Acetic acid-assisted mild dealloying of fine CuPd nanoalloys achieving compressive strain toward high-efficiency oxygen reduction and ethanol oxidation electrocatalysis

Dealloying by which the transition metal is partially or completely leached from an alloy precursor is an effective way to optimize the fundamental effects for further enhancing the electrocatalysis of a catalyst.Herein,to address the deficiencies associated with the commonly used dealloying methods,for example,electrochemical and sulfuric acid/nitric acid treatment,we report an acetic acid-assisted mild strategy to dealloy Cu atoms from the outer surface layers of CuPd alloy nanoparticles to achieve high-efficiency electrocatalysis for oxygen reduction and ethanol oxidation in an alkaline electrolyte.The leaching of Cu atoms by acetic acid exerts an additional compressive strain effect on the surface layers and exposes more active Pd atoms,which is beneficial for boosting the catalytic performance of a dealloyed catalyst for the oxygen reduction reaction(ORR)and the ethanol oxidation reaction(EOR).In particular,for ORR,the CuPd nanoparticles with a Pd/Cu molar ratio of 2:1 after acetic dealloying show a half-wave potential of 0.912 V(vs.RHE)and a mass activity of 0.213 AmgPd^(-1) at 0.9 V,respectively,while for EOR,the same dealloyed sample has a mass activity and a specific activity of 8.4 Amg^(-1) and 8.23 mA cm^(-2),respectively,much better than their dealloyed counterparts at other temperatures and commercial Pd/C as well as a Pt/C catalyst.

Influence of compressive strain on the incorporation of indium in InGaN and InAlN ternary alloys

In order to investigate the influence of compressive strain on indium incorporation in In Al N and In Ga N ternary nitrides, In Al N/Ga N heterostructures and In Ga N films were grown by metal–organic chemical vapor deposition. For the heterostructures, different compressive strains are produced by Ga N buffer layers grown on unpatterned and patterned sapphire substrates thanks to the distinct growth mode; while for the In Ga N films, compressive strains are changed by employing Al Ga N templates with different aluminum compositions. By various characterization methods, we find that the compressive strain will hamper the indium incorporation in both In Al N and In Ga N. Furthermore, compressive strain is conducive to suppress the non-uniform distribution of indium in In Ga N ternary alloys.

Towards efficient strain engineering of 2D materials:A four-points bending approach for compressive strain

Strain engineering,as a powerful strategy to tune the optical and electrical properties of two-dimensional(2D)materials by deforming their crystal lattice,has attracted significant interest in recent years.2D materials can sustain ultra-high strains,even up to 10%,due to the lack of dangling bonds on their surface,making them ideal brittle solids.This remarkable mechanical resilience,together with a strong strain-tunable band structure,endows 2D materials with a broad optical and electrical response upon strain.However,strain engineering based on 2D materials is restricted by their nanoscale and strain quantification troubles.In this study,we have modified a homebuilt three-points bending apparatus to transform it into a four-points bending apparatus that allows for the application of both compressive and tensile strains on 2D materials.This approach allows for the efficient and reproducible construction of a strain system and minimizes the buckling effect caused by the van der Waals interaction by adamantane encapsulation strategy.Our results demonstrate the feasibility of introducing compressive strain on 2D materials and the potential for tuning their optical and physical properties through this approach.

Sub-2 nm IrO_(2)/Ir nanoclusters with compressive strain and metal vacancies boost water oxidation in acid

IrO_(2)exhibits good stability but limited electrocatalytic activity for oxygen evolution reaction in acid.Defect engineering is an effective strategy to improve the intrinsic ability of electrocatalysts by tailoring their electronic structure.Herein,we have successfully synthesized IrO_(2)/Ir heterophase with compressive strain and metal vacancies via a simple substitution-etching method.In virtue of the solubility of Cr in strong alkali,metal vacancies could be formed at surface after etching Cr-doped IrO_(2)/Ir in alkali,which leaded to modulated electronic structure.Meanwhile,the substitution of Cr with smaller atom radius would induce the formation of compressive strain and the relocated atoms made the d-band center shifted.With the regulated electronic structure and tuned d-band center,the obtained electrocatalyst only needed 285 mV to reach 10 mA·cm^(−2)in 0.1 M HClO4.Reaction kinetic has been rapidly accelerated as indicated by the smaller Tafel slope and charge transfer resistance.Theoretical calculations revealed that the d-band center and charge density distribution have been regulated with the introduction of defects in IrO_(2)/Ir,which significantly decreased the free energy barrier of rate determining step.This work provides a valuable reference to design effective and defects-rich electrocatalysts.

