U.S. patent application number 10/357452 was filed with the patent office on 2003-12-11 for nanotube, nano thermometer and method for producing the same.
Invention is credited to Bando, Yoshio, Gao, Yihua, Sato, Tadao.
Application Number | 20030227958 10/357452 |
Document ID | / |
Family ID | 27606579 |
Filed Date | 2003-12-11 |
United States Patent
Application |
20030227958 |
Kind Code |
A1 |
Bando, Yoshio ; et
al. |
December 11, 2003 |
Nanotube, nano thermometer and method for producing the same
Abstract
In order to provide a novel nano thermometer, which can use for
temperature measurement of a wide temperature range, in a
micrometer size environment, and a method for producing the same,
the nano thermometer, comprising a carbon nanotube filled with a
continuous columnar gallium, which enables measurement of
environmental temperature by length change of the columnar gallium
is produced by the method comprising mixing Ga.sub.2O.sub.3 powder
and carbon powder uniformly, and performing heat treatment for this
mixed powder at a temperature range of 1200 to 1400.degree. C.
under an inert gas flow.
Inventors: |
Bando, Yoshio; (Ibaraki,
JP) ; Gao, Yihua; (Ibaraki, JP) ; Sato,
Tadao; (Ibaraki, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
27606579 |
Appl. No.: |
10/357452 |
Filed: |
February 4, 2003 |
Current U.S.
Class: |
374/100 ;
374/E5.006; 977/845 |
Current CPC
Class: |
Y10S 977/833 20130101;
Y10S 977/955 20130101; B82Y 30/00 20130101; B82Y 15/00 20130101;
G01K 5/08 20130101; Y10S 977/762 20130101; Y10S 977/811
20130101 |
Class at
Publication: |
374/100 |
International
Class: |
G01K 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2002 |
JP |
2002-067661 |
Claims
What is claimed is:
1. A nano thermometer, comprising a carbon nanotube filled with a
continuous columnar gallium, which enables measurement of
environmental temperature by length change of the columnar
gallium.
2. A nano thermometer according to claim 1, having length of 1-10
.mu.m and diameters of 40-150 nm.
3. A nano thermometer according to claims 1 or 2, which enables
measurement of the temperature at least of the range of 50 to
500.degree. C.
4. A nano thermometer according to any one of claims 1-3, whose
error is within 0.25.degree. C.
5. A nanotube, comprising a carbon nanotube filled with a columnar
gallium.
6. A method for producing a nano thermometer, said method
comprising mixing Ga.sub.2O.sub.3 powder and carbon powder
uniformly, performing heat treatment for this mixed powder at a
temperature of 966.degree. C. or more under an inert gas flow to
vaporize, and making reaction at a temperature of 835.degree. C. or
less.
7. A method for producing a nano thermometer according to claim 6,
wherein a weight ratio of Ga.sub.2O.sub.3 powder to carbon powder
is 7.8:1.
8. A method for producing a nano thermometer according to claims 6
or 7, wherein carbon powder is an amorphous active carbon.
9. A method for producing a nano thermometer according to any one
of claims 5-8, wherein inert gas is nitrogen gas.
10. A method for producing a nano thermometer according to any one
of claims 6-9, wherein heat treatment is performed using a vertical
radio-frequency furnace.
11. A method for producing a nano thermometer according to any one
of claims 6-10, wherein heat treatment is performed for 1 hour or
more at a temperature of 1300 to 1400.degree. C.
Description
FIELD OF THE INVENTION
[0001] The present invention relates a nanotube, a nano thermometer
and a method for producing the same. More particularly, the present
invention relates to a nanotube, and novel nano thermometer using
the nanotube, which can use for temperature measurement of a wide
temperature range, in a micrometer size environment, and a method
for producing the same.
BACKGROUND OF THE INVENTION
[0002] As a result of many researchers' having studied of many
about carbon nanotubes (CNTs) since its discovery in 1991, CNTs
found those uses in many fields. For example, they can serve as
field-effect devices, probe-tips for scanning probe microscope,
superconducting material, high-sensitivity microbalances,
structural materials, tiny tweezers for nanoscale manipulation, gas
detectors and hydrogen energy storage devices etc.
