Dielectric, ferroelectric and piezoelectric properties of 0-3 barium titanate–Portland cement composites

In this work, barium titanate (BT) and cement composites of 0-3 connectivity were produced with BT concentrations of 30%, 50% and 70% by volume using the mixing and pressing method. The dielectric constant (ε _r ) and the dielectric loss (tan δ) at room temperature and at various frequencies (0.1–20 kHz) of the ferroelectric BT-Portland cement composites with different BT concentrations were investigated. The results show that the dielectric constant of BT-PC composites was found to increase as BT concentration increases, and that the highest value for ε _r —of 436—was obtained for a BT concentration of 70%. In addition, the dielectric loss tangent decreased with increasing BT concentration. Moreover, several mathematical models were used; the experimental values of the dielectric constants are closest to those calculated from the cube model. The 0-3 cement-based piezoelectric composites show typical ferroelectric hysteresis loops at room temperature. The instantaneous remnant polarization (P _ir ), at an applied external electrical field (E ₀) of 20 kV/cm (90 Hz) of 70% barium titanate composite, was found to have a value ≈3.42 μC/cm². Furthermore, the piezoelectric coefficient (d ₃₃) was also found to increase as BT concentration increases, as expected. The highest value for d ₃₃ was 16 pC/N for 70% BT composite.     

Plasma synthesis of nanosized W–Co composite powder followed by carburization with a methane–hydrogen mixture

Nanosized tungsten carbide and cobalt composite powder was synthesized by a two-step reaction via a thermal plasma process. Ammonium paratungstate (APT) and cobalt oxide were used as the precursors. The injected precursors were vaporized in the plasma flame and the subsequent reduction of the vaporized precursors produced uniformly mixed nanosized tungsten and cobalt composite powder. The subsequent carburization of this powder by CH₄–H₂ mixture resulted in the formation of nanosized WC–Co composite powder with a particle size <110 nm. This new method represents an alternative route that avoids the post-treatment required for the WC_1?x produced when methane was used for direct carburization in the powder production step.     

Fabrication and characterization of TiN–Ag nano-dice

TiN–Ag nanocomposite was synthesized by dc arc-plasma method. Microstructures of TiN–Ag nanocomposite were carefully characterized by powder X-ray diffraction method and transmission electron microscopy, and nano-morphologies by three-dimensional electron tomography. It was found that the surface of nanocrystalline TiN matrix was densely covered by finely dispersed Ag nanoparticles, and it was found that they were physically attached but not chemically bonded from their orientation relationships.     

Yb-doped yttria–alumino–silicate nano-particles based optical fibers: Fabrication and characterization

An efficient method to fabricate transparent glass ceramic fibers containing in-situ grown Yb³⁺ doped oxide nano-particles based on yttria–alumino–silicate glass is presented. These large-mode area Yb³⁺ doped fibers having a core diameter around 25.0 μm were drawn by a proper control over the involved process parameters; by this, the size of nano-particles was maintained within 5–10 nm. The main spectroscopic and laser properties of the fabricated fibers along with the nano-structuration results are reported. These results reveal that the developed method offers new scopes for the contemporary Yb³⁺ fiber based devices.     

Mechanical Deformation–Assisted Fabrication of Plasmonic Nanobowties with Broken Symmetry and Tunable Gaps

A symmetry broken and gap tunable gold nanobowtie array is demonstrated by nanosphere lithography performed on a mechanically uniaxially prestretched elastomeric substrate. Due to symmetry breaking of each nanotriangle with its three neighboring nanotriangles once the uniaxial prestretch is released, the structure exhibits polarization-dependent optical properties. In addition, the decrease in the gap between adjacent triangles provided by mechanical relaxation of the substrate enhances the electric field enhancement between adjacent triangles, which in turn results in enhanced Raman scattering from molecules present in the gap. Triangle apex-to-apex gaps as small as 20 nm are generated using a colloidal crystal formed from 500 nm colloids on at 30% prestretched substrate (gaps formed when an unstretched substrate is used are ≈115 nm).     

Fabrication and characterization of Cu–CdSe–Cu nanowire heterojunctions

The Cu–CdSe–Cu nanowire heterojunctions were fabricated by sequential electrochemical deposition of layers of Cu metal and CdSe semiconductor within the nano-pores of anodic alumina membrane templates. X-ray diffraction reveals the cubic phase for Cu and hexagonal phase for CdSe in the electrodeposited Cu–CdSe–Cu nanowire heterojunctions. The composition of the nanowire heterojunction segments is characterized by energy dispersive X-ray spectroscopy. The morphological study of nanowire heterojunctions has been made using scanning electron microscope and high resolution transmission microscopy. The nanowire heterojunctions grown in 100 and 300 nm nano-pore size templates have been found to have optical band gaps of 1.92 and 1.75 eV, respectively. The absorption spectra of 100 nm nanowire heterojunctions show a blue shift of 0.18 eV. The collective nonlinear current–voltage (I–V) characteristics of the 300 and 100 nm nanowire heterojunctions show their rectifying and asymmetric behaviour, respectively.     

