Use Of Nanocomposites Research Articles

Influence of the Addition of Montmorillonite in an Epoxy Powder Coating Applied on Carbon Steel

Polymer coatings have been used for the corrosion protection of metal surfaces acting as a physical barrier against several corroding media. In spite of the good efficiency of these coatings their resistance is limited due to the presence of localized defects which give place to localized corrosion. Aiming to improve the barrier properties of these coatings this work has proposed the use of nanocomposites as powder coatings based on a standard formulation of a commercial powder varnish. Nanocomposites with 2 and 4 wt% contents of organophilic montmorillonite (OMMT) were obtained in the molten state through of a co-rotating twin-screw extruder. The application of the nanocomposite coatings was performed by electrostatic pulverization on mild steel panels. The coatings were characterized to determine their structure using X-ray diffraction (XRD). The morphologies of the coatings were assessed using transmission electron microscopy (TEM). Gloss and adhesion measurements and the flexibility and impact resistance of the coatings were included in the physical assessment of the coatings. The corrosion performance was evaluated by the salt spray test and by electrochemical impedance spectroscopy (EIS). The coatings with clays presented predominantly exfoliated structures, with good dispersion of OMMT in the epoxy matrix. The addition of OMMT reduced the impact resistance, flexibility and gloss but increased the barrier properties of the coatings. The best corrosion performance in NaCl solution was achieved for 4 wt% OMMT.

Synthesis of SWCNT–GO/MnO2 nanocomposites for use as electrodes of electrochemical capacitors by microwave and hydrothermal methods

HNO3-oxidized single-wall carbon nanotubes (SWCNTs) and graphene oxide (GO) were ultrasonically dispersed in water to which potassium permanganate was added, and the resulting mixtures were treated under microwave radiation at 100 °C for 1 h or hydrothermal conditions at 100 °C for 1, 5 and 10 h to prepare SWCNT–GO/MnO2 composites as electrode materials of electrochemical capacitors. Results indicate that the composite prepared using the microwave method has a higher specific capacitance (173 F/g at 0.2 A/g), lower pseudo-charge transfer resistance (1.425 Ω ) and longer cyclic stability (3.74% capacitance loss after 1000 cycles at the scan rate of 20 mV/s) than the ones prepared using the hydrothermal method. Moreover, the microwave method has the advantages of simplicity of operation and shorter heating time. [New Carbon Materials 2015, 30(3): 214–221]

Thermo-stable carbon nanotube-TiO2 nanocompsite as electron highways in dye-sensitized solar cell produced by bio-nano-process

We produced a thermostable TiO2-(anatase)-coated multi-walled-carbon-nanotube (MWNT) nanocomposite for use in dye-sensitized solar cells (DSSCs) using biological supuramolecules as catalysts. We synthesized two different sizes of iron oxide nanoparticles (NPs) and arrayed the NPs on a silicon substrate utilizing two kinds of genetically modified cage-shaped proteins with silicon-binding peptide aptamers on their outer surfaces. Chemical vapor deposition (CVD) with the vapor–liquid-solid phase (VLS) method was applied to the substrate, and thermostable MWNTs with a diameter of 6 ± 1 nm were produced. Using a genetically modified cage-shaped protein with carbon-nanomaterials binding and Ti-mineralizing peptides as a catalyst, we were able to mineralize a titanium compound around the surface of the MWNT. The products were sintered, and thin TiO2-layer-coated MWNTs nanocomoposites were successfully produced. Addition of a 0.2 wt% TiO2-coated MWNT nanocomposite to a DSSC photoelectrode improved current density by 11% and decreased electric resistance by 20% compared to MWNT-free reference DSSCs. These results indicate that a nanoscale TiO2-layer-coated thermostable MWNT structure produced by our mutant proteins works as a superior electron transfer highway within TiO2 photoelectrodes.

XPS PHASE COMPOSITION STUDY OF por−Si/SnOx NANOCOMPOSITE SAMPLES EXPOSED TO THERMAL OXIDATION

Results of XPS and AES investigation of por−Si/SnOxnanocomposite samples after different modes of heat treatment have been presented. We show that thermaltreatment increases the penetration depth of tin and the stoichiometric coefficient x of the SnOx compound. However, annealing at 600 °C leads to a strong oxidation of the porous matrix and eventual blockage of the tin diffusion channels. Optimization of the heat treatment modes allows one to obtain nanocomposite layers with a sufficient thickness of the por−Si/SnOx nanocomposite for use in gas microsensors.

