Introducing Carbon Nanotubes Research Articles

Increasing the Strength of Soldered Joints by Introducing Carbon Nanotubes into Soldering Pastes

Increasing the Strength of Soldered Joints by Introducing Carbon Nanotubes into Soldering Pastes

Synergistic effect of Mn3+ and oxygen vacancy on the bifunctional oxygen electrocatalytic performance of MnOX/CNTs composites

Manganese oxides have been proved to be a promising low-cost electrocatalyst for oxygen reduction reaction (ORR) and a critical step in systems of zinc-air batteries, however, which is limited by the poor electrical conductivity. In this paper, we introduce carbon nanotubes (CNTs) as conductive supports to further prepare manganese oxide/CNTs composites with bifunctional electrocatalytic activity by the incorporation of redox and calcination two-step approach. Meanwhile, the effects of mass ratio, calcination temperature and oxidation degree on the oxygen reduction reaction (ORR) activity of the composites were studied. The electrocatalytic results showed that the MnO2/CNTs exhibited better electrocatalytic activity than that of manganese dioxide (MnO2) and CNTs when the mass ratio of CNTs to MnO2 was 60%. After calcination at 400 °C and reduction treatment of sulfur (S) to adjust the surface oxygen vacancy concentration and Mn3+ content, the ORR and oxygen evolution reaction (OER) bifunctional catalytic activity of the obtained MnOX/CNTs-400 was significantly enhanced. The ORR half-wave potential (E1/2) and bifunctional potential difference (ΔEOER-ORR) between the ORR half-wave potential and OER potential at 10 mA cm−2 were 0.77 V and 0.92 V, respectively, due to the introducing of highly conductive CNTs, increase of Mn3+ content and oxygen vacancy concentration. Furthermore, the composite also exhibits higher methanol tolerance and long-term stability than the commercial Pt/C catalyst, which provided a class of highly efficient ORR/OER bifunctional electrocatalysts with great energy potential.

Multiwalled Carbon Nanotube-Filled Polymer Composites for Direct Injection Molding of Bipolar Plates

Fuel cell bipolar plates are commonly fabricated from graphite and stainless steel, however machining intricate channels into these materials can be a costly and time-consuming process. For this reason, we are exploring injection molding of polymer composite bipolar plates. Polymer composites offer the potential for lightweight, low-cost plates [1]. Several factors impact the ability of a polymer composite to conduct electricity. The geometry, filler weight percentage, dispersion, and the physical properties of the fillers are important in forming an electrical pathway through the composite. In this study, polymer composites based on nylon were injection molded with different weight percentages of conductive filler. Initially, carbon fiber was added to nylon at weight percentages ranging from 10 to 50%. Results show that the percolation threshold for carbon fiber in nylon occurs around 25 wt%. While carbon fiber loadings beyond 50 wt% would further increase conductivity, the increased viscosity of the polymer blends can inhibit proper injection molding.Multiwalled carbon nanotubes were then added to the direct injection-molded nylon/carbon fiber composites to investigate the synergistic effects of multiple conductive fillers [2]. By introducing carbon nanotubes into the polymer matrix, the nanotubes act as a bridge between the carbon fibers. SEM images show that the MWCNTs fill the void between each fiber due to their smaller size and their ease of dispersion. This bridging creates more conductive pathways within the composite, thereby increasing the electrical conductivity. Samples with MWCNTs reached conductivities nearing the United States Department of Energy technical target for bipolar plate conductivity (> 100 S/cm). Mighri, F.; Huneault, M. A.; Champagne, M. F., Electrically conductive thermoplastic blends for injection and compression molding of bipolar plates in the fuel cell application. Polymer Engineering and Science 2004, 44 (9), 1755-1765.Zameroski, R.; Kypta, C. J.; Young, B. A.; Sanei, S. H. R.; Hollinger, A. S., Mechanical and Electrical Properties of Injection-Molded MWCNT-Reinforced Polyamide 66 Hybrid Composites. Journal of Composites Science 2020, 4 (4), 14. Figure 1

Multiwalled Carbon Nanotube-Filled Polymer Composites for Direct Injection Molding of Bipolar Plates

