• Korean Journal of Materials Research
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• 제28권1호
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• pp.62-67
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• 2018

Active clay, bentonite and zeolite were used as porous materials for humidity controlling ceramic boards. The specific area and the pore volume of active clay were higher than bentonite and zeolite. The flexible strength of the gypsum board decreased with an increasing amount of porous material, and the flexible strength was lowest when active clay with a higher specific surface area than others porous materials was added. The specific surface area and total pore volume of ceramic boards containing porous material were highest at $102.25m^2/g$, $0.142cm^3/g$, respectively, when the active clay was added. In addition, as the amount of added porous materials increased, the specific surface area and total pore volume of the ceramic board increased, but the average pore diameter decreased. The addition of s porous materials with a high specific area and a large pore volume improved the moisture absorptive and desorptive performance of the ceramic board. Therefore, in this experiment, the moisture absorptive and desorptive properties were the best when active clay was added. Furthermore, as the amount of added porous materials increased, the moisture absorptive and desorptive properties improved. When 70 mass% of active clay was added to ${\alpha}$-type gypsum, the hygroscopicity was the highest, about $300g/m^2$, in this experiment.

• Analytical Science and Technology
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• 제5권4호
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• pp.359-366
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• 1992

Using micro-Raman spectrometer, we investigated the evaluation of microstress on silicon surface after the local thermal oxidation. The induced stress of silicon surface after local thermal oxidation shows maximum value at the interface of silicon oxide and active area. The smaller the size of active area, the larger stress. From the evaluation of three other device isolation processes, A, B and moB, whose active size has $0.45{\mu}m$ in length, moB process is turned out to have the lowest stress value and the smallest bird's beak effect.

• Electrical & Electronic Materials
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• 제10권7호
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• pp.719-726
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• 1997

This research was conducted to analyze the change of surface tension, viscosity, streaming current and conductivity of transformer oil when it were injected with the interface active substances.(anionic:S-111, cationic:S-121, amphoteric:S-131) The changes properties of the surface tension and viscosity of the oil which were injected with the interface active substances were divided into the changes area and the minimum reduction area. The surface tension and viscosity of the oil which were injected with three different kinds of interface active substances showed remarkable change at the point where the concentration of the substance in anionic, in cationic and in amphoteric were 100[ppm], 10[ppm] and 1[ppm] respectively. The streaming current and conductivity of the same sample oil were also changed at the same densities of the surface tension and viscosity. For this factor, it was possibile for us to interpret the mechanism of the streaming current and conductivity. Therefore the interface active substances of the three kinds were injected into the oil within the limit of optimal volume, prevention effects of electrification were showed more excellence than unmixed insulating oil.

• Journal of Environmental Health Sciences
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• 제38권6호
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• pp.568-574
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• 2012

Objectives: The purpose of this experiment is to understand the phosphorus removal ratio effects of iron plates per unit of surface area through the iron electrolysis system, which consists of an anoxic basin, aerobic basin, and iron precipitation apparatus. Methods: Iron electrolysis, which uses an iron precipitation reactor in anoxic and oxic basins, consisted of iron plates with total areas of 400 $cm^2$, 300 $cm^2$ and 200 $cm^2$ respectively. The FNR process was operated with a hydraulic retention time and a sludge retention time of 12 hours and three days, respectively. Wastewater used in the experiments was prepared by dissolving $KH_2PO_4$ in influent water. Results: The iron plates 400 $cm^2$ (16.6 $mA/cm^2$), 300 $cm^2$ (13.3 $mA/cm^2$) and 200 $cm^2$ (7.3 $mA/cm^2$) in surface area in the phosphorus reactor had respective phosphorus of 2.4 mg/l, 2.7 mg/l and 3.2 mg/l in the effluent and phosphorus removal respective efficiencies of 90.3%, 89.1% and 87.1%. The effluent in the reactor, where the iron plate was not used, had relatively very low phosphorus removal efficiency showing phosphorus concentration of 15.3 mg/l and a phosphorus removal efficiency about 38.3%. Phosphorus removal per ferrous was 0.472 mgP/mgFe in the iron electrolysis system where the surface area of iron was low. Phosphorus pollution load per active surface area and the phosphorus removal efficiency had an interrelation of RE = -0.27LS + 89.0 (r = 0.85). Conclusion: With larger iron plate surface area, the elution of iron concentration and phosphorus removal efficiency was higher. The removal efficiency of phosphorus has decreased by increasing the initial phosphate concentration in the iron electrodes. This shows a tendency of decreasing phosphorus removal efficiency because of decreasing of iron deposition as the phosphorus pollution load per active surface area increases.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제22권6호
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• pp.269-273
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• 2012

Ammonia decomposition over titanium carbides were investigated using eight different samples which have been synthesized by TPR (temperature-programmed reduction) method of titanium oxide ($TiO_2$) with pure $CH_4$. The resulting materials which were synthesized using wo different heating rates and space velocity exhibited the different surface areas. These results indicated that the structural properties of these materials have been related to heating rates and space velocity employed. The titanium carbides prepared in this study proved to be active for ammonia decomposition, and the activity changed with the particle size/surface area. These showed the relationship between ammonia decomposition activity and the different active species. Compared to molybdenum carbide, the titanium carbides were one order of magnitude less active, suggesting the correlation between the activity difference and the degree of electron transfer between metals and carbon in metal carbides.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.753-756
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• 2001

This research made a study of MnO$_2$electrode for supercapacitor with a diffuser (Polyvinyl alcohol). Manganese dioxide was used as active material. We tried to increase specific surface area by adding PVA. Manganese dioxide was synthesized by a sol-gel method using fumaric acid and oxalic acid in low temperature with high yield. Therefore, We prepared Manganese dioxide powder. This powder was used by active materials. The electrode was made by a mixture of active material, ketjen-black which is a large specific surface area, and PVdF-co-HFP as binder agent with using Nickel mesh as current collector. Here we reported on the synthesis and electrochemical performance of a enhanced material. All active materials have been submitted to X-ray diffraction and Scanning electron microscopy.

