• 한국자기학회지
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• 제6권4호
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• pp.225-234
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• 1996

자기 기록용 전구체에 적합한 침상형 $\alpha-Fe_{2}O_{3}$ 입자를 수열반응법에 의해 수용액 중에서 비정질 수산화제이철로부터 직접 제조하였다. Ellipsoidal 또는 rectangular 형상의 $\alpha-Fe_{2}O_{3}$ 입자는 염기도 10.75~11.75 범위에서 생성되었다. 구연산 농도가 증가함에 따라 침상 입자의 길이와 침상비는 점차 감소하였으며, 구연산 농도 $1.5{\times}10^{-4}\;mol$ 이상 일때는 침상형 $\alpha-Fe_{2}O_{3}$ 입자로의 결정화가 저해되었다. 수열 반응 온도 $140^{\circ}C$에서 가장 침상성이 우수한 $\alpha-Fe_{2}O_{3}$ 입자가 제조되었으며, $220^{\circ}C$ 이상에서는 침상형 입자의 생성을 기대할 수 없었다.

• 한국세라믹학회지
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• 제45권3호
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• pp.185-189
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• 2008

In order to fabricate porous ceramics, hydrated sodium silicate was synthesized by hydrothermal reaction using anhydrous sodium silicate. The microstructural and the structural characteristics of the expanded ceramics were observed depending on heat treatment temperature (550, 600, 650, $700^{\circ}C$) and then the effect of these characteristics on the compressive strength and the temperature gradient was investigated. As the heat treatment temperature was increased, the compressive strength was decreased from $0.717KN/cm^2\;(550^{\circ}C)\;to\;0.166KN/cm^2\;(700^{\circ}C)$. The temperature gradient was increased with increasing the experimental temperature regardless of the heat treatment temperature. The temperature gradient of the expanded ceramics which was heat treated at $650^{\circ}C\;was\;300^{\circ}C$. The bulk specific gravity, porosity, pore size, pore characteristics and wall thickness were varied depending on heat treatment temperature, and the compressive strength and the temperature gradient were governed by the complex effects of these factors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.200-200
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• 2011

Hierarchical mesoporous ZSM-5 with enhanced mesoporosity was synthesized by microwave through the rapid assembly via ionic interaction between sulfonic acid functionalized ZSM-5 nano particles and cationic surfactant. The catalytic performance of enhanced accessibility due to mesoporosity and acidity were investigated in the alkylation of mesitylene with benzyl alcohol as alkylating agent. The effect of mole ratio of aromatic with benzyl alcohol, reaction time and alkylation agent were also studied. The enhanced mesoporosity and acidity of sulfonic acid functionalized mesoporous ZSM-5 induced activity enhancement compared with non-functionalized mesoporous ZSM-5, sulfonic functionalized mesoporous ZSM-5 synthesized by hydrothermal method and conventional microporous ZSM-5. The sulfonic acid functionalized mesoporous ZSM-5 showed much higher chemoselectivity of benzylated mesitylene than others, whereas the others mainly show dibenzyl ether as product. This significant difference in catalytic selectivity was resulted from the existence of mesopores, which definitely allowed the benzylation in mesopores.

• 자원환경지질
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• 제30권4호
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• pp.379-393
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• 1997

Geology of the Zbezkazgan copper deposit in Kazhkstan is mainly composed of Permian and Carboniferous sedimenary rocks in which copper minerals are mainly contained in grey sandstone of Carboniferous age. There are 28 layers of copper ore bodies in Zbezkazgan suite. Thickness of the ore bodies ranges from one to 35 meters, grade of the crude ore ranges from 2 to 5 wt % Cu and the extension of the orebodies is 5 to 7 km. Microscopic study on specimens from the Zbezkazgan ore deposit has exposed clues to understand the origin of this deposit. Alternatively deposited grey sandstone and red sandstone are mainly composed of quartz and feldspar grains. A big difference between the grey sandstone and the red sandstone is in grain size, the former is larger than the latter. Chalcocites as main copper minerals have cemented through grain boundary. It is assumed that quartz, feldspar and copper were derived from granitoid in which copper mineralization had taken place before exposing to weathering. The chalcocites were precipitated by a sudden change of geochemical condition (Eh, pH, temperature, etc.) of fluid which had carried quartz, feldspars, copper ions and sulphate during formation of grey sandstones. The copper ions and sulphate were stable in fluid during sedimentation of oxidation environment, however, the copper ions were no more stable at the reduced environment and changed to stable forms to precipitate copper minerals by reaction of copper ions and hydrogen sulfides. This chemical precipitation of copper minerals in the sandstone attributes to the assumption of hydrothermal origin on this sedimentary origined deposit.

