Produção de estrutura com gradiente de porosidade a partir da sinterização por plasma da mistura de pós Ti-Nb-Sn

Porous structures are being widely investigated for use in biomedical implants, aiming to mechanically integrate and functionally the implant inside the bone tissue. Moreover, this structure is also important for drugs that can be stored and can induce and accelerate the process of osseointegration. With the purpose to investigate this effect, Ti, Nb and Sn metal powders, were sintered by plasma using a hollow cathode discharge. Sintering was performed in argon plasma set at 4 mbar pressure and temperatures of 500 ° C, 600 ° C and 700 ° C. Samples were also sintered in the electrical resistance furnace at 1200 ° C in order to compare plasma sintering with the conventional method. It was observed that plasma samples sintered with the hollow cathode configuration showed a gradient in porosity, while the samples sintered in the resistive furnace did not. Furthermore, differences in the microstructure of the samples were found, were a surface with higher porosity and ales porous core were obtained at different temperatures. The percolation profile of distilled water and the chemical compositions of the porous layers of the plasma treated samples were the main results obtained. Based on these results, we can conclude that this structure is particularly important for application in the biomedical field such as scaffolds for drug delivery and implants

Síntese e caracterização de pigmentos nanométricos encapsulados pelos métodos dos precursores poliméricos, hidrotermal de microondas e co-precipitação associado à química sol-gel convencional

The demand for materials with high consistency obtained at relatively low temperatures has been leveraging the search for chemical processes substituents of the conventional ceramic method. This paper aims to obtain nanosized pigments encapsulated (core-shell) the basis of TiO2 doped with transition metals (Fe, Co, Ni, Al) through three (3) methods of synthesis: polymeric precursors (Pechini); hydrothermal microwave, and co-precipitation associated with the sol-gel chemistry. The study was motivated by the simplicity, speed and low power consumption characteristic of these methods. Systems costs are affordable because they allow achieving good control of microstructure, combined with high purity, controlled stoichiometric phases and allowing to obtain particles of nanometer size. The physical, chemical, morphological, structural and optical properties of the materials obtained were analyzed using different techniques for materials characterization. The powder pigments were tested in discoloration and degradation using a photoreactor through the solution of Remazol yellow dye gold (NNI), such as filtration, resulting in a separation of solution and the filter pigments available for further UV-Vis measurements . Different calcination temperatures taken after obtaining the post, the different methods were: 400 º C and 1000 º C. Using a fixed concentration of 10% (Fe, Al, Ni, Co) mass relative to the mass of titanium technologically and economically enabling the study. By transmission electron microscopy (TEM) technique was possible to analyze and confirm the structural formation nanosized particles of encapsulated pigment, TiO2 having the diameter of 20 nm to 100 nm, and thickness of coated layer of Fe, Ni and Co between 2 nm and 10 nm. The method of synthesis more efficient has been studied in the work co-precipitation associated with sol-gel chemistry, in which the best results were achieved without the need for the obtainment of powders the calcination process

Comparação entre técnicas de nitretação em cátodo oco e gaiola catódica na deposição de TiN

The plasma nitriding has been used in industrial and technological applications for large-scale show an improvement in the mechanical, tribological, among others. In order to solve problems arising in the conventional nitriding, for example, rings constraint (edge effect) techniques have been developed with different cathodes. In this work, we studied surfaces of commercially pure titanium (Grade II), modified by plasma nitriding treatment through different settings cathodes (hollow cathode, cathodic cage with a cage and cathodic cage with two cages) varying the temperature 350, 400 and 430oC, with the goal of obtaining a surface optimization for technological applications, evaluating which treatment generally showed better results under the substrate. The samples were characterized by the techniques of testing for Atomic Force Microscopy (AFM), Raman spectroscopy, microhardness, X-ray diffraction (XRD), and a macroscopic analysis. Thus, we were able to evaluate the processing properties, such as roughness, topography, the presence of interstitial elements, hardness, homogeneity, uniformity and thickness of the nitrided layer. It was observed that all samples were exposed to nitriding modified relative to the control sample (no treatment) thus having increased surface hardness, the presence of TiN observed by XRD as per both Raman and a significant change in the roughness of the treated samples . It was found that treatment in hollow cathode, despite having the lowest value of microhardness between treated samples, was presented the lowest surface roughness, although this configuration samples suffer greater physical aggressiveness of treatment

