WO2003099717A1 - High-density carbon nanohorns and process for producing the same - Google Patents

High-density carbon nanohorns and process for producing the same Download PDF

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Publication number
WO2003099717A1
WO2003099717A1 PCT/JP2003/001927 JP0301927W WO03099717A1 WO 2003099717 A1 WO2003099717 A1 WO 2003099717A1 JP 0301927 W JP0301927 W JP 0301927W WO 03099717 A1 WO03099717 A1 WO 03099717A1
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Prior art keywords
carbon nanohorn
density
aggregate
aggregates
nanohorn
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PCT/JP2003/001927
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French (fr)
Japanese (ja)
Inventor
Sumio Iijima
Masako Yudasaka
Katsuyuki Murata
Katsumi Kaneko
Elena Hristova
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Japan Science And Technology Agency
Nec Corporation
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Priority to JP2004507381A priority Critical patent/JP3854294B2/en
Publication of WO2003099717A1 publication Critical patent/WO2003099717A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B01J20/205—Carbon nanostructures, e.g. nanotubes, nanohorns, nanocones, nanoballs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/18—Nanoonions; Nanoscrolls; Nanohorns; Nanocones; Nanowalls

Definitions

  • the invention of this application relates to a high-density carbon nanohorn and a method for producing the same. More specifically, the invention of this application relates to a high-density carbon nanohorn in which not only the carbon nanohorn aggregates are densified but also the adsorption characteristics are further improved, and a method for producing the same. Background art
  • the carbon nanohorn aggregate found by the inventors of the present application is a single-walled carbon nanotube having a shape in which one end of a single-walled carbon nanotube has a conical shape, and a carbon nanohorn is formed into a spherical shape having a diameter of about 80 to 10 O nm.
  • Dahlia-like carbon nanohorn agglomerates with their horn-shaped tips outside, and bud-like carbon nanohorn aggregates with smooth surfaces without horn-like protrusions Gathering is known.
  • the inventors of the present application have stated that these carbon nanohorn aggregates are lightweight and chemically stable because dalaite is a constituent unit, and have an adsorption function without any activation treatment.
  • It can be used as a new functional material such as a material (Japanese Patent Application No. 2000-35083), and by opening the wall and tip of the carbon nanohorn, it can be used not only on the surface of the carbon nanohorn but also inside it. It is possible to realize a new carbon nanohorn adsorbent with higher performance and higher functionality because it can adsorb the substance to be adsorbed and exhibits selective adsorption characteristics and a high-efficiency molecular sieving function. 2 0 0 2—2 0 7 7 3).
  • the adsorption capacity of the carbon nanohorn adsorbent is excellent as described above, it cannot be said that the carbon nanohorn adsorbent is sufficiently satisfactory, for example, in consideration of application to a hydrogen gas storage material, a methane gas storage material, or a fuel cell. Therefore, the invention of this application has been made in view of the circumstances described above, and solves the problems of the prior art. Not only is the carbon nanohorn aggregate increased in density, but the adsorption characteristics are further improved. It is an object of the present invention to provide a high-density carbon nanohorn and a method for manufacturing the same. Disclosure of the invention
  • the invention of this application provides a high-density single-bon nanohorn characterized by being a solid obtained by aggregating a plurality of carbon nanohorn aggregates at a high density.
  • the invention of the present application is directed to the high-density carbon characterized in that the carbon nanohorn aggregate is a Darier-like carbon nanohorn aggregate, a bud-like carbon nanohorn aggregate, or a mixture thereof.
  • the third is the high-density carbon nanohorn, which is characterized in that the carbon nanohorn aggregate has an opening in the wall of the carbon nanohorn tube.
  • the fourth is the bulk density of the carbon nanohorn aggregate, which is higher than the carbon nanohorn aggregate itself.
  • the high-density force-bonded carbon nanohorn is characterized by its increased specific surface area and pore volume.Fifth, it absorbs more gas per volume and weight than the carbon nanohorn aggregate itself.
  • a high-density carbon nanohorn is provided.
  • the invention of this application relates to a method for producing a high-density carbon nanohorn, comprising dispersing a plurality of carbon nanohorn aggregates in an organic solvent and evaporating the organic solvent.
  • a method for producing high-density carbon nanohorns which comprises dispersing a plurality of carbon nanohorn aggregates in an organic solvent and then irradiating ultrasonic waves, is eighth.
  • a method for producing high-density carbon nanohorns, which is characterized by pressurizing carbon nanohorns is to disperse a plurality of carbon nanohorn aggregates in an organic solvent.
  • a method for producing high-density carbon nanohorns, which comprises evaporating the medium and pressurizing the precipitated carbon nanohorn aggregates is described in the tenth aspect. Provided is a method for producing a high-density carbon nanohorn.
  • the invention of this application is directed to the method of the invention described above, wherein, firstly, the carbon nanohorn aggregates are chemically modified in advance to increase the affinity between the carbon nanohorn aggregates.
  • FIG. 1 is a diagram illustrating the results obtained by examining the nitrogen gas adsorption characteristics of the high-density carbon nanohorns (A) and (B) of the invention of the present application and the Darrier-type SWNH aggregate (C).
  • FIG. 2 is a diagram exemplifying the results of examining the methane gas adsorption characteristics of the high-density carbon nanohorn of the invention of the present application and Darrie-type SWNH aggregates.
  • FIG. 3 is a diagram illustrating a result of examining nitrogen gas adsorption characteristics of the OH-modified high-density carbon nanohorn of the invention of this application.
  • Figure 4 shows examples of (a) nitrogen adsorption isotherm at 77 K, (b) pore size distribution, and (c) FHH plot for as-grown SWNH, eth-SWNH and compressed SWNH.
  • FIG. 4 shows examples of (a) nitrogen adsorption isotherm at 77 K, (b) pore size distribution, and (c) FHH plot for as-grown SWNH, eth-SWNH and compressed SWNH.
  • FIG. 5 is a diagram exemplifying (a) a nitrogen adsorption isotherm at 77 K and (b) a pore size distribution for o ⁇ 3 ⁇ 1 ⁇ 11 compression 0 X —SWNH.
  • the high-density carbon nanohorn provided by the invention of this application is characterized in that the carbon nanohorn aggregate is a solid that is aggregated at high density.
  • the carbon nanohorn aggregate includes a Darya-like carbon nanohorn aggregate in which a plurality of carbon nanohorns are gathered with the angular tip outside, and a smooth surface without horn-like protrusions on the surface. And a mixture thereof and the like.
  • these carbon nanohorn aggregates may have openings formed in the tube wall of the carbon nanohorn.
  • “high density” means that the bulk density is 0.5 mg Zm 1 or more, and practically, it is in the range of about 0.5 to 2.5 mg / ml. This is, for example, 10 times or more higher than the bulk density of the as-produced dahlia-like carbon nanohorn aggregates being about 0.01 to 0.05 mgZml.
  • the high-density carbon nanohorn of the invention of this application has a higher bulk density than the ordinary carbon nanohorn aggregate itself.
  • the specific surface area and pore (micropore) capacity have also been increased.
  • specific examples for example, typical values of the specific surface area and pore volume per unit volume of the dahlia shaped Kabon'nanoho over down agglomerates as produced, respectively 3 0 8 m 2 // g, whereas a 0. LLML / g, dense carbon nanohorn of the invention of this application, respectively 3 5 0 ⁇ 6 0 0 m 2 Z g, increased to 0. 1 3 ⁇ 0. 40m l / g It will be realized as a result.
  • the invention of this application consisting of a Darya-like carbon nanohorn aggregate having pores For high-density carbon nanohorns, these values will be significantly increased to 100 to 1200 m2Zg and 0.4 to 0.7 ml / g, respectively.
  • the high-density carbon nanohorn of the invention of this application also has a higher gas adsorption amount per volume and weight than the carbon nanohorn aggregate itself in terms of adsorption characteristics.
  • the methane gas adsorption amount per weight (per volume) of the as-produced dahlia-like carbon nanohorn aggregates is 15 to 2 at 303 K and 3.5 MPa. 0 mg / g (approximately 10 mg / ml), whereas the high-density carbon nanohorn of the invention of the present application adsorbed methane gas at 35 to 40 mg / g (about 25 mg / m1). ), which is about twice as high. It has been confirmed that the adsorption characteristics of this high-density carbon nanohorn are improved for most gases other than hydrogen and helium in addition to the methane gas exemplified here.
  • the high-density carbon nanohorn of the invention of this application as described above can be manufactured by, for example, the following method for manufacturing a high-density carbon nanohorn provided by the invention of this application. That is, the method for producing the high-density carbon nanohorn of the present invention is as follows.
  • the carbon nanohorn aggregates as a starting material include Bon nanohorn agglomerates, bud-like carbon nanohorn agglomerates, those having openings in them, and mixtures thereof can be used.
  • a carbon nanohorn aggregate having an opening in the carbon nanohorn tube wall In order to increase the specific surface area, the pore volume, the adsorption capacity, and the like, it is preferable to use a carbon nanohorn aggregate having an opening in the carbon nanohorn tube wall.
  • the carbon nanohorn aggregate as a starting material is dispersed in an organic solvent.
  • the organic solvent is not limited to the organic solvent, and various solvents can be used as long as the carbon nanohorn aggregate can be dispersed.
  • the type of the organic solvent is not particularly limited. Examples thereof include hydrocarbons such as benzene, toluene, and xylene, alcohols such as ethanol, methanol, ethylene glycol, and glycerin, ethers such as dimethyl ether, and esters.
  • Various organic solvents such as derivatives thereof can be used. For the sake of simplicity, it is preferable to use a volatile organic solvent having a high vapor pressure even at normal temperature and a low boiling point at normal pressure.
  • desired solvents such as ethyl ether, ethanol, ethyl acetate, benzene and hexane are used.
  • Use of an organic solvent having volatility near the temperature of the production atmosphere is exemplified as a simple method.
  • the organic solvent can be selected in consideration of this point. Specifically, for example, when ethanol is used as the organic solvent, the specific surface area and the pore (micropore) volume of the obtained high-density carbon nanohorn are 509 m 2 Z, respectively. g, 0.20 m 1 / g, but when glycerin is used, it is exemplified that it becomes 385 m 2 Zg, 0.16 ml / g.
  • the amount of the organic solvent in which the carbon nanohorn aggregates are dispersed there is no particular limitation on the amount of the organic solvent in which the carbon nanohorn aggregates are dispersed, and the amount may be such that the carbon nanohorn aggregates can be dispersed in the organic solvent without being aggregated. Wear. However, if the amount of the organic solvent with respect to the carbon nanohorn aggregates is too large, the efficiency of the next evaporation will decrease, so the standard is, for example, 100 mg of carbon nanohorn aggregates. Thus, an example in which the organic solvent is set to 10 m 1 or more, for example, about several 10 m 1 is shown. In dispersing the carbon nanohorn aggregate, operations such as stirring can be performed as necessary.
  • the carbon nanohorn aggregates may be dispersed in an organic solvent and then irradiated with ultrasonic waves.
  • This ultrasonic irradiation can disperse the carbon nanohorn aggregates in the organic solvent and have the effect of bringing the arrangement (the degree of clogging) closer to the closest packing.
