KR101647356B1 - Apparatus for detecting gas using carbon polymer-nanotube composite - Google Patents

Abstract

A carbon dioxide detection device is disclosed. The carbon dioxide detection device has a sensing element whose electrical resistance changes due to interaction with carbon dioxide. The sensing element includes a polymer matrix in which the volume changes in response to carbon dioxide, and carbon nanotubes dispersed in the polymer matrix. Such a carbon dioxide detection device can quickly and accurately detect the presence and concentration of carbon dioxide at room temperature.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus for detecting carbon dioxide using a polymer-carbon nanotube composite,

The present invention relates to an apparatus for detecting carbon dioxide using a polymer-carbon nanotube composite, and can detect carbon dioxide based on a resistance change of a polymer-carbon nanotube composite according to reaction with carbon dioxide.

Recently, there is an increasing demand for gas sensors and the like. In particular, a sensor capable of detecting carbon dioxide is needed to detect leaks in the underground storage of carbon dioxide or prevent grain corruption due to carbon dioxide in a large grain warehouse, and various sensors are being researched and developed at present.

Since ceramics are the most reliable materials in harsh conditions such as high temperature, high humidity, reactive or corrosive atmosphere, ceramic sensors among practical gas sensors are most widely used. However, the ceramic sensor exhibits its performance at a high temperature of about 200 to 450 DEG C, and its volume is so large that there are many limitations in its use and power consumption is high.

Recently, researches on small size and low power gas sensor which can detect carbon dioxide at room temperature and are in the form of thin film have been actively carried out.

An object of the present invention is to provide a carbon dioxide detection device capable of accurately detecting carbon dioxide at room temperature using a composite material of a siloxane polymer matrix and a carbon nanotube.

The carbon dioxide detection apparatus according to an embodiment of the present invention includes a sensing body whose electrical resistance changes due to interaction with carbon dioxide. The sensing element includes a polymer matrix which changes its volume by reacting with the carbon dioxide, and carbon nanotubes dispersed in the polymer matrix.

In one embodiment, the carbon dioxide detection device may further include first and second electrodes which are disposed to be spaced apart from each other, and electrically connect the sensing body and a circuit for measuring resistance change of the sensing body.

In one embodiment, the polymer matrix may be comprised of polysiloxane or polystyrene. For example, the polymer matrix may be composed of a siloxane polymer compound including vinyl methyl siloxane, octyl methyl siloxane, and dimethyl siloxane. In this case, the siloxane polymer compound may comprise from 3 to 5% of the vinyl methyl siloxane, from 35 to 40% of the octyl methyl siloxane and from 55 to 62% of the dimethyl siloxane.

In one embodiment, the carbon nanotubes may include multi-wall carbon nanotubes. For example, the content of the carbon nanotubes may be XX to YY% by volume based on the total volume of the sensing element.

In one embodiment, the sensing body may have a thin layer structure having a thickness of 10 to 30 탆.

A method of manufacturing a carbon dioxide detection device according to an embodiment of the present invention includes the steps of forming a first electrode and a second electrode that are spaced apart from each other on a substrate, forming a polymer solution in which the siloxane polymer compound is dissolved, Forming a nanocomposite solution containing nanotubes, and applying the nanocomposite solution onto the substrate to form a sensing body in contact with the first and second electrodes.

In one embodiment, the step of preparing the nanocomposite solution comprises the steps of preparing a polymer solution containing a polymer compound including vinylmethylsiloxane, octylmethylsiloxane, and dimethylsiloxane in a solvent to prepare the polymer solution, Adding nanotubes and ultrasonic agitation. In this case, the polymeric compound may comprise from 3 to 5% of vinyl methyl siloxane, from 35 to 40% of octyl methyl siloxane and from 55 to 62% of dimethyl siloxane.

In one embodiment, the nanocomposite solution may be applied on the substrate by a method of spray printing.

According to the present invention, the presence and concentration of carbon dioxide can be quickly and accurately detected at room temperature through the siloxane polymer matrix and the carbon nanotubes dispersed therein. Also, since a silane polymer matrix is used as a relatively inexpensive material to form a sensing body in a thin film form, a cheap and compact carbon dioxide sensing device can be manufactured.

