Synthesis of LiFePO4@carbon nanotube core-shell nanowires with a high-energy efficient method for superior lithium ion battery cathodes

A high-energy efficient method is developed for the synthesis of LiFePO4@CNT core-shell nanowire structures. The method consists of two steps: liquid deposition approach to prepare FePO4@CNT core-shell nanowires and solvothermal lithiation to obtain the LiFePO4@CNT core-shell nanowires at a low temperature. The solution phase method can be easily scaled up for commercial application. The performance of the materials produced by this method is evaluated in Li ion batteries. The one-dimensional LiFePO4@CNT nanowires offer a stable and efficient backbone for electron transport. The LiFePO4@CNT core-shell nanowires exhibit a high capacity of 132.8 mAh g^-1 at a rate of 0.2C, as well as high rate capability (64.4 mAh g^-1 at 20C) for Li ion storage.

Field emission properties from boron nitride nanotube field emitters

Boron nitride nanotubes (BNNTs) have been studied as a field emission material due to their unique and excellent properties such as high oxidation resistance and negative electron affinity. However, field emission properties of BNNT field emitters were rarely reported until now because it is difficult to synthesize high purity BNNTs and fabricate stable BNNT field emitters. Here, we report high field emission properties from BNNT field emitters fabricated on a tungsten rod.

Carbon nanotube dispersion using Portland cement-compatible surfactants

Carbon nanotubes (CNTs) are among the strongest known materials. Their potential as nanoscale reinforcement for cementitious materials is significant, with some reported compressive strength increases in excess of 50%. However, there is a great deal of variability in the results obtained, with some researchers showing zero-to-marginal increases in mechanical properties. One major reason for this is the poor dispersion of CNTs within the cementitious matrix. Many different approaches have been employed to disperse the highly hydrophobic CNTs within water and cement paste, with varying degrees of success. This paper presents the results of dispersion trials undertaken on CNTs within neutral and alkaline aqueous solutions and assesses the relative performance of different surfactants to facilitate dispersion.

Processing and characterization of srTiO₃-TiO₂ nanoparticle-nanotube heterostructures on titanium for biomedical applications

Surface properties such as physicochemical characteristics and topographical parameters of biomaterials, essentially determining the interaction between the biological cells and the biomaterial, are important considerations in the design of implant materials. In this study, a layer of SrTiO3-TiO2 nanoparticle-nanotube heterostructures on titanium has been fabricated via anodization combined with a hydrothermal process. Titanium was anodized to create a layer of titania (TiO2) nanotubes (TNTs), which was then decorated with a layer of SrTiO3 nanoparticles via hydrothermal processing. SrTiO3-TiO2 heterostructures with high and low volume fraction of SrTiO3 nanoparticle (denoted by 6.3-Sr/TNTs and 1.4-Sr/TNTs) were achieved by using a hydrothermal processing time of 12 and 3 h, respectively. The in vitro biocompatibility of the SrTiO3-TiO2 heterostructures was assessed by using osteoblast cells (SaOS2). Our results indicated that the SrTiO3-TiO2 heterostructures with different volume fractions of SrTiO3 nanoparticles exhibited different Sr ion release in cell culture media and different surface energies. An appropriate volume fraction of SrTiO3 in the heterostructures stimulated the secretion of cell filopodia, leading to enhanced biocompatibility in terms of cell attachment, anchoring, and proliferation on the heterostructure surface.

One-pot synthesis of aminated multi-walled carbon nanotube using thiol-ene click chemistry for improvement of epoxy nanocomposites properties

A non-oxidative method based on thiol-ene click chemistry for functionalization of multi-walled carbon nanotube (CNT) was performed in order to improve the interfacial interactions between epoxy matrix and CNT. In this way, the CNT was aminated using 2-aminoethanethiol hydrochloride radicals thermally produced by a peroxide radical initiator. The aminated CNT (CNT-NH2) was characterized by FTIR, TGA, and solubility evaluations, confirming that thiol radicals are successfully grafted onto the CNT surface with a proper yield. Various percentages of pure CNT (p-CNT) and CNT-NH2 were then incorporated into epoxy matrix to evaluate the effect of the functionalization of CNT on thermal, mechanical, and morphological properties. The nanocomposites were characterized by DMA, tensile testing, and TGA. Results showed that glass transition temperature, tensile properties and thermal stability of epoxy nanocomposites containing CNT-NH2 improves significantly compared to those containing unmodified CNT. These results prove the role of amino-functionalization in improving the interfacial adhesion between epoxy and CNT, which was further confirmed by morphological observations of fracture surfaces of the nanocomposites.

