阅读说明：本技术 一种基于纳米流体液滴凝固的堆叠成型方法 (Stacking forming method based on nano fluid droplet solidification ) 是由 赵玉刚 汤海波 黄承志 王东民 于 2020-12-29 设计创作，主要内容包括：本发明涉及一种基于纳米流体液滴凝固的堆叠成型方法,采用堆叠成型装置进行,具体包括以下步骤：(1)制备纳米流体悬浮液；(2)注射单元吸入纳米流体,逐滴滴在设定好过冷度的承载底板上,凝固面由液滴底面向顶部推移,在完全凝固后,纳米颗粒随补偿流移动,密集堆积至顶面,形成一个光滑平台；(3)等待前一液滴凝固后,在其平台正中心继续放置液滴,形成第二个圆柱体或圆台,如此反复,堆叠出圆柱体。本发明利用纳米流体液滴凝固过程中的特征形变,在凝固液滴顶部产生平台结构,利用堆叠原理一次成型制备大高径比的圆柱或塔形结构。纳米流体液滴的堆叠结构稳定可控,精确度更高。(The invention relates to a stacking forming method based on nano fluid droplet solidification, which is carried out by adopting a stacking forming device and specifically comprises the following steps: (1) preparing a nanofluid suspension; (2) the injection unit sucks nano fluid, the nano fluid is dripped on a bearing bottom plate with a set supercooling degree drop by drop, a solidification surface is pushed from the bottom to the top of the liquid drop, and after the nano fluid is completely solidified, nano particles move along with compensation flow and are densely accumulated to the top surface to form a smooth platform; (3) after the former liquid drop is solidified, the liquid drop is continuously placed in the right center of the platform to form a second cylinder or a circular table, and the steps are repeated to stack the cylinders. The invention utilizes the characteristic deformation of the nano fluid liquid drop in the solidification process to generate a platform structure on the top of the solidified liquid drop, and utilizes the stacking principle to prepare a cylindrical or tower-shaped structure with large height-diameter ratio by one-step molding. The stacking structure of the nano fluid droplets is stable and controllable, and the accuracy is higher.)

1. A stacking and forming method based on nano fluid droplet solidification is characterized in that a stacking and forming device is adopted, the stacking and forming device comprises an injection unit for dripping droplets and a low-temperature platform for droplet solidification, the low-temperature platform comprises a circulating cooling device provided with a refrigerating working medium inlet and a refrigerating working medium outlet, and a bearing bottom plate arranged on the circulating cooling device, a cooling liquid working medium is circularly introduced into the circulating cooling device to enable the bearing bottom plate to be in a low-temperature state,

the method specifically comprises the following steps:

(1) preparing a nanofluid suspension;

(2) the injection unit sucks nano fluid, the nano fluid is dripped on a bearing bottom plate with a set supercooling degree drop by drop, a solidification surface is pushed from the bottom to the top of the liquid drop, and after the nano fluid is completely solidified, nano particles move along with compensation flow and are densely accumulated to the top surface to form a smooth platform;

(3) after the former liquid drop is solidified, the liquid drop is continuously placed in the right center of the platform to form a second cylinder or a circular table, and the steps are repeated to stack the cylinders.

2. The nanofluid droplet solidification-based stack molding method according to claim 1, wherein the carrier substrate is made of a heat conductive material.

3. The stacking and forming method based on nano-fluid droplet solidification of claim 1, wherein the bearing bottom plate is connected with a temperature controller, the temperature of the bearing bottom plate is controlled by the temperature controller, and the working temperature of the low-temperature stage is set according to the solidification point of the selected nano-fluid suspension.

4. The stacking and forming method based on nano fluid droplet solidification as claimed in claim 1, wherein the cooling liquid working medium circulated in the circulation cooling device is a glycol aqueous solution with a mass concentration of 40%.

5. The nanofluid droplet solidification-based stack molding method according to claim 1, wherein the injection unit comprises an injector.

6. The nanofluid droplet solidification-based stack molding method according to claim 5, wherein the injector is a constant temperature injector.

7. The stacking and forming method based on nano-fluid droplet solidification of claim 1, wherein the injection unit is connected to a movement control device and is matched with a computer program to change a droplet placement position so as to realize a three-dimensional printing function.