Fuel cell bipolar plates are commonly fabricated from graphite, however the associated machining costs are a major limitation to fuel cell commercialization. A promising alternative approach to bipolar plate manufacturing is injection molding of polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of the bipolar plate. In this study, polymer composites based on nylon were injection molded with different weight percentages of conductive filler. Initially, carbon fiber was added to nylon 6,6 at weight percentages ranging from 10 to 50%. Results show that the percolation threshold for carbon fiber in nylon occurs around 25 wt%. Multiwalled carbon nanotubes (MWCNTs) were then added to the direct injection-molded nylon/carbon fiber composites to investigate the synergistic effects of multiple conductive fillers. By introducing carbon nanotubes into the polymer matrix, the nanotubes act as a bridge between the carbon fibers. SEM images show that the MWCNTs fill the void between fibers due to their smaller size and their ease of dispersion. This bridging creates more conductive pathways within the polymer matrix, increasing the electrical conductivity of the composite. Samples with MWCNTs reached conductivities of 64 S/cm, nearing the United States Department of Energy technical target for bipolar plate conductivity (>100 S/cm).

An experimental study on the effects of introducing carbon nanotube on low velocity impact behavior of carbon/aramid fiber reinforced intra-ply hybrid composites

In this research, the addition effects of Multi Wall Carbon Nanotube (MWCNT) on low velocity impact behavior of Carbon/Aramid Fiber Reinforced (CAFRP) intra-ply hybrid composites were studied. In this regard, three types of pure, 0.1 wt.% and 0.5 wt.% introduced CAFRP intra-ply hybrid composites were fabricated by Vacuum Assisted Resin Infusion Molding (VARIM) method. The profile energy method was used to determine the penetration and perforation threshold. The main purpose of this research was to improve the impact behavior of CAFRP by addition of MWCNT to the matrix of these composites. The low velocity impact test was also carried out in 30, 50, 80 and 120 J energy values. The effect of addition MWCNTs in the matrix of composite was investigated by plotting force, absorbed energy and deflection vs. time and the key parameters of impact test such as maximum contact force, absorbed energy, deflection and duration time were compared for pure and multi scale CAFRP composited. According to the results, the addition of MWCNT improved the low velocity impact behavior of CAFRP intra-ply hybrid composites by not only increasing the toughness of epoxy matrix but also upgrade the adhesion of carbon fibers to the epoxy matrix. It was also found that fiber breakage, fiber pull out, matrix cracking, delamination and fiber matrix debonding were the most important failure modes in these types of tested composites.

Elevating the Photothermal Conversion Efficiency of Phase-Change Materials Simultaneously toward Solar Energy Storage, Self-Healing, and Recyclability.

To alleviate the predicament of resource shortage and environmental pollution, efficiently using abundant solar energy is a great challenge. Herein, we prepared unique photothermal conversion phase-change materials, namely, CNT@PCMs, by introducing carbon nanotubes (CNTs) used as photothermal conversion materials into the recyclable matrix of phase-change materials (PCMs). These devised CNT@PCMs cleverly combine the photothermal conversion capability of CNTs and the thermal energy storage capability of traditional PCMs. Especially, the surface temperature of the prepared CNT@PCMs can be raised to 100 °C within 165 s under the solar simulator (150 mW cm-2), showing a surprising heating rate that is much higher than that of the reported works and achieving a higher photothermal conversion efficiency for solar energy in this work. Furthermore, these CNT@PCMs can hold high melting latent heat with a maximum value at 110.0 J g-1, exhibiting remarkable thermal storage ability aside from preeminent photothermal conversion capability. Intriguingly, the introduction of dynamic oxime group-carbamate bonds into the molecular structure can endow CNT@PCMs with an outstanding self-healing performance and recyclability. The broken CNT@PCMs sample can be healed in 2 min under IR-laser irradiation. Importantly, the phase-change and mechanical properties and photothermal conversion efficiency of CNT@PCMs can also remain virtually unchanged after multiple recycles. It is of great significance to design this style of CNT@PCMs for achieving the efficient utilization of solar energy and environmental protection.

