Application Of Tensile Strain Research Articles

High intrinsic dissipation of graphyne nanotubes

We utilize molecular-dynamics simulations to report the first investigation of energy dissipation of two different doubly clamped graphyne nanotubes (GNTs), where the point of emphasis is to compare their dissipation characteristics with those of carbon nanotube (CNT). The obtained results demonstrate that: (a) GNTs exhibit significantly higher energy dissipation, and thus lower quality (Q) factor which is generally five times lower than that of CNT; (b) the Q factor of GNT further reduces with the increasing percentage of acetylenic linkages, which originates from the larger vibrational mismatch between the acetylenic linkage (sp C-C bonds) and the hexagonal ring (sp2 C-C bonds); (c) the application of tensile strain is found to be highly beneficial to improving the Q factor of GNTs, especially for those with higher percentage of acetylenic linkages. These findings enable a first insight into the damping behavior of GNTs and also offer a significant guideline for the future design of GNT-based devices.

Computational exploration of two-dimensional silicon diarsenide and germanium arsenide for photovoltaic applications.

The properties of bulk compounds required to be suitable for photovoltaic applications, such as excellent visible light absorption, favorable exciton formation, and charge separation are equally essential for two-dimensional (2D) materials. Here, we systematically study 2D group IV–V compounds such as SiAs2 and GeAs2 with regard to their structural, electronic and optical properties using density functional theory (DFT), hybrid functional and Bethe–Salpeter equation (BSE) approaches. We find that the exfoliation of single-layer SiAs2 and GeAs2 is highly feasible and in principle could be carried out experimentally by mechanical cleavage due to the dynamic stability of the compounds, which is inferred by analyzing their vibrational normal mode. SiAs2 and GeAs2 monolayers possess a bandgap of 1.91 and 1.64 eV, respectively, which is excellent for sunlight harvesting, while the exciton binding energy is found to be 0.25 and 0.14 eV, respectively. Furthermore, band-gap tuning is also possible by application of tensile strain. Our results highlight a new family of 2D materials with great potential for solar cell applications.

MoS2 edges and heterophase interfaces: energy, structure and phase engineering

The transition metal dichalcogenides exhibit polymorphism; i.e. both 2H and 1T′ crystal structures, each with unique electronic properties. These two phases can coexist within the same monolayer microstructure, producing 2H/1T′ interfaces. Here we report a systematic investigation of the energetics of the experimentally most important MoS2 heterophase interfaces and edges. The stable interface and edge structures change with chemical potential (these edges/interfaces are usually non-stoichiometric). Stable edges tend to be those of highest atomic density and the stable interfaces correspond to those with local atomic structure very similar to the 2H crystal. The interfacial energies are lower than those of the edges, and the 1T′ edges have lower energy than the 2H edges. Because the 1T′ edges have much lower energy than the 2H edges, a sufficiently narrow 1T′ ribbon will be more stable than the corresponding 2H ribbon (this critical width is much larger in MoTe2 than in MoS2). Similarly, a large 2H flake have an equilibrium strip of 1T′ along its edge (again this effect is much larger in MoTe2 than in MoS2). Application of tensile strains can increase the width of the stable 1T′ strip or the critical thickness below which a ribbon favors the 1T′ structure. These effects provide a means to phase engineer transition metal dichalcogenide microstructures.

Surface-dominated conduction up to 240 K in the Kondo insulator SmB6 under strain.

SmB6 is a strongly correlated mixed-valence Kondo insulator with a newly discovered surface state, proposed to be of non-trivial topological origin. However, the surface state dominates electrical conduction only below T∗ ≈ 4 K (ref.), limiting its scientific investigation and device application. Here, we report the enhancement of T∗ in SmB6 under the application of tensile strain. With 0.7% tensile strain we report surface-dominated conduction at up to a temperature of 240 K, persisting even after the strain has been removed. This can be explained in the framework of strain-tuned temporal and spatial fluctuations of f-electron configurations, which might be generally applied to other mixed-valence materials. We note that this amount of strain can be induced in epitaxial SmB6 films via substrate in potential device applications.

Magnetic modeling and effect of biaxial strain on the Haldane chain compoundSrNi2V2O8

Using combination of first-principles density-functional theory and quantum Monte Carlo technique we study the magnetic behavior of $S=1$ spin chain compound ${\mathrm{SrNi}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{8}$. The magnetic model, derived in a first-principles Wannier function basis, shows the presence of finite next-neighbor intrachain coupling, in addition to interchain couplings, thereby deviating from the ideal Haldane chain description. The computed single-ion anisotropy turns out to be of easy axis type and of appreciable magnitude. Solution of the first-principles derived spin model confirms the spin-gapped ground state of the compound. The spin gap is found to close at a critical value of magnetic field, which is estimated to be much reduced compared to that of an ideal Haldane chain. Our study highlights the effectiveness of the next-nearest-neighbor intrachain coupling in reducing the spin gap from the ideal Haldane chain limit. Further study on the effect of biaxial strain on the magnetic behavior predicts that the application of tensile strain should enable the closing of the spin gap in the ground state.

