BITS Faculty Publications

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Subject: search.filters.subject.Carbon nanotubes (CNTs)

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    Study on bending characteristics of CNT-reinforced metal Timoshenko composite porous beam exposed to transverse patch loading
    (Sage, 2025-03) Kumar, Rajesh
    Bending characteristics of porous composite beams reinforced by carbon nanotubes (CNTs) under localized transverse loading is examined in the current study. Initially, single-walled carbon nanotubes (SW-CNTs) are utilized as nanofillers within a metal matrix to enhance the beam’s mechanical properties. The effective mechanical properties of the beam are assessed using the Eshelby-Mori-Tanaka method. Next, the porosity of the beam is modeled as being distributed layer-by-layer through the beam’s thickness, either uniformly or in a non-uniform manner, with three distinct distribution types considered: uniform, symmetric non-uniform, and asymmetric non-uniform. The beam is mathematically modeled using theory of Timoshenko beam combining nonlinearity of von-Kármán. The governing nonlinear algebraic equations are derived from the principle of minimizing total potential energy. These equations are then simplified using the Galerkin method and solved implementing Newton-Raphson technique to determine the load-deformation path. Finally, the study is performed using different parameters to analyze their impact on the bending behavior of CNT-metal reinforced porous composite beams. This includes the mass fraction of SW-CNTs, porosity distribution types, agglomeration effects of CNTs, porosity coefficients, aspect ratio, types of transverse loading, and different metal matrices.
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    Iron terephthalate MOF-MWCNTs based composite paste two-electrode system for selective detection of lead in contaminated stream
    (Elsevier, 2024-10) Chatterjee, Somak
    A composite paste combining iron terephthalate metal-organic framework (MOF-235) and multi-walled carbon nanotubes (MWCNTs) was synthesized for potentiometric lead detection in aqueous solutions. Synthesis yielded a homogeneous and well-dispersed composite by blending MOF/CNT with silicon oil as a binder. This novel material combination of materials has been explored for the first time focussing more into potentiometric and electrochemical lead detection with various control settings, including MOF concentration, electrolyte pH, temperature, electrode spacing and saturation time as well as real-life water analysis. Optimal sensor was selected for electrochemical studies, including, cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry for analysis of various electrode configuration and effect of scan rates on peak currents. Amperometric studies assessed the impact of interfering ions, while leachate solution analysis determined the content of different ions from modified electrodes. Linear behaviour of peak current with scan rates indicated adsorption-controlled kinetics. ECSA for unmodified and modified electrodes were 0.033 cm² and 0.053 cm², with surface coverage areas of 8.5 mM cm−2 and 2.3 mM cm−2. Sensor exhibited a quasi-reversible nature with a sensitivities of 3075.5 mA.cm⁻².mg/l⁻¹ and 226.5 mA.cm⁻².mg/l⁻¹ and detection limits of 0.2 µg/l and 39 µg/l over dynamic ranges. This cost-effective sensor, with a material cost of 1893 INR (22.8 US$) per gram of paste, offers an alternative for lead detection.
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    Adsorption of hydrogen on single-walled carbon nanotubes with defects
    (Elsevier, 2015-10) Ghosh, Sarbani
    We present molecular dynamics (MD) simulations and density functional theory (DFT) calculations of hydrogen adsorption on single-walled carbon nanotubes (SWCNT) with various kinds of defects. The nature of defects, which is characterized here by the number of carbon atoms present in a ring on the surface of nanotube, plays a significant role in determining the hydrogen adsorption capacity of the SWCNT. Nanotubes containing the Stone–Wales defect with 5 and 8-member rings were found to have the largest hydrogen adsorption ability that increases further with the number of rings with such defects. Whereas, the presence of defects with 5, 3-5-8-member rings and the Stone–Wales defect with 5 and 7-member rings decreases the adsorption ability of the defective SWCNT significantly with respect to defect-free nanotubes. Our results indicate that the huge discrepancies in hydrogen storage capacities of SWCNT reported in the literature could be attributed to the nature of defects present in nanotubes. DFT calculations also reveal that the adsorption energy depends not only on the nature and number of defects present on the surface of nanotube but also on the equilibrium structure of rings.
