• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.60-67
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• 2017

In this study, we performed surface modification of biodegradable microcrystalline cellulose (MCC) to use as a filler in polyethylene (PE) composite in food packaging application. We modified MCC surface with (3-trimethoxysilylpropyl)diethylenetriamine (TPDT) silane coupling agent, which has one primary amino group and two secondary amino groups per molecule, to introduce amino groups with a carbon dioxide adsorption capability in MCC. Effects of each of the reaction conditions such as amount of TPDT introduced, swelling time, reaction temperature, and reaction time on surface modification degree of MCC were investigated by changing a variety of above reaction conditions. The amount of TPDT grafted on MCC surface and formation of chemical bonds were confirmed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and solid state $^{29}Si$ nuclear magnetic resonance (NMR) spectroscopy. We confirmed increase of grafted amount of TPDT on MCC with increasing reaction time, reaction temperature, and amount of introduced TPDT.

• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.649-656
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• 2002

In situ patterned zinc oxide thin films were prepared by precipitation of Zn(NO$_3$)$_2$ aqueous solution containing urea and by microcontact printing using Self-Assembled Monolayers(SAMs) on A1/SiO$_2$/Si substrates. The visible precipitation of Zn(OH)$_2$ that was formed in the Zn(NO$_3$)$_2$ aqueous solution containing urea was enhanced with an increase of the reaction temperature and the amount of urea. As the reaction time of Zn(NO$_3$)$_2$ with urea was prolonged, the thickness and grain size of Zn(OH)$_2$ thin layers were increased, respectively. The optimum precipitation condition was at 80$\^{C}$ for 1 h for the solution with the ratio of Zn(NO$_3$)$_2$ to urea of 1 : 8. Homogeneous ZnO thin films were fabricated by the heat treatment of 600$\^{C}$ for 1 h of Zn(OH)$_2$ precipitation on Al/SiO$_2$/Si substrate. This was available to the in-situ patterned ZnO thin films with uniform grain size. Hydrophobic SAM, Octadecylphosphonic Acid(OPA) and hydrophilic SAM, 2-Carboxyethylphosphonic Acid(CPA) were applied on the Al/SiO$_2$/Si substrate by microcontact printing method. In situ patterned ZnO thin film was successfully prepared by the heat treatment of Zn(OH)$_2$ precipitated on the surface of hydrophilic SAM, CPA.

• Clean Technology
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• v.26 no.2
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• pp.131-136
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• 2020

Biomass bamboo charcoal is utilized as anode for lithium-ion battery in an effort to find an alternative to conventional resources such as cokes and petroleum pitches. The amorphous phase of the bamboo charcoal is partially converted to graphite through a low temperature graphitization process with iron oxide nanoparticle catalyst impregnated into the bamboo charcoal. An optimum catalysis amount for the graphitization is determined based on the characterization results of TEM, Raman spectroscopy, and XRD. It is found that the graphitization occurs surrounding the surface of the catalysis, and large pores are formed after the removal of the catalysis. The formation of the large pores increases the pore volume and, as a result, reduces the surface area of the graphitized bamboo charcoal. The partial graphitization of the pristine bamboo charcoal improves the discharge capacity and coulombic efficiency compared to the pristine counterpart. However, the discharge capacity of the graphitized charcoal at elevated current density is decreased due to the reduced surface area. These results indicate that the size of the catalysis formed in in-situ graphitization is a critical parameter to determine the battery performance and thus should be tuned as small as one of the pristine charcoal to retain the surface area and eventually improve the discharge capacity at high current density.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.296-302
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• 2006

ILow-temperature $TiO_2$ sol was synthesized with various catalyst contents by using a sol-gel method. $TiO_2$ thin films were produced by a dip-coating method and their optical, structural and photocatalytic properties were examined. Transmittance of $TiO_2$ thin films with 0.10 mol, 0.25 mol, 0.50 mol and 0.75 mol catalyst content showed high transmittance in the visible range. XRD results showed the anatase-to-rutile phase transition was accelerated with increasing catalyst content and the crystallinity size of the $TiO_2$ thin films increased with increasing catalyst content. SEM results indicated that the particle size of the $TiO_2$ thin films was the smallest with catalyst content of 0.25 mol. Photocatalytic results showed that methylene blue was completely decomposed in the presence of anatase film prepared with 0.10 mol, 0.25 mol and 0.50 mol catalyst content.

• Journal of the Korean Magnetics Society
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• v.11 no.1
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• pp.21-25
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• 2001

$\alpha$-Fe$_2$O$_3$ thin films were prepared on Si substrate by a pulsed laser deposition system and characterized by X-ray and Mossbauer spectroscopy. The appropriate conditions of pulsation was the power of 5.128 W/cm2 at on oxygen pressure of 0.1 Torr at a substrate temperature of 30$0^{\circ}C$. After that the film was heated at 80$0^{\circ}C$ for 1 day. The particles shape deposited on the film was ellipsoidal and the average length and width were 200~300 nm, 70~150 am respectively. The crystal structure was conformed to be of corundums symmetry with the hexagonal unit cell having a lattice constant of u = 5.03$\pm$0.05 $\AA$, c = 13.735$\pm$0.05 $\AA$. The average angles between the atomic spin and the magnetic hyperfine field of Fe ion were 38$^{\circ}$and 48$^{\circ}$ at above and blow the Morin transition temperature respectively. The Morin transition was found to occur at the temperature ranges from 200 K to room temperature and atomic spin direction was assumed to change from 48$^{\circ}$ to 80$^{\circ}$in respect to the c-axis.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.220-224
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• 2000

Ultra-fine $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$ferrite powders have been prepared by the sol-gel method. The crystallographic and magnetic properties of the sample have been investigated by means of x-ray diffraction, Mossbauer spetroscopy and vibrating sample magnetometry. The formation of nano crystallized particles is confirmed. The x-ray diffractions of all samples with various compositions clearly indicate the presence of spinel structure. The Mossbauer spectra could be fitted as the superposition of two sextets due to F $e^{3+}$ A-site and B-site. The IS and QS values nearly constant with substituted Co-Ti contents, whereas $H_{hf}$ of B-site decreases with increasing Co-Ti substitution in $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$. The magnetic behaviour of powders shows that the saturation magnetization and the coercivity decrease with increasing x in $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$.$.X>.

