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Study on low-temperature crack resistance of zirconium tungstate modified asphalt mastic and asphalt mixtures
Published in Inge Hoff, Helge Mork, Rabbira Saba, Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields, Volume 1, 2021
Z.S. Pei, J.Y. Yi*, D.C. Feng, J.J. Li
Zirconium tungstate (ZT) was successfully prepared in 1996 by Mary et al (Mary et al. 1996). They found that the negative thermal expansion temperature range of zirconium tungstate is - 273 ℃ ~ 777 ℃, and the isotropic properties of ZT was good. This discovery makes it possible for the practical application of negative thermal expansion materials. ZT has been widely used in the preparation of composite materials due to its wide range of reverse expansion temperature range and isotropy. ZT was combined with aluminum alloy to make the alloy. When the volume of ZT was three times that of aluminum alloy, the contraction coefficient of the alloy could reach 0 (Matsumoto et al. 2003). ZT and zirconia were used to produce composite materials, and the expansion coefficient of the composites was close to 0 when the mass of zirconia was twice that of ZT (Niwa et al. 2004). Also, ZT was used to improve the performance of cement concrete, and the results show that the contraction coefficient of cement concrete was close to 0 when the mass fraction of ZT reaches 60% (Kofteros et al. 2001). If the thermal contraction coefficient of asphalt mixture can be improved by using ZT, it will greatly change the anti-cracking ability of asphalt mixture at low temperatures.
Variety of Shapes of Water Molecule Interactions
Published in Makoto Yasutomi, The Physics of Liquid Water, 2021
Based on the results of experiments and numerical experiments, it has been reported that liquid–liquid phase transition occurs with density anomaly [Mayer and Stanley (1999); Mishima and Stanley (1998); Poole (1992); Sciortino (2003); Sun (2014)]. From this, some people proposed an idea that the liquid–liquid phase transition generates the density anomaly. However, they merely describe the experimental results phenomenologically, they do not explain why the phase transition occurs and why the phase transition produces negative thermal expansion. Since all the phase transitions that occur in normal materials are accompanied by positive thermal expansion, the difference should be explained why only the liquid–liquid phase transition of water produces negative thermal expansion. Just because liquid–liquid phase transition occurs with density anomaly, it cannot be said that liquid–liquid phase transition induces density anomaly. Even if a liquid–liquid phase transition occurs in real water, the author believes that the phase transition may be an accompanying phenomenon as a result of density anomaly caused by the thermodynamic mechanism elucidated in this book.
Thermal Properties of Polymer/Ceramic Composites
Published in Noureddine Ramdani, Polymer and Ceramic Composite Materials, 2019
Zirconium tungstate (ZrW2O8) is a unique ceramic filler showing an isotropic-negative thermal expansion behavior over a wide range of temperature [104]. The addition of ZrW2O8 to polymeric matrices is expected to enhance their dimensional stabilities by decreasing the overall CTE values. Thermomechanical analysis revealed that the inclusion of ZrW2O8 engendered a reduction in the CTE value of cyanate ester at temperatures above and below its Tg. Phenolic resin/ZrW2O8composites were produced, and their CTE data was investigated. The CTE of the resulting composites reduced from 46 to 14 ppm/°C as the ZrW2O8 volume ratio increased from 0 to 52 vol.% [105].
The Taming of Plutonium: Plutonium Metallurgy and the Manhattan Project
Published in Nuclear Technology, 2021
Joseph C. Martz, Franz J. Freibert, David L. Clark
By early 1945, Martin and Selmanoff had constructed a high-temperature quartz dilatometer capable of uniquely determining the anomalous length changes that accompany plutonium allotropic transformations and determining the density and thermal expansion of the various phases.34 Their work clearly showed the presence of five phases in pure, unalloyed plutonium as seen in Fig. 5. The bulk density of α-phase was reported as 19.6 g/cm3 for temperatures below 130°C; β-phase was reported as 17.3 g/cm3 for averaged temperature range of 150°C to 210°C; γ-phase was reported as 16.8 g/cm3 for averaged temperature range of 230°C to 300°C; and δ-phase was reported as 15.8 g/cm3 over the temperature range of 330°C to 470°C. Quite unexpectedly, the δ-phase showed a negative thermal expansion coefficient! Finally, the ε-phase was reported as 16.8 g/cm3 for temperatures above 500°C. Knowing the unique temperature ranges of each allotrope enabled other physical properties to be determined, such as crystal structure, electrical resistivity, hardness, thermal conductivity, etc.35
Large programmable coefficient of thermal expansion in additively manufactured bi-material mechanical metamaterial
Published in Virtual and Physical Prototyping, 2021
Kai Wei, Xiaoyujie Xiao, Wentao Xu, Zhengtong Han, Yazhuo Wu, Zhonggang Wang
On the other hand, for the planar metamaterials with the negative programmable CTE, the thermal displacements are summarised in Figure 8. The contour plots indicate that the left and right semi-circles induce the thermal displacement U along the positive and negative x direction, respectively. That is, the negative thermal expansion along the horizontal direction is generated. Similarly, the negative thermal expansion along the vertical direction can be also obtained. These thermal displacement evolutions in Figures 7 and 8 illustrate the expected thermal expansion and lay the foundation to generate the predicted either positive or negative programmable CTEs. Additionally, it is observed that the interfaces of the members with different materials were not separated before and after the CTE tests up to 60.0°C, demonstrating the reliability of the additive manufacturing.
Temperature dependent anomalous fluctuations in water: shift of ≈1 kbar between experiment and classical force field simulations
Published in Molecular Physics, 2019
Harshad Pathak, Alexander Späh, Katrin Amann-Winkel, Fivos Perakis, Kyung Kyung Hwan Kim, Anders Nilsson
Thermal expansion coefficient (α): Here we discuss this property based on a new analysis where we estimate the thermal expansion coefficient (α). Thermal expansion coefficient is proportional to a combined effect of density and entropy fluctuations. Although for most liquids, density and entropy fluctuations are positively correlated, but for liquid water at 1 bar and colder than 277 K, these are anti-correlated. This results in a negative thermal expansion coefficient for supercooled water. Here we attempt to relate the structure factor of water to its thermal expansion coefficient since the decrease in density originates from the growth of tetrahedral structures with its open network. In the section ‘Tetrahedral structure’, we discussed about the observation of a maxima in (∂q1/∂T)P.