Micro-fluidic-based spherical particle preparation system and method
Technical Field
The invention relates to the field of initiating explosive devices, in particular to a system and a method for preparing spherical particles based on microfluidics.
Background
Energetic materials (Energetic materials) are compounds or mixtures containing explosive groups or oxidizers and combustibles, which can independently carry out chemical reactions and output energy, and are important components of military explosives, propellants and rocket propellant formulations. With the extensive and intensive research on energetic materials, special requirements are put forward on the particle size and shape of the main charge thereof. Taking the elementary explosive as an example, the surface state and shape of the crystal and the defect of the crystal directly affect the fluidity, stability and mechanical strength of the explosive, so that the charge density, sensitivity and explosive property of the explosive are also greatly affected. The sensitivity performance and output energy of the same explosive can be greatly different due to different crystal forms. Meanwhile, after studying hot spots of crystals of energetic materials, scholars at home and abroad think that lattice defects such as dislocations in the crystals are direct causes of the hot spots. The crystals cause the climb and accumulation of dislocations due to deformation, causing hot spots in the crystals of energetic materials and causing their ignition, which raises a series of safety issues. Therefore, the spheroidization of the energetic material crystal has many advantages, such as regular crystal shape, smooth surface, few edges and corners and good free-running property; the crystal form of the crystal after the spheroidization treatment is similar to a sphere, so that the crystal structure is effectively improved; the crystal after the spheroidization treatment has the advantages of improved thermal decomposition temperature, better thermal stability, reduced crystal defects and the like.
In view of the special properties of energetic materials, solvent-non-solvent recrystallization is generally used to spheroidize energetic materials for the purpose of improving their performance. The method mainly controls the granularity and appearance form of crystals by changing the solvent, temperature, stirring speed, pH value of the solution, introduction of additives and the like in the crystallization process. However, too many variables lead to a great increase in the workload of experimental screening in the process of preparing the spheroidized crystals, which is time-consuming and labor-consuming. In addition, the energetic material obtained by the method has wide particle size distribution, poor controllability of crystal morphology, large consumption of solvent and non-solvent, higher cost, risk of environmental pollution and the like. Meanwhile, in China, in order to reduce cost and protect environment, people try to realize the spheroidization of energetic materials by a physical method. The mechanical ball milling method is a method for crushing particles by mechanical force action such as impact, extrusion, shearing and the like of a ball milling medium, but the particles prepared by the method have the advantages of uneven size, wide particle size distribution range and easy introduction of impurities. In conclusion, the existing method has the disadvantages of complex operation steps, long research and development period, large reagent consumption, poor repeatability, potential danger and the like, and is difficult to realize the rapid preparation of the spherical crystals of the energetic materials.
The microfluidic technology is a technology for precisely controlling and controlling micro-scale fluid by using a micro-pipeline, particularly a technology of a submicron structure, and is a multi-cross discipline comprising engineering, physics, chemistry, micro-processing and biological engineering. In recent decades, with the rapid development of microfluidic technology, people begin to explore the dynamics principle and the flow behavior of multi-phase flow droplets on a microscale, the droplet control technology in microchannels, and the application research of the technology, one of which is widely applied to the preparation of micro-nano particles. Compared with the traditional batch reaction, the micro-fluidic technology has higher mixing efficiency, faster heat and mass transfer rate, lower reagent consumption and more accurate reaction parameter control.
Disclosure of Invention
The invention aims to provide a micro-fluidic-based spherical particle preparation system and a spherical particle preparation method based on the system.
