Materials Research

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List of Papers (Total 161)

Thermal, mechanical and morphological properties of poly (hydroxybutyrate) and polypropylene blends after processing

The ever increasing accumulation of plastic waste in the environment has motivated research on polymers that degrade rapidly after being discarded as possible substitutes for conventional inert plastics. Biodegradable polymers can be an alternative, since they have non-toxic residual products and low environmental permanence. Poly (hydroxybutyrate) is a biodegradable polymer with...

Evaluation axisymmetric analysis of thermal stress residual near fiber/epoxy interface

The finite element method is used to compute and analyze the residual stresses particularly near the fiber/epoxy interface, and these stresses need to be taken into account. An axisymmetric model has been used for stress computation and analysis, in this work two cases are considered by using an epoxy matrix with respectively glass and carbon fibers with a different volume fiber...

Mechanical strength and thermal conductivity of low-porosity gypsum plates

The thermal conductivity and mechanical strength of gypsum and gypsum-cellulose plates made from commercial plaster by a new process have been measured. The gypsum parts made by the new process, 'novogesso', have high mechanical strength and low porosity. The gypsum strength derives from both the high aspect ratio of the gypsum crystals and the strong adhesion among them by nano...

Nanocomposites: synthesis, structure, properties and new application opportunities

Nanocomposites, a high performance material exhibit unusual property combinations and unique design possibilities. With an estimated annual growth rate of about 25% and fastest demand to be in engineering plastics and elastomers, their potential is so striking that they are useful in several areas ranging from packaging to biomedical applications. In this unified overview the...

Microstructural development and tensile strength of an ECAP: deformed Al-4 wt. (%) Cu alloy

The tensile strength of metals and alloys can be considerably increased by severe plastic deformation, a consequence of the extreme grain refinement thus achieved. In the present work the deformation was performed by Equal Channel Angular Pressing and the material was an Al-4% Cu alloy. Characterization included tensile tests, and microstructural observation by optical and...

Correlation among volumetric conductivity, electrical threshold field and compensation plots by oxidation induction time on LDPE/CB composites

The thermodynamic compensation effect plot derived from Eyring rate process theory was applied to the thermal and UV ageing of LDPE/Carbon Black composites containing commercial carbon black (CB) and carbon black surface oxidized with nitric acid. Correlations were tested among compensation effect, electrical threshold field and volumetric electrical conductivity. Compensation...

The fracture evaluation of NiTi SMA endodontics files

The purpose of this study was to evaluate the fracture resistance and the fracture surface of NiTi SMA engine-driven endodontics files submitted to clockwise torsion. The maximum angular deflection and the maximum torque were analyzed without axial loading. The helical plastic deformations and the fracture surface morphology were evaluated by Scanning Electron Microscopic. The...

Degree of conversion and molecular weight of one denture base and three reline resins submitted to post-polymerization treatments

The effect of post-polymerization treatments (MW-microwave irradiation and WB-water-bath) on the degree of conversion (DC) of three reline resins (Ufi Gel hard-U, Kooliner-K, and Tokuso Rebase Fast-T) and one denture base resin (Lucitone 550-L), submitted to two polymerization cycles (LS-short and LL-long), was evaluated by using FT-Raman spectroscopy (n = 5). The molecular...

Surface characterization of alumina reinforced with niobium carbide obtained by polymer precursor

Active filler controlled pyrolysis of polymers (AFCOP) is a recent method for obtaining near-net shaped ceramic bodies. Alumina based composites have been developed for use as cutting tools, so knowledge of the surface composition is extremely important because it is directly related to the hardness and wear resistance Samples containing a fixed concentration of 60 wt. (%) of...

Electro-thermomechanical characterization of Ti-Ni shape memory alloy thin wires

The use of shape memory alloys (SMA) as smart structures and other modern applications require a previous evaluation of its performance under load as well as a training procedure. In general, these requirements lead to the design and assembly of a specific test bench. In this work, an experimental set-up was specially designed to perform the electro-thermomechanical...

Surface processing to improve the fatigue resistance of advanced bar steels for automotive applications

With the development of new steels and processing techniques, there have been corresponding advances in the fatigue performance of automotive components. These advances have led to increased component life and smaller power transfer systems. New processing approaches to enhance the fatigue performance of steels are reviewed with an emphasis on carburizing and deep rolling...

Hygrothermal effects on dynamic mechanical snalysis and fracture behavior of polymeric composites

Polymer composites used above their glass transition temperatures Tg present a substantial degradation of physical properties; therefore a material's glass transition temperature and its change with moisture absorption are of practical importance. Little attention has been paid to the role of the adhesive bonding between the reinforcing fiber and matrix, particularly for BMI...

