• 한국재료학회지
• /
• 제13권8호
• /
• pp.524-530
• /
• 2003

In order to prepare the uniform copper particles from copper sulfate solution by using hydrazine as a reduction agents, the reduction behavior of copper particles from copper sulfate was investigated in detail at room temperature by the observation of reaction products. The effects of $NH_4$OH and $Na_4$$P_2$$O_{7}$ on the formation of uniform copper particles were discussed. ($NHCu_3$)$_4$$SO_4$was completely formed at over pH 11 by adding $NH_4$OH in copper sulfate solution. The fine $Cu_2$O with the particle size of 50 nm was produced in the initial reduction process of (NH$Cu_3$)$_4$$SO_4$solution with $Na_4$$P_2$$O_{ 7}$ and then the Cu$_2$O was converted into copper particles by inserting additional hydrazine. When Cu(NH$_3$)$_4$SO$_4$solution with $Na_4$$P_2$$O_{ 7}$ was reduced at $80^{\circ}C$ by hydrazine, the highly dispersed copper particles with the particle size of about 0.8 $\mu\textrm{m}$ was obtained.

• 센서학회지
• /
• 제22권5호
• /
• pp.346-351
• /
• 2013

We developed a one-step method for fabrication of addressable suspended SWNT films and demonstrate excellent detection performance of paraoxon based on OPH-immobilized SWNT films for environmental monitoring. For dispersed SWNT suspension, COOH-SWNT was prepared by the oxidation of carbon nanotubes using acid treatment and sonication. Suspended SWNT-film was fabricated between cantilever electrodes by dielectrophoretic force and surface tension of the water meniscus. After that, OPH were immobilized on suspended SWNT-films by nonspecific binding for enzymatic hydrolysis of paraoxon. The electrical properties of the SWNT films were measured in real time at room temperature. Structurally suspended SWNT films from substrate surface made possible rapid and highly sensitive detection of target molecules with increased convectional and diffusional fluxes of the molecules and with a large binding surface area. SWNT film FET resulted in a real-time, label-free, and electrical detection of paraoxon to the concentration of ca. $10{\mu}m$ with a step-wise rapid response time of several seconds.

• Environmental Engineering Research
• /
• 제10권1호
• /
• pp.38-44
• /
• 2005

Electro-thermal production of white phosphorus(WP, P4) generates substantial amount of highly toxic phossy water and sludges. Because of their high phosphorus contents and lack of reliable processing technology, large tonnages of these hazardous wastes have accumulated from current and past operations in the United States. In this study, two different methods for treatment of phosphorus sludge were investigated. These were bulk removal of WP by physical separation(froth flotation) and transformation of WP to oxyphosphorus compounds by air oxidation in the sludge medium. Kerosene, among other collectors, resulted in selective flotation of WP from the associated mineral gangue. Solvent action of kerosene occurring on the WP surface(by rendering WP particles hydrophobic) might produce the high selectivity of WP. The WP recovery in the froth was 79.3% from a sludge assaying 34.2% of WP. In the oxidation study, air gas was dispersed in the sludge medium by the rapid rotation of the impeller blades. The high level of sludge agitation intensity caused a fast completion of the oxidation reactions and it resulted in the high percentage conversion of WP to PO4-3 with PO3-3 making up almost all portion of oxyphosphorus compounds. The WP analysis on the treated sludge showed that supernatant solution and solid residue contained an average of 4.2 μg/L and 143 ppm respectively from the sludge containing about 26 g of WP. Further investigation will be required on operational factors to better understand the processes and achieve an optimum condition.

• 폴리머
• /
• 제24권3호
• /
• pp.399-406
• /
• 2000

히드로퀴논과 p-히드록시 벤조산, 그리고 1,6-디브로모헥산을 이용하여 유연한 알킬기를 주사슬에 가지는 열방성 액정 고분자(TLCP)를 얻었다. TLCP의 녹음 전이온도 이상에서 도데실 암모니움-몬모릴로나이트(C$_{12}$-MMT)를 첨가하여 나노복합재료를 만들었다. $C_{12}$-MMT를 TLCP에 대해 1 wt%만 섞어도 액정성은 파괴되었으며, 그 이상의 $C_{12}$-MMT양에 대해서도 마찬가지였다. 첨가된 $C_{12}$-MMT중 일부는 TLCP에 잘 분산되었으나, 일부는 뭉쳐진 형태로 존재하였다. 합성된 나노복합재료의 열적 성질과 몰폴로지는 시차주사 열분석기 (DSC), 열중량 분석기 (TGA), 편광 현미경, 그리고 전자 현미경 (SEM, TEM) 등을 이용하여 분석하였다.다.

• 폴리머
• /
• 제31권2호
• /
• pp.111-116
• /
• 2007

폴리우레탄 변형 아크릴레이트(PUA)/실리카 하이브리드 필름은 자외선 경화에 의해 제조되었고, 필름의 표면물성은 경도시험과 접착력 테스트를 통해 분석되었다. 이들 필름은 유기, 무기함량을 mole비로 조성하여 실험하였으며, 무기조성은 실리카 입자의 함량을 기준으로 설정하였다. 필름 층 내의 실리카 입자는 함량에 따라 혹은 분산정도에 따라 내스크래치성이나 필름자체 경도 등의 물성이 많은 차이를 보였는데, 이는 PUA필름 층 내의 실리카 입자들이 균일하게 분포되어 가교결합되어 있었기 때문이다.

