• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.743-745
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• 2015

Amorphous cobalt phosphates were synthesized with their distinct morphology by controlling the amount of base in the synthetic condition. The crystallinity and morphology of cobalt phosphates were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The prepared cobalt phosphates were applied as a heterogeneous catalyst for generating hydrogen gas from the hydrolysis reaction of sodium borohydride. We found that the catalyst prepared using the least amount of base condition at room temperature showed a plate shape with less than 10 nm thickness, which resulted in the best catalytic activity among all catalysts due to the large surface area.

• Journal of the Korean Applied Science and Technology
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• v.35 no.2
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• pp.350-356
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• 2018

Hydroxyapatite has been used for biomaterials since it has high biocompatibility. In this study, c-plane oriented hydroxyapatite was synthesized by hydrolysis of dicalcium phosphate intermediate by controlling temperature, concentration and pH. In basic condition, rod-like hydroxyapatite crystals were aggregated to form irregular particles in low concentration and plate-like particles exposed c-plane of hydroxyapatite crystal were obtained in high concentration, causing difference of 3 mV in zeta potential. Physicochemical properties of product were characterized by XRD, SEM, FT-IR, zeta potential measurement.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.3
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• pp.113-120
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• 2011

Precipitated calcium carbonate(PCC), particularly calcite crystal, is extensively used as a pigment, filler or extender in various industries such as paper, paint, textile, detergents, adhesives, rubber and plastics, food, cosmetics, and biomaterials. PCC is conventionally produced through the gas-liquid carbonation process, which consists on bubbling gaseous $CO_2$ through a concentrated calcium hydroxide slurry. This study is aimed to find some factors for controlling the morphology of engineered PCC in lab-scaled mixing batch. The experimental designs were based on temperature variables, $Ca(OH)_2$ concentration, $CO_2$ flow rate, and electrical conductivity. The model of engineered PCC morphology was finally controlled by adjustment of electrical conductivity(6.0~7.0 mS/cm) and $Ca(OH)_2$ concentration(10 g/L). Orthorhombic calcite crystals were mostly created at high concentration and electrical conductivity conditions because the increased ratio of $Ca^{2+}$ and $CO{_3}^{2-}$ ions affects the growth rate of orthorhombic faces. Excess calcium spices were contributed to the growth of faces in calcium carbonate crystal, and the non-stoichiometric reaction was occurred between $Ca^{2+}$ and $CO{_3}^{2-}$ ions during carbonation process.

• Journal of the Korean institute of surface engineering
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• v.49 no.5
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• pp.472-476
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• 2016

The nano-array of the vertically aligned rod-like particles grown on ZnO coated glass-substrates was obtained via hydrothermal process. ZnO thin film coatings were prepared on the glass substrates using a MOD (metallorganic deposition) dip-coating method with zinc chloride dihydrate as starting material and 2-ethylhexanol as solvent. ZnO nanorods were synthesized on the seeded substrates by hydrothermal method at $80^{\circ}C$ using zinc-nitrate hexahydrate as a Zn source and sodium hydroxide as a mineralizer. Under the hydrothermal condition, the rod-like nanocrystals were easily attaching on the already ZnO seeded (coated) glass surface. It has been shown that the hydrothermal synthesis parameters are key factors in the nucleation and growth of ZnO crystallites. By controlling of hydrothermal parameters, the ZnO particulate morphology could be easily tailored. Rod-shaped ZnO arrays on the glass substrates consisted of elongated crystals having 6-fold symmetry were predominantly developed at high Zn precursor concentration in the pH range 7~11.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.32.1-32.1
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• 2018

Novel soft magnetic materials can be achieved by altering material properties such as morphology, composition, crystallinity, and grain size of soft magnetic alloys. Especially, magnetic properties (i.e., saturation magnetization, coarcivity) of soft magnetics are significantly affected by grain boundaries which act as a control of magnetic domain wall movement. Thus, we herein develop a two-step electroless plating method to control morphology and grain size of FeCo films for excellent magnetic properties. Accordingly, the chemical composition to control the degree of polarization of FeCo alloys was altered by electroless deposition parameters; for example, electrolyte concentration and temperature. The grain size and crystallinity of FeCo alloys was dramatically affected by the reaction temperature because the grain growth mechanism dominantly occurs at $90^{\circ}C$ where as the neucleation only happens at $50^{\circ}C$. By simply controlling the temperature, the micron-sized FeCo grains embedded FeCo film was synthesized where the large grains allow high magnetization originated from larger magnetic domain with low corecivity and the nano-sized grains allow excellent soft magnetic properties due to the magnetic correlation length.

