Aspect Ratio Of Multiwalled Carbon Nanotubes Research Articles

Effect of hybrid filler comprising cryptocrystalline graphite and multi‐wall carbon nanotubes on the mechanical and conductive properties of styrene butadiene rubber

AbstractStyrene butadiene rubber (SBR) composites reinforced by cryptocrystalline graphite (CG) and multi‐wall carbon nanotubes (MWCNTs) were prepared. The SBR composite with 50 phr CG content displays superior mechanical reinforcement achieving 20.7 MPa in tensile strength. However, the electrical conductivity enhancement is modest. After incorporating MWCNTs as a secondary filler, the electrical conductivity significantly improved. The results show that the electrical conductivity of the SBR composite reinforced with 10 phr of CG and an additional 5 phr of MWCNTs surpasses that achieved by using 50 phr of CG solely. This enhancement can be attributed to the inherent excellent electric conductivity and high aspect ratio of MWCNTs, with their presence also preventing the re‐agglomeration of CG. Furthermore, within 10–40 phr content of CG, the mechanical reinforcement of CG‐SBR composites is enhanced with the addition of MWCNTs, whereas a minor decline in tensile strength is noted when the concentration of CG above 40 phr. Overall, the SBR composite reinforced with a synergistic combination of CG and MWCNTs is achieved, demonstrating both exceptional mechanical and conductive properties.Highlights Styrene butadiene rubber (SBR) composites with different cryptocrystalline graphite (CG) phr and additional multi‐wall carbon nanotubes (MWCNTs) were characterized. CG‐SBR displays good mechanical property but limited electrical conductivity. Proper ratio of CG/MWCNTs significantly enhances various properties. MWCNTs act as a “bridge” structure connecting isolated CG filler in SBR matrix. MWCNTs network effectively prevents the re‐agglomeration of CG nanosheets.

Water-like thermal conductivity of ionanofluids containing high aspect ratio multi-walled carbon nanotubes and 1-ethyl-3-methylimidazolium-based ionic liquids with cyano-functionalized anions

In the era of growing climatic requirements, the search for efficient heat transfer and storage fluids for both industrial and domestic applications is a very important point on the road map of energy transformation in the economies of countries around the world. To achieve the assumed process parameters, working fluids must be characterized by many, often seemingly contradictory, parameters, such as high thermal conductivity and low viscosity, for effective heat transfer. Therefore, the media usually have a very complex structure, which is often designed on the atomic level. An example of such are ionanofluids (INFs) – colloidal dispersions of solid nanoparticles in ionic liquids (ILs). This work aimed to determine the impact and comparison of various cyano-functionalized anions ([SCN]−, [N(CN)2]−, [C(CN)3]−) in 1-ethyl-3-methylimidazolium ([Emim]+) ILs on key properties, such as thermal conductivity, density, viscosity, and structure of INFs, in a wide range of temperature and concentration (up to 10 wt%) of in-house synthesized multi-walled carbon nanotubes (MWCNTs) and carboxyl-functionalized (oxidized) MWCNTs, as well as commercially-available helical carbon nanotubes. Very promising results have been obtained, especially in the case of 1-ethyl-3-methylimidazolium tricyanomethanide [Emim][C(CN)3] with 5.0 wt% loading of ultra-high aspect ratio (up to 11,000) in-house 16 h MWCNTs – thermal conductivity reached 0.532 W·m−1·K−1 at 25 °C which is a threefold improvement (200 %) over the base IL. The thermal conductivity of this value is close to that of water, i.e., an absolute record holder among the conventional heat transfer fluids (0.606 W·m−1·K−1 at 25 °C). The nanofluids were characterized by long-term stability and a wide spectrum of rheological properties, from liquid-like INFs to solid-like ‘bucky gels’, which can be controlled mainly by the morphology and concentration of MWCNTs. For instance, liquid-like [Emim][N(CN)2] + 1.0 wt% in-house 16 h MWCNTs had a viscosity of 34.0 mPa·s (at 186 s−1, 25 °C), which was lower than those of many conventional heat transfer fluids including propylene glycol (42.3 mPa·s, 25 °C), Duratherm® S (49.2 mPa·s, 27 °C), Therminol® 66 (70.8 mPa·s, 27 °C), or Xiameter® PMX-210 (100 mPa·s, 25 °C), while solid-like [Emim][SCN] + 3.0 wt% in-house 16 h MWCNTs had a viscosity up to 8.9 Pa·s (at 18.6 s−1, 25 °C) and may be used in next-generation phase-change materials for efficient thermal energy storage.

