Mechanical Properties and In Vitro Physico‐chemical Reactivity of Gel‐derived SiO2–Na2O–CaO–P2O5 Glass from Sand

In the present report, a bioactive glass was synthesized from silica sand as economic substitute to alkoxy silane reagents. Sodium metasilicate (Na₂SiO₃) obtained from the sand was hydrolyzed and gelled using appropriate reagents before sintering at 950 °C for 3 h to produce glass in the system SiO₂? Na₂O? CaO? P₂O₅. Compression test was conducted to investigate the mechanical strength of the glass, while immersion studies in simulated body fluid (SBF) was used to evaluate reactivity, bioactivity and degradability. Furthermore, the glass samples were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X‐ray spectroscopy (EDX) to evaluate the microstructure and confirm apatite formation on the glass surface. The glass, dominated by bioactive sodium calcium silicate, Na₂Ca₂Si₃O₉ (combeite) crystals, had mechanical strength of 0.37 MPa and showed potentials for application as scaffold in bone repair.     

Dielectric,thermal, and mechanical properties of CeO2‐filled HDPE composites for microwave substrate applications

Cerium oxide‐filled high density polyethylene (HDPE) composites for microwave substrate applications were prepared by sigma‐blend technique. The HDPE was used as the matrix and the dispersion of CeO₂ in the composite was varied up to 0.5 by volume fraction, and the dielectric properties were studied at 1 MHz and microwave frequencies. The variations of thermal conductivity (k_eff), coefficient of thermal expansion (α_c) and Vicker's microhardness with the volume fraction of the filler were also measured. The relative permittivity (ε_eff) and dielectric loss (tan δ) were found to increase with increase in CeO₂ content. For 0.4 volume fraction loading of the ceramic, the composite had ε_eff = 5.7, tan δ = 0.0068 (at 7 GHz), k_eff = 2.6 W/m °C, α_c = 98.5 ppm/°C, Vicker's microhardness of 18 kg/mm² and tensile strength of 14.6 MPa. Different theoretical approaches have been used to predict the effective permittivity, thermal conductivity, and coefficient of thermal expansion of composite systems and the results were compared with the experimental data. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 998–1008, 2010     

Use of metal composite MOF‐5‐Ag2O‐NPs as an adsorbent for the removal of Auramine O dye under ultrasound energy conditions

In this work, MOF‐5 composited with Ag₂O nanoparticles was prepared and characterized via X‐ray diffraction, field emission‐scanning electron microscopy, energy‐dispersive spectroscopy and FT‐IR analysis. This new material was subsequently employed for removing basic yellow dye [Auramine O (AO)] from aqueous solution under ultrasound irradiation. Several experiments were designed by central composite design in which operational parameters such as such as pH, MOF‐5‐Ag₂O mass and initial concentration of AO involved in the process were optimized. The significance of individual parameters and their possible interactions were investigated using analysis of variance (anova ). The optimum values of 6, 0.025 g and 6 mg l^?1 were obtained for the pH, MOF‐5‐Ag₂O‐NPs mass and the initial concentrations of AO, respectively, with desirability of 1.0. At such conditions, the efficiency for the removal of AO was found to be 89.45%. Various isotherm models for fitting the experimental equilibrium data were studied, and it was found that the Langmuir model has the highest efficiency for correlation of experimental equilibrium data, so that the monolayer adsorption capacity of MOF‐5‐Ag₂O for successful removal of AO was 260.70 mg g^?1 at optimal conditions.     

