CN114369878A - Flexible ceramic nanofiber large-scale continuous manufacturing device - Google Patents

Abstract

The invention relates to a flexible ceramic nanofiber large-scale continuous manufacturing device, which comprises: a sol spinning solution preparation mechanism; an electrostatic spinning mechanism: the first liquid storage tank is connected with a spinning solution outlet of the sol spinning solution preparation mechanism, and the electrostatic spinning nozzle is connected with the first liquid storage tank and used for outputting spinning fibers; the fiber calcining and forming mechanism comprises: the device comprises an analysis component, a solvent gradient displacement component, a drying component and a variable atmosphere calcining component which are sequentially arranged along the processing advancing direction of spinning fibers. Compared with the prior art, the method is suitable for integrated equipment such as batch preparation of inorganic polymer sol spinning solution without adding high molecular polymer, rapid electrostatic spinning fiber formation of spinnable sol, low-temperature calcination molding of gel nanofiber and the like, and realizes large-scale preparation of ceramic nanofiber with excellent mechanical properties.

Description

Flexible ceramic nanofiber large-scale continuous manufacturing device

Technical Field

The invention belongs to the technical field of electrostatic spinning devices, and relates to a large-scale continuous manufacturing device for flexible ceramic nanofibers.

Background

The ceramic fiber is a fibrous ceramic material with the diameter in the micro-nano level, and has the advantages of excellent high temperature resistance and low thermal conductivity of the traditional ceramic material, light weight and high porosity of the fiber material, so that the ceramic fiber is widely applied to various industrial fields. When the size of the ceramic fiber is reduced to the nanometer order of magnitude, the surface effect and the quantum size effect of the nanometer fiber endow the ceramic fiber with unique mechanical, optical, electrical, thermal and other properties, so that the application performance of the ceramic fiber in the fields of environment, energy, aerospace, national defense and the like can be obviously improved.

The electrostatic spinning method utilizes high-voltage electric field force to realize jet flow stretching thinning-solidification fiber forming, has the advantages of simple manufacturing device, good fiber structure adjustability, various aggregate structures and the like, and becomes one of the main ways for effectively preparing ceramic nanofibers at present. In the existing electrostatic spinning method, inorganic precursor micromolecules and oligomers thereof are mainly used as spinning sol, and the nanofiber can be formed only by the assistance of a polymer template. The content of the polymer in the hybrid nanofiber prepared by adding the polymer as an auxiliary spinning template is usually more than 50%, and the organic polymer component is removed by high-temperature calcination, so that not only can serious environmental pollution be caused, but also the ceramic nanofiber has too high crystallinity and large grain size, so that the ceramic nanofiber has poor flexibility and is easy to brittle failure.

The patent "ceramic nanofiber and preparation method and apparatus thereof" (CN201611154343.9) discloses a ceramic nanofiber and preparation method and apparatus thereof, the method comprises providing a precursor solution with spinnability, the precursor solution contains ceramic precursor, polymer and solvent; stretching the precursor solution into nanofibers by using air flow, and collecting the nanofibers by using a collector; and sintering the collected nano fibers to obtain the ceramic nano fibers. However, the preparation method and apparatus are both directed to a precursor spinning solution to which a high molecular polymer is added, and then the spinning solution is drawn into nanofibers by using an air flow, and are not suitable for a precursor spinning solution without the addition of the high molecular polymer because the introduction of the polymer has an important influence on the rheological properties of the spinning solution. The patent "a method and apparatus for preparing inorganic nanofibers" (CN201910054836.2) discloses a method and apparatus for preparing inorganic nanofibers, which comprises uniformly dispersing inorganic nanopowder into a solution to form a dispersion, adding a polymer into the dispersion, uniformly mixing to form a precursor, stretching the precursor into nanofibers by high-speed airflow, drying the nanofibers, sintering after drying the nanofibers, and sintering to obtain the inorganic nanofibers. Similarly, the preparation method adds high molecular polymer, so that high-temperature calcination equipment is necessarily matched to remove organic matters subsequently, and the large-scale production line manufacturing of the ceramic nano-fiber is difficult to realize.

In summary, the preparation of the ceramic nanofibers is basically in the laboratory stage at present, and a large amount of high molecular polymers are added to adjust the spinnability of the precursor spinning solution, so that the problems of high preparation cost of the spinning solution, high energy consumption of high-temperature calcination, serious pollution in the organic matter removal process and the like exist, and the practical application of the ceramic nanofibers is severely limited. Therefore, it is urgently needed to develop a stable spinnable precursor spinning sol without polymer addition, and on the basis, to develop an integrated device suitable for batch stable synthesis of the sol spinning solution, electrostatic spinning fiber formation of spinnable sol, continuous calcination molding of gel fiber and the like, so as to realize large-scale stable preparation of ceramic nanofibers with excellent performance.

Disclosure of Invention

The invention aims to provide a large-scale continuous manufacturing device for flexible ceramic nanofibers, so as to realize large-scale stable preparation of the ceramic nanofibers with excellent performance.

The purpose of the invention can be realized by the following technical scheme:

a flexible ceramic nanofiber large-scale continuous manufacturing device comprises:

a sol spinning solution preparation mechanism;

an electrostatic spinning mechanism: the first liquid storage tank is connected with a spinning solution outlet of the sol spinning solution preparation mechanism, and the electrostatic spinning nozzle is connected with the first liquid storage tank and used for outputting spinning fibers;

the fiber calcining and forming mechanism comprises: the device comprises an analysis component, a solvent gradient displacement component, a drying component and a variable atmosphere calcining component which are sequentially arranged along the processing advancing direction of spinning fibers.

Furthermore, the sol spinning solution preparation mechanism comprises a feeding kettle, a core reaction kettle, a stirring assembly, a high-purity dry gas inlet assembly, a cold and wet gas transmission assembly and a first negative pressure suction assembly, wherein the core reaction kettle is connected with the feeding kettle through a feeding and suction pipeline, the stirring assembly is arranged inside the core reaction kettle, and the high-purity dry gas inlet assembly, the cold and wet gas transmission assembly and the first negative pressure suction assembly are respectively connected with the core reaction kettle.

Furthermore, the stirring assembly comprises a stirring motor, a central shaft connected with the stirring motor and positioned in the core reaction kettle, and a plurality of layers of stirring rollers which are arranged on the central shaft and rotate along with the central shaft. Preferably, a hollow cavity with the interior communicated with each other is arranged between the central shaft and the stirring roller, a hollowed hole communicated with the hollow cavity is processed on the stirring roller, and the cold and moisture transmission assembly extends into the core reaction kettle from the bottom and is connected with the bottom of the hollow cavity.

Further, the electrostatic spinning nozzle comprises a nozzle body and an insulating support base, the middle area of the nozzle body and the insulating support base is hollowed to form a spinning flow channel penetrating through the nozzle body and the insulating support base, the spinning flow channel is composed of a first-level section flow channel, a second-level section flow channel and a third-level section flow channel which are sequentially connected along the flowing direction of spinning solution, the width of the first-level section flow channel is larger than that of the third-level section flow channel, a plurality of protruding metal electrodes are further arranged on a line liquid outlet of the third-level section flow channel, and a wiring terminal connected with an external high-voltage power supply is further arranged on the nozzle body.

Furthermore, a cooling duct surrounding the secondary section flow passage and the tertiary section flow passage is further processed on the nozzle body, and cooling fluid is introduced into the cooling duct.

Furthermore, the axial section of the secondary section runner is of a conical structure, two side edges of the conical structure are 1/4 sections of circular arcs which are symmetrically arranged, the size of the front end of the secondary section runner is the same as that of the primary section runner, the size of the rear end of the secondary section runner is the same as that of the tertiary section runner, and the secondary section runner is further in smooth transition connection with the tertiary section runner.

Furthermore, a conveyer belt for receiving and transmitting the spinning fibers sent out by the three-stage section flow passage is arranged at the position right opposite to the three-stage section flow passage below the spinning nozzle. Furthermore, a microwave heating unit is arranged under the conveying belt, and the vertical distance between the heating part of the microwave heating unit and the conveying belt is less than 50 cm.

Furthermore, the analysis assembly comprises an analysis cabin, and a spraying unit and a negative pressure suction unit which are positioned in the analysis cabin, wherein the spraying unit is positioned above the negative pressure suction unit, and the ceramic nanofibers penetrate through the space between the spraying unit and the negative pressure suction unit after entering the analysis cabin, and are soaked with analysis liquid sprayed by the spraying unit;

the solvent gradient displacement assembly comprises a displacement cabin positioned behind the analysis cabin, and an alcohol-water bath, a displacement bath and an alcohol bath which are sequentially arranged in the displacement cabin along the advancing direction of the ceramic nano fibers;

the drying component comprises a drying cabin positioned behind the replacing cabin and a drying unit which is arranged in the drying cabin and used for heating and drying the ceramic nano-fibers;

the atmosphere-variable calcining component comprises a pre-sintering cabin, a constant temperature cabin and a cooling cabin which are arranged behind the drying cabin and are sequentially arranged along the advancing direction of the ceramic nano fibers and are mutually independent, and the pre-sintering cabin, the constant temperature cabin and the cooling cabin are respectively connected with external oxygen supply equipment and/or inert gas supply equipment through independent pipelines.

Furthermore, the spraying unit comprises a spraying head arranged in the analysis cabin, and a second liquid storage tank, a liquid pump and an analysis liquid tank which are sequentially connected with the spraying head, the second liquid storage tank is also connected with an ultrasonic generator, and an energy converter is also arranged between the second liquid storage tank and the spraying head;

the negative pressure suction unit comprises a hollow tray arranged in the analysis cabin and positioned below the conveyor belt for conveying the ceramic nanofibers, and a negative pressure suction pump connected with the hollow tray through a suction pipeline, wherein the plane of the hollow tray is just parallel to the plane of the conveyor belt.

Furthermore, the pre-sintering cabin, the constant temperature cabin and the cooling cabin are respectively connected with an external microwave generator through waveguide tubes;

the working atmosphere of the pre-sintering cabin and the cooling cabin is oxygen atmosphere, and the working atmosphere of the sintering cabin and the constant temperature cabin is mixed atmosphere of oxygen and inert gas;

the working temperature in the pre-sintering chamber is set to be 100-150 ℃, the working temperature in the sintering chamber is set to be 200-500 ℃, the working temperature in the constant-temperature chamber is set to be 200-500 ℃, and the working temperature in the cooling chamber is set to be 60-80 ℃.

The invention aims to solve the technical problems that inorganic precursor micromolecules and oligomers thereof are mainly used as spinning sol for preparing the ceramic nanofiber by the current electrostatic spinning method, a large amount of high-molecular polymer templates are needed for assistance to form the nanofiber, and the subsequent calcination process for removing the templates can cause serious environmental pollution, so that the ceramic fiber has low yield and weak mechanical property. Therefore, when the method is adopted in the amplification production process of the ceramic nano-fiber, the problems of high production cost, high production efficiency, high pollution, poor product quality and the like can be caused. The applicant develops an inorganic polymer sol with a low branching degree linear structure in the early period, and can realize the preparation of the ceramic gel nanofiber under the condition of not adding a high molecular polymer. The invention develops a batch preparation device (namely a sol spinning solution preparation mechanism), an electrostatic spinning device (namely an electrostatic spinning mechanism) of sol and a low-temperature calcination forming device (namely a fiber calcination forming mechanism) of ceramic nano-fiber based on the linear inorganic polymer sol spinning solution, thereby not only realizing the large-scale continuous manufacture of the flexible ceramic nano-fiber, but also improving the production efficiency and mechanical property of the ceramic nano-fiber product.

