Propriedades mecânicas e tribológicas de filmes sintetizados mediante técnica de deposição e implantação iônica por imersão em plasma
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Data
2004
Autores
Silva, Paulo Augusto de Faria [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho, a técnica de implantação iônica e deposição por imersão em plasmas foi utilizada para a síntese de filmes finos de polímero com características distintas dos preparados pelo método convencional de PECVD (Plasma Enhanced Chemical Vapor Deposition). Plasmas de radiofrequência (13,56 MHz) de benzeno e de misturas de acetileno/argônio e metano/argônio foram empregados. Para promover bombardeamento iônico do filme em crescimento, os substratos foram polarizados com pulsos de alta tensão negativa (25 kV). A freqüência e o ciclo de trabalho dos pulsos foram variados simultaneamente entre 0 - 125 Hz e 0 - 1, respectivamente. Investigou-se o efeito destes parâmetros nas propriedades dos filmes. Com as técnicas de nanoindentação e nanoriscos, avaliou-se as propriedades mecânicas (dureza, e parâmetro de resistência plástica) e tribológicas (coeficiente de atrito e resistência ao risco) dos filmes. A composição elemental foi determinada por espectroscopia de fotoelétrons de raios-X e a rugosidade por imagens de microscopia de varredura de força atômica. Resultados revelam a presença de oxigênio atmosférico em todas as amostras e que esta incorporação cresce com a intensidade do bombardeamento iônico. Houve aumento de mais de duas vezes na dureza e de cerca de oito vezes no parâmetro de resistência plástica dos filmes quando os parâmetros de pulso foram aumentados de 0 - 125 Hz (0 - 1 ). Para esta mesma faixa, a rugosidade e o coeficiente de atrito diminuíram enquanto a resistência ao risco aumentou. Pôde-se constatar também que a taxa de deposição e a pressão dos gases afetam as características dos polímeros. Filmes mecanicamente mais resistentes foram obtidos quando plasmas de hidrocarbonetos diluídos em argônio foram empregados. Por outro lado, o aumento na pressão dos gases induziu queda... .
In this work, plasma immersion ion implantation and deposition was employed to prepare thin polymer films with properties different from those synthesized by the conventional PECVD (Plasma Enhanced Chemical Vapor Deposition) technique. Radiofrequency (13.56 MHz) benzene, acetylene/argon and methane/argon glow discharges were employed. To promote ion bombardment of the growing layer, the substrates were biased with high voltage negative pulses (25 kV). Pulse frequency and duty cycle were simultaneously varied between 0 - 125 Hz and 0 - 1, respectively. It was investigated the effect of such parameters on the film properties. Nanoindentation and nanoscratch techniques allowed the evaluation of mechanical (hardness and plastic resistance parameter) and tribological (friction coefficient and scratch resistance) properties of the films. Elemental composition was assessed by X-ray photoelectron spectroscopy while roughness was evaluated from scanning probe microscopy images. Results reveal the presence of atmospheric oxygen in all the samples and that such incorporation grows with the bombardment intensity. Hardness increased more than twice and plastic resistance parameter around eight times as the pulse parameter was enhanced from 0 - 125 Hz (0 - 1). In the same range, roughness and friction coefficient decreased while the scratching resistance increased. It could be also verified the influence of the deposition rate and gas pressure on the film characteristics. Films mechanically more resistant were obtained as hydrocarbon plasmas were diluted in argon. On the other hand, the enhancement of the gas pressure induced fall in the hardness due to the lowering of the ion mean energy. The results showed that ion bombardment during film deposition is beneficial to the mechanical and tribological properties of polymers.
In this work, plasma immersion ion implantation and deposition was employed to prepare thin polymer films with properties different from those synthesized by the conventional PECVD (Plasma Enhanced Chemical Vapor Deposition) technique. Radiofrequency (13.56 MHz) benzene, acetylene/argon and methane/argon glow discharges were employed. To promote ion bombardment of the growing layer, the substrates were biased with high voltage negative pulses (25 kV). Pulse frequency and duty cycle were simultaneously varied between 0 - 125 Hz and 0 - 1, respectively. It was investigated the effect of such parameters on the film properties. Nanoindentation and nanoscratch techniques allowed the evaluation of mechanical (hardness and plastic resistance parameter) and tribological (friction coefficient and scratch resistance) properties of the films. Elemental composition was assessed by X-ray photoelectron spectroscopy while roughness was evaluated from scanning probe microscopy images. Results reveal the presence of atmospheric oxygen in all the samples and that such incorporation grows with the bombardment intensity. Hardness increased more than twice and plastic resistance parameter around eight times as the pulse parameter was enhanced from 0 - 125 Hz (0 - 1). In the same range, roughness and friction coefficient decreased while the scratching resistance increased. It could be also verified the influence of the deposition rate and gas pressure on the film characteristics. Films mechanically more resistant were obtained as hydrocarbon plasmas were diluted in argon. On the other hand, the enhancement of the gas pressure induced fall in the hardness due to the lowering of the ion mean energy. The results showed that ion bombardment during film deposition is beneficial to the mechanical and tribological properties of polymers.
Descrição
Palavras-chave
Implantação iônica, Plasma (Gases ionizados)
Como citar
SILVA, Paulo Augusto de Faria. Propriedades mecânicas e tribológicas de filmes sintetizados mediante técnica de deposição e implantação iônica por imersão em plasma. 2004. 67 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, 2004.