Characterization,antibacterial and in vitro compatibility of zinc–silver doped hydroxyapatite nanoparticles prepared through microwave synthesis

We investigated the possibility of enhancing hydroxyapatite (HA) bioactivity by co-substituting it with zinc and silver. Zn–Ag–HA nanoparticles were synthesized by using the microwave-assisted wet precipitation process, and their phase purity, elemental composition, morphology, and particle size were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). FTIR, XRD, and EDX results showed the characteristic peaks of the Zn–Ag–HA structure, while SEM results demonstrated that the nanoparticles were of spherical shape with a particle size of 70–102 nm. Antibacterial tests of the nanoparticles revealed their antibacterial activity against Staphylococcus aureus and Escherichia coli. By using simulated body fluid (SBF), an apatite layer formation was observed at 28 days. In vitro cell adhesion assay confirmed the cell attachment of normal human osteoblast (NHOst) cells to the disc surface. MTT [(3(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide] assay indicated that the cells were viable, and the cells proliferated faster on the disks than on the control surface due to the presence of metal ions. In conclusion, the novel Zn–Ag–HA nanoparticles were found to be compatible with in vitro experiments and having potential antibacterial properties. Therefore these nanoparticles could be a promising candidate for future biomedical applications.     

Characterization and X-ray peak broadening analysis in PZT nanoparticles prepared by modified sol–gel method

Lead zirconate titanate nanoparticles (PZT-NPs) were synthesized by a modified sol–gel method and were calcinated at temperatures of 600, 650 and 700 °C. Fourier transform infrared (FTIR), powder X-ray diffraction (XRD) and thermal analysis (TGA/DTA), indicate that single-phase perovskite PZT-NPs are obtained after heat treatment at a temperature of 650 °C. The TEM results obtained from the PZT-NPs confirm that the morphology of the PZT nanoparticles is spherical, with an average diameter size of 17 nm. We also investigated the crystallite development in the nanostructured PZT by X-ray peak broadening analysis. The individual contribution of many small crystallite sizes and lattice strains to the peak broadening in the PZT nanoparticles prepared at different temperatures were studied using Williamson–Hall (W–H) analysis in the range of 2θ = 15–80°.     

Characterization and reactivity of VMgO catalysts prepared by wet impregnation and sol–gel methods

This paper reports the study of physicochemical, surface, and catalytic properties of two series of VMgO catalysts prepared by two different methods: wet impregnation and sol–gel. The characterizations of the elaborated materials were performed using N₂-sorption (Brunauer, Emmett and Teller (BET)), X-ray diffraction, Raman, transmission electron microscopy–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analyses. The catalytic properties of the elaborated materials were investigated in the isopropanol decomposition reaction to determine their acid–base character and in the selective oxidation of n-butane to evaluate their dehydrogenation properties. The preparation method and vanadium content strongly affected the properties of our materials. The sol–gel method leads to smaller crystallite size, higher specific surface area, and uniform particle distribution compared to the impregnation one. Both impregnation and SG solids promote the formation of acetone, which is related to the presence of strong basic sites (O^2? species) on the catalytic exposed surface. The more pronounced basic character was obtained through the SG samples. The sol–gel samples exhibited the highest catalytic activity and C4-olefin selectivity in the partial oxidation of n-butane. Whatever the preparation procedure, the nature of surface oxygen species plays an important role in the orientation of catalytic performances.     

Mechanical properties and thermal stability of ambient-cured thick polysiloxane coatings prepared by a sol–gel process of organoalkoxysilanes

