Ammonium thiocyanate microcapsules, their preparation method, and their application methods

Abstract

This invention discloses an ammonium thiocyanate microcapsule, comprising: a core material, wherein the core material is an ammonium thiocyanate solution at a predetermined mass ratio, the ammonium thiocyanate solution being capable of crystallizing at a predetermined pressure and a predetermined temperature; and a wall material, which covers the core material to isolate the core material from the external environment of the wall material, the wall material being a predetermined material to allow pressure acting on the wall material to be transmitted to the core material. This invention can solve the technical problem of corrosion of ammonium thiocyanate in liquid cooling systems.

Description

Technical Field

[0001] This invention relates to the field of new heat exchange materials technology, and in particular to an ammonium thiocyanate microcapsule, its preparation method, and its application method. Background Technology

[0002] With the rapid development of refrigeration technology towards higher efficiency and lower carbon emissions, ammonium thiocyanate aqueous solution, with its unique "dissolution-pressure effect," can achieve rapid and efficient refrigeration under pressure changes. It also boasts significant advantages such as low cost, high water solubility, zero fluorine emissions, and excellent heat transfer efficiency, making it a core candidate coolant for next-generation green refrigeration technology. Currently, commonly used materials for radiators, pipes, CDUs, and other components in refrigeration systems include carbon steel, chromium-manganese austenitic stainless steel, copper, aluminum, and their alloys. These materials possess good mechanical and heat transfer properties under normal operating conditions, meeting the basic requirements for coolant circulation and heat exchange. However, during actual service, the thiocyanate ions (SCN) in the aqueous solution of ammonium thiocyanate coolant... - Ammonium thiocyanate (AmCthiocyanate) coolant exhibits significant corrosive effects on commonly used metallic materials, a problem that has become a core technological bottleneck restricting its large-scale application. This corrosion leads to surface damage and thinning of components such as radiators, pipes, and CDUs, potentially causing leaks, reduced radiator heat exchange efficiency, and CDU malfunctions. This not only necessitates frequent replacement of damaged components, increasing equipment maintenance costs and downtime losses, but also poses safety hazards due to coolant leaks, limiting the widespread application of AmCthiocyanate coolant in various refrigeration systems. Therefore, addressing the corrosiveness of AmCthiocyanate coolant to core refrigeration system components and developing corrosion-resistant technologies adapted to its properties is of significant practical importance and engineering value for promoting the industrial application of AmCthiocyanate coolant and improving the operational stability and service life of refrigeration systems. It is also a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0003] This invention provides ammonium thiocyanate microcapsules, their preparation method, and their application method, which can solve the technical problem of corrosion of ammonium thiocyanate in liquid cooling systems.

[0004] To solve the above-mentioned technical problems, the present invention provides an ammonium thiocyanate microcapsule, comprising: The core material is an ammonium thiocyanate solution with a predetermined mass ratio, and the ammonium thiocyanate solution is capable of crystallizing under a predetermined pressure and a predetermined temperature. A wall material is used to cover the core material so that the core material is isolated from the external environment of the wall material. The wall material is a predetermined material so that the pressure acting on the wall material can be transmitted to the core material.

[0005] As a preferred embodiment of the above technical solution, the wall material is polyurea (PU), and the preset temperature is 20-30℃.

[0006] As a preferred embodiment of the above technical solution, the ammonium thiocyanate aqueous solution is formed by dissolving the ammonium thiocyanate in deionized water, and the ammonium thiocyanate aqueous solution further includes a dispersing stabilizer.

[0007] As a preferred embodiment of the above technical solution, the dispersing stabilizer is polyvinylpyrrolidone.

[0008] As a preferred embodiment of the above technical solution, the ammonium thiocyanate microcapsule further includes a heat-conducting layer, which is distributed in layers on the outer side of the wall material.

[0009] As a preferred embodiment of the above technical solution, the heat-conducting layer is a graphene layer.

[0010] Another aspect of the present invention provides a method for preparing ammonium thiocyanate microcapsules, the method comprising the following steps: Step (100): Prepare an ammonium thiocyanate aqueous solution with a preset mass ratio as the core material solution; Step (200): Prepare a microfluidic chip and inject the ammonium thiocyanate aqueous solution prepared in step (100) into the aqueous phase inlet of the microfluidic chip. At the same time, inject mineral oil containing surfactant into the oil phase inlet of the microfluidic chip. Control the flow rate of the ammonium thiocyanate aqueous solution and the mineral oil to obtain emulsion droplets and collect the emulsion droplets. Step (300): The emulsion droplets are attached to form a wall material to form microcapsules via interfacial polymerization reaction; Step (400): The microcapsules are assembled in layers to form a thermally conductive layer on the outside of the microcapsules; Step (500): The microcapsule forming the heat-conducting layer is sealed by atomic layer deposition to form the finished microcapsule product; Step (600): The microcapsule product prepared in step (500) is flash-frozen with liquid nitrogen and then freeze-dried at -50°C and 0.1 mbar for 24 hours.

