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In this research, core−shell electrospun fibers loaded with the shell of cellulose acetate and the core of oleic acid and alkyd varnish resin were synthesized and used within poly(dimethyl siloxane) (PDMS) to prepare self-healing and pH-responsive coatings for a steel substrate. The morphology of the electrospun fibers was characterized by scanning electron microscopy, transmission electron microscopy and confocal fluorescence microscopy. Thermo gravimetric analysis and Fourier transform infrared spectroscopy revealed that the self-healing agents were loaded successfully with a loading rate of 2.9%. The properties of the fiber-PDMS composite coating were characterized by water contact angle measurements, mechanical tests, electrochemical impedance spectroscopy, and scanning Kelvin probe. Results show that the maximum self-healing efficiencies of the fiber-PDMS coating in alkaline and acidic solution are 95.96% and 97.04%, respectively. The composition of the self-healing agents at the damaged part of the coating was verified by an infrared mapping test and using an energy dispersive spectrometer. In addition, the sandpaper abrasion test shows the hydrophobic effect of fiber-PDMS coating remains above 88.2% and decreases slightly through the addition of abrasion cycles. This research can pave the way for the industrial applications of pH-responsive self-healing coatings.

Motivated by the recent discovery of MA2Z4 family materials, we perform a systematic study on the structural stability and electronic properties of MSi2N4 nanosheets with 4d and 5d transition metal...

A new three-layered film was fabricated on magnesium (Mg) alloy via electroplating to guard against corrosion in a chloride aqueous environment, which consisted of an underlying double-layered zinc/copper (Zn/Cu) and a top aluminum-zirconium (Al-Zr) layer. The Zn/Cu underlayers not only impeded the galvanic corrosion between the Al-Zr coating and Mg alloy but also improved the adhesive ability between the substrate and the upper Al-Zr layer. Herein, we discussed the nucleus sizes of Al-Zr coatings at the stage of nucleation carried out with different contents of ZrCl4 in AlCl3-1-butyl-3-methylimidazolium chloride ionic liquid. The sandwichlike three-layered Zn/Cu/Al-Zr coatings were systematically investigated by surface morphology, phase structure, hardness, anticorrosion performances, and first-principles calculations. The corrosion current density declined from 1.461 × 10-3 A·cm-2 of bare Mg to 4.140 × 10-7 A·cm-2 of the Zn/Cu/Al-Zr3 sample. Neutral salt spray testing demonstrated that the Zn/Cu/Al-Zr3 sample showed no evident signs of corrosion after 6 days of exposure. The enhancement of the corrosion protection property was related to the fact that the application of the Cu layer changed the corrosion direction from initial longitudinal corrosion to extended lateral corrosion and the top Al-Zr coating hindered the transmission of aggressive ions. In addition, upon increasing the Zr content in the alloy films, the Fermi energy reduced initially and then increased. The Al-Zr3 alloy with 8.3 atom % Zr showed the lowest Fermi energy (-3.0823 eV), which exhibited the most efficient corrosion protection. These results showed that the prepared three-layered coating provided reliable corrosion protection to Mg alloy and may thus promote its practical applications.

In order to significantly enhance the fluorescence and mechanical properties of polyvinyl alcohol (PVA) fluorescent fibers, HBP(P-L) is synthesized by lysine, phenylalanine and N,N-methylene bisacrylamide via Michael addition reaction. Acidified multiwalled carbon nanotubes (MWCNTs) are added in HBP(P-L) solution, which are sonicated to obtain MWCNTs-HBP(P-L). Moreover, MWCNTs-HBP(P-L) is incorporated with PVA polymer to fabricate PVA fluorescence fibers via wet spinning. The fluorescence and mechanical properties of fabricated PVA fluorescence fibers are characterized by SEM, FTIR, XRD, DSC, fibers tensile tester and fluorescence spectroscopy. The results display that the neat PVA fibers could not emit fluorescence when emission peak is at 450–480 nm, while MWCNTs-HBP(P-L)/PVA fibers could emit green fluorescence. The neat PVA fibers still could not emit fluorescence when emission peak is at 530–550 nm, while MWCNTs-HBP(P-L)/PVA fibers could emit dark red fluorescence. Furthermore, the crystallinity, the degree of orientation, the breaking strength and modulus of MWCNTs-HBP(P-L)/PVA fibers are 65.0%, 93.8%, 6.52 cN/dtex and 76.33 cN/dtex, respectively. Especially, the breaking strength and modulus of MWCNTs-HBP(P-L)/PVA fibers are 15.2% and 82.1% higher than that of neat PVA fibers. The fabricated MWCNTs-HBP(P-L)/PVA fibers exhibit unique mechanical and fluorescence properties, which make it be potentially envisaged in biomedical application.

