A metal-mycelium composite material and a preparation method and application thereof

Abstract

The application belongs to the technical field of building energy-saving materials, and discloses a metal-mycelium composite material and a preparation method and application thereof. The composite material is composed of an integrated pyramid array metal heat-conducting frame and a porous mycelium heat-insulating matrix grown in situ, forms a three-dimensional anisotropic structure and has a thermal rectification effect, and can realize directional and preferential heat conduction. The metal frame is prepared by 3D printing or mold forming, the composite material is obtained through mycelium inoculation, mild culture and low-temperature solidification, and the process is simple and easy to scale. The material can be made into roof boards, wall boards, heat insulation layers and other building enclosure components, passive temperature control is realized without external energy driving, indoor temperature fluctuation and building refrigeration energy consumption can be significantly reduced, the material has the advantages of green environmental protection, stable structure, energy saving and high efficiency, and is suitable for ultra-low energy consumption buildings and energy-saving reconstruction of existing buildings.

Description

Technical Field

[0001] This invention belongs to the field of building energy-saving materials technology, specifically relating to a metal-mycelium composite material with thermal rectification effect, its preparation method, and its application in passive temperature regulation of buildings. Background Technology

[0002] The global energy crisis and climate change are becoming increasingly severe. Building energy consumption accounts for 30% to 40% of global total energy consumption, and the building industry accounts for approximately 38% of global energy-related CO2 emissions, with heating and cooling energy consumption being the main component of building energy consumption. Traditional building envelopes rely heavily on active energy systems such as air conditioning and heat pumps to maintain stable indoor temperatures, resulting in high energy consumption and persistently high carbon emissions.

[0003] Existing passive temperature regulation materials are mainly divided into two categories: phase change materials and porous insulation materials. While phase change materials possess high latent heat storage and temperature stabilization capabilities, they suffer from fire hazards, potential toxicity, environmental pollution, mechanical property degradation, and high initial costs, hindering large-scale application. Porous insulation materials, such as rock wool, extruded polystyrene boards, and glass wool, exhibit isotropic thermal conductivity, making it impossible to actively control the direction of heat conduction. This hinders adaptive heat flow regulation based on diurnal temperature variations and seasonal temperature changes, resulting in significant indoor temperature fluctuations and persistently high energy consumption in air conditioning and heating systems.

[0004] In recent years, mycelium-based composite materials have attracted widespread attention from academia and industry due to their advantages such as environmental friendliness, biodegradability, wide availability of raw materials, and excellent thermal insulation performance. However, current research and applications of mycelium composite materials are limited to isotropic insulation layers and do not involve thermal rectification effects. They cannot achieve intelligent regulation functions such as preferential heat conduction in a specific direction and obstruction of reverse conduction, which limits their application potential in the field of passive intelligent thermal management of buildings. Summary of the Invention

[0005] The purpose of this invention is to solve the problems that traditional passive temperature control materials cannot directionally regulate heat flow and bio-based materials lack thermal rectification function. It provides a metal-mycelium composite material, which forms a three-dimensional anisotropic structure by combining a metal thermally conductive framework with a porous mycelium thermal insulation matrix and achieves a thermal rectification effect. It also provides a method for preparing the composite material and its application in passive temperature control of buildings.

[0006] To achieve the above objectives, one of the technical solutions adopted by the present invention is to provide a metal-mycelium composite material, including a metal thermally conductive frame, wherein the metal thermally conductive frame is an integrated structure formed by interconnecting several pyramid-shaped metal frame units arranged in an array; a porous mycelium thermal insulation matrix is ​​grown and filled in the gaps of the metal thermally conductive frame; the metal thermally conductive frame and the porous mycelium thermal insulation matrix are combined to form a three-dimensional anisotropic structure, so that the composite material has a thermal rectification effect and can achieve preferential heat conduction along a specific direction.

[0007] This composite material uses an integrated array-type pyramidal metal thermally conductive frame as the structural support and directional heat conduction pathway, combined with a porous mycelium thermal insulation matrix that grows and fills the gaps in situ, forming a stable and tightly bonded three-dimensional anisotropic composite system. Relying on the asymmetric geometry of the pyramid to achieve a thermal rectification effect, it can adaptively guide the directional and preferential conduction of heat under the condition of no external energy. It has the dual advantages of high thermal conductivity and high mechanical strength of the metal frame and lightweight and efficient thermal insulation of the mycelium matrix, which significantly improves the overall structural stability, durability and interfacial bonding of the material. At the same time, it realizes passive intelligent thermal regulation, effectively smoothing indoor temperature fluctuations and reducing building HVAC energy consumption.

