Crystal structure,phase transitions,and thermodynamic properties of magnesium metavanadate(MgV_(2)O_(6))

As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.

Phase2接触单元在岩土工程接触分析中的应用

接触分析是工程中岩土体与结构、岩体内部的节理裂隙相互作用时面对的关键问题之一。文章基于Phase2软件接触单元模型,介绍了接触单元的滑移准则,提出了法向刚度和切向刚度这两个参数的估算方法。结果表明:接触单元可以较好地模拟接触面之间的黏接、脱开、相对滑动这三种状态,强度折减安全系数法的计算结果与Goodman-Bray法计算结果基本一致;接触单元对不同材料之间的接触面模拟有较好的效果,同时接触单元也可选择是否考虑接触面内的孔隙水压力。

Optimal parameter space for stabilizing the ferroelectric phase of Hf_(0.5)Zr_(0.5)O_(2) thin films under strain and electric fields

Hafnia-based ferroelectric materials, like Hf_(0.5)Zr_(0.5)O_(2)(HZO), have received tremendous attention owing to their potentials for building ultra-thin ferroelectric devices. The orthorhombic(O)-phase of HZO is ferroelectric but metastable in its bulk form under ambient conditions, which poses a considerable challenge to maintaining the operation performance of HZO-based ferroelectric devices. Here, we theoretically addressed this issue that provides parameter spaces for stabilizing the O-phase of HZO thin-films under various conditions. Three mechanisms were found to be capable of lowering the relative energy of the O-phase, namely, more significant surface-bulk portion of(111) surfaces, compressive c-axis strain,and positive electric fields. Considering these mechanisms, we plotted two ternary phase diagrams for HZO thin-films where the strain was applied along the in-plane uniaxial and biaxial, respectively. These diagrams indicate the O-phase could be stabilized by solely shrinking the film-thickness below 12.26 nm, ascribed to its lower surface energies. All these results shed considerable light on designing more robust and higher-performance ferroelectric devices.

采用PHASE2软件的隧洞一次支护数值模拟与分析

处于V类围岩的隧洞施工时,通常要采取一次支护以保证围岩稳定。采用PHASE2岩土工程弹塑性有限元分析软件,对某引调水工程中处于V类围岩的隧洞围岩位移与塑性区分布进行模拟分析。结果表明:在不采取支护措施情况下,隧洞施工时将发生坍塌破坏,具有极大的安全隐患;在采取拟定措施后,围岩总位移满足规范要求,且未发生塑性破坏,因此支护后隧洞达到稳定且安全的状态,验证支护措施的有效性。但为保证工程安全,建议施工期间做好排水措施,并缩短施工开挖、一次支护措施之间的施工间隔,使支护尽早发挥作用。

Regulating crystal phase of TiO_(2) to enhance catalytic activity of Ni/TiO_(2) for solar-driven dry reforming of methane

Ni/TiO_(2) catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO_(2) remains unclear.In this work,the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO_(2).Structural characterizations revealed that a distinct TiO_(x) coating on the Ni nanoparticles(NPs)was evident for Ni/TiO_(2)-700 catalyst due to strong metal-support interaction.It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased,thereby enhancing the exposure of Ni active sites.The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4,which led to the much elevated catalytic activity for Ni/TiO_(2)-950 in which rutile dominated.Therefore,the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio.Ni/TiO_(2)-950,characterized by a predominant rutile phase,exhibited the highest DRM reactivity,with remarkable H_(2) and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h),respectively.These rates were approximately 257 and 130 times higher,respectively,compared to those obtained on Ni/TiO_(2)-700 with anatase.This study suggests that the optimization of crystal structure of TiO_(2) support can effectively enhance the performance of photothermal DRM reaction.

