Pyramidal Units Research Articles

Three-dimensional graded metamaterials with customizable thermal responses under space-variant temperature stimuli

Metamaterials with customizable thermal expansions are desirable for important engineering applications. However, existing metamaterials were designed by considering uniform temperature distributions. In the current study, a new design strategy is proposed to develop metamaterials with customizable thermal deformations under space-variant temperature (SVT) stimuli which are non-uniform. Three types of bi-material pyramidal units are first devised through using different material distributions and geometrical configurations. The coefficients of thermal expansion (CTEs) of these units are derived in closed-form expressions. Graded metamaterials are then constructed from the pyramidal units through combined periodic and graded tessellations. Based on targeted thermal deformations under prescribed stimuli, geometrical parameters are identified, and the thermal strains are determined using the newly derived analytical formulas and finite element simulations. The two sets of predictions are found to agree well, which indicates the effectiveness of the new design strategy for the graded metamaterials. The numerical results reveal that the graded metamaterials exhibit customizable uniform deformations under the SVT stimuli. In addition, targeted customizable thermal deformations with quadric-shape strain profiles are achieved in the graded metamaterials. Compared with the conventional design with uniform temperature distributions, the newly proposed design of metamaterials under non-uniform SVT stimuli is more versatile and flexible, thereby providing a systematic strategy for developing graded metamaterials.

Evaluation of DNA and BSA-Binding, Nuclease Activity, and Anticancer Properties of New Cu(II) and Ni(II) Complexes with Quinoline-Derived Sulfonamides

Four complexes of essential metal ions, Cu(II) and Ni(II), with the new sulfonamide ligand N-(pyridin-2-ylmethyl)quinoline-8-sulfonamide (HQSMP) were synthesized and physicochemically and structurally characterized. Complex [Cu(QSMP)Cl]n (2) consists of a polymeric chain formed by distorted square pyramidal units. In 2, the sulfonamide ligand acts as a bridge coordinating to one Cu(II) through its three N atoms and to another metal ion via one O atom in the sulfonamido group, while the pentacoordinate complex [Cu(QSMP)(C6H5COO)] (3) presents a highly distorted square pyramidal geometry. Complex [Ni(QSMP)(C6H5COO)(CH3OH)][Ni(QSMP)(CH3COO)(CH3OH)] (4) consists of two mononuclear entities containing different anion coligands, either a benzoate or an acetate group. Both units exhibit a distorted octahedral geometry. The interaction of the complexes with CT-DNA was studied by means of UV-Vis and fluorescence spectroscopy, interestingly revealing that the Ni(II) complex presents the highest affinity towards the nucleic acid. Complexes 1 and 2 are able to cleave DNA. Both compounds show promising nuclease activity at relatively low concentrations by mediating the production of a reactive oxygen species (ROS). The interaction of the four complexes with bovine serum albumin (BSA) was also investigated, showing that the compounds can bind to serum proteins. The antitumor potential of complexes 1 and 2 was evaluated against the A549 lung adenocarcinoma cell line, revealing cytotoxic properties that were both dose- and time-dependent.

Vibration transmission characteristics of the pyramidal cylinder lattice truss structure

In this work, an innovative cylindrical metamaterial inspired by origami was developed. It featured arrays of pyramid units arranged both circumferentially and axially. The vibration transfer characteristics were determined using numerical method (Frequency Domain Frequency Response Solver of COMSOL) and dynamic testing (Scanning Vibrometer System). The results indicate that the structure effectively attenuates vibrations within the 0–6000 Hz range. Adjusting key geometric parameters can widen or shift vibration attenuation bands toward low–frequencies. Increasing the rod diameter weakens the vibration attenuation capability, while an increase in circumferential and axial angles has a positive impact on the frequency band for vibration attenuation. The significance of this work lies in providing an appropriate method to enhance vibration attenuation for the design and optimization of engineering structures.

