Structural and electrical properties of Cr-doped SrTiO3 porous materials

Series of single-phase materials with assumed formula SrTi_1?xCr_xO₃ (where x = 0, 1, 4, 6 mol.%) were obtained by sol-gel method. The structure and microstructure of materials were characterised by X-ray diffraction and scanning electron microscopy methods. Moreover, the study of electrical properties and evaluation of chemical stability in CO₂/H₂O atmosphere was performed by electrochemical impedance spectroscopy and thermogravimery methods, respectively. The possibility of participation of Cr-doped strontium titanate in oxidation–reduction processes was analysed by temperature-programed reduction (TPR) and temperature-programed oxidation (TPOx) measurements. The changes of lattice parameters together with XPS analysis, the Seebeck coefficient measurements results and TPR profiles obtained for SrTi_1?xCr_xO₃ materials prove the presence of chromium on +3 and +6 oxidation stages. Thus, chromium can be treated as both acceptor- and donor-type dopant in the SrTiO₃ structure. The Cr³⁺/Cr⁶⁺ ratio strongly affects the electrical properties, as the change of conduction mechanism was observed. The results of performed stability test clearly indicate that incorporation of chromium into SrTiO₃ structure results with decrease of chemical stability in CO₂ atmosphere.     

Method for analysis of 68 organic contaminants in food contact paper using gas and liquid chromatography coupled with tandem mass spectrometry

Food contact materials (FCMs) have been reported as a source of various xenobiotics. This study investigates the possibility of simultaneous analysis of 68 potential contaminants in paper FCMs, specifically phthalates, polycyclic aromatic hydrocarbons, photoinitiators, bisphenols, and polyfluorinated compounds. Target compounds were co-isolated using a technique based on ultrasonic extraction by mixture of acetonitrile and water followed by QuEChERS-like liquid–liquid partition in the presence of inorganic salts. Resulting extracts were analyzed using gas and high performance liquid chromatography coupled with tandem mass spectrometry (GC–MS/MS, HPLC–MS/MS). Acceptable recoveries (70–120%) and RSDs (<20%) were achieved for most of the analytes at spiking levels of 0.05, 0.2 and 1 mg/kg. LOQs ranged from 0.0013 to 0.22 mg/kg. The proposed method was successfully applied to analysis of 15 real samples. Complex mixtures of contaminants reaching levels up to 48 mg/kg were identified in the samples.     

A refined FSDT for the static analysis of functionally graded sandwich plates

This paper presents a static analysis of functionally graded plates (FGPs) by using a new first shear deformation theory (FSDT). This theory contains only four unknowns, with is even less than the classical FSDT. In this paper a simply supported FG square sandwich plate is subjected to a bi-sinusoidal load. The governing equations for static bending analysis are derived by employing the principle of virtual works. These equations are then solved via Navier-type, closed form solutions. The accuracy of the present theory is ascertained by comparing it with various available solutions in the literature.     

Novel polymer composites of RuO2@nBaTiO3/PVDF with a high dielectric constant

The dielectric properties of a novel polymer dielectric material were investigated. The conductive phase of RuO₂ was synthesized for deposition on the surface of a nanosized BaTiO₃ (nBT). The RuO₂@nBT hybrid particles were incorporated into a poly (vinylidene fluoride) (PVDF) as a three-phase composite (RuO₂@nBT/PVDF). The obtained dielectric constant (ε′) was significantly high (3837.16) for the composite with a volume fraction of $f_{Ru{O}_2@nBT}$ = 0.50. The large interfacial polarization between the RuO₂?nBT and RuO₂?PVDF interfaces considerably increased the value of ε′. Therefore, interfacial polarization is a critical factor in improving the dielectric properties. The dielectric behavior of the RuO₂@nBT/PVDF composites can be described using the effective medium percolation theory model, which indicates the significant contributions of the conductive RuO₂ phase and high-permittivity nBT phase.     

Method for measuring thermal contact resistance of graphite thin film materials

Thermal contact resistance (TCR) is an important parameter in thermal analysis of materials. Because of many influential factors, it is difficult to find a general model or computational formula to calculate the TCR of a solid interface. In many engineering applications, TCR values are usually obtained through experiments. Unlike extensive research focusing on ordinary columnar materials, this paper aims at measuring the TCR values of graphite thin film materials. The technical challenge is that it is not convenient to embed thermocouples into such materials. To overcome this challenge, a steady-state method using a copper heat flux meter is developed, which provides a useful tool for indirect TCR measurement. In our experiments, the TCR values of the graphite thin film materials are successfully measured under different temperature and pressure levels. The results provide a valuable guideline for the use of this type of material in high-temperature, high-pressure applications.     

