Proton conductivity in sol–gel-derived P2O5–TiO2–SiO2 glasses

The sol–gel method was applied to prepare the P₂O₅–TiO₂–SiO₂ glasses with high proton conductivities and chemical stability. The glasses were prepared by the reaction of the Ti- and Si-alkoxides with PO(OCH₃)₃ or H₃PO₄, followed by heating at 600 °C. The obtained glasses were porous, the average pore diameter of which was <2 and 4 nm for glasses prepared using PO(OCH₃)₃ and H₃PO₄, respectively. The phosphorous ions, occurring as PO(OH)₃ in the TiO₂-free glass, were polymerized with one or two bridging-oxygen ions per PO₄ unit with the increasing TiO₂ content. Despite the P₂O₅–SiO₂ binary glasses exhibiting high conductivities of ∼10⁻² S/cm at room temperature, they also dissolved after immersing for 24 h in water. The chemical stability of these glasses increased significantly on the addition of TiO₂.     

The interfacial effect on ionic conduction of AgI–anatase TiO2 composites

AgI–anatase TiO₂ nanoparticle composites, (x)AgI–(1 ? x)anatase, with different porosities were fabricated over a wide range of 0–1 of AgI content. The electrical conductivity was measured at room temperature as function of AgI content (x) and porosity (p). The conductivity varies considerably with both x and p. In the vicinity of x = 0.4 and p = 0.31, the conductivity attains a maximum (2.5 × 10^? 3 S/cm). The conductivity is enhanced by three orders of magnitude in comparison with that of pristine AgI. The mechanism of the observed conductivity enhancement is discussed in the light of the scanning electron microscope images and X-ray diffraction patterns of the different (x)AgI–(1 ? x)anatase composites.     

Optical properties of sol-gel fabricated Mn/SiO2 nanocomposites: Observation of surface plasmon resonance in Mn nanoparticles

Manganese nanoparticles were grown in silica glass and silica film on silicon substrate by annealing of the sol-gel prepared porous silicate matrices doped with manganese nitrate. Annealing of doped porous silicate matrices was performed at various conditions that allowed to obtain the nanocomposite glasses with various content of metallic Mn. TEM of Mn/SiO₂ glass indicates the bimodal size distribution of Mn nanoparticles with mean sizes of 10.5 nm and 21 nm. The absorption and photoluminescence spectra of Mn/SiO₂ glasses were measured. In the absorption spectra at 300 nm (4.13 eV) we observed the band attributed to the surface plasmon resonance in Mn nanoparticles. The spectra proved the creation of Mn²⁺ and Mn³⁺ ions in silica glass as well. The absorption spectra of Mn/SiO₂ glasses annealed in air prove the creation of manganese oxide Mn₂O₃. The measured reflection spectra of Mn/SiO₂ film manifest at 240-310 nm the peculiarity attributed to surface plasmons in Mn nanoparticles.     

Formation of the HgI2 crystalline phase in the bulk and on the surface of nanocrystalline matrices

This paper reports on the results of investigations into the phase composition of HgI₂ microcrystals formed in the bulk and on the surface of different nanocrystalline matrices: pressed, finely dispersed (with a specific surface of more than 210 m²/g) aluminum oxide powders; porous borosilicate glasses with pore radii ranging from 2 to 20 nm; and Al₂O₃-HgI₂ and SiO₂-HgI₂ nanocrystalline composites. The results of spectroscopic analysis (diffuse reflection, absorption, and luminescence spectroscopy) are complemented by the data of atomic-force microscopy (AFM) and x-ray diffraction. The experimental results indicate that nonequilibrium modifications, namely, the high-temperature yellow phase and the orange phase metastable in bulk crystals at all temperatures, can be stabilized in HgI₂ nanoparticles at room temperature.     

Chemical Analyses of Potash–Lime Silicate Glass Artifacts from the Warring States Period in China

Potash–lime silicate (K₂O–CaO–SiO₂) glass dated to the Warring States Periods is one of the earliest glass types that have been found in China, but scientific research about this type of glass is scarce at home and abroad. In the present study, a total of 23 potash–lime silicate glass samples of the Warring States Period, excavated from different areas of China, were analyzed noninvasively using a portable X-ray fluorescence spectrometer (pXRF). The chemical composition of these K₂O–CaO–SiO₂ glasses was analyzed and compared with that of the potash silicate (K₂O-SiO₂) glasses of the Han Dynasties. The possible raw materials used to make the ancient K₂O–CaO–SiO₂ glasses were discussed. It appears that the ancient K₂O–CaO–SiO₂ glasses were produced in China and the potash glasses were of versatile origins. This research provides useful clues to trace the technical development of ancient Chinese glass.     