Strain-controlled nanocrack formation in a Pd film on polydimethylsiloxane for the detection of low H2 concentrations

We report quantitative nanocrack formation upon adjusting the mechanical tensile strain applied to a Pd thin film on an elastomeric polydimethylsiloxane (PDMS) substrate and its detection properties for H2 gas in air. Nanocrack formation in Pd/PDMS substrates was controlled through the application of tensile strains that varied in the range 30–120 % during mechanical stretching/compression. This method can be used to modulate nanocrack formation along both the x- and y-axes over a large area. Increasing the applied tensile strain to 90 % induced the appearance of horizontal cracks along the y-axis in addition to an increased number of vertical cracks along the x-axis. When the strain reached 120 %, ordered nanocracks abundantly propagated on the Pd surface in both the directions. Gas detection properties were dramatically enhanced, with a very low detection limit of 50 ppm H2 in air observed for 120 % strain. This was attributed to the large surface area in the Pd nanocrack pattern, which readily allowed for volume expansion. These results provide a simple mechanism for controlling the detection properties of H2 gas sensors with low detection limits in air.

Tailoring percolating conductive networks of natural rubber composites for flexible strain sensors via a cellulose nanocrystal templated assembly.

Conductive polymer composites (CPCs) just above the percolation threshold exhibit a unique strain-reversible electric response upon application of tensile strain, which can be used to prepare strain sensors. However, it is difficult to balance the electric conductivity which is fundamental to a stable output signal and the strain sensing sensitivity due to the relatively dense conductive pathways of the traditional CPCs. Constructing a "brittle" but effective conductive network structure in CPCs is the essential foundation of a desirable sensing material. Here, we demonstrate for the first time that highly flexible, stretchable, sensitive, and reversible strain sensors can be fabricated by a facile latex assembly approach, in which nontoxic, sustainable and biodegradable cellulose nanocrystals played a key role in tailoring the percolating network of conductive natural rubber (NR)/carbon nanotube (CNT) composites. The resulting nanocomposites with a continuous 3D conductive structure exhibited a very low electrical conductivity percolation threshold (4-fold lower than that of the conventional NR/CNT composites), high resistivity and sensitivity (gauge factor ≈ 43.5) and meanwhile good reproducibility of up to 100% strain. The proposed materials and principles in this study open up a novel practical approach to design high performance flexible sensors for a broad range of multifunctional applications.

Electronic Properties of MoS2/MX2/MoS2 Trilayer Heterostructures: A First Principle Study

In this work, we have presented a first principle simulation study on the electronic properties of MoS2/MX2/MoS2 (M = Mo or W; X = S or Se) trilayer heterostrcuture. We have investigated the effect of stacking configuration, bi-axial compressive and tensile strain on the electronic properties of the trilayer heterostructures. In our study, it is found that, under relaxed condition all the trilayer heterostructures at different stacking configurations show semiconducting nature. The nature of the bandgap however depends on the inserted TMDC monolayer between the top and bottom MoS2 layers and their stacking configurations. Like bilayer heterostructures, trilayer structures also show semiconducting to metal transition under the application of tensile strain. With increased tensile strain the conduction band minima shifts to K point in the brillouin zone and lowering of electron effective mass at conduction band minima is observed. The study on the projected density of states reveal that, the conduction band minima is mostly contributed by the MoS2 layers and states at the valance band maxima are contributed by the middle TMDC monolayer.

J0310106 Ni基超合金における負荷ひずみと回折X線プロファイル半価値の関係

J0310106 Ni基超合金における負荷ひずみと回折X線プロファイル半価値の関係

Significant enhancement of the thermoelectric performance of phosphorene through the application of tensile strain

First-principles calculations based on density functional theory showed that the thermoelectric performance of single-atomic-layer phosphorus, referred to as phosphorene, is significantly enhanced by the application of tensile strain along a particular direction. Phosphorene subjected to a 10% strain exhibits a very large power factor exceeding 10 mW/(m·K2), which is almost two orders of magnitude greater than the power factors of conventional flexible thermoelectric materials. This extreme enhancement of the thermoelectric performance is explained by the new concept of a strain-induced energy valley.

