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Advances in the Science and Technology of Carbon Nanotubes and Their Composites: A Review
Abstract
Since their first observation nearly a decade ago by Iijima (Iijima S. Helical microtubules of graphitic carbon Nature. 1991; 354:56–8), carbon nanotubes have been the focus of considerable research. Numerous investigators have since reported remarkable physical and mechanical properties for this new form of carbon. From unique electronic properties and a thermal conductivity higher than diamond to mechanical properties where the stiffness, strength and resilience exceeds any current material, carbon nanotubes offer tremendous opportunities for the development of fundamentally new material systems. In particular, the exceptional mechanical properties of carbon nanotubes, combined with their low density, offer scope for the development of nanotube-reinforced composite materials. The potential for nanocomposites reinforced with carbon tubes having extraordinary specific stiffness and strength represent tremendous opportunity for application in the 21st century. This paper provides a concise review of recent advances in carbon nanotubes and their composites. We examine the research work reported in the literature on the structure and processing of carbon nanotubes, as well as characterization and property modeling of carbon nanotubes and their composites.
... In recent years, there has been a growing interest in research and development in the field of natural fibre composites due to their better formability, abundance, renewability, cost-effectiveness and environmentally friendly properties [Saheb and Jog 1999;La Mantia and Morreale 2011;Misnon et al. 2014;Sanjay et al. 2016]. In addition to the modification of composites, through the use of various types of reinforcement, fillers and nanofillers are also used [Thostenson, Ren and Chou 2001]. Carbon nanotubes possess unique electric properties and thermal conductivity higher than diamond; to mechanical properties in which stiffness, strength and elasticity surpass any current material, carbon nanotubes offer great opportunities for the development of entirely new material systems. ...
... Carbon nanotubes possess unique electric properties and thermal conductivity higher than diamond; to mechanical properties in which stiffness, strength and elasticity surpass any current material, carbon nanotubes offer great opportunities for the development of entirely new material systems. In particular, the unique mechanical properties of carbon nanotubes, combined with their low density, open the door to the development of nanotube-reinforced composite materials [Thostenson, Ren and Chou 2001]. ...
The study aimed to analyse the influence of aluminum powder on the mechanical properties of polyester-glass composites. Composite materials were made of glass fibres with random fibre direction and polyester resin with the addition of aluminum powder as a filler. The strength parameters of materials obtained during the static tensile test and hardness test were compared. The results were subjected to statistical analysis, taking into account the change in the amount of filler, microstructure was also observed using optical microscopy. An analysis of the results showed that the addition of aluminum powder amounting to 2% of the weight of the composites reduces their hardness and, at the same time, the longitudinal modulus of elasticity.The addition of aluminum powder amounting to 5% and 10% of the weight of the composites increased the hardness of the composites while reducing the Young's modulus. The values of hardness measurements were subjected to statistical analyses at significance level α = 95. The Shapiro-Wilk test confirmed that the hardness variables for all tested samples were in normal distributions, and therefore the most powerful parametric tests were used to test the differences. Using the Student's t-test, it was confirmed that between pairs of variables in configurations: a standard sample with a modified sample, for all tested samples there are significant statistical differences in the distributions of hardness values. Studies have shown that the modification of the mechanical and strength properties of composite materials, through the use of an aluminum filler, makes it possible to obtain materials with variable parameters that can be useful and attractive in many new areas, depending on the application and user requirements.
... Since Ijima's 1990 discovery of carbon nanotubes (CNTs) [2], there has been a surge of interest in the fields of nanoscience and nanotechnology. In the fields of sensing [3], energy storage [4], and composites [5], CNTs offer an array of novel applications, with many more in development [6]. Boron nitride nanotubes (BNNTs) have a similar atomic structure as CNTs, with boron and nitrogen elements replacing all carbon atoms. ...
... CNTs demonstrate the possibility of extensive band gaps depending on their diameter and chiral angle [20]. Significant shifts in the nanotube characteristics are possible; for instance, armchair CNTs always have a metallic character, but zigzag CNTs may either have a metallic or semiconducting character [5]. The distinctive properties of nanotubes have engendered substantial scientific interest, prompting extensive research into their one-dimensional structural nature. ...
The piezoelectric properties of carbon nanotubes (CNTs) doped with boron (B) and nitrogen (N) were studied using the classical molecular dynamics (MD) simulation software package Large Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The interactions among the nanotube atoms C, N, and B were calculated using the Tersoff potential. MD simulations were performed to observe the changes in the piezoelectric coefficient of the doped CNTs under loading conditions like tension, torsion, and a combination of both. We considered a wide range of chirality to determine the influence of structural variation on the piezoelectric effect. The study revealed that B-CNTs exhibit superior piezoelectric coefficients compared to N-CNTs, indicating the significant role of dopant type. Moreover, under tensile loading, zigzag-oriented B-CNTs showed higher piezoelectric coefficients with a maximum e33 = 0.2441 C/m2, whereas under torsional loading, armchair-oriented B-CNTs showed enhanced response with a maximum e36 = 0.0564 C/m2. A notable observation was that under combined loading conditions (tensile and torsional), the piezoelectric behavior of the B-CNTs was dependent on the nanotube’s chirality and did not yield a linear additive response. The polarization induced under combined loading in most doped CNTs is significantly higher than the sum of polarization generated under individual tensile and torsional loading conditions. This behavior suggests that the overall piezoelectric effect under combined loading can be enhanced, which emphasizes the need for an approach to optimize the mechanical loading condition. The results showcase the potential of B-/N-CNTs to be engineered for efficient performance by demonstrating that tailored mechanical loading can enhance the piezoelectric responses in doped CNTs, opening a pathway for highly functional and efficient nanoscale piezoelectric devices.
... This means that it has a theoretical strength that is roughly 10-100 times stronger than steel. Additionally, CNT has a capability for conveying electric current over 1000 times superior to copper wire, a thermal efficiency roughly twice as great as diamond, and is thermostable up to 2800°C in a vacuum [7][8][9][10][11][12]. Notably, CNT possesses an ample specific surface area for a type of nanomaterial. ...
... Due to these exceptional qualities, CNT makes a superior reinforcement material [13]. The review papers [7,[14][15][16][17][18] are available for a detailed study of mechanical characteristics as well as the behavior of CNT-reinforced composites (CNTRCs). In composite materials, the arrangement and set of the orientation of CNTs have been established by some experimental techniques [19][20][21][22][23]. ...
The current research work investigates the static, buckling, and free vibration behavior of carbon nanotube-reinforced composite (CNTRC) beam using the inverse hyperbolic shear deformation theory. This theory is based upon the shear strain shape function yielding a nonlinear distribution of transverse shear stresses and inherently satisfies the traction-free boundary conditions at the upper and lower surfaces of the beam structures omitting the requirement of the shear correction factor. The governing differential equations are developed using Hamilton's principle, and the closed-form solutions are obtained using Navier's approach. The rule of mixture is adopted to estimate the material characteristics of CNTRC beams. The four different ways of CNT’s reinforcement distribution are used such as uniform distribution, O-beam, X-beam, and V-beam for the analysis. The analytical results in terms of deflection, stresses, critical buckling load as well as natural frequencies of the CNT-reinforced composite beam are obtained for various span thickness ratios, CNT volume fractions, and CNT reinforcement distributions. The result shows that the present theory predicts the responses of the CNTRC beam quite accurately as compared to the existing theories. Some new results are also included for the benchmark solutions of the new research.
... The testing of these spinning CNTs under constant duress was evaluated on the assumption that the MWCNTs were perfectly cylindrical. The results calculated by N. Khandoker et al in [7] showed that the strength of these spinning CNTs can 15 be anywhere between 20 to 90 GPa with a mean of 48 GPa under the assumption. Since the nanotube walls themselves are only held together by relatively weak Van der Waals forces, when a hollow cylindrical MWCNT was considered, the mean value of the tensile strength jumped to 378 GPa [7]. ...
... Carbon nanotubes (CNTs) have piqued the interest of researchers as a reinforcement for polymer-matrix composites due to their unique structural and transport features, such as outstanding modulus and strength, high electrical and thermal conductivities, and great chemical stability, as well as their low densities [15][16][17] II. ...
... Another type of one-dimensional reinforcement is nanotubes. Carbon nanotubes are the most important of these [17]. This category of materials emerged in the early 1990s. ...
