Multiwalled Carbon Nanotube Buckypaper Research Articles

Evidencing contributions arising from disorder-rich rhombohedral stacking-order regions in S-doped carbon nanotube buckypapers

The recent observations of superconductive-ordering in carbon-based systems consisting of rhombohedral stacking-faults, trilayer graphene (ABC-stacks) or dislocation-rich interfaces (pyrolytic graphite) have attracted a significant attention. Here we report an unusual nucleation of rhombohedral (ABC) stacking-faults in low-dimensional systems comprising of multiwall carbon nanotube (CNT) buckypapers, in experiments involving doping with sulfur. Interestingly, at low sulfur-concentrations, a broad-band at the Raman shift from 1800 to 2000 cm−1 was frequently identified, evidencing contributions arising from disorder-rich regions with rhombohedral stacking-order (ABC-stacks), as confirmed by X-ray diffraction and Rietveld refinements. These observations were further supported by a broadening in the left-shoulder of the 2D band at higher frequencies. T-ESR in the T range from 300 K to 77 K revealed multiple resonant signal splitting, indicative of paramagnetic contributions arising from the conduction π-electrons of the CNT and from amorphous iron-based-sulfides. Presence of CS bonding was revealed by Raman- and X-ray photoelectron-spectroscopy, evidencing a modification of the CNT. A sulfur-induced collapse within the CNTs-structure was found at high concentrations, as a consequence of a substitutional doping process and investigated through XRD, Rietveld refinements, TEM, HRTEM and magnetometry. ZFC/FC and magnetization vs field acquisitions revealed an interplay of ferromagnetic, paramagnetic and diamagnetic components with the diamagnetic-susceptibility χ being −2.85 ∗ 10−6 (emu/gOe) at T ~ 30 K.

Thermal Conductivity of Carbon/Boron Nitride Heteronanotube and Boron Nitride Nanotube Buckypapers: Implications for Thermal Management Composites.

To date, there has been limited reporting on the fabrication and properties of macroscopic sheet assemblies (specifically buckypapers) composed of carbon/boron nitride core-shell heteronanotubes (MWCNT@BNNT) or boron nitride nanotubes (BNNTs). Herein we report the synthesis of MWCNT@BNNTs via a facile method involving Atmospheric Pressure Chemical Vapor Deposition (APCVD) and the safe h-BN precursor ammonia borane. These MWCNT@BNNTs were used as sacrificial templates for BNNT synthesis by thermal oxidation of the core carbon. Buckypaper fabrication was facilitated by facile sonication and filtration steps. To test the thermal conductivity properties of these new buckypapers, in the interest of thermal management applications, we have developed a novel technique of advanced scanning thermal microscopy (SThM) that we call piercing SThM (pSThM). Our measurements show a 14% increase in thermal conductivity of the MWCNT@BNNT buckypaper relative to a control multiwalled carbon nanotube (MWCNT) buckypaper. Meanwhile, our BNNT buckypaper exhibited approximately half the thermal conductivity of the MWCNT control, which we attribute to the turbostratic quality of our BNNTs. To the best of our knowledge, this work achieves the first thermal conductivity measurement of a MWCNT@BNNT buckypaper and of a BNNT buckypaper composed of BNNTs not synthesized by high energy techniques.

MWCNT buckypaper disc films as alternative to the drop casting method to modify electrode surfaces

We report the comparison of the modification of glassy carbon electrode (GCE) with multiwalled carbon nanotubes (MWCNTs) and nitroaromatic compounds using two different methodologies, the traditional drop casting (DC) method and an alternative buckypaper disc film (BP) method. The methodology for the construction of the BP disc film electrodes consists of a simple filtration of MWCNT and polystyrene (PS) dispersion in 1,3-dioxolane through a nylon membrane filter and then disc-shaped cutting. The adhesion of the disc film to the GCE is achieved by a direct STAMP process.The electrode surfaces were characterized by Raman spectroscopy (RS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM) while the electrochemical responses were followed by voltammetry and electrochemical impedance spectroscopy (EIS).The results showed an important enhancement in the reproducibility of the electrochemical response of the electrodes with coefficient of variation (c.v.) values for the faradaic response of 3.82 and 11.42% for the BP and DC methods, respectively. In addition, c.v. values for the capacitive response of 2.2 and 19.2% for the BP and DC methods, respectively. The preparation of BP disc film electrodes improves homogenization in MWCNT deposits causing this increase in the reproducibility of the electrodes.

