melted in an electrical furnace under argon atmosphere. The ingots (25 mm thick) are homogenized at 400 °C during 72 h and then rolled at 430 °C to a thickness of 5 mm. The mean grain size after rolling is 55 µm for the 6%Mg alloy and 61 µm for the 8%Mg alloy. Tensile test specimens are machined from the rolled plate in the rolling direction. Strain-rate-change tests at temperatures between 300 and 450 °C and strain rates between 1x10-4 and 1x10-1 s-1 are carried out to determine the strain rate sensitivity of the flow stress. Finally, elongation to failure tests are conducted at temperatures and strain rates where the alloys show a high strain rate sensitivity. Elongations higher than 390 % are obtained for the 8%Mg alloy. It is observed that the grip regions of the deformed samples show coarser grains than the regions near to the fracture surface. This means that grain refinement takes place during deformation, suggesting that the principal deformation mechanism is dislocation creep.
Microstructure and Electrochemical Properties of Post Heat-Treated Li(Ni1/3Co1/3Mn1/3)O2 Cathode Materials for Lithium Ion Battery
Authors: Kim Seon Hye , Shim Kwang Bo , Han Kyoung Ran , Kim Chang Sam
Published: March 2009

Li(Ni1/3Co1/3Mn1/3)O2 powders were synthesized by using an ultrasonic spray pyrolysis method, and then heat-treated at 900 or 1000°C for 20 h. The morphology of the as-synthesized powder was spherical. The post heat-treatment changed the particle size and morphology of the synthesized powders. Structural characteristics of the heat-treated powders were analyzed using XRD and SEM, and their electrochemical properties were compared. Higher first discharge capacity
was obtained from the powder heat-treated at 1000°C, but its rough and rugged surface might cause a rapid decrease of the capacity retention.
A Slow Strain Rate Test Experiment to Evaluate the Characteristics of High-Strength Al-Mg Alloy for Application in Ships
Authors: Kim Seong Jong , Jang Seok Ki
Published: March 2009

Recently, there has been increased interest in using aluminum alloys in ship construction instead of fiber-reinforced plastic (FRP). This is because aluminum alloy ships are faster, have a greater load capacity, and are easier to recycle than FRP ships. In this study, we investigated the mechanical and electrochemical properties of aluminum alloys using the slow strain rate and potentiostatic tests under various potential conditions. The optimum protection potential range with
regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between -1.5 and -0.7 V (SSCE). These results can be used as reference data for ship design.
Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route
Authors: Yoon Young Ok , Jo Hyung Ho , Lee Jin Kyu , Jang Dong In , Kim Shae K.
Published: March 2009

Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present
study focuses on 7075 Al wrought alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al wrought alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal
holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.
Cyclic-Oxidation of Ti3SiC2 and Ti3AlC2 between 900 and 1200°C in Air
Authors: Lee Dong Bok , Han Jae Ho , Kim Young Do , Park Sang Whan
Published: March 2009

Using the hot pressing method, the Ti3SiC2 materials having fine and coarse grains were synthesized from TiC0.6 and Si powders, and the Ti3AlC2 materials having fine and coarse grains were also synthesized from TiC0.6 and Al powders. The cyclic oxidation between 900 and 1200oC for 40 hr in air resulted in the formation of an outer TiO2 layer and an inner (TiO2+ amorphous SiO2) mixed layer for Ti3SiC2, and the formation of an outer TiO2 layer and an inner (TiO2+ Al2O3) mixed layer for Ti3AlC2. The effect of the grain size on the cyclic oxidation resistance was not significant.
Comparison of Silicon Coatings Deposited by Vacuum Plasma Spraying (VPS) & Atmospheric Plasma Spraying (APS)
Authors: Niu Ya Ran , Liu Xuan Yong , Ding Chuan Xian
Published: March 2009

In this work, silicon coatings were deposited using VPS and APS technologies. Their
structure and composition were characterized using XPS, SEM, and XRD. The porosity and surface-roughness of coatings were evaluated. The results showed that the VPS silicon coating possessed lower porosity compared with the APS silicon coating. The APS silicon coating surface was almost all covered by many small particles whose size is about 100 nm. The Si 2p XPS spectra indicated that silicon oxide existed in both coatings. The oxidation may have occurred during the
plasma spray process. However, the VPS process could inhibit silicon from being oxidated.
Influence of Two-Step Sintering on Transparency of High Purity Alumina
Authors: Sung Rak Joo , Kim Dong Suk , Ji Su Ah , Park Jeong Sik , Kim Sang Woo
Published: March 2009

