Efeito do plasma frio atmosférico em revestimento de cera de carnaúba na inativação de Colletotrichum brevisporum

Cera de carnaúba é utilizada, com sucesso, em revestimento de frutos por formar uma barreira contra a perda de umidade, troca de gases e ação antimicrobiana. No presente trabalho, pretende-se melhorar esta última propriedade através do tratamento por plasma. Plasma produzido por descarga de barreira dielétrica (DBD), usando pulsos de voltagem de 45 kV, repetidos na frequência de 405 Hz, durante 9 min, foi aplicado diretamente sobre esporos de fungo Colletotrichum brevisporum (4x104 conidia.cm-1) ou sobre superfície dos revestimentos de cera. Verificou-se que o revestimento, após tratado por plasma, apresentou resistência antifúngica equivalente àquela existente quando aplicada diretamente sobre os fungos. Este resultado foi justificado com base na literatura, em que o tratamento com plasma em lipídios estimula a oxidação das cadeias lipídicas, resultando na formação de compostos carboxílicos, que possuem propriedades antimicrobianas. Palavras-chave: Plasma DBD, eletrodos coplanares, antifúngico, atmosférico, inativação

Changing the characteristics of the nitrided layer using three different plasma configurations

Direct current (DC) plasma nitriding offers some disadvantages, especially in parts with complex geometries,where the presence of edges is significant, such as gears, molds, and needle punched parts are stronglyaffected by this effect, leading to irregular formation of nitrided layers and high variation in surface hardness.To solve these problems two techniques were developed as alternatives, namely: pulsed plasma nitriding andcathodic cage nitriding. In this work, these three nitriding techniques were compared using AISI 1045 steel assubstrate. Steel discs were nitrided with the purpose of evaluating the influence of these different plasmaconfigurations on the characteristics of the nitrided layer. The treatments in the three techniques were carriedout at the same pressure, temperature, time and gas atmosphere. The samples were characterized for themicrostructure, microhardness and crystalline phases present. X-ray diffraction with grazing incidence wasused to verify the order of the nitrites formed and to estimate the thickness of the single-phase layers.Differences between the configurations with respect to the occurrence of restriction rings, total thickness (xε+ xγ') and relative (xε/xγ') compound layers were observed.Keywords: Plasma DC; cathodic cage; pulsed plasma; nitriding; GIXRD

Mecanismo de crescimento e caracterização de cristais formados na superfície de águas residuais de salinas

Sob condições ainda desconhecidas, cristais denominados de flor de sal, ou fleur de sel, como é comumente conhecido, pode ser formado na superfície de uma salmoura supersaturada durante a evaporação da água do mar nas salinas. Visando produzir flor de sal de uma maneira controlada e fazer melhor uso da solução residual de salinas, denominada de água-mãe, o presente trabalho foi proposto. O mecanismo de crescimento, morfologia, microestrutura e composição química dos sais obtidos foram estudados durante a evaporação da água-mãe, cuja densidade variou de 1,230 g/cm³ para 1,244 g/cm³, mantendo fixos o gradiente térmico e umidade relativa do ar. Análises quimicas, microestruturais e morfológicas foram usadas para caracterização. Cristais cúbicos ocos foram obtidos cujas concentrações iônicas foram dependents da densidade da solução. O tamanho e massa dos cristais também foram dependentes da densidade da solução. As amostras apresentaram fases contendo sulfatos como NaK3(SO4)2, Mg (SO4). (H2O) e K2SO4, cuja porcentagem aumentou levemente com o aumento da densidade. Mesmo assim, as porcentagens de NaCl foram acima de 90% para todas as amostras, mostrando que é possível extrair flor de sal de alta pureza a partir de uma solução residual hipersalina.Palavras chaves: flor de sal, água-mãe, crescimento de cristais, mecanismo, salina.