[0011] As a preferred embodiment of the above technical solution, the step (100) of preparing the ammonium thiocyanate aqueous solution with a preset mass ratio specifically includes: stirring the ammonium thiocyanate solid and deionized water at a preset ratio at a temperature of 30-50°C until completely dissolved; then adding polyvinylpyrrolidone as a dispersing stabilizer to the solution; using ultrasonic treatment to remove air bubbles from the solution; and then filtering to remove undissolved particles to obtain the core material solution; the microfluidic chip in step (200) is a T-type microfluidic chip, the material of the microfluidic chip is polydimethylsiloxane (PDMS), the main channel size of the microfluidic chip is 200 μm wide × 100 μm high, and the side channel size is 100 μm × 100 μm. The main channel and the side channel are respectively connected to two high-precision injection pumps through polytetrafluoroethylene conduits, the inner diameter of the polytetrafluoroethylene conduits is 0.5 mm, and the flow rates of the ammonium thiocyanate aqueous solution and the mineral oil are controlled at 0.2 mL / min and 2.0 mL / min, respectively. mL / min, the mineral oil is ultrasonically treated at 20 kHz for 10 minutes before use, and the step (300) involves the formation of a wall material by interfacial polymerization reaction on the emulsion droplets to form microcapsules. Specifically, this includes adding an aqueous solution of 1,6-hexanediamine to the collected emulsion droplets, followed by adding a hexamethylene diisocyanate oil phase solution dropwise, and then performing a polymerization reaction at a preset temperature to form a polyurea wall material on the outside of the emulsion droplets.

[0012] As a preferred embodiment of the above technical solution, the heat-conducting layer in step (400) is a graphene layer. Step (400) of layering the microcapsules to form a heat-conducting layer on the outside of the microcapsules specifically includes: immersing the microcapsules in an aqueous solution of polydiallyldimethylammonium chloride and oscillating to adsorb for a preset time, washing with deionized water, and then transferring the microcapsules to a graphene oxide dispersion for adsorption and oscillation to form the graphene layer on the outside of the microcapsules. Step (500) of sealing the microcapsules that form the heat-conducting layer by atomic layer deposition to form the finished microcapsule specifically includes: using trimethylaluminum and H2O as precursors, performing 100 cycles of deposition at 80°C.

[0013] In another aspect, the present invention provides a method for applying ammonium thiocyanate microcapsules, wherein the aforementioned ammonium thiocyanate microcapsules are used in refrigeration and heat storage.

[0014] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0015] Figure 1A schematic diagram of the structure of an ammonium thiocyanate microcapsule according to an embodiment of the present invention is shown.

[0016] Figure 2 A schematic flowchart of a method for preparing ammonium thiocyanate microcapsules according to an embodiment of the present invention is shown.

[0017] In the diagram: 10, core material; 20, wall material; 30, heat conduction layer; 40, sealing layer. Detailed Implementation

[0018] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0019] See Figure 1 As shown, an embodiment of the present invention provides an ammonium thiocyanate microcapsule, comprising: Core material 10 is an ammonium thiocyanate solution with a preset mass ratio. The ammonium thiocyanate solution can crystallize under a preset pressure and a preset temperature. The wall material 20 covers the core material 10 so that the core material 10 and the external environment of the wall material 20 are isolated from each other. The wall material 20 is a preset material so that the pressure acting on the wall material 20 can be transmitted to the core material 10.

[0020] In a further embodiment of this example, the wall material 20 is made of polyurea (PU) and the preset temperature is 20-30°C.

[0021] In this embodiment, the ammonium thiocyanate solution is isolated by the wall material 20, which can effectively inhibit the corrosiveness of ammonium thiocyanate.

[0022] In a further embodiment of this invention, the ammonium thiocyanate aqueous solution is formed by dissolving ammonium thiocyanate in deionized water, and the ammonium thiocyanate aqueous solution also includes a dispersing stabilizer.

[0023] In a further embodiment of this example, the dispersion stabilizer is polyvinylpyrrolidone.

