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Thermal runaway is a major safety concern for Lithium-ion batteries in manufacture, storage, and transport. Facing the frequent incidents in the air transport of massive batteries, more reliable fire prediction and protection strategies under low-pressures conditions are urgently needed. Herein, thermal runaway criticality of the open-circuit cylindrical battery piles (up to 9 cells with 30% SOC) under a hot boundary is investigated inside a novel low-pressure chamber (20–100 kPa). Characteristics battery temperatures for the safety venting and thermal runaway are measured to analyze the influences of pressure and cell number on battery failures. Results indicate that lowering the pressure could promote an earlier and stronger safety venting and weaken the intensity of the exothermic reactions inside cells, which is verified by the surface morphology of the electrodes. The overall fire risk is higher with higher pressure and larger battery-pile size, as indicated by the lower minimum boundary temperature for thermal runaway (255 °C~385 °C). Moreover, a simplified heat transfer model is established to explain the trend of thermal-runaway criteria and the influence of the low-pressure environment. This work delivers new insights into the effects of pressure and pile size on battery thermal runaway, which can help to improve the safe storage and transport of large-scale lithium-ion battery piles under varied pressure conditions.

Ir-Ni-Ta metallic glasses (MGs) exhibit an array of superior high-temperature properties, making them attractive for applications at high temperatures or in harsh environments. However, Ir-Ni-Ta bulk MGs are quite brittle and often fracture catastrophically even before plastic yielding, significantly undercutting their high-strength advantage. Here, we show that the Ir-Ni-Ta MGs are not intrinsically brittle, but rather malleable when the feature size is reduced to micro/nano-scales. All tested Ir-Ni-Ta MG micropillars with a diameter ranging from ~500 nm to ~5 µm display a large plastic strain above 25% (the maximum up to 35%), together with a yield strength up to 7 GPa, well exceeding the strength recorded in most metallic materials. The intrinsic shear stability of Ir-Ni-Ta MGs, as characterized by the normalized shear displacement during a shear event, is much larger than those malleable Zr- and Cu-based MGs. Our results suggest that Ir-Ni-Ta MGs are excellent candidates for micro/nanoscale structural applications used at high-temperature or extreme conditions.

Micrometer-grade spherical LiMn1.5Ni0.5O4(LMNO) particles with a uniform particle size distribution were synthesized by a carbonate coprecipitation method in a continuous stirred tank reactor. LMNO...

The fast exploration of low energy configuration by surface atoms is believed to favor the formation of ultrastable metallic glasses, prepared by physical vapor deposition. Here, we find that the rearrangement of surface atoms is collective, rather than being dominated by individual atoms. Specifically, we experimentally observe the growth process of ultrastable metallic glasses at monolayer resolution, which follows a periodic island-layer-island pattern with morphology variation between islands and flat surfaces. The estimated surface diffusion coefficient is orders of magnitude higher than that for bulk diffusion. The fast surface dynamics allow the newly deposited clusters on the flat surface to form local islands with spherical shape, which substantially reduces the surface free energy in each island-layer-island growth cycle. Our findings are helpful for understanding the growth mechanisms of ultrastable metallic glasses and potentially for tailoring their properties. Ultrastable metallic glasses form by surface diffusion on a substrate during deposition. Here, this process is shown to involve the collective diffusion of atoms in a cyclic process, involving the formation of islands, their coalescence into a layer, followed by further island formation.

Quality and property control have become one of the critical problems for the metallic parts produced by selective laser melting. In this paper, the crack spontaneously formed in the Ti-6Al-4V alloy by selecting laser melting is investigated. The crack is C-shape without branching in macro view. In micro view, the crack originates from and propagates toward the selective laser melting (SLM) processing defects. The crack surface topography shows that the crack is typical dimple cleavage. A few heads of martensitic α′ laths appear at the bottom of the dimple. And the secondary crack nucleates and grows up near by the martensitic α′ laths. A lot of spatters and cavities formed at the top surface of the SLM body and the residual stress accumulated in the SLM body is up to 640 MPa, which confirms that the SLM processing defects and the residual stress induced the origination and propagation of the crack. The research results indicate that preventing spatter and controlling residual stress are important to SLM processing.

Strengthening with externally bonded CFRP reinforcement is widely used in structural reinforcement and attractive to stakeholders and engineers because of ease and speed of construction, corrosion resistance, lightweight, high strength, and versatility stiffness which can be oriented according to the need. Numerous research studies were carried out to explore RC beams’ flexural and shear performance when subjected to dynamic impact loading. The results were auspicious in using such a technique of strengthening. Regular square section reinforced concrete frame members strengthened by CFRP material is taken as the research object. However, little attention to the impact behavior of CFRP-shear-strengthened square reinforced concrete (RC) specimens has been paid. The dynamic response of CFRP to reinforced concrete members under unequal cross-impact is discussed. This paper investigates the effectiveness of CFRP strengthening on the square RC specimen in preventing shear failure and evaluation of the flexural performance of the strengthened specimen under the impact load. The drop hammer impact test is firstly conducted on RC specimens with and without CFRP strengthening. The results show that using CFRP to strengthen the RC specimen in shear is very effective at preventing shear failure and leading the specimen’s response to flexural domination. This result is also the motivation for developing a numerical model supported by experimental tests to study the flexural performance of strengthened RC specimens. It is found that the strengthened specimen is prone to exhibit pure bending deformation under the impact load in terms of dynamic amplification factor (DAF) for section moment. Then, an extensive parameter study is carried out to evaluate further the influence of impact velocity, reinforcement ratio, and concrete strength on the flexural performance of the strengthened specimen and CFRP layers. Such a holistic study may provide preliminary research regarding the use of CFRP to strengthen RC specimens in shear under impact loads and will enhance the current state of knowledge in this area; also, the optimal value of the CFRP reinforcement layer was proposed.

