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The conversion of bioethanol to ethylene in gas phase and atmospheric pressure was investigated over γ-Al2O3 supported copper and nickel catalysts. These catalysts were prepared by co-precipitation and pre-treated with hydrogen at 450 °C. Six catalysts were studied at 450 °C under a nitrogen atmosphere. It was found that the monometallic Cu/γ-Al2O3 catalyst exhibited the highest ethylene concentration, with a selectivity of around 90 %. The bioethanol conversion obtained was between 57 %-86 %. Another catalyst that exhibited high concentration values was the NiCu1 : 7 bimetallic catalyst. The catalysts were characterised using XRD, SEM, EDS, TEM, TGA, FTIR, Raman, and N2-physisoption techniques. Furthermore, the Cu/γ-Al2O3 catalyst was studied under different reduction temperatures and gas flow conditions. It was found that the catalysts reduced at 350 °C and 35 ml/min N2 flow presented ethylene concentrations between (0.18-0.21) g/L. Moreover, the catalyst deactivation was identified to be first order and the equation of the Cu/γ-Al2O3 catalyst deactivation model was determined. Carbonaceous deposits over the used sample were not detected by Raman and FTIR. It was determined that the Cu/γ-Al2O3 catalyst deactivation could be mainly attributed to the blocking of the catalytic sites by strongly adsorbed compounds and hydroxylation of the catalyst surface.

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The present work aims to develop a production method of pre-sintered zirconia-toughened-alumina (ZTA) composite blocks for machining in a computer-aided design and computer-aided manufacturing (CAD-CAM) system. The ZTA composite comprised of 80% Al2O3 and 20% ZrO2 was synthesized, uniaxially and isostatically pressed to generate machinable CAD-CAM blocks. Fourteen green-body blocks were prepared and pre-sintered at 1000 °C. After cooling and holder gluing, a stereolithography (STL) file was designed and uploaded to manufacture disk-shaped specimens projected to comply with ISO 6872:2015. Seventy specimens were produced through machining of the blocks, samples were sintered at 1600 °C and two-sided polished. Half of the samples were subjected to accelerated autoclave hydrothermal aging (20h at 134 °C and 2.2 bar). Immediate and aged samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Optical and mechanical properties were assessed by reflectance tests and by biaxial flexural strength test, Vickers indentation and fracture toughness, respectively. Samples produced by machining presented high density and smooth surfaces at SEM evaluation with few microstructural defects. XRD evaluation depicted characteristic peaks of alpha alumina and tetragonal zirconia and autoclave aging had no effect on the crystalline spectra of the composite. Optical and mechanical evaluations demonstrated a high masking ability for the composite and a characteristic strength of 464 MPa and Weibull modulus of 17, with no significant alterations after aging. The milled composite exhibited a hardness of 17.61 GPa and fracture toughness of 5.63 MPa m1/2, which remained unaltered after aging. The synthesis of ZTA blocks for CAD-CAM was successful and allowed for the milling of disk-shaped specimens using the grinding method of the CAD-CAM system. ZTA composite properties were unaffected by hydrothermal autoclave aging and present a promising alternative for the manufacture of infrastructures of fixed dental prostheses.

