WO2013105740A1

WO2013105740A1 - Cement composite comprising carbon nanotube, preparation method thereof, and method for manufacturing carbon nanotube-cement structure using cement composite thereof

Info

Publication number: WO2013105740A1
Application number: PCT/KR2012/010718
Authority: WO
Inventors: 이행기; 김형기; 남일우; 전정희
Original assignee: 한국과학기술원
Priority date: 2012-01-13
Filing date: 2012-12-10
Publication date: 2013-07-18
Also published as: KR20130083649A; KR101339904B1

Abstract

The present invention relates to: a cement composite comprising a carbon nanotube (CNT)to implement the high dispersion of a carbon nanotube in a cement matrix when preparing a cement composite by mixing a carbon nanotube with low dispersion in cement; a preparation method thereof; and a method for manufacturing a carbon nanotube-cement structure using the cement composite. According to the present invention, the preparation method of the cement composite comprises: (a) a step of mixing a carbon nanotube, silica fume, cement, and fine aggregate and dry mixing the same for a set amount of time; and (b) a step of adding water and a polycarboxylic acid-based superplasticizer to the dry-mixed mixture and mixing the same for a set amount of time.

Description

Cement Composites Containing Carbon Nanotubes and Manufacturing Method Thereof and Manufacturing Method of Carbon Nanotube-Cement Structures Using the Cement Composites

The present invention relates to a cement composite material containing carbon nanotubes and a method for manufacturing the same, and more particularly, to a cement composite material having improved dispersion performance by improving carbon nanotube dispersion performance by physical methods using nanomaterials and The manufacturing method and the method of manufacturing a carbon nanotube-cement structure using this cement composite material.

Carbon nanotube (CNT), one of the advanced nanomaterials, has been steadily researched and commercialized in various fields since its discovery in 1991 based on its unique structural, chemical, mechanical and electrical properties due to its highly stable chemical bonding. . However, in the process of dispersing and using carbon nanotubes having various characteristics as various base materials, it is difficult to research due to the low dispersion performance of carbon nanotubes, which has limited its use as construction materials.

This low dispersion performance is not evenly dispersed in aqueous solutions and organic solvents due to the high length to diameter ratio, strong hydrophobic and van der Waals forces of carbon nanotubes. In some bundles. Such unevenly dispersed carbon nanotubes act as cracks and voids in polymer and cement matrix materials, thereby reducing physical, electrical, and thermal performance. Accordingly, researches on carbon nanotube dispersion are being made at home and abroad, and carbon nanotube dispersion methods using special surfactants and sonication have been generally used.

Sonication, a method of dispersing carbon nanotubes, which has been used in the related art, is a method of physically separating and dispersing entangled carbon nanotubes using a sound wave of 10-20 Hz after putting carbon nanotubes in a surfactant.

However, such a prior art has a problem of an increase in manufacturing cost by the sonication process and a decrease in material performance by the surfactant. As the construction material development research using carbon nanotubes is carried out, large-scale Sony equipment is needed by field application and mass production, and the time and production cost due to the addition of the Sony software process for dispersing carbon nanotubes in the cement composite material mixing process Causes the problem of increase. In addition, the surfactant acts as an air entrainer in the material at the time of formulation, generating a large number of bubbles to reduce the physical and electrical performance of the cement structure.

The present invention is to solve the conventional problems as described above, an object of the present invention is to mix the carbon nanotubes (CNT) with low dispersibility to the cement to prepare a cement composite material of the carbon nanotubes in the cement matrix The present invention provides a cement composite material and a method for manufacturing the same, and a method for producing a carbon nanotube-cement structure using the cement composite material.

According to one category of the present invention for achieving the above object, it comprises a carbon nanotube, silica fume (Silica fume), cement and a polycarboxylic acid-based admixture as a main component Cement composite material is provided.

According to another category of the present invention, the method comprises the steps of: (a) mixing the carbon nanotubes, silica fume and cement to dry beam for a set time; (b) adding a water and a polycarboxylic acid superfluiding agent to the dry non-beamed mixture to provide a method for producing a cement composite material, comprising the step of beaming for a predetermined time.

According to another category of the invention, the step of injecting a cement composite material produced by the cement composite material manufacturing method into a mold; (b) demolding after a set time to obtain a carbon nanotube-cement structure base material of a specific type; (c) providing a method for producing a carbon nanotube-cement structure, comprising curing the demolded carbon nanotube-cement structure base material in water for a set time.

