Corrosion resistance of 2024 aluminum alloy coated with plasma deposited a-C:H:Si:O films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fabricação e caracterização de diodo Schottky orgânico com arquitetura planar

Usually organic polymeric diodes are made with a semiconductor layer placed between two electrodes in a sandwich-like architecture, where the electrodes are deposited on the surfaces of a polymeric semiconductor film. This methodology leads to two main problems: i) the polymeric film top surface is rough and irregular, resulting in non-uniform electric field into the device; ii) during the deposition of metallic electrode in the top surface polymeric film, by thermal evaporation, occurs the diffusion of metal atoms into the polymeric film, changing the material electronic structure. Thus, the metal-semiconductor junction is not well defined, which is essential for the production of good quality Schottky diode, which exhibits ideality factor close to the unity and low turn-on voltage. In order to avoid these two problems, in the present research was proposed to manufacture an organic diode with the semiconductor polymeric layer deposited over bimetallic (gold and aluminum) interdigitated electrodes. The doping of the active layer was performed by immersing the device in hydrochloric acid solution with pH 2 during different times in order to promote different doping levels of the semiconductor polymer. Was verified that the proposed diode, which exhibits well-defined metal-semiconductor junction, operates as a Schottky diode, with good ideality factor, 10 ± 3, and low turn-on voltage, 1,2 ± 0,2 V, in comparison with conventional organic polymeric diodes. Contrasting with the ideality factor and turn-on voltage, the diode rectification ratio was obtained as 7, a value lower than the expected for a good organic diode. Was also showed that the diode characteristics were dependent on the semiconductor polymer doping level, and that the diode characteristics were optimized with doping promoted by immersion in the acid solution for times longer than 50 s. Furthermore, as was showed that the diodes properties are dependent on the semiconductor...

Effect of Zn Sputtering Rate on the Morphological and Optical Properties of ZnO Films

Zinc oxide (ZnO) and aluminum-doped zinc oxide (ZnO:Al) thin films were deposited onto glass and silicon substrates by RF magnetron sputtering using a zinc-aluminum target. Both films were deposited at a growth rate of 12.5 nm/min to a thickness of around 750 nm. In the visible region, the films exhibit optical transmittances which are greater than 80%. The optical energy gap of ZnO films increased from 3.28 eV to 3.36 eV upon doping with Al. This increase is related to the increase in carrier density from 5.9 × 1018 cm-3 to 2.6 × 1019 cm-3. The RMS surface roughness of ZnO films grown on glass increased from 14 to 28 nm even with only 0.9% at Al content. XRD analysis revealed that the ZnO films are polycrystalline with preferential growth parallel to the (002) plane, which corresponds to the wurtzite structure of ZnO.

Grinding of AISI 4340 steel with interrupted cutting by aluminum oxide grinding wheel

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Investigação das propriedades ópticas de ZnO e ZnO:Al

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Doping e suplementação no MMA: um estudo documental de caso

The first records of the use of substances that enhance athletic performance began in antiquity. The objective of this study is to analyze the use of doping methods and supplements by amateur athletes and MMA professionals and what motivates usage. The work consisted of desk research in which use of work carried out at fifteen amateur and professional athletes, which underwent a data collection; these athletes are all over eighteen years old, male and practicing MMA for at least two years. The questionnaire that they were submitted corresponded to ten multiple-choice questions, which are: Age, what type of fight practiced as a basis for MMA, how long practices martial arts, sees the sport of competitive or recreational way, has already made use dietary supplements, have made use of banned substances (steroids) in the sport, it has already made use of steroids which the substance used and to what end was done using, know the side effects of anabolic steroids, know one or more people who have already made use of steroids in order to increase their performance in the fight, he believes it is possible an athlete achieve success in modern MMA without the use of anabolic steroids. The results showed that, of the fifteen athletes interviewed, only two said they never made use of dietary supplements, and four said they have already made use of anabolic steroids. All fifteen athletes claim to know the side effects of steroid use, and 14 of them say they know one or more sport-mates who have already made use of steroids. Given the results, it can be concluded that the use of steroids is common in MMA

Comparison of the Fuel Needed to Transport Plastic Recyclables Verses Aluminum Recyclables from Yellowstone National Park

Research has provided no definitive answers on whether PET plastic bottles or aluminum cans are a more environmentally sustainable choice as soda containers. This paper researches the fuel used in recycling each of these materials from Yellowstone National Park to processing locations. The data is used to determine which of these alternatives use less fuel in this process. It was found that plastics use more fuel when transported from Yellowstone National Park to the processing center. Aluminum uses less fuel per ton to transport from Yellowstone to the processing center. The conclusions from this research may have implications on which material would be advised to use in selling soda in Yellowstone National Park.

Exponential depletion of neutral dangling bonds density (D-0) by rare-earth doping in amorphous Si films

In this work we study the effect reduction in the density of dangling bond species D-0 states in rare-earth (RE) doped a-Si films as a function concentration for different RE-specimens. The films a-Si-1_(x) REx, RE=Y3+, Gd3+, Er3+, Lu3+) were prepared by co-sputtering and investigated by electron spin resonance (ESR) and Raman scattering experiments. According to our data the RE-doping reduces the ESR signal intensity of the D-0 states with an exponential dependence on the rare-concentration. Furthermore, the reduction produced by the magnetic rare-earths Gd3+ and Er3+ is remarkably greater than that caused by Y3+ and Lu3+, which led us to suggest an exchange-like coupling between the spin of the magnetic REs3+ and the spin of silicon neutral dangling bonds. (C) 2011 Elsevier B.V. All rights reserved.

