Poly(vinylidenefluoride)-hexafluoropropylene–methyl N-methylpyrrolidinium-N-acetate trifluoromethanesulfonylimide–lithium trifluoromethanesulfonylimide gel electrolytes

New polymer-ionic liquid-lithium salt gel electrolytes (PILGEs) were prepared using poly(vinylidenefluoride)-hexafluoropropylene copolymer (PVdF(HFP)), methyl N-methylpyrrolidinium-N-acetate trifluoromethanesulfonimide ([MMEPyr][TFSI]), and lithium trifluoromethanesulfonylimide (LiTFSI) in order to investigate the effects of ionic liquids containing an ester group on the electrochemical properties of polymer gel electrolytes. Free standing ionic gels consisting of PVdF(HFP), [MMEPyr][TFSI], and LiTFSI were prepared in a range of weight ratio of polymer/[MMEPyr][TFSI]/LiTFSI = 1/2/0.1 ～ 1. Ionic conductivities for the prepared PILGEs were measured with changing temperature and weight ratio of LiTFSI and the obtained values were found to be reasonable (10^?4 S cm^?1) over the operating temperatures.     

Preparation of SiO2–SiC composites with a precursor method

SiO₂–SiC composite particles were prepared through a hybrid sol–gel precursor process. Compacts were prepared by using a conventional sintering process. The techniques of DSC–TG, SEM and XRD were use to characterize the composite particles and the sintered compacts. It was found that a core–shell structure was constructed in the composite particles with cores of SiC and shells of amorphous SiO₂. Nucleation of SiO₂ occurred at about 1200 °C. The optimized sintering temperature for 30SiO₂–70SiC (vol.%) composites was about 1400 °C with a relatively homogeneous microstructure. The maximum density was about 2.03 g cm^?3.     

Mechanical properties of nano-grain SiO2 glass prepared by spark plasma sintering

Silicon carbide (SiC) layers were deposited on silica (SiO₂) glass powder by rotary chemical vapor deposition (RCVD) to form SiO₂ glass (core)/SiC (shell) powder; this powder was consolidated by spark plasma sintering (SPS). SiO₂ glass powder with a particle size of 250 nm was coated with 5–10-nm-thick SiC layers. The resultant SiO₂ glass (core)/SiC (shell) powder was consolidated to form a nano-grain SiO₂ glass composite at a relative density above 90% by SPS in the sintering temperature range of 1573–1823 K. The Vickers hardness and fracture toughness of the SiO₂ glass composite at 1723 K were found to be 14.2 GPa and 5.4 MPa m^1/2, respectively.     

Porous membrane based on chitosan–SiO2 for coin cell proton battery

Porous chitosan–SiO₂ membranes were prepared by ultrasonic mixing solution-cast and porogen removal method at different SiO₂ weight ratios. To remove SiO₂ from chitosan membranes, NaOH solution was used to dissolve SiO₂. Porous chitosan:SiO₂ membrane with the weight ratio 1:2 produced optimum average pore size (8.5 μm) with an amorphous structure and the highest water uptake (257.1%). Further soaking of this membrane in NH₄CH₃COO electrolyte solution for two days produced the highest conductivity (3.6×10⁻³ S cm⁻¹) and optimum breakdown voltage (1.8 V). Fabrication of coin cell proton battery displayed an open circuit potential of 1.5 V for 7 days, maximum power density (6.7 mW cm⁻²) and small current resistance (0.03 Ω). The specific discharge capacities obtained from discharge profile of 39.7 mA h g⁻¹ (0.5 mA) and 43.8 mA h g⁻¹ (1.0 mA) increased as the discharge currents were increased. These results showed that a porous chitosan–SiO₂ membrane is suitable membrane for the proton batteries.     

Glasses for laser joining of zirconia ceramics

Laser joining of ZrO₂ ceramics using glasses and glass ceramics as sealing components requires optimized systems. The ternary systems SiO₂–BaO–B₂O₃ and BaO–SrO–SiO₂ were selected as a basis for development of suitable glass compositions for the laser joining process. Additives such as CaO, TiO₂, Al₂O₃, and MgO were used to control the crystallization processes and hence the thermal expansion coefficients during glass synthesis. The glass viscosity, the strength of the ceramic-glass-ceramic joint, and the joint tightness are other important glass properties which were optimized for the laser process. For glass G018-345, this yielded strengths of up to 225 MPa (Weibull modulus of m = 8.6) and He leak rates of up to 4.3 × 10⁻⁵ mbar l s⁻¹. Because of the varying viscosities obtained, the optimized glass systems could be used selectively in a temperature range of 700–900 °C.     

