A method for preparing impermeable graphite

Abstract

The present invention relates to the field of chemical material production and processing, and specifically to a method for preparing impermeable graphite. A graphite workpiece is placed in a sealed container and the impermeable graphite is prepared by direct laser irradiation or indirect laser irradiation. The direct laser irradiation method is to irradiate a laser beam on the graphite workpiece to liquefy part of its graphite structure, form a dense surface after condensation, and block the pores on the surface of the graphite workpiece; the indirect laser irradiation method is to irradiate a laser beam on a carbon target material to eject an ion cloud from the target material surface into space, aim the ion cloud at the surface of the permeable graphite workpiece, and after the particles in the ion cloud are deposited on the surface of the permeable graphite workpiece and electrically neutralized, form a dense carbon layer to block the pores on the surface of the graphite workpiece. The present invention uses carbon elements to block the pores on the surface of the permeable graphite, which can meet the requirements of the chemical equipment industry for impermeable graphite and improve the applicability of graphite materials in high-temperature corrosive occasions.

Description

Technical Field

[0001] The invention relates to the field of chemical material production and processing, and in particular to a method for preparing impermeable graphite. Background Art

[0002] Currently, graphite easily forms a porous structure during the sintering process. Generally, it can achieve the impermeability requirements of graphite materials for chemical equipment only after being impregnated and calcined with thermosetting resins. However, due to the characteristics of thermosetting resins, a type of polymer compound, the maximum operating temperature of impregnated graphite for chemical equipment generally does not exceed 200°C (equipment wall temperature), which makes the high-temperature and corrosion-resistant characteristics of graphite itself not be utilized in high-temperature corrosion situations.

[0003] Therefore, there is an urgent need for a method that can replace the solid resin to meet the impermeability requirements of the graphite material and allow the graphite to exert its own high temperature and corrosion resistance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing impermeable graphite, which uses carbon elements to block the pores on the surface of permeable graphite, meet the requirements of the chemical equipment industry for impermeable graphite, and improve the applicability of graphite materials in high-temperature corrosive environments.

[0005] In order to solve the above technical problems, the present invention provides a method for preparing impermeable graphite, wherein a graphite workpiece is placed in a sealed container and the impermeable graphite is prepared by laser irradiation.

[0006] Furthermore, the laser irradiation method is a direct laser irradiation method, in which a laser beam is emitted from a laser to irradiate a graphite workpiece to liquefy part of the graphite structure, and a dense surface is formed after condensation to seal the pores on the surface of the graphite workpiece.

[0007] Furthermore, the laser irradiation method is an indirect laser irradiation method, in which a laser is used to emit a laser beam onto a carbon target material so that the target material surface ejects an ion cloud into space, and the ion cloud is aimed at the surface of the permeable graphite workpiece. After the particles in the ion cloud are deposited and electrically neutralized on the surface of the permeable graphite workpiece, a dense carbon layer is formed to seal the pores on the surface of the graphite workpiece.

[0008] Furthermore, the sealed container is a vacuum kettle, which is provided with a glass window. The glass window is used for the laser beam to pass through the surface of the glass window and enter the vacuum kettle. The vacuum kettle is provided with a rotating table for driving the graphite workpiece to rotate.

[0009] Furthermore, the sealed container is provided with an inert gas filling system, an exhaust system and a vacuum system. The inert gas filled is any one of helium, neon, argon and nitrogen. The exhaust system and the vacuum system respectively use a rotary vane pump and a turbomolecular pump.

[0010] Furthermore, the sealed container is a tubular furnace.

[0011] Furthermore, the laser directly irradiating the graphite workpiece adopts an ns laser;

[0012] Furthermore, the laser irradiating the carbon target is a ps or fs laser.

[0013] Furthermore, there are a plurality of lasers that are evenly distributed in the circumferential direction of the sealed container, and each of the lasers is mounted on a reciprocating motion mechanism that performs linear motion along the optical axis.

[0014] Furthermore, the laser is installed on a laser path control robot arm controlled by PLC.

[0015] The beneficial effects of the present invention are:

[0016] 1. The laser irradiation method of the present invention can use carbon elements to block the pores on the surface of permeable graphite, meeting the requirements of the chemical equipment industry for impermeable graphite, and can greatly improve the applicability of graphite materials in high-temperature corrosive environments.

[0017] 2. The laser direct irradiation method of the present invention uses a laser beam adjusted to a linear output through a lens, or a laser beam linear scanning to form a certain irradiation intensity on the graphite workpiece, so that most of the graphite tissue is liquefied, and a dense surface is formed after condensation, thereby sealing the pores on the surface of the graphite workpiece. The method is simple to operate, and the method can reasonably utilize the resources of the graphite workpiece itself to achieve the purpose of sealing the pores, meet the requirements of the chemical equipment industry for impermeable graphite, and can greatly improve the applicability of graphite materials in high-temperature corrosive occasions.