A congruent-melting rubidium zinc vanadium oxychloride exhibiting strong mid-infrared second-harmonic generation and high laser-induced damage threshold

A novel mid-infrared (MIR) nonlinear optical (NLO) crystal Rb4ZnV5O15Cl (RZVC) has been designed and sythesized by the aliovalent substitution strategy based on the parent structure Rb2(VO)(V2O7). Modification of square pyramidal VO5 units through introduction of chlorine ion and zinc metal caion significantly enhanced the dipole moments in a unit cell from 1.653 D for Rb2(VO)(V2O7) to 6.559 D for RZVC. Consequently, polycrystalline RZVC exhibits strong SHG responses of 12.5 × KDP @1064 nm and 1.2 × AGS @2 μm. Furthermore, RZVC features a congruent melting property, an ultra-high LIDT value (62 × AGS @1064 nm), and a deep IR transparency cutoff edge (10 μm). Most importantly, RZVC can achieve full-wavelength phase matching in a very wide MIR transparency range of 1.69–10 μm, completely covering the important atmospheric window (3–5 μm) through NLO processes. Because of its many outstanding properties, RZVC can be a highly desirable candidate for practical MIR NLO applications.

The correlation between structural factors and Stokes shifts in zero-dimensional Antimony(III) halides

Zero-dimensional (0D) hybrid metal halides (HMHs) have recently garnered significant attention as promising light emitters due to their distinctively Stokes-shifted broadband emissions resulting from self-trapped excitons (STEs). However, the influence of crystalline structures on the Stokes shift remains inadequately understood. Herein, we design and synthesize a series of 0D (Ph4P)2SbCl5-xBrx (Ph4P = tetraphenylphosphonium, x = 0–5) compounds to elucidate the intrinsic relationship between structural factors and the Stokes shift in 0D Sb(III) halides. Our comprehensive investigations into their crystalline structures and photoluminescence (PL) properties unveil that the Stokes shift correlates with intra- and inter-pyramidal [SbCl5-xBrx]2- units. Specifically, a shorter vertical Sb–Cl bond within the square pyramid, coupled with a greater Sb⋯Sb distance between the pyramidal units, facilitates significant structural relaxation in excited states, resulting in a larger Stokes shift, and vice versa. Notably, this principle applies not only within identical space groups but also across different crystal systems. Furthermore, our findings are supported by analyses of the structures and PL properties of other reported 0D Sb(III) halides with square pyramidal coordination. This study elucidates the structure-dependent nature of the Stokes shift in 0D Sb(III) halides, offering a novel avenue for the design of functional 0D metal halide materials.

A novel phosphate with CoII square planar coordination, BaCo0.5Fe(PO4)2: structural and magnetic features.

A novel phosphate containing barium, cobalt, and iron was synthesized in single-crystal and polycrystalline forms. Single crystal-based X-ray measurements revealed that it crystallizes in the monoclinic system with the P21/c space group. The structure is made up of linkages between FeO6 octahedra, CoO4 square planar units, CoO5 square pyramidal units, and PO4 tetrahedra through edges and/or vertices. The interconnection of these polyhedra leads to a three-dimensional framework with tunnels along the a-axis where the Ba2+ cations are located. The polycrystalline form was prepared via the sol-gel method and its XRD pattern was refined by the Le Bail method. Morphological and elemental mapping analyses of this phosphate were performed by scanning electron microscopy. In addition, infrared and Raman spectroscopy provided more insights into chemical bonding. The magnetic behavior was antiferromagnetic below TN ∼ 20 K. Optical measurements revealed a direct bandgap with an energy Eg of 2.83 eV.

Mechanism of Negative Thermal Expansion in Monoclinic Cu2P2O7 from First Principles.

Negative thermal expansion (NTE) materials generally have high-symmetry space groups, large average atomic volumes, and corner-sharing octahedral and tetrahedral coordination structures. By contrast, monoclinic α-Cu2P2O7, which has a small average atomic volume and edge-sharing structure, has been reported to exhibit NTE, the detailed mechanism of which is unclear. In this study, we investigate the A2B2O7 polymorphs and analyze the NTE behavior of α-Cu2P2O7 using first-principles lattice-dynamics calculations. From the polymorphism investigation in 20 A2B2O7 compounds using 6 representative crystal structures, small A and B cationic radii are found to stabilize the α-Cu2P2O7-type structure. We then analyze the NTE behavior of α-Cu2P2O7 using quasi-harmonic approximation. Our calculated thermal expansion coefficients and anisotropic atomic displacement parameters were in good agreement with those of the experimental reports at low temperatures. From the mode-Grüneisen parameter distribution plotted over the entire first-Brillouin zone, we found that the phonon contributing most significantly to NTE emerges not into the special points but between them. In this phonon mode, the O connecting two PO4 tetrahedra rotates, and the Cu and O vibrate perpendicular to the bottom of the CuO5 pyramidal unit, which folds the ac lattice plane. This vibration behavior can explain the experimentally reported anisotropic NTE behavior of α-Cu2P2O7. Our results demonstrate that the most negative mode-Grüneisen parameter contributing to NTE behavior is not always located on high-symmetry special points, indicating the importance of lattice vibration analyses for the entire first-Brillouin zone.

