Nanostructured Nanocomposites Research Articles

Synthesis of Au/Co3O4/PVA hybrid nanocomposites via eco-friendly method based on pulsed laser ablation process for water treatment

A portable nanostructured nanocomposite film, based on cobalt oxide and gold nanoparticles (NPs) embedded in a polyvinyl alcohol structure (PVA), Au/Co3O4/PVA, was prepared via a novel way based on pulsed laser ablation to be applied as an effective catalytic degradation material for a hazardous chemical structure as nitro compounds. Au/Co3O4/PVA was investigated by the techniques of UV–Vis, FT-IR, SEM, and XRD. From XRD, the decrease in crystallinity of PVA is attributed to the intermolecular hydrogen bonding between PVA and Au/Co3O4. In addition, there are five interplanar peaks, with three shared peaks by both phases and one unique peak for each phase of Au and Co3O4. From FT-IR, the modes observed at a 500–1200 cm-1 wavenumber range correspond to the stretching vibration modes of Au/Co3O4. From UV–VIS, as the embedding of Co3O4 on Au-PVA structure increases, the energy band gap is shifted to a lower value. This is due to the embedding of Co3O4 NPs. From SEM, in the case of embedding PVA with Au NPs, the bright semi-spherical shape of the nanostructured materials has a bright semi-spherical light area. Moreover, in the case of the embedded PVA with Co3O4 NPs, the faint semi-spherical form of the nanostructured materials is discernible. Besides, the catalytic activity performance is tested for the degradation of 4-nitrophenol, which reveales that the reaction followed first-order kinetics, as indicated by linear regression analysis. The results shows that the sample completely convertes 4-nitrophenol to 4-aminophenol within 6 min.

Green engineered Mo-CeO2@C nanocomposites for visible light-assisted dye decomposition and microbial apoptosis

The profound contamination of reservoirs triggered by industrial dyes and the growing phenomenon of antibiotic-resistant bacteria present substantial risks to both the environment and human health. Conventional approaches to water treatment and microbiological disinfection can frequently become ineffective, expensive, and detrimental to the environment, and this issue underscores the need for novel materials that possess refined photocatalytic and antibacterial characteristics that thrive efficiently in a setting of visible light. An innovative nanostructured nanocomposite, Mo-CeO2@C, was synthesized using a green chemistry method coupled with Mo-CeO2 nanoparticles and pristine CeO2. The impact of Ce, Mo, and carbon-based nanocomposites has been validated by leveraging XRD, FTIR, UV–vis spectra, and FE-SEM/EDX. The sunlight-mediated photodegradation performance of carbon-based nanocomposite exhibited a superior photodegradation efficiency of 99.5 %, higher than others. The photocatalytic activity of M.B. dye concentration, catalyst dosage, scavenger test, and recyclability were also conducted, which confirm the optimal catalyst loading of 20 mg, dye concentration 40 ppm, and pH 8 with reusability up to sixth cycles. The carbon-coated doped nanocomposite displays superior antibacterial efficacy against gram-positive S. aureus, gram-negative E. coli, and P. vulgaris bacteria in comparison to CeO2 and Mo-doped CeO2. This may be attributed to the combined effects of the generation of reactive oxygen species (R.O.S.) and the intrinsic characteristics of the dopant and carbon matrix. The results of our research emphasize the potential of carbon-based nanoparticles as versatile agents in the realms of environmental rehabilitation and biomedical research. These nanoparticles provide a method to achieve more efficient and resilient solutions in these areas.