Processing of highly porous titanium parts by metal injection moulding in combination with innovative plasma treatment

A combinação da Moldagem por Injeção de pós Metálicos (Metal Injection Moulding MIM) e o Método do Retentor Espacial (Space Holder Method - SHM) é uma técnica promissora para fabricação de peças porosas de titânio com porosidade bem definida como implantes biomédicos, uma vez que permite um alto grau de automatização e redução dos custos de produção em larga escala quando comparado a técnica tradicional (SHM e usinagem a verde). Contudo a aplicação desta técnica é limitada pelo fato que há o fechamento parcial da porosidade na superfície das amostras, levando ao deterioramento da fixação do implante ao osso. E além disso, até o presente momento não foi possível atingir condições de processamento estáveis quando a quantidade de retentor espacial excede 50 vol. %. Entretanto, a literatura descreve que a melhor faixa de porosidade para implantes de titânio para coluna vertebral está entre 60 - 65 vol. %. Portanto, no presente estudo, duas abordagens foram conduzidas visando a produção de amostras altamente porosas através da combinação de MIM e SHM com o valor constante de retentor espacial de 70 vol. % e uma porosidade aberta na superfície. Na primeira abordagem, a quantidade ótima de retentor espacial foi investigada, para tal foram melhorados a homogeneização do feedstock e os parâmetros de processo com o propósito de permitir a injeção do feedstock. Na segunda abordagem, tratamento por plasma foi aplicado nas amostras antes da etapa final de sinterização. Ambas rotas resultaram na melhoria da estabilidade dimensional das amostras durante a extração térmica do ligante e sinterização, permitindo a sinterização de amostras de titânio altamente porosas sem deformação da estrutura.

Tecnologia eletroquímica como tratamento alternativo de efluentes derivados da indústria têxtil e petroquímica

In this work, the treatment of wastewater from the textile industry, containing dyes as Yellow Novacron (YN), Red Remazol BR (RRB) and Blue Novacron CD (NB), and also, the treatment of wastewater from petrochemical industry (produced water) were investigated by anodic oxidation (OA) with platinum anodes supported on titanium (Ti/Pt) and boron-doped diamond (DDB). Definitely, one of the main parameters of this kind of treatment is the type of electrocatalytic material used, since the mechanisms and products of some anodic reactions depend on it. The OA of synthetic effluents containing with RRB, NB and YN were investigated in order to find the best conditions for the removal of color and organic content of the dye. According to the experimental results, the process of OA is suitable for decolorization of wastewaters containing these textile dyes due to electrocatalytic properties of DDB and Pt anodes. Removal of the organic load was more efficient at DDB, in all cases; where the dyes were degraded to aliphatic carboxylic acids at the end of the electrolysis. Energy requirements for the removal of color during OA of solutions of RRB, NB and YN depends mainly on the operating conditions, for example, RRB passes of 3.30 kWh m-3 at 20 mA cm-2 for 4.28 kWh m-3 at 60 mA cm-2 (pH = 1); 15.23 kWh m-3 at 20 mA cm-2 to 24.75 kWh m-3 at 60 mA cm-2 (pH 4.5); 10.80 kWh m-3 at 20 mA cm-2 to 31.5 kWh m-3 at 60 mA cm-2 (pH = 8) (estimated data for volume of treated effluent). On the other hand, in the study of OA of produced water effluent generated by petrochemical industry, galvanostatic electrolysis using DDB led to the complete removal of COD (98%), due to large amounts of hydroxyl radicals and peroxodisulphates generated from the oxidation of water and sulfates in solution, respectively. Thus, the rate of COD removal increases with increasing applied current density (15-60 mAcm-2 ). Moreover, at Pt electrode, approximately 50% removal of the organic load was achieved by applying from 15 to 30 mAcm-2 while 80% of COD removal was achieved for 60 mAcm-2 . Thus, the results obtained in the application of this technology were satisfactory depending on the electrocatalytic materials and operating conditions used for removal of organic load (petrochemical and textile effluents) as well as for the removal of color (in the case of textile effluents). Therefore, the applicability of electrochemical treatment can be considered as a new alternative like pretreatment or treatment of effluents derived from textiles and petrochemical industries.