The severe shuttle effect and slow kinetics of lithium polysulfide (LiPS) conversion are two major obstacles to the practical application of lithium sulfur batteries. Ultra-thin 2D MoO2 nanosheets (MoO2 NSs) have been synthesized by chemical vapor deposition and then mixed with carbon nanotubes (CNTs) using as coating materials of the Celgard 2400 polypropylene separator to solve these problems. The 2D character of MoO2 NSs produced high surface/volume ratios and abundant active binding sites for anchoring LiPSs. In addition, the partial reduction of MoO2 NSs in a H2/Ar mixture introduced oxygen vacancies in their surface, which acted as catalytic sites for LiPS conversion, while the CNT network ensured rapid electron transfer for LiPS conversion reactions. Symmetric dummy cell tests showed that a 30wt%MoO2/CNT coated separator reduced the energy barrier for Li2S nucleation, and first-principles calculations verified its strong binding energy to entrap LiPSs and increase Li2S precipitation. Because of these features, a cell with a 30wt%MoO2/CNT coated separator had an improved specific capacity of 738 mAh·g−1 at 1 C with a slow decay rate of 0.053% for 800 cycles.

Single-phase high- and medium-entropy alloys with face-centred cubic (fcc) structure can exhibit high tensile ductility1,2 and excellent toughness2,3, but their room-temperature strengths are low1–3. Dislocation obstacles such as grain boundaries4, twin boundaries5, solute atoms6 and precipitates7–9 can increase strength. However, with few exceptions8–11, such obstacles tend to decrease ductility. Interestingly, precipitates can also hinder phase transformations12,13. Here, using a model, precipitate-strengthened, Fe–Ni–Al–Ti medium-entropy alloy, we demonstrate a strategy that combines these dual functions in a single alloy. The nanoprecipitates in our alloy, in addition to providing conventional strengthening of the matrix, also modulate its transformation from fcc-austenite to body-centred cubic (bcc) martensite, constraining it to remain as metastable fcc after quenching through the transformation temperature. During subsequent tensile testing, the matrix progressively transforms to bcc-martensite, enabling substantial increases in strength, work hardening and ductility. This use of nanoprecipitates exploits synergies between precipitation strengthening and transformation-induced plasticity, resulting in simultaneous enhancement of tensile strength and uniform elongation. Our findings demonstrate how synergistic deformation mechanisms can be deliberately activated, exactly when needed, by altering precipitate characteristics (such as size, spacing, and so on), along with the chemical driving force for phase transformation, to optimize strength and ductility. Increased strength and ductility in a medium-entropy alloy of Fe, Ni, Al and Ti is demonstrated using nanoprecipitates that simultaneously hinder phase transformation and block dislocation motion.

A Cr2O3 diffusion barrier was formed in situ between Ni coating and 316L through electroplating a Ni(NiO) transition layer first and then annealing at 900°C for 8 h in Ar. The obtained Cr2O3 is dense, continuously grown, and well bonded with 316L. The diffusion and corrosion resistance of Ni coating with and without Cr2O3 diffusion barrier were investigated. No visible outer diffusion of elements was found during the heat treatment at 750°C for 150 h, and the Ni coating with a Cr2O3 diffusion barrier can provide a good protection for 316L in molten (Li,Na,K)F.

Although layered metal dinitrides (MN2) have been proposed as the cousins of transition-metal dichalcogenides, the non-MoS2-type geometries are found to be more favourable in two-dimensional (2D) MN2 nanosheets. In this work, motivated by the recent synthesis of the SiO2-like SN2 solid, we perform a comprehensive first-principles study on the bilayer hexagonal structure (BHS) of the SN2 nanosheet. It is found that the BHS-phase is the real lowest-energy structure of the 2D SN2 form, which possesses robust dynamical, mechanical and thermal stabilities. The BHS-SN2 nanosheet is a quasi-direct semiconductor, whose top valence band is quite flat. As a result, Stoner ferromagnetism could be induced by hole doping, which causes half-metallic or ferromagnetic metallic behaviour depending on the hole concentration. Moreover, at a doping level of one hole per cell, the doped BHS-SN2 nanosheet exhibits a spin-polarized semi-metallic feature without considering the spin–orbit coupling (soc). After the inclusion of the soc effect, this system exhibits quantum anomalous Hall (QAH) insulating behaviour with a non-trivial band gap of 18 meV. The non-trivial topology is characterized by a non-zero Chern number of C = 1, which is confirmed by a quantized Hall conductance and a single gapless edge state in the bulk gap. The QAH behaviour is not only present in the doped system, but also appears in the P-substituted BHS-SN2 derivative, i.e. the PS3N8 nanosheet. The non-trivial gap increases to 26 meV when the PS3N8 nanosheet is supported on a fluorographene substrate, which facilitates the experimental observation of QAH effect. Our study demonstrates that intriguing QAH behavior can emerge in the system composed solely of light non-metal elements, which provides a new avenue in the design of novel topological materials.

Porous intermetallic membrane with extensive interconnected pores are potential candidates as functional materials for high-temperature particulate matter (PM) capturing. However, fabrication of intermetallic membrane with a combined performance of high filtration efficiency and high-temperature oxidation resistance remains a challenge. To tackle this issue, a hierarchical micro-/nano-dual-scale sized pores was constructed on the inner cell walls of a porous support through mutual diffusion and chemical reaction. Benefited from its hierarchical micro/nano-dual-scaled pore structural features, the high Nb containing TiAl-based porous composite microfiltration membrane demonstrates ultrahigh PM>2.5 removal efficiency (99.58%) and favorable oxidation/sulfidation performance at high temperature. These features, combined with our experimental design strategy, provide insight into designing high-temperature PM filtration membrane materials with enhanced performance and durability.

