Strain Release Research Articles

Surface Facet Dependent Cycling Stability of Layered Cathodes

AbstractHigh chemical and mechanical stability of cathode surface are the prerequisites enabling high‐performance rechargeable battery. Surface facet is among the surface properties that dictate surface stability and cycling performance, while its underlying mechanism remains elusive. Herein, it is reported that surface stability is closely related to the surface facet for a variety of layered cathodes. The investigation shows that surface structure of P2 layered cathode undergoes sequential transformation upon cycling, which results in severe surface degradation. This study finds that the surface facets perpendicular to the (002) planes experience severe cracking and corrosion, while other surface facets are much more stable. The surface stability difference mainly comes from a geometric effect on strain release, which determines the mechanical stability of surface. Chemically, transition metal condensation forms a passivation layer to effectively prevent the inward propagation of surface degradation. Therefore, the surface facets oblique to the layered‐planes are intrinsically more resistant to mechanical cracking and chemical corrosion, which is further verified as a common effect in several O3‐type layered cathodes. This work not only deepens the understanding of the mechanism how surface facet affects surface stability, but also validates surface facet regulation can be a promising strategy for optimizing battery materials.

Aromatic C–C Bond Cleavage in a Curved π-System of Aminocorannulene

We report a metal- and oxidant-free aromatic C-C bond cleavage in the curved corannulene skeleton. Reaction of 1-aminocorannulene with hydrazonyl chloride generates an amidrazone intermediate that undergoes facile intramolecular proton migrations and ring annulation to give a 1,2,4-triazole derivative of planar benzo[ghi]fluoranthene, in which the release of strain associated with the curved π-surface and the formation of an aromatic triazole moiety are the driving forces. This report provides new insights into the aromatic C-C bond cleavage.

Substantial Upper Plate Faulting Above a Shallow Subduction Megathrust Earthquake: Mechanics and Implications of the Surface Faulting During the 2016 Kaikoura, New Zealand, Earthquake

AbstractThe 2016 moment magnitude 7.8 Kaikoura, New Zealand, earthquake occurred at the southern end of the Hikurangi subduction zone where the upper plate above the shallow megathrust is exposed sub‐aerially. As a result, the substantial co‐seismic deformation in the upper plate above the megathrust rupture was observed geologically and geodetically. We explore the relationship between this surface faulting and the subduction megathrust rupture and find that the greatest upper plate fault slip occurred coincident (in time and location) with the megathrust rupture. Models of Coulomb stress change demonstrate that these surface faults become positively loaded as the upper plate rebounds during the megathrust event, favoring fault slip. In addition, during the megathrust rupture these faults terminate against an uncoupled subduction plate interface. We simulate the effects of decoupling at the base of these faults and find that very large fault slip is an expected consequence of this decoupling, allowing near‐complete strain release. In contrast, typical strike‐slip faults, pinned at their base, would have lower amounts of fault slip. These two conditions—increased Coulomb stress and basal decoupling—combine to produce the extreme co‐seismic upper plate faulting observed above the shallow Kaikoura megathrust earthquake. Similar conditions occur in other global subduction zones, but in most subduction zones the region above the coupled megathrust is underwater and poorly observed. Our analysis of the Kaikoura earthquake indicates a need to reevaluate patterns of strain accumulation and release in these regions, rather than assuming simple models of elastic rebound.

Internal prestressing of ultra‐high performance concrete using shape memory fibers

AbstractUsing shape memory fibers to reinforce concrete is a novel concept in civil engineering. Pre‐stretched fibers are brought into concrete and after activating the shape memory effect, a compressive prestress state is introduced. The present work investigates this method numerically. A brief introduction to the relevant behavior of shape memory alloys is given. Fiber activation is modeled by an empirical phase transition model. Simulations are carried out by applying the Finite Element Method to solve the CAUCHY‐FOURIER equations. Results of studies are presented for single‐fiber, improved single‐fiber and multi‐fiber configurations. Special focus is put on the geometric type of strain release. Key findings are that compressive stresses can be introduced into the concrete, however, local tension will occur. By altering the fiber geometry and applying an elastomeric coating, these regions can be eliminated. Furthermore, when using multiple fibers, there are synergies between regions of compression.

Photocatalytic C-C Cleavage of Methylenecyclobutanes for γ,δ-Unsaturated Aldehydes by Strain Release.

