• Journal of the Korean Applied Science and Technology
• /
• v.33 no.4
• /
• pp.734-740
• /
• 2016

The micron-sized indium zinc tin oxide (IZTO) particles were prepared by spray pyrolysis from aqueous precursor solution for indium, zinc, and tin and organic additives such as citric acid (CA) and ethylene glycol (EG) were added to aqueous precursor solution for indium, zinc, and tin. The obtained IZTO particles prepared by spray pyrolysis from the aqueous solution without organic additives had spherical and filled morphologies, whereas the IZTO particles obtained with organic additives had more hollow and porous morphologies. The micron-sized IZTO particles with organic additives were changed fully to nano-sized IZTO particles, whereas the micron-sized IZTO particles without organic additives were not changed fully to nano-sized IZTO particle after post-treatment at $700^{\circ}C$ for 2 hours and wet-ball milling for 24 hours. Surface resistances of micron-sized IZTO's before post-heat treatment and wet-ball milling were much higher than those of nano-sized IZTO's after post-heat treatment and wet-ball milling. From IZTO with composition of 80 wt. % $In_2O_3$, 10 wt. % ZnO, and 10 wt. % $SnO_2$ which showed a smallest surface resistance IZTO after post-heat treatment and wet-ball milling, thin films were deposited on glass substrates by pulsed DC magnetron sputtering, and the electrical and optical properties were investigated.

• Membrane Journal
• /
• v.19 no.1
• /
• pp.47-53
• /
• 2009

The aim of this paper is to prepare metal/ceramic composite ultrafiltration membranes by coating inorganic particles on a metallic hollow fiber filter. The diameter and the pore size of the filter was 2.0 mm and $2{\sim}8{\mu}m$. The metal/ceramic composite ultrafiltration membranes were obtained by a coating process of silica and titania sols on top of the metallic filter. For this purpose the method of fast freeze drying and dip-coating were used. It was found that the pore size of the membrane was about 50 nm from SEM and PMI characterization. The pore size was controlled by changing the size of the particles, sintering period and temperature.

• Membrane Journal
• /
• v.9 no.3
• /
• pp.185-192
• /
• 1999

The ultrafiltration characteristics of wafer processing wastewater produced from semicon¬ductor industry was investigated for wastewater reuse. Using the pilot-scale ultrafiltration system con¬taining poly sulfone hollow fiber membranes (MWCO : 10,000, 20,000, 30,(00), the membrane performance, such as flux, rejection rate and concentration factor for flux was examined. The SDhs, turbidity, electrical conductivity and concentration of Si particles were measured, and the possibility of permeate reuse was validated from the experimental results. It was shown that the flux was recovered by the sweeping with air and water effectively. The permeate flux of 30,000 MWCO membrane was about 5 times higher than that of 10,000 and 20,000 MWCO membranes. The concentration of Si particle in the saw wastewater was analyzed 3.8-5.6 mg/$\ell$ and that of Si particle in the permeate was analyzed less than 0.2${\mu}g$/$\ell$. This means the rejection of silicon particle was over 96%.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.44 no.3
• /
• pp.1-8
• /
• 2012

The effects of several factors including organic pigment blending and calending conditions on the surface and optical properties of coated paper were investigated. When clay and calcium carbonate are blended in the ratio of 7 to 3, highest smoothness and relative sediment volume were obtained. When organic pigments were added to the mixture of clay and calcium carbonate, the relative sediment volume did not changed significantly. However, when organic pigments were added to calcium carbonate, sheet gloss and smoothness were improved, and showed the better results than that obtained from the mixture of organic pigment and clay. When organic pigment is blended with clay, the particles of organic pigment are buried in the packing structure of coating layer. However, the particle shape of calcium carbonate is quite different from that of clay, and the aspect ratio of calcium carbonate is similar to that of organic pigment. Thus organic pigment particles are not buried and improved effectively the physical characteristics of coating layer. When the hollow sphere pigment was blended, opacity and sheet gloss were improved significantly. Even though the coating color applied was reduced, the similar level of opacity was maintained. Also, if particle size and void volume are increased, gloss is improved, because coating layer is easily transformed in calendering. Therefore, even though lower pressure was applied during calendering, the smoothness of surface of coating layer was improved, and the decrease of void volume in coating layer was reduced, and the quality of coated sheet can be improved.

• Resources Recycling
• /
• v.25 no.6
• /
• pp.92-97
• /
• 2016

Spray dried $Cr_2O_3$ powder having an agglomerated structure of particles was twice treated into a plasma flame to increase its apparent density. The powder subjected to the first densification treatment did not show the entirely melted state keeping inner particle hollows, and it was fully melted after the second processing only. The powder size as a result of the second treatment decreased, and the apparent density as well as flowability were increased due to melting and surface smoothing effects. But a part of particles after the second densified treatment showed the hollow structure, especially those which were above $30{\mu}m$ in size. This densification behavior of the powder has been qualitatively discussed in terms of the thermal conductivity and inner gas pressure within aggregates exposed to the plasma flame.

