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-...

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The use of combustion synthesis to prepare ceramic-metal composites containing alumina and metal as well as carbide or boride was discussed by Feng et a1. l ,2 The combustion synthesis of Nb-Al intermetallics and composites containing a NbB reinforcement phase was studied. 3 Metal-ceramic composites were also prepared by the same technique. 4 A number of intermetallic compounds were produced from a mixture of metals and metal oxides 5 or from a mixture of constituent metals 6 through the use of combustion synthesis.Okabe et a1.7 investigated the fundamental aspects of synthesizing fine niobium aluminide powders from Nb 2 0 3 and aluminum powder by calciothermic reduction. A mathematical model for laser cladding by powder injection was forwarded. 8 PYROMETALLURGY Kinetics and MechanismsSohn and Aboukheshem 9 experimentally verified the rate-enhancing effect of pressure cycling on gas-solid reactions using the hydrogen reduction of porous nickel oxide pellets. Proctor et a1.10 investigated the reduction of iron oxide pellets in a CO-COz-Hz-Hp mixture. A nonisothermal technique was used to evaluate the kinetics of hydrogen reduction of molybdenum oxides. 11 The oxidation of copper concentrate particles during their downward flight in an N Z -0 2 gas stream was investigated experimentally.12 Bonsack13 studied the reaction of ilmenite with FeC1 2 vapor, producing TiCl 4 and metallic iron.The sequence of carbo thermic reduction reaction of ilmenite was established using the M6ssbauer effect. 14 The kinetics of the carbothermic .reduction of niobium pentoxide and pyrochlore concentrate in the presence of iron were studied in an argon arc plasma. ls Kale et al.I 6 determined the kinetics of carbothermic reduction of phosphogypsum. Langlais and Harris l7 extracted strontium from strontium carbonate by aluminothermic reduction.The kinetics of decarburization of iron by oxygen 18 and water vapor 19 were measured. Fruehan zo reviewed the fun-40 damentals of the reaction of FeO dissolved in slag with the carbon dissolved in iron and with coal char. The process of slag forming was also discussed. The kinetics of the reduction of FeO in slag by Fe-C drops21 and by graphitell were determined. Kulunk and Guthrie2 3 studied the kinetics of the removal of sodium from aluminum and alUminum-magnesium melts by chlorine gas. The rates of iron desulfurization using calcium carbide and lime-magnesiummixtures 24 and by CaO-CaFz based fluxes 25 were examined and reported. Phase Equilibria and ThermochemistryAtomic models of liquids and amorphous oxides of the CaO-SiOz system were constructed by continuous statistical relaxation and molecular dynamic model methods. Z6 The feasibility of evaluating the thermodynamic properties of the melts from structural data was also discussed.Sommerville and Masson z7 described how the optical basicities of individual anions in slags may be calculated. The ionic structure of cryolite-based melts was evaluated based on vapor pressure data. 2s An improved analysis of the carbonoxygen equilibrium in liqU...