Lone‐Pair‐Driven, Brightly Emitting Lead‐Free Zero‐Dimensional Inorganic Luminescent Member

AbstractZero‐dimensional (0D) 5s2‐metal halide (MH) materials offer potential for use in solid‐state lighting, optical thermography, and scintillation applications. The organic components of most highly luminescent materials are inherently unstable under moisture and thermal stress, which restricts their practical use in advanced applications. Hence, highly luminescent and stable inorganic luminescent materials are required. In this work, to the best of current knowledge, a 0D completely inorganic luminescent member of K2SbCl5 that exhibits orange emission at 610 nm with an 80% photoluminescence quantum yield (PLQY) is reported for the first time. Density functional theory calculations reveal that the [SbCl5]2‐ square pyramidal units are the only optically active emission centers in K2SbCl5. The white light‐emitting device utilizing K2SbCl5 demonstrates impressive performance metrics, boasting a substantial color rendering index (CRI) of 94 and an exceptional luminous efficacy of 118.1 lm W−1. Hence, this isolated [SbCl5]2−square pyramidal environment serves as a design principle for the development of highly efficient inorganic Sb3+‐based luminescent materials for future optoelectronic applications.

Evidence of Chlorotellurate(IV) – Hydroxochlorotellurate(IV) species equilibrium upon dissolution of tellurite glasses in aqueous hydrochloric acid: A Raman spectroscopic study

Raman spectroscopy has been used to elucidate the structure of tellurium (IV) oxide and its binary mixtures with thallium oxide both in the glassy state and in aqueous hydrochloric acid solutions. The addition of Tl2O in pure TeO2 glass results in the progressive transformation of TeO4 trigonal bipyramid (tbp) to TeO3 trigonal pyramid (tp) units in agreement with the literature findings. Thallium oxide acting as a modifier for the tellurite network, reduces the functionality of the initial unit and lowers the continuous network rigidity. The spectral changes upon dissolution of the 0.2Tl2O-0.8TeO2 glass in aqueous hydrochloric acid solution have also been measured revealing that the main structural units of the glass structure did not survive in a solution state and the connectivity of the glass network has completely collapsed. The systematics and the concentration dependence of the spectra acquired from different solutions indicate the presence of several chlorotellurate(IV) and hydroxochlorotellurate(IV) ionic species. The spectroscopic data are interpreted in such a way in order to indicate a dynamic equilibrium between the TeCl62− anion and the TeCl4(OH)− species. A combined analysis of the polarized and depolarized scattered intensity is presented here which aimed at elucidating the presence of additional species including the TeCl4(OH)22− and TeCl3(OH) species, respectively. The proposed model is discussed in the framework of the current phenomenological status of the field.

Scalable 3D textile with hierarchically functionalized pyramidal units using nanostructured polyamide@carbon/Fe3O4 fibers for tunable microwave absorption

