The direct method of low-temperature synthesis of carbon nanotube on base material
Technical field
The present invention is the synthetic method of relevant a kind of CNT (carbon nano-tube) (carbon nanotubes), and especially relevant a kind of mode by the low temperature thermal chemical vapor deposition contains on the base material of the active catalyst system capable of sandwich framework the directly method of growth CNT (carbon nano-tube) one.
Background technology
CNT (carbon nano-tube) (carbon nanotubes) has very special character, special or the like such as low density, high strength, high tenacity, deflection, high surface area, big, the high thermal conductance degree of surperficial curvature, electroconductibility, so attract many research workers to be absorbed in exploitation its possible application mode, for example matrix material, micromodule, flat-panel screens, cableless communication, fuel cell and lithium ion battery or the like.With Field Emission Display (the carbon nanotube field emission displays of CNT (carbon nano-tube) as electron emission source, be called for short CNT-FED) be one to have the novel planar indicating meter of potentiality, usually relatively large CNT-FED processing procedure is with CNT (carbon nano-tube) blending conductive rubber, be implanted in the conducting glass substrate surface through mixing technology such as slurry, wire mark, again through the sintering steps of 450 to 550 degree Celsius to remove the polymer substance in the slurry, to form electroconductibility good electron radiation film.Such CNT-FED processing procedure except need through several steps, technology are comparatively loaded down with trivial details, and CNT (carbon nano-tube) is difficult for being dispersed in this conductive rubber.
The method that can synthesize the CNT (carbon nano-tube) that possesses the field emission electron function at present has arc discharge method (arc discharge), laser method of evaporation (1aser vaporization) and thermal chemical vapor deposition method (thermal chemical vapor deposition, thermal CVD) or the like.The length and the caliber of arc discharge method and the not only uncontrollable CNT (carbon nano-tube) product of laser method of evaporation, and its productive rate is quite low.Considerable non-setting carbon (amorphous carbon) can be produced in addition, processing need be further purified.In addition, the service temperature of these processing procedures all surpasses 1000 degree, directly synthesis of carbon nanotube on glass baseplate Celsius.Therefore, it is generally acknowledged the most potential technology main flow that becomes the temperature production CNT (carbon nano-tube) of thermal chemical vapor deposition method.
Past thermal chemical vapor deposition method synthesis of carbon nanotube technology, mainly be to be carrier, and be deposited on reactive metal catalyst on this carrier with impregnation method (impregnation) preparation with poriness silicon oxide (porous silica), zeolite (zeolite), aluminum oxide (alumina) or magnesium oxide (magnesiumoxide).The major cause of selecting above carrier for use is because this type of carrier is the indifferent oxide of quite stable, is difficult for when heating and the reaction of reactive metal catalyst, makes the reactive metal catalyst lose activity, and can't carry out the building-up reactions of CNT (carbon nano-tube).The reactive metal of selecting for use is mainly iron, cobalt or nickel, and adds in addition conditioned reaction activity such as trace metal such as copper, molybdenum, manganese, zinc or platinum etc.The reaction conditions that uses this reactive metal catalyst that is deposited on carrier to carry out catalysis carbon distribution reaction generation CNT (carbon nano-tube) in reactor comprises: reactor is imported rare gas element (helium, argon, nitrogen), hydrogen, reaches carbon-source gas, temperature of reaction is generally 650 to 1000 ℃, pressure is 1 to 2 normal atmosphere, and the reaction times is 1 to 120 minute.Employed carbon source comprises hydrocarbon polymer or carbon monoxide.Need after reaction finishes carrier to be removed, just can obtain purer CNT (carbon nano-tube), use or other purposes for the CNT-FED processing procedure with acid solution.
