CONTINUOUS LOW-TEMPERATURE PLASMA POWDER TREATMENT AND BALL-MILLING PRODUCTION DEVICE AND METHOD THEREOF

Abstract

Disclosed are a continuous low-temperature plasma powder treatment and ball-milling production device, and a method thereof. The device includes a powder circulating and conveying pipeline system (1), a ball mill (2), a low-temperature plasma discharge pipeline (3), a vacuum discharge system (4) and a controllable atmosphere system (5), where the powder circulating and conveying pipeline system (1) is sequentially connected to the ball mill (2) and the low-temperature plasma discharge pipeline (3) through pipelines; and the controllable atmosphere system (5) is connected to the powder circulating and conveying pipeline system (1). The powder circulating and conveying pipeline system (1) is used for circulating and conveying to-be-treated powder at a controllable air pressure and flow speed. On one hand, a double-dielectric barrier discharge structure is introduced in a powder conveying process to form the low-temperature plasma discharge pipeline (3), thereby realizing a plasma discharge treatment on a transfer material powder; and on the other hand, the ball mill (2) is introduced to perform ball-milling refining or alloying on a powder subjected to plasma discharge treatment, thereby treating the powder through a large-area, uniform and high-energy non-equilibrium plasma in cooperation with mechanical ball milling and being capable of being used for performing a surface circulating modification treatment on a conventional metal, macromolecule or oxide powder.

Claims

1. A continuous low-temperature plasma powder treatment and ball-milling production device, comprising a powder circulating and conveying pipeline system (1), a ball mill (2), a low-temperature plasma discharge pipeline (3), a vacuum discharge system (4) and a controllable atmosphere system (5), wherein the powder circulating and conveying pipeline system (1) is sequentially connected to the ball mill (2) and the low-temperature plasma discharge pipeline (3) through pipelines; the low-temperature plasma discharge pipeline (3) is connected to the powder circulating and conveying pipeline system (1); and the controllable atmosphere system (5) is connected to the powder circulating and conveying pipeline system (1).

2. The continuous low-temperature plasma powder treatment and ball-milling production device according to claim 1, wherein the powder circulating and conveying pipeline system (1) comprises a feeding bin (11), a temporary storage bin (13), a feeding pipeline (15), a negative-pressure fan (110) and a back-blowing system (111); the feeding bin (11) is connected to the temporary storage bin (13); a bottom discharging outlet of the temporary storage bin (13) is connected to a vacuum discharging system (4); the back-blowing system (111) is arranged on the temporary storage bin (13); the back-blowing system (111) is connected to the negative-pressure fan (110) through a pipeline; and the negative-pressure fan (110) is sequentially connected to the ball mill (2), the low-temperature plasma discharge pipeline (3) and the temporary storage bin (13) through pipelines.

3. The continuous low-temperature plasma powder treatment and ball-milling production device according to claim 2, further comprising a first pneumatic butterfly valve (12), a rotary discharging valve (14), a second pneumatic butterfly valve (16), a regulating gate valve (17), a third pneumatic butterfly valve (18) and a silencer (19), wherein the first pneumatic butterfly valve (12) is arranged between the feeding bin (11) and the temporary storage bin (13); the rotary discharging valve (14) is arranged at a discharging port of the temporary storage bin (13); the silencer (19) is arranged at an outlet of the negative-pressure fan (110); and the third pneumatic butterfly valve (18), the regulating gate valve (17) and the second pneumatic butterfly valve (16) are arranged on a pipeline between the silencer (19) and the ball mill (2).

4. The continuous low-temperature plasma powder treatment and ball-milling production device according to claim 1, wherein the low-temperature plasma discharge pipeline (3) comprises a feeding port (31), a discharging port (32), an external dielectric barrier layer (33), an internal dielectric barrier layer (34), an external high-voltage electrode (35), an internal ground electrode (36), a cooling liquid (37), a pipeline discharge gap (38) and a pulse high-voltage power supply (39); the internal dielectric barrier layer (34) forms a pipeline wall surface, the internal ground electrode (36) is arranged in the pipeline, the internal ground electrode (36) is hollow and is internally provided with the cooling liquid (37), and the external dielectric barrier layer (33) is arranged on an outer wall surface of the internal ground electrode (36); and the external high-voltage electrode (35) is arranged outside the internal dielectric barrier layer (34), and the pulse high-voltage power supply (39) is connected between the external high-voltage electrode (35) and the internal ground electrode (36).