An Unconventional Route to Monodisperse and Intimately Contacted Semiconducting Organic–Inorganic Nanocomposites

We developed an unconventional route to produce uniform and intimately contacted semiconducting organic-inorganic nanocomposites for potential applications in thermoelectrics. By utilizing amphiphilic star-like PAA-b-PEDOT diblock copolymer as template, monodisperse PEDOT-functionalized lead telluride (PbTe) nanoparticles were crafted via the strong coordination interaction between PAA blocks of star-like PAA-b-PEDOT and the metal moieties of precursors (i.e., forming PEDOT-PbTe nanocomposites). As the inner PAA blocks are covalently connected to the outer PEDOT blocks, the PEDOT chains are intimately and permanently tethered on the PbTe nanoparticle surface, thereby affording a well-defined PEDOT/PbTe interface, which prevents the PbTe nanoparticles from aggregation, and more importantly promotes the long-term stability of PEDOT-PbTe nanocomposites. We envision that the template strategy is general and robust, and offers easy access to other conjugated polymer-inorganic semiconductor nanocomposites for use in a variety of applications.

An Unconventional Route to Monodisperse and Intimately Contacted Semiconducting Organic–Inorganic Nanocomposites

AbstractWe developed an unconventional route to produce uniform and intimately contacted semiconducting organic–inorganic nanocomposites for potential applications in thermoelectrics. By utilizing amphiphilic star‐like PAA‐b‐PEDOT diblock copolymer as template, monodisperse PEDOT‐functionalized lead telluride (PbTe) nanoparticles were crafted via the strong coordination interaction between PAA blocks of star‐like PAA‐b‐PEDOT and the metal moieties of precursors (i.e., forming PEDOT–PbTe nanocomposites). As the inner PAA blocks are covalently connected to the outer PEDOT blocks, the PEDOT chains are intimately and permanently tethered on the PbTe nanoparticle surface, thereby affording a well‐defined PEDOT/PbTe interface, which prevents the PbTe nanoparticles from aggregation, and more importantly promotes the long‐term stability of PEDOT–PbTe nanocomposites. We envision that the template strategy is general and robust, and offers easy access to other conjugated polymer–inorganic semiconductor nanocomposites for use in a variety of applications.

New benzoxazines containing polyhedral oligomeric silsesquioxane from eugenol, guaiacol and vanillin

In this article we have selected renewable raw materials such as eugenol, guaiacol and vanillin as bio-phenols, which react with octaamine functionalized POSS and paraformaldehyde to synthesize fully renewable POSS–polybenzoxazine nanocomposites for use in microelectronic packaging applications.

Microporous bamboo biochar for lithium-sulfur batteries

Being simple, inexpensive, scalable and environmentally friendly, microporous biomass biochars have been attracting enthusiastic attention for application in lithium-sulfur (Li-S) batteries. Herein, porous bamboo biochar is activated via a KOH/annealing process that creates a microporous structure, boosts surface area and enhances electronic conductivity. The treated sample is used to encapsulate sulfur to prepare a microporous bamboo carbon-sulfur (BC-S) nanocomposite for use as the cathode for Li-S batteries for the first time. The BC-S nanocomposite with 50 wt.% sulfur content delivers a high initial capacity of 1,295 mA·h/g at a low discharge rate of 160 mA/g and high capacity retention of 550 mA·h/g after 150 cycles at a high discharge rate of 800 mA/g with excellent coulombic efficiency (⩾95%). This suggests that the BC-S nanocomposite could be a promising cathode material for Li-S batteries.

Facile synthesis of heterogeneous Ni-Si@C nanocomposites as high-performance anodes for Li-ion batteries

A scalable solution-based method for fabricating carbon-coated Ni-Si nanocomposites for use as anode materials in Li-ion batteries is reported. This facile process involves a one-pot synthesis using an electrical pulse technique in oleic acid containing Si nanoparticles at room temperature and a subsequent carbonization route. In these nanocomposites, the Si nanoparticles are individually and separately coated with a carbon shell with a nanoscale thickness. Furthermore, the nanocomposites have a large specific surface area with a spherical complex-structure in which Ni nanoparticles and carbon layers play various pivotal roles, as a mechanically supporting barrier against the aggregation of Si nanoparticles and as an electronic pathway between the active Si nanoparticles. Because of these favorable features, the obtained nanocomposites exhibit not only better cycling performances, but also rate capability, in comparison with bare Si anode materials.

