Powder modification device and modification method

Abstract

The powder modification device and the modification method provided by the application are characterized in that powder particles enter the cavity through a feeding port and are in a flowing state in the cavity under the action of a gas jet; a modifier is sprayed on the surface of the powder particles in the flowing state through a modifier jet; the inner layer graphite is heated to a target temperature at a temperature rising rate of 90-110 DEG C / s under the condition of Joule heat triggered by an external current, and heat is transferred to the alumina; the alumina is rapidly heated to the target temperature, and the powder particles sprayed with the modifier are obtained by multiple transient collision and contact with the high-temperature alumina to obtain surface modification. The powder modification device and the modification method have a short process time, greatly improve the modification production efficiency, and improve the modification uniformity and surface modification effect of the silicon dioxide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder engineering, in particular to a powder modification device and a modification method. BACKGROUND

[0002] With the development of electronic devices towards miniaturization, electronic packaging technology has gradually transitioned from one-dimensional packaging to three-dimensional packaging, the distance between the chip and the substrate becomes smaller and smaller, and silica powder has been widely concerned in this field due to its low thermal expansion coefficient, good thermal stability and chemical stability, and plays an important role in electronic packaging materials such as underfill adhesive, epoxy molding compound and insulating adhesive film. However, silica powder without any surface modification has a large specific surface area and surface free energy, and is usually difficult to disperse uniformly in the resin matrix, and is prone to agglomeration, thereby affecting the bonding performance between the powder and the resin matrix and damaging the thermal mechanical properties of the material. Therefore, it is necessary to modify or graft silane coupling agent on the surface of nano-silica to reduce the cohesion between silica powders, thereby solving the problems of poor dispersibility, high viscosity and poor thermal mechanical properties of the powder in the application of underfill adhesive.

[0003] The current surface modification method of silica powder mainly includes alcohol lipid modification method, polymer grafting method and silane coupling agent method, etc., and the main purpose is to reduce the silicon hydroxyl groups on the surface of silica, so as to form an organic matrix-silane coupling agent-inorganic matrix combination layer on the surface and improve the application performance in underfill adhesive. However, the existing surface modification technology usually obtains a high temperature environment by oil bath or electric heating, and then reacts silica with modifiers in a high temperature environment by wet or dry method for modification treatment. Since the traditional heating method has a slow heating rate and a long modification time, the modification production efficiency of the powder is greatly reduced, which is not conducive to reducing the processing cost. In addition, the reaction rate of the traditional heating modification method is slow, which is prone to problems such as silica agglomeration and mutual condensation of modifiers during the modification process, not only causing uneven surface modification of silica, but also causing problems such as large amount of modifier and low controllability of experiments. SUMMARY

[0004] Therefore, it is necessary to provide a powder modification device and a modification method with high modification production efficiency, good modification uniformity and good surface modification effect in view of the defects in the prior art.

[0005] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0006] One of the purposes of the present application is to provide a powder modification device, comprising: a metal shell forming a cavity, a modifier spray head arranged on the metal shell, a gas spray head arranged on the metal shell, a discharge port arranged on the metal shell, a joule heat heating assembly arranged on the inner wall of the metal shell, the joule heat heating assembly comprising an inner layer of graphite and aluminum oxide covering the inner layer of graphite, the inner layer of graphite being triggered to joule heat condition under external current to rise to a target temperature at a temperature rise rate of 100℃ / s, and transferring heat to the aluminum oxide to achieve pulse instantaneous temperature rise and cooling treatment.

[0007] In some embodiments, the gas spray head is at least one, and the powder particles flow in a clockwise direction in the cavity under the action of the gas spray head.

[0008] In some embodiments, the modifier is added to the cavity in a mist spraying manner through the modifier spray head.

[0009] In some embodiments, the inner layer of graphite is several and is uniformly spaced on the inner wall of the metal shell.

[0010] In some embodiments, an insulating layer is further arranged between adjacent inner layers of graphite.

[0011] The second purpose of the present application is to provide a modification method of the powder modification device, comprising the following steps:

[0012] The powder particles enter the cavity through the feed port;

[0013] The modifier is sprayed on the surface of the powder particles in a flowing state through the modifier spray head;

[0014] The inner layer of graphite is triggered to joule heat condition under external current to rise to a target temperature at a temperature rise rate of 100℃ / s, and transfers heat to the aluminum oxide;

[0015] The aluminum oxide is rapidly heated to a target temperature, and the powder particles sprayed with the modifier are obtained by multiple instantaneous collision and contact with the high-temperature aluminum oxide to obtain surface modification;

[0016] The modified powder particles are transferred through the discharge port.

