• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1997.10a
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• pp.45-52
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• 1997

Ocean seabed is usually covered with various types of marine soils. A marine soil is a mixture of two phases: soil particles that forms an interlocking skeletal frame, pore fluids that occupy a major portion of pore space. When gravity water waves propagate over a porous movable seabed, a hydrodynamic pressure on the fluid-seabed interface and fluid flow in the porous medium are induced. (omitted)

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.173-177
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• 2006

Porous surfaced Ti implant compacts were fabricated by electro-discharging-sintering (EDS) of atomized spherical Ti powders. Powders of $50-100{\mu}m$ in diameter were vibratarily settled into a quarts tube and subject to a high voltage and high density current pulse in Ar atmosphere. Single pulse of 0.7 to 2.0 kJ/0.7 gpowder, from 150, 300, and $450{\mu}F$ capacitors was applied in less than $400{\mu}sec$ to produce twelve different porous-surfaced Ti implant compacts. The solid core formed in the center of the compact shows similar microstructure of cp Ti which was annealed and quenched in water. Hardness value at the solid core was much higher than that at the particle interface and particles in the porous layer, which can be attributed to both heat treatment and work hardening effects induced by EDS. Compression tests were made to evaluate the mechanical properties of the EDS compacts. The compressive yield strength was in a range of 12 to 304MPa which significantly depends on input energy. Selected porous-surfaced Ti-6Al-4V dental implant compacts with a solid core have much higher compressive strengths compared to the human teeth and sintered Ti dental implants fabricated by conventional sintering process.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.434-438
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• 2013

Monodispersed 3Y-$ZrO_2$ spherical agglomerates were synthesized by thermal hydrolysis process followed by crystallization processes (hydrothermal treatment and calcination). The crystallization process affected the properties of the final particles, such as the primary particle size, the agglomeration state, and the fraction of $ZrO_2$ monoclinic phase. The hydrothermal treated spherical particles were porous microstructures (weak agglomerates) composed of small primary particles with a size of 14 nm, but the calcined spherical particles had a dense microstructure due to the hard aggregation between primary particles. While the calcined particles had a low green density due to the hard aggregation, hydrothermal treated ones were soft agglomerates and had a deflection point at 50 MPa due to the rearrangement of secondary spherical particles and the filling of the interstices with the primary particles. Finally, the green density of hydrothermally treated $ZrO_2$ particles was 58% at 200 MPa.

• Journal of Industrial Technology
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• v.35
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• pp.67-71
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• 2015

Various structures of particles were prepared by electrospray technique. In this research, solid particles were formed by electrospraying a solution of ethanol containing polyvinyl and tetraethyl orthosilicate. During the electrospray process, the ethanol solvent was evaporated, resulting in the solidification of precursors, forming solid particles. Evaporation of ethanol solvent also enhanced the mass transport which facilitated the development of porous and hollow structures.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.159-166
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• 2012

We have introduced the Pickering emulsion systems to generate novel confining geometries for the selforganization of monodisperse polymer microspheres using nanoparticle-stabilized emulsion droplets encapsulating the building block particles. Then, through the slow evaporation of emulsion phases by heating, these microspheres were packed into regular polyhedral colloidal clusters covered with nanoparticle-stabilizers made of silica. Furthermore, polymer composite colloidal clusters were burnt out leaving nonspherical hollow micro-particles, in which the configurations of the cluster structure were preserved during calcination. The selfassembled porous architectures in this study will be potentially useful in various applications such as novel building block particles or supporting materials for catalysis or gas adsorption.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.347-357
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• 2018

Steady shear response of a magnetorheological fluid (MRF) system containing porous mono-disperse magnetite ($Fe_3O_4$) spheres synthesized by solvothermal method is demonstrated. In applied magnetic field the interaction between the spherical particles leads to form strong columnar structures enhancing the yield strength and viscosity of the MRFs. The yield strengths of the MRFs also scale up with the concentration of magnetic particles in the fluid. Considering magnetic dipolar interaction between the particles the magneto-mechanical response of the MRFs is explained. Unlike metallic iron particles, the low-density corrosion resistant soft-ferrimagnetic $Fe_3O_4$ spherical particles make our studied MRF system efficient and reliable for shock-mitigation/vibration-isolation applications.

