Electrode for aluminum electrolysis cell and method for producing same

Abstract

The present disclosure relates to a method for producing an electrode for use in an electrolysis cell, the method comprising: 2 The method includes forming the feedstock into a shaped article to achieve a suitable density. The method also includes producing a final shaped article from the shaped article by exposing the shaped article to an elevated temperature. The exposing step results in the final shaped article having a plurality of pores and achieving one or more properties and / or characteristics.

Description

[Background technology]

[0001] An electrolysis cell is a vessel containing an electrolyte in which an externally generated electric current is passed through a system of electrodes (e.g., anodes and cathodes) to change the composition of the material. For example, aluminum compounds (e.g., Al2O3) are decomposed into pure aluminum metal (Al) through an electrolysis cell. Traditionally, the electrodes of an aluminum electrolysis cell are made of carbon. Summary of the Invention

[0002] Broadly, the present disclosure relates to a method for manufacturing an electrode for use in an electrochemical cell, such as an aluminum electrolysis cell or an aluminum purification cell. In some embodiments, the method includes forming a TiB2 feedstock into a shaped article to achieve the appropriate density, average grain size, intergranular porosity, average pore size, and / or random grain orientation.

[0003] Referring to FIG. 1, in one aspect, a method (100) includes forming (110) a TiB2 feedstock into a predetermined shaped product and producing (130) a final shaped product from the predetermined shaped product. In one embodiment, the predetermined shaped product achieves a density between 40% and 70% of a theoretical density, which is the density of pure TiB2. In another embodiment, the density is a preselected density, and the predetermined shaped product achieves a preselected density, the preselected density being between 40% and 70% of the theoretical density. In one embodiment, the producing step (130) includes exposing the predetermined shaped product to one or more elevated temperatures. In one embodiment, the exposing step, at least in part, results in the final shaped product achieving a plurality of porosity and one or more properties. In one embodiment, referring to Figure 3a, the one or more properties (132) realized by the final shaped product may be at least one of: (i) a density between 85% and 98% of the theoretical density of pure TiB2, (ii) an average grain size of 15 micrometers or less, (iii) an intergranular porosity between 1 and 15 volume percent, (iv) an average pore size of 120% or less of the average grain size, and (v) a random grain orientation. In other embodiments, the one or more properties (132) realized by the final shaped product may include one or more of (i)-(v) above and may be selected prior to manufacturing the final shaped product.

[0004] As discussed above, the TiB2 raw material can be used to form a shaped product. Referring now to FIG. 2, in one embodiment, the TiB2 raw material comprises TiB2 particles (20). In another embodiment, the TiB2 raw material comprises TiB2 granules (30). In yet another embodiment, the TiB2 raw material comprises a combination of TiB2 particles (20) and TiB2 granules (30). In another embodiment, the TiB2 raw material consists mostly of TiB2 particles (20). In yet another embodiment, the TiB2 raw material consists mostly of TiB2 granules (30). In another embodiment, the TiB2 raw material consists essentially of TiB2 particles (20). In yet another embodiment, the TiB2 raw material consists essentially of TiB2 granules (30).

[0005] As discussed above, the method can include forming (110) the TiB2 feedstock into a shaped product. Referring now to FIG. 2, in one embodiment, the forming step (110) involves forming the TiB2 feedstock into a shaped product using one or more of pressing (114), casting (120), and extruding (126). In one embodiment, the forming step is completed at ambient temperature. In one embodiment, the forming step (110) includes applying a pressure of at least 5000 psi. In another embodiment, the forming step (110) includes applying a pressure of at least 6000 psi. In yet another embodiment, the forming step (110) includes applying a pressure of at least 7000 psi. In another embodiment, the forming step (110) includes applying a pressure of at least 7500 psi.

[0006] As noted above, the forming step (110) can include pressing (114) the TiB2 feedstock into a shaped product. With continued reference to FIG. 2, in one embodiment, the pressing step (114) includes isostatic pressing (116). In one embodiment, the pressing step (114) includes ambient temperature pressing (117). In one embodiment, the pressing step (114) includes uniaxial dry pressing (118).

