bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Characterization of Intermetallic NiTi Coatings Obtained by Thermal Spray Technologies
Authors: Guilemany J.M. , Cinca Nuria , Dosta Sergi , Fernández Javier
Published: January 2010

NiTi alloy is known to have a potential interest specially for its superelasticity and shape memory effect (SME). Most of the research undergone up to now investigates such properties in bulk materials. The few works related to overlays (coatings) use magnetron sputtering for thin films and Vacuum Plasma Spray (VPS) for thicker coatings. VPS is the mostly used thermal spray technique regarding the Ti oxidation problems which considerably affect the so desired SME. The present work compares the microstructure of VPS NiTi coatings with those of High Velocity Oxygen Fuel HVOF and a liquid cooling device coupled to a Atmosphere Plasma Spraying (APS+Q), with optimized spraying conditions trying to minimize Ti oxidation. Apart from their characterization by Scanning Electron Microscopy, the main purpose is to further study how particles are retained within the coating so that Transmission Electron Microscopy is also employed. This has allowed the observation of amorphous and nanocrystalline phases as well as to the change from cubic B2 NiTi lattice to metastable lattices.
Finite Element Modelling of Ni-Ti Shape Memory Alloys
Authors: Silva Daniel P.L. , Martins Rui F. , Braz Fernandes Francisco Manuel
Published: January 2010

Shape Memory Alloys (SMA) belong to a special group of metallic materials, which are capable of returning to a pre-determined shape or size when submitted to an appropriate thermal cycle. Generally, these alloys can be easily deformed at a relatively low temperature and, when exposed to a higher temperature, can return to their original shape, that is, to the shape they had before the mechanical deformation was imposed. Although there are a vast variety of materials that can achieve the Shape Memory Alloy effect, only those in which it is possible to have a significant recovery of the deformation – or in which it is possible to generate an important force during the shape's change – can be functionally and commercially interesting. The Ni-Ti alloys, which are one type of SMA, were numerically modelled through Ansys software and these studies are presented in this paper. These special alloys, among many others applications, could be used, for instance, in the form of wires (fibres), in smart composites, as actuators to recover partially the structural integrity of a matrix with cracks. Some 2D and 3D cracked plates were modelled through finite elements and the Stress Intensity Factor, in Mode I, KI, at each crack tip, was determined and compared with the result obtained through the analytical solution. Wires of Ni-Ti, with very small diameters and with different length/diameter ratios, were modelled and mechanical load cycles, at different temperatures, were applied and the material’s behaviour/response was obtained. The thermo-mechanical behaviour of the material was defined based on results published by other authors. Also, a composite material with Ni-Ti fibres embedded was modelled and a mechanical load was applied to it.
Modelling of Low Cycle Fatigue Initiation of 316LN Based on Crystalline Plasticity and Geometrically Necessary Dislocations
Authors: Schwartz Julien , Fandeur Olivier , Rey Colette
Published: January 2010

Initiation of intragranular cracks during low cycle fatigue is governed by complex microstructural phenomena. Depending on the loading amplitude, number of cycles, lattice structure and/or chemical composition, different dislocation structures (veins, cells or Persistent Slip Bands) develop and induce heterogeneous localization of strain and stress in the material. For a better comprehension of crack initiation in 316LN stainless steel, low cycle fatigue tests and numerical simulations were performed. Specimens of 316LN steel with polished shallow notch were cycled with constant loading amplitude and Persistant Slip Bands were identified by SEM observations. In parallel, numerical studies were carried out with the model of cristalline plasticity CristalECP. Simulations were performed on 3D polycristalline aggregates of 316LN steel with the finite elements code Abaqus® and Cast3m®. The results show a heterogeneous localization of strain in bands. For a more precise computation of the mechanical fields and to introdruce a grain size effect, Geometrically Necessary Dislocations were introduced in CristalECP. The GNDs are directly related and computed with the lattice curvature.
Analytical Solution for Free Vibration of Sandwich Structures with a Functionally Graded Syntactic Foam Core
Authors: Rahmani O. , Malekzadeh K. , Mohammad S. , Khalili R.
Published: January 2010

In this study, after a brief introduction to recent investigations on syntactic foam, the free vibration of sandwich structures with syntactic foam as a functionally graded flexible core based on higher order sandwich panel theory is investigated. The formulation uses the classical beam theory for the face sheets and an elasticity theory for the functionally graded core. In the following a numerical study of free vibration of a simply-supported sandwich beam is carried out and corresponding eigenmodes are obtained.
Fatigue Crack Growth Modeling in Stiffened Panels Considering Residual Stress Effects
Authors: Tavares Sérgio M.O. , Richter-Trummer Valentin , Moreira Pedro Miguel Guimarães Pires , de Castro Paulo Manuel Salgado Tavares
Published: January 2010

