Benchmarking the Effect of Particle Size on Silicon Anode Materials for Lithium-Ion Batteries.

High-capacity silicon has been regarded as one of the most promising anodes for high-energy lithium-ion batteries. However, it suffers from severe volume expansion, particle pulverization, and repeated solid electrolyte interphase (SEI) growth, which leads to rapid electrochemical failure, while the particle size also plays key role here and its effects remain elusive. In this paper, through multiple-physical, chemical, and synchrotron-based characterizations, the evolutions of the composition, structure, morphology, and surface chemistry of silicon anodes with the particle size ranging from 50 to 5 µm upon cycling are benchmarked, which greatly link to their electrochemical failure discrepancies. It is found that the nano- and micro-silicon anodes undergo similar crystal to amorphous phase transition, but quite different composition transition upon de-/lithiation; at the same time, the nano- and 1 µm-silicon samples present obviously different mechanochemical behaviors from the 5 µm-silicon sample, such as electrode crack, particle pulverization/crack as well as volume expansion; in addition, the micro-silicon samples possess much thinner SEI layer than the nano-silicon samples upon cycling, and also differences in SEI compositions. It is hoped this comprehensive study and understanding should offer critical insights into the exclusive and customized modification strategies to diverse silicon anodes ranging from nano to microscale.

[Safety performance of self-expandable NiTi alloy stent].

In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three L-type stents of Φ8×30 mm, Φ10×30 mm, Φ12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent's original diameter.

Impact of light-aged microplastic on microalgal production of dissolved organic matter.

Microplastics (MPs) can affect phytoplankton and its photosynthetic performance in many but often in negative ways. Phytoplankton is an important source of dissolved organic matter (DOM) in aquatic ecosystems, but the impact of MPs on the algal production of DOM is poorly known. We investigated the impacts of polyvinyl chloride MPs on the growth and DOM production by Chlamydomonas reinhardtii microalgae in a 28-day-long experiment. During the exponential growth phase of C. reinhardtii, MPs slightly affected algal growth and DOM production. At the end of experiment, MPs decreased the biomass of C. reinhardtii by 43 % in the treatment with MPs exposed to simulated solar radiation prior the experiment (light-aged) and more than in the treatment with virgin MPs. The light-aged MPs decreased algal DOM production by 38 % and modified the chemical composition of DOM. According to spectroscopic analyses, the light-aged MPs increased aromaticity, average molecular weight and fluorescence of DOM produced by C. reinhardtii. The elevated fluorescence was associated with humic-like components identified by a 5-component parallel factor analysis (PARAFAC) from the excitation-emission matrices. We conclude that although MPs can leach DOM to aquatic ecosystems, they potentially modify the aquatic DOM more by interfering with the algal production of DOM and changing the composition of produced DOM.

[Impacts of ultraviolet irradiation on the sperm motility and longevity of Acipenser baerii].

This paper studied the impacts of different dose ultraviolet irradiation (254 nm, UVC) on the sperm motility and longevity of Acipenser baerii. Ultraviolet irradiation had significant impacts on the sperm motility, its fast motion time, and longevity. With the increasing dose of ultraviolet irradiation, the sperm motility decreased rapidly first, increased rapidly then, and decreased rapidly again. The sperm fast motion time had the similar variation trend as the sperm motility, but the sperm longevity kept decreasing with increasing dose of ultraviolet irradiation. When the ultraviolet irradiation dose increased to 288 mJ x cm(-2), the sperm fast motion disappeared; when the ultraviolet irradiation dose increased up to 324 mJ x cm(-2), the sperm had no motility and died. According to the "Hertwig effect", the optimum ultraviolet irradiation dose for inactivating A. baerii sperm was 216 mJ x cm(-2).