Continuous low temperature plasma powder processing and ball milling production apparatus and method

Abstract

A continuous low-temperature plasma powder processing and ball milling production apparatus and method includes a powder circulation and transport pipe system (1), a ball mill (2), a low-temperature plasma discharge pipe (3), a vacuum exhaust system (4), and a controllable atmosphere system (5). The powder circulation and transport pipe system (1) is connected to the ball mill (2) and the low-temperature plasma discharge pipe (3) via a pipe, and the controllable atmosphere system (5) is connected to the powder circulation and transport pipe system (1). The powder circulation and transport pipe system (1) circulates and transports the powder to be processed under controllable air pressure and flow rate. On the one hand, a double dielectric barrier discharge structure is introduced into the powder transport process to form the low-temperature plasma discharge pipe (3), which realizes plasma discharge treatment of the fluidized powder. On the other hand, a ball mill (2) is introduced to ball mill the plasma discharge-treated powder for ball milling refinement or alloying. This realizes powder processing through the combination of large-area, uniform, and high-energy non-equilibrium plasma and mechanical milling. This can be used for surface circulatory modification of general metal, polymer, or oxide powders.

Description

[Technical field]

[0001] The present invention belongs to the technical field of powder material processing and powder metallurgy, and relates to plasma gas powder surface treatment and ball milling technology, particularly to a continuous low-temperature plasma powder treatment and ball milling production device. [Background technology]

[0002] With the rapid development of new materials and intelligent manufacturing industries, the development of low-cost, non-polluting, high-performance functional powder manufacturing technology is an important foundation for the fields of electronic information, mechanical manufacturing, biomedicine, national defense and military, etc. Low-temperature plasma, on the one hand, has active material with high enough energy to excite, ionize or break the bonds of reactant molecules, and on the other hand, does not thermally decompose or ablate the treated material, and has unique application value in the surface modification of powder materials.

[0003] Plasma is the fourth state of matter, excluding solids, gases and liquids, and is composed of atoms, molecules, ions and radicals with equal numbers of positive and negative charges. The excitation of plasma is mainly when sufficient energy acts on the molecules of a gas, causing the molecules to ionize and generate a quasi-neutral gas that exhibits collective behavior, consisting of a large number of positively and negatively charged particles, electrons, neutral particles and radicals. Compared with traditional physical synthesis methods and chemical synthesis methods, plasma methods can avoid high temperatures and long reaction times, and can rapidly build and dope defects on the surface of materials without destroying the nanostructure of the material, and can change the structure, components, groups and wettability of the material surface. Low-temperature plasma has the characteristics of high electron temperature, low gas temperature and high energy, and is therefore widely used in material synthesis and surface modification. Dielectric barrier discharge is a common method of low-temperature plasma, which is filled with a working gas between two discharge electrodes, added with an insulating dielectric, and applied with a sufficiently high AC voltage between the two electrodes, causing the gas between the electrodes to break down and discharge. In addition, dielectric barrier discharge can break free from the constraints of the vacuum system required for low-pressure discharge plasma.

[0004] However, in the application of conventional low-temperature plasma in material synthesis and surface treatment, the mature technology is mainly focused on the surface treatment of polymer materials and defect construction, doping, etc. on the surface of catalytic materials. For example, the energy possessed by active particles in low-temperature plasma is generally close to or exceeds the bond energy of carbon-carbon or other carbon-containing bonds, so that the plasma has enough energy to cause the breaking or rebonding of various chemical bonds in the polymer, and is easy to introduce polar groups or active sites on the surface of polymer materials. However, low-temperature plasma has not been widely applied to the production and modification of materials such as metal materials and ceramic oxides. At present, the mature application technology is described in CN 1718282 A and CN 104549658 A The above two patents mainly introduce how to improve and realize the function and effect of plasma discharge assisted ball milling based on the general ball mill. The materials applied to this technology include simple metals, cemented carbide, hydrogen storage alloy, graphite-based electrode materials, oxide ceramics, laser glass, electrocatalyst, infrared stealth sheet-like materials, processing of chlorine-containing solid waste materials, 3D printing powder, etc., which shows the huge value of low-temperature plasma assisted ball milling technology in the beginning. However, the main problem facing this technology is that the ball mill tank is the plasma discharge space, and is limited by the conventional dielectric barrier discharge gap being too large, so it is difficult for the volume of the ball mill tank to exceed 10 liters. This is mainly because, when the space of the ball mill tank increases, the distance between the electrode rod and the ground electrode and the tank wall of the ball mill tank increases, and the discharge distance for destroying the ionized gas increases, and the larger the discharge distance, the more difficult it is to discharge. When the volume of the ball mill tank is more than 10 liters, the discharge voltage exceeds 40KV, and the life of the electrode rod is rapidly attenuated under high voltage operating conditions. Therefore, this problem limits the application of plasma-assisted ball milling technology in the powder scale manufacturing industry.

[0005] In addition, CN 101239334 A and CN101239336 A discloses a plasma-assisted high-energy drum ball mill and a plasma-assisted stirred ball mill, which are mainly modified versions of conventional drum and stirred ball mills, respectively, and neither of them can solve problems such as the limited discharge distance relative to the space of the discharge ball mill tank.

