• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.231-236
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• 1988

In order to investigate the effect of second phase on $Al_2O_3$ matrix, SiC particles were dispersed in $Al_2O_3$ matrix as a second phase over the content range of 5 vol.% to 20 vol.%. To this mixture, $Y_2O_3$ or $TiO_2$ powders were added as a sintering additive before isostatically pressing and pressurelessly sintering at 180$0^{\circ}C$ for 90 min in $N_2$ atmosphere. With increasing SiC content, relative densities of composites were decreased but mechanical properties of composites were improvjed. In the case of adding $Y_2O_3$ as a sintering additive, maximum values of flexural strength, hardness and fracture toughness were 525 MPa, 17.1 GPa, 4.1 MPa.m1/2 respectively. In the case of adding X$TiO_2$ as a sintering additive, maximum values of flexural strength, hardness were 285 MPa, 12.1 GPa respectively. Improved mechanical properties were found to be the results of grain growth control of $Al_2O_3$ matrix and crack deflection by the second phase SiC particles.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.392-396
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• 2009

AlON was fabricated by the pressureless reaction sintering of $Al_2O_3$-AlN powder mixtures. The ratio of AlN to $Al_2O_3$ as well as various sintering aids were the main variables for this study. The optimum ratio of AlN in the $Al_2O_3$-AlN mixture was approximately 35.0 mol%. For the sintering aids, only when a small amount of MgO was added together with $Y_2O_3$ and BN, AlON specimens could be sintered to a full density with negligible pores and high transparency. Other combinations of $Y_2O_3$, BN, CaO and MgO resulted in enough pores in the sintered specimens to have in-line transmittance only between 0% and 30%. The in-line transmittance reached over 80% after sintering at $1975^{\circ}C$ for 10 h for the specimen containing 0.15 wt% MgO, 0.08 wt% $Y_2O_3$ and 0.02 wt% BN.

• Membrane and Water Treatment
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• v.8 no.1
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• pp.51-71
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• 2017

Antimicrobial polyethersulfone ultrafiltration membranes containing zerovalent iron ($Fe^0$) and magnetite ($Fe_3O_4$) nanoparticles were synthesized via phase inversion method using polyethersulfone (PES) as membrane material and nano-iron as nanoparticle materials. Zerovalent iron nanoparticles (nZVI) were prepared by the reduction of iron ions with borohydride applying an inert atmosphere by using $N_2$ gases. The magnetite nanoparticles (nMag) were prepared via co-precipitation method by adding a base to an aqueous mixture of $Fe^{3+}$ and $Fe^{2+}$ salts. The synthesized nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction, and dynamic light scattering analysis. Moreover, the properties of the synthesized membranes were characterized by scanning electron microscopy energy dispersive X-ray spectroscopy and atomic force microscopy. The PES membranes containing the nZVI or nMag were examined for antimicrobial characteristics. Moreover, amount of iron run away from the PES composite membranes during the dead-end filtration were tested. The results showed that the permeation flux of the composite membranes was higher than the pristine PES membrane. The membranes containing nano-iron showed good antibacterial activity against gram-negative bacteria (Escherichia coli). The composite membranes can be successfully used for the domestic wastewater filtration to reduce membrane biofouling.

• Journal of Korean Society of Forest Science
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• v.52 no.1
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• pp.31-36
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• 1981

The infrared specta of wood powders have been recorded both in the untreated stste and after treatment through 1%-NaOH extraction(2hrs) and alcohol-benzene mixture extraction. Differences between the spectra of 3 species(Pinus densiflora, Populus alba x glandulosa and Quercus mongolica) can be explained chiefly in terms of theirs chemical compositions through comparisions of the spectra of pure cellulose powders. 1. The peak near $3400cm^{-1}$ from wood powders appeared at $3420cm^{-1}$, which was shifted to left compared with pure cellulose powders. 2. Many new peaks appeared at 2725, 1730, 1660, 1640, 1600, 1510, 1500, 1460, 1385, 1270, 830 and $810cm^{-1}$ etc., which were not appeared in pure cellulose powders. 3. Pinus densiflora spectra of untreated powders showed small peak appeared at $2840cm^{-1}$, which was the most characteristic band. There were peaks at $1240cm^{-1}$ in Populus alba x glandulosa and Quercus mongolica spectra of untreated wood powders. 4. Treated wood powder spectra showed weak or no peaks at near $1730cm^{-1}$ and also at near $2920cm^{-1}$. $2840cm^{-1}$, near $1385-1365cm^{-1}$, near $1235cm^{-1}$ and $1110-1095cm^{-1}$ etc. 5. The Alcohol-benzene extractive spectrum from Pinus densiflora showed many peaks at $3600-2300cm^{-1}$, $3100-2800cm^{-1}$, $1700cm^{-1}$, $1450cm^{-1}$ and $1375cm^{-1}$ etc. The most characteristic band of the extractives appeared at $3100-2900cm^{-1}$.

