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– The current study aims to prepare an Nb,Ta-containing ordered mesoporous catalyst MCM-41, using hydrated mixed oxide of niobium and tantalum, extracted from the columbite ore processing, as an alternative source of these metals. Direct hydrothermal synthesis was employed to incorporate the metals into the molecular sieve structure using the TEOS + sodium silicate mixture as silica source and varying Nb and Ta content in terms of Si/Me (Me = Nb and Ta) molar ratios of 60, 30 and 15 to evaluate the influence of the charge of these metals on both structural formation and properties of the material. The material was characterized by XRD, SEM, TEM, N2 adsorption, UV–Vis-DRS, and FTIR investigations to the incorporation of the metal into the MCM-41 framework. The techniques employed proved the successful replacement of Si atoms by metallic cations of Nb and Ta. The catalyst showed good structural order preservation and surface area (>600 m2 g-1) with mesoporous behavior with capillary condensation even at a higher metal load. This research signifies a successful procedure of a novel bimetallic mesoporous material with promising properties for several applications using an abundant ore as a metal source.

WC-Ni nanoparticles were synthesized using the gas-solid reaction method in a fixed-bed reactor. The studied parameters were the influence of the synthesis temperatures (800 °C, 850 °C and 900 °C), the reaction time (90 min, 120 min, and 150 min) and the nickel concentration (5 wt%Ni, 10 wt%Ni and 15 wt%Ni) on the average crystallite size by means of a 2³ factorial experimental design based on the results obtained by XRD. These powders had their chemical and morphological characteristics evaluated using XRD, BET, SEM and EDS analyzes. The XRD analysis results show that the method was effective in obtaining WC-Ni nanostructured composite powders with good particle dispersion, desired purity, mean crystallite size ranging from 24.2 nm to 38 nm, and surface area ranging from 24.6 m2/g to 46.7 m2/g. The statistical analysis showed that the synthesis temperature variable had the greatest influence on the increase in crystallite size. Furthermore, the combination of temperature and isotherm also has a relevant effect on the response variable (crystallite size).

2030 This paper presents new results for the recycling of electronic waste, specifically those from printed circuit boards (PCBs) of obsolete computers of the Federal University of Rio Grande do Norte. The main objective of this study is the comprehension of the extraction process of tin and cop per from PCBs by a hydrometallurgical route followed by electrodeposition using copper electrodes. PCBs powder were leached using 1N HNO3 and 3N HCl (aqua regia) aqueous solutions. The process permitted the extraction of all tin present on the PCBs. The electrodeposition processes were performed with currents from 0.5 to 1.5 A, at a constant time of 60 min, with and without mechanical stirring, and with different concentrations of leachate. The results showed that diluting the leachate favors the extraction of tin from the solution. At certain conditions we were able to extract approximately 100% of the tin, copper and lead present in the leachate

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International audience

The synthesis of ceramic materials such as ferrite has been widely studied in recent years, due to their properties that make these materials have excellent applications in technology, as well as in photocatalytic processes and as catalysts. To obtain the copper ferrite phase the EDTA-Citrate complexation method was used, varying pH (5, 7 and 9), temperature (600, 800 and 1000 °C) and calcination time (2, 7 and 12 h). Composition, morphology and structural analyzes were performed by X-ray fluorescence spectroscopy, X-ray dispersive energy, scanning electron microscopy and X-ray diffraction, respectively. Crystalline phase of copper ferrite (CuFe2O4) with tetragonal structure and secondary phase of Fe2O3 and CuO was verified by XRD analysis. Regarding the chemical composition analyzes, percentage deviations of the samples and the theoretical value for copper and iron were calculated. It was obtained minimum values of 0.16 - 0.08% (atomic%, EDS) and 16 - 8% (atomic%, XRF) in relation to copper and iron, respectively, for the sample obtained under pH 9, calcined at 600 °C for 12 h. The variation of the synthesis condition via EDTA-Citrate directly influenced the morphology of copper ferrite, presenting agglomerated particles, pore formation, irregular spheres, and even powder sintering.