A 27 GHz,simple 2-bit 1×8 phased array

This study demonstrates a simple 2-bit phased array operating at 27 GHz that supports one-dimensional beam scanning with left-handed circular polarization(LHCP).The antenna is constructed using a compact four-layer printed circuit board(PCB)structure,consisting of a 90°phase shifter layer with microstrip structures,a ground(GND)layer,a direct current(DC)control layer,and a circularly polarized annular radiation patch layer with 1-bit phase shifting.Based on the proposed unit structure,a 1×8 array with half-wavelength inter-element spacing was designed and validated.Experimental results show that the array achieves a peak gain of 10.23 dBi and is capable of beam scanning within±50°.

Durable hierarchical phosphorus‐doped biphase MoS_(2)electrocatalysts with enhanced H^(*)adsorption

Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.

Biphase-to-monophase structure evolution of Na_(0.766+x)Li_(x)Ni_(0.33-x)Mn_(0.5)Fe_(0.1)Ti_(0.07)O_(2) toward ultradurable Na-ion batteries

Layered composite oxide materials with O3/P2 biphasic crystallographic structure typically demonstrate a combination of high capacities of the O3 phase and high operation voltages of the P2 phase.However,their practical applications are seriously obstructed by difficulties in thermodynamic phase regulation,complicated electrochemical phase transition,and unsatisfactory cycling life.Herein,we propose an efficient structural evolution strategy from biphase to monophase of Na_(0.766+x)Li_(x)Ni_(0.33-x)Mn_(0.5)Fe_(0.1)Ti_(0.07)O_(2) through Li+substitution.The role of Li+substitution not only simplifies the unfavorable phase transition by altering the local coordination of transition metal(TM)cations but also stabilizes the cathode–electrolyte interphase to prevent the degradation of TM cations during battery cycling.As a result,the thermodynamically robust O_(3)-Na_(0.826)Li_(0.06)Ni_(0.27)Mn_(0.5)Fe_(0.1)Ti_(0.07)O_(2) cathode delivers a high capacity of 139.4 mAh g^(-1) at 0.1 C and shows prolonged cycling life at high rates,with capacity retention of 81.6%at 5 C over 500 cycles.This work establishes a solid relationship between the thermodynamic structure evolution and electrochemistry of layered cathode materials,contributing to the development of long-life sodium-ion batteries.

Generalized Mechanism for the Solid Phase Transition of M_(2)O_(3)(M=Al,Ga)Featuring Single Cation Migration and Martensitic Lattice Transformation

Al_(2)O_(3)and Ga_(2)O_(3)exhibit numerous crystal phases with distinct stabilities and materialproperties.However,the phase transitions among thosematerialsare typicallyundesirable in industrial applications,making it imperative to elucidate the transition mechanisms between these phases.The configurational similarities between Al_(2)O_(3)and Ga_(2)O_(3)allow for the replication of phase transition pathways between these materials.In this study,we investigate the potential phase transition pathway of alumina from the 0-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials,while extending an existing Ga_(2)O_(3)phase transition path.Through this exploration,we identify a novel single-atom migration pseudomartensitic mechanism,which combines martensitic transformation with single-atom diffusion.This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases.

Phase equilibria relations in the V_(2)O_(5)-rich part of the Fe_(2)O_(3-)TiO_(2)-V_(2)O_(5) system at 1200℃ related to converter vanadium-bearing slag

The efficient recycling of vanadium from converter vanadium-bearing slag is highly significant for sustainable development and circular economy.The key to developing novel processes and improving traditional routes lies in the thermodynamic data.In this study,the equilibrium phase relations for the Fe_(2)O_(3)-TiO_(2)-V_(2)O_(5)system at 1200℃in air were investigated using a high-temperature equilibrium-quenching technique,followed by analysis using scanning electron microscopy-energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy.One liquid-phase region,two two-phase regions(liquid-rutile and liquid-ferropseudobrookite),and one three-phase region(liquid-rutile-ferropseudobrookite)were determined.The variation in the TiO_(2)and V_(2)O_(5)contents with the Fe_(2)O_(3)content was examined for rutile and ferropseudobrookite solid solutions.However,on further comparison with the predictions of FactSage 8.1,significant discrepancies were identified,highlighting that greater attention must be paid to updating the current thermodynamic database related to vanadium-bearing slag systems.

