Yeongmin Kim

High yield synthesis of Ni-BTC metal-organic framework with ultrasonic irradiation: Role of polar aprotic DMF solvent.

Nickel based porous solid was synthesized with 20 kHz ultrasonic irradiation. The reaction of Ni(II) nitrate hexahydrate with 1,3,5-benzene tricarboxylic acid in N,N-Dimethylformamide (DMF) as the sole solvent under ultrasonic radiation produced porous Ni-BTC MOF. Choice of correct solvent for the ultrasonic treatment was proven important. The effect of varying ultrasonic powers (40%, 60% and 80% of 750 W) along with different temperature conditions (50 °C, 60 °C, 70 °C and 80 °C) influenced the respective yield. A very high yield of 88% Ni-BTC MOF was obtained from 80% ultrasonic power at 60 °C. BET surface areas of the MOF crystals measured by N2 gas adsorption isotherms were in the range of 960-1000 m(2)/g.

Synthesis of porous Cu-BTC with ultrasonic treatment: Effects of ultrasonic power and solvent condition.

Cu-BTC (BTC=1,3,5-benzenetricarboxylate) metal organic framework (MOF) was synthesized using different solvent conditions with ultrasonic treatment. Solvent mixtures of water/N,N-dimethylformamide (DMF), water/ethanol were used for the reactions with or without a variety of bases under 20 kHz ultrasonically treated conditions. Prepared crystals were purified through 30 min of sonication to remove unreacted chemicals. Treatment time and ultrasonic power effects were compared to get optimum synthetic condition. The characterization of MOF powders was performed by scanning electron microscopy, X-ray powder diffraction, infrared-spectroscopy, thermo-gravimetric analysis and specific surface determination using the BET method. Isolated crystal yields varied with different solvent and applied ultrasonic power conditions. A high isolated crystal yield of 86% was obtained from water/ethanol/DMF solvent system after 120 min of ultrasonic treatment at 40% power of 750 W. Different solvent conditions led to the formation of Cu-BTC with different surface area, and an extremely high surface area of 1430 m(2)/g was obtained from the crystals taken with the solvent condition of water:DMF=70:30.

SCOPE OF VARIOUS SOLVENTS AND THEIR EFFECTS ON SOLVOTHERMAL SYNTHESIS OF Ni-BTC

Ni-BTC (BTC = 1,3,5-benzene tricarboxylate) metal organic framework (MOF) was synthesized using different solvent conditions. Solvent mixtures of water/N,N-dimethylformamide (DMF), water/ethanol, and water/ethanol/DMF were used for the reactions with or without a variety of bases at 160 oC for 48 hours. Even with same green crystals, prepared MOFs show all different BET surface areas and different XRD patterns. The highest BET surface area of the crystals was 850 m2/g obtained from water/DMF solvent with NH4OH as a base. The measured surface areas of the crystals follows the order of Ni-BTC(water/DMF-NH4OH) > Ni-BTC(water/DMF-TMA) > Ni-BTC(water/DMF) > Ni-BTC(water/DMF-Pyridine)> Ni-BTC(water/ethanol)> Ni-BTC(water/DMF-aniline)> Ni-BTC(water/DMF-NaOH).

Cost effective and low energy consuming hydrothermal synthesis of Ni based MOF

The mesoporous metal organic framework structure of Ni-BTC was successfully synthesized in a low temperature and short operation time via hydrothermal synthesis process. Such operational route virtuously consumed less electrical and thermal energy. It proved time saving along with acceptable product yield (38%). The product was characterized through FESEM, FT-IR, XRD and N2 gas adsorption measurement. Hightemperature stability of synthesized MOF was gauged by diffraction indexing of XRD patterns of as synthesized and heat treated samples of MOFs. The mathematically calculated particle size of Ni-BTC was found to be 42㎚.

Performance Analysis on Solar Tracking Daylighting Systems Using Different Types of Solar Collectors: Parabolic Dish vs. Fresnel Lens

This paper presents the effect of solar collectors on the performance of solar tracking daylighting systems. A series of measurements were made for two different types of solar collectors mounted on double axis solar trackers: Parabolic dish concentrator and Fresnel Lens. Indoor light levels were measured at different locations of an office space (longitude: 126.33 E, latitude 33.45 N) as photo sensors were placed on a task plane 80 cm above the floor. To accurately monitor the applicability of the systems, measurements were performed under clear and overcast sky conditions with the roll-screen (on the south window) in the down position. Comparing the illuminance data, the system with Fresnel lens outperformed that of parabolic dish concentrator. On clear days, the former delivered the light levels of 400~600 lux on the task plane whereas the latter recorded 100~200 lux. Depending on the amount of cloud cover, on overcast days, illuminance readings fluctuated to some extent.