Os corantes sintéticos apresentam uma grande aplicabilidade em diversos segmentos da indústria. Na indústria têxtil, devido às ineficiências nos processos de tingimento, 200.000 toneladas por ano desses produtos passam para o efluente industrial, sendo parte dele despejada no meio ambiente sem tratamento prévio. Quando lançados em corpos hídricos mesmo em pequenas concentrações, os corantes podem afetar o processo de fotossíntese dos organismos presentes, devido à diminuição da penetração solar, causando um desequilíbrio no ecossistema. Dessa forma, se faz necessária a realização de um método de tratamento capaz de remover esses compostos. No caso dos corantes solúveis, os processos envolvendo adsorção se mostram eficazes em sua remoção. Com isso, este trabalho tem como objetivo produzir e caracterizar carvão ativado obtido a partir do bagaço de cana-de-açúcar, determinar sua eficiência no processo de adsorção do corante Erionyl Yellow A-R, bem como utilizar técnicas estatísticascom a finalidade de avaliare otimizar os diferentes parâmetros do processo de adsorção desse corante no carvão ativado. O resultado das caracterizações do adsorvente mostrou grande presença de microporos, resultando numa área específica superior a 1200 m²g. Os ensaios de adsorção foram realizados variando-se o pH e a temperatura do meio. Através dos dados obtidos estatisticamente, verificou-se que as variáveis estudadas apresentaram efeitos significativos, dentro da faixa de níveis experimentais estudada, extrapolando a linha de referência correspondente ao intervalo de confiança de 95%. Verificou-se também que o ensaio a 30°C e pH 2 obteve a maior quantidade de corante adsorvido pelo carvão ativado (q), atingindo um valor de 61,1 mg/g Synthetic dyes are widely applicable in various industry segments. In the textile industry, due to inefficiencies in dyeing processes, 200,000 tons per year of these products mix with the industrial effluent, part of which is discharged into the environment without previous treatment. When released into water bodies, even in small concentrations, the dyes can affect the photosynthesis process of living beings, due to decreased solar penetration, causingan imbalance in the ecosystem. In this sense, a treatment method capable of removing these compounds is required. In the case of soluble dyes, the processes involving adsorption are effective in their removal. Thus, this work aims to produce and characterize activated charcoal obtained through sugarcane,determine its efficiency in the process of adsorption of Eryonil Yellow A-R, and utilize statistical techniques intended to evaluate and optimize different parameters of the process of adsorption of this dye in activated charcoal. The results of characterization of the adsorbent has indicated a large presence of micropores, resulting in a specific area greater than 1200 m2g-1. The adsorption experiments were conducted while varying the pH and temperature ofthe medium. From the statistical data analysis, it was possible to confirm that these variables presented significant effects, within confidence interval of 95%. Furthermore, the experiment at 30°C and pH 2 presented the greater amount of dye adsorbed by activated charcoal (q), reaching a value of 61,1 mg/g

International audience; The catalytic efficiency as well as the electrical conduction mechanism of Ce2(WO4)3 powders synthetized for the oxidation of methane were investigated. Total and partial oxidation reactions were observed in the temperature range between 600 and 750 °C under CH4/dry air flux, for low CH4 concentrations. The electrical conduction mechanism is based on electron tunneling at low temperature (< 650 °C) and hopping over an ion barrier at high temperature, which favors the catalytic oxidation of CH4 in air; these mechanisms occur during the partial and total oxidation under weak gas flow. The occurrence of these types of conduction mechanism was related both to the distorted monoclinic structure of Ce2(WO4)3 and to the larger structural cavities, as evidenced respectively by X-ray diffraction analyses (Rietveld analyses) and high-resolution transmission electron microscopy. The oxidation state of cerium is 3 + in the compound, as revealed by XPS investigations.

