• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1117-1123
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• 2005

In this study, our varistors based on M. Matsuoka's composition were fabricated with ZnO nano-powder whose sizes were 50 nm and 100 nm. Before fabrication of ZnO nano-powder varistors, structure and Phase were analyzed by FE-SEM and XRD with size of ZnO nano-powders to obtain manufacturing information to fabricate the first ZnO varistors using by nano-powders. As a results of these analyses, calcination and sintering temperatures were respectively designed at $600^{\circ}C\;and\;1050^{\circ}C$. ZnO nano-powder varistors were analyzed by SEM and XRD to measure the changes of microstructures and phase after sintered by out process conditions. Also, electrical properties of ZnO nano-powder varistors were obtained by capacitance-voltage, frequency-teal impedance, and current-voltage corves. Our ZnO nano-powder varistors had about 2.5 times of electric field at varistor voltage as compared with normal ZnO varistors fabricated with micro-powder. Also, leakage current and non-liner coefficient respectively had $2.0{\times}10^{-6}A/cm^{-2}$ and 41 for ZnO nano-powder varistors with 50 nm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.183-184
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• 2005

In this study, our varistors based on M.Matsuoke's composition were fabricated with ZnO nano-powder whose sizes were 50nm and 100nm. Electrical properties of ZnO nano-powder varistors were obtained by capacitance-voltage and frequency-real impedance. nano-powder varistors are indicated the change of the interface defects density $N_t$ at the grain boundaries and the donor concentration $N_d$ in the ZnO grains. Frequency analysis was accomplished to understand the equivalent circuit.

• Journal of Sensor Science and Technology
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• v.26 no.5
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• pp.360-365
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• 2017

In this study, a heat treatment process was applied to ZnS nano-powder to improve the optical properties of ZnS ceramic, and the characteristics of heat treatment time were studied. The ZnS nano-powders were synthesized by hydrothermal synthesis. The heat treatment was carried out at $550^{\circ}C$ for 0.5, 1, 2, and 4 hours in a vacuum atmosphere ($10^{-2}torr$). X-ray diffraction and scanning electron microscope analyzes confirmed the change of crystal phase and grain size to confirm the structural change with heat treatment time. The heat treated ZnS nano-powder was sintered by hot pressing, and the change of optical properties of the ZnS ceramic was analyzed by infrared spectroscopy.

• Journal of Powder Materials
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• v.15 no.4
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• pp.292-296
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• 2008

The electromagnetic (EM) wave absorption properties of the $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline powder mixed with 5 to 20 vol% of Ni-Zn ferrites has been investigated in a frequency range from 100MHz to 10GHz. Amorphous ribbons prepared by a planar flow casting process were pulverized and milled after annealing at 425 for 1 hour. The powder was mixed with a ferrite powder at various volume ratios to tape-cast into a 1.0mm thick sheet. Results showed that the EM wave absorption sheet with Ni-Zn ferrite powder reduced complex permittivity due to low dielectric constant of ferrite compared with nanocrystalline powder, while that with 5 vol% of ferrite showed relatively higher imaginary part of permeability. The sheet mixed with 5 vol% ferrite powder showed the best electromagnetic wave absorption properties at high frequency ranges, which resulted from the increased imaginary part of permeability due to reduced eddy current.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.562-567
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• 2022

Novel self-illuminated smart windows were fabricated consisting of Cu-doped ZnS (ZnS:Cu) powder and polymer-dispersed liquid crystal (PDLC). This smart window shows not only switchable transparency but also self-illumination without any attachable luminous body. Its electro-optical characteristics, transmittance, and luminance were investigated in relation to various applied voltages and composition ratios. The optical transmittance and luminous intensity increased with increasing applied voltages. However, the optical transmittance decreased with increasing ZnS:Cu powder content. One of the self-illuminated smart windows, which was fabricated with 9 wt% of ZnS:Cu, achieved the optical transmittance of 60.5% (at 550 nm) and the luminance of 11.0 cd/m² at 100 V. This smart window could be used as a normal switchable smart window in daytime and light-emitting signage at night.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.538-543
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• 2008

Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.173-180
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• 2004

