Preparation system of silver angstrom crystal colloid with high purity and high particle size consistency

Abstract

The invention provides a preparation system of high-purity and high-particle-size-consistency silver angstrom crystal colloid. The preparation system comprises an arc discharge chamber, an arc discharge power supply, a high-purity inert gas storage tank, a regulating valve, a vacuumizing device, a microfluidic gas-liquid mixer, a gas-liquid separator, a liquid storage container and a liquid circulating pump. The arc discharge chamber is provided with a silver electrode pair and generates high-temperature arc through a power supply. High-purity inert gas is conveyed to a discharge chamber through a regulating valve, and silver clusters are transferred into high-purity deionized water or a low-concentration silver angstrom crystal colloidal solution through a micro-fluidic gas-liquid mixer. The gas-liquid separator realizes gas-liquid separation through gravity and inertia force. The system design ensures timely cooling and stable generation of silver clusters. According to the system, the preparation efficiency and purity of the silver angstrom crystal colloid are effectively improved, and the particle size consistency is controlled under low-voltage and small-current operation conditions; the system and the process are environment-friendly and harmless, the product performance is stable, and dispersants and modifiers except water and silver elements are not contained.

Description

Technical Field

[0001] The invention relates to the field of nanocrystalline material preparation, and in particular to a silver angstrom crystal colloid preparation system with high purity and high particle size consistency. Background Art

[0002] Currently, there is no public continuous preparation system for silver angstrom crystal colloidal materials. It is also difficult to find stably dispersed silver angstrom crystal colloidal materials with high purity and high particle size consistency.

[0003] Plasma gas phase preparation of metal nanocrystalline materials technology is an important and promising method for preparing nanocrystalline materials. With its high temperature and rapid reaction characteristics, it can achieve nanocrystallization of metal materials and is widely used in high-tech fields such as catalysis, electronics, and optics. At present, the methods for preparing metal nanocrystalline materials in plasma gas phase mainly include DC arc plasma method, radio frequency plasma method and microwave plasma method. Among them, DC arc plasma method occupies an important position in research and application due to its relatively simple equipment and low cost.

[0004] The existing plasma gas phase preparation method of metal nanocrystalline materials mainly uses a tungsten electrode as the cathode and a metal as the anode. However, there are the following major technical difficulties in practical applications:

[0005] High-temperature jets can easily blow away molten metal materials, making it impossible for metal particles to be effectively deposited into nanocrystalline powders. Instead, they adhere to the container wall in the arc discharge zone, reducing the yield of collectible powder and increasing the difficulty of equipment cleaning and maintenance. Droplets in the molten metal pool are prone to splashing during the heating process, and form larger particles after cooling, affecting the uniformity and quality of the nanocrystalline powder. Due to the uneven temperature distribution in the plasma, the condensation and coagulation process of the metal vapor is unstable, and the particle size of the prepared nanocrystalline powder is uneven. At the same time, most methods for preparing nanocrystalline colloids are liquid reaction preparations. Due to the introduction of various reaction media and precursors, there are many impurity components in the product, and the purification cost is high. It is not easy to prepare high-purity silver angstrom colloids.

[0006] In this article, nanocrystals describe a larger size range than angstroms. Summary of the invention

[0007] The purpose of the present invention is to disclose a high-purity and high-particle size consistency silver angstrom colloid preparation system, which provides ultra-high purity, high particle size consistency, small trial scale, stable process, and repeatable materials for scientific research and related industrial function development.

[0008] The technical solution of the present invention is as follows:

[0009] A system for preparing silver angstrom colloids with high purity and high particle size consistency, comprising an arc discharge chamber provided with a gas input port and a gas output port, an arc discharge power supply provided with a pair or more pairs of segment output terminals, and a protective gas storage tank provided with a gas output pipeline, an airflow regulating valve, and a gas return pipeline, wherein the gas input port of the arc discharge chamber is connected to the gas output pipeline of the protective gas storage tank. The system also includes a microfluidic gas-liquid mixer, a channel-type gas-liquid separator, a liquid storage container, a liquid circulation pump, and a gas circulation pump; the microfluidic gas-liquid mixer is provided with a gas input channel, a liquid input channel, and a gas-liquid mixture discharge channel; the gas-liquid separator has a gas-liquid mixture input channel, a gas discharge channel, and a liquid discharge channel; the liquid circulation pump has a liquid input port and a liquid output port; the arc discharge chamber is provided with a pair or more pairs of silver electrodes arranged in pairs, each pair of the silver electrodes is respectively connected to a pair of power output terminals of the arc discharge power supply, and the gas output port of the arc discharge chamber is connected to the gas output port of the microfluidic gas-liquid mixer through a gas pipeline. The gas input channel is connected; the gas-liquid mixture discharge channel of the microfluidic gas-liquid mixer is connected to the gas-liquid mixture inlet of the gas-liquid separator through a gas-liquid mixture pipeline, and the liquid input channel of the microfluidic gas-liquid mixer is connected to the liquid output port of the liquid circulation pump through a liquid pipeline; the gas discharge port of the gas-liquid separator is connected to the gas circulation pump through a gas pipeline, and the liquid discharge port of the gas-liquid separator is connected to the liquid storage container through a liquid pipeline; the liquid storage container is connected to the liquid input port of the liquid circulation pump through a liquid pipeline; the liquid output port of the liquid circulation pump is connected to the liquid inlet channel of the microfluidic gas-liquid mixer through a liquid pipeline. The gas circulation pump is connected to the gas return pipeline of the protective gas storage tank.

[0010] Furthermore, a regulating valve is provided between the arc discharge chamber and the gas storage tank for regulating the flow of gas input into the arc discharge chamber.

[0011] Furthermore, the silver electrodes in the arc discharge chamber are mounted on a bracket capable of automatically adjusting the distance between the silver electrodes to adjust the gap distance between each pair of silver electrodes.

[0012] Furthermore, the system also includes a vacuum pumping device for evacuating the interior of the arc discharge chamber during the arc discharge preparation process.

[0013] Furthermore, the gas-liquid separator has a gas-liquid separation channel with multiple upper and lower baffles, which is used to separate gas and liquid by gravity and inertial force.

[0014] Furthermore, the gas circulation pump is connected to the gas return pipeline of the protective gas storage tank through a filter chamber and a cold trap, so as to remove silver angstrom particles and water vapor in the recovered gas.

[0015] Furthermore, the voltage between each pair of positive and negative output terminals of the arc discharge power supply is 0.8-1.3 kV, the current between each pair of positive and negative output terminals is 7-13 mA, and the arc discharge power supply is a pulse power supply with a pulse frequency of about 250-350 Hz.

[0016] Furthermore, the distance between each pair of silver electrodes in the arc discharge chamber is 0.3-1.0 mm, and the electrode diameter is 3-6 mm.

[0017] Furthermore, the air intake of the arc discharge chamber is 5 to 10 L / min for each pair of silver electrodes, the liquid intake of the microfluidic gas-liquid mixer is 1 to 10 ml / min, and the gas-liquid ratio (volume flow rate) entering the microfluidic gas-liquid mixer is controlled to be maintained at gas:liquid = 500:1.

[0018] Furthermore, the gas-liquid ratio entering the microfluidic gas-liquid mixer is controlled to be maintained at gas:liquid=700:1-900:1.

[0019] In order to improve the existing method of preparing metal nanocrystalline materials by plasma gas phase and solve the problems of low purity and poor particle consistency in the prior art, the technical solution proposed by the present invention mainly includes the following improvements:

[0020] Use of high-purity silver electrodes: In the present invention, both the anode and cathode of the arc discharge zone are made of high-purity silver electrodes. This configuration ensures that there will be no doping of the cathode material during the preparation process, thereby ensuring that the output has extremely high purity. The use of high-purity silver electrodes helps to improve the quality of nanocrystalline materials, making them show better performance in high-tech applications.