Recent advancements in material sciences have underscored the increasing utilization of composite materials, notably polymer-based composites, renowned for their exceptional tensile strength and lightweight characteristics. The tailored fiber structures within these composites, and their strategic placement within the polymer matrix, are pivotal in modifying the resultant composite's properties. This review article systematically examines the diverse attributes of Fiber-Reinforced Polymer (FRP) composites, including their manufacturing techniques, mechanical properties, and application domains. In this article, the role of natural and artificial fibers in the development of FRP composites is discussed. It has also been observed that new research is being done in the direction of quantum dots (QDs) in order to improve some features of FRP composites. A particular focus is placed on how different fiber weaves and orientations impact the overall performance and utility of FRP components. By aggregating and analyzing current research, this paper aims to elucidate the complexities of FRP composites and forecast trends in their development and use. Also, in the final part, a review of the importance of additive manufacturing in the development of FRP composites has been done.
... They also exhibit high electrical conductivity and high heat transfer coefficient. [189][190][191][192] Their application is possible in areas such as electronics, sensors, and biomedicine, including the delivery of drugs to target organs. [193][194][195] They have a large surface area, which enables the conjugation of various molecules on the walls in large quantities. ...
Photodynamic therapy (PDT) is a non-invasive therapy that has made significant progress in treating different diseases, including cancer, by utilizing new nanotechnology products such as graphene and its derivatives. Graphene-based materials have large surface area and photothermal effects thereby making them suitable candidates for PDT or photo-active drug carriers. The remarkable photophysical properties of graphene derivates facilitate the efficient generation of reactive oxygen species (ROS) upon light irradiation, which destroys cancer cells. Surface functionalization of graphene and its materials can also enhance their biocompatibility and anticancer activity. The paper delves into the distinct roles played by graphene-based materials in PDT such as photosensitizers (PS) and drug carriers while at the same time considers how these materials could be used to circumvent cancer resistance. This will provide readers with an extensive discussion of various pathways contributing to PDT inefficiency. Consequently, this comprehensive review underscores the vital roles that graphene and its derivatives may play in emerging PDT strategies for cancer treatment and other medical purposes. With a better comprehension of the current state of research and the existing challenges, the integration of graphene-based materials in PDT holds great promise for developing targeted, effective, and personalized cancer treatments.
... Using carbon nanotubes (CNTs) as the electro-conductive phase (filler) guarantees the acquisition of material comprising both electrostatic [3,4] and electromagnetic shielding. Carbon nanotubes, apart from their tremendous mechanical and thermal properties [5][6][7], have great electrical properties [8] and thus are a natural choice for making conductive polymer composites [3,9,10]. To obtain nanocomposites with the desired properties, there is a need for proper fabrication method usage. ...
In this article, the electromagnetic shielding properties of carbon nanotube–polymer nanocomposites are presented. The composite fabrication technique is spray-drying, the usage of which leads to a uniform dispersion of carbon nanotubes (CNTs) in a polymer matrix. Obtaining good filler dispersion is necessary to form a continuous, electrically conductive network of CNTs inside the polymer matrix. In the described nanocomposites, the network of conductive filler particles acts as an electromagnetic radiation barrier. For this reason, developing a highly effective fabrication method is very important. Also, the method should be simple enough to be easily adopted in an industrial environment. The authors shows in this text that both goals mentioned are achieved. The obtained nanocomposite material not only has electrostatic shielding capabilities but comprises electromagnetic shielding properties, which fulfills the main goal of the presented work. It is also worth mentioning that the developed manufacturing method allows for the usage of different fillers and polymers and thus the fabrication of materials capable of meeting a wide range of requirements.
... These high modulus and strength properties of carbon nanotubes offer a prominent mechanism to enhance both strength and stiffness characteristics of polymer matrix composites [8][9][10]. Especially, it has been addressed that CNTs' outstanding Young's modulus and tensile strength make them one of the most promising reinforcements in nanocomposite manufacturing [11][12][13]. However, uniform dispersion, the waviness, matrix modulus, and CNT/matrix interface bonding condition are among the important factors influencing nanocomposite effective [14]. ...
... The study of fibre reinforced polymer composites continues to be a promising field, with potential for further advancements and applications . [10] The future of fiber reinforced polymer composites is promising, with potential for advancements in various industries such as aerospace, automotive, and electronics. However, challenges such as moisture absorption and recycling of these composites remain, indicating the need for further research in these areas The development of new types of fibers, both synthetic and natural, with enhanced properties is a potential area of future research. ...
Fiber reinforced polymer composites are advanced materials composed of high strength fibers embedded within a polymer matrix, while maintaining a distinct interface between the two components. These composites harness the unique properties of each constituent, resulting in materials with exceptional characteristics. Notably, FRP composites exhibit low density, high tensile strength, and high modulus. This paper presents an extensive review of the research conducted in the field of fibre reinforced polymer composites in recent decades. The focus is on the study of various fibres and their inherent properties, of polymer composites reinforced with both natural and synthetic fibres. The paper also reviews the research works that aim at improving these properties, and thoroughly analyses the mechanisms behind the wear phenomena. The enhancement in properties can be achieved through the appropriate selection of fibre, extraction, treatment of fibres, and interfacial engineering.
... Pasaran bateri ion litium ini dijangka mencapai AS$46 bilion menjelang tahun 2022 dengan kadar pertumbuhan tahunan kompaun sebanyak 10.8% (Szostak 2016). JADUAL 1. Pembandingan antara grafin dan karbon nanotiub (CNT) daripada segi mekanik, kimia dan fizikal (Edwards & Coleman 2013;Novoselov et al. 2012;Pei & Cheng 2012;Pop et al. 2006;Spitalsky et al. 2010;Thostenson et al. 2001 *Ciri-ciri ini bergantung kepada jenis CNT sama ada jenis satu dinding (SWCNT) atau pelbagai dinding (MWCNT), arah lateral atau paksi membujur RAJAH 2. Bidang paten yang terlibat dalam teknologi grafin pada tahun 2015 (Peplow 2015) Seterusnya, kami mengkaji teknologi yang sesuai untuk menghasilkan grafit nanoplat dan grafin multilapisan untuk kegunaan sektor komposit dan penyimpanan tenaga/bateri. Rajah 4 menunjukkan enam cara utama untuk menghasilkan grafin walaupun teknologi ini boleh dibahagikan kepada dua teknik utama iaitu pertumbuhanpemendapan grafin yang melibatkan teknologi vakum dan pengelupasan grafin. ...
ABSTRAK Kertas ini mengkaji teknologi pengelupasan untuk menghasilkan grafin, grafin oksida (GO) dan grafin oksida terturun (rGO). Empat teknologi pengelupasan yang utama dikenal pasti dalam tinjauan ini iaitu pengelupasan mekanik, pengelupasan cecair, interkalasi-pengelupasan dan pengoksidaan-pengelupasan-penurunan. Setiap teknologi ini dibincangkan daripada segi kualiti grafin, grafit nanoplat, GO dan rGO yang dihasilkan dan langkah utama proses termasuk bahan kimia yang digunakan. Kami juga membuat satu kajian kemudah-capaian dan analisis sensitiviti untuk menubuhkan satu kilang penghasilan grafin yang berasaskan teknologi pengelupasan, saiz pasaran grafin dan bahan mentahnya iaitu grafit. Berdasarkan kitar gemburan Gartner, teknologi dan produk yang berasaskan grafin terletak di tiga lokasi iaitu lembah kekecewaan, cerun pencerahan dan dataran tinggi produktiviti.
ABSTRACT This paper surveys the main exfoliation technologies to produce graphene, graphene oxide or reduced graphene oxide (rGO). The four main exfoliation technologies are known as mechanical exfoliation, liquid exfoliation, intercalation-exfoliation and oxidation-exfoliation-reduction. The qualities of graphene, graphite nanoplate, GO and rGO and the different process steps as well as the chemicals used in these four techniques are discussed in this paper. The review also includes the feasibility and sensitivity analysis of setting up exfoliation-based graphene factory, the market size of graphene and its feedstock i.e. graphite. Depending on the application of the graphene-enabled product, the respective technologies are located either in the trough of disillusionment, slope of enlightenment and plateau of productivity in the Gartner hype cycle.
... In recent decades, demand for CNTs has grown in several industries, including mechanical, biomechanical, chemical, aerospace, electronics, and automotive. [1][2][3][4][5] This demand is increased due to the outstanding chemical and mechanical properties of CNTs. The addition of CNTs to elastic structures enhances their mechanical performance. ...