Most of the existing flexible microwave absorbing materials (MAMs) are in forms of nonwoven or woven composites. However, the nonwoven ones always show the poor mechanical properties and the woven ones normally involve with the complex fabrication processes and present heavy weight (>1.0 g/cm3), large thickness (>4.0 mm), and impermeability, which greatly hinder their wearable applications. Herein, a scalable 3D textile with hierarchically functionalized pyramidal units using the polyamide@carbon/Fe3O4 fibers (PCF) was successfully fabricated via a simple combined process of melt-spinning and three-dimensional (3D) weaving technologies. The core-sheath PCF can be continuously fabricated with a high production rate of 6000 m/min using pristine polyamide as core and the modified polyamide doped with carbon black and Fe3O4 nanoparticles as sheath. As a result, the as-prepared PCF are easily woven into various 3D textiles with pyramid periodic and impedance matching-lossy-dielectric multilayer structures, simultaneously achieving the impedance gradient and destructive interference. More importantly, changing the size of pyramid structures can tailor the microwave absorption performance. Consequently, the high-density polyamide@carbon/Fe3O4 textile has high-efficiency microwave absorption ability, showing lightweight (0.3 g/cm3), small-thickness (3.2 mm), strong (-47.51 dB), and broadband (5.2 GHz). Besides, the 3D structures endowed the textile with excellent mechanical property, superior flexibility, outstanding breathability and good heat insulation property, which is better than similar MAMs. This work provides a promising strategy for facile and large-scalable production of microwave absorption textiles with high overall performance.

Fluid–Structure Coupling and Aerodynamic Performance of a Multi-Dimensional Morphing Wing with Flexible Metastructure Skin

A multi-dimensional morphing wing skeleton mechanism is proposed with double-sided triangular pyramid units, which can realize continuous variable span-wise bend, span-wise twist, and sweep. A lockable morphing unit is designed, and its mechanism/structure characteristics, degree of freedom, and the deformable function of its deformable wing skeleton mechanism are analyzed. One kind of flexible skin is proposed to meet the performance requirements, consisting of an internal metastructure and a flexible surface bonded on both sides. The morphing wing skeleton mechanism and the equivalent treated metastructure flexible skin are then combined. Subsequently, a two-way fluid–structure interaction analysis is conducted to investigate the influence of aerodynamic loads on the flexible skin and skeleton mechanism in different deformation states, including the influence of structural passive deformation on the aerodynamic characteristics of the morphing wing. The computational fluid dynamics method is employed to analyze the aerodynamic characteristics of the morphing wing in its initial state, as well as in three deformation states, and to study its aerodynamic performance in different flight environments.

Synthesis, Characterization and Structural Analysis of Two New Biguanide Complexes

This study reports on the synthesis and characterization of two new coordination compounds of the active pharmaceutical ingredient metformin and transition metals. The cobalt compound with the formula [Co(Met)3][CoCl4]Cl·3H2O is a complex salt formed by a cationic Co(III) octahedral and anionic Co(II) tetrahedral subunits. The Cu(II) complex is represented by the formula [(Cu(Met)Cl)2-μ-Cl2] and is a dimeric compound with two chloride anions acting as a bridge, forming shared-edge square pyramidal units. Both compounds were characterized by single crystal X-ray diffraction, FT-IR spectroscopy and thermal analysis.

Recycled and Nickel- or Cobalt-Doped Lead Materials from Lead Acid Battery: Voltammetric and Spectroscopic Studies.

The active mass of the plates of aspent car battery with higher wear after an efficient desulfatization can be used as sources of a new electrode. This paper proposes the recycling of spent electrodes from a lead acid battery and the incorporation of NiO or Co3O4 contents by the melt-quenching method in order to enrich the electrochemical properties. The analysis of X-ray diffractograms indicates the gradual decrease in the sulfated crystalline phases, respectively, 4PbO·PbSO4 and PbO·PbSO4 phases, until their disappearance for higher dopant concentrations. Infrared (IR) spectra show a decreasing trend in the intensity of the bands corresponding to the sulfate ions and a conversion of [PbO3] pyramidal units into [PbO4] tetrahedral units by doping with high dopant levels, yielding to the apparition of the PbO2 crystalline phase. The observed electron paramagnetic resonance (EPR) spectra confirm three signals located on the gyromagnetic factor, g~2, 2.2 and 8 assigned to the nickel ions in higher oxidation states as well as the metallic nickel nanoparticles. This compositional evolution can be explained by considering a process of the drastic reduction in nickel ions from the superior oxidation states to metallic nickel. The linewidth and the intensity of the resonance lines situated at about g~2, 2.17, 4.22 and 7.8 are attributed to the Co+2 ions from the EPR data. The best reversibility of the cyclic voltammograms was highlighted for the samples with x = 10 mol% of NiO and 15 mol% of Co3O4, which are recommended as suitable in applications as new electrodes for the lead acid battery.

