Solids, Volume 1, Issue 1 (December 2020) – 5 articles

The synthesis of YBa₂Cu₃O_7−x (YBCO or 123) was carried out via the use of a variety of deep eutectic solvents (DESs), all formed by the interaction of choline hydroxide (as the cation source) and alkyl carboxylic acids with C_nH_2n+1 ranging from n = 2 to n = 10, namely acetic acid, propionic acid, butyric acid, pentanoic acid, nonanoic acid, and decanoic acid, as providers of the anion, all prepared in equimolar solutions. The behaviour of the synthetic media and the resulting morphology displayed by the crystallite product, using different molar ratios of DESs (X):1 YBaCu metal nitrates mixes, with x values of 20 ≤ x ≤ 60, is also reported. Synthetic performance results show a tendency to generate higher total phase percentage of the desired crystal with the increase of the alkyl chain length of the carboxylic acid up to butyric acid (92% belonging to the metal oxide), after which no enhancement was observed. Furthermore, the synthetic performance of the remaining, i.e., DES formed with pentanoic acid to decanoic acid, displayed a constant decay in total desired phase percentage belonging to the metal oxide. Morphological results were also analysed for all DESs (X):1 YBaCu metal nitrates mixes, with x values of 20 ≤ x ≤ 60. Well defined plate-like particles were generally observed however, in some cases fused plate-like particles of significantly bigger size were observed. Full article

When oxide glasses are modified by dissimilar alkali ions, a maximum in the electric resistivity or the expansion coefficient appears, called the mixed-alkali effect (MAE). This paper reviews the MAE on the thermal, elastic, and vibrational properties of the mixed-cesium lithium borate glasses, x{(1−y)Cs₂O-yLi₂O}-(1−x)B₂O₃. For the single-alkali borate glasses, xM₂O(1−x)-B₂O₃ (M = Li, Na, K, Rb, and Cs), the glass transition temperature, T_g = 270 °C, of a borate glass monotonically increases as the alkali content x increases. However, for the mixed-cesium lithium borate glasses the T_g shows the minimum against the lithium fraction y. The dependences of the elastic properties on the lithium fraction y were discussed regarding the longitudinal modulus, Poisson’s ratio, and Cauchy-type relation. The internal vibrational bands related to the boron-oxide structural groups and the splitting of a boson peak were discussed based on Raman scattering spectroscopy. The MAE on various physical properties are discussed on the basis of the changes in the coordination number of the borons and the nonbridging oxygens caused by the dissimilar alkali ions. Full article

The combination of hyperelastic material models with viscoelasticity allows researchers to model the strain-rate-dependent large-strain response of elastomers. Model parameters can be identified using a uniaxial tensile test at a single strain rate and a relaxation test. They enable the prediction of the stress–strain behavior at different strain rates and other loadings like compression or shear. The Marlow model differs from most hyperelastic models by the concept not to use a small number of model parameters but a scalar function to define the mechanical properties. It can be defined conveniently by providing the stress–strain curve of a tensile test without need for parameter optimization. The uniaxial response of the model reproduces this curve exactly. The coupling of the Marlow model and viscoelasticity is an approach to create a strain-rate-dependent hyperelastic model which has good accuracy and is convenient to use. Unfortunately, in this combination, the Marlow model requires to specify the stress–strain curve for the instantaneous material response, while experimental data can be obtained only at finite strain rates. In this paper, a transformation of the finite strain rate data to the instantaneous material response is derived and numerically verified. Its implementation enables us to specify hyperelastic materials considering strain-rate dependence easily. Full article