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The non-contact long pulse thermography method is commonly used to detect the defects in thermal barrier coatings (TBCs). The profile of interfacial defect in TBCs can be monitored by infrared camera under the irradiation of the excitation source. Unfortunately, the defect profile is always blurry due to heat diffusion between the defect area and the intact area. It is difficult to quantify the size of defect size in TBCs. In this work, combined with derived one-dimensional heat conduction analytical model, a non-contact long pulse thermography (LPT) method is applied to quantitatively investigate the interface defects in TBCs. Principal component analysis (PCA) and background subtraction method are used to improve the contrast of the defect profile in collected thermal images. By fitting the results between the profile of the interface defect in thermal images and the predicted shape of the model, the interface defect size can be determined. Furthermore, a simple extension of proposed method for interfacial defects with irregular shape is presented. The predicted errors for round defect with diameters of 3 mm, 5 mm and 7 mm are roughly distributed in the range of 3%~6%, which are not affected by the defect diameter.

When mesoporous nanomaterials and graphene oxide have been used in anti-corrosion coatings, new nanocoatings have attracted greater attention. Adding nano-fillers with special structures and corrosion inhibitors to epoxy coatings has been proven to effectively enhance the corrosion resistance of coatings. However, studies have pointed out that the added corrosion inhibitors are easily degraded by UV light and react with the metal substrate or materials in the coating, resulting in a significant reduction in the service life of the coating. To this end, in this study, the corrosion inhibitor was encapsulated in mesoporous silica with pH response, and the functional silica was composited with graphene oxide to prepare novel graphene oxide/functional mesoporous silica nanoparticles. Coatings with this special filler added have strong anti-corrosion potential and can be applied in marine anti-corrosion contexts, such as containers, in the future. The filler not only has a physical barrier ability but also can effectively prevent the degradation of the inhibitor due to ultraviolet rays. At the same time, in the early stage of corrosion, the release of inhibitors can be effectively controlled by the change in PH to achieve the purpose of preventing corrosion. UV spectrophotometry confirmed the stable encapsulation and controlled release of the inhibitor. Electrochemical-impedance spectroscopy showed that the |Z|0.01 Hz value of the smart anti-corrosion epoxy coating was about 10,000 times higher than that of the pure epoxy coating. Through the FT-IR mapping test, it was found that in the area of mechanical damage, the alkaline environment created by the initial corrosion can induce the release of tannic acid and react with common corrosion products to form iron tannins, which effectively inhibits the further occurrence of corrosion. This method provides an effective method for the design of heavy-duty anti-corrosion coatings.

Thermal barrier coatings (TBCs) suffer from the thermo-chemo-mechanical coupling action of thermal shock and calcium–magnesium–alumina–silicate (CMAS) corrosion. However, the failure mechanism of TBCs under the synergistic effect of thermal shock and CMAS corrosion is still unclear due to a lack of an environmental simulator. Herein, an 8YSZ ceramic coating is deposited on a PtAl bond coating/DD419 nickel-based single crystal superalloy substrate using the electron beam physical vapor deposition (EB-PVD) method. The thermo-chemo-mechanical coupling effect of TBCs is achieved in a self-developed environmental simulator. The interaction of volume expansion induced by the phase transition of ZrO2, structural degradation and thermal fatigue further increases the out-of-plane tensile stress and in-plane shear stress in the ceramic coating, which accelerates the initiation and propagation of surface vertical cracks and horizontal cracks. As multiple surface vertical cracks propagate to the interface and merge with interfacial cracks, the ceramic coating spalls from the substrate.

Second-order topological states in the artificial systems have been extensively studied, but the study in the phonons of atomic vibrations has been limited. In this paper, we propose that a phononic two-order topological phase can be realized in two-dimensional C3N, a previously synthesized and intensively investigated two-dimensional material, and its nontrivial phase arises from the mismatch between the Wannier center of the out-of-plane phonon modes and the atomic positions. Using a simplified force constant model, we find that gapped edge states and in-gap corner states can only exist on the structures with broken-pure-carbon-ring terminations, and this unexpected phenomenon can be explained by the electron-like filling anomaly for phonons. Further calculations reveal that these corner modes are robust to external disturbances. The nontrivial phononic phase in C3N provides an avenue in crystal for exploring higher-order topological phases in Bose systems.

