bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Niobium Film on Corrosion Resistance of AZ91D Magnesium Alloy
Authors: Liu Er Bao , Cui Xiu Fang , Jin Guo , Li Qing Fen , Shao Tian Min
Published: November 2012

The niobium film is prepared by magnetron sputtering on the surface of the AZ91D magnesium alloy. The morphology, phase structure, roughness, nanohardness and elastic modulus of the niobium films were studied by filed emission scanning electron microscope, X-ray diffraction, atomic force microscope and nanoindentation respectively. The influences of film deposition parameters, such as substrate temperature, negative bias and power on the properties of films were investigated. The corrosion resistance of niobium films on magnesium alloy was investigated by electrochemical system. Results show that the microstructure, phase structure, roughness, nanohardness and elastic modulus of the niobium films are determined by power, negative bias and substrate temperature. And the corrosion resistance of magnesium alloy improved obviously when coated with the niobium films.
Thermo-Mechanical Stress near Apex of a Bi-Material Wedge by a Novel Finite Element Analysis
Authors: Ping Xue Cheng , Leng Lin , Wu Si Hai
Published: November 2012

A super wedge tip element for application to a bi-material wedge is develop utilizing the thermo-mechanical stress and displacement field solutions in which the singular parts are numerical solutions. Singular stresses near apex of an arbitrary bi-material wedge under mechanical and thermal loading can be obtained from the coupling between the super wedge tip element and conventional finite elements. The validity of this novel finite element method is established through existing asymptotic solutions and conventional detailed finite element analysis.
Simulation of Spall Fracture Based on Material Point Method
Authors: Chen Wei Dong , Zhang Fan , Yang Wen Miao
Published: November 2012

The spall fracture is a shock wave induced dynamic fracture phenomenon, it’s difficult to capture the features of the spall fracture when traditional finite element method based on continuum mechanics is applied. In this paper, a new and flexible meshless method, material point method, is used to study the spall fracture of metal material in the case of hypervelocity impact. Firstly, a computational process is given in which Johnson-cook plasticity model, Mie-Grüneisen equation of state and several failure models including hydrodynamic tensile failure model, effective plastic strain model and Johnson-cook failure model are considered. Then a 3D simulation of spall fracture of an armco iron target under impact loads by a 2024-T351aluminum projectile is carried out. At last, the numerical results show that the material point method can accurately capture important features of spall fracture such as the arrival times, magnitudes and shapes of both the compressive waves and tensile reflections in the spall region, and it’s proven that material point method is suitable to simulate the spall fracture in engineering applications.
Mechanical Properties of Alumina Based Nanocomposites
Authors: Kannisto Erkka , Cura M. Erkin , Levänen Erkki , Hannula Simo Pekka
Published: November 2012

To study the microstructure and mechanical properties of alumina nanocomposites, Al2O3/2.5 vol.% Ni and Al2O3/10 vol.% ZrO2 nanocomposites were consolidated by pulsed electric current sintering (PECS). Fracture toughness was found to increase by 13 % and 16 % respectively compared to reference alumina. Hardness increased slightly in Al2O3/Ni because of a fraction of nickel particles under the critical size (2 following the rule of mixtures. By investigating the results, causes of improved mechanical properties were critically evaluated.
Experimental Analysis of Steel Plasticity Parameters during Quenching
Authors: Bendikiene Regita , Vitkeviciene Rasa
Published: November 2012

The paper presents the results of longitudinal investigations of transformation plasticity, kinetic plasticity, elastic-plastic strain and auto deformation of different grades of steel during quenching. A special device was used to evaluate transformation plasticity and determine the maximum normal bending stress, modulus of transformation plasticity for high alloyed and high corrosion resistance steel. Other targets of experiments were to determine relations between magnitude of normal bending stresses and plastic deformation of test pieces, to examine influence of hardening temperature on the transformation plasticity, to calculate modulus of transformation plasticity Etp. As a complimentary survey we study the mechanical behaviour of high chromium and medium chromium steels during quenching. Understanding phenomenon of steel behaviour during quenching it is possible to renovate and restore the details and components deformed during exploitation, for production of steels with high formability, and to predict properties of steel.
Mechanical Properties of Kaolin during Heating
Authors: Štubňa Igor , Šín Peter , Trník Anton , Veinthal Renno
Published: November 2012

Flexural strength (MOR) and Young’s modulus (YM) of Sedlec kaolin were measured using the three point-bending method and modulated force thermomechanical analysis (mf-TMA). Thermal analyses DTA, thermogravimetry and thermodilatometry (TDA). An escape of the physically bound water (20 – 250 °C) strengthens the sample and YM and MOR increase their values significantly. MOR and YM lower their values as dehydroxylation starts at 400 °C. Both quantities, MOR and YM, pass through minimum in the dehydroxylation region (400 – 650 °C). Their next increase is probably caused by the van der Waals forces acting between metakaolinite crystals and by the starting of the solid-state sintering. YM steeply increases above 950 °C as a consequence of the solid-state sintering. A Weibull’s modulus passes through the sharp maximum at the interval 300 – 400 °C.
Dynamic Compression Behavior and Numerical Modeling of Ti-6246 Alloy at Different Temperatures
Authors: Gomon Dmitri , Hokka Mikko , Kuokkala Veli Tapani
Published: November 2012