The optical absorption of gamma irradiated and heat-treated natural quartz

Quartz with aluminum as impurity absorbs energy from ionizing radiation and modifies its color. Colorless quartz becomes smoky or dark smoky (morion quartz) when exposed to gamma rays. By heat-treatment, smoky quartz may become successively greenish, yellowish, or brownish as the irradiation dose increases. Natural, colorless quartz is routinely colored by irradiation with gamma...

Evaluation of carbon fiber surface treated by chemical and cold plasma processes

Sized PAN-based carbon fibers were treated with hydrochloric and nitric acids, as well as argon and oxygen cold plasmas, and the changes on their surfaces evaluated. The physicochemical properties and morphological changes were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), tensile strength tests and...

Comparison of crystallinity between natural hydroxyapatite and synthetic cp-Ti /HA coatings

Commercial purity titanium (cp-Ti), and some of its alloys are important materials in the medical field because of their excellent biocompatibility and mechanical properties. Recently a simple chemical method to induce bioactivity in these inert metallic materials was reported. In this work, the biomimetic chemical process has been used to modify the surface of cp-Ti with the...

Erosion-oxidation behavior of thermal sprayed Ni20Cr alloy and WC and Cr3C2 cermet coatings

An apparatus to conduct high temperature erosion-oxidation studies up to 850 °C and with particle impact velocities up to 15 m.s-1 was designed and constructed in the Corrosion Laboratories of IPEN. The erosion-oxidation behavior of high velocity oxy fuel (HVOF) sprayed alloy and cermet coatings of Ni20Cr, WC 20Cr7Ni and Cr3C2 Ni20Cr on a steel substrate has been studied. Details...

Mathematical model predicts the elastic behavior of composite materials

Several studies have found that the non-uniform distribution of reinforcing elements in a composite material can markedly influence its characteristics of elastic and plastic deformation and that a composite's overall response is influenced by the physical and geometrical properties of its reinforcing phases. The finite element method, Eshelby's method and dislocation mechanisms...

Waste glass in porcelain

In this work, the feldspar used as a flux in typical porcelain was replaced by waste glass, and the resulting batch composition contained 50% kaolin, 25% quartz and 25% waste glass. The properties of this porcelain with glass powder (GP) were compared to traditional porcelain (TP), which utilizes feldspar. The samples were fired at different temperatures, ranging from 1200 °C to...

In vitro bioactivity and cytotoxicity of chemically treated glass fibers

Samples of a commercial glass fiber FM® (Fiber Max) were used to test the efficacy of a chemical sol-gel surface treatment to enhance their bioactivity. After treatment with tetraethoxysilane (TEOS), individual fiber samples were soaked into a simulated body fluid (SBF) solution, from which they were removed at intervals of 5 and 10 days. Micrographs obtained by scanning electron...

Bentonites from Boa Vista, Brazil: physical, mineralogical and rheological properties

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 composition and rheology of these clays after 40 years of exploitation...

Si3N4 ceramics sintered with Y2O3/SiO2 and R2O3(ss)/SiO2: a comparative study of the processing and properties

A comparative study was made of Si3N4 sintered with two types of additives, namely, Y2O3/SiO2 and R2O3(ss)/SiO2, R2O3(ss) being a rare earth metal oxide in solid solution. The processing conditions for both types of Si3N4 were 14 vol% of additives and a sintering temperature of 1800 ºC for 30, 60 and 240 min. To compare the efficiency of the additives in the material's sintering...

Influence of the crystallization thermal treatment on the structural and electrical properties of PZT thin films

Different methods have been proposed in the literature to deposit PZT thin films. Among these, chemical based processes have been revealed as a promising preparation route due to their low cost processing and the facility for controlling the stoichiometry of complex systems. The objective of this work was to investigate the influence of the time and temperature of crystallization...

Composite coatings of titanium-aluminum nitride for steel against corrosion induced by solid NaCl deposit and water vapor at 600 °C

Composite coatings (Ti,Al)N with different Al content were deposited on a wrought martensite steel 1Cr11Ni2W2MoV by reactive multi-arc ion plating. With the addition of Al to the coatings, the crystallographic structure of them changed from B1 NaCl to B4 ZnS, the relevant hardness and adhesive strength firstly increased then decreased and their oxidation-resistance was also...

Gas turbines: gas cleaning requirements for biomass-fired systems

Increased interest in the development of renewable energy technologies has been hencouraged by the introduction of legislative measures in Europe to reduce CO2 emissions from power generation in response to the potential threat of global warming. Of these technologies, biomass-firing represents a high priority because of the modest risk involved and the availability of waste...

The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

This work investigated the influence of the aggregate's aspect ratio on the fracture behavior of a low cement aluminum silicate refractory castable treated at two different temperatures (110 °C and 1000 °C). The aggregates were cylindrical pellets with an aspect ratio of 1, 2, 3 and 4, produced by extruding a mixture of clay and calcined alumina fired at 1600 °C for 4 h to yield...