Urea-coated titanium dioxide nanowire powder, preparation method and application of urea-coated titanium dioxide nanowire powder in rigid-flexible matrix digital controllable intelligent material

Abstract

The invention discloses urea-coated titanium dioxide nanowire powder, a preparation method and application of the urea-coated titanium dioxide nanowire powder in a rigid-flexible matrix digital controllable intelligent material. The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps: adding anatase type titanium dioxide nanowire powder into a saturated urea solution for ultrasonic treatment, and then carrying out heating treatment, standing and drying to obtain the urea-coated titanium dioxide nanowire powder. Compared with the prior art, wetting and dispersion of the urea-coated titanium dioxide nanowire powder in silicone oil are improved, agglomeration of the urea-coated titanium dioxide nanowire powder in an electric field is reduced, and interface resistance is improved to inhibit injection and micro-discharge, so that electric leakage is reduced, breakdown field strength is improved, response is faster, delay is smaller, and more stable electrorheological performance is kept under damp and hot and circulating conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new intelligent materials, and particularly relates to a urea-coated titanium dioxide nanowire powder, a preparation method thereof and application of the urea-coated titanium dioxide nanowire powder in a rigid-flexible matrix digital controllable intelligent material. BACKGROUND

[0002] An electrorheological fluid refers to a suspension system whose rheological properties (such as viscosity, yield stress, storage modulus, etc.) can be quickly and reversibly regulated under the action of an applied electric field, and is usually composed of polarizable solid particles dispersed in an insulating medium oil (such as silicone oil).

[0003] A giant electrorheological fluid is a new type of intelligent material with strong ER effect prepared by modifying solid particles. The giant electrorheological fluid can meet the needs of industrial applications and is applied to devices such as dampers, shock absorbers, clutches, hydraulic brakes and control valves. The solid materials mainly include inorganic non-metals, conductive organic matter and polymer semiconductor materials. Titanium dioxide nanowires are widely used as a polarized phase due to their high dielectric response and aspect ratio. The anisotropy of the nanowires is conducive to building a load-bearing skeleton across the electrodes and improving the yield stress; however, the high specific surface area and surface defects of the nanowires can easily induce interfacial polarization, and if the compatibility with the oil phase is insufficient, secondary agglomeration and sedimentation can also occur, which can weaken the reversibility and durability.

[0004] CN108300555A discloses a giant electrorheological fluid and a preparation method thereof. The giant electrorheological fluid comprises: metal salt nanocomposite particles coated with urea; a dispersant, the molecules of the dispersant comprising a hydrophilic end and a lipophilic end; and an insulating base fluid. The metal salt nanocomposite particles are suspended in the insulating base fluid, the molecules of the dispersant are adsorbed on the solid-liquid interface formed by the metal salt nanocomposite particles and the insulating base fluid, and the hydrophilic end tends to be adsorbed on the surface of the metal salt nanocomposite particles and the lipophilic end tends to extend into the insulating base fluid. By adding an amphiphilic dispersant, the particle size of the agglomerated particles is significantly reduced, thereby improving the anti-settling property, effectively preventing the caking of the nanoparticles, and thus improving the stability of the giant electrorheological fluid and effectively improving the breakdown resistance of the giant electrorheological fluid. SUMMARY

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present application is to improve the poor interfacial compatibility of urea-coated titanium dioxide nanowires in silicone oil, the high micro-discharge and leakage caused by moisture absorption, the easy response decay and the insufficient long-term dispersion stability.

[0006] To achieve the above-mentioned purpose, the present application provides a urea-coated titanium dioxide nanowire powder and a preparation method thereof.

[0007] A preparation method of a urea-coated titanium dioxide nanowire powder, comprising the following steps:

[0008] The anatase titanium dioxide nanowire powder is added into a saturated urea solution and ultrasonically treated, and then heated, placed, and dried to obtain the urea-coated titanium dioxide nanowire powder.

[0009] Further preferably, the preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps: at 60-70℃, 9-11g of anatase titanium dioxide nanowire powder is added into 800-1000mL of a saturated urea solution and ultrasonically treated for 30-60min, and then heated to 80-90℃ for 1-6h, and placed at 0-5℃ for 12-24h and dried to obtain the urea-coated titanium dioxide nanowire powder.

