Laüe back-reflection method for crystallographic orientation of a martensitic Cu-Zn-Al single crystal of the monoclinic system

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

Evaluation of a highly sensitive amperometric biosensor with low cholinesterase charge immobilized on a chemically modified carbon paste electrode for trace determination of carbamates in fruit, vegetable and water samples

A highly sensitive amperometric biosensor for determination of carbamate pesticides directly in water, fruit and vegetable samples has been evaluated, electrochemically characterized and optimized. The biosensor strip was fabricated in screen printed technique on a ceramic support using silver-based paste for reference electrode, and platinum-based paste for working and auxiliary electrodes. The working electrode was modified by a layer of carbon paste mixed with cobalt(II) phthalocyanine and acetylcellulose. Cholinesterase (ChE) enzymes with low enzymatic charge were immobilized on this layer. The operational simplicity of the biosensor consists in that a small drop (similar to 50 mu l) of substrate or sample is deposited on a horizontally positioned biosensor strip representing the microelectrochemical cell. The working potential of the biosensor was 370 mV versus Ag/AgI on a ship reference electrode preventing the interference of electroactive species which are oxidable at more positive potentials. The biosensor was applied to investigate the degradation of two reference ChE inhibitors in freeze dried water under different storage conditions and for direct determination of some N-methylcarbamates (NMCs) in fruit and vegetable samples at ppb concentration levels without any sample pretreatment. A comparison of the obtained results for the total carbamate concentration was done against those obtained using HPLC measurements. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Estudio de los procesos de corrosion de una aleacion metalica de cobre usada en odontologia

Corrosion phenomena in a dental copper-based alloy are experimentally studied using electrochemical techniques. Two heating sources, torch and induction, were used in the casting experiments. In the corrosion essays, the optimum casting cycle and the polarization curves were obtained. It was found that the heating sources have little influence on the corrosion processes of the metallic alloys studied.

Cutting performance of diamond coated Si3N4 tool during turning

Silicon nitride cutting tools have been used successfully for machining hard materials, like: cast irons, nickel based alloys, etc. However these cutting tools with diamond coating present little information on dry turning operations of gray cast iron. In the present work, Si3N4 square inserts was developed, characterized and subsequently coated with diamond for dry machining operations on gray cast iron. All experiments were conducted with replica. It was used a 1500, 3000, 4500 m cutting length, feed rate of 0.33 mm/rev and keeping the depth of cut constant and equal to 1 mm. The results show that wear in the tool tips of the Si3N4 inserts, in all cutting conditions, was caused by both mechanical and chemical processes. To understand the tool wear mechanisms, a morphological analysis of the inserts, after experiments, has been performed by SEM and optical microscopy. Diamond coated PVD inserts showed to be capable to reach large cutting lengths when machining gray cast iron. © (2010) Trans Tech Publications.

Automatic microstructural characterization and classification using artificial intelligence techniques on ultrasound signals

Secondary phases such as Laves and carbides are formed during the final solidification stages of nickel based superalloy coatings deposited during the gas tungsten arc welding cold wire process. However, when aged at high temperatures, other phases can precipitate in the microstructure, like the γ″ and δ phases. This work presents a new application and evaluation of artificial intelligent techniques to classify (the background echo and backscattered) ultrasound signals in order to characterize the microstructure of a Ni-based alloy thermally aged at 650 and 950 °C for 10, 100 and 200 h. The background echo and backscattered ultrasound signals were acquired using transducers with frequencies of 4 and 5 MHz. Thus with the use of features extraction techniques, i.e.; detrended fluctuation analysis and the Hurst method, the accuracy and speed in the classification of the secondary phases from ultrasound signals could be studied. The classifiers under study were the recent optimum-path forest (OPF) and the more traditional support vector machines and Bayesian. The experimental results revealed that the OPF classifier was the fastest and most reliable. In addition, the OPF classifier revealed to be a valid and adequate tool for microstructure characterization through ultrasound signals classification due to its speed, sensitivity, accuracy and reliability. © 2013 Elsevier B.V. All rights reserved.

