Tungsten Nanoparticles Accelerate Polysulfides Conversion: A Viable Route toward Stable Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT Na–S) batteries are arousing great interest in recent years. Their practical applications, however, are hindered by several intrinsic problems, such as the sluggish kinetic, shuttle effect, and the incomplete conversion of sodium polysulfides (NaPSs). Here a sulfur host material that is based on tungsten nanoparticles embedded in nitrogen-doped graphene is reported. The incorporation of tungsten nanoparticles significantly accelerates the polysulfides conversion (especially the reduction of Na2S4 to Na2S, which contributes to 75% of the full capacity) and completely suppresses the shuttle effect, en route to a fully reversible reaction of NaPSs. With a host weight ratio of only 9.1% (about 3–6 times lower than that in recent reports), the cathode shows unprecedented electrochemical performances even at high sulfur mass loadings. The experimental findings, which are corroborated by the first-principles calculations, highlight the so far unexplored role of tungsten nanoparticles in sulfur hosts, thus pointing to a viable route toward stable Na–S batteries at room temperatures

Nitrogen Doping Improves the Immobilization and Catalytic Effects of Co9S8 in Li-S Batteries

Several critical issues, such as the shuttling effect and the sluggish reaction kinetics, exist in the design of high-performance lithium–sulfur (Li-S) batteries. Here, it is reported that nitrogen doping can simultaneously and significantly improve both the immobilization and catalyzation effects of Co9S8 nanoparticles in Li-S batteries. Combining the theoretical calculations with experimental investigations, it is revealed that nitrogen atoms can increase the binding energies between LiPSs and Co9S8, and as well as alleviate the sluggish kinetics of Li-S chemistry in the Li2S6 cathode. The same effects are also observed when adding N-Co9S8 nanoparticles into the commercial Li2S cathode (which has various intrinsic advantages, but unfortunately a high overpotential). A remarkable improvement in the battery performances in both cases is observed. The work brings heteroatom-doped Co9S8 to the attention of designing high-performance Li-S batteries. A fundamental understanding of the inhibition of LiPSs shuttle and the catalytic effect of Li2S in the newly developed system may encourage more effort along this interesting direction. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Study on Distribution Characteristics of Damage Range along Smooth Blasting Hole Based on PPV

The damage range of surrounding rock has an important influence on optimization of blasting parameters. This study, based on the vibration attenuation law near the blasting source and the characteristics of the load acting on the wall of the smooth blasting hole, derives the distribution formulas of the damage range along the borehole during the expansion and quasistatic processes of detonation gas, respectively. More importantly, the quantitative relationship between the damage range and the charge weight of the single borehole is established. The experimental data are used to verify the correctness of the theoretical formulas. The results show that the damage range during the expansion process of detonation gas presents a continuous saddle-shaped distribution along the borehole and the maximum damage range is near the charge segment. The damage range during the quasistatic process of detonation gas is uniformly distributed along the borehole and can be more conservatively used to the practical prediction after corrected. The theoretical formulas are applicable to the perimeter hole with the radial and axial decoupled charge structure, which can provide a theoretical support for controlling the damage range of surrounding rock according to the charge weight

Shrinkage mechanism of red clay based on changes in the thickness of bound water film

Objective The content and existence form of bound water have an important influence on the physical and mechanical properties of red clay, and macroscopic shrinkage of red clay leads to microstructure changes of soil particles, pores and bound water, which in turn may cause soil surface cracking, triggering infiltration, destabilization, and other engineering geological problems. Methods Thermogravimetric analysis tests, BET tests, scanning electron microscopy (SEM) and zeta potential tests were conducted to study the variation characteristics of bound water during the shrinkage of undisturbed red clay. The structural model of spherical and lamellar clay particles based on the uniform distribution of bound water film was established, and the formula for the calculation of bound water film thickness was derived. Results The results showed that most of the water in undisturbed red clay exists in the form of bound water and the loss of weakly-bounded water continues throughout the shrinkage process of red clay. During the process, the zeta potential, specific surface area and the thickness of the bound water film decreased continuously. Conclusion The results reveal the intrinsic mechanism of water loss and shrinkage of red clay, which can provide theoretical support for solving environmental engineering geological problems

Study on Bending Damage Constitutive Model and Mechanical Properties of Limestone Based on Acoustic Emission

To reveal the mechanical characteristics and damage evolution mechanism of limestone in the bending process, the cumulative acoustic emission (AE) hits were used to define the damage variable, and the rock microbody hypothesis and the Weibull distribution function were applied to further improve the damage variable. Meanwhile, the bending damage constitutive model of limestone under three-point bending was developed based on the Lemaitre strain equivalence principle and the continuum damage theory. Then, the three-point bending test with acoustic emission monitoring was carried out to verify the rationality and validity of the model. Results showed that the modified damage variable D had an exponential distribution with the strain ε, and the damage was mainly concentrated in the macrocrack propagation stage. Moreover, the bending neutral layer moved towards the compressive zone in the bending damage process. The bending neutral layer, furthermore, moved slowly a small distance at the initial stage of bending fracture but moved fast a long distance at the end stage of bending fracture. In addition, the bending damage constitutive model could be quantitatively expressed by the cumulative AE hits Np, the stress σ, the strain ε, and Young’s modulus E. The theoretical stress-strain model curves agreed well with experimental results, which demonstrated that the proposed model could capture the damage evolution of limestone reasonably in the bending process

Theoretical Study on Radial Distribution Laws of Rock Mass Damage Factors under Decoupled Charge Blasting

