Abstract: An optical system includes a layer of magneto rheological (MR) fluid having a surface exposed to air or vacuum. The MR fluid has a first state wherein the surface is reflective, and a second state wherein the surface is non-reflective. A magnetic actuator selectively applies a magnetic field to the MR fluid to actuate the fluid to the second state.

Abstract: The present invention relates to a magneto sensitive fluid composition and a process of its preparation. The electrical conductivity of the composition varies reversibly in the presence of an external magnetic field. The composition, which is practically an insulator, starts behaving as a conductor in the presence of a magnetic field. The fluid is basically a magnetrheological composition in which the magnetic sensitive particles are admixed with conductive additives in the form of conductive metallic or non-metallic powder. The change in electrical conductivity of the composition is in addition to the change in rheological characteristics of the composition in the presence of an external magnetic field.

Abstract: What is disclosed is a magnetorheological fluid useful for incorporating within the working gap of magnetorheologically controllable linear or rotary devices. The MR fluid includes a carrier fluid component and a magnetic responsive particle component characterized by D10 of 2 &mgr;m up to and including a D10 of 5 &mgr;m, a D50 of 8 &mgr;m up to and including D50 of 15 &mgr;m; a D90 of 25 &mgr;m to and including a D90 of 40 &mgr;m; and further characterized by least squares regression (R2) particles size against log normal cumulative volume percent of greater than or equal to 0.77. Optional preferred additives included therewith include thixotropic agent or viscosity modifier, dispersant or surfactant, antioxidant, corrosion inhibitor, and one or more lubricants.

Abstract: Magnetorheological (MR) fluids, dispersions of magnetically soft particles in fluids (gases, liquids, or semi-solids such as greases), are disclosed. The present invention uses the initial steps of a sol-gel process to assist in preparation of MR fluids that have significantly enhanced stability and redispersibility, without the use of ceramic particles such as silica or bridging polymers such as PVP.

Abstract: The present invention provides a magnetorheological fluid in which magnetic particles coated with a hydrophilic surfactant are dispersed in a water in oil emulsion, and a process for preparing the same. The magnetorheological fluid of the present invention is prepared by adding water to oil dissolved with emulsifier, stirring it to give a mobile phase of water in oil emulsion, and dispersing magnetic particles coated with a hydrophilic surfactant in the water in oil emulsion. The invented magnetorheological fluid is improved in terms of stability through the interaction between surfactant of the magnetic particle surface and water molecule, which makes possible its practical application in the development of variable devices employing the magnetorheological fluid.

Abstract: The present invention relates to a magnetorheological fluid composition and a process for preparing the same, which has excellent magnetorheological properties. The fluid composition exhibits change in rheological characteristics in the presence of an external magnetic field. Further, the magnetorheological characteristics of the fluid composition can be optimised for the improved magnetic sensitivity to external magnetic field and negligible magnetic retentivity after removal of the external magnetic field. The sensitivity of the fluid to external magnetic field can be varied by varying the pure iron content of the magnetic sensitive particles composition while, the magnetic retentivity of the fluid (after removal of external magnetic field) can be varied by varying the ferrite alloy content of the same. The fluid composition utilises a magnetic sensitive particles stabiliser or surfactant, which is synthesised from the carrier fluid used in the fluid composition.

Abstract: A magnetorheological fluid formulation exhibiting consistently high yield stress during use. The MR fluid comprises martensitic or ferritic stainless steel particles prepared by a controlled water or inert gas atomization process. The stainless steel particles are resistant to corrosion and oxidation, are generally smooth and spherical, and maintain their shape and size distribution throughout their use under an applied magnetic field.

Abstract: A durable magnetorheological fluid for use in a vibration dampening device is described. The MR fluid includes magnetizable particles having a particle size less than about 25 microns, a carrier fluid, a thixotropic agent, and a lubricative additive. The carrier fluid includes a polyalphaolefin and a plasticizer. The lubricative additive has a particle size equal to or less than 10 microns such that the ability of the additive to lubricate the magnetizable particles is optimized. The lubricative additive includes at least one of polytetrafluoroethylene, graphite, and molybdenum disulfide.

