Ce travail porte sur l’étude de la résistance à la corrosion en milieu acide (HCl 1M) et des propriétés mécaniques de l’acier au carbone (XC38) par nitruration par plasma froid radiofréquence (13,56MHz). La grande originalité de ce travail consiste en la mise en œuvre d’un procédé de nitruration par plasma froid radiofréquence d’azote ou azote/hydrogène sans chauffer le substrat. Cette étude a permis de montrer que le rôle de l’hydrogène dans le plasma, consiste non seulement à réduire la couche d’oxyde présente à la surface du matériau, mais surtout à accélérer la cinétique d’enrichissement d’azote en surface. La caractérisation de la surface par microsonde castaing (EPMA) et spectroscopie des photoélectrons X (XPS) montrent que le traitement plasma conduit à la formation d’une couche nitrurée de l’ordre de quelque dizaine de microns pour un temps de traitement de 8 h. Les propriétés mécaniques, notamment la microdureté Vickers de la surface de l’acier traité augmente en fonction du temps de nitruration, elle passe de 247 Hv0.005 pour le substrat non traité à plus de1057 Hv0.005 pour l’échantillon nitruré pendant 8h. L’amélioration des propriétés anticorrosion a été mise en évidence par un couplage de mesures pondérales et de techniques électrochimiques telles que les courbes de polarisation et la spectroscopie d’impédance électrochimique en milieu HCl 1M. Pour des conditions optimales de traitement, l’efficacité inhibitrice des couches nitrurées dépasse 95% pour un temps de traitement de 8h et persiste pour des temps d’immersion supérieurs à 72 en milieu agressif (HCl 1M). / The aim of this work concerns the study of the improvement of the corrosion resistance in acidic medium (1M HCl) and mechanical properties of carbon steel (XC38) using a radiofrequency cold plasma nitriding process. The originality of this work consists in nitriding substrates using nitrogen cold plasma, where the process temperature is roughly ambient temperature and without heating the substrate. The nitriding was carried using nitrogen and nitrogen/ hydrogen plasma gas mixtures. The hydrogen role in the plasma consists not only in reducing the iron oxide layer on the substrate, but also accelerates the nitrogen diffusion in the substrate. Surface characterizations performed by means of the Electron Probe Microanalysis (EPMA) and X-ray Photoelectron spectroscopy (XPS) indicate that the treatment plasma induces the formation of a layer where the nitrided thickness is higher than ten microns for long treatment times (8h). The mechanical properties were studied by Vickers microhardness. The surface microhardness of the nitrided steel increases as the plasma processing time increases to reach a maximum of 1057Hv0.005 for the nitrided sample that was treated during 8h, when compared to sample untreated (247Hv0.005). The improvement of the corrosion resistance properties were investigated by gravimetric and electrochemical techniques such as potentiodynamic polarisation curves and electrochemical impedance spectroscopy (EIS) in 1M HCl medium. For the optimal conditions of treatment, the inhibition efficiency obtained is more than 95 % for 8h of treatment and remains constant for immersion times higher than 72h in aggressive medium (HCl 1M).

En este estudio se midió la microdureza Vickers del esmalte dental después de la exposición a tres bebidas industrializadas más consumidas en la ciudad de Lima y una bebida control, para evaluar el efecto erosivo de esta bebidas ácidas y su relación con la acidez titulable, el nivel de pH y el efecto buffer de las mismas. Se elaboraron 60 bloques de esmalte superficial de 2mm de espesor por 2-4mm de longitud; se colocaron en acrílico de curado rápido en moldes circunferenciales de 10mm de diámetro y 5mm de altura en diferentes colores (azul para la bebida carbonatada, anaranjado para la bebida refrescante, verde para la bebida isotónica y blanco para la bebida control; para poder diferenciarlos) los cuales se les dieron el paralelismo ente la superficie libre y la base del molde; luego se les dio un pulido tipo espejo para después ser llevados al microdurómetro Buehler donde se les midió la microdureza. Los datos obtenidos fueron analizados a través de la prueba estadística de TSTUDENT, ANALISIS DE VARIANZA ANOVA, TUKEY HSD, KRUSKAL WALLIS Y U DE MANN WHITNEY. Se concluyó que la microdureza superficial del esmalte disminuye significativamente luego de ser sometido a la acción de las bebidas ácidas estudiadas y que el efecto erosivo es inmediato y se incrementa con cada exposición. Se obtuvo como resultado que la bebida isotónica es más erosiva que las otras bebidas; y se concluyó que no hay una relación entre el efecto erosivo y los valores de pH, acidez titulable y efecto buffer las bebidas. / In this study we measured the Vickers microhardness of enamel after exposure to three industrialized beverages more consumed in the city of Lima, and a control beverage; we want to evaluate the erosive effect of the acidic beverages and their relation with the titratable acidity, the level of pH and buffer effect of this beverages. 60 blocks of surface enamel were made of 2mm thickness, and 2-4mm in length, were placed in fast curing acrylic circumferential mold of 10mm in diameter and 5mm in height, in different colors (blue for the carbonated drink, orange for the drink refreshing, green for the drink isotonic and white for the control beverage; to be differentiated); we gave them that the free surface being parallel with the base of the mold, then they were given a mirrorpolished for microhardness after that, they were being taken to Buehler where microhardness was measured. The data were analyzed by the statistical test T-STUDENT, ANALYSIS OF VARIANCE ANOVA, HSD TUKEY, YU WALLIS KRUSKAL WHITNEY MANN. It was concluded that the enamel surface microhardness decreases significantly after being subjected to the action of acidic drinks and the erosive effect is immediate and increases with each exposure. The result was that the isotonic beverage is more erosive than other drinks, and it was concluded that there is not a relationship between the erosive effect of pH values, titratable acidity and buffer effect of the beverages.