In this work, the static, buckling, and free vibration analysis of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) beam resting on a Pasternak elastic foundation are studied. The secant function-based shear deformation theory (SFSDT) is used for this analysis. This theory fulfills the traction-free boundary conditions at the top and bottom surfaces of the beam, hence there is no need for a shear correction factor. Hamilton’s principle is used to determine the governing differential equations and boundary conditions whereas Navier’s solution technique is used for determining the closed-form solution. The analytical approach is used to examine the deflection, stresses, critical buckling load, and natural frequencies of the FG-CNTRC beam resting on the Pasternak elastic foundation including a shear layer and Winkler springs. To determine the material characteristics of FG-CNTRC beams, the Rule of the mixture is used. Uniform distribution (UD-beam), FG-X beam, FG-O beam, and FG-V beam are the different forms of CNT reinforcement distribution that are used in this study. Considering different span thickness ratios, the volume fraction and distribution of CNT, the Winkler spring, and the shear layer constant factors, all the structural responses are predicted. It is also observed that the present theory predicts the structural responses of the FG-CNTRC beam accurately when compared to other existing theories. A few new results are also included as the benchmark solutions for the new research.
... A number of polymorphic modifications of the carbon structure have already found application. For example, the addition of carbon nanotubes to polymeric substances has been developed in new composite structural materials [1][2][3]. At the same time, studies have been carried out to create materials with high hardness and excellent electrical conductivity based on polymorphic carbon structures [4]. ...
... Many literatures have reported that CNTs as a reinforcement improves mechanical and thermal properties of MMCs. [3][4][5][6][7][8][9][10][11][12][13][14] Choi et al 15 reported high yield stress (600 MPa) and very low coefficient of friction (<0.1) for the ultrafine-grained Al 2024 alloy reinforced with 4.5 vol% of MWCNTs fabricated by powder metallurgy (PM) route. Bakshi et al 16 reported reduction of wear volume by 68% for 5 wt% CNTs reinforced with aluminum-silicon composites produced by plasma spraying technique. ...
In order to improve the wear and frictional behavior of the aluminum metal matrix composites, carbon nanotube, and fly ash were added as reinforcements. Powder metallurgy technique was used to fabricate the hybrid metal matrix composites. Experimentations were carried out using pin on disc type wear test rig. The analyzed experimental results showed that, in comparison to the pure aluminum and mono reinforcement combination, the wear loss and coefficient of friction of hybrid metal matrix composites were greatly reduced. It was noted that compared to pure aluminum wear loss was decreased to 89.58%, 86.97%, 83.3% by adding 0.25, 0.5, 0.75 wt% carbon nanotube (CNT), respectively. By the addition of 4, 8 and 16 wt% FA to pure Al wear loss was decreased to 83.85%, 89.58%, and 78.12%, respectively. It was also noted that compared to Al/8 wt% FA mono reinforced composites, wear loss was decreased to 77%, 71.26%, and 53.22% with the addition of 0.25, 0.5, 0.75 wt% CNT, respectively. With the addition of 4, 8, 16 wt% FA, wear loss decreased to 81%, 88%, and 75% over Al/0.25 wt% CNT composites, respectively. The microstructural study of the worn‐out surfaces revealed low abrasive and adhesive wear by the presence of carbon nanotubes and fly ash in aluminum metal matrix. The reinforcing mechanisms of the wear and frictional properties were also discussed.
... The discovery of carbon nanotubes (CNTs) in 1991 by Iijima [1] was an influential achievement because of their strength, low weight, and high mechanical, thermal, and electrical properties [2,3]. To take advantage of these extraordinary physical properties, CNT-reinforced composites are developed as an emerging class of advanced lightweight nanocomposites [4][5][6][7]. ...
Electrical conductivity of most polymeric insulators can be drastically enhanced by introducing a small volume fraction [Formula: see text] of conductive nanofillers. These nanocomposites find wide-ranging engineering applications from cellular metamaterials to strain sensors. In this work, we present a mathematical model to predict the effective electrical conductivity of carbon nanotubes (CNTs)/polymer nanocomposites accounting for the conductivity, dimensions, volume fraction, and alignment of the CNTs. Eshelby’s classical equivalent inclusion method (EIM) is generalized to account for electron-hopping—a key mechanism of electron transport across CNTs, and is validated with experimental data. Two measurements, namely, the limit angle of filler orientation and the probability distribution function, are used to control the alignment of CNTs within the composites. Our simulations show that decreasing the angle from a uniformly random distribution to a fully aligned state significantly reduces the transverse electrical conductivity, while the longitudinal conductivity shows less sensitivity to angle variation. Moreover, it is observed that distributing CNTs with non-uniform probability distribution functions results in an increase in longitudinal conductivity and a decrease in transverse conductivity, with these differences becoming more pronounced as the volume fraction of CNTs is increased. A reduction in CNT length decreases the effective electrical conductivity due to the reduced number of available conductive pathways while reducing CNT diameter increases the conductivity.
... Carbon nanotubes p0065 CNTs are at the forefront of nanotechnology research for their extraordinary physicochemical properties since their discovery and can be used safely in water treatment applications [6]. CNTs are long, thin, and cylindrical graphite sheets, in the nanorange, rolled up into tubes with a latticework fence-like appearance ( Fig. 20.3A & B) [7]. Single-walled CNTs (SWCNTs) may form when a single layer of graphite is rolled into a seamless cylinder. ...
... The Single-Walled Carbon Nanotube (SWCNT) is the progenitor of 1D materials and is characterized by a single layer of sp 2 hybridized carbon atoms rolled up to form a cylindrical structure. The extensive surface area, the π conjugation inside and outside the nanotube and the consequent high thermal and electrical conductivity are properties that are useful for a variety of potential technological applications [1]. ...
Titanium dioxide nanotubes (TNT) have been extensively studied because of their unique properties, which make such systems ideal candidates for biomedical application, especially for the targeted release of drugs. However, knowledge about the properties of TiO2 nanotubes with typical dimensions of the order of the nanometer is limited, especially concerning the adsorption of molecules that can be potentially loaded in actual devices. In this work, we investigate, by means of simulations based on hybrid density functional theory, the adsorption of Vitamin C molecules on different nanotubes through a comparative analysis of the properties of different structures. We consider two different anatase TiO2 surfaces, the most stable (101) and the more reactive (001)A; we evaluate the role of the curvature, the thickness and of the diameter as well as of the rolling direction of the nanotube. Different orientations of the molecule with respect to the surface are studied in order to identify any trends in the adsorption mechanism. Our results show that there is no preferential functional group of the molecule interacting with the substrate, nor any definite spatial dependency, like a rolling orientation or the concavity of the nanotube. Instead, the adsorption is driven by geometrical factors only, i.e., the favorable matching of the position and the alignment of any functional groups with undercoordinated Ti atoms of the surface, through the interplay between chemical and hydrogen bonds. Differently from flat slabs, thicker nanotubes do not improve the stability of the adsorption, but rather develop weaker interactions, due to the enhanced curvature of the substrate layers.
... (1) Colonization step: Cell surface charge, van der Waals force, hydrophobicity, and electrostatic force could help microorganisms to reversibly adhere to the covering of objects [18]. (2) Aggregation step: microorganisms swim in the liquid or aggregate on the solid surface to form microcolonies by synthesizing rotating flagella [19]. (3) Maturation step: mature biofilm microcolonies are surrounded by water transport channels, which can transport nutrients, enzymes, metabolites, and waste products. ...
Bacterial infections continue to pose a significant global health challenge, with the emergence of multidrug-resistant (MDR) bacteria and biofilms further complicating treatment options. The rise of pan-resistant bacteria, coupled with the slow development of new antibiotics, highlights the urgent need for new therapeutic strategies. Nanotechnology-based biosensors offer fast, specific, sensitive, and selective methods for detecting and treating bacteria; hence, it is a promising approach for the diagnosis and treatment of MDR bacteria. Through mechanisms, such as destructive bacterial cell membranes, suppression of efflux pumps, and generation of reactive oxygen species, nanotechnology effectively combats bacterial resistance and biofilms. Nano-biosensors and related technology have demonstrated their importance in bacteria diagnosis and treatment, providing innovative ideas for MDR inhibition. This review focuses on multiple nanotechnology approaches in targeting MDR bacteria and eliminating antimicrobial biofilms, highlighting nano-biosensors via photodynamics-based biosensors, eletrochemistry biosensors, acoustic-dynamics sensors, and so on. Furthermore, the major challenges, opportunities of multi-physical-field biometrics-based biosensors, and relevant nanotechnology in MDR bacterial theranostics are also discussed. Overall, this review provides insights and scientific references to harness the comprehensive and diverse capabilities of nano-biosensors for precise bacteria theranostics and MDR inhibition.
