Abstract in Portuguese:RESUMO Os metais pesados são amplamente utilizados em diversos setores industriais, tais como, metalurgia, mineração, galvanoplastia, têxtil, fertilizantes, baterias, pesticidas, circuito impresso, entre outros, sendo comumente encontrados no efluente gerado por estas indústrias. Por serem extremamente tóxicos, podendo contaminar tanto o ecossistema quanto a comunidade ao seu entorno, se faz necessário um tratamento eficiente dos efluentes, a fim de se reduzir a concentração destes elementos, a níveis aceitáveis, antes do descarte. Dentre os diversos tratamentos de efluentes possíveis, a adsorção é amplamente empregada por sua simplicidade, eficiência e baixo custo. Nesse trabalho, foram produzidas, pelo método de gelificação interna, microesferas porosas contendo alumina e hematita em diferentes concentrações, que foram utilizadas como adsorventes em ensaios de adsorção, em batelada e em coluna de leito fixo, de soluções aquosas contendo Zn2+, Ni2+ e Mn2+. As microesferas foram caracterizadas quanto à morfologia e distribuição de tamanho de partículas, área de superfície específica, adsorção gasosa e fases cristalinas. Foi possível avaliar o efeito da composição e da distribuição de tamanho das microesferas na adsorção dos metais pesados. Obteve-se mais de 90% de adsorção dos metais pesados, no regime de coluna de leito fixo, indicando alta eficiência dessas microesferas como adsorventes destes íons.
Abstract in English:ABSTRACT Heavy metals are widely used in several industrial sectors, such as metallurgy, mining, electroplating, textiles, fertilizers, batteries, pesticides, printed circuit boards, among others, and are commonly found in the effluent generated by these industries. As they are extremely toxic and may contaminate both the ecosystem and the surrounding community, an efficient effluent treatment is necessary in order to reduce the concentration of these elements to acceptable levels before disposal. Among the various possible effluent treatments, adsorption is widely used for its simplicity, efficiency, and low cost. In this work, were produced, by internal gelation method, porous microspheres containing alumina and hematite in different concentrations, which were used as adsorbents in adsorption assays, in batch and fixed bed column, of aqueous solutions containing Zn2+, Ni2+ e Mn2+. The microspheres were characterized regarding morphology and particle size distribution, specific surface area, gas adsorption and crystalline phases. It was possible to evaluate the effect of the composition and size distribution of the microspheres on the adsorption of heavy metals. It was obtained more than 90% of adsorption of heavy metals, in the fixed bed column regime, indicating high efficiency of these microspheres as adsorbents of these ions.
Abstract in English:ABSTRACT The basic aim of this in vitro study was to investigate the effects of different silver deposition times on the two-body wear, antibacterial and cytotoxicity properties of silver ions on Ti15Mo alloy. The direct current (DC) magnetron sputtering technique was used to create silver films at different times (30, 45 and 60 minutes); the experimental setup was predetermined. The phase structures, cross-sectional morphology, surface roughness, two-body wear behavior, antibacterial and cytotoxicity properties of all specimens were researched in detail. The surfaces of all films showed a homogeneous distribution. It was observed that silver films enhanced the two-body wear resistance of Ti15Mo alloys. Furthermore, significant correlations were discovered between hardness, surface roughness and wear volume loss. Compared to Ti15Mo alloys, the antibacterial and cytotoxicity test results showed that silver films deposited 30 and 45 min had superior antibacterial and biocompatibility properties.
Abstract in Portuguese:RESUMO A pasta de cimento é a parte do compósito cimentício que possui baixa resistência ao atrito e suas propriedades mecânicas e microestruturais são determinantes para a durabilidade do material. As técnicas de microscopia são comumente utilizadas para elucidar esses comportamentos mecânicos, físicos e químicos de compósitos cimentícios. O objetivo deste trabalho foi elucidar a importância de técnicas de microscopia para avaliação direta do comportamento abrasivo de pastas de cimento com micropartículas de carbeto de silício (SiC). A metodologia do trabalho consistiu na fabricação das amostras de pastas cimentícias de referência e com 10% de adição de SiC, análise das propriedades mecânicas compressivas e abrasivas, além de ensaios de Microscopia Eletrônica de Varredura (MEV) e Microscopia de Força Atômica (MFA). Os resultados mostraram que a intensificação das propriedades mecânicas com adição de micropartículas de SiC podem ser relacionados com as micrografias obtidas no MEV, através do acentuado preenchimento dos poros, e por meio da atenuada rugosidade superficial identificada no MFA. Concluiu-se que os resultados de rugosidade e porosidade, adquiridos pelas técnicas de MEV e MFA, podem fornecer informações relevantes para análise da durabilidade de materiais cimentícios.
Abstract in English:ABSTRACT The cement mass is the part of the cementitious composite that has low resistance to friction and its mechanical and microstructural properties are decisive for the durability of the material. Microscopy techniques are commonly used to elucidate these mechanical, physical and chemical behaviors of cementitious compounds. The objective of this work was to elucidate the importance of microscopy techniques for the direct evaluation of the abrasive behavior of cement pastes with silicon carbide (SiC) microparticles. The methodology of the work consists of the manufacture of Exceptions of reference cementitious masses and with 10% SiC addition, analysis of the compressive and abrasive mechanical properties, in addition to Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) tests. The results that the intensification of the mechanical properties with the addition of SiC microparticles can be related to the external micrographs in the SEM, through the accentuated filling of the pores, and through the attenuated surface roughness identified in the AFM. It was concluded that the roughness and porosity results, acquired by the SEM and AFM techniques, can provide relevant information for the analysis of the durability of cementitious materials.
Abstract in English:Abstract The aim to evaluate the raw material (agroforestry residues) for particleboard manufacture from the: pseudostem of Musa paradisiaca; the stem and pods of Theobroma cacao; and the sawdust of Ceiba pentandra. The particleboards produced from these cellulosic residues are mixed with cassava starch’s natural adhesive and urea formaldehyde’s synthetic adhesive. The results indicate that lignin, α-cellulose, hemicellulose, and extractives ranged from 6.2–19.0%, 41.4–50.2%, 24.4–31.5%, and 6.8–18.8% respectively and they were significantly different from each other. Additionally, tannins, alkaloids, saponins, flavonoids, phenols, glycosides, and sterols were the phytochemicals present in biomass materials in different quantities. Also, carbon, oxygen, nitrogen, and boron were the elementals significantly present in the manufactured particleboards in the range of 35.3–52.8, 30.2–43.0, 4.2–24.0, and 3.2–9.9 percentage concentration respectively. As for the mechanical properties, it was verified that the cellulose content influenced 96.5% of the variability of the modulus of rupture (MOR) values. Understanding the distribution, functional properties, and impact of biomass organic, phytochemicals and elemental constitutions is an impetus to the improvement of processes with higher retention of these constitutions in the utilization of agroforest residues in the particleboard industry. These chemical compositions of the residues under study contributed largely to the characteristics of the manufactured particleboards.