Fabrication and electrochemical performance of graphene–ZnO nanocomposites

Graphene–ZnO nanocomposites were synthesized successfully through a one-step solvothermal approach. The morphology, structure, and composition of the prepared nanocomposites were investigated by scanning electron microscopy(SEM), transmission electron microscope(TEM), laser micro Raman spectroscopy, and Fourier transform infra-red spectroscopy(FT-IR). The outcomes confirmed that this approach is comparatively steady, practicable, and operable compared with other reported methods. The electrochemical performance of the graphene-ZnO electrodes was analyzed through cyclic voltammetry, altering-current(AC) impedance, and chronopotentiometry tests. The graphene–ZnO electrodes exhibited an improved electrode performance with higher specific capacitance(115 F·g-1), higher electrochemical stability, and higher energy density than the graphene electrodes and most reported graphene–ZnO electrodes. Graphene–ZnO nanocomposites have a steady reversible charge/discharge behavior, which makes them promising candidates for electrochemical capacitors(ECs).     

Properties of Sr- and Sb-doped PZT–Portland cement composites

Lead zirconate titanate (PZT) ceramic-cement-based composites have increasingly been recognized as an attractive new composite material for use as a sensor in structural applications. In this work, PZT was doped with Sr and Sb (PSZT) to give it greater dielectric constant (ε _r) and higher piezoelectric coefficient (d ₃₃) values than normal PZT and is the first time that it is mixed with normal Portland cement to produce a 0–3 connectivity PSZT–Portland cement composite using PSZT contents of 50% and 70% by volume. Scanning electron micrographs show PSZT ceramic particles closely surrounded by the hydrated cement matrix where a dense microstructure can be observed in the interfacial zone. Both the ε _r and d ₃₃ values were found to increase with PSZT content and the values are amongst the highest so far for these types of composites, where the ε _r and d ₃₃ values reached 590 and 48 pC/N, respectively.     

Fabrication and characterization of bismuth oxide–holmia nanofibers and nanoceramics

In this article, a novel and simple method to produce both boron doped and undoped holmia stabilized bismuth oxide nanoceramic materials has been put forward. Boron doped and undoped poly (vinyl alcohol)/bismuth–holmia acetate nanofibers were produced using the electrospinning technique and were calcined at 850 °C afterward in order to obtain nanopowder. The characteristics of the nanofibers were investigated with FT-IR, XRD, and SEM. XRD analyses showed that boron undoped holmia stabilized bismuth oxide nanopowders have the face-centered cubic structure (δ-phase), and that the incorporation of boron atoms into the composite prevents the nucleus formation and turns the structure into a more amorphous glassy form. The SEM micrographs of the fibers showed that the addition of boron results in the formation of cross-linked bright-surfaced fibers. The average fiber diameters for electrospun boron doped and undoped PVA/Bi–Ho acetate nanofibers were calculated using the ImageJ software as 102 nm and 171 nm, respectively.     

Preparation and performance of sulfur–carbon composite based on hollow carbon nanofiber for lithium-sulfur batteries

A unique structured hollow carbon nanofiber–sulfur composite material (HCF–S) was fabricated and characterized in lithium-sulfur batteries. It is found that a part of spherical sulfur particles are located in the voids formed by the intertwined fibers and the others are confined in hollow channel of the HCF. The high conductive and porous HCF favors the construction of stable three-dimensional conducting network and convenient infiltration of the electrolytes into the cathode. The HCF–S cathode exhibits excellent electrochemical performance in the electrolyte with LiNO₃. By contrast, the ionic liquid electrolyte provides insufficient shuttle suppression and weakens ion transport, which leads to poor cycle and rate capability.     

Fabrication and Characterization of Bioglass-Modified HA–ZrO2 Biocomposites

Hydroxyapatite (HA) being the main mineral constituent of human hard tissues is highly bioactive. Good chemical bonds can be generated between HA and natural bone. However, the low strength and inherent brittleness of HA restrict its application usually to non-load-bearing conditions. In this work, production of a new kind of HA–ZrO₂ composite by hot-press sintering method is described. Bioglass which has been widely used in reconstruction of damaged or diseased tissues was added into HA–ZrO₂ composites. Comparing with pure HA ceramic, this type of composite possesses better mechanical strength and retains the bioactivity of HA as well. The liquid phase generated by bioglass has been effective in improving the sintering process of HA–ZrO₂ composites. The phase composition of HA composite was characterized by XRD and their fracture surfaces were observed by SEM. The XRD results show that introducing a small amount of bioglass into HA–ZrO₂ composite cannot enhance decomposition of HA. The SEM images show that there were fewer pores on the fracture surfaces of HA–ZrO₂–bioglass composite than in the HA–ZrO₂ composite. The flexural strength and toughness of HA–ZrO₂ composite containing 2 wt% bioglass were 157 MPa and 1.63 MPa·m^1/2, respectively.     