According to the present invention, in the conventional sonication process by simplifying the carbon nanotube dispersion process by using a physical dispersion method using nanomaterials instead of the dispersion method using a surfactant and sonication that has been widely used in the prior art It can reduce the time and cost and can also solve the physical degradation of the cement structure that can be caused by the surfactant.

In addition, the carbon nanotube dispersion method and the dispersibility of the carbon nanotubes in the cement matrix can be improved compared to the conventional dispersion technology, thereby increasing the usability as a construction material and improving the field applicability.

1 is a flow chart illustrating a method for producing cement mortar as a cement composite material according to the present invention.

Figure 2 is a flow chart illustrating a method for producing a carbon nanotube-cement structure using the cement composite material of the present invention.

3 is a view showing an embodiment of a test specimen used in measuring the compressive strength of the carbon nanotube-cement structure of the present invention.

4 is an SEM observation picture of the carbon nanotube-cement structure according to the present invention.

5 is a graph showing compressive strength according to silica fume incorporation rate of a carbon nanotube-cement structure according to the present invention.

6 is a flowchart illustrating a method of manufacturing a cement paste and a carbon nanotube-cement structure using the same as a cement composite material according to another embodiment of the present invention.

FIG. 7 is a view schematically showing a test specimen used in an electromagnetic shielding experiment as an example of a carbon nanotube-cement structure manufactured by the manufacturing method of FIG. 6.

8 is a graph showing electromagnetic shielding performance according to silica fume mixing rate in the 2.46 GHz frequency band.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of a cement composite material containing carbon nanotubes according to the present invention and a method for manufacturing the carbon nanotube-cement structure using the cement composite material.

The cement composite material according to the present invention is a mixture of carbon nanotubes (CNT) and nanomaterial silica fume (Silica fume), cement, fine aggregate, polycarboxylic acid-based admixture (water) Are manufactured.

Carbon nanotubes are small sized nanoparticles in the form of tubes, and are used in various fields based on their unique structural, chemical, mechanical and electrical properties due to the strong chemical bond called sp2. The carbon nanotubes may be used in various kinds, but it is preferable to use multi-wall carbon nanotubes having various lengths.

The present invention is a silica fume having a small particle size, such as carbon nanotubes of 10 ~ 500 nm in carbon nanotubes having low dispersibility due to the high length-to-diameter ratio, strong hydrophobicity and van der Waals attraction as described above By suggesting a method of physically dispersing by incorporating materials, a cement composite material capable of effectively dispersing carbon nanotubes in a cement matrix is prepared, and a carbon nanotube-cement structure is realized using the cement composite material thus prepared. Give a way.

Silica fume incorporated in the cement composite material of the present invention is preferably 10 to 20% by weight of the cement, respectively.

Example 1

Hereinafter, an embodiment of a method of manufacturing cement mortar as a cement composite material according to the present invention will be described in detail with reference to FIG. 1.

First, a predetermined amount of carbon nanotubes, silica fume, cement and fine aggregates are mixed and dry-beamed for a predetermined time (for example, about 4 minutes) using a rotary stirrer (step S11). In this dry beam step, the carbon nanotubes are mixed with 0.15 to 0.3 wt% based on the weight of cement mixed together. In addition, silica fume may be mixed with 10-30% by weight (preferably 10-20% by weight) of the cement weight, but is not limited thereto.

After the completion of the dry beam, the cement composite material of the present invention is completed by adding water and a polycarboxylic acid-based superfluiding agent to the beam and performing the beam for a predetermined time (for example, about 2 minutes). S12).

In the cement composite material, silica fume, a nanomaterial for dispersing portland cement and carbon nanotubes, is used as cement, and the chemical and physical properties of the portland cement and silica fume are shown in Table 1 below.

Table 1

	Class 1 Portland Cement (C)	Silica Fume (SF)
Chemical composition (% by weight)
CaO	64.07	1.30
Al ₂ O ₃	4.96	4.00
SiO ₂	22.00	90.70
Fe ₂ O ₃	3.66	1.09
K ₂ O	0.91	2.00
MgO	1.92
SO ₃	1.92

Physical properties
importance	3.15	2.20
Surface area (/ g)	0.35 (Blaine)	19.62 (BET)

The cement composite material of the present invention made through the above process has a high dispersion performance by helping the physical dispersion of carbon nanotubes in the cement matrix by using silica fume which is a nanomaterial, thereby realizing physical performance improvement.

