Wave-absorbing and heat-guiding integrated material with ultrathin carbon layer coating structure, preparation method thereof and wave-absorbing and heat-guiding sheet

Abstract

The invention provides a wave-absorbing and heat-conducting integrated material with an ultrathin carbon layer coating structure, preparation of the wave-absorbing and heat-conducting integrated material and a wave-absorbing and heat-conducting piece. A preparation method comprises the steps that heat-conducting substrate filler is transferred into a quartz tube vertically arranged in a gas-solid fluidized bed, and after the gas-solid fluidized bed is assembled, the air tightness is checked; after the air tightness meets the requirement, inert gas is introduced into the quartz tube, so that the heat-conducting substrate filler is in a fluidized state; heating the heat-conducting substrate filler to 400-600 DEG C, and keeping the temperature for 1-30 minutes; and starting a plasma generator, introducing a carbon source gas into the quartz tube at a flow rate of 0.1-1L / min after the plasma is stable, depositing an active carbon component generated by cracking of the carbon source gas on the surface of the heat-conducting substrate filler through a vapor deposition reaction under the action of the plasma, and continuing the vapor deposition reaction for 1-15 minutes to obtain the material. The material obtained by the invention has good heat-conducting property while effectively realizing electromagnetic wave absorption.

Description

Technical Field

[0001] This invention relates to an integrated microwave absorbing and thermally conductive material with an ultra-thin carbon layer coating structure, its preparation, and a microwave absorbing and thermally conductive sheet, belonging to the field of materials technology, particularly the field of carbon-based composite integrated microwave absorbing and thermally conductive materials. Background Technology

[0002] With the rapid development of 5G and radar communication technologies, the demand for highly intelligent electronic devices has greatly increased. Electronic devices are becoming increasingly miniaturized, integrated, and high-powered, creating increasingly complex electromagnetic environments. However, within the limited space of electronic devices, it is difficult to combine thermal pads and microwave absorbing materials. Electronic devices generate significant amounts of residual heat during operation, which cannot be effectively removed by a single microwave absorbing material. This leads to increased device temperature, resulting in decreased performance or even damage. Therefore, developing novel integrated microwave absorbing and thermally conductive materials is urgently needed to simultaneously address electromagnetic interference and heat dissipation issues.

[0003] Currently, most microwave-absorbing and thermally conductive materials on the market are simple mixtures of single-function fillers, essentially where the microwave-absorbing filler and the thermally conductive filler function separately. For such products to simultaneously possess high thermal conductivity and microwave absorption capabilities, both fillers need to be kept at high filler levels. However, there is an upper limit to the amount of powder filler in polymers; excessive filler leads to a significant decrease in the material's mechanical properties. Therefore, the two fillers are mutually restrictive and inversely related, making it difficult for such mixed materials to simultaneously possess high thermal conductivity and strong microwave absorption properties. There is an urgent need to develop dual-function integrated materials with both microwave absorption and thermal conductivity properties to fundamentally solve the problems of limited functional powder filler addition and poor performance.

[0004] Dielectric loss carbon materials have attracted widespread attention due to their advantages such as low density, good electrical properties and corrosion resistance. However, their thermal conductivity and microwave absorption properties are difficult to reconcile effectively, which involves the problem of impedance matching during microwave absorption.

[0005] Therefore, researching, developing, and providing a novel integrated microwave absorption and thermal conductivity material with an ultrathin carbon layer coating structure to achieve both microwave absorption and thermal conductivity has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the aforementioned shortcomings and deficiencies, the present invention aims to provide an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure, its preparation, and a microwave absorbing and thermally conductive sheet. By precisely constructing a dense, ultrathin carbon layer coating structure on the surface of a thermally conductive substrate filler, the present invention enables the resulting composite material to effectively absorb electromagnetic waves while possessing excellent thermal conductivity.

[0007] To achieve the above objectives, on the one hand, the present invention provides a method for preparing an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure, wherein the preparation method includes:

[0008] Step (1): Transfer the thermally conductive substrate packing to a vertically arranged quartz tube in the gas-solid fluidized bed. After assembling the gas-solid fluidized bed, check the air tightness. If the air tightness meets the requirements, introduce inert gas into the quartz tube to make the thermally conductive substrate packing fluidized.

