CN101339872B - Double layer mixing structure carbon nano tube membrane field emission cathode and preparation thereof - Google Patents
Double layer mixing structure carbon nano tube membrane field emission cathode and preparation thereof Download PDFInfo
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- CN101339872B CN101339872B CN2008101506392A CN200810150639A CN101339872B CN 101339872 B CN101339872 B CN 101339872B CN 2008101506392 A CN2008101506392 A CN 2008101506392A CN 200810150639 A CN200810150639 A CN 200810150639A CN 101339872 B CN101339872 B CN 101339872B
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Abstract
The invention discloses a membrane field emitting cathode of a carbon nanotube with double-layer blending structure and a preparation method thereof. Ti nano-powder is adopted to be mixed for preparing composite sizing agent (CNT), and CNT cathode membrane with single-layer Ti blending structure is printed by screen printing technique. The CNT composite membrane cathode with the double-layer blending structure that is TiO2 blending structure at the upper layer and Ti blending structure at the lower layer is formed by two-step sintering technique. On the surface layer of the composite membranecathode, conductive Ti is transformed into non-conductive dielectric material TiO2; shielding effect caused by the mutual contact of CNT is reduced, thereby being beneficial to the increase of enhancement factor of a CNT emitter. At the bottom of the composite membrane cathode, the blending nanophase material Ti enlarges the contact area between the CNTs and between the CNT and an underlay, reduces the contact resistance between the conductive electrode layers and the CNT layers and improves the electronic transportation performance of the self of CNT at the lower layer of the composite membrane cathode.
Description
Technical field
The present invention relates to a kind of field emission cathode structure and preparation method thereof, membrane field emission cathode of particularly a kind of CNT double layer mixing structure and preparation method thereof.
Background technology
Since Lijima found CNT, CNT emission on the scene field had obtained using widely.Compare arrays such as traditional silicon tip, tungsten point and molybdenum point, CNT has more sharp-pointed field emission tip, higher mechanical strength and more stable chemical characteristic, and material source is extensive, and preparation technology is simple relatively.At present, the method for preparing the CNT field-transmitting cathode has two kinds, chemical vapour deposition technique (CVD) and grafting.Because it is higher to utilize the CVD technology to prepare the cost of CNT negative electrode, the negative electrode cost that particularly is used for preparing large display device is higher, is unfavorable for that the CNT Field Emission Display is towards industrialized development.The silk screen print method price is not only cheap, but also is easier to make large-area CNT film cathode, make large scale, low-power and cheaply flat-panel monitor become possibility.Yet the CNT film cathode of silk screen print method preparation freely distributes because of CNT and at random to the factors such as poor adhesive force of substrate, and is poor than the field emission performance of the directed vertical CNT film cathode of CVD method direct growth.For example, the cut-in voltage height, the life-span is short etc.In order to strengthen the field emission performance of silk screen printing CNT negative electrode, more effective post-processing approach has mechanical crushing method, plasma bombardment method, adhesive tape sticking etc.Mechanical crushing method causes toppling of CNT during organic bond easily on removing the CNT film surface, and the firmly uneven damage that will cause the CNT film surface; The plasma bombardment method is a cost and remove organic machine adhesive effectively to destroy portion C NT; Adhesive tape sticking can stay cull and cause secondary pollution.Therefore, how to eliminate or avoid the influence of these reprocessings, just become problem of being concerned about very much of numerous scientific and technical personnel thereby seek the field emission performance that new method improves CNT to the CNT film cathode.
The nano particle completion method be because of improving the adhesive force between CNT and the substrate, stops CNT coming off and cause an emission unsteadiness to be subject to people's attention under stronger electrostatic field gravitation.More effective nano particle completion method has metal dust alloyage, slurry to mix Yin Fa and slurry is mixed glass dust method etc.; These methods can both obtain the CNT cathode thin film of individual layer mixing structure.Because of the electric conductivity difference of blending nano particle, the enhancing of blending CNT film cathode mechanism and field emission performance also have nothing in common with each other.Yet the blending particle of conduction in the contact resistance, is unfavorable for the raising of CNT emitter enhancer because of screen effect between reduction CNT and substrate; On the contrary, the blending material of dielectric property helps the raising of the enhancer of CNT emitter, has but increased the contact resistance between CNT and the substrate.
