EP1958272A2 - High density nanowire arrays in a glassy matrix, and methods for drawing the same - Google Patents
High density nanowire arrays in a glassy matrix, and methods for drawing the sameInfo
- Publication number
- EP1958272A2 EP1958272A2 EP06844870A EP06844870A EP1958272A2 EP 1958272 A2 EP1958272 A2 EP 1958272A2 EP 06844870 A EP06844870 A EP 06844870A EP 06844870 A EP06844870 A EP 06844870A EP 1958272 A2 EP1958272 A2 EP 1958272A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- glass
- fibers
- cable
- thermoelectric
- active material
- 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.)
- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
- C03B37/01214—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube for making preforms of multifibres, fibre bundles other than multiple core preforms
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
- C03B37/01225—Means for changing or stabilising the shape, e.g. diameter, of tubes or rods in general, e.g. collapsing
- C03B37/0124—Means for reducing the diameter of rods or tubes by drawing, e.g. for preform draw-down
- C03B37/01245—Means for reducing the diameter of rods or tubes by drawing, e.g. for preform draw-down by drawing and collapsing
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/026—Drawing fibres reinforced with a metal wire or with other non-glass material
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/028—Drawing fibre bundles, e.g. for making fibre bundles of multifibres, image fibres
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/02—Disposition of insulation
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/01—Manufacture or treatment
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
- H10N10/85—Thermoelectric active materials
- H10N10/851—Thermoelectric active materials comprising inorganic compositions
- H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
- H10N10/85—Thermoelectric active materials
- H10N10/857—Thermoelectric active materials comprising compositions changing continuously or discontinuously inside the material
-
- 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
Definitions
- the present invention is directed to high density nanowire arrays in a glassy matrix, and methods for drawing the same.
- thermoelectric materials generate electricity when subjected to a thermal gradient and produce a thermal gradient when electric current is passed through them.
- scientists have been trying to harness practical thermoelectricity for decades because practical thermoelectricity could, inter alia: (1) replace fluorocarbons used in existing cooling systems such as refrigerators and air conditioners; and (2) reduce harmful emissions during thermal power generation by converting some or most of the waste heat into electricity.
- practical thermoelectricity has not yet been fulfilled.
- One problem is that, because of its low efficiency, the industry standard in thermoelectric technology cannot be functionally integrated into everyday heating and cooling products and systems.
- thermoelectric devices such as thermoelectric generators (TEG), thermoelectric refrigerators (TER) and thermoelectric heat pumps are used for the direct conversion of heat into electricity, or for the direct conversion of electricity into heat.
- TOG thermoelectric generators
- TER thermoelectric refrigerators
- thermoelectric heat pumps are used for the direct conversion of heat into electricity, or for the direct conversion of electricity into heat.
- ⁇ the efficiency of energy conversion and/or coefficient of performance of these bulk form thermoelectric devices are considerably lower than those of conventional reciprocating or rotary heat engines and vapor-compression systems.
- bulk form thermoelectric devices have not attained immense popularity.
- thermoelectric junctions were fashioned from two different metals or alloys capable of producing a small current when subjected to a thermal gradient. A differential voltage is created as heat is carried across the junction, thereby converting a portion of the heat into electricity.
- junctions can be connected in series to provide greater voltages, connected in parallel to provide increased current, or both.
- Modern thermoelectric generators can include numerous junctions in series, resulting in higher voltages.
- Such thermoelectric generators can be manufactured in modular form to provide for parallel connectivity to increase the amount of generated current.
- Thomas Johann Seebeck discovered the first thermoelectric effect, referred to as the Seebeck effect.
- Seebeck discovered that a compass needle is deflected when placed near a closed loop made of two dissimilar metals, when one of the two junctions is kept at a higher temperature than the other. This established that a voltage difference is generated when there is a temperature difference between the two junctions, wherein the voltage difference is dependent on the nature of the metals involved.
- the voltage (or EMF) generated per oC thermal gradient is known as Seebeck coefficient.
- Peltier discovered the second thermoelectric effect, known as the Peltier effect. Peltier found that temperature changes occur at a junction of dissimilar metals, whenever an electrical current is caused to flow through the junction. Heat is either absorbed or released at a junction depending on the direction of the current flow.
- thermoelectric effect relates to the heating or cooling of a single homogeneous current-carrying conductor subjected to a temperature gradient.
- Lord Kelvin also established four equations (the Kelvin relations) correlating the Seebeck, Peltier and Thomson coefficients.
- Alterikirch suggested using the principles of thermoelectricity for the direct conversion of heat into electricity, or vice versa. He created a theory of thermoelectricity for power generation and cooling, wherein the Seebeck coefficient (thermo- power) was required to be as high as possible for best performance. The theory also required that the electrical conductivity to be as high as possible, coupled with a minimal thermal conductivity.
- Altenkirch established a criterion to determine the thermopower conversion efficiency of a material, which he named the power factor (PF).