The technical solution for realizing the purpose of the invention is as follows:
a micro-fluidic-based spherical particle preparation system comprises a fluid driving unit, a spherical unit, a sample collecting unit and a connecting assembly. Wherein the fluid driving unit includes a continuous phase driving unit that drives a continuous phase liquid and a dispersed phase driving unit that drives a dispersed phase liquid; the spheroidization unit comprises a temperature control device, a micropore array chip and an array chip clamp for fixing and connecting. Wherein, the micropore array chip is formed by processing a 675 mu m silicon chip, micropores with the same aperture are arranged on the micropore array chip, the micropores are separated by the diameter of one micropore, the models are divided according to the aperture, and the micropore array chip has various specifications of 10 mu m, 20 mu m, 30 mu m or 40 mu m respectively so as to meet the requirement of sphericizing particles with different sizes; the array chip clamp consists of an upper layer structure, a middle layer structure and a lower layer structure with micro-channels and corresponding sealing screws, wherein the upper layer structure is provided with 1mm micro-channels and 4M 3 through holes, the micro-channels are used for inflow of dispersed phases, and the through holes are used for tight connection with the middle layer structure; two sides of the middle layer structure are provided with 2 1mm micro-channels for the inflow and outflow of continuous phases, the middle part is provided with a sunken platform for supporting a micropore array chip and 4M 3 threaded holes for tightly fixing with the upper layer structure, the back part is provided with a 1mm deep micro-channel, and the micro-channel and the lower layer structure form sealing through corresponding PTFE gaskets; the lower layer structure is processed with a micro-channel corresponding to the back of the middle layer structure, sealing is formed between the middle layer structure and the middle layer structure through a corresponding PTFE gasket, the middle layer structure and the lower layer structure are respectively provided with 6M 6 through holes and threaded holes, so that the middle layer structure and the lower layer structure can be conveniently sealed by screws, and the upper, middle and lower layer structures are all processed by Polytetrafluoroethylene (PTFE); the sample collection unit is mainly used for collecting the prepared spherical energetic material particles; the connecting assembly comprises connecting pipelines and corresponding connecting devices between the units, and the fluid driving unit, the sphericizing unit and the sample collecting unit are sequentially connected by the connecting assembly.
The preparation method of the spherical particles by using the microfluidic-based spherical particle preparation system comprises the following specific steps:
preparing a corresponding dispersed phase solution, namely dissolving an energetic material in a corresponding solvent to prepare a dispersed phase solution, and placing the dispersed phase solution in a dispersed phase driving unit, wherein the flow rate is set to be 0.1-2.0mL/min for later use;
selecting continuous phase carrier liquid which is not soluble with the dispersed phase solution and placing the continuous phase carrier liquid in a continuous phase driving unit, wherein the flow rate is set to be 0.2-5.0mL/min for later use;
and step three, selecting a proper micropore array chip according to the particle size of the needed spherical particles, and placing the micropore array chip into the array chip clamp to complete the assembly of the array chip clamp. Meanwhile, the connection assembly is used for completing the connection of the fluid driving unit, the spheroidizing unit and the sample collecting unit;
step four, starting a temperature control device, and setting the temperature to be 20-80 ℃;
step five, when the temperature of the temperature control device reaches a set value, starting the fluid driving unit, pushing the continuous phase carrier liquid and the dispersed phase solution to flow into the spheroidization unit, and generating a corresponding suspension;
and step six, collecting the energetic material suspension flowing out of the spheroidization unit to a sample collection unit, standing, washing, filtering, and drying to finally obtain the needed spheroidization particles.
Compared with the prior art, the invention has the following remarkable advantages: 1. the micropore array chip of the spherical particle preparation system has different specifications according to different pore diameters, and can realize the preparation of spherical particles with different particle diameters so as to meet different application requirements; 2. the spherical particles prepared by the spherical particle preparation system have regular appearance, narrow particle size distribution, good monodispersity and excellent physicochemical and explosive properties; 3. the system has the advantages of high speed, high efficiency, short research and development period, low energy and material consumption, and little environmental pollution, and is very suitable for quickly and effectively preparing the spheroidized particles with good appearance; 4. the preparation method for the spherical particles has the advantages that the process is relatively simple and stable, and the repeatability is high; 5. the method takes the microreactor as a platform, increases the number of cycles of a unit by simple quantity amplification, can greatly improve the yield on the premise of not influencing the product quality, realizes industrialization and scale production with low cost, and has good economic benefit and application prospect.
The present invention is described in further detail below with reference to the attached drawing figures.
Drawings
Fig. 1 is a schematic diagram of a microfluidics-based spheroidized particle preparation system.
FIG. 2 is a schematic view of a structure of a micro well array chip holder.
FIG. 3 is a schematic diagram of a microwell array chip.