Effect of composition on sinter-crystallization and properties of low temperature co-fired α-cordierite glass–ceramics

This article investigates effect of composition, including SiO₂ and impurity defined to contain K₂O, Na₂O, Fe₂O₃, etc., from K-feldspar, on sinter-crystallization and properties of the low temperature co-fired α-cordierite glass–ceramics. Increasing impurity content from 5.72 wt% to 9.16 wt% leads to enhanced crystallinity, formation of leucite and more pores but the crystallinity and porosity decreased with a further increase to 10.8 wt%. The main impurity K₂O is critical for formation of α-cordierite and leucite. Only α-cordierite was precipitated from the glasses with different SiO₂ contents but an increase of SiO₂ content slightly improves their densification. The impurity and SiO₂ contents greatly affect the properties of glass–ceramics. Notably, some glass–ceramics from K-feldspar show high densification at low temperature, low dielectric constant (6–8), low loss (about 0.005), appropriate linear CTEs (4.32–5.87 × 10⁻⁶ K⁻¹) and flexural strength (above 100 MPa), all of which meet the requirements of LTCC substrates.     

Transparent and high infrared reflection film having sandwich structure of SiO2/Al:ZnO/SiO2

New transparent and high infrared reflection films having the sandwich structure of SiO₂/Al:ZnO(AZO)/SiO₂ were deposited on the soda-lime silicate glass at room temperature by radio frequency (R.F.) magnetron sputtering. The optical and electrical properties of SiO₂ (110 nm)/AZO (860 nm)/SiO₂ (110 nm) sandwich films were compared with those of single layer AZO (860 nm) films and double layer SiO₂ (110 nm)/AZO (860 nm) films. The results show that these sandwich films exhibit high transmittance of over 85% in the visible light range (380–760 nm), and low reflection rate of below 4.5% in the wavelength range of 350–525 nm, which is not shown in the conventional single layer AZO (860 nm) films and double layer SiO₂ (110 nm)/AZO (860 nm) films. Further these sandwich films display a low sheet resistance of 20 Ω/sq by sheet resistance formula and high infrared reflection rate of above 80% in the wavelength range of 15–25 μm. In addition, the infrared reflection property of these sandwich films is determined mainly by the AZO film. The outer SiO₂ film can diminish the interference coloring and increase transparency; the inner SiO₂ film improves the adhesion of the coating to the glass substrate and prevents Ca²⁺ and Na⁺ in the glass substrate from entering the AZO film.     

Transport properties of sealants for high-temperature electrochemical applications: RO–BaO–SiO2 (R = Mg,Zn) glass–ceramics

The electrical properties and oxygen permeability of glass–ceramics 55SiO₂–27BaO–18MgO, 55SiO₂–27BaO–18ZnO and 50SiO₂–30BaO–20ZnO (%mol), which possess thermal expansion compatible with that of yttria-stabilized zirconia (YSZ) solid electrolytes, were studied between 600 and 950 °C in various atmospheres. The ion transference numbers, determined by the modified electromotive force (e.m.f.) technique under oxygen partial pressure gradients of 21 kPa/(1–8) × 10² Pa and 21 kPa/(1 × 10⁻¹⁸–2 × 10⁻¹²) Pa, are close to unity both under oxidizing and reducing conditions. The electronic contribution to the total conductivity increases slightly on increasing temperature, but is lower than 2% and 7% for the Zn- and Mg-containing compositions, respectively. The conductivity values measured by impedance spectroscopy vary in the range (1.4–7.8) × 10⁻⁶ S/cm at 950 °C under both oxidizing and reducing conditions, with activation energies of 122–154 kJ/mol and a minor increase in H₂-containing atmospheres, indicating possible proton intercalation. In agreement with the electrical measurements which indicate rather insulating properties of the glass–ceramics, the oxygen permeation fluxes through sintered sealants and through sealed YSZ/glass–ceramics/YSZ cells are very low, in spite of an increase of 15–40% during 200–230 h under a gradient of air/H₂–H₂O–N₂ due to slow microstructural changes.     