- the equation can be rendered dimensionless by multiplying it by the absolute temperature, T, at which the measurements for S, p and k are conducted such that the dimensionless thermoelectric figure of merit or ZT factor equals (S 2 * ⁇ /k)T. It follows that to improve the performance of a thermoelectric device the power factor should be increased as much as possible, whereas k (thermal conductivity) should be decreased as much as possible.
- the ZT factor of a material indicates its thermopower conversion efficiency. Forty years ago, the best ZT factor in existence was about 0.6. After four decades of research, commercially available systems are still limited to ZT values that barely approach 1. It is widely recognized that a ZT factor greater than 1 would open the door for thermoelectric power generation to begin supplanting existing power-generating technologies, traditional home refrigerators, air conditioners, and more. Indeed, a practical thermoelectric technology with a ZT factor of even 2.0 or more will likely lead to the production of the next generation of heating and cooling systems. In view of the above, there exists a need for a method for producing practical thermoelectric technology that achieves an increased ZT factor of around 2.0 or more.
- thermoelectric coolers and thermoelectric generators in nano- structures have recently been shown to be capable of enhanced thermoelectric performance over that of corresponding thermoelectric devices in bulk form. It has been demonstrated that when certain thermoelectrically active materials (such as PbTe, Bi 2 Te 3 and SiGe) are reduced in size to the nanometer scale (typically about 4-100 nm), the ZT factor increases dramatically. This increase in ZT has raised expectations of utilizing quantum confinement for developing practical thermoelectric generators and coolers [refrigerators].
- thermoelectrically active materials such as PbTe, Bi 2 Te 3 and SiGe
- the present invention pertains to nanostructures formed from fibers of thermoelectrically active materials that are substantially one-dimensional, having a diameter that is significantly smaller than their length.
- the fibers from which these nanostructures are composed have a diameter of approximately 200 nm or less.
- the inventive nanostructures described herein are referred to as, “nanowires", cables”, “arrays”, “heterostructures” or “composites” that contain a plurality of one-dimensional fibers.
- the cables preferably comprise at least one thermoelectrically active material and a glassy material, which acts as an electrical insulator for the thermoelectrically active material, which is also referred to herein as the "thermoelectric material”.
- the thermoelectric material comprises a large concentration (e.g., 10 6 -10 10 /cm 2 ) of nano-sized wires embedded in a suitable glass forming a cable, wherein the thermoelectric material is in the form of a glass-clad nanowires comprising a plurality of one-dimensional fibers that extend over large distances along the length of the cable without coming in contact with other fibers.
- the thermoelectrically active material may comprise a suitable metal, alloy or semiconductor material, which maintains the integrity of the interface between the thermoelectric material and the glassy material without any appreciable smearing and/or diffusion of the thermoelectric material.
- a process for fabricating cables includes increasing the population of thermoelectric fibers to more than 10 9 /cm 2 of the cross- section of the cable.
- Each cable includes an array of fibers haying a distribution of diameters, wherein the variation in fiber diameter may be reduced by employing automated draw-towers, which are commonly employed in the fiber-optic industry for drawing optical fibers.
- a preferred cable produced in accordance with the principles of the present invention preferably comprises at least one thermoelectric fiber embedded in an electrically insulating material, wherein the thermoelectric material exhibits quantum confinement.
- the preferred cable comprises a plurality of fibers such that there is electrical connectivity between the ends of all the fibers.
- the glass cladding for the cable preferably comprises an electrically insulating material such as pyrex, borosilcate, aluminosilicate, quartz or a glass having lead oxide, tellurium dioxide and silicon dioxide as its main constituents.
- the thermoelectric material may be chosen from the group consisting of a metal, a semi-metal, an alloy and a semiconductor, such that the thermoelectric material exhibits electrical connectivity and quantum confinement.
- the present invention also provides a method of drawing a thermoelectrically active material in a glass cladding, comprising sealing off one end of a glass tube such that the tube has an open end and a closed end, introducing the thermoelectrically active material inside the glass tube and evacuating the tube by attaching the open end to a vacuum pump, heating a portion of the glass tube such that the glass partially melts and collapses under the vacuum such that the partially melted glass tube provides an ampoule containing the thermoelectric material to be used in a first drawing operation, introducing the ampoule containing the thermoelectric material into a heating device, increasing the temperature within the heating device such that the glass tube melts just enough for it to be drawn and drawing fibers of glass clad thermoelectrically active material.
- the method may further comprise bunching the fibers of glass clad thermoelectrically active material together and redrawing one or more times in succession to produce a multi-core cable having a plurality of individual thermoelectric fibers that are insulated from each other by the glass cladding.
- the above-described method may further comprise the steps of breaking the glass clad fibers into shorter pieces, introducing the pieces of glass clad fibers into another glass tube having a sealed end and an open end, evacuating the tube by attaching the open end to a vacuum pump, heating a portion of the glass tube such that the glass partially melts and collapses under the vacuum such that the partially melted glass tube provides an ampoule containing the pieces of glass clad fibers, introducing the ampoule into a heating device, increasing the temperature within the heating device such that the glass tube melts just enough for it to be drawn and drawing fibers of glass clad thermoelectrically active material to produce a cable having a plurality of multi-core fibers.