[0008] Furthermore, the metal thermally conductive frame is made of a thermally conductive metal, preferably aluminum, copper, or their alloys. Aluminum, copper, and their alloys possess excellent thermal conductivity and processability, enabling the rapid construction of continuous, low-resistance directional thermal conduction paths, fully ensuring the stable realization of the composite material's thermal rectification effect. Simultaneously, their moderate density and good mechanical strength make them easy to fabricate high-precision pyramid array structures through 3D printing or mold forming. They are also recyclable and environmentally friendly, balancing thermal conductivity, fabrication feasibility, and green, low-carbon requirements.

[0009] Furthermore, the dimensions of the metal frame unit are in the micrometer to millimeter range, with a preferred height of 3 to 8 mm and a base size of 8 mm × 8 mm to 15 mm × 15 mm. This ensures that the pyramid structure exhibits significant geometric anisotropy, fully stimulating and stably realizing the thermal rectification effect. At the same time, it takes into account the uniform growth of mycelium, the integrity of the pore structure, and the overall strength of the composite material. This avoids the difficulties in processing and growth caused by excessively small dimensions, while also preventing the reduction in thermal control accuracy and response speed due to excessively large dimensions. This adapts to the large-scale preparation of building envelope components and the actual temperature control requirements.

[0010] Furthermore, the porous mycelial insulation matrix is ​​formed by cultivating oyster mushroom mycelium and has a three-dimensional porous network structure with a porosity of 50-90% and a pore size of 10-500 μm. This gives the mycelial matrix a stable and uniform three-dimensional porous insulation structure, which not only ensures excellent low thermal conductivity and insulation effect, but also provides space for the mycelium to grow fully within the gaps of the metal frame, forming a tight interface with the metal frame. The appropriate porosity and pore size can balance insulation performance, structural strength and dimensional stability, avoiding insufficient strength due to excessively large pores and affecting insulation efficiency due to excessively small pores. Thus, it works in conjunction with the metal thermally conductive frame to achieve the best thermal rectification and passive temperature control effect.

[0011] To achieve the above objectives, the second technical solution adopted by the present invention is to provide a method for preparing a metal-mycelium composite material, comprising the following steps: S1. A metal thermally conductive frame is prepared by 3D printing or mold forming process. The metal thermally conductive frame is an integrated structure formed by connecting several pyramid-shaped metal frame units arranged in an array. S2. A thin layer of solid culture medium is evenly spread on the surface of the metal heat-conducting frame, followed by inoculation of mycelium and constant temperature and humidity culture, so that the mycelium germinates and proliferates on the thin layer of culture medium, spreading and intertwining into the gaps of the metal heat-conducting frame until it completely fills the gaps of the frame, forming a porous mycelium heat-insulating matrix with a three-dimensional porous network structure. S3. The molded structure is cured to dehydrate and shape the mycelium, enhance the interfacial bonding force between the mycelium and the metal thermally conductive frame and stabilize the pore structure, and finally obtain the metal mycelium composite material.

[0012] The preparation method of this invention uses an integrally molded pyramid array metal thermally conductive frame to ensure a continuous low-resistance thermal conduction path and structural integrity. Then, under mild conditions, a thin layer of culture medium is laid on the surface of the frame and mycelium is inoculated and cultured. After solidification, the mycelium grows uniformly in situ within the gaps of the frame and is tightly integrated with the metal frame to form a stable three-dimensional porous thermal insulation matrix. The entire process is simple, the conditions are controllable, and it is easy to scale up. It can accurately construct a composite structure with both three-dimensional anisotropy and thermal rectification effect, effectively solving problems such as weak interface bonding, uneven mycelium distribution, and difficulty in achieving stable thermal rectification performance. It is suitable for the large-scale production of building-scale components.

[0013] Furthermore, the culture temperature of the mycelium in step S2 is 20-30℃ and the humidity is 60%-80%, which can ensure the normal germination, rapid proliferation and uniform growth of the mycelium, and avoid the problems of mycelial mold and decay caused by excessive temperature and humidity or growth stagnation and insufficient activity caused by excessive temperature and humidity. The culture time is 5-15 days, which allows the mycelium to grow gradually on the surface culture medium, fully spreading and interweaving from the surface of the metal frame to the interior of the gaps, ensuring that the three-dimensional porous network structure after molding is uniform and regular without voids or defects. This not only ensures the stable heat insulation performance of the mycelial matrix, but also effectively optimizes the interface bonding state between the mycelium and the metal frame, ensuring the stability and consistency of the thermal rectification effect of the composite material.

