CN109550941B

CN109550941B - Carbon nano tube coated titanium spherical composite powder and preparation method thereof

Info

Publication number: CN109550941B
Application number: CN201811359015.1A
Authority: CN
Inventors: 杨亚锋; 李少夫; 刘宇; 谭冲
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2018-11-15
Filing date: 2018-11-15
Publication date: 2020-05-26
Anticipated expiration: 2038-11-15
Also published as: CN109550941A

Abstract

The invention relates to the technical field of preparation of titanium-based composite material raw materials, and relates to carbon nanotube-coated titanium spherical composite powder and a preparation method thereof. The composite powder takes titanium or titanium alloy as a matrix, the coating layer comprises carbon nano tubes, and the carbon nano tubes account for 0.1-5.0% of the total weight of the composite powder. The invention is mainly realized by combining powder surface treatment with a fluidized bed chemical vapor deposition technology, and compared with the traditional mechanical mixing technology, the technology has the advantages of simple process, short production flow, low cost, easy realization of large-scale production and good industrial prospect.

Description

Carbon nano tube coated titanium spherical composite powder and preparation method thereof

Technical Field

The invention relates to the technical field of preparation of titanium-based composite material raw materials, in particular to carbon nanotube-coated titanium spherical composite powder and a preparation method thereof.

Background

Titanium and titanium alloys have long played a great role in key parts in important fields such as aerospace, military and the like. However, with the rapid development of the aerospace industry and the defense technology in China, higher requirements are put forward on the aspects of light weight, high strength, heat resistance, high-efficiency forming and the like of a material structural member. For example, material structural members in aerospace and military products such as ring bodies, fans and high-pressure compressors in blade discs of aircraft engines need to have excellent comprehensive properties such as high-temperature strength, wear resistance and high thermal conductivity, and the intrinsic characteristics of titanium alloys determine that the overall optimization of the comprehensive properties is close to the upper regulation limit. In contrast, the introduction of a second phase with corresponding functional characteristics into a high-strength titanium alloy matrix has become an effective way for comprehensively improving the high-temperature strength, the wear resistance and the thermal conductivity of the titanium material. Therefore, the high-performance titanium-based composite material becomes an irreplaceable common key material in a plurality of high-end technical fields such as modern aerospace technology, space technology, energy development, national defense technology and the like. The action outline of "China manufacturing 2025" proposes to list titanium-based composite materials as one of the key development directions in the new material field in China.

The method is completely different from other traditional materials, and the titanium material generally has the problems of difficult mechanical processing, poor processing precision, high production cost and the like. With current cast forging processes, the effective utilization rate of raw materials processed to obtain the final parts is less than 12%, and titanium part manufacturers often have to purchase 8 times of the required parts weight for processing and manufacturing. Through decades of development, although the material utilization rate of the titanium material processing industry is improved to a certain extent, the effective utilization ratio of the titanium material processing industry is still less than 20% and is nearly the limit. Although the powder metallurgy technology can shorten the processing flow of parts to a certain extent and further reduce the cost, the formation of a large number of pore defects makes the density, the mechanical property and the thermoelectric property of a sintered part difficult to meet the rigorous requirements of high-end technical fields such as current aerospace, national defense science and technology and the like on the comprehensive properties of structural materials. Therefore, both casting and powder metallurgy processes have difficulty in fundamentally achieving low cost manufacturing of high performance titanium-based composite components.

The 3D printing additive manufacturing technology has the advantages of high raw material utilization rate, short production period, integrated forming of a complex structure and the like, and is very suitable for near-net forming manufacturing of complex-structure parts made of difficult-to-machine materials. In addition, the 3D printing additive manufacturing technology has the characteristics of high melt temperature, high solidification speed, small size of a molten pool and the like, and can effectively avoid coarsening of a matrix structure and a reinforcing phase, so that high performance of the formed material is ensured, and a small-size molten pool generated in the 3D printing process is beneficial to reducing surface roughness, and accurate control of the size precision of parts is realized. Therefore, the 3D printing additive manufacturing technology provides a new approach of a material preparation-part forming-performance regulation and control integrated technology for parts difficult to machine in important equipment in the high-end technical field.