Oxidation of metallic glasses has been shown to be different from crystalline alloys due to the disordered atomic structures and far-from-equilibrium state, and quick characterization is required to reveal their early stage oxidation. In this study, we investigated the oxidation behavior of a Zr46Cu46Al7Gd1 bulk metallic glass by measuring the changes of optical constants via spectroscopic ellipsometry. Characterizations with X-ray diffraction, scanning electron microscopy, and thermogravimetric analyzer confirmed that the changes of pseudo-optical constants reflected not only the onset temperature at which the alloys underwent obvious oxidation, but also the subtle oxidation which was tedious to characterize. Our study suggests a more efficient and accurate approach to understand the oxidation of metallic glasses with temperature, time and compositions.

Refractory high-entropy alloys (HEAs) exhibit remarkable mechanical properties desired for high-temperature applications. However, their oxidation resistance at high temperatures received less attention. Recent work indicates that MoTaTiCrAl alloy exhibits excellent oxidation resistance, but the effects of Al and Cr remain unclear. In this work, we demonstrate that the addition of Al is unnecessary for preventing oxidation of the MoTaTiCrAl alloy and the removal of Al leads to a more oxidation resistant MoTaTiCr medium entropy alloy. Structural and chemical analyses indicate that the excellent oxidation resistance of MoTaTiCr is mainly associated with the formation of continuous CrTaO4 oxide layer. The results indicate that complex oxides can be adopted as effective candidates for enhancement of oxidation resistance, in addition to typical strategy of forming Al2O3, Cr2O3 or SiO2 barrier layer.

Thermal-runaway propagation in battery systems can escalate the battery fire hazard and pose a severe threat to global users. In this work, the thermal-runaway propagation over 18650 cylindrical lithium-ion battery was tested in the linear-arranged module with a 3-mm gap. State of charge (SOCs) from 30% to 100%, ambient temperatures from 20°C to 70°C, and three tab-connection methods were investigated. Results indicate that the battery thermal-runaway propagation speed was about 0.35 ± 0.15 #/min, which increased with SOC and ambient temperature. The critical surface temperature of thermal runaway ranged from 209°C to 245°C, which increased with ambient temperature while decreased with SOC. Compared to the open-circuit module, the flat tab connection could cause an external short circuit to accelerate the thermal-runaway propagation, and the non-flat tab connection was more likely to trigger an explosion. A heat transfer analysis was proposed to qualitatively explain the speed and limiting conditions of thermal-runaway propagation, as well as the influence of SOC, ambient temperature, and tab connection. This work reveals the thermal-runaway propagation characteristics under well-controlled environments, which could provide scientific guidelines to improve the safety of the battery module and reduce battery fire hazards.

A high efficiency and compact band-pass filter based on coplanar waveguide (CPW) is investigated in this paper, which lower and upper cut-off frequencies of the proposed filter can be tuned independently. In the proposed design, interdigital structure is used to filter the low frequency wave and a quasi-spoof surface plasmon polaritons (Q-SSPPs) structure is designed for tuning the higher cut-off frequency. The proposed Q-SSPPs structure contains only one cross-shaped element and keeps the similar properties of periodic SSPPs structure. The operating principle of the proposed design is explained by field distribution, dispersion curves, and equivalent circuits. The studies of vital parametric are carried out for better understanding the influences of the concerning parameters on the tunability. The simulated results indicate that the proposed design can obtain a wide bandwidth from 8.8 GHz to 17 GHz (about 63.6%) with high transmission efficiency (IS11I 21I > -0.2 dB). A prototype of the proposed design is fabricated and the measured results show good agreement with the simulated ones.

The titanium carbide phase was synthesized in laser melted-pool in situ as the reinforced particles of nickel based composite coating on Ti-6Al-4V alloy surface using the nickel and graphite blending powder by laser cladding. The microstructure investigation showed that the petals-shaped particles and granular particles were two main morphology of titanium carbide particles. And a few spiral-shaped titanium carbide pattern and eutectic titanium carbide appeared on the cross-sections of the coating. The spiral-shaped titanium carbide pattern composed of some slender arc-shape titanium carbide particles and the eutectic titanium carbide was fine. The morphology and distribution of the spiral-shaped titanium carbide patterns and eutectic titanium carbide confrmed that their growth mechanism was the dissolution-precipitation mechanism and was affected by the convection behavior of the laser melted pool. The spiral-shaped titanium carbide pattern would precipitate out the high-temperature melts under high-speed convection. The eutectic titanium carbide would precipitate out when the melts stopped convection or dropped to eutectic temperature.

The energy absorption characteristic of steel tube material and concrete material is an important indicator to reflect the impact resistance of circular concrete-filled steel tubular (CFST) members. In order to efficiently simulate the material energy absorption of the steel tube and concrete under lateral impact, a nonlinear finite element model considering the material strain rate of the circular CFST member was established and validated based on the drop weight tests. Then, the energy absorption mechanism of circular CFST members subjected to lateral impact was investigated including the revelation of the energy absorption process and the determination of the energy absorption distribution for the steel tube material and concrete material, which are obtained respectively based on the comprehensive analysis of dynamic response and innovative establishment of the segmented numerical model. In addition, the influence of impact momentum on energy absorption process and the effect of impact location on energy absorption distribution are further carried out. The observations of this investigation can provide reference for the anti-impact design and damage reinforcement of circular CFST members subjected to lateral impact.