Made available in DSpace on 2014-06-12T17:38:40Z (GMT). No. of bitstreams: 2 arquivo4087_1.pdf: 3717955 bytes, checksum: c558abb160a867b5f16716ff3c05269c (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Faculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco / O petróleo bruto é uma substância altamente corrosiva, por isso, provoca rápida degradação das superfícies metálicas com as quais tem contato direto, como no caso de tanques de armazenamento e transporte desse material. Dessa forma, uma alternativa para solucionar esse problema é utilizar um tipo de revestimentos inerte a essa corrosão. Materiais cerâmicos geralmente apresentam essa característica e podem ser uma opção de material para esse revestimento. Esse estudo é de suma importância, pois com a abertura da refinaria de petróleo no estado de Pernambuco, a necessidade de armazenar e transportar petróleo cru irá crescer e com isso serão necessárias formas de transporte e armazenamento que sejam resistentes a corrosão provocada por esse petróleo. Nesse sentido é importante investigar novos materiais cerâmicos de alto desempenho que sejam inertes a corrosão e que possam ser utilizados como revestimentos para tanques. Neste contexto, o trabalho destina-se ao processamento e caracterização de compósitos cerâmicos, através da produção de peças com matriz metálica, e posterior análise de viabilidade na aplicação, por processos adequados, em tanques e tubulações em escala laboratorial, revestidas com as cerâmicas Al2O3-ZrO2 variando entre 5 a 20% (em peso) de ZrO2, com aditivos de óxido de terra rara CeO2 e a avaliação do desempenho em condições reais de petróleo cru oriundo de diferentes poços de petróleo do nordeste. O objetivo deste trabalho é estudar materiais intrinsecamente suscetíveis à fratura devido a sua pouca deformação plástica e destina-se ao desenvolvimento e caracterização de compósitos cerâmicos alumina-zircônia-céria compatíveis ao problema em questão. As cerâmicas foram produzidas por reação em estado sólido e sinterizadas de maneira direta (1200ºC à 1400ºC) num intervalo de até 24hrs e produzidas por processo; de moagem, termo-mecânico, e tratamentos térmicos em proporções adequadas. A caracterização estrutural e microestrutural foi realizada por método de difração de raio-X (DRX) e microscopia eletrônica de varredura (MEV). As propriedades mecânicas foram avaliadas por ensaios de densidade e dureza Vickers (HV). Na fase final foi avaliado o desempenho do revestimento em petróleo cru. Os resultados das propriedades mecânicas encontradas em 0,20 de ZrO2 se mostram superiores aos outros analisados, mostrando-se mais adequados a aplicação em questão

Many of the pre-contact and early contact cultures of the Northern Plains have been the subjects of debate in archaeological circles. Mortlach and Vickers focus are no exception. One of the issues to date is the possible relationship between these two groups. A key to understanding this relationship lies in the Makotchi-Ded Dontipi locale in Manitobas Lauder Sandhills. This unique ecological island is home to a great number of sites (Hamilton and Nicholson1999), including neighboring Vickers focus and Mortlach sites.<p>This study offers the results of a comprehensive analysis of the pottery assemblages recovered from the Jackson, Vera, Twin Fawns, Schuddemat and Hollow B sites of the Makotchi-Ded Dontipi locale. In addition, it examines the prior cultural affiliation of these sites. Though in many ways different from eastern Vickers focus assemblages, Jackson and Vera assemblages should be considered Vickers focus. Many of the discrepancies are due to the changing nature of the sites over time in conjunction with contact with neighboring Mortlach groups. Schuddemat and Twin Fawns also differ from typical Mortlach assemblages. These differences can be attributed to their location on the eastern periphery of the Mortlach spatial distribution where they came in contact with, and were likely joined by Vickers focus people.<p>Mortlach, Vickers focus and Wascana ware are likely all a part of a larger phenomenon of eastern Woodlands migration onto the Canadian Plains. These cultures became distinct over time through interaction with neighboring groups and exploitation of territorial resource bases. Though distinct, they share a number of similarities reflecting common ancestors. These similarities culminate in the Makotchi-Ded Dontipi locale where interaction between Mortlach and Vickers focus people likely resulted in the amalgamation of Vickers focus into Mortlach. This amalgamation is reflected in the pottery assemblages of Twin Fawns and Schuddemat which seem to represent a Vickers variant of the Lake Midden subphase of Mortlach.

