• Macromolecular Research
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• v.16 no.7
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• pp.620-625
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• 2008

A novel nitrogen-phosphorus compound, diphenyl piperazine-1,4-diylbis(methylphosphinate)(DPPMP) was synthesized via a two step reaction and its flame retarding efficiency as a single component additive was investigated. The success of synthesis was confirmed by FTIR and $^1H$ and $^{31}P$ NMR analysis. The product was mixed with polycarbonate (PC), poly(butylene terephtalate) (PBT), ethylene-vinyl-acetate copolymer (EVA), and acrylonitrile-butadiene-styrene copolymer (ABS). The flame-retarding efficiency was evaluated using the limiting oxygen index (LOI) and the UL-94 vertical test methods. The addition of DPPMP enhanced the flame retardancy of the polymers and the V-0 ratings were obtained for the polymers examined in this study at a loading of 7-30 wt%. The gas-phase flame retardancy mode of action was suggested for this material from the thermogrametry experiment results.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.936-936
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• 2006

Bulk amorphous materials have been intensively studied to apply for various advanced industry fields due to their high mechanical, chemical and electrical properties. These materials have been produced by several techniques such as mechanical alloying, melt spinning and gas atomization, etc. Among them, the atomization is the most potential technique for commercialization due to high cooling rate during solidification of the melt and mass productivity. However, the amorphous powders still have some limitations because of their low ductility and toughness. Therefore, intensive efforts have to be carried out to increase the ductility and toughness. In this study, the Ni-based amorphous powder was produced by the gas atomization process. And in order to increase the ductile toughness, ductile Cu phase was coated on the Ni amorphous powder by spray drying process. The characteristics of the as-synthesis powders have been examined and briefly mentioned. The master alloy with $Ni_{57}Zr_{20}Ti_{16}Si_2Sn_3$ was prepared by vacuum induction melting furnace with graphite crucible and mold. The atomization was conducted at $1450^{\circ}C$ under the vacuum of $10^{-2}$ torr. The gas pressure during atomization was varied from 35 to 50 bars. After making the Ni amorphous powders, the spray drying was processed to produce the Cu -coated Ni amorphous composite powder. The amorphous powder and Cu nitrate solution were mixed together with a small amount of binder and then it was sprayed at temperature of $130^{\circ}C$ and rotating speed of 15,000 R.P.M.

• Particle and aerosol research
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• v.6 no.2
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• pp.61-67
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• 2010

In this paper, we describe a new method to form polymer thin films, in which carbon nanotubes (CNTs) are homogeneously distributed so that they can strengthen the mechanical property of resulting polymer film. To do so, we first homogeneously mixed CNTs with polymer in a DMF solvent. With the assistance of ultrasonic nebulizer, the polymer/CNT solution was then aerosolized into micro-sized droplets and finally turned into solidified polymer/CNT composite particles by gas-phase drying process. As the results of SEM and TEM analysis, CNTs were found to be homogeneously immobilized in the polymer matrix particles due to rapid drying process in the gas phase. For comparison purpose, (i) the polymer/CNTs composite particles prepared by aerosol processing method and (ii) polymer/CNTs sheets prepared by simple solution-evaporation method were employed to form polymer/CNTs composite thin films using a hot press. As the result, the aerosol processing of composite particles was found to be a much more effective method to form homogeneously distributed-CNTs in the polymer matrix thin film.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.515-521
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• 2004

Fe(C) nanocapsules were prepared by the chemical vapor condensation(CVC) process using the pyrolysis of iron pentacarbonyl $(Fe(CO)_5)$. Their characterizations were studied by means of X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy. The long-chained Fe(C) nanocapsules hav-ing the mean size of under 70 nm could be obtained below $1100^{\circ}C$ in different gas flow rates. The particle size of the powders was increased with increasing decomposition temperature, but it was decreased with increasing CO gas flow rate. The Fe powders produced at $500^{\circ}C$ consisted of three layers of ${\alpha}$-Fe/$Fe_3C$/amorphous phases, but it had two phase core-shell structure which consited of $Fe_3C$ phase of core and graphite of shell at $1100^{\circ}C$.

