Phase change material for aircraft brake disc

Abstract

The invention discloses a phase change material for an aircraft brake disc, and belongs to the technical field of aircraft brake discs. The phase change material for the airplane brake disc is prepared from the following preparation raw materials in percentage by weight: 1 to 5 percent of NaCl, 1 to 5 percent of KCl, 1 to 5 percent of MgCl2, 10 to 20 percent of LiF, 10 to 20 percent of MgF2, 15 to 30 percent of AlSi alloy, 15 to 30 percent of AlMg alloy, 10 to 30 percent of graphite and 10 to 20 percent of paraffin. In addition, the phase change material provided by the invention can be formed by mixing and pressing various solid powder materials, and also can be obtained by melting various powder materials at a high temperature and then casting and carrying out eutectic molding. The prepared phase change material is good in thermal conductivity and high in latent heat, and can be better applied to the field of preparation of aircraft brake discs.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft brake discs, and more specifically relates to a phase change material for aircraft brake discs. Background Art

[0002] With the development of technology, aircraft braking devices are developing towards the trends of lightweight and miniaturization, and at the same time, they need to meet demanding requirements such as large load capacity and ultra-short takeoff and landing. Under the condition that the total braking energy of the aircraft remains unchanged, it is required that the brake disc absorbs more energy. At the same time, the miniaturization of the brake disc will inevitably lead to a reduction in the heat reservoir, resulting in the temperature of the brake disc exceeding the effective use temperature of the anti-oxidation coating, which will increase the oxidation loss and wear rate of the brake disc, thereby reducing the performance and service life of the brake disc. Phase change materials have the following characteristics: 1. High latent heat storage capacity, which can absorb or release a large amount of heat during the phase change process with little temperature change; 2. Temperature stability, during the phase change process, the temperature of the material is relatively constant until the phase change is completed; 3. Reversibility, the phase change process is usually reversible, and the material can be used in multiple cycles. Therefore, applying phase change materials to aircraft brake discs can solve the above problems.

[0003] Phase change materials can be divided into four types according to the physical states before and after phase change, namely solid-gas, liquid-gas, solid-solid, and solid-liquid phase change materials. Phase change materials only undergo changes in physical states during the phase change process and do not undergo temperature changes. An ideal phase change material should have characteristics such as high phase change latent heat, good reversibility, good thermal conductivity, fast phase change rate, small volume change, stable performance, inexpensive and easily available, safe and non-toxic, and non-corrosive. Therefore, it is commonly used in heat storage or heat release environments, such as solar energy heat storage devices.

[0004] Among the four types of phase change materials, the first two materials will have a large change in volume during the phase change, which places extremely harsh requirements on the structure and working conditions of the heat storage system; while the solid-solid phase change materials have disadvantages such as small phase change latent heat, serious plastic crystal phenomenon, and poor thermal conductivity. Therefore, there is little research and practical application on these three types of materials; while the solid-liquid phase change materials have a large phase change latent heat and small volume change during the phase change, and the process is controllable, which is the main research and application object at present. Solid-liquid phase change materials can be roughly divided into three categories: inorganic, organic, and composite eutectic. Among them, the organic category mainly includes paraffin, alcohols, and fatty acids, etc., and the inorganic category mainly includes crystalline hydrates, molten salts, and metals, etc.

[0005] Most of the domestic records on phase change material brake discs are based on the design of their structures and do not involve the records of the preparation methods related to phase change material brake discs. At the same time, there are a series of problems with existing phase change materials (such as poor thermal conductivity, high cost, etc.), which limit their application in the field of aircraft brake disc preparation. In addition, the phase change temperature of commonly used phase change materials is generally below 400 °C, and the heat absorption is limited under a certain volume ratio. However, when the aircraft brakes, the energy is large, and the highest brake temperature can reach above 1000 °C. As a result, it is difficult for existing phase change materials to be used in the aircraft brake field. Summary of the Invention

[0006] The purpose of the present invention is to provide a phase change material for aircraft brake discs to solve the problems existing in the above-mentioned prior art and realize the preparation of a high-performance phase change material for aircraft brake discs.