Summary The surface of glass is crucial for understanding many fundamental processes in glassy solids. A common notion is that a glass surface is a thin layer with liquid-like atomic dynamics and a thickness of a few tens of nanometers. Here, we measured the shear modulus at the surface of both millimeter-size and micrometer-size metallic glasses (MGs) through high-sensitivity torsion techniques. We found a pronounced shear-modulus softening at the surface of MGs. Compared with the bulk, the maximum decrease in the surface shear modulus (G) for the micro-scale MGs reaches ~27%, which is close to the decrease in the G upon glass transition, yet it still behaves solid-like. Strikingly, the surface thickness estimated from the shear-modulus softening is at least 400 nm, which is approximately one order of magnitude larger than that revealed from the glass dynamics. The unusually thick surface is also confirmed by measurements using X-ray nano-computed tomography, and this may account for the brittle-to-ductile transition of the MGs with size reductions. The unique and unusual properties at the surface of the micrometer-size MGs are physically related to the negative pressure effect during the thermoplastic formation process, which can dramatically reduce the density of the proximate surface region in the supercooled liquid state., Graphical abstract, Public summary • The shear modulus and thickness of metallic glass (MG) surface is determined through torsion testing on micrometer-size wires • The surface region of MG wires has a significant shear-modulus softening close to the supercooled liquid, yet still behaves solid-like • The thickness of the soft surface of MG wires is at least 400 nm, which is about one order of magnitude larger than those revealed from surface dynamics • The unusually thick surface accounts for the brittle-to-ductile transition of the MGs with size reduction

Fracture of glasses can proceed through the organized nucleation, growth, and coalescence of nanocavities., Crack propagation is the major vehicle for material failure, but the mechanisms by which cracks propagate remain longstanding riddles, especially for glassy materials with a long-range disordered atomic structure. Recently, cavitation was proposed as an underlying mechanism governing the fracture of glasses, but experimental determination of the cavitation behavior of fracture is still lacking. Here, we present unambiguous experimental evidence to firmly establish the cavitation mechanism in the fracture of glasses. We show that crack propagation in various glasses is dominated by the self-organized nucleation, growth, and coalescence of nanocavities, eventually resulting in the nanopatterns on the fracture surfaces. The revealed cavitation-induced nanostructured fracture morphologies thus confirm the presence of nanoscale ductility in the fracture of nominally brittle glasses, which has been debated for decades. Our observations would aid a fundamental understanding of the failure of disordered systems and have implications for designing tougher glasses with excellent ductility.

The surface-enhanced Raman spectroscopy (SERS) is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale, yet the fabrication of SERS materials such as nanoparticles or arrays of coinage metals often involve multiple complex steps with the high cost and pollution, largely limiting the application of SERS. Here, we report a complex hierarchical metallic glassy (MG) nanostructure by simply replicating the surface microstructure of butterfly wings through vapor deposition technique. The MG nanostructure displays an excellent SERS effect and moreover, a superhydrophobicity and self-cleaning behavior. The SERS effect of the MG nanostructure is attributed to the intrinsic nanoscale structural heterogeneities on the MG surface, which provides a large number of hotspots for the localized electromagnetic field enhancement affirmed by the finite-difference time-domain (FDTD) simulation. Our works show that the MG could be a new potential SERS material with low cost and good durability, well extending the functional application of this kind of material.

Transition metal oxides and sulfides have been intensively investigated as host materials for the S cathode in lithium-sulfur (Li-S) batteries; however, the distinctions between them in battery operation have remained unclear. In this study, VO2 and VS2 nanosheets were systematically studied as host materials for Li-S batteries through theoretical calculations and experimental testing. First-principles calculations demonstrated that VS2 showed more favorable properties, including the inherent semi-metallic conductivity of VS2 , moderate adsorption strength for Li2 Sn , fast Li+ transport with a low diffusion barrier, and accelerated surface redox reactions with a low Li2 S decomposition barrier. In comparison, the low electronic conductivity and strong adsorption strength of VO2 increased Li+ diffusion as well as Li2 S decomposition barriers of the electrode, resulting in relatively poor rate capability and cycle stability. In experiments, the VS2 @S electrode exhibited superior electrochemical performance compared with VO2 @S, giving a large capacity of 713 mAh g-1 at 5 C and a low capacity fading rate of 0.13 % per cycle over 200 cycles at 1 C. The constructed relationships between S cathode and host materials could guide the future design of high-performance S cathodes for Li-S batteries.

Multiple negative factors, including the poor electronic conductivity of sulfur, dissolution and shuttling of lithium polysulfides (Li2Sn), and sluggish decomposition of solid Li2S, seriously hinder practical applications of lithium-sulfur (Li-S) batteries. To solve these problems, a general strategy was proposed for enhancing the electrochemical performance of Li-S batteries using surface-functionalized Ti3C2 MXenes. Functionalized Ti3C2T2 (T = N, O, F, S, and Cl) showed metallic conductivity, as bare Ti3C2. Among all Ti3C2T2 investigated, Ti3C2S2, Ti3C2O2, and Ti3C2N2 offered moderate adsorption strength, which effectively suppressed Li2Sn dissolution and shuttling. This Ti3C2T2 exhibited effective electrocatalytic ability for Li2S decomposition. The Li2S decomposition barrier was significantly decreased from 3.390 eV to ∼0.4 eV using Ti3C2S2 and Ti3C2O2, with fast Li+ diffusivity. Based on these results, O- and S-terminated Ti3C2 were suggested as promising host materials for S cathodes. In addition, appropriate functional group vacancies could further promote anchoring and catalytic abilities of Ti3C2T2 to boost the electrochemical performance of Li-S batteries. Moreover, the advantages of a Ti3C2T2 host material could be well retained even at high S loading, suggesting the potential of surface-modified MXene for confining sulfur in Li-S battery cathodes.

