Graphene Carbon Nanotubes Research Articles

Synthesis of bio-based toughening phosphorus-nitrogen flame retardant and study on high toughness EPS flame retardant insulation sheet

In this paper, a variety of biological phosphorus-nitrogen synergistic flame retardants were synthesized from the perspective of molecular design. At the same time, tannic acid (TA) modified graphene (GE) and multiwalled carbon nanotubes (MWCNTs) nanomaterials were prepared by combining nanocomposite technology. Then, the flame retardant was applied to expandable polystyrene (EPS) through a coating process to prepare toughened composites. And the effect of the synthesized high-efficiency phosphorus-nitrogen flame retardant on the flame retardancy efficiency and brittleness of EPS was studied. The flame retardant (PAU) was synthesized by complexing phytic acid (PA) and urea (U) in an aqueous medium, and then using polydopamine (PDA) as an adhesive. Next, on the basis of PAU, using GE and MWCNTs as tougheners, EPS-PAUCG composites were prepared by coating method. Research has found that in the UL-94 test, the flame-retardant EPS-PAUCG composites could reach V-0 level. In the CCT experiment, compared to pure EPS, the PHRR, THR, PSPR, and TSP of EPS-PAUCG2 decreased by 88.4 %, 72.3%, 74.9 %, and 80.9 %, respectively. Through mechanism analysis, it has been proven that PAUCG undergoes thermal decomposition to form a dense expandable protective carbon layer, preventing further degradation of the matrix. In addition, compared to EPS, the compressive strength of the EPS-PAUCG2 composites have increased by 22.5%. This was because the composites contained GE and MWCNTs with high molecular chain structure rigidity and specific surface area, which had a toughening effect of ductile particles.

Comprehensive analysis of CNT/NS/GO composites: Dispersion effect of graphene oxide for environmental sensor application

This study presents a comprehensive analysis of conductive and hygroscopic nanocomposites using graphene oxide (GO), carbon nanotubes (CNT), and nano-silica. Nanocomposite suspensions for vacuum filtration were prepared by dispersion via ultrasonication in water. The dispersed phase of each nanomaterial was evaluated through ultraviolet absorbance, extinction coefficient, and zeta potential. The dispersion was performed at a ratio of CNT to GO well over 0.4 without any surfactants or additives because of the rich functional groups on the GO surface. In addition, the morphology of the fabricated nanocomposite generated after vacuum filtration, verified through scanning electron microscopy and Raman spectroscopy, showed a lamellar structure of GO and was easily separated as a membrane at composite-to-GO ratios of over 0.4. The fabricated membrane exhibited an excellent moisture collection ability and good responsivity as an environmental (humidity) sensor. This study supports the use of GO for the formation of well-dispersed nanocomposites for various applications.

Dispersion characteristics and mechanical properties of epoxy nanocomposites reinforced with carboxymethyl cellulose functionalized nanodiamond, carbon nanotube, and graphene

AbstractCarbon‐based nanoparticles are widely regarded as promising nanofillers in nanocomposites to pursue advanced properties. To date, there has been a lack of systematic investigation into the structural variations of nanofillers and their influences on dispersion characteristics, as well as the resulting mechanical properties of nanocomposites. In this study, nanodiamond (ND), carbon nanotube (CNT), and graphene (GNP) were selected as the representative zero‐, one‐, and two‐dimensional nanofillers, respectively. A novel functionalization technique utilizing carboxymethyl cellulose (CMC) was employed to disperse nanofillers. The various characterization techniques and experimental results revealed that CMC functionalization was effective in reducing the agglomeration and improving the distribution uniformity of all three nanofillers. Among the three nanofillers, zero‐dimensional ND exhibited the most homogeneous dispersion quality in epoxy nanocomposites. The strongest abrasion resistance was found in ND‐reinforced epoxy nanocomposites, while CNT‐reinforced epoxy nanocomposites exhibited the best tensile properties.Highlights Nanodiamond with a spherical structure had better dispersion characteristics. Cylindrical carbon nanotube and planar graphene tended to agglomerate. Nanodiamond reinforced nanocomposites had better abrasion resistance. Carbon nanotube reinforced nanocomposites had better tensile properties. Carboxymethyl cellulose functionalization was valid for all three nanofillers.

