CN2700876Y

CN2700876Y - Carbon nano tube thin film gas transducer

Info

Publication number: CN2700876Y
Application number: CN 200320109975
Authority: CN
Inventors: 刘君华; 李昕; 朱长纯; 沈蕾
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2003-12-23
Filing date: 2003-12-23
Publication date: 2005-05-18
Anticipated expiration: 2013-12-23

Abstract

The utility model discloses a carbon nanometer tube thin film gas sensor which comprises a substrate made of glass, semiconductor material or metal and an exterior leading wire. The utility model is characterized in that the substrate is provided with a silicon dioxide insulation layer in which interdigital electrodes are distributed. The interdigital electrodes are separated by the silicon dioxide insulation layer and covered by the silicon dioxide insulation layer. On the topside of the utility model is provided with a composite film layer which is formed by mixing a multi-walled carbon nanometer tube with silicon dioxide. The composite film layer which is formed by mixing a multi-walled carbon nanometer tube with silicon dioxide (SiO2 and MWNTS) is transplanted onto the interdigital capacitor electrodes to serve as a gas sensing element of the interdigital capacitor type carbon nanometer tube thin film gas sensor. The utility model has the advantages of simple structure, reliable work, long service life, simple preparation process, good sensitivity, etc. The utility model can be widely used for testing of the gases such as methane, carbon monoxide, hydrogen gas, acetylene, etc.

Description

The carbon nano-tube film gas sensor

One, technical field

The utility model relates to the absorption type gas sensor in thin film sensor field, is specifically related to a kind of employing and transplants the gas sensor of multi-walled carbon nano-tubes-silicon dioxide (SiO2 and MWNTS) laminated film as gas sensitive element on the interdigitation capacitance electrode.This sensor comes the concentration of detected gas by the chemisorption situation of tested gas on the gas sensitive element surface.

Two, background technology

A class important in the sensor is a chemical sensor, and gas sensor is the important component part of chemical sensor.The particle size of forming the gas sensing modulator material is more little, and specific surface area is high more, and sensor takes place to interact big more with contacting of ambient gas, and susceptibility is high more.The hollow structure of carbon nano-tube and outer wall make it have very big surface area for gas absorption.And in the different atmosphere at room temperature, their electrology characteristic can change again, therefore is being with a wide range of applications aspect the making senser element.The applied research of nano-sensor is just at the early-stage, but it has demonstrated the advantage that other sensors can't be reached: the susceptibility height, and body is little, and energy consumption is low, and function is many etc.According to the data-searching that the applicant carried out, do not find the document relevant with the utility model.

Three, summary of the invention

The purpose of this utility model provides a kind of simple in structure, reliable operation, long service life, the simple gas sensor of preparation technology, can be widely used in methane, carbon monoxide, and hydrogen, the test of gases such as acetylene has satisfied susceptibility.

To achieve these goals, the technical solution adopted in the utility model is: a kind of carbon nano-tube film gas sensor comprises the substrate and the outside lead of glass or semiconductor material or metal; It is characterized in that, in substrate, be printed with the interdigitation electrode, and on the interdigitation electrode, be coated with silicon dioxide insulating layer, the THIN COMPOSITE rete that on silicon dioxide insulating layer, has one deck multi-walled carbon nano-tubes and silicon dioxide to mix.

Some other characteristics of the present utility model are that described silicon dioxide insulating layer is a silica sol-gel.

Silica sol-gel adopts regular acetoacetic ester, absolute ethyl alcohol, concentrated hydrochloric acid, deionized water to mix in proportion.

The THIN COMPOSITE rete that multi-walled carbon nano-tubes and silicon dioxide mix adopts the dispersion in isopropyl alcohol, through stirring, after ultrasonic, the heating, fully mixing to obtain SiO2 and MWNTS composite mortar with the SiO2 sol-gel;

The interdigitation electrode adopts the silk-screen printing technique preparation, and electrode material is selected golden or silver-colored or other conductive material slurrying of aluminium to print to form; Also can adopt rotation to get rid of and be coated with the method preparation.

