Anisotropic Expansion Research Articles

The first polyanion-substitution-driven centrosymmetric-to-noncentrosymmetric structural transformation realizing an excellent nonlinear optical supramolecule [Cd4P2][CdBr4

Crystallographically, noncentrosymmetricity (NCS) is an essential precondition and foundation of achieving nonlinear optical (NLO), pyroelectric, ferroelectric, and piezoelectric materials. Herein, structurally, octahedral [SmCl6]3- is substituted by the acentric tetrahedral polyanion [CdBr4]2-, which is employed as a templating agent to induce centrosymmetric (CS)-to-NCS transformation based on the new CS supramolecule [Cd5P2][SmCl6]Cl (1), thereby providing the NCS supramolecule [Cd4P2][CdBr4] (2). Meanwhile, this replacement further results in the host 2D ∞2[Cd5P2]4+ layers converting to yield the twisted 3D ∞3[Cd4P2]2+ framework, which promotes the growth of bulk crystals. Additionally, phase 2 possesses well-balanced NLO properties, enabling considerable second-harmonic generation (SHG) responses (0.8-2.7 × AgGaS2) in broadband spectra, the thermal expansion anisotropy (2.30) together with suitable band gap (2.37 eV) primarily leading to the favorable laser-induced damage threshold (3.33 × AgGaS2), broad transparent window, and sufficient calculated birefringence (0.0433) for phase-matching ability. Furthermore, the first polyanion substitution of the supramolecule plays the role of templating agent to realize the CS-to-NCS transformation, which offers an effective method to rationally design promising NCS-based functional materials.

THE RELATIVISTIC OBSERVER: Consequences of a Linear Expansion of Spacetime

Communication Dynamics Theory, defined in a companion paper, offers a new approach to understanding Spacetime. In Communication Dynamics Theory, physical reality is assumed to arise from an anisotropic expansion of a one-dimensional communication network. In this paper, we perform a first approximation mathematical transformation of the theory into hyperbolic geometry. The resulting model provides a potential basis for developing insight pertaining to previously poorly understood fundamental constants of physics. As a demonstration, we define a proton, neutron, and electron, demonstrate the emergence of observable space and time, and generate heuristic estimates of Euler’s number, the fine structure constant, and π, as well as geometric descriptions of fundamental forces of nature, occurring as natural consequences of the linear dynamic expansion of Spacetime.

Long-term behaviour of a dam affected by alkali–silica reaction studied by a multi-scale model

This paper aims to employ a 2D thermo-mechanical multi-scale ASR model for the analysis of a concrete gravity dam in Western Switzerland. Simulation results are compared to the field measurements and observations. Analysis of the results reveals negligible effect of temperature variation on the ASR advancement. The difference in length between the upstream and the downstream faces is identified as the main source for the upstream drift at the level of the crest. Study of the structural effects reveals ASR-related expansion anisotropy and cracks alignment being more pronounced along the upstream part and the foundation. If the former is explained by the transmission of the self-weight, the latter is attributed to the constraining effect of the underlying rock.

Anisotropic behavior in the lithiation of a silicon nanopillar

There are reports on experimental observation of anisotropic expansion/swelling in the lithiation of crystal silicon (Si) nanopillars/nanowires. Such anisotropic expansion/swelling can cause the cracking of Si electrodes, leading to the capacity fading in Si-based lithium-ion batteries (LIBs). In this paper, we propose an anisotropic chemo-mechanical model that takes into account anisotropic characteristics of the physical properties of crystalline Si, including stiffness tensor (matrix), diffusion tensor and partial-molar volume tensor. Using direction-cosine matrix for the tensor transformation, we determine the orientation-dependent elastic constants, diffusion coefficients and partial molar volumes in the anisotropic chemo-mechanical model instead of using phenomenal parameters associated with experimental results. For the purpose of demonstration, we analyze the lithiated Si phase of Li15Si4, which exhibits cubic structure, and illustrate geometrical profiles of the lithiated Si nanopillars of [110] and [111] in longitudinal direction at Li15Si4 state. The numerical results reveal that the cross section of the [111]-oriented Si nanopillar remain circular and the cross section of the [110]-oriented Si nanopillar evolves to elliptical shape. Such results are in good accordance with the experimental observation reported by Lee et al. [P. Natl. Acad. Sci. 109(11) (2012) 4080–4085]. The numerical results also show that the anisotropic expansion likely reduces von-Mises stress in the [110]-oriented Si nanopillar, retarding mechanical degradation of the Si-based electrodes. This work provides a new insight into the anisotropic expansion and stress generation in crystalline electrodes.