The current research concentrates on the characterization of the mechanical behavior of Ti-6Al-2Sn-4Zr-6Mo alloy. The material was studied in compression using the Split Hopkinson Pressure Bar (SHPB) equipment at high strain rates and conventional servohydraulic materials testing devices at low strain rates. The tests were performed at temperatures ranging from room temperature up to 600 °C. According to the results of the compression tests, the strain hardening rate of the studied material decreases strongly with increasing strain rate. The observed strong decrease in the strain hardening rate with increasing strain rate is a consequence of the extremely strong adiabatic heating of the material due to its high strength and low thermal conductivity. In this study, the Johnson-Cook material model parameters were obtained from isothermal stress-strain curves that were calculated from the experimental (adiabatic) stress-strain data. In this paper, the results of the mechanical testing at high strain rates and the numerical modeling of the material behavior are presented and discussed in details.
Wear Estimation Using 3D Surface Roughness Parameters
Authors: Linins Oskars , Krizbergs Juris , Boiko Irina
Published: November 2012

The aim of this work is to propose a methodology of lifetime prediction of details by new approach for linear wear intensity determination using 3D surface roughness parameters. For qualitative evaluation of the wear process the linear wear intensity (Ih), which may be determined separately for the plastic and elastic contact, is commonly used. Since the elastic contact is mainly required in pairs of details in mechanical engineering in these paper this kind of contact was examined. In our research, the random surface model was used. The surface machined with abrasive instruments (grinding, polishing, honing, etc) has the irregular shape of surface roughness, which can be described with random function. Irregular surface is expressed by a random field h(x, y) of two variables x and y which are Cartesian coordinates of a surfaces point, where the height of roughness asperity h(x, y) has a normal probability distribution. In wear research the probability theory was used. Further in deformed volume calculation, as well as in determination of the length of the surface’s contact the 3D surface roughness parameters were used. The strong correlation between 3D roughness parameters Sa (arithmetic mean height) and Str=Rsm1/Rsm2 (texture aspect ratio of the surface) was revealed. As a result of research, the methodology of lifetime prediction of details by new approach for linear wear intensity determination using 3D surface roughness parameters was elaborated and proposed. After calculation of linear wear intensity Ih, it is possible to estimate lifetime of wearing details. So, at a first time in wear estimation the 3D surface roughness parameters were used. The results of this work have wide practical application, for example in design, texture specification on drawings etc.
Wear Behaviour of Recycled Hard Particle Reinforced NiCrBSi Hardfacings Deposited by Plasma Transferred Arc (PTA) Process
Authors: Žikin Arkadi , Hussainova Irina , Katsich Christian , Kulu Priit , Goljandin Dmitri
Published: November 2012

The main goal of present work was to study room temperature wear behaviour of advanced cermet particle reinforced hardfacings. For this purpose three different recycled powders: WC-Co, TiC-NiMo and Cr3C2-Ni were used as reinforcements for the commercially used NiCrBSi matrix alloy. Plasma transferred arc hardfacing process was used for deposition of the hardfacings. Manufactured hardfacings show only average wear resistance compared to WC/W2C reinforced NiCrBSi hardfacing with two times higher wear values. However, in combined impact/abrasive and erosive contacts, manufactured hard particle reinforced hardfacings have shown very promising results with high wear resistance. It was shown, that double structuring along with right material constituent and coating procedure selection may provide high wear resistance.
UV or AO Irradiation Effects on the Tribological Properties of the Talc/GF/PI Composites
Authors: Zhao Gai , Wang Qi Hua , Liu Bai Xing , Wang Ting Mei
Published: November 2012

The development of polyimide (PI) composites, particularly for use in aerospace and tribological applications, has gained importance over the past decades. However, there have been scarce studies on the ultraviolet (UV) or atomic oxygen (AO) irradiation characteristics of the polyimide composites, the understanding of which may aid in expanding its application in space environment. To study the irradiated effects of UV and AO on the tribological behaviour of the PI composites, glass fibers (GF)-reinforced PI composites filled with Talc were irradiated by UV or AO in a ground based simulation system. Glass fibers (GF) reinforced PI composites filled with talc were fabricated by means of a hot press molding technique. The volume contents of the talc (10, 20, 30 %) were chosen to study the effects of filler content on the tribological behavior of the composites, while the proportion of the glass fiber was kept at 15 vol %. To contrast the different effects of UV and AO irradiation on the tribological properties of the composites, experiments without irradiation and after UV or AO irradiation were conducted. The specimens of the composites were irradiated with UV for a period of 4h, while AO irradiation chosen for 6h. Dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA) measurements were conducted. The friction and wear behaviors of the composites, rotating against GCr15 steel balls, were investigated on a ball-on-disk test rig. at room temperature and at a rotating speed of 0.1256 m/s and a load of 1N. Experimental results revealed that the composites exhibited high modulus and wear rate values with increasing talc content, but low coefficients of friction (COF). After AO irradiation, the COF of the composites increased, but UV irradiation had no obvious effect on the tribological property of the composites. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) study of the composite surface showed that the chemical composition of the surface changed after UV irradiation because of the photooxidation and rough surface or even mountain-like structures were formed after AO erosion. The experiments indicated that the different space environments had an important effect on the tribological properties of the polymer composites. It is expected that this study may help expand the application of the polyimide composites in the field of space.
Reactive Sintering of ZrC-TiC Composites
Authors: Yung Der Liang , Kollo Lauri , Hussainova Irina , Žikin Arkadi
Published: November 2012