[0018] 3. The laser indirect irradiation method of the present invention utilizes a laser beam to irradiate a carbon target material so that the surface of the target material ejects an ion cloud into space, and the ion cloud is aimed at the surface of the permeable graphite workpiece. The particles in the ion cloud are deposited on the surface of the permeable graphite workpiece and electrically neutralized to form a dense carbon layer, thereby sealing the pores on the surface of the graphite workpiece. The interatomic force adsorption between the particles and the permeable graphite substrate is utilized to achieve the preparation of impermeable graphite, which can meet the requirements of the chemical equipment industry for impermeable graphite and improve the applicability of graphite materials in high-temperature corrosive environments.

[0019] 4. The processing environment of the present invention adopts an inert gas inflation system, which can keep the carbon atoms emitted from the laser irradiated surface in a single substance form and not be oxidized, prevent the smoke and dust in the processing environment from interfering with the laser irradiation path, and reduce carbon dioxide emissions.

[0020] 5. The present invention has good application prospects in working conditions such as flue gas rapid cooling and dew point corrosion, especially for chlor-alkali chemical systems. It is free from the thermal resistance of the thermosetting resin impregnation layer, and the impermeable graphite prepared can better utilize the high thermal conductivity of the graphite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a schematic structural diagram of the laser direct irradiation method of the method for preparing impermeable graphite of the present invention;

[0023] Figure 2 2. It is a schematic diagram of the glass window structure of the sealed container of the present invention being a vacuum kettle;

[0024] Figure 3 It is a schematic structural diagram of the laser indirect irradiation method of the method for preparing impermeable graphite of the present invention;

[0025] In the figure: 1-vacuum reactor, 2-laser, 3-reciprocating motion mechanism, 4-inert gas filling system, 11-rotating table, 12-carbon target, 13-glass window, 100-graphite workpiece. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] A method for preparing impermeable graphite includes placing a graphite workpiece 100 in a sealed container in a vacuum environment and using a laser to emit a laser beam to prepare the impermeable graphite.

[0028] like Figure 1 As shown, impermeable graphite is prepared by direct laser irradiation method (hereinafter referred to as method 1): a laser beam is irradiated on a graphite workpiece 100 to liquefy part of the graphite structure, which forms a dense surface after condensation, sealing the pores on the surface of the graphite workpiece to obtain impermeable graphite.

[0029] Among them, because it is necessary to form a strong temperature effect on and below the surface of the graphite workpiece 100, the laser 2 irradiated on the graphite workpiece adopts a ns laser, so that the energy conversion between photons and molecules can fully develop below the radiation surface over a long period of time, forming a molten pool of a certain thickness. After two pulse laser intervals, a dense graphite layer of a certain thickness can be formed on the surface of the graphite workpiece.

[0030] like Figure 3 As shown, impermeable graphite is prepared by an indirect laser irradiation method (hereinafter referred to as method 2): the laser beam emitted by the laser 2 irradiates the carbon target 12 so that the target surface ejects an ion cloud into space, and the ion cloud is aimed at the surface of the permeable graphite workpiece 100. The particles in the ion cloud are deposited on the surface of the permeable graphite workpiece and electrically neutralized to form a dense carbon layer to seal the pores on the surface of the graphite workpiece 100, thereby finally obtaining impermeable graphite.

[0031] Among them, because it is necessary to form a high-quality ion cloud and avoid too wide a particle size distribution of the product formed during the cooling process of the ion cloud, the laser uses a ps or fs laser. In the early stage of ion cloud formation, gaseous carbon atoms condense into nuclei driven by supersaturation, and carbon particles with uniform particle size can be formed after condensation. Under the ultra-high pressure of the ion cloud core, the carbon particles collide with the surface of the permeable graphite workpiece and the pores on the surface at high speed. After a certain period of cumulative effect, all the pores on the surface of the permeable graphite are completely blocked.

[0032] Specifically, both the above-mentioned method 1 and method 2 can use a closed container of a vacuum kettle 1, which is provided with a glass window 13 (such as Figure 2 ), which enables the laser beam to penetrate the glass window 13 and enter the vacuum vessel 1. A rotary table 11 is provided in the vacuum vessel 1 for driving the graphite workpiece to rotate. An inert gas charging system 4, an exhaust system, and a vacuum system are provided in the sealed container. The inert gas charged can be any one of helium, neon, argon, and nitrogen. A rotary vane pump and a turbomolecular pump are used for the exhaust system and the vacuum system, respectively. For example, when the inner volume of the vacuum vessel is large, an exhaust mechanism connected in series with a Roots vacuum pump and a rotary vane pump is used. The turbomolecular pump is used to maintain an extremely high vacuum degree.