Fig. 4 is a schematic diagram of a parallel system for microfluidic-based preparation of spherulized microparticles.
FIG. 5 is a diagram of the morphology of the spherical nitrocotton prepared by the system for preparing the spherical particles.
Detailed Description
Referring to fig. 1, a microfluidic-based spheroidized particle preparation system according to the present invention includes a fluid driving unit, a spheroidizing unit, a sample collecting unit, and a connecting assembly. Wherein the fluid drive unit comprises a continuous phase drive unit 1 driving a continuous phase carrier liquid 2 and a disperse phase drive unit 3 driving a disperse phase solution 4; the spheroidization unit comprises a temperature control device 9, a micropore array chip 8 and an array chip clamp for fixing and connecting. Wherein, the micropore array chip 8 is processed by a 675 μm silicon chip, and micropores with the same aperture are arranged on the micropore array chip; the array chip clamp is composed of an upper layer structure, a middle layer structure and a lower layer structure with micro channels and corresponding sealing screws, wherein the upper layer structure 5 is used for inflow of a dispersed phase solution 4, the middle layer structure 6 is used for shearing the dispersed phase solution 4 by a continuous phase carrier liquid 2 under the action of a micro-pore array chip 8, and the lower layer structure 7 is sealed with the middle layer structure 6 through a corresponding PTFE gasket. The dispersed phase driving unit 3 drives the dispersed phase solution 4 to flow into the micropore array chip 8 through the upper layer structure 5 of the array chip clamp, and the dispersed phase solution is extruded into spherical liquid drops under the action of micropores, the continuous phase driving unit 1 drives the continuous phase carrier liquid 2 to shear the spherical liquid drops at the bottom of the micropore array chip 8 through the middle layer structure 6 of the array chip clamp, so that oil-in-water-shaped liquid drops are formed, the sphericization of energetic material particles is realized under the cooperation of the temperature control device 9, and corresponding suspension liquid is generated; the sample collection unit 10 is used for collecting the suspension flowing out of the sphericizing unit, and further standing, washing, filtering and drying the suspension to finally obtain sphericized particles; the connecting assembly comprises connecting pipelines and corresponding connecting devices between the units, and the fluid driving unit, the sphericizing unit and the sample collecting unit are sequentially connected by the connecting assembly.
Referring to fig. 2, the array chip holder is composed of an upper, middle and lower three-layered structure with micro-channels and corresponding sealing screws, wherein the upper layer 5 has 1mm micro-channels, 1M 6 threaded hole and 4M 3 through holes, the micro-channels are used for the inflow of dispersed phase, the M6 threaded hole is used for the connection of external pipes and the array chip holder through a connection assembly, and the M3 through hole is used for the tight connection with the middle layer 6; two sides of the middle layer structure 6 are provided with 2 1mm micro-channels and 2M 6 threaded holes which are respectively used for the inflow and outflow of continuous phase carrier liquid 2 and the connection of an external pipeline and an array chip clamp through a connecting component, the middle part is processed with a sunken platform for supporting a micropore array chip 8 and 4M 3 threaded holes for tightly fixing with the upper layer structure 5, the bottom part is processed with 1mm deep micro-channels, and the sealing with the lower layer structure 7 is realized through corresponding PTFE gaskets; the lower layer structure 7 is processed with a micro-channel corresponding to the bottom of the middle layer structure 6, the micro-channel and the middle layer structure 6 form sealing through a corresponding PTFE gasket, 6M 6 through holes and threaded holes are formed in the middle layer structure 6 and the lower layer structure 7 respectively, the middle layer structure and the lower layer structure are convenient to form sealing through screws, and the upper layer structure, the middle layer structure and the lower layer structure are all processed by Polytetrafluoroethylene (PTFE).
Referring to fig. 3, the micro-pore array chip (2mm × 2.5mm) is fabricated from a 675 μm silicon wafer, on which micro-pores having the same pore diameter are arranged, and the micro-pores are spaced from each other by the diameter of one micro-pore; the micropore array chip has multiple specifications of 10 mu m (11), 20 mu m (12), 30 mu m (13) or 40 mu m (14) respectively according to the type division of the pore diameter so as to meet the requirement of the sphericization of particles with different sizes.
