Measurement of the Diffusion Coefficient of Water in RP-3 and RP-5 Jet Fuels Using Digital Holography Interferometry

The diffusion coefficient of water in jet fuel was measured employing double-exposure digital holographic interferometry to clarify the diffusion process and make the aircraft fuel system safe. The experimental method and apparatus are introduced in detail, and the digital image processing program is coded in MATLAB according to the theory of the Fourier transform. At temperatures ranging from 278.15 K to 333.15 K in intervals of 5 K, the diffusion coefficient of water in RP-3 and RP-5 jet fuels ranges from 2.6967?×?10 ^?10 m²·s^?1 to 8.7332?×?10 ^?10 m²·s^?1 and from 2.3517?×?10 ^?10 m²·s^?1 to 8.0099?×?10^?10 m²·s^?1, respectively. The relationship between the measured diffusion coefficient and temperature can be well fitted by the Arrhenius law. The diffusion coefficient of water in RP-3 jet fuel is higher than that of water in RP-5 jet fuel at the same temperature. Furthermore, the viscosities of the two jet fuels were measured and found to be expressible in the form of the Arrhenius equation. The relationship among the diffusion coefficient, viscosity and temperature is analyzed according to the classic prediction model, namely the Stokes–Einstein correlation, and this correlation is further revised via experimental data to obtain a more accurate predication result.     

Atmospheric Fine and Coarse Mode Aerosols at Different Environments of India and the Bay of Bengal During Winter-2014: Implications of a Coordinated Campaign

In this paper, we present mass concentrations of particulate matter [PM_2.5, PM₁₀ size fractions and total suspended particulates (TSP)] measured simultaneously over land stations (Kullu, Patiala, Delhi, Ajmer, Agra, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Jorhat, Itanagar, Imphal, Bhubaneswar, and Kadapa), mostly distributed across the Indo-Gangetic plain (IGP) of India as well as in the marine atmosphere over Bay of Bengal (BoB) in the period from 20 January to 3 February, 2014. The main objective of this study was to quantify the continental outflow of particulates (PM_2.5, PM₁₀ and TSP) from IGP and associated regions into the BoB along with low level north-east wind flow during winter monsoon period. The present study provides a glimpse of the aerosol loading over the IGP region. During this campaign, the highest average PM_2.5 (187.8 ± 36.5 µg m^?3, range 125.6–256.2 µg m^?3), PM₁₀ (272.6 ± 102.9 µg m^?3, range 147.6–520.1 µg m^?3) and TSP (325.0 ± 71.5 µg m^?3, range 220.4–536.6 µg m^?3) mass concentrations were recorded at Varanasi, Kolkata and Lucknow over middle and lower IGP regions. The PM_2.5 (average 41.3 ± 11.9 µg m^?3; range 15.0–54.4 µg m^?3), PM₁₀ (average 53.9 ± 18.9 µg m^?3; range 30.1–82.1 µg m^?3) and TSP (average 78.8 ± 29.7 µg m^?3; range 49.1–184.5 µg m^?3) loading over BoB were found to be comparable to land stations and suggests possible continental outflow. Over the continental region, the highest PM_2.5/PM₁₀ ratio was recorded at Delhi (0.87). The PM_2.5/PM₁₀ ratio over BoB (0.77) was found to be quite high and comparable to Varanasi (0.80) and Agra (0.79).     

The usefulness of diffusion-weighted imaging for differentiating portal vein thrombus from tumour embolus

