Water-based magnetorheological fluid with wide operating temperature range and good viscosity stability

Abstract

The application discloses a water-based magnetorheological fluid with a wide working temperature range and good kinetic viscosity stability, which comprises hydrophobic group modified magnetic particles, a water-based carrier liquid with water as a main component, and additives added into the carrier liquid, wherein the working temperature T of the water-based magnetorheological fluid is in the range of 0 DEG C < T <= 40 DEG C, and the kinetic viscosity change value of the water-based magnetorheological fluid measured at a working temperature of 20 DEG C to 30 DEG C and a shear rate of 800 s-1 to 2000 s-1 is in the range of + / - 50 mPa.s. ‑1 ​

Description

Technical Field

[0001] This invention relates to magnetorheological fluids, specifically to water-based magnetorheological fluids in which the carrier fluid is mainly composed of water. Background Technology

[0002] Water-based magnetorheological fluids, serving as the polishing "grinding head" in magnetorheological polishing technology, provide excellent removal efficiency and a stable removal function for the entire polishing process. Since there is virtually no subsurface damage on the workpiece surface during polishing, magnetorheological polishing technology is also more suitable for the ultra-precision machining of complex workpieces. In use, the high-speed stirred magnetorheological fluid is pumped to the polishing wheel for polishing. To ensure a stable flow rate, the magnetorheological fluid needs to be stirred to a high-shear state, as the viscosity of the magnetorheological fluid at high shear rates has a stable range, within which the viscosity is relatively easy to control. However, in practical applications, the density difference between the magnetic powder and other components of the carrier fluid is significant, resulting in poor stability of the entire magnetorheological fluid, such as viscosity stability. In particular, substantial agglomeration tends to occur between particles, ultimately affecting polishing stability.

[0003] To improve the stability of magnetorheological fluids, patent CN200710018973.8 discloses a novel magnetorheological polishing slurry and its preparation method. It points out that by reducing the average particle size of the magnetic particles and selecting magnetic particles with an average particle size ≤3.5μm, sedimentation and agglomeration caused by significant density differences can be overcome, thus improving the overall physical stability of the magnetorheological fluid. Under normal circumstances, untreated magnetic powder placed in water will quickly oxidize / corrode, which will significantly affect the stability of the magnetic particles during polishing. Therefore, the magnetic powder used in water-based magnetorheological fluids applied in polishing often has to be surface-treated. Patent CN200710018973.8 uses a ball mill to adsorb surfactants onto the surface of the magnetic particles before preparing the magnetorheological fluid, thereby significantly reducing the ability of particles to aggregate and improving the overall chemical stability of the magnetorheological fluid.

[0004] It is also important to note that for water-based magnetorheological fluids, rusting is inevitable as the magnetic particles disperse in water for longer periods. The main cause of rusting is the corrosion from hydrogen ions ionized in the water. To improve the corrosion resistance of the magnetic particles, common methods include passivating their surface or introducing inactive metal particles. However, these methods ultimately affect the polishing efficiency of the magnetorheological fluid. Therefore, a common approach is to adjust the pH of the magnetorheological fluid system to an alkaline environment. Patent CN200810030904.3 discloses a water-based magnetorheological polishing fluid for optical processing and its preparation method, indicating that substances such as borax and sodium carbonate can be used to adjust the pH of the entire magnetorheological fluid. A pH range of 9.5 to 10.5 yields a magnetorheological fluid with good stability, significantly extending its polishing life and ultimately saving on consumable costs.

[0005] Although the above methods offer solutions for the stability of magnetorheological fluids themselves, existing water-based magnetorheological fluids still have at least the following drawbacks in practical working environments:

[0006] 1. At high shear rates, the stable viscosity range is narrow. Since the flow rate of water-based magnetorheological fluid will be lost during the pumping process, the narrow constant viscosity range of water-based magnetorheological fluid is not conducive to precise flow control.

[0007] 2. The operating temperature is relatively demanding. The viscosity of the magnetorheological fluid changes significantly when the temperature is higher or lower than the set operating temperature. Therefore, existing technologies must control the operating temperature / ambient temperature within a precise range to ensure the viscosity stability of the water-based magnetorheological fluid used in the polishing process.

[0008] Patent CN1202848A points out that the optimal temperature for magnetorheological fluids (MRFs) is typically maintained within the range of 21–22°C. This is because in water-based MRF polishing equipment, the MRF is affected by the operation of the internal electromagnets and the fluid circulation pump during system circulation, absorbing heat from the circulating system and ultimately increasing the MRF's evaporation rate. Simultaneously, when the MRF operates on the external polishing wheel, the water-based MRF carrier exposed to air gradually evaporates due to the inherent evaporation characteristics of water, eventually leaving only solid components such as carbonyl iron powder. Ambient temperature and water evaporation are closely related; as temperature increases, water evaporation accelerates, reducing the liquid component in the MRF system and increasing the overall viscosity, ultimately leading to decreased fluid stability. All of these issues ultimately affect the precision and stability of MRF polishing. Although existing equipment can cool the MRF by adding water cooling devices and using inductors to monitor the liquid flow and viscosity, employing strategies such as additional water replenishment to maintain MRF stability, these issues cannot be addressed.

