Interface,lattice strain and dislocation density of SiC_p/Al composite consolidated by equal channel angular pressing and torsion

Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites was characterized by transmission electron microscopy （TEM） and high resolution transmission electron microscopy （HRTEM）. The selected area electron diffraction （SAED） for the interface was investigated. The elements at the interface were scanned by energy dispersive spectroscopy （EDS） and the EDS mapping was also obtained. X-ray diffraction （XRD） analysis was carried out for the composites fabricated by 1 pass, 2 passes and 4 passes ECAP-T. According to the XRD analysis, the influences of ECAP-T pass on the Bragg angle and interplanar spacing for AI crystalline planes were studied. The results show that after ECAP-T, the interface between A1 and SiC within the composites is a belt of amorphous SiO2 containing a trace of A1, Si and C which diffused from the matrix and the reinforcement. With the growing ECAP-T pass, the Bragg angle decreases and interplanar spacing increases for A1 crystalline planes, due to the accumulated lattice strain. The increasing lattice strain of A1 grains also boosts the density of the dislocation within A1 grains.

In-situ doping-induced lattice strain of NiCoP/S nanocrystals for robust wide pH hydrogen evolution electrocatalysis and supercapacitor

Developing high-efficiency multifunctional nanomaterials is promising for wide p H hydrogen evolution reaction(HER) and energy storage but still challenging. Herein, a novel in-situ doping-induced lattice strain strategy of NiCoP/S nanocrystals(NCs) was proposed through using seed crystal conversion approach with NiCo_(2)S_(4) spinel as precursor. The small amount of S atoms in NiCoP/S NCs perturbed the local electronic structure, leading to the atomic position shift of the nearest neighbor in the protocell and the nanoscale lattice strain, which optimized the H* adsorption free energy and activated H_(2)O molecules, resulting the dramatically elevated HER performance within a wide p H range. Especially, the NiCoP/S NCs displayed better HER electrocatalytic activity than comical 20% Pt/C at high current density in 1 M KOH and natural seawater: it only needed 266 m V vs. reversible hydrogen electrode(RHE) and660 m V vs. RHE to arrive the current density of 350 m A cm^(-2) in 1 M KOH and natural seawater, indicating the application prospect for industrial high current. Besides, NiCoP/S NCs also displayed excellent supercapacitor performance: it showed high specific capacity of 2229.9 F g^(-1) at 1 A g^(-1) and energy density of87.49 Wh kg^(-1), when assembled into an all-solid-state flexible device, exceeding performance of most transition metal phosphides. This work provides new insights into the regulation in electronic structure and lattice strain for electrocatalytic and energy storage applications.

A combined electrochemical and DFT study of the lattice strain effect on the surface reactivity of Pd

We report a combined study of electrochemical experiments and ab initio calculations on tuning the surface reactivity of Pd via a compressive lattice strain achieved by employing nanoparticles of Pd-Cu alloys with a Pd-rich surface. Surface oxygen-containing species were used as the probing molecule for revealing the surface reactivity. Both density functional theory （DFT） calculations and experiments showed linear relationships, with very close slopes, between the adsorption strength of OHads and the Pd lattice constant. Not only is this work a successful realization of controllable modulation in the surface reactivity, but it also provides valuable information for the rational design of Pd-based catalysts for fuel cell applications.

Surface chemical disorder and lattice strain of GaN implanted by 3-MeV Fe^(10+)ions

Chemical disorder on the surface and lattice strain in GaN implanted by Fe^(10+)ions are investigated.In this study,3-MeV Fe^(10+)ions fluence ranges from 1×10^(13)ions/cm^(2)to 5×10^(15)ions/cm^(2)at room temperature.X-ray photoelectron spectroscopy,high-resolution x-ray diffraction,and high-resolution transmission electron microscopy were used to characterize lattice disorder.The transition of Ga-N bonds to oxynitride bonding is caused by ion sputtering.The change of tensile strain out-of-plane with fluence was measured.Lattice disorder due to the formation of stacking faults prefers to occur on the basal plane.