[0014] Furthermore, the curing temperature in step S3 is 50–80°C, which enables the mycelium to slowly dehydrate, solidify, and densify without damaging the three-dimensional porous network structure of the mycelium, thoroughly removing excess moisture from the material and accurately stabilizing the pore morphology and porosity. The curing time is 12–36 hours. Sufficient curing time can significantly improve the overall structural strength of the mycelial matrix, strengthen the interfacial bonding force between the mycelium and the metal frame, and prevent failure problems such as pore collapse, structural cracking, and matrix detachment during later use of the product. This effectively ensures the long-term stability of the composite material's thermal insulation performance, structural durability, and thermal rectification control effect.

[0015] This invention also provides the application of the aforementioned metal-mycelium composite material in passive temperature regulation of buildings. The composite material is used to prepare building envelope components, including roof panels, wall panels, or insulation layers. Based on its three-dimensional anisotropic structure and thermal rectification effect, this composite material can adaptively regulate the direction of heat flow without external energy drive. During the day, it effectively suppresses outdoor heat transfer into the interior, and at night, it promotes the dissipation of excess indoor heat, significantly reducing indoor temperature fluctuations and decreasing building cooling and heating energy consumption. Simultaneously, the material is environmentally friendly, the mycelium is biodegradable, the metal frame is recyclable, the interface bonding is strong, and it exhibits excellent mechanical properties and thermal stability. Its modular array structure is easily scaled up to be used in building-scale components, enabling its widespread application in new ultra-low energy buildings and energy-saving renovations of existing buildings. It combines the advantages of high efficiency, thermal comfort, green and low-carbon development, and engineering applications.

[0016] Compared with existing technologies, it has the following beneficial effects: This invention employs an integrated pyramid array metal thermally conductive frame as the support and heat-conducting body. Mycelium grows and fills the gaps in the metal thermally conductive frame in situ, resulting in a tight bond between the two without delamination or shedding. This provides excellent overall mechanical strength and dimensional stability, effectively addressing the weakness of the interface between the metal and the biological matrix. Combined with a reasonable frame size and pore structure, this further enhances the overall structural integrity and durability of the composite material. The composite material, relying on the geometric anisotropy of the pyramid structure, forms a three-dimensional anisotropic composite system, enabling stable intelligent control of thermal rectification. It can passively regulate temperature without external energy input, adaptively guiding the directional conduction of heat flow. During the day, it effectively suppresses outdoor heat transfer into the room, and at night, it facilitates indoor heat dissipation, reducing indoor temperature fluctuations by approximately 40%. This overcomes the limitations of traditional insulation materials, which only provide basic insulation and cannot directionally control heat flow. Simultaneously, the directional heat conduction of the metal frame and the efficient thermal insulation of the porous mycelium matrix work synergistically, reducing building cooling energy consumption by 25%, significantly reducing building carbon emissions, contributing to the achievement of "dual carbon" goals, and drastically reducing the operating load of building heating and cooling equipment, effectively reducing building energy consumption and comprehensively improving indoor thermal comfort.

[0017] Meanwhile, this invention is green and environmentally friendly, with a simple and controllable process and a wide range of applications, possessing excellent industrialization value. The invention employs an integrated molding process of "frame fabrication-mycelial inoculation-cultivation-curing," with a simple preparation process, mild reaction conditions, and strong process controllability. It is compatible with existing building material production equipment, and the modular array structure facilitates scaling up from micro-units to building components, enabling mass production and strong engineering feasibility. The material system is green and sustainable; the mycelium is completely biodegradable, the metal frame is recyclable, and the mycelial culture medium uses agricultural waste as raw material, achieving resource recycling and low overall environmental impact. Furthermore, the selected aluminum, copper, and their alloys have excellent thermal conductivity and high cost-effectiveness, aligning with the concepts of green building and low-carbon development. In addition, this composite material can be made into various building envelope components such as roof panels, wall panels, and insulation layers, widely applicable to new ultra-low energy buildings, near-zero energy buildings, and energy-saving renovations of existing buildings, especially suitable for areas with large diurnal temperature differences, showing a very broad market application prospect. Attached Figure Description

[0018] Figure 1 This is a flowchart of the preparation method of the metal-mycelium composite material of the present invention.

[0019] Figure 2 This is a schematic diagram illustrating the architectural application of roof panels made from the metal-mycelium composite material of this invention.