The type of reinforcing phase is the most important factor for determining each performance index of the titanium-based composite material. Compare TiC and TiB₂In other words, carbon nanotubes have many advantages of small density, high strength, high thermal conductivity, extremely low friction coefficient, and the like, and are the most accepted ideal reinforcing phase of the existing titanium-based composite material. However, a production technology of high-quality carbon nanotube-titanium composite powder is still lacking at present, which also becomes a major technical bottleneck restricting the 3D printing preparation development and application of the carbon nanotube reinforced titanium-based composite material. For the conventional atomization powder preparation technology, the reinforcing phase and the titanium matrix in the composite powder are easy to separate due to the large physical property difference of density, wettability and the like between the reinforcing phase and the titanium matrix, and meanwhile, the introduction of the reinforcing phase deteriorates the viscosity of a melt to cause nozzle blockage, so that a second phase with a high volume fraction is difficult to introduce. Although the carbon nanotube-titanium composite powder can be successfully prepared by adopting a mechanical mixing method and the mass fraction of the carbon nanotube reinforcing phase can be quantitatively controlled, the following serious defects still exist, so that the carbon nanotube-titanium composite powder cannot be widely applied: (1) the sphericity and fluidity of the powder are seriously damaged; (2) the carbon nano tubes are not uniformly dispersed; (3) the composition and structural integrity of the carbon nanotubes is compromised; (4) a large amount of impurities such as oxygen, nitrogen and the like are introduced in the mechanical mixing process.

Disclosure of Invention

The invention aims to provide a carbon nano tube coated titanium spherical composite powder and a preparation method thereof. Aiming at the problems, the invention prepares the novel carbon nano tube-titanium composite powder by combining powder surface treatment with a fluidized bed chemical vapor deposition technology, and the composite powder has the advantages of high sphericity, good fluidity, adjustable carbon content, uniform carbon nano tube distribution, complete structure, low impurity content and the like. The preparation method breaks through the technical bottleneck of high-quality titanium-based composite powder preparation, and solves the problems of low sphericity, poor fluidity, incomplete carbon nanotube structure, impurity pollution and the like in the carbon nanotube-titanium composite powder. The powder can be directly used as a powder raw material for 3D printing of the carbon nanotube/titanium carbide reinforced titanium-based composite material, but the application is not limited to the powder raw material, and the powder raw material can also be used for preparing the powder raw material of the titanium-based composite material by using a powder metallurgy technology.

The specific technical scheme of the invention is as follows:

the invention provides a titanium spherical composite powder coated with carbon nano tubes, which is characterized in that the composite powder takes titanium or titanium alloy as a matrix, and a coating layer comprises the carbon nano tubes, wherein the carbon nano tubes account for 0.1-5.0% of the total weight of the composite powder.

Preferably, the coating layer of the composite powder takes carbon nanotubes as a main component, and also comprises a trace amount of unavoidable by-products generated by pyrolysis of carbon source gas, such as graphite nanoparticles and/or amorphous carbon.

The invention provides a preparation method of carbon nano tube coated titanium spherical composite powder, which comprises the following steps:

1) carrying out surface treatment on the powder raw material through a chemical etchant, and then cleaning and drying to obtain powder for chemical vapor deposition;

2) putting the powder obtained in the step 1) into a fluidized bed reactor, connecting a gas control system, the fluidized bed reactor, a heating system and a tail gas treatment device, checking the gas tightness, and introducing inert gas to remove air in the whole system;

3) putting the fluidized bed reactor in the step 2) into a heating system, heating to a preset temperature, and introducing a mixed gas of inert gas, auxiliary gas and carbon source gas according to a preset proportion to perform chemical vapor deposition reaction;

4) and after the preset reaction time is reached, stopping introducing the auxiliary gas and the carbon source gas, simultaneously increasing the flow of the inert gas, stabilizing for 30-60 min, taking out the fluidized bed reactor from the heating system, cooling to room temperature, and taking out the composite powder in the fluidized bed reactor.

