Synthesis of nanopowders with low agglomeration by elaborating Φ values for producing Gd2O3-MgO nanocomposites with extremely fine grain sizes and high mid-infrared transparency

Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd₂O₃-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd₂O₃-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd₂O₃ and MgO (93 and 78 nm, respectively) and high density.     

Low-temperature exfoliated graphene oxide incorporated with different types of natural rubber latex: Electrical and morphological properties and its capacitance performance

A simple with cost-effective method in the production and fabrication of graphene-based rubber nanocomposites as electrode materials is still remain a global challenge. In this work, we proposed one- and two-step approaches to fabricate an exfoliated graphene oxide (GO) as nanofiller in three different types of rubber latex polymer, namely, low ammonia natural rubber latex (NRL), radiation vulcanized NRL (RVNRL), and epoxy NRL 25 (ENRL 25). The electrical conductivity and capacitive behavior of nanocomposite samples were investigated under a four-point probe and cyclic voltammetry measurements, respectively. Meanwhile, the morphological properties were observed using field emission scanning electron microscopy, energy dispersive X-ray, optical polarization microscope, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The thermal stabilities of the nanocomposites were also investigated by thermogravimetric analysis. Among all, the GO/RVNRL polymer nanocomposite samples performed a better homogeneity with an improved electrical conductivity (~8.6 × 10⁻⁴ Scm⁻¹) as compared with the GO/ENRL 25 (~3.1 × 10⁻⁴ Scm⁻¹) and GO/NRL (~2.6 × 10⁻⁴ Scm⁻¹) polymer nanocomposite samples. In addition, the GO/RVNRL polymer nanocomposite electrodes showed acceptable specific capacitance (5 Fg^-1). The successfully fabricated conductive GO-based rubber nanocomposites are suitable for new supercapacitor electrodes.     

Synthesis and Characterization of Co Nanocomposite Based on Poly(benzimidazole-amide) Matrix and Their Behavior as Catalyst in Oxidation Reaction

2,6-Bis(5-amino-1H-benzimidazol-2-yl)pyridine was prepared and characterized by Fourier transform infrared spectroscopy, elemental analysis, ¹H-NMR, and ¹³C-NMR spectroscopic methods. Then a new poly(benzimidazole-amide) was synthesized by polymerization of the corresponding diamine and isophthalic acid. The obtained poly(benzimidazole-amide) exhibited good yield and high thermal stability. Due to the existence of benzimidazole moieties in polymer’s structure, it has the tendency to form complexes with metal ions. So, a new poly(benzimidazole-amide)/Co nanocomposite was prepared. Morphological studies revealed that metal nanoparticles were dispersed in the polymer matrix without any aggregation. poly(benzimidazole-amide)/Co nanocomposite was used as a catalyst in the oxidation of ethyl benzene to acetophenone with tert-butyl hydroperoxide.     

Ion beam induced evolution of surface morphology and optical properties of SnO2–ZnO nanocomposite thin films

SnO₂–ZnO nanocomposite thin films, prepared by a simple carbothermal reduction based vapor deposition method, were irradiated with 8 MeV Si³⁺ ions for engineering the morphological and optical properties. The surface morphology of the nanocomposites was studied by atomic force microscopy (AFM), while the optical properties were investigated by photoluminescence spectroscopy (PL) and Raman spectroscopy. AFM studies on the irradiated samples revealed growth of nanoparticles at lower fluence and a significant change in surface morphology leading to the formation of nanosheets and their aggregates at higher fluences. A tentative mechanism underlying the observed ion induced evolution of surface morphology of SnO₂–ZnO nanocomposite is proposed. PL studies revealed strong enhancement in the UV emissions from the nanocomposite thin film at lower fluence, while a drastic decrease in the UV emissions along with a significant enhancement in the defect emissions has been observed at higher fluences.     

Facile and efficient synthesis of magnetic fluorescent nanocomposites based on carbon nanotubes

Multifunctional nanomaterials composed of magnetic and fluorescent nanoparticles have been one of the most extensive pursuits because of the potential application in bio-research. In this paper, we demonstrated an efficient method by coupling CdSe/CdS/ZnS quantum dots (QDs) with Fe₃O₄ magnetic nanoparticles(MNPs) while functionalized multiwall carbon nanotubes (f-MWCNTs) were used as matrix to synthesize a kind of magnetic fluorescent nanocomposite. Compared with other matrix materials, carbon nanotubes have the advantages of high surface areas and good biocompatibility. The incorporation of f-MWCNTs supplies plenty of nucleation sites for the preferential growth of Fe₃O₄ nanoparticles, avoiding the agglomeration phenomenon of Fe₃O₄ MNPs in traditional co-precipitation method. Moreover, the un-reacted functional groups of f-MCNTs can further adsorb biological species and drugs, averting the decline of fluorescent intensity caused by the modification of biological species and drugs. The synthetic product maintains the unique properties of rapid magnetic response and efficient fluorescence, which shows a broad application prospect in fluorescent labeling, biological imaging, cell tracking and drug delivery.     

