Pre-existing orthorhombic embryos-induced hexagonal-orthorhombic martensitic transformation in MnNiSi_(1-x)(CoNiGe)_x alloy

The thermal-elastic martensitic transformation from high-temperature Ni_(2)In-type hexagonal structure to low-temperature TiNiSi-type orthorhombic structure has been widely studied in MnMX(M=Ni or Co,and X=Ge or Si)alloys.However,the answer to how the orthorhombic martensite nucleates and grows within the hexagonal parent is still unclear.In this work,the hexagonal-orthorhombic martensitic transformation in a Co and Ge co-substituted MnNiSi is investigated.One can find some orthorhombic laths embedded in the hexagonal parent at a temperature above the martensitic transformation start temperature(M_(s)).With the the sample cooing to M_(s),the laths turn broader,indicating that the martensitic transformation starts from these pre-existing orthorhombic laths.Microstructure observation suggests that these pre-existing orthorhombic laths do not originate from the hexagonal-orthorhombic martensitic transformation because of the difference between atomic occupations of doping elements in the hexagonal parent and those in the preexisting orthorhombic laths.The phenomenological crystallographic theory and experimental investigations prove that the pre-existing orthorhombic lath and generated orthorhombic martensite have the same crystallography relationship to the hexagonal parent.Therefore,the orthorhombic martensite can take these pre-existing laths as embryos and grow up.This work implies that the martensitic transformation in MnNiSi_(1-x)(CoNiGe)_(x) alloy is initiated by orthorhombic embryos.

F-doped orthorhombic Nb_(2)O_(5) exposed with 97% (100) facet for fast reversible Liþ-Intercalation

Orthorhombic Nb_(2)O_(5)(T-Nb_(2)O_(5))is attractive for fast-charging Li-ion batteries,but it is still hard to realize rapid charge transfer kinetics for Li-ion storage.Herein,F-doped T-Nb_(2)O_(5) microflowers(F-Nb_(2)O_(5))are rationally synthesized through topotactic conversion.Specifically,F-Nb_(2)O_(5) are assembled by single-crystal nanoflakes with nearly 97%exposed(100)facet,which maximizes the exposure of the feasible Li^(+)transport pathways along loosely packed 4g atomic layers to the electrolytes,thus effectively enhancing the Li^(+)-intercalation performance.Besides,the band gap of F-Nb_(2)O_(5) is reduced to 2.87 eV due to the doping of F atoms,leading to enhanced electrical conductivity.The synergetic effects between tailored exposed crystal facets,F-doping,and ultrathin building blocks,speed up the Li^(+)/electron transfer kinetics and improve the pseudocapacitive properties of F-Nb_(2)O_(5).Therefore,F-Nb_(2)O_(5) exhibit superior rate capability(210.8 and 164.9 mAh g^(-1) at 1 and 10 C,respectively)and good long-term 10 C cycling performance(132.7 mAh g^(-1) after 1500 cycles).

A Dugdale-Barenblatt model for elliptical orifice problem with asymmetric cracks in one-dimensional orthorhombic quasicrystals

By means of Muskhelishvili’s method and the technique of generalized conformal mapping,the physical plane problems are transformed into regular mathematical problems in quasicrystals(QCs).The analytical solution to an elliptical orifice problem with asymmetric cracks in one-dimensional(1D)orthorhombic QCs is obtained.By using the Dugdale-Barenblatt model,the plastic simulation at the crack tip of the elliptical orifice with asymmetric cracks in 1D orthorhombic QCs is performed.Finally,the size of the atomic cohesive force zone is determined precisely,and the size of the atomic cohesive force zone around the crack tip of an elliptical orifice with a single crack or two symmetric cracks is obtained.

