Synthesis and characterization of Cu2O·TeO2 and CuI·Cu2O·TeO2 glasses

Cu₂O·TeO₂ and CuI·Cu₂O·TeO₂ glasses were synthesized and characterized by complex impedance measurement, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy techniques. Samples of the binary and the ternary systems are found to have both Cu⁺ and Cu²⁺ with their relative concentration being composition dependent. Bonds like -O-Cu²⁺-O-, leading to the formation of bridging oxygen are found to form in the binary system. Structural units like (Te₃O₈ ^4–)_n are also found to form when Cu₂O content is high in the binary system. Phase separation is observed in the ternary system. The glass structure and hence the ionic conduction behavior are found to depend upon chemical composition. When CuI content exceeds 60 mol%, the crystalline phase of -Cul gets stabilized at room temperature, thus causing the enhancement in conductivity.     

Synthesis and Study of Sr[HSiUO6]2·2H2O and Ba[HSiUO6]2·2H2O

Uranosilicates of the general formula M^{I I}[HSiUO₆]₂·2H₂O (M^{I I} = Sr, Ba) were prepared by hydrothermal synthesis. Previously unknown intermediate crystal hydrates were separated and studied by X-ray diffraction (XRD), IR spectroscopy, and thermal analysis. Polymorphic transitions -Sr[HSiUO₆]₂ -Sr[HSiUO₆]₂ and -Ba[HSiUO₆]₂ -Ba[HSiUO₆]₂ were revealed at 700 and 780°C, respectively.     

Preparation of DyFe_2 and TbFe_2 by Reduction-Diffusion Process

The pure intermetallic compounds (Tb1-x;Dyx)Fe2 are super-magnetostriction materials, which were produced from DyFe2 and TbFe2 in this paper. The thermodynamic possibility and kinetic feasible conditions for DyFe2 and TbFe2 preparation by reduction-diffusion in Ca-Dy2O3-Fe and Ca-Tb4O7-Fe systems were analyzed and the products of DyFe2 and TbFe2 were confirmed by XRD. The contracting core model was applied to describe the reduction-diffusion process in which the diffusion is a rate-controlled step. The apparent activation energies of DyFe2 and TbFe2 processes are 45 and 39 kJ/mol respectively.     

Controlled microstructure and production of TiO2 nanostructures by Ar and Ar–H2 atmosphere

Titanium dioxide nanostructures have been synthesised by annealing the Pd loaded titanium foil at 680°C under the atmosphere of Ar or Ar–H₂ gas mixture. The microstructure and production of titanium dioxide are found to depend critically on the concentration of Pd catalyst and the Ar–H₂ atmosphere. The catalyst of Pd and the introduction of 5%H₂ gas are the key factor for the formation of the long (about 100?μm in the average) and smooth titanium dioxide nanowires at low temperature. Scanning electron microscope and X-ray diffraction show that they are all rutile phase. The further result shows that the titanium dioxide nanowires possess good crystallinity and high surface photovoltage response.     

Stability Limits and Properties of Tl2TeBr6 , Cs2TeBr6 , and Rb2TeBr6

The composition stability limits of the compounds Tl₂TeBr₆, Cs₂TeBr₆, and Rb₂TeBr₆were determined from differential thermal analysis, microstructural, and microhardness data. The congruently melting composition was found to differ from the stoichiometric composition for Tl₂TeBr₆and Cs₂TeBr₆and to coincide with it for Rb₂TeBr₆. Single crystals of the compounds studied were prepared using growth charges with the congruently melting compositions, and their properties were investigated.     

c-axis Superfluid Response and Quasiparticle Conductivity in Bi2Sr2CaCu2O8+δ and Bi2Sr2CuO6+δ

Josephson plasma resonance for underdoped Bi ₂ Sr ₂ CaCu ₂ O ₈₊ and Bi ₂ Sr ₂ CuO ₆₊ have been measured by sweeping the microwave, frequency continuously. The resonance enables us to determine the superfluid density and quasiparticle conductivity in the c-axis accurately. We show that the. superfluid response and the low energy excitations out of the condensate in the c-axis of these materials are very different from those in the ordinary Josephson multilayer tunnel junctions. The Josephson coupling energy in single layer Bi ₂ Sr ₂ CuO ₆₊ is more than 5000 times smaller than is predicted in interlayer tunneling model.     

