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As the desired sulfur host of lithium-sulfur battery, the strong polarity and fast electron migration capability are indispensable for achieving effective adsorption and conversion of lithium polysulfides (LiPSs), that is, restricting the shuttle effect. Herein a porous microdisk Ti4O7/TiN/C heterojunction with strong polar N-Ti-O covalent bonds is precisely constructed. Compared with O-Ti-O or N-Ti-N bond in single Ti4O7 or TiN, the N-Ti-O bond with stronger polarity could adsorb and bond with S and Li atoms in LiPSs, which is beneficial for LiPSs adsorption. Beside, the Ti4O7/TiN heterostructure favors the electron transfer, which could promote the conversion of LiPSs. The design strategy is to construct abundant polar N-Ti-O bonds at Ti4O7/TiN heterogeneous interface that would realize the associative process of LiPSs adsorption, trapping, and conversion, thereby restraining the shuttle effect efficiently. In the current study, as the host of the sulfur cathode, the porous microdisk TiN/Ti4O7/C heterojunction exhibits a high specific capacity of 1204.5 mAh g−1 at 0.2 C, and a high specific capacity of 616.5 mAh g−1 at an ultrahigh current density of 4 C. In addition, 86.4% and 116.9% capacity are retained over 1000 cycles at 1 C and 2 C, respectively. This strategy provides an insight into developing lithium-sulfur battery with extraordinary performance, and opens promising routes to design the next-generation electrochemical energy storage devices.

The alkaline hydrogen evolution reaction (HER) of MoS2 is hampered by its sluggish water dissociation kinetics as well as limited edge sites. Herein, Ni3S2/MoS2 is fabricated as a model catalyst to highlight interfacial structural and electronic modulations of MoS2 for realizing its high performance in the alkaline HER. Experiments and density functional theory results demonstrate that the coupled Ni3S2 species can not only promote the adsorption and dissociation of H2O to boost the alkaline HER kinetics but also tailor the inert plane of MoS2 to create abundant unsaturated edge-like active sites, while the interfacial electron interaction can regulate the band gaps and Gibbs free energy of hydrogen adsorption of MoS2 to improve the electron conductivity as well as HER activity. Moreover, field emission scanning electron microscopy, transmission electron microscopy, Raman, ex situ synchrotron radiation X-ray absorption, and X-ray photoelectron spectroscopy results reveal the excellent structural stability of Ni3S2/MoS2 during the HER. As expected, the target Ni3S2/MoS2 achieves an ultralow overpotential of 68 mV at 10 mA cm-2, a fast alkaline HER kinetics, and remarkable durability. The proposed concept of interfacial structural and electronic reorganization could be extended to develop other functional materials.

Single-phase Al–Mg alloys processed by severe plastic deformation (SPD) usually suffer from unsatisfactory thermal stability at moderate to high temperatures with recrystallization occurring and obvious grain coarsening. In the present work, an Al–7Mg alloy prepared by equal-channel angular pressing (ECAP) possessed markedly enhanced thermal stability upon annealing at moderate to high temperatures (200–275 ℃), compared with those ultrafine-grained dilute Al–Mg alloys with a uniform microstructure. The enhanced thermal stability is due primarily to the multimodal grain structure consisting of nano-, ultrafine- and micron-sized grains, strong segregation and/or clusters of Mg solute along grain boundaries (GBs), and Al3Mg2 precipitates formed during annealing. First, extensive recovery predominates over recrystallization and consumes most of the stored energy in the ECAPed Al–7Mg alloy annealed at ≤ 275 ℃, leading to the recrystallization and growth of nano/ultrafine grains being retarded or postponed. Moreover, Mg solute segregation and/or clusters along GBs of nano/ultrafine grains could further suppress grain growth via diminishing GB energy and dragging GBs efficiently. In addition, Al3Mg2 precipitates formed with increasing annealing time could inhibit grain growth by pinning GBs. The present multimodal-grained Al–7Mg alloy with enhanced thermal stability is believed to be particularly attractive in potential engineering applications at moderate to high temperatures.

The development of stable, high-energy electrode materials for lithium ion-batteries requires an elaborate effort to optimize the active materials as well as the chemical bonds and electron/ion transport in the electrode. However, hindered by the intrinsic structure and electrochemical degradation which is attributed to the volume expansion of materials, an increase in battery safety and reliability is concerned. Here, taking silicon as an example, we propose a strategy to stabilize this anode by successive chemical bonds reconstructing the surface. In this study, silicon nanoparticles are assembled in a carbon-copper framework via a facile and scalable pyrolysis process to provide a short-range electron transfer and pulverization suppression. Dissimilar to the current carbon coating methods, with the aid of Cu-O-C, Si-O-C, and Si-C chemical bonds, silicon hybridized reduced graphene oxide (rGO) and double-faced adhesive tape derived carbon composite (Si+rGO@DFAT-C) exhibits high structural integrity and immune to delamination. Hence, it demonstrates superior capacity (1536 mAh g at 0.1 A g ), high rate capability (1126 mAh g at 2 A g ), and stable electron stability (968.1 mAh g after 200 cycles at 0.5 A g ). This study emphasizes the crucial importance of well-tailor surface chemical bond reconstruction for the anode stabilization for high-performance LIBs. −1 −1 −1 −1 −1 −1

The influence of graphite content (volume fraction, 0, 3, 6, 9, 12%) on the microstructure, mechanical properties, thermal physical properties, and wear properties of silicon carbide particle–reinf...