Antimicrobial,mechanical, barrier,and thermal properties of bio‐based poly (butylene adipate‐co‐terephthalate) (PBAT)/Ag2O nanocomposite films for packaging application

Bio‐based nanocomposites of poly (butylene adipate‐co‐terephthalate) (PBAT)/silver oxide (Ag₂O) were prepared by the composite film casting method using chloroform as the solvent. The prepared Ag₂O at different ratios (1, 3, 5, 7, and 10 wt%) is incorporated in the PBAT. The PBAT nanocomposite films were subjected to structural, thermal, mechanical, barrier, and antimicrobial properties. The electron micrographs indicated uniform distribution of Ag₂O in the PBAT matrix. However, the images indicated agglomeration of Ag₂O particles at 10 wt% loading. The thermal stability of the nanocomposite films increased with Ag₂O content. The tensile strength and elongation of the composite films were found to be higher than those of PBAT and increased with Ag₂O content up to 7 wt%. The PBAT‐based nanocomposite films showed the lower oxygen and water vapor permeability when compared to the PBAT film. Antimicrobial studies were performed against two food pathogenic bacteria, namely, Klebsiella pneumonia and Staphylococcus aureus.     

Temperature dependence of strain energy and thermodynamic properties of V2O5‐based single‐walled nanotubes: Zone‐folding approach

A zone‐folding approach is applied to estimate the thermodynamic properties of V₂O₅‐based nanotubes. The results obtained are compared with those from the direct calculations. It is shown that the zone‐folding approximation allows an accurate estimation of nanotube thermodynamic properties and gives a gain in computation time compared to their direct calculations. Both approaches show that temperature effects do not change the relative stability of V₂O₅ free layers and nanotubes derived from the α‐ and γ‐phase. The internal energy thermal contributions into the strain energy of nanotubes are small and can be ignored. © 2016 Wiley Periodicals, Inc.     

Electrospun poly(ε‐caprolactone)‐based composites using synthesized β‐tricalcium phosphate

Non‐woven hybrid membranes based on poly(ε‐caprolactone) (PCL) and as‐synthesized β‐tricalcium phosphate (β‐TCP) were obtained by the electrospinning technique. A wide range of composition was investigated, the filler content spanning between 2 and 60 wt%. The synthesis of the β‐TCP powder was accomplished by titration of calcium hydroxide with phosphoric acid followed by calcination of the resulting precipitate at 1100°C. The as‐dried calcium phosphate was characterized by Inductive Coupled Plasma (AES‐ICP), thermal analysis (TG‐DTA), Fourier Transform Infrared Spectroscopy (FT‐IR), Scanning Electron Microscopy (SEM), and high temperature X‐ray diffraction analysis (HT‐XRD). The specific surface area (SSA) was evaluated by N₂ adsorption. Microstructure of PCL/TCP membranes was investigated by SEM, energy dispersion spectroscopy (EDS), XRD analysis, and SSA measurements. The average fiber diameter ranged between 1 and 2 µm, the porosity was 80–90%, and the SSA 16 m²/g. Mechanical properties were determined by uniaxial tensile test. A remarkable enhancement of the tensile modulus was observed for composites containing up to 4 wt% β‐TCP. The ultimate tensile strength ranged between 2 and 3 MPa for samples loaded up to 8 wt%. For most of the samples, the elongation at break was in the range 100–150%. Copyright © 2010 John Wiley & Sons, Ltd.     

Novel Flower‐Like Ag‐SiO2‐MgO‐Al2O3 Material: Preparation,Characterization and Catalytic Application in Methanol Dehydrogenation

Catalytic direct dehydrogenation of methanol to formaldehyde was carried out over Ag‐SiO₂‐MgO‐Al₂O₃ catalysts prepared by sol‐gel method. The optimal preparation mass fractions were determined as 8.3% MgO, 16.5% Al₂O₃ and 20% silver loading. Using this optimum catalyst, excellent activity and selectivity were obtained. The conversion of methanol and the selectivity to formaldehyde both reached 100%, which were much higher than other previously reported silver supported catalysts. Based on combined characterizations, such as X‐ray diffraction (XRD), scanning electronic microscopy (SEM), diffuse reflectance ultraviolet‐visible spectroscopy (UV‐Vis, DRS), nitrogen adsorption at low temperature, temperature programmed desorption of ammonia (NH₃‐TPD), desorption of CO₂ (CO₂‐TPD), etc., the correlation of the catalytic performance to the structural properties of the Ag‐SiO₂‐ MgO‐Al₂O₃ catalyst was discussed in detail. This perfect catalytic performance in the direct dehydrogenation of methanol to formaldehyde without any side‐products is attributed to its unique flower‐like structure with a surface area less than 1 m²/g, and the strong interactions between neutralized support and the nano‐sized Ag particles as active centers.     

