CN114850422B - Method for preparing metal micro-nano fibers through centrifugal melt electrostatic spinning - Google Patents

Abstract

The invention belongs to the field of electrospinning, and in particular relates to a novel method for preparing metal micro-nano fibers by centrifugal melt electrospinning. The method comprises the following steps: 1) putting a certain quality of pure metal block into the customized crucible, covering the end cover, installing the thermocouple, starting the power supply of the integrated console, turning on the electromagnetic induction coil heating switch, and heating the customized crucible, Until the metal block is completely melted; 2) Start the high-voltage power supply and high-speed motor, and drive the customized crucible to rotate through the action of the rotating shaft to provide centrifugal force. The metal melt inside the customized crucible passes through the porous nozzle in the form of fibers under the double action of centrifugal force and high-voltage electrostatic force Evenly falling onto the collecting plate, long metal fibers with many advantages such as small fiber diameter and wide application range are obtained. The method of the invention is simple and convenient to prepare metal fibers, has low production cost and high spinning efficiency, and can produce thinner and longer micro-nano metal fibers.

Description

A method for preparing metal micro-nano fibers by centrifugal melt electrospinning

technical field

The invention relates to a method for preparing metal micro-nano fibers by using a centrifugal melt electrospinning process, and belongs to the field of electrospinning.

Background technique

The micro-nano metal fiber mat prepared by electrospinning has a porous structure, and a large number of interconnected pores inside it can make the sound wave diffuse and consume inside the material, and its high specific surface area is conducive to the collision consumption between the middle and low frequency sound waves and the fiber surface. Therefore, the micro-nano metal fibers prepared by electrospinning have significant advantages in absorbing middle and low frequency sound waves. In addition, metal fiber also has many advantages such as good mechanical strength, high temperature resistance, impact resistance, etc., and has a wider range of applications. Metal fibers with fiber diameters of micronano scale can absorb and reduce noise in various extreme environments. It is an inevitable trend in the future to develop light-weight and durable metal fiber-based sound-absorbing materials.

At present, the preparation of metal fibers mainly includes drawing method, cutting method, grinding method and plating metal sintering method. Among them, although the fiber prepared by the drawing method has a smooth surface and precise size, the production efficiency is low, the mold cost is high, the price is expensive, and the fiber diameter is large. Although the cutting method is simple, the production cycle is short, and the cost is low, it is difficult to obtain fibers with uniform and smooth cross-sections, and is mainly used to produce short metal fibers. The grinding method can prepare metal short fibers with the required diameter, but the fiber diameter is seriously affected by various factors, such as the coarser the abrasive particle size, the thicker the diameter of the prepared metal fiber. However, the preparation of metal fibers by plating metal sintering method has the problems of large investment and high process cost. These methods of preparing metal fibers all have their own shortcomings.

Zhang Shuling and others prepared titanium-based metal fibers with a diameter of 20-50 μm by melt drawing method. This type of fiber has a uniform diameter, smooth surface, and a maximum length of 20 cm. It has an amorphous structure, good thermal stability, and excellent mechanical properties, but its disadvantages are that the preparation process is relatively complicated and the cost is relatively high. Xu Peimin and others used the electroplating method to deposit an iron-coated layer on the surface of 316L stainless steel wire, and prepared 12 μm stainless steel fiber through the processes of pipe threading, drawing, annealing, and electrolysis. However, the surface quality of the fiber is poor, there are obvious precipitates and grooves, and the fiber breaking strength and elongation are small. At this time, it is necessary to anneal the electroplated wire and use a continuous annealing furnace with a water cooling device for annealing. to improve.

Various methods currently used to prepare metal fibers have problems such as low production efficiency, high cost, large diameter and insufficient length of produced fibers, etc. In order to solve the above problems, the present invention is proposed. The electrospinning process can not only efficiently prepare micro-nano metal fibers, but also produce long fibers. Compared with short fibers produced by mechanical force or gas pressure spinning and cutting methods, the long fibers have a more complex entanglement structure , the complex entanglement makes the gap structure between the fibers more diverse, which can realize the effective absorption of sound waves of different wavelengths; compared with the electrospinning process, the electrospinning process does not require complex physical and chemical treatments, and the process is simpler and less costly. Relatively lower. At the same time, the fiber produced by electrospinning has the advantage of small fiber diameter (the diameter of melt electrospun fiber is generally several hundred nanometers to several microns), and the finer fiber can effectively absorb long-wavelength low-frequency sound waves that are difficult to eliminate , so the study of electrospinning technology suitable for spinning micro-nano metal fibers to prepare sound-absorbing materials has great application prospects.