The research on the highly efficient reutilization of mixed recycled aggregates (MRA) produced from construction and demolition waste has attracted significant attention globally. In this study, the feasibility of using 100% MRA in cement-stabilized materials was investigated. The mechanical properties and microstructures of cement-stabilized MRA (CSMRA) materials containing 100% MRA were systematically examined through unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, drying shrinkage test, X-ray diffraction analysis, mercury intrusion porosimetry, and scanning electron microscopy. Results showed that the UCS and ITS of CSMRA materials were significantly enhanced with the increase of cement content and curing age, and there was almost a linear relationship between the UCS and ITS. The failure behavior of CSMRA materials under load showed three typical stages: compaction stage, elastic stage, and yield stage. The increase of the cement content caused the drying shrinkage deformation of CSMRA to increase sharply when the cement content exceeded 4%. The microstructural analysis indicated that cement had both filling and binding effects on CSMRA materials. The strength growth with cement content and curing age was because of the constant hydration of cement minerals, producing more calcium silicate hydrate binders between aggregates. Moreover, the increasing cement content could reduce the porosity and optimize the pore structure distribution of CSMRA materials. The findings of this study demonstrate that the use of 100% MRA in cement-stabilized materials as a road base is feasible, which will significantly enhance the utilization efficiency of MRA.

Oxygen vacancies play a positive role in optimizing the physical and chemical properties of metal oxides. In this work, we demonstrated oxygen vacancy-promoted enhancement of Li-ion diffusion kinetics in Li2GeO3 nanoparticle-encapsulated carbon nanofibers (denoted as Li2GeO3-x/C) and accordingly boosted lithium storage. The introduction of the oxygen vacancies in Li2GeO3-x/C can enhance electronic conductivity and evidently decrease activation energy of Li-ion transport, thus resulting in evidently accelerated Li-ion diffusion kinetics during the lithiation/delithiation process. Thus, the Li2GeO3-x/C nanofibers exhibit an exceptionally large discharge capacity of 1460.5 mA h g-1 at 0.1 A g-1, high initial Coulombic efficiency of 81.3%, and excellent rate capability. This facile and efficient strategy could provide a reference for injecting the oxygen vacancies into other metal oxides for high-performance anode materials.

As the use time of concrete structures increases, defects such as concrete cracks, corrosion and exposure of steel bars gradually appear, resulting in additional repair of concrete structures to increase their durability and life. In this article, the effects of nano-modified polymer cement-based materials as repair material on the bending behavior of repaired concrete beams were studied. Based on the moment, deflection, strain, surface quality and cracking development monitor of repaired concrete beams, the bending behavior of repaired beams with polymer, nano-modified polymer and fibers was compared and the failure mechanism of the beams was analyzed. The results showed that the nano-modified polymer cement-based materials are helpful in improving the performance of repaired beams, manifested by the increase in the ultimate bending moment and the significant improvement in the quality of the interface between repair and matrix concrete. Compared with polymer cement-based materials, nano-modified polymer cement-based materials result in a 27% increase in ultimate bending moment of the repaired beam and a 58% increase in cracking moment, while reducing the total number of cracks by 23% and the average width of cracks by 17% in the repaired beam. This article demonstrated the availability of nanomaterials for improving the loading behavior of structural components with polymer-modified cement-based materials.

Although metal silicates are considered as the promising electrode materials for lithium-ion batteries, metal silicate-based materials suffer from inadequate cycling performance and dimensional unreliability evoked by the large volume changes during cycling, which hinders their practical applications. In principle, the poor electrochemical kinetics during the redox reactions of metal silicates is originated from the instinct structure. Hence, the precise and delicate ability to construct hetero-layers to tailor intercalation reaction remains elusive. Herein, a facile strategy of designing and constructing heterostructure in a cobalt-copper silicates nano-architecture (CNT@CoCuSiOx) with synergistic interaction between cobalt silicate (Co2SiO4) with copper silicate (CuSiO3) on the surface of carbon nanotubes (CNTs). Moreover, Co2SiO4/CuSiO3 heterojunction with unbalanced charge distributions that rooted from in-situ generation on CNTs by a facile one-step hydrothermal process, can efficiently tailor the electrochemical activities of Cu3+/Cu2+ and Co3+/Co2+ redox reactions by elevating transfer of electrons and delivering the heterointerface effect. The tough and conductive nanostructure of CNTs basement facilitate the ion diffusion and improve the rate capability. The heterostructure-incorporated CNT@CoCuSiOx-(2/1) exhibits not only outstanding electrochemical capacity (545 mAh g−1 at 0.1 A g−1), superior ion/electron transmission efficiency but also robust cycling performance (516 mAh g−1 after 900 cycles at 0.5 A g−1 and an excellent capacity retention rate of 95%). Beyond energy storage, our delicate methodology in manipulating the electrochemical behavior of metal silicates opens up a critical insight into rational fabrication of next-generation anodes for lithium-ion battery.

Although transition metal silicates are recognized as high potential and attractive materials for next-generation lithium-ion batteries (LIBs) due to their efficient energy storage, earth-abundance...

