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Thermal expansion

About: Thermal expansion is a research topic. Over the lifetime, 21040 publications have been published within this topic receiving 349407 citations. The topic is also known as: heat expansion.


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TL;DR: In this paper, the authors measured the thermal expansion of various fiber- and particle-reinforced metal-matrix composites and the experimentally obtained values compared with the predictions of various theoretical models, and observed behavior of these particulate and fibrous composites is described on the basis of the thermal stresses developed in such composites as a result of the differences in the coefficient of thermal expansion between the reinforcement and the matrix.

135 citations

Journal ArticleDOI
TL;DR: It is shown that in the perovskites reported here, theTemperature coefficient of thermal expansion is large and accounts for the positive temperature coefficient of the band gap, and a detailed analysis of the exciton line width allows us to distinguish between static and dynamic disorder.
Abstract: In this Letter, we investigate the temperature dependence of the optical properties of methylammonium lead iodide (MAPbI3 = CH3NH3PbI3) from room temperature to 6 K. In both the tetragonal (T > 163 K) and the orthorhombic (T < 163 K) phases of MAPbI3, the band gap (from both absorption and photoluminescence (PL) measurements) decreases with decrease in temperature, in contrast to what is normally seen for many inorganic semiconductors, such as Si, GaAs, GaN, etc. We show that in the perovskites reported here, the temperature coefficient of thermal expansion is large and accounts for the positive temperature coefficient of the band gap. A detailed analysis of the exciton line width allows us to distinguish between static and dynamic disorder. The low-energy tail of the exciton absorption is reminiscent of Urbach absorption. The Urbach energy is a measure of the disorder, which is modeled using thermal and static disorder for both the phases separately. The static disorder component, manifested in the excit...

134 citations

Journal ArticleDOI
Bo Wei1, Zhe Lü1, Shuyan Li1, Yuqiang Liu1, Keyan Liu1, Wenhui Su 
TL;DR: A newly developed cathode material, Ba0.5Sr 0.5Co0.8Fe0.2O3-delta, was synthesized and characterized in this paper.
Abstract: A newly developed cathode material, Ba0.5Sr0.5Co0.8Fe0.2O3-delta, was synthesized and characterized. X-ray diffraction results identified it as a cubic perovskite structure. Thermogravimetric results showed that lattice oxygen loss was about 2% in weight between 50 and 1000 degrees C. Thermal expansion coefficient results in air and argon were extraordinarily high, with slope changes occurring at about 382 and 360 degrees C, respectively. Electrical conductivity values were sufficient for cathode application with the maximum of about 28.1 S cm(-1) at 500 degrees C in air and 17.3 S cm(-1) at 900 degrees C in N-2, correspondingly. Both thermal and electrical properties were closely associated with lattice oxygen behaviors and oxygen partial pressure. (c) 2005 The Electrochemical Society.

134 citations

Journal ArticleDOI
Kazuhiro Ito1, K Ihara1, Katsushi Tanaka1, M. Fujikura2, Makoto Yamaguchi1 
TL;DR: The T2 phase in the Mo-Si-B system is a refractory molybdenum borosilicide with great potential for ultra-high temperature structural applications.

134 citations

Journal ArticleDOI
TL;DR: It is proposed that the negative thermal expansion effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between magnetism and the crystal lattice.
Abstract: Most solids expand when they are heated, but a property known as negative thermal expansion has been observed in a number of materials, including the oxide ZrW2O8 (ref. 1) and the framework material ZnxCd1-x(CN)2 (refs 2,3). This unusual behaviour can be understood in terms of low-energy phonons, while the colossal values of both positive and negative thermal expansion recently observed in another framework material, Ag3[Co(CN)6], have been explained in terms of the geometric flexibility of its metal-cyanide-metal linkages. Thermal expansion can also be stopped in some magnetic transition metal alloys below their magnetic ordering temperature, a phenomenon known as the Invar effect, and the possibility of exploiting materials with tuneable positive or negative thermal expansion in industrial applications has led to intense interest in both the Invar effect and negative thermal expansion. Here we report the results of thermal expansion experiments on three magnetic nanocrystals-CuO, MnF2 and NiO-and find evidence for negative thermal expansion in both CuO and MnF2 below their magnetic ordering temperatures, but not in NiO. Larger particles of CuO and MnF2 also show prominent magnetostriction (that is, they change shape in response to an applied magnetic field), which results in significantly reduced thermal expansion below their magnetic ordering temperatures; this behaviour is not observed in NiO. We propose that the negative thermal expansion effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between magnetism and the crystal lattice.

134 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023603
20221,249
2021683
2020742
2019759
2018767