흐름전극을 이용한 축전식 탈염 공정의 실험적 연구

전성일 충남대학교 녹색에너지기술전문대학원 2013 국내석사

중수로 사용후핵연료 결함 기구 및 결함 판정기준 연구

김용찬 忠南大學校 녹색에너지기술전문대학원 2013 국내석사

When CANDU reactor has defective fuel bundle during its operation, then the defective fuel bundle should be discharged by 2(two) fuel bundles at a time from the corresponding fuel channel until the failed fuel bundle is found. Existing fuel failure detection system GFP(Gaseous Fission Product) & DN(Delayed Neutron) Monitoring System can’t exactly distinguish fuel elements failure from each fuel bundle. Because of fuelling machine mechanism and discharge procedure, always two fuel bundles at a time are being inspected. Although there are no defects and damaged marks on the surface of outer fuel elements visually, fission nuclide will be emitted from defected hole of the fuel rod. Therefore, the purpose of this study was to study threshold value which is capable of inspecting whether each fuel bundle is failed or not. This paper also describes the behavior of each nuclide according to leaking out damaged fuel rods.

Particle Fluctuations and Dispersion in Three-phase Fluidized Beds with Viscous and Low Surface Tension Media

Hyun-Oh Lim 충남대학교 녹색에너지기술전문대학원 2012 국내석사

Particle fluctuations and dispersion were investigated in a three-phase (gas-liquid-solid) fluidized bed of inside diameter is 0.102m and 2.5m in height. Effects of gas and liquid velocities, particle size (0.5~3.0mm), viscosity (1.0~3810-3Pa.s) and surface tension (52~7210-3N/m) of continuous liquid media on the fluctuating frequency and dispersion coefficient of fluidized particles were examined, by adopting the relaxation method base on the stochastic model. The fluctuations and dispersion of fluidized solid particles were successfully analyzed by means of the pressure drop variation with time, which was chosen as a state variable, based on the stochastic model. The fluctuating frequency and dispersion coefficient of particles increased with increasing gas velocity, due to the increase of bubbling phenomena andbed porosity in which particles could move, fluctuate and travel. The frequency and dispersion coefficient of particles showed local maximum values, respectively, with a variation of liquid velocity. The two values of fluctuating frequency and dispersion coefficient of particles increased with increasing particle size, but decreased with increasing liquid viscosity due to the restricted movement and motion of particles in the viscous liquid medium. Both of fluctuating frequency and dispersion coefficient of particles increased with decreasing surface tension of liquid phase, due to the increase of bubbling phenomena with decreasing σL. The values of obtained particle dispersion coefficient were well correlated in terms of dimensionless groups as well as operating variables.

