Encontrados 12 documentos, a visualizar página 1 de 2
Self-mated tribological systems based on multilayer micro/nanocrystalline CVD d...
Salgueiredo, E.; Abreu, C. S.; Amaral, M.; Oliveira, F. J.; Gomes, J. R.; Silva, R. F.The tribological response of multilayer micro/nanocrystalline diamond coatings grown by the hot filament CVD technique is investigated. These multigrade systems were tailored to comprise a starting microcrystalline diamond (MCD) layer with high adhesion to a silicon nitride (Si3N4) ceramic substrate, and a top nanocrystalline diamond (NCD) layer with reduced surface roughness. Tribological tests were carried ou...
A DLC/diamond bilayer approach for reducing the initial friction towards a high...
Amaral, M.; Carreira, D. J; Fernandes, A. J. S.; Abreu, C. S.; Oliveira, F. J.; Gomes, J. R.; Silva, R. F.Sliding contact mechanics is used to account for the net increase of the bearing capacity of high wear-resistant CVD diamond coatings when an outer layer of a DLC lubricant film is deposited on their top surface. Experimental results,namely the critical failure load, taken from reciprocating ball-on-plate tribological testing of such DLC/diamond bilayers, are on the basis of this statement. DC magnetron sputter...
Use of a Blood Gas Analyzer to Measure Blood Hemoglobin During Liver Transplant...
Rivas Chirino, L.; Viana, J. da Silva; Tavares, C. A.; Palmeiro, A.; Oliveira, F. J.http://www.sciencedirect.com/science/article/B6VJ0-4JT975Y-1M/1/4195ad663e143d9e808bace249290f61
Tribological testing of self-mated nanocrystalline diamond coatings on Si3N 4 c...
Abreu, C. S.; Amaral, M.; Oliveira, F. J.; Tallaire, A.; Bénédic, F.; Syll, O.; Cicala, G.; Gomes, J. R.; Silva, R. F.Due to their much lower surface roughness compared to that of microcrystalline diamond, nanocrystalline diamond (NCD) films are promising candidates for tribological applications in particular when deposited on hard ceramic materials such as silicon nitride (Si3N4). In the present work, microwave plasma assisted chemical vapour deposition of NCD is achieved using Ar/H2/CH4 gas mixtures on plates and ball-shaped...
In-situ friction monitoring of self-mated CVD diamond coatings using acoustic e...
Abreu, C. S.; Oliveira, F. J.; Gomes, J. R.; Belmonte, M.; Fernandes, A. J. S.; Silva, R. F.In-situ measurements of acoustic emission (AE) in self-mated tribological pairs of CVD diamond coated silicon nitride (Si3N4) were made with the purpose of investigating the relationship between AE signal and friction events. A good correlation is found between the energy dissipation/emission processes, therefore enabling the possibility of monitoring the different friction regimes occurring during the sliding ...
CVD diamond coated silicon nitride self-mated systems : tribological behaviour ...
Abreu, C. S.; Oliveira, F. J.; Belmonte, M.; Fernandes, A. J. S.; Gomes, J. R.; Silva, R. F.Friction and wear behaviour of self-mated chemical vapour deposited (CVD) diamond films coating silicon nitride ceramics (Si3N4) were investigated in ambient atmosphere. The tribological tests were conducted in a reciprocal motion ball-on-flat type tribometer under applied normal loads up to 80 N (~10 GPa). Several characterisation techniques - including scanning electron microscopy (SEM), atomic force microscopy...
Friction and wear performance of HFCVD nanocrystalline diamond coated silicon n...
Abreu, C. S.; Amaral, M.; Fernandes, A. J. S.; Oliveira, F. J.; Silva, R. F.; Gomes, J. R.Silicon nitride (Si3N4) ceramics were selected as substrates due to their thermal and chemical compatibility to diamond that ensure the adequate NCD adhesion for mechanical purposes. NCD deposition was performed by hot-filament chemical vapour method (HFCVD) using Ar/H2/CH4 gas mixtures. The tribological assessment of homologous pairs of NCD films was accomplished using reciprocating ball-on-flat tests using NC...
Revestimentos de diamante CVD em Si3N4: Atrito e desgaste no deslizamento de pa...
Abreu, C. S.; Oliveira, F. J.; Belmonte, M.; Fernandes, A. J. S.; Silva, R. F.; Gomes, J. R.O diamante natural, dada a sua extrema dureza, apresenta elevada resistência ao desgaste. No entanto, além do seu elevado custo, caracteriza-se por uma forte anisotropia no comportamento tribológico. Estas limitações são ultrapassadas pela utilização de revestimentos de diamante obtidos por deposição química em fase vapor (CVD), que pela sua natureza policristalina combinada com a retenção das propriedades de e...
Grain size effect on self-mated CVD diamond dry tribosystems
Abreu, C. S.; Oliveira, F. J.; Belmonte, M.; Fernandes, A. J. S.; Silva, R. F.; Gomes, J. R.Chemical vapour deposited (CVD) diamond coatings are important for tribological applications due to their unique combination of properties. Previous work demonstrated that silicon nitride (Si3N4) excels as a substrate for diamond coatings due to its low thermal expansion coefficient mismatch relative to diamond films resulting in a significant adhesion improvement. In this study, dense Si3N4 substrates were fab...
Functionality diagrams for hybrid mechanical seals with silicon nitride rings
Carrapichano, J. M.; Oliveira, F. J.; Silva, R. F.; Gomes, J. R.Ring-on-ring tribological experiments were performed with hybrid mechanical seals with silicon nitride (Si3N4) rings. The K x PV product, where K is the wear coefficient, P the sealing pressure, and V the linear speed, is proposed as a novel parameter to characterize the total working range of a mechanical seal system, with the advantage of directly indicating the thickness reduction for a certain time of servic...
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