On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and ɛ phases) have been successfully ...reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K) and pressure range (0-100 GPa), compare favorably well with experimental or theoretical ones when the uncertainties are considered.
The high conductivity anomalies observed in the oceanic asthenosphere have shown anisotropic signature parallel to the plate motion. Anisotropic alignment of partial melt has been considered to one ...of probable explanations for the observed anisotropic conductivity structure, but the effect of temperature on the distribution of melt, the composition of melt, and the magnitude of electrical anisotropy for partial molten peridotite is unknown under shear deformation. In this study, the electrical conductivity of partially molten peridotite (KLB-1) under shear deformation was measured at 1 GPa in a DIA type apparatus with a uniaxial deformation facility to provide new constraints on the anisotropic signature in the oceanic asthenosphere. The conductivity measurements were performed simultaneously in two directions of three principal axes: parallel and normal to the shear direction on the shear plane, and perpendicular to the shear plane, by using impedance spectroscopy at temperature ranges of 1483-1548 K. Our results indicate that the total melt fraction, the absolute conductivity values, and the magnitude of electrical anisotropy of partially molten peridotite increase with increasing temperature. Although the Na2O content varies widely at constant temperature in the recovered melt, very small changes of shear-parallel conductivities (σx) before and after shear deformation suggest that the electrical conductivity of partially molten peridotite is mainly controlled by temperature, rather than alkali content in partial melt. Microstructural observations of the recovered samples reveal that the development of conductivity anisotropy was caused by the realignment of melt pockets parallel to the shear direction, which forms two melt-rich regions. Furthermore, we estimate how much melt fraction is partitioned into melt-rich regions by calculating the area ratio of two melt-rich regions to the whole area. Our calculations show that once melt segregation occurs, more than 50% of the total melt fraction will partition into the melt-rich regions, and this proportion will continue to increase with the increase of temperature. This finding suggests that development of electrical anisotropy in partially molten peridotite under shear deformation will increase with increasing temperature, which may provide new constraints on interpretation of high conductivity anomalies observed in the oceanic asthenosphere.
•We report in-situ 3D EC measurements on partial molten peridotite under shear.•Electrical anisotropy of partially molten peridotite increase with temperature.•Melt fraction in the upper mantle may be underestimated in previous studies.
Solution-processed organic light-emitting diodes (s-OLEDs) have received a great deal of interest owing to the huge market application potentials as large-size, flexible, high-quality self-luminous ...display panels and lighting sources. It is anticipated that those electronic products can be easily manufactured by modern wet-processing techniques, e.g. ink-jet printing and ‘roll-to-roll’ coating methods. However, issues related to power efficiency (PE) are highly hampering the progress of s-OLEDs towards real applications. Herein, we will demonstrate current development of s-OLEDs targeting for high PE with emphasis on introducing (i) theoretical and practical significance in simultaneously achieving close-to-unity (∼100 %) exciton emission and low driving voltage realized by advanced interface modification, bipolar-transporting-type host, all-exciton-harvesting emissive material and customized device architectures to integrate their functions, (ii) novel low-driving-voltage techniques for phosphorescent and thermally activated delayed fluorescence (TADF) s-OLEDs, i.e. barrier-free exciplex host or bipolar co-host scaffold, and charge-trapping- or charge-scattering-free emissive layer (EML) structures by matching the frontier molecular orbitals (FMOs) between host and dopant emitters, (iii) a variety of tactics to effectively alleviate the efficiency roll-off issue at the practically high luminance value, e.g. removing or largely restraining exciton-quenching in the EML and/or interfaces, the utilization of novel emitters with fast radiative decay rate and/or the EML architectures with prompt and efficient Förster energy transfer process.
The thermal diffusivity and thermal conductivity of four natural granitoid samples were simultaneously measured at high pressures (up to 1.5 GPa) and temperatures (up to 988 K) in a multi-anvil ...apparatus using the transient plane-source method. Experimental results show that thermal diffusivity and thermal conductivity decreased with increasing temperature (<600 K) and remain constant or slightly increase at a temperature range from 700 to 988 K. Thermal conductivity decreases 23-46% between room temperature and 988 K, suggesting typical manifestations of phonon conductivity. At higher temperatures, an additional radiative contribution is observed in four natural granitoids. Pressure exerts a weak but clear and positive influence on thermal transport properties. The thermal diffusivity and thermal conductivity of all granitoid samples exhibit a positive linear dependence on quartz content, whereas a negative linear dependence on plagioclase content appears. Combining these results with the measured densities, thermal diffusivity, and thermal conductivity, and specific heat capacities of end-member minerals, the thermal diffusivity and thermal conductivity and bulk heat capacities for granitoids predicted from several mixing models are found to be consistent with the present experimental data. Furthermore, by combining the measured thermal properties and surface heat flows, calculated geotherms suggest that the presence of partial melting induced by muscovite or biotite dehydration likely occurs in the upper-middle crust of southern Tibet. This finding provides new insights into the origin of low-velocity and high-conductivity anomaly zones revealed by geophysical observations in this region.
