• Asian Journal of Atmospheric Environment
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• v.8 no.3
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• pp.154-161
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• 2014

The present study was undertaken to evaluate the chemical characteristics of Asian dust (hereafter called "AD") particles with the aid of the most advanced micro-PIXE (Particle-induced X-ray emission) analytical technique. To this end, size-selected particles were sampled on a rural peninsula of Korea (Byunsan, 35.37N; 126.27E) during AD and non-AD periods in 2004. The coarse particle (> $2{\mu}m$) number density during an AD event were 170 times higher than those of the non-AD counterpart. The average net-count of silica in individual particles collected on AD event was roughly 11 times higher than that of non-AD counterpart. The X-ray net-counts of trace elements (Zn, Co, Mn, and V) were also considerably high in AD relative to the non-AD day. Particle classification based on the inter ratio analysis of elemental net-count suggests that a large portion of the coarse particles collected during AD event underwent chemical transformation to a certain degree. The visual interpretation of micro-PIXE elemental maps and elemental localization data in and/or on individual AD particles clarified the internal mixture of AD particles with sea-salt and artificial metallic particles.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.404-408
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• 1999

Gallium doped zinc oxide(GZO) films were deposited on soda-lime glass substrates without substrate heating $(T_s<50^{\circ}C$) by dc planar magnetron sputtering using GZO ceramic oxide targe with different inert gas (Ar, or Ne). For the GZO films deposited under different total gas pressure $(P_{tot})$, structural and electrical properties were investigated by XRD and Hall effect measurements. Crystallinity of GZO films deposited using Ar was degraded with increase in $(P_{tot})$, suggesting that it was heavily affected by kinetic energy of sputtered Zn particles$(PA_{zn})$ arriving at substrate surface. Whereas, crystallinity of GZO films deposited at lower Ptot than 3.0 Pa using Ne gas was degraded with decrease in $(P_{tot})$. This degradation was considered to be result of film damage caused by the bombardment of high-energy neutrals ($Ne^{\circ}$). On the basis of a hard sphere collision processes, the average final energy of particles (sputtered Zn, $Ar^{\circ}$and $Ne^{\circ}$)arriving at substrate surface were estimated.

• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.634-645
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• 2008

In this study, surface composites were fabricated with Fe-based amorphous alloy powders and VC powders by high-energy electron beam irradiation, and the correlation of their microstructure with hardness and fracture toughness was investigated. Mixture of Fe-based metamorphic powders and VC powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders without flux to fabricate surface composites. The composite layers of 1.3~1.8 mm in thickness were homogeneously formed without defects and contained a large amount (up to 47 vol.%) of hard $Cr_2B$ and $V_8C_7$ crystalline particles precipitated in the solidification cell region and austenite matrix, respectively. The hardness of the surface composites was directly influenced by hard $Cr_2B$ and $V_8C_7$ particles, and thus was about 2 to 4 times greater than that of the steel substrate. Observation of the microfracture process and measurement of fracture toughness of the surface composites indicated that the fracture toughness increased with increasing additional volume fraction of $V_8C_7$ particles because $V_8C_7$ particles effectively played a role in blocking the crack propagation along the solidification cell region heavily populated with $Cr_2B$ particles. Particularly in the surface composite fabricated with Fe-based metamorphic powders and 30 % of VC powders, the hardness and fracture toughness were twice higher than those of the surface composite fabricated without mixing of VC powders.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.193-194
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• 2005

• Journal of the Korean Society of Clothing and Textiles
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• v.19 no.5
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• pp.765-773
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• 1995

Effect of interfacial electrical conditions such as, the f potential of PET fiber and u-Fe203 particles, the stability parameter and potential energy of interaction on adhesion of a-Fe903 particles to PET fabric and their removal from the fabric, were investigated as functions of pH, electrolyte and ionic strength. The stability parameter, potential energy of interaction between a-Fe2O3 particles and PET fabric were calculated by using the heterocoagulation theory for a sphere-plate model The adhesion of a-Fe2O3 particles to PET fabric and their removal from PET fabric were carried out by using water bath shaker and Terg-O-Tometer under various solution conditions. The adhesion of a-Fe2O3 particles to the PET fabric and the removal of a-Fe2O3 particles from the PET fabric were biphasic and were maximum and minimum at pH 7~8, respectively. With high pH and polyanion electrolytes in solution, the adhesion of a-Fe2O3 particles to the PET fabric was low but effects of electrolytes on the removal of a-Fe2O3 particles from the PET fabric was small. The adhesion of a-Fe2O3 particles to the PET fabric and the removal of a-Fe2O3 Particles from the PET fabric were biphasic, and were lowest and highest at the ionic strength 1$\times$10-3, respectively. The adhesion of a-Fe2O3 particles to PET fabric was well related with the interfacial electrical conditions; it was negatively correlated with the f potentials of a-Fe2O3 Particles of its absolute value, the stability parameter and the maximum of total potential energy, while, the adhesion was not related with the t potentials of PET fiber itself. Therefore, the primary factor determining the adhesion of a-Fe203 particles to PET fabric may be the stability of dispersed particles caused by the electrical repulsion of particles. The removal of a-Fe203 particles from PET fabric was not related to such interfacial electrical conditions as the t potentials of PET fiber, the stability parameter and the maximum of total potential energy but removal was related to t potential of a-Fe203 particles.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.4
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• pp.201-208
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• 1992

