• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.591-595
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• 2007

The membrane filter coated with nanostructured porous surface layer was made by heat treatment after depositing nanoparticles onto a conventional micron-fibrous metal filter as a substrate filter. The nanostructured porous layer membrane filter (NSPL-MF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by coating the nanoparticle agglomerates of dendrite structure onto the micron-fibrous metal filter. Pressure drop of nanostructured porous layer membrane filter decreased with increasing the heat treatment temperature to make the nanostructured porous layer adhered on the filter surface because the nanoparticle agglomerates shrank, but filtration efficiency did not decrease clearly.

• Journal of the Korean Applied Science and Technology
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• v.25 no.2
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• pp.211-218
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• 2008

The performance of positive plates depends on the structure of the lead dioxide active mass. The positive active materials (PAM) consists of a skeleton, built up of agglomerates and macropores. Agglomerates, in their turn, comprise particles and micropores. This paper described a study conducted to determine the effects of different soaking times between the acid fill and formation stages of the tubular plate production. For the positive plates a lead oxide were filled into tubular bag with a red lead. After filling the positive plates were soaked in $H_2SO_4$ solution. X-ray diffraction(XRD), scanning electron microscopy(SEM) and electrical testing had been used to study the compositional and morphological aspects of the positive active material(PAM) just prior and after formation. Results indicate that PAM compositions were effected by the soaking time and acid density of $H_2SO_4$ solution. It can be seen that as the soaking time duration increases, $\alpha$-PbO, $Pb_3O_4$, and Pb were all gradually sulphating. Composition of 3BS reached a maximum at around 3 h duration and $H_2SO_4$ of sp. gr. 1.10 on soaking. This results would suggest that the most beneficial conditions for soaking were the $H_2SO_4$ of sp. gr. 1.10 and 2 to 6 h of soaking.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.179.1-179.1
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• 2015

Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates were investigated in the very thin thickness range of 20 to 120 nm. A very unusual transition phenomenon, in which electrical resistance increases with an increase in film thickness, was observed. From structural and compositional analyses, this transition behavior was explained to arise from metallic Zn agglomerates dispersed in non-crystalline Zn-O matrix. It was unveiled that film thickness more than 80 nm is required for the development of hexagonal crystal structure of ZnO. ZnO films on PET substrates exhibited high optical transmittance and good mechanical flexibility in the thickness range. The results of this study would provide a valuable guideline for the design of ZnO thin films on organic substrates for practical applications.

• KSBB Journal
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• v.27 no.4
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• pp.237-242
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• 2012

In this study, zein microparticles and drug-loaded zein microparticles were prepared using supercritical ASES technique. The effects of operating parameters on particle size and morphology were investigated. ASES-processed zein microparticles consisted of agglomerates of very fine unit particles. As temperature increased, the size of unit particles increased and their morphology became more spherical. The addition of water to the solvents for zein resulted in the formation of more spherical microparticles. The release characteristics of drug-loaded zein microparticles were also studied.

• Journal of Energy Engineering
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• v.3 no.2
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• pp.130-150
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• 1994

Coal-water mixture(CWM) fuel has attracted much attention as a substitute fuel for oil by which high economics and short-term commercialization might be realized in comparison with other coal conversion technologies. There are many factors that affect the CWM combustibility, such as the physical properties of CWM, the performance of atomizer and burner, operating conditions, capacity and load of the boiler, etc. Particularly, atomization quality is extremely critical to achieving acceptable carbon conversion efficiency of CWM fuel and maintaining the flame stability, because the coal particles in the CWM droplets burn as agglomerates. This paper presents the R&D results about the CWM atomization characteristics, including the significance of CWM atomization the R&D results about the CWM atomization characteristics, including the significance of CWM atomization quality, the atomization and combustion mechanism, the type of CWM atomizer, size and size distribution of CWM droplets and some factors that influence the atomization performance.

