CN113088849B

CN113088849B - Composite strengthening method for synthesizing nano diamond by laser induction

Info

Publication number: CN113088849B
Application number: CN202110257289.5A
Authority: CN
Inventors: 胡耀武; 张啸寒
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2021-03-09
Filing date: 2021-03-09
Publication date: 2022-08-05
Anticipated expiration: 2041-03-09
Also published as: CN113088849A

Abstract

The invention discloses a composite strengthening method for synthesizing nano-diamond by laser induction, which comprises the following steps: (1) uniformly coating a carbon source on the surface of the component, and transmitting a laser beam by means of a carbon dioxide laser and continuously irradiating the surface of the carbon source to convert the carbon source into a graphene or activated carbon layer; (2) laying a constraint layer above the carbon layer; (3) a femtosecond laser is adopted to emit pulse laser beams, and a heating laser is adopted to emit continuous laser beams, so that the centers of two laser spots are overlapped and irradiated on the surface of the carbon layer; (4) and carrying out laser shock composite strengthening operation on the three-dimensional numerical control mobile platform or the laser to the next strengthening position. According to the method, nano diamond particles can be induced and generated on the outer surface of the easily damaged component to form a compression stress layer, so that the direct strengthening of the high-hardness diamond is realized, the surface grains of the component are refined, the grain structure distributed in a gradient manner along the thickness direction is generated, and the strength of the material can be effectively improved without sacrificing the ductility of the material.

Description

Composite strengthening method for synthesizing nano diamond by laser induction

Technical Field

The invention relates to the technical field of material surface modification, in particular to a composite strengthening method for synthesizing nano-diamond by laser induction.

Background

The nano-diamond is a multifunctional material, is widely applied to the fields of biosensors, quantum computing, fuel cells, computer chips and the like because of excellent thermodynamic properties, and can obviously improve the comprehensive mechanical properties of metal base materials as a dispersion strengthening phase of a composite material. In engineering, the nano-diamond can be directly or indirectly applied to surface strengthening of a vulnerable component to improve the strength and the tribological performance of the component, for example, Wang Wentang et Al (publication number: CN101728279A) propose a preparation method of a high-performance diamond-strengthened Al-based electronic packaging composite material, and an electronic packaging material with excellent comprehensive mechanical properties can be obtained by adding single-crystal diamond particles and compositing the single-crystal diamond particles with high-thermal-conductivity metal Al, but the process flow of the diamond strengthening mechanism is complicated, and plasma sintering often needs temperature and pressure with better adaptability to the material. Yao Jinyuan et al (publication No. CN1896303A) propose a strengthening method for preparing a diamond film on the surface of a tantalum spinneret by chemical vapor deposition, which effectively improves the hardness and the alkali corrosion resistance of the surface of the tantalum spinneret, but the method needs strict requirements on pressure, carbon source concentration and temperature. In conclusion, the direct or indirect application of diamond to material strengthening has clear feasibility.

Because the activation energy required for the conversion of graphite to diamond is high and the thermal stability of diamond at high temperatures is poor due to the special carbon structural properties of diamond, the efficient synthesis of diamond material directly from graphite is a great challenge. With the development of scientific technology, scholars in the related field have gradually accumulated a series of diamond preparation methods, which can be generally divided into two main categories: one is to convert non-diamond carbon in a diamond stable region into diamond, and the preparation of the diamond usually needs high temperature and high pressure conditions, for example, the Nayadong et al (publication No. CN103409746A) provides a method for cladding a nano-diamond composite coating by using a millisecond laser, which mixes microcrystalline graphite powder and catalyst powder in proportion and adopts laser irradiation with high energy density to obtain a high self-lubricating wear-resistant coating with high bonding strength and fine tissue; the other is that activated carbon groups in a diamond metastable zone are re-aggregated to form diamond, the preparation method of the diamond can be realized under the condition of low pressure, for example, Jinzengsun et al (publication number: CN1091996A) provides a method for preparing diamond seed crystals by using surface modified graphite as a raw material under the high-pressure environment by adopting a chemical vapor deposition method, and the large-particle high-pressure diamond with controllable growth quantity and size is obtained, compared with the traditional diamond synthesis pressure, the method can reduce the synthesis pressure of the diamond by 0.5GPa, and improve the conversion efficiency and the coarse particle size of the diamond. In summary, the synthesis of diamond from graphite at the present stage often requires extreme operating environments, such as high temperatures greater than 2000K and high pressures greater than 10GPa, and the above-mentioned methods for producing diamond often correspond to high costs and low yields due to these extreme operating environments. Therefore, how to efficiently synthesize nano-diamond through graphite has become one of the major technical bottlenecks that restrict further application of diamond in the field of surface strengthening at the present stage.