On twin substantially improved thermal properties and stability of pyrrolidinium-based ionanofluids with long multi-walled carbon nanotubes

The quest for advanced heat transfer fluids with superior thermal properties has led to the exploration of ionanofluids (INFs). Such systems are composed of ionic liquids (ILs) and thermoactive dispersed nanoparticles, and offer promising opportunities for the enhanced heat transfer. In this work, we selected long multi-walled carbon nanotubes (MWCNTs) as well as 1-propyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C3C1pyr][NTf2]) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4C1pyr][NTf2]) as base liquids. The chosen ILs have the same thermal conductivity and similar viscosity which results in the ‘twin’ thermal conductivity of related INFs in the whole range of MWCNTs loading as well as similar rheological performance. We find the remarkable synergistic effects of incorporating 5.0 wt% of long MWCNTs into [C3C1pyr][NTf2]-based INF, resulting in a sky-rocketing 560% increase in thermal conductivity of INF compared to the base IL. The [C4C1pyr][NTf2]-based INFs exhibited excellent thermal and sedimental long-term stability (4 years), characterized by change in thermal conductivity and in density lower than declared uncertainties. We proved that remarkably enhanced thermal conductivity was mainly influenced by the high aspect ratio of MWCNTs enabling formation of long-range, 3D nanotube networks additionally stabilized by nanolayers of IL on the MWCNTs surface.

Non-linear buckling analysis of MWCNT reinforced hybrid composite shell subjected to hydrostatic pressure: A numerical and experimental investigation

The present study is focused on the numerical and experimental investigation of the non-linear buckling behavior and ply-failure analysis of a hybrid composite shell under uniform hydrostatic pressure exposed on its outer surface. Laminated composite shells made of glass fiber reinforced polymer (GFRP) composites with and without multi-walled carbon nanotubes (MWCNT) reinforcement are considered for the investigation. The critical buckling pressure is numerically determined by performing a buckling analysis on a hybrid composite shell with consideration of various non-linearities such as material non-linearity, geometric non-linearity, and geometric imperfection using the commercially available software ANSYS®. The governing non-linear differential equations of composite shell structures are solved using the arc-length approach and non-linear finite element analysis. The nanotubes dispersion, distribution, structural integrity, aspect ratio, functional group, and purity level of CNT reinforcement with epoxy matrix materials are quantified using field emission scanning electron microscopy (FE-SEM). The elastic and plastic properties of the GFRP lamina with and without MWCNT reinforcement are experimentally determined based on ASTM D3039. The critical buckling pressure obtained through experiments on a GFRP composite shell with and without MWCNT reinforcement is compared with the results obtained from the numerical analysis to validate the effectiveness of the present numerical model. Parametric studies are undertaken to investigate the first ply failure analysis, the effect CNT reinforcement, aspect ratio of MWCNT, and different lamination sequences on the critical buckling pressure of the composite shell. It was observed that the Von-Misses stresses developed on the composite structures with ply angles of either all layers as 0° or combination of ply angles with 0° and 90° is always less than those of the structures having ply-angles such as 45° and 60°, irrespective of CNTs reinforcement. Furthermore, the highest critical buckling pressure was obtained with reinforcement of 1.5 wt% MWCNT in the composite shell with ply orientation of [90°]4s.