Summary of the invention
The purpose of this invention is to provide a kind of double layer mixing structure carbon nano tube membrane field emission cathode and preparation method thereof.The structure of this bilayer film is by the electric conductivity of structural advantage and blending material, from the adhesive force that strengthened CNT and substrate, improved the enhancer of CNT and reduced the field emission performance that the CNT film cathode has been improved in three aspects of contact resistance between CNT and substrate, reduced the unlatching field intensity of CNT and prolonged life-span of feds.
Technical scheme of the present invention is achieved in that
Double layer mixing structure carbon nano tube membrane field emission cathode comprises the negative electrode glass substrate, on the negative electrode glass substrate electrode is set, the double layer mixing carbon nano-tube film is set on the electrode, described carbon nano-tube film is divided into two-layer, the upper strata is the blending of non-conductive medium nano-powder, and lower floor is the nano-powder blending of conduction.
Described electrode is ITO electrode or silicon chip or silver electrode or other conductive films.
A kind of preparation of double layer mixing structure carbon nano tube membrane field emission cathode, realize according to the following steps:
At first nano powder titanium (Ti) is distributed in the terpinol with excusing from death wavelength time ground, adds ethyl cellulose, be heated to 60-120 ℃ and stirring for a long time, all dissolve, promptly form Ti dispersion slurry up to ethyl cellulose with magnetic stirring apparatus; Again Ti slurry and common CNT slurry are mixed, form Ti blending CNT composite mortar;
Secondly, adopt silk-screen process that Ti blending CNT composite mortar is printed on and be prepared as individual layer mixing structure CNT film on the conductive substrates;
At last; adopt two-step sintering technology: at first in protective gas 400-550 ℃ sintering 2-3 hour; impel the organic bond decomposition evaporation and solidify the CNT laminated film, then in atmosphere 250-350 ℃ sintering temperature 1-2 hour, form double layer mixing structure carbon nano tube membrane field emission cathode.
Described protective gas is argon gas inert gas, hydrogen or ammonia reducing gas.
Be used to improve the double-deck cathode thin film of silk screen printing CNT field emission performance among the present invention, the CNT film of individual layer blending originally organically be divided into two-layer up and down.Blending material in the upper strata becomes the TiO of non-conductive performance
2, help reducing that the CNT emitter is in contact with one another and the screen effect that causes, improved the enhancer of CNT emitter; The nanometer Ti powder particles of electric conductivity energy and CNT form good matching structure in the lower floor, increase the CNT contact area, reduce CNT and substrate, CNT contact resistance each other.Therefore, double-deck CNT cathode thin film can improve the field emission performance of silk screen printing CNT effectively.
Description of drawings
Fig. 1 is scanning electron microscopy (SEM) photo of double layer mixing structure CNT film cathode among the present invention.
Fig. 2 is small angle x-ray diffraction (SAXD) (XRD) collection of illustrative plates of double layer mixing structure CNT cathode thin film among the present invention.
Fig. 3 is the I-V characteristic curve of double layer mixing structure CNT film cathode among the present invention.
Fig. 4 is the life curve of the double layer mixing structure CNT film cathode among the present invention.
Fig. 5 is the CNT field emission display structure chart of diode structure.
Below in conjunction with accompanying drawing content of the present invention is described in further detail.
Embodiment
With reference to shown in Figure 1, nanometer Ti powder can be distributed in the CNT film and with CNT equably has good matching performance; The laminated film surface is good uniformity, evenness height in large-area scope, the TiO of upper surface
2(behind the Ti particulate oxidation) most grain diameter is still less than 50nm, and the grain diameter that has only only a few is greater than 100nm; Organic bond on the CNT film surface is decomposed and evaporation fully.
With reference to shown in Figure 2, the part Ti in the CNT composite membrane changes anatase or rutile, i.e. titanium dioxide into behind sintering.When the angle of diffraction 2 θ were 35.1 °, 40.1 °, 52.8 ° and 76.0 °, corresponding was (100), (101), (102) and (112) crystal face of Ti respectively, the characteristic diffraction peak of Ti promptly occurred, and illustrating still has the existence that does not partly have oxidation Ti.Chief reason can reasoning be 2 points: 1. in air during oxidation, the Ti of CNT laminated film upper surface forms TiO easily
2Diaphragm, the continuation oxidation that stops or slowed down the Ti of film lower floor; 2.CNT laminated film is a kind of structure of porous, this structure can keep static air, and top layer oxygen will be consumed by partial C NT or Ti, the oxidation of protection residue Ti.The temperature of sintering, time and concentration of oxygen all can change the degree of the oxidation of Ti.Therefore, the realization of suitable agglomerant artistic skill assurance double layer mixing structure CNT film cathode.
