• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.139-148
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• 2018

In this study, surface analysis of Ni-Cr and Co-Cr alloys with addition of Ti and Mo for dental CAD/CAM use has been researched experimentally. The surface characteristics of the alloys were examined by Vickers hardness test, bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction spectroscopy. The shrinkage of the sintered Ni-Cr alloy alloy was slightly larger than that of Ni-Cr-Ti alloy, and larger than Co-Cr alloy. Also, the addition of Mo showed a tendency to decrease shrinkage somewhat. From the result of XRD analysis, NiCr, $Ni_3Cr$ and $Ni_3Ti$ were observed in the sintered Ni-13Cr-xTi and Ni-13Cr-xMo alloys. In addition, ${\sigma}-CrCo$, $Co_2Mo_3$ and $TiCo_2$ were formed in the sintered Co-Cr-xTi and Co-Cr-xMo alloys. Surface hardness of Ti and Mo added alloy was higher than those of Ni-Cr and Co-Cr alloy. The bond strength between sintered alloy and porcelain was $16.1kgf/mm^2$ for Ni-13Cr alloy, $17.8kgf/mm^2$ for Ni-13Cr-5Ti alloy, and $8.2kgf/mm^2$ for Ni-13Cr-10Ti alloy, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1483-1490
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• 2011

The protection effect of a $ZrO_2$ coating layer on a $LiCoO_2$ thin film was characterized. A wide and smooth $LiCoO_2$ thin film offers sufficient opportunity for careful observation of the reaction at the interface between cathode (coated and uncoated) and electrolyte. The formation of a $ZrO_2$ coating on a $LiCoO_2$ thin film was confirmed by secondary ion mass spectrometry. Scanning electron and atomic force microscopy were used to characterize the surface morphologies of coated and uncoated films before and after cycling. A $ZrO_2$-coated $LiCoO_2$ film showed a higher discharge capacity and rate capability than an uncoated film. This may be associated with a surface protection effect of the coating. The surface of a pristine film was damaged during cycling, whereas the coated film maintained a relatively clear surface under the same measurement conditions. This result clearly demonstrates the protection effect of a $ZrO_2$ coating on a $LiCoO_2$ thin film.

• Journal of Soil and Groundwater Environment
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• v.20 no.1
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• pp.41-55
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• 2015

Monitoring of $CO_2$ release through the ground surface is essential to confirm the safety of carbon storage projects. We conducted a feasibility study of the multi-channel surface-soil $CO_2$-concentration monitoring (SCM) system as a soil $CO_2$ monitoring tool with a small scale injection test. The background concentrations showed the distinct diurnal variation. The negative relation of $CO_2$ with temperature and the low $CO_2$ concentrations during the day imply that surface-soil $CO_2$ depends on photosynthesis and respiration. After 4.2 kg of $CO_2$ injection (1 m depth for 29 minutes), surface-soil $CO_2$ concentrations increased in the all five chambers, which were located less than 2.8 m of distance from each other. The $CO_2$ concentrations seem to be recovered to the background around 4 hours after the injection ended. To determine the leakage, the data from Chamber 2 and 5 with low increase rates were used for statistical analyses. Coefficient of variation for 30 minutes ($CV_{30min}$.) is efficient to determine a leakage signal, with reflecting the fast change in $CO_2$ concentrations. Consequently, SCM and $CV_{30min}$ could be applied for an efficient monitoring tool to detect $CO_2$ release through the ground surface. Also, this study provides ideas for establishing action steps after leakage detection.

• Ocean and Polar Research
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• v.30 no.3
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• pp.335-345
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• 2008

In order to study spatial variabilities and major controlling factors, we measured fugacity of $CO_2(fCO_2)$, temperature, salinity and nutrients in surface waters of the North Pacific($7^{\circ}30'{\sim}33^{\circ}15'N$, $123^{\circ}56'E{\sim}164^{\circ}24'W$) between September$\sim$October 2007. The North Pacific and the marginal sea were distinguished by $fCO_2$ distribution as well as unique characteristics of temperature and salinity. There was a distinct diurnal SST variation in the tropical North Pacific area, and surface $fCO_2$ coincidently showed diurnal variation. In the North Pacific area, surface $fCO_2$ was mainly controlled by temperature, while in the marginal sea area it was primarily dependent on alkalinity and dissolved inorganic carbon concentrations. Air-sea $CO_2$ flux showed a large spatial variation, with a range of $-6.10{\sim}5.06\;mmol\;m^{-2}day^{-1}$. The center of subtropical gyre of North Pacific acted as a source of $CO_2(3.09{\pm}0.95\;mmol\;m^{-2}day^{-1})$. Tropical western North Pacific (i.e. the 'warm pool' area and the subtropical western North Pacific) acted as weak sources of $CO_2$($1.07{\pm}1.20\;mmol\;m^{-2}day^{-1}$ and $0.50{\pm}0.53\;mmol\;m^{-2}day^{-1}$, respectively). In the marginal sea, however, the flux was estimated to be $-0.68{\pm}1.17\;mmol\;m^{-2}day^{-1}$, indicating that this area acted as a sink for $CO_2$.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.5
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• pp.263-271
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• 2003