The slow hydrogen oxidation reaction (HOR) kinetics under alkaline conditions remain a critical challenge for the practical application of alkaline exchange membrane fuel cells. Herein, Ru/RuO2 ...in‐plane heterostructures are designed with abundant active Ru–RuO2 interface domains as efficient electrocatalysts for the HOR in alkaline media. The experimental and theoretical results demonstrate that interfacial Ru and RuO2 domains at Ru–RuO2 interfaces are the optimal H and OH adsorption sites, respectively, endowing the well‐defined Ru(100)/RuO2(200) interface as the preferential region for fast alkaline hydrogen electrocatalysis. More importantly, the metallic Ru domains become electron deficient due to the strong interaction with RuO2 domains and show substantially improved inoxidizability, which is vital to maintain durable HOR electrocatalytic activity. The optimal Ru/RuO2 heterostructured electrocatalyst exhibits impressive alkaline HOR activity with an exchange current density of 8.86 mA cm−2 and decent durability. The exceptional electrocatalytic performance of Ru/RuO2 in‐plane heterostructure can be attributed to the robust and multifunctional Ru–RuO2 interfaces endowed by the unique metal–metal oxide domains.
A Ru/RuO2 in‐plane heterostructure is designed as an efficient electrocatalyst toward the alkaline hydrogen oxidation reaction (HOR). The interfacial Ru and RuO2 domains are the optimal H and OH adsorption sites, respectively. The Ru domains are electron deficient and show substantially improved inoxidizability. The results highlight the significance of establishing robust and multifunctional heterointerfaces toward fast alkaline HOR and beyond.
The recent development of Cu-based electrocatalysts for electrochemical reduction of carbon dioxide（CO2） has attracted much attention due to their unique activity and selectivity compared to other ...metal catalysts. Particularly, Cu is the unique electrocatalyst for CO2 electrochemical reduction with high selectivity to generate a variety of hydrocarbons. In this review, we mainly summarize the recent advances on the rational design of Cu nanostructures, the composition regulation of Cu-based alloys, and the exploitation of advanced supports for improving the catalytic activity and selectivity toward electrochemical reduction of CO2. The special focus is to demonstrate how to enhance the activity and selectivity of Cubased electrocatalyst for CO2 reduction. The perspectives and challenges for the development of Cu-based electrocatalysts are also addressed. We hope this review can provide timely and valuable insights into the design of advanced electrocatalytic materials for CO2 electrochemical reduction.
•Fe-Mg interdiffusion in wadsleyite was investigated as a function of T and water content at 16 GPa.•The presence of water resulted in significantly enhanced interdiffusivity of Fe-Mg in ...wadsleyite.•0.1–0.5 wt.% H2O can account for the high conductivity anomalies in the upper part of the MTZ.
Fe–Mg interdiffusion rates in polycrystalline wadsleyite aggregates have been determined as a function of water content (up to ∼0.345 wt.% H2O) at 16 GPa and 1373–1773 K in a Kawai-type multi-anvil apparatus. Pre-synthesized water-poor and -rich polycrystalline wadsleyite were used as starting materials. Diffusion profiles were obtained across the interface between Fe-free and -bearing diffusion couples, namely, Mg2SiO4 and (Mg0.9Fe0.1)2SiO4 aggregates by electron microprobe. Fe–Mg interdiffusivities by experiments yield DFe−Mg(m2/s)=D0XFenCH2Orexp−(E+αXFe+βCH2O)/RT, where D0 = 1.33−0.23+0.20× 10−11 m2/s, n = 0.19 ± 0.04, r = 0.29 ± 0.12, E = 92 ± 2 kJ/mol, α = −45 ± 12, and β = −134 ± 2. Our results indicate that water significantly enhances the rates of Fe–Mg interdiffusion in wadsleyite (a factor of 2.4 for fixed temperature and Fe concentration) compared to that in ringwoodite. Although under hydrous condition the transition zone shows the maximum Fe–Mg mixing efficiency as revealed by diffusivity-depth profile in the mantle, homogenization of existing chemical heterogeneity is still very limited at geological time scale only through solid-state diffusion. Combined with the Nernst–Einstein relation, the results suggest that the contribution of water to the electrical conductivity of wadsleyite or ringwoodite may be overestimated from Fe–Mg interdiffusion data at high water content. Further calculation demonstrates that ∼0.1–0.5 wt.% H2O is sufficient to account for the high conductivity values in the upper part (410–520 km) of the mantle transition zone as observed by electromagnetic induction studies.
