• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.15-23
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• 2009

Saturation-coverage silyl, $-SiH_3(a)$, overlayers were prepared from $Si_2H_6$ adsorption on three comparative surfaces: clean unmodified; D-precovered; and atomically roughened Si(100). Together with its precursor-mediated adsorption behavior, the surface reactivity of $Si_2H_6$ was found to be the highest on the unmodified Si(100)-$2{\times}1$ surface. This was correlated with its dissociative adsorption mechanism, in which both the $H_3Si-SiH_3$ bond scission and the dual surface $Si-SiH_3(a)$ bond formation require a surface dangling bond 'pair'. The unusually high thermal stability of $-SiH_3(a)$ on the unmodified surface was ascribed to a nearly close-packed $-SiH_3(a)$ coverage of ${\sim}0.9$ monolayer and the consequent lack of dangling bonds on the silyl-packed surface.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.599-602
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• 2001

In this study, we fabricated chemically polymerized PPy and PANi films with different selectivity by controlling dedoping time. And the sensing properties and mechanism of VOCs adsorption to conducting polymers were investigated. Thin sensor had higher sensitivity compared to thick one, and dedoped sensor for 1-minute highest sensitivity. Upon gas absorption, polypyrrole exhibited positive sensitivity while polyaniline had negative sensitivity. PPy film show hydrophilic property and PANi film show hydrophobic property. After the gas absorption, the sensitivity increased as a function of polarity of absorbed molecules. These behaviors are due to the polar molecules absorbed with the movable polaron or free carrier, and then it interrupt or generate the movement of polaron and carrier, and then it changes the conductivity of polymer. We found that conducting polymer sensors are very sensitive to the difference in polarity of gas molecules.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.3
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• pp.158-163
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• 2012

The purpose of this study is to improve recycling rate of the coal reject ash by investigating bloating mechanism for artificial lightweight aggregate of reject ash. In this study, we use reject ash (R/A) and dredged soil (D/S) as raw materials. The artificial lightweight aggregates were formed by plastic forming (${\phi}$ = 10 mm) and sintered by temperature raising method at different temperatures (between 1200 and $1275^{\circ}C$). The physical properties of the aggregates such as bulk specific gravity, adsorption and microstructure of surface and cross-section are investigated with the sintering temperature and rate of R/A-D/S contents. As the result of the bulk specific gravity graphs, we can found out the inflection point at content of R/A 80 wt.%. From the microstructure images, we considered the artificial lightweight aggregates content of R/A over 80 wt.% are distributed numerous uniform micro-pores by vitrification without Black Core and the artificial lightweight aggregates of R/A below 80wt.% are distributed macro-pores with Black Core.

• Journal of Surface Science and Engineering
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• v.39 no.3
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• pp.115-120
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• 2006

The codeposition behavior of WC particles from an additive-free nickel sulfate and sulfamate solution has been investigated. Electroplating of Ni/WC composites was carried out at different current density with variation of WC particle size. The Guglielmi adsorption mechanism is applied to the electroplating of the fine WC in Ni matrix. The contents of WC in Ni composite coating were increased both by increasing current density and WC concentration in the bath. The hardness of Ni/WC composite coating at low current density is higher than that at high current density since finer WC particles dispersed through the coating. The codeposition behaviors of Co coated WC particles were also investigated. Conducting layer of particles promoted the codeposition behavior of Ni/WC-Co composite coatings.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.803-807
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• 2010

Schorl modified by $H_2SO_4$ has been successfully developed to enhance schorl-catalyzed Fenton-like reaction for removal of phenol in an aqueous solution. The phenol removal percentage can be increased from 4% to 100% by the system of modified schorl and $H_2O_2$. Batch experiments indicate that the percent increases in removal of phenol by increasing the dosage of catalyst, temperature and initial concentration of $H_2O_2$. The results of XRD, FT-IR and SEM suggest that no new phases are formed after removal of phenol by modified schorl. ICP-AES results reveal that more dissolution of iron results in higher catalytic oxidant activity in the system of modified schorl and $H_2O_2$. Besides minor adsorption, mineral-catalyzed Fenton-like reaction governs the process.

