• Title/Summary/Keyword: 단일 입자

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Electrochemical Study of a Single Particle of Active Material for Secondary Battery using the Microelectrode (마이크로 전극에 의한 2차 전지용 활물질 단일 입자의 전기화학적 평가)

  • Kim Ho-Sung;Lee Choong-Gon
    • Journal of the Korean Electrochemical Society
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    • v.9 no.2
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    • pp.95-99
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    • 2006
  • Electrochemical properties were studied for a single particle of active material of hydrogen storage alloy $(MmNi_{3.55}Co_{0.75}Mn_{0.4}Al_{0.3})$ and nickel hydroxides $(NiOH)_2$ for the secondary Nickel Metal Hydride (Ni-MH) batteries using the microelectrode, which was manipulated to make electrical contact with an active material particle for cyclic voltammograms (CV) and potential-step experiments. As a result of CV test, it was found that three kinds of hydrogen oxidation peaks at -0.9, -0.75 and -0.65 V and hydrogen evolution peak at -0.98 V for hydrogen storage alloy were separately observed and two kinds of peaks of proton oxidation/reduction at 0.45 and 0.32 V and oxygen evolution reaction (OER) at 0.6 V for nickel hydroxides were also more clearly observed. Furthermore hydrogen diffusion coefficient within a single particle was also found to vary the order between $10^{-9}\;and\;10^{-10}cm^2/s$ over the course of hydrogenation and dehydrogenation process for potential-step experiments.

Authentication Test of Archaeological Materials using Single Grain Regenerative Dose Method (단일입자재현법(單一粒子再現法)을 활용한 고고유물의 진위판별 연구)

  • Kim, Myung-Jin;Youn, Min-Young;Hong, Duk-Geun
    • Journal of Conservation Science
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    • v.23
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    • pp.73-80
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    • 2008
  • This article aims to turn out the authentication of archaeological materials by using the paleodose measurement to fine sand-size quartz grains obtained by micro sampling technique. We firstly revealed the validity of micro sampling technique from the paleodoses of two bricks related to Muryong Royal Tomb of Baekje Kingdom. For the purpose of authentication test, four archaeological materials were selected, because they have been insisted that they were manufactured in Goguryeo Kingdom era. After obtaining very few quartz grains by micro sampling technique, each paleodose was evaluated by using SGR (single grain regenerative dose method). All values were very low below 0.2Gy and the reliability was found from those values by using SAR (single aliquot regenerative dose method). Considering the archaeological situation and the general paleodose, the burial time for 1,000 years generally corresponds to about 3.5Gy in Korea, it is concluded that these archaeological materials are all modern counterfeits.

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Characterization of CdS-quantum dot particles using sedimentation field-flow fractionation (SdFFF) (침강 장-흐름 분획법을 이용한 CdS 양자점 입자의 특성 분석)

  • Choi, Jaeyeong;Kim, Do-Gyun;Jung, Euo Chang;Kwen, HaiDoo;Lee, Seungho
    • Analytical Science and Technology
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    • v.28 no.1
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    • pp.33-39
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    • 2015
  • CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.

Crushing Characteristics of Single Particle of Recycled Aggregate from Waste Concrete (폐콘크리트 순환골재의 단입자 파쇄 특성)

  • Park, Sung-Sik;Kim, Sang-Jung;Moon, Hong-Duk
    • Journal of the Korean Geotechnical Society
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    • v.32 no.12
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    • pp.23-32
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    • 2016
  • A single particle crushing test was carried out for recycled aggregates from waste concrete while demolishing various structures. When the recycled aggregates were used for backfill or road subbase materials, load-displacement and crushing characteristics were analyzed. The recycled aggregates with hydrates and aggregates were sorted into 40 mm size (75-40 mm) and 20 mm size (40-20 mm). At initial loading, their irregular surface was closed to and then crushed by loading plate. Such first crushing stage was called 'Surface crushing'. Further loading, some hydrate was crushed and detached from aggregate, and such process repeated several times. This state is called 'hydrate crushing'. The final state is called 'aggregate crushing' in which aggregate crushed and following load suddenly dropped down. As the load increased, such crushing cycle is repeated several times. The shapes of aggregates are round or square, and triangle or long shaped. Depending on their shapes and surface conditions, they crushed in different ways. The 63% of aggregates showed more than 50% load reduction due to aggregate crushing. The 90% load reduction occurred at 15% of aggregates. The 40 mm aggregate crushed at maximum load between 3.05-4.38 kN and 70% of crushed aggregates were less than 20 mm.

