• 한국지하수토양환경학회지:지하수토양환경
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• 제27권1호
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• pp.17-24
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• 2022

This work examined the effect of mixing transition metal-based additives [FeCl₃, Fe-containing paper mill sludge (PMS), CoCl₂·H₂O, ZrO₂, and α-Fe₂O₃] on the thermochemical conversion of coffee waste (CW) in carbon dioxide-assisted pyrolysis process. Compared to the generation amounts of syngas (0.7 mole% H₂ & 3.0 mole% CO) at 700℃ from single pyrolysis of CW, co-pyrolysis in the presence of Fe- or Zr-based additives resulted in the enhanced production of syngas, with the measured concentrations of H₂ and CO ranging 1.1-3.4 mole% and 4.6-13.2 mole% at the same temperature, respectively. In addition, α-Fe₂O₃ biochar possessed the adsorption capacity of As(V) (19.3 mg g^-1) comparable to that of ZrO₂-biochar (21.2 mg g^-1). In conclusion, solid-type Fe-based additive can be highly considered as an efficient catalyst to simultaneously produce syngas (H₂ & CO) as fuel energy resource and metal-biochar as sorbent.

• 한국표면공학회지
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• 제50권3호
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• pp.141-146
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• 2017

We investigated configuration of metallic and insulating domains in $VO_2$ thin films, while spanning metal-insulator phase transition. Kelvin probe force microscopy, of which spatial resolution is less than 100 nm, enables us to measure local work function (WF) at the sample surface. The WF of $VO_2$ thin films decreased (increased) as increasing (decreasing) the sample temperature, during the phase transition. The higher and lower WF regions corresponded to the insulating and metallic domains, respectively. The metallic fraction, estimated from the WF maps, well explained the temperature-dependent resistivity based on the percolation model. The WF mapping also showed us how the structural defects affected the phase transition behaviors.

• 한국전기전자재료학회논문지
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• 제21권10호
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• pp.943-949
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• 2008

We report on the development of transition edge sensors for x-ray detection. The sensor technology was based on the fabrication of a superconducting film on a thin membrane. A bilayer of a superconductor, Ti, and a noble metal, Au, was e-beam evaporated on a micromachined SiNx. Another Au layer was evaporated on the two side edges of the bilayer in order not to be affected by structural imperfections at the boundaries. With the method described in the present report, the superconducting transition temperature of the device was consistently achieved to near 80 mK with a sharp transition. The energy spectrum ueasured with the device provided 37 eV FWHM for 5.9 x-rays. We also discuss the design and fabrication considerations as well as the performance of the device in detail.

• Journal of Welding and Joining
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• 제4권3호
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• pp.58-71
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• 1986

Mechanical and corrosion property of duplex stainless steel weldments made by the GTAW and SMAW process were studied. Fracture toughness, general and local corrosion resistance of GTAW and SMAW weldments were evaluated in terms of Charpy V notch impact test, anodic polarization diagram, pitting corrosion rate, respectively. SMA weld metal showed much lower impact toughness and higher ductile-brittle transition temperature than GTA weld metal. Fractographic and EDX analysis on fracture surface of SMA weld metal demonstrated the existence of (Si, Ti), oxide in large amounts. Potentiodynamic anodic polarization diagram of GMA weld metal showed much lower passive current density than SMA weld metal in 4% $H_2/SO_4$ solution. And pitting corrosion rate test showed the same tendency. Relating the microstructure, chemistry and property, it can be concluded that GTA weld metal gives better toughness due to lower oxygen content, i.e. lower inclusion content, and better corrosion resistance due to higher Pitting Index(PI) than SMA weld metal.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.36-37
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• 2002

귀금속(noble metal)이나 전이금속(transition metal) 밑층(substrate) 위에 높여진 금속 웃층(metal overlayer)의 자성(magnetism) 연구는 오랫동안 많은 관심의 대상이 되었고, 특히 전이금속을 웃층으로 사용한 경우에 대해서 많은 연구가 있었다 [1]. 전이금속 중에서 바나듐(vanadium; V)은 덩치(bulk) 상태에서는 자성을 가지지 않지만, 귀금속인 Ag(001) 혹은Cu(001) 위에 놓여지면 자성을 가지게 된다는 보고가 있었다 [2]. (중략)

• 분석과학
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• 제11권4호
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• pp.248-253
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• 1998

수용액에서 poly-dibenzo-18-crown-6를 이용한 알칼리, 알칼리토금속이온 및 전이금속이온들의 흡착 및 분리특성을 조사하였다. 알칼리금속이온들과 알칼리토금속이온들의 흡착정도와 분포비의 순위는 각각 Li(I)

• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.130-137
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• 1991