A model to determine Stress Intensity Factors (SIFs) and simulate the fatigue crack growth in stiffened structures taking into consideration residual stresses is presented in this paper. The stress field required to estimate the SIF was calculated using the Finite Element Method (FEM) considering the residual stress as an initial condition. The residual stress field redistribution as a function of crack growth is taken into account using the Abaqus software. Specimens without and with residual stresses, resulting from different welding techniques, were considered for the present study. The residual stress fields can significantly deteriorate or improve the fatigue life of the structure, depending upon the location of the initial crack; consequently these effects should be analyzed and modelled in order to better understand the consequences of the application of the considered manufacturing processes.
Application of the Dang Van Fatigue Criterion to the Rail/Wheel Contact Problem
Authors: Peixoto D.F.C. , Ferreira L.A.A. , de Castro Paulo Manuel Salgado Tavares
Published: January 2010

Great interest is dedicated to the wheel/rail contact problem, in particular as a result of some accidents worldwide and also in Portugal. In the present work a three dimensional finite element analysis of the wheel/ rail contact problem was performed using the software ABAQUS. A preliminary study on simpler geometries was carried out, in order to identify the solution strategies giving more accurate solutions. The influence of mesh refinement, friction coefficient, and numerical techniques as Lagrange and penalty functions were analysed in the simpler cases of contact of two cylinders along a generatrix, and the contact of a cylinder and a rigid plane. The corresponding Hertz solutions were programmed using MATLAB in order to compare with the finite element analyses. The numerical procedures giving better results were later applied to the wheel/rail contact problem, using standard rail and wheels profiles used by the Portuguese Railways company (CP). The influence of small geometry variations on the stress analysis results was then studied, and the study of initiation of defects using the Dang Van fatigue criterion was performed.
Kinetics of Defect-Induced Cation Redistribution in (CoxMg1-x)2SiO4 Olivines
Authors: Shi Jian Min , Becker Klaus Dieter
Published: January 2010

Olivines are high-temperature materials in which divalent cations occupy two non-equivalent octahedral sites, M1 and M2. Cation redistribution processes between the M1 and M2 sites are fundamental steps for cation diffusion in olivines. We have performed temperature-jump relaxation experiments on both M1 and M2 sites in (CoxMg1-x)2SiO4 olivines by monitoring the time evolution of optical absorption of Co2+ ions on M1 and M2 sites. Results derived from the modeling of the experimental relaxation curves show that the kinetics of cation exchange is strongly temperature- and composition-dependent and that relaxation times for cation redistribution at about 1000 oC are less than 1 s. The activation energy of cation redistribution is about 2.0 eV.
A Numerical Study on the Mechanical Behaviour of Hard Coatings with Ductile Interlayers under Depth-Sensing Indentation
Authors: Sakharova Nataliya A. , Fernandes José Valdemar , Oliveira Marta C. , Antunes Jorge M.
Published: January 2010

In the present study, numerical simulations of nanohardness tests of titanium aluminium nitride (TiAlN) hard coatings with titanium and aluminium ductile interlayers were performed in order to determine the influence of interlayers of ductile metals on the overall mechanical properties of multilayer coatings. The investigation was designed to determine the role of ductile interlayers in altering the hardness value and the Young´s modulus of the multilayer coating as a whole, in comparison with a monolayer TiAlN hard coating, for the cases of composites with different numbers and thicknesses of interlayers.
An Experimental Characterization of Cork Storage Modulus for Cork-Steel Applications in Vibration Attenuation
Authors: Policarpo Hugo , Neves M.M. , Ribeiro A.M.R.
Published: January 2010

This study presents an experimental characterization of cork storage modulus used to model the vibration response of bars built using alternate layers of cork and steel. In the experimental setup, the specimen was suspended from a fixed support by two thin lines while a shaker was suspended from a mobile support by metallic chains. The shaker was connected to the bar specimen through a force transducer imposing a dynamical deformation that propagates through the specimen. An accelerometer in the opposite extremity of the bar measures the corresponding vibration response and the cork storage modulus is then obtained from the first peak of this frequency response. The proposed methodology successfully characterized the storage modulus of the cork material used in the multilaminated periodic bars. The results obtained illustrate a satisfactory correlation between
New Construction Materials: Calcined Paper Sludges as Active Additions
Authors: Frías M. , Rodríguez Olga , Sánchez de Rojas M.I. , Ferreiro S. , Nebreda B. , Olmeda Javier
Published: January 2010

This paper shows the possibility of reutilize paper sludge waste as supplementary cementing material for the cement manufacture. This industrial waste consists essentially of a mixture of organic matter (30%) and inorganic compound, such as calcite and clay minerals. The raw paper sludge does not present pozolanic properties, but once calcined at 650°C during 2 hours, exhibits a good pozolanic activity. Calcined paper sludge was used as partial Portland cement replacements of 0 and 10%. It was a sligth increment in compressive strength for 10 % of substitution from 7 days on. Furthermore, calcined paper sludge reduces the initial and final setting times of cement paste.
The White Cement Behaviour with Different Materials Addition Submitted to UltraViolet Light Exposure
Authors: Rodríguez Olga , Sánchez de Rojas M.I. , Frías M. , Costa A.R.
Published: January 2010

