Compressive Strain Research Articles

Substrate-induced strain upshot on the optical and optoelectronic properties of trilayer MoS2.

The characteristics of 2D layered MoS2 film are highly dependent on the substrate it is grown on which leaves us privileged to achieve unique and tunable properties. In this study, trilayer MoS2 films have been grown on fused quartz, crystalline quartz (z-cut), sapphire (0001), and silicon (100) substrates. MoS2 film grows as freestanding on amorphous fused quartz, while it experiences an in-plane tensile strain on the sapphire and silicon. Unprecedentedly we show that due to a large mismatch in the lattice parameter as well as in the thermal expansion coefficient, MoS2 grows with a significant compressive strain both along both in-plane on the crystalline quartz. The developed strain causes an alteration in its electronic structure, causing a 30 meV blue shift in the photoluminescence peak and an increased band gap in addition to fewer sulphur vacancies. Comparatively, the film on sapphire having tensile strain along the in-plane exhibits more sulphur vacancies increasing the electron density. The photoresponse time, photosensitivity, and charge separation distinctly vary for the MoS2 films depending on the substrates. This study underscores the influence of substrate on MoS2 film opening further research scopes on tunable properties owing to 2D layer-substrate interactions.

Band gap engineering and photoelectronic properties of novel pentagonal materials penta-XN2 (X = Ni, Pt): a first principle calculations

Abstract Two-dimensional pentagonal materials as the next-generation nanoelectronic devices are promising candidates due to their interesting structures and novel electronic, mechanical, optical and other properties. Penta-NiN2, a newly synthesized material with pentagonal atomic arrangement under high pressure (ACS Nano 15 (2021), 13 539), has also sparked considerable interest. This study systematically investigates the effects of the biaxial strain on the electronic structure of monolayer penta-NiN2 (penta-PtN2). Furthermore, combining the non-equilibrium Green’s function approach, we research the optoelectronic and transport properties of penta-NiN2 (PtN2). The results indicate that biaxial strain can effectively modulate the bandgap of penta-NiN2 (PtN2), particularly achieving a semiconductor-to-metal transition under compressive strain. Moreover, tensile and compressive strains effectively enhance the optical characteristics of penta-NiN2 (PtN2) in visible light range. Under tensile and compressive strains, the absorption peak of penta-NiN2 shows a red shift and a blue shift in visible region, respectively. The pin-junction photodiode of penta-NiN2 (PtN2) exhibit significant photocurrent under illumination. The strongest photocurrent is observed in penta-NiN2 photodiodes under −3% compressive strain, showing the highest response to yellow light. Under the tensile stress of 7% and compressive stress of −3%, the photocurrent of the Penta-PtN2 photodiode is enhanced in the yellow and green light regions. Additionally, applying compressive strain reduces the bandgap of penta-NiN2 (PtN2), significantly enhancing its transport properties and thereby inducing a switch effect in devices. In summary, our study demonstrates that penta-XN2 (X = Ni, Pt) is a promising material in the fields of nanoelectronics and optoelectronic devices.

Programmable Shape-Morphing Enables Ceramic Meta-Aerogel Highly Stretchable for Thermal Protection.

Ceramic aerogels hold significant potential for thermal insulation, yet their mechanical stretchability and thermal stability fall short in extreme environments. Here, the study presents a programmable shape-morphing strategy aimed at engineering a binary network topology structure within ceramic aerogels to effectively dissipate stress and block heat transfer. The special topology design, which includes kirigami lamellated aerogels for bearing loading stress and randomly assembled aerogels for mechanical energy pre-storage to transfer tensile stress, effectively achieves unexpected mechanical tensile properties and thermal stability. The resulting robust meta-aerogels demonstrate remarkable structural stability with topology-derived mechanical tensile of up to 85% strain, excellent resilience to 500 cycles of 50% tensile strain, 1000 cycles of 60% buckling strain, and 500 cycles of 50% compressive strain, temperature-invariant tensile recovery capability; simultaneously, low thermal conductivity of 33.01mW m-1 K-1 and tensile-invariant thermal insulation makes the ceramic meta-aerogels an ideal substitute material for various applications.

