In situ processing and properties of nanostructured hydroxyapatite/alginate composite

A series of hydroxyapatite/alginate (HA/Alg) nanocomposites with alginate amounts varying from 10 to 40 wt% were prepared through in situ hybridization technique. The inorganic phase in the composites was carbonate-substituted HA with low crystallinity. The crystallinity of HA decreased with the increase of alginate content. HA crystallites were needle-like in shape with a typical size of 20 to 50 nm in length and 5 nm in width. FT-IR spectroscopy indicated that the chemical interaction occurred between the mineral phase and the polymer matrix. As compared to pure HA without alginate, the composites showed more homogeneous microstructures, where HA nanocrystals were well embedded in alginate matrix. Among all the samples, the composite containing 30 wt% alginate exhibited a highly ordered three-dimensional network, similar to natural bone’s microstructure.     

Nonlinear optical properties of polyaniline composite materials

The nonlinear optical properties of polyaniline composite materials (PANI/Au) were studied using the single-beam Z-scan technique.These molecules exhibited a strong reverse saturable absorption and an interesting optical limiting performance with a nanosecond Nd:YAG laser pulses at 532 nm.     

Enhancement of thermoelectric properties of SrTiO_3/LaNb–SrTiO_3 composite by different doping levels

Strontium titanate(STO)is an n-type oxide thermoelectric material,which has shown great prospects in recent years.The doping of La and Nb into STO can improve its power factor,whereas its thermal conductivity is still very high.Thus,in order to obtain a high thermoelectric figure-of-merit z T,it is very important to reduce its thermal conductivity.In this paper,using a combination of a hydrothermal method and a high-efficiency sintering method,we succeed in preparing a composite of pure STO and La Nb-doped STO,which simultaneously realizes lower thermal conductivity and higherSeebeck coefficient,therefore,the thermoelectric properties of STO are significantly improved.In the SrTiO_3/La Nb–SrTiO_3 bulk samples,the lowest thermal conductivity is 2.57 W·m~(-1)·K~(-1)and the highest z T is 0.35 at 1000 K for the STO/La_(10)Nb_(20)–STO sample.     

DC conductivity and magnetic properties of piezoelectric–piezomagnetic composite system

A series of composites (1−x) (Ni_0.8Zn_0.2Fe₂O₄)+x (BaTiO₃), where x=0%, 20%, 40%, 60%, 80% and 100% BT content, have been prepared by the standard ceramic technique, then sintered at 1200 °C for 8 h. X-ray diffraction analysis shows that the prepared composites consist of two phases, ferrimagnetic and ferroelectric. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been studied at different temperatures. It was found that the DC electrical conductivity increases with increasing BT content. The values of the thermoelectric power were positive and negative for the composites indicating that there are two conduction mechanisms, hopping and band conduction, respectively. Using the values of DC electrical conductivity and thermoelectric power, the values of charge carrier mobility and the charge carrier concentration were calculated. Magnetic measurements (hysteresis loop and magnetic permeability) show that the magnetization decreases by increasing BT content. M–H loop of pure Ni_0.6 Zn_0.4 Fe₂O₄ composite indicates that it is paramagnetic at room temperature and that the magnetization is diluted by increasing the BT content in the composite system. The value of magnetoelectric coefficient for the composites decreases by increasing BT content for all the compositions except for 40% BT content, which may be due to the low resistivity of magnetic phase compared with the BT phase that causes a leakage of induced charges on the piezoelectric phase. Since both ferroelectric and magnetic phases preserve their basic properties in the bulk composite, the present BT–NZF composite are potential candidates for applications as pollution sensors and electromagnetic waves.     

Structure and magnetic properties of flower-like α-NiS nanostructures

In this paper we report the structure and magnetic properties of flower-like α-NiS nanostructure prepared by a facile one-step hydrothermal method. The flowers consist of polycrystalline nanoflakes, and the nanoflakes are composed of single crystalline nanocrystals with an average size of about 15 nm. The α-NiS flowers exhibit the transition from paramagnetism to ferromagnetism with the blocking temperature of about 12 K. The field dependences of the magnetization prove that these flowers demonstrate a coexistence of antiferromagnetism and ferromagnetism at 5 K, and exhibit a strong paramagnetic response at temperature higher than 100 K.     

Electrical properties and photoconductivity of polyaniline/sulfonated poly(arylene ether sulfone) composite films

Temperature dependent electrical conductivity of the polyaniline-sulfonated poly(arylene ether sulfone) with 35 mol percent sulfonation (PANI-BPS35) composite films were investigated in the temperature range of 80–380 K. These composite films showed semiconductor behavior with the exponential variation of inverse temperature dependence of electrical conductivity. Calculated Mott’s parameters showed that variable range hopping mechanism is the dominant transport mechanism for the carriers in low temperature region. Photoconductivity of the PANI-BPS35 composite films having 10, 20, and 40 weight percent conductive filler under various illumination intensities was also studied. Photocurrent of the composite films increased with increasing both polyaniline weight fraction and temperature. Finally, the effect of doping on both electrical conductivity and the photoconductivity of the composite films was investigated.     