Contents of the invention

In order to produce long metal fibers with more advantages such as small fiber diameter and wide application range, and reduce production costs, the present invention proposes a method for preparing metal micro-nano fibers by centrifugal melt electrospinning.

The method uses a novel centrifugal melt electrospinning device to prepare metal micro-nano fibers, which includes a spinning system, an electromagnetic heating system, a collection system, a transmission system, a frame and a high-voltage power supply, wherein the spinning system consists of a custom-made crucible, Composed of insulation sleeve, end cap and porous nozzle, the customized crucible is made of graphite as the main material, which not only has good electromagnetic induction ability, but also has a smooth inner wall, so that the molten metal liquid inside is not easy to leak and adhere to the inner wall of the crucible , so that the metal liquid has good fluidity and castability. At the same time, the corrosion resistance of the graphite crucible is excellent. For the metal residue that may exist after spinning, it can be cleaned with nitric acid or hydrochloric acid and lightly ground with fine sand, which is very convenient and convenient. It will damage the crucible; the insulation sleeve is used to prevent the wall of the customized crucible from dissipating heat too quickly, thereby reducing the temperature difference between various parts of the crucible and avoiding affecting the spinning process of the porous nozzle; an observation port is opened on the end cover to view the metal block inside the customized crucible According to the melting situation, a small hole is opened in the middle of the end cover to allow the K-type thermocouple to pass through and extend into the metal melt. At the same time, the existence of the end cover can reduce the heat loss, thereby reducing the gap between the upper part and the bottom of the customized crucible. temperature difference; the bottom of the customized crucible is provided with a boss and a hole is opened, and is connected to the rotating shaft through a threaded joint. A hole is opened on the side of the custom-made crucible at 3/5 height for melt flow, and the capacity of the raw material is increased while ensuring that the rotation speed can be adjusted in a wide range, and it is connected to the multi-hole nozzle through a threaded connection In order to realize spinning; the multi-hole nozzle is composed of four parts: upper module, lower module, positioning ring and fixed end cap. The top of the upper module is processed into a threaded form and connected with the customized crucible. The upper and lower modules are combined to form a flow channel. The diameter of the main channel is From thin to thick, the shunt position is set as an arc-shaped protrusion, thereby reducing the impact pressure of the metal melt on each part. The multi-hole nozzle uses the positioning ring to locate the position of each part, and then uses 12 set screws to connect with the other three parts through the fixed end cover to fix the whole. All parts of the nozzle are made of stainless steel, which has the advantages of not being easy to accumulate material and impurities, and is convenient to disassemble and replace at any time. The electromagnetic heating system is composed of electromagnetic induction coil, K-type thermocouple and integrated console. Among them, the electromagnetic induction coil is connected to the bracket through threads, and the bracket is fixed on the frame through screws. The K-type thermocouple is directly inserted into the metal melt in the customized crucible for real-time temperature monitoring and feedback to the integrated console. Through the display and recording of the instrument, it is convenient to control the heating of the electromagnetic induction coil according to the real-time temperature, and realize the heating and temperature control of the metal melt in the customized crucible. The K-type thermocouple is equipped with a metal protection tube outside, which is convenient for maintenance and replacement, and can play a fixed role and avoid high-temperature metal melt bonding to ensure that the thermocouple is not damaged by high-temperature metal melt. The collection system is composed of a collection plate and an alumina partition, and the connection between the collection plate and the alumina partition, and the alumina partition and the frame are respectively fixed by screws. The alumina partition does not have electrical conductivity and has a high melting point. While being able to well support and fix the collecting plate, it will not be damaged by the splashing of molten metal. The transmission system consists of a high-speed motor and a rotating shaft. The high-speed motor is fixed on the ground and placed perpendicular to the frame. The speed is 0-3000r/min. The integrated console controls the start and adjusts the working frequency, and drives the customized crucible by driving the rotation of the rotating shaft. Rotate to provide centrifugal force for spinning. The rotating shaft is connected with the custom-made crucible through threaded joints and fixed on the frame through bearings. The frame supports the entire device and is grounded for protection. The positive pole of the high-voltage power supply is connected to the collecting plate, and the negative pole is grounded, thereby forming a high-voltage electrostatic field between the customized crucible and the collecting plate to realize electrospinning. The entire centrifugal melt electrospinning device is placed horizontally, and the rotating shaft is respectively connected to the custom-made crucible and the frame. The three have good electrical conductivity and are protected by the frame grounding. There is a certain distance between the porous nozzle and the collecting plate, and the control voltage is within a certain range to ensure that there will be no breakdown and short circuit between the two, which will affect the spinning process.

