CN110747038A

CN110747038A - Suspension preparation method

Info

Publication number: CN110747038A
Application number: CN201910888366.XA
Authority: CN
Inventors: 巫金波; 袁欣; 温维佳; 梁宇岱; 张萌颖; 薛厂; 时权
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2019-09-19
Filing date: 2019-09-19
Publication date: 2020-02-04

Abstract

The invention provides a suspension preparation method, which comprises the steps of selecting particles to be dispersed as a dispersed phase, and selecting a continuous phase A and a continuous phase B of a liquid medium dispersant, wherein the wettability of the continuous phase A and the particles is larger than that of the continuous phase B and the particles, and the continuous phase A and the continuous phase B are mutually soluble and have similar density; and mixing the continuous phase A and the continuous phase B until the continuous phase A and the continuous phase B are mutually dissolved to obtain a compound liquid, and dispersing the particles in the compound liquid to obtain a suspension. The preparation method of the suspension liquid of the invention compounds two liquids with different wettability as continuous phases, and can relieve the agglomeration of particles and weaken the phenomena of sedimentation and hardening by adding the liquid phase with poor wettability, thereby greatly prolonging the sedimentation time of the particles in the suspension liquid and reducing the sedimentation and hardening of the suspension liquid.

Description

Suspension preparation method

Technical Field

The invention relates to the technical field of suspension preparation, in particular to a suspension preparation method capable of reducing sedimentation and hardening of suspended particles in a suspension.

Background

The solid particles are dispersed in the liquid and cannot sink quickly due to brownian motion, and the mixture of the solid dispersion phase and the liquid is called a suspension. Taking electrorheological fluid (ERF) as an example, the electrorheological fluid is composed of an insulating liquid medium and dielectric particles dispersed in the insulating liquid medium, and due to the density mismatch between the two, the micro-nano particles are easy to agglomerate, and the like, the particles are easy to settle and harden under the action of gravity, and the fluid has solid-liquid separation, which can seriously limit the practical application of the electrorheological fluid.

Currently, precipitate hardening is relieved mainly by modifying particles or using additives, wherein the former mainly adopts methods of changing internal structures or surface morphologies, such as preparing hollow or porous structures, coating organic layers on the surfaces of dispersed phase particles, modifying the surfaces of the particles to increase the specific surface area of the particles and the like, so that the particle density is reduced, the wetting between the particles and a continuous phase is improved, and the stability of a suspension is finally improved. The additive mainly refers to various surfactants, such as sodium dodecyl sulfate, sodium dodecyl sulfate and the like. The use of the additive can enhance the stability of dispersed phase particles in continuous phase liquid, so that the particles are not easy to precipitate and flocculate, thereby prolonging the service life.

However, for the existing method for relieving the precipitation and hardening of the suspension, the preparation process of the particles with special structures or shapes is generally complicated, the large-scale production difficulty is high, the particles are easy to aggregate or agglomerate, and the precipitation process is accelerated. In the case of additives, the addition of additives tends to increase the viscosity of the fluid and reduce its performance. In addition, the same surfactant has different effects on different disperse phase and continuous phase systems, the selection of the surfactant is determined according to the characteristics of the systems, long-time screening is needed, and the use of the additive also increases the cost.

Disclosure of Invention

Accordingly, the present invention is directed to a method for preparing a suspension, which can prepare a suspension capable of reducing precipitation and hardening of dispersed phase particles.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a method of preparing a suspension, the method comprising the steps of:

step a, selecting particles to be dispersed as a dispersed phase;

b, selecting a continuous phase A and a continuous phase B of a liquid-phase medium dispersant, wherein the wettability of the continuous phase A and the particles is larger than that of the continuous phase B and the particles, and the continuous phase A and the continuous phase B are mutually soluble and have similar density;

c, mixing the continuous phase A and the continuous phase B until the continuous phase A and the continuous phase B are mutually dissolved to obtain a compound liquid;

and d, dispersing the particles in the compound liquid to obtain a suspension.

Further, the suspension is an electrorheological fluid or a magnetorheological fluid.