Silica–zirconium phosphate–phosphoric acid composites: preparation,proton conductivity and use in gas sensors

Mesoporous composites made of silica and α-zirconium phosphate (SiO₂·xZrP) were synthesized starting from mixtures of delaminated ZrP dispersions and tetrapropylammonium oligosilicate solutions. The surface area of the composites reaches a maximum of 700 m²/g for x≈0.02, while the average pore diameter is about 40 Å for x in the range 0.05–0.35. In order to increase proton conductivity at low relative humidity (r.h.), SiO₂·xZrP·yH₃PO₄ composites were prepared and characterised by ²⁹Si and ³¹P MAS NMR and conductivity measurements. At 100 °C and 6% r.h., the conductivity of the composites, with H₃PO₄ loadings of 80% of the pore volume, rises from 5×10⁻⁴ to 2×10⁻² S/cm for x decreasing between 0.35 and 0.05, as a consequence of the concomitant increase of pore volume. For the composite with x=0.18, the dependence of conductivity on H₃PO₄ loading was also investigated at different temperatures and r.h. values. The combined increase of humidity, temperature and H₃PO₄ loading results in an increase of conductivity from 1×10⁻⁷ S/cm (y=0.09, T=25 °C, 0% r.h.) to 4×10⁻² S/cm (y=0.61, T=100 °C, 30% r.h.). SiO₂·0.18ZrP·0.61H₃PO₄ was also tested as a proton electrolyte in an oxygen sensor consisting of a disk of the composite sandwiched between a platinum sensing electrode and a reference electrode based on Ni_1−xO. The sensor is able to detect O₂ at room temperature in a dry environment with a response time of 20–30 s.     

Synthesis and Characterization of Sol–Gel-Derived SiO2–CaO Particles: Size Impact on Glass (Bio)Properties

Four highly bioactive glasses in a binary SiO₂–CaO system are prepared following a sol−gel method using Ca(OH)₂ as a calcium precursor. In the synthesis of glass according to the modified Stöber method, Ca(OH)₂ suspended in polyethylene glycol allows the elimination of the presence of calcite and the increase of ammonia concentration causes formation of spherical particles with different sizes in the range of 26–266 nm. The relation among the size and properties, including bioactivity, of the glass particles is evaluated. New glasses that vary in composition (10–25 wt% CaO), porosity (15–113 m² g⁻¹), and hydroxyl groups content greatly enhance the formation process of hydroxyapatite (HA) in simulated physiological fluids. For all glasses, superior apatite-mineralization ability in time as short as 2 h in the physiological-like buffer is achieved, thus exceeding the bioactivity of the known bioactive glasses, including 45S5 glass (Bioglass). The assessment of the safety and toxicity profile of the obtained glasses is verified in a wide range of concentrations (1–1000 µg mL⁻¹) against human dermal fibroblasts and MC3T3 mouse osteoblast precursors, but also to human erythrocytes by determining hemocompatibility. Two glasses of different sizes, 73 and 266 nm, are promising and warrant further research.     

含分散第二相粒子的离子导体AgI的电学性质

测量了纯AgI和AgI含分散第二相粒子(简称DSPP)η-Al₂O₃(0.05μm)和γ-Fe₂O₃(0.6μm)的电导率随成分和温度的变化。β-AgI的电导率随加入第二相粒子含量的增加而明显增加,大约在40—50mol％时电导出现极大值。室温下含DSPP的电导率比纯AgI增加二到三个数量级。含DSPP的α-AgI电导率降低,激活能增加。电导率测量和差热分析(DTA)表明第二相的加入明显地影响AgI从α相到β相的相转变温度,AgI(η-Al₂O₃,50mol％)α相到β相的转变温度比纯AgI低17℃。室温下对AgI(γ-Fe₂O₃,50mol％)的直流极化实验表明电子电导是n型导体,电子电导率与总电导率相比可以忽略。 关键词：     

Mesopore size dependence of the ionic diffusivity in alumina based composite lithium ionic conductors

Ordered-mesoporous Al₂O₃ was synthesized by a sol–gel method using neutral copolymer surfactants as structure-directing agents. The pore size was controlled over the 3–15 nm range by the use of various surfactants. Composites composed of the synthesized mesoporous Al₂O₃ and a lithium ion conductor (LiI) were prepared. The maximum dc electrical conductivity, 2.6 × 10^− 4 S cm^− 1 at 298 K, was observed for 50 LiI·50 Al₂O₃ composite with 4.2 nm average mesopore size, which was considerably higher than the previously reported LiI-alumina composites. A systematic dependence of conductivity upon pore size was observed, in which conductivity increased with decreasing pore size, except for samples with a pore size of 2.8 nm. The lithium ion diffusion coefficient determined by the ⁷Li pulsed field gradient nuclear magnetic resonance (PFG-NMR) showed excellent agreement with the measured conductivity calculated by the Nernst-Einstein equation. On the other hand, lithium migration activation energies obtained by quasielastic neutron scattering (QENS) and ⁷Li NMR spin-lattice relaxation time (T₁) were considerably smaller than those obtained from electrical conductivity and PFG-NMR. This could be explained by the ion migration mechanism in heterogeneous composites and a possible enhancement of conductivity in mesoscopically confined spaces.     