[0010] The surface of the urea contains a large number of active groups -NH2 and -C(=O)- groups, and the urea shell is prone to cracking and peeling, which affects the poor wettability of the urea-coated titanium dioxide nanowire powder with non-polar medium such as silicone oil, and the particles are more likely to be secondarily aggregated through hydrogen bonds or Van der Waals forces and form agglomerates, resulting in high static viscosity, accelerated sedimentation, and yield stress drift in the start-stop cycle. On the basis of the above, the present application first hydrolyzes mercapto POSS in an aqueous solution and condenses with the Ti-OH on the surface of the nanowire to form Ti-O-Si, then adds Irgacure 2959 to graft onto the surface through thiol-ene click chemistry under 365nm conditions, and finally induces the heterogeneous nucleation and directional recrystallization of urea on the titanium dioxide nanowire to form a layered gradient structure; at the same time, a small amount of 1,3-divinyl tetramethyl disiloxane participates in the same type of click, and a sparse dot-shaped bridging network is formed between POSS and the grafted organic chains. Thus, the wettability and dispersion of the urea-coated titanium dioxide nanowire powder in silicone oil are improved, the agglomeration in the electric field is reduced, the interface resistance is increased to inhibit injection and micro-discharge, thereby realizing lower leakage, higher breakdown field strength, faster response, smaller hysteresis, and more stable electrorheological properties under wet heat and cycling conditions.

[0011] Further preferably, the preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0012] S1 at 60-70℃, 9-11g of anatase titanium dioxide nanowire powder is added into 800-1000mL of a saturated urea solution and mixed uniformly, then 20-40mg of mercapto POSS is added and treated at room temperature for 10-30min, and nitrogen gas is bubbled for 10-20min to degas; cooled to 20-25℃, ultrasonically dispersed for 10-30min, 1-5mg of 1,3-divinyl tetramethyl disiloxane, 20-40mg of vinyl silylated PVA, and 0.1-0.3g of a photoinitiator are added, and irradiated with 365nm light for 5-15min under a nitrogen atmosphere, and heated to 60-70℃ for 20-30min;

[0013] S2 heating to 80-90 DEG C, 100-300 rpm stirring, connecting vertical condenser normal pressure distillation and collecting distillate, constant temperature 1-6h, get concentrated slurry;

[0014] S3 the above concentrated slurry is reduced to 0-5 DEG C and is placed for 12-24h;

[0015] S4 suction filtration, ethanol rinsing, vacuum drying at 60-70 DEG C, -0.095MPa for 12-24h, through 100-200 mesh sieve, get urea coated titanium dioxide nanowire powder.

[0016] The preparation method of the vinyl silane PVA is as follows: 8-10g PVA is added into 80-100mL water and mixed uniformly, heated to 80-90 DEG C and treated for 10-20min, then cooled to 30-40 DEG C, the pH is adjusted to 4-4.5, nitrogen is introduced for 10-20min, to obtain a PVA solution; 0.1-0.7g vinyl trimethoxysilane is added into 50-80mL 80-90wt% aqueous ethanol solution and mixed uniformly, stirred for 30-60min, to obtain a vinyl trimethoxysilane solution; the PVA solution and the vinyl trimethoxysilane solution are mixed uniformly, treated at 30-40 DEG C for 1-3h, after the reaction is completed, the water is dialyzed through a 10kDa dialysis bag for 24-48h, rotary evaporation and drying are carried out, to obtain the vinyl silane PVA.

[0017] The application further discloses a urea coated titanium dioxide nanowire powder prepared by the preparation method.

[0018] The application further discloses application of the urea coated titanium dioxide nanowire powder in rigid-flexible matrix digital controllable intelligent materials.

[0019] The application has the following beneficial effects:

[0020] Compared with the prior art, the application first makes the mercapto POSS mildly hydrolyze in water and condense with the Ti-OH on the surface of the nanowire to form Ti-O-Si, then adds Irgacure 2959 to graft on the surface through mercapto-ene click chemistry reaction under the condition of 365nm, finally, urea is induced to heterogeneously nucleate and directionally recrystallize on the titanium dioxide nanowire, to form a layered gradient structure; meanwhile, a small amount of 1,3-divinyl tetramethyl disiloxane participates in the same kind of click through the double bond, and a sparse dot-shaped bridging network is formed between the POSS and the grafted organic chain. Thus, the wetting and dispersion of the urea coated titanium dioxide nanowire powder in silicone oil are improved, the agglomeration in the electric field is reduced, the interface resistance is increased to inhibit injection and micro-discharge, so that the leakage current is reduced, the breakdown field strength is improved, the response is faster, the hysteresis is smaller, and the electrorheological performance is more stable under the conditions of wet heat and cycle. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values specified in this disclosure are not limited to the precise values recited. The ranges and values should be interpreted as being approximate. Values that are near to or approximate to the recited values are also intended to be encompassed by the ranges and values. For ranges, the endpoints are included within the ranges. Values between the endpoints are also included within the ranges. Values outside the endpoints are also included within the ranges.