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A composite material composed of anodized aluminum oxide (AAO), carbon (C), and magnesium oxide (MgO) was developed for CO2 capture applications. Inspired by the bryophyte organism, the AAO/C/MgO composite mirrors two primary features of these species-(1) morphological characteristics and (2) elemental composition-specifically carbon, oxygen, and magnesium. The synthesis process involved two sequential steps: electroanodization of aluminum foil followed by a hydrothermal method using a mixture of glucose and magnesium chloride (MgCl2). The concentration of MgCl2 was systematically varied as the sole experimental variable across five levels-1 mM, 2 mM, 3 mM, 4 mM, and 5 mM-to investigate the impact of MgO formation on the samples' chemical and physical properties, and consequently, their CO2 capture efficiency. Thus, scanning electron microscopy analysis revealed the AAO substrate's porous structure, with pore diameters measuring 250 ± 30 nm. The growth of MgO on the AAO substrate resulted in spherical structures, whose diameter expanded from 15 nm ± 3 nm to 1000 nm ± 250 nm with increasing MgCl2 concentration from the minor to major concentrations explored, respectively. X-ray photoelectron spectroscopy (XPS) analysis indicated that carbon serves as a linking agent between AAO and MgO within the composite. Notably, the composite synthesized with a 4 mM MgCl2 concentration exhibited the highest CO2 capture efficiency, as determined by UV-Vis absorbance studies using a sodium carbonate solution as the CO2 source. This efficiency was quantified with a 'k' constant of 0.10531, significantly higher than those of other studied samples. The superior performance of the 4 mM MgCl2 sample in CO2 capture is likely due to the optimal density of MgO structures formed on the sample's surface, enhancing its adsorptive capabilities as suggested by the XPS results.

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This study investigates the profound impact of the ZrO2 inclusion volume on the characteristics of Al2O3/ZrO2 nanocomposites, particularly influencing the formation of calcium phosphates on the surface. This research, aimed at advancing tissue engineering, prepared nanocomposites with 5, 10, and 15 vol% ZrO2, subjecting them to chemical surface treatment for enhanced calcium phosphate deposition sites. Biomimetic coating with Sr-enriched simulated body fluid (SBF) further enhanced the bioactivity of nanocomposites. While the ZrO2 concentration heightened the oxygen availability on nanocomposite surfaces, the quantity of Sr-containing phosphate was comparatively less influenced than the formation of calcium phosphate phases. Notably, the coated nanocomposites exhibited a high cell viability and no toxicity, signifying their potential in bone tissue engineering. Overall, these findings contribute to the development of regenerative biomaterials, holding promise for enhancing bone regeneration therapies.

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OBJECTIVE: To determine the effect of airborne particle abrasion (APA) on micro-tensile bond strength (µTBS) to dentin using different air-abrasion/polishing powders. METHODS: The bonding effectiveness of G2 Bond Universal (G2B), used in etch-and-rinse (E&R) and self-etch mode (SE), was tested on bur-cut dentin and dentin air abraded/polished using six different powders (aluminum oxide 29 µm (AO29) and 53 µm (AO53), aluminum trihydroxide (AT), sodium bicarbonate (SB), sodium bicarbonate soft (SBsoft) and bioactive glass (BG); Velopex). Adhesive-composite resin specimens were immersed in distilled water at 37 °C for one week and cut into microspecimens. Half of the specimens were subjected to 50,000 thermocycles (aged). Immediate and aged µTBS to dentin were measured. Statistical analysis was performed using linear mixed-effects (LME) modeling (p < 0.05). RESULTS: Comparing the aged bond strengths to air-abraded/polished dentin with bur-cut dentin, pretreatment with SB and SBsoft in combination with G2B used in E&R mode, and BG air polishing in combination with both application modes (E&R, SE), resulted in a significantly higher bond strength. Dentin bond strength was only significantly lower when air abraded with AO29 and using G2B in SE mode. Aging did not significantly influence bond strength for both application modes (E&R, SE), except for AO29 and AT-treated dentin, where bond strengths decrea sed significantly using G2B in SE mode. In general, G2B reached significantly higher bond strengths on air-abraded/polished dentin in E&R mode than in SE mode. CONCLUSION: Air-abrasion/polishing did not impair dentin bond strength using G2B, except when dentin was air abraded with AO29 and using G2B in SE mode. Air polishing positively influenced the bond strength to dentin in specific groups. CLINICAL SIGNIFICANCE: APA is safe concerning bonding to dentin. The E&R application mode is preferred using G2B as adhesive on air-abraded/polished dentin. Air polishing with BG positively influenced dentin bond strength for both application methods.