Further, the suspension is electrorheological fluid, and the particles are core-shell structure particles (NH) consisting of urea and barium titanyl oxalate₂CONH₂@BaTiO(C₂O₄)₂)。

Further, the preparation steps of the particles comprise:

step a1, dissolving barium chloride and rubidium chloride in deionized water, and performing ultrasonic water bath to obtain barium chloride and rubidium chloride aqueous solution;

step a2, dissolving oxalic acid in deionized water, and performing ultrasonic water bath to obtain an oxalic acid solution;

step a3, dissolving urea in deionized water to obtain a urea solution;

step a4, slowly adding titanium tetrachloride into ice to obtain a clear titanium tetrachloride water solution;

step a5, slowly pouring a titanium tetrachloride aqueous solution into a barium chloride and rubidium chloride aqueous solution in an ultrasonic water bath, and quickly stirring to obtain a solution A;

step a6, pouring a urea solution into an oxalic acid solution in an ultrasonic water bath to obtain a solution B;

step a7, after the temperatures of the solution A and the solution B reach the water bath temperature, slowly adding the solution A into the solution B in an ultrasonic water bath, quickly stirring, and generating coprecipitation reaction in the mixing process to generate urea-coated barium titanyl oxalate particles;

step a8, adding deionized water, cooling to finish coprecipitation reaction, washing with water, filtering with suction, and drying to obtain core-shell structure particles (NH)₂CONH₂@BaTiO(C₂O₄)₂)。

Further, the continuous phase A is silicone oil, and the continuous phase B is one of liquid alkane, liquid alkane derivatives, mineral oil, white oil, paraffin, vegetable oil, kerosene or hydrogen chloride.

Further, the continuous phase A is dimethyl silicone oil or hydroxyl silicone oil.

Further, the liquid alkane is one of dodecane, tetradecane or hexadecane, and the liquid alkane derivative is one of chlorododecane, phenyldodecane, 1-phenylheptane, 1-phenyloctane, 1-phenylnonane, 1-phenyl-n-decane or 1-phenylundecane.

Further, the continuous phase A and the continuous phase B are mixed through ultrasound to obtain a compound liquid.

Further, in the step b, the wettability of the liquid-phase medium dispersing agent is characterized by measuring the contact angle of the liquid-phase medium dispersing agent and the particles to be dispersed.

Further, in the step d, the particles are dispersed in the compound liquid by mechanical stirring, magnetic stirring or sonic mixing.

Compared with the prior art, the invention has the following advantages:

based on the wettability of liquid to particles, the invention adds another liquid with poor wettability to the particles into the liquid with good wettability to the particles, and then disperses the particles into the mixed liquid to prepare the suspension. The preparation method of the suspension liquid comprises the steps of compounding two liquids with different wettabilities to serve as continuous phases, and adding the liquid phase with poor wettability can relieve particle agglomeration and reduce sedimentation and hardening phenomena, so that sedimentation time of particles can be greatly prolonged, and sedimentation and hardening of the suspension liquid are reduced.

In addition, the preparation method can simplify the preparation steps, and particles with special structures and appearances do not need to be specially prepared in the whole preparation process, and additives do not need to be used, so that the preparation method has better practicability.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a graph of the rheological properties (yield strength vs. electric field strength) of a silicone oil based-GERF versus a (silicone oil + dodecyl) based-GERF (inset is the current density vs. electric field strength);

FIG. 2 is a graph comparing the rheological properties (yield strength vs. electric field strength) of a silicone oil-based GERF with a (silicone oil + tetradecyl) based GERF (the inset is the current density vs. electric field strength);

FIG. 3 is a graph comparing the rheological properties (yield strength vs. electric field strength) of a silicone oil based-GERF with a (silicone oil + hexadecane) based-GERF (the inset is the current density vs. electric field strength);

FIG. 4 is a graph comparing the rheological properties (zero field viscosity) of a silicone oil based-GERF with a (silicone oil + dodecyl) based-GERF;

FIG. 5 is a graph comparing the rheological properties (zero field viscosity) of the silicone oil-based-GERF versus the (silicone oil + tetradecyl) based-GERF;

FIG. 6 is a graph of the rheological properties (zero field viscosity) of the silicone oil based-GERF versus the (silicone oil + hexadecane) based-GERF;

FIG. 7 is a graph comparing the zero field shear strength of the silicone oil based-GERF with the (silicone oil + dodecane/tetradecane/hexadecane) based-GERF;

fig. 8 is a graph comparing ER efficiency for silicone oil based-GERF and (silicone oil + dodecane/tetradecane/hexadecane) based-GERF at E ═ 5 KV/mm;

