Porous metal-based material grinding and polishing air floating main shaft and porous metal-based material preparation method

Abstract

The invention discloses a porous metal-based material grinding and polishing air floating spindle and a metal-based material preparation method, the grinding and polishing air floating spindle comprises a spindle rotating body and a spindle fixing piece, and the spindle rotating body comprises a thrust plate and a supporting shaft; the main shaft fixing piece at least comprises a motor cooling sleeve, and a stator outer shaft sleeve, a thrust bearing pad, a radial bearing and a thrust bearing seat which are sleeved on the outer surface of the motor cooling sleeve; a water channel is arranged between the motor cooling sleeve and the stator outer shaft sleeve. The radial bearing is clamped between the supporting shaft and the thrust bearing seat, and a radial bearing gap is formed between the radial bearing and the supporting shaft; the thrust bearing pad is arranged in a groove of the thrust bearing seat, and a thrust plate gap is formed between the thrust bearing pad and the thrust plate; and the thrust bearing pad and the radial bearing are made of a porous metal-based material. Surface grooving machining is omitted, self-excited vibration caused by cyclone of compressed air in a groove and unsmooth exhaust is avoided, and the porous metal-based material can prevent upper and lower thrust surfaces from being scratched or even locked due to falling of particles on the surface of the bearing pad.

Description

Technical Field

[0001] The invention relates to the technical field of grinding and polishing air-floating spindles, and in particular to a porous metal-based material grinding and polishing air-floating spindle and a method for preparing the porous metal-based material used in the grinding and polishing air-floating spindle. Background Art

[0002] The grinding and polishing air-floating spindle is an advanced technology involving the field of high-speed precision machining. The grinding and polishing air-floating spindle is mainly composed of motors, air-floating bearings, grinding wheel connectors and other parts. The motor rotor and the air-floating bearing are connected by screws, and the integrated design increases the stability of both. Due to the low kinematic viscosity of the gas, when the spindle rotates at high speed, the compressed gas forms a certain thickness of air film between the upper and lower thrust bearings and the graphite material, and the friction coefficient is low, which makes it have the advantages of high precision, low heat generation, no wear, and no pollution.

[0003] A wafer thinning machine is a device commonly used for grinding and thinning semiconductor materials with ultra-high precision. Before semiconductor integrated circuit packaging, the wafer thinning machine is responsible for removing excess substrate material behind the wafer to achieve the required thickness under working conditions. This step helps to make subsequent packaging more difficult, improve chip heat dissipation efficiency, reduce internal stress, and improve electrical performance. As the core component of the wafer thinning machine, the air-floating spindle consists of a water-cooled motor and an air-floating bearing. The air-floating bearing is driven to rotate by the motor, which plays a vital role in the wafer thinning process.

[0004] The design and material selection of thrust pads for grinding and polishing air bearings are important links in the stability of the spindle. If the design and material selection are unreasonable, pore blockage, uneven thickness of the air film, spindle locking, etc. are prone to occur, affecting the stability of the spindle. The existing grinding and polishing air bearing spindle mainly uses graphite small hole throttling, graphite open ring grooves and other methods to ventilate the internal structure. The structure is complex and the process requirements are high. In particular, the size of the air supply pores and the depth of the graphite ring groove have a great impact on the spindle. If the design is unreasonable or there is negligence in the process processing, the spindle is very likely to have pore blockage, locking, etc. Summary of the invention

[0005] The present invention aims to provide a porous metal-based material polishing air-floating spindle and a method for preparing the porous metal-based material. The graphene / bronze material porous bearing is used to replace the graphite bearing. Compared with the small-hole throttling graphite, the ventilation area is wider and the air film is more uniform; there is no need for an open-ring groove on the surface, and the probability of particle accumulation inside the bearing is lower, thereby avoiding spindle locking.

