DEVICE FOR RAPIDLY PREPARING BETA-Si3N4 BY GAS-SOLID REACTION, AND METHOD THEREOF

Abstract

A device for rapidly preparing β-Si3N4 by gas-solid reaction and a method thereof, and relates to the technical field of recycling and reuse of waste fine silicon powder. The bottom of a stock bin communicates with a first opening and closing passage, a first connection passage, and the top of a first transitional bin; the bottom of the first transitional bin communicates with the first opening and closing passage, a second connection passage, and the top of a reaction bin; the bottom of the reaction bin communicates with a second opening and closing passage, the first connection passage, and the top of a second transitional bin; the bottom of the second transitional bin communicates with the top of a conveying passage through the first opening and closing passage; a material outlet of the conveying bin communicates with the collection bin.

Claims

1. A device for rapidly preparing β-Si.sub.3N.sub.4 by gas-solid reaction, comprising a stock bin (1), a first transitional bin (2), a reaction bin (3), a second transitional bin (4), a conveying bin (5), and a collection bin (6), wherein the bottom of the stock bin (1) communicates with a first opening and closing passage (7), a first connection passage (8), and the top of the first transitional bin (2) in sequence; the bottom of the first transitional bin (2) communicates with the first opening and closing passage (7), a second connection passage (9), and the top of the reaction bin (3) in sequence; the bottom of the reaction bin (3) communicates with a second opening and closing passage (10), the first connection passage (8), and the top of the second transitional bin (4) in sequence; the bottom of the second transitional bin (4) communicates with the top of the conveying bin (5) through the first opening and closing passage (7); a material outlet of the conveying bin (5) communicates with the collection bin (6); the first connection passage (8) is a hollow pipeline and is provided with a pressure gauge (11), a vacuum pump (12), and a gas inlet (17) on a side wall; the second connection passage (9) is a hollow pipeline and is provided with a pressure gauge (11) and a pressure exhaust valve (13) on a side wall; and a gas intake pipeline (14) is arranged in the middle of the second opening and closing passage (10).

2. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 1, wherein the first opening and closing passage (7) is composed of a first passage pipe (701), a fan blade fixing piece (702), a first fan blade (703), and a transmission pair (704); the ringlike fan blade fixing piece (702) is fixed inside the first passage pipe (701); three or more first fan blades (703) are provided; one end of each first fan blade (703) is hinged to the fan blade fixing piece (702), and the bottom of the other end of the first fan blade (703) is connected with a driven wheel (706) of the transmission pair (704) through a rotating shaft (705); the driven wheel (706) is sleeved in the first passage pipe (701); the driven wheel (706) is engaged with a driving wheel (707); the driving wheel (707) is rotatably arranged in a side wall of the first passage pipe (701); one side of the driving wheel (707) is provided with a rotating handle (708); and a free end of the rotating handle (708) is located on the outer side of the first passage pipe (701).

3. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 1, wherein the second opening and closing passage (10) is composed of a second passage pipe (1001), a fan blade fixing piece (702), a second fan blade (1002), and a transmission pair (704); the ringlike fan blade fixing piece (702) is fixed inside the second passage pipe (1001); three or more second fan blades (1002) are provided; one end of each second fan blade (1002) is hinged to the fan blade fixing piece (702), and the bottom of the other end of the second fan blade (1002) is connected with a driven wheel (706) of the transmission pair (704) through a rotating shaft (705); the driven wheel (706) is sleeved in the second passage pipe (1001); the driven wheel (706) is engaged with a driving wheel (707); the driving wheel (707) is rotatably arranged in a side wall of the second passage pipe (1001); one side of the driving wheel (707) is provided with a rotating handle (708); a free end of the rotating handle (708) is located on the outer side of the second passage pipe (1001); the gas intake pipeline (14) is composed of a gas intake pipe (1401) and a gas sprayer (1402); one end of the gas intake pipe (1401) passes through the side wall of the second passage pipe (1001) and is connected with a gas intake device, and the other end of the gas intake pipe (1401) is connected with the gas sprayer (1402); the gas sprayer (1402) is located at the bottom of the reaction bin (3); and the second fan blade (1002) is in close contact with the outer side wall of the gas intake pipe (1401) at the lower part of the gas sprayer (1402) after being closed.

4. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 1, wherein a transfer guide plate (901) is arranged on the inner side of the top of the second connection passage (9), and a rotating chute (902) is arranged below the transfer guide plate (901).

5. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 1, wherein the reaction bin (3) is composed of a heating furnace tube (301), a heat insulation layer (302), a shell (303), a microwave generator (304), and a temperature measurement device (305); the heating furnace tube (301) communicates with the second opening and closing passage (10); a space between the shell (303) and the heating furnace tube (301) is filled with a heat insulation layer (302); and the microwave generator (304) and the temperature measurement device (305) are distributed on the shell (303).

6. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 5, wherein three rows of the microwave generators (304) are uniformly disposed along a height direction of the heating furnace tube (301); in each row, three microwave generators are uniformly distributed along a radial direction of the heating furnace tube (301); and three temperature measurement devices (305) are uniformly provided along the height direction of the heating furnace tube (301).

7. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 3, wherein the second transitional bin (4) is composed of an inner pipe (401) and an outer pipe (402) which are coaxially disposed; the gas intake pipe (1401) is wound on the outer side wall of the inner pipe (401); a gap formed by the outer side wall of the inner pipe (401) and the inner side wall of the outer pipe (402) is filled with a heat insulation material (15) to preheat gas in the gas intake pipe (1401).

8. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 1, wherein the conveying bin (5) is L-shaped, a horizontal section of which is internally provided with a transfer screw rod (501); one end of the transfer screw rod (501) is connected with a motor (502); and the collection bin (6) is arranged below the other end of the transfer screw rod (501).

9. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to claim 8, wherein a water cooling device (16) is arranged on the outer side wall of the horizontal section of the conveying bin (5).

10. The device for rapidly preparing the β-Si.sub.3N.sub.4 by gas-solid reaction according to any one of claims 1 to 9, wherein a method of the device for producing β-Si.sub.3N.sub.4 is as follows: 1) opening the first opening and closing passage (7) between the stock bin (1) and the first transitional bin (2) so that waste fine silicon powder enters the first transitional bin (2), closing the first opening and closing passage (7), vacuumizing the first transitional bin (2), filling the vacuumized first transitional bin with pure N.sub.2, and maintaining the pressure at 0.1 MPa to 0.3 MPa; 2) opening the first opening and closing passage (7) between the first transitional bin (2) and the reaction bin (3) so that the waste fine silicon powder enters the reaction bin (3), spraying at least one of N.sub.2 and NH.sub.3 by the gas intake pipeline (14), synchronously heating reactants at a temperature rise rate of 100° C./min, maintaining the temperature for 5 to 20 min when the temperature in the reaction bin (3) reaches 1250+/−100° C., and maintaining the gas pressure in the reaction bin (3) at 0.1 MPa to 0.3 MPa; 3) in the reaction process, synchronously vacuumizing the second transitional bin (4), then filling the vacuumized second transitional bin with the pure Na, and maintaining the pressure at 0.1 MPa to 0.3 MPa; after the reaction ends, opening the second opening and closing passage (10) between the reaction bin (3) and the second transitional bin (4); and after reaction products enter the second transitional bin (4), opening the first opening and closing passage (7) between the second transitional bin (4) and the conveying bin (5) so that the reaction products enter, through the conveying bin (5), the collection bin (6) for collection and storage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic structural diagram of the present disclosure.

[0033] FIG. 2 is a schematic structural diagram of a reaction bin of the present disclosure.

[0034] FIG. 3 is a schematic structural diagram of a first opening and closing passage in the present disclosure.

[0035] FIG. 4 is a schematic diagram of an opened/closed state a first opening and closing passage in the present disclosure.

[0036] FIG. 5 is a schematic structural diagram of a second opening and closing passage in the present disclosure.

[0037] FIG. 6 is a schematic diagram of an opened/closed state a second opening and closing passage in the present disclosure.

[0038] FIG. 7 is a schematic structural diagram of a first connection passage in the present disclosure.

[0039] FIG. 8 is a schematic structural diagram of a second connection passage in the present disclosure.

[0040] FIG. 9 is a schematic structural diagram of a second transitional bin in the present disclosure.

[0041] FIG. 10 is a diagram of a macro appearance of a β-Si.sub.3N.sub.4 material prepared in the present disclosure.

[0042] FIG. 11 is a diagram of a micro appearance of a β-Si.sub.3N.sub.4 material prepared in the present disclosure.