FIG. 9 is a graph of the magnitude of the backscattered light reference value of a silicone oil-based-GERF versus time;

FIG. 10 is a graph of the magnitude of the backscattered light intensity reference value for (silicone oil + dodecane) based-GERF (dodecane volume fraction 50%) versus time;

FIG. 11 is a graph of the magnitude of the back-scattered light parameter for (silicone oil + tetradecyl) yl-GERF (tetradecyl volume fraction 50%) as a function of time;

FIG. 12 is a graph of the magnitude of the back-scattered light parameter value for a (silicone oil + hexadecane) based-GERF (50% hexadecane volume fraction) versus time;

FIG. 13 is a graph of the trend of the TSI index over time during the (silicone oil + dodecyl) yl-GERF resting process;

FIG. 14 is a graph of the trend of the TSI index over time during the (silicone oil + tetradecyl) yl-GERF resting process;

FIG. 15 is a graph showing the trend of TSI index over time during the (silicone oil + hexadecane) yl-GERF resting process;

FIG. 16 is the variation of the square of the pressure difference (bar) with time(s);

FIG. 17 is a graph showing the temperature dependence of the GERF yield strength under an applied electric field of 3KV/mm (the inset shows the temperature dependence of the current density);

FIG. 18 is a plot of zero field viscosity versus temperature for the silicone oil-based-GERF;

FIG. 19 is a graph showing the trend of zero field viscosity of (silicone oil + dodecylbenzene) -based GERF with temperature;

FIG. 20 is a graph of the TSI index over time during the GERF resting process.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

The embodiment of the invention relates to a suspension liquid preparation method, which mainly comprises the following steps in the aspect of integral design:

step a: selecting particles to be dispersed as a dispersed phase;

step b: selecting a continuous phase A and a continuous phase B of a liquid-phase medium dispersant, wherein the wettability of the continuous phase A and the particles is larger than that of the continuous phase B and the particles, and the continuous phase A and the continuous phase B are mutually soluble and have similar density;

step c: mixing the continuous phase A and the continuous phase B until the continuous phase A and the continuous phase B are mutually dissolved to obtain a compound liquid;

step d: the particles are dispersed in a compounding liquid to obtain a suspension.

The preparation method of this embodiment will be specifically described with the suspension as the electro-rheological fluid, but the preparation method of this embodiment may be applied to the preparation of suspensions of other fluids, such as magneto-rheological fluids, by referring to the electro-rheological fluid.

Based on the above suspension as an electrorheological fluid, in the above step a, the particles to be dispersed as a dispersed phase may be, for example, core-shell structured particles composed of urea and barium titanyl oxalate, the chemical formula of which is (NH)₂CONH₂@BaTiO(C₂O₄)₂) The electrorheological fluid obtained by adopting the core-shell structure particles is actually giant electrorheological fluid, and the core-shell structure particles can be called as GER particles. Meanwhile, the core-shell structure particles comprise the following steps in specific preparation.

The preparation method of the core-shell structure particles comprises the following steps:

step a 1: mixing barium chloride (BaCl)₂) Dissolving rubidium chloride (RbCl) in deionized water, and performing ultrasonic water bath to obtain barium chloride and rubidium chloride aqueous solution;

step a 2: dissolving oxalic acid in deionized water, and performing ultrasonic water bath to obtain an oxalic acid solution;

step a 3: dissolving urea in deionized water to obtain a urea solution;

step a 4: titanium tetrachloride (TiCl)₄) Slowly adding into ice to obtain a clear titanium tetrachloride water solution;

step a 5: slowly pouring a titanium tetrachloride aqueous solution into a barium chloride and rubidium chloride aqueous solution in an ultrasonic water bath, and quickly stirring to obtain a solution A;

step a 6: pouring a urea solution into an oxalic acid solution in an ultrasonic water bath to obtain a solution B;

step a 7: after the temperature of the solution A and the solution B reaches the water bath temperature, slowly adding the solution A into the solution B in an ultrasonic water bath, quickly stirring, and carrying out coprecipitation reaction in the mixing process to generate urea-coated barium titanyl oxalate particles;

step a 8: adding deionized water, cooling to finish coprecipitation reaction, washing with water, filtering, and drying to obtain core-shell structure particles (NH)₂CONH₂@BaTiO(C₂O₄)₂)。

Wherein, the temperature of each ultrasonic water bath in the particle preparation process is 65 ℃, a liquid-transfering dropper is adopted to absorb titanium tetrachloride and slowly drip the titanium tetrachloride into ice to obtain a titanium tetrachloride solution, and a liquid A is also adopted to slowly drip the solution into a solution B. In addition, in the above step a8, a large amount of deionized water should be added to lower the temperature and terminate the precipitation reaction. And drying to remove excessive water in the barium titanyl oxalate particles coated by urea to obtain solid powder, namely the core-shell structure particles.