The electrical conductivity of (Mg
1−
x
, Fe
x
)SiO
3
orthopyroxene with various iron contents
X
Fe
= Fe/(Fe + Mg) = 0, 0.1, 0.3, 0.5, 0.7 and 1.0 was measured in a Kawai-type multianvil apparatus ...by impedance spectroscopy over a wide range of pressure (
P
) and temperature (
T
) covering the stability field of orthopyroxene. Impedance spectroscopy measurements indicated that the electrical conductivity of orthopyroxene systematically increased with increasing total iron content. The conductivity slightly decreased with increasing pressure at a constant temperature. For samples with lower Fe content, two conduction mechanisms were identified from the Arrhenius behavior. A change in the activation enthalpy indicated that the dominant conduction mechanism changed from small polaron to ionic conduction with increasing temperature. At temperature below 1373 K, relatively low activation enthalpies and small positive activation volumes suggest that the dominant mechanism of charge transport is Fe
2+
‒Fe
3+
hopping (small polaron). At higher temperatures above 1473 K, ionic conduction (via Mg vacancy mobility) dominates, with higher activation enthalpy exceeding 2 eV and larger positive activation volume. All electrical conductivity data fit the formula for electrical conductivity
σ
=
σ
0
i
exp
-
Δ
E
0
i
+
P
Δ
V
0
i
k
B
T
+
σ
0
p
X
Fe
exp
-
Δ
E
0
p
-
α
X
Fe
1
/
3
+
P
Δ
V
0
p
-
β
X
Fe
k
B
T
,
where
σ
0
is the pre-exponential term, Δ
E
0
and Δ
V
0
are the activation energy and the activation volume at very low total iron concentration,
k
B
is the Boltzmann constant,
T
is the absolute temperature, and superscripts
i
and
p
denote the ionic and small polaron conductions, respectively. Electrical conductivity of Al-free orthopyroxene with
X
Fe
= 0.1 is distinctly lower than that of olivine with
X
Fe
= 0.1. Above 3 GPa Al content in orthopyroxene becomes smaller in association with garnet formation. Unless iron content in orthopyroxene is considerably high (
X
Fe
> 0.2), orthopyroxene has little influence on the electrical structure of the upper mantle.
The multi‐electron reduction of CO2 to hydrocarbons or alcohols is highly attractive in a sustainable energy economy, and the rational design of electrocatalysts is vital to achieve these reactions ...efficiently. Single‐atom electrocatalysts are promising candidates due to their well‐defined coordination configurations and unique electronic structures, which are critical for delivering high activity and selectivity and may accelerate the explorations of the activity origin at atomic level as well. Although much effort has been devoted to multi‐electron reduction of CO2 on single‐atom electrocatalysts, there are still no reviews focusing on this emerging field and constructive perspectives are also urgent to be addressed. Herein recent advances in how to design efficient single‐atom electrocatalysts for multi‐electron reduction of CO2, with emphasis on strategies in regulating the interactions between active sites and key reaction intermediates, are summarized. Such interactions are crucial in designing active sites for optimizing the multi‐electron reduction steps and maximizing the catalytic performance. Different design strategies including regulation of metal centers, single‐atom alloys, non‐metal single‐atom catalysts, and tandem catalysts, are discussed accordingly. Finally, current challenges and future opportunities for deep electroreduction of CO2 are proposed.
This minireview summarizes the design strategies for single‐atom electrocatalysts toward multi‐electron reduction of CO2, including regulation of metal centers, single‐atom alloys, non‐metal single‐atom catalysts, and tandem catalysts. Current challenges and future opportunities are also proposed in this field. This minireview offers directions for exploring single‐atom catalysts and boosting the understanding and development of CO2 electroreduction.
To meet the demand for canopy morphological parameter measurements in orchards, a mobile scanning system is designed based on the 3D Simultaneous Localization and Mapping (SLAM) algorithm. The system ...uses a lightweight LiDAR-Inertial Measurement Unit (LiDAR-IMU) state estimator and a rotation-constrained optimization algorithm to reconstruct a point cloud map of the orchard. Then, Statistical Outlier Removal (SOR) filtering and European clustering algorithms are used to segment the orchard point cloud from which the ground information has been separated, and the k-nearest neighbour (KNN) search algorithm is used to restore the filtered point cloud. Finally, the height of the fruit trees and the volume of the canopy are obtained by the point cloud statistical method and the 3D alpha-shape algorithm. To verify the algorithm, tracked robots equipped with LIDAR and an IMU are used in a standardized orchard. Experiments show that the system in this paper can reconstruct the orchard point cloud environment with high accuracy and can obtain the point cloud information of all fruit trees in the orchard environment. The accuracy of point cloud-based segmentation of fruit trees in the orchard is 95.4%. The R
and Root Mean Square Error (RMSE) values of crown height are 0.93682 and 0.04337, respectively, and the corresponding values of canopy volume are 0.8406 and 1.5738, respectively. In summary, this system achieves a good evaluation result of orchard crown information and has important application value in the intelligent measurement of fruit trees.
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