1 is a conceptual diagram for explaining a carbon dioxide detection apparatus according to an embodiment of the present invention.
2 is a graph showing a result of sensing carbon dioxide using a carbon dioxide detection device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises ", or" having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, or combinations thereof, , Steps, operations, elements, or combinations thereof, as a matter of principle, without departing from the spirit and scope of the invention.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a conceptual diagram for explaining a carbon dioxide detection apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a carbon dioxide detecting device 100 according to an embodiment of the present invention includes a first electrode 110 and a second electrode 120 spaced apart from each other, and first and second electrodes 110 and 120 (Not shown).

The first and second electrodes 110 and 120 function to electrically connect the external circuit 140 and the sensing member 130, which can measure resistance change of the sensing member 130. The first and second electrodes 110 and 120 may be formed of a conductive material such as a metal and the material of the first and second electrodes 110 and 120 may be electrically connected to the sensing element 130 and the external circuit 140 are electrically connected to each other. Although not shown in the drawings, the first and second electrodes 110 and 120 may be formed on a support substrate (not shown), in which case the support substrate applied to a known gas sensor is not limited Can be used.

The sensing element 130 may include a polymer matrix 131 and carbon nanotubes 132 dispersed in the polymer matrix 131. Such a sensing element 130 may change electrical resistance through reaction with carbon dioxide.

The polymer matrix 131 may be formed of a polymer material capable of expanding in volume by reacting with carbon dioxide at room temperature. In one embodiment, the polymer matrix 131 may be formed of polysiloxane, polystyrene (PS), or the like. For example, the polymer matrix 131 may be formed of polysiloxane. The polysiloxane may include one or two or more monomers having a structure represented by the following formula (1).

[Chemical Formula 1]

In the above formula (1), R 1 and R 2 represent a hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different from each other.

Since polysiloxane is more porous than other polymeric materials, it is easy to penetrate carbon dioxide and has a rubber structure. Thus, it is possible to reversibly expand and shrink the volume by reaction with carbon dioxide, and has a hydrophobic property and a high corrosion resistance, Which is not affected by water vapor or water. In addition, polysiloxanes are cheap, easy to manufacture and non-toxic.

In one embodiment of the present invention, the polymer matrix 131 may be formed of a crosslinked polysiloxane. When the crosslinked polysiloxane is used, not only the mechanical stability of the sensing element 130 can be improved but also the dewetting of the polymer matrix can be prevented to improve the robustness of the sensing element 130, As a result, the life span of the carbon dioxide detection device 100 can be improved.

In one embodiment, the polymer matrix 131 comprises a first siloxane monomer having a hydrocarbon side group that is cross-linkable with the dimethyl siloxane monomer during the curing or crosslinking process, and a hydrocarbon side chain group having at least 6 carbon atoms And the second siloxane monomer. The crosslinkable hydrocarbon side chain group may be a vinyl group, an allyl group, or the like, and the hydrocarbon side chain group having a carbon number of 8 or more may be an octyl group, a phenyl group, or the like. When the hydrocarbon side chain group having 6 or more carbon atoms is contained, the temperature stability and sensing sensitivity of the sensing body 131 can be improved.

For example, the polymer matrix 131 may be formed of a siloxane polymer comprising a dimethylsiloxane monomer, a vinylmethylsiloxane monomer, and an octylmethylsiloxane monomer. For example, the polymer matrix 131 may be formed of a terpolymer compound comprising about 3 to 5% vinyl methyl siloxane, about 35 to 40% octyl methyl siloxane, and about 55 to 62% dimethyl siloxane .

The carbon nanotubes 132 impart electrical conductivity to the sensing element 130. In one embodiment, the carbon nanotubes 132 may be multi wall carbon nanotubes. In order to impart electrical conductivity to the sensing body 130, the carbon nanotubes 132 may be dispersed in the polymer matrix 131 at a concentration higher than a percolation threshold. For example, the carbon nanotubes 132 may be dispersed in the polymer matrix 131 at a concentration of about 3 to 10 mass% based on the total mass of the sensing element 130. When the content of the carbon nanotubes 132 is less than 3 mass%, it is impossible to impart electrical conductivity to the sensing body 130. When the content of the carbon nanotubes 132 exceeds 10 mass% The brittleness of the sensing element 130 is increased and a crack may be generated in the sensing element 130. Preferably, the carbon nanotubes 132 may be dispersed in the polymer matrix 131 at a concentration of about 3 to 4% by mass.

