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.     

New processes in material production under high pressure

Abstract

To investigate processes of producing high-quality materials using high pressures of gas VNIIMETMASH has developed 3-400 MN hot isostatic presses (HIPes) with working pressure up to 200 MPa and temperature up to 2000°C. Ar and N2 are used as working gases. Frame and vessel units of such machines are of multi-element structure which eliminates the possibility of its fragmentation failure and instant release of compressed gas energy. HIPes are intended for healing defects in casting and compacting metallic, ceramic and composite materials.     

Possibility of Campylobacter jejuni inactivation in smoked salmon by high-pressure treatment

The sterile samples of cold-smoked salmon were placed in polyamide–polyethylene pouches and inoculated with three-strain composite of Campylobacter jejuni (inoculum ca 10⁷ CFU g^?1). The inoculated samples were sealed under vacuum and subjected to 200, 300 and 400 MPa of hydrostatic pressure for 0, 5, 10 and 15 min. The number of surviving C. jejuni per gram was determined by the 10-fold dilution method followed by plating on Karmali agar. D ₁₀ values were calculated. This work has shown that for reducing C. jejuni in cold-smoked salmon by 6 log units, the application of 200 MPa for 64.26 min or 300 MPa for 17.10 min or 400 MPa for less than 5 min is needed. Applying such parameters of high-pressure processing should not change significantly the organoleptic properties of the product.     

Influence of the current magnitude and working gas temperature on electrode erosion in the discharge chambers of high-power pulsed plasmatrons

Results are presented from experimental studies of the erosion of different electrode materials in the discharge chambers of high-power pulsed plasmatrons—the main component of light-gas electric-discharge accelerators of solid bodies. The specific erosion as a function of both the discharge current and the mass-average temperature of the working gas (hydrogen) is determined. The experiments were carried out at discharge currents of 300–1400 kA, average gas temperatures of 700–4500 K, electric charges of 70–700 C, initial hydrogen pressures of up to 42 MPa, and pulsed gas pressures in the chamber of 100–520 MPa.     

A low‐cost X‐ray‐transparent experimental cell for synchrotron‐based X‐ray microtomography studies under geological reservoir conditions

A new modular X‐ray‐transparent experimental cell enables tomographic investigations of fluid rock interaction under natural reservoir conditions (confining pressure up to 20 MPa, pore fluid pressure up to 15 MPa, temperature ranging from 296 to 473 K). The portable cell can be used at synchrotron radiation sources that deliver a minimum X‐ray flux density of 10⁹ photons mm^?2 s^?1 in the energy range 30–100 keV to acquire tomographic datasets in less than 60 s. It has been successfully used in three experiments at the bending‐magnet beamline 2BM at the Advanced Photon Source. The cell can be easily machined and assembled from off‐the‐shelf components at relatively low costs, and its modular design allows it to be adapted to a wide range of experiments and lower‐energy X‐ray sources.     

Three-dimensional textile structural composites under high strain rate compression: Z-transform and discrete frequency-domain analysis

Z-transform theory was applied to several three-dimensional (3D) textile structural composites, including an angle-interlock woven composite, a multilayer multi-axial warp knitted composite and a 4-step braided composite, to characterize their system dynamic behaviour in the frequency domain. More specifically, the analysis focused on the relationship between the compressive load and the system response under static (strain rate 0.001?s^?1) and impulsive (strain rate up to 2700?s^?1) strain along both the in-plane and out-of-plane directions, respectively. The high strain rate compressions were tested using a split Hopkinson pressure bar apparatus, and the input and output (the stress–strain curve) of the test specimen was obtained by recording the signals using a computer for further analysis. Z-transform was then used to analyze the dynamic response and stability of the composites of different preform structures and at various loading conditions. This is the first such attempt to study the compression behaviour of 3D textile structural composites at various strain rates in the frequency domain in order to reveal their mechanical behaviour and features of the materials from a new perspective.     