8. The method of claim 1, wherein the nanofluid suspension comprises water, polymer or liquid metal as a base liquid, and the nanoparticles comprise Cu and Al₂O₃Or TiO₂Particles having a particle size at least three orders of magnitude smaller than the droplet size.

9. The method of claim 1, wherein the time for forming the platform after solidification of the nano-fluid suspension droplets under super-cooling conditions is 0.1-100 seconds, depending on the droplet size.

Technical Field

The invention relates to the field of liquid drop solidification forming, in particular to a stacking forming method based on nano fluid liquid drop solidification.

Background

Nanofluids generally refer to liquids that suspend nanometer-scale solid particles, and are small, lightweight, and thermally conductive. The method is widely applied to the fields of energy, chemical industry and materials. When a traditional three-dimensional printing technology is used for processing linear parts, the structure is fragile due to material limitation, the structure cannot be maintained for a long time, and the traditional three-dimensional printing technology cannot be used in an industrial process. Or when the columnar structures are stacked, the surface is also rough. The use of conventional droplets for coagulation stacking suffers from the following limitations: 1) the single liquid drop is spherical under the influence of surface tension, and is also single spherical after solidification under the condition of not increasing external conditions. 2) The liquid drops are continuously dripped on the surface of the spherical solidified liquid drops, the supercooling degree is enough, the dripping position cannot be accurately determined if the liquid drops cannot roll, and gaps are generated even after solidification, so that the mechanical strength and the air tightness of the material are influenced.

Disclosure of Invention

The present invention provides a stack forming method based on solidification of nano fluid droplets, in which the nano fluid droplets solidify under the action of surface tension to form a smooth surface and form a stable structure at low temperature, and a platform is formed on the top of the droplets to facilitate further precise stacking.

The purpose of the invention is realized by the following technical scheme:

the utility model provides a pile up forming device based on solidification of nanometer fluid liquid drop, is including the injection unit that is used for dropwise add the liquid drop and be used for the low-temperature platform that the liquid drop solidifies, the low-temperature platform is including the circulative cooling device who is equipped with refrigeration working medium entry and refrigeration working medium export, and locate the last load-bearing bottom plate of circulative cooling device, the circulative cooling device inner loop lets in the coolant working medium, makes the load-bearing bottom plate is in the low temperature state.

The method is characterized in that a low-temperature platform is adopted to provide enough supercooling degree, nanometer fluid droplets dripped on a bearing bottom plate drop by drop through an injection unit are pushed from the bottom surface to the top surface of the droplets, after the nanometer fluid droplets are completely solidified, nanometer particles move along with compensating flow and are densely accumulated to the top surface to form a smooth platform, a platform structure is generated at the top of the solidified droplets by utilizing characteristic deformation in the solidification process of the nanometer fluid droplets, and a cylindrical or tower-shaped structure with a large height-diameter ratio is prepared by one-step molding according to the stacking principle.

Preferably, the bearing bottom plate is made of heat conducting materials, the heat conducting materials which are good in chemical stability and not prone to corrosion or oxidation are adopted, such as smooth copper sheets, and the heat conducting materials are fixed to the top of the circulating cooling device through heat conducting glue.

Preferably, the bearing bottom plate is connected with a temperature controller, the temperature is controlled by the temperature controller, and the working temperature of the low-temperature platform is set according to the freezing point of the selected nano-fluid suspension.

Preferably, the working medium of the cooling liquid circularly introduced into the circulating cooling device is an ethylene glycol aqueous solution with the mass concentration of 40%.

Preferably, the injection unit comprises an injector, preferably the injector is a thermostatic injector.

A stacking forming method based on nano fluid droplet solidification is carried out by adopting the stacking forming device, and comprises the following steps:

(1) preparing a nanofluid suspension;

(2) the injection unit sucks nano fluid, the nano fluid is dripped on a bearing bottom plate with a set supercooling degree drop by drop, a solidification surface is pushed from the bottom to the top of the liquid drop, and after the nano fluid is completely solidified, nano particles move along with compensation flow and are densely accumulated to the top surface to form a smooth platform;

(3) after the former liquid drop is solidified, the liquid drop is continuously placed in the right center of the platform to form a second cylinder or a circular table, and the steps are repeated to stack the cylinders.

