Multi-walled Structures Research Articles

Role of carbon nanotubes (CNTs) in transgenic plant development.

Carbon nanotubes (CNTs) are nanostructures, allotropes of carbon which are made up of graphene sheets wrapped around it forming cylindrical structures. CNTs have been regarded to have interesting and attractive physical and chemical properties and have been tremendously used in genetic engineering. Understanding the role of CNTs in development of transgenic plants, review of research papers in the field was done. CNTs are classified into two categories: the single-walled and multiwalled (MWCNTs) structures. They are valuable vectors in various biomedicine fields such as Gene delivery, Drug delivery, Immunotherapy, Tissue engineering, and Biomedical imaging and also, they deliver the DNA without damaging the cells. Based on recent studies, the functionalization of CNTs when combined with some other suitable molecules can drastically subside their toxic effects. Having unique properties such as small size, larger surface area is useful in delivering DNA into mammalian cells as well. Modifications in CNTs can make nucleic acids adhere to them even more efficiently. Also, MWCNTs are crucial in delivery DNA into the cytoplasm. Based on other methods, the CNTs-DNA are a preferred choice and the inclination toward double-stranded DNA is used over single-stranded DNA in gene delivery shows effective results. The only downside of CNTs is that they are hydrophobic and are difficult to form an aqueous solution, thus limiting their applicability. This review will aid you in comprehending useful knowledge related to a general overview of topics related to CNTs.

Single-Walled vs. Multi-Walled Carbon Nanotubes: Influence of Physico-Chemical Properties on Toxicogenomics Responses in Mouse Lungs.

Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are nanomaterials with one or multiple layers of carbon sheets. While it is suggested that various properties influence their toxicity, the specific mechanisms are not completely known. This study was aimed to determine if single or multi-walled structures and surface functionalization influence pulmonary toxicity and to identify the underlying mechanisms of toxicity. Female C57BL/6J BomTac mice were exposed to a single dose of 6, 18, or 54 μg/mouse of twelve SWCNTs or MWCNTs of different properties. Neutrophil influx and DNA damage were assessed on days 1 and 28 post-exposure. Genome microarrays and various bioinformatics and statistical methods were used to identify the biological processes, pathways and functions altered post-exposure to CNTs. All CNTs were ranked for their potency to induce transcriptional perturbation using benchmark dose modelling. All CNTs induced tissue inflammation. MWCNTs were more genotoxic than SWCNTs. Transcriptomics analysis showed similar responses across CNTs at the pathway level at the high dose, which included the perturbation of inflammatory, cellular stress, metabolism, and DNA damage responses. Of all CNTs, one pristine SWCNT was found to be the most potent and potentially fibrogenic, so it should be prioritized for further toxicity testing.

Material extrusion of highly-loaded silicon nitride aqueous inks for solid infilled structures

The material extrusion technique of direct ink writing (DIW) has garnered recent interest for the ability to create near-net shapes using polymer and/or ceramic based inks using low-cost commercially-available equipment. While most foundational work in the field has shown promise for single-walled structures, the nature of the circular cross-section of extruded ink has led to the reported issue of interfilament voids when multi-walled structures are attempted. In addition, particularly for ceramic-loaded aqueous inks, multi-walled structures have proven difficult to dry post-processing without cracking or void formation. In this study, DIW was used to produce bulk infilled samples of silicon nitride (Si3N4), a high-temperature ceramic of interest for various high-temperature aerospace, automotive, and structural applications. Here, an ink feedstock was developed and modified from an aqueous-based Si3N4 suspension previously developed for room-temperature injection molding. Tailoring the rheological properties for DIW to exhibit low yield stresses (< 100 Pa), and low equilibrium storage moduli (<1000) resulted in little to no interstitial void defects which are common with the infilled aligned print pattern. A drying analysis varying humidity and sample size revealed that bulk infilled samples required a controlled humidity around 90% for the initial drying phase to produce defect free samples. Through careful control of the ink rheology and drying kinetics, mechanical test bars were sintered to high density (∼95%) with four-point flexural strengths greater than 500 MPa (in-line with other reported values for similar sintering conditions). There was no discernable effect of nozzle size (i.e. 1.2 mm or 0.6 mm) on resulting flexural strength, indicating strong interfilament welding. In fact, X-ray CT analysis of fractured mechanical test bars revealed microstructures with minimal large pores (i.e > 100 µm) and no pore channels observed between printed filaments, common issues reported in other works on solid infilled DIW.