In this embodiment, step b may characterize the wettability of the liquid-phase medium dispersant by measuring a contact angle of the liquid-phase medium dispersant with the particles to be dispersed, and the contact angle may be measured by, for example, a sitting drop method, a capillary rising method, or the like. The smaller the contact angle, the better the wettability of the liquid medium with the particles, and vice versa, the poorer the wetting of the particles. And mixing the continuous phase A with a small contact angle and the continuous phase B with a large contact angle according to a certain proportion until the two phases are mutually dissolved to obtain the compound liquid (A + B).

Since the suspension of this embodiment is an electrorheological fluid, for the continuous phase a and the continuous phase B, the suspension prepared from the continuous phase a and the continuous phase B should have an electrorheological effect, and the wettability of the particles by the two continuous phases a and B should be greatly different (for example, when the wettability is characterized by a contact angle, the difference of the contact angle is several tens of orders of magnitude), and as mentioned above, the two continuous phases should be miscible with each other and have similar densities, that is, have smaller density difference, for example, when the density units are both g/mL, the density value difference between the two continuous phases is 0 to 0.3. In this embodiment, the suspension is giant electrorheological fluid, and the giant electrorheological particles are NH₂CONH₂@BaTiO(C₂O₄)₂As an example, the continuous phase a may be a silicone oil, and the continuous phase B may be one of a liquid alkane, a liquid alkane derivative, a mineral oil, a white oil, a paraffin, a vegetable oil, kerosene, or hydrogen chloride.

Specifically, as a preferred example, the continuous phase a may be dimethyl silicone oil or hydroxy silicone oil, while the liquid alkane as the continuous phase B may be one of dodecane, tetradecane or hexadecane, and the liquid alkane derivative may be one of chlorododecane, phenyldodecane, 1-phenylheptane, 1-phenyloctane, 1-phenylnonane, 1-phenyl-n-decanone or 1-phenylundecane.

The dimethyl silicone oil has stable performance, low surface tension and good wetting to particles, and the liquid alkane and the derivative thereof have very weak polarity, are not matched with the strong polarity of the particles and have poor wetting to the particles. In this embodiment, the above continuous phase a and continuous phase B may be specifically mixed by ultrasonic to obtain a compound liquid. In addition, in the step d, the dispersion of the particles in the compound liquid may be promoted by mechanical stirring, magnetic stirring, sonic mixing, or the like.

In addition, it should be noted that, in addition to the core-shell structure particles (NH)₂CONH₂@BaTiO(C₂O₄)₂) Other methods of making the resulting ER particles may also be used. Instead of using contact angles to characterize the wettability of the continuous phase, other methods can be used to characterize wettability, which can be, for example, the Amott method, the USBM method, and the self-priming method.

According to the preparation method of the suspension provided by the embodiment of the invention, on the basis of the continuous phase A, by adding the continuous phase B with poor wettability, the aggregation of particles can be relieved, and the phenomena of sedimentation and hardening are weakened, so that the problem that the suspension is easy to sediment and harden in a long-term standing process can be solved, and meanwhile, the steps of the preparation method are simple, and the problem that the steps in the existing preparation of the anti-sedimentation type suspension are complicated can be solved. The suspension liquid preparation method is suitable for various liquid phases and different suspension liquid systems, and has good application prospect.

Specifically, the electrorheological fluid prepared by the preparation method of the embodiment can reduce the precipitation and hardening of ER particles, thereby greatly widening the application range of the ERF, prolonging the service life of the ERF, and having good practicability.

The following description will further describe the suspension preparation method of the present invention by taking an electrorheological fluid as an example and several specific preparation examples and several detection analyses of the prepared electrorheological fluid.