Lithium-ion capacitors with 2D Nb2CTx (MXene) - carbon nanotube electrodes

There is a growing interest to hybrid energy storage devices, such as lithium-ion capacitors, in which battery-type electrodes are combined with capacitor-type ones. It is anticipated that the energy density (either gravimetric or volumetric) of lithium-ion capacitors is improved if pseudocapacitive or fast insertion materials are used instead of conventional activated carbon (AC) in the capacitor-type electrode. MXenes, a new family of two-dimensional transition metal carbides, demonstrate metallic conductivity and fast charge-discharge behavior that make them suitable for this application. In this study, we move beyond single electrodes, half-cell studies and demonstrate three types of hybrid cells using Nb2CTx-carbon nanotube (CNT) films. It is shown that lithiated graphite/Nb2CTx-CNT, Nb2CTx-CNT/LiFePO4 and lithiated Nb2CTx-CNT/Nb2CTx-CNT cells are all able to operate within 3 V voltage windows and deliver capacities of 43, 24 and 36 mAh/g (per total weight of two electrodes), respectively. Moreover, the polarity of the electrodes can be reversed in the symmetric Nb2CTx-CNT cells from providing a positive potential between 0 and 3 V to a negative one from -3 to 0 V. It is shown that the volumetric energy density (50-70 Wh/L) of our first-generation devices with MXene electrodes exceeds that of a lithium titanate/AC capacitor.

Fabrication of graphene foam supported carbon nanotube/polyaniline hybrids for high-performance supercapacitor applications

A large-scale, high-powered energy storage system is crucial for addressing the energy problem. The development of high-performance materials is a key issue in realizing the grid-scale applications of energy-storage devices. In this work, we describe a simple and scalable method for fabricating hybrids (graphenepyrrole/ carbon nanotube-polyaniline (GPCP)) using graphene foam as the supporting template. Graphene-pyrrole (G-Py) aerogels are prepared via a green hydrothermal route from two-dimensional materials such as graphene sheets, while a carbon nanotube/polyaniline (CNT/PANI) composite dispersion is obtained via the in situ polymerization method. The functional nanohybrid materials of GPCP can be assembled by simply dipping the prepared G-py aerogels into the CNT/PANI dispersion. The morphology of the obtained GPCP is investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed that the CNT/PANI was uniformly deposited onto the surfaces of the graphene. The as-synthesized GPCP maintains its original three-dimensional hierarchical porous architecture, which favors the diffusion of the electrolyte ions into the inner region of the active materials. Such hybrid materials exhibit significant specific capacitance of up to 350 F g^-1, making them promising in large-scale energy-storage device applications.

Electrical conductivity of single walled and multiwalled carbon nanotube containing wool fibers

The main purpose of this study was producing conductive wool fabric applying carbon nanotubes. Raw and oxidized wool samples were treated with carbon nanotubes in the impregnating bath in the presence of citric acid as a crosslinking agent and sodium hypophosphite as a catalyst while sonicating them in the ultrasonic bath. Electrical resistance, washing durability, and color variation of treated samples were assessed. Through SEM images, the surface morphology of treated samples was studied confirming the surface coating through carbon nanotubes. According to the results, the electrical resistance of treated wool with carbon nanotubes reduced substantially. However, the single-walled carbon nanotubes are more useful to increase the conductivity. In addition, the wool color changed into gray after the treatment.

Boron Nitride nanotube reinforced Titanium matrix composite

 Boron nitride nanotube reinforcement at titanium matrix composite increased the strength of the composite both at room and high temperature. At higher sintering temperature, nanotube reacts with titanium first forming TiB2 transition phase at the interface and then in-situ formed TiB phases in the matrix, which is also responsible for enhanced mechanical properties.