[0009] Step (2): Heat the thermally conductive substrate filler to 400-600℃ and maintain this temperature for 1-30 minutes;

[0010] Step (3): Turn on the plasma generator and, after the plasma stabilizes, introduce carbon source gas into the quartz tube at a flow rate of 0.1-1 L / min. Under the action of the plasma, the active carbon component generated by the decomposition of the carbon source gas is deposited on the surface of the thermally conductive substrate filler through a vapor deposition reaction. After the vapor deposition reaction lasts for 1-15 minutes, an integrated microwave absorbing and thermally conductive material with an ultra-thin carbon layer coating structure is obtained.

[0011] In step (1) of the preparation method described above, the quartz tube in the gas-solid fluidized bed is vertically arranged, which allows the thermally conductive substrate filler to form a fluidized state under the action of airflow, thereby improving the coverage of the integrated microwave absorbing and thermally conductive material.

[0012] As a specific embodiment of the preparation method described above in this invention, the thermally conductive substrate filler includes one or a combination of several thermally conductive materials such as boron nitride, alumina, and magnesium oxide, which have high temperature resistance, corrosion resistance, and low thermal expansion coefficient at low temperatures.

[0013] In one specific embodiment of the preparation method described above in this invention, the bed height of the thermally conductive substrate filler in the quartz tube is 5-40 cm.

[0014] In one specific embodiment of the preparation method described above in this invention, the inert gas includes argon and / or nitrogen, etc.

[0015] In one specific embodiment of the preparation method described above in this invention, the flow rate of the inert gas is 1-8 L / min.

[0016] In one specific embodiment of the preparation method described above in this invention, the thermally conductive substrate filler is heated to 400-600°C at a heating rate of 5-15°C / min.

[0017] In one specific embodiment of the preparation method described above in this invention, the carbon source gas includes one or a combination of several of methane, ethylene, acetylene, and propylene.

[0018] This invention does not impose specific requirements on the plasma generator and its parameters used in the above-described preparation methods; they can be selected as needed, as long as they can generate a stable plasma atmosphere. For example, in some embodiments of this invention, a 300W high-voltage radio frequency power supply can be used to generate the plasma atmosphere in the plasma generator.

[0019] On the other hand, the present invention also provides a microwave absorbing and thermally conductive integrated material with an ultrathin carbon layer coating structure, which is prepared by the above-described method for preparing a microwave absorbing and thermally conductive integrated material with an ultrathin carbon layer coating structure. It has a core-shell structure, including a thermally conductive substrate filler and an ultrathin carbon layer coating structure covering the surface of the thermally conductive substrate filler.

[0020] In one specific embodiment of the material described above in this invention, the thickness of the ultrathin carbon layer coating structure is 2-12 nm.

[0021] In another aspect, the present invention also provides a wave-absorbing heat-conducting sheet, which comprises the wave-absorbing heat-conducting integrated material with an ultra-thin carbon layer coating structure as described above.

[0022] This invention uses carbon-containing gas as the carbon source gas and a thermally conductive substrate filler as the matrix to prepare an integrated microwave absorbing and thermally conductive composite material with an ultrathin carbon layer coating structure via plasma-enhanced chemical vapor deposition (PECVD) in a gas-solid fluidized bed. The preparation method has the following advantages:

[0023] First, the preparation method provided by this invention can achieve dense and uniform ultrathin coating on any thermally conductive substrate filler and enable mass production. Micro- and nano-sized thermally conductive powder materials, i.e., thermally conductive substrate fillers, are prone to agglomeration, making it difficult for the carbon source gas to fully contact the surface of each particle. However, gas-solid fluidized bed technology, by suspending the powder material in the gas flow, allows the reactant gas to uniformly contact the surface of the powder material, fundamentally improving the problem of agglomeration of thermally conductive powder materials and achieving a dense and uniform growth of an ultrathin carbon layer coating structure on the surface of the thermally conductive substrate filler.

