Effect of LiYO2 on the synthesis and pressureless sintering of Y2SiO5

Y2SiO5 has potential applications as a high-temperature structural ceramic and environmental/thermal barrier coating. In this work, we synthesized single-phase Y2SiO5 powders utilizing a solid–liquid reaction method with LiYO2 as an additive. The reaction path of the Y2O3/SiO2/LiYO2 mixture with variation in temperatures and the role of the LiYO2 additive on preparation process were investigated in detail. The powders obtained by this method have good sinterability. Through a pressureless sintering process, almost fully dense Y2SiO5 bulk material was achieved with a very high density of 99.7% theoretical

BaZr(0.8)Y(0.2)O(3-delta)-NiO Composite Anodic Powders for Proton-Conducting SOFCs Prepared by a Combustion Method

BaZr0.8Y0.2O3-∂ (BZY)-NiO composite powders with different BZY-NiO weight ratios were prepared by a combustion method as anodes for proton-conducting solid oxide fuel cells (SOFCs). After heating to 1100°C for 6 h, the composite powders were made of a well-dispersed mixture of two phases, BZY and NiO. Chemical stability tests showed that the BZY-NiO anodic powders had good stability against CO2, whereas comparative tests under the same conditions showed degradation for BaCe0.7Zr0.1Y0.2O3-∂- NiO, which is at present the most used anode material for proton-conducting SOFCs. Area specific resistance (ASR) measurements for BZY-NiO anodes showed that their electrochemical performance depended on the BZY-NiO weight ratio. The best performance was obtained for the anode containing 50 wt % BZY and 50 wt % NiO, which showed the smallest ASR values in the whole testing temperature range (0.37 Ω cm2 at 600°C). The 50 wt % BZY and 50 wt % NiO anode prepared by combustion also showed superior performance than that of the BZY-NiO anode conventionally made by a mechanical mixing route, as well as that of Pt

Electric-field induced droplet vertical vibration and horizontal motion: Experiments and simulations

In this work, Electrowetting on Dielectric (EWOD) and electrostatic induction (ESI) are employed to manipulate droplet on the PDMS-ITO substrate. Firstly, we report large vertical vibrations of the droplet, induced by EWOD, within a voltage range of 40 to 260 V. The droplet's transition from a vibrating state to a static equilibrium state are investigated in detail. It is indicated that the contact angle changes synchronously with voltage during the vibration. The electric signal in the circuit is measured to analyze the vibration state that varies with time. By studying the influence of driving voltage on the contact angle and the amplitude in the vibration, it is shown that the saturation voltage of both contact angle and amplitude is about 120 V. The intrinsic connection between contact angle saturation and amplitude saturation is clarified by studying the surface energy of the droplet. A theoretical model is constructed to numerically simulate the vibration morphology and amplitude of the droplet. Secondly, we realize the horizontal motion of droplets by ESI at the voltage less than 1000 V. The charge and electric force on the droplet are numerically calculated. The frictional resistance coefficients of the droplet are determined by the deceleration of the droplet. Under consideration of frictional resistance of the substrate and viscous resistance of the liquid, the motion of the droplet is calculated at 400 V and 1000 V, respectively. This work introduces a new method for manipulating various forms of droplet motion using the single apparatus

Literature review of condensation and evaporation of R290

Nowadays, an increasing attention in environmental issues including the global warming effect and ozone layer depletion has been attracted. R22 is urged to be ruled out until 2020 and 2030 for developed and developing countries. R290 (propane) has been regarded as a promising alternative refrigerant for the air-conditionings. Comparing to other alternatives, R290 has zero ozone depletion potential and negligible GWP. However, R290 has different thermo-physical properties than conventional refrigerants and it would influence the application in tubes such as shear forces, gravity and surface tension. The condensation and evaporation behavior of R290 would has a great effect in designing suitable heat exchanger for R290. In recent years, researchers have made great efforts in studying different working fluids behaviors and multiple semi-empirical correlations have been established to predict the heat transfer and pressure drop. However, the study about R290 behavior is very limited. According to the past experiences in condensation and evaporation studies, the semi-empirical models may be not very accurate in the working conditions outside the range where they are established. This paper presents a detailed review of research work done on the condensation and evaporation of R290. It also gives a comparison between R290 and other working fluid behavior and makes a summarization on predicting correlations for R290 heat transfer and pressure drop. This paper is a starting point for future R290 studies and R290 applications in air conditioning systems.

Atomic-Scale Investigation on the Ultra-large Bending Behaviours of Layered Sodium Titanate Nanowires

Study on mechanical properties of one-dimensional layered titanate nanomaterials is crucial since they demonstrate important applications in various fields. Here, we conducted ex situ and in situ atomic-scale investigation on bending properties of a kind of ceramic layered titanate (Na2Ti2O4(OH)2) nanowires in a transmission electron microscopy. The nanowires showed flexibility along direction and could obtain a maximum bending strain of nearly 37%. By analysing the defect behaviours, the unique bending properties of this ceramic material was found to correlate with a novel arrangement of dislocations, an accessible nucleation and movement along the axial direction resulting from the weak electrostatic interaction between the TiO6 layers and the low b/a ratio. These results provide pioneering and key understanding on bending behaviours of layered titanate nanowire families and potentially other one-dimensional nanomaterials with layered crystalline structures.Comment: 9 pages, 5 figure

A germanium/single-walled carbon nanotube composite paper as a free-standing anode for lithium-ion batteries

Paper-like free-standing germanium (Ge) and single-walled carbon nanotube (SWCNT) composite anodes were synthesized by the vacuum filtration of Ge/SWCNT composites, which were prepared by a facile aqueous-based method. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Electrochemical measurements demonstrate that the Ge/SWCNT composite paper anode with the weight percentage of 32% Ge delivered a specific discharge capacity of 417 mA h g−1 after 40 cycles at a current density of 25 mA g−1, 117% higher than the pure SWCNT paper anode. The SWCNTs not only function as a flexible mechanical support for strain release, but also provide excellent electrically conducting channels, while the nanosized Ge particles contribute to improving the discharge capacity of the paper anode