Conventional Carbon Nanotubes Research Articles

CNTFET-Based Single-Ended Fractional Order Colpitts Oscillator: Design, Simulation and Comparative Analysis

In this paper, we design and simulate a Single-Ended Colpitts Oscillator (CO) in integer and fractional order domains. The oscillators are realized in 32[Formula: see text]nm node conventional MOSFET and carbon nanotube field effect transistor (CNTFET) technologies. Therefore, four COs have been designed, simulated and rigorously compared. These include integer order conventional MOSFET-based CO, fractional order MOSFET-based CO, CNTFET-based integer order CO and CNTFET-based fractional order CO, all based on 32-nm technology nodes. The fractional order approach has been used as it results in better control over the phase and frequency of the oscillator. Herein, fractional order capacitors of various orders, used in realizing the fractional order COs, are realized and their frequency responses are studied. This is being done to ensure whether the designed pseudo-capacitances have fractional behavior or not in the desired frequency and phase spectrum. It has been observed that the variation of fractional order [Formula: see text] from 0.4 to 0.81 has resulted in a slight reduction of oscillation frequency from 1.68[Formula: see text]GHz ([Formula: see text]) to 1.351[Formula: see text]GHz ([Formula: see text]) keeping the pseudo-capacitance same at 0.3[Formula: see text]nF in MOS-based topology. Since the fractional order realization increases the circuit complexity and power consumption, therefore, CNTFET-based integer order as well as fractional order COs have been designed. The CNTFET-based fractional order CO retains the advantages of the fractional order domain as well as the power efficiency of CNTFETs. Further, it has been observed that integrating fractional-order capacitor (FOC) with the CNTFET CO results in a much larger constant phase zone (CPZ), an important performance measuring parameter. A rigorous comparative analysis of the four COs designed in this work has been performed.

Synthesis and photodegradation performance of a heterostructure ferromagnetic photocatalyst based on MWCNTs functionalized with (3-glycidyloxypropyl)trimethoxysilane and decorated with tungsten trioxide for metronidazole and acetaminophen degradation in aqueous environments.

The presence of metronidazole (MNZ) and acetaminophen (ACE) in aquatic environments has raised growing concerns regarding their potential impact on human health. Incorporating various patterns into a photocatalytic material is considered a critical approach to achieving enhanced photocatalytic efficiency in the photocatalysis process. In this study, WO3 nanoparticles, which were immobilized onto ferromagnetic multi-walled carbon nanotubes that were functionalized using (3-glycidyloxypropyl)trimethoxysilane (FMMWCNTs@GLYMO@WO3), exhibited remarkable efficiency in removing MNZ and ACE (93% and 97%) in only 15 min. In addition, the new visible-light FMMWCNTs@GLYMO@WO3 nanoparticles as a magnetically separable photocatalyst were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), EDS-mapping, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), diffuse reflectance spectroscopy (DRS), high-performance liquid chromatography (HPLC), and total organic carbon (TOC) due to detailed studies (morphological, structural, magnetic and optical properties) of the photocatalyst. In-depth spectroscopic and microscopic characterization of the newly developed ferromagnetic FMMWCNTs@GLYMO@WO₃ (III) photocatalyst revealed a spherical morphology, with nanoparticle diameters averaging between 23 and 39 nm. Compared to conventional multiwall carbon nanotube and WO₃ photocatalysts, FMMWCNTs@GLYMO@WO₃ (III) demonstrated superior photocatalytic activity. Remarkably, it exhibited excellent reusability, maintaining its efficiency over a minimum of five cycles in the degradation of metronidazole (MNZ) and acetaminophen (ACE).

Densely Branched Carbon Nanotubes for Boosting the Electrochemical Performance of Li-S Batteries.