[0009] However, there is currently no effective solution from a materials perspective for improving the stability of fluids at different temperatures. To date, no concept of water-based magnetorheological fluids for use over a wide operating temperature range has been discussed or studied in existing technologies.

[0010] Therefore, with the development and changes in technology and application scenarios, there is an urgent need in this field for novel water-based magnetorheological fluids to overcome the aforementioned technical defects in existing technologies and solve the above-mentioned shortcomings and other technical problems.

[0011] The information included in this background section of the present invention specification, including any references cited herein and any descriptions or discussions thereof, is included for technical reference purposes only and is not intended to limit the scope of the invention. Summary of the Invention

[0012] The present invention is proposed in view of the foregoing and other further ideas.

[0013] According to one aspect of the invention, it is intended to provide a water-based magnetorheological fluid with a wide operating temperature range and good kinematic viscosity stability.

[0014] One of the characteristics of this magnetorheological fluid is that it has good viscosity stability over a relatively wide temperature range at high shear rates. At the same time, other performance indicators, such as shear stress (initial shear stress or maximum shear stress) under the same magnetic field environment, shear stress (initial shear stress or maximum shear stress) under the same shear rate, viscosity, polishing efficiency (removal rate or viscosity stability), etc., do not show substantial reduction or these changes have no substantial impact on practical use.

[0015] This water-based magnetorheological fluid can maintain good viscosity stability over a wider temperature range without affecting its intended applications, such as applications in environments of approximately 21–22°C, etc.

[0016] The theoretical operating temperature range for water-based magnetorheological fluids is, for example, 0–40°C. However, in actual use, both the equipment temperature and the ambient temperature can be controlled within a fixed range. When the ambient or operating temperature changes significantly, the stability of the magnetorheological fluid is affected, thus impacting the stability of the entire magnetorheological polishing system and ultimately greatly limiting its practical performance. This necessitates that magnetorheological fluids possess good viscosity stability over a wide operating temperature range, especially at higher temperatures.

[0017] Generally, to reduce the evaporation rate of magnetorheological fluids (MRFs) at high temperatures, the content of volatile or low-boiling-point components in the carrier liquid system needs to be reduced. However, in water-based MRFs, water, as the main component, evaporates very easily at ambient temperatures. As the ambient temperature increases, the evaporation rate also increases. This excessively rapid evaporation often leads to a sudden increase in the viscosity of the entire MRF system, ultimately affecting its viscosity stability. From a liquid perspective, to prevent excessively rapid evaporation of the MRF carrier liquid, the content of non-volatile components in the entire carrier liquid system can often be increased. However, non-volatile components often have high viscosity, and a high content of non-volatile components will further increase the viscosity of the MRF at high shear rates. In typical MRF polishing equipment, when the stirring speed remains constant, the higher the viscosity of the MRF, the more difficult it is to pump it out per unit time, resulting in a lower pumped-out content. When the liquid passes through the flow monitoring device, the unstable output value often affects the final polishing efficiency. Therefore, high-viscosity magnetorheological fluids are not conducive to their stable circulation and transport in magnetorheological polishing equipment.

[0018] The inventors of this application have discovered that the viscosity of magnetorheological fluid at high shear rates directly affects the polishing stability in magnetorheological polishing equipment. The higher the viscosity of the magnetorheological fluid, the more difficult it is for the equipment to control the flow rate and viscosity of the magnetorheological fluid, which is very disadvantageous in the actual polishing process.

[0019] Magnetorheological fluids are non-Newtonian fluids, meaning their shear rate and shear stress are non-linear. Magnetorheological fluids do not obey Newton's law of viscosity and exhibit complex rheological laws and properties. Among common rheological models, magnetorheological fluids are closer to the Bingham plasticity model, and their viscosity shows significant thixotropic characteristics. Referring to the relevant theories proposed in RS Lenk's book "Polymer Rheology," in a static state, the additive components inside a magnetorheological fluid (MRF) can form a framework structure, effectively preventing aggregation and sedimentation. However, with the movement of the MRF and the increase of the shear rate, the thixotropic structure of the MRF is gradually destroyed. When the shear rate increases to a certain value, all the framework structures inside the MRF are destroyed. When the rate of framework entanglement is much lower than the rate of destruction, the slippage between magnetic particles becomes easier, and the viscosity at this point tends to a relatively stable value, known as the "limiting shear viscosity." As the shear rate increases, the viscosity of the MRF in this region tends to stabilize, known as the "second Newton's zone." Monitoring and controlling the flow rate of the MRF within this region becomes more convenient. The lower the viscosity value corresponding to a constant "second Newton's zone," the better the operation of the MRF in the entire device can be controlled. At the same time, the more stable the "limiting shear viscosity" of the MRF at different temperatures, the wider the application scenarios of the MRF will be.