In consideration of the high-density dislocations from the lithiation process of high-capacity electrodes in Li-ion batteries, in this paper, a new elastoplastic model is established to describe the diffusion-induced deformation and damage fracture. With the help of the relative physical quantities and state of charge, the surface damage and fracture behaviors of electrode materials are discussed based on the elastic-perfectly plastic (PP) and the strain gradient plasticity (SGP) theories, respectively. The results show that the lithiation deformation could be alleviated by reducing the electrode scale, and the plastic flow can play an essential role in the extrusion ratcheting effect relating to the upper surface fracture. Furthermore, the interface damage is more likely to appear by increasing the initial bond stiffness at the upper surface, which has little effect on the later fracture. A strong size effect is also found in the damage and fracture critical curves for the PP and SGP models.

There is an urgent need for reasonably designed matrixes with strong adsorption for polysulfides, fast reaction kinetics, and simple preparation for lithium–sulfur battery (Li–S battery) applications. Therefore, in this study, potassium ferrate was used to carbonize the petals of a hibiscus flower, and the doping of Fe3C was realized at the same time as the carbonization to prepare in one step a porous biochar nanosheet (Fe3C-HSB) composite material loaded with Fe3C particles. Fe3C plays a key role in lithium polysulfide (LiPS) chemical adsorption and other aspects, which can greatly improve the cycle stability of Li–S batteries. Because the prepared composite material has a unique nanosheet structure, it can effectively shorten the ion diffusion length, improve the electron charge transfer ability, and accelerate the progress of the electrochemical reaction. When sulfur is injected at 80.0 wt%, the discharge capacity of the Fe3C-HSB@S composite material is 777.1 mA h g−1, and it is stable at a rate of 1C. After 500 cycles, its reversible capacity can still reach 451.3 mA h g−1, with a single-turn capacity attenuation rate of 0.083%. Therefore, the rational design of porous biochar nanosheets doped with Fe3C particles is of great significance for improving the electrochemical performance of Li–S batteries, realizing renewable energy technologies, and promoting industrial applications.

TiO2-coated sulfur-acetylene black composite with a core-shell structure is synthesized via a simple process and investigated as a cathode for the lithium-sulfur batteries. The composite nanoparticle sizes are in the range of 50–100 nm, and the thickness of TiO2 shell is about 10–50 nm. The composites can greatly slow down the dissolution of lithium polysulfide and stabilize the structure during the charge and discharge process to achieve good long cycle and rate performances. After 500 cycles at a current density of 200 mA g−1, it still delivers a reversible capacity of 312.8 mAh g−1. And the nanocomposite can still remain a specific capacity of 625.4 mAh g−1 with the current density of 1000 mA g−1.

Poor long-term cycling stability and rate capability seriously restricted the commercial applications of silicon (Si) anodes, because of the huge volume change and the kinetic problems linked to th...

To improve the safety performance of lithium-ion batteries, the research of composite separator with high temperature resistance is one of the strategies. Herein, a poly(vinylidene fluoride-hexafluoropropylene)/cellulose/carboxylic titanium dioxide (PVDF-HFP/cellulose/C-TiO2) composite separator is prepared by the phase inverse method. The composite separator has higher porosity (63.65%) and electrolyte uptake (210.3%) than PP separator, exhibiting good heat resistance that can keep its shape and size under 160 °C for 0.5 h. Additionally, it has a superior ionic conductivity of 1.24–1.49 mS cm−1 and a lower charge transfer impedance at a room temperature, which brings about better cycle and rate performance. Promisingly, the cell assembled with the PVDF-HFP/cellulose/C-TiO2 composite separator has a high electrochemical working window and a high current charge of ability, and can undergo 10 charge-discharge cycles normally under 120 °C. The PVDF-HFP/cellulose/C-TiO2 composite separator has promising potentials for high current and voltage charging, which can improve the safety performance of the lithium-ion battery.

CFx@MnO2-nanowires composite materials are designed and synthesized for high energy density and high power density primary lithium batteries. The MnO2-nanowires intertwine with each other and coate...

A kind of binder-free CNTs/(Ni-P)/Sn composites are designed and electroplated on Cu current collector as anodes for lithium-ion battery. The influence of the Ni-P alloys on the physical and electrochemical performance of the CNTs/Sn anode is examined. XPS emphatically exhibits the buildup of the chemical binding force at the surface of Sn-CNTs electrode formed by the alloying reaction of Sn and Ni elements. The CNTs/(Ni-P)/Sn composites exhibit remarkable cycle performances with a reversible specific capacity of 400 mAh g−1 after 100 cycles which is much higher than that of the CNTs/Sn electrodes, and deliver an excellent rate performance of 372.3 mAh g−1 at 4 C. The positive-going effect of combining CNTs with Ni-P alloys was experimentally established to ensure the significant improvement of the electrochemical performance for Sn anode.

