Chemical thermodynamic representation of very nonstoichiometric phases: 〈Ceo2−x〉

The entire 〈CeO_2−x〉² data base for the dependence of the nonstoichiometry, x, on temperature and chemical potential of oxygen (oxygen potential) was retrieved from the literature and represented by a thermodynamic method. The method resulted in partial molal Gibbs free energy quantities that are useful for any thermodynamic calculation involving 〈CeO_2−x〉. It also accurately represents, for the first time, the complex behavior of the experimental data, including the low-temperature miscibility gap. The method appears to be generally applicable to many very nonstoichiometric phases.     

Real-time failure detection on complex mechanical structures via parallel data processing

Automatic testing and failure detection on complex mechanical structures requires the measurement, data processing and classification of differential physical values. If an automatic diagnostic system has to compete with the capabilities of human testers, parallel computation is an equivalent approach.     

A new two-dimensional position sensitive proportional counter

A new scheme for two dimensional position encoding has been devised for position sensitive proportional counters (PSPC). The method involves charge division at the cathode of the detector, similar to the “wedge and strip” approach. The intrinsic spacial resolution of the encoding scheme suggests the possibility of applying this scheme to other two-dimensional detectors, such as micro-channel plates or photodiodes.     

Structure,dielectric properties of novel Ba(Zr,Ti)O3 based ceramics for energy storage application

(1-x) Ba(Zr_0.2Ti_0.8)O₃-x Na_0.5Bi_0.5TiO₃ (x = 0, 10, 20 30, 40, 50 mol%) (BZTN) ceramics are prepared by the traditional solid phase method. All BZTN ceramics exhibit a pseudo-cubic BZT based perovskite structure. Both the average grain size and the relaxor ferroelectricity of BZTN ceramics gradually increase with increasing NBT content. The W_rec of 3.22 J/cm³ and η of 91.2% is obtained for the BZTN40 ceramic at 241 kV/cm. BZTN40 ceramic also exhibits good temperature stability from room temperature to 150 °C and frequency stability from 1 Hz to 100 Hz. A P_D of 0.621 J/cm³ and a t_0.9 of 82 ns is obtained for the BZTN40 ceramic at 120 kV/cm. BZTN ceramics show application potential in energy storage and pulse power capacitors.     

Unique cyclic performance of post-treated carbide-derived carbon as an anode electrode

Carbide-derived carbon (CDC) is an attractive anode material for Li-ion battery applications because diverse pore textures and structures from amorphous to highly ordered graphite can be controlled by changing the synthesis conditions and precursor, respectively. To elucidate the unique cycling behavior of the post air-treated CDC anode, electrochemical performance was studied under variation of C-rates with structural changes before and after cycling. By tailoring the pore texture of CDCs as removal of amorphous phase by post air-activation, the anode electrode showed a high increase of capacity under prolonged cycling and under high C-rate conditions such as 0.3–1.0 C-rates. The discharge capacities of the treated CDC increased from 400 mAh g⁻¹ to 913 mAh g⁻¹ with increasing cycle number and were close to high initial irreversible value, 1250 mAh g⁻¹, at the 220th cycle under a 0.1C-rate condition, which are unique and unusual cyclic properties in carbon anode applications. Under high C-rate conditions, the discharge capacities started to increase from around 160 mAh g⁻¹ and values of 415 mAh g⁻¹, 372 mAh g⁻¹, and 336 mAh g⁻¹, were observed at 0.3, 0.5, and 1.0 C-rates, respectively, at 600 cycles, demonstrating stable capacity performance.     

Enhanced energy storage performance in Sn doped Sr0.6(Na0.5Bi0.5)0.4TiO3 lead-free relaxor ferroelectric ceramics

SnO₂ doped Sr_0.6(Na_0.5Bi_0.5)_0.4TiO₃ (NBT-ST) ceramics were prepared by a conventional solid-state reaction method. Their phase structures, microstructures and electrical properties were characterized in details. It is found that SnO₂ doping could increase the lattice parameters, density and average grain size. A suitable amount of SnO₂ can improve dielectric properties, and affect the relaxor behavior of the NBT-ST matrix, thereby it can effectively reduce the energy loss and optimize the energy storage performance. Furthermore, the energy storage properties are improved with SnO₂ doping. Especially, the 1 at. % SnO₂ doped NBT-ST achieves a high recoverable energy density of 2.35 J/cm³, which is mainly attributed to large maximum polarization of 43.2 μC/cm², small remnant polarization of 5.83 μC/cm² and high breakdown strength of 180 kV/cm. Also, relatively good temperature stability for dielectric performance and excellent fatigue resistance are observed in this composition. These properties are attractive for lead-free energy storage applications.     

High pressure phase equilibria of ethyl esters in supercritical ethane and propane

The high pressure phase equilibria of ethyl esters (ethyl decanoate/caprate, ethyl dodecanoate/laurate, ethyl tetradecanoate/myristate and ethyl hexadecanoate/palmitate) in supercritical ethane and propane have been measured in the temperature ranges 311–358 K (T_R = 1.02–1.17) and 376–409 K (T_R = 1.02–1.11), respectively. The measurements were conducted in a high pressure view cell for ethyl ester mass fractions between 0.015 and 0.65. The results show a generally linear relationship between the phase transition temperature and pressure. No temperature inversions or three phase regions were observed. An increase in hydrocarbon backbone length leads to an increase in phase transition pressure. For ethane as supercritical solvent, this increase is linear. For propane as supercritical solvent, the nature of the increase was not quantified as the magnitude of the increase would be significantly influenced by the experimental measurement error as the observed increase is not very large. Comparison of the phase behaviour of ethyl esters with methyl esters shows very little difference, yet the phase transition pressure of ethyl esters in supercritical ethane and propane is significantly lower than those of the corresponding acids. The phase transition pressure of ethyl esters in ethane and propane is also lower than those in carbon dioxide.     

Origin of abnormal glass transition behavior in metallic glasses

In this paper, the phenomenon of two glass-transition-like appearance in the supercooled liquid region of metallic glasses was investigated. It is confirmed that this abnormal behavior is attributed to the transition process of an amorphous state from higher energy to lower energy. The amorphous state with higher energy comes from the uneven distribution of compositions in glasses, which is mainly caused by the component with significant differences in atomic size and nonnegative values of enthalpy of mixing. The results were verified by high resolution transmission electron microscopy and energy-dispersive spectrometry.     

Effects of Sn content on thermal stability and mechanical properties of the Ti60Zr10Ta15Si15 amorphous alloy for biomedical use

The (Ti₆₀Zr₁₀Ta₁₅Si₁₅)_100−xSn_x (x = 0, 4, 8, 12 at.%) amorphous ribbons were prepared by the single roll melt-spinning method, and the effects of the Sn content on the thermal stability, the elastic modulus and nanohardness of the Ni-free Ti-based alloys were investigated. It is found that Sn additions decrease the glass formation ability of the Ti₆₀Zr₁₀Ta₁₅Si₁₅ alloy. The content of Sn addition has an important impact on the elastic modulus and nanohardness of the alloys. The amorphous alloy with 4% Sn addition exhibits the highest the elastic modulus and nanohardness, which are 111 GPa and 7.0 GPa, respectively. The correlation between the mechanical properties and Sn content was discussed based on the free volume containing in the as-spun ribbons.