Large quasi-elastic deformation with high degree of rebound resilience was reported in dense, monolithic ceramics for the first time, which was achieved in the cyclic compression-resilience tests on bulk amorphous Al2O3–ZrO2–Y2O3 at 600 °C. As the compression strain was 4%, the resilience ratios in the three cycles were 89.5%, 100% and 100%, respectively; for compression strain of 8%, the resilience ratios were 74.5%, 90.6% and 92.0%. The superior elastic deformation in amorphous Al2O3–ZrO2–Y2O3 was due to the round trip migration of atoms through free volume in amorphous phase, and the residual strain after deformation of 4% and 8% are resulted from structural densification and shear band formation, respectively. This work could inspire new guidance on elastic deformation in ceramics, and provide new guidance to ceramic materials with high elastic deformation and rebound resilience in engineering applications.

Due to the extraordinary electronic and magnetic properties, transition-metal dinitrides (TMDNs) and their derivatives are gaining importance in low-dimensional layered materials. In this work, through first-principles calculations, we have comprehensively investigated the structural and electronic properties of hydrogenated group V TMDN nanosheets. We find that surface hydrogenation can well stabilize the H-, T- and M-phase structures of group V TMDNs, for which the formed MN2H2 nanosheets have robust energetic, dynamical and thermal stabilities. Different from pristine MN2 systems, the H-phase system has become the most favorable structure of MN2H2 nanosheets. Intrinsic ferromagnetism is present in these H-MN2H2 nanosheets, which even exhibit bipolar magnetic semiconducting behaviors. More interestingly, large spontaneous valley polarization occurs in the H-MN2H2 nanosheets, and is attributed to the coexistence of remarkable spin-orbit coupling and magnetic exchange interactions according to the k·p model analysis. Among them, the H-NbN2H2 nanosheets are found to be a promising ferrovalley material, whose valley polarization value reaches as large as 0.11 eV and the Curie temperature is up to 225 K. Besides that, versatile electronic properties are obtained in the T- and M-phase structures of the MN2H2 nanosheets, which will be magnetic/nonmagnetic metals/semiconductors depending on the metal species and phase structures. Our study demonstrates that the hydrogenation can bring robust structural stabilities and unconventional electronic properties into the group V TMDN nanosheets, which enable many potential applications in spintronics and valleytronics.

Very recently, a black-phosphorus-like nitrogen (bp-N) bulk has been synthesized in high-pressure experiments [D. Laniel, et al., Phys. Rev. Let., 2020, 124, 216001 and C. Ji, et al., Sci. Adv., 2020, 6, eaba9206]. However, the corresponding bp-N monolayer, i.e. a puckered N nanosheet, is unstable, which will decompose to loose N zigzag lines. Based on first-principles calculations, we find that the puckered geometry can be stabilized by inserting C2 dimers between the upper and lower N zigzag lines. The formed C2N2 nanosheet possesses good energetic, dynamical, mechanical, thermal and chemical stabilities, which can maintain the free-standing state even in the presence of O2 gas. Owing to the phosphorene-like geometrical character, this C2N2 nanosheet exhibits an auxetic mechanical behaviour with a negative Poisson's ratio in the out-of-plane direction. The C2N2 nanosheet is an indirect-gap semiconductor with a noticeable linear dichroism. More interestingly, a giant anisotropy appears in the hole mobility of the C2N2 nanosheet, which has a high (low) hole mobility of about 1700 (20) cm2 V−1 s−1 along the armchair (zigzag) direction. The corresponding anisotropic ratio is as large as 85 in the C2N2 nanosheet, which is the maximum mobility anisotropy reported in two-dimensional materials. The high hole mobility and large anisotropic ratio are also preserved in the multilayer C2N2 nanosheets. Our study demonstrates that the puckered N-based nanosheets possess robust structural stabilities and unconventional physical properties, which endow the system with many potential applications in flexible electronics, optoelectronics, and direction-sensitive sensors.

Current creep-fatigue evaluation approaches based on the creep-fatigue Damage-diagram are complex and very conservative. Simplified Model Test (SMT) method is an alternative approach to determine cyclic life at elevated temperatures. The SMT-based creep-fatigue evaluation methodology avoids parsing the damage into creep and fatigue components and greatly simplifies the evaluation procedure for elevated-temperature cyclic service. In this study, the effects of sustained primary-stress loading are evaluated in support of the development of SMT-based creep-fatigue design curves for Alloy 617. Experiments were designed and performed using internal pressurized tubular specimens at 950 °C on Alloy 617. The sustained primary-load was introduced by the internal pressure. A newly developed SMT technique, single-bar SMT, was extended to these tests and SMT creep-fatigue test data were generated with various elastic follow-ups, internal pressures and strain ranges. The test results from this study along with the original SMT data on Alloy 617 demonstrate that, although internal pressure is within the allowable stress limit per ASME Section III Division 5 Code Case N-898, the SMT creep-fatigue cycles to failure were reduced for the cases tested with primary-pressure load. The reduction of SMT creep-fatigue life due to primary-load was found to be dependent on strain ranges and elastic follow up. Approaches to handle the primary-load effect on SMT design curves are discussed.

