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The existing yoke magnetizers can be used for large diameter bridge cable detection, but cannot provide the optimal bias magnetic field due to the repulsion of the polarities arranged in the circumferential direction, which reduces the energy conversion efficiency of the magnetostrictive longitudinal mode guided wave transducer. A magnetostrictive longitudinal mode guided wave transducer with the ring permanent biased magnet is provided to improve energy conversion efficiency for large diameter bridge cables. Firstly, a ring magnetizer for the axial magnetization is proposed, which inspired by the structure of the yoke magnetizer and the adjustable bias magnetic field generated by the solenoid coil. Then, the specific transducer with the ring magnetizers is designed for PES(C) 7–127 cable. Based on the magnetostrictive coupling coefficient curves and magnetization curve of the cable steel wire, the finite element models verify that the magnetization effect of the ring magnetizer is better than the yoke magnetizer for PES(C) 7–127 cables. Furthermore, the structural parameters of the ring magnetizers are optimized based on magnetization strength and magnetization uniformity. Finally, the improved efficiency of the transducer is verified by experiments. The energy conversion efficiency of the transducer is increased by 43.65% at the transmitting side, 4.76% at the receiving side, 48.41% at the both sides. Besides, the weight of the ring magnetizers is 19.85% lower than the yoke magnetizers.

Silicon photonics is the leading candidate technology for high-speed and low-energy-consumption networks. Thermal and process variations are the two main challenges of achieving high-reliability photonic networks. Thermal variation is due to the heat issues created by application, floorplan, and environment, while process variation is caused by fabrication variability in the deposition, masking, exposition, etching, and doping. Tuning techniques are then required to overcome the impact of the variations and efficiently stabilize the performance of silicon photonic networks. We extend our previous optical switch integration model, BOSIM, to support the variation and thermal analyses. Based on device properties, we propose indirect feedback tuning (IFT) to simultaneously alleviate thermal and process variations. IFT can improve the BER of silicon photonic networks to 10−9 under different variation situations. Compared to state-of-the-art techniques, IFT can achieve an up to $1.52 \times 10^{8}$ times bit-error-rate improvement and 4.11X better heater energy efficiency. Indirect feedback does not require high-speed optical signal detection, and thus, the circuit design of IFT saves up to 61.4% of the power and 51.2% of the area compared to state-of-the-art designs.

In order to realize the resource and sustainable utilization of quartz sand waste discarded from the mineral processing, Mg2+-doped cobalt blue composite pigments are prepared based on quartz sand via co-precipitation method followed by high-temperature crystallization. The obtained composite pigments are characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and magic angle spinning nuclear magnetic resonance. The results indicate that the incorporation of Mg2+ ion and quartz sand improves the color properties and decreases the production cost of composite pigments, and the color can be facilely adjusted by controlling the added amount of Mg2+. The optimal color properties are obtained as the molar ratio of Mg2+ to Co2+ is 6:4, and Mg2+ enters into the crystal lattice and occupies the tetrahedral sites of spinel cobalt blue. Therefore, this study is expected to develop feasible approach for the resource and sustainable utilization of quartz sand waste, and fabrication of low-cost bright cobalt blue composite pigments as well.

Pump it up Carbon nanotube yarns can be used as electrochemical actuators because infiltration with ions causes a contraction in length and an expansion in diameter. Either positive or negative ions can cause this effect. Chu et al. constructed an all-solid-state muscle that eliminated the need for an electrolyte bath, which may expand the potential for its use in applications. By infiltrating the yarns with charged polymers, the fibers start partially swollen, so the length can increase through the loss of ions. It is thus possible to increase the overall stroke of the muscle. Further, these composite materials show a surprising increase in stroke with scan rate. Science , this issue p. 494

The inferior acid resistance and high cost of BiVO4 pigments seriously hinder their wide applications in some fields. Inspired by the superhydrophobic properties of some plants and insects in nature, the reversible thermochromic superhydrophobic coatings with self-cleaning performance and environmental stability were successfully designed by combining with the surface roughness of kaolinite/BiVO4 hybrid pigments (Kaol/BiVO4-HP) and the modification with hexadecyltrimethoxysilane (HDTMS). When the concentration of HDTMS was 4.58 mmol/L, the yellow superhydrophobic coatings exhibited excellent self-cleaning properties and chemical and environmental stability. Furthermore, the superhydrophobic Kaol/BiVO4-HP coatings exhibited the reversible thermochromic behavior with the change of the external temperatures from room temperature to 270 °C. Interestingly, this facile strategy also can be used to fabricate a series of superhydrophobic clay mineral/BiVO4-HP coatings based on the different clay minerals, and there was no relationship between the superhydrophobic properties of the coatings and the morphologies of clay minerals, which was different from the reported color superhydrophobic coatings prepared with Maya-like blue pigments. Thus, the low-cost and thermochromic superhydrophobic clay mineral/BiVO4-HP coatings presented a promising application in temperature sensors and switches with the excellent weather resistance to record and monitor the temperature changes.

To improve the accuracy of laser-induced breakdown spectroscopy (LIBS) in the classification of tea leaves, a modified adaptive mutation probability for genetic algorithm (GA) was proposed to optimize support vector machines (SVM). The implementation process of the GA-SVM algorithm was discussed, and the key parameters were analyzed. The penalty factor and kernel function parameters in SVM were optimized by GA. The spectral line intensities of Mg (279.55 nm), Mn (279.83 nm), Mg (280.27 nm), CN (0–0) (388.34 nm), Ca (393.37 nm), Al (396.15 nm), Ca (396.84 nm), C2 (0–0) (516.45 nm), Fe (517.46 nm) and K (766.49 nm) compared to C (247.86 nm) were selected as the analysis indexes according to the differences of LIBS spectra. LIBS spectra pre-processed by multiple scattering correction (MSC) with the optimal input feature were used to construct the GA-SVM model for different tea species. The results showed that the average correct classification rate was 99.73% in the training set. In addition, the average accuracy was 98.40% in the test set. The classification accuracy of the improved GA-optimized SVM was obviously higher than that of cross validation-support vector machine (CV-SVM) and particle swarm optimization-support vector machine (PSO-SVM). This work demonstrates that the GA-SVM can avoid the blindness of parameter selection and can effectively increase the accuracy of tea classification. The results indicated that LIBS is an effective technology in identificating tea leaves; moreover, it has a real-time, rapid and reliable measurement prospect.

