• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.182-182
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• 1999

The chemisorption effect of CO on the Ni/Cu(001) surface was investigated using LEED(Low Energy Electron Diffraction) and EELS(Electron Energy Loss Spectrscopy0 under the UHV conditions. after mounting the Cu(001) single crystal in the UHV chamber (base pressure 1$\times$10-10Torr), a clean surface was obtained after a few cycles of repeated Ar+ ion sputtering and annealing at about 40$0^{\circ}C$. The epitaxial thin Ni films were formed on the Cu(001) by evaporation from 99.999% Ni block. The pseudomorphic growth and the orderness of the thin Ni films were monitored by c(2$^{\circ}C$2) LEED pattern. CO adlayers on Ni epitaxial thin films were prepared by dosing pure CO has through a leak valve. After CO adsorpton at room temperature, two pairs of peaks were observed by EELS, whose relative intensities are changed as the film thickness is varied and time is elapsed. These two pair of peaks are likely related to different bonding sites (-top and bridge sites) of C-Ni as well as C-O vibration. Experimental results and qualitative interpretation of the spectra wille be discussed. The possibility of using EELS in combination with probe species (CO) to investigate the nature of thin film growth is mentioned. We will report the experimental result of O2 dosage on Ni film and interaction of CO and O2.

• Journal of architectural history
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• v.19 no.4
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• pp.71-90
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• 2010

The names of Seokgatab and Dabotab are almost generalized among the people along with Bulguksa the most well-known temple in Korea. But, despite this generalized situation, the names of Seokgatab and Dabotab have not secured the clear standpoint till now. It is because the names of Seokgatab and Dabotab can be found only in the 18C documents like and . More complicatedly, in the record of the Goryeo sarira case found during the dismantling of Seokgatab, the name of Seokgatab was 'Mugujeonggwangtab' or 'Seoseoktab'. This paper is to secure the nominal validity of Seokgatab and Dabotab to remove the confusion due to their names and to raise the efficiency of studies related with Bulguksa in the future. First, their names and the problems related with them were summarized in Chapter 2. Based on this critical consciousness, Chapter 3 deals with the tragedy of Asadal related with the creation of the stone pagodas and its symbolic re-interpretation. In this process, we can see that there could be a viewpoint of the great comprehension in them through the completion of 'the Buddhist Nation'. Then, the architectural features of Seokgatab and Dabotab were analyzed in the ritual view point of . Finally, in Chapter 4, on the basis that the viewpoint of one specific sect can not be predominantly applied in the construction of Buddhist land, it is held that Avatamsaka Idea and Saddharma-pundarika Idea can coexist without any conflict. It is shown in the fact that Seokgatab and Dabotab can make harmony together in the Avatamsaka Idea while keeping their names. With these efforts, we can clearly see that the peculiar titles of Seokgatab and Dabotab can be said to secure sufficient validity.

• Korean Journal of Materials Research
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• v.28 no.2
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• pp.108-112
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• 2018

The present study demonstrates the effect of raw powder on the pore structure of porous W-Ni prepared by freeze drying of camphene-based slurries and sintering process. The reduction behavior of $WO_3$ and $WO_3-NiO$ powders is analyzed by a temperature programmed reduction method in Ar-10% H2 atmosphere. After heat treatment in hydrogen atmosphere, $WO_3-NiO$ powder mixture is completely converted to metallic W without any reaction phases. Camphene slurries with oxide powders are frozen at $-30^{\circ}C$, and pores in the frozen specimens are generated by sublimation of the camphene during drying in air. The green bodies are hydrogen-reduced at $800^{\circ}C$ and sintered at $1000^{\circ}C$ for 1 h. The sintered samples show large and aligned parallel pores to the camphene growth direction, and small pores in the internal wall of large pores. The strut between large pores, prepared from pure $WO_3$ powder, consists of very fine particles with partially necking between the particles. In contrast, the strut densification is clearly observed in the Ni-added W sample due to the enhanced mass transport in activation sintering.

