CA1142734A - Method for growing graphite fibers - Google Patents
Method for growing graphite fibersInfo
- Publication number
- CA1142734A CA1142734A CA000376848A CA376848A CA1142734A CA 1142734 A CA1142734 A CA 1142734A CA 000376848 A CA000376848 A CA 000376848A CA 376848 A CA376848 A CA 376848A CA 1142734 A CA1142734 A CA 1142734A
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- Canada
- Prior art keywords
- wall
- graphite fibers
- contacting
- natural gas
- gas
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
METHOD FOR GROWING GRAPHITE FIBERS
Abstract of the Disclosure In the preferred embodiment, graphite fibers that are 5 to 15 microns in diameter and up to several centimeters long are grown within a thin-walled stainless steel tube by flowing natural gas through the tube, concurrently contacting the outer tube surface with wet hydrogen gas and heat-ing to between 925°C to 1075°C to decompose methane in the natural gas, whereupon fibers grow on the adjacent tube surface.
Abstract of the Disclosure In the preferred embodiment, graphite fibers that are 5 to 15 microns in diameter and up to several centimeters long are grown within a thin-walled stainless steel tube by flowing natural gas through the tube, concurrently contacting the outer tube surface with wet hydrogen gas and heat-ing to between 925°C to 1075°C to decompose methane in the natural gas, whereupon fibers grow on the adjacent tube surface.
Description
2~3~
METHOD FOR GROWING GRAPHITE FIBERS
Background of the Invention This invention relates to the manufacture of graphite fibers that are suitable for use as a filler in plastic or other composites. Said graphite fibers are preferably 5 to 15 microns in diameter and up to several centimeters in length.
It is an object of this invention to provide a new method for manufacturing graphite fibers by the pyrolysis of a methane-containing gas, which fibers are suitable for filler in plastic or other composites.
More particularly, it is an object of this invention to provide a relatively inexpensive method for producing a high yield of graphite fibers from commercial natural gas, which method comprises thermally decomposing methane from the gas in contact with a thin, hydrogen-permeable iron-chromium alloy wall, while remotely contacting the wall with wet hydrogen gas so as to create conditions at the natural gas-wall interface that cause the decomposing methane to form the fibers~
Summary of the Invention -In accordance with a preferred embodiment, graphite fibers are grown within a thin wall stain-less steel tube by flowing natural gas through the tube, while surrounding it with wet hydrogen gas, ~Z'~3~
and hea-ting the gases and tube between 925C and 1075C. Under these conditions, the natural gas readily decomposes within the tube and grows thin~
straight graphite fibers that protrude obliquely from the inner tube surface in a downstream direction.
The fibers are characterized by a cross-section resembling a rolled-up scroll. Pyrolysis is continued for a sufficient time to form fiber diameters between 5 to 100 microns, preferably between 5 to 15 microns, which fibers may be up to several centimeters long. The product fibers are well suited for plastic filler and are relatively inexpensive, in part because they are derived from relatively inexpensive natural gas.
Description of the Drawings The only Figure is a cross-sectional schematic view of an apparatus for growing fibers in accordance with this invention.
Detailed Description of the Invention Referring now to the Figure, in the preferred embodiment, graphite fibers were grown within a cylindrical steel -tube 10. Tube 10 was preferably composed of type 304 stainless steel containing about 20% chromium. The outer diameter was 1.25 centimeters and -the wall thickness was about 0.5 millimeter. The overall length was ;273~
about 75 centimeters, although fibers were grown only within a portion about 20 centimeters long.
At one end of tube 10 was a gas inlet 12 that was suitably connected to a source of natural gas 14, through a valve 16 and a flow meter 18 for regulating the natural gas flow. A gas outlet 20 having a valve 22 was connected to the other end of tube 10 for venting exhausted gases.