Abstract in English:ABSTRACT Partial replacement of Portland cement by industrial waste or materials of natural origin can improve the mechanical strength of concrete and mortar and reduce production cost. In this context, ash from burning bamboo appears as a potential material for use, as it is natural with a renewable source and fast growth, which presents a higher concentration of silica in the outer walls of the stalks. Therefore, the objective of this work is to evaluate the use of bamboo stalk ash (Bambusa Vulgaris) as a partial replacement for Portland cement. For this purpose, bamboo ash was produced at three calcination temperatures (500ºC, 600ºC and 700ºC). The ashes were not characterized as pozzolans based on their chemical composition, however the ash produced at 600ºC obtained a performance index higher than that established by the Standard. The hydration of cement partially replaced by this ash was evaluated, in proportions of 0%, 6%, 10% and 14%, in relation to its mass. Mortars with the same replacement proportions were evaluated in the fresh state and hardened. The consistency in the fresh state remained constant at 227 mm, while the compressive strength, in the hardened state, increased by 15% with the addition of bamboo stem ash.
Abstract in English:ABSTRACT Digital welding machine (DWM) is an advanced tool for material forming. The lifespan and health status of DWMs are closely related to the safety and reliability. To address the problem of low accuracy in the lifespan prediction of DWMs, a model based on immune algorithm (IA) and long short-term memory network (LSTM) with attention mechanism is proposed. First, the degradation characteristic indicators of the lifespan of DWMs are evaluated and selected. Then, a health index is constructed using linear regression to quantitatively reflect the lifespan status of DWMs. The optimized model is used to predict the remaining lifespan, and compared with various models using 5 indicators. Finally, predictive maintenance of DWMs is carried out based on product inspection and production scheduling. the optimal solution for the objective function is obtained to calculate the best predictive maintenance method for the digital welding machine.During the lifespan prediction process, the optimized model has a 20% decrease in root mean square error and a 35.8% decrease in mean square error compared to the traditional LSTM model. The average absolute error is decreased by 14.2% and the average absolute percentage error is closer to 0, while the coefficient of determination increases by 23%. By combining with actual production line arrangements, maintenance of DWMs can be performed at the most appropriate time to minimize maintenance costs.
Abstract in Portuguese:RESUMO Nos impulsores das bombas centrífugas submersíveis instaladas nas estações elevatórias de esgoto, ocorrem perdas prematuras por desgaste hidroabrasivo, reduzindo drasticamente a eficiência hidráulica e aumento das despesas energéticas do equipamento. A finalidade deste estudo é de contribuir na melhor escolha de material, minimizando as perdas, a partir do desgaste hidroabrasivo das ligas de aço inoxidável super duplex, ferro fundido cinzento temperado e ferro fundido branco de alto cromo, comumente utilizadas em bombas. Além disso, analisou-se o aspecto macrossuperficial das amostras após o ensaio hidroabrasivo. Os testes de desgaste hidroabrasivo foram realizados em uma solução 10:1 de água e areia sílica em duas velocidades de 5,2 m/s e 7,1 m/s. Os testes foram realizados num hidroabrasômetro por 216 horas, com medições de perda de massa feitas em intervalos de 24 horas. Os resultados mostraram que nas velocidades de 5,2 m/s e 7,1 m/s a perda de massa é linear e progressiva, sendo menos acentuada na liga de ferro fundido branco de alto cromo com menor perda de massa ao desgaste hidroabrasivo. Na velocidade de teste de 7,1 m/s resultou em maiores perdas de massa nas ligas estudadas do que a velocidade de teste de 5,2 m/s. As perdas de massa devido ao desgaste hidroabrasivo das ligas investigadas foram relacionadas à dureza, às características microestruturais e à morfologia das superfícies desgastadas. Esses fatores foram utilizados para descrever os resultados e justificar o melhor e o pior desempenho das ligas investigadas. Portanto, o ferro fundido de alto cromo (FBACr) apresentou o melhor desempenho devido a sua alta dureza decorrente de suas características microestruturais (matriz e M7C3), e superfície desgastada que apresenta aspecto brilhante e polido com menos crateras e sulcos que as demais ligas estudadas.
Abstract in English:ABSTRACT Premature losses due to hydroabrasive wear occur in the impellers of submersible centrifugal pumps installed in sewage lift stations, reducing hydraulic efficiency and increasing energy consumption. The purpose of this study is to contribute to the best choice of material, minimizing losses from hydroabrasive wear of super duplex stainless steel alloys, tempered gray cast iron and high chromium white cast iron, commonly used in pumps. In addition, the macrosurface aspect of the samples after the hydroabrasive test was analyzed. The hydroabrasive wear tests were performed in a 10:1 solution of water and silica sand at two speeds of 5.2 m/s and 7.1 m/s. The tests were run on a hydroabrasive machine for 216 hours, with mass loss measurements taken at 24-hour intervals. The high chromium white cast iron had the lowest mass loss due to wear. Furthermore, the test speed of 7.1 m/s resulted in greater mass losses in the studied alloys than the test speed of 5.2 m/s. The mass losses due to hydroabrasive wear of the alloys investigated were linked to hardness, microstructural characteristics, and the morphology of the worn surfaces. These factors were used to describe the results and justify the best and worst performance of the alloys investigated. Therefore, the high chromium cast iron (FBACr) showed the best performance due to its high hardness resulting from its microstructural characteristics (matrix and M7C3), and its worn surface morphology that presents a shiny and polished aspect with less craters and grooves than the other studied alloys.
Abstract in English:ABSTRACT Through orthogonal experimental design, the influence of the water-binder ratio, binder-sand ratio, ultrafine mineral admixture content, and steel fiber content on the fluidity and basic mechanical properties of rapid-repair materials was studied. The optimal mixing ratio parameters were determined, and its swelling and shrinkage performance and microstructure were analyzed. The results showed that the water-binder ratio and steel fiber content were the most significant factors affecting the properties of rapid-repair materials. The steel fiber content in the rapid-repair material led to pull-out failure and significantly affected flexural strength but had a relatively small effect on compressive strength. With the determined optimal mix proportion, the rapid-repair material had good fluidity and high early strength, bonding strength, and volume stability. At age 3 h, the material’s flexural strength and compressive strength were 13.7 MPa and 27.8 MPa, respectively, and the adhesive strength was 3.65 MPa. The limited expansion rate of 56 d-age repair material was 326.5 × 10−6, which can better meet the requirements of repairing highway pavement and bridge expansion joints to reopen to traffic within 3 h of repair.
Abstract in English:ABSTRACT Springback is the reverse elastic deformation produced by the unloading process, which is a common phenomenon in the sheet metal stamping and forming process and affects the final forming accuracy of the part. Aiming at the problem of springback error in the multi-point forming process of hyperbolic component for ships, the springback phenomenon of hyperbolic component was studied by combining theoretical analysis, numerical simulation and forming test. The mechanical property parameters and stress-strain curves were obtained by tensile tests using a new corrosion-resistant aluminum alloy as the sheet material. The springback compensation method is introduced, the springback compensation formula based on surface curvature is derived, and the compensated mold surface is further corrected and fitted using the cubic B-sample method. The multi-point punch tooling was generated and modeled by the multi-point 3D modeling software MPFCAD and finite element software to simulate the multi-point forming and unloading springback process of the hyperbolic member. Multi-point forming tests were conducted on a multi-point forming press for corrosion-resistant aluminum alloy hyperbolic component, and the formed parts were checked for accuracy and error analysis by 3D scanning and GOM Inspect software. The results show that the springback compensation method used in this paper can effectively reduce the springback error in the multi-point forming process of corrosion-resistant aluminum alloy hyperbolic component, and the effect is very good.