In each preparation example, the GER particles as the dispersed phase still adopt the core-shell structure particles, the continuous phase a adopts silicone oil, and specifically, dimethyl silicone oil, and the continuous phase B adopts liquid alkane and alkane derivative as examples. Further, for convenience of description, the suspension prepared in the present invention, that is, the electrorheological fluid, is described as "GERF", and if the continuous phase uses only silicone oil, the electrorheological fluid prepared at this time may be referred to as "silicone oil base-GERF", and if the continuous phase uses a compounded continuous phase a (e.g., silicone oil) and a continuous phase B (e.g., liquid alkane or a derivative thereof), the electrorheological fluid prepared at this time may be referred to as "(silicone oil + alkane) base-GERF". In this example, a silicone oil based-GERF is generally used for comparative reference.

Example 1

This example is to prepare a (silicone oil + alkane) -based macroelectrorheological fluid.

The dispersion media used in this example were: 10cSt Silicone oil (Silicone oil), Dodecane (Dodecanoe), Tetradecane (tetradecanoe), Hexadecane (Hexadecanoe), wherein the Silicone oil is specifically dimethyl Silicone oil. TABLE 1 shows

The contact angles of the GER particles and the four liquids measured by a K100 mechanics method surface tensiometer are known to be better than that of alkane in wetting the GER particles by silicone oil through the table 1, so that the GER particles are selected as a continuous phase A, and the alkane is selected as a continuous phase B.

TABLE 1 relative contact angle of continuous phase and GER particles

	γ^d	γ^d	γ	Polarity	Contact angle
						Powder	8.1	68.8	76.9	Polar
Silicone oil	18.5	0.7	19.2	Waek polarity	3.6°
						Dodecane	25.4	0	25.4	Non-polar	82.6°
Tetradecane	26.5	0	26.5	Non-polar	83.9°
						Hexadecane	27.6	0	27.6	Non-polar	85.2°

When dodecane, tetradecane, hexadecane, respectively, were used as the continuous phase B, (silicone oil + alkane) -based giant electrorheological fluids, namely, (silicone oil + dodecane) yl-GERF, (silicone oil + tetradecane) yl-GERF and (silicone oil + hexadecane) yl-GERF, respectively, were obtained. The concentration of the prepared giant electrorheological fluid is 0.5, wherein 20g of giant electrorheological particles are selected, 10mL of (silicone oil + alkane) compound continuous phase is selected, and the preparation method of the suspension is referred to the above, specifically, the continuous phase A and the continuous phase B are mixed and then added into the giant electrorheological particles, and the mechanical mixing is carried out for 2 hours.

Compared with the silicone oil-based giant electrorheological fluid, the electrorheological fluid prepared by the embodiment has greatly reduced sedimentation rate and reduced zero-field viscosity, which will be illustrated by the following verification results.

Fig. 1 to 6 are graphs comparing rheological properties of silicone oil-based-GERF and (silicone oil + alkane) -based-GERF, in which the arrangement sequence of the respective curves inside the insets of fig. 1 to 3 from top to bottom is identical to that of the respective curves outside the insets, with the right end point of the curve as a positional reference. The results reflected in fig. 1 to 3 indicate that the current density of GERF decreases as the amount of alkane added increases, and that the effect of decreasing the current density becomes more pronounced the shorter the alkane chain. It is shown that the addition of alkane can suppress the overflow of electrons, thereby achieving the effect of reducing the current density.

In the prior art, the over-high zero field viscosity of the ERF is a problem troubling researchers, because the conventional method for reducing the zero field viscosity often causes the reduction of the electrorheological efficiency and the stability of the ERF. As can be seen from fig. 4 to 6 of the present invention, the zero-field viscosity of the GERF is greatly reduced by adding the alkane to the silicone oil, and the inventors also found that the smaller the alkane chain added, the greater the reduction in the GERF viscosity. By utilizing the two points, the comprehensive performance of the GERF can be greatly improved, so that the GERF has wider application range and can reduce the energy consumption in use.