[0003] Nowadays, many researches have been entering into the size
area of at least micrometer. Therefore, the conventional four kinds
of thermometers designed for a macroscopic environment are no
longer appropriate for a micrometer-size environment, and a nano
thermometer, which can perform temperature measurement of
micrometer size environment, is needed.
[0004] Moreover, the conventional thermometer had the comparatively
narrow temperature range which can be measured, and some
thermometers needed to be prepared for every measurement
temperature when a wide range temperature was measured.
[0005] Therefore, in the present invention, the object is to
provide a solution to the above-mentioned problems of the
conventional thermometer, and to provide a novel nano thermometer,
which enables temperature measurement of a wide temperature range
in a micrometer size environment, and a method for producing the
same.
BRIEF DESCRIPTION OF DRAWINGS
[0006] FIG. 1(a) shows the morphology of a wire indicated by the
arrow, (b) shows the morphology of that the wire is wrapped by a
thin layer on its round tip and body, (c) shows the HRTEM image of
the thin wrapping layer, (d) shows an EDS spectrum from the region
in (c).
[0007] FIG. 2 shows the morphologies of the Ga tip when the
temperature increases from 18.degree. C. (a), via 58.degree. C. (b)
and 294.degree. C. (c), to 490.degree. C. (d), as well as the
morphologies when the temperature decreases from 490.degree. C.
(d), via 330.degree. C. (e), 170.degree. C. (f) and 45.degree. C.
(g), to 22.degree. C. (h).
[0008] FIG. 3 shows the curves of height of the Ga tip-level vs
temperature.
SUMMARY OF THE INVENTION
[0009] The present invention firstly provides, as a means to solve
the above-mentioned problems, a nano thermometer, comprising a
carbon nanotube filled with a continuous columnar gallium, which
enables measurement of environmental temperature by length change
of the columnar gallium.
[0010] Also, the present invention secondly provides a nano
thermometer, having length of 1-10 .mu.m and diameters of 40-150
nm. The invention thirdly provides a nano thermometer, which
enables measurement of the temperature of the range of at least 50
to 500.degree. C. The present invention fourthly provides a nano
thermometer, whose error is within 0.25.degree. C.
[0011] And the present invention fifthly provides a nanotube,
comprising a carbon nanotube filled with a columnar gallium.
[0012] Further, the present invention sixthly provide a method for
producing a nano thermometer said method comprising mixing
Ga.sub.2O.sub.3 powder and carbon powder uniformly, performing heat
treatment for this mixed powder at a temperature of 966.degree. C.
or more under an inert gas flow to vaporize, and making a reaction
at a temperature of 835.degree. C. or less. The present invention
seventhly provides a method for producing a nano thermometer,
wherein a weight ratio of Ga.sub.2O.sub.3 powder to carbon powder
is 7.8:1. The present invention eighthly provides a method for
producing a nano thermometer, wherein carbon powder is an amorphous
active carbon. The present--invention ninthly provides a method for
producing a nano thermometer, wherein inert gas is nitrogen gas,
and tenthly provides a method for producing a nano thermometer,
wherein heat treatment is performed using a vertical
radio-frequency furnace. Also, the present invention eleventhly
provides a method for producing a nano thermometer, wherein heat
treatment is performed for 1 hour or more at a temperature of 1300
to 1400.degree. C.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present inventions provide a nano thermometer which can
also be considered as novel potential application of a carbon
nanotube (CNT). That is, the nanotube of the present invention
comprising a carbon nanotube filled with a columnar gallium
(Ga).
[0014] And the nano thermometer of the present invention comprising
a CNT filled with a continuous columnar Ga, which enables
measurement of environmental temperature by length change of the
columnar Ga. This potential application is based on the expansion
characteristic of Ga in the inside of a CNT. In the nano
thermometer of the present invention, since the hollowcylinder of
CNT is filled with Ga, Ga has the form of as a continuous
column.
[0015] In the present invention, the reason why Ga rather than
another metal is chosen as the filling material is that Ga has one
of the longest liquid ranges of any metal, i.e. 29.78-2,403.degree.
C., and has a low vapor pressure even at high temperatures, which
makes it suitable for use in a wide-temperature-range thermometer.
Therefore, the nano thermometer of the present invention has a
potential wide measuring range due to the wide liquid range of Ga,
29.78 to 2,403.degree. C., which is much wider than that of Hg,
-38.87 to 356.58.degree. C.
