Th.--Sci. phys.--Besançon, 1977. N°: 119.

Th. 3e cycle--Physicochim. des matér.--Toulouse--I.N.P., 1977. N°: 14.

Th. 3e cycle--Sci. et tech. des procédés chim.--Toulouse 3, 1980. N°: 2338.

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Made available in DSpace on 2014-06-11T19:27:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-06Bitstream added on 2014-06-13T20:16:09Z : No. of bitstreams: 1 faria_jc_me_guara.pdf: 670580 bytes, checksum: 14cc14d5017a0f594f71c629f2abc792 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / As ligas de níquel possuem uma composição química com elevado teor de elementos de liga, os quais são responsáveis por suas propriedades mecânicas e térmicas; porém estas características dificultam demasiadamente sua usinagem, levando a ocorrência de alguns problemas durante o processo. O objetivo deste trabalho é o estudo da usinagem por torneamento cilíndrico externo da liga a base de níquel Nimonic 80A, visando a otimização da usinagem desta liga, buscando proporcionar aumentos reais de produtividade sem a necessidade de investimentos em novos meios de produção. Além disto, resultados deste trabalho devem oferecer informações mais detalhadas a respeito do comportamento desta liga em relação a usinagem por torneamento. Os ensaios de usinagem foram realizados em um corpo de prova da liga, considerando os parâmetros de usinagem: velocidade de corte (75 e 90 m/min), profundidade de usinagem (0,8 e 1,6 mm) e avanços (0,12; 0,15 e 0,18 mm/v). Os ensaios foram realizados em um torno CNC e ferramentas com pastilha de metal duro. Após cada etapa do torneamento foram realizadas as medidas do comprimento de corte, do desgaste das ferramentas (através de uma lupa (8x)) e a rugosidade das peças (avaliada em cada fase do processo), com o auxílio de um rugosímetro portátil. Por meio de microscopia óptica, foi possível observar o desgaste das ferramentas de corte para cada condição avaliada. Microscopicamente, observou-se que, apesar da grande variação do comprimento de corte para os diversos testes, o mecanismo predominante de desgaste nas ferramentas foi sempre o mesmo (abrasão no flanco). Os valores de rugosidade Ra e Ry, para as condições avaliadas foram sempre superiores aos valores teóricos. Após análise dos resultados foi possível concluir que o melhor desempenho para esta faixa de trabalho testada foi obtido para ap=0,8mm; f=0,15mm/volta e vC=75m/min, o que resultou em um maior comprimento de corte (1811 m). / The nickel alloys have a chemical composition with high tenor of alloy elements which are responsible for your mechanical and thermal properties, however these characteristics hinder your too much machining, taking the occurrence of some problems during the process. The objective of this work is the study of the machining by external cylindrical turning of the nickel based alloy Nimonic 80A, seeking the machining optimization of this alloy looking for to provide real increases of productivity without the need of investments in new production means. Besides, the results of this work should offer more detailed information regarding the behavior of this alloy in relation to machining by turning. The machining experiences were accomplished in a specimen of the nickel alloy, considering the machining parameters: cutting speed (75 and 90 m/min), cutting depth (0,8 and 1,6 mm) and feed rate (0,12; 0,15 and 0,18 mm/v). The valuations were accomplished in a CNC lathe and tools with of hard metal inserts. After each stage of the turning the measures of the cutting length were accomplished, of the waste of the tools through a magnifying glass (8x) and the roughness of the specimen evaluated in each phase of the process, with the aid of a portable roughness meter. Through light optical microscopy it was possible to observe the wear of the cutting tools for each appraised condition. Aided by microscopy was observed that, in spite of the great variation of the cutting length for the several tests, the predominant mechanism of tool wear was always the same (abrasion in the flank). The roughness values, Ra and Ry, for the appraised conditions were always superiors to the theoretical values. After analysis of the results it was possible to end that, the best acting for this work strip tested it was obtained for ap=0,8mm: f=0,15mm/rev and VC=75m/min, what resulted in a larger cutting length (1811 m).

