• Journal of Magnetics
• /
• v.11 no.3
• /
• pp.108-110
• /
• 2006

We successfully enhanced the performance of a spin valve by inserting an ultra-thin layer of partially oxidized Fe in the pinned and free layers. With the exchange bias field kept large, the spin valve reached a GMR of 12%, which corresponded to a 55% increase in GMR when we compared it with that of spin valves without any inserted layer. The layer of partially oxidized Fe was more effective for improving the properties of the spin valve than the layer of partially oxidized $Co_{90}Fe_{10}$. Considering all the results, we can contribute the significant improvement to the combined effect of the modified local electronic structures at the Fe impurities and theenhanced spin-dependent reflections at the $\alpha-Fe_{2}O_{3} phase in the magnetic layer.

• Journal of the Korean Ceramic Society
• /
• v.43 no.12 s.295
• /
• pp.805-811
• /
• 2006

The microstructural changes in Ni/YSZ anode substrate and crack formation during Ni oxidation were investigated. The composition of as-sintered anodes was 56 wt% NiO+44 wt% YSZ and that of electrolyte was 8 mol% yttria. After complete reduction, specimens were oxidized in $N_2$ + air at $600\sim800^{\circ}C$. Oxygen partial pressure was controlled in between 0.05 atm and 0.2 atm $O_2$. When the anode was oxidized, at higher than $690^{\circ}C$, three layers were formed in the specimens. The first was fully oxidized layer(NiO/YSZ), the second was a mixed layer and the third, near-intact layer. Under $640^{\circ}C$ such distinctive layers were not observed. Cracks formed at electrolyte layer when weight gain attained at $65\sim75%$ of the total gain due to complete oxidation despite of different oxidation temperature and oxygen partial pressure.

• Korean Journal of Food Science and Technology
• /
• v.33 no.2
• /
• pp.216-220
• /
• 2001

This study was conducted to examine the effect of oxidized cellulose that had been selectively oxidized with TEMPO(2, 2, 6, 6-tetramethyl-1-piperidine oxoammonium ion), NaBr and NaOCl substituting for 10% of the wheat flour in a yellow layer cake formula. Physicochemical and sensory characteristics of a cake containing oxidized cellulose were compared with a control cake and a cake containing non-oxidized cellulose(CNC). The cake sample with oxidized cellulose(COC) had smaller L and a values and greater b value than the control, with a greater cake volume. Results of sensory evaluation showed that grittiness of COC was about the same as that of the control, but weaker than that of CNC, and COC was more moist and less hard than the control. These observations indicated the possibility that the oxidized cellulose could be used as a dietary fiber in a cake without causing detrimental effect on textural characteristics.

• Transactions on Electrical and Electronic Materials
• /
• v.7 no.1
• /
• pp.16-20
• /
• 2006

In this paper, we investigated the effects of short-term oxygen plasma treatment of semiconducting silicone layer to improve interfacial performances in joints prepared with a insulating silicone materials. Surface characterizations were assessed using contact angle measurement and x-ray photoelectron spectroscopy (XPS), and then adhesion level and electrical performance were evaluated through T-peel tests and electrical breakdown voltage tests of treated semi-conductive and insulating joints. Plasma exposure mainly increased the polar component of surface energy from $0.21\;dyne/cm^2$ to $47\;dyne/cm^2$ with increasing plasma treatment time and then leveled off. Based on XPS analysis, the surface modification can be mainly ascribed to the creation of chemically active functional groups such as C-O, C=O and COH on semi-conductive silicone surface. This oxidized rubber layer is inorganic silica-like structure of Si bound with three to four oxygen atoms ($SiO_x,\;x=3{\sim}4$). The oxygen plasma treatment produces an increase in joint strength that is maximum for 10 min treatment. However, due to brittle property of this oxidized layer, the highly oxidized layer from too much extended treatment could be act as a weak point, decreasing the adhesion strength. In addition, electrical breakdown level of joints with adequate plasma treatment was increased by about $10\;\%$ with model samples of joints prepared with a semi-conducting/ insulating silicone polymer after applied to interface.

• Nuclear Engineering and Technology
• /
• v.52 no.9
• /
• pp.2054-2063
• /
• 2020

The high-temperature oxidation behavior of ZrSi₂ used as a coating material for nuclear fuel cladding was investigated for developing accident-tolerant fuel cladding of light water reactors. Bulk ZrSi₂ samples were prepared by spark plasma sintering. In situ X-ray diffraction was conducted in air at 900, 1000, and 1100 ℃ for 20 h. The microstructures of the samples before and after oxidation were examined by scanning electron microscopy and transmission electron microscopy. The results showed that the oxide layer of zirconium silicide exhibited a layer-by-layer structure of crystalline ZrO₂ and amorphous SiO₂, and the high-temperature oxidation resistance was superior to that of Zircaloy-4 owing to the SiO₂ layer formed. ZrSi₂ was coated on the Zircaloy-4 tube surface using laser 3D printing, and the coated tube was oxidized for 2000 s at 1200 ℃ under a vapor/argon mixture atmosphere. The outer surface of the coated tube was hardly oxidized (10-30 ㎛), while the inner surface of the uncoated tube was significantly oxidized to approximately 300 ㎛.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.4
• /
• pp.218-224
• /
• 2016