The cement composite material of the present invention can be made into a carbon nanotube-cement structure of a particular type by a mold. That is, as shown in Fig. 2, the cement composite material according to the present invention is injected into a mold having a cavity of a specific type (step S13), and demolded after a set time (for example, 24 hours) to form a carbon nano of a specific type. A tube-cement structure base material is obtained (step S14). Subsequently, in order to suppress cracking or shrinkage of the demolded carbon nanotube-cement structure base material, the carbon nanotube-cement structure base material is cured for a set time (for example, 14 to 15 days) (step S15), and the set time. After the passage, the completed carbon nanotube-cement structure is taken out (step S16).

3 is a test specimen used for compressive strength experiments for measuring physical performance improvement according to the improvement of carbon nanotube dispersion of cement composites according to the present invention. Cylindrical carbon nanoparticles manufactured using the cement composite material according to the present invention. The tube-cement structure 1 is shown. This carbon nanotube-cement structure 1 is a cylindrical specimen of 100 mm (diameter) x 200 ± 5 mm (height).

FIG. 4 is an SEM observation photograph of the carbon nanotube-cement structure (1), in which a cross section of a cured specimen was observed for 24 hours, and it was confirmed that silica fume particles were uniformly dispersed between individual carbon nanotubes. . This confirms that silica fume helps the dispersion of carbon nanotubes. That is, the cement composite material according to the present invention was confirmed that the carbon nanotubes are dispersed by silica fume as a nano material.

As described above, in order to measure the physical performance improvement according to the improvement of the carbon nanotube dispersion of the cement composite according to the present invention, silica fume content is set to 0 wt%, 10 wt%, 20 wt%, and 30 wt%, respectively. The cement composite material was prepared according to the above-described cement composite material manufacturing method of the present invention on the basis of 12 different formulations by varying the tube mixing rate of 0.0 wt%, 0.15 wt%, and 0.3 wt%, respectively, as shown in FIG. 2. The carbon nanotube / cement structure 1 was produced in the same manner as described above, and the compressive strength of the carbon nanotube-cement structure 1 was measured. The following measurement results were obtained.

5 is a graph showing the compressive strength of the 14-day cement composite material showing the change in the compressive strength according to the silica fume mixing rate of the carbon nanotube mixing rate of the different specimens. The relative compressive strength in the graph shows the ratio of each specimen to the compressive strength of cement composite material without carbon nanotubes. In the case of cement composites containing 0.15% by weight of carbon nanotubes, the relative compressive strength of the comparative group increased significantly from 10% by weight of silica fume, and then decreased from 20% by weight, and slightly improved by 30% by weight. Showed. In the case of the mortar mixed with 0.3 wt% of carbon nanotubes, the compressive strength was continuously increased for the comparative group until the silica fume was 20 wt%, and the compressive strength was decreased at the silica fume incorporation rate of 30 wt%. Such a result can be predicted because silica fume itself performs a pozzolanic reaction, thereby making a tighter structure than a test sample in which silica fume is not incorporated, thereby improving compressive strength. When the carbon nanotubes are mixed, it can be expected that the agglomeration of the carbon nanotubes generating the voids is effectively dispersed by silica fume, thereby reducing the voids in the structure, thereby making the chamber more compact, and improving the compressive strength.

As a result, an effective carbon nanotube dispersion was achieved at a silica fume mixing rate of 10 to 20% by weight, and thus the compressive strength was improved.

Example 2

Figure 6 shows another embodiment of a method for producing a cement paste as a cement composite material according to the present invention, the cement composite material of this second embodiment is different from the cement composite material of the above-described embodiment without mixing the fine aggregate It is proposed a method of preparing a cement composite material on a paste by further mixing nylon fibers in a step of mixing and mixing water and a polycarboxylic acid superfluiding agent.

That is, the cement composite material according to this second embodiment is prepared by mixing carbon nanotubes (CNT: Carbon Nanotube) and nanomaterial silica fume, cement, polycarboxylic acid-based superfluidizer, nylon fibers with water.

First, a predetermined amount of carbon nanotubes, silica fume, and cement are mixed and dried for a predetermined time (for example, about 3 minutes) (step S21). In the dry beam step, the carbon nanotubes are preferably mixed with 0.3 to 1.0% by weight based on the weight of the cement mixed together. Silica fume may be mixed with 10-30% (preferably 10-20%) by weight of cement, but is not limited thereto.

After the completion of the dry beam, after the addition of water and polycarboxylic acid-based superfluidizing agent to the dry beam, and performing the beam for a set time (for example, about 3 minutes), and finally after the addition of nylon fiber set time ( For example, about 3 minutes) to perform the beam beam to complete the paste-like cement composite material according to the present invention (step S22).