Designing muscle-inspired hydrogels that possess structure and bioactivity similar to muscles is an eternal pursuit in material sciences and tissue engineering. However, the development of a muscle-inspired hydrogel via the formation of noncovalent interactions remains challenging, and its application in sustained loading situations such as cyclic stresses is limited. Herein, H-bonds and microcrystalline domains were introduced, and a noncovalent muscle-inspired hydrogel was developed to mimic both the physical structure and functionality of muscles at the macroscopic level. The hydrogel exhibited excellent mechanical properties (a fracture strength of 2.16 ± 0.08 MPa, fracture strain of 830 ± 23%, elastic modulus of 275 ± 9 KPa, and toughness of 7.04 ± 0.80 MJ/m

Purpose This paper aims to explore the influence of the reinforcement included either glass beads (GBs) or carbon fiber (CF) on the reinforced polyamide 12 (PA12) composite samples prepared by selective laser sintering (SLS). Design/methodology/approach In this paper, the microstructure and mechanical properties are investigated, and the results are compared with those obtained for non-reinforced pure PA12 samples prepared by SLS. Findings The tensile fracture surface of the non-reinforced pure PA12 sample presents strong micro-deformation within the crack origination zone between the melted PA12 matrix and the un-melted PA12 particle cores. As a result, the pure PA12 sample exhibits the greatest maximum elongation. The maximum tensile strength is obtained for the CF reinforced sample because of the strengthening effect of CF and the relatively good bonding between CFs and the PA12 matrix. The minimum tensile strength is obtained for the GB reinforced PA12 sample because of the relatively weak bonding between GBs and the PA12 matrix. Originality/value These results demonstrate that the characteristics of the interfaces between the reinforcement and the PA12 matrix have an important influence on the fracture mechanisms and mechanical properties of PA12 composites fabricated by SLS.

In this study, hot deformation is performed in the β-phase region in Ti-40Al-8Nb-(0, 0.5, 1)B alloys (at. %) in order to modify the microstructures of the β phase and borides in the alloys. Special attention is paid to the effect of boron content on the microstructure of the transformed α phase. The obtained results show that the microstructure of the α phase is significantly different in compressed samples with different boron contents. The α phase has a lath-like morphology in the Ti-40Al-8Nb alloy, whereas it has equiaxed features in the boron-added alloys. The morphology of the α phase is closely related to whether the α phase follows the Burgers orientation relationships (BORs) with the β matrix, i.e., lath-like morphologies of the α phase when it follows the BORs and equiaxed morphologies when it does not follow the BORs. In addition, in the compressed samples of the Ti-40Al-8Nb, Ti-40Al-8Nb-0.5B, and Ti-40Al-8Nb-1B alloys, the α phase has an 〈11−20〉 fiber texture, an 〈11–20〉–〈10–10〉 double fiber texture, and randomly crystallographic orientations, respectively. Detailed analyses demonstrate that the intensity of the 〈11–20〉 fiber texture of the α phase is governed by a combination of the volume fraction of the α phase that has BORs with the β matrix and the intensity of the 〈111〉 fiber texture of the β phase, whereas the intensity of the 〈10−10〉 fiber texture of the α phase is affected by the reorientation behavior of borides during the deformation.

Binary Ir-P compounds have been considered as the excellent candidates for catalytic applications with high activity. However, the difficulties associated with synthesis with novel structures and chemical stoichiometry in general remain. Herein, using the swarm structure searching technique in combination with density functional theory, the hitherto unknown binary Ir-P phase diagram was investigated in a wide pressure range with various chemical compositions. In particular, two novel phases of IrP-P4/nmm and IrP2-I41/amd were discovered at high pressure. The phonon dispersion curves suggest that all these phases are dynamical stable. Our calculated electronic properties show that the mixture behavior of covalent, ionic and metallic bonds simultaneously exits in the novel two phases. The bond population shows a high delocalized metalloid electron between the P-P atoms in IrP-P4/nmm phase, while the sp3 hybridized present in the buckled 2D P-P chains in IrP2-I41/amd phase. The theoretical electronic band structures reveal pressure-induced electronic topological transitions in IrP-P4/nmm phase, while it is absent in other stoichiometry of Ir-P system. The current theoretical results enrich the crystal structures and chemical stoichiometry of the binary Ir-P system and benefit the further understanding of the corresponding physical and chemical properties.

The implement of sustainable hydrogen production is a prerequisite to cater to our further energy demand. Herein, an excellent electrocatalyst of CoMoP nanosheet arrays grown on nickel foam (CoMoP NAs @NF) composite is constructed via a combination of hydrothermal and phosphating process for hydrogen evolution reaction (HER). SEM and TEM characterizations indicate the composite has a unique three-dimension structure, where CoMoP nanosheets uniformly grow on NF substrate. Due to the unique structure and the synergetic effect between CoMoP nanosheet and bare NF, electrochemical tests suggest that the composite has an excellent HER performance with a low overpotential of only 24 mV to achieve a current density of 10 mA cm−2 and Tafel slope of 44.6 mV dec−1. Moreover, a certain overpotential can be maintained at 10 mA cm−2 for over 20 h, suggesting its superior stability. Considering its superior HER performance and stability, we envision that this composite could be a prospective substitute for non-noble-metal HER catalysts for practical applications.

