1,721,042 research outputs found
DESIGN OF AL3(TI,V,ZR) SYSTEMS THROUGH PHASE-STABILITY CALCULATIONS
No full textFor many purposes, a fundamental basis for understanding a material's microstructure, and hence properties, can be found in alloy thermodynamics. An understanding of multicomponent phase equilibria can give specific data on which one can base alloy design decisions regarding modifications of existing alloys. Such an approach has been adopted in the present study to design Al3(Ti,V,Zr) intermetallic compounds. The compositions of Al3(Ti,V,Zr) intermetallic compounds were optimized in terms of the melting point, competition between D0(22) and D0(23) phases, specific gravity and another property such as tetragonality ratio which seems to be partially related to the ductility. This approach is suggested as a guide for alloy development
INTERACTION PARAMETERS OF LEAD-BASE TERNARY-SYSTEMS
No full textA series of analytical expressions for predicting and representing ternary thermodynamic properties from binary data have been modified by ternary interaction parameters to describe the binary and ternary liquid systems containing lead. The experimental data of the Bi - Cd - Pb and Sn - Cd - Pb systems at 773K and the Ag - Sn - Pb system at 1073K are found to be excellently represented by the Redlich - Kister Muggianu model including the ternary interaction parameters
The Effect of the Geometrical Shape and Size of the Cross Section on the Spin-Polarized Transport and the Giant Magnetoresistance
No full textSITE FRACTION BEHAVIOR OF TRANSITION-ELEMENTS IN AL3(TI, V, ZR) PHASE
No full textCalculations of fcc aluminum matrix/Al3M equilibria for the Al-2at% (Ti, V, Zr) system have been made to predict the behavior of site fractions of transition elements in the D0(23) Al3(Ti, V, Zr) phase. It has been found out that Ti and Zr behave similarly, but V behave differently. Results show that the nominal Ti:V:Zr ratio formulated in the alloy composition is not carried through to the trialuminide phase
A thermodynamic study of phase equilibria in the Sn-Bi-Pb solder system
No full textAs a basis for the design and development of low-temperature solder alloys, the thermodynamic calculation of phase equilibria has been carried out on the binary Bi-Pb and ternary Sn-Bi-Pb systems over the entire composition range. The Gibbs free energy of individual phases has been approximated using the sub-regular solution model and thermodynamic parameters for each phase have been evaluated using available experimental information on phase boundaries and other related thermodynamic properties. The calculated phase diagrams and thermodynamic quantities of the Bi-Pb binary system show good agreement with the experimental data, and the liquidus projection and vertical sections in the Sn-Bi-Pb ternary system are well reproduced using assessed thermodynamic parameters derived in this work
Adsorption properties of hydrogen on (10,0) single-walled carbon nanotube through density functional theory
No full textThe density functional theory (DFT) has been used to simultaneously investigate physi-/chemi- sorption properties of hydrogen on the (10,0) single-walled carbon nanotube (SWCNT) walls. Physisorption of H-2 outside the CNT with a vertical orientation to the tube axis above the center of a hexagon surface is the most stable state of physisorption and its binding energy is very weak, -0.792 kcal/mol. In the chemisorp ion of two hydrogen atoms the most stable state is above two adjacent carbon atoms of a hexagon with a C-H bond length of 1.10 Angstrom and one C-H bond energy of -45.761 kcal/mol. Based on these results, we have also investigated the transition state and the reaction pathway from physisorption to chernisorption of hydrogen on the CNT. The energy barrier of the reaction from physisorption to chemisorption is about 78.837 kcal/mol and the reaction is not spontaneous at 0 K. Through the calculations of the Gibbs free energy change from physisorption to chemisorption with temperatures, we learned that it is not easy for the reaction to occur, which is a major obstacle for the practical use of the CNT as a hydrogen storage medium. (C) 2004 Elsevier Ltd. All rights reserved.This research was supported by a grant (code #:
03K1501-02210) from ‘Center for Nanostructured
Materials Technology’ under ‘21st Century Frontier
R&D Programs’ of Ministry of Science and Technology,
Korea
Ni층의 두께에 따른 Sn-3.5wt%Ag 솔더 합금의 계면 반응
No full textSn-3.5Ag (compositions are all in weight percent unless specified otherwise) solder alloys were soldered on the various substrates of bare Cu plate, Cu plate/Ni(2㎛), Cu plate/Ni(4㎛), and bare Ni plate. The morphology, composition and phase identification of the intermetallic compounds(IMC) at the interface were examined using Scanning Electron Microscopy(SEM) and X-ray diffraction(XRD). With varying the Ni layer thickness, various IMCs were formed, which were Cu_6Sn_5 on bare Cu plate, metastable NiSn₃ ＋ Ni₃Sn₄ on Cu plate/Ni(2㎛), Ni₃Sn₄ on Cu plate/Ni(4㎛) and Ni₃Sn ＋ Ni₃Sn₄ on bare Ni plate. And it was also observed that the wetting behavior was dependent on the Ni layer thickness. Such phenomena seemed to be caused by the type of IMCs differently formed on each substrate. As the soldering time was increased, the changes of the IMC morphology and the wetting behavior were observed on the various substrates. Therefore it was postulated that the Ni layer thickness should be considered as an important parameter in the interfacial reaction and the wetting behavior
Investigation of the thermodynamic stability in phase separating thin films using the cluster variation method
No full textThe thermodynamic stability of the thin film of the fcc-based phase separating binary system is investigated using the pair approximation of the cluster variation method (CVM), which includes short-range order correlation. The concentration profiles through the lattice plane parallel to the free surface are calculated as a function of temperature and film thickness for both(100) and (111) thin films. It is observed that the thermodynamic stability of the thin film depends on the film thickness and orientation, and the critical temperature beyond which the thin film cannot phase separate decreases as the film thickness decreases. The calculated Warren-Cowley short-range order parameter shows that the (100) and (111) thin films have different segregation behavior at the surface and the interphase boundary
Study on cap closure mechanism of single-walled carbon nanotubes by molecular dynamics
No full textThe closing mechanism of zigzag single-walled carbon nanotubes (SWCNT) was investigated using the molecular dynamics (MD) simulation at the experimental arcdischarge temperature of 3000 K. The (10,0) SWCNT with a diameter of 0.78 nm showed a dome-shape tip which evolved into a saddle-shaped cap that was caused by double heptagon-octagon pairs. In the case of (18,0) SWCNT with a diameter of 1.404 nm, a zipper-like closing mechanism was observed and the flat cap was obtained.This research was performed by the financial support of
‘Center for Nanostructured Materials Technology’ under
‘21st Century Frontier R&D Programs’ of the Ministry of
Science and Technology, Korea
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