A bidirectional gradual forming system for preparing graphitized nanofiber aerogels

Abstract

The present application relates to a kind of bidirectional gradient forming system for preparing graphitized nanofiber aerogel, the bidirectional gradient forming system includes raw material storage tank, high-temperature auxiliary microjet high-pressure homogenization unit, intermittent high-frequency ultrasonic stirring unit, gradient gradient liquid supply unit and bidirectional freeze-drying unit connected in sequence, metering pump is provided between each raw material storage unit and high-temperature auxiliary microjet high-pressure homogenization unit, and the bidirectional gradient forming system also includes temperature-controlled graphitization unit.Compared with prior art, the present application is dispersed efficiently to fiber solution by setting high-temperature auxiliary microjet high-pressure homogenization unit and intermittent high-frequency ultrasonic stirring unit, and uniform fiber dispersion liquid is obtained;Through the regulation and control of gradient gradient liquid supply unit and bidirectional freeze-drying unit, and after graphitization treatment, graphitized nanofiber aerogel with excellent performance and gradient gradient cell structure is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spinning forming, and particularly relates to a two-way gradient forming system for preparing graphitized nanofiber aerogel. BACKGROUND

[0002] Compared with ordinary conductive materials, the conductive nanofiber aerogel has a more abundant internal conductive network, can generate more contact sites during deformation, and has a more sensitive characteristic to external stimulation, and has been widely applied in the fields of sensors, energy storage, catalysis, wastewater treatment, electromagnetic shielding and the like.

[0003] At present, the methods for preparing conductive aerogel mainly include supercritical drying, electrostatic direct spraying and freeze drying. Among them, the freeze drying method has become a necessary means for preparing the conductive nanofiber aerogel because it greatly retains the original structure and properties of the sample and the prepared aerogel has stable structure. The freeze drying method first freezes the fiber dispersion liquid, uses ice crystal growth to build the nanofiber aerogel cell structure, and then prepares the nanofiber aerogel through vacuum drying.

[0004] Because the ice crystal growth needs a certain time, the dispersion liquid prepared from the inert hydrophobic fiber will have problems such as agglomeration and stratification during this period of time, thereby causing the aerogel cell structure to be non-uniform and easy to collapse. In addition, the existing freeze drying system only forms the aerogel with a single cell structure, and cannot prepare the two-way freeze aerogel with a continuous gradient cell structure, thereby limiting the further improvement of the conductive performance of the nanofiber aerogel.

[0005] Therefore, it is urgent to develop a forming system suitable for preparing the nanofiber aerogel to obtain the nanofiber aerogel with a continuous gradient cell structure. SUMMARY

[0006] The purpose of the present application is to overcome the defects that the existing freeze drying system cannot obtain the nanofiber aerogel with a continuous gradient cell structure, and to provide a two-way gradient forming system for preparing graphitized nanofiber aerogel.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A two-way gradient forming system for preparing graphitized nanofiber aerogel, comprising a raw material storage unit, a high-temperature auxiliary micro-jet high-pressure homogenization unit, an intermittent high-frequency ultrasonic stirring unit, a gradient gradient liquid supply unit and a two-way freeze drying unit connected in sequence through pipelines, and a metering pump is arranged between the raw material storage unit and the high-temperature auxiliary micro-jet high-pressure homogenization unit; the two-way gradient forming system further comprises a temperature control graphitization unit.

[0009] Further, the raw material storage units each include a plurality of raw material storage tanks.

[0010] Further, the number of the raw material storage tanks is not less than 3, at least meeting the storage of nanofiber, binder and solvent respectively.

[0011] Further, the volume of a single raw material storage tank is 80-120L.

[0012] Further, the metering pump mixes the raw materials in the raw material storage tanks in different proportions and then delivers them to the corresponding high-temperature auxiliary micro-jet high-pressure homogenization units.

[0013] Further, the high-temperature auxiliary micro-jet high-pressure homogenization unit includes a pressurizing pump, a dispersion cavity and a liquid storage tank connected in sequence.

[0014] Further, the input end of the pressurizing pump is connected with the metering pump, and the output end of the liquid storage tank is connected with the intermittent high-frequency ultrasonic stirring unit.

[0015] Further, the input end of the pressurizing pump is connected with a pressure gauge.

[0016] Further, the pressure range controlled by the pressurizing pump and the pressure gauge is 0.5-1.5MPa.

[0017] Further, the dispersion cavity includes a plurality of dispersion gaps.

[0018] Further, the number of the dispersion gaps is 3-10.

[0019] Further, the fluid flow rate in the dispersion cavity is 400-1800m / s.

[0020] Further, an electric high-temperature heating module is arranged outside the dispersion cavity to heat the dispersion cavity.

[0021] Further, the temperature control range of the electric high-temperature heating module is 30-100℃.

[0022] Further, the fiber dispersion liquid generates a plurality of active turbulent flow regions in the dispersion cavity at an ultrahigh flow rate under high temperature and high pressure, controls the directional migration-stability of each component in the solution during the dispersion process, and forms a nanoscale mixing and dispersion effect through impact, shear and dispersion.

[0023] Further, the intermittent high-frequency ultrasonic stirring unit includes a high-frequency ultrasonic module, a stirring module and a timing device.

[0024] Further, the high-frequency ultrasonic module comprises a water tank, an ultrasonic container and an ultrasonic assembly arranged in the water tank, and the high-temperature auxiliary micro-jet high-pressure homogenization unit is connected with the input end of the ultrasonic container through a pipeline, and the output end of the ultrasonic container is connected with the gradient gradual liquid supply unit.

[0025] Further, the high-frequency ultrasonic module and the stirring module alternately act on the fiber dispersion liquid in the ultrasonic container, and the dispersion effect of the fiber dispersion liquid is controlled by adjusting the alternating frequency and times of the high-frequency ultrasonic and the stirring, so that the dispersion efficiency is maximized.

[0026] Further, the high-frequency ultrasonic module and the stirring module alternately act on the fiber dispersion liquid in the ultrasonic container, and the dispersion effect of the fiber dispersion liquid is controlled by adjusting the alternating frequency and times of the high-frequency ultrasonic and the stirring, so that the dispersion efficiency is maximized.

[0027] Further, the center frequency of the high-frequency ultrasonic module is 10-15 MHz.

[0028] Further, the number of ultrasonic assemblies is 4-10.

[0029] Further, the time of each ultrasonic is 10-90 min.

[0030] Further, the stirring speed of the stirring module is 4000-5000 rpm,

[0031] Further, the time of each stirring is 10-90 min.

[0032] Further, the stirring mode of the stirring module is preferably magnetic stirring, and the stirring module is arranged below the high-frequency ultrasonic module.

[0033] Further, the gradient gradual liquid supply unit comprises a low-concentration liquid storage tank and a high-concentration liquid storage tank connected through a pipeline, and a high-temperature auxiliary micro-jet high-pressure homogenization unit and an intermittent high-frequency ultrasonic stirring unit are arranged between the raw material storage tank and the low-concentration liquid storage tank and between the raw material storage tank and the high-concentration liquid storage tank.