  • the carbon nanohorn aggregates dispersed in the organic solvent gradually begin to precipitate by evaporating the organic solvent. It is preferable that the organic solvent be evaporated slowly and completely. For example, when ethanol is used as the organic solvent, a preferable example is that the organic solvent is naturally evaporated to dryness at room temperature. Of course, depending on the type of the solvent, for the sake of simplicity, the evaporation of the organic solvent can be performed, for example, by heat treatment, vacuum treatment, or a combination thereof. During this precipitation, the carbon nanohorn aggregates naturally form a close-packed structure, A high-density carbon nanohorn according to the present invention, in which the bon nanohorn aggregates approach each other in an efficient arrangement, will be obtained.
  • the carbon nanohorn aggregates are pressed to mechanically bring the carbon nanohorn aggregates closer together to obtain the high-density carbon nanohorn of the invention of the present application.
  • the method of pressurization in this case is not particularly limited, but the pressure applied to the carbon nanohorn aggregate is 5 MPa or more, more preferably about 10 to 50 MPa, more specifically about 5 OMPa.
  • the strength of the obtained high-density force-bonded nanohorn can be made to a certain degree.
  • a high-density carbon nanohorn can be obtained as a solid, but it becomes brittle.
  • the carbon nanohorn aggregate without pores is used as a starting material, the high density in the invention of this application can be easily achieved.
  • the carbon nanohorn aggregates can be formed into a desired shape under pressure.
  • the high-density carbon nanohorn obtained by the second method does not have a close-packed structure, it has a slightly sparser structure than that obtained by the first method, The connections themselves are considered to be the same.
  • TEM transmission electron microscopy
  • the second method is performed following the first method, and the carbon nanohorn aggregates are arranged closer to each other after being arranged efficiently.
  • a high-density carbon nanohorn with a higher bulk density is obtained.
  • the arrangement of the individual carbon nanohorn aggregates changes depending on the organic solvent, the presence or absence of pressurization, and the type or condition.
  • the structure of the pores will also change. So, for example, this When the high-density force nanohorn of the invention of the application is used as an adsorbent, its adsorbing ability can be adjusted, and an adsorbent having a desired pore structure can be easily realized. become.
  • the carbon nanohorn aggregates as the starting material are chemically modified in advance to increase the affinity of the carbon nanohorn aggregates.
  • a good orientation of the carbon nanohorn aggregate in the high-density carbon nanohorn can be obtained.
  • the carbon nanohorn aggregates can be brought closer to each other, and a high-density carbon nanohorn having a higher bulk density can be obtained.
  • adsorbents for gas storage require high specific surface area and well-developed micropores, as well as high bulk density. Therefore, it can be said that the high-density nanohorn of the invention of this application is extremely useful as an adsorbent for gas storage.
  • the pellets were slowly evaporated, and then pressurized at 50 kgf / cm 2 to obtain pelleted high-density carbon nanohorns.
  • the bulk density of this high-density carbon nanohorn was investigated and is shown in Table 1. This The bulk density of the high-density carbon nanohorn was 0.6 to 0.8 g / cm 3 , and it was confirmed that the bulk density was higher than that of the Darier-type carbon nanohorn aggregate used and general activated carbon.
  • a high-density carbon nanohorn (A) produced in Example 1 a high-density carbon nanohorn (B) produced by dispersing Darrie-type SWNH aggregates in ethanol and slowly evaporating the ethanol, and The Darrier-type carbon nanohorn aggregate (C) was examined for nitrogen gas adsorption characteristics. The results are shown in FIG. 1 and Table 2.
  • the high-density nanohorn (A) (B) It was confirmed that the adsorption characteristics were improved. In addition, it was confirmed that the adsorption characteristics of the high-density nanohorn (A), which was further pressurized, were significantly improved, compared to the high-density nanohorn (B), which was densified by ethanol evaporation. . The adsorption surface area and pore volume of (A) and (B) were also clearly increased compared to (C).
  • the Darrier-type carbon nanohorn aggregate was dispersed in ethanol, the ethanol was slowly evaporated, and then pressurized at 50 kgf Z cm 2 to obtain a pellet-like high-density carbon nanohorn.
  • the methane gas adsorption characteristics of the high-density carbon nanohorn and the Darrier-type carbon nanohorn aggregate were examined, and the results are shown in FIG. Table 3 shows the amount of methane gas adsorbed at 3.5 MPa.
  • the high-density nanohorn of the invention of this application is superior to the as-produced Darier-type carbon nanohorn aggregate.
  • the adsorption of methane gas on the high-density nanohorn was more than twice that of the as-produced dary-type carbon nanohorn aggregate.
  • the Darrier-type carbon nanohorn aggregate heat-treated at 420 ⁇ was mixed with an aqueous hydrogen peroxide solution, immersed for 24 hours, filtered, and the filtrate was dried at 6 ox :.
  • this Dary-type nano-bonnet aggregate is heat-treated at 900 in argon, and the force whose surface is modified with OH group One bon nanohorn aggregate was obtained.
  • the OH group-modified force one Bon'nanohon aggregate was dispersed in ethanol, after boiled create evaporated ethanol, by pressurizing at 50 kgf Z cm 2, to obtain a pelletized high density OH modified carbon nanohorn.
  • the bulk density of this high-density OH-modified carbon nanohorn was 0.6 to 0.8 gZ cm 3 .
  • the specific surface area, micropore volume, and nitrogen gas adsorption characteristics were examined. The results are shown in Table 4 and FIG. The results are also shown for the high-density OH-modified carbon nanohorn and OH-modified carbon nanohorn fabricated without pressurization.
  • This high-density OH-modified carbon nanohorn was confirmed to have improved dispersibility due to the addition of the OH group, and also increased both the amount of dissolved pores and the specific surface area.
  • FIG. 4 a shows nitrogen adsorption isotherms at 77 K for as-grown SWNH, eth-SWNH, and compressed SWNH. Prior to the adsorption test, each sample was preheated at 423 K for 2 hours in a vacuum of 10-4 Pa or less. In the markers in the figure, triangles indicate as-grown SWNH, diamonds indicate eth-S WNH, and circles indicate compressed SW N H, respectively.
  • the adsorption isotherm of as-grown SWNH was in the middle between Type I and IV.
  • the hysteresis-free behavior seen in this isotherm is related to the presence of wedge-shaped mesopores formed at the junction of two adjacent spherical SWNH aggregate particles.
  • the isotherm of the compressed SWNH has a narrow hysteresis loop of type HI according to the IUPAC classification, indicating that spherical SWNH aggregate particles of almost uniform size are aggregated or densely packed. In other words, it indicates that when the SWNH aggregate particles were dispersed in ethanol and dried, they rearranged due to the surface tension of ethanol and formed a close-packed structure with meso-sized particle gaps. And capillary condensation in this particle gap, This gives a hysteresis loop in the isotherm.
  • the isotherm of the compressed SW NH is compared with as-grown S WNH and eth-S WNH, it is PZP.
  • the Ds rating includes:
  • the FHH equation represented by The FHH plot is shown in Fig. 4c.
  • the linearity collapses in the region where the POZP is extremely low and deviates downward due to the filling of the micropores.
  • the FHH plot of the compressed SWNH is deviated downward even at relatively high pressure, and it is considered that the SWNH particles are well packed so as not to leave macropores (5 O nm or more).
  • Opening can be made in the closed nanohorn by heat treatment in oxygen.
  • heat treatment at 693 K holes are formed in almost all the tube walls of dahlia-shaped SWNH.
  • the oxidized SWNH aggregate was designated as oX-SWNH, and the oX-SWNH was dispersed in ethanol by ultrasonic treatment and compressed under the same conditions as ⁇ A>.
  • Nitrogen adsorption tests were performed on ox-SWNH and compressed oX-SWWH at 77 K, and the results are shown in Figure 5a. In the figure, diamonds indicate o X — SWN H, and circles indicate oX — S WWH.
  • the adsorption isotherm of the compressed o X — SWNH shows a greater increase in the amount of adsorption as seen between the as-grown SWN and the compressed SWNH in ⁇ A> above than the ox—SWNH without compression. Not observed. However, the hysteresis seen in the isotherm of the compressed 0X-SWNH is similar to that of the compressed SWNH in ⁇ A> above, indicating that the adsorbed molecules are blocked at the pore entrance. The difference between the isotherms of o X — S WNH and compression o X — S WWH was clearly observed at relatively high pressures.
  • SWNH samples oxidized at 693 K after compression showed the same nitrogen adsorption isotherm as compressed oX-SWNH. Therefore, when the compressed SWNH was subjected to oxygen treatment, there was no restriction on the permeation of oxygen into the SWNH, and it was confirmed that the compressed body was oxidized homogeneously.
  • the mesopore volume (Vme) of as-grown S WNH and eth-SWNH indicates that Vme greatly increases after ethanol treatment. confirmed.
  • the increased porosity of the mesopores is, as described above, a gap formed by the SWNH aggregates being in a close-packed state after the ethanol treatment.
  • the reason why Vme is larger in ox-SWNH than in as-grownS WNH is explained by the fact that mesopores of 2 nm or more were formed in the carbon nanohorn by oxidation treatment.
  • Vme is also reduced by compression for both eth-S WNH and oX_S WNH, but the application of such high pressure reduces the original gap of SWNH aggregate particles, When the corners protruding from are pushed into the bulk, they rearrange into a structure with a smooth surface, as shown by fractal analysis.
  • micropore volume of the compressed SWNH increases almost twice as large as as-grown SWN. This is thought to be due to the fact that the carbon nanohorns were partially opened by compression and the micropores increased.
  • Particle density S WNH aggregates obtained by helium method is to prove this hypothesis, the particle density of the compressed SWNH is than the density 1. 2 5 g cm 3 of as-grown S WNH Rukani It was large 1.69 g Z cm 3 . From this, it was confirmed that holes were formed in the defect site of the carbon nanohorn by mechanical compression. Also, the volume of the micropores were determined using Dubinin-Radushkevicli (DR) equation from put that C0 2 adsorption amount to 27 3 K.
  • DR Dubinin-Radushkevicli
  • the resulting narrow micropore volume was 0.10 cm 3 Zg, consistent with the micropore volume increase after compression. Furthermore, the pores formed after compression were shown to be mainly ultra-micro pores with a pore size of less than 0.7 nm. On the other hand, eth-S WNH also showed a slight increase in micropore volume. This is thought to be because ultrasonic irradiation during the ethanol treatment promoted the formation of holes in the carbon nanohorn and opened some of the defects.
  • o X The microvolume of SWNH remains almost unchanged after compression because almost all carbon nanohorns are open after oxidation. Therefore, nano gap between particles No increase in the new surface area and micropore volume due to the above. Note that such compression is not high enough to reduce the voids between SWNH aggregates to micropore size.
  • the bulk density and specific surface area of the Dahlia-like SWNH aggregate particles are significantly increased and the pore structure is changed by compressing subsequent to the pretreatment by ultrasonic treatment in ethanol. all right.
  • the bulk density and the specific surface area were further increased by providing openings in the Darrie-like SWNH aggregate.
  • the present invention provides a high-density carbon nanohorn in which not only the carbon nanohorn aggregates are densified but also the adsorption characteristics are further improved, and a method for producing the same.