The present invention adopts following steps to prepare superfine metal fiber:

Step 1: Put a certain quality of pure metal block into the custom-made crucible, cover the end cover, install and fix the K-type thermocouple;

Step 2: Start the power supply of the integrated console, turn on the electromagnetic induction heating switch, and heat the customized crucible through the electromagnetic induction coil;

Step 3: Observe through the observation port until the metal block is heated to completely melt and then keep it warm for a certain period of time;

Step 4: Start the high-voltage power supply and high-speed motor, the high-voltage power supply provides high-voltage electrostatic force, the high-speed motor sets a certain speed, and drives the customized crucible to rotate through the action of the rotating shaft to provide spinning centrifugal force;

Step 5: Under the double action of centrifugal force and high-voltage electrostatic force, the metal melt in the custom-made crucible falls evenly on the collecting plate in the form of fibers through the porous nozzle to obtain long metal fibers with many advantages such as small fiber diameter and wide application range.

Furthermore, the mass of the metal block in the step 1 is 10-50g.

Further, the heat preservation time in the step 3 is 10-30min.

Further, the speed range in step 4 is 1000r/min-2000r/min.

The beneficial effects of the present invention are:

(1) The customized crucible is made of graphite as the main material, which not only has good electromagnetic induction ability, electrical conductivity and corrosion resistance, but also has a smooth inner wall, which is not easy to adhere to the metal melt.

(2) The method of electromagnetic induction coil heating is non-contact heating, which has the advantages of high heating temperature, high heating efficiency, fast heating speed, and easy temperature control.

(3) The method of contact temperature measurement is adopted, and the K-type thermocouple directly contacts the metal melt, which can reflect the real temperature of the metal melt. At the same time, a metal protection tube is installed on the outside, which is convenient for maintenance and replacement, and the thermocouple is increased. It has the advantages of high measurement accuracy, wide measurement range, simple structure, convenient use and low price.

(4) The switch for controlling the heating of the electromagnetic induction coil, the switch for controlling the start-up and adjusting the speed of the high-speed motor, and the display instrument, recording instrument and electronic regulator used in conjunction with the K-type thermocouple are set on the integrated console, and the melt temperature It can be transmitted to the display instrument in real time, so that it is more convenient to realize the heating interruption of the electromagnetic induction coil, and ensure that the melt temperature is always within a certain range, which is conducive to the stable spinning process.

(5) Self-made multi-hole nozzle is used, which is composed of four parts: upper module, lower module, positioning ring and fixed end cover. The upper and lower modules are combined to form a flow channel. The diameter of the main channel is from thin to thick, and the diversion position is set to be arc-shaped. The protrusion can effectively reduce the impact pressure of the metal melt on each part. Each part of the nozzle is connected by set screws, which is convenient to disassemble and replace, and the material is stainless steel, which is not easy to accumulate material and adhere to impurities, and has a high melting point and good electrical conductivity. Thinner and longer metal fibers effectively improve spinning efficiency.

(6) The spinning device can freely change the spinning method. Not only can centrifugal melt electrospinning be realized, but also solution centrifugal electrospinning at room temperature can be performed when the temperature control device is not activated. When the high-voltage power supply is not turned on, Centrifugal spinning without electrostatic interaction is also possible.