Abstract in English:ABSTRACT This study examined the effects of cold working and subsequent annealing treatment for a short time on the corrosion behavior of a lean duplex stainless steel (LDSS). The as-received sample was solution treated at 1100 °C for 1800 s and cold rolled. The cold deformation (75%) was followed by isochronic annealing at 900, 950, 1000, 1050 and 1100 °C for 180 s. The microstructural changes were evaluated by scanning electron microscopy (SEM) and Vickers hardness, while corrosion behavior was investigated by cyclic potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution at 22 ± 2 °C. After cyclic polarization, pits morphology was characterized by SEM. Cold rolling lowered lamellar spacing between the phases and increased hardness. Hardness at temperatures higher than 950 °C was equal to the 2304 LDSS solution treated. Although grain refinement is observed due to recrystallization, the corrosion resistance was not significantly improved. The highest pitting potential and charge transfer resistance were obtained after annealing at 1000 °C for 180 s. The pit distribution indicates that the corrosion behavior of the phases changed during the cold rolling and annealing treatment, and pitting was initiated preferentially in the α/γ boundaries and inside the α domains.
Abstract in Portuguese:RESUMO Neste artigo avaliou-se o efeito nos parâmetros de resistência de um solo SM estabilizado com teores de emulsão asfáltica variando entre 16% e 28% em massa. A metodologia consistiu na coleta e caracterização do solo, mistura dos materiais e exposição ao ar por 24 horas, compactação no teor ótimo pela energia Marshall (22%), e em teores acima (28%) e abaixo (16%) do ótimo, e realização de ensaios de compressão triaxial CIU em condições saturadas. O solo apresentou comportamento típico ao de um material elastoplástico com endurecimento, enquanto que as misturas apresentaram comportamento semelhante ao de um material elástico perfeitamente plástico. À medida em que o teor de emulsão foi aumentado, menores foram os ângulos de atrito e, para as misturas com 16% e 22%, maiores foram os interceptos coesivos. A mistura 28% de emulsão teve uma redução em sua coesão, devido ao excesso de ligante, o que prejudicou o contato grão a grão. Constatou-se que após determinado nível de deformação axial as misturas obtiveram um leve ganho de resistência, justificado pelo deslocamento da película de asfalto.
Abstract in English:ABSTRACT In this article, the effect on the resistance parameters of a stabilized SM soil with asphalt emulsion contents varying between 16% and 28% by mass was evaluated. The methodology consisted of collecting and characterizing the soil, mixing the materials and exposing them to air for 24 hours, compacting at the optimal level by Marshall energy (22%), and at levels above (28%) and below (16%) the optimum, and carrying out CIU triaxial compression tests under saturated conditions. The soil presented behavior typical of an elastic-plastic material with hardening, while the mixtures presented behavior similar to that of an elastic perfectly plastic material. As the emulsion content was increased, the friction angles were smaller and, for mixtures with 16% and 22% of content, the cohesive intercepts were higher. The mixture with 28% content of asphalt emulsion had a reduction in its cohesion, due to the excess of binder, which impaired the grain-to-grain contact. It was found that after a certain level of axial deformation, the mixtures obtained a slight gain in resistance, justified by the displacement of the asphalt film.
Abstract in Portuguese:RESUMO A incorporação de adições de nanomateriais à base de celulose aos materiais cimentícios é interessante pois utiliza uma matéria-prima renovável e de grande disponibilidade global. Esta pesquisa buscou avaliar o efeito da adição de polpa de celulose nanofibrilada (CNF) em argamassas de revestimento. Foi produzido um traço referência (1:2:8, em volume), e outros três traços, com adição de polpa de CNF nos teores de 1,5%, 2,5% e 3,5%, em relação a massa de cimento. As argamassas foram avaliadas nos estados fresco (consistência, densidade de massa, ar incorporado e comportamento reológico pelo método squeeze-flow) e, endurecido (absorção de água por capilaridade, por imersão e resistência à compressão). Os resultados mostraram que, no estado fresco, as maiores diferenças em relação à argamassa referência foram apresentadas pela argamassa CNF_3,5%. Além do que, à medida que o teor de polpa de CNF aumentava, havia uma redução na capacidade de espalhamento das argamassas, um aumento do índice de absorção de água por capilaridade e imersão e evidenciou-se ainda que o ganho da resistência ocorria mais tardiamente. As amostras com polpa de CNF se mostraram estatisticamente iguais às de referência no que diz respeito à resistência à compressão na maior parte dos casos.
Abstract in English:ABSTRACT The incorporation of additions of cellulose-based nanomaterials to cementitious materials is interesting because it uses a renewable raw material that is widely available globally. This research sought to evaluate the effect of adding nanofibrillated cellulose pulp (NFC) in coating mortars. A reference mix (1:2:8, by volume) was produced, and three other mixes, with the addition of NFC pulp at the levels of 1.5%, 2.5%, and 3.5%, about the mass of cement. The mortars were evaluated in the fresh state (consistency, bulk density, air content and rheological behavior by the squeeze-flow method) and, hardened (water absorption by capillarity, immersion, and compressive strength), The results showed that, in the fresh state, the greatest differences in the reference mortar were presented by NFC_3.5% mortar. In addition, as the NFC pulp content increased, there was a reduction in the spreading capacity of the mortars, and an increase in the index of water absorption by capillarity and immersion and it was also evidenced that the compressive strength gain occurred later. Samples with NFC pulp were statistically equal to the reference ones about compressive strength in most cases.
Abstract in English:ABSTRACT Magnesium based nanocomposites are new lightweight and high-performance materials for potential applications in biomedical, electronics, aerospace and automotive sectors owing to their lower density when compared with aluminum-based materials and steel. This article discusses the effect of pulse duration, pulse interval, current, gap voltage on Surface Roughness (SR), Material Removal Rate (MRR) and Electrode Wear Rate (EWR) of AZ61/7.5% B4C composites have been studied based on the different dielectric medium, kerosene, Electrical Discharge Machining (EDM) oil and nanosilicon carbide added EDM oil. The magnesium nanocomposites have been prepared through stir casting. The L16 orthogonal array has been selected based on the four factors with four levels. The Complex Proportional Assessment (COPRAS) method has been used to find the optimum process parameters. An overall analysis found that the AZ61/7.5% B4C composites has produced high mechanical properties compared with 2.5, 5, and 10wt.% B4C nanocomposites. The pulse duration has most influencing factor for affecting the MRR and SR using analysis of variance. The developed quadratic models have well fit with experimental values. Using COPRAS, the optimal parameters are observed to be a maximum of 0.00730 g/s MRR, a minimum of 0.00127 g/s EWR, and a SR of 3.196 µm. The nano-SiC powder with EDM oil has a higher improvement than that of kerosene and EDM oil. The nano-SiC mixed EDM oil produces an improved performance measure of 81% MRR, 55% EWR, and 47% SR.