Microstructural stability of long term aging treated Ti-22Al-26Nb-1Zr orthorhombic titanium aluminide

The microstructure development of lamellar structure of an orthorhombic Ti2AlNb-based Ti？22Al？26Nb？1Zr alloy, includingB2 decomposition and spheroidization ofO phase, was investigated. The results show that the lamellar structure is fabricated by heating the samples in the singleB2 phase field and cooling slowly in the furnace. Aging treatments are conducted in the （O＋B2） phases field by air cooling. After aging at 700 °C for a short time within 100 h, there is no significant change of microstructures, whereas the coarsening of lamellae is observed in the long-term aged microstructure. Ti？22Al？26Nb？1Zr alloy exhibits microstructural instability including the severe dissolution ofB2 lamella, discontinuous precipitation and spheroidization of O phase during the long term aging process at 700 °C up to 800 h. In addition, a pronounced formation of branch-shapedO phase lamella is observed for the alloy aged over 100 h.

Fracture prediction approach for oil-bearing reservoirs based on AVAZ attributes in an orthorhombic medium

Fracture systems in nature are complicated. Normally vertical fractures develop in an isotropic background. However, the presence of horizontal fine layering or horizontal fractures in reservoirs makes the vertical fractures develop in a VTI（a transversely isotropic media with a vertical symmetry axis） background. In this case, reservoirs can be described better by using an orthorhombic medium instead of a traditional HTI（a transversely isotropic media with a horizontal symmetry axis） medium. In this paper, we focus on the fracture prediction study within an orthorhombic medium for oil-bearing reservoirs. Firstly, we simplify the reflection coefficient approximation in an orthorhombic medium. Secondly, the impact of horizontal fracturing on the reflection coefficient approximation is analyzed theoretically. Then based on that approximation, we compare and analyze the relative impact of vertical fracturing, horizontal fracturing and fluid indicative factor on traditional ellipse fitting results and the scaled B attributes. We find that scaled B attributes are more sensitive to vertical fractures, so scaled B attributes are proposed to predict vertical fractures. Finally, a test is developed to predict the fracture development intensity of an oil-bearing reservoir. The fracture development observed in cores is used to validate the study method. The findings of both theoretical analyses and practical application reveal that compared with traditional methods, this new approach has improved the prediction of fracture development intensity in oil-bearing reservoirs.

Constitutive relation of an orthorhombic polycrystal with the shape coefficients

An orthorhombic polycrystal is an orthorhombic aggregate of tiny crystallites. In this paper, we study the effect of the crystalline mean shape on the constitutive relation of the orthorhombic polycrystal. The crystalline mean shape and the crystalline orientation arrangement are described by the crystalline shape function （CSF） and the orientation distribution function （ODF）, respectively. The CSF and the ODF are expanded as an infinite series in terms of the Wigner D-functions. The expanded coefficients of the CSF and the ODF are called the shape coefficients s^lm0 and the texture coefficients c^lmn respectively. Assuming that Ceff in the constitutive relation depends on the shape coefficients s^lm0 and the texture coefficients c^lmn by the principle of material frame-indifference we derive an analytical expression for C^eff up to terms linear in s^lmo and c^lmn and the expression would be applicable to the polycrystal whose texture is weak and whose crystalline mean shape has weak anisotropy. C^cff contains six unspecified material constants （λ, μ, c, s1, s2, s3）, five shape coefficients （s^2 00, s^2 20, s^4 00, s^4 20, s^4 40）, and three texture coefficients （c^4 99,c^4 20, c^4 40）, The results based on the perturbation approach are used to determine the five material constants approximately. We also find that the shape coefficients 2 and a s^2mo and s^4m0 are all zero if the crystalline mean shape is a cuboid. Some examples are given to compare our computational results.

Seismic AVAZ inversion for orthorhombic shale reservoirs in the Longmaxi area, Sichuan