Radical additions onto olefins have surfaced as an increasingly powerful strategy for the synthesis of difunctionalized scaffolds. However, despite of major advances, known approaches continue to be largely limited to two manifolds, namely 1,2-difunctionalization of alkenes and remote difunctionalization via hydrogen atom transfer (HAT). Herein, we describe a mechanistically distinct approach by photoinduced carbon-carbon (C-C) activation/ring-opening to access γ,δ-unsaturated aldehydes from methylenecyclobutanols and sulfonyl chlorides by strain release. Remarkably, the sulfonyl motif on the products was easily removed by another photocatalytic process, which enabled the concise assembly of the natural product alatanone A. The synthetic utility of our approach was reflected by versatile functional group tolerance, ample substrate scope, and scalability. The photocatalysis represents a conceptually distinct alternative to existing approaches for remote 1,4-diversifications, with a double bond remaining in the thus obtained products.

Photokatalytische Ringöffnung von Methylencyclobutanen zur Synthese von γ,δ‐ungesättigten Aldehyden

AbstractRadikalische Additionsreaktionen an Olefine haben sich als eine zunehmend leistungsfähige Strategie für die Synthese von difunktionalisierten Verbindungen entwickelt. Trotz signifikanter Fortschritte sind die bekannten Methoden weitgehend auf zwei Ansätze beschränkt, welche entweder die 1,2‐Difunktionalisierung von Alkenen oder die distale Funktionalisierung mittels Wasserstoffatomtransfer (HAT) verfolgen. In dieser Arbeit wird nun die photoinduzierte Kohlenstoff‐Kohlenstoff (C−C)‐Aktivierung/Ringöffnung als ein anderer Ansatz beschrieben, welcher Zugang zu γ,δ‐ungesättigten Aldehyden aus Methylencyclobutanolen und Sulfonylchloriden unter Freisetzung der Ringspannungsenergie ermöglicht. Bemerkenswerterweise konnte das Sulfonyl‐Motiv der erhaltenen Produkte durch einen weiteren photokatalytischen Prozess leicht entfernt werden, was den effizienten Aufbau des Naturprodukts Alatanon A ermöglichte. Die synthetische Anwendbarkeit unseres Ansatzes spiegelte sich außerdem in der hohen Toleranz gegenüber vielfältigen funktionellen Gruppen und damit großen Anwendungsbreite sowie der Skalierbarkeit der Reaktion wider. Die Photokatalyse stellt eine konzeptionell eigenständige Alternative zu bestehenden Ansätzen für die distale 1,4‐Difunktionalisierung dar, welche die Doppelbindung in den so erhaltenen Produkten beibehält.

Palladium‐Catalyzed Skeletal Reorganization of Cyclobutanones Invoving Successive C—C Bond/C—H Bond Cleavage

Comprehensive SummaryThe utilization of cyclobutanones as the synthon in transition metal catalysis has been made great success. Because C(carbonyl)−C bond of cyclobutanones can be cleaved through strain release. Despite those advancements, the main catalysts in literature are Rh catalysts or Ni catalysts and the reaction with C—H bond is still underdeveloped. Herein, we realized the first palladium‐catalyzed skeletal reorganization of cyclobutanones involving successive cleavage of C(carbonyl)−C bonds and C—H bond cleavage, which constitutes an rapid access to diverse indanones. In contrast to the previous Rh‐catalytic system, the Pd‐catalytic system herein involves different mechanism and features several advantages: 1) no need of directing group to facilitate the C(carbonyl)−C bond cleavage; 2) much milder reaction condition and 3) simplified work‐up.

Rhodium-Catalyzed [4+2+1] Annulation Harnessing the Strain Release of a Methylenecyclopropyl Group

Key words rhodium catalysis - [4+2+1] annulation - carbon monoxide - methylenecyclopropyl group - cyclopropane

Microstructure and mechanical properties of a novel twinning induced plasticity steel with two different grain morphologies

A novel heterogeneous-structure (HS) twinning-induced plasticity (TWIP) steel containing alternating columnar grain (CG) and equiaxed grain (EG) domains was successfully fabricated via prestraining, partial recrystallization, and directional solidification. Compared with the traditional EG sample, the HS sample exhibited a better tensile strength–elongation combination (yield strength ≈ 263 MPa, ultimate tensile strength ≈ 573 MPa, total elongation ≈ 101.5%). The mutually constrained structure could effectively control the unique deformation modes of the EG and CG domains at different deformation stages. The HS sample exhibited stable and continuous plastic deformation owing to the timely release of localized high strain or stress, postponed plastic instability, and restrained crack propagation owing to the constrained structure. The stress relaxation was due to twinning and the effects of geometrically necessary dislocations, which accommodated deformation incompatibility. The improved mechanical properties of the HS sample were due to the persistent occurrence of the TWIP effect under very low to high strain levels during the entire deformation process, the effective grain boundary hardening in the EG domain, and the additional work hardening provided by the GNDs.