[0016] And to a surprising thing, in this thermometer, the length
of the columnar Ga increases linearly with increasing temperature
in the temperature range of 50 to 500.degree. C. Therefore, with
the nano thermometer of the present invention, environmental
temperature can be measured from the length of Ga simpler and
correctly in the temperature range of 50 to 500.degree. C. The
present nano thermometer, even more surprising, can realize a very
highly precise nano thermometer within 0.25.degree. C. of
errors.
[0017] Moreover, since the nano thermometer of the present
invention uses the detailed structure of a CNT, the very small
thermometer of a micrometer-size is realized. For example, the nano
thermometer having length of 1-10 .mu.m and diameters of 40-150 nm
is realized. And in the case of this nano thermometer of the
present invention, for example, Ga can be made to extend up to
about 8 mm in CNT.
[0018] The nano thermometer of the present invention can play an
important role in various researches involving temperature
measurement of a wide temperature range in micrometer
environment.
[0019] The nano thermometer of the present invention is producible
by a method of present invention as follows. That is, in the method
of the present invention, it is made to manufacture a nano
thermometer by mixing Ga.sub.2O.sub.3 powder and carbon powder
uniformly, performing heat treatment for this mixed powder at a
temperature of 966.degree. C. or more under an inert gas flow to
vaporize, and making a reaction at a temperature of 835.degree. C.
or less.
[0020] In the method of the present invention, carbon powder can be
used as raw material of the CNT part which constitutes a nano
thermometer. As carbon powder, carbon powder of comparatively high
purity, for example 90% or more of purity, can be used. And it is
desirable to be activated carbon and to be amorphous activated
carbon more preferably. Ga.sub.2O.sub.3 powder can be used as raw
material of the columnar Ga filling in the CNT.
[0021] In the method on the present invention, a weight ratio of
Ga.sub.2O.sub.3 powder to carbon powder can be adjusted in the
range of about 7:1 to 8:1, and is 7.8:1 more preferably.
[0022] Ga.sub.2O.sub.3 powder and carbon powder are mixed
uniformly, and are performed heat treatment at a temperature of
966.degree. C. or more under an inert gas flow. Although the mixed
powder of Ga.sub.2O.sub.3 and carbon is vaporizable at a
temperature of 966.degree. C. or more, it is more desirable that
heat treatment is performed at the temperature range from 1200 to
1400.degree. C. Herein, an inert gas is desirable nitrogen gas. The
vapors are carried by the inert gas flow, and they can react at the
temperature of 835.degree. C. or less and are deposited. In the
method of the present invention, it is simple and is desirable that
the heat treatment is performed using, a vertical radio-frequency
furnace. For example, a vertical radio-frequency furnace can be
used in the method of the present invention. If a susceptor of the
vertical radio-frequency furnace has one bottom inlet pipe and one
top outlet pipe of the inert gas flow, the nano thermometer of the
present invention can be obtained on the inner surface of the top
outlet pipe as depositions, for example.
[0023] In the present invention, heat treatment can be performed at
a temperature range from 1200 to 1400.degree. C. as
above-mentioned. More specifically, a heat treatment of 1 hour or
more at the temperature from 1300 to 1400.degree. C. can be made as
a rough standard.
[0024] The mode for carrying out the invention is explained in more
detail by the following example.
EXAMPLE
[0025] The nano thermometer was produced using the vertical
radio-frequency furnace as described by the reference; Golberg, G.
et al. Large-scale synthesis and HRTEM analysis of single-walled B-
and N-doped carbon nanotube bundles. Carbon 38, 2017-2027 (2000).
In the open graphite crucible, the reactant was a homogenous mixed
powder of Ga.sub.2O.sub.3 and pure amorphous active carbon (AAC) in
the weight ratio 7.8:1. The graphite susceptor of the vertical
radio-frequency furnace had one bottom inlet pipe and one top
outlet pipe made of 99.99% purity graphite. Pure N.sub.2 gas flow
was introduced into the furnace. Heat treatment at 1,360.degree. C.
for 2 hours was performed for the reactant. After the heat
treatment, the reactant in the graphite crucible disappeared, while
some materials were found to have deposited on the inner surface of
the top outlet graphite pipe. In the deposition zone, the
temperature was measured to be .sup.-800.degree. C.
