Effect of copper addition on the thermal contraction of indium melt clusters

The structure of In-1 %Cu and In-5%Cu (mass fraction) alloy melts werestudied at different temperatures above liquidus by using a high-temperature X-ray diffractometerand were compared with that of pure In melt. Experimental results show that with the addition of 1%Cu or 5% Cu, the thermal contraction phenomenon of atom clusters occurs in melts with thetemperature increasing like pure In melt. With the addition of 1% Cu, the thermal contraction ofatom clusters increases and the contraction is not homogeneous in the whole measurement temperaturerange. The sudden change and noticeable contraction can be found in the range of 280-390 ℃. Thetemperature range of the sudden change is lower than that of pure In melt. With the addition of 5%Cu, the thermal contraction of atom clusters decreases and the contraction is not consistent in thewhole measurement temperature range. The anomalous change can be measured at about 600 ℃. At thesame superheating temperature, the nearest interatomic distance r_1 of the melts containing copperis smaller than that of pure In melt, implying that the cluster structure of melts containing copperis more compact.

Remarkable Thermal Contraction in Small Size Single-Walled Boron Nanotubes

Density functional theory combined with the Gr¨uneisen approximation is used to calculate the thermal properties of single-walled boron nanotubes(BNTs).The specific heat and thermal expansion are investigated.The thermal expansion coeffi-cient of the BNT is found to be significantly correlated with tube size and chirality.A remarkable thermal contraction is found at small tube diameters.These results indicate that BNTs would have potential applications in sensors,actuators,and memory materials.

Precursor route synthesis and thermal contraction of compounds ZrW_(2-x)Mo_xO_8 (x=0, 0.4, 0.6, 0.8, 1.2, 1.6)

A series of title compounds as well as their precursors were synthesized by precursor route. Their PXRD patterns were characterized with ZrW2O8 or ZrMo2O8 model by Rietveld method. The thermal contractions of the compounds were determined according to the variable-temperature PXRD data and NTE coefficients were presented. The two-phase mixture of ZrW0.4Mo1.6O8 was also analyzed individually.

The import contract on the generating equipment of Hanfeng Thermal Power Plant signed in Beijing

On November 8, 1996. the import contract signing ceremony on the two 660 MW coal-fired generating units of Hanfeng Thermal Power Plant 1st phase was held in the Great Hall of People, Beijing.

Possible controlling factors in the development of seasonal sand wedges on the Ordos Plateau,North China

Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of either permafrost or seasonal frost during the Late Pleistocene and early Holocene. Wedges of about 1 m in depth form polygonal nets of 2-3 m in diameter(type B). They contrast with wedges of 3-4 m in depth that form polygons of 10-15 m in diameter(type A).This review focuses upon the highly variable size of the inferred polygon nets and discusses the problem of differentiating between seasonally and perennially frozen ground, or between seasonal frost and permafrost.

Negative thermal expansion: Mechanisms and materials

Negative thermal expansion(NTE)of materials is an intriguing phenomenon challenging the concept of traditional lattice dynamics and of importance for a variety of applications.Progresses in this field develop markedly and update continuously our knowledge on the NTE behavior of materials.In this article,we review the most recent understandings on the underlying mechanisms(anharmonic phonon vibration,magnetovolume effect,ferroelectrorestriction and charge transfer)of thermal shrinkage and the development of NTE materials under each mechanism from both the theoretical and experimental aspects.Besides the low frequency optical phonons which are usually accepted as the origins of NTE in framework structures,NTE driven by acoustic phonons and the interplay between anisotropic elasticity and phonons are stressed.Based on the data documented,some problems affecting applications of NTE materials are discussed and strategies for discovering and design novel framework structured NET materials are also presented.