bluuebunny/crossref_metadata_2025 huggingface dataset:
Genes encoding adhesion factors and biofilm formation in methicillin-resistant Staphylococcus aureus in Morocco
Authors: Serray Bahija , Oufrid Salwa , Hannaoui Imane , Bourjilate Fatna , Soraa Nabila , Mliji Mostafa , Sobh Mohammed , Hammoumi Abderrahmane , Timinouni Mohammed , El Azhari Mohamed
Published: August 2016

Introduction: Infections involving methicillin-resistant Staphylococcus aureus (MRSA) remain a serious threat to hospitalized patients worldwide. MRSA is characterized by recalcitrance to antimicrobial therapy, which is a function not only of widespread antimicrobial resistance, but also the capacity to form biofilms. The present study evaluated the presence of genes encoding adhesion factors and the biofilm-forming capacity in MRSA. Methodology: In this study, 53 isolates of MRSA, recovered from December 2010 to May 2014 in a mother and child hospital, CHU Mohamed VI in Marrakech, Morocco, were screened for the presence of bap and ica genes associated with biofilm formation, and for bbp, cna, ebpS, eno, fib, fnbA, fnbB, clfA, and clfB genes that encode microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). The biofilm formation assay was performed in 96-well microtiter polystyrene plates. The presence of genes was determined by polymerase chain reaction (PCR). Results: An association was found between icaD gene detection and biofilm formation; 100% of the strains harbored icaD and produced biofilm. None of the isolates harbored bap or bbp. Furthermore, 96.23% isolates were positive for fnbA, 60.37% for eno, 43.39% for clfA and clfB, 11.32% for cna, 9.34% for ebpS, 5.66% for fib, and 1.89% for fnbA. Conclusions: Our findings showed that the MRSA carriage in Marrakech children was high. The genetic variations of adhesion genes require further investigation.
Aprendendo a investigar através de uma atividade investigativa sobre Ciência Forense e Investigação Criminal
Authors: Sebastiany Ana Paula , Pizzato Michelle Camara , Miskinis Salgado Tania Denise
Published: August 2016

O presente trabalho tem por objetivo avaliar uma proposta didática sobre a temática da Ciência Forense e a Investigação Criminal, e identificar as curiosidades e interesses do público participante. Nesse sentido, as atividades foram organizadas sob a forma de um Ambiente Interativo de Aprendizagem (AIA), de âmbito informal e presencial ligado ao Ensino de Ciências, como estratégia para a aprendizagem de atitudes investigativas e a divulgação da Ciência e da Tecnologia. O AIA proposto está orientado para abordar as ciências pela aproximação destas com o cotidiano utilizando metodologias investigativas. Esta orientação se baseia no Modelo Didático Investigativo (Porlán, 1993), o qual propõe a investigação como metodologia didática em alternativa aos métodos passivos de ensino. Além disso, para que esse ambiente tivesse caráter lúdico buscou-se inspiração nos jogos de RPG – Roleplaying Game. E escolhemos como eixos temáticos a Ciência Forense e a Investigação Criminal, considerando que o AIA só seria significativo para o estudante se estivesse ligado a seus interesses, curiosidades, necessidades e objetivos pessoais. Afinal, as pessoas aprendem melhor em um contexto realista, usando o que já sabem e desenvolvendo habilidades a partir disso. E, por serem temas de rara abordagem no ensino formal e informal, mas de grande interesse pelo público em geral.
Aprendizagem Docente proporcionada pela participação no PIBID/Física: a visão dos coordenadores de área
Authors: Darroz Luiz Marcelo , Wannmacher Clóvis Milton Duval
Published: August 2016

O presente artigo apresenta os resultados de uma pesquisa fenomenológica qualitativa realizada com os coordenadores de área dos subprojetos do PIBID/Física do Rio Grande do Sul. Esta investigação visou identificar indícios da ocorrência da aprendizagem docente nos licenciandos de Física participantes do programa. A coleta de dados ocorreu por meio de entrevistas semiestruturadas gravadas em áudio e posteriormente transcritas. A análise dos dados se deu a partir dos materiais coletados, onde se realizou uma Análise Textual Discursiva que tinha como categorias a priori os cinco focos da aprendizagem docente estabelecidos por Arruda et al. (2012). Os resultados indicam que a participação nas atividades do PIBID/Física pode promover a aprendizagem docente, uma vez que elementos dos cinco focos foram identificados nas falas dos coordenadores de área.
A New Approach to Evaluating Performance
Authors: Bleich Michael R.
Published: August 2016

A leadership task is evaluating the performance of individuals for organizational fit. Traditional approaches have included leader–subordinate reviews, self-review, and peer review. A new approach is evolving in team-based organizations, introduced in this article.

J Contin Educ Nurs.
2016;47(9):393–394.
Working Toward a Competency-Based Preceptor Development Program
Authors: Gueorguieva Vera , Chang Ann , Fleming-Carroll Bonnie , Breen-Reid Karen M. , Douglas Mary , Parekh Sandhaya
Published: August 2016

Preceptorship programs are widely used in nursing education and transition to practice. This article describes a variety of improvements implemented in an academic health sciences center on the basis of findings from a study previously conducted with preceptors in the same institution. A long-standing preceptor preparation program was redesigned and expanded into two levels—an introductory workshop directed toward meeting the needs of new preceptors, and an advanced workshop for experienced preceptors. Organization-specific preceptor competencies were developed as a foundation for preceptor practice. The competencies also informed the revised preceptor development program that included selection, ongoing development, and evaluation. A more structured support system, a standardized performance feedback process, and additional recognition strategies were incorporated in the new competency-based preceptor program.