The building materials used as a coating on the walls are exposed at different conditions of the weather for long periods of time, reason why is very important to determine the effects of sunlight, heat, humidity and other effects of climate change in the colour and the properties of these materials. In this work was carried out a study on the behaviour of colour and gloss of white cement with some different industrial waste additions submitted to ultra-violet light exposure. The addition of the different materials employed in this work does not modify lightness or chromatic coordinates after the exposure at ultraviolet light, however reduces significantly the gloss of the samples, including white Portland cement.
Nucleation of Portlandite Clusters in Cement Paste at Very Early Stage of Hydration
Authors: Demo Pavel , Sveshnikov Alexej , Hošková Šárka , Tichá Petra , Kožíšek Zdeněk
Published: January 2010

A very early stage of cement paste hydration is studied at microscopic level of description. Within context of nucleation theory the critical (and, thus, growable) size of clusters of calcium hydroxide (so-called portlandite) is estimated for chosen water to cement ratios at given temperature. Furthermore, also the barrier of portlandite nulceation is determined. It is shown that these static characteristics of process are practically unchanged contrary to number density of portlandite critical clusters formed in unit volume of mixture per unit time.
Influence of Surface Area on the Flowability Behaviour of Self-Flow Refractory Castables
Authors: Pinto D.G. , Silva Abílio P. , Segadães Ana M. , Devezas T.C.
Published: January 2010

Alumina, with high melting point (2050°C), high hardness and mechanical strength, and excellent abrasion resistance, is one of the most common raw materials used in self-flow refractory castables (SFRC) for monolithic linings and is commercially available in various fine to coarse size classes. However, the performance of the refractory lining depends not only on the properties of its ingredients but also on its easy installation (good flowability). The aim of this work was to evaluate the relationship between the flowability index (FI) of fresh castable and the specific surface area (SSA) of its particles, which is mostly determined by the finer particles content. The results obtained showed that, by controlling the proportion between matrix and aggregate, it is possible to control the SSA of the refractory castable and find a mathematical relationship between the specific surface area and the minimum flowability index required to obtain a self-flow refractory castable. It is, thus, possible to optimize the refractory castable size composition and obtain an estimate for FI as a function of SSA. Using a minimum 45 wt.% matrix content in the castable mixture, a SSA value above 2.215 m2/g is obtained, which leads to FI ≥ 80%, the recommended value for self-flow.
The Application of Fluorescence Microscopy and Scanning Electron Microscopy in the Detection of Delayed Ettringite Formation in Concrete
Authors: Matos L. , Silva António Santos , Soares D. , Salta Manuela M. , Mirão José , Candeias António Estevao
Published: January 2010

The degradation of concrete structures caused by delayed ettringite formation (DEF) is a problem that nowadays affects many concrete structures worldwide. This pathology is due to the formation of an expansive compound – ettringite - inside the material. This is a hydrated calcium sulphoaluminate produced by the chemical reaction between sulphate ions, calcium hydroxide and alumina present in the Portland cement paste. This product, normally formed during the hydration of cement, presents an acicular morphology (needles) that can be observed by scanning electron microscopy (SEM). However, DEF can also be formed after the setting of the cement causing, in this case, a deleterious expansion of the concrete. This secondary ettringite can also be produced after an excessive heating of the concrete, caused by a high amount of cement or by the use of heat cure. SEM has been used to distinguish between expansive and non expansive ettringite based normally in morphology analysis, since the former is characterized by a compressed or compact nature where the needle shapes disappear or are welded together. Furthermore, the use of other techniques, like X-ray diffraction or micro-XRF, has been limited because the compressed or compact ettringite is badly crystallized or even amorphous and the elemental composition is similar and therefore it is difficult to detect. This article presents a methodology for the diagnosis of DEF using polished concrete thin sections and combining polarised and fluorescence light optical microscopy with SEM-EDS.
Air Lime Mortars: The Influence of Calcareous Aggregate and Filler Addition
Authors: Fragata A. , Veiga R.
Published: January 2010

Many historical buildings with renders based in air lime still exist in Portugal. These old mortars have proved to be durable and reliable materials. However, new lime mortars prepared nowadays to be used in conservation practice, often present low strength in comparison with cement mortars.
This paper presents a study of the viability of improving the performance of lime mortars through the use of different nature aggregates (Tagus River siliceous sand and crushed calcareous sand) as well as different size distributions, varying the filler contents. For that purpose a set of mortars with volumetric proportion of 1:3 (lime:aggregate), using siliceous sand from Tagus river or calcareous sand and including different volume percentages of aggregate replacement by filler (0% of incorporation, 5% of incorporation, 10% of incorporation), were prepared. An evaluation of the main characteristics of this set of mortars was made in terms of: i) hygric behaviour (water absorption by capillarity), and ii) mechanical resistance (flexural and compressive strength and elastic modulus). This study aims to assess the viability and possible advantages of using calcareous aggregate in lime mortars and to evaluate the possibility of improving characteristics through a better compaction obtained by the incorporation of different ratios of filler.
Addition of Calcareous Quarry to Bricklaying Mortars - Analysis of the Properties in Fresh State
Authors: Santos M. Luiza Lopes O. , Martinelli Antonio Eduardo , Melo M.A.F. , Melo D.M.A.
Published: January 2010

