Effects of Nano-Diamond on Magnetorheological Fluid Properties

Abstract

In order to analyze the e®ects of nano-diamond on the performance of magnetorheological°uids (MRFs), in this paper, the MRF-1 with a 2% mass fraction in nano-diamond and the MRF-2 without nano-diamond were prepared by the carbonyl iron powder as the dispersed phase and the synthetic mineral oil as the continuous phase. The viscosity and shear stress of MRFs under di®erent magnetic¯elds were measured by the Anton-Paar rheometer (MCR 302). The MRF settling stability was studied by a standing observation method. A four-ball wear machine was utilized for the wear test at 0.1 T of magnetic¯eld, whereas the magnetic¯eld was provided by an external coil. Also, the three-dimensional white light interferometer was utilized to observe the surface of the ball wear spot, in order to determine the MRF friction properties. The results demonstrated that the nano-diamond had a signi¯cant increase in the surface wear. The shear yield strength and settling stability of the MRF could be highly enhanced. The higher the strength of the magnetic¯eld was, the higher the di®erence in the shear yield strength was. These phenomena demonstrated that the physical properties of the nano-diamond could have a higher impact on MRF, which was of high signi¯cance to the preparation of MRFs with excellent performance.

Electronic structure, magnetoexcitons and valley polarized electron gas in 2D crystals

“…There is currently interest in the electronic and optical properties of van der Waals (vW) crystals [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]. Bulk van der Waals crystals are found to be insulators, metals, ferromagnets, superconductors and semiconductors.…”

“…Bulk van der Waals crystals are found to be insulators, metals, ferromagnets, superconductors and semiconductors. vW crystals 5 are built of weakly bound atomic planes, hence atomic layers from different vW crystals can now be peeled off and reassembled into new materials with properties not readily available in nature [8,14,15,16]. When bulk vW crystal is reduced to a single atomic layer, the properties can change drastically.…”

“…For example, bulk M oS 2 , a well-known transition metal dichalcogenide (TMDC), is 10 an indirect gap semiconductor while a single layer is an example of a truly twodimensional, direct gap, semiconductor. TMDCs share hexagonal lattice with graphene and the low energy spectra can be understood in terms of massive Dirac Fermions [14]. The two nonequivalent valleys can be addressed optically [12,13,17], topology leads to valley spin Hall effect [9,10] and electron-electron 15 interactions can lead to a broken symmetry valley polarized electronic state [17].…”

“…The two nonequivalent valleys can be addressed optically [12,13,17], topology leads to valley spin Hall effect [9,10] and electron-electron 15 interactions can lead to a broken symmetry valley polarized electronic state [17]. The absorptivity of 2D TMDC layers is very strong due to band nesting [25,26] and excitonic effects are pronounced due to reduced dimensionality and screening [14]. Here we describe some of our work toward the understanding of the electronic and optical properties of semiconductor TMDCs [9,20,25].…”

Active control of a nonlinear suspension with output constraints and variable-adaptive-law control

“…Magnetorheological damper (MRD) is a damper that uses the magnetorheological fluid (MRF). The shear stresses in the MRF can change with a varying magnetic field [3]. This property can be utilized for adjusting the damping coefficient of the MRD using a varying current that gives rise to a varying magnetic field.…”