Filling and nucleation are the mechanisms of modifying cement paste with nanomaterials, as investigated by previous studies, and are difficult to reflect the different effects of nanomaterials, especially on the changes of cement clinker and hydration products in the cement hydration process. In this study, the mechanisms of modifying cement paste with nano-calcium carbonate (NC), nano-graphene oxide (NG), nano-silica (NS), and nano-titanium dioxide (NT) were investigated by determining the mechanical properties of cement paste treated with nanomaterials and analysing the changes in the cement clinker (tricalcium silicate and dicalcium silicate), hydration products (portlandite and ettringite), and microstructure through many micro-test methods. The results indicate that the incorporation of nanomaterials could improve the early strength of cement paste specimens due to more consumption of cement clinker. Meanwhile, different nanomaterials promote the formation of different hydration products at early ages. C–A–S–H gel, flower-like ettringite, and C–S–H seeds are widely distributed in the cement paste with the incorporation of NC, NG, and NS, respectively. NT exhibits insignificant nucleation effect and has inhibitory effect on portlandite precipitation. This study provides key insights into the mechanism of nanomaterials from the perspective of cement hydration, which may promote the further research and application of nanomaterials in the cement and concrete industries.

In this study, the effect of SiO2/Al2O3 (S/A), Na2O/Al2O3 (N/A) and H2O/Na2O (H/N) molar ratios on bending and compressive strength of geopolymer were investigated. The geopolymerization mechanism was also analyzed from microstructure difference by FTIR. The experimental results showed that compressive strength and bending strength of geopolymer has an opposite reaction under different critical molar ratios. The increase of S/A molar ratio and the decrease of N/A and H/N molar ratios have resulted in an increase of the compressive strength. However, it caused a noticeable decrease in bending strength. The microstructure of geopolymer indicated that the degree of polymerization and cohesion of geopolymer have systematical depending on these critical molar ratios, making the mechanical properties of geopolymer susceptible to different types of loads. This paper reveals the relationship between the microstructure of geopolymer and different mechanical properties and helps to selectively prepare corresponding geopolymer for different loading patterns.

Lipase-loaded hollow colloidosomes are prepared for Pickering interfacial biocatalysis (PIB). Unlike in other systems, colloidosomes are self-assembled by lipases and silica nanoparticles, achieving a high enzyme-loading process without chemical crosslinking, and can stabilize Pickering emulsion due to the amphiphilic lipase confined in the porous shell. Remarkably, the enzyme encapsulation rate is 95.2%, which is better than other enzyme-loaded carriers in PIB reported so far. This system maintains 80.4% of the initial enzyme activity after 10 cycles, which provides a powerful and green platform for interfacial biocatalysis.

Metal-organic frameworks (MOFs) have been extensively used in the fabrication of new advanced electrode materials for lithium ion batteries (LIBs). However, low-productivity and high-cost are some of the main challenges of MOF-derived electrodes. Herein, we report a simple solvothermal procedure to fabricate novel Fe4-based metal-organic clusters (Fe-MOCs) with their subsequent conversion to an S,N dual-doped carbon framework incorporating iron oxides under a N2 atmosphere (namely Fe2O3@Fe3O4-SNC). The as-prepared Fe2O3@Fe3O4-SNC composite, owing to the strong interaction between the dual-doped carbon and iron oxides, shows excellent lithium storage performance as an anode with high pseudocapacitance. Furthermore, DFT computational analyses confirm that the hybrid shows excellent adsorption ability with a low energy barrier due to strong electronic interactions between the iron oxides and S,N-doped carbon matrix. In addition, Fe2O3@Fe3O4-SNC-based LIB shows high energy and power densities at the full-cell level, confirming this synthesis strategy to be a promising approach towards MOC-derived electrode materials for their application in LIBs and beyond-lithium batteries.

Nano-materials modified cement-based materials have attracted wide attention due to their advantages of improving strength and durability. In this paper, the effect of nano-SiO2 (NS) with particle sizes of 15 and 50 nm on the mechanical properties and microstructure of cement paste was studied. The results showed that 50 nm NS provided a greater compressive strength than that of 15 nm NS, while 15 nm NS afforded a denser microstructure than that of 50 nm NS. A fluctuation in the compressive strength was revealed using a physicochemical reaction equation, and the microstructure was interpreted by a pore structure analysis. In addition, the orientation index of calcium hydroxide (CH) with 15 nm NS could be reduced significantly in the early stages (the early stages refer to the first three days from the maintaining of specimens) compared with when the 50 nm NS was used. The experimental results also showed that NS helped increase the mechanical strength of cement paste, advance the endothermic peak of CH, and refine the size of the CH crystals. The microstructural changes at different stages of cement paste with different particle sizes of NS were investigated by X-ray diffraction, scanning electron microscopy, mercury intrusion porosimetry and differential thermal analysis. This study is expected to promote the research and application of nano-materials in the cement industry by clarifying the performance of NS with different particle sizes.

Interface electronic and structural reorganization in metal-based/support catalysts will unlock great potential for realizing their high efficiency electrocatalytic activities. Herein, we employ Mn...

The stereospecific design of the interface effects can optimize the electron/Li-ion migration kinetics for energy-storage materials. In this study, an electric field was introduced to silicon-based materials (C-SiOx@Si/rGO) through the rational construction of multi-heterostructures. This was achieved by manipulating the physicochemical properties at the atomic level of advanced Li-ion batteries (LIBs). The experimental and density functional theory calculations showed that the unbalanced charge distribution generated a large potential difference, which in turn induced a large-scale electric-field response with a boosted interfacial charge transfer in the composite. The as-prepared C-SiOx@Si/rGO anode showed advanced rate capability (i.e., 1579.0 and 906.5 mAh g-1 at 1000 and 8000 mA g-1, respectively) when the migration paths of the Li-ion/electrons hierarchically optimized the large electric field. Furthermore, the C-SiOx@Si/rGO composite with a high SiOx@Si mass ratio (73.5 wt %) demonstrated a significantly enhanced structural stability with a 40% volume expansion. Additionally, when coupled with the LiNi0.8Co0.1Mn0.1O2 (NCM) cathode, the NCM//C-SiOx@Si/rGO full cell delivers superior Li-ion storage properties with high reversible capacities of 157.6 and 101.4 mAh g-1 at 500 and 4000 mA g-1, respectively. Therefore, the electric-field introduction using optimized electrochemical reaction kinetics can assist in the construction of other high-performance LIB materials.