J Contin Educ Nurs
. 2016;47(9):427–432.
Kinetic of Self-Reducing Mixtures of Iron Ore and Biomass of Elephant Grass
Authors: Rocha E.P. , de Castro José Adilson , Vitoretti Flavia de Paula , Junior F.V.
Published: August 2016

In this work, kinetic runs of self-reducing mixtures composed by pellet feed, BOF dust and biomass of elephant grass were performed using TGA-DSC method, for the temperatures, 900, 950, 1000, 1050 and 1100°C, and carbon percentages (15, 20 and 30% of carbon). The converted fraction versus time was calculated, and the different regions of the reactions progress were selected to analyze the reactions kinetics that occur in the mixture (devolatilization of biomass, Boudouard and sequence of reduction reactions). The kinetic behavior for the different steps showed good agreement with the first-order kinetic law. Using Arrhenius plot, was possible to estimate the apparent activation energy values obtained for the reaction mechanisms corresponding to Fe3O4→FeO and FeO→Fe. The kinetic constants for the 1100°C temperature and mixture containing 30% of carbon were the higher values: 0.0037 s-1 for the reaction Fe3O4 → FeO and 0.0258 s-1 for the mechanism FeO →Fe.
Influence of Clay Swelling Inhibitor in Filtration Properties of Water-Based Drilling Fluids
Authors: Leite Raquel Santos , Dantas Ana Paula Tertuliano , Amorim Luciana Viana
Published: August 2016

This work aims to evaluate the influence of the clay swelling inhibitor in the filtration properties of water-based drilling fluids. Drilling fluids were prepared with and without adding potassium citrate clay inhibitor. The following additives were used in the composition of the fluid: viscosity agent (xanthan gum), filtrate reducer (starch and low viscosity carboxymethylcellulose (CMC LV)), antifoam, bactericide, sealant (calcite), lubricant and pH controller. The concentration of inhibitor was used of 15, 20, 25 and 30 g/ 350 mL of water. We determined the filtration properties (filtrate volume (FV), spurt loss (SL), cake thickness (CT) and permeability (K)) of drilling fluids. According to the results, it was concluded that: (i) adding the inhibitor to the fluid promoted reduction of FV and K of fluids containing starch in the composition and (ii) the inhibitor promoted satisfactory reductions in the CT and increased of SL for all the studied fluids. Finally, the inhibited fluids prepared with higher concentrations of starch, CMC LV, calcite and potassium citrate than 25 g/ 350 mL of water showed the best performance compared to FV and SL.
Contaminants Recovery from Acid Mine Drainage
Authors: Lima Paulo , Fukuma Henrique Takuji , Nakamatsu Sandra , Campos Maria Gabriela Nogueira , Campos Maria Gabriela Nogueira , Ramos Erika Coaglia Trindade , Mariano Neide Aparecida
Published: August 2016

In some mines where sulfide minerals can occur in form of pyrite acid mine drainage (AMD) may occur, and it constitutes one of the main environmental impact. In order to prevent that AMD compromises aquifers layers and reaches mine surroundings, a treatment that consists in its neutralization with the use of a hydrated lime suspension is usually conducted. Contaminants that are soluble in AMD are precipitated, remaining in the solid phase. The work here presented aims recover uranium and rare earths found in one of these precipitates, which consists of calcium diuranate and metal hydroxides in a calcium sulfate matrix. This material contains approximately 0.25% of triuranium octoxide (U3O8) and 2.5% of rare earth oxides (TR2O3). The recovery of uranium and rare earths contained in the precipitate was performed through a hydrometallurgical process. The test resulted in a leaching with sulfuric acid presented solubilization of 96% for uranium and 90% for rare earths. A percentage yield of 99.7% and 99.9% was obtained in the steps of uranium extraction and re-extraction from the leachate, respectively.
Hydration and Dehydration of High Initial Strength Portland Cement Type CP V - ARI
Authors: de Araújo Jr. Aloízio Geraldo , da Silva Leandro José , Panzera Túlio Hallak , da Souza Azevedo Adriano Galvão , Strecker Kurt
Published: August 2016

It is known that the hydration of cement paste is influenced by a variety of factors, it is also known that some hydration products are gradually dehydrated at elevated temperatures. In doing so, different author studied the dehydration of hydrated cement pastes under different condition. In this work, samples of Hydrated Cement Paste (HCP) were prepared from Portland cement of high initial strength (CP V-ARI) with a water/cement ratio of 0.5. The morphological changes during hydration and dehydration by subsequent heat-treatments were analyzed by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Thermal Gravimetric Analysis (TGA) was used to study the thermal stability of the HCP. Dehydrated cement powder samples (DCP) were obtained heat treating samples of HCP at 300, 500, 700 and 900°C. After 7 days of curing HCP samples exhibited no significant changes in its structure. HCP dehydrated at 500°C showed the absence of Ca (OH)2 and calcium silicate hydrate. At 700°C the formation of β-2CaO.SiO2, 3CaO.SiO2 and CaO is observed. During heat treatment at 900°C the HCP revealed a significant mass loss of 36%.
A Study of the Chemical and Physical Characteristics of the Soils from the South of Piauí for Soil-Cement Brick Production
Authors: de Araújo Francisca Pereira , Silva Filho Edson Cavalcanti , Nery de Souza João Sammy , Osajima Josy Anteveli , Furtini Marcelo Barbosa
Published: August 2016