Influência da dopagem com oxigênio nas propriedades anelásticas e biocompatibilidade de ligas Ti-5%pNb e Ti-10%pNb

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

Utilização de técnicas do planejamento de experimentos na otimização de um processo de torneamento da superliga NIMONIC 80A

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da usinagem em torneamento da superliga a base de niquel NIMONIC 80

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito de elementos substitucionais e intersticiais na microestrutura, dureza e módulo de elasticidade de ligas Ti-Nb

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

Efeito da aplicação do fluido de corte na usinagem da superliga Nimonic 80A

The nickel alloys have a chemical composition with high tenor of alloy elements which are responsible for the material's mechanical and thermal properties, but also are the main causative of problems during the machining, making the process difficult. 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, seeking the best condition of lubricant fluid use, providing 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 mm) and feed rate (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. 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)

Avaliação da usinagem do INCONEL 718

The nickel superalloys are known as being a material with poor machinability, they have some properties like high hardness, good resistance at high temperature, tendency to weld with the tool material at high temperature, etc. In the aerospace, biomedical and petrochemical industry, are increasing the need to use materials that resist to aggressive process and environment. In these uses, it has increased the use of nickel-based superalloys like Inconel 718 and consequently the need to research new techniques and tools to improve the machinability of this material. For the superalloys and resistant alloys at high temperatures is considered that the difficulty in the machining regards to the combination of the relatively high cutting forces and high temperatures that grow during the machine process, causing deformation or breakage of the cutting tool. This work purpose is to develop the study of the machining of external cylindrical turning of the nickel based alloy Inconel 718, using ceramic tools, seeking the optimization of machining this alloy, looking to provide real productive increases without the need of investments in new production means. The machining test were accomplished using commercials hard metal tools and the results were compared each other to find the best tool and the best parameter. The conclusion is that the tool TNMG160408-23 -class 1005- was the better one, when used with the parameter 60_15_08

Usinagem da liga de níquel inconel 718 com pastilhas de cerâmica

The machining of super alloys resistant to high temperatures such as nickel alloys, inconel 718 specifically, is a very difficult job to obtain improvements in the process, due to the difficulty of machining at high cutting speeds, the use of these alloys in industries showed great developments in recent years, its application in aeronautical industry spread being used in vane turbo, compressor parts, props and set elements. The automotive, chemical, medical and others also took advantage of the great features of inconel 718 and has used the material. The high temperature resistant alloys have high machining difficulty, a fact that is associated with high cutting forces generated during machining which result in high temperatures. High levels of temperatures can cause deterioration of the cutting edge, with subsequent deformation or breakage, wear most common obtained in machining such materials are flank wear the formation of built-up edge for cutting and notch wear. The experimental part of the work consists in machining of nickel-based alloy Inconel 718 heat treated for hardness, using a tool based ceramic silicon nitride Sandvik (Si3N4) in order to compare the best results obtained in the master's thesis of SANTOS (2010) who used a tool ceramics also the basis of silicon nitride which was developed in the doctoral thesis of SOUZA (2005). Assays were performed on a CNC lathe and was noted for each cutting edge results obtained. Tests were made starting from an initial condition of the tool with cutting speed of 200 m/min, feed 0.5 mm and 0.5 mm depth of cut was reduced cutting speed for the subsequent tests with the same conditions of feed and depth of cut. The tool presented wear instant under two 200 m/min and 100 m/min, premature rupture of 50 m/min and finally cut provided with difficulty... (Complete abstract click electronic access below)

Effect of veneering material on the deformation suffered by implant-supported fixed prosthesis framework