A jacket 24 comprising an alumina cylin-der 25, coaxially surrounded a central portion of tube 10. The inner diameter of cylinder 25 was
METHOD FOR GROWING GRAPHITE FIBERS
Background of the Invention This invention relates to the manufacture of graphite fibers that are suitable for use as a filler in plastic or other composites. Said graphite fibers are preferably 5 to 15 microns in diameter and up to several centimeters in length.
It is an object of this invention to provide a new method for manufacturing graphite fibers by the pyrolysis of a methane-containing gas, which fibers are suitable for filler in plastic or other composites.
More particularly, it is an object of this invention to provide a relatively inexpensive method for producing a high yield of graphite fibers from commercial natural gas, which method comprises thermally decomposing methane from the gas in contact with a thin, hydrogen-permeable iron-chromium alloy wall, while remotely contacting the wall with wet hydrogen gas so as to create conditions at the natural gas-wall interface that cause the decomposing methane to form the fibers~
Summary of the Invention -In accordance with a preferred embodiment, graphite fibers are grown within a thin wall stain-less steel tube by flowing natural gas through the tube, while surrounding it with wet hydrogen gas, ~Z'~3~
and hea-ting the gases and tube between 925C and 1075C. Under these conditions, the natural gas readily decomposes within the tube and grows thin~
straight graphite fibers that protrude obliquely from the inner tube surface in a downstream direction.
The fibers are characterized by a cross-section resembling a rolled-up scroll. Pyrolysis is continued for a sufficient time to form fiber diameters between 5 to 100 microns, preferably between 5 to 15 microns, which fibers may be up to several centimeters long. The product fibers are well suited for plastic filler and are relatively inexpensive, in part because they are derived from relatively inexpensive natural gas.
Description of the Drawings The only Figure is a cross-sectional schematic view of an apparatus for growing fibers in accordance with this invention.
Detailed Description of the Invention Referring now to the Figure, in the preferred embodiment, graphite fibers were grown within a cylindrical steel -tube 10. Tube 10 was preferably composed of type 304 stainless steel containing about 20% chromium. The outer diameter was 1.25 centimeters and -the wall thickness was about 0.5 millimeter. The overall length was ;273~
about 75 centimeters, although fibers were grown only within a portion about 20 centimeters long.
At one end of tube 10 was a gas inlet 12 that was suitably connected to a source of natural gas 14, through a valve 16 and a flow meter 18 for regulating the natural gas flow. A gas outlet 20 having a valve 22 was connected to the other end of tube 10 for venting exhausted gases.
A jacket 24 comprising an alumina cylin-der 25, coaxially surrounded a central portion of tube 10. The inner diameter of cylinder 25 was
3.1 centimeters and the length was 42.5 centi-meters. Metal end caps 26 hermetically sealed tube 10 to cylinder 25 and included bellows 27 to compensate for differential thermal expansion.
Compression fittings (not shown) between tube 10 and caps 26 permit the tube to be uncoupled and removed for conveniently collecting fibers. An inlet 28 to jacket 24 at the end near tube inlet 12 was suitably connected to a source of hydrogen 29 through a valve 30, a bubbler 32 containing water 34 and a flowmeter 36. An outlet 38 comprising a valve 40 was provided at the other end of jacket 24.
Tube 10 and jacket 24 were positioned through an insulated furnace 42 having a coiled 73~
resistance heating element 44. Furnace 42 heated about 20 centimeters of tube 10 at the desired temperature and fiber growth occurred substan-tially in that portion of the tube.
Before heating furnace 42, tube 10 and jacket 24 were evacuated and checked for air leaks, and then thoroughly flushed with natural gas and hydrogen, respectively. Tube 10 and jacket 25 were then heated to about 970C. The natural gas flow through tube 10 was adjusted to about 20 cc/min, corresponding to a residence time of about 60 seconds within the 20 centimeter length where fiber growth occurred. The hydrogen flow through jacket 24 was adjusted to about 15 200 cc/min. Bubbler 32 was maintained at about room temperature and substantially saturated the hydrogen flowing therethrough. The gas pressures within the tube and the jacket were about atmos-pheric.
