Agglomeration Of Carbon Nanotubes Research Articles

An investigation of slurry erosion behaviour in plasma-sprayed carbon nanotube-reinforced fly ash/alumina coatings using experimental analysis and artificial neural computing for marine and offshore applications

This study investigates carbon nanotube (CNT)-reinforced alumina fly ash (FA) coatings, namely AF (unreinforced), 1CAF (with 1 wt% CNT), and 2CAF (with 2 wt% CNT), on marine-grade steel. Microstructural analysis shows 1CAF coatings denser by ∼15.32% due to CNT reinforcement, while 2CAF coatings display ∼9.68% increased porosity from CNT agglomeration. Raman spectroscopy confirms CNT retention. 1CAF coatings exhibit ∼14.66% higher microhardness, ∼15.96% higher adhesion strength, and ∼15.66% improved fracture toughness compared to AF coatings, attributed to pore sealing through CNT reinforcement. Enhanced erosion resistance (∼14.59%) in 1CAF coatings was observed due to improved mechanical properties and CNTs mitigating crack propagation. Validation through an artificial neural network (ANN) modeling and regression analysis supports 1CAF coatings’ promise for harsh marine environments, offering enhanced durability.

Bed structure of CNT agglomerates in gas–solid fluidized beds

In this study, the bed structure according to the flow regime of fine particles in gas–solid fluidized beds was studied by measuring the pressure drop and heat transfer coefficient. Two types of carbon nanotube (CNT) agglomerates with behavior similar to Geldart A and Geldart B and two types of glass bead (GB) particles corresponding to Geldart A and Geldart B classification were used. CNTs fluidized in the form of agglomerates, and in some CNT agglomerates, a homogeneous expansion regime with suppressed generation of bubbles, were observed. In the homogeneous expansion regime of CNT agglomerates, the relationship between superficial velocity and voidage was consistent with the Richardson–Zaki equation, and had a higher n value than that of Geldart A particles and fumed silica agglomerates. In this regime, small-diameter channels coexisted, and due to unstable fluidization at low superficial velocity, intermittent bed collapse occurred. In the homogeneous expansion regime of GB particles, the heat transfer coefficient remained constant, and as bubbles were generated, the heat transfer coefficient increased. On the other hand, as the superficial velocity increased, the heat transfer coefficient of CNT agglomerates continuously increased, regardless of the flow regime transition. In the homogeneous expansion regime of CNT agglomerates, unlike Geldart A particles, movement of agglomerates within the bed was confirmed, and a dynamic bed structure was present, in which the movement increased according to the superficial velocity.

Nonlinear Optimized PID Vibration Control of Thermal-Dependent FG Composite Porous Plates Reinforced by Agglomerated CNTs

This research study aims to delve into the effects of carbon nanotubes (CNTs) agglomeration on the dynamic characteristics of smart functionally graded (FG) porous sandwich plates. The structure of the sandwich plate comprises a core layer that incorporates dispersed CNTs within a polymer matrix. In addition, two layers are equipped with piezoelectric sensors and actuators. The agglomeration of CNTs is mathematically modeled using the Eshelby–Mori–Tanaka approach, accounting for both complete and partial agglomeration states. Moreover, the study takes into account the thermal-dependent behavior of CNTs. Subsequently, an optimal nonlinear proportional-integral-derivative (PID) control scheme based on the Bat optimization algorithm is applied to mitigate vibrations within the composite structure. Unlike the fixed gains of the classical PID, the nonlinear version dynamically adjusts its parameters in real time, ensuring enhanced responsiveness and stability. Furthermore, a comprehensive numerical investigation is conducted to assess the impact of several parameters on the natural frequencies in the frequency domain. These parameters encompass porosity distributions, porosity coefficients, reinforcement patterns, weight fractions of nanofillers, temperature, and the agglomeration of CNTs. The vibration attenuation performance of both nonlinear and classical PID controllers is evaluated through numerical simulations. The findings indicate the robustness and rapid disturbance rejection of the proposed control scheme.

Role of the Carbon Nanotube Junction in the Mechanical Performance of Carbon Nanotube/Polyethylene Nanocomposites: A Molecular Dynamics Study.

