Bioinspired Nacre‐Like Ceramic with Nickel Inclusions Fabricated by Electroless Plating and Spark Plasma Sintering

Hybrid composites of layered brittle‐ductile constituents assembled in a brick‐and‐mortar architecture are promising for applications requiring high strength and toughness. Mostly, polymer mortars have been considered as the ductile layer in brick‐and‐mortar composites. However, low stiffness of polymers does not efficiently transfer the shear between hard ceramic bricks. Theoretical models point to metals as a more efficient mortar layer. However, infiltration of metals into ceramic scaffold is non‐trivial, given the low wetting between metals and ceramics. The authors report on an alternative approach to fabricate brick‐and‐mortar ceramic‐metal composites by using electroless plating of nickel (Ni) on alumina micro‐platelets, in which Ni‐coated micro‐platelets are subsequently aligned by a magnetic field, taking advantage of ferromagnetic properties of Ni. The assembled Ni‐coated ceramic scaffold is then sintered using spark plasma sintering (SPS) to locally create Ni mortar layers between ceramic platelets, as well as to sinter the ceramic micro‐platelets. The authors report on materials and mechanical properties of the fabricated composite. The results show that this approach is promising toward development of bioinspired ceramic‐metal composites.

     

High‐Entropy Alloy (HEA)‐Coated Nanolattice Structures and Their Mechanical Properties

Nanolattice structure fabricated by two‐photon lithography (TPL) is a coupling of size‐dependent mechanical properties at micro/nano‐scale with structural geometry responses in wide applications of scalable micro/nano‐manufacturing. In this work, three‐dimensional (3D) polymeric nanolattices are initially fabricated using TPL, then conformably coated with an 80 nm thick high‐entropy alloy (HEA) thin film (CoCrFeNiAl_0.3) via physical vapor deposition (PVD). 3D atomic‐probe tomography (APT) reveals the homogeneous element distribution in the synthesized HEA film deposited on the substrate. Mechanical properties of the obtained composite architectures are investigated via in situ scanning electron microscope (SEM) compression test, as well as finite element method (FEM) at the relevant length scales. The presented HEA‐coated nanolattice encouragingly not only exhibits superior compressive specific strength of ≈0.032 MPa kg^?1 m³ with density well below 1000 kg m^?3, but also shows good compression ductility due to its composite nature. This concept of combining HEA with polymer lattice structures demonstrates the potential of fabricating novel architected metamaterials with tunable mechanical properties.

     

Packaging‐related properties of protein‐ and chitosan‐coated paper

The mechanical and gas‐barrier properties of paper and paperboard coated with chitosan–acetic acid salt (chitosan), whey protein isolate, whey protein concentrate and wheat gluten protein were studied. Paper sheets were solution‐coated using a hand applicator. In addition, bi‐layer composites of wheat gluten and paper or paperboard were produced by compression moulding, and the chitosan solution was also applied on paperboard using curtain coating. Young's modulus, fracture stress, fracture strain, tearing strength, air permeance and oxygen permeability were assessed. The mechanical and air permeance measurements of solution‐coated paper showed that chitosan was the most effective coating on a coat weight basis. This was due to its high viscosity, which limited the degree of penetration into the paper. The proteins, however, also enhanced the strength and toughness of the paper. Compression‐moulded wheat gluten/paper or paperboard, as well as curtain‐coated chitosan paperboard laminates, showed oxygen barrier properties comparable to those of paper and paperboard coated with commercial barrier materials. None of the composites could be delaminated without fibre rupture, indicating good adhesion between the coatings and the substrates. Copyright © 2005 John Wiley & Sons, Ltd.     

The Strength and Compaction of Millispheres: The design of a controlled-release drug delivery system for ibuprofen in the form of a tablet comprising compacted polymer-coated millispheres

Abstract

This paper reviews a case study of the design of a controlled-release drug delivery system for ibuprofen in the form of a tablet comprising compacted polymer-coated millispheres (multiparticulate pellets). The particular challenge was to prepare coated millispheres of ibuprofen (a high-dose drug) with the addition of minimal excipients so that the drug-release retarding polymeric membrane surrounding the millispheres remains intact during and after tablet compression, disintegration and release of the millispheres. The study included (a) the design of the uncoated core and its manufacture by wet massing, extrusion, spheronization and drying; (b) the coating of these millispheres with a range of possibly suitable polymers; (c) an assessment of the drug release profiles from these pellets; (d) the quantification by indentation rheology of the mechanical properties of the polymer films used to coat the spheres; (e) the measurement of the mechanical properties of individual uncoated and coated millispheres and f. the design, manufacture and evaluation of compressed tablets containing coated millispheres