To investigate the usefulness of diffusion-weighted imaging (DWI) for differentiating bland portal vein thrombus from tumour thrombus. Fifteen patients with clinical comprehensive diagnoses of portal vein thrombus were analysed retrospectively. The thrombus signal intensity on 21 DWI slices and apparent diffusion coefficient (ADC) values were analysed quantitatively. The portal vein thrombus was divided into four types (low/low, high/low, low/high, and high/high) based on the DWI/ADC ratios between the thrombus and liver parenchyma (rDWI and rADC, respectively). Twenty patients with portal vein tumour thrombi were used for comparison as controls. The average ADC value for the bland thrombus was 1.84?±?0.70?×?10^?3?mm²?s^?1 (range: 0.46–2.77?×?10^?3?mm²?s^?1), and was 2.18?±?0.51?×?10^?3?mm²?s^?1 (range: 1.39–2.82?×?10^?3?mm²?s^?1) for the liver parenchyma; the rADC was therefore 0.90?±?0.45 (range: 0.26–1.86). The tumour thrombi were high/low and high/high type. The average ADC for the tumour thrombus was 1.25?±?0.26?×?10^?3?mm²?s^?1 (range: 0.68–1.67?×?10^?3?mm²?s^?1), and 1.56?±?0.33?×?10^?3?mm²?s^?1 (range: 1.11–2.34?×?10^?3?mm²?s^?1) for the liver parenchyma; the rADC was therefore 0.82?±?0.16 (range: 0.39–1.08). There was no statistical difference in rADC values and rDWI/rADC classification performance between the bland and tumour thrombi. The ADC difference between portal vein bland and tumour thrombi was statistically significant, but the ADC values of bland thrombi have a wider range, which contains the ADC values of tumour thrombi with a narrower range. The elevated ADC values of the liver parenchyma adjacent to portal vein emboli may be helpful for the diagnosis of bland thrombi.     

Nanospheres Containing Urea: Photothermic Properties

In the present research, nanospheres of chitosan (CS), maltodextrin, and sodium tripolyphosphate (STPP), loaded with urea, were synthesized by using an ionic gelation technique. In the nanosphere synthesis was used a central composite experimental design, obtaining nanospheres with an average size of 275?±?32 nm and 27.5 mV zeta potential. The nanospheres were characterized by their hydrodynamic diameter, polydispersity index, nitrogen content, and thermal properties such as thermal diffusivity (α), effusivity (e), and conductivity (k); also melting temperature was obtained by differential scanning calorimetry. The thermal properties of nanospheres show that the sample with the smallest size has a thermal diffusivity value of (14.4?±?0.4)?×?10^?8 m²·s^?1 and a thermal conductivity value of (6.4?±?0.1)?×?10^?1 W·m^?1·K^?1, and the obtained melting temperature was 157 °C. Higher concentrations of CS increase the values of these thermal properties, probably because chitosan interacts ionically with STPP forming a reticular network due to the opposite charges of both molecules.     

High‐Performance Hierarchical Black‐Phosphorous‐Based Soft Electrochemical Actuators in Bioinspired Applications

Bioinspired methods allowing artificial actuators to perform controllably are potentially important for various principles and may offer fundamental insight into chemistry and engineering. To date, the main challenges persist regarding the achievement of large deformation in fast response‐time and potential‐engineering applications in which electrode materials and structures limit ion diffusion and accumulation processes. Herein, a novel electrochemical actuator is developed that presents both higher electromechanical performances and biomimetic applications based on hierachically structured covalently bridged black phosphorous/carbon nanotubes. The new actuator demonstrates astonishing actuation properties, including low power consumption/strain (0.04 W cm^?2 %^?1), a large peak‐to‐peak strain (1.67%), a controlled frequency response (0.1–20 Hz), faster strain and stress rates (11.57% s^?1; 28.48 MPa s^?1), high power (29.11 kW m^?3), and energy (8.48 kJ m^?3) densities, and excellent cycling stability (500 000 cycles). More importantly, bioinspired applications such as artificial‐claw, wings‐vibrating, bionic‐flower, and hand actuators have been realized. The key to high performances stems from hierachically structured materials with an ordered lamellar structure, large redox activity, and electrochemical capacitance (321.4 F g^?1) for ions with smooth diffusion and flooding accommodation, which will guide substantial progress of next‐generation electrochemical actuators.     