Evolution of electrical and magnetotransport properties with lattice strain in La0.7Sr0.3MnO3 film

In this paper,we investigate the effects of lattice strain on the electrical and magnetotransport properties of La0.7Sr0.3MnO3(LSMO)films by changing film thickness and substrate.For electrical properties,a resistivity upturn emerges in LSMO films,i.e.,LSMO/STO and LSMO/LSAT with small lattice strain at a low temperature,which originates from the weak localization effect.Increasing film thickness weakens the weak localization effect,resulting in the disappearance of resistivity upturn.While in LSMO films with a large lattice strain(i.e.,LSMO/LAO),an unexpected semiconductor behavior is observed due to the linear defects.For magnetotransport properties,an anomalous in-plane magnetoresistance peak(pMR)occurs at low temperatures in LSMO films with small lattice strain,which is caused by two-dimensional electron gas(2DEG).Increasing film thickness suppresses the 2DEG,which weakens the pMR.Besides,it is found that the film orientation has no influence on the formation of 2DEG.While in LSMO/LAO films,the 2DEG cannot form due to the existence of linear defects.This work can provide an efficient way to regulate the film transport properties.

Enhancing energy storage efficiency in lead-free dielectric ceramics through relaxor and lattice strain engineering

Dielectric capacitors with high power density and fast charge-discharge speed play an essential role in the development of pulsed power systems.The increased demands for miniaturization and practicality of pulsed power equipment also necessitate the development of dielectric materials that possess high energy density while maintaining ultrahigh efficiency(η).In particular,ultrahigh efficiency signifies minimal energy loss,which is essential for practical applications but challenging to effectively mitigate.Here,we demonstrate a strategy of incorporating heterovalent elements into Ba(Zr_(0.1)Ti_(0.9))O_(3),which contributes to achieving relaxor ferroelectric ceramics and reducing lattice strain,thereby improving the comprehensive energy storage performance.Finally,optimal energy storage performance is attained in 0.85Ba(Zr_(0.1)Ti_(0.9))O_(3)-0.15Bi(Zn_(2/3)Ta_(1/3))O_(3)(BZT-0.15BiZnTa),with an ultrahighηof 97.37%at 440 kV/cm(an advanced level in the lead-free ceramics)and an excellent recoverable energy storage density(Wrec)of 3.74 J/cm^(3).Notably,the BZT-0.15BiZnTa ceramics also exhibit exceptional temperature stability,maintaining fluctuations in Wrec within∼10%andηconsistently exceeding 90% across the wide temperature range of−55℃ to 160℃,and under a high electric field of 250 kV/cm.All these features demonstrate that the relaxor and lattice strain engineering strategies have been successful in achieving high-performance lead-free ceramics,paving the way for designing high-efficiency dielectric capacitors with a wide temperature range.

Tailoring lattice strain in ultra-fine high-entropy alloys for active and stable methanol oxidation

High-entropy alloys(HEAs)have been widely studied due to their unconventional compositions and unique physicochemical properties for various applications.Herein,for the first time,we propose a surface strain strategy to tune the electrocatalytic activity of HEAs for methanol oxidation reaction(MOR).High-resolution aberration-corrected scanning transmission electron microscopy(STEM)and elemental mapping demonstrate both uniform atomic dispersion and the formation of a face-centered cubic(FCC)crystalline structure in Pt Fe Co Ni Cu HEAs.The HEAs obtained by heat treatment at 700℃(HEA-700)exhibit 0.94%compressive strain compared with that obtained at 400℃(HEA-400).As expected,the specific activity and mass activity of HEA-700 is higher than that of HEA-400 and most of the state-of-the-art catalysts.The enhanced MOR activity can be attributed to a shorter Pt–Pt bond distance in HEA-700 resulting from compressive strain.The nonprecious metal atoms in the core could generate compressive strain and down shift d-band centers via electron transfer to surface Pt layer.This work presents a new perspective for the design of high-performance HEAs electrocatalysts.

Facile lattice tensile strain compensation in mixed-cation halide perovskite solar cells

Despite the rapid development of power conversion efficiency(PCE)for halide perovskite solar cells(PSCs),the lattice strain engineering in perovskite thin films has been rarely probed in recent years.Herein,a strain compensation by homogeneous crystallization in perovskite films is achieved with the aid of precursor aging in the mixed-cation perovskite of Cs_(0.05)(FA_(0.83)MA_(0.17))Pb(I_(0.90)Br_(0.10))_(3)with near 20%PCE in inverted devices.The homogeneous crystallization releases the residual tensile stress and induces more compressive stress at the edges of perovskite films,thus elongating the carrier lifetime and reducing the trap-assisted carrier recombination.The high dependence on the perovskite components in strain engineering strategy was systematically revealed,wherein MAPbI_(3)and Cs_(0.05)(FA_(0.83)MA_(0.17))PbI_(3)film showed an increased compressive strain and FAPbI3 film showed adverse tensile strain after aging.The density functional theory(DFT)calculations are further performed to reveal the change of electronic features.The precursor aging-induced strain modulation was correlated with a systematic characterization of the charge carrier transport and recombination dynamics in the mixed-cation perovskite films.We believe that this facile approach provides a novel strain engineering strategy for PSCs technology.