The matching of millisphere and polymer mechanical properties was found to be essential in order to ensure minimal damage to the millispheres and the release of virtually intact coated spheres without destruction of their retarded drug-release characteristics. Aqueous polymeric dispersions which formed a film with similar elastic and tensile properties to the uncoated millisphere formulation resulted in the most satisfactory film coating for application to spherical particles which must withstand compaction. Those polymeric films exhibiting significantly greater resilience than the uncoated cores were inappropriate for the film coating of millispheres for compaction into tablets     

Carbon‐Coated Li3VO4 Spheres as Constituents of an Advanced Anode Material for High‐Rate Long‐Life Lithium‐Ion Batteries

Lithium‐ion batteries are receiving considerable attention for large‐scale energy‐storage systems. However, to date the current cathode/anode system cannot satisfy safety, cost, and performance requirements for such applications. Here, a lithium‐ion full battery based on the combination of a Li₃VO₄ anode with a LiNi_0.5Mn_1.5O₄ cathode is reported, which displays a better performance than existing systems. Carbon‐coated Li₃VO₄ spheres comprising nanoscale carbon‐coating primary particles are synthesized by a morphology‐inheritance route. The observed high capacity combined with excellent sample stability and high rate capability of carbon‐coated Li₃VO₄ spheres is superior to other insertion anode materials. A high‐performance full lithium‐ion battery is fabricated by using the carbon‐coated Li₃VO₄ spheres as the anode and LiNi_0.5Mn_1.5O₄ spheres as the cathode; such a cell shows an estimated practical energy density of 205 W h kg^?1 with greatly improved properties such as pronounced long‐term cyclability, and rapid charge and discharge.     

One Step Synthesis of Gold‐Loaded Radial Mesoporous Silica Nanospheres and Supported Lipid Bilayer Functionalization: Towards Bio‐Multifunctional Sensors

A simple synthetic route is developed to achieve gold functionalized radial mesoporous silica nanoparticles (Au‐MsNP) synthesized by a one step procedure fully compatible with basic conditions required for the preparation of monodispersed nanospheres. In a second step, Au‐MsNP particles have been coated with phospholipid bilayers in order to design an advanced biofunctional platform with the gold metallic nanoparticles previously grown into the pore channels and responsible for a plasmonic activity relevant for biosensing. The size of Au‐MsNP is checked by dynamic light scattering while zeta potential measurements reflect their surface charge. The particle morphology is characterized by transmission and scanning electron microscopy and the Si/Au ratios are obtained from energy dispersive X‐ray analysis. The textural properties of Au‐MsNP, specific surface area and pore size, are determined from N₂ adsorption. The supported bilayers are achieved from vesicles of different phospholipids incubated with Au‐MsNP particles. The coating efficiency is investigated by zeta potential and cryo‐ transmission electron microscopy. The plasmonic activities of bare Au‐MsNP particles and coated lipid bilayer Au‐MsNP platform are evidenced for two model systems: direct adsorption of bovine serum albumin and molecular recognition events between avidin molecules and biotin receptors integrated in the supported lipid bilayer.     

The Strength and Compaction of Millispheres: The design of a controlled-release drug delivery system for ibuprofen in the form of a tablet comprising compacted polymer-coated millispheres

This paper reviews a case study of the design of a controlled-release drug delivery system for ibuprofen in the form of a tablet comprising compacted polymer-coated millispheres (multiparticulate pellets). The particular challenge was to prepare coated millispheres of ibuprofen (a high-dose drug) with the addition of minimal excipients so that the drug-release retarding polymeric membrane surrounding the millispheres remains intact during and after tablet compression, disintegration and release of the millispheres. The study included (a) the design of the uncoated core and its manufacture by wet massing, extrusion, spheronization and drying; (b) the coating of these millispheres with a range of possibly suitable polymers; (c) an assessment of the drug release profiles from these pellets; (d) the quantification by indentation rheology of the mechanical properties of the polymer films used to coat the spheres; (e) the measurement of the mechanical properties of individual uncoated and coated millispheres and f. the design, manufacture and evaluation of compressed tablets containing coated millispheres