Abstract: A magnetorheological fluid formulation in which the base liquid is optimized to exhibit an acceptable viscosity, a low volatility, improved low temperature flow properties, and an improved elastomeric compatibility. The fluid formulation includes a base liquid containing a mixture of 1-dodecene polyalphaolefin and a diester, such as dioctyl sebacate. The diester is added to the mixture in an amount effective to produce seal swelling and to lower the pour point. The viscosity of the fluid formulation is suitable for diverse vibration damping applications that require a vibration damping device to operate in the temperature range of about −40° C. to about 100° C. The low volatility and seal swelling properties of the fluid formulation reduce, inhibit or eliminate fluid loss about the seals of the vibration damping device.

Abstract: A magnetorheological fluid (32) having controlled-shaped particles (56,68), such as rod, prism, tetrahedral, and other regularly shaped particles. The regularly shaped particles (56, 68) increase the field yield and responsive to particle interaction forces. The magnetorheological material has particular use for space applications such as vibration isolators, vibration dampeners, and latch mechanisms.

Abstract: A durable magnetorheological fluid suitable for use in high compression vibration dampening devices comprising mechanically hard magnetizable particles of unreduced carbonyl iron, cobalt-iron alloys, or mixtures thereof, a carrier fluid of a mixture of polyalphaolefin and a plasticizer, unreduced fumed silica and optionally an ethoxylated amine.

Abstract: A magnetorheological fluid formulation comprising magnetizable particles dispersed in a multi-component liquid vehicle comprising an organoclay stabilization mixture. At least one organoclay is selected for each liquid vehicle component, each organoclay having a surface chemistry that renders it preferentially compatible with the surface functionality of one of the liquid components relative to its compatibility to the remaining components whereby it is effective to stabilize, or gel, that component. A method of making an MR fluid is also provided in which liquid vehicle components are blended together, the organoclay mixture is added to the blend, and magnetizable particles are suspended therein, resulting in a stable MR fluid of suitable viscosity and yield stress.

Abstract: A magnetorheological fluid formulation comprising magnetizable particles dispersed in a multi-component liquid vehicle comprising an organoclay stabilization mixture. At least one organoclay is selected for each liquid vehicle component, each organoclay having a surface chemistry that renders it preferentially compatible with the surface functionality of one of the liquid components relative to its compatibility to the remaining components whereby it is effective to stabilize, or gel, that component. A method of making an MR fluid is also provided in which liquid vehicle components are blended together, the organoclay mixture is added to the blend, and magnetizable particles are suspended therein, resulting in a stable MR fluid of suitable viscosity and yield stress.

Abstract: An MR fluid formulation comprising water-atomized iron powder dispersed in a liquid vehicle, wherein the atomized iron powder contributes to a higher magnetic effect, a lower viscosity and suitability for high temperature applications. The magnetizable particles are prepared by controlled water atomization and comprise iron having a passivating oxide surface layer. The passivating oxide surface layer advantageously comprises iron oxide and at least one alloying metal oxide, such as manganese oxide. Advantageously, the particles have a grain size of at least 4 &mgr;m and a mean diameter in the range of about 8-25 &mgr;m. The liquid vehicle advantageously comprises a mixture of at least two liquid components of different surface functionality and an organoclay stabilization mixture in which at least one organoclay is selected for each liquid vehicle component.

Abstract: The invention provides a magnetorheological device employing narrow design gap and containing a magnetic-responsive composition exhibiting reduced off-state forces and good performance. Specifically, this invention is directed to a magnetorheological device of defined gap, and employing a magnetic-responsive composition characterized by comprising non-sperical magnetic-responsive particles of average number diameter distribution (d50) from 6 to 100 microns and at least one friction-reducing additive that reduces the interparticle friction between the magnetic-responsive particles.