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

(1) according to the flexible ceramic nanofiber large-scale continuous manufacturing device, in a batch preparation device of linear inorganic polymer sol spinning solution, liquid water is introduced into a reaction system in a cold moisture mode, and a stirring roller layering differential reverse stirring mode is combined, so that moisture is stably and uniformly input into the solution system, and efficient and stable hydrolysis reaction is guaranteed; the solution in the core reaction kettle is subjected to reduced pressure concentration distillation by using a negative pressure suction mode, the product of the hydrolysis reaction is removed from a reaction system, the forward reaction is promoted, and the rapid, efficient, stable and controllable preparation of the spinnable sol is ensured.

(2) According to the flexible ceramic nanofiber large-scale continuous manufacturing device, in the linear inorganic polymer sol electrostatic spinning device, the flow resistance of a spinning solution in a multistage section transportation process is reduced, turbulence in the solution is avoided, laminar flow transportation of the spinning solution is realized, the fluid electrification quantity of the spinning solution is reduced, and the safe continuous production of spinning equipment is ensured; in the spinning process, external cold air is respectively arranged on the walls of the two sides of the secondary section flow channel and the tertiary section flow channel of the narrow-slit spinning nozzle, so that the phenomenon that the viscosity of the linear inorganic polymer sol spinning solution is continuously improved along with the prolonging of time is effectively inhibited, and the continuity and the stability of the spinning process are ensured; the split type spinning device is provided with the isolation cushion blocks, so that the transmission and accumulation of static charges in the device can be greatly reduced, the phenomenon of electrostatic discharge damage to spinning equipment is avoided, the whole split type spinning device can be detached, and the follow-up cleaning is very convenient.

(3) According to the device for continuously manufacturing the flexible ceramic nanofibers on a large scale, in the ceramic nanofiber low-temperature calcination forming device, the harmless deep analytic device of ultrasonic spraying-negative pressure suction is used for realizing mild and efficient removal of organic micromolecule ligands on the ceramic gel nanofiber membrane without damaging the nanofiber membrane; the microwave plasma sintering of the ceramic gel nanofiber membrane is realized through the variable-atmosphere microwave calcining device, the microwave heating temperature field is uniform, the thermal stress is small, the sintering speed is high, in addition, the crystal grains in the ceramic fiber are further refined by matching with the change of the gas atmosphere in different cabin bodies, the abnormal growth of the crystal grains is effectively inhibited, and the mechanical property of the finally obtained finished product is improved.

Drawings

FIG. 1 is a schematic diagram of a flexible ceramic nanofiber mass continuous manufacturing apparatus according to the present invention;

FIG. 2 is a schematic view of a batch preparation apparatus of a linear inorganic polymer sol spinning solution in a flexible ceramic nanofiber mass continuous manufacturing apparatus according to the present invention;

fig. 3 is a schematic diagram of a stirring roller of a batch preparation device of linear inorganic polymer sol spinning solution in a flexible ceramic nanofiber large-scale continuous manufacturing device of the present invention (a, b, c are examples in which the shape of a hollow hole on the surface of the stirring roller is circular, triangular, or square, respectively);

FIG. 4 is a schematic diagram of the flow velocity distribution of the spinning solution in different flow states during electrospinning;

FIG. 5 is a schematic view of an electrostatic spinning apparatus for linear inorganic polymer sol in a flexible ceramic nanofiber mass continuous manufacturing apparatus according to the present invention;

FIG. 6 is a top view of an electrospinning apparatus for linear inorganic polymer sol in a flexible ceramic nanofiber mass continuous manufacturing apparatus according to the present invention;

FIG. 7 is an overall schematic view of a narrow slit type spinning nozzle (a secondary cross-sectional flow passage and a tertiary cross-sectional flow passage) of an electrostatic spinning device for linear inorganic polymer sol in a flexible ceramic nanofiber large-scale continuous manufacturing device according to the present invention;

FIG. 8 is a cross-sectional view of an insulating support base of an electrospinning apparatus for linear inorganic polymer sol in a flexible ceramic nanofiber mass continuous manufacturing apparatus according to the present invention;

FIG. 9 is a schematic diagram of a two-stage cross-sectional flow channel structure on a narrow-slit spinning nozzle of an electrostatic spinning device for linear inorganic polymer sol in a flexible ceramic nanofiber large-scale continuous manufacturing device according to the present invention;

fig. 10 is a schematic diagram showing the shape and arrangement of a metal electrode protruding from a flow channel with a three-stage cross section on a narrow slit spinning nozzle of an electrostatic spinning device for linear inorganic polymer sol in a flexible ceramic nanofiber large-scale continuous manufacturing device according to the present invention (a, b, c take a cylinder, a triangular prism, and a rectangular pyramid as examples, respectively);

FIG. 11 shows the change of the viscosity of the linear inorganic polymer sol spinning solution when the electrostatic spinning device of the linear inorganic polymer sol is filled with high temperature (35 ℃) and low temperature (-2 ℃) gas;

FIG. 12 is a schematic view of a low-temperature calcination forming device for ceramic nanofibers in a flexible ceramic nanofiber large-scale continuous manufacturing device according to the present invention;

FIG. 13 is a schematic view of a desorption device in a ceramic nanofiber low-temperature calcination forming device in a flexible ceramic nanofiber large-scale continuous manufacturing device according to the present invention;

FIG. 14 is a schematic view of a solvent gradient displacement device in a ceramic nanofiber low-temperature calcination forming device in a flexible ceramic nanofiber large-scale continuous manufacturing device according to the present invention;

FIG. 15 is a schematic view of a vacuum drying apparatus and a variable-atmosphere microwave calcining apparatus in a low-temperature ceramic nanofiber calcining and forming apparatus in a flexible ceramic nanofiber large-scale continuous manufacturing apparatus according to the present invention;

the notation in the figure is:

1-a feeding kettle, 2-a feeding cavity, 3-a sealing valve, 4-a weighing sensor, 5-a feeding extraction pipeline, 6-a core reaction kettle, 7-a first negative air pressure suction component, 8-a high-purity dry gas inlet component, 9-a cold and wet gas transmission component, 10-a central shaft, 11-a stirring roller, 12-a stirring motor, 13-an induction probe, 14-a sensor and 15-a control panel;

16-a first-stage section flow channel, 17-a second-stage section flow channel, 18-a third-stage section flow channel, 19-a metal electrode, 20-an insulating support base, 21-a conveying belt, 22-a first microwave generator, 23-a waveguide connector, 24-a heater, 25-a high-voltage power supply, 26-a wiring terminal, 27-a spinning nozzle main body side wall, 28-a side wall opening, 29-an isolation cushion block, 30-a screen, 31-a first liquid storage tank, 32-a liquid supply pump, 33-a groove, 34-laminar flow and 35-turbulent flow;

36-an ultrasonic generator, 37-a resolving liquid tank, 38-a liquid pump, 39-a second liquid storage tank, 40-a transducer, 41-a spray head, 42-a negative pressure suction pump, 43-a hollowed-out tray, 44-a resolving cabin, 45-a first heat preservation layer, 46-a first heat preservation shell, 47-an alcohol water bath preparation kettle, 48-a replacement bath preparation kettle, 49-an alcohol bath preparation kettle, 50-an alcohol water bath, 51-a replacement bath, 52-an alcohol bath, 53-a second heat preservation layer, 54-a second heat preservation shell, 55-a drying cabin, 56-a vacuum pump, 57-an infrared heating unit, 58-an oxygen bottle, 59-an inert gas bottle, 60-a pre-burning cabin, 61-a sintering cabin, 62-a constant temperature cabin and 63-a cooling cabin, 64-a second microwave generator, 65-a third heat-insulating layer, 66-a third heat-insulating shell, 67-a rolling component, 68-a coaxial infusion tube and 69-a tension roller.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the following embodiments or examples, unless otherwise specified, functional components or functional structures are all conventional components or conventional structures used in the art to implement corresponding functions.

In order to realize the large-scale stable preparation of ceramic nanofibers with excellent performance and the like, the invention provides a large-scale continuous manufacturing device of flexible ceramic nanofibers, please refer to fig. 1 to 15, which structurally comprises:

a sol spinning solution preparation mechanism;

an electrostatic spinning mechanism: the first liquid storage tank 31 is connected with a spinning solution outlet of the sol spinning solution preparation mechanism, and the electrostatic spinning nozzle is connected with the first liquid storage tank 31 and used for outputting spinning fibers;

the fiber calcining and forming mechanism comprises: the device comprises an analysis component, a solvent gradient displacement component, a drying component and a variable atmosphere calcining component which are sequentially arranged along the processing advancing direction of spinning fibers, and in addition, a winding component 67 for winding and forming ceramic nano fibers is further arranged behind the variable atmosphere calcining component.

In some specific embodiments, the sol spinning solution preparation mechanism comprises a feed kettle 1, a core reaction kettle 6, a stirring component, a high purity dry gas inlet component 8, a cold moisture transmission component 9 and a first negative pressure suction component, wherein the core reaction kettle 6 is connected with the feed kettle 1 through a feed extraction pipeline 5, the stirring component is arranged inside the core reaction kettle 6, and the high purity dry gas inlet component 8, the cold moisture transmission component 9 and the first negative pressure suction component are respectively connected with the core reaction kettle 6.

In a more specific embodiment, please refer to fig. 2 and the like again, a feeding cavity 2 with an upper opening and capable of containing a certain amount of solid-liquid raw materials is arranged at the side top of the feeding kettle 1, a sealing valve 3 is arranged at the upper opening of the feeding cavity 2, and a weighing sensor 4 is arranged at the bottom of the feeding cavity 2. The bottom of the feeding cavity 2 can adopt a flip open-close structure, namely, when the weight of the added raw materials is weighed, the bottom cover is closed and sealed, the weight of each added raw material is weighed by the weighing sensor 4, and then the bottom cover is opened, so that the raw materials enter the feeding kettle 1. The feeding kettle 1 can be also provided with a stirring paddle, so that the added raw materials can be premixed.

In a more specific embodiment, please refer to fig. 2 and the like again, one end of the feeding extraction pipeline 5 is connected to the bottom discharge port of the feeding kettle 1, the other end is connected to the feed port of the core reaction kettle 6, and the feeding extraction pipeline 5 is further provided with a suction pump. Meanwhile, the end part of the feeding extraction pipeline 5 connected with the feeding kettle 1 can be provided with a discharge valve, when the materials in the feeding kettle 1 are required to be extracted into the core reaction kettle 6, the discharge valve is opened, and the discharge valve can be closed in other time.

