Tratamento de superfícies metálicas por nanotecnologia

Trabalho Final de Mestrado para obten����o do grau de Mestre em Engenharia Qu��mica e Biol��gica

Revestimento de superfícies metálicas com TiN e AIN produzidos com plasma magnetr��o

Este trabalho visa a obten����o e o estudo das caracter��sticas dos revestimentos de AlN e TiN em substratos met��licos, produzidos por pulveriza����o cat��dica em plasma magnetr��o, num equipamento com c��todo oco, desenvolvido no LEF do CEFITEC. Este equipamento foi adaptado para o presente trabalho, atrav��s de alguns elementos adicionais, designadamente de um porta-amostras que permitiu o revestimento de provetes em lotes. Deste estudo conclui-se que a aplica����o de uma tens��o de ���bias��� na amostra altera a morfologia dos revestimentos e as caracter��sticas dos materiais que constituem o filme, n��o s�� no que diz respeito �� sua composi����o, como tamb��m proporciona estruturas mais densas e com menos porosidade. As tens��es de ���bias��� t��picas foram de ���100 V no caso de AlN e de ���75 V e com uma pot��ncia de 2,0 kW no c��todo no caso de TiN. Neste ��ltimo foi considerado apenas o objectivo da obten����o da fase d, de estrutura CFC (cor dourada), por ser a ��nica de interesse industrial. Por difrac����o de raios x verificou-se a obten����o de TiN e TiN0,9 com as caracter��sticas pretendidas. Tamb��m se verificou que as tens��es residuais dos filmes s��o de compress��o e isotr��picas.

Desenvolvimento de um prot��tipo para an��lise din��mica da dureza de superfícies metálicas

In this paper we developed a prototype for dynamic and quantitative analysis of the hardness of metal surfaces by penetration tests. It consists of a micro-indenter which is driven by a gear system driven by three-rectified. The sample to be tested is placed on a table that contains a load cell that measures the deformation in the sample during the penetration of micro-indenter. With this prototype it is possible to measure the elastic deformation of the material obtained by calculating the depth of penetration in the sample from the difference of turns between the start of load application to the application of the load test and return the indenter until the complete termination of load application. To determine the hardness was used to measure the depth of plastic deformation. We used 7 types of steel trade to test the apparatus. There was a dispersion of less than 10% for five measurements made on each sample and a good agreement with the values of firmness provided by the manufacturers.

Compara����o entre os exames radiogr��ficos convencional e digitalizado em rela����o ao plano de tratamento de superfícies oclusais

O objetivo deste estudo foi comparar as decis��es de tratamento restaurador de superfícies oclusais, sem cavita����o, quando realizadas atrav��s dos aspectos cl��nicos e radiogr��ficos, convencional e digitalizado. Foram examinados, 33 s��tios das superfícies oclusais de 30 molares permanentes extra��dos, com e sem pigmenta����o. O plano de tratamento para cada regi��o foi realizado por 5 cirurgi��es-dentistas, professores universit��rios, utilizando dois tipos de exames: exame visual de fotografias e radiografia interproximal convencional (IV + RXC); e exame visual de fotografias e radiografia digitalizada (IV + DIGORA). O padr��o de valida����o para os planos de tratamento foi realizado atrav��s do aspecto histol��gico. A sensibilidade em determinar a n��o-necessidade de tratamento restaurador foi, em m��dia, tanto para a IV + RXC quanto para a IV + DIGORA, de 0,23. A especificidade foi, em m��dia, de 0,83 e 0,86, para a IV + RXC e IV + DIGORA, respectivamente. Quando comparou-se os planos de tratamento intra-examinadores, n��o foi encontrada diferen��a estatisticamente significante �� n��vel de 5%. Baseado nestes dados, pode-se concluir que os m��todos radiogr��ficos, convencional e digitalizado, n��o demonstraram diferen��as na efetividade da determina����o do plano de tratamento de superfícies oclusais sem cavita����o.