The role of strain in oxygen evolution reaction

The oxygen evolution reaction(OER)is a crucial step in metal-air batteries and water splitting technologies,playing a significant role in the efficiency and achievable heights of these two technologies.However,the OER is a four-step,four-electron reaction,and its slow kinetics result in high overpotentials,posing a challenge.To address this issue,numerous strategies involving modified catalysts have been proposed and proven to be highly efficient.In these strategies,the introduction of strain has been widely reported because it is generally believed to effectively regulate the electronic structure of metal sites and alter the adsorption energy of catalyst surfaces with reaction intermediates.However,strain has many other effects that are not well known,making it an important yet unexplored area.Based on this,this review provides a detailed introduction to the various roles of strain in OER.To better explain these roles,the review also presents the definition of strain and elucidates the potential mechanisms of strain in OER based on the d-band center theory and adsorption volcano plot.Additionally,the review showcases various ways of introducing strain in OER through examples reported in the latest literature,aiming to provide a comprehensive perspective for the development of strain engineering.Finally,the review analyzes the appropriate proportion of strain introduction,compares compressive and tensile strain,and examines the impact of strain on stability.And the review offers prospects for future research directions in this emerging field.

Effects of vertical electric field and compressive strain on electronic properties of bilayer ZrS2

Using first-principles calculations,including Grimme D2 method for van der Waals interactions,we investigate the tuning electronic properties of bilayer zirconium disulfides（ZrS_2/ subjected to vertical electric field and normal compressive strain.The band gap of ZrS_2 bilayer can be flexibly tuned by vertical external electric field.Due to the Stark effect,at critical electric fields about 1.4 V/？,semiconducting-metallic transition presents.In addition,our results also demonstrated that the compressive strain has an important impact on the electronic properties of ZrS_2 bilayer sheet.The widely tunable band gaps confirm possibilities for its applications in electronics and optoelectronics.

High temperature deformation and recrystallization behavior of magnesium bicrystals with 90°<1010>and 90°<1120>tilt grain boundaries

The deformation mechanisms and dynamic recrystallization(DRX)behavior of specifically grown bicrystals with a symmetric 90°<1010>and 90°<1120>tilt grain boundary,respectively,were investigated under deformation in plane strain compression at 200℃and 400℃.The microstructures were analyzed by panoramic optical microscopy and large-area electron backscatter diffraction(EBSD)orientation mapping.The analysis employed a meticulous approach utilizing hundreds of individual,small EBSD maps with a small step size that were stitched together to provide comprehensive access to orientation and misorientation data on a macroscopic scale.Basal slip primarily governed the early stages of deformation at the two temperatures,and the resulting shear induced lattice rotation around the transverse direction(TD)of the sample.The existence of the grain boundary gave rise to dislocation pile-up in its vicinity,leading to much larger TD-lattice rotations within the boundary region compared to the bulk.With increasing temperature,the deformation was generally more uniform towards the bulk due to enhanced dislocation mobility and more uniform stress distribution.Dynamic recrystallization at 200℃was initiated in{1011}-compression twins at strains of 40%and higher.At 400℃,DRX consumed the entire grain boundary region and gradually replaced the deformed microstructure with progressing deformation.The recrystallized grains displayed characteristic orientations,such that their c-axes were perpendicular to the TD and additionally scattered between 0°and 60°from the loading axis.These recrystallized grains displayed mutual rotations of up to 30°around the c-axes of the initial grains,forming a discernible basal fiber texture component,prominently visible in the{1120}pole figure.It is noteworthy that the deformation and DRX behaviors of the two analyzed bicrystals exhibited marginal variations in response to strain and deformation temperature.

RECRYSTALLIZATION BEHAVIOR AND PRIOR AUSTENITE GRAIN BOUNDARY CORROSION IN THE PLANE STRAIN COMPRESSION CONDITION FOR A LOW CARBON X70 PIPELINE STEEL

Recrystallization behavior of a low carbon X70 pipeline steel was studied in the plane strain compression condition. It was found that the dynamic recovery but no dynamic recrystal- lization occurred in the current experimental condition. A method for examining the prior austenite grain boundary corrosion was supposed.