In a more specific embodiment, referring to fig. 2 again, the stirring assembly includes a stirring motor 12, a central shaft 10 connected to the stirring motor 12 and located in the core reaction tank 6, and a plurality of layers of stirring rollers 11 mounted on the central shaft 10 and rotating therewith. Preferably, a hollow cavity with mutually communicated inner parts is arranged between the central shaft 10 and the stirring roller 11, a hollow hole communicated with the hollow cavity is processed on the stirring roller 11, and the cold and moisture transmission assembly 9 extends into the core reaction kettle 6 from the bottom and is connected with the bottom of the hollow cavity. By means of this arrangement, the cold moisture provided by the cold moisture transport assembly 9 can be released through the hollow space in the core reaction vessel 6 via the hollow-out openings in the stirring roller 11. The main purpose of the process is to slowly and uniformly release raw material liquid water necessary in the hydrolysis reaction process in a core reaction kettle 6 solution system in a moisture mode, prevent the gelation phenomenon caused by the local reaction of the solution in a mode of directly adding the liquid water, and ensure the high efficiency and stability of the sol preparation process. The material of the central shaft 10 and the stirring roller 11 can be one of stainless steel, carbon steel or ceramic with wear-resistant and corrosion-resistant coatings.

More preferably, referring to fig. 3 again, the hollowed holes are arranged along the axial direction of the stirring roller 11, and the shape of the hollowed holes is one or a combination of several of circular, oval, square, rectangular, triangular, other polygonal or irregular figures. Meanwhile, the arrangement density of the hollow holes can be 1-2/cm²。

In a more specific embodiment, please refer to fig. 2 and the like, the stirring roller 11 is provided with three layers from top to bottom on the central shaft 10 at equal intervals, and the three layers of stirring rollers 11 are arranged in a reverse differential stirring manner, i.e. the rotation directions of the two adjacent layers of stirring rollers 11 are just opposite and the rotation speeds are different (the implementation manner of the differential stirring here belongs to the prior art, and reference can be made to the following [1] wufany, wangsu, mai-wu-yu, canyon-yu-co-axial counter-rotating paddles in the propylene slurry reaction kettle [ J ] chemical engineering, 2019,47(04):45-49+ 68.). If the layer of stirring roller 11 closest to the motor at the top of the core stirring kettle rotates clockwise, the middle layer of stirring roller 11 rotates anticlockwise, and the layer of stirring roller 11 closest to the liquid discharging port at the bottom of the core stirring kettle rotates clockwise.

More preferably, there are three stirring rollers 11 per layer, and each stirring roller 11 forms an angle of 0 to 75 °, preferably 60 °, with the central axis 10 (here, the stirring rollers 11 are not arranged horizontally, preferably in a downward inclined manner on the central axis 10).

In a more specific embodiment, referring to fig. 2 and the like, the core reactor 6 is further provided with a sensor 14 (including a viscosity sensor and a temperature sensor). The viscosity sensor and the temperature sensor measure the temperature and the viscosity signal of the liquid in the kettle through an induction probe 13 which is arranged at the lower part of the kettle body, feed the temperature and the viscosity signal back to a control system (such as a PLC control system) and display the temperature and the viscosity signal by a monitor panel (namely a control panel 15). The temperature range of the monitoring agent can be 20-150 ℃, and the viscosity range is 0-100000 mPa.

In a more specific embodiment, the high-purity dry gas inlet assembly 8 is used for delivering high-purity dry gas into the core reaction kettle 6, the type of the high-purity dry gas is one of nitrogen, helium, neon, argon, krypton and xenon, so as to ensure that the environment of the core reaction kettle 6 is sufficiently dry before the solution in the feed kettle 1 is transferred to the core reaction kettle 6, and prevent the liquid transferred to the core reaction kettle 6 from immediately reacting with the residual water in the kettle, which affects the overall uniformity of the subsequent solution, even causes local gelation;

the cold and wet gas transmission assembly 9 is used for transmitting cold and wet gas formed by mixing air in a low-temperature state and water vapor into the core reaction kettle 6. The absolute humidity of the cold moist gas may be 8g/m³The temperature of the cold and wet air can be 5-25 ℃;

the first negative pressure suction assembly is used for sucking gas in the core reaction kettle 6, so that the gas is kept in a low-pressure or negative-pressure state.

In some specific embodiments, please refer to fig. 5 again, the electrostatic spinning nozzle includes a nozzle body and an insulating support base 20, a middle region between the nozzle body and the insulating support base 20 is hollowed out to form a spinning flow passage penetrating through the nozzle body and the insulating support base 20, the spinning flow passage is composed of a primary section flow passage 16, a secondary section flow passage 17 and a tertiary section flow passage 18 which are connected in sequence along a flowing direction of a spinning solution, wherein a width of the primary section flow passage 16 is larger than that of the tertiary section flow passage 18, a plurality of protruding metal electrodes 19 are further arranged on a liquid outlet along the tertiary section flow passage 18, and the nozzle body is further provided with a terminal 26 connected with an external high voltage power supply 25. The metal electrode 19 is disposed on the outlet along the line of the tertiary-section flow path 18 (the "outlet along the line" herein means an outlet where the solution flows out from the tertiary-section flow path 18, and a region where a quadrangle of the outlet spinning position is located), and exhibits a convex shape. According to the electrostatic spinning principle: the spinning solution flows through the three-stage cross-section flow channel 18 and overflows from the tip of the convex metal electrode 19, and when the charge repulsion of the liquid surface exceeds the surface tension thereof, the Taylor cone surface at the tail end of the metal electrode 19 tells that a solution trickle is sprayed. These jets undergo high speed stretching by electric field force, solvent volatilization and solidification, and finally deposit on a receiving plate to form fibers.

In the invention, the binding post 26 of the copper-iron alloy is arranged on the narrow-slit spinning nozzle and is connected with the high-voltage power supply 25 and the binding post 26 through a lead, so that the high-voltage electric loading of a spinning solution system can be conveniently and quickly realized.

In a more specific embodiment, referring to fig. 6 again, the nozzle body is further processed with a cooling channel surrounding the secondary cross-sectional flow channel 17 and the tertiary cross-sectional flow channel 18, and a cooling fluid is introduced into the cooling channel. The cooling fluid may specifically be cold air, the temperature of which is in the range of-10-15 ℃. The method can effectively inhibit the phenomenon that the viscosity of the linear inorganic polymer sol spinning solution is continuously improved along with the prolonging of time, and ensure the continuity and stability of the spinning process.

In a more specific embodiment, the axial section of the secondary cross-section flow channel 17 is a conical structure, and two sides of the conical structure are 1/4 circular arcs symmetrically arranged. Specifically, as shown in fig. 9, the shape of the truncated cube is a truncated cube structure, one face of the cube is provided with four vertexes a, b, c and d, the opposite face is provided with four vertexes a ', b ', c ' and d ' in a one-to-one correspondence manner, a cc ' edge of the cube is provided with a point e close to c and a point e close to c ', a dd ' edge of the cube is provided with a point f close to d and a point f close to d ', a cd edge, an ef edge and an e ' f ' edge are parallel to each other, the length of the ce edge is equal to a c edge, the length of the c ' e ' edge is equal to a c ' a ' edge, a quarter cylinder with c as a center, ce as a radius and cd as a height is truncated, and a quarter cylinder with c ' as a center, c ' e ' as a radius and c'd ' as a height is truncated; the length of the edge ee' (namely the width of the three-stage section flow channel 18) is less than or equal to 5 mm; the structure of the secondary cross-sectional flow channel 17 of the slot-type spinneret is schematically shown in fig. 7, where it is desired to ensure that the cross-sectional flow channel is gradually contracted. If the cross section area of the flow channel is suddenly changed, because the turning point can not be arranged on the flow line, the formed flow stream is contracted, local separation and flow separation occur after the section is suddenly changed, then the flow stream is attached to the wall, in the contracted flow channel, the flow stream not only has accelerated contracted flow, but also has decelerated diffused flow, and both the accelerated contracted flow stream and the decelerated diffused flow generate resistance, namely turbulent flow is easily formed.

More preferably, the front end of the secondary section flow passage 17 is the same as the primary section flow passage 16, the rear end of the secondary section flow passage 17 is the same as the tertiary section flow passage 18, and the secondary section flow passage 17 is further in smooth transition connection with the tertiary section flow passage 18.

In a more specific embodiment, please refer to fig. 7 and 8, etc., the first-stage cross-section flow channel 16 is disposed on the insulating support base 20, the second-stage cross-section flow channel 17 and the third-stage cross-section flow channel 18 are disposed on the showerhead body, the insulating support base 20 is provided with a groove 33, and the showerhead body is provided with a protrusion capable of being correspondingly inserted into the groove 33. Referring to fig. 8, etc., the boundary area between the showerhead body and the insulating support base 20 is partially or completely provided with an isolation pad 29, and specifically, the boundary area between the groove 33 and the primary cross-sectional flow channel 16 may be further provided with an isolation pad 29. The insulating support base 20 is made of Polyamide (PA), Polymethacrylate (PMMA), Polyformaldehyde (POM), Polyurethane (PU) or Polycarbonate (PC), and the insulating support base 20 can be tightly embedded with the narrow-slit type nozzle body to play a role in supporting and insulating. The isolation cushion block 29 is made of polytetrafluoroethylene, polyformaldehyde, phenolic resin, polyarylate, polyethylene, polypropylene, poly-p-phenylene terephthalamide or polyarylate, the length is 0.5-2 m, the width is 5-20 cm, and the thickness is 1-3 cm, so that the effect of isolating the narrow-slit spinning nozzle from the embedded base in a static manner is achieved, the static charge is effectively prevented from being transferred and accumulated, and the safe and stable operation of the spinning process is ensured.

In a more specific embodiment, please refer to fig. 5 again, the metal electrode 19 is disposed on the liquid outlet along the line of the three-stage cross-section flow channel 18 and is convex, and the disposition manner of the metal electrode can be as shown in fig. 10, that is, the shape of the metal electrode 19 can be one or more combinations of a cone, a cylinder, a prism, a pyramid and a frustum, the distribution density is 1-2/cm, and the material is one or more combinations of an iron alloy, a cobalt alloy, a nickel alloy, a copper alloy, an aluminum alloy, a platinum alloy and an iridium alloy. The arrangement of the metal electrodes 19 may be specifically oriented in an axial direction perpendicular to the tertiary cross-sectional flow channel 18. According to the electrostatic spinning principle: the spinning solution flows through the three-stage cross-section flow channel 18 and overflows from the tip of the convex metal electrode 19, and when the charge repulsion of the liquid surface exceeds the surface tension thereof, the Taylor cone surface at the tail end of the metal electrode 19 tells that a solution trickle is sprayed. These jets undergo high speed stretching by electric field force, solvent volatilization and solidification, and finally deposit on a receiving plate to form fibers.

In a more specific embodiment, referring again to fig. 5, the inlet end of the primary cross-sectional flow channel 16 is further provided with a screen 30. Specifically, the screen 30 is a metal screen 30 woven by brass wires, the screen 30 has 400 meshes, the diameter of the wire is 0.03mm, and the diameter of the wire is 0.035mm, so that the effects of isolating impurities and removing bubbles in the spinning solution are achieved.