• Journal of Korea Foundry Society
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• v.2 no.3
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• pp.2-15
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• 1982

In this study, the influenced of graphite shape on the boriding of cast iron and boride structure was investigated. Gray cast iron, ferritic and pearlitic ductile cast iron were borided at 750,850,900 and $950^{\circ}C$ for 1,3 and 5 hours by powder pack method with the mixture of $B_4C_9\;Na_2B_4O_7$, $KBF_4$ and Shc. The boride layer was consisted of FeB(little), $Fe_2B$ (main) and graphite. Some possibility of the existence of unknown Fe-B-C compound in the boride layer was suggested. And precipitates in the diffusion zone was $Fe_3(B,C)$. The concentration of Si and precipitation of $Fe_3(B,C)$ in the ${\alpha}$ layer raised the hardness of this Zone. The depth and hardness of boride layer increased with the increase of treating temperature and tim. But high temperature (over $950^{\circ}C)$ caused pore at graphite position and long treating time (5hrs) sometimes caused formation of graphite layer beneath the boride layer. So, for the practical application of borided cast iron, treating in short time and at low temperature was recommended. And for ductile cast iron, ferritizing or pearlitizing heat treatment was seemmed to be possible at the same time with boriding. The graphite in the boride layer was deeply concerned with the qualitx and characteristics of the boride layer. And it greatly influenced on the shape of the boride phase, structure of the boride layer. Generally speaking, the existance of graphite restrained the growth of the boride phase. But the boundary between the gsaphite and the matrix acted as the shortcut of boron diffusion. So, for gray cast iron, the graphite layed length-wise led the formation of boride layer.

• Journal of the Korean Wood Science and Technology
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• v.16 no.4
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• pp.3-9
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• 1988

Infrared (IR) spectroscopic techniques for the analysis of wood samples and the absorbance spectra of solid woods were presented. KBr pellets were prepared by throughly mixing approximately 300 mg of dried KBr and 1 mg of finely milled wood powder extracted with ethanol-cyclohexane previously. This mixture was made into a transparent disc by means of a pellet-making die (10 ton/$cm^2$ for 10 min). This IR techniques were applied for the analysis of archaeological wood samples. The most notable difference in the IR spectra between the recent and the archaeological waterlogged woods is that the absorption band centered at $1,730cm^{-1}$ was significantly diminished in the waterlogged ones. Total loss of absorption in $1,730cm^{-1}$ might be mainly due to the result of hemicellulose degradation. Another feature indicated by IR spectral comparision are that the degraded waterlogged wood samples showed 1) the increased intensity of the 1,600, 1,500 and $1,270cm^{-1}$ due to the residual lignin and the increased intensity at 1,470 and $1,425cm^{-1}$ due to the degradation of hemicellulose and 2) to the emergence of single band around $1,050cm^{-1}$ instead of three bands at 1,110, 1,060 and $1,040cm^{-1}$ in recent wood due to the degradation of cellulose crystalline. It was revealed from the IR examinations that the first change of wood in the waterlogged situation was the lysis of hemicellulose and the second the lysis of cellulose. It was also suggested that IR spectroscopy could serve a fast method for the investigation on the chemical characteristics of archaeological wood samples.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.612-616
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• 2009

