• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.466-470
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• 2022

The catalytic thermal oxidizer process has recently attracted considerable attention for the oxidation and decomposition of volatile organic compounds at low temperatures (< 450 ℃) with high efficiency (> 95%). Although many noble metal catalytic materials are well established, they are expensive and hazardous. Herein, highly active and low-cost Cu-Mn bimetallic catalysts were prepared using a simple and facile synthesis method involving the co-precipitation of Cu and Mn precursors. The synthesis of the catalyst was optimized by controlling the composition ratio of Cu and Mn. The optimized catalyst exhibited a large surface area of 230.8 m²/g with a mesoporous structure. To demonstrate the catalytic performance, the Cu-Mn catalyst was tested for the oxidation reaction of ethyl acetate, showing a high conversion efficiency of 100% at a low temperature of 250 ℃.

• Analytical Science and Technology
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• v.21 no.2
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• pp.109-116
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• 2008

Resins were synthesized by mixing 1-aza-18-crown-6 macrocyclic ligand into styrene(dangerous matter) divinylbenzene(DVB) copolymer with crosslink of 1%, 2%, 6% and 12% by substitution reaction. The synthesis of these resins was confirmed by content of chlorine, elemental analysis, thermogravimetric analysis, electron microscopy, and IR. The effects of pH, time, crosslink of resins and dielectric constant of solvent on adsorption of uranium ion by resin adsorbent were investigated. Uranium ion showed a great adsorption above pH 3 and adsorption equilibrium of metal ions was established in about two hours. In addition, adsorptive selectivity of resin in ethanol solvent was $UO{_2}^{2+}$ > $Zn^{2+}$ > $Lu^{3+}$ ion and adsorption of uranium ion increased with the increase of the degree of crosslinking (1%~12%) and was inversely in proportional to the order of dielectric constant of solvents.

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.479-487
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• 2023

Copper is cost-effective and abundantly available as a biocidal coating agent for a wide range of material surfaces. Natural oxidation does not compromise the efficacy of copper, allowing it to maintain antimicrobial activity under prolonged exposure conditions. Furthermore, copper compounds exhibit a broad spectrum of antimicrobial activity against pathogenic yeast, both enveloped and non-enveloped types of viruses, as well as gram-negative and gram-positive bacteria. Contact killing of copper-coated surfaces causes the denaturation of proteins and damage to the cell membrane, leading to the release of essential components such as nucleotides and cytoplasm. Additionally, redox-active copper generates reactive oxygen species (ROS), which cause permanent cell damage through enzyme deactivation and DNA destruction. Owing to its robust stability, copper has been utilized in diverse forms, such as nanoparticles, ions, composites, and alloys, resulting in the creation of various coating methods. This mini-review describes representative coating processes involving copper ions and copper oxides on various material surfaces, highlighting the antibacterial and antiviral properties associated with different oxidation states of copper.

• Journal of the Korean Applied Science and Technology
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• v.33 no.2
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• pp.352-360
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• 2016

The purpose of this study was to determine the electrochemical properties develop DSA electrode for sewage sludge solubilization. Using Ir as a main catalyst, the catalyst selected for the sewage sludge solubilization durability and proceeds to functional electrode suitable for sewage sludge electrolysis experiment were obtained the following results. Less mass reduction of the sintering temperature of the main catalyst, Ir coated electrodes, the endothermic reaction zone $300^{\circ}C$ to $500^{\circ}C$, which was selected from a range of experiments. The efficiency of the catalyst results came up to $350^{\circ}C$ best. Each Binder stars (Ta, Sn, W) in this experiment was the biggest catalyst efficiency at $350^{\circ}C$. Used as a binder, $TaCl_5$, $SnCl_4$, $WCl_6$ of the Ta and without affecting the other characteristics of the main catalyst than Sn, W. For the 50% $IrO_2$ electrode is 1.4 V (vs. Ag / AgCl) in a current of about $29mA/cm^2$ was caused to evaluate the effectiveness of the electrode.