[0021] Low voltage and low current operating conditions: Different from the prior art, the present invention uses lower voltage, smaller current and pulsed power supply for operation. This low power operating condition helps to control the energy input of arc discharge, so that the particle size of the produced metal nanocrystal particles is small enough to reach the angstrom level and has high consistency. Under the conditions of low voltage, small current and stable energy input, the condensation process of metal vapor is more stable, which is conducive to the formation of uniform angstrom crystals.

[0022] Large cross-section and narrow spacing electrode design: In order to solve the problem of unstable arc discharge at low voltage and low current, the present invention adopts a design in which the distance between the metal anode and the metal cathode is very narrow. This design makes the ionization process easier to occur, and the arc can exist stably and continuously during the preparation process. The narrow spacing electrode design not only improves the stability of the discharge, but also reduces the disturbance of the arc, ensuring that the metal vapor is evenly condensed into nanocrystalline powder. At the same time, a larger cross-sectional area of ​​the silver metal electrode is selected, so that under the same erosion rate, the distance between the silver electrodes remains relatively stable, ensuring the system's continuous and stable output of silver angstrom crystal colloids.

[0023] Nanocrystalline particle size homogenization technology: Inert gas is blown through the silver electrode discharge gap to introduce air flow disturbance, promote the uniform condensation of silver atom clusters, and reduce the width of the generated silver angstrom grain size distribution. The disturbed cooling airflow forms a multi-stage cooling process, gradually reducing the temperature during the condensation of metal vapor to ensure the stability and uniformity of the condensation process.

[0024] The advantages of the present invention are: the technical solution of the present invention not only solves the main problems encountered in the existing process, but also significantly improves the purity of the silver angstrom crystal colloid and ensures the consistency of the silver angstrom crystal particle size distribution. This will provide more reliable and efficient technical support for the practical application of nanocrystalline materials. The present invention provides a continuous preparation process for high-purity, high-particle size consistency angstrom crystal colloids, the raw materials are easily available, the preparation process is simple, the carrier gas is recycled, it is environmentally friendly, and the product performance is stable. The concentration of the obtained silver angstrom crystal colloid can reach 50ppm, and it does not contain dispersants and modifiers other than water and silver elements, and can stably exist for more than 1 year under room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 It is the system principle diagram of the present invention;

[0027] Figure 2 is a schematic diagram of the placement of electrodes in an arc discharge chamber;

[0028] Figure 3 Schematic diagram of the structure of the gas-liquid mixing zone;

[0029] Figure 4 It is a schematic diagram of the gas-liquid separation channel structure;

[0030] Figure 5 a is a TEM image of the silver angstrom colloid prepared in Example 10 of the present invention;

[0031] Figure 5 b is a particle size distribution diagram of the silver angstrom colloid prepared in Example 10 of the present invention;

[0032] Figure 6 This is the XRD pattern of the silver angstrom powder prepared in Example 11 of the present invention;

[0033] Figure 7 This is the XRD-standard PDF card of silver crystal;

[0034] Figure 8 is the relationship between the concentration of silver angstrom colloid and different cycle times;

[0035] Fig. 9 is a graph showing the relationship between the concentration of silver angstrom colloid and different gas-liquid ratios in Example 13;

[0036] Fig.10 The particle size distribution diagram of the silver angstrom colloid in Example 13 with a gas-liquid ratio between 100:1 and 500:1;

[0037] Fig.11 The particle size distribution diagram of the silver angstrom colloid in Example 13 with a gas-liquid ratio between 600:1 and 900:1;

[0038] Fig.12 The particle size distribution diagram of the silver angstrom colloid in Example 13 with a gas-liquid ratio between 1000:1 and 1500:1;

[0039] Fig.13 a is deionized water without Tyndall effect;

[0040] Fig.13 b is the Tyndall effect of the low-stage gas-liquid ratio (100:1-500:1) of Example 5;

[0041] Fig.13 c is the Tyndall effect of the gas-liquid ratio (500:1 to 900:1) in the stage of Example 5;

[0042] Fig.13 d is the Tyndall effect of the high-stage gas-liquid ratio (1000:1-1500:1) of Example 5; DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings, but it should be understood that the present invention is not limited to the scope of the following embodiments. The methods described are all conventional methods unless otherwise specified.

[0045] Embodiment 1:

[0046] Angstrom: The approximate particle size range of nanocrystalline materials in academia is 1 to 10 nm. In the present invention, because of the stable size distribution colloidal state of nanocrystalline metals in water determined by the process, "Angstrom" is used to represent high-purity nanocrystalline colloids with a particle size of 2 to 4 nm.

[0047] Plasma gas phase preparation of metal nanocrystalline materials technology is an important and promising method for preparing nanocrystalline materials. With its high temperature and rapid reaction characteristics, it can achieve nanocrystallization of metal materials, and the prepared products are widely used in high-tech fields such as catalysis, electronics, and optics. At present, the methods for preparing metal nanocrystalline materials in plasma gas phase mainly include DC arc plasma method, radio frequency plasma method and microwave plasma method. Among them, DC arc plasma method occupies an important position in research and application due to its relatively simple equipment and low cost.

[0048] Most of the existing plasma gas phase preparation of metal nanocrystalline materials uses a tungsten electrode as the cathode and the metal to be prepared as the anode. Although this method is feasible in theory, there are still many technical problems to be solved in practical applications. The following are the main problems encountered in the current DC arc plasma method for preparing nanocrystalline metal powders:

[0049] Jet problems of plasma jet: The high-temperature jet of plasma jet easily blows away the molten metal itself, causing these blown-away metal particles to be unable to effectively deposit into nanocrystalline metal powder, but to adhere to the container wall in the arc discharge area. This not only reduces the yield of collectible nanocrystalline metal powder, but also increases the difficulty of cleaning and maintenance of the equipment. In addition, the metal particles attached to the container wall will affect the purity and consistency of subsequent experiments, reducing the overall quality of the product.

[0050] Droplet splashing during heating: During the heating process, droplets in the molten metal pool tend to splash out. These splashed droplets form larger particles after cooling, resulting in large particles always existing in the nanocrystalline powder. The presence of large particles not only affects the uniformity and quality of the product, but also has an adverse effect on subsequent application performance. For example, in catalyst applications, nanocrystalline powders with a wide particle size distribution can lead to uneven catalytic reactions, thereby reducing catalytic efficiency.

[0051] Problem of uneven particle size of nanocrystalline powder: The nanocrystalline powder prepared by the current process has uneven particle size and a wide particle size distribution. This is mainly due to the uneven temperature distribution in the plasma, which leads to unstable condensation and coagulation processes of metal vapor. Uneven particle size will directly affect the physical and chemical properties of nanocrystalline materials and reduce their performance in practical applications. For example, in electronic materials, nanocrystalline powders with uneven particle size will affect the conductivity and stability of the material. The existing technology either cannot prepare silver angstrom crystal materials with good particle size consistency, or requires the addition of complex sorting processes in the subsequent process, which is complicated and has high system costs. The preparation system provided by the present invention can prepare silver angstrom crystal materials with very consistent particle size at one time, while also reducing the time and cost costs brought about by multiple sorting processes.

[0052] At the same time, most methods for preparing silver nanocrystalline colloids are liquid reaction preparation. Due to the introduction of various reaction media and precursors, there are many impurity components in the product, the purification cost is high, and it is not easy to prepare high-purity silver angstrom colloids. In addition to high-purity silver electrodes and deionized water, the system provided by the present invention does not introduce any other additives in the preparation process, so it can prepare very high-purity silver angstrom colloids at one time.

[0053] To this end, the present invention proposes a system for preparing high-purity silver angstrom crystal colloid by physical vapor phase method plus vapor phase transport, which can stably prepare high-purity and high-particle consistency silver angstrom crystal colloid in one time without complicated post-purification treatment, and has the advantages of simple process and good consistency of silver angstrom crystal particles.