In geothermal mining, the mechanical properties and micro‐structure of the rock under different temperature or cooling modes are highly relevant to the stability of the artificial reservoir. For reflect the actual working conditions, an experimental study is carried out on high‐temperature granite that has been cooled both naturally and rapidly with water. The following conclusions are reached. (a) The wave velocity, elastic modulus, and uniaxial compressive strength of the test specimen decrease with an increase in its heating temperature under both cooling modes. (b) The characteristics of the stress‐strain curve of granite are different after different temperatures and cooling modes. With natural cooling, the stress‐strain curve features double peaks in the range of 200‐300°C, whereas such phenomenon occurs at temperatures greater than 300°C with water cooling. (c) When the temperature is less than 300°C, no obvious change occurs in the crystal structure of the sample. When the temperature is more than 300°C, the original micro‐cracks gradually expand and eventually develop into larger cracks.

Recycling of red mud (RM) has attracted more attention in recent years due to severe environmental problems caused by landfilling. The effect of composition optimization and Nano-strengthening on the properties of a binder based on RM was studied in this paper. Results showed that modifying ratios of main oxides and adding Nano-SiO2could obviously affect the mechanical properties and microstructure of the binder. Specimens with high SiO2/Al2O3molar ratio (S/A) displayed considerable increase in compressive strength, while decreasing Na2O/Al2O3molar ratio (N/A) improved the workability of the fresh mix. The compressive strength was developed significantly to be 45 MPa at 28 days by adding Nano-SiO2with 0.4 wt.% of RM. Phase transformation and microstructure change at different stages of RM decomposition and binder geopolyerization were investigated by X-ray diffraction (XRD), Fourier transformation infrared (FTIR) and Scanning electron microscopy (SEM). The results of this study may provide a prospective method to use RM more widely in construction applications.

Influence of nano-strengthening immersion on the properties of recycled aggregate (RA) and recycled aggregate concrete (RAC) and the microstructure of interfacial transition zones (ITZs) between mortar and aggregate were studied in this paper. Results showed that nano-strengthening immersion was helpful to reduce the crushing value and total pore area of RA, to significantly improve the mechanical strength of RAC, and to modify the bond strength between RAC and steel rebar and the structural properties of RAC beams. Mercury intrusion porosimetry (MIP), micro-hardness (MH) and scanning electron microscope (SEM) observation were conducted in order to reveal the enhancement mechanism of nano-strengthening immersion. Results showed that the density and mechanical properties in ITZs were obviously improved by nano-strengthening because the coating and penetration of nano-materials was helpful to block the pores and cracks in ITZs, to avoid the directed gathering of CH crystal, and to accelerate the hydration of cement and mineral additions.

The concept of geopolymers has been widely studied since it was proposed. However, the wide range of applications of geopolymers is affected by brittleness and poor crack resistance. In this study, the mechanical properties of geopolymers with single-doped PVA fibres, single-doped carbon nanotubes, and mixed PVA fibers and carbon nanotubes were studied respectively first. It was found that PVA fibres and carbon nanotubes had a positive effect on improving the mechanical properties of geopolymers, especially bending strength and flexural strength. Moreover, the incorporation of PVA fibre could improve the damage morphology of geopolymers. Additionally, the phase analysis, structural group analysis, and strengthening mechanism were studied via scanning electron microscopy, mercury intrusion porosimetry analysis, X-ray diffraction pattern characterisation, Fourier transform infrared spectroscopy analysis, and magic angle spinning nuclear magnetic resonance analysis. It was found that the strengthening effect of PVA fiber to the geopolymer was primarily a physical strengthening effect, whereas the strengthening effect of carbon nanotubes to the geopolymers was both chemical and physical. Finally, based on the previous study, a multi-scale dual-fibre strengthening mechanism was proposed. Micro-nano fibre composites were used to improve microstructure via physical and chemical effects. This is helpful to improve the performance and application of geopolymers. Furthermore, it lays a preliminary theoretical foundation for engineering applications and technical improvement of geopolymers in the future.

The use of recycled mixed aggregates (RMA) in cement-stabilized materials (CSM) is an effective way to dispose of and reuse demolition waste. However, this approach faces various challenges, for example, the drying shrinkage of CSM with 100% RMA is very high, which is unfavorable for use in road engineering. In order to use a simple method to reduce the drying shrinkage of the CSM with 100% RMA and give it reliable strength, the effect of fly ash on the mechanical properties, drying shrinkage, and abrasion resistance of CSM with 100% RMA was investigated in this study, and the mechanism was examined by X-ray Diffraction (XRD), Mercury Intrusion Porosimetry (MIP), and Scanning Electron Microscopy (SEM). The results revealed that the addition of fly ash would decrease the drying shrinkage of CSM with 100% RMA. Moreover, when the amount of fly ash was less than 20%, the later strength increased remarkably despite the slight decrease in the early unconfined compressive strength, indirect tensile strength, compressive and splitting elastic modulus, and abrasion resistance of CSM with 100% RMA. The microstructure analysis results indicated that fly ash increased the decline range of diffraction intensity of C2S and C3S at a later age and also helped to optimize the pore structure. Research results of this article can be used to optimize the mechanical properties of CSM with 100% RMA and guide its application in road base.