Crafting Semiconductor Organic-inorganic Nanocomposites Via Placing Conjugated Polymers in Intimate Contact with Nanocrystals for Hybrid Solar Cells

Recent advances in the synthesis and assembly of nanocrystals (NCs) provide unique opportunities to exploit NCs for the development of next generation organic/inorganic hybrid solar cells as one of the most promising alternatives to Si solar cells to deliver efficient energy conversion with inexpensive fabrication. Herein, we report two simple yet robust routes to conjugated polymer-quantum rod (CP-QR) nanocomposites, dispensing with the need for ligand exchange chemistry. In the first strategy CdSe QRs were passivated with bromobenzylphosphonic acid (BBPA) which not only induced elongated growth but also functionalized the CdSe QR surface, forming BBPA-CdSe QRs. Subsequently, P3HT-CdSe QRs were yielded by Heck coupling of vinyl-terminated P3HT with BBPA-CdSe QRs. The reduced insulating length of BBPA facilitated improved electron interaction between CP and QR, greatly promoting the potential of P3HT-CdSe QR nanocomposites for use in solar cells with enhanced performance. In the second strategy the alkyne–azide cycloaddition, which belongs to an emerging field of click chemistry, was utilized in the preparation of P3HT-CdSe QR nanocomposites. The aryl bromide of BBPA was converted into azide functional group, forming N3-BPA-CdSe QRs. Subsequent catalyst-free Huisgen 1,3-dipolar cycloaddition between ethynyl-terminated P3HT and N3-BPA-CdSe QRs successfully yielded intimate P3HT-CdSe QR nanocomposites without introducing any deleterious metallic impurity. The charge transfer occurred at the P3HT/CdSe QR interface and was confirmed by systematic UV-Vis absorption, photoluminescence (PL), and time-resolved PL studies. The nanocomposites made by the catalyst-free click reaction exhibited a faster charge transfer from P3HT to CdSe than those produced by Heck coupling.

Microscale Characterization of a Mechanically Adaptive Polymer Nanocomposite With Cotton-Derived Cellulose Nanocrystals for Implantable BioMEMS

A mechanically adaptive polymer nanocomposite for use as a structural material for microelectromechanical system (MEMS)-based penetrating implantable biosensors, particularly for the brain, is presented as a solution to the limited clinical implementation of such sensors. Micromechanical testing of MEMS-scale test structures was used to determine the Young's moduli of the polymer nanocomposite in both its dry rigid state (E = 2414 MPa) and its wet compliant state (E = 4.9 MPa), as well as the rate of mechanical switching upon immersion in an aqueous solution. The softening of the composite materials after implantation in the cortex of a Sprague-Dawley rat was studied by ex vivo environmentally controlled microtensile testing. A microfabrication process for producing metallized neural probes for recording of electrical signals was also developed. The results support the mechanically adaptive nanocomposite as a viable option for MEMS-based penetrating implantable biosensors.

Synthesis of three-dimensionally ordered macroporous manganese dioxide–carbon nanocomposites for supercapacitors

In this article, we report a composite of MnO2 nanoparticles supported by three-dimensionally ordered macroporous carbon (MnO2/3DOM carbon nanocomposites) fabricated by means of a simple multi-component infiltration of three-dimensional templates. MnO2 nanoparticles of 2 nm–6 nm are observed to be highly dispersed on the 3DOM carbon scaffolds. Cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques are employed to assess the properties of these nanocomposites for use in supercapacitors. The results demonstrate that MnO2 can be effectively utilized with assistance of the 3DOM carbon in the electrode. The specific capacitance of the nanocomposite electrode can reach as high as 347 F g−1 at a current density of 0.5 A g−1. Moreover, the electrode exhibit excellent charge/discharge rate and good cycling stability, retaining over 92% of its initial charge after 5500 cycles at a current density of 2.5 A g−1. Such MnO2/3DOM carbon nanocomposite represents a promising exploring direction for enhancing the device performance of metal oxide-based electrochemical supercapacitors.