In the processing procedure of present CNT-FED, CNT (carbon nano-tube) must see through aforesaid loaded down with trivial details step, just can be attached at substrate surface, so that the distribution of the CNT (carbon nano-tube) of substrate surface and arrangement will be subjected to the influence of many processing procedure factors, for example the number of the purity of CNT (carbon nano-tube) and specification, addition, CNT (carbon nano-tube) are in the dispersion situation of mixing the slurry process and skill of wire mark or the like, reduce the yield of CNT-FED virtually, increased the manufacturing cost of CNT-FED.If but CNT (carbon nano-tube) can be directly grown in substrate surface, how then above problem will not exist, the processing procedure of CNT-FED just can obtain major improvement, and CNT (carbon nano-tube) synthetic will become the root module in the processing procedure of CNT-FED, can in same processing procedure, monitor the QC whole manufacturing process systematically, improve the good rate of CNT-FED.
Generally speaking, can reach as high as 650 ℃ through the deformation temperature (strain temperature) of the heatproof glass of calcination, about 550 ℃ or lower of relatively poor soda glass deformation temperature, so if will directly CNT (carbon nano-tube) be grown in substrate surface with thermal chemical vapor deposition method, then its temperature of reaction can not surpass the deformation temperature of base material, that is is preferably lower than 600 ℃.Yet process temperatures is too low, and general catalyst activity just is not enough to synthesis of carbon nanotube, so need exploitation one highly active special catalyst system capable, to carry out CNT (carbon nano-tube) under 600 ℃ the low temperature synthetic to be lower than.
European patent application EP 1061041 A1 have disclosed a kind of low temperature hot CVD equipment and have utilized the method for equipment synthesis of carbon nanotube, be that the reaction tubes in this equipment is divided into abutting gas importation spatially, is used for first district of thermolysis input gas, with on the space in abutting connection with discharge portion, be used to utilize aforesaid decomposition gas synthesis of carbon nanotube second district, and, the temperature that keeps two districts makes the temperature in second district be lower than the temperature in first district.Formation reaction district in CNT (carbon nano-tube) uses two kinds of different catalyst substrates, wherein a slice is used as accelerator, mainly act as to quicken the acetylene cracking, and composition is Pd, Cr and Pt etc., another sheet then deposits iron, cobalt, nickel or its catalytic alloy film, is the catalyst that mainly generates CNT (carbon nano-tube).The catalyst substrate etching gas corrosion that will have iron, cobalt, nickel or its catalytic alloy film, form nano level catalytic particle, utilize aforesaid device prior to the pyrolytic decomposition carbon source gas in first district, then, under the temperature that is equal to or less than the substrate deformation temperature, use the carbon source gas that is decomposed by accelerator by second district, through thermal chemical vapor deposition reaction, growth of vertical carbon nanotubes arranged on each isolated nano level catalytic metal particles on the substrate.The case technology is except the low-temp reaction section that uses 450 to 650 degree Celsius before this, still must use the high temperature of 700 to 1000 degree Celsius to carry out the thermolysis (first district) of carbon source gas, be not to be pure low temperature process, also therefore preceding case technology must be used special CVD reactor.Must on two base materials, form two kinds of different metal solvent layers in this external technology of case before this, again with these two kinds of base materials to be placed in the thermal cvd reactor device across a segment distance between the relative mode of metal level.Clearly, the processing procedure complexity of case technology, cost height and be not easy to implement before this.
European patent application EP 1061043 A1 have disclosed a kind of method of utilizing metal solvent layer low temperature synthesizing carbon nanotubes.In this synthetic method, on base material, form metal solvent layer, the isolated nano level catalytic metal particles of the etched formation of this metal solvent layer.Then, by under the temperature that is equal to or less than the substrate deformation temperature, using the carbon source gas that is decomposed, through thermal chemical vapor deposition, growth of vertical carbon nanotubes arranged on each isolated nano level catalytic metal particles on the substrate.The carbon source gas that this is decomposed is to use a carbon source gas decomposing metal catalyst layer.Must on two base materials, form two kinds of different metal solvent layers in the case technology before this, again with these two kinds of base materials to be placed in the thermal cvd reactor device across a segment distance between the relative mode of metal level.Clearly, the case technology is for improving the processing procedure patent of EP1061041 A1 before this, main progressive is for to change to the one-part form heating system with the two-part heating system, but there is no tangible progressive for catalyst system capable, still needs to use on two plate bases two kinds of different catalyst system capables.