Since their discovery in 19601, metallic glasses based on a wide range of elements have been developed2. However, the theoretical prediction of glass-forming compositions is challenging and the discovery of alloys with specific properties has so far largely been the result of trial and error3–8. Bulk metallic glasses can exhibit strength and elasticity surpassing those of conventional structural alloys9–11, but the mechanical properties of these glasses are critically dependent on the glass transition temperature. At temperatures approaching the glass transition, bulk metallic glasses undergo plastic flow, resulting in a substantial decrease in quasi-static strength. Bulk metallic glasses with glass transition temperatures greater than 1,000 kelvin have been developed, but the supercooled liquid region (between the glass transition and the crystallization temperature) is narrow, resulting in very little thermoplastic formability, which limits their practical applicability. Here we report the design of iridium/nickel/tantalum metallic glasses (and others also containing boron) with a glass transition temperature of up to 1,162 kelvin and a supercooled liquid region of 136 kelvin that is wider than that of most existing metallic glasses12. Our Ir–Ni–Ta–(B) glasses exhibit high strength at high temperatures compared to existing alloys: 3.7 gigapascals at 1,000 kelvin9,13. Their glass-forming ability is characterized by a critical casting thickness of three millimetres, suggesting that small-scale components for applications at high temperatures or in harsh environments can readily be obtained by thermoplastic forming14. To identify alloys of interest, we used a simplified combinatorial approach6–8 harnessing a previously reported correlation between glass-forming ability and electrical resistivity15–17. This method is non-destructive, allowing subsequent testing of a range of physical properties on the same library of samples. The practicality of our design and discovery approach, exemplified by the identification of high-strength, high-temperature bulk metallic glasses, bodes well for enabling the discovery of other glassy alloys with exciting properties. Bulk metallic glasses made from alloys of iridium, nickel, tantalum and boron are developed by combinatorial methods, with higher strength at high temperature than those previously produced.

There is recently an increasing interest in replacing ordinary Portland cement (OPC) with a sustainable binder used in construction materials because of heavy energy consumption and greenhouse gas emissions in OPC production. Alkali-activated binder made from industrial waste is therefore developed as an alternative to OPC. It is essential to assess the mechanical properties of construction materials using the new binders. Since materials behave differently when subjected to dynamic loading as compared to its response under static loading conditions, this paper aims to evaluate the mechanical properties of alkali-activated binder based mortars subjected to dynamic loading. Mortars containing low-calcium (fly-ash) and high-calcium (ground granulated blast-furnace slag) alkali-activated binders were tested. NaOH and sodium silicate solutions were used together as activators, and two groups of specimens made with different water ratios were tested for both fly-ash and blast furnace slag based mortars. The split Hopkinson pressure bar (SHPB) system was used to conduct dynamic tests, and dynamic compressive strength and tensile strength were measured to provide a comprehensive understanding of the dynamic behaviors of alkali-activated mortars. The results show that dynamic compressive and tensile strengths of alkali-activated mortars increase with the loading rates. In addition, water ratio and curing time significantly affect the dynamic compressive and tensile strengths of alkali-activated mortars. Finally, empirical formulas were established to describe dynamic behaviors for fly-ash and slag based mortars with different water ratios and curing time.

Biodegradable polymer stents are attracting more attention with their advantages of biocompatibility and biodegradable and dispensing with surgical removal. However, the lower radial force is the main bottle neck of their application. In the present research, poly-L-lactic monofilaments with three different diameters were adopted to produce multi-ply strands and then fabricated into Z-structure stents. The effects of strand parameters on stent radial force were studied. The monofilament, strand and stents were subsequently degraded in vitro for 48 weeks. The thermal properties, morphology change, mass retention and strength retention of samples were recorded to forecast the long-term application effects of the stents. The results of this research provided theory to optimize the processing technique of stents with a textile structure to acquire higher radial force.

The vulcanising response and mechanism of the silicon rubber embedded polyarylacetylene prepolymers (PAAP) were investigated to determine the proper vulcanising conditions that could be used to obt...

VC2, a new two-dimensional transition metal carbide containing C2 dimers, was predicted by the swarm-intelligent global-structure search method. The structural properties and Li+ storage ability of VC2 monolayers and stacked VC2 multilayers were systematically investigated by first-principles calculations, and the high structural stability and electronic conductivity of the materials suggested promising Li+ storage properties. VC2 monolayers showed a theoretical capacity of 1073 mA h g−1 based on multilayer Li+ adsorption, while stacked VC2 showed an even larger theoretical capacity of 1430 mA h g−1. Intercalated Li+ formed ordered arrangements between VC2 layers, retaining a well-ordered layered structure. Li+ near the VC2 layer formed ionic bonds with the host material, while Li in middle layers formed metallic Li–Li bonds. All Li+ was stored in the interlayer space with low diffusion barriers, which demonstrated high rate capability of the material for lithium ion batteries. Remarkably, the predicted VC2 carbide achieved more than 1000 mA h g−1 capacity irrespective of being in monolayer or stacked layer structures, which rendered them very convenient for practical material preparation and battery applications.

Binary skutterudite-type IrP3 possesses a unique structural configuration that exhibits unusual electronic, thermoelectric, and dynamical properties and can be applied in thermoelectric generators; IrP3 has unique square (P4) rings stacked with a relatively loose arrangement and thus has been expected to exhibit fascinating evolution in the bonding patterns and electronic properties under high pressure. Herein, we systematically investigated the global energetically stable structures of IrP3 under ambient- and high-pressure conditions using the swarm intelligence-based structure searching technique in combination with first-principles calculations. Our theoretical prediction shows that the skutterudite-type structure with the Im3[combining macron] symmetry is most stable under ambient conditions. An orthorhombic structure with the Pmma space group was predicted to be energetically superior to the Im3[combining macron] phase above 47.60 GPa. The abrupt volume collapse at the corresponding phase boundaries even reached 14.67%, stemming from the abrupt collapse of large voids in the Im3[combining macron] phase. To explore the possibility of the occurrence of pressure-induced metallization and superconducting states under compressive conditions, the electronic band structures were investigated. Our results showed that the Im3[combining macron] phase was a narrow-gap semiconductor with the band gap of 1.04 eV, whereas the high-pressure Pmma IrP3 was a metallic phase with the superconducting transition temperature of 2.40 K. The current results are beneficial for the further understanding of other skutterudite-type compounds under high pressure.