Abstract: This invention provides a polishing apparatus using a polishing material freely varying its shape in a tri-dimensional space in accordance with the shape of a work, and capable of polishing a narrow, recessed surface inaccessible to human hands or a tool, and a polishing method used therefor.

Abstract: A durable MR fluid formulation is described which includes mechanically hard magnetizable particles, a carrier fluid derived from a polyalphaolefin and a plasticizer, and at least one colloidal additive such as colloidal polytetrafluoroethylene or colloidal graphite. The use of these colloidal additives inhibits surface-to-surface contact and scuffing while providing reliable lubrication under boundary lubrication conditions.

Abstract: Magnetorheological materials are provided comprising magnetic particles, a polymeric gel and a carrier material. The polymerization of the gel is preferentially accomplished in the presence of the magnetic particles and the carrier material. Magnetorheological materials are provided having a selected off-state viscosity and a selected on-state apparent viscosity. The method of preparing these magnetorheological materials is also provided. The carrier material, the polymeric gel and the magnetic particles are selected so that the resulting magnetorheological material has the desired off-state viscosity and on-state apparent viscosity. These materials have good dispersion characteristics, reduced settling, superior off-state viscosity and superior apparent viscosity in the presence of a magnetic field.

Abstract: A magnetorheological fluid formulation in which the base liquid is optimized to exhibit an acceptable viscosity, a low volatility, improved low temperature flow properties, and an improved elastomeric compatibility. The fluid formulation includes a base liquid containing a mixture of 1-dodecene polyalphaolefin and a diester, such as dioctyl sebacate. The diester is added to the mixture in an amount effective to produce seal swelling and to lower the pour point. The viscosity of the fluid formulation is suitable for diverse vibration damping applications that require a vibration damping device to operate in the temperature range of about −40° C. to about 100° C. The low volatility and seal swelling properties of the fluid formulation reduce, inhibit or eliminate fluid loss about the seals of the vibration damping device.

Abstract: The subject invention provides a magnetorheological (MR) composition having improved resistance to oxidation and increased dispersability in a carrier fluid. The composition includes a plurality of metal particles and a surfactant including a hydrocarbon with at least one of a hydroxyl, a carbonyl, and an amine group bonded to the hydrocarbon for reacting with the metal particles. The surfactant is present in an amount such that from about 1% to about 20% of the amount of the surfactant is adsorbed to the metal particles. The surfactant is reacted with the metal particles such that about 75% to about 100% of a maximum amount of the surfactant adsorbs to the metal particles for improving the resistance of the metal particles to oxidation and for increasing the dispersability of the magnetorheological composition in the carrier fluid. The MR composition according to the subject invention is utilized in a magnetorheological (MR) fluid.

Abstract: One embodiment of the invention includes an MR fluid of improved durability. The MR fluid is particularly useful in devices that subject the fluid to substantial centrifugal forces, such as large fan clutches. A particular embodiment includes a magnetorheological fluid including 10 to 14 wt % of a hydrocarbon-based liquid, 86 to 90 wt % of bimodal magnetizable particles, 0.05 to 0.5 wt % fumed silica, and an additive package including a paraffin oil, a phenol and a sulfide.

Abstract: Magnetorheological materials are provided comprising magnetic particles, a polymeric gel and a carrier material. The polymerization of the gel is preferentially accomplished in the presence of the magnetic particles and the carrier material. Magnetorheological materials are provided having a selected off-state viscosity and a selected on-state apparent viscosity. The method of preparing these magnetorheological materials is also provided. The carrier material, the polymeric gel and the magnetic particles are selected so that the resulting magnetorheological material has the desired off-state viscosity and on-state apparent viscosity. These materials have good dispersion characteristics, reduced settling, superior off-state viscosity and superior apparent viscosity in the presence of a magnetic field.

Abstract: One embodiment of the invention includes an MR fluid of improved durability. The MR fluid is particularly useful in devices that subject the fluid to substantial centrifugal forces, such as large fan clutches. A particular embodiment includes a magnetorheological fluid including a liquid, magnetizable particles, and a molybdenum-amine complex.