Carbon nanotube (CNT)-based networks are promising reinforcements for polymer nanocomposites without the issue of CNT agglomeration. In this study, the CNT junction, a vital and representative structure of CNT-based networks, was applied as the reinforcement of the polyethylene (PE) matrix. The tensile properties of the CNT-junction/PE nanocomposite were investigated via molecular dynamics (MD) simulations and compared with those of pure PE matrix and conventional CNT/PE nanocomposites. The CNT junction was found to significantly increase the mechanical properties of the PE matrix. The Young's modulus, yield strength, and toughness rose by 500%, 100%, and 200%, respectively. This mechanism is related to the enhanced interfacial energy, which makes the polymer matrix denser and stimulates the bond and angle deformations of the polymer chains. Furthermore, the CNT junction demonstrated a more profitable reinforcement efficiency compared to conventional straight CNTs in the PE matrix. Compared to the ordinary CNT/PE model, the improvements in the Young's modulus and toughness induced by the CNT junction were up to 60% and 25%. This is attributed to the reduced mobility induced by the geometry of the CNT junction and stronger interfacial interactions provided by the Stone-Wales defects of the CNT junction, slowing down the void propagation of the nanocomposite. With the understanding of the beneficial reinforcing effect of the CNT junction, this study provides valuable insights for the design and application of CNT-based networks in polymer nanocomposites.

Nozzle-Free Printing of CNT Electronics Using Laser-Generated Focused Ultrasound.

Printed electronics have made remarkable progress in recent years and inkjet printing (IJP) has emerged as one of the leading methods for fabricating printed electronic devices. However, challenges such as nozzle clogging, and strict ink formulation constraints have limited their widespread use. To address this issue, a novel nozzle-free printing technology is explored, which is enabled by laser-generated focused ultrasound, as a potential alternative printing modality called Shock-wave Jet Printing (SJP). Specifically, the performance of SJP-printed and IJP-printed bottom-gated carbon nanotube (CNT) thin film transistors (TFTs) is compared. While IJP required ten print passes to achieve fully functional devices with channel dimensions ranging from tens to hundreds of micrometers, SJP achieved comparable performance with just a single pass. For optimized devices, SJP demonstrated six times higher maximum mobility than IJP-printed devices. Furthermore, the advantages of nozzle-free printing are evident, as SJP successfully printed stored and unsonicated inks, delivering moderate electrical performance, whereas IJP suffered from nozzle clogging due to CNT agglomeration. Moreover, SJP can print significantly longer CNTs, spanning the entire range of tube lengths of commercially available CNT ink. The findings from this study contribute to the advancement of nanomaterial printing, ink formulation, and the development of cost-effective printable electronics.

A comprehensive morphology study on the carbon nanotube agglomerations in cementitious composite

To comprehensively understand the fundamental role of carbon nanotubes (CNTs) in cementitious composites, three independent methods were employed to investigate the morphological characteristics of the composites. The embedding method and the depositing method controlled the direction of hydrate reactions by compulsorily segregating CNTs and cement grains, helping to more accurately deduce the formation process of various morphologies. The sectioning method used focused ion beam for precise cutting, enabling in-situ morphology information that cannot be observed through mechanical polishing. This study provides the first visual evidence to demonstrate that the micro-agglomerations of CNTs were sufficiently incorporated into the hydration products, indicating that CNT agglomerations may not be the primary cause for the decline in the mechanical properties of carbon nanotube cementitious composites. Furthermore, this study proposes the physical entrapment mechanism as a substitute for the ambiguous nucleation mechanism.

Predicting mechanical properties of 3D printed nanocomposites using multi-scale modeling

The main objective of this research is to predict the Young’s modulus of 3D-printed specimens made of nanocomposites. Printable nanocomposites filaments reinforced with various portions of carbon nanotubes (CNTs) are produced at the first stage. At the second stage, extruded nanocomposite filaments are fed into a 3D desktop printer and tensile specimens are printed with two different infill patterns. A multi-scale modeling is developed as a hierarchical computational procedure covering involved scales of micro, meso and macro. Treating CNT length, orientation and agglomeration as random parameters, stochastic modeling is performed. CNT length is considered at microscale, while CNT agglomeration and orientation are taken into account at the scale of meso. The infill patterns and printing parameters are captured at the uppermost scale of macro. The Young’s modulus of both nanocomposite filaments and 3D printed samples are predicted and compared with the results of experimental characterization.