Small-scale plasticity of ultra-fine grained alloy and nanostructured nanocomposite: Ambient and elevated-temperature nanoindentation

This article presents the experimental and modeling results of nanoindentation testing at ambient and elevated temperatures (i.e. 300 to 523 K), examining the small-scale plasticity of ultra-fine grained (UFG) alloy and nanostructured nanocomposite (NS) materials. The complex small-scale deformation mechanisms are highlighted to assess the material flow behavior under the indenter, which involves the interaction of dislocations and nanoparticles restricting the slip/glide of dislocations. Combined with UFG band propagation and transition stages, these lead to a stabilized mechanical strength at elevated temperatures. Accordingly, the activation energy for softening during localized deformation behavior of the nanocomposite is increased compared to the UFG alloy. It is attributed to a shift in the dislocations activation volume and energy aided by altered grain boundary diffusion and sliding mechanisms. It is shown that the straining role of nanoparticles leads to substantial grain size refinement to the nano-scale with enhanced generation of geometrically necessary dislocations. However, these nanoparticles' presence on the boundaries of nano-sized sub-grains can reduce the migration energy and restrict the sliding-based deformation mechanism.

Facile fabrication of graphene oxide/Nafion/indium oxide for humidity sensing with highly sensitive capacitance response

A high-performance graphene oxide/Nafion/indium oxide (GO/Nafion/In2O3) humidity sensor is demonstrated in this paper. The morphology and nanostructure of nanocomposites were characterized by SEM, TEM, XRD, BET and XPS measurements. The humidity measurement platform was established by using saturated salt solutions and the 0–97% RH levels were achieved at 25 °C to investigate its humidity-capacitance performance. The GO/Nafion/In2O3 film humidity sensor exhibited ultrahigh sensitivity, low hysteresis, good stability and outstanding repeatability. Furthermore, the possible humidity sensing mechanism of the GO/Nafion/In2O3 sensor was discussed by complex impedance spectroscopy and Bode diagrams. The GO/Nafion/In2O3 nanocomposite based capacitance-type humidity sensor is promising in many fields for humidity sensing.

Nanostructures and space charge characteristics of MgO/LDPE nanocomposites

The electrical properties of nanocomposites are closely related to their nanostructures. In order to investigate the nanostructures and space charge characteristics of magnesium oxide (MgO)/low-density polyethylene (LDPE), samples of LDPE with nano-MgO from 0.1 to 2.0 wt% are prepared, as well as pure LDPE. The nanostructures of nanocomposites are investigated by the technology of synchrotron radiation small-angle x-ray scattering (SAXS), and the space charge distributions in nanocomposites and LDPE are measured by the pulsed electro-acoustic (PEA) method. Results of the synchrotron radiation SAXS experiments reveal that there is obvious interphase between the nano-MgO particle and the LDPE matrix, the thickness of which increases along with the increase in nano-MgO concentration. The agglomeration and mass fractal exist in all nanocomposites, and become more obvious at higher concentration. Results of space charge measurements indicate that the apparent trap-controlled mobilities and the apparent trap depths are respectively larger and smaller than those in LDPE during the initial phase of depolarization when the concentrations are 0.1 and 0.5 wt%, and are respectively smaller and larger than those in LDPE when the concentrations are 1.0 and 2.0 wt%. The space charge amount decreases after the addition of nano-MgO. This is mainly due to the introduction of shallow traps which promote the charge recombination in 0.1 and 0.5 wt% MgO/LDPE nanocomposites, and the introduction of deep traps which restrict the charge transportation in 1.0 and 2.0 wt% MgO/LDPE nanocomposites. The space charge characteristics of MgO/LDPE nanocomposites are explained combined with the nanostructures obtained from the synchrotron radiation SAXS experiments.

Thermal expansion of bulk nanostructured n-type SiGe nanocomposite from 300 to 1400 K