Ambient-curable polysiloxane coatings were prepared by pre-hydrolysis/condensation of phenyltrimethoxysilane (PTMS) and dimethyldimethoxysilane (DMDMS) in the presence of ammonia solution and subsequently mixing with aminopropyltriethoxysilane (APS). The mechanical properties of coatings were thoroughly examined at both macro- and micro-level and the thermal stability of coatings was characterized by thermogravimetic analysis, both of which were correlated with coating composition and the hydrolysis/condensation degree of polysiloxane oligomer. It was found that pro-hydrolysis step is essential for fabrication of thick crack-free coatings (18–35 μm). Higher DMDMS molar ratio, more APS dosage and lower hydrolysis/condensation degree of polysiloxane oligomer favor enhancing the hardness. Excellent impact resistance (50 cm kg) of coatings was obtained at 5% and 10% APS dosage, despite of the type and structure of polysiloxane oligomer. Whatever, the best scratch resistance of coatings was attained using the polysiloxane oligomer, prepared at PTMS-to-DMDMS molar ratio of 2:8 and water-to-precursor molar ratio of 1:1, and 5% APS dosage. The polysiloxane coatings exhibit high thermal stability, however, which strongly depends on the coating composition.     

Microstructure and ablation behavior of SiC coated C/C–SiC–ZrC composites prepared by a hybrid infiltration process

In this study, C/C–SiC–ZrC composites coated with SiC were prepared by precursor infiltration pyrolysis combined with reactive melt infiltration. The pyrolysis behavior of the hybrid precursor was investigated using thermal gravimetric analysis-differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy techniques. The microstructure and ablation behavior of the composites were also investigated. The results indicate that the composites exhibit an interesting structure, wherein a ceramic coating composed of SiC and a small quantity of ZrC covers the exterior of the composites, and the SiC–ZrC hybrid ceramics are partially embedded in the matrix pores and distributed around the carbon fibers as well. The composites exhibit good ablation resistance with a surface temperature of over 2300 °C during ablation. After ablation for 120 s, the mass and linear ablation rates of the composites are 0.0026 g/s and 0.0037 mm/s, respectively. The great ablation resistance of the composites is attributed to the formation of a continuous phase of molten SiO₂ containing SiC and ZrO₂, which seals the pores of the composites during ablation.     

Characterization of spherical silica–titania mixed oxide particles synthesized by using a dry process

Silica–titania mixed oxides have excellent properties, such as a low thermal expansion coefficient and a refractive index that can be adjusted by changing the Ti content. However, when the Ti content increases, silica and titania phases in silica–titania mixed oxides can separate. This phase separation leads to the precipitation of the titania component as rutile or anatase crystals. When silica–titania mixed oxides undergo phase separation, their properties become unstable; for example, the refractive index of the particles becomes non-uniform. Therefore, it is preferable to synthesize silica–titania mixed oxides in an amorphous state without causing phase separation. Based on our previous studies on particle size control in silica synthesis, we employed a dry process using organosilicon compounds to synthesize silica–titania mixed oxides. In this study, spherical amorphous silica–titania mixed oxide particles were obtained via flame synthesis using organosilicon and organotitanium compounds. The purpose of this study was to characterize the obtained powder and explore the possibility of controlling particle size during synthesis. By studying the dry process synthesis of spherical silica–titania mixed oxide particles, we confirmed the relationships: between the Si/Ti molar ratio and the obtained crystal structure and between the adiabatic flame temperature and the particle size.     

Characterization of doped tin dioxide anodes prepared by a sol–gel technique and their application in an SPE-reactor

Anodes for the electrocatalytic oxidation of organic pollutants in water have been prepared by depositing novel Sb-doped SnO₂ material on Ti supports by the sol–gel technique. Surface analysis of the anodes by nuclear microprobe and XPS-measurements confirmed the formation of a doped film on the substrate. Large scale porous titanium electrodes, up to 50 cm², have been coated with doped SnO₂ for a galvanostatic solid polymer electrolyte (SPE) application, resulting in very low voltage across the stack, even without adding supporting electrolytes to the water. Assessment of the cell performance was carried out using N,N-dimethyl-p-nitrosoaniline (RNO) as a spin trap for ·OH-radicals and phenol as a standard organic contaminant. Kinetic studies were done for the formation of the ·OH-radicals.     