- FIG. 1 is a cross-sectional view of a tubular furnace for drawing a thermoelectrically active material embedded in a glass cladding, in accordance with the principles of the present invention
- FIG. 2 is an x-ray diffraction pattern of a PbTe-based cable constructed, in accordance with the principles of the invention
- FIG. 3 is a side view of a glass-clad PbTe-based cable constructed in accordance with the principles of the invention
- FIG. 4 is an enlarged cross-sectional view of the glass-clad PbTe-based cable of FIG. 3 taken along line 3 A-3A;
- FIG. 5 is a cross-sectional view of the glass-clad PbTe-based cable of FIG. 3 after a second drawing of the PbTe fibers;
- FIG. 8 is a chart illustrating the DC resistance of a PbTe cable of FIG. 5 (after a second drawing of the PbTe fibers).
- FIG. 9 is a chart illustrating the DC resistance of a PbTe cable of FIG. 6 (after a third drawing of the PbTe fibers).
- thermoelectric materials Macroscopic-sized thermoelectric materials that are typically larger than 1 micron or 1 micrometer in all three dimensions.
- Chemical Vapor Deposition Deposition of thin films (usually dielectrics/insulators) on wafer substrates by placing the wafers in a mixture of gases, which react at the surface of the wafers. This can be done at medium to high temperature in a furnace, or in a reactor in which, the wafers are heated but the walls of the reactor are not. Plasma enhanced chemical vapor deposition avoids the need for a high temperature by exciting the reactant gases into a plasma.
- PbTe is one of the most commonly used thermoelectric material other than Bi 2 Te 3 .
- PbTe is typically used for power generation because this material exhibits its highest ZT at temperatures between 400 and 500°C and has an effective operating range of about 200 0 C around 500 0 C.
- Quantum Confinement takes place when carriers of electricity (electrons or holes) are confined in space by reducing the size of the conductor.
- a very thin conducting film reduces the freedom of a carrier by limiting its freedom to propagate in a direction perpendicular to the plane of the film.
- the film is said to be a 2-d structure and the carrier in such a film is said to be quantum confined in one direction. It can move around in two other directions, i.e., in the plane of the film.
- Thermal conductivity is an inherent property of a material that specifies the amount of heat transferred through a material of unit cross-section and unit thickness for unit temperature gradient. Though thermal conductivity is an intrinsic property of a medium, it depends on the measurement temperature. The thermal conductivity of air is about 50 % greater than that of water vapor, whereas the thermal conductivity of liquid water is about 25 times that of air. Thermal conductivities of solids, especially metals, are thousands of times greater than that of air.
- the present invention is directed to nanostructures referred to herein as
- Nanowires in accordance with the present invention generally comprise heterostructures of at least one thermoelectrically active material and one other compositionally and structurally different material (e.g., glass), wherein an interface or junction is formed there between.
- the thermoelectrically active material is reduced in thickness or diameter to nano- dimensions in order to harness the advantages of quantum confinement. In this manner, the thermoelectric efficiency of the thermoelectrically active material is enhanced.
- the thermoelectrically active material is also referred to herein as the "thermoelectric material”.
- the cladding material preferably comprises a suitable glass such as a glass comprising an amorphous material having no long range ordering of its constituent atoms.
- thermoelectric figure of merit Z
- T absolute temperature
- ZT factors increase with temperatures between about 300 K and 750 K.
- the value of S 2 * ⁇ tends to peak at a certain level with the ZT factors increasing with decreasing nanowire width.
- ZT factors begin to fall with decreasing nanowire width.
- the PbTe-based nanowires described herein may be easily tailored to exhibit n-type or p-type conduction, either by changing the stoichiometry of Pb and Te or by adding some minor components/impurities.
- thermoelectric materials including PbTe, are sensitive to oxygen, which can degrade thermoelectric performance. For this reason, it is advantageous to have such thermoelectric materials sealed off and protected from oxygen contamination within the target environment range. Of course, a thermoelectric device is not commercially viable if it cannot withstand the elements and environment it is intended to function under.
- thermoelectric material is the preferred thermoelectric material
- other thermoelectric materials may be employed, such as Bi 2 Te 3 , SiGe, ZnSb, Zn 2 2 and CdO -8 Sb 3 , without departing from the scope of the present invention.
- the thermoelectric material may initially be in any convenient form, such as granules or powder.
- thermopower using a conventional method (e.g. by employing the Seebeck coefficient determination system, marketed by MMR Technologies, Mountain View, California) did not produce any result on account of the high resistivity of the glass cladding.
- electrical conductivity and thermoelectric power of PbTe-embedded cables was readily measurable, indicating that the measured values of electrical conductivity and thermoelectric power are attributable to the continuous nanowires along the length of the cable.