The use of the nanostructured nanocomposites aims to improve the peak figure of merit (ZT) values of thermoelectric alloys. In addition to ZT, the coefficients of the thermal linear expansion (CTLE) of these alloys are equally important for estimating stresses imposed by the thermal cycling inherent to waste heat recovery operations. In this study, we report the calculated “technical alpha”, i.e., the experimental mean CTLE values for the bulk nanostructured n-type Si80Ge20 alloy doped with phosphorus at 298–1220 K. The elemental composition of the spark plasma sintered (SPS)-specimen after thermal cycling in the infrared furnace is characterized by means of AES spectroscopy in combination with ion sputtering. Small amounts of contaminants, such as Fe and O, and large losses of P are detected. Elongations have been measured using ULVAC DL-1500-RH high-speed dilatometer with various rates of heating and cooling. Anomalous thermal behavior of the n-type Si80Ge20(P2.2) composite is observed at high temperatures. Previously, the same anomaly was detected in the temperature dependence of the elongation of pure silicon. There are some discrepancies between our measurements of the thermal expansion of nanostructured n-SiGe composites and those reported in the literature. Moreover, in this study, SiGe solid solution is also studied to verify the additive scheme and to explore deviations from it for predicting CTLE values at higher temperature on the basis of the properties of the pure components. These calculations of the CTLE of undoped SiGe alloys match with the results of the dilatometric and X-ray experiments conducted during the period 1964–1987 and the calculations based on other theoretical approaches.

Facile synthesis of CoFe2O4 nanoparticles anchored on graphene sheets for enhanced performance of lithium ion battery

Recently, metal oxides as high capacity anode materials had been investigated for lithium ion batteries. However, the fast capacity fading upon cycling leaded poor durability, which hindered their application as higher energy density of lithium ion battery. In this paper, a nanostructured nanocomposite with graphene supported CoFe2O4 nanoparticles (NPs) was prepared via simple hydrothermal reaction. The uniform CoFe2O4 NPs were anchored on graphene sheets, which brought a good performance on cyclability. Combined with the optimization of graphene content, the anode delivered a better capacity retention of 944mAhg−1 over 50 cycles at current density of 100mAg−1 and the good reversible capacity as 990mAh g−1 when the rate returned from 5Ag−1 to 0.1Ag−1 after 60 cycles. The present work provided a desired structure for conversion anode materials or other electrode materials of large volume change.

CdS–Polymer Nanocomposites and Light‐Emitting Fibers by In Situ Electron‐Beam Synthesis and Lithography

A straightforward, electron-beam induced synthesis and patterning approach to the in situ generation of CdS nanocrystals in nanocomposite films and light-emitting electrospun nanofibers is used. Smartly combining room-temperature nanoimprinting, electrospinning, and electron-beam decomposition of nanocrystal precursors and subsequent nucleation of nanoparticles in a polymer matrix allows exploitation of the most favorable flow conditions of organics to produce various nanocomposite nanostructures.

Role of crystal arrangement on the mechanical performance of enamel

The superior mechanical properties of enamel, such as excellent penetration and crack resistance, are believed to be related to the unique microscopic structure. In this study, the effects of hydroxyapatite (HAP) crystallite orientation on the mechanical behavior of enamel have been investigated through a series of multiscale numerical simulations. A micromechanical model, which considers the HAP crystal arrangement in enamel prisms, the hierarchical structure of HAP crystals and the inelastic mechanical behavior of protein, has been developed. Numerical simulations revealed that, under compressive loading, plastic deformation progression took place in enamel prisms, which is responsible for the experimentally observed post-yield strain hardening. By comparing the mechanical responses for the uniform and non-uniform arrangement of HAP crystals within enamel prisms, it was found that the stiffness for the two cases was identical, while much greater energy dissipation was observed in the enamel with the non-uniform arrangement. Based on these results, we propose an important mechanism whereby the non-uniform arrangement of crystals in enamel rods enhances energy dissipation while maintaining sufficient stiffness to promote fracture toughness, mitigation of fracture and resistance to penetration deformation. Further simulations indicated that the non-uniform arrangement of the HAP crystals is a key factor responsible for the unique mechanical behavior of enamel, while the change in the nanostructure of nanocomposites could dictate the Young’s modulus and yield strength of the biocomposite.