Low-Cost and Highly Sensitive Pressure Sensor with Mold-Printed Multi-Walled Carbon Nanotubes Dispersed in Polydimethylsiloxane.

Flexible pressure sensors with piezoresistive polymer composites can be integrated into elastomers to measure pressure changes in sealings, preemptively indicating a replacement is needed before any damage or leakage occurs. Integrating small percentages of high aspect ratio multi-walled carbon nanotubes (MWCNTs) into polymers does not significantly change its mechanical properties but highly affects its electrical properties. This research shows a pressure sensor based on homogeneous dispersed MWCNTs in polydimethylsiloxane with a high sensitivity region (0.13% kPa, 0–200 kPa) and sensitive up to 500 kPa. A new 3D-printed mold is developed to directly deposit the conductive polymer on the electrode structures, enabling sensor thicknesses as small as 100 μm.

Role of inflammation in the malignant transformation of pleural mesothelial cells induced by multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) are one of the most widely used types of novel nano-fiber materials. The aim of this study was to establish an experimental system based on actual exposure dosage and environments and explore the roles and mechanisms of inflammation in the malignant transformation of pleural mesothelial cells induced by MWCNTs after low doses and long-term exposure. Here, we established an in vitro system by co-culturing macrophages and mesothelial cells and exposing these cells to high aspect ratio MWCNTs (0.1 μg/mL) for three months. Results indicated that IL-1β, secreted by macrophages stimulated by MWCNTs, may significantly enhance the release of inflammatory cytokines, such as IL-8, TNF-α, and IL-6, from mesothelial cells. Results obtained from proliferation, migration, invasion, colony formation, and chromosomal aberration studies indicated that MWCNTs may promote malignant transformation of mesothelial cells after long-term and low-dose exposure via inflammation. Furthermore, the obtained results demonstrated that the NF-κB/IL-6/STAT3 pathway was active in the malignant transformation of Met 5A cells, induced by MWCNTs, and played an important role in the process. In conclusion, our results showed that the NF-κB (p65)/IL-6/STAT3 molecular pathway, which was mediated by inflammation, played an important role in the malignant transformation of pleural mesothelial cells induced by MWCNTs. These findings also provide novel ideas and references for the treatment of mesothelioma and offers options for the occupational safety of nanomaterial practitioners.

Effect of aspect ratio of multi-wall carbon nanotubes on the dispersion in ethylene-α-octene block copolymer and the properties of the Nanocomposites

Effects of aspect ratio of multi-wall carbon nanotubes (MWCNTs) on the dispersion of MWCNTs in ethylene-α-octene block copolymer (OBC) and the properties of OBC/MWCNTs nanocomposites were studied, and two series of MWCNTs with different aspect ratios based on the same length and the same diameter were considered. Scanning electron microscope (SEM) and transmission electron microscope (TEM) results show that small and large agglomerates induced by intra- and inter-entanglement of MWCNTs are present for MWCNTs with high aspect ratio having smaller diameter and larger length, respectively. Rheological, electrical and tensile properties of OBC/MWCNTs nanocomposites are related to the aspect ratio and dispersion of MWCNTs. The formation of agglomerates, especially large agglomerates, influence the network perfection, weakening the contribution of MWCNTs to the rheology and electrical properties. The inter-entanglement shows less negative effect on the enhancement for the modulus and strength of OBC nanocomposites, and intra-entanglement of MWCNTs shows discounted enhancing properties. The aspect ratios of MWCNTs related to not only the length but also the diameter play the dominant role on the dispersion in polymers and the properties of polymer nanocomposites.