With reference to shown in Figure 3, the CNT laminated film negative electrode of double layer mixing structure has field emission performance preferably.Open electric field and (be defined as 10 μ A/cm
2) extremely low, only be 1.75V/ μ m.According to the Fower-Nordheim equation, this double-deck electrode F-N slope of a curve when high relatively electric field changes very fast, illustrates that the ability of output electronics of membrane electrode is stronger.Therefore after the CNT composite cathode film of the Ti mixing structure process two-step sintering PROCESS FOR TREATMENT, the field emission performance of CNT can be improved significantly.
With reference to shown in Figure 4, judge a length in the life-span of emission by the part behavior that declines of the field emission current of testing the film cathode that two kinds of different disposal methods obtain.The sintering condition of sample 1 is earlier behind 450 ℃ of constant temperature sintering 30min, to put into 300 ℃ of sintering 2h of air again in nitrogen; The sintering condition of sample 2 is direct 300 ℃ of sintering 2h in air.Through after the lighting of 90min, the constantly not decay of the field emission current of sample 1 is increased to 449 μ A by opening beginning electric current 400 μ A on the contrary; The field emission current of sample 2 presents continuous downward trend, and field current is reduced to 379 μ A by opening beginning electric current 400 μ A.Presentation of results, sample 1 can significantly improve the life-span of its emission behind two-step sintering.Chief reason can be summed up as: the CNT composite cathode film of Ti mixing structure is in the process of high temperature sintering, and temperature is high more, and the Ti nano particle each other, the adhesion between Ti nano particle and the CNT can be stronger.This strong adhesion will reduce the tunnel and the binding ability of the contact resistance, enhancing and the substrate that produce; Thereby stoped the probability of being pulled out by strong electrostatic attraction in the CNT emitter emission process on the scene, reduced tunnel effect and produce Joule heat burning CNT.
With reference to shown in Figure 5, the present invention includes a substrate material ito glass, negative electrode glass substrate 4 adopts wet etching to prepare ITO electrode 5 on substrate, prepares the Ti blending CNT cathode thin film of single layer structure by screen printing technique; Carry out two-step sintering technology subsequently, changing into the upper strata is TiO
2The CNT laminated film of mixing structure, lower floor are the CNT laminated film of Ti mixing structure, do not have the CNT film cathode 6 of tangible interface double layer mixing structure between the levels.1. anode glass substrate; 2. anode ITO electrode; 3. fluorescent material; 4. negative electrode glass substrate; 5. electrode; 6. double layer mixing carbon nano-tube film; 7. insulation is supported.
Embodiment 1:
Concrete technology comprises following two steps:
The first step, the CNT composite cathode film of preparation individual layer Ti mixing structure.1. the mixed liquor (volume ratio is: 4: 1) that many walls CNT is put into nitric acid and sulfuric acid carries out acidifying, removes amorphous carbon and catalyst, and through washed with de-ionized water, filter paper filters and drying box is dried.2. CNT is distributed in the terpinol aggregate that the silk screen filter removing is bigger with excusing from death wavelength time ground; Add ethyl cellulose, be heated to 100 ℃ and stirring for a long time with magnetic stirring apparatus, all dissolve up to ethyl cellulose, the dispersion that forms homogeneous is the CNT slurry; Nanometer Ti powder slurry is adopted the preparation that uses the same method.3. material is fallen in CNT and Ti nano powder slurry (mass ratio: 1: 1) mixes, be heated to 100 ℃ and long-time the stirring with magnetic stirring apparatus once more, the CNT composite mortar of formation Ti blending.4. by screen printing technique the CNT composite mortar of Ti blending is printed onto on the ITO substrate, forms the CNT composite cathode film of individual layer Ti blending.
