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51.
52.
S.M.C. MirandaM. Peres T. MonteiroE. Alves H.D. SunT. Geruschke R. ViandenK. Lorenz 《Optical Materials》2011,33(7):1139-1142
Zinc oxide epilayers grown by metal organic vapour phase epitaxy on (0 0 0 1) sapphire substrates were doped with Praseodymium and Europium by ion implantation. The as-implanted samples were either annealed in air for 20 min in a tube furnace or rapid thermal annealing (RTA) was performed, for 2 min, in a nitrogen atmosphere. The samples were characterized by Rutherford Backscattering Spectrometry/Channelling and photoluminescence. The presented results indicate that in the as-implanted samples the majority of the rare earth (RE) ions are incorporated into substitutional Zn-sites. Furnace annealing at 1000 °C recovers the crystal quality of the samples but leads to an out-diffusion of the RE. RTA suppresses diffusion but lattice damage is not fully recovered at 1000 °C. More importantly, during RTA the RE ions are driven from the substitutional site and are now found mainly on random interstitial sites and no optical activation could be achieved. 相似文献
53.
Shirley Possidonio Roberto Koji Onmori Laura O. Peres Shu Hui Wang 《Journal of Materials Science》2007,42(7):2329-2333
Poly(N-vinylcarbazole) (PVCz) is well known as an electroactive material due to its good photoconductivity, charge-transfer complexes,
photoluminescence and electroluminescence properties. The block copolymers of N-vinylcarbazole were prepared and the effects of the relative composition, molar masses, architecture and doping on its electrical
behavior were investigated. Controlled free radical polymerization has been carried out using nitroxide-mediated process in
order to prepare a series of block copolymers of N-vinylcarbazole. 2,2,6,6-Tetramethyl-1-piperidinyloxy radical (TEMPO) was used to end-cap “living” homopolymer of p-bromostyrene, which was further used as a macroinitiator to polymerize N-vinylcarbazole and styrene. The copolymers have been doped at room temperature with LiClO4 and the electrical conductivities were measured by two-probe method, which have shown to depend on copolymer’s relative composition
and molar masses. 相似文献
54.
Herman Jacobus Cornelis Voorwald Mauro Pedro Peres Midori Yoshikawa Pitanga Costa Maria Odila Hilário Cioffi 《Journal of Materials Science》2010,45(22):6094-6100
In spite of toxicity, hydrogen embrittlement susceptibility, and environmental issues, cadmium electroplating is usually applied
on high strength AISI 4340 aeronautical steel due to its efficient protection against electrochemical corrosion. Ion vapor
deposition (IVD) process with pure aluminum also offers good protection against corrosion with the advantages of decreasing
hydrogen embrittlement susceptibility and improving the fatigue strength of metallic components. In this research, the effects
of aluminum electroplating and IVD aluminum coating on the rotating bending fatigue strength of AISI 4340 steel were evaluated
in comparison with cadmium electroplated specimens. Experimental fatigue results showed that both aluminum electroplating
and IVD aluminum coatings are possible alternatives to cadmium electroplating. 相似文献
55.
A. Kahouli A. Sylvestre J.-F. Laithier L. Lutsen S. Pairis E. André J.-L. Garden 《Materials Chemistry and Physics》2014
58% semi-crystalline thin parylene-VT4 (–H2C–C6F4–CH2−)n films, have been investigated by dielectric spectroscopy for temperature and frequency ranges of [−120 to 380 °C] and [0.1–105 Hz] respectively. The study comprises a detailed investigation of the dielectric constant, dielectric loss and AC conductivity of this fluoropolymer. Dielectric behavior of parylene-VT4 is represented by a low dielectric constant with values in the range of 2.05–2.35 while the dielectric losses indicate the presence of two relaxation processes. Maxwell−Wagner−Sillars (MWS) polarization at the amorphous/crystalline interfaces with activation energy of 1.6 eV is due to the oligomer orientation. Electrical conductivity obeys to the well-known Jonscher law. The plateau in the low frequency part of this conductivity is temperature-dependent and follows an Arrhenius behavior with activation energy of 1.17 eV (deep traps) due to the fluorine diffusion. Due to its thermal stability with a high decomposition temperature (around 400 °C under air and 510 °C under nitrogen) and due to its good resistivity at low frequency (1015–1017 Ω m−1), parylene-VT4 constitutes a very attractive polymer for microelectronic applications as low k dielectric. Moreover, when parylene-VT4 is subjected to an annealing, the dielectric properties can be still more improved. 相似文献
56.
Britnell L Gorbachev RV Jalil R Belle BD Schedin F Katsnelson MI Eaves L Morozov SV Mayorov AS Peres NM Neto AH Leist J Geim AK Ponomarenko LA Novoselov KS 《Nano letters》2012,12(3):1707-1710
We investigate the electronic properties of ultrathin hexagonal boron nitride (h-BN) crystalline layers with different conducting materials (graphite, graphene, and gold) on either side of the barrier layer. The tunnel current depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field. It offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel. 相似文献
57.
Maria A. Zazycki Priscila A. Borba Rafaela N.F. Silva Enrique C. Peres Daniele Perondi Gabriela C. Collazzo Guilherme L. Dotto 《Advanced Powder Technology》2019,30(8):1494-1503
Chitin was used to prepare an alternative, eco–friendly and low–cost adsorbent by a simple pyrolysis process. The adsorbent, named chitin derived biochar, was characterized and applied to treat colored effluents containing methyl violet dye (MV). Pyrolysis using N2 flow rate of 0.25 L min?1, heating rate of 10 °C min?1 until 800 °C was suitable to prepare a chitin derived biochar with good characteristics. Chitin derived biochar presented surface area of 275.0 m2 g?1. The MV adsorption on the chitin derived biochar was favored in alkaline conditions and ambient temperature. The adsorption process presented fast kinetics and, the maximum adsorption capacity was higher than 1000 mg g?1. Chitin derived biochar can be used for 7 consecutive adsorption/desorption cycles maintaining the same adsorption capacity. Also, the material was suitable to treat colored effluents, reaching color removal percentage of 95%. In brief, it was demonstrated that chitin derived biochar is a low–cost and efficient material to treat colored effluents. 相似文献
58.
A Peres 《Canadian Metallurgical Quarterly》1985,32(6):3266-3276
59.
This paper proposes a solution to the
2 guaranteed cost control problem for uncertain, continuous-time linear systems. It consists of the determination of a constant state feedback stabilizing matrix gain and a
2-norm upper bound, valid for all feasible models. The uncertainties are only assumed to be convex-bounded, a concept which generalizes the important case of interval matrices uncertainties. The results follow from a new parameterization of all stabilizing gains over a convex set. As an additional property, the above mentioned
2-norm upper bound reduces to the minimum
2 cost in case of precisely known linear systems. 相似文献
60.