• Korea-Australia Rheology Journal
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• v.13 no.2
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• pp.61-65
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• 2001

Thermoplastic nanocomposites based on the copolymers of polypropylene (PP)-polystyrene (PS) and organically modified montmorillonite (org-MMT) were produced by using power ultrasonic wave in an intensive mixer. Owing to the unique action of the ultrasonic wave, free radicals of styrene monomers and macroradicals of PP were generated, by which copolymers of PP and PS were formed. Another important aspect of using ultrasonic wave during the mixing process was to enhance nano-scale dispersion of org-MMT by destructing the agglomerates of org-MMT in the polymer matrix. Optimum conditions for the in-situ copolymerization and melt intercalation were studied with various concentrations of styrene monomer, sonication time and different kinds of clay. It was found that a novel attempt carried out in this study yielded further improvement in the mechanical performance of the nanocomposites compared to those produced by the conventional melt mixing process.

• Journal of the Korean institute of surface engineering
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• v.43 no.6
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• pp.255-259
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• 2010

In this work, Ni-Co composites incorporated with nano-sized SiC particles in the range of 45-55 nm are prepared by electroplating. The effects of plating duration on the chemical composition, surface morphology, crystalline structures and hardness have been studied. The maximum hardness of Ni-Co-SiC composite coating is approximately 633 Hv at plating duration of 1 h. The hardness is gradually decreased with increasing plating duration, which can be attributed to the growth of crystalline size and the agglomerates of SiC nano-particles. It is therefore explained that the grain refinement of Ni-Co matrix and stable dispersion of SiC particles play an important role for strengthening, which indicate Hall-Petch relation and Orowan model were dominant for hardening of Ni-Co-SiC composite coatings.

• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.61-65
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• 2015

The effect of Sr addition on the flexural strength of bulk SiOC ceramics was investigated in polymer-derived SiOC ceramics prepared by conventional hot pressing. Crack-free, dense SiOC discs with a 30 mm diameter were successfully fabricated from commercially available polysiloxane with 1 mol% strontium isopropoxide derived Sr as an additive. Agglomerates formed after the pyrolysis of polysiloxane led to the formation of domain-like structures. The flexural strength of bulk SiOC was strongly dependent on the domain size formed and Sr addition. Both the minimization of the agglomerate size in the starting powders by milling after pyrolysis and the addition of Sr, which reinforces the SiOC structure, are efficient ways to improve the flexural strength of bulk SiOC ceramics. The typical flexural strength of bulk Sr-doped SiOC ceramics fabricated from submicron-sized SiOC powders was ~209 MPa.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.153-159
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• 2019

In this study, fly ash of a fluidized bed boiler produced in a power plant was stabilized by hydration and carbonation reaction. Then, each raw material was pulverized by two kinds of grinding equipment (Planetary mills and pot mills); the degree of grinding and the agglomeration behavior were observed. It was found that there were changes of specific surface area and particle size distribution according to grinding time. The surface of the raw material was observed using an optical microscope. As a result, agglomerates of about 75 ㎛ or more due to electrostatic phenomenon were formed as the grinding time became longer; it was confirmed that the crushing efficiency slightly increased with use of antistatic agent.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1353-1364
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• 1996

Recently semiconductor doped glasses have attracted attention as nonlinear optical materials because of their large third order nonlinear optical properties. The transparent and homogeneous CdS-doped SiO2 glass thin films were obtained by the dip=coating process of the sol-gel method. Thin films were consisted of glasses containing CdS microcrystallites which were formed by dissolved Cd2+ and S2- ions in a SiO2 matrix solutions. A subsequent thermal treatment of this samples led the formation of colloidal agglomerates and finally of microcrystallites. The size of CdS microcrystallites was about 4 to 15 nm after thermal treatments at various heating conditions. From the optical absorption spectra of the CdS-doped SiO2 glass films it was found that the absorption edge was blue-shifted compared with that of the bulk CdS crystal(~2, 4 eV) and that the amount of energy shift was inversely proportional to the crystal size. And the band gap energy increased with the decrease in crystallite size indicating that the quantum size effects occured.