The purpose of this study was to propose low gas pressure effects on lifetime of natural gas high-density polyethylene (HDPE) pipes by thermal-oxidative aging. The new method to assess the lifetime of HDPE natural gas pipes is based on gas pressure testing. An approach to monitor oxidative induction time (OIT) has been used to predict lifetime. Natural gas HDPE pipes were used to evaluate the effects of low gas pressures on oxidative induction time. In order to emphasize the pressure effects, relatively low temperatures at 45, 55, 65, and 75 °C were utilized for the exposure. The low-pressure conditions were created using air at levels of 0, 0.1, 0.2, 0.3, and 0.4 MPa. The property of high density polyethylene pipes was effectively monitored using the low pressure OIT test. The results show that the aging reaction rate of high density polyethylene pipes increased exponentially with temperature and gas pressure according to the Arrhenius equation. Analytical models were developed to predict the aging reaction rate and lifetime of natural gas HDPE pipes.

Mixed recycled aggregate (MRA) is a kind of recycled aggregate containing discarded bricks and other impurities that is inferior to ordinary recycled concrete aggregate. To study the effect of MRA in concrete, specimens with 100% MRA under different water–cement ratios (W/C) of 0.50, 0.42, 0.36 and 0.30 were prepared, and the mechanical properties and microstructure were tested. Results show that compared with ordinary concrete, the compressive strength of mixed recycled aggregate concrete (MRAC) with the same W/C was reduced by more than 50% at 28 days, but the axial compression ratio was relatively high, reaching over 0.87. Affected by the high water absorption of MRA, the hydration rate of cement slowed, which was beneficial to the long-term development of the properties of MRAC. An appropriate increase in cement content could strengthen MRA and densify the pore structure of MRAC. The research results of this article prove that MRA has high utilization value and could be used to prepare MRAC with application potential using optimal gradation, which is of positive significance for promoting the consumption of construction waste.

The relationship between percolation mechanism and pore characteristics for recycled permeable bricks with different porosities is investigated in this study based on X-ray computed tomography (X-CT). Permeability coefficients are measured and some characteristics including size, amount, and distribution of the pore are analysed. The results show that the effective porosity and permeability coefficient of the recycled permeable bricks exhibit a linear relationship first and then a quadratic curve relationship, where the critical effective porosity is 12%. Meanwhile, we discovered that nonlinear channels in permeable bricks are larger and fewer compared with linear percolation channels, regardless of whether the percolation stage is linear or nonlinear. Additionally, when the area and number ratios of the linear and nonlinear percolation channels reached 80% and 10%, respectively, the overall percolation state of the permeable bricks changed from linear to nonlinear percolation. This research is helpful to improve the mechanical and percolation properties of recycled concrete bricks and promote the application of porous permeable material. ispartof: Reviews on Advanced Materials Science vol:60 issue:1 pages:207-215 status: published

We found that the high solid solution Al-9 Mg alloy with a bimodal grain structure processed by hard-plate rolling (HPR) exhibited enhanced thermal stability despite annealing at 275 °C for 24 hours. The notable thermal stability originates from the inherent stable deformation microstructure dominated by (101)-oriented coarse grains induced by a high solute Mg content, which further stabilizes the microstructure upon static annealing. Moreover, recovery occurs preferentially in coarse grains, leading to slow coarsening of the ultrafine grains. This paper provides a new way to improve thermal stability of severely deformed Al-Mg alloys by tailoring grain orientations.

A trade-off between minimized premature leakage and rapid cargo release on demand is an intractable obstacle faced by smart delivery systems that restrains them from lab to market. To address this dilemma, dynamic hybrid colloidosomes relying on strong yet reversible electrostatic interactions are developed, simply through one-pot cooperative self-assembly of silica nanoparticles and fluorescent carbon dots at the interface of emulsion droplets. Specifically, pH-driven charge reversal of zwitterionic carbon dots leads to immediate electrostatic conversion between the two building blocks from attraction to repulsion. This makes robust locking and instantaneous breakdown of the colloidosomes subtly balanced, thus enabling low off-state leakage (10.5% over 7 days) while ultrafast on-state release (>90% within 5 min) upon an acidic stimulus. We envision that such biocompatible, traceable, and smart colloidosomes will offer unique opportunities for broad applications as on-demand release is desired.

An ammonia self-managed vaporization propulsion (ASVP) system for micro-nano satellites is presented. Compared with a normal cold gas or liquefied gas propulsion system, a multiplex parallel sieve type vaporizer and related vaporization control methods are put forward to achieve self-managed vaporization of liquefied propellant. The problems of high vaporization latent heat and incomplete vaporization of liquefied ammonia are solved, so that the ASVP system takes great advantage of high theoretical specific impulse and high propellant storage density. Furthermore, the ASVP operation procedure and its physical chemistry theories and mathematical models are thoroughly analyzed. An optimal strategy of thrust control is proposed with consideration of thrust performance and energy efficiency. The ground tests indicate that the ASVP system weighs 1.8 kg (with 0.34-kg liquefied ammonia propellant) and reaches a specific impulse of more than 100 s, while the power consumption is less than 10 W. The ASVP system meets multiple requirements including high specific impulse, low power consumption, easy fabrication, and uniform adjustable thrust output, and thus is suitable for micro-nano satellites.