Because adopting, the utility model on the interdigitation capacitance electrode, transplants multi-walled carbon nano-tubes-silicon dioxide (SiO2 and MWNTS) laminated film, as the absorption type interdigital capacitor type carbon nano-tube film gas sensor of gas sensitive element, have simple in structure, reliable operation, long service life, an advantage such as preparation technology is simple, susceptibility is good.Can be widely used in methane, carbon monoxide, hydrogen, the test of gases such as acetylene.

Description of drawings

Fig. 1 is the utility model cross section structure figure;

Fig. 2 is the carbon nano-tube Electronic Speculum figure of transmission electron microscope observation, and wherein (a) amplifies 10000 times figure; (b) be to amplify 50000 times figure;

Fig. 3 is the utility model interdigital capacitor electrode domain;

Fig. 4, Fig. 5 are sample 1# and 2# test result curve map in hydrogen;

Fig. 6 is sample 2# test result curve in C2H2.

Embodiment

The embodiment that finishes by technique scheme below in conjunction with accompanying drawing and designer is described in further detail the utility model.Following embodiment is more excellent example just, and utility model is not limited to this embodiment.

Referring to Fig. 1, a kind of carbon nano-tube film gas sensor comprises the substrate 1 and the outside lead of glass or semiconductor material or metal; In substrate 1, be printed with interdigitation electrode 4, and on interdigitation electrode 4, be coated with silicon dioxide insulating layer 2, the THIN COMPOSITE rete 3 that on silicon dioxide insulating layer 2, has one deck multi-walled carbon nano-tubes and silicon dioxide to mix.

Silicon dioxide insulating layer 2 is silica sol-gels, is regular acetoacetic ester, absolute ethyl alcohol, concentrated hydrochloric acid, deionized water to be mixed with by a certain percentage form; MWNT and SiO ₂Carbon nano-tube in the mixolimnion 3 is to be prepared from by the low pressure chemical vapor deposition method, and impurity content is low, and carbon nano-tube is twined as shown in Figure 2 mutually.Dispersion in isopropyl alcohol, through stirring, after ultrasonic, the heating, with SiO ₂Sol-gel fully mixes and obtains SiO ₂With the MWNTS composite mortar; The domain of interdigitation electrode 4 as shown in Figure 3, interdigitation electrode 4 is separated by silicon dioxide insulating layer 2, and is covered by silicon dioxide insulating layer 2 above making interdigitation electrode 4.Figure 1 shows that the sensor cross-section structure, with silk-screen printing technique the silver slurry is printed as the interdigitation electrode in substrate, thickness of electrode is 20～30um, and electrode separation is 500um, and live width is 500um.

Adopt SiO ₂With the MWNTS laminated film, the hollow structure of carbon nano-tube and outer wall make it have very big surface area for gas absorption, and sensor takes place to interact big more with contacting of ambient gas, and susceptibility is high more.

The preparation method of described carbon nano-tube also can adopt other form, such as pyrolysismethod, arc discharge and PEVCD method etc.

Described SiO ₂With the moulding of MWNTS laminated film, both can adopt silk screen print method, also can adopt rotation to get rid of Tu Fa etc.

Described interdigitation capacitance electrode material can be selected other materials such as aluminium, gold, silver.

The carbon nano-tube film gas sensor of making is placed in the closed type gas test device measures.

1. closed type gas test device

It is 25 * 25 * 30cm that closed type gas test device is one ³The sealing gas tank, band valve control device draft tube and escape pipe are installed, gas tank one side is equipped with the round rubber gas injection window that diameter is 3cm, can inject gas to be measured by this window in gas tank with syringe, gas concentration to be measured is:

c = \frac{V_{i}}{V} - - (1)

Wherein, c is a gas concentration to be measured, V _iBe the gas volume to be measured that injects, V is the gas tank volume.Place one bottle of saturated NaCl solution in the gas tank, guarantee that wherein relative humidity is 75%, to get rid of the interference of humidity test.

