The Continuous-flow aging system
The aging experiments on the Ag0Z in different types of gases for long times up to 6 months (10 minutes - 6 months) were performed to determine the impact of off-gas streams on the Ag0Z. The experiments were done with the experimental system shown in Figure 1. The Ag0Z was loaded into column sets, which are connected with stainless steel gas tubing in two ovens, and each column consisted of 5 sections. Each column was connected with gas-stream lines of dry-air and humid-air (d.p. -40oC, -15 oC, and +15oC), respectively. Thermocouples were placed at each stainless steel line in both ovens to monitor the gas temperature. The Ag0Z loaded into column sets dried in a N2 stream at 150 oC for 1 hour before starting the aging experiment to remove moisture and dust which may have existed in or on the Ag0Z. Each gas was passed into each column through the gas lines for the designed periods at 150oC; flow rates were controlled by mass flow controllers at 500 ml/min. Water vapor was generated by a water vapor generator (Easidew, Michell Instruments) by controlling a dew point hygrometer which can be controlled by flow rates of the dry air stream. Each of the aged Ag0Z samples were obtained after completion of aging at each desired aging time.