[0022] The mercapto-POSS used in the examples is octa-mercapto-POSS, which is prepared according to the method of preparing octa-mercapto-POSS in Example 1 of CN1127356 73B.

[0023] The PVA used in the examples is Selvol™ 205;

[0024] The other raw materials not mentioned are common raw materials, and the above content is only for the purpose of helping to illustrate the present application, and should not be understood as a strict limitation of the present application. Those skilled in the art can directly purchase or prepare the same / similar raw materials from the market.

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with specific embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] Example 1

[0027] The preparation method of the anatase titanium dioxide nanowire powder comprises the following steps:

[0028] Step (1) 240 mL of tetrabutyl titanate is added dropwise into 600 mL of 10 mol / L NaOH aqueous solution at a speed of 5 mL / min, and mixed uniformly. After the dropwise addition is completed, the stirring is continued for 60 min, and a milky white sodium titanate precursor suspension is obtained.

[0029] Step (2) The above suspension is transferred into a polytetrafluoroethylene-lined high-pressure reaction kettle, and heated to 180℃ at a rate of 2℃ / min and kept for 24 h. After stopping heating, it is naturally cooled to room temperature, and a white product is obtained.

[0030] Step (3) The product is transferred into a 500 mL centrifugal cup, centrifuged at 10000 rpm for 15 min, and the supernatant is discarded. After ultrasonic dispersion for 5 min, 400 mL of water is added and centrifuged again. The operation is repeated until the pH of the supernatant is 7. Subsequently, the precipitate is dispersed in 2 L of 0.1 M HCl solution, stirred at 300 rpm for 2 h, and then washed with water until the pH of the supernatant is 7, and a hydrogen-type titanate nanowire is obtained.

[0031] Step (4) The hydrogen type titanic acid nanowires were dried at 80℃ for 24h, ground and placed in an alumina crucible, heated to 500℃ at 5℃ / min, kept for 2h, then decreased to 200℃ at 2℃ / min, and cooled to room temperature with the furnace, to obtain anatase titanium dioxide nanowire powder.

[0032] Example 2

[0033] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0034] S1 At 65℃, 10g of the anatase titanium dioxide nanowire powder obtained in Example 1 was added into 1000mL of saturated urea solution and ultrasonically dispersed (600W, 3s on / 2s off) for 30min;

[0035] S2 The temperature was increased to 80℃, 200rpm stirring, connected to a vertical condenser for atmospheric distillation and collection of distillate, constant temperature for 5h, to obtain concentrated slurry;

[0036] S3 The above concentrated slurry was decreased to 4℃ and stood for 12h, to promote the recrystallization of urea on the surface of the nanowires to form a coating layer;

[0037] S4 Suction filtration, ethanol washing, vacuum drying at 60℃ and -0.095MPa for 12h, and passing through a 200-mesh sieve, to obtain the urea-coated titanium dioxide nanowire powder.

[0038] Example 3

[0039] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0040] S1 At 65℃, 10g of the anatase titanium dioxide nanowire powder obtained in Example 1 was added into 1000mL of saturated urea solution and mixed uniformly, then 40mg of mercapto-POSS was added and treated at room temperature for 15min, nitrogen was bubbled for 10min for degassing; cooled to 25℃, ultrasonically dispersed (600W, 3s on / 2s off) for 15min, 40mg of vinyl-silane PVA and 0.3g of photoinitiator Irgacure 2959 were added, irradiated with 365nm light for 8min under nitrogen atmosphere, and heated to 65℃ for 20min;

[0041] S2 The temperature was increased to 80℃, 200rpm stirring, connected to a vertical condenser for atmospheric distillation and collection of distillate, constant temperature for 5h, to obtain concentrated slurry;

[0042] S3 The above concentrated slurry was decreased to 4℃ and stood for 12h, to promote the recrystallization of urea on the surface of the nanowires to form a coating layer;

[0043] S4: filtration, ethanol rinsing, vacuum drying at 60℃, -0.095 MPa for 12 h, and sieving through a 200-mesh screen to obtain the urea-coated TiO2 nanowire powder.