Density, purity, grain, and grain size distribution are the key factors that influence the
transparency of an optical ceramics. To achieve high transmittance, efforts should be made to eliminate or minimize scattering or absorption of light. The aim of this paper is to verify the effect of two-step sintering technique for translucent alumina. The density and transmittance of the samples were enhanced by pre-heat treating at 800°C for 50 hours before the high temperature sintering. Abnormal grain growth was successfully suppressed by a two-step sintering technique and a small amount of MgO as additives. It is a very effective technique for designing
homogeneous microstructure and high transparency in high purity alumina.
Influences of the Crystallization Behavior of n-HA Reinforced PA66 Biocomposite on Its Mechanical Properties
Authors: Zhang Xiang , Li Yu Bao , Zuo Yi , Lv Guo Yu , Mu Yuan Hua
Published: March 2009

The crystallization behavior of n-HA/PA66 biocomposites at different processing
pressure and annealing temperature were investigated by XRD and DSC. The results showed that increasing annealing temperature would weaken the crystalline intensities of pure PA66 and its composites. For n-HA/PA66 composites, the peaks of α1 crystals of PA66 disappeared, only α2 crystals existed, and with the increase of injection pressure and annealing temperature, the crystalline intensity of PA66 decreased. The degree of crystallinity (Xc) of PA66 in composites increased with the increase of injection pressure, however, annealing temperature had no obvious
effects on crystalline degree. The mechanical properties had close relationship with the crystallization behavior of the materials.
Microstructural Tailoring of Open-Pore Microcellular Aluminium by Replication Processing
Authors: Despois Jean-François , Marmottant Ariane , Conde Yves , Goodall Russell , Salvo Luc , San Marchi Chris W. , Mortensen Andreas
Published: March 2009

The replication process is presented and discussed with emphasis on methods for microstructural tailoring of open-pore microcellular aluminium-based foams, highlighting methods it offers for control of principal foam mesostructural and microstructural parameters: pore volume fraction, pore shape, pore size(s), as well as the composition and microstructure of the metal making the foam.
EBSD and TEM Characterization of Ultrafine Grained High Purity Aluminum Produced by Accumulative Roll-Bonding
Authors: Kamikawa Naoya , Huang X. , Tsuji Nobuhiro , Hansen Niels , Minamino Yoritoshi
Published: March 2009

High purity aluminum (99.99% purity) was severely deformed by accumulative
roll-bonding (ARB) to a thickness reduction of 98.4%. Quantitative microstructural characterization of the deformed sample was carried out by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). EBSD scans at various locations from the sample surface to the mid-thickness revealed a fairly uniform and equiaxed structure, although a small fraction of an elongated structure parallel to rolling direction (RD) was also observed. Misorientation angle
distributions for grain boundaries of which misorientation angle was larger than 2° were evaluated by EBSD, showing that more than 70% of the boundaries were high-angle ones (>15°). More detailed structural features, such as low-angle boundaries (<2°) and dislocations between boundaries were characterized by TEM. The TEM results indicated that about 17% of the boundaries have
misorientations <2° and that the fraction of high-angle boundaries is about 52%. An estimated yield strength based on the structural parameters determined by TEM was in good agreement with the measured value.
Synthesis of N-Carboxymethyl Chitosan Beads for Controlled Drug Delivery Applications
Authors: Jayakumar Rangasamy , Reis Rui L. , Mano João F.
Published: March 2009

N-Carboxymethyl chitosan (NCMC) is a water soluble derivative of chitosan. The
NCMC beads were prepared by using ionotropic gelation process with the counter polyanion tripolyphoshate at pH 4.0 and characterized by scanning electron microscopy. The swelling behavior of the beads at different time intervals was monitored at different pH conditions. The in vitro drug release behavior in various pH solutions was studied using indomethacin as a model drug with two different concentrations (0.3 and 0.6% w/w). The release percent of indomethacin from
NCMC beads was found to increase with increasing of pH in phosphate buffer solution medium due to the ionization of carboxymethyl group and high solubility of indomethacin in alkaline medium. These results indicated that the NCMC beads are useful for controlled drug delivery systems through oral administration by avoiding the drug release in the highly acidic gastric fluid region of the stomach.
Influence of Molecular Weight and Crystallinity of Poly(L-Lactic Acid) on the Adhesion and Proliferation of Human Osteoblast Like Cells
Authors: Salgado António J. , Wang Ya Ming , Mano João F. , Reis Rui L.
Published: March 2009