Since the carbon nanotubes 132 have higher electrical conductivity and a larger aspect ratio than other carbon-based materials such as carbon black, the concentration of carbon nanotubes to reach a percolation threshold is significantly higher than other carbon- . Therefore, when the carbon nanotubes 132 are dispersed in the polymer matrix 131 as in the present invention, the polymer matrix 131 is more likely to be dispersed than other carbon-based materials such as carbon black, Carbon dioxide can be detected with a high sensitivity even when a small amount of carbon nanotubes 132 are dispersed in the carbon nanotubes 132. This can reduce the manufacturing cost of the sensing body 130 and reduce the brittleness of the sensing body 130 .

When the carbon nanotubes 132 are dispersed in the polymer matrix 131 and the carbon nanotubes 132 are dispersed in the polymer matrix 131, 130 can be improved in rigidity and stability.

The sensing element 130 may be formed to have a thickness of about 10 to 30 [mu] m. If the thickness of the sensing element 130 is more than 30 탆, carbon dioxide may hardly penetrate into the sensing element 130, resulting in a problem of lowering the sensitivity of the sensing element 130 to carbon dioxide. When the thickness is less than 10 탆, the manufacturing process of the sensing body 130 becomes difficult, and a part of the carbon nanotubes 132 dispersed therein is exposed to the outside, thereby lowering the stability of the sensing body 130 Lt; / RTI > For example, the sensing element 130 may be formed as a thin film having a thickness of about 20 μm.

In one embodiment of the present invention, the sensing element 130 may be formed in the following manner.

First, a nanocomposite solution for forming the sensing body 130 may be prepared. The nanocomposite solution is prepared by dissolving a polymer compound including vinylmethylsiloxane, octylmethylsiloxane, and dimethylsiloxane in a solvent such as chloroform, adding multi-walled carbon nanotubes in a specific ratio, It is possible to produce a nanocomposite solution in which multi-walled carbon nanotubes are uniformly dispersed. The polymeric compound may comprise about 3 to 5% of vinyl methyl siloxane, about 35 to 40% of octyl methyl siloxane, and about 55 to 62% of dimethyl siloxane.

Next, the nanocomposite solution is coated on a support substrate on which the first and second electrodes are formed, and dried to form a sensing body having a thin film structure having a thickness of about 10 to 30 mu m. As an example, the nanocomposite solution may be applied on the support substrate by a spray printing method.

When the sensing element 130 is formed using the insulating polymer matrix 131 and the carbon nanotubes 132 dispersed in the insulating polymer matrix 131, a conductive network is formed in the sensing element 130 , So that the sensing element 130 has a relatively low resistance. A tunneling effect according to an electron mobility path and quantum mechanics due to contact between carbon nanotubes, that is, an electron hopping (electromagnetism) phenomenon in the inside of the sensing element 130 composed of the polymer matrix 131 in which the carbon nanotubes 132 are dispersed, ) Is formed. Accordingly, when the polymer matrix 131 interacts with carbon dioxide at room temperature to increase its volume, not only the number of contacts between the carbon nanotubes 132 dispersed in the polymer matrix 131 decreases, but also the number of carbon nanotubes The gap between the first electrode 132 and the second electrode 132 increases, and the electrical resistance of the entire sensing element 130 increases. Also, since the carbon nanotubes 132 have a large surface area and a high surface energy, the carbon nanotubes 132 may interact with the carbon dioxide penetrating the polymer matrix 131 at room temperature to change electrical resistance. For example, carbon dioxide adsorbed on the surface of the carbon nanotubes 132 by a van der Waals attraction force at room temperature can form a nonconductive layer on the surface of the carbon nanotubes, The resistance of the entire sensing element 130 may be reduced.