After a few hours under these conditions, fibers began to grow out from the inner surface of tube 10 at an acute angle thereto pointing generally downstream. ~ery thin fibers rapidly grew to substantially full length and thereafter principally grew radially. After about 24 hours, tube 10 was uncoupled from the remaining equipment 273~
and the fibers were knocked out using a brush.
The product fibers were generally straight and cylindrical and resembled very hard, very thin pencil leads. The fibers varied in length froTn less than a centimeter up to about 12 centimeters.
However, the fibers were remarkably uniform in diameter, ranging, for example, between 10 and 15 microns. Electron microscopic examination re-vealed that the fiber cross-section was spiral or scroll-like. That is, the graphite basal planes were helically oriented, in contrast to the radial basal plane orientation found in commer-cially available graphite fibers derived from pitch pyrolysis. Young's modulus was measured for a representative batch of fibers using an Instron tensile testing machine and was found to range between 0.8 and 3.8 x 10" Pascals, thinner fibers generally having a higher modulus. Thus, the fibers were well suited for use as a filler material.
Although not limited to any particular theory, it is believed that thermally decomposing methane in the natural gas adjacent one surface of the tube wall, i.e., the inner surface in the described embodiment, while concurrently diffusing hydrogen through the metal to the surface, carburiæes the surface in a manner that results in fiber growth.
~2~34 The surface initially bears a very thin, air-derived, integral oxide film composed of iron and chromium. Carburization transforms the oxide to carbide comprising a mixture of iron and chromium that is believed to catalytically decompose the methane to grow the fibers.
In addition, in the described embodiment, a portion of the pyrolytic carbon derived from the natural gas diffuses through the stainless steel wall to the outer ~ube surface and is extracted into the wet hydrogen, presumably as a result of oxidation by the water. It is estimated that up to one-eighth of the carbon in the natural gas introduced into the tube is exhausted with the hydrogen in the jacket.
While decarburization by the jacket gas is not believed to be essential, it does significantly improve the density of product fibers. Thus, dry hydrogen, which is not considered decarburizing, produces fibers, although significantly fewer in density, provided that soot buildup within the tube does not inhibit fiber growth.
In the apparatus of the preferred embodiment, the density of fiber growth is relatively insensitive to the flow rate of wet hydrogen gas ~14Z~34 through the jacket. Rates up to about 400 cc/min are suitable. Also, brief interruptions do not apparently affect fiber growth. However, fiber size is related to the water content of the hydrogen gas. Drier hydrogen produces generally longer fibers that are more uniform in diameter, whereas wetter hydrogen produces a greater density of shorter fibers. Other hydrogen-containing decarburizing atmospheres, for example, hot mixtures of water and inert gas or carbon dioxide and hydrogen, are also believed suitable.
As discussed herein, fiber growth is believed to be related to chromium oxide initially on the inner tube surface, which in turn is related to the chromium content of the preferred steel.
It has been found that the logarithm of the fiber population density is directly related to the logarithm of the chromium concentration. Type 304 stainless steel containing 20 weight percent chromium produces a high density of fibers and is preferred. Type 4130 steel containing about 1%
chromium also produces dense fiber growth. Steel selected from the 1010 series and containing 0.1~
chromium produces more widely scattered fibers and may be preferred for growing thicker fibers.
~owever, 1010-series steel containing about 0.01 chromium did not appreciably grow fibers.
2~3'1 In another embodiment, the apparatus in the Figure was modified to flow wet hydrogen through tube 10 and natural gas through jacket 24.
Fiber growth occurred on the outer surface of the tube. The method of this invention is also suit~
able for fiber growth on nontubular walls having opposite surfaces in contact with natural gas and wet hydrogen. Wall thicknesses are suitably less than about 3.0 mm and preferably between about 0.5 to 1.0 mm. In general, thinner walls enhance fiber growth. This is at least partially attributed to the higher diffusion rate of carbon or hydrogen through a thinner wall.