Improving Oxygen Transport in Perovskite-Type LaGaO3 Solid Electrolyte through Strain

Lattice strain is a promising possibility to improve materials performance in view of their application in thin-film devices. In particular, defect and transport properties in ionic conductors may be tailored through strain effects, since defect formation energy and migration barriers are correlated to structural parameters which, in turn, are influenced by strain-induced deformations. In this computational study we predicted that oxide-ion diffusion in perovskite-type lanthanum gallate can be improved through application of tensile strain. The structural deformations required to accommodate tensile lattice strain in the perovskite system are shown to result in a preferential localization of the oxygen vacancies in the equatorial plane of the GaO6 octahedra, while oxide-ion diffusion becomes anisotropic.

Tuning of the electronic and optical properties of single-layer black phosphorus by strain

Using first principles calculations we showed that the electronic and optical properties of single-layer black phosphorus (BP) depend strongly on the applied strain. Due to the strong anisotropic atomic structure of BP, its electronic conductivity and optical response are sensitive to the magnitude and the orientation of the applied strain. We found that the inclusion of many body effects is essential for the correct description of the electronic properties of monolayer BP; for example, while the electronic gap of strainless BP is found to be 0.90 eV by using semilocal functionals, it becomes 2.31 eV when many-body effects are taken into account within the ${G}_{0}{W}_{0}$ scheme. Applied tensile strain was shown to significantly enhance electron transport along zigzag direction of BP. Furthermore, biaxial strain is able to tune the optical band gap of monolayer BP from 0.38 eV (at $\ensuremath{-}8%$ strain) to 2.07 eV (at 5.5%). The exciton binding energy is also sensitive to the magnitude of the applied strain. It is found to be 0.40 eV for compressive biaxial strain of $\ensuremath{-}8%$, and it becomes 0.83 eV for tensile strain of 4%. Our calculations demonstrate that the optical response of BP can be significantly tuned using strain engineering which appears as a promising way to design novel photovoltaic devices that capture a broad range of solar spectrum.

Three-dimensional development of tensile pre-strained annulus fibrosus cells for tissue regeneration: An in-vitro study

Prior research has investigated the immediate response after application of tensile strain on annulus fibrosus (AF) cells for the past decade. Although mechanical strain can produce either catabolic or anabolic consequences to the cell monolayer, little is known on how to translate these findings into further tissue engineering applications. Till to date, the application and effect of tensile pre-strained cells to construct a three-dimensional (3D) AF tissue remains unknown. This study aims to investigate the effect of tensile pre-strained exposure of 1 to 24h on the development of AF pellet culture for 3 weeks. Equibiaxial cyclic tensile strain was applied on AF monolayer cells over a period of 24h, which was subsequently developed into a cell pellet. Investigation on cellular proliferation, phenotypic gene expression, and histological changes revealed that tensile pre-strain for 24h had significant and lasting effect on the AF tissue development, with enhanced cell proliferation, and up-regulation of collagen type I, II, and aggrecan expression. Our results demonstrated the regenerative ability of AF cell pellets subjected to 24h tensile pre-straining. Knowledge on the effects of tensile pre-strain exposure is necessary to optimize AF development for tissue reconstruction. Moreover, the tensile pre-strained cells may further be utilized in either cell therapy to treat mild disc degeneration disease, or the development of a disc construct for total disc replacement.

Flexible Transparent Heaters with Heating Films Made of Indium Tin Oxide Nanoparticles

In this study, flexible transparent heaters with heating films made of indium tin oxide (ITO) are fabricated on plastic substrates. The optical transmittance of a representative flexible heater is above 90% in the visible and near infrared regions. The steady-state temperature is determined by the bias voltage and reaches about 180 degrees C at a bias voltage of 50 V. The heat-generating properties are nearly the same before and after the application of tensile strain. Furthermore, the defrosting ability is demonstrated using a block of dry-ice.

Influence of Copper Volume Fraction on Tensile Strain/Stress Tolerances of Critical Current in a Copper-Plated DyBCO-Coated Conductor

The influence of the volume fraction (Vf) of copper, plated at room temperature over a DyBa2Cu3O7¹¤-coated conductor, on the tensile strain tolerance and stress tolerance of critical current at 77K was studied over a wide range of copper Vf values. The copper plating exerts a tensile stress during cooling because copper has a higher coefficient of thermal expansion than the substrate conductor. Before application of tensile strain, the copper plated at room temperature yielded at 77K when the copper Vf was lower than a critical value, and was in an elastic state at 77K when the copper Vf was higher than the critical value. The strain tolerance of critical current increased with increasing copper Vf due to an increase in thermally induced compressive strain in the substrate tape. The stress tolerance of critical current decreased with increasing copper Vf because copper is softer than the substrate tape. These results, together with the trade-off between strain tolerance and stress tolerance (i.e., stress tolerance decreases with increasing strain tolerance), were analyzed by modeling. The results show that the restriction imposed by the trade-off, which limits the ability to simultaneously obtain a high strain tolerance and a high stress tolerance, can be relaxed by strengthening the copper. [doi:10.2320/matertrans.MBW201201]

