• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.7
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• pp.747-753
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• 2004

In this paper, nanocrystalline indium tin oxide (ITO) particles were fabricated by using synthesis without harmful elements. The synthetic method is to eliminate the chloridic and nitridic elements which are included in the current wet type synthetic method. Therefore, it is possible to lower synthetic temperature below 600 $^{\circ}C$ to eliminate the harmful elements. Accordingly, fine particle can be achieved by applying the process. Particle size, surface area, crystal structure, and composition ratio of the synthesized nanocrystalline ITO particle by using the method were analyzed with high resolution transmission electron microscopy (HRTEM), BET surface area analyzer, X-ray diffraction (XRD), and energy dispersion spectroscopy (EDS). As a result, its particle size is less than 10 nm, and the surface area exceeds 100 m$^2$/g. The XRD analysis indicates that the cystal structure of the powder is cubic one with orientation of <222>, <400>, <440>. Also, the analysis of the composition demonstrates that the around 8 wt% tin is uniformly included in In$_2$O$_3$ lattice of the nanoparticle.

• Korean Journal of Materials Research
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• v.33 no.3
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• pp.101-105
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• 2023

A mixture of elemental Co₅₀Si₅₀ powders was subjected to mechanical alloying (MA) at room temperature to prepare a CoSi thermoelectric compound. Consolidation of the Co₅₀Si₅₀ mechanically alloyed powders was performed in a spark plasma sintering (SPS) machine using graphite dies up to 800 ℃ and 1,000 ℃ under 50 MPa. We have revealed that a nanocrystalline CoSi thermoelectric compound can be produced from a mixture of elemental Co₅₀Si₅₀ powders by mechanical alloying after 20 hours. The average grain size estimated from a Hall plot of the CoSi intermetallic compound prepared after 40 hours of MA was 65 nm. The degree of shrinkage of the consolidated samples during SPS became significant at about 450 ℃. All of the compact bodies had a high relative density of more than 94 % with a metallic glare on the surface. X-ray diffraction data showed that the SPS compact produced by sintering mechanically alloyed powders for 40-hours up to 800 ℃ consisted of only nanocrystalline CoSi with a grain size of 110 nm.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1733-1739
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• 2017

Molecular dynamics simulations were performed to investigate the uniaxial tensile properties of nanocrystalline $U_{0.5}Th_{0.5}O_2$ solid solution with the Born-Mayer-Huggins potential. The results indicated that the elastic modulus increased linearly with the density relative to a single crystal, but decreased with increasing temperature. The simulated nanocrystalline $U_{0.5}Th_{0.5}O_2$ exhibited a breakdown in the Halle-Petch relation with mean grain size varying from 3.0 nm to 18.0 nm. Moreover, the elastic modulus of $U_{1-y}Th_yO_2$ solid solutions with different content of thorium at 300 K was also studied and the results accorded well with the experimental data available in the literature. In addition, the fracture mode of nanocrystalline $U_{0.5}Th_{0.5}O_2$ was inclined to be ductile because the fracture behavior was preceded by some moderate amount of plastic deformation, which is different from what has been seen earlier in simulations of pure $UO_2$.

• Journal of the Korean Magnetics Society
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• v.17 no.6
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• pp.226-231
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• 2007

High frequency loss property of nanocrystalline amorphous ribbon with a high resistivity insulation layer of $TiO_2$ and $SiO_2$ was studied. The insulation layer was fabricated by sol-gel method using dip-coating. The optimum composition ratio of metal alkoxide and slurry for fabrication of insulation layer was established and insulation layer with high adhesion was coated on the nanocrystalline amorphous ribbon. Frequency loss of magnetic core material manufactured on nanocrystalline amorphous ribbon with the surface insulation layer decreased over 40 % compared with that of magnetic core material without surface insulation layer. The insertion loss of an inductive coupler, which was prepared by using magnetic core material coated insulation layer, decreased due to reduction of frequency loss for magnetic core material and insertion loss decreased in proportion to frequency.