- thermoelectric material for the nanowire cables of the present invention is PbTe because of its advantageous thermoelectric properties and reasonable cost.
- the calculated ZT ((S 2 ⁇ aZk)*!) factor at 750 K is > 2.5.
- the S ⁇ of PbTe exhibits a definite tendency to peak at a certain nanowire width.
- the best known ZT factors for bulk PbTe is around 0.5
- the resultant ZT factors of around 2.0 or more is considered to be significantly enhanced by quantum confinement.
- the ZT factor increases with decreasing nanowire width until this maximum value is reached, and then the ZT factor begins to decrease with further decrease in nanowire width.
- other thermoelectric materials having suitable thermoelectric properties e.g., Bi2Te 3
- a maximum diameter of the nanowires is preferably less than approximately 200 nm, most preferably between approximately 5 nm and approximately 100 nm.
- the term "diameter” in this context refers to the average of the lengths of the major and minor axis of the cross-section of the nanowires, with the plane being normal to the longitudinal axis of the nanowires.
- Nanowires having diameters of approximately 50 nm to approximately 100 nm that may be prepared using a method of drawing of a thermoelectric material in glass cladding, as described hereinbelow.
- the cables of the present invention preferably are manufactured to exhibit a high uniformity in diameter from end to end.
- the maximum diameter of the glass cladding may vary in a range of less than approximately 10% over the length of the cable.
- the diameter of the nanowires may vary in a larger range (e.g., 5-500 nm, depending on the application).
- the glass is preferably several orders of magnitude more resistive than the thermoelectric material it is employed to clad.
- the cables are generally based on a semiconducting wire, wherein the doping and composition of the wire is primarily controlled by changing the composition of the thermoelectric material to yield a wire that exhibits either p-type or an n-type thermoelectric behavior.
- the cables may be used to develop superior thermoelectric devices in a cost-effective manner.
- a method of drawing a thermoelectric material in glass cladding involves drawing the glass-clad thermoelectric material to form individual fibers (or monofibers) of thermoelectric materials, which are preferably about 500 microns in diameter or less.
- the monofibers may have diameters greater than 500 microns without departing from the scope of the invention. Cable diameters may be brought down to 5-100 nm by repeatedly drawing fiber bundles of monofibers, and the concentration of wires in a cross-section of the cable may be increased to ⁇ 109/cm2 or greater.
- Such cables advantageously exhibit quantum confinement for providing enhanced thermopower generation efficiency.
- the method of drawing a thermoelectric material in glass cladding may further comprise bunching the cable together and redrawing several times in succession to produce a multi-core cable comprising glass-clad thermoelectric fibers.
- the material to forming the fibers of a cable may comprise PbTe or Bi 2 Te 3 .
- the resulting cable comprises a multi-core cable having a plurality of individual fibers that are insulated from each other by the glass cladding.
- a particular glass cladding may be chosen to contain a specific composition to match the physical, chemical, thermal and mechanical properties of a selected thermoelectric material.
- the glass cladding is preferably several orders of magnitude higher in electrical resistivity than the metal, alloy or semiconductor material that forms the thermoelectric fibers.
- Suitable commercial glasses for most applications include, but are not limited to, pyrex, vycor and quartz glass.
- the metal, alloy or semiconductor material that forms the fibers is varied to render a cable either n-type or p-type, such that individual cables may be used as the n-type and p-type components of a thermoelectric device.
- the cables may be induced to exhibit quantum confinement by reducing the thickness or the diameter of the fibers to a predetermined range, thereby increasing the efficiency of thermopower generation.
- vertical tube furnace 10 is employed to provide heat for drawing glass-clad thermoelectric fibers.
- vertical tube furnace 10 includes a central lumen 11 for receiving a preform 12 comprising a glass tube 14 that is sealed at an area of reduced cross-section 18 to form vacuum space 20 that is at least partially filled with thermoelectric material 22.
- the furnace is used to melt the thermoelectric material 22 and glass tube 14 in preparation for one or more drawing operations for producing glass-clad thermoelectric fibers 24.
- vertical tube furnace 10 comprises furnace shroud 26, thermal insulation 28 and muffler tube 30. Suitable materials for muffler tube 30 include conductive metals such as aluminum.
- Vertical tube furnace 10 further comprises one or more heater coils 34 embedded therein. More precisely, heater coils 34 are disposed between muffler tube 30 and thermal insulation 28, and refractory cement 38 is disposed between heater coils 34 and thermal insulation to direct the heat produced by heater coils 34 inwardly to form a hot zone 40 within muffler tube 30.
- Heater coils 34 are provided with leads 44 that may be insulated using a ceramic insulator 48. Additionally, a thermocouple probe 50 is provided for measuring the temperature within hot zone 40, which may include a length of approximately one inch.
- thermoelectrically active material 22 comprising an array of metal, alloy or semiconductor rods embedded in a glass cladding.