In addition, in some embodiments, the length of the primary cross-sectional flow channel 16 is 1-10 cm, the width thereof is 10-20 cm, and the length of the tertiary cross-sectional flow channel 18 is 10-40 cm, and the width thereof is 1-5 mm.

In some embodiments, referring to fig. 5 again, a conveyer belt 21 is disposed under the spinneret and opposite to the tertiary section flow passage 18 for receiving and conveying the spun fibers fed from the tertiary section flow passage 18. Furthermore, a microwave heating unit is arranged under the conveyor belt 21, and the vertical distance between the heating part of the microwave heating unit and the conveyor belt 21 is less than 50 cm. The microwave heating unit may include a first microwave generator 22, a waveguide connector 23, and a heater 24 connected in sequence, the heater 24 being located below the conveyor belt 21 and at a vertical distance of less than 50cm from the conveyor belt, the first microwave generator 22 receiving power to generate microwaves, and then transmitting the microwaves to the heater 24 through the waveguide connector 23, thereby drying the received nanofibers. More preferably, the conveying belt 21 is further provided with hollow meshes. The shape of the hollow meshes on the surface of the conveying belt 21 is one or a combination of more of a circle, an ellipse, a square, a rectangle, a triangle, other polygons and irregular patterns, and the arrangement density is 50-200/m². In addition, the conveyor belt 21 is also subjected to grounding treatment.

In a more specific embodiment, during a specific spinning operation, a pre-prepared linear inorganic polymer sol spinning solution is contained in the first liquid storage tank 31, the linear inorganic polymer sol spinning solution is pumped to the liquid inlet at the bottom of the insulating support base 20 through the liquid supply pump 32, impurities and bubbles in the spinning solution are removed through the screen 30, the spinning solution flows into the first-stage cross-section channel along with the first-stage cross-section channel, the spinning solution enters the second-stage cross-section channel on the narrow-slit spinning nozzle after the channel solution is filled, similarly, the solution flows into the third-stage cross-section channel after the second-stage cross-section channel is filled, and finally the solution flows to the protruded metal electrode 19 after the third-stage cross-section channel is filled. The solution overflowing the metal electrode 19 is wiped clean, and the spinning solution pouring speed is adjusted by the solution supply pump 32, so that the solution reaches a state of about to flow out without falling to a receiving mechanism (i.e. a conveying belt 21 and the like) below. Meanwhile, the openings at two sides of the main body of the second-stage and third-stage section flow channels 18 of the narrow-slit spinning nozzle are externally connected with cold air, and the temperature range of the cold air is-10-15 ℃. One end of the lead is connected with a binding post 26, the other end of the lead is connected with a high-voltage power supply 25, under the action of a high-voltage electrostatic field, the solution at the electrode tip forms a Taylor cone, and when the solution is subjected to electrostatic force to exceed the surface tension, the surface of the Taylor cone sprays out of the flow at high speed. These jets undergo the drawing of the electric field forces, solvent evaporation and solidification, and are finally deposited on a receiving plate. The receiving mechanism is provided with a microwave drying unit, and the fibers deposited on the conveying belt 21 are dried in time through the conversion of microwave heat, so that the influence of air humidity on the obtained fibers is prevented.

In some specific embodiments, referring to fig. 12 and the like again, the analysis assembly includes an analysis chamber 44, and a spraying unit and a negative pressure suction unit located in the analysis chamber 44, wherein the spraying unit is located above the negative pressure suction unit, and after entering the analysis chamber 44, the ceramic nanofibers pass through between the spraying unit and the negative pressure suction unit, and are soaked with the analysis liquid sprayed by the spraying unit;

the solvent gradient displacement assembly comprises a displacement cabin positioned behind the analysis cabin 44, and an alcohol-water bath 50, a displacement bath 51 and an alcohol bath 52 which are sequentially arranged in the displacement cabin along the advancing direction of the ceramic nano fibers;

the drying component comprises a drying cabin 55 positioned behind the replacing cabin and a drying unit which is arranged in the drying cabin 55 and used for heating and drying the passing ceramic nano-fiber;

the atmosphere-variable calcining assembly comprises a pre-sintering cabin 60, a sintering cabin 61, a constant temperature cabin 62 and a cooling cabin 63 which are positioned behind the drying cabin 55 and are sequentially arranged along the advancing direction of the ceramic nano fibers and are mutually independent, wherein the pre-sintering cabin 60, the sintering cabin 61, the constant temperature cabin 62 and the cooling cabin 63 are respectively connected with external oxygen supply equipment and/or inert gas supply equipment through independent pipelines.

In a more specific embodiment, referring to fig. 13 again, the spraying unit includes a spraying head 41 disposed in a resolution compartment 44, and a second reservoir 39, a liquid pump 38 and a resolution liquid tank 37 sequentially connected to the spraying head 41, the second reservoir 39 is further connected to an ultrasonic generator 36, and a transducer 40 is further disposed between the second reservoir 39 and the spraying head 41. Here: (1) the ultrasonic generator 36, also known as an ultrasonic driving power supply, an electronic box, and an ultrasonic controller, is an important component of the high-power ultrasonic system. The ultrasonic generator 36 is used for converting the commercial power into a high-frequency alternating current signal matched with the ultrasonic transducer 40 and driving the ultrasonic transducer 40 to work. (2) The transducer 40 functions to convert the input electric power into mechanical power (i.e., ultrasonic waves) and transmit the mechanical power, while consuming a small portion of the power by itself. (3) During operation, compressed air forms high-speed airflow through the fine nozzle, the generated negative pressure drives liquid or other fluid to be sprayed onto the obstacle together, and the liquid drops splash to the periphery under high-speed impact to be changed into mist-shaped particles to be sprayed out of the air outlet pipe. The working principle of the ultrasonic atomization spraying device is the same as that of the current ultrasonic atomization spraying device, and the ultrasonic atomization spraying device belongs to the common knowledge in the industry.

In a more specific embodiment, please refer to fig. 13 and so on, the negative pressure suction unit includes a hollow tray 43 disposed in the analysis chamber 44 and below the conveyor belt for conveying the ceramic nanofibers, and a negative pressure suction pump 42 connected to the hollow tray 43 through a suction pipe, wherein a plane of the hollow tray 43 is opposite to and parallel to a plane of the conveyor belt. In addition, the shape of the hollow on the hollow tray 43 is one or a combination of a circle, a triangle, a quadrangle, a polygon and other irregular figures, and the hollow area of the tray accounts for 60-90% of the whole area.

In a more specific embodiment, the analysis solution is an alcohol solution of an alkali, and the concentration of the alcohol solution can be 0.1-5 mol/L, specifically, the alkali can be sodium hydroxide or potassium hydroxide, and the alcohol solvent can be one or a combination of ethanol, propanol, n-butanol or tert-butanol. Preferably, the vacuum degree in the analysis cabin 44 is-0.098 to-0.01 MPa, the temperature is controlled at 60 to 100 ℃, and the analysis can be realized by heating with resistance wires.

In a more specific embodiment, referring to fig. 14 again, the alcohol-water bath 50 is further connected to an alcohol-water bath preparation kettle 47 for providing an alcohol-water mixed solution, the substitution bath 51 is further connected to a substitution bath preparation kettle 48 for providing a substitution solvent, and the alcohol bath 52 is further connected to an alcohol bath preparation kettle 49 for providing an alcohol solvent.

More preferably, the temperature of the alcohol-water mixed solution in the alcohol-water bath 50 is 10 to 30 ℃, the temperature of the substitution solvent in the substitution bath 51 is 60 to 80 ℃, and the temperature of the alcohol solvent in the alcohol bath 52 is 10 to 30 ℃. More preferably, the alcohol-water mixed solution is prepared from alcohol and water, and specifically can be composed of 95 wt% of alcohol and 5 wt% of water, wherein the alcohol can be one or a combination of more of ethanol, propanol, n-butanol and tert-butanol. More preferably, the displacement solvent may be one or more of carbon tetrachloride, benzene, toluene, dichloroethane, dichloromethane, chloroform, diethyl ether, diphenyl ether, ethyl acetate, acetone, tetrahydrofuran, N-methylpyrrolidone, and N, N-dimethylformamide. More preferably, the alcohol solvent can be one or more of ethanol, propanol, n-butanol and tert-butanol.

In a more specific embodiment, referring again to fig. 12, the drying unit includes an infrared heating unit 57 located in a drying chamber 55, and a vacuum generating device (such as a vacuum pump 56) connected to the drying chamber 55 through a pipe, wherein the drying chamber 55 is a substantially sealed chamber. Here, the infrared heating unit 57 may be an infrared heating pipe, and the power thereof may range from 300W to 3500W. Preferably, the working temperature in the drying chamber 55 is 60-80 ℃, and the vacuum degree is-0.1-0.098 MPa.

In a more specific embodiment, referring to fig. 15 again, the pre-sintering chamber 60 and the cooling chamber 63 are respectively connected to an oxygen supply device (which may be an oxygen cylinder 58) through a gas pipeline, and the sintering chamber 61 and the constant temperature chamber 62 are both connected to an oxygen supply device and an inert gas supply device (which may be an inert gas cylinder 59) through a gas pipeline.

In a more specific embodiment, please refer to fig. 15 again, the pre-sintering chamber 60, the sintering chamber 61, the constant temperature chamber 62 and the cooling chamber 63 are respectively connected to an external second microwave generator 64 through waveguides; and (3) ionizing the gas by utilizing microwave to form plasma, and then heating the gel ceramic nanofiber membrane by the plasma to obtain the compact nanofiber membrane. The microwave plasma heating is adopted in the invention, which is different from the conventional microwave heating, and the microwave sintering is that alternating electromagnetism can repeatedly adjust dipoles in the material to generate strong vibration and friction, so that the material is heated, and the purpose of heating and sintering is achieved. The essence of microwave plasma sintering is that microwave energy is used to excite gas discharge to generate plasma, and the green body is heated by the plasma to obtain a dense ceramic sintered body. It is noted that during the sintering of the ceramic, some of the energy also heats the sample in the form of microwaves, accompanied by the heating of the high temperature plasma. The microwave plasma sintering method overcomes the defects that selective heating is realized during simple microwave sintering of ceramics, and all materials cannot be effectively heated, and simultaneously, the problems of large temperature gradient and uneven heating of a plasma space are reduced to a certain extent.

In a more specific embodiment, the working atmosphere of the pre-sintering chamber 60 and the cooling chamber 63 is an oxygen atmosphere, and the working atmosphere of the sintering chamber 61 and the constant temperature chamber 62 is a mixed atmosphere of oxygen and an inert gas, and is generally controlled to have an oxygen gas content of 80-95% and an inert gas content of 5-20% (both by volume fraction). The inert gas may include one or more combinations of nitrogen, helium, neon, argon, and the like.