[0017] In some embodiments, before the powder particles enter the cavity through the gas spray head, the following steps are further included:

[0018] The powder particles are preheated under vacuum conditions at 180-200℃.

[0019] In some embodiments, the powder particles include silica powder.

[0020] In some embodiments, in the step of spraying the modifier through the modifier spray head on the surface of the powder particles in a flowing state, the modifier comprises one or a mixture of several of vinyltrimethoxysilane, vinyltriethoxysilane, trimethoxy({[4-(epoxy-2-yl)phenyl]methyl})silane, triethoxy({[4-(oxirane-2-yl)phenyl]methyl})silane, trimethoxy({4-[2-(oxirane-2-yl)ethyl]phenyl}methyl)silane, trimethoxy({4-[(epoxy-2-oxyl)methyl]phenyl}methyl)silane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxytriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane.

[0021] In some embodiments, in the step of spraying the modifier through the modifier spray head on the surface of the powder particles in a flowing state, the weight percentage of the modifier to the powder particles is 0.1-5%.

[0022] In some embodiments, in the step of raising the temperature of the inner layer of graphite to a target temperature at a rate of 100℃ / s under the condition of external current triggered Joule heat, and transferring heat to the alumina, the specific process is: opening the heating switch, using electrically triggered Joule heat pulse type temperature rising and cooling processing, the target temperature is 800-1200℃, the pulse interval is 8-12s, that is, one cycle is 8-12s of temperature rising and 8-12s of temperature falling, and the process is repeated for 5-8 times.

[0023] The application adopts the above technical solutions, and has the following beneficial effects:

[0024] The powder modification device and modification method provided by the application are characterized in that: the powder particles enter the cavity through the feeding port; the modifier is sprayed on the surface of the powder particles in a flowing state through the modifier spray head; the inner layer of graphite is raised to a target temperature at a rate of 100℃ / s under the condition of external current triggered Joule heat, and heat is transferred to the alumina; the alumina is rapidly raised to the target temperature, and the powder particles sprayed with the modifier are obtained by multiple instantaneous collision and contact with the high-temperature alumina for surface modification. The above powder modification device and modification method have a shorter process time, greatly improve the modification production efficiency, and improve the modification uniformity and surface modification effect of the silicon dioxide. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application or the prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0026] Figure 1 The structural schematic diagram of the powder modification device provided by the embodiments of the present application.

[0027] Figure 2 The step flow chart of the powder modification method provided by the embodiments of the present application. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0029] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0030] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0031] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and embodiments.

[0032] Please refer to Figure 1A structural schematic diagram of a powder modification device provided by an embodiment of the present application comprises: a metal shell 4 forming a cavity, a modifier spray head 1 arranged on the metal shell 4, a gas spray head 3 arranged on the metal shell 4, a discharge port 2 arranged on the metal shell 4, a Joule heat heating assembly arranged on the inner wall of the metal shell 4, the Joule heat heating assembly comprising an inner layer of graphite 6 and an aluminum oxide 7 covering the inner layer of graphite 6. The implementation of each component is described in detail below.

[0033] In the present embodiment, the gas spray head 3 is at least one, and the powder particles flow in a clockwise direction in the cavity under the action of the gas spray head 3.

[0034] In the present embodiment, the modifier is added to the cavity in a spraying manner through the modifier spray head 1.

[0035] In the present embodiment, the inner layer of graphite 6 is several and is arranged uniformly and at intervals on the inner wall of the metal shell 4.

[0036] In the present embodiment, an insulating layer 5 is further arranged between adjacent inner layers of graphite 6.

[0037] It can be understood that the arrangement of the insulating layer 5 provides assembly space for accessories such as the gas spray head on the one hand, avoiding the direct assembly of the accessories on the graphite layer and adversely affecting the heating performance thereof; on the other hand, the insulating layer uniformly provides multiple heating assemblies, improving the heating efficiency and stability.