[0020] From this perspective, an ideal water-based magnetorheological fluid should have a low viscosity value within the "second Newtonian zone," while maintaining good stability at different temperatures. A stable viscosity value facilitates the stable operation of the magnetorheological fluid in magnetorheological polishing equipment, ultimately improving the surface finish of the polished material.

[0021] Those skilled in the art will readily understand that by altering, for example, the operating temperature of the magnetorheological fluid (MRF), one can influence, for example, increase the evaporation rate of the carrier fluid, and consequently, increase, for example, the limiting shear viscosity of the entire MRF. An increase in the limiting shear viscosity of the MRF makes it more difficult to control the liquid circulation in the MRF polishing equipment. Using a water-based MRF with good viscosity stability over a wide operating temperature range allows for better control of the viscosity of the MRF operating in the MRF polishing equipment, resulting in stable removal efficiency.

[0022] According to one aspect of the present invention, the inventors have surprisingly discovered that surface modification of magnetic particles used in conventional magnetorheological fluids, by coating the surface of the magnetic powder with a layer of organic functional groups that delay corrosion using a hydrophobic material, can improve the surface energy of the magnetic particles and effectively reduce the interaction forces between the magnetic powder particles in practice.

[0023] Surprisingly, the inventors of this invention have also discovered that using nonionic surfactant dispersants can improve the dispersion ability of magnetic powder. Preferred dispersants include polyhydroxy polymers, polyvinyl alcohol polymers, polysaccharide uronic acid compounds, and cellulose polymers. These dispersants can maintain good compatibility with alcohol wetting agents, ensuring that the entire magnetorheological system maintains a high surface tension, thereby improving the stability of the entire magnetorheological fluid system.

[0024] According to one aspect of the present invention, the water-based magnetorheological fluid can maintain the excellent mechanical properties and viscosity characteristics of water-based magnetorheological fluids, while also taking into account the stability of viscosity changes at different temperatures, resulting in a wider controllable range and a stable second Newton region. It also improves upon the problems of traditional water-based magnetorheological fluids being prone to agglomeration and the formation of hard precipitates.

[0025] According to the inventors' discovery, in practice, hydrophobic group-modified magnetic particles can be used as magnetic powder, and the excellent magnetic field performance of traditional water-based magnetorheological fluids can still be maintained. After a certain degree of sedimentation occurs after a long period of storage, they can still be easily remixed and have good redispersibility.

[0026] Moreover, when the water-based magnetorheological fluid of the present invention is used over a wide temperature range, its limiting shear viscosity corresponding to the second Newton region can be maintained within a wide and stable range, thus giving the magnetorheological fluid a wider operating temperature range.

[0027] More specifically, according to one aspect of the present invention, a water-based magnetorheological fluid with a wide operating temperature range and good kinematic viscosity stability is provided, comprising: hydrophobic group-modified magnetic particles; a carrier liquid with water as the main component, wherein the magnetic particles are dispersed in the carrier liquid; and an additive added to the carrier liquid; wherein the operating temperature T of the water-based magnetorheological fluid is in the range of 0℃ < T ≤ 40℃; and the water-based magnetorheological fluid operates at a temperature of 20-30℃ and a viscosity of 800-2000s. -1 The kinematic viscosity change measured at the shear rate is within ±50 mPa·s.

[0028] According to an embodiment of the present invention, the water-based magnetorheological fluid is subjected to a temperature of 20-30°C and a duration of 800-2000 s. -1 The change in kinematic viscosity at shear rate is within ±30 mPa·s.

[0029] According to an embodiment of the present invention, the water-based magnetorheological fluid is subjected to a temperature of 20-30°C and a duration of 800-2000 s. -1 The kinematic viscosity measured at the shear rate is in the range of 350±50 mPa·s, preferably 350±20 mPa·s.

[0030] According to an embodiment of the present invention, the water-based magnetorheological fluid is subjected to a temperature of 20-30°C and a duration of 800-2000 s. -1 The kinematic viscosity measured at the shear rate is in the range of 250±30 mPa·s, preferably 250±15 mPa·s.

[0031] According to one embodiment of the present invention, the kinematic viscosity of the water-based magnetorheological fluid at an operating temperature of 25°C is selected from 50-400 mPa·s, for example, from 50-100, 100-200 or 200-400 mPa·s.

[0032] According to one embodiment of the present invention, the initial viscosity of the water-based magnetorheological fluid at zero magnetic field and a temperature of about 25°C is in the range of 50,000-75,000 mPa·s, for example, 50,000-60,000, 65,000-70,000, or 72,000-75,000 mPa·s.

[0033] According to an embodiment of the present invention, the additive comprises at least one of the following: antioxidants, dispersants, wetting agents, thixotropic agents, pH adjusters, polishing particles, and combinations thereof.