[0007] To achieve the above purpose, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention: Provide a phase change material for aircraft brake discs, which includes the following preparation raw materials by weight percentage:

[0009] NaCl 1-5 wt%, KCl 1-5 wt%, MgCl2 1-5 wt%, LiF 10-20 wt%, MgF2 10-20 wt%, AlSi alloy 15-30 wt%, AlMg alloy 15-30 wt%, graphite 10-30 wt% and paraffin 10-20 wt%.

[0010] Preferably, by weight percentage, in the AlSi alloy, the proportion of Al is 80-95 wt%, and the proportion of Si is 5-20 wt%; in the AlMg alloy, the proportion of Al is 90-99 wt%, and the proportion of Mg is 1-10 wt%.

[0011] The phase change temperature of the phase change material prepared using the above raw materials is 600-800 °C, which is significantly higher than the phase change temperature of existing phase change materials below 400 °C, so it has better practicability when used in the aircraft brake field.

[0012] Another technical solution of the present invention: Provide a preparation method for the above-mentioned phase change material for aircraft brake discs, which includes the following steps:

[0013] Mix the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin according to the specified dosage and then press them into shape to obtain the phase change material for aircraft brake discs.

[0014] Preferably, the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite, and paraffin are all added in the form of powders; the particle sizes of the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite, and paraffin are independently 30 to 75 μm.

[0015] Preferably, the pressure for pressing and forming is 200 MPa.

[0016] Technical solution three of the present invention: Provide a preparation method of the phase change material for an aircraft brake disc, including the following steps:

[0017] According to the specified dosage, mix and melt the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite, and paraffin, and then cool to eutectic to obtain the phase change material for the aircraft brake disc.

[0018] Preferably, the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite, and paraffin are all added in the form of powders; the particle sizes of the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite, and paraffin are independently 30 to 75 μm.

[0019] Preferably, the mixing and melting of the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite, and paraffin includes: first mix and melt the AlSi alloy and the AlMg alloy, then add NaCl, KCl, MgCl2, LiF, and MgF2 and mix and melt, and finally add graphite and mix and melt.

[0020] By controlling the addition sequence of each material in the mixing and melting process, the present invention can ensure uniform dispersion of metals and non-metals, which helps to improve the thermal conductivity of the material and fully exert the characteristics of high thermal conductivity, specific heat, and latent heat of the phase change material.

[0021] Preferably, the temperature of the mixing and melting is 850 °C; the cooling to eutectic includes: placing the molten material in a mold and air-cooling it to room temperature to complete the cooling to eutectic.

[0022] Technical solution four of the present invention: Provide an application of the phase change material for an aircraft brake disc in an aircraft brake disc.

[0023] Preferably, before the phase change material for the aircraft brake disc is used in the aircraft brake disc, it further includes a packaging step; the packaging includes: packaging the phase change material for the aircraft brake disc into a shell prepared from a copper foil or a high-thermal-conductivity metal material such as paraffin, and completing the sealing through precision welding.

[0024] Compared with the existing phase change materials that need to be encapsulated by methods such as porous adsorption method and microcapsule encapsulation method, the encapsulation method of the present invention is more convenient. The present invention only needs to encapsulate the phase change material into the shell prepared from copper foil or high thermal conductivity metal material of paraffin through precision welding to achieve the encapsulation of the phase change material. The technical principle of the present invention is:

[0025] The present invention uses a powder mixture composed of NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin to prepare a phase change material for aircraft brake discs, including organic, inorganic and eutectic materials, and solves the problems such as poor thermal conductivity of the existing phase change materials. Among them, the inorganic eutectic materials composed of NaCl, KCl, and MgCl2 can improve the sensible heat and specific heat of the material, the inorganic materials composed of LiF and MgF2 can improve the latent heat of the material, the eutectic materials composed of AlSi alloy and AlMg alloy can improve the thermal conductivity of the material, graphite as a high-temperature resistant material can improve the specific heat and thermal conductivity of the material, and paraffin as an organic material is an effective dispersant. Through the synergistic effect of each material such as NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin in the present invention, such as the dispersion effect of paraffin enables the added raw materials to be evenly dispersed in the phase change material, a phase change material with stable performance is obtained, and the thermal conductivity of the phase change material is significantly improved. The phase change temperature of the phase change material prepared using the above raw materials is 600 - 800 °C, which is significantly higher than the phase change temperature of the existing phase change materials below 400 °C, so it has better practicability when used in the field of aircraft brake disc preparation.