Nowadays, plasticizing has become a critical issue for the engineering application of bulk metallic glasses (BMGs). What is the origin of plastic flow and how to evaluate the plasticity of BMGs with a unified standard are still open questions. Here we report a universal fragility criterion to scale the plasticity of BMGs from the equilibrium liquids and supercooled liquids. Based on our experimentally measured and previously reported viscosities at superheated and supercooled region for 51 glasses, the plasticity (e) of BMGs has been found to positively correlate to the supercooling liquid fragility (m) with the equation of e = 92exp[− 73/(m−15)], where e is the plastic strain and m the fragility near glass transition temperature, but negatively correlate to the fragile-to-strong (F-S) transition tendency characterized by F-S transition factor and temperature. The intrinsic mechanism of the plasticity can be well interpreted in the frame of structural relaxation theory. This work provides a new insight into the microscopic essence of the plasticity of glassy solids and a universal approach to scale the fluidity of metallic glasses.

Identifying high performance electrode materials particularly with a large capacity and appropriate working voltage is one of the most promising approaches for improving the energy density of rechargeable batteries. Herein, a tetra-VN2 monolayer with intrinsic thermal/dynamic stability and excellent electronic conductivity is described that was identified using energy and stability directed screening as a potential electrode material for rechargeable alkali ion batteries. The maximum alkali ion storage was found for Li2VN2, Na4VN2 and K4VN2, which corresponded to specific capacities of 679, 1358 and 1358 mA h g−1. The average working voltages of tetra-VN2 in Li-, Na-, and K-ion batteries were 2.59, 1.59, and 1.62 V, which produced specific energies of 1761, 2162, and 2206 W h kg−1, which were much larger than those of most well-known cathode materials. This suggested that the tetra-VN2 monolayer could be a promising alkali ion storage material for high energy rechargeable batteries. Interestingly, different from intercalation-type cathode materials, alkali ions were stored in the tetra-VN2 monolayer via an adsorption/desorption process. With this surface storage mechanism, the alkali ions could migrate in the electrode with low energy barriers, which were found to be 0.237, 0.018, and 0.075 eV for Li+, Na+, and K+, respectively. This feature was representative of the excellent rate capability of tetra-VN2 in rechargeable batteries.

Alginate scaffold with high porosity has great potential in the field of tissue engineering due to its biocompatibility and degradability. However, the poor mechanical performance of pure alginate scaffold has limited its use in many applications. Cellulose nanofibers (CNFs) have attracted attention as reinforcing agents to fabricate composite scaffolds with alginate. In this paper, CNF obtained from raw ramie fibers was incorporated with sodium alginate to make a composite scaffold by the freeze-drying method. CNF contents of 0.025, 0.05, 0.1, 0.2, 0.4, 0.8, and 1.6% were selected to study the effect of CNF on scaffold characterization. The composite scaffold exhibited fewer pores but more compact structure than the pure alginate scaffold. Fourier transform infrared spectroscopy was used to study the changes in the functional groups between the ramie fiber and its CNF, pure alginate scaffold, and the composite scaffold. X-ray diffraction indicated that the crystallinity of scaffold increased with addition of CNF. The mechanical performance of scaffold was successfully improved by adding CNF, but the porosity and swelling ratio were decreased. Hence, by combining CNF with alginate, the porous structure, mechanical properties, and swelling behaviors could be tailored, which could expand its use in the field of tissue engineering.

Metallic glasses possess amorphous structures with inherent heterogeneity at the nanoscale. A combined experimental and modeling investigation to elucidate the chemical effect on such nanoscale heterogeneity in a Cu-Zr-Al metallic glass system is conducted. By using the dynamic atomic force microscopy, we reveal a reduction of the nanoscale spatial heterogeneity in the local viscoelastic response after introducing Al into the Cu50Zr50 metallic glass. The change of such nanoscale heterogeneity can be contributed to the variation of local atomic structures. The addition of Al increases the population of the icosahedral short-range ordered clusters, thus reducing the structural heterogeneity at the nanoscale.

The mechanism underlying the crowding effects that assist the condensation process by multivalent cations under confinement is not yet reported. Based on the strong correlation model, Monte Carlo simulation was implemented to detect the crowding effects on DNA condensation within a capsule-like space, and its geometry controlled by the aspect ratio. With the addition of crowders, the condensed conformations confined within the spherical space (aspect ratio is 1) become more compact than those without crowders. The DNA-condensed conformations undergo a transition from the initial random coil structure to toroid structure, followed by the extended rod-like structure, and finally to totally compacted structure. The critical volume fraction corresponding to the transition from the rod-like structure to totally compacted structure pertained to the crowder size proportionally. Moreover, the critical volume fraction corresponding to the phase transition strongly depends on the confinement geometry, the critical volume fraction for the case with constant radius is inversely proportional to the aspect ratio. Conversely, the case with constant cylinder length showed that the critical volume fraction is proportional to the aspect ratio. These phenomena are consistent with their corresponding phase diagram re-expressed in the space of volume fraction and aspect ratio. The effects of confinement geometry and crowder size on the response of DNA condensation to crowding are elucidated and generalized into the space diagram in the space of aspect ratio and crowder size. When the aspect ratio less than 1.6 and the crowder size larger than 2.0 nm or when the aspect ratio ≥ 1.6 and the crowder size larger than the critical d c ∗ , the DNA conformation undergo the transition from the initial random coil structure to toroid structure, followed by totally compacted structure; when the aspect ratio ≥ 1.6 and the crowder size ≤ d c ∗ , the DNA condensed conformations will be condensed further from the totally compacted structure to the extended rod-like structure. Furthermore, the transition from the totally compacted structure to the extended rod-like structure is entirely due to the crowder size and the confinement geometry between the de Gennes and Odijk regimes.