[0034] According to an embodiment of the present invention, the material of the magnetic particles comprises at least one of the following: iron alloys, iron oxides, iron nitride, iron carbide, iron carbonyl, nickel, cobalt, and combinations thereof.

[0035] According to one embodiment of the present invention, the additive comprises polishing particles, the polishing particles being made of at least one of the following: nano-diamond, nano-cerium oxide, nano-zirconia, nano-alumina, nano-silicon carbide, nano-silicon dioxide, nano-iron oxide, nano-boron carbide, nano-tungsten carbide, and combinations thereof.

[0036] According to an embodiment of the present invention, the additive comprises a modifier having the hydrophobic group, the modifier comprising at least one of the following: short-chain alkane silane coupling agents, long-chain alkane silane coupling agents, fluoroalkane silane coupling agents, monofunctional end-capped silane coupling agents, silane oligomers, and combinations thereof.

[0037] According to one embodiment of the present invention, the specific gravity of the magnetic particles in the whole system is in the range of 0.5-0.95, for example 0.5-0.93, 0.5-0.9, or 0.83-0.88.

[0038] According to one embodiment of the present invention, the polishing particles have a small particle size.

[0039] According to one embodiment of the present invention, the magnetic particles have good sphericity.

[0040] According to one embodiment of the present invention, the kinematic viscosity of the magnetorheological fluid is in the range of 40-240 mPa·s, for example 40-50, 50-100, 100-200 mPa·s.

[0041] According to one embodiment of the present invention, the initial viscosity is in the range of 50,000-75,000 mPa·s, for example, 50,000-60,000, 65,000-70,000, or 72,000-75,000 mPa·s.

[0042] According to one embodiment of the present invention, the average particle size or equivalent particle size of the magnetic particles is in the range of 0.05-5 micrometers, for example, 0.1-2, 0.1-5 or 0.2-3 micrometers.

[0043] According to one embodiment of the invention, the volume percentage of the magnetic particles is in the range of 20-45%, for example 35-45%.

[0044] According to one embodiment of the present invention, the additive comprises an antioxidant, which is an amine antioxidant, a phenolic antioxidant, a metal salt, or a combination thereof.

[0045] According to one embodiment of the present invention, the additive comprises a dispersant, which is mostly a polyvinyl alcohol polymer or a polysaccharide uronic acid compound, a cellulose polymer, or a combination thereof.

[0046] According to one embodiment of the present invention, the additive includes a wetting agent, which is mostly a low molecular weight alcohol compound, preferably glycerol, ethylene glycol and combinations thereof.

[0047] According to one embodiment of the present invention, the additive comprises a thixotropic agent, which is mostly cellulose ether and its derivatives, polyurethane thickener, fumed silica and combinations thereof.

[0048] According to one embodiment of the present invention, the additive comprises a pH adjuster, which is mostly sodium hydroxide, triethanolamine, sodium carbonate, sodium phosphate, disodium hydrogen phosphate, and combinations thereof.

[0049] According to one or more embodiments of the present invention, the kinematic viscosity change in the second Newton region of the water-based magnetorheological fluid at different temperatures is much lower than that of existing water-based magnetorheological fluids, exhibiting superior viscosity stability.

[0050] Further embodiments of the present invention can achieve other advantageous technical effects not listed hereafter, which may be partially described below and can be expected and understood by those skilled in the art after reading the present invention. Attached Figure Description

[0051] The above-described features and advantages of these embodiments, as well as other features and advantages, and the ways in which they are implemented, will become more apparent and the embodiments of the invention will be better understood by referring to the following description in conjunction with the accompanying drawings, in which:

[0052] Figure 1 This is a schematic diagram comparing the rheological properties of a water-based magnetorheological fluid at 20°C, 25°C, and 30°C under zero magnetic field, according to the first embodiment of the present invention.

[0053] Figure 2 This is a schematic diagram comparing the viscosity of a water-based magnetorheological fluid at 20°C, 25°C, and 30°C under zero magnetic field, according to the first embodiment of the present invention.

[0054] Figure 3 This is a comparative schematic diagram of the second Newtonian zone of the water-based magnetorheological fluid at 20°C, 25°C, and 30°C under zero magnetic field, according to the first embodiment of the present invention.

[0055] Figure 4 This is a schematic diagram comparing the rheological properties of a water-based magnetorheological fluid at 20°C, 25°C, and 30°C under 240 mT according to the first embodiment of the present invention.

[0056] Figure 5 This is a ribbon stability curve after 24 hours of water-based magnetorheological fluid polishing cycle according to the first embodiment of the present invention.

[0057] Figure 6 This is a ribbon stability curve after 48 hours of water-based magnetorheological fluid polishing cycle according to the first embodiment of the present invention.

[0058] Figure 7 This is a polishing model diagram after a 24-hour polishing cycle using a water-based magnetorheological fluid according to the first embodiment of the present invention.

