Luís César Fontana

Active screen plasma system applied to polymer surface modification: poly(lactic acid) surface activation before polyaniline graft polymerization in aqueous medium

Abstract An active screen plasma system (ASPS) was used for the surface activation of poly(lactic acid) (PLA) as a pretreatment before the oxidative graft polymerization of polyaniline (PANI). In ASPS, the plasma glow discharge occurs outside the grid, and the samples to be treated are placed inside the cage where they are subjected to a floating potential (about −12 V). An increase in hydrophilicity was observed for all samples after Ar plasma treatment. In addition, a decrease in thermal stability and changes in crystallization behavior were observed for PLA samples treated for a longer time. After PANI graft polymerization, smoothing of the surface topography was noticed in samples treated for short time periods. Such a change in the topography, in addition to surface activation, provides better conditions for subsequent PANI grafting.

Pulsed bias effect on crystallinity and nano-roughness of Ti6Al4V-N films deposited by grid assisted magnetron sputtering system

This paper reports the effect of pulsed bias in comparison with DC bias on reactive deposition of Ti6Al4V-N films, obtained by Grid Assisted Magnetron Sputtering. The results obtained by X-Ray diffraction (XRD), Energy Dispersive X-ray Fluorescence Spectrometer (EDX) and Atomic Force Microscopy (AFM) show that bias condition affects the crystalline texture and change the roughness and morphology of the films. The DC bias favors the film crystallinity, however the pulsed bias produces smoother films.

ESTUDO DE TRATAMENTO TERMOQUÍMICO SUPERFICIAL POR PLASMA EM AMOSTRAS COM GRADIENTE DE TEMPERATURA

Neste trabalho e apresentado um metodo de ensaio que atraves da aplicacao de um gradiente termico na amostra durante um tratamento termoquimico de superficie por plasma, permite o estudo da influencia da temperatura sobre a microestrutura das camadas formadas na peca tratada, para uma ampla faixa de trabalho (350 a 850oC) e em um unico ensaio. Como exemplo de aplicacao, emprega-se tal metodo durante a carbonitretacao a plasma do aco ferramenta AISI D2. As tecnicas utilizadas para a caracterizacao das amostras foram: Difratometria de Raios-X (DRX), Microscopia Otica (MO), Microscopia Eletronica de Varredura (MEV), Energia de Dispersao de Raios-X (EDX) e Microdureza Vickers (MDV). Detectou-se a formacao de camadas visiveis de difusao e a presenca de fases de nitretos (e-Fe 2-3 N, (γ’-Fe 4 N, CrN) para varias temperaturas no aco ferramenta AISI D2 carbonitretado. Na temperatura de tratamento de 753°C ocorre uma transformacao de fases no aco AISI D2.