To address the inherent limitations of conventional carbon nanotubes (CNTs), such as their tendency to agglomerate and scarcity of catalytic sites, the development of branched carbon nanotubes (BCNTs) with a unique hierarchical structure has emerged as a promising solution. Herein, gram scale quantities of densely branched and structurally consistent Ni-Fe decorated branched CNTs (Ni-Fe@BCNT) have been prepared. This uniform and densely branched architecture ensures excellent dispersibility and superior electrical conductivity. Additionally, each branched tip is equipped with Ni-Fe particles, thereby providing numerous catalytic sites which endow them with exceptional catalytic activity for the conversion of polysulfides. The polypropylene (PP) separator modified with Ni-Fe@BCNT interlayer is fabricated as a multifunctional barrier for Li-S batteries. The experimental results demonstrate that Ni-Fe@BCNT interlayer can effectively suppress the shuttle effect of polysulfides and enhance their redox kinetics. The outstanding catalytic ability of Ni-Fe@BCNT interlayer enables batteries with high specific capacities, outstanding rate performance, and remarkable cycling stability. This approach proposed in this work paves a new path for synthesizing BCNTs and shows great potential for scaling up the production of BCNTs to address more demanding applications.

Graphene nanoribbons: A novel additive for enhancing the fire resistance of cementitious composites

This study investigated the effectiveness of graphene nanoribbons (GNRs) as nanoadditives for enhancing fire resistance of cementitious composites and compared their performance with conventional carbon nanotubes (CNTs). First, GNRs with striped structures exhibited superior dispersion stability compared to CNTs. Second, GNRs demonstrated excellent thermal stability, remaining structurally intact at 800 °C, while CNTs began decomposing above 450 °C. At room temperature, the GNRs significantly promoted the hydration reaction of cement clinkers, reduced the porosity, and refined the pore structure, thereby enhancing the mechanical properties of the cementitious composites. In high-temperature environments, GNRs act as bridges for cracks, effectively mitigating the deterioration of the mechanical strength caused by the dehydration and decomposition of hydration products. Moreover, the GNRs inhibited pore development and elongation, improving fire resistance. Overall, this study highlights the potential of GNRs as promising nanomaterials for enhancing the performance of cementitious composites under high-temperature conditions.

On the vibrational behavior of the conventional and hetero-junction carbon nanotubes

The shortcomings and insufficiency in the state-of-the-art investigations about the resonance in the hetero-junction carbon nanotubes with respect to the number of models and connection types highlight the necessity of a comprehensive study of the resonance frequency of these nanostructures for applications of these nanomaterials in nanodevices, such as nano-scale electromechanical systems (NEMS) and NEMS-based resonators. Hence in this study, 50 conventional and 73 hetero-junction middle-length (15 nm) carbon nanotubes, with armchair-armchair, zigzag-zigzag, armchair-zigzag, armchair-chiral, zigzag-chiral and chiral-chiral connections, were modeled. Then, the resonance in their structure was comprehensively studied using the finite element method to present a more reliable estimated range for the natural frequency (fundamental frequency) of hetero-junction carbon nanotubes. The analysis showed that the natural frequency of conventional carbon nanotubes lies in the range of 7.09 and 48.75 GHz. An inverse correlation between this quantity and the aspect ratios of the conventional carbon nanotubes was found, leading to proposing a mathematical relation for the prediction of such an inverse correlation. The natural frequency of hetero-junction carbon nanotubes oscillated between 4.04 and 60.20 GHz. The results revealed that the natural frequency of hetero-junction carbon nanotubes lies outside the frequency range of their constructive carbon nanotubes and majorly depends on the boundary conditions and the difference between the diameters of the connected tubes. Finally, it was observed that the existence of an armchair carbon nanotube in the structure of hetero-junction models improves their vibrational stabilities.

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.

Carbon Kagome nanotubes-quasi-one-dimensional nanostructures with flat bands.