Effect of Precipitation Heat Treatment on a Mechanically Alloyed Al‐Based Composite Reinforced with Metallic Glassy Powder

An Al‐based composite reinforced with titanium‐based metallic glassy particles is synthesized by the powder metallurgy method through mechanical alloying followed by hot extrusion. The effect of precipitation heat treatment on the structure and properties of the composite is studied. During aging of the solution‐treated composite, crystallization of the metallic glassy reinforcement becomes more pronounced as the solutionizing temperature, solutionizing time, aging temperature, and aging time increase. A reaction layer has formed at the interface between the reinforcement and the matrix after the aging treatment. It is found that the addition of metallic glassy particles promotes precipitation of the nanophase in the matrix. With appropriate heat treatment, the compressive strength, yield strength, and fracture strain of the composite have increased to 942, 635 MPa, and 27%, respectively. Herein, it is demonstrated that the mechanical properties of these composites can be further enhanced through an appropriate heat treatment process, thereby having significant potential for a variety of industries, including aerospace, automotive, and defense, where high‐strength, lightweight materials are critical for performance and safety.

Promising 2D Carbon Allotropes with Intrinsic Bandgaps Based on Bilayer α‐Graphyne

2D carbon allotropes with moderated electronic bandgaps are highly desirable for next‐generation carbon‐based nanoelectronics beyond graphene. Herein, the structural and electronic properties of bilayer α‐graphyne have been systematically investigated by using first‐principles calculations. Consequently, in addition to typical van der Waals (vdW) stacks of single‐layer α‐graphyne, new 2D carbon allotropes with purely sp2 or sp3 hybridizations can be achieved, arising from the absence of intralayer acetylene linkages during structural relaxation. Compared to the Dirac semimetallic behavior of monolayer α‐graphyne, the electronic structure of vdW bilayer α‐graphyne can be further modulated by stacking patterns, yet retains metallic characteristics. In contrast, intrinsic semiconducting characteristics can be observed in the proposed new 2D carbon allotropes with tunable bandgaps dependent on the in‐plane biaxial strain. Correspondingly, a pristine 2D carbon sheet with only sp2 hybridization exhibits a promising direct bandgap of 1.062 eV, while the sp3‐hybridized carbon network possesses an indirect bandgap of 1.708 eV, which can be further converted to the direct type under small compressive strains, implying great potential in future carbon‐based nanoelectronic applications beyond graphene. Also, this work provides a new approach for developing novel carbon allotropes via the vertical stacking of graphyne with acetylenic linkages.

Insights into the Influence of Tensile and Compressive Strain on the Microstructure and Corrosion Performance of 304 L Stainless Steel

The effects of tensile and compressive strain, originating from U-bent deformation, on the corrosion behavior of 304 L stainless steel were studied via analyses of the material’s microstructure and electrochemistry in a 3.5% NaCl solution. In contrast with the as-received 304 L steel with the largest grain size, the deformed 304 L material with a small grain size had the lowest number of Σ3 grain boundaries and an overall low fraction, with special low-Σ values (≤29). Moreover, the dislocation density increased to 1.13 × 1016/m2 and 1.4 × 1016/m2 for the tensile and compressive 304 L steel testing, respectively. The decrease in Epit and increase in ipit suggested that there was a decrease in anti-corrosion properties due to tensile and compressive deformation. This might be attributed to the higher plastic strain found in deformed 304 L steel, which can induce the rupture of passive film and have a harmful influence on corrosion resistance. In particular, the compressive 304 L steel with the highest content of deformed grains (42.12%) promoted the formation of microgalvanic cells, thereby facilitating the nucleation of pits. Then, these pits grew to a large size through grain shedding. Subsequently, massive chloride ions were generated during metal dissolution and diffused along grain boundaries, which promoted the initiation and propagation of intergranular corrosion cracks.

