• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.97-102
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• 2006

Anodic alumina with self-organized and ordered nano hole arrays can be a good candidate of an irradiation mask to modify the properties of nano-scale region. In order to try using porous anodic alumina as a mask for ion-beam patterning, ion beam transmittance of anodic alumina was tested. 4 Um thick self-standing AAO templates anodized from Al bulk foil with two different aspect ratio, 200:1 and 100:1, were aligned about incident ion beam with finely controllable goniometer. At the best alignment, the transmittance of the AAO with aspect ratio of 200:1 and 100:1 were $10^{-8}\;and\;10^{-4}$, respectively. However transmittance of the thin film AAO with low aspect ratio, 5:1, were remarkably improved to 0.67. The ion beam transmittance of self-standing porous alumina with a thickness larger than $4{\mu}m$ is extremely low owing to high aspect ratio of nano hole and charging effect, even at a precise beam alignment to the direction of nano hole. $SiO_2$ nano dot array was formed by ion irradiation into thin film AAO on $SiO_2$ film. This was confirmed by scanning electron microscopy that the $SiO_2$ nano dot array is similar to AAO hole array.

• Journal of Korea Soil Environment Society
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• v.4 no.1
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• pp.109-118
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• 1999

Recently, transport parameters of conservative solutes such as KCl in a porous medium have been successfully determined using time domain reflectometry (TDR) . This study was initiated to Investigate the applicability of TDR technique to monitoring the fate of a heavy metal ion in a sandy soil and the distribution of its concentration along travel distance with time. A column test was conducted in a laboratory that consists of monitoring both resident and flux concentrations of $ZnCl_2$in a sandy soil under a breakthrough condition. A tracer of $ZnCl_2$(10 g/L) was injected onto the top surface of the sample as pulse type as soon as a steady-state condition was achieved. Time-series measurements of resistance and electrical conductivity were performed at 10 cm and 20 cm of distances from the inlet boundary by horizontal-positioning of parallel TDR metallic rods and using an EC-meter for the effluent exiting the bottom boundary respectively. In addition. Zn ions of the effluent were analyzed by ICP-AES. Since the mode and position of concentration detected by TDR and effluent were different, comparison between ICP analysis and TDR-detected concentration was made by predicting flux concentration using CDE model accommodating a decay constant with the transport parameters obtained from the resident concentrations. The experimental results showed that the resident concentration resulted in earlier and higher peak than the flux concentration obtained by EC-meter, implying the homogeneity of the packed sandy soil. A close agreement was found between the predicted from the transport parameters obtained by TDR and the measured $ZnCl_2$concentration. This indicates that TDR technique can also be applied to monitoring heavy metal concentrations in the soil once that a decay constant is obtained for a given soil.

• Clean Technology
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• v.20 no.4
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• pp.375-382
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• 2014

This work investigated the plasma-catalytic decomposition of isopropyl alcohol (IPA) and the behavior of the byproduct compounds over monolith-supported metal oxide catalysts. Iron oxide ($Fe_2O_3$) or copper oxide (CuO) was loaded on a monolithic porous ${\alpha}-Al_2O_3$ support, which was placed inside the coaxial electrodes of plasma reactor. The IPA decomposition efficiency itself hardly depended on the presence and type of metal oxides because the rate of plasma-induced decomposition was so fast, but the behavior of byproduct formation was largely affected by them. The concentrations of the unwanted byproducts, including acetone, formaldehyde, acetaldehyde, methane, carbon monoxide, etc., were in order of $Fe_2O_3/{\alpha}-Al_2O_3$ < $CuO/{\alpha}-Al_2O_3$ < ${\alpha}-Al_2O_3$ from low to high. Under the condition (flow rate: $1L\;min^{-1}$; IPA concentration: 5,000 ppm; $O_2$ content: 10%; discharge power: 47 W), the selectivity towards $CO_2$ was about 40, 80 and 95% for ${\alpha}-Al_2O_3$, $CuO/{\alpha}-Al_2O_3$ and $Fe_2O_3/{\alpha}-Al_2O_3$, respectively, indicating that $Fe_2O_3/{\alpha}-Al_2O_3$ is the most effective for plasma-catalytic oxidation of IPA. Unlike plasma-alone processes in which tar-like products formed from volatile organic compounds are deposited, the present plasma-catalyst hybrid system did not exhibit such a phenomenon, thus retaining the original catalytic activity.

