• Proceedings of the KSME Conference
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• 2004.04a
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• pp.967-972
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• 2004

The role of transfer films formed during sliding of polymer composites against steel counterfaces was studied in terms of the tribological behaviors of composites. Four kinds of composites were included in this study: (1) unfilled PPS, (2) PPS+2%CuO, (3) PPS+2%CuO+5% carbon fiber (CF), and (4) PPS+2%CuO+15%Kevlar. The filler material CuO was in nanoscale particulate form and the reinforcing material was in the form of short fibers. The composites were prepared by compression molding at $310^{\circ}C$ and sliding tests were run in the pin-on-disk sliding configuration. The counterface was made of tool steel hardened to 55-60 HRC and finished to a surface roughness of 0.09-0.10 ${\mu}m$ Ra. Wear tests were run for 6 hrs at the sliding speed of 1 m/s and contact pressure of 0.65 MPa. Transfer films formed on the counterfaces during sliding were investigated using AFM and SEM. The results showed that as the transfer film became smooth and uniform, wear rate decreased. PPS+2%CuO+15%Kevlar composite showed the lowest steady state wear rate in this study and its transfer film showed the smoothest and the most uniform characteristics. The examination of worn surfaces of PPS+2%CuO composite using X-ray area scanning (dot mapping) showed back-transfer of steel counterface material to the polymer pin surface. This behavior is believed to strengthen the polymer pin surface during sliding thereby contributing to the decrease in wear rate.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.149-153
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• 2016

Nanosized zeolites were prepared in an autoclave using tetraethoxysilane (TEOS), tetrapropylammonium hydroxide (TPAOH), and $H_2O$, at various hydrothermal synthesis temperatures. Using transmission electron microscopy and particle size analysis, the nanopowder particulate sizes were revealed to be 10-300 nm. X-ray diffraction analysis confirmed that the synthesized nanopowder was silicalite-1 zeolite. Using atomic layer deposition, the fabricated zeolite nanopowder particles were coated with nanoscale $TiO_2$ films. The $TiO_2$ films were prepared at $300^{\circ}C$ by using $Ti[N(CH_3)_2]_4$ and $H_2O$ as precursor and reactant gas, respectively. In the TEM analysis, the growth rate was ${\sim}0.7{\AA}/cycle$. Zeta potential and sedimentation test results indicated that, owing to the electrostatic repulsion between $TiO_2$-coated layers on the surface of the zeolite nanoparticles, the dispersibility of the coated nanoparticles was higher than that of the uncoated nanoparticles. In addition, the effect of the coated nanoparticles on the photodecomposition was studied for the irradiation time of 240 min; the concentration of methylene blue was found to decrease to 48%.

• Resources Recycling
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• v.19 no.3
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• pp.24-32
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• 2010

In the present work, a new separation system with rotating rakes has been developed to separate the film-based plastics from the recyclable materials, and environment assessment is also carried out during operation of the device. Capacity of the device was about 5.3 ton/hr at a rakes rotation speed of 26.0 rpm (the number of rakes in the 1st, 2nd and 3rd trials were 39, 52 and 48, respectively) and a belt conveyor speed of 38.5m/min, which satisfied the initial design capacity (5.0 ton/hr). Recovery ratio and purity of the plastic films were 92.6% and 96.5%, respectively at a rotation speed of 28 rpm. The levels of noise, vibration and particulate emission were below material standard regulatory limits. Plastic refused fuel (RPF) was also prepared with the recovered films. The calorific value and chlorine content of the prepared RPF were 9,740 kcal/kg and 0.18%, respectively which satisfy the first grade quality specification of the Korean RPF standard. As a result of this work, recovery of energy resources from the municipal solid waste is possible by adopting the developed separation device.

• Transactions of the Korean hydrogen and new energy society
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• v.11 no.3
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• pp.119-125
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• 2000

To improve the photochemical energy conversion efficiency and the stability of CdS particulate film electrode which is used to produce hydrogen from the aqueous $H_2S$ solution photoelectrochemically, surface treatment of this film was carried out using $TiCl_4$ solution. CdS particles for preparation of the films were synthesized by precipitation reaction of $Cd({NO_3})_2{\cdot}9H_2O$ and $Na_2S{\cdot}4H_2O$. Then, the CdS sol was hydrothermally treated for 12hr in an autoclave with the variation of treatment temperature to control the crystalline phase of particles. CdS film electrode was thus prepared by annealing at $400^{\circ}C$ for 12hr of the wet-film cast at room temperature, and subsequently surface treated with $TiCl_4$ solution. The electrodes were characterized using XRD, SEM, and the photocurrent meter. The photocurrents of Cds film electrodes prepared with surface treatment were up to two times higher than the electrodes without surface treatment, indicating about $4.0mA/cm^2$. Hydrogen production rate in a continuous flow system using photoelectrochemical or photochemical cells prepared with surface treatment also increased in proportion to the increase of photocurrents.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.31-44
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• 1985

The application of anaerobic attached microbial films in the expanded bed process has recently been examined at high temperatures ($55^{\circ}C$) and with particulate matter. Extrapolation of the kinetics suggested that waste activated sludge (WAS) could be efficiently digested at hydraulic retention times as short as six hours in the expanded bed process. This would represent a 99 percent digester reactor volume reduction and would introduce interesting solids management alternatives if such a high rate process were developed. This paper presents a summary of a 1.5 year study of the feasibility of such a process. Three continuously fed $55^{\circ}C$ laboratory reactor systems were used to define the kinetics and the site of reactions-control completely mixed reactors were compared to the expanded beds (AAFEB) with and without a hydrolysis unit preceding the attached film unit. Well defined laboratory-generated WAS was compared to actual WAS from a domestic sewage treatment facility. Sixty percent of the biodegradable organics were converted in an AAFEB at a 15-hour hydraulic retention time without hydrolysis, whereas greater than 95 perccent of the biodegradable organics were stabilized in a two-stage system consisting of a 3-day HRT hydrolysis reactor followed by a 15-hour HRT AAFEB. The limitations of this high rate process and its potential application are discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.230-237
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• 2007

Titania nanotube(TiNT) and CdS sol were synthesized by hydrothermal reaction under strongly basic condition and by precipitation reaction of $Cd(N0_3)_2$ and $Na_2S$ aqueous solutions, respectively. After preparing a series of CdS-TiNT composite films on $F:SnO_2$ conducting glass with variation of the mole ratio (r) of TiNT/(CdS+TiNT), their visible light absorption, photocatalytic activities for hydrogen production, and the photocurrent generation were examined. In general, this CdS-TiNT series showed lower photocatalytic activities and photocurrent generation under Xe light irradiation compared to their counterparts, i.e., CdS-$TiO_2$ particulate series. It appeared that TiNTs are not so effective photocatalyic material in spite of their larger specific surface areas compared to $TiO_2$ nanoparticles, because they indicate a poor crystallinity and less intimate interaction or contact with CdS particles owing to the tubular morphology and an easy agglomeration among themselves.