Abstract: One embodiment of the invention includes an MR fluid of improved durability. The MR fluid is particularly useful in devices that subject the fluid to substantial centrifugal forces, such as large fan clutches. A particular embodiment includes a magnetorheological fluid including 10 to 14 wt % of a hydrocarbon-based liquid, 86 to 90 wt % of bimodal magnetizable particles, and 0.05 to 0.5 wt % fumed silica.

Abstract: One embodiment of the invention includes an MR fluid of improved durability. The MR fluid is particularly useful in devices that subject the fluid to substantial centrifugal forces, such as large fan clutches. A particular embodiment includes a magnetorheological fluid including a liquid, magnetizable particles, a stearate and a thiophosphate.

Abstract: The present invention provides a magnetorheological fluid in which magnetic particles coated with a hydrophilic surfactant are dispersed in a water in oil emulsion, and a process for preparing the same. The magnetorheological fluid of the present invention is prepared by adding water to oil dissolved with emulsifier, stirring it to give a mobile phase of water in oil emulsion, and dispersing magnetic particles coated with a hydrophilic surfactant in the water in oil emulsion. The invented magnetorheological fluid is improved in terms of stability through the interaction between surfactant of the magnetic particle surface and water molecule, which makes possible its practical application in the development of variable devices employing the magnetorheological fluid.

Abstract: A method of polishing an object is disclosed. In one embodiment, the method comprises the steps of creating a polishing zone within a magnetorheological fluid; determining the characteristics of the contact between the object and the polishing zone necessary to polish the object; controlling the consistency of the fluid in the polishing zone; bringing the object into contact with the polishing zone of the fluid; and moving at least one of said object and said fluid with respect to the other. Also disclosed is a polishing device. In one embodiment, the device comprises a magnetorheological fluid, a means for inducing a magnetic field, and a means for displacing the object to be polished or the means for inducing a magnetic field relative to one another.

Abstract: The invention relates to new single- or multi-metallic magnetic colloid particles (for example, Fe, Co, Ni, Fe/Co) having a size of up to 20 nm, the surface of which is protected against corrosion by precious metals, such as Pd, Ag, Pt or Au. The invention also relates to a method for producing such materials. In isolated form or in solution said materials are used among other things as sealing media against dust and gas in magnetic fluid seals (liquid O ring), for lubricating and mounting rotating shafts (magnetic levitation bearing), for the magnetooptic storage of information as well as for the magnetic marking of cells and their separation in biological samples or for the local administration of medicines.

Abstract: A magnetic fluid and a process for producing the same are provided. The magnetic fluid is an excellent fluid which mightily and precisely actuates by the action of an external magnetic field so that its viscosity can be significantly increased and be easily and precisely controlled by regulating the external magnetic field applied thereto. The magnetic fluid is also excellent in the unsusceptibility to oxidation and dispersibility of the particles and has a sufficiently wide viscosity range.

Abstract: Magnetic polishing fluid compositions comprising various size colloidal and/or non-colloidal magnetic particle and colloidal size polishing particle compositions suitable for polishing ceramic and glass substrates are described. The compositions are usually aqueous compositions having highly basic pHs. Methods for preparing the various polishing fluids compositions are also discussed.

Abstract: There are disclosed a composition for resin magnets which comprises a thermoplastic resin and magnetic powders and which, when determined in a heated molten state, has specific viscosity characteristics characterized in that the almost linear line which is obtained by taking &eegr;R/&eegr;O as ordinate and &ggr; as abscissa has a slope of at most 0.02, preferably at most 0.01 within a specific temperature range in which &eegr;O falls within the range of from 2.0×106 to 1.0×107 dyne/cm2, wherein &eegr;R denotes shear stress (dyne/cm2), &eegr;O denotes yield stress (dyne/cm2) and &ggr; denotes shear rate (S−1); a magnetic member which is produced by the use of the above composition for resin magnets; and a process for efficiently producing the magnetic member from the composition by an extrusion molding in a magnetic field under specific temperature and pressure conditions.

