Magnetorheology of Multiwalled Carbon Nanotube Mineral Dispersions

2006 ◽  
Author(s):  
Zhengtao Yang ◽  
Ali Shaito ◽  
Nandika Anne D'Souza
Keyword(s):  
Magnetic Field ◽  
Carbon Nanotube ◽  
Power Law ◽  
Volume Fraction ◽  
Loss Modulus ◽  
Complex Viscosity ◽  
Mineral Oil ◽  
Multiwalled Carbon ◽  
Strain Sweep ◽  
Dynamic Yield

Multi-walled carbon nanotube (MWCNT) were dispersed in mineral oil and the magnetorheological response was measured. 0.5, 1.5 and 2.53 vol% nanotubes were dispersed in mineral oil. Strain sweep, frequency sweep, magneto sweep and steady shear tests were conducted in various magnetic field strengths. Storage modulus G', loss modulus G", complex viscosity η* and dynamic yield stress τy increased with magnetic field, which was partially attributed to the increasing degree of alignment of nanotubes in stronger magnetic field. G' and G" of MWCNT/mineral oil dispersions scaled with nanotube volume fraction φ by a power-law. The shear thinning behavior of MWCNT/mo dispersions followed the Ostwald-de Waele or power law.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

scholarly journals Analysis of Tribological Behavior of Carbon Nanotube Based Industrial Mineral Gear Oil 250 cSt Viscosity

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Shubrajit Bhaumik ◽  
S. Prabhu ◽  
Kingsly Jeba Singh
Keyword(s):  
Carbon Nanotube ◽  
Bearing Capacity ◽  
Wear Test ◽  
Mineral Oil ◽  
Load Test ◽  
Multiwalled Carbon Nanotube ◽  
Load Bearing Capacity ◽  
Multiwalled Carbon ◽  
Sem Images ◽  
Load Bearing

The paper investigates the exceptional antiwear and extreme pressure properties of multiwalled carbon nanotube based mineral oil. Different samples of oil containing varying proportions of MWNT (MWNT) and graphite were prepared. The samples were tested for their antiwear and load bearing capacity according to ASTM G99 and ASTM D-2783 standards. After pass load test in four ball tester the rubbed surfaces were investigated with Scanning Electron Microscope (SEM) images. The wear test results show a decrease wear by 70–75% in case of multiwalled nanotube based mineral oil as compared with pure mineral oil. Furthermore, it has been observed that the load bearing capacity in case of multiwalled carbon nanotube based mineral oil increases by 20% as compared to pure mineral oil. A comparison in the antiwear and load bearing capacity properties of graphite and nanotube based mineral oil was studied which showed the inefficiency of graphite based lubricant over MWNT based oil. Thus, the finding would be helpful in developing new nanoparticle based lubricants.

NATURAL RUBBER/CARBON NANOTUBE NANOCOMPOSITES PREPARED BY ULTRASONICALLY AIDED EXTRUSION

2013 ◽  
Vol 86 (1) ◽  
pp. 109-131 ◽  
Author(s):  
Jaesun Choi ◽  
Avraam I. Isayev
Keyword(s):  
Carbon Nanotube ◽  
Power Consumption ◽  
Natural Rubber ◽  
Ultrasonic Treatment ◽  
Complex Viscosity ◽  
Chain Scission ◽  
Optical Microscope ◽  
Dispersion Analysis ◽  
Multiwalled Carbon ◽  
Link Density

ABSTRACT Natural rubber/multiwalled carbon nanotube (MWCNT) nanocomposites at loadings from 2 to 25 phr were prepared by ultrasonically aided extrusion at ultrasonic amplitudes up to 7.5 μm. Die pressure significantly decreased with an increase of ultrasonic amplitude, especially at higher loadings. Power consumption increased with ultrasonic amplitude and was almost insensitive to loadings until an amplitude of 5.0 μm. However, lower values of power consumption were observed at an amplitude of 7.5 μm for loadings of 10 and 15 phr. At these loadings, complex viscosity, storage, and loss moduli of compounds and vulcanizates were unaffected by ultrasonic treatment, whereas at other loadings, these properties were reduced with ultrasonic amplitude, indicating chain scission. Bound rubber in compounds decreased with treatment. The induction time during vulcanization was unaffected by ultrasonic treatment but decreased with loading, with the largest decrease observed at the lowest loading. The maximum torque in curing, cross-link density, and gel fraction of vulcanizates at loadings of 2, 3.5, 5, 7.5, and 25 phr decreased with ultrasonic amplitude, with the largest decrease observed at loading of 25 phr at an amplitude of 7.5 μm. The modulus at 100% and 300% and tensile strength of vulcanizates at loadings up to 15 phr were unaffected by the ultrasonic treatment, but these properties significantly decreased at a loading of 25 phr at an amplitude of 7.5 μm. Atomic force microscope studies of vulcanizates at a loading of 3.5 phr showed a deagglomeration at an amplitude of 7.5 μm, although dispersion analysis from an optical microscope at loadings of 3.5 and 7.5 phr did not show an improvement of dispersion by ultrasonic treatment. Optical microscope and AFM studies of vulcanizates at a loading of 25 phr indicated that ultrasonic treatment at an amplitude of 7.5 μm significantly improved dispersion of MWCNT. Such a behavior led to a strong Payne effect and an increase in hardness of vulcanizates.