Preparation and properties of silylated PTFE/SiO2 organic–inorganic hybrids via sol–gel process

A study on poly(tetrafluoroethylene) (PTFE) reinforced with tetraethoxysilanes (TEOS) derived SiO₂ is described. It included the manufacturing process of SiO₂‐reinforced PTFE and the effects of silylation agent on the properties of the hybrid material, such as porosity, hydrophobic, thermal resistance, dielectric and mechanical properties, and microstructure. PTFE/SiO₂ hybrids of 50 wt % SiO₂ loading were prepared via a sol–gel process and were shaped by a two‐roll milling machine. Trimethylchlorosilane and hexamethydisilazane were used as the silylation agents. Our results showed that the water absorption and dielectric loss of PTFE/SiO₂ hybrid had significantly improved with silylation agent. The silylation process replaced Si? OH with Si? CH₃ on the surface of the TEOS‐derived silica colloidal particle. The existence of trimethylsilyl [? Si(CH₃)₃] on the surface of the modified PTFE/SiO₂ hybrid was confirmed via infrared and solid‐state ²⁹Si magic‐angle spinning nuclear magnetic resonance spectra. Nitrogen‐sorption techniques were used to characterize the modified and unmodified PTFE/SiO₂ hybrids. The microstructure of SiO₂ in the matrix was also evaluated with scanning electron microscopy and transmission electron microscopy. Our results showed that the silylated sol–gel‐derived PTFE/SiO₂ hybrids had exhibited high porosity (53.7%) with nanosize pores (10–40 nm) and nanosize colloidal particles (20–50 nm). This manifests itself as have the ultralow dielectric properties (D_k = 1.9 and D_f = 0.0021), low coefficient of thermal expansion (66.5 ppm/°C), high tensile modulus (141 MPa), excellent thermal resistance (T_d = 612 °C), and an increased hydrophobia (θ = 114°); moreover, the hydrophobic property of the PTFE/SiO₂ hybrid was thermally stable up to 400 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1789–1807, 2004     

Preparation of porous g‐C3N4/Ag/Cu2O: a new composite with enhanced visible‐light photocatalytic activity

From previous reports, graphitic carbon nitride (g‐C₃N₄) can be used as a photocatalyst, although the low efficiency of solar energy utilization, small specific surface area and high recombination rate of photogenerated electron–hole pairs limit its practical application. For the purpose of increasing photocatalytic activity, especially under irradiation of visible light, we successfully synthesized a new composite, namely porous g‐C₃N₄/Ag/Cu₂O, through chemical adsorption of Ag‐doped Cu₂O on porous g‐C₃N₄, which has not been investigated carefully worldwide. The composition, morphology and optical properties of the composite were investigated through methods including X‐ray diffraction, energy‐dispersive X‐ray, Fourier transform infrared, UV–visible and photoluminescence spectroscopies and transmission electron microscopy. Using rhodamine B as organic pollutant to be degraded under the irradiation of visible light, different mass ratios of Ag/Cu₂O doped on porous g‐C₃N₄ led to enhanced photocatalytic performance of the composite compared to pure porous g‐C₃N₄. When the mass ratio of Ag/Cu₂O is 15%, porous g‐C₃N₄/Ag/Cu₂O exhibits a degradation rate 2.015 times higher than that of pure porous g‐C₃N₄. The reasons for this phenomenon may be attributed to the increased utilization efficiency of visible light, high‐speed separation of photogenerated electron–hole pairs, accelerated interfacial transfer process of electrons and increased surface area of the composite. Copyright © 2016 John Wiley & Sons, Ltd.     