[0007] As noted above, the forming step (110) can include casting (120) the TiB2 feedstock into a shaped article. With continued reference to FIG. 2, in one embodiment, the casting step (120) includes slip casting (122). In another embodiment, the casting step (120) includes tape casting (124).

[0008] As discussed above, the shaped product formed from the TiB2 feedstock may achieve a density between 40% and 70% of the theoretical density of pure TiB2. In one embodiment, the shaped product achieves a density of at least 45% of the theoretical density of pure TiB2. In another embodiment, the shaped product achieves a density of at least 50% of the theoretical density of pure TiB2. In yet another embodiment, the shaped product achieves a density of at least 55% of the theoretical density of pure TiB2. In another embodiment, the shaped product achieves a density of at least 58% of the theoretical density of pure TiB2. In yet another embodiment, the shaped product achieves a density of at least 60% of the theoretical density of pure TiB2. In one embodiment, the shaped product achieves a density of 68% or less of the theoretical density of pure TiB2.

[0009] As discussed above, the method can include producing (130) a final shaped product from the shaped product. Now referring to Figures 1 and 3c, in one embodiment, the producing step (130) includes a first heating (140) of the shaped product at a first temperature for a first time. In one embodiment, the producing step includes a second heating (144) of the shaped product at a second temperature for a second time. In one embodiment, the second temperature is higher than the first temperature.

[0010] As noted above, and with continued reference to Figures 1 and 3c, the manufacturing step (130) can include first heating (140) the shaped article at a first temperature for a first time period, which can be performed isothermally or non-isothermally. In one embodiment, the first temperature is at least 200°C (141). In another embodiment, the first temperature is at least 300°C. In yet another embodiment, the first temperature is at least 400°C. In another embodiment, the first temperature is at least 500°C. In one embodiment, the first time period is at least 1 minute (143). In another embodiment, the first time period is at least 10 minutes. In yet another embodiment, the first time period is at least 30 minutes. In another embodiment, the first time period is at least 60 minutes. In one embodiment, the first temperature is no greater than 1200°C. In one embodiment, the first time period is no greater than 48 hours. In one embodiment, the first heating step is carried out at a first temperature for a first time sufficient to remove volatile compounds (e.g., organics) that may be undesirable to be present during a subsequent heating step, such as a second heating step described herein.

[0011] As noted above, and with continued reference to FIG. 1 and FIG. 3c, the manufacturing step (130) can include subjecting the shaped article to a second heating (144) at a second temperature for a second time period, which can be performed isothermally or non-isothermally. In one embodiment, the second temperature is at least 1600° C. (145). In another embodiment, the second temperature is at least 1700° C. In yet another embodiment, the second temperature is at least 1800° C. In another embodiment, the second temperature is at least 1825° C. In one embodiment, the second time period is at least 1 minute. In another embodiment, the second time period is at least 10 minutes. In yet another embodiment, the second time period is at least 30 minutes. In another embodiment, the second time period is at least 1 hour (147). In yet another embodiment, the second time period is at least 4 hours. In another embodiment, the second time period is at least 8 hours. In yet another embodiment, the second time period is at least 12 hours. In one embodiment, the second temperature is no greater than 2300° C. In one embodiment, the second period of time is up to 96 hours.

[0012] As discussed above, the manufacturing step (130) can include a first heating (140) of the shaped article at a first temperature for a first time. In one embodiment, the first heating includes 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 10° C. / min or less. In another embodiment, the first heating rate is 8° C. / min or less. In yet another embodiment, the first heating rate is 6° C. / min or less. In another embodiment, the first heating rate is 5° C. / min or less.

[0013] As discussed above, the manufacturing step (130) can include subjecting the shaped article to a second heating (144) at a second temperature for a second time. In one embodiment, the second heating includes heating from the first temperature to the second temperature at a second heating rate. In one embodiment, the second heating rate is 8° C. / min or less. In another embodiment, the second heating rate is 7° C. / min or less. In yet another embodiment, the second heating rate is 6° C. / min or less. In another embodiment, the second heating rate is 5° C. / min or less.