Soil-cement bricks are good examples of environmentally friendly products. This brick is the combination of soil with compacted cement with no combustion in its production. In this work the physical chemical characteristics of the soil from Piaui for producing this material were investigated. Samples of the soil were collected in three potteries from the county of Bom Jesus and pH analysis were carried out, as well as the rate of organic matter, texture, particle density, limits of liquidity and plasticity rates. The results have shown that the soils have acid tones (pH 5,49 a 6,11), which can be neutralized by adding cement, and organic matter percentages up to 1%. The samples have shown predominantly clay-rich textures with adequate plasticity limits, however, values of liquidity limits and particle density above recommended. Altogether, these soils tend to present viability concerning soil-cement brick production, provided that corrections with additives are made in order to minimize this effect.
Moisture Expansion during the Formation of Crystalline Phases in Clay/CaCO3 Mixtures
Authors: Andrade R.A. , Ferreira Heber Carlos , Menezes Romualdo Rodrigues , Neves Gelmires Araújo
Published: August 2016

Information from technical literature indicates moisture expansion in ceramic materials is reduced due to calcium oxide being incorporated in their raw materials, and, therefore, 12.0% and 18.0% calcium carbonate was used to obtain fired products at temperatures of 850, 900, 950 and 1000oC. Some of these were re-fired to 1000oC, autoclaved and pulverized. Important reductions in moisture expansion occurred for re-fired products obtained from clay/carbonate mixtures. It was found that a few crystalline phases, resulting from incorporating calcium carbonate, appear at temperatures below 900oC in autoclaved and pulverized samples, obtained on using 12.0% and 18.0% calcium carbonate.
Evaluation of a Tacking Stage for Adherence, between Mortar and Ceramic Brick
Authors: de Azevedo Afonso Rangel Garcez , Alexandre Jonas , de Castro Xavier Gustavo , Barnabé Zanelato Euzébio , Monteiro Sergio Neves , Bozzi Piazzarollo Carla , Mendonça Thales Otal , Coelho França Fernando Cesar , de Oliveira Braga Fabio
Published: August 2016

The civil construction industrial sector is one of the most important in Brazil both for job opportunity and amount of utilized materials. However, it is also the sector that produces one of the highest volume of waste materials. In fact, it is estimated that total wastes to be around 30% of the raw materials supplied to the constructions. Several factors have been indicated as responsible for this wastage in civil construction, from lack of qualified labor to inappropriate technical procedures. One of the constructive stages, which has been the subject of doubt, is the previous preparation of a crude brick wall to receive a layer of mortar before painting. This previous preparation is known as tacking, which consists of coating the bricks surface with a light mixture of water, cement and sand to improve the mortar adherence. Since the tacking increases the masonry construction cost in approximately 2%, the present work evaluated its necessity. Tests were conducted without and with tack between the bricks and the mortar. The results showed a tendency to increase the adherence with time after tacking.
Study on the Piezoelectric Behavior and Structural Changes of Strontium Doped PZT Ceramics
Authors: da Silva Margarete Soares , Silva Lucas L. , Souza Eliane F. , Longo Elson , Zaghete Maria A. , Cavalheiro Alberto A.
Published: August 2016

Some piezoelectric properties of lead zirconate titanate PbZr0.53Ti0.47O3 ceramic samples sintered at 1100oC for 3 hours has been investigated in this work and compared to the strontium modification at 0.2, 0.4, and 0.6 mol%. Polarization versus Electric Field curve and d33 and Kp piezoelectric parameters was taken at room temperature in order to investigate the correlation with phase amount and lattice parameters of crystalline phases calculated through Rietveld refinement. The results indicated the lead substitution with 0.4 mol% of strontium enhances the d33 and Kp piezoelectric parameters, but there is no systematic variation of the piezoelectric properties with strontium content. By the other hand, tetragonal phase seems plays an important rule on piezoelectric devices operating near the room temperature and some correlations could be found.
Utilization of Foundry Waste to Produce Ceramic Matrix Composites
Authors: Rodriguez A.L. , Queiroz É.V. , López D.A.R. , Wermuth Tiago Bender , Basegio T.M. , Bergmann Carlos Pérez
Published: August 2016

The metallurgic industry, especially foundries, is a significant source of waste. For this reason, alternatives that involve reuse and recycling are necessary to minimize waste disposal in landfills and recover matter and energy. The feasibility of elaborating ceramic matrix composites with the incorporation of foundry waste was investigated in this study. Two types of residues were used to elaborate the composites. Green sand and grit blasting powder, in formulations with concentrations that ranged from 5.0 to 10.0% (m/m). The specimens were molded by uniaxial pressing, and a thermal treatment at 1000 °C was performed. The materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), particle size determination, linear retraction, water absorption, mechanical strength, leaching and solubilization. The results indicate that the incorporation of waste to the ceramic mass enables the processing of specimens with properties of industrial interest, such as mechanical strength and water absorption.
Organofunctionalization of Natural Palygorskite with Ethylene Sulfide in the Absence of a Solvent
Authors: Silva Marcos Pereira , Oliveira Marília Evelyn Rodrigues , Batista Francisco Marcos Costa , Santos Maria Rita de Morais Chaves , Fonseca Maria Gardennia , Silva Filho Edson Cavalcanti
Published: August 2016