[0033] During operation, the graphite workpiece 100 is placed on the rotating table 11 through the top inlet of the vacuum reactor 1, and then the top inlet is closed. The vacuum system ensures the vacuum inside the vacuum reactor 1, and the inert gas is filled into the reactor through the inert gas filling system 4 to keep the carbon atoms released from the laser irradiated surface in a single substance form and not be oxidized. The switch driving the rotating table is turned on to drive the graphite workpiece 100 on the rotating table to rotate;

[0034] Then, according to the process requirements, set the number of lasers 2, such as Figure 1The lasers 2 are arranged into two groups symmetrical on the left and right. The lasers 2 are mounted on the reciprocating mechanism 3 through a laser mounting bracket with adjustable height. The height of the mounting position of the laser 2 is set according to the process requirements to ensure that the laser beam can pass through the glass window 13 and irradiate the surface of the graphite workpiece 100. Then, the distance between the laser beam emitted by the laser 1 and the graphite workpiece 100 is adjusted by the reciprocating mechanism 3. The laser beam is adjusted by a full-reflection mirror, a plano-convex lens, an optical table, a laser power detector, a spectroscope, and a Gaussian lens. For example, method one can adjust the laser beam to a linear output through a lens, or scan the laser beam linearly to form a certain irradiation intensity on the graphite workpiece, so that most of the graphite tissue is liquefied, and a dense surface is formed after condensation, thereby sealing the pores on the surface of the graphite workpiece and preparing impermeable graphite.

[0035] like Figure 3 As shown, in this embodiment, the carbon target 12 is preferably arranged above the graphite workpiece 100, and the carbon target 12 extends into the vacuum reactor 1. During operation, it is necessary to adjust the installation height of the laser 2 and the irradiation intensity of the laser beam so that it can irradiate the carbon target 12 through the glass window 13, so that the surface of the target sprays an ion cloud into the space, and the ion cloud is aimed at the surface of the permeable graphite workpiece 100. The particles in the ion cloud are deposited on the surface of the permeable graphite workpiece and electrically neutralized to form a dense carbon layer to seal the pores on the surface of the graphite workpiece, and finally impermeable graphite is obtained.

[0036] Preferably, method 2 can also use a closed container of a tubular furnace (the structural schematic diagram of the closed container being a tubular furnace in this embodiment is not shown), maintain a high temperature of 1000-1500°C in the furnace, and then extend the cooling time of the carbon particles, which can make the new carbon layer more tightly bonded to the original porous graphite workpiece, and can greatly improve the pore sealing efficiency of the permeable graphite surface.

[0037] In addition, in other embodiments, the laser 2 can be installed on a PLC-controlled laser path control robot arm, which can flexibly adjust the distance between the laser beam and the graphite workpiece 100 to improve the pore blocking efficiency of the permeable graphite surface.

[0038] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing impermeable graphite, characterized in that: The graphite workpiece is placed in a sealed container and impermeable graphite is prepared by laser irradiation. The laser irradiation method is a direct laser irradiation method, wherein a laser beam is emitted by a laser to irradiate a graphite workpiece to liquefy part of the graphite structure, and a dense surface is formed after condensation, thereby sealing the pores on the surface of the graphite workpiece; Alternatively, the laser irradiation method is an indirect laser irradiation method, in which a laser beam is emitted from a laser to irradiate a carbon target material so that the target material surface ejects an ion cloud into space, and the ion cloud is aimed at the surface of the permeable graphite workpiece. After the particles in the ion cloud are deposited and electrically neutralized on the surface of the permeable graphite workpiece, a dense carbon layer is formed to seal the pores on the surface of the graphite workpiece.

2. The method for preparing impermeable graphite according to claim 1, wherein: The sealed container is a vacuum kettle, which is provided with a glass window. The glass window is used for the laser beam to pass through the surface of the glass window and enter the vacuum kettle. A rotating table for driving the graphite workpiece to rotate is provided in the vacuum kettle.

3. The method for preparing impermeable graphite according to claim 2, wherein: The sealed container is provided with an inert gas filling system, an exhaust system and a vacuum system. The inert gas filled is any one of helium, neon, argon and nitrogen. The exhaust system and the vacuum system respectively use a rotary vane pump and a turbomolecular pump.

4. The method for preparing impermeable graphite according to claim 1, wherein: The sealed container of the laser indirect irradiation method is a tube furnace.

5. The method for preparing impermeable graphite according to claim 1, wherein: The laser used in the laser direct irradiation method is a ns laser.

6. The method for preparing impermeable graphite according to claim 1, wherein: The laser used in the indirect laser irradiation method is a ps or fs laser.

7. The method for preparing impermeable graphite according to claim 1, wherein: There are a plurality of lasers evenly distributed in the circumferential direction of the sealed container, and each of the lasers is mounted on a reciprocating motion mechanism that performs linear motion along the optical axis.

8. The method for preparing impermeable graphite according to claim 1, wherein: The laser is installed on a laser path control robot arm controlled by PLC.

Images