[0054] Reference Figure 1 As shown, a high-purity and high-particle-size-consistency silver angstrom colloid preparation system used in the present invention includes an arc discharge chamber 01 provided with a gas input port and a gas output port, an arc discharge power supply 012 provided with one or more pairs of segment output terminals, and a protective gas storage tank 010 provided with a gas output pipeline, an airflow regulating valve 011, and a gas return pipeline. The gas input port of the arc discharge chamber 01 is connected to the gas output pipeline of the protective gas storage tank 010.

[0055] The system further comprises a microfluidic gas-liquid mixer 04, a channel-type gas-liquid separator 05, a liquid storage container 06, a liquid circulation pump 013, and a gas circulation pump 08;

[0056] The microfluidic gas-liquid mixer 04 is provided with a gas input channel, a liquid input channel and a gas-liquid mixture discharge channel; the gas-liquid separator 05 has a gas-liquid mixture input channel, a gas discharge channel and a liquid discharge channel; the liquid circulation pump 013 has a liquid input port and a liquid output port; the arc discharge chamber 01 has a pair of or more pairs of silver electrodes 02, 03 arranged in pairs, each pair of the silver electrodes is respectively connected to a pair of power output terminals of the arc discharge power supply 012, and the gas output port of the arc discharge chamber 01 is connected to the gas input channel of the microfluidic gas-liquid mixer 04 through a gas pipeline; the gas-liquid The mixture discharge channel is connected to the gas-liquid mixture inlet of the gas-liquid separator 05 through a gas-liquid mixture pipeline, and the liquid input channel of the microfluidic gas-liquid mixer 04 is connected to the liquid output port of the liquid circulation pump 013 through a liquid pipeline; the gas discharge port of the gas-liquid separator 04 is connected to the gas circulation pump 08 through a gas pipeline, and the liquid discharge port of the gas-liquid separator 04 is connected to the liquid storage container 06 through a liquid pipeline; the liquid storage container 06 is connected to the liquid input port of the liquid circulation pump 013 through a liquid pipeline; the liquid output port of the liquid circulation pump 013 is connected to the liquid inlet channel of the microfluidic gas-liquid mixer 04 through a liquid pipeline. The gas circulation pump 08 is connected to the gas return pipeline of the protective gas storage tank 010.

[0057] Figure 1 A schematic diagram of a system for preparing silver angstrom crystal colloid provided by the present invention, wherein 01 is an arc discharge chamber, the arc discharge chamber 01 is provided with a gas input port, a gas output port, and a pair or more pairs of silver electrodes 02 and 03 arranged in pairs, the gas input port is connected to the output pipeline of the protective gas storage tank 010, the gas output port is connected to the gas input channel of the microfluidic gas-liquid mixer 04 through the gas output pipeline, and each pair of silver electrodes is respectively connected to a pair of power output terminals of the arc discharge power supply 012.

[0058] The silver electrodes are placed on a bracket of the arc discharge chamber 01 with an automatically adjustable distance. Each pair of silver electrodes is respectively connected to a pair of power output terminals of the arc discharge power supply 012. The arc discharge chamber 01 is connected to a gas storage tank 010 storing high-purity inert gas. The gas in the gas storage tank 010 can be adjusted by a regulating valve 011 and then input into the arc discharge area in the arc discharge chamber 01 through a gas input port. A vacuum pumping device is provided on the gas path connected to the gas output port. During the arc discharge preparation process, the interior of the arc discharge chamber 01 is first vacuumed, and then high-purity argon gas is input through the gas input port, and the voltage of the arc discharge power supply 012 is adjusted to induce an arc between the silver electrode pairs. After the arc is generated, the output voltage and output current of the arc discharge power supply 012 are adjusted, and the gap distance between the electrode pairs is adjusted to maintain the arc discharge stable.

[0059] Before the formal preparation begins, various preparations are usually carried out. High-purity deionized water is placed in the liquid storage container 06. The deionized water is used to elute the silver atomic clusters from the transport gas. High-purity silver electrodes 02 and 03 are placed in pairs in the arc discharge chamber 01. Unlike the usual gas phase physical preparation method of nanocrystalline metal materials, the prior art uses tungsten metal with a very high melting point as the cathode, and the target metal to be prepared, such as silver, as the anode. Inert gases such as argon are used as the protective atmosphere and transport gas. Usually, in order to prevent oxidation reactions at high temperatures, a small amount of highly reducing hydrogen is mixed into the inert gas to prevent the target metal (such as metallic silver) from being oxidized at high temperatures. Most of the prior art is industrialized production, and the voltage used is relatively high, so the distance between the anode and the cathode is also relatively large.

[0060] In order to achieve the effect of stable preparation, the present invention adjusts the spacing between the silver electrode 02 and the silver electrode 03 to 0.3-1.0 mm. In order to ensure that the silver electrode or silver angstrom particles will not be oxidized due to oxidation during the working process, the airtight arc discharge chamber 01 will be evacuated using a vacuum pump in the preparation stage, and then an inert gas will be introduced into the arc discharge chamber 01 through the protective gas storage tank 010. In order to achieve a better inert gas protection atmosphere, after the inert gas is introduced into the arc discharge chamber 01, the gas circulation pump 08 on the gas circulation path can be turned on to circulate the gas on the gas circulation path, and the collected inert gas will pass through the filter chamber 07 and the cold trap 09 in turn, and then the gas in the gas circulation path will be discharged, and the protective gas storage tank 010 will be maintained to ventilate the gas circulation path for more than 2 minutes to ensure that the non-inert gas impurities in the circulation path are well isolated before starting the formal preparation.

[0061] At the same time, in order to further improve the purity of the inert protective gas in the gas circulation path, the arc discharge chamber 01 and the gas circulation path can be evacuated twice, the extracted gas is discharged, and high-purity inert gas is introduced into the arc discharge chamber 01 again to ensure that there is no impurity interfering gas in the gas circulation path. In our practice, we found that if a small amount of hydrogen is mixed into an inert gas such as argon as a protective gas, although theoretically it can better protect the silver angstrom particles generated by the arc discharge chamber 01 from oxidation, hydrogen will have a greater impact on the service life of the gas circulation pump 08, so the present invention uses high-purity argon without hydrogen as a protective gas, and the recommended purity of the argon is 99.999%.

[0062] After the gas circulation path is established and maintains normal operation, the inert gas intake volume is controlled at 5-10 L / min, the arc discharge power supply 012 is controlled, a high-voltage arc is initiated between the silver electrode 02 and the silver electrode 03 of the arc discharge chamber 01, the positive and negative electrode voltages are controlled to be 0.8-1.3 kV, the current between the positive and negative electrodes is 7-13 mA, and the pulse frequency is about 250-350 Hz to maintain the continuous existence of the high-voltage arc.

[0063] It should be noted here that the voltage for initiating a high-voltage arc is often higher than the normal working voltage for preparation. After the arc is initiated, the working voltage needs to be controlled to a lower working voltage. At the same time, the initial current intensity when the arc is initiated is often greater than the normal working current for preparation, but the large current will affect the consistency and particle size of the prepared silver angstrom crystal particles. Therefore, it is particularly important in the present invention that after the normal preparation begins, the positive and negative electrode voltages are controlled to be 0.8-1.3 kV, the current between the positive and negative electrodes is 7-13 mA, and the pulse power supply is pulsed with a pulse frequency of about 250-350 Hz to maintain the continuous existence of the high-voltage arc. The lower voltage and smaller current relative to the prior art, the pulse power supply is the core feature of the present invention. Only in this state can the prepared silver angstrom crystal particles maintain better size consistency.

[0064] During the normal preparation process, the arc discharge power supply 012 applies a high-voltage electric pulse of about 300Hz between the two poles of each pair of silver electrodes. The high-voltage electric pulse breaks through the inert gas (usually argon) filled in the arc discharge chamber and is adjusted to form a stable arc. The high-temperature arc acts on the silver electrode. The arc temperature generated by the high-voltage pulse between the silver electrodes in the normal pressure inert atmosphere is about 3000K-6000K, which can instantly heat and evaporate the atoms on the surface of the silver electrode, and then quickly diffuse into the inert gas molecular atmosphere. Most of them will collide with the inert gas molecules due to Brownian motion and cool and condense into silver atomic clusters. At this time, the surface energy of the silver atomic clusters is relatively high. In order to better avoid impurities affecting the surface activity and purity, they need to be mixed with relevant media as soon as possible.

