33 documents found, page 1 of 4
Effect of different acidic media on the corrosion behaviour of hardmetals with ...
Pereira, P.; Rocha, A. M. Ferro; Sacramento, J.; Oliveira, F. J.; Malheiros, L. F.; Senos, A. M. R.; Bastos, AlexandreHighly corrosive agents, such as saltwater, hydrogen sulphide, hydrofluoric or hydrochloric acids, are frequently found in oil and gas exploration. The high costs associated with the premature replacement of equipment damaged by corrosion and the consequent production losses justify the search for more resistant materials. In this work, the corrosion behaviour of cemented carbides with different Ni-based binder...
Corrosion resistance of WC hardmetals with different Co and Ni-based binders
Pereira, P.; Rocha, A.M. Ferro; Sacramento, J.; Oliveira, F. J.; Senos, A. M. R.; Malheiros, L. F.; Bastos, AlexandreIn this work, industrially relevant WC composites with alternative binders (Ni, CoNi, NiCr, CoCr, CoNiCr and NiCrMo) were produced and their corrosion resistance in 0.5 M NaCl was compared to conventional WC-Co system. The main objective is to develop hardmetals with higher corrosion resistance to extend the lifetime of tools and equipment, reducing the demand for new parts and maintenance, thus decreasing the ...
Diamond-based nanostructured materials for detection of water contaminants
Girão, A. V.; Neto, M. A.; Oliveira, F. J.; Rui F. SilvaSustainability is presently one of the most heard watchwords. Water environment is of great importance to all living beings and climate changes, with cleaning and preservation of our largest natural resource as the number one priority. It can only be attained if environmental conscience is put into practice and, involuntarily or not, the scientific community inherited the additional responsibility to cope with ...
Effect of relative humidity and temperature on the tribology of multilayer micr...
Shabani, M.; Abreu, C. S.; Gomes, J. R.; Silva, R. F.; Oliveira, F. J.The tribological behavior of tenfold micro/nanocrystalline CVD diamond multilayers is here investigated in self–mated configuration using ball-on-plate reciprocating wear testing. The effects of relative humidity (RH) and temperature (T) on friction and wear coefficients are assessed. The strongest effect of humidity was found on the value of the critical load (no delamination) that triples from 40 N at 10%RH t...
Surface modifications on as-grown boron doped CVD diamond films induced by the ...
Neto, M. A.; Pato, G.; Bundaleski, N.; Teodoro, O. M. N. D.; Fernandes, A. J. S.; Oliveira, F. J.; Silva, R. F.The surface termination of as-grown microcrystalline (MCD) and nanocrystalline (NCD) boron-doped diamond films was assessed by X-ray photoelectron spectroscopy (XPS) and water contact angle techniques. The diamond coatings were grown on mirror-polished silicon nitride ceramic substrates using the hot-filament chemical vapor deposition (HFCVD) technique. The boron doping source, boron oxide (B2O3) diluted in eth...
Extremely low wear rates in hip joint bearings coated with nanocrystalline diamond
Amaral, M.; Maru, M. M.; Rodrigues, S. P.; Gouvea, C. P.; Trommer, R. M.; Oliveira, F. J.; Achete, C. A.; Silva, R. F.A hip joint wear simulator is used for the first time to evaluate the performance of acetabular liners and femoral heads made of silicon nitride ceramic coated with nanocrystalline diamond (NCD), grown by a hot filament chemical vapor deposition (HFCVD) method. Wear is assessed by gravimetry, by which volume and linear wear are estimated. Even with only one million cycles of test, a very stimulating finding is ...
The High performance of nanocrystalline CVD diamond coated hip joints in wear s...
Maru, M. M.; Amaral, M.; Rodrigues, S. P.; Santos, R.; Gouvea, C. P.; Archanjo, B. S.; Trommer, R. M.; Oliveira, F. J.; Silva, R. F.; Achete, C. A.The superior biotribological performance of nanocrystalline diamond (NCD) coatings grown by a chemical vapor deposition (CVD) method was already shown to demonstrate high wear resistance in ball on plate experiments under physiological liquid lubrication. However, tests with a close-to-real approach were missing and this constitutes the aim of the present work. Hip joint wear simulator tests were performed with...
Multifunctional Carbon Nanotube/Bioceramics Modulate the Directional Growth and...
Mata, D.; Oliveira, F. J.; Ferro, M.; Gomes, P. S.; Fernandes, M. H.; Lopes, M. A.; Silva, R. F.Biomaterials can still be reinvented to become simple and universal bone regeneration solutions. Following this roadmap, a bone graft of carbon nanotube (CNT)/glass/hydroxyapatite (HA) with controlled CNT agglomeration state was designed with multifunctionalities able to stimulate the bone cell phenotype. The preparation route, the mechanical and electrical behavior and the in vitro profiles of degradation and ...
Mechanical characterization of WC-10 wt% AISI 304 cemented carbides
Fernandes, C. M.; Vilhena, L. M.; Pinho, C. M. S.; Oliveira, F. J.; Soares, E.; Sacramento, J.; Senos, A. M. R.Growing demands for new composites showing high performance and enlarging fields of application have drawn a great interest on hard metal industry. In this work, new composites of WC stainless steel AISI 304 (SS) binder, containing Fe, Cr and Ni as main elements have been developed and their mechanical behavior was investigated. Powder mixtures of WC-10 wt% SS without and with carbon addition were prepared, tes...
Processing strategies for smart electroconductive carbon nanotube-based biocera...
Mata, D.; Oliveira, F. J.; Ferreira, N. M.; Araujo, R. F.; Fernandes, A. J. S.; Lopes, M. A.; Gomes, P. S.; Fernandes, M. H.; Silva, R. F.Electroconductive bone grafts have been designed to control bone regeneration. Contrary to polymeric matrices, the translation of the carbon nanotube (CNT) electroconductivity into oxide ceramics is challenging due to the CNT oxidation during sintering. Sintering strategies involving reactive-bed pressureless sintering (RB + P) and hot-pressing (HP) were optimized towards prevention of CNT oxidation in glass/hy...