• 한국재료학회지
• /
• 제30권8호
• /
• pp.383-392
• /
• 2020

In this paper, AgCl/Ag₃PO₄/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag₃PO₄/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag₃PO₄/diatomite composite under visible light are evaluated. In the AgCl/Ag₃PO₄/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag₃PO₄/diatomite remains at 95 % of the original level, much higher than that of pure Ag₃PO₄ (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag₃PO₄/diatomite composites can be attributed to the synergistic effect of Ag₃PO₄, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO₂ and H₂O. Even more remarkably, AgCl/Ag₃PO₄/diatomite can maintain above 95 % photo-degradation activity after five cycles.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 춘계학술발표대회
• /
• pp.49.2-49.2
• /
• 2011

$PbMoO_4$ nanoparticles were successfully obtained in the presence of ethylene glycol (EG) with the assistance of a prolonged sonication process. The nanoparticles were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and adsorption-desorption $N_2$ isotherms (BET). The catalyst prepared sonochemically showed higher photocatalytic activity than $PbMoO_4$ prepared by solid-state reaction in the degradation reactions of rhodamine B (rhB), indigo carmine (IC), orange G (OG), and methyl orange (MO) under UV-Vis light radiation. In order to elucidate aspects of the degradation mechanism of the organic dyes, some experimental variables were modified such as pH, $O_2$ level in solution, and radiation source. In general, the photocatalytic activity for the degradation of organic dyes followed the sequence IC>OG>rhB>MO.

• 한국환경과학회지
• /
• 제18권11호
• /
• pp.1225-1234
• /
• 2009

The aim of this research was to apply experimental design methodology in the optimization condition of electrochemical oxidation of Rhodamine B(RhB). The reactions of electrochemical oxidation were mathematically described as a function of parameters amounts of current, NaCl dosage, pH and time being modeled by the use of the central composite design, which was used for fitting quadratic response surface model. The application of response surface methodology using central composite design(CCD) technique yielded the following regression equation, which is an empirical relationship between the removal efficiency of RhB and test variable in actual variables: RhB removal (%) = 3.977 + 23.279$\cdot$Current + 49.124$\cdot$NaCI - 5.539$\cdot$pH - 8.863$\cdot$time - 22.710$\cdot$Current$\cdot$NaCl + 5.409$\cdot$Current$\cdot$time + 2.390$\cdot$NaCl$\cdot$time + 1.061$\cdot$pH$\cdot$time - $0.570{\cdot}time^2$. The model predicted also agree with the experimentally observed result($R^2$ = 91.9%).

• Restorative Dentistry and Endodontics
• /
• 제40권2호
• /
• pp.143-148
• /
• 2015

Objectives: This study evaluated the maximum depth and percentage of irrigant penetration into dentinal tubules by passive ultrasonic irrigation (PUI). Materials and Methods: Thirty extracted human teeth were instrumented and divided into three groups. According to final irrigation regimen, 5.25% sodium hypochlorite (Group A, NaOCl), 2% chlorhexidine (Group B, CHX) and saline solution (Group C, control group) were applied with Irrisafe 20 tips (Acteon) and PUI. Irrigant was mixed with 0.1% rhodamine B. Sections at 2 mm, 5 mm, and 8 mm from the apex were examined with confocal laser scanning microscopy (CLSM). The percentage and maximum depth of irrigant penetration were measured. Kruskal-Wallis test and Mann-Whitney test were performed for overall comparison between groups at each level and for pairwise comparison, respectively. Within a group, Wilcoxon test was performed among different levels. p values less than 0.05 were considered significant. Results: In all groups, highest penetration depth and percentage of penetration were observed at the 8 mm level. At 2 mm level, Groups A and B had significantly greater depths and percentages in penetration than Group C (p < 0.05), but there were no significant differences between Groups A and B. At 5 mm level, penetration depths and percentage of penetration was not significantly different among the groups. Conclusions: NaOCl and CHX applied by PUI showed similar depth and percentage of penetration at all evaluated levels.

• 한국세라믹학회지
• /
• 제46권3호
• /
• pp.263-270
• /
• 2009

The effect of photoelectrocatalytic (PEC) degradation for different dyes with the CNT/$TiO_2$ electrode was studied. The prepared electrode was characterized with surface properties, structural crystallinity, elemental identification, and PEC activity. The $N_2$ adsorption data showed that the composites had decreased surface area compared with the pristine CNT. This indicated the blocking of micropores on the surface of CNT, which was further supported by observation via FESEM. XRD patterns of the composites showed that the CNT/$TiO_2$ composite contained a mixing anatase and rutile phase. EDX spectra showed the presence of C, O and Ti peaks for all samples. The decomposition efifciency of the prepared electrode was evaluated by the PEC degradation of three dyes (methylene blue (MB), rhodamine B (RH.B), methyl orange (MO)). The variations of the FT-IR spectra and pH value of dye solutions were measured during the PEC system; it was found that the CNT/$TiO_2$ electrode has better PEC degradation for MB solution than that of RH.B and MO. The proposed degradation mechanism was present.