Meanwhile, the inventors found that the mechanical strength of the (silicone oil + alkane) based-GERF under an electric field is lower than that of the pure silicone oil based-GERF, and the yield strength is more decreased as the volume fraction of the alkane is increased. The shear strength of four electrorheological fluids (silicone oil base-GERF), (silicone oil + dodecyl) base-GERF, (silicone oil + tetradecyl) base-GERF and (silicone oil + hexadecyl) base-GERF) under the condition of no electric field is tested and then is determined according to the formulaThe ER efficiencies of the above four suspensions at 5kV/mm field strength were calculated and the results are shown in FIGS. 7 and 8. It can be seen that the ER efficiency of the silicone oil-based-GERF is 3874, whereas the ER efficiency of the GERF with dodecane additive is 6870, the ER efficiency of the ERF with tetradecane and hexadecane is also greatly improved, with the highest ERF with hexadecane reaching 7739.

The intensity of the backscattered light at the very bottom of the silicon oil-based GERF sample is negative, and according to the principle of multiple optical tests, the situation occurs because the bottom of the sample is hard to precipitate, namely the concentration of particles is continuously increased, and the particles are continuously agglomerated and increased, and a certain degree of hardening (flocculation) phenomenon occurs, and after paraffin with the volume fraction of 50% is added in the continuous phase, the parameter value of the backscattered light is obviously changed along with the change of days, the absolute value of the intensity of the top ① area is reduced, which shows that the migration of particles in the top area is slow, and the parameter values of the ② and ③ areas in the middle areas reach the maximum values at 5-6 days and are basically close to the maximum values, which means that compared with the layered sedimentation condition of the ② and ③ areas of the silicon oil-based GERF, the addition of the paraffin makes the ② and ③ areas of the sample have more integrity, which has positive significance for the overall stability of the GERF.

In addition, the light intensity values in the bottom ④ area show that the particles only settle unilaterally in the bottom area after the alkane is added, and do not settle (flocculate) hard, which is beneficial to the redispersion of the GERF, in addition, the addition of the alkane can also be found to have a positive effect on the improvement of the overall stability of the GERF by measuring the dynamic Index of stability of the Turbiscan Stability Index (TSI) of the whole GERF, as can be seen from FIGS. 13 to 15, the TSI can be reduced by the addition of the alkane, namely the overall stability of the GERF is better by the addition of the alkane, therefore, the settling stability and ER efficiency of the GERF are improved, the current density and the zero field viscosity are also reduced, and the safety of the GERF can be improved, the energy consumption is reduced, and the application of the GERF in the field with low viscosity can be widened.

Example 2

This example is to prepare a (silicone oil + alkane derivative) -based giant electrorheological fluid.

In the preparation of giant electrorheological fluids, liquid alkane derivatives which may be used are chlorododecane, phenyldodecane, 1-phenylheptane, 1-phenyloctane, 1-phenylnonane, 1-phenyln-decanone, 1-phenylundecane, etc. As an example, the dispersion medium specifically used in the present embodiment is: 10cSt silicone oil and dodecyl benzene, and the silicone oil is still dimethyl silicone oil.

FIG. 16 is a (Δ P)2-t relationship diagram measured by a JF99A powder contact angle measuring instrument based on the Washburn method, and the relative contact angles of the GER particles with silicone oil and dodecylbenzene are shown in Table 2. As can be seen from table 2, the silicone oil wets the particles better, so that the (silicone oil + dodecylbenzene) -based giant electrorheological fluid can be obtained by the preparation method described above by selecting the silicone oil as the continuous phase a and the dodecylbenzene as the continuous phase B. Moreover, the concentration of the giant electrorheological fluid is also 0.5, wherein 20g of giant electrorheological particles are selected, and 10mL of the (silicone oil + dodecylbenzene) compound continuous phase is selected.

TABLE 2 relative contact angles of GER particles with oil phase

	Silicone oil	Dodecyl benzene
			Surface tension/(dyne/cm)	19.11	31.6
viscosity/CP	9.74	5.92
			Relative contact Angle/°	0	61.31

The results of testing the GERF produced in this example under an applied electric field of 3kV/mm as a function of temperature are shown in FIG. 17. As can be seen from FIG. 17, due to the addition of dodecylbenzene, the fluctuation range of the yield strength of the GERF within the range of 0-90 ℃ is reduced, and the environmental temperature stability of the GERF can be effectively improved. At the same time, the current density exhibited a tendency to increase with temperature substantially in accordance with that of the silicone oil-based GERF, and the magnitude of the current density was lower than that of the silicone oil-based GERF.

