Grain-Boundary-Rich Triphasic Artificial Hybrid Interphase Toward Practical Magnesium Metal Anodes

Magnesium metal anodes have attracted widespread attention for their high volumetric capacity and natural abundance, but are precluded from practical applications by poor rate capability and limited lifespan due to sluggish ion-transfer kinetics and uneven deposition behavior. Herein, for the first time a grain-boundary-rich triphasic artificial hybrid interphase, consisting of Sb metal, Mg₃Sb₂ alloy, and MgCl₂, is designed on Mg anode surface by a facile solution treatment method, enabling high-rate and long-cycle Mg plating/stripping behavior. The triphasic artificial hybrid interphase affords high magnesiophilicity and ionic conductivity to reduce the energy barriers for Mg²⁺ desolvation and deposition. Meanwhile, the abundant grain boundaries redistribute Mg²⁺ flux at the electrode-electrolyte interface and guide uniform Mg deposition. Accordingly, the as-designed Mg metal anode achieves ultralong cycling life of 350 h at a high current density of 5 mA cm⁻² and a large areal capacity of 5 mAh cm⁻², outperforming previously reported Mg metal anodes with artificial interphases. Full cells with Mo₆ cathode also show extraordinary stability over a long lifespan of 8000 cycles at a high rate of 5 C. The rational artificial interphase design and the understanding of composition-structure-function relationships shed deep insights into the development of fast-charging and long-cycling Mg metal batteries.     

Computations of model narrow nanotubes closed by fragments of smaller fullerenes and quasi-fullerenes

New type of carbon nanotubes—narrow nanotubes—has recently been observed with diameters of 4–5 Å. It has been postulated that the narrow nanotubes are closed by fullerene fragments of C₂₀ and C₃₆. This paper presents computational results on related model nanotubes with stoichiometries such as C₈₀, C₈₄, C₉₆, C₁₀₈, or C₁₂₀. The computations were carried out at the PM3, AM1, SAM1, HF/3-21G, HF/4-31G, and B3LYP/6-31G^* levels. Two C₃₆ fullerenes were considered, D_6h and D_2d. At the PM3 level and with the C₈₄ nanotube stoichiometry, the D_2d cage closure gave a lower energy (by 185 kcal/mol and a diameter of 5.42 Å). There is another possible candidate, a C₃₂ cage with D_4d symmetry (two four-membered rings). At the PM3 level and with the C₉₆ nanotube stoichiometry, the D_4d closure (with a diameter of 5.43 Å) had energy lower by 210 kcal/mol than that of the D_6h nanotube closure. On the other hand, four-membered rings should not play a significant role for narrow nanotubes with a diameter of 4 Å, where the dodecahedron-related closure should be exclusive. Still narrower nanotubes are briefly discussed.     

Effect of the phase volume ratio on the potential of a liquid-membrane ion-selective electrode

Two-phase liquid system IA(w)|IX(o) comprising the interface between the aqueous solution (w) of uni-univalent electrolyte IA and an organic solvent solution (o) of a uni-univalent electrolyte IX with the common cation I(+) is considered as a simple model of a liquid-membrane ion-selective electrode (ISE). Taking into account the electroneutrality and mass balance conditions, the equilibrium Galvani potential difference (pd) between the aqueous and organic phases, phi = phi(w) - phi(o), is calculated numerically as a function of the ratio of the initial electrolyte concentrations, x = / = 10(-)(4)-10(4), for the selected values of the phase volume ratio r = V(o)/V(w) = 10(-)(3), 1, and 10(3), and the standard ion transfer potentials of the present ions ranging from -0.5 to 0.5 V. Numeric results corroborate the symbolic expressions derived for the cases when X(-) and A(-) are extremely lipophilic and hydrophilic ions, respectively, or when the concentration ratio x is extremely large or small. In contrast to the extraction system, where both electrolytes are initially present in the aqueous phase, the effect of the phase volume ratio on the equilibrium pd in the ISE model is rather weak, unless the counterions X(-) and A(-) differ little in their lipophilicity from the target ion I(+). It is shown that both the ISE and extraction model exhibit the Nernstian behavior only in a limited range of the concentration ratio x depending on the value of the standard ion transfer potentials of the counterions. When this ratio is extremely large or small, equilibrium pd approaches the limiting value given by the distribution potential of the electrolyte IA or IX, respectively. Similar conclusions can be drawn for the two-phase liquid system AI(w)|XI(o) with the common anion I(-).     

