Desenvolvimento de argamassa para restauração utilizando resíduo do polimento do porcelanato

The coatings mortars are essential elements of building structures because they execute an important role in protecting walls and are particularly exposed to aggressive action responsible for its degradation over time. The importance of wall coverings has been the subject of discussion and analysis in the conservation and rehabilitation of old buildings. Are sometimes removed and replaced with inappropriate solutions of constructive point of view or architecture. The most commonly used coatings on walls of old buildings is based on traditional hydraulic lime mortars. The present study aims at the formulation of new lime- based mortars and aerial fine aggregate, in order to contribute to a better field of conservation and restoration mortar coating of old buildings. Residue was used for polishing porcelain as fine aggregate, replacing the aggregate (sand), in percentages 05-30% by mass. We conducted a thorough evaluation of the mortar properties in fresh and hardened state by comparing the performance of the same with a reference mortar. The residue used was characterized as the density, bulk density, and particle size laser, scanning electron microscopy, X-ray diffraction and X-ray fluorescence. Formulations were produced 7, 6 with residue and one commonly used formulation, which served as a reference. In the formulations of lime mortars air (hydrated lime powder CH-I) has been adopted a stroke volume (1:3) with constant binder, was varied and the water / binder and aggregate and waste. For evaluation of mortars fresh, proceeded to consistency analysis, specific gravity, water retention and air content embedded. In the hardened state assays were performed in specific gravity, water retention, modulus of elasticity, tensile strength in bending, compressive strength, water absorption by capillary action, adhesion, tensile strength, resistance to shrinkage and salts by of crystallization trials with resources chloride solution, nitrate and sulfate all sodium in prismatic at 90 days of age, in addition to the micro structural analysis of mortars. Based on the results we can see that the mortar formulated with 10% content of waste and the reference free retraction feature more stable closer to neutrality. The composition of 10% was obtained better performance against the action of the salt crystallization. The mortar with 15% residue obtained better density, lower air content embedded and high capacity for water retention developing good workability. The replacement of 20% of waste generates a satisfactory utilization of resistance to compression, flexion and traction grip the base. And, finally, it can be seen that the mortar with 10, 15 and 20% residual show, in principle, good suitability as coatings, thus enabling a final result consistent with durability, workability and aesthetics developing therefore a material with better performance to repair or replace existing mortars in old buildings

Efeito da adição do poli(etileno acrilato de metila) (ema) e da fibra de linter de algodão nas propriedades do poli(tereftalato de etileno) reciclado (petrec)

The development of new materials to fill the demand of technological advances is a challenge for many researchers around the world. Strategies such as making blends and composites are promising alternatives to produce materials with different properties from those found in conventional polymers. The objective of this study is to evaluate the effect of adding the copolymer poly(ethylene methyl acrylate) (EMA) and cotton linter fibers (LB) on the properties of recycled poly(ethylene terephthalate) (PETrec) by the development of PETrec/EMA blend and PETrec/EMA/LB blend composite. In order to improve the properties of these materials were added as compatibilizers: Ethylene - methyl acrylate - glycidyl methacrylate terpolymer (EMA-GMA) and maleic anhydride grafted polyethylene (PE-g-MA). The samples were produced using a single screw extruder and then injection molded. The obtained materials were characterized by thermogravimetry (TG), melt flow index (MFI) mensurements, torque rheometry, pycnometry to determinate the density, tensile testing and scanning electron microscopy (SEM). The rheological results showed that the addition of the EMA copolymer increased the viscosity of the blend and LB reduces the viscosity of the blend composite. SEM analysis of the binary blend showed poor interfacial adhesion between the PETrec matrix and the EMA dispersed phase, as well as the blend composite of PETrec/EMA/LB also observed low adhesion with the LB fiber. The tensile tests showed that the increase of EMA percentage decreased the tensile strength and the Young s modulus, also lower EMA percentage samples had increased the elongation at break. The blend composite showed an increase in the tensile strength and in the Young`s modulus, and a decrease in the elongation at break. The blend formulations with lower EMA percentages showed better mechanical properties that agree with the particle size analysis which showed that these formulations presented a smaller diameter of the dispersed phase. The blend composite mechanical tests showed that this material is stronger and stiffer than the blend PETrec/EMA, whose properties have been reduced due to the presence of EMA rubbery phase. The use of EMA-GMA was effective in reducing the particle size of the EMA dispersed phase in the PETrec/EMA blend and PE-g-MA showed evidences of reaction with LB and physical mixture with the EMA

Efeito de argilas organofílicas na estrutura e propriedades de nanocompósitos de poli(metacrilato de metila)

