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排序方式: 共有42条查询结果,搜索用时 15 毫秒
1.
The tetragonal (t) to monoclinic (m) transformation behaviour and its relationship to microstructural evolution were investigated by means of dilatometry and transmission electron microscopy for ZrO2–9.7 mol% MgO during cyclic heating and cooling between room temperature and 1490 K. In the as-sintered specimens, fine oblate ellipsoidal t-phase precipitates, 20–50 nm in diameter and 100–200 nm long, were distributed in the cubic (c)-phase matrix. They were below a critical size for transformation and exhibited no transformation in the first three cycles. In the fourth and further cycles, transformation occurred in two distinct stages. A low-temperature stage appeared at 850–1000 K on heating and at 400–700 K on cooling, while a high-temperature stage appeared at 1350–1400 K on heating and at 1000–1200 K on cooling. With the increasing number of cycles, at first the size of low-temperature stages increased and then decreased above ten cycles accompanying the development of the high-temperature stage. During cyclic heating and cooling, coarsening of ellipsoidal precipitates and decomposition of c- and t-phases occurred. As a result of the decomposition, MgO particles and a new m-phase containing a very low concentration of MgO were produced. The coarsened ellipsoidal t-phase precipitates were responsible for the low-temperature stage. The new m- or t-phase containing very low MgO produced by the decomposition was responsible for the high-temperature stage. 相似文献
2.
MASATO MACHIDA KOICHI EGUCHI HIROMICHI ARAI 《Journal of the American Ceramic Society》1988,71(12):1142-1147
The formation process of barium hexaaluminate (BaO 6Al2 O3 ) from BaCO3 /γ-Al2 O3 powders or hydrolyzed alkoxides was studied by analytical electron microscopy. Barium hexaaluminate is produced by a two-step solid-state reaction from BaCO3 and Al2 O3 via formation of BaO·Al2 O3 . Marked grain growth and inclusion of nonequilibrium phase were inevitable in this powder mixture process. However, in an alkoxide-derived precursor, homogeneous mixing of components is attained and hence the formation of BaO·6Al2 O3 proceeds readily. Powders obtained by this latter route consisted of fine planar particles with a uniform size and retained a large surface area (20.2 m2 /g) even after heating at 1300°C. Electron diffraction results implied that suppression of crystal growth along the c axis is the reason for the large surface area of BaO·6Al2 O3 . 相似文献
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HARUHIKO SATO SHIN SAITO SHOTA MIZUNO KOICHI AKAHANE HIRONAGA UCHIDA 《Electrical Engineering in Japan》2017,198(3):27-33
The spin‐dependent scattering of conduction electron in metallic magnetic multilayers was investigated to reveal the optical properties which corresponded to the magnetization state. From the measurement of magnetorefractive effect in antiferro‐magnetically exchange coupled Co/Ru multilayers, it was found that (1) the transmittance varied around 1% at wavelength of 1550 nm during the parallel/antiparallel spin alignment changes, (2) as a result of number of repetition and Co thickness for the multilayers, transmittance difference between the parallel and antiparallel spin alignment states had trade‐off relationship with the magnitude of transmittance, and (3) asymmetric Co/Ru/Co stacking structure brought different interlayer exchange coupling fields in each layer, which resulted in magnetic field sensitive transmittance. 相似文献
5.
CHU Man-sheng YANG Xue-feng SHEN Feng-man YAGI jun-ichiro NOGAMI Hiroshi 《钢铁研究学报(英文版)》2006,13(6):8-15
To date ,blast furnace operators have a relative-ly good understanding of internal mechanisms ,andno longer treat blast furnace as a“black box”. Forthe blast furnace , however , one of the most com-plex metallurgical units inthe field of chemical engi-neering,the complexity keeps proliferating with theadoption of newtechnologies ,such as high rate in-jection of pulverized coal ,effective use of carbona-ceous andferrous materials ,and so on.If merely bydirect instrumentation and empirical kno… 相似文献
6.
TOSHIO HIRAI KOICHI NIIHARA TAKASHI GOTO 《Journal of the American Ceramic Society》1980,63(7-8):419-424
A thermo gravimetric study of the oxidation behavior of chemically vapor-deposited amorphous and crystalline Si3 N4 (CVD Si3 N4 ) was made in dry oxygen (0.1 MPa) at 1550° to 1650°C. The specimens were prepared under various deposition conditions using a mixture of SiCl4 , NH3 , and H2 gases. The crystalline CVD Si3 N4 indicated a parabolic oxidation kinetics over the whole temperature range, whereas the amorphous CVD Si3 N4 changed from a parabolic to a linear law with increased temperature. The oxidation mechanism is discussed in terms of the activation energy for the oxidation and the microstructure of the formed oxide films. 相似文献
7.
This paper presents an. application, of functional analysis to the minimal?time control problem where two or more energy constrained systems of the same order must be taken to an initially unknown common point in state space. Two different types of problems with different forms of the energy constraint are described in detail. The development depends on the fact that the reachable region of a system with an energy constraint on the input vector is an ellipsoid. 相似文献
8.
The effect of milling on the intrinsic coercive force of Ba ferrite powders has been ascribed to (1) thermal fluctuations caused by superparamagnetic fine particles and (2) lattice defects introduced by milling. To test these interpretations, the Moessbauer absorption spectra and angular variation of coercive force for ball-milled powders were determined. With increasing milling time, the Moessbauer absorption spectrum becomes ambiguous, and the absorption lines are broadened; the quadrupole-split center line corresponding to superparamagnetic BaFe12 O19 cannot be detected. The angular variation of coercive force shows that milling considerably lowers either the nucleation field of the reverse domain or the effective anisotropy field or both. It is concluded that lattice defects, rather than superparamagnetic fine particles introduced by milling, greatly affect the intrinsic coercive force of Ba ferrite powders. 相似文献
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10.
This paper presents the functional analysis and iterative procedure for the minimum-time control problem subject to energy and magnitude constraints on the control functions. The necessary change of Swiger's method is described to solve a multi-boundary problem and numerical results are presented for a linear control system. 相似文献