Owing to the destructiveness of the coal–gas outburst (CGO) two-phase flow, a custom-made large-scale test system was used to perform CGO experiments under different gas pressures in this study. The effects of the gas pressure on the migration, the CGO intensity, and the impact characteristics of the CGO two-phase flow were examined. Finally, a physical model containing three key structures was established. The results revealed that a higher initial gas pressure resulted in a higher solid–gas ratio of the coal–gas two-phase flow, a higher initial motion speed of the CGO coal, and a higher CGO intensity. Considerable choking of the two-phase flow occurred in the roadway, and it became more severe with the increasing gas pressure. During the attenuation of the impact force, strong and weak disturbances occurred intermittently. During the CGO process, a strong-disturbance zone developed in the middle of the roadway.

Failure of the cables can cause a bridge to collapse. Fatigue damage of steel wire is one of the causes of cable failure. In this paper, we study the relationship between the fatigue damage and the group speed of guided waves in the steel wire. The relationship between cyclic loading times and group speed of steel wire is obtained by applying tension to steel wire. The results show that the group speed of guided waves increases linearly before the 6.02 million cyclic-loading times, increases exponentially from 6.02 to 6.97 million times. The curve of the relationship between the group speed of the guided waves and the number of cyclic loading times can be fitted to an exponential function, and this curve can be used as a calibration curve to evaluate the fatigue damage of steel wire.

The reinforcing bar connected by threaded sleeve is widely used. The end contacting status under the sleeve indicates the tightness of the threaded sleeve connection. In this paper, the feasibility of using magnetostrictive guided wave to detect the end contacting status of the reinforcing bar is studied. Firstly, the propagation characteristic of the wave propagating through the threaded sleeve connection is analyzed. The end contacting status affects the reflection and transmission of the wave. Then, experiments are carried out on a thread-sleeve-connected reinforcing bar. The passing signals of the threaded sleeve connection at an exciting frequency of 30 kHz can be used to distinguish end contacting status of the reinforcing bar. Additionally, the peak voltage of the passing signal’s first passing wave decreases with the increasing loosening angle of the threaded sleeve connection. The study proves the feasibility of detecting the end contacting status using magnetostrictive guided wave.

The flexural mode guided waves of pipes which are sensitive the axial crack and suitable for wave focused gain more attention recently. In this paper, a non-contact flexural mode guided wave transducer based on magnetostrictive effect is provided for pipes. Based on the magnetostrictive transduction principle and the wave structure of the flexural mode guided wave, the sensing method for generating and receiving the flexural mode guided waves based on magnetostrictive effect is obtained. According to the theoretical analysis, a non-contact magnetostrictive transducer for F (3, m) mode guided waves is given. Six permanent magnets which are evenly distributed in the circumferential direction of the pipe and arranged in opposite polarities are employed to provide the bias magnetic field in the circumferential direction. A solenoid coil is employed to induce the axial alternating magnetic field. The bias magnetic field distribution of the flexural mode guided wave in the pipeline is analyzed by the finite element simulation. The mode of the transduction guided wave in the pipe is verified by experiments based on the dispersion curves.

The use of pseudocapacitive electrode materials can enable devices to store more energy than electrical double-layer capacitors (EDLCs). However, only a few pseudocapacitive materials can maintain excellent performance at low temperatures, which limits their application in harsh climate conditions. Here we demonstrate that a pseudocapacitor with two-dimensional transition metal carbide (MXene) electrode can exhibit excellent low-temperature performance like EDLC. The MXene electrodes contain electrolyte between 2D sheets, and the electrolyte ions can unimpededly reach redox-active sites and interact with surface oxygen groups rapidly, even at low temperatures. With a combination of 40 wt.% sulfuric acid solution as the electrolyte, the working temperature of the MXene electrode extends to -60 °C. The electrode exhibits temperature-insensitive performance at a low scan rate, and the capacity of MXene (88 mAh g−1 at 5 mV s−1) stays almost constant when the temperature decreases from 20 to -50 °C. Moreover, at -50 °C, MXene electrodes show a high capacity retention of > 75% at 100 mV s−1, indicating good low-temperature rate performance. Interestingly, a broad working potential window of 1.5 V is achieved at -60 °C. Such an excellent low-temperature performance demonstrates that MXene is a promising electrode candidate for low-temperature pseudocapacitive energy storage applications.

Active silica nanorod (OPal) was prepared from natural palygorskite (RPal) using an updated acid leaching route, and then the effect of RPal and OPal as nano-filler on the network structure, mechanical, thermal and anti-aging properties of chitosan/polyvinylpyrrolidone (CS/PVP) films was studied comparatively. It was revealed that OPal had a better dispersibility than RPal in CS/PVP substrate, and its incorporation improved the mechanical properties and thermal stability of the films significantly. The optimal composite film containing OPal shows the maximum tensile strength of 27.53 MPa (only 14.87 MPa and 22.47 MPa for CS/PVP and CS/PVP/RPal films, respectively), resulting from the more uniform dispersion of OPal in polymer substrate and its stronger interaction with 3D polymer network. By a controllable acid-leaching process, the metal ions in octahedral sheets of RPal were dissolved out continuously, which is favorable to alleviate the adverse effects of variable metal ions on the film under UV light irradiation, and thus improve the aging-resistant ability of films. This study provides new ideas for improving the reinforcing ability of natural clay minerals towards biopolymer-based material, finds a new way to resolve the aging problem of polymer composites caused by incorporation of natural clay minerals.

The mechanical strength and stability of particulate materials are controlled by their frictional behavior, which plays a vital role in evolving of landslides and geological hazards. While deformation of particles is closely related to the stress localization, the shear displacement processes controlling local stresses are difficult to be observed directly. In this paper, the laboratory direct shear experiments were designed to explore the relationship between local stresses and particles’ behavior, as well as clarify the particle size effect on the particle-filled joint’s mechanical properties. A new method was proposed, which combined the 3D scanning technology and statistical analysis for reconstructing the aperture distribution evolution during the shear process. The local stress regions were assessed by analyzing the aperture evolution. The direct shear tests on artificial joints filled with particles of different sizes were conducted with a normal load of 30 kN. The results obtained proved that the filled joint’s mechanical behavior had a close correlation with the particle size, which involved not only the peak strength but also the residual shear strength. The particles’ deformation determined the normal strain, while the shear displacement controlled the aperture distribution, further influencing the local stress. Three modes of particle deformation were proposed based on the analysis of mechanical behavior and the local stress region. The findings of this study are considered instrumental in investigating failure mechanism with an increasing fault or landslide displacement that may trigger localization—delocalization events and, therefore, control the macroscopic stability and prevent the occurrence of potential geological hazards.