Inherently, zirconium carbide (ZrC) suffers from low fracture toughness (~3 MPa*m1/2) and excessive porosity when sintered in vacuum. One way to improve ZrC’s sinterability and fracture toughness is the addition of binder metal or other carbides to increase densification. Using mechanical activated synthesis (MAS) to homogenously mix ZrC and titanium carbide (TiC) powders, followed by sintering at 1900 °C, produces a ZrC-TiC composite with hardness and fracture toughness at 20 GPa & ~7 MPa*m1/2, respectively. 80ZrC-20TiC (wt%) gave the highest fracture toughness value compared to other ratios. Varying TiC ratio from 20 - 50 wt% does little to affect mechanical hardness or densification of the composite. However, fracture toughness appears to increase marginally with decreasing TiC concentration down to ~20 wt%.
Development of Innovative Algorithm for Nanomechanics and its Applications to the Characterization of Materials
Authors: Jeng Yeau Ren
Published: November 2012

Understanding major mechanisms affecting material strength such as grain size, grain orientation and dislocation mechanism from atomistic viewpoint can empower scientists and engineers with the capability to produce vastly strengthened materials. Computational studies can offer the possibility of carrying out simulations of material properties at both larger length scales and longer times than direct atomistic calculations. The study has conducted theoretical modeling and experimental testing to investigate nanoscale mechanisms related to material strength and interfacial performance. Various computational algorithms in nanomechanics including energy minimization, molecular dynamics and hybrid approaches that mix atomistic and continuum methods to bridge the length and time scales have been used to thoroughly study the deformation and strengthening mechanisms. Our study has also performed experiments including depth-sensing indentation technique andin-situpico-indentation to characterize the nanomechanisms related to material strength and tribological performance. In this project, we have developed the innovative mutil-scale algorithms in the area of nanomechanics. These approaches were used to studies the defect effect on the mechanical properties of thin film, mechanical properties of nanotubes, and tribological phenomena at nanoscale interfaces.
Finite Element Analyses of Extrusion with a Two Stage Die and Manufacturing of Gradient Micro-Structures
Authors: Hwang Yeong-Maw , Alexandrov Sergei , Jeng Yeau Ren , Huang Tze Hui , Naimark Oleg Borisovich
Published: November 2012

This paper aims to manufacture aluminum alloy metals with gradient micro-structures using hot extrusion process. The extrusion die is designed to have a straight channel part combined with a conical part. Materials pushed through this specially-designed die generate a non-uniform velocity distribution at cross sections inside the die and result in different strain and strain rate distributions. Accordingly, a gradient microstructure product can be obtained. At first, temperature, effective strain, and effective strain rate distributions at the die exit are discussed for different inclination angles in the conical die using the finite element analysis. Then, hot extrusion experiments are conducted to obtain aluminum alloy products with gradient micro-structures. The effects of the inclination angle on the grain size distribution at cross sections of the products are also discussed.
A Correlation between the Magnetic Behaviour and Damage of Metal Materials under Plastic Deformations
Authors: Gorkunov E.S.
Published: November 2012

The effect of plastic tensile deformation on changes in density and magnetic behaviour has been studied on low-carbon steel specimens under hydrostatic pressure of 0.1 to 500 MPa in a test chamber. It has been shown that the parameters of minor magnetic hysteresis loops can be used to estimate the amount of plastic strain and the strain-related structural damage of metal.
Examination of the Microstructure of Findings from Bronze Age
Authors: Pflischl Klára , Barkóczy Péter , Kovács Árpád , Czibik Ádám
Published: November 2012

Examination of three findings (a hammer axe from the Bronze Age, a bracelet of Aunjetitz, and a pick with neck-disc) from the Bronze Age was performed by the Research Group on Archeometallurgy of the University of Miskolc. The chemical composition, the phase constituents and the microstructure of the findings was examined. Beyond the common analysis of chemical composition features of the microstructure was examined, and data from the production process were collected (metallurgical processes, casting, cold and hot deformation). It was stated that the bracelet is produced by casting; the hammer axe and the pick give the final shapes by hammering after casting. Not only the annealed and hammered microstructure, but the casted primer microstructures were analyzed by application of different etching techniques. The chemical compositions and structures of inclusions were analyzed by SEM-EDS technique. The amount, shape and ordering was examined of the inclusion on micrographs. The aforementioned results gives a detailed study of producing process of the findings which was compared the newest technological knowledge.
Thermal Induced Phase Transformations in Duplex Stainless Steel
Authors: Mészáros István
Published: November 2012