BaCeO3 has attracted great interest in research worldwide, whether doped with other elements on the site A and / or B of perovskite ABO3 or not, thus enabling its use in different applications. However, the properties exhibited by perovskite depend on partial or total replacement at the site, as well as the applied synthesis method. In this work we studied crystal structure, crystallographic parameters, morphology and textural properties of BaPrO3 perovskite synthesized by EDTA-Citrate complexation process. The adopted methodology makes it possible to obtain powders with orthorhombic crystal structure ( a=6.07 Å; b=6.3 Å e c=8.7 Å) and crystallite size of approximately 100 nm. That perovskite has dense and irregular agglomerates with surface area and pore volume of about 2.37 m2 g-1 and 0.7x10-8m3g-1, respectively. Finally, the methodology has demonstrated effectiveness in achieving crystalline phase with similar characteristics and properties obtained by different methods.

The carbides of refractory metals like tungsten carbide (WC), tantalum carbide (TaC) and niobium carbide (NbC), has been extensively studied due to their applications in several areas of industry, because of their specific properties; such as high melting point, high hardness, wear resistance, oxidation resistance and good electrical conductivity. The tungsten carbide, particularly, is generally used at hardmetal industries due to its high hardness and wear resistance. New synthesis techniques have been developed to reduce the synthesis temperature of refractory metal carbides using more reactive precursors and gas-solid reactions for carbon reduction. The result is producing pure carbides suitable properties for production of high quality cemented carbides and more selective catalysts. In this work, pure and nanostructured WC was obtained from the ammonium paratungstate hydrate (APT), at low temperature and short reaction time. Hydrogen (H2) and methane (CH4) were used as a reducing gas and carbon source, respectively. The precursor and obtained product were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results obtained by diffraction of X-rays showed that complete reduction and carburization of APT have been took place resulted in pure WC formation. The average crystallite size was in nanometer order reaching values of approximately 20.8 nm and a surface area (BET) of 26.9 m2/g.

Nanoparticles of cobalt ferrite (CoFe 2 O 4 ) were synthesized by the EDTA/Citrate complexing method and hydrothermal method without addition of surfactant. The influence of the pH of the reaction medium (8, 9 or 10), the temperature of the thermal treatment (600 °C, 800 °C or 1000 °C for the EDTA/Citrate method, and 120 °C, 140 °C or 160 °C for the hydrothermal method), and the duration of the thermal treatment (2, 4 or 6 h for the EDTA/Citrate complexing method, and 6, 15 or 24 h for the hydrothermal method) on the average crystallite size was studied by means of an experimental design based on the results obtained by XRD. Statistical analysis led to quantification of the influence of the synthesis parameters on the crystallite size of the powders. Results showed that the pH of the reaction medium is the parameter that shows the greatest influence on the growth of the crystallites of the powders obtained by the hydrothermal method, while calcination temperature is the most significant one for the powders produced by the EDTA/Citrate complexing method.

In this paper, the study of an acid and thermal treatment in a mixture of niobium and tantalum oxides obtained from columbite mineral was performed. Initially, the mineral was physically prepared by milling and sifting, followed by characterization by X-ray diffraction (XRD), X-ray fluorescence (XRF) and Scanning Electron Microscope (SEM). Subsequently, the mineral performed an acid leaching in order to remove iron and manganese present in its composition. A second acid leaching was necessary to eliminate the persistent cassiterite impurity by precipitation of Nb and Ta hydrated oxides. These oxides were characterized by XRF, XRD and SEM. Then the oxides were calcined at 800 °C, 900 °C and 1000 °C at different heating rates and calcination times to study their crystallization. The mixed oxides were characterized by XRF, XRD, SEM and nitrogen adsorption (BET method). The influence of heating rate was verified at 800 °C. An increase in crystal size was observed when the rate was reduced from 10 °C.min−1 to 5 °C.min−1. Greater crystallinity and formation of peaks related to the change of phase from hexagonal to orthorhombic were observed when the temperature was raised from 800 °C to 900 °C. At the temperature of 1000 °C, intermediate and low peaks related to formation of monoclinic phase of niobium pentoxide were observed. The change in calcination time from 5 h to 10 h at 1000 °C caused reduction in Nb2O5 to NbO2 and a decrease in crystal size and hence an increase in the surface area. The oxides heated at 900 °C showed the largest surface area.