(7) The method of the present invention prepares metal micro-nano fibers, which not only have high production efficiency and low cost, but also the prepared metal fibers are thinner and longer, and have more complex entanglement structures between long fibers, and complex entanglements make the fibers between The more diverse pore structure is conducive to the effective absorption of sound waves of different wavelengths, and the thinner fibers can effectively absorb low-frequency sound waves that are difficult to eliminate, which is of great significance for the preparation of sound-absorbing materials with excellent sound absorption and noise reduction performance.

Description of drawings:

Figure 1 is a schematic diagram of a device for preparing micro-nano metal fibers by centrifugal melt electrospinning. Fig. 2 is a schematic structural view of the porous nozzle, and Fig. 3 is a top view of the porous nozzle.

In the figure: 1-collection plate, 2-electromagnetic induction coil, 3-customized crucible, 4-insulation sleeve, 5-end cover, 6-metal protection tube, 7-K type thermocouple, 8-observation port, 9- Porous nozzle, 10-metal fiber, 11-high voltage power supply, 12-rotating shaft, 13-high-speed motor, 14-bracket, 15-frame, 16-alumina partition, 17-integrated console, 18-upper module, 19 -lower module, 20-locating ring, 21-fixed end cap.

The spinning system is composed of a custom-made crucible 3, an insulating sleeve 4, an end cap 5 and a porous nozzle 9. The porous nozzle 9 is composed of four parts: an upper module 18, a lower module 19, a positioning ring 20 and a fixed end cap 21. The electromagnetic heating system It is composed of electromagnetic induction coil 2, K-type thermocouple 7 and integrated console 17. The collection system is composed of collection plate 1 and alumina partition 16. The transmission system is composed of rotating shaft 12 and high-speed motor 13. The frame 15 is used to support the entire device, the bracket 14 is used to support the electromagnetic induction coil 2 .

Detailed ways

Example 1:

In the device as shown in Figure 1, add 30g metal block to the custom-made crucible 3, cover the end cover 5, install and fix the K-type thermocouple 7, then connect the power supply of the integrated console 17, and pair the custom-made crucible through the electromagnetic induction coil 2 The metal block in 3 is heated, and its temperature is monitored in real time through the K-type thermocouple 7, and the signal is fed back to the integrated console 17, and observed through the observation port on the end cover 5 until the pure metal block is completely melted into a melt Afterwards, keep warm for another 10 minutes, then start the high-voltage power supply 11 and high-speed motor 13, set the rotating speed to 1000r/min, drive the customized crucible 3 to rotate through the rotating shaft 12, and finally the metal melt passes through the customized crucible under the double action of centrifugal force and high-voltage electrostatic force. The porous spray nozzle 9 on the 3 falls evenly on the collecting plate 1 in the form of fibers, and the long metal fibers 10 with many advantages such as small fiber diameter and wide application range are obtained.

Matters not covered in the present invention are known technologies.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (5)

