Patent application title: Reusable Vacuum Pumping Apparatus with Nanostructure Material
Timothy J. Imholt (Richardson, TX, US)
IPC8 Class: AF04B3702FI
Class name: Pumps electrical or getter type getter heating, vaporizing, or regeneration
Publication date: 2010-02-11
Patent application number: 20100034669
According to one embodiment, a vacuum system comprises a vacuum chamber, a
construct of nanotubes, and a heat source. The vacuum chamber contains
one or more gases. The construct of nanotubes is located proximate to the
vacuum chamber and is operable to absorb or adsorb gases from the vacuum
chamber. The hear source is located proximate to the construct of
nanotubes and is operable to heat the construct of nanotubes such that
the construct of nanotubes desorbs the gases from the vacuum chamber.
1. A vacuum system comprising:a vacuum chamber containing one or more
gasses;a construct of nanotubes located proximate to the vacuum chamber,
the construct of nanotubes operable to absorb or adsorb gases from the
vacuum chamber; anda heat source located proximate to the construct of
nanotubes, the heat source operable to heat the construct of nanotubes
such that the construct of nanotubes desorbs the gases from the vacuum
2. The vacuum system of claim 1, wherein the vacuum chamber contains Hydrogen.
3. The vacuum system of claim 1, wherein the nanotubes are carbon single-walled nanotubes.
4. The vacuum system of claim 1, wherein the nanotubes are carbon multi-walled nanotubes.
5. The vacuum system of claim 1, further comprising:a vacuum pipe containing the construct of nanotubes; anda vacuum valve connecting the vacuum pipe to the vacuum chamber.
6. The vacuum system of claim 5, further comprising an atmosphere valve connecting the vacuum pipe to the outside atmosphere.
7. The vacuum system of claim 6, wherein the atmosphere valve is a one-way valve operable to block gases from the outside atmosphere from reentering the vacuum pipe.
8. The vacuum system of claim 1, wherein the heat source is a microwave energy generator, the microwave energy generator operable to produce a microwave field.
9. The vacuum system of claim 8, further comprising a device for directing the microwave field from the microwave energy generator toward and through the construct of nanotubes.
10. The vacuum system of claim 8, wherein the microwave energy generator generates a frequency between 0.1 GHz and 100 GHz.
11. The vacuum system of claim 8, wherein the microwave energy generator comprises at least one of a dual cavity klystron with planar triodes, a reflex klystron, a backward wave oscillator, or a magnetron.
12. A method of removing gases from a chamber, comprising:providing a vacuum chamber containing one or more gases;placing a construct of nanotubes located proximate to the vacuum chamber such that the construct of nanotubes can absorb or adsorb gases from the vacuum chamber; andheating the construct of nanotubes such that the construct of nanotubes desorbs the gases from the vacuum chamber.
13. The method of claim 12, wherein the gases from the vacuum chamber includes Hydrogen.
14. The method of claim 12, wherein the nanotubes are carbon single-walled nanotubes.
15. The method of claim 12, wherein the nanotubes are carbon multi-walled nanotubes.
16. The method of claim 12, further comprising:pumping gases out of the vacuum chamber with a vacuum pump.
17. The method of claim 12, wherein heating the construct of nanotubes such that the construct of nanotubes desorbs the vacuum chamber comprises:sealing the construct of nanotubes from the vacuum chamber;heating the construct of nanotubes such that the construct of nanotubes desorbs the gases from the vacuum chamber; andreleasing the desorbed gases into the outside atmosphere.
18. The method of claim 12, wherein heating the construct of nanotubes such that the construct of nanotubes desorbs the vacuum chamber further comprises:generating a microwave field.
19. The method of claim 18, further comprising providing a device for directing the microwave field from toward and through the construct of nanotubes.
20. The method of claim 18, wherein the microwave field has a frequency between 0.1 GHz and 100 GHz.
21. The method of claim 18, wherein generating a microwave field further comprises:generating a microwave field with at least one of a dual cavity klystron with planar triodes, a reflex klystron, a backward wave oscillator, or a magnetron.
TECHNICAL FIELD OF THE DISCLOSURE
This disclosure generally relates to vacuum systems, and more particularly, to a reusable vacuum pumping apparatus with nanostructure material and a method of using the same.