Neutronics analysis was conducted for a proposed megawatt-class gas cooled space nuclear reactor design. The reactor design has a high operating temperature of up to 1500 K. Annular UO2 fue...

Effect of nano-SiO2(NS) with the sizes of 15nm and 50nm on the hydration heat of cement mortar was measured and its behavior in the hydration kinetics of NS was analyzed based on the Krstulovic-Dabic model. Results showed that NS could improve the value and shorten the occurrence time of hydration exothermic peak. Moreover, NS was helpful to increase the hydration degree and hydration rate in nucleation and crystal growth (NG) stage, while it may shorten the duration time of phase boundary reaction (I) stage and decrease the hydration rate in diffusion reaction (D) stage. Compare to 50nm NS, 15nm NS accelerated hydration rate in early period more effectively, promoted hydration into D stage earlier and inhibited diffusion reaction in late period more obviously. A hydration model was proposed to interpret the difference in hydration process of cement with and without NS.

A megawatt-class, gas-cooled fast reactor was designed to provide 2.2MWth power for space application. The reactor concept adopts 90% enriched annular UO2 rods as the fuel and He-Xe mixture as the coolant. The thermal power is converted into electric power through Brayton turbines. The neutron flux distributions of four selected reactor configurations with different control rod arrangement are calculated using Monte Carlo code. In addition, calculations with different combinations of inserted control rods are conducted to investigate their effects on the power profile. Results show that control rods arranged in the central region help reduce the neutron flux peak and the radial flux peaking factor. The outer control rods, however, show limited effects on the central power profile. Instead, they only affect the region of the control rod neighborhood. Besides, since the outer control rods will increase the radial peaking factor, they are better to be used as safety rods for emergency. Based on the calculation and analysis, three control strategy candidates are proposed considering power profile flattening and control flexibility.

The pore structure and the connectivity of the pore space within transversely isotropic calcareous sediments play important roles in the hydraulic properties of underground engineering. Therefore, it is essential to clarify the pore structure evolution of rocks subjected to triaxial pressure and high temperature. This study used self-designed triaxial permeability testing equipment and a micro-CT experimental system to study the evolutions of the permeability and pore structure. The results show that when the pore pressure is less than 2.5 MPa, the permeability decreases gradually with increasing pore pressure, and when the pore pressure is greater than 2.5 MPa, the permeability increases gradually with increasing pore pressure. The dramatic decrease is due to the Klinkenberg effect. The relationship between temperature and permeability is complicated. A decrease in the permeability was observed in two temperature stages. The decrease in the lower temperature range occurs because the expansion deformation is restricted by the high axial and confining pressures. The second decrease occurs because the rate of fracture closing is higher than the rate of crack opening. As the temperature increases, the size and quantity of fractures clearly change. The variations in the MCT (microcomputed tomography) images are consistent with the permeability evolution, indicating that the permeability is closely correlated with the crack distribution and pore structure.

Two-phase flow instabilities in parallel boiling channels under natural circulation condition were experimentally studied at low pressure (0.2–0.6 MPa). The parallel boiling channels composed of two different form channels, namely a 3 × 3 rod bundle channel and a tube channel, were used as the testing section. In the present experiment, the flow oscillation behaviors can be classified into three typical modes based on their frequency spectrum characteristics: (1) small amplitude out-of-phase flow instability induced by the type-1 density wave oscillations in parallel boiling channels, (2) large amplitude out-of-phase flow instability with reversal flow induced by the occurrence of geysering in tube channel and (3) a kind of compound flow instability superposed by geysering and natural circulation instability. The influence of thermal hydraulic parameters on the evolution process of above three flow instabilities were analyzed. The marginal stability boundaries presented by the subcooling number (Nsub) and phase change number (Npch) at different system pressures are obtained and all unstable flow occurs in the negative region of the outlet equilibrium quality in the present experiment. Besides, the effects of asymmetric heating between two parallel channels on NC flow instability were also studied. The asymmetric heating can change the NC flow distribution in parallel boiling channels and reduce the system stability. The occurrence of out-phase oscillations in parallel channels can be suppressed with the increasing of heating power asymmetry.

To calculate the thermal characteristics of the rectangle liquid droplet radiator more accurately, a novel method, which estimated the characteristics of each droplet, was introduced. The shape factors of two and three droplets were theoretically deduced and verified by the Monte Carlo method. It was found that the shape factor of two droplets depends only on the ratio of the distance between the two droplets to the radii of droplets. According to this characteristic, the shape factor of two droplets was calculated and fitted to be a formula, which makes it convenient to calculate the shape factor in the following analysis. Based on the superposition rule of the shape factor, a shape factor matrix was introduced to calculate the effect of surrounding droplets when analyzing the heat transfer of the droplet sheet. The temperature distribution of the droplet sheet was calculated based on the shape factor matrix, which obtained using the combination of theoretical method and Monte Carlo method. The results showed that the temperature difference among the droplets on a same width-thickness plane was negligible. Therefore, a simplified model was developed based on this characteristic. The discrepancies of the temperature distributions obtained by the original model and the simplified model were found to be less than 0.35%, which demonstrates the feasibility of the simplified model to analyze the thermal characteristics of the rectangle droplet radiator. By further analyzing the heat transfer characteristics of the droplet sheet, proposals were made for design of the rectangle liquid droplet radiators.

