Autor: Lim, H.-K. - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Combined Effect of Zr and Si on Isothermal Oxidation of Ti
Autorzy:: Ha, S.-H.
Kim, B.-H.
Yoon, Y.-O.
Lim, H.-K.
Kim, S. K.
Tematy:: Ti
Zr
Si
silicide
oxidation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/353260.pdf Link otwiera się w nowym oknie
Opis:: In this study, the combined effect of Zr and Si on isothermal oxidation of Ti for 25 and 50h at 820°C, which is the temperature related to exhaust valves operation, was investigated. Si addition into Ti-5mass%Zr alloy led to a distribution of silicide Ti₅Si₃ phase formed by a eutectic reaction. The Ti sample containing only Zr showed more retarded oxidation rate than Ti-6Al-4V, the most prevalent Ti alloy, at the same condition. However, while a simultaneous addition of Zr and Si resulted in greater increase of oxidation resistance. The oxide layer formed after the addition of Zr and Si comprised TiO₂, ZrO₂, and SiO₂.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Incorporation of Resonators Into Plenum Window
Autorzy:: Lee, H. M.
Haris, A.
Lim, K. M.
Xie, J.
Lee, H. P.
Tematy:: plenum window
Helmholtz resonators
noise pollution
ventilation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/176744.pdf Link otwiera się w nowym oknie
Opis:: A plenum window with incorporation of Helmholtz resonators in between two glass panes was tested in a reverberation room. The effects of jagged flap on reducing strength of diffracted sound was also investigated in the present studies where white, traffic and construction noises were examined Turing each set of experiment. When the noise source was located at the central line of the plenum window, the plenum window with Helmholtz resonators was able to mitigate 8.5 dBA, 8.9 dBA and 8.2 dBA of white, traffic and construction noises, respectively, compared with the case of without window. These amounts of noises that attenuated by the plenum window were slightly higher than the case where noise source was diverged 30° away from the plenum window. The effects of jagged flaps on the acoustical performance of the plenum window were negligible. The Helmholtz resonators had the best performance in the frequency region between 900 Hz to 1300 Hz where in this frequency range, the plenum window with Helmholtz resonators was able to attenuate additional 1.7 dBA, 1.9 dBA and 1.6 dBA of white, traffic and construction noises, respectively, compared with the case of without resonators.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Evaluation of Surface Characteristics and Physical Properties on Biodegradable Magnesium-Calcium Alloys by Anodic Oxidation
Autorzy:: Kim, J.
Lee, J.
Yang, H.
Park, S.
Lim, H.
Oh, G.
Yun, K.
Tematy:: 87.85.jj
87.85.jc; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1191716.pdf Link otwiera się w nowym oknie
Opis:: The purpose of this study was to determine the effect of calcium (Ca) on the surface characteristics and physical properties of magnesium-calcium alloys after anodization. A novel binary alloy Mg-xCa (in which x=0.5, 1, or 5 wt.%) was cast by combining magnesium (99.9%) and calcium (99.9%) in an argon gas (99.99%) atmosphere. A magnesium alloy rod having a diameter of 15 mm was cut into discs, each 2 mm thick. The specimens were subjected to anodic oxidation at 120 V for 15 minutes at room temperature in an electrolyte solution consisting of calcium gluconate, sodium hexametaphosphate, and sodium hydroxide. Surface and cross-sectional morphological changes were observed using scanning electron microscopy, and the microstructures and phases were detected by means of X-ray diffraction. Hardness and surface roughness were assessed by means of a Vickers hardness tester and a surface roughness meter, respectively. The results show that the physical properties of these magnesium-calcium alloys have been improved, because it was possible to control the dissolution rate according to the amount of calcium added.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Biological Evaluation of Anodized Biodegradable Magnesium-Calcium Alloys
Autorzy:: Kim, J.
Lee, J.
Lee, K.
Park, S.
Lim, H.
Park, C.
Bae, J.
Yun, K.
