CN213537800U - Microfluidic synthesis device for silver nanofluid - Google Patents

Abstract

A microfluidic synthesis device for silver nanofluid relates to the field of nanofluid preparation and heat transfer. The invention aims to solve the technical problems that the existing preparation method of the silver nanofluid is complicated, the particle size distribution of prepared nanoparticles is uneven, the dispersibility is poor and the like. Based on the silver nanofluid preparation system of T-shaped tee bend, "8 font" is around flowing the little mixing of heating member/reactor to continuous stream of circling replaces mechanical stirring process, and the device is simple with low costs, easily control.

Description

Microfluidic synthesis device for silver nanofluid

Technical Field

The utility model relates to a nanometer fluid preparation and heat transfer field, concretely relates to micro-fluidic reaction system of preparation silver nanometer fluid.

Background

In the fields of aerospace, energy chemical industry, microelectronic technology and the like, the heat load of advanced equipment and high-power devices is continuously improved, and the transient heat flow density exceeds 100W/cm²Traditional heat dissipation working media such as water, heat conduction oil and the like can not meet the heat dissipation requirements more and more, and nanofluid as a new heat exchange working medium has higher heat conduction performance, so that the heat dissipation working media have wider application prospects.

In 1995, Choi et al, Argonne national laboratory in the united states, proposed nanofluids: the stable suspension formed by suspending metal or nonmetal particles with the particle size of 1-100nm in a base liquid is an innovative research of the application of nanotechnology in the field of thermal energy engineering. The preparation methods of nanofluids have hitherto been classified into a single-step method and a two-step method, and the single-step method and the two-step method are distinguished in that the preparation process and the dispersion process of nanoparticles are performed in one step. The single-step method has the advantages of uniform dispersion of nano particles and better heat transfer performance, but has more complex preparation process, higher cost and difficult large-scale production, and most of the preparation processes of the traditional single-step method are carried out in a batch reactor and cannot be continuously and stably synthesized. The preparation of the nanofluid by the two-step method has the advantages of simple process, low cost, easiness in batch production and the like, but also has the defects of reduced heat exchange performance and the like caused by difficult dispersion of particles.

The nanometer fluid prepared by the traditional method has poor stability in a heat exchange system, and the phenomenon that nanometer particles are easy to agglomerate, age and the like after long-time use restricts the application development of the nanometer fluid. Therefore, the research on a method for preparing the nanofluid with small solid particle size, high stability and good heat exchange performance is the key point for solving the problem.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a novel synthetic method and a device for preparing silver nanofluid by microfluidics. Compare in traditional one step wet chemistry preparation, the utility model provides a silver nanofluid preparation system based on T type tee bend, "8 font" flows around and adds the heat-insulating material micromixer/reactor to flow around replacing the mechanical stirring process in succession, the device is simple with low costs, easily control.

Through the utility model discloses preparation system and relevant key position design for the dwell time of reaction in the system is long, can realize the controllability of nanoparticle size, and the nanometer fluid particle size of preparation is little, and the homogeneity is good, is difficult for deposiing, consequently uses the utility model discloses the method can solve above-mentioned prior art not enough.

In order to achieve the above object, the utility model provides a following technical scheme: the method specifically comprises the following steps:

(1) preparing silver nitrate according to a molar ratio, dissolving quantitative silver nitrate into a base solution, carrying out magnetic stirring and ultrasonic oscillation simultaneously to ensure that the silver nitrate is uniformly dispersed, and loading the silver nitrate into a micro-injector; the polyvinyl pyrrolidone and the ascorbic acid are stirred in the same way, uniformly shaken and loaded on the other micro-injector, wherein the ascorbic acid is used as a reducing agent to reduce the nano-silver;

(2) connecting the liquid outlets of the two micro syringes in the step (1) with two openings of a T-shaped three-way pipe respectively by using a capillary, and connecting a third opening with a product collecting device after passing through an 8-shaped bypass heating zone and a low-temperature constant-temperature water bath box in sequence;

adjusting the temperature of the 8-shaped streaming heating area to 40-60 ℃ by adjusting a temperature controller, respectively pushing the microinjectors by two injection pumps, mixing and starting reaction in a T-shaped tee pipe, fully reacting the mixture flowing through the 8-shaped streaming heating area, cooling the mixture flowing through a constant temperature water bath box at 25 ℃, and finally obtaining silver nanofluid in a product collecting device;

the device for realizing the method is characterized by comprising two micro injection pumps, a T-shaped three-way micro mixer, a microreactor with an 8-shaped channel, a constant-temperature water bath box, a collecting device and a temperature controller, wherein liquid outlets of the two micro injectors are respectively connected with two through ports of the T-shaped three-way pipe, a third through port of the T-shaped three-way pipe is connected with the microreactor with the 8-shaped channel through a capillary tube, the microreactor with the 8-shaped channel is connected with a spiral or snakelike bent capillary tube, the spiral or snakelike bent capillary tube is connected with the collecting device, the spiral or snakelike bent capillary tube is arranged in the constant-temperature water bath box, and the temperature controller is connected with the microreactor with the 8-shaped channel and is used for controlling the microreactor with the 8-shaped channel.