The search for functional materials has increased daily in order to improve their functionality while maintaining a low cost. Among the materials of considerable interest are clays and within them is a particular clay known as palygorskite, which contains a hydrated silicate of aluminum and magnesium with a fibrous morphology. This work achieved the organofunctionalization of palygorskite with ethylene sulfide in the absence of a solvent. Through the elemental analysis of sulphur, the incorporation of 9.73 ± 0.36 mmol g-1 was identified. A significant decrease in the crystallographic planes (110) and (040) was identified in the XRD. The FTIR showed vibrations of stretching and deformation of the methylene groups in the region below 3000 and in 1421 cm-1, respectively. The deformation related to the C-S group in the region of 700 and 600 cm-1, and the surface area (BET) showed a significant reduction from 113 to 7 m2 g-1. Additionally, the SEM presented a loss of fibrous character.
Structural and Microstructural Properties of Si-C and Si-C-B Powders Obtained by High-Energy Ball Milling
Authors: Ferreira Lucas Moreira , Mégda D.S. , de Souza A.C. , Marques Rodrigo Fernando Costa , Ramos Erika Coaglia Trindade , Chad Vanessa Motta , Ramos Alfeu Saraiva
Published: August 2016

This work evaluated on the structural modification during high-energy ball milling of the Si-50C, Si-42.9C-19.1B e Si-33.3C-44.4B (at.-%) powder mixtures from elemental powders. Electron images revealed on occurrence of continuous fracture mechanisms in brittle particles during their processing, which presented rounded particles lower than 10 μm. X-ray diffraction results of Si-50C powders indicated that the intensity of Si peaks was slightly reduced after milling for 17 h, which were moved to the direction of larger diffraction angles after 7 h of milling, suggesting that carbon atoms were dissolved into the Si lattice in order to form an extended solid solution. Following, these values were increased due to the discrete exothermic formation of the SiC compound. In Si-C-B powder mixtures, the SiC and B4C compounds were formed after milling for 7 h.
Chemical-Mineralogical and Microscopic Characterization of Clay Used as Raw Materials in Santa Gertrudes' Ceramic Pole
Authors: del Roveri Carolina , Cunha R.A. , Zanardo Antenor , Godoy Letícia Hirata , Moreno Maria Margarita Torres , Rocha R.R. , Maestrelli Sylma Carvalho
Published: August 2016

The Santa Gertrudes ́ Ceramic Polo is the Brazilian region with national and international prominence in the manufacturing of ceramic tiles. Some raw materials used by ceramic industry and coatings industries in this region were characterized in terms of chemical-mineralogical and microscopic view, in order to promote the best technological characterization of them. For this, chemical analysis of major elements and trace X-ray diffraction and microscopic analysis by SEM, TEM and Electron microprobe were performed by ICP-MS. The results showed that the raw materials commonly referred to as "clays" are actually constituted by various mineral phases, which directly influence the properties of the same ceramics. Also showed that, by virtue of this constitution, different formulations can be developed, using the best raw materials found in the region of Santa Gertrudes, SP.
Dynamic-Mechanical Performance of Sponge Gourd Fiber Reinforced Polyester Composites
Authors: Scarpini Cândido Verônica , Picanço Oliveira Michel , Monteiro Sergio Neves
Published: August 2016

The engineering applications of natural materials to replace synthetic ones has marked increased in past decades owing to environmental, societal and economical issues. Among these natural materials, the lignocellulosic fibers obtained from plants are successfully being used as polymer composites reinforcement is substitution of the traditional glass fiber. One relatively unknown lignocellulosic fiber with potential for composite reinforcement is that extracted from the sponge gourd. In the present work, the dynamic-mechanical performance of unsaturated orthophtalic polyester matrix composites was evaluated for different volume fractions of continuous and aligned sponge gourd fiber reinforcement. The results revealed that an increasing incorporation of sponge gourd fiber improved the composite viscoelastic stiffness, while decreasing its glass transition temperature.
Use of Statistical Techniques in the Optimization of the Process "Starch Consolidation"
Authors: Storion Ana Gabriela , del Roveri Carolina , Ramalho Pinto Eric , Ramos Erika Coaglia Trindade , Mendes Patrícia Neves , Maestrelli Sylma Carvalho
Published: August 2016

The Starch Consolidation method of molding technique is based on the ability of starch swell and gelatinize in water, so the green bodies are formed from suspensions, generating controlled porosity after firing; however, it is strongly influenced by gelatinization temperature, starch used, content and type of dispersant, pH and viscosity. This work involves the statistical analysis of possible relations between viscosity, content of dispersant and pH. Slurries containing alumina, water and starch were prepared, settling the solids in 40% and varying the starch content of 10, 20, 30, 40 and 50%, compared to the solids at the mixture. PH and viscosity measurements were made of the slurries as a function of added dispersant. Were obtained and analyzed measures of each parameter, using the Pearson correlation, verifying the existence of an almost perfect correlation between most of the parameters studied.
Development of Ni/h-BN Self-Lubricating Composite Powder by High-Energy Ball Milling
Authors: Parucker Moisés Luiz , da Costa César Edil , Soethe Viviane Lilian
Published: August 2016

