Resumo em Inglês:

Abstract The purpose of this study was the development of a low-cost ceramic tubular membrane, using inexpensive materials, namely natural clay, and graphite as a porogenic agent. Such a low-cost membrane can be used as filters or porous supports for the preparation of multilayer ceramic membranes. Extrusion was used as a shape-forming method for this purpose. Graphite was selected as a porogenic additive. Raw materials were physicochemically and morphologically characterized. A comparative study of the influence of porogen content on membrane characteristics was carried out. Finally a graphite addition of 15 wt% and 850 °C as the sintering temperature were chosen. The obtained membrane had 41 vol% of porosity, diametral compression strength of 4 MPa, and relatively good corrosion resistance in basic and acid conditions. The performance of the membrane support was evaluated for diesel-in-water emulsion depuration as a function of pressure. Filtration test using 15% of porogen sample led to turbidity rejection factor of 95%. Therefore, it was considered that this membrane can be suitable for diesel/water emulsion treatment.

Resumo em Inglês:

Abstract The present investigation aimed at a sustainable green turning operation of Ti-6Al-4V alloy using multi-objective optimization of surface roughness, tool flank wear, material removal rate, and tool wear loss with cutting speed, feed rate, and depth of cut as input parameters. The experiments were performed on a CNC lathe machine using an alumina-zirconia (Al2O3-ZrO2) ceramic insert under a dry machining environment. The experiments were performed to examine the influence of input parameters with three levels and their interactions on the output responses. The experiment trials were designed according to Taguchi’s L25 orthogonal array. A hybrid approach of grey Taguchi-based response surface methodology (GT-RSM) was exposed for estimating the optimal integration of turning parameters. The weights to the output characteristics were assigned by the analytical hierarchy process (AHP). According to the ANOVA, cutting speed was the most influencing factor in the grey relation grade (GRG) succeeded by the depth of cut and feed rate. The optimized turning settings improved the surface roughness, tool flank wear, and tool wear loss by 10.31%, 6.51%, and 7.69% respectively with a 2.21% decrease in material removal rate. The result indicated that the GT-RSM methodology provided an excellent database that was effective to enhance the output quality responses.

Resumo em Inglês:

Abstract The use of industrial waste in compositions of ceramic masses has attracted great interest from the scientific community, as they can be considered abundant and diversified alternative sources of raw materials. At the same time, there is a growing interest in the development of porous ceramics due to their wide possibilities for use in various fields of engineering. In this sense, the present work aimed to provide a literature review on the use of industrial waste as alternative raw materials in the production of porous ceramics, highlighting the innovations and technological potential of research carried out in recent years. Increasingly higher levels of industrial waste in ceramic formulations have been studied, as well as high-performance porous ceramic bodies obtained entirely from waste materials. In addition to promoting the diversification of products, the incorporation of waste in ceramic masses represents an alternative to minimize their negative effects on the environment.

Resumo em Inglês:

Abstract In the last decades, clays have been used in sectors such as health and cosmetics. This requires products that are increasingly pure and present homogeneous properties, hardly found in natural clays. The use of synthetic clays can be a solution. For this, it is necessary to explore techniques for their production. The main focus of this study was to synthesize a smectite clay in a simple, fast and economic way at low temperature and pressure, called static and dynamic methods. To regulate the pH of the reaction and bring it closer to the ideal synthesis conditions, two different acids were used: nitric acid (the most widely used in the literature) and hydrochloric acid (more accessible and cheaper). The results showed characteristics of uniform crystalline material with a porous structure similar to that of the smectite group. Small particle sizes of approximately 100 nm were observed by scanning electron microscopy. Stevensite clay was obtained by both synthesis methods using two different acids; the static method with hydrochloric acid stood out. The greater practicality in its development provides a more viable option for large-scale industrial production.

Resumo em Inglês:

Abstract ZnWO4 crystallizes in a monoclinic wolframite-like structure, which has been studied for applications in heterogeneous photocatalysis for degradation, oxidation, and reduction of various contaminants. This type of tungstate has proved to be an efficient photocatalyst under both ultraviolet and visible light irradiation and, when ZnWO4 forms a heterostructure with other semiconductors or when it is doped with different ions, it has a great efficiency under sunlight irradiation. For instance, the optimization of ZnWO4 efficiency has been attained by its heterojunction with different semiconductors such as ZnO, one of the most used materials for this purpose, but also with other compounds such as BiOBr, FeWO4, TiO2, WO3, Bi2WO6, among others. In addition, doping ZnWO4 with the Ti4+, Bi3+, Ce3+, and Co2+ metal ions or with nonmetals (F- and N3-) can also increase the photocatalytic yield of the material. The photocatalytic properties of ZnWO4-based catalysts have been explored toward inorganic and organic molecules. However, among the variety of target molecules, organic pollutants such as methylene blue, methyl orange, and rhodamine B dyes appear as the most investigated in studies involving photocatalysis in the presence of ZnWO4. In our review, we summarize important literature works, highlighting the advancement in photocatalysis using ZnWO4.

