Constitutive model and failure criterion for orthotropic ceramic matrix composites under macroscopic plane stress

To predict the nonlinear stress-strain behavior and the rupture strength of orthotropic ceramic matrix composites (CMCs) under macroscopic plane stress, a concise damage-based mechanical theory including a new constitutive model and two kinds of failure criteria was developed in the framework of continuum damage mechanics (CDM). The damage constitutive model was established using strain partitioning and damage decoupling methods. Meanwhile, the failure criteria were formulated in terms of damage energy release rate (DERR) in order to correlate the failure property of CMCs with damage driving forces, and the maximum DERR criterion and the interactive DERR criterion were suggested simultaneously. For the sake of model evaluation, the theory was applied to a typical CMC with damageable and nonlinear behavior, that is, 2D-C/SiC. The damage evolution law, strain response and rupture strength under incremental cyclic tension along both on-axis and off-axis directions were completely investigated. Comparison between theoretical predictions and experimental data illustrates that the newly developed mechanical theory is potential to give reasonable and accurate results of both stress-strain response and failure property for orthotropic CMCs.     

Static and dynamic oxidation behaviour of silicon carbide at high temperature

SiC has extensive applications in high-temperature oxidation environments. However, few studies have investigated the differences between the static and dynamic oxidation behaviour. In this study, the static and dynamic oxidation of SiC were investigated in air and in plasma wind tunnels, respectively. The results demonstrated that the activation energy of static oxidation was ～68.02 kJ/mol at 1300–1600 ℃, which was approximately ten times that of dynamic oxidation ～7.05 kJ/mol at 1290–1534 ℃. The observed Si-O-C transition layer located at the SiO₂/SiC interface, and its thickness after dynamic oxidation for 300 s was thicker than that after static oxidation for 30 h. In dynamic oxidation, high-speed flowing atomic oxygen reacted directly with SiC, whereas molecular oxygen needed extra energy to break the OO bond and react with SiC in static oxidation. Atomic oxygen also migrated easier in the amorphous SiO₂ coating, contributing to a thicker Si-O-C layer and lower activation energy.     

Enhanced electrode kinetics and electrochemical properties of low-cost NaFe2PO4(SO4)2 via Ca2+doping as cathode material for sodium-ion batteries

In recent years,sodium-ion batteries(SIBs)have been considered as one of the most promising alterna-tives to lithium-ion batteries(LIBs).Here,a new Na-super-ionic conductor(NASICON)cathode material NaFe2PO4(SO4)2 is successfully prepared through solid state method for SIBs.While the poor electronic conductivity of iron-based materials results in its poor rate and cycle performance.Then the electro-chemical is effectively promoting via Ca2+doping.Na0.84Ca0.08Fe2PO4(SO4)2 have achieved considerable electrochemical properties.The first discharge specific capacity is 121.6mAhg-1 at 25mAg-1 with the voltage platform(～3.1 V)corresponding to Fe2+/3+.After 100 cycles,the capacity retention is 55.1％.The excellent electrochemical performance is caused by some Na+is substituted by Ca2+and leading to the fast sodium kinetics,which is well proved by the powder X-ray diffraction pattern and well corresponding to the galvanostatic intermittent titration technique and cyclic voltammetry testing result(the diffusivity values are around at 10-12 cm2 s-1).     

Short-range ordering and its effects on mechanical properties of high-entropy alloys

In this letter,we briefly summarize experimental and theoretical findings of fo rmation and characterization of short-range orderings(SROs)as well as their effects on the defo rmation behavior of high-entropy alloys(HEAs).We show that existence of SROs is a common yet key structural feature of HEAs,and tuning the degree of SROs is an effective way for optimizing mechanical properties of HEAs.In additional,the challenges concerning about formation mechanism and characterization of SROs in HEAs are discussed,and future research activities in this regard are also proposed.     

Computational and experimental study of dental resin composites with high filler content

Journal of Materials Science - Nanocomposites have been used in various industries due to their excellent properties. For some of them, high filler content (over 50 wt%) is beneficial to improving...     

A refinement strategy for identification of scientific software from bioinformatics publications

In the field of bioinformatics, a large number of classical software becomes a necessary research tool. To measure the influence of scientific software as one kind of important intellectual products, a few strategies have been proposed to identify the software names from full texts of papers to collect the usage data of packages in bioinformatics research. However, the performance of these strategies is limited because of the highly imbalance of data in the full texts. This study proposes EnsembleSVMs-CRF, a two-step refinement strategy based on ensemble learning that gradually increases the sentences that contain software mentions to improve the performance of named entity recognition. The experiment on the bioinformatics corpus shows that the performance of EnsembleSVMs-CRF, in terms of the local F1 (78.81%) and the global F1-A (73.49%), is superior to the rule-based bootstrapping method and direct CRF. Application of this strategy to the articles published between 2013 and 2017 in 27 bioinformatics journals extracted 8,239 unique packages. The most popular 50 packages thus identified demonstrate that most of them are professional software which generally requires inter-discipline knowledge, rather than programming skill. Meanwhile, we found that researchers in bioinformatics tend to use free scientific software, and the application of general software is increasing compared with professional software.

     

Effect of current density on the densification of 3%mol yttria-stabilized zirconia/carbon nanotube by flash sintering

Journal of Materials Science: Materials in Electronics - Flash sintering (FS) is a promising method with a great potential for the ceramic fabrication with rapid densification process. However, the...     

Effects of cation doping on thermoelectric properties of Bi2S3 materials

Bi₂S₃ polycrystals doped with Al, Mn, Ag, and In were fabricated by vacuum melting and plasma activated sintering process, and the phase, microstructure, electrical, and thermal properties were investigated. The electrical conductivity is enhanced via Al and Ag doping. Compared with the Ag dopant, a higher electrical conductivity is achieved in the Al-doped sample, resulting in a peak power factor value of 1.96 μW/cmK² at 423 K. Meanwhile, the thermal conductivity of Bi_1.99Al_0.01S₃ sample is very low in the Bi₂S₃ system due to the high-density defects, and is only 0.39 Wm^?1 K^?1 at 740 K. By combining a power factor and a low thermal conductivity, a peak ZT value of 0.29 at 740 K is achieved in the Bi_1.99Al_0.01S₃ sample, being about two times larger than that of pristine Bi₂S₃.

     

Effect of pasteurization on membrane proteins and oxidative stability of oil bodies in various crops

Oil bodies (OBs) are natural pre-emulsion systems and an ideal green food additive. However, their proclivity to oxidation limits the applications of OBs. In this study, the effect of pasteurization (85 and 125 °C; 1 min) on membrane proteins and the oxidative stability of various OBs (soybean, sunflower, peanut, sesame, and walnut) were investigated. The membrane proteins are extracted from the OBs. The ultrahigh-temperature pasteurization (125 °C, 1 min) eliminated lipoxygenase of soybean and peanut OBs. Furthermore, oleosin exhibited a higher denaturation temperature (approximately 100 °C) than extrinsic proteins (approximately 50 °C). Pasteurization induced the conversion of the α-helix structure to a disordered structure by rearranging the hydrogen bonds. The pasteurized soybean and peanut OBs exhibited a high oxidative stability owing to their stable membrane structures and decreased lipoxygenase activity, while sunflower, sesame, and walnut OBs did not exhibit good oxidative stability because of their vulnerable membranes, a large number of unsaturated fatty acids, and severe aggregation of droplets. Simulated milk based on pasteurized soybean and peanut OBs (125 °C, 1 min) maintained outstanding storage stability. These results confirmed that pasteurized soybean and peanut OBs have the potential as a skim milk additive for the benefit of the consumer.