Abstract The sintering is an essential step in the processing of ceramics materials. A number of researchers have reported new techniques for sintering. However, in general, the process still demands high temperatures. This paper reports the results of the cold sintering of ZnO-BaTiO3 composites. The microstructural, structural, and electric properties of the composite were studied. We obtained high densities (>95%) for pure ZnO and for the composition with 10 wt% of BaTiO3 at a low temperature of sintering (250 °C/1 h). The increase of BaTiO3 content reduced the grain size and degraded the sinterability of ZnO. The crystalline structure was investigated by X-ray diffraction and confirmed the separation of the phases after the cold sintering. The BaTiO3 added in the composite reduced the values of conductivity, permittivity, and also the dielectric loss.

ABSTRACT In Brazil there is a wide availability of residues, which have been used in the production of biogas and biofertilizers. The engine-generator by biogas is grid connected, and produce electricity for self-consumption and the surplus is inserted into the grid. The aim of the present study was to evaluate energetic efficiency and exhaust gas emission of two cases: two engine-generators sets of 100 kVA running on biogas, produced from residues of a poultry slaughterhouse unit (PSU) and swine fattening unit (SFU). Load variation in the engine-generator set was evaluated in the SMCP (system of protection and synchronism). There was an increase in the emission of nitrogen oxide, sulfur dioxide and exhaust gas temperature, in both cases. The elevation in the load of the engine-generator increased its global efficiency (mechanical plus electric), with levels between 6.12% with load of 10 kW and 20.91% with 70 kW. The average specific consumption of biogas in the load of 70 kW was 0.76 m3 kWh-1 in the swine fattening unit and 0.80 m3 kWh-1 in the slaughterhouse unit with load of 70 kW. The last results show an engine-generator on biogas of 100 kVA (load of 70 kW), spent an average of 1.4 m3 of biogas to produce 1.0 kWh of electricity.

Malvasia di Candia aromatica is an aromatic white grape (Vitis vinifera L.) cultivar that grows in the Emilia-Romagna and Lombardy regions and is used for manufacturing sweet and dry white wines. A study of the gas chromatography analysis of the aromatic profile was carried out during the winemaking process for the production of a sweet semi-sparkling wine. At the end of the monitoring period, free monoterpenic and fermentative compounds characterised the aromatic profile of the wine. Linalool and nerol had a similar concentration, while the main fermentative compounds were the isoamyl alcohols, 2-phenylethanol, medium-chain fatty acids and their corresponding ethyl esters, and isoamyl acetate. All these compounds showed increasing trends during the fermentation process. The amount of linalool at the end of the monitoring period exceeded the threshold of perception, hence contributing to the floral scent of the wine. The higher alcohols (concentration up to 200 mg/L) and their esters also made a pleasant contribution to the aroma definition. Finally, the low temperature of fermentation helped to preserve the varietal aroma and enhanced the production of fermentative compounds, with a corresponding restraint of higher alcohols. This work is a first approach to a study of the sweet semi-sparkling wine (vino frizzante) obtained from Malvasia di Candia aromatica grapes. A more detailed investigation is required to understand how to improve the varietal and fermentative aromas of the wine.

São apresentados os resultados de sinterização de filmes espessos de BaTi0,85Zr0,15O3 (BTZ15), depositados pela técnica de eletroforese, utilizando como fonte de calor um laser de CO2. A montagem experimental foi otimizada de modo a permitir a sinterização de filmes com dimensões de até 70 mm de comprimento por 10mm de largura e espessuras variáveis. Os processos térmicos envolvidos durante a varredura contínua a laser atuaram de modo similar à sinterização em duas etapas. Os tempos de patamares em cada etapa foram dependentes da velocidade e do número de varreduras. A temperatura máxima que se pode atingir no filme espesso, durante cada varredura e para uma potência nominal do laser fixa, foi correlacionada com a densidade relativa. Após sinterizados, os filmes apresentaram homogeneidade microestrutural e uma porosidade aparente de ~7%.

The results for sintering of BaTi0.85Zr0.15O3 (BTZ15) thick films, deposited by electrophoresis, using as heat source a CO2 laser are presented. The characteristics of the experimental apparatus were optimized in such a way as to allow the sintering of thick films whose dimensions were up to 70 mm in length, 10 mm in width and variable thicknesses. The related thermal process during the continuous laser scanning acted in a similar way as a two-step sintering. The step times in each stage were dependent on the speed and scan number. The maximum temperature that can be achieved in the thick film, during each scanning, and for a fixed rated laser power, was correlated with the relative density. After sintering the films presented a microstructural homogeneity and an apparent porosity of ~7%.

Pós nanométricos de titanato de bário e cálcio (Ba1-xCa xTiO3: x = 0,05/0,10/0,15/0,23 mol%) foram sintetizados a temperaturas relativamente baixas (800 °C) por meio do método de precursores poliméricos modificado. Corpos cerâmicos foram obtidos com alta densidade relativa (> 97%) e microestrutura com tamanho de grãos homogêneos, a temperatura e tempo de sinterização relativamente baixos (1275 °C/1 h). Observamos também que o tamanho de cristalitos no pó calcinado e o tamanho médio de grãos nos corpos cerâmicos sinterizados diminuem com o aumento da concentração de Ca.

Barium calcium titanate nanopowders (Ba1-xCa xTiO3: x = 0.05, 0.10, 0.15 and 0.23 mol%) have been synthesized at relative low temperature ( 800 ºC) through the modified polymeric precursor method. High relative density ceramics (> 97%) and microstructure with homogeneous grain size were obtained at relative low temperature and time of sintering (1275 °C/1 h). It was also observed that the crystallite size of the calcined powder and the average grain size of the sintered ceramics decrease with the increase of the calcium concentration.

Cerâmicas de BaZrO3 foram produzidas a partir de pós sintetizados pelo método de Pechini modificado. Os pós apresentaram tamanho médio de partícula de ~130 nm e 100% de fase cristalina de BaZrO3 depois de tratados termicamente a 800 °C / 2h. Os corpos sinterizados apresentaram alta densidade relativa (98%) e tamanho médio de grão de ~1 µm, para a condição experimental otimizada de 1250 °C / 6 h, em atmosfera ambiente. As temperaturas de calcinação e sinterização, fase cristalina, densidades dos corpos cerâmicos e a microestrutura foram determinadas e comparadas com amostras de referência preparadas por reação no estado sólido.

BaZrO3 ceramics were obtained from powders synthesized by Pechini´s modified method. The powders showed average particle size of ~130 nm and 100% of crystalline phase after heat-treated at 800 °C / 2 h. The sintered ceramics presented high relative density (98%) and average grain size of ~ 1 µm for experimental condition of 1250 °C / 6 h, at ambient atmosphere. The calcination and sintering temperatures, crystalline phase, relative density and microstructure were determinate and the results were compared to a reference sample produced by solid state reaction.