Improvement of electrical properties and thermal conductivity of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO<Subscript>3</Subscript>) by carbon blacks and carbon fibers

The aim of the study was to use carbon fibers and carbon blacks to improve the thermal conductivity, mechanical and dielectric properties of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO₃) composites. It was found that 7.5 vol% carbon blacks, with high specific surface area, can make complex viscosity of EPDM/BaTiO₃ compound to become non-sensitive to varying shear. Due to the sulfuric atom and C=C groups on surface of carbon blacks, 10 vol% carbon blacks can enhance the tensile strength and tear strength of EPDM/BaTiO₃ (70/30) from 9.00 MPa and 21.06 kN m^?1 to 14.32 MPa (59% increase) and 30.02 kN m^?1 (43% increase). It was found that the 10 vol% spherical carbon blacks with high specific area can partially contact BaTiO₃ and fill the gap between BaTiO₃ particles to increase thermal conductivity and dielectric constant of EPDM/BaTiO₃(70/30) from 0.323 W m^?1 K^?1and 7 at 5 MHz to 0.632 W m^?1 K^?1 (95% increase) and 746 (106 times increase) at 5 MHz, respectively. When the filler content was 10 vol%, carbon blacks and carbon fibers can decrease the volume resistivity of EPDM/BaTiO₃ (70/30) from 2.23?×?10¹³ to 6.37?×?10⁵ Ω m (eight order of magnitude drop) and 4.25?×?10¹¹ Ω m (two order of magnitude drop), respectively.     

Effet Hall dans les films d'argent déposés par voie chimique

Study of the Hall effect on silver films prepared by chemical reduction shows an electronic conductivity. At 25°C the Hall coefficient R_H is ?(12 ± 1) × 10^?11 m³ C^?1 and the number of conduction electrons n = 0.89 electrons per atom agrees within 10% of the result obtained from measurement of the conductivity.The mobility of the electron transport in the annealed films, μ_Hr(25°C) = 4.85 × 10^?3 m²V^?1s^?1 is six to seven time greater than that of the same unannealed films, μ_Hi(25°C) = 0.75 × 10^?3 m² V^?1 s^?1.     

Influence of diffusion-annealing temperature on physical and mechanical properties of Cu-diffused bulk MgB2 superconductor

This study reports not only the effect of Cu diffusion on physical and mechanical properties of bulk MgB₂ superconductors with the aid of Vickers microhardness (H_v) measurements but also the diffusion coefficient and the activation energy of copper (Cu) in the MgB₂ system using the resistivity measurements for the first time. Cu diffusion is examined over the different annealing temperature such as 650, 700, 750, 800 and 850 °C via the successive removal of thin layers and resistivity measurement of the sample. Further, Vickers microhardness, elastic modulus, yield strength, fracture toughness and brittleness index values of the samples studied are evaluated from microhardness measurements. It is found that all the results obtained depend strongly on the diffusion annealing temperature and applied load. The microhardness values increase with ascending the annealing temperature up to 850 °C owing to the increment in the strength of the bonds between grains but decreasing with the enhancement in the applied load due to Indentation Size Effect behaviour of the bulk samples. Moreover, the diffusion coefficient is observed to enhance from 2.84 × 10^?8 to 3.22 × 10^?7 cm² s^?1 with the increase of the diffusion-annealing temperature, confirming that the Cu diffusion is more dominant at higher temperatures compared to lower ones. Besides, temperature dependence of the Cu diffusion coefficient is described by the Arrhenius relation D = 2.66 × 10^?3 exp(?1.09 ± 0.05 eV/k_BT) and the related activation energy of the Cu ions in the MgB₂ system is obtained to be about 1.09 eV. Based on the relatively low value of activation energy, the migration of the Cu ions primarily proceeds through defects such as pore surfaces and grain boundaries in the polycrystalline structure, resulting in the improvement of the physical and mechanical properties of the bulk MgB₂ samples.     