A template-free method is successfully designed to originally synthesize novel porous Bi2O2CO3 hexagonal nanoplate (PBHN) and the Bi2O2CO3 hexagonal nanoplate/nitrogen-doped graphene nanomaterials (PBHN/NG). Notably, PBHN-2 and PBHN/NG-2 have not yet been reported in previous literatures. For the first time, PBHN/NG-2 as the oxygen reduction reaction (ORR) catalyst has been investigated in detail for cathode of fuel cell. The measurement results show that PBHN/NG-2 has exhibited fascinating ORR performances, duo to its orthogonal-layered porous structures from porous Bi2O2CO3 and NG sheets. The values of onset potential and limiting current density for PBHN/NG-2 are 1.179 V and 7.38 mA cm−2 in 0.1 M HClO4 respectively. The PBHN/NG-2 possess small electrochemical impedance and good methanol immunity in 0.1 M HClO4 media. Remarkably, the relative current density of PBHN/NG-2 in acidic electrolyte can still keep 98.58% of its original density after 18000 s durable measurement. Therefore, the PBHN/NG-2 is a promising ORR catalyst to solve the problems of high costs, sluggish ORR kinetics and low durability, applied in fuel cells, metal-air batteries and other renewable energy devices.

A Nb:TiO2 nanofibers/PANI electrically conductive composite coating is electropolymerized on 316 stainless steel for bipolar plates of a proton-exchange membrane fuel cell. The corrosion behavior of the composite coating in the simulated cathodic and anodic environments (0.3 M HCl bubbled with air or H2 at 25 °C) is investigated by the potentiodynamic polarization, potentiostatic polarization, open circuit potential and electrochemical impedance measurements. The experimental results indicate that the corrosion current density of the composite coating coated 316 stainless steel decreases to about 2.75 and 6.31 µA cm−2 in the simulated cathodic and anodic environments, respectively. The corrosion potential increases by more than 400 mV vs. SCE. During the 180 h immersion, the composite coating shows high chemical stability and provides effective protection for the 316 stainless steel through its physical barrier effect and in-situ anodic protection effect.

The composite structurehttp://mts.hindawi.com/update/) in our Manuscript Tracking System and after you have logged in click on the ORCID link at the top of the page. This link will take you to the ORCID website where you will be able to create an account for yourself. Once you have done so, your new ORCID will be saved in our Manuscript Tracking System automatically."?> with aluminum foam not only has the strength and toughness of the dense material but also reduces the weight of the component and increases specific deformation energy absorption performance. In this paper, advanced pore morphology (APM) foam elements are combined with thin-walled circular steel pipes by epoxy-bonding and epoxy foam-bonding processes to prepare composite circular pipes. The direct epoxy-bonding process using epoxy resin refers to coating the surface of APM spheres, whereas the epoxy foam-bonding process involves the mixing of the epoxy resin with the epoxy foaming agent and then coating the surface of APM spheres with this mixed epoxy resin. The compression performances and energy absorption performances were analyzed by quasistatic compression tests. Results indicate that the different bonding modes change the deformation mode of the specimen under compression. The epoxy foam-bonding APM composite pipe has a higher compression load level than the epoxy-bonding APM filled pipe. The epoxy foam-bonding APM composite pipe is superior to the epoxy-bonding APM composite and thin-wall hollow pipe. Hence, the combination of foaming and bonding of epoxy can be used as a new filling process for APM fillers.

Octyl(triphenylethynyl)silane monomer(OTPES) was synthesized with ethyl bromide, octyltrichlorosilane and phenylethylene by Grignard reaction. The molecular structure was confirmed by FTIR and NMR. The poly[octyl(triphenylethynyl)]silane resin(POTPES) was prepared by thermal polymerization and the corresponding thermal degradation behavior wasstudied by thermogravimetric analysis(TG) combining with model and model-free fitted methods. The dielectric property of resin was also studied by vector network analyzer. The results show that the melt point of OTPES was 50 °C and the processing window was over 236 °C. The resin degradation temperature of Td5 occurred over 433 °C and the char yield was over 60% at 800 °C. Based on Kissinger, Flynn-Wall-Ozawa, Coats-Redfern, Achar, Vyazovkin-Wight and Tang methods, the reaction activity(E) was 155.51, 152.97, 150.82, 146.02, 148.38 and 148.77 kJ/mol, respectively. Dielectric properties analysis displayed that the real part(e′) and the imaginary part(e″) of the relative complex permittivity of POTPES was 2.5 and 0.05, respectively, and the dielectric loss tangent was between 0.03 and 0.25. The reflection loss of resin was more than −2.85 dB in all range of 1–5 mm thicknesses and 2–18 GHz frequency, which indicated that POTPES resin was a real wave-transparent resin matrix.