β-MnO2/three-dimensional graphene-carbon nanotube hybrids as cathode for aqueous zinc-ion battery

Aqueous zinc-ion batteries (RZIBs) are one of the favorable complementary candidates for lithium-ion batteries. The cathode material determines the whole performance. Herein, β-MnO2/3D GPE-CNTs hybrid cathode materials were fabricated by intermittent high-energy vibratory ball milling method. It delivered a higher specific discharge capacity of 313.31 mAh·g−1 and excellent cycling stability compared to the bare β-MnO2 sample. Morphological characterizations revealed that the enhanced electrochemical performance of the β-MnO2/3D GPE-CNTs hybrid was mainly attributed to the three-dimensional framework structure, large specific surface area, and good conductivity of GPE-CNT, as well as its resulting particle refinement with uniform dispersion and partial suppression of grain amorphization. This article provided a new sight of fabricating Mn-based materials/conducting carbon material hybrid for good performance cathode in RZIBs.

NANOCOMPOSITE-BASED THIN FILM CARBON MONOXIDE SENSORS

Over the past decade, organic semiconductors have been of great interest in basic research and practical applications. Composites based on organic materials have become widespread due to their unique properties and partial biodegradability: they are also suitable as sensitive materials — sensors for detecting various gases. One such gas is carbon monoxide or a different carbon monoxide. Carbon monoxide occurs wherever conditions exist for incomplete combustion of carbon-containing substances. One of the industrial industries where carbon monoxide is emitted in large volumes is the oil and gas industry. The main source in this industry are flares for combustion of associated gases, during the operation of gas turbine plants, as well as exhaust gases from internal combustion engines of construction, drilling equipment, vehicles, etc. Due to the high toxicity of carbon monoxide, it is necessary to create highly sensitive materials for CO sensors. So, when inhaling small concentrations of carbon monoxide (up to 1000 mg/m3), a person feels heaviness in the head, dizziness, nausea, a feeling of pleasant exhaustion, due to which a person cannot soon leave the affected area, and with prolonged (2–3 months) contact with CO, chronic carbon monoxide poisoning is possible at a concentration of 10-50 mg/m3. Therefore, the search for a new material having high sensitivity and selectivity to carbon monoxide is relevant. The purpose of this study is to develop a highly sensitive electronic gas sensor for detecting carbon monoxide at room temperature. The films were made by irrigation from a polymer solution containing graphene oxide and carbon nanotubes. The morphology of the surface of thin polymer films was investigated, spectral chemical analysis was carried out, voltampere characteristics of sensors were measureed0 and an IoT (Internet of Things) solution for remote monitoring was developed. The results show a good response and repeatability of the results at room temperature, allowing the thin films of the graphene polymer-CNT oxide composite to be considered a promising electronic sensor material for CO detection.

Influence of multi-scale three-dimensional pore characteristics on the mechanical properties of graphene oxide and carbon nanotube incorporated cement paste

The correlation between the three-dimensional pore characteristics and mechanical properties of graphene oxide (GO)-and carbon nanotube (CNT)-incorporated cement pastes were investigated. The nano and micro-scale pore characteristics were evaluated by analyzing pore shapes and spatial distribution properties using a radial distribution function (RDF). As a result of the nucleation sites effect, blade-like and plate-like pores were primarily formed in the GO-incorporated samples and rod-like pores in the CNT-incorporated samples, as compared to the plain samples without nanomaterials. In addition, the pore scattering, instead of the pore clustering property, was improved in the nanomaterial-incorporated samples. Notably, results obtained from X-ray nanoimaging and micro-CT analyses revealed a strong positive linear correlation between the strengths (compressive and splitting tensile strengths) of the composites and the degree of pore scattering.