Before a coal mining operation, it is necessary to carry out coal-bed methane (CBM) pre-extraction to prevent coal and gas explosions, causing accidents. However, gas extraction and coal mining will lead to coal damage, which results in a change in the gas migration law. Especially, under deep mining conditions, the gas migration mechanism is more complicated owing to a high ground temperature. Coal permeability is the most important constituent that determines gas flow properties. Therefore, the coal permeability evolutionary law related to damage-induced conditions under different temperatures should be further researched. In this paper, a series of triaxial seepage experiments during the whole stress-induced process, and in the changing of the effective stress process were carried out. The results have shown that during the whole stress–strain process, with an increase in axial strain, coal permeability gradually decreases to a minimum value at first, then increases sharply, and finally keeps nearly constant. A higher temperature resulted in a lower elastic modulus, peak strain, and peak strength, but it caused higher thermal damage. When the coal fractures, coal permeability increases with the increase in temperature. During a change in the effective stress process, higher temperatures resulted in higher permeability. Under higher effective stress, the impact of temperature on permeability was not significant. Based on the above results, a novel damage-based permeability model was developed to describe the permeability evolutionary law caused by damage-induced conditions under compaction, and in a fracturing situation. In the proposed model, an exponential function has been used for the combination between permeability and damage variable. The damage variable is composed of thermal damage and mechanical damage. In addition, the damage variable has been modified by introducing a modified function of the initial damage. Finally, the proposed model has been applied to fit two sets of experimental data available. The fitting results showed that the proposed permeability model could well reflect the permeability behaviors of damage-induced coal at different temperatures.

High-performance bismuth yellow hybrid pigments based on SiO2, Al2O3, and MgO were successfully fabricated by chemical precipitation followed by annealing at 700 °C. Interestingly, the colors of the hybrid pigments depended on the oxide contents, and the optimal yellow value of +92.07 was obtained at an Al2O3/SiO2/MgO mass ratio of 1:0.375:0.750. X-ray diffraction results indicated the formation of pure monoclinic-scheelite-type BiVO4 with high crystallinity, suggesting that the incorporated Si, Al, and Mg entered the crystal lattice of BiVO4. Doping with these elements effectively adjusted the band gap of BiVO4, and thus the color of the hybrid pigments could be easily controlled using these oxides. Furthermore, the hybrid pigments also exhibited good suspension properties and chemical stability in acid and alkaline solutions, water, and ethanol. Importantly, these pigments were applied in high-grade automotive top finishes and exhibited excellent color and dispersion properties.

Oil shale semi-coke (SC) is a bulk solid waste produced after shale oil being extracted from oil shale. It is abundant on the earth, but most of them are discarded or piled up as solid waste, and their reuse as resources is very limited. In this paper, adhering to the concept of “waste to materials“, the α-Fe2O3/SC hybrid pigments with the red color (a* = 29.68) better than commercial iron red pigments (a* = 26.92) were synthesized by an one-pot hydrothermal reaction of pretreated SC with Fe(III), using SC as a cheap starting material. The microscopic structure, chemical composition and color of the hybrid pigments were studied, and the reaction parameters for synthesizing the best hybrid pigments from SC were optimized. The results indicate that the hybrid pigments are mainly composed of SiO2 and Fe2O3, where α-Fe2O3 particles grow on the surface of SC-derived silicate substrate with a better dispersion. The hybrid pigments showed a good stability, especially an outstanding high temperature-resistant stability. The secondary heat treatment induced the further improvement of red color value of the hybrid pigments. This work provides a new way and solution for the rational disposal and functional application of SC waste.

Microwave radiation (MWR), a type of electromagnetic excitation source, reduces the synthesis temperature and processing time for chemical reactions compared to traditional synthesis methods. Recently, we demonstrated that MWR can engineer ceramics with different crystal phases compared to traditional methods [Journal of Materials Chemistry A5, 35 (2017)]. In this study, we further apply the MWR-assisted technique to improve the electrochemical performance of LiCoO2 cathodes by engineering TiO2 and ZrO2 ceramic coatings. Electrochemical tests suggest that the TiO2 coating improves the rate capability of the LiCoO2 electrode. Both TiO2 and ZrO2 coatings improve the high-voltage (4.5 V) cycling stability of LiCoO2. The capacity remaining is improved from 52.8 to 84.4% and 81.9% by the TiO2 coating and the ZrO2 coating, respectively, after 40 cycles. We compare these results with existing studies that apply traditional methods to engineer TiO2/ZrO2 on LiCoO2, and find that the MWR-assisted method shows better performance improvement. X-ray photoelectron spectroscopy measurements suggest that the improved cycling stability arises from the formation of metal fluorides that protect the electrode from side reactions with electrolytes. This mechanism is further supported by the reduced Co dissolution from TiO2/ZrO2-coated LiCoO2 electrode after cycling. This study provides a new toolbox facilitating the integration of many delicate, low melting point materials like polymers into battery electrodes.

The pore and microcrystalline structure of coal are studied by combining field emission-scanning electron microscopy (FE-SEM), nuclear magnetic resonance (NMR), and Raman spectroscopy to better understand the physicochemical evolution of bituminous coal treated by high-voltage electric pulses (HVEP) under different capacitance conditions. Experimental results show that the capacitance has no significant impact on the breakdown voltage of the coal body during HVEP treatment. However, increasing the capacitance can effectively increase the porosity of coal cores. In particular, the influence of increasing the capacitance on the macropores is obviously more significant than that on the micropore; besides, increasing the capacitance improved connectivity between the mesopores and macropores. In addition, following HVEP treatment, the microcrystalline defect of coal became smaller and pore arrangement more orderly. Thus, the larger the capacitance is, the more is the energy injected into the coal and the more obvious the change of the coal microcrystalline structure.

Fiber-shaped supercapacitors (FSSCs) are promising devices in the wearable electronics because of their good flexibility, weavability, tiny volume and lightweight. However, the low stretchability and energy density limit their practical applications on wearable electronics requiring deformation and high energy density. It remains challenging to increase the energy densities of FSSCs without sacrificing their stretchability. Herein, we design and construct a wearable, stretchable and high-energy density CNT/MnO2 nanosheets FSSCs by wrapping the fiber supercapacitors on the spandex yarn. The CNT/MnO2 FSSCs show high stretchability up to 80%, ultrahigh capacitances of 685 mF cm−2 and energy density of 15.2 μWh cm−2. Furthermore, the CNT/MnO2 FSSCs have the good flexibility, stability and ultralong cycle life. In addition, we also develop the in situ characterization strategy to evaluate the structure evolution during the stretching process of the CNT/MnO2 FSSCs for better understanding the structure evolution of stretchable FSSCs. This work paves the way for the high-performance stretchable energy storage devices.