Synthesis and structural characterization of Zn_3N_2 powder

1 Introduction In the field of wide band gap semiconductors, many studies have been carried out on zinc compounds. For example, ZnO, as a semiconductor material of n-type with a wide direct band gap of 3.37 eV[1—3], can function as transparent conducting films of low cost; ZnO, with an extremely large exciton binding energy of 60 meV and a strong ultra- violet (UV) stimulated emission at room temperature, has enormous potential for serving as short-wave light devices[4], such as light-emit…     

Photocatalytic disinfection of water with Ag–TiO2 nanocrystalline composite

A method of solution impregnation and calcination has been demonstrated for synthesizing nanoparticles of Ag–TiO₂ composite photocatalysts for use in the disinfection of water. Only a small proportion of the TiO₂ surface is covered by nano-islands of Ag corresponding to a loading of 4 wt.% of Ag; thus, most of the TiO₂ surface is available for photocatalytic function. Although the primary particles of both Ag and TiO₂ are in the 10- to 20-nm range, microscopic studies indicate that the primary particles of Ag are deposited on nano-agglomerates of 30- to 70-nm-sized TiO₂. It is seen that the relatively small loading of Ag has not caused any UV–vis spectral shift but has enhanced the rate of photocatalytic antibacterial action of TiO₂, presumably by electron trapping.     

Fabrication and temperature-dependent photoluminescence spectra of Zn–Cu–In–S quaternary nanocrystals

A series of Zn-Cu-In-S nanocrystals （ZCIS NCs） are prepared and the optical properties of the ZCIS NCs are tuned by adjusting the reaction time. It is interesting to observe that the temperature-dependent photoluminescence （PL） spectra of the ZCIS NCs show a redshift with decreasing intensity at low temperature （50-280 K） and a blueshift at high temperature （318--403 K）. The blueshift can be explained by the thermally active phonon-assisted tunneling from the excited states of the low-energy emission band to the excited states of the high-energy emission band.     

Surface and interfacial morphologies of PAN-CVI carbon–carbon composite

Scanning electron microscopy (SEM), polarized light microscopy (PLM), and transmission electron microscopy (TEM) techniques have been used to characterize the normal surface and flank surface microstructure of a polyacrylonitrile (PAN)-based carbon fiber reinforced chemical vapor infiltrated (CVI) matrix carbon–carbon composite. Optical and SEM results indicate that the CVI deposit consists of two structures: an isotropic phase is present in the fiber bundle-bundle junctions and a second highly oriented lamellar structure is present in the intrabundle matrix. TEM shows that matrix platelets are highly parallel to the fiber axis and the crystallites of the matrix near the fiber surface exhibit better alignment than those farther away from fibers.     

Synthesis and characterisation of polypyrrole–indium phosphide composite film

Polypyrrole (PPy)–indium phosphide (InP) composite material was electrochemically prepared by the incorporation of InP into a PPy matrix during electrochemical synthesis (cycling) under magnetic stirring from the acetonitrile/LiClO4 electrolyte containing the Py and InP particles. The PPy–InP composite material was designed to explore new approaches to improve light-collection efficiency in polymer photovoltaic. The samples were characterised by cyclic voltammetry, impedance spectroscopy measurement, scanning electron microscopy, energy dispersive X-ray spectroscopy, UV–visible and photoelectrochemical measurements. It was observed that the photocurrent of the composites was higher than that of the single PPy films and increased with InP concentration. The study showed that the presence of InP particles in the polymeric film improves the optical and the photovoltaic properties of PPy and give information on the use possibility of these films for photovoltaic cells' application.     

Preparation and luminescence of (SBA-15)–Eu2O3 composite materials

In this study, (SBA-15)–Eu₂O₃ host-guest composites have been prepared with SBA-15 mesoporous sieve as host and Eu₂O₃ as guest via the solid-phase ultrasonic method and liquid-phase medium ultrasonic method. The host–guest composite materials showed the properties of luminescence. Four excitation peaks appeared in the excitation spectra of the samples. The excitation peaks are located at 397, 415, 466, 537 nm; 392, 408, 464, 532 nm and 393, 406, 465, 533 nm for the nano-Eu₂O₃, the liquid-phase medium ultrasonic method (LPMUM) and the solid-phase ultrasonic method (SPUM) samples, respectively. SBA-15 has the well-ordered hexagonal arrays of mesopores, which makes centrosymmetry of Eu³⁺ higher in the prepared (SBA-15)–Eu₂O₃ samples. The intensity of ⁵D₀→⁷F₁ transition strengthens, and the intensity of ⁵D₀→⁷F₂ transition weakens.     

Fabrication and Characterization of YBa2Cu3Oy Superconducting Nanowires

Ordered YBa2Cu3Oy nanowires have been fabricated by filling YBa2Cu3Oy melting liquid into the pores of the anodized alumina templates. X-ray powder diffraction proves that YBa2Cu3Oy nanowires crystallized in the Y-123 structure. The temperature dependence of ac susceptibility indicates a superconducting transition at 91 K for the YBa2Cu3Oy nanowire array.