The molecular weight and crystallinity of systems based on poly(L-lactic acid) PLLA is an important issue as it can influence, besides the general physical properties of the polymer, the patterns of cell adhesion, proliferation and cell morphology. The objective of the present study was to evaluate how crystallinity and molecular weight of PLLA influence the referred parameters. Four conditions were tested: low molecular weight amorphous and semi-crystalline PLLA disks, and
high molecular weight amorphous and semi-crystalline PLLA disks, obtained from hot press. The thermal properties of the studied materials were accessed by differential scanning calorimetry. For the cell culture studies a human osteosarcoma cell line (SaOS-2) was chosen. Disks were immersed in a cell suspension containing 5x104 cells/ml and kept in culture for periods up to two weeks. Cell
viability and proliferation of SaOS-2 cells was assessed by MTS test and a total protein assay, respectively. The adhesion and morphology of SaOS-2 cells on PLLA disks was assessed by scanning electronic microscopy. Results showed that cell viability was not affected by the different tested conditions. However, cell proliferation was increased in the high molecular weight amorphous samples and cells seemed to have higher adhesion patterns on semi-crystalline samples.
This is probably happening due to different rates of integrin interaction with the substrate leading to different patterns of focal adhesion points formation.
Organic Vapour Discrimination Using Sorption Sensitive Chemocapacitor Arrays
Authors: Igreja Rui , Dias C.J.
Published: March 2009

An interdigital chemocapacitor (IDC) sensor array has been developed to discriminate organic vapour samples with pure organics and mixtures. Sensors were coated with diverse polymers (PEUT, PDMS and modified PDMS). Dedicated signal conditioning circuits were developed with a reduced S/N ratio enabling measurement of capacitance changes as low as 0.07 fF. A new sampling technique was also developed to improve isobaric sampling conditions on the
sensors chamber. Linear techniques such as Principal Component Analysis (PCA) for discrimination between the different samples were sucessfully applied. As far as we know, this is the first time that an array of interdigital chemocapacitors is used for organic vapour discrimination.
Non-Isothermal Crystallisation of SiO2-MgO-K2O-3CaO·P2O5 Glass Studies by Impedance Spectroscopy
Authors: Queiroz Carlos M. , Fernandes Maria Helena F.V. , Frade Jorge R.
Published: March 2009

Impedance spectroscopy was used to monitor the non-isothermal crystallisation of a
phosphate phase in bulk samples of a glass with the molar composition 0.45SiO2–0.36MgO– 0.09K2O–0.1(3CaO⋅P2O5), intended for biomedical applications. The K+ alkali ions are probably the main charge carriers in glass of this composition [1]. Impedance spectra were obtained as a function of temperature, following non-isothermal heat treatments at 2°Cmin-1. It is shown that suitable analysis of impedance spectra can be used to evaluate the crystallization peak of a orthophosphate phase, Ca9MgK(PO4)7. Results obtained by this method are comparable to those obtained by differential thermal analysis (DTA) of the corresponding glass frits. Impedance spectroscopy is thus suitable to study the crystallization of bulk samples, and can be used both with variable temperature
and under isothermal conditions.
The Modulus Formalism Used in the Dielectric Analysis with Optical Characterization of Hydroxyapatite and CaTi4P6O24 Ceramic Formers by Dry Ball Milling
Authors: Silva Cléber C. , Valente Manuel A. , Graça Manuel P.F. , Sombra António S. B.
Published: March 2009

The bioceramic hydroxiapatite [Ca10(PO4)6 (OH)2 – HAP] is the main mineral constituent of teeth and bones with excellent biocompatibility with hard and muscle tissues. These materials exhibit several problems of handling and fabrication, which can be overcome by mixing them with a suitable binder. The dry milling process of fabrication of HAP presents the advantage that melting is not necessary and the powder obtained is nanocrystalline. The HAP has been obtained from three
different experimental procedures (HAPA: Ca(H2PO4)2 + Ca(OH)2; HAPB: Ca(H2PO4)2 + CaCO3; and HAPC: CaHPO4 + CaCO3). In the reactions HAPA and HAPB the hydroxiapatite phase was obtained after 5, 10 and 15 hours of milling and after 15 hours in the reaction HAPC. In order to improve the mechanical properties of HAP, calcium phosphate ceramics with titanium (CaP-Ti) has
been prepared by dry ball milling (Ca(H2PO4)2 + TiO2). The calcium titanium phosphate phase, CaTi4P6O24, was obtained. The dielectric study in function of frequency, at constant temperature of the ceramics, was made using the Modulus (M*) formalism and a distribution of relaxation times was observed. The values of the dielectric constant of the ceramics measured at room temperature are between 5.04 (CaP-Ti_5H) and 13.70 (HAPA_10H). The structure of the samples was studied by X-Ray diffraction, infrared and Raman scattering spectroscopy.
Tribological Study of the Damage Mechanics of Polymer-Metal Contacts Used in Implants
Authors: Silva Ruthilene C. Lima da , de Santana Janaina Silva , Silva Jr José F. , Silva Ademir Oliveira da , Medeiros João Telésforo Nóbrega
Published: March 2009