scholarly journals High-Performance Thermal Management Nanocomposites: Silver Functionalized Graphene Nanosheets and Multiwalled Carbon Nanotube

2018 ◽  
Author(s):  
Yongcun Zhou ◽  
Xiao Zhuang ◽  
Feixiang Wu ◽  
Feng Liu
Keyword(s):  
Carbon Nanotube ◽  
Thermal Management ◽  
High Performance ◽  
Volume Fraction ◽  
Graphene Nanosheets ◽  
Multiwalled Carbon Nanotube ◽  
Interfacial Structure ◽  
Processing Unit ◽  
Functionalized Graphene ◽  
Multiwalled Carbon

Silver functionalized graphene nanosheets (GNS) and multiwalled carbon nanotube (MWCNT) composites with excellent thermal properties were developed to meet the requirements of thermal management. The effects of composites on interfacial structure and properties of the composites were identified, and the microstructures and properties of the composites were studied as a function of the volume fraction of fillers. An ultrahigh thermal conductivity of 12.3 W/mK for polymer matrix composites was obtained, which is an approximate enhancement by 69.1 times compared with that of the polyvinyl alcohol (PVA) matrix. Moreover, these composites showed more competitive thermal conductivities compared with those of untreated fillers/PVA composites applied to the desktop central processing unit, making these composites a high-performance alternative to be used for thermal management.

Coupled flow and heat transfer of power-law Nanofluids on a non-isothermal rough rotary disk subject to magnetic field

2021 ◽  
Author(s):  
Yunxian Pei ◽  
Xuelan Zhang ◽  
Liancun Zheng ◽  
Xinzi Wang
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Power Law ◽  
Numerical Solutions ◽  
Volume Fraction ◽  
Rotating Disk ◽  
Coupled Flow ◽  
Friction Coefficients ◽  
Nanoparticle Shape ◽  
Flow And Heat Transfer

Abstract In this paper, we study coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subject to a magnetic field. The problem is formulated in terms of specified curvilinear orthogonal coordinate system. An improved BVP4C algorithm is proposed and numerical solutions are obtained. The influence of volume fraction, types and shapes of nanoparticles, magnetic field and power-law index on the flow and heat transfer behavior are discussed.<br/>Results show that the power-law exponents (PLE), nanoparticle volume fraction (NVF) and magnetic field inclination angle (MFIA) are almost no effects on velocities in wave surface direction, but have small or significant effects on azimuth direction. NVF have remarkable influence on local Nusselt number (LNN) and friction coefficients (FC) in radial and azimuth directions (AD). LNN increases with NVF while FC in AD decrease. The types of nanoparticles, magnetic field strength and inclination have small effects on LNN, but they have remarkable effects on the friction coefficients with positively correlated while the inclination is negatively correlated with heat transfer rate. The size of the nanoparticle shape factor is positively correlated with LNN.

Composition – Property Relations in Shear Thickening Fluids

2014 ◽  
Vol 87 ◽  
pp. 91-97
Author(s):  
Łukasz Wierzbicki ◽  
Marcin Leonowicz
Keyword(s):  
High Strain ◽  
Volume Fraction ◽  
Solid Phase ◽  
Loss Modulus ◽  
Shear Thickening ◽  
Complex Viscosity ◽  
High Viscosity ◽  
Polypropylene Glycol ◽  
Shear Thickening Fluids ◽  
Composition Property