[0043] In the drawings: 1: stock bin; 2: first transitional bin; 3: reaction bin; 301: heating furnace tube; 302: heat insulation layer; 303: shell; 304: microwave generator; 305: temperature measurement device; 4: second transitional bin; 401: inner pipe; 402: outer pipe; 5: conveying bin; 501: transfer screw rod; 502: motor; 6: collection bin; 7: first opening and closing passage; 701: first passage pipe; 702: fan blade fixing piece; 703: first fan blade; 704: transmission pair; 705: rotating shaft; 706: driven wheel; 707: driving wheel; 708: rotating handle; 8: first connection passage; 9: second connection passage; 901: transfer guide plate; 902: rotating chute; 10: second opening and closing passage; 1001: second passage pipe; 1002: second fan blade; 11: pressure gauge; 12: vacuum pump; 13: pressure exhaust valve; 14: gas intake pipeline; 1401: gas intake pipe; 1402: gas sprayer; 15: heat insulation material; 16: water cooling device; 17: gas inlet.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to make the objectives, technical solutions, and advantages of the present disclosure clearer, the invention is further described below in detail with reference to accompanying drawings and embodiments. It should be understood that the specific embodiments described here are merely to explain the present invention, and not intended to limit the present disclosure.

[0045] FIG. 1 illustrates a device for rapidly preparing β-Si.sub.3N.sub.4 by gas-solid reaction. The device includes a stock bin 1, a first transitional bin 2, a reaction bin 3, a second transitional bin 4, a conveying bin 5, and a collection bin 6. The bottom of the stock bin 1 communicates with a first opening and closing passage 7, a first connection passage 8, and the top of the first transitional bin 2 in sequence; the bottom of the first transitional bin 2 communicates with the first opening and closing passage 7, a second connection passage 9, and the top of the reaction bin 3 in sequence; the bottom of the reaction bin 3 communicates with a second opening and closing passage 10, the first connection passage 8, and the top of the second transitional bin 4 in sequence; the bottom of the second transitional bin 4 communicates with the top of the conveying passage 5 through the first opening and closing passage 7; and a material outlet of the conveying bin 5 communicates with the collection bin 6. As shown in FIG. 7, the first connection passage 8 is a hollow pipeline and is provided with a pressure gauge 11, a vacuum pump 12, and a gas inlet 17 on a side wall. As shown in FIG. 8, the second connection passage 9 is a hollow pipeline and is provided with a pressure gauge 11 and a pressure exhaust valve 13 on a side wall; and a gas intake pipeline 14 is arranged in the middle of the second opening and closing passage 10. For the convenience of transfer, a transfer guide plate 901 is arranged on the inner side of the top of the second connection passage 9, and a rotating chute 902 is arranged below the transfer guide plate 901.

[0046] The conveying bin 5 is L-shaped, a horizontal section of which is internally provided with a transfer screw rod 501; one end of the transfer screw rod 501 is connected with a motor 502; and the collection bin 6 is arranged below the other end of the transfer screw rod 501. To further cool a silicon nitride product, a water cooling device 16 is arranged on the outer side wall of the horizontal section of the conveying bin 5.

[0047] The stock bin 1 has a conical top. To realize automatic feeding, a feeding belt conveyor is arranged above it. For the convenience of opening and closing of the first opening and closing passage 7, as shown in FIG. 3, the first opening and closing passage 7 is composed of a first passage pipe 701, a fan blade fixing piece 702, a first fan blade 703, and a transmission pair 704; the ringlike fan blade fixing piece 702 is fixed inside the first passage pipe 701; three first fan blades 703 are provided; one end of each first fan blade 703 is hinged to the fan blade fixing piece 702, and the bottom of the other end of the first fan blade is connected with a driven wheel 706 of the transmission pair 704 through a rotating shaft 705; and the rotating shaft 705 passes through a sliding chute arranged on the fan blade fixing piece 702. The transmission pair 704 here can select mutually perpendicular bevel gears. The rotating shaft 705 is connected with the driven wheel 706 in the transmission pair 704; the driven wheel 706 is sleeved in the first passage pipe 701 and is engaged with a driving wheel 707; the driving wheel 707 is rotatably arranged in a side wall of the first passage pipe 701; one side of the driving wheel 707 is provided with a rotating handle 708; and a free end of the rotating handle 708 is located on the outer side of the first passage pipe 701.

