The brittle compressive failure of fresh-water columnar ice under biaxial loading

The brittle compressive failure of fresh-water, columnar ice was investigated under biaxial loading at a strain rate of ϵ = 10^⇔2s⁻¹ at temperatures of −10 and −40°C. Tests were performed through proportional loading over the range 0 ⩽R<1 where R is the ration of the major to major comprehensive stress, i.e. R = σ₂/σ₁. Two types of confinement were considered, across the long axis of the columnar grains (type-A) and along the columns (type-B). For both types the major stress was orthogonal to the columns. The results reveal two failure regimes under cross-column loading: the failure stress first increases rapidly with increasing R_A in the range 0 ⩽R_A ⩽ R_t, and then decreases as R_A increases further. The transition ratio, R_t, decreases from ∼0.2 at −10°C to ∼0.1 at −40°C. Correspondingly, the failure mode changes from splitting along the columns along the loading direction at zero confinement to shear faulting in the loading plane at 0 < R_A ⩽ R_t to a combined mode of splitting across the columns and shear faulting out of the loading plane at R_A >R_t. The failure envelope at both temperatures resembles a truncated Coulomb envelope. Under along-column confinement (type-B) neither the failure stress nor the failure mode depends upon the confining stress. High-speed photography and thin-section examinations revealed that wing cracking and localized fragmentation are important elements in the failure process. The observations ae explained in terms of two failure mechanisms; viz. frictional crack sliding and contact tensile fractures.     

One-step synthesis of CuCo2O4-Sm0.2Ce0.8O1.9 nanofibers as high performance composite cathodes of intermediate-temperature solid oxide fuel cells

One-dimensional nanostructured CuCo₂O₄-Sm_0.2Ce_0.8O_1.9 (SDC) nanofibers are prepared by the electrospinning method and one step sintering as a cathode with low polarization resistance for intermediate temperature solid oxide fuel cells (IT-SOFC). The CuCo₂O₄-SDC nanofibers cathodes form a porous network structure and have large triple-phase boundaries. Correspondingly, the electrochemical performance of the CuCo₂O₄-SDC nanofibers composite cathodes shows significantly improve, achieving the polarization resistance of 0.061 Ω cm² and the maximum power densities of 976 mW·cm⁻² at 750 °C. Thus, these results suggest that CuCo₂O₄-SDC nanofiber could be a highly active cathode material for IT-SOFCs.     

Photocured PEO-based solid polymer electrolyte and its application to lithium–polymer batteries

A solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) is prepared by photocuring of polyethylene glycol acrylates. The conductivity is greatly enhanced by adding low molecular weight poly(ethylene glycol) dimethylether (PEGDME). The maximum conducticity is 5.1×10⁻⁴ S cm⁻¹ at 30°C. These electrolytes display oxidation stability up to 4.5 V against a lithium reference electrode. Reversible electrochemical plating/stripping of lithium is observed on a stainless steel electrode. Li/SPE/LiMn₂O₄ as well as C(Li)/SPE/LiCoO₂ cells have been fabricated and tested to demonstrate the applicability of the resulting polymer electrolytes in lithium–polymer batteries.     

A new chain-coding algorithm for binary images using run-length codes

This paper presents a new algorithm for converting a binary image into chain codes using its run-length codes. The basic idea of conventional chain-coding algorithm is to follow boundary pixels by convolving a 3 × 3 window with the image and to sequentially generate chain codes. The proposed algorithm has two phases, namely run-length coding and chain-code generation. We use connectivity information between runs as well as their coordinates in the phase of run-length coding. In the second phase (chain-code generation) the connectivity information extracted in the first phase is utilized for sequentially tracking runs containing the boundary pixels to be followed. This algorithm has an advantage that we can detect easily the inclusion relationship between boundaries at the same time as chain-code generation.     

Insight into the vacancy effects on mechanical and electronic properties of Tantalum Silicide

The effects of the vacancies on the structural stability, elastic constants, elastic moduli, brittle-to-ductile transition and electronic properties of Tantalum Silicide (TaSi₂) are investigated in detail by first-principles calculations. The values of vacancy formation energy confirm that the perfect TaSi₂ and TaSi₂ with different atomic vacancies can exhibit the structural stability at ground state. It is found that Ta atom vacancies are more stable than Si atom vacancies in TaSi₂ with vacancies. The elastic constants and elastic moduli describe the mechanical behavior for TaSi₂ and TaSi₂ with vacancies. The different atomic vacancies weaken the elastic stiffness for TaSi₂. But the values of B/G confirm that the brittle-to-ductile transition occurs with different atomic vacancies for TaSi₂. Although these vacancies make the shear and volume deformation resistance of TaSi₂ weaker, they obviously improve the brittle behavior of TaSi₂. The difference charge density and electronic structures are calculated to discuss and analyze the structural stability and mechanical properties for the perfect TaSi₂ and TaSi₂ with vacancies.     