Morphological, electrical, mechanical and thermal properties of high-density polyethylene/multiwall carbon nanotube nanocomposites: effect of aspect ratio

The effects of the aspect ratio and the addition of multiwall carbon nanotubes (MWCNTs) on the morphological, electrical, mechanical and thermal properties of high-density polyethylene (HDPE)-based nanocomposites are investigated. The HDPE nanocomposites with various amounts up to 18.74 wt% of MWCNTs that have two different aspect ratios (AR) (200–400 (M58) and 500–3000 (M12)) were prepared by a melt mixing method, followed by compression molding. The results demonstrate that the addition of MWCNTs enhances the electrical, mechanical and thermal properties of the HDPE/MWCNTs nanocomposites. The HDPE nanocomposites with higher aspect ratio MWCNTs demonstrated a slightly better enhancement in the morphological and electrical properties than the other ones with lower aspect ratio MWCNTs. Additionally, Young’s modulus and the thermal stability increased with increasing aspect ratio of MWCNTs.

Thermo-Mechanical Post Buckling Analysis of Multiwall Carbon Nanotube-Reinforced Composite Laminated Beam under Elastic Foundation

Abstract In present paper, buckling analysis is performed over laminated composite beam incorporating multi walled carbon nanotube (MWCNT) polymer matrix and then reinforced with E-glass fiber in an orthotropic manner under inplane varying thermal and mechanical loads by finite element method (FEM). Aim of the study is to develop a model which accurately perform the buckling deterministic analysis of multi-walled carbon nanotube reinforced composite laminated beam (MWCNTRCLB) with the evaluation of material property by applying Halpin–Tsai model. Combined Higher order shear deformation theory and Pasternak elastic foundation based on von Karman nonlinear kinematics and Winkler cubic nonlinearity respectively, are successfully implemented. Through minimum potential energy principle, generalized static analysis is performed using FEM, based on interactive MATLAB coding. The critical buckling load and critical buckling temperature is presented under the action of inplane variable mechanical and thermal load, with different boundary conditions, beam thickness ratio and MWCNT aspect ratio, variation with MWCNT volume fraction and coefficient of thermal expansion, with and without foundation for linear and nonlinear cases.

Improved Functionalization of Multiwalled Carbon Nanotubes in Ultra-Low Acid Volume: Effect of Solid/Liquid Interface

A comprehensive study of a less harmful functionalization of multiwalled carbon nanotubes (MWCNT) was performed. The influence of ultrasonic cavitation and solid/liquid interface was indirectly evaluated by statistical characterization of MWCNT aspect ratio and degree of functionalization. MWCNT aspect ratio was determined through hundreds of electron microscopy images. Degree of functionalization of MWCNT was characterized by elemental analysis and thermogravimetry. Distribution of different oxygen-containing functional groups was assessed by potentiometric titration. MWCNT aqueous dispersions were evaluated by electrophoretic mobility and dynamic light scattering. An acid volume over 90% lower than usually reported in literature guaranteed MWCNTs with significantly larger aspect ratio, higher proportion of carboxylic groups and a more negative zeta potential in aqueous suspension. These results can be related to a more localized ultrasonic cavitation in MWCNTs/acid interface for reduced liquid volumes. This distinguished influence of ultrasonic cavitation may be a valuable contribution to more eco-friendly processes with nanomaterials.

Effects of the aspect ratio of multi-walled carbon nanotubes on the structure and properties of regenerated collagen fibers

Collagen is a natural one-dimensional nanomaterial. Multi-walled carbon nanotubes (MWNTs) have been previously shown to interact with biomolecules and to have promising applications in reinforced biopolymers for tissue engineering and regenerative medicine. In this work, collagen/MWNT composite fibers are prepared using dry-jet wet-spinning technology. Three types of MWNTs with aspect ratios of 40, 150, and 4000 are used to investigate the effects of the MWNT aspect ratio on the properties of the composite fibers. There results show that there are strong molecular interactions between the MWNTs and collagen molecules. The mechanical properties and thermal stability of the composite fibers are significantly improved compared to those of the collagen fibers. The diameter and aspect ratio of the MWNTs are the main factors affecting the self-assembled structure of the collagen molecules, the alignment of the microfibrils, and the mechanical and thermal performance of the composite fibers.