Is the Core-cusp Problem a Matter of Perspective? Jeans Anisotropic Modeling against Numerical Simulations

Mock member stars for 28 dwarf galaxies are constructed from the cosmological auriga simulation, which reflects the dynamical status of realistic stellar tracers. Axisymmetric Jeans Anisotropic Multi-Gaussian Expansion (jam) modeling is applied to 6000 star particles for each system to recover the underlying matter distribution. The stellar or dark matter component individually is poorly recovered, but the total profile is constrained more reasonably. The mass within the half-mass radius of tracers is recovered the tightest, and the mass between 200 and 300 pc, M(200–300 pc), is an unbiasedly constrained ensemble, with a scatter of 0.167 dex. If using 2000 particles and only line-of-sight velocities with typical errors, the scatter in M(200–300 pc) is increased by ∼50%. Quiescent Saggitarius dSph–like systems and star-forming systems with strong outflows show distinct features, with M(200–300 pc) mostly underestimated for the former, and likely overestimated for the latter. The biases correlate with the dynamical status, which is a result of contraction motions due to tidal effects in quiescent systems or galactic winds in star-forming systems, driving them out of equilibrium. After including Gaia DR3 proper motion errors, we find proper motions can be as useful as line-of-sight velocities for nearby systems at < ∼60 kpc. By extrapolating the actual density profiles and the dynamical constraints down to scales below the resolution, we find the mass within 150 pc can be an unbiasedly constrained ensemble, with a scatter of ∼0.255 dex. We show that the contraction of member stars in nearby systems is detectable based on Gaia DR3 proper motion errors.

High temperature structure and vibrational properties of GdVO4

In this manuscript the temperature evolution of crystal structure and vibrational properties of tetragonal GdVO4 as observed from in situ high temperature powder XRD and Raman spectroscopic studies are reported. The material shows anisotropic expansion with a larger coefficient of thermal expansion along c-axis (αc) compared to that along the a-axis (αa). The average axial thermal expansion coefficients in the temperature range of 298–1373 K are: αa = 3.75 × 10−6 K−1 and αc = 11.1 × 10−6 K−1. The degree of anisotropy in thermal expansion decreases with increasing temperature. The thermal expansion behavior of GdVO4 was mainly contributed by the orientation and expansion of Gd–O bonds in the structure. The temperature dependent Raman spectroscopic investigations indicate decreasing trend of all the observed phonon mode frequencies. All the low energy modes show larger anharmonicity compared to the high energy stretching modes and they contribute significantly to the expansion of GdVO4.

Organic Crystals with Response to Multiple Stimuli: Mechanical Bending, Acid-Induced Bending and Heating-Induced Jumping.

Multiple stimuli-responsive molecular crystals are attracting extensive attentions due to their potential as smart materials, such as molecular machines, actuators, and sensors. However, the task of giving a single crystal multiple stimuli-responsive properties remains extremely challenging. Herein, we found two polymorphs (Form O and Form R) of a Schiff base compound, which could respond to multiple stimuli (external force, acid, heat). Form O and Form R have different elastic deformability, which can be attributed to the differences in the molecular conformation, structural packing and intermolecular interactions. Moreover, both polymorphs exhibit reversible bending driven by volatile acid vapor, which we hypothesize is caused by reversible protonation reaction of imines with formic acid. In addition, jumping can be triggered by heating due to the significant anisotropic expansion. The integration of reversible bending and jumping into one single crystal expands the application scope of stimuli-responsive crystalline materials.

