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Numerical simulations of epitaxial growth in MOVPE reactor as a tool for aluminum nitride growth optimization

100%

Skibinski J. , Caban P. , Wejrzanowski T. , Grybczuk M. , Kurzydlowski K. J.

tom Vol. 96, nr 2

110--114

The present study concerns numerical simulations and experimental measurements on the influence of inlet gas mass flow rate on the growth rate of aluminum nitride crystals in Metalorganic Vapor Phase Epitaxy reactor model AIX-200/4RF-S. The aim of this study was to design the optimal process conditions for obtaining the most homogeneous product. Since there are many agents influencing reactions relating to crystal growth such as temperature, pressure, gas composition and reactor geometry, it is difficult to design an optimal process. Variations of process pressure and hydrogen mass flow rates have been considered. Since it is impossible to experimentally determine the exact distribution of heat and mass transfer inside the reactor during crystal growth, detailed 3D modeling has been used to gain insight into the process conditions. Numerical simulations increase the understanding of the epitaxial process by calculating heat and mass transfer distribution during the growth of aluminum nitride crystals. Including chemical reactions in the numerical model enables the growth rate of the substrate to be calculated. The present approach has been applied to optimize homogeneity of AlN film thickness and its growth rate.

Rheology of concentrated suspensions of plasma-processed fine alumina

100%

Jakobsons E. , Faitelson L. , Palcevskis E.

2003

tom Vol. 8, no spec.

251-258

The rheological properties (flow curves and viscoelastic behavior) of the injection-moulded suspensions prepared from two nanosized plasma-processed Al2O3 powders and water were investigated on wide ranges of shear rates and frequencies . Tiron (disodium salt of 4,5-dihydroxy-1,3-benzene-disulfonic acid) was chosen as a surfactant for preparation of the concentrated alumina suspensions. It is stated that, at an optimal Tiron content in suspensions, their viscosity, yield stress, and complex shear modulus have minimal values. A correlation was shown to exist between the optimal concentration of the dispersant obtained by rheological tests on the alumina powder water suspensions and the mentioned optimal concentration determined by measuring the zeta potential.