Preferably, the powder raw material in the step 1) is titanium or titanium alloy spherical powder, and further preferably, the powder raw material comprises one or more of Ti, Ti-6Al-4V, Ti-10V-2Fe-3V, Ti-Ni alloy, Ti-Nb-Zr-Sn alloy, Ti-Al-Mn alloy and Ti-Al-Mo-V alloy, the purity is higher than 98%, and the particle size distribution is 5-150 μm.

Preferably, the ratio of the powder raw material to the chemical etchant in the step 1) is 5 g-100 g: 20ml to 500 ml.

Preferably, the chemical vapour deposition in step 1) is carried out by a fluidized bed technique. Further preferably, the chemical etchant in step 1) includes one or more of hydrofluoric acid, nitric acid, hydrochloric acid, concentrated sulfuric acid, deionized water and absolute ethyl alcohol.

Preferably, the heating system in step 2) comprises a high-temperature resistance furnace and a temperature control device, which can completely accommodate and uniformly heat the fluidized bed reactor.

Preferably, in the step 2), the gas speed of the inert gas is 0.1-1.2 m/min, and the exhaust time is 5-60 min.

Preferably, the inert gas in the step 2) is a gas which does not react with the powder raw material, and further preferably, the inert gas comprises one or more of helium, neon and argon, and the purity is higher than 99.99%.

Preferably, the preset temperature of the heating system in the step 3) is 500-850 ℃.

Preferably, the carbon source gas in step 3) is a gas that does not or only slightly react with the powder raw material at a preset reaction temperature and can obtain pyrolytic carbon, and further preferably, the carbon source gas comprises one or more of methane, ethane, propane, ethylene, propylene, acetylene, propyne and carbon monoxide, and has a purity higher than 99.99%.

Preferably, the auxiliary gas in step 3), further preferably, the auxiliary gas comprises hydrogen and/or carbon dioxide, and the purity is higher than 99.99%.

Preferably, the carbon source gas in the mixed gas in step 3): auxiliary gas: the volume ratio of the inert gas is (1-10): (0-10): (2-100).

Preferably, the gas velocity of the mixed gas in the step 3) is 0.1-1.2 m/min.

Preferably, the preset reaction time in the step 4) is 5min to 120 min.

Preferably, the fluidized bed reactor in the step 4) is cooled by air cooling or furnace cooling.

Preferably, the composite powder in the step 4) is a titanium spherical composite powder coated with carbon nanotubes, the mass fraction and the length-diameter ratio of the carbon nanotubes in the composite powder are improved along with the extension of the reaction time, and the composition, the thickness and the structure of the coating layer are changed along with the change of the reaction time.

Preferably, the preparation method of the carbon nanotube-coated titanium spherical composite powder comprises the following steps:

1) under an ultrasonic vibration or mechanical stirring mode, performing surface treatment on the powder raw material through a chemical etchant, performing ultrasonic cleaning on the treated powder by adopting absolute ethyl alcohol, and then placing the cleaned powder in an oven for drying to obtain the powder raw material for chemical vapor deposition;

2) putting the powder subjected to surface treatment into a fluidized bed reactor, connecting a gas control system, the fluidized bed reactor, a heating system and a tail gas treatment device through a silicone tube, checking the gas tightness, and introducing high-purity inert gas to exhaust the air in the whole system;

3) putting the fluidized bed reactor into a heating system, heating to a preset temperature, stabilizing for a period of time, reducing the flow of inert gas, and introducing inert gas, auxiliary gas and carbon source gas according to a preset proportion to perform chemical vapor deposition reaction;

4) stopping introducing the auxiliary gas and the carbon source gas after the preset reaction time is reached, simultaneously increasing the flow of the inert gas, taking out the fluidized bed reactor after the auxiliary gas and the carbon source gas are stabilized for a period of time, cooling the fluidized bed reactor to room temperature, and taking out the composite powder in the chemical vapor deposition fluidized bed;

5) and screening the composite powder by adopting a standard screen according to the selection standard of the metal 3D printing on the particle size of the powder raw material, and storing in a vacuum sealing manner.