[0006] In order to achieve the above-mentioned object, according to one aspect of the present invention, there is provided an air-floating spindle for polishing porous metal-based materials, the air-floating spindle for polishing porous metal-based materials comprising a spindle rotating body and a spindle fixing member, the spindle rotating body at least comprising a thrust plate and a support shaft;

[0007] The spindle fixing member at least comprises a motor cooling sleeve, a stator outer sleeve, a thrust bearing pad, a radial bearing and a thrust bearing seat; the outer surface of the motor cooling sleeve is sleeved with a stator outer sleeve, and a water channel is also arranged between the motor cooling sleeve and the stator outer sleeve;

[0008] The radial bearing is clamped between the support shaft and the thrust bearing seat, and there is a radial bearing gap between the radial bearing and the support shaft; the thrust bearing pad is arranged in the groove of the thrust bearing seat, and there is a thrust plate gap between the thrust bearing and the thrust plate; wherein the thrust bearing pad and the radial bearing are porous metal-based materials.

[0009] Compared with the existing small-hole throttling air-floating bearing structure, the structure of the present invention eliminates the processing techniques of processing small holes and bearing pad grooving. Due to the comprehensive air permeability of the porous metal-based material, the air film in the bearing gap is more uniform and stable, reducing the possibility of locking caused by the shedding and accumulation of particles on the thrust bearing pad, which causes the friction between the upper and lower thrust plates and the self-excited vibration of the main shaft.

[0010] In one embodiment, a water inlet and a water outlet are respectively provided on the stator outer sleeve, the water outlet is located above the stator outer sleeve, and the water inlet is located below the stator outer sleeve; the water channel arranged between the motor cooling sleeve and the stator outer sleeve is a spiral water channel, and the spiral water channel is respectively connected to the water inlet and the water outlet.

[0011] In one embodiment, the thrust plate includes an upper thrust plate and a lower thrust plate, and a groove is respectively arranged on the upper and lower surfaces of the thrust bearing seat, and the two thrust bearing pads are respectively installed in the two grooves of the thrust bearing seat, and there is a thrust plate gap between the two thrust bearing pads and the upper thrust plate and the lower thrust plate.

[0012] In one embodiment, the thrust bearing seat is provided with an air inlet hole, and an air inlet pipe joint is installed in the air inlet hole. A plurality of air channels are also arranged inside the thrust bearing seat, and the plurality of air channels include at least two axial air supply loops and one radial air supply loop. The axial air supply loop supplies air to the two thrust bearing pads respectively, and the radial air supply loop supplies air to the radial bearing.

[0013] In one embodiment, the thrust bearing seat is further provided with an exhaust hole, and the gas is discharged from the grinding and polishing air-floating spindle through the exhaust hole and the gap between the thrust plate.

[0014] In one embodiment, the spindle fixing member also includes a motor end cover fixed to the motor cooling sleeve and the end of the stator outer sleeve, a motor top cover plate and a motor cover ring fixed to the motor end cover, and a motor stator arranged in the inner cavity of the motor cooling sleeve.

[0015] In one embodiment, the spindle rotating body also includes a motor rotor fixedly connected to the upper thrust plate, a motor rotor shaft arranged at the center of the motor rotor, a sensor light shielding plate placed on the top of the motor rotor, a grinding wheel connecting plate arranged at the bottom of the lower thrust plate, and a front end cover fixedly connected to the grinding wheel connecting plate, and a front end plug is also installed on the front end cover.

[0016] In one embodiment, the porous metal-based material is a graphene / bronze composite material.

[0017] In one embodiment, the graphene / bronze composite material is prepared by chemical vapor deposition of bronze powder and acetylene gas.

[0018] The present invention also provides a method for preparing a porous metal-based material used for the porous metal-based material grinding and polishing air-floating spindle, the method comprising:

[0019] High-purity bronze powder with a particle size of 5-8 μm is evenly filled into a cylindrical mold;

[0020] The bronze powder is placed under a pressure of 150 MPa±2 MPa for 10 minutes and is cold isostatically pressed to obtain a three-dimensional porous bronze blank;

[0021] A certain flow of C2H2 is introduced into a high-temperature tube furnace as a carbon source, and three-dimensional continuous graphene is obtained on the surface of the porous bronze skeleton through a two-step chemical vapor deposition method.