碳基荧光纳米探针在生物成像领域展现出诱人的应用前景. 本文通过调节合成方法合成了一种磺酸基修饰的石墨烯量子点(S-GQDs)荧光探针. 该探针呈现出优异的光学和理化性能, 如荧光强度高、 pH稳定、表面带负电等. 研究表明其发光机理主要依赖荧光分子发光机制. 与我们之前报道的氨基化量子点A-GQDs和肿瘤细胞核靶向探针GTTN对比, 该探针具有良好的生物安全性, 可以在相当短的时间内即跨膜进入细胞, 而GTTN在正常的体外培养条件下无法进入细胞. 为此, 我们探究了产生该差异的原因. 结果表明, S-GQDs与A-GQDs截然不同的合成原料导致了他们的毒性差异, 而S-GQDs的不稳定性则是导致其进入细胞、与GTTN明显不同的主要原因.

An effective route was originally reported to synthesize a series of iron–nickel–nitrogen codoped carbon nanocomposites, derived from bimetallic iron/nickel metal–organic frameworks (Fe/Ni-MOFs) an...

Two-dimensional (2D) carbon-coated sandwich-like mesoporous SnO2/graphene/mesoporous SnO2 nanosheets (C@SnO2-rGO-SnO2) is conceived and synthesized as a novel anode material towards advanced lithium-ion battery. The nanocrystals size of SnO2 could efficiently manipulate using sandwich-like mesoporous SiO2/graphene/mesoporous SiO2 (SiO2-rGO-SiO2) nanosheets as template. The existence large quantity of mesoporous nanostructure not only could provide sufficient buffer space for alleviating volume change of SnO2 during the discharge/charge process, but also supply more surface reaction sites for facilitating the penetration of electrolyte into electrode and enhancing surface lithium storage capacity. The graphene acts as mini-current collector provides rapid Li+ diffusion and transportation, and the carbon-coated protection layer prevents SnO2 aggregation effectively, which contributes to form stable solid electrolyte interface (SEI) film during cycling. Furthermore, the synergistic effect of graphene and carbon-coated shell constitutes excellent conductive network, which overcomes low electrical conductivity shortage of SnO2. The C@SnO2-rGO-SnO2 electrode exhibits excellent reversibility (1211 mAh g−1 after 300 cycles at 0.2 A g−1), good rate capability (545 mAh g−1 at 5 A g−1, 315 mAh g−1 at 10 A g−1) and superior long-cycle stability (703 mAh g−1 after 1200 cycles at 1 A g−1, 525 mAh g−1 after 1200 cycles at 2 A g−1).

In order to investigate proton irradiation damage on ferritic/martensitic T92 steels, both the unaged and aged (650 °C for 15,000 h) T92 steels were irradiated with 250 keV protons to 0.01, 0.05 and 0.20 dpa at room temperature due to the lower dose rate of protons compared with heavy-ions. The microstructural evolution induced by thermal aging and proton irradiation was studied by transmission electron microscopy and positron annihilation spectroscopy, and the corresponding micromechanical property changes were investigated by nano-indentation. After 0.20 dpa proton irradiation, the dominant irradiation-induced dislocation loops were a 0 1 0 0 type loops for both the unaged and aged samples. The dislocation-type defects in the aged T92 sample were larger in size and higher in number density, compared with those in the unaged samples. Less vacancy-type defects induced by protons were detected in the aged than the unaged T92 samples under the same irradiation conditions. The higher number density of dislocation-type defects led to more severe irradiation hardening in the aged T92 samples.

Novel hierarchically porous titanium-metal organic frameworks/nitrogen-doped graphene (Ti-MOFs/NG) nanocomposite derived from titanium-metal organic frameworks (Ti-MOFs) and the nitrogen-doped graphene (NG) has been originally synthesized successfully. Notably, the Ti-MOFs/NG nanocomposite has been for the first time investigated in detail, as oxygen reduction reaction (ORR) catalyst of cathodic materials for fuel cells. The results show that the Ti-MOFs/NG nanocomposite possesses excellent ORR performances, whether in alkaline or acidic medium, due to existences of the Ti3N2-x, C2O7Ti2.3, H2Ti5O11, Ti and TiO active ORR segments. Specifically, the onset potential (E0) and the Tafel slope value of the Ti-MOFs/NG nanocomposite are 1.14 V and 17.84 mV dec−1 in 0.1 M HClO4, respectively. Similarly, high ORR efficiency of the Ti-MOFs/NG nanocomposite also exhibit in alkaline medium. The relative current density can still keep 99.88% of the original value after 10800 s measurements in 0.1 M KOH. Additionally, small electrochemical impedance and excellent tolerance toward fuel molecules have been exhibited in both electrolytes. These ORR properties are superior to those of most of previously reported materials derived from other MOFs, in both alkaline and acidic media. Thus, the Ti-MOFs/NG nanocomposite is as a novel promising candidate for ORR catalyst to solve the main problems of sluggish reaction kinetics of the ORR, high cost of precious metal catalysts and low durability of the traditional catalysts, applied to fuel cells, metal-air batteries and further to water splitting in energy conversion and storage devices.

