• 제목/요약/키워드: Transition metal oxide

검색결과 171건 처리시간 0.022초

암모니아로부터 수소 제조를 위한 다양한 촉매 활성 테스트에 관한 연구 (A Study on Activity Testing of Various Catalysts for Hydrogen Production from Ammonia)

  • 이재혁;신경하;강진실;신현희;박세연;최유진;송완규;안호근
    • 한국수소및신에너지학회논문집
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    • 제34권6호
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    • pp.587-593
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    • 2023
  • This research project focused on the production of hydrogen through ammonia decomposition reactions while investigating how the reactivity of this process varies when employing different catalysts. Several metal oxide supports (Al2O3, La2O3, CeO2) were utilized as catalysts, with active metals from both the transition metal group (Co, Ni, Fe, Cr, Cu) and the noble metal group (Ru, Rh, Pd, Pt) impregnated onto these supports. Furthermore, the study examined how the reactivity evolves with changes in reaction temperature when employing the prepared catalysts. Additionally, the research delved into the distinctive activation energies associated with each of the catalysts. In this research, In the noble metal catalyst system, the order of high activity for ammonia decomposition reaction to produce hydrogen is Ru > Rh > Pt ≈ Pd. In the transition metal catalyst system, the order of high activity is Co > Ni > Fe > Cr > Cu.

전이금속을 함침한 γ-Al2O3 촉매의 Toluene 분해 (Decomposition of Toluene by γ-Al2O3 Catalysts Impregnated with Transition Metal)

  • 최성우;이철규
    • 한국환경과학회지
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    • 제22권8호
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    • pp.945-951
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    • 2013
  • Alumina-supported catalysts containing different transition metals such as Cu, Cr, Mn, Zn, Co, W were investigated for their activity in the selective oxidation of toluene. Catalytic oxidation of toluene was investigated at atmospheric pressure in a fixed bed flow reactor system over transition metals with $Al_2O_3$ catalyst. The result showed the order of catalytic activities for the complete oxidation of toluene was Mn > Cu> Cr> Co> W> Zn for 5wt.% transition $metals/Al_2O_3$. $Mn/Al_2O_3$ catalysts containing different amount of Mn were characterized by X-ray diffraction spectroscopy for decision of loading amount of metal to alumina. 5 wt.%$Mn/Al_2O_3$ catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of $289^{\circ}C$.

Resistive Switching Properties of N and F co-doped ZnO

  • Kim, Minjae;Kang, Kyung-Mun;Wang, Yue;Chabungbam, Akendra Singh;Kim, Dong-eun;Kim, Hyung Nam;Park, Hyung-Ho
    • 마이크로전자및패키징학회지
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    • 제29권2호
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    • pp.53-58
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    • 2022
  • One of the most promising emerging technologies for the next generation of nonvolatile memory devices based on resistive switching (RS) is the resistive random-access memory mechanism. To date, RS effects have been found in many transition metal oxides. However, no clear evidence has been reported that ZnO-based resistive transition mechanisms could be associated with strong correlation effects. Here, we investigated N, F-co-doped ZnO (NFZO), which shows bipolar RS. Conducting micro spectroscopic studies on exposed surfaces helps tracking the behavioral change in systematic electronic structural changes during low and high resistance condition of the material. The significant difference in electronic conductivity was observed to attribute to the field-induced oxygen vacancy that causes the metal-insulator Mott transition on the surface. In this study, we showed the strong correlation effects that can be explored and incorporated in the field of multifunctional oxide electrons devices.

강상관계 소재를 이용한 수소 센서 및 수소 뉴로모픽 소자 (Hydrogen Sensor and Neuromorphic Applications Using Correlated Materials)

  • 오차돌;손준우
    • 세라미스트
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    • 제22권1호
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    • pp.17-26
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    • 2019
  • The metal-to-insulator transition (MIT) with external stimuli is one of the main issues in correlated oxides. The physical properties are extremely sensitive to band filling, because the MIT is attributed to the strong correlation between electrons in narrow d-band. Since hydrogen is the smallest and lightest element, it is not only likely to doped reversibly in oxides, but also acts as a dopant to provide electrons. The correlated oxides showing MIT are structurally expanded after hydrogenation, and their electrical properties are drastically changed. Researches on this phenomenon have been actively carried out to date. They are of great scientific importance, and the use of this material is very diverse, including the development of next-generation hydrogen sensor, or hydrogen-based neuromorphic devices.