Disclosure of Invention

The invention aims to provide a composite strengthening method for synthesizing nano-diamond by laser induction, which can realize direct or indirect strengthening of the surface of a component and improve the comprehensive mechanical property of the surface of a vulnerable component while synthesizing the diamond by laser induction.

The invention aims to provide a composite strengthening method for synthesizing nano-diamond by laser induction, which is characterized by comprising the following steps: comprises the following steps:

(1) uniformly coating a carbon source on the surface of the component, and transmitting a laser beam by means of a carbon dioxide laser and continuously irradiating the surface of the carbon source to convert the carbon source into a graphene or activated carbon layer;

(2) laying a constraint layer above the carbon layer;

(3) a femtosecond laser is adopted to emit pulse laser beams, a heating laser is adopted to emit continuous laser beams, and the centers of two laser spots are ensured to be superposed and irradiated on the surface of the carbon layer;

(4) and carrying out laser shock composite strengthening operation on the three-dimensional numerical control mobile platform or the laser to the next strengthening position.

Preferably, in the step (1), a layer of carbon source is uniformly coated on the surface of the member to be reinforced, and the uniform coating mode includes a brush coating method, a spray coating method, a dip coating method, a blade coating method, a roll coating method, an injection method and a hot melting method, so as to realize efficient and uniform coating of the carbon source on the surface of the vulnerable member; before the carbon dioxide laser is irradiated, a heating platform is adopted to heat and solidify the carbon source, the heating temperature is not higher than 200 ℃, and the heating time is not more than 15 min.

Further, in the step (2), a constraint layer is laid on the graphene, and the constraint layer comprises BK-7 glass or quartz glass.

Further, in the step (3), a heating laser is used to emit a continuous laser beam, and the heating laser is a heating laser with a wavelength higher than 400nm and is used to provide an auxiliary heat source.

Furthermore, in the step (3), the process parameters of the femtosecond pulse laser include voltage, current, laser frequency, laser energy, laser wavelength, laser pulse width and spot size; the technological parameters of the semiconductor laser include the laser action distance and the laser spot size.

Preferred embodiments are as follows: in the step (1), the thickness range of the carbon layer is 1-10 mm; in the step (3), the wavelength of the femtosecond pulse laser is 248nm, the pulse width is 25ns, and the pulse energy is 300 mJ/Hz; the technological parameters of the semiconductor laser include the laser action distance and the laser spot size.

The strengthening mechanism of the invention is as follows:

the femtosecond pulse laser is a frequency-adjustable discontinuous laser beam generated by a femtosecond pulse laser, and the laser beam is irradiated on the surface of a material and interacts with the material, so that the surface of the material is ionized and generates plasma explosion, and then laser impact pressure of several GPa is generated, and nano diamond particles are generated. The heating laser can realize local accurate heating of the surface of the component, reduce harmful residual stress of the component and effectively increase the quantity of laser-induced synthesized nano-diamonds. The pulsed laser generated by the femtosecond laser and the laser generated by the heating laser act on CO at the same time ₂ On the carbon layer prepared by the laser, on one hand, nano diamond particles are induced to generate, and the direct strengthening of high-hardness diamonds attached to the outer surface of a vulnerable component is realized, on the other hand, the surface of the carbon layer is ablated and generates plasma, the plasma is prevented from diffusing under the action of the transparent constraint layer, and high-strength stress shock waves are generated, after the shock waves act on the diamond particles, the nano diamond particles have a strengthening effect on the base material, so that the crystal grains on the surface of the base material are refined, and a compression stress layer is formed on the surface of the base material, so that the gradient distribution of the crystal grain size of a strengthening region from the outside to the inside is realized, and the strength of the material can be effectively improved while the ductility of the material is not sacrificed.

The invention has the following advantages and beneficial effects:

(1) the femtosecond pulse laser can generate pulse laser which can induce the carbon layer to generate nano diamond particles;

(2) the shock wave pressure generated by the pulse laser acts on the surfaces of the diamond particles, so that the diamond is firmly and mechanically occluded with the surface and the subsurface of the component to be strengthened, and the surface hardness and the tribological performance of the component can be effectively improved;

(3) the heating laser can realize local accurate heating of the surface of the component, reduce harmful residual stress of the component and effectively improve the yield of laser-induced synthesized nano-diamond;

(4) by adopting the composite strengthening method for synthesizing the nano-diamond by laser induction, nano-diamond particles can be generated on the outer surface of the damageable component, and a microstructure with the grain size distributed in a gradient manner is generated on the surface layer of the component through the nano-diamond particles, so that the strength of the surface of the material is effectively improved while the ductility of the material is not sacrificed.

Drawings

Fig. 1 is a schematic diagram of a method for laser-fabricating a carbon layer according to the present invention.

Fig. 2 is a schematic diagram of the composite strengthening method for laser-induced synthesis of nano-diamond according to the present invention.