[0022] Preferably, C2H2 gas is introduced into the high temperature tube furnace at a flow rate of 4 ml / min.

[0023] Specifically, hydrogenated graphite is first obtained by chemical vapor deposition at a low temperature of 200°C for 10 minutes; then the obtained hydrogenated graphite is placed in an environment of 650-680°C for high-temperature pyrolysis for 3-5 hours to be converted into graphene, for example, high-temperature pyrolysis at 660°C.

[0024] While hydrogenated graphite is cracked and converted into graphene at high temperature, bronze powder is sintered to form a continuous skeleton. Three-dimensional continuous graphene is formed on the skeleton surface of porous bronze, thereby obtaining a graphene / bronze-based porous composite material with a certain strength, completing the preparation of the graphene / bronze composite material.

[0025] Beneficial effects of the present invention:

[0026] The present invention uses porous metal-based materials as thrust bearing pads, and the air-floating bearing has a wider air permeability area, which avoids the situation where the spindle is locked due to the blockage of small holes; compared with small-hole throttling graphite, the porous material eliminates the surface grooving process, avoiding the self-excited vibration caused by the cyclone of compressed air in the groove and the poor exhaust. The porous metal-based material is stronger than graphite, which prevents the particles on the surface of the bearing pad from falling off and causing scratches on the upper and lower thrust surfaces or even locking. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the porous metal-based material grinding and polishing air flotation spindle of the present invention.

[0028] Figure 2 It is a schematic diagram of the exhaust system structure of the porous metal-based material grinding and polishing air flotation spindle of the present invention.

[0029] Figure 3 It is a schematic diagram of the thrust bearing pad structure of the porous metal-based material grinding and polishing air-floating spindle of the present invention.

[0030] Figure 4 It is a schematic diagram of the radial bearing structure of the porous metal-based material grinding and polishing air-floating spindle of the present invention.

[0031] In the figure: 1-motor cooling jacket, 2-motor end cover, 3-sensor fixing plate, 4-motor top cover, 5-motor cover ring, 6-sensor light shielding plate, 7-motor rotor shaft, 8-motor rotor, 9-motor stator, 10-stator outer shaft sleeve, 11-upper thrust plate, 12-intake pipe joint, 13-lower thrust plate, 14-front end cover, 15-front end plug, 16-grinding wheel connecting plate, 17-thrust bearing pad, 18-radial bearing, 19-support shaft, 20-thrust bearing seat, W1-water inlet, W2-water outlet. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of this application clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] Embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The terms "first", "second", "third", etc. (if any) in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the objects described in this way can be interchanged where appropriate. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. The directional terms mentioned in the present invention, such as: up, down, left, right, front, back, inside, outside, side, etc., are only reference directions of the accompanying drawings. The embodiments described below by reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention. In addition, the present invention repeats reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but a person of ordinary skill in the art can recognize the application of other processes and / or the use of other materials.

[0034] The present invention provides a porous metal-based material polishing air-floating spindle, which uses the effect of gas pressure to support and drive the spindle. By accurately controlling the flow and drive of the gas, a uniform air film is formed between the upper and lower thrust plates and the bearing seat of the spindle. This air film not only supports the spindle, but also avoids problems such as friction and noise. Part of the excess gas is discharged from the outer side, and part is discharged from the inside of the support shaft through the exhaust hole.

[0035] The porous metal-based polishing air bearing of the present invention uses gas as a lubricating medium, has the characteristics of low friction coefficient, small friction resistance, and good high-speed performance, can avoid the loss of bearings under conditions of friction, heat, etc., and has the advantages of long service life and strong adaptability. The reason why the thrust bearing pad and the radial bearing are made of porous metal-based materials is that the surface of the porous metal-based material can be regarded as forming countless small hole throttling. The surface of the porous material conforms to the law of small hole throttling, and its interior still conforms to Darcy's law. Due to machining and other reasons, the dense layer is thicker, like a collection of countless capillaries, and when the gas passes through the dense layer, it is similar to flowing through capillaries. Therefore, it can be achieved that there is no need for an open ring groove on the surface, the probability of particle accumulation inside the bearing is lower, and the effect of avoiding spindle locking can be achieved.

