The method of coating metal nano granule by laser synthesizing carbon
[technical field]: the invention belongs to the nano material manufacture technology field, particularly a kind of method of coating metal nano granule by laser synthesizing carbon.
[background technology]: the carbon-clad metal nano particle is a kind of nano material with core/shell structure that is formed by fullerene carbon-coating coating metal particles.Because carbon-coating has protective effect to nano-metal particle, has expanded the range of application of this nano-metal particle material greatly, makes it demonstrate huge potential using value in many science and technology field such as biomedical engineering, catalysis and new forms of energy.
The carbon-clad metal nano particle is as a kind of advanced composite material (ACM), and the research of its preparation, performance and application has become the research focus of material science.At present, the method for preparing the carbon-clad metal nano particle mainly contains: 1, arc discharge method---and the carbon-clad metal nano particle of finding is first obtained when the graphite anode rod of La is mixed in employing arc process evaporation gasification in 1933 by U.S. Rouff group, it is the novel nano-material that is coated the La nanoparticle core by multilayer graphite synusia, referring to RSRuoff, DC Lorents, B Chan et al, Science, 1993,259:346~348.This method is under inert atmosphere, with the electrode that direct-current arc discharge evaporation is made up of powdered graphite and the metal simple-substance that will coat or its hopcalite, acquisition carbon-coated nano metallic particles in the product on being deposited on negative electrode or reaction chamber wall.Adopt at present arc process can obtain the carbon-clad metal nano particle of the less and narrow distribution of size, the crystallization degree of shell carbon is also higher.But because the complexity of reaction outside the de-carbon coating metal nano granule, also with a lot of accessory substances (as CNT, fullerene and carbon black etc.), makes that the purity of carbon-clad metal nano particle is low in the arc process product; The equipment more complicated used of the method in addition, technological parameter is wayward, and power consumption is big, and the cost height is difficult to realize extensive synthetic.2, chemical vapour deposition technique---people such as Wendy Teunisen introduce the template medium in calendar year 2001 and have prepared the NiFe composition metal carbon-coated nano material that structure is intact and be evenly distributed, its grain graininess is at 20~40nm, carbon-coating thickness is 5~10nm, referring to Teunissen W, de Groot FMF, Geus J., Journal of Catalysis, 2001,204:169-174.Chemical vapour deposition technique is that to prepare the carbon-clad metal nano particle relatively commonly used and be the more method of research, the product structure that obtains is intact, be evenly distributed and yield than arc process height, but it also has some shortcomings: the particle diameter of (1) gained carbon-clad metal nano particle and distribution are limited by the granular size and the distribution thereof of the preceding metallic catalyst of spreading on substrate of reaction, preparation of nanocatalyst in early stage and the even dispersion more complicated on substrate thereof, later stage product and substrate and catalyst carrier separate the comparison difficulty; (2) in the product outside the de-carbon coating metal nano granule, also can generate CNT and unbodied carbon granule simultaneously, purity is still lower.3, pyrolysismethod---this method forms the principle that carbon-coated nano metal crystalline substance is based on the liquid-phase catalysis thermal polycondensation, Huo Jun equality people utilizes the pyrolysis synthetic method, by the carbon-coated nano metallic particles of selecting metallic compound and aromatic compound type and control thermal response degree to obtain to have different shape and size, referring to H H Song, X H Chen, Chemical Physics Letters, 2003,374 (3-4): 400-404.The technology of pyrolysismethod is fairly simple, and preparation cost is lower, but it need select suitable source metal and carbon source, and the thermal response degree is also wayward, the possibility that this has just limited the kind of the nano-metal particle that carbon coats and has reduced successful preparation.
[summary of the invention]: the objective of the invention is wayward and problem such as product purity is low, output is little at reaction in the existing preparation carbon-clad metal nano particle technology, utilize laser technology to prepare the advantage of nano material, provide a kind of and be not subjected to carbon and the restriction of metallic presoma, technology is simple and the new method of the coating metal nano granule by laser synthesizing carbon that can prepare in a large number.
The method of coating metal nano granule by laser synthesizing carbon provided by the invention, this method may further comprise the steps:
The first, be raw material with micron order carbon dust and metal dust, metal powder and graphite atomic ratio are 1~2: 1, the mixed-powder of ball milling metal powder and carbon dust in absolute ethyl alcohol, and abrading-ball and raw material mass ratio are 5~10: 1.Adopting ball-milling technology is in order to make the refinement of micron order metal dust and evenly to mix with carbon dust.