[0038] The modification device provided by the above embodiment of the present application has the following working mode:

[0039] The inner layer of graphite 6 can be raised to a target temperature at a temperature rise rate of 100 degrees Celsius per second under the condition of an external current triggering Joule heat, and heat is transmitted to the outer layer of aluminum oxide 7, and the pulse type power supply mode can realize the pulse type instantaneous temperature rise and cooling processing capability.

[0040] In the powder modification process, the pulse interval is set to 10s, i.e. a cycle of 10s of temperature rise and 10s of temperature drop is repeated 5 times, and the modification process takes a total of 100s; in the powder modification process, the powder particles in the cavity of the device flow in a clockwise direction under the action of the gas spray head 3, and a certain amount of modifier is added to the cavity in a spraying manner through the modifier spray head 1. The outer wall of the aluminum oxide 7 in the cavity is rapidly heated to a target temperature by pulse type electric triggering Joule heat, the powder sprayed with the modifier is obtained by multiple instantaneous collision and contact with the outer wall of the high-temperature aluminum oxide 7 to obtain surface modification, and the modified powder is transferred through the discharge port 2 after the modification is completed.

[0041] The powder modification device provided by the above embodiments has a short process time, greatly improves the modification production efficiency, and improves the modification uniformity and surface modification effect of the silicon dioxide.

[0042] Please refer to Figure 2 The application further provides a modification method of the powder modification device, which comprises the following steps:

[0043] Step S110: The powder particles enter the cavity through the feeding port.

[0044] In some embodiments, before the powder particles enter the cavity through the gas nozzle, the following step is further included: preheating the powder particles under a vacuum condition at 180-200°C.

[0045] Step S120: The modifier is sprayed on the surface of the powder particles in a flowing state through the modifier nozzle.

[0046] In some embodiments, the powder particles include silicon dioxide powder.

[0047] In some embodiments, in the step of spraying the modifier on the surface of the powder particles in a flowing state through the modifier nozzle, the modifier includes one or a mixture of several of the following: vinyltrimethoxysilane, vinyltriethoxysilane, trimethoxy({[4-(epoxy-2-yl)phenyl]methyl})silane, triethoxy({[4-(oxirane-2-yl)phenyl]methyl})silane, trimethoxy({4-[2-(oxirane-2-yl)ethyl]phenyl}methyl)silane, trimethoxy({4-[(epoxy-2-oxyl)methyl]phenyl}methyl)silane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxytriethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane.

[0048] In some embodiments, in the step of spraying the modifier on the surface of the powder particles in a flowing state through the modifier nozzle, the weight percentage of the modifier to the powder particles is 0.1-5%.

[0049] Step S130: The inner layer graphite is heated to a target temperature at a heating rate of 100°C / s under a condition of Joule heat triggered by an external current, and heat is transferred to the alumina.

[0050] In some embodiments, in the step of raising the temperature of the inner layer of graphite to a target temperature at a temperature raising rate of 100℃ / s under an externally connected current triggered Joule heat condition and transferring heat to the alumina, specifically, a heating switch is opened, and a target temperature of 800-1200℃ is reached through a pulse type temperature raising and cooling process triggered by electricity, and the pulse interval is 8-12s, i.e., one cycle is 8-12s of temperature raising and 8-12s of temperature lowering, and the process is repeated for 5-8 times.

[0051] Step S140: The alumina is rapidly raised to a target temperature, and the powder particles sprayed with the modifier collide with the high-temperature alumina multiple times to obtain surface modification.

[0052] Step S150: The modified powder particles are transferred through the discharge port.

[0053] The powder modification method provided by the above embodiments has a short process time, greatly improves the modification production efficiency, and improves the modification uniformity and surface modification effect of the silica.

[0054] The above technical solutions of the present application are described in detail below in combination with specific embodiments.