Tematy:: 87.85.jj
87.85.J-; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398763.pdf Link otwiera się w nowym oknie
Opis:: The objective of this study was to evaluate the biocompatibility of studied binary magnesium-calcium (Mg-Ca) alloys for biodegradable intraosseous implants. Mg is necessary for health and is a non-toxic biodegradable material that decomposes naturally in the body. Nevertheless, Mg has been implicated in problems including diminished physical properties and corrosion resistance when degradation is too rapid prior to bone healing. This study has explored the effect of Ca on the corrosion resistance and biological evaluation after anodizing treatment with different contents of Ca alloy. Binary Mg-0.5Ca, Mg-1Ca and Mg-5Ca alloys were prepared by the casting method under an argon atmosphere and cut into disc-shaped pieces. Pure Mg alloy was used as the control. Anodic oxidation was performed for 15 minutes at a voltage of 120 V using an electrolyte solution containing Ca gluconate, sodium hexametaphosphate, and sodium hydroxide at room temperature. Corrosion resistance was analyzed using a corrosion tester. After a hydrogen evolution test, the surface pattern and phase changes were observed on a scanning electron microscop (SEM) and energy dispersive spectroscop (EDS). Microscopic evaluation of the adhesion and cell biological functions of Mg was conducted by observing the response of human fetal osteoblastic 1.19 cells with regard to changes in surface film properties, depending on the amount of Ca. Our results support the view that in Mg-xCa alloys (x=0.5, 1, 5 wt.%) treated using anodic oxidation, the increasing Ca content controls the rate of decomposition and improves corrosion resistance.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Demarcation energy properties of regenerated fiber Bragg grating sensors in few-mode fibers
Autorzy:: Mohd Nazal, N. A.
Lai, M.-H.
Lim, K.-S.
Gunawardena, D. S.
Chong, W.-Y.
Yang, H.-Z.
Ahmad, H.
Tematy:: regenerated fiber Bragg grating
thermal regeneration
thermal decay
few-mode fibers; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/174756.pdf Link otwiera się w nowym oknie
Opis:: In this work, thermal regeneration of fiber Bragg gratings inscribed in single-mode fibers, two-mode step index fibers and four-mode step index fibers is performed, where the single-mode fibers are used as the reference in the analysis. Specifically, we investigate the behavior of the thermal decay, recovery and eventually the permanent erasure of the gratings in the temperature range from 25 to 1300°C. In the domain of demarcation energy, the thermal responses of the gratings can be normalized and they share similar characteristic curves despite the different temperature ramping rates used in the annealing treatment. It is found that the demarcation energy at the regeneration point and the attempt-to-escape frequency for each grating can be associated with the confinement factors of the fibers. The finding in this work has provided a new insight in the manufacture of regenerated fiber Bragg grating sensors by using few-mode fibers for multiparameter sensing in high temperature environments.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Fabrication of High-Strength Gray Cast Iron Using Permanent Magnet Scrap
Autorzy:: Park, S.-Y.
Kim, J. H.
Seo, S. J.
On, J. S.
Lim, K. M.
Tematy:: gray cast iron
rare earth element
Nd-Fe-B magnet scrap
graphite formation
microstructure; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/352204.pdf Link otwiera się w nowym oknie
Opis:: In this study, we have developed the manufacturing technology for high strength gray cast irons by using the spent permanent magnet scraps. The cast specimen inoculated by using a spent magnet scraps showed the excellent tensile strength up to 306MPa. This tensile strength value is 50MPa higher than that of the specimen cast without inoculation, and is similar to that of the specimen inoculated by using the expensive misch-metal. These superior mechanical properties are attributed to complex sulfides created during solidification that promote the formation and growth of Type-A graphite. It is therefore concluded that spent magnets scrap can provide an efficient and cost-effective inoculation agent for the fabrication of high-performance gray cast iron.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Reaction Kinetics and Morphological Study of TiNb2O7 Synthesized by Solid-State Reaction
Autorzy:: Choi, S. H.
Ali, B.
Choi, K. S.
Hyun, S. K.
Sim, J. J.
Choi, W. J.
Joo, W.
Lim, J. H.
Lee, T. H.
Kim, T. S.
Park, K. T.
Tematy:: solid state reaction
kinetic analysis
quantitative phase analysis
TiNb2O7 synthesis; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/355326.pdf Link otwiera się w nowym oknie
Opis:: Although TiNb₂O₇ is regarded as a material with high application potential in lithium-ion batteries (LIBs) and solid-oxide fuel cells (SOFCs), it has been difficult to find suitable cost-effective conditions for synthesizing it on a commercial scale. In this study, TiNb₂O₇ compounds were synthesized by a solid state synthesis process. For stoichiometrically precise synthesis of the TiNb₂O₇ phase, the starting materials, TiO₂ and Nb₂O₅ were taken in a 1:1 molar ratio. Activation energy and reaction kinetics of the system were investigated at various synthesis temperatures (800,1000,1200, and 1400°C) and for various holding durations (1,5,10, and 20 h). Furthermore, change in the product morphology and particle size distribution were also evaluated as a function of synthesis temperature and duration. Additionally, quantitative phase analysis was conducted using the Rietveld refinement method. It was found that increases in the synthesis temperature and holding time lead to increase in the mean particle size from 1 to 4.5 μm. The reaction rate constant for the synthesis reaction was also calculated.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Microstructure and Mechanical Properties of Hot-deformed AlMg4 Alloys with the Variations of Mn, Fe, and Si Contents
Autorzy:: Lee, Da B.