In a more specific embodiment, the working temperature in the pre-sintering chamber 60 is set to be 100-150 ℃, the working temperature in the sintering chamber 61 is set to be 200-500 ℃, the working temperature in the constant temperature chamber 62 is set to be 200-500 ℃, and the working temperature in the cooling chamber 63 is set to be 60-80 ℃. In addition, during specific work, according to actual conditions, the gel nanofiber membrane can keep differential drafting and proper tension compensation in the whole process from the moment when the gel nanofiber membrane does not enter the pre-burning cabin 60 to the moment when the gel nanofiber membrane leaves the cooling cabin 63, wherein the differential speed between the inlet and the outlet of the pre-burning cabin 60 is 20%, the differential speed between the inlet and the outlet of the sintering cabin 61 is 30%, the differential speed between the inlet and the outlet of the constant temperature cabin 62 is 30%, and the differential speed between the inlet and the outlet of the cooling cabin 63 is 5%. The above can be routinely adjusted empirically.

For example, a heat-insulating shell and a heat-insulating layer can be arranged outside the analysis cabin 44, the replacement cabin, the drying cabin 55, the pre-sintering cabin 60, the sintering cabin 61, the constant-temperature cabin 62, the cooling cabin 63 and the like, namely, a first heat-insulating layer 45 and a first heat-insulating shell 46 are arranged outside the analysis cabin 44, and a second heat-insulating layer 53 and a second heat-insulating shell 54 are arranged outside the replacement cabin; the drying chamber 55, the pre-burning chamber 60, the sintering chamber 61, the constant temperature chamber 62 and the cooling chamber 63 can be collectively arranged in the same large-scale chamber body, and thus, a third heat-insulating layer 65 and a third heat-insulating shell 66 are uniformly arranged.

In summary, the technical problems to be solved by the present invention are that currently, electrostatic spinning ceramic nanofibers can be normally spun only by adding a polymer to a precursor solution to adjust spinnability, but introduction of the polymer usually requires high-temperature calcination (above 600 ℃) to remove organic polymer components, which not only causes serious environmental pollution, but also causes oversize crystal grains of finally obtained ceramic nanofibers and micro-defect structures in the fibers, so that finally obtained pure ceramic nanofibers have poor flexibility and serious mechanical properties. The method is characterized in that linear inorganic polymer sol is synthesized in the early stage, the sol can be normally spun under the condition that no high molecular polymer is added in a precursor solution, and on the basis, an electrostatic spinning device for preparing the flexible ceramic nanofiber in a large scale is developed, so that the ceramic gel nanofiber is industrially prepared from the linear inorganic polymer sol through an electrostatic spinning process. However, in the process of obtaining ceramic gel nanofibers from inorganic polymer sols through electrostatic spinning, although no polymer is added, a small amount of small-molecule organic ligands still exist on the molecular chains of the gel fibers, so that the temperature for removing the organic ligands subsequently is also high, and in addition, the crystal grain growth speed also exists in the conventional air atmosphere calcination process treatment, and the quality of the subsequent finished products is also seriously influenced. According to the invention, through the matching use of the analysis mechanism, the solvent gradient displacement mechanism, the decompression drying mechanism and the variable-atmosphere microwave calcining mechanism, the mild removal of the micromolecule organic ligand can be realized, the inhibition effect on the grain growth of the ceramic gel fiber is obvious, and the mechanical property of the final pure ceramic fiber is obviously improved. The specific mechanism is as follows:

on the one hand, a small part of organic ligands on the ceramic gel fiber are formed by chelating polydentate ligands on metal alkoxide in the process of preparing spinning sol for limiting the reactivity of the metal alkoxide (particularly, zirconium and titanium atoms have high electropositivity, the metal alkoxide formed by the ligands has severe hydrolysis reaction, and the local gelation phenomenon is very easy to occur rapidly when water is encountered). Therefore, the organic ligand on the gel fiber needs to be removed by using a related method to obtain pure ceramic fiber, and the calcination temperature of the fiber after the ligand is removed can be greatly reduced.

The following takes a linear zirconium sol prepared by chelating zirconium metal alkoxide with acetic acid as an example to illustrate the chemical reaction of zirconium gel nanofibers obtained by zirconium sol electrospinning in an analytical mechanism:

however, it should be noted that, compared with the traditional woven fabric and knitted fabric, the strength of the electrospun nanofiber membrane in the longitudinal and transverse directions is inferior, so the developed analysis mechanism adopts an ultrasonic spray-negative pressure suction method, for example, an ethanol solution of sodium hydroxide is used as an analysis solution to be ultrasonically sprayed on the surface of the nanofiber membrane, and then the spray solution is immersed into the fiber membrane by the negative pressure suction method, so that the spray solution is sufficiently soaked to achieve the effect of deep analysis. However, if the soaking treatment similar to the conventional fabric is adopted, not only the process is time-consuming and energy-consuming, but also the strength of the fiber membrane is greatly impaired (the strength of the fiber membrane in a wet state is poor).

On the other hand, the ceramic gel nanofiber membrane is treated by adopting a variable-atmosphere microwave calcining mechanism, mainly because the microwave heating mode is different from the conventional heating mode, the microwave heating mode is that the microwave interacts with a dielectric material in a rapidly-changing high-frequency electromagnetic field, the microwave is absorbed by the dielectric material to generate body heating, the heating starts from the inside and the outside of an object at the same time, and the inside and the outside can be simultaneously heated, so that the microwave heating temperature field is uniform, the thermal stress is small, and the ceramic gel nanofiber membrane is suitable for rapid sintering. In addition, the microwave electromagnetic field promotes diffusion, accelerates the sintering process, can refine the grains of the ceramic material, effectively inhibits the abnormal growth of the grains, and improves the uniformity of the microstructure of the material. More importantly, different gas atmospheres of the cabin body are set (the pre-sintering stage is an oxygen atmosphere, the sintering and constant temperature stage is controlled to be a mixed atmosphere of oxygen and inert gas, wherein the oxygen content is 80-95%, the inert gas content is 5-20%, and the cooling stage is an oxygen atmosphere), microwave ionized gas is further utilized to form plasma, and then the plasma heats the gel ceramic nanofiber membrane to obtain the compact nanofiber membrane. Due to rapid heating, the coarsening of crystal grains caused by surface diffusion (mainly occurring in the low-temperature stage of traditional sintering) is reduced, and a strong driving force and a short diffusion path are provided for grain boundary diffusion and volume diffusion, so that the microstructure of the ceramic is refined, and the rapid densification of the fiber membrane is promoted. This is because there is an extremely small amount of residual carbon in the environment of incomplete oxygen during the sintering stage, which can be trapped at the grain boundaries, inhibiting grain growth, and the resulting increase in densification of the ceramic fiber is associated with smaller grain size and more additional oxygen vacancies created during the reducing atmosphere heat treatment.

The above embodiments may be implemented individually, or in any combination of two or more.

The above embodiments will be described in more detail with reference to specific examples.

Example 1:

in order to realize stable large-scale preparation of ceramic nanofibers with excellent performance, and the like, the present embodiment provides a flexible ceramic nanofiber large-scale continuous manufacturing apparatus, please refer to fig. 1 to 15, which includes:

a sol spinning solution preparation mechanism;

an electrostatic spinning mechanism: the device comprises a first liquid storage tank 31 connected with a spinning solution outlet of a sol spinning solution preparation mechanism, and an electrostatic spinning nozzle connected with the first liquid storage tank 31 and used for outputting spinning fibers;

the fiber calcining and forming mechanism comprises: the device comprises an analysis component, a solvent gradient displacement component, a drying component and a variable atmosphere calcining component which are sequentially arranged along the processing advancing direction of spinning fibers, and in addition, a winding component 67 for winding and forming ceramic nano fibers is further arranged behind the variable atmosphere calcining component.

Sol spinning liquid preparation mechanism includes feed kettle 1, core reation kettle 6, stirring subassembly, high-purity dry gas inlet assembly 8, cold moisture transmission subassembly 9 and first negative pressure suction subassembly, wherein, is connected through feeding extraction pipeline 5 between core reation kettle 6 and the feed kettle 1, and the stirring subassembly is arranged inside core reation kettle 6, and high-purity dry gas inlet assembly 8, cold moisture transmission subassembly 9 and first negative pressure suction subassembly connect core reation kettle 6 respectively.

Referring to fig. 2 and the like again, a feeding cavity 2 having an upper opening and capable of containing a certain amount of solid-liquid raw materials is disposed at the top of the feeding kettle 1, a sealing valve 3 is disposed at the upper opening of the feeding cavity 2, and a weighing sensor 4 is mounted at the bottom of the feeding cavity 2. The bottom of the feeding cavity 2 can adopt a flip open-close structure, namely, when the weight of the added raw materials is weighed, the bottom cover is closed and sealed, the weight of each added raw material is weighed by the weighing sensor 4, and then the bottom cover is opened, so that the raw materials enter the feeding kettle 1. The feeding kettle 1 can be also provided with a stirring paddle, so that the added raw materials can be premixed.

Referring to fig. 2, one end of the feeding extraction pipeline 5 is connected to the bottom discharge port of the feeding kettle 1, the other end is connected to the feed port of the core reaction kettle 6, and the feeding extraction pipeline 5 is further provided with a suction pump. Meanwhile, the end part of the feeding extraction pipeline 5 connected with the feeding kettle 1 can be provided with a discharge valve, when the materials in the feeding kettle 1 are required to be extracted into the core reaction kettle 6, the discharge valve is opened, and the discharge valve can be closed in other time.

Referring again to fig. 2, the stirring assembly includes a stirring motor 12, a central shaft 10 connected to the stirring motor 12 and located in the core reaction vessel 6, and a plurality of layers of stirring rollers 11 mounted on the central shaft 10 and rotating therewith. Preferably, a hollow cavity with the inside communicated with each other is arranged between the central shaft 10 and the stirring roller 11, a hollow hole communicated with the hollow cavity is processed on the stirring roller 11, and the cold and moisture transmission assembly 9 extends into the core reaction kettle 6 from the bottom and is connected with the bottom of the hollow cavity. By means of this arrangement, the cold moisture provided by the cold moisture transport assembly 9 can be released through the hollow space in the core reaction vessel 6 via the hollow-out openings in the stirring roller 11. The main purpose of the process is to slowly and uniformly release raw material liquid water necessary in the hydrolysis reaction process in a core reaction kettle 6 solution system in a moisture mode, prevent the gelation phenomenon caused by the local reaction of the solution in a mode of directly adding the liquid water, and ensure the high efficiency and stability of the sol preparation process. The material of the central shaft 10 and the stirring roller 11 can be one of stainless steel, carbon steel or ceramic with wear-resistant and corrosion-resistant coatings.

Referring to fig. 3 again, the hollow holes are arranged along the axial direction of the stirring roller 11, and the shape of the hollow holes is circular, and the arrangement density of the hollow holes can be 1-2/cm²。

Referring to fig. 2 and the like again, the three layers of stirring rollers 11 are arranged on the central shaft 10 at equal intervals from top to bottom, and the three layers of stirring rollers 11 are arranged in a reverse differential stirring manner, that is, the rotation directions of the two adjacent layers of stirring rollers 11 are just opposite, and the rotation speeds are different. If the layer of stirring roller 11 closest to the motor at the top of the core stirring kettle rotates clockwise, the middle layer of stirring roller 11 rotates anticlockwise, and the layer of stirring roller 11 closest to the liquid discharging port at the bottom of the core stirring kettle rotates clockwise. Three stirring rollers 11 are provided per layer, and each stirring roller 11 is arranged at an angle of 60 ° to the central axis 10 (here, it is indicated that the stirring rollers 11 are not arranged horizontally, but are preferably arranged on the central axis 10 in a downwardly inclined manner).

