Patent Application
20240425378
An electrolysis cell is a container containing an electrolyte through which an externally generated electric current is passed via a system of electrodes (e.g., an anode and cathode) in order to change the composition of a material. For example, an aluminum compound (e.g., Al2O3) may be decomposed into pure aluminum metal (Al) via an electrolysis cell. Traditionally, the electrodes of aluminum electrolysis cells are made from carbon.
Broadly, the present disclosure relates to methods of making electrodes for use in electrochemical cells, such as an aluminum electrolysis cell or an aluminum purification cell. In some embodiments, the method includes forming a TiB2 feedstock into a predetermined shaped product to realize an appropriate density, average grain size, intergranular porosity, average pore size, and/or random grain orientation.
Referring now to
As noted above, a TiB2 feedstock may be used to form the predetermined shaped product. Referring now to
As noted above, a method may comprise forming a TiB2 feedstock into a predetermined shaped product (110). Referring now to
As noted above, the forming step (110) may include pressing (114) a TiB2 feedstock into a predetermined shaped product. With continued reference to
As noted above, the forming step (110) may include casting (120) a TiB2 feedstock into a predetermined shaped product. With continued reference to
As noted above, the predetermined shaped product that is formed from a TiB2 feedstock may realize a density of from 40% to 70% of a theoretical density of pure TiB2. In one embodiment, the predetermined shaped product realizes a density of at least 45% of the theoretical density of pure TiB2. In another embodiment, the predetermined shaped product realizes a density of at least 50% of the theoretical density of pure TiB2. In yet another embodiment, the predetermined shaped product realizes a density of at least 55% of the theoretical density of pure TiB2. In another embodiment, the predetermined shaped product realizes a density of at least 58% of the theoretical density of pure TiB2. In yet another embodiment, the predetermined shaped product realizes a density of at least 60% of the theoretical density of pure TiB2. In one embodiment, the predetermined shaped product realizes a density of not greater than 68% of the theoretical density of pure TiB2.
As noted above, a method may comprise producing a final shaped product from the predetermined shaped product (130). Referring now to
As noted above, and with continued reference to
As noted above, and with continued reference to
As noted above, the producing step (130) may comprise first heating the predetermined shaped product at a first temperature and for a first period of time (140). In one embodiment, the first heating comprises heating from an initial temperature to the first temperature at a first heating rate. In one embodiment, the initial temperature is ambient temperature. In one embodiment, the first heating rate is not greater than 10° C./min. In another embodiment, the first heating rate is not greater than 8° C./min. In yet another embodiment, the first heating rate is not greater than 6° C./min. In another embodiment, the first heating rate is not greater than 5° C./min.
As noted above, the producing step (130) may comprise second heating the predetermined shaped product at a second temperature and for a second period of time (144). In one embodiment, the second heating comprises heating from the first temperature to the second temperature at a second heating rate. In one embodiment, the second heating rate is not greater than 8° C./min. In another embodiment, the second heating rate is not greater than 7° C./min. In yet another embodiment, the second heating rate is not greater than 6° C./min. In another embodiment, the second heating rate is not greater than 5° C./min.
As noted above, and with continued reference to
As noted above, the final shaped product that is produced from the predetermined shaped product may realize an average grain size of not greater than 15 micrometers. With continued reference to
As noted above, the final shaped product that is produced from the predetermined shaped product may realize from 1 to 15 vol. % intergranular porosity. With continued reference to
As noted above, the final shaped product that is produced from the predetermined shaped product may realize an average pore size not greater than 120% of the average grain size. With continued reference to
As noted above, a method may comprise producing a final shaped product from a predetermined shaped product (130). In one embodiment, the final shaped product realizes an ODF intensity of not greater than 3 times random. In another embodiment, the final shaped product realizes an ODF intensity of not greater than 2.75 times random. In yet another embodiment, the final shaped product realizes an ODF intensity of not greater than 2.5 times random. In another embodiment, the final shaped product realizes an ODF intensity of not greater than 2.25 times random. In yet another embodiment, the final shaped product realizes an ODF intensity of not greater than 2.0 times random. In another embodiment, the final shaped product realizes an ODF intensity of not greater than 1.75 times random. In yet another embodiment, the final shaped product realizes an ODF intensity of not greater than 1.5 times random.