5. The continuous low-temperature plasma powder treatment and ball-milling production device according to claim 1, wherein the controllable atmosphere system (5) comprises a working gas cylinder (51), a pressure-regulating valve (52), a pressure sensor (53), a fourth pneumatic butterfly valve (54) and a dust remover (55); the working gas cylinder (51) is respectively connected to outlet pipelines of the back-blowing system (111) and the negative-pressure fan (110); the dust remover (55) is arranged on a pipeline between the working gas cylinder (51) and the back-blowing system (111); and the pressure-regulating valve (52), the pressure sensor (53) and the pneumatic butterfly valve (54) are arranged on a pipeline between outlets of the working gas cylinder (51) and the negative-pressure fan (110).

6. A use method of the device according to claim 1, wherein the powder circulating and conveying pipeline system (1) circulates and conveys to-be-treated material powder through a controllable gas pressure and a transfer speed; in this process, on one hand, a dielectric barrier discharge structure is introduced into some powder conveying pipelines to form the low-temperature plasma discharge pipeline (3) and to realize plasma discharge treatment on a transfer material powder in the pipeline, and on the other hand, the ball mill (2) is introduced in the powder pipeline conveying process, and the powder subjected to plasma discharge treatment is subjected to ball-milling refining or alloying; a powder transfer speed, a gas pressure and a discharge atmosphere are regulated and controlled by the controllable atmosphere system (5) during the whole process, and the treated material powder enters the vacuum discharging system (4) for recycling and packaging; the powder circulating and conveying pipeline system (1) operates under a negative-pressure condition; the ball mill (2) adopts vibration ball milling or roller ball milling; the low-temperature plasma discharge pipeline (3) utilizes powder conveying pipelines to construct a double-dielectric barrier discharge low-temperature plasma device and is matched with the pulse high-voltage power supply; the controllable atmosphere system (5) is connected to the powder circulating and conveying pipeline system to provide a protective or reaction atmosphere required in a powder treatment and conveying process, thereby achieving the effect of modifying a surface of a processed powder by a plasma through ionized discharge in the low-temperature plasma discharge pipeline; and the atmosphere comprises argon, nitrogen, ammonia, hydrogen or oxygen.

7. The use method of the device according to claim 6, wherein a transfer conveying distance of the material powder in a single circulation ranges from 6 meters to 20 meters, an internal diameter of a circulating pipeline ranges from 35 millimeters to 60 millimeters, a mass ratio of the material powder to the gas ranges from 5:1 to 12:1, a pressure of a transfer gas and a discharge gas ranges from 0.3 bar to 0.1 bar, and a transfer speed of the material powder and the gas ranges from 10 m/s to 15 m/s.

8. The use method of the device according to claim 6, wherein in the powder circulating and conveying pipeline system (1), a powder is fed and enters the feeding bin (11), 10 L to 50 L of powder is fed at one time, the powder automatically enters the temporary storage bin (13) under a working gas protection state through a feeding port of the feeding bin, a gas is subjected to solid-gas separation in the back-blowing system (111), the residual solid material powder enters the material circulating system through the rotary discharging valve (14) and the feeding pipeline (15) and is respectively subjected to mechanical ball milling through the ball mill (2) and passes through the low-temperature plasma discharge pipeline (3) from bottom to top under the action of a specific gas suspension force for surface treatment, then the material powder enters the temporary storage bin (13) and the back-blowing system (111) again for solid-gas separation, and the material powder is subjected to circulating treatment and enters the vacuum discharging system (4) for packaging; the gas separated in the back-blowing system (111) respectively passes through the negative-pressure fan (110), the silencer (19), the pneumatic butterfly valve (18), the regulating gate valve (17) and the pneumatic butterfly valve (16), and pressurized gas is fed to the material circulating system to provide power for the conveying of the material powder; and an inner diameter of the feeding pipeline (15) ranges from 100 millimeters to 180 millimeters, and an inner diameter of other circulating pipelines ranges from 35 millimeters to 60 millimeters.