• Microbiology and Biotechnology Letters
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• v.26 no.6
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• pp.483-489
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• 1998

We carried out the expression and characterization of yeast thioredoxin system including thioredexin 1 (Trx1), Trx2, thioredoxin reductase (TR), and a novel thioredoxin (Trx3), which was reported in the data base of Saccharomyces genome. The Trx1, 2 and TR were expressed as soluble proteins in E. coli and the sizes of purified proteins were equal to the reported their molecular weights. The expressed Trx3 was found in both soluble fraction and precipitate. The size of Trx3 purified from soluble fraction of E. coli crude extracts was estimated as 14 kDa on SDS-PAGE instead of 18 kDa for Trx3 in precipitate. N-terminal amino acid sequence of the small size of purified Trx3 from soluble fraction was analyzed as FQSSYTS which is correspond to the sequence from 20 to 26 for Trx3. Trx3 together with thioredoxin reductase and NADPH was able to reduce the disulfide bridge of insulin and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). Trx3 stimulated the antioxidant effect of thioredoxin peroxidase 1 (TPx1) which inhibited inactivation of glutamine synthetase (GS) in dithiothreitol (DTT) containing metal catalyzed oxidation system. The stimulation effect of Trx3 was 10% of the effect of either Trx1 or Trx2. In addition, Trx3 could reduce the disulfide of TPx to thiol, so that the TPx had thioredoxin dependant peroxidase activity. In western blotting analysis, antibodies against purified Trx3 did not cross-react with crude extracts of yeast, purified Trx1, and Trx2 proteins. But, in PCR reaction using the cDNA library of yeast as a template, gene encoding of trx3 was amplified.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.3
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• pp.31-36
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• 2018

This research scrutinizes the reason of failure after pressure cooker test (PCT) for DRAM device. We use the physical inspecting tools, such as microscope, SEM and TEM, and finally find the discolor phenomenon, corrosion of Al and delamination of inter-metal dielectric (IMD) in the failed devices after PCT. Furthermore, we discover the abnormal $Al_XO_Y$ layer on Al through the careful additional measurements. To find the reason, we evaluate the effect of package ball size and pinhole in passivation layer. Unfortunately, those aren't related to the problems. We also estimate halide effect of Al. The halogens such like Cl are contained within EMC material. Those result in the slight improving of PCT characteristics but do not perfectly solve the problems. We make a hypothesis of Galvanic corrosion. We can find the residue of Ti at the edge of pad open area. We can see the improving the PCT characteristics by the time split of repair etch. The possible mechanism of the PCT failure can be deduced as such following sequence of reactions. The remained Ti reacts on the pad Al by Galvanic corrosion. The ionized Al is easily react with the $H_2O$ supplied under PCT environment, and finally transfers to the abnormal $Al_XO_Y$ layer.

• Korean Journal of Microbiology
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• v.48 no.4
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• pp.298-304
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• 2012

Among 63 Bacillus strains grown at $60^{\circ}C$ from sixteen samples of homemade Korean soybean paste, one strain was selected for producing the thermostable protease. The isolate has been identified as Bacillus licheniformis on the basis of its 16S rDNA sequence, morphology and biochemical properties. Culture filtrate of the isolate showed maximal protease activity at the reaction condition of $60-65^{\circ}C$ and pH 11. The culture filtrate retained more than 87% of initial protease activity after incubation for 30 min at $60^{\circ}C$ without substrate. In order to develop the medium composition, effects of ingredients including nitrogen sources, carbon sources, metal ions and phosphate were examined for protease production of the isolate. Lactose and soytone peptone were the most effective carbon and nitrogen source for the enzyme production. After the late logarithmic growth phase the isolate began to produce the protease, and the maximum protease productivity was reached to 550 unit/ml in the optimized medium consisting of lactose (3%), soytone peptone (1.5%), $MgSO_4$ (0.1%), $K_2HPO_4$ (0.03%), and $KH_2PO_4$ (0.03%) at 28 h of incubation.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.43-43
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• 2009

