Narrow Results

This theoretical study examines the effects of thermal radiation, viscous dissipation, and a magnetic field effect on a nanofluid that contains carbon nanotubes in blood and moves over a two-way expanding surface. We consider both the stretching and contracting directions when examining the bidirectional nature of the expanding surface. We define the problem’s governing equations, which include energy and momentum, and transform them into a set of ordinary differential equations using suitable similarity transformations. We semi-numerically solve the resulting equations using HAM methods and the BVPh. 2.0 program. We also discuss the consequences of heat radiation and viscosity dissipation in the nanofluid. The Rosseland approximation models the effect of thermal radiation, while the incorporation of fluid’s internal friction represents viscous dissipation. This research aims to investigate the combined effects of various parameters, such as thermal radiation, Eckert number, nanoparticle volume fraction, couple stress parameter, power law index, magnetic field, and Prandtl number, on the heat, flow, and transfer properties of single-walled carbon nanotube (SWCNT), multi-walled carbon nanotube (MWCNT), and blood-based nanofluids. A fascinating field of study, this study will reveal useful details about the possible uses of carbon nanotube blood-based nanofluids across bidirectional expanding surfaces in drug delivery systems, heat transfer processes, and biomedical engineering. Blood-based nanofluids can benefit from the inclusion of carbon nanotubes to improve fluid behavior and thermal conductivity, which is crucial for a number of industrial and medicinal applications.

In this paper, the nanocrystalling composite Mg-Ni-TiO₂-CNTs was made by mechanical ball milling under hydrogen pressure of 5.0×10^-5Pa, The hydrogen storage properties and operation temperatures were investigated. It was found that the composite can absorb 7.5wt.% hydrogen in 60s under 5.0×10^-5Pa hydrogen pressure and desorb 6.5wt% hydrogen in 600s at 260°C under 5.0×10^-5Pa hydrogen pressure. The composite has very high absorption, hydrogen capacity and remarkable kinetic properties in hydriding /dehydeiding process. TiO₂, Ni and CNTs were used as additive to improve the hydrogen storage performance. They can be utilized as an effective catalyst to improve hydriding/dehydriding performance of hydrogen storage material and lead to pronounced enhancement on the hydrogen storage property of Mg. The results showed that the composite has potential application in the future.

Here we used the iron oxide nanoparticles derived from ferritin as catalyst for the synthesis of carbon nanotubes (CNTs) by the chemical vapor deposition (CVD) of coal gas. It has been found that the structure and morphology of CNTs can be tailored, to some degree, by varying the experimental conditions such as catalyst loading and process parameters. In addition to straight CNTs, some Y-branched CNTs were also obtained, which might be due to the sulfur species in the coal gas.

Multi-walled carbon nanotubes (CNTs) were grown via pyrolytic chemical vapor deposition technique and explored for their infrared sensing behavior. CNT synthesis was carried out over cobalt zinc ferrite $({\mathrm{\text{Co}}}_{0.5}{\mathrm{\text{Zn}}}_{0.5}{\mathrm{\text{Fe}}}_2{\mathrm{\text{O}}}_4)$ catalyst nanoparticles under different gas flow conditions to control outside diameter of the nanotubes. It was found that a progressive decrease in the carbon precursor gas (acetylene in this case) from 5:1 to 9:1 (v/v) causes reduction of average CNT diameter from 85 nm to 635 nm. Growth conditions involving higher temperatures yield nanotubes/nanofibers with outer diameter of $>$500 nm, presumably due to surface aggregation of nanoparticles or increased flux of carbonaceous species at the catalyst surface or both. Current–voltage characteristics of the nanotubes depending on the CNT diameter, revealed linear or nonlinear behavior. When incorporated as sensing layer, the sensitivity of $\sim$5.3 was noticed with response time of $\sim$4.1 s. It is believed that IR sensing characteristics of such CNT-based detectors can be further enhanced through post-synthesis purification and chemical functionalization treatments.

In this paper, we study the behavior of three-dimensional extremely-short optical pulses propagating in a system made of carbon nanotubes in the presence of an external magnetic field applied perpendicular both to the nanotube axis and to the direction of propagation of the pulse. The evolution of the electromagnetic field is classically derived on the basis of the Maxwell’s equations. The electronic system of carbon nanotubes is considered in the low-temperature approximation. Our analysis reveals the novel and unique ability of controlling the shape of propagating short optical pulses by tuning the intensity of the applied magnetic field. This effect paves the way for the possible development of innovative applications in optoelectronics.