9. The use method according to claim 6, wherein in the low-temperature plasma discharge pipeline (3), the whole low-temperature plasma discharge pipeline ranges from 2 meters to 5 meters long, the external dielectric barrier layer (33) and the internal dielectric barrier layer (34) are made of a quartz glass material or a high-purity zirconia ceramic material, and a distance between an outer wall of the internal dielectric barrier layer and an inner wall of the external dielectric barrier layer, that is a unilateral distance of the pipeline discharge gap (38) is selected to range from 5 millimeters to 15 millimeters; and a peak-to-peak value of a pulse voltage of a power supply ranges from 20 KV to 40 KV, a discharge frequency valve of the power supply ranges from 10 KHz to 40 KHz, and the cooling liquid (37) is mainly used to cool and protect an electrode material to control a temperature of an electrode system below 150 C.

10. The use method according to claim 6, wherein in the controllable atmosphere system (5), by regulating the pressure of the working gas cylinder, the whole pipeline system is vacuumized, the required gas is replaced and the transfer speed of the material powder is regulated and controlled; and the gas cylinder realizes the work of the back-blowing system (111) in the dust remover (56) by setting a characteristic gas pressure and flow rate.

11. The use method according to claim 7, wherein in the controllable atmosphere system (5), by regulating the pressure of the working gas cylinder, the whole pipeline system is vacuumized, the required gas is replaced and the transfer speed of the material powder is regulated and controlled; and the gas cylinder realizes the work of the back-blowing system (111) in the dust remover (56) by setting a characteristic gas pressure and flow rate.

12. The use method according to claim 8, wherein in the controllable atmosphere system (5), by regulating the pressure of the working gas cylinder, the whole pipeline system is vacuumized, the required gas is replaced and the transfer speed of the material powder is regulated and controlled; and the gas cylinder realizes the work of the back-blowing system (111) in the dust remover (56) by setting a characteristic gas pressure and flow rate.

13. The use method according to claim 9, wherein in the controllable atmosphere system (5), by regulating the pressure of the working gas cylinder, the whole pipeline system is vacuumized, the required gas is replaced and the transfer speed of the material powder is regulated and controlled; and the gas cylinder realizes the work of the back-blowing system (111) in the dust remover (56) by setting a characteristic gas pressure and flow rate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] FIG. 1 is a structural schematic diagram of a low-temperature plasma powder treatment and ball-milling production device according to the present invention;

[0035] FIG. 2 is a structural schematic diagram of a power circulating and conveying pipeline system and a controllable atmosphere system according to the present invention;

[0036] FIG. 3 is a structural schematic diagram of a low-temperature plasma discharge pipeline according to the present invention;

[0037] FIG. 4 is the morphology of Fe powder subjected to low-temperature plasma treatment and ball milling according to Embodiment 1;

[0038] FIG. 5a is a morphology SEM result of WO3-20 wt % C composite powder particles subjected to low-temperature plasma treatment and ball milling according to Embodiment 3;

[0039] FIG. 5b is a DSC result diagram of WO3-20 wt % C composite powder particles subjected to low-temperature plasma treatment and ball milling according to Embodiment 3; and

[0040] FIG. 6 is an SEM result diagram of synthesizing WC after performing heat preservation for 1 hour on WO3-20 wt % C composite powder subjected to low-temperature plasma treatment and ball milling in a vacuum sintering furnace at 1150 C.

[0041] In the drawings: power circulating and conveying pipeline system 1, ball mill 2, low-temperature plasma discharge pipeline 3, vacuum discharge system 4, controllable atmosphere system 5, feeding bin 11, first pneumatic butterfly valve 12, temporary storage bin 13, rotary discharging valve 14, feeding pipeline 15, second pneumatic butterfly valve 16, regulating gate valve 17, third pneumatic butterfly valve 18, silencer 19, negative-pressure fan 110, back-blowing system 111, feeding port 31, discharging port 32, external dielectric barrier layer 33, internal dielectric barrier layer 34, external high-voltage electrode 35, internal ground electrode 36, cooling liquid 37, pipeline discharge gap 38, pulse high-voltage power supply 39, working gas cylinder 51, pressure-regulating valve 52, pressure sensor 53, fourth pneumatic butterfly valve 54, dust remover 55.

DETAILED DESCRIPTION OF EMBODIMENTS

[0042] Specific implementation of the present invention is described below in detail with reference to the accompanying drawings and specific embodiments, but the implementation and protection of the present invention are not limited to this.

