Na-ion batteries have been considered promising candidates for stationary energy storage. However, their wide application is hindered by issues such as high cost and insufficient electrochemical ...performance, particularly for cathode materials. Here, we report a solvent-free mechanochemical protocol for the in-situ fabrication of sodium vanadium fluorophosphates. Benefiting from the nano-crystallization features and extra Na-storage sites achieved in the synthesis process, the as-prepared carbon-coated Na
(VOPO
)
F nanocomposite exhibits capacity of 142 mAh g
at 0.1C, higher than its theoretical capacity (130 mAh g
). Moreover, a scaled synthesis with 2 kg of product was conducted and 26650-prototype cells were demonstrated to proof the electrochemical performance. We expect our findings to mark an important step in the industrial application of sodium vanadium fluorophosphates for Na-ion batteries.
Ceramic aerogels are attractive for thermal insulation but plagued by poor mechanical stability and degradation under thermal shock. In this study, we designed and synthesized hyperbolic ...architectured ceramic aerogels with nanolayered double-pane walls with a negative Poisson's ratio (-0.25) and a negative linear thermal expansion coefficient (-1.8 × 10
per °C). Our aerogels display robust mechanical and thermal stability and feature ultralow densities down to ~0.1 milligram per cubic centimeter, superelasticity up to 95%, and near-zero strength loss after sharp thermal shocks (275°C per second) or intense thermal stress at 1400°C, as well as ultralow thermal conductivity in vacuum ~2.4 milliwatts per meter-kelvin (mW/m·K) and in air (~20 mW/m·K). This robust material system is ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft.
Abstract
The rapid response of stomatal conductance (gs) to fluctuating irradiance is of great importance to maximize carbon assimilation while minimizing water loss. Smaller stomata have been proven ...to have a faster response rate than larger ones, but most of these studies have been conducted with forest trees. In the present study, the effects of stomatal anatomy on the kinetics of gs and photosynthesis were investigated in 16 Oryza genotypes. Light-induced stomatal opening includes an initial time lag (λ) followed by an exponential increase. Smaller stomata had a larger maximum stomatal conductance increase rate (Slmax) during the exponential increase phase, but showed a longer time lag and a lower initial stomatal conductance (gs,initial) at low light. Stomatal size was, surprisingly, negatively correlated with the time required to reach 50% of maximum gs and photosynthesis (T50%gs and T50%A), which was shown to be positively correlated with λ and negatively correlated with gs,initial. With a lower gs,initial and a larger λ, small stomata showed a faster decrease of intercellular CO2 concentration (Ci) during the induction process, which may have led to a slower apparent Rubisco activation rate. Therefore, smaller stomata do not always benefit photosynthesis as reported before; the influence of stomatal size on dynamic photosynthesis is also correlated with λ and gs,initial.
Smaller stomata have a faster rate of increase of light-induced stomatal conductance, but have a longer time lag before reaching the exponential increase phase.
Thermal energy storage system in concentrating solar power plants can guarantee sustainable and stable electricity output in case of highly unstable solar irradiation conditions. In this paper, the ...lumped parameter method is used to develop the models of different thermal energy storage systems. In order to improve the reliability as well as the prediction accuracy of developed models, the charging/discharging process is firstly simulated, and then the dynamic characteristics of thermal energy storage systems are fully tested by imposing 15% step disturbance of mass flow. The results show that the charging/discharging characteristics of the three different thermal energy storage systems are almost the same, which have little to do with the storage mediums used in the systems. Besides, for the representative 1MWe solar parabolic trough power plant, a 15% step up disturbance of oil mass flow will result in a small increase (1.8% and 1.3% respectively) on the outlet temperature of oil and molten salt. On the other side, a 15% step down disturbance of oil mass flow will lead a 2.7% and 2.2% decrease on the outlet temperature of oil and molten salt respectively. In order to verify the validity of the proposed models, the simulation results are compared with both the design points and representative experimental data from the 1MWe solar parabolic trough power plant. The results show that the maximum relative error is not more than 1% when comparing with the design points and the maximum relative error is not more than 12% when comparing with the representative experimental data. Conclusions of this paper are good references for system design, control and commissioning of concentrating solar power plants.