Enhancing the solar absorption capacity of expanded graphite-paraffin wax composite phase change materials by introducing carbon nanotubes additives

The potential solar thermal utilization of solar energy based on phase change materials (PCMs) is limited by their low thermal conductivity and weak solar absorption capacity. Among various additives used to enhance the thermal conductivity of PCMs, expanded graphite (EG) has been proved to be a low-cost but effective choice. This work aims to further enhance the solar absorption capacity of EG-paraffin wax composite PCMs by adding small amounts of carbon nanotubes (CNTs) as the light absorbent. The prepared composite PCMs with 5 wt.% EG and 2 wt.% CNTs show superior thermal conductivity (2.05 W/m⋅K), high solar absorption capacity (94.2%) while maintaining the high latent heat (159 kJ/kg). Moreover, these superior thermal and optical properties can be maintained after 1000 melting-freezing cycles. Our results provide a high-performance composite PCM that may be used in solar-thermal conversion applications.

Revealing the intrinsic effects of introduced carbon nanotubes for Bi2O3 energy storage materials

A lot of works have revealed that the introduction of Carbon nanotubes (CNTs) into oxide-based electrode materials is an efficient strategy to improve their energy storage performance. In this work, we firstly demonstrated the intrinsic effects of introduced CNTs for bismuth oxide (Bi2O3) electrode materials, including the physical, chemical and energy storage performance. Our results revealed that the optimal value of introduced CNTs into Bi2O3 is 1.5% (in weight ratio), which demonstrated a specific capacitance of 1012 C g−1 at 1 A g−1, about 1.52 times higher than the pristine Bi2O3. The obtained optimal energy storage performance by introduced CNTs can be explained by; 1) the introduced CNTs were helpful to reduce the average particle size of Bi2O3 powder, here the particle size was greatly reduced from 363 nm to 112 nm; 2) the small Bi2O3 particle with the introduced CNTs demonstrated more than 1.97 times enhancement of specific surface area; 3) the total conductivity of the obtained composite electrode was greatly enhanced by 320.31 times and, 4) however, due to the lower theoretical capacity of CNTs, the total specific capacitance of composite electrode showed a significant reduction by introducing excess CNTs. We believe that this work provides a strong support to guide the introduction of CNTs into Bi2O3-based energy storage materials for optimizing electrochemical performance.

MWCNT-modified MXene as cost-effective efficient bifunctional catalyst for overall water splitting.

Utilization of cost-effective, bifunctional, and efficient electrocatalysts for complete water splitting is desirable for sustainable clean hydrogen energy. In last decade, MXenes, a family of emerging two-dimensional (2D) materials with unique physiochemical properties, enticed scientists because of their use in different applications. However, insufficient electron transport, lower intrinsic chemical activity and limited active site densities are the factors inhibiting their use in electrocatalytic cells for hydrogen production. Here, we have presented material design to address this issue and introduced carbon nanotubes (CNTs) on V2CTx MXene sheets for conductive network channels that enhance the ion diffusion for enhanced electrochemical activity. The SEM reveals the uniform dispersion of the MWCNTs over the MXene surface that resulted in the formation of conductive network channels and enhances reaction kinetics. The as-synthesized electrocatalyst was subjected to linear sweep voltammetry (LSV) measurements for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The hybrid catalyst M2 exhibited an enhanced HER activity with a lower over-potential of 27 mV which is comparable to commercially available Pt-based catalysts (32 mV). Similarly, an enhanced OER activity was observed with a lower over-potential of 469 mV as compared to pristine V2CTx MXene. The electrocatalyst was subjected to a durability test through chronoamperometry and was observed to be stable for 16 hours. Hence, this study opens a new avenue for future cost-effective efficient catalysts for overall water splitting as a solution to produce clean hydrogen.

Thermo-Modulated Nanofibrous Skin Covered Janus Membranes for Efficient Oil/Water Separation