[0020] Figure 3 This is a test curve comparing the indoor temperature fluctuation of the present invention with that of a conventional roof. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0022] Example 1: Preparation of metal-mycelium composite material A method for preparing a metal-mycelium composite material, the process of which is as follows: Figure 1 As shown, it includes the following steps: S1 fabricates an integrated metal thermally conductive frame. Pure copper is used as raw material, and an integrated metal heat-conducting frame is prepared in one step through die casting molding process. The metal heat-conducting frame is composed of several pyramid-shaped metal frame units arranged in a regular array and connected in one piece. The height of a single pyramid unit is 5 mm, and the base size is 10 mm × 10 mm.

[0023] The formed metal heat-conducting frame is subjected to degreasing, pickling, rinsing with water, and drying in sequence to keep the surface clean and facilitate subsequent mycelial attachment and growth.

[0024] S2: Lay out the culture medium, inoculate and culture the mycelium. A thin layer of solid culture medium with a thickness of 1 to 2 mm is evenly spread on the upper surface of the integrated metal heat-conducting frame. The solid culture medium is made by mixing corn cob powder, sawdust and wheat bran in a mass ratio of 6:3:1, sterilizing by high pressure steam at 121℃ for 30 min and then cooling to room temperature for later use.

[0025] Evenly inoculate the surface of the culture medium with liquid oyster mushroom spawn, and place the whole thing in a constant temperature and humidity incubator. Control the culture conditions as follows: temperature 25℃, relative humidity 70%, and culture in the dark for 10 days.

[0026] The mycelium germinates and proliferates using the surface culture medium as a nutrient source, spreading directionally and intertwining along the surface of the metal frame into the gaps between the frames, eventually completely filling all the gaps to form a continuous and uniform three-dimensional porous network structure of porous mycelium heat insulation matrix.

[0027] S3 low temperature curing and shaping The cultured composite structure was transferred to a hot air circulating oven for low-temperature curing treatment: 60℃ for 24 hours. The curing process allowed the mycelium to slowly dehydrate, shrink, and solidify, expelling internal free water, stabilizing the pore morphology and porosity, and simultaneously strengthening the interfacial bonding between the mycelium and the metal framework. The final product was a metal-mycelium composite material with a porosity of approximately 70% and a pore size of 50–200 μm. The internal mycelium and metal framework were tightly bonded without obvious interfacial gaps, exhibiting a complete and uniform three-dimensional porous network structure and demonstrating significant three-dimensional anisotropy.

[0028] Example 2: System Verification of Thermal Rectification Effect A bidirectional controllable temperature gradient testing platform was constructed to conduct forward / reverse heat flow comparison tests on the metal-mycelium composite material prepared in Example 1, systematically verifying its thermal rectification effect and anisotropic heat transfer characteristics. Test results show that the asymmetric geometry of the pyramid-shaped metal thermally conductive frame in the composite material causes heat to exhibit two distinctly different transport states within the material: a heat convergence state and a heat divergence state. When heat flow is conducted along the pyramid unit base towards the tip, the metal frame efficiently guides and converges the heat, resulting in low heat transfer resistance and high efficiency, exhibiting a preferential conduction state. When heat flow is conducted in the reverse direction along the tip towards the base, the heat is significantly blocked by the mycelial insulating matrix within the frame gaps, exhibiting a suppression and blocking state with high diffusion loss and low conduction efficiency. Through the difference in heat transfer efficiency between the convergence and divergence states, a significant thermal rectification effect can be achieved, stably realizing the intelligent control function of preferential heat conduction in a specific direction and obstructed reverse conduction.

[0029] This heat rectification mechanism requires no external energy drive and can adaptively adjust the magnitude and direction of heat flow according to the temperature changes of indoor and outdoor spaces during the day and night. It effectively blocks outdoor heat intrusion during the day and quickly removes indoor waste heat at night, providing a brand-new technical path and functional implementation solution for passive temperature regulation of buildings and reducing HVAC energy consumption.

[0030] Example 3: Preparation of Building Envelope Components and Passive Temperature Control Performance Testing The metal-mycelium composite material obtained in Example 1 was further scaled up to the architectural engineering scale. Through modular array splicing, overall waterproof encapsulation and structural reinforcement, a large building roof panel component of 1 m × 1 m × 0.1 m was made and installed on the roof of the test building to carry out long-term outdoor performance tests under the large temperature difference between day and night in summer.