The following new cryptand 221 complexes of lanthanides(Ⅲ) and dioxouranium(Ⅵ) nitrate have been synthesized: $(Ln(C_{16}H_{32}N_2O_5)(H_2O)_2(NO_3)_3\ and \((UO_2)_2(C_{16}H_{32}N_2O_5)(H_2O)_4(NO_3)_4$. These complexes have been identified by elemental analysis, moisture titration, conductivity measurements and various spectroscopic techniques. The proton and carbon-13 NMR as well as calorimetric measurements were used to study the interaction of cryptand 221 with La(Ⅲ), Pr(Ⅲ ), Ho(Ⅲ) and $UO_2(Ⅱ)$ ions in nonaqueous solvents. The bands of metal-oxygen atoms, metal-nitrogen atoms and O-U-O in the IR spectra shift upon complexation to lower frequencies, and the vibrational spectra ({\delta}NMN$) of metal-amide complexes in the crystalline state exhibit lattice vibrations below 300 $cm^{-1}$. The NMR spectra of the lanthanides(Ⅲ) and dioxouranium(Ⅵ) nitrate complexes in nonaqueous solvents are quite different, indicating that the ligand exists in different conformation, and also the $^1H$ and $^{13}C-NMR$ studies indicated that the nitrogen atom of the ring has greater affinity to metal ions than does the oxygen atom, and the planalities of the ring are lost by complexation with metal ions. Calorimetric measurements show that cryptand 221 forms more stable complexes with $La^{3+}$ and $Pr^{3+}$ ions than with $UO^{22+}$ ion, and $La^{3+}/Pr^{3+}$ and $UO^{22+}/Pr^{3+}$ selectivity depends on the solvents. These changes on the stabilities are dependent on the basicity of the ligand and the size of the metal ions. The absorption band (230-260 nm) of the complex which arises from the direct interaction of macrocyclic donor atoms with the metal ion is due to n-{\delta}*$ transition and also that (640-675 nm) of $UO^{22+}$-cryptand 221 complex, which arises from interaction between two-dioxouranium(Ⅵ) ions in being out of cavity of the ligand ring is due to d-d* transition.

• 한국환경과학회지
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• 제2권1호
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• pp.61-72
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• 1993

[에멀존]계에서 거대고리화합물에 의한 효과적인 수송현상을 두가지 관점에서 논의하였다. 하나는 중금속이온($Cd^{2+}$. $Pb^{2+}$ 및 $Hg^{2+}$)을 토루엔막으로 추출하는 경우.만일 금속=거대고리 화합물의 상로작용이 크다면 이 추출효과는 증가한다. 주번째 토루엔-경꼐면에서, 금속이온을 정량적으로 용리시키기 위해서는 금속이온 -Re-cieving Phase와 금속이온-거대고리화합물 사이의 상호작용에 대한 LogK의 사가 충분히 커야한다 첫번째는 거대고리 화합물의 주개원자, 치환제, 그리고 공동반경을 고려함으로써 해결된다. 이 연구의 결과들은 이론과 잘 일치하며, 시료용액의 종류는 에멀존망에 의한 금속이온의 수송현상에 영향을 준다.$SCN^-$,$1^-$ 및 $Br^-$이온과 같은 $A^-$이온을 사용할 경구, 수송순서는 $A^-$ 이온의 용매화순서의 크기에 일치하며, 용해도의 차이때문에 금속이온의 소송능력은 Receiving Phase의 화학종 농도의 크기에 영향을 받는다. 이 연구에서는 적당한 실험조건하에서 조절된 토루엔막을 사용함으로써 $Cd^{2+}$, $Pb^{2+}$, 및 $Hg^{2+}$ 이온의 혼합물로부터 각각의 단일이온들을 효과적으로 분리농축할 수 있었다. 그리고 $Cu^{2+}$,$Ni^{2+}$,$Zn^{2+}$,$Fe^{2+}$, 이온들은 중금속이온들을 분히 농축하는데 부분적으로 방해를 하였다. 그러나 알칼리 및 알칼토금속이온은 방해하지 않았다.

• 한국분말재료학회지
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• 제8권3호
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• pp.186-191
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• 2001

Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.

• Bulletin of the Korean Chemical Society
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• 제17권9호
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• pp.840-845
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• 1996

Rate constants have been measured spectrophotometrically for the reactions of p-and m-nitrophenyl 2-thiophenecarboxylate (5a and 5b, respectively) with alkali metal ethoxides (EtO-M+) in absolute ethanol at 25.0±0.1 ℃. The reactivity of EtO-M+ exhibits dependence on the size of alkali metal ions, i.e. the reactivity of EtO-M+ toward 5a decreases in the order EtO-K+ ≥ EtO-Na+ > EtO-Li+ > EtO-, while the one toward 5b does in the order EtO-Na+ ≥ EtO-K+ > EtO-Li+ > EtO-. This result indicates that ion paired EtO-M+ is more reactive than dissociated EtO-, and alkali metal ions form complexes with the substrate more strongly at the transition state than at the ground state. The catalytic effect shown by alkali metal ions appears to be less significant in the reaction of 5 than in the corresponding reaction of 4, indicating that complexation of alkali metal ions with 5 is not as strong as the one with 4.