Síntese de nanocompósitos de WC-12wt%Co por moagem de alta energia e sua caracterização morfológica

In this work micrometric particles of WC and Co were processed by high energy ball milling in a planetary ball mill. We evaluated the phase formation and changes in microstructure of WC-12wt%Co as a result of the following milling parameters: ball-to-powder weight ratio, milling time and speed. The material was characterized by X-ray diffraction (crystalline phases and crystallite size), particle size analysis (average grain diameter), the BET method (surface area), and scanning electron microscopy (powder morphology). The average particle size (D50) and crystallite size were respectively 1.63µm and 13.8nm, for a surface area of 4.709 m2 /g, using a ball-to-powder weight ratio of 1:20, a milling time of 5h and a milling speed of 500 rpm.Neste trabalho, partículas micrométricas de WC e Co foram processadas por moagem de alta energia em um moinho planetário. Avaliamos a formação de fases e mudanças na microestrutura do WC-12wt%Co como resultado dos seguintes parâmetros de moagem: razão mássica bolas/pó, tempo e velocidade de moagem. O material foi caracterizado por difração de Raios-X (fases cristalinas e tamanho de cristalito), análise granulométrica (diâmetro médio), método BET (área superficial) e microscopia eletrônica de varredura (morfologia do pó). O tamanho médio de partícula e o tamanho de cristalito foram 1.63µm e 13.8nm, respectivamente, para uma área superficial de 4.709m2 /g, usando razão mássica bolas/pó de 1:20, tempo de moagem de 5h e velocidade de moagem de 500rpm

Elimination and control of aquatic pests in the environment

The present paper is a brief review of possible methods that can be used to control or elimenate aquatic pests from the environment, with particular emphasis on the golden mussel, Limnoperna fortunei (Dunker 1856). This bivalve mollusk, native of Southeast Ásia, has infested most of the rivers in Northen Argentina, Uruguay, Paraguay and Southern Brazil and is causing serious environmentals difficulties and biofuling. in addition, it causes serious problems to water treatment atations and hydroelectric power plants.O presente trabalho apresenta uma breve análise dos métodos que podem ser usados para combater ou eliminar várias pestes aquáticas com ênfase sobre o mexilhão dourado, Limnoperna fortunei (Dunker 1856). Este molusco bivalve, originário do Sudeste da àsia, invadiu grande parte dos rios do norte da Argentina, Uruguai, Paraguai e sul do Brasil e está degradando o meio ambiente na região. Além disso, está causando sérios problemas no abastecimento de energia hidroelétrica

Titanate nanotubes produced from microwave-assisted hydrothermal synthesis : characterization, adsorption and photocatalytic activity

A microwave-assisted hydrothermal (MAH) method was employed to synthesize TiO2 nanotubes (TNTs) and these were compared to the conventional hydrothermal (CH) method. The nanotubes were characterized for their crystallinity, morphology, surface area and photocatalytic activity. The TiO2 P25 was used for comparison purposes and efficiently degraded both dyes. However, methylene blue was adsorbed on the nanotube surfaces, which can be attributed to the electrostatic interaction between the cationic methylene blue and the negatively charged TNT surface. On the other hand, all nanotubes had a photocatalytic performance with methyl orange (anionic dye). Additional degradation was observed for nanotubes synthesized via the MAH method at 150 °C. This can be directly related to their larger surface area. Adsorption mechanisms of TNTs were also discussed by applying the Langmuir and Freundlich isotherm. The results show an efficient dye wastewater treatment through the application of TNT photocatalyst

Solution combustion synthesis of Mo-Fe/MgO : influence of the fuel composition on the production of doped catalyst nanopowder

Among the techniques for producing oxide catalysts, the solution combustion synthesis (SCS) has been widely used to produce high-quality nanostructured powders at lowcost. Through SCS, due to the high exothermic energy liberated by the reaction between the transition metal nitrate and the fuel, it is possible to homogeneously incorporate dopant ions into the catalyst. Besides, SCS allows the production of nanopowders with sizes in the decimal scale, which is extremely important for powdered catalysts. The smaller the particle is, the larger the surface area is. Based on these possibilities, the aim of this work is to produce Fe- Mo/MgO nanopowders by SCS. The influence of concentration and composition of the fuels glycine and polyethylene glycol (PEG) on the final product were investigated. The morphology and the physicochemical properties were characterized by X-ray diffraction (XRD), electron microscopy (SEM), granulometry and surface area analysis. The results indicated high crystallinity for the samples produced with PEG and a wide variation on the nanoparticles sizes depending on the fuel properties

Synthesis of hydro-sodalite as a heterogeneous catalyst for reaction kinetics of soybean oil trans-esterification

coal fly ash as a catalyst, under reaction conditions with different temperatures and reaction times. The catalyst characterization revealed that zeolite type hydro-sodalite was synthesized and consists of mesoporous agglomerates particles with a specific surface area of 7.53 m² g-1 and a basic catalytic character. The conversion rate of soybean oil to its methyl esters was found to increase with an increase in temperature. An ester yield of 92.5% was the highest methyl ester achieved at 65°C and at a 12:1 methanol-to-oil molar ratio. The reaction followed pseudo-first order kinetics with a calculated activation energy (Ea) of 27.23 kJ mol-1