Structure of microreactor with "figure 8" channel: the capillary tube is bent and folded into an 8-shaped structure, an inlet and an outlet are arranged at the middle thin waist part of the 8-shaped structure, so that material flow in the capillary tube firstly enters the 0-shaped tube on one side from the middle of the 8-shaped structure to flow for a circle, then passes through the middle of the 8-shaped structure to enter the 0-shaped tube on the other side to flow for a circle, and finally flows out from the middle of the 8-shaped tube, the counter-clockwise flow is performed in the 0-shaped tube on one side, the clockwise flow is performed in the 0-shaped tube on the other side, and the 8-shaped flow-winding structure is arranged in the structure with the 8-shaped groove to form the microreactor with.

The diameter of the capillary is preferably 300-350 microns, and the inner diameter of the T-shaped tee pipe is equivalent to that of the capillary.

The molar concentration range of silver nitrate in the micro-syringe is 1-4 mmol/L. The base solution corresponding to the silver nitrate is deionized water or ethylene glycol water solution.

The ultrasonic oscillation time is 40-60 min.

The base liquid adopted by the ascorbic acid solution is deionized water or ethylene glycol. The ascorbic acid is used as a reducing agent and a protective agent, and the concentration and the flow rate of the ascorbic acid are adjusted according to the condition that the silver can be completely reduced.

Molar concentration ratio of silver nitrate to polyvinylpyrrolidone 1: (1-5), the ascorbic acid is used in an amount sufficient to reduce the silver nitrate.

Further, the molar concentration ratio of the silver nitrate to the polyvinylpyrrolidone is 1: 5, the absorbance was the highest at this time, and the stability was the best.

Controlling the injection flow rate of the micro injector filled with silver nitrate to be 0.1ml/min-0.3ml/min, and obtaining the particle size range of 20-60nm, for example, the injection flow rate is 0.1ml/min and 0.3ml/min, and the particle size range is 20-30nm and 40-60nm correspondingly.

The heating element channels are designed in a "figure-8" shape to facilitate a better mixing reaction of silver nitrate and reducing agent.

The nanometer fluid is rapidly cooled by the low-temperature constant-temperature water bath, and the generation of byproducts can be prevented.

Compared with the prior art, the utility model discloses following profitable technological effect has:

the synthesis reaction precursor and the product collection of the utility model are not interfered with each other, the reaction can be carried out continuously, and the controllability is strong.

The utility model uses ascorbic acid as a reducing agent, which is convenient for adjusting the pH value of the solution and can weaken the oxidation reaction of the silver particles to the maximum extent.

Third the utility model discloses the micro reactor channel design of zone of heating is for "8 font", and the fluid gets into and flows through 0 type pipe of upper part of following the counter-clockwise at first after the zone of heating and flows through 0 type pipe of lower part of following clockwise again, because the effect of inertial force and centrifugal force can produce the secondary cycle on the cross section, this can increase the mixed efficiency of interference and reinforcing precursor solution and reducing agent solution, can increase the dwell time of reaction solution in the zone of heating to make the reaction go on more thoroughly.

The micro-reactor channel in the heating area is designed to be 8-shaped, so that the micro-mixing/reaction system is simplified while the sufficient mixing reaction is ensured, and the space occupation of the micro-mixing/reaction system is reduced.

The stability of the obtained nanofluid is improved compared with the two-step method, and no agglomeration and precipitation phenomenon is found after standing for two months.

The particle size obtained when the silver nanofluid is prepared by the microfluidic method is more uniform, and the heat conductivity is higher.

Drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention.

Fig. 1 is the utility model discloses a micro-fluidic system's structural schematic diagram, 1 is little syringe pump, 2 is T type tee bend micromixer, 3 for being carved with the micro-reactor of "8 font" channel, 4 is constant temperature water bath case, 5 is collection device, 6 is temperature controller, wherein 2 and 3 constitution micromixers/reaction systems.

Fig. 2 is a micro-reactor of the 8-shaped bypass channel designed by the utility model.

Fig. 3 is a graph of absorbance of silver nanofluids with different ratios of PVP added for the examples.

Detailed Description

In order to make the technical problem, technical scheme and beneficial effect that the utility model will solve more clearly understand, combine the embodiment below, it is right the utility model discloses further detailed description proceeds. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Example 1

(1) Silver nitrate (AgNO) with a mass of 0.034g was weighed out with a precision balance₃) And 0.1554g of polyvinylpyrrolidone (mass of PVP calculated as the molecular weight of the monomer) (concentration ratio of the amount of Ag to that of PVP 1: 7) dissolving silver nitrate in 100ml of deionized water to serve as a precursor solution, dissolving polyvinylpyrrolidone in 100ml of 5g/L ascorbic acid solution to serve as a reducing agent, and then completely dissolving the polyvinylpyrrolidone by magnetic stirring for 15min and ultrasonic oscillation for 45 min.