Seismic AVAZ inversion method based on an orthorhombic model can be used to invert anisotropy parameters of the Longmaxi shale gas reservoir in the Sichuan Basin..As traditional seismic inversion workfl ow does not suffi ciently consider the infl uence of fracture orientation,we predict fracture orientation using the method based on the Fourier series to correct pre-stacked azimuth gathers to guarantee the accuracy of input data,and then conduct seismic AVAZ inversion based on the VTI constraints and Bayesian framework to predict anisotropy parameters of the shale gas reservoir in the study area.We further analyze the rock physical relation between anisotropy parameters and fracture compliance and mineral content for quantitative interpretation of seismic inversion results.Research results reveal that the inverted anisotropy parameters are related to P-and S-wave respectively,and thus can be used to distinguish the effect of fracture and fl uids by the joint interpretation.Meanwhile high values of anisotropy parameters correspond to high values of fracture compliance,so the anisotropy parameters can refl ect the development of fractures in reservoir.There is two sets of data from different sources,including the content of brittle mineral quartz obtained from well data and the anisotropy parameters inverted from seismic data,also show the positive correlation.This further indicates high content of brittle mineral makes fractures developing in shale reservoir and enhances seismic anisotropy of the shale reservoir.The inversion results demonstrate the characterization of fractures and brittleness for the Longmaxi shale gas reservoir in the Sichuan Basin.

Synthesis and Structure Transformation of Orthorhombic LiMnO2 Cathode Materials by Sol-gel Method

Orthorhombic LiMnO2 cathode materials were synthesized successfully at lower temperature by sol-gel method. When LiMnO2 precursor prepared by sol-gel method was fired in air, the product was a mixture of spinel structure LiMn2O4 and rock-salt structure Li2MnO3, whereas in argon single-phase orthorhombic LiMnO2 could obtain at the range of 750℃ to 920℃. The substitution of Mn by Zn2+ or Co3+ in LiMnO2 led to the structure of LiMnO2 transiting to Qα-LiFeO2. The results of electrochemical cycles indicated that the discharged capacity of orthorhombic-LiMnO2 was smaller at the initial stages, then gradually increased with the increasing of cycle number, finally the capacity stabilized to certain value after about 10th cycles. This phenomenon reveals that there is an activation process for orthorhombic LiMnO2 cathode materials during electrochemical cycles, which is a phase transition process from orthorhombic LiMnO2 to tetragonal spinel Li2Mn2O4. The capacity of orthorhombic LiMnO2 synthesized at lower temperature is larger than that synthesized at high temperature.

Structures and local ferroelectric polarization switching properties of orthorhombic YFeO_3 thin film prepared by a sol–gel method

Orthorhombic YFeO_3 thin film was prepared on La_(0.67)Sr_(0.33)MnO_3/LaAlO_3 substrate by a sol-gel spin-coating method. The structures of the YFeO_3/La_(0.67)Sr_(0.33)MnO_3/LaAlO_3(YFO/LSMO/LAO) sample were detected by x-ray diffraction pattern, Raman spectrometer, scanning electron microscopy, and atomic force microscope. The local ferroelectric polarization switching properties of the orthorhombic YFO film were confirmed by piezoresponse force microscopy(PFM) for the first time. The results show that the YFO film deposited on LSMO/LAO possesses orthorhombic structure,with ultra-fine crystal grains and flat surface. The leakage current of the YFO film is 8.39 × 10^(-4) A·cm^(-2) at 2 V,with its leakage mechanism found to be an ohmic behavior. PFM measurements indicate that the YFO film reveals weak ferroelectricity at room temperature and the local switching behavior of ferroelectric domains has been identified. By local poling experiment, polarization reversal in the orthorhombic YFO film at room temperature was further observed.

Predicting Physical Properties of Tetragonal,Monoclinic and Orthorhombic M_3N_4(M=C,Si,Sn) Polymorphs via First-Principles Calculations

The recently discovered tetragonal, monoclinie and orthorhombic polymorphs of M3N4 （M=C, Si, Sn） are in- vestigated by using first-principles calculations. A set of anisotropic elastic quantities, i.e., the bulk and shear moduli, Young＇s modulus, Poisson ratio, H/G ratio and rickets hardness of M3N4 （M=C, Si, Sn） are predicted. The quasi-harmonic Debye model, assuming that the solids are isotopic, may lead to large errors for the non-cubic crystals. The thermal effects are obtained by the traditional quasi-harmonic approach. The dependences of heat capacity, thermal expansion coefficient and Debye temperature on temperature and pressure are systematically discussed in the pressure range of 0 IOGPa and in the temperature range of 0-1100 K. More importantly, o- C3N4 is a negative thermal expansion material. Our results may have important consequences in shaping the understanding of the fundamental properties of these binary nitrides.

