Haibin Cheng

Magnetorheology and sedimentation behavior of an aqueous suspension of surface modified carbonyl iron particles

Surface modified carbonyl iron particles (SMCIPs) were synthesized by coating carbonyl iron particles with an organic reagent (N-polyether, N, N, N,-acetyloxy) 2, 6-aminion-1, 3, 4-thiadiazole dimer. The properties of these SMCIPs, including morphology, structure, and magnetic behavior, were characterized using scanning electron microscopy and a vibrating sample magnetometer. Aqueous magnetorheological (MR) fluids were prepared using SMCIPs. MR properties were measured via a strain-controlled parallel disk rheometer equipped with a magnetic field source. Addition of the organic surface coating layer was found to greatly improve sedimentation stability of the aqueous MR fluids at a small cost of a reduction in field dependent yield stress.

Design and Fabrication of 500-kN Large-scale MR Damper

This article presents a thorough investigation of a large-scale MR damper which can produce 500 kN damping force and is prepared for application in the vibration reduction of civil engineering. It is known that it is quite important to prepare a high-performance MR fluid for the large-scale MR damper. The high-performance MR fluid is developed and its essential performance characteristics are tested. Test results show that the sedimentation-proof stability, maximum yield shear stress, and response time of the MR fluid satisfy the requirements for applications of the MR damper in the vibration reduction of engineering structures. The designing process is introduced and several key techniques for the MR damper design, including built-in disk-spring accumulator, magnetic-flux leakage prevented design, leakage prevention of magnetorheological fluid, and stability enhancement of the controller for large-scale MR damper are proposed. Finally, the performance experiments of the MR damper are carried out.

Nanostructural M-type barium hexaferrite synthesized by spark plasma sintering method

This investigation shows that the spark plasma sintering (SPS) method may not only absolutely prevent the formation of intermediate phase α-Fe2O3 but also significantly lower the crystallization temperature of M-type barium hexaferrite. A kind of textured sample composed of major phase M-type barium hexaferrite and trace amount of BaFe0.24Fe0.76O2.88 has been successfully synthesized in one step by SPS process at 800°C for 10min. Scanning electron microscopy, energy dispersive spectroscopy, x-ray-diffraction, transimission electron microscopy, and vibrating-sample magnetometer techniques are used to study the microstructure, composition, phase formation, crystal orientation, and magnetism of the textured sample, respectively. It is confirmed that nanostructural M-type barium hexaferrites in the holes of the textured sample are in nanobelt and nanorod microstructures; these nanobelts and nanorods are nonstoichiometric and completely random and are characterized by barium or iron surplus, and that their com...

Intelligent control for braking-induced longitudinal vibration responses of floating-type railway bridges

This paper presents an intelligent control method and its engineering application in the control of braking-induced longitudinal vibration of floating-type railway bridges. Equations of motion for the controlled floating-type railway bridges have been established based on the analysis of the longitudinal vibration responses of floating-type railway bridges to train braking and axle-loads of moving trains. For engineering applications of the developed theory, a full-scale 500 kN smart magnetorheologic (MR) damper has been designed, fabricated and used to carry out experiments on the intelligent control of braking-induced longitudinal vibration. The procedure for using the developed intelligent method in conjunction with the full-scale 500 kN MR dampers has been proposed and used to control the longitudinal vibration responses of the deck of floating-type railway bridges induced by train braking and axle-loads of moving trains. This procedure has been applied to the longitudinal vibration control of the Tian Xingzhou highway and railway cable-stayed bridge over the Yangtze River in China. The simulated results have shown that the intelligent control system using the smart MR dampers can effectively control the longitudinal response of the floating-type railway bridge under excitations of braking and axle-loads of moving trains.

Synthesis of nonstoichiometric M-type barium ferrite nanobelt by spark plasma sintering method

This study investigated the feasibility of ultrafast crystallization of M-type barium ferrite when the coprecipitation precursors in stoichiometric proportions as BaFe12O19, Fe(OH)3 and BaCO3 nanoparticles, had been heated by spark plasma sintering (SPS) process. The results show that SPS method may realize the ultrafast crystallization of M-type barium ferrite, absolutely prevent the crystallization of intermediate phase α-Fe2O3, and significantly decrease the crystallization temperature of M-type barium ferrite. The sintered samples obtained at 800 °C by sintering the precursors for 10 minutes are a kind of multiphase ferrites composed of major phase M-type barium ferrite and trace amount of BaFe0.24Fe0.76O2.88. It is discovered that M-type barium ferrites in the holes of the sintered samples are in nanobelt microstructure about 100–300 nm in width and several micrometers in length. These M-type barium ferrite nanobelts are non-stoichiometric and may be expressed as BaFe12+xO19+1.5x (−4.77⩽x⩽6.50). Their composistions suggest completely random Fe-rich or Ba-rich domains.