Polyurethane is a biocompatible material and its use is increasing as human or animal
implants. However, problems due to wear debris and their interaction with the host require a better understanding of wear mechanisms and the genesis of the debris formation. Some effects of the contact pressure and geometry were experimentally investigated to identify the response, obtained by contact temperature, mass variation, Scanning Electron Microscopy and EDS microanalysis, of polyurethane samples from sliding against metallic surfaces.
Adsorption Mechanism of 5-Flourouracil on Different Hydroxyapatite Particles
Authors: Santos Catarina , Martins M.A. , Almeida Margarida M. , Costa Maria Elisabete V.
Published: March 2009

The adsorption of the drug 5-Flourouracil (5-FU) on Hydroxyapatite (HAP) particles having different surface conditions is studied at 37°C. Commercial HAP particles, either as received or soaked in citrate solutions are used as drug adsorbents and compared to a third category of HAP particles which consists of granules obtained by spray drying suspensions of HAP nanoparticles previously precipitated in citrate solutions. The adsorbed amount of 5-FU on the HAP particles
surface is conditioned by the existing pre-adsorbed citrate ions which contribute to modify the particle surface charge and thus decrease the drug adsorption. However the obtained results also demonstrate that the particle surface charge is not the unique factor to govern the 5-FU adsorption on the HAP particles surface.
Layer-by-Layer Deposition of Organically Capped Quantum Dots
Authors: Neves Márcia C. , Pereira Angela S. , Peres Marco , Kholkin Andréi L. , Monteiro Teresa , Trindade Tito
Published: March 2009

Cadmium chalcogenide quantum dots (QD’s) were synthesised using a single source approach while zinc oxide QD’s were obtained by a colloidal technique. In both situations the dots were surface capped with tri-octylphosphine oxide (TOPO) hence leading to nanodispersed systems in organic solvents such as toluene. The organically capped QD’s (CdSe, CdS and ZnO) were used
as building-units to fabricate LbL (layer-by-layer) films on glass and quartz substrates. A linear increase in the visible light absorbance (due to the QD’s) with the number of deposited layers indicates that multi-layered systems have been fabricated. In order to investigate the effect of the LbL manipulation on the integrity of the QD’s, comparative studies on the optical properties of the starting QD’s and the nanostructured films have been performed. The observation of quantum size
effects in both cases suggests minimal degradation of the QD’s though clustering had probably occurred, a point which was further confirmed by AFM analysis.
Ion Beam Analysis of Ge/Si Dots Grown on Ultrathin SiO2 Interlayers
Authors: Fonseca Alexandra , Alves Eduardo , Leitão Joaquim P. , Sobolev Nikolai A. , Carmo M. Celeste , Nikiforov Alexander I.
Published: March 2009

Monolayer (ML) thick Ge deposition on (100) Si substrates by molecular beam epitaxy (MBE) technique using an ultrathin SiO2 interlayer has been studied by ion beam analysis and photoluminescence (PL). The dependence of the Ge layer growth mode on the amount of the deposited Ge and the SiO2 thickness has been investigated. Atomic hydrogen treatment has been performed in order to passivate non-radiative recombination channels and to enhance the PL intensity. We conclude the formation of Ge quantum dots for the sample with the thickest Ge and SiO2 layers (9 Å and 1 ML, respectively).
Image Restoration of One-Dimensional HgTe Crystals Formed within Single Walled Carbon Nanotubes
Authors: Sloan Jeremy , Carter Robin , Kirkland Angus I. , Meyer Rüdiger R. , Vlandas Alexis , Green Malcolm L.H. , Hutchison John L.
Published: March 2009

Restored high resolution transmission electron microscopy (HRTEM) images have been recorded from 1D semiconductor crystals formed within narrow diameter (ca. 1.4 nm) single walled carbon nanotubes (SWNTs). Two unique projections were obtained from separate crystal fragments encapsulated within separate nanotubes that has facilitated the reconstruction of the three
dimensional arrangement of atoms within the two encapsulated fragments.
Influence of the Crystallographic Orientation on the Mechanical Behaviour of Sputtered Silver Thin Films
Authors: Piedade Ana P. , Gomez Guenis , Vieira Maria-Teresa Freire , Staia Mariana
Published: March 2009

