• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.286-293
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• 1998

Two methods were used to enhance the adsorption capacity of activated carbons. One is to impregnate activated carbons with chemical compounds which have a good affinity for $CO_2$. The other is to activate by heat-treating after impregnation with KOH on activated carbons(AC). The chemical compounds impregnated on AC were alkali metal, alkaline earth metal, and transition metal chlorides. The adsorption capacity of $CO_2$ on AC impregnated with these metals was less than that of pure AC. These compounds have not the chemical affinity for $CO_2$ and obstruct the micropore of AC. The experiment of breakthrough for $CO_2$ on AC impregnated with KOH showed the increase of the adsorbed amount of $CO_2$ in influent gases containing water vapor. This means that KOH adsorbes $CO_2$ gas. However, the adsorbents impregnated with KOH had not the reproducibility because of the production of $K_2CO_3$ by the reaction of KOH with $CO_2$. The amount of $CO_2$ adsorbed on the heat-treated AC at $800^{\circ}C$ increased with the amount of impregnation. The adsorption capacity of $CO_2$ was the largest when the ratio of weight of KOH to AC equal to 4. The isosteric heat of adsorption was calculated by the equation of Clausius-Clapeyron form adsorption capacity data of $CO_2$ for the temperature change. In addition, the characteristics of $CO_2$ breakthrough curve were surveyed for the change of flow rate and concentration.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.364-370
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• 1995

The catalytic oxidations of several olefins in $CH_2Cl_2$ have been investigated using non-redox metalloporphyrin (M=Ga(III), In(III), Tl(III)) complexes as catalyst and sodium hypochlorite as terminal oxidant. Porphyrins were $(p-CH_3O)TPP,\;(p-CH_3)TPP,\;TPP,\;(p-F)TPP,\;(p-Cl)TPP\;and\;(F_20)TPP$ (TPP=tetraphenylporphyrin), and olefins were $(p-CH_3O)-,\;(p-CH_3)-,\;(p-H)-,\;(p-F)-,\;(p-Cl)-\;and\;(p-Br)styrene$styrene and cyclopentene and cyclohexene. The substrate conversion yield was discussed according to the substituent effects of metalloporphyrin and substrate, and the radius effect of non-redox metal ion. The conversion yield of substrate by changing the substituent of TPP increased in the order of $p-CH_3O$ < $p-CH_3$ < H < p-F < p-Cl, which was consistent with the sequence of $4{\sigma}$ values of TPP. But the substituent effect of substrate on the conversion yield decreased with increasing the ${\sigma}^+$ values on substrates in the order of p-CH3O > p-CH3 > H > p-Cl > p-Br. For the oxidation of several olefins, the complexes of In(III)- and Tl(III)-porphyrins turned out to be more active catalysts than Ga(III)-porphyrin.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.504-509
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• 2004

The reaction of Cu metal with mixed alkali metal polyselenide flux ($KNaSe_x$) produced large plate-like crystals of $KCu_4Se_3$. The structure of $KCu_4Se_3$, determined with X-ray single crystal diffraction techniques, is tetragonal (P4/mmm, a=4.013(1))${\AA}$, c=9.712(1))${\AA}$, z=1, R=6.7%). The structure is composed $[Cu_4Se_3]_n^{n-}$double layers which are made of fused anti PbO-type Cu2Se2 layers. Temperature variable resistivity measurement on single crystal of $KCu_4Se_3$ shows metallic behavior ranging from $1.8{\times}10^{-4}{\Omega}{\cdot}cm$ (at 300 K) to $1.0{\times}10^{-6}{\Omega}{\cdot}cm$ (at 20 K).

• Journal of Welding and Joining
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• v.15 no.6
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• pp.24-31
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• 1997