Lattice strain suppresses point defect formation in halide perovskites

We computationally investigate the impact of crystal strain on the formation of native point defects likely to be formed in halide perovskites;A-site cation antisite(I_(A)),Pb antisite(I_(Pb)),A-site cation vacany(V_(A)),I vacancy(V_(I)),Pb vacancy(V_(Pb)),and I interstitial(I_(i)).We systematically identify compressive and tensile strain to CsPbI_(3),FAPbI_(3),and MAPbI_(3)perovskite structures.We observe that while each type of defect has a unique behaviour,overall,the defect formation in FAPbI3 is much more sensitive to the strain.The compressive strain can enhance the formation energy of neutral I_(Pb)and I_(i)up to 15%for FAPbI_(3),depending on the growth conditions.We show that the strain not only controls the formation of defects but also their transition levels in the band gap:A deep level can be transformed into a shallow level by the strain.We anticipate that tailoring the lattice strain can be used as a defect passivation mechanism for future studies.

Quantification of Compositional and Residual Stress Efects on Lattice Strain in Dual-phase Stainless Steels by Means of Diferential Aperture X-ray Micro-difraction

Residual stress is an important factor for evaluating the deformation and failure of engineering materials. Diffraction-based measurement assumes that the full measured lattice strain tensor contributes to residual stress according to Hookers Law. The present work focuses on the lattice strain determination of individual grains in a dual-phase stainless steel （DPSS） by means of differential-aperture X-ray micro-diffraction （DAXM）. The results show that the residual stress only takes part of the responsibility of the total measured lattice strain. In fact, the compositional variation inside the material was found to cause greater strain gradient in both ferrite （c~） and austenite （~） phases in DPSS. Therefore, quantification of compositional and residual stress effects on lattice strain was conducted in order to evaluate the true residual stress inside engineering materials.

Lattice strain driven dielectric insulation response of Sr_(1-x)Ca_(x)Bi_(2)Nb_(2)O_(9) ceramics

In this paper,effects of lttice strain on dielectric properties of Sr_(1-x)Ca_(x)Bi_(2)Nb_(2)O_(9)(x=0.0-0.5 in steps of 0.1)ceramics are reported.High frequency dipolar polarization is observed to increase for 10%calcium addition and suppresses thereafter on higher calcium concentrations.The dielectric loss values for all doped samples were lower compared to undoped one at frequencies beyond 1 kHz.The sample with x=0.1 shows room temperature dielectric constant in the range(130±12)over a wide frequency range from 50Hz to 1 MHz also minimum dielectric loss among all other sample for the same frequeny range.Remarkable increase in Curie temperature(T_(c))by 50℃ is recorded in the present work by increasing 10%calcium content in SBN compostion.All higher doped samples indicate increase in T_(c) by further higher amount.In addition,dc conductivity of all samples is measured for all samples and increase in calcium content is observed to generate more insulating compositions compared to undoped SBN with higher intrinsic activation energies.

A Modified Lattice Model of the Reversible Effect of Axial Strain on the Critical Current of Polycrystalline REBa2Cu3O7-δ Films

The strain effect on the critical current is one of the most important properties for polycrystalline YBa2 Cu3O7-δ （REBCO, RE： rare earth） films, in which the reversible effect is intrinsic in the range of strain 0 and the irreversible strain εirr. By introducing the applied strain, a modified grain boundaries （GBs） in the REBCO film is developed. lattice model combining the strain and misorientation of A good agreement of the calculation on the lattice model with the experimental data shows that the lattice model is able to well describe the reversible effect of axial strain on the critical current of the REBCO film, and provides a good understanding of the mechanism of the reversible effect of the strain. Moreover, the effects of the crystallographic texture of the REBCO film and the residual strain εr on the variation of the critical current with the applied strain are extensively investigated. Furthermore by using the developed lattice model, the irreversible strain εirr of the REBCO film can be theoretically determined by comparing the calculation of the critical current-strain curve with the experimental data.