Exploration of synergic effect assessment on the electrochemical behaviour of graphene and multiwall carbon nanotube (MWCNT) modified BiFeO3-MoS2 heterogeneous composites

Nanocomposite systems of BiFeO3-MoS2, BiFeO3-MoS2-MWCNT, and BiFeO3-MoS2-graphene have been synthesized through the sol-gel method. The synthesized composite powders were taken for various characterization tools like XRD, Raman, FT-IR, UV–Vis-NIR, FE-SEM, and electrochemical studies. XRD, Raman, FT-IR, and FE-SEM studies have confirmed the formation of binary and ternary composites. The loading of graphene and MWCNT on the BiFeO3-MoS2 systemsis reasonably tuned to the band gaps. Electrochemical measurements suggest that the synergic effect was found to have decreased in ternary composites (BiFeO3-MoS2-graphene and BiFeO3-MoS2-MWCNT) when compared to the binary composites (BiFeO3-MoS2). The electrochemical results of the synthesized composite have been discussed in detail.

The modified CUF-EFG method for the dynamic analysis of GPLs-CNTs-reinforced FG multilayer thick cylindrical shells under shock loadings: A modified meshless implementation

The main scope of this paper is to develop the Carrera unified formulation in cylindrical coordinates for two-dimensional meshless modelling of graphene platelet and carbon nanotube reinforced functionally graded multilayer thick cylindrical shells with the same accuracy of three-dimensional modelling. The cylindrical shell is composed of several homogeneous layers with uniform distribution of both GPL and CNT contents in each layer. The effective macroscopic mechanical properties of each GPLs and CNTs reinforced layer are estimated using the modified Halpin-Tsai (H-T) micromechanical model and rule of mixture. The volume fraction of nanofillers gradually changes layer to layer by nonlinear continuous function which leads to functionally graded (FG) distribution of nanofillers. Five grading patterns of layer distribution along the thickness direction of cylindrical shell are considered to investigate the effect of layer arrangement on dynamic behavior of cylindrical shells. The FG multilayer hybrid nanocomposite cylindrical shell is assumed to be under mechanical shock loading. The numerical method for dynamic analysis of multilayer cylindrical shell is based on element free Galerkin (EFG) method with radial basis shape functions in the framework of displacement-based Carrera unified formulation (CUF). The present EFG-CUF method is compared with analytical method for isotropic homogeneous shells and results available in the literature for FG multilayer cylindrical shells. Considering the results related to various expansion orders, proved accuracy and efficiency of proposed method for dynamic analysis of thin to thick FG multilayer cylindrical shells at high expansion orders ‘n > 2’. After verifying the analytical method, the effects of several key factors such as layer distribution patterns, volume fraction index, number of layers, nanofiller weight fraction, aspect ratios of cylinder, and damping ratio on static, free vibration, time history and wave propagation of cylinder are studied in detail.

Covalently Bonded Graphene Sheets on Carbon Nanotubes: Direct Growth and Outstanding Properties

AbstractIntegrating 1D carbon nanotubes (CNTs) and 2D graphene with covalent bonds can inherit the outstanding properties of both components and obtain additional advantages. Here, this work reports the preparation of covalently bonded graphene/CNT (G/CNT) structure by a normal chemical vapor deposition method. Specifically, the pre‐synthesized defects on the sidewall of CNTs act as nucleation sites for the growth of graphene sheets to form a branch‐leaf structure. Graphene leaves restrict the sliding and re‐stacking of CNTs, endowing G/CNT hybrid demonstrates excellent anti‐agglomeration properties that are not present in either graphene or CNTs. In addition, the covalently bonded structure and high graphitization degree of graphene sheets and CNTs significantly enhance the comprehensive properties of the G/CNT hybrid material, such as large specific surface area, excellent thermal stability, and high electrical conductivity. Consequently, the microwave absorption properties of G/CNT are significantly enhanced compared with CNTs. This work provides a feasible pathway to synthesize high‐performance covalently bonded G/CNT hybrids.