Many of the pre-contact and early contact cultures of the Northern Plains have been the subjects of debate in archaeological circles. Mortlach and Vickers focus are no exception. One of the issues to date is the possible relationship between these two groups. A key to understanding this relationship lies in the Makotchi-Ded Dontipi locale in Manitobas Lauder Sandhills. This unique ecological island is home to a great number of sites (Hamilton and Nicholson1999), including neighboring Vickers focus and Mortlach sites.<p>This study offers the results of a comprehensive analysis of the pottery assemblages recovered from the Jackson, Vera, Twin Fawns, Schuddemat and Hollow B sites of the Makotchi-Ded Dontipi locale. In addition, it examines the prior cultural affiliation of these sites. Though in many ways different from eastern Vickers focus assemblages, Jackson and Vera assemblages should be considered Vickers focus. Many of the discrepancies are due to the changing nature of the sites over time in conjunction with contact with neighboring Mortlach groups. Schuddemat and Twin Fawns also differ from typical Mortlach assemblages. These differences can be attributed to their location on the eastern periphery of the Mortlach spatial distribution where they came in contact with, and were likely joined by Vickers focus people.<p>Mortlach, Vickers focus and Wascana ware are likely all a part of a larger phenomenon of eastern Woodlands migration onto the Canadian Plains. These cultures became distinct over time through interaction with neighboring groups and exploitation of territorial resource bases. Though distinct, they share a number of similarities reflecting common ancestors. These similarities culminate in the Makotchi-Ded Dontipi locale where interaction between Mortlach and Vickers focus people likely resulted in the amalgamation of Vickers focus into Mortlach. This amalgamation is reflected in the pottery assemblages of Twin Fawns and Schuddemat which seem to represent a Vickers variant of the Lake Midden subphase of Mortlach.

The Lovstrom site (DjLx-1) is a Late Precontact multicomponent site located in the Tiger Hills of southwestern Manitoba. Two occupation levels identified in Block E are separated by an approximate 400 year time span, the oldest identified as Blackduck at 800 BP and a later Vickers Focus group occupying the site around 400 BP. Excavations took place between 1986 and 1991 as part of the Brandon University archaeological field school. In addition to the information gained from the recovery of amounts of cultural material, later excavations were also opened in an effort to gain knowledge about the amount of site disturbance. The amount of material artifacts uncovered during test pitting necessitated a number of excavation blocks be opened. This thesis focuses on the faunal material recovered from Block E. Although a number of species were identified, bison represents the vast majority of faunal material. The faunal analysis was undertaken to determine the composition of the bison herd and seasonality. Due to the nature of the site and the fragmented faunal assemblage an in-depth analysis took place to identify any taphonomic forces that may have disturbed the archaeological record. This includes both cultural and natural forces that acted on the Block E assemblage. The occupant’s butchering practices are compared and contrasted with additional comparisons made to similar nearby archaeological sites, including the Blackduck Stott site and the Vickers Focus Jackson site.

The focus of this research was to quantify the post-fire mechanical properties of 5083-H116 and 6082-T6 aluminum alloys. Post-fire exposure is considered heating the material to a particular temperature then cooling the material back to room temperature. The research included evaluating parent materials as well as welded samples. Post-fire mechanical properties of parent materials were evaluated at temperatures ranging from ambient to 500oC with isothermal and transient heating. Changes in material properties were evaluated through static tensile tests and hardness testing on cooled samples. Using this data, an assessment was performed to investigate the relationship between hardness and mechanical properties. For the alloys evaluated, empirical relationships were found between Vickers hardness and post-fire strength. Testing was also performed on butt welded samples of 6082-T6 exposed isothermally to temperatures ranging from ambient to 500oC. Vickers hardness profiles were measured across a sample to quantify the hardness of the weld, heat affected zone, and parent material. This was performed at room temperature and following different heat exposures. Static tensile tests were used to evaluate the effect of reheating on the welded samples. Post-fire strength of welded samples was strongly affected by weld geometry. Parent material hardness varied with reheating while weld hardness remained constant. At select temperatures, this resulted in the weld having a higher Vickers hardness than the parent material. Despite this tensile failure always occurred within the weld. / Master of Science