Biomass has rich porous texture and unique physical and chemical properties, so it is widely used to enhance the electrochemical performances of lithium-sulfur batteries. In this paper, porous biochar is fabricated by easily obtained folium cycas. Acetic acid (HAc) is used to clean the ash content in cavity and solve the problem of pore blockage. The results showed that the folium cycas biochar (FCB) treated with HAc increased the specific surface area by 44.7% (2954 m2/g) and the cumulative pore volume by 67.5% (1.39 cm3/g). The FCB has rich nano-scale meso/microporous tubular pores which provide a natural high-efficiency space for sulfur storage and buffer the volume expansion, so that the prepared composite cathode material of FCB/S has a first discharge capacity of up to 1317 mAh/g and stable at 910 mAh/g after 5 cycles. The capacity can still reach 790 mAh/g after 200 cycles with an attenuation rate of only 0.068% for each cycle.

The Co doping effects on the interfacial strength of Sn electrode-collector interface for lithium-ion batteries are investigated by using first-principles calculations. The results demonstrate that by forming strong chemical bonds with interfacial Sn, Li, and Cu atoms, Co doping in the interface region can enhance interfacial strengths and stabilities during lithiation. With doping, the highest strengths of Sn/Cu (1.74 J m

The most suitable activated carbon from three kinds of biomass wastes: walnut shell, peanut shell and pistachio hull is chosen to prepare the activated carbon–sulfur composites (AC-S) for rechargeable lithium–sulfur (Li–S) battery, due to the advantages of a relatively cheap, simple and non-toxic compositing progress. It indicates that the activated carbon (ACpe) derived from peanut shell owns flat, narrow and long shape macroporous structure with large micropores on its surface and is more suitable for the reaction in the Li–S battery. The ACpe/S composite containing about 57 wt% sulfur (sulfur loading of 0.83 mg cm− 2) shows a best initial discharge capacity of 943 mAhg− 1 at the rate of 0.2 C. It still retains a comparably high specific capacity of 619 mAh g− 1 with a coulombic efficiency of 95% after 100 cycles. This fact implies that the inherent flat pore construction of ACpe is beneficial for keep cycling stability for the lithium sulfur battery.

When lithium-ion batteries serve in extreme environments like space, severe irradiation might induce significant decay of the electrochemical performances and mechanical properties. In this paper, ...

Using a first-principles method and an effective model, we propose that the real material family NaAlSi(Ge) behaves as dual double node-line semimetals (DNLSs) with unconventional topological surface states. The dual DNLSs locate in kz = 0 and kz = π/a planes, respectively. Both of the DNLSs consist of homocentric two nodal lines: one is a type-I nodal line and the other one is a type-I nodal line embedded with four type-III nodal points. The type-III nodal points accompanied by a single-direction flat band are proposed to be a new platform for studying correlated phases. More intriguingly, because of the large proportion of Na ions, the NaAlSi(Ge) family is a potential candidate for topological sodium ion batteries (SIBs) with a high theoretical reversible capacity (476(238) mA h g−1) and suitable migration barrier.

By using first-principles calculations, we investigate the interfacial failure between a lithiated Sn electrode and a Cu current collector for lithium-ion batteries. The results show that segregation of Li ions at the interfacial region leads to the transformation of interfacial bonding from Sn‒Cu to Li‒Cu bonds, and weak Li‒Sn bonds near the interface region. This leads to the weakened interfacial strength upon lithiation and failure of most lithiated Sn/Cu interfaces within LixSn slabs. In addition, the formation of CuxSn alloys at interface could increase the interface strength and enhance the deformation resistance of electrode materials, which explains why CuxSn containing composite electrodes exhibits the excellent electrochemical performance.

Although the well-known anatase, one of the allotropic forms of natural TiO2, was recently proposed for lithium-ion battery electrodes, the material generally suffers from reduced cyclability and limited power, due to kinetic drawbacks and to its poor charge transport properties. Here, boron (B)-doping anatase TiO2 nanofibers were synthesized via a facile sol-gel method and the electrospinning method for use as anodes. The incorporation of B element not only promotes the crystallization of the building subunits of the microporous TiO2, but also improves the electrochemical performance at higher current rates and longer cycles. A capacity of 147 mA h g−1 at a current density as high as 4 A g−1 and an excellent long-term cycling stability with a capacity retention of 167.6 mA h g−1 at the current rate of 2 A g−1 over 5000 cycles could be achieved when an appropriate amount of B was doped into TiO2 anodes. The reasons for the improvement of rate capability may be attributed to the enhancement of electronic conductivity, lithium ion diffusion kinetics, and the surface storage property for the B-doping anatase TiO2 anodes.