[0034] Further, the output end of the low-concentration liquid storage tank and the high-concentration liquid storage tank is provided with a valve and a flowmeter, and the concentration of the dispersion liquid entering the two-way freeze-drying unit is adjusted by opening and closing the valve, and the size of the aerogel cell is controlled.

[0035] Further, the concentration of the fiber dispersion liquid in the low-concentration liquid storage tank is 0.12-10 mg / mL, and the storage volume of the low-concentration liquid storage tank is 80-120 L.

[0036] Further, the concentration of the fiber dispersion liquid in the high-concentration liquid storage tank is 10-100 mg / mL, and the storage volume of the high-concentration liquid storage tank is 80-120 L.

[0037] Further, the low-concentration storage tank inputs the fiber dispersion liquid to the high-concentration storage tank at a dropwise adding speed of 10-100 L / h.

[0038] Further, the high-concentration storage tank inputs the fiber dispersion liquid to the two-way freeze-drying unit at a dropwise adding speed of 10-100 L / h.

[0039] Further, the two-way freeze-drying unit comprises a first shell and a first temperature control cabin and a second temperature control cabin arranged in the first shell, and the first temperature control cabin and the second temperature control cabin are respectively connected with a temperature adjusting module.

[0040] Further, the temperature adjusting module comprises a conventional compressor, an evaporator, a condenser, a condenser pipe, a condenser pipe temperature sensor and the like temperature adjusting module, and the real-time temperature of the two temperature control cabins is cooperatively adjusted through the components.

[0041] Further, the controllable temperature range of the first temperature control cabin is-150-0℃.

[0042] Further, the controllable temperature range of the second temperature control cabin is-50-0℃.

[0043] Further, the first temperature control cabin and the second temperature control cabin are connected through a high-thermal-conductivity cold plate, and a low-thermal-conductivity heat preservation mold is arranged on the high-thermal-conductivity cold plate, and the fiber dispersion liquid in the gradient gradual liquid supply unit is introduced into the cavity composed of the high-thermal-conductivity cold plate and the low-thermal-conductivity heat preservation mold.

[0044] Further, the high-thermal-conductivity cold plate is a heat transfer medium prepared by bending a high-thermal-conductivity material, and the high-thermal-conductivity material includes silver, copper, aluminum and the like.

[0045] Further, the volume of the low-thermal-conductivity heat preservation mold is 10-50 L.

[0046] Further, the material around the low-thermal-conductivity heat preservation mold includes one or more of polytetrafluoroethylene, polystyrene foamed foam, polyurethane foam, carbon foam or inorganic aerogel.

[0047] Further, a plurality of freeze temperature sensors with different temperature control ranges are arranged on the high-thermal-conductivity cold plate along the length direction.

[0048] Further, the sensing temperature ranges of the freeze temperature sensors are increased, and the sensing temperature ranges of the freeze temperature sensors along the length direction of the high-thermal-conductivity cold plate are-150--100℃, -100--50℃ and-50-0℃ in sequence.

[0049] Further, one freeze temperature sensor is arranged on each of the upper and lower surfaces of the low-thermal-conductivity heat preservation mold.

[0050] Further, the sensing temperature range of the upper surface and lower surface freezing temperature sensors is -50-0℃ and -150-0℃.

[0051] Further, the first shell is connected with a first vacuum pump, and a vacuum degree sensor is arranged on the first shell.

[0052] Further, the vacuum degree in the first shell is maintained at 1-100 Pa.

[0053] Further, the first shell is also connected with a circulating pump for regulating the temperature in the first shell of the bidirectional freeze-drying unit.

[0054] Further, the surface of the first shell is also provided with an intelligent integrated display screen.

[0055] Further, the intelligent integrated display screen is connected with each freezing temperature sensor and vacuum degree sensor through a circuit, and can display the temperature and vacuum degree of each region in real time, and can regulate the temperature of the two temperature control cabins through the screen, thereby regulating the temperature and vacuum degree of each region in real time.

[0056] Further, the temperature-controlled graphitization unit comprises a second shell, a heating module, a graphite crucible and an optical infrared temperature control system arranged in the second shell.

[0057] Further, the heating module is arranged above and below the graphite crucible respectively, and is used for heating the nanofiber aerogel in the graphite crucible.

[0058] Further, the heating module is composed of a branch pulse heating power supply, a metal pressure head and a water cooling system.

[0059] Further, the control temperature range of the heating module is 20-2800℃, the heating rate is 5-100℃ / min, and the cooling rate is 5-50℃ / min.

[0060] Further, the graphite crucible has an upper and lower hollow structure, and a porous placing plate for containing the nanofiber aerogel is arranged in the graphite crucible. The upper and lower hollow design can ensure that the porous placing plate can maintain temperature stability under the clamping of the upper and lower stationary air layers.

[0061] Further, the porous placing plate is provided with 10-20 porous structures to ensure uniform heating of the heated aerogel material from top to bottom and to avoid structure collapse.

[0062] Further, a plurality of infrared temperature measurement holes are arranged on the outer wall of the graphite crucible.

[0063] Further, the optical infrared temperature control system is installed on the inner wall of the second shell and corresponds to the infrared temperature measurement holes one by one, and is used for measuring the real-time temperature in the infrared temperature measurement holes.

[0064] Further, the infrared temperature measuring hole can reflect the temperature of each unit area (10*10 cm range) in the crucible, and ensure that the temperature deviation of each area is within 3 DEG C.

[0065] Further, the second shell is further connected with a second vacuum pump.

[0066] Further, the vacuum range in the second shell is controlled to be 1-100 Pa.

[0067] The application also provides a method for preparing graphitized nanofiber aerogel using a bidirectional gradient forming system, comprising the following steps:

[0068] S1: nanofiber, binder and solvent respectively stored in the raw material storage unit are transported into a high-temperature auxiliary microjet high-pressure homogenization unit through a pipeline, and a fiber dispersion liquid is obtained after high-pressure homogenization is completed;

[0069] S2: the fiber dispersion liquid obtained in S1 is transported into an intermittent high-frequency ultrasonic stirring unit for alternating ultrasonic and stirring, and a stable fiber dispersion liquid is obtained;

[0070] S3: the fiber dispersion liquid obtained in S2 is transported into a gradient gradient liquid supply unit, and a fiber dispersion liquid with a concentration gradient is obtained;

[0071] S4: the fiber dispersion liquid with a gradient obtained in S3 is introduced into a bidirectional freeze-drying unit to rapidly freeze and crystallize, and nanofiber aerogel is obtained;

[0072] S5: the nanofiber aerogel obtained in S4 is placed in a temperature-controlled graphitization unit for high-temperature graphitization, and finally graphitized nanofiber aerogel is obtained.

[0073] The application also provides a graphitized nanofiber aerogel with a continuous gradient gradient cell structure, which is prepared by the above method.

[0074] Compared with the prior art, the application has the following beneficial effects:

[0075] (1) The application can efficiently disperse the fiber by setting the high-temperature auxiliary microjet high-pressure homogenization unit and the intermittent high-frequency ultrasonic stirring unit, and obtain a uniform fiber dispersion liquid; at the same time, through the regulation of the gradient gradient liquid supply unit and the bidirectional freeze-drying unit, a high-continuous gradient cell structure with various layers can be obtained, so that a nanofiber aerogel with a gradient gradient cell structure with excellent performance is obtained.