Preparation and Properties of Some Chemical and Electrochemical γ-MnO_2

Chemically prepared electrolytic γ-MnO2 and an electrodeposited MnO2 doped with Ce(III)were subjected to physicochemical studies. X-ray diffractometry, density measurements, chemical analysis and thermal analysis were used to determine the structure and chemical disorder present.The samples prepared chemically(CMD) or electrochemically (EMD) showed a variable amount of de Wolff disorder(Pr) and microtwinning (Tw). Manganese dioxide prepared in the presence of Ce(III) showed appreciable decrease in de Wolff defect and a large amount of microtwinning. Thermal analysis showed a loss of weight due to the physically adsorbed and the structural(OH)water, from which the activation energy was calculated. Chemical composition and formulae calculated on the bases of cation vacancy model, cleared that Ce(III)-doped sample has a remarkable increase in the vacancies population associated with higher structural water content. This leads to lower activation energy of water release, and consequently it is supposed to acquire higher electrochemical activity.     

Biocompatibility and bioactivity of PDLLA/TiO2 and PDLLA/TiO2/Bioglass® nanocomposites

Biocompatibility and bioactivity of polymer matrix composites containing titanium dioxide (TiO₂) nanoparticles were investigated. The solvent casting method was used to prepare poly (d,l-lactic acid) (PDLLA) films with 0 and 20 wt.% TiO₂ nanoparticles and with 20 wt.% TiO₂ mixed with 5 wt.% micrometre-sized (< 5 μm) Bioglass® particles. The samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy Dispersive X-ray (EDX) analyses. A Zygo® light interferometer was used to examine the surface roughness of the samples. The bioactivity and the surface reactivity of the materials were determined by investigating the formation of hydroxyapatite (HA) on the surface of samples upon immersion in simulated body fluid (SBF) for up to 28 days. Heterogeneous distributed HA crystals were found on composite films containing TiO₂ after 21 days exposure to SBF. Cell cytotoxicity and viability were determined by using live/dead and MTS assay on osteoblast-like MG-63 cells. The PDLLA films containing different concentrations of TiO₂ and Bioglass® particulate inclusions showed no effect on cell viability in live/dead assay after incubation period of 7 days. All three groups of samples demonstrated significant increase in relative metabolic activity in MTS assay after 7 days incubation (while a slower proliferation rate was obtained for cells on the PDLLA film containing both TiO₂ and Bioglass® compared to the Thermanox® control). The bioactive behaviour of the nanocomposites may make them attractive materials for fabrication of tissue engineering scaffolds.     

Preparation and Properties of Nano-TiO_2 Powders

This paper reports the preparation of nano-TiO2 (about 10 nm) powder by the method of precipitation. In detail, some breparation conditions were investigated in order to find out how to control the grain size and reduce the agglomeration of powders. Also, the reflex spectra of nano-scale powders with different grain size were studied. It tvas found that the wave length and width of reflex spectra are connected with the grain size of nano-TiO2 powders     

Rugate absorbing thin films and the 2 × 2 inhomogeneous matrix

The 2 × 2 matrix formalism proposed by Bovard is extended to absorbing inhomogeneous thin films for propagating the electromagnetic field. The contribution of each order into multiple reflections inside the film is analyzed.     

Mechanical properties and microstructure of ZrO2–SiO2 composite

ZrO2–SiO2 composite powder has been prepared by a wet chemical route using zirconyl chloride and fumed silica as starting materials and subsequently sintered by the hot-pressing method to obtain a ZrO2–SiO2 ceramic. The mechanical properties of the silica matrix have been much increased by the addition of 20 vol% zirconia. The microstructural features of the composite are observed by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The stabilibity of tetragonal zirconia in the matrix is attributed to the particle-size effect, and to the constraint effect of the silica matrix and that of the interphasic reaction layer. The increase in mechanical properties is discussed in relation to the residual stress and the enhanced elastic modulus caused by the incorporated ZrO2 particles.     

Laser deposition and study of CuInS2x Se2(1−x) crystals and films

Single-phase films of CuInS_2x Se_2(1−x) solid solutions with a chalcopyrite structure were deposited by laser evaporation of CuInS_2x Se_2(1−x) crystal targets (0≤x≤1). The structural and optical characteristics of the films depend on the chalcogen concentrations.     

Mn4+ Luminescence in 2MgO · GeO2 and 2MgO · GeO2 · MgF2

The oxidation state of the Mn activator in 2MgO · GeO₂, 2MgO · GeO₂ · MgF₂ was shown to be 4+. The observed luminescence behavior of these phosphors was accounted for by a large crystal-field splitting. The²T₁ and²E excited states of Mn⁴⁺ were found to be close in lifetime (100-120 ώs). The slower luminescence decay in magnesium fluorogermanate is attributable to the energy transfer between the activator and electron traps through the conduction band.     