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Dental zirconias have been broadly utilized in dentistry due to their high mechanical properties and biocompatibility. Although initially introduced in dentistry as an infrastructure material, the high rate of technical complications related to veneered porcelain has led to significant efforts to improve the optical properties of dental zirconias, allowing for its monolithic indication. Modifications in the composition, processing methods/parameters, and the increase in the yttrium content and cubic phase have been presented as viable options to improve zirconias' translucency. However, concerns regarding the hydrothermal stability of partially stabilized zirconia and the trade-off observed between optical and mechanical properties resulting from the increased cubic content remain issues of concern. While the significant developments in polycrystalline ceramics have led to a wide diversity of zirconia materials with different compositions, properties, and clinical indications, the implementation of strong, esthetic, and sufficiently stable materials for long-span fixed dental prostheses has not been completely achieved. Alternatives, including advanced polycrystalline composites, functionally graded structures, and nanosized zirconia, have been proposed as promising pathways to obtain high-strength, hydrothermally stable biomaterials. Considering the evolution of zirconia ceramics in dentistry, this manuscript aims to present a critical perspective as well as an update to previous classifications of dental restorative ceramics, focusing on polycrystalline ceramics, their properties, indications, and performance.

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In the presented study, a novel approach for thermal atomic layer deposition (ALD) of Al2O3 thin films using plasma-activated water (PAW) as a co-reactant, replacing traditionally employed deionized (DI) water, is introduced. Utilizing ex situ PAW achieves up to a 16.4% increase in the growth per cycle (GPC) of Al2O3 films, consistent with results from plasma-enhanced atomic layer deposition (PEALD). Time-resolved mass spectrometry (TRMS) revealed disparities in CH4 partial pressures between TMA reactions with DI water and PAW, with PAW demonstrating enhanced reactivity. Reactive oxygen species (ROS), namely H2O2 and O3, are posited to activate Si(100) substrate sites, thereby improving GPC and film quality. Specifically, Al2O3 films grown with PAW pH = 3.1 displayed optimal stoichiometry, reduced carbon content, and an expanded bandgap. This study thus establishes "PAW-ALD" as a descriptor for this ALD variation and highlights the significance of comprehensive assessments of PAW in ALD processes.

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Soil pollution with potentially toxic elements (PTE) from incipient basic sanitation, dumps and industrial activities developed in the Amazon has been of international interest due to health and environmental issues. This study aimed to evaluate the concentration of PTE in five adjacent land occupations (a dump, a alumina refinery area and three residential centers) in the municipality of Barcarena, Amazon Region, Brazil. In a total area of 912 ha, 274 soil samples were collected at a depth of 0-0.2 m. Afterwards, the concentrations of As, Ba, Pb, Co, Cu, Cr, Hg, Ni and Zn were determined. The results were explored using descriptive and multivariate statistics, as well as geostatistical. Considering the data by location, maximum concentrations exceeding the prevention values of Brazilian soils were found for Cu, Ni and Zn in Dump (148; 42.8 and 356 mg kg-1), for Cu and Hg in Bom Futuro (333 and 1.99 mg kg-1) and for Cu in Itupanema (91.2 mg kg-1). Cu, Hg, Pb and Zn were grouped in the same principal component and showed the highest similarity measure in the cluster analysis. The interpolation point maps of the two principal components and of the individual concentrations of the PTEs showed the area of influence of the dump as the main reason for the increase in soil contamination. These results show the need for public policies aimed at the proper disposal of solid waste, in order to promote the reduction of pollutants in the soil, health and well-being for the local population, and also the environmental quality of the study area.