[0024] Secondly, in order to reduce the energy consumption of the carbon source gas cracking reaction and reduce the impact of high temperature on the thermally conductive substrate, the preparation method adopts plasma-enhanced chemical vapor deposition and sets a plasma generator at the front end of the gas-solid fluidized bed reaction tube, i.e., the quartz tube. Under relatively low temperature conditions (400-600℃), the controllable coating of ultrathin carbon layers is achieved. The carbon layer obtained under this temperature condition plays a key role in the subsequent absorption of electromagnetic waves. Its adjustable defect structure and conductivity can enhance the polarization loss of electromagnetic waves and also improve the thermal conductivity of the material to a certain extent.

[0025] Third, the preparation method provided by this invention can simultaneously achieve high thermal conductivity and strong microwave absorption performance in a single material. The ultrathin carbon-coated heterostructure obtained by this method, i.e., the integrated microwave absorption and thermal conductivity material with an ultrathin carbon-coated structure, effectively constructs a heat conduction pathway, promotes efficient heat transfer, and induces interfacial polarization relaxation, further improving the material's electromagnetic wave absorption performance. Furthermore, the ultrathin carbon-coated structure constructed on the surface of the thermally conductive substrate filler by this method causes minimal change to the volume of the thermally conductive substrate filler, enabling the resulting material to possess high dual-functionality of thermal conductivity and microwave absorption even with low filler content, solving the technical challenge of conventional microwave absorption and thermal conductivity requiring two different functional fillers. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The microwave absorption performance curve of the BN@C integrated microwave absorbing and thermally conductive material provided in Embodiment 1 of the present invention is shown.

[0028] Figure 2 The image shows the microwave absorption performance curve of the BN@C integrated microwave absorbing and thermally conductive material provided in Embodiment 2 of the present invention.

[0029] Figure 3 The image shows the microwave absorption performance curve of the BN@C integrated microwave absorbing and thermally conductive material provided in Embodiment 3 of the present invention.

[0030] Figure 4 The image shows the microwave absorption performance curve of the BN@C integrated microwave absorbing and thermally conductive material provided in Embodiment 4 of the present invention.

[0031] Figure 5 The microwave absorption performance curve of the BN@C integrated microwave absorbing and thermally conductive material provided in Embodiment 5 of the present invention is shown.

[0032] Figure 6 The microwave absorption performance curve of the BN@C integrated microwave absorbing and thermally conductive material provided in Embodiment 6 of the present invention is shown.

[0033] Figure 7 The image shows the microwave absorption performance curve of the Al2O3@C integrated microwave absorbing and thermally conductive material provided in Embodiment 7 of the present invention.

[0034] Figure 8 The image shows the microwave absorption performance curve of the sample obtained in Comparative Example 1.

[0035] Figure 9The image shows the microwave absorption performance curve of the sample obtained in Comparative Example 2.

[0036] Figure 10 The image shows the microwave absorption performance curve of the sample obtained in Comparative Example 3.

[0037] Figure 11 The image shows the microwave absorption performance curve of the sample obtained in Comparative Example 4.

[0038] Figure 12 This is a TEM image of the BN@C integrated wave-absorbing and heat-conducting material provided in Embodiment 2 of the present invention.

[0039] Figure 13 This is a TEM image of the sample obtained in Comparative Example 4. Detailed Implementation

[0040] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0041] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0042] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0043] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0044] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0045] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0047] Example 1

[0048] This embodiment provides an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated boron nitride (BN@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0049] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0050] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0051] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by the cracking of ethylene is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction. Continue fluidization to make the vapor deposition reaction for 10min.

[0052] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the BN@C wave-absorbing and heat-conducting integrated material.

[0053] Example 2

[0054] This embodiment provides an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated boron nitride (BN@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0055] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0056] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0057] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by the cracking of ethylene is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction. Continue fluidization to make the vapor deposition reaction for 3 minutes.

[0058] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the BN@C wave-absorbing and heat-conducting integrated material.

[0059] Example 3

[0060] This embodiment provides an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated boron nitride (BN@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0061] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0062] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0063] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of plasma, the active carbon component generated by ethylene cracking is deposited on the surface of the boron nitride powder sample through vapor deposition reaction. Continue fluidization to allow the vapor deposition reaction to proceed for 5 minutes.