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.243-247
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• 2014

Spherical NiO-YSZ particles were synthesized by ultrasonic spray pyrolysis (USP). The morphology of the synthesized particles can be modified by controlling parameters such as precursor pH, carrier-gas flow-rate, and temperature of the heating zone. The synthesized spherical NiO-YSZ particles have rough surface morphology at high carrier-gas flow-rates due to rapid gas exhaustion and insufficient particle ordering. The Ni-YSZ cermet anode synthesized by ultrasonic spray pyrolysis at a flow rate of l L/min, with precursor solution at pH4, showed a higher maximum power density of 256 $mW/cm^2$ compared to a conventionally mixed Ni-YSZ anode (185 $mW/cm^2$) at $800^{\circ}C$. While the area-specific resistance of conventionally mixed Ni-YSZ anodes increases gradually with operation time (indicating performance degradation), the Ni-YSZ anode synthesized by USP does not exhibit any performance degradation, even after 500 h.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.337-343
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• 2018

The influence of solid loading in the slurry composition on the morphology of 3Y-TZP granules fabricated by two-fluid spray drying was investigated for solid contents varying between 30 wt% and 50 wt%. The resulting 3Y-TZP granules showed a sphere-like shape with diameters of $40-70{\mu}m$. However, a donut-like shape and a few cracks were observed on the granule surfaces fabricated using the slurry with 50 wt% solid content. The green density after cold isostatic pressing at 200 MPa was $2.1-2.2g/cm^3$, and a homogeneous fracture surface was obtained by complete destruction of granules. After sintering at $1500^{\circ}C$ for 2 h, all specimens had relative densities of 96.2 - 98.3%. With increasing solid content, the relative density decreased from 98.3% to 96.2%, but the grain size increased from $0.3{\mu}m$ to $0.6{\mu}m$. Highly sinterable zirconia granule powder could be obtained by controlling the slurry composition.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.119-119
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• 2016

Over the last years the anodic formation of ordered $TiO_2$ nanotube layers has created significant scientific interest. Titanium oxide nanotube formation on the titanium or titanium alloy surface is expected to be important to improve cell adhesion and proliferation under clinical conditions. It should be possible to control the nanotube size and morphology for biomedical implant use by controlling the applied voltage, alloying element, current density, anodization time, and electrolyte. $TiO_2$ nanotubes show excellent biocompatibility, and the open volume in the tubes may be exploited as a drug release platform and so on. Therefore, in this study, Nanotube shape on the Ti-29Nb-xHf alloys with applied potentials was reserched. $TiO_2$ nanotube formation on Ti-29Nb-xHf alloys was carried out using anodization technique as a function of applied DC potential (10 V to 30 V and 30 V to 10 V) and anodization time for 60~120 min in $1MH_3PO_4$ with small additions of (0.8 wt. %, to 1.2 wt. %) NaF. The morphology change of anodized Ti-29Nb-xHf alloys was determined by FE-SEM, XRD, and EDS.

• Fisheries and Aquatic Sciences
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• v.25 no.8
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• pp.429-440
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• 2022

This study assessed the effects of oxygen and ozone nanobubbles on gill morphology, weight gain, and mortality of Pacific white shrimp (Penaeus vannamei), as well as the level of Vibrio parahaemolyticus and water quality of shrimp culture tanks under lab conditions. Two experiments were carried out with oxygen macrobubble, ozone macrobubble, oxygen nanobubble, ozone nanobubble, and control treatments (air-stone macrobubble). Experiments were done in triplicate in 100 L tanks with 15‰ saline water, and 20 shrimp per tank. Tanks in Experiment 1 were not inoculated with bacteria; tanks in Experiment 2 were inoculated with V. parahaemolyticus at a concentration of 10⁶ CFU/mL. The results revealed that short treatments with ozone nanobubbles had minimal impact on shrimp gills, mortality, and growth rates, reduced V. parahaemolyticus concentration in water compared to the other groups, and improve water quality. These laboratory results indicate that ozone nanobubble treatment may be useful for controlling V. parahaemolyticus. More work is needed to find the best protocol to apply the technology on a commercial scale.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.1
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• pp.9-15
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• 2024

Nd-Fe-B permanent magnets have been utilized on various industrial fields such as electric vehicles, generator, robots with actuator, etc, due to their outstanding magnetic properties even 10 times better than conventional magnets. Recently, there are many researches that report magnetic properties improved by controlling microstructure through adjusting alloying elements or conducting various processing. Especially, post-sintering annealing (PSA) can significantly improve the coercivity by modifying the distribution and morphology of Nd-rich phase which formed at grain boundaries. In this study, Nd-Fe-B sintered magnets were subjected to primary heat treatment followed by secondary heat treatment at 460℃, 500℃, and 540℃ to investigate the changes in microstructure and magnetic properties with the secondary heat treatment temperature. EBSD analysis was conducted to compare anisotropic characteristics. Through the SEM and TEM observation for analyzing the morphology and distribution of Nd-rich phase, we investigated the relationship between microstructure and magnetic properties of sintered Nd-Fe-B magnets.