Impact of Electric Field and Biaxial Strain on the Structural, Phonon, and Optical Features of Bulk and Monolayer Potassium Nitride

First-principles calculations are used within the framework of density functional theory to investigate the electronic, structural, magnetic and optical properties of Potassium Nitride (KN) in the bulk and monolayer states. This compound is dynamically stable according to phonon calculations. The results show that the energy gap decreases from the bulk to the monolayer. The equilibrium lattice constant increases when changing from bulk to monolayer, and the half-metallic (HM) character remains preserved in that case. According to the Slater–Pauling statute (Zt-4), the total magnetic moment equals 2 µB per unit cell. The electric field and biaxial strain affect the monolayer's electronic and magnetic characteristics were investigated. The magnitude of the spin-up channel concerning the energy gap changes under the biaxial strain. In particular, it decreases under tensile strain and increases under compression strain. Given that the values of magnetic moments remain unchanged, the HM property can be preserved for significant strains. When the electric field reaches -0.6 V/nm, the half-metallic property of this compound will be destroyed. It affects the energy gap and eliminates the HM trait since the magnetic moment of the K grew significantly greater than the moment of the N, and the N played a significant role in the realization of the half-metallic characteristic.

ZrS2/Ga2SSe heterojunction: A direct Z-scheme heterojunction with excellent photocatalytic performance across the entire pH range and high solar-to-hydrogen efficiency

Developing photocatalytic water splitting materials for hydrogen production is a crucial strategy for achieving sustainable energy utilization. This study proposes a ZrS2/Ga2SSe van der Waals heterojunction and conducts an in-depth analysis through first-principle calculations. The results show that the heterojunction possesses an indirect bandgap of 1.33 eV, which contributes to its superior optical performance. Its band structure and built-in electric field promote the Z-scheme electron transfer mechanism. High carrier mobility in the heterojunction improves photocatalytic efficiency. Strain engineering further enhances its electronic and optical properties, allowing water splitting across all pH levels within a biaxial strain range of −4% to +2%. Under a −6% compressive strain, there is a 63.06% enhancement in optical performance within the visible light spectrum, and the solar-to-hydrogen efficiency reached 10.93%. Gibbs free energy analysis indicates that the hydrogen evolution reaction, powered by photogenerated electrons, requires only 0.19 eV of energy. Therefore, the ZrS2/Ga2SSe heterojunction is identified as a promising visible-light-driven catalyst for water splitting.

Experimental and Numerical Analysis of PIP Slip Joint Subjected to Bending

Detachable circular hollow sections (CHSs) offer an innovative solution to tackle the complexities of installation, maintenance, upgrades, and repairs in offshore monopile systems, particularly in challenging environments with limited access. As an alternative to traditional tubular joints, the PIP slip joint presents advantages in terms of ease of installation, time efficiency, and reduced susceptibility to failure. This study conducts an experimental investigation on PIP (Pile-in-Pile) slip joints under pure bending conditions, accompanied by comprehensive numerical analyses to examine the relationship between section slenderness, contact properties, and structural performance. The results highlight a strong correlation between force-displacement curves and include a comparison of compressive and tensile strain values for both experimental and numerical models. The experimental and numerical models showed strong agreement across all results, demonstrating the robustness of the findings. Additionally, numerical models were utilized to investigate various D/t ratios, revealing insights into the normalized moment, rotational capacity, and the impact of local buckling and contact mechanics. Furthermore, a comparison of these findings with established code guidelines, such as Eurocode and AISC-LRFD, has been conducted and reviewed in the context of this study. From analysis, it was found that the rise in the D/t ratio prompted a transformation in the buckling mode, which substantially altered the rotational ratio. This shift indicates the importance of understanding how these variables interact in engineering applications. These findings significantly enhance the understanding of PIP slip joints and emphasize their potential as a compelling alternative for offshore wind turbine support structures.

Effect of Compressive Strain Rates on Viscoelasticity and Water Content in Intact Porcine Stomach Wall Tissues.

Laparoscopic staplers are used extensively to seal and transect tissue. These devices compress tissue between the stapler jaws to achieve a desired compressed tissue thickness in preparation for stapling. The extent and rate of compression are dependent on surgeon technique, tissue characteristics, and stapler type, all of which can impact stapling outcomes such as bleeding, staple line leaks, and tissue healing. Historically, surgeons have relied on their experience, training, and tactile feedback from the device to optimize stapling. In recent years, the transition to electromechanical and robotic staplers has greatly impacted the tactile feedback available to the surgeon. This raises new questions about the optimal rates of tissue compression and the resultant tissue forces. This study quantifies the transmural biomechanics of the porcine stomach wall. Multi-rate indentation tests were used to observe the effects of indentation rate on the viscoelastic behavior of the stomach tissue during indentation, stress relaxation, and unconstrained recovery. Results show that the stomach wall demonstrates higher stress relaxation (88% vs 80%) and greater strain recovery (52% vs 47%) when indented at high rates (37.5%/s) vs slow rates (7.5%/s). Additionally, water content analysis was used to study fluid flow away from indented regions. Unindented regions were found to have greater water content compared to indented regions (78% compared to 75%). This data generated in this study may be used to enable the development of constitutive models of stomach tissue, which in turn may inform the control algorithms that drive compressive surgical devices.