Referring to fig. 2 and the like, a viscosity sensor 14 and a temperature sensor 14 are also disposed in the core reaction kettle 6. The viscosity sensor 14 and the temperature sensor 14 measure the temperature and viscosity signals of the liquid in the kettle through the sensing probe 13 arranged at the lower part of the kettle body, and feed the signals back to a control system (such as a PLC control system) and are displayed by a monitor panel. The temperature range of the monitoring agent can be 20-150 ℃, and the viscosity range is 0-100000 mPa.

The high-purity dry gas inlet assembly 8 is used for conveying high-purity dry gas into the core reaction kettle 6, the type of the high-purity dry gas is one of nitrogen, helium, neon, argon, krypton and xenon, so that the environment of the core reaction kettle 6 is fully dried before the solution in the feeding kettle 1 is transferred to the core reaction kettle 6, and the situation that the liquid transferred to the core reaction kettle 6 immediately reacts with residual water in the kettle to influence the overall uniformity of subsequent solution and even cause local gelation is avoided; the cold moisture transfer assembly 9 is used for transferring cold moisture mixed by air in a low temperature state and water vapor into the core reaction kettle 6. The absolute humidity of the cold moist gas may be 8g/m³The temperature of the cold and wet air can be 5-25 ℃; the first negative pressure suction assembly is used for sucking the gas in the core reaction kettle 6, so that the gas is kept in a low pressure or negative pressure state.

Referring to fig. 5 again, the electrostatic spinning nozzle includes a nozzle body and an insulating support base 20, a middle region between the nozzle body and the insulating support base 20 is hollowed to form a spinning flow passage penetrating through the nozzle body and the insulating support base 20, the spinning flow passage is composed of a primary section flow passage 16, a secondary section flow passage 17 and a tertiary section flow passage 18 which are connected in sequence along a flowing direction of a spinning solution, wherein a width of the primary section flow passage 16 is larger than that of the tertiary section flow passage 18, a plurality of protruding metal electrodes 19 are further arranged on a liquid outlet along the tertiary section flow passage 18, and a terminal 26 connected with an external high voltage power supply 25 is further arranged on the nozzle body. The metal electrode 19 is disposed on the outlet along the line of the tertiary-section flow path 18 (the "outlet along the line" herein means an outlet where the solution flows out from the tertiary-section flow path 18, and a region where a quadrangle of the outlet spinning position is located), and exhibits a convex shape.

In this embodiment, the binding post 26 of the copper-iron alloy is arranged on the narrow slit spinning nozzle, and is connected with the high-voltage power supply 25 and the binding post 26 through a wire, so that the high-voltage electricity loading of the spinning solution system can be conveniently and rapidly realized.

Referring to fig. 6, the nozzle body is further provided with a cooling channel surrounding the secondary cross-sectional flow channel 17 and the tertiary cross-sectional flow channel 18, and a cooling fluid is introduced into the cooling channel. The cooling fluid may specifically be cold air, the temperature of which is in the range of-10-15 ℃. The method can effectively inhibit the phenomenon that the viscosity of the linear inorganic polymer sol spinning solution is continuously improved along with the prolonging of time, and ensure the continuity and stability of the spinning process.

As shown in fig. 9, the axial section of the secondary cross-section flow channel 17 is a conical structure, and two sides of the conical structure are 1/4 circular arcs symmetrically arranged. Specifically, the shape of the truncated cube is a truncated cube structure, one face of the cube is provided with four vertexes a, b, c and d, the opposite face is provided with four vertexes a ', b', c 'and d' in a one-to-one correspondence manner, a cc 'edge of the cube is provided with a point e close to c and a point e close to c', a dd 'edge of the cube is provided with a point f close to d and a point f' close to d ', a cd edge, an ef edge and an e' f 'edge are parallel to each other, the length of the ce edge is equal to a edge, the length of the c' e 'edge is equal to a c' a 'edge, a quarter cylinder with c as the center of circle, ce as the radius and cd as the height is truncated, and a quarter cylinder with c' as the center of circle, c 'e' as the radius and c'd' as the height is truncated; the length of the edge ee' (namely the width of the three-stage section flow channel 18) is less than or equal to 5 mm; the structure of the secondary cross-sectional flow channel 17 of the slot-type spinneret is schematically shown in fig. 7, where it is desired to ensure that the cross-sectional flow channel is gradually contracted. The front end of the secondary section flow passage 17 is the same as the primary section flow passage 16, the rear end of the secondary section flow passage 17 is the same as the tertiary section flow passage 18, and the secondary section flow passage 17 is also in smooth transition connection with the tertiary section flow passage 18.

Referring to fig. 7 and 8, the first-stage cross-section flow channel 16 is disposed on the insulating support base 20, the second-stage cross-section flow channel 17 and the third-stage cross-section flow channel 18 are disposed on the head main body, the insulating support base 20 is provided with a groove 33, and the head main body is provided with a protrusion which can be correspondingly inserted into the groove 33. Referring to fig. 8, etc., an isolation pad 29 is partially or completely disposed at a boundary area between the main body of the showerhead and the insulating support base 20, and specifically, the isolation pad 29 is disposed at a boundary area between the groove 33 and the first-stage cross-sectional flow channel 16. The insulating support base 20 is made of Polyamide (PA), Polymethacrylate (PMMA), Polyformaldehyde (POM), Polyurethane (PU) or Polycarbonate (PC), and the insulating support base 20 can be tightly embedded with the narrow-slit type nozzle body to play a role in supporting and insulating. The isolation cushion block 29 is made of polytetrafluoroethylene, polyformaldehyde, phenolic resin, polyarylate, polyethylene, polypropylene, poly-p-phenylene terephthalamide or polyarylate, the length is 0.5-2 m, the width is 5-20 cm, and the thickness is 1-3 cm, so that the effect of isolating the narrow-slit spinning nozzle from the embedded base in a static manner is achieved, the static charge is effectively prevented from being transferred and accumulated, and the safe and stable operation of the spinning process is ensured.

Referring to fig. 5 again, the metal electrode 19 is disposed on the liquid outlet along the line of the three-stage cross-section flow channel 18 and is convex, and the arrangement manner of the metal electrode can be as shown in fig. 10, that is, the shape of the metal electrode 19 can be one or more combinations of a cone, a cylinder, a prism, a pyramid and a frustum of a pyramid, the distribution density is 1-2/cm, and the material is one or more combinations of iron alloy, cobalt alloy, nickel alloy, copper alloy, aluminum alloy, platinum alloy and iridium alloy. The arrangement of the metal electrodes 19 may be specifically oriented in an axial direction perpendicular to the tertiary cross-sectional flow channel 18.

Referring again to fig. 5, the inlet end of the primary cross-sectional flow channel 16 is further provided with a screen 30. Specifically, the screen 30 is a metal screen 30 woven by brass wires, the screen 30 has 400 meshes, the diameter of the wire is 0.03mm, and the diameter of the wire is 0.035mm, so that the effects of isolating impurities and removing bubbles in the spinning solution are achieved. The length of the first-stage section flow channel 16 is 1-10 cm, the width of the first-stage section flow channel is 10-20 cm, the length of the third-stage section flow channel 18 is 10-40 cm, and the width of the third-stage section flow channel is 1-5 mm.

Referring to fig. 5 again, a conveyer belt 21 is disposed under the spinning nozzle and opposite to the tertiary section flow passage 18 for receiving and conveying the spun fibers fed from the tertiary section flow passage 18. Furthermore, a microwave heating unit is arranged right below the conveyor belt 21, and the vertical distance between the heating part of the microwave heating unit and the conveyor belt 21 is less than 50 cm. The microwave heating unit may include a first microwave generator 22, a waveguide connector 23, and a heater sequentially connected theretoAnd a heater 24 disposed below the conveyor belt 21 at a vertical distance of less than 50cm from the conveyor belt, wherein the first microwave generator 22 receives power from a power source to generate microwaves, and then transmits the microwaves to the heater 24 through the waveguide connector 23, thereby drying the received nanofibers. The conveyer belt 21 is also provided with hollow meshes. The shape of the hollow meshes on the surface of the conveying belt 21 is one or a combination of more of a circle, an ellipse, a square, a rectangle, a triangle, other polygons and irregular patterns, and the arrangement density is 50-200/m². In addition, the conveyor belt 21 is also subjected to grounding treatment.

Referring to fig. 12 and the like, the analysis assembly includes an analysis chamber 44, and a spraying unit and a negative pressure suction unit located in the analysis chamber 44, wherein the spraying unit is located above the negative pressure suction unit, and the ceramic nanofibers, after entering the analysis chamber 44, pass through between the spraying unit and the negative pressure suction unit, and are soaked with the analysis liquid sprayed by the spraying unit;

the solvent gradient displacement assembly comprises a displacement cabin positioned behind the analysis cabin 44, and an alcohol-water bath 50, a displacement bath 51 and an alcohol bath 52 which are sequentially arranged in the displacement cabin along the advancing direction of the ceramic nano fibers;

the drying component comprises a drying cabin 55 positioned behind the replacing cabin and a drying unit which is arranged in the drying cabin 55 and used for heating and drying the passing ceramic nano-fiber;

the atmosphere-changing calcining assembly comprises a pre-sintering cabin 60, a sintering cabin 61, a constant temperature cabin 62 and a cooling cabin 63 which are positioned behind the drying cabin 55 and are sequentially arranged along the advancing direction of the ceramic nano fibers and are mutually independent, wherein the pre-sintering cabin 60, the sintering cabin 61, the constant temperature cabin 62 and the cooling cabin 63 are respectively connected with external oxygen supply equipment and/or inert gas supply equipment through independent pipelines.

Referring to fig. 13 again, the spraying unit includes a spraying head 41 disposed in the analysis chamber 44, and a second liquid storage tank 39, a liquid pump 38 and an analysis liquid tank 37 sequentially connected to the spraying head 41, the second liquid storage tank 39 is further connected to the ultrasonic generator 36, and a transducer 40 is further disposed between the second liquid storage tank 39 and the spraying head 41.

Referring to fig. 13 and the like again, the negative pressure suction unit includes a hollow tray 43 disposed in the analysis chamber 44 and located below the conveyor belt for conveying the ceramic nanofibers, and a negative pressure suction pump 42 connected to the hollow tray 43 through a suction pipe, wherein a plane of the hollow tray 43 is parallel to a plane of the conveyor belt. In addition, the shape of the hollow on the hollow tray 43 is one or a combination of a circle, a triangle, a quadrangle, a polygon and other irregular figures, and the hollow area of the tray accounts for 60-90% of the whole area.

The analysis solution is an alcoholic solution of alkali, the concentration of the alcoholic solution can be 0.1-5 mol/L, specifically, the alkali can be sodium hydroxide or potassium hydroxide, and the alcoholic solvent can be one or a combination of ethanol, propanol, n-butanol or tert-butanol. Preferably, the vacuum degree in the analysis cabin 44 is-0.098 to-0.01 MPa, the temperature is controlled at 60 to 100 ℃, and the analysis can be realized by heating with resistance wires.