[0076] (2) The gradient gradual liquid supply unit in the application obtains nanofiber aerogel with lung-imitating gradient gradual cell structure through the design of gradient gradual liquid supply, while retaining the lightness advantage of aerogel and maintaining good conductivity.

[0077] (3) The bidirectional freeze-drying unit in the application, unlike the traditional single temperature gradient control, can more easily obtain various layered high-continuous cell structures by intelligently adjusting the left-to-right and top-to-bottom bidirectional temperature gradient, shorten the electron transfer path, and obtain nanofiber aerogel with excellent conductivity.

[0078] (4) The high-temperature auxiliary micro-jet high-pressure homogenization unit in the application can realize more efficient impact, shear, migration, dispersion, and stability through the design of high-temperature auxiliary micro-jet high-pressure homogenization, taking advantage of the high sensitivity of the fiber dispersion liquid to temperature.

[0079] (5) The intermittent high-frequency ultrasonic stirring unit in the application gives hydrophobic fibers an electrostatic repulsion structure charge through the design of intermittent high-frequency ultrasonic stirring, avoids agglomeration, and provides a guarantee for the uniformity of the subsequent aerogel structure, while the intermittent design ensures maximum dispersion efficiency.

[0080] (6) The temperature-controlled graphitization unit in the application designs an upper and lower hollow graphite crucible to ensure that the porous placement plate can maintain temperature stability under the clamping of the upper and lower stationary air layers, and the porous structure of the middle placement plate can ensure that the heated aerogel material is evenly heated from top to bottom, avoiding structure collapse. BRIEF DESCRIPTION OF DRAWINGS

[0081] Figure 1 It is a schematic diagram of the overall structure of the bidirectional gradual forming system in the application.

[0082] Figure 2 It is a schematic diagram of the high-temperature auxiliary micro-jet high-pressure homogenization unit of the bidirectional gradual forming system in the application.

[0083] Figure 3 It is a schematic diagram of the intermittent high-frequency ultrasonic stirring unit of the bidirectional gradual forming system in the application.

[0084] Figure 4 It is a schematic diagram of the gradient gradual liquid supply unit of the bidirectional gradual forming system in the application.

[0085] Figure 5 It is a schematic diagram of the bidirectional freeze-drying unit of the bidirectional gradual forming system in the application.

[0086] Figure 6 It is a schematic diagram of the temperature-controlled graphitization unit of the bidirectional gradual forming system in the application.

[0087] Figure 7The schematic diagram of the bionic design inspiration of the bidirectional gradual forming system in the application and the electron microscope image of the nanofiber aerogel with continuous gradient cell structure.

[0088] Marked description in the figure:

[0089] 1-raw material storage unit, 11-raw material storage tank;

[0090] 2-metering pump;

[0091] 3-high temperature auxiliary micro-jet high pressure homogenization unit, 31-pressurizing pump, 32-pressure gauge, 33-electric high temperature heating module, 34-dispersion cavity, 341-dispersion gap, 35-liquid storage tank;

[0092] 4-intermittent high-frequency ultrasonic stirring unit, 41-high-frequency ultrasonic module, 411-water tank, 412-ultrasonic container, 413-ultrasonic assembly, 42-stirring module, 43-timing device;

[0093] 5-gradient gradual liquid supply unit, 51-low concentration liquid storage tank, 52-high concentration liquid storage tank, 53-valve, 54-flow meter;

[0094] 6-bidirectional freeze drying unit, 61-first shell, 611-vacuum degree sensor, 62-first temperature control cabin, 63-second temperature control cabin, 64-high thermal conductivity cold plate, 65-low thermal conductivity heat preservation mold, 66-frozen temperature sensor, 67-first vacuum pump, 68-circulating pump, 69-intelligent integrated display screen;

[0095] 7-temperature control graphitization unit, 71-second shell, 72-heating module, 73-graphite crucible, 731-multi-hole storage plate, 732-infrared temperature measurement hole, 74-optical infrared temperature control system, 75-second vacuum pump. DETAILED DESCRIPTION

[0096] The application will be described in detail below in combination with the drawings and specific embodiments. The embodiments are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0097] Unless otherwise specified, the raw materials, methods, instruments and systems used in the application are conventional raw materials, methods, instruments and systems in the art.

[0098] Example 1:

[0099] A bidirectional gradual forming system comprises raw material storage units 1, high-temperature auxiliary micro-jet high-pressure homogenization units 3, intermittent high-frequency ultrasonic stirring units 4, gradient gradual liquid supply units 5 and bidirectional freeze-drying units 6 connected in sequence through pipelines, and a metering pump 2 is arranged between each raw material storage unit 1 and high-temperature auxiliary micro-jet high-pressure homogenization unit 3.

[0100] Each raw material storage unit 1 comprises three raw material storage tanks 11. A metering pump 2 is arranged between the raw material storage unit 1 and the high-temperature auxiliary micro-jet high-pressure homogenization unit 3, and is used to mix raw materials in the raw material storage unit 1 in different proportions and then deliver the raw materials to the corresponding high-temperature auxiliary micro-jet high-pressure homogenization unit 3.

[0101] As shown in Figure 2 , the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 comprises a pressurizing pump 31, a dispersion cavity 34 and a liquid storage tank 35 connected in sequence. The input end of the pressurizing pump 31 is connected with the metering pump 2, and the output end of the liquid storage tank 35 is connected with the intermittent high-frequency ultrasonic stirring unit 4. The input end of the pressurizing pump 31 is also connected with a pressure gauge 32, and the control pressure is about 1 MPa. The dispersion cavity 34 comprises six dispersion slits 341, and the fluid flow rate in the dispersion cavity 34 is 1200 m / s. An electric high-temperature heating module 33 for heating the dispersion cavity 34 is arranged outside the dispersion cavity 34, and the temperature control range of the electric high-temperature heating module 33 is 30-100℃.

[0102] As shown in Figure 3 , the intermittent high-frequency ultrasonic stirring unit 4 comprises a high-frequency ultrasonic module 41, a stirring module 42 and a timing device 43. The high-frequency ultrasonic module 41 comprises a water tank 411 and an ultrasonic container 412 and an ultrasonic assembly 413 arranged in the water tank 411, the liquid storage tank 35 of the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 is connected with the input end of the ultrasonic container 412 through a pipeline, and the output end of the ultrasonic container 412 is connected with the gradient gradual liquid supply unit 5. The high-frequency ultrasonic module 41 and the stirring module 42 alternately act on the fiber dispersion liquid in the ultrasonic container 412. The center frequency of the high-frequency ultrasonic module 41 is 15 MHz, the number of ultrasonic assemblies 413 is 8, and the ultrasonic time is 60 min each time. The stirring module 42 is arranged below the ultrasonic container 412, the stirring mode is magnetic stirring, the stirring speed is 4000-5000 rpm, and the stirring time is also 60 min each time. The dispersion effect of the fiber dispersion liquid is controlled by timing and alternating use of 6 times through the timing device 43, so as to maximize the dispersion efficiency.