The matching of millisphere and polymer mechanical properties was found to be essential in order to ensure minimal damage to the millispheres and the release of virtually intact coated spheres without destruction of their retarded drug-release characteristics. Aqueous polymeric dispersions which formed a film with similar elastic and tensile properties to the uncoated millisphere formulation resulted in the most satisfactory film coating for application to spherical particles which must withstand compaction. Those polymeric films exhibiting significantly greater resilience than the uncoated cores were inappropriate for the film coating of millispheres for compaction into tablets     

Quasi‐Epitaxial Growth of Magnetic Nanostructures on 4H‐Au Nanoribbons

Phase engineering of nanomaterials is an effective strategy to tune the physicochemical properties of nanomaterials for various promising applications. Herein, by using the 4H‐Au nanoribbons as templates, four novel magnetic nanostructures, namely 4H‐Au @ 14H‐Co nanobranches, 4H‐Au @ 14H‐Co nanoribbons, 4H‐Au @ 2H‐Co nanoribbons, and 4H‐Au @ 2H‐Ni nanoribbons, are synthesized based on the quasi‐epitaxial growth. Different from the conventional epitaxial growth of metal nanomaterials, the obtained Co and Ni nanostructures possess different crystal phases from the Au template. Due to the large lattice mismatch between Au and the grown metals (i.e., Co and Ni), ordered misfit dislocations are generated at the Co/Au and Ni/Au interfaces. Notably, a new super‐structure of Co is formed, denoted as 14H. Both 4H‐Au @ 14H‐Co nanobranches and nanoribbons are ferromagnetic at room temperature, showing similar Curie temperature. However, their magnetic behaviors exhibit distinct temperature dependence, resulting from the competition between spin and volume fluctuations as well as the unique geometry. This work paves the way to the templated synthesis of nanomaterials with unconventional crystal phases for the exploration of phase‐dependent properties.     

Transition‐Metal‐Ions‐Induced Coalescence: Stitching Au Nanoclusters into Tubular Au‐Based Nanocomposites

Rod‐shaped assemblages of Au nanoclusters (AuNCs) can serve as self‐templating solid precursors to produce tubular Au‐based nanocomposites via the coalescence induced by transition metal ions. Specifically, when the AuNC assemblages react with transition metal ions with relatively high standard oxidation potentials such as Cu(II), Ag(I), Pd(II), and Au(III), a series of polycrystalline and ultrathin Au and Au_xM_y (where M = Cu, Ag, and Pd) alloy hollow nanorods (HNRs) can be obtained with further reduction; these metallic products are evaluated for electrooxidation of methanol. Alternatively, the above transition metal ions‐induced transformations can also be carried out after coating the AuNC assemblages with a layer of mesoporous SiO₂ (mSiO₂), giving rise to many mSiO₂‐coated Au‐based HNRs. Onto the formed AuPd_0.18 alloy HNRs, furthermore, a range of transition metal oxides such as TiO₂, Co₃O_4, and Cu₂O nanocrystals can be deposited easily to prepare metal oxide–AuPd_0.18 HNRs nanocomposites, which can be used as photocatalysts. Compared with those conventional galvanic replacement reactions, the controlled coalescence of AuNCs induced by transition metal ions provides a novel and efficient chemical approach with improved element efficiency to tubular Au‐based nanocomposites.     

Seed‐Induced Growth of Flower‐Like Au–Ni–ZnO Metal–Semiconductor Hybrid Nanocrystals for Photocatalytic Applications

The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au–Ni–ZnO metal–semiconductor hybrid nanocrystals with a flower‐like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room‐temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as‐prepared Au–Ni–ZnO nanocrystals are strongly photocatalytic and can be separated and re‐cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications.     

Microstructure and Modeling of the High‐Temperature Deformation Behavior of Carbide‐Hardened Superalloys

Thermal barrier coatings (TBC) have the potential to improve considerably the efficiency of stationary gas or aircraft turbines by increasing the operating temperature. This report describes the use of creep experiments and microstructure investigations in order to predict the deformation behavior of uncoated and TBC‐coated superalloys NiCr22Co12Mo9 and CoCr22Ni22W14. The results of mechanical tests and transmission electron microscopy investigations have been used as input data into two models in order to describe the hot deformation behavior. The deterioration in the creep properties of the superalloy NiCr22Co12Mo9 as a result of coating was due to the degraded state of the M₂₃C₆ precipitates in the substrate metal, as well as to the weakening of the solid solution‐ and precipitation‐hardening mechanisms responsible for the creep strength of the material, in the region of the boundary surface.     