[0059] Figure 8 This is a polishing model diagram after 48 hours of water-based magnetorheological fluid polishing cycle according to the first embodiment of the present invention. Detailed Implementation

[0060] In the following description of the accompanying drawings and detailed embodiments, details of one or more embodiments of the invention will be set forth. Other features, objects, and advantages of the invention will become apparent from these descriptions, drawings, and claims.

[0061] It should be understood that the illustrated and described embodiments are not limited in application to the details of the construction and arrangement of the components set forth in the following description or illustrated in the drawings. The illustrated embodiments may be other embodiments and can be implemented or performed in various ways. The examples are provided by way of explanation rather than limitation of the disclosed embodiments. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the invention without departing from the scope or spirit of the disclosure. For example, features illustrated or described as part of one embodiment may be used with another first embodiment to still produce another embodiment. Therefore, this disclosure covers such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0062] Similarly, it is understood that the phrases and terms used in this document are for descriptive purposes and should not be considered restrictive. The use of “including,” “contains,” or “has,” and their variations, in this document is intended to include, in an open-ended manner, the items listed thereafter, their equivalents, and any additional items.

[0063] The present invention will now be described in more detail with reference to several specific embodiments thereof.

[0064] First Embodiment

[0065] In this embodiment, the preparation method of the water-based magnetorheological fluid includes the following steps:

[0066] Step 1: Premix carbonyl iron powder and ethanol solution at a mass ratio of approximately 1:5. The main particle size range of carbonyl iron powder is approximately 2-3 μm. Place the mixed liquid into a ball mill jar and premix at a speed of approximately 200-350 r / min for approximately 40-120 min to obtain a uniform magnetic particle solution.

[0067] Step 2: Add γ-(methacryloyloxy)propyltrimethoxysiloxane and carbonyl iron powder to a ball mill jar at a mass ratio of about 1:3, and mix in the ball mill jar at a speed of about 350 r / min for about 18-25 h.

[0068] Step 3: Pour the carbonyl iron powder solution from the ball mill jar after the reaction, remove the precipitate, absorb the excess solution with gauze, and place the resulting final solid particles in a vacuum oven for drying. The oven temperature is about 80℃ and the drying time is 4 hours, finally obtaining hydrophobic group modified magnetic particles.

[0069] Step 4: Premix deionized water, naphthylamine, hydroxypropyl cellulose, ethylene glycol, fumed silica, sodium carbonate, and nanodiamond in the specified proportions, and stir in an ultrasonic environment at room temperature for about 18-30 hours.

[0070] Step 5: Mix the alkylated carbonyl iron powder obtained in Step 3 with the magnetorheological fluid carrier liquid obtained in Step 4 in a predetermined ratio, and mix at room temperature for about 12 hours to obtain the desired water-based magnetorheological fluid.

[0071] A comparative schematic diagram of the rheological properties of the magnetorheological fluid prepared according to this embodiment of the present invention at 20°C, 25°C, and 30°C under zero magnetic field is shown below. Figure 1 As shown, Figure 1 This is a schematic diagram comparing the rheological properties of the A285 magnetorheological fluid of the first embodiment with those of a similar magnetorheological fluid (QED-C10) on the market. Tests using an Anton Paar MCR302 magnetorheological instrument show that it exhibits superior rheological properties at 20°C, 25°C, and 30°C for 1000 seconds. -1 The corresponding shear stresses are 283 Pa, 276 Pa, and 287 Pa, respectively, with a maximum and minimum shear stress deviation of 11 Pa. It exhibits good rheological stability across three temperature ranges. Commercially available magnetorheological fluids of the same type (QED-C10) show similar stability at 20℃, 25℃, and 30℃ for 1000 seconds. -1 The corresponding shear stresses were 266 Pa, 253 Pa, and 272 Pa, respectively, with a maximum and minimum deviation of 19 Pa. The rheological properties showed large deviations in the three temperature ranges. This experiment indicates that the magnetorheological fluid prepared in this invention has better rheological property stability in the range of 20℃ to 30℃.

[0072] Figure 2 This is a schematic diagram comparing the viscosity of the A285 type magnetorheological fluid prepared according to this embodiment of the invention with that of a commercially available magnetorheological fluid (QED-C10). Testing with an Anton Paar MCR302 magnetorheological instrument shows that the magnetorheological fluid prepared according to this invention exhibits better viscosity at 20°C, 25°C, and 30°C, with a viscosity of 0s. -1 1000s -1 The corresponding dynamic viscosity values ​​are shown in Table 1. The magnetorheological fluid prepared by this invention has the same initial viscosity as commercially available magnetorheological fluids of the same type (QED-C10). The high initial viscosity allows the liquid to exhibit better thixotropic properties, which improves the anti-settling performance of the magnetorheological fluid itself and maintains good dispersibility. Meanwhile, the magnetorheological fluid prepared by this patent can maintain better viscosity stability within the temperature range of 20℃ to 30℃, which facilitates the control of the magnetorheological fluid at different temperatures.