Abstract in English:ABSTRACT For drilling polyamide 6 (PA6) hybrid nano composites reinforced with copper nanoparticles and multi-walled carbon nano tubes (MWCNT), this work optimizes the process variables including reinforcing percentage, drill bit diameter, feed rate, and spindle speed. In this work, the Taguchi method was used to construct the experiments. L9 orthogonal arrays were used in the trials. Torque, surface roughness, and thrust force were the three different responses on which the influence of different process factors and their combinations were examined. The ideal values of the process factors have been found by employing the grey relational code produced by the grey relational analysis. The crucial process factors were identified using analysis of variance (ANOVA). To verify the test results, a confirmation test was carried out. The surface of the drilled holes was examined with a scanning electron microscope. The optimal drilling process parameters for PA 6 nanocomposites were 0.6 weight %, 500 rpm, 90 mm/min, and 6 mm in drill diameter. The weight percentage of the nano Cu particles (60.618%) clearly has a greater impact on drilling of Polyamide 6 hybrid nanocomposites reinforced with Cu nanoparticles and MWCNT than did the drill diameter (26.699%), speed (7.407%), and feed rate (5.271%). Verification of testing results at the best standard shows that the thrust force is reduced from 288.8 N to 281.4 N, the torque is decreased from 27.01 Nm to 24.52 Nm, and the surface polish is improved from 1.414 to 1.23 μm.
Abstract in English:ABSTRACT In order to make full use of aged asphalt, a light oil regenerant for cold mixing was prepared in this paper, and the ratio of regenerant and regeneration effect was studied through the performance test of recycled asphalt. The ratio of regenerant was determined by 60 °C kinematic viscosity, mass loss before and after aging, and asphalt three indicators. The thermogravimetric analysis determined the four-component ratio of recycled asphalt, and the mechanical properties of the recycled asphalt mixture were determined by the 15 °C splitting and 20 °C compression tests. Finally, the road performance of the recycled asphalt mixture was analyzed by rutting, low-temperature bending, and dry-wet splitting tests. When the mass ratio of light base oil: plasticizer: stable equilibrium agent: penetrant: the anti-aging agent is 80:20:25:8:5, it has a good regeneration effect. After adding 8% regenerant, the regenerated asphalt is compared with the recycled asphalt. The content of saturates and aromatics increases, and the content of resins and asphaltenes decreases. The four-component content of recycled asphalt is close to that of new asphalt. The mechanical properties test shows that the optimum content of the regenerant is 0.9%. With increased RAP content, the water stability and low-temperature crack resistance are also improved, and the high-temperature stability is reduced. However, it still meets the requirements of the regeneration specification.
Abstract in Portuguese:RESUMO Atualmente, o substrato de titânio é um dos mais importantes biomateriais metálicos com aplicação em ortopedia, odontologia, fixação de fraturas e artroplastia de joelho e quadril. Apesar de todas estas propriedades atrativas, sua inércia biológica e baixa capacidade bactericida acaba limitando sua osseointegração. Neste sentido, revestimentos de TiO2 e TiO2(MgO) são realizados para aprimorar as características do titânio, como a resistência à corrosão. Os objetivos deste estudo foram analisar a resistência à corrosão do óxido de titânio e óxido de titânio com adição de magnésio, topografias, morfologias e cristalinidade em um substrato de titânio através da eletrodeposição com corrente constante. As eletrodeposições foram realizadas em um sistema de três eletrodos, sendo o titânio eletrodo de trabalho, Ag/AgCl como eletrodo de referência e um contra eletrodo de platina em um potenciostato e foram utilizadas correntes constantes de 1,0 mA/cm2 para todos os processos. Foram utilizadas as caracterizações por microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), microscopia confocal, difração de raios X (DRX) e polarização potenciodinâmica. As análises de topografia e morfologia indicaram uma alteração nas rugosidades (Ra) e todas demonstraram uma superfície uniforme. As análises de DRX indicaram apenas o titânio metálico, porém todas tiveram uma diferença no FWHM, indicando possíveis fases amorfas ou Mg intersticial, causando também uma variação na altura dos picos. Por fim, a polarização potenciodinâmica indicou que o revestimento com TiO2 houve uma melhora de 37,90% e o TiO2 com adição de magnésio houve uma perda de 13,43%. Portanto, os revestimentos causaram alterações nas rugosidades, morfologias, redes cristalinas e nas propriedades anticorrosivas, possibilitando assim a modulação das propriedades desejadas de acordo com o ambiente de oxidação utilizado.
Abstract in English:ABSTRACT Currently, the titanium substrate is one of the most important metallic biomaterials with application in orthopedics, dentistry, fracture fixation and knee and hip arthroplasty. Despite all these attractive properties, its biological inertia and low bactericidal capacity ends up limiting its osseointegration. In this sense, TiO2 and TiO2(MgO) coatings are performed to improve titanium characteristics, such as corrosion resistance. The objectives of this study were to analyze the corrosion resistance of titanium oxide and titanium oxide with addition of magnesium, topographies, morphologies and crystallinity on a titanium substrate through electrodeposition with constant current. Electrodepositions were performed on a three-electrode system, with titanium working electrode, Ag/AgCl as reference electrode and a platinum counter electrode in a potentiostat, and constant currents of 1.0 mA/cm2 were used for all processes. Characterizations by scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal microscopy, X-Ray diffraction (XRD) and potentiodynamic polarization were used. Topography and morphology analyze indicated a change in roughness (Ra) and all demonstrated a uniform surface. The XRD analyzes indicated only metallic titanium, but all of them had a difference in the FWHM, indicating possible amorphous phases or interstitial Mg, also causing a variation in the height of the peaks. Finally, the potentiodynamic polarization indicated that the coating with TiO2 there was an improvement of 37.90% and the TiO2 with addition of magnesium there was a loss of 13.43%. Therefore, the coatings caused changes in roughness, morphologies, crystalline networks and anticorrosive properties, thus enabling the modulation of the desired properties according to the oxidation environment used.
Abstract in English:ABSTRACT The use of natural lignocellulosic fiber (NLF) biocomposites for the construction industry has been growing over the years, due to technical and environmental advantages. However, fiber-matrix incompatibility remains a major challenge. Various surface treatments have been investigated to improve fiber-matrix bonding, including sodium lignosulfonate (SLS), a potentially effective and environmentally friendly chemical. In this study, SLS treatment protocols were applied to piassava fibers to evaluate their influence on the fibers. Thermogravimetric Analysis (TG/DTG), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM/EDS), Fourier-transform Infrared Spectroscopy (FTIR), moisture absorption measurements and tensile tests were performed to characterize the modifications. Results demonstrated, for the first time, the efficiency of SLS to remove extractives from the piassava surface. In general, partial degradation of the cellulosic structure was observed, noticeable by the slight drop in crystallinity index (from 42.80 to 39.82%), and an increase in the TG residual mass (from 21.35 to 31.90%), along with changes in DTG curves. However, a particular SLS treatment using ultrasonic bath was able to fully clean the surface preserving the cellulosic structure, and increasing the strength of fibers (from 386 ± 140 MPa to 524 ± 126 MPa).
Abstract in English:ABSTRACT The goal of this study is to increase the impact toughness of the borided steel without much compromising the surface microhardness. An optimization technique known as Response Surface Methodology was employed to achieve the goal of this work. The pack borided specimens at optimized conditions were analyzed in terms of microstructure, microhardness, XRD, and Impact toughness and compared with borided specimens treated for 950°C for 180minutes. The poly-phase iron borides zone, transition zone, and base metal were all evident. In the iron borides zone, the microhardness was 1745HV, then 345HV in the transition zone, and lastly 245HV in the matrix area. The XRD technique was used to identify the growth of Fe2B and FeB phases. The impact toughness was 44.182 J when the specimens treated at optimized conditions.
