Pressing and clamping plastic crystal material and method for improving reversible pressing and clamping effect of pressing and clamping plastic crystal material by controlling granularity
By controlling the particle size of the plastic crystal material and utilizing cold pressing technology, the problem of insufficient reversible compression effect of the plastic crystal material under low pressure was solved, achieving a highly efficient cooling effect with low phase change thermal hysteresis.
Patent Information
- Application Number
- CN202410645904.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-23
- Publication Date
- 2025-11-11
AI Technical Summary
Existing plastic crystal materials have limited reversible pressure-carrying effect under low pressure and large phase change thermal hysteresis, which limits their application in solid-state refrigeration equipment.
By controlling the particle size of the plastic crystal material, and using a high-strength mold and a hydraulic press for cold pressing, plastic crystal materials with different particle sizes can be prepared, thereby reducing phase change thermal hysteresis and improving the reversible compressive effect.
The reversible pressure effect of the plastic crystal material was significantly improved under low pressure, the phase change thermal hysteresis was reduced, and the cooling performance of the material was optimized.
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Figure CN120924237A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid phase change refrigeration materials, specifically relating to a method for improving the reversible capillary effect of plastic crystal materials by controlling particle size. Background Technology
[0002] Solid-state refrigeration technology, due to its environmental friendliness and high efficiency, holds promise for replacing traditional vapor compression refrigeration. Solid-state refrigeration materials can exhibit various thermal effects under the influence of external fields such as magnetic fields, uniaxial stress, hydrostatic pressure, and electric fields, including magnetocaloric, tumble-clamping, pressure-clamping, and electroclamping effects. Recent reports indicate that disordered crystalline materials can induce a large pressure-clamping effect under relatively low isostatic pressure, suggesting that pressure-clamping refrigeration using crystalline phase change materials is a promising solid-state refrigeration technology.
[0003] Although these crystalline materials significantly improve the upper limit of the isothermal entropy change of compressive refrigeration materials, there is still considerable room for improvement in obtaining a reversible compressive effect useful for refrigeration equipment by reducing the driving pressure. This is mainly because most crystalline materials have a large phase transition thermal hysteresis, which limits their reversible compressive effect. Currently, many researchers are beginning to explore crystalline materials with low phase transition hysteresis. Among them, an inorganic crystalline material, KPF6, reported in 2023, can simultaneously possess a large compressive effect and a low phase transition hysteresis during the phase transition process, with a phase transition thermal hysteresis of only about 8K (heating and cooling rate of 10K / min). However, the reversible compressive effect produced by this type of material under low pressure conditions is still limited (the reversible isothermal entropy change induced under low pressure conditions of 30MPa is about 20J·kg). -1 ·K -1 Against this backdrop, exploring methods to induce a greater reversible capacitive effect in plastic crystal materials under low pressure can provide effective insights for the development of solid-state refrigeration applications. Summary of the Invention
[0004] The purpose of this invention is to provide a method for improving the reversible compressive effect of plastic crystal materials by controlling particle size. The plastic crystal material is ground and the particle size of the plastic crystal material is controlled by sieves of different mesh sizes. The plastic crystal materials of different particle sizes are cold-pressed into shape using a high-strength mold and a hydraulic press to prepare phase change materials of different particle sizes. This method effectively reduces the phase change thermal hysteresis of plastic crystal materials and improves the reversible compressive effect of plastic crystal materials under low pressure fields.
[0005] The technical solution of this invention is as follows:
[0006] The plastic crystal pressing phase change material with different particle sizes is characterized in that: the particle size of the plastic crystal material is respectively the original untreated particles, 150-300μm, 75-150μm, 37.5-75μm, and less than or equal to 37.5μm.
[0007] As a preferred technical solution:
[0008] The pressure-sensitive plasticizing material is potassium hexafluorophosphate (KPF6).
[0009] By changing the grinding time of the pressure-pressed plastic crystal material, the particle size and reversible pressure-heat effect of the plastic crystal material can be controlled.