To meet the needs of corrosion resistance and electrically conductivity for metallic bipolar plates that are employed in proton exchange membrane fuel cells (PEMFCs), a TiSiN nanocomposite coating was fabricated on to a Ti–6Al–4V substrate using reactive sputter-deposition through the double cathode glow discharge plasma technique. The microstructure of the TiSiN coating comprised nanocrystallite TiN grains embedded in an amorphous Si3N4 matrix. Electrochemical measurements were employed to investigate the corrosion behavior of the TiSiN coating in the simulated operating environments of a PEMFC, specifically 0.5 M H2SO4 solution containing different HF concentrations (namely 2, 4 and 6 ppm) at 70 °C pumped with H2 at the anode and air at the cathode. With increasing HF concentration, a higher corrosion current density and lower corrosion potential were observed from both the coating and the uncoated substrate, indicating that the addition of HF accelerated their corrosion rates under these conditions. Compared to the uncoated substrate, the TiSiN coating showed a markedly higher corrosion resistance at all HF concentrations. The passive film that formed on the TiSiN coating, with a resistance of the order of magnitude of ~107 Ω cm2, displayed good electrochemical stability and was less affected by changes in HF concentration. For the TiSiN coating, the values of interfacial contact resistance (ICR) were 14.7 mΩ cm−2 and 18.3 mΩ cm−2, respectively, before and after 2.5 h potentiostatic polarization with 6 ppm HF under cathodic conditions under a compaction pressure of 140 N cm−2. Both values are much lower than those for the bare substrate. Moreover, the TiSiN coating was shown to improve the hydrophobicity of Ti–6Al–4V that would help facilitate water management in the PEMFC operating environment. This coating, which exhibited excellent corrosion resistance, electro-conductivity and hydrophobicity, is therefore a promising material for protecting metallic bipolar plates from corrosive attack.

Electrocatalytic hydrodechlorination (ECH) has been proposed as a potential technology for the effective degradation of organochlorine contaminants. In this study, a nanoscale Pd/TiC catalyst with low resistance was dip-coated onto Ti, aiming to fabricate a stable Pd/TiC/Ti electrode with enhanced ECH reactivity for efficient dechlorination. Electrochemical techniques indicated that the Pd/TiC/Ti electrode had a larger electrochemically active surface area and more rapid interfacial charge transfer than the conventional Pd/C/Ti electrode. In a batch experiment, the dechlorination rate for ECH of 2,4-dichlorobenzoic acid (2,4-DCBA, a model pollutant) by Pd/TiC/Ti was 1.3–14.5 times higher than those by Pd/C/Ti, Pd/MWCNTs/Ti, and Pd/MoS2/Ti, respectively. Scavenger experiments, ESR spin-trapping spectroscopy, and cyclic voltammetry clarified the intensified atomic H* generation by Pd/TiC/Ti. DFT calculations revealed that Pd/TiC/Ti had stronger binding ability with atomic H* (Eads: −2.89 eV vs. −2.44 eV) and 2,4-DCBA (Eads: −3.62 eV vs. −2.15 eV), respectively, when compared with Pd/C/Ti. As a result, enhanced generation of atomic H*, together with strengthened adsorption of atomic H* and 2,4-DCBA, would contribute to a faster ECH reaction. The Pd/TiC/Ti electrode retained its reactivity after 10 successive batch experiments (80 h), and showed high tolerance to the constituents in actual water matrices including lake water and river water. This study proposed a promising ECH electrode for the treatment of chlorinated organics in water matrices.

Achieving high performance during low-temperature operation of lithium-ion (Li+) batteries (LIBs) remains a great challenge. In this work, we choose an electrolyte with low binding energy between Li+ and solvent molecule, such as 1,3-dioxolane-based electrolyte, to extend the low temperature operational limit of LIB. Further, to compensate the reduced diffusion coefficient of the electrode material at ultralow temperature, nanoscale lithium titanate is used as electrode material, which finally, we demonstrate a LIB with unprecedented low-temperature performance, delivering ∼60% of its room-temperature capacity (0.1 °C rate) at −80 °C. Though insufficient ionic conductivity of the electrolyte is generally considered as the main reason for the poor low-temperature performance in LIBs, we found that the sluggish desolvation of solvated Li+ at the liquid-solid interface might be the critical factor. These findings provide evidence for the effective design of robust LIBs for ultralow temperature applications.

Coal and gas outburst is a dynamic phenomenon in underground mining engineering that is often accompanied by the throwing and breakage of large amounts of coal. To study the crushing effect and its evolution during outbursts, coal samples with different initial particle sizes were evaluated using a coal and gas outburst testing device. Three basic particle sizes, 5–10 mesh, 10–40 mesh, and 40–80 mesh, as well as some mixed particle size coal samples were used in tests. The coal particles were pre-compacted at a pressure of 4 MPa before the tests. The vertical ground stress (4 MPa) and the horizontal ground stress (2.4 MPa) were initially simulated by the hydraulic system and maintained throughout. During the tests, the samples were first placed in a vacuum for 3 h, and the coal was filled with gas (CH4) for an adsorption time of approximately 5 h. Finally, the gas valve was shut off and the coal and gas outburst was induced by quickly opening the outburst hole. The coal particles that were thrown out by the outburst test device were collected and screened based on the particle size. The results show the following. (1) Smaller particle sizes have a worse crushing effect than larger sizes. Furthermore, the well-graded coal particles are weakly broken during the outburst process. (2) As the number of repeated tests increases, the relative breakage index grows; however, the increment of growth decreases after each test, showing that further fragmentation becomes increasingly difficult.

The seepage problem of coal-bed methane (CBM) has attracted increasing attention from the research and industry communities. Coal permeability, which is a key parameter for CBM production, has been extensively studied through both laboratory and field tests, mathematical modeling, and numerical simulations. However, relatively little work has been done to investigate the effect of matrix water content on coal permeability evolution. Because most coal seams contain water, it may have direct impact on the CBM seepage capacity. Therefore, in this paper, CBM seepage at different matrix water contents was investigated experimentally. Results demonstrate that coal permeability decreases with the increase in water content. It was also found that both pore pressure and water content can greatly affect CBM migration characteristics and that the sorption strain and permeability were mostly controlled by pore pressure. In addition, water can have an impact on gas adsorption and sorption-induced deformation, which can further affect seepage channel width, leading to change in coal permeability. In general, coal permeability was observed to decrease exponentially with the increase in water content and pore pressure. Moreover, a coal adsorption model and an adsorption-permeability model were established, considering water content and excess adsorption under constant external stress and triaxial strain conditions. The proposed permeability model showed good agreement with the experimental results. The present study provides for better understanding of coal permeability evolution in a water-bearing condition and for developing an improved model to simulate the CBM migration process under such condition more accurately.