Formulated quasi-solid state electrolyte based on polypyrrole/polyaniline–polyurethane nanocomposite for dye-sensitized solar cell

A polymer-based quasi-solid state electrolyte using polyurethane (PU) matrix was applied for dye-sensitized solar cell (DSSC). To further improve the performance of the electrolyte, 10 wt% of conductive polymer [polypyrrole (PPy) and polyaniline (PANi)] nanoparticles were introduced into the matrix. The samples were named PU-10%PPy and PU-10%PANi, and characterized using ATR–FTIR, TEM, DLS, a transmitted light microscope, a reflected light microscope, and TGA. The formulated polymeric nanocomposites were immersed in the liquid electrolyte and the polymer matrix absorbency, conductivity (σ), ion diffusion coefficient (D_ff), and photovoltaic performance in the DSSC were measured. Polymer matrix absorbency and D_ff of PU-10%PPy (1.72 g g^?1, 1.52 µcm² s^?1) and PU-10%PANi (1.74 g g^?1, 1.31 µcm² s^?1) were lower than the PU matrix (2.01 g g^?1, 1.68 µcm² s^?1). However, the conductivity of PU-10%PPy and PU-10%PANi was higher than the PU matrix (2.64, 2.69, and 2.59 mS cm^?1, respectively). The efficiency of the DSSC based on PU-10%PANi was the highest, with open circuit voltage of 709 mV, short circuit current of 3.67 mA cm^?2, fill factor of 0.62, and light-to-energy conversion efficiency of 2.68%.     

Synthesis of Manganese Ferrite/Graphene Oxide Nanocomposites for Biomedical Applications

In this study, MnFe₂O₄ nanoparticle (MFNP)‐decorated graphene oxide nanocomposites (MGONCs) are prepared through a simple mini‐emulsion and solvent evaporation process. It is demonstrated that the loading of magnetic nanocrystals can be tuned by varying the ratio of graphene oxide/magnetic nanoparticles. On top of that, the hydrodynamic size range of the obtained nanocomposites can be optimized by varying the sonication time during the emulsion process. By fine‐tuning the sonication time, MGONCs as small as 56.8 ± 1.1 nm, 55.0 ± 0.6 nm and 56.2 ± 0.4 nm loaded with 6 nm, 11 nm, and 14 nm MFNPs, respectively, are successfully fabricated. In order to improve the colloidal stability of MGONCs in physiological solutions (e.g., phosphate buffered saline or PBS solution), MGONCs are further conjugated with polyethylene glycol (PEG). Heating by exposing MGONCs samples to an alternating magnetic field (AMF) show that the obtained nanocomposites are efficient hyperthermia agents. At concentrations as low as 0.1 mg Fe mL^?1 and under an 59.99 kA m^?1 field, the highest specific absorption rate (SAR) recorded is 1588.83 W g^?1 for MGONCs loaded with 14 nm MFNPs. It is also demonstrated that MGONCs are promising as magnetic resonance imaging (MRI) T₂ contrast agents. A T₂ relaxivity value (r₂) as high as 256.2 (mM Fe)^?1 s^?1 could be achieved with MGONCs loaded with 14 nm MFNPs. The cytotoxicity results show that PEGylated MGONCs exhibit an excellent biocompatibility that is suitable for biomedical applications.     

Static and dynamic compression strength of hot-pressed boron carbide using a dumbbell-shaped specimen

Dumbbell-shaped specimens were machined from a tile of a commercially available boron carbide and subjected to static and dynamic compressive loads. Static experiments were performed using a screw-driven load frame, and the fracture process was recorded with a high-speed camera. Dynamic experiments were performed using a split-Hopkinson pressure bar and an ultra-high-speed camera to record the fracture process. The average static (~10^?1 s^?1) compressive strength of this boron carbide was determined to be 6.1 ± 0.3 GPa, and the dynamic compression strength, up to a strain rate of 300 s^?1, was 6.2 ± 0.3 GPa. These strength values are twice the value reported by the manufacturer and approximately 30% higher than the values reported by others for the same boron carbide but when using a cuboidal specimen geometry.     