One of the major current environmental concerns is the excessive or inefficient consumption of non-renewable natural resources. The construction industry is one of the largest consumers of natural raw materials, playing an important role in the degradation of the environment. Recycling and reusing are concepts that can be effectively applied in the formulation of construction materials, especially mortars. In particular, calcareous quarry can replace, at least to some extent, the cement used in the composition of bricklaying mortars. The objective of this study was to prepare and characterize mortars containing calcareous quarry. The mortars were prepared using Portland CP II F – 32 cement, CH I hydrated lime, river sand and tap water. Different concentrations of residues, ranging from 5 to 30% were used to replace the cement. Mortars with volume ratio of 1:0.5:4.5, commonly used in bricklaying structural masonry, were evaluated. The water to cement ration was set to 1.45. The residue used was fully characterized to determine their specific mass, unitary mass, particle size distribution and morphology, and composition. The mortars were characterized both in their fresh and the results compared to those obtained from a residue-free composition. The results showed that the use of calcareous quarry partially replacing the cement did not significantly affect the performance of the mortars. Compositions containing up to 30% of calcareous quarry can be classified according to NBR 13281 (ABNT, 2005) as bricklaying mortars, and can be used by the construction industry.
Microtomography-Based Pore Structure Modelling of Geologic Materials Used as Building and Dimension Stones
Authors: Maurício António , Figueiredo Carlos , Alves Carlos , Pereira M.F. , Aires-Barros Luís , Neto J.A.N.
Published: January 2010

In this paper, an initial X-ray Computed Tomography study of sulphate salt degradation of two Portuguese Dimension Stones (“Semi-rijo” and “Mocacreme”) is presented, based on the Standard EN 12370 (1999). This study was performed using a high resolution X-ray Computed Tomography, a 3D X-ray microscopy non-destructive technique, in order to get representative digital information on 3D texture of the external surface and of the interior of visible light opaque objects for imaging and eventually measuring them, at resolutions in the m range. This will produce spatial quantitative information map on the density distribution of the scanned samples, usually associated to different mineral phases and voids’ textures constituting the natural materials. Both types of stones are also being investigated by the combined application of classic methods: Optical Microscopy, Scanning Electron Microscopy and Mercury Injection Porosimetry (MICP). Most of those classic studies use mainly traditional 2D imaging techniques, none of these being able to produce the 3D resolution details that X-ray micro-tomography enables. In order to achieve future better qualitative and quantitative integrated models, it will be important to combine its non destructive and 3D characteristics results with those of 3D MICP models obtained for such complex materials. This enables to qualitatively and/or quantitatively assess the evolution and decay potential of different phases and voids (pores + fissures) textures in different environmental interaction conditions. So, in order to set-up more efficient forecasts of their engineering properties behaviour in a given environment this study is an essential initial complementary step to compare and integrate in near future studies all the advantages and disadvantages of the application of these classic and new methods, based respectively upon visual examination of the samples’ exteriors and on micro-tomographic image models of the samples’ interiors and surfaces, to these geologic materials.
Assessment of the Flexural Behavior of Concrete Block Masonry Beams
Authors: Haach V.G. , Vasconcelos G. , Lourenço Paulo B.
Published: January 2010

This paper focus on the experimental flexural behavior of masonry beams. In the sequence of the development of a novel structural solution for reinforced masonry walls at University of Minho, different possibilities for the construction of lintels with concrete block masonry have been tested. Reinforced concrete beams with three and two hollow cell concrete blocks and with different reinforcement ratios have been built and tested in a four point loading test configuration. It was clear that horizontal bed joint reinforcement increased the ultimate flexure capacity as well as the ultimate deflection, leading to much more ductile responses. Moreover, it was also clear that a more deep analysis should be made regarding the role of the compressive strength of masonry in the parallel direction to the bed joints on the global behavior of the masonry beams.
Analysis of Strength Scaling Effect in Portuguese Limestone: Comparison between Three- and Four-Point Bending Tests
Authors: Fernandes Jorge Cruz , Pires Vera , Amaral Pedro M. , Rosa Luis Guerra
Published: January 2010

This paper presents a comparative study between 3- and 4-point bending tests applied to five Portuguese limestones. The study has been conducted on sawed limestone specimens, all showing the same surface finishing. The materials were compared for two distinct situations: i) using a 3-point flexure loading configuration in batches of materials with larger cross sectional specimen dimension (50 × 30 mm2); and ii) using a 4-point flexure loading configuration in the same batch of materials but with smaller cross sectional dimensions (30 × 25 mm2). In all situations, the materials have broken due to intrinsic volume defects. Formulae for the effective volumes and effective surfaces for rectangular beam specimens loaded in flexure were reviewed in order to analyse the strength scaling effect. The results show the applicability of the Weibull statistics to explain the differences in the results of the 3-point and 4-point bending tests, even when different cross sectional sizes are employed. Among other important remarks, in all the different limestone specimens used it was possible to confirm that the strength values determined experimentally via 3-point bending are of the same order as those estimated for the same loading configuration but via experimental data of 4-point bending tests using the Weibull strength scaling approach, even if employing a different cross-sectional dimension.
A Study on the Chloride Diffusion into Portland Limestone Cement Concrete
Authors: Tsivilis Sotiris , Asprogerakas A.
Published: January 2010