The cement paste of the present invention may be made into a specific type of carbon nanotube-cement structure by a plastic mold. That is, the cement paste according to the present invention is injected into a plastic mold having a specific type of cavity (step S23), and demolded after a set time (for example, 24-48 hours) to obtain a carbon nanotube-cement structure of a specific type. . Subsequently, in order to suppress cracking or shrinkage of the demolded carbon nanotube-cement structure, the carbon nanotube-cement structure is cured in water for a set time (for example, 28 days) (step S24).

FIG. 7 shows an example of a carbon nanotube-cement structure 2 fabricated using the above cement paste composite material. The present invention comprises a donut shape having an inner diameter of 3 mm, an outer diameter of 7 mm, and a thickness of 4.5 mm. It was used as an experiment for measuring physical performance improvement according to the improvement of carbon nanotube dispersibility of cement composite material according to the second embodiment of.

The silica fume incorporation rate of the test body of the carbon nanotube-cement structure (2) was set to 0 wt%, 10 wt%, 20 wt%, and 30 wt%, respectively, and the carbon nanotube incorporation rates were 0.0 wt%, 0.3 wt%, and 0.6 wt%, respectively. The cement composite material was prepared according to the method of manufacturing the cement composite material of the second embodiment based on the 16 kinds in different amounts by weight and 1.0 weight%, and then carbon nanotubes in the form as shown in FIG. 8- The cement structure 2 was fabricated, and the electromagnetic shielding performance of the carbon nanotube-cement structure 2 was measured. As a result, measurement results as shown in FIG. 8 were obtained.

Figure 8 shows the electromagnetic shielding performance according to the silica fume mixing rate in the 2.46 GHz frequency range, the overall silica shielding performance was increased up to the silica fume mixing rate up to 20% by weight as the silica fume mixing rate is increased, the silica fume mixing rate 30 weight Above%, the electromagnetic shielding performance was reduced overall. This phenomenon was remarkable in the cement paste containing 0.6 wt% of carbon nanotubes. Through this, it was confirmed that the carbon nanotubes having conductivity at the silica fume mixing rate of 10 to 20% by weight were most effectively dispersed by silica fume and exhibit the highest electric wave shielding performance.

As described above, the cement composite material of the present invention and the carbon nanotube-cement structure using the same have improved dispersibility of carbon nanotubes by silica fume and thus have excellent compressive strength and electromagnetic shielding performance.

In the above description, the technical idea of the present invention has been described with the accompanying drawings. However, the present invention has been described by way of example and is not intended to limit the present invention. In addition, it is apparent that any person having ordinary knowledge in the technical field to which the present invention belongs may make various modifications and imitations without departing from the scope of the technical idea of the present invention.

The present invention can be applied to cement composites such as cement paste and concrete mortars, cement structures, concrete structures and methods for producing them.

Claims

A cement composite material comprising carbon nanotubes, silica fume, cement, and polycarboxylic acid-based admixture as main components.
The cement composite material according to claim 1, further comprising fine aggregate.
The cement composite of claim 1, further comprising nylon fibers.
The cement composite material according to any one of claims 1 to 3, wherein the amount of incorporation of the carbon nanotubes is 0.15 to 0.3 wt% based on the weight of the cement.
The cement composite material according to any one of claims 1 to 3, wherein the silica fume is mixed in an amount of 10 to 30% by weight based on the weight of the cement.
(a) mixing the carbon nanotubes with silica fume and cement to dry beam for a set time;

(b) adding water and a polycarboxylic acid-based superfluidizing agent to the dry non-beamed mixture, and then beaming the mixture for a predetermined time period.
The method of manufacturing a cement composite material according to claim 6, wherein the fine aggregate is further mixed in the step (a) to dry beam.
The method of manufacturing a cement composite material according to claim 6, wherein in the step (b), the nylon fibers are further mixed and then beamed.
The method of claim 6, wherein the carbon nanotubes mixed in the step (a) is 0.15 to 0.3 wt% based on the weight of the cement.
7. The method of claim 6, wherein the silica fume mixed in the step (a) is 10 to 30% by weight based on the weight of the cement.
(a) injecting a cement composite material produced by the method of any one of claims 6 to 10 into a mold;

(b) demolding after a set time to obtain a carbon nanotube-cement structure base material of a specific type;

(c) curing the demodulated carbon nanotube-cement structure base material in water for a set time, the method of producing a carbon nanotube-cement structure.