[0043] As shown in FIG. 1 to FIG. 3, a continuous low-temperature plasma powder treatment and ball-milling production device includes a powder circulating and conveying pipeline system 1, a ball mill 2, a low-temperature plasma discharge pipeline 3, a vacuum discharge system 4 and a controllable atmosphere system 5, where the powder circulating and conveying pipeline system 1 is sequentially connected to the ball mill 2 and the low-temperature plasma discharge pipeline 3 through pipelines; the low-temperature plasma discharge pipeline 3 is connected to the powder circulating and conveying pipeline system 1; and the controllable atmosphere system 5 is connected to the powder circulating and conveying pipeline system 1. The powder circulating and conveying pipeline system 1 includes a feeding bin 11, a temporary storage bin 13, a feeding pipeline 15, a negative-pressure fan 110 and a back-blowing system 111; the feeding bin 11 is connected to the temporary storage bin 13; a bottom outlet of the temporary storage bin 13 is connected to a vacuum discharging system 4; the back-blowing system 111 is arranged on the temporary storage bin 13; the back-blowing system 111 is connected to the negative-pressure fan 110 through a pipeline; and the negative-pressure fan 110 is sequentially connected to the ball mill 2, the low-temperature plasma discharge pipeline 3 and the temporary storage bin 13 through pipelines. The continuous low-temperature plasma powder treatment and ball-milling production device further includes a first pneumatic butterfly valve 12, a rotary discharging valve 14, a second pneumatic butterfly valve 16, a regulating gate valve 17, a third pneumatic butterfly valve 18 and a silencer 19, where the first pneumatic butterfly valve 12 is arranged between the feeding bin 11 and the temporary storage bin 13; the rotary discharging valve 14 is arranged at a discharging port of the temporary storage bin 13; the silencer 19 is arranged at an outlet of the negative-pressure fan 110; and the third pneumatic butterfly valve 18, the regulating gate valve 17 and the second pneumatic butterfly valve 16 are arranged on a pipeline between the silencer 19 and the ball mill 2. The low-temperature plasma discharge pipeline 3 includes a feeding port 31, a discharging port 32, an external dielectric barrier layer 33, an internal dielectric barrier layer 34, an external high-voltage electrode 35, an internal ground electrode 36, a cooling liquid 37, a pipeline discharge gap 38 and a pulse high-voltage power supply 39, where the internal dielectric barrier layer 34 forms a pipeline wall surface, the internal ground electrode 36 is arranged in the pipeline, the internal ground electrode 36 is hollow and is internally provided with the cooling liquid 37, and the external dielectric barrier layer 33 is arranged on an outer wall surface of the internal ground electrode 36; and the external high-voltage electrode 35 is arranged outside the internal dielectric barrier layer 34, and the pulse high-voltage power supply 39 is connected between the external high-voltage electrode 35 and the internal ground electrode 36. The controllable atmosphere system 5 includes a working gas cylinder 51, a pressure-regulating valve 52, a pressure sensor 53, a pneumatic butterfly valve 54 and a dust remover 55, where the working gas cylinder 51 is respectively connected to outlet pipelines of the back-blowing system 111 and the negative-pressure fan 110; the dust remover 55 is arranged on a pipeline between the working gas cylinder 51 and the back-blowing system 111; and the pressure-regulating valve 52, the pressure sensor 53 and the pneumatic butterfly valve 54 are arranged on a pipeline between outlets of the working gas cylinder 51 and the negative-pressure fan 110.