Propriedades magn��ticas de nanoestruturas adsorvidas em superfícies metálicas

Neste trabalho, utilizamos o m��todo de primeiros princ��pios RS-LMTO-ASA (Real Space ��� Linear Muffin-Tin Orbital - Atomic Sphere Approximation) baseado na Teoria do Funcional da Densidade (DFT - Density Functional Theory) e implementado para o c��lculo de estruturas magn��ticas n��o-colineares, para investigar as propriedades magn��ticas de nanoestruturas adsorvidas em superfícies metálicas. Consideramos aglomerados com diferentes geometrias e tamanhos como ad��tomos, d��meros, tr��meros, nanofios e nanoestruturas de geometria triangular de Fe, Fe-Co e Fe-Pt adsorvidos sobre a superf��cie de Pt(111) e tratamos tamb��m nanoestruturas de Mn sobre a superf��cie de Ag(111). Mostramos que os nanofios de Fe-Co sobre a superf��cie de Pt(111) apresentam um ordenamento ferromagn��tico. Devido �� redu����o do n��mero de coordena����o presente na superf��cie, os momentos de spin e orbital nos s��tios de Fe e Co mostram-se elevados comparados com os respectivos valores dos momentos destes metais como bulk. Analisamos tamb��m como estes momentos variam em fun����o da concentra����o destes elementos nos nanofios. Para os sistemas compostos por nanofios Fe-Pt adsorvidos em Pt(111), mostramos que �� poss��vel sintonizar as intera����es de troca entre os ad��tomos magn��ticos Fe atrav��s da introdu����o de um diferente n��mero de ��tomos Pt para lig��-los. Por exemplo, a intera����o de troca entre os ad��tomos de Fe pode ser consideravelmente aumentada pela introdu����o de cadeias de Pt que os conectem e tanto configura����es ferromagn��ticas, antiferromagn��ticas ou n��o-colineares entre os ad��tomos de Fe podem ser estabilizadas, dependendo da espessura do espa��ador Pt. Para os aglomerados Mn sobre a Ag(111) mostramos que a intera����o de troca entre os s��tios de Mn depende n��o somente da dist��ncia entre os ��tomos, mas tamb��m do n��mero de coordena����o de cada s��tio. Desta forma, verificamos um magnetismo n��o-colinear nestas nanoestruturas causado tanto por frustra����o geom��trica, quanto pela competi����o de intera����es de curto e longo alcance. Nossos resultados est��o em boa concord��ncia com os resultados experimentais da literatura e com os resultados te��ricos obtidos por outros m��todos, quando existentes.

Controle de crescimento e redu����o de biofilmes pela aplica����o de potencial ou corrente el��tricos em superfícies metálicas, condutoras ou semicondutoras

Descrito como o presente Privil��gio de Inven����o, refere-se a um processo para a desinfec����o de superfícies condutoras ou semicondutoras, evitando a forma����o ou eliminando biofilmes preexistentes, para tanto, o presente processo �� realizado por meio da aplica����o de um potencial ou corrente el��tricos sobre as referidas superfícies sendo vantajosa por dispensar o uso de agentes biocidas, bem como n��o necessitar do uso de materiais ou produtos abrasivos, ou seja, com a tecnologia proposta no presente processo �� poss��vel controlar ou eliminar a presen��a de biofilmes em sistema industriais sem adi����o de subst��ncias ao sistema, pois no presente processo o reagente �� o el��tron ou o campo el��trico formado por ele.

Estudo de um ciclo de vapor utilizado para tratamento de superificies metálicas: estudo preliminar de caso

The use of heat in parallel with relative low temperatures and applied to several areas of the industry is essential for the main manufacturing processes, like drying, dehydrating, concentration, annealing, production of chemical reactions, and microbiological sterilization. Without neither the heat nor the coming of a great quantity of thermal heat, with high quality, there would not be the ���modern society���, with its high standards of living plus its high consumption levels; from services to goods in general. Within an almost absolute way, the heat flows are obtained from vapor systems. Thus, in this work we are going into the operation of a vapor system, composed of two firetube boilers dimensioned to supply vapor for three processes. However, with the transfer of one of the processes to another plant, the system got over-dimensioned. But, taking advantage of this scenario, the two boilers were used to supply vapor to further processes, causing their intermittent usage. Moreover, the operational alternative adopted by the maintenance engineering of the plant for a creating a solution has been presented; both the positive points and negative ones were disclosed, likewise the possibility of improvement points

Desenvolvimento de um prot��tipo para an��lise din��mica da dureza de superfícies metálicas