Nacomposites of polymers and lamellar clayminerals, has generated high scientific and technological interest, for having mechanical properties and gas barriers differentiated of polymers and conventional composites. In this work, it was developed nanocomposites by single screw extruder and injection, utilizing commercial raw material, with the goal to investigate the quality of new developed materials. It was evaluated the influence of the content and the kind of clay in the structure and in the nanocomposites properties. It was used regular and elastomeric poly (methyl methacrylate) (Acrigel LEP 100 and Acrigel ECP800) and six montmorillonites (Cloisite 10A, 11B, 15A, 20A, 25A e 30B) at the concentration of 1% e 3% in weight. The nanocomposites were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), colorimetric, optical transparency, flexural and tensile tests, Rockwell hardness and esclerometry. It was founded that is possible to obtain intercalated and exfoliated nanocomposites PMMA/MMT, and the top results was obtained in the materials with 1%in clay weight organophilizated with 2M2HT (Cloisite 15A and 20A) presented intercalate and hybrid morphology (exfoliated and flocullated). The ones that was produced with organophilizated clay with 2MHTL8 (Cloisite 30B) had excellent visual quality, but the majority presented hybrid morphology. In the materials processed with organophilizated clay with MT2ETOH (Cloisite 30B), there were color change and loss of transparency. It occurs improvement in a few mechanical properties, mainly in the materials produced with PMMA elastomeric (Acrigel ECP800), being more significant, the increase in the resistance to stripping in those nanocomposites

Síntese e caracterização do poli(ácido láctico) para potencial uso em sistemas de liberação controlada de fármacos

With the advances in medicine, life expectancy of the world population has grown considerably in recent decades. Studies have been performed in order to maintain the quality of life through the development of new drugs and new surgical procedures. Biomaterials is an example of the researches to improve quality of life, and its use goes from the reconstruction of tissues and organs affected by diseases or other types of failure, to use in drug delivery system able to prolong the drug in the body and increase its bioavailability. Biopolymers are a class of biomaterials widely targeted by researchers since they have ideal properties for biomedical applications, such as high biocompatibility and biodegradability. Poly (lactic acid) (PLA) is a biopolymer used as a biomaterial and its monomer, lactic acid, is eliminated by the Krebs Cycle (citric acid cycle). It is possible to synthesize PLA through various synthesis routes, however, the direct polycondensation is cheaper due the use of few steps of polymerization. In this work we used experimental design (DOE) to produce PLAs with different molecular weight from the direct polycondensation of lactic acid, with characteristics suitable for use in drug delivery system (DDS). Through the experimental design it was noted that the time of esterification, in the direct polycondensation, is the most important stage to obtain a higher molecular weight. The Fourier Transform Infrared (FTIR) spectrograms obtained were equivalent to the PLAs available in the literature. Results of Differential Scanning Calorimetry (DSC) showed that all PLAs produced are semicrystalline with glass transition temperatures (Tgs) ranging between 36 - 48 °C, and melting temperatures (Tm) ranging from 117 to 130 °C. The PLAs molecular weight characterized from Size Exclusion Chromatography (SEC), varied from 1000 to 11,000 g/mol. PLAs obtained showed a fibrous morphology characterized by Scanning Electron Microscopy (SEM)

Desenvolvimento de filtros cerâmicos impregnados com nanopartículas de prata para desinfecção de água potável

Brazil has vast amounts of hydric resources, whose quality has been deteriorating due to pollutant dumping. Household waste disposal is one of the main sources of water pollution, stimulating bacteria proliferation and introducing microorganisms, including those from fecal matter. Conventional water disinfection methods are a solution, but on the downside, they lead to the formation byproducts hazardous to human health. In this study, aiming to develop bactericidal filters for the disinfection of drinking water; silver nanoparticles were deposited on alumina foams through three routes: sputtering DC, dip coating and in situ chemical reduction of silver nitrate. The depositions were characterized through X-ray diffraction, scanning electron microscopy and EDS element mapping. The influence of the depositions on permeability and mechanical properties of the ceramic foams was assessed and, in sequence, a preliminary antibacterial efficiency analysis was carried out. Characterization results indicate that the chemical reduction routes were efficient in depositing homogeneously distributed silver particles and that the concentration of the metallic precursor salt affects size and morphology of the particles. The antibacterial efficiency analysis indicates that the chemical reduction filters have potential for water disinfection

Síntese do Poli (ácido láctico) por policondensação direta utilizando um planejamento fatorial