Dielectric losses and ac conductivity of Si–LiNbO3 heterostructures grown by the RF magnetron sputtering method

Single-axis <0001> textured polycrystalline LiNbO₃ films were grown on (001) Si substrates by the RF magnetron sputtering method. Dielectric losses that occur in the Si–LiNbO3 heterostructures are caused by the conductivity of the LiNbO3 films. Analysis of temperature and frequency dependence of ac conductivity in the frequency range f = 25/10⁵ Hz has demonstrated that it is expressed by the power law σ(ω) = Aω^s and is described in the framework of the correlated barrier-hopping model. Thermal annealing (TA) of the Si–LiNbO3 heterostructures causes an increase in the density of the localized states in the band gap of LiNbO3 from D = 7 × 10²⁴ m^?3 to D = 2 × 10²⁵ m^?3. The conduction mechanism is changed radically after TA and phonon-assisted tunneling influences ac conductivity at the frequency of up to 800 Hz. At high frequency (f > 800 Hz), dielectric relaxation predominates affecting frequency dependence σ(ω) on relaxation time τ = 6.6 × 10^?5 s.     

Measurement of thermal diffusivity for alumina borosilicate glass bearing TRISO fuel particles: experiment and modelling correlation

A long-term disposal of a nuclear waste package requires a matrix material that possesses a high thermal conductivity in order to release the decay heat from the fission products. In this study, the thermal diffusivity (α) of alumina borosilicate glass (ABG), encapsulating surrogated tristructural-isotropic (TRISO) particles, has been measured experimentally using the laser flash analysis (LFA) methodology. Image-based models were developed using X-ray computed tomography for glass samples bearing different proportions of TRISO particles. Simpleware software generated finite element (FE) models which then were solved using Abaqus software. The matrices were examined at different waste loadings (10, 20 and 30 wt%) at a temperature of 50 °C. The modelling results were in close agreement with the experimental results and the deviations were within the bounds of standard numerical error (<5 %). The thermal diffusivity of the samples was increased with increasing proportion of TRISO particles. For the maximum mechanically stable matrix, the thermal diffusivity was found to be 0.92 ± 0.021 × 10^?6 and 0.94 × 10^?6 m² s^?1 measured by LFA and modelling, respectively.     

Photothermal Beam Deflection Spectroscopy for the Determination of Thermal Diffusivity of Soils and Soil Aggregates

Photothermal beam deflection spectroscopy (BDS) with a red He–Ne laser (632.8 nm, 35 mW) as an excitation beam source and a green He–Ne laser (543.1 nm, 2 mW) as a probe was used for estimating thermal diffusivity of several types of soil samples and individual soil aggregates with small surfaces (2?×?2 mm). It is shown that BDS can be used on demand for studies of changes in properties of soil entities of different hierarchical levels under the action of agrogenesis. It is presented that BDS clearly distinguishes between thermal diffusivities of different soil types: Sod-podzolic [Umbric Albeluvisols, Abruptic], 29?±?3; Chernozem typical [Voronic Chernozems, Pachic], 9.9?±?0.9; and Light Chestnut [Haplic Kastanozems, Chromic], 9.7?±?0.9 cm²·h^?1. Aggregates of chernozem soil show a significantly higher thermal diffusivity compared to the bulk soil. Thermal diffusivities of aggregates of Chernozem for virgin and bare fallow samples differ, 53?±?4 cm²·h^?1 and 45?±?4 cm²·h^?1, respectively. Micromonoliths of different Sod-podzolic soil horizons within the same profile (topsoil, depth 10–14 cm, and a parent rock with Fe illuviation, depth 180–185 cm) also show a significant difference, thermal diffusivities are 9.5?±?0.8 cm²·h^?1 and 27?±?2 cm²·h^?1, respectively. For soil micromonoliths, BDS is capable to distinguish the difference in thermal diffusivity resulting from the changes in the structure of aggregates.     