Abstract

High-density carbon nanohorns obtained by dispersing carbon nanohorn aggregates in an organic solvent, evaporating the organic solvent, and pressing the residual carbon nanohorn aggregates to thereby unite the carbon nanohorn aggregates together at a high density. The high-density carbon nanohorns not only are composed of highly densified carbon nanohorn aggregates but have enhanced adsorption characteristics.

Description

明 細 書 高密度カーボンナノホーンとその製造方法 技術分野  Description High-density carbon nanohorn and its manufacturing method
この出願の発明は、 高密度カーボンナノホーンとその製造方法に関 するものである。 さらに詳しくは、 この出願の発明は、 カーボンナノ ホーン凝集体が高密度化されたのみならず、 吸着特性がより高められ た高密度カーボンナノホーンとその製造方法に関するものである。 背景技術  The invention of this application relates to a high-density carbon nanohorn and a method for producing the same. More specifically, the invention of this application relates to a high-density carbon nanohorn in which not only the carbon nanohorn aggregates are densified but also the adsorption characteristics are further improved, and a method for producing the same. Background art
この出願の発明者らが見出したカーボンナノホーン凝集体は、 管状 の単層カーボンナノチューブの一端が円錐状となった形状を有する力 一ボンナノホーンが、直径 8 0〜 1 0 O n m程度の球状に集合したも のであり、 その角状の先端部を外にして集合したダリヤ状力一ボンナ ノホーン凝集体や、 その表面に角状の突起が見られず、 滑らかな表面 を有するつぼみ状カーボンナノホーン凝集体が知られている。 そして、 この出願の発明者らは、 これらのカーボンナノホーン凝集体は、 ダラ フアイ卜が構成単位であるため軽量で化学的に安定で、一切の活性化 処理無しで吸着機能を有することから、吸着材等の新しい機能材とし て利用できること （特願 2 0 0 0— 3 5 8 3 6 2 ) や、 カーボンナ ノホーンの壁部および先端部を開口することで、 カーボンナノホーン の表面だけでなくその内部にまで被吸着物質を吸着させることがで き、 また選択吸着特性や、 高効率の分子ふるい機能などを示すことか ら、 より高性能かつ高機能な新しいカーボンナノホーン吸着材が実現 できること （特願 2 0 0 2— 2 0 7 7 3 ) などを見出してもいる。  The carbon nanohorn aggregate found by the inventors of the present application is a single-walled carbon nanotube having a shape in which one end of a single-walled carbon nanotube has a conical shape, and a carbon nanohorn is formed into a spherical shape having a diameter of about 80 to 10 O nm. Dahlia-like carbon nanohorn agglomerates with their horn-shaped tips outside, and bud-like carbon nanohorn aggregates with smooth surfaces without horn-like protrusions Gathering is known. The inventors of the present application have stated that these carbon nanohorn aggregates are lightweight and chemically stable because dalaite is a constituent unit, and have an adsorption function without any activation treatment. It can be used as a new functional material such as a material (Japanese Patent Application No. 2000-35083), and by opening the wall and tip of the carbon nanohorn, it can be used not only on the surface of the carbon nanohorn but also inside it. It is possible to realize a new carbon nanohorn adsorbent with higher performance and higher functionality because it can adsorb the substance to be adsorbed and exhibits selective adsorption characteristics and a high-efficiency molecular sieving function. 2 0 0 2—2 0 7 7 3).
このようにカーボンナノホーン吸着材の吸着能は優れたものである が、 たとえば水素ガス吸蔵体、 メタンガス吸蔵体、 あるいは燃料電池 等への応用を考慮した場合、 決して十分なものとはいえなかった。 そこで、 この出願の発明は、 以上の通りの事情に鑑みてなされたも のであり、 従来技術の問題点を解消し、 カーボンナノホーン凝集体が 高密度化されたのみならず、 吸着特性がより高められた高密度カーボ ンナノホーンとその製造方法を提供することを課題としている。 発明の開示 Although the adsorption capacity of the carbon nanohorn adsorbent is excellent as described above, it cannot be said that the carbon nanohorn adsorbent is sufficiently satisfactory, for example, in consideration of application to a hydrogen gas storage material, a methane gas storage material, or a fuel cell. Therefore, the invention of this application has been made in view of the circumstances described above, and solves the problems of the prior art. Not only is the carbon nanohorn aggregate increased in density, but the adsorption characteristics are further improved. It is an object of the present invention to provide a high-density carbon nanohorn and a method for manufacturing the same. Disclosure of the invention
そこで、 この出願の発明は、 上記の課題を解決するものとして、 以 下の通りの発明を提供する。  Therefore, the invention of this application provides the following inventions to solve the above problems.
すなわち、 まず第 1には、 この出願の発明は、 複数のカーボンナノ ホーン凝集体を、 高密度に凝集させた固体であることを特徴とする高 密度力一ボンナノホーンを提供する。  That is, first of all, the invention of this application provides a high-density single-bon nanohorn characterized by being a solid obtained by aggregating a plurality of carbon nanohorn aggregates at a high density.
そしてこの出願の発明は、 上記の発明について、 第 2には、 カーボ ンナノホーン凝集体が、 ダリァ状カーボンナノホーン凝集体、 つぼみ 状カーボンナノホーン凝集体、 あるいはその混合物であることを特徴 とする高密度カーボンナノホーンを、 第 3には、 カーボンナノホーン 凝集体が、 カーボンナノホーン管壁に開孔を有することを特徴とする 高密度カーボンナノホーンを、 第 4には、 力一ボンナノホーン凝集体 そのものよりも嵩密度、 比表面積および細孔容量が高められているこ とを特徴とする高密度力一ボンナノホーンを、 第 5には、 カーボンナ ノホーン凝集体そのものよりも体積当たりおよび重量当たりのガス吸 着量が多いことを特徴とする高密度カーボンナノホーンを提供する。  Secondly, the invention of the present application is directed to the high-density carbon characterized in that the carbon nanohorn aggregate is a Darier-like carbon nanohorn aggregate, a bud-like carbon nanohorn aggregate, or a mixture thereof. The third is the high-density carbon nanohorn, which is characterized in that the carbon nanohorn aggregate has an opening in the wall of the carbon nanohorn tube. The fourth is the bulk density of the carbon nanohorn aggregate, which is higher than the carbon nanohorn aggregate itself. The high-density force-bonded carbon nanohorn is characterized by its increased specific surface area and pore volume.Fifth, it absorbs more gas per volume and weight than the carbon nanohorn aggregate itself. A high-density carbon nanohorn is provided.
またこの出願の発明は、 第 6には、 複数のカーボンナノホーン凝集 体を有機溶媒に分散させたのち、 この有機溶媒を蒸発させることを特 徵とする高密度カーボンナノホーンの製造方法を、 第 7には、 この複 数のカーボンナノホーン凝集体を有機溶媒に分散させたのち、 超音波 を照射することを特徴とする高密度カーボンナノホーンの製造方法 を、 第 8には、 複数のカーボンナノホーン凝集体を加圧することを特 徴とする高密度カーボンナノホーンの製造方法を、 第 9には、 複数の カーボンナノホーン凝集体を有機溶媒に分散させたのち、 この有機溶 媒を蒸発させ、 析出したカーボンナノホーン凝集体を加圧することを 特徴とする高密度カーボンナノホーンの製造方法を、 第 1 0には、 1 O MP a以上の圧力で加圧することを特徴とする高密度カーボンナ ノホーンの製造方法を提供する。 Sixth, the invention of this application relates to a method for producing a high-density carbon nanohorn, comprising dispersing a plurality of carbon nanohorn aggregates in an organic solvent and evaporating the organic solvent. A method for producing high-density carbon nanohorns, which comprises dispersing a plurality of carbon nanohorn aggregates in an organic solvent and then irradiating ultrasonic waves, is eighth. Ninth, a method for producing high-density carbon nanohorns, which is characterized by pressurizing carbon nanohorns, is to disperse a plurality of carbon nanohorn aggregates in an organic solvent. A method for producing high-density carbon nanohorns, which comprises evaporating the medium and pressurizing the precipitated carbon nanohorn aggregates, is described in the tenth aspect. Provided is a method for producing a high-density carbon nanohorn.
そして、この出願の発明は、上記発明の方法において、第 1 1には、 予めカーボンナノホーン凝集体を化学修飾してカーボンナノホーン凝 集体同士の親和力を高めておくことを特徴とする高密度ナノホーン の製造方法を、 第 1 2には、 カーボンナノホーン凝集体が、 ダリァ状 カーボンナノホーン凝集体、 つぼみ状力一ボンナノホーン凝集体、 あ るいはその混合物であることを特徴とする高密度ナノホーンの製造 方法を提供する。 図面の簡単な説明  The invention of this application is directed to the method of the invention described above, wherein, firstly, the carbon nanohorn aggregates are chemically modified in advance to increase the affinity between the carbon nanohorn aggregates. A method for producing a high-density nanohorn, wherein the carbon nanohorn aggregate is a Darya-like carbon nanohorn aggregate, a bud-like carbon nanohorn aggregate, or a mixture thereof. I will provide a. BRIEF DESCRIPTION OF THE FIGURES
図 1は、 この出願の発明の高密度カーボンナノホーン （A) (B) と、 ダリァ型 SWNH凝集体 （C) について窒素ガス吸着特性を調 ベた結果を例示した図である。  FIG. 1 is a diagram illustrating the results obtained by examining the nitrogen gas adsorption characteristics of the high-density carbon nanohorns (A) and (B) of the invention of the present application and the Darrier-type SWNH aggregate (C).
図 2は、 この出願の発明の高密度カーボンナノホーンと、 ダリァ型 S WN H凝集体についてメタンガス吸着特性を調べた結果を例示し た図である。  FIG. 2 is a diagram exemplifying the results of examining the methane gas adsorption characteristics of the high-density carbon nanohorn of the invention of the present application and Darrie-type SWNH aggregates.
図 3は、 この出願の発明の OH修飾高密度カーボンナノホーンにつ いて窒素ガス吸着特性を調べた結果を例示した図である。  FIG. 3 is a diagram illustrating a result of examining nitrogen gas adsorption characteristics of the OH-modified high-density carbon nanohorn of the invention of this application.
図 4は、 as- grownS WN H、 eth-S WN Hおよび圧縮 S WN Hに ついて、 （a) 7 7 Kにおける窒素吸着等温線、 （b) 細孔径分布、 ( c ) FHHプロッ トを例示した図である。  Figure 4 shows examples of (a) nitrogen adsorption isotherm at 77 K, (b) pore size distribution, and (c) FHH plot for as-grown SWNH, eth-SWNH and compressed SWNH. FIG.
図 5は、 o -3\ 1^11ぉょび圧縮0 X — SWNHについて、 （a) 7 7 Kにおける窒素吸着等温線および （b) 細孔径分布を例示した 図である。 発明を実施するための最良の形態 FIG. 5 is a diagram exemplifying (a) a nitrogen adsorption isotherm at 77 K and (b) a pore size distribution for o −3 \ 1 ^ 11 compression 0 X —SWNH. BEST MODE FOR CARRYING OUT THE INVENTION
この出願の発明は、 上記の通りの特徴を持つものであるが、 以下に その実施の形態について説明する。  The invention of this application has the features as described above, and embodiments thereof will be described below.