The Fe–Ni–P matrix composites reinforced with carbon nanotubes (CNTs) were prepared by means of liquid phase sintering at 950${}^{\circ }$C. The effects of the mass fraction of CNTs on the microstructures and properties of the composites were investigated. It is noteworthy that the structures of CNTs were hardly damaged during the sintering process via evaluation of microstructures on as-sintered composites. The strength and ductility increased gradually with the increase of CNT content while the saturation magnetization decreased gradually. The sample containing 1 wt.% CNTs showed a good combination of a compression ratio of 60% and a compressive strength of approximately 3800 MPa, which indicated its potential application in modern power generation systems.

Carbon nanotubes (CNTs) have been successfully synthesized by using in-house fabricated Double Stage Chemical Vapor Deposition (DS-CVD) technique, using acetylene (C₂H₂) and hydrogen (H₂) as the precursor gases. The purity, morphology and the structure of CNTs were then characterized using Field Emission Scanning Microscope (FESEM), Transmission Electron Microscope (TEM) and Thermogravimetric Analysis (TGA). The effects of the process parameters were examined whereby the experimental design of the investigation was conducted using Design Expert^® Version 6.0.8. The statistical analysis reveals that the optimized conditions for the best CNTs yield production at 850°C reaction temperature, 60 min reaction time, with gas flow rates at 40 and 150 ml/min for C₂H₂ and H₂, respectively. The CNTs produced were successfully used as column chromatographic media. Due to its nanosized structured dimension, CNTs' have tremendously large surface area and that lead to highly efficient protein purification. Skim latex protein has been used as the model protein and we aim to recover useful proteins and enzymes from this known wasteful material. During the purification, the process parameters such as pH and ionic strength of the running buffer were optimized to enhance protein purification. Results reveal that CNTs behave efficiently as a hydrophobic interaction chromatographic media.

The effectiveness of stannum (Sn²⁺) removal from aqueous solution by using magnetic biochar and functionalized multiwalled carbon nanotube (FMWCNT) was investigated. The effect of various factors, namely pH, adsorbent dosage, agitation speed and contact time was statistically studied through analysis of variance (ANOVA). Statistical analysis revealed that the optimum conditions for the highest removal of Sn²⁺ are at pH 5, dosage 0.1 g with agitation speed and time of 100 rpm and 90 min, respectively. At the initial concentration of 0.1 mg/L, the removal efficiency of Sn²⁺ using FMWCNTs was 93% and 85% with magnetic biochar. The Langmuir and Freundlich constant for both FMWCNTs and magnetic biochar were 13.397 L/mg, 18.634 L/mg and 17.719 L/mg, 25.204 L/mg, respectively. Hence, results prove that FMWCNTs are a better adsorbent with a higher adsorption capacity compared to magnetic biochar. Adsorption kinetic obeyed pseudo-second-order.

Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone–Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

A floating catalyst chemical vapor deposition (FC-CVD) method was designed and fabricated to produce high quality and quantity carbon nanotubes. The reaction temperature was optimized to produce high yield and purity of the carbon nanotubes. The reaction temperatures were varied from 500–850°C. The result shows that carbon nanotubes were observed from 600°C to 850°C with maximum numbers and high purity at 850°C. The diameter range of CNTs varied from 2 to 55 nm. The results of the present investigation suggest that the observed changes in catalytic activity and selectivity accompanying an increase in temperature are probably due to major alterations in the distribution of atoms at the metal/gas interface. Thermodynamically, higher temperatures favor the surface decomposition of hydrocarbon rather than the hydrogenation reactions.

Cadmium (Cd${}^{2+}$) is one of the toxic heavy metals that is frequently used in many industrial products. The wastewater from these industries and their products contains residual cadmium that are difficult to be removed economically from the effluent. Carbon nanotubes (CNTs) were synthesized in several batches and tested for their removal efficacy with regards to cadmium removal from synthetic wastewater. Fixed catalyst chemical vapor deposition (FCCVD) reactor system was fabricated in the laboratory for the synthesis of CNTs on the powdered activated carbons (PACs). The PACs were impregnated with Fe${}^{3+}$ catalysts, and growth parameters such as the reaction time, gas flow rates and reaction temperature were optimized. The sorption capacity of the raw CNT–PAC was not satisfactory until the sorbents were functionalized which eventually led to high adsorption capacities. The surface properties of CNT–PAC were modified by oxidative functionalization using two different methods: sonication with KMnO₄ and refluxing with HNO₃ at 140${}^{\circ }$C. KMnO₄-treated CNT–PAC exhibited the highest sorption capacity for cadmium uptake which increased from 4.77mg/g (untreated CNT–PAC) to 11.16mg/g; resulting in Cd${}^{2+}$ removal efficiency from 38.87% to 98.35%.