2매의 금속을 맞대어 그 한 쪽에 접촉면과 평행하게 고주파진동을 가하면 단 시간에 접합된다. 이공정을 초음파 용접이라고 하며 그 물리적인 본질은 아직 불분명 하지만, 첫째로는 강한 마찰에 의해 금속 자유면의 산화물층이 제거되기 때문이라는 점과 둘째로는 마찰에 의해 금속 표면이 강하게 가열되어 이에 따른 연화에 의해 접합 이 된다고 하는 점이다. 그러나 이와 같이 가열된다고 하더라도 가열은 표면부에만 국한되고 다른 부분은 가열되지 않는다. 따라서 초음파용접은 냉간접합이라고도 한다. 또 가압력과 진동에 의한 힘이 동시에 작용하기 때문에 용접할 면을 미리 청정하게 할 필요는 없고 용접전의 단계에서 자연적으로 청정화가 이루어진다고 하는 사실이 간접 적으로 증명되고 있다. 초음파 용접(Ultrasonic welding)의 특징을 요약하면 고상용접 의 일종으로서 용접중에 국부적으로 고주파 진동에너지와 압력을 가하여 용접하는 방법이다. 이 때 모재를 용융시키지 않고 건전한 야금학적 결합부가 얻어진다는 데에 큰 특징이 있다. 또한 초음파용접은 다른 용접법에 비해 경제성이 매우 높고, 초음파 용접에 필요한 출력이 전기아크 용접에 필요한 출력의 5 - 10%로 충분한 경우가 많다. 초음파 용접은 통상의 방법으로는 용접하기 어려운 동종 금속이나 이종 금속의 용접에 널리 사용된다. 이 용접법은 반도체, 미세회로, 전기 접점의 형성에 대한 생산기술 로서 사용되고 있는데 소형 모터, 알루미늄 박의 가공, 알루미늄 합금의 조립 등에 이용되고 있다. 한편 최근에는 자동차, 우주항공산업 분야의 구조제 용접용으로도 채용되고 있다.출함이 바람직하다.분비되는 배설-분비 항원의 자극과 깊은 관계가 있음을 알 수 있었다.넌트 명세서를 대한 XML DTD(Document Type Definition)를 정의하고, HTML 기반 검색 방법과 XML 기반 검색 방법에 대한 컴포넌트 검색 성능을 비교한다.따라 NO 생산 및 세포독성이 증가하였고. NO 생산을 저하시키는 약제들은 활성화된 복강 대식세포 및 RAW264.7 세포에 의한 질편모충에 대한 세포독성을 현저히 감소시키는 것으로 보아 NO는 질편모충에 대한 대식세포의 숙주 방어기전에서 중요한 역할을 감당할 것으로 생각된다.nction index) 와 최대개구시 동통의 정도는 시술전과 시술 4주후간에 유의한 차이가 관찰되었다.피부온도는 검사자간에는 특정부위에 따라 다소 차이가 있을 수 있으나 일반적으로 높은 재현성을 보여줌으로서 향후 교근 및 측두근의 임상연구 평가에 피부온도조사는 도움이 되리라 사료된다. lactobacilli의 양은 peroxidase system을 함유하거나(p < 0.01) 함유하지 않은(p < 0.05) 치약을 사용한 군 모두에서 양치전에 비해 유의성있게 감소하였다. 6. 양치후 30분에 채취한 구강건조증 환자의 자극성 전타액내 S. mutans 양은 peroxida system을 함유한 세치제를 사용한 군에서 대조군에 비해 유의성있게 낮았다(p < 0.05). 7. 양치후 30분에 채취한 구강건조증 환자의 자극성 전타액내 lactobacilli양은 peroxidase system을 함유한 세치제를 사용한 군에서 대조군에 비해 상대적으로 낮게 나타났으나(p = 0.067)

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.92-100
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• 1994

Ultrafine cobalt-substituted iron oxide particles were prepared by the thermal decomposition and oxidation of the new organometallic precursor, $Co_xFe_{1-x}(N_2H_3COO)_2(N_2H_4)_2$ (x = 0, 0.01, 0.02, 0.03, 0.05, 0.10, 1.00). The organometallic precursors were synthesized by the reaction of Co(II) and Fe(II) ion in a mole ratio of x : 1-x with hydrazinocarboxylic acid, and characterized by quantitative analysis, elemental analysis and infrared spectroscopy. The mechanistic study on the thermal decomposition of the organometallic precursors was performed by TG-DTG and DSC. The cobalt-substituted iron oxide particles were obtained by the heat treatment of the precursors at $350^{\circ}C$ and $450^{\circ}C$ for six hours in air. The prepared iron oxide was found to have two phases such as ${\gamma}-Fe_2O_3$ and a mixture of ${\gamma}-Fe_2O_3\;and\;{\alpha}-Fe_2O_3$ at $350^{\circ}C$ and $450^{\circ}C$ respectively. The particle shape was equiaxial and the particle size was less than 0.05 ${\mu}m.$ The coercivity and squareness of the cobalt substituted iron oxide particles increased with increasing cobalt content. Both coercivity and squareness showed higher values at $450^{\circ}C.$

• Korean Journal of Materials Research
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• v.11 no.2
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• pp.120-125
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• 2001

Generally, hydroxyapatite(HAp), zeolite, carbon molecular sieve , activated carbon and alumina are used as heavy metal ions adsorption materials. Among those adsorption materials, HAp which has good positive ion-exchange ability with metal ion, and zeolite are utilized in wastewater treatment. Most of water pollutions are caused by hazardous heavy metals ions as well as bacteria in waste water. In this study, a adsorption materials (HAP and zeolite) are ion-exchanged with a well known antimicrobial metal ions, such as $Ag^+,\;Cu^{2+},\;and\;Zn^{2+}$, in order to give a adsorption of heavy metal ions and a killing effects of bacteria. The antimicrobial effects of adsorption materials are observed using by E. Coli. The results show that there is a complete antimicrobial effect in the adsorption materials with $Ag^+$ at the concentration of $1{\times}10^{-4}$cell/$m\ell$ of E. Coli until 24 hours. However, there is not good antimicrobial effects in the adsorption materials with $Cu^{2+},\;and\;Zn^{2+}$ substitution. Feng et. al. showed the denaturation effects of silver ions which induces the condensed DNA molecules and losing their replication abilities.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.671-678
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• 2021