Effect of multi-walled structure on microstructure and mechanical properties of 1.25Cr-1.0Mo steel fabricated by GMAW-based WAAM using metal-cored wire

Wire-arc additive manufacturing (WAAM) offers multiple benefits, such as high metal deposition, low capital cost, suitable mechanical properties, and reasonable costs. In the present work, Gas metal arc welding (GMAW) based WAAM was employed to manufacture a multi-walled component of 1.25Cr-0.5Mo at optimized parameters using metal-cored wire. The fabricated multi-walled structure was observed with seamless fusion and free from disbonding. The fabricated multi-walled component was studied through microstructure investigations, mechanical properties such as microhardness (MH), tensile test, and impact test at various positions (top side, middle side, and bottom side) of the built structure. Microstructure results have shown a tempered martensite structure in the bottom zone with coarse grains and finer microstructures in the middle and top zones. MH values throughout the component were uniform and thus indicated a similar nature to the multi-walled component. A comparison of tensile properties was carried out among the results of metal-cored wires and multi-walled structures to check the internal eminence of the obtained component. For all sides of the multi-walled structure, all the tensile properties were found to be in the range values of 1.25Cr-0.5Mo metal-cored wire. The results of all three conditions for impact toughness showed far better strength than the requirement. Fracture surface morphologies of tensile and impact test parts showed the presence of large dimples with the homogenous distribution. Thus, all the obtained results have suggested the suitability of the GMAWAM process for the fabrication of a multi-walled structure of 1.25Cr-0.5Mo metal-cored wire for various industrial applications.

The NH4Cl/Rice Husk Carbon as Promoters and Assisted Carbon Sources in Catalyzing Polypropylene into Carbon Nanotubes

AbstractContinuously increasing practical relevance required the mass production of carbon nanotubes (CNTs) through environmentally benign and sustainable routes. In the work, it is found that loading trace amounts of NH4Cl on rice husk carbon can effectively act as promoters and assisted carbon source inthe catalytic growth of CNTs from polypropylene byNi−Mo−Mg catalysts. The synthesized CNTs was characterized by Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffractometer (XRD), Raman spectroscopy, and Thermogravimetric analysis (TGA). Results show that the added rice husk carbon can take part in the formation of CNTs to a certain extent, and the trace of NH4Cl incorporated into rice husk carbon can significantly improve the conversion rate of polypropylene. The CNT products possess multiwalled structures and highgraphitization degrees. Finally, the prepared CNTs were investigated for the removal of methylene blue (MB) from water.

Manufacture of braided-textile reinforced multi-walled tubular structures and axial compression behaviors

Carbon fiber reinforced polymer (CFRP) thin-walled tubular structures have been widely used in lightweight energy absorbing components. In this paper, CFRP tubular braided-textiles, foam-filling technique, and sandwich structure were applied to make low-cost multi-walled sandwich tubular structures. Through axial compression tests, the compression behaviors, crushing modes and energy absorption performance of the braided-textile reinforced multi-walled sandwich tubes were contrastively analyzed. Experimental results show that the foam-filling technique and the sandwich structure are both effective in modifying the crushing patterns and improving the energy absorption efficiency. Especially for the multi-walled sandwich structure, it can increase the specific energy absorption (SEA) by at least 66% and change the crushing mode from local bucking to progressive diamond folding.