A study on thermal resistance evaluation of carbon nanotube buckypaper with cellulose material for thermal interface material

Multi-walled carbon nanotubes (MWCNTs), which has been studied as a heat conduction material, has excellent thermal properties, with thermal conductivity value of 3000 W/m·K. This study aims to reduce the thermal resistance of MWCNTs–buckypaper (BP) as a thermal interface material (TIM). Three methods are used in this experiment: ultrasonication, oxidation, and the addition of cellulose nanocrystal (CNC). The oxidation process is to remove impurities, which when prepared as a suspension, disturb the particle dispersion, and reveal a tendency to agglomerate. Therefore, a strong acid treatment removes impurities, and improves the dispersibility of nanofluids. The third method, the addition of CNC, which has been in the limelight recently, can affect structural stability, is eco-friendly, and is used for composite material synthesis with high tensile strength. These preeminent effects of CNC help improve the thermal resistance of CNC/treated CNT (C–tCNTs) mixed buckypaper. The thermal performances of TIMs used an ASTM D5470 standard tester, and various ratios of BP were tested using thermal resistance test. BP manufactured by adding MWCNTs and CNC had a resistance value of 0.776. This provided a 33.1 % decrease, compared to the oxidized MWCNTs BP. As a result, it was confirmed that CNC–CNTs BP has the possibility of being applied as TIM. • Cellulose nanocrystals, an eco-friendly material, are applied to carbon nanotubes. • It is made of paper-type buckypaper for use as a thermal interface material. • ASTM D5470 standard instrument is used for thermal resistance comparison. • It achieves maximum heat transfer performance at the optimum ratio.

Designing Sandwich Architecture Towards Glass Fiber/Epoxy Reinforced Multi-walled Carbon Nanotube Buckypaper Composites for Electromagnetic Interference Shielding

Designing Sandwich Architecture Towards Glass Fiber/Epoxy Reinforced Multi-walled Carbon Nanotube Buckypaper Composites for Electromagnetic Interference Shielding

Stochastic multiscale multimode interlaminar fracture toughness of buckypaper nanocomposites

Delamination is one of the primary damage mechanisms in laminated composites that affects the lifetime integrity of the composite systems. The present study examines the effects of Buckypaper (BP) nano-reinforcement on the multimodal interlaminar fracture properties of the carbon fiber reinforced polymer (CFRP) composites reinforced with BP membranes. The novelty and the focus of this study is the effects of multi-wall carbon nanotube (MWCNT) network size and interphase in the interlaminar fracture toughness of BP nanocomposites. Dry and pre-infused non-functionalized MWCNT BP were integrated at the mid layer of the composite before laminate curing. The Atomic Force Microscopy Peak Force Quantitative Nanomechanics Mapping (AFM PFQNM) technique and the Weibull model were applied to study the effects of random CNT network size and interphase on mode I, II, and mixed-mode I-II fracture properties. Weibull analysis of 150 dry and pre-infused BP data confirms a high scatter of CNT network size in dry BP compared to pre-infused BP. Weibull modulus of CNT network size (2.33 for large size and 5.18 for small size) and interphase thickness (3.46) show a robust, consistent entangled structure of CNTs in pre-infused BP. Dry BP improves the propagation energy release rate of the CFRP laminates up to 54%. However, it does not provide additional toughening in the initiation crack energy for modes I, II, and I-II. Mode I initiation and propagation, mode II initiation and mixed-mode I/II fracture energy of pre-infused BP nanocomposites are ∼33%, ∼52.5%, ∼14%, and ∼28% higher than the reference. The interlaminar crack either moves exclusively through the BP layer by circumventing the rigid CNT networks or moves forward through the interface of the carbon fiber monofilament above and below the reinforcing BP layer. This saw-like interlaminar crack path triggers numerous toughening mechanisms such as nano-toughened epoxy, nanoscale CNT bridging and pullout, and crack deflection, and it increases the total crack propagation path.