Resumo em Inglês:

Abstract Motivated by their low cost, lignosulfonate-based water reducers are the most used type of admixture in the concrete industry worldwide. Due to the plurality of types of lignosulfonates (LSs) and the recent update to the Brazilian standard for admixtures for concrete, the objective of this work was to investigate the impact of sodium (Na-LS) and magnesium (Mg-LS) lignosulfonates, raw materials present in the Brazilian market, in pastes and concretes produced with cement type CP II F 40 under different dosages (0.40% and 0.80%). For this, the following tests were performed: adsorption curves, isothermal calorimetry, microanalytical tests (TGA/DTG and DRX), and application in the concrete according to NBR 11768-1 standard. The results showed different hydration evolutions among the pastes produced with these lignosulfonates. As a consequence, despite the similarity in water reduction, it was verified that Mg-LS was more suitable for RA1-R (water reducer-retarder, setting time 120-360 min), while Na-LS was more suitable for RA1 (water reducer, setting time 30-160 min).

Resumo em Inglês:

Abstract Ceramic additive manufacturing allows the fabrication of small series of complex parts without the high costs of molds usually associated with traditional ceramic processing. Although research into ceramic 3D printing by all technologies started back in the 90s, its industrial application is still quite restricted when compared to polymers and metals, which is related to the limited availability and costs of equipment and materials for such applications. This review examined the advantages and limitations of each process (binder jetting, direct ink writing, directed energy deposition, fused deposition, material jetting, selective laser sintering, selective laser melting, and vat photopolymerization), discussing their particularities. It also summarized the commercially available 3D printers and raw materials for ceramic processing, pointing out to trends and challenges of each technology.

Resumo em Inglês:

Abstract Neodymium-iron-boron alloy, Nd2Fe14B, is used as a material for magnets. Neodymium is one of the valuable and expensive rare earth elements and is often recovered to reduce costs and environmental impact. Recently, a method for recovering neodymium as neodymium phosphate from mixed solutions was reported. This method was very useful because the main component of rare earth ores is rare earth phosphates, and there are well-established methods for refining rare earths from rare earth phosphates. This study attempts to obtain neodymium phosphate using acid to dissolve waste magnets, reducing agent, phosphoric acid, and pH adjuster. The diluted acid (hydrochloric acid and nitric acid), amount of ascorbic acid and phosphoric acid, and the pH values were studied to clear the suitable conditions. The color of the heat-treated product, the precipitate yield, and the Fe/Nd molar ratio indicated that a low concentration of acid is suitable and ascorbic acid is required. Excessive use of phosphoric acid improved the precipitate composition. The high pH value decreased the selectivity of neodymium phosphate due to the easy formation of iron phosphate and hydroxide. The process addressed in this study is very promising because it does not require heating at high temperatures or special reagents.

Resumo em Inglês:

Abstract Alumina is a polymorphic bioceramic that has been extensively investigated for application in bone regeneration. Dense α-alumina has been considered a suitable biomaterial for dental and orthopedic implants due to its superior mechanical properties. However, its use is limited due to its high inertia in a biological environment. Recent investigations have focused on its distinct phases and surface characteristics through the control of morphology, physical properties, and chemical composition to enhance bioactivity. This article presents a brief review of the developments in porous α-alumina and amorphous-γ-alumina transition. Most studies have shown that composites and alumina coated with bioactive materials, high surface area, and hydroxylated surface can significantly improve biological properties. Cellular responses such as fixation, growth, and proliferation, as well as biomineralization, are the main studies to validate improvements in bioactive properties.

Resumo em Inglês:

Abstract This research evaluates the behavior of plaster with a water-repellent additive when submitted to a natural aging process. Casting plaster and silane/siloxane-based water-repellent were used as materials. The water/plaster ratio was set at 0.7 and the contents of 0.2% and 0.4% of water-repellent were used, in relation to the plaster mass. Plaster pastes without water-repellent (reference) and containing mass water-repellent were evaluated at ‘zero’ age and after 30, 60, 90, 120, and 150 days of natural aging. After 150 days of natural aging, it was observed that the mechanical properties of the material (compressive strength and hardness) did not undergo significant variations and remained above the minimum required by a standard. The addition of water-repellent resulted in a considerable reduction in water absorption, demonstrating the water repellency capacity of the material, compared to the reference specimen.

Resumo em Inglês:

Abstract Pelletization of zeolitic materials is required to facilitate their practical industrial and commercial applications. Zeolite-NaA was synthesized from fly ash by the fusion method and shaped into spherical granules. Bentonite, kaolinite, and a combination of bentonite with kaolinite were tested as binders with different contents from 5 to 10 wt%. The pellet formation was optimized. The physicochemical properties of binders, zeolite powder, and zeolite granular were characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption isotherm, and scanning electron microscopy (SEM) among other techniques. Deformation and breakage behavior of spherical granulates by compression was also studied. The best performance was obtained by the pellet with 10% bentonite with satisfactory mechanical strength and water resistance. The XRD and SEM results revealed NaA zeolite granular with a typical cubic shape and high crystallinity formed on the surface of bentonite. This result presents a potential use of the coal fly ash to obtain pelletized NaA zeolite following the principles of circular economy and the sustainable development goals (SDGs), particularly SDG 12.