CN110744045A - Method for in-situ synthesis of carbon nano tube on surface of aluminum alloy spherical powder - Google Patents

Abstract

The invention discloses a method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder, and relates to the technical field of high light-absorbing aluminum-based powder preparation. The method includes the following steps: S100, preparing Ni/2024Al catalyst; S200, The CNTs/2024Al-Ni composite powder was obtained by calcining the Ni/2024Al catalyst in a mixed gas atmosphere. The preparation method of the invention utilizes the strong light absorption and nanoscale surface effect of the carbon tube to improve the absorption efficiency of the aluminum alloy powder to the laser energy, reduces the energy loss, avoids the adverse effect of the high input energy on the microstructure of the sample, and overcomes the disadvantage of the metal powder. The low absorbance has an adverse effect on the application of 3D printing technology, and at the same time, the sphericity of the original powder is preserved to the maximum extent to meet the requirements of 3D printing.

Description

Method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder

technical field

The invention relates to the technical field of preparation of high light-absorbing aluminum-based powder, in particular to a method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder.

Background technique

In the current aerospace field, the lightweight of engine materials is mainly reflected in a large number of applications of magnesium, aluminum alloy and composite materials. Among them, the use of magnesium and aluminum alloy composite materials is an important way to achieve lightweight aircraft, which is called "material lightweighting". Applying additive manufacturing technology to the design and manufacture of complex aerospace structures can change the traditional component design mode and realize the concept of "function-first design". As long as the function of the part and the technical process requirements of additive manufacturing are met, the structural design can be performed arbitrarily. Therefore, the significant role of additive manufacturing technology in lightweighting parts cannot be ignored. What is more noteworthy is that additive manufacturing technology can realize the integrated manufacturing of components, and the integral forming of aerospace engine components can reduce the assembly and connection structure relationship between existing parts and achieve the purpose of weight reduction. As a kind of additive manufacturing technology, laser selective melting technology, because the powder has undergone a complete melting/solidification process during the forming process, has high forming accuracy, and can realize mold-free, fast, fully dense direct precision net forming of small and medium-sized components. It is especially suitable for parts with complex structures. The performance of the components can reach the level of forgings with the same composition, taking into account the needs of precise forming and high-performance forming. Its technical characteristics are especially suitable for the development requirements of "material-design-manufacturing" integration of aerospace complex components.

At present, the commonly used aluminum alloy material for aerospace engines is 2024, which has the advantages of light density, high specific stiffness and specific strength. However, due to its high thermal conductivity and thermal expansion coefficient, and there is light absorption on the powder surface in the process of laser selective melting and forming The problem of too low rate has become the main technical bottleneck restricting the engineering application of 2024 aluminum alloy materials. The process of laser selective melting technology is mainly manifested in that the metal powder to be processed absorbs the laser energy and converts the energy into heat energy for melting and forming; therefore, the absorption efficiency of the material to the laser energy plays an important role in the processing process. Limited by its own performance, the laser produces strong reflection on the surface of the 2024Al alloy powder, taking away most of the energy (the electric field of the laser near the surface of the metal powder will form a standing wave node, and the free electrons will be generated by the forced vibration of the light wave electromagnetic field. The secondary wave, the secondary wave causes a strong reflected wave, which eventually leads to energy loss); and this phenomenon is especially obvious for long-wavelength lasers (in the long-wavelength, the photon energy is low, mainly acting on the free electrons in the metal, almost total reflection , only a small amount of absorption). Therefore, large laser energy is required when using laser to melt metal powder, but this will cause excessive heat input to the substrate, resulting in large deformation of the formed parts, coarse grains, and deterioration of the structure, which seriously affects the printed parts. of various performances. It can be seen that improving the absorption rate of the printing powder to the laser is an urgent problem to be solved in the field of 3D printing.

In order to enhance the laser absorption efficiency of the metal surface, a common practice is to coat the surface of the metal material with a coating with high resistivity and few free electrons. However, when this method is applied to the field of metal powder, some new problems will arise: the coating material is easy to introduce impurities and change the original composition of the metal matrix, and it is difficult to achieve smooth surface and uniform thickness coating on the surface of micron powder.

With the development of additive manufacturing technology, selective laser melting technology, which uses laser to melt metal powder layer by layer and form it into metal parts, has gained extensive attention from scholars at home and abroad. Therefore, it has become an urgent need to develop a new method to improve the laser energy absorption rate of metal powders. In recent years, the rapid development of nano-composite material technology has provided the possibility for 2024 aluminum alloy laser selective melting and forming, replacing the traditional 2024 aluminum alloy brazing process, and providing technology for the national defense strategic fields of aerospace engines, national defense, military industry, weapons and missiles support.