In addition, the results of the measurement of the viscosity of the GERF under different temperature conditions are shown in fig. 18 and 19. As can be seen from fig. 18 and 19, the GERF viscosity becomes larger as the temperature decreases, and the lower the temperature, the larger the magnitude of the viscosity increase. In addition, for silicone oil-based GERF, the viscosity of the silicone oil-based GERF is too high at a low temperature of-15 ℃, so that the sample is thrown out of the test platform in the test process. The addition of the dodecylbenzene greatly reduces the viscosity change range of the GERF in a low-temperature environment, the GeRF added with the dodecylbenzene has lower viscosity at normal temperature, and the viscosity reduction amplitude at high temperature is relatively smaller. The viscosity of the silicone oil based GERF, taken together with the range of viscosity change with temperature, varied over a 12Pas range, which is twice that of a GERF with 50% dodecylbenzene added.

FIG. 20 is a graph showing the change in TSI index with time when GERF is left for 100 days. As can be seen from fig. 20, the addition of dodecylbenzene also had a positive effect on the mitigation of settling. Therefore, the addition of dodecylbenzene in the continuous phase of this embodiment not only can improve the settling stability and rheological properties of the GERF, but also can enhance the stability of the rheological properties of the GERF in different temperature environments.

In conclusion, the preparation method provided by the invention adopts the compound liquid medium with different wetting degrees of the particles to disperse the solid-phase particles, so that the suspension which is not easy to settle and harden is prepared, the method is simple and efficient, and the other properties of the suspension are hardly weakened. Meanwhile, unlike the existing methods of changing the properties of particles or using additives, the preparation method starts from a continuous phase, and thus can be applied to different suspension systems, not only to a specific object.

Particularly, the electrorheological fluid prepared by the preparation method of the invention has the advantages of slow sedimentation rate, increased dynamic stability, greatly improved time stability, reduced zero-field viscosity due to the addition of the low-viscosity liquid phase and improved fluidity. And various properties of the suspension can be regulated and controlled by changing the type and content of the low-wetting liquid phase, and the zero-field viscosity of the electrorheological liquid can be regulated and controlled by changing the proportion and viscosity of the added continuous phase, so that the electrorheological liquid can be applied to devices requiring low-viscosity fluid.

The preparation method has the advantages of wide continuous phase selection range, high operability, simple operation steps, capability of easily realizing the purpose of reducing the precipitation and hardening of the suspension liquid, and better practicability.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A method for preparing a suspension, comprising the steps of:

step a, selecting particles to be dispersed as a dispersed phase;

and d, dispersing the particles in the compound liquid to obtain a suspension.

2. A method for preparing a suspension according to claim 1, characterized in that: the suspension is an electrorheological fluid or a magnetorheological fluid.

3. A method for preparing a suspension according to claim 2, characterized in that: the suspension is electrorheological fluid, and the particles are core-shell structure particles (NH) consisting of urea and barium titanyl oxalate₂CONH₂@BaTiO(C₂O₄)₂)。

4. A method for preparing a suspension according to claim 3, characterized in that: the preparation steps of the particles comprise:

step a3, dissolving urea in deionized water to obtain a urea solution;

5. A method for preparing a suspension according to claim 3, characterized in that: the continuous phase A is silicone oil, and the continuous phase B is one of liquid alkane, liquid alkane derivatives, mineral oil, white oil, paraffin, vegetable oil, kerosene or hydrogen chloride.

6. A method for preparing a suspension according to claim 5, characterized in that: the continuous phase A is dimethyl silicone oil or hydroxyl silicone oil.

7. A method for preparing a suspension according to claim 5, characterized in that: the liquid alkane is one of dodecane, tetradecane or hexadecane, and the liquid alkane derivative is one of chlorododecane, phenyldodecane, 1-phenylheptane, 1-phenyloctane, 1-phenylnonane, 1-phenylnormal decane or 1-phenylundecane.

8. A method for preparing a suspension according to claim 5, characterized in that: and ultrasonically mixing the continuous phase A and the continuous phase B to obtain the compound liquid.

9. A method for preparing a suspension according to claim 1, characterized in that: and c, in the step b, the wettability of the liquid-phase medium dispersing agent is characterized by measuring the contact angle of the liquid-phase medium dispersing agent and the particles to be dispersed.

10. A method for preparing a suspension according to any one of claims 1 to 9, characterized in that: in the step d, the particles are dispersed in the compound liquid through mechanical stirring, magnetic stirring or sound wave mixing.