Dynamic response of an FGM cylindrical shell under moving loads

This paper presents an analytical study on the dynamic behavior of the infinitely-long, FGM cylindrical shell subjected to combined action of the axial tension, internal compressive load and ring-shaped compressive pressure with constant velocity. It is assumed that the cylindrical shell is a mixture of metal and ceramic that its properties changes as a function of the shell thickness. The problem is studied on the basis of the theory of vibrations of cylindrical shells. Derived formulas for the maximum static and dynamic displacements, dynamic factors and critical velocity for the FGM cylindrical shell subjected to moving loads. Numerical calculations have been made for fully metal, fully ceramic and FGM (Si₃N₄/SUS304) cylindrical shells. A parametric study is conducted to demonstrate the effects of the material property gradient, the radius to thickness ratio and the velocity of the moving load on the dynamic displacements and dynamic factors of the inner and ring-shaped pressures for FGM cylindrical shells.     

Active control of FGM plates subjected to a temperature gradient: Modelling via finite element method based on FSDT

An efficient finite element formulation based on a first‐order shear deformation theory (FSDT) is presented for the active control of functionally gradient material (FGM) plates with integrated piezoelectric sensor/actuator layers subjected to a thermal gradient; this is accomplished using both static and dynamic piezothermoelastic analyses. The formulation based on FSDT can be applied to a range of relatively thin‐to‐moderately thick plates. A constant displacement‐cum‐velocity feedback control algorithm coupling the direct and inverse piezoelectric effects is applied to provide active feedback control of the integrated FGM plate in a self‐monitoring and self‐controlling system. Numerical results for the control of bending and torsional deflections and/or vibrations are presented for a FGM plate comprising zirconia and aluminium. The effects of constituent volume fraction and the influence of feedback control gain on the static and dynamic responses of the FGM plates are examined in detail. Copyright © 2001 John Wiley & Sons, Ltd.     

Systematic Analysis of the Improvements in Magnetic Resonance Microscopy with Ferroelectric Composite Ceramics

The spatial resolution and signal‐to‐noise ratio (SNR) attainable in magnetic resonance microscopy (MRM) are limited by intrinsic probe losses and probe–sample interactions. In this work, the possibility to exceed the SNR of a standard solenoid coil by more than a factor‐of‐two is demonstrated theoretically and experimentally. This improvement is achieved by exciting the first transverse electric mode of a low‐loss ceramic resonator instead of using the quasi‐static field of the metal‐wire solenoid coil. Based on theoretical considerations, a new probe for microscopy at 17 T is developed as a dielectric ring resonator made of ferroelectric/dielectric low‐loss composite ceramics precisely tunable via temperature control. Besides the twofold increase in SNR, compared with the solenoid probe, the proposed ceramic probe does not cause static‐field inhomogeneity and related image distortion.     

A FEM model for the active control of curved FGM shells using piezoelectric sensor/actuator layers

In this paper, a generic finite element formulation is developed for the static and dynamic control of FGM (functionally graded material) shells with piezoelectric sensor and actuator layers. The properties of the FGM shell are graded in the thickness direction according to a volume fraction power‐law distribution. The proposed finite element model is based on variational principle and linear piezoelectricity theory. A constant displacement and velocity feedback control algorithm coupling the direct and inverse piezoelectric effects is applied in a closed‐loop system to provide feedback control of the integrated FGM shell structure. Both static and dynamic control of FGM shells are simulated to demonstrate the effectiveness of the proposed active control scheme within a framework of finite element discretization and piezoelectric integration. Copyright © 2002 John Wiley & Sons, Ltd.     

Optimal solid shell element for large deformable composite structures with piezoelectric layers and active vibration control

In this paper, we present an optimal low‐order accurate piezoelectric solid‐shell element formulation to model active composite shell structures that can undergo large deformation and large overall motion. This element has only displacement and electric degrees of freedom (dofs), with no rotational dofs, and an optimal number of enhancing assumed strain (EAS) parameters to pass the patch tests (both membrane and out‐of‐plane bending). The combination of the present optimal piezoelectric solid‐shell element and the optimal solid‐shell element previously developed allows for efficient and accurate analyses of large deformable composite multilayer shell structures with piezoelectric layers. To make the 3‐D analysis of active composite shells containing discrete piezoelectric sensors and actuators even more efficient, the composite solid‐shell element is further developed here. Based on the mixed Fraeijs de Veubeke–Hu–Washizu (FHW) variational principle, the in‐plane and out‐of‐plane bending behaviours are improved via a new and efficient enhancement of the strain tensor. Shear‐locking and curvature thickness locking are resolved effectively by using the assumed natural strain (ANS) method. We also present an optimal‐control design for vibration suppression of a large deformable structure based on the general finite element approach. The linear‐quadratic regulator control scheme with output feedback is used as a control law on the basis of the state space model of the system. Numerical examples involving static analyses and dynamic analyses of active shell structures having a large range of element aspect ratios are presented. Active vibration control of a composite multilayer shell with distributed piezoelectric sensors and actuators is performed to test the present element and the control design procedure. Copyright © 2005 John Wiley & Sons, Ltd.     