[0044] The preparation method of the vinyl-silane PVA is as follows: 10 g of PVA is added to 100 mL of water and uniformly mixed, heated at 85℃ for 10 min, then cooled to 35℃, the pH is adjusted to 4.2, and nitrogen is introduced for 10 min to obtain a PVA solution; 0.7 g of vinyl trimethoxysilane is added to 50 mL of 85 wt% aqueous ethanol solution and uniformly mixed, stirred for 30 min, and a vinyl trimethoxysilane solution is obtained; the PVA solution and the vinyl trimethoxysilane solution are uniformly mixed, treated at 35℃ for 2 h, and after the reaction is completed, the water is dialyzed through a 10 kDa dialysis bag for 24 h, and rotary evaporation and drying are performed to obtain the vinyl-silane PVA.

[0045] Example 4

[0046] The preparation method of the urea-coated TiO2 nanowire powder comprises the following steps:

[0047] S1: 10 g of the anatase TiO2 nanowire powder obtained in Example 1 is added to 1000 mL of saturated urea solution and uniformly mixed at 65℃, then 60 mg of mercapto-POSS is added and treated at room temperature for 15 min, and nitrogen is introduced for 10 min for degassing by bubbling; cooled to 25℃, ultrasonic dispersion (600 W, 3 s on / 2 s off) for 15 min, 30 mg of vinyl-silane PVA and 0.3 g of a photoinitiator Irgacure 2959 are added, and treated at 65℃ for 20 min under 365 nm light irradiation in a nitrogen atmosphere;

[0048] S2: the temperature is raised to 80℃, 200 rpm stirring, connection of a vertical condenser for constant pressure distillation and collection of the distillate, constant temperature for 5 h, to obtain a concentrated slurry;

[0049] S3: the above concentrated slurry is lowered to 4℃ and left to stand for 12 h, to promote the recrystallization of urea on the surface of the nanowires to form a coating layer;

[0050] S4: filtration, ethanol rinsing, vacuum drying at 60℃, -0.095 MPa for 12 h, and sieving through a 200-mesh screen to obtain the urea-coated TiO2 nanowire powder.

[0051] The preparation method of the vinyl silylated PVA is as follows: 10 g of PVA is added into 100 mL of water and uniformly mixed, heated at 85°C for 10 min, then cooled to 35°C, the pH is adjusted to 4.2, nitrogen is introduced for 10 min, and a PVA solution is obtained; at 25°C, 0.7 g of vinyl trimethoxysilane is added into 50 mL of 85 wt% aqueous ethanol solution and uniformly mixed, stirred for 30 min, and a vinyl trimethoxysilane solution is obtained; the PVA solution and the vinyl trimethoxysilane solution are uniformly mixed, treated at 35°C for 2 h, after the reaction is completed, the product is dialyzed against water for 24 h through a 10 kDa dialysis bag, and rotary evaporation, drying are performed to obtain the vinyl silylated PVA.

[0052] Example 5

[0053] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0054] S1 at 65°C, 10 g of the anatase titanium dioxide nanowire powder obtained in Example 1 is added into 1000 mL of saturated urea solution and uniformly mixed, then 40 mg of mercapto-POSS is added and treated at room temperature for 15 min, nitrogen is introduced for 10 min for bubble degassing; cooled to 25°C, ultrasonic dispersion (600 W, 3 s on / 2 s off) is performed for 15 min, 60 mg of vinyl silylated PVA and 0.3 g of a photoinitiator Irgacure 2959 are added, 8 min of 365 nm light irradiation is performed under a nitrogen atmosphere, and the temperature is increased to 65°C for 20 min of treatment;

[0055] S2 the temperature is increased to 80°C, 200 rpm stirring is performed, a vertical condenser is connected for normal pressure distillation and collection of distillate, and constant temperature is maintained for 5 h, and a concentrated slurry is obtained;

[0056] S3 the above concentrated slurry is reduced to 4°C and placed for 12 h, so as to promote the recrystallization of urea on the surface of the nanowire to form a coating layer;

[0057] S4 suction filtration is performed, ethanol is used for washing, vacuum drying at 60°C and -0.095 MPa is performed for 12 h, and the product is passed through a 200-mesh sieve to obtain the urea-coated titanium dioxide nanowire powder.

