• Journal of Powder Materials
• /
• v.11 no.2
• /
• pp.111-117
• /
• 2004

The oxidation behavior of 91 WC-9Co hardmetal in weight percentage has been studied in the present work as a part of the development of recycling process. The morphological and compositional changes of the WC-Co hardmetal with oxidation time at 90$0^{\circ}C$ were analyzed by using surface observation and X-ray diffraction. respective]y. As the oxidation time increased, the WC-Co hardmetal was continuously expanded to form porous oxide mixtures of $CoWO_4$ and $WO_3$. The morphology of porous oxide mixture was basically dependent on initial shape of the WC-Co hardmetal. From thermo-gravimetric (TG) analysis, it was found that the oxidation rate was increased with increasing oxidation temperature and oxygen content in the flowing atmospheric gas. The fraction of oxidation versus time curves showed S-curve relationship at a given of oxidation temperature. These oxidation behaviors of the WC-Co hardmetal were discussed in terms of previously proposed kinetic models.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.217-217
• /
• 2009

In this work, the oxidation-induced characteristics of five nuclear graphites (NBG-17, NBG-18, NBG-25, IG-110, and IG-430) were studied. The oxidation characteristics of nuclear graphites were measured at the three temperature areas (300, 600, and $900^{\circ}C$). As experimental results, the pore size of oxidized graphite was increased with increasing of oxidation time. It was also found that the oxdation rate was propotional to the oxidation temperature and time. This was probably due to the oxidation was occurred on the surface and inner bulk phase of nuclear graphites at the same time by the socalled chemical regime.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.2
• /
• pp.121-126
• /
• 2004

In this paper, the effects of the ozone oxidation of the landing polycrystalline silicon on the cell contact resistance of the DRAM device were studied. For this study, the ozone oxidation of the landing polycrystalline silicon layer was performed under various conditions, which was followed by the normal DRAM processes. Then, the cell contact resistance and $t_{WR}$ (write recovery time) of the devices were measured and analyzed. The experimental results showed that the cell contact resistance was more significantly increased for higher temperature of oxidation, longer time of oxidation, and higher concentration of ozone in the oxidation furnace. In addition, the TEM cross-sectional micrographs clearly showed that the oxide layer at the interface between the landing polycrystalline silicon layer and the plug polycrystalline silicon layer was increased by the ozone oxidation. Furthermore, the rate of the device failure due to too large write recovery time was also found to be well correlated with the increase of the cell contact resistance.

• Nuclear Engineering and Technology
• /
• v.52 no.12
• /
• pp.2880-2886
• /
• 2020

A small leak occurring on the surface of a fuel rod due to damage exposes UO₂ to a steam atmosphere. During this time, fission gas trapped inside the fuel rod leaks out, and the gas leakage can be increased due to UO₂ oxidation. Numerous studies have focused on the steam oxidation and its thermodynamic calculation in UO₂. However, the thermodynamic calculation of the UO₂ oxidation in a pressurized water reactor (PWR) environment has not been studied extensively. Moreover, the kinetics of the oxidation of UO₂ pellet also has not been investigated. Therefore, in this study, the thermodynamics of UO₂ oxidation under steam injection due to a damaged fuel rod in a PWR environment is studied. In addition, the diminishing radius of the UO₂ pellet with time in the PWR environment was calculated through an experiment simulating the initial time of steam injection at the puncture.

• Tribology and Lubricants
• /
• v.25 no.6
• /
• pp.432-437
• /
• 2009

The effect of oxidation in SAE 5W30 engine oils on friction and wear characteristics was investigated using reciprocating bench tester and shell 4-ball tester. Commercial engine oils were collected and oxidized using the KS M 2021 method modifying the oxidation time. Kinematic viscosity, total acid number(TAN), FT-IR spectrum and total base number(TBN) also measured to examine the chemical change of oils with oxidation. The results showed that TAN was slightly changed and Kinematic viscosity was suddenly increased during the oxidation stage. however, TBN results keep a constant slope after TBN linearly decreased with oxidation time. Spectroscopy results showed that spectrums were orderly increased at $1710cm^{-1}$ during the oxidation time. Friction test results showed that oxidation of oils formed unstable friction layers causing higher fluctuating friction. however, the wear resistance was independent of oxidized time due to the different friction characteristics by oxidation. We found several factors in relation to lubrication properties with oxidation time. This factors were Viscosity, TBN, change of FT-IR spectrum, friction coefficient using reciprocating bench tester and wear scar.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.4
• /
• pp.373-379
• /
• 2002