- the preferred thermoelectric material of the present invention comprises PbTe that is initially in granular form. Additional suitable thermoelectric materials include, but are not limited to, Bi 2 T ⁇ 3 , SiGe and ZnSb.
- the next step involves selecting a suitable material for forming the glass tubing 14. The glass material preferably is selected to have a fiber drawing temperature range that is slightly greater than the melting temperature of the thermoelectric material (e.g., > 920 ° C for PbTe).
- Vertical tubular furnace 10 is then employed to seal off one end of glass tubing 14. Alternatively, a blowtorch or other heating device may be used to seal off the glass tubing 14 and create vacuum space 20.
- the next steps involve introducing the thermoelectric granules inside the vacuum space 20 and evacuating the tube by attaching the open end of the glass tube to a vacuum pump. While the vacuum pump is on, an intermediate portion of the glass tubing 14 is heated such that the glass partially melts and collapses under the vacuum. The partially melted glass tube provides an ampoule 54 containing the thermoelectric material 22 to be used in a first drawing operation.
- the next step involves introducing the end of ampoule 54 containing the thermoelectric material 22 into the vertical tube furnace 10.
- the tubular furnace 10 is configured such that the ampoule 54 is introduced vertically, wherein the end of the ampoule 54 containing the thermoelectric granules is disposed within hot zone 40 adjacent to heater coils 34.
- the temperature is increased such that the glass encasing the thermoelectric granules melts just enough for it to be drawn, as is done in a conventional glass draw-tower, which is per se known in the art.
- the composition of the glass is preferably chosen such that the fiber drawing temperature range is slightly greater than the melting point of the thermoelectric granules.
- PbTe is selected as the thermoelectric material
- pyrex glass is a suitable material for drawing'the glass with PbTe fibers embedded therein.
- the physical, mechanical and thermal properties of glass tubing 14 and thermoelectric material 22 will have a bearing on the properties of the resulting cables. Glasses exhibiting a minimal deviation of these properties with respect to those of the thermoelectric material 22 are preferably chosen as the cladding material.
- the above-described glass tubing 14 may comprise commercially available pyrex tubing having a 7 mm outside diameter and a 2.75 mm inside diameter, wherein the tube is filled with PbTe granules over a length of about 3.5 inches.
- Evacuation of glass tubing 14 may be achieved overnight under a vacuum of approximately 30 mtorr. After evacuation, the section of glass tubing 14 containing the thermoelectric material 22 is heated gently with a torch for several minutes to remove some residual gas, and then the glass tubing 14 is sealed under vacuum above the level of thermoelectric material 22.
- vertical tube furnace 10 is used for drawing the glass-clad thermoelectric fibers.
- Vertical tube furnace 10 includes a short hot zone 40 of about 1 inch, wherein the preform 12 is placed in the vertical tube furnace 10 with the end of the tube slightly below hot zone 40. With the furnace at about 1030oC, the weight from the lower tube end is sufficient to cause glass tubing 14 to extend under its own weight. When the lower end of glass tubing 14 appears at the lower opening of the furnace, it may be grasped with tongs for hand pulling. Preform 10 may be manually advanced periodically to replenish the preform material being used up during the fiber drawing process.
- Fiber 24 preferably includes a diameter between about 70 microns and about 200 microns. According to additional embodiments of the present invention, the drawing operation may be performed using an automatic draw-tower that results in very little variation in diameter.
- short fiber sections may be formed by drawing the heterostrucrures and then breaking or cutting the heterostructures into shorter pieces.
- these shorter pieces may be machined to be approximately 3 inches in length.
- the pieces are then bundled inside another pyrex tube, which is sealed at one end using the vertical tube furnace or using a blowtorch, as described hereinabove.
- the open end is attached to a vacuum pump and an intermediate section is heated. This heating causes the glass tube to collapse, thereby sealing the tube and forming an ampoule for a second drawing operation, which produces a cable having a plurality of multi-core fibers.
- the fibers are collected and placed in the bore of yet another sealed tube.
- the preform is evacuated and sealed under vacuum. Fiber drawing is then performed on the twice-drawn fibers. This process is repeated as needed to obtain a final thermoelectric material diameter of about 100 nm.
- FIG. 2 depicts an x-ray diffraction pattern of a PbTe-based cable constructed in accordance with the principles of the present invention, wherein the characteristic spectrum of PbTe is overlaid on a glassy x-ray diffraction pattern.
- the x-ray diffraction pattern clearly indicates the presence of PbTe peaks and a lack of other peaks, thus illustrating that the glass material has neither reacted with PbTe nor devitrified during fiber drawing. These peaks are exclusively characteristic to those of PbTe crystals.
- FIG. 3 depicts a glass-clad PbTe-based cable 60 constructed using the method of drawing a thermoelectrically active material embedded in a glass cladding described hereinabove.