BACKGROUND OF THE DISCLOSURE
Vacuum pumps are devices that remove gas molecules from a sealed volume in order to leave behind a partial vacuum. Vacuum systems are used in many types of scientific research, as well as in many fields of manufacturing and industry. Vacuum systems are especially critical in fields such as electronics manufacturing and experimental sciences, where trace gases left in the sealed volume may disrupt manufacture and research.
SUMMARY OF THE DISCLOSURE
This disclosure generally relates to vacuum systems, and more particularly, to a reusable vacuum pumping apparatus with nanostructure material and a method of using the same.
According to one embodiment, a vacuum system comprises a vacuum chamber, a construct of nanotubes, and a heat source. The vacuum chamber contains one or more gases. The construct of nanotubes is located proximate to the vacuum chamber and is operable to absorb or adsorb gases from the vacuum chamber. The hear source is located proximate to the construct of nanotubes and is operable to heat the construct of nanotubes such that the construct of nanotubes desorbs the gases from the vacuum chamber.
Certain embodiments of the disclosure may provide numerous technical advantages. For example, a technical advantage of one embodiment may include the capability to achieve lower pressures in a vacuum chamber by adsorbing trace gases in the system. Other technical advantages of other embodiments may include the capability to achieve low vacuum pressures faster than alternative vacuum systems. Yet other technical advantages of some embodiments may include the capability to recycle nanostructure materials and provide a long-lasting vacuum system.
Although specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of embodiments of the disclosure and its advantages, reference is now made to the following detailed description, taken in conjunction with the accompanying drawings, in which:
FIGS. 1 and 2 show vacuum systems according to several embodiments;
FIG. 3 show the results of an experiment testing the adsorptive power of nanotubes in a vacuum system;
FIGS. 4A and 4B show two techniques for generating microwave fields according to some embodiments; and
FIG. 5 show the results of an experiment testing the recyclability of nanotubes in a vacuum system.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
It should be understood at the outset that, although example implementations of embodiments of the invention are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or not. The present invention should in no way be limited to the example implementations, drawings, and techniques illustrated below. Additionally, the drawings are not necessarily drawn to scale.
FIG. 1 shows a vacuum system 100 according to several embodiments. Vacuum system 100 features a vacuum chamber 110 and a vacuum pump 120.
Embodiments of the vacuum chamber 110 may include any sealed enclosure operable to maintain a vacuum at a pressure lower than the outside atmospheric pressure. Two concepts help characterize the strength of a vacuum in the vacuum chamber 110. First, the "mean free path" of a molecule or atom of gas is defined as the average distance it can travel before colliding with another atom or molecule. A lower vacuum pressure will result in a higher mean free path for each molecule or atom remaining in the vacuum chamber 110. Second, "particle flux" is the rate at which particles hit the surface of a vacuum vessel. The particle flux rate depends on the gas's number density and molecular weight. Number density is how many particles of gas are contained in the vacuum chamber 110, and molecular weight is the mass of one molecule of a substance relative to the unified atomic mass unit. A lower vacuum pressure will result in a lower particle flux rate inside the vacuum chamber 110.
Embodiments of the vacuum pump 120 may include any device operable to remove gas molecules from the vacuum chamber 110 and create a partial vacuum. In general, certain embodiments of the vacuum pump 120 may be broadly categorized into two categories: gas-transfer pumps (such as turbomolecular and diffusion pumps) and gas-capture pumps (such as cryo and ion pumps).
The vacuum pump 120 may be rated based on various performance measures. For example, "pumping speed" refers to the volume flow rate of the pump at its inlet. Pumping speed measures how many liters of gas a vacuum pump can permanently remove from a vacuum chamber every second. Pumping speed may identify whether a vacuum pump can achieve a specified vacuum pressure in a specified amount of time.
The vacuum system 100 may include more than one type of the vacuum pump 120. For example, not all vacuum pumps will work at atmospheric pressures. Some embodiments of the vacuum system 100 may include a rough pump designed to reduce the pressure in vacuum chamber 110 from atmospheric pressure to some lower pressure, at which point another type of the vacuum pump 120 can then obtain even lower pressures. One example of a rough pump is a coarse vane pump. A course vane pump may reduce vacuum chamber pressure from atmospheric pressure to approximately 10-3 to 10-4 torr.
Once the rough pump has lowered the vacuum chamber 110 pressure to an appropriate level, the vacuum system 100 may employ a gas-transfer pump, such as a turbomolecular pump, which may lower the vacuum chamber pressure from 10-4 to 10-10 torr. A turbomolecular pump, for example, may include a stack of rotors, each rotor containing many angled blades that rotate at a very high speed. When a gaseous atom or molecule hits the blades, the blade momentum and pressure differences force the atom or molecule in the direction of the exhaust.