Inspired by steaming bread, a novel three dimensional N and S co-doped reduced graphene oxide (3D NS-rGO) foam is fabricated via a gas foaming method similar to steaming bread procedure, in which (NH4)2S2O3 is selected as the foaming agent as well as N and S source. Such cross-linked 3D structure not only has the high specific surface area also enable more transport channels for electrons/ions transport. Furthermore, introducing of N and S-containing functional groups creates lattice defects in graphene, which provides more active sites where the Faradaic pseudocapacitance occurs. Consequently, the electrochemical test of 3D NS-rGO sample in a three-electrode system demonstrates a high specific capacity of 306.3 F g−1 at 1 A g−1, two times higher than that of rGO prepared at the same temperature. Moreover, 3D NS-rGO sample reveals the superb cycling stability with less than 2% capacitance loss after 10,000 cycles and it exhibits potential application for high performance supercapacitors.

Developing economical and highly efficient noble metal-free electrocatalysts for overall water splitting is an essential precondition for renewable energy conversion. Herein, we highlight atomic heterointerface engineering in constructing highly efficient cobalt phosphide (CoP)/Co9S8 electrocatalysts for full water splitting. A CoP/Co9S8 hybrid was prepared for the first time by partial homogeneous transformation of in situ-formed Co9S8, in which the atomic heterointerface was formed between CoP and Co9S8. Systematic experiments and theoretical calculations confirm that the as-formed atomic heterointerface can induce local charge distribution in CoP/Co9S8, which can not only accelerate the charge transfer but also optimize the hydrogen adsorption energy of CoP in favor of the fast transformation of Hads into H2. Meanwhile, the Co9S8 component can also increase the water adsorption capability of CoP/Co9S8. Benefiting from these outstanding advantages, an alkaline electrolyzer based on CoP/Co9S8 as both ele...

Atomic interface engineering can endow electrode materials with fascinating properties by tailoring their physicochemical behaviors, which will unlock great potential for achieving high-performance...

The purpose of this study was to propose a lifetime prediction model of aging natural gas polyethylene (PE) pipeline with various internal pressures by thermal-oxidative aging (TOA) test and oxidative induction time (OIT) test. By using a pressured natural gas PE80 pipe under the condition similar to actual urban natural gas working condition, an improved TOA experimental set-up was built, and had been used for accelerated TOA test of pressured PE pipes at different test temperatures. By using dynamic curve linearization method and based on Arrhenius fit of the data, an empirical lifetime prediction model of thermal oxidative aging law for PE pipes was developed to extrapolate lifetime of PE80 pipes with internal pressures. The results show that under the test internal pressure of 0.1 MPa, 0.2 MPa, 0.3 MPa, and 0.4 MPa, the lifetimes of aging PE gas pipes with internal pressure are 14%, 24.5%, 36.1%, and 41.6% shorter than those without internal pressure.

Sluggish Li-ion diffusion kinetics and low initial coulombic efficiency (CE) are two big issues to be urgently solved for the MoO2 anode. Herein, we achieve significantly improved Li-ion diffusion kinetics and reversibility of Li2O in a MoO2 anode by elaborately constructing oxygen vacancies and atomic-level spatial distribution of a Ni catalyst, therefore evidently boosting its rate behavior and initial CE. The oxygen vacancy and highly distributed metallic Ni modulation is achieved by finely controlling the annealing time. The density functional theory (DFT) calculations reveal that the creation of oxygen vacancies results in unbalanced charge distribution within MoO2, thus inducing a foreign coulomb force to boost the Li-ion transfer. Furthermore, the metallic Ni in Ni/MoO2−δ can perform as an effective catalyst to ensure the fully reversible conversion of the as-formed Li2O, thereby increasing the initial CE. Benefiting from this multiscale coordinated design, Ni/MoO2−δ displays high discharge capacity (1630.9 mA h g−1 at 0.2 A g−1), large initial CE (83.7%), and excellent rate capability, and outperforms most of the previously reported MoO2-based anodes. Such a design concept not only brings MoO2 one big step closer to practical application, but also can be extended to guide the design of other anode materials with high theoretical capacity.

Li4Ti5O12 (LTO)-carbon (C)-reduced graphene oxide (rGO) microspheres are synthesized via in situ supramolecular self-assembly, combined with spray drying and high-temperature calcination. Dopamine can polymerize on the surface of Ti(OH)4 and form polydopamine, through which graphene oxide(GO) connects with Ti(OH)4 uniformly and tightly to form a homogeneous supramolecular sol system. During the high-temperature calcination, polydopamine is carbonized to carbon to connect LTO with rGO, so that the aggregation of rGO is inhibited, and small-sized LTO particles are obtained. The scanning electron microscopy (SEM) image shows that in the as-prepared LTO-C-rGO microspheres, LTO particles with diameters of ∼50 nm remained homogeneous and wrapped in a three-dimensional network built by the rGO nanosheets. Electrochemical measurements show that the LTO-C-rGO anode exhibits a high reversible capacity of 184 mAh g–1 at 1 C and a high capacity retention of 94.5% after 500 cycles at 20 C. The above excellent electroc...

Based on the project background of salt caverns used for oil and gas storage in laminated salt rock, this study examined the combined mode fracture toughness, the fracture pattern, the morphological evolution of fracture surfaces, and the fracture criterion of gypsum interlayers under confining pressure. Series of laboratory tests, including fracture strength tests and scanning electron microscopy tests, were performed at four confining pressures. The results indicate that the failure load of gypsum increased with the increase of confining pressure. By contrast, the failure load of specimens first decreased and then increased with the increase of pre-existing flaw inclination angle. As the confining pressure increased, the residual energy gradually decreased and the brittleness index gradually increased. Although increasing the confining pressure (i.e., 1–7 MPa) shifted the behaviour of a specimen from brittle to ductile, the major failure mechanism still fell within the brittle failure regime. For the case where the confining pressures are 1 MPa and 3 MPa, cleavage fractures characterized by cleavage steps, river lines, and tearing ridges were observed on the surface, indicating that typical brittle failure occurred in the specimens. However, typical ductile failure occurred in the specimens subjected to confining pressures of 5 MPa and 7 MPa. Subsequently, the size of the fracture process zone at varying confining pressures was obtained using a modified maximum tangential stress criterion to optimally fit the experimental results. The results of this study can be used to evaluate the safety of salt caverns in bedded salt formations.