리튬 이차 전지용 음극활물질의 전해질 성분에 따른 계면 및 열적 특성 평가

김민정 忠南大學校 綠色에너지技術專門大學院 2014 국내석사

Exothermal Mechanisms of the battery is occured from the decomposition of the components of the SEI layer that is formed by electrolyte reduction reaction at the interface between electrode and electrolyte. the components of the SEI layer, high temperature largely influence on the thermal stability of batteies. Especially the surface modification on the anode using additives in the electrolyte in the battery improves thermal stability and electrochemical behavior at the same time. It is usually studied as an effective method to improve thermal stability and electrochemical behavior. The effect of electrolyte’s composition on the surface chemical and thermal stability of anode materials were studied in this paper .anode materials use soft carbon as carbon and si as non-carbon. The electrolytes used in the experiments were 1 M LiPF6 solutions composed of ethylene carbonate(EC)/ ethylmethylene carbonate (EMC) (30:70 v/v) with VC for P-doped soft carbon anodes and ethylene carbonate (EC)/ diethyl carbonate (DEC) (30:70 v/v) with LiBOB for Si anodes. Attenuated total reflectance Fouriertransform infrared (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) were used to investigate SEI layer of anode materials. It was found that the SEI layer formed in VC & LiBOB-containing electrolyte possessed better properties. The presence of VC in electrolyte brought out the VC-reduced products and decreased the LiF content in SEI layer. The major components of SEI layer. And LiBOB derived –SEI layer is formed lithium oxalate, B2O3.the additive can form a stable anode SEI layer that inhibits electrolyte decomposition. Namely,, The ex situ ATR-FTIR and XPS results for the delithiated anodes, confirmed that the reduction decomposition of electrolyte components is effectively alleviated by the VC & LiBOB-derived SEI and It improve the thermal stability of anodes(soft carbon, Si). The thermal behavior of the fully lithiated anode electrodes (Soft carbon, Si) in contact with an electrolyte is investigated by differential scanning calorimetry (DSC) in the temperature range 40~400°C. Consequently, It found that the onset temperature of the exothermic reaction of the soft carbon was shifted from 80 °C to 116.56 °C when cycled in the presence of an VC additive. also the onset temperature of the thermal runaway is shifted from 120°C to 250 °C charged LixSi is heated in the presence of LiBOB in the electrolytes,

N, O, F based surface-modification of carbon molecular sieves and their CO2/CH4 separation properties : 탄소분자체 표면에 도입된 N, O, F와 CO2/CH4의 분리 특성

Byong Chol Bai 충남대학교 녹색에너지기술전문대학원 2012 국내석사

본 연구에서는 다양한 표면관능기를 도입한 탄소분자체의 CO2/CH4 분리효율에 대해 고찰하였다. 다양한 표면관능기를 탄소분자체에 부여하고자 암모니아수, 기상 불소화, 기상 함산소불소화 방법이 사용되었다. 각각의 표면처리 방법을 통하여 탄소분자체의 미세 (micro) 기공 구조의 변화와 CO2/CH4 분리효율을 확인할 수 있었다. 표면처리된 탄소분자체에 도입된 표면 관능기를 알아보기 위해 X선 광전자분광기를 사용하였다. 암모니아수로 처리한 탄소분자체의 경우 그 처리 정도에 따라 아미노 관능기가 도입된 것을 확인할 수 있었다. 기상 불소화 및 함산소불소화 처리한 탄소분자체의 경우 불소 및 산소 관능기가 도입된 것을 확인하였다. 또한 표면처리된 탄소분자체 각각의 미세 기공 분포와 CO2 흡착량을 확인하였다. 그 결과, 암모니아수 처리된 탄소분자체는 도입된 아미노 관능기와 CO2간의 화학적 흡착에 따라 흡착량이 증가한 결과를 얻을 수 있었다. 하지만 농도가 짙은 암모니아수로 처리한 탄소분자체의 경우 오히려 흡착량이 감소하였고 이는 미세 기공 구조가 무너져 나온 결과로 해석된다. 기상불소화로 처리된 탄소분자체는 그 처리 정도에 따라 CO2 흡착량이 증가하였고 이는 염기성 관능기인 불소와 CO2간 전자끼리의 인력에 의해 나온 결과로 해석된다. 또한 기상함산소불소화로 처리된 탄소분자체도 그 처리 정도에 따라 CO2 흡착량이 증가하였으며 이 또한 도입된 산소 관능기와 CO2간 전자의 인력으로 인한 결과로 보여진다. 이러한 결과는 탄소분자체의 CO2/CH4 분리실험에서도 비슷한 경향을 보였다. 각각의 처리조건에 따라 탄소분자체는 CH4보다 CO2의 흡착정도가 증가하는 결과를 보였고 이는 미세기공의 발달 및 도입된 관능기의 영향으로 해석된다. 또한 처리 조건이 과할 경우 오히려 CO2의 흡착량 감소 및 CH4 흡착량 증가 등 분리효율이 떨어지는 결과를 보였고 이는 미세 기공 구조의 붕괴 또는 확장에 따른 결과로 해석된다.

