• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.429-429
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• 2009

Nanoporous anodic alumina membranes (NAAM) with high-density through-hole pores fabricated by hard anodization of aluminum in 0.3 M oxalic acid under the applied voltage of 40 (mild anodization), 80, 100, 120 and 140 V were investigated. The current-time responses monitored using a PC-controlled anodization cell and the corresponding pore structures attainable from field-enhanced scanning electron microscopy (FE-SEM) were analyzed in order to establish the optimum fabrication process. The nanoporous structure can be produced for all the voltage conditions, while the stabilized through-hole pore formation seems to occur at 40, 80 and 140 V. The growth rate under 140 V hard anodization was over 30 times higher than under 40 V mild anodization (1.5 um/hr).

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.230-233
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• 2007

A system of anodic process of aluminum thin film has implemented for nanofabrication. The manufactured equipment consists of three main parts: chiller, reaction bath and power supply. The chiller module consists of refrigeration compressor, copper tube and coolant with a thermostat. The reaction bath has kept in same temperature as a thermodynamic canonical ensemble system during the anodic reaction process. The magnetic bar has stirred oxalic acid in bath for uniform reaction. The DC power supply has applied into two electrodes, aluminum for anode and platinum for cathode in the oxalic acid. The anodization process results in the formation of nanoporous thin films.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.91-99
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• 1989

The concentrations of hydroxide, carbonate and oxalate for Y(III), Ba(II) and Cu(II) ions in an aqueous solution have been theoretically calcuated with respect to pH and their solubility diagram could be obtained. The optimum pH ofr oxalate coprecipitates at room temperature was estimated as<4, which was not influenced by carbonates and hydroxides in H2O solvent. The yield is dependent on the concentration of added oxalic acid, but the concentration of oxalic acid was fixed as 0.1M in this calculation for simplicity.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.230-233
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• 2010

The authors investigated the anodization mechanism of aluminum in an oxalic acid solution, and the electrochemical reaction is very unique for pore formation via the dissolution process, which is very dependent on the surface geometry in nanoporous alumina templates. The cross-sectional nanochannels showed that the geometrical curvature of the initial surface can cause the branching of nanochannels to be adjusted in volume occupancy to be direct to the electric field normal to the surface. The nanoporous alumina with the crystalline $\gamma-Al_2O_3$ phase showed hexagonal ordering at a voltage of 40 V, with a nanohole distance of 102 nm from the charge density oscillation of the oxalic acid solution.

• Korean Journal of Microbiology
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• v.11 no.2
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• pp.51-58
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• 1973

Three kinds of organic matter such as glucose, oxalic acid, and ethanol were added to the media(N-free or $NO_{3}$-riched) and their effects on the nitrogen fixation of Nostoc pruniforme were measured by manometric technique through the experiments in vivo. 1) The organic matters used in this experiments showed effective results as a role of substrate for the fixation of atmospheric nitrogen. 2) In the nitrogen-free medium treated with the both of flucose nad ethanol, the highest nitrogen uptakes were detected in the treated of low concentrations (glucose ; 0.1%, 0.5%, ethanol : 0.1%, 0.5%). On the contrary, the highest nitrogen uptakes in $NO_{3}$-riched medium were measured at the treated of high concentrations (glucose ; 2%, 1%, ethanol ; 1.5%, 1.0%). 3) The highest nitrogen uptakes in N-free medium treated with oxalic acid were measured at the concentration of 2% and 1%, respectively. In the medium of $NO_{3}$-riched, the nitrogen uptakes were in the opposite directions.

• Journal of the Korean Ceramic Society
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• v.23 no.4
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• pp.11-16
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• 1986

$BaTiO_3$ ceramics powder was prepared by coprecipitation method either in oxalic acid solution or in potassium hydroxide solution. Thermal decomposition of coprecipitated $BaTiO(C_2O_4)_2$.$4H_2O$ powder in oxalic acid solution was investigated by means of Themogravimetry Differential Thermal Analysis and X-ray Diffraction Analysis. Low temperature decomposition of coprecipitated $BaTiO(C_2O_4)_2$.$4H_2O$ caused narrow particle size distribution whereas high temperature decomposition caused fairly wide particle size distribution by partial sintering. As the reaction time increased the average particle size of coprecipitated $BaTiO_3$ powder in KOH solution was increased. The most narrow paticle size distribution was obtained when the coprecipi-tates were ripened for 4hrs.