[0006] However, the combination of plasma and ball milling mechanical force can realize multiple advantageous manufacturing factors for powder materials to be ball milled. First, the electron temperature of high-energy electrons is very high, which instantly heats up a small area of ​​powder during ball milling. When the powder leaves the plasma, the temperature drops rapidly, generating huge thermal stress, which causes the powder to melt, heat explosion and other phenomena, and at the same time generates the "rapid heating-rapid cooling" powder refinement mechanism. Second, the highly active particles of the plasma collide with and adsorb onto the powder to be ball milled, which increases the activity of the material surface, and the new surface and large number of defects caused by the ball milling mechanical force further increase the activity of the powder to be ball milled, making the diffusion, phase transition and chemical reaction very easy. Finally, the powder is heated by the plasma and collided by the balls at the same time, so the deformation is carried out at a certain temperature. Therefore, it is very significant how to apply low-temperature plasma to the large-scale production or modification of industrial-grade powder materials.

[0008] A plasma generator generally applies a high-frequency electric field to the environment of a reactive gas under negative pressure (vacuum), and the gas is ionized under the excitation of the high-frequency electric field to generate plasma. These ions are highly active, and their energy is enough to break almost all chemical bonds, causing chemical reactions on all exposed surfaces of materials, changing the structure, components and groups of the material surface to obtain a surface that meets actual requirements. In addition, plasma has a fast reaction rate and high processing efficiency, and the modification only occurs on the surface of the material, without affecting the performance of the main body material inside the material, making it a preferred surface modification method. Surface modification by plasma is widely applied to materials in shapes such as film, block and particle, and materials in different shapes must use different plasma processing methods. For example, film-shaped materials (including films, woven fabrics, nonwoven fabrics, screens, etc.) can be rolled and packaged, so roll-shaped batch processing can be used. Block-shaped materials can be arranged one by one, making them suitable for processing multi-layer flat electrodes. Plasma has few applications in the treatment of powder particles, and has been mainly focused on the surface treatment of polymer materials and the construction of defects on the surface of catalytic materials, doping, etc.

[0009] In order to expand the large-scale application of low-temperature plasma treatment of powder materials to the fields of metal powder and oxide ceramic powder, the following problems must be solved: (1) In the process of powder plasma treatment, there is powder deposition and aggregation between particles, and the surface of the particles not exposed to the plasma atmosphere is not treated, making it difficult to achieve complete treatment of the particles, resulting in incomplete and uneven treatment of the particles and poor treatment effect. (2) To realize controllable plasma discharge intensity and energy. Since the binding energy of polymer materials is much lower than that of metal and oxide materials, the conventional plasma for polymer material treatment has low energy and is not suitable for metal materials, oxide materials, etc. (3) In general, the dielectric barrier plasma discharge space or radio frequency plasma discharge space is both limited, so the development of a large-area plasma discharge structure is an important problem to solve the large-scale production or treatment of powder by plasma. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] China Patent Publication No. 1718282 [Patent Document 2] China Patent Publication No. 104549658 [Patent Document 3] China Patent Application Publication No. 101239334 [Patent Document 4] China Patent Application Publication No. 101239336 Summary of the Invention [Problem to be solved by the invention]

[0011] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to overcome the above-mentioned drawbacks in the prior art and to provide a continuous low temperature plasma powder processing and ball milling production apparatus and method. [Means for solving the problem]

[0012] The object of the present invention is achieved by at least one of the following technical solutions:

[0013] A continuous low-temperature plasma powder processing and ball milling production apparatus, comprising: a powder circulation transport pipe system, a ball mill, a low-temperature plasma discharge pipe, a vacuum exhaust system, and a controllable atmosphere system, the powder circulation transport pipe system is connected to the ball mill and the low-temperature plasma discharge pipe in sequence via a pipe, the low-temperature plasma discharge pipe is connected to the powder circulation transport pipe system, and the controllable atmosphere system is connected to the powder circulation transport pipe system.

[0014] Furthermore, the powder circulation transport pipe system includes a feed chamber, a temporary storage chamber, a supply pipe, a negative pressure fan, and a blowback system, the feed chamber is connected to the temporary storage chamber, the bottom supply outlet of the temporary storage chamber is connected to a vacuum exhaust system, the blowback system is installed in the temporary storage chamber, the blowback system is connected to the negative pressure fan through a pipe, and the negative pressure fan is sequentially connected to the ball mill, the low-temperature plasma discharge pipe and the temporary storage chamber through a pipe.

[0015] The above-mentioned device further includes a first air-operated butterfly valve, a rotary feed valve, a second air-operated butterfly valve, an adjustable gate valve, a third air-operated butterfly valve, and a muffler, in which the first air-operated butterfly valve is installed between the feed chamber and the temporary storage chamber, the rotary feed valve is installed at the outlet of the temporary storage chamber, the muffler is installed at the outlet of the negative pressure fan, and the third air-operated butterfly valve, the adjustable gate valve, and the second air-operated butterfly valve are installed in a pipe between the muffler and the ball mill.

[0016] Furthermore, the low-temperature plasma discharge pipe includes an inlet, an outlet, an outer dielectric barrier layer, an inner dielectric barrier layer, an outer high-voltage electrode, an inner grounding electrode, a cooling liquid, a pipe discharge gap, and a pulse high-voltage power supply, wherein the inner dielectric barrier layer forms the wall surface of the pipe, an inner grounding electrode is installed inside the pipe, the inner grounding electrode is hollow and has a cooling liquid installed inside, an outer dielectric barrier layer is installed on the outer wall surface of the inner grounding electrode, an outer high-voltage electrode is installed outside the inner dielectric barrier layer, and a pulse high-voltage power supply is connected between the outer high-voltage electrode and the inner grounding electrode.