Characterization of wollastonite coatings prepared by sol–gel on Ti substrate

Wollastonite coatings were prepared by sol–gel on Ti substrate and their microstructures have been studied. The phase compositions and the surface morphologies of these coatings were examined by X-ray diffraction and scanning electron microscopy. Thermal behavior of dried gel was examined by differential scanning calorimetry (DSC) and thermogravimetry (TG). There are many cracks among coatings and particles with size about 200–300 nm distributing inside cracks. DSC and TG results show that the glass transformation temperature of dried gel is about 850°C. After calcined at temperature 900°C, the phase of coatings consists of wollastonite, SiO₂, and CaSi₂O₅.     

Effect of yttria on crystallization and microstructure of an alumina–YAG fiber prepared by aqueous sol–gel process

Continuous fiber development is needed for high performance and high temperature composites. Various methods have been used to make ceramic fibers. In this research, composite fibers (yttrium aluminum garnet (YAG)/Al₂O₃) were prepared by a sol–gel method using aqueous solution. They were synthesized from aluminum salt, aluminum metal, yttrium oxide and water used as solvent. Transparent gel fibers were obtained by immersing a thin wire into the viscous sol, then pulling it out by hand. The obtained fibers contained very fine grains with diameter ranging from 10 to 80 μm after heat treatment. When yttria content was increased, the crystallization of YAG shifted to a lower temperature, whereas the transformation temperature to α-Al₂O₃ shifted to a higher temperature. Nevertheless, the fibers with different amounts of yttria contained alumina and YAG after heat treatment at 1400 °C. The composite fibers had vermicular structure and were denser than alumina fibers. The yttria percent concerning the limits of this study (≤10 wt%) effected on fiber diameter. As the yttria content was increased, the fiber diameter increased, whereas grain size and densification of the composite fibers decreased.     

Characterization and in vitro drug release properties of core–shell hydrogel prepared by gamma irradiation

A hydrogel system was prepared based on core–shell approach for the delivery of trifluoperazine. Acrylonitrile (AN) core and methacrylic acid (MAA) shell copolymer were performed using gamma irradiation. The resulted system has been characterized by FTIR, TGA, TEM, and SEM techniques. The in vitro release study showed that the maximum drug released was 6.11?mg?g^?1 for AN–MAA copolymer through 120?min and 22.34?mg?g^?1 for AN-core–MAAc shell through 240?min. The results demonstrated that AN-core–MAAc had better properties than AN–MAA copolymer which means the preparation technique highly affects the properties of the system.     

Use of a nickel-boride–silica nanocomposite catalyst prepared by in-situ reduction for hydrogen production from hydrolysis of sodium borohydride

Hydrogen was produced by hydrolysis of sodium borohydride (NaBH₄) using nickel-boride–silica nanocomposite catalyst. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry (EDX). The Ni-B–silica nanocomposite catalyst was found to consist of amorphous Ni-B nanoparticles attached to the surface of amine-modified silica nanosphere. The kinetics of hydrolysis of NaBH₄ by Ni-B–silica composite catalyst was investigated. The effects of temperature, NaBH₄ concentration, and catalyst concentration on hydrogen generation were also investigated. A rate of hydrogen generation as high as 1916 ml H₂/min/g Ni was achieved by catalytic hydrolysis of NaBH₄. The stability of the composite catalyst was also explored.     

Dielectric relaxation properties of PbTiO3-multiwalled carbon nanotube composites prepared by a sol–gel process

Dielectric composites fabricated by combining multi-walled carbon nanotubes (MWCNT) and PbTiO₃ (PTO) powder were prepared using a sol–gel process. Well-dispersed PTO powder with various volume ratios of MWCNT was compressed to form a pellet, and then silver electrodes were coated on both sides for electrical measurements. The PTO–MWCNT composite with 0.4 vol% MWCNT showed the highest dielectric constant (912 at 1 kHz), which is approximately 25 times larger than that (37 at 1 kHz) of a pure PbTiO₃ pellet. Furthermore, a strong frequency dependence of the dielectric constant in the low frequency range was shown for the PTO–MWCNT composites. Interfacial effects related to dielectric relaxation in composite materials were used to explain an observed increase of the dielectric constant near the percolation threshold.     