However, pumps such as turbomolecular pumps are limited by their rotational speeds and may not be able to pump all types of gases. For example, hydrogen at approximately 25 degrees Centigrade moves at approximately 1700 meters per second. A turbomolecular pump with a 6 inch diameter rotating at 36,000 revolutions per minute can only achieve speeds of approximately 280 meters per second, thus allowing the hydrogen and other gases to flow back into the vacuum chamber. Hydrogen is not the only problematic gas, but it can be one of the most difficult for turbomolecular pumps to pump.
However, some applications require extremely low vacuum pressures. Most pumping schemes have a tendency to leave some types of residual trace gases, such as Hydrogen, Helium, Nitrogen, water vapor (a primary source of Hydrogen), and several others. This residual gas may cause the pressure in the vacuum chamber to be higher than some applications requiring vacuum conditions will allow. There are two normal choices when faced with this situation: spend an enormous amount of money on pumps--most of which will only partially deal with the problem--or simply allow the problem to exist.
Accordingly, teachings of certain embodiments recognize the use of nanotubes as an adsorbant in a vacuum chamber. Teachings of certain embodiments recognize that nanotubes may adsorb particles from the vacuum chamber, thus lowering the gas's number density, particle flux, and vacuum chamber pressure. Additionally, teachings of certain embodiments recognize that nanotubes have the capability to adsorb many residual gases, such as Hydrogen, Helium, Nitrogen, water vapor, and several others. Furthermore, teachings of certain embodiments recognize that nanotubes may allow lower vacuum chamber pressures than alternative pumping systems.
FIG. 2 shows a vacuum system 200 according to several embodiments. Vacuum system 200 features a vacuum chamber 210, a valve 215 connecting vacuum chamber 210 to a vacuum pipe 220, a valve 225 connecting vacuum pipe 220 to the outside atmosphere, a construct of nanotubes 230, and a heat source 240. Some embodiments of vacuum system 200 may also include additional vacuum pumps such as the vacuum pumps 110, not illustrated in FIG. 2.
Embodiments of the vacuum chamber 210 and the vacuum pipe 220 may include any sealed enclosure operable to maintain a pressure lower than the outside atmospheric pressure. Embodiments of the valves 215 and 225 may include any device operable to regulate the flow of fluid by opening, closing, or partially obstructing various passageways. For example, the valve 215 may open to allow gases to flow from the vacuum chamber 210 to the vacuum pipe 220, and the valve 225 may open to allow gases to flow from vacuum pipe 220 to the outside atmosphere. In some embodiments, the valves 215 and 225 may be one-way valves, only allowing gas flow from the vacuum chamber 210 to the vacuum pipe 220 and from the vacuum pipe 220 to the outside atmosphere.
Some embodiments of the vacuum system 200 may also include a waveguide 245 in embodiments where the heat source 240 is a microwave heat source. Microwave waveguide 245 may represent any device or structure operable to guide microwave waves toward and through the nanotubes 230. For example, in some embodiments, the microwave waveguide 245 may include a hallow metallic conductor. Some embodiments may include a rectangular or circular waveguide. Other embodiments may include waveguides of other shapes and sizes. Yet other embodiments may incorporate the functionality of the waveguide 245 into other vacuum system 200 components, such as the vacuum pipe 220.
Nanotubes 230 may include any nanometer-scale tube-like structures, such as carbon nanotubes. Conceptually, a nanotube is a very small cylinder, typically capped at each end by a hemisphere of atoms, such as carbon atoms. There are two categories of nanotubes: multi-walled nanotubes (MWNT) and single-walled nanotubes (SWNT). MWNTs may be thought of as a number of layers of concentric pipes or tubes. MWNTs also include double-walled nanotubes and triple-walled nanotubes, which may exhibit different properties from SWNTs and other MWNTs.
SWNTs are nanotubes with only a single shell of atoms. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of atoms into a seamless cylinder. In this manner, SWNTs can be thought of as little pipes or tubes with diameters typically ranging from, but not limited to, approximately 0.6 to 5.0 nanometers. The lengths of SWNTs can range from a few hundred nanometers to several centimeters in length.
