Introduction Of Nanotubes Research Articles

Increasing the Strength of Fine-Grained Concrete with the Use of Carbon Nanotubes and Mechanical Activation of the Mixture

The results of studies to determine the effect of introducing a complex additive of carbon nanotubes and plasticizer into the composition of fine-grained concrete are presented. Two series of tests of beam samples were performed, and the strength characteristics of the studied compositions were determined. Two methods of introducing nano-additives into concretes were compared: using an ultrasonic dispersant and a linear induction wave action apparatus (LIA) by analyzing two series of tests of different compositions. It was established that the introduction of nanotubes using LIA provides a minimally greater increase in the compressive strength due to the activation of the cement binder by means of regrinding. However, the maximum increase in strength is achieved equally for each of the injection methods.

Tubular Clay Nano-Straws in Ordered Mesoporous Particles Create Hierarchical Porosities Leading to Improved CO2 Uptake

The use of solid adsorbents for CO2 capture is of importance in the development of technologies to remove this greenhouse gas. High surface area mesoporous materials are used to encapsulate or functionalize amines that selectively capture CO2. The MCM-41 class of hexagonally ordered mesoporous silicas have surface areas between 1000 and 1500 m2/g, which in principle allows a significant degree of capture when amines such as polyethyleneimine (PEI) are encapsulated within the pores and occupy the entire surface area of the materials. However, the tight 3 nm pore channels of MCM-41 create a challenge to the infiltration of PEI throughout the pore volume, resulting in much lower CO2 uptake at high PEI concentrations. This work describes the introduction of clay nanotubes (halloysite) with an inner diameter of 15–30 nm into MCM-41 pellets to mitigate such diffusional restrictions. The introduction of the nanotubes is through a one-step ship-in-a-bottle approach to synthesis in an aerosol-assisted system where MCM-41 is synthesized in droplets containing the halloysite. The morphology of the composite material is such that several nanotubes extend from the interior and protrude through the surface of the pellet like straws. These ceramic nanotubes are 0.5–2 μm in length, and their lumen diameter ranges from 15 to 30 nm, thus providing an improved entry pathway for molecules to access the interior of the MCM-41 pellets. The concept is used to enhance PEI loading in MCM-41, which leads to a significant increase in CO2 uptake levels. MCM-41 composites with halloysite nano-straws (MCM-41/HNT) show a doubling of CO2 uptake levels (7.1 wt %) and uptake kinetics (k = 0.11 s–1) in comparison to MCM-41 sorbents (3.9 wt % and k = 0.05 s–1) at 50 wt % PEI loading. This indicates the potential validity of the nano-straws to improve access to the interior of MCM-41, thus coupling enhanced molecular transport with a high surface area material. The generality of the concept indicates further applications to adsorption and catalysis.

Strengthening of polymer ropes based on polypropylene with carbon nanotubes

The issues of using carbon nanotubes as fillers to strengthen polymer ropes used in the mining industry, oil and gas production, metallurgy, power engineering, etc. are considered in the work. The method for producing a nanocomposite based on polypropylene doped with carbon nanotubes has been developed. Experimental studies of the most significant strength characteristics of the created prototypes of polymer composite materials have been carried out. To determine the mechanisms acting upon the introduction of nanotubes into the polymer matrix, DFT calculations of the interaction of propylene monomer with the surface of single-walled nanotubes of different diameters and chirality have been performed.

Change in the Surface of Elastomers Based on Epichlorhydrin Rubber Modified by Functionalized Carbon Nanotubes

In this paper, we study the possibilities of the modification of epichlorohydrin rubbers by special-type functionalized carbon nanotubes activated by oxygen. The purpose of this modification is to improve the tribological properties and increase frost resistance. Two types of samples with the addition of 1 and 10% nanotubes are compared with the initial unmodified rubber. The operating conditions are simulated using tribological tests performed in the express mode. Electron microscopic surface studies of the initial elastomer and samples after tribological tests reveal a change. The introduction of nanotubes is shown to promote the formation of agglomerates of a characteristic shape, increasing the surface uniformity, and its greater stability during friction. Differences in the surface topography are already evident in samples with 1% nanotubes and noticeably increase in samples with 10% nanotubes. Using scanning probe microscopy, sample sections (topography and elastic properties) are studied after tribological tests. The surface at the cut edge is found to be denser and smoother than in the bulk layers of the sample as the elastic moduli of these regions are almost identical. The introduction of activated functionalized carbon nanotubes into epichlorohydrin rubber is shown to lead to hardening of the elastomer and increases its wear resistance.