The aim of this work is to study the microstructural changes in 2507 type superduplex stainless steel due to heat treatments. Two series of specimens were studied. The first series were heat treated isothermally at 800 °C for different times up to 42 minutes. The second ones were heat treated isochronically for 20 minutes in the temperature range of 720-900 °C. The microstuctural changes were investigated by metallography and by magnetic tests. The first magnetization curves and the saturation magnetization loops were measured by a double yoke DC magnetometer.
Nitrocarburising of Low Alloyed Case Hardening Steels Applying Three Different Temperatures
Authors: Biró Andrea Szilágyi , Tisza Miklós
Published: November 2012

Nitriding is one of the most important processes among surface technologies. The purpose of this process is to produce a wear resistant layer on the surface of components, to meet the complex requirements. Ferritic nitrocarburising was carried out at three different temperatures (520, 570 and 620°C) and with five different process times, to study the effects on process parameters . The experiments proved that in case of ferritic nitrocarburising, it is possible to produce larger diffusion zone during the same time. If the temperature is higher than the iron-nitrogen eutectoid temperature, the diffusion is deeper, but we should consider the softening of the core.
The Relation between the Surface Tension and the Bulk Properties of Diluted Silver Based Melts
Authors: Weltsch Zoltán , Lovas Antal
Published: November 2012

The wettability of graphite by the Ag-M based (M: Cd, In Sn, Sb) liquid alloys was measured using the sessile drop method at a temperature interval of 1273 1473 K. Except the Ag-Cd alloys, the investigated systems exhibit worse wettability than that of Ag (host metal) melt, within the investigated temperature range. The compositional and concentration dependence of contact angle (Θ) exhibits similar trends, than the residual resistivity change measured in the same alloys in solid state. Nevertheless, the measured segregation effects during the solidification are not significant.
Studying of Microstructural Effects of Surface Rolling in Materials of Railway-Car Wheel Axles by EBSD and Non-Destructive Magnetic Evaluation
Authors: Berecz Tibor , Mészáros István
Published: November 2012

Surface rolling is a cold-working technology for hardening the surface of components made from steel or ductile cast iron. This process is able to increase the hardness of surfaces and to improve fatigue properties, so it is usually used on the axles (shafts) of railway-car wheels. In this paper the influence of surface strengthening technology on the microstructure of the material of railway car wheel axles is studied by Vickers microindentation hardness test, optical microscopy, scanning electron microscopy (SEM) automated EBSD (Electron Backscatter Diffraction) and non-destructive magnetic evaluation.
Quantitative Metallography of Microstructure of Austenitic and Transformed States in Microalloyed Steels
Authors: Kardos Ibolya , Verő Balázs , Bereczki Péter
Published: November 2012

In the course of our experiments we have developed an etching process by means of which the austenite grains formed subsequent to roughing can be made visible in the case of Grade X80Mo0 and X80Mo2 microalloyed steels. The definition of the size and elongation of the grains enables the production process to be optimized and the microstructure features associated with the desired mechanical properties attained thereby.
Stent Fracture Analysis
Authors: Kertész Anna , Bognár Eszter , Micsik Tamás , Dévényi László
Published: November 2012

Almost half of the deaths in the European Union are a consequence of cardiovascular diseases, which can be reduced significantly by dietary changes, physical activity and suitable medications. Since changing lifestyle and healthcare is a slow process, a more efficient and quicker solution is to improve medical devices. Stents are mesh-structured implants, which support arterial wall and allow dilatation of the narrowed section. The material analyses of stents removed from cadavers allow further development and improvement of these special devices.
Despite of the widespread application of stents, not many publications deal with their technical analysis and most of them have a medical approach. This paper presents a technical analysis of three stents removed from cadavers. The results may promote the evaluation of the stent development. Until now these kind of feedback was missing from the improvement cycle.
Development of Electrically Conductive Polymers
Authors: Király Anett , Ronkay Ferenc
Published: November 2012

Conducting composites based on graphite, carbon black and polypropylene have been prepared and the effect of composition on the flexural modulus and electrical conductivity has been studied. The conductivity of polymers containing only one kind of filler did not increase significantly, their modulus of elasticity was the highest for graphite filling, and the lowest for nanotube filling. The conductivity of dual filler hybrids increased significantly due to the synergetic interaction between the two fillers. At lower graphite contents, because of the better dispersion of graphite, the material became more flexible, but at higher carbon black contents the stiffness increased significantly. In the case of triple filler hybrids, if keeping the graphite content at a certain level and varying only the carbon black/nanotube ratio, the conductivity and the flexural modulus varied according to exponential and linear rules respectively.
Intercrystalline Cracking of Austenitic Steel during Brazing
Authors: Májlinger Kornél , Szabó Péter János
Published: November 2012