The theoretical basis for the calculation of shell side condensation of the spiral coil heat exchanger is weak. In order to solve the problem of pure steam film condensation heat transfer of the shell side of the spiral coil heat exchanger, the theoretical model of the homogeneous flow was established. Considering the centrifugal force, two different mathematical models were established and the heat transfer characteristics were studied. The solution formula of the heat transfer coefficient and thickness of first layer liquid film, meanwhile, was obtained. The theoretical formula of the membrane-like condensation heat transfer of the heat exchanger was worked out, based on the calculation model of the heat transfer coefficient of one-component working fluid outside the tube bundle, considering the effect of tube bundle. The two calculated results in this paper and the theoretical result of Bays and McAdams were compared with experimental values respectively. The results show that the relative error between the calculated values obtained by the two theoretical models and experimental values is 7.48% (ignoring centrifugal force), 3.05% (considering centrifugal force), while the relative error between Bays and McAdams’s result and the experimental value is 61.3%. The correctness of the theoretical models proposed in this paper are verified. The theoretical models can be used to calculate the film condensation heat transfer of the spiral coil heat exchanger.

Plastic deformation of metallic glasses (MGs) has long been considered to be confined to nanoscale shear bands, but recently an affected zone around the shear band was found. Yet, due to technical limitations, the shear-band affected zone (SBAZ), which is critical for understanding shear banding and design of ductile MGs, has yet to be precisely identified. Here, by using magnetic domains as a probe with sufficiently high sensitivity and spatial resolution, we unveil the structure of SBAZs in detail. We demonstrate that shear banding is accompanied by a micrometer-scale SBAZ with a gradient in the strain field, and multiple shear bands interact through the superimposition of SBAZs. There also exists an ultra-long-range gradual elastic stress field extending hundreds of micrometers away from the shear band. Our findings provide a comprehensive picture on shear banding and are important for elucidating the micro-mechanisms of plastic deformation in glasses., Metallic glasses deform along nanoscale shear bands, and while it is known that they affect the neighboring glass regions, exactly how is unclear. Here, the authors use magnetic force microscopy to atomically resolve the shear-band affected zone and show its effects extends much further than previously thought.

Stretchable electrodes are essential components for wearable electronics. However, the stretchability of the electrodes is often achieved with the sacrifice of electronic conductivity along with huge variation in resistance. In this work, stretchable metallic glass electrodes (MG-electrodes) that have both high electronic conductivity and excellent electronic stability are developed. The stretchability of the MG-electrode is significantly improved by shrinking MG films deposited on substrates with pre-strain. We demonstrate two types of MG-electrodes. One is a transparent MG-electrode for uniaxial stretching, and the other with better conductivity is for biaxial stretching. Compared with previous electrodes, the MG-electrodes exhibit a combination of high conductivity and negligible resistivity change (

Despite the importance of glass forming ability as a major alloy characteristic, it is poorly understood and its quantification has been experimentally laborious and computationally challenging. Here, we uncover that the glass forming ability of an alloy is represented in its amorphous structure far away from equilibrium, which can be exposed by conventional X-ray diffraction. Specifically, we fabricated roughly 5,700 alloys from 12 alloy systems and characterized the full-width at half-maximum, Δq, of the first diffraction peak in the X-ray diffraction pattern. A strong correlation between high glass forming ability and a large Δq was found. This correlation indicates that a large dispersion of structural units comprising the amorphous structure is the universal indicator for high metallic glass formation. When paired with combinatorial synthesis, the correlation enhances throughput by up to 100 times compared to today’s state-of-the-art combinatorial methods and will facilitate the discovery of bulk metallic glasses. The glass forming ability of alloys is found to be strongly correlated with the full-width at half-maximum of the first diffraction peak in the X-ray diffraction pattern, which facilitates the discovery of bulk metallic glass compositions.

Current works focus on detecting macromolecule crowding effects on the phase separation of the mixture between semi-flexible polymer and crowders (hydrophilic polymers) in confined space by Monte Carlo simulations. With the increasing addition of crowders into the spherical confined space, the semi-flexible polymer was first compressed into a condensed state from the initial coil state, and then the condensed conformation expanded and deposited on the inner surface of the spherical confined space with an extended state. The phase diagram in the phase space of the volume fraction of crowders and the scaled radius of spherical confined space by crowder diameter, and the direct conformation transition of semi-flexible polymer have validated the phase transition process successfully. In addition, the deposition of extended conformation on the inner surface of the spherical confined space was qualified by the vertex density, its curve shifted along the radial direction with the increasing volume fraction of crowder. During the phase separation process, the critical volume fraction φ(∗) relates to the crowder diameter approximately linearly and the relation between the critical volume fraction and the crowder diameter strongly depends on the size of the spherical confined space.