• Korean Journal of Materials Research
• /
• v.13 no.3
• /
• pp.180-184
• /
• 2003

Ce-doped $Y_2$SiO$_{5}$ phosphor particles of spherical morphology, fine size, high crystallinity and high photoluminescence (PL) intensity were prepared by spray pyrolysis. When nitrate precursor solution is adopted, hollow particles were formed by uneven drying rate between surface and inside of droplet. Citric acid and ethylene glycol were introduced as polymeric precursor to control the morphology of particles. When polymeric solution is adopted, polymeric chain is formed by the esterification reaction between carboxyl and hydroxy groups of citric acid and ethylene glycol, and considered as controlling the drying characteristics of droplet. $Y_2$$SiO_{5}$ :Ce phosphor particles prepared from polymeric precursor solution were spherical, filled, fine size and not agglomerate before and after post heat treatment. The optimum doping concentration of cerium was 0.5 mol% of overall solution concentration. The optimum amount of TBOS of high PL intensity and pure crystallinity of X2-type $Y_2$$SiO _{5}$ was 105% of stoichiometric amount. The PL intensity of $Y_2$X$/_{5}$ :Ce phosphor particles prepared using the polymeric precursor solution was 164% of that of the nitrate precursor solution due to homogeneous composition and good morphology.y.

• Membrane and Water Treatment
• /
• v.13 no.6
• /
• pp.291-301
• /
• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• Journal of Powder Materials
• /
• v.12 no.3
• /
• pp.167-173
• /
• 2005

Production of weakly agglomerated nanopowders with the characteristic size of about 10 nm and a narrow particle size distribution is still a topical problem especially if the matter is an acceptable output (>50 g/hour), a high purity of the final product, and a low (energy consumption. The available experience and literature data show that the most promising approach to production of such powders is the evaporation-condensation method, which has a set of means for heating of the target. From this viewpoint the use of pulsed electron accelerators for production of nanopowders is preferable since they allow a relatively simple adjustment of the energy, the pulse length, and the pulse repetition rate. The use of a pulsed electron accelerator provides the following opportunities: a high-purity product; only the target and the working gas will interact and their purity can be controlled; evaporation products will be removed from the irradiation zone between pulses; as a result, the electron energy will be used more efficiently; adjustment of the particle size distribution and the characteristic size of particles by changing the pulse energy and the irradiated area. Considering the obtained results, we developed a design and made an installation for production of nanopowders, which is based on a hollow-cathode pulsed gas-filled diode. The use of a hollow-cathode gas-filled diode allows producing and utilizing an electron beam in a single chamber. The emission modulation in the hollow cathode will allow forming an electron beam 5 to 100 ms long. This will ensure an exact selection of the beam energy. By now we have completed the design work, manufactured units, equipped the installation, and began putting the installation into operation. A small amount of nanopowders has been produced.

• Clean Technology
• /
• v.30 no.1
• /
• pp.55-61
• /
• 2024

Efforts are actively underway to address the issues related to the high cost of Pt-based catalysts for oxygen reduction reactions by designing high-performance Pt-based alloys through the control of their nanostructures. In this study, a method was proposed to control the nanostructure of Pt-based alloys, either hollow or core-shell, by adjusting the pH of the solution during the galvanic replacement reaction between the carbon-supported nickel-nickel nitride composite and the Pt ions. The physical characteristics, including the state, quantity, and morphology of the metal particles under different preparation conditions, were evaluated through X-ray diffraction, transmission electron microscopy, and inductively coupled plasma. When the prepared catalysts were employed for the oxygen reduction reaction, they exhibited an improvement in area specific-activity compared to a commercial Pt/C, with a 1.7 and 1.9-fold enhancement for the hollow and core-shell structured catalysts, respectively.

• Membrane Journal
• /
• v.32 no.2
• /
• pp.150-162
• /
• 2022

In the field of water treatment and pharmaceutical bio an alumina hollow fiber membrane used for mixture separation. However, due to the lack of strengths it is very brittle to handle and apply. Therefore, it is necessary to study and improve the bending strength of the membrane to 100 MPa or more. In this study, as the mixing ratio of the nano-particles increased to 0, 1, 3, and 5 wt%, the viscosity of the fluid mixture increased. The pore structure of the hollow membrane produced by interrupting the diffusion exchange rate of the solvent and non-solvent during the spinning process suppresses the formation of the finger-like structure and gradually increases the ratio of the sponge-like structure to improve the membrane mechanical strength to more than 100 MPa. As a result, an interparticle space was ensured to improve the porosity of the sponge-like structure with high permeability, and it showed excellent N2 permeability of about 100000 GPU and high water permeability of 3000 L/m² h. Therefore, it can be concluded, that the addition of γ-Al₂O₃ nanoparticles as sintering aid is an important method to enhance the mechanical strength of the α-alumina hollow fiber membrane to maintain high permeability.