[0036] like Figures 1 to 4 As shown, the porous metal-based material grinding and polishing air-floating spindle of the present invention includes two major parts: a spindle rotating body and a spindle fixing part. The spindle rotating body at least includes a thrust plate and a support shaft 19, and the spindle fixing part at least includes a motor cooling sleeve 1, a stator outer sleeve 10, a thrust bearing pad 17, a radial bearing 18 and a thrust bearing seat 20.

[0037] Specifically, the outer surface of the motor cooling jacket 1 is sleeved with a stator outer shaft sleeve 10, and a water channel is further arranged between the motor cooling jacket 1 and the stator outer shaft sleeve 10. Preferably, the water channel is a spiral water channel, arranged from bottom to top.

[0038] The stator outer sleeve 10 is provided with a water inlet W1 and a water outlet W2, the water outlet W2 is located above the stator outer sleeve 10, and the water inlet W1 is located below the stator outer sleeve 10. The spiral water channel is provided between the motor cooling jacket 1 and the stator outer sleeve 10, and the spiral water channel is connected with the water inlet W1 and the water outlet W2 respectively.

[0039] Optionally, a spiral groove is provided on the outer surface of the motor cooling jacket 1 , and the inner surface of the stator outer sleeve 10 and the spiral groove form a spiral water channel.

[0040] Specifically, the motor cooling water of the grinding and polishing air flotation spindle enters from the water inlet W1 through a pipe joint (not shown), passes through the spiral water channel between the motor cooling jacket 1 and the stator outer sleeve 10, and is discharged from the pipe joint (not shown) at the water outlet W2. The cooling water channel is introduced from bottom to top, and the cooling water flow rate is first reduced to ensure that the spiral water channel is full, so that the stator water cooling effect is optimal.

[0041] The radial bearing 18 is sandwiched between the support shaft 19 and the thrust bearing seat 20, and a radial bearing gap is provided between the radial bearing 18 and the support shaft 19. The thrust bearing pad 17 is arranged in the groove of the thrust bearing seat 20, and has a thrust plate gap between it and the thrust plate.

[0042] Specifically, the thrust plate includes an upper thrust plate 11 and a lower thrust plate 13, and a groove is respectively provided on the upper and lower surfaces of the thrust bearing seat 20. Two thrust bearing pads 17 are respectively installed in the two grooves of the thrust bearing seat 20, and there is a thrust plate gap between the two thrust bearing pads 17 and the upper thrust plate 11 and the lower thrust plate 13.

[0043] The thrust bearing seat 20 is provided with an air inlet hole, and an air inlet pipe joint 12 is installed in the air inlet hole. A plurality of air passages are also arranged inside the thrust bearing seat 20. The plurality of air passages include at least two axial air supply loops and one radial air supply loop. The axial air supply loop supplies air to the two thrust bearing pads 17 respectively, and the radial air supply loop supplies air to the radial bearing 18.

[0044] Optionally, the thrust bearing seat 20 is also provided with an exhaust hole, and the gas is discharged from the grinding and polishing air-floating spindle through the exhaust hole and the gap between the thrust plate.

[0045] In the present invention, the air supply pressure of the porous metal-based material grinding and polishing air flotation spindle is about 0.45-0.55 MPa.