[0026] The present invention controls the dosages of NaCl, KCl, and MgCl2 as follows: NaCl 1 - 5 wt%, KCl 1 - 5 wt%, MgCl2 1 - 5 wt%. The best specific heat can be obtained at these dosages.

[0027] The present invention controls the dosages of LiF and MgF2 as follows: LiF 10 - 20 wt%, MgF2 10 - 20 wt%. The best latent heat can be obtained at these dosages.

[0028] The present invention controls the dosages of AlSi alloy and AlMg alloy as follows: AlSi alloy 15 - 30 wt%, AlMg alloy 15 - 30 wt%. The best thermal conductivity can be obtained at these dosages.

[0029] The present invention controls the dosage of graphite as follows: graphite 10 - 30 wt%. At this dosage, it can ensure that graphite is better dispersed inside the phase change material, plays the best thermal conductivity role, and at the same time can reduce the fluidity of the material after phase change and avoid leakage.

[0030] The present invention discloses the following technical effects:

[0031] 1. The phase change material forming process involved in the present invention is simple and flexible, and can be formed by pressing a mixture of various solid powders, or by melting various powders at high temperature and then casting and eutectic forming.

[0032] 2. The phase change material involved in the present invention is different from the existing phase change materials. The phase change material of the present invention mixes organic, inorganic and eutectic materials, solving the problems such as poor thermal conductivity existing in the existing phase change materials. Moreover, the raw materials used to prepare the phase change material of the present invention are simple and easy to obtain, with low cost, effectively reducing the preparation cost.

[0033] 3. The encapsulation of the phase change material of the present invention is simple and easy to operate. Existing phase change materials are generally encapsulated by methods such as porous adsorption method and microcapsule encapsulation method; the phase change material of the present invention is mixed and then pressed into shape, or melted and then cast and eutectic formed, and then welded and encapsulated with a high thermal conductivity metal shell to achieve the encapsulation of the phase change material. Detailed Embodiments

[0034] The various exemplary embodiments of the present invention will be described in detail below. This detailed description should not be considered as a limitation to the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0035] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0037] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are only exemplary.

[0038] Regarding the terms "comprising", "including", "having", "containing", etc. used in this article, they are all open-ended terms, meaning including but not limited to.

[0039] It should be noted that the operations not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0040] Unless otherwise specified, the raw materials used in the following examples and comparative examples of the present invention are all commercially available products, and the sources of the commercially available products do not affect the technical effects achieved by the present invention.

[0041] The carbon-carbon composite material used in the performance test of the present invention is provided by our company (Beijing Beimo Hi-Tech Friction Materials Co., Ltd.), and the model is GA31687BM.

[0042] In the AlSi alloy involved in the following examples and comparative examples of the present invention, the proportion of Al is 85 wt%, and the proportion of Si is 15 wt%; in the AlMg alloy, the proportion of Al is 95 wt%, and the proportion of Mg is 5 wt%.

[0043] Unless otherwise specified, the room temperature in the following examples and comparative examples of the present invention is calculated as 25 ± 5 °C.

[0044] The standards for testing the thermal physical properties of the phase change material in the following examples and comparative examples of the present invention are as follows: According to the GB / T 3398.1-2009 standard, a DTG-60H differential thermal / thermogravimetric synchronous analyzer is used to measure the specific heat and latent heat; according to the GB / T10294-2008 standard, a BT2.15 thermal conductivity calorimeter is used to measure the thermal conductivity of the phase change material.

[0045] Example 1

[0046] This example provides a phase change material for aircraft brake discs, specifically as follows:

[0047] The raw materials and their dosages for preparing the phase change material for aircraft brake discs are shown in Table 1.

