• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1565-1568
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• 2005

A surface renewable pH electrode was prepared by utilizing composite electrode technique. Iridium oxide micro-fine particles was prepared by hydrolysis of $(NH_4)_2IrCl_6$ at elevated temperature. The iridium oxide particles were mixed with well-dispersed carbon black and then filtered. The mixture was suspended in DMF containing PVC as a binder. The mixture was precipitated rapidly by adding large amount of water. The precipitate was ground and pressure-molded to iridium oxide composite electrode material. The electrode showed linear response between pH 1-13 with 50 to 60 mV/pH slope. The electrode maintained the pH response without appreciable slope drift for 170 days if stored in deionized water. The electrode surface can be renewed reproducibly by simple grinding process whenever contaminated or deactivated.

• Food Science and Biotechnology
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• v.14 no.3
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• pp.334-339
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• 2005

An instrument using thermal probe method was designed to measure thermal conductivity of liquid and solid foods. Thermal conductivity probe was designed with diameter to length ratio of 100 and diameter of 0.51 mm to minimize axial flow effect on thermal conductivity measurement. Thermal conductivities of distilled/deionized water, glycerin, and beef frankfurter meat were measured at $20-80^{\circ}C$. Mean thermal conductivity values of water showed less than 2.0% difference from several reference values without using time correction factor or probe calibration constant. For glycerin, difference was less than 0.7% from reference values at $20-50^{\circ}C$. Mean values of thermal conductivity for beef frankfurter meat ranged from 0.389 to $0.350\;W/m{\cdot}K$ at $20-80^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.431-435
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• 1999

An organic precipitate flotation of Cd(Ⅱ) and Pb(Ⅱ) was investigated by the coprecipitation with lanthanum 8-hydroxyquinolinate. Trace amounts of Cd(Ⅱ) and Pb(Ⅱ) with a significantly large amount of La(Ⅲ) were simultaneously precipitated in a 1,000 mL sample solution with the ethanolic 8-hydroxyquinoline solution. The pH was adjusted to 9.0 with 2 M ammonia solution. The precipitates were floated with the aid of tiny nitrogen bubbles and supported by the stable foam layer of sodium lauryl sulfate. The floats were collected on the fritted glass filter by a suction. The material collected was dissolved with 5.0 mL of ethanol and 1.5 mL of concentrated nitric acid, and then diluted to 25.0 mL with a deionized water. The analytes were determined by a flame atomic absorption spectrophotometry. The recoveries of the analytes spiked in the sample were 94.8% for Pb(Ⅱ) and 92.0% for Cd(Ⅱ). This flotation technique is simple and rapid, and also applicable to the determination of trace Cd(Ⅱ) and Pb(Ⅱ) at lew ppb levels.

• Journal of Powder Materials
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• v.16 no.3
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• pp.217-222
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• 2009

This paper presents a novel single-step method to prepare the Ag nanometallic particle dispersed fluid (nanofluid) by electrical explosion of wire in liquid, deionized water (DI water). X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) were used to investigate the characteristics of the Ag nanofluids. Zeta potential was also used to measure the dispersion properties of the as-prepared Ag nanofluid. Pure Ag phase was detected in the nanofluids using water. FE-SEM analysis shows that the size of the particles formed in DI water was about 88 nm and Zeta potential value was about -43.68 without any physical and chemical treatments. Thermal conductivity of the as-prepared Ag particle dispersed nanofluid shows much higher value than that of pure DI water.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.801-809
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• 2013

We investigate sensitivity and limit of detection (LOD) of trace copper (Cu) metal using pristine carbon nanotube (CNT) and acidified CNT (ACNT) electrodes. Squarewave based anodic stripping voltammetry (SWASV) is used to determine the stripped Cu concentration. Prior to performing the SWASV measurements, its optimal conditions are determined and with that, effects of potential scan rate and $Cu^{2+}$ concentration on stripping current are evaluated. The measurements indicate that (1) ACNT electrode shows better results than CNT electrode and (2) stripping is controlled by surface reaction. In the given $Cu^{2+}$ concentration range of 25-150 ppb, peak stripping current has linearity with $Cu^{2+}$ concentration. Quantitatively, sensitivity and LOD of Cu in ACNT electrode are 9.36 ${\mu}A\;{\mu}M^{-1}$ and 3 ppb, while their values are 3.99 ${\mu}A\;{\mu}M^{-1}$ and 3 ppb with CNT electrode. We evaluate the effect of three different water solutions (deionized water, tap water and river water) on stripping current and the confirm types of water don't affect the sensitivity of Cu. It turns out by optical inspection and cyclic voltammetry that superiority of ACNT electrode to CNT electrode is attributed to exfoliation of CNT bundles and improved interfacial adhesion occurring during oxidation of CNTs.

• Journal of Magnetics
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• v.16 no.4
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• pp.435-439
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• 2011

In this work, we prepared Fe-Ni alloy nanopowders by wire electrical explosion in deionized water and ethanol. Particles size and morphology of the as-synthesized nanoparticles prepared in water and ethanol were observed by transmission electron microscopy. In both cases, the as-synthesized nanoparticles were in nearly spherical shape and their size distribution was broad. The particles prepared in the water were in core-shell structure due to the oxidation of Fe element. X-ray diffraction was used to analyze the phase of the nanopowders. It showed that the nanopowders prepared in water had ${\gamma}$-Fe-Ni solid solution and FeO phase. The samples obtained in ethanol were in two phases of Fe-Ni solid solution, ${\gamma}$-Fe-Ni and ${\alpha}$-Fe-Ni. Bulk samples were made from the as-synthesized nanopowders by spark plasma sintering at $1000^{\circ}C$ for 10 min. Structure of the bulk sample was observed by scanning electron microscope. Magnetic properties of the as-synthesized nanopowders and the bulk samples were investigated by vibrating sample magnetometer. The hysteresis loop of the assynthesized nanopowders and the sintered bulk samples revealed a ferromagnetic characteristic.