まず、 この出願の発明が提供する高密度カーボンナノホーンは、 力 一ボンナノホーン凝集体が、 高密度に凝集された固体であることを特 徵としている。 このカーボンナノホーン凝集体としては、 複数の力一 ボンナノホーンが角状の先端部を外にして集合したダリヤ状カーボン ナノホーン凝集体や、 その表面に角状の突起が見られず、 滑らかな表 面を有するつぼみ状カーボンナノホーン凝集体、 さらにはそれらの混 合物等とすることができる。 また加えて、 これらのカーボンナノホーン 凝集体は、 そのカーボンナノホーンの管壁に開孔が設けられたもので あってもよい。  First, the high-density carbon nanohorn provided by the invention of this application is characterized in that the carbon nanohorn aggregate is a solid that is aggregated at high density. The carbon nanohorn aggregate includes a Darya-like carbon nanohorn aggregate in which a plurality of carbon nanohorns are gathered with the angular tip outside, and a smooth surface without horn-like protrusions on the surface. And a mixture thereof and the like. In addition, these carbon nanohorn aggregates may have openings formed in the tube wall of the carbon nanohorn.
そしてこの出願の発明において、 高密度とは、 嵩密度が 0. 5mg Zm 1以上、 実際的にはおよそ 0. 5〜2. 5mg/m l程度の範 囲のものであることを示している。 これは、 たとえば、 一般的な製造 されたままのダリヤ状カーボンナノホーン凝集体の嵩密度が 0. 0 1 〜 0. 0 5mgZm l程度であることと比べて 1 0倍以上の高い値 である。  In the invention of this application, “high density” means that the bulk density is 0.5 mg Zm 1 or more, and practically, it is in the range of about 0.5 to 2.5 mg / ml. This is, for example, 10 times or more higher than the bulk density of the as-produced dahlia-like carbon nanohorn aggregates being about 0.01 to 0.05 mgZml.
このように、 この出願の発明の高密度カーボンナノホーンは、 通常 の力一ボンナノホーン凝集体そのものよりも嵩密度が高めらたもので あるが、 さらにその構造を詳細に検討すると、 単位体積当たりの比表 面積および細孔 （ミクロ孔） 容量についても増大されている。 具体的 に例示すると、 たとえば、 製造されたままのダリヤ状カーボンナノホ ーン凝集体についての単位体積当たりの比表面積および細孔容量の 代表的な値が、 それぞれ 3 0 8 m2// g、 0. l l m l /gであるの に対して、 この出願の発明の高密度カーボンナノホーンは、 それぞれ 3 5 0〜 6 0 0 m2Z g、 0. 1 3〜0. 40m l /gにまで増大さ れたものとして実現されることになる。そして驚くべきことに、 開孔を 有するダリヤ状カーボンナノホーン凝集体からなるこの出願の発明の 高密度カーボンナノホーンについては、 これらの値は、 それぞれ 1 0 0 0〜 1 2 0 0 m 2Zg、 0. 4〜 0. 7 m l /gと、 著しく増大さ れることになる。 As described above, the high-density carbon nanohorn of the invention of this application has a higher bulk density than the ordinary carbon nanohorn aggregate itself. The specific surface area and pore (micropore) capacity have also been increased. Specific examples, for example, typical values of the specific surface area and pore volume per unit volume of the dahlia shaped Kabon'nanoho over down agglomerates as produced, respectively 3 0 8 m 2 // g, whereas a 0. LLML / g, dense carbon nanohorn of the invention of this application, respectively 3 5 0~ 6 0 0 m 2 Z g, increased to 0. 1 3~0. 40m l / g It will be realized as a result. Surprisingly, the invention of this application consisting of a Darya-like carbon nanohorn aggregate having pores For high-density carbon nanohorns, these values will be significantly increased to 100 to 1200 m2Zg and 0.4 to 0.7 ml / g, respectively.
また、 このような構造的特長から、 この出願の発明の高密度カーボ ンナノホーンは、 吸着特性についても、 力一ボンナノホーン凝集体そ のものよりも体積当たりおよび重量当たりのガス吸着量が高められる ことになる。 すなわち、 具体的には、 たとえば、 製造されたままのダ リャ状カーボンナノホーン凝集体の重量当たり （体積当たり） のメタ ンガス吸着量が、 3 0 3 K、 3. 5 MP aで 1 5〜 2 0 mg/g (お よそ 1 0 m g/m l ) であるのに対し、 この出願の発明の高密度カー ボンナノホーンのメタンガス吸着量は 3 5〜 4 0 mg/g (およそ 2 5 m g/m 1 ) と、 約 2倍以上にも高められることになる。 この高密 度カーボンナノホーンの吸着特性は、 ここに例示したメタンガス以外 にも、 水素、 ヘリウムを除く殆どの気体について向上されることが確 認されている。  In addition, due to such structural features, the high-density carbon nanohorn of the invention of this application also has a higher gas adsorption amount per volume and weight than the carbon nanohorn aggregate itself in terms of adsorption characteristics. become. That is, specifically, for example, the methane gas adsorption amount per weight (per volume) of the as-produced dahlia-like carbon nanohorn aggregates is 15 to 2 at 303 K and 3.5 MPa. 0 mg / g (approximately 10 mg / ml), whereas the high-density carbon nanohorn of the invention of the present application adsorbed methane gas at 35 to 40 mg / g (about 25 mg / m1). ), Which is about twice as high. It has been confirmed that the adsorption characteristics of this high-density carbon nanohorn are improved for most gases other than hydrogen and helium in addition to the methane gas exemplified here.
以上のようなこの出願の発明の高密度カーボンナノホーンは、 たと えば下記に示すような、 この出願の発明が提供する高密度カーボンナ ノホーンの製造方法により製造することができる。 すなわち、 この出 願の発明の高密度カーボンナノホーンの製造方法は、  The high-density carbon nanohorn of the invention of this application as described above can be manufactured by, for example, the following method for manufacturing a high-density carbon nanohorn provided by the invention of this application. That is, the method for producing the high-density carbon nanohorn of the present invention is as follows.
1. 複数のカーボンナノホーン凝集体を有機溶媒に分散させたの ち、 この有機溶媒を蒸発させるようにする、  1. After dispersing a plurality of carbon nanohorn aggregates in an organic solvent, the organic solvent is evaporated.
2. 複数のカーボンナノホーン凝集体を加圧するようにする、 あるいは、  2. Pressurize multiple carbon nanohorn aggregates, or
3. 複数のカーボンナノホーン凝集体を有機溶媒に分散させたの ち、 この有機溶媒を蒸発させ、 析出したカーボンナノホーン 凝集体を加圧するようにする  3. After dispersing a plurality of carbon nanohorn aggregates in an organic solvent, the organic solvent is evaporated, and the deposited carbon nanohorn aggregates are pressurized.
等といった方法である。 And so on.
これらの高密度カーボンナノホーンの製造方法において、 出発材料 としてのカーボンナノホーン凝集体は、 前記のとおりのダリァ状カー ボンナノホーン凝集体や、 つぼみ状カーボンナノホーン凝集体、 さら にこれらに開孔を設けたもの、 またそれらの混合物等を用いることが できる。比表面積、細孔容量および吸着容量等を増大させるためには、 カーボンナノホーン管壁に開孔を有するカーボンナノホーン凝集体を 用いることが好ましい。 In these methods for producing high-density carbon nanohorns, the carbon nanohorn aggregates as a starting material include Bon nanohorn agglomerates, bud-like carbon nanohorn agglomerates, those having openings in them, and mixtures thereof can be used. In order to increase the specific surface area, the pore volume, the adsorption capacity, and the like, it is preferable to use a carbon nanohorn aggregate having an opening in the carbon nanohorn tube wall.
上記の 1つ目の方法においては、 この出発材としての力一ボンナノ ホーン凝集体を有機溶媒に分散させるようにしている。 この有機溶媒 としては、 実際的には、 カーボンナノホーン凝集体を分散させること ができるものであれば有機溶媒に限らず各種の溶媒を用いることがで きる。 この有機溶媒としてはその種類等に制限はなく、 ベンゼン、 ト ルェン、 キシレン等の炭化水素や、 エタノール、 メタノール、 ェチレ ングリコール、 グリセリン等のアルコール、 ジェチルェ一テル等のエー テル、 およびエステル等のその誘導体等、 各種の有機溶媒等を用いる ことができる。 簡便のためには、 常温でも高い蒸気圧を持ち、 常圧で の沸点が低い揮発性の有機溶媒を用いることが好ましく、 たとえば、 ェチルエーテル、 エタノール、 酢酸ェチル、 ベンゼン、 へキサン等の、 所望の製造雰囲気温度付近で揮発性を有する有機溶媒を用いること が簡便なものとして例示される。  In the first method, the carbon nanohorn aggregate as a starting material is dispersed in an organic solvent. In practice, the organic solvent is not limited to the organic solvent, and various solvents can be used as long as the carbon nanohorn aggregate can be dispersed. The type of the organic solvent is not particularly limited. Examples thereof include hydrocarbons such as benzene, toluene, and xylene, alcohols such as ethanol, methanol, ethylene glycol, and glycerin, ethers such as dimethyl ether, and esters. Various organic solvents such as derivatives thereof can be used. For the sake of simplicity, it is preferable to use a volatile organic solvent having a high vapor pressure even at normal temperature and a low boiling point at normal pressure. For example, desired solvents such as ethyl ether, ethanol, ethyl acetate, benzene and hexane are used. Use of an organic solvent having volatility near the temperature of the production atmosphere is exemplified as a simple method.
一方で、 この有機溶媒は、 得られる高密度力一ボンナノホーンの細 孔構造にやや影響を与えることから、 この点を考慮して有機溶媒を選 択することもできる。 具体的に一例をあげてみると、 たとえば、 有機 溶媒としてエタノールを用いた場合には、 得られた高密度カーボンナ ノホーンの比表面積および細孔 （ミクロ孔） 容量がそれぞれ、 5 0 9 m 2 Z g、 0 . 2 0 m 1 / gであったのに対し、 グリセリンを用いた 場合には、 3 8 5 m 2 Z g、 0 . 1 6 m l / gとなることが例示され る。 On the other hand, since this organic solvent slightly affects the pore structure of the obtained high-density force nanohorn, the organic solvent can be selected in consideration of this point. Specifically, for example, when ethanol is used as the organic solvent, the specific surface area and the pore (micropore) volume of the obtained high-density carbon nanohorn are 509 m 2 Z, respectively. g, 0.20 m 1 / g, but when glycerin is used, it is exemplified that it becomes 385 m 2 Zg, 0.16 ml / g.