[0055] Example 1 (comparative example):

[0056] 1) Under vacuum conditions at 180-200℃, 1 kg of silica powder with an average particle size of 500 nm is preheated for 3 hours;

[0057] 2) 2% by weight of γ-glycidoxypropyltrimethoxysilane is sprayed in the form of a spray on the silica powder at room temperature;

[0058] 3) The target temperature is set to 115℃, and after 60 minutes of temperature raising, high-speed stirring is performed at 600 rpm at this temperature for 60 minutes, and then the epoxy modified silica powder is obtained after cooling;

[0059] 4) 60% by weight of the epoxy modified silica powder is added to the bisphenol A epoxy resin, and is uniformly mixed and degassed under the conditions of 2000 rpm and vacuum in a mixer, and the room temperature viscosity (shear rate 50 / s) is tested by a rheometer;

[0060] 5) 60% by weight of the epoxy modified silica powder is added to the bisphenol A epoxy resin containing a curing agent, and is uniformly mixed and degassed under the conditions of 2000 rpm and vacuum in a mixer, and a cured sample is prepared by curing at 160℃ for 2 hours, and the thermal expansion coefficient is tested on a TMA, and the elastic modulus is tested on a DMA.

[0061] Example 2:

[0062] 1) 1 kg of silica powder with an average particle size of 500 nm was preheated for 3 hours under vacuum at 180-200 degrees Celsius;

[0063] 2) The silica powder was transferred to the ultrafast heating powder modification machine, the stirrer switch and the air jet switch were turned on, and the silica powder flowed in a clockwise direction in the modification equipment under the action of the air jet airflow;

[0064] 3) The target temperature was set to 1000 degrees Celsius, the pulse interval was 10 seconds, i.e. 10 seconds of heating and 10 seconds of cooling were repeated for 5 cycles, the heating switch was turned on, and electrically triggered joule heat pulse heating and cooling treatment was adopted;

[0065] 4) The weight percentage of 0.1% vinyltrimethoxysilane modifier was sprayed on the silica powder flowing in the equipment through the modifier nozzle in the form of spray for modification treatment;

[0066] 5) The silica powder mixed with the modifier completed surface modification during multiple transient contacts with the high-temperature inner wall of the equipment;

[0067] 6) 60% by weight of the epoxy-modified silica powder was added to the bisphenol A epoxy resin, mixed uniformly and degassed in a mixer at 2000 rpm / min and under vacuum conditions, and the room temperature viscosity (shear rate 50 / s) was tested by a rheometer;

[0068] 7) 60% by weight of the epoxy-modified silica powder was added to the bisphenol A epoxy resin containing a curing agent, mixed uniformly and degassed in a mixer at 2000 rpm / min and under vacuum conditions, cured at 160 degrees Celsius for 2 hours to prepare a cured sample, and the thermal expansion coefficient was tested on a TMA and the elastic modulus was tested on a DMA.

[0069] Example 3:

[0070] 1) 1 kg of silica powder with an average particle size of 500 nm was preheated for 3 hours under vacuum at 180-200 degrees Celsius;

[0071] 2) The silica powder was transferred to the ultrafast heating powder modification machine, the stirrer switch and the air jet switch were turned on, and the silica powder flowed in a clockwise direction in the modification equipment under the action of the air jet airflow;

[0072] 3) The target temperature was set to 1000 degrees Celsius, the pulse interval was 10 seconds, i.e. 10 seconds of heating and 10 seconds of cooling were repeated for 5 cycles, the heating switch was turned on, and electrically triggered joule heat pulse heating and cooling treatment was adopted;

[0073] 4) Adopting spray form, spraying 0.1% of trimethoxyl ({4-[(epoxy-2-oxyl) methyl] phenyl} methyl) silane modifier on the silica powder in the flow state in the equipment through the modifier nozzle to carry out modification treatment;

[0074] 5) The silica powder mixed with the modifier completes surface modification in the process of multiple transient contact with the high temperature inner wall of the equipment;

[0075] 6) Adding 60% of the epoxy modified silica powder by weight into the bisphenol A epoxy resin, mixing uniformly and defoaming under the condition of 2000 revolutions / minute and vacuum in the mixer, testing the room temperature viscosity (shear rate 50 / second) by the rheometer;

[0076] 7) Adding 60% of the epoxy modified silica powder by weight into the bisphenol A epoxy resin containing curing agent, mixing uniformly and defoaming under the condition of 2000 revolutions / minute and vacuum in the mixer, curing for 2 hours at 160 degrees Celsius to prepare the cured sample, testing the thermal expansion coefficient on the TMA and the elastic modulus on the DMA.