Weathering and erosion fluxes of arsenic in watershed mass budgets

Arsenic in natural waters and in soils represents a serious health hazard. Natural sources of this element in soil are the subject of this communication. Weathering mass balance of As and rates of weathering in soils are evaluated from monitored inputs and outputs in two small watersheds. These watersheds are located within the Celina-Mokrsko gold district, Czech Republic. Annual chemical weathering fluxes of As are calculated from the monthly weighted means of stream water and groundwater. The fluxes are corrected for atmospheric precipitation, agrochemical inputs, and biological uptake. Mechanical and chemical weathering rates of the arsenopyrite-bearing rocks in the watersheds were estimated from mass balance data on sodium and silica. The input of As due to total weathering of bedrock was estimated to be 1369 g ha(-1)yr(-1) in the Mokrsko watershed (MW) and 81 g ha(-1)yr(-1) in the Celina watershed (CW). These results indicate that the annual weathering rate of As in the watersheds represents more than 95% of the total As input to the soil. Accumulation rate of As in the soil was estimated at 311 g ha(-1)yr(-1) in MW and 69 g ha(-1)yr(-1) in CW. The mass balance method for calculation of weathering rate of As was used, and the results suggest that weathering could be the most important process in the As biogeochemistry of the areas with elevated As content in the bedrock. Simple model of weathering and erosion can be used successfully in estimating their role in As pollution on the scale of small watershed. The method is also useful for indicating the mass balance of As in soils that is controlled by both the natural and anthropogenic inputs and outputs of As.     

Optical properties of SnO2:F films deposited by atmospheric pressure CVD

Atmospheric pressure chemical vapor deposition (APCVD) system, designed for the deposition of F-doped SnO₂ thin films, is compatible with industrial requirements such as high process speed, scaling to wide substrate widths and low costs. Precise method for measuring the optical absorptance in the spectral range 300–1700 nm combines transmittance, reflectance and photothermal deflection (PDS) spectra measured on the same spot of the sample immersed in the transparent liquid with a relatively high index of refraction. The effects of the film thickness, doping gas addition and the susceptor temperature on the optical absorptance and electrical resistivity of the TCO films are assessed. We show that the doping gas concentration and the susceptor temperature influence both the incorporation ratio of dopants into SnO₂ film as well as the defect concentration. The SnO₂ films growth at optimum APCVD conditions have thickness 0.7 µm, average surface roughness about 40 nm, sheet electrical resistance 10 Ω/sq and the optical absorption 1% at 500 nm and about 5% at 1000 nm.     

Non-hydrolytic sol–gel route to a family of hybrid mesoporous aluminosilicate ethanol dehydration catalysts

Journal of Materials Science - Hybrid materials are intensely studied for potential applications in heterogeneous catalysis. Organic groups at the catalyst surface can modify not only its...     

Z50LS 特技飞行机

正捷克斯洛伐克的ZLIN Z-50是世界上第一架投入量产的特技飞行机第一架原型机于1975年完成其首次飞行。在接下来的19年里,该系列机型在Moravan Otrokovice厂生产出了80架各种改型。该机型的优异质量从飞行员多年来获得的诸多国际奖项便可见一斑,其中两位还是享誉国际的捷克斯洛伐克特技飞行锦标赛世界冠     

Crack resistance curve in glass matrix composite reinforced by long Nicalon<Superscript>®</Superscript> fibres

Theoretical micromechanical analysis of bridged crack development at chevron-notch tip of three-point bend specimens has been applied to determine the crack resistance curve for a composite made of a glass matrix reinforced by continuous Nicalon^® fibres. Fracture toughness (K _IC) values were determined using the chevron-notch technique at room temperature. The theoretical predictions were based on micromechanical analysis exploiting weight functions. Detailed FEM analysis using the ANSYS package was applied to determine numerically the weight functions for orthotropic materials. Appropriate bridging models for the theoretical prediction of the R-curve behaviour typical of the investigated composite were applied together with the weight functions. Experimental observations confirmed the theoretical calculations.     

On the control of distributed parameter systems using a multidimensional systems setting

The unique characteristic of a repetitive process is a series of sweeps, termed passes, through a set of dynamics defined over a finite duration with resetting before the start of the each new one. On each pass an output, termed the pass profile is produced which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. This leads to the possibility that the output, i.e. the sequence of pass profiles, will contain oscillations which increase in amplitude in the pass-to-pass direction. Such behavior cannot be controlled by standard linear systems approach and instead they must be treated as a multidimensional system, i.e. information propagation in more than one independent direction. Physical examples of such processes include long-wall coal cutting and metal rolling. In this paper, stability analysis and control systems design algorithms are developed for a model where a plane, or rectangle, of information is propagated in the pass-to-pass direction. The possible use of these in the control of distributed parameter systems is then described using a fourth-order wavefront equation.