Papers by Keyword: Magnetic Fluid

Abstract: Fe₃O₄ magnetic nanoscale water-based magnetic fluid was fabricated by co-precipitation with citric acid (CA) and polyethylene amine (PEI) as dispersant. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to investigate the samples.The modified magenetic nanoparticles (MNPs) size of about 50nm and have a saturation magnetization about 0.25emu/g.These nanoparticles can be applied to the study of genophore.

Abstract: It is difficult to sort fine non-magnetic particles only by the buoyancy of magnetic fluid. Therefore, based on the magneto hydrostatic separation, the centrifugal separation under the condition of centrifugal force would be an effective method to improve the efficiency. By establishing the mechanical model of centrifugal separation in magnetic fluid, this paper analyzes the kinematical equations of non-magnetic particles in three directionstangential direction, radial direction, and axial direction, and then theoretically explores the separation mechanism of this method.

Abstract: This paper introduces a method of preparation of photonic crystals with non-magnetic ellipsoid as building blocks. Under the condition of above its glass-transition temperature, monodispersed polystyrene (PS) spheres with the diameter of 260 nm and 360 nm were respectively elastic stretched by applying external force with different values to get different ellipsoids with different aspect ratios. The assembly procedure was carried out by applying the vertical deposition self-assembly method in a magnetic field under the guidance of magnetic fluids. In this paper, We report the crystalline structure with long range order.

Abstract: Magnetic fluid is the key core of magnetic fluid sensor. Here magnetic model of magnetic fluid is analyzed. The magnetic curve of magnetic fluid is divided into 3 parts and the liner area is presented to make magnetic fluid sensor more sensitively. The magnetic force of magnetic fluid in magnetic field is calculated and analyzed. The magnetic permeability of magnetic fluid in sensor could be treated as a constant in the linear area of magnetization curve. And the magnetic force of magnetic fluid in magnetic field could be ignored if the length to diameter ratio of the solenoid is large enough.

Abstract: The FEM model of lubricating oil film was built with mill oil-film bearing as the research target, the analysis system of magnetic-fluid lubricating oil film for oil-film bearing was developed. APDL and CEL languages were applied to compile the inner analytical programs, and the combination of VB, ANSYS Mechanical with ANSYS CFX was perfectly realized. Through the numerical simulation of magnetic-fluid lubricating film, the load-carrying performances of oil-film bearing with magnetic-fluid lubrication were analyzed, and the relationship among magnetic field intensity with oil-film pressure and temperature was quantitatively calculated. The numerical results have shown that the magnetic-fluid lubrication has obvious influences on oil-film pressure when magnetic field was applied on oil-film bearing, the lubricating viscosity increases with the magnetic-fluid intensity, and the oil-film pressure and temperature also increase with magnetic-field intensity. However, the increasing increment of oil-film temperature is far lower than that of oil-film pressure. The above conclusions prove that magnetic fluid with proper magnetic field can effectively improve the load-carrying capacity of lubricating oil film and enhances the stability of oil-film pressure. Moreover, the adjustable intelligent oil-film pressure with magnetic field is deduced to be feasible.

Abstract: Acceleration sensor with magnetic fluid is a novel application of buoyancy principle of magnetic fluid. The model of the sensor was established in the paper. To improve the design of the acceleration sensor with magnetic fluid, motion equation of the sensor was deduced, which is the second-order vibration equation. From the equation, the damping coefficient is determined by magnetic viscosity coefficient of the liquid and the sensor structural parameters.

Abstract: Magnetic fluid is a special class of materials which possesses the advantages of a liquid state of the carrier and a magnetic state of the particles. In addition to the conventional uses in mechanical engineering, magnetic fluids containing magnetite (Fe₃O₄) superparamagnetic nanoparticles are under research and development for drug delivery, hyperthermia and MRI contrast agents. On the other hand, iron-platinum (FePt) is investigated as materials for ultrahigh density recording. Before their assembly into patterned media, the as-synthesized FePt nanoparticles in superparamagnetic state are commonly stored in forms of magnetic fluids. In this work, iron-platinum (FePt) nanoparticles with their surface modified by oleic acid and oleyleamine were synthesized from the polyol process. The starting material was an environmental friendly iron(III) acetylacetonate and the products were dispersed in n-hexane. In small-angle X-ray scattering (SAXS) measurements at the Synchrotron Light Research Institute, Thailand, each magnetic fluid was injected into a sample cell with aluminum foil windows and the X-ray of wavelength 1.55 Å from BL2.2 was used. The measured SAXS intensity profiles as a function of the scattering vector from 0.27 to 2.30 nm^-1 were fitted and compared between two different reactions. Nanoparticles synthesized by using a higher amount of Fe(acac)₃ were matched with monodisperse spheres of radius 2.4±0.3 nm. The other reaction with a reducing agent gave rise to smaller nanoparticles of two size distributions. From this work, the potential of synchrotron radiation to complement conventional characterization techniques in the investigation of nanoparticles for high density recording and biomedical applications is underlined.

Abstract: In view of the highly heat exchanger efficient of heat pipe, two vacuum heat pipes of water and Fe3O4-water were prepared and test system was designed to test the heat transfer efficiency of them when they are within and without magnetic field. The experimental results showed that the heat exchange of heat pipe with magnetic fluid was more efficient than the other one. According to the results and combine the physical properties of two kinds of refrigerant, analyze the heat transfer characteristics of the magnetic fluid in magnetic field.

Abstract: Base on the fluid dynamics，electromagnetism，Newton’s law and some other basic theories，the paper analyses the equations of motion and Bernoulli for nonmagnetic mineral particles in magnetic fluid. And apply these theories to establish the mechanical model for the nonmagnetic mineral particles in magneto hydrostatic static separation (MHSS). In MHSS, the particles would be stressed by gravity force, magnetic buoyancy, ordinary buoyancy, etc. The wedge-shaped magnetic poles can set up the magnetic buoyancy of which direction is straight up, and the levitation force could be stronger in ferromagnetic fluid. And it can be calculated equating normal buoyant weight to the magnetic buoyant force that any nonmagnetic substance can be floated in magnetic fluid. The paper also analyses some parameters that affect the separation result, such as the magnetic field intensity and the magnetic field gradient. These tasks may give some supports for MHSS applied in industrial.

Abstract: A MEMS actuator using a magnetic fluid enclosed with polyimide (PI) diaphragms is proposed. The actuator produces a large displacement and force thanks to its structure in which a magnetic fluid is confined between two thin-film PI diaphragms (diameter: 5 mm) fabricated on two silicon substrates. The two substrates with diaphragms are glued together by sandwiching a polyester sheet to form a diaphragm unit. The thickness of the diaphragms is 8.5 µm so that they can deflect greatly. The magnetic fluid inserted between the two diaphragms is composed of magnetite and isoparaffin. The diaphragm unit (containing the magnetic fluid) is deflected by applying an external magnetic field to it with a magnet coil. Response times and displacements of the diaphragms were measured when a magnetic field was applied. Under an applied voltage of 10 V, the diaphragm unit could produce displacements of 4 µm at the diaphragm center. Response time to reach 90% of the maximum diaphragm displacement was about 2 s. Under an applied voltage of 80 V, force generated by the diaphragm unit was 0.065N. It is concluded from these experimental results that the proposed actuator is applicable to MEMS devices such as micro pumps and give another example here.