Described carbon dust is graphite granule or carbon black granules, and its particle diameter should be smaller or equal to 10 microns; The metal dust raw material is micron order iron, cobalt or nickel particle, and particle diameter should be smaller or equal to 50 microns.
The second, the mixed-powder of metal powder behind the first step ball milling and carbon dust is put into liquid medium and form suspension, the mixed-powder of metal powder and carbon dust can be flowed freely in liquid medium.
The effect of liquid medium is that carbon dust and metal dust are suspended in wherein, and therefore, liquid medium can be water, alcohol, ketone, ether or the solution that is formed by these liquid, and by any two or more mixed liquor that forms between them.
The metal powder in the suspension and the mixed-powder of carbon dust utilize ultrasonic wave that suspension is evenly disperseed and fully act on laser.
Three, use the mixed-powder suspension of pulse laser bombardment metal powder and carbon dust, wherein pulse laser is irradiated in the liquid by the liquid surface top, and the focus of pulse laser converges at below the liquid surface, and focal plane and liquid level distance are greater than 1mm.
The focus of pulse laser converges the laser power density (referring to that output power of laser is divided by the resulting numerical value of the facula area at laser spot place) in zone 10
5W/cm
2To 10
9W/cm
2, the time of pulsed laser action was at 2~4 hours.
In the pulsed laser action process, adopt the outside water-bath type of cooling to absorb unnecessary heat to the container of the mixed-powder suspension that holds metal powder and carbon dust, suspension is under the normal temperature.
Four, the product after the 3rd pace pulse laser bombardment is obtained the carbon-clad metal nano particle through purifying.
A kind of device that is used for said method, this device comprises the Nd:YAG laser instrument, the pulse laser that laser instrument sends enters in the container of the mixed-powder suspension that fills metal powder and carbon dust successively after mirror reflects, condenser converge, and the focus that makes pulse laser converges at below the liquid level of suspension, and the container that fills the mixed-powder suspension of metal powder and carbon dust is followed successively by recirculated cooling water and supersonic generator outward.
The present invention has following advantage: the present invention has overcome deficiencies such as the wayward and degree of purity of production low yield of the presoma, the reaction condition that require to select suitable carbon and metallic particles in the technology of above-mentioned existing preparation carbon-clad metal nano particle is few, realize synthesizing of carbon-clad metal nano material at normal temperatures and pressures, obtained the higher carbon-clad metal nano particle of purity.In addition, synthetic method of the present invention has advantages such as technology is simple, course of reaction safety carbon-clad metal nano particle diameter controlled, that obtained is evenly distributed.
[description of drawings]:
Fig. 1 is the device schematic diagram of laser irradiation suspension.
Number in the figure is: 1, Nd:YAG laser instrument, 2, pulse laser, 3, nanocarbon/metal mixed-powder suspension, 4, supersonic generator, 5, prism, 6, condenser, 7, focus, 8, recirculated cooling water.
Fig. 2 is the carbon-coating nickel nano-particle transmission electron microscope photo without the suspension preparation of the laser bombardment graphite/nickel of purifying.
Fig. 3 is the height explanation transmission electron microscope photo of the carbon-coating nickel nano-particle after purifying.
[specific embodiment]:
Embodiment 1
As shown in Figure 1, the device among the present invention mainly is made up of Nd:YAG laser instrument 1, pulse laser 2, nanocarbon/metal mixed-powder suspension 3, speculum 5, condenser 6, supersonic generator 4 and recirculated cooling water 8.Converge through condenser 6 again after pulse laser 2 process prisms 5 reflections by 1 generation of Nd:YAG laser instrument.The focus 7 of pulse laser 2 is converged at below the liquid level of mixed-powder suspension 3 of metal powder and carbon dust suitably distance, usually focal plane and liquid level distance is good at 1~2mm, particle in the mixed-powder suspension 3 of metal powder and carbon dust disperses by supersonic generator 4, and cools off with 8 pairs of systems of recirculated cooling water in its outside.
Embodiment 2
Micron order metal dust (particle diameter should smaller or equal to 50 microns) and carbon dust (particle diameter should smaller or equal to 10 microns) be mixed and make raw material, add absolute ethyl alcohol ball milling in ball mill, abrading-ball and raw material mass ratio are 10: 1,1 hour ball milling time, this routine metal dust is a nickel powder, and nickel powder and graphite atomic ratio are 1: 1.Mixture behind the ball milling is suspended in forms suspension in the liquid medium, utilize ultrasonic wave to make its even dispersion.