[0048] As shown in FIG. 4, under the action of an external force, the rotating handle 708 rotates, and the driving wheel 707 drives the driven wheel 706 to rotate. The driven wheel 706 drives the rotating shaft 705 to rotate. The first fan blade 703 rotates with the rotating shaft 705 around a position where the other end is hinged to the fan blade fixing piece 702, thus realizing opening and closing of the first fan blade 703.

[0049] Similarly, as shown in FIG. 5, the second opening and closing passage 10 is composed of a second passage pipe 1001, a fan blade fixing piece 702, a second fan blade 1002, and a transmission pair 704; the ringlike fan blade fixing piece 702 is fixed inside the second passage pipe 1001; three first fan blades 1002 are provided; one end of each second fan blade 1002 is hinged to the fan blade fixing piece 702, and the bottom of the other end of the second fan blade is connected with a driven wheel 706 of the transmission pair 704 through a rotating shaft 705; and the rotating shaft 705 passes through a sliding chute arranged on the fan blade fixing piece 702. The transmission pair 704 here can select mutually perpendicular bevel gears. The rotating shaft 705 is connected with the driven wheel 706 in the transmission pair 704; the driven wheel 706 is sleeved in the second passage pipe 1001 and is engaged with a driving wheel 707; the driving wheel 707 is rotatably arranged in a side wall of the second passage pipe 1001; one side of the driving wheel 707 is provided with a rotating handle 708; and a free end of the rotating handle 708 is located on the outer side of the second passage pipe 1001.

[0050] The gas intake pipeline 14 is composed of a gas intake pipe 1401 and a gas sprayer 1402; one end of the gas intake pipe 1401 passes through the side wall of the second passage pipe 1001 and is connected with a gas intake device, and the other end of the gas intake pipe 1401 is connected with the gas sprayer 1402; the gas sprayer 1402 is located at the bottom of the reaction bin 3; and the second fan blade 1002 is in close contact with the outer side wall of the gas intake pipe 1401 at the lower part of the gas sprayer 1402 after being closed. To prevent the gas sprayer 1402 from being blocked, the gas sprayer 1402 is a triangular pyramid or conical, in which three or more gas spray passages are arranged. The tail ends of the gas spray passages are horizontal so that the gas is sprayed out from a horizontal direction to prevent the power generated by the reaction from blocking the gas sprayer 1402.

[0051] As shown in FIG. 6, under the action of an external force, the rotating handle 708 rotates, and the driving wheel 707 drives the driven wheel 706 to rotate. The driven wheel 706 drives the rotating shaft 705 to rotate. The second fan blade 1002 rotates with the rotating shaft 705 around a position where the other end is hinged to the fan blade fixing piece 702, thus realizing opening and closing of the second fan blade 1002.

[0052] To further increase the reaction rate and reduce the reaction temperature, as shown in FIG. 2, the reaction bin 3 is composed of a heating furnace tube 301, a heat insulation layer 302, a shell 303, a microwave generator 304, and a temperature measurement device 305; the heating furnace tube 301 communicates with the second opening and closing passage 10; a space between the shell 303 and the heating furnace tube 301 is filled with a heat insulation layer 302; and the microwave generator 304 and the temperature measurement device 305 are distributed on the shell 303. To make the heating more uniform and the temperature control more accurate, three rows of the microwave generators 304 are uniformly disposed along a height direction of the heating furnace tube 301; and in each row, three microwave generators are uniformly distributed along a radial direction of the heating furnace tube 301. Three temperature measurement devices 305 that use infrared thermometers are uniformly disposed along the height direction of the heating furnace tube 301. The height is consistent with that of the temperature measurement device 305.

[0053] To further use the high-temperature waste heat of the reacted silicon nitride, as shown in FIG. 9, the second transitional bin 4 is composed of an inner pipe 401 and an outer pipe 402 which are coaxially disposed; the gas intake pipe 1401 is wound on the outer side wall of the inner pipe 401; a gap formed by the outer side wall of the inner pipe 401 and the inner side wall of the outer pipe 402 is filled with a heat insulation material 15.