• Food Science of Animal Resources
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• v.21 no.1
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• pp.64-70
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• 2001

The extraction procedure and HPLC condition were modified to analyze the residues of oxytetracycline, sulfamethoxazole and chloramphenicol in pork, simultaneously. The antibacterial agents in pork were extracted with 0.02M EDTA-Mcilivine buffer:ethanol:acetonitrile (5:3:2). After the removal of fat with n-hexane, the extracts were evaporated and purified with Sep-pak $C_{18}$ cartridge column using 0.01M oxalic acid 0.1% (v/v) triethylamine (TEA) in acetonitrile. The peak of antibacterial agents was detected with $\mu$ Bondapak C18 column, UV detector (280nm) and 0.01M oxalic acid: methanol: acetonitrile (7.5:2.0:0.5). Detection limits for three antibacterial standards were 0.03 ppm. Calibration curves were linear between 0.03 and 2.0 ppm (R$^2$>0.999). When spiked the level of 1.0 ppm of oxytetracycline, sulfamethoxazole and chloramphenicol into meats, the recoveries from meats were 77.3%, 79.7% and 59.3%, respectively. These results showed that the modified extraction method provided good analytical resolution and the recoveries of the above antibacterial agents in meats.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.514-517
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• 2011

Herein, we fabricated magnesium oxalate nanostructures by chemical etching of a magnesium foil in alcoholic solvents containing acidic media. Interestingly, we could obtain magnesium oxalate nanowires in ethanolic oxalic acid. Growth mechanism for magnesium oxalate nanowires was investigated in terms of etching time. Annealing conditions were determined from TGA results. Magnesium oxalate nanowires were converted to magnesium oxide nanowires by thermal treatment and the magnesium oxide nanowires were examined by FE-SEM and FT-IR measurement.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.04a
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• pp.118-118
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• 2003

편의와 fresh-like quality를 선호하는 소비 경향에 맞추어 가공한 fresh-cut사과의 선도 연장을 위한 저해제를 탐색하였다. 실험에 사용된 사과는 박피하여 속심을 제거한 사과를 8조각으로 절단하여 저해제에 3분간 침지한 후 물기를 제거하고 각각 LDPE 포장지에 포장하여 실온에서 저장하면서 colorimeter와 rheometer를 이용하여 색도와 물성을 측정하였다. 저해제로는 1% ascorbic acid, citric acid, NaCl, MgCl$_2$, CaCl$_2$, KCl, CaSO$_4$, MgSO$_4$, $Na_2$SO$_4$, oxalic acid, calcium lactate, calcium citrate를 사용하였으며 천연저해제로는 건칡, 맥문동, 목향, Rhubarb, 당귀, 오약, 시체, 지각, 천문동, 청피, 계피, 구기자, 당귀, 진피, 감초, 녹차, 후추 등을 열수추출하여 사용하였다. 물리적인 변화는 시간이 경과함에 따라 감소하는 추세를 보였으며 일부 건조로 인해 texture의 증가를 나타내기도 했다. 처리에 따른 물리적인 변화로는 CaCl$_2$, NaSO$_4$, Cl, 시금치를 처리하였을 때 그 변화가 가장 작았으나 시금치의 경우 시금치로 인한 사과의 색변화로 관능적으로 좋지 않았다. 한약재는 목향, 당귀, 지각, 계피를 처리하였을 때 물리적인 변화가 가장 작았으나 시금치와 마찬가지로 처리 초기에 한약재 자체의 향과 색으로 인하여 관능적으로 좋지 못한 결과를 나타냈다. 갈변 정도를 나타내는 ΔE의 변화는 KCl과 CaCl$_2$, CaSO$_4$를 처리한 구에서 변화가 가장 작았으며 한약재를 처리하였을 경우 당귀, 천문동을 처리한 구에서 효과를 보였다. oxalic acid는 갈변저해에는 효과적이었으나 시간이 경과함에 따라 수분의 용출이 증가하였으며 물성의 변화도 컸다. 또한 ZnCl$_2$를 처리한 구에서는 이취 발생과 수분 용출이 컸으며 색의 변화도 컸다.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.05a
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• pp.214-223
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• 2005

In order to recover valuable metals from fine-grained electronic waste, bioleaching of Cu, Zn, Al, Co, Ni, Sn and Pb were carried out using Aspergillus niger as a leaching microorganism in a shaking flask. Aspergillus niger was able to grow in tile presence of electronic scrap. The formation of organic acids(citric and oxalic acid) from Aspergillus niger caused the mobilization of metals from waste electronic scrap. In a preliminary study, in order to obtain the data on the leaching of Cu, Zn, Al, Co and Ni, the metal leaching behaviours were accomplished using Organic acid(Citric acid and Oxalic acid) instead of Aspergillus niger. At the electronic scrap concentration of 50g/L, Aspergillus niger were able to leach more than 95% of the available Cu, Co. But Al, Zn, Pband Sn were able to leach about 15-35%. Ni and Fe were detected in the leachate less than 10%.