Synthesis of self-healing inhibitor releasing nanocapsules blended phenol novolac resin for high performance anticorrosion coating

The present work intended to synthesize a composite material exhibiting self-healing and enhanced anticorrosion properties. In this context, MWCNT incorporated nanocapsule (NC) filler material was synthesized, then it is blended with phenol novolac resin (PNR). The surface characterization studies of MWCNT/NC-PNR composite material signify the nano-size, spherical, and multiwalled structures of NC and CNT. The composite materials consisting of different weight percentages of MWCNT inserted NC were coated on the mild steel (MS) surface by the doctor blade method. The 0.3 wt% MWCNT/NC blended PNR showed significantly enhanced hydrophobicity of the coating which is evidenced by the high value of water contact angle (98.2°) amongst the coating materials prepared. Further, electrochemical impedance spectroscopy (EIS) tests of the coating confirm a high impedance value of 3.039× 107 ohm cm2 at the low frequency region for 50 days of immersion in 3.5 wt% NaCl solution. Thus, it was found that 0.3 wt% MWCNT incorporated NC filler increased the corrosion protection efficiency of NC/PNR coating by 32.61%. Therefore, the results show that the MWCNT/NC-PNR composite coating exhibits significantly elevated corrosion resistance, and can be used as a self-healing inhibitor coating material for long-term anti-corrosion shield.

Towards 3D self-assembled rolled multiwall carbon nanotube structures by spontaneous peel off.

Controlling the 3D assembly of individual nanomaterials can be a challenging task. However, it opens up opportunities for the production of increasingly complex nanostructures. Unusual rolled multiwall carbon nanotube structures are synthesized here by simply inducing a change of precursor composition during the growth of multiwall carbon nanotube forests. The multiwall carbon nanotube structures are comprised of nitrogen-doped and undoped sections, and are obtained via a detailed peel off and roll mechanism. These results open new doors for the development of increasingly complex nanostructures.

Assembling Carbon Nanotube Architectures.

Well-defined multiwalled carbon nanotube structures are generated on stainless steel AISI 304 (EN AW 1.4301) by chemical vapor deposition. Pulsed laser-induced dewetting (PLiD) of the surface, by 532 nm nanosecond laser pulses, is utilized for the preparation of metal oxide nanoparticle fields with a defined particle number per area. The reduction of the precursor particles is achieved in an Ar/H2 (10% H2) atmosphere at 750 °C, thereby generating catalytic nanoparticles (c-NPs) for carbon nanotube (CNT) growth. Ethylene is used as a precursor gas for CNT growth. CNT lengths and morphology are directly related to the c-NP aerial density, which is dependent on the number of dewetting cycles during the PLiD process. Within a narrow window of c-NP per area, vertically aligned carbon nanotubes of great lengths are obtained. For more intense laser treatments, three-dimensional dewetting occurs and results in the formation of cauliflower-like structures. The laser process enables the creation of all kinds of CNT morphologies nearby on the microscale.

Crashworthiness analysis of multi-configuration thin walled co-axial frusta tube structures under quasi-static loading

Abstract In the present study crashworthiness performance of monolithic and co-axial multi-wall (double, triple, and four layered) frusta tube structures was investigated under the quasi-static axial loading. The developed layered frusta tubular structures having a total equivalent thickness of 2.3 mm were made of aluminium alloy AA-1080 sheet. A series of layered configurations were simulated and analysed using non-linear finite element analysis code LS-DYNA, keeping volume approximately the same as the monolithic frusta tube. For the effectiveness of the simulated results, double-tubular structure was examined through experimental results. A parametric study was performed by keeping taper angle constant as 5.71° with the variation in height (91.6 and 82 mm for double layered, 91.6, 86 and 78 mm for triple layered and 91.6, 87, 82 and 77 mm for four layered), thickness (2.3–0.4 mm) and diameter (smaller end diameter in the range of 42.8 mm–48.4 mm while larger end diameter varied from 61 mm to 64 mm) to analyse the crushing performance of layered structures. The crashworthiness performance indicator like peak force (PF), mean force (MF), energy absorbing capacity (EAC), specific energy absorption (SEA) and crush load efficiency (CLE) which is defined as the ratio of MF to the PF, were studied for the various layered frusta tubular structures. Moreover, optimization technique GRA (Grey Relational Analysis) was employed to obtain a better combination of multi-wall layered structures. With the increase in the layer, the initial peak force was reduced compared to the monolithic frusta. The optimization technique suggested the triple-layer configuration showed better crashworthiness performance.