(2) 10ml of precursor solution is loaded on a micro-injector and fixed on an injection pump by a clamp, the other injector is loaded with reducing agent solution, a quartz capillary tube (the inner diameter is 320 microns and the outer diameter is 450 microns) is added with a sealing gasket and is respectively connected with the injector, the PEEK T-shaped tee joint and the collecting device, and a connecting sleeve is used at the joint to prevent leakage.

(3) The temperature controller was adjusted to 60 ℃ and the constant temperature water tank was opened. Setting the flow rate of the injection pump to be 0.1ml/min, as shown in figure 1, under the driving of the injection pump, the solution enters the reaction capillary from the injector, the precursor solution and the reducing agent solution are mixed in the T-shaped tee joint, and simultaneously, the solution is reacted by taking the liquid drop as a reaction unit to generate silver nanoparticles, and the silver nanoparticles flow into the collection device under the continuous flow of the base liquid.

Example 2

(1) Firstly preparing a precursor solution, and weighing silver nitrate (AgNO) with the mass of 0.034g by using a precision balance₃) And 0.111g of polyvinylpyrrolidone (mass of PVP calculated as the molecular weight of the monomer) (concentration ratio of Ag to PVP 1: 5) dissolving silver nitrate in 100ml of deionized water to serve as a precursor solution, dissolving polyvinylpyrrolidone in 100ml of 5g/L ascorbic acid solution to serve as a reducing agent, and then carrying out magnetic stirring for 15min and ultrasonic oscillation for 45min to completely dissolve the polyvinylpyrrolidone.

(2) A microfluidic preparation system was constructed as in step (2) of example 1.

(3) The synthesis of silver nanofluid was performed as in example 1, step (3).

Example 3

(1) Silver nitrate (AgNO) with a mass of 0.034g was weighed out with a precision balance₃) And 0.0666g of polyvinylpyrrolidone (mass of PVP calculated as the molecular weight of the monomer) (the ratio of the mass concentration of the substances Ag and PVP is 1: 3) dissolving silver nitrate in 100ml of deionized water to serve as a precursor solution, dissolving polyvinylpyrrolidone in 100ml of 5g/L ascorbic acid solution to serve as a reducing agent, and then carrying out magnetic stirring for 15min and ultrasonic oscillation for 45min to completely dissolve the polyvinylpyrrolidone.

(2) A microfluidic preparation system was constructed as in step (2) of example 1.

(3) The synthesis of silver nanofluid was performed as in example 1, step (3).

Example 4

(1) Silver nitrate (AgNO) with a mass of 0.034g was weighed out with a precision balance₃) And 0.0222g of polyvinylpyrrolidone (mass of PVP calculated as the molecular weight of the monomer) (the ratio of the mass concentrations of the substances of Ag and PVP is 1: 1) dissolving silver nitrate in 100ml of deionized water to serve as a precursor solution, dissolving polyvinylpyrrolidone in 100ml of 5g/L ascorbic acid solution to serve as a reducing agent, and then carrying out magnetic stirring for 15min and ultrasonic oscillation for 45min to completely dissolve the polyvinylpyrrolidone.

(2) A microfluidic preparation system was constructed as in step (2) of example 1.

(3) The synthesis of silver nanofluid was performed as in example 1, step (3).

The prepared silver nano fluid has uniform particle size distribution and good stability, and does not generate agglomeration and precipitation phenomenon after standing for two months.

Claims (2)

1. A micro-fluidic synthesizer of silver nanofluid is characterized by comprising two micro injection pumps, a T-shaped three-way micro mixer, a micro reactor with an 8-shaped channel, a constant temperature water bath box, a collecting device and a temperature controller, wherein liquid outlets of the two micro injectors are respectively connected with two through ports of the T-shaped three-way pipe, a third through port of the T-shaped three-way pipe is connected with the micro reactor with the 8-shaped channel through a capillary tube, the micro reactor with the 8-shaped channel is connected with a spiral or snakelike bent capillary tube, the spiral or snakelike bent capillary tube is connected with the collecting device, the spiral or snakelike bent capillary tube is arranged in the constant temperature water bath box, and the temperature controller is connected with the micro reactor with the 8-shaped channel and is used for controlling the micro reactor with the 8-shaped channel;

structure of microreactor with "figure 8" channel: the capillary tube is bent and folded into an 8-shaped structure, an inlet and an outlet are arranged at the middle thin waist part of the 8-shaped structure, so that material flow in the capillary tube firstly enters the 0-shaped tube on one side from the middle of the 8-shaped structure to flow for a circle, then passes through the middle of the 8-shaped structure to enter the 0-shaped tube on the other side to flow for a circle, and finally flows out from the middle of the 8-shaped tube, the counter-clockwise flow is performed in the 0-shaped tube on one side, the clockwise flow is performed in the 0-shaped tube on the other side, and the 8-shaped flow-winding structure is arranged in the structure with the 8-shaped groove to form the microreactor with.

2. The microfluidic synthesis device for silver nanofluid as claimed in claim 1, wherein the diameters of the capillaries are all 300 and 350 microns, and the inner diameter of the T-shaped tee is equal to that of the capillaries.

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