[0046] Specifically, the gas is introduced from the air inlet pipe joint 12, that is, the A1 air path. According to the internal channel of the bearing thrust seat 20, the A1 air path can be divided into three gas paths, A2, A3, and A4. Since the internal channel is arranged in a ring shape, there are three air paths, A7, A8, and A9, at the corresponding exhaust hole position of the thrust bearing seat 20. Among them, A2 and A7 and A3 and A8 respectively constitute two axial air supply loops. The axial air supply loop composed of A2 and A7 supplies air to the thrust bearing pad 17 arranged above the thrust bearing seat 20, and the axial air supply loop composed of A3 and A8 supplies air to the thrust bearing pad 17 arranged below the thrust bearing seat 20. A4 and A9 constitute a radial air supply loop, which supplies air to the radial bearing 18.

[0047] The thrust bearing pad 17 and the radial bearing 18 are made of porous metal-based materials.

[0048] Specifically, the porous metal-based material is a graphene / bronze composite material. Compared with conventional graphite materials, the graphene / bronze composite material as a metal-based porous material can achieve advantages such as thinner thickness, higher strength, and better air permeability compared with graphite.

[0049] Preferably, the graphene / bronze composite material can be prepared by chemical vapor deposition of bronze powder and acetylene gas (C2H2).

[0050] Since the thrust bearing pad 17 and the radial bearing 18 are made of porous metal-based materials, the gas passes through the porous thrust bearing pad 17 and the radial bearing 18. Since the thrust bearing pad 17 and the radial bearing 18 are fully breathable, the gas is throttled through the countless small holes of the thrust bearing pad 17 and the radial bearing 18 into the thrust plate gap and the radial bearing gap, thereby lifting the main shaft rotating body and placing its bearing in an air-floating suspended state inside the main shaft.

[0051] The excess gas is discharged through the gaps between the four thrust plates A5, A6, A11 and A12. At the same time, part of the gas is also discharged through the A10 gas path of the exhaust hole.

[0052] Furthermore, the spindle fixing part also includes a motor end cover 2 fixed to the motor cooling jacket 1 and the end of the stator outer shaft sleeve 10, a motor top cover plate 4 and a motor cover ring 5 fixed to the motor end cover 2, and a motor stator 9 arranged in the inner cavity of the motor cooling jacket 1.

[0053] Furthermore, the spindle rotating body also includes a motor rotor 8 fixedly connected to the upper thrust plate 11, a motor rotor shaft 7 arranged at the center of the motor rotor 8, a sensor light shielding plate 6 arranged at the top of the motor rotor 8, a grinding wheel connecting plate 16 arranged at the bottom of the lower thrust plate 13, and a front end cover 14 fixedly connected to the grinding wheel connecting plate 16, and a front end plug 15 is also installed on the front end cover 14.

[0054] Preferably, the parts to be connected of the porous metal-based material grinding and polishing air-floating spindle can be connected by screws / bolts, gluing, etc.

[0055] In order to better achieve the purpose of the present invention, the porous metal-based material of the graphene / bronze composite material adopts high-purity bronze powder with a particle size of 5-8 μm.

[0056] The present invention also provides a method for preparing a porous metal-based material, comprising the following steps:

[0057] High-purity bronze powder with a particle size of 5-8 μm is evenly filled into a cylindrical mold;

[0058] The bronze powder is placed under a pressure of 150MPa±2MPa for 10 minutes and is cold isostatically pressed to obtain a three-dimensional porous bronze blank having a certain air permeability.

[0059] A certain flow of C2H2 is introduced into a high-temperature tube furnace as a carbon source, and three-dimensional continuous graphene is obtained on the surface of the porous bronze skeleton through a two-step chemical vapor deposition method.

[0060] Preferably, C2H2 gas is introduced into the high temperature tube furnace at a flow rate of 4 ml / min.

[0061] Specifically, hydrogenated graphite is first obtained by chemical vapor deposition at a low temperature of 200°C for 10 minutes; then the obtained hydrogenated graphite is placed in an environment of 650-680°C for high-temperature pyrolysis for 3-5 hours to be converted into graphene, for example, high-temperature pyrolysis at 660°C.

[0062] While hydrogenated graphite is cracked and converted into graphene at high temperature, bronze powder is sintered to form a continuous skeleton. Three-dimensional continuous graphene is formed on the skeleton surface of porous bronze, thereby obtaining a graphene / bronze-based porous composite material with a certain strength, completing the preparation of the graphene / bronze composite material.