Bridging the Buried Interface with Piperazine Dihydriodide Layer for High Performance Inverted Solar Cells.

Given that it is closely related to perovskite crystallization and interfacial trap densities, buried interfacial engineering is crucial for creating effective and stable perovskite solar cells. Compared with the in-depth studies on the defect at the top perovskite interface, exploring the defect of the buried side of perovskite film is relatively complicated and scanty owing to the non-exposed feature. Herein, the degradation process is probed from the buried side of perovskite films with continuous illumination and its effects on morphology and photoelectronic characteristics with a facile lift-off method. Additionally, a buffer layer of Piperazine Dihydriodide (PDI2 ) is inserted into the imbedded bottom interface. The PDI2 buffer layer is able to lubricate the mismatched thermal expansion between perovskite and substrate, resulting in the release of lattice strain and thus a void-free buried interface. With the PDI2 buffer layer, the degradation originates from the growing voids and increasing non-radiative recombination at the imbedded bottom interfaces are suppressed effectively, leading to prolonged operation lifetime of the perovskite solar cells. As a result, the power conversion efficiency of an optimized p-i-n inverted photovoltaic device reaches 23.47% (with certified 23.42%) and the unencapsulated devices maintain 90.27% of initial efficiency after 800h continuous light soaking.

Coseismic Slip Model of the 19 September 2022 Mw 7.6 Michoacán, Mexico, Earthquake: A Quasi-Repeat of the 1973 Mw 7.6 Rupture

AbstractOn 19 September 2022, a major earthquake struck the northwestern Michoacán segment along the Mexican subduction zone. A slip model is obtained that satisfactorily explains geodetic, teleseismic, and tsunami observations of the 2022 event. The preferred model has a compact large-slip patch that extends up-dip and northwestward from the hypocenter and directly overlaps a 1973 Mw 7.6 rupture. Slip is concentrated offshore and below the coast at depths from 10 to 30 km with a peak value of ∼2.9 m, and there is no detected coseismic slip near the trench. The total seismic moment is 3.1×1020 N·m (Mw 7.6), 72% of which is concentrated in the first 30 s. Most aftershocks are distributed in an up-dip area of the mainshock that has small coseismic slip, suggesting near-complete strain release in the large-slip patch. Teleseismic P waveforms of the 2022 and 1973 earthquakes are similar in duration and complexity with high cross-correlation coefficients of 0.68–0.98 for long P to PP signal time windows, indicating that the 2022 earthquake is a quasi-repeat of the 1973 earthquake, possibly indicating persistent frictional properties. Both the events produced more complex P waveforms than comparable size events along Guerrero and Oaxaca, reflecting differences in patchy locking of the Mexican megathrust.

O-, N- and C-bicyclopentylation using thianthrenium reagents

Rigid 1,3-disubstituted bicyclo[1.1.1]pentanes (BCPs) are linear bioisosteres for para-substituted benzene rings in drug development and can lead to an improved pharmacokinetic profile. The construction of BCPs commonly requires the cumbersome use of labile [1.1.1]propellane in solution, and more stable reagents do not show the versatile reactivity of propellane itself. Here we report stable thianthrenium-based BCP reagents for practical O-, N- and C-alkylation reactions that expand the scope of bicyclopentylation beyond that of any other reagent, including [1.1.1]propellane. The redox and stereoelectronic properties of the thianthrene scaffold are relevant for both the synthesis of the BCP-thianthrenium reagents via strain release as well as their subsequent reactivity. The weak exocyclic C–S bond can undergo selective mesolytic cleavage upon single-electron reduction to produce BCP radicals that engage in transition metal-mediated C–O, C–N and C–C bond formations, even at a late stage of multistep reactions with a wide variety of functional groups present.

Chelated Ion-Exchange Strategy toward BiOCl Mesoporous Single-Crystalline Nanosheets for Boosting Photocatalytic Selective Aromatic Alcohols Oxidation.

The photoresponse and photocatalytic efficiency of bismuth oxychloride (BiOCl) are greatly limited by rapid recombination of photogenerated carriers. The construction of porous single-crystal BiOCl photocatalyst can effectively alleviate this issue and provide accessible active sites. Herein, a facile chelated ion-exchange strategy is developed to synthesize BiOCl mesoporous single-crystalline nanosheets (BiOCl MSCN) using acetic acid and ammonia solution respectively as chelating agent and ionization promoter. The strong chelation between acetate ions and Bi3+ ions introduces acetate ions into the precipitated product to exchange with Cl- ions, resulting in large lattice mismatch, strain release, and formation of void-like mesopores. The prepared BiOCl MSCN photocatalyst exhibits excellent catalytic performance with 99% conversion and 98% selectivity for oxidation of benzyl alcohol to benzaldehyde and superior general adaptability for various aromatic alcohols. The theoretical calculations and characterizations confirm that the superior performance is mainly attributed to the abundant oxygen vacancies, plenty of accessible adsorption/active sites and fast charge transport path without grain boundaries.