Boron nitride nanotube films: preparation, properties, and implications for biology applications

The difference in the chemical and physical properties of boron nitride nanotube (BNNT) films and carbon nanotube (CNT) films can benefit tissue scaffolding and engineering. However, the production of dense films of pure BNNTs is more challenging than that of CNT films. In addition, BNNT films are usually extremely nonwettable to water, so surface modification is required before they can be used in bioapplications. In this chapter, the synthesis routes of high-density BNNT films are introduced, followed by their wettability properties and surface modification by plasma treatments. The cell proliferation on both pristine and wettability-modified BNNT films is discussed.

A systematic investigation into a novel method for preparing carbon fibre–carbon nanotube hybrid structures

By electrospraying solvent dispersed carbon nanotubes (CNTs) with a binder onto carbon fibre (CF), hybrid structures, with an end aim to improve interfacial bonding in composites, were formed. The electrospray parameters controlling the modification of the CNT morphologies were studied. High-speed camera observations found applied voltage was critical for determining spray mode development. Electric field simulations revealed a concentrated electric field region around each fibre. Both voltage and distance played an important role in determining the CNT morphology by mediating anchoring strength and electric field force. The forming mechanism investigation of different surface morphologies suggested that binder with appropriate wetness gives freedom to the CNTs, allowing them to orientate radially from the CF surface. Linear density (LD) measurements and thermogravimetric analysis revealed that a 10 min coating increased the LD of a single CF filament by up to 31.7% while a 1 h treatment increased fibre bundle mass by 1%.

Interfacial characterization and reinforcing mechanism of novel carbon nanotube – carbon fibre hybrid composites

Carbon nanotube (CNT) deposition onto carbon fibre resulting in hybrid surface structures with various morphologies were successfully carried out using electrospray technique. In terms of tensile testing and Weibull analysis this process did not degrade fibre mechanical properties. When incorporated into composites, the interfacial shear strength (IFSS), as measured by single fibre fragmentation testing, increased by up to 124%. Experimental work was carried out to develop a deeper understanding of the interfacial reinforcing mechanism. Contact angle measurements demonstrated that the CNT deposition resulted in good wettability by the resin. Significant increases in roughness, friction and surface area were also found after CNT deposition, especially for the sample prepared using the parameter of 20 kV/10 cm at 100 °C. Surface energy analysis revealed that an increase in the dispersive surface energy due to the CNTs likely contributed to the improvement of interaction between fibre and matrix. Fractographic analysis revealed that the length of fibre pull-out and the size of cracks between the fibre and matrix were markedly decreased in the hybrid CNT surface structure, indicating that the stress transfer and interfacial shear strength have been improved. Finally, the potential for further improvement in interfacial composite properties by this approach was assessed.

The influence of titania-zirconia-zirconium titanate nanotube characteristics on osteoblast cell adhesion

Studies of biomaterial surfaces and their influence on cell behavior provide insights concerning the design of surface physicochemical and topography properties of implant materials. Fabrication of biocompatible metal oxide nanotubes on metallic biomaterials, especially titanium alloys such as Ti50Zr via anodization, alters the surface chemistry as well as surface topography of the alloy. In this study, four groups of TiO2-ZrO2-ZrTiO4 nanotubes that exhibit diverse nanoscale dimensional characteristics (i.e. inner diameter Di, outer diameter Do and wall thicknesses Wt) were fabricated via anodization. The nanotubes were annealed and characterized using scanning electron microscopy and 3-D profilometry. The potential applied during anodization influenced the oxidation rate of titanium and zirconium, thereby resulting in different nanoscale characteristics for the nanotubes. The different oxidation and dissolution rates both led to changes in the surface roughness parameters. The in vitro cell response to the nanotubes with different nanoscale dimensional characteristics was assessed using osteoblast cells (SaOS2). The results of the MTS assay indicated that the nanotubes with inner diameter (Di)≈40nm exhibited the highest percentage of cell adhesion of 41.0%. This result can be compared to (i) 25.9% cell adhesion at Di≈59nm, (ii) 33.1% at Di≈64nm, and (iii) 33.5% at Di≈82nm. The nanotubes with Di≈59nm exhibited the greatest roughness parameter of Sa (mean roughness), leading to the lowest ability to interlock with SaOS2 cells.