This work reports the production of WC-10 wt%Ni nanostructured powders synthesized via carboreduction of a mixture of APT and low-temperature nickel nitrate with a short reaction time in a single synthesis process. The powders were characterized by XRD, TG/DSC, SEM, EDS, TEM and particle size analysis. The WC-10 wt%Ni powders were consolidated by the Spark Plasma Sintering process at different temperatures (1350 °C and 1450 °C). The effect of the sintering temperature on the mechanical properties and microstructure of the sintered composites was investigated through Vickers hardness and density measurements, as well as by SEM and EDS analyzes. The produced powders presented an average crystallite size of 24 nm for the WC and 41 nm for Ni. The samples sintered at 1350 °C showed the best results in terms of morphology and mechanical properties of Vickers hardness (2120 HV) and density (97.67%) when compared to samples sintered at 1450 °C which showed Vickers hardness of 945 HV and a density of 94.60%. The preparation of nanocomposite powders by carboreduction is a highly promising strategy for manufacturing hard metals by SPS, ensuring homogeneity of the phases and refined grain sizes, as well as providing good densification and excellent WC-Ni hardness.

2030 This paper proposes the synthesis characterization and factorial design for the development and composition of carbon quantum dots (CQDs). These are promising nanomaterials obtained from two renewable precursors which are biomass-derived materials namely chitin (CH), chitosan (CS), and graphite (G) as a third material used. These raw materials are low cost, non-toxic, and eco-friendly. The combination of these nanoparticles at quantum composition dots has shown promising properties of high thermal conductivity and high solar absorption. The determination of composition of (CQDs)n using 32 full factorial design with two factors at (CH/CS) ratio and mass (G) was first realized. The response surface methodology (RSM) was used to investigate the effect of band gap energy (Eband gap) engineering for semiconductor CQDs obtained via hydrothermal carbonization synthesis at 200 °C for 6 h and characterization of the composition (CQDs)9 to present Eband gap value of 3.16 eV and present the data with quantum yield of 17.1% thus promising for solar energy conversion application

Nos últimos anos, pós cerâmicos à base de óxidos de estrutura do tipo perovskita ganharam atenção considerável devido às suas aplicações tecnológicas na área de membranas permeáveis de oxigênio. O óxido misto BaCeO3 apesenta-se como um material amplamente estudado em uma grande diversidade de aplicações, seja como materiais eletrolíticos em células a combustível, ou mesmo como catalisadores nas reações de catálise. Dessa forma, o presente trabalho teve como objetivo sintetizar a fase BaCeO3, pelo método de coprecipitação em meio oxalato, verificando o efeito da sinterização com diferentes aglutinantes na estabilidade térmica e densificação da membrana. A técnica de coprecipitação em meio oxalato mostrouse eficaz na obtenção da perovskita BaCeO3. As amostras obtidas durante as sínteses foram caracterizadas por difração de raios-x, observando-se a formação da fase ortorrômbica da perovskita BaCeO3. Para determinar o tamanho médio de cristalito foi utilizada a equação de Scherrer e de Williamson Hall, chegando-se a um valor próximo a de 107 nm. Conforme a literatura [1,2] e diante dos resultados apresentados definiu-se como condições favoráveis para formação de material com o menor tamanho de cristalito e maior pureza da fase formada, a amostra de pH 13 e de temperatura de calcinação de 1000 ºC. Através da microscopia eletrônica de varredura (MEV) pode-se observar a formação de cristais homogêneos. Por fim, foi possível observar que a sinterização na presença dos aglutinantes parafina e álcool polivinílico a 1300 ºC com patamar de 5 h, permitiu a obtenção de pastilhas densas com bons níveis de retração, possuindo estabilidade térmica ideal para serem utilizadas como membranas permeáveis de oxigênio e como eletrólito de células a combustível In recent years, ceramic powders based on oxides with structure of the perovskite have gained considerable attention due their technological applications in oxygen permeable membranes. The mixed oxide BaCeO3 is introduced as a broadly studied material in a large variety of uses, either as electrolyte materials for fuel cells, or as catalysts in catalysis reactions. Thus, this study had the goal to synthesize the BaCeO3 phase by coprecipitation method amid oxalate, verifying the effect of sintering with different binders in thermal stability and densification of the membrane. The co-precipitation technique in oxalate was effective to obtain the perovskite BaCeO3. The samples obtained during the syntheses were characterized by X-ray diffraction, and it was possible to notice the formation of the orthorhombic phase of perovskite BaCeO3. To stablish the average crystallite size it was used the equation of Scherrer and Williamson Hall, coming to a value close to 107 nm As the literature [1,2] and against the results defined as favorable conditions for formation of material with the smallest size of crystallite and greater purity of the phase formed the sample pH 13 and calcination temperature of 1000° C. By scanning electron microscopy (SEM) it could be seen the formation of homogeneous crystals. Finally, it was observed that the sintering in the presence of binders paraffin and polyvinyl alcohol at 1300ºC allowed the obtaining of dense pellets with good shrinkage levels, having ideal thermal stability for use as oxygen permeable membranes and as a fuel cell electrolyte

