Materials Literature
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The purpose of this study was to evaluate the degree of conversion (DC) of the Z250 composite, using six photo-activation methods, two storage periods and two preparation techniques of the FTIR specimens (n = 3). For the KBr pellet technique, the composite was placed into a metallic mold and photo-activated as follows…
Porous silicon layers (PSL) were produced by stain etching from a HF:HNO3 500:1 mixture with etching time varying in the range of 1 up to 10 min. The samples have presented nanometric porosity as a function of etching time, characteristic of heavily doped p type silicon. The residual stress and the correlation length…
Several techniques have been utilized for the preparation of hydroxyapatite (HA) and other calcium phosphates for the development of biomaterials. It is vital to know the reaction kinetics to be able to control the material obtained by the aqueous solution route. In the present work, HA has been produced by different…
New types of copolymers using monomers which form inorganic polymers network (glass-like) and organic networks have been developed, known as ormocers. The aim of this work was to study how a particular dental filling material is degraded when subjected to a caries challenge by using low pH solutions. The supernadants…
A styrene-butadiene-styrene modified asphalt cement was characterized by infrared, differential scanning calorimetry, thermogravimetric analysis and empirical tests such as ring and ball softening point, penetration and elastic recovery. After aging in the rolling thin-film oven, the polymer-modified asphalt presented…
The need for new materials to substitute injured or damaged parts of the human body has led scientists of different areas to investigate bioceramics since the 70's, when other materials in use started to show rejection problems. Ceramics show some advantages like being the material that best mimics the bone tissue, al…
In this work was employed a 2³ factorial experiment design to evaluate the castor oil polyurethane-poly(methyl methacrylate) semi-IPN synthesis. The reaction parameters used as independent variables were NCO/OH molar ratio, polyurethane polymerization time and methyl methacrylate (MMA) content. The semi-IPNs were cure…
The present work is aimed to simulate the Friction Stir Welding process as a three-dimensional thermally coupled viscoplastic flow. A Finite Element technique is employed, within the context of a general purpose FEM framework, to provide the temperature distributions and the patterns of plastic flow for the material i…
Purpose: To evaluate the microtensile bond strength (µTBS) to dentin of 4 adhesive systems, the micromorphology of the adhesive/dentin interface and to compare the results to the µTS (cohesive strength) of sound dentin and resin composite. Occlusal surfaces of 24 extracted caries-free human molars were cut flat to exp…
The aim of this work is to characterize physically and mineralogically six samples of natural and industrialized bentonites from Paraíba, Brazil, and to study its rheological properties to be used as a components of water based drilling fluids. Also it is intended to compare the evolution of the mineralogical composit…
The amount, distribution, size and chemical composition of non-metallic inclusions have a direct influence on steel properties. By controlling size and chemical composition of these inclusions, it is possible to get a product with good quality. The identification of the nature and the control of inclusion formation ar…
The constant heating rate method employed in sintering studies offers several advantages over the isothermal method, particularly the fact that all the parameters that describe the sintering phenomena can be obtained from a single sample. The purpose of this work is to determine the parameters of sintering kinetics of…
Five different batches of class C20 concrete, containing Dramix-RC-80/60-BN steel fibers (SFs) as additives at doses of 0, 30, 40, 50 and 60 kg/m3, and six Ø 15x30 cm prisms were poured from each batch. Standard crushing tests were run on all the specimens and the respective load-displacement and stress-strain curves…
The present study explores the stability of different superplasticizer (polycarboxylate, vinyl copolymers, melamine and naphthalene derivatives) and shrinkage-reducing (polyproplyene glycol derivatives) admixtures in water and several alkaline media: NaOH (pH= 11.7 and 13.6), Ca(OH)2 (pH=l2.4) and waterglass (pH=13.0)…
Capillarity and Wetting Phenomena: Drops, Bubbles, Pearls, Waves , Pierre-Gilles de Gennes , Françoise Brochard-Wyart , and David Quéré (translated from French by Axel Reisinger) Springer-Verlag, New York, 2004. $69.95 (291 pp.). ISBN 0-387-00592-7 Buy at Amazon
Al- and Mg-based alloys are being used for reducing the weight of automobiles. For structural applications, they must have adequate stress corrosion resistance, and yet, under some circumstances, stress corrosion cracking can occur in both alloy systems. Precipitation of the Mg-rich β-phase (Al3Mg2) at grain boundarie…
The problems of HVAC/DC gas insulated systems (GIS) dielectric strength coordination and support spacers design criteria are discussed in this paper. The most important challenge is to protect the spacers against flashover and consequently exclude them from consideration when coordinating an insulation of GIS. Both ex…