Thermal behavior of LaPO<Subscript>4</Subscript>·<Emphasis Type=Italic>n</Emphasis>H<Subscript>2</Subscript>O and NdPO<Subscript>4</Subscript>·<Emphasis Type=Italic>n</Emphasis>H<Subscript>2</Subscript>O nanopowders

Thermal behavior of LaPO₄·nH₂O and NdPO₄·nH₂O nanopowders from room temperature to 973 K was investigated by DSC, TA/DTG, ESM, and X-ray study. Mass loss due to the release of adsorbed and hydrate water was found in the range from 323 to 623 K. Phase transitions from hexagonal structure nanopowders to monoclinic one for bulk specimens were found above 873 K.     

Theoretical Study of the Structures,Properties and Spectroscopies on Fullerene Hydrides C<Subscript>26</Subscript>H<Subscript><Emphasis Type=Italic>n</Emphasis></Subscript> (<Emphasis Type=Italic>n</Emphasis> = 2, 4, 6, 8)

The structures, stability patterns of C₂₆H _n (n = 2) formed from the initial D _3h C₂₆ fullerene were investigated by use of second-order-Moller–Plesset perturbation theory. The study of the stability patterns of hydrogenation reaction on C₂₆ cage revealed that type (β) carbons were the active site and the analyses of π-orbital axis vector indicated that the reactivity of C₂₆ was the result of the high strain and the hydrogenation reaction on C₂₆ cage was highly exothermic. The calculated ¹³C NMR spectra of C₂₆H _n (n = 2) predicted that the two sp ³ hybridization carbons in C₂₆H _n (n = 2) obviously moved to high field compare with that in D _3h C₂₆. Hence, the C₂₆H₂ should be obtained and detected experimentally. Similarly, the structures and reaction energies of C₂₆H _n (n = 4, 6, 8) were further studied at HF/6-31G*, B3LPY/6-31G* and MP2/6-31G* level. The results suggested the hydrogenation products of C₂₆, C₂₆H _n (n = 4, 6, 8), were more stable than the C₂₆ cage.     

X-ray,SEM, and DSC studies of ferroelectric Pb<Subscript>1−<Emphasis Type=Italic>X</Emphasis></Subscript>Ba<Subscript><Emphasis Type=Italic>X</Emphasis></Subscript>TiO<Subscript>3</Subscript> ceramics

The polycrystalline ferroelectric compounds of general formula Pb_1−X Ba _X TiO₃ with X = 0.00, 0.1, 0.2 and 0.5 were prepared by high temperature solid-state reaction technique using high purity oxides and carbonates. The compounds formation was confirmed by X-ray diffraction and all the X-ray peaks were indexed with tetragonal structure of space group P4mm. Morphology and particle size of the compounds were obtained using scanning electron microscopy. Ferroelectric phase transition, enthalpy change, and specific heat of the compounds were obtained using modulated differential scanning calorimetry. It was observed that the phase transition temperature decreased linearly with the increase of substitution concentration.     

Synthesis and studies of magnesium hexafluorozirconates MgZrF<Subscript>6</Subscript> · <Emphasis Type=Italic>n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type=Italic>n</Emphasis> = 5, 2, 0)

Crystalline magnesium hexafluorozirconate MgZrF₆ · 5H₂O isostructural to MnZrF₆ · 5H₂O, and having a chain-like structure, was synthesized and studied. According to thermogravimetry, the compound undergoes stepwise dehydration in the temperature range of 50–420°C to give the stable phase MgZrF₆ · 2H₂O and the final product MgZrF₆ isostructural to the cubic modification of MZrF₆ (M = Cu, Fe). The vibrational spectra of the initial compound and the dehydration products are analyzed and the structures of the compounds are considered.     

Crystal structures of [<Emphasis Type="Italic">M</Emphasis>(Еn)<Subscript>3</Subscript>](ReO<Subscript>4</Subscript>)<Subscript>2</Subscript> (<Emphasis Type="Italic">M</Emphasis> = Ni,Zn)

The structures of two isostructural phases of [M(Еn)₃](ReO₄)₂ (M = Ni, Zn; Еn is ethylenediamine) are studied. The crystal structures belong to the triclinic system, but demonstrate a pseudohexagonal packing motif. It is shown that the product of thermal decomposition of [Zn(Еn)₃](ReO₄)₂ (hydrogen atmosphere, 400 °C) is a homogeneous mixture of nanocrystalline zinc and rhenium powders with coherent scattering regions of ~30 nm.     