Nanostructuring‐Promoted Non‐Equilibrium Phase Transformation of Bi Anodes Toward Diffusion‐Controlled Reaction for K‐Ion Batteries

AbstractNanostructuring is regarded as a significant method for improving the reversibility of alloying anodes for potassium‐ion batteries (PIBs). However, it is still unclear how nanostructuring suppresses the mechanical deterioration upon potassiation/depotassiation. In this study, by in situ X‐ray diffraction, a size‐dependent phase transformation mechanism in a nano‐Bi material (≈15 nm), which avoids the voltage plateau mutation of bulk‐Bi material (≈250 nm) caused by an incomplete and irreversible two‐phase reaction is revealed. The potassiation of nano‐Bi follows a stepwise solid‐solution pathway without any phase transitions under nonequilibrium conditions, circumventing the nucleation of a new phase. The distinctive transition pathway, dominated by the diffusion‐controlled reaction, is accompanied by fast ionic transport kinetics and homogeneous diffusion. As a result, particle fracture is inhibited by isotropic expansion stress, developing a route for stable potassium storage. By contrast, the two‐phase transformation of bulk‐Bi is governed by an interface‐controlled reaction under equilibrium conditions with slow and heterogeneous diffusion, leading to a rapid capacity decay from anisotropic expansion. The comparison between equilibrium thermodynamic‐ and non‐equilibrium kinetic‐phase transformations uncovers the intrinsic mechanism explanatory of the mechanical robustness of the size‐reduced alloying anodes, and also emphasizes that solid‐state diffusion must be improved to attain highly fast kinetics with PIBs.

The structure and 3D kinematics of vela OB2

ABSTRACT The kinematics of stars in OB associations can provide insights into their formation, dynamical evolution, and eventual fate. The low-mass stellar content of OB associations are sufficiently numerous as to provide a detailed sampling of their kinematic properties, however spectroscopy is required to confirm the youth of individual stars and to get 3D kinematics. In this paper, we present and analyse results from a large spectroscopic survey of Vela OB2 conducted using 2dF/HERMES on the AAT. This spectroscopy is used to confirm the youth of candidate young stars and determine radial velocities, which are combined with proper motions and parallaxes from Gaia to measure 3D positions and velocities. We identify multiple separate kinematic groups in the region, for which we measure velocity dispersions and infer their virial states. We measure expansion rates for all these groups and find strong evidence for anisotropic expansion in the Vela OB2 association of at least 11σ significance in all three dimensions, as well as some evidence for expansion in the γ Vel and P Puppis clusters. We trace back the motions of these groups into the past and find that the open cluster NGC 2547 is an interloper in the Vela OB2 region and actually formed &amp;gt;100 pc away from the association. We conclude that Vela OB2 must have formed with considerable spatial and kinematic substructure over a time-scale of ∼10 Myr, with clear temporal substructure within the association, but no clear evidence for an age gradient.

Shank-localized cell wall growth contributes to Arabidopsis root hair elongation.

Root hairs are highly elongated tubular extensions of root epidermal cells with a plethora of physiological functions, particularly in establishing the root-rhizosphere interface. Anisotropic expansion of root hairs is generally thought to be exclusively mediated by tip growth-a highly controlled apically localized secretion of cell wall material-enriched vesicles that drives the extension of the apical dome. Here we show that tip growth is not the only mode of root hair elongation. We identified events of substantial shank-localized cell wall expansion along the polar growth axis of Arabidopsis root hairs using morphometric analysis with quantum dots. These regions expanded after in vivo immunolocalization using cell wall-directed antibodies and appeared as distinct bands that were devoid of cell wall labelling. Application of a novel click chemistry-enabled galactose analogue for pulse chase and real-time imaging allowed us to label xyloglucan, a major root hair glycan, and demonstrate its de novo deposition and enzymatic remodelling in these shank regions. Our data reveal a previously unknown aspect of root hair growth in which both tip- and shank-localized dynamic cell wall deposition and remodelling contribute to root hair elongation.

