This paper aims to evaluate the synthesis and annealing parameters for production of nanometric Bi4Ti3O12 and its properties. The powders were obtained through the solution combustion route and the impacts of annealing temperature on the materials’ physicochemical features as well as their optical and electrical properties were investigated. Thus, the prepared powders were annealed at 600ºC, 700ºC and 800ºC and then characterized by several techniques. The results demonstrated that the combustion method was effective for production of nanocrystalline powders with high levels of purity. A trend for particle and crystallite growth was observed as the calcination temperature increased. X-Ray, HRTEM and Raman spectroscopy confirmed the crystalline nature of the powders, whereas impedance spectroscopy demonstrated a reduction of electrical resistance according to the calcination temperature applied. Optical properties were not highly influenced by annealing. The temperature of 600ºC was appropriate to produce crystalline particles with desirable low sizes for application.

This paper describes the development of TiO2 and ZnO particles by a chemical route, using two different wet synthesis methods: polymeric precursor (PP) and sol-gel (SG). This study aimed to shed a light on how the synthesis method affects the photocatalytic activity of these oxides. Rhodamine B (RhB) degradation was used as a probe reaction to test the as-synthesized TiO2 and ZnO photoactivity. It was observed that surface availability, which is related to the presence of synthesis residue, is the key parameter to determine photoactivity. ZnO PP and ZnO SG presented degradation of 88% to RhB. Both samples presented synthesis residue on the surface. On the other hand, TiO2 PP presented a better performance than TiO2 SG, once 90% of RhB was degraded, while TiO2 SG degraded 80% of the dye. In this case, TiO2 PP was free of synthesis residue on the surface, while TiO2 SG presented residues.

A solubilização do calcário no solo, sem o que não ocorre neutralização da acidez, demanda tempo e exige incorporação para aumentar o contato entre o corretivo e os colóides do solo. Com o objetivo de avaliar a correção da acidez do solo em função de diferentes modos de incorporação de calcário, foi conduzido um experimento, no ano agrícola 1993/94, em um Latossolo vermelho-escuro, distrófico, de campo nativo, do município de Ponta Grossa (PR). O delineamento experimental empregado foi o de blocos ao acaso, em parcelas subdivididas, com três repetições. Os tratamentos foram constituídos por cinco modos de incorporação: arado de discos mais duas gradagens, grade aradora mais duas gradagens, enxada rotativa, arado escarificador mais duas gradagens e distribuição na superfície sem incorporação, e por quatro doses de calcário dolomítico: 0, 2,8, 6,6 e 10,3 t ha-1, visando a elevar a saturação por bases do solo a 30, 60 e 90%. A planta teste utilizada foi o milho. Verificou-se que o modo de incorporação do corretivo no solo afeta a sua eficiência em relação à profundidade no perfil, na qual há neutralização da acidez. Houve elevação da saturação por bases do solo até a camada de 20cm, 15cm e 10cm, respectivamente, para os seguintes modos de incorporação: enxada rotativa, arado de discos ou grade aradora e arado escarificador ou calcário distribuído na superfície sem incorporação. Os valores de saturação por bases desejados não foram alcançados, três meses após a calagem, independente do modo de incorporação de calcário.

The solubilization of lime in soil, without which the acidity neutralization does not occur, demands time and requires incorporation for increasing the contact between lime and soil coloides. In order to study the correction of soil acidity in function of lime incorporation manners, a field experiment was carried out, in Ponta Grossa, State of Paraná, Brazil, in a dystrophic Dark Red Latosol, in native field. A randomized complete block design was used, with three replications, in a split-plot experiment. The treatments consisted of five incorporation methods: disk plowing plus two spring disk harrowing, off-set harrowing plus two spring disk harrowing, rotary tilling, chisel plowing plus two spring disk harrowing and lime distribution on the surface without incorporation (main plots), and four rates of dolomitic limestone: 0, 2.8, 6.6 and 10.3 t ha-1, in order to raise base saturation of soil to 30, 60 and 90% (subplots). The cultivated plant was maize. The results showed that the lime incorporation manner in the soil affects its efficiency in relation to the depth in the profile in which there is neutralization of the acidity. There was elevation in base saturation of the soil to the layer of 20cm, 15cm and 10cm, respectively, for the following incorporation manners: rotary tilling, disk plowing or off-set harrowing and chisel plowing or lime distribution on the surface without incorporation. The saturation values for wanted bases were not reached, three months after liming, independent in the incorporation manner of lime.