Fabrications and dielectric performances of novel composites: Calcium copper titanate / Polyvinylidene fluoride

CCTO (Calcium copper titanate) powder as inorganic filler was synthesized by the Sol-gel method firstly. CCTO/PVDF (Polyvinylidene fluoride) composite was fabricated by solution mixing based on high temperature resistance of PVDF and insulated property of CCTO. The composite of CCTO/PVDF were characterized by X-ray diffraction, Fourier Transform infrared spectroscopy, Scanning Electron Microscope and impedance analysis. The results showed that the addition of CCTO and increasing in its content did not affect the phase- and micro-structure of the composites,but the increase of CCTO content can induce the generation of C–F new bonds. PVDF/CCTO composites were enhanced in performance of thermal and frequency-depended stability with increasing in the fraction of CCTO. The dielectric constant of CCTO/PVDF composite materials with 50% CCTO achieved to a maximum value of 50 almost, which is 5 times higher the pure PVDF. The conductivity felled into 10⁻⁸ to 10⁻¹ S m⁻¹ during the frequency of 10²–10⁸ Hz. The composite material would be expected to be applied in the field of integrated circuit.     

A twins-structural Sn@C core–shell composite as anode materials for lithium-ion batteries

In this paper, we report a facile method to prepare a twins-structural Sn@C core–shell composite that is used as anode materials for lithium-ion batteries. Its surface morphology and microstructures were characterized by the scanning electron microscope, X-ray diffraction, and transmission electron microscope. The electrochemical performances of Sn@C were measured by charge–discharge tests, cyclic voltammogram, and electrochemical impedance spectra. It is shown that such a composite exhibits a high initial specific capacity of 970 mA h g^?1 and a capacity retention of 400 mA h g^?1 after 50 cycles at the current density of 100 mA g^?1.     

Preparation and characterization of PbTiO3–epoxy resin compositionally graded thick films

The preparation and properties of compositionally graded PbTiO₃ (PT)–epoxy resin (EPR) composite thick films are reported in this study. Various graded specimens were prepared using gravity casting method by embedding PT powders into the EPR matrix. The existence of a graded structure with two distinct phases, a good intermixing, some air pores, and different morphologies, was confirmed by scanning electron microscopy micrographs. The dielectric constants of these composites have values in the range 5–12 at the frequency of ～10⁴?Hz and about 3–13 at ～5?×?10^8?Hz. The composites with permittivity gradient act as a natural impedance match system in the frequency range 2–4?GHz, resulting in very low reflections. Therefore, the compositionally graded PT–EPR composite thick films are suitable as adapting impedance materials for microwave applications.     

Synthesis of graphene/nickel oxide composite with improved electrochemical performance in capacitors

A novel reduced graphene oxide/NiO nanosheet composite (r-GO/NiO) (ca. 75 % NiO in weight) was synthesized by a facile two-step method, where the NiO nanosheets were decorated with some voids. The composite was characterized by using X-ray diffraction, transmission electron microscopy, thermal gravimetric analysis, and Raman spectroscopy. The electrochemical properties of the composite were investigated by cyclic voltammetry, galvanostatic charge, and discharge measurements. The results show that the r-GO/NiO composite exhibits a stable average specific capacitance of ca. 1,139 F g^?1 (at 0.5 A g^?1) during 1,000 charge–discharge cycles, suggesting that the r-GO/NiO composite is a potential supercapacitor material. The main correlation between the electrochemical performance and the structure of the materials was studied, and the formation process of the composite was also discussed.     

The electrochemical characteristics of sulfur composite cathode

The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated based on different charge/discharge manner. The sulfur composites showed novel electrochemical characteristics as well as the high specific capacity and the good cycleability. The investigation showed that the deep discharge down to less than 1.0 V benefited the performance of the sulfur composite cathode, and the overcharge up to 4.0 V deteriorated its performance. The compaction of the sulfur composite electrode was also investigated. The electrochemical performance of the sulfur composite electrodes was tested at the compaction strength from 0 to 24 MPa, showing that the sulfur composites electrode presented the best electrochemical characteristics at the certain compaction strength of 8 MPa. Its performance seriously deteriorated at the compaction strength of 24 MPa. The study reveals that the appropriate compaction strength benefits the electrochemical performance of the sulfur composite electrode.     