Tetrachloroferrate containing ionic liquids: Magnetic- and aggregation behavior

The magnetic behavior of a binary salt of tricaprylylmethylammonium tetrachloroferrate and tricaprylylmethylammonium chloride, [A336][FeCl₄]_0.73[Cl]_0.27, was evaluated. With a magnetic susceptibility of 0.011 emu mol^? 1 this binary salt exhibited a remarkable response to an external magnetic field. Dynamic light scattering (DLS) measurements allowed to study the aggregation behavior of [A336][FeCl₄]_0.73[Cl]_0.27 as well as of further magnetic ionic liquids [PR_6,6,6,14][FeCl₄] and (BMIM)[FeCl₄] in ethylacetate and ethanol.     

Synthesis and characterization of magnetic polyHIPEs with humic acid surface modified magnetic iron oxide nanoparticles

Magnetic macroporous polymer monoliths have been prepared using styrene/divinylbenzene (S/DVB) high internal phase emulsions (HIPEs) as templates. Humic acid surface modified iron oxide magnetic nanoparticles (Fe₃O₄@HA) have been used to prepare magnetic emulsion templates. The effect of magnetic particle concentration has been investigated by changing the ratio of Fe₃O₄@HA nanoparticles in the continuous phase. Highly macroporous polymers with magnetic response were obtained by the removal of the internal phase after the curing of emulsions at 80 °C. Fe₃O₄@HA particles were characterized by XRD and FTIR. The porosity, pore morphology and magnetic properties of the macroporous polymers were characterized as a function of the Fe₃O₄@HA concentration by scanning electron microscopy (SEM), Brunauer–Emmet–Teller (BET) molecular adsorption method and vibrating sample magnetometry (VSM), respectively. BET and VSM measurements demonstrated that the specific surface area and the saturation magnetization of the polymer monoliths were changed according to the Fe₃O₄@HA concentration between 8.77–35.08 m² g^?1 and 0.63–11.79 emu g^?1, respectively. Resulting magnetic monoliths were tested on the adsorption of Hg(II) and atomic absorption spectroscopy (AAS) was used to calculate the adsorption capacities. The maximum adsorption capacity of the magnetic monoliths was calculated to be 20.44 mmol g^?1 at pH 4.     

Effects of La2O3–B2O3 on the flexural strength and microwave dielectric properties of low temperature co-fired CaO–B2O3–SiO2 glass–ceramic

The La₂O₃–B₂O₃ (LB) addition, synthesized using the traditional solid-state reaction process, was chosen as a novel sintering aid of the low temperature co-fired CaO–B₂O₃–SiO₂ (CBS) glass–ceramic. The effects of LB on the flexural strength and microwave dielectric properties have been investigated. The LB addition promotes the crystallization of the CaSiO₃ but high amount of the LB addition leads to the formation of more pores. The CBS sample with 4 wt% LB addition sintered at 850 °C for 15 min shows good properties: flexural strength = 193 MPa, ?_r = 6.26 and loss = 9.96 × 10^?4 (10 GHz).     

An intriguing NO2⋯π and CN⋯π interactions in [1-(4′-nitrobenzyl)pyrazinium][Ni(mnt)2]: Crystal structure,magnetic property and DFT calculation

A charge-transfer compound, [NO₂BzPz][Ni(mnt)₂] (NO₂BzPz⁺ = 1-(4′-nitrobenzyl)pyrazinium and mnt^2? = maleonitriledithiolate), has been structurally characterized, which shows rare noncovalently intermolecular interactions between lone-pair electron and electron-deficient pyrazine rings (NO₂?π and CN?π), theoretical analysis reveals that such intermolecular interactions can be attributed to Coulomb interaction. The paramagnetic [Ni(mnt)₂]^? anions in [NO₂BzPz][Ni(mnt)₂] form a dimerized stack and strong antiferromagnetic coupling interaction is observed in such a spin dimer which lead to weak paramagnetic feature in this compound.     