펠톤 水車의 러너 버킷 改善에 따른 水力 性能과 出力 增加

박노현 충남대학교 녹색에너지기술전문대학원 2013 국내석사

Energy has been very closely used in the life of human being and with progress of civilization, become a key-element in transportation, production activity and cultural needs. Accordingly, the consumption of energy has increased and the increase of energy consumption causes the problems like climatic change and global warming which result in threat of disasters. Under these circumstances, in order to overcome the risk of disaster, the development of sustainable energy resources becomes now a critical and urgent issue. Getting out of existing and old paradigm where the policy of conflict and hostility were carried out to secure limited natural resources like oil, coal, gas, etc., which was called "Energy War" staking the national destiny, new technologies according to each country's geographical and environmental conditions, were recently introduced to use the new & renewable natural energies like water, wind, sun light and solar radiation, wastes, sea energy resources using tidal and wave power and bio-mass using energy from plants. Furthermore, many countries are trying to upgrade existing energy technologies, which become an engine for future growth but also a new technical weapon to secure the energy. Among various natural energy resources, the hydro-power, a part of renewable energy, which has a long historical background, can be estimated as highly efficient and valuable means from environmental and economical point of view. It should be especially noted that the hydro-power generation using head and flow to rotate the turbine, which is the most fundamental principle to get energy, has little effect to the environment when it is grafted onto new or existing structures. By this benefit, it has been a target of continuous technical developments. The hydro-power turbines are classified, based on their universality and frequency of use, as Pelton turbine of impulse type used at high head, Francis turbine of reaction type used at high and middle heads, and Kaplan turbine for low head. Most of advanced countries having the original technology have developed the hydro-power turbines that show 90% efficiency, through steady and persistent studies. For Pelton turbine, the technical foundation of hydro-power generation in advanced countries, the increase of rotatory power by means of bucket weight causes the increase the power output. Through the study of correlation between bucket weight and power output, we expect the performance improvement, as well as the power increase by bucket shape and weight, which is the original technology of power generation in Korea and abroad. Through the design and manufacturing techniques of runner, the basics of water turbine, apart from Pelton turbine using high head which is formed by energy collection process from desalination plants and surplus pressure, the study of runners for Francis and Kaplan turbines that are suitable to geographical and environmental conditions of Korea will be especially meaningful. This study will be the beginning of studies of performance increase and improvement by examination on correlation with runner weight, and contribute to raise the commercial and technical values which can be used practically and universally.

반응가스에 따른 SiOx 나노입자의 미세구조 및 전기화학 특성 연구

전영식 忠南大學校 綠色에너지技術專門大學院 2013 국내석사

SiOx nanoparticles were synthesized by an evaporation and condensation process using induction melting of silicon (Si)-chunks followed by the injection of O2/Ar mixed gas or H2/Ar mixed gas into the melt. In particular, this research studies the effects of oxygen gas or hydrogen gas on nanoparticles’ microstructural and electrochemical properties, etc. During the microstructural analysis, regardless of gas contents, all the nanoparticles were observed to have random shapes their average particle sizes were 30 ~ 35 nm. However, crystalline Si phase, even if it was small amount, was formed when H2/Ar gas was injected. From XPS analysis, the amount of SiO2.0 phase in SiOx decreased to a relative degree when the H2/Ar gas ratio was higher than 1.0 vol.%. injected hydrogen resultedin Si-H network in SiOx and the Si-H concentration was independent on the amount of injected gas. Consequently, due to the hydrogen incorporation, not only crystalline Si phase was formed, but also the amount of SiO2.0 phase decreased. In addition, Si-H bonds were formed in nanoparticles. Crystalline Si phase and relatively small amount of SiO2.0 phase resulted in enhancement of specific capacity when those nanoparticles were applied for an as an anode material for the Li-ion battery. Furthermore, cycle performance was improved even when hydrogen was incorporated. For the sample synthesized with 5.0 vol.% H2/Ar gas, discharge capacity and columbic efficiency at the 21st cycle were 889.1 mAh/g and 95.0 %, respectively.