In the preferred embodiment, fibers were produced from natural gas containing, by weight, 0.5% nitrogen, 0.6% carbon oxides, 4.0% ethane, 1.1% higher hydrocarbons, and the balance methane.
This gas was commercially obtained, in bottled form, from Airco, Inc., and designated methane grade 1.3.
City natural gas containiny 1.2% nitrogen, 0.7%
total carbon oxides, 1.9% ethane, 0.6% hydrogen, 0.5% heavy hydrocarbons and the balance methane also produces good fibers. Natural gas produces eight or more times the fiber density as methane, indicating that minor constituents in natural gas, such as carbon oxides or ethane, significantly promote fiber growth.
Z7~3~
Although the method of this invention has been adapted to produce fibers having diameters of over 600 microns, the preferred fiber diameter for filler use is between 5 and 15 microns. The length of the longest fibers is believed to be mainly limited by the length of the heated section of the tube. In general, increasing the natural gas flow rate, tem-perature or fiber-growing time increases fiber size, particularly diameter. For the described apparatus, flow rates suitably range between 10 to 70 cc/min, corresponding to residence time in the fiber growth section of between about 120 seconds -to about 17 seconds. Diluting the natural gas before pyrolysis, for example, with hydrogen gas, affects fiber growth similar to reducing the undiluted flow rate. Suitable temperatures range from about 925C to 1075C or higher, and about 970C to 1000C is preferred. Also, in the preferred embodiment, tube and gases were heated at a con-stant temperature for about twenty-four hours.
During this time, it is believed that the metal carbide forms first and thereafter catalyzes fiber growth.
The growing time may be reduced by adjusting selected reaction conditions to more rapidly form the carbide.
For example, at a flow rate of 20 cc/min, the onset of fiber growth occurred after about twelve hours.
~14Z~
Increasing to 60 cc/min reduces the time to about three hours. Similarly, increasing the temperature reduces the time before fibers begin to grow. After fiber growth begins, the reaction conditions may be adjusted for optimum fiber growth, which typically requires only a few hours, depending on the desired diameter. Careful removal of the fibers may permit the carburized tube to be reused and may reduce the time required to initiate fiber growth.
Although this invention has been described in terms of certain embodiments thereof, it is not intended that it be limited to the above description but rather only to the extent set forth in the claims that follow.
Compression fittings (not shown) between tube 10 and caps 26 permit the tube to be uncoupled and removed for conveniently collecting fibers. An inlet 28 to jacket 24 at the end near tube inlet 12 was suitably connected to a source of hydrogen 29 through a valve 30, a bubbler 32 containing water 34 and a flowmeter 36. An outlet 38 comprising a valve 40 was provided at the other end of jacket 24.
Tube 10 and jacket 24 were positioned through an insulated furnace 42 having a coiled 73~
resistance heating element 44. Furnace 42 heated about 20 centimeters of tube 10 at the desired temperature and fiber growth occurred substan-tially in that portion of the tube.
Before heating furnace 42, tube 10 and jacket 24 were evacuated and checked for air leaks, and then thoroughly flushed with natural gas and hydrogen, respectively. Tube 10 and jacket 25 were then heated to about 970C. The natural gas flow through tube 10 was adjusted to about 20 cc/min, corresponding to a residence time of about 60 seconds within the 20 centimeter length where fiber growth occurred. The hydrogen flow through jacket 24 was adjusted to about 15 200 cc/min. Bubbler 32 was maintained at about room temperature and substantially saturated the hydrogen flowing therethrough. The gas pressures within the tube and the jacket were about atmos-pheric.