[0058] The preparation method of the vinyl silane PVA is as follows: 10 g of PVA is added into 100 mL of water and uniformly mixed, heated at 85°C for 10 min, then cooled to 35°C, the pH is adjusted to 4.2, nitrogen is introduced for 10 min, and a PVA solution is obtained; 0.7 g of vinyl trimethoxysilane is added into 50 mL of 85 wt% aqueous ethanol solution and uniformly mixed, stirred for 30 min, and a vinyl trimethoxysilane solution is obtained; the PVA solution and the vinyl trimethoxysilane solution are uniformly mixed, treated at 35°C for 2 h, and after the reaction is completed, the water is dialyzed through a 10 kDa dialysis bag for 24 h, rotary evaporated, and dried to obtain the vinyl silane PVA.

[0059] Example 6

[0060] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0061] S1 10 g of the anatase titanium dioxide nanowire powder obtained in Example 1 is added into 1000 mL of saturated urea solution and uniformly mixed at 65°C, then 40 mg of mercapto-POSS is added and treated at room temperature for 15 min, nitrogen is introduced for 10 min for bubble degassing; cooled to 25°C, ultrasonic dispersed (600 W, 3 s on / 2 s off) for 15 min, 5 mg of 1,3-divinyltetramethyldisiloxane, 40 mg of vinyl silane PVA, and 0.3 g of a photoinitiator Irgacure 2959 are added, irradiated with 365 nm light for 8 min under a nitrogen atmosphere, and heated to 65°C for 20 min;

[0062] S2 heated to 80°C, stirred at 200 rpm, connected to a vertical condenser for normal pressure distillation and collection of distillate, and kept at constant temperature for 5 h to obtain concentrated slurry;

[0063] S3 the above concentrated slurry is cooled to 4°C and placed for 12 h to promote recrystallization of urea on the surface of the nanowire to form a coating layer;

[0064] S4 suction filtered, washed with ethanol, vacuum dried at 60°C and -0.095 MPa for 12 h, and sieved through a 200 mesh screen to obtain the urea-coated titanium dioxide nanowire powder.

[0065] The preparation method of the vinyl silylated PVA is as follows: 10 g of PVA is added into 100 mL of water and uniformly mixed, heated at 85°C for 10 min, then cooled to 35°C, the pH is adjusted to 4.2, and nitrogen is introduced for 10 min to obtain a PVA solution; 0.7 g of vinyl trimethoxysilane is added into 50 mL of 85 wt% aqueous ethanol solution and uniformly mixed, stirred for 30 min under light-proof conditions at 25°C to obtain a vinyl trimethoxysilane solution; the PVA solution and the vinyl trimethoxysilane solution are uniformly mixed, treated at 35°C for 2 h, and then dialyzed against water for 24 h through a 10 kDa dialysis bag after the reaction is completed, and rotary evaporated and dried to obtain the vinyl silylated PVA.

[0066] Example 7

[0067] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0068] S1 10 g of the anatase titanium dioxide nanowire powder obtained in Example 1 is added into 1000 mL of saturated urea solution and uniformly mixed at 65°C, treated at room temperature for 15 min, and degassed by bubbling nitrogen for 10 min; cooled to 25°C, ultrasonically dispersed (600 W, 3 s on / 2 s off) for 15 min, and 40 mg of vinyl silylated PVA and 0.3 g of a photoinitiator Irgacure 2959 are added, treated at 65°C for 20 min under 365 nm light irradiation in a nitrogen atmosphere;

[0069] S2 The temperature is raised to 80°C, and the mixture is stirred at 200 rpm, connected with a vertical condenser for normal pressure distillation, and the distillate is collected, and the temperature is kept constant for 5 h to obtain a concentrated slurry;

[0070] S3 The concentrated slurry is cooled to 4°C and left to stand for 12 h to promote the recrystallization of urea on the surface of the nanowires to form a coating layer;

[0071] S4 Filtration, ethanol washing, vacuum drying at 60°C and -0.095 MPa for 12 h, and sieving through a 200-mesh screen to obtain the urea-coated titanium dioxide nanowire powder.

[0072] The preparation method of the vinyl silylated PVA is as follows: 10 g of PVA is added into 100 mL of water and uniformly mixed, heated at 85°C for 10 min, then cooled to 35°C, the pH is adjusted to 4.2, and nitrogen is introduced for 10 min to obtain a PVA solution; 0.7 g of vinyl trimethoxysilane is added into 50 mL of 85 wt% aqueous ethanol solution and uniformly mixed, stirred for 30 min under light-proof conditions at 25°C to obtain a vinyl trimethoxysilane solution; the PVA solution and the vinyl trimethoxysilane solution are uniformly mixed, treated at 35°C for 2 h, and then dialyzed against water for 24 h through a 10 kDa dialysis bag after the reaction is completed, and rotary evaporated and dried to obtain the vinyl silylated PVA.