• 대한기계학회논문집B
• /
• 제30권2호
• /
• pp.153-160
• /
• 2006

A technique for measuring surface temperature field in micro scale is newly proposed, which uses temperature-sensitive fluorescent (TSF) dye coated on the surface and is easily implemented with a fluorescence microscope and a CCD camera. The TSF dye is chosen among mixtures of various chemical compositions including rhodamine B as the fluorescent dye to be most sensitive to temperature change. In order to examine the effectiveness of this temperature measurement technique, numerical analysis and experiment on transient conduction heat transfer for two different substrate materials, i. e., silicon and glass, are performed. In the experiment, to accurately measure the temperature with high resolution temperature calibration curves were obtained with very fine spatial units. The experimental results agree qualitatively well with the numerical data in the silicon and glass substrate cases so that the present temperature measurement method proves to be quite reliable. In addition, it is noteworthy that the glass substrate is more appropriate to be used as thermally-insulating locally-heating heater in micro thermal devices. This fact is identified in the temperature measuring experiment on the locally-heating heaters made on the wafer of silicon and glass substrates. Accordingly, this technique is capable of accurate and non-intrusive high-resolution measurement of temperature field in microscale.

• 대한기계학회논문집B
• /
• 제26권8호
• /
• pp.1145-1152
• /
• 2002

A non-intrusive Planar Laser-Induced Fluorescence(PLIF) technique was applied to study the turbulent mixing process in a Rushton turbine reactor. Instantaneous and ensemble averaged concentration fields was obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by a thin Nd:Yag laser sheet illuminating the whole center plane of the stirred tank. The gray level images captured by a 14-bit cooled CCD camera could be transformed to the local concentration values using a calibration matrix. The dye injection point was selected at the tank wall with three quarter. height (3/4H) from the tank bottom to observe the mixing characteristics in upper bulk flow region. There exist distinct two time scales: the rapid decay of mean concentration after the dye infusion reflects the large scale turbulent mixing while the fellowed slow decay reveals the small scale molecular mixing. The temporal change of concentration variance field conjectures the two sequential processes for the batch type mixing. An inactive column of water is existed above the impeller disk, in which the fluid rotates with the shaft but is isolated from the mean bulk flow.

• 한국재료학회지
• /
• 제19권10호
• /
• pp.555-561
• /
• 2009

Expanded graphite (EG) is synthesized by chemical intercalation of natural graphite (NG) and rapid expansion at high temperature, with titanium n-butoxide (TNB) used as titanium source by a sol-gel method to prepare EG-TiO$_2$ composite. The performances of the prepared EG-TiO$_2$ composite are characterized by BET surface area measurement, scanning electron microscopy (SEM), X-ray diffraction patterns (XRD) and energy dispersive X-ray analysis (EDX). To compare the photocatalytic activities of the EG-TiO$_2$ composite, three kinds of dye solutions, methylene blue (MB), methylene orange (MO) and rhodamine B (RhB), and two kinds of light source, UV light and visible light (VL), are used. Comparing the results, it can be clearly seen that the degradation of all of the dye solutions under irradiation by UV light is much better than that under irradiation by visible light, and the decomposition of MB solution was better than that of both of MO and RhB solution.

• 한국환경과학회지
• /
• 제29권4호
• /
• pp.383-393
• /
• 2020

To increase electrolysis performance, the applicability of seawater to the iron-fed electro-Fenton process was considered. Three kinds of graphite electrodes (activated carbon fiber-ACF, carbon felt, graphite) and dimensionally stable anode (DSA) electrode were used to select a cathode having excellent hydrogen peroxide generation and organic decomposition ability. The concentration of hydrogen peroxide produced by ACF was 11.2 mg/L and those of DSA, graphite, and carbon felt cathodes were 12.9 ~ 13.9 mg/L. In consideration of durability, the DSA electrode was selected as the cathode. The optimum current density was found to be 0.11 A/㎠, the optimal Fe²⁺ dose was 10 mg/L, and the optimal ratio of Fe²⁺ dose and hydrogen peroxide was determined to be 1:1. The optimum air supply for hydrogen peroxide production and Rhodamine B (RhB) degradation was determined to be 1 L/min. The electro-Fenton process of adding iron salt to the electrolysis reaction may be shown to be more advantageous for RhB degradation than when using iron electrode to produce hydrogen peroxide and iron ion, or electro-Fenton reaction with DSA electrode after generating iron ions using an iron electrode.

• 대한기계학회논문집B
• /
• 제30권9호
• /
• pp.834-841
• /
• 2006

In the present wort the Laser-induced Fluorescence (LIF) technique and Confocal Laser Scanning Microscopy (CLSM) have been combined to measure the temperature distribution across a micro-scale liquid layer as a direct and non-invasive method. Only the fluorescent light emitted from a very thin volume around a focal plane can be selectively detected, and it enables us to measure the liquid temperatures even at the close vicinity of the walls. As an experimental verification, a test section consists of two flat plates (for heating and cooling, respectively) separated by about 240 microns was made, and the methanol mixed with a temperature-sensitive dye, Rhodamine B, was filled in the gap between them. The measured temperature distribution across the gap showed good linearity, which is a typical characteristic of conduction heat transfer through a thin liquid layer. In result, the CLSM-LIF technique proposed in the present study was found to be a promising method to measure the local temperatures in the liquid flow field in microfluidic devices.