• Environmental Analysis Health and Toxicology
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• v.16 no.3
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• pp.139-142
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• 2001

Acetanilide is a High Production Volume Chemical, which is produced about 2,300 tons/year in Korea as of 1998 survey. Most is used as an intermediate for synthesis of pharmaceuticals and dyes, and the chemical is one of seven chemicals of which human and environmental risk are being assessed by National Institute of Environmental Research under the frame of OECD SIDS program. The Atmospheric Oxidation Program for Microsoft Windows (AOPWIN) is used to estimates the rate constant for the atmospheric, gas－phase reaction between photochemically produced hydroxyl radicals and organic chemicals. It is also used to estimates the rate constant for the gas－phase reaction between ozone and olefinic/acetylenic compounds. The rate constants estimated by the program are then used to calculate atmospheric half－lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals and ozone. AOPWIN requires only a chemical structure to make these predictions. Structures are entered into AOPWIN by SMILES (Simplified Molecular Input Line Entry System) notations. In this study, one of environmental fate/distribution of the chemical elements, photodegradation of acetanilide was estimated using AOPWIN model based on SMILES notation and chemical name data.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.461-468
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• 2005

Transparent TiO$_{2}$ sols were prepared by hydrothermal synthesis to heat Ti precursor solutions, from Ti hydroxides obtained with neutralizing aqueous TiOCl$_{2}$ solutions having various concentrations of NaCI by aqueous NaOH solution, in the autoclave at 120$^{\circ}C$ The photocatalytic abilities of glass beads coated with the sol for gaseous benzene were evaluated. As a result, it was found that due to the increase of brookite phase in TiO$_{2}$ by controlling the concentration of Na ion the optical absorption of TiO$_{2}$ increases toward long wavelength but that in the area of short wavelength becomes relatively low and consequently the photocatalytic performance of TiO$_{2}$ thin film for benzene gas rather decreases, compared to that of composite film of anatase and brookite phases. These results suggest that in order for coated TiO$_{2}$ thin film to have high dissociation performance for benzene gas it is effective to form anatase and brookite phases compositely in TiO$_{2}$.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.331-339
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• 2021

Environmental barrier coatings(EBCs) are applied to the SiC/SiC ceramic matrix composites(CMCs) in order to protect CMCs from being corroded with water vapor by combustion gas in gas turbine engines. Ytterbium silicates, such as ytterbium monosilicate and ytterbium disilicate, are ones of the candidate materials for EBCs due to their excellent resistance to water vapor corrosion as well as thermal-expansion match with SiC. In this study, ytterbium silicates are fabricated with 2-step solid-state synthesis targeting ytterbium disilicate. After synthesizing ytterbium monosilicate, the mixtures of ytterbium monosilicate and SiO₂ are heat-treated and densified by using pressureless sintering or hot pressing with a variety of heating conditions. The phase formation, thermal expansion, and oxidation behavior are examined with fabricated specimens. The final densified bodies are found to be composites between ytterbium monosilicate and ytterbium disilicate with different ratios, which results in 4.43 to 6.72×10^-6/K range of coefficients of thermal expansion. The probability of these ytterbium silicates for EBC applications is also discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.2
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• pp.132-139
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• 2007

Popular techniques for producing synthesis gas by converting methane include steam reforming and catalyst reforming. However, these are high temperature and high pressure processes limited by equipment, cost and difficulty of operation. Low temperature plasma is projected to be a technique that can be used to produce high concentration hydrogen from methane. It is suitable for miniaturization and for application in other technologies. In this research, the effect of changing each of the following variables was studied using an AC Glidarc system that was conceived by the research team: the gas components ratio, the gas flow rate, the catalyst reactor temperature and voltage. Glidarc plasma reformer was consisted of 3 electrodes and an AC power source. And air was added for the partial oxidation reaction of methane. The result showed that as the gas flow rate, the catalyst reactor temperature and the electric power increased, the methane conversion rate and the hydrogen concentration also increased. With $O_2/C$ ratio of 0.45, input flow rate of 4.9 l/min and power supply of 1 kW as the reference condition, the methane conversion rate, the high hydrogen selectivity and the reformer energy density were 69.2%, 36.2% and 35.2% respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.369-369
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• 2011

In the current work, we demonstrate the gas phase plasma synthesis of ultrafine boron nanoparticles by decomposing boron trichloride (BCl3) gas in an argon-hydrogen thermal plasma and quenching the hot plasma by expansion through a ceramic nozzle, driving the homogeneous nucleation of nanoparticles. It is shown that ultrafine nanoparticles can be produced from the experiments. We also show the characterization results regarding the oxidation of boron nanoparticles at room temperature using X-ray Photoelectron Spectroscopy (XPS) and the combined Scanning Transmission Electron Microscope (STEM) and Electron Energy Loss Spectroscopy (EELS).

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.376-382
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• 2006

In the $Al(OH)_3-SiO_2-AlF_3$ system, leaf-shaped fluorotopaz was first formed at $800^{\circ}C$ and mullite whisker was formed at $1,100^{\circ}C$. The mass transportation of Al and Si as gas phase, the fast reaction and growth, and the absence of liquid phase existence in mullite whisker showed that the formation and growth of mullite was from the solid-vapor reaction.