Interlaminar fracture toughness, adhesion and mechanical properties of MWCNT–glass fiber fabric composites: Effect of MWCNT aspect ratios

Multi‐walled carbon nanotubes (MWCNTs) with various aspect ratios were first designed onto the glass fiber fabric (Gf), for the purpose of fabricating a series of MWCNT–glass fiber fabric (MGf) composites with controllable interlaminar fracture toughness, adhesion and mechanical properties. The dispersal ability of MWCNT on the Gf surface was closely related to its aspect ratios, which may greatly affect the toughness and strength of epoxy‐based composites. An interesting result showed that the interlaminar fracture toughness of MGf composites with MWCNT aspect ratios of ~667 to ~1333 was significantly improved. Under an optimal MWCNT aspect ratio (~1333), the interlaminar shear, tensile and flexural strength of the MGf composite were raised by 43.8, 38.2, and 34.2%, respectively, and its dynamic mechanical properties had a similar rule, as compared with neat Gf composite. Almost all the MGf composites with MWCNT exhibited some ductile fracture behavior whether in tensile or flexural tests. POLYM. COMPOS., 40:E1329–E1337, 2019. © 2018 Society of Plastics Engineers

Thermal and electrical properties of carbon nanotube-based epoxy composite materials

The novel properties of carbon nanotubes have generated much interest in nanostructured polymer composite materials. The effect of multi-walled carbon nanotube aspect ratio on the thermal and electrical properties of nanostructured epoxy composite materials was investigated both experimentally and theoretically. Both thermal and electrical conductivity measurements were performed, and comparisons were made between the results obtained for the nanostructured composite materials containing carbon nanotubes with different aspect ratios. Potential applications of these nanostructured composite materials were discussed, and design recommendations were also made. The numerical and experimental results indicated that the aspect ratio plays an important in determining the physical properties of the nanostructured epoxy composite materials. The electrical conductivity of the nanostructured composite materials is highly dependent on the aspect ratio of carbon nanotubes. In contrast, the aspect ratio plays a considerable role in the thermal conductivity of the composite materials. Multi-walled carbon nanotubes are capable of improving both thermal and electrical performance of the polymer matrix. In contrast to the orders of magnitude enhancement in electrical conductivity with a very low loading of carbon nanotubes, the thermal conductivity of the composite materials has shown only moderate improvement. The improvement in physical properties of the composite materials can be interpreted in terms of carbon nanotube networks.

Towards fractional-order capacitors with broad tunable constant phase angles: multi-walled carbon nanotube-polymer composite as a case study

In this study, multi-walled carbon nanotube (MWCNT) filled polyevinelidenefluoride-trifluoroethylene-chlorofluoroethylene composites are used to realize fractional-order capacitors (FOCs). A solution-mixing and drop-casting approach is used to fabricate the composite. Due to the high aspect ratio of MWCNTs, percolation regime starts at a small weight percentage (wt%), 1.00%.The distributed MWCNTs inside the polymer act as an electrical network of micro-capacitors and micro-resistors, which, in effect, behaves like a FOC. The resulting FOCs’ constant phase angle (CPA) can be tuned from to by changing the wt% of the MWCNTs. This is the largest dynamic range reported so far at the frequency range from 150 kHz to 2 MHz for an FOC. Furthermore, the CPA and pseudo-capacitance are shown to be practically stable (with less than 1% variation) when the applied voltage is, changed between 500 µV and 5 V. For a fixed value of CPA, the pseudo-capacitance can be tuned by changing the thickness of the composite, which can be done in a straightforward manner via the solution-mixing and drop-casting fabrication approach. Finally, it is shown that the frequency of a Hartley oscillator built using an FOC is almost 15 times higher than that of a Hartley oscillator built using a conventional capacitor.