In this research work, sputtering was used to deposit silver thin films under different
deposition parameters, namely by changing deposition pressure, substrate bias and discharge gas. The main objective of the present work was to study the influence of the textured grain in the mechanical behaviour of the modified surfaces. The deposition rate, chemical composition (EPMA), morphology (SEM) and hardness were also assessed. In the slide alternating wear tests,
where poly(tetrafluoroethylene) (PTFE) was used as counterbody, the loads varied from 10 to 30 N. One of the major conclusions of this work is that the thin films with the strongest (111) preferential crystallographic orientation correspond to the highest deposition rate. These sample present higher hardness and lower wear coefficient if compared with other orientations
Laminated Composite Thin Films: A Solution to Improve Cutting Tools Performance
Authors: Castanho José M. , Vieira Maria-Teresa Freire
Published: March 2009

In cutting applications hard thin films of coated tools are expected to be wear and
oxidation resistants, and with strong adhesion to the substrate. Due to the high loads involved in the contacts, the main efforts must be supported by the substrate and it is supposed that the coatings follow their elasto-plastic deformation, with a subsequent delay of the crack propagation. The commercial thin films used for these applications are generally monolithic and homogeneous or heterogenous(chemical compositional gradient up-down). Even the nanostructured coatings will
perform under these loads as monolithic coatings, and the crack generation and propagation will be ruled by the same mechanisms as in the monolithic coatings. Hence, the hard coatings for cutting tools must be able to deflect surface cracks and exhibit the highest adhesion to the substrate. In order to achieve these characterisitics, the common Ti-Al-N was selected as hard coating, and thin
ductile metal interlayers (few tenths of nanometres) were introduced inside Ti-Al-N thin film as long period multilayer coatings – nanolaminate coatings. The presence of interlayers revealed efficiency in dissipation of the energy generated during the application, decreasing the propagation cracks across the coating and ensuring the best adhesion. The mechanical behavior observed is homotethic of macrolaminate composite bulk materials. The failure of the coating is layer-by-layer, always exposing the ductile layer, which function is also to be a fuse that protect the remaining coating. The material of the interlayer and the period (interlayer/coating) selected resulted from the balance between the maximum performance of coating to avoid service failure and the minimum decrease of relevant mechanical properties of the monolitic hard coating as hardness.
Photoluminescence Changes Induced by Self-Organisation in Bridged Silsesquioxanes
Authors: Carlos Luís D. , Ferreira Rute A. Sá , Nobre Sonia S. , Wong Chi Man Michel , Moreau Joël J. E. , Bied Catherine , Pichon Benoit
Published: March 2009

Two organo-bridged silsequioxanes derived from the same molecular precursor were
synthesized with completely different local structure, namely long-range ordering. The photoluminescence features (emission, excitation, and time-resolved modes) were studied in the temperature range 13-300 K and compared with those of the molecular precursor. The effects of the self-assembling of the nanobuild blocks on these emission properties were discussed in terms of the magnitude of the hydrogen bonds between adjacent organic groups.
Electrodeposition and Thermal Treatment of Nickel Coatings Containing Molybdenum and Silicon
Authors: Popczyk Magdalena , Kubisztal Julian , Budniok Antoni
Published: March 2009

Ni+Mo+Si coatings were obtained by electrolytic codeposition of crystalline nickel with molybdenum and silicon powders from an electrolyte containing suspension of these powders. These coatings were obtained in galvanostatic conditions, at the current density of -0.100 A cm-2. Thermal treatment of these coatings in argon atmosphere was done at temperature of 1100oC for 1 hour. A scanning electron microscope was used for surface morphology characterization of the coatings. Chemical composition of obtained coatings was determined by Xray
fluorescence spectroscopy method and phase composition investigations were conducted by Xray diffraction method. It was found that introduction of molybdenum and silicon into nickel matrix, causes of obtained coatings about very rough surface. Thermal treatment of these coatings influenced their surface. The surface after thermal treatment is more compact and less rough than the as-deposited one.
Preparation and Characterization of Hybrid Organic/Inorganic Nanocomposites by In Situ Miniemulsion Polymerization
Authors: Lehocký M. , Esteves A. Catarina , Barros-Timmons Ana M. , Coutinho João A.P.
Published: March 2009