[0064] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the BN@C wave-absorbing and heat-conducting integrated material.

[0065] Example 4

[0066] This embodiment provides an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated boron nitride (BN@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0067] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0068] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 600℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0069] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by the cracking of ethylene is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction. Continue fluidization to make the vapor deposition reaction for 10min.

[0070] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the BN@C wave-absorbing and heat-conducting integrated material.

[0071] Example 5

[0072] This embodiment provides an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated boron nitride (BN@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0073] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0074] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 400℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0075] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by the cracking of ethylene is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction. Continue fluidization to make the vapor deposition reaction for 10min.

[0076] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the BN@C wave-absorbing and heat-conducting integrated material.

[0077] Example 6

[0078] This embodiment provides an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated boron nitride (BN@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0079] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0080] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0081] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the propylene control valve and flow meter valve and introduce propylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by propylene cracking is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction. Continue fluidization to make the vapor deposition reaction for 10min.

[0082] Step (4): After the reaction stops, close the propylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the BN@C wave-absorbing and heat-conducting integrated material.

[0083] Example 7

[0084] This embodiment provides a microwave absorbing and thermally conductive integrated material with an ultrathin carbon layer coating structure. It is an ultrathin carbon layer-coated alumina (Al2O3@C) composite material, prepared in a gas-solid fluidized bed using plasma-enhanced chemical vapor deposition. The preparation process includes the following specific steps:

[0085] Step (1): Weigh a certain mass of alumina powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the alumina powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, argon inert gas protective gas (4L / min) is introduced into the quartz tube, and the alumina powder sample is in a fluidized state.

[0086] Step (2): Set the heating furnace temperature program system, and heat the alumina powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0087] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of plasma, the active carbon component generated by ethylene cracking is deposited on the surface of the alumina powder sample through vapor deposition reaction. Continue fluidization to allow the vapor deposition reaction to proceed for 10min.

[0088] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally. Then take out the black and fluffy sample, which is the Al2O3@C wave-absorbing and heat-conducting integrated material.

[0089] Comparative Example 1

[0090] This comparative example aims to prepare an ultrathin carbon-coated boron nitride (BN@C) composite material using plasma-enhanced chemical vapor deposition in a gas-solid fluidized bed. The preparation process includes the following specific steps:

[0091] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0092] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 350℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0093] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve to introduce ethylene into the quartz tube as a carbon source (0.4L / min). Continue fluidization to allow the gas phase deposition reaction to proceed for 10min.

[0094] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally before taking out the sample.

[0095] The difference between Comparative Example 1 and Example 1 is that the temperature in step (2) is 350°C, that is, the temperature of the vapor deposition reaction is 350°C.

[0096] Comparative Example 2

[0097] This comparative example aims to prepare an ultrathin carbon-coated boron nitride (BN@C) composite material using chemical vapor deposition in a gas-solid fluidized bed. The preparation process includes the following specific steps:

[0098] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state.

[0099] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0100] Step (3): Then open the ethylene control valve and flow meter valve, and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Continue fluidization to allow the gas phase deposition reaction to proceed for 10min.

[0101] Step (4): After the reaction stops, close the ethylene control valve and flow meter valve, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally before taking out the sample.

[0102] The difference between Comparative Example 2 and Example 1 is that plasma enhancement is not used in the chemical vapor deposition process.

[0103] Comparative Example 3

[0104] This comparative example aims to prepare an ultrathin carbon-coated boron nitride (BN@C) composite material using plasma-enhanced chemical vapor deposition in a horizontal tube furnace. The preparation process includes the following specific steps:

[0105] Step (1): Weigh a certain mass of boron nitride powder sample and place it in a ceramic boat. Transfer it to the quartz tube of a horizontal tube furnace. The upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes. After assembling the horizontal tube furnace, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube.

[0106] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0107] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve, and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by the cracking of ethylene is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction, and the vapor deposition reaction is carried out for 10min.

[0108] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally before taking out the sample.

[0109] The difference between Comparative Example 3 and Example 1 is that the equipment used in the chemical vapor deposition process is a horizontal tube furnace, rather than a gas-solid fluidized bed.