The environmental impact caused by the disposal of non-biodegradable polymer packaging on the environment, as well as the high price and scarcity of oil, caused increase of searches in the area of biodegradable polymers from renewable resources were developed. The poly (lactic acid) (PLA) is a promising polymer in the market, with a large availability of raw material for the production of its monomer, as well as good processability. The aimed of this study was synthesis PLA by direct polycondesation of lactic acid, using the tool of experimental design (DOE) (central composite rotatable design (CCRD)) to optimize the conditions of synthesis. The polymer obtained was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), viscosimetric analysis, differential scanning calorimeter (DSC) and size exclusion chromatography (SEC). The results confirmed the formation of a poly (lactic acid) semicrystalline in the syntheses performed. Through the central composite rotatable design was possible to optimize the crystallization temperature (Tc) and crystallinity degree (Xc). The crystallization temperature maximum was found for percentage of catalyst around the central point (0,3 (%W)) and values of time ranging from the central point (6h) to the upper level (+1) (8h). The crystallization temperature maximum was found for the total synthesis time of 4h (-1) and percentage of catalyst 0,1(W%) (-1). The results of size exclusion chromatography (SEC) showed higher molecular weights to 0,3 (W%) percent of catalyst and total time synthesis of 3,2h

Efeito do tratamento por plasma na proliferação de fibroblastos e esterilização de membranas de quitosana

Chitosan is being studied for use as dressing due their biological properties. Aiming to expand the use in biomedical applications, chitosan membranes were modified by plasma using the following gases: nitrogen (N2), methane (CH4), argon (Ar), oxygen (O2) and hydrogen (H2). The samples were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle, surface energy and water absorption test. Biological Tests were also performed, such as: test sterilization and proliferation of fibroblasts (3T3 line). Through SEM we observed morphological changes occurring during the plasma treatment, the formation of micro and nano-sized valleys. MFA was used to analyze different roughness parameters (Ra, Rp, Rz) and surface topography. It was found that the treated samples had an increase in surface roughness and sharp peaks. Methane plasma treatment decreased the hydrophilicity of the membranes and also the rate of water absorption, while the other treatments turned the membranes hydrophilic. The sterilization was effective in all treatment times with the following gases: Ar, N2 and H2. With respect to proliferation, all treatments showed an improvement in cell proliferation increased in a range 150% to 250% compared to untreated membrane. The highlights were the treatments with Ar 60 min, O2 60 min, CH4 15 min. Observing the results of the analyzes performed in this study, it appears that there is no single parameter that influences cell proliferation, but rather a set of ideal conditions that favor cell proliferation

Desenvolvimento de bioblendas poliméricas a partir de gelatina bovina e de tilápia com amido de milho

The natural raw materials acquired special importance beside the mineral raw materials with the need for using alternative sources to oil, because they can be used to produce biopolymers. Gelatin, produced from the denaturation of collagen, and starch, an abundant polysaccharide in various plants, are examples of biopolymers which have several technological applications, especially in films. The objective of this work is to produce polymeric bioblends with gelatin and corn starch using two types of gelatin: commercial bovine gelatin and gelatin produced from mechanically separated flesh of tilapia (Oreochromis niloticus). For the extraction of tilapia gelatin 3 distinct pretreatments, followed by extraction in distilled water under heating were performed. The properties of gelatin extracted were similar to bovine gelatin, and the differences can be explained by the difference in extraction processes and sources. Blends of commercial gelatin and starch were produced in an internal mixer from a Haake torque rheometer, to study the behavior of the gelatin mixture with starch, thus, the same compositions were processed by twin screw extrusion, to define the mixing parameters. Subsequently, the extrusion of blends of tilapia gelatin and corn starch was carried out in the same twin screw extruder. The physico-chemical, rheological and morphological properties of the blends with thermoplastic starch and gelatin were studied. It was found that various properties vary linearly with increasing concentration of the components. The blends produced are immiscible, and among the two gelatins, tilapia gelatin showed a better interfacial adhesion with the corn starch. Regarding the morphology, gelatins formed the dispersed phase in all compositions studied, even in compositions rich in starch. Can be concluded that the procedure for tilapia gelatin extraction is feasible and advantageous, and the increasing in its scale to a reactor of 30 liters is possible, with a satisfactory yield. The bioblends of bovine gelatin/corn starch and tilapia gelatin/corn starch were successfully produced, and the processing conditions were appropriate

Desenvolvimento e caracterização de compósito a partir da borra da piaçava para construção da parábola de um fogão solar a concentração

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Estudo da influência da temperatura de brasagem nas uniões zircônia/aço inox 304 utilizando metalização mecânica