Structural relaxation in IR transmitting (GeSe4)100-x(As2Se3)x glasses

(GeSe4)100-x (As2Se3)x glasses in the GeSe4-As2Se3 pseudo-binary joint are prepared by the melt quenching method. In this tie-line, the entire composition 0 ≤ x ≤ 100 is characterized by fixed average network connectivity of 2.40, which is considered to be optimal connectivity as the number of constraints and the number degrees of freedom available to the atoms are balanced at this average connectivity. The glass forming ability of the glasses having this average connectivity of 2.40 is usually found to be maximum. Glass transition temperature (Tg) decreases till x = 30 and remains invariant in the range 40 ≤ x ≤ 70. For x > 70, Tg shows an increasing trend. The jump in specific heat capacity (ΔCp), non-reversing heat flow (ΔHnr), Tg and the optical bandgap (Eg) show a distinct change in the composition range 40 and 70 mol.% of As2Se3. The fragility index (m) lies in the range of 15 and 32 for all the prepared glasses, representing the strong nature of these glass forming melts in the (GeSe4)100-x (As2Se3)x glasses. The viscosity as a function of reduced temperature (Tg/T) shows almost an Arrhenius nature for 0 ≤ x ≤ 70 and for x > 70, a slight deviation from the Arrhenius behviour is observed. The structural network of these glasses primarily consists of GeSe4/2 and Se-Se chains for x ≤ 30. For 40 ≤ x ≤ 70, the network is dominated by AsSe3/2 pyramidal units and As-As homopolar bonds. For x > 70, the structural network is characterized by AsSe3/2 pyramidal units. All the prepared glasses are found to transmit infrared (IR) light over a wide wavelength range from 2 to 17 μm. The super strong nature of the melts indicates that optical devices can be easily made for IR applications.

Regulating multiple self-trapped exciton emissions in zero-dimensional antimony halides with pyramidal units

The [SbCl5]2− distortions modulate triplet STE emissions. The enhancement of high-energy triplet emission is ascribed to enhanced electron–phonon coupling, promoted intersystem crossing process, as well as restrained nonradiative transitions.

Trustworthy and Reliable Deep Learning-based Cyberattack Detection in Industrial IoT.

A fundamental expectation of the stakeholders from the Industrial Internet of Things (IIoT) is its trustworthiness and sustainability to avoid the loss of human lives in performing a critical task. A trustworthy IIoT-enabled network encompasses fundamental security characteristics such as trust, privacy, security, reliability, resilience and safety. The traditional security mechanisms and procedures are insufficient to protect these networks owing to protocol differences, limited update options, and older adaptations of the security mechanisms. As a result, these networks require novel approaches to increase trust-level and enhance security and privacy mechanisms. Therefore, in this paper, we propose a novel approach to improve the trustworthiness of IIoT-enabled networks. We propose an accurate and reliable supervisory control and data acquisition (SCADA) network-based cyberattack detection in these networks. The proposed scheme combines the deep learning-based Pyramidal Recurrent Units (PRU) and Decision Tree (DT) with SCADA-based IIoT networks. We also use an ensemble-learning method to detect cyberattacks in SCADA-based IIoT networks. The non-linear learning ability of PRU and the ensemble DT address the sensitivity of irrelevant features, allowing high detection rates. The proposed scheme is evaluated on fifteen datasets generated from SCADA-based networks. The experimental results show that the proposed scheme outperforms traditional methods and machine learning-based detection approaches. The proposed scheme improves the security and associated measure of trustworthiness in IIoT-enabled networks.

Effect of Er3+ ions on the structural, optical and Judd-Ofelt (JO) intensity parameters of (Bi2O3-BaTiO3) glass system and their application as fiber-amplifier