Revisiting the OSL Ages of Marine Terrace Sediments at Suryum Fault Site, Gyeongju, South Korea: Single Grain OSL Dating (수렴단층노두 해안단구 퇴적층의 OSL 연대에 대한 재고찰: 단일입자 OSL 연대측정 연구)

  • Heo, Seoyoung;Choi, Jeong-Heon;Hong, Duk-Geun
    • The Journal of the Petrological Society of Korea
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    • v.23 no.3
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    • pp.187-195
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    • 2014
  • In this paper, we report new OSL ages of the marine terrace sediments at Suryum fault site, using single grains of quartz, and briefly discuss their chronological implications on the timing of terrace formation along the southeastern coast of Korea. Of 1200 grains measured, 93 quartz grains were found to have OSL properties suitable for dating, the equivalent dose ($D_e$) values of which varied significantly, ranging from 50 Gy to 610 Gy with the overdispersion of $30{\pm}4%$. Applied to the Central Age Model (CAM) and Minimum Age Model (MAM), these quartz grains showed the OSL ages of $83{\pm}4ka$ and $60^{+3}{_{-7}}ka$, respectively, both of which are stratigraphically inconsistent with the previously reported OSL ages of lower $2^{nd}$ terrace (MIS 5a; ~80 ka). However, Finite Mixture Model (FMM) revealed that a small fraction of the measured quartz grains ($6{\pm}4%$) were of the ages ($194{\pm}24ka$) corresponding to MIS 7. Conclusively, based on single grain OSL ages, it would be prudent not to exclude the possibility that the marine terrace sediments at Suryum fault site have formed during MIS 7. Further, our single grain OSL ages imply that multiple grain(single aliquot) OSL dating methods are not applicable to the marine sediments at Suryum fault site.

Comparison Study on Burning and Ignition Characteristics for Single Aluminum and Magnesium Particles (EDB에 의해 부양된 알루미늄과 마그네슘 단일 입자의 점화 및 연소 특성 비교 연구)

  • Lim, Ji-Hwan;Yoon, Woong-Sup
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.311-316
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    • 2010
  • The ignition and the burning characteristics of aluminum and magnesium particles ($30-110{\mu}m$ in diameter) isolated due to electrodynamic levitation were experimentally investigated. The burning time, the ignition delay time, the flame temperature, and the flame diameter were measured. The thermal radiation intensity was measured using the photomultiplier tube and the combustion history was monitored by high-speed cinematography. Two-wavelength pyrometry measured the temperature of the burning particles. The burning times of aluminum particles were measured approximately 5 to 8 times longer than those of magnesium particles. Exponents of $D^n$-law, for the burning rate of magnesium and aluminum particles of diameters less than $110{\mu}m$, are found to be 0.6 and 1.5, respectively. The instant of aluminum ignition is clearly distinguished with the ignition delay time little less than 10 ms, however the burning history of magnesium particle exhibits no distinct instant of the ignition. The ignition delay time of magnesium particle (less than $110{\mu}m$) were approximately shown in the range from 50 to 200 ns. The flame temperatures of single metal particles are lower than the boiling point of the oxide. The nondimensional flame diameters for magnesium are decreased with increasing of the diameter. The nondimensional flame diameters for aluminum are not changed significantly.

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Characterization of submicron Particles Using a Single Particle Mass Spectrometer(I) - Non - Linear Correlation Between Particle Size and Mass Spectra Signals - (단일입자 질량분석기를 애용한 서브마이크론 입자의 특성화(I) - 입자의 크기와 질량분광신호의 비선형성 -)

  • Zachariah Michael R.;Lee Donggeun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.4
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    • pp.453-459
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    • 2005
  • In this paper, we are proposing a robust tool which is capable of measuring the size and elemental composition of submicron particles from twenty to several hundreds nanometers at the same time, i.e., named Single Particle Mass Spectrometer (SPMS). The home-made SPMS employs a laser ablation/multi-photon ionization method to tear a nanoparticle into the constituent elemental ions. One thing different from the conventional Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) is the power of the ionization laser. Much strong laser used in this work makes it possible to generate elemental ions rather than molecular ions from a nanoparticle. Also the use of high power laser may guarantee a complete ionization of a particle, which was confirmed by the existence of multiple charged ions. If a particle is evaporated/ionized completely and detected through electric field-free TOF tube without any loss, we can extract the original particle volume from the measured total ion numbers. Collecting a number of particles mass spectra, we get a database of size and elemental composition of nanoparticles, with which we may take a took into any kinds of chemical reaction occurring at nanoscale. Several issues related to size estimation by SPMS will be discussed.