Referring again to fig. 14, the alcohol-water bath 50 is further connected to an alcohol-water bath preparation tank 47 for supplying an alcohol-water mixed solution, the substitution bath 51 is further connected to a substitution bath preparation tank 48 for supplying a substitution solvent, and the alcohol bath 52 is further connected to an alcohol bath preparation tank 49 for supplying an alcohol solvent.

The temperature of the alcohol-water mixed solution in the alcohol-water bath 50 is 10-30 ℃, the temperature of the replacement solvent in the replacement bath 51 is 60-80 ℃, and the temperature of the alcohol solvent in the alcohol bath 52 is 10-30 ℃. More preferably, the alcohol-water mixed solution is prepared from alcohol and water, and specifically can be composed of 95 wt% alcohol and 5 wt% water, wherein the alcohol can be one or more of ethanol, propanol, n-butanol and tert-butanol. More preferably, the displacement solvent may be one or a combination of more of carbon tetrachloride, benzene, toluene, dichloroethane, dichloromethane, chloroform, diethyl ether, diphenyl ether, ethyl acetate, acetone, tetrahydrofuran, N-methylpyrrolidone, N-dimethylformamide. More preferably, the alcohol solvent can be one or more of ethanol, propanol, n-butanol and tert-butanol.

Referring again to fig. 12, the drying unit includes an infrared heating unit 57 located in the drying chamber 55, and a vacuum generating device connected to the drying chamber 55 through a pipe, and the drying chamber 55 is a substantially sealed chamber. Here, the infrared heating unit 57 may be an infrared heating pipe, and the power thereof may range from 300W to 3500W. Preferably, the working temperature in the drying chamber 55 is 60-80 ℃, and the vacuum degree is-0.1-0.098 MPa.

Referring to fig. 15 again, the pre-sintering chamber 60 and the cooling chamber 63 are connected to an oxygen supply device (which may be an oxygen cylinder 58) through gas pipes, and the sintering chamber 61 and the constant temperature chamber 62 are connected to an oxygen supply device and an inert gas supply device (which may be an inert gas cylinder 59) through gas pipes.

Referring to fig. 15 again, the pre-sintering chamber 60, the sintering chamber 61, the constant temperature chamber 62 and the cooling chamber 63 are respectively connected to an external second microwave generator 64 through waveguides; and (3) ionizing the gas by utilizing microwave to form plasma, and then heating the gel ceramic nanofiber membrane by the plasma to obtain the compact nanofiber membrane. The working atmosphere of the pre-sintering chamber 60 and the cooling chamber 63 is oxygen atmosphere, and the working atmosphere of the sintering chamber 61 and the constant temperature chamber 62 is oxygen and inert gas mixed atmosphere, and is generally controlled in the oxygen gas content of 80-95% and the inert gas content of 5-20% (both volume fraction). The inert gas may include one or more combinations of nitrogen, helium, neon, argon, and the like. The working temperature in the pre-sintering cabin 60 is set to be 100-150 ℃, the working temperature of the sintering cabin 61 is set to be 200-500 ℃, the working temperature of the constant-temperature cabin 62 is set to be 200-500 ℃, and the working temperature of the cooling cabin 63 is set to be 60-80 ℃. In addition, during specific work, according to actual conditions, the gel nanofiber membrane can keep differential drafting and proper tension compensation in the whole process from the moment when the gel nanofiber membrane does not enter the pre-burning cabin 60 to the moment when the gel nanofiber membrane leaves the cooling cabin 63, wherein the differential speed between the inlet and the outlet of the pre-burning cabin 60 is 20%, the differential speed between the inlet and the outlet of the sintering cabin 61 is 30%, the differential speed between the inlet and the outlet of the constant temperature cabin 62 is 30%, and the differential speed between the inlet and the outlet of the cooling cabin 63 is 5%. The above can be routinely adjusted empirically.

The specific process for continuously manufacturing the flexible ceramic nanofibers in a large scale by using the device of the embodiment comprises the following steps:

firstly, sequentially weighing inorganic precursor, polydentate ligand and solvent and adding the inorganic precursor, the polydentate ligand and the solvent into a feeding kettle 1, wherein the weights of the three raw materials are measured by a feeding cavity 2, and the bottom of the feeding cavity 2 is provided with a weighing sensorAnd the device 4 realizes accurate weighing of the added raw materials. After all the raw materials are added into the feeding kettle 1, the sealing valve 3 is closed, water bath heating is carried out again, and the mixture is fully stirred for 12 hours, so that a homogeneous transparent inorganic precursor solution modified by the polydentate ligand can be obtained (the number of functional groups with reaction activity on the average single inorganic precursor is limited to 2). Then, dry high-purity nitrogen is input into the core reaction kettle 6 by utilizing the high-purity dry gas inlet assembly 8, original gas in the core reaction kettle 6 is discharged, the high-purity dry gas inlet assembly 8 is closed after the operation is repeated for 3 times in a circulating mode, the dry and clean environment of the core reaction kettle 6 is ensured, and particularly the influence of moisture on subsequent reaction is avoided. Subsequently, the inorganic precursor solution in the feed tank 1 is transferred to the core reaction tank 6 by using the feed extraction line 5, and the solution is vigorously stirred under the combined action of the central shaft 10 and the stirring roller 11 and the heating of the water bath. The cold and wet gas transmission assembly 9 is opened, cold and wet gas (the water vapor content is 5 wt%, the temperature of the cold and wet gas is 15 ℃) is transmitted into the central shaft 10 through the gas transmission pipeline, and the cold and wet gas passes through the holes on the stirring roller 11 (the shape of the hollow holes on the surface of the stirring roller 11 is circular, and the arrangement density of the circular holes is 1/cm) because the central shaft 10 and the three layers of stirring rollers 11 are in hollow connection (the materials of the stirring rollers 11 and the central shaft 10 are both carbon steel, and the included acute angle between the stirring rollers 11 and the central shaft 10 is 60 ℃)²) And gradually released. In addition, the three layers of stirring rollers 11 keep differential speed reverse stirring, the layer 3 stirring rollers 11 closest to the stirring motor 12 at the top of the core stirring kettle rotate clockwise (100r/min), the middle layer 3 stirring rollers 11 rotate anticlockwise (25r/min), and the layer 3 stirring rollers 11 closest to the tapping hole at the bottom of the core stirring kettle rotate clockwise (100 r/min). In the process, raw material liquid water necessary for hydrolysis reaction is slowly and uniformly released in a solution system of the core reaction kettle 6 in a moisture mode, so that the phenomenon of gelation caused by the fact that the local reaction of the solution is too fast due to the mode of directly adding the liquid water is avoided, and the high efficiency and stability of the sol preparation process are ensured. Finally, the prepolymer solution hydrolyzed for 4 hours in the core reaction kettle 6 is subjected to reduced pressure distillation (the heating temperature is set to be 60 ℃, the vacuum degree is set to be-0.08 MPa) by using the first negative air pressure suction component 7, the induction probe 13 of the real-time temperature and viscosity monitoring device is placed in the solution in the kettle, and the sensor 14 receives the solutionAnd information is transmitted to a control panel 15, the viscosity of the system is gradually increased along with the extension of the reduced pressure distillation time, the viscosity displayed by the control panel 15 is increased to 90 mPa.S, namely, the first negative air pressure suction component 7 is automatically closed and the heating is stopped, and the linear inorganic polymer sol spinning solution is obtained after the temperature of the spinning solution is cooled, wherein the conductivity of the spinning solution is 450 mu.S/cm, the surface tension is 30mN/m, the branching degree is lower than 0.05, and the polymerization degree is 120. The process utilizes a negative pressure suction mode to quickly concentrate the solution in the core reaction kettle 6 in a short time, so that the polymerization degree of the sol is improved, the linear structure is kept, and the sol can be stably spun for a long time.

The linear inorganic polymer sol obtained from the mass preparation device of the sol spinning solution is transported to a first liquid storage tank 31 in the electrostatic spinning device of the linear inorganic polymer sol through a coaxial liquid transport pipe 68, and is pumped to a liquid inlet at the bottom of the insulating support base 20 through a liquid supply pump 32, impurities and bubbles in the spinning solution are removed through a screen 30, the spinning solution flows into a primary section channel along with the primary section channel, the spinning solution enters a secondary section channel on a narrow slit spinning nozzle (namely a nozzle main body) after the channel solution is filled, the solution flows into a tertiary section channel after the secondary section channel is filled, and finally the solution flows to a protruded metal electrode 19 after the tertiary section channel is filled. The solution overflowing the electrodes is wiped clean, and the solution feed rate is adjusted by the solution feed pump 32 so that the solution reaches the state of about to flow out without falling onto the conveyor belt 21 of the receiving device below. Meanwhile, the side wall openings 28 of the side wall 27 of the spinning nozzle main body of the secondary section flow passage 17 and the tertiary section flow passage 18 of the narrow slit type spinning nozzle are externally connected with cold air, and the temperature range of the cold air is-10-15 ℃. One end of the lead is connected with a binding post 26, the other end of the lead is connected with a high-voltage power supply 25, under the action of a high-voltage electrostatic field, the solution at the electrode tip forms a Taylor cone, and when the solution is subjected to electrostatic force to exceed the surface tension, the surface of the Taylor cone sprays out of the flow at high speed. These jets undergo the drawing by the force of an electric field, solvent evaporation and solidification, and are finally deposited on the conveyor belt 21. The receiving device is provided with a microwave drying device which receives power from a first microwave generator 22 to generate microwaves, and then transmits the microwaves to a heater 24 through a waveguide connector 23, wherein the heater 24 is at a vertical distance of less than 50cm from the conveyor belt 21. The fibers deposited on the conveying belt 21 are dried in time through the conversion of microwave heat, and the influence of air humidity on the obtained fibers is prevented. Here, the linear inorganic polymer sol spinning solution was selected for electrospinning, and compared with the change trend of the viscosity of the linear inorganic polymer sol spinning solution at high temperature (35 ℃) and at low temperature (-2 ℃) when gas was introduced, as shown in fig. 11, it was found that the change of the sol viscosity at low temperature (-2 ℃) was slowed down, the viscosity transition region was significantly extended, and the gel time was extended as a whole. This is because temperature is a macroscopic indicator of the average kinetic energy of the molecule, i.e. the lower the temperature, the slower the molecular motion speed. The lower the temperature of the reaction system, the slower the various reactions proceed, macroscopically appearing as the slower the change in viscosity of the sol, under otherwise identical conditions.