단련용 다결정 Ni기 초내열합금은 우수한 가공성, 내산화성, 고온특성 등으로 가스터빈 연소기, 디스크, 증기발생기 전열관 등 발전용 고온부품 소재에 널리 적용되고 있다. 최근 발전설비의 고효율화를 꾀하기 위해 작동 온도를 현격히 증가시키는 기술방향으로 발전하고 있고, 소재측면에서는 기존의 초내열합금 대비 고기능성을 확보할 수 있는 차세대 Ni기 초내열합금 개발이 유럽, 미국, 일본, 중국 등을 중심으로 활발히 이루어지고 있다. 이러한 소재의 고온강도 (온도수용성)를 향상시키기 위해서는 통상 규칙격자 금속간화합물인 $Ni_3(Al,Ti)-{\gamma}'$상의 분율을 증가시킬 수 있지만, ${\gamma}'$상분율이 증가할 경우 용접 및 후열처리 동안 용접열영향부 (HAZ)에서 액화균열이 발생할 가능성이 높아진다. 결정립계를 따라 발생하는 HAZ 액화균열은 입계특성에 의해 크게 영향을 받을 것으로 판단된다. 한편, 본 연구자들은 최근 입계 serration 현상을 단련용 합금에 도입시키는 특별한 열처리를 이론적 접근법을 통해 개발하였다. 형성된 파형입계는 결정학적인 관점에서 조밀 {111} 입계면을 갖도록 분해 (dissociation)되어 낮은 계면에너지를 갖게 됨을 확인하였으며, 입계형상 변화뿐만 아니라 탄화물 특성변화까지 유도하여 크리프 수명을 기존대비 약 40% 정도 향상시킴을 확인하였다. 이러한 직선형 입계 대비 'special boundary'로 간주되는 파형입계가 도입될 경우, HAZ 결정립크기 변화 및 액화거동에 미치는 영향을 고찰하고, 아울러 입계특성 제어가 용접성/용접부 품질 향상에 기여할 수 있는 가능성도 토의하고자 하였다. 본 연구에서는 재현 HAZ 열사이클 시험을 통해 미세구조를 정량적으로 비교하였다. 상대적으로 입계구조가 안정된 파형입계의 이동속도가 高계면 에너지를 갖는 직선형 입계보다 느려 HAZ 결정립 성장이 효과적으로 억제됨을 확인할 수 있었다. 입계 액화거동을 살펴보면, 두 시편 모두 $M_{23}C_6$, MC 등 입계탄화물 계면이 빠른 승온중 액화반응 (constitutional liquation)에 의해 입계가 액화되었으며, 이후 급냉에 의해 입계에 액상막이 존재한 흔적이 발견되었다. 최고온도별로 입계액화 폭/비율을 정량적으로 비교한 결과, 파형입계가 직선입계 대비 대체로 낮음을 확인할 수 있었으며, 때때로 액화되지 않고 잔존하는 입계 탄화물이 관찰되었다. 재현 HAZ 미세조직을 통해 Hot ductility 시험 결과를 유추하자면, 파형입계가 직선입계 보다 좁은 취성온도영역 (Brittle Temperature Range)을 나타낼 것으로 예상되어, 입계특성제어에 의해 Ni기 초내열합금의 용접성을 향상 가능성을 확인하였다.

• Polymer(Korea)
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• v.30 no.6
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• pp.519-524
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• 2006

Poly(4-vinyl pyridine) (PVP) and its copolymers, poly(4-vinyl pvridine- co-acrylamide) and poly(4-vinyl pyridine-co-allylamine), were synthesized and evaluated for application to organic solder-ability preservatives (OSP). The copolymers were synthesized by radical polymerization of vinyl pyridine in the presence of acrylamide or allylamine as a comonomer. Various kinds of polymers with different chemical composition were synthesized by varying the feed ratio of monomers and their low $M_w$ polymers can be obtained by adding 2-mercaptoethanol as a chain transfer agent during poly-merization. All the polymers showed good adhesion properties on Cu pad when they were spin-coated. Especially, allylamine -containing copolymers showed both good adhesion and solubility properties. Also, they exhibited better thermal stability than PVP homopolymer and such thermal properties were changed depending on the chemical composition and their $M_w$, which were evidenced by the measurement of oxygen induced temperature (OIT). From the OIT measurement, poly(4-vinyl pyridine- co-allylamine) was thermally stable up to $230^{\circ}C$ for 70 min in the 100% oxygen environment. As a result, allylamine-containing copolymers can be considered as a promising OSP coating material that has excellent thermal and adhesive properties applicable to the present microelectronic package processes.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.153-153
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• 1999

