• Nuclear Engineering and Technology
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• v.38 no.3
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• pp.201-210
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• 2006

This article presents a brief overview of an important area of neutron scattering: the general principles and techniques of elastic, quasielastic and inelastic scattering from a system composed predominately of incoherent scatterers. The methodology is then applied to the study of water, specifically when it is confined in nanometer-scale environments. The confined water exhibits uniquely anomalous properties in the supercooled state. It also nourishes biological functions, and supports essential chemical reactions in living systems. We focus on recent investigations of water encapsulated in nanoporous silica and carbon nanotubes, hydrated water in proteins and water or hydroxyl species incorporated in nanostructured minerals. Through these scientific examples, we demonstrate the advantages derived from the high sensitivity of incoherent neutron spectroscopy to hydrogen atom motions and hydrogen-bond dynamics, aided by rigorous data interpretation method using molecular dynamics simulations or theoretical modelling. This enables us to probe the inter-/intramolecular vibrations and relaxation/diffusion processes of water molecules in a complex environment.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.108-108
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• 2011

Organometallic complexes containing unpaired spins, such as metalloporphyrin or metallophthalocyanine, have extensively studied with increasing interests of their promising model systems in spintronic applications. Additionally, the use of these complexes as an acceptor molecule in chemical sensors has recently received great attentions. In this presentation, we have investigated adsorption of nitric oxide (NO) molecules at Co-porphyrin molecules on Au(111) surfaces with scanning tunneling microscopy and spectroscopy at low temperature. At the location of Co atom in Co-porphyrin molecules, we could observe a Kondo resonance state near Fermi energy in density of states (DOS) before exposing NO molecules and the Kondo resonance state was disappeared after NO exposing because the electronic spin structure of Co-porphyrin were modified by forming a cobalt-NO bonding. Furthermore, we could locally control the chemical reaction of NO dissociations from NO-CoTPP by electron injections via STM probe. After dissociation of NO molecules, the Kondo resonance state was recovered in density of state. With a help of density functional theory (DFT) calculations, we could understand that the modified electronic structures for NO-Co-porphyrin could be occurred by metal-ligand hybridization and the dissociation mechanisms of NO can be explained in terms of the resonant tunneling process via molecular orbitals.

• Journal of Surface Science and Engineering
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• v.36 no.2
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• pp.148-154
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• 2003

Short ($\tau$=40 $mutextrm{s}$) and high-voltage ($U_{sub}$=2~8 kV) negative substrate bias pulses were used to assist pulsed magnetron sputtering DLC films deposition. Space- and time-resolved probe measurements of the plasma characteristics have been performed. It was shown that in case of high-voltage substrate bias spatial non-uniformity of the magnetron discharge plasma density greatly affected DLC deposition process. By Raman spectroscopy it was found that maximum percentage of s $p^3$-bonded carbon atoms (40 ~ 50%) in the coating was attained at energy $E_{c}$ ~700 eV per deposited carbon atom. Despite rather low diamond-like phase content these coatings are characterized by good adhesion due to ion mixing promoted by high acceleration voltage. Short duration of the bias pulses is also important to prevent electric breakdowns of insulating DLC film during its growth.wth.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.327-334
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• 2004

Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics with or without a metal plate for a 10-㎾-class direct-current arcjet Heat fluxes into the plate from the plasma were also evaluated with a Nickel slug and thermocouple arrangement. Ammonia and mixtures of nitrogen and hydrogen were used. The NH$_3$ and $N_2$+3H$_2$ plasmas in the nozzle and in the downstream plume without a plate were in thermodynamical nonequilibrium states. As a result, the H-atom electronic excitation temperature and the $N_2$ molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. Each temperature was kept in a small range in the plume without a plate except for the NH rotational temperature for NH$_3$ gas. On the other hand, as approaching the plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one because the plasma flow tended to stagnate in front of the plate. The electron temperature had a small radial variation near the plate. Both the electron number density and the heat flux decreased radially outward, and an increase in H$_2$ mole fraction raised them at a constant radial position. In cases with NH$_3$ and $N_2$+3H$_2$ a large number of NH radical with a radially wide distribution was considered to cause a large amount of energy loss, i.e., frozen flow loss, for arcjet thrusters.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.135-135
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• 2007

AgInSbTe물질은 compact disc rewritable(CD-RW)와 rewritable digital versatile disc (DVD+RW)과 같은 상변화 기록매체에 널리 쓰여지고 있다. 본 논문에서는 기존 AgInSbTe조성에 Te가 증가되었을때 변화하는 상변화 특성에 대한 연구를 수행하기 위하여 ($Ag_{3.4}In_{3.7}Sb_{76.4}Te_{16.5})x(Te)1-x$의 조성 (x=1,0.9,0.8,0.7)의 벌크 및 박막시료를 제작하였고 열증착방식을 이용하여 200nm 두께의 박막을 형성하였다. 각 박막은 질소분위기에서 100-300도 범위에 1 시간동안 열처리 하였고 XRD와 UV-ViS-NIR Spectrophotometer룰 통해 각 조성의 구조 및 광학적 특성 분석을 살시하였다. 또한 as-deposited 박막에 대하여 4-point probe를 사용하여 면저항을 측정하였고 AFM (atom force microscopy)을 통해 표면분석을 실시하였다.