[0103] As shown in Figure 4As shown, the gradient gradient liquid supply unit 5 includes a low concentration liquid storage tank 51 and a high concentration liquid storage tank 52 communicated by a pipeline, and a high temperature auxiliary micro-jet high pressure homogenization unit 3 and an intermittent high frequency ultrasonic stirring unit 4 are sequentially arranged between the raw material storage unit 1 and the low concentration liquid storage tank 51 and between the raw material storage unit 1 and the high concentration liquid storage tank 52. The output ends of the low concentration liquid storage tank 51 and the high concentration liquid storage tank 52 are respectively provided with a valve 53 and a flow meter 54. The concentration of the fiber dispersion liquid in the low concentration liquid storage tank 51 can be adjusted in the range of 0.12-10 mg / mL, and the storage volume of the low concentration liquid storage tank 51 is 100 L. The concentration of the fiber dispersion liquid in the high concentration liquid storage tank 52 can be adjusted in the range of 10-100 mg / mL, and the storage volume of the high concentration liquid storage tank 52 is 100 L. The low concentration liquid storage tank 51 inputs the fiber dispersion liquid to the high concentration liquid storage tank 52 at a dropping speed of 50 L / h, and the high concentration liquid storage tank 52 inputs the fiber dispersion liquid to the bidirectional freeze-drying unit 6 at a dropping speed of 50 L / h.

[0104] As Figure 5As shown, the bidirectional freeze-drying unit 6 comprises a first shell 61, and a first temperature control cabin 62 and a second temperature control cabin 63 arranged in the first shell 61, and the first temperature control cabin 62 and the second temperature control cabin 63 are respectively connected with temperature adjusting modules. The temperature adjusting module in this embodiment comprises a conventional compressor, an evaporator, a condenser, a condenser pipe, a condenser pipe temperature sensor, etc., and the real-time temperature of the two temperature control cabins is cooperatively adjusted through the cooperation between the components. The controllable temperature range of the first temperature control cabin 62 is -150-0℃, and the controllable temperature range of the second temperature control cabin 63 is -50-0℃. The first temperature control cabin 62 and the second temperature control cabin 63 are connected through an aluminum high-thermal-conductivity cold plate 64, and three freeze temperature sensors 66 are arranged on the high-thermal-conductivity cold plate 64 along the length direction, and the sensing temperature ranges of the freeze temperature sensors are -150--100℃, -100--50℃ and -50-0℃ in sequence. A low-thermal-conductivity heat preservation mold 65 is arranged on the high-thermal-conductivity cold plate 64, and one freeze temperature sensor 66 is arranged on the upper and lower surfaces of the low-thermal-conductivity heat preservation mold 65 respectively, and the sensing temperature ranges are -50-0℃ and -150-0℃ respectively. The dispersion liquid in the high-concentration liquid storage tank 52 is introduced into the cavity composed of the high-thermal-conductivity cold plate 64 and the low-thermal-conductivity heat preservation mold 65. The volume of the low-thermal-conductivity heat preservation mold 65 is 40L, and the material around the low-thermal-conductivity heat preservation mold 65 is polystyrene foamed foam. The first shell 61 is connected with a first vacuum pump 67, and a vacuum degree sensor 611 is arranged on the first shell 61, and the vacuum degree in the first shell 61 is kept at 1-100Pa. The first shell 61 is also connected with a circulating pump 68 for adjusting the overall temperature in the first shell 1 of the bidirectional freeze-drying unit. An intelligent integrated display screen 69 is also arranged on the surface of the first shell 61, and the intelligent integrated display screen 69 is connected with each freeze temperature sensor 66 and vacuum degree sensor 611 through a line, and the temperature and vacuum degree of each region are displayed in real time, and the temperature of the two temperature control cabins can be adjusted through the screen, so as to adjust the temperature and vacuum degree of each region in real time

[0105] The embodiment also provides a method for preparing nanofiber aerogel using the above bidirectional gradual forming system, comprising the following steps:

[0106] S1: The nanofiber, the binder and the solvent respectively stored in the raw material storage unit 1 are transported into the high-temperature auxiliary microjet high-pressure homogenization unit 3 through the pipeline, and the fiber dispersion liquid is obtained after the high-pressure homogenization is completed;

[0107] S2: The fiber dispersion liquid obtained in S1 is transported into the intermittent high-frequency ultrasonic stirring unit 4 for alternating ultrasonic and stirring to obtain a stable fiber dispersion liquid;

[0108] S3: The fiber dispersion liquid obtained in S2 is transported into the gradient gradual liquid supply unit 5 to obtain a fiber dispersion liquid with a concentration gradient;

[0109] S4: The gradient gradient fiber dispersion liquid obtained in S3 is introduced into the bidirectional freeze-drying unit 6 to rapidly freeze and crystallize to obtain nanofiber aerogel.

[0110] The nanofiber aerogel prepared according to the above steps has a continuous gradient gradient cell structure.

[0111] Example 2:

[0112] A bidirectional gradient forming system for preparing graphitized nanofiber aerogel, as shown in Figure 1 , includes raw material storage units 1, high-temperature auxiliary micro-jet high-pressure homogenization units 3, intermittent high-frequency ultrasonic stirring units 4, gradient gradient liquid supply units 5 and bidirectional freeze-drying units 6 connected in sequence through pipelines. Each raw material storage unit 1 and high-temperature auxiliary micro-jet high-pressure homogenization unit 3 is provided with a metering pump 2. The bidirectional gradient forming system further comprises a temperature-controlled graphitization unit 7.

[0113] Each raw material storage unit 1 includes three raw material storage tanks 11, and the volume of a single raw material storage tank 11 is 100L. The metering pump 2 is also provided between the raw material storage unit 1 and the high-temperature auxiliary micro-jet high-pressure homogenization unit 3, which is used to mix the raw materials in the raw material storage unit 1 in different proportions and then deliver them to the corresponding high-temperature auxiliary micro-jet high-pressure homogenization unit 3.

[0114] As shown in Figure 2 , the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 includes a pressurizing pump 31, a dispersion cavity 34 and a liquid storage tank 35 connected in sequence. The input end of the pressurizing pump 31 is connected with the metering pump 2, and the output end of the liquid storage tank 35 is connected with the intermittent high-frequency ultrasonic stirring unit 4. The input end of the pressurizing pump 31 is also connected with a pressure gauge 32, and the control pressure range is 0.5-1.5MPa. The dispersion cavity 34 includes a plurality of dispersion gaps 341, the number of which is 6, and the fluid flow rate in the dispersion cavity 34 is 1200m / s. An electric high-temperature heating module 33 is provided outside the dispersion cavity 34 to heat the dispersion cavity 34, and the temperature control range of the electric high-temperature heating module 33 is 30-100℃. The fiber dispersion liquid generates a plurality of active turbulent flow regions in the dispersion cavity 34 under high temperature and high pressure at ultra-high flow rate, controls the directional migration-stability of each component in the solution during the dispersion process, and forms a nanoscale mixing and dispersion effect after impact, shear and dispersion.