Enhanced dielectric performance and energy storage of PVDF‐HFP‐based composites induced by surface charged Al2O3

In order to enhance dielectric properties and energy storage density of poly(vinylidene fluoride‐hexafluoro propylene) (PVDF‐HFP), surface charged gas‐phase Al₂O₃ nanoparticles (GP‐Al₂O₃, with positive surface charges, ε’ ≈ 10) are selected as fillers to fabricate PVDF‐HFP‐based composites via simple physical blending and hot‐molding techniques. The results show that GP‐Al₂O₃ are dispersed homogeneously in the PVDF‐HFP matrix and the existence of nanoscale interface layer (matrix‐filler) is investigated by SAXS. The dielectric constant of the composites filled with 10 wt % GP‐Al₂O₃ is 100.5 at 1 Hz, which is 5.6 times higher than that of pure PVDF‐HFP. The maximum energy storage density of the composite is 4.06 J cm^?3 at an electrical field of 900 kV mm^?1 with GP‐Al₂O₃ content of 1 wt %. Experimental results show that GP‐Al₂O₃ could induce uniform fillers’ distribution and increase the concentration of electroactive β‐phase as well as enhance interfacial polarization in the matrix, which resulted in enhancements of dielectric constant and energy storage density of the PVDF‐HFP composites. This work demonstrates that surface charged inorganic‐oxide nanoparticles exhibit promising potential in fabricating ferroelectric polymer composites with relatively high dielectric constant and energy storage. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 574–583     

Effect of Fe3O4‐doped sepiolite on the flammability and thermal degradation properties of epoxy composites

As‐received sepiolite/epoxy systems and Fe₃O₄‐doped sepiolite/epoxy systems were prepared, and the contents of sepiolite and Fe₃O₄‐doped sepiolite were kept as 2 and 4 wt%, respectively. Compared with sepiolite, the effect of Fe₃O₄‐doped sepiolite on the flame retardancy, combustion properties, thermal degradation, thermal degradation kinetics and thermomechanical properties of epoxy resin was investigated systematically by limiting oxygen index (LOI), cone calorimeter (Cone), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Some interesting results had been acquired. The addition of sepiolite decreased heat release rate, total smoke production and smoke production rate, and obviously improved LOI values of epoxy composites. Compared with sepiolite, the addition of Fe₃O₄‐doped sepiolite further reduced parameters mentioned above of epoxy composites, and further enhanced LOI values and char residues after cone test. There might be a synergistic effect between sepiolite and Fe₃O₄ on flame retardant epoxy composite. TGA results indicated that the addition of sepiolite had a slight effect on the thermal degradation of epoxy composites; however, the addition of Fe₃O₄‐doped sepiolite accelerated the thermal degradation of epoxy composites. DMA results showed that the addition of both sepiolite and Fe₃O₄‐doped sepiolite increased the glass transition temperature (T_g) of epoxy composite. The results obtained in this paper supplied an effective solution for developing excellent flame retardant properties of polymeric materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Low Temperature Synthesis and Characterization of Li1.2-y NayV3O8(0≤y≤1.2) from V2O5 Gel

Without overnight heating and stirring,Li1.2V3O8 and its analogs Li1.2-y NayV3O8(0≤y≤1.2) were successfully synthesized by adding mixed solution of LiOH and NaVO3 to V2O5 gel and dehydrating the prepared gel in 150-350℃.The simplicity awards this synthesis process superiority over other low temperature synthesis routes when mass production is concerned.TG-DTA,XRD and TEM experiments were carried out for physical characterization.By galvanostatic charge-discharge and cyclic voltammetry tests,these products showed better electrochemical performance than high temperature products as cathode active materials in secondary lithium batteries.After treatment of Li1.2V3O8 at 250℃,it exhibited a capacity of 350mAh/g when cycled at current rate of about 60 mA/g over the voltage range of 3.8-1.7V vs,Li^ /Li.The influence of partial substitution of Li by Na was also extensively studied.     