During brazing of austenitic stainless steel with copper based brazing material a common failure occurs, namely that the brazing material solutes along grain boundaries, which look like cracks. This unfortunate effect occurred when AISI 304 steel is brazed. To avoid this unwanted effect since the cracks propagate mainly on high angle grain boundaries our goal was to enhance the number of special coincident site lattice type grain boundaries with thermomechanical treatment. Experiments were performed for 1, 48 and 72 hour heat treatments at different level of cold rolled materials. After the thermomechanical treatment significant decrease in the crack size was found in depth and width, respectively. The grain boundaries were investigated on electro polished samples in an electron microscope with electron backscattered diffraction technique. The brazing was made with Boehler SG-CuSi3 brazing material.
Abrasive Wear Testing of Si3N4 Ceramic Composites
Authors: Koncsik Zsuzsanna , Maros M.B. , Kuzsella László
Published: November 2012

Silicon nitride-based nanocomposites with different quantities (0, 1, 2 wt%) of multiwall carbon nanotubes (MWCNT) have been prepared by isostatic pressing. Abrasive tribological tests were carried out at room temperature in ambient atmosphere with various types of abrasives (different material and grain size) and lubricants respectively. Worn surfaces were characterized by surface roughness parameters, surface topography and scanning electron microscope while wear rate was featured by the worn mass. Results indicate that increase in MWCNT-content leads to decrease of abrasive wear resistance which is proven by increase of Ra and Rz roughness parameters and SEM-analyses of the abrasive worn surfaces.
Production and Examination of Colour-Galvanized Steel Test Sheets by Modern Analytical Methods
Authors: Lévai Gábor , Godzsák Melinda , Ender Alfred , Márkus Róbert , Török Tamas I.
Published: November 2012

Nowadays the most commonly used baths for hot-dip galvanizing are the ones which contain about 0.1 ... 0.2% of aluminium. Besides aluminium, the effects of the addition of small quantities of titanium (up to 0.0005%) to the bath have recently been studied in detail by Culcasi et al. [2]. They proved the strong impact of adding a small amount of titanium on the development of the iron-zinc layer, which influences primarily the building up of the intermetallic compound film Fe2Al5 on the surface of the steel piece in contact with the molten zinc. This aluminium-alloyed hot-dip bath with titanium usually does not form a nicely coloured surface [. Therefore, our experiments were limited to test only the effect of adding titanium to the molten zinc which contains only traces of aluminium in order to study the impact of titanium on surface colouring using GD-OES spectrometry.
Production of Thermoplastic Matrix Towpregs for Highly Demanding and Cost-Effective Commercial Applications
Authors: Nunes João Pedro , Silva Joao F.
Published: November 2012

This work reviews the work made in last years to produce thermoplastic matrix towpregs to highly demanding and more cost-effective commercial applications using a powder coating technology developed in Portugal by Minho and Porto Universities. Different thermoplastic matrices and continuous fibre reinforcements were used in the towpregs produced for highly demanding markets (e.g., carbon fibre reinforced PrimospireÒ towpreg) and for more commercial applications (e.g., glass fibre reinforced polypropylene and polyvinyl chloride towpregs). The relevant processing parameters, such as, fibre pull-speed and furnace temperature were varied to determine their influence on the polymer mass fraction obtained in the studied raw materials. Several technologies were also developed and used (compression moulding, pultrusion and filament winding) to process composite parts with adequate properties for the envisaged markets at compatible production rates. The obtained results lead us to conclude that the studied thermoplastic matrix towpregs and their processed composite parts have very interesting conditions for being applied both in highly advanced and cost-effective markets.
Nanosecond Near-Infrared Laser Discoloration of Gamma Irradiated Silicate Glasses
Authors: Silva Catarina , Coelho João M.P. , Ruivo Andreia , Botelho Maria Luísa , de Matos António Pires
Published: November 2012

Due to its non-crystalline, amorphous structure, glass is particularly susceptible to radiation-induced coloration/discoloration. Oxide glasses reveal a variety of colors depending upon their composition when exposed to high energy radiations such as gamma and X-rays, and the colors induced have been explained in terms of the formation of color centers. These effects can be reversed by heating or upon exposure to light at wavelengths corresponding to the absorption region of the color centers, a process known as discoloration. Laser can be an efficient process for accomplish this in a localized manner. The aim of this work was to study local discoloration of gamma radiation exposed silicate glasses by application of a nanosecond pulses infrared laser beam. Experimental results validated a numerical model and proved the viability of local laser discoloration of gamma ray irradiated silicate glasses. Although there has been much work focusing the creation and destruction of color centers in glasses, to the best of our knowledge, the application of infrared laser radiation in the local annealing of gamma irradiated glasses was for the first time explored.
Wetting Oxide and Non-Oxide Ceramics with Active Metals
Authors: Martinelli Antonio E. , Nascimento Rubens M. , de Andrade Tarcisio E. , Buschinelli Augusto J.A. , Pereira Jorge C.L.B.S , Gross Sonja M. , Reisgen Uwe
Published: November 2012