Clustering of Yb in silica-based glasses synthesized by SPCVD

Light absorption and scattering are studied in silica-based slab lightguides with different contents of aluminum, ytterbium and phosphorous in the silica core. The slab lightguides used in the experiments were fabricated from the structures of doped silica deposited on the inner surface of a substrate silica tube via surface-plasma chemical vapor deposition (SPCVD). The synthesized glasses contained 0.004–0.4 at. % of Yb, as well as various contents of Al and P ranging from 0 to 1 at. %. Loss spectra of the slab lightguides are measured in the 300–1050 nm wavelength band, with the influence of the profusion of deposited glass on the loss spectra investigated by means of substrate tube external processing at a temperature of ∼1600 °C in the flame of a hydrogen-oxygen burner. We found that a combination of the temperature of the inner surface of the substrate tube during the deposition process and the subsequent profusion of the deposited structure essentially influence the distribution uniformity of ytterbium ions in the glass volume. If aluminum and phosphorous are present in the glass, such profusion can influence the formation of ytterbium clusters in opposite ways.     

Polyurethane/graphite nano-platelet composites for thermal energy storage

In this work new polyurethane-based phase change materials containing segments of poly(ethylene glycol) with average molar mass of 8000 g/mol with and without chain extender and modified with graphite nano-platelets have been fabricated and characterized. Structure, morphology and phase behaviour of these solid-solid phase change materials were investigated, as well as the thermal stability and conductivity. The heat of phase transition was in the range of 118.0–164.5 J/g for polyurethane without chain extender and 128.0–148.5 J/g for polyurethane with chain extender. The highest heat of phase transition and crystallinity were found for system modified with 0.3% of graphite nano-platelets in polyurethane without chain extender. Modulated differential scanning calorimetry results showed some changes in the phase transition behaviour and the crystallinity of the polyurethane matrix due to graphite nano-platelets confinement effect. Enhancements in the thermal stability in polyurethane modified with graphite nano-platelets, attributed to the barrier effect, were found based on thermogravimetric analysis data. The thermal conductivity increased with an increase of graphite nano-platelets content for both polyurethane systems, with and without chain extender, which is important for modern thermal energy storage applications.     

Fabrication of attractive Li4SiO4 pebbles with modified powders synthesized via surfactant-assisted hydrothermal method

Li₄SiO₄ pebbles have been widely studied as attractive tritium breeding materials in the fusion reactor blanket of international thermonuclear experimental reactor (ITER). In this work, surfactant-assisted hydrothermal method was first employed to prepare ultrafine ceramic powders for fabricating attractive Li₄SiO₄ pebbles. SEM analysis revealed that the introduction of sodium dodecyl sulfate could eliminate the particle aggregation to prepare monodispersed precursor powders, and thus generated the green bodies of pebble with homogeneous microstructure, which was helpful to eventually obtain high-quality Li₄SiO₄ pebbles. Moreover, the effects of sintering temperature on the grain size, relative density, and crush load of Li₄SiO₄ pebbles were also investigated. Li₄SiO₄ pebbles sintered at 700 °C had a high crush load (average value 27.39 N), small grain size (average value 0.57 μm), satisfactory density (88.13%T.D.) and abundant pore structure, which were expected to show favorable tritium release behavior as a promising tritium breeding material for fusion reactor blanket.     

The effect of tape casting operational parameters on the quality of adjacently graded ceramic film

For small length tape casting of ceramic slurries varying green film thickness is often a problem. To optimise this, the following parameters were investigated: single blade, double blade, using a pump system and a modelled speed change mode have been analysed. Advantages and limitations of every method are described here. The tape casting experiments were built to be generic in order to allow the control of various processing conditions.From these results, the single-blade technique was chosen for a study of side-by-side tape casting. The influence of the geometric parameters of partitioning the casting tank into chambers, on the quality of graded tape was studied. Tape casting experiments at different speeds and partition tongue lengths in combination with rheological tests revealed that high casting speeds and absence of the partition under the blade are detrimental to the formation of the smooth well-controlled interface between the co-cast slurries, required for most of applications.     

“太空人参酵母”在化妆品中潜在应用研究

通过体外细胞平台,从多角度对应用太空育种技术和现代发酵技术而获得的"太空人参酵母"提取物进行功效验证,为其在化妆品中的应用提供理论依据和科学指导。结果揭示"太空人参酵母"可以明显促进人原代角质细胞的增殖能力、克隆形成能力及划痕修复能力,并且可以促进基底层基底源生蛋白(Perlecan)的表达;此外"太空人参酵母"还有助于重离子辐照后的人原代成纤维细胞恢复细胞形态,恢复基底源生蛋白、Ⅰ型胶原蛋白和弹性蛋白表达的能力。以上结果表明,"太空人参酵母"具有提高细胞再生能力的活性,具有应用于促肌肤再生类化妆品的潜力。