SiO2/polystyrene nanocomposite particles were synthesized via miniemulsion
polymerization using sodium dodecyl sulfate (SDS) as surfactant and hexadecane as hydrophobe in
the presence of silica particles coated with methacryloxy(propyl)trimethoxysilane (MPS) surface
coupling agent. The silica particles were individually coated with polymer yielding a very
homogenous nanocomposite latex which was very stable in a wide range of ionic strengths.
Monomer conversion was reasonably high and fast.
Effect of Confinement on the Freezing-Melting Dynamics of Water
Authors: Banys Juras , Kinka Martynas , Macutkevic Jan , Völkel Georg , Böhlmann Winfried , Umamaheswari Venkatesan , Hartmann Martin , Pöppl Andreas
Published: March 2009

Melting-freezing dynamics of water confined in three MCM-41 materials with pore
diameters of 2.0 nm, 2.5 nm and 3.7 nm was analyzed using dielectric spectroscopy method.
Obtained results show, that reorientation of water molecules is strongly affected by confinement and
interaction with the pore surface, which leads to the formation of highly disordered hydrogen
bonded network. Defects of this network play the key role in the overall relaxation of confined
water.
Optical Emission Spectroscopy Study of Magnetron Assisted Ni-Ti DC Sputtering
Authors: Silva Marcia , Gordo Paulo R. , Maneira Manuel J.P. , Braz Fernandes Francisco Manuel
Published: March 2009

Ni-Ti thin films where the R-phase transformation occurs between 55°C and 30°C, the
peak temperature being 40°C, have been produced. These thin films have been grown using a
magnetron assisted system of dc sputtering, with a Glow-Discharge Optical Emission Spectroscopy
device. The OES technique has been used to investigate the spatial distribution of sputtered atoms
from the cathode to the substrate in different operating conditions: Argon pressure of 5 and 9x10 – 4
Torr, without polarization and with – 60 V bias. Structural characterization of the thin films has
been made by XRD and the transformation temperatures associated to the shape memory effect
have been determined by DSC. A discussion of the optimization of the processing parameters
(Argon pressure and polarization) is then presented.
Photoluminescence of Nanocrystalline Bismuth Titanate Thin Films Synthesized by the Sol-Gel Method
Authors: Lisińska-Czekaj Agata , Czaja M. , Kozielski Lucjan , Czekaj Dionizy , Piechowiak M. , Nowakowski M. , Zawiślok K.
Published: March 2009

The present study is devoted to synthesis and investigation of photoluminescence in the nanosized Bi4Ti3O12 (BTO) thin films. The randomly oriented BTO thin films have been obtained by a modified hybrid sol-gel process. Bismuth nitrate and titanium (IV) butoxide were used as the starting materials. The thin films were deposited on silicon, glass and stainless steel by spin coating and crystallized by the conventional thermal annealing at temperature T=650°C. Formation of the layer perovskite-type structure of the orthorhombic symmetry was confirmed by X-ray diffraction method. Conservation of the chemical composition was investigated by energy dispersive spectroscopy. The UV luminescence has been observed in BTO thin films at room temperature. Results on luminescence excitation and emission in bismuth titanate thin films are given in the present paper.
Structural, Microstructural and Magnetic Properties of Ball Milled Boron-Substituted Sm(Co,Fe,Cu,Zr)7.5 Compounds
Authors: Makridis Sofoklis S. , Pavlidou Eleni , Konstantakou Mary , Stubos Athanasios K.
Published: March 2009

The powders in the micrometer scale of Sm(Co0.86Fe0.1B0.04)7.5,
Sm(Co0.82Fe0.1Zr0.04B0.04)7.5, Sm(Co0.715Fe0.1Cu0.12Zr0.04B0.025)7.5, Sm(Co0.69Fe0.1Cu0.12Zr0.04B0.05)7.5
compounds have been prepared by using a high-energy planetary ball miller. The X-ray diffraction
patterns have an amorphous state after 42 hours milling while the average grain size is in the range
of 0.5-10 μm, as measured by using a scanning electron microscope. Amorphization has been
achieved at shorter milling times for samples with higher boron content. Depending on the
annealing temperature, the major phases are 1:7, 2:17 hexagonal or fcc-Co as revealed from the Xray
patterns. The annealing at temperature over 900 oC for 1h helps the formation of the fcc-Co
which becomes the dominant phase, mostly on the higher boron doped samples. From the hysteresis
curve of Sm(Co0.715Fe0.1Cu0.12Zr0.04B0.025)7.5, a coercive field of ~9 kOe has been determined. For
this sample there is difference between the two coercive fields, Ηc(χirr=max) and Ηc(M=0). The
zirconium doped sample has higher coercive field than the Sm(Co0.86Fe0.1B0.04)7.5 one. The coercive
field is significant increases to the copper doped samples. In the thermomagnetic curves of the asmilled
powders, it has been evidenced that there is crystallization, connected to the increase of the
magnetization under the constant applied field. The initial and demagnetization curves exhibit slope
variations that are connected to the soft fcc-Co phase. Almost zero hydrogen absorption was found
for the Cu-doped samples at room temperature.
Lead-Cadmium Fluorogermanate Glasses and Transparent Glass-Ceramics. Spectroscopy and Structure
Authors: Ribeiro Sidney José Lima , Messaddeq Younes , Bueno L.A. , Dexpert-Ghys J. , Gouveia-Neto A.S. , Tambelli C.C. , Donoso J.P. , Magon C.
Published: March 2009