The carbon dioxide detection device 100 according to the present invention can detect the presence or concentration of carbon dioxide by measuring the resistance change of the sensing body 130, and as a result, can quickly and reliably detect carbon dioxide at room temperature.

2 is a graph showing a result of sensing carbon dioxide using a carbon dioxide detection device according to an embodiment of the present invention. Specifically, the graph of FIG. 2 is a graph showing the relationship between the thickness of a 20 mu m thick multi-walled carbon nanotube dispersed in a polymer matrix composed of a siloxane polymer compound of vinyl methyl siloxane, octyl methyl siloxane and dimethyl siloxane, This is the result of measurement using a carbon dioxide detection device including lag. The above measurements were performed with a commercialized infrared (IR) sensor in a closed chamber space with a carbon dioxide separator installed and minimally affected by moisture. In the graph of FIG. 2, the carbon dioxide concentration measured by the infrared sensor was about 2500 ppm at the time of about 100 seconds when the first resistance change peak appeared, and the carbon dioxide concentration measured by the infrared sensor at the interval between 100 seconds and 200 seconds was 500 ppm .

Referring to FIG. 2, it can be seen that the gas detection apparatus according to the present invention detects all of the high concentration and low concentration of carbon dioxide with high sensitivity.

The carbon dioxide detection device of the present invention detects carbon dioxide using a siloxane polymer matrix and a sensing element including carbon nanotubes dispersed therein, so that the presence and concentration of carbon dioxide can be detected quickly and accurately at room temperature.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

100: Dioxide detection device 110, 120: Electrode
130: Sensing element 131: Polymer matrix
132: Carbon nanotubes 140: External circuit

Claims (14)

1. A carbon dioxide detection device including a sensing body whose electrical resistance changes due to interaction with carbon dioxide, the sensing body comprising:
A polymer matrix which changes its volume by reacting with carbon dioxide;
And a carbon nanotube dispersed in the polymer matrix,
Wherein the polymer matrix is formed of a polymer of a dimethyl siloxane monomer, a first siloxane monomer having a vinyl group or an allyl group crosslinkable with the dimethyl siloxane monomer, and a second siloxane monomer containing an octyl group or a phenyl group. The method according to claim 1,
Further comprising first and second electrodes which are arranged to be spaced apart from each other and electrically connect the sensing body and a circuit for measuring resistance change of the sensing body. The method according to claim 1,
Wherein the polymer matrix is comprised of polysiloxane. The method according to claim 1,
Wherein the polymer matrix is comprised of a crosslinked polysiloxane. delete The method according to claim 1,
Wherein the first siloxane monomer is vinyl methyl siloxane and the second siloxane monomer is octyl methyl siloxane. The method according to claim 6,
Wherein the polymer matrix is formed of a terpolymer comprising from 3 to 5% of the vinyl methyl siloxane, from 35 to 40% of the octyl methyl siloxane and the balance of the dimethyl siloxane. The method according to claim 1,
Wherein the carbon nanotubes include multi-walled carbon nanotubes. 9. The method of claim 8,
Wherein the content of the carbon nanotubes is 3 to 10 mass% based on the total mass of the sensing element. The method according to claim 1,
Wherein the sensing body has a thin layer structure having a thickness of 10 to 30 占 퐉. Forming a first electrode and a second electrode on the substrate, the first electrode and the second electrode being spaced apart from each other;
Preparing a nanocomposite solution containing a polymer solution in which a siloxane polymer compound is dissolved and carbon nanotubes uniformly dispersed in the polymer solution; And
Applying the nanocomposite solution onto the substrate to form a sensing body in contact with the first and second electrodes,
The step of preparing the nanocomposite solution comprises:
Mixing the solvent with 3 to 5% vinylmethylsiloxane monomer, 35 to 40% octylmethylsiloxane monomer and the remainder dimethylsiloxane monomer; And
And adding the multi-walled carbon nanotube to the mixed solution and ultrasonic agitation. delete delete 12. The method of claim 11,
Wherein the nanocomposite solution is applied on the substrate by spray printing. ≪ RTI ID = 0.0 > 8. < / RTI >

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