[0073] Table 1

[0074]

[0075] Figure 3This is a schematic diagram comparing the second Newton's zone of the A285 magnetorheological fluid of the first embodiment with that of a commercially available magnetorheological fluid of the same type (QED-C10). Testing with an Anton Paar MCR302 magnetorheological instrument shows that the magnetorheological fluid prepared in this invention exhibits better performance in the second Newton's zone at approximately 20°C, 25°C, and 30°C for 500–2000 seconds. -1 The corresponding second Newtonian zone viscosity values ​​are approximately 321 mPa·s, 328 mPa·s, and 338 mPa·s, respectively. Commercially available magnetorheological fluids of the same type (QED-C10) have viscosity values ​​of approximately 20℃, 25℃, and 30℃, and 400–2000 s⁻¹. -1 The corresponding second Newtonian zone viscosity values ​​are approximately 253 mPa·s, 290 mPa·s, and 381 mPa·s. It can be seen that as temperature increases, the viscosity in the second Newtonian zone increases for both the magnetorheological fluid prepared according to this invention and other magnetorheological fluids. This is because during high-speed operation, the evaporation rate of the magnetorheological fluid increases with the rising temperature, ultimately resulting in an increase in viscosity in the second Newtonian zone. The magnetorheological fluid prepared according to this invention exhibits a relatively narrower viscosity variation range with increasing temperature. The inventors of this patent have surprisingly discovered that after modifying the magnetic particles with hydrophobic groups, the smaller magnetic particles form a very thin hydrophobic film on the surface of the magnetorheological fluid. This hydrophobic film effectively prevents water evaporation, thereby ensuring the viscosity stability of the magnetorheological fluid at different temperatures.

[0076] Figure 4 This is a comparative schematic diagram of the rheological properties of the A285 type magnetorheological fluid prepared according to this embodiment of the invention at approximately 240 mT at approximately 20°C, 25°C, and 30°C. Since a magnetic field exists around the magnetorheological fluid during the operation of the magnetorheological polishing equipment, an Anton Paar MCR302 magnetorheologist is used to provide a magnetic field environment of approximately 240 mT for the liquid, thereby simulating the actual working environment. The magnetorheological fluid prepared by this invention exhibits rheological properties at approximately 20°C, 25°C, and 30°C for 5 seconds. -1 100s -1 The corresponding shear stress values ​​are shown in Table 2. It can be seen from this that the magnetorheological fluid prepared by this invention has a shear stress of 5 s. -1 The corresponding shear stress is approximately 15 kPa, over 100 seconds. -1 The corresponding shear stress is about 18 kPa. As the shear rate increases, the shear stress increases to a stable level. Furthermore, the shear stress value remains within a stable range as the temperature changes, indicating that the magnetorheological fluid prepared in this invention has good stability.

[0077] Table 2

[0078]

[0079] Figures 5-8 The results are from the test conducted on fused silica glass using the A285 magnetorheological fluid of the first embodiment. The removal function after approximately 24 hours and 48 hours of polishing stability was selected as a reference to investigate the stability of the magnetorheological fluid. Ribbon stability represents the high stability of the ribbon-like fluid formed by the magnetorheological fluid sprayed onto the polishing wheel surface. When the height of the magnetorheological fluid remains consistent within a unit of time, the penetration depth of the polished material is ensured to be stable, ultimately guaranteeing the fineness of the polishing. Ribbon stability can be used to measure the stability during the liquid circulation process. Figures 5-6 The displayed ribbon stability curves show that the 3σ value is within the range of approximately 0.02–0.03 mm, indicating that the magnetorheological fluid prepared in this invention has good cyclic stability. Meanwhile, the stability of the removal rate (mainly volumetric removal rate (μm / min) and peak removal rate (μm / min)) over long-term operation can also reflect the stability of the magnetorheological fluid. Table 3 shows the relevant values ​​during the polishing process. Figures 7-8 As can be seen from the color region of the removal function and the appearance shape shown, the magnetorheological fluid prepared by this invention has good stability.

[0080] Table 3

[0081]

[0082] The above test data and comparisons show that the performance stability of the water-based magnetorheological fluid in the second Newton region at different temperatures in this embodiment is much higher than that of the water-based magnetorheological fluid in the prior art, and the variation range of its parameters (such as dynamic viscosity) is much lower than that of the corresponding parameters (such as dynamic viscosity) of the water-based magnetorheological fluid in the prior art.

[0083] Second Embodiment

[0084] In this embodiment, the preparation method of the water-based magnetorheological fluid includes the following steps:

[0085] Step 1: Anisotropic magnetorheological powder (e.g., anisotropic magnetic powder developed and produced by the applicant itself, the composition, preparation process, and equipment of which are described in detail in the applicant's patents CN106486240B and CN106486241B, which are incorporated herein by reference) is premixed with an ethanol solution at a mass ratio of approximately 1:5. The mixed liquid is then placed in a ball mill jar and premixed at a speed of approximately 350 r / min for approximately 60 min to obtain a homogeneous magnetic particle solution.