カーボンナノホーン凝集体を分散させる有機溶媒の量については 特に制限はなく、 有機溶媒中でカーボンナノホーン凝集体が凝集する ことなく、 各々が分散された状態が得られる程度の量とすることがで きる。 ただし、 カーボンナノホーン凝集体に対する有機溶媒の量が多 すぎる零合には、 次の蒸発の効率が低下することになるため、 目安と しては、 たとえば、 カーボンナノホーン凝集体 1 0 0 m gに対して、 有機溶媒を 1 0 m 1 以上、 たとえば数 1 0 m 1 程度とすることが例 示される。 このカーボンナノホーン凝集体の分散にあたっては、 必要 に応じて、 攪拌等の操作を行なうことができる。 There is no particular limitation on the amount of the organic solvent in which the carbon nanohorn aggregates are dispersed, and the amount may be such that the carbon nanohorn aggregates can be dispersed in the organic solvent without being aggregated. Wear. However, if the amount of the organic solvent with respect to the carbon nanohorn aggregates is too large, the efficiency of the next evaporation will decrease, so the standard is, for example, 100 mg of carbon nanohorn aggregates. Thus, an example in which the organic solvent is set to 10 m 1 or more, for example, about several 10 m 1 is shown. In dispersing the carbon nanohorn aggregate, operations such as stirring can be performed as necessary.
そしてこの出願の発明においては、 カーボンナノホーン凝集体を有 機溶媒に分散させたのち、 超音波を照射するようにしてもよい。 この 超音波の照射は、カーボンナノホーン凝集体を有機溶媒中の分散させ るとともに、 その配置 （詰まり具合） を最密充填に近づける効果を得 ることができる。 液溶媒に照射する超音波は、 使用するカーボンナノ チューブの状態や液溶媒の種類、 およびそれらの量等と関連するため 一概には言えないが、 エネルギーが 2 5 0 W / c m 2未満のものを 5 〜3 0分程度照射することを目安とすることができる。 In the invention of this application, the carbon nanohorn aggregates may be dispersed in an organic solvent and then irradiated with ultrasonic waves. This ultrasonic irradiation can disperse the carbon nanohorn aggregates in the organic solvent and have the effect of bringing the arrangement (the degree of clogging) closer to the closest packing. Ultrasonic irradiated to the liquid solvent, state or liquid type of the solvent of the carbon nanotubes to be used, and can not be said sweepingly because associated with their amount, etc., energy is 2 5 0 W / cm 2 less than that For about 5 to 30 minutes.
また一方で、 2 5 0〜3 5 0 W Z c m 2程度の比較的エネルギーの 強い超音波を 5〜 3 0分程度照射することもできる。 この比較的強 い超音波の照射は、 グラフアイトシートの六員環ネットワークを切断 するために必要とされるエネルギーを供給することになり、 開孔を設 けられた高密度カーボンナノホーンを簡便に製造することができる。 ただし、 この場合も、 最後はエネルギーが 2 5 0 W Z c m 2未満の超 音波を照射することが望ましい。 On the other hand, it is also possible to irradiate an ultrasonic wave having a relatively high energy of about 250 to 350 WZ cm 2 for about 5 to 30 minutes. This relatively intense ultrasonic irradiation will supply the energy required to cut the six-membered ring network of the graphite sheet, allowing the perforated high-density carbon nanohorns to be easily provided. Can be manufactured. However, also in this case, it is desirable to irradiate an ultrasonic wave whose energy is less than 250 WZ cm 2 at the end.
有機溶媒に分散されたカーボンナノホーン凝集体は、有機溶媒を蒸 発させることで徐々に析出し始める。 この有機溶媒はゆつくりと完全 に蒸発させることが好ましく、 たとえば有機溶媒としてエタノールを 用いる場合には、 室温にて自然に蒸発乾固させることが好ましい例と して示される。 もちろん、 溶媒の種類等によっては、 簡便のために、 有機溶媒の蒸発に際して、 たとえば加熱処理、 真空処理、 またはこれ らを組み合わせて施すこと等も可能とされる。 この析出に際して、 力 一ボンナノホーン凝集体は自然に最密充填構造を形成するため、 カー ボンナノホーン凝集体同士が効率よい配置で接近したこの出願の発 明の高密度カーボンナノホーンが得られることになる。 The carbon nanohorn aggregates dispersed in the organic solvent gradually begin to precipitate by evaporating the organic solvent. It is preferable that the organic solvent be evaporated slowly and completely. For example, when ethanol is used as the organic solvent, a preferable example is that the organic solvent is naturally evaporated to dryness at room temperature. Of course, depending on the type of the solvent, for the sake of simplicity, the evaporation of the organic solvent can be performed, for example, by heat treatment, vacuum treatment, or a combination thereof. During this precipitation, the carbon nanohorn aggregates naturally form a close-packed structure, A high-density carbon nanohorn according to the present invention, in which the bon nanohorn aggregates approach each other in an efficient arrangement, will be obtained.
上記の 2つ目の方法においては、 カーボンナノホーン凝集体を加圧 することで機械的に力一ボンナノホーン凝集体同士を接近させて、 こ の出願の発明の高密度カーボンナノホーンを得るようにしている。 こ の場合の加圧の方法は特に制限されないが、 カーボンナノホーン凝集 体に加える圧力としては、 5 M P a以上、 より好ましくは 1 0〜 5 0 M P a程度、 より具体的には 5 O M P a程度とすることが例示され る。 この圧力により、 得られる高密度力一ボンナノホーンの強度をあ る程度所望のものとすることができる。 たとえば 5〜 1 O M P a程度 の圧力では、 固体として高密度カーボンナノホーンを得ることができ るものの、 もろいものとなってしまう。 なお、 出発材料として開孔の ないカーボンナノホーン凝集体を用いる場合には、 この出願の発明に おける高密度は簡便に達成される。 もちろん、 ここで、 カーボンナノ ホーン凝集体を所望の形状に加圧成形することなどもできる。  In the second method, the carbon nanohorn aggregates are pressed to mechanically bring the carbon nanohorn aggregates closer together to obtain the high-density carbon nanohorn of the invention of the present application. I have. The method of pressurization in this case is not particularly limited, but the pressure applied to the carbon nanohorn aggregate is 5 MPa or more, more preferably about 10 to 50 MPa, more specifically about 5 OMPa. The following is an example. By this pressure, the strength of the obtained high-density force-bonded nanohorn can be made to a certain degree. For example, at a pressure of about 5 to 1 OMPa, a high-density carbon nanohorn can be obtained as a solid, but it becomes brittle. When a carbon nanohorn aggregate without pores is used as a starting material, the high density in the invention of this application can be easily achieved. Of course, the carbon nanohorn aggregates can be formed into a desired shape under pressure.
この 2つ目の方法により得られた高密度カーボンナノホーンは最密 構造をとらないため、 1つ目の方法により得られたものに比べてやや 疎な構造であるものの、 力一ボンナノホーン凝集体同士のつながり自 体は同じであると考えられる。 ただ、 透過型電子顕微鏡 （T E M ) 観 察からは、 加圧によりナノホーン先端部の構造が変化している可能性 が見てとれる。  Since the high-density carbon nanohorn obtained by the second method does not have a close-packed structure, it has a slightly sparser structure than that obtained by the first method, The connections themselves are considered to be the same. However, transmission electron microscopy (TEM) observations suggest that the structure of the tip of the nanohorn may have changed due to pressure.
そして、 上記の 3つ目の方法においては、 1つ目の方法に引き続い て 2つ目の方法を施すようにしており、 カーボンナノホーン凝集体同 士を、 効率よい配置とした後により接近させるようにして、 さらに嵩 密度が高められた高密度カーボンナノホーンを得るようにしている。  In the third method, the second method is performed following the first method, and the carbon nanohorn aggregates are arranged closer to each other after being arranged efficiently. Thus, a high-density carbon nanohorn with a higher bulk density is obtained.
このようにこの出願の発明の 3通りの方法で得られる高密度力一 ボンナノホーンは、 有機溶媒および加圧の有無、 そしてその種類ある いは条件によって、 個々のカーボンナノホーン凝集体の配置が変化さ れ、 細孔の構造もが変わってくることになる。 従って、 たとえばこの 出願の発明の高密度力一ボンナノホーンを吸着材として用いる場合 には、 その吸着能についても調整が可能であって、 所望の細孔構造を 有する吸着剤の実現が容易に可能とされることになる。 As described above, in the high-density carbon nanohorn obtained by the three methods of the invention of this application, the arrangement of the individual carbon nanohorn aggregates changes depending on the organic solvent, the presence or absence of pressurization, and the type or condition. As a result, the structure of the pores will also change. So, for example, this When the high-density force nanohorn of the invention of the application is used as an adsorbent, its adsorbing ability can be adjusted, and an adsorbent having a desired pore structure can be easily realized. become.
加えてこの出願の発明においては、 出発材料のカーボンナノホーン 凝集体を予め化学修飾しておき、カーボンナノホーン凝集体同士の親 和力を高めておくことなどを考慮することができる。 たとえば、 カー ボンナノホーン凝集体を予めベンゼンゃァミノ基等で修飾することで、 高密度カーボンナノホーンにおける力一ボンナノホーン凝集体の配向 を良好なものとして得られることなどが例示される。 これによつて、 カーボンナノホーン凝集体同士を互いにより接近させることができ、 嵩密度がより高められた高密度カーボンナノホーンを得ることができ る。  In addition, in the invention of this application, it is possible to consider, for example, that the carbon nanohorn aggregates as the starting material are chemically modified in advance to increase the affinity of the carbon nanohorn aggregates. For example, by modifying the carbon nanohorn aggregate in advance with a benzenediamino group or the like, a good orientation of the carbon nanohorn aggregate in the high-density carbon nanohorn can be obtained. As a result, the carbon nanohorn aggregates can be brought closer to each other, and a high-density carbon nanohorn having a higher bulk density can be obtained.
以上のこの出願の発明の方法は、 一見極めて単純ではあるものの、 このような簡便な方法により、 一つの粒子としてのカーボンナノホ一 ン凝集体を最密充填構造とし、またより近接して配置させることを可 能としているのである。  Although the above-described method of the invention of this application is seemingly very simple, such a simple method allows the carbon nanophone aggregates as one particle to have a close-packed structure and to be arranged closer to each other. It is possible.
たとえばガス貯蔵用の吸着材に求められる条件は、高い比表面積お よび十分に発達したミクロ細孔を有することに加えて、 嵩密度が高い ことである。 したがって、 この出願の発明の高密度ナノホーンは、 ガ ス貯蔵を目的とする吸着材として極めて有用であるといえる。  For example, adsorbents for gas storage require high specific surface area and well-developed micropores, as well as high bulk density. Therefore, it can be said that the high-density nanohorn of the invention of this application is extremely useful as an adsorbent for gas storage.
以下に実施例を示し、 この発明の実施の形態についてさらに詳しく 説明する。 実 施 例  Examples will be shown below, and the embodiments of the present invention will be described in more detail. Example
(実施例 1 )  (Example 1)
ダリァ型カ一ボンナノホーン凝集体をエタノールに分散し、 ェタノ Disperse Darier-type carbon nanohorn aggregates in ethanol, and add ethanol
—ルをゆっくりと蒸発させた後、 5 0 k g f / c m 2で加圧すること で、 ペレッ ト状の高密度カーボンナノホーンを得た。 The pellets were slowly evaporated, and then pressurized at 50 kgf / cm 2 to obtain pelleted high-density carbon nanohorns.