[0026] The deposited materials were collected and analyzed by a 300
kv field emission analytical high-resolution transmission electron
microscope (HRTEM, JEM-3000F) equipped with an x-ray energy
dispersive spectrometer (EDS) FIG. 1(a) shows several 1-dimensional
(1D) nanoscale wires of the deposited materials, which have lengths
of 1-10 .mu.m and diameters of 40-150 nm. The bar at the lower
right corner corresponds to 1 .mu.m. The wire indicated by the
arrow was analyzed carefully. FIG. 1(b) shows that the wire is
wrapped by a thin layer on its round tip and body, where d.sub.1=75
nm. The HRTEM image in FIG. 1(c) shows that this thin layer is
carbon. The d-spacing of the fringes is .sup..about.0.34 nm. FIG.
1(d), an EDS spectrum from the region in (c). The horizontal axis
is Energy axis, while the vertical is Intensity in arbitrary unit.
The peaks of C-K.sub..alpha. (0.28 keV), Ga-L.sub..alpha. (1.10
keV), Ga-K.sub..alpha. (9.24 keV) and Ga-K.sub..beta. (10.26 keV)
are shown, the Cu peak was originated from the Cu TEM grid. That
is, it shows that the wire contains Ga and C.
[0027] Based on the above analysis, it can be concluded that
the--indicated wire is a CNT filled with Ga. From the left to the
right of the CNT shown in (a), there are round tips, a long
columnar Ga, a hollow space beside the arrowhead, a short columnar
Ga and another hollow space. In (b), the length and outer diameter
d.sub.0 of the CNT are 9,180 nm and 85 nm, while the length L.sub.0
and diameter d.sub.1 of the longer columnar Ga are 7,560 nm and 75
nm, respectively. The round tip keeps its shape and size when the
temperature changes.
[0028] The transmission electron microscope (TEM) specimen of the
deposited materials was heated in the microscope using a Gatan
heating holder and its twin heating system (Hot Stage Powder
Supply, Model 628-0500). The position of the Ga tip-level of the
longer columnar Ga vs temperature was investigated in the range
18-500.degree. C. When the temperature increases, the Ga tip-level
rises, as shown in FIGS. 2(a), (b), (c) and (d). Conversely, the Ga
tip-level goes down when the temperature decreases., as shown in
FIGS. 2(e), (f), (g) and (h). The Ga tip-level goes up when'the
temperature increases, while it goes down when the temperature
decreases. The bar in (a) corresponds to 85 nm. If the Ga tip-level
at 58.degree. C. is set as the reference zero point, the height of
the Ga tip-level vs temperature can be plotted as shown in FIG. 3,
where the lines which connect a black circles and a black triangles
correspond to the increase process and reduction process of
temperature, respectively. Moreover, when the temperature was
changed from 20.degree. C. to 500.degree. C., the changes of the
complete length and the inner-diameter of the CNT were measured and
estimated to be -1% due to the very small linear expansion
coefficient of graphite (-1.times.10.sup.-6/.degree. C. along a
axis in the range of 20-500.degree. C.). Therefore, it is believed
that the influence of the expansion of the CNT on the Ga tip-level
position can be neglected and the height vs temperature is
dominated by the volumetric change of the longer columnar Ga
related to the environment temperature.
[0029] In general, the volumetric change (expansion or contraction)
of a liquid is described by
v.sub.t=v.sub.0(1+a.DELTA.t+b.DELTA.t.sup.2+c.DELTA.t.sup.3)
(1)
[0030] where v.sub.t and v.sub.0 are the liquid volumes at
temperature t and t.sub.0, respectively, .DELTA.t=t-t.sub.0, and a,
b and c are the coefficient of cubical expansion. A calculation on
the slopes of the curves in FIG. 3 and the volume of the longer
columnar Ga in FIG. 1(a) shows that the value of coefficient of a
Ga is 0.100.times.10.sup.-3/.deg- ree. C. at 58.degree. C., which
is comparable with the value (=0.1815.times.10.sup.-3/.degree. C.,
0-300.degree. C.) of mercury (Hg). The coefficients b and c of Ga
can be regarded as zero in the range 50-500.degree. C. FIG. 3 shows
that the height of the Ga tip-level is reproducible and linearly
changes in the range 50-500.degree. C. However, the characteristic
in the range 20-50.degree. C. is complicated and may be related to
a liquefaction (or solidification) process when increasing (or
decreasing) the temperature. Hence, the CNT filled with along
continuous columnar Ga can be used as a thermometer in the range of
at least 50-500.degree. C. For a nano-thermometer, the height of
the Ga tip-level is determined by
.DELTA.H=(4av.sub.0/.pi.d.sub.1.sup.2).DELTA.t (2)
[0031] where v.sub.0 is the volume of a continuous columnar Ga at
temperature t.sub.0, and .DELTA.H is the difference between the
heights of the Ga tip-level at temperatures t and t.sub.0.
