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The utilization of magnetic nanofluids as the base carrier fluid of magnetorheological fluids represents an effective approach to enhance the magnetorheological effect. However, achieving highly stable nano-composite magnetorheological fluids remains a significant challenge, encompassing both the synthesis of magnetic nanofluids and the prevention of composite particle agglomeration. In this study, Fe3O4 silicone oil-based magnetic nanofluids were prepared using silane coupling agent KH550 as a dispersant, followed by a novel process of co-coating dispersants to obtain nano-composite magnetorheological fluids. The surface morphology, physical phase composition and magnetic properties were characterized and analyzed using XRD, FI-IR, TEM, FE-SEM and VSM. The sedimentation stability and redispersibility of the novel nano-composite magnetorheological fluids were investigated. The results show that surface modification of micron-sized particles significantly enhances the stability and redispersibility of the nano-composite magnetorheological fluids, with optimal sedimentation stability and redispersibility observed at nanoparticle volume fraction of 8%. Furthermore, the novel nano-composite magnetorheological fluids demonstrate superior temperature resistance, remaining stable within the temperature range form -40 °C to 120 °C over extended durations. Rheological properties of novel nano-composite magnetorheological fluid were also investigated demonstrating higher off-state viscosity and magnetorheological effect in comparison to conventional magnetorheological fluids. Moreover, both static and dynamic yield stresses increase with nanoparticle concentration and magnetic field strength. [ABSTRACT FROM AUTHOR]

Corn oil as a nanofluid base fluid has the problem of easy oxidation, and the addition of tertiary butyl-hydroquinone is expected to improve the antioxidant property of corn oil. In this paper, a new environmentally friendly nanofluid was prepared by using corn oil as a base fluid, A12O3 as nanoparticles, and tertiary butylhydroquinone as an antioxidant to study its settlement stability and antioxidant properties. The content of oxidation products and viscosity of the nanofluids at different times were investigated from the perspectives of particle size, particle mass fraction, antioxidant type, and antioxidant addition. The results showed that the nanofluids produced without surfactant, 100 mL of corn oil, Al2O3 nanoparticles with a particle size of 20 nm and a particle mass fraction of 1.1083% had the best sedimentation stability. The nanofluid with 0.7% of tertiary butylhydroquinone added had the optimum antioxidant properties. There are two phenolic hydroxyl groups in the molecule of tertiary butylhydroquinone, and each of the two phenolic hydroxyl groups provides one hydrogen ion, which forms stable quinone compounds in corn oil, making the oxidation rate of the corn oil slower. When the content of tertiary butylhydroquinone was added at less than 0.4%, the content of tertiary butylhydroquinone was not enough to effectively retard the oxidation reaction of the oil. When the addition of tertiary butylhydroquinone exceeded 0.7%, the antioxidant property of the nanofluid could only be improved slightly, and the oxidation induction time increased slowly, but on the contrary, the viscosity of the nanofluid would be increased greatly. The nanofluid prepared in this paper has the characteristics of environmental friendly and good antioxidant performance, which can effectively slow down the generation of oxidised substances. This study contributes to the further development of antioxidant research of environmentally friendly nanofluids. [ABSTRACT FROM AUTHOR]

To solve the problem of the error of frequency measurement algorithm with time-varying frequency in mine power supply system, an improved software zero-crossing algorithm is proposed.The relationship among the phase angle, the time and the frequency of the voltage of the system is established.The relation formula between the real-time frequency and the period of zero-crossing point is derived when rate of frequency variation is not zero according to the relationship between two adjacent with the direction of the zero-crossing phase difference of 2π.The exact calculation formula of the period is obtained by using the Newton three interpolation polynomial, the Newton iteration method and the Qin Jiushao algorithm.Hence, the frequency and rate of frequency variation can be obtained.A variety of situations , including signals without harmonics, signals with harmonics and random noise, as well as the frequency rapid decline process in system failure, are simulated using MATLAB, The simulation results show that the algorithm of this paper can accurately measure the real-time frequency of the system and rate of frequency variation in above situations, and this method is superior to conventional zero-crossing algorithm in measurement accuracy, instantaneity and computation.This algorithm is suitable for application of protection, control and monitoring devices and automation equipment in mine intelligent power supply system.

In order to research the sedimentation stability of water-based magnetic fluid, the sedimentation stability of water-based Ni0.5Zn0.5 Fe2O4 magnetic fluid at different pH values was studied, and the experimental phenomena were analyzed. The results show that when the mass fraction of OA (oleic acid) is 4%, the mass fraction of SDS (sodium dodecyl sulfate) is 3%, and the mass fraction of Ni0.5Zn0.5 Fe2O4 is 2. 5%, the magnetic fluid as-prepared has the best stability. When pH value is <7, the sedimentation stability of magnetic fluid decreases with the decrease of pH value, but the viscosity increases with the decrease of pH value. When pH is >7, the sedimentation stability of MHD decreases with the increase of pH value. The higher the temperature is, the better the dispersion is. The pH value has a certain influence on the thermal dispersion of the magnetic fluid. The pH value has an important influence on the magnetic field settling stability and magnetic viscosity of magnetic fluid. Under the action of constant or increasing magnetic fields, the settling coefficient and viscosity of magnetic fluid change with the change of magnetic field and pH value. [ABSTRACT FROM AUTHOR]