MWCNT Buckypaper as Electrochemical Sensing Platform: A Rapid Detection Technology for Phthalic Acid Esters in Solutions*

AbstractPhthalic Acid Esters (PAEs) are a well‐known ubiquitous environmental pollutant that holds a significant threat to human health. Despite their harmful effects, the constant use of PAEs in producing flexible plastic products has awakened society‘s great concern, especially with their ability to leach, migrate, or evaporate from plastics to the surrounding. Therefore, rapid and easy monitoring of the PAEs presence in different environments is crucial. This study introduces a rapid PAE detection technique that shows potential for overcoming the limitations of already existing PAE detecting methods. This novel PAE sensing platform (buckypaper) is developed using highly conducting Multi‐Walled Carbon Nanotubes (MWCNT). The buckypaper adsorbs PAEs in solutions and decreases its conductivity. This conductivity decrement is detected using the Nyquist and Bode plots obtain from three‐electrode Electrochemical Impedance Spectroscopy (EIS) analysis. This novel method has shown that it has the potential to distinguish DEHP (di‐(2‐ethylhexyl) phthalate), DPHP (di‐(2‐propylheptyl) phthalate), and DnOP (di‐octyl phthalate) from other aromatic molecules such as toluene, xylene, naphthalene, and bisphenol‐A. Moreover, the developed buckypaper is sensitive down to 1000 (v/v) ppm concentrated PAEs in methanol solutions at room temperature, which exhibits the potential of using this platform as an in‐situ and real‐time PAE detecting sensor.

Synthesis, characterization, and heavy-ion rejection rate efficiency of PVA/MWCNTs and Triton X-100/MWCNTs Buckypaper membranes

Buckypaper membranes were prepared through the dispersion of multi-walled carbon nanotubes (MWCNTs) in the presence of surfactants (Triton X-100) and (PVA) in a separate manner. The dispersed solutions were vacuum filtered and Buckypapers, which are self-supporting membranes were obtained. The results revealed that the incorporation of both Triton X-100 and PVA surfactants increased the permeability and rejection efficiency of the MWCNTs. The rejection performance for the heavy metal ions of both membranes is investigated for the first time. The physico-chemical and morphological characteristics of the membranes were reported. PVA and Triton X-100 BP membranes displayed electrical conductivity (32.749 ± 2 S cm−1 and 58.3072 ± 1 S cm−1), contact angle (58 ± 3° and 34 ± 3°), water permeability (20 ± 2 Lm−2 h−1 bar−1 and 79 ± 4 Lm−2 h−1 bar−1), surface area (67.7 and 88.5 m2/g) and mechanical properties (Young's module was found to be 10.25 ± 0.2 and 6.07 ± 0.7) respectively. Both PVA/MWCNTs BP and Trix-100/MWCNTs BP membranes significantly reject Cu+2, Cd+2, Co+2, Ba+2, Ni+2, and Pb+2 at PH = 6–8 from aqueous medium. Furthermore, the rejection of metal ions was more efficient in PVA-based membranes compared to Trix-based membranes.

Lightweight multi-walled carbon nanotube buckypaper/glass fiber–epoxy composites for strong electromagnetic interference shielding and efficient microwave absorption

Multi-walled carbon nanotube buckypaper (BP) reinforced glass fiber–epoxy (GF/EP) composites were selected to fabricate electromagnetic interference (EMI) shielding and microwave absorbing materials. Six different composite configurations with 3.0 mm thick have been conceived and tested over the X-band (8.2–12.4 GHz). Flexible and low-density (0.29 g/cm3) BP provided a high specific EMI SE of 76 dB with controlled electrical conductivity. GF/EP/BP111 and GF/EP/BP101 composites possess EMI SE as high as of 50–60 dB, which can be attributed to the number of BP inserted and variation in the wave-transmitting layer of the laminates. Furthermore, the shielding mechanism was discussed and suggested that the absorption was the dominant contribution to EMI SE. GF/EP/BP110 laminate demonstrated suitable EMI performance (~ 20 dB), whereas GF/EP/BP011 composite revealed excellent microwave performance, achieving an effective − 10 dB bandwidth of 3.04 GHz and minimum reflection loss (RL) value of − 21.16 dB at 10.37 GHz. On the basis of these results, GF/EP/BP composites prepared in this work have potential applications as both EMI shielding and microwave absorber materials given their facile preparation and lightweight use.