Building supercapacitors that can provide high energy density over a wide range of temperatures, where traditional energy storage devices fail to operate, requires tailoring of electrolyte and/or electrode material. Here, we show that record gravimetric capacitances of 164 and 182 F g−1 can be attained at −100 and 60 °C, respectively, nearly equivalent to the room-temperature value of 177 F g−1, when activated carbon-based electrodes with predominantly slit-shaped micropores and a low freezing-point electrolyte are used. Experimental data and density functional theory calculations suggest that electrode material characteristics, such as pore size and shape, matched with the effective size of partially solvated ions of the electrolyte, are the key factors in achieving such performance. This study provides evidence for the effective design of robust supercapacitors with sustained performance at both low and high temperatures.

The existing magnetostrictive guided wave transducers are usually circumferential symmetric and cannot be installed on semi-exposed pipes, such as water wall pipes. To test the semi-exposed pipes, we proposed a magnetostrictive transducer with semicircular structure, which consists of a semi-ring magnet and a semicircular coil. Firstly, energy coupling mechanism of magnetostrictive guided wave in the semi-exposed pipe is analyzed. The finite element models of the semi-ring magnet and the semicircular coil are established to study the magnetic field distributions in the pipes. From the simulation results, the semi-ring magnet can provide an axial static magnetic field that is uniform in circumferential direction and the axial direction of the pipe. The semicircular coil can generate the asymmetry axial alternating magnetic field. The magnetic field strength of the pipe surface covered by the semicircular coil is about two times than the uncovered pipe surface. The asymmetry magnetic field causes the induced guided waves include not only axisymmetric modes, but also non-axisymmetric modes. A prototype magnetostrictive guided wave transducer for semi-exposed pipe is provided. Experiments are carried out on two pipes with notch and wear defects respectively. The results show that the transducer can generate the longitudinal mode guided waves as the mainstay and the flexural mode as the auxiliary. The flexural mode is removed by the chirplet transform and the proposed transducer can be used to detect the flaw in the semi-exposed pipe.

Knowledge regarding the time-dependent behavior of rocks is essential to estimate the long-term deformation and stability of underground structures. The rock strength increases with the increasing loading rate. However, the loading rate dependence in postfailure regions under confining pressure remains unclear. In this study, triaxial compression tests were conducted on four types of rocks to examine the loading rate dependence in both peak and postfailure regions. Results demonstrate that an increase in residual strength with a tenfold increase in the strain rate was approximately proportional to 4% of the residual strength. Furthermore, the increase in peak strength with a tenfold increase in the strain rate increased at a rate of approximately 4% of peak strength. The obtained results were applicable to all the sample rocks and can be easily employed for improving the constitutive equations. Finally, the effect mechanism of the confining pressure on the loading rate dependence of rock strength is discussed.

As the relative displacement of the pile-rock interface increases, the sliding and mutual squeezing between asperities of the pile-rock interface causes the normal stress increases by Δσn with the normal displacement. All prevalent theoretical methods use the elastic solution of cylindrical cavity expansion in an infinite medium to calculate the normal stress increment Δσn during an increase in the relative displacement of the pile-rock interface. To further optimize the calculation method for the normal stress increment Δσn of the bore wall of the rock-socketed pile, this study conducts an elasto-plastic analysis of the stress and displacement fields during expansion using cavity expansion theory and the Hoek-Brown failure criterion. Based on the obtained elasto-plastic solution, some validation cases are represented to illustrate the difference between the results of Δσn due to both elastic and elasto-plastic solutions. When the normal displacement is greater than the critical normal displacement and the rock of the bore wall yields, the elastic method overestimates the Δσn and shear strength at the pile-rock interface, which renders the design unsafe. Three modifications are then proposed to calculate the shear strength at the pile-rock interface. After that, parametric studies are conducted to examine the effects of geometric and rock-related parameters on the Δσn of the bore wall. Finally, the radial and tangential stress paths and possible crack formation of rock of the bore wall during expansion are discussed.

In order to increase the thermal efficiency, combustion are designed to operate at higher temperature, which requires highly efficient cooling structures for combustion walls. Impingement is an effective structure to enhance the convective heat transfer in the combustion cooling. In the present study, two array impingement cooling structures with cross-flow are presented, and the heat transfer characteristics are obtained experimentally. The heat transfer performance of the impingement cooling structures are studied by using the transient liquid crystal thermography technique for turbulent flow in rectangular channels within the Reynolds number range from 75,000 to 125,000. The impingement hole diameters of the two test pieces were 12mm and 11mm, respectively. The impingement distances-to-hole diameter ratios (z/d) were 1.25 and 2, and the dimensionless hole spacing (x/d) was 2.5 and 2.727. It is found that crossflow shifts the jet downstream, resulting in asymmetric flow, the heat transfer coefficient upstream of the jet weakens, and the shape of stagnation area transitions from circular to hoof-shaped. The cross-flow disturbance accelerates the diffusion of the jet, which makes the distribution of the Nusselt number on the target more uniform, and the overall heat transfer on the target is enhanced. With the change of cross-flow intensity, there are differences in the influence of heat transfer on target under different impact geometries.

Sulfur-containing iron materials such as sulfidized nanoscale zerovalent iron (SNZVI) have shown outstanding water remediation performance in many recent studies, which is largely attributed to its high hydrophobicity compared to that of NZVI. However, the role of sulfur in the reactions, and the origin of the hydrophobicity of SNZVI, were still unclear. In this paper, for the first time, we conducted ab initio molecular dynamics simulation using an explicitly solvated model on both Fe and S-containing Fe surfaces, to explore the hydrophobicity of S-containing Fe materials. We found that the high hydrophobicity of these S-containing Fe surfaces originates from the hydrophobic nature of S: both doping S on top of the Fe surface and inserting S onto an Fe surface can significantly improve the surface hydrophobicity by increasing the distance between the water layer and the Fe surface. This exposes empty Fe sites which do not interact with water and in turn reduces hydrogen evolution. To compare with the theoretical analysis, we experimentally analyzed the hydrophobicity of both NZVI and SNZVI surfaces, leading to a good agreement with our theoretical analysis. We then theoretically show that the doping of other p-block elements (e.g., N and P) to iron surfaces can also create a hydrophobic phenomenon. Most importantly, this study points out that the potential contribution of hydrophobicity to the reactivity on liquid-phase reaction materials should not be ignored in the mechanistic analysis.