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    Hydrogen storage in Titanium-doped single-walled carbon nanotubes with Stone-Wales defects
    (Elsevier, 2017) Ghosh, Sarbani
    The hydrogen storage capacity of Titanium-doped single-walled carbon nanotubes (SWCNT) containing the Stone-Wales 5,8 defects was studied using molecular dynamics simulations. The equilibrium doping sites and their stability were estimated using density functional theory. Although introduction of structural defects and dopant atom decreases the formation and cohesive energies, the drop in these energies is not large enough to hinder the thermodynamic feasibility of formation of these structures. Moreover, we observed that the stability of SWCNTs, where Ti is doped by replacing two carbon atoms is similar to that of the defect-free nanotube. This particular novel configuration (D5) was also obtained by rearranging the bonds in the 5 and 8-member rings of the Stone-Wales defect. Doping Ti on the defective rings has a more significant effect on the adsorption of hydrogen than doping on the regular 6-member rings. The D5 SWCNT showed the highest gravimetric and volumetric storage capacities at a temperature of 298K and a moderate pressure of 140atm. We also compared the performance of the D5 SWCNT with a recently reported Ti-doped porphyrin SWCNT and observed that the storage capacity of the D5 SWCNT was significantly higher at similar conditions. Our results suggest that Ti-doped SWCNTs with the Stone-Wales (5,8) defects show a promising potential to meet the ultimate goal set by the US Department of Energy for hydrogen storage.
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    Beryllium-doped single-walled carbon nanotubes with Stone-Wales defects: A promising material to store hydrogen at room temperature
    (Elsevier, 2017-09) Ghosh, Sarbani
    Hydrogen storage in single-walled carbon nanotubes containing the Stone-Wales defects and doped with metal atoms (titanium and beryllium) has been studied using molecular dynamics simulations and density functional theory calculations. Although, Be is known to be toxic at high temperatures, Be-doped SWCNT shows a promising potential to exceed the DOE target at moderate temperatures and pressures. One of the major advantages of doping Be is its lower atomic weight, which increases the gravimetric storage capacity compared to SWCNTs doped with heavy-wight Ti atoms. In addition, the binding energy of Be is higher than that of Ti, which enhances the capture of hydrogen molecules. The gravimetric and volumetric storage capacities depend not only on the dopant atom but also on the location of doping. SWCNTs in which Be is doped on the octagonal ring of the Stone-Wales defects exhibits higher storage capacity than Be doped on defect-free SWCNTs. At room temperature (298 K), the storage capacity of Be-doped SWCNT containing the Stone-Wales defect exceeds the DOE target of 5.5 wt% (gravimetric) and 40 g H2/L (volumetric) at a pressure of 267 atm, which is significantly lower than that used in high pressure vessels.
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    Semianalytical Development of Dynamic Instability and Response of a Multiscale Laminated Hybrid Composite Plate
    (ASCE, 2021-01) Patel, Shuvendu Narayan; Kumar, Rajesh
    The use of carbon nanotubes (CNTs) in augmenting the mechanical properties of fiber-reinforced laminated composites is a fact. In this paper, the semianalytical studies on the dynamic instability behavior and linear and nonlinear responses of a randomly distributed CNT and fiber-reinforced interlamina hybrid composite (CNTFRHC) plate with and without damping under time-dependent in-plane uniaxial uniform compression loading are presented. Each lamina of the laminate is made of multiscale materials such as CNT/polymer/fiber. The effective mechanical properties of the lamina are estimated in two steps. First, the Eshelby–Mori–Tanaka technique is used to compute the effective mechanical properties of randomly distributed CNTs in a polymer matrix (i.e., CNT-embedded matrix). Second, the effective mechanical properties of the CNT-embedded matrix reinforced with fiber (either carbon or glass) are estimated by using various homogenization techniques. The plate is modeled by using higher-order shear deformation theory (HSDT) and von Kármán nonlinearity. Governing partial differential equations of the CNTFRHC plate are obtained by Hamilton’s principle and reduced to Mathieu–Hill equations by using the Galerkin method. Mathieu–Hill equations are solved by the Bolotin method to trace the boundaries of the instability region corresponding periods and . Finally, the influence of different parameters such as CNT agglomerations, CNT mass fraction, edge-to-thickness ratio, compression preloading, boundary conditions, and damping on the dynamic instability region of the CNTFRHC plates are studied in detail. Numerical results provide useful insights into the selection of parameters with different combinations for the desired design of the CNTFRHC plate against instability. Furthermore, to know the characteristics of the instability region of a CNTFRHC plate such as the existence of beats, dependence on geometric nonlinearity, and forcing frequency for which the linear and nonlinear responses with and without damping in both stable and unstable regions are presented.