Template‐Assisted Electroforming of Fully Semi‐Hard‐Magnetic Helical Microactuators

The authors report on the fabrication of semi‐hard‐magnetic microhelices using template‐assisted electroforming. The method consists of electrodepositing a material on a sacrificial mandrel on which a pattern has been previously written. To electroform the helical microswimmers, a helical template on a polymer‐coated metallic mandrel is created using a laser, which precisely ablates the polymer coating and exposes the mandrel surface. Subsequently, the semi‐hard‐magnetic material is electrodeposited in the trenches produced by the laser. In this investigation, the helical structures are obtained from an electrolyte, which enables the production of hard‐magnetic CoPt alloys. The authors also show that electroformed semi‐hard‐magnetic helical microswimmers can propel in viscous environments such as silicon oil in three dimensions and against gravity. Their manufacturing approach can be used for the fabrication of more complex architectures for a wide range of applications and can be potentially extended to any electroplatable material.

     

Ni/PSt/TiO2多层芯-壳结构电磁响应

制得了粒径均匀、兼有电磁响应的镍／聚苯乙烯／二氧化钛(Ni／PSt／TiO2)三层核-壳结构的复合微球．用红外光谱、X射线衍射及透射电镜对微球进行了表征，研究了包覆前后微粒的沉降性、导电性、耐蚀性、热稳定性以及在电、磁场作用下的运动．结果表明，所制得的镍／聚苯乙烯／二氧化钛(Ni／PSt／TiO2)复合微球对电磁场有良好的响应性，在相互垂直的电场与磁场作用下排列形成了一种网状花样结构，为利用电、磁场调控排列粒子成三维有序结构提供基础．     

Characterisation of Mechanical Properties of Magnetite‐Polymer Composite Films

Abstract: Time dependent mechanical properties of magnetic polymer films were investigated. These polymer films, synthesised by using solution polymerisation followed by the inverse emulsion process, consist of poly (MMA‐co‐MAA‐co‐BA) and different weight ratios of magnetite nano‐particles. This study deals with the influence of weight ratios of magnetite nano‐particles on the time dependent mechanical properties of hybrid copolymer films. The viscoelastic properties of aforementioned polymer films with 0, 20 and 40% of magnetite nano particles were studied. Ramp‐hold experiments were performed by using a custom‐made tension testing apparatus to evaluate the time dependent stress‐strain behaviour of magnetic polymer films under uniaxial tensile load at different loading strain rates. It can be seen that the magnetite nano‐particles weight percentage of polymer has a strong effect on the stress‐strain relations of polymer films. The polymer with a higher weight ratio of magnetite nano‐particles can sustain higher stress under the same test condition. Experimental data were fitted into 3, 5 and 7 parameter linear viscoelastic models. It is shown that the 7‐parameter Wiechert model leads to better curve‐fitting results for the magnetic polymer material under ramp‐hold experiments.     

Ni/PSt/TiO2多层芯-壳结构电磁响应

制得了粒径均匀、兼有电磁响应的镍/聚苯乙烯/二氧化钛(Ni/PSt/TiO₂)三层核-壳结构的复合微球。用红外光谱、X射线衍射及透射电镜对微球进行了表征,研究了包覆前后微粒的沉降性、导电性、耐蚀性、热稳定性以及在电、磁场作用下的运动。结果表明,所制得的镍/聚苯乙烯/二氧化钛(Ni/PSt/TiO₂)复合微球对电磁场有良好的响应性,在相互垂直的电场与磁场作用下排列形成了一种网状花样结构,为利用电、磁场调控排列粒子成三维有序结构提供基础。     

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.     