One-step simple sonochemical fabrication and photocatalytic properties of Cu2O–rGO composites

An easy, one-step synthesis of Cu₂O–reduced graphene composites (Cu₂O–rGO) was developed using a simple sonochemical route without any surfactants or templates. The morphology and structure of the Cu₂O–rGO composites were characterised using techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results indicated that the Cu₂O sphere is approximately 200 nm in diameter and composed of small Cu₂O particles approximately 20 nm in diameter. The morphology and composition of the Cu₂O–rGO composites could be well controlled by simply changing the mole ratio of the reactants under ultrasonic irradiation. The Cu₂O–rGO composites displayed better photocatalytic performance for the degradation of methyl orange (MO) than pure Cu₂O spheres, which may have potential applications in water treatment, sensors, and energy storage.     

Luminescence of II–VI and III–V nanostructures

Photoluminescence of HgCdTe epitaxial films and nanostructures and electroluminescence of InAs(Sb,P) light-emitting diode (LED) nanoheterostructures were studied. For HgCdTe-based structures, the presence of compositional fluctuations, which localized charge carriers, was established. A model, which described the effect of the fluctuations on the rate of the radiative recombination, the shape of luminescence spectra and the position of their peaks, was shown to describe experimental photoluminescence data quite reasonably. For InAs(Sb,P) LED nanoheterostructures, at low temperatures (4.2–100 K) stimulated emission was observed. This effect disappeared with the temperature increasing due to the resonant ‘switch-on’ of the Auger process involving transition of a hole to the spin-orbit-splitted band. Influence of other Auger processes on the emissive properties of the nanoheterostructures was also observed. Prospects of employing II–VI and III–V nanostructures in light-emitting devices operating in the mid-infrared part of the spectrum are discussed.     

Effects of a Cu-contained compound on the microstructures and thermoelectric properties of Zn–Sb based alloys

Zn–Sb based alloys with Cu₂Sb addition were prepared using spark plasma sintering technique and the effects of a Cu-contained intermetallic phase on the microstructures and thermoelectric properties were examined. Rietveld refinement reveals that there are many phases in the alloys, which involve β-Zn₄Sb₃, a major phase ZnSb, a small amount of an intermetallic compound Cu₅Zn₈ and unidentified impurity phases, the quantities of ZnSb and Cu₅Zn₈ increase from 67.3 wt.% to 91.8 wt.% and 0–4.3 wt.% with Cu₂Sb additive increasing, respectively. The ZnSb plays a fundamental role in controlling the thermoelectric properties, and Cu₅Zn₈ is of great significance to optimize the transport properties. The maximum thermoelectric figure of merit ZT of 0.72 is obtained for the alloy (Cu₂Sb)_0.05–(Zn₄Sb₃)_0.95 at 654 K, which is 0.25 higher than that of undoped β-Zn₄Sb₃ at the same conditions. Therefore, we conclude that a proper addition of Cu₂Sb can contribute to the improvement of thermoelectric properties of Zn–Sb based alloys.     

Fracture mode,microstructure and temperature-dependent elastic moduli for thermoelectric composites of PbTe–PbS with SiC nanoparticle additions

Twenty-six (Pb_0.95Sn_0.05Te)_0.92(PbS)_0.08–0.055% PbI₂–SiC nanoparticle (SiC_np) composite thermoelectric specimens were either hot pressed or pulsed electric current sintered (PECS). Bloating (a thermally induced increase in porosity, P, for as-densified specimens) was observed during annealing at temperatures >603?K for hot-pressed specimens and PECS-processed specimens from wet milled powders, but in contrast seven out of seven specimens densified by PECS from dry milled powders showed no observable bloating following annealing at temperatures up to 936?K. In this study, bloating in the specimens was accessed via thermal annealing induced changes in (i) porosity measured by scanning electron microscopy on fractured specimen surfaces, (ii) specimen volume and (iii) elastic moduli. The moduli were measured by resonant ultrasound spectroscopy. SiC_np additions (1–3.5 vol.%) changed the fracture mode from intergranular to transgranular, inhibited grain growth, and limited bloating in the wet milled PECS specimens. Inhibition of bloating likely occurs due to cleaning of contamination from powder particle surfaces via PECS processing which has been reported previously in the literature.     

Correction to: Design,fabrication, and characterization of thermal and optical properties of nano‑composite self‑cleaning smart window

Optical and Quantum Electronics - Optical properties of polymerized polyethylene layers deposited on glass substrates by PECVD technique at different radio frequency powers are studied through...     

