• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1217-1223
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• 2008

A series of Zr,S co-doped $TiO_2$ were synthesized by a modified sol-gel method and characterized by various spectroscopic and analytical techniques. The presence of sulfur caused a red-shift in the absorption band of $TiO_2$. Co-doping of sulfur and zirconium (Zr-$TiO_2$-S) improves the surface properties such as surface area, pore volume, and pore diameter and also enhances the thermal stability of the anatase phase. The Zr-$TiO_2$-S systems are very effective visible-light active catalysts for the degradation of toluene. All reactions follow pseudo firstorder kinetics with the decomposition rate reaching as high as 77% within 4 h. The catalytic activity decreases in the following order: Zr-$TiO_2$-S >$TiO_2$-S >Zr-$TiO_2$>$TiO_2$$\approx$ P-25, demonstrating the synergic effect of codoping with zirconium and sulfur. When the comparison is made within the series of Zr-$TiO_2$-S, the catalytic performance is found to be a function of Zr-contents as follows: 3 wt % Zr-TiO2-S >0.5 wt % Zr-$TiO_2$-S> 5 wt % Zr-$TiO_2$-S >1 wt % Zr-$TiO_2$-S. Higher calcination temperature decreases the reactivity of Zr-$TiO_2$-S.

• Journal of Powder Materials
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• v.26 no.6
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• pp.455-462
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• 2019

ZrB₂ ceramic and ZrB₂ ceramic composites with the addition of SiC, WC, and SiC/WC are successfully synthesized by a spark plasma sintering method. During high-temperature oxidation, SiC additive form a SiO₂ amorphous outer scale layer and SiC-deplete ZrO₂ scale layer, which decrease the oxidation rate. WC addition forms WO₃ during the oxidation process to result in a ZrO₂/WO₃ liquid sintering layer, which is known to improve the anti-oxidation effect. The addition of SiC and WC to ZrB₂ reduces the oxygen effective diffusivity by one-fifth of that of ZrB₂. The addition of both SiC and WC shows the formation of a SiO₂ outer dense glass layer and ZrO₂/WO₃ layer so that the anti-oxidation effect is improved three times as much as that of ZrB₂. Therefore, SiC- and WC-added ZrB₂ has a lower two-order oxygen effective diffusivity than ZrB₂; it improves the anti-oxidation performance 3 times as much as that of ZrB₂.

• Journal of the Korean Applied Science and Technology
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• v.34 no.3
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• pp.643-649
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• 2017

Biodegradable enzymes such as lipase and proteinase can hydrolyze not only fatty acid esters and triglycerides, but also aliphatic polyesters. We measured the biodegradability that biodegradable enzymes have an important role in the degradation of natural aliphatic poly material such as PLA, corn starch, and polyethylene glycol in the natural environment. However, we investigated on the biodegradability of PLA, PLA and Polyethylene acrylate blended, and PLAcoPolyethylene polymerized with PLA graft copolymer Polyethylene glycol acrylate. When prepared biodegradable polymers. the Mechanical properties of them were measured on Biodegradability, thermal properties, real time in-situ electrical monitoring of polymers resin. Therefore BOD and biodegradation of PLAcoPolyethylene was graft copolymerized with PLA and polyethylene acrylate were measured at a lower rate than the other samples.

• Elastomers and Composites
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• v.35 no.4
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• pp.272-280
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• 2000

The experimental kinetics was analyzed for commercial rubbers such as NR, IR, BR, SBR 1500, and SBR 1700. Kinetic analysis for the commercial rubbers was performed using a thermogravimetric method, which the activation energies of NR obtained by Kissinger, Friedman, ana Ozawa's method were 195.0, 198.3, and 186.3 kJ/mol, respectively. whereas that of SBR 1500 were 246.4, 247.5, and 254.8 kJ/mol, respectively. It was shown that the yield of pyrolytic oil was generally increased with increasing the final temperature. Considering the effect of heating rate. it was found that the yield of pyrolytic oil was not consistent for each sample. The number average molecular weight of pyrolitic oil of SBR 1500 was in the range of 740-2486. The calorific value of SBR 1500 was 39-40 kJ/g, and it might be a considerable energy potential although it was lower than the conventional fuel such as kerosene, diesel, light fuel, and heavy fuel.

• Korean Journal of Materials Research
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• v.15 no.3
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• pp.149-154
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• 2005

Teflon like fluorocarbon thin films have been deposited on silicon and oxide molds as an antistiction layer for the hot embossing process by an inductively coupled plasma (ICP) chemical vapor deposition (CVD) method. The process was performed at $C_4F_8$ gas flow rate of 2 sccm and 30 W of plasma power as a function of substrate temperature. The thickness of film was measured by a spectroscopic ellipsometry. These films were left in a vacuum oven of 100, 200 and $300^{\circ}C$ for a week. The change of film thickness, contact angle and adhesion and friction force was measured before and after the thermal test. No degradation of film was observed when films were treated at $100^{\circ}C$. The heat treatment of films at 200 and $300^{\circ}C$ caused the reduction of contact angles and film thickness in both silicon and oxide samples. Higher adhesion and friction forces of films were also measured on films treated at higher temperatures than $100^{\circ}C$. No differences on film properties were found when films were deposited on either silicon or oxide. A 100 nm silicon template with 1 to $500\;{\mu}m$ patterns was used for the hot embossing process on $4.5\;{\mu}m$ thick PMMA spun coated silicon wafers. The antistiction layer of 10 nm was deposited on the silicon mold. No stiction or damages were found on PMMA surfaces even after 30 times of hot embossing at $200^{\circ}C$ and 10 kN.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.540-544
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• 2008

Pyrolytic characteristics of mixed plastics containing 22 wt.% HDPE, 17 wt.% LDPE, 27 wt.% PP, 12 wt.% PS, 16 wt.% ABS, 6 wt.% PVC have been studied in the batch-type microreactor of stainless steel. Thermal degradation experiments were performed at temperature of $410{\sim}450^{\circ}C$. The yield of each pyrolytic products were obtained by the weight measurement and molecular weight distribution of pyrolytic liquid products determined by the GC-SIMDIS method. It was shown that the yield and molecular weight of pyrolytic liquid product were decreased with the increase of reaction temperature and time. It was know that 20wt% of PVC composing of the mixed plastics was converted to the gas products of chloride during the pyrolysis process. The chain-end scission rate parameter was determined to be 50.2 kcal/mole of mixed plastics by the Arrhenius plot.