Metal-Ceramic (M/C) Zirconia-stainless steel interfaces have been processed through brazing techniques due to the excellent combination of properties such as high temperature stability, high corrosion resistance and good mechanical properties. However, some M/C interfaces show some defects, like porosity and cracks results in the degradation of the interfaces, leading even to its total rupture. Most of time, those defects are associated with an improper brazing parameters selection to the M/C system. In this work, ZrO2 Y-TZP and ZrO2 Mg - PSZ were joint with the stainless steel grade 304 by brazing using a eutectic silver-copper (Ag28Cu) interlayer alloy with different thermal cycles. Ceramic surfaces were previous mechanically metallized with titanium to improve adhesion of the system. The effect of temperature on the M/C interface was studied. SEM-EDS and 3 point flexural bend test were performed to evaluate morphology, chemical composition and mechanical resistance of the M/C interfaces. Lower thermal cycle temperatures produced better results of mechanical resistance, and more regular/ homogeneous reaction layers between braze alloy and metal-ceramic surfaces. Also was proved the AgCu braze alloy activation in situ by titanium

Efeito da Gália como aditivo de sinterização em eletrólitos cerâmicos à base de céria sintetizados pelo método de complexação de cátions

Fuel cells are considered one of the most promising ways of converting electrical energy due to its high yield and by using hydrogen (as fuel) which is considered one of the most important source of clean energy for the future. Rare earths doped ceria has been widely investigated as an alternative material for the electrolyte of solid oxide fuel cells (SOFCs) due to its high ionic conductivity at low operating temperatures compared with the traditional electrolytes based on stabilized zirconia. This work investigates the effect of gallium oxide (Gallia) as a sintering aid in Eu doped ceria ceramic electrolytes since this effect has already been investigated for Gd, Sm and Y doped ceria electrolytes. The desired goal with the use of a sintering aid is to reduce the sintering temperature aiming to produce dense ceramics. In this study we investigated the effects on densification, microstructure and ionic conduction caused by different molar fraction of the dopants europium (10, 15 and 20%) and gallium oxide (0.3, 0.6 and 0.9%) in samples sintered at 1300, 1350 and 1450 0 C. Samaria (10 and 20%) doped ceria samples sintered between 1350 and 1450 °C were used as reference. Samples were synthesized using the cation complexation method. The ceramics powders were characterized by XRF, XRD and SEM, while the sintered samples were investigated by its relative density, SEM and impedance spectroscopy. It was showed that gallia contents up to 0.6% act as excellent sintering aids in Eu doped ceria. Above this aid content, gallia addition does not promote significant increase in density of the ceramics. In Ga free samples the larger densification were accomplished with Eu 15% molar, effect expressed in the microstructure with higher grain growth although reduced and surrounded by many open pores. Relative densities greater than 95 % were obtained by sintering between 1300 and 1350 °C against the usual range 1500 - 1600 0 C. Samples containing 10% of Sm and 0.9% of Ga reached 96% of theoretical density by sintering at 1350 0 C for 3h, a gain compared to 97% achieved with 20% of Sm and 1% of Ga co-doped cerias sintered at 1450 0 C for 24 h as described in the literature. It is found that the addition of gallia in the Eu doped ceria has a positive effect on the grain conductivity and a negative one in the grain boundary conductivity resulting in a small decrease in the total conductivity which will not compromise its application as sintering aids in ceria based electrolytes. Typical total conductivity values at 600 and 700 °C, around 10 and 30 mS.cm -1 respectively were reached in this study. Samples with 15% of Eu and 0.9 % of Ga sintered at 1300 and 1350 °C showed relative densities greater than 96% and total conductivity (measured at 700 °C) between 20 and 33 mS.cm -1 . The simultaneous sintering of the electrolyte with the anode is one of the goals of research in materials for SOFCs. The results obtained in this study suggest that dense Eu and Ga co-doped ceria electrolytes with good ionic conductivity can be sintered simultaneously with the anode at temperatures below 1350 °C, the usual temperature for firing porous anode materials

Síntese e caracterização de catalisadores de LaNiO3 não suportados e suportados em Al2O3 e ZrO2 para a reforma a vapor do metano