Avaliação do controle da diagênese na qualidade de reservatório siliciclástico do cenomaniano superior da formação Açu, sudoeste da bacia potiguar

The distribution of diagenetic alterations in Late Cenomanian siliciclastic reservoirs from Potiguar Basin was influenced by the stratigraphic framework and the depositional system. Seismic sections and geophysical logs of two wells drilled in the SW portion of the mentioned basin above register regional stratigraphic surfaces representing maximum floods related to a transgressive event. The sequential analysis of 80 m of drill core (~450 m deep) recognized nine depositional facies with an upwards granodecrescent standard piling that limits cycles with an erosional conglomeratic base (lag) overlain by intercalations of medium to very fine sandstones showing cross bedding (channel, planar and low angled) and horizontal bedding (plane-parallel , wave and flaser). The top of the cycles is marked by the deposition of pelites and the development of paleosoils and lagoons. The correlation of genetically related facies reveals associations of channel fillings, crevasse, and flood plains deposited in a transgressive system. Detailed descriptions of seventy nine thin sections aided by MEV-EBSD/EDS, DRX and stable isotope analyses in sandstones revealed an arcosian composition and complex textural arrays with abundant smectite fringes continuously covering primary components, mechanically infiltrated cuticles and moldic and intragrain pores. K-feldspar epitaxial overgrowth covers microcline and orthoclase grains before any other phase. Abundant pseudomatrix due to the compactation of mud intraclasts concentrate along the stratification planes, locally replaced by macrocristalline calcite and microcrystalline and framboidal pyrite. Kaolinite (booklets and vermicular), microcrystalline smectite, microcrystalline titanium minerals and pyrite replace the primary components. The intergrain porosity prevails over the moldic, intragrain and contraction porosities. The pores are poorly connected due to the presence of intergranular smectite, k-feldspar overgrowth, infiltrated mud and pseudomatrix. The sandstones were subjected to eodiagenetic conditions next to the surface and shallow burial mesodiagenetic conditions. The diagenetic alterations reduced the porosity and the permeability mainly due to the precipitation of smectite fringes, compactation of mud intraclasts onto the pseudomatrix and cementing by poikilotopic calcite characterizing different reservoir petrofacies. These diagenetic products acted as barriers and detours to the flow of fluids thus reducing the quality of the reservoir.

Aplicação de tratamentos eletroquímicos integrados para remediação de solos e águas contaminadas com petróleo e pesticidas

Electrochemical technologies have been proposed as a promising alternative for the treatment of effluents and contaminated soils. Therefore, the objective of this work was to study the treatment of contaminated soils and wastewaters using electrochemical technologies. Thus, the study regarding the scale-up of the electrochemical system with continuous flow treatment of wastewater of the petrochemical industry was investigated using platinum electrodes supported on titanium (Ti / Pt), and boron-doped diamond (BDD). The results clearly showed that under the operating conditions studied and electrocatalytic materials employed, the better removal efficiency was achieved with BDD electrode reducing the chemical oxygen demand (COD) from 2746 mg L-1 to 200 mg L-1 in 5 h consuming 56.2 kWh m-3 . The decontamination of soils and effluents by petrochemical products was evaluated by studying the effects of electrokinetic remediation for removal of total petroleum hydrocarbons (HTP) from contaminated soil with diesel. The efficiency of this process was dependent on the electrolyte used Na2SO4 (96.46%), citric acid (81.36%) and NaOH (68.03%) for 15 days. Furthermore, the effluent after treatment of the soil was treated by electrochemical oxidation, achieving a good elimination of the organic polluting load dissolved. Depending on the physical behavior of wastewater contaminated with oil (emulsified state); atrazine emulsified effluents were investigated. The main characteristics of the effluent produced during the washing of contaminated soil were studied, being dependent on the surfactant dosage used; which determined its electrolytic treatment with BDD. The electrochemical oxidation of emulsified effluent of atrazine was efficient, but the key to the treatment is reducing the size of micelles.