As noted above, a method may comprise forming a TiB2 feedstock into a predetermined shaped product (110). Referring now to
As noted above, due to one or more of a dispersant and a binder, TiB2 granules may realize one or more properties. Referring now to
As noted above, a method may comprise preparing a TiB2 feedstock (90) for the forming step (110). Referring now to
As noted above, prior to the preparing step (90), a method may comprise a deagglomeration step (50), and the deagglomeration step (50) may comprise deagglomerating a first TiB2 powder to produce a second TiB2 powder. Referring now to
As noted above, a method may comprise producing a final shaped product from the predetermined shaped product (130). In one approach, the final shaped product is an electrode. In one embodiment, the electrode is a cathode. In another embodiment, the electrode is an anode.
In one embodiment, an electrochemical cell comprises the final shaped product in the form of an electrode. The electrochemical cell may include any number and type of final shaped products in the form of an electrode, i.e., an electrochemical cell may include any number of final shaped products in the form of anode(s) and/or cathode(s) therein. In one embodiment, the electrochemical cell is an aluminum electrolysis cell. In another embodiment, the electrochemical cell is an aluminum purification cell.
In one embodiment, a method may include using the final shaped product as an electrode in an electrochemical cell. In one embodiment, the electrochemical cell is an aluminum electrolysis cell wherein the final shaped product is an electrode and the electrode is used to produce aluminum metal in the aluminum electrolysis cell (e.g., as anode(s) and/or cathode(s)). In another embodiment, the electrochemical cell is an aluminum purification cell wherein the final shaped product is an electrode and the electrode is used to produce aluminum in an aluminum purification cell (e.g., as an anode(s) and/or cathode(s)).
The TiB2 powders may have a median particle size. As used herein, “median particle size” is defined per ASTM B822. Median particle size values of the TiB2 powders are measured using a Malvern Mastersizer 2000 according to ASTM B822. As noted above, the TiB2 powders may have a surface area. Surface area values of TiB2 powders are measured using a Micromeritics Tristar II Plus according to ASTM C1274. As noted above, the TiB2 powders may have an oxygen content and a carbon content. Oxygen content of TiB2 powders is measured using a LECO ON836 according to ASTM 1409. Carbon content of TiB2 powders is measured using a LECO CS844 according to ASTM E1915.
As noted above, the TiB2 powders may have an irregular particle morphology. As used herein, the term “irregular particle morphology” means the particles are angular and have no specific shape, i.e., no regular/repeated geometric shapes are seen in a scanning electron micrograph of TiB2 powders having an irregular morphology. As noted above, the TiB2 granules may have a PSD D90 or a PSD D10. As used herein, “particle size distribution” or “PSD” refers to the relative amounts of particles present, sorted according to the number of sizes present. For example, a PSD D10 of 7 microns means that 10% of the particles are smaller than about 7 microns while 90% of the particles are equal to or greater than about 7 microns. As another example, a PSD D50 of 12 microns means that half of the particles are smaller than about 12 microns while the other half are equal to or greater than about 12 microns, and PSD D90 of 20 microns means that 90% of the particles are smaller than about 20 microns while 10% of the particles are equal to or greater than about 20 microns. Generally, in referencing the same material, the particle size distributions of D10 to D90 will be ascending (i.e., D90 values are larger than both D50 and D10 values, while D50 values are larger than D10 values). Although D10, D50, and D90 are referenced herein, it is readily recognized that in measuring the particle size, the PSD may be any PSD that is useful, and is not limited to D10, D50, and D90 values. Particle size distribution values of the TiB2 powders were measured according to ASTM B214.
As noted above, the TiB2 granules may have a bulk density, moisture content, and flow rate. The bulk density of the TiB2 granules is measured according to ASTM D7481. The moisture content of the TiB2 granules is measured using a Mettler Toledo Moisture Analyzer HE53. The flow rate of the TiB2 granules is measured according to ASTM B213.
As noted above, the predetermined shaped product (e.g., green electrode) may have a density. The density of the predetermined shaped product is calculated using the total mass and the dimensions of the predetermined shaped product.
As noted above, the final shaped product (e.g., TiB2 plate) may have a density. The density of the final shaped product is measured according to ASTM B962.