An Orthorhombic Phase of Superhard o-BC_4N

A potential superhard o-BC_4 N with Imm2 space group is identified by ab initio evolutionary methodology using CALYPSO code. The structural, electronic and mechanical properties of o-BC_4N are investigated. The elastic calculations indicate that o-BC_4N is mechanically stable. The phonon dispersions imply that this phase is dynamically stable under ambient conditions. The structure of o-BC_4N is more energetically favorable than o-BC_4N above the pressure of 25.1 GPa. Here o-BC_4N is a semiconductor with an indirect band gap of about 3.95 eV, and the structure is highly incompressible with a bulk modulus of 396.3 GPa and shear modulus of 456.0 GPa. The mechanical failure mode of o-BC_4N is dominated by the shear type. The calculated peak stress of 58.5 GPa in the(100)[001] shear direction sets an upper bound for its ideal strength. The Vickers hardness of o-BC_4N reaches 78.7 GPa, which is greater than that of t-BC_4N and bc-BC_4N proposed recently, confirming that o-BC_4N is a potential superhard material.

Hydrothermal Synthesis and Electrochemical Behavior of Nanosized Orthorhombic LiMnO_(2)

Nanosized orthorhombic LiMnO2 was successfully synthesized using Mn2O3 and LiOH.H2O as starting materials.Not only the reaction temperature was lower, but the reaction time for synthesizing was notably shortened to 1 h.In this hydrothermal process, the cations of the starting materials were capable of mixing and interacting in ionic scale, which resulted in the rapid formation of o-LiMnO2 powders at relatively low temperature. The particle size conformed by transmission electron microscopy is around 50-150 nm. Benefiting from its small particle size and good uniformity, the obtained o-LiMnO2 can reach the maximum discharge capacity of 163 mA-h.g^-1 at 0.1 C rate after several cycles. X-ray diffraction data and electrochemical properties suggested the phase transformation from orthorhombic LiMnO2 to defect-type spinel LiMn204 with minor Li2MnO3, which resulted in the capacity fading during cycling.

Infrared laser-induced fast photovoltaic effect observed in orthorhombic tin oxide film

The SnO_2/SnO with an orthorhombic structure is a material known to be stable at high pressures and temperatures and expected to have new optical and electrical properties. The authors report a new finding of the infrared laser induced a fast photovoltaic effect arising from orthorhombic tin oxide film with an indirect band gap（~2.4 e V） which is deposited by pulsed laser deposition. The rising time of the photovoltaic signal is about 3 ns with a peak value of 4.48 mV under the pulsed laser beam with energy density 0.015 m J/mm^2. The relation between the photovoltages and laser positions along the line between two electrodes of the film is also exhibited. A possible mechanism is put forward to explain this phenomenon.All data and analyses demonstrate that the orthorhombic tin oxide with an indirect band gap could be used as a candidate for an infrared photodetector which can be operated at high pressures and temperatures.

Propagation behavior of SH waves in a piezomagnetic substrate with an orthorhombic piezoelectric layer

The dispersion behavior of the shear horizontal （SH） waves in the coupled structure consisting of a piezomagnetic substrate and an orthorhombic piezoelectric layer is investigated with different cut orientations. The surface of the piezoelectric layer is mechanically free, electrically shorted, or open, while the surface of the piezomagnetic substrate is mechanically free, magnetically open, or shorted. The dispersion relations are derived for four electromagnetic boundary conditions. The dispersion characteristics are graphically illustrated for the layered structure with the PMN-PT layer perfectly bonded on the CoFe2O4 substrate. The effects of the PMN-PT cut orientations, the electromagnetic boundary conditions, and the thickness ratio of the layer to the substrate on the dispersion behavior are analyzed and discussed in detail. The results show that, （i） the effect of the cut orientation on the dispersion curves is very obvious, （ii） the electrical boundary conditions of the PMN-PT layer dominate the propagation feature of the SH waves, and （iii） the thickness ratio has a significant effect on the phase velocity when the wave number is small. The results of the present paper can provide valuable theoretical references to the applications of piezoelectric/piezomagnectic structure in acoustic wave devices.