... Incorporating CNTs into geopolymers holds promise for substantial improvements in their mechanical and functional properties, owing to the remarkable strength, electrical conductivity, and high aspect ratio shown by these nanomaterials [27,28]. Prior studies [29][30][31][32] have shown that incorporating CNTs can potentially enhance the flexural strength, fracture toughness, and electrical conductivity of geopolymers. The mechanical characteristics of CNT-containing geopolymers are strongly influenced by the dispersion effect of CNT inside the geopolymer matrix and the interaction between these materials [29,33]. ...
Underwater concrete finds application in many underwater structures, such as port facilities, bridge footings, tunnels, and analogous infrastructural elements. In recent years, a growing significance has been attributed to the investigation of sustainable geopolymer studies conducted on land. Hence, the necessity of researching underwater sustainable geopolymer composites emerged. This study produced metakaolin and slag-based geopolymer paste samples containing carbon nanotubes (CNTs) cast and cured in a dry environment, lake water, and seawater. Also, the present work examined the relation between CNTs and metakaolin and slag-based geo-polymers in the context of underwater cast and curing. In order to achieve the intended objective, geopolymer samples with CNTs at 0%, 0.05%, 0.15%, and 0.25% ratios poured in under three distinct environments were prepared and subjected to various tests. Subsequently, examinations were conducted to determine the mechanical and microstructural characteristics of the geopolymer samples poured in the three environments. The conducted tests encompassed compressive strength assessment, temperature measurements, pH measurements, and microstructural analyses. Consequently, the compressive strength of the 0.25% CNT geopolymer samples increased by 32.7% and 34.4% compared to the CNT free-geopolymer samples poured in lake water and seawater, respectively. Thus, in this study, underwater geopolymer samples with compressive strengths of 46 MPa and 49.6 MPa were produced in lake water and seawater, respectively.
Copper and copper‐based materials are widely used in power electronics, automobiles, mechanical manufacturing and high‐tech manufacturing fields such as aerospace, telecommunications and integrated circuits owing to their comprehensive advantages in mechanical, electrical conductivity and processing properties. With the rapid development of technology, many emerging technical fields have introduced more challenging requirements for the electrical conductivity of copper. This article reviews the research status of high‐conductivity copper‐based materials and introduces three methods to improve electrical conductivity, including purification, alloying and addition of nanocarbon materials. We summarise the advantages, disadvantages and future development trends of methods for improving copper conductivity. The key to producing high‐conductivity copper‐based materials is development of low‐cost, continuous and stable processes.
Екструзійне обладнання широко використовуються у виробництві полімерних матеріалів. Одним з актуальних питань яке виникає при дослідженні процесів отримання полімерних виробів методом екструзії є питання вивчення абразивного зносу від якого може залежить ефективність роботи обладнання, тривалість та надійність його роботи. В контексті абразивного зносу, процес, який потребує уваги - це екструзія полімерних матеріалів з вуглецевими нанотрубками. Метою даної роботи є розробка чисельної методики визначення еволюції абразивного зносу матеріалу обладнання робочої зони екструдера в процесі переробки наномодифікованих полімерних гранул та визначення терміну життєвого циклу експлуатації цього обладнання з метою підвищення параметрів їх довговічності. Конкретні цілі дослідження включають: 1) визначення впливу вмісту ВНТ у ПВХ на швидкість зносу сталевої поверхні екструдера; 2) аналіз залежності між тертям і вмістом ВНТ у полімерному композиті; 3) встановлення оптимальних умов екструзії для мінімізації абразивного зносу сталевої поверхні; 4) порівняння результатів моделювання з експериментальними даними для перевірки достовірності моделі. Робота спрямована на розуміння процесів, які відбуваються під час екструзії нанокомпозитів та їх вплив на зносостійкість матеріалів обладнання, що може сприяти вдосконаленню технологічних процесів та забезпеченню більш тривалої та ефективної роботи екструдерів у виробничих умовах.
This review aims to capture the current state of electrochemical actuators and set a trajectory for future innovation in this field.
A sizing agent mainly consisting of polyethersulfone and acidified multi‐walled carbon nanotubes (MWCNT) was developed for surface modification of carbon fibers (CF) to enhance the interfacial bond and to form carbon fiber‐carbon nanotube (CF‐MWCNT) multiscale reinforcements. To prepare the modified carbon fiber/epoxy resin composites (CFRP), a vacuum molding technique was used in this study. The effects of the MWCNT‐containing sizing agent on the morphology and chemical structure of the CF surface were observed by scanning electron microscopy and Fourier transform infrared spectroscopy. The influence of MWCNT length and content on the mechanical properties of CFRP were also studied. The experimental results showed that the strength of the CFRP decreased with the increase of MWCNT length, and the MWCNT with a content of 0.05 wt% had a good reinforced effect on the CFRP. After the sizing treatment, the interlaminar shear strength (ILSS) of the CFRP is increased. These enhancements are attributed to the improved mechanical bonding and chemical bonding between CF and resin matrix. The MWCNT provides nanosized rough surface to CF and these acidified MWCNTs attached to the surface of CF with polar oxygen‐containing functional groups improve the compatibility with reinforcement and resin matrix.
Highlights
Carbon fiber was modified by a sizing agent mainly consisting of polyethersulfone and acidified carbon nanotube (CNT).
CNTs enhance the interfacial chemical bonding and mechanical bonding.
The CNT length affects the mechanical properties of the carbon fiber/epoxy resin composites (CFRP).
The modified carbon fiber has enhanced the mechanical properties of the CFRP.
Advancements in scientific research have always been the driving force behind human progress, unlocking new realms of understanding and pushing the boundaries of what is possible. In the dynamic and ever-evolving field of chemical science, the quest for knowledge and innovation is relentless. "Advances in Chemical Science: Exploring New Frontiers" stands as a testament to the collective efforts of pioneering researchers who have ventured into uncharted territories, pushing the frontiers of chemical knowledge to unprecedented heights. This edited volume serves as a comprehensive compendium of the latest breakthroughs and emerging trends in chemical science. As the scientific community continues to unravel the complexities of matter and explore the intricacies of chemical interactions, this book provides a snapshot of the diverse and groundbreaking research that defines the contemporary landscape of the discipline. The chapters contained within this volume reflect the multidisciplinary nature of modern chemical science, encompassing a wide array of subfields such as organic chemistry, inorganic chemistry, physical chemistry, biochemistry, nano technology, chemical biology and materials science. From fundamental theoretical studies to practical applications, each contribution illuminates a unique facet of chemical science, contributing to the mosaic of knowledge that shapes our understanding of the world around us. The journey through "Advances in Chemical Science" begins with a thought-provoking exploration of theoretical frameworks that underpin our understanding of chemical phenomena. From there, the reader is guided through a spectrum of research endeavors, ranging from the synthesis of novel compounds to the design of innovative materials with tailored properties. The interplay between theory and experiment, a hallmark of successful scientific inquiry, is exemplified in each chapter, underscoring the collaborative efforts of theorists and experimentalists alike. In addition to traditional areas of study, this volume also delves into the burgeoning intersections of chemical science with other disciplines. The exploration of the interface between chemistry and biology, the development of environmentally sustainable practices, and the application of advanced analytical techniques showcase the dynamic and interconnected nature of contemporary chemical research. I hope that "Advances in Chemical Science: Exploring New Frontiers" will inspire researchers, students, and enthusiasts to delve into the fascinating world of chemical science. May the discoveries within these pages spark new ideas, foster collaborations, and ignite a passion for pushing the boundaries of knowledge. Together
A carbon nanotube-reinforced composite (CNTRC) beam resting on a Pasternak elastic foundation which consists of a Winkler spring and shear layer is investigated to obtain the bending, buckling, and free vibration responses using inverse hyperbolic shear deformation theory (IHSDT). The shear strain shape function is employed in this study to construct a nonlinear distribution of transverse shear stresses. The theory fulfills the traction-free boundary conditions on both the upper and lower surfaces of the beam, hence no shear correction factor is needed.
Hamilton’s principle is employed to derive the equation of motion and Navier’s solution technique is used to determining the closed-from solution for the CNTRC beam on the Pasternak foundation. To determine the material properties of CNTRC beams, the rule of mixture is used. In this study, various types of CNT reinforcement distribution are used such as uniform distribution (UD-Beam), X-Beam, O-Beam, and V-Beam.
The deformation, stresses, critical buckling load, and natural frequencies of the simply supported CNTRC beam resting on the Pasternak elastic foundation are investigated using an analytical approach, that takes into account various length-to-thickness ratios, CNT volume fraction, CNT distribution, Winkler spring constant factor, and shear layer constant factor.