With the increase in the national and world energy demand, we have sought the development of new processes of energy production that have a positive cost-benefit ratio with low environment risk, and that is ease for transportating and using. In recent years transitional metal carbides have received special attention in the area of heterogeneous catalysis, due to their physical and chemical properties. The molybdenum carbide (Mo2C) is an excellent low cost catalytic material. Doping it with nickel is thought to yield satisfactory catalytic activity. Thus, this work aims to develop the study of the synthesis, characterization and sintering of semiconductor materials with carbide type structure, using the gas-solid reaction method in a fixed bed reactor. The composition of the materials studied was Ni-doped Mo2C in the percentage of 5 and 10% of this dopant. This material had its chemical and morphological characteristics evaluated using the XRD, TGA, BET, dilatometry, SEM and EDS analyzes. When analyzing the results of the characterization by XRD, it was possible to identify the characteristic phases of carbides and nickel metal, in the surface area analysis for the different percentages of dopant, we can say that as the dopant content increased, an increase occurred in its surface areas. When plotting the isotherms of adsorption x dessortion and comparing with the models suggested by IUPAC, it was possible to identify that they are isotherms similar to the type II model, which characterize non-porous materials.

The catalytic efficiency of ternary strontium cerium tungstate Sr0.5Ce0.35WO4, for the production of syngas through methane oxidation, was investigated and compared to those of binary strontium tungstate SrWO4. Total and partial oxidation reactions were observed for both samples in the temperature range 600–750 °C under CH4/dry air flux. At high CH4 concentration and low temperature with the ternary tungstate as catalyst, the partial oxidation, leading to CO/H2, prevails. This indicates the potentiality of the new strontium cerium tungstate scheelite compound for the catalysis of CH4. Sr0.5Ce0.35WO4 and SrWO4 exhibit different conduction mechanisms. Conduction in the binary compound is related to the overlapping large polaron tunneling model, whereas conduction in the ternary one is due to a correlated barrier hopping phenomenon. The activation energies, in the low temperature range where the partial oxidation occurs, are significantly lower for the ternary compound than for the binary one. These electrical tendencies favor both partial and total oxidation of methane. The correlated barrier hopping conduction in the ternary compound leads to a better partial oxidation rate than conduction through large polaron tunneling.