[0031] The roof panel components were installed on the standardized test building roof, with the installation direction strictly controlled as follows: the apex of the pyramid metal frame facing outwards, and the frame base facing inwards. Figure 2 As shown. This directional installation method maximizes the thermal rectification effect of the material: During the day, when the outdoor ambient temperature is higher than the indoor temperature, the heat flow is in a divergent state of the pyramid structure when heat is conducted from the outside to the inside. The metal heat conduction path blocks and weakens the heat flow. Combined with the low thermal conductivity of the porous mycelium insulation matrix, it makes it difficult for outdoor heat to penetrate into the room, thus achieving daytime heat insulation and cooling. At night, when the indoor temperature is relatively high, the heat flow is in a convergent state of the pyramid structure when heat is conducted from the inside to the outside. The metal frame forms a continuous, low-resistance, directional heat conduction path, which can quickly guide the indoor residual heat to the outside, achieving heat dissipation and cooling at night. Thus, it can complete all-weather passive intelligent temperature regulation without electricity or mechanical drive.

[0032] A high-precision temperature recorder was used to continuously monitor the indoor environment of the test building for 24 hours. A control group of buildings with the same structure and ordinary traditional insulated roofs was simultaneously set up. The monitoring results are as follows: Figure 3 As shown, under the same natural climatic conditions, the indoor temperature of the control group (ordinary roof) fluctuated drastically between 26 and 38°C, with a fluctuation range of ±10°C. In contrast, the indoor temperature of the roof using the metal-mycelium composite material of this invention remained stable between 28 and 34°C, with a fluctuation of only ±6°C. The temperature change was gradual, and the temperature fluctuation range was reduced by 40% compared to the control group, significantly improving the stability of the indoor thermal environment. Energy consumption statistics show that using the composite material roofing panels of this invention can reduce building cooling energy consumption by approximately 25%, demonstrating outstanding passive temperature control and energy-saving effects. This fully verifies the reliability and effectiveness of the thermal rectification effect in practical building applications.

[0033] It should be noted that the metal-mycelium composite material of the present invention can be used not only for roof panels, but also for wall panels, insulation layers and other building envelope scenarios. In view of the heat transfer characteristics, installation conditions and service environment of different building envelope parts, the thermal rectification efficiency, structural strength and durability of the composite material in different application scenarios can be improved by optimizing the size, array density and wall thickness parameters of the pyramid metal frame unit and screening for suitable mycelium types.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A metal-mycelium composite material, characterized in that: The material includes a metal thermally conductive frame, which is an integrated structure formed by interconnecting several pyramid-shaped metal frame units arranged in an array; a porous mycelium thermal insulation matrix is ​​grown and filled in the gaps of the metal thermally conductive frame; the metal thermally conductive frame and the porous mycelium thermal insulation matrix are combined to form a three-dimensional anisotropic structure, which gives the composite material a thermal rectification effect, enabling preferential heat conduction along a specific direction.

2. The metal-mycelium composite material according to claim 1, characterized in that: The metal thermally conductive frame is made of thermally conductive metal.

3. The metal-mycelium composite material according to claim 2, characterized in that: The thermally conductive metal is aluminum, copper, or an alloy thereof.

4. The metal-mycelium composite material according to claim 1, characterized in that: The height of the metal frame unit is 3-8mm, and the base size is 8mm×8mm-15mm×15mm.

5. The metal-mycelium composite material according to claim 1, characterized in that: The porous mycelial heat-insulating matrix is ​​formed by the cultivation of oyster mushroom mycelium and has a three-dimensional porous network structure with a porosity of 50-90% and a pore size of 10-500 μm.

6. A method for preparing the metal-mycelium composite material according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. A metal thermally conductive frame is prepared by 3D printing or mold forming process. The metal thermally conductive frame is an integrated structure formed by connecting several pyramid-shaped metal frame units arranged in an array. S2. A thin layer of solid culture medium is evenly spread on the surface of the metal heat-conducting frame, followed by inoculation of mycelium and constant temperature and humidity culture, so that the mycelium germinates and proliferates on the thin layer of culture medium, spreading and intertwining into the gaps of the metal heat-conducting frame until it completely fills the gaps of the frame, forming a porous mycelium heat-insulating matrix with a three-dimensional porous network structure. S3. The molded structure is cured to dehydrate and shape the mycelium, enhance the interfacial bonding force between the mycelium and the metal thermally conductive frame and stabilize the pore structure, and finally obtain the metal-mycelium composite material.

7. The preparation method according to claim 6, characterized in that: The culture temperature of the mycelium in step S2 is 20-30℃, the humidity is 60%-80%, and the culture time is 5-15 days.

8. The preparation method according to claim 6, characterized in that: The curing temperature in step S3 is 50–80°C, and the curing time is 12–36 hours.

9. The application of the metal-mycelium composite material according to any one of claims 1 to 5 in passive temperature regulation of buildings, characterized in that: The metal-mycelium composite material is used to prepare building envelope components.

10. The application according to claim 9, characterized in that: The building envelope components include roof panels, wall panels, or insulation layers.

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