In second step, the CNT film of conversion individual layer blending is a double layer mixing structure.1. the individual layer Ti mixing structure CNT laminated film of silk screen printing is put into the protective gas argon gas and carried out 450 ℃ of high temperature sinterings 2 hours, the CNT slurry of Ti blending is solidified effectively, and impel organic bond to decompose fully and evaporate.2. the Ti mixing structure CNT cathode thin film after solidifying is inserted in the common sintering furnace, under atmospheric conditions, carry out 300 ℃ of thermal oxidations 2 hours; The Ti of individual layer Ti mixing structure CNT film upper epidermis is oxidized to TiO
2, can form upper epidermis is TiO
2Mixing structure, lower floor is the double layer mixing CNT film cathode of Ti mixing structure.
Embodiment 2:
The preparation of double layer mixing structure carbon nano tube membrane field emission cathode, at first nano powder titanium (Ti) with the excusing from death wavelength time be distributed in the terpinol, add ethyl cellulose, be heated to 100 ℃ and stirring for a long time with magnetic stirring apparatus, all dissolve up to ethyl cellulose, promptly form Ti dispersion slurry; Again Ti slurry and common CNT slurry are mixed, form Ti blending CNT composite mortar;
Secondly, adopt silk-screen process that Ti blending CNT composite mortar is printed on and be prepared as individual layer mixing structure CNT film on the conductive substrates;
At last; adopt two-step sintering technology: 500 ℃ of sintering 3 hours in hydrogen or protection of ammonia gas at first; impel the organic bond decomposition evaporation and solidify the CNT laminated film, 300 ℃ of sintering temperatures 1.5 hours in atmosphere form double layer mixing structure carbon nano tube membrane field emission cathode then.
Claims (4)
1. double layer mixing structure carbon nano tube CNT membrane field emission cathode comprises negative electrode glass substrate (4), and electrode (5) is set on the negative electrode glass substrate (4), double layer mixing CNT film (6) is set on the electrode (5), it is characterized in that described CNT film (6) is divided into two-layer, the upper strata is TiO
2The CNT laminated film of mixing structure, lower floor is the CNT laminated film of Ti mixing structure.
2. double layer mixing structure CNT membrane field emission cathode according to claim 1 is characterized in that, described electrode (5) is ITO electrode or silicon chip or silver electrode or other conductive films.
3. the preparation of a double layer mixing structure CNT membrane field emission cathode as claimed in claim 1 is characterized in that, realizes according to the following steps:
At first nano powder titanium Ti is distributed in the terpinol with excusing from death wavelength time ground, adds ethyl cellulose, be heated to 60-120 ℃ and stirring for a long time, all dissolve, promptly form Ti dispersion slurry up to ethyl cellulose with magnetic stirring apparatus; Again Ti slurry and common CNT slurry are mixed, form Ti blending CNT composite mortar;
Secondly, adopt silk-screen process that Ti blending CNT composite mortar is printed on and be prepared as individual layer mixing structure CNT film on the conductive substrates;
At last; adopt two-step sintering technology: at first in protective gas 400-550 ℃ sintering 2-3 hour; make the organic bond decomposition evaporation and make CNT solidify to form laminated film; then in atmosphere 250-350 ℃ sintering temperature 1-2 hour, promptly obtain double layer mixing structure CNT membrane field emission cathode.
4. the preparation of double layer mixing structure carbon nano tube membrane field emission cathode according to claim 3 is characterized in that, described protective gas is argon gas inert gas, hydrogen or ammonia reducing gas.
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| CN1482065A (en) * | 2003-04-15 | 2004-03-17 | 清华大学 | Process for preparing nanometer zirconium dioxide powder by hydrolyzing zirconium oxynitrate |
| CN1556548A (en) * | 2004-01-08 | 2004-12-22 | 西安交通大学 | Preparation method of large surface area carbon nano pipe film for field emitting display cathode |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1482065A (en) * | 2003-04-15 | 2004-03-17 | 清华大学 | Process for preparing nanometer zirconium dioxide powder by hydrolyzing zirconium oxynitrate |
| CN1556548A (en) * | 2004-01-08 | 2004-12-22 | 西安交通大学 | Preparation method of large surface area carbon nano pipe film for field emitting display cathode |
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| 商世广等.高温烧结和等离子轰击改善碳纳米管薄膜的场发射性能.西安交通大学学报.2008,第42卷(第4期),466-470. * |
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