Compared with the traditional mechanical mixing technology for preparing the carbon nano tube-titanium composite powder, the invention has the advantages that:

the carbon nano tube coated titanium or titanium alloy composite powder prepared by the invention is a composite powder with a core-shell structure, and has good sphericity, good fluidity and low impurity content; the carbon nano tubes are uniformly distributed on the surface of the titanium powder, have strong binding force with a matrix and are not easy to fall off, the carbon nano tubes have complete structures and are not easy to damage, and the mass fraction, the thickness, the length-diameter ratio and the like of the carbon nano tubes in the composite powder can be actively regulated and controlled through experiments of experimental parameters such as reaction temperature, carbon source concentration, operation gas speed, deposition time and the like. The method is mainly realized by combining powder surface treatment with a fluidized bed chemical vapor deposition technology, and compared with the traditional mechanical mixing technology, the method has the advantages of simple process, short production flow, low cost, easiness in realization of large-scale production and good industrial prospect.

Drawings

FIG. 1 is an SEM image of the Ti-6Al-4V powder after surface treatment in example 1 of the present invention;

FIG. 2 is an SEM image of carbon nanotube-coated Ti-6Al-4V spherical composite powder in example 1 of the present invention;

FIG. 3 is a Raman spectrum of the carbon nanotube-coated Ti-6Al-4V spherical composite powder in example 1 of the present invention;

FIG. 4 is an SEM image of carbon nanotube-coated Ti-6Al-4V spherical composite powder in example 2 of the present invention;

FIG. 5 is a high-magnification SEM image of carbon nanotubes coated on the surface of Ti-6Al-4V spherical composite powder in example 2 of the present invention;

FIG. 6 is an SEM image of carbon nanotube-coated Ti-6Al-4V spherical composite powder in example 3 of the present invention;

FIG. 7 is a high-magnification SEM image of carbon nanotubes coated on the surface of Ti-6Al-4V spherical composite powder in example 3 of the present invention;

FIG. 8 is an SEM image of carbon nanotube-coated Ti spherical composite powder in example 4 of the present invention;

FIG. 9 is a high-magnification SEM image of carbon nanotubes coated on the surface of a Ti spherical composite powder in example 4 of the present invention;

FIG. 10 is an SEM image of carbon nanotube-coated Ti-6Al-4V spherical composite powder in example 5 of the present invention.

Detailed Description

The present invention will be further described with reference to the following specific examples.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to two specific embodiments and with reference to the accompanying drawings, but the scope of the present invention is not limited thereto. Insubstantial changes, such as simple changes or substitutions, made in the same or similar features without departing from the spirit of the invention are intended to be covered by the claims.

Specifically, as one aspect of the present invention, a titanium spherical composite powder coated with carbon nanotubes is provided, wherein a surface coating layer uses carbon nanotubes as a main component, and further includes one or more of trace graphite nanoparticles and amorphous carbon, and the composite powder has the advantages of high sphericity, good fluidity, controllable carbon content, uniform carbon nanotube distribution, complete structure, low impurity content, and the like.

As another aspect of the present invention, a method for preparing a titanium spherical composite powder coated with carbon nanotubes is provided, which comprises the following steps:

example 1

1. The gas atomized Ti-6Al-4V spherical powder is selected as a raw material, the purity of the powder is 98.5%, and the particle size distribution is 15-53 mu m. And (3) adding deionized water: hydrofluoric acid: the nitric acid is mixed according to the volume percentage of 92: 3: 5 chemical erosion agent. Weighing 50g of Ti-6Al-4V powder, pouring the powder into 200ml of a chemical etchant, and carrying out surface treatment on the powder raw material in an ultrasonic vibration mode, wherein the ultrasonic frequency is 60HKz, and the treatment time is 10 min. And ultrasonically cleaning the powder subjected to surface treatment by adopting absolute ethyl alcohol, and then drying the powder in a vacuum drying oven at the temperature of 60 ℃ for 360min to obtain the powder for chemical vapor deposition.