The present theory predicts the structural responses quite accurately compared to the available theories in the literature. Some new results are also included for the benchmark solutions for the new research.
Carbon is one of the highly explored materials because of its exceptional properties such as high chemical stability, superior mechanical strength, catenation property, anisotropy and conductivity. Researchers have investigated numerous morphologies of carbon, specially at the nanoscale for their utilization in the advancements of various operational areas. This chapter deals with the overview of various carbon based nanoadsorbents (CNs): Carbon nanotubes (CNTs), Graphene and its derivatives, fullerenes and carbon quantum dots (CQDs). The structure, exceptional properties and synthetic strategies of these nanoadsorbents have been discussed and compared. The shifts and advancements in these strategies were observed towards a greener perspective, so that CNs can be adopted as a suitable and efficient alternative for conventional techniques of water purification.
From their foundational role in electronics to their pivotal contributions in the structural domain, carbon nanotubes (CNTs) exemplify a revolutionary nanomaterial with broad applications. The chemical inertness of the CNT surface is a primary limitation that restricts the full utilization of CNTs for mass use in several applications. Herein, works performed on the development of surface‐modified CNTs known as periodically patterned structures are focused. Different structures including shish kebab, nanofiber, nanoflower, and cheetah skin CNT have been studied. Periodic patterning on CNTs offers a chance to improve the nanotube's surface properties and roughness, facilitating better interaction with a matrix. Additionally, the fully controllable processing procedure opens significant opportunities for additional modification and attachment of phases onto specific areas of periodically patterned CNTs. The periodic patterning aspect holds promise for the mass production of surface‐modified CNTs, enhancing their surface multifunctionality. This advancement has the potential to cater to a diverse array of applications, offering improved surface functionality in a mass‐production setting.
In this paper, the quantum effects of fine scaling on the buckling behavior of carbon nanotubes (CNTs) under axial loading are investigated. Molecular mechanics and quantum mechanics are respectively utilized to study the buckling behavior and to obtain the molecular mechanics coefficients of fine-scale nanotubes. The results of buckling behavior of CNTs with different chiralities with finite and infinite dimensions are given, and a comparison study is presented on them. The differences between finite and infinite nanotubes reflect the quantum effects of fine scaling on the buckling behavior. In addition, the results show that the dimensional changes highly affect the mechanical properties and the buckling behavior of CNTs to certain dimensions. Moreover, dimensional changes have a significant effect on the critical buckling strain. Beside, in addition to the structure dimensions, the arrangement of structural and boundary atoms have a major influence on the buckling behavior.
Nanotechnology is revolutionising different areas from manufacturing to therapeutics in the health field. Carbon nanotubes (CNTs), a promising drug candidate in nanomedicine, have attracted attention due to their excellent and unique mechanical, electronic, and physicochemical properties. This emerging nanomaterial has attracted a wide range of scientific interest in the last decade. Carbon nanotubes have many potential applications in cancer therapy, such as imaging, drug delivery, and combination therapy. Carbon nanotubes can be used as carriers for drug delivery systems by carrying anticancer drugs and enabling targeted release to improve therapeutic efficacy and reduce adverse effects on healthy tissues. In addition, carbon nanotubes can be combined with other therapeutic approaches, such as photothermal and photodynamic therapies, to work synergistically to destroy cancer cells. Carbon nanotubes have great potential as promising nanomaterials in the field of nanomedicine, offering new opportunities and properties for future cancer treatments. In this paper, the main focus is on the application of carbon nanotubes in cancer diagnostics, targeted therapies, and toxicity evaluation of carbon nanotubes at the biological level to ensure the safety and real-life and clinical applications of carbon nanotubes.
Metal-sulfur (M-S) batteries with high theoretical energy densities and acceptable production costs have placed great expectations on the large-scale energy storage applications in the post-Li-ion battery (LIBs) era. However, the serious shuttle effect of polysulfides and high-reactivity metal anodes with unstable stripping/plating electrochemistry significantly limited their performance and applications. This chapter briefly introduces the working principle and challenges of M-S batteries as well as the structures and manipulation of carbon nanotubes (CNTs). Emphatically, the important progress and mechanism of CNTs-based materials in addressing the above-mentioned issues via acting as efficient hosts of S cathode and metal anode, as well as functionalized interlayers and artificial solid electrolyte interphase (SEI) film, are summarized. Finally, a few key points that need to be particularly concerned are proposed. These breakthroughs are believed to promote the understanding of the fundamental electrochemistry in M-S batteries as well as accelerate their rational design, development, and commercialization.
Gene therapeutics are promising for treating diseases at the genetic level, with some already validated for clinical use. Recently, nanostructures have emerged for the targeted delivery of genetic material. Nanomaterials, exhibiting advantageous properties such as a high surface-to-volume ratio, biocompatibility, facile functionalization, substantial loading capacity, and tunable physicochemical characteristics, are recognized as non-viral vectors in gene therapy applications. Despite progress, current non-viral vectors exhibit notably low gene delivery efficiency. Progress in nanotechnology is essential to overcome extracellular and intracellular barriers in gene delivery. Specific nanostructures such as carbon nanotubes (CNTs), carbon quantum dots (CQDs), nanodiamonds (NDs), and similar carbon-based structures can accommodate diverse genetic materials such as plasmid DNA (pDNA), messenger RNA (mRNA), small interference RNA (siRNA), micro RNA (miRNA), and antisense oligonucleotides (AONs). To address challenges such as high toxicity and low transfection efficiency, advancements in the features of carbon-based nanostructures (CBNs) are imperative. This overview delves into three types of CBNs employed as vectors in drug/gene delivery systems, encompassing their synthesis methods, properties, and biomedical applications. Ultimately, we present insights into the opportunities and challenges within the captivating realm of gene delivery using CBNs.
We have studied the low frequency vibrational modes and the structural rigidity of long graphitic carbon tubules consisting of 100, 200, and 400 atoms. Our calculations have been performed using an empirical Keating Hamiltonian with parameters determined from first principles. We have found the “beam bending” mode to be one of the softest modes in these structures. The corresponding beam rigity of a “bucky tube” is compared to an found to exceed the highest values found in presently available materials.
Experimental observations of various deformation and fracture modes under compression of single multiwalled carbon nanotubes, obtained as a result of embedment within a polymeric film, are reported. Based on a combination of experimental measurements and the theory of elastic stability, the compressive strengths of thin- and thick-walled nanotubes are found to be about 2 orders of magnitude higher than the compressive strength of any known fiber.
Carbon nanotubes–Fe–Al2O3 massive composites have been prepared by hot-pressing the corresponding composite powders, in which the carbon nanotubes are arranged in bundles smaller than 100nm in diameter and several tens of micrometers long, forming a web-like network around the Fe–Al2O3 grains. In the powders, the quantity and the quality of the carbon nanotubes both depend on the Fe content (2, 5, 10, 15 and 20wt%) and on the reduction temperature (900 or 1000°C) used for the preparation. Bundles of carbon nanotubes are present in the hot-pressed materials but with a decrease in quantity in comparison to the powders. This phenomenon appears to be less pronounced for the powders containing higher-quality carbon, i.e. a higher proportion of nanotubes with respect to the total carbon content. The presence of carbon as nanotubes and other species (Fe carbides, thick and short tubes, graphene layers) in the powders modifies the microstructure of the hot-pressed specimens in comparison to that of similar carbon-free nanocomposites: the relative densities are lower, the matrix grains and the intergranular metal particles are smaller. The fracture strength of most carbon nanotubes–Fe–Al2O3 composites is only marginally higher than that of Al2O3 and are generally markedly lower than those of the carbon-free Fe–Al2O3 composites. The fracture toughness values are lower than or similar to that of Al2O3. However, SEM observations of composite fractures indicate that the nanotubes bundles, which are very flexible, could dissipate some fracture energy.
Well-aligned bundles of single-wall carbon nanotubes under tensile stresses were observed to fracture in real-time by transmission electron microscopy. The expansion of elliptical holes in the polymer matrix results in a tensile force in bridging nanotubes. The polymer matrix at both ends of the bundles deforms extensively under the tension force, and fracture of the nanotubes occurs in tension within the polymer hole region rather than in shear within the gripping polymer region at the ends of the bundles. This provides evidence of significant polymer-nanotube wetting and interfacial adhesion.
We report high resolution electron microscope (HREM) observations and atomistic simulations of the bending of single and multi-walled carbon nanotubes under mechanical duress. Single and multiple kinks are observed at high bending angles. Their occurrence is quantitatively explained by the simulations, which use a realistic many-body potential for the carbon atoms. We show that the bending is fully reversible up to very large bending angles, despite the occurrence of kinks and highly strained tube regions. This is due to the remarkable flexibility of the hexagonal network, which resists bond breaking and bond switching up to very high strain values.