[0086] Step 2: Add tetraethyl orthosilicate, octadecyltrimethoxysilane and anisotropic magnetic powder into a ball mill jar at a mass ratio of approximately (1:1:6) and mix in the ball mill jar at a speed of approximately 350 r / min for approximately 18 h.

[0087] Step 3: Pour the anisotropic magnetic powder solution from the ball mill jar after the reaction, remove the precipitate, absorb the excess solution with gauze, and place the resulting final solid particles in a vacuum oven for drying. The oven temperature is about 80°C, and the drying time is about 4 hours, finally obtaining hydrophobic group modified magnetic particles.

[0088] Step 4: Premix deionized water, tea polyphenols, glucuronic acid, glycerol, hydroxypropyl cellulose, sodium hydroxide, and nano-cerium oxide in a mass percentage of approximately 89:1.5:3:3:1:0.5:2, and stir in an ultrasonic environment at room temperature for approximately 18 hours.

[0089] Step 5: Mix the alkylated anisotropic magnetic powder obtained in Step 3 with the magnetorheological fluid carrier liquid obtained in Step 4 at a volume ratio of approximately 41:59 (weight ratio of approximately 84:16) and mix at room temperature for approximately 12 hours to obtain the desired water-based magnetorheological fluid.

[0090] Third Embodiment

[0091] In this embodiment, the preparation method of the water-based magnetorheological fluid includes the following steps:

[0092] Step 1: Premix carbonyl iron powder and ethanol solution at a mass ratio of 1:5. The main particle size range of carbonyl iron powder is about 3 to 5 μm. Place the mixed liquid into a ball mill jar and premix at a speed of about 350 r / min for about 60 min to obtain a uniform magnetic particle solution.

[0093] Step 2: Add tetraethyl orthosilicate, n-propyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane and carbonyl iron powder into a ball mill jar at a mass ratio of approximately (1:1:0.2::6) and mix in the ball mill jar at a speed of approximately 350 r / min for approximately 18 h.

[0094] Step 3: Pour the carbonyl iron powder solution from the ball mill jar after the reaction, remove the precipitate, absorb the excess solution with gauze, and place the resulting final solid particles in a vacuum oven for drying. The oven temperature is about 80℃ and the drying time is 4 hours, finally obtaining hydrophobic group modified magnetic particles.

[0095] Step 4: Premix deionized water, sodium ascorbate, polyethylene glycol-2000, glycerol, fumed silica, sodium phosphate, and nano-zirconia in a mass percentage of approximately 88:2:3:3.5:1:2:0.5, and stir in an ultrasonic environment at room temperature for approximately 18 hours.

[0096] Step 5: Mix the fluoroalkylated carbonyl iron powder obtained in Step 3 with the magnetorheological fluid carrier liquid obtained in Step 4 at a volume ratio of approximately 41:59 (a weight ratio of approximately 85:15) and mix at room temperature for approximately 12 hours to obtain the desired water-based magnetorheological fluid.

[0097] Fourth embodiment

[0098] In this embodiment, the preparation method of the water-based magnetorheological fluid includes the following steps:

[0099] Step 1: Premix carbonyl iron powder and ethanol solution at a mass ratio of approximately 2:5. The main particle size range of carbonyl iron powder is approximately 5-10 μm. Place the mixed liquid into a ball mill jar and premix at a speed of approximately 350 r / min for approximately 60 min to obtain a uniform magnetic particle solution.

[0100] Step 2: Add tetraethyl orthosilicate, hexadecyltrimethoxysilane and carbonyl iron powder into a ball mill jar at a mass ratio of approximately 1:1:6, and mix in the ball mill jar at a speed of approximately 350 r / min for approximately 18 h.

[0101] Step 3: Pour the carbonyl iron powder solution from the ball mill jar after the reaction, remove the precipitate, absorb the excess solution with gauze, and place the resulting final solid particles in a vacuum oven for drying. The oven temperature is about 80°C, and the drying time is about 4 hours, finally obtaining hydrophobic group modified magnetic particles.

[0102] Step 4: Premix deionized water, sodium polyphosphate, polyvinyl alcohol, ethylene glycol, α-cellulose, disodium hydrogen phosphate, and silicon carbide in a mass percentage of approximately 86.5:1.5:4:4:1:2:1, and stir in an ultrasonic environment at room temperature for approximately 18 hours.

[0103] Step 5: Mix the alkylated carbonyl iron powder obtained in Step 3 with the magnetorheological fluid carrier liquid obtained in Step 4 at a volume ratio of approximately 41:59 (a weight ratio of approximately 85:15) and mix at room temperature for approximately 12 hours to obtain the desired water-based magnetorheological fluid.

[0104] The foregoing description of several embodiments of the invention has been provided for illustrative purposes. This foregoing description is not intended to be exhaustive, nor is it intended to limit the invention to the precise steps and / or forms disclosed; clearly, many modifications and variations can be made in light of the teachings above. The scope of the invention and all its equivalents are intended to be defined by the appended claims.