α-Fe2O3 hollow microspheres assembled by ultra-thin nanoflakes exposed with (241) high-index facet: Solvothermal synthesis,lithium storage performance,and superparamagnetic property

Hierarchical α-Fe₂O₃ hollow microspheres are synthesized through a convenient and effective solvothermal method. The α-Fe₂O₃ hollow microspheres have a mean diameter of 1 μm and they are composed of ultra-thin nanoflakes with an average thickness of only 5 nm. More importantly, the primary α-Fe₂O₃ nanoflakes are preferentially enclosed by (241) high-index facet. When the α-Fe₂O₃ hollow microspheres are served as anodes for lithium-ion batteries, their first discharge capacities is 1749.1 mAh g⁻¹ at 0.1 A g⁻¹, and the corresponding values are 914.0, 628.7, and 420.5 mAh g⁻¹ at high current densities of 0.2, 0.5, and 1 A g⁻¹, respectively. The improved electrochemical performance can be attributed to the synergistic effect of the hierarchical hollow microstructure, exposed high-index (241) facet, and thin primary nanoflakes. Additionally, the α-Fe₂O₃ hollow microspheres have superparamagnetic properties due to the ultra-thin thickness of the primary α-Fe₂O₃ nanoflakes.     

A hierarchical Ti2Nb10O29 composite electrode for high-power lithium-ion batteries and capacitors

Ti₂Nb₁₀O₂₉ (TNO) is a suitable electrode for high-performance lithium-ion batteries and capacitors because of its large lithium storage capacity and high Li⁺ diffusivity. Currently, the rate or power capability of TNO-based systems is limited by the poor electronic conductivity of the material. Here we report our findings in design, synthesis, and characterization of a hierarchical N-rich carbon conductive layer wrapped TNO structure (TNO@NC) using a novel polypyrrole-chemical vapor deposition (PPy-CVD) process. It was found that carbon coating with PPy–carbon partially reduces Ti and Nb cations, forms TiN, and creates oxygen vacancies in the TNO@NC structure that further increase overall electronic and ionic conductivity. Various defect models and density functional theory (DFT) calculations are used to show how oxygen vacancies influence the electronic structure and Li-ion diffusion energy of the TNO@NC composite. The optimized TNO@NC sample shows notable rate capability in half-cells with a reversible capacity of 300 mAh g⁻¹ at 1 C rate and maintains 211 mAh g⁻¹ at a rate of 100 C, which is superior to that of most M_xNb_yO_z materials. Full cell LiNi_0.5Mn_1.5O₄ (LNMO)||TNO@NC lithium-ion batteries (LIB) and active carbon (AC)||TNO@NC hybrid lithium-ion capacitors (LIC) exhibited notable volumetric and gravimetric energy and power densities.     

Cathode made by silver-precursor ink for all-solution processed quantum dots light-emitting diodes

To realize all-solution processed quantum dots (QDs) light-emitting didoes (QLEDs) with every functional layer processed via wet coating, silver-precursor ink converted cathode is introduced for the first time. One challenge to utilize solution-processed cathode is that the silver-precursor ink reacts with the electron transport layer zinc oxide (ZnO). Another one is that the silver ions permeate through ZnO to quench the QDs' fluorescence. To overcome the challenges, the annealing temperature of ZnO is optimized to 180 °C, while the silver-precursor ink's annealing condition of 180 °C/5 min is selected. As a result, the all-solution processed QLEDs achieve a maximum brightness of 1.32 × 10⁴ cd m⁻², a maximum current efficiency of 8.98 cd A⁻¹, and a maximum external quantum efficiency of 6.92% which reaches 61% of the efficiency of QLEDs with evaporated silver cathode.     

Sintering,microstructure and electricity properties of ITO targets with Bi2O3–Nb2O5 addition

High density and low electrical resistivity ITO targets were prepared by normal pressure sintering in oxygen with Bi₂O₃–Nb₂O₅ addition. The relative density, microstructure and electrical properties of the ITO targets can be adjusted by changing the sintering temperature (1350 °C~1550 °C) and the content of Bi₂O₃–Nb₂O₅. The results show that the sintering temperature of ITO targets with Bi₂O₃–Nb₂O₅ decreased from 1550 °C to 1450 °C, and the maximum relative density (99.6%) and the lowest electrical resistivity (1.78×10⁻⁴ Ω cm) were reached when the sintering temperature was 1450 °C with 5 wt% Bi₂O₃–Nb₂O₅. The carrier concentration increased as the increase of the contents of Bi₂O₃–Nb₂O₅ and sintering temperature. The mobility first increased, and then decreased above 1450 °C as the sintering temperature increased.