Atomic H* has been regarded as the key active species for the electrocatalytic hydrodechlorination (ECH), and the electrode design and operation conditions are related to the atomic H* generation. However, there is limited understanding of how the operation parameters affect the atomic H* generation and utilization. Due to the fact that Pd was inefficient in water dissociation step, MnO2 was combined with Pd to construct a novel Pd/MnO2/Ni foam cathode. Cyclic voltammetry confirmed that Pd/MnO2/Ni foam cathode with MnO2 load of 0.51 mg cm−2 possessed the highest atomic H* generation and ECH activity. Excessive Pd load (>0.44 mg cm−2) was detrimental to ECH because of the side hydrogen evolution reaction (HER). Operation conditions (e.g. applied current and electrolyte concentration) would directly affect the cathode potential, which was an important indicator of the atomic H* generation. The optimal cathode potential was determined to be −0.85 V when the applied current was 10 mA in this study. The electrolyte concentration of 10–15 mM was able to provide sufficient atomic H* for ECH, while excessive input of electrolyte would favor HER but inhibit ECH. ECH at acidic and neutral/alkaline solution underwent different pathways for atomic H* generation and further affect the utilization of atomic H*. After 120 min reaction, >70% of atomic H* could be selectively used for ECH at initial pH of 4.0 and 5.0, while only ∼37% was used for ECH at initial pH of 7.0. This work correlated the reactivity of electrode with the atomic H* and cathode potential, which would provide strategies for ECH catalyst design and operation optimization.

A ZrC nanoceramic coating was prepared on the bare 316 stainless steel for improving the cavitation erosion resistance by the double glow discharge sputter technique. The phase constitution and surface microstructure of the ZrC nanoceramic coating were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscopy. A 10-µm-thick ZrC nanoceramic coating exhibited equiaxed grains with an average grain size of 9 nm. The adhesion strength and mechanical properties for the ZrC nanoceramic coating were evaluated by scratch test and nanoindentation. The hardness value of the ZrC nanoceramic coating was about four times that of the uncoated 316 stainless steel. The cavitation erosion behavior of the ZrC nanoceramic coating in tap water was characterized by the combination of an ultrasonic vibration system with an electrochemical workstation. The volume loss, erosion depth, scanning electron microscope morphology, and electrochemical test were adopted to assess the surface damage of the ZrC nanoceramic coating. The results show that the volume loss of the ZrC nanoceramic coating is 0.53 mm3, which is only 46% of the 316 stainless steel (1.14 mm3) after cavitation test, and erosion damage of the ZrC nanoceramic coating is significantly decreased as compared to the uncoated 316 stainless steel. The electrochemical test results also indicate that the ZrC nanoceramic coating shows higher corrosion resistance than the 316 stainless steel under cavitation erosion condition. Thus, the ZrC nanoceramic coating can be adopted to enhance the cavitation erosion resistance of the 316 stainless steel.

The effect of Ag additions on the structural, mechanical and thermodynamic properties of α-Nb5Si3 is systematically investigated using the first-principles calculations based on density functional theory. The calculated formation enthalpies show that when Nb atoms in α-Nb5Si3 are replaced by one and two Ag atoms, Ag atoms prefer Nb4c sites rather than Nb16l sites. With increasing concentration of Ag atoms, the elastic moduli and theoretical Vickers hardness of the α-(Nb1-xAgx)5Si3 compounds decrease, while they become more ductile. Ag additions slightly raise the mechanical anisotropies of α-(Nb1-xAgx)5Si3 compounds and increases the linear thermal expansion coefficients of the α-(Nb1-xAgx)5Si3 compounds along the c and a axes, with a decrease in the αc/αa ratios. Finally, the anisotropy of acoustic velocities and Debye temperatures for the α-(Nb1-xAgx)5Si3 compounds were also calculated.

Viscosity behavior of coal ash slag in the slagging gasifier is the key for the stable operation. The oxidation state of iron in the slag is sensitive to the gas chemistry, which influences the viscosity behavior. The atmosphere in the gasifier varies from weak oxidizing to strong reducing, and the effect on slag viscosity behavior is still not available. In this study, viscosities of two coal ash slags of which chemical compositions located in the anorthite and gehlenite regions in the phase diagram SiO2-Al2O3-CaO, were investigated under argon, mild reducing atmosphere and strong reducing atmosphere by the high temperature rotating viscometer. The wet chemical analysis was used to analyze the oxidation state of iron in coal ash slag. Thermodynamic calculation, XRD analysis and SEM-EDX were used to investigate crystallization behavior of the slags during cooling. The results show that the effect of atmosphere on the viscosity of fully molten slag is not obvious. The slag has the lowest viscosity value under the mild reducing atmosphere for the abundance of Fe2+ (80% total iron). Under strong reducing atmosphere, the precipitation of metallic iron in coal ash slag increases slag viscosity as the content of network modifier declines. However, the effect of atmosphere on the slag viscosity is significant after the slag crystallizes. For the slag located in the anorthite region, the presence of metallic iron acts as crystal seed and significantly accelerates the crystallization of anorthite, resulting in a sharp increase of slag viscosity. However, the effect of atmosphere on the viscosity of slag located in the gehlenite region is not obvious because the crystallization propensity of gehlenite is too strong to be influenced by metallic iron precipitation.

The purpose of this paper is to study the effect of chemical heat treatments on cavitation erosion resistance of the 304 stainless steel. Three types of diffusion layers are prepared on the 304 stainless steel using gas nitriding, gas carburizing, and carbonitriding treatments. Phase composition and surface microstructure of the diffusion layers are characterized by X-ray diffraction and scanning electron microscopy. And then, the cavitation erosion behavior of the diffusion layers are tested and compared with the one of the 304 stainless steel. The cavitation test is performed in an ultrasonic vibration system integrated with an electrochemical workstation. The mass loss, scanning electron microscopic morphology, and electrochemical test are adopted to assess the surface damage of the diffusion layers. A measurement for the mechanical properties of the diffusion layers shows that the hardness and the elastic modulus of the gas nitrided diffusion layer, carbonitrided diffusion layer, carburized diffusion layer, and 304 stainless steel are 5.3 GPa and 260 GPa, 4.2 GPa and 236 GPa, 4.0 GPa and 210 GPa, 2.5 GPa and 193 GPa, respectively. A cavitation erosion test of 14 h shows that mass loss of the gas nitrided diffusion layer, carbonitrided diffusion layer, carburized diffusion layer, and 304 stainless steel is 5.19 mg, 8.97 mg, 14.37 mg, and 6.62 mg, respectively. The electrochemical test results also indicate that the gas nitrided diffusion layer has a higher corrosion resistance than the carburized diffusion layer, carbonitrided diffusion layer, and stainless steel under cavitation erosion condition. As a conclusion, the gas nitrided diffusion layer is capable of enhancing the cavitation erosion resistance of the stainless steel, while the carburized diffusion layer and carbonitrided diffusion layer increases the mass loss of the stainless steel under cavitation erosion condition.