Effects of non-uniformity in thickness and volume fraction of agglomerated CNTs on the dynamics of a spinning CNT-reinforced nanocomposite truncated conical shell

In the presented work, the free vibration analysis of a rotating truncated conical shell whose thickness varies in the meridional direction is examined. The material that the shell is made of is a polymeric matrix (epoxy) enriched with carbon nanotubes (CNTs) whose volume fraction varies in the meridional direction. CNTs agglomeration is considered and the density and elastic constants of such a two-phase nanocomposite are calculated sequentially based on the Eshelby–Mori–Tanaka approach alongside the rule of mixture. The conical shell is modeled using the first-order shear deformation theory (FSDT) including the relative acceleration, Coriolis acceleration, and centrifugal acceleration along with the initial hoop tension, and the governing equations are obtained utilizing Hamilton’s principle. The solution of governing equations is performed via the combination of an analytical solution in the circumferential direction and a numerical one in the meridional direction via the differential quadrature method (DQM). The impacts of several parameters on the forward and backward natural frequencies of such a rotating shell are studied such as chirality, mass fraction and dispersion pattern of the CNTs, thickness variation parameters, and boundary conditions. It is observed that higher natural frequencies and critical rotational speeds can be achieved for CNT-reinforced conical shells when the volume fraction of the CNTs and the thickness of the shell increase from its small radius to the large one.

Surface modification of carbon nanotubes and their nanocomposites for fuel cell applications: A review

<abstract> <p>Carbon nanotubes (CNTs) have drawn great attention as potential materials for energy conversion and storage systems such as batteries, supercapacitors, and fuel cells. Among these energy conversion and storage systems, the fuel cells had stood out owing to their high-power density, energy conversion efficiency and zero greenhouse gasses emission. In fuel cells, CNTs have been widely studied as catalyst support, bipolar plates and electrode material due to their outstanding mechanical strength, chemical stability, electrical and thermal conductivity, and high specific surface area. The use of CNT has been shown to enhance the electrocatalytic performance of the catalyst, corrosion resistivity, improve the transmission performance of the fuel cell and reduce the cost of fuel cells. The use of CNTs in fuel cells has drastically reduced the use of noble metals. However, the major drawback to the utilization of pristine CNTs in fuel cells are; poor dispersion, agglomeration, and insolubility of CNTs in most solvents. Surface engineering of CNTs and CNT nanocomposites has proven to remarkably remedy these challenges and significantly enhanced the electrochemical performance of fuel cells. This review discusses the different methods of surface modification of CNTs and their nanocomposite utilized in fuel cell applications. The effect of CNTs in improving the performance of fuel cell catalyst, membrane electrode assembly and bipolar plates of fuel cells. The interaction between the CNTs catalyst support and the catalyst is also reviewed. Lastly, the authors outlined the challenges and recommendations for future study of surface functionalized CNTs composite for fuel cell application.</p> </abstract>

Dynamic analysis of piezolaminated shell structures reinforced with agglomerated carbon nanotubes using an enhanced solid-shell element

Dynamic analysis of piezolaminated shell structures reinforced with agglomerated carbon nanotubes using an enhanced solid-shell element

Non-linear stability characteristics of randomly distributed CNT-reinforced fiber composite beams under thermo-mechanical loadings

The aim of the present study is to elucidate the non-linear stability characteristics of randomly distributed carbon nanotube-reinforced fiber composite (RD-CNTRFC) beams subjected to thermo-mechanical loading. Effective material properties of RD-CNTRFC are estimated using the Eshelby-Mori-Tanaka approach and Halpin–Tsai micromechanical techniques. The material properties are considered to be temperature-dependent, and the influence of carbon nanotube (CNT) agglomeration is also incorporated in material properties estimation of hybrid matrix. The strain-displacement relations are assumed by incorporating the higher-order shear deformation theory and geometrical nonlinearity (von Kármán). The governing partial differential equations are obtained by minimizing the total potential energy of the beam. Buckling loads of beam subjected to in-plane compressive loads are estimated using Eigen value approach. Similarly, buckling temperatures are also determined by solving Eigenvalue problem iteratively due to temperature-dependent material properties. The non-linear equilibrium paths under thermal and mechanical loadings are traced through iterative Eigenvalue approach. Numerical results are presented to elucidate the influence of various parameters like CNT agglomeration, ply sequences, span-to-depth ratio, boundary conditions, and mass fraction of CNTs.