[0048] Table 1 Raw materials and their dosages for preparing the phase change material for aircraft brake discs in Example 1

[0049]

[0050] The preparation steps are as follows:

[0051] Take the powder materials of NaCl, KCl, MgCl₂, LiF, MgF₂, AlSi alloy, AlMg alloy, graphite and paraffin wax respectively according to the dosages specified in Table 1. The particle sizes of the above powder materials are correspondingly 75 μm, 75 μm, 75 μm, 35 μm, 35 μm, 75 μm, 75 μm, 30 μm and 75 μm in sequence. Mix the powder materials and put them into a mold, and press and form at room temperature under a pressure of 200 MPa to obtain a phase change material for aircraft brake discs.

[0052] The thermal physical properties of the obtained phase change material for aircraft brake discs are shown in Table 2.

[0053] Table 2 Thermal physical property results of the phase change material for aircraft brake discs obtained in Example 1

[0054] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 73 780 0.9 2.2

[0055] Example 2

[0056] This example provides a phase change material for aircraft brake discs, which is as follows:

[0057] The raw materials and their dosages for preparing the phase change material for aircraft brake discs are shown in Table 3.

[0058] Table 3 Raw materials and their dosages for preparing the phase change material for aircraft brake discs in Example 2

[0059]

[0060]

[0061] The preparation steps are as follows:

[0062] Take the powder materials of NaCl, KCl, MgCl₂, LiF, MgF₂, AlSi alloy, AlMg alloy, graphite and paraffin wax respectively according to the dosages specified in Table 3. The particle sizes of the above powder materials are correspondingly 75 μm, 75 μm, 75 μm, 35 μm, 35 μm, 75 μm, 75 μm, 30 μm and 75 μm in sequence; take each powder material. Under the condition of 850 °C, first melt the AlSi alloy and AlMg alloy, then put NaCl, KCl, MgCl₂, LiF, MgF₂ for melting, and finally add graphite. After stirring evenly, pour the mixed melt into the mold and air-cool to room temperature to obtain a phase change material for aircraft brake discs.

[0063] The thermal physical properties of the obtained phase change material for aircraft brake discs are shown in Table 4.

[0064] Table 4 Thermal physical property results of the phase change material for aircraft brake discs obtained in Example 2

[0065] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 65 690 1.2 2.0

[0066] Example 3

[0067] This example provides a phase change material for aircraft brake discs, specifically as follows:

[0068] The raw materials and their dosages for preparing the phase change material for aircraft brake discs are shown in Table 5.

[0069] Table 5 Raw materials and their dosages for preparing the phase change material for aircraft brake discs in Example 3

[0070]

[0071] The preparation steps are as follows:

[0072] Take the powder materials of NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin wax respectively according to the dosages specified in Table 5. The particle sizes of the above powder materials correspond to 75μm, 75μm, 75μm, 35μm, 35μm, 75μm, 75μm, 30μm and 75μm in sequence; take each powder material. Under the condition of 850°C, first melt the AlSi alloy and AlMg alloy, then put NaCl, KCl, MgCl2, LiF, MgF2 for melting, and finally add graphite. After stirring evenly, pour the mixed melt into the mold and air-cool to room temperature to obtain the phase change material for aircraft brake discs.

[0073] Example 4

[0074] This example provides a phase change material for aircraft brake discs, specifically as follows:

[0075] The raw materials and their dosages for preparing the phase change material for aircraft brake discs are shown in Table 6.

[0076] Table 6 Raw materials and their dosages for preparing the phase change material for aircraft brake discs in Example 4

[0077]

[0078] The preparation steps are as follows:

[0079] Take the powder materials of NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin wax respectively according to the dosages specified in Table 6. The particle sizes of the above powder materials correspond to 75μm, 75μm, 75μm, 35μm, 35μm, 75μm, 75μm, 30μm and 75μm in sequence. Mix each powder material and put it into the mold, and press and form it at a pressure of 200 MPa at room temperature to obtain the phase change material for aircraft brake discs.