Multiscale Approach to Analysis of Composite Joints Incorporating Nanocomposites

This study focuses on the benefits of using nanocomposites in aerospace structural components to prevent or delay the occurrence of unique composite failure modes, such as delamination. A three-scale approach was considered to determine the mechanical properties of the nanocomposites. First, the effective carbon nanotube properties were calculated based on the composite cylinder assemblage method. Second, the effective properties of the carbon nanotube embedded in an epoxy matrix were obtained using the Mori–Tanaka method. Finally, the effective properties of the composite lamina were also acquired using the Mori–Tanaka method assuming that the nanocomposite obtained in stage two was the matrix of that lamina surrounding the fibers. These properties were then used to analyze the structural response of a -section stringer using detailed finite element models. The stringer was analyzed under different loading conditions and assuming different flaw types in the structure. Initial damage was detected via the virtual crack closure technique implemented in the finite element analysis, and it was assumed to be the characteristic variable to compare the different behaviors. It was found that the use of nanocomposites in the manufacturing process of composite stringers would improve the overall performance against unique composite failure modes.

Multifunctional γ-Fe2O3@Ca3(PO4)2@YPO4:Tb3+,Ce3+ nanocomposites as a potential drug carrier

Multifunctional γ-Fe2O3@Ca3(PO4)2@YPO4:Tb3+,Ce3+ nanocomposites were synthesized using an easy direct-precipitation method. The nanocomposites had a monodispersed spherical morphology with a narrow size distribution, and dispersed well in water. The nanocomposites showed the characteristic emission peaks of Ce3+ (5d–4f) and Tb3+ (5D4–7F3 to 5D4–7F6). Magnetism measurements revealed that the samples were nearly superparamagnetic. The multifunctional nanocomposites were used for in vitro drug delivery tests under ambient conditions, and we discuss the influence of different media on the release of cisplatin (cis-diamminedichloroplatinum). We assessed the loading and release performance for cisplatin by means of UV–visible spectrophotometry. Our findings will provide guidance for engineering similar multifunctional nanocomposites for use in future drug delivery applications.

An investigation into the performance of composite hat stringers incorporating nanocomposites using a multiscale framework

In this paper, an effort has been made to investigate the incorporation of carbon nanotubes in structural composites in order to improve damage characteristics, such as delamination. The nanocomposite material is introduced in the damage-prone regions of complex aerospace stiffener sections; the methodology proposed is an alternative to traditional approaches used to suppress delamination in composites, such as the use of metallic fittings. Numerical simulations are conducted using a multiscale modeling framework. The effective properties of the nancomposites are computed using a micromechanics-based approach and the results are compared with those obtained using a Kalman filter algorithm. The information is then used to analyze the structural response of a hat stringer using detailed finite element models. The stringer is analyzed under different loading conditions and varying levels of defects in the structure. Results obtained indicate that the use of nanocomposites improves the structural performance by improving the initial failure load. It is anticipated that the use of carbon nanotubes during the manufacturing process will help delay the onset of initial damage and damage growth, which can ultimately lead to a more robust structural design with enhanced performance against unique composite failure modes.

Exotic 3D Hierarchical ZnO–Ag Hybrids as Recyclable Surface‐Enhanced Raman Scattering Substrates for Multifold Organic Pollutant Detection

AbstractRecyclable and sensitive surface‐enhanced Raman scattering (SERS) sensors for the detection of a variety of organic pollutants were fabricated from 3D hierarchical ZnO–Ag hybrids, which were synthesized by an efficient and green approach. The ZnO nanostructure could be controlled by applying a facile organic‐chemical‐assisted hydrothermal method. The obtained structures were then decorated with different‐sized Ag nanoparticles (Ag NPs) on their side surfaces and top ends to construct 3D hierarchical ZnO–Ag nanocomposites for use as multifunctional SERS substrates. The obtained SERS sensor manifested a high sensitivity to rhodamine 6G (R6G) at a low concentration of 1 × 10–13 M and a detection limit as low as 5 × 10–9 M for the organic herbicide 4‐chlorophenol (4‐CP). Moreover, because of the good, stable photocatalytic properties of this exotic 3D hierarchical structure, the ZnO–Ag hybrids could self‐clean under UV irradiation; this allowed repeatable SERS detection of many organic pollutants over more than three cycles with tolerable intensity attenuation. Finally, the unique repeatable detection of the organic dye R6G and the persistent organic pollutant (POP) 2,4‐dichlorophenoxyacetic acid (2,4‐D) demonstrates a new route to eliminate the single‐use problem of traditional SERS substrates and suggests promising applications of such materials as real‐time online sensors for organic pollutant detection.