Investigations of the local distortions and EPR parameters for Cu2+ in xNa2O‐(30–x)K2O‐70B2O3 (5 ≤ x ≤ 25 mol%) glasses

The local distortions and electron paramagnetic resonance parameters for Cu²⁺ in the mixed alkali borate glasses xNa₂O‐(30–x)K₂O‐70B₂O₃ (5 ≤ x ≤ 25 mol%) are theoretically studied with distinct modifier Na₂O compositions x. Owing to the Jahn–Teller effect, the octahedral [CuO₆]¹⁰⁻ clusters show significant tetragonal elongation ratios p ~19% along the C₄ axis. With the increase of composition x, the cubic field parameter Dq and the orbital reduction factor k exhibit linearly and quasi‐linearly decreasing tendencies, respectively, whereas the relative tetragonal elongation ratio p has quasi‐linearly increasing rule with some fluctuations, leading to the minima of g factors at x = 10 mol%. The composition dependences of the optical spectra and the electron paramagnetic resonance parameters are suitably reproduced by the linear or quasi‐linear relationships of the relevant quantities (i.e., Dq, k, and p) with x. The above composition dependences are analyzed from mixed alkali effect, which brings forward the modifications of the local crystal‐fields and the electronic cloud distribution around Cu²⁺ with the variation of the composition of Na₂O.     

Photocatalytic properties of CuO/(001)‐TiO2 composites synthesized by the vapor–thermal method

Composites of (001)‐face‐exposed TiO₂ ((001)‐TiO₂) and CuO were synthesized in water vapor environment at 250°C with various Cu/Ti molar ratios (R_Cu/Ti). The resulting CuO/(001)‐TiO₂ composites were characterized using a variety of techniques. The synthesis under high‐temperature vapor allows close contact between CuO and (001)‐TiO₂, which results in the formation of heterojunctions, as evidenced by the shift of valence band maximum towards the forbidden band of TiO₂. An appropriate ratio of CuO can enhance the absorption of visible light and promote the separation of photogenerated carriers, which improve the photocatalytic performance. The degradation rate constant K_app increased from 5.5 × 10^?2 to 8.1 × 10^?2 min^?1 for R_Cu/Ti = 0.5. Additionally, the results showed that superoxide radicals (^?O₂^?) play a major role in the photocatalytic degradation of methylene blue.     

Characterization and anticorrosive properties of poly(2,3‐dimethylaniline)/nano‐Al2O3 composite synthesized by emulsion polymerization

Poly(2,3‐dimethylaniline)/nano‐Al₂O₃ composite (PAC) was synthesized by emulsion polymerization using dodecyl benzene sulfonic acid as emulsifier and dopant. The structure of PAC was characterized by Fourier fransformation infrared spectroscopy, UV–visible adsorption spectroscopy, and field emission scanning electron microscopy. The thermal stability was studied by thermogravimetric analysis, and the electrochemical performances were studied by cyclic voltammetry measurements. Epoxy coatings containing PAC and poly(2,3‐dimethylaniline) (P(2,3‐DMA)), respectively, were painted on steel, and accelerated immersion tests were performed to evaluate the anticorrosion property of the coatings in 3.5% NaCl solution. The results showed that the addition of PAC and P(2,3‐DMA) could improve the anticorrosion performance of epoxy coating significantly and the PAC coating had higher corrosion resistance than that of P(2,3‐DMA). Copyright © 2013 John Wiley & Sons, Ltd.     

One‐pot synthesis of magnetic palladium–NiFe2O4–graphene oxide composite: an efficient and recyclable catalyst for Heck reaction

A magnetically separable NiFe₂O₄@GO–Pd composite (GO = graphene oxide) was successfully prepared by a facile one‐pot hydrothermal strategy. This new kind of hybrid material was fully characterized using powder X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy and vibrating sample magnetometry. Structural characterizations confirmed the formation of NiFe₂O₄ and Pd nanocrystals, and the close anchoring between nanoparticles and GO sheets. Additionally, the as‐prepared NiFe₂O₄@GO–Pd nanocomposite was effectively employed in the palladium‐catalyzed Heck reaction in an ethanol–water system as a green solvent. The catalyst was completely recoverable with the simple application of an external magnetic field and with no obvious loss of catalytic activity even after six repeated cycles. Copyright © 2016 John Wiley & Sons, Ltd.     