[0024] In a further embodiment of this invention, the ammonium thiocyanate microcapsules also include a thermally conductive layer 30, which is distributed in layers on the outer side of the wall material 20.

[0025] In a further embodiment of this example, the heat-conducting layer 30 is a graphene layer.

[0026] In this embodiment, the thermal conductivity of the microcapsules can be improved by using a graphene layer.

[0027] In addition, a sealing layer 40 is attached to the outside of the heat conduction layer 30 in this embodiment.

[0028] In this embodiment, the sealing layer 40 can improve the sealing performance of the microcapsules and prevent leakage of the ammonium thiocyanate solution.

[0029] See Figure 2 As shown, another aspect of this invention provides a method for preparing ammonium thiocyanate microcapsules, which includes the following steps: Step (100): Prepare an aqueous solution of ammonium thiocyanate with a preset mass ratio as the core material 10 solution; Step (200): Prepare a microfluidic chip and inject the ammonium thiocyanate aqueous solution prepared in step (100) into the aqueous phase inlet of the microfluidic chip. At the same time, inject mineral oil containing surfactant into the oil phase inlet of the microfluidic chip. Control the flow rate of the ammonium thiocyanate aqueous solution and the mineral oil to obtain emulsion droplets and collect the emulsion droplets. Step (300): Wall material 20 is formed by the adhesion of emulsion droplets through interfacial polymerization to form microcapsules; Step (400): The microcapsules are layered to form a thermally conductive layer 30 on the outside of the microcapsules; Step (500): The microcapsules forming the thermally conductive layer 30 are sealed by atomic layer deposition to form the finished microcapsule product; Step (600): After the microcapsule product prepared in step (500) is quick-frozen with liquid nitrogen, it is freeze-dried at -50℃ and 0.1mbar for 24 hours.

[0030] The step (100) of preparing the ammonium thiocyanate aqueous solution with a preset mass ratio specifically includes: stirring the ammonium thiocyanate solid and deionized water at a preset ratio at a temperature of 30-50°C until completely dissolved, then adding polyvinylpyrrolidone as a dispersing stabilizer to the solution, using ultrasonic treatment to remove air bubbles in the solution, and then filtering to remove undissolved particles to obtain the core material 10 solution. Preferably, in this embodiment, the mass ratio of polyvinylpyrrolidone added is 0.3 wt.%, the molecular weight is ≈40,000, and in this embodiment, the ultrasonic wave is controlled at 20 kHz and the ultrasonic treatment time is controlled at 10 minutes. In this embodiment, the ammonium thiocyanate (NH4SCN, ≥99.0%) is from Sigma-Aldrich, the deionized water (resistivity 18.2 MΩ·cm) is prepared by the Millipore pure water system, and the polyvinylpyrrolidone is purchased from Alfa Aesar.

[0031] The microfluidic chip in step (200) is a T-type microfluidic chip made of polydimethylsiloxane (PDMS). The main channel of the microfluidic chip is 200 μm wide × 100 μm high, and the side channel is 100 μm × 100 μm. The main channel and the side channel are connected to two high-precision injection pumps through polytetrafluoroethylene (PTFE) tubing. The inner diameter of the PTFE tubing is 0.5 mm. The flow rates of ammonium thiocyanate aqueous solution and mineral oil are controlled at 0.2 mL / min and 2.0 mL / min, respectively. The mineral oil is ultrasonically treated at 20 kHz for 10 minutes before use. In this embodiment, the emulsion generated at the outlet is collected in a centrifuge tube kept in an ice bath, and the droplet size is monitored in real time using an optical microscope (Olympus BX53). Image analysis is performed using ImageJ software. The diameter of the obtained emulsion droplets is approximately 100 micrometers. The chip is also configured on a temperature control platform (Linkam PE120, temperature control accuracy ±0.1℃).