Development of Nanocomposites Reinforced with Carboxylated Poly(ether ether ketone) Grafted to Zinc Oxide with Superior Antibacterial Properties

Novel poly(ether ether ketone) (PEEK) based nanocomposites have been fabricated via melt-blending by addition of a carboxylated polymer derivative covalently grafted onto the surface of hydroxyl-terminated ZnO nanoparticles. Their morphology, thermal, mechanical, tribological, and antibacterial properties have been analyzed and compared with those of composites reinforced with pristine ZnO. The Fourier transform infrared (FT-IR) spectra corroborate the success of the grafting reaction, showing the appearance of signals related to ester linkages. Microscopic observations demonstrate that the polymer grafting improves the nanoparticle dispersion within the matrix. A progressive rise in thermal stability and flame retardant ability is found with increasing ZnO concentration, with an exceptional increment in the maximum degradation rate temperature of 70 °C at 5.0 wt % loading. The crystallization and melting temperature of PEEK decrease upon incorporation of the grafted nanofillers, attributed to the restrictions on polymer chain mobility and crystal growth imposed by the strong ZnO-matrix interactions. Nanocomposites with polymer-grafted nanoparticles exhibit higher stiffness, strength, ductility, toughness and glass transition temperature whilst lower coefficient of friction and wear rate than the neat polymer and composites with bare ZnO. Further, they show superior antibacterial activity against both the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus bacteria. The antimicrobial effect increases upon raising nanoparticle content, and is stronger on E. coli. The approach used in this work is a simple, scalable, and efficient method to improve the performance of PEEK/ZnO nanocomposites for use in biomedical applications such as trauma, orthopedics, and spinal implants.

A composite made from palladium nanoparticles and carbon nanofibers for superior electrocatalytic oxidation of formic acid

We report on a novel type of nanocomposite for use in the electrooxidation of formic acid in fuel cells. The material is composed of palladium nanoparticles (Pd-NPs) and carbon nanofibers (CNFs) and was prepared by electrospinning of the precursors Pd(acac)2 and polyacrylonitrile, respectively, followed by thermal treatment to generate in-situ Pd-NPs that are well dispersed within the CNF framework. The nanocomposite was characterized by TEM, high-resolution TEM, SEM, XRD, Raman spectroscopy, and XPS. The size of the Pd-NPs ranges from 12 to 82 nm, depending on the temperature for carbonization (700–1,000 °C). The length and width of the CNF is in the order of tens of micrometers and 300 to 500 nm, respectively. TEM and XPS studies indicate that the Pd-NPs are firmly embedded in the CNF, resulting in a good electrochemical stability of the composite. The electrocatalytic properties of the composite with respect to the oxidation of formic acid were studied by cyclic voltammetry and chronoamperometry. They showed a distinctly improved electrocatalytic activity and stability compared to a commercial Pd-on-carbon catalyst. The Pd/CNF composite carbonized at 900 °C was found to display the best performance.

Investigation of a Branchlike MoO3/Polypyrrole Hybrid with Enhanced Electrochemical Performance Used as an Electrode in Supercapacitors

A branchlike MoO3/polypyrrole conductive nanocomposite was facilely prepared by wrapping a homogeneous polypyrrole (PPy) layer around MoO3 nanobelts via the in situ oxidative polymerization of a self-assembled pyrrole monomer. X-ray powder diffraction characterization demonstrated that the PPy polymer does not hinder the crystallization of the MoO3 nanobelts substrate. The electrochemical tests show that the specific capacitance of 129 F g(-1) for the MoO3/PPy hybrid is higher than both pristine MoO3 and pure PPy. Moreover, the hybrid electrode with good electrical conductivity displays good cyclic stability of 90% retention after 200 cycles of charge/discharge. These results indicate a promising potential application of the MoO3/PPy nanocomposite for use as an effective electrode material in supercapacitors.

Preparation and characterization of silicone rubber/nano-copper nanocomposites for use in intrauterine devices

In this work, a novel silicone rubber/nano-copper nanocomposite for use in intrauterine devices (IUDs) was developed. Moreover, the release rate of Cu2+ ions and the water absorption of the prepared nanocomposite were investigated in detail. The results indicate that the release rate of Cu2+ ions and water absorption capability of the silicone rubber/nanocopper nanocomposite increase as the nano-copper content increases. SEM analysis suggested there is a uniform dispersion of nano-copper in the silicone matrix. Further, systematic analysis indicated that the release rate of Cu2+ ions in the prepared nanocomposite-based IUD can be stabilized for months, which is not possible in the case of traditional IUDs.