[0065] The microfluidic gas-liquid mixer 04 has a gas inlet channel, a liquid inlet channel, and a gas-liquid mixture outlet channel, and the gas inlet channel, the liquid inlet channel and the gas-liquid mixture outlet channel are connected through a plurality of gas-liquid mixing chambers inside the microfluidic gas-liquid mixer 04 .

[0066] The newly formed silver atom cluster aerosol quickly enters the gas path of the microfluidic gas-liquid mixer 04 through the gas inlet channel of the gas-liquid mixer 04, and is divided into two paths according to probability, which intersect in a serpentine shape; at the same time, high-purity water (or the already generated low-concentration silver angstrom crystal colloidal solution) enters the liquid path of the gas-liquid mixer through the liquid inlet channel of the microfluidic gas-liquid mixer 04, and moves forward in a straight line.

[0067] The intersection of the two serpentine gas paths in the microfluidic gas-liquid mixer 04 is connected to the cross passage of the liquid path, and the faster airflow brings the water in the liquid path (or the low-concentration silver angstrom colloidal solution that has been generated) into the airflow for oscillation and mixing.

[0068] The internal effective mixing volume of the microfluidic gas-liquid mixer 04 is about 2mL, which includes multiple gas-liquid mixing chambers connected in series, and the volume of a single gas-liquid mixing chamber is between 0.001mL and 0.01mL. The inert gas carrying the silver atomic clusters and the liquid in the liquid path (water or a low-concentration silver angstrom crystal colloidal solution that has been generated) are sequentially passed through multiple gas-liquid mixing chambers for multiple oscillations and mixing. The silver angstrom crystal particles transported in the gas are eluted into the liquid, completing the transportation of the silver atomic cluster particles from the arc discharge chamber 01 to the liquid, and reaching the gas-liquid mixture discharge channel of the microfluidic gas-liquid mixer 04 to complete the mixing.

[0069] The channel-type gas-liquid separator 05 has a gas-liquid mixture inlet, a gas outlet, a liquid outlet and a gas-liquid separation channel with multiple upper and lower baffles. The separation channel of the gas-liquid separator 05 is closed at both ends except for the gas-liquid mixture inlet, the gas outlet and the liquid outlet. It is usually cylindrical, with a gas-liquid mixture inlet at one end, a gas outlet at the top of the other end, and a liquid outlet at the bottom. The channel-type gas-liquid separator 05 is usually in the shape of a long cylinder, and its cross-section can also be circular, elliptical or other shapes. Staggered baffles are respectively arranged at the upper and lower parts of the gas-liquid separation channel. In the process of passing through the gas-liquid separation channel, the gas-liquid mixture is naturally separated into gas containing a small amount of liquid molecules and liquid molecules by the upper and lower baffles and gravity. The gas is discharged from the gas outlet at the top of the other end, and the liquid is discharged from the liquid outlet at the bottom.

[0070] The gas-liquid mixture discharge channel of the microfluidic gas-liquid mixer 04 is connected to the gas-liquid mixture inlet of the gas-liquid separator 05. The gas-liquid mixture is separated into gas and liquid through a gas-liquid separation channel composed of multiple upper and lower baffles. By utilizing the density difference between gas molecules, liquid molecules and metal atom clusters in the gas-liquid mixture, the gas-liquid mixture enters from one end of the gas-liquid separation channel of the gas-liquid separator 05, passes through multiple baffles, and the lighter gas molecules are discharged from the top through the gas discharge channel, while the heavier metal atom clusters and water molecules fall to the bottom of the separation tube and flow out along the liquid discharge outlet channel to form a silver angstrom crystal colloidal solution.

[0071] The silver angstrom crystal colloidal solution of the gas-liquid separator 05 is transported to the liquid storage container 06 through the solution passage, and the colloidal solution in the liquid storage container 06 can be further transported to the liquid entry channel of the microfluidic gas-liquid mixer 04 through the liquid circulation channel for further gas-liquid mixing circulation. After a period of circulation and mixing, the silver angstrom crystal particles in the argon gas carrying the silver angstrom crystal aerosol are continuously eluted, and finally reach a certain concentration, that is, the successfully prepared high-purity silver angstrom crystal colloid.

[0072] The liquid storage container 06 collects the silver angstrom crystal colloidal solution separated from the gas-liquid separator 05. At the beginning of the preparation, high-purity deionized water is placed in the liquid storage container 06, and a liquid pump 013 with an adjustable flow rate is arranged on the liquid passage from the liquid storage container 06 to the microfluidic gas-liquid mixer 04. The liquid pump 013 is responsible for pumping the liquid in the liquid storage container 06 into the liquid passage inlet of the microfluidic gas-liquid mixer 04 according to the set flow rate.

[0073] The liquid in the liquid storage container 06 is initially high-purity deionized water, and as the preparation process progresses, it gradually becomes a colloidal solution of silver angstrom crystals with a concentration varying from low to high. As the preparation process continues, the concentration of silver angstrom crystal particles in the liquid storage container 06 gradually increases, and finally reaches the concentration required for the preparation.

[0074] In order to timely understand the concentration of silver colloid in the final product, a laser particle size analyzer is usually set up to detect the abundance of silver angstrom crystal particles in the solution online. Since the silver angstrom crystal particles dispersed in the solution have the Tyndall effect, the liquid storage container 06 is usually a transparent glass container. The laser pen is turned on to let the laser pass through the temporary storage pool. The increase in the concentration of silver angstrom crystal colloid can be roughly known by observing the degree of laser scattering. See Figure 013 for a photo of the Tyndall effect of silver angstrom crystal colloid. From left to right, the Tyndall effect becomes more obvious as the concentration of silver angstrom crystal particles increases.

[0075] The inert gas separated from the gas-liquid separator 05 usually carries trace amounts of silver atom clusters and a small amount of water vapor. The separated inert gas is transported to the protective gas storage tank 010 by the gas circulation pump 08. In order to avoid the possible influence of water vapor on the normal operation of the arc discharge chamber 01, a cold trap 09 is usually arranged between the gas circulation pump 08 and the protective gas storage tank 010, and the water vapor carried in the separated inert gas is removed by forced condensation in the cold trap 09.

[0076] In order to prevent the silver angstrom crystal particles that may be carried by the separated inert gas from accumulating in the cold trap 09 and the protective gas storage tank 010, a filter chamber 07 can usually be set between the cold trap 09 and the gas circulation pump 08 to filter and intercept the silver angstrom crystal particles that may be carried in the separated inert gas through multiple layers of filter membranes to prevent the silver angstrom crystal particles from accumulating in the cold trap 09 and the protective gas storage tank 010.

[0077] The present invention aims to obtain a non-surface-modified silver angstrom colloidal aqueous solution (2-4nm, ≥20ppm)

[0078] The raw materials are obtained as follows:

[0079] Argon: purity 99.999%, available on the market.

[0080] Deionized water: Available in the market.

[0081] The purity of the silver electrode is 99.999%, and the sum of other impurity elements in the electrode does not exceed 1ppm.

[0082] High-voltage arc plasma preparation of nanocrystalline powder technology principle description:

[0083] Figure 2 The schematic diagram of the placement of electrodes in the arc discharge chamber is shown. Silver aerosol is formed when the electrons in the inert gas used as the protective gas are accelerated by the electric field under the action of the electric field. When their speed (kinetic energy) reaches a certain value, neutral atoms or molecules are ionized to obtain more free electrons. These electrons further accelerate and excite other neutral particles to produce an ionization process similar to the avalanche phenomenon, resulting in the discharge of the inert gas to form plasma. The high temperature of the plasma (up to 3000K-30000K) is used to melt and evaporate the metal to form gaseous metal atoms.