• Korean Journal of Materials Research
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• 제19권10호
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• pp.538-543
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• 2009

Active clays, Diatomite, bentonite and zeolite were used as porous materials for fabricating hygroscopic gypsum boards. Pohang active clay and Cheolwon diatomite showed excellent characteristics of moisture adsorption and desorption. These characteristics were caused by higher surface area and pore volume of porous materials. Moisture adsorption content of gypsum board with 10% active clay(P1) was 62.0 g/m$^2$, and moisture desorption content was 50.2 g/m$^2$. Moisture adsorption content of gypsum board with 10% diatomite(P) was 59.5 g/m$^2$, and moisture desorption content was 49.0 g/m$^2$. Moisture adsorption contents of gypsum boards with porous materials were higher than that moisture desorption contents of gypsum board without porous materials. Correlation coefficient between surface area and moisture adsorption content of gypsum boards was 0.98. Also, correlation coefficient between surface area and moisture desorption content of gypsum boards was 0.97. Moisture adsorption and desorption contents were influenced by surface area and pore volume of the gypsum boards, and surface area had a larger effect on moisture adsorption and desorption.

• Carbon letters
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• 제28권
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• pp.105-110
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• 2018

Owing to their scalability, flexible operation, and long cycle life, vanadium redox flow batteries (VRFBs) have gained immense attention over the past few years. However, the VRFBs suffer from significant polarization, which decreases their cell efficiency. The activation polarization occurring during vanadium redox reactions greatly affects the overall performance of VRFBs. Therefore, it is imperative to develop electrodes with numerous catalytic sites and a long cycle life. In this study, we synthesized heteroatom-rich carbon-based freestanding papers (H-CFPs) by a facile dispersion and filtration process. The H-CFPs exhibited high specific surface area (${\sim}820m^2g^{-1}$) along with a number of redox-active heteroatoms (such as oxygen and nitrogen) and showed high catalytic activity for vanadium redox reactions. The H-CFP electrodes showed excellent electrochemical performance. They showed low anodic and cathodic peak potential separation (${\Delta}E_p$) values of ~120 mV (positive electrolyte) and ~124 mV (negative electrolyte) in cyclic voltammetry conducted at a scan rate of $5mV\;s^{-1}$. Hence, the H-CFP-based VRFBs showed significantly reduced polarization.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.411-411
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• 2012

Over the recent years, surface enhanced Raman spectroscopy (SERS) has dramatically grown as a label-free detecting technique with the high level of selectivity and sensitivity. Conventional SERS-active nanostructured layers have been deposited or patterned on rigid substrates such as silicon wafers and glass slides. Such devices fabricated on a flexible platform may offer additional functionalities and potential applications. For example, flexible SERS-active substrates can be integrated into microfluidic diagnostic devices with round-shaped micro-channel, which has large surface area compared to the area of flat SERS-active substrates so that we may anticipate high sensitivity in a conformable device form. We demonstrate fabrication of flexible SERS-active nanostructured substrates based on soft-lithography for simple, low-cost processing. The SERS-active nanostructured substrates are fabricated using conventional Si fabrication process and inkjet printing methods. A Si mold is patterned by photolithography with an average height of 700 nm and an average pitch of 200 nm. Polydimethylsiloxane (PDMS), a mixture of Sylgard 184 elastomer and curing agnet (wt/wt = 10:1), is poured onto the mold that is coated with trichlorosilane for separating the PDMS easily from the mold. Then, the nano-pattern is transferred to the thin PDMS substrates. The soft lithographic methods enable the SERS-active nanostructured substrates to be repeatedly replicated. Silver layer is physically deposited on the PDMS. Then, gold nanoparticle (AuNP) inks are applied on the nanostructured PDMS using inkjet printer (Dimatix DMP 2831) to deposit AuNPs on the substrates. The characteristics of SERS-active substrates are measured; topology is provided by atomic force microscope (AFM, Park Systems XE-100) and Raman spectra are collected by Raman spectroscopy (Horiba LabRAM ARAMIS Spectrometer). We anticipate that the results may open up various possibilities of applying flexible platform to highly sensitive Raman detection.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.295-295
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• 2013

Supercapacitors with higher energy and power density are attracting growing attention for their wide range of potential applications such as portable electronic equipments, hybrid vehicle and cellular devices. In various classes of materials for supercapacitors, the redox pseudocapacitive materials such as conducting polymers and metal oxides have been most widely studied recently. The nanostructuring of the electrode surface has also been focused on since it can provide large surface area and consequently easy diffusion of ions in the capacitors. Among the active materials, in this work, we have used polyaniline (PANi) and manganese oxide ($MnO_2$). PANi is one of the promising electrode and active materials due to its desirable properties such as high electrochemical activity, high doping level and stability. $MnO_2$ is also widely studied material for supercapacitors since it is relatively cheap and environmentally friendly. In this work, we fabricated PANi hollow nanospheres by polymerizing aniline monomers on the polystyrene (PS) nanospheres and then dissolving the inner PS spheres. This nanostructuring of the PANi surface can provide large surface area and hence easy diffusion of electrolyte ions. We also incorporated $MnO_2$ nanoparticles into the PANi hollow nanospheres and investigated its electrochemical properties. It is expected that the combination of these two active materials with slightly different working potential windows show synergetic effects such as broader working potential range and enhanced specific capacitance.