Synthesis and mechanical properties of lightweight hybrid geopolymer foams reinforced with carbon nanotubes

AbstractA lightweight hybrid geopolymer foams reinforced with carbon nanotubes (CNTs) was exploited by adding the CNTs into geopolymeric matrix through hydrogen peroxide method. The synergistic effects of nanotubes and foaming agent on the phase evolution, microstructure, and mechanical properties were investigated. After introduction of nanotubes, the geopolymer foams reinforced with CNTs (CNTs/KGP) still showed amorphous structure. Porosity of the foams increased with the H2O2 content and decreased with the increase in CNTs content. The addition of CNTs (1‐9 wt%) in foams refined the distribution of pore size from 523 to 352 μm. Compression strength of the CNTs/KGP samples elevated with the increasing content of CNTs, which was contributed to the crack propagation and bridging of CNTs in foams. The CNTs/KGP foams with considerable porosity show potential applications in adsorption, filtration, membrane supports, other industries, etc

The effect of temperature on fatigue strength of poly(ether‐imide)/multiwalled carbon nanotube/carbon fibers composites for aeronautical application

AbstractThis work concerns the fatigue behavior at three different temperature conditions (−40, 20, and 80°C) and the addition of multiwalled carbon nanotube (MWCNT) into a carbon‐fiber reinforced poly(ether‐imide) composite. The incorporation of MWCNT into the composite increased the tensile strength and Young's modulus by up 5 and 2%, respectively. At low temperature, the incorporation of the nanoparticles improved the fatigue strength of the laminates by 15%. The shear strength results obtained by interlaminar shear strength and compression shear test tests have shown an increase of about 16 and 58%, respectively, by the introduction of nanotubes into the laminates. Fractographic observations revealed that the surface of carbon nanotube laminate (PEI/MWCNT/CF) presented a ductile behavior, and differences in the fracture aspects of the material compared to the traditional PEI/CF laminate have been observed.

Microorganisms and Carbon Nanotubes: Interaction and Applications (Review)

The review addresses various aspects of the interaction between carbon nanotubes (CNTs) and microorganisms: the antimicrobial effects of single-walled, multiwalled, functionalized, and nonfunctionalized CNTs; the mechanism of action of these nanomaterials at the single-cell level; and their effects on soil and aquatic microorganisms. Among the mechanisms of action of CNTs on the microbial cell, one should note direct contact, which leads to disruption of the cell wall and cytoplasmic membrane, changes in membrane fluidity, oxidative stress, enzyme inhibition, and reduced transcription of several key genes. It has been shown that the antimicrobial effect of CNTs strongly depends on their diameter, length, aggregation degree, concentration, surface functionalization, degree of purification, and time and intensity of contact. The possibilities of the CNT biodegradation by microorganisms have been studied. It has been shown that the introduction of nanotubes into soils results in changes in the abundances of bacteria of certain taxonomic groups involved in biogeochemical cycles of carbon and nitrogen. This may adversely affect the cycling of these elements in the nature. The review also focuses on recent trends in the development of microbial fuel cells, biosensor technologies, bioremediation, and wastewater treatment in which CNTs display their unique electron-conducting and adsorption properties and serve as a bridge for an understanding of the beneficial aspects of microorganisms.

Review of current trends in research and applications of sandwich structures

Abstract The review outlines modern trends in theoretical developments, novel designs and modern applications of sandwich structures. The most recent work published at the time of writing of this review is considered, older sources are listed only on as-needed basis. The review begins with the discussion on the analytical models and methods of analysis of sandwich structures as well as representative problems utilizing or comparing these models. Novel designs of sandwich structures is further elucidated concentrating on miscellaneous cores, introduction of nanotubes and smart materials in the elements of a sandwich structure as well as using functionally graded designs. Examples of problems experienced by developers and designers of sandwich structures, including typical damage, response under miscellaneous loads, environmental effects and fire are considered. Sample applications of sandwich structures included in the review concentrate on aerospace, civil and marine engineering, electronics and biomedical areas. Finally, the authors suggest a list of areas where they envision a pressing need in further research.

Analysis of the surface morphology, structure and properties of polyamidoimide nanocomposites with tubular hydrosilicates

The surface morphology, structure and transport properties of polyamidoimide (PAI) films prepared from poly(diphenyloxidiamido-N-phenylphtalimidene) synthesized by low temperature polycondensation, and composites with chrysotile-type hydrosilicate nanotubes (NTs) based on it are investigated using АFМ (atomic force microscopy), X-ray diffraction analysis and pervaporation methods. The dependence of the free surface morphology of PAI films on their thicknesses is found: the minimal value of the roughness parameters is achieved at a film thickness of 15 μm, in this case the minimal value of the sizes of macromolecular “nodules” is also recorded, which is 50 nm. It is established that upon the introduction of NTs up to 7 wt % into PAI films with a thickness of 35 μm, the mesomorphic polymer structure is retained. An antibatic dependence of the nanocomposite transport characteristics on surface roughness parameters is detected. The maximal value of the ideal separation factor for a methanol-cyclohexane mixture is demonstrated to correspond to a composite containing 1 wt % of NTs and possessing minimal values of the surface-roughness parameters.

Mechanical properties of carbon, silicon carbide, and boron nitride nanotubes: effect of ionization

This paper studies the effect of ionization of finite-length single-walled carbon nanotubes, boron nitride nanotubes, and silicon carbide nanotubes on their mechanical properties. The PBE/SVP calculations show that the ionization affects the elastic properties of studied models. The nanotubes demonstrate little changes in Young’s modulus upon ionization; however, the changes in bulk and shear moduli as well as in Poisson’s ratio are more pronounced. The introduction of nanotubes into composite materials, which may undergo a radiation exposure, is a promising way to enhance their performance.