[0115] As shown in Figure 3As shown, the intermittent high-frequency ultrasonic stirring unit 4 comprises a high-frequency ultrasonic module 41, a stirring module 42 and a timing device 43. The high-frequency ultrasonic module 41 comprises a water tank 411 and an ultrasonic container 412 and an ultrasonic assembly 413 arranged in the water tank 411, the liquid storage tank 35 of the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 is connected with the input end of the ultrasonic container 412 through a pipeline, and the output end of the ultrasonic container 412 is connected with the gradient gradual liquid supply unit 5. The high-frequency ultrasonic module 41 and the stirring module 42 alternately act on the fiber dispersion liquid in the ultrasonic container 412. The center frequency of the high-frequency ultrasonic module 41 is 15 MHz, and the ultrasonic time is 60 min each time. The stirring mode of the stirring module 42 is magnetic stirring, the stirring speed is 5000 rpm, and the stirring time is also 60 min each time.

[0116] As shown in Figure 4 As shown, the gradient gradual liquid supply unit 5 comprises a low-concentration liquid storage tank 51 and a high-concentration liquid storage tank 52 connected through a pipeline, and the raw material storage unit 1 and the low-concentration liquid storage tank 51 and the raw material storage unit 1 and the high-concentration liquid storage tank 52 are sequentially provided with the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 and the intermittent high-frequency ultrasonic stirring unit 4. The output end of the low-concentration liquid storage tank 51 and the high-concentration liquid storage tank 52 is provided with a valve 53 and a flow meter 54, the concentration of the fiber dispersion liquid in the low-concentration liquid storage tank 51 can be adjusted in the range of 0.12-10 mg / mL, and the concentration of the fiber dispersion liquid in the high-concentration liquid storage tank 52 can be adjusted in the range of 10-100 mg / mL. The low-concentration liquid storage tank 51 inputs the fiber dispersion liquid to the high-concentration liquid storage tank 52 at a dropping speed of 50 L / h, and the high-concentration liquid storage tank 52 inputs the fiber dispersion liquid to the bidirectional freeze-drying unit 6 at a dropping speed of 50 L / h.

[0117] As shown in Figure 5As shown, the bidirectional freeze-drying unit 6 comprises a first shell 61, and a first temperature control cabin 62 and a second temperature control cabin 63 arranged in the first shell 61, and the first temperature control cabin 62 and the second temperature control cabin 63 are respectively connected with temperature adjusting modules. The temperature adjusting module in the embodiment comprises a conventional compressor, an evaporator, a condenser, a condenser pipe, a condenser pipe temperature sensor, etc., and the real-time temperature of the two temperature control cabins is cooperatively adjusted and controlled through the cooperation between the components. The controllable temperature range of the first temperature control cabin 62 is -150-0℃, and the controllable temperature range of the second temperature control cabin 63 is -50-0℃. The first temperature control cabin 62 and the second temperature control cabin 63 are connected through an aluminum high-thermal-conductivity cold plate 64, and three freeze temperature sensors 66 are arranged on the high-thermal-conductivity cold plate 64 along the length direction, and the sensing temperature ranges of the freeze temperature sensors are -150--100℃, -100--50℃ and -50-0℃ in sequence. The high-thermal-conductivity cold plate 64 is provided with a low-thermal-conductivity heat preservation mold 65, and one freeze temperature sensor 66 is arranged on the upper and lower surfaces of the low-thermal-conductivity heat preservation mold 65 respectively, and the sensing temperature ranges are -50-0℃ and -150-0℃ respectively. The dispersion liquid in the high-concentration liquid storage tank 52 is introduced into the cavity composed of the high-thermal-conductivity cold plate 64 and the low-thermal-conductivity heat preservation mold 65. The material around the low-thermal-conductivity heat preservation mold 65 is polystyrene foamed foam. The first shell 61 is connected with a first vacuum pump 67, and the first shell 61 is provided with a vacuum degree sensor 611, and the vacuum degree in the first shell 61 is kept within 100 Pa. The first shell 61 is also connected with a circulating pump 68 for adjusting and controlling the overall temperature in the first shell 1 of the bidirectional freeze-drying unit. The surface of the first shell 61 is also provided with an intelligent integrated display screen 69, and the intelligent integrated display screen 69 is connected with each freeze temperature sensor 66 and vacuum degree sensor 611 through a line, and the temperature and vacuum degree of each region are displayed in real time, and the temperature of the two temperature control cabins can be adjusted and controlled through the screen, so as to adjust and control the temperature and vacuum degree of each region in real time.

[0118] As Figure 6As shown, the temperature-controlled graphitization unit 7 includes a second housing 71 and a heating module 72, a graphite crucible 73 and an optical infrared temperature control system 74 arranged in the second housing 71. The heating module 72 is arranged above and below the graphite crucible 73, respectively, for heating the nanofiber aerogel in the graphite crucible 73. The heating module 72 is composed of a branch pulse heating power supply, a metal pressure head and a water cooling system, and has a temperature control range of 20-2800°C, a heating rate of 60°C / min and a cooling rate of 30°C / min. The graphite crucible 73 has an upper and lower hollow structure, and a porous placing plate 731 for containing the nanofiber aerogel is arranged in the graphite crucible 73. The upper and lower hollow design can ensure that the porous placing plate 731 can maintain temperature stability under the clamping of the upper and lower stationary air layers. The porous placing plate 731 is provided with 20 porous structures to ensure uniform heating of the heated aerogel material from top to bottom and to avoid structural collapse. The outer wall of the graphite crucible 73 is also provided with a plurality of infrared temperature measurement holes 732, and the optical infrared temperature control system 74 is installed on the inner wall of the second housing 71 and corresponds to the infrared temperature measurement holes 732 one by one for measuring the real-time temperature in the infrared temperature measurement holes 732. The infrared temperature measurement holes 732 can reflect the temperature of each unit area (10x10 cm range) inside the graphite crucible 73, ensuring that the temperature deviation of each area is within 3°C. The second housing 71 is also connected with a second vacuum pump 75, and the vacuum range in the second housing 71 is controlled within 100 Pa.

[0119] The present embodiment also provides a method for preparing graphitized nanofiber aerogel using the above-mentioned bidirectional gradient forming system, comprising the following steps:

[0120] S1: The nanofiber, binder and solvent respectively stored in the raw material storage unit 1 are respectively delivered into the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 through the pipeline by the metering pump, and the fiber dispersion liquid is obtained after high-pressure homogenization is completed;

[0121] S2: The fiber dispersion liquid obtained in S1 is delivered into the intermittent high-frequency ultrasonic stirring unit 4 through the pipeline to alternately perform high-frequency ultrasonic and magnetic stirring, and a stable fiber dispersion liquid is obtained;

[0122] S3: The fiber dispersion liquid obtained in S2 is delivered into the gradient gradient liquid supply unit 5 through the pipeline to obtain a fiber dispersion liquid with a concentration gradient;

[0123] S4: The gradient gradient fiber dispersion liquid obtained in S3 is introduced into the bidirectional freeze-drying unit 6 to rapidly freeze and crystallize, and nanofiber aerogel is obtained;

[0124] S5: The nanofiber aerogel obtained in S4 is placed in a temperature-controlled graphitization unit for high-temperature graphitization, and finally graphitized nanofiber aerogel is obtained.