Abstract in English:ABSTRACT Bitumen draining in stone mastic asphalt mixtures has become a potential problem. Due to the storage and laying temperatures as well as difficulties in providing the necessary compaction, the temperatures of the asphalt mix cannot be lowered to prevent or reduce drainage. In stone mastic asphalts, generally cellulose or mineral-based fibers are preferred to reduce draining down of bitumen. Conventional fibers commonly used in stone mastic asphalt increase pavement costs because they are expensive. The aim of this research is investigation of textile waste used to prevent bitumen drainage problem in stone mastic asphalt pavements instead of traditional fibers. Following the determination of the bitumen content, Marshall Stability tests, Schellenberg bitumen drainage test and Indirect Tensile Strength tests were conducted to evaluate the mechanical properties of the stone mastic asphalt mixtures in comparison to mixes containing textile waste. The results indicated that it is possible to produce stone mastic asphalt mixes with textile waste that exhibits similar mechanical properties mixes including cellulose fiber. Moreover, it was found that samples prepared with textile waste exhibits advantage in terms of cost compared to samples prepared with cellulose fiber.
Abstract in Portuguese:RESUMO A construção civil exerce função importante no consumo de energia em todo o mundo e influência, de forma significativa, o consumo total de recursos naturais e as emissões de CO2. A utilização de materiais renováveis está intrinsecamente relacionada à pesquisa e à inovação. A reutilização, a reciclagem, bem como o desenvolvimento de novos materiais e a descoberta de novas aplicações para materiais renováveis já conhecidos, podem contribuir de maneira expressiva para o desenvolvimento sustentável. A quitosana (CS) é um biopolímero com uma estrutura química e características únicas aliadas à sua farta disponibilidade como derivado da quitina, fazem com que suas possibilidades de aplicação nos mais diferentes campos tecnológicos, tenha se expandido consideravelmente. No presente trabalho, a utilização da quitosana para produção de concretos por meio de teores ótimos é investigada. Os valores de quitosana incorporados na dosagem foram 0,1%; 0,3% e 0,4%, com relação à massa de cimento. Os diferentes concretos obtidos foram submetidos a ensaios de propriedades mecânicas e microestrutural. Os resultados mostraram que a microestrutura foi favorecida com a utilização da quitosana. Bem como, apresentaram resultados favoráveis à incorporação dos teores utilizados de quitosana (se desatacando as amostras com 0,1% de substituição), sendo positivos quanto às propriedades mecânicas para a maioria das técnicas utilizadas, o que indica fortemente que a quitosana pode ser considerada como material promissor a ser incorporado na produção de concreto.
Abstract in English:ABSTRACT Civil construction plays an important role in energy consumption worldwide and significantly influences the total consumption of natural resources and CO2 emissions. The use of renewable materials is intrinsically related to research and innovation. Reuse and recycling, as well as the development of new materials and the discovery of new applications for already known renewable materials, can significantly contribute to sustainable development. Chitosan is a biopolymer with unique characteristics and chemical structure which, combined with its wide availability as a chitin derivative, have considerably expanded its application possibilities in the most different technological fields. In the present work, the use of chitosan for the production of concrete through optimal levels is investigated. The chitosan values incorporated in the dosage were 0.1%; 0.3% and 0.4%, in relation to the cement mass. The different concretes obtained were submitted to tests of mechanical and microstructural properties. The results showed that the microstructure was favored with the use of chitosan. In addition, they presented favorable results for the incorporation of the chitosan levels used (especially considering the samples with 0.1% of substitution), also being positive regarding the mechanical properties for most of the techniques used. This strongly indicates that chitosan can be considered as a promising material to be incorporated in the production of concrete.
Abstract in English:ABSTRACT Bacterial cellulose (BC) has stood out in the biomedical field for its biocompatibility, non-toxicity and high liquid absorption capacity. Thus, studies have been conducted aiming at the functionalization of BC with substances that add properties, such as anti-inflammatory and antimicrobial action. Hamamelis virginiana plant extract is known for its astringent, anti-inflammatory and antimicrobial properties. Thus, the present work aimed to incorporate aqueous (AE) and glycolic (GE) extracts of witch hazel in different concentrations to BC, aiming at its application as a curative. BC membranes incorporated with the extracts were characterized by thermogravimetric analysis (TGA), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and antimicrobial activity. The TGA results indicated a reduction in thermal stability and the appearance of a new stage of degradation in the samples that underwent incorporation. Furthermore, the FTIR showed the presence of aromatic compounds not found in the BC, corroborating the TGA. The micrographs revealed that the incorporation of the extracts resulted in the formation of a film on the surface of the membranes, covering the nanofibers. These results show that incorporating the aqueous and glycol extracts in the BC membrane was successful. However, despite the crude extracts’ antimicrobial potential, antimicrobial activity in the functionalized BC samples was not observed.
Abstract in English:ABSTRACT The use of construction and demolition (C&D) waste as aggregate in concrete results in a reduction in strength due to its porosity. To compensate, mix designs often require higher cement contents, which increase the material’s environmental impact. This study presents an experimental and numerical analysis of the effect of steel fibres on the mechanical properties of the concrete produced with recycled C&D aggregates with varying densities. The variation in fibre content did not present any influence on the compressive strength of concrete, which is significantly affected by the lower density of the recycled C&D aggregate. The fibres collaborate to mitigate the loss of flexural strength of the steel fibre reinforcement in recycled coarse aggregate concrete (SFRRCAC) provoked by lower density of recycled aggregates when the water-to-cement ratio is lower. When the water-to-cement ratio is above 0.65, there is a great reduction of the matrix strengths due to the paste porosity and the influence of aggregate density and fibre content was insignificant.
Abstract in Portuguese:Resumo Na Amazônia, a produção local de energia elétrica é muito importante devido ao grande número de comunidades isoladas, geralmente distantes da rede convencional. Nesse contexto, as turbinas a vapor são tecnologias relevantes a serem utilizadas na região, uma vez que a biomassa está amplamente disponível em diversas comunidades, inclusive, onde ocorrem atividades agrícolas sustentáveis como a utilização do caroço do açaí, bagaço de cana, entre outros. Atualmente, não existem muitos estudos relevantes na literatura para pequenas turbinas a vapor operando em baixa pressão, condicionadas à realidade da região amazônica. Assim, o objetivo principal deste trabalho é desenvolver um estudo experimental de uma pequena turbina a vapor operando em baixa pressão, a fim de aplicá-la a pequenas demandas de energia, tipicamente encontradas na região. Desenvolvemos medições do comportamento das potências mecânica e elétrica em relação à velocidade de rotação do eixo da pequena turbina a vapor, levando em consideração as pressões de 0,1, 0,2 e 0,3 MPa. Concluímos que o levantamento experimental preliminar, feito neste trabalho, demonstra um bom comportamento mecânico da pequena turbina e pode ser uma alternativa para o sistema de geração de energia elétrica suprir pequenas demandas em comunidades isoladas na Amazônia, aproveitando a biomassa oriunda de atividades agrícolas sustentáveis.
Abstract in English:Abstract In the Amazon, local electrical energy production is very important due to the large number of isolated communities, usually far from the conventional grid. In this context, steam turbines are relevant technologies to be used in the region, since waste biomass is widely available in several communities, besides, where sustainable agricultural activities take place, such as the use of açaí seeds, sugarcane bagasse, among others. Currently, there are not many relevant studies in the literature for small steam turbines operating at low pressure, conditioned to the reality of the Amazon region. Hence, the main goal of this work is to develop an experimental study of a small steam turbine operating at low pressure, in order to apply it to small energy demand, typically found in the Amazon. We developed measurements on the behavior of mechanical and electrical powers in relation to the shaft rotational speed of the small steam turbine, taking into account pressures of 0.1, 0.2 and 0.3 MPa. We concluded that the preliminary experimental survey, made in this work, demonstrates a good mechanical behavior of the small turbine and could be an alternative for electricity generation system to supply small demands in isolated communities in the Amazon, taking advantage of biomass from sustainable agricultural activities.