Well‐Defined Metal Nanoparticles@Covalent Organic Framework Yolk–Shell Nanocages by ZIF‐8 Template as Catalytic Nanoreactors

Yolk–shell nanoreactors have received considerable interest for use in catalysis. However, the controlled synthesis of continuous crystalline shells without imperfections or cracks remains challenging. Here, a strategy for the synthesis of yolk–shell metal nanoparticles@covalent organic framework (MNPs@COF) nanoreactors by using MNPs@ZIF‐8 core–shell nanostructures as a self‐template is designed and developed. The COF shell is formed through an amorphous‐to‐crystalline transformation process of a polyimine shell in a mildly acidic solution, while the ZIF‐8 is etched in situ, generating a void space between the MNPs core and the COF shell. With the protection of the COF shell, multiple ligand‐free MNPs are confined inside of the hollow nanocages. Importantly, the synthetic strategy can be generalized to engineer the functions and properties of the designed yolk–shell nanocages by varying the structure of the COF shell and/or the composition of the core MNPs. Representative Pd@H‐TpPa yolk–shell nanocages with active Pd NP cores and permeable TpPa shells exhibit high catalytic activity and stability in the reduction of 4‐nitrophenol by NaBH₄ at room temperature.     

Generalized coupled thermoelasticity of functionally graded cylindrical shells

In this paper, the response of a circular cylindrical thin shell made of the functionally graded material based on the generalized theory of thermoelasticity is obtained. The governing equations of the generalized theory of thermoelasticity and the energy equations are simultaneously solved for a functionally graded axisymmetric cylindrical shell subjected to thermal shock load. Thermoelasticity with second sound effect in cylindrical shells based on the Lord–Shulman model is compared with the Green–Lindsay model. A second‐order shear deformation shell theory, that accounts for the transverse shear strains and rotations, is considered. Including the thermo‐mechanical coupling and rotary inertia, a Galerkin finite element formulation in space domain and the Laplace transform in time domain is used to formulate the problem. The inverse Laplace transform is obtained using a numerical algorithm. The shell is graded through the thickness assuming a volume fraction of metal and ceramic, using a power law distribution. The effects of temperature field for linear and non‐linear distributions across the shell thickness are examined. The results are validated with the known data in the literature. Copyright © 2006 John Wiley & Sons, Ltd.     

One‐Step Construction of N,P‐Codoped Porous Carbon Sheets/CoP Hybrids with Enhanced Lithium and Potassium Storage

Despite the desirable advancement in synthesizing transition‐metal phosphides (TMPs)‐based hybrid structures, most methods depend on foreign‐template‐based multistep procedures for tailoring the specific structure. Herein, a self‐template and recrystallization–self‐assembly strategy for the one‐step synthesis of core–shell‐like cobalt phosphide (CoP) nanoparticles embedded into nitrogen and phosphorus codoped porous carbon sheets (CoP?NPPCS), is first proposed. Relying on the unusual coordination ability of melamine with metal ions and the cooperative hydrogen bonding of melamine and phytic acid to form a 2D network, a self‐synthesized single precursor can be attained. Importantly, this approach can be easily expanded to synthesize other TMPs?NPPCS. Due to the unique compositional and structural characteristics, these CoP?NPPCSs manifest outstanding electrochemical performances as anode materials for both lithium‐ and potassium‐ion batteries. The unusual hybrid architecture, the high specific surface area, and porous features make the CoP?NPPCS attractive for other potential applications, such as supercapacitors and electrocatalysis.     