Mesoporous TiO2–SiO2 aerogels with hierarchal pore structures

Freestanding blocks of binary oxides, TiO₂–SiO₂ aerogel containing highly ordered mesophase structures were successfully prepared by a new synthesis method involving partial solvent evaporation followed by supercritical extraction and drying. The new method allows the routine preparation of large, crack-free aerogels of high titanium content (i.e., Ti/Si ? 0.75 or up to 50 wt.% Ti), ordered mesopores (i.e., 2–20 nm), large surface area (i.e., 400–900 m² g^?1) and pore volume (i.e., 0.7–2.6 cm³ g^?1). Aerogels with well-ordered mesopores were obtained for Ti/Si atom ratios of 0.04–0.08. The size of ordered mesopore domains decreases with increasing titanium loading, and TS75 aerogels with Ti/Si = 0.75 display discontinuous microdomains of ordered mesoporosity within disordered phases interspersed with crystalline anatase TiO₂. The greater permeability of the TS75 pore network resulted in fifteen times better activity for photocatalytic oxidation of airborne trichloroethylene compared to commercial Degussa P25 TiO₂ and more than twice that TiO₂–SiO₂ aerogel (TS100) of similar titanium loading but with disordered and tortuous pore network.     

Density and Young׳s Modulus of ternary glasses close to the eutectic composition in the CaO–Al2O3–SiO2-system

The elastic properties and the density of ternary glass forming systems within the CaO–SiO₂–Al₂O₃-system (CAS) were evaluated. Different glass compositions near the lowest eutectic (1170 °C) composition within the CaO–Al₂O₃–SiO₂-system have been melted from pure raw materials. Their target compositions differed not more than 4 wt% for each component. Exact chemical compositions were measured by x-ray fluorescence. The density, and acoustic properties were determined and the Young׳s Moduli were derived herefrom. It was of special interest to obtain information on these properties and their dependencies upon small variations in the composition. The density values were between 2.600 and 2.667 g cm⁻³ and the packing density factors V_p of the oxides glasses using the ionic radii of Pauling were in the range from 0.559 to 0.571. The determined data were compared to different model calculations. Density model calculations show relative deviations between 2 and 6%. The values calculated from the model for Young׳s Modulus by Makishima and Mackenzie (1973) [1] were somewhat smaller than the measured ones. The correction by Rocherulle et al. (1989) [3] of the Makishima model showed better agreement with the measured values.     

Application of BaO–CaO–Al2O3–B2O3–SiO2 glass–ceramic seals in large size planar IT-SOFC

BaO–CaO–Al₂O₃–B₂O₃–SiO₂ (BCAS) glass–ceramics can be used as sealant for large size planar anode-supported solid oxide fuel cells (SOFCs). BCAS glass–ceramics after heat treatment for different times were characterized by means of thermal dilatometer, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the coefficients of thermal expansion (CTE) of BCAS glass–ceramics are 11.4×10⁻⁶ K⁻¹, 11.3×10⁻⁶ K⁻¹ and 11.2×10⁻⁶ K⁻¹ after heated at 750 °C for 0 h, 50 h, and 100 h, respectively. The CTE of BCAS matches that of YSZ, Ni–YSZ and the interconnection of SOFC. Needle-like barium silicate, barium calcium silicate and hexacelsian are crystallized in the BCAS glass after heat-treatment for above 50 h at 750 °C. The glass–ceramics green tape prepared by aqueous tape casting can be directly applied in sealing the cell of SOFCs with 10 cm×10 cm. The open circuit voltage (OCV) of the cell keeps 1.19 V after running for 280 h at 750 °C and thermal cycling 10 times from 750 °C to room temperature. The maximum power density is 0.42 W/cm² using pure H₂ as fuel and air as oxidation gas. SEM images show no cracks or pores exist in the interface of BCAS glass–ceramics and the cell.     

TaB2–SiC–Si multiphase oxidation protective coating for SiC-coated carbon/carbon composites

To improve the oxidation resistance of the carbon/carbon (C/C) composites, a TaB₂–SiC–Si multiphase oxidation protective ceramic coating was prepared on the surface of SiC coated C/C composites by pack cementation. Results showed that the outer multiphase coating was mainly composed of TaB₂, SiC and Si. The multilayer coating is about 200 μm in thickness, which has no penetration crack or big hole. The coating could protect C/C from oxidation for 300 h with only 0.26 × 10^?2 g²/cm² mass loss at 1773 K in air. The formed silicate glass layer containing SiO₂ and tantalum oxides can not only seal the defects in the coating, but also reduce oxygen diffusion rates, thus improving the oxidation resistance.     