• Korean Journal of Materials Research
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• v.8 no.6
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• pp.493-498
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• 1998

CdTe films were deposited by close spaced sublimation with various substrate temperatures, cell areas, and thicknesses of CdTe and ITO layers and their effects on the CdS/CdTe solar cells were investigated. The resistivity of CdTe layers employed in this study was 3$\times$ $10^{4}$$\Omega$cm For constant substrate temperature the optimum substrate ternperature for CdTe deposition was $600^{\circ}C$. To obtain larger grain size and more compact microstructure, CdTe film was initially deposited at 62$0^{\circ}C$, and then deposited at 54$0^{\circ}C$. The CdTe film was annealed at 62$0^{\circ}C$ and $600^{\circ}C$ sequentially to maintain the CdTe film quality. The photovoitaic cell efficiency improved by the "two-wave" process. For constant substrate temperature, the optimum thickness for CdTe was 5-6$\mu m$. Above 6$\mu m$ CdTe thickness, the bulk resistance of CdTe film degraded the cell performance. As the cell area increased the $V_{oc}$ remained almost constant, while $J_{sc}$ and FF strongly decreased because of the increase of lateral resistance of the ITO layer. The optimum thickness of the ITa layer in this study was 300~450nm. In this experiment we obtained the efficiency of 9.4% in the O.5cm' cells. The series resistance of the cell should be further reduced to increase the fill factor and improve the efficiency.

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.377-382
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• 1998

Atomic layer deposition(ALD) of amorphous TiN films on $SiO_2$ between 17$0^{\circ}C$ and 21O$^{\circ}C$ has been investigated by alternate supply of reactant sources, Ti[N($C_2,H_5,CH_3)_2]_4$ [tetrakis(ethylmethylamminoltitanium: TEMAT] and $NH_3$. Reactant sources were injected into the reactor in the order of TEMAT vapor pulse, Ar gas pulse, $NH_3$. gas pulse and Ar gas pulse. Film thickness per cycle was saturated at around 1.6 monolayer(MU per cycle with sufficient pulse times of reactant sources at 20$0^{\circ}C$. The results suggest that film thickness per cycle could be beyond 1 MLicycie in ALD, which were explained by rechemisorption mechanisms of reactant sources. The ideal linear relationship be¬tween number of cycles and film thickness is confirmed. As a results of surface limited reactions of ALD, step cover¬age was excellent. Particles caused by the gas phase reactions between TEMAT and NH3 were almost free because TEMAT was seperated from $NH_3$ by the Ar pulse. In spite of relatively low substrate temperature, carbon impurity was incorporated below 4 at%.

• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.67-74
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• 2016

The Prussian Blue Analogue(PBA) has three dimensional structure and the metal - organic framework material, and it has a variety configurations depending on the type of organic ligands. PBA has been receving an attention in the fields of biosensors, optical, catalytic, and hydrogen storage device. Also, it is an environmental friendly substance with a chemical stability. In addition, PBA is widely used in the filed of adsorption art since we can adjust the size of the fine pores. In this study, we synthesized $Mn_3[Fe(CN)_6]_2$, an organometallic framework chains by using a hydrothermal synthesis method. We used $K_4[Fe(CN)_6]$ and $MnCl_2$ as precursors. We also produced a manganese iron oxide, by baking the synthesized material. The effect of the size and shape of the particles was examined by controling pH of the precursor solution, the molar concentration of the precursor, and reaction time as the experimental variables. Synthesized absorbent was analyzed by XRD, SEM, FT-IR, UV-Vis, and TG / DTA to evaluate the adsorption properties of several dyes.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.6
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• pp.629-636
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• 1991

Yellowtail fishes(Seriola quinqueeradiata) were submitted to the storages using ice-cooling($0^{\circ}C$), partial freezing($-3^{\circ}C$) and freezing $-20^{\circ}C$) method. Changes in the structures of muscle during storage at different temperatures were investigated. The ice-cooling and partial freezing storage caused early decomposition of glycogen granules and mitochondrial inner membrane, but it was accorded to much slower manner comparing with that of ice-cooling storage. The scars of ice crystals were appeared after three days of storage. The number and size of the crystal increased as progressing of the storage. They were circular and mostly located between fibers. When using the freezing storage, glycogen granules were mostly found from the muscle cell even after fourteen days of storage. Mitochonidral inner membrane maintained their integrity. The scars of ice crystals were also found, however, different from those of partial freezing storage. Their existing sites were random and their shapes were irregular. In many cases, they located in the fiber and had keen edges. Fibers were broken mostly at the Z-lines on fourteen days of storage. From these results, it was concluded that partial freezing storage can repress autolytic enzymic action and can reduce the physical damage from ice crystals which is caused by freezing.