Kim, Bong H.
Choi, Kweon H.
Yang, Seung Y.
Kim, Nam S.
Ha, Seong H.
Yoon, Young O.
Lim, Hyun K.
Kim, Shae
Hyun, Soong K..
Tematy:: Al-Mg alloy
intermetallic compounds
homogenization
hot-rolling
microstructure; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/351603.pdf Link otwiera się w nowym oknie
Opis:: This paper aims to investigate the microstructural evolution and mechanical properties of hot-deformed AlMg4 alloys with Mn, Fe, and Si as the main impurities. For this purpose, solidification behavior and microstructural evolution during hot-rolling and heat-treatment processes are investigated by using theoretical calculations and experimental characterization. The crystallization and morphological transformation of intermetallic Al₃ Fe, Al₆ Mn, and Mg₂ Si phases are revealed and discussed in terms of the variation in chemical composition. Following a homogenization heat-treatment, the effect of heat treatment on the intermetallic compounds is also investigated after hot-rolling. It was revealed that the Mg₂ Si phase can be broken into small particles and spherodized more easily than the Al₃ Fe intermetallic phase during the hot-rolling process. For the Mn containing alloys, both yield and ultimate tensile strength of the hot-rolled alloys increased from 270 to 296 MPa while elongation decreased from 17 to 13%, which can be attributed to Mn-containing intermetallic as well as dispersoid.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Fabrication of a Spherical Titanium Powder by Combined Combustion Synthesis and DC Plasma Treatment
Autorzy:: Choi, S. H.
Ali, B.
Hyun, S. K.
Sim, J. J.
Choi, W. J.
Joo, W.
Lim, J. H.
Lee, Y. J.
Kim, T. S.
Park, K. T.
Tematy:: combustion synthesis
DC plasma treatment
titanium powder
3D printing process
combustion parameters; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/356067.pdf Link otwiera się w nowym oknie
Opis:: Combustion synthesis is capable of producing many types of refractory and ceramic materials, as well as metals, with a relatively lower cost and shorter time frame than other solid state synthetic techniques. TiO₂ with Mg as reductant were dry mixed and hand compacted into a 60 mm diameter mold and then combusted under an Ar atmosphere. Depending on the reaction parameters (Mg concentration 2 ≤ α ≤ 4), the thermocouples registered temperatures between 1160°C and 1710°C . 3 mol of Mg gave the optimum results with combustion temperature (T_c) and combustion velocity (U_c) values of 1372°C and 0.26 cm/s respectively. Furthermore, this ratio also had the lowest oxygen concentration in this study (0.8 wt%). After combustion, DC plasma treatment was carried out to spheroidize the Ti powder for use in 3D printing. The characterization of the final product was performed using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and N/O analysis.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Warm Tensile Deformation Behavior and Constitutive Equation of Supersaturated Solid-Solutionized Al-9Mg Extruded Alloy
Autorzy:: Yang, Seung Y.
Kim, Bong H.
Lee, Da B.
Choi, Kweon H.
Kim, Nam S.
Ha, Seong H.
Yoon, Young O.
Lim, Hyun K.
Kim, Shae
Kim, Young J.
Tematy:: aluminum alloy
Al-9Mg alloy
tensile test
constitutive equation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/2048882.pdf Link otwiera się w nowym oknie
Opis:: In this paper, as a purpose to apply the supersaturated solid-solutionized Al-9Mg alloy to the structural sheet parts of automotive, tensile tests were conducted under the various conditions and a constitutive equation was derived from the tensile test results. Al-9Mg alloy was produced using a special Mg master alloy containing Al2Ca during the casting process and extruded into the sheet. In order to study the deformation behavior of Al-9Mg alloy in warm temperature forming environments, tensile tests were conducted under the temperature of 373 K-573 K and the strain rate of 0.001/s~0.1/s. in addition, by using the raw data obtained from tensile tests, a constitutive equation of the Al-9Mg alloy was derived for predicting the optimized condition of the hot stamping process. Al-9Mg alloy showed uncommon deformation behavior at the 373 K and 473 K temperature conditions. The calculated curves from the constitutive equation well-matched with the measured curves from the experiments particularly under the low temperature and high strain rate conditions.
Dostawca treści:: Biblioteka Nauki

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