Shear bond strength of metallic and ceramic brackets using color change adhesives

Objective: To determine the shear bond strength of orthodontic brackets using color change adhesives that are supposed to aid in removing excess of bonding material and compare them to a traditional adhesive. Methods: Ninety metallic and ninety ceramic brackets were bonded to bovine incisors using two color change adhesives and a regular one. A tensile stress was applied by a universal testing machine. The teeth were observed in a microscope after debonding in order to determine the Adhesive Remnant Index (ARI). Results: The statistical analysis (ANOVA, Tukey, and Kruskall-Wallis tests) demonstrated that the mean bond strength presented no difference when metallic and ceramic brackets were compared but the bond resistance values were significantly different for the three adhesives used. The most common ARI outcome was the entire adhesive remaining on the enamel. Conclusions: The bond strength was similar for metallic and ceramic brackets when the same adhesive system was used. ARI scores demonstrated that bonding with these adhesives is safe even when ceramic brackets were used. On the other hand, bond strength was too low for orthodontic purposes when Ortho Lite Cure was used.Objetivo: determinar a resistência adesiva à tração de braquetes ortodônticos usando resinas coloridas que se propõem a ajudar na remoção do excesso de material adesivo e compará-las com um adesivo tradicional. Métodos: Noventa braquetes metálicos e 90 cerâmicos foram colados com dois adesivos coloridos e com um adesivo tradicional em incisivos inferiores bovinos, sendo aplicada tração com uma máquina de ensaios universal. Após a descolagem, os dentes foram observados em microscópio para a determinação do índice de adesivo remanescente (ARI). Resultados: a análise estatística (testes ANOVA, de Tukey e de Kruskall-Wallis) demonstrou que a força de união média foi significativa entre os adesivos usados. Os ARIs mais comuns foram aqueles onde o adesivo permaneceu no esmalte. Conclusão: a resistência adesiva foi similar entre braquetes metálicos e cerâmicos quando o mesmo adesivo foi usado. Os resultados do ARI demonstraram que esses adesivos são seguros, mesmo com o uso de braquetes cerâmicos. A resistência adesiva foi muito baixa para Ortodontia no grupo colado com Ortho Lite Cure

Produção de pastilha vítrea com a adição de vidro sodo-cálcico, cinza da casca de arroz e carbonato de cálcio como agente espumante

Universidade Federal do Rio Grande do SulEngenhariaDepositad

Synthesis, characterization and application by HVOF of a WCCoCr/NiCr nanocomposite as protective coating against erosive wear

The scope of this work is to synthetize and characterize a WCCoCr/NiCr nanocomposite evaluating its application as protective coating against erosive wear when applied by High Velocity Oxygen Fuel (HVOF). The composite was formed by carbide of tungsten-cobalt-chrome (WCCoCr) processed by high energy milling and a metallic matrix of nickel-chrome (NiCr). The milled material was added to the NiCr in the fraction of 5%wt. The powders were investigated by X-ray diffraction and and scanning electron microscopy, analysing particle size distribution and surface area. The protective layers were deposited by HVOF and evaluated for their microhardness, microstructure, porosity, and erosive wear. Their microstructure showed lamellar character, with a low level of oxides and porosity between 0.5 % and 1 %. The coating formed by NiCr and WCCoCr milled for 3 hours presented microhardness of 635 HV and erosion rates 50 % smaller than the commercial coating

Production and characterization of magnetic Fe3O4 nanoparticles coated with PCL for biomedical applications

Currently, magnetic nanoparticles are widely studied with regard to their application in cancer treatment. This study aims to show a straightforward strategy for the production of Fe3O4 nanoparticles (NPs) with biocompatible surface modifications with polycaprolactone (PCL) for biomedical purposes. The effects of the polymer coating on the properties of magnetite were evaluated. Crystallinity, morphology, composition, hydrodynamic size and magnetic properties of the produced nanoparticles were analysed via X-ray diffractometry (XRD), Transmission Electron Microscopy (TEM), Fourier-Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and Vibrating Sample Magnetometry (VSM), respectively. The proposed method produced nanoparticles of magnetite with an average size between 9 and 11 nm, with spherical morphology and superparamagnetic properties. Magnetization values were not compromised even when the highest amount of polymer was used in the surface modification. On the other hand, the coating resulted in the decrease of the hydrodynamic size of the composites, indicating greater colloidal stability when the polymer was present. The obtained nanoparticles showed maintenance of significant superparamagneticbehavior, even in the presence of PCL on their surface. This phenomenon would allow for their application as a further optimized vector in hyperthermia cancer treatment, controlled drug delivery and resonance imaging

Processo para fabricar compósitos poliméricos laminados mediante moldagem assistida a vácuo e compósitos poliméricos laminados

Universidade Federal do Rio Grande do SulEngenhariaDepositad