Nano sized ZnO particle as 20-30nm applies for material, pigments, rubber additives, gas sensors, varistors, fluorescent substance as well as new material such as photo-catalyst, sensitizer, fluorescent material. ZnO with a particle size in the range 20-30nm has provided to be an excellent UV blocking material in the cosmetics industry, which can be used in sunscreen product to enhance the sun protection factor and natural makeup effect. But pure ZnO particles application limits for getting worse wearing feeling. We make high-functional inorganic-composite that coated with nano-ZnO on the plate-type particle such as sericite, boron nitride and bismuthoxychloride. In this experiment, we synthesized composite powder using hydrothermal precipitation method. The starting material was ZnCl$_2$ Precipitation materials were used hexamethylenetetramine(HMT) and urea. We make an experiment with changing as synthesis factors that are concentrations of starting material, precipitation materials, nuclear formation material, reaction time, and reaction temperature. We analyzed composite powder's shape, crystallization and UV-blocking ability with FE-SEM, XRD, FT-IR, TGA-DTA, In vitro SPF test. The user test was conducted by product's formulator. In the results of this study, nanometer sized ZnD was coated regardless of the type of plate-powder at fixed condition range. When the coated plate-powders were applied in pressed powder product, the glaze of powder itself decreased, but natural make-up effect, spreadability, and adhesionability were increased.

• Journal of Powder Materials
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• v.14 no.3 s.62
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• pp.180-184
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• 2007

The material design and synthesis are of important to modem science and technology. Here, we report the synthesis of multifunctional nanomaterials with different properties: feroelecties $YMnO_3$ and multiferroic materials such as $CoFe_2O_4-YMnO_3,\;Fe_3O_4-YMnO_3,\;CoFe_2O_4-Cd_{0.85}Zn_{0.15}S,\;and\;Fe_3O_4-Cd_{0.85}Zn_{0.15}S$ nano-composites by using a chemical synthesis process. These results provide a simple and convenient synthesis process to produce multifunctional nanocomposites.

• Restorative Dentistry and Endodontics
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• v.48 no.1
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• pp.3.1-3.14
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• 2023

Objectives: This study evaluated the effect of different nanoparticulated zinc oxide (nano-ZnO) and conventional-ZnO ratios on the physicochemical properties of calcium aluminate cement (CAC). Materials and Methods: The conventional-ZnO and nano-ZnO were added to the cement powder in the following proportions: G1 (20% conventional-ZnO), G2 (15% conventional-ZnO + 5% nano-ZnO), G3 (12% conventional-ZnO + 3% nano-ZnO) and G4 (10% conventional-ZnO + 5% nano-ZnO). The radiopacity (R_ad), setting time (S_et), dimensional change (D_c), solubility (S_ol), compressive strength (C_st), and pH were evaluated. The nano-ZnO and CAC containing conventional-ZnO were also assessed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Radiopacity data were analyzed by the 1-way analysis of variance (ANOVA) and Bonferroni tests (p < 0.05). The data of the other properties were analyzed by the ANOVA, Tukey, and Fisher tests (p < 0.05). Results: The nano-ZnO and CAC containing conventional-ZnO powders presented particles with few impurities and nanometric and micrometric sizes, respectively. G1 had the highest Rad mean value (p < 0.05). When compared to G1, groups containing nano-ZnO had a significant reduction in the S_et (p < 0.05) and lower values of D_c at 24 hours (p < 0.05). The C_st was higher for G4, with a significant difference for the other groups (p < 0.05). The S_ol did not present significant differences among groups (p > 0.05). Conclusions: The addition of nano-ZnO to CAC improved its dimensional change, setting time, and compressive strength, which may be promising for the clinical performance of this cement.

• Journal of Powder Materials
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• v.12 no.4 s.51
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• pp.279-283
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• 2005

In this study, the ZnS composite powders for host material in phosphor was synthesized in situ by mechanical alloying. As the mechanical alloying time increases, particle size of ZnS decreases. ZnS powders of $1.85\;\mu{m}$ in a mean size was fabricated by mechanical alloying for 10h. The crystal structures of ZnS powders were investigated by X-ray diffraction and the photo-luminescence properties was evaluated with the optical spectra analyzer. The steady state condition of mechanically alloyed ZnS was obtained as a mean particle size of $2\;\mu{m}$ in 5h milling. The sphalerite and wurtize structures coexist in the ZnS mechanically alloyed for 5h. The ZnS powder mechanically alloyed for 10h grows to the sphalerite structure. And the strong emission peaks of ZnS are observed at 480 nm wave length at the powders of mechanically alloyed for 10h, but the sphalerite and wurtize structures in ZnS coexist and emission peaks are not appeared at the powders of mechanically alloyed for 10h.