Synthesis and X-ray diffraction of Cd<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>Hg<Subscript>1 − <Emphasis Type=Italic>x</Emphasis></Subscript> Te solid solutions

The Cd _x Hg_{1 − x} Te solid solutions were synthesized by combining two methods: immersion of CdTe single crystals in liquid mercury and thermal homogenization in mercury vapors. The samples obtained were studied by X-ray diffraction and X-ray fluorescence analyses. Nonstoichiometric cadmium microinclusions were shown to present in the initial CdTe single crystals and the solid solutions synthesized. The samples annealed in mercury vapors have smaller unit cell volumes than unannealed samples.     

Heat capacity of GdBaSr(Cu<Subscript>3−x</Subscript><Emphasis Type="Italic">M</Emphasis><Subscript>x</Subscript>)O<Subscript>7−δ</Subscript> superconductor (<Emphasis Type="Italic">M</Emphasis>=Zn and Ni)

In this study, GdBaSr(Cu_3−x M _x)O_7−δ bulk samples (M=Zn and Ni; 0≤x≤0.1) were prepared via solid-state reaction. Specific heat measurement (measured with thermal relaxation technique using PPMS) shows an obvious specific heat jump around the T _c for GdBaSrCu₃O_7−δ sample as observed in most of the high temperature superconductors. It shifts towards lower temperature with increasing of both Zn and Ni doping contents, whose tendency is similar to the decreasing of T _c. Debye temperature, Θ_D (derived from specific heat measurements) calculated at around 10 K is found to be directly proportional to the T _c.     

PW based phase change nanocomposites containing <Emphasis Type=Italic>γ</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Phase change nanocomposites were prepared by dispersing γ-Al₂O₃ nanoparticles into melting paraffin wax (PW). Intensive sonication was used to make well dispersed and homogeneous composites. Differential scanning calorimetric (DSC) and transient short-hot-wire (SHW) method were employed to measure the thermal properties of the composites. The composites decreased the latent heat thermal energy storage capacity, L _s, and melting point, T _m, compared with those of the PW. Interestingly, the composites with low mass fraction of the nanoparticles, have higher latent heat capacity than the calculated latent heat capacity value. The thermal conductivity of the nanocomposites was enhanced and increased with the mass fraction of Al₂O₃ in both liquid state and solid state.     

Electrophysical properties of layered perovskites LnBaCo<Subscript>2 − <Emphasis Type=Italic>x</Emphasis></Subscript>Cu<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>O<Subscript>5 + δ</Subscript> (Ln = Sm,Nd) for solid oxide fuel cells

The influence of doping with copper oxide on the phase composition, electric conductivity, and linear thermal expansion coefficient (LTEC) of SmBaCo₂O_{5 + δ} and NdBaCo₂O_{5 + δ} was studied. The sample homogeneity region has been determined with using XRD. The samples conductivity decreased as the dopant concentration increased. The character of the temperature dependence of conductivity changed at high copper contents. In a reductive atmosphere, the conductivity of the samples at first decreased and then remained constant. The linear thermal expansion coefficient decreased as the amount of the incorporated dopant increased.     

Preparation and properties of new materials: Solid solutions (GaSb)<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>(ZnTe)<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript>

Solid substitutional solutions of cubic (sphalerite) lattice based on the binary semiconducting compounds GaSb and ZnTe in the range of their mutual solubility were synthesized. Their identification was performed on the basis of X-ray and electrophysical studies.     

Synthesis of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@Au core–shell nanoparticles

A new two-step synthesis of Fe₃O₄@Au core–shell nanoparticles stabilized in polyethylene glycol is described. The nanoparticles were characterized by transmission electron microscopy, X-ray powder diffraction, UV and Mössbauer spectroscopy. Fe₃O₄@Au nanoparticles featured both optical properties (they featured a plasmon resonance band) and magnetic properties (they responded to an external magnetic field), typical of individual gold and magnetite nanoparticles, respectively.