A high-tortuosity holey graphene in-situ derived from cytomembrane/cytoderm boosts ultrastable potassium storage

• A high-tortuosity holey graphene was successfully prepared based on the unique flake structure and chemical composition of cytomembrane and cytoderm. • Benefiting from the unique nanoholes shortening the ion-diffusion length, the synergy of wrinkled and holey structure stabilizing volume fluctuation, the enhanced electronic conductivity and specific surface area. • The anode achieves excellent reversible capacity, and exceptional rate capability with an ultra-long cycle lifespan in PIBs. • The anode exhibits a high energy density as well as considerable cycling stability for potassium-ion full cells. The sluggish K + kinetics and structural instability of the generally-used graphite and other carbon-based materials hinder the development of potassium-ion batteries (PIBs) for high-rate capability and long-term cycling. Herein, inspired by the unique flake structure and chemical composition of cytomembrane and cytoderm, we design high-tortuosity holey graphene as a highly efficient anode for PIBs. The flake cytomembrane and cytoderm shrink into wrinkled morphology during drying and sintering and then convert into high-tortuosity graphene after oxidative exfoliating and thermal reducing process. Meanwhile, the proteins, sugars, and glycolipids embedded in cytomembrane and cytoderm can in-situ form nanoholes with highly abundant oxygenic groups and heteroatoms around, which can be easily removed and finally the high-tortuosity holey graphene is obtained after a thermal reducing process. The stress distribution after K + intercalation confirms the optimized release of strain caused by the volume change through the finite element method. Benefiting from the unique nanoholes shortening the ion-diffusion length, the synergy of wrinkled and holey structure stabilizing volume fluctuation, and the enhanced electronic conductivity and specific surface area, the high-tortuosity holey graphene demonstrates high reversible capacities of 410 mAh g –1 at 25 mA g –1 after 150 cycles and retains 91.5% at 2 A g –1 after 2500 cycles.

Temporal sequence of deformation twinning in CoCrNi under tribological load

Microstructural evolution under tribological load is known to change the friction and wear response of the entire tribological system. It is however not yet fully understood, how these changes take place on an elementary, mechanistic level. Revealing the temporal sequence of deformation mechanisms under a tribological load by experiments is scarce. The discrete strain release in the case of deformation twinning allows the identification of their temporal sequence. Therefore, a medium stacking fault energy material, namely CoCrNi, was investigated due to the significant contribution of deformation twinning to the overall deformation at room temperature. The investigated grain showed three activated twin systems. The evolution sequence of these is discussed critically based on several twin intersection mechanisms. The experimental analysis decodes the temporal sequence of the active twinning systems of highest resolved shear stresses for the first time. This approach gives experimental indications for the stress field under tribological load.

Impaction procedure influences primary stability of acetabular press-fit components.

The aim of the study was to investigate whether the primary stability of press-fit acetabular components can be improved by altering the impaction procedure. Three impaction procedures were used to implant acetabular components into human cadaveric acetabula using a powered impaction device. An impaction frequency of 1 Hz until complete component seating served as reference. Overimpaction was simulated by adding ten strokes after complete component seating. High-frequency implantation was performed at 6 Hz. The lever-out moment of the acetabular components was used as measure for primary stability. Permanent bone deformation was assessed by comparison of double micro-CT (µCT) measurements before and after impaction. Acetabular component deformation and impaction forces were recorded, and the extent of bone-implant contact was determined from 3D laser scans. Overimpaction reduced primary acetabular component stability (p = 0.038) but did not significantly increase strain release after implantation (p = 0.117) or plastic deformations (p = 0.193). Higher press-fits were associated with larger polar gaps for the 1 Hz reference impaction (p = 0.002, R2 = 0.77), with a similar trend for overimpaction (p = 0.082, R2 = 0.31). High-frequency impaction did not significantly increase primary stability (p = 0.170) at lower impaction forces (p = 0.001); it was associated with smaller plastic deformations (p = 0.035, R2 = 0.34) and a trend for increased acetabular component relaxation between strokes (p = 0.112). Higher press-fit was not related to larger polar gaps for the 6 Hz impaction (p = 0.346). Overimpaction of press-fit acetabular components should be prevented since additional strokes can be associated with increased bone damage and reduced primary stability as shown in this study. High-frequency impaction at 6 Hz was shown to be beneficial compared with 1 Hz impaction. This benefit has to be confirmed in clinical studies.