Although SWNTs share some physical similarities with MWNTs, they exhibit important properties not shared by MWNT variants, such as unique spectroscopical and electrical characteristics. The difference between SWNTs and MWNTs originates at the formation or synthesis level. For example, MWNT synthesis does not require a catalytic material, whereas SWNT synthesis requires a metallic catalyst of some sort to give the nanotubes a nucleation point. In addition, MWNTs form individually, although MWNTs may resemble a tiny plate of spaghetti under electron microscopy. On the other hand, SWNTs rarely form individually, but instead form as entwined nanotubes resembling ropes. These ropes tend to have some number of SWNTs forming strands, which may also resemble a tiny plate of spaghetti under electron microscopy.
These differences in formation or synthesis may cause MWNTs and SWNTs to exhibit unqiue qualities. For example, SWNTs form with unique electrical properties, with some being very good conductors and others being very good semiconductors. In addition, SWNTS also exhibit higher potential for reversible gas storage.
SWNTs can also achieve a high purity level. Purity in a nanotube refers to how much catalyst material and carbonaceous material has been removed from the sample. In general, nanotubes may form in very impure ways, such as forming with large amounts of unformed carbon or including leftover pieces of catalyst material clinging to the nanotubes. However, once purified, SWNTs may provide a very large surface area as compared to other structures as well as a very high affinity to adsorb hydrogen and other gases.
Several techniques are available to purify nanotubes. For example, some embodiments may include nanotubes 230 purified by the following purification technique. The first step is performing acid reflux in 3 Molar HNO3 for ten to twenty hours. The next step is pouring the mixture through filter paper. A membrane of approximately 0.20 μm will suffice. Then, the remainder of the material on the filter is rinsed with deionized water until the pH of the filtrate approaches neutral. Finally, the nanotubes 230 are then dried overnight in atmospheric conditions and then oxidized at some raised temperature. However, there are other techniques available, such as techniques involving electromagnetic waves. Some embodiments of nanotubes 230 may employ purification techniques other than the technique described above.
Both SWNTs and MWNTs exhibit the ability to adsorb gases such as Hydrogen, Nitrogen, and water vapor. The adsorptive nature of both SWNTs and MWNTs depend on various factors, such as degree of crystallinity, tube diameter, tube wall structure, bundling behavior, and Van der Waals forces.
FIG. 3 shows the results of an experiment testing the adsorptive power of nanotubes in a vacuum system. In this experiment, a purified 20 milligram SWNT sample with an average diameter of approximately 1.5 nanometers was placed in a 24 liter vacuum system. The SWNT adsorbed enough hydrogen to reduce the hydrogen background pressure by a full order of magnitude. This in turn caused the overall chamber pressure to be reduced. This experiment, along with similar testing, confirms that nanotubes make good adsorbents for various gases. More importantly, however, this research represents the first time that nanotubes have demonstrated the ability to improve the quality of background gases in a high vacuum or ultra high vacuum system.
Once the nanotubes 230 adsorb the trace gases, the nanotubes may still require a technique for releasing the trace gases outside of the vacuum chamber. Accordingly, teachings of certain embodiments recognize the use of a heat source 240 for desorbing the nanotubes. For example, in one embodiment, the heat source 240 may heat nanotubes 230 to 800 degrees Centigrade above the ambient temperatures to remove adsorbed Hydrogen. Other embodiments of the heat source 240 may include different types of heat sources that provide various levels of heat to desorb different types of gases.
The heat source 240 may include any device operable to heat the nanotubes 230 and desorb the trace gases. In some embodiments, regular resistive heating can achieve this desorption, although this may take several minutes. Some applications may require a faster method of achieving desorption. Thus, in some embodiments, the heat source 240 may include a microwave field generator. Teachings of certain embodiments recognize the use of microwave fields to create a reusable device that will efficiently and inexpensively remove these trace gases from the vacuum system. These teachings recognize that desorption may be achieved in mere milliseconds. Additionally, teachings of certain embodiments recognize that microwave fields may provide rapid and complete desorption as compared to some other desorption techniques.
One example of a microwave heat source 240 is described in U.S. Patent Application Publication No. 2004/0180244 A1, entitled PROCESS AND APPARATUS FOR MICROWAVE DESORPTION OF ELEMENTS OR SPECIES FROM CARBON NANOTUBES, filed Sep. 16, 2004. U.S. Patent Application Publication No. 2004/0180244 is hereby incorporated by reference.