In Lead-cadmium fluorogermanate glasses (PbF2-CdF2-PbGeO3) the addition of metal
fluorides to the base PbGeO3 glass leads to a decrease of the glass transition temperature (Tg) and
to an enhancement of the ionic conductivity properties. Based on different spectroscopic techniques
(19F NMR, Ge K-edge X-ryas absorption and Raman scattering) an heterogeneous glass structure is
proposed at the molecular scale, which can be described by fluoride rich regions permeating the
metagermanate chains. The temperature dependence of the 19F NMR lineshapes and relaxation
times exhibits the qualitative and quantitative features associated with the high fluoride mobility in
these systems. Eu3+ emission and vibronic spectra are used to follow the crystallization process
leading to transparent glass ceramics.
Insights on Amorphous Silicon Nip and MIS 3D Position Sensitive Detectors
Authors: Martins Rodrigo , Costa Daniel , Águas Hugo , Soares Fernanda , Marques António , Ferreira Isabel , Borges P.M.R. , Pereira Sergio , Raniero Leandro , Fortunato Elvira
Published: March 2009

This work aims to report results of the spatial and frequency optical detection limits of integrated arrays of 32 one-dimensional amorphous silicon thin film position sensitive detectors with nip or MIS structure, under continuous and pulsed laser operation conditions. The arrays occupy a total active area of 45 mm2 and have a plane image resolution better than 15 m with a cut-off frequency of about 6.8 kHz. The non-linearity of the array components varies with the frequency, being about 1.6% for 200 Hz and about 4% for the cut-off frequency (6.8 kHz).
Effect of Interlayer on the Residual Stresses within High-Temperature Coating
Authors: Zhang Xian Cheng , Xu Bin Shi , Wang Hai Dou , Wu Yi Xiong
Published: March 2009

The effect of NiCoCrAlYx-ZrO2 (1-x) interlayer on the residual stresses in the
ZrO2/NiCoCrAlY thermal barrier coating due to thermal cycling was analyzed using the finite
element method. Modeling results showed that the magnitude and distribution of the residual
stresses in the coating were strongly influenced by the material combination characterized by the
value of x and the thickness of interlayer. The maximum tensile stresses at the different regions (i.e.
coating/substrate interface, coating surface, et al.) as functions of the material combination and the
thickness of the interlayer were obtained. The physical meaning of the above results was also
discussed.
Joining of TiAl Using a Thin Multilayer
Authors: Duarte Liliana I. , Ramos Ana Sofia , Vieira Manuel F. , Viana Filomena , Vieira Maria-Teresa Freire
Published: March 2009

As TiAl based alloys begin to approach maturity, the development of successful and cost
effective joining methods will be required. The growing industrial interest in these materials,
particularly in aerospace and automotive industry, led to an interesting challenge - how to joint parts
and components in order to produce integrated and resistant structures. Diffusion bonding of
materials produces components with thinner interfaces than other joining techniques do. The
absence of abrupt microstructure discontinuity and the small deformation induced maximize joint
strength.
This work focuses on the joining of TiAl using a thin multilayer obtained by alternating nanometric
layers of titanium and aluminium. The Ti/Al layers were deposited onto the γ-TiAl samples by DC
magnetron sputtering. The interfaces of these diffusion bonded joints depend on processing and
deposition conditions. In this work we describe the influence of bilayer thickness (period) and on
microstructure and chemical composition of the joining interfaces.
Use of Electroless Plating Copper Thin Films for Catalysis
Authors: Carvalho Alexsander T. , Nascimento Filho António Pereira , Silva Lilian Marques , Silva Maria Lucia Pereira , Madaleno Joana Catarina , Pereira Luiz
Published: March 2009