Heat Transfer in the Enclosing Structures of a Blast Furnace. Part 3. Mathematical Model of the Heat Transfer Process

The article is part of 3rd cycle of articles under the general title “Heat transfer in the enclosing structures of a blast furnace”. In Part 1, with the subheading “Statement of the problem and the prerequisites for calculation”, typical multiwalled enveloping structures of a blast furnace are considered. The description of the layers in these structures is given. The main attention is paid to the lining layer. Briefly described the process of smelting cast iron and temperature conditions in the characteristic layers of the internal environment of the furnace. Based on the theory of A.V. Lykov, the initial equations describing the interconnected transfer of heat and mass in a solid are analyzed in relation to the problem posed (a proper description of the processes for the purpose of further rational design of the multilayered enclosing structure of the blast furnace). A priori enclosure from the mathematical point of view is considered as an unlimited plate. In Part 2 with the subtitle “Solving the boundary-value problems of heat transfer,” the boundary-value problems of heat transfer in separate layers of the design with various boundary conditions are considered, and their solutions are given that are basic in the development of the mathematical model of the nonstationary heat transfer process in a multilayered enclosing structure. Part 3 presents a mathematical model of the process of heat transfer in the enclosure and an algorithm for its implementation.The proposed mathematical model allows to solve the following problems: - assess the thermophysical state of the designed structures under different operating conditions and, as a consequence, rationally design them for a particular mode or range of modes; - to calculate the temperature field in complex multi-layer constructions, for example, when the arrangement of the layers is discrete;- when temperature is measured at characteristic points (at the joints of layers and structural surfaces), it is possible to determine the thermophysical characteristics of the materials constituting the surveyed structure; - in laboratory tests it is possible to significantly shorten the test time, the researchers have the opportunity not to wait for the establishment of a regular regime;- it becomes possible to abandon the climate chamber and expensive instrumentation for experiments and research;- when solving the inverse problem, directly determine the resistance to heat transfer of the entire layered structure and its individual layers from the unsteady temperature field.

Heat Transfer in the Enclosing Structures of a Blast Furnace. Part 4. Examples of Calculation

The article is part of 4th cycle of articles under the general title “Heat transfer in the enclosing structures of a blast furnace”. In Part 1, with the subheading “Statement of the problem and the prerequisites for calculation”, typical multiwalled enveloping structures of a blast furnace are considered. The description of the layers in these structures is given. The main attention is paid to the lining layer. Briefly described the process of smelting cast iron and temperature conditions in the characteristic layers of the internal environment of the furnace. Based on the theory of A.V. Lykov, the initial equations describing the interconnected transfer of heat and mass in a solid are analyzed in relation to the problem posed (a proper description of the processes for the purpose of further rational design of the multilayered enclosing structure of the blast furnace). A priori enclosure from the mathematical point of view is considered as an unlimited plate. In Part 2 with the subtitle “Solving the boundary-value problems of heat transfer,” the boundary-value problems of heat transfer in separate layers of the design with various boundary conditions are considered, and their solutions are given that are basic in the development of the mathematical model of the nonstationary heat transfer process in a multilayered enclosing structure. Part 3 presents a mathematical model of the process of heat transfer in the enclosure and an algorithm for its implementation. The proposed mathematical model allows to solve the following problems: - assess the thermophysical state of the designed structures under different operating conditions and, as a consequence, rationally design them for a particular mode or range of modes; - to calculate the temperature field in complex multi-layer constructions, for example, when the arrangement of the layers is discrete; - when temperature is measured at characteristic points (at the joints of layers and structural surfaces), it is possible to determine the thermophysical characteristics of the materials constituting the surveyed structure; - in laboratory tests it is possible to significantly shorten the test time, the researchers have the opportunity not to wait for the establishment of a regular regime; - it becomes possible to abandon the climate chamber and expensive instrumentation for experiments and research; - when solving the inverse problem, directly determine the resistance to heat transfer of the entire layered structure and its individual layers from the unsteady temperature field. Part 4 gives a number of examples of calculation of the heat transfer process in a multiwalled fencing of a blast furnace, which show the effectiveness of the proposed calculation procedure.

Reversibly Thermochromic Cyclic Dipeptide Nanotubes.