[0080] Comparative Example 1

[0081] The differences from Example 1 are as follows: the dosage of MgCl2 is adjusted to 10 wt%, while the dosage of MgF2 is reduced so that the sum of the weight percentages of all raw materials is 100 wt%. Other conditions are the same as in Example 1. The thermophysical properties of the obtained phase change material are shown in Table 7.

[0082] Table 7 Thermophysical property results of the phase change material obtained in Comparative Example 1

[0083] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 45 520 0.9 2.0

[0084] Comparing the thermophysical property results of Example 1 and Comparative Example 1, it can be seen that the thermal conductivity and latent heat of the phase change material obtained in Example 1 are greater, indicating that it has better thermal conductivity. It also shows that adjusting the dosage ratio of MgCl2 and MgF2 inorganic materials will significantly reduce the thermal conductivity of the phase change material.

[0085] Comparative Example 2

[0086] The differences from Example 2 are as follows: the dosage of KCl is adjusted to 10 wt%, while the dosage of MgF2 is reduced so that the sum of the weight percentages of all raw materials is 100 wt%. Other conditions are the same as in Example 2. The thermophysical properties of the obtained phase change material are shown in Table 8.

[0087] Table 8 Thermophysical property results of the phase change material obtained in Comparative Example 2

[0088] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 44 510 1.2 2.0

[0089] Comparing the thermophysical property results of Example 2 and Comparative Example 2, it can be seen that the thermal conductivity and latent heat of the phase change material obtained in Example 2 are greater, indicating that it has better thermal conductivity. It also shows that adjusting the dosage ratio of KCl and MgF2 inorganic materials will significantly reduce the thermal conductivity of the phase change material.

[0090] Comparative Example 3

[0091] The differences from Example 1 are as follows: the dosage of LiF is adjusted to 35 wt%, the dosage of KCl is adjusted to 1 wt%, and the dosage of AlMg alloy is reduced so that the sum of the weight percentages of all raw materials is 100 wt%. Other conditions are the same as in Example 1. The thermophysical properties of the obtained phase change material are shown in Table 9.

[0092] Table 9 Thermophysical property results of the phase change material obtained in Comparative Example 3

[0093] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 22 630 1.0 2.0

[0094] Comparing the thermophysical property results of Example 1 and Comparative Example 3, it can be seen that the thermal conductivity and latent heat of the phase change material obtained in Example 1 are greater, indicating that it has better thermal conductivity. It also shows that adjusting the dosage ratio of LiF and MgF2 inorganic materials and eutectic materials such as AlMg alloy will significantly reduce the thermal conductivity of the phase change material.

[0095] Comparative Example 4

[0096] The difference from Example 2 is as follows: the amount of LiF is adjusted to 35 wt%, the amount of MgCl2 is adjusted to 1 wt%, and the amount of AlMg alloy is reduced so that the sum of the weight percentages of all raw materials is 100 wt%. Other conditions are the same as those in Example 2. The thermophysical properties of the obtained phase change material are shown in Table 10.

[0097] Table 10 Thermophysical property results of the phase change material obtained in Comparative Example 4

[0098]

[0099]

[0100] Comparing the thermophysical property results of Example 2 and Comparative Example 4, it can be seen that the phase change material obtained in Example 2 has a higher thermal conductivity and latent heat, indicating that it has better thermal conductivity. It also shows that adjusting the dosage ratio of inorganic materials such as LiF and MgCl2 and eutectic materials such as AlMg alloy will significantly reduce the thermal conductivity of the phase change material.

[0101] Comparative Example 5

[0102] The difference from Example 1 is as follows: the amount of AlSi alloy is adjusted to 10 wt%, and the amount of NaCl is increased so that the sum of the weight percentages of all raw materials is 100 wt%. Other conditions are the same as those in Example 1. The thermophysical properties of the obtained phase change material are shown in Table 11.