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.121-129
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• 2015

The platinum anode for the electrolytic reduction process is generally surrounded by a nonporous ceramic shroud with an open bottom to offer a path for $O_2$ gas produced on the anode surface and prevent the corrosion of the electrolytic reducer. However, the $O^{2-}$ ions generated from the cathode are transported only in a limited fashion through the open bottom of the anode shroud because the nonporous shroud hinders the transport of the $O^{2-}$ ions to the anode surface, which leads to a decrease in the current density and an increase in the operation time of the process. In the present study, we demonstrate the electrolytic reduction of 1 kg-uranium oxide ($UO_2$) using the porous shroud to investigate its long-term stability. The $UO_2$ with the size of 1~4mm and the density of $10.30{\sim}10.41g/cm^3$ was used for the cathode. The platinum and 5-layer STS mesh were used for the anode and its shroud, respectively. After the termination of the electrolytic reduction run in 1.5 wt.% $Li_2O-LiCl$ molten salt, it was revealed that the U metal was successfully converted from the $UO_2$ and the anode and its shroud were used without any significant damage.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.222-222
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• 2012

Metal oxide gas sensors based on semiconductor type have attracted a great deal of attention due to their low cost, flexible production and simple usability. However, most works have been focused on n-type oxides, while the characteristics of p-type oxide gas sensors have been barely studied. An investigation on p-type oxides is very important in that the use of them makes possible the novel sensors such as p-n diode and tandem devices. Monoclinic cupric oxide (CuO) is p-type semiconductor with narrow band gap (~1.2 eV). This is composed of abundant, nontoxic elements on earth, and thus low-cost, environment-friendly devices can be realized. However, gas sensing properties of neat CuO were rarely explored and the mechanism still remains unclear. In this work, the neat CuO layers with highly ordered mesoporous structures were prepared by a template-free, one-pot solution-based method using novel ink solutions, formulated with copper formate tetrahydrate, hexylamine and ethyl cellulose. The shear viscosity of the formulated solutions was 5.79 Pa s at a shear rate of 1 s-1. The solutions were coated on SiO2/Si substrates by spin-coating (ink) and calcined for 1 h at the temperature of $200{\sim}600^{\circ}C$ in air. The surface and cross-sectional morphologies of the formed CuO layers were observed by a focused ion beam scanning electron microscopy (FIB-SEM) and porosity was determined by image analysis using simple computer-programming. XRD analysis showed phase evolutions of the layers, depending on the calcination temperature, and thermal decompositions of the neat precursor and the formulated ink were investigated by TGA and DSC. As a result, the formation of the porous structures was attributed to the vaporization of ethyl cellulose contained in the solutions. Mesoporous CuO, formed with the ink solution, consisted of grains and pores with nano-meter size. All of them were strongly dependent on calcination temperature. Sensing properties toward H2 and C2H5OH gases were examined as a function of operating temperature. High and fast responses toward H2 and C2H5OH gases were discussed in terms of crystallinity, nonstoichiometry and morphological factors such as porosity, grain size and surface-to-volume ratio. To our knowledge, the responses toward H2 and C2H5OH gases of these CuO gas sensors are comparable to previously reported values.

• Journal of the Korean Electrochemical Society
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• v.4 no.4
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• pp.172-175
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• 2001

Nanophase catalyst layer for direct methanol fuel cell has been fabricated by magnetron sputtering method. Catalyst metal targets and carbon were sputtered simultaneously on the Nafion membrane surface at abnormally higher gas (Ar/He mixture) pressure than that of normal thin film processing. They could be coated as a novel structure of catalyst layer containing porous PtRu or Pt and carbon particles both in nanometer range. Membrane electrode assembly made with this layer led to a reduction of the catalyst loading. At the catalyst loading of 1.5mg $PtRu/cm^2$ for anode and 1mg $Pt/cm^2$ for cathode, it could provide $45 mW/cm^2$ in the operation at 2 M methanol, 1 Bar Air at 80"C. It is more than $30\%$ increase of the power density performance at the same level of catalyst loading by conventional method. This was realized due to the ultra fine particle sizes and a large fraction of the atoms lie on the grain boundaries of nanophase catalyst layer and they played an important role of fast catalyst reaction kinetics and more efficient fuel path. Commercialization of direct methanol fuel cell for portable electronic devices is anticipated by the further development of such design.

• Korean Journal of Environmental Agriculture
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• v.33 no.4
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• pp.245-253
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• 2014