[0073] Example 8

[0074] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0075] S1, 10 g of the anatase titanium dioxide nanowire powder obtained in Example 1 was added into 1000 mL of saturated urea solution and mixed uniformly at 65°C, then 40 mg of mercapto-POSS was added and treated at room temperature for 15 min, nitrogen was introduced for bubbling degassing for 10 min; cooled to 25°C, ultrasonic dispersion (600 W, 3 s on / 2 s off) for 15 min, 40 mg of vinyl-silane PVA was added, and irradiated with 365 nm light under nitrogen atmosphere for 8 min, and heated to 65°C for 20 min;

[0076] S2, heated to 80°C, stirred at 200 rpm, connected to a vertical condenser for normal pressure distillation and collection of distillate, constant temperature for 5 h, to obtain concentrated slurry;

[0077] S3, the above concentrated slurry was cooled to 4°C and stood for 12 h, to promote the recrystallization of urea on the surface of the nanowire to form a coating layer;

[0078] S4, suction filtration, ethanol washing, vacuum drying at 60°C and -0.095 MPa for 12 h, and sieving through a 200 mesh sieve to obtain the urea-coated titanium dioxide nanowire powder.

[0079] The preparation method of the vinyl-silane PVA is as follows: 10 g of PVA was added into 100 mL of water and mixed uniformly, heated at 85°C for 10 min, then cooled to 35°C, adjusted to pH 4.2, and introduced with nitrogen for 10 min to obtain a PVA solution; 0.7 g of vinyltrimethoxysilane was added into 50 mL of 85 wt% aqueous ethanol solution and mixed uniformly at 25°C in the dark, stirred for 30 min to obtain a vinyltrimethoxysilane solution; the PVA solution and the vinyltrimethoxysilane solution were mixed uniformly, treated at 35°C for 2 h, and after the reaction was completed, dialyzed against water for 24 h through a 10 kDa dialysis bag, rotary evaporated, and dried to obtain the vinyl-silane PVA.

[0080] Example 9

[0081] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0082] S1 at 65℃, 10g of the anatase titanium dioxide nanowires powder obtained in Example 1 was added into 1000mL saturated urea solution and mixed uniformly, then 40mg of thiol-POSS was added and treated at room temperature for 15min, nitrogen was bubbled for 10min to remove the air; cooled to 25℃, ultrasonic dispersion (600W, 3s on / 2s off) for 15min, 40mg of PVA and 0.3g of photoinitiator Irgacure 2959 were added, irradiated by 365nm light for 8min under nitrogen atmosphere, and heated to 65℃ for 20min;

[0083] S2 heated to 80℃, stirred at 200rpm, connected to a vertical condenser for normal pressure distillation and collected the distillate, constant temperature for 5h, to obtain concentrated slurry;

[0084] S3 the above concentrated slurry was cooled to 4℃ and stood for 12h, to promote the recrystallization of urea on the surface of nanowires to form a coating layer;

[0085] S4 suction filtration, ethanol washing, vacuum drying at 60℃ and -0.095MPa for 12h, and sieved through a 200 mesh screen to obtain urea-coated titanium dioxide nanowire powder.

[0086] Example 10

[0087] The preparation method of the urea-coated titanium dioxide nanowire powder comprises the following steps:

[0088] S1 at 65℃, 10g of the anatase titanium dioxide nanowires powder obtained in Example 1 was added into 1000mL saturated urea solution and mixed uniformly, then 40mg of thiol-POSS was added and treated at room temperature for 15min, nitrogen was bubbled for 10min to remove the air; cooled to 25℃, ultrasonic dispersion (600W, 3s on / 2s off) for 15min, 40mg of PVA and 0.3g of photoinitiator Irgacure 2959 were added, irradiated by 365nm light for 8min under nitrogen atmosphere, and heated to 65℃ for 20min;

[0089] S2 heated to 80℃, stirred at 200rpm, connected to a vertical condenser for normal pressure distillation and collected the distillate, constant temperature for 5h, to obtain concentrated slurry;

[0090] S3 the above concentrated slurry was cooled to 4℃ and stood for 12h, to promote the recrystallization of urea on the surface of nanowires to form a coating layer;

[0091] S4 suction filtration, ethanol washing, vacuum drying at 60℃ and -0.095MPa for 12h, and sieved through a 200 mesh screen to obtain urea-coated titanium dioxide nanowire powder.

