ABSTRACT Due to its combination of high mechanical properties, good formability, and low production cost, steel is a key material with potential for improvement in the metallurgical industry. Based on these conditions, this research evaluated the influence of material composition and incomplete austenitization parameters on the final metallurgical and mechanical properties of high-strength microalloyed steels after cooling in a medium with high severity. The applied cycle was based on the intercritical thermal treatment of microalloyed steels with niobium (Nb) and titanium (Ti) to increase the mechanical resistance and guarantee the tenacity of the material. An experimental study was carried out testing three intercritical temperatures, 806 °C, 775 °C, and 740 °C, with subsequent cooling in polymeric solutions in water. The studies showed that the intercritical temperature variation directly contributed to the difference in the second phase microstructure present in the samples. The heat treatment findings resulted in a microhardness of 434.2 HV0.01, characterizing the low-carbon martensite. The presence of a matrix consisting of ferrite and a second phase of low-carbon martensite promoted the typical behavior of dual phase steel. In the x ray diffraction, the presence of retained austenite was not evidenced, indicating the efficiency of the cooling rate. The experiments confirmed the influence of different engineering parameters and intercritical treatment on the mechanical properties. The study enriches the current knowledge about the development of variables for the development of dual phase steel from microalloying elements.

Resumo Estudos realizados com o pó de forno elétrico a arco (PAE) indicam um retardo no tempo de hidratação do cimento Portland. A incorporação de resíduos ricos em cálcio, como a lama de carbonato de cálcio (LCC), é uma das formas de redução deste retardo, a fim de suprimir a deficiência deste elemento para a produção de C-S-H. Este estudo teve como objetivo avaliar a influência do uso do PAE, combinado ou não com o LCC no processo de hidratação de pastas de cimento em relação ao tempo de pega e calor de hidratação. A metodologia utilizada envolve a caracterização física, química e microestrutural das amostras de resíduos, a formulação e produção de pastas de cimento com diferentes teores de substituição de resíduos e sem substituição (amostra de referência) e a avaliação das propriedades das pastas de cimento em relação ao tempo de pega e à evolução do calor de hidratação. Os resultados mostraram que a substituição de 1% de PAE combinado ou não com LCC apresentaram um calor de hidratação semelhante à amostra referência, sugerindo que nessa quantidade, a incorporação de PAE+LCC não afetaria significativamente as reações de hidratação do cimento, possibilitando a reciclagem destes resíduos em materiais de construção.

Abstract Studies have indicated that the use of electric arc furnace dust (EAFD) results in a delay in the hydration time of Portland cement. Calcium-rich waste such as lime kiln waste (LKW) is one of the techniques used to offset this delay as it accounts for the lack of this element in calcium silicate hydrate (C-S-H) production in the mixture. The objective of this study was to evaluate the influence of electric arc furnace dust (EAFD) and lime kiln waste (LKW) in the hydration process of Portland cement pastes and their influence in setting time and hydration heat. The methodology used required several steps: physiochemical and micro-structural characterization of waste samples; definition and production cement pastes with different levels of waste substitution and a reference paste and evaluation of the cement pastes with respect to setting time and hydration heat. Results showed that the substitution of 1% EAFD with or without LKW presented similar hydration heats as the reference paste. This indicated that EAFD+LKW substitution would not affect substantially the hydration reactions of cement and could allow waste recycling in construction materials.

Since epoxy resins are used as composite matrix with excellent results, and silica is one of the fillers most often employed, this study compared the performance of rice husk ash (RHA) as filler in epoxy composites, in replacement for high-purity silica. Composites were molded containing 20%, 40%, and 60% (wt) silica or RHA. Viscosity analysis, infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) as well as mechanical and water absorption tests were carried out to evaluate composites. Glass transition temperature after curing and thermal degradation temperature of all samples analyzed were approximately 140 ºC and 370 ºC, respectively. RHA and silica exhibited similar mechanical and water absorption characteristics, indicating that rice husk ash may be a suitable replacement for silica. SEM imaging showed good filler dispersion and distribution in the polymer matrix, highlighting the more effective adhesion interface between RHA particles and the matrix.

