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31.
Yucel Birol 《Materials Chemistry and Physics》2012,131(3):694-697
Response to T6 heat treatment of thixoextruded EN AW 2014 aluminium alloy was investigated in the present work. Extrusion of a 2014 slug heated to a liquid fraction of 15%, takes place in the semi-solid state until the liquid fraction in the final part of the slug is reduced via segregation to a level where semi-solid forming is no longer possible. Hence, the final part of the slug is extruded in the solid-state with a concurrent recrystallization process. This process has produced two distinctly different structures at the front and rear ends and an unexpected hardness profile in T6 temper along the length of the thixoextruded rod. The response to T6 heat treatment of the globular front has been age hardening as usual. The inferior age hardening potential with respect to the hot extruded counterpart is attributed to the grain boundary Al2Cu phase which has grown too coarse via liquid segregation to be readily solutionized at typical solutionizing temperatures. The rear end of the extrudate on the other hand, has softened upon T6 heat treatment owing to Cu depletion and a fully recrystallized structure. 相似文献
32.
33.
Hansu Birol Dragan Damjanovic Nava Setter 《Journal of the American Ceramic Society》2005,88(7):1754-1759
The processing and characterization of electrical properties of potassium niobate ceramic, KNbO3 (KN) have been studied. The difficulty of obtaining dense samples by conventional methods limits the knowledge on electrical properties of this material. In this paper, a complete route for processing of KN with density over 94% is described. Piezoelectric and dielectric data are presented. It is observed that the major problem concerning the density is related to incorrect stoichiometry, which is believed to be a more critical issue for this system compared with other electro-ceramics. 相似文献
34.
Yücel Birol 《Journal of Materials Science》1999,34(7):1653-1657
Aluminum has been a key material, particularly in the aerospace and automotive industries, owing to its low density, high specific strength, good corrosion resistance and recyclability. Aluminum based metal matrix composites have also become attractive candidates for various applications where monolithic aluminum alloys cannot meet the strict design requirements. Recently, particulate reinforced aluminum composites have attracted a great deal of attention. Among various techniques which have been employed in the synthesis of these composites, incorporation of the reinforcing phase particles directly into the melt is practical and economic; yet it is not trouble-free. In situ processing of particulate reinforced composites, on the other hand, yields superior microstructures and thus better properties. In the present work, such a method to manufacture TiCp-Al composites and the microstructures obtained thereof will be described. 相似文献
35.
π‐Conjugated Polymers Incorporating a Novel Planar Quinoid Building Block with Extended Delocalization and High Charge Carrier Mobility 下载免费PDF全文
Yunseul Kim Hansu Hwang Nam‐Koo Kim Kyoungtae Hwang Jong‐Jin Park Ga‐In Shin Dong‐Yu Kim 《Advanced materials (Deerfield Beach, Fla.)》2018,30(22)
Two novel conjugated polymers incorporating quinoidal thiophene are successfully synthesized. By combining 1D nuclear magnetic resonance (NMR) and 2D nuclear Overhauser effect spectroscopy analyses, the isomeric form of the major quinoid monomer is clearly identified as the asymmetric Z, E‐configuration. The quinoidal polymers are synthesized via Stille polymerization with thiophene or bithiophene. Both quinoidal polymers exhibit the low band gap of 1.45 eV and amphoteric redox behavior, indicating extended conjugation owing to the quinoidal backbone. These quinoidal polymers show ambipolar behaviors with high charge carrier mobilities when applied in organic field‐effect transistors. In addition, the radial alignment of polymer chains achieved by off‐center spin‐coating leads to further improvement of device performance, with poly(quinoidal thiophene–bithiophene) exhibiting a high hole mobility of 8.09 cm2 V?1 s?1, which is the highest value among the quinoidal polymers up to now. Microstructural alteration via thermal annealing or off‐center spin‐coating is found to beneficially affect charge transport. The enhancement of crystallinity with strong π–π interactions and the nanofibrillar structure arising from planar well‐delocalized quinoid units is considered to be responsible for the high charge carrier mobility. 相似文献
36.