Robust, freestanding, and bendable multi-walled carbon nanotube buckypapers as electrode materials for quasi-solid-state potassium-ion supercapacitors

We report here on the performance of quasi-solid-state potassium ion electrolyte filling electrochemical supercapacitors. The electrolyte is composed of aqueous-based polyvinyl alcohol with potassium and sulfate ions. This electrolyte is first investigated filling the coin cells with two identical multi-walled carbon nanotube buckypapers as the electrode materials, and later, it was analyzed in a pouch cell. Our electrochemical results, obtained from different techniques, show that the cell's working voltage window is as wide as 1.6 V, yielding a volumetric capacitance of 18 F cm−3, and equivalent series resistance smaller than 2.5 Ω. We prepare a pouch cell with our best coin cell findings to investigate the cell's mechanical behavior. Our findings showed that quasi-solid-state potassium ion-based supercapacitors are highly flexible and robust, thus encouraging further investigation on the development of flexible supercapacitors to be applied on various wearable and bendable devices.

In situ formation of a carbon nanotube buckypaper for improving the interlaminar properties of carbon fiber composites

To improve the interlaminar properties of carbon fiber reinforced polymer composites (CFRPs), a hybrid fiber mat (i-MBP-PCF) was prepared by in situ deposition of a multiwalled carbon nanotube buckypaper (i-MBP) on the surface of functionalized CF fabric (PCF). The effect of the hybrid fiber mat on the interlaminar and electrical properties was systematically investigated. The results showed that the i-MBP-PCF hybrid fiber mat showed excellent interlaminar and electrical property enhancement functions. The interlaminar shear strength (ILSS), Mode-II interlaminar fracture toughness (GIIC), and electrical conductivity in the out-of-plane direction of i-MBP-PCF/EP increased 68.6%, 44.4%, and 6080%, respectively, compared to those of the CF/EP composite.

Electrical conductivity and electromagnetic shielding performance of glass fiber-reinforced epoxy composites with multiwalled carbon nanotube buckypaper interlayer

Glass fiber/epoxy-reinforced multi-walled carbon nanotube buckypaper composites (GF/EP/BP) were fabricated by hot compression molding process to evaluate its electromagnetic interference (EMI) shielding efficiency (SE) in the X-band (8.2–12.4 GHz) frequency range. Scanning electron microscopy (SEM) revealed a porous structure for the CNT film and good overall quality of the GF/EP/BP composite with no apparent voids or defects associated to the lamination process. The electrical conductivity of the CNT film was around 996 S/m and its incorporation at the mid-plane of the laminates had no influence in the electrical conduction of the composites. EMI SE results of about 18 dB were obtained for the 3 mm nanostructured composite over the X-band so that the dielectric properties, the total electrical conductivity, and the interfacial polarization phenomenon had great importance in the EMI shielding properties of the manufactured composites.

Multi-Functional Properties of MWCNT/PVA Buckypapers Fabricated by Vacuum Filtration Combined with Hot Press: Thermal, Electrical and Electromagnetic Shielding.

The applications of pure multi-walled carbon nanotubes (MWCNTs) buckypapers are still limited due to their unavoidable micro/nano-sized pores structures. In this work, polyvinyl alcohol (PVA) was added to a uniform MWCNTs suspension to form MWCNT/PVA buckypapers by vacuum infiltration combined with a hot press method. The results showed an improvement in the thermal, electrical, and electromagnetic interference (EMI) shielding properties due to the formation of dense MWCNTs networks. The thermal and electrical properties rose from 1.394 W/m·k to 2.473 W/m·k and 463.5 S/m to 714.3 S/m, respectively. The EMI performance reached 27.08 dB. On the other hand, ABAQUS finite element software was used to simulate the coupled temperature-displacement performance. The electronic component module with buckypapers revealed a homogeneous temperature and thermal stress distribution. In sum, the proposed method looks promising for the easy preparation of multi-functional nanocomposites at low-cost.