The impact of cyclodextrins (CDs) on physical properties of the compound gel of κ-carrageenan/konjac glucommanan (KC/KGM) was investigated by texture profile analysis (TPA), compression modulus test, freeze-thaw stability test, scanning electron microscopy (SEM) and X-ray diffraction (XRD). TPA results showed that CDs had remarkable influence on mechanical properties of the compound gel. In concentration range of 0.5%–1.5% (w/w), hardness was strengthened with the increase of CDs concentrations, then gradually decreased at higher CDs concentrations. Cohesiveness, gumminess and chewiness showed similar tendency as the hardness. However, influence of CDs on gel springiness was slight. Compressive experiment indicated that the CDs increased the compressive elastic modulus (S) of the compound gel and improved the deformation resistance of the gel network. In the freeze-thaw stability test, stability of the compound gels was obviously improved after adding CDs, about 10% more water was preserved after the first freeze-thaw cycle. SEM results showed that the microstructures of the compound gels containing CDs were much denser with smaller voids. XRD results indicated that the crystallization peaks of the compound gels decreased after CDs were added. The exclusion of CDs from the polysaccharides chains in the sol state led the KC/KGM compound solution to form a denser network after cooling and benefited the texture and freeze-thaw stability of the formed gel. CDs improved the synergistic interaction between KC and KGM polysaccharides. The influence of methyl-β-cyclodextrin (M-β-CD) on the formation and characteristics of KC/KGM compound gel was the most significant among all the selected CDs.

A direct relationship between the microstructural evolution and macroscopic fracture behaviors of a thermally aged (at 475 °C for 400 h) duplex stainless steel (DSS) has been established with experimental results from atom probe tomography (APT), nanoindentation and in situ synchrotron-based high-energy X-ray diffraction (HE-XRD). The APT experiments demonstrate that ferrite in DSS spinodally decomposes into Cr-enriched and Cr-depleted domains during thermal aging, which leads to a severe hardening effect in ferrite. The lattice strain development during deformation acquired with the in situ HE-XRD measurements confirms the cleavage fracture of α{110} and α{200} ferrite grains aligned perpendicular to loading direction. The thermally aged DSS can be readily fractured by connecting the cleavage cracks in ferrite. The spinodal-decomposition-induced hardening in ferrite and the premature failure of ferrite control the final brittle fracture in the aged DSS.

The sluggish redox kinetic and the severe shuttle effect remain the key issues for the application of lithium–sulfur batteries, resulting in low sulfur utilization and rapid capacity fading. Herein, a nanostructured VS4 anchored on defect-rich carbon nanofibers (CNF-VS4) was coated on the commercial separator as both physical blocks to mitigate the shuttle effects and as an electrocatalyst to enhance the reaction kinetics of polysulfides/Li2S. Besides, polar nanostructured VS4 shows a high affinity to polysulfides, and conductive CNF network serves as “second collector” to trap and reutilize the active materials. The functional coating layer also provides rich defects for the dispersion and stabilization of Li2S. When the CNF-VS4 functional separator based on a high-sulfur content (80 wt%) cathode was applied in Li–S batteries, a high initial capacity of 1135 mA h g−1 at 0.2C and a superior rate capacity of 780 mA h g−1 at 2C were achieved. Even under a higher rate (5C), it still delivered a stable capacity of 300 mA h g−1 over 1000 cycles with a high coulombic efficiency of 95%.

Zircaloy-4 with 200 wppm hydrogen was irradiated with 3 MeV Fe11+ ions and the microstructural evolution of δ-hydride precipitation under ion irradiation was investigated. TEM observation of unirradiated sample shows the needle-like δ-hydride and the orientation relationship between α-Zr matrix and δ-hydride is (0002)α//(1 1 ¯ 1)δ, [2 1 ¯ 1 ¯ 0]α//[011]δ. After ion irradiation, both and -type dislocation loops were observed in α-Zr matrix. Some circular structures with obviously different contrast from the α-Zr matrix were observed in the irradiated Zircaloy-4-200 wppm H samples. The circular structures were identified as δ-hydrides with an fcc structure by indexing the FFT patterns of HRTEM images. There is an orientation relationship of (01 1 ¯ 1 ¯ )α//(200)δ, [01 1 ¯ 2]α//[011]δ between the circular δ-hydride and α-Zr. The formation of circular δ-hydride is related with ion irradiation and the formation process is explained by the hydrogen trapping mechanism.

Tracking inorganic photochemistry with high resolution poses considerable challenges. Here, sub-picosecond electronic and structural motions and MLCT/d-d intersystem crossing in a cationic iron-porphyrazine are probed using ultrafast transient absorption, stimulated Raman spectroscopy, and quantum calculations. By delineating photoinduced energy relaxation, strategies for extending the lifetime of MLCT state are discussed.

Novel microporous carbon materials (DCMC) with excellent electron conductivity and ultrahigh surface area (1896.9 m 2 g −1 ) are successfully prepared from discarded clothes. The porous carbon-encapsulated sulfur composites were synthesized by a feasible melting process and used as host materials for lithium sulfur batteries. Because of the unique microporous, ultrahigh surface area and irregular wrinkled surface coexisting structure, the resulting microporous carbon/sulfur (DCMC/S) composite cathode possesses a good rate capability and long-term cycling performance. The initial discharge capacity of the DCMC2/S composite electrode with 74.3 wt% sulfur content is 1082.6 mAh g −1 at a current rate of 0.2 C. At a higher current rate of 1 C, it possesses excellent cyclic performance and retained a capacity of 422.8 mAh g −1 after 500 cycles with a low capacity fading rate of 0.11% per cycle. The coulombic efficiency remains over 98% during cycling.

