• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.610-617
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• 2004

For preparation $\alpha$-Al$_2$O$_3$ platelets having 20 $\mu$m in average diameter and 0.2∼0.3 $\mu$m in thickness, we have prepared aluminum hydroxides gel by using aluminum sulfate and sodium sulfate as starting materials. In this study, we investigated the effect of the amount of sodium phosphate on particle size, morphology and thickness of $\alpha$-Al$_2$O$_3$ platelets. When sodium phosphate was not added to aluminum hydroxides gel, most of $\alpha$-Al$_2$O$_3$ platelets had hexagonal shape but the thickness was over 1.0 $\mu$m, and this sample was not adequate for pearlescent pigment. On the other hand, introduction of sodium phosphate caused an increase of aspect ratio (particle diameter/thickness) with a decrease in $\alpha$-Al$_2$O$_3$ platelet thickness.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.24-32
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• 2012

A large fraction of urban $PM_{10}$ concentrations is due to non-exhaust traffic emissions including road dust, tire wear particles, and brake lining particles. Although potential health and environmental impacts associated with tire wear debris have been increased, few environmentally and biologically relevant studies of actual tire wear debris have been conducted. Tire wear particles (TWP) are released from the tire tread as a result of the interaction between the tire and the pavement. Roadway particles (RP), meanwhile, are particles on roads composed of a mixture of elements from tires, pavements, fuels, brakes, and environmental dust. The main objective of present study is to identify the contribution of tires to the generation of RP and to assess the potential environmental and health impacts of this contribution. First, a mobile measurement system was constructed and used to measure the roadway particles on asphalt road according to vehicle speed. The equipment of the mobile system provides $PM_{10}$ concentrations by Dusttrak DRX and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and an aerosol particle sizer (APS). When traveling on an asphalt road at constant speed, there is a clear tendency for PM10 concentration to increase slightly in accordance with an increase in the vehicle speed. It was also found that considerable brake wear particles and particles from tire/road interface were generated by rapid deceleration of the vehicle. The morphology and elements of the roadway particles were also analyzed using SEM-EDX technique.

• Journal of Pharmaceutical Investigation
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• v.39 no.1
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• pp.59-63
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• 2009

Soybean phosphatidylcholine microparticles loaded with cyclosporin A (CsA) were prepared by the modified emulsion solvent diffusion and ionic gelation method, in which chitosan on the surface of the microparticles was crosslinked with various concentrations of tripolyphosphate (TPP). The morphology of the particles was characterized by scanning electron microscopy (SEM). The change of particle size and zeta-potential by chitosan on the surface of the lipid microparticles were systematically observed. The encapsulation efficiency and loading capacity of CsA in the particles were determined by high performance liquid chromatography (HPLC). In vitro release kinetics was studied using the dialysis method. In the results, the mean particle size and the zeta-potential of lipid microparticles increased when the attached chitosan was cross-linked (from 2.5 to 6.2 ${\mu}m$ and from -37.0 to +93.0 mV, respectively). The cyclosporin A-loaded lipid microparticles appeared discrete and spherical particles with smooth surfaces. The encapsulation efficiency of CsA was between 79% and 90% while the loading capacity was between 41% and 56%. In vitro release study showed that the crosslinkage of chitosan by TPP significantly delayed the release of CsA from the particles in a concentration-dependent manner. Thus, the release of CsA from the lipid microparticles could be controlled by tripolyphosphate used as a cross-linking agent.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.1
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• pp.1-11
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• 2011

Tetraethoxysilane(TEOS) as a silica precursor and hydrochloric acid as an acid catalyst have been used in a surfactant-template synthesis of micrometer-sized mesoporous silica microspheres based on the macroemulsion technique. Increase in the concentration of tetraethoxysilane of the reaction mixture has a serious destructive effect on the particle shape and pore structure. As the acid concentration increases, relatively small microspheres are formed without destroying their spherical morphology of the particles as well as the pore structures. However, due to the attractive interaction between particles in an acidic condition, strong silica agglomerates are formed, and therefore are subject to a post-ultrasonic treatment to separate into an individual single particle.

• Analytical Science and Technology
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• v.11 no.4
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• pp.260-265
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• 1998

Spherical, ${\mu}m$-sized particles of barium titanyl oxalate were prepared by thermal decomposition of dimethyl oxalate in acidic barium and titanium solutions. Precipitation was carried out in the presence of several supporting anions. Spherical particles having a specific type of particle size distribution. i.e., unimodal or bimodal distribution, with mean size in the range of $0.2{\sim}3{\mu}m$, were formed depending on the supporting anions, oxalate ion generation rate and aging time. Particles of barium titanyl oxalate settled on the bottom of the beaker at the aging time of 120 min grew to the critical monosize of about $1.5{\sim}3{\mu}m$. XRD spectra and chemical analyses of barium titanate showed that barium titanyl oxalate with high qualities could be synthesized by choosing chloride ion as a supporting anion and increasing the reaction temperatures.

• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.186-192
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• 2001

A primary culture of human fetal hepatocytes was obtained through a therapeutic abortion process at 26 weeks of gestation period. More than $10^8$ cells were seeded on a plastic plate. These hepatocytes were infected with hepatitis B virus (HBV). The HBV was purified from serum of one chronic HBV carrier. Transformed hepatocytes were subcultured in a 10% FBS-supplemented medium. The morphology of the transformed cell was epithelial-like. The cells from the first pass showed signs of early proliferation and had a latent period of more than 3 months after 6-7 passages. After the rest period, the transformed cell proliferated actively and they were subcultured every three days. Transformed hepatocytes were characterized by detection of the HBV transcript by RT-PCR. The secretion of virions from transformed cells was investigated by PCR with the cell medium. Two types of virions secreted into the culture medium were examined by using the transmission electron microscope. Another approach to study the secretion of virions in to culture medium was carried out with HBV antibody. HBsAg was detected in the culture medium of transformed cells using ELISA and Western blot analyses. These data suggested that the human fetal hepatocyte cell line has been established by infection of HBV, in which this cell line secreted viral particles into the culture medium.

• Journal of Powder Materials
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• v.10 no.1
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• pp.26-33
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• 2003

Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders rapidly solidified by the gas atomization method were subjected to mechanical milling(MM). The morphology, microstructure and hardness of the powders were investigated as a function of milling time using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Vickers microhardness tester. Microstructural evolution in gas-atomized Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders was studied during mechanical milling. It was noted that the as-solidified particle size of $200\mutextrm{m}$ decreases during the first 48 hours and then increases up to 72 hours of milling due to cold bonding and subsequently there was continuous refinement to $20\mutextrm{m}$ on milling to 200 hours. Two microstructurally different zones, Zone A, which is fine microstructure area and Zone B, which has the structure of the as-solidified powder, were observed. The average thickness of the Zone A layer increased from about 10 to $15\mutextrm{m}$ in the powder milled for 24 hours. Increasing the milling time to 72 hours resulted in the formation of a thicker and more uniform Zone A layer, whose thickness increased to about $30~50\mutextrm{m}$. The TEM micrograph of ball milled powder for 200 hours shows formation of nano-particles, less than 20 nm in size, embedded in an Al matrix.

• Journal of Powder Materials
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• v.21 no.2
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• pp.119-123
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• 2014

Pt has been widely used as catalyst for fuel cell and exhausted gas clean systems due to its high catalytic activity. Recently, there have been researches on fabricating composite materials of Pt as a method of reducing the amount of Pt due to its high price. One of the approaches for saving Pt used as catalyst is a core shell structure consisting of Pt layer on the core of the non-noble metal. In this study, the synthesis of Pt shell was conducted on the surface of $TiO_2$ particle, a non-noble material, by applying ultraviolet (UV) irradiation. Anatase $TiO_2$ particles with the average size of 20~30 nm were immersed in the ethanol dissolved with Pt precursor of $H_2PtCl_6{\cdot}6H_2O$ and exposed to UV irradiation with the wavelength of 365 nm. It was confirmed that Pt nano-particles were formed on the surface of $TiO_2$ particles by photochemical reduction of Pt ion from the solution. The morphology of the synthesized Pt@$TiO_2$ nano-composite was examined by TEM (Transmission Electron Microscopy).

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.466-472
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• 2012

Visible-light-responding photocatalysts, $N-TiO_2$, were prepared by nitrogen doping onto $TiO_2$. The crystalline structure and morphology, doping state of the prepared photocatalysts were characterized by XRD, FE-SEM, and XPS. The activity of the prepared photocatalysts was examined by the decomposition of methyleneblue. The prepared catalysts were anatase type and the crystallinity was increased with pH. The particle sizes of the prepared catalysts were 5.42, 5.99, 7.58 nm at pH 2.2, 4.7, 9.0, respectively. The particle sizes of the prepared catalysts were slightly increased with pH. The activity of the photocatalysts was directly proportional to the crystallinity of the catalysts. $N-TiO_2$ prepared by nitrogen doping onto $TiO_2$ showed activity under visible light. The doped nitrogen was located not in the lattice but on the surface.

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.153-159
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• 2002

The co-deposited behavior was investigated under varied bath compositions and current densities from Watt Ni plating bath containing Al and A1$_2$O$_3$powders. For single-particle bath, Al and A1$_2$O$_3$particles were agglomerated. The area percentage of A1$_2$O$_3$on plating surface decreased with increasing the current density, while that of Al on plating surface increased. On the other hand, in case of double-particle bath with 1.25g/$\ell$ of Al and 5.0g/$\ell$ of A1$_2$O$_3$5g, the area percentage of Ni-Al-A1$_2$O$_3$increased with increasing current density and the surface morphology was fine without agglomeration. Intermetallic compounds such as $\gamma$'and $\gamma$+$\gamma$' phases appeared when the co-deposited film was annealed.