Transparent conductive oxide (TCO) films have been widely used in the field of flat panel display industry. Transparent conductive indium zinc oxide (IZO) thin films with excellent chemical stability have attracted much attention as an alternative material for indium tin oxide (ITO) films. In this study, using a $In_2O_3$ and ZnO powder mixture with a ratio of 90 : 10wt% as a target, IZO films were prepared on polynorbornene (PNB) substrates by electron beam evaporation. The effect of substrate temperature and $O_2$ introduction flow rate were investigated in terms of electrical and optical properties of deposited IZO films. The best electrical and optical properties we obtained from this study were sheet resistance value of $5.446{\times}10^2{\Omega}/{\boxempty}$ and optical transmittance of 87.4% at 550 nm at $O_2$ introduction flow rate of 4 sccm, deposition rate of $2{\AA}$/sec, thickness of 1000 $\AA$ and substrate temperature of $150^{\circ}C$.

• Applied Biological Chemistry
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• v.47 no.3
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• pp.325-331
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• 2004

In order to study the effect of formulation type on the burning characteristics of smoke generator, fenarimol smoke generators containing the powdered rice chaff as a combustible carrier were prepared by molding the kneaded mixtures into various shapes. Smoke generators containing wood flour as a combustible carrier were also prepared and compared with smoke generators containing rice chaff. All the fenarimol smoke generators moulded into powders, granules, and rods continuously burned out when the sodium chlorate content exceeded 11%. Regardless of their types, the highest smoking rate of fenarimol was observed with more than 13% of sodium chlorate. The smoking rate of active ingredient followed with the increasing order of powder (64.5%) < granule (78.4%) < rod (90.9%). The smoke rod was robust, easy to ignite, and showed the highest smoking rate among the tested formulations. When the mixture of wood flour and anti-flame agent was used as a combustible carrier, the burning rate was so slow that wood flour formulation seemed to be more suitable to a slow-burning fumigant rather than smoke generator.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.218-224
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• 1998

2nO and $Al_{2}O_{3}$ powder were weighed in 1 : 1 mole ratio and ball-milled in ethanol for 3 h. Dried mixture were pressed and then sintered at $900^{\circ}C{\sim}1200^{\circ}C$ for 3 h in vacuum($3{\times}10^{-5}$ Torr). According to XRD, remnant ZnO and $Al_{2}O_{3}$ not converted to $ZnAl_{2}O_{4}$ were observed up to $1100^{\circ}C$, which were completely changed to$ZnAl_{2}O_{4}$ ternary compound at $1200^{\circ}C$. Optical bandgap is calculated at 4.75 eV. With increasing sintering temperature, PL spectrums shifted to shorter wavelengths and are appeared 430nm at $1200^{\circ}C$.

• Korean journal of food and cookery science
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• v.2 no.1
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• pp.59-64
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• 1986

This study was designed to revive the disappeared Younsa and to investigate the optimum processing condition and characteristics of Younsa nade of the glutinous rice powder. Agitating time of base mixture, thickness of Younsa base, and frying time were examined as the influencing factors in Younsa processings. The textural parameters of Younsa were determined by sensory cvaluation and hardness of Younsa was measured by Rheometer. The results were found as follows; 1. In the sensory evaluation, 1) The Younsa base agitated for 10 minutes by agitating machine was favorable. It, however, did not showed any significant difference among products prepared under varying agitaing time-10 minutes, 20 minutes, and 30 minutes. (p<0.05) 2) The thinnest Younsa base (5 cm$\times$4cm, 1.1-1.5g) showed the most favorable quality and the second quality went to 5cm$\times$4cm, 1.6-2.0g, the third 5cm$\times$4cm, 2.1-2.5g, the fourth 5 cm$\times$4 cm, 2.6-3.0g. (p<0.05) 3) In examination of varying frying time, the optimal time for frying Younsa was 12 minutes was 12 minutes in $150 ^{\circ}C$. However, the quality was found no significant difference between 12 minutes's fried Younsa and 14 minutes's. (p<0.05). 2. The hardness of the most favorable Younsa, agitated for 10 minutes, the thinnest (5 cm$\times$4 cm, 1.1-1.5g), ana fried for 12 minutes in $150^{\circ}C$ was 0.59-0.73 kg/wt measured by Rheometer. The thickest Younsa base (5 cm$\times$4 cm, 2.6-3.0g) is the hardest (1.26 kg/wt). The most optimal conditions in this experiment were found the same ones which was written in historical literature.