Utilização do titâneo na confecção de estruturas metálicas em prótese parcial removível

Due to properties such as excellent biocompatibility, high resistance to corrosion and low specific weight, titanium has been considered a material of great interest for Dentistry. It has been widely used in implants and orthognathic surgeries. Recently, titanium has been seen as a feasible alternative for the fabrication of removable partial denture frameworks, either in pure titanium (99.75%) or in titanium alloy forms (Ti-6Al-4V; Ti-6A1-7Nb). Based on a review of the literature, this work studied the use of titanium for the fabrication of removable partial denture frameworks, focusing on its advantages and disadvantages as well as its characteristics. It was concluded that the use of titanium is a convenient option for partially edentulous arches rehabilitation with quite satisfactory and promising clinical results. However, the need for highly-equipped laboratories increases the cost, preventing its large scale use.

Utilização do titâneo na confecção de estruturas metálicas em prótese parcial removível

Due to properties such as excellent biocompatibility, high resistance to corrosion and low specific weight, titanium has been considered a material of great interest for Dentistry. It has been widely used in implants and orthognathic surgeries. Recently, titanium has been seen as a feasible alternative for the fabrication of removable partial denture frameworks, either in pure titanium (99.75%) or in titanium alloy forms (Ti-6Al-4V; Ti-6A1-7Nb). Based on a review of the literature, this work studied the use of titanium for the fabrication of removable partial denture frameworks, focusing on its advantages and disadvantages as well as its characteristics. It was concluded that the use of titanium is a convenient option for partially edentulous arches rehabilitation with quite satisfactory and promising clinical results. However, the need for highly-equipped laboratories increases the cost, preventing its large scale use.

Estudo da produção eletroquímica de espécies de cloro ativo para tratamento de efluentes sintéticos

The treatment of wastewater is essential to human health. One of the most important steps is the disinfection treatment which uses chlorine to eliminate bacteria as required by environmental agencies. However, the identification of potentially toxic byproducts generated by this method, such as trihalomethanes, has stimulated the development of new alternative disinfection technologies. Among them, heterogeneous photocatalysis, TiO2 photocatalysis and electrochemical disinfection are considered suitable alternatives to the chlorination method. Thus, the present dissertation analyzes the evolution of active chlorine species in a synthetic NaCl solution and it is tested to treat a synthetic solution of the dye Reactive Blue 19 using boron-doped diamond (BDD) and ruthenium oxide (Ti/Ru0.3Ti0.7O2) as anodes. The indirect electrochemical process was discussed in terms of mineralization of the total organic load and percentage of color removal in order to evaluate the applicability of electrochemical technology. Electrochemical experiments were carried out with different current densities (25, 50 and 75 mA.cm-2) during 120 minutes. On the other hand, other important parameter in this study was the influence of the proportion sp3/sp2 on BDD anode on the performance of the evolution of active chlorine species which was investigated by electrolytic techniques (linear polarization), with the intention of determining the related training oxidizing species and consumption energy to chemical or electrochemical reactions. From the results, it can be noted that the BDD electrode showed better efficiency throughout the electrochemical process.

Estudo da produção eletroquímica de espécies de cloro ativo para tratamento de efluentes sintéticos

The treatment of wastewater is essential to human health. One of the most important steps is the disinfection treatment which uses chlorine to eliminate bacteria as required by environmental agencies. However, the identification of potentially toxic byproducts generated by this method, such as trihalomethanes, has stimulated the development of new alternative disinfection technologies. Among them, heterogeneous photocatalysis, TiO2 photocatalysis and electrochemical disinfection are considered suitable alternatives to the chlorination method. Thus, the present dissertation analyzes the evolution of active chlorine species in a synthetic NaCl solution and it is tested to treat a synthetic solution of the dye Reactive Blue 19 using boron-doped diamond (BDD) and ruthenium oxide (Ti/Ru0.3Ti0.7O2) as anodes. The indirect electrochemical process was discussed in terms of mineralization of the total organic load and percentage of color removal in order to evaluate the applicability of electrochemical technology. Electrochemical experiments were carried out with different current densities (25, 50 and 75 mA.cm-2) during 120 minutes. On the other hand, other important parameter in this study was the influence of the proportion sp3/sp2 on BDD anode on the performance of the evolution of active chlorine species which was investigated by electrolytic techniques (linear polarization), with the intention of determining the related training oxidizing species and consumption energy to chemical or electrochemical reactions. From the results, it can be noted that the BDD electrode showed better efficiency throughout the electrochemical process.