As noted above, the predetermined shaped product and final shaped product may have a theoretical density. A theoretical density (ptheory) is the highest density that a material could achieve as calculated from the atomic weight and crystal structure.
Where: Nc=number of atoms in unit cell
For the purposes of this patent application the theoretical density is 4.52 g/cc, which is the approximate theoretical density of pure TiB2.
As noted above, the final shaped product may have an average grain size and an average pore size. As used herein, “average grain size” and “average pore size” are defined according to ASTM E112. As used herein, “pore” means a generally small (e.g., ≤1 cm) opening or interstice due to exposing the predetermined shaped product to one or more elevated temperatures. As used herein “porosity” means the ratio of the volume of pores in a material to a volume of the material. As used herein “intergranular porosity” means porosity that is in between TiB2 grains, as opposed to “intragranular porosity,” which means porosity within a TiB2 grain.
As noted above, the final shaped products are analyzed via scanning electron microscopy. Scanning electron microscopy is performed using a JOEL SEM instrument or other suitable SEM. Samples for SEM analysis are prepared by first obtaining sections of plates via electron discharge machining, diamond saw cutting, or other appropriate machining methods. Samples are then mounted and ground using diamond, silicon carbide, or other grinding media until the sample is flat. Finally, samples are polished to an acceptable finish using diamond, silicon carbide, alumina, silica or other polishing media.
Samples are analyzed via scanning electron (SE) mode and electron backscatter diffraction (EBSD) mode. The average grain size of the final shaped product is measured using SEM in EBSD mode via orientation imaging microscopy (OIM) analysis. Briefly, EBSD patterns are obtained by tilting the sample to about 70° and obtaining a diffraction pattern of the sample. The resulting Kikuchi patterns are analyzed to obtain grain orientation information.
As noted above, the final shaped product may have an average pore size. The average pore size and the vol. % of intergranular and intragranular porosity are measured on an SEM micrograph according to a modified procedure of ASTM E112 § 13 (linear intercept method). Briefly, three lines are drawn on an SEM micrograph. The lengths of each pore intersecting each line are measured. The OIM image is used to determine whether each measured pore is an intergranular pore or an intragranular pore. The average of these lengths is calculated to obtain an average intergranular pore size and an average intragranular pore size. The intergranular pore lengths are added to obtain a sum of intergranular pores. The intragranular pore lengths are added to obtain a sum of intragranular pores. All measured pore lengths are then added to obtain a sum of all pore lengths. A volume % of intragranular and intragranular porosity is calculated from the above values. A total pore volume is calculated by dividing the sum of all pore lengths by the sum of all three line lengths.
As used herein, “random grain orientation” means that there is no or limited preference for grains to align in a specific direction, i.e., the crystallographic orientation of a grain is independent of the crystallographic orientation of its neighbors.
The distribution of crystallographic orientations within a sample of polycrystalline TiB2 can be determined from the inverse pole figure. The inverse pole figure is a stereographic projection with orientation aligned to one of the known axis of the specimen's identified crystal structure.
The inverse pole figure is derived from electron back scatter patterns generated in a scanning electron microscope where intersecting bands of diffracted electrons represent crystallographic planes of a crystalline sample.
The diffracted beam produces a pattern composed of intersecting bands, termed electron backscatter patterns. These patterns can be used to determine the orientation of the crystal lattice with respect to a specific crystallographic direction.
Measured intensities of the represented crystallographic orientation are generally normalized by calculating the amount of background intensity, or random intensity, and comparing that background intensity to the intensity of the orientations present in the image.
Orientation Imaging Microscopy (OIM) employs electron back scatter patterns to analyze the orientation of each crystallite or grain being imaged in a sample.
OIM analysis may determine a background (random) intensity and use orientation distribution functions (ODFs) to produce relative ODF intensity values for a population of a sample's imaged crystallites.
A series of ODF plots containing intensity (times random) representations may be created for imaged samples.
ODF plots contain maximum intensity ratings relative to a predetermined scale and can be used as a quantitative measure of the degree of orientation among a polycrystalline sample's individual crystallites.
Higher ODF intensities indicate a high degree of crystallographic orientation among crystallites within a sample and lower ODF intensities indicate a lower degree of orientation, relative to the sample's population of individual crystallites.