리튬이차전지용 주석계 음극재의 계면안정화를 통한 전기화학적 성능향상에 대한 연구

추명호 忠南大學校 綠色에너지技術專門大學院 2014 국내석사

In lithium rechargeable batteries, Tin (Sn)-based materials have received as alternative anode materials to graphite because of about three times higher theoretical capacity (992 mAhg-1) and advantage of tin is high electronic conductivity. However, tin suffers from a rapid cycle performance fade due to significant volume change by up to 300 % and interfacial instability of tin in electrolyte including LiPF6 to produce various acids that etch active tin material during alloying/dealloying with lithium. Also continued electrolyte decomposition in the absence of solid-electrolyte interphase (SEI) layer has been noticed to be another cause for poor cycling ability. In order to improve cycling ability of tin-based anodes, various research have been reported such as making nano structure, tin-carbon composites and control of SEI layer. Most of all, control of electrode-electrolyte interfacial reaction and the formation of solid electrolyte interphase (SEI) layer is a promising approach to suppress particle disintegration and to improve cycling ability among them. In this part 1 of thesis, we control interfacial reaction using trimethyl phosphite additive in LiPF6-containing ethylene carbonate (EC)-based electrolyte, and doped fluorine to tin-nickel thin film anodes that were prepared by pulsed laser deposition to improve cycling ability. The use of trimethyl phosphite (TMP) additive and fluorine-dopant to LiPF6-contiaing EC-based electrolyte improves significantly electrochemical performance compared to electrode without fluorine-dopant or TMP additive. The interfacial stability of tin for acidic electrolyte species was analyzed by ex situ furier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As a result, tin fluoride and stable SEI layer consisting of carbonate decomposition products form mainly on the tin-nickel anode and formation of organic phosphorus fluorides decreases. It notes that TMP additive and F-dopant play a role of restraining Lewis acids such as PF-containing compounds and HF in LiPF6-containing EC-based electrolyte. In this part 2 of thesis, we prepared micron scale tin-nickel-graphite composite electrodes by ball-milling and LiPF6-containing fluoro ethylene carbonate (FEC)-based electrolytes apply to tin-nickel-graphite composite electrodes. In addition, interfacial stabilization effect using TMP additive and F-dopant apply to tin-nickel-graphite composite electrodes in LiPF6-containing FEC-based electrolytes. F-doped tin-nickel-graphite electrode in LiPF6-containing FEC-based electrolyte with TMP additive enhance electrochemical performance compared to tin-nickel-graphite electrodes in LiPF6-containing EC-based electrolytes. The interfacial stability of electrodes for SEI compounds was analyzed by ex situ FT-IR, XPS and SEM. As a result, stable SEI layer consisting of lithium carbonate, polycarbonate and SnF2/SnF4 form mainly on the tin-nickel-graphite anode. The formation of stable SEI layer passivates tin-nickel-graphite anode from combined effect of FEC-based electroyte to form polycarbonate with TMP additive and F-dopant to resist Lewis acids in LiPF6-containing FEC-based electroyte. In conclusion, controling electrode-electrolyte interfacial reaction is essential to improve electrochemical performance in tin-based anodes for lithium rechargeable batteries.

