Plastic Bricks Research Articles

Spatiotemporal reaction propagation of electrochemically controlled non-linear iron current oscillator

Self-sustained non-linear electrochemical oscillation was investigated with an iron electrode under anodic polarization in an aqueous sulfuric acid solution. The propagation of the reaction front of an oxide formation and reduction along the iron wire electrode was successfully monitored by means of a 16-channel platinum potential probe array. A pulse of the current oscillation was found to consist of both a sequential propagation of the oxide reduction, which makes the rise of the current, and a random formation of the oxide at the electrode surface for the current decay. It was also shown that the traveling velocity of the oxide reduction increased as the potential of the iron electrode became more cathodic. A resistance inserted in series between an iron electrode and a potentiostat appeared to change the oscillation waveform and the propagation speed of the reduction front. When the propagation was blocked by an insulator coating or a small piece of plastic brick on the electrode, the rising current was disturbed and modulated, having independent occurrence of the reduction propagation at each separated branch of the electrode. These results suggest a coupling between the ohmic potential drop in the solution and the reaction propagation along the electrode surface.

Heating Rates in Flexible Packages Containing Entrapped Air During Overpressure Processing

ABSTRACTExperiments were performed in two steam/air retorts and one water immersion retort to test the influence of included air on heating rate index (fh) values at the center of thin plastic bricks packaged in retort pouches and processed under various temperature and overpressure conditions. In general, high air overpressures (>80 kPa) allowed up to 30 mL air to be included with no detrimental effect on heating rates; however, even small amounts of entrapped air (<5 mL) degraded heat transfer when processed at low air overpressures (<40 kPa). Processing medium and retort type were important factors in the sensitivity of heating rate to increases of air volumes beyond a threshold value.