1. A method for preparing metal micro-nanofibers through centrifugal melt electrostatic spinning is characterized in that a centrifugal melt electrostatic spinning device is adopted to prepare the metal micro-nanofibers, the device comprises a spinning system, an electromagnetic heating system, a collecting system, a transmission system, a rack and a high-voltage power supply, wherein the spinning system consists of a customized crucible, a heat-insulating sleeve, an end cover and a porous nozzle, the customized crucible is made of graphite serving as a main material, the inner wall of the customized crucible is smooth, and metal residues possibly existing after spinning can be cleaned by nitric acid or hydrochloric acid and subjected to fine sand light grinding treatment; the heat-insulating sleeve is used for preventing the wall of the customized crucible from radiating too fast and reducing the temperature difference of each part of the customized crucible; the end cover is provided with an observation port for checking the melting condition of the metal block in the customized crucible, and the middle part of the end cover is provided with a small hole for enabling the K-type thermocouple to pass through and extend into the metal melt; the bottom of the customized crucible is provided with a boss and a hole, the customized crucible is connected with the rotating shaft through a threaded joint, the rising direction of the thread is the same as the rotating direction of the rotating shaft, and the customized crucible is ensured to be connected with the rotating shaft more and more firmly in the rotating process and cannot be thrown away; a hole for melt flowing is formed in the side face of the customized crucible at the position of 3/5 of the height, the capacity of raw materials is increased under the condition that the rotating speed can be adjusted in a large range, and the raw materials are connected with a multi-hole spray head in a threaded connection mode to realize spinning; the multi-hole spray head is composed of an upper module, a lower module, a locating ring and a fixed end cover, wherein the top end of the upper module is processed into a thread form and is connected with the customized crucible, the upper module and the lower module are combined to form a flow channel, the diameter of the main flow channel is from thin to thick, and the flow distribution position is provided with an arc-shaped bulge, so that the impact pressure of the metal melt on each part is reduced; the porous nozzle uses a positioning ring to position each part, and then 12 set screws are connected with other three parts through a fixed end cover to play a role in fixing the whole; all parts of the porous spray head are made of stainless steel, so that the porous spray head is convenient to disassemble and replace at any time; the electromagnetic heating system consists of an electromagnetic induction coil, a K-type thermocouple and a comprehensive console; the electromagnetic induction coil is connected with the support through threads, the support is fixed on the rack through screws, the K-type thermocouple directly extends into the metal melt in the customized crucible, real-time temperature monitoring is carried out on the metal melt, the metal melt is fed back to the comprehensive control console, and the metal melt is displayed and recorded through the instrument, so that whether the electromagnetic induction coil is heated or not is controlled according to the real-time temperature, and the heating and the temperature control of the metal melt in the customized crucible are realized; a metal protection tube is arranged outside the K-type thermocouple; the collecting system consists of a collecting plate and an alumina clapboard, wherein the collecting plate is connected and fixed with the alumina clapboard and the alumina clapboard is connected and fixed with the rack through screws; the transmission system consists of a high-speed motor and a rotating shaft, the high-speed motor is fixed on the ground and is vertical to the rack, the starting and the adjustment of the working frequency are controlled by the comprehensive control console, and the customized crucible is driven to rotate by driving the rotating shaft to provide the spinning centrifugal force; the rotating shaft is connected with the customized crucible through a threaded joint and is fixed on the rack through a bearing; the frame supports the whole device and is protected in parallel, the positive pole of the high-voltage power supply is connected with the collecting plate, and the negative pole is grounded, so that a high-voltage electrostatic field is formed between the customized crucible and the collecting plate, and electrostatic spinning is realized; the whole centrifugal melt electrostatic spinning device is horizontally placed, the rotating shaft is respectively connected with the customized crucible and the rack, the customized crucible, the rack and the rack have good conductivity, and the centrifugal melt electrostatic spinning device is protected by grounding of the rack; the porous spray head and the collecting plate have a certain distance, and the voltage is controlled within a certain range, so that the short circuit caused by breakdown can be avoided between the porous spray head and the collecting plate, and the spinning process is not influenced.

2. The method for preparing the metal micro-nano fiber by centrifugal melt electrospinning according to claim 1, characterized by comprising the following steps:

the method comprises the following steps: putting a pure metal block with certain mass into a customized crucible, covering an end cover, and installing and fixing a K-type thermocouple;

step two: starting a power supply of the comprehensive control console, turning on an electromagnetic induction heating switch, and heating the customized crucible through an electromagnetic induction coil;

step three: observing through an observation port until the metal block is heated to be completely melted and then preserving heat for a certain time;

step four: starting a high-voltage power supply and a high-speed motor, wherein the high-voltage power supply provides high-voltage electrostatic force, the high-speed motor is set to have a certain rotating speed, and the customized crucible is driven to rotate under the action of a rotating shaft so as to provide spinning centrifugal force;

step five: the metal melt in the customized crucible uniformly falls onto a collecting plate in a fiber form through a porous spray head under the double actions of centrifugal force and high-pressure electrostatic force to obtain long metal fibers.

3. The method for preparing the metal micro-nano fiber through centrifugal melt electrospinning according to claim 2, wherein the mass of the metal block in the first step is 10-50g.

4. The method for preparing the metal micro-nano fiber through centrifugal melt electrospinning according to claim 2, wherein the heat preservation time in the third step is 10-30min.

5. The method for preparing the metal micro-nano fibers through centrifugal melt electrospinning according to claim 2, wherein the rotating speed interval in the fourth step is 800r/min-2000r/min.

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