Economical treatment of reverse osmosis reject of textile industry effluent by electrodialysis–evaporation integrated process

Membrane separation methods such as electrodialysis (ED) can reduce the volume load on evaporators by facilitating further concentration of rejects from reverse osmosis (RO) plants. ED studies were carried out on a bench-scale system using five membrane cell pairs to obtain a textile effluent concentrate containing approximately 6 times the quantity of salts present in the RO reject. The limiting current densities were determined to be in the range 2.15–3.35 amp/m² for feed flow rates varying from 18 to 108 L/h. Apart from feed rate, the influence of volume of concentrate and current on membrane performance was evaluated to optimize current utilization. An estimation of energy requirement of an integrated process constituting ED and evaporation for concentration of inorganics present in textile effluent from 4.35% to 24% was made and found to be approximately one eighth of the operating cost incurred by evaporation alone. Detailed design of a commercial ED system revealed that a membrane area of 13.1 m² was required to treat a feed rate of 1500 L/h. The payback period to recover capital investment was found to be 110 days.     

Synthesis and study of the biologically active lysozyme–silver nanoparticles–montmorillonite K10 complexes

Bioinorganic complexes based on silver nanoparticles coated with lysozyme shell (bioconjugates) and aluminosilicate matrices have been synthesizeed. Layered aluminosilicates with the structure of montmorillonite of grade K10 were used as matrices. Complexes with the silver mass fraction 0.3% (from the chemical analysis data) were obtained through fivefold treatment of the aluminosilicate matrix by a sol of bioconjugates with an average particle size of 18 nm and a thickness of the biological cell of ～4 nm. The produced biocomplexes were investigated by the methods of X-ray diffraction, scanning electron microscopy, and UV spectroscopy. The samples’ antibacterial activity against Gram-negative (E. coli ML-35p, P. aeruginosa ATCC 27853) and Gram-positive (MRSA ATCC 33591, L. monocytogenes EGD) bacteria has been studied. The presence of the biocomplex activity toward antibiotic-resistant strains E. coli ML-35p and MRSA has been revealed.     

Photoluminescence of ZnO layer on commercial glass substrate prepared by sol–gel process

Amorphous ZnO thin film on soda–lime–silica glass substrate was prepared by the sol–gel process at low-temperature processing, i.e., 100 °C. No distinct grain structure was observable in the surface of the film. The photoluminescence spectrum of the ZnO thin film with an intense near band edge emission was observed while the defect-related broad green emission was nearly quenched.     

Characterization of copper/alumina catalysts prepared by deposition—precipitation using urea hydrolysis : I. Nitrous Oxide Decomposition and Reaction of Ethanol

Copper—alumina catalysts with a wide range of copper loadings (4 to 34 wt.-%) were prepared by depositing Cu²⁺ on suspended γ-alumina through precipitation from a homogeneous solution using urea hydrolysis at 90–95°C. The effect of copper content on the crystallographic phase and BET surface area of the catalysts calcined at 400°C for 24 h was investigated. Catalysts containing ≤16 wt.-% copper did not show any copper containing phase indicating the presence of highly dispersed or amorphous copper species. These catalysts have shown high copper metal areas ranging from 308 to 108 m²/g-Cu as determined by the reaction of nitrous oxide with copper surfaces at 90°C. While catalysts with low copper content exhibited both dehydration and dehydrogenation activity, those with high copper content showed only dehydrogenation activity at reaction temperatures of 250–300°C. The selectivities for dehydrogenation products were correlated with copper areas of the catalysts.     

Characterization of Zn–Ni–Fe hydrotalcite-derived oxides and their application in the hydrolysis of carbonyl sulfide

A series of Zn, Ni and Fe containing hydrotalcite-like compounds with various M²⁺/M³⁺ ratios were synthesized by co-precipitation method at pH = 10. The products were characterized by XRD, SEM, TG-DTA, FTIR, CO₂-TPD and N₂ adsorption/desorption techniques. The results showed that M²⁺/M³⁺ ratio affected the formation of hydrotalcite crystal seriously. The precursors with M²⁺/M³⁺ mole ratio of 2 and 3 showed pure hydrotalcite phase. After calcination at 250 °C, the derived oxides with larger surface area and more basic sites were obtained. Desulfurization tests showed that the Zn–Ni–Fe hydrotalcite-derived oxide exhibited an excellent activity in low temperature hydrolysis of COS. The optimum M²⁺/M³⁺ mole ratio was 3.     