[0032] Step (300) involves forming microcapsules by adhering the wall material 20 to the emulsion droplets through interfacial polymerization. Specifically, this includes adding a 1,6-hexanediamine aqueous solution to the collected emulsion droplets, followed by dropwise addition of a hexamethylene diisocyanate oil phase solution. A polymerization reaction occurs at a preset temperature, resulting in the adhering of the polyurea wall material 20 to the outside of the emulsion droplets. In this embodiment, the mass ratio of 1,6-hexanediamine (HDA, 98%, TCI) in the 1,6-hexanediamine aqueous solution is 1 wt%. Furthermore, the volume ratio of the emulsion to the HDA aqueous solution is controlled at 10:1. The mass ratio of hexamethylene diisocyanate (HDI, 99%, Merck) in the hexamethylene diisocyanate (HDI, 99%, Merck) oil solution is 1 wt%, and the volume ratio of the emulsion to the HDI oil phase solution is 10:1. The temperature is controlled at 25°C during the polymerization reaction of HDA and HDI. The polymerization reaction formula is H2N(CH2)6NH2 + OCN(CH2)6NCO → PU (polyurea). During the reaction, 0.1 M... The pH of the system was adjusted and maintained at 8-9 (preferably pH=8.5) using NaOH solution, and the reaction was continued for 30 minutes. After the reaction was completed, the mixture was centrifuged at 4000-8000 rpm (preferably 5000 rpm) for 5 minutes (4°C) to collect the microcapsules, which were then washed 3-5 times (preferably 3 times) with n-hexane, and finally purged with nitrogen to remove residual solvent.

[0033] The thermally conductive layer 30 in step (400) is a graphene layer. Step (400) of layered assembly of microcapsules to form the thermally conductive layer 30 on the outside of the microcapsules specifically includes: immersing the microcapsules in an aqueous solution of polydiallyldimethylammonium chloride and shaking to adsorb for a preset time; washing with deionized water and then transferring the microcapsules to a graphene oxide dispersion for adsorption and shaking to form a graphene layer on the outside of the microcapsules. Specifically, the molecular weight of polydiallyldimethylammonium chloride is 200,000-350,000, and the aqueous solution of polydiallyldimethylammonium chloride contains 0.5 M NaCl to control the pH value to 9. After immersing the microcapsules in the polydiallyldimethylammonium chloride solution and shaking to adsorb for 5 minutes at 25°C and 150 rpm, they are washed 3 times with deionized water. In this embodiment, the graphene oxide dispersion is a 1 mg / mL graphene oxide dispersion with a layer ratio >95%. The microcapsules are adsorbed at 25°C and 120 rpm. The graphene oxide dispersion was oscillated and adsorbed for 10 minutes under rpm conditions, and then washed three times with deionized water. The adsorption process of the microcapsules in polydiallyldimethylammonium chloride and graphene oxide dispersion was repeated three times each. Then, the microcapsules were placed in azeotropic vapor of 57wt% saturated hydroiodic acid (Maclean) and reduced at 60°C for 1 hour. Finally, the residual hydrogen iodide was removed by purging with nitrogen to form the final graphene microcapsules. In this embodiment, the adsorption thickness of the graphene layer was controlled by controlling the concentration of graphene oxide dispersion and the adsorption time.

[0034] Step (500) involves sealing the microcapsules that form the thermally conductive layer 30 with atomic layer deposition to form the finished microcapsule product. Specifically, this includes using trimethylaluminum and H2O as precursors and performing 100 cycles of deposition at 80°C. In this embodiment, the atomic layer deposition sealing process is completed using a thermal ALD system (Cambridge NanoTech Savannah 200), and the growth rate is controlled to be approximately 0.1 nm / cycle.

[0035] In step (600), the microcapsules are stored at 4°C in the dark. In addition, the prepared microcapsule products need to be tested. The morphological characteristics of the prepared microcapsule products are observed by field emission scanning electron microscopy (Hitachi SU8010, 5 kV) and transmission electron microscopy (JEOL JEM-2100). The phase transition performance is determined by differential scanning calorimetry (TA Q200, heating rate 5°C / min). The sealing performance is evaluated by ultraviolet spectrophotometry (detecting the characteristic absorption of NH4SCN at 230 nm).

[0036] Another aspect of this invention provides a method for applying ammonium thiocyanate microcapsules, which are used in refrigeration and heat storage.

[0037] During use, pressure is applied to the microcapsules to control the pressure on the ammonium thiocyanate solution. When pressure is applied, NH4SCN crystallizes out of the near-saturated solution, releasing heat and raising the solution temperature. When the pressure is released, the crystals dissolve rapidly, absorbing a large amount of heat and causing the solution temperature to drop sharply.

[0038] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An ammonium thiocyanate microcapsule, characterized in that, include: The core material is an ammonium thiocyanate solution with a predetermined mass ratio, and the ammonium thiocyanate solution is capable of crystallizing under a predetermined pressure and a predetermined temperature. A wall material is used to cover the core material so that the core material is isolated from the external environment of the wall material. The wall material is a predetermined material so that the pressure acting on the wall material can be transmitted to the core material.