[0044] Firstly, a material powder is fed into the feeding bin through the powder circulating and conveying pipeline system, more than 10 L of material powder is fed at one time, and the material powder automatically enters the temporary bin under the protection state of argon through the feeding port of the feeding bin for solid-gas separation; the material powder is circulated and conveyed in a specific atmosphere in the system pipeline through negative-pressure conveying, is subjected to mechanical ball milling through the ball mill and passes through the low-temperature plasma discharge pipeline from bottom to top under a specific gas thrust for surface treatment; and after circulating treatment is performed for a certain time, the material powder enters the vacuum discharging system for packaging. During the whole process, the powder flows in the circulating pipeline uniformly in a suspending manner; and in the process of passing through the low-temperature plasma discharge pipeline, all powder particles are completely immersed in the plasma, thereby treating all the powder particles. Secondly, a double-dielectric barrier structure adopted in the present invention can effectively avoid the damage and breakdown of arc discharge to the electrode dielectric layer, can provide a discharge stability, and has high utilization rate of energy density of the plasma. Meanwhile, the peak-to-peak value of the pulse voltage of the power supply is 20 KV to 40 KV, and the discharge frequency valve of the power supply ranges from 10 KHz to 40 KHz, thereby ensuring high discharge energy and avoiding the problem of excessively high heating quantity of the electrode. Finally, according to the present invention, in the low-temperature plasma discharge pipeline, the whole low-temperature plasma discharge pipeline ranges from 2 meters to 5 meters long, the external dielectric barrier layer and the internal dielectric barrier layer are made of a quartz glass material or a high-purity zirconia ceramic material, and a distance between an outer wall of the internal dielectric barrier layer and an inner wall of the external dielectric barrier layer, that is a unilateral distance of the pipeline discharge gap is selected to range from 5 millimeters to 15 millimeters. A pipeline discharge technology of flowing powder is used to achieve a discharge structure of the long-distance and large-area plasma treated powder, which is a key to solving the plasma large-scale preparation or powder treatment.

Embodiment 1

[0045] Step 1: a controllable atmosphere system was started to vacuumize a whole pipeline and a ball-milling cavity to below 1 Pa to be replaced with argon; secondly, a vibration ball mill and a powder circulating and conveying pipeline system were started; and finally, a low-temperature plasma discharge pipeline and a cooling system thereof were started.

[0046] Step 2: 15 kilograms of superfine Fe powder material was fed into a feeding bin at one time and entered a temporary storage bin under the protection state of the argon automatically through a feeding port of the feeding bin, a gas was subjected to solid-gas separation in a back-blowing system, and the residual solid material powder entered a material circulating system through a rotary discharging valve and a feeding pipeline, where an inner diameter of a powder circulating pipeline is 35 millimeters, a mass ratio of the material powder to the gas is 5:1, and a pressure of a transfer gas and a discharge gas is 0.3 bar.

[0047] Step 3: the to-be-treated superfine Fe powder was respectively subjected to mechanical ball milling through a vibration ball mill, passed through the low-temperature plasma discharge pipeline from bottom to top under the action of a specific gas suspension force for surface treatment, and then entered a temporary storage bin and the back-blowing system again for solid-gas separation, and after circulating treatment for a certain time, the material powder enters a vacuum discharging system for packaging, where the vibration ball mill adopts 1400 rpm, a gravitational acceleration of 10 g, an amplitude peak-to-peak value of 15 mm and a ball-to-material ratio of 100:1; in the low-temperature plasma discharge pipeline, a peak-to-peak value of a discharge voltage is 29 kV, a discharge current is 150 mA and a discharge frequency is 15 kHz; and an inner diameter of the feeding pipeline is 100 millimeters.

[0048] The result shows that the transfer speed of the superfine iron powder and the gas may be adjustable from 10 m/s to 13 m/s, and the powder is uniformly dispersed and flows in the pipeline; 8 hours after continuous work, in the low-temperature plasma discharge pipeline, discharge glow maintains a diffuse scattering state, and the temperature of the electrode does not exceed 150 C.; and the temperature of the negative-pressure fan is close to 80 C., and the transfer conveying distance of the material powder in a single circulation is 6 meters. The prepared Fe powder has a sheet-like structure of about 30 microns, as shown in FIG. 4. It shows that the Fe powder with the sheet-like structure can be effectively prepared by coordinating the negative-pressure argon plasma with ball milling, which is mainly because the high discharge intensity of the negative-pressure argon plasma improves the electro-thermal coupling effect, the heat effect of the plasma makes the local temperature of the ball-milled powder higher than the recrystallization temperature of Fe, thermal processing occurs in the ball milling process, and the processing hardening effect is weakened; and the electroplastic effect improves the plasticity of the powder, so that the powder is further extended from a thin block to a thinner sheet, and then is broken and refined into a fine sheet under the action of the strong mechanical force of a grinding ball.