Investigation of the Micro-Mechanics of an Extruded Precipitation-Strengthened Magnesium Alloy under Cyclic Loading

Precipitation strengthening is a crucial microscopic mechanism for enhancing the strength of magnesium alloys. In order to elucidate the influence of precipitation on the microscopic deformation mechanisms and macroscopic mechanical response of magnesium alloys under cyclic loading conditions, we employed a crystal plasticity model to analyze the stress-strain curves, specific crystal plane diffraction intensities, and the temporal evolution of various microscopic deformation mechanisms and twinning volume fractions for an extruded magnesium alloy, AXM10304, containing coherent precipitates. The research findings indicate that precipitation does not fundamentally alter the microscopic mechanisms of this alloy. However, it hinders twinning during the compression stage, mildly promotes detwinning during the tension stage, and enhances tension secondary hardening by elevating the difficulty of activation of the prismatic slip.

Anchimetamorphism of the Neoproterozoic and the Lower Paleozoic along the Profile of Yuanguping in Western Hunan Province, China

The Neoproterozoic and Lower Paleozoic along the profile of Yuanguping in western Hunan Province, China underwent anchimetamorphism. The illite crystallinity (IC) of the <2 μm fractions ranges from 0.23-0.34°△2θfor the Neoproterozoic to 0.23-0.35°△A2θ for the Lower Paleozoic (calibrated with the Kisch IC set, Kisch, 1991). This indicates that the metamorphic grade of the Neoproterozoic and Lower Paleozoic is the anchizone. The peak metamorphic temperature is estimated to be 290-210℃. This result does not agree with the greenschist or subgreenschist facies of the Banxi Group, nor with the lower-greenschist facies or sedimentary cover of the Sinian to Lower Paleozoic, as most previous researchers thought. The illite (K-mica) b0 values range from 0.9074 to 0.8963 (nm) for the Neoproterozoic and the Lower Paleozoic. Based on cumulative frequency curves of the illite (K-mica) b0, the peak metamorphic pressure of the Banxi Group was derived to be of a type that is slightly higher than that of the N. New Hampshire low-intermediate pressure type. Most illites occur as the 2M1 polytype and some in the Neoproterozoic as a mixture of the 2M1+1M types. The distributions of coherent scanning domains (CSDs) of illites along the profile, measured with the XRD method, display a lognormal model and spread out with decreasing Kubler Index of IC. It indicates that illites underwent an Ostwald ripening. The post-anchimetamorphic structural movement not only results in a series of faults but also induces the lattice strain in minerals along the faults and hence impacts the illite crystallinity and causes diagenetic samples to occur within the anchizone. Compared with the cases in eastern and central Hunan Province, the Neoproterozoic and Lower Paleozoic rocks in the west underwent a lower-temperature anchimetamorphism with a pressure lower than that in the east and higher than that in the center of Hunan Province.

A New Method for Clay Mineral Analysis and Its Application in Geology

X-ray diffraction (XRD) peaks in a low-angle diffraction section of clayminerals, especially those of authigenic origin, have broadening and tailing features in shape.Using the five basic parameters, peak position, peak height, width, shape coefficient and asymmetry,to describe an XRD peak is more accurate, comprehensive and integrated than using only 3 of them,position, height and width. Following the concept of the five basic parameters of an XRD peak, theprogram Decoform proposed in this study provides more information in mineralogical analyses byfitting actual XRD profiles. In combination with the HW-IR plot, Decoform can he systematically andaccurately used in the comprehensive analyses of crystallinity, domain size, lattice strain andquantitative phase. It is also of value for the geological investigations of diagenesis,metamorphism, basin maturity, structural stress field and so on.