[0110] Comparative Example 4

[0111] This comparative example aims to prepare an ultrathin carbon-coated boron nitride (BN@C) composite material using plasma-enhanced chemical vapor deposition in a gas-solid fluidized bed. The preparation process includes the following specific steps:

[0112] Step (1): Weigh a certain mass of boron nitride powder sample and transfer it to a vertically arranged quartz tube in the gas-solid fluidized bed, so that the bed height of the boron nitride powder sample in the quartz tube is 10cm, and the upper and lower ends of the quartz tube are equipped with wound high-voltage electrodes and ground electrodes; after assembling the gas-solid fluidized bed, check the air tightness. After the air tightness meets the requirements, introduce argon inert gas protective gas (4L / min) into the quartz tube and put the boron nitride powder sample into a fluidized state;

[0113] Step (2): Set the heating furnace temperature program system, and heat the boron nitride powder sample to the preset reaction temperature of 500℃ at a heating rate of 10℃ / min through the temperature control program, and hold it at the temperature for 30min.

[0114] Step (3): Then turn on the plasma generator. After the plasma stabilizes, open the ethylene control valve and flow meter valve, and introduce ethylene into the quartz tube as a carbon source (0.4L / min). Under the action of the plasma, the active carbon component generated by the cracking of ethylene is deposited on the surface of the boron nitride powder sample through the vapor deposition reaction, and the vapor deposition reaction is carried out for 30 minutes.

[0115] Step (4): After the reaction stops, close the ethylene control valve, flow meter valve and plasma generator, turn off the temperature control program of the heating furnace, and wait for the quartz tube in the gas-solid fluidized bed to cool down to room temperature naturally before taking out the sample.

[0116] The difference between Comparative Example 4 and Example 1 is that the vapor deposition reaction time in step (3) is extended to 30 min.

[0117] Performance test examples

[0118] This performance test example conducts electromagnetic wave absorption performance tests and vertical thermal conductivity tests on the black, fluffy samples obtained in Examples 1-7 of this invention and the samples obtained in Comparative Examples 1-4:

[0119] The electromagnetic wave absorption performance test was conducted using the coaxial method, which included the following specific steps:

[0120] Step 1) Sample Preparation: Weigh a certain amount of epoxy resin and fatty amine curing agent, ensuring a mass ratio of 1:1. Add a certain proportion of the sample powder obtained in Examples 1-7 and Comparative Examples 1-4 of this invention, and stir thoroughly to achieve uniform mixing, obtaining a mixture. Place the mixture into a coaxial ring mold, pre-casting it into concentric rings with an inner diameter of 3.04 mm, an outer diameter of 7.0 mm, and a thickness of 2.0 mm. Place the coaxial ring mold containing the mixture sample into a 70℃ oven for curing for 2 hours, then demold. This yields uniform concentric rings of epoxy resin / sample mixture with different filler contents (as shown in Table 1 below), ready for testing. Multiple concentric rings can be obtained from the same sample, reducing experimental error in multiple measurements.

[0121] Step 2) Testing: The instrument used for testing was a vector network analyzer (model N5232B) from DETECH (China) Co., Ltd. Calibration was performed using a calibration kit before testing. The concentric rings were tested using the coaxial method within the frequency range of 2-18 GHz to obtain the corresponding electromagnetic parameters. The absorption performance curves were then plotted after calculation using formulas.

[0122] The microwave absorption performance curves of the samples obtained in Examples 1-7 and Comparative Examples 1-4 of this invention are shown below. Figures 1-11 As shown.

[0123] From such Figure 1 As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Embodiment 1 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 35wt%, the minimum reflection loss value corresponding to multiple thicknesses is less than -20dB, the strongest reflection loss reaches -36.20dB (matching thickness is 1.69mm), and the widest effective absorption bandwidth can reach 4.00GHz, indicating that the black fluffy sample provided in Embodiment 1 of the present invention has good electromagnetic wave absorption performance.