Esta trabalho enfoca o método de síntese de coprecipitação para preparação da perovsquita SrCo0,8Fe0,2O3-d e suas caracterizações, desenvolvendo uma rota metodológica alternativa de síntese a partir da coprecipitação via meio oxalato. No intuito de verificar a influência do método, a perovsquita foi sintetizada também com base no método de complexação combinando EDTA - Citrato. Ambos os métodos de síntese permitiram obter pós monofásicos. A síntese com base no método via coprecipitação em meio oxalato permitiu obter tamanho de partículas na mesma ordem de grandeza que os obtidos a partir do método de complexação combinando EDTA – Citrato. A natureza do reagente utilizado no método via coprecipitação em meio oxalato produziu um material com aproximadamente 80 % menor em relação ao tamanho médio de cristalito. Além disso, o método via coprecipitação em meio oxalato obteve precursores em estado sólido, em baixa temperatura (~26oC), menor tempo de síntese, maior estabilidade térmica e um rendimento maior da ordem 90 a 95%, mantendo na mesma ordem de grandeza o tamanho médio de cristalito que o método de complexação combinando EDTA - Citrato This work focuses on the coprecipitation synthesis method for preparation of ceramic materials with perovskite structure and characterization, developing a methodological alternative route of synthesis from the middle via oxalate coprecipitation material SrCo0.8Fe0.2O3-. In order to check the influence of this method, it was also synthesized using a combined citrate - EDTA complexing method. Both methods led to post-phase synthesis. The synthesis based on the method via oxalate coprecipitation among particles led to the crystalline phase as those obtained using a combined citrate - EDTA complexing method under the same conditions of heat treatment. The nature of the reagent used via oxalate coprecipitation method produced a material with approximately 80 % lower than the average size of crystallites. Moreover, the via oxalate coprecipitation method precursors obtained in the solid state at low temperature (26 ºC), shorter synthesis, greater thermal stability and a higher yield of around 90-95 %, maintaining the same order of magnitude the crystallite size that the combined citrate - EDTA complexing method

The search for alternative processes for the removal of sulfur compounds in fuels is a constant, as environmental legislation around the world is becoming increasingly rigorous regarding reductions in the fraction of these compounds in fuels. This study evaluated the adsorptive capacity of zeolite ZSM-35 pure and impregnated with 2.5% and 5% molybdenum in the removal of the thiophene, organosulfur compound, of a model gasoline. The materials were prepared via wet impregnation and characterized by XRD, SEM, thermal analysis (TG/DTG). Adsorption kinetics were performed at temperatures of 303 K and 313 K in a batch system under agitation of 140 rpm for 12 hours. The kinetics of adsorption was evaluated by kinetic models of pseudo first order, pseudo second order, intraparticle diffusion and Elovich. The results showed that the increase in temperature and the concentration of molybdenum in the structure of the zeolite has an influence on the increase of the sulfur removal efficiency of the gasoline.

The use of niobium containing materials' has gained much attention of the scientific community in the late years due its various applications in diverse fields. NbC is a highly versatile material. Copper addition may alter several of its properties, such as morphology, crystal structure etc. as well as enhance its catalytic behavior. Nanostructured NbC with copper addition synthesis' presented here had the precursor [(NH4)3[NbO(C2O4)3]xH2O] as starting material, which was doped with Cu(NO3)2 at 5% and 10% (molar) ratios. Doped NbC was obtained via gas solid reaction in fixed bed reactor at lower temperature (980°C) and with shorter reaction time (2h) than traditional methods. Reaction products' were characterized by XRD, crystal sizes were estimated according to HWL method, and SEM, XRF, BET and laser particle size analysis were performed. XRD indicated the formation of NbC and Cu phases with cubic crystal structure of ~20nm. SEM showed slight morphological change upon increasing copper content, indicating a less porous structure, which is consistent with BET data (43.7m2/g for 5%Cu-NbC and 37m 2/g for the 10% Cu-NbC). Crystal size calculations showed that increasing dopant content particle sizes were also increased, probably due to the presence of the dopant, in some extent, in the crystal structure.