• Steel and Composite Structures
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• v.36 no.6
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• pp.631-642
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• 2020

This paper studies nonlinear stability behavior of a nanocrystalline silicon curved nanoshell considering strain gradient size-dependency. Nanocrystallines are composite materials with an interface phase and randomly distributed nano-size grains and pores. Imperfectness of the curved nanoshell has been defined based on an initial deflection. The formulation of nanocrystalline nanoshell has been established by thin shell theory and an analytical approach has been used in order to solve the buckling problem. For accurately describing the size effects related to nano-grains or nano-pores, their surface energies have been included. Nonlinear stability curves of the nanoshell are affected by the size of nano-grain, curvature radius and nano-pore volume fraction. It is found that increasing the nano-pore volume fraction results in lower buckling loads.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.169-172
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• 2003

Silicon nanocrystalline thin films on p-type (100) silicon substrate have been fabricated by pulsed laser deposition technique using a Nd:YAG laser with the wavelength of 355, 532, and 1064 nm. The base vacuum in the chamber was down to $10^-6$ Torr and the laser energy densities were 1.0~3.0 J/$\textrm{cm}^2$ After deposition, silicon nanocrystalline thin films have been annealed at nitrogen gas. Strong Blue and green luminescence from silicon nanocrystalline thin films have been observed at room temperature by photoluminescence and its peak energies shift to green when the wavelength is increased from 355 to 1064 nm.

• Journal of Sensor Science and Technology
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• v.16 no.1
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• pp.11-16
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• 2007

CuO is an important transition metal oxide with many practical applications such as catalysts, p-type semiconductor, solar cells, magnetic storage media and cathode materials. In this contribution, nanocrystalline CuO powders were prepared by solution reduction method using copper chloride ($CuCl_{2}{\cdot}2H_{2}O$), hydrazine ($N_{2}H_{4}$) and NaOH and subsequent heat treatment. The gas sensor using nanocrystalline CuO powders showed high sensitivities to acetone and ethanol.

• 한국신재생에너지학회:학술대회논문집
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• 2005.11a
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• pp.656-659
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• 2005

Nanocrystalline ceria powders were prepared by hydrothermal treatment of cerium(IV) ammonium nitrate solution without a precipitating agent. A systematic investigation of the effect of hydrothermal temperature and react ion time on the physical properties of the product powders was carried out. When the hydrothermal temperature was increased, the product ceria powders exhibited larger crystallite size with higher yield. Increasing reaction time produced more crystalline ceria powders attributed to further hydrothermal reactions and structural rearrangement. The physical properties of ceria powders can be control led by adjusting the hydrothermal conditions.

• Journal of Powder Materials
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• v.10 no.2
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• pp.129-135
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• 2003

Nanocrystalline powders of $MnFeP_{1-x}As_x$(x=0.45-0.6) have been synthesized by mechanochemical reaction at room temperature using high-energy ball milling from mixtures of Mn, Fe, P, and As Powders. It has been found that a mechanically induced self-propagating reaction (MSR) occurs within 2 hours of milling and it produces very fine polycrystalline powder having a hexagonal $Fe_2P$ structure. Further milling up to 24 hours did not change the crystalline and average particle sizes or the phase composition of the milling product. When x is 0.65, no reaction among the reactants has been observed even after 24 hours of milling. As the P content decreases in $MnFeP_{1-x}As_x$, the incubation time for the MSR has increased and the lattice constants in both a and c axes have changed.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1593-1596
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• 2007

Various yellow-emitting $Y_3Al_5O_{12}:Ce^{3+}$ (YAG:Ce) nanocrystalline phosphors, where some $Al^{3+}$ sites are substituted with $Ga^{3+}$ or some Y sites with Gd3+, have been synthesized. The rare earth ions such as $Pr^{3+}$ and $Tb^{3+}$ were also co-doped into YAG:Ce system, leading to the tunability of CIE coordinates of emission.