[0124] From such Figure 2 As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Embodiment 2 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 40wt%, the minimum reflection loss value corresponding to multiple thicknesses is also lower than -20dB, the strongest reflection loss reaches -55.02dB (matching thickness is 1.78mm), and the widest effective absorption bandwidth can reach 4.40GHz, indicating that the black fluffy sample provided in Embodiment 2 of the present invention also has good electromagnetic wave absorption performance.

[0125] From such Figure 3 As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Embodiment 3 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 40wt%, the minimum reflection loss value corresponding to multiple thicknesses is also lower than -20dB, the strongest reflection loss reaches -58.33dB (matching thickness is 3.55mm), and the widest effective absorption bandwidth can reach 5.28GHz, indicating that the black fluffy sample provided in Embodiment 3 of the present invention also has good electromagnetic wave absorption performance.

[0126] From such Figure 4 As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Example 4 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 35wt%, the minimum reflection loss value corresponding to multiple thicknesses is also lower than -20dB, the strongest reflection loss reaches -29.19dB (matching thickness is 4.97mm), and the widest effective absorption bandwidth can reach 4.64GHz, indicating that the black fluffy sample provided in Example 4 of the present invention also has good electromagnetic wave absorption performance.

[0127] From such Figure 5As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Embodiment 5 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 40wt%, the minimum reflection loss value corresponding to multiple thicknesses is also lower than -20dB, the strongest reflection loss reaches -44.49dB (matching thickness is 1.72mm), and the widest effective absorption bandwidth can reach 4.2GHz, indicating that the black fluffy sample provided in Embodiment 5 of the present invention also has good electromagnetic wave absorption performance.

[0128] From such Figure 6 As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Embodiment 6 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 40wt%, the minimum reflection loss value corresponding to multiple thicknesses is also lower than -20dB, the strongest reflection loss reaches -66.24dB (matching thickness is 1.62mm), and the widest effective absorption bandwidth can reach 4.96GHz, indicating that the black fluffy sample provided in Embodiment 6 of the present invention also has good electromagnetic wave absorption performance.

[0129] From such Figure 7 As shown in the electromagnetic wave reflection loss performance curve of the black fluffy sample provided in Example 7 of the present invention, when the filling amount of the black fluffy sample in epoxy resin is 70wt%, the minimum reflection loss value corresponding to multiple thicknesses is also lower than -20dB, the strongest reflection loss reaches -42.89dB (matching thickness is 2.37mm), and the widest effective absorption bandwidth can reach 4.96GHz, indicating that the black fluffy sample provided in Example 7 of the present invention also has good electromagnetic wave absorption performance.

[0130] From such Figure 8 As shown in the electromagnetic wave reflection loss performance curve of the sample provided in Comparative Example 1, when the epoxy resin filling amount of the sample provided in Comparative Example 1 is 40wt%, the minimum reflection loss values ​​corresponding to multiple thicknesses are all higher than -10dB, indicating that the sample finally prepared in Comparative Example 1 does not have electromagnetic wave absorption performance. This is because under the condition of 350℃, ethylene is difficult to decompose, carbon coating fails, and boron nitride itself does not have wave absorption performance, thus the sample finally prepared in Comparative Example 1 does not have electromagnetic wave absorption performance.

[0131] From such Figure 9As shown in the electromagnetic wave reflection loss performance curve of the sample provided in Comparative Example 2, when the filling amount in epoxy resin of the sample provided in Comparative Example 2 is 40wt%, the minimum reflection loss values ​​corresponding to multiple thicknesses are all higher than -10dB, indicating that the sample finally prepared in Comparative Example 2 also does not have electromagnetic wave absorption performance. This is because Comparative Example 2 does not use plasma enhancement in the chemical vapor deposition process, and the pyrolysis deposition of ethylene introduced in step (3) at a temperature of 500℃ does not meet the reaction requirements, resulting in very little carbon deposited on the surface of boron nitride, failing to form a conductive path, thus making it difficult for the final sample to have wave absorption performance.