[0103] Table 11 Thermophysical property results of the phase change material obtained in Comparative Example 5

[0104] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 32 530 1.0 2.1

[0105] Comparing the thermophysical property results of Example 1 and Comparative Example 5, it can be seen that the phase change material obtained in Example 1 has a higher thermal conductivity and latent heat, indicating that it has better thermal conductivity. It also shows that adjusting the dosage ratio of inorganic materials such as KCl and eutectic materials such as AlSi alloy will significantly reduce the thermal conductivity of the phase change material.

[0106] Comparative Example 6

[0107] The difference from Example 2 is as follows: the amount of AlSi alloy is adjusted to 45 wt%, the amount of AlMg alloy is adjusted to 15 wt%, and the amount of MgF2 is reduced so that the sum of the weight percentages of all raw materials is 100 wt%. Other conditions are the same as those in Example 2. The thermophysical properties of the obtained phase change material are shown in Table 12.

[0108] Table 12 Thermophysical property results of the phase change material obtained in Comparative Example 6

[0109] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 45 520 0.9 2.0

[0110] Comparing the thermal physical property results of Comparative Example 2 and Comparative Example 6, it can be seen that the thermal conductivity coefficient and latent heat of the phase change material obtained in Example 2 are greater, indicating that it has better thermal conductivity performance. It also shows that adjusting the dosage ratio of the MgF2 inorganic material and the eutectic materials of AlSi alloy and AlMg alloy will significantly reduce the thermal conductivity performance of the phase change material.

[0111] Comparative Example 7

[0112] The difference from Example 1 is that the dosage of AlSi alloy is adjusted to 10 wt%, and at the same time, the dosage of AlMg alloy is increased so that the sum of the weight percentages of all raw materials is 100 wt%, and the others are the same as in Example 1. The thermal physical properties of the obtained phase change material are shown in Table 13.

[0113] Table 13 Thermal physical property results of the phase change material obtained in Comparative Example 7

[0114] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 48 600 1.2 2.0

[0115] Comparing the thermal physical property results of Example 1 and Comparative Example 7, it can be seen that the thermal conductivity coefficient and latent heat of the phase change material obtained in Example 1 are greater, indicating that it has better thermal conductivity performance. It also shows that adjusting the dosage ratio of the eutectic materials of AlSi alloy and AlMg alloy will significantly reduce the thermal conductivity performance of the phase change material.

[0116] Comparative Example 8

[0117] The difference from Example 1 is that AlSi alloy is replaced with Al in equal amount, and the others are the same as in Example 1. The thermal physical properties of the obtained phase change material are shown in Table 14.

[0118] Table 14 Thermal physical property results of the phase change material obtained in Comparative Example 8

[0119] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 70 510 0.9 2.0

[0120] Comparing the thermal physical property results of Example 1 and Comparative Example 8, it can be seen that the latent heat of the phase change material obtained in Example 1 is greater, indicating that the eutectic materials play an important role in enhancing the latent heat of the phase change material.

[0121] Comparative Example 9

[0122] The difference from Example 1 is that AlMg alloy is replaced with Al in equal amount, and the others are the same as in Example 1. The thermal physical properties of the obtained phase change material are shown in Table 15.

[0123] Table 15 Thermal physical property results of the phase change material obtained in Comparative Example 9

[0124] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 71 520 0.9 2.0

[0125] Comparing the thermal physical property results of Comparative Example 1 and Comparative Example 9, it can be seen that the latent heat of the phase change material obtained in Example 1 is greater, indicating that the eutectic material plays an important role in enhancing the latent heat of the phase change material.

[0126] Comparative Example 10

[0127] The difference from Example 1 is that NaCl, KCl and MgCl2 are replaced with MgF2 in equal amounts, and the others are the same as in Example 1. The thermal physical properties of the obtained phase change material are shown in Table 16.

[0128] Table 16 Thermal physical property results of the phase change material obtained in Comparative Example 10

[0129] Performance indicators Thermal conductivity W / (m·K) Latent heat J / g Specific heat J / (g·K) <![CDATA[Density g / cm 3 > Results 60 500 0.7 2.0

[0130] Comparing the thermal physical property results of Example 1 and Comparative Example 10, it can be seen that the thermal conductivity and latent heat of the phase change material obtained in Example 1 are greater, indicating that the present invention significantly improves the thermal conductivity of the obtained phase change material by selecting specific dosage ratios and specific types of inorganic materials.