2. The fluidized bed reactor for chemical vapor deposition is made of high-purity quartz, and consists of a conical fluidized bed inner tube and an original cylindrical sleeve, wherein the conical angle of the conical fluidized bed inner tube is 15 degrees, the diameter of the conical fluidized bed inner tube is 40mm, the distribution plate is a quartz sintered plate, the diameter of the cylindrical sleeve is 60mm, and the diameters of the air inlet and the air outlet are 8 mm.

3. Weighing 40g of Ti-6Al-4V powder subjected to surface treatment, adding the powder into a fluidized bed reactor, connecting a gas control system, the fluidized bed reactor and a tail gas treatment device through a silicone tube, introducing high-purity argon to discharge air in the whole experiment system, wherein the gas speed is 0.5m/min, and the exhaust time is 60 min.

4. A high-temperature resistance furnace is used as a heating device, the fluidized bed reactor is placed into the resistance furnace, the temperature is raised to 650 ℃, the stabilization is carried out for 5min, the argon flow is reduced to 0.4m/min, and simultaneously, high-purity acetylene and high-purity hydrogen with the air velocity of 0.05m/min are introduced for carrying out chemical vapor deposition reaction for 15 min.

5. And after the reaction is finished, stopping introducing acetylene and hydrogen, simultaneously increasing the gas velocity of high-purity argon to 0.5m/min, stabilizing for 10min, taking out the fluidized bed reactor, performing air cooling on the fluidized bed reactor to room temperature, taking out the powder, and screening the composite powder by using 300-mesh and 1000-mesh standard mesh screens respectively to obtain the carbon nano tube coated Ti-6Al-4V spherical composite powder for 3D printing.

FIG. 1 is an SEM image of the Ti-6Al-4V powder subjected to surface treatment in example 1, wherein the surface of the Ti-6Al-4V powder is corroded to show an uneven morphology, and the good sphericity is still maintained;

FIG. 2 is an SEM image of the Ti-6Al-4V spherical composite powder coated with carbon nanotubes in example 1, wherein the main component of the coating layer on the surface of the powder is carbon nanotubes and the carbon nanotubes are uniformly distributed;

FIG. 3 is a Raman spectrum of the Ti-6Al-4V spherical composite powder coated with carbon nanotubes in example 1, wherein the peak intensity ratio of amorphous carbon to graphite is less than 1, which indicates that the coating layer has a high graphitization degree.

Example 2

The present embodiment 2 differs from embodiment 1 in that: the erosion reagent is deionized water: hydrofluoric acid is mixed according to the volume percentage of 9: 1 is formulated as a chemical etching agent. The surface treatment time is increased from 10min to 30min, the gas velocity of the mixed gas is 1.2m/min, and the acetylene: hydrogen gas: the gas speed ratio of argon is 1: 1: 3, the chemical vapor deposition temperature is changed from 650 ℃ to 500 ℃;

FIG. 4 is an SEM image of the Ti-6Al-4V spherical composite powder coated with carbon nanotubes in example 2, wherein the erosion time is increased, the surface roughness of the powder is increased, but the sphericity is not obviously reduced;

FIG. 5 is a high-magnification SEM image of carbon nanotubes coated on the surface of Ti-6Al-4V spherical composite powder in example 2, wherein the mass fraction and number density of the carbon nanotubes are increased with the increase of the carbon source gas concentration.

Example 3

The present embodiment 3 differs from embodiment 1 in that: the chemical vapor deposition time was increased from 15min to 120 min.

Fig. 6 is an SEM image of the carbon nanotube-coated Ti spherical composite powder in example 3, and fig. 7 is an SEM image of the carbon nanotube-coated Ti spherical composite powder in example 3, in which the carbon nanotubes are distributed on the surface of the powder more uniformly. The chemical vapor deposition time is increased, and the number of the carbon nanotubes on the surface and the thickness of the carbon layer are increased.

Example 4

The present embodiment 4 differs from embodiment 1 in that: the Ti-6Al-4V powder is replaced by Ti spherical powder, the purity of the powder is 99.0 percent, and the particle size distribution is 15-53 mu m.