[0084] Silver atom cluster aerosol generation: First, use arc evaporation target to generate metal plasma. The arc temperature generated by the high-voltage pulse between metal electrodes in an inert atmosphere at normal pressure is about 3000K-6000K, which can instantly heat and evaporate the atoms on the surface of the metal electrode, and then quickly diffuse into the inert gas molecule atmosphere. Most of them will cool and condense into atomic clusters due to Brownian motion and collision with gas molecules. At this time, the surface energy of the atomic clusters is relatively high. In order to better avoid impurities affecting surface activity and purity, they need to be mixed with relevant media as soon as possible. The parameters in this process are controlled as follows:

[0085] Positive and negative voltage: 1kV

[0086] Current between positive and negative electrodes: 10mA

[0087] Pulse frequency: about 300Hz

[0088] Distance between electrodes: 0.5mm (0.3~0.5mm)

[0089] Electrode diameter 6mm (3mm~6mm)

[0090] Electrode cross section: round, oval, teardrop

[0091] Figure 3 It is a structural schematic diagram of the gas-liquid mixing zone.

[0092] Silver atom cluster aerosol transport: The focus is on gas-liquid mixing, eluting the silver atom clusters into the solution. The newly formed aerosol quickly enters the gas path of the gas-liquid mixing chamber through the gas entry channel of the gas-liquid mixing chamber, and is divided into two paths according to probability, which intersect and forcefully intersect in a serpentine shape; at the same time, high-purity water (or the already generated low-concentration silver angstrom colloid solution) enters the liquid path of the gas-liquid mixing chamber through the liquid entry channel of the gas-liquid mixing chamber, and moves forward in a straight line. The intersection of the two gas paths serpentinely forward is connected to the cross passage of the liquid path, and the faster airflow brings the water in the liquid path or the already generated low-concentration silver angstrom colloid solution into the airflow for oscillation mixing. The gas-liquid mixture that reaches the gas-liquid mixing chamber is discharged from the channel to complete the mixing. The parameters in this process are controlled as follows:

[0093] The gas is argon, the purity of argon is greater than 99.999%, the moisture content is below 0.05ppm, and the air intake volume is 5-10L / min.

[0094] The liquid is deionized water, and the liquid inlet rate is 1-10 ml / min.

[0095] The gas-liquid ratio (volume flow rate) in the gas-liquid mixture is maintained at gas:liquid = 1000:1 to 500:1.

[0096] The temperature is 20°C to 40°C, and the system pressure is 900mbar to 1013mbar.

[0097] In the actual preparation process of silver angstrom colloid, if the final required silver angstrom colloid has a higher concentration than the silver angstrom colloid directly prepared by the system, the solution obtained in the gas-liquid separator can usually be heated and concentrated to obtain silver angstrom colloid solutions of different concentrations. In order to prevent the silver element from reacting with the environment during the heating process and introducing unnecessary impurities, silver angstrom colloid solutions of different concentrations can be prepared by vacuum distillation to improve production efficiency and ensure the high purity of the silver angstrom colloid solution.

[0098] The method provided by the present invention can also be used to prepare silver angstrom crystal powder with high purity and high particle size consistency. The solution obtained in the gas-liquid separator is heated and concentrated, and the liquid is fully dried to obtain a silver angstrom crystal powder. Since the silver angstrom crystal powder has a high surface energy, it is easily oxidized when directly exposed to oxygen-containing air, so it should be noted that the preparation of the silver angstrom crystal powder usually needs to be carried out at a lower temperature.

[0099] Features and advantages of the present invention:

[0100] High-purity products: High-purity silver electrodes and inert gases are used to ensure that the generated silver angstrom colloid is of high purity.

[0101] High efficiency: The yield and stripping efficiency of silver atom clusters are improved by using multiple pairs of silver electrodes and adjusting the corresponding gas flow.

[0102] Stable and continuous arc discharge: The current increases proportionally with the silver electrode pair to ensure a stable supply of arc discharge energy.

[0103] Optimized gas processing: The system uses a low-temperature cold trap to effectively remove moisture from the gas and reduce the interference of water vapor on system operation.

[0104] To further illustrate various possible situations and different implementations, the present invention may have many different embodiments.

[0105] Embodiment 2:

[0106] According to the above embodiment, a regulating valve 011 is further provided between the arc discharge chamber 01 and the protective gas storage tank 010 for adjusting the gas flow rate input into the arc discharge chamber 01. The gas intake volume of the arc discharge chamber is 5 to 10 L / min corresponding to the gas supply volume for each pair of silver electrodes.

[0107] Before the reaction starts, ensure that the gas in the arc discharge zone reaches a vacuum degree below 0.01Mpa, and then introduce protective gas (such as argon) to ensure the purity and stability of the reaction.

[0108] The production and efficiency of silver atom clusters can also be increased by using multiple pairs of electrodes. At the same time, with each additional pair of silver electrodes, the volume flow rate of the introduced inert gas (such as argon) needs to be increased synchronously to ensure that the silver atom clusters can be transported to the next processing unit in a timely manner.

[0109] Embodiment 3:

[0110] According to the above-mentioned embodiment, the silver electrodes in the arc discharge chamber 01 are mounted on a bracket capable of automatically adjusting the distance, so as to adjust the gap distance between each pair of silver electrodes.

[0111] The gap distance between the silver electrode pairs is very important for stable preparation. If the distance between the silver electrode pairs is too far, the voltage and current intensity of the initial high-voltage arc need to be increased. Excessive voltage and current lead to too high energy input power during the preparation process, which can easily cause the silver angstrom particles to be too large or uneven in size. Therefore, it is necessary to start with a smaller electrode gap to better initiate the arc. At the same time, after the arc is working stably, the electrode gap distance should be appropriately increased to maintain stable arc operation.

[0112] Another reason for adjusting the gap distance is that as the preparation progresses, the surface of the silver electrode is continuously eroded and the electrode gap gradually increases. If the electrode gap is not adjusted in time, the arc will be interrupted and the preparation cannot proceed normally. Therefore, it is necessary to automatically adjust the gap distance between each pair of silver electrodes.

[0113] By setting up an electrode bracket with automatically adjustable distance, the gap distance between each pair of silver electrodes can be automatically adjusted, which is beneficial to initiating arc generation during initial operation, maintaining long-term stable operation of the preparation system, and reducing the adverse effects of arc interruption caused by excessive distance between electrodes on the continuous preparation process.

[0114] Embodiment 4:

[0115] According to the above-mentioned embodiment, the system further comprises a vacuuming device for evacuating the interior of the arc discharge chamber during the arc discharge preparation process.

[0116] In order to ensure that the silver electrode or silver angstrom particles will not be oxidized due to oxidation during the working process, the airtight arc discharge chamber 01 will be evacuated using a vacuum pump in the preparation stage, and then inert gas will be introduced into the arc discharge chamber 01 through the protective gas storage tank 010. In order to achieve a better inert gas protection atmosphere, after the inert gas is introduced into the arc discharge chamber 01, the gas circulation pump 08 on the gas circulation path can be turned on to circulate the gas on the gas circulation path, and the collected inert gas will pass through the filter chamber 07 and the cold trap 09 in turn, and then the gas in the gas circulation path will be discharged, and the protective gas storage tank 010 will be maintained to ventilate the gas circulation path for more than 2 minutes to ensure that the non-inert gas impurities in the circulation path are well isolated before starting the formal preparation.

[0117] At the same time, in order to further improve the purity of the inert protective gas in the gas circulation path, the arc discharge chamber 01 and the gas circulation path can be evacuated twice, the extracted gas can be discharged, and high-purity inert gas can be introduced into the arc discharge chamber 01 again to ensure that there is no impurity interfering gas in the gas circulation path.

[0118] Embodiment 5:

[0119] According to the above-mentioned embodiment, the gas-liquid separator has a gas-liquid separation channel with multiple upper and lower baffles, which is used to separate gas and liquid by gravity and inertial force.