Carrier properties of B atomic-layer-doped Si films grown by ECR Ar plasma-enhanced CVD without substrate heating

Abstract

The atomic-layer (AL) doping technique in epitaxy has attracted attention as a low-resistive ultrathin semiconductor film as well as a two-dimensional (2-D) carrier transport system. In this paper, we report carrier properties for B AL-doped Si films with suppressed thermal diffusion. B AL-doped Si films were formed on Si(100) by B AL formation followed by Si cap layer deposition in low-energy Ar plasma-enhanced chemical-vapor deposition without substrate heating. After fabrication of Hall-effect devices with the B AL-doped Si films on unstrained and 0.8%-tensile-strained Si(100)-on-insulator substrates (maximum process temperature 350°C), carrier properties were electrically measured at room temperature. Typically for the initial B amount of 2?×?10¹⁴ cm^?2 and 7?×?10¹⁴ cm^?2, B concentration depth profiles showed a clear decay slope as steep as 1.3 nm/decade. Dominant carrier was a hole and the maximum sheet carrier densities as high as 4?×?10¹³ cm^?2 and 2?×?10¹³ cm^?2 (electrical activity ratio of about 7% and 3.5%) were measured respectively for the unstrained and 0.8%-tensile-strained Si with Hall mobility around 10–13 cm² V^?1 s^?1. Moreover, mobility degradation was not observed even when sheet carrier density was increased by heat treatment at 500–700 °C. There is a possibility that the local carrier (ionized B atom) concentration around the B AL in Si reaches around 10²¹ cm^?3 and 2-D impurity-band formation with strong Coulomb interaction is expected. The behavior of carrier properties for heat treatment at 500–700 °C implies that thermal diffusion causes broadening of the B AL in Si and decrease of local B concentration.     

The influence of the structure and the composition of water/AOT-Tween 85/IPM microemulsion system on transdermal delivery of 5-fluorouracil

The purpose of this study was to investigate the influence of the structure and the composition of water/Aerosol-OT (AOT)-Tween 85/isopropylmyristate (IPM) microemulsion system (WATI) on transdermal delivery of 5-fluorouracil (5-FU). The structure of WATI was characterized by measuring surface tension, density, viscosity, electric conductivity, and differential scanning calorimetry. The effect of the drug loading, water content, component compositions and the amount of mixed surfactant on permeation of 5-FU through mice skin was evaluated by using Franz-type diffusion cells. The results in vitro implied that WATI was W/O microemulsion when the water content was below 20 wt% at fixed 20 wt% of mixed surfactant at 25°C, then might be transformed to a bicontinuous structure, finally, formed O/W microemulsion with water content over 30 wt%. Increase of the drug loading can directly facilitate the penetration of the drug across the skin. Drug diffusion after 12?h from the bicontinuous microemulsion (795.1?±?22.3 µg·cm^?2) would be fastest compared to that from the W/O microemulsion (650.2?±?11.7 µg·cm^?2) and the O/W microemulsion (676.6?±?14.8 µg·cm^?2). The combination of AOT and IPM could bring about synergistic effect on the skin enhancement, however, Tween 85 in WATI decreased the cumulative permeation amount of 5-FU. The content of mixed surfactant had no effect on the permeation of 5-FU at fixed surfactant/cosurfactant ratio (K_m?=?2). Thus, the increased transdermal delivery the hydrophilic drug of 5-FU was found to be concerned with both of the structure and the composition of WATI.     

Rate-dependent low cycle fatigue and ratcheting of 25Cr2MoVA steel under cyclic pulsating tension

Low cycle fatigue and ratcheting deformation of 25Cr2MoVA steel under cyclic tension were tested at 550°C. The effects of stress rates for 0·1, 0·5, 2·5, 5, 10, and 40 MPa s^?1 on ratcheting effect and fracture appearance were discussed systematically. Results indicate that the steady static creep rate very approaches to the ratcheting strain rates for 0·1 MPa s^?1, but it is obviously greater than those of greater stress rates tested. Moreover, the steady ratcheting strain rate reduces rapidly with increasing the frequency when the frequency is less than 36·8 h^?1, and then changes slightly for the greater frequency. This implies the steady ratcheting rate of 25Cr2MoVA is approximately rate-independent when the stress rate is greater than 10 MPa s^?1. Additionally, there are some microvoids in the central fibrous regions of specimens under static creep and cyclic tension with 0·1, 0·5, and 5 MPa s^?1, but very few microvoids for the specimen under cyclic tension with 10 MPa s^?1 can be observed. Furthermore, the low cycle fatigue life is relatively short when the stress rate is less than 10 MPa s^?1, but it enhances exponentially subsequently.     