Tuneability amplification factor and loss of high-contrast composites

The problem of tuneability of nonlinear ferroelectric–dielectric composite materials is addressed. Attention is concentrated on the analysis of the tuneability amplification factor, K, of a composite material, which is introduced as the ratio of the effective tuneability of a composite material to the tuneability of its ferroelectric (tuneable) component. Previously, ferroelectric–dielectric composite materials have been designed with an effective tuneability amplification factor slightly greater than 1 (i.e. 1.1–1.4) [A.K. Tagantsev et al., J. Electroceramics 11 (2003) p.5; A.G. Kolpakov et al., J. Electroceramics 18 (2007) p.129]. It is demonstrated that the tuneability amplification factor can take values significantly greater than 1. Numerical prototypes (structural designs integrated with finite element method tools) of microstructures are presented with K in the range 3 to 30. The effective tuneability of nonlinear composite materials strongly depends on the microgeometry and microtopology of the material and, in general, cannot be described in terms of volume fraction of components of composite material. In the designs presented, the increased tuneability is due to concentration of the high electric field in narrow regions with carefully selected geometry. The problem of loss in ferroelectric–dielectric composite materials is discussed. In the general case, the loss tangent stays between that of the components of the composite. For high-contrast ferroelectric–dielectric composite materials, the effective loss tangent is practically equal to the loss tangent of the ferroelectric.     

Microstructure of multilayer interface in an Al matrix composite reinforced by TiNi fiber

A multilayer interface was formed in the Al matrix composite which was reinforced by 30% volume fraction of TiNi fiber. The composite was fabricated by pressure infiltration process and the interface between the TiNi fiber and Al matrix was investigated by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). When the TiNi fiber was pre-oxidized in the air at 773 K for 1 h, three layers have been found and characterized in the interface: TiNi–B₂ layer near the TiNi fiber, Ti–Al compound layer with Ti and granular TiO₂ near the Al matrix, and Ti–Ni compound layer between TiNi–B₂ and Ti–Al compound layers. The effect of the multilayer interface on the mechanical properties of the composite was also discussed. The result showed that the uniaxial tensile strength of the composite at room temperature was 318 MPa, which was very close to the theoretical calculation value of 326 MPa. Moreover, the composite with good ductility exhibited a typical ductile-fracture pattern.     

Liquid petroleum gas sensing performance of polyaniline-carboxymethyl cellulose composite at room temperature

In the present research, liquid petroleum gas (LPG) sensing properties of polyaniline-carboxymethyl cellulose (PANI-CMC) composite have been investigated. For the purpose of investigation, PANI and PANI-CMC composite are synthesized at room temperature by chemical polymerization of aniline without/with CMC. The prepared materials are characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) techniques. Shift in d-space of PANI in the composite as confirmed by its XRD analysis suggests ordered PANI chain arrangement in the composite. Surface morphology and size of the particles are studied by SEM technique. Nature of the material and mechanism of conduction of both PANI and PANI-CMC composite are investigated by studying complex plane impedance plot in the frequency range of 10²–10⁶ Hz. Based on structural characterizations and impedance studies, sensitivity of PANI and PANI-CMC composite to LPG at room temperature are tested and compared. Further, to examine the efficiency of the composite as a sensor, its stability, recovery and response time have also been studied with a special focus on its ability to work at room temperature.     

Investigation of the design of a metal-lined fully wrapped composite vessel under high internal pressure

In this study, a Type III composite pressure vessel (ISO 11439:2000) loaded with high internal pressure is investigated in terms of the effect of the orientation of the element coordinate system while simulating the continuous variation of the fibre angle, the effect of symmetric and non-symmetric composite wall stacking sequences, and lastly, a stacking sequence evaluation for reducing the cylindrical section-end cap transition region stress concentration. The research was performed using an Ansys^® model with 2.9 l volume, 6061 T6 aluminium liner/Kevlar^® 49-Epoxy vessel material, and a service internal pressure loading of 22 MPa. The results show that symmetric stacking sequences give higher burst pressures by up to 15%. Stacking sequence evaluations provided a further 7% pressure-carrying capacity as well as reduced stress concentration in the transition region. Finally, the Type III vessel under consideration provides a 45% lighter construction as compared with an all metal (Type I) vessel.     

Porous Silicon@Polythiophene Core–Shell Nanospheres for Lithium‐Ion Batteries

Polythiophene‐coated porous silicon core–shell nanospheres (Si@PTh) composite are synthesized by a simple chemical oxidative polymerization approach. The polythiophene acts as a flexible layer to hold silicon grains when they are repeatedly alloying/dealloying with lithium during the discharge/charge process. The long lifespan and high‐current‐density rate ­capability (at a current of 8 A g^?1) of the Si@PTh composite are vastly improved compared with as‐prepared Si spheres. Typically, these Si@PTh composite electrodes achieve a reversible capacity of 1130.5 mA h g^?1 at 1 A g^?1 current density after 500 cycles, and can even possess a discharge capacity up to 451.8 mA h g^?1 at 8 A g^?1. The improved electrochemical performance can be ascribed to the synergy effects of the flexible PTh coating and the distinctive core–shell nanospheres with porous structure, which can largely alleviate the volume expansion of the Si during alloying with lithium.     