Brazing has been used to join structural ceramics to devices mostly manufactured using metal alloys. Direct brazing employs filler alloys containing an active metal, usually Ti, to wet the ceramic substrate. However, the cost of active filler alloys is usually around 10 times higher than that of active metal-free alloys. In addition, the concentration of the active metal is usually small, thus limiting the formation of a continuous reaction layer onto the entire ceramic surface. Alternatively, ceramic substrates can be previously metallized and fully coated with an active element to be wetted by conventional active metal free filler alloys. Ceramics can be metallized by different techniques, including mechanical metallization. It consists in frictioning an active metal bit, traditionally made of Ti, against the ceramic. Conventional tools can be used and the method is easily automated to large batches. Moreover, contrary to other techniques, mechanical metallization is carried out at room temperature and no hazardous fluxing agents are used. Although Ti is traditionally employed in mechanical metallization, the technique is not limited to it. Indeed, the exclusive use of Ti univocally determines the microstructure of the resulting ceramic/titanium and titanium/filler alloy interfaces. Although the formation of a reaction layer is beneficial to the mechanical strength and reliability of brazed components, precipitation zones and intermetallics embrittle the joints and affect their mechanical behavior. Therefore, the objective of the present study was to assess the potential use of alternative active metals in the mechanical metallization of structural oxide (alumina e zirconia) and non-oxide (silicon carbide and nitride) ceramics. Ceramic substrates were mechanically metallized using Ti, Ta, Nb and Zircaloy 2 (mainly 98.25 % Zr and 1.45% Sn). These metals are abundant in Brazil and therefore strategically important. The wettability of the metallized surfaces was evaluated using three commercially available active metal free filler alloys: VH 780 (Ag-28 Cu), VH 950 (Au – 18 Ni) and SCP 2 (Ag – 31.5 Cu – 10 Pd). The results showed that it was possible to mechanically metallize all ceramic surfaces with the active metals investigated. The wetting tests revealed limited potential for the use of Nb and Ta. On the other hand Zircaloy 2 was successfully employed as active metal for both oxide and non oxide ceramics.
Carbon Deposition on Beryllium Substrates and Subsequent Delamination
Authors: Mateus Rodrigo , Carvalho Patricia A. , Franco Nuno , Alves Luís C. , Fonseca Micaela , Alves Eduardo
Published: November 2012

Beryllium and carbon are foreseen as materials for plasma facing components of future fusion devices. Erosion, re-deposition and thermal annealing events arising from heat-loads during reactor operation will produce mixed material layers and compounds on the plasma facing surfaces, leading to changes in the material properties. In order to mimic the erosion/deposition and compound formation processes, carbon layers have been evaporated onto beryllium plates and annealed in the 373 to 1073 K range for 90 min. Ion beam measurements revealed a smooth beryllium and carbon interdiffusion at the samples interface up to 773 K. A carbide formation reaction front became apparent for higher temperatures in scanning electron microscopy observations, with the volume fraction of Be2C crystals resulting also evident in X-ray diffraction patterns. The annealing route induced delamination of large surface areas of the samples through telephone cords blistering, attributed to strain energy release. At 973 and 1073 K, cracking occurred preferentially along the blisters boundaries and evolved in time, leading to their final removal. This fracture behaviour seems caused by the different thermal expansion coefficients of the phases. The superficial films remain unchanged at lower temperatures. The results prove that the compound formation promotes by itself the occurrence of dust emission events in tokamaks.
Effect of the Injection Moulding Processing Conditions on Biopolymers Final Properties
Authors: Teixeira Pedro , Pontes António , Henriques Elsa
Published: November 2012

This research work intended to study the effect of the main injection moulding parameters in the final properties of biopolymers mouldings. An experimental procedure was carried out in which four biopolymers containing different composition percentages of poly-lactic acid (PLA) and plasticized starch (PLS) were compared with polypropylene (PP). For each material the effect of the processing conditions (mould temperature, injection temperature and holding pressure) on the final properties was discussed and the possibility of using biopolymers as a substitute of PP in household utility products was evaluated.
Localized Electrografting of Diazonium Salts in the SECM Environment
Authors: Charlier Julienne , Grisotto Federico , Ghorbal Achraf , Goyer Cédric , Palacin Serge
Published: November 2012

Electronic, biology and chemical biology have pushed the scientists to develop new techniques to graft locally organic molecules on surfaces. The objective of the work was to develop a cheap and lithography-free technique by combining Scanning Electrochemical Microscopy (SECM) and electrografting processes in view of tuning locally chemical and physical surface properties on initially homogeneous substrates. The electrografting process was carried out with diazonium salts Plots, lines or more complex 2D-patterns have been “imprinted” on conducting substrates.
Production and Characterization of Composite Material Useful as a Protective Barrier in Electronic Applications
Authors: Lima Roberto R. , Hernandez Leonardo F. , Pecoraro Edsion , Rosim-Fachini Estevão , da Silva Maria L.P.
Published: November 2012

