• Journal of radiological science and technology
• /
• v.46 no.3
• /
• pp.187-195
• /
• 2023

A shield was made by mixing materials such as bismuth(Bi) and barium(Ba) with silicon to evaluate its shielding ability. Bismuth was made into a shield by mixing a bismuth oxide(Bi₂O₃) colloidal solution and a silicon base and applied to a fibrous fabric, and barium was made by mixing lead oxide(PbO) and barium sulfate(BaSO₄) with a silicon curing agent and solidifying it to make a shield. The test was conducted according to the lead equivalent test method for X-ray protective products of the Korean Industrial Standard. The experiment was conducted by increasing the shielding body one by one from the test condition of 60 kVp, 200 mA, 0.1sec and 100 kVp, 200 mA, 0.1 sec. At 60 kVp, 2 lead oxide-barium sulfate shields, 2 bismuth oxide 1.5 mm shields, and 5 bismuth oxide 0.3 mm shields showed shielding ability equal to or higher than that of lead 0.5 mm. At 100 kVp, 2 lead oxide-barium sulfate shields and 2 bismuth oxide 1.5 mm shields showed shielding ability equal to or higher than that of lead 0.5 mm. It was confirmed that when using 2 pieces of lead oxide-barium sulfate and 1.5 mm of bismuth oxide, respectively, it has shielding ability equivalent to that of lead. Bismuth oxide and lead oxide-barium sulfate are lightweight and have excellent shielding ability, thus they have excellent properties to be used as an apron for radiation protection or other shielding materials.

• Korean Journal of Materials Research
• /
• v.33 no.2
• /
• pp.77-86
• /
• 2023

High-temperature oxidation of a Ni-based superalloy was analyzed with samples taken from gas turbine blades, where the samples were heat-treated and thermally exposed. The effect of Cr/Ti/Al elements in the alloy on high temperature oxidation was investigated using an optical microscope, SEM/EDS, and TEM. A high-Cr/high-Ti oxide layer was formed on the blade surface under the heat-treated state considered to be the initial stage of high-temperature oxidation. In addition, a PFZ (γ' precipitate free zone) accompanied by Cr carbide of Cr₂₃C₆ and high Cr-Co phase as a kind of TCP precipitation was formed under the surface layer. Pits of several ㎛ depth containing high-Al content oxide was observed at the boundary between the oxide layer and PFZ. However, high temperature oxidation formed on the thermally exposed blade surface consisted of the following steps: ① Ti-oxide formation in the center of the oxide layer, ② Cr-oxide formation surrounding the inner oxide layer, and ③ Al-oxide formation in the pits directly under the Cr oxide layer. It is estimated that the Cr content of Ni-based superalloys improves the oxidation resistance of the alloy by forming dense oxide layer, but produced the σ or µ phase of TCP precipitation with the high-Cr component resulting in material brittleness.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.16 no.2
• /
• pp.11-22
• /
• 1998

For the purpose of preparation of monodispersed spherical zinc oxide fine particles, an experimental research on the preparation of zinc oxide particles from zinc salts solutions by high temperature precipitation reaction was performed. Zinc oxide particles were precipitated from all the precipitation solutions tested if the precipitation temperature was higher than 60$^{\circ}$. As the precipitation temperature Increased until 80$^{\circ}$, the average particle diameter of zinc oxide particles decreased and the narrower particle size distribution were obtained. Spherical zinc oxide fine particles with relatively narrow particle size distribution were precipitated from the ZnSO$_4$ solutions with NaOH as precipitant. Final pH of precipitation solution had an effect on the amount of zinc oxide precipitated, but had no effect on the their particle size or size distribution.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.128-128
• /
• 2009

The effect of seed layer on the preparation of tin oxide thin film by ALD using tetrakis(ethylmethylamino) tin precursor was examined. The average growth rate of tin oxide film is about 1.4 A/cycle from $50^{\circ}C$ to $150^{\circ}C$. The rate rapidly decreases at the substrate temperature at $200^{\circ}C$. The seed effect was not observed in crystal growth of thin oxide. However, the crystalline growth of seed material in tin oxide was detected by thermal annealing. ALD-grown seeded tin oxide thin film after thermal annealed was characterized by ellipsometry, XRD, AFM and XPS.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.8
• /
• pp.2675-2678
• /
• 2012

Studies on niobium anodization in the mixture of 1 M $H_3PO_4$ and 1 wt % HF at galvanostatic anodization are described here in detail. Interestingly, duplex niobium oxide consisting of thick barrier oxide and correspondingly thick porous oxide was prepared at a constant current density of higher than 0.3 $mAcm^{-2}$, whereas simple porous type oxide was formed at a current density of lower than 0.3 $mAcm^{-2}$. In addition, simple barrier or porous type oxide was obtained by galvanostatic anodization at a single electrolyte of either 1 M $H_3PO_4$ or 1 wt % HF, respectively. The formation mechanism of duplex type structures was ascribed to different forming voltages required for moving anions.