[0054] A specific method for preparing β-Si.sub.3N.sub.4 by using the above device is as follows:

[0055] 1) The rotating handle 708 is rotated to open the first opening and closing passage 7 between the stock bin 1 and the first transitional bin 2 so that waste fine silicon powder enters the first transitional bin 2 under the action of gravity. The first transitional bin 2 is a hollow pipeline, and the first opening and closing passage 7 is closed. The vacuum pump 12 on the first connection passage 8 is turned on to firstly vacuumize the first transitional bin. After the vacuumizing is completed, the vacuum pump 12 is turned off, and the first transitional bin is then filled with pure N.sub.2 from the gas inlet 17. The pressure in the first transitional bin 2 is maintained at 0.1 MPa to 0.3 MPa. The first transitional bin 2 may be made of a transparent quartz glass tube so that the volume of a material inside can be directly observed. By means of the above step, foreign gas, particularly oxygen, in the waste fine silicon powder can be removed to keep the waste fine silicon powder pure and to also make the pressures in the first transitional bin 2 and the reaction bin 3 balanced.

[0056] 2) The rotating handle 708 is rotated to open the first opening and closing passage 7 between the first transitional bin 2 and the reaction bin 3 so that waste fine silicon powder enters the reaction bin 3. The material enters the rotating chute via the transfer guide plate and is uniformly distributed in the heating furnace tube 301 of the reaction bin 3. The heating furnace tube 301 uses an alundum tube, and the external heat insulation layer is filled by polycrystalline mullite fibers. The temperature measurement device 305 uses an infrared thermometer.

[0057] The gas intake pipeline at the bottom sprays N.sub.2 and NH.sub.3 mixed gas. N.sub.2 and NH.sub.3 are mixed according to a ratio of 3:1 and are blown into the heating furnace tube 301 at a speed of 0.4 m/s so that the waste fine silicon powder is suspended and forms a vortex flow. After the waste fine silicon powder all enters the reaction bin 3, the first opening and closing passage 7 between the first transitional bin 2 and the reaction bin 3 is closed, and the microwave generator 304 is synchronously turned on to heat the reactant at a temperature rise rate of 100° C./min. When the temperature in the reaction bin 3 reaches 1250+/−100° C., this temperature is maintained for 5 to 20 min. The gas pressure in the reaction bin 3 is maintained at 0.1 MPa to 0.3 MPa. Redundant gas is discharged through the pressure exhaust valve 13 and is then recycled.

[0058] 3) In the reaction process, the second transitional bin 4 is synchronously vacuumized firstly and is then filled with the pure N.sub.2, and the pressure is maintained at 0.1 MPa to 0.3 MPa. After the reaction of the material in the reaction bin 3 ends, the second opening and closing passage 10 between the reaction bin 3 and the second transitional bin 4 is opened. After a reaction product enters the second transitional bin 4, the second opening and closing passage 10 is closed. The first opening and closing passage 7 between the second transitional bin 4 and the conveying bin 5 is opened, and the reaction product, i.e., silicon nitride, enters, through the conveying bin 5, enters the collection bin 6 for collection and storage.

[0059] After the waste fine silicon powder all enters the reaction bin 3, the first opening and closing passage 7 between the stock bin 1 and the first transitional bin 2 is opened again, and the waste fine silicon powder enters the first transitional bin 2 under the action of gravity. The first transitional bin is firstly vacuumized and is then filled with the N.sub.2. The steps 1) to 3) are repeated. After the waste fine silicon powder enters the second transitional bin 4 from the reaction bin 3, the next batch of waste fine silicon powder enters the reaction bin 3 from the first transitional bin 2, and at the same time, another batch of waste fine silicon powder enters the first transitional bin 2 from the stock bin 1. In this way, continuous production of the β-Si.sub.3N.sub.4 is realized.

[0060] The silicon powder is heated to 1250° C. under the nitrogen pressure of 121 kPa and is then maintained for 20 min, which achieves a good nitriding effect, and the transformation rate of the nitridation reaction can be up to 97.96%. Products mainly include uniformly shaped and columnar β-Si.sub.3N.sub.4, as shown in FIG. 10 and FIG. 11. Compared with a traditional preparation method, this method has the advantages that the nitridation reaction time is shortened by 77.7% or above, the energy consumption is reduced by 88.6%, and the preparation efficiency of Si.sub.3N.sub.4 is improved.

[0061] Although the present disclosure has been described with reference to a number of explanatory embodiments of the present disclosure, it should be understood that many other modifications and implementation modes can be devised by those skilled in the art. These modifications and implementation modes will fall within the scope and spirit of principles of the disclosure of the present application. More specifically, within the scope of the disclosure, drawings, and claims of the present application, various variations and improvements can be made to the component parts or the layout. In addition to the variations and improvements of the component parts or the layout, other uses will also be obvious to those skilled in the art.