• Journal of the Korean institute of surface engineering
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• v.43 no.6
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• pp.266-271
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• 2010

Ternary Mo-Cu-N films were deposited on Si wafer substrates with various copper contents by magnetron sputtering method using Mo target and Cu target in $Ar/N_2$ gaseous atmosphere. As increasing $N_2$ pressure, the microstructure of Mo-N films changed from ${\gamma}-Mo_2N$ of (111) having face-centered-cubic (FCC) structure to $\delta$-MoN of (200) having hexagonal structure. Detailed the microstructures of the Mo-Cu-N coatings were studied by X-ray diffraction, scanning electron microscopy and field emission transmission electron microscope. The results indicated that the incorporation of copper into the growing Mo-N coating led to the $Mo_2N$ and MoN crystallites were more well-distributed and refined and the copper existed in grain boundary. Ternary Mo-Cu-N films had a composite microstructure of the nanosized crystal crystalline ${\gamma}-Mo_2N$ and $\delta$-MoN surrounded by amorphous $Cu_3N$ phase.

• Journal of Powder Materials
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• v.19 no.2
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• pp.122-126
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• 2012

The Fe-based self-fluxing alloy powders and TiC particles were ball-milled and subsequently compacted and sintered at various temperatures, resulting in the TiC particle-reinforced Fe self-fluxing alloy hybrid composite, and the microstructure and micro-hardness were investigated. The initial Fe-based self-fluxing alloy powders and TiC particles showed the spherical shape with a mean size of approximately 80 ${\mu}m$ and the irregular shape of less than 5 ${\mu}m$, respectively. After ball-milling at 800 rpm for 5 h, the powder mixture of Fe-based self-fluxing alloy powders and TiC particles formed into the agglomerated powders with the size of approximately 10 ${\mu}m$ that was composed of the nanosized TiC particles and nano-sized alloy particles. The TiC particle-reinforced Fe-based self-fluxing alloy hybrid composite sintered at 1173 K revealed a much denser microstructure and higher micro-hardness than that sintered at 1073 K and 1273 K.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.658-664
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• 2020

Zeolite HY is wet impregnated with Ni (0.1, 0.3, 0.4, 0.5 wt%), Pt (0.1 wt%) and reduced in presence of hydrogen to form nanosized particles of Ni and Pt. All the catalysts were characterized by XRD, TEM, ESCA, NH₃-TPD, Pyridine adsorbed FT-IR and BET. Characterization results confirm that the Ni and Pt fractions effectively rehabilitated the physio-chemical properties of the zeolite HY catalysts. Further, all the reduced catalyst were screened with hydroisomerization of m-xylene at LHSV = 2.0 h^-1 in the temperature range 250-400 ℃ in steps of 50 ℃ in hydrogen atmosphere (20 ml/g). The addition of Ni to Pt catalyst increases hydroisomerization conversion, as well as maximizes p-xylene selectivity by restricting the pore size. The increasing trend in activity continues up to 0.3 wt% of Ni and 0.1 wt% Pt addition over zeolite HY. The increasing addition of Ni increases the total number of active metallic sites to exposed, which increases the metallic sites/acid sites ratio towards the optimum value for these reactions by better balance of synergic effect for stable activity. The rate of deactivation is pronounced on monometallic catalysts. The results confirm the threshold Ni addition is highly suitable for hydroisomerization reaction for product selectivity over Ni-Pt bimetallic/support catalysts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.558-561
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• 2001

In this study, the ZnS nanosized thin films were grown by the solution growth technique (SGT), and their structural and optical properties were examined. X-ray diffraction patterns showed that the ZnS thin film obtained in this study had the cubic structure ($\beta$-ZnS). With decreasing growth temperature and decreasing concentration of precursor solution, the surface morphology of film was found to be improved. In particular, this is the first time that the surface morphology dependence of ZnS film grown by SGT on the ammonia concentration is reported. The energy band gaps of samples were shown to vary from 3.69 eV to 3.91 eV, demonstrating that the quantum size effect of SGT grown ZnS is remarkable. Photoluminescence (PL) peaks were observed at the positions corresponding to the lower energy than that to energy band gap, illustrating that the surface states were induced by the ultra-fineness of grains in ZnS films.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.4 no.1
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• pp.36-42
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• 2018