Improved Electrochemical Performance of Orthorhombic LiMn(1-x)CrxO_2 Synthesized by Hydrothermal Method

Single phase chromium-substituted orthorhombic LiMn1-xCrxO2 （0≤x≤0.05） were successfully synthesized by hydrothermal treatment of Mn2O3, Cr2O3 and lithium hydroxide aqueous solution. Structure and morphologies of the o-LiMn1-xCrxO2 were characterized by X-ray diffraction and transmission electron microscopy. Compared to the particle size of o-LiMnO2 ranging from 50 to 150 nm, the Cr-doped one is larger with about 500 nm, which is agglomerated by small grains. There are high stacking faults in nanosized grains that cause easier phase transformation from the orthorhombic to the spinel-like structure on cycling. High-resolution transmission electron microscopy image analysis of electrochemically cycled o-LiMn1-xCrxO2 （x=0, 0.05） samples showed that the nanodomain structure in o-LiMn0.95Cr0.05O2 was comparatively perfect to that in o-LiMnO2. Particle agglomeration and the relatively perfect crystal structure are two key factors for improving cycle performance of o-LiMn0.95Cr0.05O2. The obtained o-LiMn0.95Cr0.05O2 can reach a maximum discharge capacity of 174 mA·h·g^-1 at 0.1 C rate in seventh cycle. The discharge capacity fade rate of the samples decreased with increasing Cr amount. Furthermore, o-LiMn0.95Cr0.05O2 gives a highest discharge capacity of 150 mA·h·g^-1 at a high current rate of 0.5 C, and retains 130 mA·h·g^-1 after 40 cycles.

In operando study of orthorhombic V_(2)O_(5) as positive electrode materials for K-ion batteries

Herein, the electrochemical performance and the mechanism of potassium insertion/deinsertion in orthorhombic V_(2)O_(5) nanoparticles are studied. The V2O5 electrode displays an initial potassiation/depotassiation capacity of 200 mAh g^(−1)/217 mAh g^(−1) in the voltage range 1.5–4.0 V vs. K^(+)/K at C/12 rate, suggesting fast kinetics for potassium insertion/deinsertion. However, the capacity quickly fades during cycling, reaching 54 mAh g^(−1) at the 31st cycle. Afterwards, the capacity slowly increases up to 80 mAh g^(−1) at the 200th cycle. The storage mechanism upon K ions insertion into V2O5 is elucidated. In operando synchrotron diffraction reveals that V_(2)O_(5) first undergoes a solid solution to form K_(0.6)V_(2)O_(5) phase and then, upon further K ions insertion, it reveals coexistence of a solid solution and a two-phase reaction. During K ions deinsertion, the coexistence of solid solution and the two-phase reaction is identified together with an irreversible process. In operando XAS confirms the reduction/oxidation of vanadium during the K insertion/extraction with some irreversible contributions. This is consistent with the results obtained from synchrotron diffraction, ex situ Raman, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Moreover, ex situ XPS confirms the “cathode electrolyte interphase” (CEI) formation on the electrode and the decomposition of CEI film during cycling.

Room-temperature ferromagnetism and half-metallicity in monolayer orthorhombic CrS_(2)

Two-dimensional materials with high-temperature ferromagnetism and half-metallicity have the latest applications in spintronic devices.Based on first-principles calculations,we have investigated a novel two-dimensional CrS_(2) phase with an orthorhombic lattice.Our results suggest that it is stable in dynamics,thermodynamics,and mechanics.The ground state of monolayer orthorhombic CrS_(2) is both ferromagnetic and half-metallic,with a high Curie temperature of 895 K and a large spin-flipping gap on values of 0.804 eV.This room-temperature ferromagnetism and halfmetallicity can maintain stability against a strong biaxial strain ranging from–5%to 5%.Meanwhile,increasing strain can significantly maintain the out-of-plane magnetic anisotropy.A density of states analysis,together with the orbital-resolved magnetic anisotropy energy,has revealed that the strain-enhanced MAE is highly related to the 3d-orbital splitting of Cr atoms.Our results suggest the monolayer orthorhombic CrS_(2) is an ideal candidate for future spintronics.