In recent years, a number of bulk materials and heterostructures have been explored due their connections with exotic materials phenomena emanating from flat band physics and strong electronic correlation. The possibility of realizing such fascinating material properties in simple realistic nanostructures is particularly exciting, especially as the investigation of exotic states of electronic matter in wire-like geometries is relatively unexplored in the literature. Motivated by these considerations, we introduce in this work carbon Kagome nanotubes (CKNTs)-a new allotrope of carbon formed by rolling up Kagome graphene, and investigate this material using specialized first principles calculations. We identify two principal varieties of CKNTs-armchair and zigzag, and find both varieties to be stable at room temperature, based on ab initio molecular dynamics simulations. CKNTs are metallic and feature dispersionless states (i.e., flat bands) near the Fermi level throughout their Brillouin zone, along with an associated singular peak in the electronic density of states. We calculate the mechanical and electronic response of CKNTs to torsional and axial strains, and show that CKNTs appear to be more mechanically compliant than conventional carbon nanotubes (CNTs). Additionally, we find that the electronic properties of CKNTs undergo significant electronic transitions-with emergent partial flat bands and tilted Dirac points-when twisted. We develop a relatively simple tight-binding model that can explain many of these electronic features. We also discuss possible routes for the synthesis of CKNTs. Overall, CKNTs appear to be unique and striking examples of realistic elemental quasi-one-dimensional materials that may display fascinating material properties due to strong electronic correlation. Distorted CKNTs may provide an interesting nanomaterial platform where flat band physics and chirality induced anomalous transport effects may be studied together.

Effect of CNT content and size on the high-temperature particle-erosion resistance of ablative materials for thermal protection systems

Advanced spacecraft development requires high-performance thermal protection systems composed of materials with high particle-erosion resistance. In this study, a particle-erosion test motor was designed to produce a high-temperature particle jet. Subsequently, the effects of carbon nanotube (CNT) content and size on the particle-erosion resistance of ethylene propylene diene monomer (EPDM) composites were analyzed. Composites with an optimum CNT content exhibited the lowest ablation rates; extremely high or low CNT contents increased the ablation rate. Furthermore, the charring rate of the composites with long CNTs were 78.0% and 43.6% lower than those with the baseline-formula composition and those containing conventional CNTs, respectively. Here, the influence of CNT content and size on the particle-erosion resistance of EPDM composites was analyzed from the perspective of the thermal stability of the composites, as well as the char-layer characteristics and vapor deposition.

Recent Advances of Carbon Materials in Anodes for Aqueous Zinc Ion Batteries.

Carbon-based materials have been successfully applied in the zinc ion batteries to improve the energy storage capability and durability of zinc anodes. In this review, four types of carbon materials (conventional carbons, fiber-like carbons, carbon nanotubes, graphene and other 2D carbon materials) are introduced based on the electrode preparation, physicochemical property and battery performance. Several modification strategies are also illustrated, such as heteroatom doping, hierarchical design and metal/carbon composites. Besides the discussion of existing issues of zinc anodes, the structure-performance relationships are analyzed in depth. Finally, conclusive remarks of this review are summarized and prospects of the future improvement are proposed.

Ultra-High Strength Carbon Nanotube Yarn Made by New Growth Method

We have been focusing on carbon nanotubes (CNTs) as a material for next-generation electric wires that are lighter and more conductive than copper and aluminum wires. CNT single fiber has a greater conductivity than copper and the highest tensile strength of any known material. Aiming at the practical application of CNT electric wires, we have discovered the effectiveness of applying tensile stress to CNTs during the growing process from iron catalysts. In addition, at the University of Tsukuba, where a joint research was conducted, the growth of centimeter-class single fibers was observed in high-speed airflow, suggesting that stress applied during the growth contributes to the lengthening of CNTs. Using this principle as a basis for the growth method, we have created a metric-class CNT yarn that aggregates these long CNT single fibers. The new yarn has several times the strength of the conventional CNT yarn and exceeds the tensile strength of commercially available carbon fibers. This yarn will not only replace carbon fibers but also create new applications that have never been seen before.

Carbon Nanotube Field-Effect Transistor Biosensor for Ultrasensitive and Label-Free Detection of Breast Cancer Exosomal miRNA21.