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Using groundwater for human consumption is an alternative for places with no nearby surface water resources. Fluoride is commonly found in groundwater, and the consumption of this water for a prolonged time in concentrations that exceed established limits by WHO and Brazilian legislation on water potability (1.5 mg L-1) can cause harmful problems to human health. For this reason, fluoride removal is an important step before water consumption. In this work, activated alumina was impregnated with Fe-Al-La composite and employed for the first time as an adsorbent for fluoride removal from an aqueous environment. XRD, SEM/EDS, FT-IR, and point of zero charge were used to characterize the prepared adsorbent. The adsorptive performance of adsorbent material was investigated by employing a 23-central composite design (CCD), and the obtained experimental conditions were pH = 6.5 and adsorbent dosage = 3.0 g L-1. A maximum adsorption capacity of 8.17 mg g-1 at 298 K and pH = 6.5 was achieved by Langmuir isotherm to describe the adsorption. The kinetic model that better described experimental data was Avrami, with the kav parameter increasing with the initial concentration from 0.076 to 0.231 (min-1)nav. The nature of adsorption was found to be homogeneous, and it occurs in a monolayer. The fluoride removal performance for the prepared adsorbent was higher than granular activated alumina, showing that supporting Fe-Al-La at the alumina surface increased its fluoride adsorption capacity from 16 to 42% at the same experimental conditions. Finally, the influence of co-existing ions Cl-, SO42-, and NO3- was evaluated in fluoride adsorption, and the material presented great selectivity to fluoride. Thus, Fe-Al-La/AA adsorbent is a promising material for fluoride removal from water.

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Biodegradable polymers of natural origin are ideal for the development of processes in tissue engineering due to their immunogenic potential and ability to interact with living tissues. However, some synthetic polymers have been developed in recent years for use in tissue engineering, such as Poly-ε-caprolactone. The nanotechnology and the electrospinning process are perceived to produce biomaterials in the form of nanofibers with diverse unique properties. Biocompatibility tests of poly-ε-caprolactone nanofibers embedded with hydroxyapatite and alumina nanoparticles manufactured by means of the electrospinning technique were carried out in Wistar rats to be used as oral dressings. Hydroxyapatite as a material is used because of its great compatibility, bioactivity, and osteoconductive properties. The PCL, PCL-HA, PCL-α-Al2O3, and PCL-HA-α-Al2O3 nanofibers obtained in the process were characterized by infrared spectroscopy and scanning electron microscopy. The nanofibers had an average diameter of (840 ± 230) nm. The nanofiber implants were placed and tested at 2, 4, and 6 weeks in the subcutaneous tissue of the rats to give a chronic inflammatory infiltrate, characteristic foreign body reaction, which decreased slightly at 6 weeks with the addition of hydroxyapatite and alumina ceramic particles. The biocompatibility test showed a foreign body reaction that produces a layer of collagen and fibroblasts. Tissue loss and necrosis were not observed due to the coating of the material, but a slight decrease in the inflammatory infiltrate occurred in the last evaluation period, which is indicative of the beginning of the acceptance of the tested materials by the organism.

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The photocatalytic degradation of methylene blue (MB) in aqueous solutions and under visible light was investigated with dispersed and supported zinc oxide (ZnO) as catalysts. The ZnO catalyst was successfully impregnated in asymmetric alumina hollow fibers by the simple vacuum-assisted dip-coating method. According to energy-dispersive analyses, the photocatalyst was homogenously distributed in the substrate. A strong correlation was observed between the initial dye concentration and the efficiency of the supported photocatalyst. For the initial MB concentration of 5 mg L-1 and catalyst dosage of 1 g L-1, the photocatalytic system with both dispersed and supported catalysts reached almost 100% of MB degradation. The photocatalytic process followed the pseudo-first-order kinetic model, and, for the initial MB concentration of 5 mg L-1, the apparent constants were 0.05415 and 0.00642 min-1 for suspended and supported catalysts, respectively. The treated MB solutions presented low phytotoxicity to the germination Lactuca sativa seeds with germination indexes greater than 80% after irrigation with the treated MB solutions. The produced supported ZnO catalyst showed suitable photocatalytic stability even after several reuse cycles.