Novel ceramic matrix nanocomposites, that contain in-situ formed carbon nanotubes have been prepared in the form of powders and massive materials. In the powders, the nanotubes are very long (several tens of μm) and are arranged in bundles making a kind of web around the metal-oxide grains. In the massive composites, a significant amount of carbon nanotube bundles, albeit lower than in the powders, has been observed. The bundles, several μm long, are not larger than 100 nm in diameter and appear to be remarkably flexible. The densification, microstructural characteristics and mechanical properties are presented and compared with those of pure alumina and carbon-free iron-alumina nanocomposites.
Analytical expressions for the velocities of the longitudinal and the torsional sound waves in single-walled carbon nanotubes are derived using Born’s perturbation technique within a lattice-dynamical model. These expressions are compared to the formulas for the velocities of the sound waves in an elastic hollow cylinder from the theory of elasticity to obtain analytical expressions for the Young’s and shear moduli of nanotubes. The calculated elastic moduli for different chiral and achiral (armchair and zigzag) nanotubes using force constants of the valence force field type are compared to the existing experimental and theoretical data.
Owing to their single atom-layer structure, actual bending stiffness of single-walled carbon nanotubes is much lower than that given by the elastic shell model if the commonly defined representative thickness is used. In this paper, it is proposed that the effective bending stiffness of single-walled nanotubes should be regarded as an independent material parameter not related to the representative thickness by the classic bending stiffness formula. Based on this concept, the modified formulas for the critical axial strain and the wavelength of axially compressed buckling are found to agree well with known data of molecular-dynamic simulations. On the other hand, in contrast to single-walled nanotubes, bending stiffness of multiwalled nanotubes is found to be well estimated by the classic bending stiffness formula when adjacent nanotubes are squeezed severely so that the induced high friction barrier prevents interlayer slips. In particular, these results offer a plausible interpretation for the wavelength of large-strain local buckling of multiwalled carbon nanotubes under bending observed by Falvo et al. [Nature (London) 389, 582 (1997)].
In this paper, the theory of lattice dynamics of single-walled carbon nanotubes is presented. The screw symmetry of the system is used to reduce the rank of the dynamical matrix to six, independent of the number of atoms in the unit cell. Calculations of the lattice dynamics are carried out within a valence force field model and of the Raman intensity—within a bond-polarizability model. It is found that the breathing mode frequency is inversely proportional to the radius of the tube that can be used for the characterization of the samples on the basis of Raman-scattering data. The results for the Raman intensity are compared to available Raman spectra.
A modified elastic honeycomb model is presented to study elastic buckling of single-walled carbon nanotube ropes under high pressure. Simple formula is given for the critical pressure as a function of the Young’s modulus and the thickness-to-radius ratio. For single-walled carbon nanotubes of diameters around 1.3 nm, the predicted critical pressure is about 1.8 GPa, which is in excellent agreement with the known data reported in the literature. This suggests that the elastic buckling would be responsible for the pressure-induced abnormalities observed for vibration modes and electric resistivity of single-walled carbon nanotube ropes.
The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a “nanostressing stage” located
within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope
and was recorded on video. The MWCNTs broke in the outermost layer (“sword-in-sheath” failure), and the tensile strength of
this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves
for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube
fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
Vertically aligned carbon nanotubes were synthesized on Ni-deposited Si substrates using microwave plasma-enhanced chemical vapor deposition. The grain size of Ni thin films varied with the rf power density during the rf magnetron sputtering process. We found that the diameter, growth rate, and density of carbon nanotubes could be controlled systematically by the grain size of Ni thin films. With decreasing the grain size of Ni thin films, the diameter of the nanotubes decreased, whereas the growth rate and density increased. High-resolution transmission electron microscope images clearly demonstrated synthesized nanotubes to be multiwalled. © 2000 American Institute of Physics.
An elastic model is presented to study infinitesimal buckling of a double-walled carbon nanotube under axial compression. A simple formula is derived for the critical axial strain, which clearly indicates the role of the van der Waals forces between the inner and outer tubes characterized by two parameters. In particular, the analysis shows that inserting an inner tube into a single-walled nanotube does not increase the critical axial strain as compared to the single-walled nanotube under otherwise identical conditions, despite the fact that the total critical axial force of the double-walled nanotube could be increased due to an increase in the cross-sectional area. © 2000 American Institute of Physics.
We report the observation of single nanotube fragmentation, under tensile stresses, using nanotube-containing thin polymeric films. Similar fragmentation tests with single fibers instead of nanotubes are routinely performed to study the fiber-matrix stress transfer ability in fiber composite materials, and thus the efficiency and quality of composite interfaces. The multiwall nanotube-matrix stress transfer efficiency is estimated to be at least one order of magnitude larger than in conventional fiber-based composites. © 1998 American Institute of Physics.
To probe the one-dimensional nature of single-wall carbon nanotubes (SWNTs) in bulk samples, we have devised a simple method for generating fibers of aligned SWNTs. We measured polarization-dependent Raman spectra on the oriented fibers. Contrary to what is expected from their theoretically assigned vibration-mode symmetries, all the Raman line intensities are observed to decrease in nearly equal amounts for the 647.1 nm laser excitation polarized perpendicular to the fiber axis versus that polarized parallel to the fiber axis. The effect is explained as a loss of resonance Raman scattering for the perpendicular polarization case. © 2000 American Institute of Physics.
The Young's modulus, strength, and toughness of nanostructures are important to proposed applications ranging from nanocomposites
to probe microscopy, yet there is little direct knowledge of these key mechanical properties. Atomic force microscopy was
used to determine the mechanical properties of individual, structurally isolated silicon carbide (SiC) nanorods (NRs) and
multiwall carbon nanotubes (MWNTs) that were pinned at one end to molybdenum disulfide surfaces. The bending force was measured
versus displacement along the unpinned lengths. The MWNTs were about two times as stiff as the SiC NRs. Continued bending
of the SiC NRs ultimately led to fracture, whereas the MWNTs exhibited an interesting elastic buckling process. The strengths
of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical
values. Because of buckling, the ultimate strengths of the stiffer MWNTs were less than those of the SiC NRs, although the
MWNTs represent a uniquely tough, energy-absorbing material.
We have induced large elastic strains in ropes of single-wall carbon nanotubes, using an atomic force microscope in lateral force mode. Freely suspended ropes were observed to deform as elastic strings with tension proportional to elongation. Ropes were elastically deformed over > 10 cycles without showing signs of plastic deformation. The maximum strain observed, 5.8 +/- 0.9%, gives a lower bound of 45 +/- 7 GPa for the tensile strength (specifically, yield stress) of single-wall nanotube ropes. (C) 1999 American Institute of Physics. [S0003-6951(99)04325-9].
Large-scale molecular dynamics simulations were used to study the response of carbon nanotubes to a tensile load. Plastic or brittle behaviors can occur depending upon the external conditions and tube symmetry. All tubes rule: brittle at high strain and low temperature, while at low strain and high temperature: armchair (tl,rr) nanotubes can be completely or partially ductile. In zigzag (n,0) tubes ductile behavior is expected for tubes with n < 14, while larger tubes are completely brittle. In both cases the curvature determines the mechanical response. [S0031-9007(98)07696-0].
Nanoscale composites have been a technological dream for many years. Recently, increased interest has arisen in using carbon nanotubes as a filler for polymer composites, owing to their very small diameters on the order of 1 nm, very high aspect ratios of 1000 or more, and exceptional strength with Young's modulus of approximately 1 TPa. A key issue for realizing these composites is obtaining good interfacial adhesion between the phases. In this work, we used force-field based molecular mechanics calculations to determine binding energies and sliding frictional stresses between pristine carbon nanotubes and a range of polymer substrates, in an effort to understand the factors governing interfacial adhesion. The particular polymers studied were chosen to correspond to reported composites in the literature. We also examined polymer morphologies by performing energy-minimizations in a vacuum. Hydrogen bond interactions with the ∏-bond network of pristine carbon nanotubes were found to bond most strongly to the surface, in the absence of chemically altered nanotubes. Surprisingly, we found that binding energies and frictional forces play only a minor role in determining the strength of the interface, but that helical polymer conformations are essential.