[0017] Further, the controllable atmosphere system includes a working gas cylinder, a pressure regulating valve, a pressure sensor, an air-operated butterfly valve, and a dust remover, the working gas cylinder is respectively connected to the outlet line of the blowback system and the negative pressure fan, the dust remover is installed in the line between the working gas cylinder and the blowback system, and the pressure regulating valve, the pressure sensor, and the air-operated butterfly valve are installed in the line between the working gas cylinder and the outlet of the negative pressure fan.

[0018] The method of using the device includes the following steps: the powder circulation transport system circulates and transports the powder material to be treated with controllable air pressure and flow rate, during which, on the one hand, a dielectric barrier discharge structure is introduced into a part of the powder transport pipe to form a low-temperature plasma discharge pipe, and plasma discharge treatment is realized for the flow powder material in the pipe, on the other hand, a ball mill is introduced into the powder pipe transport process, and the powder to be plasma discharge treated is simultaneously subjected to ball milling fineness or alloying, and the powder flow rate, air pressure and discharge atmosphere are adjusted by a controllable atmosphere system during the entire process, and the powder material after treatment is put into a vacuum discharge system for recovery and packaging; The powder circulation transport pipe system operates using negative pressure conditions; The ball mill is a vibration ball mill or a drum ball mill, The low-temperature plasma discharge pipe is a double dielectric barrier discharge type low-temperature plasma device using a powder transport pipe, and is combined with a pulse high-voltage power supply. The controllable atmosphere system is connected to the powder circulation transport pipe system to provide a protective or reactive atmosphere required for the powder processing and transport process, the atmosphere including argon gas, nitrogen gas, ammonia gas, hydrogen gas or oxygen gas, the atmosphere can be ionized and discharged in the low-temperature plasma discharge pipe, and the plasma realizes the effect of modifying the surface of the powder being processed.

[0019] In the above method, the powder flow transport distance in one circulation is 6 to 20 meters, the inner diameter of the circulation pipe is 35 to 60 mm, the mass ratio of the powder to the gas is 5:1 to 12:1, the pressure of the flowing gas and the discharge gas is -0.3 bar to -0.1 bar, and the flow speed of the powder and the gas is 10 m / s to 15 m / s.

[0020] In the above method, the powder circulation transport pipe system feeds the powder material into the feed chamber, feeds 10L-50L at a time, and automatically enters the temporary storage chamber under the working gas protection state through the feed chamber supply port, and the gas is separated into solid and gas through the blowback system. The remaining solid powder material is fed into the material circulation system through the rotary feed valve and the feed pipe, and is mechanically milled by the ball mill, and is surface-treated through the low-temperature plasma discharge pipe from bottom to top under the action of a specific gas suspension force, and then is fed into the temporary storage chamber and the blowback system again to perform solid-gas separation. The powder material is circulated and then fed into the vacuum discharge system for packaging. The gas separated in the blowback system passes through the negative pressure fan, the muffler, the air-operated butterfly valve, the control gate valve, and the air-operated butterfly valve, and then the pressurized gas is sent to the material circulation system to provide power for the transportation of the powder material. The inner diameter of the feed pipe is 100mm-180mm, and the inner diameter of the other circulation pipe is 35mm-60mm.

[0021] In the above method, the low-temperature plasma discharge pipe has an overall length of 2 to 5 meters, the outer and inner dielectric barrier layers are made of quartz glass or high-purity zirconium oxide ceramic material, the distance between the outer wall of the inner dielectric barrier layer and the inner wall of the outer dielectric barrier layer, i.e., the one-side distance of the pipe discharge gap, is selected to be 5 to 15 mm, the peak value of the pulse voltage peak of the power supply is 20KV-40KV, the discharge frequency value of the power supply is 10 to 40KHz, and the coolant mainly realizes cooling and protection of the electrode material, and realizes controlling the electrode system temperature below 150°C.

[0022] In the above method, the controllable atmosphere system adjusts the pressure of the working gas cylinder to adjust the flow rate of gas and powder material required for vacuuming and replacement of the entire pipe system, and sets a specific gas pressure and flow rate for the gas cylinder to operate the blowback system in the dust collector. Effect of the Invention

[0023] The present invention utilizes a combination of a powder circulation transport pipe and a double dielectric barrier discharge plasma, and realizes a technology that can control the intensity of the plasma inside the pipe by using a pipe discharge structure with a double dielectric barrier, and realizes a stable cooperative action between a large-area, uniform and high-energy non-equilibrium plasma and downstream mechanical milling, and the technology has the following advantages:

[0024] First, the double dielectric barrier discharge plasma can be generated at almost normal pressure and normal pressure, and meets the atmospheric pressure requirement of the atmosphere in the powder circulation transport pipe. In this application, the pressure of the flowing gas and the discharge gas is selected in the range of -0.3 bar to -0.1 bar. When the atmospheric pressure is lower than -0.3 bar, the discharge intensity is high, but the flowing force of the powder is insufficient, the distribution of the powder in the circulation pipe is not uniform, and the power of the negative pressure fan increases rapidly, and the heat generation increases rapidly. When the gas pressure is higher than -0.1 bar, the flowing force of the powder is sufficient, the distribution of the powder in the circulation pipe is uniform, and the power of the negative pressure fan is low, but the plasma discharge intensity in the low-temperature plasma discharge pipe is insufficient, and a large amount of filamentary discharge and spark discharge etc. appear, which will harm the life of the electrodes.

[0025] And the double dielectric barrier discharge prevents the dielectric barrier discharge from transforming into a spark discharge or an arc discharge, since the dielectric layer suppresses the infinite strengthening of the micro-discharge, and ensures that the plasma is not a thermal plasma which is highly destructive to materials, and can also avoid the burnout of the electrode material.