[0077] Example 4:

[0078] 1) Preheating 1 kg of silica powder with an average particle size of 500 nanometers under the condition of vacuum at 180-200 degrees Celsius for 3 hours;

[0079] 2) Transferring the silica powder into the ultrafast heating powder modification machine, opening the stirrer switch and the air nozzle switch, and making the silica powder in the clockwise flow state in the modification equipment under the action of the air nozzle airflow;

[0080] 3) Setting the target temperature to 700 degrees Celsius, the pulse interval to 10s, i.e. repeating 5 times with one cycle of heating for 10s and cooling for 10s, opening the heating switch, and adopting the electric trigger joule heat pulse type heating and cooling treatment;

[0081] 4) Adopting spray form, spraying 0.1% of vinyl trimethoxyl silane modifier on the silica powder in the flow state in the equipment through the modifier nozzle to carry out modification treatment;

[0082] 5) The silica powder mixed with the modifier completes surface modification in the process of multiple transient contact with the high temperature inner wall of the equipment;

[0083] 6) Adding 60% of the epoxy modified silica powder by weight into the bisphenol A epoxy resin, mixing uniformly and defoaming under the condition of 2000 revolutions / minute and vacuum in the mixer, testing the room temperature viscosity (shear rate 50 / second) by the rheometer;

[0084] 7) 60% by weight of the epoxy modified silica micro powder is added to the bisphenol A epoxy resin containing the curing agent, mixed uniformly and degassed under the condition of 2000 rpm of the mixer and vacuum, and a cured sample is prepared by curing at 160 degrees Celsius for 2 hours, and the thermal expansion coefficient is tested on the TMA and the elastic modulus is tested on the DMA.

[0085] Example 5:

[0086] 1) 1 kg of silica micro powder with an average particle size of 500 nm is preheated at 180-200 degrees Celsius under vacuum for 3 hours;

[0087] 2) The silica micro powder is transferred to the ultrafast heating powder modification machine, the stirrer switch and the air jet switch are turned on, and the silica micro powder flows in a clockwise state in the modification equipment under the action of the air jet airflow;

[0088] 3) The target temperature is set to 700 degrees Celsius, the pulse interval is 20 s, that is, 20 s of temperature rise and 20 s of temperature drop are repeated for one cycle, the heating switch is turned on, and the electric trigger joule heat pulse type temperature rise and cooling treatment is adopted;

[0089] 4) The 0.1% by weight of vinyl trimethoxysilane modifier is sprayed on the silica micro powder in a flow state in the equipment through the modifier nozzle in the form of spray to modify the silica micro powder;

[0090] 5) The silica powder mixed with the modifier completes the surface modification in the process of multiple transient contact with the high temperature inner wall of the equipment;

[0091] 6) 60% by weight of the epoxy modified silica micro powder is added to the bisphenol A epoxy resin, mixed uniformly and degassed under the condition of 2000 rpm of the mixer and vacuum, and the room temperature viscosity (shear rate 50 / s) is tested by the rheometer;

[0092] Example 6:

[0093] 1) 1 kg of silica micro powder with an average particle size of 500 nm is preheated at 180-200 degrees Celsius under vacuum for 3 hours;

[0094] 2) The silica micro powder is transferred to the ultrafast heating powder modification machine, the stirrer switch and the air jet switch are turned on, and the silica micro powder flows in a clockwise state in the modification equipment under the action of the air jet airflow;

[0095] 3) The target temperature is set to 700 degrees Celsius, the pulse interval is 20 s, that is, 20 s of temperature rise and 20 s of temperature drop are repeated for one cycle, the heating switch is turned on, and the electric trigger joule heat pulse type temperature rise and cooling treatment is adopted;

[0096] 4) Adopting spray form, spraying 0.1% of vinyl trimethoxysilane modifier in weight percentage on the silica micro powder in flow state in the equipment through the modifier nozzle to carry out modification treatment;

[0097] 5) The silica powder mixed with the modifier completes surface modification in the process of multiple transient contact with the high temperature inner wall of the equipment;

[0098] 6) Adding 60% of epoxy modified silica micro powder in weight percentage into bisphenol A epoxy resin, mixing uniformly and defoaming under the condition of 2000 revolutions / minute and vacuumizing in the mixer, and testing the room temperature viscosity (shear rate 50 / second) by the rheometer.