[0010] The present invention also provides a method for improving the reversible pressing effect of the press-fitting crystalline material, characterized in that: firstly, the press-fitting crystalline material is ground and its particle size is controlled by sieve during the grinding process; then, samples of different particle sizes are poured into a mold and cold-pressed using a hydraulic press.
[0011] Furthermore, the press-fit plastic crystal material with different particle sizes was weighed using an electronic balance.
[0012] Furthermore, the grinding method is to use an agate mortar and pestle.
[0013] Furthermore, the pressure applied during the cold pressing is preferably 5 MPa, and the holding time is 30 s.
[0014] Furthermore, in order to ensure uniform stress on the sample during the cold pressing process, the sample is pressed at three angles by horizontal rotation under vertical pressure.
[0015] Furthermore, all steps are performed under the protection of an inert gas (e.g., under the protection of a low-oxygen, low-water inert gas environment in a glove box).
[0016] Furthermore, molds of different sizes can be selected to prepare samples for testing the DSC curves and reversible isothermal entropy changes of the press-fit material, so as to obtain press-fit plastic crystal materials of different shapes and sizes (the diameter of the selected mold is preferably a 3mm disc).
[0017] This invention employs a method of controlling the particle size of the compressive crystal material to reduce the phase transition thermal hysteresis of the material and achieve a large reversible compressive heating effect under low pressure. This results in the preparation of a compressive crystal material with low phase transition thermal hysteresis and a large reversible compressive heating effect. This method effectively enhances the reversible compressive heating effect of the compressive crystal material under low driving field. Attached Figure Description
[0018] Figure 1 The DSC curves of the plastic crystal materials with different particle sizes in Examples 1-4 at a heating and cooling rate of 10K / min in the temperature range of 247.5 to 267.5K.
[0019] Figure 2The reversible piezoresistive isothermal entropy change curves of the original untreated KPF6 plastic crystal material and the KPF6 plastic crystal material with a particle size of 75-150μm in Example 1 within the temperature range of 250-270K. Detailed Implementation
[0020] The grinding method described in the following examples is grinding with an agate mortar and pestle, and the instruments used for testing the DSC curves at normal pressure and under pressure are DSC, TA-Q100 and Setaram-μDSC 7EVO, respectively.
[0021] Example 1
[0022] KPF6 plastic crystal material with a particle size of 150-300 μm
[0023] 1) The plastic crystal material (raw, untreated KPF6 plastic crystal material with a particle size of 300μm-600μm) was ground in an inert gas (nitrogen) environment in a glove box using an agate mortar and pestle, and the plastic crystal material with a particle size of 150μm-300μm was screened out using 100-mesh and 50-mesh sieves (passing through the 50-mesh sieve and being retained by the 100-mesh sieve).
[0024] 2) Under nitrogen protection, pour 23.31 mg of powder obtained in step 1) into a cylindrical mold with an inner diameter of 3 mm, and use a hydraulic press to apply a pressure of 5 MPa to the powder sample in the mold from top to bottom along the axial direction. The pressure holding time is 30 s to complete the first pressing.
[0025] 3) Pressing again: Under nitrogen protection, after depressurization, rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) by 120° in the horizontal direction, and apply a pressure of 5MPa to the powder sample in the mold from top to bottom for 30s using a hydraulic press.
[0026] Repeat step 3) twice more, and rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) 360° in the horizontal direction, for a total of 3 times.
[0027] 4) After depressurization, the pressed sample was taken out to obtain a KPF6 plastic crystal material sample with a particle size of 150μm to 300μm and a thickness of 0.30mm to 0.35mm. The DSC curve of the sample was tested using a differential scanning calorimeter. At a heating and cooling rate of 10K / min (range of 240 to 270K), the phase change thermal hysteresis of the original untreated KPF6 plastic crystal material was (8.1K), and the phase change thermal hysteresis of the KPF6 plastic crystal material with a particle size of 150μm to 300μm was 7.6K.