Abstract in English:ABSTRACT In this research, an investigational study on the use of CFRP laminates with 4 types of configurations (Series-A: laminated with confinement wrap, Series-B: single flat & L wrap, Series-C: confinement wrap, and Series-D: double flat & confinement wrap) to repair partially damaged reinforced cement composite column-beam joints is presented. The project’s primary goal was to examine how retrofitting configurations affected the behaviour of repaired RC column-beam junctions when subjected to cyclic loads (FL + RL). To examine the effectiveness of repairs for enhancing the stiffness, strength capacity, and behaviour of damaged RC joints (Partially – 25%, 50%, and 75%), seventeen samples were fabricated and investigated. Cyclic loading was used to test the control specimen all the way to failure. Sixteen samples were subjected to a load level that was around 75% of the projected pre-failure load (26 kN) under seismic condition. The maximum load, ductility index, and load versus displacement were all used to analyse the data. Also, CFRP debonding and the failure modes due to fracture pattern were observed. The findings highlighted the significance of repairing and improving joint performance. All repaired joints have increased strength that is virtually as strong as the beam-column joint’s actual shear strength. As a result, compared to the reference specimen, the Series-D joints had a substantially greater strength capacity (30.77%).
Abstract in English:ABSTRACT In recent decades, greenhouse gas emission and global warming are the major threat to climatic change variability. The quality of concrete can be enhanced by the addition of a supplementary cementitious material to portland cement. In this study, fly ash is utilized as a supplemental cementitious material (SCM). The purpose of this research is to test and study the mechanical and thermal properties of blended concrete containing ordinary portland cement, fly ash and zinc sulphate as well as to investigate the microstructure in order to study the influence of zinc sulphate on the hydration process of concrete. This research mainly focused on the changes occurring in the strength, retarding mechanism, setting time, mineralogy, and microstructure caused by the addition of zinc sulphate in concrete. Ordinary portland cement, fly ash, pulverized fly ash and zinc sulphate are used in the blended concrete. The varied proportions of fly ash and zinc sulphate in the mix are 15%, 30%, 45%, and 60% respectively. The strength characteristics can be increased by fly ash pulverization. Hence the research focuses in exploring the addition of fly ash, pulverized fly ash and zinc sulphate anhydride to the concrete mix.
Abstract in English:ABSTRACT In recent decades, concrete technology has reached the broad-based areas of operations through the implementation of Self Compacting Concrete to increase the concrete performance. Due to high silica content, the pozzolonic characteristic of RHA makes it as a supplementary material for cement. In this paper, Cement was partially replaced with Rice Hush Ash of 5%, 10% 15%, 20%, 30% and 40% influencing the properties of SCC. The aim of this report is to explore the effect of cement replacement by RHA on the fresh and mechanical properties of SCC. In addition, the bucking behaviour of the axial loaded reinforced concrete column was predicted using Artificial Neural Network. Experimental data are collected and 100 experimental data is used for training the ANN model and 20 sets of data is utilized for testing. From the results it is observed that SCC blended with RHA shows the positive relationship between 30% replacement of RHA with an increase in the strength of compression and tensile strength of around 6. The buckling behaviour of the 70% Cement + 30% RHA SCC reinforced column was predicted by ANN- PSO is a precision and efficient model.
Abstract in English:ABSTRACT Carbonation chambers, in general, are used in civil engineering laboratories both for verification tests of the useful life of reinforced concrete, and for CO2 curing tests of unreinforced cementitious materials. These chambers can be purchased from specialized manufacturers at a high cost, or they can be built by the researchers themselves. It so happens that in the literature there is no manual for making and operating an accelerated carbonation chamber. It is observed that its development and manufacture depend a lot on the needs and financial conditions of the research, with no standard or Technical Norm to be followed. This article presents a compilation of concepts related to the accelerated carbonation reaction and brings a bibliographical review about the different carbonation chambers made by researchers, in which it was possible to verify a great variation regarding the material to be used in the structure of the chamber, location of CO2 and air inlet and outlet valves, temperature and humidity control, among others; and in addition, it presents a descriptive memorial for the construction of an automated and accessible carbonation chamber to be used in laboratories.
Abstract in Portuguese:RESUMO A Madeira Lamelada Colada (MLC) é uma alternativa viável para o aproveitamento racional da madeira, possibilitando o uso de madeiras jovens. Ainda, ao engenheirar a madeira, pode-se viabilizar o uso de troncos de menor qualidade e menor diâmetro. Entretanto, o desempenho do produto depende da espécie utilizada, das espessuras e posições das lamelas, do tipo de adesivo, do desempenho da colagem. Este trabalho teve como objetivo estudar a viabilidade do uso de uma madeira de rápido crescimento para a produção de MLC. A espécie de madeira selecionada foi Eucalyptus urophylla, clonal COP 1404, que se caracteriza por ter rápido crescimento e por ter uma lacuna em estudos que visam sua aplicação na construção civil. Empregou-se o adesivo poliuretano bicomponente à base de óleo mamona. O programa experimental teve como foco a caracterização da madeira in natura e o desempenho mecânico da MLC comparada à madeira maciça, empregando métodos estatísticos para a análise de resistência dos protótipos. Os resultados indicaram que o adesivo foi eficiente na colagem da madeira, de modo que o cisalhamento ocorreu na madeira, além da verificação à flexão ter mostrado comportamento de um corpo único, não tendo pontos de descontinuidade por conta da linha de cola.
Abstract in English:ABSTRACT Glulam is a viable alternative for the rational use of wood, allowing the use of young timber. Also, when engineering the timber, it is possible to use lower quality trunks with a smaller diameter. However, the performance of the product depends on the species used, the thickness and position of the lamellae, the type of adhesive, the bonding performance. This work aimed to study the feasibility of using a fast growing timber for the production of glulam. The selected timber species was Eucalyptus urophylla, clonal COP 1404, which is characterized by its fast growth and lack of studies regarding its application in civil construction. A two-component polyurethane adhesive based on castor oil was used. The experimental program focused on the characterization of fresh timber and the mechanical performance of glulam compared to solid wood, using statistical methods to analyze the resistance of the prototypes. The results indicated that the adhesive was efficient in gluing the timber, so that shearing occurred in the timber, in addition to the flexural verification showing behavior of a single body, with no points of discontinuity due to the glue line.
Abstract in Portuguese:RESUMO O trabalho tem como objetivo a caracterização química e microestrutural dos compósitos, verificando o índice de inibição das fibras vegetais com a matriz cimentícia, sua interferência na hidratação do cimento Portland, a composição química da fibra e do compósito, e possíveis processos de degradação da fibra na matriz. As matérias-primas utilizadas para formar os compósitos incluíram: cimento Portland, fibras kraft e água. Foram avaliados diferentes teores de adição de fibras kraft (referência, 0,5%, 1,0% e 3,0%) em relação a massa de cimento e três relações água/cimento (0,40; 0,45 e 0,50). Foi possível avaliar a interferência das fibras kraft na hidratação do cimento Portland, sendo essa classifica da como baixa inibição, demonstrando a compatibilidade das fibras com a matriz cimentícia de acordo com as análises realizadas. Em relação à temperatura não foram constatadas grandes diferenças que evidenciassem um retardo da hidratação devido os componentes inibitórios da fibra vegetal, assim como não foi detectado processo de degradação das fibras kraft (mineralização).