この高密度カーボンナノホーンの嵩密度を調べ、 表 1に記した。 こ の高密度カーボンナノホーンの嵩密度は 0. 6 ~ 0. 8 g/c m3で あり、 用いたダリァ型カーボンナノホーン凝集体および一般的な活性 炭よりも高密度であることが確認された。 The bulk density of this high-density carbon nanohorn was investigated and is shown in Table 1. This The bulk density of the high-density carbon nanohorn was 0.6 to 0.8 g / cm 3 , and it was confirmed that the bulk density was higher than that of the Darier-type carbon nanohorn aggregate used and general activated carbon.
Figure imgf000012_0001
Figure imgf000012_0001
(実施例 2 )  (Example 2)
実施例 1で作製した高密度カーボンナノホーン （A) と、 ダリァ型 S WNH凝集体をエタノールに分散してエタノールをゆつくりと蒸 発させることで作製した高密度力一ボンナノホーン （B)、 およびダリ ァ型カーボンナノホーン凝集体 （C) について、 窒素ガス吸着特性を 調べた。 その結果を図 1および表 2に示した。  A high-density carbon nanohorn (A) produced in Example 1, a high-density carbon nanohorn (B) produced by dispersing Darrie-type SWNH aggregates in ethanol and slowly evaporating the ethanol, and The Darrier-type carbon nanohorn aggregate (C) was examined for nitrogen gas adsorption characteristics. The results are shown in FIG. 1 and Table 2.
表 2  Table 2
Figure imgf000012_0002
出発材である作製したままのダリァ型カ一ボンナノホーン凝集体
Figure imgf000012_0002
As-prepared dary-shaped carbon nanohorn aggregates as starting material
(C) に比べて、 この出願の発明の高密度ナノホーン （A) (B) の ほうが吸着特性が高められていることが確認された。 また、 エタノー ル蒸発により高密度化された高密度ナノホーン （B) に比べて、 さら に加圧を施した高密度ナノホーン （A) の吸着特性は、 著しく高めら れていることが確認された。 これら （A) (B) の吸着表面積および 細孔容積についても、 （C) に比べて明らかに増大されていることがわ かった。 Compared with (C), the high-density nanohorn (A) (B) It was confirmed that the adsorption characteristics were improved. In addition, it was confirmed that the adsorption characteristics of the high-density nanohorn (A), which was further pressurized, were significantly improved, compared to the high-density nanohorn (B), which was densified by ethanol evaporation. . The adsorption surface area and pore volume of (A) and (B) were also clearly increased compared to (C).
(実施例 3 )  (Example 3)
ダリァ型カーボンナノホーン凝集体をエタノールに分散し、 ェ夕ノ ールをゆっくりと蒸発させた後、 5 0 k g f Z c m 2で加圧すること で、 ペレット状の高密度カーボンナノホーンを得た。 この高密度力一 ボンナノホーンと、 ダリァ型カーボンナノホーン凝集体について、 メタ ンガスの吸着特性調べ、 その結果を図 2に示した。 また、 3. 5 MP aにおけるメタンガス吸着量を表 3に示した。 The Darrier-type carbon nanohorn aggregate was dispersed in ethanol, the ethanol was slowly evaporated, and then pressurized at 50 kgf Z cm 2 to obtain a pellet-like high-density carbon nanohorn. The methane gas adsorption characteristics of the high-density carbon nanohorn and the Darrier-type carbon nanohorn aggregate were examined, and the results are shown in FIG. Table 3 shows the amount of methane gas adsorbed at 3.5 MPa.
表 3  Table 3
Figure imgf000013_0001
メタンガスの吸着特性についても、 この出願の発明の高密度ナノホー ンは、 製造したままのダリァ型カーボンナノホーン凝集体よりも優れ ていることが示された。 とくに、 3. 5 MP a以上では、 高密度ナノ ホーンのメタンガス吸着量は、 製造したままのダリァ型カーボンナノ ホーン凝集体の 2倍以上となった。
Figure imgf000013_0001
With respect to the adsorption characteristics of methane gas, it was shown that the high-density nanohorn of the invention of this application is superior to the as-produced Darier-type carbon nanohorn aggregate. In particular, above 3.5 MPa, the adsorption of methane gas on the high-density nanohorn was more than twice that of the as-produced dary-type carbon nanohorn aggregate.
(実施例 4)  (Example 4)
4 2 0 ^で加熱処理をしたダリァ型カ一ボンナノホーン凝集体を 過酸化水素水溶液に混合して 2 4時間浸漬後、 ろ過してろ過物を 6 ox:にて乾燥した。 次いでこのダリァ型力一ボンナノホーン凝集体を アルゴン中、 9 0 0でで加熱処理して、 表面が OH基で修飾された力 一ボンナノホーン集合体を得た。 The Darrier-type carbon nanohorn aggregate heat-treated at 420 ^ was mixed with an aqueous hydrogen peroxide solution, immersed for 24 hours, filtered, and the filtrate was dried at 6 ox :. Next, this Dary-type nano-bonnet aggregate is heat-treated at 900 in argon, and the force whose surface is modified with OH group One bon nanohorn aggregate was obtained.
OH基修飾力一ボンナノホーン集合体をエタノールに分散し、 エタ ノールをゆつくり蒸発させた後、 50 k g f Z c m 2で加圧すること で、 ペレット状の高密度 OH修飾カーボンナノホーンを得た。 この高 密度 OH修飾カーボンナノホーンの嵩密度は、 0. 6〜 0. 8 gZ cm3であった。 また、 比表面積、 ミクロ孔容積、 および窒素ガス吸 着特性を調べ、 表 4および図 3に示した。 また、 加圧せずに作製した 高密度 OH修飾カーボンナノホーン、 および OH修飾カーボンナノホ ーンについても併せて結果を示した。 The OH group-modified force one Bon'nanohon aggregate was dispersed in ethanol, after boiled create evaporated ethanol, by pressurizing at 50 kgf Z cm 2, to obtain a pelletized high density OH modified carbon nanohorn. The bulk density of this high-density OH-modified carbon nanohorn was 0.6 to 0.8 gZ cm 3 . In addition, the specific surface area, micropore volume, and nitrogen gas adsorption characteristics were examined. The results are shown in Table 4 and FIG. The results are also shown for the high-density OH-modified carbon nanohorn and OH-modified carbon nanohorn fabricated without pressurization.
表 4  Table 4
Figure imgf000014_0001
Figure imgf000014_0001
この高密度 OH修飾カーボンナノホーンは、 OH基が付加されてい ることにより分散性が向上したとともに、 細孔溶量、 比表面積ともに 増大していることが確認された。 This high-density OH-modified carbon nanohorn was confirmed to have improved dispersibility due to the addition of the OH group, and also increased both the amount of dissolved pores and the specific surface area.
(実施例 5)  (Example 5)
1 0 1. 3 2 5 k P a ( 1 a t m) の A r雰囲気で C02レーザ 一 ·アブレーシヨンによりダリァ状の SWNH凝集体を製造した。 こ のダリヤ状 SWNH凝集体の直径は、 約 8 0 nmでほぼ均一であつ た。 また、 この SWNH凝集体の表面形状は、 透過型電子顕微鏡（T EM) 観察によると、 球面から突き出る多くのホーンによりギザギザ していた。 この製造したままのダリァ状 SWNH凝集体を、 以下、 as-grown S WNHと示す。 Was produced Daria shaped SWNH aggregate by 1 0 1. 3 2 5 k P a C0 2 laser one-Abureshiyon in A r atmosphere (1 atm). The diameter of this dahlia-like SWNH aggregate was approximately uniform at about 80 nm. According to transmission electron microscope (TEM) observation, the surface shape of the SWNH aggregate was jagged by many horns protruding from the spherical surface. This as-produced Dallia-like SWNH aggregate is Shown as as-grown S WNH.
< A> この as-grownS WNHをエタノールに入れ、 超音波照射す ることでエタノール中に分散させ、 空気中、 室温でエタノールを蒸発 させた。 このようなエタノール処理された as-grownS WNHを、 eth- S WNHと示す。 得られた eth-S WNHを 50 MP aで圧縮し、 直 径 1 c m2の円柱状に一体化して、 圧縮 S WNHとした。 この圧縮 S WNHは、 ばらばらになることなく、 機械的な操作に耐え得る程度十 分に安定していた。 一方、 エタノール処理のない as-grownSWNH を同様に圧縮して円柱体としたところ、 硬度が低く、 取り扱いに際し て容易に破壊してしまった。 <A> This as-grown S WNH was put in ethanol and irradiated with ultrasonic waves to disperse it in ethanol, and the ethanol was evaporated in air at room temperature. Such ethanol-treated as-grown S WNH is referred to as eth-S WNH. The obtained eth-S WNH was compressed at 50 MPa and integrated into a column having a diameter of 1 cm 2 to obtain a compressed SWNH. The compressed SWNH was stable enough to withstand mechanical operations without falling apart. On the other hand, when as-grown SWNH without ethanol treatment was similarly compressed into a cylindrical body, the hardness was low and it was easily broken during handling.
図 4 aに、 as-grown S WNH、 eth- S WN Hおよび圧縮 S WN H について、 7 7 Kにおける窒素吸着等温線を示した。 なお、 各試料に は、 吸着試験に先立って、 1 0-4P a以下の真空で、 42 3 K：、 2 時間の予備加熱処理を施した。 図中のマーカーは、 三角が as-grown SWNHを、 菱形が eth-S WNHを、 丸が圧縮 S W N Hをそれぞれ 示している。  FIG. 4 a shows nitrogen adsorption isotherms at 77 K for as-grown SWNH, eth-SWNH, and compressed SWNH. Prior to the adsorption test, each sample was preheated at 423 K for 2 hours in a vacuum of 10-4 Pa or less. In the markers in the figure, triangles indicate as-grown SWNH, diamonds indicate eth-S WNH, and circles indicate compressed SW N H, respectively.