Solid lubricants have had good acceptance when used in problem areas where the conventional lubricants cannot be applied: under extreme temperatures, high charges and in chemically reactive environments. In case of materials manufactured by powder metallurgy, particles of solid lubricants powders can be easily incorporated to the matrix volume at the mixing stage. In operation, this kind of material provides a thin layer of lubricant that prevents direct contact between the surfaces. The present study aimed at incorporating particles of second phase lubricant (h-BN) into a matrix of nickel by high-energy ball milling in order to obtain a self-lubricating composite with homogeneous phase distribution of lubricant in the matrix. Mixtures with 10 vol.% of h-BN varying the milling time of 5, 10, 15 and 20 hours and their relationship ball/powder of 20:1 were performed. The effect of milling time on the morphology and microstructure of the powders was studied by X-ray diffraction, SEM and EDS. The composite powders showed reduction in average particle size with increasing milling time and the milling higher than 5 hours resulted in equiaxial particles and the formation of nickel boride.
Study of the Degradability of PA6/Organoclay Nanocomposites
Authors: de Carvalho Thamyres Cardoso , Bezerra Erbertt Barros , da Paz Renê Anísio , Leite Amanda Melissa Damião , Nóbrega Medeiros Vanessa , Araújo Edcleide Maria
Published: August 2016

The study of the degradability of PA6 / organoclay nanocomposites was evaluated to minimize the effects of plastic waste in the environment. The use of clays usually accelerates the degradation of nanocomposites. A regional clay (polyamide 6, Polyform - B300) and a quaternary ammonium salt (Cetremide (hexadecyltrimethyl ammonium bromide) were used. The hybrids were obtained in a co-rotating twin screw extruder and the tensile and the impact specimens were obtained through injection. The infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) confirmed the presence of the salt molecules in the modified bentonite and its organophilization. The XRD results of the hybrids indicate that the peak of the organophilic clay disappeared when incorporated into the polyamide, showing that all systems were exfoliated and/or partially exfoliated structure. The nanocomposites showed higher tensile mechanical properties when compared to the properties of pure polyamide, and the various conditions of aging influenced the degradation of these materials.
Pure and Doped SrTiO3 Powders Obtained by Ultrasonic Synthesis
Authors: Chaves André Silva , de Andrade Raponi Olívia , Gelfuso Maria Virginia , Thomazini Daniel
Published: August 2016

Thermoelectric ceramics are those capable of converting thermal into electricity energy by the Seebeck effect. The non-conventional synthesis of ceramic powders and the doping of these powders with rare earth elements are factors that can improve the efficiency in energy conversion. The objective of this work was to synthesize and analyze pure and doped SrTiO3 powders by solid state reaction (SSR) and ultrasonic synthesis (USS). The precursors of SSR were: strontium carbonate (SrCO3), titanium oxide (TiO2) and lanthanum and neodymium oxide (La2O3 and Nd2O3). They were mixed in a ball mill for 3.5h in stoichiometric ratio to obtain SrTiO3 (STO), Sr0.96La0.04TiO3 (STO-04La), Sr0.96Nd0.04TiO3 (STO-04Nd) and Sr0.96La0.02Nd0.02TiO3 (STO-02La02Nd). The powder mixtures were calcined at 1000°C in a conventional oven for 2h. The USS powders were produced by solubilization of Ti (C4H9O)4 and SrCO3 in an HNO3 aqueous solution. The solution was precipitated with NH4OH and, then, this powder was dried at 70°C for 24h, in air. The dried powder was added to a solution of KOH and subjected to ultrasound irradiation. The same procedure was followed for the synthesis of USS doped powders, STO-04La, STO-04Nd, and STO-02La02Nd powders using as dopant lanthanum and neodymium oxides. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and crystallite sizes were calculated by the Scherrer equation to evaluate the differences on structural and microstructural properties.
Characterization of Bionanocomposites PHB, PEG and Organophilic Clay
Authors: da Silva Jr. Raimundo Miguel , Conceição Isaias Damasceno , da Silva Neto João Emídio , Alves Tatianny Soares , Barbosa Renata
Published: August 2016

In this study, it was investigated the structural and morphological characteristics of bionanocomposites of poly (3-hydroxybutyrate) (PHB), containing 5% polyethylene glycol (PEG), 1% and 3% two types of organoclays (Cloisite 20A and vermiculite). The systems in the form of films were prepared by the method of intercalation solution. The films were characterized by X-ray diffraction (XRD) spectroscopy and Fourier transform infrared (FTIR). It was observed that, according to the type of clay used, the systems showed intercalated structures or partially exfoliated ones. Regarding the FTIR results, they indicated that the addition of different clays to the PHB/PEG blend did not promote significant changes in the chemistry of the polymer matrix.
Effects of 3-APTMS-Modified Nano-SiO2 on the Mechanical Properties and Crystallization Behavior of Polyamide-6
Authors: Queiroz Breno D. , Janzantti Vitor L.P. , Ambrósio José Donato
Published: August 2016

Nanocomposites of polyamide-6 with nanoSiO2 surface modified by 3-aminopropyltrimethoxysilane (3-APTMS) were prepared by melt blending in torque rheometer. Chemical modification of nanoparticles surface with 3-APTMS were observed by FTIR. Prior to nanocomposites processing, neat polyamide-6 (PA-6) was processed in a torque rheometer with varying processing parameters: polymer residence time in the chamber, rollers rotational speed, and polymer filling volume in the chamber. Two levels for each parameter were fixed. The influence of these parameters on degradation of PA-6 was determined by dilute solution viscosity and capillary rheometry. Results indicate that the best condition was achieved with the higher polymer residence time in the chamber, the higher rollers rotational speed, and the higher polymer filling volume in the chamber. With this information, PA-6 pellets were mixed with nanosilica particles unmodified and surface-capped by 3-APTMS via melt blending in torque rheometer, obtaining PA-6 composites with 1 wt.% of nanofillers. Mechanical and thermal properties of nanocomposites were evaluated by means of tensile test and differential scanning calorimetry (DSC).
Mechanical Properties of Natural Fibers Reinforced Polymer Composites: Palm/Low Density Polyethylene
Authors: Guedes Julia R. , Florentino Wagner Martins , Rodrigues Luciano Monteiro , dos Santos Claudinei , Mulinari Daniella Regina
Published: August 2016