•Thermal energy storage can provide sustainable and stable electricity output.•Lumped parameter method is used to build the model of thermal energy storage.•The dynamic characteristics are tested by a 15% step disturbance of mass flow.•A 15% step-up will result in a 1.3% increase in molten salt outlet temperature.•A 15% step down will result in a 2.2% decrease in molten salt outlet temperature.
Water‐in‐salt (WiS) electrolytes provide a new pathway to widen the electrochemical window of aqueous electrolytes. However, their formulation strongly depends on the solubility of the chosen salts, ...imposing a stringent restriction on the number of possible WiS systems. This issue becomes more severe for aqueous Na‐ion batteries (ANIBs) owing to the relatively lower solubility of sodium salts compared to its alkaline cousins (Li, K, and Cs). A new class of the inert‐cation‐assisted WiS (IC‐WiS) electrolytes containing the tetraethylammonium (TEA+) inert cation is reported. The Na IC‐WiS electrolyte at a superhigh concentration of 31 mol kg–1 exhibits a wide electrochemical window of 3.3 V, suppresses transition metal dissolution from the cathode, and ensures singular intercalation of Na into both cathode and anode electrodes during cycling, which is often problematic in mixed alkali cation systems such as K–Na and Li–Na. Owing to these unique advantages of the IC‐WiS electrolyte, the NaTiOPO4 anode and Prussian blue analog Na1.88MnFe(CN)60.97·1.35H2O cathode can be coupled to construct a full ANIB, delivering an average voltage of 1.74 V and a high energy density of 71 Wh kg−1 with a capacity retention of 90% after 200 cycles at 0.25C and of 76% over 800 cycles at 1C.
The Na IC‐WiS electrolyte exhibits many advantages for aqueous Na‐ion batteries, including a wide electrochemical window, low viscosity, favorable solid elecrtolyte interphase (SEI) containing NaF on the surface of anode, and also for mitigating dissolution of the electrodes and the inertness of TEA+ cation intercalation to electrodes.
Three-dimensional (3D) graphene aerogels (GA) show promise for applications in supercapacitors, electrode materials, gas sensors, and oil absorption due to their high porosity, mechanical strength, ...and electrical conductivity. However, the control, actuation, and response properties of graphene aerogels have not been well studied. In this paper, we synthesized 3D graphene aerogels decorated with Fe3O4 nanoparticles (Fe3O4/GA) by self-assembly of graphene with simultaneous decoration by Fe3O4 nanoparticles using a modified hydrothermal reduction process. The aerogels exhibit up to 52% reversible magnetic field-induced strain and strain-dependent electrical resistance that can be used to monitor the degree of compression/stretching of the material. The density of Fe3O4/GA is only about 5.8 mg cm–3, making it an ultralight magnetic elastomer with potential applications in self-sensing soft actuators, microsensors, microswitches, and environmental remediation.
This work reports the fabrication and characterization of three-dimensional (3D) graphene aerogel (GA)–polydimethylsiloxane (PDMS) composites (GAPC) with outstanding mechanical, electrical and ...thermal properties. GAPC was fabricated by impregnating 3D GA frameworks with PDMS via ice-bath-assisted infiltration and vacuum curing processes. Because of the well-interconnected 3D GA frameworks, GAPC exhibits extremely large deformability (compressive strain=80% and tensile strain=90%), high electrical and thermal conductivities (1S/cm and 0.68W/(mK), respectively), a stable piezo-resistance effect, rapid electric Joule heating performance ((dT/dt)max>3°C/s under a heating power of 12W/cm3), and high hydrophobicity (contact angle=135°). Furthermore, GAPC exhibits a negative temperature coefficient of expansion with decreased electrical resistivity over a broad temperature range, indicating a typical semiconducting behavior and a dual two-dimensional/3D hopping conduction mechanism.
