Crystal Structure of the First Representative of the Eudialyte Group with Primitive Unit Cell

Crystallography Reports - The first representative of the eudialyte group with a primitive unit cell has been investigated by X-ray diffraction analysis, electron probe microanalysis, and IR...     

New Data on the Isomorphism in Eudialyte-Group Minerals. ХI: Crystal Structure of a Potentially New Mineral—A Case of Complete Substitution of Fe2+ with $${\text{Na}}_{{{\text{2/3}}}}^{{\text{ + }}}{\text{Zr}}_{{{\text{1/3}}}}^{{{\text{4 + }}}}$$ in the Eudialyte-Type Structure

Crystallography Reports - The crystal structure and crystallochemical features of a Fe-deficient zirconium-rich analog of eudialyte from the Lovozero alkaline massif (Kola peninsula) have been...     

Comparative Study of LiInSe2 Single Crystals for Thermal-Neutron Detection

Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using...     

Dynamics of the BiTeI lattice at high pressures

Raman measurements of the phonon spectrum of BiTeI at pressures of up to 20 GPa have been performed. A decrease in the linewidth of E² vibration by almost a factor of 2 with an increase in the pressure to 3 GPa has been detected. The frequencies of all four Raman active modes increase monotonically with the pressure. These lines are observed in spectra up to ～8 GPa. Sharp change in the spectrum occurs at pressures of 8–9 GPa, indicating a transition to the high-pressure phase, which holds up to 20 GPa. This transition is reversible and hardly has any hysteresis. A sample in the high-pressure phase is single crystal.     

Synthesis,crystal structure,vibrational spectra,optical properties and theoretical investigation of a two-dimensional self-assembled organic-inorganic hybrid material

Organic–inorganic hybrid material of formula (C₄H₃SC₂H₄NH₃)₂[PbI₄] was synthesized and studied by X-ray diffraction, Infrared absorption, Raman scattering, UV–Visible absorption and photoluminescence measurements. The molecule crystallizes as an organic–inorganic two-dimensional (2D) structure built up from infinite PbI₆ octahedra surrounded by organic cations. Such a structure may be regarded as quantum wells system in which the inorganic layers act as semiconductor wells and the organic cations act as insulator barriers. Room temperature IR and Raman spectra were recorded in the 520–3500 and 10–3500 cm⁻¹ frequency range, respectively. Optical absorption measurements performed on thin films of (C₄H₃SC₂H₄NH₃)₂[PbI₄] revealed three distinct bands at 2.4, 2.66 and 3.25 eV. We also report DFT calculations of the electric dipole moments (μ), polarizability (α), the static first hyperpolarizability (β) and HOMO–LUMO analysis of the title compound investigated by GAUSSIAN 09 package. The calculated static first Hyperpolarizability is equal to 11.46 × 10⁻³¹ esu.     

Research progress on Na3V2(PO4)2F3-based cathode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) have received significant attention in large-scale energy storage due to their low cost and abundant resources. To obtain high-performance SIBs, many intensive studies about electrode materials have been carried out, especially the cathode material. As various types of cathode material for SIBs, a 3D open framework structural Na₃V₂(PO₄)₂F₃ (NVPF) with Na superionic conductor (NASICON) structure is a promising cathode material owing to its high operating potential and high energy density. However, its electrochemical properties are severely limited by the poor electronic conductivity due to the insulated [PO₄] tetrahedral unit. In this review, the challenges and strategies for NVPF are presented, and the synthetic strategy for NVPF is also analyzed in detail. Furthermore, recent developments of modification research to enhance their electrochemical performance are discussed, including designing the crystal structure, adjusting the electrode structure, and optimizing the electrolyte components. Finally, further research and application for future development of NVPF are prospected.     

Synthesis of activated carbon foams with high specific surface area using polyurethane elastomer templates for effective removal of methylene blue

Carbon foams have gained significant attention due to their tuneable properties that enable a wide range of applications including catalysis, energy storage and wastewater treatment. Novel synthesis pathways enable novel applications via yielding complex, hierarchical material structure. In this work, activated carbon foams (ACFs) were produced from waste polyurethane elastomer templates using different synthesis pathways, including a novel one-step method. Uniquely, the produced foams exhibited complex structure and contained carbon microspheres. The ACFs were synthesized by impregnating the elastomers in an acidified sucrose solution followed by direct activation using CO₂ at 1000 ℃. Different pyrolysis and activation conditions were investigated. The ACFs were characterized by a high specific surface area (S_BET) of 2172 m²/g and an enhanced pore volume of 1.08 cm³/g. Computer tomography and morphological studies revealed an inhomogeneous porous structure and the presence of numerous carbon spheres of varying sizes embedded in the porous network of the three-dimensional carbon foam. X-ray diffraction (XRD) and Raman spectroscopy indicated that the obtained carbon foam was amorphous and of turbostratic structure. Moreover, the activation process enhanced the surface of the carbon foam, making it more hydrophilic via altering pore size distribution and introducing oxygen functional groups. In equilibrium, the adsorption of methylene blue on ACF followed the Langmuir isotherm model with a maximum adsorption capacity of 592 mg/g. Based on these results, the produced ACFs have potential applications as adsorbents, catalyst support and electrode material in energy storage systems.     

Heat capacity and thermodynamic functions of nano-TiO2 rutile in relation to bulk-TiO2 rutile

Several conflicting reports have suggested that the thermodynamic properties of materials change with respect to particle size. To investigate this, we have measured the constant pressure heat capacities of three 7 nm TiO₂ rutile samples containing varying amounts of surface-adsorbed water using a combination of adiabatic and semi-adiabatic calorimetric methods. These samples have a high degree of chemical, phase, and size purity determined by rigorous characterization. Molar heat capacities were measured from T = (0.5 to 320) K, and data were fitted to a sum of theoretical functions in the low temperature (T < 15 K) range, orthogonal polynomials in the mid temperature range (10 > T/K > 75), and a combination of Debye and Einstein functions in the high temperature range (T > 35 K). These fits were used to generate $\mathit{Cp}\text{,}{\text{m}}^{\circ }$, ${\mathrm{\Delta }}_0^{\text{T}}{S}_{\text{m}}^{\circ }$, ${\mathrm{\Delta }}_0^{\text{T}}{H}_{\text{m}}^{\circ }$, and ${\phi }_{\text{m}}^{\circ }$ values at selected temperatures between (0.5 and 300) K for all samples. Standard molar entropies at T = 298.15 K were calculated to be (62.066, 59.422, and 58.035) J · K⁻¹ · mol⁻¹ all with a standard uncertainty of 0.002·${\mathrm{\Delta }}_0^{\text{T}}{S}_{\text{m}}^{\circ }$ for samples TiO₂·0.361H₂O, TiO₂·0.296H₂O, and TiO₂·0.244H₂O, respectively. These and other thermodynamic values were then corrected for water content to yield bare nano-TiO₂ thermodynamic properties at T = 298.15 K, and we show that the resultant thermodynamic properties of anhydrous TiO₂ rutile nanoparticles equal those of bulk TiO₂ rutile within experimental uncertainty. Thus we show quantitatively that the difference in thermodynamic properties between bulk and nano-TiO₂ must be attributed to surface adsorbed water.