In the work, mechanical properties of palm fibers/low density polyethylene (LDPE) composites were studied. These fibers were mixed with the polymeric matrix (LDPE) in a thermokinetic mixer, in which fibers were responsible for 5 to 20 wt% in the composition. After the mixture, composites were dried, ground in mill and placed in an injector camera according to ASTM D-638 and ASTM D-790 specifications. Specimens were tested in tensile, impact, flexural and Shore A hardness mode. Results showed the addition fibers in polymeric matrix presented increase mechanical properties when compared to pure polymer
Characterization of Epoxy Matrix Reinforced with Banana Fibers Thermal Properties by Photoacoustic Technique
Authors: Salgado de Assis Foluke , Muylaert Margem Frederico , Amoy Netto Pedro , Faria Jr. Roberto da Trindade , Cordeiro Thallis Custódia , de Oliveira Braga Fabio , Monteiro Sergio Neves
Published: August 2016

Synthetic fibers are being replaced gradually by natural materials such as lignocellulosic fibers. Compared to synthetic fibers, natural fibers have shown advantages in environmental, societal, economical and technical aspects. Thus, there is a growing worldwide interest in the use of those fibers. The banana fiber, extracted from the pseudo-stem of the plant, displays significant properties yet to be studied. Few thermal properties on banana fiber as reinforcement of epoxy matrix were fully evaluated. Therefore, the present work had as its objective to investigate, by photoacoustic spectroscopy and photothermal techniques the thermal diffusivity, specific heat capacity and thermal conductivity of epoxy composites reinforced with banana fibers .The epoxy matrix was added with up to 30% in volume of continuous and aligned banana fibers. The results indicated that these composites have good insulation capacity.
Synthesis, Characterization and Photoluminescent Properties of ZrO2 Nanocrystals
Authors: da Silva Sousa Giancarlo , Cavalcante Laécio Santos , Santos Maria Rita de Morais Chaves , de Matos José Milton Elias
Published: August 2016

Nanocrystalline zirconium oxide (ZrO2) was synhesized by hydrothermal method in presence of hydrogen peroxide. Surface morphology analysis depicts the formation of the nanorods. The structural analysis confirms that the as-synthesized ZrO2 product is of pure monoclinic phase (m-ZrO2) with crystallite size of about ~8 nm. The product consists of monodispersed nanoparticles of uniform composition, high purity, and crystallinity. The Raman spectra are quantitatively analyzed and the observed peaks are attributed to various vibration modes of the m-ZrO2. Photoluminescence (PL) spectrum of ZrO2 nanostructure showed a strong and broad emission peak at around 534 nm, which can be attributed the participation of several energy levels.
Thermal Parameters, Tertiary Dendritic Growth and Microhardness of Directionally Solidified Al-3wt%Cu Alloy
Authors: Barros André Santos , de Souza da Silva Maria Adrina Paixão , da Rocha Otávio Fernandes Lima , Moreira Antonio Luciano Seabra
Published: August 2016

The main purpose of this paper is to evaluate both tertiary dendritic arm growth and microhardness of Al-3wt%Cu alloy during horizontal directional solidification under transient heat flow conditions. Experimental thermal profiles recorded during solidification process allowed to determine growth rate and cooling rate values which are associated with both tertiary dendritic arm spacings and microhardness. The results show that initial tertiary branches growth only occurs when a cooling rate value of 1.14 K/s is reached. Variation of tertiary spacings is expressed as-1.1 and-0.55 power law functions of growth rate and cooling rate, respectively. A comparative analysis with other studies published in the literature that analyze tertiary dendritic growth of Al-Cu alloys considering transient directional solidification is carried out. Dependence of microhardness on dendritic arrangement is evaluated by experimental laws of power and Hall-Petch types with a view to permitting the applicability of the resulting expressions.
Pulsed Nd:YAG Laser Welding of UNS S 32205 Duplex Stainless Steel
Authors: Crespo Gillian da S. , Padilha Josiel L. , Sokei Celso R. , Tokimatsu Ruis C. , Gallego J. , Ventrella Vicente Afonso
Published: August 2016

This paper reports an experimental study of laser welding on duplex stainless steel UNS S32205 employed in the oil and natural gas industries. A pulsed Nd:YAG laser was used to weld the specimens. Bead on plate condition was used. Scanning Electron and Optical microscopy was applied to measure and analyze the cross-sectional of the weld bead. From the experimental results, it was found that the shape and size of the welded spot depend not only on the laser energy, but also on the pulse duration and the focus position. Metallographic observations showed that the microstructure of the weld metal was characterized by large ferrite grains with intra and inter-granular austenite. Large voids delimited by the molten zone boundary were observed in weld beads with low pulse duration. The heat affected zone resulting from the welding is pretty much absent and no cracks were detected.
Effect of Corrosion of Stainless Steel Welded within Lithium Chloride
Authors: Pereira Juliete N. , Macêdo Dias David Márcio , Regone Natal Nerímio , Fernandes Marcos A. , Nakamatsu Sandra , Maestrelli Sylma Carvalho , Mariano Neide Aparecida
Published: August 2016