An elastic model is presented for column buckling of a multiwalled carbon nanotube embedded within an elastic medium. The emphasis is placed on the role of interlayer radial displacements between adjacent nano-tubes. In contrast to an existing model which treats the entire multiwalled nanotube as a single column, the present model treats each of the nested tubes as an individual column interacting with adjacent nanotubes through the intertube van der Waals forces. Based on this model, a condition is derived in terms of the parameters describing the van der Waals interaction, under which the effect of the noncoincidence of all deflected column axes is so small that it does not virtually affect the critical axial strain. In particular, this condition is met for carbon multiwalled nanotubes provided that the half-wavelength of the buckling mode is much larger than the outermost diameter. In this case, the critical axial strain can be predicted correctly by the existing single-column model. On the other hand, the existing model could overestimate the critical axial strain when the half-wavelength of the buckling mode is close to or smaller than the outermost radius.
We describe, in detail, a readily scalable purification process capable of handling single-wall carbon nanotube (SWNT) material in large batches. Characterization of the resulting material by SEM, TEM, XRD, Raman scattering, and TGA shows it to be highly pure. Resistivity measurements on freestanding mats of the purified tubes are also reported. We also report progress in scaling up SWNT production by the dual pulsed laser vaporization process. These successes enable the production of gram per day quantities of highly pure SWNT, which should greatly facilitate investigation of material properties intrinsic to the nanotubes.
A 100,000 g/mol polyethylene molecule has a cross section of about 0.5 nm and a contour length of about 0.9 μm. A typical single-walled carbon nanotube (SWCNT) has a cross-section of about 1 nm and a contour length of about 1 μm. The critical difference from a physics perspective between these two molecules is that the persistence length of the former is about 0.6 nm and the persistence length of the latter is reported as ≈ 30 μm.1 One can make a similar comparison between SWCNTs and liquid crystalline polymer molecules; in this case the key difference is that the length of the former is much larger than the length of the latter. This paper presents what is believed to be a synergistic type of behavior that is possibly related to the similarity in size of the two high aspect-ratio materials, the fact that single-walled carbon nanotubes can increase the jump in heat capacity at the glass transition. Other measurements involving the behavior of fictive temperatures and activation energies measured from calorimetric studies are also given.
During experiments aimed at understanding the mechanisms by which long-chain carbon molecules are formed in interstellar space and circumstellar shells1, graphite has been vaporized by laser irradiation, producing a remarkably stable cluster consisting of 60 carbon atoms. Concerning the question of what kind of 60-carbon atom structure might give rise to a superstable species, we suggest a truncated icosahedron, a polygon with 60 vertices and 32 faces, 12 of which are pentagonal and 20 hexagonal. This object is commonly encountered as the football shown in Fig. 1. The C60 molecule which results when a carbon atom is placed at each vertex of this structure has all valences satisfied by two single bonds and one double bond, has many resonance structures, and appears to be aromatic.
A simple method was used to assemble single-walled carbon nanotubes into indefinitely long ribbons and fibers. The processing consists of dispersing the nanotubes in surfactant solutions, recondensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. Flow-induced alignment may lead to a preferential orientation of the nanotubes in the mesh that has the form of a ribbon. Unlike classical carbon fibers, the nanotube fibers can be strongly bent without breaking. Their obtained elastic modulus is 10 times higher than the modulus of high-quality bucky paper.
The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a "nanostressing stage" located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer ("sword-in-sheath" failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
The elastic constants, Young's and bulk moduli, and Poisson ratio of triangular close-packed crystal lattices of single-walled carbon nanotubes are calculated for various tube types using analytical expressions. Some of these quantities exhibit up to three different regimes of behavior which are due to the interplay of the intertube van der Waals forces and the elastic forces in the tubes. These regimes are most prominent in the case of the bulk modulus which has a maximal value of 38 GPa at tube radius R 6 A and decreases for larger radii.
Single walled carbon nanotubes (SWNTs) were dispersed in isotropic petroleum pitch matrices to form nanotube composite carbon fibers with enhanced mechanical and electrical properties. We find that the tensile strength, modulus, and electrical conductivity of a pitch composite fiber with 5 wt % loading of purified SWNTs are enhanced by ∼ 90%, ∼150%, and 340% respectively, as compared to the corresponding values in unmodified isotropic pitch fibers. These results serve to highlight the potential that exits for developing a spectrum of material properties through the selection of the matrix, nanotube dispersion, alignment, and interfacial bonding.
Laser ablation products from fullerene materials have been studied by transmission electron microscopy and Raman spectroscopy. Using nickel and cobalt as a catalyst, single-wall carbon nanotubes were produced at an ambient temperature of 400 degrees C. The results were compared with those using graphite as starting materials. It is suggested that the formation of single-wall carbon nanotubes is controlled by both the availability of proper precursors and the activity of the metal catalyst. (C) 1999 American Institute of Physics. [S0003-6951(99)02146-4].
Aligned multiwall carbon nanotubes have been grown on silicon substrates by microwave plasma enhanced chemical vapor deposition using methane/ammonia mixtures. Scanning electron microscopy shows that the nanotubes are well aligned with high aspect ratio and growth direction normal to the substrate. Transmission electron microscopy reveals that the majority phase has a bamboo-like structure. Data are also presented showing process variable effects on the size and microstructure of the aligned nanotubes, giving insight into possible nucleation and growth mechanisms for the process.
The nucleation and growth of aligned multiwall carbon nanotubes by microwave plasma-enhanced chemical vapor deposition have been studied. The nanotubes nucleate and grow from catalytic cobalt islands on a silicon substrate surface, with both their diameter and length dependent on the size of the cobalt islands. Electron microscopy reveals that the nanotubes grow via a ``base growth'' mechanism. The nanotubes grow initially at a very rapid and constant rate (~100 nm/s) that decreases sharply after the catalyst Co particles become fully encapsulated by the nanotubes. We propose a detailed model to explain these experimental observations on nucleation and growth of nanotubes.
Multiwall carbon nanotubes have been dispersed homogeneously throughout polystyrene matrices by a simple solution-evaporation method without destroying the integrity of the nanotubes. Tensile tests on composite films show that 1 wt % nanotube additions result in 36%-42% and ~25% increases in elastic modulus and break stress, respectively, indicating significant load transfer across the nanotube-matrix interface. In situ transmission electron microscopy studies provided information regarding composite deformation mechanisms and interfacial bonding between the multiwall nanotubes and polymer matrix.
In experimental and theoretical investigations of the properties of nanostructures, the equations of continuum beam theory are often used to interpret the mechanical response of nanotubes. In particular, Bernoulli–Euler beam bending theory is being utilized to infer the Young's Modulus. In this work, we examine the validity of such an approach using a simple elastic sheet model and show that at the nanotube scale the assumptions of continuum mechanics must be carefully respected in order to obtain reasonable results. Relations are derived for pure bending of nanotubes that show the explicit dependence of the “material properties” on system size when a continuum cross-section assumption is made. Two alternate approaches are proposed that provide a more reliable scheme for property extraction from experiments.
Uniform films of well-aligned carbon nanotubes have been grown using microwave plasma-enhanced chemical vapor deposition. It is shown that nanotubes can be grown on contoured surfaces and aligned in a direction always perpendicular to the local substrate surface. The alignment is primarily induced by the electrical self-bias field imposed on the substrate surface from the plasma environment. It is found that switching the plasma source off effectively turns the alignment mechanism off, leading to a smooth transition between the plasma-grown straight nanotubes and the thermally grown ``curly'' nanotubes. The nanotubes grow at a surprisingly high rate of ~100 nm/s in our plasma process, which may be important for large-scale commercial production of nanotubes.
The mechanical behavior of multiwalled carbon nanotube/epoxy composites was studied in both tension and compression. It was found that the compression modulus is higher than the tensile modulus, indicating that load transfer to the nanotubes in the composite is much higher in compression. In addition, it was found that the Raman peak position, indicating the strain in the carbon bonds under loading, shifts significantly under compression but not in tension. It is proposed that during load transfer to multiwalled nanotubes, only the outer layers are stressed in tension whereas all the layers respond in compression. © 1998 American Institute of Physics.
Carbon nanotubes grown on a Ni substrate and an Fe–Ni–Cr alloy substrate by plasma-enhanced chemical vapor deposition were investigated by transmission electron microscope (TEM) and energy dispersive x-ray (EDX) analysis. TEM showed that the nanotubes on both substrates have a piled-cone structure with metal particles on top which determine the diameter of the nanotubes. Their diameter ranges from 60 to 80 nm. Moreover, EDX showed that the metal particles are composed of Ni when the nanotubes are grown on Ni substrate and of Fe and Ni in the case of the Fe–Ni–Cr alloy substrate. © 2000 American Institute of Physics.