Measuring the sedimentation rate in a magnetorheological fluid column via thermal conductivity monitoring

Measuring sedimentation rate of magnetorheological fluids (MRFs) is of great importance when designing and synthesizing MRFs for engineering applications. A method of characterizing sedimentation rate in an MRF column is proposed utilizing thermal conductivity correlated with particle concentration. A series of MRF samples composed of carbonyl iron particles suspended in silicone oil were prepared, and their concentrations (measured as volume fraction, ∅) and thermal conductivities, k, were tested. A calibration curve was developed to relate particle concentration, ∅, to thermal conductivity, k, using this set of MRF samples with known concentration. The particle concentration, ∅, in the MRF column was then monitored by measuring thermal conductivities (k) at a fixed location and using this calibration relationship. Finally, sedimentation rate in the MRF column was determined by examining how particle concentration varied with time. The sedimentation rate measured in the MRF column was validated using visual observation of mudline (boundary between the topmost clarified fluid zone and MRF below).

Effects of Surface Modification on the Stability of Suspension and Thermal Conductivity Enhancement of Composite Fe Nanofluids

Composite Fe nanoparticles (CINPs) were synthesized by surface modification of Fe nanoparticles with silicon alkyl ethylenediamine triacetic acid, and the silicone oil-based composite Fe nanofluids (CINPs nanofluids) were prepared with the as-synthesized CINPs and silicone oil. The surface molecular structure, magnetic properties, and surface morphology of the CINPs were characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscope, and vibrating sample magnetometer. The stability and thermal conductivity enhancement of the CINPs nanofluids were characterized via a thermal conductivity method and using a thermal property analyzer. Results show that the suspension stability of the CINPs nanofluids was greatly improved by the surface modification of the Fe nanoparticles. The thermal conductivity enhancement became more stable, and further, it was demonstrated that thermal conductivity could be tuned by applying magnetic field.

Effect of storage and ball milling on the sedimentation and rheology of a novel magnetorheological fluid

In this study, the sedimentation stability and rheology of a new magnetorheological fluid formulation were experimentally investigated before and after being stored for 24 months, as well as after being milled. The results reveal that, after undergoing 24 months of steady storage, the off-state viscosity and field-induced yield stress of the MR fluid remained constant, and that its flowability and redispersibility were maintained. After being subjected to ball milling for 2 hours at 200 rpm and 300 rpm, the field-induced yield stress was also maintained.

Co-Ni-W-P Magnetic Films Electrolessly Deposited on Nitinol and the Application in Magnetically Targeted Therapy

Co-Ni-W-P magnetic films were electrolessly deposited on the nitinol wires. Their composition, microstructure, and magnetic properties were characterized by EDS, FESEM, and VSM. Their application in magnetically targeted therapy was investigated on animals. It was found that their composition and surface morphology can be controlled by the bath pH which can strongly influence the Hc, Mr, and BHmax. The magnetic nitinol wires with the Co-Ni-W-P films, combining with the magnetic nanoparticles containing 5-FU, were confirmed to be able to effectively inhibit the growth of tumors.

Preparation and characterization of composite magnetic particles and aqueous magnetorheological fluids

Composite magnetic particles (CMPs) with carbonyl iron (CI) core and N-glucose ethylenediamine triacetic acid (GED3A) shell were prepared by an in-situ chelating reaction, where the CI surface was coated with GED3A. And novel kind of aqueous magnetorheological (MR) fluids were prepared with thus obtained CMPs. The properties of CMPs, including morphology, structure, and magnetic behaviours were characterized, and the magnetorheological properties of the MR fluids were analyzed via a strain-controlled rheometer. It was found that the MR fluids exhibited high shear stress and quick response rate to magnetic field. Furthermore, the dispersion stability and the anti-oxidation property were substantially improved as revealed by stability test.