Ex-situ measurement of thermal conductivity and swelling of nanostructured fibrous electrodes in electrochemical energy devices

Nanostructured electrodes are widely used in electrochemical energy devices, such as batteries, fuel cells, and supercapacitors. This paper presents an ex-situ experimental study to measure the thermal conductivity and volume change of nanostructured fibrous electrodes that are based on multiwall carbon nanotube (MWCNT) buckypaper. Two typical interstitial liquids are investigated, including deionic water and ionic liquid (BMIM-PF6), along with oil (HM32 hydraulic oil) for comparison. It is found the buckypaper electrodes can be a poor through-plane thermal conductor with a conductivity around 0.2 W/m K despite of highly-conductive CNTs. External compression enhances the conductivities of wet samples up to 80–90%, and after that, further compression shows no evident impacts. Adding interstitial liquids significantly increases the sample’s conductivity by up to about 10 times with liquid water exhibiting the largest enhancement. The results are compared favorably with two popular correlations established for wet soils. In addition, buckypaper swelling is observed upon liquid absorption with a thickness change as much as 70%, comparable to the literature data of cotton and viscose rayon fibers. External compression greatly reduces the swelling. The work is valuable to the thermal management and durability studies of nanostructured fibrous electrodes for fuel cells, batteries, and supercapacitor applications.

Wettability and reactivity between molten aluminum and randomly aligned carbon nanotubes

The wettability and reactivity between molten aluminum (Al) and carbon nanotubes (CNTs) are a key issue in the preparation of CNTs-reinforced Al-matrix composites using a solidification route. In this work, we measured the wettability of randomly aligned multi-walled carbon nanotubes (buckypaper) by molten Al at 973–1173 K in a high vacuum using a modified sessile-drop method and examined their interactions using a droplet-sucking technique. The wettability between Al and CNTs is even worse than that of the Al/graphite system. The contact angles are basically larger than 140° and show only a sluggish decrease with time during isothermal dwelling. The chemical stability of CNTs in contact with Al is closely related to their structural integrity. The CNTs with good crystallinity and structural integrity have relatively high chemical stability and exhibit only a weak interfacial reaction with Al at 973 K. However, the stability of structural defective parts is much lower. They are readily eroded by molten Al, leading to the fragmentation of the CNTs. These CNT fragments having an open tubular structure are then rapidly dissolved in molten Al along the axial and radial directions. Simultaneously, a large amount of Al4C3 is formed at the interfaces.

Curing of Glass Fiber/Epoxy Resin Composites Using Multiwalled Carbon Nanotubes Buckypaper as a Resistive Element

AbstractGlass fiber/epoxy resin composites (GF/EP) were prepared using one and three multiwalled carbon nanotube buckypapers (BPs) as a resistive element. Compared to the conventional hot compression molding process that demanded 4200 W to fabricate the GF/EP laminate, the proposed curing process consumed only 63 W, representing a saving power of 98.5%. The thermal distribution of the BP and their composites were recorded using an infrared thermometer. Differential scanning calorimetry (DSC) curves have not shown a residual cure, suggesting the curing process using the BP as a resistive element was effective. The cross section views of the laminates were analyzed by scanning electron microscopy (SEM), and the mechanical characterizations were performed by impulse excitation technique (IET), compression shear test (CST), and interlaminar shear strength (ILSS). The results demonstrated that the BP composites showed a good consolidation between the prepregs layers, and presented no significant variations in the mechanical tests compared to the traditional hot compression molding process. Nevertheless, dynamic mechanical analyses (DMA) showed a slight decrease in the BP composites’ storage moduli compared to GF/EP laminate.

Multifunctional Characteristics of Glass Fiber‐Reinforced Epoxy Polymer Composites with Multiwalled Carbon Nanotube Buckypaper Interlayer