In this study, a β-Ta2O5 coating was deposited onto a Ti–6Al–4V substrate using a double-cathode glow discharge plasma technique. The hardness and elastic modulus values of the β-Ta2O5 coating were...

Low-temperature tolerant supercapacitors are very important for industrial application and scientific explorations. To date, most of the studies focused on the optimization of electrolyte system to improve low temperature performance of supercapacitors. Although some improvement has been reported, the capacitance performance decreases significantly at low temperature, especially rate performance. In this work, activated carbon coated CNT core-shell nanocomposite is fabricated to investigate the temperature dependence of capacitance. We found that the poor capacitive performance at low temperature is mainly caused by ion migration at liquid-solid interface, especially for the pores whose size is smaller than the solvated ion. When the pore size of activated carbon is large, ions can freely enter these pores and the capacitance (97 F g−1) measured at −70 °C is comparable with that at room temperature (108 F g−1). Combined with both high conductivity and short diffusion path, the composite exhibits high rate performance and long cyclic stability. This study provides a practical guide for the design of supercapacitor with high performance at low temperature.

In recent years, high-voltage electric pulse (HVEP) technology has been suggested to improve the permeability of coal seams. However, the effect of moisture content on the structure evolution of coal subjected to HVEP is not clear, which restricts the wide spread application of this technology. In this study, the breakdown voltage of coal samples with different moisture content was tested, and an exponential function relationship was established between the average breakdown field strength and the moisture content of bituminous coal samples. We investigated the changes in pore structure by combing scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) results, to better understand the pore structure evolution characteristics of coal with different moisture content. Furthermore, changes in the chemical structure of the bituminous coal samples with different moisture content subjected to HVEP were investigated by Fourier transform infrared spectroscopy (FTIR). The results show that many mesopores and macropores are formed in the coal body under the action of HVEP, and the connectivity between the mesopores and the macropores is very good. In general, the higher the moisture content of coal body, the more pores and cracks will be formed in the process of electric pulse breakdown. The total porosity of coal samples with moisture content of 1%, 1.5%, and 2% is significantly higher than that of coal samples with moisture content of 0% and 0.5% after electric pulse breakdown. Therefore, the increase of moisture content is beneficial to improve gas permeability in coal body. The FTIR spectral analysis indicates that oxidation occurs on the plasma channel surface in the breakdown process of coal samples with different moisture content. Furthermore, the increase of moisture content in coal favors the generation of more oxygen-containing functional groups, which will facilitate the desorption of methane.

Ground temperature rises with the increase of mining depth. In this study, in order to investigate the seepage properties of coal with slippage and temperature effects, a thermo-fluid-solid coupling experiment on the methane-bearing coal was performed via the triaxial servo-controlled seepage equipment. Then, the permeability of coal in the gas loading-unloading processes was measured under different temperatures. Finally, a fractal slippage effect model with the temperature effect was developed to study the influences of pore pressure and temperature on permeability characteristics. The results indicate that as pore pressure rises, the axial strain of coal increases, while the radial strain decreases in the loading process. On the contrary, the axial and radial strains exhibit opposite trends with the rise of pore pressure in the unloading process. With the rise of temperature, the axial strain grows firstly and then falls, while the radial strain keeps decreasing. The permeability of coal decreases firstly and then levels off with the rise of pore pressure in both loading and unloading processes. Moreover, the slippage effect gradually weakens and flattens out with the rise of pore pressure. As the temperature rises, the slippage-induced permeability variation grows in the loading process, whereas it increases firstly and then goes down in the unloading process. The present work can provide a theoretical basis for coal seam gas extraction.

The development of hard, multi-layer coatings is an effective strategy to enhance the wear resistance of cutting tools and so extend their service life. In the present study, a sandwich structured TiN/g-TiSiN/TiSiN film (where a graded (g-) TiSiN layer with an increasing Si content from 0 to 10 at% was inserted as a transitional layer between the TiN layer and the TiSiN layer with a fixed silicon content of 10 at%) was prepared on to a M42 tool steel substrate. Its mechanical properties were compared to both a dual-layered TiN/g-TiSiN film and a monolithic TiN film. Nanoindentation testing, assisted by focused-ion-beam (FIB) microscopy, was employed to evaluate contact-induced deformation and the mode of fracture of these films. Indented regions created on samples by a 5 μm radius indenter were examined by transmission electron microscopy (TEM). Finite element analysis was used to model the stress distributions within these films and predict the regions where crack initiation and growth may occur. The deformation of the monolithic TiN film was found to be predominantly accommodated by shear sliding along columnar grain boundaries, leading to a lower resistance to deformation. For the bilayer TiN/g-TiSiN film, the g-TiSiN layer hindered the propagation of columnar cracks, however, this bilayer film exhibited a stress concentration together with radial cracks at the bottom of the film. Compared with the former two films, the sandwich-structured film that contained the graded TiSiN interlayer exhibited the highest resistance to contact damage. This is because the graded TiSiN interlayer altered the stress distribution in the film and lowered the overall stress concentration level. Keywords: TiSiN graded interlayer, Deformation mechanism, Nanoindentation, Finite element method

High-voltage electrical pulses (HVEP) can potentially be used to increase the yield of low-permeability coalbed methane (CBM) reservoirs. This study highlights the pore change and permeability evolution characteristics of anthracite coal samples using HVEP treatment. An experimental system was developed to study the variation of coal core permeability by subjecting the coal samples to HVEP treatment under confining conditions. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses were adopted to gain a clearer insight into the changes in pore structure. SEM images revealed that the surface morphologys of the raw coal samples were complete and smooth, whereas those of the coal samples subjected to HVEP developed many pores and cracks. The pores and cracks generated enhanced the permeability of HVEP-treated coal samples. MIP test results showed that the cumulative pore volume of the coal samples subjected to HVEP was significantly greater than that of raw coal samples. Importantly, the HVEP technology had a significant effect on mesopores and macropores, compared with micropores. Because the mesopores and macropores are critical for gas transport, the technology will be helpful for enhancing CBM recovery. Seepage experiments results showed that with the variation of CH4 injection pressure from 0.4 MPa to 1.2 MPa, the permeability of both raw coal samples and coal samples subjected to HVEP showed a decline at a particular confining stress. The permeability of Yangzhuang (YZ) coal sample subjected to HVEP was 1.6–2.2 times that of YZ raw coal under a constant confining pressure, and the permeability of Guhanshan (GHS) coal sample subjected to HVEP is 1.8–2.4 times that of the GHS raw coal sample. At the same confining pressure and CH4 injection pressure, the permeability of the coal samples subjected to HVEP was obviously higher than that of the raw coal samples.

