| A Study on the Development of Mullite Fibers Using the Sol-Gel Process |
93 |
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| Authors:
Goo-Dae Kim; Dong-A Lee; Hyun-Im Lee; Seok-Jin Yoon; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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 | To produce transparent composite polymeric mullite sol, polymeric alumina sol was synthesized from aluminum secbutoxide mixed with iso-propanol, acetylacetone, water and hydrochloric acid. polymeric silica sol derived from tetraethyl orthosilicate (teos), iso-propanol, water and hydrochloric acid was then added: magnesium nitrate (mg(no3)2*6h20) and boric acid (h3bo3) were also used as additives to the composite sol. short and long fiber spinners were developed at the laboratory scale. by use of these ... |
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| Superconducting Bi(PB)-Sr-Ca-Cu-O Fibres Drawn from Melt-Quenched Glasses |
93 |
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| Authors:
J. H. Park; T. S. Hahn; S. S. Choi; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| Recently the glass-to-ceramic process for the fabrication of Bi(Pb)- Sr-Ca-Cu-O superconductor has been widely investigated. The experimental results have shown that this process has the advantages of obtaining highly dense and grain-oriented superconductors as well as the ease of fabrication of any shape. In addition, superconducting fibers could be fabricated by heat-treatment of glass fibers drawn from melt-quenched glass preforms. It is well known that fiber drawability is sensitive to ... |
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| Effect of Nb2O5 Alloying on Thermal Expansion Anisotropy of 2 mol% Y2O3- Stabilized Tetragonal ZrO2 |
93 |
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| Authors:
Dae-Joon Kim; Paul F. Becher; Camden R. Hubbard; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| Tetragonal ZrO2 (t-ZrO2) solid solutions were prepared with additions of 2 mol% Y2O3 plus up to 0.45 mol% Nb2O5. The thermal expansion coefficients in both the a- and c-axis lattice directions increased with Nb2O5 alloying and the thermal expansion in the c-axis direction was greater than that in the a- axis direction over the entire composition range. This anisotropic thermal expansion behavior was related to the 4-fold coordination of Nb(5+) ... |
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| Age Hardening Behavior of a Hypo-Stoichiometric Fe3Al Intermetallic Compound |
92 |
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| Authors:
Jong-Woo Park; In-Ge Moon; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| Kinetics of age hardening and microstructural changes were studied to clarify the principal factor responsible for the hardening behavior of a hypo- stoichiometric Fe3Al alloy initially DO3 ordered at 400 C; the alloy revealed two-stage hardening behavior in a lower temperature region of two-phase fields and one-stage hardening curves in an upper region; the first stage hardening occurred very rapidly and was independent of aging temperature; an incubation time was ... |
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| Development and Properties of Tungsten-Bearing Stainless Maraging Steels |
91 |
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| Authors:
Jin I. Suk; Chang N. Park; Soon H. Hong; Young G. Kim; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| The effects of the tungsten content and heat treatment on the mechanical properties and microstructures of Fe-11Cr-10Ni-xW-0.4Al-0.3Ti stainless steels (where the composition is in approximate weight per cent) have been investigated; the increase in tungsten content from 2 to 5 wt.% increases the yield strength accompanied by decreases in elongation and Charpy impact energy; the hardness increases with increasing aging temperature up to 500 C because of enhanced precipitation of ... |
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| Transformation Characteristics of Hydrogen-Induced Amorphization of the Ordered Zr3Al Phase |
91 |
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| Authors:
Jai-Young Lee; Woo-Cheal Choi; Yong-Gyoo Kim; Jeong- Yong Lee; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| An amorphization at below 550 K is caused by the absorption of hydrogen in to the ordered Zr3Al intermetallic compound; hydrogenated Zr3Al decomposes into the equilibrium phases (ZrH2 + Zr2Al) with increasing temperature; the amorphous samples are observed by various techniques to investigate the transformation mechanism; ZrH2 + Zr2Al is crystallized from amorphous matrix during differential scanning and it is seen that the evolution of hydrogen from amorphous phase begins ... |
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| Quasicrystalline and Related Crystalline Phases in a Rapidly Solidified 2024-2Li Aluminium Alloy |
91 |
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| Authors:
D. H. Kim; K. Chattopadhyay; B. Cantor; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| TEM was used to study the formation and decomposition of quasicrystalline and crystalline phases in as-rapidly solidified and annealed AA 2024 containing 2% Li; microstructure of as-melt spun samples consisted of alpha-Al cells, containing small coherent delta prime-precipitates, and particles or continuous network of an icosahedral phase at the cell boundaries; intercellular particles of the icosahedral phase progressively coarsened and assumed more faceted shape after annealing at 300C; particles of ... |
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| Fibre-in-Tube Casting for Single-Mode Fluoride Glass Fibre |
91 |
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| Authors:
W. J. Cho; M. W. Kim; J. C. Jo; T. S. Hahn; S. S. Choi; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| Fluoride glasses are generating a great deal of interest in optical fiber laser hosts. Those with excellent transparency in the mid-infrared range have stimulated the development of fluoride glass fiber lasers which operate in the 1-3 microns wavelength regions. In this letter we present a fiber-in-tube preform fabrication method for single mode fluorozirconate glass fiber by which the ratios of the clad to core diameter could be controlled easily. ... |
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| Phase Stability and Physical Properties of Cubic and Tetragonal ZrO2 in the System ZrO2-Y2O3-Ta2O5 |
91 |
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| Authors:
Dae-Joon Kim; Tseng-Ying Tien; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| The cubic (c-ZrO2) and tetragonal zirconia (t-ZrO2) phase stability regions in the system ZrO2-Y2O3-Ta2O5 were delineated. The c-ZrO2 solid solutions are formed with the fluorite structure. The t-ZrO2 solid solutions having a c/a axial ratio (tetragonality) smaller than 1.0203 display high fracture toughness (5 to 14 MPa.square root of m, and their instability/ transformability to monoclinic zirconia (m-ZrO2) increases with increasing tetragonality. On the other hand, the ZrO2 solid solutions ... |
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| Heating Effect in Plasma-Enhanced Chemical Vapour Deposition of Silicon Nitride |
91 |
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| Authors:
I. K. Han; Y. J. Lee; J. H. Jo; J. I. Lee; K. N. Kang; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| Superplasticity of Ultra-High Carbon Steels Containing 3-5% Aluminum |
90 |
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| Authors:
Dong-Wha Kum; Hyung Kang; Tong-Hoon Kim; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| To study the effect of Al on superplasticity of ultra-high carbon steel(UHCS), 3-5% Al was added to the UHCS, and superplastic behavior was measured at 700-800 C. To produce the fine and superplastic microstructure, an isothermal rolling at 700 C was used and the grain size of ferrite was less than about 2 microns in diameter after the process. Significant improvement in superplasticity was observed: the strain-rate sensitivity was high ... |
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| Reduced Water Degradation of YBaCuO by Si3N4 Protective Coating |
90 |
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| Authors:
T. S. Hahn; S. S. Yom; Y. T. Kim; J. H. Park; S. S. Choi; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| It is reported that high T(sub c) superconductors of YBaCuO easily react with both water and carbon dioxide in atmosphere. Future practical device applications using YBaCuO require proper protective coating techniques. Recently, surface protection of YBaCuO with silver covering layers, polyfluorocarbon thin films, and dielectric films were reported. In this paper, we show that Si3N4 protective coating onto YBaCuO by plasma-enhanced chemical vapor deposition (CVD) significantly improved water degradation of ... |
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| The Rheology of Silica Sols During the Gelation Process |
90 |
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| Authors:
Jae C. Ro; In J. Ching; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| Pressureless Sintering of Alumina-Titanium Carbide Composites |
89 |
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| Authors:
Young-Wook Kim; June-Gunn Lee; KOREA INST OF SCIENCE AND TECHNOLOGY SEOUL*
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| The densification of Al2O3-TiC composites is detrimentally affected by chemical reactions between Al2O3 and TiC. These reactions must be suppressed in order to promote sintering. In this study, the specific reactions occurring in Al2O3-TiC composites were modeled, using thermodynamic calculations, and verified by experiments. The reaction between Al2O3 and TiC was suppressed by the use of specially prepared embedding powders allowing pressureless sintering to closed porosity. The Al2O3-TiC composites were ... |
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