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

The formulation of nanocrystallinc NiTi shape memory alloys has potential effects in mechanical stimulation and medical im- plantology. The present work elucidates the effect of milling time on the product＇s structural characteristics, chemical composition, and mi- crohardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fractur- ing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninter- rupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to -93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline in- termetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

A novelty strategy induced pinning effect and defect structure in Ni-rich layered cathodes towards boosting its electrochemical performance

Layered Ni-rich transition metal oxide is treated as the most promising alternative cathode due to their high-capacity and flexible composition.However,the severe lattice strain and slow Li-ion migration kinetics severely restrict their practical application.Herein,a novelty strategy induced pinning effect and defect structure in layered Ni-rich transition metal oxide cathodes is proposed via a facile cation(iron ion)/anion(polyanion)co-doping method.Subsequently,the effects of pinning effect and defect structure on element valence state,crystal structure,morphology,lattice strain,and electrochemical performance during lithiation/delithiation are systematically explored.The detailed characterizations(soft X-ray absorption spectroscopy(sXAS),in-situ X-ray diffraction(XRD),etc.)and density functional theory(DFT)calculation demonstrate that the pinning effects built-in LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)materials by the dual-site occupation of iron ions on lithium and transition metal sites effectively alleviate the abrupt lattice strain caused by an unfavorable phase transition and the subsequent induction of defect structures in the Li layer can greatly reduce the lithium-ion diffusion barrier.Therefore,the modified LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)exhibits a high-capacity of 206.5 mAh g^(-1)and remarkably enhanced capacity retention of 93.9%after 100 cycles,far superior to~14.1%of the pristine cathodes.Besides,an excellent discharge capacity of 180.1 mAh g^(-1)at 10 C rate is maintained,illustrating its remarkable rate capability.This work reports a pinning effect and defect engineering method to suppress the lattice strain and alleviate lithium-ion kinetic barriers in the Ni-rich layered cathodes,providing a roadmap for understanding the fundamental mechanism of an intrinsic activity modulation and structural design of layered cathode materials.

Improved efficiency and photo-stability of methylamine-free perovskite solar cells via cadmium doping

Although perovskite solar cells containing methylamine cation can show high power conversion efficiency,stability is a concern.Here,methylamine-free perovskite material Csx FA1–x PbI3 was synthesized by a one-step method.In addition,we incorporated smaller cadmium ions into mixed perovskite lattice to partially replace Pb ions to address the excessive internal strain in perovskite structure.We have found that the introduction of Cd can improve the crystallinity and the charge carrier lifetime of perovskite films.Consequently,a power conversion efficiency as high as 20.59%was achieved.More importantly,the devices retained 94%of their initial efficiency under 1200 h of continuous illumination.

Lattice-strained nanotubes facilitate efficient natural sunlight-driven CO_(2) photoreduction

Photocatalytic reduction of CO_(2) holds tremendous promise for alleviating the energy crisis.Despite the progress that has been,made,there are still some challenges to overcome,such as the realization under real sunlight rather than the simulation condition.In this work,ultrathin Ni_(2)(OH)(PO_(4))nanotubes(NTs)prepared through hydrothermal route are applied as a novel catalyst for photocatalytic reduction of CO_(2) under real sunlight.The prepared Ni_(2)(OH)(PO_(4))NTs exhibit a 11.3 μmol·h^(-1) CO production rate with,96.1% CO selectivity.Interestingly,Ni_(2)(OH)(PO_(4))NTs have a positive impact on the facilitation of photoreduction in diluted CO_(2).Notably,when the system is performed under real sunlight,Ni_(2)(OH)(PO_(4))NTs afford an accumulated CO of ca.26.8 nmol with,96.9% CO selectivity,exceeding most previous inorganic catalysts under simulated irradiation in the laboratory.Our experimental results demonstrate that the multisynergetic effects induced by surface-OH and the lattice strain serve as highly active sites for CO_(2) molecular adsorption and activation as well as electron transfer,hence enhancing photoreduction activity.Therefore,this work provides experimental basis that CO_(2) photocatalysis can be put into practical use.

Static strength of gold compressed up to 127 GPa

Gold powder is compressed non-hydrostatically up to 127 GPa in a diamond anvil cell （DAC）, and its angle dispersive X-ray diffraction patterns are recorded. The compressive strength of gold is investigated in a framework of the lattice strain theory by the line shift analysis. The result shows that the compressive strength of gold increases continuously with the pressure up to 106 GPa and reaches 2.8 GPa at the highest experimental pressure （127 GPa） achieved in our study. This result is in good agreement with our previous experimental result in a relevant pressure range. The compressive strength of gold may be the major source of the error in the equation-of-state measurement in various pressure environments.