9Cr ferritic/martensitic steels are promising materials for in-core components in advanced Gen-IV reactors. In these applications, their long-term microstructural stability under thermal exposure and resistance to neutron irradiation are essential. Tempered (unaged) and long-term thermal aged T92 samples were used to evaluate the effects of thermal aging and ion irradiation on the microstructure and micromechanical properties of the steel. Both the tempered and aged samples were irradiated with 3 MeV Fe11+ions to 0.25, 0.50, 1.00 and 5.00 dpa at room temperature. Using the nanoindentation technique, the irradiation hardening behaviors of T92 steel were investigated. The irradiation hardening effect was observed in both the tempered and aged T92 samples. To eliminate the soft substrate effect, the critical indentation depth was determined using the ratio of the average hardness of irradiated and unirradiated samples at the same depth. Under the same irradiation conditions, the macroscopic hardness values of the aged T92 samples after irradiation were lower than those of the tempered samples. The irradiation hardening effect was more significant in the aged T92 due to the decreased dislocation density and the coarsened martensitic lath after long-term thermal aging.

The sluggish redox kinetics and severe lithium polysulfides (LiPSs) shutting effect in lithium sulfur batteries (LSBs) greatly hinder their practical applications. In this work, phosphorus doped carbon nanosheet array (MPC) separator coating layer was synthesized by MgO template, and used as metal-free electrocatalyst to concurrently fulfill efficient polysulfide interception and conversion. By regulating the addition of phytic acid, copolymerization rate of formaldehyde, resorcinol and phytic acid can be conveniently adjusted to form a hierarchical porous MPC microstructure. Phosphorus doping introduces surface defects and enhances the polarity of MPC, which exhibits a metal-like LiPSs anchoring effect by forming Li-P and S-P bonds, avoiding the undesirable oxidation of LiPSs during adsorption. Symmetrical cell and Li2S precipitation experiments reveal that phosphorus doping reduces energy barrier for LiPSs reactions and facilitates Li2S precipitation behavior, exhibiting a strong electrocatalytic effect on Li-S chemistry. Stemming from the above advantages of MPC coated separator, cells exhibit a low interfacial reaction resistance and good anode stability. A capacity of 1161 mAh g-1 at 0.2 C and a low attenuation of 0.056% per cycle at 1 C over 800 cycles are achieved. For a high sulfur loading up to 4 mg cm-2, the areal capacity can still be stabilized at 2.86 mAh cm-2.

Mixed-metal metal-organic frameworks (MMOFs) contain more than one type of metal node, which can improve or even introduce new features compared to the single-metal frameworks. Traditionally, most of the MMOFs are synthesized by solution method which requires all the metal ions to form stable coordination with the ligand in a single framework, and therefore limits the choice of the metal ions. In this work, Pt-doped Zn-MOF-74 (PtZn-MOF-74) has been prepared through a mechanochemical conversion approach from Pt-doped ZnO (Pt-ZnO) directly. The absence of a large quantity of solvent limits the solvation and diffusion of growth species during the mechanochemical conversion and therefore prevented the agglomeration of Pt dopants in PtZn-MOF-74. CO oxidation was used to evaluate the catalytic performance of the prepared MMOFs. Compared with inert Zn-MOF-74, PtZn-MOF-74 with unsaturated coordinated Pt at elevated temperature can act as the active sites to catalyze CO oxidation reaction. This study provides a novel design strategy for the synthesis of MMOFs with extended functionalities.

Premature creep failures at the intercritical heat affected zone (ICHAZ) of creep-resistant steel weldments have been frequently reported. However, the creep degradation mechanism of different microstructure constituents in ICHAZ is complicated and needs further clarification. In this work, Grade 91 steel was intercritically heat-treated at a temperature (860 °C) between the critical temperatures AC1 and AC3, and a correlation between microstructure and mechanical properties of the heat-treated specimen was built. The effects of austenitization and tempering resulting from the intercritical treatment (IT) differentiated the local strain energies between the two microstructure constituents: newly transformed martensite (NTM) and over-tempered martensite (OTM). The formation of NTM grains led to a hardness increase from 247 HV0.5 in the base metal to 332 HV0.5 in the IT specimen. The ultimate tensile strength (UTS) increased from 739 MPa in the base metal to 1054 MPa in the IT specimen. Extensive growth of the OTM grains and rapid recovery of NTM grains took place simultaneously in the IT specimen during a typical tempering at 760 °C. These microstructure degradations led to a lowered hardness of 178 HV0.5, a reduced UTS of 596 MPa, and a poor creep resistance with a minimum creep strain rate of 0.49 %/h at 650 °C in an IT + tempering (ITT) specimen.