Co-continuous nanostructured nanocomposites by reactive blending of carbon nanotube masterbatches

Masterbatches of reactive polymers containing carbon nanotubes are used to prepare nanocomposites by reactive blending. By mixing masterbatches of low molecular-weight amino-terminated polyamide-6 (PA6) containing ∼10 wt% or ∼17 wt% of multi-walled carbon nanotubes (MWNT) with maleic anhydride functionalized polyethylene (PE*) at temperatures above melting of PA6 it is possible to obtain fine and homogeneous dispersions of carbon nanotubes. In the PA6 concentration range explored, from 19 wt% to 37 wt%, nanostructured co-continuous blend morphologies are achieved. Selective extractions show that a high amount of graft copolymer PE*-g-PA6 is synthesized during mixing. The swelling experiments in selective solvents demonstrate co-continuous blend morphologies. Electron microscopy confirms good quality of MWNT dispersion and shows structures on mesoscopic scales. Fine dispersion of carbon nanotubes and the matrix co-continuity concur to yield a unique combination of properties such as solvent resistance, electrical conductivity, mechanical strengthening and ductility.

Safety and Reliability of Carbon Nanotubes in Nanoactuator Application

This paper presents a nanoactuator device as new model of the nanocomposite application. The carbon nanotube was incorporated in the polyvinylidne fluoride and trifluoroethylene P(VDF-TrFE) copolymer matrix. The P(VDF-TrFE) was chosen for its three characteristics which is ferroelectric, piezoelectric and pyroelectric to convert directly the electrical excitation to the mechanical motion (deflection). The SWCNT/P(VDF-TrFE) nanocomposite nanostructure is proposed as nanomaterial challenge to build a nanoactuator and drive systems in nanometer scale size. A deflection the SWCNT of about 10 picometer was found using the atomic force microscopy technique combined with lock-in-amplifier. And in this paper, we present a new method based on Optimal Safety Factors (OSF) in the context of the Reliability-Based Design Optimization (RBDO) analysis of of Carbon Nanotubes in Nanoactuator. We will underline also the different methods of the RBDO analysis and we highlight the advantage of our approach. Numerical results are given to illustrate the proposed method.

Melt compounding of polylactide/organoclay: Structure and properties of nanocomposites

AbstractA Brabender mixer was used to deagglomerate and disperse organomodified montmorillonite Cloisite® 30B (3 wt %) in polylactide (PLA) matrix to obtain nanocomposite systems. The influence of compounding conditions such as blending time (6.5, 10, 20, and 30 min) and compression molding on the nanostructure of nanocomposites was investigated. Molecular weight changes of the PLA matrices induced by melt compounding were determined. Good rheological behavior of the PLA during melt blending with Cloisite® 30B was observed. Prolongation of the blending process improved homogenization of the nanocomposites with the formation of more intercalated and exfoliated structures as revealed by transmission electron microscopy (TEM) and X‐ray analysis. Some orientation of the silicate nanoplatelets induced by compression molding of the nanocomposites was revealed by TEM. It was found that an increase of dispersion degree of the silicate layers modified pronouncedly the physical properties of nanocomposites through an increase of thermal stability as revealed by the thermogravimetric analysis, a decrease of crystallizability of the PLA matrix during melt‐crystallization and upon heating from the glassy, amorphous state. Rheological properties of the nanocomposites determined during dynamic frequency sweep appeared to be very sensitive to the nanostructure evolution. Moreover, the scanning electron microscopy and light microscopy investigations showed the presence of the micron‐size inorganic contaminations in the nanocomposites originating from organoclay Cloisite® 30B. These inclusions were resistive to deagglomeration during melt processing. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3392–3405, 2006

Formation and organization of planar polymeric and nanocomposite nanostructures on liquid and solid surfaces

We describe a new approach to fabrication of organized planar polymeric and composite nanostructures based on synthetic reactions in organized polymeric Langmuir monolayer at the gas–liquid interface. Novel polymeric quasi-crystalline planar monomolecular structures were formed at the gas–aqueous phase interface using new water–insoluble amphiphilic polyelectrolyte molecules. Corresponding ultrathin polymeric nanoscale-ordered films and stable planar polymeric nanocomposite structures with organized inorganic nanoparticles (palladium, gold and iron oxide) grown in the polymeric monolayer were formed successfully on the solid substrate surfaces. The obtained nanostructures were characterized by atomic force microscopy and transmission electron microscopy techniques.