Quantum Monte Carlo study of small aluminum clusters Al-n (n=2-13)

Using fixed node diffusion quantum Monte Carlo (FN-DMC) simulations and density functional theory (DFT) within the generalized gradient approximations, we calculate the total energies of the relaxed and unrelaxed neutral, cationic, and anionic aluminum clusters, Al-n (n = 1-13). From the obtained total energies, we extract the ionization potential and electron detachment energy and compare with previous theoretical and experimental results. Our results for the electronic properties from both the FN-DMC and DFT calculations are in reasonably good agreement with the available experimental data. A comparison between the FN-DMC and DFT results reveals that their differences are a few tenths of electron volt for both the ionization potential and the electron detachment energy. We also observe two distinct behaviors in the electron correlation contribution to the total energies from smaller to larger clusters, which could be assigned to the structural transition of the clusters from planar to three-dimensional occurring at n = 4 to 5.

Indirect doping of microstructures fabricated by two-photon polymerization with gold nanoparticles

Nanoplasmonics and metamaterials sciences are rapidly growing due to their contributions to photonic devices fabrication with applications ranging from biomedicine to photovoltaic cells. Noble metal nanoparticles incorporated into polymer matrix have great potential for such applications due to their distinctive optical properties. However, methods to indirectly incorporate metal nanoparticles into polymeric microstructures are still on demand. Here we report on the fabrication of two-photon polymerized microstructures doped with gold nanoparticles through an indirect doping process, so they do not interfere in the two-photon polymerization (2PP) process. Such microstructures present a strong emission, arising from gold nanoparticles fluorescence. The microstructures produced are potential candidates for nanoplasmonics and metamaterials devices applications and the nanoparticles production method can be applied in many samples, heated simultaneously, opening the possibility for large scale processes. (C) 2012 Optical Society of America

Use of Chlorine to Remove Magnesium from Molten Aluminum

Removal of Mg from aluminum scraps, known as demagging, has been widely applied in the,aluminum industry. This work discusses bubble-formation theories and magnesium kinetic removal from aluminum scraps using chlorine and inert gas fluxing. The interfacial area of the bubbles and residence time were estimated using a mathematical model. To inject gaseous chlorine, three types of nozzles were used with varying internal diameter. In addition, a porous plug, as well as varying input chlorine flow and concentration were used. The use of lower chlorine concentration improves efficiency because the interfacial tension is reduced therefore, more and smaller bubbles are formed. The model proposed herein is consistent with the experimental data. [doi:10.2320/matertrans.M2011256]

Interstitial doping induced superconductivity at 15.3 K in Nb5Ge3 compound

It is reported superconductivity in Nb5Ge3C0.3, an interstitial carbide compound. The temperature dependence of the electrical resistivity, ac-susceptibility, and heat capacity (HC) indicate that a bulk type-II superconductivity appears at T-C - 15.3 K. Magneto-resistance measurements suggest an upper critical field of B-C2 similar to 10.6 T and a coherence length of xi similar to 55 angstrom at zero temperature. Neutron diffraction analyzes locate the carbon atoms at the interstitial 2b site of the Mn5Si3 type-structure. Heat capacity data below T-C are well described by BCS theory. The size of the jump at T-C is in good agreement with the superconducting volume fraction observed in susceptibility measurements. A Debye temperature and Sommerfeld constant were also extracted from heat capacity data as 343 K and 34 mJ/mol K-2, respectively. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730611]

Molecular organization and doping in poly(2-methoxyaniline)/Ni(dmit)(2) films obtained with the Langmuir-Blodgett technique

The control of the properties of materials at the molecular level is pursued for many applications, especially those associated with nanostructures. In this paper, we show that the coordination compound [Ni(dmit)(2)], where (dmit) is the 1,3-dithiole-2-thione-4,5-dithiolate ligand, can induce doping of poly(2-methoxyaniline) (POMA) in molecularly ordered Langmuir and Langmuir-Blodgett (LB) films. Doping was associated with interactions between the components and the compression of the Langmuir film at the air-water interface, according to polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) data. Taking these results together with in situ UV-Vis absorption measurements, we could identify the molecular groups involved in the interaction, including the way they were reoriented upon film compression. The Langmuir films were sufficiently stable to be transferred as Y-type LB films, while the hybrid POMA/[Ni(dmit)(2)] films remain doped in the solid state. As expected, the molecular charges affected the film morphology, as observed from combined atomic and electric force microscopy measurements. In summary, with adequate spectroscopy and microscopy tools we characterized molecular-level interactions, which may allow one to design molecular electronic devices with controlled electrical properties.

Synthesis of high-surface-area gamma-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)

Several types of alumina were synthesized from sodium aluminate (NaAlO2) by precipitation with sulfuric acid (H2SO4) and subsequently calcination at 500 degrees C to obtain gamma-Al2O3. The precursor aluminate was derived from aluminum scrap. The various gamma-Al2O3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption-desorption of N-2 (S-BET) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al2O3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m(2) g(-1)) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined. (C) 2012 Elsevier B.V. All rights reserved.

Texture analysis of cold rolled and annealed aluminum alloy produced by twin-roll casting

A 7.4 mm thick strip of 3003 aluminum alloy produced by the industrial twin-roll casting (TRC) process was homogenized at 500 °C for 12 hours, after which it was cold rolled in two conditions: 1) to reduce the strip's thickness by 67%, and 2) to reduce it by 91%. The alloy was annealed at 400 °C for 1 hour in both conditions. The results revealed that a rotated cube texture, the {001}<110> component, predominated in the as-cast condition and was transformed into brass, copper and S type textures during the cold rolling process. There was practically no difference between the deformation textures at the two thickness reductions.