[0132] From such Figure 10 As shown in the electromagnetic wave reflection loss performance curve of the sample provided in Comparative Example 3, when the epoxy resin filling amount of the sample provided in Comparative Example 3 is 35wt%, the minimum reflection loss values ​​corresponding to multiple thicknesses are all higher than -20dB. Compared with the sample prepared under the same fluidized bed conditions in the embodiment, and with the same filling amount of 35wt%, the absorption performance is significantly reduced, indicating that the sample provided in Comparative Example 3 does not have good electromagnetic wave absorption performance. This is because the equipment used in the chemical vapor deposition process of Comparative Example 3 is a horizontal tube furnace, not a gas-solid fluidized bed. Since boron nitride micro-nano particles are prone to agglomeration, and the gaseous precursor, ethylene, is difficult to penetrate into the powder and fully contact the surface of each particle, it is difficult to achieve uniform and dense batch coating of the powder material. As a result, ethylene only reacts with the boron nitride on the upper surface and is difficult to penetrate into the interior of the boron nitride. Therefore, carbon can only be deposited in a thin layer on the surface of the entire powder. This also illustrates that the strong gas-solid mixing characteristics and uniform temperature and concentration fields in the gas-solid fluidized bed reactor are the key to achieving high consistency in the performance of the microwave absorbing and heat-conducting products.

[0133] From such Figure 11As shown in the electromagnetic wave reflection loss performance curve of the sample provided in Comparative Example 4, when the filling amount of the sample in Comparative Example 4 in epoxy resin is 35wt%, the minimum reflection loss value corresponding to multiple thicknesses is higher than -10dB. Compared with the sample prepared under the same fluidized bed conditions in the embodiment and the filling amount of the sample is also 35wt%, the wave absorption performance is significantly reduced, indicating that the sample provided in Comparative Example 4 also does not have good electromagnetic wave absorption performance. This is because the vapor deposition reaction time in step (3) of Comparative Example 4 is further extended to 30 min, resulting in an excessively thick carbon layer coating the surface of boron nitride (transmission electron microscopy shows that its thickness reaches 20 nm). Since the carbon layer has high conductivity, an excessively thick carbon layer will cause a mismatch between the surface impedance of the material and the free space. Electromagnetic waves are reflected on the surface instead of being absorbed inside the material. Furthermore, the difference in crystal structure between the carbon layer and boron nitride will introduce interface defects and lattice mismatch. An excessively thick carbon layer increases the number of interfaces, exacerbates phonon scattering, and hinders heat conduction. Even if the carbon layer itself has good thermal conductivity, when it is too thick, the contact thermal resistance between it and boron nitride will accumulate, especially when the interface bonding is not ideal.

[0134] The vertical thermal conductivity test includes the following specific steps:

[0135] (1) Sample preparation: Weigh a certain amount of epoxy resin and fatty amine curing agent, ensuring a mass ratio of 1:1 between the epoxy resin and the fatty amine curing agent. Add a certain proportion of the sample powder obtained in Examples 1-7 and Comparative Examples 1-4 of this invention, and stir thoroughly to ensure uniform mixing, thus obtaining a mixture. Pour the mixture into a 4cm×4cm mold to pre-cast a square thermal conductivity test piece. Place the mold containing the sample into a 70℃ oven for curing for 2 hours, then demold to obtain uniform epoxy resin / sample mixture square pieces with different filler contents for testing. Multiple square thermal conductivity test pieces can be obtained from the same sample, reducing experimental errors in multiple measurements.

[0136] (2) Testing: The instrument used for testing was the interface material thermal resistance and thermal conductivity meter (model LW-9389) from Ruiling Technology Co., Ltd. The instrument should be preheated for 30 minutes before testing. The thickness of the thermally conductive test piece was measured using a micrometer and entered into the program. After 40 minutes of running the test program, the thermal conductivity of the sample was output.

[0137] The optimal vertical thermal conductivity of the sample powders obtained in Examples 1-7 and Comparative Examples 1-4 of this invention, as well as the corresponding filling amount of the sample powders in epoxy resin, are shown in Table 1 below.

[0138] Table 1

[0139]

[0140]

[0141] As can be seen from Table 1 above, the sample powders obtained in Examples 1-7 of this invention all exhibit excellent thermal conductivity. Combining the electromagnetic wave absorption performance test results and the vertical thermal conductivity test results, it can be concluded that the sample powders obtained in the embodiments of this invention all possess excellent thermal conductivity and wave absorption performance. Therefore, the final products obtained in the embodiments of this invention are all integrated wave-absorbing and thermally conductive composite materials.