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    Influence of Carbon Nanotubes on Stability and Vibration Characteristics of Plates and Panels in Thermal Environment: A Review
    (Springer, 2023-07) Kumar, Rajesh
    Laminated composites became a cutting-edge material in the twentieth century due to their extensive use in engineering, owing to their high strength and lightweight characteristics. Composites are manufactured with polymers and reinforced with fibers such as glass fiber, carbon fiber, Kevlar fiber, and many more. Delamination has been found to be a significant problem in composite materials, and it has the potential to cause catastrophic failure through brittle failure. To delay such events in polymer composites, carbon-based nanoparticles have been widely added to reinforce the polymer, resulting in an improvement in the strength of composites. After 1991, the development of carbon nanotubes (CNTs) revolutionized the plastic composite industry due to its versatile characteristics. CNT, whose strength is 100 times higher than that of steel, can reinforce polymers and enhance the mechanical strength of composites. The present study focuses on reviewing the published literature to provide an insight view for readers to predict the stability and vibration characteristics of CNT-reinforced composite panels. It also discusses the influence of temperature rise, functional gradation, volume fraction, and agglomeration effect in case of randomly distributed CNTs in composite plates/panels. The research gaps are identified at the end that may help readers understand the voids in this field of research.
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    Transparent Indium Tin Oxide Films for Liquid Crystal Display Application
    (American Scientific Publishers, 2013-12) Manjuladevi, V.; Gupta, Raj Kumar
    In this modern era, most of the device applications involve displays as one of the main components of the system. There are multi-dimensional technological advancements with the invention of liquid crystal display (LCD) devices. Indium tin oxide (ITO) deposited substrates has proved to be efficient transparent electrodes for the fabrication of the display devices. The properties of LCD are governed by the ITO, liquid crystal (LC) materials and the interfacial phenomena between the ITO and LC materials. In this article we discuss the role of ITO and LC materials on the performance of LC cells. We also discuss the interfacial properties of LC-functionalized carbon nanotubes composites on the treated ITO substrates.
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    Superior electro-optical switching properties in polymer dispersed liquid crystals prepared with functionalized carbon nanotube nanocomposites of LC for switchable window applications
    (Elsevier, 2023-03) Manjuladevi, V.; Gupta, Raj Kumar
    In this work, we are reporting the results on electro-optical switching properties of polymer dispersed liquid crystal (PDLC) devices for switchable window related applications. The PDLC cells are prepared by mixing octadecylamine functionalized single-walled carbon nanotubes (ODA-SWCNT) nanocomposites of liquid crystals (LC) and acrylate-based monomer by polymerization induced phase separation method. The important switchable device parameters such as threshold voltage, switching voltage, response time, contrast ratio and effective refractive index are investigated. The PDLC cells prepared with 0.05 wt% ODA-SWCNT nanocomposites of the LC, 7CB show almost zero threshold field and 36% less driving field compared to PDLC prepared with pure 7CB. A distinct optical response (frequency doubling) phenomenon is observed for PDLC prepared with 0.03 and 0.05 wt% ODA-SWCNT nanocomposites of 7CB compared to PDLC cells prepared with pure 7CB and lower concentrations (<0.03 wt%) of ODA-SWCNT. The relaxation of optical transmittance is observed at low frequency even when the applied electric field () is ON which is due to the strong induced internal electric field (due to free ions) which nullifies the . The physical mechanism of this unique optical behavior is discussed in detail. The PDLC prepared with 0.01 wt% ODA-SWCNT show 84% faster response time compared to PDLC prepared with pure 7CB. The working of prototype PDLC devices for use in switchable window related applications is reported. The results indicate that, the PDLC prepared with 0.05 wt% ODA-SWCNT nanocomposites of 7CB show high ON state clarity and high OFF state opacity compared to PDLC prepared with pure LC and lower concentrations of ODA-SWCNT.