• Journal of Environmental Science International
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• v.18 no.1
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• pp.61-72
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• 2009

Fabrication and oxidants production of 3 or 4 components metal oxide electrode, which is known to be so effective to destruct non-biodegradable organics in wastewater, were studied. Five electrode materials (Ru as main component and Pt, Sn, Sb and Gd as minor components) were used for the 3 or 4 components electrode. The metal oxide electrode was prepared by coating the electrode material on the surface of the titanium mesh and then thermal oxidation at $500^{\circ}C$ for 1h. The removed RhB per 2 min and unit W of 3 components electrode was in the order: Ru:Sn:Sb=9:1:1 > Ru:Pt:Gd=5:5:1 > Ru:Sn=9:1 > Ru:Sn:Gd=9:1:1 > Ru:Sb:Gd=9:1:1. Although RhB decolorization of Ru:Sn:Sb:Gd electrode was the highest among the 4 components electrode, the RhB decolorization and oxidants formation of the Ru:Sn:Sb=9:1:1 electrode was higher than that of the 3 and 4 components electrode. Electrogenerated oxidants (free Cl and $ClO_2$) of chlorine type in 3 and 4 components electrode were higher than other oxidants such as $H_2O_2\;and\;O_3$. It was assumed that electrode with high RhB decolorization showed high oxidant generation and COD removal efficiency. OH radical which is electrogenerated by the direct electrolysis was not generated the entire 3 and 4 components electrode, therefore main mechanism of RhB degradation by metal oxide electrode based Ru was considered indirect electrolysis using electrogenerated oxidants.

• Korean Journal of Materials Research
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• v.9 no.5
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• pp.503-508
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• 1999

We have investigated the physical and diffusion barrier property of Ti-Si-N film for Cu metallization. The ternary compound was deposited by using reactive rf magnetron sputtering of a TiSi$_2$target in an Ar/$N_2$gas mixture. Resistivities of the films were in range of 358$\mu$$\Omega$-cm, to 307941$\mu$$\Omega$-cm, and tended to increase with increasing the $N_2$/Ar flow rate ratio. The crystallization of the Ti-Si-N compound started to occur at 100$0^{\circ}C$ with the phases of TiN and Si$_3$N$_4$identified by using XRD(X-ray Diffractometer). The degree of the crystallization was influenced by the $N_2$/Ar flow ratio. The diffusion barrier property of Ti-Si-N film for Cu metallization was determined by AES, XRD and etch pit by secco etching, revealing the failure temperature of 90$0^{\circ}C$ in 43~45at% of nitrogen content. In addition, the very thin compound (10nm) with 43~45at% nitrogen content remained stable up to $700^{\circ}C$. Furthermore, thermal treatment in vacuum at $600^{\circ}C$ improved the barrier property of the Ti-Si-N film deposited at the $N_2$(Ar+$N_2$) ratio of 0.05. The addition of Ti interlayer between Ti-Si-N films caused the drastic decrease of the resistivity with slight degradation of diffusion barrier properties of the compound.

• Korean Journal of Materials Research
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• v.30 no.1
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• pp.38-43
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• 2020

Sand casting 3D printing uses a binder jetting method to produce a mold having complicated shape by spraying a binder on sand coated with activator. Appropriate heat treatment process in sand mold fabrication can increase the degree of polymerization to improve flexural strength. However, long heat treatment of over 24 hours decreases flexural strength and reliability due to chemical bond decomposition through thermal degradation. The main role of the activator is to control the reaction rate between the polymer chains. As a result, when the activator composition is increased from 0.15 wt% to 0.25 wt%, the flexural strength is increased by 218 N/㎠. However, excess activator (0.40 wt%) has been shown to decrease reliability without increasing flexural strength. The main role of the binder is to control the flexural strength of the specimen. As the binder composition is increased from 2.00 wt% to 4.00 wt%, the flexural strength increases to about 255 N/㎠, indicating the maximum flexural strength increase. Finally, the reliability of the flexural strength of the fabricated specimens is evaluated by a Weibull plot. Weibull modulus calculations are used to evaluate the flexural strength reliability of the specimens, and maximum reliability value of 11.7 is obtained at 0.20 wt% activator composition. Therefore, it is confirmed that this composition has maximum flexural strength reliability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.867-873
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• 2007

Thermal degradation characteristics of polypropylene and polystyrene have been studied in the thermogravimetric(TG) reactor and batch-type microreactor. The dynamic thermogravimetric curve of TG provided a valuable information about pyrolysis temperature. It was found that PS was thermally degraded at lower temperature of $30{\sim}50^{\circ}C$ than PP. It was found that the yield and molecular weight of liquid product in the microreactor were decreased with the increase of reaction temperature and time in the case of PP. The production of styrene monomer was significantly increased by the promotion of depolymerization with the increase of temperature and time. The chain-end scission rate parameters were determined to be 50.0 kcal/mole of PP, 45.2 kcal/mole of PS by the Arrhenius plot.