[0014] As discussed above, with continued reference to FIG. 1 and FIG. 3b, a final shaped product produced from the pre-determined shaped product achieves at least one of the following properties (132): (i) a density between 85% and 98% of the theoretical density of pure TiB2; (ii) an average grain size of 15 micrometers or less; (iii) an intergranular porosity between 1 and 15 volume percent; (iv) an average pore size of 120% or less of the average grain size; and (v) random grain orientation. In one embodiment, the final shaped product achieves at least two of (i)-(v). In another embodiment, the final shaped product achieves at least three of (i)-(v). In yet another embodiment, the final shaped product achieves at least four of (i)-(v). In another embodiment, the final shaped product achieves all of (i)-(v).

[0015] As noted above, the final shaped product produced from the pre-shaped product may achieve an average grain size of 15 micrometers or less. With continued reference to FIG. 3b, in one embodiment, the final shaped product achieves an average grain size (133) of 12 micrometers or less. In another embodiment, the final shaped product achieves an average grain size (133) of 10 micrometers or less. In yet another embodiment, the final shaped product achieves an average grain size (133) of 8 micrometers or less. In another embodiment, the final shaped product achieves an average grain size (133) of 6 micrometers or less. In yet another embodiment, the final shaped product achieves an average grain size (133) of 4 micrometers or less.

[0016] As discussed above, the final shaped product produced from the shaped product may achieve an intergranular porosity of 1-15% by volume. With continued reference to FIG. 3b, in one embodiment, the final shaped product achieves an intergranular porosity (134) of 14% by volume or less. In another embodiment, the final shaped product achieves an intergranular porosity of 13% by volume or less. In one embodiment, the final shaped product achieves an intergranular porosity (135) of at least 2% by volume. In another embodiment, the final shaped product achieves an intergranular porosity of at least 4% by volume. In yet another embodiment, the final shaped product achieves an intergranular porosity of at least 6% by volume. In another embodiment, the final shaped product achieves an intergranular porosity of at least 8% by volume.

[0017] As discussed above, the final shaped product produced from the pre-defined shaped product can achieve an average pore size of 120% or less of the average grain size. With continued reference to FIG. 3b, in one embodiment, the final shaped product achieves an average pore size (136) of 110% or less of the average grain size. In another embodiment, the final shaped product achieves an average pore size of 100% or less of the average grain size. In yet another embodiment, the final shaped product achieves an average pore size of 90% or less of the average grain size. In another embodiment, the final shaped product achieves an average pore size of 80% or less of the average grain size. In yet another embodiment, the final shaped product achieves an average pore size of 70% or less of the average grain size. In another embodiment, the final shaped product achieves an average pore size of 60% or less of the average grain size. The final shaped product achieves an average pore size of 60% or less of the average grain size. In yet another embodiment, the final shaped product achieves an average pore size of 50% or less of the average grain size.

[0018] As discussed above, the method may include producing 130 a final shaped product from the predetermined shaped product. In one embodiment, the final shaped product achieves a random ODF strength of no more than 3 times. In another embodiment, the final shaped product achieves a random ODF strength of no more than 2.75 times. In yet another embodiment, the final shaped product achieves a random ODF strength of no more than 2.5 times. In another embodiment, the final shaped product achieves a random ODF strength of no more than 2.25 times. In yet another embodiment, the final shaped product achieves a random ODF strength of no more than 2.0 times. In another embodiment, the final shaped product achieves a random ODF strength of no more than 1.75 times. In yet another embodiment, the final shaped product achieves a random ODF strength of no more than 1.5 times.