FIG. 3 is a schematic diagram of the strengthening effect of the diamond gradient microstructure according to the present invention.

In the figure: a member to be reinforced 1; a carbon source 2; a heating stage 3; a carbon dioxide laser 4; a carbon layer 5; sealing the chamber 6; a transparent constraining layer 7; a vacuum pump 8; a three-dimensional numerical control mobile platform 9; a femtosecond pulse laser 10; a semiconductor laser 11; the nano-diamond particles 12; the reinforced region 13.

Detailed Description

The following examples are provided to further illustrate the present invention for better understanding, but the present invention is not limited to the following examples.

Example 1

Fig. 1 is a schematic diagram of a laser-based method for producing a carbon layer. A layer of polyimide 2 is uniformly coated on the surface of a 0.2mm pure copper plate 1 by adopting a glass rod rolling coating method, and the polyimide is placed on a heating platform 3 and is cured for 7 minutes at the temperature of 110 ℃. And (3) selecting 11% of light output power of a carbon dioxide laser 4, and continuously irradiating the laser beam on the surface of the cured polyimide to generate the graphene 5. Fig. 2 is a schematic diagram of a method for composite strengthening based on laser-induced synthesis of nanodiamonds. Placing a member to be strengthened with graphene 5 generated on the surface in a sealed chamber 6, placing a BK-7 glass restraint layer 7 above the graphene 5, starting a vacuum pump 8, carrying out vacuum pumping treatment on the sealed chamber 6, and placing the sealed chamber 6 on a three-dimensional numerical control mobile platform 9 when the interior of the sealed chamber is in a negative pressure state; by building a light path, the laser beam emitted by the femtosecond pulse laser 10 and the laser beam emitted by the semiconductor laser 11 can effectively irradiate the graphene 5, the centers of the laser spots of the laser beams of the femtosecond pulse laser 10 and the semiconductor laser 11 coincide, and 50% of the overlap ratio of the laser spots of the pulse laser is selected for strengthening operation; and after the laser impact is finished, opening the air valve, balancing the sealed cavity and the external air pressure, and taking out the pure copper plate 1.

Fig. 3 is a schematic diagram illustrating the strengthening effect of the diamond gradient microstructure. The strengthening mechanism of the pure copper plate is as follows: the pulse laser generated by the femtosecond pulse laser 10 and the laser generated by the heating laser 11 act on the surface of the graphene 5 prepared by the carbon dioxide laser 4 simultaneously, on one hand, nano diamond particles 12 are generated by induction, so that the direct strengthening of high-hardness diamond attached to the outer surface of the pure copper plate 1 is realized, on the other hand, the surface of the graphene 5 is ablated and generates plasma, the plasma is prevented from being diffused and generates high-strength stress shock waves under the action of the transparent constraint layer 7, after the shock waves act on the diamond particles 12, the nano diamond particles 12 have a strengthening effect on the pure copper plate 1, so that the surface grains of the pure copper plate 1 are refined, and a compression stress layer is formed on the surface of the pure copper plate, so that the gradient distribution of the strengthening region 13 from the surface to the inside is realized, and meanwhile, the gap structure of the nano diamond particles 12 can generate the gradient micro-structure distribution on the surface layer of the pure copper plate, the strength of the material is effectively improved while the ductility of the copper material is not sacrificed.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A composite strengthening method for synthesizing nano-diamond by laser induction is characterized in that: comprises the following steps:

(2) laying a constraint layer above the graphene or activated carbon layer;

(3) a femtosecond laser is adopted to emit pulse laser beams, a heating laser is adopted to emit continuous laser beams, the centers of two laser spots are ensured to be superposed, and the two laser spots are irradiated on the surface of the graphene or activated carbon layer;

(4) carrying out laser shock composite strengthening operation on the three-dimensional numerical control mobile platform or the laser to the next strengthening position;

in the step (1), a layer of carbon source is uniformly coated on the surface of the member to be reinforced, wherein the uniform coating mode comprises a brushing method, a spraying method, a dip coating method, a blade coating method, a rolling coating method, an injection method and a hot melting method, and the purpose is to realize efficient and uniform coating of the carbon source on the surface of the damageable member; before the carbon dioxide laser is irradiated, a heating platform is adopted to heat and solidify the carbon source, the heating temperature is not higher than 200 ℃, and the heating time is not more than 15 min;

in the step (2), a restraint layer is laid above the graphene or activated carbon layer, and the restraint layer comprises BK-7 glass or quartz glass;

in the step (3), a heating laser is adopted to emit continuous laser beams, wherein the heating laser is a heating laser with the wavelength higher than 400nm and is used for providing an auxiliary heat source;

in the step (3), the process parameters of the femtosecond pulse laser include voltage, current, laser frequency, laser energy, laser wavelength, laser pulse width and light spot size; the technological parameters of the semiconductor laser include the laser action distance and the laser spot size.