O carbeto de Tântalo (TaC) e um material extremamente duro, apresentando elevada dureza, elevado ponto de fusao, elevada estabilidade quimica, boa resistencia ao ataque quimico e choque termico e excelente resistencia a oxidacao e corrosao. Desta forma, este trabalho teve como objetivo a obtencao de TaC nanoestruturado a partir do precursor tris(oxalato)oxitantalato de amonio hidratado, atraves de reacao gas-solido a baixa temperatura (1000°C) e curto tempo de reacao. Os materiais obtidos foram caracterizados atraves de difracao de Raios-X (DRX), Refinamento Rietveld, Microscopia Eletronica de Varredura (MEV), Espectroscopia de Infravermelho (espectroscopia IV), Termogravimetrica (TG). Atraves das analises de DRX e do refinamento Reitiveld para o TaC com S = 1,1584 observou-se a formacao do carbeto de tântalo puro com estrutura cubica e tamanho medio de cristalitos na ordem de 12,5 nanometros

International audience; Synopsis-A new ternary scheelite tungstate (Sr,Ce)WO 4 phase was synthesized, with a 2D incommensurately modulated structure linked to partial ordering of Sr, Ce cations and vacancies as was evidenced by high resolution electron microscopy. The bang gap of 3.2 eV makes it a promising violet emitting compound. Abstract-type the Abstract here (Style: IUCr Abstract) For the first time, a ternary tetragonal scheelite structure tungstate with strontium and cerium cations,(Sr,Ce)WO 4 , was synthesized. As much as 35 % Ce could be inserted in the structure, leaving 1/7 of the (Sr,Ce) cation sites vacant. Partial ordering of Sr and Ce, with atomic displacements, were evidenced by high resolution electron microscopy. 2D incommensurate modulations occur in this material, in small domains 20 nm in size. The band gap of this compound is significantly lower than the band gap of SrWO 4 and this was related to the distortions of WO 4 and (Sr,Ce)O 8 polyhedra. The bang gap value of 3.2 eV makes Sr 1/2 Ce 5/14 □ 1/7 WO 4 a promising candidate for violet luminescence.

The objective of this work is obtaining W-30 wt% Cu composite powder from ammonium paratungstate hydrated (APT) and hydrated copper nitrate and investigating the influence of some production process parameters of W- 30 wt% Cu in particles form which results in high sinterability and densification of W-30 wt% Cu composite. To achieve this objective, the powder was obtained by manually mixing the APT and copper nitrate and reducing under a hydrogen atmosphere at 800 °C and then compacting at 500 MPa and sintering in a tubular furnace at 1200 °C for 60 minutes. The obtained materials were characterized by XRD, SEM, EDS, particle size analysis, density and microhardness measurements. The composite powder showed a good homogenization of Cu in W with very fine and agglomerated particles and a mean crystallite size of 25.64 nm. SEM coupled with EDS with mapping analysis revealed a homogeneous distribution of Cu and W in the sintered sample. The composite had a relative density of 96.77% and a microhardness of 523.66 HV. Therefore the method of obtaining the composite powder is feasible to sinter W-30 wt% Cu powder due to a greater dispersion and homogenization of phases and the average particle size.

In this work, we report the synthesis of SrWO 4 (SWO) and Ce 2 (WO 4 ) 3 (CWO) phases, based on the ethylenediaminetetraacetic–citrate complexing method. All samples were characterized by thermogravimetric analysis, X-ray diffraction and electron microscopy to identify the structure and the morphology of each compound. The catalytic reactivity of the samples was analyzed using a homemade reactor coupled to a combined system of Fourier transform infrared spectrometer (FTIR) and mass spectrometer apparatus. The measurements were performed under methane gas flows with different gas carriers (Air and Argon), in the temperature range of 500–950 °C. The catalytic activity was determined as a function of time and temperature. In specific circumstances, FTIR experiments show that methane is partly oxidized into CO thus giving rise to syngas production at low pressure. The reactivity could be linked to oxygen species delivered by solids. Electrical impedance spectroscopy analyses have been carried out on compacted polycrystalline samples, and Nyquist representations have been interpreted. The SWO and CWO samples presented similar semiconducting behaviors with electronic and ionic mix conductions, with higher conductivity for the CWO phase.