In this paper we developed a prototype for dynamic and quantitative analysis of the hardness of metal surfaces by penetration tests. It consists of a micro-indenter which is driven by a gear system driven by three-rectified. The sample to be tested is placed on a table that contains a load cell that measures the deformation in the sample during the penetration of micro-indenter. With this prototype it is possible to measure the elastic deformation of the material obtained by calculating the depth of penetration in the sample from the difference of turns between the start of load application to the application of the load test and return the indenter until the complete termination of load application. To determine the hardness was used to measure the depth of plastic deformation. We used 7 types of steel trade to test the apparatus. There was a dispersion of less than 10% for five measurements made on each sample and a good agreement with the values of firmness provided by the manufacturers.

Propriedades tribomec��nicas de superfícies de tit��nio carbonitretadas por plasma

Interstitial compounds of titanium have been mainly studied due to the large range of properties acquired when C, N, O and H atoms are added. In this work, surfaces of TiCxNy were produced by thermochemical treatments assisted by plasma with different proportions of Ar + N2 + CH4 gas mixture. The Ar gas flow was fixed in 4 sccm, varying only N2 and CH4 gas flows. During the thermochemical treatment, the plasma was monitored by Optical Emission Spectroscopy (OES) for the investigation of the influence of active species. After treatments, C and N concentration profile, crystalline and amorphous phases were analyzed by Nuclear Reaction (NRA). Besides tribomechanical properties of the Ti surface were studied through the nanohardness measurements and friction coefficient determination. The worn areas were evaluated by profilometry and Scanning Electronic Microscope (SEM) in order to verify the wear mechanism present in each material. It has been seen which the properties like nanohardness and friction coefficient have strong relation with luminous intensity of species of the plasma, suggesting a using of this characteristic as a parameter of process

An��lise e s��ntese de antenas e superfícies seletivas de frequ��ncia utilizando computa����o evolucion��ria e intelig��ncia de enxames

The frequency selective surfaces, or FSS (Frequency Selective Surfaces), are structures consisting of periodic arrays of conductive elements, called patches, which are usually very thin and they are printed on dielectric layers, or by openings perforated on very thin metallic surfaces, for applications in bands of microwave and millimeter waves. These structures are often used in aircraft, missiles, satellites, radomes, antennae reflector, high gain antennas and microwave ovens, for example. The use of these structures has as main objective filter frequency bands that can be broadcast or rejection, depending on the specificity of the required application. In turn, the modern communication systems such as GSM (Global System for Mobile Communications), RFID (Radio Frequency Identification), Bluetooth, Wi-Fi and WiMAX, whose services are highly demanded by society, have required the development of antennas having, as its main features, and low cost profile, and reduced dimensions and weight. In this context, the microstrip antenna is presented as an excellent choice for communications systems today, because (in addition to meeting the requirements mentioned intrinsically) planar structures are easy to manufacture and integration with other components in microwave circuits. Consequently, the analysis and synthesis of these devices mainly, due to the high possibility of shapes, size and frequency of its elements has been carried out by full-wave models, such as the finite element method, the method of moments and finite difference time domain. However, these methods require an accurate despite great computational effort. In this context, computational intelligence (CI) has been used successfully in the design and optimization of microwave planar structures, as an auxiliary tool and very appropriate, given the complexity of the geometry of the antennas and the FSS considered. The computational intelligence is inspired by natural phenomena such as learning, perception and decision, using techniques such as artificial neural networks, fuzzy logic, fractal geometry and evolutionary computation. This work makes a study of application of computational intelligence using meta-heuristics such as genetic algorithms and swarm intelligence optimization of antennas and frequency selective surfaces. Genetic algorithms are computational search methods based on the theory of natural selection proposed by Darwin and genetics used to solve complex problems, eg, problems where the search space grows with the size of the problem. The particle swarm optimization characteristics including the use of intelligence collectively being applied to optimization problems in many areas of research. The main objective of this work is the use of computational intelligence, the analysis and synthesis of antennas and FSS. We considered the structures of a microstrip planar monopole, ring type, and a cross-dipole FSS. We developed algorithms and optimization results obtained for optimized geometries of antennas and FSS considered. To validate results were designed, constructed and measured several prototypes. The measured results showed excellent agreement with the simulated. Moreover, the results obtained in this study were compared to those simulated using a commercial software has been also observed an excellent agreement. Specifically, the efficiency of techniques used were CI evidenced by simulated and measured, aiming at optimizing the bandwidth of an antenna for wideband operation or UWB (Ultra Wideband), using a genetic algorithm and optimizing the bandwidth, by specifying the length of the air gap between two frequency selective surfaces, using an optimization algorithm particle swarm