[0028] Example 2
[0029] KPF6 plastic crystal material with particle size of 75-150μm
[0030] 1) Grind the plastic crystal material in an inert gas (nitrogen) in a glove box using an agate mortar and sieve using 100-mesh and 200-mesh sieves (passing through the 100-mesh sieve and being retained by the 200-mesh sieve) to obtain plastic crystal material with a particle size of 75-150μm.
[0031] 2) Under nitrogen protection, 17.78 mg of powder obtained in step 1) is poured into a cylindrical mold with an inner diameter of 3 mm, and a hydraulic press is used to apply a pressure of 5 MPa to the powder sample in the mold from top to bottom along the axial direction. The pressure holding time is 30 s to complete the first pressing.
[0032] 3) Pressing again: Under nitrogen protection, after depressurization, rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) by 120° in the horizontal direction, and apply a pressure of 5MPa to the powder sample in the mold from top to bottom for 30s using a hydraulic press.
[0033] Repeat step 3) twice more, and rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) 360° in the horizontal direction, for a total of 3 times.
[0034] 4) After depressurization, the pressed sample was taken out to obtain a KPF6 plastic crystal material sample with a particle size of 75-150μm and a thickness of 0.24mm-0.29mm. The DSC curve of the sample was tested using a differential scanning calorimeter. At a heating and cooling rate of 10K / min (range of 240-270K), the phase change thermal hysteresis of the original untreated KPF6 plastic crystal material was (8.1K), and the phase change thermal hysteresis of the plastic crystal material with this particle size was 5.7K.
[0035] 5) The DSC curves of the samples were tested using a pressurized (or high-pressure) differential scanning calorimeter at a heating / cooling rate of 2 K / min (range 240–270 K), and the reversible capacitive entropy change of the original untreated KPF6 plastic crystal material at 30 MPa (20.8 J·kg⁻¹) was calculated. -1 ·K -1 The reversible piezoelectric entropy change of this particle size KPF6 plastic crystal material at 30 MPa is 38.2 J·kg. -1 ·K -1 .
[0036] Example 3
[0037] KPF6 plastic crystal material with particle size of 37.5-75μm
[0038] 1) The plastic crystal material was ground in an inert gas (nitrogen) in a glove box using an agate mortar and sieve with a particle size of 37.5 to 75 μm using 200-mesh and 400-mesh sieves (passing through the 200-mesh sieve and being retained by the 400-mesh sieve).
[0039] 2) Under nitrogen protection, pour 23.89 mg of powder obtained in step 1) into a cylindrical mold with an inner diameter of 3 mm, and use a hydraulic press to apply a pressure of 5 MPa to the powder sample in the mold from top to bottom along the axial direction. The pressure holding time is 30 s to complete the first pressing.
[0040] 3) Pressing again: Under nitrogen protection, after depressurization, rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) by 120° in the horizontal direction, and apply a pressure of 5MPa to the powder sample in the mold from top to bottom for 30s using a hydraulic press.
[0041] Repeat step 3) twice more, and rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) 360° in the horizontal direction, for a total of 3 times.
[0042] 4) After depressurization, the pressed sample was taken out to obtain KPF6 plastic crystal material samples with particle size of 37.5-75μm. The DSC curve of the sample with particle size of 0.32mm-0.37mm was tested using a differential scanning calorimeter. At a heating and cooling rate of 10K / min (range of 240-270K), the phase change thermal hysteresis of the original untreated KPF6 plastic crystal material was (8.1K), and the phase change thermal hysteresis of the KPF6 plastic crystal material with this particle size was 6.3K.
[0043] Example 4
[0044] KPF6 plastic crystal material with a particle size of ≤37.5μm
[0045] 1) Grind the plastic crystal material in an inert gas (nitrogen) environment in a glove box using an agate mortar and sieve it through a 400-mesh sieve to obtain plastic crystal material with a particle size of less than or equal to 37.5 μm.