Abstract in English:ABSTRACT The objective of the work is the chemical and microstructural characterization of the composites, verifying the inhibition index of the vegetable fibers with the cementitious matrix, its interference in the hydration of the Portland cement, the chemical composition of the fiber and the composite, and possible processes of degradation of the fiber in the matrix. The raw materials used to form the composites included: Portland cement, kraft fibers and water. Different levels of kraft fiber addition (reference, 0.5%, 1.0% and 3.0%) were evaluated in relation to cement mass and threewater/cementratios (0.40; 0.45 and 0. 50). It was possible to evaluate the interference of kraft fibers in the hydration of Portland cement, which was classified as low inhibition, demonstrating the compatibility of the fibers with the cementitious matrix according to the analyzes carried out. Regarding the temperature, no major differences were found that would show a delay in hydration due to the inhibitory components of the vegetable fiber, as well as no degradation process of the kraf fibers (mineralization) was detected.
Abstract in English:ABSTRACT Rapid economic growth of countries requires continued expansion of the road network, which requires a huge volume of natural resources. Broken stones of coarse and finer sizes cause depletion of natural resources. On the Other hand, disposal of industrial waste is a great challenge. Hence, this research, the conventional filler (quarry dust) completely replaced by copper slag and glass fibre included in the asphalt mix varying from 0.1% to 0.4% by volume of asphalt mix with na incremente of 0.1%. The volumetric and mechanical properties investigated in the laboratory. The experimente results concluded that the asphalt mix with copper slag as filler and the fiber length of 8 mm with 0.2% by volume of mix exhibited optimum performance without compromising the volumetric properties.
Abstract in Portuguese:RESUMO A indústria de construção civil é uma das responsáveis na emissão de gás carbônico (CO2), para cada tonelada de cimento produzido é emitido na atmosfera aproximadamente uma tonelada de gás carbônico. Portanto, o presente trabalho tem como objetivo geral estudar a viabilidade técnica do uso do da Escória de Alto Forno (EAF), resfriada instantaneamente como substituição ao cimento Portland. Para este trabalho utilizou-se como materiais o clínquer, areia normatizada, gesso, água potável e EAF. Como metodologia dos ensaios foi realizado a moagem dos materiais, até a granulometria desejada, passante na peneira 0,075mm. Após esse processo iniciou-se caracterização desses materiais, sendo seguido, da substituição do clínquer, nos teores de 5, 15, 30, 50 e 75% pela EAF. Os resultados dessa substituição mostraram que o rejeito, caracterizou-se como um excelente subproduto na fabricação do cimento, apresentando características para o emprego em larga escala em busca da diminuição da emissão do CO2.
Abstract in English:ABSTRACT The civil construction industry is responsible for the emission of carbon dioxide (CO2), for each ton of cement produced, approximately one ton of carbon dioxide is emitted into the atmosphere. Therefore, the present work has as general objective to study the technical feasibility of using the Blast Furnace Slag (EAF), cooled instantly as a substitute for Portland cement. For this work, clinker, standardized sand, plaster, drinking water and EAF were used as materials. As a methodology, the materials were milled to the desired granulometry, which passed through the 0.075mm sieve. After this process, the characterization of these materials started, followed by the replacement of clinker, in the contents of 5, 15, 30, 50 and 75% by EAF. The results of this substitution showed that the tailings were characterized as an excellent by-product in the manufacture of cement, presenting characteristics for large-scale use in search of reducing CO2 emissions.
Abstract in Portuguese:RESUMO O objetivo deste trabalho foi avaliar a eficiência de um microconcreto para reforços estruturais, como ponte de aderência entre concreto velho e concreto novo. Foi avaliada a substituição da areia por um fíler, subproduto de britagem, a partir de um traço de referência. Os ligantes utilizados foram cimento Portland (85%) e sílica ativa (15%). A relação água/ligante e proporção entre cimento e sílica ativa foram obtidas de forma experimental, maximizando-se a utilização do aditivo superplastificante e obtendo-se condições aceitáveis de autoadensabilidade das misturas. Foram avaliadas as propriedades no estado fresco e endurecido, aderência do microconcreto em dois substratos e como ponte de aderência, simulando uma situação de reforço estrutural. Obtiveram-se boas propriedades de autoadensabilidade do MC, com aumento de 26% no espalhamento e 5% no tempo de escoamento do MC com 15% de substituição em relação ao MC de referência. Para 15% de substituição, observou-se aumento de 18% no módulo de elasticidade e redução de quase 9% na absorção total de água. Também se obtiveram bons resultados de aderência em substrato de concreto, demonstrados pela ruptura coesiva observada no ensaio de aderência. Em situação de reparo estrutural, o material mostrou-se satisfatório como ponte de aderência entre concretos.
Abstract in English:ABSTRACT The objective of this work was to evaluate the efficiency of a micro concrete for structural strengthening, as an adhesion bridge between old and new concrete. Contributing to environmental preservation, the replacement of sand with a filler, a by-product of crushing stones, was evaluated based on a reference mixture. The binders used were Portland cement (85%) and silica fume (15%). The water/binder ratio and the proportion between cement and silica fume were obtained experimentally, maximizing the use of the superplasticizer additive, and obtaining acceptable conditions of self-compacting of the mixtures. The properties of micro concrete in the fresh and hardened state were evaluated, in addition to the adhesion provided by the micro concrete on concrete substrates and as an adherent material between old and new concrete, simulating a situation of structural reinforcement. As a result, good MC self-compacting properties were obtained, with an increase of 26% in scattering and 5% in MC flow time with 15% replacement in relation to the reference MC. There was also considerable gain in the physical properties of the mixtures. Still, for 15% replacement, there was an increase of 18% in the modulus of elasticity and a reduction of almost 9% in the total water absorption. Good adhesion results were also obtained on concrete substrates, demonstrated by the cohesive failure observed in the adhesion test. In addition, in a situation of structural repair, the material proved to be satisfactory for use as an adhesion bridge between old and new concrete.
Abstract in Spanish:RESUMEN El manejo adecuado de estructuras porosas, en aplicaciones biomédicas, tiene una relevante importancia en evitar la reabsorción y permitir el correcto crecimiento óseo. Estas estructuras conducen a la nucleación y crecimiento del hueso en su interior, consiguiendo una óptima unión entre el implante y este. En consecuencia, este trabajo investiga un proceso de fabricación de estructuras porosas de titanio obtenidas mediante una técnica pulvimetalúrgica basada tanto en el método de gel-casting como en la sinterización. Estas técnicas nos permiten controlar la cantidad, tamaño, forma y distribución de los poros, con el objetivo de obtener una estructura metálica apta para ser utilizada en implantes biomédicos. Las muestras, se preparan mezclando diferentes fracciones en peso de polvo de hidruro de titanio y polvo de resina acrílica. Se emplean mezclas compuestas por 3%, 6%, 9%, 12%, 15%, 18% y 21% de fracción en peso de resina acrílica. Los resultados indican que es posible obtener muestras con estructuras porosas adecuadas y microestructuras con valores de porosidad de 11% a 91% de fracción de poro, con tamaños de 3 µm a 195 µm. Mediante este proceso es posible obtener estructuras porosas adecuadas para una aplicación determinada.