In this paper the diffusion of chloride ions through limestone cement concrete is studied. The Portland limestone cements have many benefits and the new European Standard EN 197-1 identifies 4 types of Portland limestone cement containing 6-20% limestone (types II/A-L and II/A-LL) and 21-35% limestone (types II/B-L and II/B-LL), respectively. Portland limestone cements of different fineness and limestone content (0-35% w/w) have been produced by inter-grinding clinker, gypsum and limestone. Six concrete mixtures were prepared and the Nordtest Method (accelerated chloride penetration) was applied for the determination of penetration parameters for estimating the resistance against chloride penetration into hardened concrete. The diffusion equation of Fick’s second law was used for the determination of the effective chloride transport coefficient. It is concluded that Portland limestone cement concrete indicates competitive behavior with the Portland cement concrete. Limestone content up to 15% has a positive effect on the concrete resistance against chloride penetration.
Malayaite Ceramic Pigments Prepared from Industrial Wastes: Formulation and Characterization
Authors: Ribeiro Ana , Hajjaji W. , Seabra M.P. , Labrincha J.A.
Published: January 2010

In this work chrome-tin red malayaite pigments Ca(Cr,Sn)SiO5 were obtained from industrial wastes: a marble sawing sludge, a galvanizing sludge from the Cr/Ni process and a foundry sand. The pigments were prepared using the common solid state reaction process. The influence of Cr2O3/SnO2 ratio, calcination temperature and introduced sludges compositions, on its structural stability, was investigated by X-ray diffraction coupled with SEM/EDS. Standard formulations, obtained from commercial reagents, were also prepared and characterized for sake of comparison. CIELab colour measurements and UV-Vis spectroscopy were used to evaluate the stability (thermal and chemical) and applicability of the synthesized pigments in colouring distinct ceramic matrixes fired at high temperatures (1050°C-1200°C). The pigment was added (1/20 wt. ratio) to a transparent and shining lead free glaze and to a porcelain stoneware body (1/10 wt. ratio). The incorporation of three industrial wastes, in the chrome-tin red malayaite pigment, was possible without a notorious change in terms of colouring effect allowing decreasing the synthesis temperature.
Photocatalytic Decolourisation of Orange II Aqueous Solutions by TiO2 and ZnO Active Layers Screen Printed on Ceramic Tiles
Authors: Rego Elisabete , Marcos P.S. , Marto John , Seabra M.P. , Labrincha J.A.
Published: January 2010

In this work TiO2 and ZnO layers have been deposited by screen-printing in common glazed ceramic tiles. These layers were evaluated for the photocatalytic degradation of Orange II in aqueous solutions, in a batch photoreactor under visible light. The photocatalytic behaviour was assessed by taking into account experimental variables which include: (i) firing temperature of the TiO2 printed layer; (ii) layer thickness; (iii) operation time; (iv) pH; and (v) dye concentration. Optimal processed layers showed an interesting decolourisation performance (over 90% efficiency after 7-8 h). It is anticipated that these new ceramic materials might be developed as an interesting alternative to TiO2 or ZnO suspensions, for example in photocatalytic applications excusing the particles removal at the end of the process.
Characterization of the Surface of Activated Carbons Produced from Tire Residues
Authors: Valente Nabais J.M. , Laginhas Carlos , Carrott Peter J.M. , Ribeiro Carrott Manuela M.L. , Galacho Cristina , Amorós J.E.C. , Gisbert Ana V.N.
Published: January 2010

The surface characterisation of new activated carbons produced from tire residues by activation with carbon dioxide was studied. The activated carbons produced were mainly basic with point of zero charge values above 8.8. The main surface functional groups identified by FTIR were ether, quinones, lactones, ketones, hydroxyls (free and phenol) and pyrones. The XRD analysis shows that the materials produced have a microstructural organisation with microcrystallite height around 1.5nm and width from 3 to 5.3nm. This analysis indicates also the possible presence of oxides (single or mixture) of the following heteroatoms: Fe, Al, Ca, Mg, Ti, Si, K, Pb, Cd, Ba, Zn and Sn. The results have shown the significant potential of this type of residues for activated carbon production. Furthermore, the environment friendly use of an industrial residue is also noteworthy.
Incorporation of Coating Plaster Residues in the Formulation of Red Ceramic Mass
Authors: Silva J.B. , Gondim Priscylla Cinthya A. , Nascimento R.M. , Gomes U.U. , Acchar W.
Published: January 2010