Fluidization and Application of Carbon Nano Agglomerations.

Carbon nanomaterials are unique with excellent functionality and diverse structures. However, agglomerated structures are commonly formed because of small-size effects and surface effects. Their hierarchical assembly into micro particles enables carbon nanomaterials to break the boundaries of classical Geldart particle classification before stable fluidization under gas-solid interactions. Currently, there are few systematic reports regarding the structural evolution and fluidization mechanism of carbon nano agglomerations. Based on existing research on carbon nanomaterials, this article reviews the fluidized structure control and fluidization principles of prototypical carbon nanotubes (CNTs) as well as their nanocomposites. The controlled agglomerate fluidization technology leads to the successful mass production of agglomerated and aligned CNTs. In addition, the self-similar agglomeration of individual ultralong CNTs and nanocomposites with silicon as model systems further exemplify the important role of surface structure and particle-fluid interactions. These emerging nano agglomerations have endowed classical fluidization technology with more innovations in advanced applications like energy storage, biomedical, and electronics. This review aims to provide insights into the connections between fluidization and carbon nanomaterials by highlighting their hierarchical structural evolution and the principle of agglomerated fluidization, expecting to showcase the vitality and connotation of fluidization science and technology in the new era.

Supercapacitors Based on Spider Nest–Shaped Nickel Foam Electrodes Operating in Seawater

Abstract An environmental-friendly supercapacitor based on aqueous electrolyte was fabricated. Electrodes with conductive spider nest–shaped three-dimensional (3D) porous structures were prepared for the assembly of symmetric supercapacitors. The nickel foam was modified by multiwalled carbon nanotubes and β-cyclodextrin. The construction of the spider nest was stabilized via the chemical bond inside carbon nanotubes, π–π stack effects among carbon nanotubes, and physical adsorption between nickel foam and carbon nanotubes substrate. The role of β-cyclodextrin is a dispersant to prevent agglomeration of carbon nanotubes, thereby enhancing electroactive surface area of nickel foam and improving the specific capacitance of the electrodes. Furthermore, the electrodes exhibited excellent rate capability. The obtained symmetrical supercapacitors exhibited an excellent power density of 17,561.3 W kg−1, a good specific capacitance of 398.8 F g−1, and an energy density of 154.8 Wh kg−1 for 4000 cycles with outstanding cycling stability. In addition, the specific capacitance, energy density, and power density of the supercapacitor operating in seawater were found to be 100.2 F g−1, 17.8 Wh kg−1, and 2568 Wh kg−1, respectively, for 3000 cycles. Overall, our findings indicate that the supercapacitor could stably operate in seawater and shows potential for use as an ecofriendly power supply to marine engineering equipment.

Insight into the carbon nanotube agglomeration deteriorated fire safety of epoxy

Carbon nanotube (CNT)/epoxy composite is a star lightweight structure material. However, the reason why well-dispersed CNTs retard the combustion of epoxy while CNT agglomerations always accelerate it instead seems still confusing, which severely limits the further understanding and design of the high-performance CNT/epoxy composite. Herein, with CNT agglomerations inside, 4coCNT/epoxy composite and 2coCNT0.5/epoxy composite were prepared to reveal the truth of the dramatically worsened flame retarding performances compared with their expected values. The void-rich CNT agglomerations were proved to be qualified candlewick-like fillers after directly observing the formations of micron-diameter fiber-like agglomerations by scanning electron microscope (SEM) and X-ray computed tomography (XCT); verifying the ability of CNT agglomerations to allow the epoxy melt to wet, spread, and flow on their surface. The thermogravimetric analysis (TG) and the limited oxygen index (LOI) results suggested that fire is necessary for the CNT agglomeration to worsen the thermostability of composites. With the presence of the liquid-phase combustible epoxy melt in the fire captured by a high-definition camera, all the requirements to induce the candlewick effect were satisfied. Ruling out a popular explanation that the agglomerated CNTs promote polymers' inflammability by cracking chars created during the combustion, a similar but distinct candlewick effect was then proposed and specially defined as “nano-candlewick effect” in the present study. The nano-candlewick effect defeated the flame-retarding free radical scavenging effect of the dangling bonds from coCNT and coCNT0.5, and further worsened the flame retardancy of the epoxy matrix. The detailed working mechanism of the nano-candlewick effect was described. The mechanism is supposed to be appropriate for polymer nanocomposites with candlewick-like fillers inside, and account for the dramatically accelerated combustion.