After a few hours under these conditions, fibers began to grow out from the inner surface of tube 10 at an acute angle thereto pointing generally downstream. ~ery thin fibers rapidly grew to substantially full length and thereafter principally grew radially. After about 24 hours, tube 10 was uncoupled from the remaining equipment 273~
and the fibers were knocked out using a brush.
The product fibers were generally straight and cylindrical and resembled very hard, very thin pencil leads. The fibers varied in length froTn less than a centimeter up to about 12 centimeters.
However, the fibers were remarkably uniform in diameter, ranging, for example, between 10 and 15 microns. Electron microscopic examination re-vealed that the fiber cross-section was spiral or scroll-like. That is, the graphite basal planes were helically oriented, in contrast to the radial basal plane orientation found in commer-cially available graphite fibers derived from pitch pyrolysis. Young's modulus was measured for a representative batch of fibers using an Instron tensile testing machine and was found to range between 0.8 and 3.8 x 10" Pascals, thinner fibers generally having a higher modulus. Thus, the fibers were well suited for use as a filler material.
Although not limited to any particular theory, it is believed that thermally decomposing methane in the natural gas adjacent one surface of the tube wall, i.e., the inner surface in the described embodiment, while concurrently diffusing hydrogen through the metal to the surface, carburiæes the surface in a manner that results in fiber growth.
~2~34 The surface initially bears a very thin, air-derived, integral oxide film composed of iron and chromium. Carburization transforms the oxide to carbide comprising a mixture of iron and chromium that is believed to catalytically decompose the methane to grow the fibers.
In addition, in the described embodiment, a portion of the pyrolytic carbon derived from the natural gas diffuses through the stainless steel wall to the outer ~ube surface and is extracted into the wet hydrogen, presumably as a result of oxidation by the water. It is estimated that up to one-eighth of the carbon in the natural gas introduced into the tube is exhausted with the hydrogen in the jacket.
While decarburization by the jacket gas is not believed to be essential, it does significantly improve the density of product fibers. Thus, dry hydrogen, which is not considered decarburizing, produces fibers, although significantly fewer in density, provided that soot buildup within the tube does not inhibit fiber growth.
In the apparatus of the preferred embodiment, the density of fiber growth is relatively insensitive to the flow rate of wet hydrogen gas ~14Z~34 through the jacket. Rates up to about 400 cc/min are suitable. Also, brief interruptions do not apparently affect fiber growth. However, fiber size is related to the water content of the hydrogen gas. Drier hydrogen produces generally longer fibers that are more uniform in diameter, whereas wetter hydrogen produces a greater density of shorter fibers. Other hydrogen-containing decarburizing atmospheres, for example, hot mixtures of water and inert gas or carbon dioxide and hydrogen, are also believed suitable.
As discussed herein, fiber growth is believed to be related to chromium oxide initially on the inner tube surface, which in turn is related to the chromium content of the preferred steel.
It has been found that the logarithm of the fiber population density is directly related to the logarithm of the chromium concentration. Type 304 stainless steel containing 20 weight percent chromium produces a high density of fibers and is preferred. Type 4130 steel containing about 1%
chromium also produces dense fiber growth. Steel selected from the 1010 series and containing 0.1~
chromium produces more widely scattered fibers and may be preferred for growing thicker fibers.
~owever, 1010-series steel containing about 0.01 chromium did not appreciably grow fibers.
2~3'1 In another embodiment, the apparatus in the Figure was modified to flow wet hydrogen through tube 10 and natural gas through jacket 24.
Fiber growth occurred on the outer surface of the tube. The method of this invention is also suit~
able for fiber growth on nontubular walls having opposite surfaces in contact with natural gas and wet hydrogen. Wall thicknesses are suitably less than about 3.0 mm and preferably between about 0.5 to 1.0 mm. In general, thinner walls enhance fiber growth. This is at least partially attributed to the higher diffusion rate of carbon or hydrogen through a thinner wall.