2. the present invention prepares according to following common process:

(1), interdigital electrode: capacitance type transducers is widely used in gas sensor, has designed plane interdigitation electrode capacitance sensor, and this geometric configuration can provide sensor and gas to make the time spent maximum surface area.The electrode domain Figure 1 shows that the sensor cross-section structure as shown in Figure 3, with silk-screen printing technique the silver slurry is printed as the interdigitation electrode on substrate of glass, and thickness of electrode is 20～30um, and electrode separation is 500um, and live width is 500um.

(2), SiO ₂Insulation course: regular acetoacetic ester, absolute ethyl alcohol, concentrated hydrochloric acid, deionized water are mixed by a certain percentage, prepare SiO ₂Sol-gel.Deposit one deck SiO on the interdigitation electrode of plane ₂, to guarantee that electrode is not by the carbon nano-tube short circuit.

(3), carbon nano-tube disperses: the carbon nano-tube impurity content that the CVD method is prepared is low, but the carbon pipe twines mutually, could prepare the carbon nano-tube slurry after needing fully to disperse.Dispersion in isopropyl alcohol, through stirring, after ultrasonic, the heating, with SiO ₂Sol-gel fully mixes and obtains SiO ₂With the MWNTS composite mortar, and after mixing, organism obtains the MWNTS organic ink.

(4), sensor component is made: with getting rid of the method that is coated with respectively with SiO ₂Get rid of to be coated in MWNTS composite mortar and pure MWNTS organic ink and made two kinds of capacitance type transducers on the interdigitation electrode of plane.The device that gets rid of after being coated with is dried at room temperature, send in high temperature (580 ℃) sintering furnace sintering under nitrogen protection, eliminate the organism in the carbon pipe, obtain purer SiO ₂With MWNTS composite membrane and MWNTS film, reduce to room temperature after, with lead ag paste electrode is drawn.

2. experiment test:

The sensor of producing is placed in the test macro to be tested, and found that SiO ₂-MWNTS composite membrane sensor demonstrates the trend that changes with gas concentration.

According to SiO ₂The size of-MWNTS composite membrane area is divided into 1# and 2# sample, and the area of 2# sample approximately is 2 times of 1# sample area.Fig. 4～6th, measurement result, tested gas is respectively hydrogen and acetylene, and testing tool is the RLC tester, and Fig. 4, Fig. 5 are respectively 1# and the test result of 2# sample in hydrogen atmosphere, and the longitudinal axis is the change in impedance value scope; Transverse axis is the density of hydrogen changing value, and unit is ppm, 1ppm=1, and 1/000th, 000, be the volumetric concentration ratio.

As can be seen from Figure 4, when the hydrogen volume concentration ratio when 0 rises to 800ppm, along with the increase of hydrogen volume concentration ratio, impedance becomes greatly gradually, from 4.75 kilo-ohms to 5.22 kilo-ohms.The different manifestations of Fig. 5 and Fig. 4 for its change in impedance value remain on one more among a small circle in, from 0 to 800ppm, resistance value rises to 1.18 kilo-ohms from 1.06 kilo-ohms.

Fig. 6 is 1# test result in acetylene atmosphere, and transverse axis is an acetylene gas concentration change value, and scope is 0～3000ppm, and the impedance variation scope is 3.83 kilo-ohms to 4.03 kilo-ohms.

As can be seen, this thin film gas sensor all has strong sensitivity to hydrogen and acetylene, and the output response is all arranged in the larger context.

Claims

1. carbon nano-tube film gas sensor comprises the substrate (1) and the outside lead of glass or semiconductor material or metal; It is characterized in that, in substrate (1), be printed with interdigitation electrode (4), and on interdigitation electrode (4), be coated with silicon dioxide insulating layer (2), the THIN COMPOSITE rete (3) that on silicon dioxide insulating layer (2), has one deck multi-walled carbon nano-tubes and silicon dioxide to mix.

2. carbon nano-tube film gas sensor as claimed in claim 1 is characterized in that, described silicon dioxide insulating layer (2) is silicon dioxide gel-gel.