Porosity-dependent stability analysis of bio-inspired cellular nanocomposite shells

This paper presents an innovative numerical model to investigate buckling behaviour of bio-inspired continuously graded porous (CGP) nanocomposite cylindrical shells. It is postulated that the shell subjected to combined lateral pressure and axial compressive load is constructed from metal foams with closed-cell structures that possess graded internal pores, which exhibit three types of continuously graded porosity profiles based on a power-law distribution. A scaling relation for the effective Young’s modulus of the cellular structure determined by a variational finite element method (FEM) is used. The effective constitutive law of an elastic isotropic metal matrix containing distributed elastic carbon-nanotubes (CNTs) is estimated in consideration of the impact of CNTs agglomeration using a continuum model based on the Eshelby–Mori–Tanaka (EMT) approach. In contrast to conventional approaches, the study employs Euler–Bernoulli beams to model stiffeners within the CGP shells. This choice allows for a more realistic representation of stiffener effects, as opposed to the prevalent approach of uniform smearing across the shell’s surface. The equilibrium equations of the CGP shell, based on the Reddy higher-order shell theory (RHST), is obtained through the application of the Euler equation. Subsequently, the equations for stability are obtained through the utilization of the variational method. This study emphasizes the effects of geometrical parameters, porosity variability, and distribution of CNTs on the buckling performance of the CGP shells. The intricate interplay between CNTs and porosity distributions critically influences the stability behaviour of CGP shells. CNTs arrangement remarkably impacts buckling behaviour at higher length-to-mean radius ratios, while symmetric porosity near the mid-surface significantly enhances stiffness. These findings provide valuable insights for designing closed-cell cellular stiffened shells with optimal porosity to enhance stability.

The effect of interphase and agglomeration on the mechanical properties of aluminum matrix nanocomposites reinforced with carbon nanotubes

The interphase phenomena are a critical problem for estimating the mechanical behavior of carbon nanotube-reinforced aluminum composites. In this research, the Aluminum-carbide (Al4C3) interphase and carbon nanotubes (CNTs) agglomeration effects on the mechanical properties of Aluminum /Carbon nanotubes composites are investigated using a numerical micromechanical model. Moreover, the impacts of the CNTs fraction, agglomeration, Al4C3 interphase, and their diameter on the elastic modulus of Aluminum (Al) composites are explored. The results demonstrated the effect of CNTs agglomeration and Al4C3 interphase on Young’s modulus of Al composites significantly when the CNT fraction increases; In addition, it observed that with increasing interphase thickness, Young’s modulus of Al composites increases and is changed with variation of agglomeration shape. The Literature’s experimental results validated the applicability of the present finite element (FE) model. The results of this study are hard evidence for CNT/ Aluminum composites creating potential applications in industry, especially for automobile and aircraft fields.

Analysis of Acid Diffusion Effects on Physical Properties of Polymer Composites: A Combined Study of Mechanical and Electrical Characterization

In this study, we examined the impact of carbon nanotube (CNT) concentration on the mechanical properties of epoxy/CNT composites under acid exposure. Samples with varying CNT concentrations (0% to 5%) were fabricated and characterized using dynamic mechanical analysis (DMA) and nanoindentation. Beyond the percolation threshold, the composites experienced decreased bulk mechanical properties due to CNT agglomeration. Acid exposure for one week and one month revealed a gradient of properties from the sample’s skin to its core. Overall, the composites exhibited modified physical properties, with degradation influenced by the CNT concentration. Higher concentrations acted as barriers but also created pathways for acid diffusion through pores surrounding CNT agglomerates. The agreement between nanoindentation and vector network analyzer (VNA) measurements further supported our findings. This convergence of mechanical and electromagnetic characterization techniques holds promise for wireless structural health monitoring (SHM) applications. Our study enhances the understanding of epoxy/CNT composites for SHM applications. The relationship between CNT concentration, acid exposure, and mechanical properties guides material selection and the development of real-time damage-detection techniques. Integrating multiple measurement techniques, as demonstrated by the agreement between nanoindentation and VNA data, provides a comprehensive understanding of structural behavior, improving SHM practices.