Recently, it was demonstrated that copper thin films show good adsorption
characteristics for organic polar and non-polar compounds. Also, these films when used in small
cavities can favor preconcentration of these organic compounds. It is also known that copper oxide
can provide catalysis of organic compounds. Therefore, the aim of this work is the study of copper
thin film catalysis when used in small cavities. Copper thin films, 25 nm thick, were deposited on
silicon and/or rough silicon. These films do not show oxide on the surface when analyzed by
Rutherford backscattering. Also, Raman analysis of these films showed only silicon bands, due to
the substrate, however infrared spectroscopy shows oxide bands for films exposed to organic
compound aqueous solutions. Cavities with copper films deposited inside were tested with a
continuous flow of n-hexane, acetone or 2-propanol admitted in the system. The effluent was
analyzed by Quartz Crystal Microbalance. It was shown that n-hexane or acetone can be trapped.
The system also shows good reproducibility. Tests of catalysis were carried out using Raman
spectroscopy and heating the films up to 300°C during 3 minutes after exposure to n-hexane, 2-
propanol and acetophenone – pure or saturated aqueous solution. After the exposure, Raman spectra
present intense bands only for 2-propanol, indicating that adsorption easily occurs. However, after
heating with all solutions it was not found only silicon bands. Raman microscopy after heating also
showed copper oxide cluster formation and, eventually, graphite formation. Although the heating
provides oxide copper formation, this reaction does not produce a high amount of residues, which
means that catalysis is possible in this condition. Thus, a simple device using copper thin films can
be useful as sample pretreatment on microTAS development.
Assessing the Influence of Heat Treatments on γ-TiAl Joints
Authors: Guedes Anibal , Pinto Ana Maria Pires , Vieira Manuel F. , Viana Filomena
Published: March 2009

The heat treatment of γ-TiAl alloy (Ti-47Al-2Cr-2Nb (at.%)) diffusion brazed joints was
investigated. Joining was performed using a Ti/Ni/Ti clad-laminated braze alloy foil at 1050 and
1150°C with a dwell time of 10 minutes. The joints were subsequently heat treated at 1250 and
1350°C for 240 and 30 minutes, respectively. The microstructure and the chemical composition of
the interfaces were analysed by scanning electron microscopy (SEM) and by energy dispersive
X-ray spectroscopy (EDS), respectively. Microhardness tests performed across the interface were
used to roughly predict the mechanical behaviour of the as-diffusion brazed and of the heat treated
joints. Diffusion brazing produced interfaces with two distinct layers essentially composed of
α2-Ti3Al and of TiNiAl; γ-TiAl was also detected for joining at 1150°C. After heat treating, the
as-diffusion brazed microstructure of the interface was completely replaced by a mixture essentially
composed of γ-TiAl and α2–Ti3Al single phase grains and of (α2 + γ) lamellar grains.
Microhardness tests showed that the hardness of the as-diffusion brazed interfaces, which ranges
from 567 to 844 HV (15 gf), is significantly higher than that of the titanium aluminide alloy
(272 HV). All post-joining heat treatments lowered substantially the hardness of the interface, as the
hardness of the main phases detected at the interfacial zone after heat treating the joints is
comprised between 296 and 414 HV.
Electrochemical Reduction of AQ27DS in Aqueous Solution
Authors: Sequeira César A.C. , Lobo Rui F. M. , Anastassakis Giorgios
Published: March 2009

It is known that anthraquinone derivatives act as aqueous sulphide oxidation catalysts, so
the redox chemistry of the compound anthraquinone 2,7-disulphonate (AQ27DS) stimulated our
interest, as reported here.
AQ27DS was reduced in aqueous solution at pH 9.0 to give a deep red coloured air-sensitive
solution. Cyclic voltammetry and exhaustive electrolysis indicated that the anthraquinone was
reversibly reduced in a two electron, one proton process at a variety of electrode surfaces. From
limiting current results at a rotating disc electrode, the diffusion coefficient of AQ27DS was
calculated to be 3.37 x 10-10 m2 s-1.
Spectroscopic results confirmed that AQ27DSH- was the major reduced species, but also indicated
that the di-anion (AQ27DS2-) and radical species AQ27DS• were also present. ESR spectroscopy
showed that the radical was formed via a comproportionation reaction between the di-anion and the
AQ27DS starting material. The peak separation from voltammetry enabled the comproportionation
constant (Kc) to be estimated, and it was found to be in the range of 0.4 to 4.