The difficulties experienced in welding processes of martensitic stainless steel led to development of a new class of them, known as stainless mild martensitic steels. Also, due to the current high demand for energy and materials to oil extraction at great depths, scientists have being developing specific researches about mechanical resistance and corrosion of steels and how these properties are influenced by high temperature processes. This research studies the effect of welding process over the corrosion resistance of the 13Cr4Ni0.02C steel in a lithium chloride solution with a concentration of 120,000 PPM Cl-. The corrosion tests were conducted by cyclic potentiodynamic polarization in the base metal, weld bead and heat affected zone (HAZ) areas of the steel, in average temperatures of 23°C (as reference) and 3°C. The results revealed that the weld bead and heat affected zones of the 13Cr4Ni0.02C steel in a temperature of 3°C are less resistant to corrosion in this environment than the base metal in the same conditions.
Microstructural Characterization of Joints of Maraging 300 Steel Welded by Laser and Subjected to Plasma Nitriding Treatment
Authors: Lombardo Sandro , Nascimento Ferreira Renan , de Souza Santos Lucas Augusto , de Jesus Silva José Wilson , Bagio Scheid Vladimir Henrique , Abdalla Antonio Jorge
Published: August 2016

Amongst the ultra high strength steels, the maraging steels have been noticed because they maintain the fracture toughness superior to other steels of their class. The main difference is the way they acquire resistance. While the conventional carbon steels raise their resistance by heat treatments forming harder phases such as martensite or bainitic constituents, the maraging steels harden by intermetallic particles precipitation. These steels are very promising for several applications, mainly for the aerospace or nuclear areas. In this work, tests of laser welding on a sample of maraging 300 steel, have been carried out, by applying aging at several times and temperatures and analyzing the influence of plasma treatment on the steel microstructure and resistance. The results are promising and show that this welding process is viable and can even be associated with nitriding to improve the surface characteristics. It was observed that the temperature choice and aging time are fundamental to reach high mechanical resistance levels. Temperature values about 480 oC and time 10,800 seconds proved to be suitable for this treatment. The loss of strength in the welded joints, after the aging treatment, was less than 10%. It was also noticed that when the plasma nitriding treatment is applied, aging occurs simultaneously, therefore it is important to select temperature and treatment time in order to optimized the aging process as well.
Study of Fatigue in AISI 4340 Steel with Different Microstructural Conditions, Submitted to a Surface Treatment of Shot Peening
Authors: Molento de Moraes Carlos Eduardo , Baptista Carlos Antonio Reis Pereira , dos Santos Torres Marcelo Augusto , Fonseca Maria Cindra , Abdalla Antonio Jorge
Published: August 2016

The AISI 4340 steel has been largely employed for structural purposes, which requires resistance levels with yield strength above 1400 MPa and it attains high levels of resistance in dual phase, bainitic or martensitic microstructural conditions. The samples of AISI 4340 steel with different microstructural conditions (martensitic, bainitic and ferritic/perlitic) have been submitted to fatigue tests on push-pull mode. Subsequently, the new specimens underwent a shot peening surface treatment and new fatigue tests. The results have been discussed in comparison to the three microstructural conditions studied and they were related to a microstructural characterization. The results have showed that a shot peening treatment is not always beneficial to fatigue life, since there is a relationship between the compressive stresses developed on the surface and its roughness formed due to the deformations. Under the three microstructural above studied it was noticed a strong fatigue life reduction in the martensitic condition because such microstructure is considered less ductile.
Work Hardening and Microstructural Effect during Dynamic Deformation of Polycrystalline Copper
Authors: Monteiro Sergio Neves , Scarpini Cândido Verônica , Santos da Luz Fernanda , Lopes dos Santos Jheison
Published: August 2016

Dynamic deformation of metals in the elevated strain rate interval of elastic-plastic wave propagation is relevant to technological conditions, such as structural response to impact, ballistic effects, and metal forming processes. In the present work, the work hardening of quasi-static and dynamically deformed copper using a split pressure bar was evaluated for two different grain sizes. From slip lines observations in conditions of both dynamic and quasi-static strain rates, as well as an insensitivity to grain size of the yield stress, it is suggested that copper behave like a single crystal under dynamic deformation. It is shown, for the first time, that the work hardening rate during dynamic deformation of polycrystalline copper remains higher up to the fracture.
Secondary Austenite Precipitation during the Welding of Duplex Stainless Steels
Authors: de Alencar Pires Sandro , de Campos Marcos Flavio , Marcelo C.J. , Xavier Carlos Roberto
Published: August 2016

In this work a multipass welding procedure was carried out on a 2205 Duplex stainless steels (DDS) plate. Due to the reheating cycle caused by the adopted procedure, it has favored the precipitation of secondary austenite at the weldment microstructure, besides of encouraging the grain growth at the heat affected zone (HAZ).
Artificial Neural Network Model for Predict of Silicon Content in Hot Metal Blast Furnace
Authors: David Sayd Farage , David Felipe Farage , Machado M.L.P.
Published: August 2016