Bending and free vibration analyses of CNTRC shell structures considering agglomeration effects with through-the-thickness stretch

The present work investigates an enhanced finite element model and numerical analysis to illustrate the agglomeration effect of Carbon Nanotubes (CNTs) on static and free vibration responses of reinforced composite plate and cylindrical panel shell. The developed model is based on the kinematics of the improved first-order-shear deformation theory (FSDT), assuming a parabolic variation of the transverse shear strains and fulfilling the zero circumstance of the transverse shear stresses at the extreme structure’ surfaces omitting the use of shear correction factors. The material properties of the nanocomposite are determined using a developed micromechanical model based on the Mori–Tanaka approach. The developed finite element formulation is based on three-dimensional constitutive equations without reduction involving the addition of one parameter of thickness change combined with the Enhanced Assumed Strain (EAS) method. Four enhancement models are established and discussed. In a first attempt, the improvement of the third bending strain using one or four parameters are presented. In a second attempt, the membrane strain is enhanced with four parameters. Due to lack of investigations on structural behavior of composite structures reinforced with agglomerated CNTs, new static and free vibration results for shell structures with three level of CNT agglomeration are examined. Parametric studies are here in developed to present the influences of the characteristic parameters on the structural behavior of the CNTRC shell in a new graphic way; such as the volume fraction and agglomeration of nanofibers, geometrical parameters, and boundary conditions. Based on numerical results, it is found that the agglomeration and distributions of the reinforcing fibers are really crucial and play a significant role on the static and vibrational performances of the structure.

Understanding the evolution of microstructure, phase homogeneity, electrochemical characteristics and surface chemistry of electrodeposited MnCrCoFeNiCu high entropy alloy coating with reinforcement of carbon nanotubes

MnCrCoFeNiCu high entropy alloy (HEA) coatings with varying volume fractions of carbon nanotube (CNT) were electrodeposited on mild steel. Morphology, phase constitution, wettability, surface oxide chemistry and corrosion of coatings were examined. Coating morphology became finer with initial CNT incorporation and then transformed to rougher surface for higher CNT volume fractions. Pristine HEA coating contained mixture of body centre cubic (bcc) and face centre cubic (fcc) phases. With the CNT addition phase homogenization happened and for the HEAC3 coating (from electrolyte with 5 mg/L concentration of CNT) single phase bcc microstructure was obtained. The phase mixture however re-evolved for the higher CNT incorporation due to CNT agglomeration and reduction in the metal-CNT interfaces. Water contact angle was 127° for HEA_C3 coating. All the HEA-CNT coatings exhibited higher corrosion resistance than the pristine HEA coating, corrosion rate trend was however not monotonic with CNT volume fraction and maximum corrosion resistance was observed for the HEA_C3 coating. Surface oxide chemistry of exposed sample showed stabler oxide over the HEA-CNT coatings when compared to the oxides of the pristine HEA coating. Higher corrosion resistance of the HEA_C3 coating was due to compact morphology, hydrophobicity, phase homogenization and evolution of stable surface oxides.

Towards a More Conductive and Stronger Cellulose-CNTs Composite Film through Controlling the Texture

ABSTRACT Dispersion state of carbon nanotubes (CNTs) in cellulose nanofibrils (CNFs) film at variant sonication time in the presence of sodium dodecyl sulfate (SDS) has been studied in this work. The sonication was extended up to 120 min, and the CNF-CNTs-SDS suspension’s viscosity was measured at different times. Overall, viscosity of CNF-CNTs-SDS suspension decreased continuously as sonication continued except for the period of 60–75 min, where an increase in the viscosity was observed. Based on morphological investigations, the partial dispersion of particles at the early stage of sonication (i.e. up to 60 min) was followed by coagulation or reagglomeration of the particles during 60–75 min and increasing sonication time by 120 min led to improved dispersion of CNTs in CNFs. Likewise, the electrical conductivity and tensile strength obeyed the same trend due to improved CNTs-CNFs film’s network (30–60 and 75–120 min) and the corresponding reduction (60–75 min) caused by the partial agglomeration of CNT and CNF moieties. These findings highlight that sonication time is not a straightforward parameter and should be elaborated to reach the desired dispersion.