BACKGROUND: Oyster shell(OS) is alkaline with pH 9.8, porous, and has high concentration of $CaCO_3$. It could be used as an alternative of lime fertilizer to immobilize cadmium(Cd) in heavy metal contaminated arable soil. Therefore, this study has been conducted to compare effects of calcium(Ca) materials [OS and $Ca(OH)_2$] on Cd extractability in contaminated soil and determined mechanisms of Cd immobilization with OS. METHODS AND RESULTS: Both Ca materials were added at the rates of 0, 0.1, 0.2, 0.4, and 0.8% (wt Ca wt-1) in Cd contaminated soil and the mixtures were incubated at $25^{\circ}C$ for 4 weeks. Both Ca materials increased pH and negative charge of soil with increasing Ca addition and decreased 1N $NH_4OAc$ extractable Cd concentration. 0.1 N HCl extractable Cd concentration markedly decreased with addition of OS. 1 N $NH_4OAc$ extractable Cd concentration was related with pH and net negative charge of soil, but not with 0.1 N HCl extractable Cd concentration. We assumed that Cd immobilization with $Ca(OH)_2$ was mainly attributed to Cd adsorption resulted from increase in pH-induced negative charge of soil. Scanning electron microscope (SEM) images and energy dispersive spectroscopy(EDS) analyses were conducted to determine mechanism of Cd immobilization with OS. There was no visible precipitation on surface of both Ca materials. However, Cd was detected in innerlayer of OS by EDS analyses but not in that of $Ca(OH)_2$. CONCLUSION: We concluded that Cd immobilization with OS was different from that with $Ca(OH)_2$. OS might adsorbed interlayer of oyster shell or have other chemical reactions.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.4
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• pp.271-276
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• 2012

In this study, the dispersion ability of powder in low viscosity solubilization system that depends on variety and amount of additives and powders was investigated. A PMMA powder shows outstanding dispersion ability because of its repulsive force of partially charged chain and low density of porous structure. A sample, which contains salts, showed better dispersion tendency than a sample without any additives. The dispersion ability was quantity of salts dependent. Furthermore, a sample with divalent ion salts, like $MgSO_4$, showed better dispersion tendency than that of monovalent ion salts, like NaCl or KCl. The reason for the better dispersion tendency was due to the existence of ionized salts around the powders which significantly improves repulsive force between powders and consequently reduces powder aggregation. The sample with chelating agent, like EDTA as an additive, had improved dispersion ability. EDTA chelates and blocks metal cation therefore anion's character is maximized and repulsive force between powders is improved. As a result, salts and EDTA help to improve the powder dispersion ability and the stability of product.

• Design & Manufacturing
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• v.14 no.1
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• pp.49-55
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• 2020

In this study, the fatigue behavior and fatigue life characteristics of PA2200 specimens fabricated by SLS 3D printer were studied. Fatigue tests were performed according to the standard specification (ASTM E468) and fatigue life curves were obtained. In order to perform the fatigue test, mechanical properties were measured according to the test speed of the simple tensile test, and the self-heating temperature of the specimen according to the test speed was measured using an infrared temperature measuring camera in consideration of heat generation due to plastic deformation. There was no significant difference within the set test speed range and the average self-heating temperature was measured at 38.5 ℃. The mechanical strength at the measured temperature showed a relatively small difference from the mechanical strength at room temperature. Fatigue test conditions were established through the preceding experiments, and the loading conditions below the tensile strength at room temperature 23 ℃ were set as the cyclic load. The maximum number of replicates was less than 100,000 cycles, and the fracture behavior of the specimens with the repeated loads showed the characteristics of Racheting. It was confirmed that SLS 3D printing PA2200 material could be applied to the Basquin's S-N diagram for the fatigue life curve of metal materials. SEM images of the fracture surface was obtained to analyze the relationship between the characteristics of the fracture surface and the number of repetitions until failure. Brittle fracture, crazing fracture, grain melting, and porous fracture surface were observed. It was shown that the larger the area of crazing damage, the longer the number of repetitions until fracture.

• Analytical Science and Technology
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• v.30 no.6
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• pp.303-311
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• 2017

A new method for obtaining the photoluminescence of footwear impression by using 1,2-indandione (1,2-IND) solution, which is a latent fingerprint-developing reagent, was studied. A binary complex of DL-alanine and 1,2-IND was prepared by spraying a DL-alanine solution and the 1,2-IND solution (an amino acid sensitive reagent) onto dry or wet origin footwear impression deposited on the surface of printed A4 paper. This binary complex reacts with the trace metal component in the footwear impression to form a ternary complex that exhibits photoluminescence. However, when 5-methylthioninhydrin (5-MTN) solution was used instead of 1,2-IND, no consistent photoluminescence was observed even under identical treatment conditions. In addition, when footwear impressions treated with DL-alanine and 1,2-IND solutions were stored under various temperature conditions (30, 40 and $50^{\circ}C$) and various humidity conditions (30 %, 40 %, 50 % and 60 % RH), the contrast between the footwear impression and the background decreased. Optimal footwear impression photoluminescence was obtained when the footwear impressions treated with DL-alanine and 1,2-IND solutions were stored at $30^{\circ}C$ and 30 % RH for 1 h. The sensitivity of the developed method was ccompared with the sensitivities of three known methods - black gelatin lifting, 2,2'-dipyridyl treatment, and 8-hydroxyquinoline treatment. The results showed that the sensitivity of the developed method was worse than that of the black gelatin lifting method but better than that of 2,2'-dipyridyl or 8-hydroxyquinoline treatment method.