The marine biofouling and corrosion of Kunifer 10 (10% Ni, 1. 5% Fe, copper alloy), was studied using a combination of analytical techniques including x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDXA) and electron microscopy. Particular emphasis was placed on the very early stages of fouling, although the study continued until a climax community of macrofouling organisms had become established. Dissolved organic matter (DOM), was successfully extracted from seawater by ultrafiltration and chloroform-emulsion separation. The collected materials were partially characterised using fourier transform infrared spectroscopy (FTIR) and standard chemical analyses. Extracted materials were found to be mainly carbohydrate in character, with lesser quantities of protein. The FTIR investigations indicated considerable seasonal variation in the extracted DOM. XPS proved to be a suitable technique to investigate the development of marine organic and inorganic films that form on the alloy. Adsorbed organic macromolecules exhibited a characteristic spectral "fingerprint". The effect of elevated DOM on the corrosion behaviour of the Kunifer 10 alloy was investigated, using DC and AC impedance electrochemistry. Studies indicated that a temporary loss of passivation occurred in the presence of DOM under transient oxygen conditions. The development of organic layers on the alloy was shown to influence subsequent stages of biofouling, Kunifer 10 coated with elevated levels' of organic extracts was less likely to become fouled by microorganisms, although certain extracts appeared to stimulate the settlement of marine protozoans. However, such effects were short lived due to the continual formation of bio/corrosion layers. An unusual form of corrosion, not previously documented, is reported and an explanation for the exfoliation of the bio/corrosion films on Kunifer 10 is suggested. A range of cupronickel-iron alloys were assessed for their short-term marine biofouling/corrosion performance. Of the alloys tested Kunifer 10 showed optimum resistance. The study includes a literature review on marine biofouling and corrosion.

The work described in this thesis examines the renal excretion of nickel in humans and the Wistar Albino male rat. The renal clearance of nickel is characterized in two groups of electrolytic nickel-refinery workers. In the animal work, the mechanisms of nickel uptake in kidney tissue and its pathological consequences are investigated. Multi-void 24-h urine collections were obtained from 26 workers, as well as serum samples at the beginning and end of this sampling period. Nickel, ?[2]-microglobulin and creatinine concentrations were measured in both body fluids. In addition, specific gravity, protein and qualitative indices of kidney disfunction (by Dip Stick) were assessed in urine. Examination of the functional dependence in individuals of urinary nickel, creatinine and specific gravity on urine flow-rate indicates that specific gravity adjustment of spot-nickel voids is more appropriate than employing creatinine. The systematic strategy devised in this study to overcome concentration-dilution effects for nickel has wide application in biological monitoring. It is demonstrated that if the specific gravity values of spot urine voids in a group of 20 individuals are between 1.010 and 1.039, then the uncompensated uncertainty in specific-gravity adjusted urinary-nickel concentrations does not exceed +/- 10% (95% Confidence Level). Nickel clearance studies and the determination of nickel in serum ultrafiltrates indicated that 24 +/- 6% of serum nickel is available for renal filtration, of which 65% on average is reabsorbed in the human kidney. It is concluded for the nickel-refinery workers studied, that there was little evidence of kidney dysfunction. Studies with rat renal slices and isolated proximal tubules showed that the uptake of Ni[2+] and its histidine complexes is probably passive. Ni(His)[2] reduced the uptake of L-histidine and proline, but not of thymidine. The renal accumulation of nickel from nontoxic i.v. doses of [63]Ni(His)[2] (6 mug Ni kg[-1]) was followed by rapid subcellular clearance during the 24-h period after injection. Autoradiography of the nephron illustrated that only the S3 segment of the proximal tubule accumulated and retained nickel. There was no evidence of nephrotoxicity in the histopathological examination of these tissues. By contrast, high i.p. doses (3 and 6 mg Ni kg[-1] induced a decrease in Bowman's space and minor changes along the entire length of affected nephrons. Compartmentalization of nickel within subcellular fractions of the rat kidney is interpreted in terms of an "Equilibrium" model for metal- ion uptake under steady state conditions (i.e., at fixed pH, redox potential, intracellular and extracellular ligand concentrations). Effectively, nickel distribution is determined by thermodynamic parameters such as complex stability. The human and animal evidence support a passive mechanism of nickel reabsorption in the kidney. Simple pulmonary deposition and absorption considerations in man suggest that the dose of nickel acquired during an 8- h shift of work at a Threshold Limit Value (TLV) of 0.1 mg Ni m[-3] is roughly equivalent to the 6 mug Ni kg[-1] dose used in the rat study. Therefore, the absence of signs of significant nephrotoxicity in both the human and animal models appears to be consistent.

Made available in DSpace on 2014-10-09T12:23:59Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:58Z (GMT). No. of bitstreams: 1 01070.pdf: 2677585 bytes, checksum: 886f210d3f6431136fa09330d68b8fa2 (MD5) / Dissertacao (Mestrado) / IEA/D / Faculdade de Filosofia Letras e Ciencias Humanas, Universidade de Sao Paulo - FFLCH/USP