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Optical properties of LFZ grown β-Ga2O3:Eu3+ fibres
Santos, N.F.; Rodrigues, J.; Fernandes, A.J.S.; Alves, L.C.; Alves, E.; Costa, F.M.; Monteiro, T.Due to their relevance for electronic and optoelectronic applications, transparent conductive oxides (TCO) have been extensively studied in the last decades. Among them, monoclinic β-Ga2O3 is well known by its large direct bandgap of ∼4.9 eV being considered a deep UV TCO suitable for operation in short wavelength optoelectronic devices. The wide bandgap of β-Ga2O3 is also appropriate for the incorporation of s...
ZnGa2O4:Mn2+ phosphors grown by Laser Floating Zone
Santos, N.F.; Rodrigues, J.; Nico, C.; Fernandes, A.J.S.; Costa, F.M.; Monteiro, T.Cubic zinc gallate (c-ZnGa2O4) has attracted the attention of the scientific community due to its potential phosphor applications, namely in field emission displays (FEDs) and other electroluminescent devices. Among other advantages, this oxide matrix shows superior thermal and chemical stability when compared to ZnS based phosphors. Most of the above mentioned works comprise nanostructures, thin films or press...
Laser assisted flow deposition: a new method to grow ZnO
Rodrigues, J.; Soares, M.R.N.; Fernandes, A.J.S.; Monteiro, T.; Costa, F.M.Zinc oxide (ZnO) has been one of the most studied materials in the last decades. Either as bulk material, epilayers or nanostructures, this direct wide band gap semiconductor is known to possess great potential for fundamental science and modern technology applications.
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...
Structural and optical properties of europium doped zirconia single crystals fi...
Soares, M.R.N.; Nico, C.; Peres, M.; Ferreira, N.; Fernandes, A.J.S.; Monteiro, T.; Costa, F.M.Yttria stabilized zirconia single crystal fibers doped with europium ions were developed envisaging optical applications. The laser floating zone technique was used in order to grow millimetric high quality single crystal fibers. The as-grown fibers are completely transparent and inclusion free, exhibiting a cubic structure. Under ultraviolet (UV) excitation, a broad emission band appears at 551 nm. The europiu...
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...
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