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1.
Ho-Yong Lee Yeong-Kyeun Pack Byoung-Ki Lee Suk-Joong L. Kang 《Journal of the American Ceramic Society》1995,78(8):2149-2152
When sintered 85Al2 O3 –15Fe2 O3 (in wt%) specimens consisting of corundum grains and spinel particles were annealed at temperature where only a corundum phase was stable, phase transformation of spinel into metastable FeAIO3 and subsequently complete dissolution of the metastable phase occurred together with the migration of grain boundaries at the surface of the specimens. Since the grain boundary migration was induced by grain boundary diffusion of Fe2 O3 from the transforming and dissolving particles, the boundary migration by temperature decrease corresponds to a discontinuous dissolution of the spinel particles and a chemically induced grain boundary migration by temperature change. Inside the specimens, however, the transformation—dissolution and the grain boundary migration were suppressed because of unavailable accommodation of the volume expansion due to the transformation. 相似文献
2.
When BaTiO3 ceramics were sintered at relatively low temperatures (≤1250°C), the grains with reentrant edges caused by a (111) double twin grew exclusively. As a result, a microstructure with a bimodal grain-size distribution composed of platelike large grains and fine matrix grains was obtained. In contrast, at the usual sintering temperature between 1250° and 1350°C, grains containing a (111) double twin did not exhibit any growth advantage. In this case, a coarse and uniform microstructure was obtained. When this coarse-grained specimen was further heat-treated at 1365°C, the grains possessing a double twin were observed to grow exclusively again. The results were explained in terms of a coarsening process controlled by two-dimensional nucleation. 相似文献
3.
Ui-Jin Chung Jong-Keuk Park Nong-Moon Hwang Ho-Yong Lee Doh-Yeon Kim 《Journal of the American Ceramic Society》2002,85(12):3076-3080
Pb(Mg1/3 Nb2/3 )O3 -35 mol% PbTiO3 (PMN-35PT) specimens with a 5 mol% excess PbO were prepared by excessive heat treatment at 1150°C to induce abnormal grain growth. Through electron backscatter diffraction analysis and the observation of a three-dimensional morphology, the abnormally grown PMN-35PT grains were found to be twinned crystals with penetration characteristics. The morphology of the PMN-35PT twinned crystal was crystallographically analyzed. The abnormal grain growth of PMN-35PT is suggested to be due to preferential growth at the reentrant angles formed by twins. 相似文献
4.
In Yang Syehee Ahn In-gyu Choi Ho-Yong Kim Seichang Oh 《Journal of Industrial and Engineering Chemistry》2009,15(3):398-402
With an abrupt increase of petrochemical prices and the critical environmental issue related to the volatile organic compounds emitted from the adhesive resins, the development of environmentally friendly new adhesive systems is common issue. In our study, the okara, which is a residue from the production of tofu, was introduced to develop competitive bio-based adhesives for the production of fancy-veneered floor boards. Okara (AC and AK) was hydrolyzed with 1% sulfuric acid solution and 1% sodium hydroxide solution. Phenol–resorcinol–formaldehyde (PRF) prepolymer was prepared as a crosslinker of AC and AK. Adhesive resins were formulated with AC, AK and PRF prepolymer. The adhesive resins were used to fabricate floor boards composed of oak veneers onto high-density fiberboard. The experimental variables were three weight ratio of AC/AK to PRF (45/45/10, 40/40/20 and 35/35/30), three assembly time (0, 10 and 20 min), and two press time (90 and 120 s), respectively. The fancy-veneered high-density fiberboards were prepared and subject to testing of the dry tensile strength, glueline failure by wetting and formaldehyde emission. Dry tensile strengths of the boards exceeded the requirement of KS standard. The formaldehyde emissions were satisfied with the limitation specified in KS standard. Based on these results, okara has a potential to be used as a renewable raw material of environmentally friendly adhesive resin systems for production of floor boards, but further researches, such as biological hydrolysis of okara and various formulations of PRF prepolymer, are required to improve the adhesive strength and to reduce formaldehyde emission of okara-based adhesive resins. 相似文献
5.