Deformation behaviour of magnesium bicrystals with symmetrical 90°<1120>tilt grain boundaries analysed by large area EBSD mapping

Grain boundaries play a significant role in the deformation of polycrystals.Their response to deformation is however not completely understood,particularly with respect to how they accommodate lattice rotation of adjoining crystallites by changing their structure and geometry.The current study thus investigates the deformation behaviour of Mg bicrystals with 90°<1120>symmetric tilt boundary strained in plane-strain compression up to different final strains.Due to the initial soft orientation of the two crystals,activation of basal slip in each crystal gave rise to lattice rotation around the transverse direction towards the compression direction of the channel-die.Hundreds of single EBSD maps with a small step size were obtained from the GB region and stitched together to produce large panoramic maps of a macroscopic scale.Although very time-consuming,this technique has proven useful in clarifying the origin of the non-uniform deformation zones in the vicinity of the grain boundary and explains the mechanisms,by which the grain boundary was able to cope with the imposed strain before fracture.Interestingly,several variants of extension twins were observed as an additional deformation mechanism despite having negative Schmid factors.Systematic investigation of their resulting combined shear components with respect to the sample coordinate system revealed an alignment along the longitudinal direction of the channel-die,therefore justifying their nucleation.

Local buckling failure analysis of high-strength pipelines

Pipelines in geological disaster regions typically suffer the risk of local buckling failure because of slender structure and complex load. This paper is meant to reveal the local buckling behavior of buried pipelines with a large diameter and high strength, which are under different conditions, including pure bending and bending combined with internal pressure. Finite element analysis was built according to previous data to study local buckling behavior of pressurized and unpressurized pipes under bending conditions and their differences in local buckling failure modes. In parametric analysis, a series of parameters,including pipe geometrical dimension, pipe material properties and internal pressure, were selected to study their influences on the critical bending moment, critical compressive stress and critical compressive strain of pipes.Especially the hardening exponent of pipe material was introduced to the parameter analysis by using the Ramberg–Osgood constitutive model. Results showed that geometrical dimensions, material and internal pressure can exert similar effects on the critical bending moment and critical compressive stress, which have different, even reverse effects on the critical compressive strain. Based on these analyses, more accurate design models of critical bending moment and critical compressive stress have been proposed for high-strength pipelines under bendingconditions, which provide theoretical methods for highstrength pipeline engineering.

Research on China's high-grade highway design index of asphalt pavement with granular base

Based on the 2006 Chinese asphalt pavement deflection value design index, we used KENLAYER Pavement Analysis and Design software and lstOpt statistical analysis software to can-y on the nonlinear regression, this paper establish high-grade highway design equations for the compressive slrain of soil sub-base top （CSSBT） and the radial compressive stress of semi-rigid base top （RCSRBT）. The correlation coefficients inspection standard to get precise proof, which means that our granular base design equations have high credibility and can be used in the Chinese design index of asphalt pavement with granular base （APGB）.

Compressively-strained GaSb nanowires with core-shell heterostructures

GaSb-based nanowires in a gate-all-around geometry are good candidates for binary p-type transistors,however they require the introduction of compressive strain to enhance the transport properties.Here,we for the first time demonstrate epitaxial GaSb-GaASxSb1-x core-shell nanowires with a compressively strained core.Both axial and hydrostatic strain in GaSb core have been measured by X-ray diffraction(XRD)and Raman scattering,respectively.The optimal sample,almost without plastic relaxation,has an axial strain of-0.88%and a hydrostatic strain of-1.46%,leading to a noticeable effect where the light hole band is calculated to be 33.4 meV above the heavy hole band at the T-point.This valence band feature offers more light holes to contribute the transport process,and thus may provide enhanced hole mobility by reducing both the interband scattering and the hole effective mass.Our results show that lattice-mismatched epitaxial core-shell heterostructures of high quality can also be realized in the promising yet demanding GaSb-based system.