A High‐Temperature Order–Disorder Phase Transition Coupled With Conformational Change in the Hybrid Material [C6H13NH]2⋅ZnBr4

A new high‐temperature, hybrid, phase‐transition material, 1‐methylpiperidinium tetrabromozincate ( 1 ), that shows a reversible transition at 345 K was synthesized. Differential scanning calorimetry and specific heat capacity measurements confirmed this reversible transformation with a large heat hysteresis of 25 K, which describes a typical first‐order phase transition in 1 . The dielectric constant exhibited a steplike anomaly and showed high and low dielectric states in the high‐ and room‐temperature phases, respectively, and therefore, this hybrid might be considered as a potential switchable dielectric material. The variable‐temperature powder X‐ray diffraction patterns displayed remarkable shifts between the experimental patterns at the two different phases. Single‐crystal X‐ray diffraction analyses at various temperatures revealed that the origin of this transformation could be attributed to disordering of the bromine atoms in the anion and the nitrogen atom of the cation. The cation also assumed a conformational change, which was likely induced by the disordered nitrogen atom. The conformational onset of the transformation of the cation from a planar conformer into a relaxed chair also occurred upon decreasing the temperature below transition point; thus, the combined order–disorder and conformational change induced the structural transformation and the change in symmetry.     

Magnetized inorganic–bioorganic nanohybrid [nano Fe3O4‐SiO2@Glu‐Cu (II)]: A novel nanostructure for the efficient solvent‐free synthesis of thiazolidin‐2‐imines

In this research, a solvent‐free four‐component one‐pot reaction of phenyl isothiocyanate, phenylacetylene, various kinds of aldehydes, and amines was interpreted to obtain the desired five‐membered heterocycles named thiazolidin‐2‐imines. The promotor of this transformation is a novel magnetite‐based multilayered inorganic–bioorganic nanohybrid prepared via embedding glutamic acid on the magnetized silica followed by anchoring Cu (II) [nano Fe₃O₄‐SiO₂@Glu‐Cu (II)]. The newly synthesized nanostructure is characterized through Fourier‐transform infrared (FT‐IR), field‐emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis (EDAX), transmission electron microscopy (TEM), X‐ray fluorescence (XRF), thermogravimetric analysis or derivative thermogravimetric (TGA/DTG), vibrating sample magnetometer (VSM), X‐ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) techniques. This protocol is a straightforward one‐step procedure to obtain thiazolidin‐2‐imines without requirement to propargylamines or imines as substrates. In addition, easy work‐up procedure, high yields of products, absence of organic solvents in the reaction media, recovery and reusability of nano Fe₃O₄‐SiO₂@Glu‐Cu ( II) to promote the reaction at least for three runs without activity lost, simple separation of the catalyst from reaction mixture via an external magnet, and regioselectivity of the method are some highlighted aspects of the approach.     

Green synthesis of Fe3O4@SiO2‐Ag magnetic nanocatalyst using safflower extract and its application as recoverable catalyst for reduction of dye pollutants in water

This paper reports the green and in situ preparation of Fe₃O₄@SiO₂‐Ag magnetic nanocatalyst synthesized using safflower (Carthamus tinctorius L.) flower extract without the addition of any stabilizers or surfactants. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4‐nitrophenol (4‐NP), methylene blue (MB) and methyl orange (MO) in an environment‐friendly medium at room temperature. The main factors such as pH, temperature and amount of catalyst influencing the nanocatalyst performance were studied. The apparent rate constants for 4‐NP, MO and MB reduction were calculated, being 0.756 min^?1, 0.064 s^?1 and 0.09 s^?1, respectively. The catalyst was recovered using an external magnet and reused several times with negligible loss of catalytic activity. The as‐synthesized nanoparticles were characterized using powder X‐ray diffraction, transmission electron microscopy, UV–visible, Fourier transform infrared and inductively coupled plasma atomic emission spectroscopies, dynamic light scattering and vibrating sample magnetometry.