With reference to fig. 4, a microfluidic-based parallel system for preparing spheroidized particles includes a set of continuous phase driving units and a set of dispersed phase driving units, two or more sets of micro-pore array chips and corresponding array chip clamps, the specifications of the micro-pore array chips are selectable, two or more sets of spheroidizing units and sample collecting units with the same number as the spheroidizing units are formed together, wherein one set of continuous phase driving units are divided by a connecting component to form two channels 15 and 16, which are respectively connected with the middle layer structures 6 of the two or more sets of array chip clamps; a group of dispersed phase driving units form two paths of channels 17 and 18 after being shunted by the connecting component, and the two paths of channels are respectively connected with the upper layer junctions 5 of two or more groups of array chip clamps; each group of the spheroidizing units and the corresponding sample collecting units form a group of preparation units, and the preparation units are arranged in parallel.
The preparation method of the spherical particles by using the microfluidic-based spherical particle preparation system comprises the following specific steps:
preparing a corresponding dispersed phase solution 4, namely dissolving an energetic material in a corresponding solvent to prepare a dispersed phase solution, and placing the dispersed phase solution in a dispersed phase driving unit 3, wherein the flow rate is set to be 0.1-2.0mL/min for later use;
selecting a continuous phase carrier liquid 2 which is not soluble with the dispersed phase solution and placing the continuous phase carrier liquid 2 in a continuous phase driving unit 1, wherein the flow rate is set to be 0.2-5.0mL/min for later use;
and step three, selecting a proper micropore array chip 8 according to the particle size of the needed spherical particles, and placing the micropore array chip into the array chip clamp to complete the assembly of the array chip clamp. Meanwhile, the connection assembly is used for completing the connection of the fluid driving unit, the spheroidizing unit and the sample collecting unit;
step four, starting the temperature control device 9, and setting the temperature to be 20-80 ℃;
step five, when the temperature of the temperature control device 9 reaches a set value, starting the fluid driving unit, pushing the continuous phase carrier liquid 2 and the dispersed phase solution 4 to flow into the spheroidization unit, and generating a corresponding suspension;
collecting the energetic material suspension flowing out of the spheroidization unit to a sample collection unit 9, standing, washing, filtering, and drying to finally obtain the needed spheroidization particles;
the following examples are merely illustrative of the present invention and should not be construed as limiting thereof.
Example 1: preparation of spherical propellant Nitrocotton (NC)
Spherical/quasi-spherical nitrocotton is prepared by adopting a spherical particle preparation system. Deionized water is used as a continuous phase carrier liquid, and ethyl acetate is used as a solvent to prepare the spherical/quasi-spherical nitrocotton. Dissolving 2.0g of nitrocotton raw material in 50mL of ethyl acetate solvent to prepare a dispersed phase solution 4, and placing the dispersed phase solution 4 in a dispersed phase driving unit 3, wherein the flow rate is set to be 0.1 mL/min; the continuous phase carrier liquid 2 is driven by the continuous phase driving unit 1, and the flow rate is controlled at 1.0 mL/min. The spheronization temperature was set at 20 ℃. Starting the continuous phase driving unit 1, and driving the continuous phase carrier liquid 2 to flow into the interior of the spheroidizing unit through the middle layer structure 6 of the array chip clamp; and starting the disperse phase driving unit 3, driving the disperse phase solution 4 to be conveyed to the spheroidizing unit through the upper layer structure 5 of the array chip clamp along a pipeline, forming spherical liquid drops with uniform shapes under the extrusion of the micropore array chip 8, attaching the spherical liquid drops to the bottom of the micropore array chip 8, shearing the spherical liquid drops by the continuous phase carrier liquid 2 driven by the continuous phase driving unit 1 to form oil-in-water liquid drops with uniform shapes, and preparing the spherical nitrocotton particles at a certain temperature to generate suspension. And collecting the suspension in a sample collection unit, standing, washing, filtering, drying, finally obtaining the spherical nitrocotton particles, and performing subsequent characterization. As can be seen from FIG. 5, the nitrocellulose particles obtained by the microfluidic-based spherical particle preparation system have good surface appearance and uniform crystal form.