Therefore, in order to overcome the low absorptivity of 2024 aluminum alloy micron powder to laser in the prior art, which in turn leads to many limitations in the application of selective laser melting technology, those skilled in the art are committed to developing an aluminum alloy powder The preparation method and the method for in-situ synthesis of carbon nanotubes can not only improve the absorption efficiency of aluminum alloy powder to laser energy by utilizing the strong light absorption and surface effect of carbon nanotubes, but also enhance the aluminum alloy matrix through the strengthening effect of carbon nanotubes. It can retain the sphericity of the powder to the maximum extent to meet the needs of 3D printing.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder, which can not only utilize the strong light-absorbing parts and surface effects of carbon tubes to improve the aluminum alloy. The absorption efficiency of the powder to the laser energy, at the same time, the aluminum alloy matrix is enhanced by the strengthening effect of carbon nanotubes, and the sphericity of the powder can be retained to the maximum extent to meet the needs of 3D printing.

In order to achieve the above purpose, the present invention provides a method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder, the method comprising the steps of:

S100, preparing Ni/2024Al catalyst;

S200, calcining the Ni/2024Al catalyst in a mixed gas atmosphere to obtain a CNTs/2024Al-Ni composite powder.

The present invention also provides a method for preparing a Ni/2024Al catalyst, the method comprising:

S100. Weigh 2024Al alloy powder and nickel nitrate hexahydrate, mix them in absolute ethanol, and ultrasonically disperse them uniformly;

S200, the mixture dispersed in step S101 is continuously stirred by a magnetic stirrer at 50° C. until the absolute ethanol is completely volatilized to obtain powder;

S300, placing the powder obtained in S200 in a quartz boat, and calcining under the protection of a protective gas atmosphere to obtain NiO/2024Al composite powder;

S400 and the NiO/2024Al composite powder obtained by reducing S300 to obtain a Ni/2024Al catalyst.

Compared with the prior art, the present invention has the following technical advantages:

The method of the invention for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder utilizes the strong light absorption and nanoscale surface effect of carbon tubes to improve the absorption efficiency of aluminum alloy powder to laser energy, reduce energy loss, and avoid high input energy to samples. The adverse effect of the microstructure overcomes the adverse effect of the low absorbance of the metal powder on the application of 3D printing technology, and at the same time preserves the sphericity of the original powder to the greatest extent to meet the requirements of 3D printing.

The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, characteristics and effects of the present invention.

Description of drawings

1 is a flow chart of a method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder according to a preferred embodiment of the present invention;

Fig. 2(a) to Fig. 2(b) are SEM and TEM pictures of CNTs/2024Al-Ni composite powder with nickel content of 1.0 wt.% prepared by a preferred embodiment of the present invention, wherein Fig. 2(a) is SEM image of the prepared CNTs/2024Al-Ni composite powder with a nickel content of 1.0 wt.%; Figure 2(b) is a TEM image of the prepared CNTs/2024Al-Ni composite powder with a nickel content of 1.0 wt.%;

Figures 3(a) to 3(b) are SEM and TEM pictures of the CNTs/2024Al-Ni composite powder with a nickel content of 2.5wt.% prepared by a preferred embodiment of the present invention; Figure 3(a) Figure 3(b) is the TEM photo of the prepared CNTs/2024Al-Ni composite powder with a nickel content of 1.0 wt.%;

FIG. 4 is a comparison chart of the absorbance of CNTs/2024Al-Ni composite powder and pure 2024Al prepared in Example 1 and Example 2 of the present invention;

FIG. 5 is a graph showing the relationship between the yield of CNTs prepared by a preferred embodiment of the present invention and the variation of nickel content.

Detailed ways

The following describes several preferred embodiments of the present invention with reference to FIGS. 1 to 5 of the specification, so as to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned herein.

As shown in the flow chart of the method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder in a preferred embodiment of the present invention, the method includes the following steps:

S100, preparing Ni/2024Al catalyst;

S200, calcining the Ni/2024Al catalyst in a mixed gas atmosphere to obtain a CNTs/2024Al-Ni composite powder.

The method of the invention for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder utilizes the strong light absorption and nanoscale surface effect of carbon tubes to improve the absorption efficiency of aluminum alloy powder to laser energy, reduce energy loss, and avoid high input energy to samples. The adverse effect of the microstructure overcomes the adverse effect of the low absorbance of the metal powder on the application of 3D printing technology, and at the same time preserves the sphericity of the original powder to the greatest extent to meet the requirements of 3D printing.