Composites of uniaxially oriented multiwalled carbon nanotubes embedded in polymer matrices were fabricated and investigated by transmission electron microscopy. In strained composite films, buckling was ubiquitously observed in bent nanotubes with large curvatures. By analyses of a large number of bent nanotubes, the onset buckling strain and fracture strain were estimated to be ≈5% and ⩾18%, respectively. The buckling wavelengths are proportional to the dimensions of the nanotubes. Examination of the fracture surface showed adherence of the polymer to the nanotubes. © 1999 American Institute of Physics.
We report a method to fabricate polymer-based composites with aligned carbon nanotubes, and a procedure to determine the nanotube orientation and the degree of alignment. The composites were fabricated by casting a suspension of carbon nanotubes in a solution of a thermoplastic polymer and chloroform. They were uniaxially stretched at 100 °C and were found to remain elongated after removal of the load at room temperature. The orientation and the degree of alignment were determined by x-ray diffraction. The dispersion and the alignment of the nanotubes were also studied by transmission electron microscopy. © 1998 American Institute of Physics.
The lattice dynamics of pristine graphite is presented with the use of a
Born-von Kármán model. With the consideration of
interactions to fourth neighbor both intraplane and interplane, good
agreement is simultaneously obtained with ir, Raman, and inelastic
neutron scattering measurements of lattice modes and with the measured
elastic constants. The second-order Raman spectrum is also calculated
and compared with experiment.
CARBON nanotubes are predicted to have interesting mechanical properties—in particular, high stiffness and axial strength—as a result of their seamless cylindrical graphitic structure1–5. Their mechanical properties have so far eluded direct measurement, however, because of the very small dimensions of nanotubes. Here we estimate the Young's modulus of isolated nanotubes by measuring, in the transmission electron microscope, the amplitude of their intrinsic thermal vibrations. We find that carbon nanotubes have exceptionally high Young's moduli, in the terapascal (TPa) range. Their high stiffness, coupled with their low density, implies that nanotubes might be useful as nanoscale fibres in strong, lightweight composite materials.
CARBON nanotubes1 are expected to have a wide variety of interesting properties. Capillarity in open tubes has already been demonstrated2–5, while predictions regarding their electronic structure6–8 and mechanical strength9 remain to be tested. To examine the properties of these structures, one needs tubes with well defined morphologies, length, thickness and a number of concentric shells; but the normal carbon-arc synthesis10,11 yields a range of tube types. In particular, most calculations have been concerned with single-shell tubes, whereas the carbon-arc synthesis produces almost entirely multi-shell tubes. Here we report the synthesis of abundant single-shell tubes with diameters of about one nanometre. Whereas the multi-shell nanotubes are formed on the carbon cathode, these single-shell tubes grow in the gas phase. Electron diffraction from a single tube allows us to confirm the helical arrangement of carbon hexagons deduced previously for multi-shell tubes1.
CARBON exhibits a unique ability to form a wide range of structures. In an inert atmosphere it condenses to form hollow, spheroidal fullerenes1–4. Carbon deposited on the hot tip of the cathode of the arc-discharge apparatus used for bulk fullerene synthesis will form nested graphitic tubes and polyhedral particles5–8. Electron irradiation of these nanotubes and polyhedra transforms them into nearly spherical carbon 'onions'9. We now report that covaporizing carbon and cobalt in an arc generator leads to the formation of carbon nanotubes which all have very small diameters (about 1.2 nm) and walls only a single atomic layer thick. The tubes form a web-like deposit woven through the fullerene-containing soot, giving it a rubbery texture. The uniformity and single-layer structure of these nanotubes should make it possible to test their properties against theoretical predictions10–13.
This article discusses the mechanical properties of vapor-grown carbon fiber (VGCF)/nylon and VGCF/polypropylene composites. Fibers in the as-produced condition yielded composites with marginally improved mechanical properties. Microscopic examination of these composites clearly showed regions of uninfiltrated fibers, which could account for the unsatisfactory mechanical properties. The infiltration of the fibers by both polymers was improved by carefully ball milling the raw fiber so as to reduce the diameter of the fiber clumps to less than 300 μm. Properties of composites made with ball-milled material were improved in every respect. VGCF reinforcement in nylon slightly improved the tensile strength and doubled the modulus, while VGCF in polypropylene doubled the tensile strength and quadrupled the modulus compared to unreinforced material. Moreover, the composites were sufficiently improved that differences in fiber surface preparation became important. For example, air-etched fibers and fibers covered with low concentrations of aromatics produced polypropylene composites with significantly better mechanical properties than did fibers whose surfaces were heavily coated with aromatics. Both the tensile strength and the modulus of the composites fabricated with clean fibers exceeded theoretical values for composites made with fibers randomly oriented in three dimensions, indicating that the injection-molding process oriented the fibers to some extent.
Interfacial interaction is one of the most critical issues in carbon nanotube/polymer composites. In this paper the role of nonionic surfactant is investigated. With the surfactant as the processing aid, the addition of only 1 wt % carbon nanotubes in the composite increases the glass transition temperature from 63 °C to 88 °C. The elastic modulus is also increased by more than 30%. In contrast, the addition of carbon nanotubes without the surfactant only has moderate effects on the glass transition temperature and on the mechanical properties. This work points to the pathways to improve dispersion and to modify interfacial bonding in carbon nanotube/polymer composites.
We have developed a new approach for preparing graphitic carbon nanofiber and nanotube ensembles. This approach entails chemical vapor deposition (CVD) based synthesis of carbon within the pores of an alumina template membrane with or without a Ni catalyst. Ethylene or pyrene was used in the CVD process with reactor temperatures of 545 °C for Ni-catalyzed CVD and 900 °C for the uncatalyzed process. The resultant carbon nanostructures were uniform hollow tubes with open ends. Increasing the deposition time converted the carbon nanotubes into carbon nanofibers. Transmission electron microscopy and electron diffraction data show the as deposited graphitic carbon nanofibers synthesized with the Ni catalyst were not highly ordered. Heating the carbon-containing membrane at 500 °C for 36 h, however, converts the carbon nanofibers into highly ordered graphite. The electron diffraction data show a spotted diffraction pattern characteristic of single-crystal graphite with the graphitic planes parallel to the long axis of the nanofibers.
Are nanotubes ideally suited to a straightforward reinforcing role? Results reported here indicate that that may not be the case, but they could find application as a polymer modifier. A successful route is described for the fabrication of large composite films containing carbon nanotubes based on the formation of a stable colloidal intermediate, a route that should be broadly applicable to a range of nanotube materials and polymers. The resulting thermo-mechanical and electrical properties are discussed. While the stiffness of the composites at room temperature is rather low they show promise at high temperatures.
The local elasticity of individual single-walled carbon nanotube (SWNT) bundles and the load transfer in epoxy composites containing SWNTs and carbonaceous soot material formed during nanotube synthesis were studied. The composites were loaded to failure, axially in tension and compression, after which the fracture surface was examined. Micro-Raman spectra and scanning electron micrographs revealed that it is the low-modulus features of the bundles, and not the axial modulus of individual tubes, that control the mechanical stability and strength of the composite. Nanotube reinforcement increases the toughness of the composite by absorbing energy because of their highly flexible elastic behavior during loading.
Using a graphite rod with a hole filled with the powder of a mixture of Y–Ni alloy and graphite or calcium carbide and nickel as anode, single-wall carbon nanotubes (SWCNTs) with high yield were produced in quantity of tens of grams a day under the arc conditions of 40∼60 A d.c. and helium pressure of 500 or 700 torr. The yield of SWCNTs can be quantitatively determined by thermogravimetric analysis (TGA) method. The morphology and structure of SWCNTs were observed by SEM, HREM and Raman spectroscopy. The results showed that the helium atmosphere strongly affects the yield of SWCNTs and the diameter distributions of SWCNTs are different when different catalyst was used, proving that the diameter of SWCNTs is dependent on the properties of the metal catalysts. Our results suggested a formation mechanism of SWCNTs and the roles played by nickel and yttrium or calcium atoms.
Carbon nanotubes–nano-SiC ceramic has been fabricated by the hot-press method. The preparation steps involved the use of dispersing nano-SiC powders and carbon nanotubes in butylalcohol using an ultrasonic shaker. The reasonable relative density of about 95% has been achieved by hot-pressing at 2273 K (at 25 MPa in Ar for 1 h). The three-point bending strength and fracture toughness of the composite has about 10% increment over monolithic SiC ceramic which was fabricated under the same process. The reasons for the increment are the strengthening and toughening role of carbon nanotubes occuring in the matrix.