as-grown SWNHの吸着等温線は、タイプ Iと IVの中間に相当す るものであった。 この等温線中に見られるヒステリシスなしの挙動は、 2つの隣り合う球状の SWNH凝集体粒子の接点に形成されるくさ び形状のメソ孔の存在に関係するものである。 また、 eth-SWNHの 等温線は、 極低圧では as-grownS WNHと同様の曲線を描き、 相対 圧力 PZP。= 0. 1以上で僅かに上方に逸れて、 P/P。= l近く で極めて急峻な上昇を示した。 一方の圧縮 SWNHの等温線は、 I UPAC分類によるタイプ H Iの狭いヒステリシスループを有するこ とから、ほぼ均一の大きさの球状 SWNH凝集体粒子が凝集あるいは 緻密に詰まっていることがわかる。 すなわち、 球状の SWNH凝集体 粒子がエタノール中に分散されて乾する際に、 エタノールの表面張力 によって再配列し、 メソサイズの粒子間隙をもって最密充填構造を形 成したことを示差している。 そしてこの粒子間隙における毛管凝縮が、 等温線中にヒステリシスループを与えているのである。 この圧縮 S W NHの等温線を as- grownS WNHおよび eth-S WN Hに対して比 較すると、 PZP。が極低い範囲では最も急峻な上昇を示し、 PZP 。== 1でほぼ飽和している。 この圧縮 SWNHの等温線には狭く大き なヒステリシスループが見られるが、 このようなループ形状は、 気孔 内で被吸着分子の拡散が不十分なとき、 すなわち気孔入り口で被吸 着分子が遮断されるときによく見られるものである。 The adsorption isotherm of as-grown SWNH was in the middle between Type I and IV. The hysteresis-free behavior seen in this isotherm is related to the presence of wedge-shaped mesopores formed at the junction of two adjacent spherical SWNH aggregate particles. At very low pressure, the isotherm of eth-SWNH draws the same curve as as-grownS WNH, and the relative pressure is PZP. = 0.1 Deflected slightly upwards above 1, P / P. = Extremely steep rise near l. On the other hand, the isotherm of the compressed SWNH has a narrow hysteresis loop of type HI according to the IUPAC classification, indicating that spherical SWNH aggregate particles of almost uniform size are aggregated or densely packed. In other words, it indicates that when the SWNH aggregate particles were dispersed in ethanol and dried, they rearranged due to the surface tension of ethanol and formed a close-packed structure with meso-sized particle gaps. And capillary condensation in this particle gap, This gives a hysteresis loop in the isotherm. When the isotherm of the compressed SW NH is compared with as-grown S WNH and eth-S WNH, it is PZP. Shows the steepest rise in the extremely low range, PZP. == almost saturated at 1. A narrow and large hysteresis loop can be seen in the isotherm of the compressed SWNH, but such a loop shape is formed when the diffusion of the adsorbed molecules in the pores is insufficient, that is, the adsorbed molecules are blocked at the pore entrance. Is often seen when
次に、 Barrett-Joyner-Halenda (B J H) 法によりこれらの窒素 等温線から細孔径分布を求め、 図 4 bに示した。 as-grownS WNH および eth-S WNHには 2 ~ 5 n mの範囲の微細なメソ孔が多く存 在しているものの、細孔径は全体として 1 0〜 50 nmの広い範囲に 分布していることがわかった。 一方の圧縮 SWNHについては、 20 nmより大きい細孔がなくなるとともに、 2~4 nmの範囲に鋭いピ ークが見られる。これは気孔サイズ 2 nm以上 50 nm未満のメソ細 孔が変化し、 2 nm未満のミクロ孔が極度に発達したことを示すもの である。  Next, the pore size distribution was determined from these nitrogen isotherms by the Barrett-Joyner-Halenda (BJH) method and shown in Figure 4b. As-grown S WNH and eth-S WNH have many fine mesopores in the range of 2 to 5 nm, but the pore size is distributed over a wide range of 10 to 50 nm as a whole I understood. On the other hand, in the compressed SWNH, pores larger than 20 nm disappear, and sharp peaks are observed in the range of 2 to 4 nm. This indicates that mesopores with a pore size of 2 nm or more and less than 50 nm changed, and micropores with a size of less than 2 nm were extremely developed.
また The fractal Frenkel-Halsey-Hi 11 (FHH) 理論を窒素吸 着等温線に適用して、 表面フラクタル次元 （D s ) によって SWN Hの幾何学的な表面粗さを分析した。 D sの評価には、  In addition, the theoretical surface roughness of SWNH was analyzed by the surface fractal dimension (D s) by applying the fractal Frenkel-Halsey-Hi 11 (FHH) theory to the nitrogen adsorption isotherm. The Ds rating includes:
Θ〜 I n ( P。/ P )] Ds-3  Θ ~ In (P./P)] Ds-3
(式中、 Θは表面被覆率を示す）  (In the formula, Θ indicates the surface coverage.)
で表される FHH方程式を使用した。この FHHプロットを図 4 cに 示した。 as- grown SWNHおよび eth-S WN Hについて、 POZPが 極低い領域で線形性が崩れて下方へ逸れるのは、微小孔が充填してい ることに起因するものである。 しかしながら圧縮 SWNHの FHHプ ロットは、 これに比べて比較的高圧でも下方へ逸れており、 SWNH 粒子がマクロ孔 （5 O nm以上） を残さない程度によく充填されてい ると考えられる。 The FHH equation represented by The FHH plot is shown in Fig. 4c. For as-grown SWNH and eth-SWNH, the linearity collapses in the region where the POZP is extremely low and deviates downward due to the filling of the micropores. However, the FHH plot of the compressed SWNH is deviated downward even at relatively high pressure, and it is considered that the SWNH particles are well packed so as not to leave macropores (5 O nm or more).
FHH分析の結果、 as-grownS WNH、 eth-S WN Hおよび圧縮 5 WNHについて、 それぞれ、 D s = 2. 8 0、 2. 7 5および 2.FHH analysis results, as-grownS WNH, eth-S WNH and compression For 5 WNH, Ds = 2.80, 2.75 and 2.
6 8が得られた。 D s値は小さいほど表面が滑らかであることを示し、 完全に平担な表面では D s = 2となる。 また、 D s値が 3に近づくほ ど表面は荒くなる。 SWNH凝集体粒子は角を持つので、得られる D s値は 3に近い値となる。 しかし圧縮 S WNHについては、 SWNH 凝集体から突き出ているナノホーンをバルク内に押し込むことにより、 表面の荒さをわずかに減少させていると考えられる。 6 8 were obtained. The smaller the D s value, the smoother the surface. For a perfectly flat surface, D s = 2. The surface becomes rougher as the Ds value approaches 3. Since the SWNH aggregate particles have corners, the resulting D s value is close to 3. However, for compressed SWNH, it is thought that pushing the nanohorns protruding from the SWNH aggregates into the bulk has slightly reduced the surface roughness.
<B> 酸素中での熱処理によって、 閉じられたナノホーンに開孔を 設けることができる。 たとえば 6 9 3 Kでの加熱処理により、 ダリア 状 SWNHのほぼ全ての管壁に開孔が設けられる。 ここで、 上記と同 様にダリァ状 SWNH凝集体を製造し、 02気流下 6 9 3 Kで 1 0 分間の酸化処理を施した。 この酸化処理された SWNH凝集体を o X — SWNHとし、 この o X — S WN Hを超音波処理にてエタノー ル中に分散し、 前記 <A>と同条件で圧縮した。 o x— SWNHお よび圧縮 o X - S WW Hについて、 7 7 Kで窒素吸着試験を行い、 その結果を図 5 aに示した。 図中のマ一力一は、 菱形が o X — S WN Hを、 丸が圧縮 o X — S WWHを示している。 <B> Opening can be made in the closed nanohorn by heat treatment in oxygen. For example, by heat treatment at 693 K, holes are formed in almost all the tube walls of dahlia-shaped SWNH. Here, to produce Daria shaped SWNH aggregates above the same way, subjected to oxidation treatment for 1 0 minutes at 0 2 stream under 6 9 3 K. The oxidized SWNH aggregate was designated as oX-SWNH, and the oX-SWNH was dispersed in ethanol by ultrasonic treatment and compressed under the same conditions as <A>. Nitrogen adsorption tests were performed on ox-SWNH and compressed oX-SWWH at 77 K, and the results are shown in Figure 5a. In the figure, diamonds indicate o X — SWN H, and circles indicate oX — S WWH.
圧縮 o X — S WNHの吸着等温線は、 圧縮なしの o x— SWNH と比較して、上記 <A>で as-grownS WNHと圧縮 S WNHとの間 で見られたような吸着量の増大が観察されなかった。 しかし、 圧縮 0 X — S WNHの等温線にみられるヒステリシスは、上記 < A >での圧 縮 SWNHと同様で、 気孔入り口で被吸着分子が遮断されることを 示すものである。 o X — S WNHと圧縮 o X — S WWHの等温線の 差異は、 比較的高圧領域で明確に観察された。 すなわち、 高圧領域で は、 o X — SWNHの等温線が険しく上昇している一方で、 圧縮 o X - SWNHの等温線は P/P。= 1付近で飽和しており、 圧縮に より粒子間の空隙が著しく減少されることが示された。粒子間の空隙 の大きさは、 吸着等温線によって示唆されるようなミクロ孔領域にあ ることが、 図 5 bに示した細孔径分布によって確認された。 この細孔 径分布曲線からは、 o X — S WNHの圧縮の前後でメソ孔の分布範 囲に大きな変化が見られない。 また、 フラクタル FHH分析から、 o X — S WN H、 圧縮 o X — S WN Hについて D s = 2. 9 0、 2. 6 1がそれぞれ得られ、 o X — SWNHの極めて荒い表面が圧縮によ つて滑らかになることが確認された。 The adsorption isotherm of the compressed o X — SWNH shows a greater increase in the amount of adsorption as seen between the as-grown SWN and the compressed SWNH in <A> above than the ox—SWNH without compression. Not observed. However, the hysteresis seen in the isotherm of the compressed 0X-SWNH is similar to that of the compressed SWNH in <A> above, indicating that the adsorbed molecules are blocked at the pore entrance. The difference between the isotherms of o X — S WNH and compression o X — S WWH was clearly observed at relatively high pressures. In other words, in the high pressure region, the isotherm of o X — SWNH rises steeply, while the isotherm of compressed o X-SWNH is P / P. It is saturated around = 1 and it is shown that voids between particles are significantly reduced by compression. The pore size distribution in the micropore region as suggested by the adsorption isotherm was confirmed by the pore size distribution shown in Figure 5b. This pore The diameter distribution curve shows no significant change in the distribution range of mesopores before and after the compression of o X — SWNH. From the fractal FHH analysis, D s = 2.90 and 2.61 were obtained for o X — SWN H and compression o X — SWN H, respectively. It was confirmed that it became smoother.
加えて、 酸化処理および圧縮処理の順序が孔隙率に与える影響を 調べた。 圧縮の後に 6 9 3 Kで酸化した SWNH試料は、 圧縮 o X 一 SWNHと同じ窒素吸着等温線を示した。 したがって、 圧縮 SW NHを酸素処理する場合において酸素が SWNH内部に浸透するの に制限は受けず、 圧縮体は均質に酸化されることが確認された。  In addition, the effect of the order of oxidation and compression on porosity was investigated. SWNH samples oxidized at 693 K after compression showed the same nitrogen adsorption isotherm as compressed oX-SWNH. Therefore, when the compressed SWNH was subjected to oxygen treatment, there was no restriction on the permeation of oxygen into the SWNH, and it was confirmed that the compressed body was oxidized homogeneously.
<C> 以上の議論では、 SWNH凝集体の気孔構造の変化を理解 するためにそれぞれの吸着等温線を互いに比較したが、 気孔構造パラ メ一ターの正確な評価については、 S WNH凝集体の気孔構造が単 純でないことから困難である。 そこで、 S WNH凝集体の気孔構造と してスリツト形モデルを仮定し、 極めて有効な手段である高解像度 α sプロットを利用した the Subtracting Pore Effect ( S P E ) 法 によって気孔構造パラメ一夕一を評価した。 S P E法によって計算し た気孔構造パラメ一ターを、 表 5に示した。  <C> In the above discussion, the adsorption isotherms were compared with each other in order to understand the change in the pore structure of SWNH aggregates.However, for accurate evaluation of the pore structure parameters, It is difficult because the pore structure is not simple. Therefore, we assumed a slit-shaped model as the pore structure of SWNH aggregates, and evaluated the pore structure parameters by the Subtracting Pore Effect (SPE) method using a high-resolution α s plot, which is an extremely effective means. did. Table 5 shows the pore structure parameters calculated by the SPE method.