Coating plaster residues (CPR) used in the civil construction industry account for a considerable percentage of building debris. The debris generated at construction sites represents 40% of domestic waste in Brazilian municipalities, causing serious environmental problems, given that a large portion of the residue is discarded in inappropriate places. The incorporation of CPR into the mass formulations of red ceramic may be economically and environmentally beneficial. In the present study 5%, 10% and 15% of CPR was added to formulation D, with a 1:1 composition by weight of different medium plastic clays, a composite that showed the best physical and mechanical properties in a study conducted with three formulations of a ceramic industry containing compositions of 1:1, 1:2 and 2:1. The test specimens were compressed uniaxially, oven-dried (110 °C) and sintered at 850 °C, 950 °C and 1050 °C, with constant temperature for two hours. Lineal shrinkage, water absorption, apparent density, bending stress failure and section of fracture micrographs of the sample, with EDS microanalysis, were analyzed.
Waste Fibre Reinforced Ecocomposites
Authors: Lundahl Anna , Sousa Fangueiro Raul Manuel Esteves , da Cunha Soutinho Hélder Filipe , Duarte Fernando M.
Published: January 2010

With a significant production of waste fibrous material, textile companies are now looking for applications where waste materials could be an added-value material. One viable application of these waste materials is in the combination with polymeric matrices, producing composite materials with interesting properties for specific applications, from furniture to thermal and acoustic insulations. The aim of this work was to study the physical and mechanical properties of waste fibre reinforced composites and the influence of different parameters on their mechanical behaviour. Results show that a wide range of different properties and performances may be designed by altering various production parameters, such as thickness of the nonwovens used, time and temperature of the compression moulding, relationship between fibre/matrix ratio, polymeric film used and number of layers.
On the Thermal Characterization of Fibers Prepared by Cryogenic Grinding of Scrap Tires
Authors: García Francisco José Parres , Crespo J.E. , Nadal A. , Macias-Garcia A. , Cuerda-Correa E.M.
Published: January 2010

The importance of recovering and valorising the residues generated by industrialized societies is mainly due to the environmental impact that such residues may cause. In this connection, scrap tires constitute a major source of pollution. In the recent years large amounts of scrap tires have been recycled in order to recover the metals contained in this residue. Tires have also been grinded and the small particles produced have found different applications. In addition to metals and rubber particles, reinforcing fibers are also produced in the recycling process of scrap tires. As a previous step for the valorisation of this third constituent of waste tires, a characterization of such fibers is strongly recommended. Thermal analysis techniques make it possible to identify the fibers through the thermal transitions that may take place. Usually, such transitions result mainly in cotton and rayon. Furthermore, the combination of pyrolysis, gas chromatography and mass spectrometry techniques corroborates the identification of several compounds derived from the decomposition of the fibers as well as some materials used in the preparation of tires.
Characterisation of Cutting Systems on Physical Processing of Spent Batteries
Authors: Cabral Marta , Nogueira Carlos A. , Margarido Fernanda
Published: January 2010

Laboratorial studies were carried out to characterise the influence of different cutting systems (grab shredder and cutting mill) on the physical processing efficiency of spent Zn-MnO2 batteries. The grab shredder operate based on an indented cutting rotor which applies shear and abrasion stresses with a moderate rotation speed, while the cutting mill operation is based on shear and impact stresses at higher rotation speed. After shredding with the grab shredder, two fractions of material were obtained (above and below the 6 mm discharge grid), which allows a previous separation of the scrap. With the cutting mill, all the grinded material passed the bottom grid (with the same 6mm opening). Results obtained showed that alkaline batteries were more efficiently shredded than saline batteries, mainly with the grab shredder. Average diameters (d50) for saline and alkaline batteries fragmented with the grab shredder were 2.29 and 1.47 mm respectively, while with the cutting mill were 3.09 and 1.54 mm respectively. Chemical analyses were carried out for different size fractions allowing identifying metals distribution through size categories. In general chemical composition was not substantially different using both shredding systems. Zinc distribution was almost constant with the grain size while manganese distribution decreased with particle size. More than 94% of the iron scrap from the battery cases presents a particle size higher than 1.4 mm using both cutting systems. Due to this result, it is possible to separate the scrap retained in the coarse fraction by sieving with the identified mesh. Maximum selectivity points, corresponding to the maximum separation of zinc plus manganese from iron, were also determined. Higher zinc and manganese recoveries were obtained with the grab shredder, despite iron contamination (20-25%) can be considered significant.
Relation between the Mechanical Behaviour of a High Strength Steel and the Microstructure in Gigacycle Fatigue
Authors: Huang Zhi Yong , Du Wei Wei , Wagner Danièle , Bathias Claude
Published: January 2010

Many components can reach or exceed 109 cycles in their service time. When fatigue life is beyond 106, the Wöhler S-N curve was always considered to be asymptotic in horizontal axis, but the fatigue behaviour over 106 cycles can not be neglected. It is not usual to carry out a fatigue test beyond 109 cycles due to the conventional fatigue test’s constraints, time consuming and expensive. High strength steel is widely applied in automobile, railway industry after surface treatment in order to improve performance of material in practice. Carburizing process hardens surface to increase wear and fatigue resistance and shot peening has a beneficial effect on the material fatigue strength from the surface residual compressive stresses. A piezoelectric gigacycle fatigue machine is used to do the tests in gigacycle regime on specimens with different surface treatments. The effect of different surface treatments is investigated in gigacycle regime at a frequency of 20KHz with a fixed stress ratio R=0.1 at room temperature. Moreover, Scanning Electron Microscopy (SEM) observations of fracture surfaces are analyzed to evaluate the mechanism of damage related to surface treatments, microstructure scored inclusion size. The role of inclusions and microstructure is emphasized at 109 cycles.
SANS Investigation of γ´ Precipitate Morphology Evolution in Creep Exposed Single Crystal Ni Base Superalloy
Authors: Zrník Jozef , Strunz Pavel , Maldini Maurizio , Davydov Vadim
Published: January 2010