[0142] This performance test example also involved transmission electron microscopy (TEM) analysis of the sample powders obtained in Example 2 and Comparative Example 4 of the present invention, respectively. The obtained TEM images are shown below. Figure 12 and Figure 13 As shown. Figure 12 As shown, transmission electron microscopy revealed the successful construction of a core-shell heterogeneous interface by observing multilayer carbon deposition on the boron nitride surface. Due to the controlled short reaction time of 3 minutes, only a 3 nm ultrathin carbon layer grew on the boron nitride surface. Figure 13 As shown, transmission electron microscopy revealed that multiple carbon layers were deposited on the surface of boron nitride. Due to the controlled reaction time of 30 min, a relatively thick carbon layer of 20 nm grew on the surface of boron nitride.

[0143] In addition, the carbon layer thickness in the sample powders obtained in Examples 1-7 and Comparative Example 4 of the present invention, as well as the vapor deposition reaction time used in Examples 1-7 and Comparative Example 4, are listed in Table 2 below.

[0144] Table 2

[0145] project Vapor deposition reaction time / min Carbon layer thickness / nm Example 1 10 8 Example 2 3 3 Example 3 5 5 Example 4 10 10 Example 5 10 6 Example 6 10 10 Example 7 10 6 Comparative Example 4 30 20

[0146] As can be seen from Table 2 above, the carbon layer thickness in the sample powders obtained in Examples 1-7 of this invention is all within the range of 2-12 nm, which meets the requirements.

[0147] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A method for preparing an integrated microwave absorbing and thermally conductive material with an ultrathin carbon layer coating structure, wherein, The preparation method includes: Step (1): Transfer the thermally conductive substrate packing to a vertically arranged quartz tube in the gas-solid fluidized bed. After assembling the gas-solid fluidized bed, check the air tightness. If the air tightness meets the requirements, introduce inert gas into the quartz tube to make the thermally conductive substrate packing fluidized. Step (2): Heat the thermally conductive substrate filler to 400-600℃ and maintain this temperature for 1-30 minutes; Step (3): Turn on the plasma generator and, after the plasma stabilizes, introduce carbon source gas into the quartz tube at a flow rate of 0.1-1 L / min. Under the action of the plasma, the active carbon component generated by the decomposition of the carbon source gas is deposited on the surface of the thermally conductive substrate filler through a vapor deposition reaction. After the vapor deposition reaction lasts for 1-15 minutes, an integrated microwave absorbing and thermally conductive material with an ultra-thin carbon layer coating structure is obtained.

2. The preparation method according to claim 1, wherein, The thermally conductive substrate filler includes one or a combination of boron nitride, aluminum oxide, and magnesium oxide.

3. The preparation method according to claim 1 or 2, wherein, The bed height of the thermally conductive substrate filler in the quartz tube is 5-40cm.

4. The preparation method according to claim 1, wherein, The inert gas includes argon and / or nitrogen.

5. The preparation method according to claim 1 or 4, wherein, The flow rate of the inert gas is 1-8 L / min.

6. The preparation method according to claim 1, wherein, The thermally conductive substrate filler is heated to 400-600℃ at a heating rate of 5-15℃ / min.

7. The preparation method according to claim 1, wherein, The carbon source gas includes one or a combination of several of methane, ethylene, acetylene, and propylene.

8. A microwave absorbing and thermally conductive integrated material with an ultrathin carbon layer coating structure, prepared by the preparation method of the microwave absorbing and thermally conductive integrated material with an ultrathin carbon layer coating structure according to any one of claims 1-7, wherein it has a core-shell structure, including a thermally conductive substrate filler and an ultrathin carbon layer coating structure coating the surface of the thermally conductive substrate filler.

9. The material according to claim 8, wherein, The thickness of the ultrathin carbon layer coating structure is 2-12 nm.

10. A wave-absorbing heat-conducting sheet comprising the integrated wave-absorbing heat-conducting material with an ultra-thin carbon layer coating structure as described in claim 8 or 9.

Images