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RESUMO A má distribuição geográfica de águas em território nacional aliada ao seu desperdício, à poluição dos cursos d'água próximos aos centros urbanos e industriais e à eficiência inadequada de processos de tratamento convencionais faz com que o tratamento e o reúso de água sejam tópicos de crescente importância no Brasil. Um dos métodos de tratamento de água são os processos de separação por membranas, como a nanofiltração. No entanto, esses processos estão sujeitos ao fenômeno de incrustação, que provoca diminuição gradativa de sua eficiência. Sendo assim, o presente trabalho visou à avaliação de diferentes métodos de pré-tratamento de água para mitigação da formação de biofilme em membranas de nanofiltração. Os processos de adsorção em partículas de alumina e desinfecção por meio de carvão ativado impregnado com nanopartículas de prata foram aplicados em uma amostra de um corpo d'água superficial. As amostras com e sem pré-tratamento foram nanofiltradas e a propensão à incrustação de cada uma foi avaliada. As eficiências de remoção de compostos orgânicos dos adsorventes empregados separadamente e em conjunto e as análises de absorção UV/Vis, microscópio eletrônico de varredura e espectroscopia de energia dispersiva do carvão ativado impregnado com nanopartículas de prata mostraram que os materiais empregados no pré-tratamento puderam ser apropriadamente sintetizados. Foi possível também identificar os principais grupos funcionais dos biopolímeros presentes nos biofilmes formados ao longo do tempo. Por fim, pôde-se observar que a adsorção da matéria orgânica é mais eficiente para o controle da incrustação rápida, enquanto o efeito bactericida se destaca no controle a longo prazo.

ABSTRACT The poor geographical distribution of water in the national territory combined with its waste, the pollution of watercourses close to urban and industrial centers, and the inadequate efficiency of conventional treatment processes make the treatment and reuse of water topics of increasing importance in Brazil. One of the advanced water treatment methods is membrane separation processes, such as nanofiltration. However, these processes are subject to fouling phenomenon, which causes a gradual decrease in the efficiency of the process. Therefore, the present work aims to evaluate different methods of pretreatment of water to mitigate the formation of biofilm in nanofiltration membranes. The adsorption processes on alumina particles and disinfection through activated carbon impregnated with silver nanoparticles were applied to a sample of a surface water body. Samples with and without pretreatment were nanofiltered and the propensity to fouling was evaluated. The efficiency of the adsorbents, used both separately and together, in removing organic compounds and the UV/Vis, scanning electron microscope, and Energy-dispersive X-ray spectroscopy analyses of the activated carbon impregnated with silver nanoparticles showed that the materials used in the pre-treatment were properly synthesized. It was also possible to identify the main functional groups of the biopolymers present in biofilms formed over time. Finally, it was observed that the adsorption of organic matter is more efficient for the control of rapid fouling while the bactericidal effect stands out in the long-term fouling control.

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The worldwide known and employed spice of Asian origin, turmeric, receives significant attention due to its numerous purported medicinal properties. Herein, we report an optimized synthesis of curcumin and symmetric curcuminoids of aromatic (bisdemethoxycurcumin) and heterocyclic type, with yields going from good to excellent using the cyclic difluoro-boronate derivative of acetylacetone prepared by reaction of 2,4-pentanedione with boron trifluoride in THF (ca. 95%). The subsequent cleavage of the BF2 group is of significant importance for achieving a high overall yield in this two-step procedure. Such cleavage occurs by treatment with hydrated alumina (Al2O3) or silica (SiO2) oxides, thus allowing the target heptanoids obtained in high yields as an amorphous powder to be filtered off directly from the reaction media. Furthermore, crystallization instead of chromatographic procedures provides a straightforward purification step. The ease and efficiency with which the present methodology can be applied to synthesizing the title compounds earns the terms "click" and "unclick" applied to describe particularly straightforward, efficient reactions. Furthermore, the methodology offers a simple, versatile, fast, and economical synthetic alternative for the obtention of curcumin (85% yield), bis-demethoxycurcumin (78% yield), and the symmetrical heterocyclic curcuminoids (80-92% yield), in pure form and excellent yields.