Effects of nitric acid treatment of an activated carbon and impregnation of metal chlorides on the activated carbon were investigated to improve ammonia adsorption performance. It was confirmed that functional groups such as hydroxyl and carboxyl groups were introduced onto a surface of the activated carbon with nitric acid treatment. Then, each metal chloride (NiCl₂, MgCl₂, CuCl₂, MnCl₂ or CoCl₂) was impregnated onto the surface-modified activated carbon using an ultrasonic impregnation method. The physicochemical properties and ammonia adsorption performance of various impregnated activated carbons were observed. Metal chlorides were well dispersed by sonication and evenly distributed on the surface of the activated carbon. Despite the reduced specific surface area and pore volume, the surface-modified activated carbon impregnated with metal chlorides exhibited excellent ammonia adsorption performance. In particular, HNO₃-NiCl₂ AC prepared by impregnating NiCl₂ showed the best ammonia adsorption capacity of 3.736 mmol·g^-1, which was improved by about 57 times compared to that of an untreated activated carbon (0.066 mmol·g^-1).

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.296-301
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• 2022

Due to the fact that zirconium based metal-organic frameworks (Zr-MOFs), such as UiO-66, have a large specific surface area and excellent selective adsorption capacity, Zr-MOFs are gaining attention as materials that can provide protection from the attack of chemical warfare agents in battleground. However, most of the metal-organic frameworks have an issue of selective adsorption capacity degraded by water molecules when exposed to the atmosphere, because of the weak metal-organic ligand bonds and the presence of voids. Therefore, polydimethylsiloxane (PDMS), a representative hydrophobic polymer material, was coated on the surface of UiO-66 to enhance the sustainability of the diisopropyl methylphosphonate (DIMP) sorption capacity in the battleground condition. Through the analysis of surface structure and organic functional group distribution of PDMS coated UiO-66, silicon was confirmed to be evenly coated. The contact angle increased by over 30° for the PDMS coated UiO-66, indicating that the hydrophobicity was improved. In addition, both the UiO-66 and PDMS coated UiO-66 were used as adsorbents for DIMP, a similar chemical warfare agent, to investigate the durability of adsorption capacity in a high humidity environment. The PDMS coated UiO-66 showed higher durability of adsorption capacity for 20 days than that of pristine UiO-66.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1591-1593
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• 2004

압력센서는 몇 가지 센싱 메카니즘을 가지고 있으므로 종류가 다양하고 크기 변에서도 여러 가지가 이용되고 있다. 최근에는 센싱 부분이 작으며 제어부분도 포함되는 ASIC화된 센서 시스템이 개발되고 있다. 여기에 이용되는 대부분의 탄성물질은 힘을 받았을 때 물질 내부의 벌크에서 저항 값이 변화하는 특성을 갖고 있다. 이러한 특성은 피에조 저항률(piezoresistivity)로 언급되며 스트레인 게이지의 감도에 영향을 주는 중요한 요소로 작용한다. 다이어프램으로 금속대선 세라믹을 사용하면 안정성이 우수한 특정을 가칠 수 있으며, 부식성 가스 류 및 화학성분에 대해서 내성이 강하고 환경변화에 따른 변형과 공정의 단순화 등 우수한 특성을 갖고 있는 것이 큰 장점이다. 센싱부는 산화 루세니움($RuO_2$)을 주 성분으로 하는 분말을 Paste화 하여 다이어프램 위에 스크린 프린팅을 하여 기본성능을 나타내었으며 특히, 상품화에서 중요한 일반성능에서는 온도 특성에 대한 Span 과 Offset 그리고 공정의 단순화에 대해서 고찰을 하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.45.1-45.1
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• 2010

소성 온도에 따른 전면 전극과 태양전지 에미터와의 계면에서 전기적 특성을 평가하였다. Ag 전극 형성 시 특정 온도 이상의 열처리 과정을 통해 에미터와 전극 간 양질의 전기적 접촉을 형성하기 위해 소성 온도에 따라 Ag paste 내의 siver가 결정화되어 에미터 내부로 성장함을 확인 하고 Ag 전극의 전기적 특성을 평가하였다. 소성 온도 $650{\sim}750^{\circ}C$에서 전기적 특성이 가장 좋았으며 silver의 결정 생성에 의해 Ag paste와 에미터 간 전기적 접촉이 잘 형성됨을 확인 하였다.