Ion transport and structure in silver borate glasses

A study of ionic conductivity in silver borate glasses is presented, which includes (i) a full characterization of the ion transport properties in the AgI:Ag₂O:B₂O₃ glasses, (ii) results for glasses where iodine is totally or partially substituted by another halide, (iii) mixed-cation effects. A substantial portion of the paper discusses the relationship between local order and ion transport properties of borate glasses and vitreous electrolyte systems.     

Vitreous solid state electrolytes in the system of RNO3–Zn(NO3)2–KHSO4–P2O5

The structure and electric conductivity of glasses in the system RNO₃–Zn(NO₃)₂–KHSO₄–P₂O₅ (R = Na, K) obtained at different temperatures were investigated by IR and impedance spectroscopy. Glasses fused at 250–350 °C demonstrated an increase of their ionic conductivity in 10³ times in comparison with the same compositions fused at 550 °C. The influence of the chemical composition on the structure and properties of the obtained glasses was analyzed. It is proposed that the high ionic conductivity of glasses obtained at low temperatures is related to the incorporation of the nitrate ions between long (PO₃)_n chains, similar to the iodide ions; this resulted in a maximal coordination of the local conduction space for the cation associated with a disordered glass network.     

Flowability and Mechanical and Thermal Properties of Nylon 6/Ethylene bis-Stearamide/Carboxylic Silica Composites

Nylon 6 (PA 6)/ethylene bis-stearamide (EBS)/SiO₂- carboxylic acid-functionalized silica nanoparticles (COOH) composites were prepared by in-situ polymerization of caprolactam. SiO₂-COOH was used to enhance the compatibility between SiO₂ and PA 6 matrix. For comparison, pure PA 6 and PA 6/EBS composites were also prepared via the same method. The PA 6/EBS/SiO₂-COOH composites with low content of EBS and SiO₂-COOH had greater melt-flow index (MFI) (the value of MFI increased by 50%–80%) than the pure PA 6. The results of mechanical properties showed almost no decrease in the tensile strength of PA 6/EBS/SiO₂-COOH composites, with the bending strength decreasing by 17%–21%. However, the Izod impact strength of the PA 6/EBS/SiO₂-COOH composites was greatly improved compared with pure PA 6, which indicated that the toughness of PA 6/EBS/SiO₂-COOH had been greatly improved. The morphology of Izod impacted fractured surfaces of PA 6/EBS/SiO₂-COOH was observed by scanning electron microscopy. The results revealed that the PA 6/EBS/SiO₂-COOH composites presented a typical ductile fracture behavior with large amounts of long and large strip-like cracks. When the content of SiO₂-COOH was 0.2 wt%, the SiO₂-COOH particles were uniformly dispersed over the entire body of the PA 6 matrix. The results from differential scanning calorimetry indicated that the melting point (T_m), degree of crystallinity (X_c), and crystallization temperatures (T_c) of PA 6/EBS/SiO₂-COOH composites were lower than the pure PA 6.     

129I-Mössbauer spectroscopic study of iodide-containing chalcogenide glasses

¹²⁹I-Mössbauer spectroscopy was used to study the short-range order in I-containing chalcogenide glasses. It was found that AsXI glasses, where X=S or Se, are molecular solids composed from molecular units of arsenic iodide and arsenic chalcogenide. The local environment of iodide ions in ternary superionic conducting glasses AgI?Ag₂S?As₂S₃ is similar to that in the crystalline superionic conductor Ag₃SI and differs distinctly from iodide local order in binary vitreous alloys AgI?As₂S₃ and crystalline AgI.¹²⁹I-Mössbauer spectra of all glasses were fitted satisfactory, when a distribution of the electric-quadrupole coupling constant is taken into account.     

Nanotubes of piezoelectric BNT–BT0.08 obtained from sol–gel precursor

The results of investigations of porous glasses (PG) and porous glasses–ammonium hydrogen sulfate ferroelectric nanocomposites (AHS–PG) are presented. On the basis of dielectric and calorimetric measurements it was shown that in the AHS–PG nanocomposites with average pore size of 44, 68, 95, and 320 nm the anomalies of dielectric permittivity and specific heat similar to those in bulk crystals AHS are observed. An influence of the mean value of pores sizes on the ferroelectric phase transition temperatures of AHS nanocrystals embedded into the porous matrices was determined. It was shown that in AHS–PG dispersion of the dielectric permittivity is observed in both para- and ferro-electric phases and above room temperature AHS–PG nanocomposites exhibit the ionic conductivity.     