The aim of this study was to evaluate the deformation suffered by cantilevered implant-supported fixed prostheses frameworks cast in silver-palladium alloy and coated with two occlusal veneering materials: acrylic resin or porcelain. Material and Methods: Two strain gauges were bonded to the inferior surface of the silver-palladium framework and two other were bonded to the occlusal surface of the prosthesis framework covered with ceramic and acrylic resin on each of its two halves. The framework was fixed to a metallic master model and a 35.2 N compression force was applied to the cantilever at 10, 15 and 20 mm from the most distal implant. The measurements of deformation by compression and tension were obtained. The statistical 2-way ANOVA test was used for individual analysis of the experiment variables and the Tukey test was used for the interrelation between all the variables (material and distance of force application). Results: The results showed that both variables had influence on the studied factors (deformation by compression and tension). Conclusion: The ceramic coating provided greater rigidity to the assembly and therefore less distortion compared with the uncoated framework and with the resin-coated framework. The cantilever arm length also influenced the prosthesis rigidity, causing higher deformation the farther the load was applied from the last implant.

Method development using ICP-MS and LA-ICP-MS and their application in environmental and material science

Within this PhD thesis several methods were developed and validated which can find applicationare suitable for environmental sample and material science and should be applicable for monitoring of particular radionuclides and the analysis of the chemical composition of construction materials in the frame of ESS project. The study demonstrated that ICP-MS is a powerful analytical technique for ultrasensitive determination of 129I, 90Sr and lanthanides in both artificial and environmental samples such as water and soil. In particular ICP-MS with collision cell allows measuring extremely low isotope ratios of iodine. It was demonstrated that isotope ratios of 129I/127I as low as 10-7 can be measured with an accuracy and precision suitable for distinguishing sample origins. ICP-MS with collision cell, in particular in combination with cool plasma conditions, reduces the influence of isobaric interferences on m/z = 90 and is therefore well-suited for 90Sr analysis in water samples. However, the applied ICP-CC-QMS in this work is limited for the measurement of 90Sr due to the tailing of 88Sr+ and in particular Daly detector noise. Hyphenation of capillary electrophoresis with ICP-MS was shown to resolve atomic ions of all lanthanides and polyatomic interferences. The elimination of polyatomic and isobaric ICP-MS interferences was accomplished without compromising the sensitivity by the use of a high resolution mode as available on ICP-SFMS. Combination of laser ablation with ICP-MS allowed direct micro and local uranium isotope ratio measurements at the ultratrace concentrations on the surface of biological samples. In particular, the application of a cooled laser ablation chamber improves the precision and accuracy of uranium isotopic ratios measurements in comparison to the non-cooled laser ablation chamber by up to one order of magnitude. In order to reduce the quantification problem, a mono gas on-line solution-based calibration was built based on the insertion of a microflow nebulizer DS-5 directly into the laser ablation chamber. A micro local method to determine the lateral element distribution on NiCrAlY-based alloy and coating after oxidation in air was tested and validated. Calibration procedures involving external calibration, quantification by relative sensitivity coefficients (RSCs) and solution-based calibration were investigated. The analytical method was validated by comparison of the LA-ICP-MS results with data acquired by EDX.