Coal ash slag viscosity is the most important parameter for the design and the stable running of entrained flow gasifier. Iron serves as the most abundant variable-valence element in coal ash slag, but the effects of iron in coal ash slag on viscosity and slag crystallization under the gasification conditions are not available. In this research, the iron transformation behaviors are discussed, and predictive models for iron transformation based on the ash chemical composition, atmosphere, slag residence time and temperature are established. In the fully liquid slag, Fe2+/Fe3+ increases with SiO2/Al2O3 (mass ratio) and temperature, but it decreases with the increasing iron content, α value (α = CaO/(SiO2+Al2O3), mass ratio), and oxygen partial pressure. The equilibrium and kinetic model considering CO and H2 diffusion is built for prediction of Fe2+/Fe3+ in slag at given temperature, oxygen partial pressure, and residence time. The model is applied to predict the Fe2+/Fe3+ of Yanzhou coal and it is found that Fe2+ in Shell slag is higher than that in Texaco slag. In partial crystalline slag, the iron transformation is sensitive to the variations of SiO2+Al2O3 and SiO2/Al2O3 because of the formations of melilite and spinel. The prediction models for melilite and spinel transformation are also built, but the result has not been validated due to lack of in-situ results in the commercial gasifier. The above models offer the guidance for the prediction and adjustment of slag behavior in the gasifier, especially for the iron-rich coal.

In this study, a novel approach was developed for the dechlorination of 2,4-dichlorobenzoic acid (2,4-DCBA) via the combination of the moveable activated carbon (AC) supported palladium (Pd) nanoparticles and nickel (Ni) foam electrode. The morphology and chemical structure of Pd/AC catalyst was investigated by various characterization techniques, including SEM, TEM, EXS-mapping, XRD, and XPS. Pd nanoparticles was successfully loaded and dispersed on the AC, accompanied with the significantly enhanced reactivity. The removal rate of 2,4-DCBA by Ni electrode with moveable Pd/AC catalyst was 222, 25, and 5 folds higher than dispersed AC and Ni electrode system, chemical deposited Pd/Ni electrode, and electrodeposited Pd/Ni electrode, respectively. Compared with the conventional electrocatalytic reductive approach which deposited Pd on the Ni foam electrode, moveable Pd/AC catalyst possesses higher surface area, more atomic H∗ production and more active sites, favored mass transfer, and enhanced reactivity, without the consideration of catalyst loss and deactivation. The effects of Pd:AC mass ratio, constant current, initial solution pH, and electrolyte concentration on the dechlorination of 2,4-DCBA were studied. Generally, high Pd loading, constant current, and acidity favored the dechlorination of 2,4-DCBA, while excessive electrolyte would inhibit the dechlorination of 2,4-DCBA. Good longevity and recyclability of moveable Pd/AC catalyst was confirmed via consecutive experiments. The findings of the present study show that making the catalyst moveable is a promising strategy for electrocatalytic remediation technology.

Coalbed methane (CBM) development is in progress in northwestern China, where there are deposits of medium volatile bituminous coal (MVBC) and high volatile bituminous coal (HVBC). Stress sensitivity can lead to low gas-production during CBM development. In this study, three groups of HVBC samples and one group of MVBC samples are applied for low-field nuclear magnetic resonance (LF-NMR) and permeability-porosity tests (P-PT) under confining pressure. Each group contained two cores with similar physical properties, and one is used for LF-NMR and the other for P-PT under confining pressure. The key apertures dominating the reduction of permeability are revealed by comparative analysis of the results of LF-NMR and PP-T under confining pressure. Influences of multiscale pores and structure of macro-pores and fractures (MP-F) on stress sensitivity are discussed. In addition, this paper discusses the methods for determination of compressibility coefficients. The results shows that MP-F are the key apertures influencing stress sensitivity. Compressibility of macro-pore is the greatest, followed by meso-pores (MEP), and that of micro-pores and transition pores (MP-TP) is the lowest. Stress sensitive stages are influenced by structure of MP-F. Method A (based on P-PT) is suitable for calculating compressibility coefficient of coal with a high proportion of MP-F and method B (based on LF-NMR) has advantages for calculating compressibility coefficients of MP-TP, MEP, and MP-F, respectively. An improved model, considering matrix deformation of low rank coal and compressibility coefficient of key apertures, is proposed to calculate permeability under increased effective stress.

In the study, a series of monotonic triaxial compression tests were carried out on Emochi andesite to evaluate the effects of confining pressure on progressive failure behaviors. The three-dimensional digital image correlation (3D-DIC) system consisting of six cameras was used to capture the images based on the transparent pressure cell. The effects of confining pressures on stress thresholds, energy evolution, field strain patterns and crack evolution were investigated qualitatively or quantitatively. The crack initiation (σci), crack damage (σcd) and peaks stress (σc) increased with confining pressure and the ratios σci/σc and σcd/σc respectively varied from 57.74% and 75.11% to 64.02% and 85.33%. Total energy U, elastic energy Ue, and dissipation energy Ud at different characteristic points increased with confining pressures. Field strain patterns indicated that localization developed rapidly in the post-peak region due to the acceleration of crack propagation and damage evolution. The failure mechanisms of Emochi andesite under the uniaxial and triaxial condition are respectively tension-shear destruction and shear destruction. Furthermore, the stress-strain response inside and outside the localization zone are characterized by strain accumulation or inelastic unloading. Finally, a method of confirming the stress level of localization initiation is proposed based on the DIC technique. The stress level decreases with confining pressure. The study provides a useful reference for understanding the failure process of rocks and improving the stability and safety of underground structures.

To investigate the effects of Al alloying on the erosion-corrosion resistance of β-Ta5Si3, both a β-Ta5Si3 coating and an Al-alloyed β-Ta5(Si0.83Al0.17)3 coating were synthesized on a 316 substrate by the double cathode glow discharge technique. The phase constitution, composition and microstructure of the two coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The two coatings were composed of nearly rounded D8m-β-Ta5Si3 grains with an average size of ∼4 nm, and after the addition of Al, the preferred growth orientation for the β-Ta5Si3 coating changed from (4 0 0) to (0 0 2). The hardness, elastic modulus and contact damage resistance of the coatings were measured using a nanoindentation tester. The results showed that Al alloying improved the contact damage resistance of β-Ta5Si3 with only a slight decrease in hardness. The erosion-corrosion behavior of the two coatings was performed in a 3.5 wt% NaCl solution containing a 12 wt% concentration of silica sand under two phase slurry flow condition and in a 3.5 wt% NaCl solution under ultrasonic cavitation erosion conditions. This revealed that the Al alloyed β-Ta5Si3 has a higher resistance to both erosion-corrosion and ultrasonic cavitation erosion as compared to the binary β-Ta5Si3 coating.