Lithium/fluorinated carbon (Li/CFx) primary batteries have essential applications in consumer electronics and medical and high-power military devices. However, their application is limited due to the difficulty in achieving simultaneous high power density and high energy density in the CFx cathode. The tradeoff between conductivity and fluorine content is the decisive factor. Herein, by rational design, 3D porous fluorinated graphene microspheres (FGS-x) with both high conductivity and a high F/C ratio are successfully synthesized for the first time. FGS-x possesses an F/C ratio as high as 1.03, a nanosheet structure with hierarchical pores, abundant C═C bonds, few inactive C-F2 bonds, and electrochemically active C-F bonds. The beneficial features that can increase discharge capacity, shorten the diffusion length for both ions and electrons, enhance the Li+ intercalation kinetics, and accommodate the volume change are demonstrated. The Li/FGS-1.03 coin cell delivers an unprecedented power density of 71,180.9 W/kg at an ultrahigh rate of 50 C (43.25 A/g), coupled with a high energy density of 830.7 Wh/kg. Remarkably, the Li/FGS-1.03 pouch cell exhibits a record cell-level power density of 12,451.2 W/kg at 20 C. The in-depth investigation by the ex situ method on structural evolution at different discharge depths reveals that the excellent performance benefits from the structural stability and the uniform formation of LiF. The FGS-1.03 cathode also has excellent performance in extreme operating temperatures (0 to 100 °C) and high active material mass loading (4.3 mg/cm2). These results indicate that the engineered fluorinated graphene developed here has great potential in applications requiring both high power density and high energy density.

Quick capacity loss due to the polysulfide shuttle effects and poor rate performance caused by low conductivity of sulfur have always been obstacles to the commercial application of lithium sulfur batteries. Herein, an in-situ doped hierarchical porous biochar materials with high electron-ion conductivity and adjustable three-dimensional (3D) macro-meso-micropore is prepared successfully. Due to its unique physical structure, the resulting material has a specific surface area of 2124.9 m2 g-1 and a cumulative pore volume of 1.19 cm3 g-1 . The presence of micropores can effectively physically adsorb polysulfides and mesopores ensure the accessibility of lithium ions and active sites and give the porous carbon material a high specific surface area. The large pores provide channels for the storage of electrolyte and the transmission of ions on the surface of the substrate. The combined effect of these three kinds of pores and the N doping formed in-situ can effectively promote the cycle and rate performance of the battery. Therefore, prepared cathode can still reach a reversible discharge capacity of 616 mAh g-1 at a rate of 5 C. After 400 charge-discharge cycles at 1 C, the reversible capacity is maintained at 510.0 mAh g-1 . This new strategy has provided a new approach to the research and industrial-scale production of adjustable hierarchical porous biochar materials.

Low conductivity of the sulfur cathode and dissolution of lithium polysulfides are main obstacles for the application of lithium-sulfur batteries (LSB). So, cotton-like CNTs/(Ni-P)/S composites are prepared in this study. In the composites, Ni-P alloy nanoparticles are uniformly deposited on the surface of CNTs by electroless nickel plating and forming a three dimensional conductive framework. CNTs/(Ni-P) composites with different Ni-P alloy contents are studied. Then, the CNTs/(Ni-P)/S cathode material are obtained by melting method. The results show that, in the cotton-like composites, CNTs can effectively improve the electrical conductivity of positive electrode materials, and the Ni-P alloy on CNTs introduces strong polar adsorption and alleviates the ‘shuttle effect’. In particular, the CNTs/(Ni-P)/S composites can reach an initial discharge specific capacity as high as 1344.6 mAh g − 1 at 0.2 C, and the discharge specific capacity remained at 885.6 mAh g − 1 after 200 cycles.