[0125] The graphitized nanofiber aerogel prepared according to the above steps has a continuous gradient gradient cell structure.

[0126] Example 3:

[0127] The embodiment provides a bidirectional gradient forming system for preparing nanofiber aerogel, which comprises a high-temperature assisted microjet high-pressure homogenization unit 3, an intermittent high-frequency ultrasonic stirring unit 4, a gradient gradient liquid supply unit 5 and a bidirectional freeze-drying unit 6. The whole device is shown in Figure 1 The specific contents include a raw material storage unit 1, a metering pump 2 connected to the raw material storage unit 1 through a conveying pipeline, a high-temperature assisted microjet high-pressure homogenization unit 3 connected to the metering pump 2 through a pipeline, an intermittent high-frequency ultrasonic stirring unit 4 connected to the high-temperature assisted microjet high-pressure homogenization unit 3 through a pipeline, a gradient gradient liquid supply unit 5 connected to the intermittent high-frequency ultrasonic stirring unit 4 through a pipeline, and a bidirectional freeze-drying unit 6 installed at the lower output end of the gradient gradient liquid supply unit 5.

[0128] The raw material storage unit 1 of the embodiment comprises three raw material storage tanks 11, and the storage volume of each raw material storage tank 11 is 100 L, so as to meet the separate storage of nanofiber, binder and solvent. The raw materials of the raw material storage tanks 11 enter the metering pump 2 through the pipeline, and then enter the high-temperature assisted microjet high-pressure homogenization unit 3 through the pipeline, so as to realize the fixed proportioning of the fiber dispersion liquid.

[0129] The high-temperature assisted microjet high-pressure homogenization unit 3 is provided with a pressurizing pump 31, a pressure gauge 32, an electric high-temperature heating module 33, a dispersion cavity 34 and a liquid storage tank 35. The fiber dispersion liquid is pressurized and heated by the pressurizing pump 31 and the electric high-temperature heating module 33, so that the fiber dispersion liquid is subjected to impact, shearing and dispersion in the narrow dispersion gap 341 in the dispersion cavity 34 at an ultra-high flow rate under high temperature and high pressure, and finally enters the liquid storage tank 35 for storage. The pressure range controlled by the pressurizing pump 31 and the pressure gauge 32 is 0.5-1.5 Mpa, the number of the narrow dispersion gaps 341 in the dispersion cavity 34 is 5, the temperature control range of the electric high-temperature heating module 33 is 30-100 DEG C, and the ultra-high flow rate of the fiber dispersion liquid in the dispersion cavity 34 is 1200 m / s. See Figure 2 .

[0130] The intermittent high-frequency ultrasonic stirring unit 4 is internally provided with a high-frequency ultrasonic module 41, a stirring module 4 and a timing device 43. See Figure 3The high-frequency ultrasonic module 41 comprises a water tank 411 and an ultrasonic container 412 and an ultrasonic assembly 413 arranged in the water tank 411. The liquid storage tank 35 of the high-temperature auxiliary micro-jet high-pressure homogenization unit 3 is connected with the input end of the ultrasonic container 412 through a pipeline, and the output end of the ultrasonic container 412 is communicated with the corresponding low-concentration liquid storage tank 51 or high-concentration liquid storage tank 52. The high-frequency ultrasonic module 41 and the stirring module 42 alternately act on the fiber dispersion liquid in the ultrasonic container 412, and the number of times of alternating use is 6 times, so as to control the dispersion effect of the fiber dispersion liquid and maximize the dispersion efficiency. The center frequency of the high-frequency ultrasonic module 41 is 10-15 MHz, and the stirring speed of the stirring module 42 is 5000 rpm. The time of each high-frequency ultrasonic and intermittent stirring is 60 min.

[0131] The gradient gradual liquid supply unit 5 comprises a low-concentration liquid storage tank 51, a high-concentration liquid storage tank 52, a valve 53 and a flow meter 54. The low-concentration liquid storage tank 51 is a storage tank for low-concentration fiber dispersion liquid, the concentration range is 0.12-10 mg / mL, the bottom is provided with a four-fluorine stirring blade, and the storage volume is 100 L. The high-concentration liquid storage tank 52 is a storage tank for high-concentration fiber dispersion liquid, the bottom is provided with a four-fluorine stirring blade, the concentration range is 10-100 mg / mL, and the storage volume is 100 L. The two liquid storage tanks are communicated by a pipeline and the valve 53, and the flow rate is controlled by the flow meter 54. The low-concentration fiber dispersion liquid in the low-concentration liquid storage tank 51 is added into the high-concentration fiber dispersion liquid in the high-concentration liquid storage tank 52 at a fixed flow rate, and the concentration in the high-concentration liquid storage tank 52 changes dynamically, wherein the addition speed is 10-100 L / h. The dispersion liquid with different concentrations in the high-concentration liquid storage tank 52 is added into the space composed of the high-thermal-conductivity cold plate 64 and the low-thermal-conductivity heat preservation mold 65 of the bidirectional freeze-drying unit 6 at a fixed flow rate through the pipeline, the valve 53 and the flow meter 54, wherein the addition speed is 10-100 L / h. The two valves 53 are opened at the same time, the concentration of the dispersion liquid added into the bidirectional freeze-drying unit 6 is controlled by adjusting, the size of the aerogel cell is controlled, and the nanofiber aerogel with a lung-imitating gradient gradient cell structure is obtained.

[0132] The bidirectional freeze-drying unit 6 is composed of a first shell 61, a first temperature control cabin 62, a second temperature control cabin 63, a high-thermal-conductivity cold plate 64, a low-thermal-conductivity heat preservation mold 65, a freeze temperature sensor 66, a first vacuum pump 67, a vacuum degree sensor 611, a circulating pump 68 and an intelligent integrated display screen 69, as shown in Figure 5The first temperature control cabin 62 and the second temperature control cabin 63 each further include conventional compressor, evaporator, condenser, condenser tube, condenser tube temperature sensor and other modules, and the real-time temperature of the two temperature control cabins is cooperatively controlled through the components. The controllable temperature of the first temperature control cabin 62 is low, controlled at-150-0℃; the temperature range of the second temperature control cabin 63 is controlled at-50-0℃. The high thermal conductivity cold plate 64 is made of aluminum AL6061 bending, with a thickness of about 8mm, a length of 2m, a width of 1m and a height of 1m. The low thermal conductivity heat preservation mold 65 is made of polytetrafluoroethylene around, with a volume of 30L. Three freezing temperature sensors 66 are distributed along the length direction of the high thermal conductivity cold plate 64 from left to right, and the temperature control ranges of the three freezing temperature sensors 66 are-150--100℃, -100--50℃ and-50℃-0℃, respectively; one freezing temperature sensor 66 is arranged on the upper and lower surfaces of the low thermal conductivity heat preservation mold 65 to monitor and adjust the freezing temperature of the fiber dispersion liquid in real time, and the temperature control ranges of the two freezing temperature sensors 66 are-100-0℃ and-150℃-0℃, respectively. The bidirectional freeze-drying unit 6 further includes a first vacuum pump 67 and a vacuum degree sensor 611 arranged on the first shell 61 to maintain a vacuum drying environment, and the vacuum range is 1Pa-100Pa. In addition, the bidirectional freeze-drying unit 6 further includes a circulating pump 68, a compressor, an evaporator, a condenser, a condenser tube, a condenser tube temperature sensor and other adjustment modules to realize the lossless drying of nanofiber aerogel in a vacuum environment. The intelligent integrated display screen 69 is connected to each freezing temperature sensor 66 and vacuum degree sensor 611 through a circuit, and displays the temperature and vacuum degree of each area in real time; and the temperature of the two temperature control cabins can be controlled through the screen, so as to control the temperature and vacuum degree of each area in real time.