Polyacrylate/silica hybrids prepared by emulsifier-free emulsion polymerization and the sol–gel process

Polyacrylate/silica hybrids were prepared by emulsifier-free emulsion polymerization and the sol–gel process. The influence on the properties of polyacrylate/silica hybrids of the synthetic conditions, such as the dosage of polyvinyl alcohol, the ratio of the monomers, the dosage of tetraethoxysilane and the dosage of γ-methacryloxypropyltrimethoxysilane, was investigated. The hybrid material was characterized by Fourier transform infrared, differential scanning calorimeter, thermal gravimetric analyzer and dynamic light scattering. The results indicated that there were chemical bonds between SiO₂ and polyacrylate, that the thermal stability and the average diameter of polyacrylate emulsion particle increased with the incorporation of SiO₂, and that the glass transition temperature (T _g) of polyacrylate/SiO₂ was 8 °C higher compared with that of pure polyacrylate.     

Microstructure and mechanical properties of Al2O3–Ti(C,N)–cBN composites prepared by a novel hot-forging process

Al₂O₃–cBN has received considerable attention in the field of ceramic cutting tools due to its high hardness, high wear resistance, and low cost, but poor interfacial bonding affects the performance of the composite. In this study, a novel hot-forging process was used to prepare high-performance Al₂O₃–cBN composites using Ti(C,N) as a binder. The evolution of the morphology, phase, and microstructure of the hot-forged Al₂O₃–Ti(C,N)–cBN composites was determined, and the mechanical properties were measured. The relative density of the composites increases significantly after hot forging, and the deformation of the composites increases with the hot-forging temperature. The highest performing Al₂O₃–Ti(C,N)–cBN composite was prepared by hot forging at 1600°C and has a hardness of 20 GPa, a bending strength of 647 MPa and a fracture toughness of 5.37 MPa m^1/2, which are superior to those of a directly hot-pressed sintered composite. However, at hot-forging temperatures higher than 1700°C, Al₅O₆N and TiB₂ are formed in the composite. In the composite hot forged at 1800°C, serrated grain boundaries promote the strength and toughness of the composite to 877 MPa and 6.76 MPa m^1/2, respectively. Therefore, the novel hot-forging process is expected to enhance material properties.     

Investigation of mixing performance in a semi-active T-micromixer actuated by magnetic nanoparticles: Characterization via Villermaux–Dushman reaction

A semi-active T-type micromixer is designed to intensify micromixing by actuating magnetic nanoparticles (MNPs). Five permanent magnets in a zig-zag arrangement are located next to the mixing channel of the micromixer to apply the magnetic field to the fluid flow. Micromixing performance is considered in terms of the segregation index (X_S) by the Villermaux/Dushman reaction test. The effects of magnetic flux intensity (B = 380–500 mT), the concentration of MNPs (φ = 0.002–0.01 [w/v]), and flow rate ratios on X_S and pressure drop are investigated. By increasing MNPs concentration from φ = 0.002–0.008 (w/v), X_S decreased and the rise in φ up to 0.008 (w/v) has not been significant on X_S. Maximum mixing efficiency (i.e., minimum X_S = 0.0088) is achieved for B = 500 mT and φ = 0.01 (w/v). By applying the magnetic field, the mixing performance increased due to the motion of MNPs, but its negative effect is an increase in the pressure drop along the micromixer reactor. Generally, with the formation of MNPs barriers inside the mixing channel, the main fluid flows through these layers and creates the sinusoidal flow paths compared to no magnetic field conditions, and thus, a superior mixing efficiency could be attained.