A natural biomaterial promotes hybridization chain reaction for ultra-sensitive detection of miRNA-155

MicroRNA (miRNA) is an important biomarker for early diagnosis of cancers. However, sensitive and convenient methods for miRNA detection remain a challenge. Here, we use a natural biopolymer sporopollenin purified from Ganoderma lucidum spores as a substrate for isothermal amplification (hybridization chain reaction, HCR). Sporopollenin capsules (SP) promotes HCR and forms longer and more abundant double-stranded DNA (dsDNA) than graphene oxide (GO) and carbon nanotubes (CNTs). The nanoporous structure of sporopollenin capsules containing abundant water provides a hydrous environment and enhances the hybridization efficiency of DNA significantly. We construct an ultrasensitive fluorescent biosensor to detect miR-155. The efficient HCR amplification on SP leads to an ultralow detection limit of 1 aM for miR-155 and a wide linear range of 1 aM–10 fM (R2 = 0.99). Furthermore, our fluorescence biosensor can discriminate miRNA mutants with high selectivity. This biosensor is also highly sensitive in human serum (detection limit 10 aM). It adsorbs less serum protein than GO and CNTs, thus minimizing the interference caused by the non-specific adsorption. Our study would promote medical application of SP-based biosensor in the future.

Au/NG/SWCNTs/FTO-glass modified electrode based electrochemical biosensor for DNA detection

An easy, quick, and efficient detection of Multidrug Resistance (MDR) of cancer cells at the clinical level is the need of the hour for the effective treatment of leukemia patients. In this study, we reported carbon nanomaterials-based biosensors based on Au nanoparticles (Au-NPs) decorated on Nitrogen-doped Graphene (NG) and Single-Walled Carbon Nanotubes (SWCNTs) for effective, efficient, and sensitive detection of affected DNA. Three Au/NG/SWCNT-based Modified Electrode (ME) were made containing 2, 4, and 6 mg SWCNTs. The thiol group attached at the 5′end was immobilized at ME due to a strong bond between the Au-NPs and thiol group. NG/SWCNTs enhanced the performance of the composite due to its better sensitivity and fast electron transport. Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), and Differential Potential Voltammetry (DPV) analysis were performed to monitor the performance of the sensor after the hybridization of target DNA onto the capture probe on the modified electrode surface. Different target DNA sequences were used to check the selectivity and sensitivity of the fabricated biosensor. The selectivity performance of prepared DNA sensors was also proved to be good shown by DPV results. The findings of this study provide insights for developing new highly sensitive, selective, and cost-effective portable biosensors for MDR gene detection, which will enable the early diagnosis of cancer more effective at the clinical level. Compared with previous DNA sensors with oligonucleotides directly incorporated on carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics dramatically increased DNA attachment quantity and complementary DNA detection sensitivity.

Quantitative morphometry of topological graphene-based aerogels and carbon foams by x-ray micro-computed tomography

In this work, we report quantitative morphometry of freeze-dried graphene-based aerogels (i.e., graphene aerogel-GA, nitrogenated GA-NGA, graphene-carbon nanotube hybrid-Gr-MWCNTs, carbon foam-CF, and CF-GA hybrid-CF-GA) and monoliths, prepared by hydrothermal and organic sol-gel methods, respectively. X-ray micro-computed tomography (XMCT) in combination with scanning and transmission electron microscopy allowed visualization of internal microstructures in three-dimensional space. Quantitative morphometry analysis through the reconstructed volume renderings from two-dimensional sliced images revealed hierarchical structures possessing interlaced thin sheets, honeycomb organization, and topological interconnected pore background domains. The influence of small-diameter functionalized multi-walled carbon nanotubes (MWCNTs) inclusions to graphene-like sheets and integration with CF is assessed through quantitative morphometry analysis in terms of volume-weighted pore size, wall thickness, and porosity levels. Hybrid composite porous solids elucidated cross-linking reinforced by a homogeneous distribution of CNTs into complex sheets of GA and CF matrices. A consistent trend impacting porosity and interconnectedness was found following NGA ≥ GA > CF > Gr-MWCNT2:1 > CF-GA > Gr-MWCNT3:1 > Gr-MWCNT5:1, from XMCT image processing and analyses in corroboration with physical properties and reliability. The experimental results provide insights and guide the design of characteristic porous carbonaceous and graphene-based functional nanomaterials for energy sciences, environmental engineering, and fundamental reactive transport of fluids.