[0133] The temperature control graphitization unit 7 comprises a second shell 71 and a heating module 72, a graphite crucible 73 and an optical infrared temperature control system 74 arranged in the second shell 71. The heating module 72 is arranged above and below the graphite crucible 73 respectively, and is used for heating the nanofiber aerogel in the graphite crucible 73. The heating module 72 is composed of a branch pulse heating power supply, a metal pressure head and a water cooling system, and has a control temperature range of 20-2800℃, a heating rate of 5-100℃ / min and a cooling rate of 5-50℃ / min. The graphite crucible 73 has an upper and lower hollow structure, and a porous placing plate 731 for containing the nanofiber aerogel is arranged in the graphite crucible 73. The upper and lower hollow design can ensure that the porous placing plate 731 can maintain temperature stability under the clamping of the upper and lower stationary air layers. The porous placing plate 731 is provided with 20 porous structures to ensure uniform heating of the heated aerogel material from top to bottom and to avoid structural collapse. The outer wall of the graphite crucible 73 is also provided with a plurality of infrared temperature measurement holes 732, and the optical infrared temperature control system 74 is installed on the inner wall of the second shell 71 and corresponds to the infrared temperature measurement holes 732, and is used for measuring the real-time temperature in the infrared temperature measurement holes 732. The infrared temperature measurement holes 732 can reflect the temperature of each unit area (10x10cm range) in the graphite crucible 73, and ensure that the temperature deviation of each area is within 3℃. The second shell 71 is also connected with a second vacuum pump 75, and the vacuum range in the second shell 71 is controlled within 100Pa.

[0134] The bidirectional gradual forming system is also used to prepare graphitized nanofiber aerogel with a lung structure in the embodiment, and the specific operation is as follows:

[0135] Three raw material storage tanks 11 are used to store nanofiber, binder and solvent respectively, and the raw materials with a mass ratio of 4:1:1000 and 4:1:100 are delivered to the corresponding high-temperature auxiliary micro-jet high-pressure homogenization unit 3 through pipelines by using the metering pump 2. The pressure control pump 31 controls the pressure to be 0.8MPa, the narrow dispersion gap in the dispersion cavity 34 is 5, and the temperature of the electric high-temperature heating module 33 is set to 80℃. The fiber dispersion liquid is sheared and dispersed in the dispersion cavity 34 at an ultra-high flow rate of 1200m / s.

[0136] After the shearing and dispersion of high-pressure homogenization is completed, the fiber dispersion liquid enters the intermittent high-frequency ultrasonic stirring unit 4, the ultrasonic center frequency is 12MHz, the magnetic stirring speed is 3000rpm, the ultrasonic time is 20min, the stirring time is 30min, and the above steps are repeated alternately for 6 times, and high and low concentration of homogenized and stable fiber dispersion liquid is obtained.

[0137] And then through the pipeline into the gradient gradually into the liquid unit 5 of the low concentration of liquid tank 51 and high concentration of liquid tank 52, two liquid tank by pipeline and valve 53 communication, at the same time through the flow meter 54 control flow rate is 50L / h; high concentration of liquid tank 52 in the dispersion liquid through the pipeline, valve 53 and flow meter 54 to fixed flow rate 50L / h into the space composed of high thermal conductivity cold plate 64 and low thermal conductivity heat preservation mold 65 in the two-way freeze drying unit 6. Among them, the first temperature control cabin 62 temperature setting is-150℃, the second temperature control cabin 63 temperature setting is 0℃; high thermal conductivity cold plate 64 material is copper, thickness is 8mm, length is 2m, width is 1m, height is 1m; low thermal conductivity heat preservation mold 65 around the material is polytetrafluoroethylene, the volume is 10L, the vacuum setting is 20Pa.

[0138] When the gradient gradually into the liquid unit 5 in 2 valve 53 is opened at the same time, at the same time, the fiber dispersion liquid is rapidly frozen crystallization in the two-way freeze drying unit 6 with the temperature set in advance, with the different concentration of fiber dispersion liquid is constantly dropped, can control the size of aerogel cell.

[0139] Finally, the prepared nanofiber aerogel is placed in the graphite crucible 73 of the graphitization unit 7 for high temperature graphitization treatment, further improving the graphitization degree to improve the conductivity of the nanofiber aerogel, and finally obtaining high conductivity graphitized nanofiber aerogel.

[0140] Figure 7 The bionic design inspiration diagram and the electron microscope diagram of the aerogel of the two-way gradual forming system of the lung structure high conductivity graphitized nanofiber aerogel in the application, as shown in the figure, the obtained lung structure high conductivity graphitized nanofiber aerogel has a layered gradient structure, a continuous conductive network and good mechanical properties.

[0141] The above description of the embodiments is for the convenience of the ordinary skilled in the art to understand and use the application. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the application should be within the scope of protection of the application.

Claims

1. A bi-directional gradual forming system for preparing graphitized nanofiber aerogels, characterized by, It comprises raw material storage units (1), high-temperature auxiliary microjet high-pressure homogenization units (3), intermittent high-frequency ultrasonic stirring units (4), gradient gradual liquid supply units (5) and bidirectional freeze-drying units (6) connected in sequence through pipelines, and a metering pump (2) is arranged between each raw material storage unit (1) and the high-temperature auxiliary microjet high-pressure homogenization unit (3); The bidirectional gradual forming system further comprises a temperature-controlled graphitization unit (7); The gradient gradual liquid supply unit (5) comprises a low-concentration liquid storage tank (51) and a high-concentration liquid storage tank (52) communicated through pipelines, and the raw material storage unit (1) and the low-concentration liquid storage tank (51) and the raw material storage unit (1) and the high-concentration liquid storage tank (52) are sequentially provided with the high-temperature auxiliary microjet high-pressure homogenization unit (3) and the intermittent high-frequency ultrasonic stirring unit (4); the output ends of the low-concentration liquid storage tank (51) and the high-concentration liquid storage tank (52) are provided with valves (53) and flow meters (54).

2. A bi-directional gradient forming system for producing graphitized nanofiber aerogels according to claim 1, wherein, The raw material storage unit (1) comprises a plurality of raw material storage tanks (11), and the volume of a single raw material storage tank (11) is 80-120L; The metering pump (2) mixes the raw materials in the raw material storage tank (11) at different proportions and then respectively delivers them into the corresponding high-temperature auxiliary microjet high-pressure homogenization unit (3).