[0026] Third, a double dielectric barrier discharge type low-temperature plasma device is constructed using a powder transport pipe. The entire length of the low-temperature plasma discharge pipe is 2 to 5 meters. The powder transport pipe not only transports powder material, but also acts as a discharge plasma generator. These aspects realize a long distance, large area, uniform and stable glow discharge, high utilization rate of plasma energy density, and avoid local high-intensity electric field breakdown, realizing large-scale production and surface treatment technology of powder material using plasma.

[0027] Fourth, the double dielectric barrier discharge can spread evenly on the surface of the dielectric layer, and the powder flows in a uniform suspension in the circulation pipe during the entire process. During the process of passing through the low-temperature plasma discharge pipe, all powder particles are completely wetted by the plasma, realizing the complete treatment of the powder particles.

[0028] Fifth, the stable cooperative action of this high-energy non-equilibrium plasma with mechanical milling can significantly reduce the reaction activation energy, refine the crystal grains, greatly improve the activity of the powder, improve the uniformity of particle distribution, strengthen the interfacial bonding between the body and the substrate, promote the diffusion of solid-solid ions and solid-gas ions, and induce low-temperature reactions, thereby improving the performance of materials in all aspects, and is a power-saving, high-efficiency materials manufacturing technology established based on theory.

[0029] Sixth, in terms of the design of the gas line system, this application realizes the standardization of parameters such as the composition of the atmosphere in the powder transport pipe, pressure, and powder flow through the gas line system, and realizes a technology that can control the gas discharge intensity in conjunction with the physicochemical properties of the powder material.

[0030] Finally, the device has the function of "one device with two roles", that is, during the operation of the ball mill, plasma treatment is performed on the ball milling powder by the low-temperature plasma discharge pipe, and the multi-physics coupling effect of mechanical milling and plasma is established to produce powder material; and when the mechanical milling stops operating, the whole device only uses the low-temperature plasma discharge pipe to perform plasma surface modification function on the powder material. [Brief description of the drawings]

[0031] [Figure 1] FIG. 2 is a structural schematic diagram of the continuous low-temperature plasma powder processing and ball milling production apparatus of the present invention. [Diagram 2] FIG. 2 is a structural schematic diagram of the powder circulation transport pipe system and the controllable atmosphere system of the present invention. [Diagram 3] FIG. 2 is a schematic diagram of the structure of the low-temperature plasma discharge pipe of the present invention. [Figure 4] 1 shows the morphology of the Fe powder after low-temperature plasma treatment and ball milling in Example 1. [Figure 5a] 1 shows the SEM results of the morphology of composite powder particles of WO3 and 20 wt% C after low-temperature plasma treatment and ball milling in Example 3. [Figure 5b] FIG. 10 is a DSC result diagram of a composite powder of WO3 and 20 wt% C after low-temperature plasma treatment and ball milling in Example 3. [Figure 6] This is an SEM image of the synthesis of WC by heating a composite powder of WO3 and 20 wt% C after low-temperature plasma treatment and ball milling in a vacuum sintering furnace at 1150°C for 1 hour. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific implementations of the present invention will be described in detail in conjunction with the drawings and specific embodiments, but the implementation and protection of the present invention are not limited thereto.

[0033] As shown in Figures 1 to 3, this is a continuous low-temperature plasma powder processing and ball milling production equipment, which includes a powder circulation transport pipe system 1, a ball mill 2, a low-temperature plasma discharge pipe 3, a vacuum exhaust system 4, and a controllable atmosphere system 5, and the powder circulation transport pipe system 1 is connected to the ball mill 2 and the low-temperature plasma discharge pipe 3 in sequence via pipes, the low-temperature plasma discharge pipe 3 is connected to the powder circulation transport pipe system 1, and the controllable atmosphere system 5 is connected to the powder circulation transport pipe system 1. The powder circulation transport pipe system 1 consists of a feed chamber 11, a temporary storage chamber 13, a supply pipe 15, a negative pressure fan 110, and a blowback system 111. The feed chamber 11 is connected to the temporary storage chamber 13, the bottom outlet of the temporary storage chamber 13 is connected to the vacuum exhaust system 4, the blowback system 111 is installed in the temporary storage chamber 13, the blowback system 111 is connected to the negative pressure fan 110 through a pipe, and the negative pressure fan 110 is connected to the ball mill 2, the low-temperature plasma discharge pipe 3, and the temporary storage chamber 13 in sequence through a pipe. The mill further includes a first air-operated butterfly valve 12, a rotary feed valve 14, a second air-operated butterfly valve 16, an adjustment gate valve 17, a third air-operated butterfly valve 18, and a muffler 19, the first air-operated butterfly valve 12 being installed between the feed chamber 11 and the temporary storage chamber 13, the rotary feed valve 14 being installed at the outlet of the temporary storage chamber 13, the muffler 19 being installed at the outlet of the negative pressure fan 110, and the third air-operated butterfly valve 18, the adjustment gate valve 17, and the second air-operated butterfly valve 16 being installed in a pipe between the muffler 19 and the ball mill 2.The low-temperature plasma discharge pipe 3 includes an inlet 31, an outlet 32, an outer dielectric barrier layer 33, an inner dielectric barrier layer 34, an outer high-voltage electrode 35, an inner grounding electrode 36, a cooling liquid 37, a pipe discharge gap 38, and a pulse high-voltage power supply 39, wherein the inner dielectric barrier layer 34 forms the wall surface of the pipe, the inner grounding electrode 36 is installed inside the pipe, the inner grounding electrode 36 is hollow and has cooling liquid 37 installed inside, the outer dielectric barrier layer 33 is installed on the outer wall surface of the inner grounding electrode 36, the outer high-voltage electrode 35 is installed outside the inner dielectric barrier layer 34, and the pulse high-voltage power supply 39 is connected between the outer high-voltage electrode 35 and the inner grounding electrode 36. The controllable atmosphere system 5 includes a working gas cylinder 51, a pressure regulating valve 52, a pressure sensor 53, an air operated butterfly valve 54, and a dust remover 55, the working gas cylinder 51 is connected to the outlet pipes of the blowback system 111 and the negative pressure fan 110, respectively, the dust remover 55 is installed in the pipe between the working gas cylinder 51 and the blowback system 111, and the pressure regulating valve 52, the pressure sensor 53, and the air operated butterfly valve 54 are installed in the pipe between the working gas cylinder 51 and the outlet of the negative pressure fan 110.

