Júlio César Pereira Barbosa

Effect of cage configuration in structural and optical properties of tin films grown by cathodic cage discharge

Cathodic cage discharge was developed recently in order to eliminate phenomena as edge effect and overheating, which occurs during conventional processes. In this study, the effect of cage configuration in active species during the deposition process and optical properties of TiN film were studied. TiN compound was chosen because its optical properties are very sensitive to slight variations in microstructure and film thickness, becoming a good monitoring tool in fabrication process control. Cages were made of titanium and have different holes numbers and holes diameter. Electrical efficiency of the system and optical properties of TiN films were strongly influenced by experimental conditions. It was found that with more holes at the top of cage, deposition rate and crystallinity were higher, if compared to cages with a small number of holes at the top. On the other hand, the opposite behavior was observed when more holes were located at the sidewall of cage.

Influência das espécies do plasma na modificação das propriedades superficiais do titânio tratado por plasma de N2 - Ar - O2

The present study correlates plasma active species with titanium surface properties. This was achieved by performing optical emission spectroscopy (OES) analysis of N2+ (391.4 nm) and O (844.6 nm) within a N2-Ar-O2 plasma. The fluxes of gases were established to be 1 and 4 sccm (standard cubic centimeter) for nitrogen and argon, while that of oxygen was varied between 2 and 4 sccm. A non-linearity of the intensity of N2+ (391.4 nm) species with the increase on O2 flux was observed with an intensity peak at 3 sccm. It was also concluded that the active species influence the modification of properties after the plasma treatment. The N2+ (391.4 nm) species were more effective to form nitrides and the surface roughness was bigger when those species presented higher intensity. Surface hardness and surface stress were also higher whenever using higher intensity fluxes of N2+ (391.4 nm). Furthermore, while the N2+ (391.4 nm) specie influenced the dispersive component, the O (844.6 nm) specie influenced the polar component.

Modificação da superfície e das propriedades tribológicas do titânio por carbonitretação a plasma

TiCxNy surfaces were produced by thermochemical treatment achieved by N2 - Ar - CH4 plasma mixture. The influence of methane concentration and C and N atoms inserted into the crystalline lattice of Ti were investigated through the characterization of its tribomechanical properties. Therefore, commercially pure Ti (grade II) samples were carbonitrided in the x N2 - y Ar - z CH4 plasma mixture (where x and y = 4 SCCM and z = 2, 3 and 4 SCCM) at 500 °C, during 1 h. C and N concentration profile after treatments were determinate by NRA. The superficial phases were identified by GIXRD. Pin-on-disk assays were utilized to determine the friction coefficient, whose damaged areas were studied by perfilometry and scanning electron microscopy (SEM) techniques. It was observed that the friction coefficient and the damage mechanism of Ti are intensively dependent of C and N concentration on the surface. However, the concentration profile of those interstitial elements is not directly proportional to the methane gas flow.

Nitretação em gaiola catódica: influência do tempo de tratamento

AISI 316 austenitic stainless steel samples have been nitrided by cathodic cage technique in same treatment conditions: pressure 250 Pa, temperature 500 oC and nitriding mixtures 80%N2/H2. The variance is limited just to process duration, from 1 to 5 hours. In this work the objective is to observe the increase of nitrided layer. It has been seen that there was layer formation to all times of nitriding. They are confirmed through optical microscopy and microhardness analysis. The X-ray difratogram presents similar phases proving that is possible obtain nitrided layer using cathodic cage technique even to short during treatment.

Características elétricas e eficiência energética de um sistema de descarga de barreira dielétrica

de uma descarga de barreira dieletrica (DBD) com eletrodos assimetricos em ar atmosferico foram investigadas experimentalmente. As tensoes na faixa de 18-29kV e frequencia de 18-22kHz foram aplicadas ao sistema DBD, produzindo descargas filamentosas e difusas na superficie de um dieletrico de vidro. Essas descargas atingiram correntes de pico ate 4mA. Em termos de eficiencia energetica, o sistema obteve potencia minima de 5W necessaria para produzir um regime difuso de plasma. As melhores condicoes do sistema foram encontradas para a distância entre eletrodos de 0,8 mm

NON-LINEARITY OF N 2 – Ar – H 2 PLASMA MONITORED BY OES

New and efficient monitoring strategies are necessary to obtain interesting answers of the plasma. In order to comprehend the dynamic involved in such an ambient when interactions occur between solids and free particles, it has been utilized the plasma diagnostic by Optical Emission Spectroscopy – OES. Due to the large publication of studies related to plasma combinations of N2, H 2 and Ar, the atmosphere of N 2 – Ar – H 2 plasma was analysed by OES technique. The species N 2 + , N 2 , and H α were identified and monitored observing the relative intensities increasing of those three species versus flow of H 2 gas; it has been observed a non-linear comportment.