Hyoung Chan Kim

Synthesis of Nanosized TiO2-Ag-SiO2 Sols by Modified Sol-Gel Method and their Application for Methane Hydrate Formation

Nanosized TiO2-Ag-SiO2 sols were prepared with modified sol-gel method using reduction agent. The physical properties of the prepared particles were investigated by TEM, XRD and FT-IR. The titanium tetraisopropoxide (TTIP, 98% Aldrich), teraethylorthosilicate (TEOS, 98% Aldrich) and silver nitrate were used as precursors of titania, silica and silver, respectively. Sodium citrate tribasic dihydrate (C6H5Na3.2H2O, Aldrich) was used as a reduction agent. This paper presents the effect of nanosized TiO2-Ag-SiO2 sols on the formation of methane hydrate in a semi-batch vessel. The micrographs of TEM showed that the TiO2-Ag-SiO2 particles possessed a spherical morphology with a narrow size distribution. The crystallite size of particles decreased with an increasing the SiO2 content. In addition, the water solution with 1.0 wt% of TiO2-Ag-SiO2 particles acted as promoter for methane hydrate formation.

Effects of Organic Additives on the Residual Stress of Ni and Ni Alloys Electrodeposited from the Sulfamate Bath

The residual stress in the deposits of Ni and Ni alloys was estimated from the deflection of one side deposited test strips (Specialty testing & Development Co.). 2,6-Naphthalene- disodiumsulfate (2,6-NDS) and 1,3,6-Naphthalenetrisodiumsulfate (1,3,6-NTS) were adopted instead of saccharin and , among the three additives, the lowest residual stress was obtained with 1,3,6-NTS. However, to adjust compressive stress, certain quantity of amine additives such as MEA (Monoethanolamine), DEA (Diethanolamine) and TEA(Triethanolamine) were added stepwise to the bath containing 1,3,6-NTS while electrodepositon proceeded. Effects on reducing residual stress was in order of MEA<DEA<TEA, which seemed to have a connection with lone pair and basicity of the nitrogen attached to the amine additives. The highest Vickers hardness was attained with the Ni-Co alloy deposit from the Ni-Co(Ni:80g/L-Co:4.8g/L) bath and the cobalt content of the deposit was 28.4%(wt./wt.). Properties and cobalt content of the deposits were evaluated and analyzed with SEM, XRD, EDS and ICP respectively.

Determination of Current Efficiency of Anodic Film Formation in the Molten Melt by ICP-AES

The results of the current efficiency measurements using the ICP-AES technique are described in this paper. The specimen, of known surface area, was anodized in the anodizing cell containing a known melt volume. After anodizing, trace amounts of any aluminum ions in the melt were analyzed by the ICP-AES technique. From Faradays law, when the amount of aluminum in the melt after anodizing is zero, the current efficiency of the film formation is 100 %. When the amount of aluminum in the electrolyte is not zero, the charge carried by these aluminum ions is effectively wasted, i.e. such ions are not employed in solid film growth, and the current efficiency falls from 100 %. Anodic films were formed at various anodizing conditions in the molten melt under the following conditions;