Claims

1. A water-based magnetorheological fluid with a wide operating temperature range and good kinematic viscosity stability, comprising: Magnetic particles modified with hydrophobic groups; The carrier liquid is mainly composed of water, and the magnetic particles are dispersed in the carrier liquid; and Additives added to the carrier fluid; The operating temperature T of the water-based magnetorheological fluid is within the range of 0℃ < T ≤ 40℃; and The water-based magnetorheological fluid operates at a temperature of 20-30℃ and a duration of 800-2000s. -1 The kinematic viscosity change measured at the shear rate is within ± 50 mPa·s.

2. The water-based magnetorheological fluid according to claim 1, characterized in that, The water-based magnetorheological fluid operates at a temperature of 20-30℃ and a time of 800-2000s. -1 The change in kinematic viscosity at the shear rate is within ±30 mPa·s.

3. The water-based magnetorheological fluid according to claim 1, characterized in that, The water-based magnetorheological fluid operates at a temperature of 20-30℃ and a time of 800-2000s. -1 The kinematic viscosity measured at the shear rate was 350 ± 50 mPa·s.

4. The water-based magnetorheological fluid according to claim 3, characterized in that, The water-based magnetorheological fluid operates at a temperature of 20-30℃ and a time of 800-2000s. -1 The kinematic viscosity measured at the shear rate was in the range of 350 ± 20 mPa·s.

5. The water-based magnetorheological fluid according to claim 2, characterized in that, The water-based magnetorheological fluid operates at a temperature of 20-30℃ and a time of 800-2000s. -1 The kinematic viscosity measured at the shear rate was 250 ± 30 mPa·s.

6. The water-based magnetorheological fluid according to claim 5, characterized in that, The water-based magnetorheological fluid operates at a temperature of 20-30℃ and a time of 800-2000s. -1 The kinematic viscosity measured at the shear rate was in the range of 250 ± 15 mPa·s.

7. The water-based magnetorheological fluid according to claim 1, characterized in that, The kinematic viscosity of the water-based magnetorheological fluid is in the range of 40-400 mPa·s at an operating temperature of 20-30℃.

8. The water-based magnetorheological fluid according to claim 7, characterized in that, The kinematic viscosity of the water-based magnetorheological fluid is in the range of 40-100 mPa·s at an operating temperature of 20-30℃.

9. The water-based magnetorheological fluid according to claim 7, characterized in that, The kinematic viscosity of the water-based magnetorheological fluid is in the range of 100-200 mPa·s at an operating temperature of 20-30℃.

10. The water-based magnetorheological fluid according to claim 7, characterized in that, The kinematic viscosity of the water-based magnetorheological fluid is in the range of 200-400 mPa·s at an operating temperature of 20-30℃.

11. The water-based magnetorheological fluid according to any one of claims 1-10, characterized in that, The initial viscosity of the water-based magnetorheological fluid at zero magnetic field and 25°C is 50,000 - 75,000 mPa·s.

12. The water-based magnetorheological fluid according to claim 11, characterized in that, The initial viscosity of the water-based magnetorheological fluid at zero magnetic field and 25°C is in the range of 50,000-60,000 mPa·s.

13. The water-based magnetorheological fluid according to claim 11, characterized in that, The water-based magnetorheological fluid has an initial viscosity of 65,000-70,000 mPa·s at zero magnetic field and 25°C.

14. The water-based magnetorheological fluid according to claim 11, characterized in that, The initial viscosity of the water-based magnetorheological fluid at zero magnetic field and 25°C is in the range of 72,000-75,000 mPa·s.

15. The water-based magnetorheological fluid according to any one of claims 1-10, characterized in that, The additive comprises at least one of the following: antioxidants, dispersants, wetting agents, thixotropic agents, pH adjusters, polishing particles, and combinations thereof.

16. The water-based magnetorheological fluid according to any one of claims 1-10, characterized in that, The material of the magnetic particles includes at least one of the following: iron alloys, iron oxides, iron nitride, iron carbide, iron carbonyl, nickel, cobalt, and combinations thereof.

17. The water-based magnetorheological fluid according to any one of claims 1-10, characterized in that, The additive comprises polishing particles, the polishing particles being made of at least one of the following: nano-diamond, nano-cerium oxide, nano-zirconia, nano-alumina, nano-silicon carbide, nano-silicon dioxide, nano-iron oxide, nano-boron carbide, nano-tungsten carbide, and combinations thereof.

18. The water-based magnetorheological fluid according to any one of claims 1-10, characterized in that, The additive comprises a modifier having the hydrophobic group, the modifier comprising at least one of the following: short-chain alkane silane coupling agents, long-chain alkane silane coupling agents, fluoroalkane silane coupling agents, monofunctional end-capped silane coupling agents, silane oligomers, and combinations thereof.

Images