Barium titanate-based bismuthate glasses doped with Er3+ ions have been fabricated by employing the conventional melt quench technique. Various characterization studies have been performed on the samples for their physical, structural and optical analysis such as the density and molar volume measurements, X-Ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, and UV–Vis spectroscopies. The amorphous nature of the prepared glass samples has been confirmed by the broad humps observed in the X-Ray diffractograms. The FTIR spectra confirmed an increment in the non-bridging oxygen atoms (NBOs) and also the transformation of [BiO6] units to [BiO3] pyramidal units in the structural network of the glass matrix. Raman spectra in the high-frequency region have also been recorded which provided information related to the structural changes in the glass system upon the building of Er-O linkages. Absorption spectra of UV–Vis spectroscopy depicted six transition states such as 4F7/2, 2H11/2, 4S3/2, 4F9/2, 4I11/2, and 4I13/2. The spectroscopic and optical parameters such as energy band gap, optical conductivity, penetration depth, Judd-Ofelt (JO) parameters, refractive index, dielectric constant, Urbach energy, and transmission coefficient for the glasses have been determined, among others. The nephelauxetic ratio (β) and bonding parameters (δ) obtained from transitions of rare-earth ions have revealed the ionic character of the glasses. The calculated values of indirect and direct energy bandgap (Eg) of the prepared samples have been found to decrease from 2.04 to 1.93 and 2.67 to 2.45 resp. on increasing Er3+ ions. Judd-Ofelt (JO) parameters follow the order given by Ω2> Ω6> Ω4 and have been consistent with the literature. A decrement in the values of Ω2 from 3.761 to 2.699, confirmed the lowest asymmetry in the crystal field of rare-earth ions of glass system. The obtained values of refractive index, Urbach energy, dielectric constant, electronic & ionic polarizability and the metallization criterion suggest that the presently studied glass samples are amorphous semiconducting, optically non-linear and are suitable for the applications in erbium-doped fiber-amplifier (EDFA), lasers and optoelectronic devices.

Silver Ion-Induced Formation of Unprecedented Thorium Nonamer Clusters via Lacuna-Construction Strategy

Silver Ion-Induced Formation of Unprecedented Thorium Nonamer Clusters via Lacuna-Construction Strategy

On the Total Reflectivity Estimation of Microwave Calibration Targets by Backscattering Measurements

Before practical usage in microwave radiometers, the calibration targets must be tested for its emissivity/total reflectivity. In this work, we address the issue that remains in the total reflectivity determination, which is estimating the total reflectivity based on measured backscattering in the monostatic configuration, specifically at high frequencies. Based on the efficient modeling on periodic unit of the array-shaped calibration target, we quantitatively evaluate the relationship between backscattering and the total reflectivity, on the common structure of coated cones and coated pyramids. It is found that the total reflectivity estimation becomes target-specific for the coated cones; meanwhile, stable compensation can be concluded for the pyramidal units, which is important for practical testing in submillimeter applications. Then, the disturbing effects of the geometric defects on the total reflectivity estimation are discussed, and it is inferred that wideband measurement is vital for diagnosing those defects. Furthermore, actual test results are analyzed, showing the complex scenario in estimating the total reflectivity of a prototype with shape defects. Also, the numerical concluded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{g}$ </tex-math></inline-formula> compensation is verified in the clear case of a fine prototype. The findings in this work offer a direct reference for the application of microwave radiometer calibration, especially in the region of submillimeter waves.

Topology optimization design and research of lightweight biomimetic three-dimensional lattice structures based on laser powder bed fusion

In this paper, a topological structure based on the three-dimensional (3D) bionic lattice method had been used to optimize the structure of the U-Shape ring, a typical type of load-bearing structure, in order to minimize the weight of the structure, while ensuring the U-Shape ring's sufficient strength and stiffness. Three kinds of 3D lattice sandwich structures for U-shaped sample were established and analyzed by the way of computer aided design (CAD) and finite element analysis (FEA). The pyramidal sandwich unit had been adopted to the lightweight design of the U-shaped sample, which had been optimized from the full-rod unit structure into the pyramid unit with “rod system and thin wall”. At the same time, according to the process characteristics of laser powder bed fusion (LPBF), the local structure had been optimized again, which not only met the technical requirements of LPBF, but also improved the equivalent strength and stability of the interface between element core and U-shaped inner wall. Through the above measures, the weight of the U-Shape bearing ring could be reduced by nearly 30%. Then the U-shaped load-bearing parts had been made by the LPBF process, and a special test device had been designed to test the mechanical properties of the samples. The results showed that the loading test was basically consistent with the FEA, and both met the design requirements. The design of 3D bionic lattice spatial structure used in this paper effectively solved the problem of the loss of strength and stiffness caused by the lightweight structure. The research work of this paper can be used as a reference for those who are engaged in lightweight structure design.