© 1963-2012 IEEE. A millimeter-wave (mm-wave) multibeam array antenna based on folded C-type substrate integrated waveguide (FCSIW) is presented for the first time. The design steps for its two main elements are described, namely an FCSIW Butler matrix (BM) and an FCSIW single-branch slot array antenna. Both of them exhibit a significant miniaturization in comparison with their substrate integrated waveguide (SIW) counterparts, leading to 40% and 33.2% reduction in occupied surface for the BM and the whole multibeam array antenna while maintaining similar performances, respectively. In addition, an optimized transition connection structure from ground coplanar waveguide (GCPW) to FCSIW is designed to facilitate the measurement of the multibeam array antenna. Finally, the FCSIW multibeam array antenna is optimized, manufactured, and measured, which can help verify the feasibility of FCSIW for the miniaturized multibeam array antenna.

The search for novel structures and chemical stoichiometry of binary Ir–Sb compounds is of great importance in view of their catalytic applications. Based on the results of swarm structure searching technique combined with density functional theory, we proposed the hitherto unknown Ir–Sb phase diagram in a wide pressure range with various chemical compositions. Besides two ambient pressure phases of IrSb3-Im and IrSb2-P21/c, five novel phases of IrSb-C2/c, IrSb-P, IrSb2-P21m, IrSb2-I4/mmm and Ir2Sb-Pmmn were identified at high pressures. The phonon dispersion curves reveal that these phases are all dynamically stable. The calculated electronic results show that a mixed behavior of covalent, ionic and metallic bonds simultaneously exits in these novel phases. A pressure-induced electronic topological transition in Ir2Sb-Pmmn phase occurs according to the theoretical electronic band structures, while is not shown in other stoichiometries of the Ir–Sb system. Our work provides a potential opportunity for experimental synthesis of crystal structures with different chemical stoichiometries of the binary Ir–Sb system.

Axial force has a great influence on the dynamic behavior and the impact resistance of concrete-filled steel tubular (CFST) members. Based on numerical simulation and theoretical analysis, the impact response and deflection calculation method for axially loaded CFST members subjected to lateral impact are investigated in this paper. The nonlinear numerical model of an axially loaded CFST member considering the strain rate effects has been established, and the simulation accuracy has been validated by comparing with existing test results. The contrastive investigation is carried out to illustrate the influence of axial load on the variation pattern of impact force for CFST members under various structural and impact parameters, and its result indicates that the impact force-time histories for CFST members with different axial loads are mainly characterized by rectangular pulse and triangular pulse. Moreover, a simplified calculation method considering the effect of axial force is proposed based on the equivalent single degree of freedom (SDOF) method, devoted to predicting the deflection of axially loaded CFST members subjected to lateral impact. The comparisons with the numerical simulation prove that the deflection calculation method has a reasonable accuracy; thus, the proposed method can be utilized in the damage assessment and anti-impact design for CFST members subjected to lateral impact and axial load.

A comparison of bending flexibility between bare biodegradable polydioxanone biliary stents (BBPBSs) and fully covered biodegradable polydioxanone biliary stents (FCBPBSs) developed for humans is p...

We describe a sensor for measuring the electrical resistance of a conducting thin-film material as a function of temperature and composition. The sensor has excellent sensitivity and can be used at temperatures as high as the melting temperature of the material of interest. The sensor is fabricated by applying a simple lift-off process to a thin film. By combining combinatorial sputtering to fabricate composition spreads with arrays of sensors, the phase transformation behavior of complex alloys can be mapped. We demonstrate this capabilities by using the sensor to determine the glass transition and crystallization temperatures of several PdSiCu-based metallic glasses. We found that in two glass-forming systems, PdCuSi and NiZr, the ratio of the resistance of the crystallized to as-deposited material is correlated with the glass-forming ability. The ability to readily determine glass forming ability, suggests that the sensor is a powerful tool for measuring the glass-forming ability in a high-throughput manner over large compositional spaces.

Crystalline silicon is dominating the current solar cell market due to the significant efficiency improvement and cost reduction in last decades. However, its indirect band gap nature leads to inefficient visible-light absorption, which seriously impedes further performance enhancement in silicon-based photovoltaic devices. Thus, it is highly desirable to develop direct band gap silicon materials. Herein, by means of ab initio swarm-intelligence structure-searching method, we predicted a quasi-direct gap semiconducting tri-layer silicene structure consisting of alternating arrays of six-membered Si rings, which can be converted into a direct gap semiconductor of 0.86 eV by applying a low tensile strain (~ 2.5%). Our calculations revealed that the photovoltaic efficiency of the tri-layer silicene reaches 29% at 1.0 µm, which is comparable to that of bulk GaAs with the highest conversion efficiency among thin-film solar cell absorbers.

A novel type of silicon rubber composite with benzoxazine resins (BZs) and ZrO2 was prepared. The ablative response of the composites was investigated. The results showed that the composites with BZs had superior thermal stability and higher resides compared to the pristine composites. The linear ablation rate of the composites decreased significantly with the increase in ZrO2 content. The maximum back-face temperature of the burnt samples was no more than 100 &deg, C for the obtained composites. Three major ablation processes were carried out simultaneously during the ablation processing. These mainly involved the carbonization of the composite, and the formation of ceramic compounds such as SiC and ZrC, as well as the shielding effect of the ablated layer, which subsequently enhanced the ablation resistance of the composites.

A novel needled carbon/rubber woven laminate was fabricated using heat vulcanizing silicone rubber and polyarylacetylene (PAA) as the matrix and two-dimensional carbon fiber (TCF) woven fabrics as the reinforcement phase. The tensile strength and hardness of the laminates were increased with the increasing of the content of PAA due to better compatibility between PAA and TCF. Ablation testing results demonstrated that the ablation rate firstly deceased and then increased with increasing of PAA content due to charring action of PAA and the formation of a loose ablation layer with cracks.