[0120] Figure 4 Schematic diagram of the gas-liquid separation channel structure. Gas-liquid separation is achieved by passing the gas-liquid mixture through a gas-liquid separation channel composed of multiple upper and lower baffles. The gas-liquid mixture 4 enters from one end of the channel and passes through multiple baffles. The lighter gas molecules are discharged from the top through the gas discharge channel 5, and the heavier metal atom clusters and water molecules fall to the bottom of the separation tube and flow out along the channel to form a silver angstrom crystal colloidal solution 6. The silver angstrom crystal colloidal solution 6 can further enter the gas-liquid mixing cycle.

[0121] The channel-type gas-liquid separator 05 has a gas-liquid mixture inlet, a gas outlet, a liquid outlet and a gas-liquid separation channel with multiple upper and lower baffles. The separation channel of the gas-liquid separator 05 is closed at both ends except for the gas-liquid mixture inlet, the gas outlet and the liquid outlet. It is usually cylindrical, with a gas-liquid mixture inlet at one end, a gas outlet at the top of the other end, and a liquid outlet at the bottom. The channel-type gas-liquid separator 05 is usually in the shape of a long cylinder, and its cross-section can also be circular, elliptical or other shapes. Staggered baffles are respectively arranged at the upper and lower parts of the gas-liquid separation channel. In the process of passing through the gas-liquid separation channel, the gas-liquid mixture is naturally separated into gas containing a small amount of liquid molecules and liquid molecules by the upper and lower baffles and gravity. The gas is discharged from the gas outlet at the top of the other end, and the liquid is discharged from the liquid outlet at the bottom.

[0122] The gas-liquid mixture discharge channel of the microfluidic gas-liquid mixer 04 is connected to the gas-liquid mixture inlet of the gas-liquid separator 05. The gas-liquid mixture is separated into gas and liquid through a gas-liquid separation channel composed of multiple upper and lower baffles. By utilizing the density difference between gas molecules, liquid molecules and metal atom clusters in the gas-liquid mixture, the gas-liquid mixture enters from one end of the gas-liquid separation channel of the gas-liquid separator 05, passes through multiple baffles, and the lighter gas molecules are discharged from the upper part through the gas discharge channel, while the heavier metal atom clusters and water molecules fall to the bottom of the separation tube and flow out along the liquid discharge outlet channel to form a silver angstrom crystal colloidal solution.

[0123] It should be noted that this embodiment provides an implementation scheme for realizing gas-liquid separation, and does not limit other feasible implementation schemes. For example, modifying the horizontal separation channel to a vertical one, or modifying the staggered baffles to spiral baffles or spiral staircase-style baffles are all within the protection scope of the present invention.

[0124] Embodiment 6:

[0125] According to the above-mentioned embodiment, the gas circulation pump is connected to the gas return pipeline of the protective gas storage tank through a filter chamber and a cold trap, so as to remove silver angstrom grains and water vapor in the recovered gas.

[0126] The inert gas separated from the gas-liquid separator 05 usually carries a trace amount of silver atom clusters and a small amount of water vapor. The separated inert gas is transported to the protective gas storage tank 010 by the gas circulation pump 08. In order to avoid the possible influence of water vapor on the normal operation of the arc discharge chamber 01, a cold trap 09 is usually set between the gas circulation pump 08 and the protective gas storage tank 010, and the water vapor carried in the separated inert gas is removed by forced condensation in the cold trap 09. In order to avoid the accumulation of silver angstrom crystal particles that may be carried by the separated inert gas in the cold trap 09 and the protective gas storage tank 010, a filter chamber 07 can usually be set between the cold trap 09 and the gas circulation pump 08, and the silver angstrom crystal particles that may be carried in the separated inert gas are filtered and intercepted by a multi-layer filter membrane to avoid the accumulation of silver angstrom crystal particles in the cold trap 09 and the protective gas storage tank 010.

[0127] Embodiment 7:

[0128] According to the above implementation, the voltage between each pair of positive and negative output terminals of the arc discharge power supply is 0.8-1.3 kV, the current between each pair of positive and negative output terminals is 7-13 mA, and the arc discharge power supply is a pulse power supply with a pulse frequency of about 250-350 Hz.

[0129] It should be noted that the use of multiple pairs of silver electrodes can increase the generation efficiency and stripping efficiency of silver atom clusters to a certain extent. However, if the arc discharge current is not increased synchronously, the energy allocated to each electrode pair may not be enough to maintain the stable operation of the arc discharge current, resulting in work interruption, requiring manual intervention, and reducing the system output efficiency.

[0130] However, it should be noted that when the arc discharge voltage remains unchanged, the current should be increased proportionally according to the number of silver electrode pairs to ensure that the current between each pair of positive and negative output terminals is 7 to 13 mA. Preferably, an isolation circuit can be set on the arc discharge power supply to independently control the power supply current for each pair of silver electrodes, and the flow rate of the protective gas introduced needs to be increased synchronously. Actual tests have shown that if the number of silver electrode pairs is simply increased without increasing the flow rate of the protective gas introduced, the newly generated silver atom clusters may not be effectively transported, and thus adhere to and accumulate on the inner surface of the arc discharge chamber, and the output efficiency cannot be effectively improved.

[0131] Arc discharge zone parameters:

[0132] Arc discharge current: Increases in proportion to the number of silver electrode pairs, 10mA per pair of electrodes Initial vacuum: Below 0.01Mpa

[0133] Protective gas: high purity inert gas (such as argon).

[0134] Embodiment 8:

[0135] According to the above embodiment, the distance between each pair of silver electrodes in the arc discharge chamber is 0.3-1.0 mm, and the electrode diameter is 3-6 mm.

[0136] As described in Example 3, the spacing between the electrode pairs affects the initiation of the arc and the subsequent continuous preparation. The present invention recommends that the spacing between each pair of silver electrodes is 0.3-1.0 mm, preferably 0.5 mm.

[0137] At the same time, the diameter of the electrode also affects the normal preparation. When the electrode diameter is relatively thick, the gap between the electrodes can be kept relatively stable, which is conducive to continuous preparation. However, if the electrode diameter is too large, the silver atom clusters generated inside the electrode cannot be effectively diffused and transported, which will also affect the quality of the prepared product. At the same time, if too much silver powder is loaded on the electrode surface, it may cause arc interruption and affect the smooth progress of the preparation. The size of the electrode is actually related to many factors, especially the voltage, current and the flow rate of the inert gas, and these parameters need to be perfectly matched.

[0138] Therefore, the present invention recommends an electrode diameter of 3 to 6 mm, preferably 6 mm.

[0139] Embodiment 9:

[0140] According to the above-mentioned embodiment, the air intake amount of the arc discharge chamber is 5-10 L / min corresponding to the air supply amount of each pair of silver electrodes, the liquid intake amount of the microfluidic gas-liquid mixer is 1-10 ml / min, and the gas-liquid ratio (volume flow rate) entering the microfluidic gas-liquid mixer is controlled to be maintained at gas: liquid = 500:1.

[0141] Under the protection of inert gas, a pair of high-purity silver electrode surfaces are continuously vaporized into silver atomic clusters using a high-voltage arc in the arc discharge chamber 01, and the inert gas intake at room temperature into the arc discharge chamber is maintained at 5 to 10 L / min. The inert gas is passed through the silver electrode gap of the arc discharge chamber to obtain an aerosol containing silver atomic clusters, and the aerosol is sent to the microfluidic gas-liquid mixer. The microfluidic gas-liquid mixer generally has a gas inlet channel, a liquid inlet channel, and a gas-liquid mixture outlet channel. The flow rate of the aerosol entering the microfluidic gas-liquid mixer is controlled at 5 to 10 L / min, and the flow rate of the liquid entering the microfluidic gas-liquid mixer through the liquid passage is controlled at 1 to 10 ml / min, and the gas-liquid mixing volume ratio is 100:1 to 1500:1.