Adhesion,morphology, and heat resistance properties of polyurethane coated poly(methyl methacrylate)/fullerene-C60 composite films

Novel polyurethane (PU) adhesive was prepared and coated on poly(methyl methacrylate) (PMMA) and poly(methyl methacrylate)/fullerene (PMMA/Full-C₆₀) composite. Dip-coating technique was employed as facile and cost-effective procedure to coat polyurethane on film substrate. The properties of PU/PMMA and PU/PMMA/Full-C₆₀ composite were studied using Fourier transform infrared spectroscopy, Field Emission Scanning Electron Microscopy, tensile, adhesion, thermal and flammability measurement. Testing polyurethane-coated PMMA exhibited crumpled surface while fullerene addition formed unique pattern of dispersed spherical structures. Fullerene nanofiller loading improved the adhesion and mechanical properties of composite films due to polymer–carbon interaction. In PU/PMMA/Full-C₆₀ 0.5 composite with 0.5 wt.% nanofiller, tensile strength (71.4 MPa) was increased by 18.6% while tensile modulus was increased by 143.85% compared with PU/PMMA. In PU/PMMA/Full-C₆₀ 0.5, T₀ of 473 °C and T_max of 655 °C were observed. Increasing the fullerene content up to 0.5 wt.% decreased the peak heat release rate to 131 kW/m². Novel polyurethane-coated PMMA/Full-C₆₀ composite have potential applications as adhesive coatings in electronic and automotive appliances.     

Synthesis of graphene oxide-poly(2-hydroxyethyl methacrylate) composite by dispersion polymerization in supercritical CO2: adsorption behavior for the removal of organic dye

The use of a biocompatible and thermoresponsive polymer, poly(2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO₂. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability were observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g^?1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8% of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications.     

Electrochemical behavior of Mg-doped 7LiFePO4–Li3V2(PO4)3 composite cathode material for lithium-ion batteries

Mg-doping effects on the electrochemical property of LiFePO₄–Li₃V₂(PO₄)₃ composite materials, a mutual-doping system, are investigated. X-ray diffraction study indicates that Mg doping decreases the cell volume of LiFePO₄ in the composite. The cyclic voltammograms reveal that the reversibility of the electrode reaction and the diffusion of lithium ion is enhanced by Mg doping. Mg doping also improves the conductivity and rate capacity of 7LiFePO₄–Li₃V₂(PO₄)₃ composite material and decreases the polarization of the electrode reaction. The discharge capacity of the Mg-doped composite was 93 mAh?g^?1 at the current density of 1,500 mA?g^?1, and Mg-doped composite has better discharge performance than the original 7LiFePO₄–Li₃V₂(PO₄)₃ composite at low temperature, too. At ?30 °C, the discharge capacity of Mg-doped LFVP is 89 mAh?g^?1, higher than that of the original composite. Electrochemical impedance spectroscopy study shows that Mg²⁺ doping could enhance the electrochemical activity of 7LiFePO₄–Li₃V₂(PO₄)₃ composite. Mg doping has a positive influence on the electrochemical performance of the LiFePO₄–Li₃V₂(PO₄)₃ composite material.     

Luminescence study of SHI irradiated nano semiconductor: Conducting polymer composite

Semiconductor nanoparticle and conducting polymer composite is an interesting class of materials for optoelectronic and photovoltaic device application. We have synthesized a composite of nanocrystalline PbS and conducting polymer MEH-PPV by chemical synthesis and studied the effect of swift heavy ion (SHI) irradiation on the composite material. The irradiation of the composite materials in thin film form is carried out with 120 MeV Si⁺⁹ ion beam at fluences from 5×10¹⁰ to 10¹³ ions/cm². Fluence dependent optical and structural properties have been observed in optical absorption, PL and TEM studies. Reduction of nanoparticle size has been observed after irradiation.