無灰分炭을 燃料로 使用한 直接炭素燃料電池

진선미 충남대학교 녹색에너지기술전문대학원 2013 국내석사

Carbon-rich coal can be utilized as a fuel for DCFC. However, left-behind ashes in coal that stack up may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by using a thermal extraction method and then characterized it using ultimate/proximate analysis, FT-IR and XRD. Also, the parent raw coal, carbon black and graphite were characterized. According to analysis results, coals (AFC and raw coal) contained more functional groups than carbon black and graphite, indicating that coals would be more reactive at anode. DCFC was built using a YSZ, electrolyte and then the electrochemical performance of various fuels (AFC, raw coal, carbon black and graphite) was compared with one another. AFC performs better than the other fuels with regard to the power density and durability, which seems to be related to the concentration of pyrolyzed gases as well as the electrochemical reactivity of the solid fuels. When each fuel is internally gasified with steam or carbon dioxide, the power density was improved by 1.3~10 times, compared to N2 pyrolysis environment. These results indicates that internal gasification of carbon fuel increases the power density because gaseous fuels (H2, CO) are produced via coal-water, water-gas shift and Boudouard reaction. When AFC with K2CO3 are compared to AFC without catalyst, an increase of the power density is shown by catalytic pyrolysis. Significantly more fuel gases are evolved by catalytic steam gasification of AFC in the presence of K2CO3, showing that a catalyst activates the steam gasification reactions producing more H2 and CO. The power density of AFC is strongly temperature dependent, increasing with temperature. A thin YSZ (30 μm) exhibits higher power density than a thick one (1 mm).

쌀밥으로 제조된 활성탄을 사용하는 전기이중층형 슈퍼커패시터 전극의 전기화학적 특성

조운 忠南大學校 綠色에너지技術專門大學院 2014 국내석사

쌀밥을 출발물질로 활용하고 수열합성법과 화학적 활성화를 위한 KOH용액 진공함침 등의 방법으로 제조된 활성탄의 전기이중층 초고용량 커패시터의 전극에 대한 전기화학적 전극특성을 확인하였다. 제조된 활성탄의 물성을 SEM, EDS, XRD, TG, 비표면적, 기공크기 분포 등의 분석을 통해 조사하였다. 또한, 슈퍼커패시터의 전극에 대한 순환전류 측정과 교류 임피던스 측정 실험을 통해 전기화학적 특성을 확인하였다. 수열합성법을 통하여 직경 5∼7 ㎛인 구형의 탄소 입자를 얻었으며 활성화 온도 800℃로 제조된 활성탄은 비표면적이 1631.8 m2/g, 기공크기 분포가 0.9∼2.1 nm에 집중적으로 분포하였으며, 마이크로 기공체적이 0.6154 cm3/g 임을 알 수 있었다. 이 활성탄을 사용하여 제작된 전극은 6M KOH 전해액에서 비용량 236 F/g(@5 mV/s), 194 F/g(@100 mV/s), 137 F/g(@500 mV/s)의 우수한 특성을 나타내었다. 충방전 싸이클 수명시험 결과, 200 mV/s의 주사속도에서 100,000회 충방전 시험 후에도 초기용량 대비 91.2%의 용량을 유지함을 확인하였다. From the cooked-rice as a raw material, activated carbons throughout a hydrothermal synthesis and vacuum soak of KOH for chemical activation were obtained. Activated carbon electrodes for electric double layer supercapacitors were prepared and electrochemical characteristics were examined. Including the specific surface area by BET method and pore size distribution by NLDFT method, physical properties of activated carbons were investigated by means of SEM, EDS, XRD, and TG analyses. Cycle voltammetry and AC-impedance measurements were conducted to confirm the electrochemical characteristics for the electrodes. From hydrothermal synthesis, 5∼7 ㎛ diameters of spherical carbons were obtained. After the activation at 800℃, it was notable for the activated carbon to be the specific surface 1631.8 m2/g, pore size distribution in 0.9∼2.1 nm, and micro-pore volume 0.6154 cm3/g. As electrochemical characteristics of the activated carbon electrode in 6M KOH electrolyte, it was confirmed that the specific capacitances of 236, 194, and 137 F/g at the scan rate of 5, 100, and 500 mV/s respectively were exhibited and 91.2% of initial capacitance after 100,000 cycles at 200 mV/s was maintained.