Porosity elimination

Figure 10.15 Geometric constructions used to model porosity elimination, assuming (a) bulk diffusion, where the vacancies are assumed to be eliminated at the grain surface, and (6) grain boundary diffusion, where vacancies are restricted to diffusing along a grain boundary of width gb-...

Technological characteristics of the oxide films, in particular adhesive, protective, and dielectric properties, are determined by the porosity of the films. Decreasing porosity and complete porosity elimination, which improves film characteristics, can be achieved by optimization of the amplitude, duration, and frequency of the voltage pulses, as well as the current density. 

Elimination. Porosity in general can be minimized by using clean, dry materials and by properly controlling weld current and arc length. 

In general, fungal mycelia are filtered relatively easily, because mycelia filter cake has sufficiently large porosity. Yeast and bacteiia are much more difficult to handle because of thefr small size. Alternative filtration methods, which eliminate the filter cake, are becoming more acceptable for bacterial and yeast separation. Micro-filtration is achieved by developing large cross-flow fluid velocities across the filter surface while the velocity vector normal to the surface is relatively small. Build up of filter cake and problems of high cake resistance are therefore prevented. Micro-filtration is not discussed in this section. 

Economically, the elimination of lead and nickel emissions will result in an improved product because exposure of the metal to combustion gases in the current process results in porosity and entrainment of hydrogen gas in the metal. Overall, AMPCO estimates an annual savings in operations and maintenance expenses of USD 1.2 million with the use of this technology. Assuming the same 70% industry adoption, economic savings by 2010 could reach USD 5.8 million. Without the new electric induction heating process, the capital costs required for compliance could be USD 3 million. 

The vacuum extruder was developed to eliminate unwanted gases from rubber compounds, so that the profiles produced from rubber stocks could be vulcanised at atmospheric pressure without problems of porosity occurring. Removal of the volatiles is achieved in principle by combining the actions of two individual machines in series, into one machine. The first part of the extruder screw... 

General Aspects and Heat Treatment Effects. After him formation, for most of the hlms aimed at electronic applications (other than amorphous oxides, such as Si02), the hlms are subjected to a heat treatment process for removal of residual organic species (entrapped solvent as well as the organic constituents associated with the precursor species), densihcation (elimination of residual porosity and structural free volume in the him), and crystallization. 

---