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The oxidation of pure copper in oxygen with and without water vapor was investigated as a function of temperature, oxygen pressure, and water vapor pressure using thermogravimetric analysis. The rate of the oxidation was increased with increasing temperature from 500 to 700°C and followed by the parabolic rate law regardless of the presence of water vapor. The activation energy for the oxidation was 90.67 kJ/mol in dry oxygen and 95.86 kJ/mol in oxygen with water vapor. The change of oxygen pressure without water vapor does not affect the oxidation rate at given temperatures. However, increasing water vapor pressure from 0.39 to 0.58 atm resulted in higher oxidation rate due to the increase of copper vacancies. CuO whiskers were observed and their growth seems to be enhanced by the presence of water vapor.KEY WORDS: oxygen pressure; water vapor pressure; parabolic rate law; activation energy; CuO whisker.by scanning electron microscope (SEM) and X-ray diffraction (XRD). Experimental Experimental ProcedureA copper foil (99.99 % Cu) was purchased and was cut to make coupon specimens with a dimension of 1.5 cm in width and 2 cm in length. Before oxidation, the specimens were polished with SiC-paper in the order of size, 320, 500, 800, 1 200, 2 400, and 4 000, and then subsequently polished with diamond polishing suspension of grade 1 mm. After polishing, the specimens were cleaned in an ultrasonic cleaning bath with acetone.The oxidation of copper was carried out using thermogravimetric apparatus as shown in Fig. 1. The oxidizing gas mixture was passed through drierites to remove moisture before flowing into the reactor tube. Copper turning furnace was installed to reduce oxygen impurity in argon gas prior to passing through the reaction zone. The oxidizing gas mixture flows to the reaction zone from the bottom of the quartz tube, while purified argon gas flow is maintained through the electrobalance during the oxidation. A copper coupon specimen is suspended with a platinum wire in the reaction zone of the quartz tube and then heated up in ultrahigh pure argon. Once the desired temperature was reached, a mixture of reaction gases was introduced into the reaction tube until oxidation tests were finished. Oxygen partial pressure was controlled by mixing argon and oxygen. Continuous Oxidation with Water VaporThe oxidation of copper was also carried out in the presence of water vapor and the experimental apparatus consisted of thermogravimetric apparatus and heat-circulating bath which supplies water vapor continuously. A flask bottle containing water was placed in the bath and remained at constant temperature during the oxidation. Heating tapes were put on the top and bottom of the reactor tube as well as copper tubing between the reactor and the flask bottle. Some alumina balls were placed at the bottom of the reaction tube to mix the reaction gases. The gas mixture of oxygen and argon after passing through a mixing chamber were passed through water. A copper specimen placed in the reaction zone was heated in ultra-...

Oxidation behavior of low carbon steel was investigated in oxygen and water vapor using continuous thermogravimetric analysis (TGA). The effect of temperature, oxygen pressure, and water vapor content on the oxidation of the steel was studied. The morphology, composition, and microstructure of oxides formed in moist atmosphere were examined and analyzed by X‐ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X‐ray analysis (EDX). The oxidation mechanism was discussed based on oxidation rate, oxide defects, and microstructure of the substrate and oxide layers.

The metallic tantalum powder was successfully synthesized via reduction of tantalum pentoxide (Ta2O5) with magnesium gas at 1073~1223 K for 10 h inside the chamber held under an argon atmosphere. The powder obtained after reduction shows the Ta–MgO mixed structure and that the MgO component was dissolved and removed fully via stirring in a water-based HCl solution. The particle size in the tantalum powder obtained after acid leaching was shown to be in a range of 50~300 nm, and the mean internal crystallite sizes measured by the Scherrer equation varied from 11.5 to 24.7 nm according to the increase in reduction temperatures. The temperature satisfactory for a maximal reduction effect was found to be 1173 K because the oxygen content was minimally saturated to about 1.3 wt %.

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