Li–CO2 and Na–CO2 Batteries: Toward Greener and Sustainable Electrical Energy Storage

Metal–CO₂ batteries, especially Li–CO₂ and Na–CO₂ batteries, offer a novel and attractive strategy for CO₂ capture as well as energy conversion and storage with high specific energy densities. However, some scientific issues and challenges existing restrict their practical applications. Here, recent progress of crucial reaction mechanisms on cathodes in Li–CO₂ and Na–CO₂ batteries are summarized. The detailed reaction pathways can be modified by operation conditions, electrolyte compositions, and catalysts. Besides, specific discussions from aspects of catalyst design, stability of electrolytes, and anode protection are presented. Perspectives of several innovative directions are also put forward. This review provides an intensive understanding of Li–CO₂ and Na–CO₂ batteries and gives a useful guideline for the practical development of metal–CO₂ batteries and even metal–air batteries.     

Preparation of MgH2–Ni, MgH2–Ni–Si and MgH2–Ni–Ni2Si composites by mechanochemical method and their hydrogen absorption and desorption properties

To improve kinetics for hydrogen absorption of Mg and hydrogen desorption of MgH₂, ternary composites were prepared from MgH₂, Ni and Si or Ni₂Si by a mechanochemical technique. The X-ray diffraction spectra of the resultant ternary composites after the initial hydrogen desorption treatment at 400 °C in vacuum suggested that in all composites the nanocrystalline Mg₂Ni would be formed in the intergrain region between Mg and Ni components, while in the MgH₂–Ni–Si composite the nanocrystalline Mg₂Si would also be formed in the intergrain region between Mg and Si components. However, Ni₂Si did not form any alloys with Mg. The hydrogen absorption rate at 250 °C for the MgH₂–Ni–Ni₂Si composite was comparable to that for the MgH₂–Ni and MgH₂–Ni–Si composites, while the hydrogen desorption rate at 250 °C decreased in the order of MgH₂–Ni > MgH₂–Ni–Ni₂Si > MgH₂–Ni–Si. In contrast, the hydrogen desorption rate at 220 °C for the MgH₂–Ni–Ni₂Si composite was faster than that for the MgH₂–Ni composite, suggesting that Ni₂Si was a key material in the improvement of hydrogen desorbability at lower temperatures. Moreover, the most plausible reaction model and the rate-determining process for hydrogen absorption and desorption at 250 °C were determined.     

Anomalous Scattering Rate and Microwave Absorption in Bi2Sr2CaCu2O8+δ and YBa2Cu3O7?δ

We determine the scattering rate from microwave measurements for an optimally doped Bi-2212 single crystal, using a simple two-fluid model with a d-wave symmetry order parameter. In the superconducting state, the calculated scattering rate is three orders of magnitude smaller than that determined from ARPES experiments. A similar anomalously large decrease in the scattering rate is also required to explain the data within a gap-quasiparticle scenario for other HTS, such as YBa₂Cu₃O_7–. The results suggest that the assumption of normal excitations vanishing at low T is invalid and an additional charge mode is responsible for the microwave absorption.     

Photoluminescence and scintillation properties of Eu2O3–BaO–Nb2O5–TeO2 glass and glass ceramics

Journal of Materials Science: Materials in Electronics - 1Eu2O3–3BaO–20Nb2O5–76TeO2 glass and the corresponding glass-ceramics were synthesized with the aim to investigate the...     

PbO_2-ABS plastics electrode and its characteristics

The process for preparation of PbO_2-ABS plastics electrode was described, and its polarization curves and service life were measured. The experimental results showed that the electrode has excellent stabililty     

Fabrication and characterisation of MnOOH and β-MnO2 nanorods with rectangular cross-sections

MnOOH nanorods with rectangular cross-sections have been successfully prepared in high yield via a hydrothermal reduction process at a low temperature. After the subsequent heat treatment of the as-prepared MnOOH nanorods at 350°C for 6?h in air, β-MnO₂ nanorods with rectangular cross-section that retained the similar morphologies of MnOOH nanorods were obtained. The products were characterised by powder X-ray diffraction and field-emission scanning electron microscopy. The influences of different degrees of pH on the morphology and phase of the final products under hydrothermal conditions are discussed.