Grain boundary effect on structural, optical, and electrical properties of sol-gel synthesized Fe-doped SnO_(2) nanoparticles

Tin oxide(SnO_(2)) and iron-doped tin oxide(Sn_(1-x)Fe_(x)O_(2),x=0.05 wt%,0.10 wt%) nanoparticles are synthesized by the simple sol-gel method.The structural characterization using x-ray diffraction(XRD) confirms tetragonal rutile phases of the nanoparticles.The variations in lattice parameters and relative intensity with Fe-doping concentration validate the incorporation of iron into the lattice.The compressive strain present in the lattice estimated by using peak profile analysis through using Williamson-Hall plot also exhibits the influence of grain boundary formation in the lattice.The radiative recombination and quenching observed in optical characterization by using photoluminescence spectrum(PL) and the shift in the band gap estimated from UV-visible diffused reflectance spectrum corroborate the grain boundary influence.Raman spectrum and the morphological analysis by using a field emission scanning electron microscope(FESEM) also indicate the formation of grain boundaries.The compositional analysis by using energy dispersive x-ray spectrum(EDAX) confirms Fe in the SnO_(2) lattice.The conductivity studies exhibit that the impendence increases with doping concentration increasing and the loss factor decreases at high frequencies with doping concentration increasing,which makes the Sn_(1-x)Fe_(x)O_(2) a potential candidate for device applications.

Morphology and strain control of hierarchical cobalt oxide nanowire electrocatalysts via solvent effect

Designing highly efficient and low-cost electrocatalysts for oxygen evolution reaction is important for many renewable energy applications.In particular,strain engineering has been demonstrated as a powerful strategy to enhance the electrochemical performance of catalysts;however,the required complex catalyst preparation process restricts the implementation of strain engineering.Herein,we report a simple self-template method to prepare hierarchical porous Co_(3)O_(4)nanowires(PNWs)with tunable compressive strain via thermal-oxidation-transformation of easily prepared oxalic acid-cobalt nitrate(Co(NO_(3))_(2))composite nanowires.Based on the complementary theoretical and experimental studies,the selection of proper solvents in the catalyst preparation is not only vital for the hierarchical structural evolution of Co_(3)O_(4) but also for regulating their compressive surface strain.Because of the rich surface active sites and optimized electronic Co d band centers,the PNWs exhibit the excellent activity and stability for oxygen evolution reaction,delivering a low overpotential of 319 mV at 10 mA·cm^(−2)in 1 M KOH with a mass loading 0.553 mg·cm^(−2),which is even better than the noble metal catalyst of RuO_(2).This work provides a cost-effective example of porous Co_(3)O_(4)nanowire preparation as well as a promising method for modification of surface strain for the enhanced electrochemical performance.

Strain Engineering for the Kapitza Resistance of the ZrO_(2)/α-Al_(2)O_(3)and YSZ/α-Al_(2)O_(3)Interfaces

The Kapitza resistance is of fundamental importance for the thermal stability of the interface between the ceramic top coat and the thermal growth oxide layer in the thermal barrier coating structure,which is widely used to protect high-temperature components in current gas turbine engines.The top coat typically consists of the ZrO_(2)partially stabilized by 8%Y2O3(YSZ),and the main component of the thermal growth oxide isα-Al_(2)O_(3).In this work,the Kapitza resistance is found to be a small value of 0.69 m^(2)K/GW for the YSZ/α-Al_(2)O_(3)interface based on the heat dissipation simulation method.It indicates that the localization of thermal energy is rather weak,which is beneficial for the thermal stability of the YSZ/α-Al_(2)O_(3)interface.This Kapitza resistance can be further reduced to 0.50 m^(2)K/GW by a mechanical or thermal compressive strain of 8%.To explore the underlying mechanism for this strain effect,we analyze the phonon vibration and the microscopic deformation in the interface region.It is revealed that the interface becomes denser through the compression-induced twisting of some Al-O_(zr)and A1-O_(Al)chemical bonds in the interface region,which is responsible for the reduction in the Kapitza resistance.The temperature effect and crystal size effect on the Kapitza resistance of the YSZ/α-Al_(2)O_(3)interface are also systematically studied.These findings shall provide valuable information for further understanding of the thermal conductivity and thermal stability of the thermal barrier coating structures.

A method to access the electro-mechanical properties of superconducting thin film under uniaxial compression

Superconducting thin films are widely used in superconducting quantum interferometers,microwave devices,etc.The electrical performance of a superconducting thin film is often affected by structural deformation or stress.Based on four-point bending of a Cu-Be beam,we constructed a device that could apply uniaxial,uniform.compressive strain to a superconducting thin film at both room temperature and the temperature of liquid nitrogen.The thin film was placed into a slot carved in the Cu-Be beam.We optimized the size of this slot via numerical simulation.Our results indicated that the slot width was optimal when it was same as the width of the Cu-Be beam.Notably,the sample bended hardly after machining two slits along width direction on both sides of the slot.A YBa2Cu3O7-δSrTiO3(YBCO-STO)film was used as an example.It was loadedby the aforementioned device to determine its electrical characteristics as functions of the uniaxial-uniform-compressive strain.The optimized design allowed the sample to be compressed to a larger strain without breaking it.