The Use of Crystalline Carbon-Based Nanomaterials (CBNs) in Various Biomedical Applications

This review study aims to present, in a condensed manner, the significance of the use of crystalline carbon-based nanomaterials in biomedical applications. Crystalline carbon-based nanomaterials, encompassing graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and graphene quantum dots, have emerged as promising materials for the development of medical devices in various biomedical applications. These materials possess inorganic semiconducting attributes combined with organic π-π stacking features, allowing them to efficiently interact with biomolecules and present enhanced light responses. By harnessing these unique properties, carbon-based nanomaterials offer promising opportunities for future advancements in biomedicine. Recent studies have focused on the development of these nanomaterials for targeted drug delivery, cancer treatment, and biosensors. The conjugation and modification of carbon-based nanomaterials have led to significant advancements in a plethora of therapies and have addressed limitations in preclinical biomedical applications. Furthermore, the wide-ranging therapeutic advantages of carbon nanotubes have been thoroughly examined in the context of biomedical applications.

Efficient regeneration of shoots and roots in graphene oxide and carbon nanotubes mediated callus cultures: A qualitative and quantitative study

The applications of nanomaterials have been assessed for the regeneration of plants and secondary metabolite content. The purpose of this study was to investigate the effects of carbon nanotubes and reduced graphene oxide nanosheets on callus cultures of Fagonia indica. We aimed to assess for the first time whether reduced graphene oxide and carbon nanotubes causes plant regeneration in the absence of plant growth regulators. The callus cultures of Fagonia indica were grown in Murashige and Skoog media enriched with different concentrations of nanomaterials to examine their effect on its regeneration, biomass accumulation, and phytochemical content. Morphological and biochemical responses are measured upon interaction with nanomaterials at different time periods. Results show that calli treated with the highest concentration of carbon nanotubes showed regeneration, while the media containing reduced graphene oxide induces regeneration of shoots and roots at all concentrations. Moreover, the callus growth and biomass accumulation were increased upon addition of both nanomaterials, but the significant results are obtained at low concentration (1 mg/L and 2 mg/L). The media containing carbon nanotubes at a concentration of 2 mg/L produced the maximum biomass yield (FW= 0.7914 g, DW= 0.067 g), whereas the media containing reduced graphene oxide at a concentration of 1 mg/L produced the lowest yield (FW= 6.02985 g, DW= 0.3405 g). The highest total phenolic and flavonoid content values are obtained at the highest concentration of nanomaterials. However, the callus treated with reduced graphene oxide showed increased total phenolic content (107.4 µg GAE/mL) and total flavonoid content (8.06 µg QE/mL) as compared to total phenolic content (32.3 µg GAE/mL) and total flavonoid content (7.11 µg Q/mL) observed in callus treated with carbon nanotubes. Further, the data from High-Performance Liquid Chromatography shows that carbon nanotubes alone have the potential to trigger the pathways of secondary metabolism while reduced graphene oxide triggers only the production of Quercetin and Gallic acid. This study gives the first evidence that the use of reduced graphene oxide gives better results than carbon nanotubes as an elicitor for inducing plant regeneration, biomass accumulation, and the in vitro biosynthesis of valuable secondary metabolites.

Influence of Ion Diffusion on the Lithium-Oxygen Electrochemical Process and Battery Application Using Carbon Nanotubes-Graphene Substrate.

Lithium-oxygen (Li-O2) batteries are nowadays among the most appealing next-generation energy storage systems in view of a high theoretical capacity and the use of transition-metal-free cathodes. Nevertheless, the practical application of these batteries is still hindered by limited understanding of the relationships between cell components and performances. In this work, we investigate a Li-O2 battery by originally screening different gas diffusion layers (GDLs) characterized by low specific surface area (<40 m2 g-1) with relatively large pores (absence of micropores), graphitic character, and the presence of a fraction of the hydrophobic PTFE polymer on their surface (<20 wt %). The electrochemical characterization of Li-O2 cells using bare GDLs as the support indicates that the oxygen reduction reaction (ORR) occurs at potentials below 2.8 V vs Li+/Li, while the oxygen evolution reaction (OER) takes place at potentials higher than 3.6 V vs Li+/Li. Furthermore, the relatively high impedance of the Li-O2 cells at the pristine state remarkably decreases upon electrochemical activation achieved by voltammetry. The Li-O2 cells deliver high reversible capacities, ranging from ∼6 to ∼8 mA h cm-2 (referred to the geometric area of the GDLs). The Li-O2 battery performances are rationalized by the investigation of a practical Li+ diffusion coefficient (D) within the cell configuration adopted herein. The study reveals that D is higher during ORR than during OER, with values depending on the characteristics of the GDL and on the cell state of charge. Overall, D values range from ∼10-10 to ∼10-8 cm2 s-1 during the ORR and ∼10-17 to ∼10-11 cm2 s-1 during the OER. The most performing GDL is used as the support for the deposition of a substrate formed by few-layer graphene and multiwalled carbon nanotubes to improve the reaction in a Li-O2 cell operating with a maximum specific capacity of 1250 mA h g-1 (1 mA h cm-2) at a current density of 0.33 mA cm-2. XPS on the electrode tested in our Li-O2 cell setup suggests the formation of a stable solid electrolyte interphase at the surface which extends the cycle life.