The creep degraded nickel base single crystal superalloy CMSX-4 of two axial orientations [001] and [111] was investigated with aim to assess the structure degradation. Constant load creep tests were conducted in the stress/temperature ranges of 250–780 MPa/750 – 50°C resulting in rupture time variation from 50 to 4000 hours. A combination of scanning electron microscopy (SEM) and non-destructive small-angle neutron scattering method (SANS) was used to investigate the directional coarsening (rafting) of the gamma prime (γ') precipitates in relation to the stress and temperature applied as well as to the initial crystallographic orientation of the specimens. The SANS results are discussed in terms of the correlation with the raft development, the axial orientation of specimen, the creep parameters and the mechanical properties.
Mechanical Behaviour of Functionally Graded Composite Vitreous Enamelled Steel Sheets
Authors: Rossetti L. , Dal Re V. , Zucchelli Andrea
Published: January 2010

Among various coatings for industrial and engineering applications, vitreous enamel ones have advantages of chemical inertness, high temperature stability and superior mechanical properties with reference to abrasion or impact as a comparison to other coating materials applied by thermal spraying. The enamelled composite, due to its internal composition, functionalization and architecture can be considered as a functionally graded composite material. In the present work, a first systematic characterization of the mechanical behaviour of enamelled steel sheets is presented. Tests were performed under four-point bending load with displacement control and acoustic emission monitoring. The mechanical response of tested materials was used to determine some key elastic parameters (e.g. Young Modulus), and the First Crack Failure parameter. Moreover, the mechanical performance of tested coated specimens was also related and discussed with reference to microstructure, surface characteristics, and residual strains in the coated structure.
The Effect of Synthesis Parameters on the Structure and Properties of Metakaolin Based Geopolymers
Authors: Tsitouras A. , Perraki T. , Perraki Maria , Tsivilis Sotiris , Kakali Glykeria
Published: January 2010

In the present work the geopolymerisation of metakaolin under varying conditions is investigated.The experimental part comprises the following parts: i) the synthesis of metakaolin based geopolymers and the investigation of the effect of the Si/Al ratio and the kind of alkali ion on the development of the compressive strength and ii) the characterization of the geopolymers by means of XRD, FTIR and SEM. As it is found the development of the compressive strength is strongly affected by the Si/Al ratio in the starting material and the kind of alkali metal, with the maximum being 70.1 MPa for a Si/Al ratio equal to 2.00. The Na- geopolymers show higher compressive strength compared to the NaK-geopolymers. Finally, low Si/Al ratios favour the formation of crystalline compounds (mainly zeolites), while Si/Al ratios higher than 1.5 lead to the formation of amorphous materials.
Effect of Water Jet and Electroerosion Cutting on Fatigue Strength of Thick Al-Alloy Sheet
Authors: Černý Ivo , Mikulová Dagmar
Published: January 2010

Results of an experimental investigation of effects of two advanced technologies for materials cutting, namely water-jet and electroerosive cutting, respectively, are described. Water jet cutting, with abrasive particles and specific parameters, and electroerosive cutting were applied to an aircraft Al-alloy sheet Al 2124 T851 of a considerable thickness, namely 50.8 mm. Reference batch of specimens was manufactured using fine finishing milling. Surface quality of each of the cutting and machining technologies was evaluated and fatigue strength was investigated. Three point bend fatigue tests performed at constant stress amplitude showed a considerable deterioration effect of both technologies on fatigue strength. The damaging effect of both technologies was comparable. Fractographical analysis using scanning electron microscopy (SEM) showed fatigue crack initiation in numerous surface micro-notches occurring as a result of the cutting. In addition, the crack initiation was frequently accelerated by surface or subsurface fairly large particles of intermetallic phases. This mechanism also occurred with milling specimens.
Synthesis and Characterisation of Slag Based Geopolymers
Authors: Panagiotopoulou C. , Kakali Glykeria , Tsivilis Sotiris , Perraki T. , Perraki Maria
Published: January 2010