The effect of multi-wall carbon nanotube morphology on electrical and mechanical properties of polyurethane nanocomposites

In this study, we examine the effect of multi-wall carbon nanotubes (MWCNT) morphology on electrical and mechanical properties of MWCNT-filled polyurethane (PU) nanocomposites. The main objective of this study is to understand the role of aspect ratio and length of MWCNTs in determining the performance of nanocomposites. Highly aligned MWCNTs were prepared by aerosol-assisted chemical vapour deposition method and compared to commercially available MWCNTs in PU matrix for ease of dispersibility and performance. We observed opposing influence of the MWCNT on electrical and mechanical behaviour of the nanocomposites. The electrical properties were proportional to length of the MWCNTs whereas the mechanical properties were dependent on the aspect ratio of the MWCNTs. Moreover, thicker nanotubes (approximately 40nm) with a higher aspect ratio (approximately 225) are less prone to shortening and impart better tensile and storage modulus along with improved electrical and therefore are more suitable for the MWCNT nanocomposites.

Effects of aspect ratio of multi-walled carbon nanotubes on coal washery waste water treatment

The dependency of adsorption behaviour on the aspect ratio of multi-walled carbon nanotubes (MWCNTs) has been explored. In this study, effect of growth temperature on yield and aspect ratio of MWCNTs by catalytic chemical vapour deposition (CCVD) method is reported. The result revealed that yield and aspect ratio of synthesised MWCNTs strongly depend on the growth temperature during CCVD operation. The resulting MWCNTs were characterized by High Resolution Transmission Electron Microscope (HRTEM), Dynamic Light Scattering (DLS) and X-ray diffraction (XRD) techniques to determine it diameter, hydrodynamic diameter and crystallinity respectively. Aspect ratio and length of the grown MWCNTs were determined from the HRTEM images with the hydrodynamic diameter using the modified Navier-Stokes and Stokes-Einstein equations. The effect of the prepared MWCNTs dosage were investigated on the Turbidity, Iron (Fe) and Lead (Pb) removal efficiency of coal washery effluent. The MWCNTs with higher length (58.17 μm) and diameter (71 nm) tend to show high turbidity and Fe removal, while MWCNTs with lower length (38.87 μm) and diameter (45 nm) tend to show high removal of Pb. Hence, the growth temperature during CCVD operation shows a great effluence on the aspect ratio of MWCNTs which determines it area of applications.

Performance of 2G-HTS REBCO Undulator Coils Impregnated Epoxies Mixed With Different Fillers

The use of second-generation high-temperature superconducting-coated conductors enables an enhancement of the performance of undulator magnets. However, preventing the motion of the wire and providing sufficient conduction cooling to the winding stacks have remained challenges. In this study, we have evaluated epoxy impregnation techniques to address these issues. Epoxy resin was prepared with different nanopowders and the effect on the performance of the undulator coil pack was investigated. All epoxy impregnated coils showed smaller n values and some degree of deterioration of the critical current I c . The I c degradation was most pronounced for epoxy mixed with high aspect ratio multiwalled carbon nanotubes (MWCNTs). It has been found that the crack formation in the epoxy results in plastic deformation of the copper stabilizer layer, which causes the underlying ceramic REBCO superconducting layer to crack resulting in degradation of the superconducting tape performance. Careful adjustment of epoxy thickness surrounding the superconductor and the powder ratio in the epoxy eliminate the performance degradation.

Fresh and mechanical properties, and strain sensing of nanomodified cement mortars: The effects of MWCNT aspect ratio, density and functionalization