Fabrication of a Spherical Superstructure of Carbon Nanorods

Hierarchical superstructures in nano/microsize have attracted great attention owing to their wide potential applications. Herein, a self‐templated strategy is presented for the synthesis of a spherical superstructure of carbon nanorods (SS‐CNR) in micrometers through the morphology‐preserved thermal transformation of a spherical superstructure of metal–organic framework nanorods (SS‐MOFNR). The self‐ordered SS‐MOFNR with a chestnut‐shell‐like superstructure composed of 1D MOF nanorods on the shell is synthesized by a hydrothermal transformation process from crystalline MOF nanoparticles. After carbonization in argon, the hierarchical SS‐MOFNR transforms into SS‐CNR, which preserves the original chestnut‐shell‐like superstructure with 1D porous carbon nanorods on the shell. Taking the advantage of this functional superstructure, SS‐CNR immobilized with ultrafine palladium (Pd) nanoparticles (Pd@SS‐CNR) exhibits excellent catalytic activity for formic acid dehydrogenation. This synthetic strategy provides a facile method to synthesize uniform spherical superstructures constructed from 1D MOF nanorods or carbon nanorods for applications in catalysis and energy storage.     

Fabrication of Micropatterned Self‐Oscillating Polymer Brush for Direction Control of Chemical Waves

The propagation control of chemical waves via a pentagonal patterned structure in a self‐oscillating polymer brush composed of N‐isopropylacrylamide and a metal catalyst for the Belousov–Zhabotinsky (BZ) reaction is reported. The patterned self‐oscillating polymer brush is prepared by combining surface‐initiated atom transfer radical polymerization and maskless photolithography. Surface modification is confirmed by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, 3D measuring laser microscopy, and fluorescence microscopy. The polymer brush patterns are fabricated with gaps between the pentagonal regions, and investigations on the effect of the gap distance on the BZ reaction reveal that at the appropriate distance, chemical waves propagate across the array from the plane to the corner between the patterns. Unidirectional control is achieved not only in the 1D array, but also in a 2D curved array. This patterned self‐oscillating polymer brush is a novel and advantageous approach for creating an autonomous dynamic soft interface.     

Flyweight,Superelastic, Electrically Conductive,and Flame‐Retardant 3D Multi‐Nanolayer Graphene/Ceramic Metamaterial

A ceramic/graphene metamaterial (GCM) with microstructure‐derived superelasticity and structural robustness is achieved by designing hierarchical honeycomb microstructures, which are composited with two brittle constituents (graphene and ceramic) assembled in multi‐nanolayer cellular walls. Attributed to the designed microstructure, well‐interconnected scaffolds, chemically bonded interface, and coupled strengthening effect between the graphene framework and the nanolayers of the Al₂O₃ ceramic (NAC), the GCM demonstrates a sequence of multifunctional properties simultaneously that have not been reported for ceramics and ceramics–matrix–composite structures, such as flyweight density, 80% reversible compressibility, high fatigue resistance, high electrical conductivity, and excellent thermal‐insulation/flame‐retardant performance simultaneously. The 3D well‐ordered graphene aerogel templates are strongly coupled with the NAC by the chemically bonded interface, exhibiting mutual strengthening, compatible deformability, and a linearly dependent relationship between the density and Young's modulus. Considerable size effects of the ceramic nanolayers on the mechanical properties are revealed in these ceramic‐based metamaterials. The designed hierarchical honeycomb graphene with a fourth dimensional control of the ceramic nanolayers on new ways to scalable fabrication of advanced multifunctional ceramic composites with controllable design suggest a great potential in applications of flexible conductors, shock/vibration absorbers, thermal shock barriers, thermal insulation/flame‐retardant skins, and porous microwave‐absorbing coatings.     

Quasi‐static and Impact Responses of Multi‐layered Corrugated Paperboard Cushion by Virtual Mass Method

Quasi‐static compressive and impact behaviours of multi‐layered corrugated paperboard (MLCP) cushioning structure were analysed by a recently proposed virtual mass method. First, virtual mass method was applied and verified analytically to solve quasi‐static compressive responses for representative two‐layer corrugated paperboard cushioning structure. The results show that the two layers in the cushioning structure reach the buckling state in chronological order because of the existence of the small perturbations triggered by inertial force related to virtual mass, which leads to the two typical stress peaks in stress–strain curves. Second, the quasi‐static compressive behaviours of MLCP cushioning structure were further studied numerically, showing that the buckling order of multi‐layer cushioning structure depends on virtual mass, but the stress–strain curves remain unchanged when the virtual mass is smaller than some certain value. Finally, quasi‐static and dynamic impact tests of MLCP cushioning structure composed of C‐flute corrugated paperboard were carried out to further validate the capacity of the virtual mass method to describe layer‐wise collapse mechanism given the constitutive relationship of the monolayer corrugated paperboard. Copyright © 2014 John Wiley & Sons, Ltd.     