Beam multiplexing of diode laser arrays

Design and experimental studies on the wavelength multiplexing and polarization multiplexing of diode laser arrays were carried out. First, the structure of a A1GalnAs/GaAs/AIGaAs quantum well under compressive strain was used because the characteristic of wavelength was easier to adjust. We obtained diode laser arrays lasing in five different wavelengths, about 760 nm, 800 nm, 860 nm, 930 nm, and 976 nm. At the same time, four edge filters were designed, and an experimental study on the beam multiplexing of diode laser arrays was carried out. Second, two beams with different polarization states were composited using a half wave plate and a polarizing beam-splitter prism. After that, the beam focusing system was designed. Ultimately, ten beams of diode laser arrays in five wavelengths and two polarization states were composited, the total output power was 196 W and the overall efficiency was 76%. The size of the output focus spot was 144 × 1330μm2, and the power density of the focused light was as high as 1.02 ×105 W/cm2. Compared with a single diode laser array, the power density of the composite beam was improved by 4.3 times.

TEMPERATURE SENSITIVITY AND PREDICTION OF THE MECHANICAL BEHAVIORS OF ULTRAFINE GRAINED ALUMINUM UNDER UNIAXIAL COMPRESSION

In the present work, we explore the strain hardening behaviors as well as the effect of temperature on the plastic deformation of ultrafine grained aluminum. The temperature sensitivity is determined and compared with that of coarse grained material. The results indicate that the flow stress of ultrafine grained aluminum displays enhanced sensitivity to temperature. The reduction in activation volume is suggested to be the major reason for the enhanced temperature sensitivity as grain size is refined into the sub-micrometer regime. Finally, a phenomenological constitutive model is proposed to describe the post-yield response of ultrafine grained aluminum.

Effect of deformation parameters in unrecrystallization range on microstructural characteristics in Al-bearing hot-rolled TRIP steel

The scanning electron microscope,transmission electron microscope,optical microscope,X-ray diffraction and hardness tests were used to investigate the effect of deformation parameters in unrecrystallization range on microstructural characteristics in Al-bearing hot-rolled transformation-induced plasticity steel.The thermomechanical-controlled processing was carried out with thermomechanical simulation machine,and the samples were compressed to compression strains of 0,0.15,0.25 and 0.35 at compression temperatures of 850,900 and 950°C.The results showed that the volume fraction of polygonal ferrite increased with the increasing compression strain,while the volume fraction of retained austenite reached the maximum value at compression strain of 0.25.The volume fraction of polygonal ferrite decreased with the increasing compression temperature,whereas the volume fraction of retained austenite possessed the maximum value at compression temperature of 850°C.Some granular retained austenite was present in uncompressed samples,and some pearlite appeared at large compression strain,while the hardness of the samples exhibited the similar variation tendency to the volume fraction of retained austenite.

Multi-Pass Simulation of Heavy Plate Rolling Including Intermediate Forced Cooling

Thermomechanical Controlled Processing (TMCP) including accelerated cooling after the final hot rolling pass is a well-established technology,widely applied in HSLA steel plate production.However,there are still certain limitations,especially for thicker plate.The rolling schedule includes a long holding period (HP) after the roughing stage to allow the temperature to fall sufficiently for optimised TMCP during finishing.Intermediate Forced Cooling (IFC) applied during the HP can increase productivity by decreasing the required hold time,can restrict austenite grain growth,and can also improve the subsequent strain penetration in thick plate with further metallurgical benefits.Multi-pass plane strain compression (PSC) tests have been performed on the thermomechanical compression (TMC) machine at Sheffield University including different severities of IFC.Clearly it is impossible to simulate all aspects of the temperature and strain gradients present in thick plates in laboratory specimens,and most of the tests were conducted at temperatures and strains calculated by Finite Element modelling as relevant to specific positions through the plate thickness.However,some aspects of the gradients were addressed with tests using cold platens.The results have indeed shown that IFC can shorten the HP and reduce austenite grain growth and its variation across thick plate.