In the preferred embodiment, fibers were produced from natural gas containing, by weight, 0.5% nitrogen, 0.6% carbon oxides, 4.0% ethane, 1.1% higher hydrocarbons, and the balance methane.
This gas was commercially obtained, in bottled form, from Airco, Inc., and designated methane grade 1.3.
City natural gas containiny 1.2% nitrogen, 0.7%
total carbon oxides, 1.9% ethane, 0.6% hydrogen, 0.5% heavy hydrocarbons and the balance methane also produces good fibers. Natural gas produces eight or more times the fiber density as methane, indicating that minor constituents in natural gas, such as carbon oxides or ethane, significantly promote fiber growth.
Z7~3~
Although the method of this invention has been adapted to produce fibers having diameters of over 600 microns, the preferred fiber diameter for filler use is between 5 and 15 microns. The length of the longest fibers is believed to be mainly limited by the length of the heated section of the tube. In general, increasing the natural gas flow rate, tem-perature or fiber-growing time increases fiber size, particularly diameter. For the described apparatus, flow rates suitably range between 10 to 70 cc/min, corresponding to residence time in the fiber growth section of between about 120 seconds -to about 17 seconds. Diluting the natural gas before pyrolysis, for example, with hydrogen gas, affects fiber growth similar to reducing the undiluted flow rate. Suitable temperatures range from about 925C to 1075C or higher, and about 970C to 1000C is preferred. Also, in the preferred embodiment, tube and gases were heated at a con-stant temperature for about twenty-four hours.
During this time, it is believed that the metal carbide forms first and thereafter catalyzes fiber growth.
The growing time may be reduced by adjusting selected reaction conditions to more rapidly form the carbide.
For example, at a flow rate of 20 cc/min, the onset of fiber growth occurred after about twelve hours.
~14Z~
Increasing to 60 cc/min reduces the time to about three hours. Similarly, increasing the temperature reduces the time before fibers begin to grow. After fiber growth begins, the reaction conditions may be adjusted for optimum fiber growth, which typically requires only a few hours, depending on the desired diameter. Careful removal of the fibers may permit the carburized tube to be reused and may reduce the time required to initiate fiber growth.
Although this invention has been described in terms of certain embodiments thereof, it is not intended that it be limited to the above description but rather only to the extent set forth in the claims that follow.
Claims (11)
1. A method for manufacturing graphite fibers by methane pyrolysis, said method comprising thermally decomposing methane adjacent a surface of an iron wall while concurrently diffusing hydrogen from a remote source through the wall to said surface, said surface initially bearing an integral oxide film containing chromium, said methane decomposition and hydrogen diffusion cooperating and continuing for a suitable time to form graphite fibers on said surface.
2. A method for manufacturing graphite fibers by high temperature methane decomposition, said method comprising contacting a first surface of a thin, iron-chromium alloy wall with gaseous methane, concurrently contacting a second opposite surface of the wall with gaseous hydrogen, and heating the wall and the gases at a temperature and for a time sufficient to form graphite fibers on the first wall surface.
3. A method for manufacturing graphite fibers by high temperature methane decomposition, said method comprising contacting a first surface of a steel wall with natural gas, said steel wall containing at least 1 weight percent chromium and being no thicker than about 3 millimeters, concurrently contacting a second opposite surface of the wall with a gas adapted to supply hydrogen to said wall, and heating the wall and the gases to between about 925°C and about 1075°C to form graphite fibers on the first wall surface.
4. A method for manufacturing graphite fibers by high temperature methane decomposition, said method comprising contacting a first surface of a thin chromium-containing iron alloy wall with a methane-containing gas adapted to carburize said surface, contacting a second surface of the wall with a gas adapted to decarburize the wall and to dissolve hydrogen into the wall, said first and second surfaces being arranged and spaced such that hydrogen dissolved into the wall at the second surface diffuses to the first surface and carbon dissolved into the first surface diffuses to the second surface, and heating the wall and contacting gases at a suitable temperature to decompose methane to carburize the first wall surface and to decarburize the second wall surface and continuing for a time sufficient to form graphite fibers on said first wall surface.