Tumor-derived exosomal miRNAs may have important functions in the onset and progression of cancers and are potential biomarkers for early diagnosis and prognosis monitoring. Yet, simple, sensitive, and label-free detection of exosomal miRNAs remains challenging. Herein, an ultrasensitive, label-free, and stable field-effect transistor (FET) biosensor based on a polymer-sorted high-purity semiconducting carbon nanotube (CNT) film is reported to detect exosomal miRNA. Different from conventional CNT FETs, the CNT FET biosensors employed a floating gate structure using an ultrathin Y2O3 as an insulating layer, and assembled Au nanoparticles (AuNPs) on Y2O3 as linkers to anchor probe molecules. A thiolated oligonucleotide probe was immobilized on the AuNP surface of the sensing area, after which miRNA21 was detectable by monitoring the current change before and after hybridization between the immobilized DNA probe and target miRNA. This method achieved both high sensitivity (LOD: 0.87 aM) and high specificity. Furthermore, the FET biosensor was employed to test clinical plasma samples, showing significant differences between healthy people and breast cancer patients. The CNT FET biosensor shows the potential applications in the clinical diagnosis of breast cancer.

Directional, Low-Energy Driven Thermal Actuating Bilayer Enabled by Coordinated Submolecular Switching.

The authors reveal a thermal actuating bilayer that undergoes reversible deformation in response to low‐energy thermal stimuli, for example, a few degrees of temperature increase. It is made of an aligned carbon nanotube (CNT) sheet covalently connected to a polymer layer in which dibenzocycloocta‐1,5‐diene (DBCOD) actuating units are oriented parallel to CNTs. Upon exposure to low‐energy thermal stimulation, coordinated submolecular‐level conformational changes of DBCODs result in macroscopic thermal contraction. This unique thermal contraction offers distinct advantages. It's inherently fast, repeatable, low‐energy driven, and medium independent. The covalent interface and reversible nature of the conformational change bestow this bilayer with excellent repeatability, up to at least 70 000 cycles. Unlike conventional CNT bilayer systems, this system can achieve high precision actuation readily and can be scaled down to nanoscale. A new platform made of poly(vinylidene fluoride) (PVDF) in tandem with the bilayer can harvest low‐grade thermal energy and convert it into electricity. The platform produces 86 times greater energy than PVDF alone upon exposure to 6 °C thermal fluctuations above room temperature. This platform provides a pathway to low‐grade thermal energy harvesting. It also enables low‐energy driven thermal artificial robotics, ultrasensitive thermal sensors, and remote controlled near infrared (NIR) driven actuators.

Structural and electronic properties of double-walled [formula omitted]-graphyne nanotubes

The structural and electronic properties of double-walled α-graphyne nanotubes (α-DWGNTs) are investigated using a combination of computation and theoretical methods, including density functional theory. DWGNTs differ from conventional double-walled carbon nanotubes by the presence of carbon atoms featuring both sp and sp2 hybridizations, endowing DWGNTs with a set of desirable properties that could lead to a number of applications. Classical molecular dynamics (MD) and Born–Oppenheimer molecular dynamics (BOMD) simulations were performed to reveal the structural stability of these nanotubes at room temperature. Their dynamical stability was confirmed using tight-binding based phonons calculations. The high flexibility of the graphyne sheet and van der Waals interactions between the shells lead to strong deformations of the outer tube. Consequently, the electronic structure of the component single-walled tubes undergoes significant changes once cast into the double-walled geometries due to the coupling of electronic states from the inner wall with the outer tube. Such strong inter-wall hybridization can not only modulate the electronic band gap of semiconducting tubes, in comparison to their isolated single-walled counterparts, but can also affect the electronic properties of the double-walled systems. These behaviors open up possibilities of using such nanostructures in the design of electronic device applications.