Actively tuning anisotropic light-matter interaction in biaxial hyperbolic materialα-MoO_(3) using phase change material VO_(2) and graphene

Anisotropic hyperbolic phonon polaritons(PhPs)in natural biaxial hyperbolic materialα-MoO_(3) has opened up new avenues for mid-infrared nanophotonics,while active tunability ofα-MoO_(3) PhPs is still an urgent problem necessarily to be solved.In this study,we present a theoretical demonstration of actively tuningα-MoO_(3) PhPs using phase change material VO_(2) and graphene.It is observed thatα-MoO_(3) PhPs are greatly dependent on the propagation plane angle of PhPs.The insulator-to-metal phase transition of VO_(2) has a significant effect on the hybridization PhPs of theα-MoO_(3)/VO_(2) structure and allows to obtain actively tunableα-MoO_(3) PhPs,which is especially obvious when the propagation plane angle of PhPs is 900.Moreover,when graphene surface plasmon sources are placed at the top or bottom ofα-MoO_(3) inα-MoO_(3)/VO_(2)structure,tunable coupled hyperbolic plasmon-phonon polaritons inside its Reststrahlen bands(RB s)and surface plasmonphonon polaritons outside its RBs can be achieved.In addition,the above-mentionedα-MoO_(3)-based structures also lead to actively tunable anisotropic spontaneous emission(SE)enhancement.This study may be beneficial for realization of active tunability of both PhPs and SE ofα-MoO_(3),and facilitate a deeper understanding of the mechanisms of anisotropic light-matter interaction inα-MoO_(3) using functional materials.

Topological phase transition in compressed van der Waals superlattice heterostructure BiTeCl/HfTe_(2)

Based on first-principles calculations,we investigate the electronic band structures and topological properties of heterostructure BiTeCl/HfTe_(2) under c-direction strain.In the primitive structure,this material undergoes a phase transition from an insulator with a narrow indirect gap to a metal by strong spin-orbital coupling.When strain effect is considered,band inversion at time-reversal invariant point Z is responsible for the topological phase transition.These nontrivial topologies are caused by two different types of band crossings.The observable topological surface states in(110)surface also support that this material experiences topological phase transition twice.The layered heterostructure with van der Waals force provides us with a new desirable platform upon which to control topological phase transition and construct topological superconductors.

Scattered Co-anchored MoS_(2)synergistically boosting photothermal capture and storage of phase change materials

Pristine phase change materials(PCMs)suffer from inherent deficiencies of poor solar absorption and photothermal conversion.Herein,we proposed a strategy of co-incorporation of zero-dimensional(OD)metal nanoparticles and two-dimensional(2D)photothermal materials in PCMs for efficient capture and conversion of solar energy into thermal energy.Highly scattered Co-anchored MoS_(2)nanoflower cluster serving as photon and phonon triggers was prepared by in-situ hydrothermal growth of ZIF67 polyhedron on 2D MoS_(2)and subsequent high-temperature carbonization.After encapsulating thermal storage unit(paraffin wax),the obtained composite PCMs integrated high-performance photothermal conversion and thermal energy storage capability.Benefiting from the synergistic enhancement of OD Co nanoparticles with localized surface plasmon resonance effect,carbon layer with the conjugation effect and 2D MoS_(2)with strong solar absorption,composite PCMs exhibited a high photothermal conversion efficiency of 95.19%,Additionally,the resulting composite PCMs also demonstrated long-term thermal sto rage stability and durable structu ral stability after 300 thermal cycles.The proposed collabo rative co-incorporation strategy provides some innovative references for developing next-generation photothermal PCMs in solar energy utilization.