The poorly crystalline calcium silicate hydrate (C‐S‐H) is the primary binding phase in portland cement concrete. In this paper, the influence of adding anatase phase nano‐TiO2, nano‐SiO2, graphene ...oxide (GO), and multiwalled carbon nanotubes (CNT) on the crystallization and morphology of C‐S‐H are systematically investigated through tests. C‐S‐H gels were prepared using the double decomposition method, and the nanomaterial additions of nano‐TiO2, nano‐SiO2, GO, and CNT were 2 wt%, 2 wt%, 0.5 wt%, and 0.5 wt%, respectively. X‐ray diffraction (XRD) results show that a more crystalline nanostructure of C‐S‐H is induced by the addition of nano‐TiO2 or GO. This phenomenon is further confirmed by the transmission electron microscopy (TEM) observations. The TEM observations demonstrate that C‐S‐H would grow on the crystal face of TiO2 to form nanocrystalline regions with a lattice fringe spacing of 3.0 Å. When incorporated with GO, it will form a square lattice structure with a lattice constant of 3.1 Å on the surface of GO and later change to the lattice fringe structure with a spacing of 3.1 Å on the region bit away the GO surface. However, when adding nano‐SiO2 or CNT, these nanocrystalline regions are not observed. Further characterization through scanning electron microscopy (SEM) and atomic force microscopy (AFM) has been performed to investigate the effect of nanomaterials on C‐S‐H morphology. Different nanomaterials take a different morphology of C‐S‐H: sheet‐shape structures for pure C‐S‐H, rod‐shape with for C‐S‐H with nano‐TiO2, and granular agglomeration for C‐S‐H with nano‐SiO2. C‐S‐H with GO or CNT forms a structure of C‐S‐H growing on the templates.
This study elucidates the factors impacting China’s apple trade, its efficiency, and opportunities for increased revenue. This study adopts a stochastic frontier gravity model on China’s apple ...exports data, covering the period from 1997 to 2022 across 38 significant trading partners. The finding demonstrates that the economic growth of China and its trading partners substantially boosts apple export volumes, with a positive correlation between GDP growth and export flows. The research also highlights the deterrent effect of geographical distance on exports and reveals a complex negative relationship between the per capita GDP of importing nations and export efficiency, shedding light on the nuanced nature of trade dynamics. Furthermore, the study finds that the appreciation of China’s currency plays a crucial role in enhancing export efficiency by lowering transaction costs. Meanwhile, increased agricultural land in importing countries presents competitive challenges, impacting export performance negatively. Geographical proximity and infrastructural features, such as shared borders and lack of access to seaport, are identified as significant factors in export efficiency. The analysis unveils considerable untapped export potential in various countries, suggesting a strategic avenue for market expansion. To optimize China’s apple export strategy, policymakers are advised to consider currency management, negotiate trade agreements that mitigate distance and per capita GDP effects, and target markets with high untapped potential, thereby facilitating sustainable growth in China’s apple export sector.
Main conclusion
Rice genotypes with larger stomata maintain higher nocturnal stomatal conductance, thus having lower nocturnal leaf temperature via transpirational cooling.
Incomplete night stomatal ...closure has been widely observed, but the mechanisms and functions of nocturnal stomatal conductance (
g
s,n
) are not fully understood. Stomatal anatomy, leaf morphology,
g
s,n
and nocturnal leaf temperature (
T
leaf,n
) were measured in 30
Oryza
genotypes. Nocturnal leaf conductance (
g
n
) showed a significant circadian rhythm; it gradually increased by 58% from 20:30 to 04:30. Contrary to cuticular conductance (
g
cut
),
g
s,n
was highly correlated with
g
n
. Moreover,
g
s,n
accounted for 76% of
g
n
.
T
leaf,n
was significantly lower than the air temperature, and was negatively correlated with both
g
s,n
and nocturnal transpiration rate (
E
n
).
g
s,n
was positively correlated with stomatal size, intervein distance between major veins (IVD
major
), leaf thickness (LT), individual leaf area (LA), and leaf width (LW). It was also found negatively correlated with stomatal density. Reversely,
T
leaf,n
was negatively correlated with stomatal size, IVD
major
, intervein distance between minor veins, LA and LW.
T
leaf,n
presented a positive correlation with stomatal density. This study highlights the importance of stomatal anatomy and leaf morphology on regulating
g
s,n
and
T
leaf,n
. The underlying mechanisms to the determinants of
g
s,n
and the physiological and ecological functions of the
T
leaf,n
regulation on rice growth and production were carefully discussed.
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