[0034] First, the powder material is fed into the feed chamber by using the powder circulation transport pipe system, and is fed at a rate of 10L or more per time. The powder material is automatically fed into the temporary storage chamber under argon gas protection through the feed chamber supply port for solid-gas separation. Then, the powder material is circulated and transported in a specific atmosphere in the system pipe by using negative pressure transport, and mechanical milling is performed by using a ball mill. The surface treatment is performed by passing through the low-temperature plasma discharge pipe from bottom to top under the thrust of a specific gas, and after a certain period of circulating treatment, the powder is put into the vacuum discharge system for packing. During the entire process, the powder flows in a uniform suspension in the circulation pipe, and all the powder particles are completely wetted by the plasma during the process of passing through the low-temperature plasma discharge pipe, thereby realizing all the treatment of the powder particles. In addition, the double dielectric barrier structure used in the present invention can effectively avoid the destruction and yield of the electrode dielectric layer caused by the arc discharge, provide discharge stability, and have a high energy density utilization rate of the plasma. In addition, the peak value of the pulse voltage peak of the power supply is 20KV-40KV, and the discharge frequency value of the power supply is 10-40KHz, which can ensure high discharge energy and avoid problems such as excessive heat generation of the electrode. Finally, in the low-temperature plasma discharge pipe used in the present invention, the entire length of the low-temperature plasma discharge pipe is 2 to 5 meters, the outer and inner dielectric barrier layers are made of silica glass or high-purity zirconium oxide ceramic material, and the distance between the outer wall of the inner dielectric barrier layer and the inner wall of the outer dielectric barrier layer, i.e., the one-side distance of the pipe discharge gap, is selected to be 5 to 15 mm. By utilizing the pipe discharge technology through which powder flows, a discharge structure in which plasma processes powder with a long distance and large area is realized, which is the key to solving the large-scale production or processing of powder by plasma.

[0035] Example 1 In step 1, first, the controllable atmosphere system is started, the pipe and the entire ball mill chamber are evacuated to less than 1 Pa, and then replaced with argon gas, then the vibration ball mill is started, the powder circulation transport pipe system is started, and finally the low-temperature plasma discharge pipe and its cooling system are started.

[0036] In step 2, 15 kg of ultrafine Fe powder is fed into the feed chamber at one time, and then automatically fed into the temporary storage chamber under argon gas protection through the feed chamber inlet. The gas is separated into solid and gas in the gas blowback system, and the remaining solid powder is fed into the material circulation system through the rotary feed valve and the feed pipe. The inner diameter of the powder circulation pipe is selected to be 35 mm, the mass ratio of the powder to the gas is 5:1, and the pressure of the flow gas and the discharge gas is -0.3 bar. In step 3, the ultrafine Fe powder to be treated is mechanically milled by a vibration ball mill, and then passed through a low-temperature plasma discharge pipe from bottom to top under the action of a specific gas suspension force for surface treatment, and then re-entered into a temporary storage chamber and a blowback system for solid-gas separation. The powder material is circulated for a certain period of time and then packaged in a vacuum discharge system. The vibration ball mill uses 1400 rpm, gravitational acceleration 10 g, amplitude peak-to-peak value 15 mm, and mill to material ratio 100:1. The low-temperature plasma discharge pipe has a discharge voltage peak-to-peak value of 29 kV, a discharge current of 150 mA, and a discharge frequency of 15 KHz. The feed pipe has an inner diameter of 100 mm.

[0037] The results show that the flow speed of ultrafine iron powder and gas can reach 10m / s~13m / s and can be adjusted, the powder flows uniformly and disperses in the pipe, and after 8 hours of continuous operation, the discharge glow in the low-temperature plasma discharge pipe maintains a diffuse scattering state, the electrode temperature does not exceed 150℃, the negative pressure fan temperature is close to 80℃, and the powder flow transport distance in one cycle is 6 meters. As shown in Figure 4, the produced Fe powder has a sheet-like structure of about 30 microns, indicating that the combination of negative pressure argon gas plasma and ball milling can effectively produce Fe powder with a sheet-like structure. This is mainly because the high discharge intensity of negative pressure argon gas plasma enhances the "electrical-thermal" coupling effect, and the thermal effect of the plasma makes the local temperature of the ball milled powder higher than the recrystallization temperature of Fe, resulting in thermal processing during ball milling and weakening the work-hardening effect. The electroplastic effect enhances the plasticity of the powder to a certain extent, which makes the powder further stretch from a thin block shape to a thinner sheet shape, and then breaks and pulverizes into small sheets under the action of the strong mechanical force of the ball.