A comprehensive analysis on the effect of aspect ratio, bulk density and functionalization of multi walled carbon nanotubes (MWCNTs) in the development of nanomodified mortars, reinforced with different types of MWCNTs is presented herein. A structural characterization of the pristine and functionalized carbon nanotubes was carried out with scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). A simple one step dispersion method, involving the application of ultrasonic energy and the use of a superplasticizer (SP) was utilized for the preparation of uniformly dispersed MWCNT suspensions. The experimental determination of the fresh and 28d mechanical properties of mortars with w/c = 0.5 and s/c = 3.0, using four different types of well dispersed pristine and functionalized MWCNTs at an amount of 0.1 wt% of cement took place through: (i) flow and time of setting tests; (ii) three point bending experiments on 4 × 4 × 16 cm specimens; and (iii) uniaxial compression on the half prisms of the flexural test specimens (4 × 4 × 8 cm). The piezoresistive behavior of the mortars reinforced with the pristine MWCNTs was experimentally determined using the 4-pole method, and compared with the strain sensing ability of the mortars reinforced with the functionalized MWCNTs. All MWCNT reinforced mortars exhibit a remarkable enhancement in the mechanical properties. However, the 28d flexural strength, young's modulus and energy absorption capability of the mortars reinforced with the mechanically functionalized MWCNTs at an amount of 0.1 wt% increased by 120%, 124%, and 103% respectively. Finally, depending on the procedure of the functionalization, chemical or mechanical, a different effect on the intrinsic properties of MWCNTs was observed. The carboxylic groups attached to the surface of the chemically functionalized MWCNTs indeed provided them with the ability of a uniform and effective dispersion, without the need of a sonication procedure. On the other hand, it was found that functionalized MWCNTs do not always retain the electrical properties of pristine MWCNTs.

Experimental Investigation on Heat Transfer Performance of a Flat Plate Heat Pipe With MWCNTS-Acetone Nanofluid

This paper experimentally investigates how different mass concentration and aspect ratio multiwall carbon nanotubes (MWCNTs) acetone nanofluid affects the heat transfer performance of a flat plate heat pipe (FPHP). Different mass concentration and aspect ratio MWCNTs-acetone nanofluids are prepared without any surfactants or additives using the two-step method. Aspect ratios of MWCNTs are 666 (M1) and 200 (M2), respectively, and their according mass concentrations are 0.002, 0.005, 0.01, and 0.015 wt. %, respectively. The thermal resistance and wall temperature of the FPHP are experimentally obtained when the above-mentioned nanofluids are used as working fluid. The results showed that different mass concentration affects the heat transfer performance, therefore, there is an optimal MWCNTs-acetone nanofluid mass concentration (about 0.005wt. %). Also, the results showed that the thermal resistances of the FPHP with M1-acetone nanofluid (0.005 wt. %) and M2-acetone nanofluid (0.005 wt. %) are reduced 40% and 16%, respectively. Based on the above experimental phenomenon, this paper discusses the reasons for enhancement and decrement of heat transfer performance of the different mass concentration. For the M1-acetone nanofluid, the investigated FPHP has a thermal resistance of 0.26 °C/W and effective thermal conductivity 3212 W/m k at a heat input of 160 W. For the M2-acetone nanofluid, the investigated FPHP has a thermal resistance of 0.33 °C/W and effective thermal conductivity 2556 W/m k at a heat input of 150 W. The nanofluid FPHP investigated here provides a new approach in designing a high efficient next generation heat pipe cooling devices.

Experimental study on density, thermal conductivity, specific heat, and viscosity of water-ethylene glycol mixture dispersed with carbon nanotubes

This article presents the effect of adding multi wall carbon nanotubes (MWCNT) in water ? ethylene glycol mixture on density and various thermophysical properties such as thermal conductivity, specific heat and viscosity. Density of nanofluids was measured using standard volumetric flask method and the data showed a good agreement with the mixing theory. The maximum thermal conductivity enhancement of 11 % was noticed for the nanofluids with 0.9 wt. %. Due to lower specific heat of the MWCNT, the specific heat of the nanofluids decreased in proportion with the MWCNT concentration. The rheological analysis showed that the transition region from shear thinning to Newtonian extended to the higher shear stress range compared to that of base fluids. Viscosity ratio of the nanofluids augmented anomalously with respect to increase in temperature and about 2.25 fold increase was observed in the temperature range of 30 ? 40 ?C. The modified model of Maron and Pierce predicted the viscosity of the nanofluids with the inclusion of effect of aspect ratio of MWCNT and nanoparticle aggregates.