Multimodal analysis of Zr substitution effects on magnetic and crystallographic properties in (Sm1−xZrx)(Fe0.8Co0.2)12 compounds with ThMn12 structure

SmFe12-based compounds containing Zr atoms have been recognized as candidates for novel high-performance permanent magnet materials with a high saturation magnetization. Partial substitution of Sm with Zr in (Sm1−xZrx)(Fe0.8Co0.2)12 has been known to enhance the magnetization of the compound. This study focused on (Sm1−xZrx)(Fe0.8Co0.2)12 single-crystalline films to evaluate the effects of Zr substitution for Sm on their structural and magnetic properties via systematic multimodal analysis. X-ray absorption fine structure (XAFS) and scanning transmission electron microscopy indicated a selective occupation of the Sm site by Zr atoms without disturbing the Fe sublattices. The chemical shift in the Zr-K edge XAFS spectra suggested electron transfer from Zr to the Fe band. Soft X-ray magnetic circular dichroism analysis proved that the magnetic moment of Sm was two orders of magnitude smaller than the magnetic moments of Fe and Co, and its contribution to the total magnetization was negligible. The partial substitution of Sm with Zr resulted in a volumetric expansion and c-axis length elongation despite Zr having a smaller atomic radius, which is unique to (Sm1−xZrx)(Fe0.8Co0.2)12 without structure-stabilizing elements such as Ti, V, and Si. This anisotropic expansion is explained by an increase in the magnetic moment and magnetic interactions in the Fe8f site, which is induced by the electron transfer from Zr to Fe8f atoms. Thus, we conclude that the electron transfer from Zr to the Fe8f atoms principally drives magnetization enhancement in (Sm1−xZrx)(Fe0.8Co0.2)12 single-crystalline films.

Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters

Multi-MeV high-purity proton acceleration by using a hydrogen cluster target irradiated with repetitive, relativistic intensity laser pulses has been demonstrated. Statistical analysis of hundreds of data sets highlights the existence of markedly high energy protons produced from the laser-irradiated clusters with micron-scale diameters. The spatial distribution of the accelerated protons is found to be anisotropic, where the higher energy protons are preferentially accelerated along the laser propagation direction due to the relativistic effect. These features are supported by three-dimensional (3D) particle-in-cell (PIC) simulations, which show that directional, higher energy protons are generated via the anisotropic ambipolar expansion of the micron-scale clusters. The number of protons accelerating along the laser propagation direction is found to be as high as 1.6 pm ,{0.3}times 10^9/MeV/sr/shot with an energy of 2.8 pm ,{1.9} MeV, indicating that laser-driven proton acceleration using the micron-scale hydrogen clusters is promising as a compact, repetitive, multi-MeV high-purity proton source for various applications.

Coupling Quantification of Pulverization with Galvanostatic Cycling of Bulk Film Alloy-Type Anodes

Alloy-type anodes, such as metallic antimony, demonstrate promise as alternative electrode materials for lithium-ion battery systems due to their high theoretical capacity of 660 mAh/g. However, antimony undergoes anisotropic volume expansion and multiple crystallographic phase transformations upon lithiation and delithiation, which often leads to fracture. This fracture can result in loss of electrical contact and poor cycling stability. These pulverization phenomena are often observed, primarily during delithiation, but are not quantified in terms of physical bulk material lost. To quantify the mass, size, volume, and density of pulverized regions in a bulk antimony film in a lithium system, we have developed a cell that enables the use of optical microscopy to capture videos of lithiation and delithiation. Using ImageJ and MATLAB® scripts developed for analysis, we have begun to quantify the amount of material lost as a function of deposition parameters.

Electrodeposition of Rhenium Sandwich Structures and the Superconducting Transition Behavior