[0131] Performance test:

[0132] Perform performance tests on the phase change materials for aircraft brake discs prepared in Examples 1 to 2 and Comparative Examples 1 to 10:

[0133] First, prepare test specimens:

[0134] Encapsulation: Respectively encapsulate the phase change materials for aircraft brake discs prepared in Examples 1 to 2 and Comparative Examples 1 to 10 into the outer shells made of copper foil, and complete the sealing by precision welding. The encapsulation amount is 20% of the inner cavity volume of the outer shell, and the shell thickness is 0.15 mm;

[0135] Loading: Load the encapsulated phase change materials into the friction and wear test specimens prepared from carbon-carbon composite materials (commercially available).

[0136] Secondly, conduct performance detection:

[0137] (1) Detect the friction and wear performance through the MM3000 manufactured by Xi'an Shuntong Experimental Equipment Manufacturing Company.

[0138] (2) Conduct 1:1 test comparison and verification through the aircraft brake ground power test bench.

[0139] The results are shown in Table 17 and Table 18.

[0140] Table 17 Friction and wear performance detected by MM3000

[0141]

[0142] Table 18 Test results of the brake power bench

[0143]

[0144] As can be seen from Table 17 and Table 18, the maximum braking temperature of the brake disc prepared using the phase change materials described in Examples 1 and 2 is significantly lower than that of the existing carbon-carbon composite materials and the phase change materials described in Comparative Examples 1 to 10. This shows that the phase change material prepared by the present invention has more excellent thermal conductivity and better practicability when used in the field of aircraft brake disc preparation.

[0145] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other.

[0146] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phase change material for aircraft brake discs, characterized in that: By weight percentage, the preparation comprises the following raw materials: NaCl 1-5wt%, KCl 1-5wt%, MgCl2 1-5wt%, LiF 10-20wt%, MgF2 10-20wt%, AlSi alloy 15-30wt%, AlMg alloy 15-30wt%, graphite 10-30wt% and paraffin 10-20wt%.

2. The phase change material for aircraft brake disc according to claim 1, characterized in that: In terms of weight percentage, in the AlSi alloy, Al accounts for 80-95wt% and Si accounts for 5-20wt%; in the AlMg alloy, Al accounts for 90-99wt% and Mg accounts for 1-10wt%.

3. The method for preparing the phase change material for aircraft brake disc according to claim 1 or 2, characterized in that: The steps include: The NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin are mixed according to the prescribed amounts and then pressed to obtain the phase change material for aircraft brake discs.

4. The preparation method according to claim 3, characterized in that: The NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin are all added in the form of powder; the particle sizes of the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin are independently 30 to 75 μm.

5. The preparation method according to claim 3, characterized in that: The pressure of the compression molding is 200 MPa.

6. The method for preparing the phase change material for aircraft brake discs according to claim 1 or 2, characterized in that: The steps include: The NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin are mixed and melted according to the prescribed amounts, and then cooled to form a eutectic to obtain the phase change material for the aircraft brake disc.

7. The preparation method according to claim 6, characterized in that: The NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin are all added in the form of powder; the particle sizes of the NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin are independently 30 to 75 μm.

8. The preparation method according to claim 6, characterized in that: The mixed melting of NaCl, KCl, MgCl2, LiF, MgF2, AlSi alloy, AlMg alloy, graphite and paraffin comprises: firstly mixing and melting AlSi alloy and AlMg alloy, then adding NaCl, KCl, MgCl2, LiF and MgF2 and mixing and melting, and finally adding graphite and mixing and melting.

9. The preparation method according to claim 6, characterized in that: The temperature of the mixed melt is 850° C.; and / or, the cooling eutectic comprises: placing the molten material in a mold and air-cooling it to room temperature to complete the cooling eutectic.

10. Use of the phase change material for aircraft brake discs according to claim 1 or 2 in aircraft brake discs.

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