Yong-Hun Oh Sang-Gug Lee Quan Le Ho-Yong Kang Tae-Whan Yoo 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2005,52(11):780-783
This brief presents a CMOS burst-mode optical transmitter suitable for use in 1.25-Gb/s Ethernet passive optical network applications. Based on feedback from the monitoring photodiode, in order to control consecutive burst data the proposed transmitter in this brief uses a reset mechanism, which allows fast responses from the beginning of a high-speed input burst. The chip is fabricated in mixed-mode 0.18-/spl mu/m CMOS technology and measurements are implemented in a chip-on-board configuration using a pig-tailed type Fabry-Perot laser. Under burst-mode operation of 1.25-Gb/s pseudorandom binary sequences, measurements show about 1-dBm averaged transmitted optical power with an over 12-dB extinction ratio over a wide temperature range. 相似文献
6.
Baek Keon-Hee Jeong Nak-Tak Hong Hee-Rok Choi Su-bin Lee Eun-Seong Kim Hyung-Min Kwon Ji-Woon Song Seok-Yong Jang Hong-Seok Lee Ho-Yong Suh Myung-Won 《Journal of Mechanical Science and Technology》2019,33(4):1689-1702
Journal of Mechanical Science and Technology - Threaded fasteners are widely used in mechanical structures primarily owing to their easy disassembly for maintenance and low cost. However, the... 相似文献
7.
Neural Computing and Applications - Internet-of-Things (IoT) devices are becoming prevalent, and some of them, such as sensors, generate continuous time-series data, i.e., streaming data. These IoT... 相似文献
8.
Ho-Yong Lee Young-Woo Rhee Suk-Joong L. Kang 《Journal of the American Ceramic Society》1996,79(6):1659-1663
When sintered 95Al2 O3 -5Fe2 O3 (wt%) specimens constituting corundum grains and iron aluminate spinel precipitates were annealed under high oxygen partial pressure (Po 2 ) where only a corundum phase is stable, fast dissolution of particulate spinel precipitates occurred, together with the migration of corundum grain boundaries. Behind the migrating boundaries, a corundum solid solution enriched with Fe2 O3 formed. Discontinuous dissolution (DD) of particulate spinel precipitates thus occurred by Po 2 increase. In contrast, when 95Al2 O3 -5Fe2 O3 specimens constituting only corundum grains were annealed under low Po 2 where both corundum and spinel phases are stable, grain boundaries migrated without spinel precipitation, leaving behind a corundum phase depleted of Fe2 O3 , similar to chemically induced grain-boundary migration (CIGM) observed during solute depletion. The volatilization of Fe2 O3 appeared to cause the boundary migration without precipitation. The observed CIGM and DD would suggest various possibilities of microstructure control in other oxide systems through oxygen partial pressure change. 相似文献
9.
John Gerard Fisher Min-Soo Kim Ho-Yong Lee Suk-Joong L. Kang 《Journal of the American Ceramic Society》2004,87(5):937-942
Abnormal grain growth in Pb(Mg1/3 Nb2/3 )O3 –35 mol% PbTiO3 (PMN-35PT) ceramics doped with Li2 O and PbO has been investigated. Replacing the PbO dopant with up to 2 mol% Li2 O caused an increase in the number of abnormal grains. For the composition containing 2 mol% Li2 O and 6 mol% PbO, the amount of abnormal grain growth decreased with increasing sintering temperature. Single crystals of ∼6 mm × 6 mm × 2 mm thickness were grown from the 2 mol% Li2 O, 6 mol% PbO-containing composition via the templated grain growth method. Grain growth behavior with temperature is explained in terms of the effect of Li2 O on interface-reaction-controlled grain growth and the critical driving force. 相似文献
10.
Shujun Zhang Sung-Min Lee Dong-Ho Kim Ho-Yong Lee Thomas R. Shrout 《Journal of the American Ceramic Society》2007,90(12):3859-3862
Pb(Mg1/3 Nb2/3 )O3 –PbZrO3 –PbTiO3 (PMN–PZT) ferroelectric single crystals near morphotropic phase boundary compositions were fabricated by solid-state crystal growth. The Curie temperatures ( T C ) of the grown PMN–PZT crystals were found to be on the order of 210°C, with ferroelectric phase transition temperatures ( T R – T ) in the range of 96°–165°C. The electromechanical coupling factors k 33 and k 32 were found to be >90% and >−87%, respectively. The coercive field E C for all the compositions was on the order of 5 kV/cm, double the value of pure Pb(Mg1/3 Nb2/3 )O3 –PbTiO3 (PMNT) crystals. The temperature dependence of the piezoelectric and electromechanical properties and dc bias effect on the dielectric behavior were investigated. The temperature usage range under dc bias was found to be improved when compared with pure PMNT crystals with similar piezoelectric properties. 相似文献