An experimental study of the constitutive response of precipitation-strengthened Al-0.55wt% Zr alloy, which consists of an Al matrix precipitation-strengthened by coherent particles, ${\beta}^{\prime}(Al_3Zr)$ with $L1_2$ structure has been performed. The deformation response of the materials has been examined by stress relaxation test at 573K, 623K and 673K. It was found that there exist the threshold stress during stress relaxation and threshold stress results from the presense of ${\beta}^{\prime}(Al_3Zr)$ particles. The ratio of threshold stress and Orowan stress decreased gradually with increasing temperature. The resistance to climb-pass of particles was independent of particles size for a fixed volume fraction although the threshold for bowing and particles cutting are sensitive to the particles dimensions. The smaller particles cutted by dislocations. This behavior of dislocations in this alloy was explained in terms of the small value antiphase boundary energy. The dislocation networks wrere more extensive in spesimens subjected to stress relaxation and there were numerous areas that have a high denstiy of jogged dislocation. This experiment results indicate that the rate controlling stress relaxation process is the climb of edge dislocation over particles.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.460-465
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• 2013

Plate-shaped inorganic particles are coated onto a stainless steel substrate by the electrophoretic deposition of a precursor slurry which includes the inorganic particles of $Al_2O_3$ and polymer resin in mixed solvents to mimic the abalone shell structure, which is a composite of plate-shaped inorganic particles and organic interlayer binding materials with a layered orientation. The process parameters of the electrophoretic deposition include the voltage, coating time, and conductivity of the substrate. In addition, the suspension parameters are the particle size, concentration, viscosity, conductivity, and stability. We prepared an organic-inorganic composite coating with a high inorganic solid content by arraying the plate-shaped $Al_2O_3$ particles and electrophoretic resin via an electrophoretic deposition method. We analyzed the effect of the slurry composition and the electrophoretic deposition process parameters on the physical, mechanical and thermal properties of the coating layer, i.e., the thickness, density, particle orientation, Young's modulus and thermogravimetric analysis results.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.595-595
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• 2016

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.96-96
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• 2016

Nanotechnology mostly employs nano-materials and nano-structures with distinctive properties based on their size, structure, and composition. It is quite difficult to produce nano-materials and nano-structures with identical sizes, structures, and compositions in large quantities, because of spatiotemporal fluctuation of production processes. In other words, fluctuation is the bottleneck in nanotechnology. We propose three strategies to suppress such fluctuations: employing 1) difference between linear and nonlinear phenomena, 2) difference in time constants, and 3) nucleation as a bottleneck phenomenon. We are also developing nano- and micro-scale guided assembly using plasmas as a plasma nanofabrication.1-5) We manipulate nano- and micro-objects using electrostatic, electromagnetic, ion drag, neutral drag, and optical forces. The accuracy of positioning the objects depends on fluctuation of position and energy of an object in plasmas. Here we evaluate such fluctuations and discuss the mechanism behind them. We conducted in-situ evaluation of local plasma potential fluctuation using tracking analysis of fine particles (=objects) in plasmas. Experiments were carried out with a radio frequency low-pressure plasma reactor, where we set two quartz windows at the top and bottom of the reactor. Ar plasmas were generated at 200 Pa by applying 13.56MHz, 450V peak-to-peak voltage. The injected fine particles were monodisperse methyl methacrylate-polymer spheres of $10{\mu}m$ in diameter. Fine particles were injected into the reactor and were suspended around the plasma/sheath boundary near the powered electrode. We observed binary collision of fine particles with a high-speed camera. The frame rate was 1000-10000 fps. Time evolution of their distance from the center of mass was measured by tracking analysis of the two particles. Kinetic energy during the collision was obtained from the result. Potential energy formed between the two particles was deduced by assuming the potential energy plus the kinetic energy is constant. The interaction potential is fluctuated during the collision. Maximum amplitude of the fluctuation is 25eV, and the average is 8eV. The fluctuation can be caused by neutral molecule collisions, ion collisions, and fluctuation of electrostatic force. Among theses possible causes, fluctuation of electrostatic force may be main one, because the fine particle has a large negative charge of -17000e and the corresponding electrostatic force is large compared to other forces.

• Journal of Powder Materials
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• v.28 no.1
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• pp.44-50
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• 2021

Zinc selenide (ZnSe) nanoparticles were synthesized in aqueous solution using glutathione (GSH) as a ligand. The influence of the ligand content, reaction temperature, and hydroxyl ion concentration (pH) on the fabrication of the ZnSe particles was investigated. The optical properties of the synthesized ZnSe particles were characterized using various analytical techniques. The nanoparticles absorbed UV-vis light in the range of 350-400 nm, which is shorter than the absorption wavelength of bulk ZnSe particles (460 nm). The lowest ligand concentration for achieving good light absorption and emission properties was 0.6 mmol. The reaction temperature had an impact on the emission properties; photoluminescence spectroscopic analysis showed that the photo-discharge characteristics were greatly enhanced at high temperatures. These discharge characteristics were also affected by the hydroxyl ion concentration in solution; at pH 13, sound emission characteristics were observed, even at a low temperature of 25℃. The manufactured nanoparticles showed excellent light absorption and emission properties, suggesting the possibility of fabricating ZnSe QDs in aqueous solutions at low temperatures.