[0142] In the present invention, the inert gas undertakes an important transport task, and the transport occurs in three links: the first link is in the arc discharge chamber, where the inert gas transports the silver atom clusters generated by the arc discharge out of the arc discharge chamber in the form of aerosol; the second link is in the microfluidic gas-liquid mixer, where the silver atom clusters in the inert gas are eluted into the liquid (initially pure water, and a silver angstrom colloid with a lower concentration during the preparation process) through the full mixing of gas and liquid; the third link is in the gas-liquid separator, where the separation of the inert gas and the liquid is completed to achieve the recovery of the inert gas. The inert gas flow rate in the first link needs to be determined according to the amount of silver atom clusters generated by the preparation. After the inert gas flow rate is determined, the gas flow rate entering the microfluidic gas-liquid mixer is determined. By matching the gas flow rate with the liquid of the corresponding flow rate, sufficient gas-liquid mixing and elution and transport of the silver atom clusters can be achieved in the microfluidic gas-liquid mixer.

[0143] Embodiment 10:

[0144] Using the preparation system proposed in the present invention, argon gas at room temperature is introduced into the arc discharge zone, and the concentration of the silver atom cluster aerosol formed per minute is controlled to be 0.1ppm, and then it quickly enters the gas-liquid mixing zone at a volume flow rate of 6L / min. The flow rate of the aerosol entering the gas-liquid mixing zone is controlled at 6L / min, and the flow rate of the liquid entering the gas-liquid mixing zone is controlled at 10mL / min. The gas-liquid mixing volume ratio is 600:1, the mixing volume of a single gas-liquid mixing zone is 2mL, the mixing time is 0.02 seconds, and the total amount of liquid is 200mL. The mixed liquid is then passed into a gas-liquid separator to form independent argon gas and independent silver angstrom crystal colloid. The separated argon gas is then circulated into the arc discharge zone, and continuously mixed with the silver angstrom crystal colloid in the subsequent gas-liquid mixing zone at a predetermined flow rate. After continuous mixing through circulation, after 1 hour of circulation, a specific concentration of silver angstrom crystal colloid is finally formed, with a concentration of 23ppm. The nanocrystalline colloid was taken and its morphology and particle size were tested by TEM, which were in the range of 2 to 4nm, see Figure 5 . Figure 5 a is a TEM image of the silver angstrom colloid prepared in Example 10 of the present invention; Figure 5 b is a particle size distribution diagram of the silver angstrom colloid prepared in Example 10 of the present invention;

[0145] The test results show that the silver angstrom colloid prepared under the conditions of this embodiment has a silver particle size of 2 to 4 nm.

[0146] Embodiment 11

[0147] Using the preparation system proposed in the present invention, argon gas at room temperature is introduced into the arc discharge zone, and the concentration of the silver atom cluster aerosol formed per minute is controlled to be 0.1ppm, and then it quickly enters the gas-liquid mixing zone at a volume flow rate of 6L / min. The flow rate of the aerosol entering the gas-liquid mixing zone is controlled at 6L / min, and the flow rate of the liquid entering the gas-liquid mixing zone is controlled at 10mL / min. The gas-liquid mixing volume ratio is 600:1, the mixing volume of a single gas-liquid mixing zone is 2mL, the mixing time is 0.02 seconds, and the total amount of liquid is 200mL. The mixed liquid is then introduced into a gas-liquid separator to form independent argon gas and independent silver angstrom crystal colloid. The separated argon gas is then circulated into the arc discharge zone, and continuously mixed with the silver angstrom crystal colloid in the subsequent gas-liquid mixing zone at a predetermined flow rate. After continuous mixing through circulation, a silver angstrom crystal colloid of a specific concentration is finally formed after 8 hours of circulation. The prepared silver angstrom colloid was freeze-dried to obtain silver angstrom powder. XRD testing confirmed that it was a crystalline structure with obvious diffraction peaks, and was consistent with the standard PDF diffraction powder card of single crystal silver. Figure 6 This is the XRD pattern of the silver angstrom powder prepared in Example 11 of the present invention; Figure 7 This is the XRD-standard PDF card of silver single crystal powder;

[0148] The test results show that the silver angstrom powder prepared under the conditions of this embodiment is a silver single crystal.

[0149] Example 12

[0150] Using the preparation system proposed in the present invention, argon gas at room temperature is introduced into the arc discharge zone, and the concentration of the silver atom cluster aerosol formed per minute is controlled to be 0.1ppm, and then it quickly enters the gas-liquid mixing zone at a volume flow rate of 6L / min. The flow rate of the aerosol entering the gas-liquid mixing zone is controlled at 6L / min, and the flow rate of the liquid entering the gas-liquid mixing zone is controlled at 10mL / min. The gas-liquid mixing volume ratio is 600:1, the mixing volume of the gas-liquid mixing zone is 2mL, the mixing time is 0.02 seconds, and the total amount of liquid is 200mL. The mixed liquid is then introduced into a gas-liquid separator to form independent argon gas and independent silver angstrom crystal colloids. The separated argon gas is then circulated into the arc discharge zone and continuously mixed with the silver angstrom crystal colloid in the subsequent gas-liquid mixing zone at a predetermined flow rate. The concentration values ​​of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, and 12h are recorded, and the correlation between the concentration value and the total cycle time is analyzed, see Figure 8 The relationship between the concentration of silver angstrom colloid and different circulation times;

[0151] The test results show that the concentration increases very slowly under the conditions of this embodiment from 8h to 12h, which is not cost-effective. The previous concentration increase is linearly positively correlated with time.

[0152] Embodiment 13

[0153] Using the preparation system proposed in the present invention, argon gas at room temperature is introduced into the arc discharge zone to ensure that the concentration of the silver atom cluster aerosol formed is 0.1 ppm per minute, and then it quickly enters the gas-liquid mixing zone at a volume flow rate of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 L / min. The flow rate of aerosol entering the gas-liquid mixing zone is controlled at 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 L / min, the flow rate of liquid entering the gas-liquid mixing zone is controlled at 10 mL / min, the gas-liquid mixing volume ratio is 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1, the mixing volume of the gas-liquid mixing zone is 2 mL, the mixing time is 0.02 seconds, and the total amount of liquid is 200 mL. The mixed liquid is then passed into a gas-liquid separator to form independent argon gas and independent silver angstrom crystal colloid. The separated argon gas is then circulated into the arc discharge zone and continuously mixed with the silver angstrom colloid in the subsequent gas-liquid mixing zone at a predetermined flow rate, and continuously mixed through circulation for 8 hours. The concentration values ​​of the gas-liquid ratio of 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, 1100:1, 1200:1, 1300:1, 1400:1, 1500:1 are recorded, and the correlation between the concentration value and the gas-liquid ratio is analyzed, see Fig. 9 The relationship between the concentration of silver angstrom colloid and different gas-liquid ratios;

[0154] The correlation analysis between the concentration value and the gas-liquid ratio shows that, among different gas-liquid mixing ratios, the concentration of silver angstrom colloid is higher when the gas-liquid ratio is between 500:1 and 1000:1, and then gradually decreases; the gas-liquid ratio is lower between 100:1 and 500:1, and the concentration of angstrom increases slowly with the increase of the gas-liquid ratio. The specific reasons are analyzed as follows: in this embodiment, the flow rate of liquid entering the gas-liquid mixing zone is controlled at 10 mL / min. When the gas-liquid ratio is between 100:1 and 500:1, the flow rate of inert gas entering the arc discharge chamber is too low. The low gas flow rate is insufficient for cooling the silver atom clusters generated by the arc discharge, so that the silver atom clusters cannot be sufficiently cooled to form agglomerations, and the silver atom clusters with large kinetic energy are sputtered for a long distance and attached to the stainless steel wall of the arc discharge chamber, reducing the number of silver atom clusters that can be transported out. The arc discharge chamber has been verified by inspection.