• Environmental Engineering Research
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• v.10 no.3
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• pp.144-154
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• 2005

The use of ozone gained acceptance in the production of ultrapure water because of its powerful oxidizing ability. Ozone is currently used to deactivate microorganisms and remove organic contaminants. However, interest also exists in using radical species, which arc stronger oxidants than ozone, in such processes. One means of producing radical species is by corona discharge. This work investigates the use of a novel pulseless corona-discharge system for the removal of organic substances in ultrapure water production. The method combines corona discharge with electrohydrodynamic spraying of oxygen, forming microbubbles. Experimental results show that pulseless corona discharge effectively removes organics, such as phenol and methylene blue, in deionized water. The corona-discharge method is demonstrated to be comparable to the direct use of ozone at a high-applied voltage. The results also show that a minimum applied voltage exists for operation of the corona-discharge method. In this work, the minimum applied voltage is approximately 4.5 kV. The kinetic rate or phenol degradation in the reactor is modeled. Modeling results show that the dominant species of the pulseless corona-discharge reactor are hydroxyl radical and aqueous electron. Several radical species produced in the pulseless corona-discharge process are identified experimentally. The. major species are hydroxyl radical, atomic hydrogen species, and ozone.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.4
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• pp.447-453
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• 1986

Germination and seedling elongation of soybeans [cult. ‘Williams’] were measured at two temperatures (15 and 3$0^{\circ}C$), three seed water contents (30, 50, and 70%), and with and without polyethylene glycol-8000 (PEG) treatments. A split-plot design was used with four replications. Observations were made from two hours to eight days for each treatment combination. Seeds were soaked with 30% PEG solution with 0.2% thiram at 15 C for six days, rinsed with deionized water and dried at 25.5$^{\circ}C$ for three days. Ten treated or untreated seeds were placed on Whatman No. I (9 cm) filter paper in plastic petridishes to which sufficient deionized water was added to adjust seed moisture content to the desired level. The dishes were then sealed with parafilm and placed in a continuous programmed temperature chamber under dark condition. Seedling growth did not occur at either temperature when moisture content was 50 percent or less. Osmo-conditioning with PEG showed positive effects on seedling moisture uptake and seedling growth at 15$^{\circ}C$ but little effect at 3$0^{\circ}C$. Seedling moisture content increased rapidly early in the germination period and reached 60% at 15 C for 56 hours and at 3$0^{\circ}C$ for 28 hours. Seedling growth started when seed moisture reached a critical point of 60% at 15$^{\circ}C$, however, growth started after 20 hours of germination at 3$0^{\circ}C$. Seedlings of soybeans elongated more than four times faster at 3$0^{\circ}C$ than at 15$^{\circ}C$. Water uptake during germination was characterized by two phases in this experiment.

• Journal of Bio-Environment Control
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• v.14 no.3
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• pp.196-202
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• 2005

This research was conducted to determine the amount of water absorbed by a polyacrylamide hydrogel such as Stocksorb C (STSB), effect of salts on inhibition in hydration of STSB, and the hydrogel effects on changes of nutrient concentration in external solution. Absorption of deionized water by STSB reached a maximum of 180 $mL{\cdot}g^{-1}$. Monovalent soluble salts such as $KH_2PO_4,\;KNO_3$, and $(NH_4)_2SO_4$ reduced absorption of the hydrogel, but the degrees of inhibition in absorption were similar in three kinds of salts. Twenty milliequivalents per liter of $Ca_{2+}\;or\;Mg_{2+}$ reduced water absorption of STSB to $14\%$ compared to those of deionized water. Solution absorption was consistently lower in the presence of divalent cations than in the presence of the monovalent cations. But the absorption was unaffected by the uncharged salt such as urea in all concentrations tested. The final $K^+\;and\;NH_4^+-N$ concentrations of the solution remaining after absorption by STSB was higher than those of the initial solution. The soaking of STSB to full strength of Hoagland solution resulted in increase of $NO_3^--N,\;H_2PO_4^-\;and\;SO_4^{2-}$ concentrations in external solution compared to initial solution, reaching 5,300, 250 and 1,500 $mL{\cdot}g^{-1}$, respectively, at 24 hrs after soaking.

• Nuclear Engineering and Technology
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• v.43 no.3
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• pp.195-204
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• 2011

The effects on pool boiling heat transfer of aqueous solutions of boric acid ($H_3BO_3$) and sodium chloride (NaCl) as working fluids have been studied. Borated and NaCl water were prepared by dissolving 0.5~5% volume concentration of boric acid and NaCl in distilled-deionized water. The pool boiling tests were conducted using $1{\times}1\;cm^2$ flat heaters at 1 atm. The critical heat flux (CHF) dramatically increased compared to boiling pure water. At the end of boiling tests it was observed that particles of boric acid and NaCl had deposited and formed a coating on the heater surface. The CHF enhancement and surface modification during boiling tests were very similar to those obtained from boiling with nanofluids. Additional experiments were carried out to investigate the reliability of the additives deposition in pure water. The boric acid and NaCl coatings disappeared after repeated boiling tests on the same surface due to the soluble nature of the coatings, thus CHF enhancement no longer existed. These results demonstrate that not only insoluble nanoparticles but also soluble salts can be deposited during boiling process and the deposited layer is solely responsible for significant CHF enhancement.