In this study, the effect of nano-SiO2 on the mechanical properties, microstructure, and hydration process of cementitious materials incorporating hydrophobic admixture (CM-HA) was studied ...

A commercially feasible sodium-ion pouch cell with a capacity of 650 mAh is fabricated using the ternary layered Na0.76Ni0.3Fe0.4Mn0.3O2 and the hard carbon as the cathode and anode materials, respectively. 1.0 M NaPF6 in the mixed carbonate solvents is served as the electrolyte. According to the calculation of the frontier molecular orbital energy, adiponitrile (ADN) has a stronger ability of electron donating than the carbonate solvents and thus is easier to be reduced on the surface of the cathode material to form the solid-electrolyte interphase (SEI) film, so ADN is selected as the electrolyte additive to improve the performance of sodium-ion battery for the first time. The transmission electron microscopy (TEM) images show that the addition of ADN enables the formation of more uniform and compact SEI film on the cathode material surface. The X-ray photoelectron spectroscopy (XPS) results indicate that ADN promotes the formation of NaF and result in the formation of NaCN as the effective components of the SEI film. The electrochemical test results demonstrate that ADN effectively improves the electrochemical performance at high -low-temperature and cycling stability of Na0.76Ni0.3Fe0.4Mn0.3O2 as the cathode material of sodium-ion batteries, that is because the adding of ADN in electrolyte result in the formation of more effective SEI film. In particular, the battery using the electrolyte with 3% ADN exhibits the most obvious improvement, which owe to the formation of most compact, stable and effective SEI film after adding 3% ADN into the electrolyte. At the operating temperature of 45 °C, −10 °C, and −20 °C, the discharge capacity increases by 10.5%, 8%, and 13%, respectively. For the cycle life, the capacity retention of the battery without addition of ADN drops rapidly to 75% after 40 cycles, while the capacity retention of the battery with 3% ADN still remains 78% after 220 cycles.

In order to realize the non-excavation continuous detection of metal loss defects of buried steel pipelines without internal testing conditions, a research was conducted about the the external detection technology for buried steel pipelines based on multi-frequency electromagnetic by the theoretical analysis and the ansys finite element simulation. This paper was mainly about the the influence of pipeline metal loss defects on the multi-frequency alternating current passing through the pipeline and the influence of pipeline metal loss defects on the different frequency magnetic fields around the pipeline, which laid the foundation for the development of multi-frequency electromagnetic-based buried steel pipeline metal loss defect detection equipment and pipeline defect identification. The results showed that the pipeline metal loss defects played a great influence on the direction and magnitude of the flowing current. When the metal loss defect existed in pipeline, the magnetic field signals around the pipeline were abnormal. There was a significant difference between the magnetic field changes caused by the inner wall defect and the outer wall defect. Therefore, it was possible to determine whether the pipeline was defective by analyzing the variation law of the magnetic field around the pipeline and to determine whether the defect was located on the inner wall or the outer wall of the pipeline.

An experimental investigation was conducted in a closed natural circulation (NC) loop to study the characteristics of pressure drop oscillations (PDO) under low pressure condition. A 3 × 3 rod bundle channel was used as the test section. The experimental results show that PDO can occur in the closed NC loop when the pressurizer is installed on the upstream of the heating channel. The large amplitude thermal–hydraulic parameters oscillations and reverse flow are the main characteristics for PDO. The oscillation amplitude and reverse flow rate of PDO can be enlarged by increasing the heat flux. Increasing the inlet subcooling degree can help to suppress the PDO occurrence in the closed NC loop. The flow instability boundary is obtain and PDO mainly occurs in the region of the outlet equilibrium quality from −0.008 to 0.012 in present experiment. The interaction between the vapor expansion in the heating channel and the compressibility of pressurizer is the main reason for the occurrence of PDO in the closed NC loop. The effects of compressible volume positions on flow instability was also studied. Moving the pressurizer from the upstream of the heating channel to the downstream can eliminate PDO while density wave oscillations (DWO) can still happen. A tentative explanation for the influence mechanism of compressible volume positions on flow instability in the closed NC loop is reported.

Introducing a bimodal grain-size distribution has been demonstrated an efficient strategy for fabricating high-strength and ductile metallic materials, where fine grains provide strength, while coarse grains enable strain hardening and hence decent ductility. Over the last decades, research activities in this area have grown enormously, including interesting results on fcc Cu, Ni and Al-Mg alloys as well as steel and Fe alloys via various thermo-mechanical processing approaches. However, investigations on bimodal Mg and other hcp metals are relatively few. A brief overview of the available approaches based on thermo-mechanical processing technology in producing bimodal microstructure for various metallic materials is given, along with a summary of unusual mechanical properties achievable by bimodality, where focus is placed on the microstructure-mechanical properties and relevant mechanisms. In addition, key factors that influencing bimodal strategies, such as compositions of starting materials and processing parameters, together with the challenges this research area facing, are identified and discussed briefly.