• Bulletin of the Korean Chemical Society
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• v.22 no.5
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• pp.481-487
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• 2001

Surface films formed prior to bulk reduction of lithium have been studied at gold, platinum, and copper electrodes in rigorously dried propylene carbonate solutions using electrochemical quartz crystal microbalance (EQCM) and secondary ion mass spectrometry experiments. The results indicate that the passive film formation takes place at a potential as positive as about 2.0 V vs. Li/Li+ , and the passive film thus formed in this potential region is thicker than a monolayer. Quantitative analysis of the EQCM results indicates that electrogenerated lithium reacts with solvent molecules to produce a passive film consisting of lithium carbonate and other compounds of larger molecular weights. The presence of lithium carbonate is verified by SIMS, whereas the lithium compounds of low molecular weights, including lithium hydroxide and oxide, are not detected. Further lithium reduction takes place underneath the passive film at potentials lower than 1.2 V with a voltammetric current peak at about 0.6 V.

• Korean Journal of Crystallography
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• v.6 no.2
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• pp.141-157
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• 1995

Single crystals of TeO2 with large diameter were grown by Czochralski technique with auto-diameter control system. The ratio of crystal to crucible was 60-70%. The effect of critical pulling and rotation rate on the crystal quality was studied. Optimum growth parameters for high quality crystal pulling rate was less than 1.2 mm/hr. The solid-liquid interface was convex at the rotation rate of 10-23 rpm and concave at the rotation rate of more than 25 rpm, depending on the size of crystal and crucible. The platinum concentration in the melts is one of the main factors of the constitutional supercooling and thus the bubble entrapment in the growing crystal. Growth axis was confirmed to {110} direction during the whole growth procedure. Infrared spectrometric study and dislocation density measurment by chemical etching method on the grown crystal were performed. Finally, the reasons of cooperation of striations, inclusions, and optical inhomogeneities were discussed.

• Korean Journal of Crystallography
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• v.4 no.1
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• pp.42-48
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• 1993

KTP(KTiOPO4) single crystals were grown by the TSSG(top seeded solution growth) method using the Ksp401s flux. A heat-pipe based growing furnace was used, and the temperature stability and the homogenity of the growing solution in the platinum crucible were within the level of It 0.5℃ and ±0.9℃, respectively. The effects of some operating variables such as operating temperature range, initial cooling rate, forced stirring, reuse of the flux were investigated. As the initial cooling rate was decreased to the degree of 0.1℃/hr and some proper stirring effect by the crystal rotation was introduced to the present experimental condition, bigger and better crystals without inclusion grew. A single crystal with the maximum sixte of 44 ×39 ×17mm3 was obtained and showed the SHG conversion efficiency of 21.39) even without the anti-refilection coating.

• Analytical Science and Technology
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• v.23 no.2
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• pp.103-108
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• 2010

Single crystals of $ZnWO_4$ with [100], [010] and [001] directions were successfully grown by the Czochralski method. The seed crystals for the single crystal growth of $ZnWO_4$ could be induced by the crystal growth using platinum wires applied by the capillary action from the melt. The growth conditions in each direction were investigated in terms of the variations of rotation speed, pulling rate and diameter of the grown crystals. The formation of cracking in the grown crystals during the cooling process could be prevented by annealing effect. The growth directions of the grown crystals were determined using Laue back reflection. The microscopic characteristics of the grown crystals in each direction were discussed, and their physical properties were evaluated for hardness, thermal expansion coefficients and dielectric constants.

• Journal of Sensor Science and Technology
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• v.10 no.1
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• pp.24-32
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• 2001

High temperature platinum resistance thermometers(HTPRTs) were designed and fabricated using a synthetic sapphire single crystal as sensor former, insulation and protection tube, and its characteristics was investigated. Several fixed points measurement showed that the sapphire HTPRTs were satisfied with the ITS-90 criteria as the interpolating thermometer. The temperature-resistance characteristics of HTPRT was fitted to the quadratic relationship in the temperature range from $500^{\circ}C$ to $1500^{\circ}C$. The reproducibility of Cu freezing point realized using the sapphire HTPRT was ${\pm}19.2\;mK$. The insulation resistance of the HTPRT exponentially decreased as temperature increased, and showed to $63\;k{\Omega}({\sim}31.5\;mK)$ at $1500^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.165-171
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• 2009

In this study, ruby single crystals were successfully grown by flux method using an alumina crucible. The alumina crucible can be a substitute for the platinum crucible of high price. The ruby single crystals were grown in the temperature range of $915{\sim}1350^{\circ}C$ for 240 h, using $PbO-B_2O_3$ mixture. The grown ruby crystals with 9.02 ${\times}$ 6.36 mm in size exhibited red color and were transparent. The optical and structural properties were examined by UV-VIS spectrometry, FTIR and XRD. The optical properties of theses crystals were similar to those of the natural ruby and synthetic ruby grown by other methods.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.34 no.3
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• pp.92-97
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• 2024

To improve the efficiency of water splitting systems for hydrogen production, the high overvoltages of electrochemical reactions caused by catalysts in the oxygen evolution reaction (OER, Oxygen Evolution Reaction) must be reduced. Among them, LDH (Layered Double Hydroxide) compounds containing transition metal such as Ni, are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metallic porous material, was used as a support, and NiCo LDH (Layered Double Hydroxide) nanocrystals were synthesized through a hydrothermal synthesis process. In addition, changes in the shape, crystal structure, and water decomposition characteristics of the Mo-doped NiCo LDH nanocrystal samples synthesized by doping Mo to improve OER properties were observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.203-203
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• 2011

The importance of stepped single-crystal surfaces as model catalysts has been well recognized [1]. We re-investigated the adsorption properties of $H_2$ and CO, most important species in platinum-based catalysts, on nearly defect-free and highly stepped surfaces of one and the same Pt(111) crystal. While both being symmetric and single-peaked from the nearly defect-free surface, temperature-programmed desorption (TPD) spectra from the highly stepped surface saturated at 90 K with H and CO were triply- and doubly-peaked, respectively. Once pre-adsorbed, CO preempted step and then terrace sites, inhibiting the dissociative $H_2$ adsorption completely. Pre-adsorbed H inhibited the CO adsorption on terrace sites only, leaving defect sites intact for CO adsorption even at the saturation H precoverage. On defect-free Pt(111), while pre-adsorbed CO inhibited the dissociative $H_2$ adsorption completely, pre-adsorbed H could not inhibit the CO adsorption completely. These intriguing, but interesting results are discussed in terms of energetics/kinetics and the role of surface step sites in the dissociative adsorption of $H_2$ on Pt(111) [2].

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.387-390
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• 1996

The study has been performed that the high purity of platinum crystal was grown by rf floating zone refined technique. Direct electric current was also present to examine the controlling striated structure during the sample grown. It has been proved that current and orientation could affect suppression of the striation structure in Pt. Substructure in Pt was thermally unstable and was able to be removed by the annealing technique.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.2045-2050
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• 2007

The reactions of mercury(II) chloride with O3S2-donor macrocyclic ligands with (L1) and without (L2) dibenzosubunit afforded respective exo- (1) and endo-coordinated (2) complexes depending on the ring rigidity of the ligands. From the X-ray crystal structures and comparative NMR studies for the complexes 1 and 2, it is confirmed that the resulting species with different coordination modes exist not only in solid state but also in solution state.