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111.
利用高温固相反应法和溶胶-凝胶法制备了La0.75Sr0.25Cr0.5Mn0.5O3钙钛矿复合氧化物粉体。采用XRD,TEM对粉体物相组成及颗粒形貌进行表征,并以制备的两种粉体作为敏感材料分别制成管状传感器,测试了其NO2气敏性能。结果表明:采用高温固相反应法和溶胶-凝胶法在不同焙烧温度下,均可制得单相La0.75Sr0.25Cr0.5Mn0.5O3粉体,采用溶胶-凝胶法在800℃焙烧2 h得到的粉体粒径约为20 nm;传感器输出电动势信号对NO2浓度之间呈良好的线性关系;溶胶-凝胶法制得粉体的气敏性能优于高温固相反应法制得粉体的气敏性能。 相似文献
112.
Yaw-Terng Chern Wen-Liang Wang 《Journal of polymer science. Part A, Polymer chemistry》1998,36(13):2185-2192
A series of new polyamides 3 were synthesized by direct polycondensation of the 1,6-bis[4-(4-aminophenoxy)phenyl]diamantane (1) with various dicarboxylic acids. The polyamides had inherent viscosities of 0.45–1.90 dL/g and number-average molecular weights (Mn) of 24,000–110,000. Dynamic mechanical analysis (DMA) reveals that polymers 3 have two relaxations on the temperature scale between −100 and 400°C. Their α relaxations occurred at high temperatures, ranging from 338 to 389°C. Moreover, these polymers remained quite stable at high temperatures and maintained good mechanical properties (G′ = ca. 108 Pa) up to temperatures close to the main transition markedly exceeding 350°C. Due to the bulky diamantane elements and the flexible ether segments, the polymers 3 were amorphous and soluble in a number of organic solvents such as pyridine, N-methyl-2-pyrrolidone (NMP), and N,N-dimethylacetamide (DMAc). The polyamides 3 have tensile strengths of 56.7–90.2 MPa, elongation to breakage values of 7.5–27.7%, and initial moduli of 1.8–2.1 GPa. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2185–2192, 1998 相似文献
113.
文章回顾了中子散射在高温超导铜氧化合物磁激发研究中的最新进展.自从铜氧化合物在20年前被发现以后,理解它们超导电性的微观来源一直是凝聚态物理中的核心课题.在传统超导体中,使得电子成对形成超导态的相互作用是以晶格振动(声子)为媒介的、而对于铜氧化合物的超导机理,人们通常认为磁激发可能起到根本的作用,因为超导电性是在可移动的“电子”或“空穴”掺杂到反铁磁母体化合物之后才发生的.文章总结了过去20年来利用非弹性中子散射研究磁激发的关键结果和现状,并指出了将来可能的研究方向. 相似文献
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118.
Peng Cheng Lei Fang Huan Yang XiYu Zhu Gang Mu HuiQian Luo ZhaoSheng Wang HaiHu Wen 《中国科学G辑(英文版)》2008,51(6):719-722
In this paper we report the fabrication and superconducting properties of GdO1−x
F
x
FeAs. It was found that when x is equal to 0.17, GdO0.83F0.17FeAs is a superconductor with the onset transition temperature T
con ≈ 36.6 K. Resistivity anomaly near 130 K was observed for all samples up to x = 0.17, and such a phenomenon is similar to that of LaO1−x
F
x
FeAs. Hall coefficient indicates that GdO1−x
F
x
FeAs is conducted by electron-like charge carriers.
Recommended by Prof. Nie Yuxin, Executive Editor of Science in China Series G-Physics, Mechanics & Astronomy
Supported by the National Natural Science Foundation of China (Grant Nos. 10221002/A0402 and 10774170/A0402), the National
Basic Research Program of China (973 Program) (Grant Nos. 2006CB601000, 2006CB921107 and 2006CB921802), and the Chinese Academy
of Sciences (ITSNEM) 相似文献
119.
Michael Plischke 《Journal of statistical physics》1974,11(2):159-167
The first ten terms of the high-temperature expansion of the susceptibility of the single-band Hubbard model in the strong correlation limit are obtained for arbitrary electron density. The series is analyzed by ratio methods and Padé approximants. A critical temperature is found for 0.2 0.8; for > 1 further terms in the series are required.Supported in part by the National Research Council of Canada. 相似文献
120.
A mean-field spin-density wave (SDW) analysis of pseudogap in the underdoped cuprates is proposed on the
basis of the t-tˊ-U Hubbard model. It is surprised to find that a
simple tˊ term will do the trick to introduce the momentum
dependence of the energy gap which mimics the pseudogap near (π,0) point
at least. It implies that the pseudogap structure near (π,0) is not sensitive to the long-range order and will survive
leading to the pseudogap phenomenon in the underdoped metallic phase. On the other hand, in the long-range ordering antiferromagnetic region, the mean-field SDW theory holds and the pseudogap structure predicated by the theory should be observable experimentally. Then one prediction is that the pseudogap would smoothly extrapolate between itinerant antiferromagnetic
phase and underdoped metallic phase. 相似文献