Nanoscale Identification of Local Strain Effect on TMD Catalysis.

Strain engineering plays a crucial role in activating the basal plane of the TMD catalysts. However, experimental evidence linking strain strength to activity and distinguishing effects of compressive and tensile strain remains elusive due to the absence of high-resolution in situ correlation techniques. Here, we utilize nanobubble imaging by on-chip total-internal reflection microscopy to visualize active sites on the basal plane of strained MoS2 during hydrogen evolution reaction and atomic force microscopy to correlatively capture the nanoscale morphology and strain maps. By integrating the activity, morphology, and strain maps into comprehensive statistical analyses, we elucidate the strain effect on local activity at both multiprotrusion and (sub)single-protrusion levels. Our findings demonstrate that strain effectively activates sulfur vacancies on the basal plane, with tensile strain significantly enhancing local activity compared to compressive strain. Furthermore, we observe a time-dependent propagation of activity from high-activity to low-activity regions within single protrusions. This work clarifies the interplay between structural morphology and catalytic activity and provides new guidelines for the rational design of optimal TMD catalysts.

Superconductivity and strain-enhanced phase stability of Janus tungsten chalcogenide hydride monolayers

Janus transition metal-dichalcogenide materials have attracted a great deal of attention due to their remarkable physical properties arising from the two-dimensional geometry and the breakdown of the out-of-plane symmetry. Using first-principles density functional theory, we investigated the phase stability, strain-enhanced phase stability, and superconductivity of Janus WSeH and WSH. In addition, we investigated the contribution of the phonon linewidths from the phonon energy spectrum responsible for the superconductivity and the electron-phonon coupling as a function of phonon wave vectors and modes. Previous work has examined hexagonal 2H and tetragonal 1T structures, but we found that neither is a ground-state structure. The metastable 2H phase of WSeH is dynamically stable with Tc≈11.60K, similar to WSH. Compressive biaxial strain—the two-dimensional equivalent of pressure—can stabilize the 1T structures of WSeH and WSH with Tc≈9.23K and 10.52 K, respectively. Published by the American Physical Society 2024

Superhydrophobic, Multifunctional, and Mechanically Durable Carbon Aerogel Composites for High-Performance Underwater Piezoresistive Sensing.

Carbon aerogel piezoresistive sensors (CAPSs), owing to their good thermal stability, self-constructed conductive network, and fast response to pressure, have attracted extensive attention in the field of flexible and wearable electronics in recent years. However, it is still a great challenge for CAPSs to monitor subtle deformations and achieve high-performance underwater piezoresistive sensing. Herein, a superhydrophobic and electrically conductive carbon aerogel composite (CAC) was fabricated by the combination of fluorination of carbon aerogels and decoration of fluorinated halloysite nanotubes (HNTs). Due to the exceptional light absorption and excellent photothermal conversion performance, CAC has a fast and accurate response to temperature with a high-temperature coefficient of resistance (TCR) of -1.06%/°C. The resistance of CAC exhibits a linear response toward compressive strain up to 80% with a high gauge factor of -1.24. Significantly, the CAC sensor can effectively detect tiny deformations, thanks to its excellent waterproof performance, and it enables stable output of sensing signals in an underwater environment. This work provides new insights into the development of superhydrophobic, multifunctional, and mechanically durable piezoresistive sensors with potential applications in underwater flexible electronics.