Pressure-driven layer-dependent phase transitions and enhanced interlayer coupling in PdSe_(2) crystals

Pressure exerts a profound influence on atomic configurations and interlayer interactions, thereby modulating the electronic and structural properties of materials. While high pressure has been observed to induce a structural phase transition in bulk PdSe_(2) crystals, leading to a transition from semiconductor to metal, the high-pressure behavior of few-layer PdSe_(2) remains elusive. Here, employing diamond anvil cell (DAC) techniques and high-pressure Raman spectroscopy, we investigate the structural evolution of layer-dependent PdSe_(2) under high pressure. We reveal that pressure significantly enhances interlayer coupling in PdSe_(2), driving structural phase transitions from an orthorhombic to a cubic phase. We demonstrate that PdSe_(2) crystals exhibit distinct layer-dependent pressure thresholds during the phase transition, with the decrease of transition pressure as the thickness of PdSe_(2) increases. Furthermore, our results of polarized Raman spectra confirm a reduction in material anisotropy with increasing pressure. This study offers crucial insights into the structural evolution of layer-dependent van der Waals materials under pressure, advancing our understanding of their pressure-induced behaviors.

Optical design of a novel near-infrared phase contrast imaging(NI-PCI)diagnostic on the HL-2A tokamak

The optical design of near-infrared phase contrast imaging(NI-PCI)diagnosis on HL-2A is introduced in this paper.This scheme benefits from the great progress of near-infrared laser technology and is a broadening of traditional phase contrast technology.This diagnostic can work as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations.Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed.The 1550 nm laser is chosen as the probe beam and highprecision optical components are designed to fit the laser beam,in which a phase plate with a 194-nm-deep silver groove is the key.Compared with the conventional 10.6μm laser-based PCI system on HL-2A,NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm^(-1)to 32.6 cm^(-1).

Effect of Sc on Al_(3)Fe phase and mechanical properties of as-cast AA5052 aluminum alloy

The AA5052 aluminum alloy is widely used in automobile and aerospace manufacturing,and with the development of light-weight alloys,it is required that these materials exhibit better mechanical properties.Previous studies have demonstrated that the addition of Sc to aluminum alloys can improve both the microstructure and properties of the alloys.In this study,the effect of Sc on the Fe-rich phase and properties of the AA5052 aluminum alloy was studied by adding 0%,0.05%,0.2%,and 0.3%Sc.The results show that with the increase of Sc,the coarse needle-like Fe-rich phase gradually transforms into Chinese-script and then nearly spherical particles,reduce the size of Fe-rich phase,and refine the grain with increase of high angle grain boundaries(HAGBs).These microstructure changes enhance the strength of the AA5052 alloy through Sc addition.The ductility of the alloy is obviously improved because the addition of a lower amount of Sc changes the morphology of Fe-rich phase from needle-like into a Chinese-script,and it is subsequently reduced as a result of significant increase in HAGBs with increasing Sc content.

Characterization and Application of S-Band Polarimetric Radar and X-Band Phased Array Radar for a Tornadic Storm Event on June 16,2022

The X-band phased array radar offers faster scanning speed and higher spatial resolution compared to the S-band radar,making it capable of enhancing tornado monitoring and early warning capabilities.This study analyzed the characteristics and nowcasting signals of a tornado case that occurred on June 16,2022 in the Guangzhou region.Our findings indicate that the violent contraction of rotation radius and the dramatic increase in rotation speed were important signal characteristics associated with tornado formation.The X-band phased array radar,with its high temporal and spatial resolution,provided an opportunity to capture early warning signals from polarimetric characteristics.The X-band phased array radar demonstrated noteworthy ability to identify apparent tornado vortex signature(TVS)features in a 10-minute lead time,surpassing the capabilities of the CINRAD/SA radar.Additionally,due to its higher scanning frequency,the Xband phased-array radar was capable of consistently identifying TVS with shorter intervals,enabling a more precise tracking of the tornado's path.The application of professional radars,in this case,provides valuable insights for the monitoring of evolutions of severe local storms and even tornadoes and the issuance of early warning signals.