Investigation of the hot cracking susceptibility of laser welds with the controlled tensile weldability test

Due to significant developments over the last decades, laser beam welding has become a well-established industrial process offering high processing speeds and causing low component distortions. But an important issue currently preventing its intense use, especially in the energy or plant construction sector where high alloy steels are applied, concerns hot crack formation. Although considerable advances in understanding hot cracking mechanisms have been made, most of the known influencing factors are metallurgical in character. The thermo-mechanical effects are barely considered or quantified. Up to the present, there exist numerous hot cracking tests that were however conceived for welding methods other than laser beam welding. Considering the special features of the laser welding process, such as high cooling rates and the narrow process zone, results obtained with other welding techniques and test procedures cannot be transferred to laser beam welding. In this study, the laser beam weldability of various stainless steels was examined in terms of their susceptibility to hot cracking by means of the controlled tensile weldability test, which was proven to be suitable for use in conjunction with CO2 laser welding. This test allows the application of tensile strain at a variable fixed cross-head speed transverse to the welding direction. Full and partial penetration bead-on-plate welds were produced. In a first attempt to determine the impact of the applied external strain on the local transient strains and strain rates near the weld pool, an optical system was used to measure the backside surface of partial penetration welds. The results showed the influence of the strain and the strain rates on hot crack formation. Furthermore, a classification of the studied austenitic, duplex and ferritic stainless steels according to the established test criteria (critical strain and cross-head speed) was conducted.

Enhancing the Humidity Sensitivity of Ga2O3/SnO2 Core/Shell Microribbon by Applying Mechanical Strain and Its Application as a Flexible Strain Sensor

The humidity sensitivity of a single β-Ga(2) O(3) /amorphous SnO(2) core/shell microribbon on a flexible substrate is enhanced by the application of tensile strain and increases linearly with the strain. The strain-induced enhancement originates from the increase in the effective surface area where water molecules are adsorbed. This strain dependence of humidity sensitivity can be used to monitor the external strain. The strain sensing of the microribbon device under various amounts of mechanical loading shows excellent reliability and reproducibility with a gauge factor of -41. The flexible device has high potential to detect both humidity and strain at room temperature. These findings and the mechanism involved are expected to pave the way for new flexible strain and multifunctional sensors.

Maximum asymmetry in strain induced mechanical instability of graphene: Compression versus tension

We demonstrate that graphene, as the thinnest possible solid membrane of only one atomic layer thick, exhibits the maximum asymmetry in tensile versus compressive strain induced mechanical instability. Using continuum mechanics analysis and molecular dynamics simulations, we show that for graphene nanoribbons (sheets) with a typical length (size) of ∼100 nm, the critical compressive strain for buckling instability is only ∼10−4%, while the critical tensile strain for fracture is ∼2%, a four orders of magnitude difference. Such a large asymmetry implies that practically, strain engineering of graphene devices is only viable with application of tensile strain but difficult with compressive strain.

Pore size characteristics of nonwoven structures under uniaxial tensile loading

Nonwovens are highly porous structures consisting pores of complex shapes and sizes which are responsible for desired functional characteristics. In general, a nonwoven is often subjected to uniaxial tensile loading in various applications and it is of paramount importance to account for changes in structural characteristics including pore sizes during the loading conditions. In this research work, the pore size of thermally bonded nonwoven structures under uniaxial tensile loading at various levels of strains has been investigated. A theoretical model has been proposed that accounted for fibre reorientation and changes in the fibre volume fraction during the application of tensile strain. A comparison has been made between theoretical and experimental pore size distributions of thermally bonded nonwoven structures at defined levels of strains. Moreover, an attempt has been made to rationalise some of the contradictory literature results of pore size distributions of nonwoven structures under uniaxial tensile loading.

Strain effects on the SERS enhancements for spherical silver nanoparticles

We demonstrate in the present work through the utilization of classical Mie scatteringtheory in conjunction with a radiation damping and dynamic depolarization-correctedelectrostatic approximation the significant effect that mechanical strain has on the opticalproperties of spherical silver nanoparticles. Through appropriate modifications of the bulkdielectric functions, we find that the application of tensile strain generates significantenhancements in the local electric field for the silver nanoparticles, leading to large SERSenhancements of more than 300% compared to bulk, unstrained nanoparticles when a 5%tensile strain is applied. While the strain-induced SERS enhancements are found to bestrongest for nanoparticle diameters where radiation damping effects are minimized, wefind that the surface plasmon resonance wavelengths are relatively unchanged bymechanical strain, and that the various measures of the far field optical efficiencies(absorption, scattering, extinction) can be enhanced by up to 150% through the applicationof tensile strain. The present findings indicate the opportunity to actively engineer andenhance the optical properties of silver nanoparticles through the application of mechanicaldeformation.