• Korean Journal of Materials Research
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• v.12 no.3
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• pp.176-181
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• 2002

Fabrication of ${\beta}-FeSi_2$ was attempted by making use of the combined process of mechanical alloying (MA) and spark plasma sintering (SPS). MA was performed under the Ar gas atmosphere using mixed powders of pure iron and silicon having the mole fraction of 1:2. SPS process was performed at 800-85$0^{\circ}C$ with the applied pressure of 50MPa and the holding time was ranging from 0 to 30min. The mechanically alloyed powder by cyclic operation of rotor for 15hrs consisted of $\varepsilon$-FeSi and Si phases. When this mechanically alloyed powder was sintered by SPS process above 85$0^{\circ}C$, $\varepsilon$-FeSi and ${\alpha}-Fe_2Si_5$ phase were formed. Bulk product sintered at 82$0^{\circ}C$ for 30min consisted of ${beta}-FeSi_2$ phase with a small fraction of $\varepsilon$-FeSi and the density of sintered specimen was 75.3% theoretical density. It was considered that the MA/SPS combined process was effective for the preparation of ${\beta}-FeSi_2$ without heat treatment process after sintering.

• Journal of Surface Science and Engineering
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• v.44 no.3
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• pp.95-104
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• 2011

Ti based nanocomposite films including V, Si and Nb (Ti-Me-N, Me=V, Si and Nb) were fabricated by hybrid physical vapor deposition (PVD) method consisting of unbalanced magnetron (UBM) sputtering and arc ion plating (AIP). The pure Ti target was used for arc ion plating and other metal targets (V, Si and Nb) were used for sputtering process at a gas mixture of Ar/$N_2$ atmosphere. Mostly all of the films were grown with textured TiN (111) plane except the Si doped Ti-Si-N film which has strong (200) peak. The microhardness of each film was measured using the nanoindentation method. The minimum value of removal rate ($0.5{\times}10^{-15}\;m^2/N$) was found at Nb doped Ti-Nb-N film which was composed of Ti-N and Nb-N nanoparticles with small amount of amorphous phases.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.678-685
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• 2011

The aim of this study was to determine the effect of applied pressure and sintering temperature on the microstructure and mechanical properties for spark plasma sintering (SPS) from commercial pure titanium (CP-Ti) powders. Spark plasma sintering is a relatively new sintering technique in powder metallurgy which is capable of sintering metal and ceramic powers quickly to full density at a fairly low temperature due to its unique features. SPS of -200 mesh or -400 mesh CP-Ti powders was carried out in an $Ar+H_2$ mixed gas flowing atmosphere between $650^{\circ}C$ and $750^{\circ}C$ under 10 to 80 MPa pressure. When SPS was carried out at relatively low temperatures ($650^{\circ}C$ to $750^{\circ}C$), the high (>60 MPa) pressure had a marked effect on densification and grain growth suppression. The full density of titanium was achieved at temperatures and pressures above $700^{\circ}C$ and 60 MPa by spark plasma sintering. The crystalline phase and microstructure of titanium sintered up to $700^{\circ}C$ consisted of ${\alpha}$-Ti and equiaxed grains. Vickers hardness ranging from 293 to 362 Hv and strength ranging from 304 to 410 MPa were achieved for spark plasma sintered titanium.

• Korean Journal of Materials Research
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• v.31 no.6
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• pp.320-324
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• 2021

Effects of growth variables and post-growth annealing on the optical, structural and electrical properties of magnetron-sputtered Ga_0.04Mg_0.10Zn_0.86O films are characterized in detail. It is observed that films grown from pure oxygen plasma showed high resistivity, ~10² Ω·cm, whereas films grown in Ar plasma showed much lower resistivity, 2.0 × 10^-2 ~ 1.0 × 10^-1 Ω·cm. Post-growth annealing significantly improved the electrical resistivity, to 4.3 ~ 9.0 × 10^-3 Ω·cm for the vacuum annealed samples and to 1.3 ~ 3.0 × 10^-3 Ω·cm for the films annealed in Zn vapor. It is proposed that these phenomena may be attributed to the improved crystalline quality and to changes in the defect chemistry. It is suggested that growth within oxygen environments leads to suppression of oxygen vacancy (Vo) donors and formation of Zn vacancy (V_Zn) acceptors, resulting in highly resistive films. After annealing treatment, the activation of Ga donors is enhanced, Vo donors are annihilated, and crystalline quality is improved, increasing the electron mobility and the concentration. After annealing in Zn vapor, Zn interstitial donors are introduced, further increasing the electron concentration.