Inside Front Cover: Trilayered Ceramic–Metal–Polymer Microcantilevers with Dramatically Enhanced Thermal Sensitivity (Adv. Mater. 9/2006)

A novel trilayered (ceramic–metal–polymer) design for highly sensitive, thermally responsive microcantilever arrays is reported on p. 1157 by Tsukruk and co‐workers. In this design, the topmost nanocomposite layer, reinforced with carbon nanotubes and silver nanoparticles, acts as a strong thermal‐stress‐driven actuator to enhance conventional biomaterial performance. These polymer–metal–ceramic microcantilevers with enhanced (fourfold) thermal sensitivity may serve as a basis for the next generation of uncooled thermal microsensor arrays because of outstanding thermal and spatial resolution.     

Nanoengineering of Particle Surfaces

The creation of core–shell particles is attracting a great deal of interest because of the diverse applicability of these colloidal particles; e.g., as building blocks for photonic crystals, in multi‐enzyme biocatalysis, and in drug delivery. This review presents the state‐of‐the‐art in strategies for engineering particle surfaces, such as the layer‐by‐layer deposition process (see Figure), which allows fine control over shell thickness and composition.     

An Elastic Autonomous Self‐Healing Capacitive Sensor Based on a Dynamic Dual Crosslinked Chemical System

Adopting self‐healing, robust, and stretchable materials is a promising method to enable next‐generation wearable electronic devices, touch screens, and soft robotics. Both elasticity and self‐healing are important qualities for substrate materials as they comprise the majority of device components. However, most autonomous self‐healing materials reported to date have poor elastic properties, i.e., they possess only modest mechanical strength and recoverability. Here, a substrate material designed is reported based on a combination of dynamic metal‐coordinated bonds (β‐diketone–europium interaction) and hydrogen bonds together in a multiphase separated network. Importantly, this material is able to undergo self‐healing and exhibits excellent elasticity. The polymer network forms a microphase‐separated structure and exhibits a high stress at break (≈1.8 MPa) and high fracture strain (≈900%). Additionally, it is observed that the substrate can achieve up to 98% self‐healing efficiency after 48 h at 25 °C, without the need of any external stimuli. A stretchable and self‐healable dielectric layer is fabricated with a dual‐dynamic bonding polymer system and self‐healable conductive layers are created using polymer as a matrix for a silver composite. These materials are employed to prepare capacitive sensors to demonstrate a stretchable and self‐healable touch pad.     

Microwave assisted hydrothermal synthesis of well-dispersed and thermally stable Ag@SnO2 core–shell nanocomposites for propane sensing applications

A simple microwave assisted hydrothermal precipitation (M–H) technique for the synthesis of Ag@SnO₂ core–shell structure nanoparticles (NPs) is reported. Ag NPs were synthesized via chemical reduction of metal salt followed by M–H deposition of tin dioxide shell for fabrication of monodispersed core–shell particles. The phase and morphology has been investigated by X-ray diffraction technique (XRD) and transmission electron microscopy (TEM) respectively. Ag@SnO₂ core–shell nanocomposites have shown distinct surface Plasmon spectrum in the range of 407–440 nm. The core–shell morphology is confirmed from the TEM images. XRD patterns have suggested the formation of silver and tin dioxide in the face-centered cubic and Cassiterite form respectively. Our investigations suggested that the formation of core–shell structure results in the enhanced thermal stability of the system. Synthesized material is used for the detection of propane gas. To understand the multi gas sensing ability and selectivity for detection of propane gas by Ag@SnO₂ core–shell materials based devices, Sinha–Tripathy soft-sensor model has been proposed.     

Mesoporous Hollow Sb/ZnS@C Core–Shell Heterostructures as Anodes for High‐Performance Sodium‐Ion Batteries