[0019] As discussed above, the method may include forming (110) the TiB2 feedstock into a shaped product. Now referring to Figures 4-5b and 7, in one embodiment, the method includes preparing (90) the TiB2 feedstock for forming (110). In one embodiment, the preparing (90) includes spray drying a slurry (80) to produce TiB2 granules (92). In one embodiment, the slurry (80) includes TiB2 powder (82) and a liquid medium. In one embodiment, the slurry (80) includes at least one of a dispersant (84) and a binder (86). In one embodiment, the binder (86) includes an organic binder. In one embodiment, one or more of the dispersant (86) and the binder (86) provide one or more properties to the TiB2 granules, as described below.

[0020] As discussed above, one or more of the dispersants and binders may provide the TiB2 granules with one or more properties. Referring now to FIG. 5b, in one embodiment, the one or more properties of the TiB2 granules include: (i) a D of 200 micrometers or less; 90 (93), (ii) D of at least 10 micrometers 10 (94), (iii) 1.0-1.8 g / cm 3% (95), (iv) a liquid medium content of 0.5 wt. % or less (96), and (v) a flow rate of at least 0.2 g / s (97). In other embodiments, the TiB2 granules achieve at least two of (i)-(v). In yet other embodiments, the TiB2 granules achieve at least three of (i)-(v). In other embodiments, the TiB2 granules achieve at least four of (i)-(v). In yet other embodiments, the TiB2 granules achieve all of (i)-(v). In other embodiments, one or more properties achieved by the TiB2 granules, including one or more of (i)-(v) above, can be preselected, i.e., selected prior to manufacture of the TiB2 granules.

[0021] As discussed above, the method may include preparing (90) the TiB2 feedstock for the forming step (110). Referring now to FIG. 6, in one embodiment, the method includes deagglomerating (50) the TiB2 powder prior to the preparing step (90). In one embodiment, the method includes deagglomerating a first TiB2 powder to produce a second TiB2 powder. In one embodiment, the method includes mixing the deagglomerated TiB2 powder with a liquid medium to form a slurry (80). In one embodiment, the mixing step (70) precedes the preparing step (90). In one embodiment, the slurry (80) includes the deagglomerated TiB2 powder and at least one of a dispersant (84) and a binder (86). In one embodiment, the binder (86) includes an organic binder.

[0022] As noted above, the method may include a deagglomeration step (50) prior to the preparing step (90), which may include deagglomerating the first TiB2 powder to produce a second TiB2 powder. Referring now to FIG. 7, in one embodiment, the deagglomerated TiB2 powder has (i) a D of 0.5 to 4.0 micrometers. 50 (ii) 1.0 to 3.0 m 2 / g surface area; (iii) 5.0 wt% or less O, or 4 wt% or less O, or 3 wt% or less O, or 2.5 wt% or less O, or 2.0 wt% or less O, or 1.5 wt% or less O, or 1 wt% or less O; (iv) 5.0 wt% or less C, or 4 wt% or less C, or 3 wt% or less C, or 2.5 wt% or less C, or 2.0 wt% or less C, or 1.5 wt% or less C, or 1 wt% or less C; and (v) irregular particle morphology. In other embodiments, the deagglomerated TiB2 powder realizes at least two of (i)-(v). In yet other embodiments, the deagglomerated TiB2 powder realizes at least three of (i)-(v). In other embodiments, the deagglomerated TiB2 powder realizes at least four of (i)-(v). In yet other embodiments, the deagglomerated TiB2 powder realizes all of (i)-(v). In other embodiments, one or more properties to be realized by the deagglomerated TiB2 powder, including one or more of (i)-(v) above, may be preselected, i.e., selected prior to the deagglomeration step (50).

[0023] As discussed above, the method can include producing 130 a final shaped product from the shaped product. In one aspect, the final shaped product is an electrode. In one embodiment, the electrode is a cathode. In another embodiment, the electrode is an anode.

[0024] In one embodiment, the electrochemical cell comprises a final shape product in the form of an electrode. The electrochemical cell may comprise any number and type of final shape products in the form of electrodes, i.e., the electrochemical cell can comprise any number of final shape products in the form of anode(s) and / or cathode(s). In one embodiment, the electrochemical cell is an aluminum electrolysis cell. In another embodiment, the electrochemical cell is an aluminum refining cell.