Design of nanoparticle systems with antimicrobial properties

Infektiöse Komplikationen im Zusammenhang mit Implantaten stellen einen Großteil aller Krankenhausinfektionen dar und treiben die Gesundheitskosten signifikant in die Höhe. Die bakterielle Kolonisation von Implantatoberflächen zieht schwerwiegende medizinische Konsequenzen nach sich, die unter Umständen tödlich verlaufen können. Trotz umfassender Forschungsaktivitäten auf dem Gebiet der antibakteriellen Oberflächenbeschichtungen ist das Spektrum an wirksamen Substanzen aufgrund der Anpassungsfähigkeit und Ausbildung von Resistenzen verschiedener Mikroorganismen eingeschränkt. Die Erforschung und Entwicklung neuer antibakterieller Materialien ist daher von fundamentaler Bedeutung.rnIn der vorliegenden Arbeit wurden auf der Basis von Polymernanopartikeln und anorganischen/polymeren Verbundmaterialien verschiedene Systeme als Alternative zu bestehenden antibakteriellen Oberflächenbeschichtungen entwickelt. Polymerpartikel finden Anwendung in vielen verschiedenen Bereichen, da sowohl Größe als auch Zusammensetzung und Morphologie vielseitig gestaltet werden können. Mit Hilfe der Miniemulsionstechnik lassen sich u. A. funktionelle Polymernanopartikel im Größenbereich von 50-500 nm herstellen. Diese wurde im ersten System angewendet, um PEGylierte Poly(styrol)nanopartikel zu synthetisieren, deren anti-adhesives Potential in Bezug auf P. aeruginosa evaluiert wurde. Im zweiten System wurden sog. kontakt-aktive kolloide Dispersionen entwickelt, welche bakteriostatische Eigenschaften gegenüber S. aureus zeigten. In Analogie zum ersten System, wurden Poly(styrol)nanopartikel in Copolymerisation in Miniemulsion mit quaternären Ammoniumgruppen funktionalisiert. Als Costabilisator diente das zuvor quaternisierte, oberflächenaktive Monomer (2-Dimethylamino)ethylmethacrylat (qDMAEMA). Die Optimierung der antibakteriellen Eigenschaften wurde im nachfolgenden System realisiert. Hierbei wurde das oberflächenaktive Monomer qDMAEMA zu einem oberflächenaktiven Polyelektrolyt polymerisiert, welcher unter Anwendung von kombinierter Miniemulsions- und Lösemittelverdampfungstechnik, in entsprechende Polyelektrolytnanopartikel umgesetzt wurde. Infolge seiner oberflächenaktiven Eigenschaften, ließen sich aus dem Polyelektrolyt stabile Partikeldispersionen ohne Zusatz weiterer Tenside ausbilden. Die selektive Toxizität der Polyelektrolytnanopartikel gegenüber S. aureus im Unterschied zu Körperzellen, untermauert ihr vielversprechendes Potential als bakterizides, kontakt-aktives Reagenz. rnAufgrund ihrer antibakteriellen Eigenschaften wurden ZnO Nanopartikel ausgewählt und in verschiedene Freisetzungssysteme integriert. Hochdefinierte eckige ZnO Nanokristalle mit einem mittleren Durchmesser von 23 nm wurden durch thermische Zersetzung des Precursormaterials synthetisiert. Durch die nachfolgende Einkapselung in Poly(L-laktid) Latexpartikel wurden neue, antibakterielle und UV-responsive Hybridnanopartikel entwickelt. Durch die photokatalytische Aktivierung von ZnO mittels UV-Strahlung wurde der Abbau der ZnO/PLLA Hybridnanopartikel signifikant von mehreren Monaten auf mehrere Wochen verkürzt. Die Photoaktivierung von ZnO eröffnet somit die Möglichkeit einer gesteuerten Freisetzung von ZnO. Im nachfolgenden System wurden dünne Verbundfilme aus Poly(N-isopropylacrylamid)-Hydrogelschichten mit eingebetteten ZnO Nanopartikeln hergestellt, die als bakterizide Oberflächenbeschichtungen gegen E. coli zum Einsatz kamen. Mit minimalem Gehalt an ZnO zeigten die Filme eine vergleichbare antibakterielle Aktivität zu Silber-basierten Beschichtungen. Hierbei lässt sich der Gehalt an ZnO relativ einfach über die Filmdicke einstellen. Weiterhin erwiesen sich die Filme mit bakteriziden Konzentrationen an ZnO als nichtzytotoxisch gegenüber Körperzellen. Zusammenfassend wurden mehrere vielversprechende antibakterielle Prototypen entwickelt, die als potentielle Implantatbeschichtungen auf die jeweilige Anwendung weiterhin zugeschnitten und optimiert werden können.