Behavior of a defect in a flexible carbon nanotube

Abstract Carbon nanotubes (CNTs) play an indispensable role in the design and application of flexible devices due to their unique physical and chemical properties. ‌This study theoretically investigates the behavior of defects in bent CNTs. The results indicate that when the defect is under compressive strain, the conductance of the device decreases as the bending angle increases. Conversely, when the defect is under tensile strain, the conductance of the device increases with a larger bending angle.This phenomenon is primarily attributed to the enhancement of scattering states corresponding to the defect under tensile strain and the weakening of these states under compressive strain. Under bias voltage, similar patterns are observed for transmission peaks corresponding to the defect. These findings contribute to the device design process, enabling the exploitation of advantages and avoidance of disadvantages, ultimately leading to the development of flexible CNTs- devices.‌

Highly Elastic, Fatigue-Resistant, and Antifreezing MXene Functionalized Organohydrogels as Flexible Pressure Sensors for Human Motion Monitoring.

Conductive organohydrogels-based flexible pressure sensors have gained considerable attention in health monitoring, artificial skin, and human-computer interaction due to their excellent biocompatibility, wearability, and versatility. However, hydrogels' unsatisfactory mechanical and unstable electrical properties hinder their comprehensive application. Herein, an elastic, fatigue-resistant, and antifreezing poly(vinyl alcohol) (PVA)/lipoic acid (LA) organohydrogel with a double-network structure and reversible cross-linking interactions has been designed, and MXene as a conductive filler is functionalized into organohydrogel to further enhance the diverse sensing performance of flexible pressure sensors. The as-fabricated MXene-based PVA/LA organohydrogels (PLBM) exhibit stable fatigue resistance for over 450 cycles under 40% compressive strain, excellent elasticity, antifreezing properties (<-20 °C), and degradability. Furthermore, the pressure sensors based on the PLBM organohydrogels show a fast response time (62 ms), high sensitivity (S = 0.0402 kPa-1), and excellent stability (over 1000 cycles). The exceptional performance enables the sensors to monitor human movements, such as joint flexion and throat swallowing. Moreover, the sensors integrating with the one-dimensional convolutional neural networks and the long-short-term memory networks deep learning algorithms have been developed to recognize letters with a 93.75% accuracy, representing enormous potential in monitoring human motion and human-computer interaction.

Strain Effects and Crystalline-Amorphous Interface of NiFe-LDH@S-NiFeOx/NF with Heterogeneous Structure for Enhancing Electrocatalytic Oxygen Evolution Reaction of Water-Electrolysis.

Electrochemical water-electrolysis for hydrogen generation often requires more energy due to the sluggish oxygen evolution reaction (OER). This work introduces a double-layered nanoflower catalyst, NiFe-LDH@S-NiFeOx/NF, featuring a crystalline NiFe-LDH coating on amorphous S-NiFeOx on nickel foam. Strategically integrating a crystalline-amorphous (c-a) heterostructure leverages strain engineering to enhance OER activity with low overpotentials (η100 = 220 and η500 = 245mV) and stability (135 h at η100 and 80 h at η500). Theoretical density functional theory (DFT) calculations reveal that the compressive strain can optimize the adsorption of oxygen-containing intermediates to reduce the reaction energy barrier, thus improving the reaction kinetics and performance of OER. Moreover, its phosphated derivative, NiFeP@S-NiFeOx/NF, exhibits high hydrogen evolution reaction (HER) performance (η10 = 64mV, η100 = 187mV). An alkaline water-electrolysis cell of NiFeP@S-NiFeOx/NF(-)||NiFe-LDH@S-NiFeOx/NF(+) requires only a cell voltage of 1.77V at 100 mA cm-2, demonstrating excellent stability over 110 h (at both 10 and 100mA cm-2). This work highlights the benefits of integrating crystal-amorphous interfaces and strain effects, offering insights into the understanding and optimizing catalytic OER mechanism and advancing water-electrolysis technology.

Shape Memory Polyurethane Foams With Tunable Mechanical Properties and Radiation Tolerance for Breast Repair and Reconstruction.

This study developed a shape memory polyurethane foam (SM-PUF) with tunable mechanical properties and exceptional radiation tolerance for potentially implanting tissue defects after mastectomy. The PUFs were synthesized via an insitu foaming strategy using water as a foaming agent, incorporating 4,4'-diphenylmethane diisocyanate (MDI) as the rigid segment and both polyoxytetramethylene glycol and polycaprolactone as the soft segment. The resultant PUFs possess an open-cell structure with a pore size of 30 ~ 800 μm, which achieves a compressive stress of 0.04 MPa under 70% compression strain and a tensile elongation of 667.9%. PUFs exhibit body temperature (37°C)-responsive softening and shape memory abilities, with recovery and fixation ratios reaching 88% and 98%, respectively. It was verified that PUFs can resist 40 Gy radiotherapy without changing their mechanical properties and biocompatibility. This study introduces an innovative approach to produce customizable foam for the reconstruction of implant prostheses for the breast.