Superconductors with enhanced superconducting critical temperatures (Tc) above the boiling point of liquid helium (4.2 K) are of interest for interconnections in superconducting quantum computing systems to avoid ohmic heating[1]. Crystalline Re in bulk is a type-I superconductor with a Tc of about 1.7K[2]. An elevated Tc up to about 6K in electrodeposited amorphous Re has been reported[3]. In addition, various elevation in Tc has also been reported for Re film under shear strain[4] or doped with foreign elements such as Tungsten (W), Osmium (Os), and Carbon (C)[5, 6].This work aims to test a hypothesis that the Tc of electrodeposited Re films can be tuned using compressive and tensile strains on the Re films generated with thermal expansions difference. Figure 1 shows a diagram of the strains on Re film sandwiched between metals with different coefficients of thermal expansions (CTEs) when the temperature is lowered. For example, Cu has a higher CTE than Re and Cr has a slightly lower CTE than Re. Such sandwich structures are prepared at room temperature using electrochemical deposition. The DC resistance measurements at cryogenic temperatures confirmed that the superconducting transition for the Re films sandwiched between Cu occurs at a lower temperature than the Re film alone. On the other hand, when Cr is used, the sandwiched Re structure shows a slightly enhanced superconducting critical temperature. The effect of thermal annealing i.e., the recrystallization of electrodeposited Re films at an elevated temperature, and electrochemical behavior of Re, Cr, and Cu electrodeposition will be discussed in the talk. References Radenbaugh, R., Refrigeration for superconductors. Proceedings of the IEEE, 2004. 92(10): p. 1719-1734.Hulm, J.K., Superconductivity of Pure Metallic Rhenium. Physical Review, 1954. 94(5): p. 1390-1391.Pappas, D.P., et al., Enhanced superconducting transition temperature in electroplated rhenium. Applied Physics Letters, 2018. 112(18): p. 182601.Mito, M., et al., Large enhancement of superconducting transition temperature in single-element superconducting rhenium by shear strain. Scientific Reports, 2016. 6(1): p. 36337.Chu, C.W., W.L. McMillan, and H.L. Luo, Superconductivity of Re-Os, Re-Ru, Ru-Os, and Re-W hcp Alloy Systems and Slightly Doped Re. Physical Review B, 1971. 3(11): p. 3757-3762.Zhu, Q., et al., Anisotropic lattice expansion and enhancement of superconductivity induced by interstitial carbon doping in Rhenium. Journal of Alloys and Compounds, 2021. 878: p. 160290. Figure 1

Imparting high polymorph transition resistance to cyclotetramethylene-tetranitramine via spherulitic aggregation enabled crystal shape constraint

The high melting explosive (HMX), i.e., cyclotetramethylene-tetranitramine, is plagued by issues such as structural instability, increased sensitivity, and unwanted deflagration at elevated temperatures, which are strongly linked to the microstructural damage generated by its β → δ polymorphic transition around 160–185 °C. An extension of the β form thermal stability is therefore desired. Herein, a new strategy to regulate such β → δ transition via particle-level aggregation is demonstrated. Using polyvinyl pyrrolidone as a growth additive, this study shows that single-crystalline β-HMX can evolve into a unique spherulitic morphology with fine control over particle sizes and compactness. The phase transition is then found sensitive to the spherulitic aggregation while highly correlating with the decrease in particle size. Remarkably, the β-HMX spherulites exhibit an onset transition temperature of up to 205 °C, corresponding to a maximum 20 °C increment as compared with the highest value achieved by its single crystalline counterpart. Mechanistic investigation reveals that the suppressed β → δ transition origins from the restricting of anisotropic expansion of the subunit crystallites in spherulitic aggregates, induced by their unusual radial packing mode. The proposed strategy is expected to be translated to other polymorphic explosives, hence bringing a fresh perspective to future high-performance energetic materials development.

Root twisting drives halotropism via stress-induced microtubule reorientation.

Plants have evolved signaling mechanisms that guide growth away from adverse environments that can cause yield losses. Root halotropism is a sodium-specific negative tropism that is crucial for surviving and thriving under high salinity. Although root halotropism was discovered some years ago, the underlying molecular and cellular mechanisms remain unknown. Here, we show that abscisic acid (ABA)-mediated root twisting determines halotropism in Arabidopsis. An ABA-activated SnRK2 protein kinase (SnRK2.6) phosphorylates the microtubule-associated protein SP2L at Ser406, which induces a change in the anisotropic cell expansion at the root transition zone and is required for root twisting during halotropism. Salt stress triggers SP2L-mediated cortical microtubule reorientation, which guides cellulose microfibril patterns. Our findings thus outline the molecular mechanism of root halotropism and indicate that anisotropic cell expansion through microtubule reorientation and microfibril deposition has a central role in mediating tropic responses.