Investigation on sulphonated zinc oxide nanorod incorporated sulphonated poly (1,4-phenylene ether ether sulfone) nanocomposite membranes for improved performance of microbial fuel cell

Hydrothermally prepared zinc oxide nanorods are sulphonated (S–ZnO NR) and incorporated into 15% Sulphonated Poly (1,4-Phenylene Ether Ether Sulfone) (SPEES) to improve the hydrophilicity, water uptake and ion transfer capacity. Water uptake and ion transfer capacity increased to 34.6 ± 0.6% and 2.0 ± 0.05 meq g^?1 from 29.8 ± 0.3% and 1.4 ± 0.04 meq g^?1 by adding 7.5 wt% S–ZnO NR to SPEES. Morphological studies show the prepared S–ZnO NR is well dispersed in the polymer matrix. SPEES +7.5 wt% S–ZnO NR membrane exhibits optimum performance after three-weeks of continual operation in a fabricated microbial fuel cell (MFC) to produce a maximum power density of 142 ± 1.2 mW m^?2 with a reduced biofilm compared to plain SPEES (59 ± 0.8 mW m^?2), unsulphonated filler incorporated SPEES (SPEES + 7.5 wt% ZnO, 68 ± 1.1 mW m^?2) and Nafion (130 ± 1.5 mW m^?2) thereby suggesting its suitability as a sustainable and improved cation exchange membrane (CEM) for MFCs.     

Nanocrystalline transition metal oxides and their composites with reduced graphene oxide and carbon nanotubes for photocatalytic applications

Transition metal oxide nanoparticles (CuO, ZnO & Fe₂O₃) and mixed metal oxides CuO. ZnO.Fe₂O₃ were fabricated by facile co-precipitation approach for photocatalytic treatment of organic dyes. The structural features, phase purity, crystallite size and morphology of individual and mixed metal oxides were analysed by X-rays diffraction patterns (XRD) and scanning electron microscopic (SEM) analysis. Electrical behaviour of CuO, ZnO, Fe₂O₃ and mixed metal oxides CuO. ZnO.Fe₂O₃ was explored by current-voltage (I-V) measurements. Functional groups present in the synthesized metal oxides were investigated by Fourier transform infrared spectroscopy (FTIR) which ensures the existence of M-O functional groups in the samples. The optical bandgap analysis was carried out by UV–visible spectroscopic technique which revealed that the blend of three different transition metal oxides reduced the bandgap energy of mixed metal oxides. The reason behind this reduced bandgap energy is formation of new electronic state which arises due to the metal-oxygen interactions. Moreover, the nanocomposites of CuO.ZnO.Fe₂O₃ with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) were prepared to study the effect of the carbonaceous materials on the rate of photodegradation. These carbonaceous nanomaterials have plethora properties which can bring advancement in sector of photocatalytic treatment of wastewater. The photocatalytic experiments were performed using methylene blue (MB) as standard dye for comparative study of metal oxides and their composites with rGO and CNTs. The percentage degradation of methylene blue (MB) by nanocomposite CuO.ZnO.Fe₂O₃/rGO is 87% which is prominent among all samples. This result ascribed the photocatalytic aspects of reduced graphene oxide along with mixed metal oxides.     

Poly(3-hydroxyalkanoate)-grafted carbon nanotube nanofillers as reinforcing agent for PHAs-based electrospun mats

Poly(3-hydroxyalkanoate)s, PHAs, have been covalently grafted onto the surface of multi-walled carbon nanotubes, MWCNTs, providing nanofillers (MWCNT-graft-PHAs) with enhanced compatibility and reinforcement effect towards PHAs. MWCNTs were first modified by in-situ generated diazonium cations obtained from a hydroxyl-containing aniline derivative, yielding MWCNTs with reactive hydroxyl surface groups, MWCNT-OH. Then, MWCNT-graft-PHAs were obtained by direct, i.e. without using any catalyst, transesterification approach. The successful chemical modification of MWCNTs surface was evidenced by Raman spectroscopy and XPS analysis confirming the covalent grafting of PHA on MWCNT. 3-Dimension mats were further produced through electrospinning of a PHA/MWCNT-graft-PHA solution providing nanocomposites with well-defined nanofibrous morphology. No aggregation of the MWCNTs was evidenced by SEM attesting that the grafting of PHA onto MWCNT improved their dispersion within the PHA matrix and consequently, the properties of the corresponding nanomaterials. Indeed, mechanical analysis results have shown that nanofibers loaded with MWCNT-graft-PHA (3 wt%) displayed excellent properties with an increase (+41%) of the tensile strain at break without any decrease of the high elastic modulus as compared to pristine PHA (131 MPa).     

Solution intercalation of polystyrene and the comparison with poly(ethyl methacrylate)

Polystyrene nanocomposites have been prepared via solution intercalation method. Combination of wide-angle X-ray diffraction and thermogravimetric analysis is used to study the effect of solvents on the morphology of the nanocomposites as a function of the amount of residual solvent. d-Spacing of the polystyrene nanocomposites has a minimum value when the residual solvent concentration is between 2 and 4 wt%. Different interaction level between the solvent molecules and polymer chains is considered to be the reason for this special d-spacing change behavior. By comparing the solution intercalation of polystyrene and poly(ethyl methacrylate) from different solvents, it is concluded that the interactions between polymer-surfactant, solvent-surfactant, and polymer-solvent play important role for the solution intercalation of polymers.     

金属/Al2O3基纳米复合材料研究最新进展

金属／Al2O3纳米复合材料在保持原有金属的功能特性时，还可以获得 很好的力学性能，是有良好发展前景的一种纳米复合材料。本文回顾了近年来金属／Al2O3基纳米复合材料在制备工艺，微观结构和力学性能，增韧强化机理方面的最新进展，并指出了今后的研究方向。