Characteristics of orthorhombic anisotropic seismic response induced by horizontal in situ stress in vertical transversely isotropic media

Sedimentary strata typically exhibit the characteristics of transverse isotropy(VTI)with a vertical axis of symmetry.However,fractures in sedimentary strata tend to produce anisotropic closure due to horizontal in situ stress,resulting in pronounced orthorhombic anisotropy in VTI media under such stress conditions and influencing the propagation behavior of seismic waves.Previous studies have primarily focused on the elastic wave velocity anisotropy induced by applied stress in isotropic background media,neglecting the impact of VTI background media on the anisotropy induced by horizontal in situ stress and the response characteristics of seismic wave propagation.To address these gaps,we first establish the effective elastic stiffness tensor of VTI media under horizontal in situ stress using nonlinear acoustoelastic theory.Then,we derive the accurate and linearized approximate equations for P-wave seismic reflectivity of VTI media under horizontal in situ stress,based on wave equations and scattering theory,respectively.Finally,we compare and analyze the characteristics of orthorhombic anisotropic seismic response induced by horizontal in situ stress at various types of elastic reflection interfaces.Our results demonstrate that the linearized approximation of the seismic reflection response characteristics closely aligns with the accurate equations under conditions of small stress below 10 MPa,effectively capturing the azimuth-dependent orthorhombic anisotropy induced by horizontal in situ stress in VTI media.The results of this study also provide a novel theoretical approach and valuable insights into the seismic prediction of in situ stress.

Insights into Formation and Li-Storage Mechanisms of Hierarchical Accordion-Shape Orthorhombic CuNb_(2)O_(6) toward Lithium-Ion Capacitors as an Anode-Active Material

The orthorhombic CuNb_(2)O_(6)(O-CNO)is established as a competitive anode for lithium-ion capacitors(LICs)owing to its attractive compositional/structural merits.However,the high-temperature synthesis(>900℃)and controversial charge-storage mechanism always limit its applications.Herein,we develop a low-temperature strategy to fabricate a nano-blocks-constructed hierarchical accordional O-CNO framework by employing multilayered Nb_(2)CT_(x)as the niobium source.The intrinsic stress-induced formation/transformation mechanism of the monoclinic CuNb_(2)O_(6)to O-CNO is tentatively put forward.Furthermore,the integrated phase conversion and solid solution lithium-storage mechanism is reasonably unveiled with comprehensive in(ex)situ characterizations.Thanks to its unique structural merits and lithium-storage process,the resulted O-CNO anode is endowed with a large capacity of 150.3 mAh g^(-1)at 2.0 A g^(-1),along with long-duration cycling behaviors.Furthermore,the constructed O-CNO-based LICs exhibit a high energy(138.9 Wh kg^(-1))and power(4.0 kW kg^(-1))densities with a modest cycling stability(15.8%capacity degradation after 3000 consecutive cycles).More meaningfully,the in-depth insights into the formation and charge-storage process here can promote the extensive development of binary metal Nb-based oxides for advanced LICs.

Dielectric tunability of magnetic properties in orthorhombic ferromagnetic monolayer CrSBr

Monolayer CrSBr is a recently discovered semiconducting spin-3/2 ferromagnet with a Curie temperature of around 146 K.In contrast to many other known 2D magnets,the orthorhombic lattice of CrSBr gives rise to spatial anisotropy of magnetic excitations within the 2D plane.Triaxial magnetic anisotropy and considerable magnetic dipolar interactions in CrSBr challenge its theoretical description in terms of spin Hamiltonians.Here,we employ a Green’s function formalism combined with first-principles calculations to study the magnetic properties of monolayer CrSBr in different regimes of surrounding dielectric screening.In the free-standing limit,the system is close to an easy-plane magnet,whose long-range ordering is partially suppressed.On the contrary,in the regime of large external screening,monolayer CrSBr behaves like an easy-axis ferromagnet with more stable magnetic ordering.Our findings suggest that anisotropic layered magnets form a potentially promising platform for studying the effects of substrate screening on magnetic ordering in 2D.