The current ASME Boiler and Pressure Vessel (B&PV) Code Section III, Division 5, Subsection HB, Subpart B has only one design fatigue curve for grade 91 steel (Gr. 91) at 540 °C (or 1000 °F). The ASME Section III Working Group on Creep-Fatigue and Negligible Creep (WG-CFNC) has taken an action to incorporate the temperature-dependent design fatigue curves for Gr. 91 developed by Japan Society of Mechanical Engineers (JSME) into ASME Section III Division 5. During the process, issues regarding the effect of mean stress on fatigue analysis, and how to consider the mean stress effect for elevated-temperature design, were brought up. To evaluate whether the design fatigue curves of Gr. 91 needed adjustment to account for mean stress, critical tests were designed and performed at 371 °C (700 °F) and 540 °C (1000 °F). This study is similar to the work performed on Alloy 617 when its fatigue design curves were established for temperature range of 538–704°C (1000–1300°F) as part of the Code Case package for Alloy 617 to be used as Class A construction material in Division 5. The effects of mean stress on Alloy 617 were evaluated at 550°C (1022°F). The results showed that the mean stresses introduced by the non-zero mean strain could not be maintained under strain-controlled fatigue and resulted in negligible effect on the fatigue life. Mean stress correction was not recommended for Alloy 617 fatigue design curves in Division 5. This study shows the same conclusion for Gr. 91.

Fatigue crack growth rates (FCGR) of multiple X100 pipeline steel welds and heat affected zones were measured in high-pressure hydrogen gas to investigate their behavior compared to lower strength pipeline welds. A total of five high strength welds and two heat affected zones (HAZ) were examined all of which were fabricated using the same X100 base material. Different welding wires and techniques were used to fabricate the welds to provide a variety of end products to evaluate susceptibility to fatigue in high pressure hydrogen gas. Residual stresses were measured for each weld and HAZ using the slitting method and the effect of residual stress on the stress intensity factor, Kres, was determined. Using Kres, the fatigue crack growth rate curves were corrected to remove the effects of residual stress by examining the influence of Kres on stress ratio, R. Comparisons were then made between the high strength welds, which were corrected for residual stress, and lower strength welds from the literature. It was found that the higher strength welds and heat affected zones exhibited comparable fatigue crack growth rates to lower strength welds, as the FCGR data of the high strength welds overlaid the lower strength welds. This suggests that despite distinct differences in strength and microstructure between the different welds, hydrogen-assisted fatigue crack growth susceptibility is similar. A comparison was made between the Kres measured in extracted coupons and residual stress estimates provided in relevant welded pipe assessment standards such as API 579-1/ASME FFS-1. It was found the residual stress values in the test coupons extracted from welded pipe were significantly lower than those expected in the intact welded pipes and highlights the importance in quantifying and removing coupon residual stresses when fatigue crack growth rates are measured and including expected weld joint residual stress when making structural assessments.

In order to investigate the acoustic radiation characteristics of underwater, a pipe casing was introduced and the effects of its main structural characteristics on underwater combustion acoustic radiation were studied by acoustic testing. The results show that the addition of the pipe casing significantly increased the sound pressure level of underwater pyrotechnic combustion, especially the peak of sound pressure level that was increased by 15.9 dB from 155.5 to 171.4 dB at the frequency of 125 and 100 Hz. But the addition of the pipe casing had little effect on the frequency. These results indicated that adding a pipe casing is effective for improving sound pressure level in underwater pyrotechnic combustion. An increase in nozzle diameter from 10 to 12.5 mm resulted in an increase of gas volume, so the peak of sound pressure level and broadband sound pressure level is higher. Changing the pipe casing direction to vertical downward will make the bubble formation period shorter, which will generate more bubbles and strong wake; the interaction between bubbles and wake results in a higher intensity of turbulence, which accounts for the coalescence and breakup of bubbles in the fluid. Besides, changing the diameter of pipe casing can be used to lower the frequency of underwater noise.

This study evaluates foaming behavior and pore structure evolution of aluminum foam by cross-sectional image processing, which was prepared by the powder compact melting (PCM) method under the constraint. The results revealed that the heating time and the heating rate are the key factors affecting the foaming behavior and pore structure of aluminum foam. The thermal decomposition of the foaming agent and aluminum melting behavior affect the foam expansion under different heating times and heating rates. The evolution of the pore structure during the foaming process includes pore formation, small-sized spherical pores, large-sized spherical pores, polygonal pores, merging, and collapse. Due to the limitation of the pipe wall, the maximum expansion height and porosity are constrained, and the macrostructure of aluminum foam is improved.

The influence of cyclodextrins (CDs) on the rheological and structural properties of κ-carrageenan (κ-CA) gel was investigated. Gelling temperature (Tg) of κ-CA was improved by CDs present in the system. Variation of the Herschel-Bulkley model parameters indicates that the addition of CDs increases plasticity of the κ-CA sol. Scanning electronic micrographs show that networks of κ-CA become flat and firm after CDs were added. κ-CA gel containing methyl-β-CD shows the most uniform and fine network structure. Moreover, a proposed model of CDs in κ-CA phase was provided. The influence of CDs on κ-CA gelation was mainly through (i) the exclusion of CDs from κ-CA in the sol state, (ii) the regular rearrangement of κ-CA random coils influenced by CDs in the sol state, (iii) the binding of CDs to the κ-CA surface by hydrogen bonds in the gel.

Owing to the fast developments of transition-metal dichalcogenides (TMDs), their cousins, that is, layered transition-metal dinitrides (TMDNs), have also drawn appreciable research interests. Gener...