• Particle and aerosol research
• /
• v.9 no.4
• /
• pp.209-219
• /
• 2013

We have used the modified diffusion flame burner to synthesize silica coated iron oxide nanoparticles having enhanced superparamagnetic property. Silica-encapsulated iron oxide particles were directly observed using a high resolution transmission electron microscope. From the energy dispersive X-ray spectroscopy (EDS) and zeta potential measurements, the iron oxide particles were found to be completely covered by a silica coating layer. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements revealed that the iron oxide core consists of ${\gamma}-Fe_2O_3$ rather than ${\alpha}-Fe_2O_3$. Our magnetization measurements support this conclusion. Biocompatibility test of the silica-coated iron oxide nanoparticles is also conducted using the protein adsorption onto the coated particle.

• BMB Reports
• /
• v.28 no.4
• /
• pp.301-305
• /
• 1995

Considering the stimulatory effects of ginsenosides from Panax ginseng C. A. Meyer on the release of nitric oxide from bovine aortic endothelial cells in vitro and vasodilatation of rabbit pulmonary artery in vivo, the present study is designed to investigate the mechanism of nitric oxide release by ginsenosides in calf pulmonary artery endothelial cells, Nitric oxide release was determined in endothelial cells treated with ginsenosides and compared with those of the receptor-dependent agonists, bradykinin and ADP and the receptor-independent calcium ionophore $A_{23187}$. The results showed that total saponin and ginsenoside $Rg_1$, not $Rb_1$, stimulated nitric oxide release measured as conversion to L-citrulline. The nitric oxide releasing properties of total saponin and ginsenoside $Rg_1$ were different; total saponin stimulated only conversion to L-citrulline, like $A_{23187}$, while ginsenoside $Rg_1$ stimulated both L-arginine transport and conversion to L-citrulline, as bradykinin or ADP did.

• Journal of the Korean Ceramic Society
• /
• v.35 no.3
• /
• pp.259-263
• /
• 1998

WSi2/CVD-Si/SiO2/Si-substrate의 폴리사이드 구조에서 실리콘 증착 POCl3 확산 그리고 WSi2 증착 유무에 따른 Thin oxide 특성을 연구했다 WSi2 막을 증착하지 않은 CVD-Si/SiO2/Si-substrate 구조에서 CVD-Si을 po-lycrystalline-Si으로 증착한 시편이 amorphous-Si을 증착한 시편보다 산화막 불량이 적다 WSi2 를 증착시킨 WSi2/CVD-Si/SiO2./Si-substrate의 구조에서 CVD-Si의 polycrystalline-Si 혹든 amorphous-Si 의 막 증착에 따른 thin oxide의 불량율 차이는 미미하다 산화막 불량은 CVD-Si에 확산시킨 인(P) 증가 즉 면저항(sheet resistance) 감소로 증가한다. Thin oxide의 절연특성은 WSi2 증착으로 저하된다 WSi2 증착으로 산화막 두께는 증가하나 막 특성은 열등해져 산화막 절연성이 떨어진다.

• Resources Recycling
• /
• v.11 no.5
• /
• pp.24-29
• /
• 2002

In this study, to improve the color of iron oxide from waste pickling acid at the cold rolling mill, the quality control technologies especially about color were investigated on the spray roaster and iron oxide powder. At the operation condition of the spray roaster, the charge amount of waste acid per hour, temperature, numbers of spray nozzle were investigated. At admixing process, titanium oxide, silica, goethite were tested. Color character of iron oxide can be improved by process control at spray roaster and by admixing process at a pigment factory Iron oxide from results of this study is enough to use as the colorant of concrete product.

• Resources Recycling
• /
• v.13 no.6
• /
• pp.3-8
• /
• 2004

From the world wide globalization of iron oxide industry, the global trend in iron oxide is changed rapidly and the production of iron oxide is increasing in China, currently. Iron oxide have a broad range of applications from construction materials to medical area. Therefore, it is expected that nanoparticulate iron oxides have many applications, too. A series of interesting applications in entirely different fields are introduced.