表 5  Table 5
Figure imgf000018_0001
表 5より、 as-grown S WNHおよび eth- S W N Hのメソ孔体積 (Vme) から、 エタノール処理後に Vmeが大きく増加することが 確認された。 ここで増加したメソ孔の孔隙率は、 先に述べたように、 エタノール処理の後に SWNH凝集体が最密充填状態となることで 形成された間隙である。 また as-grownS WNHよりも ox— SWN Hの方に Vm eが大きいのは、 酸化処理によって力一ボンナノホーン に 2 nm以上のメソ孔が開孔されたことで説明される。 また、 Vm e は、 eth-S WNHおよび o X _ S WNHの両方とも、 圧縮により減 少するが、このような高圧の印加によって S WNH凝集体粒子の元の 間隙が減少し、 SWNH凝集体から突き出ている角がバルク内部に 押し込まれることで、 フラクタル分析からも示されるように、 滑らか な表面をもつ構造へと再配列するのである。
Figure imgf000018_0001
From Table 5, the mesopore volume (Vme) of as-grown S WNH and eth-SWNH indicates that Vme greatly increases after ethanol treatment. confirmed. Here, the increased porosity of the mesopores is, as described above, a gap formed by the SWNH aggregates being in a close-packed state after the ethanol treatment. The reason why Vme is larger in ox-SWNH than in as-grownS WNH is explained by the fact that mesopores of 2 nm or more were formed in the carbon nanohorn by oxidation treatment. Vme is also reduced by compression for both eth-S WNH and oX_S WNH, but the application of such high pressure reduces the original gap of SWNH aggregate particles, When the corners protruding from are pushed into the bulk, they rearrange into a structure with a smooth surface, as shown by fractal analysis.
ここで、 圧縮 SWNHのミクロ孔体積が、 as-grownS WN Hの 2 倍近くも大きく増加することは注目すべき点である。 これは、 圧縮に よりカーボンナノホーンが部分的に開孔されて、 ミクロ孔が増加する ことによるものと考えられる。 ヘリウム法により求められた S WNH 凝集体の粒子密度は、 この仮説を立証するものであり、圧縮 SWNH の粒子密度は as-grown S WNHの密度 1. 2 5 g cm3よりもは るかに大きい 1. 6 9 g Z c m3であった。 このことから、 機械的な 圧縮により、 カーボンナノホーンの欠陥サイ卜に開孔が設けられるこ とが確認された。 また、 ミクロ孔の体積については、 27 3 Kにおけ る C02吸着量から Dubinin-Radushkevicli (DR) 方程式を利用し て決定した。 得られた狭いミクロ孔の体積は 0. 1 0 cm3Zgであ り、 圧縮の後のミクロ孔の体積増加と一致するものであった。 さらに、 圧縮の後に形成された気孔は、 主として孔径 0. 7 nm未満のウル トラミクロ孔であることが示された。 一方の eth-S WNHにもミクロ 孔体積のわずかな増加が見られた。 これは、 エタノール処理の際の超 音波照射がカーボンナノホーンへの孔の形成を促し、 欠陥のいくつか を開孔したものと予想される。 o X — SWNHのミクロ体積は、 酸化 の後にほぼすベてのカーボンナノホーンが開孔されるために圧縮後に もほとんど変わらない。 したがって、 圧縮処理により粒子間ナノ間隙 に起因する新たな表面積および微細孔体積の増加も見られない。なお、 このような圧縮は、 S W N H凝集体間の空隙をミクロ孔サイズへ減少 させるほど高いものではない。 It is noteworthy here that the micropore volume of the compressed SWNH increases almost twice as large as as-grown SWN. This is thought to be due to the fact that the carbon nanohorns were partially opened by compression and the micropores increased. Particle density S WNH aggregates obtained by helium method is to prove this hypothesis, the particle density of the compressed SWNH is than the density 1. 2 5 g cm 3 of as-grown S WNH Rukani It was large 1.69 g Z cm 3 . From this, it was confirmed that holes were formed in the defect site of the carbon nanohorn by mechanical compression. Also, the volume of the micropores were determined using Dubinin-Radushkevicli (DR) equation from put that C0 2 adsorption amount to 27 3 K. The resulting narrow micropore volume was 0.10 cm 3 Zg, consistent with the micropore volume increase after compression. Furthermore, the pores formed after compression were shown to be mainly ultra-micro pores with a pore size of less than 0.7 nm. On the other hand, eth-S WNH also showed a slight increase in micropore volume. This is thought to be because ultrasonic irradiation during the ethanol treatment promoted the formation of holes in the carbon nanohorn and opened some of the defects. o X — The microvolume of SWNH remains almost unchanged after compression because almost all carbon nanohorns are open after oxidation. Therefore, nano gap between particles No increase in the new surface area and micropore volume due to the above. Note that such compression is not high enough to reduce the voids between SWNH aggregates to micropore size.
以上のことから、エタノール中で超音波処理する予備処理に引き続 いて圧縮することにより、ダリァ状 S W N H凝集体粒子の嵩密度およ び比表面積は著しく増加し、 気孔構造が変化されることがわかった。 また、 ダリァ状 S W N H凝集体に開孔を設けることで、 嵩密度および 比表面積はさらに増大されることが確認された。  As described above, the bulk density and specific surface area of the Dahlia-like SWNH aggregate particles are significantly increased and the pore structure is changed by compressing subsequent to the pretreatment by ultrasonic treatment in ethanol. all right. In addition, it was confirmed that the bulk density and the specific surface area were further increased by providing openings in the Darrie-like SWNH aggregate.
もちろん、 この発明は以上の例に限定されるものではなく、 細部に ついては様々な態様が可能であることは言うまでもない。 産業上の利用可能性  Of course, the present invention is not limited to the above examples, and it goes without saying that various aspects are possible in detail. Industrial applicability
以上詳しく説明した通り、 この発明によって、 カーボンナノホーン 凝集体が高密度化されたのみならず、吸着特性がより高められた高密 度カーボンナノホーンとその製造方法が提供される。  As described in detail above, the present invention provides a high-density carbon nanohorn in which not only the carbon nanohorn aggregates are densified but also the adsorption characteristics are further improved, and a method for producing the same.

Claims

請求の範囲 The scope of the claims
1 . 複数のカーボンナノホーン凝集体を、 高密度に凝集させた固体 であることを特徴とする高密度カーボンナノホーン。 1. A high-density carbon nanohorn characterized by being a solid formed by aggregating a plurality of carbon nanohorn aggregates at a high density.
2 . カーボンナノホーン凝集体が、 ダリァ状カーボンナノホーン凝 集体、 つぼみ状カーボンナノホーン凝集体、 あるいはその混合物であ ることを特徴とする請求項 1記載の高密度カーボンナノホーン。  2. The high-density carbon nanohorn according to claim 1, wherein the carbon nanohorn aggregate is a Darier-like carbon nanohorn aggregate, a bud-like carbon nanohorn aggregate, or a mixture thereof.
3 . 力一ボンナノホーン凝集体が、 力一ボンナノホーン管壁に開孔 を有することを特徴とする請求項 1 または 2記載の高密度カーボン ナノホーン。  3. The high-density carbon nanohorn according to claim 1, wherein the carbon nanohorn aggregate has an opening in a wall of the carbon nanohorn tube.
4 . カーボンナノホーン凝集体そのものよりも嵩密度、 比表面積お よび細孔容量が高められていることを特徵とする請求項 1ないし 3 いずれかに記載の高密度カーボンナノホーン。  4. The high-density carbon nanohorn according to any one of claims 1 to 3, wherein the bulk density, specific surface area, and pore volume are higher than the carbon nanohorn aggregate itself.
5 . カーボンナノホーン凝集体そのものよりも体積当たりおよび重 量当たりのガス吸着量が多いことを特徴とする請求項 1ないし 3い ずれかに記載の高密度カーボンナノホーン。  5. The high-density carbon nanohorn according to any one of claims 1 to 3, wherein a gas adsorption amount per volume and per weight is larger than that of the carbon nanohorn aggregate itself.
6 . 複数のカーボンナノホーン凝集体を有機溶媒に分散させたのち、 この有機溶媒を蒸発させることを特徴とする高密度カーボンナノホ ーンの製造方法。  6. A method for producing a high-density carbon nanohorn, comprising dispersing a plurality of carbon nanohorn aggregates in an organic solvent and evaporating the organic solvent.
7 . 複数の力一ボンナノホーン凝集体を有機溶媒に分散させたのち、 超音波を照射することを特徴とする請求項 6記載の高密度カーボン ナノホーンの製造方法。  7. The method for producing a high-density carbon nanohorn according to claim 6, wherein a plurality of carbon nanohorn aggregates are dispersed in an organic solvent and then irradiated with ultrasonic waves.
8 . 複数のカーボンナノホーン凝集体を加圧することを特徴とする 高密度カーボンナノホーンの製造方法。  8. A method for producing a high-density carbon nanohorn, comprising pressurizing a plurality of carbon nanohorn aggregates.
9 . 複数のカーボンナノホーン凝集体を有機溶媒に分散させたのち、 この有機溶媒を蒸発させ、 析出したカーボンナノホーン凝集体を加圧 することを特徴とする高密度カーボンナノホーンの製造方法。  9. A method for producing a high-density carbon nanohorn, comprising dispersing a plurality of carbon nanohorn aggregates in an organic solvent, evaporating the organic solvent, and pressing the deposited carbon nanohorn aggregates.
10. 1 O M P a以上の圧力で加圧することを特徵とする請求項 8 または 9記載の高密度力一ボンナノホーンの製造方法。 10. The method for producing a high-density force-bonded nanohorn according to claim 8 or 9, wherein the pressure is increased at a pressure of 1 OMPa or more.
1 1. 予めカーボンナノホーン凝集体を化学修飾してカーボンナノホ ーン凝集体同士の親和力を高めておくことを特徴とする請求項 6な いし 1 0いずれかに記載の高密度ナノホーンの製造方法。 11. The method for producing a high-density nanohorn according to any one of claims 6 to 10, wherein the carbon nanohorn aggregates are chemically modified in advance to increase the affinity between the carbon nanohorn aggregates.
12. カーボンナノホーン凝集体が、 ダリァ状カーボンナノホーン凝 集体、 つぼみ状カーボンナノホーン凝集体、 あるいはその混合物であ ることを特徵とする請求項 6ないし 1 1いずれかに記載の高密度ナ ノホーンの製造方法。  12. The high-density nanohorn according to any one of claims 6 to 11, wherein the carbon nanohorn aggregate is a Darier-like carbon nanohorn aggregate, a bud-like carbon nanohorn aggregate, or a mixture thereof. Method.
13. カーボンナノホーン凝集体が、 カーボンナノホーンの管壁に開 孔を設けられていることを特徵とする請求項 6ないし 1 2いずれかに 記載の高密度ナノホーンの製造方法。  13. The method for producing a high-density nanohorn according to any one of claims 6 to 12, wherein the carbon nanohorn aggregate has an opening formed in a tube wall of the carbon nanohorn.
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