- the cable 60 comprises a plurality of multiple monofibers 64 that are bundled and fused to form a cable (or button) of virtually any length. This button can be broken, cut or otherwise sectioned to produce a plurality of shorter cables having a predetermined length.
- FIG. 4 is an enlarged cross-sectional view of the glass-clad PbTe-based cable 60 of FIG. 3 taken along line 3A-3A.
- Cable 60 includes a plurality of monofibers 64, has a width of approximately 5.2 mm, and was produced using a single drawing of the PbTe fibers at a temperature of approximately 300K. According to the preferred embodiment of the invention the cable 60 is bunched together and redrawn several times in succession to produce a multi-core cable having a plurality of individual thermoelectric fibers that are insulated from each other by the glass cladding.
- FIG. 5 is a cross-sectional view of the glass-clad PbTe-based cable 60 after a second drawing of the PbTe fibers. The twice-drawn cable has a width of approximately 2.78 mm.
- FIG. 6 is a cross- sectional view of the glass-clad PbTe-based cable 60 after a third drawing of the PbTe fibers, wherein the cable has a width of approximately 2.09 mm.
- FIGS. 3-6 illustrate the development of microstructure as the concentration of wires in the cable increases to ⁇ 10 /cm . These microstructures may be observed using optical and scanning electron microscopes. By way of example, energy dispersive spectroscopy may be employed to unambiguously indicate the presence of PbTe wires in the glass matrix.
- Another aspect of the present invention involves the continuity and electrical connectivity of the glass embedded fibers along the entire length of the cable. Electrical connectivity is easily demonstrated by determining the resistance of the cable at different thicknesses. According to a preferred implementation of the invention, the resistance of the glass cladding, without any thermoelectric wires embedded therein, is about 7 to 8 orders of magnitude higher than that of the continuous thermoelectric fibers.
- thermoelectric wires are in the form of "buttons" of PbTe prepared from the preforms following the one of the fiber drawing steps.
- the resistance of the thermoelectric wires embedded in the glass is approximately 1 ohm or less.
- the resistance of the glass cladding without thermoelectric wires is more than 10 s ohms, which is about 8 orders of magnitude higher than that of the PbTe-embedded cables. This difference in electrical resistance indicates that the glass-clad thermoelectric wires drawn using the methods described herein exhibit electrical connectivity from one end to the other.
- FlG. 7 is a chart illustrating the DC resistance of PbTe cable 60 after the first drawing of the PbTe fibers, wherein the resistance of the cable (Ohms) is plotted against the electrical current (amps). In particular, the DC resistance of the cable 60 steadily decreases with an increasing current.
- FIG. 8 is a chart illustrating the DC resistance of the cable 60 after the second drawing of the PbTe fibers
- FIG. 9 is a chart illustrating the DC resistance of the PbTe cable 60 after the third drawing of the PbTe fibers.
- a preferred cable produced in accordance with the principles of the present invention preferably comprises at least one thermoelectric fiber embedded in an electrically insulating material, wherein the thermoelectric material exhibits quantum confinement.
- a width of each fiber is substantially equivalent to a width of a single crystal of the thermoelectric material, wherein each fiber has substantially the same crystal orientation.
- the preferred cable comprises a plurality of fibers that are fused or sintered together such that there is electrical connectivity between all the fibers.
- the glass cladding for the cable preferably comprises an electrically insulating material comprising a binary, ternary or higher component glass structure such as pyrex, borosilcate, aluminosilicate, quartz, and lead telluride-silicate.
- the thermoelectric material may be chosen from the group consisting of a metal, a semi-metal, an alloy and a semiconductor, such that the thermoelectric material exhibits electrical connectivity and quantum confinement along a predetermined length of cable from several nanometers to miles.
- the ZT factor of the cable is preferably at least .5, more preferably at least 1.5, most preferably at least 2.5.
- thermoelectric device produced by quantum confinement in nanowires is provided.
- One skilled in the art will appreciate that the present invention can be practiced by other than the various embodiments and preferred embodiments, which are presented in this description for purposes of illustration and not of limitation, and the present invention is limited only by the claims that follow. It is noted that equivalents for the particular embodiments discussed in this description may practice the invention as well.