The effect of liquid medium is that carbon dust and metal dust are suspended in wherein, therefore, liquid medium can for water, alcohol, ketone, ether etc. all can flowing liquid or the solution that forms by these liquid, and by two or more mixed liquor that forms arbitrarily between them.
Use the mixed-powder suspension of pulse laser bombardment metal powder and carbon dust, laser spot converges at suitable distance under the liquid surface, and focal plane and liquid level distance is good at 1~2mm usually.Produced the microcell of a HTHP at the laser spot place, impelled carbon and metallic particles gasification in the microcell, and then in the process of condensation, form the metal nanoparticle that carbon coats.The focus of pulse laser converges the laser power density in zone 10
5W/cm
2To 10
9W/cm
2, the time of laser action is about 2 hours.
The mixed-powder of metal powder and carbon dust should guarantee evenly to disperse in liquid medium.Because ultrasonic wave makes laser act on different carbon and metallic particles constantly in difference to the peptizaiton of mixed-powder, helps improving the productive rate of carbon-coated nano particle.
The composition of carbon dust raw material can be various types of graphite granules, carbon black granules or other carbonaceous particles, and its particle diameter should be smaller or equal to 10 microns; The metal dust raw material is micron order iron, cobalt and nickel particle, and particle diameter should be smaller or equal to 50 microns.
In the laser bombardment process, adopt the outer loop water-bath type of cooling to absorb unnecessary heat to the reaction vessel that holds suspension, liquid medium is under the normal temperature.
Product after the laser bombardment is obtained the carbon-clad metal nano particle through centrifugal, pickling purification.
Embodiment 3
On the basis of embodiment 2, by Nd-YAG solid state laser output wavelength be 1.06 μ m pulse laser beam (pulse width 1.0ms, pulse frequency is 15Hz, laser power density is 10
6W/cm
2), after the process optical lens converges, focus on following 1mm place, liquid medium surface.Liquid medium is that deionized water (also can be alcohol, ketone, ether or the solution that formed by these liquid, and by any two or more mixed liquor that forms between them), will be through ultrasonic being scattered in wherein of graphite/nickel mixed-powder that mixes behind the ball milling.The container that holds graphite/nickel mixed-powder suspension is adopted outer loop water-bath cooling.The time of pulsed laser action, with the carbon-coating nickel nano-particle of reacted product acquisition black after centrifugal and pickling are purified, particle diameter was distributed between 20~100nm about 2 hours.See also Fig. 2 and Fig. 3, wherein Figure 2 shows that the carbon-coating nickel nano-particle transmission electron microscope photo of the suspension preparation of the laser bombardment graphite/nickel of not purifying; Figure 3 shows that the height explanation transmission electron microscope photo of the carbon-coating nickel nano-particle after the purification.
Embodiment 4
In the reaction unit of embodiment 2 or 3, changing the metal dust raw material is the micron order iron powder, is to mix at 1: 1 to be incorporated in the absolute ethyl alcohol ball milling 1 hour with itself and graphite with the iron carbon atomic ratio, liquid medium is that ether (also can be water, alcohol, ketone or the solution that formed by these liquid, and by any two or more mixed liquor that forms between them), other reaction conditions are constant, reacted product obtained the carbon-encapsulated iron nano particle of black after centrifugal and pickling are purified.
Embodiment 5
In the reaction unit of embodiment 2 or 3, changing the carbon dust raw material is carbon black (average particle size particle size is between 50nm-200nm), it is mixed (carbon nickle atom ratio is 1: 1) with nickel powder, and in absolute ethyl alcohol ball milling 1 hour, liquid medium is that ketone (also can be water, alcohol, ether or the solution that formed by these liquid, and by any two or more mixed liquor that forms between them), other reaction conditions are constant, reacted product obtained the carbon-coating nickel nano-particle of black after centrifugal and pickling are purified.
Embodiment 6
In the reaction unit of embodiment 2 or 3, changing the metal dust raw material is the micron order cobalt powder, it is mixed (carbon cobalt atom ratio is 1: 1) with graphite, and in absolute ethyl alcohol ball milling 1 hour, liquid medium is the mixed liquor of water and ketone or water and ether, other reaction conditions are constant, reacted product obtained the carbon coating cobalt nano-particle of black after centrifugal and pickling are purified.