[0038] Example 2 In step 1, first, the controllable atmosphere system is started, the pipe and the entire ball mill chamber are evacuated to less than 1 Pa, and then replaced with argon gas, then the powder circulation transport pipe system is started, and finally the low-temperature plasma discharge pipe and its cooling system are started.

[0039] In step 2, 15 kg of ultrafine Fe powder is fed into the feed chamber at one time, and then automatically fed into the temporary storage chamber under argon gas protection through the feed chamber inlet. The gas is separated into solid and gas in the gas blowback system, and the remaining solid powder is fed into the material circulation system through the rotary feed valve and the feed pipe. The inner diameter of the powder circulation pipe is selected to be 60 mm, the mass ratio of the powder to the gas is 12:1, and the pressure of the flow gas and the discharge gas is -0.1 bar. In step 3, the ultrafine Fe powder to be treated passes through the inner chamber of the vibration ball mill respectively, and passes through the low-temperature plasma discharge pipe from bottom to top under the action of a certain gas suspension force to be surface-treated, and then enters the temporary storage chamber and the blowback system again for solid-gas separation; the powder material enters the vacuum discharge system for packaging after a certain period of circulation; the vibration ball mill uses an empty load, the rotation speed is 0 rpm, the low-temperature plasma discharge pipe has a peak value of the discharge voltage peak of 29 kV, a discharge current of 150 mA, a discharge frequency of 15 KHz, and the supply pipe has an inner diameter of 180 mm.

[0040] The results show that the flow speed of ultrafine iron powder and gas can reach 10m / s~15m / s and can be adjusted, the powder flows uniformly and disperses in the pipe, and after 8 hours of continuous operation, the discharge glow in the low-temperature plasma discharge pipe shows some filamentous discharge, the electrode temperature does not exceed 150℃, the negative pressure fan temperature is lower than 70℃, and the powder flow transport distance in one cycle is 20 meters.

[0041] The above treatment only modifies the surface of the ultrafine Fe powder, and the ultrafine Fe powder after the discharge plasma modification becomes the main matrix metal of the diamond abrasive grains, which is advantageous in significantly improving the wetting condition of the diamond to the matrix, increasing the bonding strength between the diamond and the matrix, and further improving the solid-phase sintering of the Fe powder in the matrix.

[0042] Example 3 In step 1, first, the controllable atmosphere system is started, the pipe and the entire ball mill chamber are evacuated to less than 1 Pa, and then replaced with argon gas, then the vibration ball mill is started, the powder circulation transport pipe system is started, and finally the low-temperature plasma discharge pipe and its cooling system are started.

[0043] In step 2, 8 kg of WO3 and graphite are mixed with a carbon content of 20% by mass percentage, the mixed powder is pre-milled in a vibration ball mill for 1 hour, and then fed all at once into the feed chamber, and automatically fed into a temporary storage chamber under argon gas protection through the feed chamber feed port, and the gas is separated into solid and gas through the blowback system, and the remaining solid powder material is fed into the material circulation system through the rotary feed valve and the feed pipe, and the inner diameter of the powder circulation pipe is selected to be 50 mm, the mass ratio of the powder material to the gas is 10:1, and the pressure of the flow gas and the discharge gas is -0.2 bar; In step 3, the mixed powder of WO3 and graphite to be treated is mechanically milled by vibrating ball mill respectively, and then passes through low-temperature plasma discharge pipe from bottom to top under the action of a specific gas suspension force to perform surface treatment, and then enters into temporary storage chamber and blowback system again to perform solid-gas separation, and the powder material is circulated for a certain period of time and then enters into vacuum discharge system for packaging, the vibrating ball mill uses 1400 rpm, gravitational acceleration 10g, amplitude peak-to-peak value 15mm, mill to material ratio 100:1, the low-temperature plasma discharge pipe has a discharge voltage peak-to-peak value of 29kV, discharge current of 150mA, discharge frequency of 15KHz, and the feed pipe has an inner diameter of 150mm.

[0044] As shown by the results, the flow speed of the WO3-C mixed powder and gas can reach 10m / s~15m / s and can be adjusted, the powder flows uniformly and disperses in the pipe, and after 8 hours of continuous operation, the discharge glow in the low-temperature plasma discharge pipe maintains a diffuse scattering state, the electrode temperature does not exceed 150℃, the negative pressure fan temperature is close to 70℃, and the powder flow transport distance in one circulation is 10 meters.

[0045] SEM and DSC were used to test the composite powder of WO3 and 20wt% C after the above-mentioned low-temperature plasma treatment and ball milling, and it was found that 100-200nm WO3 was uniformly coated with graphite and formed good interface bonding, as shown in Figure 5a. The DSC test results show that the temperature of the in-situ reduction reaction of WO3 and C is reduced from over 1000°C after general ball milling to 900°C, as shown in Figure 5b. The higher the temperature of the in-situ reaction of WO3 and C and the longer the incubation time, the easier it is to cause the growth of WC, so the temperature of the in-situ reduction reaction of WO3 and C has a significant effect on the size of the synthesized WC particles. Therefore, it is important to reduce the temperature of the in-situ reduction reaction in order to produce nano-scale WC powder.

[0046] As shown in FIG. 6, after the above powder is kept in a vacuum sintering furnace at 1150°C for 1 hour, the synthesized WC grain size is 100-200nm. The ultrafine grain WC-Co cemented carbide produced by in-situ reduction using WO3, C and Co as raw materials has the advantages of low price and short process, and has important industrial application value. The important step in producing ultrafine grain WC-Co cemented carbide by in-situ reduction is to synthesize ultrafine WC powder containing only a single phase, because the powder may adsorb oxygen and consume carbon during the ball milling, reaction and sintering process, making it difficult to control the carbon content. Therefore, by using a continuous low-temperature plasma treatment and ball milling production device, high-performance ultrafine WC powder can be synthesized, laying the foundation for the industrial production of ultrafine grain WC-Co cemented carbide.