Embodiment 2

[0049] Step 1: a controllable atmosphere system was started to vacuumize a whole pipeline and a ball-milling cavity to below 1 Pa to be replaced with argon; secondly, a powder circulating and conveying pipeline system was started; and finally, a low-temperature plasma discharge pipeline and a cooling system thereof were started.

[0050] Step 2: 15 kilograms of superfine Fe powder material was fed into a feeding bin at one time and entered a temporary storage bin under the protection state of the argon automatically through a feeding port of the feeding bin, a gas was subjected to solid-gas separation in a back-blowing system, and the residual solid material powder entered a material circulating system through a rotary discharging valve and a feeding pipeline, where an inner diameter of a powder circulating pipeline is 60 millimeters, a mass ratio of the material powder to the gas is 12:1, and a pressure of a transfer gas and a discharge gas is 0.1 bar.

[0051] Step 3: the to-be-treated superfine Fe powder respectively passed through a vibration ball mill, passed through the low-temperature plasma discharge pipeline from bottom to top under the action of a specific gas suspension force for surface treatment, and then entered a temporary storage bin and the back-blowing system again for solid-gas separation, and after circulating treatment for a certain time, the material powder enters a vacuum discharging system for packaging, where the vibration ball mill adopts no-load at 0 rpm; in the low-temperature plasma discharge pipeline, a peak-to-peak value of a discharge voltage is 29 kV, a discharge current is 150 mA and a discharge frequency is 15 kHz; and an inner diameter of the feeding pipeline is 180 millimeters.

[0052] The result shows that the transfer speed of the superfine iron powder and the gas may be adjustable from 10 m/s to 15 m/s, and the powder is uniformly dispersed and flows in the pipeline; 8 hours after continuous work, in the low-temperature plasma discharge pipeline, partially filamentary discharge occurs in discharge glow, and the temperature of the electrode does not exceed 150 C.; and the temperature of the negative-pressure fan is less than 70 C., and the transfer conveying distance of the material powder in a single circulation is 20 meters.

[0053] The above treatment only modifies the surface of the superfine Fe powder, and the superfine Fe powder modified by the discharge plasma serves as a main casing metal of a diamond grinding block, so that the wetting state of the diamond on the casing can be obviously improved, the binding strength of the diamond and the casing can be enhanced, and solid-phase sintering of the casing Fe powder can be improved.

Embodiment 3

[0054] Step 1: a controllable atmosphere system was started to vacuumize a whole pipeline and a ball-milling cavity to below 1 Pa to be replaced with argon; secondly, a vibration ball mill and a powder circulating and conveying pipeline system were started; and finally, a low-temperature plasma discharge pipeline and a cooling system thereof were started.

[0055] Step 2: 8 kilograms of WO3 and graphite were mixed according to a carbon proportion of 20 percent by mass, the mixed powder was subjected to pre-ball milling in a vibration ball mill for 1 hour, was fed into a feeding bin at one time and entered a temporary storage bin under the protection state of the argon automatically through a feeding port of the feeding bin, a gas was subjected to solid-gas separation in a back-blowing system, and the residual solid material powder entered a material circulating system through a rotary discharging valve and a feeding pipeline, where an inner diameter of a powder circulating pipeline is 50 millimeters, a mass ratio of the material powder to the gas is 10:1, and a pressure of a transfer gas and a discharge gas is 0.2 bar.

[0056] Step 3: the to-be-treated WO3 and graphite mixed powder was respectively subjected to mechanical ball milling through a vibration ball mill, passed through the low-temperature plasma discharge pipeline from bottom to top under the action of a specific gas suspension force for surface treatment, and then entered a temporary storage bin and the back-blowing system again for solid-gas separation, and after circulating treatment for a certain time, the material powder enters a vacuum discharging system for packaging, where the vibration ball mill adopts 1400 rpm, a gravitational acceleration of 10 g, an amplitude peak-to-peak value of 15 mm and a ball-to-material ratio of 100:1; in the low-temperature plasma discharge pipeline, a peak-to-peak value of a discharge voltage is 29 kV, a discharge current is 150 mA and a discharge frequency is 15 kHz; and an inner diameter of the feeding pipeline is 150 millimeters.