The growing focus on the efficiency of the reduction process in blast furnace generates an alteration in the way they operate. This modifies the conditions of transfer of silicon for the hot metal and can cause problems in the added value of your product. To evaluate the changes of the operational parameters of the reduction on the conditions of transfer of silicon process a mathematical model based on artificial neural networks has been implemented. Through this model it was possible to predict the silicon content to determine the influence of each operational parameter. Artificial neural networks were able to predict the silicon content through parameters of the reduction in blast furnace process, and this was verified by the precision of this model. The ANN showed that Theoretical flame temperature, Pressure blow and Coke rate have a positive influence on the silicon content in hot metal, and the Hot metal rate is inversely proportional to the silicon content of the hot metal.
Effect of Boron and Carbon Addition on the Phase Transformations during High-Energy Ball Milling and Subsequent Sintering of Si3N4+B and Si3N4+C Powder Mixtures
Authors: Vicentin Maruya Luiz Otávio , Baldone Lara Bruna Rage , de Lima Belmira Benedita , Chad Vanessa Motta , Coelho Gilberto Carvalho , Ramos Alfeu Saraiva
Published: August 2016

This study reports on effect of boron and carbon addition on the phase transformations during ball milling and subsequent sintering of Si3N4+B and Si3N4+C powder mixtures. Ball milling at room temperature was conducted using stainless steel vials (225 mL) and balls (19mm diameter), 300 rpm and a bal-to-powder weight ratio of 10:1. The as-milled powders were uniaxially compacted in order to obtain cylinder samples with 10 mm diameter, which were subsequently sintered under nitrogen atmosphere at 1500°C for 1h. Characterization of the as-milled powders and sintered samples was performed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Only peaks of Si3N4 were identified in X-ray diffractograms of as-milled Si3N4+B and Si3N4+C powders, suggesting that metastable structures were found during milling. After sintering at 1500°C for 1h, the Si3N4+BN and Si3N4+SiC ceramic composites were formed from the mechanically alloyed Si3N4+B and Si3N4+C powders.
EBSD Analysis of SmCoFeCuZr Alloys
Authors: Romero Sergio Antonio , Hauegen Christien G. , Landgraf Fernando J.G. , de Campos Marcos Flavio
Published: August 2016

In the present study, EBSD was used for the characterization of alloys used for production of SmFeCoCuZr magnets. EBSD is adequate for texture analysis, but may give misleading results for phase identification. EBSD is not suitable for identifying phases with very similar crystalline structure, especially when the phases are crystallographically coherent, due to the superposition of Kikuchi lines. As consequence, for phase identification EBSD should be considered a complementary technique to other methods, as for example x-ray diffraction (XRD).
Suitable Nanostructures for Obtaining the Maximum Energy Product in Magnets
Authors: de Campos Marcos Flavio , Romero Sergio Antonio
Published: August 2016

The existence of exchange coupling or magnetostatic coupling between two phases, one magnetically hard and other magnetically soft is a way for obtaining higher maximum energy product (BHmax). In this study, it is discussed the microstructures for obtaining either exchange coupling or magnetostatic coupling in real materials. One relevant condition is that the assumptions of the Stoner-Wohlfarth model should be obeyed, with both phases, hard and soft, with dimensions less than single domain particle size. A real possibility is enveloping a spherical grain of hard phase with a first shell of soft phase, and another second shell or layer of a paramagnetic phase. The paramagnetic phase may play relevant role promoting magnetically decoupling between the grains.
Study and Development of Advanced High Strength Steel to Automotive Industry Applications
Authors: de Abreu Martins Silvana , de Abreu Martins Charles , Fonstein Nina , Barbosa Godefroid Leonardo
Published: August 2016

Steel is the main material used in the automotive industry, mainly due to its excellent mechanical properties. However, with the development of new materials and technologies in recent decades, there is a demand to improve steel competitiveness to face the market of materials and achieve improvements in quality and performance of cars. In this work it was produced on pilot scale C-Mn-V steels with Cr or Mo addition. The main objective was to evaluate the effects of Cr or Mo addition on microstructure and mechanical properties. These steels were submitted to tensile, bending and hole expansion tests, while microstructure was analyzed using OM and SEM. It could be seen that addition of Cr or Mo resulted in improvements on mechanical properties. However, C-Mn-V steel with Mo performed better, showing excellent behavior in tensile and bending tests, increasing around 30% of mechanical resistance.
The Influence of Gravity on Eutectic PbSn Alloy Grown by the Vertical Bridgman Method
Authors: Toledo Rafael Cardoso , An Chen Y. , Bandeira Irajá Newton , de Freitas Filipe Estevão
Published: August 2016

Composition profiles of eutectic alloy Pb25.9Sn74.1 atomic % grown by the normal and inverted Bridgman methods are presented and the study of the solute alloy redistribution is made. The inverted vertical Bridgman method, where the solidification occurs from the top to the bottom of the melt under a destabilizing thermal gradient, allows the growth of crystals with buoyancy-driven convection different from that with the usual vertical Bridgman configuration. The scope of this work is to study the influence of the gravity acceleration in the convection process.
Displacement of the Ingnition Furnace in the Iron Ore Sintering with Re-Circulation of Waste Gases
Authors: Guilherme Vagner Silva , de Castro José Adilson
Published: August 2016

In search of new technologies for the iron ore sintering process, the re-circulation of waste gases in the process can provide some advantages in relation to the conventional process. For such study, a sintering multi-phase model was used for the assessment of the re-circulation of waste gases in the process. Five cases of re-circulation of waste gases in the sintering process were analyzed, always aiming at a stable operation in the process. The results of the simulation indicate an enlargement of the combustion front with the re-circulation of the waste gases and the possibility of existing a reduction of the solid fuel consumption. As a result, there was an increase of the calcium-silicate fraction, providing a sinter reducibility improvement, apart from the reduction of the emission of CO2 and PCDD/Fs in the sinter machine.