FIG. 8 is an SEM image of the carbon nanotube-coated Ti spherical composite powder in example 4, in which the Ti powder is treated to have a higher surface roughness and the surface of the powder is coated with carbon nanotubes having a higher number density;

fig. 9 is a high-magnification SEM image of carbon nanotubes coated on the surface of the Ti spherical composite powder in example 4, and carbon nanotubes with uniform distribution can be successfully synthesized on the surface of Ti powder.

Example 5

The present embodiment 5 differs from embodiment 1 in that: methane was used as a carbon source gas instead of acetylene, and the experimental temperature was adjusted to 850 ℃ from 650 ℃.

FIG. 10 is an SEM image of the carbon nanotube-coated Ti-6Al-4V spherical composite powder of example 5. When methane is used as the carbon source gas, the titanium alloy composite powder uniformly coated by the carbon nano tube can be obtained by increasing the experimental temperature.

The above embodiments are only some embodiments of the present invention, and are not intended to limit the scope of the present invention; therefore, the claimed invention is intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The carbon nano tube coated titanium spherical composite powder is characterized in that titanium or titanium alloy is used as a powder raw material of the composite powder, the powder raw material is spherical powder, a coating layer comprises carbon nano tubes, and the carbon nano tubes account for 0.1-5.0% of the total weight of the composite powder; wherein the powder raw material comprises one or more of Ti, Ti-6Al-4V, Ti-10V-2Fe-3V, Ti-Ni alloy, Ti-Nb-Zr-Sn alloy, Ti-Al-Mn alloy and Ti-Al-Mo-V alloy;

the preparation method of the composite powder comprises the following steps:

1) carrying out surface treatment on the powder raw material through a chemical etching agent, wherein the surface of the powder presents an uneven appearance after being etched, and then cleaning and drying to obtain powder for chemical vapor deposition; the chemical etchant comprises one or more of hydrofluoric acid, nitric acid, hydrochloric acid, concentrated sulfuric acid, deionized water and absolute ethyl alcohol; the proportion of the powder raw material to the chemical etching agent is 5 g-100 g: 20ml to 500 ml;

2) putting the powder obtained in the step 1) into a fluidized bed reactor, connecting a gas control system, the fluidized bed reactor, a heating system and a tail gas treatment device, checking the gas tightness, and introducing inert gas to remove air in the whole system; the inert gas is gas which does not react with the powder raw material;

3) putting the fluidized bed reactor in the step 2) into a heating system, heating to a preset temperature, and introducing a mixed gas of inert gas, auxiliary gas and carbon source gas according to a preset proportion to perform chemical vapor deposition reaction; the carbon source gas is a gas which does not react with the powder raw material at a preset temperature;

4) and after the preset reaction time is reached, stopping introducing the auxiliary gas and the carbon source gas, simultaneously increasing the flow of the inert gas, stabilizing for 30-60 min, taking out the fluidized bed reactor from the heating system, and cooling to room temperature to obtain the composite powder.

2. The method for preparing the composite powder according to claim 1, wherein the purity of the powder raw material in the step 1) is higher than 98%, and the particle size distribution is 5 μm to 150 μm.

3. The method for preparing composite powder according to claim 1, wherein the inert gas in step 2) comprises one or more of helium, neon and argon, and the purity is higher than 99.99%.

4. The method for preparing composite powder according to claim 1, wherein the preset temperature of the heating system in step 3) is 500 ℃ to 850 ℃.

5. The method for preparing composite powder according to claim 1, wherein the carbon source gas in step 3) comprises one or more of methane, ethane, propane, ethylene, propylene, acetylene, propyne and carbon monoxide, and the purity is higher than 99.99%.

6. The method for preparing composite powder according to claim 1, wherein the auxiliary gas in step 3) comprises hydrogen and/or carbon dioxide, and the purity is higher than 99.99%.

7. The method for preparing a composite powder according to claim 1, wherein the carbon source gas in the mixed gas in step 3): auxiliary gas: the volume ratio of the inert gas is (1-10): (0-10): (2-100).

8. The method for preparing the composite powder according to claim 1, wherein the preset reaction time in the step 4) is 5min to 120 min.