Crystallographic, thermoelectric, and mechanical properties of polycrystalline type-I Ba8Al16Si30-based clathrates

Crystallographic, thermoelectric, and mechanical properties of polycrystalline Ba₈Al₁₆Si₃₀-based samples with type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods were investigated. The major phase of the samples was a type-I clathrate with an actual Al/Si ratio of ~15/31, strongly suggesting that framework deficiency was absent or was present in very low concentration in the samples. The Hall carrier concentration n of the samples was approximately 1 × 10²¹ cm^?3, which is lower than the values reported so far for the Ba₈Al₁₆Si₃₀ system. Other important material parameters of the samples were as follows: the density-of-states effective mass m* = 2.3m ₀, Hall mobility μ = 7.4 cm² V^?1 s^?1, and the lattice thermal conductivity κ _L = 1.2 W m^?1 K^?1. The thermoelectric figure of merit ZT reached approximately 0.4 (900 K) for a sample with n = 9.7 × 10²⁰ cm^?3. Simulation using the experimentally determined values of material parameters showed that ZT reached values >0.5 if the carrier concentration is optimized at about 3 × 10²⁰ cm^?3. Young’s, shear, and bulk moduli were estimated to be approximately 98, 39, and 117 GPa, respectively, and Poisson’s ratio was found to be 0.25 from the longitudinal and transverse velocities of sound, v _L = 6038 m/s and v _T = 3503 m/s, respectively, for a sample with ZT = 0.4. The coefficient of thermal expansion (CTE) ranged from approximately 8 × 10^?6 K^?1 to 10 × 10^?6 K^?1 (330–690 K), which is smaller than the values reported for Ba₈Ga₁₆Ge₃₀ and Sr₈Ga₁₆Ge₃₀ clathrates.     

Anisotropy of acousto–optic figure of merit in lithium tetraborate crystals

We analyse anisotropy of acousto–optic figure of merit (AOFM) for Li₂B₄O₇ crystals in order to estimate the prospects of these crystals in acousto–optics. We find that the maximal AOFM, 3.44 × 10^?15 s³/kg, is peculiar for the isotropic acousto–optic interaction of the incident ordinary optical wave with the quasi-longitudinal acoustic wave. For the case of anisotropic diffraction in Li₂B₄O₇, the maximum 1.87 × 10^?15 s³/kg can be reached using the interaction of the extraordinary optical wave with the quasi-longitudinal acoustic wave. The case of collinear diffraction is characterized by small AOFMs, with the largest value 0.26 × 10^?15 s³/kg.     

Electrochemical properties of V2O5/carbon composite electrodes in aqueous solutions

The reaction mechanism of V₂O₅ xerogel and the electrode properties of V₂O₅/carbon composites in an aqueous electrolyte solution were examined to obtain high-performance electrodes for rechargeable proton batteries. Based on the results of the chemical analysis of the electrode, proton intercalation is suggested to be the dominant reaction mechanism. By using the relationship between the capacity and current density of a thin-film electrode consisting of V₂O₅ xerogel, the diffusion coefficient in the V₂O₅ xerogel was determined to be 8 ± 1 × 10^?11 cm² s^?1. The V₂O₅/carbon composite electrode was prepared by drying a homogeneous dispersion of carbon particles in the V₂O₅ sol. The composite electrodes showed a large capacity of 460 mAh g^?1 at a current density of 1 A g^?1 and maintained a relatively large capacity of 160 mAh g^?1 at 100 A g^?1. These properties were attributed to the homogeneous microstructure of the V₂O₅/carbon composites. The V₂O₅/carbon composite electrodes were thus revealed as high-performance electrodes with large capacities and excellent high-rate capabilities.