3. The bi-directional gradient forming system for preparing graphitized nanofiber aerogels of claim 1, wherein, The high-temperature auxiliary microjet high-pressure homogenization unit (3) comprises a pressurizing pump (31), a dispersion cavity (34) and a liquid storage tank (35) connected in sequence; The input end of the pressurizing pump (31) is connected with the metering pump (2), and the output end of the liquid storage tank (35) is connected with the intermittent high-frequency ultrasonic stirring unit (4); The input end of the pressurizing pump (31) is connected with a pressure gauge (32), and the pressure range is 0.5-1.5MPa; The dispersion cavity (34) comprises a plurality of dispersion slits (341), and the number of the dispersion slits (341) is 3-10, and the fluid flow rate in the dispersion cavity (34) is 400-1800m / s; An electric high-temperature heating module (33) for heating the dispersion cavity (34) is arranged outside the dispersion cavity (34), and the temperature control range of the electric high-temperature heating module (33) is 30-100℃.

4. The bi-directional gradient forming system for preparing graphitized nanofiber aerogels of claim 1, wherein, The intermittent high-frequency ultrasonic stirring unit (4) comprises a high-frequency ultrasonic module (41), a stirring module (42) and a timing device (43); The high-frequency ultrasonic module (41) comprises a water tank (411) and an ultrasonic container (412) and an ultrasonic assembly (413) arranged in the water tank (411), the high-temperature auxiliary microjet high-pressure homogenization unit (3) is connected with the input end of the ultrasonic container (412) through a pipeline, and the output end of the ultrasonic container (412) is connected with the gradient gradual liquid supply unit (5); The high-frequency ultrasonic module (41) and the stirring module (42) alternately act on the fiber dispersion liquid in the ultrasonic container (412); The center frequency of the high-frequency ultrasonic module (41) is 10-15MHz, the number of the ultrasonic assembly (413) is 4-10, and the time of each ultrasonic is 10-90min; The stirring speed of the stirring module (42) is 4000-5000 rpm, and the stirring time is 10-90 min.

5. The bi-directional graded shaping system for preparing graphitized nanofiber aerogels of claim 1, wherein, The concentration of the fiber dispersion liquid in the low-concentration storage tank (51) is 0.12-10 mg / mL, and the storage volume of the low-concentration storage tank (51) is 80-120 L; The concentration of the fiber dispersion liquid in the high-concentration storage tank (52) is 10-100 mg / mL, and the storage volume of the high-concentration storage tank (52) is 80-120 L; The low-concentration storage tank (51) inputs the fiber dispersion liquid into the high-concentration storage tank (52) at a dropping speed of 10-100 L / h; and the high-concentration storage tank (52) inputs the fiber dispersion liquid into the bidirectional freeze-drying unit (6) at a dropping speed of 10-100 L / h.

6. The bi-directional gradient forming system for producing graphitized nanofiber aerogels of claim 1, wherein, The bidirectional freeze-drying unit (6) comprises a first shell (61) and a first temperature control cabin (62) and a second temperature control cabin (63) arranged in the first shell (61), and the first temperature control cabin (62) and the second temperature control cabin (63) are respectively connected with a temperature adjusting module; The controllable temperature range of the first temperature control cabin (62) is -150-0℃, and the controllable temperature range of the second temperature control cabin (63) is -50-0℃; The first temperature control cabin (62) and the second temperature control cabin (63) are connected through a high-thermal-conductivity cold plate (64), and the high-thermal-conductivity cold plate (64) is provided with a low-thermal-conductivity heat preservation mold (65), and the fiber dispersion liquid in the gradient gradual liquid supply unit (5) is introduced into the cavity composed of the high-thermal-conductivity cold plate (64) and the low-thermal-conductivity heat preservation mold (65); The volume of the low-thermal-conductivity heat preservation mold (65) is 10-50 L, and the material around the low-thermal-conductivity heat preservation mold (65) comprises one or more of polytetrafluoroethylene, polystyrene foamed foam, polyurethane foam, carbon foam or inorganic aerogel; A plurality of frozen temperature sensors (66) with different temperature control ranges are arranged on the high-thermal-conductivity cold plate (64) along the length direction, and one frozen temperature sensor (66) is arranged on the upper and lower surfaces of the low-thermal-conductivity heat preservation mold (65) respectively; The first shell (61) is connected with a first vacuum pump (67), and a vacuum degree sensor (611) is arranged on the first shell (61), and the vacuum degree in the first shell (61) is maintained at 1-100 Pa; The first shell (61) is also connected with a circulating pump (68), and an intelligent integrated display screen (69) is further arranged on the surface of the first shell (61).

7. The bi-directional gradient forming system for producing graphitized nanofiber aerogels of claim 1, wherein, The temperature control graphitization unit (7) comprises a second shell (71) and a heating module (72), a graphite crucible (73) and an optical infrared temperature control system (74) arranged in the second shell (71); The heating module (72) is arranged above and below the graphite crucible (73) respectively, and is used for heating the nanofiber aerogel in the graphite crucible (73); the control temperature range of the heating module (72) is 20-2800℃, the heating rate is 5-100℃ / min, and the cooling rate is 5-50℃ / min; The graphite crucible (73) is a hollow structure from top to bottom, and a porous placing plate (731) for containing the nanofiber aerogel is arranged in the graphite crucible (73), and a plurality of infrared temperature measuring holes (732) are arranged on the outer wall of the graphite crucible (73); The optical infrared temperature control system (74) is installed on the inner wall of the second shell (71) and is used for measuring the real-time temperature in the infrared temperature measuring hole (732); The second shell (71) is further connected with a second vacuum pump (75).

8. A method of preparing graphitized nanofiber aerogels using the bidirectional gradient forming system of any one of claims 1-7, characterized in that, The method comprises the following steps: S1: nanofibers, a binder and a solvent respectively stored in a raw material storage unit (1) are transported into a high-temperature auxiliary micro-jet high-pressure homogenization unit (3) through pipelines, and a fiber dispersion liquid is obtained after high-pressure homogenization is completed; S2: the fiber dispersion liquid obtained in S1 is transported into an intermittent high-frequency ultrasonic stirring unit (4) to be alternately ultrasonically treated and stirred, so that a stable fiber dispersion liquid is obtained; S3: the fiber dispersion liquid obtained in S2 is transported into a gradient gradual liquid supply unit (5), so that a fiber dispersion liquid with a concentration gradient is obtained; S4: the fiber dispersion liquid with a gradient obtained in S3 is introduced into a bidirectional freeze-drying unit (6) to be rapidly frozen and crystallized, so that nanofiber aerogel is obtained; S5: the nanofiber aerogel obtained in S4 is placed in a temperature-controlled graphitization unit (7) to be high-temperature graphitized, so that graphitized nanofiber aerogel is finally obtained.

9. A graphitized nanofiber aerogel having a continuously graded gradient cell structure, characterized in that, The method is prepared by the method of claim 8.

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