Owing to their capability of forming extensive hydrogen bondings and the facile introduction of chirality, cyclic dipeptides (CDPs) have gained great attention as scaffolds for functional supramolecules. Surprisingly, introduction of a photopolymerizable diacetylene (DA) moiety to the CDP afforded nanotubular structures with enhanced stability and reversible thermochromism. A series of CDP-containing DAs (CDP-DAs) are prepared by coupling 10,12-pentacosadiynoic acid with CDPs, cyclo(-Gly-Ser) and cis/trans cyclo(-Ser-Ser). Fabrication of CDP-DA self-assemblies in a polar chloroform and methanol solvent mixture affords nanotubes comprising single-wall and multiwall structures. The self-assembly behavior and morphology characteristic are examined by scanning electron microscopy and transmission electron microscopy. Next, X-ray diffraction analysis confirms well-ordered lamellar structures with a perfect agreement with the bilayer formation leading to the tubular structure via lamellar scrolling behavior. Upon UV irradiation, monomeric CDP-DA tubular assemblies result in the blue-colored CDP/polydiacetylene (PDA) nanotubes. Interestingly, CDP/PDA nanotubes exhibit a reversible blue-to-red color change for over 10 consecutive thermal cycles. The CDP-DA/PDA supramolecular system demonstrates potential applications in developing stimulus-responsive functional materials.

Large deformation bending responses of nanotube-reinforced polymer composite panel structure: Numerical and experimental analyses

The large deformation deflection responses of randomly oriented multi-walled carbon nanotube-reinforced polymer composite structures were examined theoretically using a novel higher order shear deformation kinematic model. Moreover, the excess geometrical distortion within the structure is incorporated via the full geometrically nonlinear strain–deformation relations (Green–Lagrange strain) including all of the nonlinear higher order terms to achieve the generality. The randomly oriented nanotube-reinforced polymer composite properties were evaluated computationally via Mori–Tanaka scheme for the theoretical analysis purpose. The deflection responses were evaluated numerically using an original MATLAB program with the help of the direct iterative method and finite element steps. The performance of the currently developed numerical model was verified by solving various numerical examples for the convergence and subsequent comparison purpose. Also, the deflection values were evaluated experimentally and compared with the current numerical results using the experimentally obtained elastic properties. Finally, the generality and the applicability of the currently developed higher order nonlinear finite element model is revealed by solving various numerical examples.

Recent studies for structural integrity evaluation and defect inspection of J-PARC spallation neutron source target vessel

An examination of the structural integrity and defects of a fabricated mercury target vessel for Japan Proton Accelerator Research Complex (J-PARC) spallation neutron source is presented. Ultrasonic testing (UT) and radiographic testing (RT) were employed as nondestructive inspection methods. The mercury target vessel is composed of SUS316L stainless steel and was designed with multi-walled structures consisting of double-guard vessels with thin walls of 3-mm thickness and assembled by tungsten inert gas welding. The mercury target vessel has complex characteristic, and the weld defect for the thin walls is often very difficult to detect using conventional UT techniques. To overcome this barrier, we employed two new UT techniques, namely 1) immersion ultrasonic with a 50-MHz ultrasonic probe and 2) phased arrays ultrasonic with the full matrix capture (FMC) and the total focusing method (TFM). The examination revealed the formation of small defects and cracks wherein the wall thickness was less than 6 mm. Therefore, new UT techniques are useful for evaluating the structural integrity and defects of the new fabricated mercury vessels.The design and the fabrication process of the mercury target vessel was also evaluated and improved in this study. The use of wire electric discharge machining (EDM) in the fabrication process is desirable to reduce the amount of welding and subsequent welding deformation. The roughness and chemical compositions of the processed surface layer by wire EDM were also examined. The oxide layer was perfectly removed by two-step chemical polishing, and the chemical composition of the layer was analyzed using energy dispersive X-ray spectrometry. In addition, the surface roughness was reduced after polishing to enhance fatigue life and minimize internal defects caused by welding.

Spontaneous Folding of CdTe Nanosheets Induced by Ligand Exchange

Two-dimensional (2D) semiconductors exhibit unique electronic and optical properties arising from the atomic-scale thickness and two-dimensional electronic structure. However, it is usually limited by an intrinsically flat morphology of 2D materials. Here, we report an effect of spontaneous folding of quasi-2D CdTe nanosheets stimulated by ligand exchange. We show that initially flat CdTe nanosheets with 100–200 nm lateral size and 5–6 ML thickness are uniformly rolled up when oleic acid is replaced by thiol-containing ligands. Detailed study shows nanosheet folding along the [110] direction forming multiwall scroll-like structures with the diameter being dependent on sheet thickness. A pronounced red shift of the exciton transitions of CdTe nanosheets is found due to thickness increase and strain appearance under thiol attachment. The folding mechanism is likely related to misfit strain at CdTe (001) basal planes as ultrathin CdS layer is formed. Possibility to precisely tune the nanostructure shape simp...