In this work, multiwalled carbon nanotube buckypaper (MWCNT‐BP) was inserted at the middle‐plane of glass fiber/epoxy resin prepregs to obtain three‐phase nanostructured composite. Preliminary tests conducted by differential scanning calorimetry and thermogravimetric analyses (TGA) revealed that the proposed curing cycle to prepare the laminates in a hot compression‐molding machine was appropriated. The mechanical properties of the BP‐based composite studied by short beam shear and compression shear tests presented no improvements compared to the base laminate. On the other hand, the thermal properties of the nanostructured composite improved as demonstrated by dynamical mechanical analyses and TGA. Besides, the reflectivity results revealed an average value of −12.2 dB in the X‐band with a maximum attenuation of 99.4% of the incident wave at 9.5 GHz. The improvements in both thermal and electromagnetic properties demonstrate the potential for both structural and multifunctional applications of the obtained BP‐composite. POLYM. ENG. SCI., 60:740–751, 2020. © 2020 Society of Plastics Engineers

Development of enhanced multiwalled carbon nanotube (MWCNT) conductive polymeric nanocomposites by using acidified derivative of MWCNT as dispersant

The agglomeration of pristine multiwalled carbon nanotubes (MWCNTs) within a polymer matrix has largely limited the efficient conductive reinforcement of MWCNTs-based polymeric nanocomposites. In this paper, the pristine MWCNTs realized well-dispersed with the assistance of nitric acid acidified MWCNTs. The as-prepared hybrid MWCNTs were used to prepare hybrid MWCNTs buckypaper and hybrid MWCNTs/polyvinyl butyral (PVB) nanocomposites. The hybrid MWCNTs dispersion maintained good dispersing stability over 3 months. The fabrication of hybrid MWCNTs buckypaper shows that the intrinsic conductivity of the hybrid MWCNTs is 25.1 ± 0.2 S/cm, higher than the pristine ones of 23.3 ± 0.2 S/cm. The SEM images of hybrid MWCNTs/PVB nanocomposites show that hybrid MWCNTs are distributed homogenously in the PVB matrix. The conductive performance of nanocomposites is significantly enhanced with a low percolation of 0.44 ± 0.05 wt. % and a high critical exponent of 3.57.

Microfluidic paper based membraneless biofuel cell to harvest energy from various beverages

The present work establishes the cost-effective and miniature microfluidic self-pumping paper based enzymatic biofuel cell (P-EBFC). The developed Y-shaped P-EBFC consists of buckeye composite multiwall carbon nanotube (MWCNT) buckypaper (BP) based bio-anode and bio-cathode that were immobilized with electro-biocatalytic enzymes glucose oxidase (GOx) and laccase, respectively. The electrocatalytic activity of enzymes on electrode surface is confirmed using cyclic voltammetry (CV) technique. Such immobilized bio-anode and bio-cathode show exquisite electrocatalytic activity towards glucose and O2, respectively. Most appealingly, P-EBFC can directly harvest energy from widely available beverages containing glucose such as Mountain Dew, Pepsi, 7up and fresh watermelon juice. This could provide potential application of P-EBFC as a portable power device.

Comparative study of structure, mechanical and electromagnetic interference shielding properties of carbon nanotube buckypapers prepared by different dispersion media

In order to prepare multi-wall carbon nanotube (MWCNT) buckypapers (BPs) with excellent comprehensive properties, an investigation was conducted regarding the effect of dispersing medium on CNT dispersions and resultant BPs. Three types of MWCNTs with different lengths and diameters, denoted as CNT-A, CNT-B and CNTC, were dispersed into water, ethanol and 1-methyl-2-pyrrolidone, respectively. The dispersion stability was monitored by UV–vis spectroscopy and conductivity meter. The results showed that all MWCNT/water dispersions were far superior to MWCNT/ethanol dispersion in stability, but slightly inferior in monodispersity. Subsequently, BPs prepared by vacuum filtration using the above-mentioned dispersions were investigated to clarify the pore structure, electrical, mechanical and electromagnetic shielding properties. Compared with BPs prepared with CNT-A/ethanol dispersion (BP-A-E), the BP prepared with CNT-A/water dispersion (BP-A-W) showed smaller pore size, and exhibited significantly improvement in electrical conductivity (74%), strength (665%). A super high absorption-dominated electromagnetic interference shielding effectiveness (SE) of 101.7 dB was achieved by BP-A-W of 450 μm thick in the range of 8.2–18 GHz, which was 26% higher than that of BP-A-E. A notable SE of 48.4 dB and a high specific SE of 29,300 dB·cm2/g were obtained by BP of 45 μm thick prepared with CNT-C/water dispersion.