We investigated the evolution of magnetoresistance and magnetic property of tunneling magnetoresistive(TMR) device with microstructure and plasma oxidation time. TMR devices have potential applications for non volatile MRAM and high density HDD reading head. We prepared the tunnel magnetoresistance(TMR) devices of Ta($50{\AA}$)/NiFe($50{\AA}$)/IrMn($150{\AA}$)/CoFe($50{\AA}$)/Al($13{\AA}$)-O/CoFe($40{\AA}$)/FiFe($400{\AA}$)/Ta(($50{\AA}$) structure which have $100{\times}100\mu\textrm{m}^2$ junction area on $2.5{\times}2.5\textrm{cm}^2$ Si/$SiO_2$(($1000{\AA}$) substrates by an inductively coupled plasma(ICP) magnetron sputter. We fabricated the insulating layer using an ICP plasma oxidation method by with various oxidation time from 30 sec to 360 sec, and measured resistances and magnetoresistance(MR) ratios of TMR devices. We found that the oxidized sample for oxidation time of 80 sec showed the highest MR radio of 30.31 %, while the calculated value regarding inhomogeneous current effect indicated 25.18 %. We used transmission electron microscope(TEM) to investigate microstructural evolution of insulating layer. Comparing the cross-sectional TEM images at oxidation time of 150 sec and 360 sec, we found that the thickness and thickness variation of 360 sec-oxidized insulating layer became 30% and 40% larger than those of 150 sec-oxidized layer, repectively. Therefore, our results imply that increase of thickness variation with oxidation time may be one of the major treasons of the MR decrease.

• Korean Journal of Materials Research
• /
• v.24 no.7
• /
• pp.388-392
• /
• 2014

$Cu_2O$ nanowires were synthesized at large scale on copper plate by thermal oxidation in air. The effect of oxidation time and temperature on the morphology of the nanowires was examined. The oxidation time had no effect on the diameter of the nanowires, while it had a great effect on the density and the length of the nanowires. The density and the length of the nanowires increased, and then decreased, with increasing oxidation time. The oxidation temperature had a tremendous effect on the size-distribution as well as the density of the nanowires. When the oxidation temperature was $700^{\circ}C$, uniform size-distribution and high density of the nanowires was achieved. At lower and higher temperatures, the density of the nanowires was lower, and they displayed a broader size-distribution. It is suggested that the $Cu_2O$ nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the nanowires.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.171-171
• /
• 2010

In this work, we investigated the effect of the oxidation temperature on the unipolar and bipolar resistance switching behaviors of the oxidized TiO-x films. TiOx films on Pt electrodes were fabricated by the oxidation of Ti films at $550^{\circ}C$ for 1 to 3 hours. The unipolar and bipolar resistance switching properties were investigated with the oxidation temperature and time. Also, the crystal structure and the physical properties such as chemical bonding states of TiOx layers were characterized in addition to the resistance switching characteristics. The resistance switching behaviors of TiOx films oxidized at above $450^{\circ}C$ and below $650^{\circ}C$ was shown. So, we investigated that the resistance switching behaviors of TiOx films oxidized at $550^{\circ}C$ with the oxidation time from 1 to 3 hour. The memory windows of unipolar switching in the oxidized TiOx films were reduced with increasing the oxidation time, but those of the bipolar switching were slightly enlarged. The enlargement of rutile TiO2 peak with increasing the oxidation time and temperature was studied by X-ray diffraction. An increase of non-lattice oxygen and Ti3+ in the TiOx films with the oxidation times was investigated by X-ray photoemission spectroscopy. It was expected that the uipolar and bipolar resistive switching of the oxidized TiOx film was strongly related with the migration of non-lattice oxygen anions and schottky barrier height, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.429-429
• /
• 2012

To investigate the gettering effect of B-doped n-type monocrystalline silicon wafer, we made the p-n junction by diffusing boron into n-type monocrystalline Si substrate and then oxidized the boron doped n-type monocrystalline silicon wafer by in-situ wet and dry oxidation. After oxidation, the minority carrier lifetime was measured by using microwave photoconductance and the sheet resistance by 4-point probe, respectively. The junction depth was analyzed by Secondary Ion Mass Spectrometry (SIMS). Boron diffusion reduced the metal impurities in the bulk of silicon wafer and increased the minority carrier lifetime. In the case of wet oxidation, the sheet resistance value of ${\sim}46{\Omega}/{\Box}$ was obtained at $900^{\circ}C$, depostion time 50 min, and drive-in time 10 min. Uniformity was ~7% at $925^{\circ}C$, deposition time 30 min, and drive-in time 10 min. Finally, the minority carrier lifetime was shown to be increased from $3.3{\mu}s$ for bare wafer to $21.6{\mu}s$ for $900^{\circ}C$, deposition 40 min, and drive-in 10 min condition. In the case of dry oxidation, for the condition of 50 min deposition, 10 min drive-in, and O2 flow of 2000 SCCM, the minority carrier lifetime of 16.3us, the sheet resistance of ${\sim}48{\Omega}/{\Box}$, and uniformity of 2% were measured.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.20 no.2
• /
• pp.161-170
• /
• 2022

The effect of oxidation time on the characteristics and mechanical properties of spent nuclear fuel cladding was investigated using Raman spectroscopy, tube rupture test, and tensile test. As oxidation time increased, the Raman peak associated with the tetragonal zirconium oxide phase diminished and merged with the Raman peak associated with the monoclinic zirconium oxide phase near 333 cm^-1. Additionally, the other tetragonal zirconium oxide phase peak at 380 cm^-1 decreased after 100 d of oxidation, whereas the zirconium monoclinic oxide peak became the dominant peak. The oxidation time had no effect on the tube rupture pressure of the oxidized zirconium alloy tube. However, the yield and tensile stresses of the oxidized nuclear fuel cladding tube decreased after 100 d of oxidation. The results of the scanning electron microscopy and transmission electron microscopy were represented with the in-situ Raman analysis result for the oxide characteristics generated on the cladding of spent nuclear fuel.