An Aqueous Process for Preparing Flexible Transparent Electrodes Using Non-Oxidized Graphene/Single-Walled Carbon Nanotube Hybrid Solution.

In this study, we prepared flexible and transparent hybrid electrodes based on an aqueous solution of non-oxidized graphene and single-walled carbon nanotubes. We used a simple halogen intercalation method to obtain high-quality graphene flakes without a redox process and prepared hybrid films using aqueous solutions of graphene, single-walled carbon nanotubes, and sodium dodecyl sulfate surfactant. The hybrid films showed excellent electrode properties, such as an optical transmittance of ≥90%, a sheet resistance of ~3.5 kΩ/sq., a flexibility of up to ε = 3.6% ((R) = 1.4 mm), and a high mechanical stability, even after 103 bending cycles at ε = 2.0% ((R) = 2.5 mm). Using the hybrid electrodes, thin-film transistors (TFTs) were fabricated, which exhibited an electron mobility of ~6.7 cm2 V-1 s-1, a current on-off ratio of ~1.04 × 107, and a subthreshold voltage of ~0.122 V/decade. These electrical properties are comparable with those of TFTs fabricated using Al electrodes. This suggests the possibility of customizing flexible transparent electrodes within a carbon nanomaterial system.

An emerging class of 3D GNPs&MWCNTs structure of Mg matrix composites with improved thermal conductivity

Graphene nanoplates (GNPs) and carbon nanotubes (CNTs) can construct efficient thermal flux channels in composites, which is becoming one of the effective methods to improve thermal conductivity (TC) of composites. In this paper, an emerging class of GNPs&MWCNTs preform with 3D orientated structures were prepared by using electrostatic self-assembly and directional freeze-drying methods, and then fabricated the GNPs&MWCNTs reinforced AZ91D magnesium (GNPs&MWCNTs/AZ91D) composites by squeeze casting process. To ensure the well preparation of the composites, the GNPs&MWCNTs preforms need to possess enough compression strength to withstand squeezing pressure. Therefore, the effects of the electrostatic self-assembly process, directional freeze drying process and thermal reduction process on the compression strength of 3D structure GNPs&MWCNTs preforms were studied. The compression strength of GNPs&MWCNTs preforms were well improved to 98KPa, which were used for the fabrication of AZ91D matrix composites. The TC of 0.5 wt.% (1:1) GNPs&MWCNTs/AZ91D composites reached 71.7 W/(m·K) in the freezing direction, which was 41.8% higher than that (50.6 W/(m·K)) of the AZ91D alloy. This work provides a novel method for preparing GNPs&MWCNTs/AZ91D composites with improved TCs.

N-SiOx/graphite/rGO-CNTs@C composite with dense structure for high performance lithium-ion battery anode

SiOx has become one of the most promising anode materials for lithium ion batteries due to its high specific capacity, abundant natural resources and suitable lithium insertion and extraction voltage. However, the low conductivity and the poor cycle performance seriously hinder its practical application. In here, a simple and effective method is proposed to disperse SiOx between carbon materials including flake graphite, reduced graphene oxide (rGO) and carbon nanotubes (CNTs), and then micron-sized N-SiOx/graphite/rGO-CNTs@C (N-SiOx/C@C) composite with dense structure is prepared by coating and pyrolysis of pitch. The synergistic effect of various carbon materials is beneficial to improve the conductivity of the material, and maintain the structural integrity during the cycle. The obtained N-SiOx/C@C anode exhibits high reversible capacity (980.2 mAh·g−1), excellent cycle stability (70 % capacity retention after 500 cycles at 0.5 A·g−1) and excellent rate performance (491.9 mAh·g−1 specific capacity of at 5 A·g−1). The strategy provided here effectively improves the electrochemical performances of SiOx, and the prepared materials show great application potential in the field of lithium ion batteries.