In general, microwave radiation includes a range of frequencies in the electromagnetic ("EM") spectrum. Microwave frequencies comprise one of the widest regions of the EM spectrum, typically ranging from 300 mega-Hertz to 300 giga-Hertz (GHz). Due to this range of wavelengths, the microwave region may be further subdivided into decimeter, centimeter, and millimeter waves.
A variety of applications use electromagnetic waves in the microwave region. For example, a microwave oven emits a microwave field that excites water molecules in foods and beverages. Scientists can also use microwave fields to accelerate many chemical reactions to the point that they take mere minutes rather than days or weeks.
In the microwave oven example, microwave radiation creates heat by driving water molecules into an excited state. However, microwaves, which exist at the lower end of the EM spectrum, do not have sufficient quantum energy to cause atoms to go from a ground state to an excited state. In fact, microwave fields several orders of magnitude away from being able to accomplish this directly. But microwave radiation can drive many different atomic species into an excited state by coupling to transitions in the hyperfine structure of a dynamical state. Of course, this is merely one method of microwave interaction, and exact interactions of microwave fields and matter will vary.
Many different methods are available for producing low powered and lower frequency magnetic fields, only a few of which are described in this disclosure. For example, one such method is generating low frequency EM signals via the transfer of electrical energy from a steady electric field into an alternating field. In this example, a signal with the desired frequency is present due to thermal noise. The desired frequency is then selectively amplified to the desired power level by feedback with the phase relation that is appropriate to the application. This technique works reasonably well for frequencies up to approximately 1 GHz.
A different technique may be necessary for frequencies of 1 GHz to 10 GHz because the finite transit times of electrons will have a degrading effect on such things as the oscillator circuit. FIG. 4A shows one alternative technique for generating microwave fields in this frequency range according to some embodiments. FIG. 4A features a dual-cavity klystron 400 with planar triodes. Electron transit time has no effect on these devices due to their geometry. These devices consist of small distances between the triodes and a high accelerating voltage. These triodes are used in conjunction with a tunable dual-resonant cavity. These devices can typically be tuned to the 1 to 10 GHz portion of the microwave spectrum, and the maximum power output from such a device is in the range of 10 Watts.
The dual-cavity klystron 400 may include a pair of resonant cavities in tandem through which an electron beam may be passed. A radio frequency ("RF") field in the first of the two cavities will bunch the electrons into groups. These groups then pass into the second cavity and induce an RF field. In other words, the first of the two cavities slightly accelerates some electrons, while others slow down. The acceleration and deceleration is determined by which portion of the RF cycle the electrons are in. After several millimeters of transit, the faster electrons will catch the slower ones and the maximum allowable "bunching" will occur. The second of the two resonant cavities is situated at this exact position. Further along the beam line, the accelerated electrons have passed the slower ones, and the electrons are again debunched.
If in some portion of the RF cycle, energy from the second resonant cavity is fed back to the first resonator in the correct phase, dual-cavity klystron 400 will become an oscillator. The frequency of oscillation is determined by the resonant frequencies of the cavities, which may be adjusted by changing their physical size. The accelerator voltage may cause a small change in the oscillation frequency.
The dual-cavity klystron 400 has an upper limit of frequency it can reach. FIG. 4B shows a technique for generating microwave fields with higher frequencies according to some embodiments. FIG. 4B features a reflex klystron 401 with only a single cavity, unlike the dual-cavity klystron 400, which features two cavities. A reflex klystron is capable of emitting higher frequencies than a dual-cavity klystron. A reflex klystron is typically not capable of emitting signals with power levels higher than 1 Watt, which makes it very useful for applications requiring continuous, low-power, very clean signals. However, due to the removal of the second cavity found in the dual-cavity klystron 400, the reflex klystron 401 includes a reflector electrode with a negative charge to reflect the electron beam. After the beam is reflected, it re-enters the cavity and delivers more energy than originally received by the cavity, provided the cavity distance is properly tuned and the "repeller" voltage is properly set.
Some embodiments may also include a backward wave oscillator ("BWO") as a microwave signal source. In a BWO, the electron beam is compressed with the application of a static magnetic field along the longitudinal axis. These sources are very useful as sweep signal generators due to their ability to be tuned over a fairly wide range of frequencies. This sweeping is not done by mechanical means, but rather by varying the electron beam voltage.