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In this research, a combined photocatalytic and biological treatment is proposed for the elimination of pollutants present in textile wastewater using a natural erionite zeolite (PE) and aluminum oxide (PA) synthesized by the sol-gel method as photocatalysts, and solar radiation. Both catalysts were characterized by XRD, SEM, and EDS. For biological treatment two bacterial consortium were used: BC1 (Escherichia coli N16, Serratia k120, Pseudomonas putida B03 and Enterobacter hormaechei), and consortium BC2 (Escherichia coli N16, Serratia Mc107, Enterobacter N9, Enterobacter hormaechei Mc9). The photocatalytic and microbiological treatments were carried out initially separately and subsequently in a sequential manner, first the photocatalytic followed by the microbiological to determine if a synergistic effect was achieved. Comparing the photocatalytic performance, erionite showed higher performance of dyes degradation (54.75%) than alumina (28.62%). While in the biological process, BC1 decreased the dye concentration to 56.93% and BC2 to 53.56%. Finally, the best combined process was PA+BC1 reaching pollutants degradation 64.62%, showing that the application of both processes promotes a decolorization in textile wastewater. The water resulting from the combined photocatalysis-microbiological degradation processes was tested for toxicity using Daphnia magna, obtaining that none of the effluents shows toxicity.

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This study presents the feasibility of using various functionalized substrates, Fe3O4 nanoparticles (NPs) and Al2O3 spheres, for the removal of Cd from aqueous solution. To improve the materials' affinity to Cd, we explored four different surface modifications, namely (3-Aminopropyl) triethoxysilane (APTES), L-Cysteine (Cys) and 3-(triethoxysilyl) propylsuccinic anhydride (CAS). Particles were characterized by FTIR, FIB-SEM and DLS and studied for their ability to remove metal ions. Modified NPs with APTES proved to be effective for Cd removal with efficiencies of up to 94%, and retention ratios up to 0.49 mg of Cd per g of NPs. Batch adsorption experiments investigated the influence of pH, contact time, and adsorbent dose on Cd adsorption. Additionally, the recyclability of the adsorbent and its potential phytotoxicity and animal toxicity effects were explored. The Langmuir, Freundlich, pseudo-first-order and pseudo-second-order models were applied to describe the behavior of the Cd adsorption processes. The adsorption and desorption results showed that Fe3O4 NPs modified with APTES are promising low-cost platforms with low phytotoxicity for highly efficient heavy metal removal in wastewater.

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A biocomposite system was developed and tested for the removal of the azo dye Reactive Red (RR195) from wastewater. The biocomposite was synthesized using ceramic particles containing 75% alumina which were coated using chitosan cross-linked with oxalic acid. The biocomposite showed high performance at low pH (maximum adsorption capacity = 345.3mg.g-1 at pH=2.0). The physicochemical and structure characteristics of the matrix were evaluated by Z-potential, FTIR-ATR, SEM-EDS, XRD, and porosity. Langmuir sorption isotherm and pseudosecond-order model gave the best fit. The electrostatic interaction between RR195 (due to the sulfonate groups) and the free amino groups of chitosan, enabled successive desorption/regeneration cycles. The maximum removal percentage (>80%) occurred at pH=2.0 due to the cross-linking effect. Experiments at different temperatures allowed the calculation of thermodynamic parameters (ΔG, ΔS, ΔH); adsorption was spontaneous, exothermic, and enthalpy controlled. The presence of inorganic ions ([Formula: see text] ) was analyzed during the adsorption process. This novel biocomposite can be applied as a cost-effective and environmentally friendly adsorbent for anionic azo dye removal from wastewater. The application of chitosan cross-linked with oxalic acid as a coating of the ceramic support enhanced the adsorption capacity and enabled its use under acidic conditions without solubilization.

