• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.469-473
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• 2017

In this study, the rheological characteristics of kerosene based gel propellants were investigated. For the gelling agent, Thixatrol$^{(R)}$ has been used with 100 nm nano-sized aluminium particle addition. Three gellant contents of 2.5 wt%, 5 wt% and 7.5 wt% kerosene gels were first investigated where aluminium particles contents of 10 wt% and 20 wt% were added to 7.5 wt% gellant case. The viscosities of each sample measured by rotational rheometer show that the viscosity augments as gellant or aluminium content increases while the 20 wt% aluminum content resulted in failure of measurement due to the agglomerations of aluminum particles.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.193-200
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• 1988

The starting materials were aluminum hydroxide prepared by precipitation method at the conditions of pH values; 7, 9, 10 and 11. The properties of alumina powder on heat-treatment were studied. After dehydrating structural water from amorphous aluminum hydroxide, the first formed phase was amorphous alumina and its specific surface are was decreased. The specific surface area was increased by dehydration of structural water from aluminum hydroxides except amorphous aluminum hydroxide. The specific surface area was increased with increase of the ratio of A1OOH to $A1(OH)_3$ in the region of transition aluminas. The rate of transition from aluminum hydroxide to alpha alumina occurred in the order of 7, 10, 9 and 11 of pH values. The morphology of alpha alumina powders was skeleton particles remaining outer shape of aluminum hydroxide. Both the elevation of heat-treatment temperature and the transition toalpha alumina decreased specific surface area and brought about the growth of particles.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.119-138
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• 2016

Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.5
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• pp.591-598
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• 2018

The reaction characteristics of aluminum-copper(II) oxide composites initiated by the electrostatic discharge were studied as changing the aluminum particle size. Three different sizes of aluminum particles with nano-size copper(II)-oxide particle were used in the study. These composites were manufactured by two methods i.e. a shock-gel method and a self-assembly method. The larger aluminum particle size was, the less sensitive and less violent these composites were based on the electrostatic test. On the analysis of high speed camera about ignition appearances and burning time, the burning speed was faster when aluminum particle size was smaller.

• Journal of the Korean Ceramic Society
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• v.31 no.5
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• pp.485-490
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• 1994

The reactive ion etching characteristics of aluminum oxide films, prepared by PECVD, were investigated in the CCl4 plasma. The atomic chlorine concentration and the DC self bias were determined at various etching conditions, and their effects on the etch rate of aluminum oxide film were studied. The bombarding energy of incident particles was found to play the more important role in determining the etch rate of aluminum oxide rather than the atomic chlorine concentration. It is considered to be because the bombardment of ions or neutral atoms breaks the strong Al-O bonds of aluminum oxide to help activate the formation reaction of AlCl3 which is the volatile etch product.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.472-475
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• 2010

Theoretical consideration on the combustion behavior of nano-aluminum and water mixture was conducted. The regions are divided into; 1)water+aluminum 2)steam+aluminum 3)reaction zone. Latent heat of vaporization was considered as a function of pressure in case of phase change of water. Also, pressure exponent was studied of various sized nano particles within the range of 0.1MPa ~ 10MPa.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.447-454
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• 2003

Aluminum coagulant was applied to two eutrophic lakes (Lake Sukchon, in Seoul, and a pond on the campus of Kangwon National University), to precipitate suspended particles and phosphate from the water column. Aluminum sulfate (alum) was used for seven treatments and polyaluminum chloride (PAC) was used for one treatment. The effect of treatment varied depending on the dose of alumium coagulant. Particles and phosphate were completely precipitated from the water column with a dose of 10.0 mgAl/l. Partial removal was observed at doses of 3.3 and 1.8 mgAl/l, but not at 0.45 mgAl/l. Therefore, coagulant should be applied at a dose over the threshold in order to remove particles effectively, which seems to be between 1.8 and 10.0 mgAl/l. The length of treatment effect was determined by new inputs of nutrients and particles from external sources. Renewal of pond water by stream water caused recovery of algal growth in Lake Sukchon, and rainfall runoff and ground water pumping caused a return of turbid water in the campus pond. During treatment there was no sign of decreasing pH, or harmful effects on fish or mussels. Aluminum coagulant may be an economically feasible alternative for water quality improvement when the external control of pollutant sources is difficult. However, repeated application is required when there is a renewal of lake water or new input of nutrients.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.851-860
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• 1990

The hydrolysis-precipitation reaction of mixed aluminum salt solutions of aluminum sulfate, aluminum nitrate, and urea has been investigated to obtain narrow-sized and unagglomerated fine spherical precipitates of aluminum hydroxide required for coating core particles. The hydrolysis-precipitatin reaction could be controlled to be appropriate to coating processes by usign urea as a pH control-agent. As the concetration of total Al3+ ion and the molar ratio of SO42-/Al3+ in starting solutions became smaller and also as the vol. ratio of water/solution for hydrolyzing mixed aluminum salt solution became larger, the morphology of precipitates tended to be more unagglomerated and spherical, while their size(0.5longrightarrow0.05${\mu}{\textrm}{m}$) to be smaller. The optimum hydrolysis condition for coating processes was to hydrolyze the mixed aluminum salt solution, in which the molar ratio of SO42-/Al3+ was 0.75, while the amount of water corresponding to the vol. ratio of water/solution of 15. The precipitate was the aluminum hydroxide which sulfate ions were strongly adsorbed on and the maximum yield in the hydrolysis-precipitation reaction was about 20%.

• Nuclear Engineering and Technology
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• v.45 no.3
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• pp.295-310
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• 2013

Industry- or regulatory-sponsored research activities on the resolution of Generic Safety Issue (GSI)-191 were reviewed, especially on the chemical effects. Potential chemical effects on the head loss across the debris-loaded sump strainer under a post-accident condition were experimentally evidenced by small-scale bench tests, integrated chemical effects test (ICET), and vertical loop head loss tests. Three main chemical precipitates were identified by WCAP-16530-NP: calcium phosphate, aluminum oxyhydroxide, and sodium aluminum silicate. The former two precipitates were also identified as major chemical precipitates by the ICETs. The assumption that all released calcium would form precipitates is reasonable. CalSil insulation needs to be minimized especially in a plant using trisodium phosphate buffer. The assumption that all released aluminum would form precipitates appears highly conservative because ICETs and other studies suggest substantial solubility of aluminum at high temperature and inhibition of aluminum corrosion by silicate or phosphate. The industry-proposed chemical surrogates are quite effective in increasing the head loss across the debris-loaded bed and more effective than the prototypical aluminum hydroxide precipitates generated by in-situ aluminum corrosion. There appears to be some unresolved potential issues related to GSI-191 chemical effects as identified in NUREG/CR-6988. The United States Nuclear Regulatory Commission, however, concluded that the implications of these issues are either not generically significant or are appropriately addressed, although several issues associated with downstream in-vessel effects remain.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.153-162
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• 2001

In this paper, space radiation environment and total ionizing dose(TID) effect have been analyzed for the KOMPSAT-2 operational orbit. It has been revealed that the trapped protons are concentrated in the SAA(South Atlantic Anomaly) area and that the trapped protons and electrons, and solar protons are main factors affecting TID. It turned out that low energy Particles can be effectively blocked by aluminum shielding thickness, but high energy Particles can not be effectively blocked by increasing aluminum shielding thickness. KOMPSAT-2 total radiation dose which is accumulated continuously to spacecraft electronics has been expressed as the function of aluminum thickness. These values ran be used as the criteria for the selection of electronic parts and shielding thinkness of the KOMPSAT-2 structure or electronic box.