[0063] Since the graphene / bronze composite material of the present invention is prepared by a two-step chemical vapor deposition method of high-purity 5-8μm bronze powder and C2H2 (acetylene gas) through low temperature 200°C and high temperature cracking, the obtained porous metal-based material can achieve the advantages of thinner thickness, higher strength, better air permeability, etc. compared with graphite.

[0064] The porous metal-based material polishing air-floating spindle of the present invention has an I-shaped bearing structure, and the upper and lower thrusts are connected by a support shaft to ensure that the air film gap can be adjusted and controlled. The I-shaped structure makes its gas contact area larger, the upper and lower thrust forces are more stable, and the axial bearing capacity is greater. The porous metal-based thrust bearing pad and radial bearing are used. The improved graphene / bronze material porous bearing replaces the graphite bearing in that compared with the small-hole throttling graphite, it has a wider ventilation area, a more uniform air film, and a higher strength, which prevents the particles on the surface of the bearing pad from falling off and causing scratches on the upper and lower thrust surfaces or even locking; the surface does not need to be grooved, and the surface grooving process is cancelled, avoiding the cyclone of compressed air in the groove and the self-excited vibration caused by poor exhaust. The probability of particle accumulation inside the bearing is lower, which avoids the situation where the spindle is locked due to the clogging of the small holes.

[0065] Example 1

[0066] 1) High-purity (purity of about 99.5%) bronze powder with a particle size of 5-8 μm is evenly filled into a cylindrical mold;

[0067] 2) The bronze powder is kept at a pressure of 150 MPa for 10 minutes and is cold isostatically pressed to obtain a three-dimensional porous bronze blank having a certain air permeability.

[0068] 3) C2H2 is introduced into a high-temperature tube furnace at a flow rate of 4 ml / min as a carbon source, and chemical vapor deposition is first performed at a low temperature of 200°C for 10 minutes to obtain hydrogenated graphite; the hydrogenated graphite is then cracked at a high temperature of 650°C for 4 hours to convert it into graphene.

[0069] In this way, three-dimensional continuous graphene is obtained on the surface of the porous bronze skeleton through a two-step chemical vapor deposition method. While the hydrogenated graphite is cracked at high temperature, the bronze powder is sintered to form a continuous skeleton, thereby obtaining a graphene / bronze-based porous composite material with a certain strength.

[0070] The ventilation method of small-hole throttling is to machine small holes on the thrust graphite pad for fixed-point ventilation, while the graphene / bronze-based porous composite material prepared in this application is ventilated over the entire area of ​​the thrust graphite pad; small-hole throttling is more likely to block the pores during operation, while the full air permeability of the porous composite material almost eliminates uneven air film pressure caused by blocked pores, which can verify that the porous bearing material has a higher load-bearing capacity and strength than the small-hole throttling material.

[0071] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A porous metal-based material grinding and polishing air-floating spindle, characterized in that: The porous metal-based material grinding and polishing air-floating spindle comprises a spindle rotating body and a spindle fixing member, wherein the spindle rotating body at least comprises a thrust plate and a support shaft (19); The main shaft fixing component at least comprises a motor cooling jacket (1), a stator outer shaft sleeve (10), a thrust bearing pad (17), a radial bearing (18) and a thrust bearing seat (20); The outer surface of the motor cooling jacket (1) is sleeved with a stator outer shaft sleeve (10), and a water channel is also provided between the motor cooling jacket (1) and the stator outer shaft sleeve (10); The radial bearing (18) is sandwiched between the support shaft (19) and the thrust bearing seat (20), and a radial bearing gap is provided between the radial bearing (18) and the support shaft (19); The thrust bearing pad (17) is arranged in a groove of the thrust bearing seat (20), and there is a thrust plate gap between the thrust bearing pad and the thrust plate; Wherein, the thrust bearing pad (17) and the radial bearing (18) are made of porous metal-based materials.

