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연소합성법을 이용한 방사성폐기물 고화체 Hollandite 분말 합성
정충환,정수지 한국재료학회 2023 한국재료학회지 Vol.33 No.10
A solution combustion process for the synthesis of hollandite (BaAl2Ti6O16) powders is described. SYNROC (synthetic rock) consists of four main titanate phases: perovskite, zirconolite, hollandite and rutile. Hollandite is one of the crystalline host matrices used for the disposal of high-level radioactive wastes because it immobilizes Sr and Lns elements by forming solid solutions. The solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between a nitrate and organic fuel, generates an exothermic reaction and that heat converts the precursors into their corresponding oxide products in air. The process has high energy efficiency, fast heating rates, short reaction times, and high compositional homogeneity. To confirm the combustion synthesis reaction, FT-IR analysis was conducted using glycine with a carboxyl group and an amine as fuel to observe its bonding with metal element in the nitrate. TG-DTA, X-ray diffraction analysis, SEM and EDS were performed to confirm the formed phases and morphology. Powders with an uncontrolled shape were obtained through a general oxide-route process, confirming hollandite powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using these methods.
연소합성법을 이용한 Ni 분말 합성에서 첨가 연료의 영향
정충환,신형철,이희균,홍계원,윤순길 한국분말야금학회 2001 한국분말재료학회지 (KPMI) Vol.8 No.1
Ni and NiO particles were made by a combustion synthesis process. The characteristics of synthesized powders were investigated with various kinds and amounts of fuels such as urea, citric acid and glycine. Ni phase particles without NiO phase were obtained through combustion synthesis process in air atmosphere with-out further calcinations process, when the content of glycine was 2.44 times of the stoichiometric ratio in the precursor solution. Primary particle sizes of synthesized Ni and NiO particles were about 20∼30 nm.
원자력 극한환경용 세라믹 열교환기 소재로서 반응소결 SiC 세라믹스 제작성
정충환,박지연,Jung, Choong-Hwan,Park, Ji-Yeon 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.1
Silicon carbide (SiC) is a candidate material for heat exchangers for VHTR (Very High Temperature Gas Cooled Reactor) due to its refractory nature and high thermal conductivity. This research has focused on demonstration of physical properties and mock-up fabrication for the future heat exchange applications. It was found that the SiC-based components can be applied for process heat exchanger (PHE) and intermediate heat exchanger (IHX), which are operated at $400{\sim}1000^{\circ}C$, based on our examination for the following aspects: optimum fabrication technologies (design, machining and bonding) for compact design, thermal conductivity, corrosion resistance in sulfuric acid environment at high temperature, and simulation results on heat transferring and thermal stress distribution of heat exchanger mock-up.
Humidity responsible chitosan Fabry-Perot resonator with photovoltaic cell
정충환,장재혁,노준석 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
We introduced a tunable Fabry-Pérot resonator in the form of a MIM (metal insulator metal) multilayer using a chitosan hydrogel insulator. Since a chitosan polymer responds to humidity, the optical properties and thickness of chitosan layers change according to RH (relative humidity). This property allows to change the resonant wavelength of the resonator. This chitosan color filter can work as a humidity sensor when combined with a PV (Photovoltaic) cell. PV cells can transduce the input light spectrum into an electrical signal to show the surrounding RH. This sensor is simple to manufacture and will have almost zero-power consumption owing to its structure, which is useful for sensing RH in situations with low external power supply.
Self-Sustaining Combustion Process를 이용한 NiO/YSZ 초미세 복합분말 제조
김선재,정충환,김경호,김영석,국일현 한국세라믹학회 1996 한국세라믹학회지 Vol.33 No.4
Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.