Dislocation modelling of the plastic relaxation and thermal ratchetting induced by zirconium hydride precipitation

The precipitation of hydrides in zirconium alloys is accompanied by a significant and anisotropic volumetric expansion. Previous literature quantified the misfit both theoretically and experimentally, but these values differ greatly; the experimental values are consistently lower. One possibility is that the experimental measurements include the effect of dislocations generated by the hydride, which relax the transformation stresses. To test this hypothesis, it is important to determine the stress field of a hydride and its associated dislocations, combined. A simple planar dislocation model was developed of the hydride—dislocation ensemble in α-Zr. By capturing details of the dislocation structures given in the literature, it is shown in this study that including the interfacial dislocations largely reconciles the predicted and experimental values. Discrete dislocation plasticity is then used to model the diffuse plastic relaxation associated with hydride formation. The effects of plastic relaxation on the equilibrium hydrogen profile, hence the implications for subsequent hydride precipitation, are discussed. In particular, precipitation–dissolution cycles were simulated to calculate the magnitude of the residual hydrostatic tension, which is argued to be the primary cause of the “memory effect” for the re-precipitation of both γ and δ hydrides.

Phase transformation of hydride-phase Nd2Co7 with superlattice structure

We investigated the phase stability of Nd2Co7 with a superlattice structure, its hydrogenation properties, and phase transformation during hydrogen absorption–desorption process. The results showed that Ce2Ni7-type and Gd2Co7-type structures coexisted in the annealed sample up to 1273 ​K. The Gd2Co7-type phase disappeared at temperatures above 1323 ​K. We successfully synthesized a largely single-phase Ce2Ni7-type Nd2Co7 when the alloy was annealed at 1373 ​K, followed by quenching in ice water. The phase transformation follows the order: hexagonal Nd2Co7 (space group P63/mmc) → hexagonal Nd2Co7H2.7 (space group P63/mmc) → orthorhombic Nd2Co7H8.1 (space group Pbcn), upon hydrogen absorption. Anisotropic lattice expansion along the c axis was observed in Nd2Co7H2.7. The unit cell of Nd2Co7H8.1 underwent isotropic expansion along the a, b, and c axes. However, the volume expansions of the MgZn2-type cell, CaCu5-type cell I, and CaCu5-type cell II were uneven at 36.0%, 8.9%, and 13.0%, respectively.

Anisotropic expansion, dissipative hydrodynamics from kinetic theory

In this paper, we consider Kasner space-time describing anisotropic three-dimensional expansion of the fluid and obtain the dissipative evolution equations for shear stress tensor and energy density from kinetic theory. For this, we use the iterative solution of relativistic Boltzmann equation with relaxation time approximation. We show that our results for second- and third-order evolution equations reduce to those of one-dimensional expansion case under suitable conditions for the anisotropic parameters in Kasner space-time.

Effect of vertical aligned carbon nanofiber/carbon nanotube on the mechanical, electrical and electromagnetic interference shielding properties of epoxy foams

In this study, one-dimensional (1D) carbonaceous blends containing multi-walled carbon nanotube (MWCNT) and carbon nanofiber (CNF) were added into epoxy resin (EP) to obtain hybrid powder though ball milling. Limited foam with vertically aligned nanofillers was fabricated through limited-foaming epoxy hybrid in a mold and Two-step foam was prepared by further freely foaming a preformed Limited foam in an oven. The cellular structure, compressive, electrically conductive and EMI shielding properties of these two kinds of epoxy composite foams were carefully investigated. Limited foam showed an isotropic electrical resistivity while the electrical anisotropy started to emerge after the second-step foaming. This result was ascribed to the twisty MWCNT bridged the aligned CNF to build conductive pathways in horizontal direction, thus eliminating the electrical anisotropy of Limited foam. However, these loose interconnections between MWCNT and CNF in horizontal direction were more seriously destroyed by the further growth of bubbles, consequently endowing the Two-step foam with electrical anisotropy. Adding CNF into EP/MWCNT foams not only improved the electromagnetic interference (EMI) shielding effectiveness (SE), which was due to the synergistic effect between hybrid nanofillers in enhancing the electrical conductivity, but also enlarged the anisotropy in EMI SE of both Limited foam and Two-step foam. As compared to anisotropic bubbles, the vertically aligned MWCNT/CNF in composite foams exhibited a weak effect on anisotropy in compressive strength. Moreover, a remarkably anisotropic expansion behavior of preformed foam during the second-step foaming was observed and this behavior can be tuned by the ball milling time and the content of vertically aligned nanofillers.