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US11/301,285 US20070131269A1 (en) | 2005-12-09 | 2005-12-09 | High density nanowire arrays in glassy matrix |
US11/299,283 US7559215B2 (en) | 2005-12-09 | 2005-12-09 | Methods of drawing high density nanowire arrays in a glassy matrix |
PCT/US2006/046500 WO2007070299A2 (en) | 2005-12-09 | 2006-12-05 | High density nanowire arrays in a glassy matrix, and methods for drawing the same |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1958272A2 true EP1958272A2 (en) | 2008-08-20 |
EP1958272A4 EP1958272A4 (en) | 2011-09-28 |
Family
ID=38163403
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP06844870A Withdrawn EP1958272A4 (en) | 2005-12-09 | 2006-12-05 | High density nanowire arrays in a glassy matrix, and methods for drawing the same |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP1958272A4 (en) |
JP (1) | JP5199114B2 (en) |
KR (1) | KR101319157B1 (en) |
CN (1) | CN102820419A (en) |
BR (1) | BRPI0620554A2 (en) |
CA (1) | CA2631366A1 (en) |
IL (1) | IL191802A (en) |
MY (1) | MY144334A (en) |
WO (1) | WO2007070299A2 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4742958B2 (en) * | 2006-04-04 | 2011-08-10 | 株式会社デンソー | Method for manufacturing thermoelectric conversion element |
GB0812483D0 (en) * | 2008-07-08 | 2009-01-07 | Bae Systems Plc | Electrical Circuit Assemblies and Structural Components Incorporating same |
JP5056673B2 (en) * | 2008-08-26 | 2012-10-24 | 株式会社デンソー | Thermoelectric conversion element and manufacturing method thereof |
JP5083145B2 (en) * | 2008-09-24 | 2012-11-28 | 株式会社デンソー | Thermoelectric conversion element |
WO2013119284A2 (en) * | 2011-11-08 | 2013-08-15 | Ut-Battelle, Llc | Manufacture of thermoelectric generator structures by fiber drawing |
US10112321B2 (en) * | 2013-03-13 | 2018-10-30 | Massachusetts Institute Of Technology | High-pressure in-fiber particle production with precise dimensional control |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2454620B1 (en) * | 1974-11-18 | 1976-02-12 | Kraftwerk Union Ag | Coaxial half-finished thermoelement of any length - which is flexible, of extremely low inertia and insertable in any medium |
US4652288A (en) * | 1984-08-04 | 1987-03-24 | Horiba, Ltd. | Method of producing infrared image guide |
US5215565A (en) * | 1987-04-14 | 1993-06-01 | Sumitomo Electric Industries, Ltd. | Method for making superconductor filaments |
US6231744B1 (en) * | 1997-04-24 | 2001-05-15 | Massachusetts Institute Of Technology | Process for fabricating an array of nanowires |
US20030079770A1 (en) * | 2001-10-24 | 2003-05-01 | Bell Lon E. | Thermoelectric hetrostructure assemblies element |
US6670539B2 (en) * | 2001-05-16 | 2003-12-30 | Delphi Technologies, Inc. | Enhanced thermoelectric power in bismuth nanocomposites |
US6772611B2 (en) * | 2001-02-06 | 2004-08-10 | Sandia National Laboratories | Making a glass rod with a step of measuring an incremental weight gain |
US6898357B2 (en) * | 2001-03-16 | 2005-05-24 | Optonest Corporation | Method of fabricating an optical fiber preform using MCVD and nonlinear optical fiber fabricated using the method |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2958451B1 (en) * | 1998-03-05 | 1999-10-06 | 工業技術院長 | Thermoelectric conversion material and method for producing the same |
JP3032826B2 (en) * | 1998-03-05 | 2000-04-17 | 工業技術院長 | Thermoelectric conversion material and method for producing the same |
US7098393B2 (en) * | 2001-05-18 | 2006-08-29 | California Institute Of Technology | Thermoelectric device with multiple, nanometer scale, elements |
-
2006
- 2006-12-05 EP EP06844870A patent/EP1958272A4/en not_active Withdrawn
- 2006-12-05 WO PCT/US2006/046500 patent/WO2007070299A2/en active Application Filing
- 2006-12-05 CN CN2012102300904A patent/CN102820419A/en active Pending
- 2006-12-05 JP JP2008544460A patent/JP5199114B2/en not_active Expired - Fee Related
- 2006-12-05 BR BRPI0620554A patent/BRPI0620554A2/en not_active IP Right Cessation
- 2006-12-05 KR KR1020087016542A patent/KR101319157B1/en not_active IP Right Cessation
- 2006-12-05 CA CA002631366A patent/CA2631366A1/en not_active Abandoned
-
2008
- 2008-05-28 IL IL191802A patent/IL191802A/en not_active IP Right Cessation
- 2008-06-05 MY MYPI20081956A patent/MY144334A/en unknown
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2454620B1 (en) * | 1974-11-18 | 1976-02-12 | Kraftwerk Union Ag | Coaxial half-finished thermoelement of any length - which is flexible, of extremely low inertia and insertable in any medium |
US4652288A (en) * | 1984-08-04 | 1987-03-24 | Horiba, Ltd. | Method of producing infrared image guide |
US5215565A (en) * | 1987-04-14 | 1993-06-01 | Sumitomo Electric Industries, Ltd. | Method for making superconductor filaments |