An efficient membrane with good antifouling ability in various complex separation environments is crucial for long-term oily wastewater treatment. Herein, a thermo-modulated nanofibrous skin covered Janus membrane was successfully developed via a scalable synergetic electrospraying/electrospinning method. By introducing carbon nanotubes, the substrate exhibited superhydrophobicity and achieved separation of oil/water mixtures with high fluxes (> 6000 L m−2 h−1) and efficiencies (> 99%) under gravity. Moreover, benefiting from synergistic effect of poly(N-isopropylacrylamide) (PNIPAM) brushes and beadlike skin surface, the opposite thermoresponsive membrane exhibited improved wettability and water permeability (average from 774.6 to 947 and max = 1022.7 L m−2 h−1) with temperature varied from 20 ℃ (below the lower critical solution temperature) to 50 °C (above the lower critical solution temperature). Additionally, the hydrophilic side had high oil-in-water emulsion separation fluxes (max = 979.6 L m−2 h−1) and separation efficiencies of > 98% under gravity. Most importantly, the material showed excellent antifouling and cleaning ability resulting from thermoresponsive property. With the water temperature increased from 20 °C to 50 °C during the cleaning process of the membrane, the flux recovery ratio increased from 59.3% to 82.8%, and the irreversible fouling ratio correspondingly decreased from 40.7% to 17.2%. The thermo-responsive cleaning ability of coating is less limited to the material and morphology of the substrate, which provides a new vision for the antifouling method of membrane. The novel thermoresponsive Janus membrane demonstrated a good oil-water separation performance and remarkable antifouling ability which has a wider application prospect.

О влиянии углеродных нанотрубок на физико-механические свойства полипропилена

One of the most interesting and promising materials of our time is carbon nanotubes. Most applications of nanotubes are associated with the possibility of combining them with other materials in the form of alloys, mixtures, composites or hybrid materials. In particular, the idea of including carbon nanotubes as a filler in various polymer-based matrices (for example, traditional polymers such as thermoplastics, thermosetting materials or elastomers, as well as conjugated polymers) for the formation of polymer/carbon nanotube nanocomposites has revolutionized materials science and engineering. The introduction of carbon nanotubes into the composite structure affects the structure and properties of the polymer binder, as well as the composite material as a whole. Currently, there are no experimental developments on the basis of which the introduction, distribution and stabilization of the dispersion of carbon nanotubes in polymer composites would be implemented in industrial technology. The development of the most effective methods for introducing carbon nanotubes into polymer materials and determining their effect on the physical and mechanical properties of polymers is an urgent and priority task. It is possible that these methods will be able to find application in the industrial production of polymer composite materials intended for use and operation in various extreme conditions (whether it is high temperatures, erosion, high force exposure or highly acidic/highly alkaline environments). The main physical and mechanical properties of polypropylene samples saturated with carbon nanotubes taken at different concentrations (0; 0.01; 0.05 and 0.1 wt. %), who found that the addition of CNT in large quantities negatively affects the tensile and bending strength limits, which may be associated with an increase in the degree of heterogeneity of the structure and the appearance of large agglomerates, which will be points of stress concentration. With an increase in the mass fraction of carbon nanotubes in the polymer nanocomposite, the tangent of the dielectric loss angle increases, which leads to better conductivity of the sample containing a larger number of nanotubes. This may be due to the fact that nanotubes become conductors of electric current in the volume of the polymer matrix.

Aqueous MnV2 O6 -Zn Battery with High Operating Voltage and Energy Density.

Aqueous Zn ion batteries (AZIBs), featuring low cost, long-term cycling stability, and superior safety are promising for applications in advanced energy storage devices. However, they still suffer from unsatisfactory energy density and operating voltage, which are closely related to cathode materials used. Herein, the use of monoclinic MnV2 O6 (MVO) is reported, which can be activated for high-capacity Zn ions storage by electrochemically oxidizing part of the Mn2+ to Mn3+ or Mn4+ while the remaining Mn2+ ions act as binders/pillars to hold the layer structure of MVO and maintain its integrity during charging/discharging process. Moreover, after introducing carbon nanotubes (CNT), the MVO:CNT composite not only provides robust 3D Zn-ion diffusion channels but also shows enhanced structural integrity. As a result, a MVO:CNT cathode delivers a high midpoint voltage (1.38V after 3000 cycles at 2 A g-1 ) and a high energy density of 597.9 W h kg-1 . Moreover, DFT analyses clearly illustrate stepwise Zn ion insertion into the MnV2 O6 lattice, and ex-situ analyses results further verify the highly structural reversibility of the MnV2 O6 cathode upon extended cycling, demonstrating the good potential of MnV2 O6 for the establishment of viable aqueous Zn ion battery systems.