Use of Electronic skin (E-skin) has attracted significant attention, as it has broad application prospects in medical care, wearable electronic equipment, and body monitoring — particularly with respect to human motion detection. In this work, we developed a flexible, tensile strain sensor based on the dry printing method. A conductive layer, with a miniaturized network structure, was obtained by: (1) packing the grooves of a grid-like silicon template with a conductive powder composed of carbon nanotubes (CNTs) and silicon dioxide (SiO${}_2)$ nanoparticles; (2) infiltrating liquid polydimethylsiloxane (PDMS) into the powder voids using a coated, flexible PDMS substrate cover; (3) transferring the solidified, patterned conductive powder onto the flexible substrate by peeling the PDMS substrate cover off the template; (4) fabricating metal electrodes at both ends of the conductive layer and (5) encapsulating the strain sensor with liquid PDMS. After manufacture, the strain sensor was tested using the tensile test. Results from the tensile test demonstrate that the sensor has excellent electrical conductivity, including super high-sensitivity $(\mathrm{\text{GF}}>1450)$, a large strain range (up to 35%), and good transparency; as ultraviolet (UV) spectrum analysis shows that the transmittance can reach $>60$%. Thus, the sensor is potentially applicable to numerous sub-specialties that require specialized electronics.

In this work, a sandwich structure electrode was prepared by a simple vacuum filtration and rolling process. The SEM showed that the active materials were uniformly embedded in the pores of the three-dimensional conductive network of the carbon nanotube (CNTs) conductive paper. The contact interface area of active material and the conductive network significantly increased and the interface resistance was greatly reduced. The porous anode can accommodate the volume expansion of the silicon and effectively alleviated pressed during cycle. The electrode also exhibited good stability in cycles. Electrochemical tests showed that the first discharge specific capacity of the sandwich electrode reached 2330mAh/g with a coulombic efficiency of 86%. After 500 cycles, the specific capacity was still maintained at 1512mAh/g. At a large current density of 2A/g, the specific capacity hold was 840mAh/g compared with the copper foil electrode of 100mAh/g.

NiCo₂S₄/CNTs (NCS/CNTs) hybrid nanostructures have been synthesized by a facile one-step solvothermal method with varying content of CNTs. The structure and morphology of the synthesized NCS/CNTs hybrid revealed the formation of platelets anchored on the CNT matrix. When evaluated as electrode materials for supercapacitor, the as-synthesized NCS/CNT-1 hybrid (with 1% of CNT) manifested remarkable specific capacitance of 1690Fg${}^{-1}$ at the current density of 5Ag${}^{-1}$. More importantly, an asymmetric supercapacitor (ASC) assembled based on NCS/CNT-1 as positive electrode and carbon nanotube paper (CNP) as a negative electrode delivered high energy density of 58Whkg${}^{-1}$ under power density of 8kWkg${}^{-1}$. Furthermore, the ASC device exhibited high cycling stability and 77.7% of initial specific capacitance retention after 7000 charge–discharge cycles at a current density of 8Ag${}^{-1}$. The large enhancement in the electrochemical performance is attributed to the benefits of the nanostructured architecture, including good mechanical stability, high electrical conductivity as well as buffering for the volume changes during charge–discharge process. These convincing results show that NCS/CNTs hybrid nanostructures are promising electrode materials for high energy density supercapacitors (SCs).

Four different dispersants, sodium dodecyl benzene sulfonate (SDBS), cetyl trimethyl ammonium bromide (CTAB), polyvinylpyrrolidone (PVP) and polyacrylic acid (PA) were used to disperse carbon nanotubes(CNTs) composite plating solution. Dispersion effect was compared by the absorbance value of the bath. The analysis indicated that dispersants had variation of different dispersants on CNTs suspension, under the same technology condition, the dispersion effect of PA was better than PVP, CTAB and SDBS. When the optimum amount of PA was added, it had the good dispersion stability, the narrow particle size distribution and small average particle diameter. Surface quality of the slide bearings were significantly improved as well.