• Applied Microscopy
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• v.48 no.4
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• pp.117-121
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• 2018

The multiple length scale analysis of previously designed Fe-Mn-Al-C based low-density model alloys reveals the difference in ordered ${\kappa}-carbide$, $(Fe,Mn)_3AlC_x$, between Fe-25Mn-16Al-5.2C (at%) alloy and Fe-3Mn-10Al-1.2C (at%) alloy. For the former alloy composition consisting of fully austenite grains, ${\kappa}-carbide$ showed majorly cuboidal and minorly pancake morphology and its chemical composition was not changed through aging for 24 h and 168 h at $600^{\circ}C$. Meanwhile, for the isothermally annealed ferritic alloy system for 1 hr at 500 and $600^{\circ}C$, the dramatic change in the chemical composition of needle-shape ${\kappa}-carbide$, $(Fe,Mn)_3(Fe,Al)C_x$, was found. Here we address that the compositional fluctuations in the vicinity of the carbides are significantly controlled by abutting phase, either austenite or ferrite. Namely, the cooperative ordering of carbon and Al is an important factor contributing to carbide formation in the high-Mn and high-Al alloyed austenitic steel, while the carbon and Mn for the low-Mn and high Al alloyed ferritic steel.

• Nuclear Engineering and Technology
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• v.30 no.2
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• pp.99-111
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• 1998

Chemical composition of the insoluble residue in a simulated spent PWR fuel(SIMRJEL) were studied. SIMFUELS were prepared by adding calculated amount of FP(fission product) elements with a burnup of 3.6% FIMA(fission per initial metal atom) to uranium in nitrate solution, evaporating the mixed solution to dryness, calcining at 90$0^{\circ}C$ in a stream of 4% H$_2$ + 96% He, and heating the pellet at 140$0^{\circ}C$ under high and low oxygen potentials. Insoluble residue was obtained from the dissolution of the SIMFUEL with HNO$_3$(1 : 1). The chemical composition of the SIMFUELs and the insoluble residues was determined by EPMA(electron probe microanalysis), XPS(X-ray photoelectron spectroscopy) and by XRD (X-ray diffraction) measurements. All of the insoluble residues suspended and precipitated were composed mainly of Mo, Ru with a small amount of Zr, Rh, Pd and Cd. The amount of insoluble residue(<1 wt.%) and a Mo/Ru ratio decreased with increasing oxygen potential. Formation of the zirconium molybdate precipitate, ZrMo$_2$O$_{7}$(OH)$_2$($H_2O$)$_2$, was observed in the residues. The possible role of Mo on the phase formation was discussed in regard to oxygen potential.l.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2071-2078
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• 2024

The precipitation of solutes is a major cause of irradiation hardening and embrittlement limiting the service life of reactor pressure vessel (RPV) steels. Impurities play a significant role in the formation of precipitation in RPV materials. In this study, the effects of carbon on cluster formation and irradiation hardening were investigated in an RPV alloy Fe-1.35Mn-0.75Ni using C and Fe ions irradiation at 290 ℃. Nanoindentation results showed that C ion irradiation led to less hardening below 1.0 dpa, with hardening continuing to increase gradually at higher doses, while it was saturated under Fe ion irradiation. Atom probe tomography revealed a broad size distribution of Ni-Mn clusters under Fe ion irradiation, contrasting a narrower size distribution of small Ni-Mn clusters under C ion irradiation. Further analysis indicated the influence of carbon on the cluster formation, with solute-precipitated defects dominating under C ion irradiation but interstitial clusters dominating under Fe ion irradiation. Simulations suggested that carbon significantly affected solute nucleation, with defect clusters displaying smaller size and higher density as carbon concentration increased. The higher hardening at doses above 1.0 dpa was attributed to a substantial increase in the number density of defect clusters when carbon was present in the matrix.

• International Journal of Oral Biology
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• v.35 no.4
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• pp.159-167
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• 2010

To provide a basis for studying the pharmacological actions of tetracaine HCl, we analyzed the membrane activities of this local anesthetic. The n-(9-anthroyloxy) stearic and palmitic acid (n-AS) probes (n = 2, 6, 9, 12 and 16) have been used previously to examine fluorescence polarization gradients. These probes can report the environment at a graded series of depths from the surface to the center of the membrane bilayer structure. In a dosedependent manner, tetracaine HCl decreased the anisotropies of 6-AS, 9-AS, 12-AS and 16-AP in the hydrocarbon interior of synaptosomal plasma membrane vesicles isolated from bovine cerebral cortex (SPMV), and liposomes derived from total lipids (SPMVTL) and phospholipids (SPMVPL) extracted from the SPMV. However, this compound increased the anisotropy of 2-AS at the membrane interface. The magnitude of the membrane rotational mobility reflects the carbon atom numbers of the phospholipids comprising SPMV, SPMVTL and SPMVPL and was in the order of the 16, 12, 9, 6, and 2 positions of the aliphatic chains. The sensitivity of the effects of tetracaine HCl on the rotational mobility of the hydrocarbon interior or surface region was dependent on the carbon atom numbers in the descending order 16-AP, 12-AS, 9-AS, 6-AS and 2-AS and on whether neuronal or model membranes were involved in the descending order SPMV, SPMVPL and SPMVTL.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.305-311
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• 2006

We propose a 7-level atom model, which takes into account two-photon coherence effects in saturation absorption spectroscopy. Using this model we explained spectral change with laser intensity and some of crossover resonance lines, which cannot be explained with Nakayama theory. The 7-level model consists of two upper levels and five lower levels, which account for $\pi-\pi$ polarization of both pump and probe beams in Zeeman sub levels. We compared our 7-level model with 4-level Nakayama theory for 5S$_{1/2}$ - 5P$_{1/2}$ transition line in $^{85}$Rb atoms. The results of the 7-level model calculation agree well the saturation absorption spectra data according to laser intensities.