This work describes the production and characterization of a selective membrane useful for electronic devices. The membrane was a composite made by a thin film of plasma-polymerized HFE (methyl nonafluoro(iso)butyl ether) immersed in plasma-polymerized HMDS (hexamethyldisilazane) film, a third phase being 5 µm starch particles included in this matrix. The film was deposited on silicon substrates and its physical, chemical and adsorption characteristics were determined. Infrared and x-ray photoelectron spectroscopy analyses showed fluorine and carboxyl groups on the bulk and the surface, respectively. SEM results indicate the film is conformal even if starch is present. Optical microscopy analysis showed good resistance toward acid and base solutions. Quartz crystal microbalance indicated adsorption of polar organic compounds on ppm range. This thin film is environment-friendly and can be used as a protective layer or in electronic devices due to adsorption of volatile organic compounds.
Vanadium Oxide Thin Films Synthesized by Reactive Ion Beam Sputter Deposition: Influence of Processing Parameters
Authors: Batista Carlos , Ribeiro Ricardo M. , Teixeira Vasco
Published: November 2012

Vanadium oxide thin films were deposited by reactive ion beam sputtering deposition onto glass substrates. The films were prepared by sputtering from a metallic vanadium target with an argon+oxygen ion beam in vacuum. Different processing conditions were evaluated with focus in obtaining monoclinic VO2(M) phase, which is known to exhibit a semiconducting-metal phase transition near room temperature. X-ray diffractometry (XRD) analyses revealed amorphous films for temperatures below 500°C. In crystalline films, the co-existence of VO2(M) with other phases was suppressed by pre-depositing a very thin metallic vanadium seeding layer which showed to promote the formation of single phase VO2(M) films. The VO2(M) films showed clearly the distinctive optical modulation behavior at the near-infrared range when going through the phase transition. The temperature dependence of sheet resistance supports the optical analyses revealing an evident semiconducting-metal behavior change up to over 2 orders of magnitude.
Creep Behavior of Lignocellulosic-Fiber/Polypropylene Matrix Composites
Authors: d'Almeida José R.M. , da Silva Anderson L.L.
Published: November 2012

Lignocellulosic residues obtained after the sustainable harvesting of heart of palm from pejibaye (Bactris gasipaes) palms were managed to produce chopped fibers. These fibers can be used to manufacture agglomerated panels and also as reinforcement in polymer-matrix composites. Polypropylene (PP) is a convenient polymer to be loaded with these residues due to its large applications, including under-the-bonnet applications by the automotive industry. PP-pejibaye composites with 10wt% of fiber mass fraction were manufactured and their creep behavior was studied. The experimental results were suitably described analyzing the variation of the creep modulus fitting the experimental data points to the three-element model where the Kelvin-Voigt element is attached to an independent spring. The results obtained show that the incorporation of the chopped pejibaye fibers to not affect the creep performance of the composite. This behavior is very promising, since untreated fibers were used, meaning that the use of expensive and many times environmentally detrimental fiber surface chemical treatments can be avoided.
Mechanical Behavior of Curauá Treated Fiber-Reinforced Sand
Authors: Santiago Gislene A. , Botaro Vagner R. , Consoli Nilo C. , Festugato Lucas
Published: November 2012

The inclusion of artificial fibers in the soil has been studied by many researchers during the last years and has shown efficient by improving the mechanical properties of the soil. This kind of association results in an interesting composite material for geotechnical engineering applications. In this context, the aim of this research is to analyze the behavior of a granular soil reinforced with random inclusion of short and curauá fibers superficially treated with recycled EPS (expanded polystyrene). The non-reinforced and reinforced soil samples were subjected to triaxial tests. Through the obtained results, it was observed that the addition of randomly distributed natural treated fibers presented significant improvements on the mechanical properties of this soil. The polymer used was shown quite applicable to the proposed analysis, promoting the decrease of the water absorption of the vegetal fibers.
Osteoconductive Nanocomposite Materials for Bone Regeneration
Authors: Stodolak-Zych Ewa , Szumera Magdalena , Blazewicz Marta
Published: November 2012

Bone defect is one of the most important problem in orthopaedic therapy in which application of a biomaterial filling is necessary. Such material should be biocompatible, osteoconductive and porous as well as bioactive and compatible with the bone tissue. Subject of the work was investigations on nanocomposite membrane materials which consisted on synthetic polymer – poly-e-caprolactone (PCL) matrix and ceramic nanoparticles; tricalcium phosphate (TCP) and silica (SiO2) as a nano-filler. The nanocomposite membrane materials were produced by two-step dispersion of the nanoparticles in the biopolymer matrix. Characteristic of nanoparticles were made using transmission electron microscope (TEM), distribution of nanoparticles size (DLS) and specific surface area (BET). The morphology of nanocomposites and homogenous distribution of nanoadditives were made using scanning electron microscope with EDS analysis. Introduction of the nanofillers into the polymer matrix was monitored by thermal analysis method (TG-DCS). It was shown that the TCP nanoparticles affected stronger pore size and distribution but also the polymer structure (crystallity, physicochemical properties of the surface). Treatment of the nanocomposite samples in the simulated body fluid (SBF) induced some changes on the surface of the material containing bioactive ceramic nanoparticles. The results of the tests with SBF showed that the material is able to produce apatite structure on its surface (EDS analysis)
Study of the High Energy Milling Effect on Composite Alloy of EUROFER97 Steel Reinforced with Niobium Carbide
Authors: Silva Jr José F. , Umbelino Gomes Uilame , de Almeida Edalmy Oliveira , Silva Ariadne  de Souza , Pinto G.B. , de Souza Carlson P.
Published: November 2012