Summary of the invention
A main purpose of the present invention is to provide a kind of directly method of low-temperature synthesis of carbon nanotube on base material, and it does not have the shortcoming of aforementioned prior art.
Another object of the present invention is to provide a kind of directly method of low-temperature synthesis of carbon nanotube on base material, it has its catalyst system capable and prepares easy advantage.
Another object of the present invention is to provide a kind of directly method of low-temperature synthesis of carbon nanotube on base material, it has its catalyst and forms the advantage of adjusting and controlling easily.
For achieving the above object, a kind of directly method of finishing according to the present invention of low-temperature synthesis of carbon nanotube on base material comprises the following step:
A) on a base material, form a metal carrier layer;
B) on this metal carrier layer, form a metal solvent layer;
C) on this catalyst metal layer, form one and cover metal level; And
D) use a carbon-source gas by the CNT (carbon nano-tube) of growing up on the side that has this metal carrier layer, metal solvent layer and covering metal level by thermal chemical vapor deposition at this base material;
This metal carrier layer and cover metal level and have a thickness between 0.1 to 50 micron respectively wherein, and the former is thick than the latter;
This metal carrier layer comprises a precious metal;
This covering metal level comprises a precious metal; And
This metal solvent layer comprises a metal of the group that chosen from Fe, cobalt, nickel and alloy thereof form.
Preferable, the metal carrier layer of step a) is by being formed by vacuum splashing and plating, chemical vapour deposition, physical vapor deposition, wire mark or galvanized mode.
Preferable, the formation of the metal carrier layer of step a) comprise with one be dispersed with particle diameter between the glue wire mark of the noble metal of 0.1-10 micron on this metal solvent layer, and the oven dry coating that sintering obtained.
Preferable, the metal solvent layer of step b) is by being formed by vacuum splashing and plating, chemical vapour deposition, physical vapor deposition, wire mark or galvanized mode.More preferable, the metal solvent layer of step b) is by being formed by galvanized mode.
Preferable, the covering metal level of step c) is by being formed by vacuum splashing and plating, chemical vapour deposition, physical vapor deposition, wire mark or galvanized mode.
Preferable, the formation of the covering metal level of step c) comprises and is dispersed with particle diameter with one and is coated on this metal solvent layer between the glue of the noble metal of 0.1-10 micron, and the coating that obtained of oven dry.
Preferable, the metal carrier layer of step a) comprises silver, gold, platinum, palladium or copper, wherein with silver for better.
Preferable, the metal carrier layer of step a) comprises an identical precious metal with the covering metal level of step c).
Preferable, the metal solvent layer of step b) comprises nickel.
Preferable, the thermal chemical vapor deposition of step d) is one between 400 to 600 ℃ temperature of reaction, and one carries out one between reaction times of 1 to 120 minute between 0.5 to 2 atmospheric pressure; This carbon-source gas comprises hydrocarbon polymer or carbon monoxide.
Compare with preceding case, major advantage of the present invention has: one, simple, the safety of the synthetic method of catalyst system capable and be easy to amplify.Two, adopt the one-part form low temperature process, processing procedure simple and safe be to be much better than the two-part processing procedure of one section Pintsch process, one section carbonization at low temperature, so also help to reduce the production cost of CNT-FED.Three, the reactive metal catalyst layer can form by plating mode, and its composition is adjusted easily and controlled and can embed the CNT-FED procedure for producing.Four, catalyst system capable is that single formula reactive system does not need extra accelerator substrate.Five, do not need mode with electric paste etching (plasmaetching) to activate catalyst system capable and can simplify processing procedure.Six, trilaminar covering metal level helps engaging of the CNT (carbon nano-tube) layer that generates and substrate surface.
Other purpose of the present invention and further processing procedure will be by cooperating icon to be described as follows by following embodiment.