Research status and prospect on nanotube/nanowire multi-scale-reinforced C/C composites

Carbon/carbon (C/C) composite has become a good candidate as an ultra-high temperature structural material for thermal structure in aerospace and other fields due to its low density and high temperature mechanical properties. However, conventional C/C composites cannot meet the application requirements of sharp thin-wall structure, because the pyrolytic carbon matrix is brittle and the single micron carbon fiber cannot effectively enhance the sharp thin-walled area. This paper reviews the preparation methods of nanotube/nanowire reinforced C/C composites and their effects on the structure and properties of the composites. The development status of introducing carbon nanotubes (CNTs), silicon carbide nanowires (SiCNWs) and hafnium carbide nanowires (HfCNWs) on the mechanical and ablative properties of C/C composites, as well as the toughening mechanism and ablation resistance mechanism of the composites are summarized. In view of the shortcomings of the composition, method and single test performance of the nano-reinforced material introduced at present, it is proposed to further improve and innovate the process technology on the base of these studies, and conduct reasonable component and structure design, so as to deeply study the high temperature mechanical properties and toughening mechanism of multi-scale toughened C/C composites.

(Invited) Carbon Nanotubes Cloaked in Synthetic Polymers: Aqueous Dispersion, Characterization, and Applications

Surface chemistry plays a crucial role in interactions of carbon nanotubes in the biological environment. Biomimetic functionalities on nanotubes could facilitate effective nano-bio interactions enabling nanoscale biological probes, sensors, and imaging agents. Synthetic polymers that facilitate aqueous solubility, biocompatibility and molecular recognition via biomimicry are highly preferred for multifunctional carbon nanotube-based biological probes. In this talk, we will introduce carbon nanotubes cloaked in synthetic mimics of biopolymers and uses of those nanoscale probes in optical sensing of target biomolecules.

Suppression of secondary phase in CrN matrix to boost the high-temperature thermoelectric performance

With the escalation of energy and environmental crisis, more and more attentions have been paid to the waste heat recovery, especially in the high-temperature range (>900 K). Chromium nitride (CrN) is expected to be a promising high-temperature thermoelectric material that can be used in harsh environments because of its high thermal stability, corrosion resistance and excellent mechanical properties. However, the relatively low figure of merit zT hinders its realistic applications. In this work, we reveal that the easily formed secondary phase Cr2N is one of the key factors restricting the CrN thermoelectric performance. Acid treatment is utilized to remove the metallic Cr2N phase from the commercially available powders. Nevertheless, after the sintering process at 1373 K, Cr2N phase can emerge again due to the decomposition of CrN. Interestingly, this decomposition process can be inhibited by introducing carbon nanotubes (CNTs), and the resulted hybrid material demonstrates greatly improved Seebeck coefficient and reduced thermal conductivity. A maximum zT value of 0.33 for the CNTs/CrN can be achieved at 973 K, which is 1.8 times as high as that of the acid-pickled CrN (0.18), and 40 times higher than that of the pristine chromium nitride (0.008). Additionally, the CNTs/CrN hybrid material exhibits outstanding mechanical hardness (11.5 GPa) as well as chemical and thermal stability. These results will promote the practical applications of CrN-based materials in the high-temperature thermoelectric field.

Case Study of Polyvinylidene Fluoride Doping by Carbon Nanotubes.

Modern material science often makes use of polyvinylidene fluoride thin films because of various properties, like a high thermal and chemical stability, or a ferroelectric, pyroelectric and piezoelectric activity. Fibers of this polymer material are, on the other hand, much less explored due to various issues presented by the fibrous form. By introducing carbon nanotubes via electrospinning, it is possible to affect the chemical and electrical properties of the resulting composite. In the case of this paper, the focus was on the further improvement of interesting polyvinylidene fluoride properties by incorporating carbon nanotubes, such as changing the concentration of crystalline phases and the resulting increase of the dielectric constant and conductivity. These changes in properties have been explored by several methods that focused on a structural, chemical and electrical point of view. The resulting obtained data have been documented to create a basis for further research and to increase the overall understanding of the properties and usability of polyvinylidene fluoride fiber composites.

Durable Polyelectrolyte Microcapsules with Near-Infrared-Triggered Loading and Nondestructive Release of Cargo.

