A busca por melhores propriedades mecânicas e maior confiabilidade de cerâmicas à base de Si3N4 faz com que seus compósitos sejam desenvolvidos e intensivamente estudados. A maioria das pesquisas realizadas foca as interações e propriedades mecânicas obtidas, mas interações químicas entre as fases foram pouco estudadas. O objetivo deste trabalho é estudar as interações químicas que ocorrem durante a sinterização do compósito Si3N4-20%vol. TiC. A cinética de sinterização foi estudada por dilatometria, com patamar a 1750 °C/1 h em atmosfera dinâmica de N2. Os resultados de dilatometria indicam alterações na cinética de sinterização, quando comparado ao Si3N4 monolítico. Para avaliar as fases que se formam em temperaturas intermediárias, os compósitos foram tratados termicamente entre 1400 °C e 1850 °C. As amostras foram caracterizadas por difração de raios X. Foi observada a formação da solução sólida TiCN e da fase SiC.

During the last years much attention was given towards the better properties and reliability of Si3N4 based composites. Most of the research focus on the improvement of the mechanical properties but not on the chemical interaction between the phases of the composite. The purpose of this work is to study the chemical interactions between Si3N4 and TiC during the sintering process. The kinetics of sintering was studied by means of dilatometry, at 1750 °C/1 h in a dynamic atmosphere of N2. Thermal treatments were carried out in the temperature range 1400 - 1850 °C to analyze the reactions. The phases were determined by X-ray diffraction. Alterations on the sintering kinetics due to the presence of the second phase were observed. These alterations must be related to the formation of the TiCN solid solution and SiC, observed in X-ray diffraction.

The finite element discretization of the incompressible steady-state Navier-Stokes equations yields a non-linear problem, due to the convective terms in the momentum equations. Several methods may be used to solve this non-linear problem. In this work we study Inexact Newton-type methods, associated with the SUPG/PSPG stabilized finite element formulation. The resulting systems of equations are solved iteratively by a preconditioned Krylov-space method such as GMRES. Numerical experiments are shown to validate our approach. Performance of the nonlinear strategies is accessed by numerical tests. We concluded that Inexact Newton-type methods are more efficient than conventional Newton-type methods.