[0155] Then, angstrom colloids with a gas-liquid ratio between 100:1 and 500:1 were mixed and tested for TEM, e.g. Fig.10 ; Mix angstrom colloids in the range of 600:1 to 1000:1 and test TEM, such as Fig.11 ; Mix angstrom colloids in the range of 1000:1 to 1500:1 and test TEM, such as Fig.12 ;

[0156] The correlation analysis between particle size distribution and gas-liquid ratio was performed according to normal distribution statistics. The experimental results showed that in the low-stage gas-liquid ratio stage (100:1-500:1), the particle size distribution of nanocrystalline colloids was 2.99nm±1.05nm, accounting for 67.2%, and the particle size distribution was 2.99±2.10nm, accounting for 95.4%. In the medium-stage gas-liquid ratio (600:1-900:1), the particle size distribution of angstrom colloids was 2.30nm±1.05nm, accounting for 67.2%, and the particle size distribution was 2.30nm±2.10nm, accounting for 95.4%. In the high-stage gas-liquid ratio (1000:1-1500:1), the particle size distribution of angstrom colloids was 1.74nm±0.40nm, accounting for 67.2%, and the particle size distribution was 1.74nm±0.80nm, accounting for 95.4%.

[0157] In summary, it can be seen that, considering the cost, this process can be used to prepare 2-4 nm nanocrystal colloids at a low gas-liquid ratio.

[0158] Silver angstrom colloid itself has Tyndall effect. Fig.13 For its Tyndall effect photo.

[0159] Embodiment 14

[0160] Quality control of the silver angstrom crystal colloidal solution preparation system provided by the present invention:

[0161] Particle size test: obtain angstrom crystal colloidal solution, take samples for TEM test and particle size statistics to ensure that the particle size distribution is between 2 and 4 nm and has obvious single crystals. Further low-temperature drying or cold drying is performed to obtain powder for XRD test to ensure that it is a single crystal.

[0162] Concentration test: obtain the angstrom colloidal solution, take samples for ICP-MS test, and ensure that the final silver angstrom colloidal concentration is not less than 20ppm.

[0163] Stability test: The formed colloidal solution will not precipitate when placed at room temperature for 6 months, and still has the Tyndall effect. The tested particle size and concentration still remain at 2-4nm and ≥20ppm.

[0164] Embodiment 15

[0165] The working condition of the whole device of the silver angstrom crystal colloid preparation system provided by the present invention has the following important monitoring points:

[0166] 1) Observe or measure the current and voltage of the arc discharge power supply to determine whether the arc discharge is maintained normally and regulate the normal progress of the arc discharge;

[0167] 2) At the colloidal solution collection pool 6, a device for detecting color, light transmittance or particle counting is set to detect the concentration of the product online in real time or offline at regular intervals. Usually, a laser particle size analyzer and a particle spectrometer can be selected to detect the particle size and distribution of the product online in real time; an atomic absorption spectrometer AAS or an atomic emission spectrometer ICP can be used to detect the concentration of the product offline at regular intervals;

[0168] Alternatively, use a level meter or quality sensor to detect the preparation process online, record the product speed under various parameter control conditions, and improve the process flow;

[0169] 3) Observe or measure the flow rate of the gas tank regulating valve, adjust the inert gas intake of the arc discharger, and maintain the effective transport gas volume ratio;

[0170] 4) Observe or measure the pressure indicator of the gas circulation pump (8) to see whether the outlet pressure is stable. This negative pressure ensures that the gas flow in the gas-liquid separator continues and can effectively separate the gas-liquid mixture; it also effectively recovers the transported gas;

[0171] 5) The present invention uses a transparent microfluidic gas-liquid mixing chamber, which can observe and monitor whether the mixing is proceeding normally;

[0172] 6) The liquid outlet of the gas-liquid separation channel can be used to observe or measure the output state and output volume of the colloidal solution, and to judge and regulate the smooth progress of the preparation process.

[0173] 7) The above-mentioned links can be linked and controlled through an automated measurement and control system to achieve complete monitoring and automated regulation of the entire preparation process.

[0174] 8) It should be noted that, without making major adjustments to the various links of the present invention, the automated preparation and production of the silver angstrom crystal colloid provided by the present invention can be achieved by adding automatic control.

[0175] It is particularly noted that the grain size of the silver angstrom crystals described herein is generally smaller than that of the silver nanocrystals.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for preparing high-purity and high-particle-size-consistent silver angstrom colloids, comprising an arc discharge chamber provided with a gas input port and a gas output port, an arc discharge power supply provided with one or more pairs of segment output terminals, and a protective gas storage tank provided with a gas output pipeline, a gas flow regulating valve, and a gas return pipeline, wherein the gas input port of the arc discharge chamber is connected to the gas output pipeline of the protective gas storage tank, and characterized in that: The system also includes a microfluidic gas-liquid mixer, a channel-type gas-liquid separator, a liquid storage container, a liquid circulation pump, and a gas circulation pump; The microfluidic gas-liquid mixer is provided with a gas input channel, a liquid input channel and a gas-liquid mixture discharge channel; The gas-liquid separator has a gas-liquid mixture input channel, a gas discharge channel and a liquid discharge channel; The liquid circulation pump has a liquid input port and a liquid output port; The arc discharge chamber is provided with one or more pairs of silver electrodes arranged in pairs, each pair of the silver electrodes is respectively connected to a pair of power output terminals of the arc discharge power supply, and the gas output port of the arc discharge chamber is connected to the gas input channel of the microfluidic gas-liquid mixer through a gas pipeline; The gas-liquid mixture discharge channel of the microfluidic gas-liquid mixer is connected to the gas-liquid mixture inlet of the gas-liquid separator through a gas-liquid mixture pipeline, and the liquid input channel of the microfluidic gas-liquid mixer is connected to the liquid output port of the liquid circulation pump through a liquid pipeline; The gas outlet of the gas-liquid separator is connected to the gas circulation pump through a gas pipeline, and the liquid outlet is connected to the liquid storage container through a liquid pipeline; The liquid storage container is connected to the liquid input port of the liquid circulation pump through a liquid pipeline; the liquid output port of the liquid circulation pump is connected to the liquid inlet channel of the microfluidic gas-liquid mixer through a liquid pipeline; The gas circulation pump is connected to the gas return pipeline of the protective gas storage tank.

2. The system according to claim 1, characterized in that A regulating valve is provided between the arc discharge chamber and the gas storage tank for regulating the flow of gas input into the arc discharge chamber.

3. The system according to claim 1, characterized in that The silver electrodes in the arc discharge chamber are mounted on a bracket capable of automatically adjusting the distance to adjust the gap distance between each pair of silver electrodes.

4. The system according to claim 1, characterized in that The system further comprises a vacuuming device for evacuating the interior of the arc discharge chamber during the arc discharge preparation process.

5. The system according to claim 1, characterized in that The gas-liquid separator has a gas-liquid separation channel with multiple upper and lower baffles, and is used for separating gas and liquid by gravity and inertial force.

6. The system according to claim 1, characterized in that The gas circulation pump is connected to the gas return pipeline of the protective gas storage tank through a filter chamber and a cold trap, and is used to remove silver angstroms and moisture in the recovered gas.

7. The system according to claim 1, characterized in that The voltage between each pair of positive and negative output terminals of the arc discharge power supply is 0.8-1.3 kV, the current between each pair of positive and negative output terminals is 7-13 mA, and the arc discharge power supply is a pulse power supply with a pulse frequency of about 250-350 Hz.

8. The system according to claim 1, characterized in that The distance between each pair of silver electrodes in the arc discharge chamber is 0.3-1.0 mm, and the diameter of the electrodes is 3-6 mm.

9. The system according to claim 1, characterized in that The air intake of the arc discharge chamber is 5 to 10 L / min corresponding to the air supply of each pair of silver electrodes, the liquid intake of the microfluidic gas-liquid mixer is 1 to 10 ml / min, and the gas-liquid ratio entering the microfluidic gas-liquid mixer is controlled to be maintained at gas:liquid=500:1 to 1000:

1.

10. The system according to claim 9, characterized in that The gas-liquid ratio entering the microfluidic gas-liquid mixer is controlled to be maintained at gas:liquid=700:1-900:1.

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