Combining the advantage of metal, metal sulfide, and carbon, mesoporous hollow core–shell Sb/ZnS@C hybrid heterostructures composed of Sb/ZnS inner core and carbon outer shell are rationally designed based on a robust template of ZnS nanosphere, as anodes for high‐performance sodium‐ion batteries (SIBs). A partial cation exchange reaction based on the solubility difference between Sb₂S₃ and ZnS can transform mesoporous ZnS to Sb₂S₃/ZnS heterostructure. To get a stable structure, a thin contiguous resorcinol‐formaldehyde (RF) layer is introduced on the surface of Sb₂S₃/ZnS heterostructure. The effectively protective carbon layer from RF can be designed as the reducing agent to convert Sb₂S₃ to metallic Sb to obtain core–shell Sb/ZnS@C hybrid heterostructures. Simultaneously, the carbon outer shell is beneficial to the charge transfer kinetics, and can maintain the structure stability during the repeated sodiation/desodiation process. Owing to its unique stable architecture and synergistic effects between the components, the core–shell porous Sb/ZnS@C hybrid heterostructure SIB anode shows a high reversible capacity, good rate capability, and excellent cycling stability by turning the optimized voltage range. This novel strategy to prepare carbon‐layer‐protected metal/metal sulfide core–shell heterostructure can be further extended to design other novel nanostructured systems for high‐performance energy storage devices.     

Electrical Conductivity,Selective Adhesion,and Biocompatibility in Bacteria‐Inspired Peptide–Metal Self‐Supporting Nanocomposites

Bacterial type IV pili (T4P) are polymeric protein nanofibers that have diverse biological roles. Their unique physicochemical properties mark them as a candidate biomaterial for various applications, yet difficulties in producing native T4P hinder their utilization. Recent effort to mimic the T4P of the metal‐reducing Geobacter sulfurreducens bacterium led to the design of synthetic peptide building blocks, which self‐assemble into T4P‐like nanofibers. Here, it is reported that the T4P‐like peptide nanofibers efficiently bind metal oxide particles and reduce Au ions analogously to their native counterparts, and thus give rise to versatile and multifunctional peptide–metal nanocomposites. Focusing on the interaction with Au ions, a combination of experimental and computational methods provides mechanistic insight into the formation of an exceptionally dense Au nanoparticle (AuNP) decoration of the nanofibers. Characterization of the thus‐formed peptide–AuNPs nanocomposite reveals enhanced thermal stability, electrical conductivity from the single‐fiber level up, and substrate‐selective adhesion. Exploring its potential applications, it is demonstrated that the peptide–AuNPs nanocomposite can act as a reusable catalytic coating or form self‐supporting immersible films of desired shapes. The films scaffold the assembly of cardiac cells into synchronized patches, and present static charge detection capabilities at the macroscale. The study presents a novel T4P‐inspired biometallic material.     

Stress‐based finite element analysis of plane plasticity problems

A stress‐based model of the finite element method is evolved for two‐dimensional quasi‐static plasticity problems. The self‐equilibrating fields of stresses are constructed by means of the Airy stress function, which is approximated by three types of elements: the Bogner–Fox–Schmit rectangle, the Hsieh–Clough–Tocher triangle and its reduced variant. Traction boundary conditions are imposed by the use of the Lagrange multiplier method which gives the possibility of calculation of displacements for boundary points. The concept of multi‐point‐constraints elements is applied in order to facilitate the application of this technique. The iterative algorithm, analogous to the closest‐point‐projection method commonly used in the displacement‐based finite element model, is proposed for solving non‐linear equations for each load increment. Two numerical examples with stress‐ and displacement‐controlled load are considered. The results are compared with those obtained by the displacement model of FEM. Bounds for limit loads are obtained. Copyright © 1999 John Wiley & Sons, Ltd.     

High‐Gain 200 ns Photodetectors from Self‐Aligned CdS–CdSe Core–Shell Nanowalls

1D core–shell heterojunction nanostructures have great potential for high‐performance, compact optoelectronic devices owing to their high interface area to volume ratio, yet their bottom‐up assembly toward scalable fabrication remains a challenge. Here the site‐controlled growth of aligned CdS–CdSe core–shell nanowalls is reported by a combination of surface‐guided vapor–liquid–solid horizontal growth and selective‐area vapor–solid epitaxial growth, and their integration into photodetectors at wafer‐scale without postgrowth transfer, alignment, or selective shell‐etching steps. The photocurrent response of these nanowalls is reduced to 200 ns with a gain of up to 3.8 × 10³ and a photoresponsivity of 1.2 × 10³ A W^?1, the fastest response at such a high gain ever reported for photodetectors based on compound semiconductor nanostructures. The simultaneous achievement of sub‐microsecond response and high‐gain photocurrent is attributed to the virtues of both the epitaxial CdS–CdSe heterojunction and the enhanced charge‐separation efficiency of the core–shell nanowall geometry. Surface‐guided nanostructures are promising templates for wafer‐scale fabrication of self‐aligned core–shell nanostructures toward scalable fabrication of high‐performance compact photodetectors from the bottom‐up.