RESUMO A disposição inadequada de areia de processos de moldagem após vazamento do metal fundido aumenta os custos de logística e impacto ambiental por causa da presença da resina fenólica na sua composição. O processo de regeneração de resíduos areia fenólica de fundição (RAFF) objetiva a reciclagem deste material. Como os métodos de regeneração mecânica não são eficientes para garantir 100% de limpeza dos grãos de areia e sua utilização novamente no processo de moldagem, este trabalho investigou a eficiência de um método de regeneração térmica deste tipo de resíduo que pode operar de forma complementar. Um reator de leito fluidizado em escala de laboratório foi projetado e construído para regenerar RAFF que foi tratada anteriormente por um método mecânico. A metodologia utilizada para projetar e construir o protótipo de leito fluidizado é descrita, assim como a caracterização do resíduo, da areia limpa padrão e da areia regenerada. Os resultados da regeneração térmica no leito fluidizado foram muito satisfatórios no que concerne a eficiência de regeneração. Para as nove condições de processos testadas, os valores de perda ao fogo foram reduzidos quando comparados a areia limpa padrão. Este estudo apresenta as vantagens de uma combinação de dois processos, regeneração mecânica e térmica, que permite reduzir o tempo e eventualmente a temperatura de remoção da resina, devido à remoção parcial da camada de resina ou seu enfraquecimento durante o processo de regeneração mecânica. Das nove condições de processo testadas, seis tiveram perda em valores de ignição abaixo da CSS. Desta forma, a regeneração térmica nos resultados do leito fluidizado foi bastante satisfatória em relação à eficiência de regeneração.

ABSTRACT Improper disposal of sand used in molding processes after casting increases logistical costs and environmental impact because of the presence of the phenolic resin in its composition. The regeneration process of waste foundry phenolic sand (WFPS) aims to recycle this material. As mechanical regeneration methods are not efficient to guarantee 100% cleaning of the sand grains and their use again in the molding process, this work investigated the efficiency of a method of thermal regeneration of this type of residue that can be employed as a complementary procedure. A laboratory-scale fluidized bed reactor was designed and built to regenerate WFPS that was previously treated by a mechanical method. The methodology used to design and construct the fluidized bed prototype is described, as well as the characterization of the residual, the standard clean sand and the regenerated sand. The results of the thermal regeneration in the fluidized bed were very satisfactory with respect to the regeneration efficiency. For the nine process conditions tested, loss on ignition values were reduced when compared to standard clean sand. This study presents the advantages of a combination of two processes, mechanical and thermal regeneration, which allows to reduce the time and eventual temperature of resin removal due to the partial removal of the resin layer or its weakening during the mechanical regeneration process. Of the nine process conditions tested, six had loss on ignition values below the CSS. Thus, the thermal regeneration in the fluidized bed results was quite satisfactory in relation to the regeneration efficiency.

Integrated circuits have several applications, including medicine and the aerospace industry, where reliability is essential. Packaging is an important step in the manufacturing of integrated circuits, and ball soldering is one of the most critical process, especially in assembling and interconnecting integrated circuits. The solder joint formed during the ball soldering process is intrinsically associated with the performance and the reliability of the electronic system. This study analyzed the influence of parameters or factors affecting the ball soldering process from the perspective of intermetallic compound formation and shear stress of the solder joint. The results indicate there is an interaction coupling between these two factors that cannot be seen when they are investigated individually, meaning that the individual effect of each factor differs from that of the combinations of factors. The results showed that the factor that most influenced shear stress and thickness of the intermetallic compound was peak temperature during ball soldering.