Abstract in English:ABSTRACT The proper handling of porous structures in biomedical applications has relevant importance to avoid bone resorption and to allow the correct bone ingrowth. This structure leads to the nucleation and growing of bone inside them, obtaining a correct bonding between implant and bone. Consequently, this work investigates a manufacturing process of porous titanium structures obtained by means of a powder metallurgy technique based on gel-casting and sintering. This technique allows us to control the size, shape and distribution of the pores aiming to obtain a metallic structure capable to be utilized for biomedical implants. Samples were prepared by mixing different weight fractions of titanium hydride powder and acrylic resin powder (analyzed mixes were composed of 3%, 6%, 9%, 12%, 15%, 18% and 21% weight fraction of acrylic resin). The results indicate that it is possible to get samples with adequate porous structure, and microstructures with different kind of porosities (11% to 91% pore fraction) and porous size (3 µm up to 195 µm) in a wide range of values. This process allows to choose the appropriate pore characteristics for a certain application.
Abstract in English:ABSTRACT In this paper, based on the analysis of oil sludge composition and environmental hazards, the microwave catalytic pyrolysis of oil sludge for recovering combustible gas and chain hydrocarbon light oil disposal process, is proposed to perform the recycling of oil sludge and reduce the risk of environmental pollution. In order to improve the yield of combustible gas and light oil in oil sludge pyrolysis, the impact of adding four catalysts (nano-CuO, nano-NiO, nano-MgO, and nano-γ-Al2O3) on the heating characteristics of oil sludge and the composition and quality of products during microwave pyrolysis, were experimentally studied and analyzed. The results show that the catalyst can increase the heating rate of sludge and the yield of pyrolysis oil and gas. The increasing order of heating is: nano-CuO > nano-γ-Al2O3 > nano-MgO > nano-NiO > blank group. Compared with the blank group, the content of combustible gas (H2 + CH4 + CO) increases by 18.824wt% (MgO), 4.511wt% (CuO), 9.28wt% (NiO), and 16.164wt% (γ-Al2O3), respectively. It can be deduced that nano-metal oxide catalysts, especially γ-Al2O3, can promote the decomposition of oil sludge, improve the content of low carbon straight chain hydrocarbons and alcohols, and improve the quality of pyrolysis oil products.
Abstract in Portuguese:RESUMO A pandemia do coronavírus além da crise de saúde global evidencia prejuízos ao meio ambiente devido ao elevado número de máscaras faciais descartadas, tornando necessário o desenvolvimento de pesquisas para minimizar os riscos ambientais associados aos de equipamentos de proteção individual utilizados pela população. Este estudo visa reduzir os resíduos gerados pela pandemia, aproveitando as máscaras faciais, inserindo-as na confecção de argamassas. Efetuou-se processamento (trituramento) das máscaras e sua inclusão em teores de 1,4% e 2,0% em relação ao consumo de cimento. Os produtos foram comparados com um traço de referência e avaliados quanto às propriedades físicas e mecânicas. Como resultado, constatou-se que a adição do fibras da máscara interfere nas propriedades ocasionando um incremento na taxa de absorção de água, bem como reduções na resistência à tração e à compressão, respectivamente 30% e 50%, em decorrência de falhas na interação matriz/fibra, o que poderá limitar o emprego da mistura. Entretanto, o presente estudo contribui para a agenda brasileira no que se refere ao desenvolvimento sustentável urbano, regional e nacional, através de uma abordagem inovadora, possibilitando a redução da degradação ambiental pelo descarte das máscaras e a confecção de novos materiais a serem empregados no setor da construção civil.
Abstract in English:ABSTRACT The coronavirus pandemic, in addition to the global health crisis, shows damage to the environment due to the high number of disposable face masks, making it necessary to develop research to minimize the environmental risks associated with personal protective equipment used by the population. This research aims to reduce the waste generated by the pandemic, taking advantage of face masks, inserting them in the manufacture of mortars. Processing (grinding) of the masks was carried out and their inclusion in contents of 1.4% and 2.0% in relation to the cement consumption. The products were compared to a reference mix and evaluated for physical and mechanical properties. As a result, it was found that the addition of mask fibers resulting an increase in the water absorption rate, as well as reductions in diametral compression strength and compressive strength, respectively 30% and 50%, due to failures in the matrix/fiber interaction, which may limit the use of the mixture. However, this research contributes to the Brazilian agenda regarding sustainable urban, regional, and national development, through multidisciplinary and innovative approaches, enabling the reduction of environmental degradation by discarding masks and the making of new materials to be employees in the construction sector.
Abstract in Portuguese:RESUMO O objetivo deste trabalho foi avaliar a influência da adição do óxido de cálcio na redução da temperatura de sinterização e nas propriedades cerâmicas de agregado sintético à base de resíduo de bauxita. Foram utilizados resíduo de bauxita, óxido de cálcio e argila para a produção de corpos de prova com a adição de 0% e 10% de óxido de cálcio. As propriedades físicas determinadas foram: absorção de água, porosidade aparente e massa específica aparente, e as matérias-primas foram submetidas a ensaios de Difração de raios X (DRX), Calorimetria Exploratória Diferencial (DSC) e Análise Termogravimétrica. A microestrutura das cerâmicas foi avaliada por Microscopia Eletrônica de Varredura (MEV) e DRX, e foi realizado o ensaio de DSC nas formulações compostas por resíduo de bauxita e argila com e sem a adição de óxido de cálcio. Os resultados indicaram que a adição do óxido de cálcio aumentou a porosidade aparente e, por consequência, a absorção de água, enquanto houve também o aumento da massa específica aparente. Quanto à mineralogia, a presença do óxido de cálcio mostrou-se diretamente ligada às alterações das fases minerais, evidenciado principalmente pelo desaparecimento de fases como quartzo e mulita e o surgimento de magnetita.
Abstract in English:ABSTRACT This paper has the objective of characterizing and studying the mineralogical behavior and the ceramic properties of aggregates produced from bauxite waste, as a function of the addition of calcium oxide that has been dumped in deposits of bauxite residue, which, in the long term, can represent a considerable increase in the concentrations of this oxide present in the waste deposit. Besides bauxite residue and calcium oxide, clay was also used. Proof bodies were prepared with the addition of 0% and 10% of calcium oxide. The proof bodies were conformed by pelletizing in a rotating cylinder. The physical and technological properties determined were Water absorption, apparent porosity, apparent specific mass. The raw materials were submitted to X-ray diffraction tests (XRD), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TG). The microstructure of the ceramics was analyzed by Scanning Electron Microscopy (SEM) and XRD. DSC was also realized for the formulations composed of bauxite residue and clay with and without the addition of calcium oxide. According to the results, the addition of calcium oxide caused an increase in the apparent porosity of the aggregates, and consequently, an increase of water absorption, while there was also an increase in the apparent specific mass. In terms of mineralogy, the presence of calcium oxide demonstrated to be directly associated with changes in the mineral phases by comparing the proof bodies produced with and without the addition of the oxide, evidenced mainly by the disappearance of phases such as quartz and mullite and the emergence of magnetite.