In this paper, the radial distribution laws of damage factors under decoupled charge blasting are studied for the optimization design of blasting parameters. Through defining the critical radial decoupling coefficient, the damage zone around the borehole is partitioned and the characteristics are described. Based on the damage factor defined by Taylor’s effective elastic modulus, the formulas of the radial distribution laws of damage factors are derived by the attenuation law of stress wave and the theory of thick-walled cylinder, respectively, which are then superposed to obtain the formula under the combined action of explosion stress wave and quasistatic gas. Experimental verification indicates that the theoretical values, which have a good correlation with the test data and are of high accuracy, can characterize the radial distribution laws of damage factors and estimate the damage range. When a radial decoupling coefficient is less than the critical value, the attenuation rate of damage factors firstly increases and then decreases with the increase of distance, and a serious damage zone is caused. Conversely, it decreases gradually, and the serious damage zone is not caused. Therefore, on the premise of stable detonation, it is necessary to apply an appropriate radial decoupling coefficient which is larger than the critical value to smooth or presplit blasting

Cr-doped Fe2F5·H2O with open framework structure as a high performance cathode material of sodium-ion batteries

The sphere-like Fe(2-x)CrxF5·H2O (x = 0, 0.03, 0.05, 0.07) composites with open framework structure are prepared via an IL based assisted approach, and served as the cathode material for Na-ion batteries (NIBs). The physicochemical and electrochemical properties of the Cr-doped Fe2F5·H2O cathode materials are systematically characterized. The results indicate that the Cr-doped materials not only reduce the crystalline size, but also remarkably enhance electronic conductivity. Meanwhile, the electrochemical tests further show that Fe1.95Cr0.05F5·H2O as the cathode active material of NIBs exhibits a high initial discharge capacity of 357 mAh gâ 1and retains a discharge capacity of 171 mAh gâ 1after 100 cycles at 0.1 C (1 C = 200 mAh gâ 1). Moreover, even at high rate of 1 C, it can still deliver a high discharge capacity of 147 mAh gâ 1. Compared with the Fe2F5·H2O, the Fe1.95Cr0.05F5·H2O shows higher discharge capacity, excellent cycle stability and better rate capability, which can be attributed to the improvement of structure stability and electronic conductivity due to the appropriate amount (5%) of Cr3+doping. Therefore, the preparation of Cr-doped Fe2F5·H2O sample provides a unique perspective to enhance the electrochemical performance of Fe2F5·H2O, which is an essential step for the development of high specific energy sodium-ion batteries

Neuroprotective effects of takinib on an experimental traumatic brain injury rat model via inhibition of transforming growth factor beta-activated kinase 1

Transforming growth factor β-activated kinase 1 (TAK1) plays a significant role in controlling several signaling pathways involved with regulating inflammation and apoptosis. As such, it represents an important potential target for developing treatments for traumatic brain injury (TBI). Takinib, a small molecule and selective TAK1 inhibitor, has potent anti-inflammatory activity and has shown promising activity in preclinical studies using rat models to evaluate the potential neuroprotective impact on TBI. The current study used a modified Feeney's weight-drop model to cause TBI in mature Sprague-Dawley male rats. At 30 min post-induction of TBI in the rats, they received an intracerebroventricular (ICV) injection of Takinib followed by assessment of their histopathology and behavior. The results of this study demonstrated how Takinib suppressed TBI progression in the rats by decreasing TAK1, p-TAK1, and nuclear p65 levels while upregulating IκB-α expression. Takinib was also shown to significantly inhibit the production of two pro-inflammatory factors, namely tumor necrosis factor-α and interleukin-1β. Furthermore, Takinib greatly upregulated the expression of tight junction proteins zonula occludens-1 and claudin-5, reducing cerebral edema. Additionally, Takinib effectively suppressed apoptosis via downregulation of cleaved caspase 3 and Bax and reduction of TUNEL-positive stained cell count. As a result, an enhancement of neuronal function and survival was observed post-TBI. These findings highlight the medicinal value of Takinib in the management of TBI and offer an experimental justification for further investigation of TAK1 as a potential pharmacological target

A strategy for enhancing luminescence thermometry via Ta5+-triggered K0.5Na0.5NbO3 : Er3+ transparent ceramics

Luminescence thermometry is a reliable approach for remote thermal sensing, and extensive studies have been devoted to designing a luminescence thermometer with heightened thermal sensitivity. Herein, we report a promising luminescence thermometric material, Ta5+-substituted K0.5Na0.5NbO3:0.003Er3+ transparent ferroelectric ceramics. The temperature sensing sensitivity is significantly improved by adjusting the concentration of Ta5+ in the material. Specifically, utilizing the fluorescence intensity ratio from the 2H11/2 and 4S3/2 thermally coupled states of Er3+ as a detecting signal within the temperature range of 273–543 K, an optimal maximum absolute sensitivity of 0.0058 K–1 and relative sensitivity of 0.0158 K–1 are achieved for K0.5Na0.5NbO3: 0.65Ta5+/0.003Er3+. Simultaneously, as the concentration of Ta5+ increase, a unique evolution of structural phase transitions is observed from orthorhombic to tetragonal and then to cubic. This is accompanied by an improvement in luminescence temperature sensing properties, and the best sensitivity is demonstrated in the cubic-phase region. Intriguingly, a huge change in infrared luminescence properties as a function of temperature is found around the structure transition temperature of the samples. These results indicate a promising potential for achieving highly sensitive thermometry or monitoring phase structure transitions through luminescence thermometry behavior in the K0.5Na0.5NbO3 host