In the present work the geopolymerisation of blast furnace slag (GGBS) under varying conditions is being investigated. The experimental comprises the following parts: i) dissolution of slag in alkaline media and the investigation of the effect of the alkali ion (K or Na) on the dissolution of Al+3 and Si4+, ii) synthesis of slag based geopolymers and the investigation of the effect of the Si/Al ratio and the kind of alkaline ion on the development of the compressive strength and iii) characterization of geopolymers by means of XRD, FTIR and SEM/EDS measurements. As it is concluded, blast furnace slag geopolymers exhibit high compressive strength, with the maximum being 112.7±2 MPa. The Si/Al ratio of the starting material is found to affect strongly the development of the geopolymer compressive strength. The microstructure of slag–based geopolymers and the incorporation of Ca in the geopolymer matrix are also discussed.
Thermal Conductivity of Porous Alumina-Zirconia Prepared by Foam Technique for Applications in Cooling Systems of Artificial Satellites
Authors: Hirschmann Ana Coh O. , Nono Maria do Carmo de Andrade , Silva Cosme Roberto Moreira
Published: January 2010

Porous ceramics are of great interest due to their numerous potential applications. The objective of the present investigation was to produce porous alumina with 3 mol % yttria-stabilized tetragonal zirconia (Y-TZP). This material will be used in cooling systems of satellites. To obtain the porous ceramics the direct foaming technique was used. This method is based on the preparation of a stable foam to which a slurry of alumina and zirconia is added. The mixture is then vigorously stirred for incorporation of air. The sintered ceramics were characterized by scanning electron microscopy, mercury porosimetry and thermal conductivity. The tests performed with the porous alumina-zirconia ceramic composite obtained by this method, showed low thermal conductivity values, high porosity and uniform microstructure with 20–100 µm open pores. The results show that the alumina-zirconia composites tested in this study have a potential for application in loop heat pipes of cooling systems of satellites.
The Properties and Structure of Infiltrated High Speed Steel-Tungsten Carbide-Copper Composites
Authors: Madej Marcin
Published: January 2010

The aim of the present study was to produce high speed steel – tungsten carbide – copper composites, which should have acceptable density, wear resistance and good sliding prosperities. Various amounts of WC powder were added to the HSS powder prior to compaction. The following compositions were investigated: 100% M3/2, M3/2 + 10% WC and M3/2 + 30%WC. The mixtures were prepared by mixing for 30 minutes in the 3-D pendulum motion Turbula® T2C mixer. Then the powders were cold pressed in a rigid cylindrical die at 800 MPa. Both green compacts and pre-sintered compacts (pre-sintering condition: 1150°C in vacuum for 60 minutes) were infiltrated with copper. The whole infiltration process was carried out in vacuum better than 10-3 Pa. Pre-weighed preforms of copper were carefully placed on top of the rigid skeletons in which porosity were predetermined, heated up to 1150°C, subsequently held at temperature for 15 minutes, and cooled down with the furnace to the room temperature. The dilatometer was used to detect some reaction in the sintering. The changes in as pressed and as sintered density, hardness, bending strength and tribological properties are discussed in this work.
Fabrication and Characterization of Halogen-Free Flame Retardant Polyolefin Foams
Authors: Román-Lorza Silvia , Sabadell J. , García-Ruiz J.J. , Rodríguez-Pérez Miguel A. , Sáez J.A.S.
Published: January 2010

Mayor advances have been made in the field of halogen-free flame retardant composites in the last years, mainly due to increasing regulatory pressures. This paper focuses in aluminium trihydroxide (ATH) as the halogen-free flame retardant and low density polyethylene (LDPE) as the polymer matrix of the fire retardancy foam. The attempt of this article is to achieve a cellular structure by foaming these materials, when high loading levels (up to 60wt %) of ATH are introduced. This is a difficult task due to the high amount of filler in the formulation. The aim is to reduce density without losing thermal and mechanical properties. In order to characterize the cellular structure as well as the thermal, mechanical and combustion properties, a complete study of the foamed samples was made by means of scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), melt flow index (MFI), air pycnometry, mechanical testing at low strain rates, limiting oxygen index (LOI) and calorimeter bomb tests.
Glass/Polyvinyl Chloride Composites
Authors: Torres L.M. , Silva João F. , Marques António Torres , Nunes João Pedro , Marques Rogerio P.
Published: January 2010

This paper summarizes the results obtained in the use of plastisols of vinyl chloride homopolymer (PVC), obtained by the process of emulsion polymerization, as thermoplastic matrix in the production of composite pipes and in pipe repairing. Two processing techniques commonly used with thermosetting matrices were studied: filament winding and hand lay up. The produced composite structures of PVC reinforced with glass fibres were subsequently subjected to tests in order to determine their mechanical properties. This paper concludes that it is possible to use the described technique for piping repairing with good results.
Mechanical Behaviour Analysis of Polymer Mortars Reinforced with Jute and Piassava Natural Fibres under Alkaline Environments
Authors: Ribeiro M.C.S. , Vogt Jordanna C. , Marques António Torres , Ferreira Antonio
Published: January 2010

The aim of this work is to assess the feasibility of using polymer mortars reinforced with untreated natural fibres instead of artificial ones, for applications requiring highly alkali resistant materials, such as tanks and drainage systems for wastewater treatment plants. For this purpose, several formulations of polyester polymer mortars reinforced with different contents of jute and piassava natural fibres were investigated. Flexural and compressive behaviour, before and after exposure to a strong alkaline solution was analysed and quantified. Test results highlighted the high potential of these materials as basis construction material for precast applications requiring specific resistance under alkaline environments.