Objetivo: Verificar a influência do nível de reaproveitamento e do tratamento de superfície sobre a resistência à flexão e microdureza Vickers de um sistema cerâmico prensado. Material e métodos: Foram utilizados sessenta corpos-de-prova do sistema cerâmico prensado IPS e.max (Ivoclar-Vivadent). Os corpos-de-prova (25X4X1,2mm) foram confeccionados seguindo a especificação ISO 6872, de acordo com o nível de reaproveitamento da cerâmica: GI 100% nova, GII 50% nova + 50% reaproveitada, GIII - 100% reaproveitada, GIV GI + ácido hidrofluorídrico, GV GII + ácido hidrofluorídrico e GVI GIII + ácido hidrofluorídrico. Foi realizado o teste de resistência à flexão de três pontos (n=10), conforme especificação ISO 10477 e ISO 6872. A microdureza Vickers foi mensurada em cinco corpos-de-prova de cada grupo, sob carga de quinhentos gramas por dez segundos. Os resultados foram submetidos ao teste de normalidade e posteriormente a ANOVA e post-hoc teste de Tukey, com nível de significância de 5%. Resultados: Os valores médios de microdureza variaram de 436,90 (GIV) a 605,97 (GII). Não foram observadas diferenças quanto ao nível de reaproveitamento, e o ácido reduziu estatísticamente os valores de dureza, para todos os grupos em estudo. Os valores médios de resistência a flexão variaram de 455,70 (GIV) a 500,56 (GIII). Não foram observadas diferenças estatísticas entre os grupos avaliados quanto ao nível de reaproveitamento e aplicação do ácido hidrofluorídrico. Conclusões: O reaproveitamento, total ou parcial, não exerceu influência sobre as propriedades mecânicas avaliadas. O condicionamento com ácido reduziu estatísticamente os valores de dureza, sem efeito sobre os resultados de resistência à flexão. / Objective: the aim of the present study was to observe the influence of the repressing level of ceramic and of the surface treatment on the flexural strength and Vickers microhardness of a pressable ceramic system. Material and methods: Sixty samples of a pressable ceramic system (IPS e.max - Ivoclar- Vivadent) were confectioned, with dimensions of 25X4X1.2mm, following specification ISO 6872, according to the level of repressing: GI - 100% new ceramic, GII - 50% new + 50% repressed, GIII - 100% repressed, GIV - GI + etching using hydrofluoric acid, GV - GII + etching using hydrofluoric acid and GVI - GIII + etching using hydrofluoric acid. Flexural strength test was accomplished by a three-point test, according to specification ISO 10477 and ISO 6872. Vickers microhardness was measured in five samples to each group, under load of five hundred grams for ten seconds. Results were submitted to ANOVA and Tukey post-hoc test, with level of significance of 5%. Results: Mean values of microhardness ranged between 436,90 (GIV) and 605,97 (GII). Statistical differences were not observed for the repressing level, but etching using hydrofluoric acid reduced statistically the mean values of hardness, for all groups. Mean values of flexural strength varied from 455,70 (GIV) to 500,56 (GIII). Statistical differences were not observed among the tested groups for repressing level and etching using hydrofluoric acid. Conclusions: Repressing the ceramic, totally or partially, did not influence the evaluated mechanical properties. Etching using hydrofluoric acid reduced statistically hardness values, with no effect on the flexural strength mean values.

No description available.

In this study, complex rolling technology is adopted to produce aluminum/copper clad metals . The aluminum alloy A1050 and the copper C1100 are used. The experimental plan : the roughness (RCu=3.5£gm¡ARAl=6.45£gm)¡A(RCu=1.0£gm¡ARAl =2.15£gm)¡A(RCu=0.35£gm¡ARAl=0.8£gm) the thickness ratio(tAl:tCu=3:1)¡A(tAl:tCu =2:2)¡A(tAl:tCu=1:3) reduction 60% and 70% are set. It shows that the influence of the thickness is more significant than the roughness on the curvature according to the experimental results. And the results of peeling tests show that the peeling strength for the reduction 70% is larger than that for 60%. And peel strength with the second time rolling is larger than that with only once. The average peeling strength of the specimen in the rolling direction is larger than that in the perpendicular direction. From the micro Vickers hardness tests , it is known that the larger of the reduction of copper is, the larger the micro Vickers hardness between the interface of the sheets is .