Effects of the 2011 Mw 9.0 Tohoku-Oki Earthquake on the Locking Characteristics and Seismic Risk of the Yishu Fault Zone in China

To ascertain the 2011 Tohoku-Oki Mw 9.0 earthquake’s impact on the stability of the Yishu fault zone, this study inverts the fault locking degree and slip rate defect distribution of the Yishu fault zone using GPS horizontal velocity field data covering the period from 1999 to 2009 and from April 2011 to 2019. This is based on the block negative dislocation model. Combined with the b value and strain field characteristics, the properties of deformation of the Yishu fault zone before and after the earthquake are comprehensively analyzed. The results show that before the 2011 Tohoku-Oki Mw 9.0 earthquake, the locking degree and depth of the northern segment of the Yishu fault zone were higher, while the locking depth of the southern segment of the fault was shallower. The 2011 Tohoku-Oki earthquake produced different coseismic effects on the southern and northern sections of the Yishu fault zone. The extension on the southern section and compression on the northern section caused the strain release in the southern sections of the Yishu fault zone following the earthquake. After it, the regional locking degree of the southern section of the Yishu fault zone was relieved. However, the locking degree of the northern segment of the fault zone was still high and the depth was deep, at about 26 km. In addition, the northern section of the Yishu fault zone was a section with an abnormally low b value and small earthquakes in the northern segment are sparse at present. The coseismic compression of the northern section caused by the 2011 Tohoku-Oki earthquake is conducive to its locking and easily accumulates stress, so it is necessary to pay attention to its seismic risk.

Constraining Fault Damage Zone Properties From Geodesy: A Case Study Near the 2019 Ridgecrest Earthquake Sequence

AbstractSeismologic studies have reported seismic velocities reduction and Vp/Vs ratio changes over damage zones associated with seismogenic faults. The structure and elastic properties of these damage zones indicate the maturity of faults and affect the rupture dynamics of future seismic events. Therefore, they contain critical information about fault properties that could inform seismic hazards. Here we present a geodetic modeling approach to constrain velocity changes and elastic properties of fault damage zones under stress perturbation from nearby earthquakes. Compared to seismic tomographic analysis that is usually limited by resolution, this geodetic approach provides tighter constraints on the elastic properties and geometry of the damage zone at shallow depths. Our results imply that a major component of the shallow strain release is distributed and inelastic. The existence of numerous shallow faults either may indicate a locally detached shallow layer or they are remnants from earlier fault evolution.

Sweet Strain Release: Donor–Acceptor Cyclopropane Mediated Glycosylation

Sweet Strain Release: Donor–Acceptor Cyclopropane Mediated Glycosylation

Strain-Relaxed Nanocrystalline Diamond Thin Films with Silicon Vacancy Centers Using Femtosecond Laser Irradiation for Photonic Applications

Nanocrystalline diamond thin (thickness of 100–500 nm) films with ensembles of negatively charged light-emitting silicon vacancy (SiV) centers might find an application in the field of photonics or biosensing due to their scalable and low-price fabrication process in comparison with monocrystalline diamond. The potential application of diamond thin films is, however, limited due to the presence of radiative and nonradiative defects. The former type is a source of an unwanted background in the photoluminescence spectra, the latter lowers the quantum efficiency of light emission, and both types of defects cause the reabsorption of SiV emission during its propagation within the layer. Here we show that femtosecond (fs) laser pulses focused via a microscope objective on a nanocrystalline diamond thin film can be employed to reduce background photoluminescence intensity by a factor of 5 with respect to the luminescence of SiV centers. Raman spectra show that this decrease is mainly caused by laser ablation of the sp2-related carbon phase present in-between the grains. The reduction of the sp2 carbon phase also leads to a local decrease in the optical absorption followed by an almost twofold increase in the SiV emission peak intensity. Moreover, the fs-irradiation also entails the release of strain inside such a layer as manifested by the observed shift of the Raman diamond peak toward the value measured in the monocrystalline diamond and by a blue-shift of the zero-phonon-line peak position of the SiV centers. Such a finding might enable the improvement of the optical quality of the nanocrystalline diamond-based photonic nanostructures or even might be employed over a larger area by defocusing the irradiation laser in order to create large-scale strain-relaxed nanocrystalline diamond thin films.