Estudo teórico das propriedades eletrônicas e termodinâmicas de nanofitas quasiperiódicas BCN

Nanoscale materials composed of boron, nitrogen, and carbon have unique properties and may be useful in new technologies. In this thesis, we investigate some properties of BCN nanoribbons constructed according to the Fibonacci quasiperiodic sequence. We analyze properties such as structural stability, electronic density of states, electronic specific heat, band structure, and energy band gap. We have performed first-principles calculations based on density functional theory implemented in the SIESTA code. The results showed that nanoribbons present a fixed value of the formation energy. The electronic density of states was used to calculate the specific heat. We found an oscillatory behavior of the electronic specific heat, in the low temperature regime. We analyze the electronic band structure to determine the energy band gap. The energy band gap oscillates as a function of the Fibonacci generation index n. Our work suggest that appropriate choice of the building block materials of the quasiperiodic sequence, may lead to a tuneable band gap of the quasiperiodic nanoribbons.

Análise da estabilidade genética de células-tronco mesenquimais humanas

Human multipotent mesenchymal stromal cells (MSCs), also known as mesenchymal stem cells, have become an important and attractive therapeutic tool since they are easily isolated and cultured, have in vitro expansion potential, substantial plasticity and secrete bioactive molecules that exert trophic effects. The human umbilical cord as a cell source for cell therapy will help to avoid several ethical, political, religious and technical issues. One of the main issues with SC lines from different sources, mainly those of embryonic origin, is the possibility of chromosomal alterations and genomic instability during in vitro expansion. Cells isolated from one umbilical cord exhibited a rare balanced paracentric inversion, likely a cytogenetic constitutional alteration, karyotype: 46,XY,inv(3)(p13p25~26). Important genes related to cancer predisposition and others involved in DNA repair are located in 3p25~26. Titanium is an excellent biomaterial for bone-implant integration; however, the use can result in the generation of particulate debris that can accumulate in the tissues adjacent to the prosthesis, in the local bone marrow, in the lymph nodes, liver and spleen. Subsequently may elicit important biological responses that aren´t well studied. In this work, we have studied the genetic stability of MSC isolated from the umbilical cord vein during in vitro expansion, after the cryopreservation, and under different concentrations and time of exposition to titanium microparticles. Cells were isolated, in vitro expanded, demonstrated capacity for osteogenic, adipogenic and chondrogenic differentiation and were evaluated using flow cytometry, so they met the minimum requirements for characterization as MSCs. The cells were expanded under different concentrations and time of exposition to titanium microparticles. The genetic stability of MSCs was assessed by cytogenetic analysis, fluorescence in situ hybridization (FISH) and analysis of micronucleus and other nuclear alterations (CBMN). The cells were able to internalize the titanium microparticles, but MSCs preserve their morphology, differentiation capacity and surface marker expression profiles. Furthermore, there was an increase in the genomic instability after long time of in vitro expansion, and this instability was greater when cells were exposed to high doses of titanium microparticles that induced oxidative stress. It is necessary always assess the risks/ benefits of using titanium in tissue therapy involving MSCs, considering the biosafety of the use of bone regeneration using titanium and MSCs. Even without using titanium, it is important that the therapeutic use of such cells is based on analyzes that ensure quality, security and cellular stability, with the standardization of quality control programs appropriate. In conclusion, it is suggested that cytogenetic analysis, FISH analysis and the micronucleus and other nuclear alterations are carried out in CTMH before implanting in a patient

Estudo da zircônia reforçado com alumina

Ceramics materials have good properties including chemical stability, high hardness and wear resistance. Moreover, due to its fragility, can suffer failure under relatively low levels of tension. Actually zirconia is the material of choice in metal free dental prostheses used in dentistry due its inertia in physiological environment, good bending strength, hardness and fracture toughness. The alumina and mixed tungsten and titanium carbides additions, acting as reinforcement elements in the zirconia matrix, have as their main objective the improvement of mechanical properties of this material. In this work, samples of zirconia, zirconia with 30% wt of alumina and zirconia with 30% wt mixed carbides were analyzed. The samples were sintered by uniaxial hot pressing on 30 MPa pressure, for 1 hour in an argon atmosphere. They were physically characterized by porosity and density measurements, and mechanically by 3-points bending strength and Vickers microhardness. The X-ray diffraction was used for the phase identifications and microstructure was examined by scanning electron microscopy (SEM). The addition of mixed carbides as reinforcement elements in zirconia matrix provides improvements in all properties analyzed in this work. The alumina addition has dropped the zirconia strength, although it caused improvement in other properties