Preparation of mullite monoliths with well-defined macropores and mesostructured skeletons via the sol–gel process accompanied by phase separation

Mullite monoliths with well-defined macropores and mesostructured skeletons have been prepared via the sol–gel process accompanied by phase separation in the presence of poly(ethylene oxide) (PEO). Gelation of Al₂O₃–SiO₂ binary system with chloride salts as an additional precursor has been mediated by propylene oxide (PO) as an acid scavenger, while PEO worked as a phase-separation inducer. The dried gel and that heat-treated at 800 °C are amorphous, and γ-Al₂O₃ or Si–Al spinel phase nanocrystals are crystallized at 900–1000 °C. After heat-treated at and above 1100 °C for 5 h, the complete crystalline mullite is generated, and the macroporous monoliths in large dimensions of more than 15 mm × 15 mm × 10 mm are obtained. Heat-treatment at 200–1400 °C does not basically spoil the macroporous structure of monoliths, while decreases the macropore size and significantly alters the phase compositions and micro-mesoporous structure.     

Preparation and characterization of BaCe0.95Tb0.05O3−α hollow fibre membranes for hydrogen permeation

BaCe_0.95Tb_0.05O_3?α (BCTb) perovskite hollow fibre membranes were fabricated by spinning the slurry mixture containing 66.67 wt% BCTb powder, 6.67 wt% polyethersulphone (PESf) and 26.67 wt% N-methyl-2-pyrrolidone (NMP) followed by sintering at elevated temperatures. The influence of sintering temperature on the membrane properties was investigated in terms of crystal phase, morphology, porosity and mechanical strength. In order to obtain gas-tight hollow fibres with sufficient mechanical strength, the sintering temperature should be controlled between 1350 and 1450 °C. Hydrogen permeation through the BCTb hollow fibre membranes was carried out between 700 and 1000 °C using 50% H₂–He mixture as feed on the shell side and N₂ as sweep gas in the fibre lumen. The measured hydrogen permeation flux through the BCTb hollow fibre membranes reached up to 0.422 μmol cm^?2 s^?1 at 1000 °C when the flow rates of the H₂–He feed and the nitrogen sweep were 40 mL min^?1 and 30 mL min^?1, respectively.     

Mass transportation in diethylmethylammonium trifluoromethanesulfonate for fuel cell applications

To use the protonic mesothermal fuel cell without humidification, mass transportation in diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), trifluoromethanesulfuric acid (TfOH)-added [dema][TfO], and phosphoric acid (H₃PO₄)-added [dema][TfO] was investigated by electrochemical measurements. The diffusion coefficient and the solubility of oxygen were ca. 10⁻⁵ cm² s⁻¹ and ca. 10⁻³ M (=mol dm⁻³), respectively. Those of hydrogen were a factor of 10 and one-tenth compared to oxygen, respectively. The permeability, which is a product of the diffusion coefficient and solubility, of oxygen and hydrogen were almost the same for the perfluoroethylenesulfuric acid membrane and the sulfuric acid solution; therefore, these values are suitable for fuel cell applications. On the other hand, a diffusion limiting current was observed for the hydrogen evolution reaction. The current corresponded to ca. 10⁻¹⁰ mol cm⁻¹ s⁻¹ of the permeability, and the diffusion limiting species was the hydrogen carrier species. The TfOH addition enhanced the diffusion limiting current of [dema][TfO], and the H₃PO₄ addition eliminated the diffusion limit. The hydrogen bonds of H₃PO₄ or water-added H₃PO₄ might significantly enhance the transport of the hydrogen carrier species. Therefore, [dema][TfO] based materials are candidates for non-humidified mesothermal fuel cell electrolytes.     

Improvement of biphasic polymerization by application of binary ionic liquid mixture

The mixture of two ionic liquids, 1-n-butyl-3-methylimidazolium and 1-(2-phenylethyl)-3-methylimidazolium chloroaluminates, [C₄-mim][AlCl₄] and [PhC₂-mim][AlCl₄], were applied as a medium to immobilize the Cp₂TiCl₂ titanocene catalyst for biphasic ionic liquid/hexane ethylene polymerization. The system makes possible to perform the reaction at lower temperatures, below the melting temperature of the aralkyl ionic liquid. A better separation of the ionic liquid phase was observed and an easier mass transfer of the polymer product from the ionic liquid to the hexane phase was obtained. The polyethylene reveals bimodal distribution of molecular weight. It is characterized by a high bulk density (500 g/dm³) and crystallinity degree (86%). The recycling of the ionic liquid medium containing the catalyst activated by AlEtCl₂, results in the highest yield obtained in such systems (550 kg PE(mol Ti)⁻¹).