Several kinds of alloys Ni-based, Fe-based and Al-based oxide dispersion strengthened (ODS) and carbide dispersion strengthened (CDS) have been produced through mechanical alloying. Precipitation-strengthened or dispersion-strengthened steels are a kind of high strengthened steel using fine precipitation or dispersion of carbides. This work present a study of EUROFER97 steel powder reinforced with 3%wt of niobium carbide. The starting materials were wet-milled in a high-energy planetary ball mill for several times up to 5 hours. The ratio of ball to powder weight was 15:1. The milled powders were characterized by SEM, XRD, EDX and laser scattering. The results are presented on base of a microstructure analysis of composite particles of steel-carbide as a function of milling time.
Evaluation of Pozzolanic Reactivity of Artificial Pozzolans
Authors: Pontes Jorge , Santos Silva António , Faria Paulina
Published: November 2012

Pozzolanicity is a very interesting issue regarding building materials, as a way to enhance mortars and concrete durability. This property results from the reaction between calcium hydroxide and silica and alumina based materials. Different types of natural and artificial pozzolans show pozzolanic activities that differ depending on the materials characteristics. Therefore, the study of this property, namely its reactivity with calcium hydroxide, reveals itself to be important in the selection of the type and content of these materials. This paper presents the results of several pozzolanic reactivity methods, applied to different pozzolanic materials. The selected pozzolanic methods include Chapelle method, Fratinni method and Strength Activity Index. Those tests have been applied to evaluate the reactivity of various kinds of artificial pozzolans. The correlation between the test methods are presented and discussed.
Evaluation of the Damages Occurred During the Installation of Non-Woven Geotextiles
Authors: Carneiro José Ricardo , Morais Luís Miguel , Moreira Simão Pedro , Lopes M. Lurdes
Published: November 2012

The geotextiles may suffer damages during installation, often causing significant changes in their properties. This paper evaluates the effect of the installation process on the mechanical and hydraulic properties of non-woven geotextiles. The geotextiles were damaged in laboratory (using a standardized procedure) with different granular materials. The changes occurred in the properties of the geotextiles were evaluated by mechanical and hydraulic tests.
Fracture Toughness of Dense Cordierite: Sintering Cycle Effect
Authors: Oliveira Fernando A. Costa , Fernandes José Cruz , Schmitt Julien , Rosa Luis Guerra , Dias Diamantino
Published: November 2012

The aim of this work was to analyse the fracture behaviour of commercial dense cordierite bodies sintered in an electrical furnace in static air at 1250°C, 1275°C and 1300°C for 30 min using different cycling schedules in order to obtain tougher materials at minimum energy costs. Using a stereomicroscope and a scanning electron microscope, fracture surfaces of as-sintered bars tested under four-point bending at room temperature were examined at different magnification levels in order to determine the origin of fracture in each sintered bar. Once the fracture origin was identified, it was possible to measure its size, and based on ASTM C1322-96a standard, we were able to estimate the fracture toughness of the sintered parts. Fracture toughness was found to increase with increasing of sintering temperature from 1.8 MPa∙m½ to 3.1 MPa∙m½ by rising the temperature from 1250°C to 1300°C as the fracture process is strongly influenced by the microstructure of the material.
The Influence of the PCL-T Concentration in PLDLA Membrane
Authors: Duarte Marcia Adriana Tomaz , Coppini Larissa , Lucchesi C. , Macedo Marcelo , Duek Eliana Aparecida De Rezende
Published: November 2012

The use of bioabsorbable polymers in biomedical application has increased greatly in recent years due to their good compatibility and bio-reabsorption. To obtain a polymeric material suitable for medical applications, the obtention and characterization of copolymer poly (L-co-DL lactic acid) (PLDLA) with the addition of poly (caprolactone triol) (PCL-T) was studied. PLDLA/PCL-T membranes were prepared by solvent casting in the 100/0, 90/10 and 70/30 (w/w) compositions. The membranes were characterized by Atomic Force Microscopy (AFM), Cellular Adhesion and Energy Dispersed Spectroscopy (EDS). Using MFA it was observed that an addition of PCL-T contributes to rough morphology and greater porosity. Increased cell adhesion on 90/10 and 70/30 membranes compared to 100/0 composition and controls was observed. From these results, it was observed that PCL-T improved cellular adhesion of the PLDLA membrane when compared to membranes without PCL-T. The PLDLA/PCL-T membrane is indicated for use in medical devices which do not require long implantation time, such as support for cell culture, dressings for skin ulceration and guided regeneration in periodontics.