As a byproduct of the combustion of rice husk to generate energy, rice husk ash (RHA) is formed by silica and carbon, apart from small amounts of other constituents. Several treatments can be used to increase the purity of the silica obtained, or even produce pure silica. The present study tested the efficiency of different techniques to obtain silica, characterizing and comparing the silicas obtained from RHA. A literature review was conducted, and then selected techniques were used to produce silica, which was characterized by XRF, XRD, particle sizing, specific weight, specific surface area, total carbon, and SEM. The literature review showed that most techniques include a pretreatment like acid or alkaline leaching followed by thermal treatment to increase the amount of silica produced by reduction of carbonaceous materials. The results showed that it is possible to produce silica from RHA using simple methods, and that these produced silica with purity above 98%. The treatments that afforded the best results were acid leaching followed by thermal treatment at 800ºC, and alkaline extraction at low temperature, with silica purity of 99.3% and 99.6%, respectively.

RESUMO A cinza de casca de arroz (CCA) é um resíduo proveniente da combustão da casca de arroz utilizada como biomassa na produção de energia. Esta cinza é gerada em grandes quantidades e possui baixa massa específica, o que dificulta o seu gerenciamento, pois demanda muito espaço para o devido armazenamento e descarte. A CCA possui um elevado teor de sílica em sua composição, fator este que pode torná-la um material atrativo para vários segmentos industriais. Neste contexto, este trabalho tem como objetivo avaliar a influência do beneficiamento físico da cinza de casca de arroz, por meio de processos de segregação granulométrica e moagem, com e sem o uso de aditivos, nas características deste material e na sua adequação como coproduto. A metodologia experimental utilizada para o desenvolvimento deste trabalho envolveu a segregação e moagem da CCA (com e sem aditivos de moagem), caracterização química, física e estrutural das amostras de CCA bruta, segregadas e moídas. Os resultados obtidos indicam que a segregação granulométrica se apresenta como fator determinante para a utilização da CCA como coproduto. Com relação à moagem, pode-se verificar que o diâmetro médio das partículas diminui e a massa específica das amostras aumenta, com o aumento do tempo de moagem. Entretanto, verifica-se que os aditivos usados neste trabalho, nas concentrações testadas, não influenciam significativamente na redução do diâmetro das partículas.

ABSTRACT The rice husk ash (RHA) is a residue from the rice husk combustion used as biomass in energy production. This ash is generated in large amount and due to its low density it makes complicate its management, in addition it demands a lot of space for proper storage and disposal. The RHA has high silica content in its composition, a factor that may turn it in an attractive material for several industries. In this context, this work aims to evaluate the influence of physical processing of rice husk ash through the sieve segregation processes and grinding with and without the additives use, the characteristics of this material and its suitability as a co-product. The experimental methodology used to develop this work involved the segregation and grinding of the RHA (with and without grinding additives), chemical, physical and structural characterization of samples raw-based RHA, segregated and ground. The results indicate that the particle size segregation presents as a determinant factor for the use of RHA as coproduct. With regard to the grinding, it can be seen that the average diameter of the particles decreases and the density of the samples increases with increasing milling time. However, it appears that the used additives did not significantly influence the reduction of particle diameter in the concentrations tested.

RESUMO Neste estudo de caso, comparou-se o potencial impacto ambiental gerado por dois cenários representativos de duas formas diferentes de gerenciamento de resíduos domésticos: o primeiro com central de triagem e aterro sanitário, e o segundo com central de triagem, compostagem e aterro sanitário. A análise dos dados baseou-se nas fases de estudo de uma Análise do Ciclo de Vida: definição de objetivo e escopo, análise de inventário, avaliação dos potenciais impactos ambientais, interpretação dos resultados e avaliação crítica. Foram elaborados fluxogramas dos processos produtivos, delimitadas as fronteiras dos sistemas e elaborados os diagramas de blocos e as planilhas de aspectos e impactos ambientais. No inventário efetuado, percebe-se que os dados são favoráveis ao Cenário 2 (aterro sanitário precedido de compostagem) com relação à geração de resíduos e de emissões atmosféricas. No Levantamento dos Aspectos e Impactos Ambientais (LAIA) do Cenário 1 (com triagem de recicláveis secos, em que todos os rejeitos são encaminhados para o aterro sanitário), verificou-se que 22,2% dos aspectos e impactos ambientais foram avaliados como significativos (ou seja, classificados como "intoleráveis" ou "sérios"). No LAIA do Cenário 2, o resultado foi de 17,6% do total avaliado, cujos dados também são favoráveis a este Cenário. Em ambos os cenários, o aspecto significativo mais relevante foi relacionado às emissões atmosféricas geradas, identificadas nos processos de coleta e transporte de resíduos e de disposição final dos rejeitos.