Description of drawings
Fig. 1 shows the process block diagram (schematicblock diagram) of a preferred embodiment of the inventive method.
Embodiment
The detailed description of preferred embodiment
The present invention discloses a kind of directly method of low-temperature synthesis of carbon nanotube on base material, is different from the mode of the cancellation synthesis of nano metal solvent that aforementioned EP application case disclosed, and the present invention prepares catalyst with the method for additive properties.At first be coated with the catalyst carrier that one deck need not be removed, that is this carrier will not influence derived product and its processing procedure at substrate surface.With CNT-FED is example, and the silver-colored particle in the elargol promptly can be used as the catalyst carrier because elargol be in the CNT-FED processing procedure the essential surperficial solid that uses, can directly be dropped in the CNT-FED processing procedure so this carrier will need not be removed.Be coated with one deck reactive metal catalyst again on this type of carrier surface then, the last thinner covering metal of coating one deck on the reactive metal catalyst layer again.The method that forms this three-layer metal layer comprises vacuum splashing and plating, chemical vapour deposition, physical vapor deposition, wire mark or plating or the like.Special like this catalyst system capable just can be in substrate surface direct growth CNT (carbon nano-tube) under the condition of thermal chemical vapor deposition reaction, and temperature of reaction is controlled at below 600 ℃ still can be fast and synthesis of carbon nanotube in large quantities.
An a kind of directly preferred embodiment of the method for low-temperature synthesis of carbon nanotube on base material of the present invention comprises step as shown in Figure 1.Get a plate substrate earlier and be immersed in the acetone and clean, be aided with the ultrasound concussion and take out drying for standby after 30 minutes.This step is pre-treatment, and purpose is that thorough cleaned base material surface is to make things convenient for the formation of metal carrier.Above-mentioned base material can be Silicon Wafer, silica glass, chilled glass, soda glass, ITO conductive glass or silicon oxide and uses soda glass in this embodiment.In the wire mark mode elargol is coated on the base material, dried sintering 30 minutes with 400 ℃ then in air, just form the metal carrier layer of one deck based on silver on the base material, its thickness is the 5-20 micron.This elargol comprises particle diameter 1-5 micron silver particles, silver solid content 50-65wt%, other be celluosic resin (Cellulose resin) and solvent dl-1-right-alkene terpene alcohol (dl-α-terpineol) (this elargol (Print silver paste) is available from the Hsinchu City, Taiwan Province: chant glad company limited, commercial disignation B-AP01).Place electrolytic solution to electroplate as negative electrode this base material again, with preparation reactive metal catalyst layer, the salt that contains transition metal in the electrolytic solution, transition metal such as iron, cobalt, nickel etc., salt can be nitrate or vitriol, to between the 1M, electroplating time is between 5 seconds to 10 minutes to salt density at 0.001M.Use nickelous nitrate in this embodiment, concentration 5mM, electroplating time 30-60sec, the reactive metal catalyst layer thickness that is obtained is the 5-30 micron.After finishing, moistening with acetone, the fulmargin that dilute of coating on the reactive metal catalyst layer again, this dilution fulmargin are aforementioned elargol 1 to be restrained be dissolved in 9 and restrain acetone solvents and prepare.The base material that coating is finished was with 100 ℃ of oven dry 30 minutes, and the covering metal layer thickness that is obtained is the 5-15 micron.
The base material that will have above-mentioned catalyst system capable places a CVD reactor to carry out the thermal chemical vapor deposition reaction, the feed gas of reaction comprises rare gas element argon gas (flow 500sccm), hydrogen (flow 75sccm) and as the acetylene (flow 25sccm) of carbon source, temperature of reaction is 475 ℃, reaction times is 3 minutes, and pressure is 1 normal atmosphere.The CNT (carbon nano-tube) that the reaction back directly grows up at substrate surface has the caliber that is distributed in the 30-70 nanometer, and these CNT (carbon nano-tube) can radiate electronics under low voltage.