Made available in DSpace on 2014-10-09T12:27:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:29Z (GMT). No. of bitstreams: 0 / Cloreto estanoso (SnCl2.2H2O) é o composto mais utilizado na redução do íon pertecnetato (TcO4-), obtido pela eluição do gerador, para a marcação de reagentes liofilizados para radiodiagnóstico. Estes reagentes liofilizados contêm um ligante, cloreto estanoso, e diferentes excipientes. Muitos métodos analíticos para a determinação de estanho não conseguem distinguir entre os íons estanoso (Sn(II)) e estânico (Sn(IV)) em soluções. Os dois métodos, descritos na literatura, para determinação seletiva de Sn(II) são análise titrimétrica e polarografia. O método mais confiável descrito para a quantificação do íon estanoso é a polarografia (voltametria) e pode ser utilizado para a determinação em concentrações de mg e g de Sn(II) e Sn(IV) (0,06-1,0 mg), com boa seletividade. Foi realizada análise titrimétrica, para quantificação de Sn(II), na matéria-prima e em 3 lotes consecutivos de 9 reagentes liofilizados produzidos pelo IPEN-CNEN/SP, utilizando-se sulfato cérico 0,1 mol L-1, diluído 10 vezes e iodo 0,05 mol L-1, diluído 10 vezes, como soluções titulantes. Polarografia por pulso diferencial foi utilizada com configuração convencional composta por três eletrodos: eletrodo de trabalho de gota de mercúrio, eletrodo referência de Ag/AgCl (saturado com KCl) e eletrodo auxiliar de platina. O intervalo de potencial analisado foi de -250 a -800 mV e o pico atribuído à redução de Sn(II) foi encontrado em -370 mV em eletrólito suporte de H2SO4 3 mol L-1 e, para Sn(IV), -470 mV, em eletrólito suporte de HCl 3 mol L-1. Para retirada do oxigênio da solução na cela polarográfica utilizou-se nitrogênio 5.0 por 5 minutos, antes e após cada introdução de amostra. Para determinação de Sn(IV) foi feita a oxidação do Sn(II), por adição de peróxido de hidrogênio, em 37 ± 5 ºC, por 5 minutos, seguida de purga com nitrogênio, e análise. A análise polarográfica desenvolvida mostrou-se adequada para a determinação de Sn(II), na presença de Sn(IV), e de estanho total nos kits radiofarmacêuticos estudados. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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A study has been made of the elasticity associated with the martensite transformation in the polycrystalline β-phase alloy of composition Cu-33.6 wt. % Zn-4 wt. % Sn tested at room temperature. The mechanical properties of the material undergoing the stress induced martensite transformation have been examined. These properties are influenced by the elastic anisotropy of the bcc β-phase, the development, preferential distribution and morphology and the mechanical properties of the transformation product. The elastic shape change associated with the elastically accommodated, stress-induced martensitic transformation was always found to be accompanied by some plastic deformation. A relationship between the β-grain size, the sample thickness and the deformation response was observed. Specimens with grains extending through the sample thickness exhibited large reversible strains (∼2.5%), whereas specimens with a much smaller grain size/thickness ratio (<1) exhibited only limited transformation elasticity. The morphology of the thermal martensite and the Ms temperature was also found to be influenced by the ratio grain size/thickness (g.s./t). A lower Ms temperature was associated with a decreasing g.s./t ratio; only self-accommodating burst martensite was observed in very fine grained material. The Af temperature increased with a decreasing g.s./t ratio. Repeated loading (cycling) reduced the hysteresis of the stress strain curve for all g.s./t ratios tested, but was always accompanied by plastic deformation of the matrix and the development of non-reversible deformation martensite. The experimentally determined habit plane for the thermal and the stress induced martensite were in moderate agreement with the planes predicted by the phenomenological martensite theory (W.L.R.) assuming a {110} <1Ī0> microscopic shear. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Thesis (M.Sc.(Metallurgy))--University of the Witwatersrand, Science Faculty, 1990. / A study of phase relations and thermodynamic properties in iron, tin, sulphide system was conducted, [Abbreviated abstract. Open document to view full version] / MT2017

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This is Part A of the Thesis. Here is the Link to Part B: http://hdl.handle.net/11375/17845 / <p> This study was focused on the absorption spectra of tin dioxide thin films on optical quartz substrates. The films were doped with antimony from zero to ten percent, indium from zero to ten percent, and intrinsically, by heating undoped samples in vacuum and air. The surface resistances were also measured.</p> <p> The results for antimony doping show that the energy required for electron transitions from valence to conduction bands, the associated phonon energies, and the optical absorption by free carriers all increase while resistance decreases with increased doping. These results are consistant with antimony acting as a donor in SnO2 and elevating the Fermi level, which is in the conduction band for the undoped material, to a higher level, thus increasing the free carrier concentration. The results possibly also indicate a strain on the lattice caused by doping.</p> <p> The results for indium doping show a similar increase in energies along with a decrease in optical absorption by free carriers and an increase in resistance with increased doping. The indium acts as an acceptor and, in so doing, causes the Fermi level to drop into the valence band, at the doping levels used in this study. This is probably due to the formation of an acceptor band above or overlapping the valence band and resulting in a reduction of the free carrier concentration. The increase in phonon energy indicates that the doping imposes a strain on the lattice.</p> </p> Heating undoped films in vacuum appears to drive off oxygen resulting in reduced resistance and therefore higher free carrier concentration due to lattice defect doping, and reduced valence to conduction band transition energy possibly due to the formation of a conduction band in the forbidden band-gap. The changes were reversible by re-heating in air.</p> / Thesis / Master of Engineering (MEngr)

This is Part B of the Thesis. Here is the Link to Part A: http://hdl.handle.net/11375/17844 / <p> This report deals with the effects of various parameters on the resistance and the temperature coefficient of resistance (or the T.C.) of tin dioxide films doped with antimony and boron. The films were produced on cylindrical ceramic substrates by the hydrolysis of SnCl4 and SbCls in the presence of HCl and H3BO3. The T.C. was measured over the range of 25 to 150°C and averaged.</p> <p> Under normal conditions, the films were produced at 950°C with an antimony concentration of 0.457 molar % and a boron concentration of 2.73 molar %. Varying this firing temperature (from 800-1100°C) was found to have no effect on the resistance but increased the T.C. by 2 to 3 ppm/°C per degree change. Varying the antimony content from 0 to about 1 molar % was found to have little effect on resistance. The effect on T.C. was to increase it at lower Sb levels and then to decrease the T.C. as the level increased.</p> <p> Varying the boron content (0 to 4.46 molar %) was also found to have little effect on resistance. A decrease in T.C. with boron content was noted when only the boron was varied, but an increase in T.C. was found when HCl and H2O volumes were varied with the boron. The introduction of additional air into the system was found to have no effect.</p> <p> Film thicknesses were varied by controlling the chemical flowrates. Thinner films were found to have dramatically higher resistances and reduced T.C. values. It was observed that below a certain flowrate resistive failure occurred in the films. It was found in this study that within the statistical distribution of film values, those samples with above average resistance had below average T.C. values and vice-versa. Annealing in vacuum at 500°C was found to produce samples of reduced resistance and increased T.C. while the opposite was found with air annealed samples. Quickly cooled samples were found to be more stable.</p> / Thesis / Master of Engineering (MEngr)

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