ABSTRACT The present paper compared the potential environmental impact generated by two representative scenarios in two different ways of managing household waste: the first one considering a central sorting and sanitary landfill, and the second one considering a central sorting, composting and sanitary landfill. Data analysis was based on the phases of a Life Cycle Analysis: goal and scope definition, inventory analysis, evaluation of potential environmental impacts, interpretation of results and critical evaluation. Flowchart of processes was developed, boundaries of systems were defined, and it was elaborated block diagrams and spreadsheets of the environmental aspects and impacts. It was noticed in the inventory that the data are in favor of Scenario 2 (composting before sanitary landfill) regarding waste generation and atmospheric emissions. The assessment of Environmental Aspects and Impacts (AEAI) of Scenario 1 (sorting of recyclables, in which all waste is sent to landfill) showed that 22.2% of environmental aspects and impacts were assessed as significant (i.e. ranked as "unacceptable" or "serious"). The result of AEAI from Scenario 2 was 17.6% of total assessed, which data is also favorable to this Scenario. In both scenarios, the more relevant significant aspect was related to atmospheric emissions identified in the processes of collection and transportation of waste, and final disposition of rejects.

O lodo de fosfatização gerado no tratamento de efluentes do processo de revestimento fosfático de aço é um resíduo sólido Classe IIA - Não Inerte, geralmente disposto em aterro industrial. Uma alternativa para o tratamento de resíduos é a estabilização por solidificação em matrizes cerâmicas e à base de cimento Portland. Isto permite a reciclagem do resíduo como matéria-prima para a construção civil, diminui os custos de tratamento e disposição final e reduz áreas de aterros. O presente estudo tem como objetivo verificar a estabilização por solidificação de lodo de fosfatização em matrizes de cerâmica vermelha, empregada na produção de blocos cerâmicos de alvenaria, e em concretos de cimento Portland. Foram realizadas caracterizações dos materiais envolvidos e ensaios de lixiviação e solubilização das matrizes estudadas com e sem a incorporação do lodo. Os resultados indicam que há uma tendência à estabilização por solidificação dos parâmetros avaliados tanto na matriz cerâmica quanto na matriz de cimento Portland.

Phosphatization sludge is a solid waste generated by the treatment of effluents from the steel recovering process via phosphatization. It is classified as Class IIA - Non Inert and it is usually disposed of in industrial landfills. A waste treatment alternative is the stabilization by solidification in ceramic and Portland cement matrices. It allows the recycling of the waste as a raw material for the construction industry, reduces the cost of treatment and final disposal, and reduces landfill areas. The aim of this study is to determine the stabilization by solidification of phosphatization sludge in red ceramic matrices, used in the production of masornry ceramic blocks, and in Portland cement concrete. The materials used were characterized and the matrices with and without sludge were evaluated by leaching and solubilization analysis. The results indicate that there is a trend of both matrices to stabilization by solidification of the parameters investigated.

Electric arc furnace dust (EAFD) is a solid waste generated in the collection of particulate material during steelmaking process in electric arc furnace. The aim of this work is to carry out a chemical and structural characterization of two EAFD samples with different Zn contents. Optical emission spectroscopy via inductively coupled plasma (ICP), X ray diffractometry (XRD) and Mössbauer spectroscopy analysis were carried out in such EAFD samples. From XRD measurements, the samples exhibits the following phases: ZnFe2O4, Fe3O4, MgFe2O4, FeCr2O4, Ca0.15Fe2.85O4, MgO, Mn3O4, SiO2 and ZnO. The phases detected by Mössbauer spectroscopy were: ZnFe2O4, Fe3O4, Ca0.15Fe2.85O4 and FeCr2O4. Magnesium ferrite (MgFe2O4), observed in the XRD patterns as overlapped peaks, was not identified in the Mössbauer spectroscopy analysis.