Conversely, the temperature t=t.sub.0+.DELTA.t can be measured
after the difference .DELTA.H is known. To create a sensitive
thermometer, the columnar Ga should have a large volume v.sub.0 and
a small diameter d.sub.1. For the nano thermometer of the present
invention, the change .DELTA.H of the Ga tip-level vs temperature
is .DELTA.H=0.792(t-58), where .DELTA.H and t are in units nm and
.degree. C., respectively. In theory, if the resolution of a
microscope is .sup..about.0.2 nm, the accuracy of the temperature
measurement can reach .sup..about.0.25.degree. C. The nano
thermometer of the present invention can be used for the
measurement in a micrometer-size environment. Nowadays, many
researches have stepped into a size of at least micrometer.
Therefore, the four kinds of thermometers designed for a
macroscopic environment are no longer appropriate for a
micrometer-size environment. The nano thermometer of the present
invention could, play an important role in various researches
involving a temperature measurement of micrometer-size environment.
The present kind of nano thermometer filled with Ga has a potential
wide measuring range due to the wide liquid range
(29.78-2,403.degree. C.) of Ga, which is much wider than that
(-38.87-356.58.degree. C.) of Hg.
[0032] Generally, there are two approaches to produce CNTs filled
with a certain material. The first is to use pre-existing nanotubes
and fill them by capillarity, molten media, and wet chemistry
solution methods. The second is to produce the nanotubes and their
fillings simultaneously. In the present invention, the method for
producing the CNTs filled with a long columnar Ga (.sup..about.7.5
mm) belongs to the second approach. The growth of the Ga filling
CNTs may involve two chemical reactions. At a temperature above
966.degree. C., Ga.sub.2O and CO vapours can be generated by the
reaction;
Ga.sub.2O.sub.3(solid)=2C(solid).fwdarw.Ga.sub.2O(vapour)+2CO(vapour),
[0033] between Ga.sub.2O.sub.3 and AAC powder in the graphite
crucible. It can be calculated that the change of volume Gibbs
energy is -140 kJ for the formation of 1 mol of Ga.sub.2O vapour at
1,360.degree. C. If high surface Gibbs energy of AAC powder is
considered, the reaction is more likely to occur. When the
Ga.sub.2O and CO vapours reach the low temperature zone
(.sup..about.800.degree. C.) of the top outlet graphite pipe, a
vapour-vapour (VV) reaction occurs as;
nGa.sub.2O(vapour)+(n+2)CO(vapour).fwdarw.2nGa(liquid)+C(solid)+(n+1)CO.su-
b.2(vapour).
[0034] leading to the formation of Ga and C. After knowing the
outer diameter d.sub.0 and inner diameter d.sub.1 of a Ga filling
CNT, we can estimate the value of n as follows,
n=(m.sub.C.rho..sub.Gad.sub.1.sup.2)/[2m.sub.Ga.rho..sub.C(d.sub.0.sup.2-d-
.sub.1.sup.2)] (3)
[0035] where m.sub.C=12 g/mol, .rho..sub.Ga=6.095 g/cm.sup.3,
m.sub.Ga=69.72 g/mol and .rho..sub.C.sup.-2.00 g/cm.sup.3. For the
Ga filling CNT in FIG. 1(a), n in estimated to be .sup..about.1. A
series of calculations on the change of Gibbs energy for the VV
reaction at n.sup.-1 illustrate that it can occur only at a
temperature below 835.degree. C., which is consistent with our
experiment that the Ga filling CNTs were obtained in the low
temperature zone (.sup.-800.degree. C.).
INDUSTRIAL APPLICABILITY
[0036] As explained in detail: above, the present invention
provides novel nano thermometer, which can use for temperature
measurement of a wide: temperature range, in a micrometer size
environment, and a method for producing the same.
* * * * *