[0047] Example 4 In step 1, first, the controllable atmosphere system is started, the pipe and the entire ball mill chamber are evacuated to less than 1 Pa, and then replaced with argon gas, then the powder circulation transport pipe system is started, and finally the low-temperature plasma discharge pipe and its cooling system are started.

[0048] In step 2, 2 kg of polyethylene powder is fed into the feed chamber at one time, and automatically fed into the temporary storage chamber under argon gas protection through the feed chamber feed port, and the gas is separated into solid and gas through the gas blowback system, and the remaining solid powder is fed into the material circulation system through the rotary feed valve and the feed pipe, and the inner diameter of the powder circulation pipe is selected to be 60 mm, the mass ratio of the powder to the gas is 5:1, and the pressure of the flow gas and the discharge gas is -0.3 bar; In step 3, the polyethylene powder to be treated passes through the inner chamber of the vibrating ball mill respectively, and passes through the low-temperature plasma discharge pipe from bottom to top under the action of a certain gas suspension force to be surface-treated, and then enters the temporary storage chamber and the blowback system again for solid-gas separation; the powder material enters the vacuum discharge system for packaging after a certain period of circulation; the vibrating ball mill uses an empty load, the rotation speed is 0 rpm, the low-temperature plasma discharge pipe has a peak value of the discharge voltage peak of 20 kV, a discharge current of 100 mA, a discharge frequency of 11 KHz, and the supply pipe has an inner diameter of 180 mm.

[0049] The results show that the flow speed of graphite powder and gas can reach 10m / s~15m / s and can be adjusted, the powder flows uniformly and disperses in the pipe, and after 8 hours of continuous operation, the discharge glow in the low-temperature plasma discharge pipe shows some filamentous discharge, the electrode temperature does not exceed 150℃, the negative pressure fan temperature is lower than 70℃, and the powder flow transport distance in one cycle is 10 meters.

[0050] The above treatment only modifies the surface of the polyethylene powder, and the wettability of the polyethylene powder in deionized water after the discharge plasma modification is significantly increased, so that the polyethylene powder before the treatment is almost entirely suspended on the water surface, and the polyethylene powder after the plasma treatment can be almost entirely rapidly precipitated in the deionized water. The same effect can be obtained in the surface treatment process of graphite powder. [Explanation of symbols]

[0051] 1. Powder circulation transport pipe system 2. Ball mill 3. Low-temperature plasma discharge pipe 4. Vacuum Evacuation System 5. Controllable Atmosphere Systems 11 Feed chamber 12 First air-operated butterfly valve 13 Temporary Storage Chamber 14 Rotating Supply Valve 15 Supply Pipe 16 Second Air-Operated Butterfly Valve 17 Adjustable Gate Valve 18 No. 3 Air Operated Butterfly Valve 19 Muffler 31 Inlet 32 Outlet 33 Outer dielectric barrier layer 34 Inner dielectric barrier layer 35 External high voltage electrode 36 Internal ground electrode 37 Coolant 38 Pipe discharge gap 39 Pulse High Voltage Power Supply 51 Working gas cylinder 52 Pressure Regulating Valve 53 Pressure Sensor 54 No. 4 Air-operated Butterfly Valve 55 Dust remover 110 Negative pressure fan 111 Blowback System

Claims

1. A continuous cold plasma powder processing and ball milling production device, comprising: a powder circulation transport pipe system (1), a ball mill (2), a cold plasma discharge pipe (3), a vacuum exhaust system (4), and a controllable atmosphere system (5), wherein the powder circulation transport pipe system (1) is connected to the ball mill (2) through a pipe, the ball mill (2) is connected to the cold plasma discharge pipe (3) through a pipe, the cold plasma discharge pipe (3) is connected to the powder circulation transport pipe system (1), and the controllable atmosphere system (5) is connected to the powder circulation transport pipe system (1); The low-temperature plasma discharge pipe (3) includes an inlet (31), an outlet (32), an outer dielectric barrier layer (33), an inner dielectric barrier layer (34), an outer high-voltage electrode (35), an inner ground electrode (36), a cooling liquid (37), a pipe discharge gap (38), and a pulse high-voltage power supply (39), characterized in that the inner dielectric barrier layer (34) forms a wall surface of the pipe, the inner ground electrode (36) is installed inside the pipe, the inner ground electrode (36) is hollow and the cooling liquid (37) is installed inside, the outer dielectric barrier layer (33) is installed on the outer wall surface of the inner ground electrode (36), the outer high-voltage electrode (35) is installed outside the inner dielectric barrier layer (34), and the pulse high-voltage power supply (39) is connected between the outer high-voltage electrode (35) and the inner ground electrode (36).

2. 2. The continuous low-temperature plasma powder processing and ball milling production apparatus according to claim 1, characterized in that the powder circulation transport pipe system (1) comprises a feed chamber (11), a temporary storage chamber (13), a supply pipe (15), a negative pressure fan (110) and a blowback system (111), the feed chamber (11) is connected to the temporary storage chamber (13), the bottom supply outlet of the temporary storage chamber (13) is connected to a vacuum exhaust system (4), the blowback system (111) is installed in the temporary storage chamber (13), the blowback system (111) is connected to the negative pressure fan (110) through a pipe, the negative pressure fan (110) is connected to a ball mill (2) through a pipe, the ball mill (2) is connected to a low-temperature plasma discharge pipe (3) through a pipe, and the low-temperature plasma discharge pipe (3) is connected to the temporary storage chamber (13) through a pipe.