Abstract: Magnetic polishing fluid compositions for polishing metal substrates containing colloidal and/or non-colloidal magnetic particles are described. The compositions contain oxidizers and, for example, oxidation inhibitors for assisting in the polishing process. Colloidal polishing particles may also be employed. The compositions are usually highly acidic. Methods for preparing the various polishing fluids compositions are described.

Abstract: The invention provides a magnetorheological composition having reduced off-state forces and good performance. Specifically, this invention is directed to a magnetorheological composition that may comprise non-sperical magnetic-responsive particles and at least one friction-reducing additive that reduces the interparticle friction between the magnetic-responsive particles.

Abstract: Hydrophobic metal particles that are useful as the magnetizable particles in magnetorheological fluids and magnetorheological elastomers are provided. Hydrophilic metal particles, such as carbonyl iron particles, are made hydrophobic by reacting a surface hydroxyl on the solid metal particle with a reactive surfactant. Particles are coated with the reactive surfactant to cover at least about 90% of the surface of the particles and then washed with a low viscosity synthetic hydrocarbon to remove any excess surfactant. The particles are stabilized against oxidation and irreversible coagulation during further processing, and formulation and use in magnetorheological fluids and elastomers.

Abstract: A durable magnetorheological fluid suitable for use in high compression vibration dampening devices comprising mechanically hard magnetizable particles of unreduced carbonyl iron, cobalt-iron alloys, or mixtures thereof, a carrier fluid of a mixture of polyalphaolefin and a plasticizer, unreduced fumed silica and optionally an ethoxylated amine.

Abstract: A durable MR fluid formulation is described which includes mechanically hard magnetizable particles, a carrier fluid derived from a polyalphaolefin and a plasticizer, and at least one colloidal additive such as colloidal polytetrafluoroethylene or colloidal graphite.

Abstract: A rheological fluid of a bright color which has excellent light resistance and weather resistance, is stable even when used in a high-temperature environment, can be stored over long, and mightily and precisely actuates in response to an electric field or a magnetic field or to both. The rheological fluid comprises a medium in which a film-coated powder comprising a base particle having thereon a coating layer(s) is dispersed.

Abstract: The invention relates to a composition and process for producing a chemically stable magnetic fluid comprising a plurality of magnetic particles covered first with a small molecular weight surface modifier, which is a nondispersant and acts as a surfactant-accepting layer, and then with at least one surfactant. The surface modifier/surfactant coated magnetic particles are then suspended in a silicone oil-based, hydrocarbon oil-based or an ester oil-based carrier liquid.

Abstract: The invention relates to a composition and a process for producing a magnetic fluid comprising finely divided magnetic particles covered with at least one surfactant. A fluorocarbon-silane surface modifier is employed which is added to cover the free oxidizable exterior surface of the outer layer of the particles to increase the acid resistance of the colloid.

Abstract: There are provided fluid compositions with particulate solid materials dispersed therein which are characterized by exceptionally low settling tendencies of the dispersed particles. Such compositions containing particulate ferromagnetic solids are useful as magnetorheological fluids.

Abstract: An ink composition suitable for use in ink jet printing comprising a coloring agent and carrier therefor which additionally contains a magneto-rheological fluid to control the viscosity and flow properties of the ink composition during use.

Abstract: Magnetorheological fluid compositions that include a carrier fluid, magnetic-responsive particles and an organoclay. These fluids exhibit superior soft sedimentation.

Abstract: A process for preparing an agglomerate-free suspension of nanosize iron-containing oxide particles coated in a stable manner comprises preparing an aqueous suspension of nanosize iron-containing oxide particles which are partially or completely in the form of agglomerates; adding a trialkoxysilane and a water-miscible polar organic solvent which has a boiling point at least 10° C. higher than the boiling point of water; treating the resulting suspension with ultrasound until at least 70% of the particles present are in the range of ±20% of the average particle diameter; removing the water by distillation under the action of ultrasound; and separating the non-disintegrated agglomerates.