• Journal of Sensor Science and Technology
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• v.33 no.5
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• pp.288-297
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• 2024

Currently, numerous studies are being conducted on metal oxide semiconductor (MOS) gas sensors for hydrogen detection, using Palladium (Pd) and Pd-based alloy nanoparticles (NPs) owing to their hydrogen absorption ability. Furthermore, several studies have reported that Pd-Iridium (Ir) alloys possess high hydrogen absorption capabilities in their bulk state. However, Ir growth is limited to above 2 nm and it does not mix extensively with other metals. Furthermore, as the hydrogen absorption capacity decreases with the reduction in particle size, it is necessary to synthesize nanoparticles of an appropriate size. Therefore, the synthesis of Pd-Ir alloy NPs larger than 10 nm is challenging. In this study, we report the synthesis of Pd-Ir NPs with an average diameter of 19 nm using a hydrothermal technique for the first time and fabricated Pd-Ir alloy NPs through calcination at 500℃ in Ar and air. To confirm alloy formation and oxidation behavior, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed. In addition, we synthesized Pd-Ir@CeO₂ core-shell nanoparticles (CSNPs) as hydrogen gas-sensing materials. The Pd-Ir core was partially oxidized during heat treatment at 500℃ in air, and Pd-Ir@CeO₂ CSNPs were finally changed into Pd-Ir(alloy)/PdO-IrO₂@CeO₂ CSNPs, which exhibited higher sensitivity and selectivity toward H₂ gas compared to totally oxidized PdO-IrO₂@CeO₂ CSNPs and pure CeO₂ NPs. The enhanced gas-sensing performance was attributed to the hydrogen absorption effect of the Pd-Ir(alloy) NPs.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.322-330
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• 2008

The properties of discharge, luminance, and spectroscopy are investigated in a longitudinal and transverse discharge fluorescent lamps with tube of outer diameter 4 mm. The sample lamps are prepared to be three kinds of gas composition such as mercury lamps of Ne(95%)+Ar(5%)+Hg(2 mg), the mercury-free lamps of Xe 100% and Ne+Xe(4%). The gas pressure is in the range of $5{\sim}300\;Torr$. In the mercury lamps, the longitudinal discharge having a positive column is high in luminance and efficiency, while the transverse discharge is no luminance at all. In the Xe-lamps, the transverse discharge shows relatively good in efficiency as compared with the longitudinal discharge which has a high discharge voltage and a low luminance and efficiency. In the transverse discharge of relatively high efficiency, a pure Xe(100%) gas discharge has a higher efficiency than the mixture gas of Ne+Xe(4%). Through these experiments, the properties of mercury and xenon lamps are verified. In the mercury lamps, the longitudinal discharge of tubular fluorescent lamps is high in luminance and efficiency, while the transverse discharge of flat panel fluorescent lamps are low in luminance efficiency. In the mercury-free lamps, the flat fluorescent lamps of transverse discharge having a high pressure ${\sim}100\;Torr$ with the pure Xe-gas are verified to be suggestable.

• Economic and Environmental Geology
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• v.23 no.3
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• pp.287-308
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• 1990

The Ogmae alunite-kaolinite deposit occurs in acidic tuff, the Hwangsan Tuff, of upper Crataceous age in the Haenam volcanic field, SW Jeonnam. This deposit characterized by advanced argillic alteration formed $71.8{\pm}2.8{\sim}73.9{\pm}2.8$ Ma ago in very shallow depth environment with acid-sulfate solution. Wallrock alteration can be classified into four zones from the center to the margin of the deposit: alunite, kaolinite, illite, and silicified zone. The mineral assemblage in the alunite zone, ore zone, is alunite-quartz-pyritekaolinite. Consideration of stability relation of these minerals suggests that the maximum alteration temperature is estimated at about $250^{\circ}C$ with solution pH of 3 or below assuming that pressure does not exceed 0.3 Kb. Alunite occurs as two different types; replacement and vein-type deposit. The former one consists of fine grained alunite and the later one coarse grained and relatively pure alunite that formed by open space filling. Isomorphous substitution of Na for K in these two types of alunites range 0 to 40 %, indicating that Na/K ratio in the solution is spontaneously changed during the alteration process. Alunite which has higher Na substitution probably formed in an earlier stage while the solution sustain high Na/K ratio. K-Ar age of alunites indicate that the replacement alunite formed earlier($73.9{\pm}2.8Ma$) than the vein-type alunite($71.8{\pm}2.8Ma$). The ${\delta}^{34}S$ value of pyrite and alunite indicate that those minerals formed at isotopically nonequillibrium state. The ${\delta}^{16}O$ and ${\delta}D$ values, of kaolintics 5.0 to 9.0‰ and -54 to -99‰, respectively, indicate that those are formed by hydrothermal solution having magmatic origin which have been diluted by low ${\delta}D$ meteoric water.