2. The ammonium thiocyanate microcapsules according to claim 1, characterized in that, The wall material is polyurea (PU), and the preset temperature is 20-30℃.

3. The ammonium thiocyanate microcapsules according to claim 1, characterized in that, The ammonium thiocyanate aqueous solution is formed by dissolving the ammonium thiocyanate in deionized water, and the ammonium thiocyanate aqueous solution also includes a dispersing stabilizer.

4. The ammonium thiocyanate microcapsules according to claim 3, characterized in that, The dispersion stabilizer is polyvinylpyrrolidone.

5. The ammonium thiocyanate microcapsules according to claim 1, characterized in that, The ammonium thiocyanate microcapsules also include a heat-conducting layer, which is distributed in layers on the outer side of the wall material.

6. The ammonium thiocyanate microcapsules according to claim 5, characterized in that, The heat-conducting layer is a graphene layer.

7. A method for preparing ammonium thiocyanate microcapsules, said preparation method being used to prepare ammonium thiocyanate microcapsules as described in any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Step (100): Prepare an aqueous solution of ammonium thiocyanate with a preset mass ratio as the core material solution; Step (200): Prepare a microfluidic chip and inject the ammonium thiocyanate aqueous solution prepared in step (100) into the aqueous phase inlet of the microfluidic chip. At the same time, inject mineral oil containing surfactant into the oil phase inlet of the microfluidic chip. Control the flow rate of the ammonium thiocyanate aqueous solution and the mineral oil to obtain emulsion droplets and collect the emulsion droplets. Step (300): The emulsion droplets are attached to form a wall material to form microcapsules via interfacial polymerization reaction; Step (400): The microcapsules are assembled in layers to form a thermally conductive layer on the outside of the microcapsules; Step (500): The microcapsule forming the heat-conducting layer is sealed by atomic layer deposition to form the finished microcapsule product; Step (600): The microcapsule product prepared in step (500) is flash-frozen with liquid nitrogen and then freeze-dried at -50°C and 0.1 mbar for 24 hours.

8. The method for preparing ammonium thiocyanate microcapsules according to claim 7, characterized in that, The step (100) of preparing the ammonium thiocyanate aqueous solution with a preset mass ratio specifically includes: stirring the ammonium thiocyanate solid in a preset ratio with deionized water at a temperature of 30-50°C until completely dissolved; then adding polyvinylpyrrolidone as a dispersing stabilizer to the solution; using ultrasonic treatment to remove air bubbles from the solution; and then filtering to remove undissolved particles to obtain the core material solution. The microfluidic chip in step (200) is a T-type microfluidic chip made of polydimethylsiloxane (PDMS). The main channel of the microfluidic chip has a width of 200 μm and a height of 100 μm, and the side channel has a size of 100 μm × 100 μm. The main channel and the side channel are connected to two high-precision injection pumps via polytetrafluoroethylene (PTFE) conduits with an inner diameter of 0.5 mm. The flow rates of the ammonium thiocyanate aqueous solution and the mineral oil are controlled at 0.2 mL / min and 2.0 mL / min, respectively. mL / min, the mineral oil is ultrasonically treated at 20 kHz for 10 minutes before use, and the step (300) involves the formation of a wall material by interfacial polymerization reaction on the emulsion droplets to form microcapsules. Specifically, this includes adding an aqueous solution of 1,6-hexanediamine to the collected emulsion droplets, followed by adding a hexamethylene diisocyanate oil phase solution dropwise, and then performing a polymerization reaction at a preset temperature to form a polyurea wall material on the outside of the emulsion droplets.

9. The method for preparing ammonium thiocyanate microcapsules according to claim 8, characterized in that, The thermally conductive layer in step (400) is a graphene layer. Step (400) of layered assembly of the microcapsules to form a thermally conductive layer on the outside of the microcapsules specifically includes: immersing the microcapsules in an aqueous solution of polydiallyldimethylammonium chloride and oscillating to adsorb for a preset time, washing with deionized water, and then transferring the microcapsules to a graphene oxide dispersion for adsorption and oscillation to form the graphene layer on the outside of the microcapsules. Step (500) of sealing the microcapsules that form the thermally conductive layer by atomic layer deposition to form the finished microcapsule specifically includes: using trimethylaluminum and H2O as precursors, performing 100 cycles of deposition at 80°C.

10. A method for applying ammonium thiocyanate microcapsules, characterized in that, The ammonium thiocyanate microcapsules as described in any one of claims 1 to 6 are used for refrigeration and heat storage.

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