• Bulletin of the Korean Chemical Society
• /
• 제21권9호
• /
• pp.913-918
• /
• 2000

Vanadium oxide catalyst supported on TiO2-ZrO2 has been prepared by adding Ti(OH)4-Zr(OH)4 powder to an aqueous solution of ammonium metavanadate followed by drying and calcining at high temperatures. The char-acterization ofthe prepared catalysts was performed using solid-state 51V NMR and FTIR.In thecase ofcalci-nation temperature at 773 K, vanadium oxide was in a highly dispersed state for the samples containing low loading V2O5 below 25 wt %, but for samplescontaining high loading V2O5 equal to or above 25 wt %, vana-dium oxidewas well crystallized due to the V2O5 loading exceeding the formation of monolayer on the surface of TiO2-ZrO2.The ZrV2O7 compound was formed through the reactionof V2O5 and ZrO2 at 773-973 K, where-as the V3Ti6O17 compound was formedthrough the reaction of V2O5 and TiO2 at 973-1073 K. The V3Ti6O17 compound decomposed to V2O5 and TiO2 at 1173 K, which were confirmed by FTIR and 51V NMR.

• Advances in Energy Research
• /
• 제3권2호
• /
• pp.81-95
• /
• 2015

Microgrid, which can be considered as an integration of various dispersed resources (DRs), is characterized by number of DRs interfaced through the power electronics converters. The microgrid comprising these DRs is often operated in an islanded mode. To minimize the cost, reduce complexity and increase reliability, it is preferred to avoid any communication channel between them. Consequently, the droop control method is traditionally adopted to distribute active and reactive power among the DRs operating in parallel. However, the accuracy of distribution of active and reactive power among the DRs controlled by the conventional droop control approach is highly dependent on the value of line impedance, R/X i.e., resistance to reactance ratio of the line, voltage setting of inverters etc. The limitations of the conventional droop control approach are demonstrated and a modified droop control approach to reduce the effect of impedance mis-match and improve the time response is proposed. The error in reactive power sharing is minimized by inserting virtual impedance in line with the inverters to remove the mis-match in impedance. The improved time response is achieved by modifying the real-power frequency droop using arctan function. Simulations results are presented to validate the effectiveness of the control approach.

• Safety and Health at Work
• /
• 제1권1호
• /
• pp.98-101
• /
• 2010

This study explored the health hazard of those exposed to methylene chloride by assessing its atmospheric concentration when a tear gas mixture was aerially dispersed. The concentration of methylene chloride ranged from 311.1-980.3 ppm (geometric mean, 555.8 ppm), 30 seconds after the dispersion started. However, the concentration fell rapidly to below 10 ppm after dispersion was completed. The concentration during the dispersion did not surpass the National Institute for Occupational Safety and Health 'immediately dangerous to life or health' value of 2,300 ppm, but did exceed the American Conference of Governmental Industrial Hygienists excursion limit of 250 ppm. Since methylene chloride is highly volatile (vapor pressure, 349 mmHg at $20^{\circ}C$), the post-dispersion atmospheric concentration can rise instantaneously. Moreover, the o-chlorobenzylidenemalononitrile formulation of tear gas (CS gas) is an acute upper respiratory tract irritant. Therefore, tear gas mixtures should be handled with delicate care.

• 한국분말재료학회지
• /
• 제26권3호
• /
• pp.220-224
• /
• 2019

The aluminum (Al)/copper oxide (CuO) complex is known as the most promising material for thermite reactions, releasing a high heat and pressure through ignition or thermal heating. To improve the reaction rate and wettability for handling safety, nanosized primary particles are applied on Al/CuO composite for energetic materials in explosives or propellants. Herein, graphene oxide (GO) is adopted for the Al/CuO composites as the functional supporting materials, preventing a phase-separation between solvent and composites, leading to a significantly enhanced reactivity. The characterizations of Al/CuO decorated on GO(Al/CuO/GO) are performed through scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping analysis. Moreover, the functional bridging between Al/CuO and GO is suggested by identifying the chemical bonding with GO in X-ray photoelectron spectroscopy analysis. The reactivity of Al/CuO/GO composites is evaluated by comparing the maximum pressure and rate of the pressure increase of Al/CuO and Al/CuO/GO. The composites with a specific concentration of GO (10 wt%) demonstrate a well-dispersed mixture in hexane solution without phase separation.

• 한국염색가공학회지
• /
• 제34권4호
• /
• pp.250-260
• /
• 2022

In this research, a high-elasticity acrylic emulsion binder with core-shell polymerization and self-crosslinking system is mixed with a flame-retardant water-dispersed polyurethane (PUD) binder. In addition, finite element analysis was conducted through virtual engineering software ANSYS by applying three representative nonlinear material models. The most suitable nonlinear material model was selected after the relative comparison between the actual experimental values and the predicted values of the properties derived from simulations. The selected nonlinear material model is intended to be used as a nonlinear material model for computational simulation analysis that simulates the experimental environment of the vibration test (ASTM E1399) and the actual fire safety test (ASTM E1966). When the mass fraction of thermally expandable graphite was 0.7%, the thermal and physical properties were the best. Among the nonlinear material models, the simulation result of the Ogden model showed the closest value to the actual result.