Effects of the existence of $CO_2$ gas and pH on the silica surface characteristics at silica/Pb(II) and sodium dodecyl sulfonate (SDS, $C_{12}H_{25}SO_3Na$) solution interface were studied. The hydrophobic characteristics of silica surface was delineated by contact angle measurement and surface force measurement using atomic force microscopy (AFM). In $CO_2$ free condition provided by purging $N_2$ gas, the contact angle of fused silica surface in $10^{-4}M$ Pb(II) and SDS solution increased greatly up to $90^{\circ}$ compared with $40^{\circ}$ in atmospheric condition. It was due to the precipitation of $PbCO_3$ in atmospheric condition. In $CO_2$ free condition the change of contact angle and adhesion force ($F_{ad}$) in AFM, affected by pH change, was similar to the distribution of $PbOH^+$ ion in speciation diagram corresponding to $10^{-4}M$ total Pb(II). Therefore, it was convinced that the $PbOH^+$ ion among Pb(II) species would be the main adsorbing type on silica surface. Both of contact angle measurement and surface force measurement using AFM showed that the Pb only treatment made the silica surface hydrophobic. However, it could not be explained theoretically by current knowledge, and required further study in atomic level to solve the problem.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.381-386
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• 2008

Adatom kinetics on the surfaces of Co overlayers, prepared on the W(110) surface, was studied with scanning tunneling microscopy. By counting the number-density of the adatom-islands, we estimated the ratio of adatom diffusion coefficients. The ratio $D_{W(110)}:D_{1ML\;Co}:D_{2ML\;Co}$ was measured to be 1 : 125 : 33000 at room temperature, where $D_{W(110)},\;D_{1ML\;Co}$, and $D_{2ML\;Co}$ are the diffusion coefficients on bare W(110) surface, on one-monolayer Co overlayer, and on two-monolayers Co overlayers, respectively. An increased diffusion coefficient on two-ML Co overlayers, relative to that on one-ML Co overlayers, was explained with the heteroepitaxial strain effect.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.389-392
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• 1999

We employed cobalt-disilicide for high-speed logic devices. We prepared stable and low resistant $CoSi_2$ through typical fabrication process including wet cleaning and rapid thermal process (RTP). We sputtered 15nm thick cobalt on the wafer and performed RTP annealing 2 times to obtain 60nm thick $CoSi_2$. We observed spherical shape voids with diameter of 40nm in the surface and inside $CoSi_2$ layers. The voids resulted in taking over abnormal junction leakage current and contact resistance values. We report that the voids in $CoSi_2$ layers are resulted from surface pits during the ion implantation previous to deposit cobalt layer. Silicide reaction rate around pits was enhanced due to Gibbs-Thompson effects and the volume expansion of the silicidation of the flat active regime trapped dimples. We confirmed that keeping the buffer oxide layer during ion implantation and annealing the silicon surface after ion implantation were required to prevent void defects in CoSi$_2$ layers.

• Journal of the Korean Magnetics Society
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• v.7 no.3
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• pp.129-133
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• 1997

To investigate the influence of the Hf concentration and the annealing effect in $Co_{1-x}Hf_x$(X=0.16, 0.24 at.%) systems, ferromagnetic resonance experiments have been carried out. Spin wave resonance spectra for all samples consist of several volume modes and one (or two) surface mode. It is suggested that both surfaces of the film have a perpendicular hard axis to the film plane (negative surface anisotropy). The surface anisotropy $K_{s2}$ at substrate-film interface is varied slowly from -0.07 to -0.32 erg/$\textrm{cm}^2$ and the surface anisotropy $K_{s1}$ at film-air interface is varied from 0.18 to -0.47 erg/ $\textrm{cm}^2$ with increasing annealing temperature in the amorphous $Co_{84}Hf_{16}$ thin films. Also, the surface anisotropy $K_{s2}$ is varied slowly from -0.31 to -0.41 erg/$\textrm{cm}^2$ and the surface anisotropy $K_{s1}$is varied from -0.19 to -0.60 erg/$\textrm{cm}^2$ with increasing annealing temperature in the amporphous $Co_{84}Hf_{16}$ thin films. We conjecture that the variation of surface anisotropy $K_{s1}$ is due to the increase of Co concentration resulted from Hf oxidation for low temperature annealing(150~175 $^{\circ}C$) and the diffusion of Co atoms near the film surfaces for high temperature annealing (200~225 $^{\circ}C$).

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.1019-1024
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• 1993

The coadsorption of carbon monoxide and oxygen on polycrystalline nickel surface has been studied using XPS at the room temperaure. The adsorption of CO on the nickel surface precovered partially with oxygen is found to take place by the following steps: The CO molecules react with the preadsorbed oxygen atoms to liberate $CO_2$ gas at the initial stage of low CO exposures, and they are coadsorbed gradually with the increasing CO exposures. The extent of coadsorption at the higher CO exposures is found to decrease with the increasing degree of oxygen preadsorption. This finding is explained in terms of the reduced adsorption site for CO as a consequence of oxygen preadsorption. The CO molecules preadsorbed on the nickel surface inhibited the adsorption of $O_2$ molecules. The increase of oxygen exposure led to the dissociation of preadsorbed CO, and the NiO layers were formed concurrently. The dissociation was rendered to arise from an oxygen-to-CO energy transfer.

• Bulletin of the Korean Chemical Society
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• v.12 no.5
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• pp.574-582
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• 1991

The CO molecules adsorbed on Ni(111) surface is studied in the cluster approximation employing EH method with self-consistent charge iteration. The effect of CO coverage is simulated by allowing the variation of valence state ionization potentials of each Ni atom in model cluster according to the self-consistent charge iteration method. The CO coverage dependent C-O stretching frequency shift, adsorption site conversion, and metal work function change are attributed to the charge transfer between metal surface and adsorbate. For CO/Ni(111) system, net charge transfer from Ni surface to chemisorbed CO molecules makes surface Ni atoms be more positive with increasing coverage, and lowers Ni surface valence band. This leads to a weaker interaction between metal surface valence band and Co $2{\pi}^{\ast}$ MO, less charge transfer to a single CO molecule, and the bule shift of C-O stretching frequency. Further increase of coverage induces the conversion of 3-fold site CO to lower coordination site CO as well as the blue shift of C-O stretching frequency. This whole process is accompanied by the continuous increase of metal work function.