Structure, tribotechnical, and thermophysical characteristics of the fluoroplastic carbonnanotubes material.

In this work, we studied a nanocomposite material made from fluoroplastic which contains 20 wt.% multi-walled nanotubes. In order to complete the present work, we have used different thermodynamic and mechanical techniques. The introduction of nanotubes in the F4 polymer matrix has completely changed the tribological and thermodynamic properties of the studied nanocomposite material. The compression strength becomes 20% higher than that of the F4 polymer matrix. Meanwhile the wear resistance achieves an order of magnitude 100 times greaterthan that of F4. Moreover, a friction coefficient is about 25% to 30% lower than that of a similar material and especially that of F4 material. Differential scanning calorimetric study showed that the glassy phase transition appears at about 330°C, which confirms that the degradation of the studied nanocomposite occurs at relatively higher temperature. This result confirms the one concerning the change in tribological properties. Dilatometric study revealed that the thermal expansion coefficient has been increased. The observed relative elongation measurement change depends on the direction along which the measurement has been done and confirms, in turn, the anisotropic character of the studied material. These results suggest that the metallic materials could be replaced by nanocomposite compounds which present good physical properties.

Nanocomposites Based on Aromatic Polyamide-Imide and Magnesium Hydrosilicate Nanotubes

Structure, morphology, and thermal properties of nanocomposites based on thermally stable poly(diphenyloxydamide-N-phenylphtalimide) (PAI) and layered magnesium hydrosilicate nanotubes (NTs) were studied using thermogravimetric analysis, dynamic mechanical analysis, atomic force microscopy, and differential scanning calorimetry. Thermal stability and glass transition temperature of the composites were shown to exceed those of the PAI matrix. Introduction of NT into the polymer matrix appreciably increased the elasticity and deformability of the composite material. The content of NT was also shown to greatly influence the surface morphology of the PAI-NT composites.

Controlling the optical properties of a conjugated co-polymer through variation of backbone isomerism and the introduction of carbon nanotubes

The need to control the formation of weakly emitting species in polymers such as aggregates and excimers, which are normally detrimental to device performance, is illustrated for the example of the polymer poly( m-phenylenevinylene-co-2,5-dioctyloxy- p-phenylenevinylene), using the model compound, 2,5-dioctyloxy- p-distyrylbenzene as a comparison. Two different methods, namely a Horner–Emmons polycondensation in dimethylformamide (DMF) and a Wittig polycondensation in dry toluene, have been used during synthesis resulting in a polymer with a predominantly trans-vinylene backbone and a polymer with a predominantly cis-vinylene backbone, respectively. Photoluminescence and absorption spectroscopy indicate that the polymer forms aggregate species in solution with spectra that are distinctly red-shifted from those associated with the intra-chain exciton. Concentration dependent optical studies were used to probe the evolution of aggregation in solution for both polymers. The results indicate that inter-chain coupling in the predominantly cis-polymer is prominent at lower concentrations than in the case of the trans-counterpart. These results are supported by pico-second pump and probe transient absorption measurements where, in dilute solutions, the polymer in a cis-configuration exhibits highly complex excited state dynamics, whereas the polymer in a trans-configuration behaves similarly to the model compound. It is proposed therefore that the degree of backbone isomerism has a profound impact on the morphology of the polymeric solid and control over it is a route towards optimising the performance of the material in thin film form. Another method to inhibit inter-chain effects using multi walled carbon nanotubes (MWNT) as nano-spacers in the polymer solutions is proposed. By comparison to spectroscopic analysis, aggregation effects are shown to be reduced by the introduction of nanotubes. Electron microscopy and computer simulation suggest a well-defined interaction between the polymer backbone and the lattice of the nanotube.

Complex nano-assemblies of polymers and carbonnanotubes

Since the discovery of carbon nanotubes in1991 [1], researchers have envisaged potentialapplications such as nanoscale electronic circuits and theconstruction of complex carbon-based nano-machines. Thus, theassembly of basic building blocks of complexnano-architectures, such as conjugated polymers and nanotubes,has been a driving goal of much of the nano-science community.A first step towards realizing this goal may be the attachmentto, or modification by carbon nanotubes of structures such aspolymers. This leads to the possibility of assemblingindividual polymer molecules onto carbon nanotubes with the neteffect being the modification of the polymer's electronicproperties and structure in a predictable way. To accomplishthis, clearly, a more detailed understanding of the interactionsbetween conjugated polymers and carbon nanotubes must besought. In this paper, we describe the assembly of the polymer,poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene)(PmPV), into a coating around single-walled carbon nanotubes.Using scanning tunnelling microscopy, andscanning tunnelling spectroscopy, we demonstrate that thelow-energy electronic structure of the assembled material isdominated by the one-dimensional nature of the nanotube asreflected in van Hove singularities. Further, we examine themodifications to electronic structure at higher energies usingspectroscopy, which suggests that the polymer's electronicstructure is altered by the introduction of nanotubes.