OES during reforming of methane by microwave plasma at atmospheric pressure

International audienc

Surface modification of bacterial cellulose by nitrogen-containing plasma for improved interaction with cells

Bacterial cellulose (BC) membranes were modified with nitrogen plasma in order to enhance cell affinity. The surface properties of the untreated and plasma modified BC (BCP) were analyzed through contact angle measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The effect of the plasma treatment on the adhesion of microvascular (HMEC-1), neuroblast (N1E-115) and fibroblast (3T3) cell lines was analyzed. The nitrogen plasma treatment did not increase the wettability of the material, but increased the porosity and surface chemistry, as noticed by the presence of nitrogen. XPS analysis revealed the stability of the modified material along time and autoclave sterilization. The cell adhesion and proliferation of HMEC-1 and N1E-115 cells was significantly improved in the BCP, in contrast with the 3T3 cells, revealing a cell-specific effect. This work highlights the potential of plasma treatment for the modification of the BC surface properties, enhancing its potential for biomedical applications.Programme Alβan, the European Union Programme of High Level Scholarships for Latin America.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brasil.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brasil.Fundação para a Ciência e a Tecnologia (FCT) – POCTI, Portugal

Bone marrow mesenchymal cell adhesion to polished and nitrided titanium surfaces

Aim: To evaluate the adhesion of mouse bone marrow mesenchymal cells (MBMMC) on different titanium surfaces. Methods: Grade II titanium discs (ASTM F86) received two different surface treatments: polished (S1) and cathodic cage plasma nitriding (S2). MBMMC were cultured on titanium discs in 24-well cell culture plates, at a density of 1 x 104 cells per well. After 24 h, the adhesion was evaluated using a hemocytometer. Results: The mean adhesion was greater on S2, though without statistically significant difference from S2 (p>0.05). Conclusions: It was demonstrated that titanium surface treatment with ionic nitriding in a cathodic cage is biocompatible since it preserved the integrity of the cultivated MBMMC for a period of 24 h, allowing their adhesion

Sumulation of Plasma Torche

The work is a study about main work features and properties of plasma of argon for designing and building plasma torches, to be employed in the projection of fine particles. The plasma properties in feature of their temperature and pressure are determinate and their behaviors inside the main element of the torche: the nozzle, is simulated. The influence of nozzles characteristics in the obtained plasma is determined, from finite elements models developed, being ended up defining the best nozzle parameters to be designed and built

Estudio preliminar acerca de recubrimientos de hidroxiapatita HAP-200 obtenidos por plasma atmosférico A preliminary study about HAP-200 hydroxyapatite coatings obtained by atmospheric plasma

La hidroxiapatita es catalogada como un material bioactivo cuya capacidad de interacción con el hueso ha permitido su uso de forma satisfactoria para aplicaciones ortopédicas y dentales. En el presente trabajo la hidroxiapatita producida por el Centro Nacional de Investigaciones Científicas fue proyectada mediante una antorcha de plasma atmosférico sobre un sustrato de acero inoxidable austenítico. El tamaño de partículas fue determinado por dispersión láser y la distancia de proyección fue variada entre 20 y 60 mm. La microestructura y composición de fase del polvo, así como la del recubrimiento obtenido fueron examinados por microscopia óptica, microscopia electrónica de barrido y difracción de rayos X (DRX). La composición química puntual del recubrimiento fue analizada por espectrometría de dispersión de energía (EDS), también fueron medidos la dureza, el espesor de capa y la cristalinidad. Los resultados indican que la cristalinidad disminuye con el incremento de la distancia de proyección, no así su dureza y espesor de capa.Hydroxyapatite is classified as a bioactive material whose ability of interaction with bone allowed its use in a satisfactory way for orthopedic and dental application. In present paper the hydroxyapatite produced by the National Center of Scientific Researches, was projected by means of an atmospheric plasma torch on an austenitic stainless steel substrate. The particles' size was determined by laser dispersion and the projection distance fluctuates between 20 and 60 mm. The microstructure and the powder phase composition, as well as the coating achieved were examined by optical microscopy, scanning electron microscopy and X-rays diffraction (XRD). The coating's point chemical composition was analyzed by energy-dispersion spectrometry (EDS) and the hardness, layer thickness and crystallization were measured. Results showed that crystallization decreases according to the increase of projection distance, but not its hardness and layer thickness