• Journal of Pharmaceutical Investigation
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• v.21 no.1
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• pp.51-55
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• 1991

Porous spheres composed of natural waxes and inorganic materials containing vitamin E acetate as a drug were prepared by impregnation method. Furthermore, the amount of vitamin E acetate entrapped in the spheres and the release rate of vitamin E acetate from the spheres were studied. The impregnation of vitamin E acetate was carried out by dipping the spheres in vitamin E acetate solutions. Entrapment mechanism of vitamin E acetate could be expressed in terms of Langmuir's adsorption isotherm. The amount of vitamin E acetate entrapped in porous spheres was influenced by the structure and concentration of the polymer used in vitamin E acetate solutions, and the concentration of vitamin E acetate. Release characteristics of vitamin E acetate from the spheres were investigated by withdrawing samples periodically and analyzing them by spectrophotomer.

• Korean Journal of Materials Research
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• v.34 no.6
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• pp.261-266
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• 2024

Although most strains of escherichia coli (E. coli) are harmless, some serotypes can cause serious food poisoning in humans. It is very difficult to eliminate E. coli from our lives. Here we show that E. coli can be eliminated by hydroxyapatite (HAp). Because HAp has a positive charge, the material and E. coli are attracted through electrostatic interactions. Additionally, because the surface of HAp is porous, it enters the pores of the HAp surface removing them from the environment. The amount of adsorption was observed to increase over time, and the zeta potential value of the material tended to be similar to that of E. coli. This phenomenon is thought to have zeta potential similar to that of E. coli as it is adsorbed onto the HAp surface over time. E. coli stained with crystal violet was spread on a glass slide and HAp porous sol powder was dropped to remove the E. coli. We expect that this analysis will open a new direction for antibacterial materials.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.573-579
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• 2004

Electroflotation, which is used as an alternative to sedimentation, is a separation treatment process that uses small bubbles to remove low-density particulates. Making allowances for recent collision efficiency diagram based on trajectory analysis, it is necessary to tailor zeta potential of bubbles that collide with negatively charged particles. In this paper, the study was performed to investigate the effects of magnesium and aluminium ions on zeta potential of bubbles. And, it was studied to find out factors which could affect the positively charged bubbles. Consequently, zeta potential of bubbles increased both with higher concentration of metal ions and in the acidic pH value. And, a probable principle that explained the procedure of charge reversal could be a combined mechanism with both specific adsorption of hydroxylated species and laying down of hydroxide precipitate. It also depended on the metal ion concentration in the solution to display its capacity to control the bubble surface.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.13-20
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• 2014

A brief overview is given of the corrosion and hydrogen diffusion behaviors of high strength pipe steel in sour environment. Firstly, hydrogen adsorption and diffusion mechanism of the pipe steel is introduced. Secondly, the effect of iron sulfide film precipitated as a result of the corrosion reaction on the steel surface on hydrogen reduction reaction and subsequent hydrogen permeation through the steel is discussed. Moreover, the hydrogen diffusion behavior of the pipe steel under tensile stress in both elastic and plastic ranges is reviewed based on a number of experimental permeation data and theoretical models describing the hydrogen diffusion and trapping phenomena in the steel. It is hoped that this paper will result in significant academic contributions in the field of corrosion and hydrogen related problems of the pipe steel used in sour environment.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.685-688
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• 2002

In this paper, it is reported that the anode current changes at the constantly applied gate voltages and the current-voltage (I-V) characteristics of Si, Co silicide and Mo silicide field emitter arrays (FEAs) depending on vacuum level from a $10^{-9}$ torr to a $10^{-6}$ torr. The mechanism of the robustness of anode current degradation of Mo silicide FEAs under poor vacuum conditions can be explained by the model of tolerance for the oxygen adsorption and oxidation at the silicide surface. Also, we present the changes of emitting area and work function of the emitters according to vacuum level.