In a preferred embodiment, the step S100 further includes:

S101, weighing 2024Al alloy powder and nickel nitrate hexahydrate and mixing them in absolute ethanol to obtain a mixture, and ultrasonicating the mixture for 30-40mins to fully disperse;

S102, the mixture dispersed in step S101 is continuously stirred by a magnetic stirrer at 50° C. until the absolute ethanol is completely volatilized to obtain powder;

S103, placing the powder in a quartz boat, and calcining at 200-250° C. for 4-5 h under the protection of Ar/N ₂ to obtain NiO/2024Al composite powder;

S104 , reducing the NiO/2024Al composite powder at 450-500° C. for 2.0-2.5 h in a hydrogen atmosphere to obtain a Ni/2024Al catalyst.

In a preferred embodiment, step S200 further includes:

S201, react the Ni/2024Al catalyst obtained in step S100 under a H ₂ /Ar/CH ₄ mixed gas atmosphere at 650-700° C. for 1-1.5 hours to obtain a sample;

S202, the sample obtained in step S201 is cooled to room temperature under N ₂ /Ar protection and taken out to obtain CNTs/2024Al-Ni composite powder.

In a preferred embodiment, the mass of the 2024Al aluminum alloy powder is 18-20 g, the mass of the nickel nitrate hexahydrate is 2.0-2.5 g, and the ultrasonic dispersion time is 30-40 mins.

In a preferred embodiment, H ₂ is 120-140 sccm, Ar is 60-70 sccm, and CH ₄ is 460-480 sccm.

The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

Example 1

1. Weigh 18g of 2024Al alloy powder and 2.0g of nickel nitrate hexahydrate (Ni content is 1.0wt.%), place them in 200mL of absolute ethanol, and keep the temperature at 50°C under continuous magnetic stirring until the absolute ethanol is completely volatilized. , the obtained powder was placed in a quartz boat, and calcined at 200 °C for 5 h under the protection of nitrogen atmosphere to obtain NiO/2024Al composite powder;

2. Switch the gas path to H ₂ , heat up to 450°C to reduce the NiO/2024Al composite powder for 2 hours, and reduce the NiO to Ni particles to obtain the catalyst Ni/2024Al composite powder;

3. The gas path is switched to H ₂ /Ar/CH ₄ / mixed gas, the ratio is 120sccm/60sccm/460sccm, the temperature is raised to 650 ℃ and the reaction is 1.5h, the gas path is switched to H ₂ , and the temperature is lowered to room temperature under the protection of H ₂ to obtain CNTs/2024Al-Ni composite powder with high absorbance with nickel content of 1.0wt%.

Fig. 2(a) to Fig. 2(b) are SEM and TEM pictures of the CNTs/2024Al-Ni composite powder with nickel content of 1.0 wt.% prepared in Example 1 of the present invention. It can be seen that the prepared CNTs/2024Al-Ni composite powder maintains its original sphericity to the greatest extent. Therefore, the preparation method of the present invention does not destroy the original shape of the powder, and the CNTs/2024Al-Ni composite powder meets the requirements of 3D Printing requirements for metal powders; as can be seen in Figure 2(b), the CNTs/2024Al-Ni composite powder prepared in Example 1 has a complete structure and uniform distribution, which can play a good role in strengthening the matrix.

Example 2

1. Weigh 20g of 2024Al alloy powder and 2.5g of nickel nitrate hexahydrate (Ni content is 2.5wt.%), place them in 200mL of absolute ethanol, keep warm at 50°C under continuous magnetic stirring, until the absolute ethanol evaporates completely , the obtained powder was placed in a quartz boat, and calcined at 250 °C for 4 h under the protection of N ₂ to obtain NiO/2024Al composite powder;

2. Switch the gas path to H ₂ , heat up to 500°C for reduction for 2.5 hours, and reduce NiO to Ni particles to obtain catalyst Ni/2024Al composite powder;

3. The gas path is switched to H ₂ /CH ₄ /N ₂ mixed gas with a ratio of 140sccm/70sccm/480sccm, the temperature is raised to 700 ℃ and reacted for 1h, the gas path is switched to H ₂ , and the temperature is lowered to room temperature under the protection of H ₂ to obtain CNTs/2024Al-Ni composite powder with high absorbance with nickel content of 2.5wt%.

Figures 3(a) to 3(b) are SEM and TEM photographs of the CNTs/2024Al-Ni aluminum alloy powder with a nickel content of 1.0 wt.% prepared in Example 2 of the present invention. It can be seen that the prepared CNTs/2024Al-Ni composite powder maintains its original sphericity to the greatest extent. Therefore, the preparation method of the present invention does not destroy the original shape of the powder, and the CNTs/2024Al-Ni composite powder meets the requirements of 3D Printing requirements for metal powder; as can be seen in Figure 3(b), the nanotubes prepared in Example 1 have a complete structure and uniform distribution, which can play a good role in strengthening the matrix.