Magnetic and mechanical properties of Ni–Mn–Ga/Fe–Ga ferromagnetic shape memory composite

A ferromagnetic shape memory composite of Ni–Mn–Ga and Fe–Ga was fabricated by using spark plasma sintering method. The magnetic and mechanical properties of the composite were investigated. Compared to the Ni–Mn–Ga alloy,the threshold field for magnetic-field-induced strain in the composite is clearly reduced owing to the assistance of internal stress generated from Fe–Ga. Meanwhile, the ductility has been significantly improved in the composite. A fracture strain of 26% and a compressive strength of 1600 MPa were achieved.     

Plasmonic properties of spheroidal spindle and disc shaped core–shell nanostructures embedded in passive host-matrices

Optical and Quantum Electronics - Numerical simulation of opto-electric characterization of GaAs/GaSb core–shell nanowire solar cells is presented, using a finite difference time-domain...     

In situ growth of sol–gel-derived nano-VO2 film and its phase transition characteristics

Fe₃O₄/C nanocomposites have been prepared by one-pot PEG-assisted co-precipitation method. The structure and morphology of the as-prepared materials were analyzed by X-ray diffraction and transmission electron microscopy. The results showed that Fe₃O₄/C nanocomposites were well crystallized. Carbon nanoparticles dispersed among Fe₃O₄ particles forming a carbon layer, which prevent Fe₃O₄ particles from contacting each other. Electrochemical performance tests showed that Fe₃O₄/C nanocomposites keep at a high discharge capacity of 902.4 mAh g^?1 at 1 C after 110 cycles. Furthermore, the samples showed much improved rate capability and better cycle stability compared with pure Fe₃O₄. The excellent electrochemical performance of Fe₃O₄/C nanocomposites can be attributed to unique nanostructure and existence of amorphous carbon in the composites. The existence of the amorphous carbon not only enhanced electric conductivity, but also buffered volume variation of Fe₃O₄/C nanocomposites during charge/discharge process.     

Study of cohesive,electronic and magnetic properties of the Ni–In intermetallic system

Cohesive, electronic and magnetic properties of the intermetallic system Ni–In, specifically the stable phases Ni₃In-hP8, Ni₂In-hP6, NiIn-hP6 and Ni₂In₃-hP5, have been investigated. At present, these materials are of great interest in connection to the application of the In–Sn alloys as lead-free micro-soldering alloys, and considering Ni as the contact material. In spite of this, scarce literature regarding basic thermodynamic properties of the Ni–In intermetallic phases has been found. Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations is used. All the calculations include spin polarization. Structural parameters, formation energies and cohesive properties of the different phases are studied through minimization of internal parameters. The electronic density of states (DOS) is analyzed for each optimized structure. We found that the NiIn-hP6 phase is the most stable one and only the Ni₃In-hP8 phase exhibits magnetic properties.     

Thermophysical properties of Cu–In–Sn liquid Pb-free alloys: viscosity and surface tension

The viscosity of a few Cu–In–Sn liquid alloys has been investigated by a number of geometric (Muggianu, Kohler, Toop) and physical thermodynamic models (Kozlov–Romanov–Petrov, Budai–Benko–Kaptay, Schick et al.) and GSM for the cross section (z/y = 1/3) in Pb-free liquid alloy Cu_x–In_y–Sn_z at 1073 K. Moreover, the surface tensions of the same liquid alloys have been investigated by a number of geometric models and the Butler model for the cross section Cu_x–In_y–Sn_z (z/(y + z) = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) at the same temperature. The best agreement of the surface tensions was obtained in the Kohler model for x_Cu = 10 at % and the Butler model for x_Cu = 20 at % and x_Cu = 30 at.%, respectively. The best agreement among chosen geometric and physical models and experiment for these selected sections Cu₈₀In₁₅Sn₅, Cu₇₅In₁₅Sn₁₀, Cu₅₅In₇Sn₃₈, Cu₃₃In₅₀Sn₁₇ and Cu₂₆In₅₅Sn₁₉ at 1073 K was obtained for the Budai–Benkö–Kaptay model.     

Electrical conduction and thermoelectric properties of perovskite-type BaBi1−xSbxO3

To elucidate the thermoelectric properties at high temperatures, the electrical conductivity and Seebeck coefficient were measured at temperatures between 423 K and 973 K for perovskite-type ceramics of BaBi_1?xSb_xO₃ solid solutions with x=0.0–0.5. All the ceramics exhibit p-type semiconducting behaviors and electrical conduction is attributed to hopping of small polaronic holes localized on the pentavalent cations. Substitution of Bi with Sb causes the electrical conductivity σ and cell volume to decrease, but the Seebeck coefficient S to increase, suggesting that the Sb atoms are doped as Sb⁵⁺ and replace Bi⁵⁺, reducing 6s holes conduction from Bi⁵⁺(6s⁰) to Bi³⁺ (6s²). The thermoelectric power factor S ²σ has values of 6×10^?8–3×10^?5 W m^?1 K^?2 in the measured temperature range, and is maximized for an Sb-undoped BaBiO_3?δ, but decreases upon Sb doping due to the decreased σ values.