[0092] Test Example 1

[0093] The urea-coated titanium dioxide nanowire powder prepared in Example 2 was tested.

[0094] (1) The urea-coated titanium dioxide nanowire powder prepared in Example 2 was observed using a scanning electron microscope, and was in a straight line shape with uniform diameter distribution (~50-100 nm) and length >10 μm.

[0095] (2) Crystal form: The X-ray diffraction pattern should be consistent with the standard anatase titanium dioxide (JCPDS No. 21-1272) card.

[0096] (3) Fourier infrared spectroscopy characterization analysis (FTIR): The urea-coated titanium dioxide nanowire powder particles were characterized using a U.S. PerkinElmer Spectrum 100 (adjustment required) infrared spectrometer. The KBr tabletting method was used to mix 0.1 wt% of the sample with KBr uniformly, and then tabletting, and the infrared scanning range was 4000 cm -1 -400 cm -1 .

[0097] The Fourier transform infrared spectrum should have characteristic absorption peaks of C=O and N-H of urea at ~1680 cm -1 and ~1600 cm -1 .

[0098] (4) Thermal stability analysis (TGA): A German NETZSCH TG209F3 Tarsus (adjustment required) test was used, with nitrogen flow rate of 20 mL / min, temperature rise rate of 10°C / min, and the test was started from room temperature to 500°C and stopped.

[0099] Thermogravimetric analysis showed a clear urea decomposition weight loss step between 200-400°C, and the coating amount can be calculated accordingly.

[0100] Test Example 2

[0101] The preparation method of the giant electro-rheological fluid was as follows: 500 g of dimethyl silicone oil with viscosity of 100 cSt was added to a beaker, and an ice water bath was used for temperature control at 5°C; mechanical stirring was performed at 500 rpm for 5 min, 10 g of 4A molecular sieves was added, and stirring was performed at 2000 rpm for 30 min, and then the 4A molecular sieves was removed by separation; 100 g of the urea-coated titanium dioxide nanowire powder prepared in each example was added, and shearing was performed at 5000 rpm for 10 min; then shearing was performed at 12000 rpm for 30 min; the mixture was transferred into a wide-mouth container, an ultrasonic probe was inserted, 800 W was set, 5 s on / 3 s off, and a total of 30 min was accumulated to complete fine dispersion and defoaming; the mixture was transferred into a vacuum planetary stirring container, and defoaming was performed at 60°C and −0.098 MPa for 60 min under conditions of 30 rpm of revolution and 50 rpm of rotation, the vacuum was released, and the material was discharged to obtain the giant electro-rheological fluid.

[0102] The test method is as follows: inject the giant current rheological liquid into the electrode gap, stand for 5 min; gradually apply an electric field, from 0.5 kV / mm to 3.5 kV / mm, after each step is stable for 1 min, use a semiconductor characteristic analyzer to measure the current value (I) passing through the sample; according to the electrode area, calculate the leakage current density J = I / A.

[0103] Table 1

[0104] Leakage current density μA / cm² Example 2 7.6 Example 3 6.1 Example 4 5.0 Example 5 7.2 Example 6 4.5 Example 7 8.8 Example 8 9.3 Example 9 5.2 Example 10 10.9

[0105] Test Example 3

[0106] Step 1 Set the rheometer at a low constant shear rate (e.g. 0.5 s -1 ).

[0107] Step 2 Use an external trigger to make the electric field jump from 0 to 3.0 kV / mm in 0.1 seconds.

[0108] Step 3 Record the shear stress versus time curve at high speed.

[0109] Step 4 Response time is defined as the time required for the stress to rise from the initial value to 90% of the final steady value.

[0110] Table 2

[0111] Response time / ms Example 2 18 Example 3 14 Example 4 13 Example 5 17 Example 6 12 Example 7 20 Example 8 21 Example 9 16 Example 10 28

[0112] Test Example 4

[0113] Place the powder prepared in each example in a constant temperature and humidity box, respectively, at 25°C, 60% RH, and expose for 24 h; after taking out, quickly prepare the ER liquid consistent with Test Example 2. Repeat Test Example 3 to obtain the response time; and calculate the yield stress retention rate before and after damp heat.