As noted above, the disclosed final shaped products in the form of electrodes may be used in an aluminum electrolysis cell. As used herein, an “aluminum electrolysis cell” is a cell where the cathode is at the bottom of the cell, the anode is at the top of the cell, and the produced aluminum moves to the bottom of the cell. One example of an aluminum electrolysis cell can be found in commonly owned U.S. Patent Publication No. 2017/0283968, entitled Apparatuses and Systems for Vertical Electrolysis Cells, and filed on Mar. 30, 2017.
As noted above, the disclosed final shaped products in the form of electrodes may be used in an aluminum purification cell. As used herein, an “aluminum purification cell,” is a cell where the cathode is at the top of the cell, the anode is at the bottom of the cell, and the purified aluminum moves to the top of the cell. One example of an aluminum purification cell can be found in commonly owned U.S. Pat. No. 10,407,786, entitled Systems and Methods for Purifying Aluminum, and filed on Feb. 11, 2016.
The above examples are intended to illustrate the invention and should not be construed as limiting the invention in any way.
Reference is now made to the accompanying figures, which at least partially illustrate various pertinent features of the technology disclosed herein. The figures shown are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the present invention. Further, some features may be exaggerated to show details of particular components. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.
Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases “in one embodiment” and “in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though they may. Furthermore, the phrases “in another embodiment” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment, although they may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.
In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on”.
These and other aspects, advantages, and novel features of this new technology are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing one or more embodiments of the technology provided by the present disclosure.
While the present disclosure is generally directed to products and methods of making products (e.g., electrodes) for use in aluminum electrochemical cells, such as an aluminum electrolysis cell or an aluminum purification cell, the products and methods described herein are applicable to other electrochemical cells, such as a magnesium electrolysis cell or a magnesium purification cell.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
Two plates were made, one invention and one non-invention. The invention plate is described in further detail below. A first powder having TiB2 particles was deagglomerated to produce a second powder having TiB2 particles. The deagglomeration was done by jet milling.
The properties of the second powder were measured. The results are shown below:
The deagglomerated TiB2 powder was then mixed with water, a dispersant and a binder to form a slurry. The slurry was then spray dried to form TiB2 granules with the following properties:
About 10 kg of spray dried TiB2 granules were transferred to a 26.5 inch×14.5 inch die. 7500 psi of pressure was then applied to the die at room temperature to form a green electrode (e.g., a predetermined shaped product). The green electrode had a density of about 60% of the theoretical density of TiB2.
The green electrode was then sintered by first heating to 500° C. at a rate of 5° C./min, then holding at 500° C. for one hour, then heating to 1825° C. at a rate of 5° C./min, and then holding at 1825° C. for 12 hours, thereby producing a final TiB2 plate (e.g., a final shaped product) (130). After holding at 1825° C., the final TiB2 plate was cooled in a furnace until it reached ambient temperature. The density of the final TiB2 plate was measured to be 4.10 g/cc (90.7% of the theoretical density of TiB2).
A non-invention plate was made via conventional methods, e.g., uniaxial hot pressing. TiB2 powder was loaded between two graphite plates inside a graphite die. Uniaxial pressure was applied to the major faces of the graphite plates while simultaneously heating the graphite die to greater than 1800° C. The TiB2 powder densified into a near-final shaped product which was then machined to remove surface reaction layers. The density of the comparative plate was measured to be 4.335 g/cc (95.9% of the theoretical density of TiB2).
Ceramic manufacturing techniques other than dry pressing can be used to form the green electrode. Possible green electrode forming techniques include but are not limited to: pressing TiB2 granules in an isostatic press, roll compacting TiB2 granules, extruding TiB2 powder, and casting TiB2 powder into the desired predetermined shape.
This application is a continuation of International Patent Application No. PCT/US2023/015120, entitled “Electrodes for Aluminum Electrolysis Cells and Methods of Making the Same,” filed Mar. 13, 2023, which claims the benefit of U.S. Provisional Patent Application No. 63/319,903, entitled “Electrodes for Aluminum Electrolysis Cells and Methods of Making the Same,” filed Mar. 15, 2022. Each of the above-identified patent applications is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63319903 | Mar 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2023/015120 | Mar 2023 | WO |
| Child | 18829880 | US |
