Anomalous thermal expansion of a new diyn-diol molecule was studied by means of variable-temperature single-crystal X-ray diffraction. Analysis of the unit cell axes as a function of temperature shows that the material experiences uniaxial negative thermal expansion. Packing analysis of the crystal structures reveals twisting of the cyclopentyl moiety relative to the diyne spine with increasing temperature.
The effect of annealing temperature and external stress on the thermal expansion of a Ti–23Nb–0.7Ta–2Zr alloy were investigated by means of thermal expansion tests under constant load and X-ray diffraction (XRD). Negative thermal expansion (NTE), which is a shrinkage
during heating, was observed in both a cold rolled and annealed specimens. The intensity of (200)β peak decreased while that of (211)β peak increased as the annealing temperature increased. The difference in expansion rate between 50 °C and
250 °C is found to decrease with an increasing annealing temperature from 600 °C to 800 °C, above which it kept almost constant. The expansion rate decreased as the applied stress increased.
Variable-temperature high-resolution capillary-mode powder X-ray diffraction is used to assess changes in unit-cell dimensions as a function of temperature over the range 188–328 K. No evidence was found for any polymorphic transformations over this temperature range and thermal expansion coefficients for urea were found to be αa= (5.27 ± 0.26) × 10−5 K−1and αc= (1.14 ± 0.057) × 10−5 K−1.
The Invar effect in 3D transition metal such as Ni and Mn, were prepared on a series composition of binary Ni1-xMnx system with x=0.3, 0.5, 0.8 by using powder metallurgy technique. In this work, the characterization of structural and thermal properties have been investigated experimentally by X-ray diffraction, thermal expansion coefficient and vibrating sample magnetometer (VSM) techniques. The results show that anonymously negative thermal expansion coefficient are changeable in the structure. The results were explained due to the instability relation between magnetic spins with lattice distortion on some of ferromagnetic metals.
The Mn3XN(X=Zn, Cu, Sn) compounds and their solid solutions with anti-perovskite structure were prepared by solid state reaction. Their magnetic transition and simultaneous abnormal thermal expansion behaviors were studied by SQUID and variable temperature X-ray diffraction. The lattice contraction was found in Mn3Cu0.5Sn0.5N and Mn3Zn0.5Sn0.5N during the magnetic transition process, however not in pure Mn3XN(X=Zn, Cu, Sn). The mechanism is discussed, combined with the different doping effects. It seems that the lattice contraction behavior is sensitive to the number of valence electrons at the X site in Mn3XN series.
Crystalline 4-isopropylphenol, C9H12O, an optically non-linear material, was studied by X-ray diffraction in order to determine its structure at several temperatures in the 95–300 K range. The thermal expansion coefficients have been calculated from the lattice parameters' dependence on temperature. The rigid-body analysis of the anisotropic displacement parameters including the correlation with the internal motion of large amplitude provided the values of the molecular translation and libration tensors at the temperatures studied and was used to characterize the torsional motion of the isopropyl group. The calculated normal modes and internal torsion frequency were compared with the wave numbers at the maximum of bands in the low-frequency Raman scattering, FTIR and inelastic neutron scattering spectra.
An examination of the thermal expansion of urea using high-resolution variable-temperature X-ray powder diffraction