• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.678-679
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• 2006

The effects of particle size on the surface properties of hydro-thermally synthesized barium titanate powders were investigated by means of particle size analysis, specific surface area, SEM, zeta potential and XPS. Particle sizes were measured by laser light scattering and are in the range of 150 to 1100nm. Zeta potential increased with increasing particle size and it was large minus value in the range of particle size from 500 to 900nm, which seems to be related with the dissolution of $Ba^{2+}$ ion in these particle sizes from the analysis of surface properties by XPS.

• Journal of the Korean Ceramic Society
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• v.43 no.4 s.287
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• pp.213-219
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• 2006

A Monte Carlo simulation based on Potts model in a three dimensional lattice was studied to analyze and design microstructures in porous sintered compacts such as porosity, pore size, grain (particle) size and contiguity of grains. The effect of surface energy of particles and the content of additional fine particles to coarse particles on microstructure development were examined to obtain fundamentals for material design in porous materials. It has been found that the larger surface energy enhances sintering (necking) of particles and increases contiguity and surface energy does not change pore size and grain size. The addition of fine particles also enhances sintering of particles and increases contiguity, but it has an effect on increment of pore size and grain size. Such a simulation technique can give us important information or wisdom for design of porous materials, e.g., material system with high surface energy and fine particle audition are available for higher strength and larger porosity in porous sintered compacts with applications in an automobile.

• Journal of the Korean institute of surface engineering
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• v.49 no.4
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• pp.331-338
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• 2016

In this work, anodic oxidation behavior of AZ31 Mg alloy was studied as a function of $Na_2CO_3$ concentration in electrolyte by voltage-time curves and observation of surface appearances and morphologies after the anodic treatments, using optical microscopy and confocal scanning laser microscopy (CSLM). The voltage-time curves of AZ31 Mg alloy surface and surface appearances after the anodic treatments showed three different regions with $Na_2CO_3$ concentration : region I, below 0.2 M $Na_2CO_3$ where shiny surface with a number of small size pits; region II, between 0.4 M and 0.6 M $Na_2CO_3$ where dark surface with relatively low number of large size burned or dark spots; region III, more than 0.8 M $Na_2CO_3$ where bright surface with or without large size dark spots were obtained. The anodically treated AZ31 Mg alloy surface became significantly brightened with increasing $Na_2CO_3$ concentration from 0.5 M to 0.8 M which was attribute to the formation of denser and smoother surface films. Pits and porous protruding reaction products were found at relatively large size and small size spots, respectively, on the AZ31 Mg alloy surface in low concentration of $Na_2CO_3$ less than 0.2 M. The formation of pits is attributed to the result of repetition of the formation and detachment of porous anodic reaction products. Based on the experimental results obtained in this work, it is concluded that more uniform, denser and smoother surface of AZ31 Mg alloy could be obtained at more than 0.8 M $Na_2CO_3$ concentration if there is no other oxide forming agent.

• Journal of Applied Reliability
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• v.16 no.2
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• pp.155-161
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• 2016

Purpose: Purpose of this study is to analyze the effect of particle size as well as number of pass on surface microstructure and hardness of SiC(p)/AZ31 surface composite fabricated by friction stir process (FSP). Method: SiC(p)/AZ31 surface composite containing different size of SiC particle (i. e., $2{\mu}m$ and $8{\mu}m$) was fabricated by multi-pass FSP. Microstructure was observed by scanning electron microscope and surface hardness was determined by Vickers hardness tester. Results: For all the FSPed specimens with and without hardening particles, grain size was refined due to dynamic recrystallization behavior. Surface hardness was observed to increase with decreasing particle size in the composite layer. Increasing number of FSP pass was effective for homogeneous distribution of the hardening particles and for resulting increase in surface hardness. Conclusion: FSP was effective to modify surface microstructure for improving surface hardness of SiC/AZ31 composite.

• Korean Journal of Materials Research
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• v.32 no.10
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• pp.414-418
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• 2022

Magnesium alloy is the lightest practical metal. It has excellent specific strength and recyclability as well as abundant reserves, and is expected to be a next-generation structural metal material following aluminum alloy. This paper investigated the possibility of thin plate fabrication by applying a overheating treatment to the melt drag method, and investigating the surface shape of the thin plate, grain size, grain size distribution, and Vickers hardness. When the overheating treatment was applied to magnesium alloy, the grains were refined, so it is expected that further refinement of grains can be realized if the overheating treatment is applied to the melt drag method. By applying overheating treatment, it was possible to fabricate a thin plate of magnesium alloy using the melt drag method, and a microstructure with a minimum grain size of around 12 ㎛ was obtained. As the overheating treatment temperature increased, void defects increased on the roll surface of the thin plate, and holding time had no effect on the surface shape of the thin plate. The fabricated thin plate showed uniform grain size distribution. When the holding times were 0 and 30 min, the grain size was refined, and the effect of the holding time became smaller as the overheating treatment temperature increased. As the overheating temperature becomes higher, the grain size becomes finer, and the finer the grain size is, the higher the Vickers hardness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1145-1150
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• 2005

The aim of this paper is to investigate the effect of surface texturing on metal surface and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 is recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.4
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• pp.118-122
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• 2001

In this study, the variation of surface roughness was tested in surface grinding for the three working materials SM45C, heat-treated SM45C, and gray cat iron. IT was performed for the various grinding wheels with two grain size #60, #100, and three grade I, O, R and various grinding depths and feeds, The fractural grinding depths which were obtained when the grinding wheels were destructed in surface grinding works, were examined and compared with the calculated value sug-gested in this study, The results showed that the surface roughness was decreased by decreasing grinding depth, and feed, and increasing grain size and grades. The fracture grinding depths were increased by increasing grain size, grade and feed.

• Journal of Sensor Science and Technology
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• v.18 no.3
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• pp.226-233
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• 2009

In this study, the optical properties of localized surface plasmon resonance sensor using optical fiber was analyzed as the variation of a size and surface density of gold nano particles on the etched optical fiber surface. It is shown that a size and surface density of gold nano particles on optical fiber surface are controlled by $Na_3$ citrate quantity and pH of gold colloid solution. To measure the sensitivity, peak wavelength of absorbance spectrum was detected as the reflective index of the solution. The sensor sensitivity is linearly dependent on the size and surface densities of gold nano particles from the results of optical experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.217-222
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• 2004

The aim of this paper is to investigate the effect of micro-dimple size on reduction friction and to understand the potential of friction reduction through micro-scale dimple to fabricate by photolithography on pin-on-disk test using flat-on-flat contact geometry. It was verify that the friction property with respect to the same pitch has been influence on the size of dimple under lubricated sliding contact. Also, we can recognize from Stribeck curve that the friction property has a connection with the size of dimple. It can explain a relationship between the friction coefficient and a dimensionless parameter for lubrication condition. The friction property has been an effect on the size of surface texture on reduction friction, not only because the density of dimple, but also because the ratio of diameter/pitch. This ratio of approximately 0.5 is recommend under the tested friction condition. It suggested that the ratio of d/p is an important parameter for surface texture design.

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.581-588
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• 2000

Phase transition of the Lennard-Jonesian binary system with a free surface was studied by employing molecular dynamics simulation. The main focus of this study was to investigate the effect of size misfit and solute concentration on phase transition during heating and quenching. For a binary system with a free surface, the melting point and the critical quenching rate decrease as size misfit and solute concentration increase.