Preferably, the injection unit is connected to the movement control device and cooperates with a computer program to change the placement position of the liquid drop, thereby realizing the three-dimensional printing function. Theoretically, the scheme can be used for printing micron-to-submicron-scale complex devices through one-step forming.

Preferably, the nano fluid suspension comprises water, polymer or liquid metal as base liquid, and the nano particles comprise Cu and Al₂O₃Or TiO₂Particles, the size of the nanoparticles being at leastSmaller than the size of the liquid drop by three orders of magnitude, and the diameter of the liquid drop is 1-4 mm.

Theoretically, the smaller the particle size of the nanoparticles, the better, the oversized particles are detrimental to heat transfer exchange and can also form agglomerates, resulting in accelerated settling, and the particle size needs to be at least three orders of magnitude smaller than the droplet size. If the diameter of the liquid drop is 3mm, the particle size is selected to be less than 3 μm.

Preferably, the plateau formation time of the nano-fluid suspension droplets after solidification under super-cooling conditions varies from 0.1 to 100 seconds, depending on the droplet size.

The cylinder needs to accurately place liquid drops to the central symmetrical position of the front liquid drop forming platform; objects in the micrometer to submicron scale are solidified stacks of nanofluidic droplets that require sufficiently small droplet sizes and are uniformly stable.

The working principle of the invention is that based on a platform structure formed after nano fluid drops are solidified, a dropwise stacking process is utilized, and a columnar or tower-shaped structure with a large height-diameter ratio is prepared by one-step forming. The realization device mainly comprises stable nanometer fluid, a bearing bottom plate, a circulating cooling device, a constant temperature injector and a temperature controller. The stable nanofluid is a uniform dispersion system prepared by a two-step method, and is dripped on the bearing bottom plate by a constant temperature injector. The temperature of the bearing bottom plate is controlled by the temperature controller, so that the bearing bottom plate has good heat-conducting property, stable chemical property and difficult oxidation. The liquid drop stacking process is carried out on the bearing bottom plate, the whole body is placed on the circulating cooling device, and the liquid drop stacking process is directly contacted with the circulating cooling device through the heat conducting glue.

The conventional pure liquid drop stacking has the defects of poor structural stability and high porosity due to the limited actual contact surface of point connection, and the stacking structure of the nano fluid liquid drops is stable and controllable, so that the accuracy is higher. Unlike conventional drop coagulation stacking, the present invention has two advantages: first, the solidified top surface of the droplet forms a platform that facilitates accurate stacking of the droplet thereon. Second, after the nanofluid droplets solidify, their top surfaces are smooth and their shapes can be controlled, reducing the porosity of the solidified stacks, suitable for metal and polymer-based three-dimensional printing and soldering processes.

Compared with the prior art, the invention has the following specific beneficial effects:

1. by utilizing the mechanism that a platform structure is formed at the top after nano fluid droplets are solidified, the gap and instability generated by pure medium droplet stacking solidification are solved through a dropwise stacking technology, and a more accurate three-dimensional structure is built;

2. meanwhile, the unit shapes of the control column (line) and the tower-shaped structure can be obtained by changing the size of the single-section platform, and more various structural designs can be realized.

Drawings

FIG. 1 is a schematic diagram of an apparatus for forming a stack of nano-fluid droplets by dropwise solidification proposed in the present invention;

FIG. 2 is a schematic diagram of the formation of a stack of pure media and nanofluidic droplets according to the working principle of the present invention;

FIG. 3 is a graph of the actual measurement results of stacking and forming of pure medium and nanofluid droplets according to the working principle of the present invention;

in the figure:

1-a circulating cooling device;

2-a load floor;

3-a refrigerant inlet;

4-a refrigerant outlet;

5-constant temperature injector;

6-nanofluid droplets;

7-solidified nanofluid droplets;

8-pure media drop-by-drop stacking of the shaped structures (schematic);

9-nanofluid drop-wise stacking of the molded structures (schematic);

10-stacking the formed structure drop by drop with pure medium (actual measurement);

the 11-nanofluid was stacked drop-wise to form a structure (measured).