Electric lighting energy saving through the use of a Fresnel lens based fiber-optic solar lighting system : Simulation and measurements

This paper deals with the effectiveness of a fiber optic solar lighting system that uses a Fresnel lens mounted on a two-axis solar tracker. A series of comparative analyses were made concerning its performance as compared to fluorescent lighting by using a simulation model based on ECOTECT and RADI...

Transient and Synchronized Behaviors of Two Coupled Thermal Acoustic Converters

AbstractIntegration of multiple sound generators is essential to the development of large-scale, sono-assisted processes such as combustion, evaporation, or CO2 capture with acoustic excitations. In this work, the transient and synchronized behaviors of a thermal acoustic converter (TAC) pair were investigated experimentally for various crossing angles and different separation distances between the converters. The two TACs were acoustically coupled through the air mass between their openings, and the only mode-locking operation that could be achieved was the one that was nearly 180° out of phase. The time to achieve synchronization was found to be dependent upon the initial mistuning of the frequencies and the crossing angle between the converter axes. The synchronization process could also be accelerated by turning on the converter with the lower power input first. When the separation distance between the two converters exceeded a certain value, synchronization of the TAC pair could not be achieved. As t...

An Experimental Study on LTD Stirling Engine (MM-7) for the Development of TM Electric Conversion System

Abstract - This study has been carried out to develop TM (Thermal to Mechanical) conversion systems for electric power generation using one of the Low Temperature Differential (LTD) Stirling engines called MM-7 capable of harnessing low temperature waste heat whose temperature is only 20~30℃ above the ambient. Measurements were made on the torque and rpm for a number of temperature differentials between the engine hot and cold ends, which could be effectively applied in developing the most suitable configuration for the high performance TM (Thermal to Mechanical) conversion system. Key words : Low Temperature Waste Heat, Stirling Engine, Thermal to Mechanical Energy Electric Conversion System 1. 서 론 저온 폐열로부터 전력을 생산하는 것은 산업계에서 확대되는 주요한 기술이다. 대규모 기계 가공 및 전력발전 시설들은 정상작동 시 다양한 공정에서 다량의 열에너지가 발생하는데, 이와 관련하여 다양한 냉각 또는 HVAC(Heating, Ventilation, Air Conditioning) 시스템을 사용하게 된다. 특히, 이러한 시설들은 주위에 비해 20~30℃ 정도 밖에 높지 않은 폐열을 지속적으로 발생시키며, 이는 잠재적으로 유용한 에너지원으로서 에너지 신소재 및 폐열회수 기술의 개발과 함께 동력생산 (발전)에 효율적으로 적용될 수 있다.일반적으로 폐열회수와 함께 현재 고려될 수 있는 발전기술은 고가의 열전발전기 (Thermoelectric generator)

Hydrothermal Synthesis of Fe Based MOFs with Energy Economy Approach

The mesoporous metal organic framework structure Fe-BTC was successfully synthesized by hydrothermal process with noticeable yield. The synthesis operation was conducted at intermediate temperature and for shortened operation time as compared to conventional procedures. This process approach with reduced operating temperature and shortened operation time may open an opportunity window towards process economy with reduction in energy consumption. A simple mathematical approach of diffraction indexing using X-ray diffraction patterns of synthesized powder was employed to confirm its crystalline nature and to investigate its high temperature stability. The crystallite size was calculated by using Debye-Scherrer equation.

An Experimental Study on the Optical Separation of Highly Concentrated Sunlight

Highly concentrated sunlight obtained from a solar concentrator mounted on a solar tracker can be divided into the infrared and visible region before it is actually applied. That is, solar rays are directed toward a unit optically separating sunlight into the infrared and visible region by a hot mirror as they impinge on the surface of a secondary reflector. The Infrared rays can be utilized for thermoacoustic applications while visible rays can be utilized for indoor lighting. This work introduces the separation of two different kinds of light; sunlight and artificial light. As for the artificial light, its wavelength extended from 400 to 720 for the visible region and 620 to 940 for the infrared region. Comparatively, a series of tests performed on sunlight revealed its separation in the visible region from 460 to 680 whereas from 620 to 940 for the artificial light.