Silica Precursor Effect on the Physical and Chemical Properties of Cobalt Incorportated MCM-41 Catalysts and Their Performance towards Single Wall Carbon Nanotubes

In this work, mesoporous silica (MCM-41) and a cobalt-incorporated catalyst (Co-MCM-41) were prepared using colloidal silica Cab-O-Sil, sodium silicate and tetraethylorthosilicate (TEOS) as the silica sources and cobalt nitrate as the cobalt source. Their physicochemical properties were analyzed, and their catalytic performance for the synthesis of single-wall carbon nanotubes (SWCNT) during chemical vapor deposition (CCVD) of methane was evaluated. When Cab-O-Sil was used, it was possible to incorporate 3% (nominal) cobalt with a good dispersion and without losing mesoporosity, resulting in minimal formation of superficial cobalt oxide. In contrast, the other catalysts product superficial cobalt oxide, according to the temperature programmed reduction (TPR) analysis. Co-MCM-41 prepared using Cab-O-Sil showed the best performance during the formation of SWCNT with a good regularity and selectivity without forming multi-wall carbon nanotubes or amorphous carbon structures.

Double-walled silicon nanotubes: an ab initio investigation

The synthesis of silicon nanotubes realized in the last decade demonstrates multi-walled tubular structures consisting of Si atoms in and the hybridizations. However, most of the theoretical models were elaborated taking as the starting point structures analogous to carbon nanotubes. These structures are unfavorable due to the natural tendency of the Si atoms to undergo . In this work, through ab initio simulations based on density functional theory, we investigated double-walled silicon nanotubes proposing layered tubes possessing most of the Si atoms in an hybridization, and with few atoms localized at the outer wall. The lowest-energy structures have metallic behavior. Furthermore, the possibility to tune the band structure with the application of a strain was demonstrated, inducing a metal-semiconductor transition. Thus, the behavior of silicon nanotubes differs significantly from carbon nanotubes, and the main source of the differences is the distortions in the lattice associated with the tendency of Si to make four chemical bonds.

The formation mechanism of chiral carbon nanotubes

The nuclei and the formation mechanism of chiral carbon nanotubes, namely, single-, double-, and triple-walled carbon nanotubes are simulated by the first principle density functional theory. The formation mechanism from nuclei to corresponding infinitely long carbon nanotubes occurs spirally and via absorbing carbon atoms layer by layer. Carbon atoms at the open end are metastable state compared with ones in the tube wall or the closed end, which indicate the growth point of chiral carbon nanotubes is located at the open end. Growth of outer layer tubular clusters takes precedence over the inner layer in the process of forming multi-walled nuclear structures. Because of the ratio of carbon atoms at the open end to all carbon atoms decreases, the stability of the tubular clusters increases with their length. The infinitely long carbon nanotubes are obtained by executing periodic boundary conditions depend on corresponding nuclear structures.

Synthesis of Antimony Nanotubes via Facile Template-Free Solvothermal Reactions.

Uniform antimony (Sb) nanotubes were successfully synthesized via a facile solvothermal method without the need for any surfactants or templates. The Sb nanotubes are confirmed to be pure rhombohedral phase and have better crystallinity. These nanotubes show middle-hollow and open-ended structures, as well as multi-walled structures with the wall thickness of about 10 nm. Also, they have an average size of the diameter of about 50 nm and the length of about 350 nm. On the basis of the structural and morphological studies, a possible rolling mechanism is proposed to explain the formation of Sb nanotubes. It is expected that uniform Sb nanotubes can further be used in wide applications. Graphical A possible rolling-formation mechanism is proposed for forming pure rhombhedral phase and high crystallinity antimony nanotubes without any surfactants or templates via a facile solvothermal method.