Dispersants have a profound influence on the suspension properties of ceramic slurries. We will illustrate the effect of polymers and polyelectrolytes on the colloidal stability and the rheological properties in both aqueous and non-aqueous media. We have related direct measurements of polymerically induced interparticle forces to the rheological properties of different ceramic systems. Simple estimates of the effective volume fractions of non-aqueous, polymerically stabilized silicon nitride suspensions gave a reasonable correspondence between calculated and measured polymer layer thicknesses. We show that PAA stabilize zirconia by an electrosteric mechanism; also, we found an excellent agreement between the presence of bridging attraction and poor colloidal stability at low surface coverage. In addition, the van der Waals forces have been quantified by theoretical calculations and direct measurements.

Abstract not available.

The effect of surface treatment on the colloidal stability and rheological properties of concentrated aqueous silicon nitride suspensions has been studied. Oxidized, leached and as-received, non-treated powders were studied using electroacoustic and rheological methods. At pH=10, the silicon nitride powder is well dispersed irrespective of surface treatment. However, the viscosity was affected by the surface treatment; oxidation caused a slightly higher and leaching a significantly lower viscosity. Several possible causes of the leaching effect on viscosity was discussed, e.g. leaching causing a smooth particle surface or facilitating break-up of strong, liquid immobilizing agglomerates. Additionally, the effect of added dispersants – anionic small molecules and polyelectrolytes – were also briefly mentioned.

In this paper, Shockley-Read-Hall (SRH) lifetime depth profiles in the drift layer of 10 kV SiC PiN diodes are calculated after MeV proton implantation. It is assumed that the carbon vacancy will be the domination trap for charge carrier recombination and the SRH lifetime is calculated with defect parameters from the literature and proton-induced defect distributions deduced from SRIM calculations. The lifetime profiles are imported to Sentaurus TCAD and static and dynamic simulations using tailored lifetime profiles are carried out to study the electrical effect of proton implantation parameters. The results are compared to measurements, specializing on optimization of the trade off between on-state and turn-off losses, represented by the forward voltage drop, VT, and reverse recovery charge, Qrr, respectively. Both the simulated and measured IV characteristics show that increasing proton dose, or energy, has the effect on increasing forward voltage drop and on-state losses, while simultaneously, the localized SRH lifetime drop decreases the plasma level, increases the speed of recombination and decreases reverse recovery charge. Finally, TCAD simulations with different combinations of proton energies and fluences are used to optimize the trade-off between static and dynamic performances. Reverse recovery charge and forward voltage drops of these groups of diodes are plotted together, showing that a medium energy which induces the most defects in the depletion region relatively close to the anode gives the best dynamic performances, with a minimum cost of static performance.