For some applications, a much higher power level may be required from a microwave source. These applications typically employ a magnetron. In a magnetron source, a static magnetic field is applied perpendicularly to the electron beam, forcing the electrons into a nearly circular path. This path extends the amount of interaction time and allows a much higher power level to be achieved.
The majority of moderate to high power commercial microwave applications will use a magnetron source. Occasionally, a scientific application will require a cleaner signal than a magnetron can produce while also requiring higher powers than can be achieved with typical clean sources. In these instances, the two typical options are either massive klystron sources or high-power amplifiers. However, both of these methods are often cost-prohibitive.
The interaction of the nanotubes with microwaves is complex, with possibly several mechanisms at work. However, although embodiments are not bound by any particular mechanism, one known interaction may be derived from previous long chain molecule research. The valence electrons in long chain, or any nonlinear molecules, do not move in a cylindrically symmetric field. For this reason, no component of their orbital angular momentum can be found to be constant. The electron orbital momentum W must be considered as a portion of the rotational momentum of the entire molecule (if one assumes that the interaction is for only one molecule at a time).
The interaction of the electron spin L and orbit S of the type ALS1 is only possible when there is a slight uncoupling of L from the rotation of the molecule, where A is the largest rotational constant of an asymmetric rotor, L is the electronic angular momentum of an entire atom or molecule, and S is the electron spin angular momentum. This must occur as a second or higher order perturbation. Thus:
W = X + Y , where ##EQU00001## X = A [ aE + β ( a NK ) 2 K 2 + γ ] N ( N + 1 ) C and ##EQU00001.2## Y = A 2 2 [ a ' E + β ' ( a NK ) 2 K 2 N ( N + 1 ) + γ ' ] 3 / 4 C ( C + 1 ) - S ( S + 1 ) N ( N + 1 ) ( 2 N - 1 ) ( 2 N + 3 ) ; ##EQU00001.3##
and where α, β, γ, α', β', and γ', are constants dependent on the structure of the molecule; E is the energy of molecular rotation without electron spin effects; αNK is the wave function in terms of symmetric top waves; J is the total angular momentum, excluding nuclear spin; N is the total orbital angular momentum, including rotation of the molecule; and C=J(J+1)-S(S+1)-N(N+1).
The first term, X, is a type of dipole interaction. The second term, Y, is a quasi-quadruple interaction with the same dependence on angular momentum. The second term must be zero when S is less than 1 (i.e., for singlet and doublet states). These interactions may allow an extensive analysis of the fine structure spectra of SWNTs to be conducted in a way similar to that performed on other nonlinear molecules. Another mechanism can be found in that both MWNT and SWNT are conductors themselves, and therefore, do not require the presence of any traditional metallic material to have a metallic type of interaction.
Recyclable Nature of Various Embodiments
Experiments regarding several embodiments establish that nanotubes can be used to improve the quality of the background gases in a high vacuum or ultra high vacuum system. These experiments also suggest that nanotubes can be recycled for this same purpose.
FIG. 5 shows the results of an experiment testing the recyclability of nanotubes in a vacuum system. Following the experiment from FIG. 3, the same 24 liter vacuum system was brought back to atmospheric pressure, and then a new vacuum was generated inside the vacuum system. Next, the same purified 20 mg SWNT sample with an average diameter of approximately 1.5 nanometers from the FIG. 3 experiment were desorbed of adsorbed material and then placed back in the vacuum system. Referring to FIG. 5, it appears that the recycled nanotubes exhibited some initial outgassing of Hydrogen in the first hour to two hours, followed by a drastic reduction in pressure from all gas species.
Further experiments established that, if the microwave source is calibrated to keep the nanotubes below 2100 degrees centigrade during desorption, the nanotubes will remain undamaged. This type of reaction can be used for a long period of time with little or no oxidation or other damage to the nanotube structures, thereby allowing for a very long lasting pump.
The present disclosure refers to the adsorption of gases in a nanostructure material. Embodiments of the present disclosure are not limited to adsorption processes, but instead may include absorption or other processes. The present disclosure also refers to the desorption of gases out of a nanostructure material; however, embodiments may include other phenomenas resulting in the release of gases out of a nanostructure material.
Although the present disclosure has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present disclosure encompass such changes, variations, alterations, transformation, and modifications as they fall within the scope of the appended claims.
To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words "means for" or "step for" are explicitly used in the particular claim.
Patent applications by Timothy J. Imholt, Richardson, TX US
Patent applications by Raytheon Company