Synergistic influence of multi-walled carbon nanotubes and graphene nanoparticles on the structural, thermal and mechanical characteristics of poly (3-hydroxybutyrate) films

Poly (3-hydroxybutyrate) (PHB) is a linear, semi-crystalline biopolymer that belongs to polyhydroxyalkanoates family. It is completely bio-based, biocompatible, and biodegradable in nature. However, due to its low melt processing window, PHB becomes unstable during high-temperature processing. Carbon-based materials such as graphene (Gr) and multi-walled carbon nanotubes (MWCNT) suffer from restacking /agglomeration problems when loaded into polymer matrix. Recent studies revealed that MWCNT could bridge the gap between Gr flakes and loading them together can solve the agglomeration problem. In the present study, tip sonication-assisted solution casting method was used to fabricate PHB-based nanocomposites loaded with 0.3 wt% Gr, 0.3 wt% MWCNT, and their combination (0.3 wt% Gr and 0.3 wt% MWCNT). The prepared films were characterized using Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and Field emission transmission electron microscope (FETEM). Furthermore, structural, mechanical and optical properties were measured. FTIR analysis evidenced that the nature of the interaction between PHB matrix and nanofillers was physical. In comparison with neat PHB, significant improvement in UV and visible light barrier was observed for PHB/0.3Gr/0.3MWCNT films. TGA revealed that reinforcement of dual nanofillers viz. 0.3 wt% Gr and 0.3 wt% MWCNT significantly improved thermal degradation temperature (over 8 ℃ compared to PHB) than single nanofiller-loaded films. Likewise, the tensile strength of PHB-based films increased from 19±1.32 to 29±4.53 MPa, and crystallinity increased from 38.15 to 47.34 % with dual nanofiller loading. Therefore, it can be concluded that the inclusion of two carbonaceous nanofillers had a positive synergistic effect on the thermal, mechanical and optical properties of PHB.

Ionanofluid flow through a triangular grooved microchannel heat sink: Thermal heightening

With recent technological advances, thermal transport from different electronic and electrical devices is the most vital concern. The microchannel heat sink (MCHS) of liquid cooling is a useful device to remove over thermal load. Ionanofluid is a brand new and super potential cooling fluid for its ionic conductivity, non-flammability, negligible volatility, and high-level heat stability. In this research, the ionanofluid's velocity and thermal field characteristics through a triangular grooved MCHS are investigated using numerical tools. The combination of ionic liquid (IL) 1-Butyl-3-methylimidazolium Bis(trifluoromethanesulfonyl)imide [C4mim]NTf2 and propylene glycol (PG) is used as base fluid whereas graphene (G) and single-walled carbon nanotube (SWCNT) are chosen as hybrid nanoparticles to make the working ionanofluid. The governing equations of nonlinear partial differential equations describing the physical phenomena along with proper border settings are resolved by applying the finite element method (FEM). Different ratios of hybrid nanoparticles (G: SWCNT) like (1: 0, 1/3: 2/3, 1/2: 1/2, 2/3: 1/3, 0: 1) are suspended in the base fluid mixture. In addition, the base fluid mixture is assumed in different combinations of (IL: PG) as (100: 0, 50: 50, 0: 100). The numerical results are displayed in the forms of streamlines, isothermal lines, and rate of thermal transfer for the pertinent parameters namely forced convection (Re = 100–900) and solid concentration (φ = 0.001–0.05). Also, pressure drop, field synergy number, relative fanning friction feature, relative Nusselt number, and temperature enhancement efficiency are calculated. The results indicate that a higher heat transport rate is found using the IL-based ionanofluid with the highest solid concentration. Moreover, the higher forced convection enhances the thermal efficiency of MCHS. Two linear regression equations along with very good correlation coefficients have been derived from the numerical results.