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.

Referring to fig. 1, a stacking and forming device based on nano fluid droplet solidification comprises an injection unit for dripping droplets and a low-temperature platform for droplet solidification, wherein the injection unit comprises a constant-temperature injector 5, the low-temperature platform comprises a circulating cooling device 1 provided with a refrigerating working medium inlet 3 and a refrigerating working medium outlet 4, and a bearing bottom plate 2 arranged on the circulating cooling device 1, and a cooling liquid working medium is introduced into the circulating cooling device 1 in a circulating manner, so that the bearing bottom plate 2 is in a low-temperature state. The method is characterized in that a low-temperature platform is adopted to provide enough supercooling degree, nanometer fluid drops which are dripped on a bearing bottom plate 2 drop by drop through a constant-temperature injector 5 are pushed from the bottom surface to the top surface of the drops, after the nanometer fluid drops are completely solidified, nanometer particles move along with compensating flow and are densely accumulated to the top surface to form a smooth platform, and based on a platform structure formed after the nanometer fluid drops are solidified, a dropwise stacking process is utilized to prepare a columnar or tower-shaped structure with a large height-diameter ratio through one-step forming.

The bearing bottom plate 2 is made of a heat conduction material which is good in chemical stability and not prone to corrosion or oxidation, the bearing bottom plate is connected with the temperature controller, the temperature is controlled through the temperature controller, the working temperature of the low-temperature platform is set according to the freezing point of the selected nano fluid suspension, and a cooling liquid working medium which is introduced into the circulating cooling device in a circulating mode is an ethylene glycol aqueous solution with the mass concentration of 40%.

This example uses water-based TiO₂The nano-fluid dropwise solidification stacking forming is carried out by adopting the stacking forming device, and comprises the following steps:

step (1): the prepared nano fluid base liquid is deionized water, and the nano particles are anatase TiO₂Particle size 40nm, particle volume concentration of 0.3%, adding 0.8mM sodium dodecyl sulfate SDS as dispersant and stabilizer.

Step (2): the circulating cooling device 1 uses a cooling working medium which is 40% glycol aqueous solution, the working temperature is set to be-20 ℃, the flow rate is 6L/Min, the bearing bottom plate 2 is 1mm thick and 4 multiplied by 4cm²The smooth copper sheet is fixed on the top of the circulating cooling device 1 by heat conducting glue.

And (3): the temperature of the constant temperature injector 5 is set to be room temperature (20 ℃), the inner diameter and the outer diameter of the selection nozzle (needle) tube are respectively 0.4mm and 0.5mm, and the dropping diameter of the nanometer fluid liquid drop 6 is about 2 mm. The actual measurement temperature of the bearing bottom plate 2 is-18 ℃, the nano fluid droplets 6 drop to contact with the bearing bottom plate 2 to be solidified and nucleated, the solidification front surface is approximately pushed along the vertical direction to finally form cylindrical solidification droplets 7, and the solidification time of a single droplet is about 10 s.

And (4): after waiting for the first nanofluid droplet 6 to solidify, the nanofluid droplet 6 is continuously placed right in the center of the platform of the solidified droplet 7, so that a second cylinder or circular truncated cone can be formed, and the process is repeated, and higher cylinders 9 (schematic) and 11 (actual measurement) can be stacked.

And (5): the more complicated structure can fix the constant temperature injector 5 on an XYZ three-dimensional moving table, and the three-dimensional printing function can be realized by regulating and controlling the placement position and the height of the nano fluid droplets 6 through a preset computer program.

As shown in fig. 2 and 3, the pure medium drop-by-drop stacking and forming structures 8 and 10 and the nanofluid drop-by-drop stacking and forming structures 9 and 11 show that by utilizing the mechanism of forming a platform structure on the top after solidification of the nanofluid drops, gaps and instability generated by pure medium drop stacking and solidification can be solved through the drop-by-drop stacking technology, and a more accurate three-dimensional structure can be built; meanwhile, the unit shapes of the control column (line) and the tower-shaped structure can be obtained by changing the size of the single-section platform, and more various structural designs can be realized.

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.