[0099] Table 1 (room temperature viscosity, thermal expansion coefficient, elastic modulus of examples 1-4):

[0100] Examples Room temperature viscosity / Pa-s coefficient of thermal expansion / 10 -6 K -1 ]] Elastic modulus (30°C) / GPa Example 1 53.25 31.13 5.94 Example 2 49.40 28.87 6.41 Example 3 50.21 29.21 6.25 Example 4 49.58 29.57 6.37 Example 5 49.87 30.25 6.52

[0101] Description: Example 1 adopts the traditional electric heating method to carry out surface modification of silica micro powder, and the modification time is long, usually needs 120 minutes to complete the modification, and the modification efficiency is low; while examples 2, 3, 4 and 5 all adopt the new method of rapid modification of silica powder surface, through the electric trigger of joule heat pulse type heating-cooling cycle treatment, the surface modification of silica powder is completed in the process of multiple transient contact with the high temperature alumina inner wall of the equipment, the modification time is short, and the surface modification of the powder can be completed within 100-400s. In addition, the room temperature viscosity, thermal expansion coefficient and elastic modulus of the modified silica powder obtained by the new method are equivalent to the test results of the powder obtained by the traditional modification method, which shows that the modification method provided by the application can not only adapt to the surface modification of silica micro powder by different modifiers, but also shorten the time consumed in the powder modification process, greatly improving the modification production efficiency.

[0102] It can be understood that the technical features of the above-described examples can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description.

[0103] The above is only a preferred embodiment of the application, and only the technical principles of the application are specifically described, and these descriptions are only for explaining the principles of the application, and cannot be explained as a limitation on the protection scope of the application in any way. Based on the explanation here, any modification, equivalent replacement and improvement made within the spirit and principle of the application, and other specific embodiments of the application that can be easily thought by those skilled in the art without creative labor, should be included in the protection scope of the application.

Claims

1. A modification method of a powder modification device, characterized by, The powder modification device comprises a metal shell forming a cavity, a modifier nozzle arranged on the metal shell, a gas nozzle arranged on the metal shell, a discharge port arranged on the metal shell, and a joule heat heating assembly arranged on the inner wall of the metal shell, wherein the joule heat heating assembly comprises an inner layer of graphite and aluminum oxide covering the inner layer of graphite. The gas nozzle is at least one, and the powder particles flow in the cavity in a clockwise direction under the action of the gas nozzle. The modifier is added to the cavity in a spraying manner through the modifier nozzle. The modification method comprises the following steps: The powder particles enter the cavity through a feeding port; The modifier is sprayed on the surface of the powder particles in a flowing state through the modifier nozzle; The inner layer of graphite is heated to 800-1200℃ at a temperature rising rate of 100℃ / s under the condition of triggering joule heat by an external current, and heat is transferred to the aluminum oxide, the pulse interval is 8-12s, and the process is repeated for 5-8 times; The aluminum oxide is rapidly heated to the target temperature, and the powder particles sprayed with the modifier are obtained by multiple instantaneous collision and contact with the high-temperature aluminum oxide to obtain surface modification; The modified powder particles are transferred through the discharge port. The powder particles are silica powder. The modifier comprises one or a mixture of several of the following: vinyltrimethoxysilane, vinyltriethoxysilane, trimethoxy({[4-(epoxy-2-yl)phenyl]methyl})silane, triethoxy({[4-(oxirane-2-yl)phenyl]methyl})silane, trimethoxy({4-[2-(oxirane-2-yl)ethyl]phenyl}methyl)silane, trimethoxy({4-[ (epoxy-2-oxymethyl]phenyl}methyl)silane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxytriethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane. The weight percentage of the modifier to the powder particles is 0.1-5%.

2. The powder modification method according to claim 1, wherein Before the powder particles enter the cavity through the gas nozzle, the following steps are further included: The powder particles are preheated under vacuum conditions at 180-200℃.

3. The powder modification method of claim 1, wherein The inner layer of graphite is several and is uniformly and spacedly arranged on the inner wall of the metal shell.

4. The powder modification method according to claim 3, wherein An insulating layer is further arranged between adjacent inner layers of graphite, which on one hand provides assembly space for accessories such as the gas nozzle, avoiding the direct assembly of the accessories on the graphite layer and adversely affecting the heating performance, and on the other hand uniformly provides multiple heating assemblies through the insulating layer, improving the heating efficiency and stability.

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