Figure 4 is a comparison chart of the absorbance of CNTs/2024Al-Ni aluminum alloy powder prepared in Example 1 and Example 2 of the present invention and pure 2024Al. It can be seen that the absorbance of pure 2024Al is between 0.10% and 0.25%, while the absorbance of the 2024Al alloy powder modified by carbon nanotubes prepared in Examples 1 and 2 of the present invention has reached more than 2%. In particular, the absorbance of the CNTs/2024Al-Ni aluminum alloy powder with a nickel content of 1.0 wt.% prepared in Example 1 is more than 10 times that of the original powder, which fully shows that the CNTs/2024Al-Ni obtained by the preparation method of the present invention The powder can significantly improve the absorptivity of the alloy powder to the laser light.

Figure 5 is a graph showing the relationship between the yield of CNTs and the content of nickel prepared by a preferred embodiment of the present invention. It can be seen from the figure that when the content of nickel increases from 0.25% to 2%, the yield of CNTs increases, and The CNTs yield reached the highest when the nickel content was 2%; when the nickel content continued to increase from 2% to 10%, the CNTs yield decreased accordingly. Therefore, according to Fig. 5, we draw a revelation that different yields of CNTs can be obtained by adjusting the nickel content. And according to the printing needs under different conditions to carry out personalized adjustment.

The preferred embodiments of the present invention have been described in detail above. It should be understood that many modifications and changes can be made according to the concept of the present invention by those skilled in the art without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protection scope determined by the claims.

Claims (9)

1. A method for in-situ synthesis of carbon nanotubes on the surface of aluminum alloy spherical powder, the method comprising the following steps: S100, preparing Ni/2024Al catalyst; S200, calcining the Ni/2024Al catalyst in a mixed gas atmosphere to obtain a CNTs/2024Al-Ni composite powder. 2. The method according to claim 1, wherein, preferably, the step S100 further comprises: S101, weighing 2024Al alloy powder and nickel nitrate hexahydrate and mixing them in absolute ethanol to obtain a mixture, and ultrasonicating the mixture for 30-40mins to fully disperse; S102, the mixture dispersed in step S101 is continuously stirred by a magnetic stirrer at 50° C. until the absolute ethanol is completely volatilized to obtain powder; S103, placing the powder in a quartz boat, and calcining at 200-250° C. for 4-5 hours under the protection of Ar/N2 to obtain NiO/2024Al composite powder; S104 , reducing the NiO/2024Al composite powder at 450-500° C. in an H ₂ atmosphere for 2.0-2.5 h to obtain a Ni/2024Al catalyst. 3. The method of claim 1, wherein the step S200 further comprises: S201, react the Ni/2024Al catalyst in a H ₂ /Ar/CH ₄ mixed gas atmosphere at 650-700° C. for 1-1.5 h to obtain a sample; S202, the sample obtained in step S201 is cooled to room temperature under the Ar/H ₂ protection and taken out to obtain CNTs/2024Al-Ni composite powder. 4. The method of claim 3, wherein in the step S201, H ₂ is 120-140 sccm, Ar is 50-70 sccm, and CH ₄ is 460-480 sccm. 5. a preparation method of Ni/2024Al catalyst, described method comprises: S100. Weigh 2024Al alloy powder and nickel nitrate hexahydrate, mix them in absolute ethanol, and ultrasonically disperse them uniformly; S200, the mixture dispersed in step S101 is continuously stirred by a magnetic stirrer at 50° C. until the absolute ethanol is completely volatilized to obtain powder; S300, placing the powder obtained in S200 in a quartz boat, and calcining under the protection of a protective gas atmosphere to obtain NiO/2024Al composite powder; S400 and the NiO/2024Al composite powder obtained by reducing S300 to obtain a Ni/2024Al catalyst. 6. The preparation method according to claim 5, wherein the mass of the 2024Al aluminum alloy powder described in S100 is 18-20 g, the mass of the nickel nitrate hexahydrate is 2.0-2.5 g, and the time of the ultrasonic dispersion is 30 g. -40mins. 7 . The preparation method according to claim 5 , wherein the protective gas in S300 is one of N ₂ , Ar or a mixed gas thereof. 8 . 8. The preparation method according to claim 5, wherein the calcination temperature in S300 is 200-250°C, and the calcination time is 4-5h. 9 . The preparation method according to claim 5 , wherein the reducing gas in S400 is H ₂ , the reducing temperature is 450-500° C., and the reducing reaction time is 2.0-2.5 h. 10 .

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