Preparation of proton conductive composites with CsHSO4/CsH2PO4 and phosphosilicate gel

New composite materials were prepared using cesium hydrogen sulfate (CsHSO₄) or cesium dihydrogen phosphate (CsH₂PO₄) and phosphosilicate gel (P₂O₅–SiO₂ gel). In X-ray diffraction patterns of these composites, diffraction peaks due to Cs₂H₅(SO₄)₂(PO₄) and CsH₅(PO₄)₂ were observed for CsHSO₄–(P₂O₅–SiO₂ gel) composites and CsH₂PO₄–(P₂O₅–SiO₂ gel) composites, respectively. These composites showed high conductivities in the order of 10^− 3 S cm^− 1 at 150 °C due to melting of Cs₂H₅(SO₄)₂(PO₄) or CsH₅(PO₄)₂ in the composites. In the cooling process, the CsHSO₄–(P₂O₅–SiO₂ gel) composites kept relatively high conductivity to 110 °C where solidification of Cs₂H₅(SO₄)₂(PO₄) occurs, whereas CsH₂PO₄–(P₂O₅–SiO₂ gel) composites showed relatively high conductivity continuously to ambient temperature.     

Hollow Silica Spheres Embedded in a Porous Carbon Matrix and Its Superior Performance as the Anode for Lithium‐Ion Batteries

Silica (SiO₂) is regarded as one of the most promising anode materials for lithium‐ion batteries due to the high theoretical specific capacity and extremely low cost. However, the low intrinsic electrical conductivity and the big volume change during charge/discharge cycles result in a poor electrochemical performance. Here, hollow silica spheres embedded in porous carbon (HSS–C) composites are synthesized and investigated as an anode material for lithium‐ion batteries. The HSS–C composites demonstrate a high specific capacity of about 910 mA h g^?1 at a rate of 200 mA g^?1 after 150 cycles and exhibit good rate capability. The porous carbon with a large surface area and void space filled both inside and outside of the hollow silica spheres acts as an excellent conductive layer to enhance the overall conductivity of the electrode, shortens the diffusion path length for the transport of lithium ions, and also buffers the volume change accompanied with lithium‐ion insertion/extraction processes.     

Structure determination of AgPO3 and (AgPO3)0.5(AgI)0.5 glasses by neutron diffraction and small angle neutron scattering

Neutron diffraction and small angle neutron scattering (SANS) were performed on AgPO₃ and (AgPO₃)_0.5(AgI)_0.5 glasses. AgPO₃ glass is made up of long chains of PO₄ tetrahedra joined together by Ag atoms. When silver iodide is added, the radial distribution function shows a large peak at 2.83 Å, due to AgI interactions. AgI does not modify the network forming unit. The existence of small clusters is confirmed by analysing the coordination number of AgI pairs obtained by subtracting the experimental structure function of the AgPO₃ glass from that of the corresponding AgI-doped glasses. A rough estimation of their size is given by SANS experiments. Not all the AgI pairs are involved in AgI cluster units. The compatibility of the results obtained with recent structural investigations by non diffractometric techniques is examined.     

Ni-GDC microtubular cermets

Ni-GDC cermet tubes (~ 3 mm inside diameter, 0.3–0.4 mm wall thickness and ～ 100 mm in length) with different amounts of porosity have been prepared by sintering of NiO-Ce_0.9Gd_0.1O_1.95 (NiO-GDC) nanopowders and further reduction. The NiO-GDC nanopowders were synthesized by chemical route and the different pore density was obtained by modifying the processing conditions (calcining and adjustment of carbonous remains).Ni-GDC cermets were obtained from the sintered NiO-GDC composites using reduction treatment at 700 °C for 3 h in reducing atmosphere (5 vol.% H₂–95 vol.% Ar). After the reduction process, tubes with 25–32% porosity were obtained. Gas permeability and Hg porosimetry studies were used to evaluate permeability, pore distribution and pore density. Electrical conductivity studies of the cermets were also performed.     

Synthesis and electrochemical properties of Li2S–B2S3–Li4SiO4

New Li⁺ ion-conductive glasses Li₂S–B₂S₃–Li₄SiO₄ were synthesized by rapid quenching, and they were transformed into glass ceramics by heat treatment. The heat treatment increased the ionic conductivities of the Li₄SiO₄-doped glasses, and the highest ionic conductivity observed in the system was 1.0 × 10^− 3 S cm^− 1 at room temperature. The glass ceramics were highly stable against electrochemical oxidation with a wide electrochemical window of 10 V.