Construção, caracterização e aplicação de eletrodos para descarga por arco de cátodo oco

The system built to characterize electrodes and, consequently, deposited fine films are constituted by a hollow cathode that works to discharges and low pressures (approximately 10-3 to 5 mbar), a source DC (0 to 1200 V), a cylindrical camera of closed borossilicato for flanges of stainless steel with an association of vacuum bombs mechanical and spread. In the upper flange it is connected the system of hollow cathode, which possesses an entrance of gas and two entrances for its refrigeration, the same is electrically isolated of the rest of the equipment and it is polarized negatively. In front of the system of hollow cathode there is a movable sample in stainless steel with possibility of moving in the horizontal and vertical. In the vertical, the sample can vary its distance between 0 and 70 mm and, in the horizontal, can leave completely from the front of the hollow cathode. The sample and also the cathode hollow are equipped with cromel-alumel termopares with simultaneous reading of the temperatures during the time of treatment. In this work copper electrodes, bronze, titanium, iron, stainless steel, powder of titanium, powder of titanium and silício, glass and ceramic were used. The electrodes were investigated relating their geometry change and behavior of the plasma of the cavity of hollow cathode and channel of the gas. As the cavity of hollow cathode, the analyzed aspects were the diameter and depth. With the channel of the gas, we verified the diameter. In the two situations, we investigated parameters as flow of the gas, pressure, current and applied tension in the electrode, temperature, loss of mass of the electrode with relationship at the time of use. The flow of gas investigated in the electrodes it was fastened in a work strip from 15 to 6 sccm, the constant pressure of work was among 2.7 to 8 x 10-2 mbar. The applied current was among a strip of work from 0,8 to 0,4 A, and their respective tensions were in a strip from 400 to 220 V. Fixing the value of the current, it was possible to lift the curve of the behavior of the tension with the time of use. That curves esteem in that time of use of the electrode to its efficiency is maximum. The temperatures of the electrodes were in the dependence of that curves showing a maximum temperature when the tension was maximum, yet the measured temperatures in the samples showed to be sensitive the variation of the temperature in the electrodes. An accompaniment of the loss of mass of the electrode relating to its time of use showed that the electrodes that appeared the spherical cavities lost more mass in comparison with the electrodes in that didn't appear. That phenomenon is only seen for pressures of 10-2 mbar, in these conditions a plasma column is formed inside of the channel of the gas and in certain points it is concentrated in form of spheres. Those spherical cavities develop inside of the channel of the gas spreading during the whole extension of the channel of the gas. The used electrodes were cut after they could not be more used, however among those electrodes, films that were deposited in alternate times and the electrodes that were used to deposit films in same times, those films were deposited in the glass substrata, alumina, stainless steel 420, stainless steel 316, silício and steel M2. As the eletros used to deposit films in alternate time as the ones that they were used to deposit in same times, the behavior of the thickness of the film obeyed the curve of the tension with relationship the time of use of the electrode, that is, when the tension was maximum, the thickness of the film was also maximum and when the tension was minimum, the thickness was minimum and in the case where the value of the tension was constant, the thickness of the film tends to be constant. The fine films that were produced they had applications with nano stick, bio-compatibility, cellular growth, inhibition of bacterias, cut tool, metallic leagues, brasagem, pineapple fiber and ornamental. In those films it was investigated the thickness, the adherence and the uniformity characterized by sweeping electronic microscopy. Another technique developed to assist the production and characterization of the films produced in that work was the caloteste. It uses a sphere and abrasive to mark the sample with a cap impression, with that cap form it is possible to calculate the thickness of the film. Through the time of life of the cathode, it was possible to evaluate the rate of waste of its material for the different work conditions. Values of waste rate up to 3,2 x 10-6 g/s were verified. For a distance of the substratum of 11 mm, the deposited film was limited to a circular area of 22 mm diameter mm for high pressures and a circular area of 75 mm for pressure strip. The obtained films presented thickness around 2,1 µm, showing that the discharge of arch of hollow cathode in argon obeys a curve characteristic of the tension with the time of life of the eletrodo. The deposition rate obtained in this system it is of approximately 0,18 µm/min