2. The porous metal-based material grinding and polishing air-floating spindle according to claim 1, characterized in that: The porous metal-based material is a graphene / bronze composite material.

3. The porous metal-based material polishing air-floating spindle according to claim 2, characterized in that: The graphene / bronze composite material is prepared from bronze powder and acetylene gas by chemical vapor deposition.

4. The porous metal-based material grinding and polishing air-floating spindle according to claim 1, characterized in that: A water inlet and a water outlet are respectively arranged on the stator outer shaft sleeve (10), the water outlet is located above the stator outer shaft sleeve (10), and the water inlet is located below the stator outer shaft sleeve (10); the water channel arranged between the motor cooling jacket (1) and the stator outer shaft sleeve (10) is a spiral water channel, and the spiral water channel is respectively connected to the water inlet and the water outlet.

5. The porous metal-based material grinding and polishing air-floating spindle according to claim 1, characterized in that: The thrust plate comprises an upper thrust plate (11) and a lower thrust plate (13); a groove is respectively arranged on the upper and lower surfaces of the thrust bearing seat (20); two thrust bearing pads (17) are respectively installed in the two grooves of the thrust bearing seat (20); and thrust plate gaps are respectively formed between the two thrust bearing pads (17) and the upper thrust plate (11) and the lower thrust plate (13).

6. The porous metal-based material grinding and polishing air-floating spindle according to claim 5, characterized in that: The thrust bearing seat (20) is provided with an air inlet hole, and an air inlet pipe joint (12) is installed in the air inlet hole. A plurality of air passages are also arranged inside the thrust bearing seat (20), and the plurality of air passages include at least two axial air supply loops and one radial air supply loop. The axial air supply loops supply air to the two thrust bearing pads (17) respectively, and the radial air supply loop supplies air to the radial bearing (18).

7. The porous metal-based material grinding and polishing air-floating spindle according to claim 1, characterized in that: The thrust bearing seat (20) is also provided with an exhaust hole, and the gas is discharged from the grinding and polishing air-floating spindle through the exhaust hole and the gap between the thrust plate.

8. The porous metal-based material grinding and polishing air-floating spindle according to claim 1, characterized in that: The spindle fixing member also includes a motor end cover (2) fixed to the motor cooling jacket (1) and the end of the stator outer shaft sleeve (10), a motor top cover plate (4) and a motor cover ring (5) fixed to the motor end cover (2), and a motor stator (9) arranged in the inner cavity of the motor cooling jacket (1).

9. The porous metal-based material grinding and polishing air-floating spindle according to claim 5, characterized in that: The spindle rotating body also includes a motor rotor (8) fixedly connected to the upper thrust plate (11), a motor rotor shaft (7) arranged at the center of the motor rotor (8), a sensor light shielding plate (6) placed on the top of the motor rotor (8), a grinding wheel connecting plate (16) arranged at the bottom of the lower thrust plate (13), and a front end cover (14) fixedly connected to the grinding wheel connecting plate (16), and a front end plug (15) is also installed on the front end cover (14).

10. A method for preparing a porous metal-based material used for a porous metal-based material grinding and polishing air-floating spindle according to any one of claims 1 to 9, characterized in that: The preparation method comprises: High-purity bronze powder with a particle size of 5-8 μm is evenly filled into a cylindrical mold; The bronze powder is placed under a pressure of 150 MPa±2 MPa for 10 minutes and is cold isostatically pressed to obtain a three-dimensional porous bronze blank; A certain flow of C2H2 is introduced into a high-temperature tube furnace as a carbon source, and three-dimensional continuous graphene is obtained on the surface of the porous bronze skeleton by a two-step chemical vapor deposition method; Preferably, hydrogenated graphite is first obtained by chemical vapor deposition at a low temperature of 200° C. for 10 minutes; and then the obtained hydrogenated graphite is placed in an environment of 650-680° C. for high-temperature pyrolysis for 3-5 hours to be converted into graphene.

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