platinum 유기착화합물을 사용하여 유리 기판 위에 Pt를 증착시켰다. Pt를 증착하기 위하여 Pt 착화합물을 용해 시킨 후, 유리 기판을 용액속에 담근 후 가열하여 Pt막을 증착하였다. 증착 후 Pt의 면저항은 200~75$\Omega$의 값을 나타내어 비교적 높은 저항값을 나타내었다. 높은 저항값을 낮추기 위해 진공 10-5Torr에서 50, 100, 150, 25$0^{\circ}C$로 열처리를 하였다. 이러한 저항값을 변화의 원인을 살펴보기 위하여 X-선 회절법을 이용하여 결정성의 변화를 살펴보았고, 화학적 조성의 변화는 X-ray 광전자 분광법을 이용하여 조사하였다. 열처리 전 Pt막은 비정질 상태를 나타내었으나, 6$0^{\circ}C$에서 30분간 열처리한 후에는 결정성이 증가하는 것으로 관찰되었다. 열처리 후 결정방향은 {111] 방향이 주 방향이였으며 [002] 방향의 피크도 관찰되었다. 따라서 성장된 막은 다결정 막임을 알 수 있었다. XPS를 이용하여 조성을 조사하여 본 결과 열처리하지 않은 시료의 경우 유기물과 반응하여 Pt의 피크가 넓게 나타나나 열처리 후에는 유기물이 분해되어 Pt의 고유한 피크를 관찰할 수 있었다. 따라서 전기전도도의 변화는 유기물의 분해를 통하여 순수한 Pt로 변해가면서 감소하는 것으로 생각되어 지며 결정성 또한 전기전도도 변화에 중요한 역할을 함을 알 수 있었다. 기존의 방법을 이용하여 Pt를 증착할 경우 기판과 쉽게 박리 되는 현상이 관찰되었으나 본 방법을 이용하여 증착된 Pt 박막의 경우 열처리 후에는 기판과의 접착력이 기존의 방법보다 뛰어나 박리되는 현상이 관찰되지 않았다.$ 이상에서 안정한 것을 볼 수 있었다. 텅스텐 박막은 $\alpha$ 및 $\beta$-W 구조를 가질 수 있으나 본 연구에서 성장된 텅스텐은 $\alpha$-W 구조를 가지는 것을 XRD 측정으로 확인하였다. 성장된 텅스텐 박막의 저항은 구조에 따라서 변화되는 것으로 알려져 있다. 증착조건에 따른 저항의 변화는 SiH4 대 WF6의 가스비, 증착온도에 따라서 변화하였다. 특히 온도가 40$0^{\circ}C$ 이상, SiH4/WF6의 비가 0.2일 경우 텅스텐을 증착시킨 후에 열처리를 거치지 않은 경우에도 기존에 발표된 저항률인 10$\mu$$\Omega$.cm 대의 값을 얻을 수 있었다. 본 연구를 통하여 산화막과의 접착성 문제를 해결하고 낮은 저항을 얻을 수 있었으나, 텅스텐 박막의 성장과정에 의한 게이트 산화막의 열화는 심각학 문제를 야기하였다. 즉, LPCVD 과정에서 발생한 불소 또는 불소 화합물이 게이트의 산화막에 결함을 발생시킴을 확인하였다. 향후, 불소에 의한 게이트 산화막의 열화를 최소화시킬 수 있는 공정 조건의 최저고하 또는 대체게이트 산화막이 적용될 경우, 개발된 연구 결과를 산업체로 이전할 수 있는 가능성이 높을 것을 기대된다.박막 형성 메카니즘에 큰 영향을 미침을 알 수 있었다. 또한 은의 전기화학적 다층박막 성장은 MSM (monolayer-simultaneous-multilayer) 메카니즘을 따름을 확인하였다. 마지막으로 구조 및 양이 규칙적으로 조절되는 전극의 응용가능성이 간단히 논의될 것이다.l 성장을 하였다는 것을 알 수 있었다. 결정성