[0114] Table 3

[0115] Yield stress retention / % Example 2 82 Example 3 85 Example 4 88 Example 5 83 Example 6 92 Example 7 74 Example 8 70 Example 9 86 Example 10 65

[0116] From the data in Tables 2-3, it can be seen that the performance of Example 3 is better than that of Example 2, wherein Example 2 is only urea-coated titanium dioxide nanowires, the shell layer is mainly urea, there are microcracks and grain boundary defects, and urea itself is hydrophilic and easy to absorb moisture, the interface barrier is not dense, which further affects its performance. Example 3 introduces mercapto POSS and vinyl silane PVA on the basis of Example 2, which undergoes click chemistry reaction under the action of photoinitiator, and finally induces urea to heterogeneously nucleate and directional recrystallize on the titanium dioxide nanowires, forming a layered gradient structure, which further improves its performance.

[0117] On the basis of example 3, 1,3-divinyltetramethyldisiloxane is added to obtain example 6, the diene participation of 1,3-divinyltetramethyldisiloxane is the same kind of click, the sparse point-like bridging network is formed between POSS and the grafted organic chain. Thus, the wetting and dispersion of the urea-coated titanium dioxide nanowire powder in silicone oil are improved, the agglomeration in the electric field is reduced, the interface resistance is improved to inhibit the injection and micro-discharge, thereby realizing the reduction of leakage, the improvement of breakdown field strength, the faster response, the smaller hysteresis, and the more stable electrorheological performance under the conditions of heat and humidity and cycling.

[0118] The preferred embodiments of the application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations without departing from the concept of the application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the prior art according to the concept of the application should be within the protection scope defined by the claims.

Claims

1. A method for preparing urea-coated titanium dioxide nanowire powder, characterized in that, Includes the following steps: Anatase titanium dioxide nanowire powder was added to a saturated urea solution and sonicated, then heated, allowed to stand, and dried to obtain urea-coated titanium dioxide nanowire powder.

2. The method for preparing urea-coated titanium dioxide nanowire powder as described in claim 1, characterized in that, Includes the following steps: At 60-70℃, 9-11g of anatase titanium dioxide nanowire powder is added to 800-1000mL of saturated urea solution and ultrasonically treated for 30-60min. Then, it is heated to 80-90℃ for 1-6h, left to stand at 0-5℃ for 12-24h, and dried to obtain urea-coated titanium dioxide nanowire powder.

3. The method for preparing urea-coated titanium dioxide nanowire powder as described in claim 1 or 2, characterized in that, The preparation method of the anatase titanium dioxide nanowire powder includes the following steps: Step (1) Tetrabutyl titanate was added to NaOH aqueous solution and the temperature was controlled to obtain a milky white sodium titanate precursor suspension; Step (2) The above suspension is transferred into a polytetrafluoroethylene-lined high-pressure reactor and hydrothermally treated to obtain a white product; Step (3) Centrifuge the product and wash it until neutral to obtain hydrogen-form titanate nanowires; Step (4) Dry and calcine the hydrogen-type titanate nanowires to obtain anatase titanium dioxide nanowire powder.

4. The method for preparing urea-coated titanium dioxide nanowire powder as described in claim 1, characterized in that, Includes the following steps: S1. Anatase titanium dioxide nanowire powder was added to a saturated urea solution and mixed evenly. Then, mercapto-POSS was added and treated at room temperature. Nitrogen gas was bubbled through to degas the solution. The mixture was cooled to room temperature, ultrasonically dispersed, and vinyl silanized PVA and a photoinitiator were added. The mixture was then treated under a nitrogen atmosphere and light, followed by a temperature treatment. Under S2 stirring conditions, the temperature was increased to obtain a concentrated slurry; S3. Cool the above concentrated slurry to 0-5℃ and let it stand. S4 filtration, washing, and drying yield urea-coated titanium dioxide nanowire powder.

5. The method for preparing urea-coated titanium dioxide nanowire powder as described in claim 4, characterized in that, The method for preparing vinylsilanized PVA is as follows: PVA is added to water and mixed evenly, heated and then cooled, the pH is adjusted, and nitrogen gas is introduced to obtain a PVA solution; under light-protected conditions, vinyltrimethoxysilane is added to an aqueous ethanol solution and mixed evenly with stirring to obtain a vinyltrimethoxysilane solution; the PVA solution and the vinyltrimethoxysilane solution are mixed evenly, dialyzed, rotary evaporated, and dried to obtain vinylsilanized PVA.

6. A urea-coated titanium dioxide nanowire powder, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. The application of urea-coated titanium dioxide nanowire powder as described in claim 6 in rigid-flexible matrix digitally controllable smart materials.