Effect of ultrasonic and mechanical vibration treatments on evolution of Mn-rich phases and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys

Effects of ultrasonic vibration(UV)and mechanical vibration(MV)on the Mn-rich phase modification and mechanical properties of Al−12Si−4Cu−1Ni−1Mg−2Mn piston alloys were investigated.The results show that the UV and UV+MV treatments can significantly refine and fragmentize the microstructures.In addition,UV treatment can significantly passivate the primary Mn-rich Al15Mn3Si2 intermetallics.The formation mechanisms of refinement and passivation of the grains and non-dendrite particles were discussed.Compared with the gravity die-cast alloys,the UV and UV+MV treated alloys exhibit improved tensile and creep resistance at room and elevated temperatures.These results can be attributed to the refinement of theα(Al)grains and the secondary intermetallics,the increased proportion of refined heat-resistant precipitates,and the formation of nano-sized Si particles.The ultimate tensile strength of the UV treated alloys at 350℃ exceeds that of commercial piston alloys.This indicates the high application potential of the developed piston alloys in density diesel engines.

Mechanism of microarc oxidation on AZ91D Mg alloy induced byβ-Mg_(17)Al_(12) phase

This work proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution ofβ-Mg_(17)Al_(12)phase in AZ91D Mg alloy.Two kinds of nano-particles(ZrO_(2)and TiO_(2))were designed to be added into the substrate of Mg alloy by friction stir processing(FSP).Then,Mg alloy sample designed with different precipitated morphology ofβ-Mg_(17)Al_(12)phase was treated by microarc oxidation(MAO)in Na_(3)PO_(4)/Na2SiO3electrolyte.The characteristics and performance of the MAO coating was analyzed using scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),contact angle meter,and potentiodynamic polarization.It was found that the coarseα-Mg grains in extruded AZ91D Mg alloy were refined by FSP,and theβ-Mg_(17)Al_(12)phase with reticular structure was broken and dispersed.The nano-ZrO_(2)particles were pinned at the grain boundary by FSP,which refined theα-Mg grain and promoted the precipitation ofβ-Mg_(17)Al_(12)phase in grains.It effectively inhibited the“cascade”phenomenon of microarcs,which induced the uniform distribution of discharge pores.The MAO coating on Zr-FSP sample had good wettability and corrosion resistance.However,TiO_(2)particles were hardly detected in the coating on TiFSP sample.

A Cu-Pd alloy catalyst with partial phase separation for the electrochemical CO_(2) reduction reaction

Cu catalysts can convert CO_(2) through an electrochemical reduction reaction into a variety of useful carbon-based products.However,this capability provides an obstacle to increasing the selectivity for a single product.Herein,we report a simple fabrication method for a Cu-Pd alloy catalyst for use in a membrane electrode assembly(MEA)-based CO_(2) electrolyzer for the electrochemical CO_(2) reduction reaction(ECRR)with high selectivity for CO production.When the composition of the Cu-Pd alloy catalyst was fabricated at 6:4,the selectivity for CO increased and the production of multi-carbon compounds and hydrogen is suppressed.Introducing a Cu-Pd alloy catalyst with 6:4 ratio as the cathode of the MEAbased CO_(2) electrolyzer showed a CO faradaic efficiency of 92.8%at 2.4 V_(cell).We assumed that these results contributed from the crystal planes on the surface of the Cu-Pd alloy.The phases of the Cu-Pd alloy catalyst were partially separated through annealing to fabricate a catalyst with high selectivity for CO at low voltage and C_(2)H_4 at high voltage.The results of CO-stripping testing confirmed that when Cu partially separates from the lattice of the Cu-Pd alloy,the desorption of~*CO is suppressed,suggesting that C-C coupling reaction is favored.