3. 3. The continuous low temperature plasma powder processing and ball milling production apparatus according to claim 2, further comprising a first air-operated butterfly valve (12), a rotary feed valve (14), a second air-operated butterfly valve (16), an adjustable gate valve (17), a third air-operated butterfly valve (18) and a muffler (19), wherein the first air-operated butterfly valve (12) is installed between the feed chamber (11) and the temporary storage chamber (13), the rotary feed valve (14) is installed at the outlet of the temporary storage chamber (13), the muffler (19) is installed at the outlet of the negative pressure fan (110), and the third air-operated butterfly valve (18), the adjustable gate valve (17) and the second air-operated butterfly valve (16) are installed in a pipe between the muffler (19) and the ball mill (2).

4. 4. The continuous low-temperature plasma powder processing and ball milling production apparatus according to claim 1, characterized in that the controllable atmosphere system (5) comprises a working gas cylinder (51), a pressure regulating valve (52), a pressure sensor (53), a fourth air-operated butterfly valve (54) and a dust remover (55), the working gas cylinder (51) being connected to the outlet lines of the blowback system (111) and the negative pressure fan (110), respectively, the dust remover (55) being installed in the line between the working gas cylinder (51) and the blowback system (111), and the pressure regulating valve (52), the pressure sensor (53) and the air-operated butterfly valve (54) being installed in the line between the working gas cylinder (51) and the outlet of the negative pressure fan (110).

5. The powder circulation transport pipe system (1) circulates and transports the powder material to be treated with controllable air pressure and flow rate. In this process, on the one hand, a dielectric barrier discharge structure is introduced into a part of the powder transport pipe to form a low-temperature plasma discharge pipe (3) to realize plasma discharge treatment on the flowing powder material in the pipe. On the other hand, a ball mill (2) is introduced into the powder pipe transport process to simultaneously perform ball milling to refine or alloy the powder to be plasma discharge treated. The powder flow rate, air pressure, and discharge atmosphere are adjusted by a controllable atmosphere system (5) throughout the entire process. After the treatment, the powder material is put into a vacuum discharge system (4) for recovery and packaging. The powder circulation transport pipe system (1) operates using negative pressure conditions, The ball mill (2) uses a vibration ball milling or a drum ball milling, The low-temperature plasma discharge pipe (3) is a double dielectric barrier discharge type low-temperature plasma device using a powder transport pipe, and is combined with a pulse high-voltage power supply. The controllable atmosphere system (5) is connected to the powder circulation transport pipe system, and provides a protective or reactive atmosphere required for the powder processing and transport process, and the atmosphere can be ionized and discharged in the low-temperature plasma discharge pipe, so that the plasma can realize the effect of modifying the surface of the powder to be processed, and the atmosphere includes argon gas, nitrogen gas, ammonia gas, hydrogen gas or oxygen gas; The powder flow transport distance in one circulation is 6 to 20 meters, the inner diameter of the circulation pipe is 35 to 60 mm, the powder to gas mass ratio is 5:1 to 12:1, the flow gas and discharge gas pressure is -0.3 bar to -0.1 bar, and the powder and gas flow speed is 10 m / s to 15 m / s; 5. The method for using the device according to claim 1, wherein the low-temperature plasma discharge pipe (3) has an overall length of 2 to 5 meters, the outer dielectric barrier layer (33) and the inner dielectric barrier layer (34) are made of quartz glass or high-purity zirconium oxide ceramic material, the distance between the outer wall of the inner dielectric barrier layer and the inner wall of the outer dielectric barrier layer, i.e., the distance on one side of the pipe discharge gap (38), is selected to be 5 to 15 mm, the peak value of the pulse voltage peak of the power supply is 20 KV-40 KV, the discharge frequency value of the power supply is 10 to 40 KHz, and the coolant (37) mainly serves to cool and protect the electrode material, and to control the temperature of the electrode system to below 150°C.

6. In the powder circulation transport pipe system (1), the powder material is fed into the feed chamber (11), fed at 10L to 50L per time, and automatically fed into the temporary storage chamber (13) under the working gas protection state through the feed chamber supply port, the gas is separated into solid and gas through the blowback system (111), and the remaining solid powder material is fed into the material circulation system through the rotary supply valve (14) and the supply pipe (15), respectively, and mechanically milled by the ball mill (2), and surface treated by passing through the low-temperature plasma discharge pipe (3) from bottom to top under the action of a specific gas suspension force, and then fed into the temporary storage chamber (13) and the blowback system (112). the gas separated in the blowback system (111) passes through a negative pressure fan (110), a muffler (19), an air-operated butterfly valve (18), an adjustable gate valve (17) and an air-operated butterfly valve (16) respectively, and then the pressurized gas is sent to the material circulation system to provide power for transporting the powder material; the inner diameter of the supply pipe (15) is 100mm-180mm, and the inner diameter of the other circulation pipes is 35mm-60mm.

7. The method for use according to claims 5 and 6, characterized in that the controllable atmosphere system (5) realizes the adjustment of the flow rate of gas and powder material required for evacuation and replacement of the entire pipe system by adjusting the pressure of the working gas cylinder, and realizes the operation of the blowback system (111) in the dust collector (56) by setting a specific gas pressure and flow rate for the gas cylinder.

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