• Particle and aerosol research
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• v.8 no.2
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• pp.89-95
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• 2012

Spherical mesoporous silica particles, of which main pore diameter was 3.8 nm, were successfully prepared by spray pyrolysis from aqueous silicic acid. The effect of precursor concentration, reaction temperature, and the addition of urea and PEG on the particle diameter and pore properties such as pore diameter, total pore volume, and specific surface area were investigated by using FE-SEM, particle size analyzer, and nitrogen absorption-desorption analysis. With an increase of the precursor concentration from 0.2 M to 0.7 M, the average particle diameter, total pore volume, and specific surface area of the porous silica particles increased from 0.56 to $0.96\;{\mu}m$, 0.434 to $0.486\;cm^3/g$, 467.8 to $610.4\;m^2/g$, respectively. Within the temperature range $(600\;^{\circ}C{\sim}800\;^{\circ}C)$, there was no significant difference in the pore diameter, total pore volume, and specific surface area. In addition, the addition of urea as an expansion aid led to slight increases in particle diameter, pore diameter, and specific surface area. However, when the polyethylene glycol (PEG) as an organic template was used, the total pore volume of porous particles increased dramatically.

• Journal of Periodontal and Implant Science
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• v.28 no.1
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• pp.87-102
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• 1998

The purpose of this stuffy was to assess and compare the osseous responses to implanted particles of porous synthetic HA (Interpore $200^{(R)}$, Interpore International, U.S.A.), resorbable natural bovine derived HA (Bio-$oss^{(R)}$, Gestlich Pharma, Switzerland) and calcium carbonate(Biocoral $450^{(R)}$, Inoteb, France) in bone defects. Four calvarial defects of 2.5mm diameter were created in earth of 16 Sprague-Dawley rats. The experimental materials were subsequently implanted hi three defects, leaving the fourth defect for control purpose. Four animals were earth sacrificed at 3 days, 1week, 2weeks and 4 weeks after surgery. The tissue response was evaluated under light microscope. Overall, histologic responses showed that all the particles were well tolerated and caused no aberrent tissue responses. There were difference in the amount of newly formed bone at the experimental sites and control site. There was more new bone formation associated with calcium carbonate site. In addition, the calcium carbonate site displayed multinucleated giant cells surrounding calcium carbonate particles after the 1st week, and osteoid tissue within the particle after the 2nd week. After 4 weeks, calcium carbonate particles were resorbed and replaced with new bone. The healing of the natural bovine derived HA site was similar to that of porous synthetic HA, except that new bone growth between the two particles have progressed more in the former site after the 2nd week. In the natural bovine derived HA site, the particle was surrounded by newly formed bone after the 4th week. After 4 weeks, the control site showed more mature bone than other sites. In conclusion, the grafted site were better in new bone formation than non-grafted sites. In particular the calcium Carbonate site showed the ability of osteoinduction and natural bovine denver HA showed osteoconduction in rat calvarial defects. This suggest that calcium carbonate and natural bovine derived HA could enhance the regenerative potential in periodontal defects.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.337-344
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• 2006

Characteristics of flocculent aggregates have great effects on membrane fouling. Floc from kaolin particles gave higher permeate throughputs than floc from natural particles at the same conditions. Therefore, the objectives of this study are to thoroughly analyze characteristics of flocculated aggregates and to investigate effects of flocculated aggregates on membrane fouling. Image analysis, specific rake resistance and cake compressibility were used for characterization of flocs. Different flocculent aggregates formed with natural and kaolin particles were employed in this study. The fractal dimensions from the image analysis were $D_2=1.79{\pm}0.07$ for floc from natural particles and $D_2=1.84{\pm}0.06$ for floc from kaolin particles. The lower fractal dimension($D_2$) of floc from natural particles indicated that the aggregates were more porous and less compact than floe from kaolin particles. In addition, both the specific cake resistances and compressible degrees of flocs from natural particles showed greater values than those of flocs from kaolin particles. The results implied that the porous and loose flocs from natural particles were more easily compressed on membrane surface than the dense and compact flocs from kaolin particles. The compressed flocs yielded the great hydraulic resistances by hindering the water flow through the cake layer.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.249-252
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• 2009

Nanocrystalline ceria particles were prepared by using the ultrasonic spray pyrolysis method. The prepared ceria particles were found to be spherical and non-agglomerated by the SEM and TEM analyses. It was found that carrier gas influences the size and morphology. It was found that the air stream of carrier gas results in porous agglomerated structure of ceria abrasives, whereas solid nano-sphere can be obtained in a more oxidizing atmosphere.