[0046] 2) Under nitrogen protection, pour 17.18 mg of powder obtained in step 1) into a cylindrical mold with an inner diameter of 3 mm, and use a hydraulic press to apply a pressure of 5 MPa to the powder sample in the mold from top to bottom along the axial direction. The pressure holding time is 30 s to complete the first pressing.
[0047] 3) Pressing again: Under nitrogen protection, after depressurization, rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) by 120° in the horizontal direction, and apply a pressure of 5MPa to the powder sample in the mold from top to bottom for 30s using a hydraulic press.
[0048] Repeat step 3) twice more, and rotate the mold and the powder sample in it clockwise around the axis (the central axis of the cylindrical mold) 360° in the horizontal direction, for a total of 3 times.
[0049] 4) After depressurization, the pressed sample was taken out to obtain a KPF6 plastic crystal material sample with a particle size of less than or equal to 37.5 μm, 0.22 mm-0.27 mm. The DSC curve of the sample was tested using a differential scanning calorimeter. At a heating and cooling rate of 10 K / min (range of 240-270 K), the phase change thermal hysteresis of the original untreated KPF6 plastic crystal material was (8.1 K), and the phase change thermal hysteresis of the KPF6 plastic crystal material with this particle size was 6.5 K.
[0050] Based on the performance test results of Examples 1-4, the following conclusions are drawn:
[0051] The preparation method provided by this invention effectively optimizes the phase change thermal hysteresis of the plastic crystal material and improves the reversible compressive heating effect of the material under low pressure fields. Furthermore, it allows for the pressing of materials into desired sizes and shapes using molds of different dimensions. This invention provides the possibility for applying press-fitted plastic crystal materials in the field of phase change energy storage.
[0052] Matters not covered in this invention are common knowledge.
[0053] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A pressure-pressed plastic crystal material, characterized in that: The plastic crystal material is composed of KPF6; the plastic crystal material is formed by pressing particles with a particle size of less than or equal to 300 μm, preferably particles with a particle size of less than or equal to 150 μm, more preferably particles with a particle size of 37.5 to 150 μm, and most preferably particles with a particle size of 75 to 150 μm.
2. A method for improving the reversible compressive effect of plastic crystal materials by controlling particle size, characterized in that: The plastic crystal material is composed of KPF6; the plastic crystal material is formed by pressing particles with a particle size of less than or equal to 300 μm, preferably particles with a particle size of less than or equal to 150 μm, more preferably particles with a particle size of 37.5 to 150 μm, and most preferably particles with a particle size of 75 to 150 μm.
3. The method according to claim 2, characterized in that: The plastic crystal materials with different particle sizes are obtained by grinding and sieving. The pressure plastic crystal materials are ground and their particle size is controlled by sieving during the grinding process.
4. The method according to claim 2 or 3, characterized in that: The reversible compressive heat effect of the plastic crystal material can be controlled by changing the particle size of the plastic crystal material. Pour a sample of the required particle size of the press-fit crystal material into a mold and cold press it using a hydraulic press.
5. The method according to claim 4, characterized in that: The pressure applied during the cold pressing process is 1-10 MPa, preferably 2-8 MPa, more preferably 3-5 MPa, and the holding time is 15-120 s, preferably 20-60 s, more preferably 30-40 s.
6. The method according to claim 4 or 5, characterized in that: During the cold pressing process, the sample is pressed and formed under vertical pressure. After the first pressing process, the sample is rotated clockwise or counterclockwise in the horizontal direction 2-6 times (preferably 2-4 times, more preferably 2-3 times) for a second pressing. The angle of each rotation is 60-150 degrees (preferably 90-130 degrees, more preferably 100-120 degrees), and a total of 3-7 angles are pressed.
7. The method according to claim 4 or 5, characterized in that: All steps are carried out under an inert atmosphere (such as nitrogen, argon or two or more) at room temperature.