Water and soil are key factors in the definition of the appropriate exploration of an agricultural area. Infiltration is a dynamic process by means of which water enters the soil, both in the descending vertical as well as in horizontal direction. The knowledge of the infiltration rate in the soil is of paramount importance in order to define the conservation, planning and dimentioning of irrigation and drainage systems. Aiming at estimating the infiltration rate in a hard dystrophic yellow Latossoil in a coastal plateau area in the State of Alagoas, an experiment was carried out consisting of three different soil preparations: conventional, minimal cultivation and direct planting, in which infiltration tests were carried out in order to compare the different empirical equations models by Kostiakov, Kostiakov-Lewis and Horton. The soil had been explored with corn cultivation (Zea Mays) for several years and in 2007 soya was cultivated there. For infiltration speed rate determination, ring infiltrometer technique was adopted. When the infiltration rate obtained in the field and the different empirical models were compared, it was possible to observe that the Kostiakov model presented the best correlation being statiscally different at the 1% probability level compared to the other models, whereas the minimal cultivation presented the best infiltration rate when compared to the conventional and direct plantings, differing statically (p ≤ 0,01). / A água e o solo são fatores de suma importância para a adequada exploração de uma área agrícola. A infiltração é um processo dinâmico através do qual a água penetra no solo, tanto no sentido vertical descendente como no horizontal. O conhecimento da velocidade de infiltração da água no solo é de fundamental importância para definir os métodos de conservação, o planejamento e o dimensionamento de sistemas de irrigação e drenagem. Objetivando estimar a velocidade de infiltração, em um Latossolo Amarelo coeso distrófico em uma área de Tabuleiros Costeiros do Estado de Alagoas, foi realizado um experimento constituído de três diferentes formas de preparo de solo: convencional, cultivo mínimo e plantio direto, onde foram realizados testes de infiltração para comparar os diferentes modelos de equações empíricas de Kostiakov, Kostiakov-Lewis e Horton. O solo foi explorado com a cultura de milho (Zea mays L.) há vários anos e no ano de 2007 cultivado com soja. Foi utilizada a técnica do infiltrômetro de anéis na determinação da velocidade de infiltração. Ao serem feitas as 2 comparações entre a velocidade de infiltração obtida em condições de campo e os diferentes modelos empíricos, constatou-se que o modelo de Kostiakov foi o que apresentou a melhor correlação, diferenciando-se estatisticamente a 1% de probabilidade dos demais modelos, enquanto o cultivo mínimo foi o que apresentou a melhor taxa de infiltração quando comparado com os tratamentos convencional e plantio direto, deferindo estaticamente a 1% de probabilidade.

The effects of metastable tetragonal zirconia on the properties of Ordinary Portland Cement were observed during which the effect of crystallite size pH on the preparation solution, precursor salt, and the presence of co-precipitates, Fe(OH)3, SnO2 and SiO2 on the crystallization temperature, enthalpy and crystal structure, immediately following the crystallization exothermic burst phenomenon in ZrO2 were measured. Thermal analysis and x-ray methods were used to determine crystallite sizes and structures immediately following the exothermic burst. Comparisons were made for zirconias prepared from oxychloride, chloride and nitrate solutions. The existence of tetrameric hydroxidecontaining ions in oxychloride precursor is used to rationalise low values of crystallization enthalpy. The position of the crystallization temperature, Tmax was not dependent on crystallite size alone but also on the pH at which the gel was made, the surface pH after washing, and the presence of diluent oxides. Enthalpy v r1/2 and Tmax v (diluent vol)1/3 relationships indicate that surface coverage effects dominate a surface nucleated phenomenon. The data established for ZrO2 systems was used to develop tetragonal-ZrO2-SnO2 powders capable of improving the mechanical properties of Ordinary Portland Cement discs. The ZrO2-OPC discs were prepared by powder mixing, water hydration and uniaxial pressing. Vicat needle tests showed that tetragonal-ZrO2 increases the initial setting rate. Microscopy indicated that porosity distribution changes near to ZrO2 particles. Zirconia has also been introduced into OPC discs by vacuum infiltration methods developed for solutions and colloidal suspensions. Comparisons between OPC discs and the OPCtetragonal ZrO2 composites have been made on the basis of diametral compression strength, Young’s modulus, hardness and toughness (K1c), as estimated by the cracked indentation method. Bell-shaped curves are found for the way the mechanical properties are changed as a function of Zirconia content.

The effects of metastable tetragonal zirconia on the properties of Ordinary Portland Cement were observed during which the effect of crystallite size pH on the preparation solution, precursor salt, and the presence of co-precipitates, Fe(OH)3, SnO2 and SiO2 on the crystallization temperature, enthalpy and crystal structure, immediately following the crystallization exothermic burst phenomenon in ZrO2 were measured. Thermal analysis and x-ray methods were used to determine crystallite sizes and structures immediately following the exothermic burst. Comparisons were made for zirconias prepared from oxychloride, chloride and nitrate solutions. The existence of tetrameric hydroxidecontaining ions in oxychloride precursor is used to rationalise low values of crystallization enthalpy. The position of the crystallization temperature, Tmax was not dependent on crystallite size alone but also on the pH at which the gel was made, the surface pH after washing, and the presence of diluent oxides. Enthalpy v r1/2 and Tmax v (diluent vol)1/3 relationships indicate that surface coverage effects dominate a surface nucleated phenomenon. The data established for ZrO2 systems was used to develop tetragonal-ZrO2-SnO2 powders capable of improving the mechanical properties of Ordinary Portland Cement discs. The ZrO2-OPC discs were prepared by powder mixing, water hydration and uniaxial pressing. Vicat needle tests showed that tetragonal-ZrO2 increases the initial setting rate. Microscopy indicated that porosity distribution changes near to ZrO2 particles. Zirconia has also been introduced into OPC discs by vacuum infiltration methods developed for solutions and colloidal suspensions. Comparisons between OPC discs and the OPCtetragonal ZrO2 composites have been made on the basis of diametral compression strength, Young’s modulus, hardness and toughness (K1c), as estimated by the cracked indentation method. Bell-shaped curves are found for the way the mechanical properties are changed as a function of Zirconia content.