5. A method for manufacturing graphite fibers comprising contacting a first surface of a wall with a gas comprising one or more alkane hydrocarbons of the type found in natural gas and carbon oxides, while concurrently dissolving hydrogen into a second wall surface opposite the first wall surface, said wall being formed of a hydrogen-permeable metal bearing initially chromium oxide on the first wall surface, and heating the wall and gas at a temperature and for a time to form graphite fibers on said first wall surface.
6. A method for manufacturing graphite fibers comprising contacting a first surface of a wall with a gas comprising predominantly methane and a constituent comprising carbon oxides or a second alkane hydrocarbon of the type found in natural gas, while concurrently dissolving hydrogen into a second wall surface opposite the first wall surface, said wall being formed of a hydrogen-permeable metal bearing initially chormium oxide on the first wall surface, and heating the wall and gas at a temperature and for a time to form graphite fibers on said first wall surface.
7. A method for manufacturing graphite fibers by high temperature methane decomposition, said method comprising contacting natural gas to a first surface on one side of a thin wall formed of an iron alloy containing chromium in an amount greater than 0.1 percent and effective for growing fibers, concurrently contacting a second surface on the other side of said wall opposite said first surface with a decarburizing gas containing hydrogen, said wall being no thicker between said surfaces than about 3 millimeters, and heating the wall and the gases to decompose the natural gas and to decarburize the second wall surface, whereupon graphite fibers grow on the first wall surface.
8. A method for manufacturing graphite fibers having a scroll-like cross section by high temperature methane decomposition, said method comprising contacting natural gas to a first surface of a wall formed of an iron-chromium alloy effective for growing fibers, concurrently contacting a second surface of the wall opposite said first surface with wet hydrogen gas, the thickness of the wall between said surfaces being less than about 3 millimeters, and heating the wall and the gases to between about 925°C and about 1075°C to form scroll-like graphite fibers on the first wall surface.
9. A method for manufacturing graphite fibers having a scroll-like cross section, said method comprising contacting a first surface of a stainless steel wall with natural gas while concurrently contacting a second surface of the wall opposite the first surface with a wet hydrogen gas, said wall being formed of a steel containing at least 1 weight percent chromium and being no thicker than about 1.0 millimeters, and heating the wall and gases to between about 925°C and about 1075°C to decompose methane in the natural gas and to grow on the first surface scroll-like graphite fibers that are 5 to 100 microns in diameter and up to several centimeters long.
10. A method for manufacturing graphite fibers comprising flowing natural gas through a thin-wall stainless steel tube while surrounding the tube with wet hydrogen gas, and heating the tube and gases at a temperature and for a time to grow graphite fibers on the natural gas-contacting surface, said fibers having a scroll-like cross section and being about 5 to 100 microns in diameter and up to several centimeters long.
11. A method for manufacturing graphite fibers having a scroll-like cross section, said method comprising flowing natural gas through a stainless steel tube having a wall thickness between about 0.5 to 1.0 millimeters, said natural gas contacting said tube at a surface initially bearing a chromium oxide, surrounding the tube with wet hydrogen gas, and heating the tube and gases to between about 970°C to 1000°C to decompose methane in the natural gas and to grow on the natural gas-contacting tube surface scroll-like graphite fibers that are about 5 to 100 microns in diameter and up to several centimeters long.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US17028280A | 1980-07-18 | 1980-07-18 | |
| US170,282 | 1988-03-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142734A true CA1142734A (en) | 1983-03-15 |
Family
ID=22619277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000376848A Expired CA1142734A (en) | 1980-07-18 | 1981-05-05 | Method for growing graphite fibers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1142734A (en) |
-
1981
- 1981-05-05 CA CA000376848A patent/CA1142734A/en not_active Expired
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