• 공업화학
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• 제27권6호
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• pp.669-671
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• 2016

본 연구에서는 수열합성법을 이용하여 수산화인회석을 합성하였다. 또한 이온 교환 반응을 통하여 수산화인회석 표면에 은을 도입하였다. 합성된 샘플의 결정성과 형태를 X-선 회절 분석과 투과전자현미경을 통하여 분석하였으며, 산란 반사 UV-vis 스펙트럼을 통하여 합성한 샘플의 광학적 특성을 조사하였다. 은이 도핑된 수산화인회석의 경우 은이 수산화인회석 표면에 나노입자 형태로 존재한다는 것을 X-선 회절 분석과 투과전자현미경 실험으로 확인하였다. 특히 수산화인회석과 비교하여 은 나노 입자가 도입된 수산화인회석의 경우에는 UV-Vis 영역에서 높은 흡광도를 나타내었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 춘계학술논문 발표대회
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• pp.75-78
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• 2007

The recycling program about waste concrete is being progressed to national research. But research on waste concrete powder which is occurred in control process of concrete powder is not enough. Waste concrete powder includes in $SiO_2,\;Al_2O_3$, and CaO so that the create of tobermorite is possibile through Hydrothermal Syntesis Reaction. Tobermorite have an advantage of high strength, sulphuric acid resistance and the lower drying shrinkage. Accordingly, this study investigate in properties of light-weight foamed concrete made with waste concrete powder. As a results, light-weight foamed concrete made with waste concrete powder is the higher than stone powder sludge of density and porosity, and the tower compressive strength. Therefore, it is thought that light-weight foamed concrete using waste concrete powder is possible.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3357-3361
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• 2013

Alumina microfibers with porous structures were prepared through hydrothermal reaction, and then used to modify the surface of carbon paste electrode (CPE). After modification with alumina microfibers, the electrochemical activity of CPE was found to be greatly improved. On the surface of alumina microfibers-modified CPE, the oxidation peak current of salvianolic acid B, a main bioactive compound in Danshen with anti-oxidative and anti-inflammatory effects, was remarkably increased compared with that on the bare CPE surface. The influences of pH value, amount of alumina microfibers and accumulation time were studied. Based on the strong signal amplification effects of alumina microfibers, a novel electrochemical method was developed for the detection of salvianolic acid B. The linear range was from 5 ${\mu}gL^{-1}$ to 0.3 mg $L^{-1}$, and the detection limit was 2 ${\mu}gL^{-1}$ (2.78 nM) after 1-min accumulation. The new method was successfully used to detect salvianolic acid B in ShuangDan oral liquid samples, and the recovery was over the range from 97.4% to 102.9%.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.51-51
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• 2012

There is a growing interest in innovative chemical synthesis in microreactors owing to high efficiency, selectivity, and yield. In microfluidic systems, the low-volume spatial and temporal control of reactants and products offers a novel method for chemical manipulation and product generation. Glass, silicon, poly(dimethylsiloxane) (PDMS), and plastics have been used for the fabrication of miniaturized devices. However, these materials are not the best due to either of low chemical durability or expensive fabrication costs. In our group, we have recently addressed the demand for economical resistant materials that can be used for easy fabrication of microfluidic systems with reliable durability. We have suggested the use of various specialty polymers such as silicon-based inorganic polymers and fluoropolymer, flexible polyimide (PI) films that have not been used for microfluidic devices, although they have been used for other areas. And inexpensive lithography techniques were used to fabricate Lab-on-a-Chip type of microreactors with differently devised microchannel design. These microreactors were demonstrated for various synthetic reactions: liquid, liquid-gas organic chemical reactions in heterogeneous catalytic processes, syntheses of polymer and non-trivial inorganic materials. The microreactors were inert, and withstand even harsh conditions, including hydrothermal reaction. In addition, various built-in microstructures inside the microchannels, for example Pd decorated peptide nanowires, definitely enhance the uniqueness and performance of microreactors. These user-friendly Lab-on-a-Chip devices are useful alternatives for chemist and chemical engineer to conventional chemical tools such as glass.

• 한국재료학회지
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• 제25권6호
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• pp.300-304
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• 2015

Nanorod ZnO and spherical nano ZnO for gas sensors were prepared by hydrothermal reaction method and hydrazine method, respectively. The nano-ZnO gas sensors were fabricated by a screen printing method on alumina substrates. The gas sensing properties were investigated for hydrocarbon gas. The effects of Co concentration on the structural and morphological properties of the nano ZnO:Co were investigated by X-ray diffraction and scanning electron microscope (SEM), respectively. XRD patterns revealed that nanorod and spherical ZnO:Co with a wurtzite structure were grown with (100), (002), (101) peaks. The sensitivity of nanorod and spherical ZnO:Co sensors was measured for 5 ppm $CH_4$ and $CH_3CH_2CH_3$ gas at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity to the $CH_4$ and $CH_3CH_2CH_3$ gas of spherical nano ZnO:Co sensors was observed at Co 6 wt%. The spherical nano ZnO:Co sensor exhibited a higher sensitivity to hydrocarbon gas than nanorod ZnO.

• 한국재료학회지
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• 제24권8호
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• pp.413-416
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• 2014

The effects of an addition of CNT on the sensing properties of nano ZnO:CNT-based gas sensors were studied for $H_2S$ gas. The nano ZnO sensing materials were grown by a hydrothermal reaction method. The nano ZnO:CNT was prepared by ball-milling method. The weight range of the CNT addition on the ZnO surface was from 0 to 10%. The nano ZnO:CNT gas sensors were fabricated by a screen-printing method on alumina substrates. The structural and morphological properties of the ZnO:CNT sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns revealed that nano ZnO:CNT powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The size of the ZnO was about 210 nm, as confirmed by SEM images. The sensitivity of the nano ZnO:CNT-based sensors was measured for 5 ppm of $H_2S$ gas at room temperature by comparing the resistance in air with that in target gases.