Investigations on the Carbon Nanotube Paste Made by the Optimized Ball-Milling Method and Its Applications for the e-Beam Source

The carbon nanotube (CNT) has the outstanding mechanical/chemical properties, which makes it a promising electron source for various applications such as the field emission display (FED), the microcolumn, and the X-ray tube. In this work, we have developed the CNT paste by applying the noble ball-milling method to the paste mixer. The newly developed CNT paste was used to fabricate the CNT field emitter whose electric characteristics were evaluated by observing the I–V curve and long-term stability of the emitter. The new CNT paste showed much better electrical characteristics than those of the conventional CNT paste. We also used the CNT tip as a source of the electron beam (e-beam) of the microcolumn and found that the operating range of the e-beam was enhanced by 100% compared to that of the conventional microcolumn where the tungsten tip was used as the e-beam source. By replacing the tungsten tip with the CNT tip, we could not only obtain more flexibility in design of the microcolumn but also remove the alignment problem between the emitter tip and the source lens.

Supersized Graphitic Tube@MoS2 Pipelines with Abundant Ion Channels Synthesized by Selective Deposition toward High-Performance Anodes

Molybdenum disulfide (MoS2) has been regarded as a promising anode material in lithium-ion batteries (LIBs) due to its high theoretical capacity. However, the poor conductivity and collapse of the structure upon cycling lead to poor stability, impeding the application of MoS2 in LIBs. Here, a novel strategy was reported to selectively deposit MoS2 nanosheets on a supersized graphitic tube (SGT) to obtain an SGT@MoS2 pipeline to tackle these problems. Compared with a conventional carbon nanotube (CNT), SGT has not only a graphitic wall but also a pipeline structure, which can act as an ion channel after immersion of an electrolyte. Additionally, the selective deposition of MoS2 on the outer surface effectively prevents the pipelines from being crammed by MoS2 nanosheets. Resultantly, diffusion efficiencies of both an electron and an ion are enhanced. Additionally, the shortened ion diffusion distance can boost pseudocapacitive behavior, contributing to high specific capacity and excellent rate performance. The results manifest that the specific capacity of the SGT@MoS2 pipeline reached 942 mAh g–1 at 100 mA g–1 after 200 cycles, 4 times higher than that of pure MoS2.

In situ growing N and O co-doped helical carbon nanotubes encapsulated with CoFe alloy as tri-functional electrocatalyst applied in Zn–Air Batteries driving Water Splitting

Currently, it is still a big challenge to develop highly active and robust trifunctional non-noble electrocatalysts to meet the practical application of renewable energy storage and conversion devices including metal-air batteries and water electrolyzers. N and O co-doped helical carbon nanotubes encapsulated with CoFe alloy (CoFe@NOCNT) were prepared in situ on carbon paper using ZIF67 as precursor through ion exchange and chemical vapor deposition (CVD) pyrolysis methods. Comparative studies found that the heterogeneous catalysis of CoFe alloy produced spiral carbon nanotubes, which had a much higher N and O doping content than conventional carbon nanotubes containing monometallic cobalt particles. On the basis of the advantages of in situ growth and 3D open structure of catalytic electrode, the helical carbon nanotubes with abundant N catalytic species, C = O functional groups and core-shell structure exhibit superior electrocatalytic activity for ORR/OER/HER. The zinc-air battery (ZAB) and water electrolysis device based on CoFe@NOCNT electrodes showed peak power density (142 mW/cm2), specific capacity (819 mAh/gZn), low overall water splitting voltage (1.57 v @ 10 mA/cm2) and good stability. Two CoFe@NOCNT based ZABs in serial connection can efficiently drive the electrolyzer with two same CoFe@NOCNT/CFP electrodes to split water and two quasi-solid state ZABs in series provide a peak power of 212 mW to light a red light-emitting diode (LED) indicator.

Reinforcement of polymer nanocomposites by ɑ-graphyne nanotubes: A multiscale simulation

In this paper, a series of simulations based on molecular dynamics and finite element methods are carried out to investigate the elastic properties of ɑ-graphyne nanotubes and their polymer nanocomposites. Using the molecular dynamics method, we investigate the geometrical effects on the five independent constants of transversely isotropic elastic ɑ-graphyne nanotubes. Then, we analyze the interphase properties of these nanostructures embedded in the polyethylene matrix. We do a comparative study to measure the interaction force between the conventional carbon nanotubes and ɑ-graphyne nanotubes with their surrounding matrices and the results reveal that ɑ-graphyne nanotubes have a remarkably stronger interaction with the polymer matrix. This makes them a much better alternative for the carbon nanotubes in nanocomposite reinforcement technology. In the end, considering the non-isotropic elastic behavior of nanotubes, we study the effects of various ɑ-graphyne nanotubes on the mechanical properties of polymer nanocomposites using the finite element method.