It was shown that fumed silica particles (FS), dispersed in polypropylene glycol (PPG), form shear thickening fluids (STF). PPGs with different molar mass were tested. The best combination of the properties (high viscosity, obtained at high shear rate) present the fluids composed of 7 nm FS and PPG 425. The highest volume fraction of FS, which was possible to disperse in PPG 425, was 25%. This fluid exhibited the highest viscosity. The highest magnitude of shear thickening effect was obtained, however, for 17.5 vol.% of the solid phase. Dynamic oscillatory shear experiments were conducted at either a constant amplitude or frequency. The constant strain amplitude tests showed, that for the frequency sweep, the systems showed viscous properties, except that of 25 vol.% of FS in PPG 425, which exhibited elastic properties in almost entire range of the frequency investigated. For the constant strain sweep, for low strains, the elastic modulus and loss modulus were hardly dependent on the strain, but for relatively high strain, this dependency was increasing. Also the complex viscosity was also growing for high strain values.

Morphology, mechanical, bound rubber, swelling, and dynamic mechanical studies of chlorobutyl elastomer nanocomposites: effect of multiwalled carbon nanotube and solvent

2014 ◽  
Vol 34 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Shashi K. Tiwari ◽  
Bibhu P. Sahoo ◽  
Shyama P. Mahapatra
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotube ◽  
Storage Modulus ◽  
Loss Modulus ◽  
Multiwalled Carbon Nanotube ◽  
Multiwalled Carbon ◽  
Dynamic Mechanical ◽  
Bound Rubber ◽  
Degree Of Swelling ◽  
Mwcnt Loading

Abstract Multiwalled carbon nanotube (MWCNT) reinforced chlorobutyl elastomer nanocomposites were prepared. The morphology of nanocomposite samples has been studied from scanning electron microscopy (SEM). The effect of MWCNT loadings on mechanical properties shows increase in tensile strength, hardness, and modulus and decrease in elongation at break with MWCNT loadings, which can be attributed toward better chlorobutyl-MWCNT interaction. At higher filler loading, the rate of increase slowly decreases. The above explanation was also verified from bound rubber (BdR) measurements, showing increase in BdR contents with MWCNT loading. Swelling of the nanocomposites in chloroform, benzene, and trichloroethylene was measured and found to be dependent on both MWCNT concentration and the type of solvent used. The degree of swelling, diffusion coefficient, and penetration rate was calculated. The effect of solvent on swelling properties at different periods of time shows that the degree of swelling increases with time and decreases with concentration of MWCNT loading. Dynamic mechanical properties of nanocomposites have been studied as a function of temperature (from -100°C to 100°C) at a constant frequency of 1 Hz and 1% strain. The effect of MWCNT loading on storage modulus, loss modulus, and loss tangent has been studied. The nonlinearity in tan δ and storage modulus and loss modulus was explained on the basis of MWCNT-elastomer interaction. The smooth Cole-Cole plots explain the nonlinearity in the nanocomposites as well as good distribution of MWCNT in the elastomer matrix.

Rheological Fluids for Energy Absorbing Systems

2013 ◽  
Vol 440 ◽  
pp. 13-18 ◽  
Author(s):  
Marcin Leonowicz ◽  
Joanna Kozłowska ◽  
Łukasz Wierzbicki
Keyword(s):  
Magnetic Field ◽  
Carbonyl Iron ◽  
Volume Fraction ◽  
Loss Modulus ◽  
Shear Thickening ◽  
High Viscosity ◽  
Polypropylene Glycol ◽  
Magneto Rheological ◽  
Energy Absorbing ◽  
Protective Performance

Two types of non-Newtonian fluids, magneto rheological (MRF) and shear thickening (STF) fluids, respectively were chosen as candidates for energy dissipation study in smart body armour. A series of magneto rheological fluids was synthesized on a basis of synthetic oil and carbonyl iron. The shear modules for the MRF containing 75 wt% of carbonyl iron, obtained in a magnetic field of 230 kA/m were as follows: complex shear modulus G* - 1.2 MPa, storage modulus G-1.2 MPa and loss modulus G 0.35 MPa. The studies revealed also that the silica fumed, dispersed in polypropylene glycol or polyethylene oxide, demonstrates shear thickening properties. The best combination of the properties (high viscosity, obtained at high shear rate) represents the material composed of the silica fumed (SF) and PEO300. Change of the volume fraction of the SF and variation of the molecular weight of the oligomer enables tailoring of the STF properties. Ballistic tests revealed that the structures containing PE bags with MRF (in magnetic field) or STF can enhance the protective performance of body armours providing their flexibility.

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