Thermally growth oxide (TGO) is formed between ceramic coat and bond coat during the service of thermal barrier coatings (TBCs). Characterization of the mechanical properties of the TGO layer is important for simulating the stress or predicting the failure of TBCs. Based on nanoindentation and tensile methods, the elastic modulus, hardness and fracture strength of TGO are obtained. Due to the influence of the indentation size effect (ISE), the measured indentation hardness and elastic modulus of TGO decrease with increasing indentation depth. These values are much smaller than those of bulk alumina. By analyzing the ISE, the intrinsic hardness and elastic modulus of TGO are obtained as 13.58 GPa and 326.46 GPa, respectively. The residual stress in TGO with the value of 133.1 MPa is determined by XRD method. Combining the tensile tests with a digital image correlation (DIC) method, the tensile fracture strain and fracture strength of TGO are determined to be 0.25% and 683 MPa, respectively.

The operating durability of lithium-ion batteries is a principal problem in universe exploration or rescuing work in the nuclear radiation area. In the study, the neutron irradiation experiments were conducted on film-tin electrodes using the radiation dose of 1011, 1012, 1013 and 1014 n cm−2, respectively. The results show that the particle size grows with the increasing radiation does by atomic force microscopy (AFM) and scanning electron microscope (SEM). In addition, the degressive trend of specific capacity of tin anodes after neutron radiations increases with the increasing radiation dose. The fade of electrochemical performances may be attributed to the increasing particle size and defects induced by neutron radiation.

Capacity fade induced by chemo-mechanical degradation during charge-discharge cycles is the bottleneck in the design of high-performance batteries, especially high-capacity electrode materials. In this paper, a flexible sigmoid function is used to create the two-phase electrochemical lithiation profile, describing a sharp phase boundary that separates the pristine core from the lithiated shell of an electrode particle. According to such a phase transition, an analytical solution of the stress evolution is obtained by introducing an electrochemical reaction layer into the plastic model. Finally, based on the theory of diffusion-induced stress and the energy principle, we determine the critical thickness of radius of a lithiated layer, at which fracture occurs.

Thermal barrier coatings (TBCs) as a kind of temperature-resistance materials have been widely applied in super high temperature components in aircraft engines. However, TBCs are subjected to harsh service environment such as high temperature oxidation and erosion, which lead to the coating failure. It is important to investigate the effect of fire temperature, angle and velocity of particle on erosion to understand the failure mechanism. In this paper, the temperature and velocity distributions of erosion particles in high temperature gas burner rig are investigated by using the fluid–solid coupling method with the discrete random walk model. The results show that a non-uniform distribution of temperature appears in different positions of the central axis, and the temperature of particle is affected obviously by the gas stream and particle size. The trajectory of particles and velocity diagrams under different particle size are determined by coupling the continuous phase with the erosion particles.

High-capacity active electrodes, such as Si anodes in Li-ion batteries, undergo a significant volume deformation of up to $$\sim $$ 400% during lithiation. Such a huge volume change could cause mechanical fracture and pulverization of electrode materials and result in harmful effects on their electrochemical performance. To have better understanding on this problem, the two-phase lithiation process of hollow core–shell and film structural electrodes is simulated by using a diffusion lithiation model. It is shown that the anisotropic hoop stress is larger than the isotropic one, which may easily induce damage of hollow core–shell negative electrodes. In addition, the anisotropic nature of mechanical properties can also remarkably magnify the edge stress intensity factor of hollow core–shell and film electrodes. These results on the morphological evolution and stress generation shed light on the design of novel and failure-resistant electrodes.

In order to clarify the interaction of electrochemistry, thermal and diffusion-induced stress, in this work, we present a coupled electrochemical–thermal–mechanical model for spiral-wound Li batteries by coupling the mass, charge, energy and mechanics conservations as well as the electrochemical kinetics. A series of temperatures and Li concentration parameters on the reaction rate and Li+ transport are employed in this model. The results show that this model is validated for both the electrochemical performances and thermal behaviors at a constant discharge current by finite element simulation. Furthermore, the heat generation of three thermal sources and stress analysis are also discussed. This work is helpful to the battery structural design and battery thermal management.

Topological semimetals, including Dirac semimetals, Weyl semimetals, and nodal line semimetals, receive enormous research interest due to their intrinsic topological nature and fascinating properties. In the present work, with the help of density functional theory (DFT), we find that nodal line semimetals and Dirac semimetals can coexist in the low energy electron of a two dimensional (2D) B2C monolayer. Intriguingly, besides type-I and type-II Dirac fermions, a kind of open nodal line appears around the Fermi level. The low energy electronic nature of the B2C sheet can be described using a tight-binding (TB) model that relies on the basis of B-py, pz and C-py, pz states. One of the important merits of the system is that the energy windows of these four types of topological semimetals are different which can be easily distinguished in experiments. Moreover, the system provides an excellent platform for studying the interplay between different type semimetals.