Screen-printed Dual-Particle-Containing Multicomponent-Blending Carbon Nanotube Cathode: Enhancement of Electron Emission Characteristics, Current Emission Stability, and Uniformity

The electron emission characteristics, current emission stability, and uniformity of screen-printed carbon nanotube were enhanced by introducing a novel dual-particle-containing multicomponent-blending carbon nanotube cathode via the comprehensive combination of baking in the air and sintering in the inert gas atmosphere. The dual-particle-containing multicomponent-blending carbon nanotube cathode’s design and manufacturing improvements ensured its steeper emission curve variation amplitude, larger maximum emission current, better electron emission current of 806.7 μA was only 2.56 V/μm. When it was increased from 2.78 to 2.91 V/μm, the enhancing current emission amplitude of the proposed cathode was increased by 600.7 μA versus 324.1 μA of the conventional non-blending carbon nanotube cathode. The maximum emission current of the proposed cathode was 3762.5 μA. After the vacant static state of 72 h, the measured emission current had no obvious attenuation, and the fluctuation rate of emission current did not exceed 5%. The backlight unit with dual-particle-containing multicomponent-blending carbon nanotube cathode was sealed, and the obtained emission image had high luminescence brightness and uniformity.

A comparative study on the influences of whisker and conventional carbon nanotubes on the electrical and thermal conductivity of polyether ether ketone composites

AbstractIn this study, the electrical and thermal conductivity of polyether ether ketone (PEEK)/carbon nanotubes (CNTs) with different types, namely whisker CNTs (Wh‐CNTs) and conventional CNTs were compared. PEEK/CNTs composites were melt mixed in PEEK via two screw extrusion technology. Moreover, the effects of different methods for mixing of PEEK/Wh‐CNTs, namely, dry mixing, wet mixing and melt mixing, were compared. The electrical and thermal properties were analyzed. A high thermal conductivity value of about 0.741 W/(m K) could be obtained upon loading with 10 wt% Wh‐CNTs and the PEEK/Wh‐CNTs composites had low volume resistivity value of 10.96 Ω cm at 10 wt% loading via melt mixing. Thermal conductivity values of 1.066 W/(m K) (out‐of‐plane) and 1.50 W/(m K) (in‐plane) were achieved with 10 wt% loading by wet mixing. Experimental results of out‐of‐plane thermal conductivity were more consistent with the Nan model. PEEK/Wh‐CNTs composites prepared by wet mixing exhibited higher thermal conductivity than the composites mixed using the two other methods. As the content of Wh‐CNTs in wet mixed PEEK/Wh‐CNTs nanocomposites increased, electromagnetic interference (EMI) shielding effectiveness (SE) was improved. The PEEK/Wh‐CNTs composites were 0.6 mm thick and showed an EMI SE of 21.5 dB.

Behavior of Polybenzoxazine Composites Reinforced with Modified Carbon Nanotubes

The surface of conventional carbon nanotube (CNTs) were modified into 4-aminobenzoyl functionalized CNTs (ABCNT) and benzoxazine functionalized CNTs (BZCNT) to improve their surface interaction with bisphenol A based benzoxazine resins (BA-a). Polybenzoxazine (PBZ) composites using these materials were prepared to investigate the effect of different functional groups on the thermal and electrical properties of the composites. The surface modification of CNTs was characterized by Fourier Transform Infrared spectroscopy and thermogravimetric analysis. The PBZ composite with BZCNT showed the better conductivity and thermal properties than the composite with ABCNT due to the chemical bond between BZCNT/BA-a during the curing process which does not exist in the ABCNT/BA-a composite.