Microcapsules formed using a "layer-by-layer" alternating deposition of oppositely charged polyelectrolytes on sacrificial templates have reached high interest because of their facile fabrication procedure using a broad range of materials and tailored properties. However, their practical applications as microcarriers are limited as the capsules commonly suffer from low mechanical stability that can be enhanced by chemical or physical crosslinking but at the expense of decreasing permeability of the capsules' walls. It is demonstrated here that the incorporation of multiwalled carbon nanotubes in a relatively small amount (3.5%) arranged in the direction perpendicular to the capsules' walls led to an almost 20-fold increase of the apparent elastic modulus of the microcapsules as shown using the osmotic pressure method. Importantly, the introduced carbon nanotubes due to their absorption in the near-infrared region and specific arrangement enabled also a light-triggered increase of permeability of the capsules in a reversible, nondestructive manner as shown using fluorescently labeled dextrans of various molar masses. Such results imply durability and facile loading/unloading of the microcapsules that are both crucial for their practical applications as microcontainers and microreactors.

Recycling Waste Crystalline-Silicon Solar Cells: Application as High Performance Si-Based Anode Materials for Lithium-Ion Batteries

Recycling useful materials such as Ag, Al, Sn, Cu and Si from waste silicon solar cell chips is a sustainable proposal to offset the ever-growing amount of waste crystalline-silicon photovoltaic panels. However, the recovery cost of the above-mentioned materials from silicon chips via acid-alkaline treatments is economically unviable. Herein, we propose a new proof-of-concept to fabricate Si-based anodes with waste silicon chips as raw materials. Nanoparticles from waste silicon chips were prepared with the high-energy ball milling followed by introducing carbon nanotubes and N-doped carbon onto the nanoparticles, which amplifies the electrochemical properties. The results showed that the Al metal in the composite possesses an adverse impact on the electrochemical performance. After removing Al, the composite was confirmed to possess a pronounced durable cycling property due to the presence of Ag, resulting in significantly more superior property than the composite having both Al and Ag removed.

Enhancing the thermoelectric performance of Cu–Ni alloys by introducing carbon nanotubes

High power factor and low thermal conductivity are imperative to maximize the energy conversion efficiency of thermoelectric materials. Constantan (Cu–Ni alloy), a widely-used material for thermocouples, has higher power factor (∼12000 μW m−1 K−2 at 950 K) [Mao et al. 2015] than the classic Bi2Te3-based thermoelectric materials (∼4500 μW m−1 K−2 at 300 K) [Poudel et al. 2008]. However, the high thermal conductivity restricts its thermoelectric performance. In this work, we demonstrate that, the thermal conductivity of Cu–Ni alloy can be effectively reduced from 48.1 to 9.6 W m−1 K−1 at 873 K by introducing carbon nanotubes (CNTs), and the thermoelectric performance is remarkably improved with the figure of merit (zT) being up to 0.41, an enhancement of about 141% over the pristine Cu–Ni alloy. Negative correlation between the total thermal conductivity of hybrid composite and the specific surface area of CNTs is further identified. The thermal conductivity suppression mechanism is ascribed to the introduction of both porous structures and carbon-nanotube-metal interfaces. Our studies provide a promising and general strategy to enhance the thermoelectric properties of materials with high thermal conductivity.

Nanomechanics of graphene oxide-bacteriophage based self-assembled porous composites

Graphene oxide, integrated with the filamentous bacteriophage M13, forms a 3D large-scale multifunctional porous structure by self-assembly, with considerable potential for applications. We performed Raman spectroscopy under pressure on this porous composite to understand its fundamental mechanics. The results show that at low applied pressure, the sp^2 bonds of graphene oxide stiffen very little with increasing pressure, suggesting a complicated behaviour of water intercalated between the graphene layers. The key message of this paper is that water in a confined space can have a significant impact on the nanostructure that hosts it. We introduced carbon nanotubes during the self-assembly of graphene oxide and M13, and a similar porous macro-structure was observed. However, in the presence of carbon nanotubes, pressure is transmitted to the sp^2 bonds of graphene oxide straightforwardly as in graphite. The electrical conductivity of the composite containing carbon nanotubes is improved by about 30 times at a bias voltage of 10 V. This observation suggests that the porous structure has potential in applications where good electrical conductivity is desired, such as sensors and batteries.