Altera����o das propriedades superficiais do alum��nio via eletr��lise e plasma

P��s-gradua����o em Ci��ncia e Tecnologia de Materiais - FC

Tratamento de pol��meros com jato de plasma em press��o atmosf��rica

P��s-gradua����o em F��sica - FEG

Compara����o entre a inspe����o visual, radiografia interproximal e a fluoresc��ncia a laser em rela����o ao diagn��stico de les��es cariosas oclusais e a determina����o do plano de tratamento

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Propriedades magn��ticas de nanoestruturas de metais de transi����o 3d em superfícies de Pd

Motivados por estudos experimentais acerca de monocamadas de metais de transi����o 3d sobre superfícies de Pd, nesta disserta����o investigamos o complexo magnetismo de nanoestruturas, embebidas ou adsorvidas, em superfícies metálicas atrav��s de c��lculos de primeiros princ��pios. Utilizamos o m��todo RS-LMTO-ASA (Real Space - Linear MuffinTin Orbital - Atomic Sphere Approximation), o qual �� baseado na teoria do funcional da densidade (DFT - Density Functional Theory) e implementado para o c��lculo de estruturas magn��ticas n��o colineares. Com este prop��sito, investigamos nanoestruturas embebidas e ligas (2 x 2) de metais 3d (Cr, Mn, Fe, Co e Ni) na superf��cie Pd (110), al��m de nanoestruturas de Cr adsorvidas sobre a superf��cie de Pd (111). Primeiro, para as nanoestruturas embebidas na superf��cie Pd (110), analisamos a varia����o do momento magn��tico de spin orbital com rela����o ao n��mero de vizinhos e de val��ncia dos metais 3d. Tamb��m mostramos que estas estruturas t��m ordenamento magn��tico colinear, exceto as de Cr e Mn, que apresentam magnetismo n��o colinear associado �� frustra����o geom��trica. Para o caso de nanofios de Cr adsorvidos sobre a superf��cie de Pd (111), verificamos uma configura����o colinear antiferromagn��tica para cadeias com at�� 9 ��tomos. Para o nanofio com 10 ��tomos obtivemos uma configura����o tipo antiferromagn��tica inclinada (canted). No caso de nanoestruturas de Cr bidimensionais, verificamos complexas configura����es magn��ticas n��o colineares com diferentes quiralidades.

Tratamento da superf��cie do alum��nio via eletr��lise a plasma

This paper presents the study on the application of the electrolytic plasma for surface treatment of aluminum. A bibliographical study on the material of interest was preliminarily performed and later designed and built an electrolytic cell, including the excitation source. Unlike conventional electrolysis process, the plasma assisted carry on in the non-linear region of characteristic current/voltage curve. Therefore it requires for the on set of the process that the power supply operates on harder conditions than those on high current process. The plasma produced during the present investigation has temperatures in the range o 6,0.10 3 -7,0 .10 3 K, well above those found in conventional chemical process. It also shows a particular dynamic to promote changes on surface and to produce new materials. The plasma is generated by microdischarge in vapor or gas bubbles involved in physic-chemical processes in electrode regions of the electrolytic cell. The electrode material was the aluminum (7075). The Process Electrolytic Plasma Processing (EPP) is sensitive to various parameters such as operating voltage, current density, electrolyte, concentration of electrolyte, geometry of reactor, temperature of electrolytic solution and dynamic of the fluid in the cell. The experiments were carried on in order to find parameters for a stable abd steady operation. The choice for the electrolytic was silicate/alkali solution in various concentrations to operate in various voltage as well. Plasma was produced on negative (cathode) and positive (anode) electrode, in specific conditions. A stable operation on the cathode process was obtained with low concentration of the electrolytic in aqueous solution, current density around 250V effective voltage. For the evolution of plasma in anodic process it was required higher concentrations and higher... (Complete abstract click electronic access below)