[0057] The result shows that the transfer speed of the WO3-C mixed powder and the gas may be adjustable from 10 m/s to 15 m/s, and the powder is uniformly dispersed and flows in the pipeline; 8 hours after continuous work, in the low-temperature plasma discharge pipeline, discharge glow maintains a diffuse scattering state, and the temperature of the electrode does not exceed 150 C.; and the temperature of the negative-pressure fan is close to 70 C., and the transfer conveying distance of the material powder in a single circulation is 10 meters.

[0058] Through the test on the WO3-20 wt % C composite powder subjected to low-temperature plasma treatment and ball milling by SEM and DSC, it is found that 100 to 200 nm of WO3 is coated with graphite in a uniform scattering manner to form a good interface combination, as shown in FIG. 5a; and the DSC test result shows that the temperature of WO3 and C in-situ reduction reaction is reduced from more than 1000 C. after ordinary ball milling to 900 C., as shown in FIG. 5b. The temperature of the WO3 and C in-situ reduction reaction obviously affects the particle size of the synthesized WC, because the higher the WO3 and C in-situ reduction reaction temperature is, the longer the heat preservation time, and the easier it is to cause WC to grow. Therefore, it is very important to reduce the temperature of the in-situ reduction reaction in order to prepare nanoscale WC powder.

[0059] After the powder is subjected to heat preservation in a 1150 C. vacuum sintering furnace for 1 hour, the grain size of the synthesized WC is 100 nm to 200 nm, as shown in FIG. 6. The preparation of a superfine grain WCCo hard alloy prepared from WO3, C and Co by an in-situ reduction method has the advantages of low price and short process flow, and has an important industrial application value. The key step of preparing the superfine grain WCCo hard ally by the in-situ reduction method is to synthesize the superfine WC powder only containing a single phase because the powder may adsorb oxygen to lose carbon in the ball milling, reaction and sintering processes, resulting in that the carbon ratio is difficult to control. Therefore, the high-performance superfine WC powder can be synthesized by a continuous low-temperature plasma treatment and ball-milling production device.

Embodiment 4

[0060] Step 1: a controllable atmosphere system was started to vacuumize a whole pipeline and a ball-milling cavity to below 1 Pa to be replaced with argon; secondly, a powder circulating and conveying pipeline system was started; and finally, a low-temperature plasma discharge pipeline and a cooling system thereof were started.

[0061] Step 2: 2 kilograms of polyethylene powder material was fed into a feeding bin at one time and entered a temporary storage bin under the protection state of the argon automatically through a feeding port of the feeding bin, a gas was subjected to solid-gas separation in a back-blowing system, and the residual solid material powder entered a material circulating system through a rotary discharging valve and a feeding pipeline, where an inner diameter of a powder circulating pipeline is 60 millimeters, a mass ratio of the material powder to the gas is 5:1, and a pressure of a transfer gas and a discharge gas is 0.3 bar.

[0062] Step 3: the to-be-treated polyethylene powder respectively passed through a vibration ball mill, passed through the low-temperature plasma discharge pipeline from bottom to top under the action of a specific gas suspension force for surface treatment, and then entered a temporary storage bin and the back-blowing system again for solid-gas separation, and after circulating treatment for a certain time, the material powder enters a vacuum discharging system for packaging, where the vibration ball mill adopts no-load at 0 rpm; in the low-temperature plasma discharge pipeline, a peak-to-peak value of a discharge voltage is 20 kV, a discharge current is 100 mA and a discharge frequency is 11 KHz; and an inner diameter of the feeding pipeline is 180 millimeters.

[0063] The result shows that the transfer speed of the graphite powder and the gas may be adjustable from 10 m/s to 15 m/s, and the powder is uniformly dispersed and flows in the pipeline; 8 hours after continuous work, in the low-temperature plasma discharge pipeline, partially filamentary discharge occurs in discharge glow, and the temperature of the electrode does not exceed 150 C.; and the temperature of the negative-pressure fan is less than 70 C., and the transfer conveying distance of the material powder in a single circulation is 10 meters.

[0064] The above treatment only modifies the surface of the polyethylene powder, the wettability of the polyethylene powder modified by the discharge plasma in deionized water is obviously improved, all the untreated polyethylene powder is basically suspended on a water surface, and most of the polyethylene powder subjected to plasma treatment can be rapidly settled in the deionized water. The experimental process achieves the same effect in the surface treatment process of graphite powder.