US6231744B1 (en) * | 1997-04-24 | 2001-05-15 | Massachusetts Institute Of Technology | Process for fabricating an array of nanowires |
US6772611B2 (en) * | 2001-02-06 | 2004-08-10 | Sandia National Laboratories | Making a glass rod with a step of measuring an incremental weight gain |
US6898357B2 (en) * | 2001-03-16 | 2005-05-24 | Optonest Corporation | Method of fabricating an optical fiber preform using MCVD and nonlinear optical fiber fabricated using the method |
US6670539B2 (en) * | 2001-05-16 | 2003-12-30 | Delphi Technologies, Inc. | Enhanced thermoelectric power in bismuth nanocomposites |
US20030079770A1 (en) * | 2001-10-24 | 2003-05-01 | Bell Lon E. | Thermoelectric hetrostructure assemblies element |
Non-Patent Citations (2)
Title |
---|
ABRAMSON A R ET AL: "FABRICATION AND CHARACTERIZATION OF A NANOWIRE/POLYMER-BASED NANOCOMPOSITE FOR A PROTOTYPE THERMOELECTRIC DEVICE", JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, IEEE SERVICE CENTER, PISCATAWAY, NJ, US, vol. 13, no. 3, 1 June 2004 (2004-06-01), pages 505-513, XP011113573, ISSN: 1057-7157, DOI: 10.1109/JMEMS.2004.828742 * |
See also references of WO2007070299A2 * |
Also Published As
Publication number | Publication date |
---|---|
MY144334A (en) | 2011-08-29 |
KR20080091136A (en) | 2008-10-09 |
CN102820419A (en) | 2012-12-12 |
KR101319157B1 (en) | 2013-10-17 |
IL191802A0 (en) | 2008-12-29 |
CA2631366A1 (en) | 2007-06-21 |
JP2009518866A (en) | 2009-05-07 |
JP5199114B2 (en) | 2013-05-15 |
IL191802A (en) | 2013-10-31 |
WO2007070299A2 (en) | 2007-06-21 |
BRPI0620554A2 (en) | 2017-11-21 |
EP1958272A4 (en) | 2011-09-28 |
AU2006324440A1 (en) | 2007-06-21 |
WO2007070299A3 (en) | 2008-04-24 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7530239B2 (en) | Method of drawing a glass clad multi core lead telluride wire | |
US20070131269A1 (en) | High density nanowire arrays in glassy matrix | |
US8143151B2 (en) | Nanowire electronic devices and method for producing the same | |
CN101836285B (en) | Nanostructures having high performance thermoelectric properties | |
Liang et al. | Thermoelectric properties of p-type PbSe nanowires | |
JP5677713B2 (en) | Thermal-electrical conversion device using the Savebeck / Pelty effect using processed layers made of semiconductor material without the need for nanostructures | |
WO2001093343A2 (en) | Nanostructured thermoelectric materials and devices | |
IL191802A (en) | High density nanowire arrays in a glassy matrix and mehods for drawing the same | |
WO2003096438A2 (en) | Self-assembled quantum dot superlattice thermoelectric materials and devices | |
JPH11317548A (en) | Thermoelectric conversion material and manufacture thereof | |
US8658880B2 (en) | Methods of drawing wire arrays | |
Smith et al. | Macro to nano: scaling effects of Bi2Te3 thermoelectric generators for applications in space | |
AU2006324440B2 (en) | High density nanowire arrays in a glassy matrix, and methods for drawing the same | |
US20070084499A1 (en) | Thermoelectric device produced by quantum confinement in nanostructures | |
Yang et al. | Characterization of cross-plane thermoelectric properties of Si/Ge superlattices | |
WO2001017035A1 (en) | Quantum dot thermoelectric materials and devices | |
Meglei | Some properties of Bi2Te3 and PbTe crystals and converters on their basis | |
WO2007047451A2 (en) | Thermoelectric device produced by quantum confinement in nanostructures, and methods therefor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 20080604 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TR |
|
AX | Request for extension of the european patent |
Extension state: AL BA HR MK RS |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: H01L 35/26 20060101ALI20110818BHEP Ipc: H01L 35/16 20060101ALI20110818BHEP Ipc: C03B 37/028 20060101ALI20110818BHEP Ipc: C03B 37/026 20060101ALI20110818BHEP Ipc: C03B 37/012 20060101ALI20110818BHEP Ipc: H01L 35/20 20060101ALI20110818BHEP Ipc: H01L 35/34 20060101AFI20110818BHEP |
|
A4 | Supplementary search report drawn up and despatched |
Effective date: 20110825 |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: H01L 35/26 20060101ALI20110819BHEP Ipc: H01L 35/16 20060101ALI20110819BHEP Ipc: C03B 37/028 20060101ALI20110819BHEP Ipc: C03B 37/026 20060101ALI20110819BHEP Ipc: C03B 37/012 20060101ALI20110819BHEP Ipc: H01L 35/20 20060101ALI20110819BHEP Ipc: H01L 35/34 20060101AFI20110819BHEP |
|
DAX | Request for extension of the european patent (deleted) | ||
17Q | First examination report despatched |
Effective date: 20140414 |
|
18D | Application deemed to be withdrawn |
Effective date: 20151009 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
R18D | Application deemed to be withdrawn (corrected) |
Effective date: 20150701 |