Dongmyung Lee Kil‐Hoon Lee Dong Hoon Baek Hansu Pae Jung‐Pil Lim Young Min Choi Young Hun Lee Sun Ik Lee Jae‐Youl Lee Kyung‐Suc Nah Gyoocheol Hwang 《Journal of the Society for Information Display》2012,20(12):661-668
An intra‐panel interface addressing all of the high‐speed, low‐power, and low‐electromagnetic interference (EMI) requirements for tablet personal computer applications is presented. This work proposes an adaptive clock window scheme to achieve 1.4‐Gbps data‐rate. For EMI suppression, data scrambling, horizontal blank period pattern scrambling, and novel clock and data recovery circuit are introduced. Lastly, for power‐saving, the proposed interface dynamically biases source driver's output buffers and employs early charge sharing by controlling the configuration data. For verification, a WQXGA thin‐film transistor liquid crystal display system is implemented with the timing controller and source driver ICs that are fabricated using 65‐nm and 180‐nm complementary metal‐oxide semiconductor (CMOS) processes, respectively. The liquid crystal display system demonstrates maximum operation speed of 1.4 Gbps and suppression of EMI noise in LTE Band‐20 and GSM 850 bands. The proposed power‐saving schemes achieve 4.3% reduction in total power consumption by source driver IC, which reaches about 85% of power consumption by enhanced reduced‐voltage differential signaling interface circuit. 相似文献
37.
Jae-Hun Kim Hun-Joon Sohn Hansu Kim Goojin Jeong Wanuk Choi 《Journal of power sources》2007,170(2):456-459
A silicon monoxide (SiO)-carbon composite prepared by ball-milling and pyrolysis is evaluated as an anode material for lithium-ion batteries. Electrochemical tests demonstrated that the first charge and discharge capacities of the material are about 1050 and 800 mAh g−1, respectively, with a first-cycle efficiency of 76%. The disproportionation reaction of pure SiO into Si and SiO2 during pyrolysis is confirmed by means of XRD and 29Si MAS NMR. The cycle performance of this material shows an excellent reversible capacity retention of 710 mAh g−1 over 100 cycles without any potential or capacity restrictions. This improved cycle performance is attributed to the stable microstructure, enhanced electrical contact afforded by the pyrolyzed carbon, and the amorphous phase transformation of the active material during cycling. 相似文献
38.
Some of the basic concerns in the analysis of spouted-bed hydrodynamics are the flow pattern and the pressure field of the fluid and the spout shape. These are closely related with other design concerns such as spoutability, minimum spouting velocity and maximum spoutable bed depth. A computer program was developed in order to determine the flow pattern, pressure distribution in the fluid phase and the spout shape for a given operational condition. The computer program relies upon a two region model with a spout and annulus element for an axisymmetric bed. The paper presents some results for grain drying beds and compares them with the existing experimental data qualitatively. 相似文献
39.
A porous NiO/yttria-stabilized zirconia (YSZ) anode substrate for zirconia-based tubular solid oxide fuel cells (SOFCs) was prepared by the gelcasting. The effect of the impregnation of SDC in the substrate was studied. Electrochemical impedance spectroscopy and I–V and I–P curves of the cells were measured. Scanning electron microscopy (SEM) was used to observe the microstructures. The results indicate that the performance of the cell can be significantly improved by incorporating the nano-structured SDC particles in the substrate. The peak power density of the cell is increased by about 60% and the area specific resistance (ASR) decreased by about 47% at 700 °C, compared with the unmodified cells. It is explained as the extended triple-phase boundary (TPB) in the anode substrate and the excellent electrocatalytic property of SDC. It is also found that the nano-scale SDC particles change a lot during the reduction of the anode substrate, and the morphology of the resultant SDC particles on the metal Ni is significantly different from that on the YSZ. After the long-term operation, the morphology of the SDC particles on the Ni changes again, but that on the YSZ keeps almost unchanged. 相似文献
40.
The response to thermal exposure of ball-milled Al/K2TiF6/KBF4 powder blends was investigated to explore the potential of PM processing for the manufacture of Al–Ti–B alloys. K2TiF6 starts to be reduced by aluminium as early as 220 °C when ball-milled Al/K2TiF6/KBF4 powder blends are heated. The reaction of KBF4 with aluminium follows soon after. The Ti and B thus produced are both solutionized in aluminium before precipitating out as Al3Ti and TiB2. All these reactions take place below the melting point of aluminium. The ball-milled Al/K2TiF6/KBF4 powder blends heat treated at approximately 525 °C can be compacted to produce Al–Ti–B pellets with in situ formed Al3Ti and TiB2 particles. These pellets are shown to be adequate grain refiners for aluminium alloys. 相似文献