MIT characteristic of VO2 thin film deposited by ALD using vanadium oxytriisopropoxide precursor and H2O reactant

  • Shin, Changhee;Lee, Namgue;Choi, Hyeongsu;Park, Hyunwoo;Jung, Chanwon;Song, Seokhwi;Yuk, Hyunwoo;Kim, Youngjoon;Kim, Jong-Woo;Kim, Keunsik;Choi, Youngtae;Seo, Hyungtak;Jeon, Hyeongtag
    • Journal of Ceramic Processing Research
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    • 제20권5호
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    • pp.484-489
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    • 2019
  • VO2 is an attractive candidate as a transition metal oxide switching material as a selection device for reduction of sneak-path current. We demonstrate deposition of nanoscale VO2 thin films via thermal atomic layer deposition (ALD) with H2O reactant. Using this method, we demonstrate VO2 thin films with high-quality characteristics, including crystallinity, reproducibility using X-ray diffraction, and X-ray photoelectron spectroscopy measurement. We also present a method that can increase uniformity and thin film quality by splitting the pulse cycle into two using scanning electron microscope measurement. We demonstrate an ON / OFF ratio of about 40, which is caused by metal insulator transition (MIT) of VO2 thin film. ALD-deposited VO2 films with high film uniformity can be applied to next-generation nonvolatile memory devices with high density due to their metal-insulator transition characteristic with high current density, fast switching speed, and high ON / OFF ratio.

습식 분무 열분해 방법으로 제조한 코발트 도핑된 티타늄 산화막의 표면 및 광학적 특성 (Surface and Optical Characteristics of Cobalt Dopped-titanium Oxide Film Fabricated by Water Spray Pyrolysis Technique)

  • 송호준;박영준
    • 한국재료학회지
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    • 제15권3호
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    • pp.209-215
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    • 2005
  • Titanium dioxide films $(TiO_2)$ doped cobalt transition metal were prepared on titanium metal by water spray pyrolysis technique. Micro-morphology, crystalline structure, chemical composition and binding state of sample groups were evaluated using field emission scanning microscope(FE-SEM), X-ray diffractometer(XRD), Raman spectrometer, X-ray photoelectron spectrometer(XPS). $TiO_2$ films of rutile structure were predominately formed on all sample groups and $Ti_2O_3$ oxide was coexisted on the surface of cobalt doped-sample groups. The optical absorption peaks measured by using UV-VIS-NIR spectrophotometer were observed at specific wavelength region in sample groups doped cobalt ion. This result could be analyzed by introducing crystal field theory.

다관능 아크릴레이트계 자외선 경화형 코팅액의 제조 및 이를 이용한 PET 필름 도막의 광학 특성 연구 (Preparation of UV curable coating solution from multi functional acrylates and characterization of optical properties of coated layer on PET film)

  • 이수;진석환
    • 한국응용과학기술학회지
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    • 제26권4호
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    • pp.467-472
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    • 2009
  • Ultraviolet curable coating solution was prepared with poly(ethylene glycol) acrylate oligomer and various mono and multi-functional acrylate monomers. The optical properties of UV cured coating layer on PET film with acrylate coating solution containing metal oxides, such as fumed silica and alumina, were also investigated to reduce light reflection on films. Poly(ethylene glycol) diacrylate which has 575 of average molecular weight was used as oligomer acrylate, and pentaerythritol triacrylate and dipentaerythritolpenta-/hexa acrylate were used as multi-functional acrylate monomers. Also, butyl acrylate was used to improve the adhesion as well as to reduce glass transition temperature to give a better flexability. 1-hydroxy cyclohexyl phenyl ketone was used as photoinitiator. We found out the metal oxides in acrylate coating solution showed a homogeneous dispersion from energy dispersive spectroscopy data. Transmittance and light reflection of coated PET film was measured with UV/vis spectrometer and gloss meter, respectively. When 1.00 g of both metal oxides was added into coating solution, the transmittance and the glossiness were reduced from 90% to 30% and from 190 GU to 35 GU, respectively. However, adding up to 1.00 g of the metal oxide into coating solution did not affect on the hardness of coating layer and adhesion between coated layer and PET film. Conclusively, we can control transmittance and light reflection of coated film by adjusting the amounts of metal oxide in coating solution.

