Abstract The electrokinetic process seems to be interesting to the earthwork portion on the construction of buildings, and transportation projects since this simple, fast, yet reliable technique could expedite dehydrating of soil and reduce delays in the construction schedule. This paper examined the technical feasibility and a brief cost analysis of using plastic electrodes for electrokinetically dehydrating clayey soils with high moisture content were also carried out. The results from the experimental program carried out on a marine clayey soil with copper and plastic electrodes showed a great deal of soil improvement since positive changes in undrained shear strength occur due to the free water dehydration process induced by electro-osmosis and to the adsorbed water dehydration process induced by electromigration. It was also observed that values of the undrained shear strength remained stable at the final stages of the electrokinetic process indicating a permanent soil improvement. Finally, it was noticed that dehydrating could be achieved at lower costs by employing plastic electrodes. buildings simple fast schedule electroosmosis electro osmosis electromigration Finally

The present work briefly reviews the convolution of crystallite shape functions and discusses its experimental limitations. The diffraction from a theoretical spherical shape powder is used to exemplify the limits of the convolution procedure. Mean lattice distortions were not considered since the discussed limitations are inherent to the convolution method using Fourier transforms. The diffraction pattern and the convolution were calculated using appropriate macros for the Topas program. It is shown that very small crystallites require a large 2θ convolution span and the smallest subdivision for the distribution will depend on this convolution span. To show the importance of the convolution limits and its application, the nanocrystalline CeO2 round-robin diffraction pattern was evaluated. The chord frequency distribution by XRD showed conformity with the chord distribution calculated from a grain size histogram obtained by transmission electron microscopy for this sample.

RESUMO Este trabalho compara as propriedades de diversos óxidos transparentes condutores para serem utilizados como contatos frontais de células solares de filmes finos de CdTe. Os filmes foram depositados à temperatura ambiente, por pulverização catódica com rádio frequência, sem tratamento térmico posterior, com o objetivo de reduzir o número de etapas do processo de fabricação. A relação resistência/transmitância foi avaliada através de uma figura de mérito, de forma a propor os materiais candidatos a atuar como eletrodo frontal da célula solar. Os óxidos investigados foram divididos em dois grupos: os de baixa resistividade e os de alta resistividade. Eletrodos fabricados com os diversos óxidos foram submetidos a testes de estabilidade térmica nas temperaturas de processamento da célula solar. Os resultados mostraram que os filmes de ZnO e Zn2SnO4 são óxidos de alta resistividade (> 0,5 (.cm), enquanto que os de SnO2, In2O3, In2O3:Sn, Cd2SnO4 e ZnO:Al são de baixa resistividade (< 5,0 x 10-3 (.cm) e alta transmitância (> 85%). Os filmes de In2O3:Sn e ZnO:Al apresentaram-se como as melhores opções para fabricação dos eletrodos, pois possuem resistividades na faixa de 10-3-10-4 (.cm e transmitâncias entre 85-92%. No entanto, levando-se em consideração questões de custo e escassez associadas ao índio, filmes de ZnO:Al são os mais adequados para esta aplicação, pois além de possuírem valores de condutividade e transmitância elevados, apresentaram elevada estabilidade térmica nas temperaturas de processamento da célula.

ABSTRACT This work compares the properties of different transparent conducting oxides for use as frontal contact in CdTe thin films solar cells. The films were deposited at room temperature by radio frequency sputtering without heat treatment, in order to reduce the manufacturing process steps. The resistance/transmittance relation was evaluated using a figure of merit, in order to propose the best material to act as front electrode of the solar cell. The oxides investigated in this work were separated into two groups: low-resistivity and high-resistivity oxides. Electrodes were prepared with these oxides and were subjected to thermal stability tests at the elevated temperatures involved in the solar cell processing. The results showed that ZnO and Zn2SnO4 films are high-resistivity oxides (> 0,5 (.cm), while SnO2, In2O3, In2O3:Sn, Cd2SnO4, and ZnO:Al are low-resistivity (< 5,0 x 10-3 (.cm) and high transmittance (> 85%) oxides. The In2O3:Sn and ZnO:Al films were the best options for the production of the electrodes, as their resistivity and transmittance values ranged from 10-3-10-4 (.cm and 85-92%, respectively. However, taking into consideration the cost and shortage issues, ZnO:Al films are the suitable choice for this application, because in addition to having high values of conductivity and transmittance, they have demonstrated thermal stability at elevated temperatures.

The present work uses multivariate statistical analysis as a form of establishing the main sources of error in the Quantitative Phase Analysis (QPA) using the Rietveld method. The quantitative determination of crystalline phases using x ray powder diffraction is a complex measurement process whose results are influenced by several factors. Ternary mixtures of Al2O3, MgO and NiO were prepared under controlled conditions and the diffractions were obtained using the Bragg-Brentano geometric arrangement. It was possible to establish four sources of critical variations: the experimental absorption and the scale factor of NiO, which is the phase with the greatest linear absorption coefficient of the ternary mixture; the instrumental characteristics represented by mechanical errors of the goniometer and sample displacement; the other two phases (Al2O3 and MgO); and the temperature and relative humidity of the air in the laboratory. The error sources excessively impair the QPA with the Rietveld method. Therefore it becomes necessary to control them during the measurement procedure.

The production of bulk Bi2+xSr3-yCa yCu 2O8+delta (Bi-2212) superconductors for fault current limiter application was developed via a partial-melting route. Aiming high Ic (critical current), which is the essential superconducting characteristic for application of this material in the construction of Fault Current Limiters (FCL), the produced blocks have predominance of Bi-2212 phase (83 wt%), which characterizes with high values of zero and onset transport critical temperature of 92K and 97.5K, respectively. A relatively low transition width, deltaT, from the superconducting to the normal state of 5.5K, revealed a good intergrain connectivity. Consequently, current measurements on the blocks of Bi-2212 show promising Ic values of 230A and 850A for direct and alternate current, respectively. It is expected that further increases in the Ic values will depend on the elimination of an observed amorphous phase and further reduction of amount and grain sizes of secondary phases, still present in the blocks obtained by the proposed partial-melting route. This may be achieved by a further optimization of the partial-melting processing parameters.

The fundamental parameters approach is used to simulate the instrument contribution to the X-Ray diffraction profile. This procedure eliminates the need to experimentally prepare a reference sample of the studied crystalline material when using the Warren-Averbach method to investigate microstrutural parameters. The Warren-Averbach method is also compared to the Balzar and Enzo methods, two other popular methods of size-strain analysis. The analysis was carried out using bohmite powder having two different nominal average crystallite sizes, 80 Å and 200 Å. A 50%-50% mixture of these materials was used as a third sample. The proposed simulation procedure provides good results and is much faster to implement than the usual procedure that includes the preparation of a reference. For larger crystallite sizes, the results calculated from the Warren-Averbach method for the volume-weighted average crystallite size differs significantly from the ones obtained from the Balzar and Enzo methods. The limitations of the Balzar and Enzo methods are also discussed.