Molecular imaging refers to detect the biochemical process in living organisms at the cellular and molecular levels and to quantify them. Due to several advantages of nanomaterials, various molecular images using nanomaterials are being tried. Attempts have been made to combine nanoparticles, known as micro- or nanosized nanomaterials, with radioactive isotopes for molecular imaging probe. The radiolabeled nanoparticles will expend the molecular imaging due to nanoparticle's size-dependent nature. In particular, iron oxide nanoparticles can be used for magnetic resonance imaging, can be adjusted in size, easily functionalized, and biocompatible, making it a very good platform for molecular imaging. In addition, iron oxide nanoparticles may be the best example for a new approach to molecular imaging techniques. In this paper, we introduce various methods for preparation of iron oxide nanoparticle combined with radioisotope starting from various synthesis methods of iron oxide nanoparticles to utilize iron oxide nanoparticles as a platform for molecular imaging through radioactive labeling.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.21-26
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• 2000

Nanosized powders of trimetallic orthoferrites containing La and Sm in different ratios were synthesised by the thermal decomposition at low temperatures of the corresponding hexacyanocomplexes. The precursors and their decomposition products were analyzed by simultaneous thermogravimetric and differential thermal analysis (TG/DTA), x-ray diffraction (XRD) and Raman spectroscopy. Single phase trimetallic precursors and oxides were obtained. The crystal structure of the perovskitic oxides was orthorhombic, and the lattice parameters were affected by the ionic size of the rare earth elements present in the oxides. Raman spectroscopy showed a disorder effect in the vibrational bands with increasing the La content.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.2
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• pp.76-81
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• 2007

A novel multi-layer type micro gas sensor for $NO_X$ detection was designed and fabricated. Micro platform defined as type II-1 in this article for micro gas sensor was fabricated using the MEMS technology to meet the demanding needs of lower power consumption. Nano composite materials were fabricated with nanosized tin oxide powder and $\underline{m}$ulti-$\underline{w}$all $\underline{c}$arbon $\underline{n}$ano $\underline{t}$ube (MWCNT) to improve sensitivity. We investigated characteristics of fabricated multi-layer type micro gas sensor with $NO_2$ concentration variations at constant 2.2 V. Sensitivity (S) of micro gas sensor were observed to increase from 2.9, to 7.4 and 11.2 as concentrations of $NO_2$ gases increased from 2.4 ppm, to 3.6 ppm and 4.9 ppm. When 2.4 ppm of $NO_2$ gas was applied, response time and recovery time of micro gas sensor were recorded as 101 seconds and 142 seconds, respectively.

• Journal of the Speleological Society of Korea
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• no.71
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• pp.5-11
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• 2006

A theoretical investigation of the solid phase mechanochemical synthesis of nano sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3 mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano TlCl by dilution of initial (2NaCl+$Tl_2SO_4$) mixture with the exchange reaction product (diluent,$zNa_2SO_4$, z=z*=11.25) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano TlCl obtained experimentally were compared with those for the model reaction KBr+TlCl+zKCl=(z+1) KCl+TlBr (z=z1*=13.5), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.516-519
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• 2011

Indium tin oxide (ITO) coatings were made using an ITO slurry and an ITO sol. This was achieved by dispersing nanosized ITO powder in a mixed solvent without any dispersant and developing an adhesive ITO sol from indium acetate and tin tetrachloride in a mixture of DMF and n-butanol. Coating was carried out in one step by spin coating an ITO slurry, which was then followed by an ITO sol over it. Here, the sol penetrates into the nano ITO particle layers to make them adhere to each other as well as to a glass substrate. This is then followed by sintering at 500$^{\circ}C$ for 1 h to produce a uniform film consisting of ITO particles of about 50 nm and 10 nm. ITO films were obtained with sheet resistances from 450 to 1500 ohm/${\Box}$ by varying spin speed and concentration. Transmittance is higher than 90% at 550 nm.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.947-954
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• 2002

HCl concentration and reaction time are the decisive factors in determining the structure of precipitates in the process of synthesis of $TiO_2$ particles from aqueous $TiOCl_2$ solution by precipitation and the volumetric proportion of brookite phase in $TiO_2$ particles can be controlled by these two factors. As reaction rate increases with increase of reaction temperature, the reaction time, at which maximum volumetric proportion of brookite phase in $TiO_2$ particles was obtained, was reduced. The brookite was transformed directly to rutile phase with only increase of reaction time. And precipitation was delayed with increase of HCl concentration because the amount of $H_2$O, which is necessary source of oxygen for conversion of $Ti^{+4}$ to $TiO_2$, was relatively reduced with increase of that. Brookite in the mixture phase powder was finally transformed to rutile phase via anatase through heat-treatment.