Cobalt Oxide Nanorods Prepared by a Template-Free Method for Lithium Battery Application

  • Kim, Seong-Jun;Kim, Eun-Ji;Liu, Meilin;Shin, Heon-Cheol
    • Journal of Electrochemical Science and Technology
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    • 제7권3호
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    • pp.206-213
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    • 2016
  • Transition metal oxide-based electrodes for lithium ion batteries have recently attracted much attention because of their high theoretical capacity. Here we report the electrochemical behavior of cobalt oxide nanorods as anodes, prepared by a template-free, one-step electrochemical deposition of cobalt nanorods, followed by an oxidation process. The as-deposited cobalt has a slightly convex columnar structure, and controlled thermal oxidation produces cobalt oxides of different Co/O ratios, while the original shape is largely preserved. As an anode in a rechargeable lithium battery, the Co/O ratio has a strong effect on initial capacity and cycling stability. In particular, the one-dimensional Co@CoxOy core shell structure obtained from a mild heat-treatment results in superior cycling stability.

In-situ Raman Spectroscopic Study of Nickel-base Alloys in Nuclear Power Plants and Its Implications to SCC

  • Kim, Ji Hyun;Bahn, Chi Bum;Hwang, Il Soon
    • Corrosion Science and Technology
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    • 제3권5호
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    • pp.198-208
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    • 2004
  • Although there has been no general agreement on the mechanism of primary water stress corrosion cracking (PWSCC) as one of major degradation modes of Ni-base alloys in pressurized water reactors (PWR's), common postulation derived from previous studies is that the damage to the alloy substrate can be related to mass transport characteristics and/or repair properties of overlaid oxide film. Recently, it was shown that the oxide film structure and PWSCC initiation time as well as crack growth rate were systematically varied as a function of dissolved hydrogen concentration in high temperature water, supporting the postulation. In order to understand how the oxide film composition can vary with water chemistry, this study was conducted to characterize oxide films on Alloy 600 by an in-situ Raman spectroscopy. Based on both experimental and thermodynamic prediction results, Ni/NiO thermodynamic equilibrium condition was defined as a function of electrochemical potential and temperature. The results agree well with Attanasio et al.'s data by contact electrical resistance measurements. The anomalously high PWSCC growth rate consistently observed in the vicinity of Ni/NiO equilibrium is then attributed to weak thermodynamic stability of NiO. Redox-induced phase transition between Ni metal and NiO may undermine the integrity of NiO and enhance presumably the percolation of oxidizing environment through the oxide film, especially along grain boundaries. The redox-induced grain boundary oxide degradation mechanism has been postulated and will be tested by using the in-situ Raman facility.

Tailoring Molecular Precursors for Multicomponent Oxides

  • Hubert-Pfalzgraf, Liliane G.
    • The Korean Journal of Ceramics
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    • 제6권4호
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    • pp.370-379
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    • 2000
  • Simple ways to build up mixed-metal molecules which can act as potential single-source precursors to multimetallic oxides are reviewed. Emphasis is given to Lewis acid-base reactions between metal alkoxides M(OR)/sub n/, and between metal alkoxides and more accessible oxide precursors, carboxylates M(O₂CR)/sub n/ and β-diketonates M(β-dik)/sub n/. Characterization of the precursors is achieved in the solid state (single crystal X-ray diffraction, FT-IR) and by multinuclear NMR in solution. The reactions proceed toward the formation of aggregates in which the different metals display their usual coordinations numbers, often six for transition metals, as shown. Strategies for fixing the stoichiometry between the metals are developed. The reactivity of the MM species (dissociation, effects of chemical modifiers, of other metallic species, hydrolytic or non-hydrolytic condensation, etc.) will be indicated. Transformations into oxides are illustrated on precursors for titanates or niobates.

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