First-principles studies of strain-tunable InN monolayer: applications for switching and optoelectronic devices

Abstract Two-dimensional (2D) materials are attracting significant attention for their potential applications in the post-Moore era. In this work, we systematically investigate the effect of strains on the electronic structure, transport and optoelectronic properties of 2D Indium nitride (InN) monolayer using density functional theory and non-equilibrium Green’s function methods. The results show that strains can modulate the electronic properties. Specifically, biaxial strain triggers the transition from semiconductor to metal and indirect to direct band gap. On this basis, the constructed InN-based nanodevice exhibits current switching ratios up to 1010. In addition, the optoelectronic device based on InN monolayer exhibits a robust photoelectric response in the red light. Meanwhile, biaxial strain can improve the optoelectronic performance of InN-based optoelectronic devices. The compressive strains blue-shift the photocurrent peaks of the InN monolayer, which effectively modulates its detection range in the visible light region. These findings underscore the potential applications in nanotechnology, particularly in nano-switches and optoelectronic devices.

First Principles Study of Bismuth Vacancy Formation in (111)-Strained BiFeO3

Epitaxial strain is known to significantly influence the structural and functional properties of oxide thin films. However, its impact on point defect concentration has been less explored. Due to the challenges in experimentally measuring thin-film stoichiometry, computational studies become crucial. In this work, we use first-principles calculations based on density functional theory to investigate the formation and stability of Bi vacancies and Bi-O vacancy pairs in BiFeO3 (BFO) under (111) epitaxial strain. Our results demonstrate that compressive strain (−4%) decreases the formation enthalpy of Bi vacancies by 0.88 eV, whereas tensile strain (4%) increases it by 0.39 eV. Out-of-plane (OP) Bi-O vacancy pairs exhibit enhanced stability under both compressive and tensile strain, with formation enthalpy reductions of 1.49 eV and 1.05 eV, respectively. In contrast, in-plane (IP) vacancy pairs are stabilized under compressive strain but are insensitive to tensile strain. Finally, we discuss how these findings influence Bi stoichiometry during thin-film growth and the role of local strain fields in the formation of conducting domain walls.

Evolution of metallicity, enhancement of [formula omitted] and magnetic anisotropy energy in Y[formula omitted]NiIrO[formula omitted]: Hydrostatic ([111]) strain influence

Ir-based double perovskite oxides (DPO) provide a distinct electronic and magnetic behavior due to entanglement among lattice distortion, strong electron correlation, and spin–orbit coupling (SOC). In this work, we investigated the hydrostatic ([111]) strain impact on the physical properties of the Y2NiIrO6 DPO using ab-initio calculations. Unstrained motif displayed the ferrimagnetic (FiM) spin state owing to strong antiferromagnetic (AFM) interactions between Ni↑ and Ir↓ ions, further confirmed by the computed partial spin magnetic moments and 3D spin-magnetization density iso-surfaces plots. A Mott-insulating state is established with an energy band gap (Eg) of 0.43 eV due to the existence of a rare Ir+4 state having Jeff.=12 and a Curie temperature (TC) of 198 K using the Heisenberg Hamiltonian model, which is up to the experimental observations. The easy magnetic axis is the [010] (b-axis) having a giant magnetic anisotropy energy (MAE) constant of 1.7 × 108 erg/cm3. Moreover, it is predicted that strain holds the FiM spin order as a magnetic ground state for the considered range of ±8%. Notably, an electronic transition from Mott-insulating to a metallic state is established at a critical compressive strain of −8%, where the admixture of Ir 5d states appears at/around the Fermi level. On the other hand, Eg solely increases with the increase of tensile strain amplitude. Due to strong and weak hybridization, the spin/orbital magnetic moment value is reduced and enhanced as a function of compressive and tensile strains, respectively. Along with this, it is found that MAE/TC increases to 25%/18% and 15%/10% at −8% compressive and ＋8% tensile strains due to larger structural distortion than that of the unstrained one, which enhances the system potential for magnetic memory devices.