Performance of Multilayered Particles: Influence of a Thin Cushioning Layer

ABSTRACT

Nowadays, oral dosage forms with controlled release kinetics have known an increasing interest. The polymer coating of drug-loaded particles is one of the most common methods used for controlling drug delivery. Such multilayered particles could be either filled into capsules or compressed into tablets for their oral administration. However, many studies have noticed that coating films are damaged during the compression process, leading to significant changes in drug release profiles. The aims of this study were to investigate the effects of a thin cushioning layer [made of HydroxyPropylMethyl Cellulose (HPMC)] applied on coated theophylline particles upon particle characteristics, tablet properties, and then upon their dissolution performance. If no significant effect was shown with particles, this thin HPMC layer played an important role in the tablets. Tablet cohesiveness was decreased due to HPMC cushioning properties and moreover, the theophylline release rate was increased, as HPMC is a water-soluble polymer creating channels in polymer film for dissolution medium. Therefore, a cushioning layer helped to protect polymer coats from fracture during compression but could also affect drug release and so, both effects must be checked in such a drug delivery system.     

X-ray photoelectron spectra and structure of composites prepared via deposition of Au,Ni, and Au + Ni nanoparticles on SiO<Subscript>2</Subscript> from colloidal solutions in triethylamine

Monometallic (Au and Ni) and bimetallic (Au + Ni) nanoparticles deposited on SiO₂ from colloidal solutions in triethylamine have been studied by x-ray photoelectron spectroscopy (XPS). The solutions were prepared through vapor-phase metal synthesis. We have determined the basic parameters of the core-level and valence-band XPS spectra of the Au/SiO₂, Ni/SiO₂, and Au-Ni/SiO₂ systems. The results indicate that the Au in these systems is in the Au(0) state, while Ni is oxidized to Ni(II). The Au/SiO₂ and Au-Ni/SiO₂ samples differ little in the shape of the Au 4f peak. In the Au-Ni/SiO₂ system, the Ni 2p _3/2-Au 4f _7/2 binding energy difference is 0.3 eV larger and the Ni 2p _3/2 peak is narrower than those in the monometallic samples. The effects characteristic of the bimetallic system may be due to the interaction between Ni and Au or may be interpreted as evidence that the Au particles level off the potential relief on the SiO₂ surface.     

Micro‐Macroporous Composite Materials – Preparation Techniques and Selected Applications: A Review

Pores, on several orders of magnitude in size, control the properties of a solid material to a large extent. This is just as true for materials containing pores in the sub‐nanometer range like zeolites as for cellular foam structures with pores of several millimeters in size. All these porous materials have their distinct potential application ranging from heterogeneous catalysis to metal melt filtration. In many cases, the (hierarchical) combination of pores with different size regimes can improve the performance of the respective porous material or can lead to entirely new properties and applications. This review addresses the preparation and properties of microporous‐macroporous composite materials based on cellular foam supports (ceramic, metal, polymer) with a coating of a microporous compound (zeolite, zeotype framework, metal‐organic framework). The manufacturing of these materials can either be performed by dispersion‐based techniques, where the microporous coating is applied from a dispersion onto the cellular support (ex situ), or in situ by crystallization of the microporous compound directly onto the struts of the foam structure. In both cases, the general procedure can be modified by a pretreatment of the cellular support in order to improve the coating layer adherence, the overall amount of deposited material, or to control of the crystal morphology of the microporous compound.

     

High‐Performance Microwave‐Derived Multi‐Principal Element Alloy Coatings for Tribological Application

The authors report the development of Al_xCoCrFeNi (x = 0.1 to 3) high entropy alloy (HEA) coatings using a simple and straightforward microwave technique. The microstructure of the developed coatings is composed of a cellular structure and diffused interface with the substrate. The microstructure of the HEA coatings varies as a direct function of Al content. An increase in Al fraction shows structural transformation from FCC to BCC along with the evolution of σ and B₂ as the major secondary phases. The diffusion of Mo from the substrate enhances the mixing entropy and promotes σ‐phase formation. The HEA coatings show significantly high hardness compared to SS316L substrate steel (227 HV) with a maximum value of 726 HV observed for three‐molar composition. The fracture toughness exhibits an inverse correlation with the Al fraction with the highest value of around 49 MPa m^1/2 observed for Al_0.1CoCrFeNi coating. The equimolar coating composition shows lowest erosion rates among all the tested samples due to optimum combination of the mechanical properties. The erosion resistance of the equimolar coating is 2 to 5 times higher than steel substrate and around 1.5 times higher than the non‐equimolar counterparts depending upon the impingement angles.