The surface of Mg alloy, AZ31 and AZ91, were treated by PEO (plasma electrolytic oxidation) in Na-P system electrolyte, with different applied voltage and time. Thickness, roughness and X-ray crystallographic analysis revealed several results. The more applied time and voltage of PEO treated, the thicker oxidized surface coating layer were covered. And surface roughness increased with the thickness of oxidized layer. It was thought that when oxide layer grew, resistivity and breakdown voltage increased with the thickness of layer, and then, the energy of micro plasma need to be higher then before. So, it made craters and pores of surface become greater, which were responsible for the coarse surface.

• Journal of the Korean institute of surface engineering
• /
• v.47 no.2
• /
• pp.93-98
• /
• 2014

The $Cr_2AlC$ carbides oxidized at 700, 850 and $1000^{\circ}C$ in air from 70 hours up to 360 days. They oxidized according to the reaction; $Cr_2AlC+O_2{\rightarrow}{\alpha}-Al_2O_3+CO(g)$. The scales consisted primarily of the thin, essentially pure $Al_2O_3$ layer and the underlying Al-dissolved $Cr_7C_3$ layer. They grew via the outward diffusion of Al and carbon, and the inward diffusion of oxygen. The oxidation resistance of $Cr_2AlC$ was excellent due to the formation of the protective $Al_2O_3$ layer. Even when $Cr_2AlC$ oxidized at $1000^{\circ}C$ for 360 days, the ${\alpha}-Al_2O_3$ layer was only about 4 ${\mu}m$-thick.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.4
• /
• pp.1033-1040
• /
• 1995

To simulate strength reliability and durability of ceramic parts under gas turbine application environments, particle impact damage behaviors in silicon carbide oxidized at 1673 K and 1523 K for 200 hours in atmosphere were investigated. The long-term oxidation produced a slight increase in the static fracture strength. Particle impact caused a spalling of oxide layer. The patterns of spalling and damage induced were dependent upon the property and impact velocity of the particle. Especially, the difference in spalling behaviors induced could be explained by introducing the formation mechanism of lateral crack and elastic-plastic deformation behavior at impact sit. At the low impact velocity regions, the oxidized SiC showed a little increase in the residual strength due to the cushion effect of oxide layer, as compared with the as-received SiC without oxide layer.

• ETRI Journal
• /
• v.26 no.4
• /
• pp.315-320
• /
• 2004

This paper proposes a 10-${\mu}m$ thick oxide layer structure that can be used as a substrate for RF circuits. The structure has been fabricated using an anodic reaction and complex oxidation, which is a combined process of low-temperature thermal oxidation (500 $^{\circ}C$ for 1 hr at $H_2O/O_2$) and a rapid thermal oxidation (RTO) process (1050 ${\circ}C$, for 1 min). The electrical characteristics of the oxidized porous silicon layer (OPSL) were almost the same as those of standard thermal silicon dioxide. The leakage current density through the OPSL of 10 ${\mu}m$ was about 10 to 50 $nA/cm^2$ in the range of 0 to 50 V. The average value of the breakdown field was about 3.9 MV/cm. From the X-ray photo-electron spectroscopy (XPS) analysis, surface and internal oxide films of OPSL prepared by a complex process were confirmed to be completely oxidized. The role of the RTO process was also important for the densification of the porous silicon layer (PSL) oxidized at a lower temperature. The measured working frequency of the coplanar waveguide (CPW) type short stub on an OPSL prepared by the complex oxidation process was 27.5 GHz, and the return loss was 4.2 dB, similar to that of the CPW-type short stub on an OPSL prepared at a temperature of 1050 $^{\circ}C$ (1 hr at $H_2O/O_2$). Also, the measured working frequency of the CPW-type open stub on an OPSL prepared by the complex oxidation process was 30.5 GHz, and the return was 15 dB at midband, similar to that of the CPW-type open stub on an OPSL prepared at a temperature of $1050^{\circ}C$ (1 hr at $H_2O/O_2$).

• Journal of the Korean Society for Heat Treatment
• /
• v.30 no.5
• /
• pp.207-214
• /
• 2017

In this study, failure behavior of piercing plug for seamless tube manufacturing process was studied. Three different kinds of passed piercing plugs (10, 90, 215 times) were prepared. The shape deformation of the passed piercing plugs was observed by 3D coordinate measuring machine, and the oxidized layer on the surface of piercing plug was observed by optical microscopy. The length reduction of piercing plug presented at 215 times passed plug. It was found that the oxidized layer consisted of outer scale, inner scale and internal oxidation layers, and the inner scale layer had vertical cracks, and interfaces had horizontal cracks. We proposed the failure mechanism of piercing plug during seamless tube manufacturing process based on the formation of vertical and horizontal crack.