Ceramic gel nanofibers obtained by subjecting linear inorganic polymer sol to an electrostatic spinning device enter a ceramic nanofiber low-temperature calcination forming device through a tension roller 69, a resolving solution is an ethanol solution of sodium hydroxide, the concentration is 2mol/L, the aperture of a circular spray hole in the surface of the spray header 41 is 4mm, and the distribution density is 32 cm²The negative pressure suction pump 42 is connected with the hollowed-out tray 43, the hollowed-out shape on the hollowed-out tray 43 is circular, the hollowed-out area accounts for 70% of the whole area, and the vacuum degree in the analysis cabin 44 is-0.075 MPa. 95 wt% ethanol and 5 wt% water are filled in the alcohol water bath preparation kettle 47, N-dimethylformamide is filled in the replacement bath preparation kettle 48, and ethanol with the mass fraction higher than 99 wt% is filled in the alcohol bath preparation kettle 49. The resolving device is heated by a resistance wire, and the temperature is 60 ℃; the solution temperature of the alcohol water bath preparation kettle 47 is 30 ℃, the solution temperature of the replacement bath preparation kettle 48 is 60 ℃, and the solution temperature of the alcohol bath preparation kettle 49 is 30 ℃. The decompression drying device utilizes a quartz glass infrared heating unit 57 (namely an infrared heating pipe) to dry the gel nanofiber membrane subjected to solvent gradient displacement to complete pre-shrinkage treatment, the power range of the heating pipe is 300W-3500W, the vacuum degree in the decompression drying process is set to be-0.1 MPa to-0.098 MPa, and the temperature is set to be 60-80 ℃. The second microwave generator 64 generates high power microwave energy using an electrovacuum device includingThe fiber film sequentially passes through a pre-sintering cabin 60, a sintering cabin 61, a constant temperature cabin 62 and a cooling cabin 63; the temperature setting range of the pre-burning cabin 60 is 100-150 ℃, the temperature setting range of the sintering cabin 61 is 200-500 ℃, the temperature setting range of the constant temperature cabin 62 is 200-500 ℃, and the temperature setting range of the cooling cabin 63 is 60-80 ℃; controlling the oxygen gas content to be 80-95% and the inert gas content to be 5-20% in the gas atmosphere in the sintering chamber 61 and the constant-temperature chamber 62; the gas contained in the inert gas bottle 59 includes nitrogen, helium, neon, or argon. The gel nanofiber membrane keeps differential drafting and proper tension compensation in the whole process from entering the pre-sintering chamber 60 to leaving the cooling chamber 63, wherein the differential speed between the inlet and the outlet of the pre-sintering chamber 60 is 20%, the differential speed between the inlet and the outlet of the sintering chamber 61 is 30%, the differential speed between the inlet and the outlet of the constant temperature chamber 62 is 30%, and the differential speed between the inlet and the outlet of the cooling chamber 63 is 5%; the analysis assembly, the solvent gradient displacement assembly, the decompression drying assembly and the variable-atmosphere microwave calcining assembly are all provided with a heat-insulating layer and a heat-insulating shell so as to maintain the temperature environment of the whole cabin body to be stable.

In addition, as the flowing state of the spinning solution in the flow channel can bring great influence to the total charge amount carried by the spinning solution, and the velocity distribution rules of the laminar flow and the turbulent flow in the pipeline have obvious difference, as shown in fig. 4, when the laminar flow is in a 34 state, the velocity distribution curve is in a parabola shape, and when the turbulent flow is in a 35 state, a larger velocity gradient is arranged in the pipeline close to the pipe wall; when the electrification quantity of the spinning solution is larger, the electrostatic breakdown phenomenon can be more easily generated, a liquid supply system and related spinning equipment are damaged, and the electrostatic spinning device provided by the embodiment can avoid the flowing disorder of the spinning solution, so that the spinning solution moves in a laminar flow mode, the electrification quantity of the spinning solution is reduced, and the safety and stability of the electrostatic spinning process are ensured. Specifically, when the electrostatic spinning device for the large-scale flexible ceramic nanofiber is adopted, a linear inorganic polymer sol spinning solution is selected for electrostatic spinning, and compared with the spinning device without the gradually-changed shrinkage section, the spinning device without the gradually-changed shrinkage section has the defects that liquid is discharged out of the spinning device and is disordered under the same condition, so that the spinning process is unstable, and the fiber thickness is uneven. Reflecting that the solution in the spinning device without the gradually-changed shrinkage section flows in a turbulent flow state, and the quantity of the electric charges accumulated in the flowing state is detected by a multimeter to be 10-30% higher than that of the spinning device. The reason is that the spinning device of the comparative example is not a tapered section, when the section area changes suddenly, because the turning point cannot be arranged on the flow line, the formed flow is contracted, local separation and defluidization occur after the section changes suddenly, and then the flow is attached to the wall, in the contraction flow channel, the fluid not only has accelerated contraction flow but also has decelerated diffusion flow, and both the accelerated contraction flow and the decelerated diffusion flow generate resistance, namely turbulent flow is easily formed.

To sum up, the flexible ceramic nanofiber large-scale continuous manufacturing device can complete continuous integration work such as batch preparation of inorganic polymer sol spinning solution without adding high-molecular polymer, rapid electrostatic spinning fiber formation of spinnable sol and low-temperature calcination molding of gel nanofiber, and can realize ceramic nanofibers (such as SiO) with excellent mechanical properties₂、TiO₂、Al₂O₃、ZrO₂、ZnO、SnO₂、Fe₂O₃、MgO、Y₂O₃、Co₃O₄、CaO、V₂O₅、Cr₂O₃、NiO、CuO、MnO₂Etc.) has great advantages in simple, rapid, efficient, low-cost, low-pollution, and large-scale continuous manufacturing.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (10)

1. A flexible ceramic nanofiber large-scale continuous manufacturing device is characterized by comprising the following components:

a sol spinning solution preparation mechanism;

an electrostatic spinning mechanism: the first liquid storage tank is connected with a spinning solution outlet of the sol spinning solution preparation mechanism, and the electrostatic spinning nozzle is connected with the first liquid storage tank and used for outputting spinning fibers;

the fiber calcining and forming mechanism comprises: the device comprises an analysis component, a solvent gradient displacement component, a drying component and a variable atmosphere calcining component which are sequentially arranged along the processing advancing direction of spinning fibers.

2. The large-scale continuous manufacturing device for the flexible ceramic nano fibers according to claim 1, wherein the sol spinning solution preparation mechanism comprises a feeding kettle, a core reaction kettle, a stirring component, a high-purity dry gas inlet component, a cold moisture transmission component and a first negative pressure suction component, wherein the core reaction kettle is connected with the feeding kettle through a feeding suction pipeline, the stirring component is arranged inside the core reaction kettle, and the high-purity dry gas inlet component, the cold moisture transmission component and the first negative pressure suction component are respectively connected with the core reaction kettle.

3. The large-scale continuous manufacturing device for the flexible ceramic nanofibers according to claim 2, wherein the stirring assembly comprises a stirring motor, a central shaft connected with the stirring motor and located in the core reaction kettle, and a plurality of layers of stirring rollers mounted on the central shaft and rotating along with the central shaft, hollow cavities with communicated interiors are formed between the central shaft and the stirring rollers, hollow holes communicated with the hollow cavities are processed in the stirring rollers, and the cold and wet gas transmission assembly extends into the core reaction kettle from the bottom and is connected with the bottom of the hollow cavities.

4. The device for continuously manufacturing the flexible ceramic nano fibers in a large scale according to claim 1, wherein the electrostatic spinning nozzle comprises a nozzle body and an insulating support base, the middle area of the nozzle body and the insulating support base is partially hollowed to form a spinning flow channel penetrating through the nozzle body and the insulating support base, the spinning flow channel consists of a primary section flow channel, a secondary section flow channel and a tertiary section flow channel which are sequentially connected along the flowing direction of a spinning solution, the width of the primary section flow channel is larger than that of the tertiary section flow channel, a plurality of convex metal electrodes are further arranged on a liquid outlet along the tertiary section flow channel, and a binding post connected with an external high-voltage power supply is further arranged on the nozzle body.

5. The device for large-scale continuous production of the flexible ceramic nanofibers according to claim 4, wherein the nozzle body is further provided with cooling holes surrounding the secondary section flow channel and the tertiary section flow channel, and a cooling fluid is introduced into the cooling holes.

6. The large-scale continuous manufacturing device for the flexible ceramic nanofibers according to claim 4, wherein the axial section of the secondary section flow channel is of a conical structure, two side edges of the conical structure are 1/4 circular arcs which are symmetrically arranged, the size of the front end of the secondary section flow channel is the same as that of the primary section flow channel, the size of the rear end of the secondary section flow channel is the same as that of the tertiary section flow channel, and the secondary section flow channel is further in smooth transition connection with the tertiary section flow channel.

7. The large-scale continuous manufacturing device for the flexible ceramic nanofibers according to claim 1, wherein a conveyer belt for receiving and conveying the spun fibers sent out from the three-stage section flow channel is further arranged at a position right opposite to the three-stage section flow channel below the spinning nozzle;

and a microwave heating unit is arranged under the conveying belt, and the vertical distance between a heating part of the microwave heating unit and the conveying belt is less than 50 cm.

8. The large-scale continuous manufacturing device for the flexible ceramic nanofibers according to claim 1, wherein the desorption assembly comprises a desorption cabin, and a spraying unit and a negative pressure suction unit which are positioned in the desorption cabin, wherein the spraying unit is positioned above the negative pressure suction unit, and the ceramic nanofibers penetrate through the space between the spraying unit and the negative pressure suction unit after entering the desorption cabin and are soaked with the desorption liquid sprayed by the spraying unit;

the solvent gradient displacement assembly comprises a displacement cabin positioned behind the analysis cabin, and an alcohol-water bath, a displacement bath and an alcohol bath which are sequentially arranged in the displacement cabin along the advancing direction of the ceramic nano fibers;

the drying component comprises a drying cabin positioned behind the replacing cabin and a drying unit which is arranged in the drying cabin and used for heating and drying the ceramic nano-fibers;

the atmosphere-variable calcining component comprises a pre-sintering cabin, a constant temperature cabin and a cooling cabin which are arranged behind the drying cabin and are sequentially arranged along the advancing direction of the ceramic nano fibers and are mutually independent, and the pre-sintering cabin, the constant temperature cabin and the cooling cabin are respectively connected with external oxygen supply equipment and/or inert gas supply equipment through independent pipelines.

9. The large-scale continuous manufacturing device for the flexible ceramic nano fibers according to claim 8, wherein the spraying unit comprises a spraying head arranged in the analysis cabin, and a second liquid storage tank, a liquid pump and an analysis liquid tank which are sequentially connected with the spraying head, the second liquid storage tank is further connected with an ultrasonic generator, and an energy converter is further arranged between the second liquid storage tank and the spraying head;

the negative pressure suction unit comprises a hollow tray arranged in the analysis cabin and positioned below the conveyor belt for conveying the ceramic nanofibers, and a negative pressure suction pump connected with the hollow tray through a suction pipeline, wherein the plane of the hollow tray is just parallel to the plane of the conveyor belt.

10. The large-scale continuous manufacturing device for the flexible ceramic nanofibers according to claim 8, wherein the pre-sintering chamber, the constant temperature chamber and the cooling chamber are respectively connected with an external microwave generator through waveguides;

the working atmosphere of the pre-sintering cabin and the cooling cabin is oxygen atmosphere, and the working atmosphere of the sintering cabin and the constant temperature cabin is mixed atmosphere of oxygen and inert gas;

the working temperature in the pre-sintering chamber is set to be 100-150 ℃, the working temperature in the sintering chamber is set to be 200-500 ℃, the working temperature in the constant-temperature chamber is set to be 200-500 ℃, and the working temperature in the cooling chamber is set to be 60-80 ℃.

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