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A study on the strength of ceramic fiber bundles based on experimental and computational procedures is presented. Tests were performed on single filaments and bundles composed of two fibers with different nominal fiber counts. A method based on fiber rupture signals was developed to estimate the amount of filament rupture during the test. Through this method, the fiber bundle true strength was determined and its variation with the initial fiber count observed. By using different load-sharing models and the single filament data as input parameter, simulations were also developed to verify this behavior. Through different approaches between experiments and simulations, it was noted that the fiber bundle true strength increased with the fiber count. Moreover, a variation of the fibers' final proportion in the bundles relative to the initial amount was verified in both approaches. Finally, discussions on the influence of different load-sharing models on the results are presented.

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Resumen Introducción: en la búsqueda de nuevos materiales útiles como dosímetros termoluminiscentes (TL) la alúmina (α-Al2O3) ha adquirido gran atención. La α-Al2O3 posee una sensibilidad TL que es perceptible a las concentraciones de impurezas y a las condiciones térmicas del crecimiento de sus cristales, por lo que encontrar nuevas variaciones del material permitirá aumentar su respuesta TL. Objetivo: analizar las curvas de brillo de matrices de alúmina pura sinterizadas bajo diferentes condiciones de calcinación y dopadas con cerio a concentración 0.1 % p/p (Al2O3:Ce), usando la función asimétrica logística, para calcular sus parámetros cinéticos termoluminiscentes y explicar el comportamiento del material. Materiales y métodos: polvo de alúmina bohemita fue utilizado para preparar muestras puras sintetizadas de bajo diferentes condiciones de calcinación (NALO y ALO). El cerio se introdujo mediante impregnación húmeda utilizando nitrato de cerio hexa-hidratado. El análisis estructural de las matrices se realizó mediante Difracción de Rayos X. La lectura TL se realizó en un TLD 4500. Resultados: la deconvolución obtenida en las curvas de brillo para los grupos ALO y NALO evidencia la presencia de tres y cuatro señales TL respectivamente, y de seis señales TL en la muestra Al2O3:Ce. Conclusión: los tratamientos térmicos aplicados introdujeron un cambio sustancial en la curva de brillo del material y en su cinética TL, en términos del número de trampas y de la cantidad inicial de portadores de carga atrapados. La introducción de impurezas de cerio produjo una modificación fundamental en la curva de brillo de las matrices de alúmina.

Abstract Introduction: in the search for new materials useful as thermoluminescent dosimeters (TL) alumina (α-Al2O3) has acquired great attention. The α-Al2O3 has a sensitivity TL that is perceptível to the concentrations of impurities and to the thermal conditions of the growth of its crystals, so finding new variations of the material will allow to increase its TL response. Objective: analyze the brightness curves of pure alumina matrices sintered under different calcination conditions and doped with cerium at a concentration of 0.1 % p/p (Al2O3:Ce), using the asymmetric logistic function, to calculate its thermoluminescent kinetic parameters and explain the behavior of the material. Materials and methods: boehmite alumina powder was used to prepare pure sintered samples of under different calcination conditions (NALO and ALO). The cerium was introduced by wet impregnation using cerium hexahydrate nitrate. The structural analysis of the matrices was carried out by X-ray diffraction. The TL reading was performed in a TLD 4500. Results: the deconvolution obtained in the brightness curves for the ALO and NALO groups evidences the presence of three and four TL signals respectively, and of six TL signals in the sample Al2O3:Ce. Conclusion: the applied heat treatments introduced a substantial change in the brightness curve of the material and its TL kinetics, in terms of the number of traps and the initial amount of charge carriers trapped. The introduction of cerium impurities produced a fundamental modification in the brightness curve of the alumina matrices.