Ionic oxides with ABO3 structure, where A represents a rare earth element or an alkaline metal and B is a transition metal from group VIII of the periodic table are potential catalysts for oxidation and good candidates for steam reforming reaction. Different methods have been considered for the synthesis of the oxide materials with perovskite structure to produce a high homogeneous material with low amount of impurities and low calcination temperatures. In the current work, oxides with the LaNiO3 formula had been synthesized using the method of the polymeric precursors. The thermal treatment of the materials took place at 300 ºC for 2h. The material supported in alumina and/or zirconia was calcined at 800 ºC temperature for 4h. The samples had been characterized by the following techniques: thermogravimetry; infrared spectroscopy; X-ray diffraction; specific surface area; distribution of particle size; scanning electron microscopy and thermo-programmed reduction. The steam reforming reaction was carried out in a pilot plant using reducing atmosphere in the reactor with a mixture of 10% H2-Argon, a mass about 5g of catalyst, flowing at 50 mL.min-1. The temperature range used was 50 - 1000 oC with a heating rate of 10 oC.min-1. A thermal conductivity detector was used to analyze the gas after the water trapping, in order to permit to quantify the consumption of hydrogen for the lanthanum nickelates (LaNiO3). The results showed that lanthanum nickelate were more efficient when supported in alumina than when supported in zirconia. It was observed that the methane conversion was approximately 100% and the selectivity to hydrogen was about 70%. In all cases were verified low selectivity to CO and CO2

Efeitos do tratamento superficial da sílica ativa com soluções de ácidos nítrico e fosfórico em propriedades do concreto

The addition of active silica potentially improves the quality of concrete due to its high reactivity and pore refinement effect. The reactivity of silica is likely related to its charge density. Variations in surface charge alter the reactivity of the material consequently affecting the properties of concrete. The present study aimed at investigating variations in the charge density of silica as a function of acid treatments using nitric or phosphoric acid and different pH values (2.0, 4.0 and 6.0). Effects on concrete properties including slump, mechanical strength, permeability and chloride corrosion were evaluated. To that end, a statistical analysis was carried out and empirical models that correlate studied parameters (pH, acid and cement) with concrete properties were established. The quality of the models was tested by variance analysis. The results revealed that the addition of silica was efficiency in improving the properties of concrete, especially the electrochemical parameters. The addition of silica treated using nitric acid at pH = 4.0 displayed the best cement performance including highest strength, reduced permeability and lowest corrosion current

Nitretação em plasma com gaiola catódica: caracterização e avaliação do desempenho da camada nitretada em facas de corte

Nowadays, in the plastic industry are used mills that accomplish the recycling of residues generated in the production of its components. These mills contain cut sheets that suffer accelerated wear, once they are submitted constantly to the tribologic efforts, decreasing its useful life. To reduce this problem, it s used noble steels or takes place superficial treatments. The ionic nitriding process presents some limitations related to the uniformity of the layer in pieces with complex geometry, committing its application in pieces as knives, head offices, engagements, etc. However, the new technique of nitriding in cathodic cage eliminates some problems, as the restrictions rings, inherent to the conventional ionic nitriding. In present work, was studied the use viabilization of steels less noble, as SAE 1020, SAE 4320 and SAE 4340, nitreded by two different techniques, to substitute the AISI 01 steels, usually used in the cut knifes fabrication, seeking to reduce the costs and at the sane time to increase the useful life of these knifes. The steel most viable was the SAE 4340, nitrided in cathodic cage, because it presented uniformity in thickness and in the hardness of the layer, besides of increased 58% in the average its useful life

Influência da vermiculita expandida na formulação de pastas leves para evitar a migração de gás em cimentação de poços petrolíferos

The gas migration during the cementing of wells is one of the main problems of oil wells engineering. Its occurrence can cause severe problems since shortly to loss of control of the well after cementation. Recently, 20/04/2010 In an accident of major proportions in the Gulf of Mexico, among other factors, faulty cementing operation provided the gas migration, causing the accident, in which 11 people died and 17 were injured occurred. Besides the serious consequences that can be caused by gas migration, remediation of the problem, which is made by injecting cement in damaged areas, usually involves additional costs and is not always effective. Therefore, preventing gas migration to be preferred. Some methods are used to prevent the migration of the pressurized gas as the annular space, application of pressure pulses, reducing the height of the cement column compressible cement pastes of low permeability, pastes and to control free filtered water, and binders of thixotropic cement expandable and flexible. Thus, the cement pastes used to prevent gas migration must meet the maximum these methods. Thus, this study aimed to formulate a cement paste to prevent gas migration, using the expanded vermiculite, and evaluate the behavior of the folder trials necessary for use in oil wells. Free water content, rheological properties, compressive strength, loss of liquid phase sedimentation of solids, specific weight, thickening time and gas migration: The following tests were performed. The results show that meets the specifications paste formulated for use in oil wells and the use of expanded vermiculite contribute to the absorption of free water, thixotropy and low density. The absorption of free water is proven to result in zero percentage test free water content, thixotropy is observed with the high value of the initial gel strength (Gi) in testing rheological properties and low density is proven in test weight specific