Resumo Introdução: na busca por novos materiais úteis como dosímetros termoluminescentes (TL), a alumina (α-Al2O3) tem adquirido grande atenção. O α-Al2O3 possui uma sensibilidade TL que é perceptível às concentrações de impurezas e às condições térmicas do crescimento de seus cristais, portanto, encontrar novas variações do material permitirá aumentar sua resposta TL. Objetivo: analisar as curvas de brilho de matrizes de alumina pura sinterizadas sob diferentes condições de calcinação e dopadas com cério na concentração de 0,1 % p/p (Al2O3:Ce), utilizando a função logística assimétrica, para calcular seus parâmetros cinéticos termoluminescentes e explicar a comportamento do material. Materiais e métodos: o pó de alumina boehmite foi usado para preparar amostras de puro sinterizado sob diferentes condições de calcinação (NALO e ALO). O cério foi introduzido por impregnação a úmido com nitrato de cério hexaidratado. A análise estrutural das matrizes foi realizada por difração de raios X. A leitura TL foi realizada em um TLD 4500. Resultados: a deconvolução obtida nas curvas de brilho para os grupos ALO e NALO mostra a presença de três e quatro sinais TL respectivamente, e de seis sinais TL na amostra Al2O3: Ce. Conclusão: os tratamentos térmicos aplicados introduziram uma mudança substancial na curva de brilho do material e sua cinética de TL, em termos do número de armadilhas e da quantidade inicial de portadores de carga aprisionados. A introdução de impurezas de cério produziu uma modificação fundamental na curva de brilho das matrizes de alumina.

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Nanotechnology is providing new tools for precision agriculture, such as agrochemical agents and innovative delivery mechanisms to improve cropping efficiency. Powder nanoinsecticides, such as experimental nanostructured alumina (NSA), show great potential for sustainable agriculture as an alternative to conventional synthetic pesticides because their mechanism of insecticide action is based on physical rather than on biochemical phenomena. However, even in highly non-reactive and hardly soluble substances such as alumina, reduced particle size may lead to an increased toxicity of the material. In order to determine whether NSA induces DNA and chromosomal damage, its toxicity was assessed in human peripheral blood lymphocytes (PBL) and contrasted with commercial nanostructured alumina, natural insecticide powders and a conventional pesticide. PBL from healthy donors were exposed for 24 h to increasing concentrations (50, 100 and 200 µg/mL) of NSA particle agglomerates (<350 nm); positive and negative NSA-particles, respectively; bulk Al2O3 (4.5 µm) or Diatomaceous Earth (SiO2, <4.5 µm). Alkaline comet assay and micronuclei (MNi) test were used to assess DNA damage and chromosomal breakage, respectively. Cell viability was tested with resazurin assay. Comet assay results revealed no significant increase in DNA damage by NSA compared to other natural substances. As expected, DNA breaks were significantly higher in cells exposed to an organophosphate [OPP] control (P < 0.05). No statistically significant differences were found in terms of cellular viability at 50 and 100 µg/mL of NSA but cell survival decreased at 200 µg/mL as well as in OPP group. Positively charged NSA particles significantly reduced cell viability and increased DNA migration and oxidative DNA damage (8-oxoG). NSA as well as the electrically charged NSA particles had no significant effect on MNi induction. Our results indicate that NSA particles are non-cytotoxic and non-genotoxic at the tested doses and do not cause obvious DNA damage in human PBL in vitro.

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HYPOTHESIS: The electrical charges that develop on the surface of the ceramic particles upon contact with water, due to the interaction with ions in solution, result in a liquid-solid interface, which utterly modifies the properties of individual particles and the way they interact with each other to form a structure. This work explores a new approach to the relationships between structure and stability of suspensions. EXPERIMENTS: For this purpose, suspensions with a constant 0.35 volume fraction of α-alumina particles, neither spherical nor smooth, and controlled ionic strength (0-90 mM KCl) were prepared and characterized in terms of flow behaviour, electrical conductivity and particle's electrokinetic mobility. FINDINGS: Electrical conductivity (132 µS/cm < conductivity < 5730 µS/cm) and rheology measurements (10-2 Pa s < viscosity < 104 Pa s) were found to complement each other to produce a more accurate picture of the suspension's structure. Deviations of experimental data from well-accepted behavioural models were elucidated when the surface area equivalent particle size was used. With the electrical double layer thickness obtained from electrical conductivity measurements, this enabled the interpretation of the relationship between the suspension's viscosity and the particles electrical conductivity, which provides a criterion for the stability of concentrated colloidal suspensions.