[0025] In one embodiment, the method can include using the final shaped product as an electrode in an electrochemical cell. In one embodiment, the electrochemical cell is an aluminum electrolysis cell, and the final shaped product is an electrode, and the electrode is used in the aluminum electrolysis cell (e.g., as an anode and / or cathode) to produce aluminum metal. In another embodiment, the electrochemical cell is an aluminum refining cell, and the final shaped product is an electrode, and the electrode is used in the aluminum refining cell (e.g., as an anode and / or cathode) to produce aluminum.

[0026] <Definition> The TiB2 powder may have a median particle size. As used herein, "median particle size" is defined according to ASTM B822. The median particle size value of the TiB2 powder is measured using a Malvern Mastersizer 2000 as specified in ASTM B822. As described above, the TiB2 powder may have a surface area. The surface area value of the TiB2 powder is measured using a Micromeritics Tristar II Plus as specified in ASTM C1274. As described above, the TiB2 powder may contain oxygen and carbon. The oxygen content of the TiB2 powder is measured using LECO ON836 as specified in ASTM 1409. The carbon content of the TiB2 powder is measured using LECO CS844 as specified in ASTM E1915.

[0027] As mentioned above, the TiB2 powder may have an irregular particle morphology. As used herein, the term "irregular particle morphology" means that the particles are angular and have no particular shape. That is, a scanning electron micrograph of a TiB2 powder having an irregular morphology does not show a regular / repeating geometric shape. As mentioned above, the TiB2 granules may have a PSD D90 or PSD D10. As used herein, the term "particle size distribution" or "PSD" refers to the relative amount of particles present, sorted according to the size number present. For example, a PSD D10 of 7 microns means that 10% of the particles are smaller than about 7 microns and 90% of the particles are equal to or larger 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 and the other half are equal to or larger than about 12 microns. And, a PSD D90 of 20 microns means that 90% of the particles are smaller than about 20 microns and 10% of the particles are equal to or larger than about 20 microns. Generally, when referring to the same material, the particle size distribution from D10 to D90 increases (i.e., the value of D90 is greater than the values ​​of D50 and D10, and the value of D50 is greater than the value of D10). Although reference is made herein to D10, D50, and D90, it will be readily recognized that when measuring particle size, the PSD can be any useful PSD and is not limited to the values ​​of D10, D50, and D90. Particle size distribution values ​​for TiB2 powder are measured according to ASTM B214.

[0028] As described above, the TiB2 granules can 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 Meter HE53. The flow rate of the TiB2 granules is measured according to ASTM B213.

[0029] As discussed above, a shaped product (e.g., a green electrode) can have a density, which is calculated using the total mass and dimensions of the shaped product.

[0030] As mentioned above, the final shaped product (e.g., TiB2 plate) can have a density. The density of the final shaped product is measured according to ASTM B962.

[0031] As mentioned above, the pre-formed and final shaped products can have a theoretical density, which is the highest density that a material can achieve, calculated from the atomic weights and crystal structure.

number

[0032] For purposes of this patent application, the theoretical density is 4.52 g / cc, which is the approximate theoretical density of pure TiB2.

[0033] As mentioned above, the final shaped product can 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, the term "pore" refers to a generally small (e.g., 1 cm or less) opening or gap that is created by exposing a shaped product to one or more elevated temperatures. As used herein, the term "porosity" refers to the ratio of the volume of pores in a material to the volume of the material. As used herein, "intergranular porosity" refers to the porosity between TiB2 particles, and "intragranular porosity" refers to the porosity within TiB2 particles.

[0034] As described above, the final product is analyzed by scanning electron microscopy. Scanning electron microscopy is performed using a JOEL SEM instrument or other suitable SEM. A specimen for SEM analysis is first prepared by obtaining a section of the plate by electrodischarge machining, diamond saw cutting, or other suitable machining method. The specimen is then mounted and ground using diamond, silicon carbide, or other grinding media until the specimen is flat. Finally, the specimen is polished to an acceptable finish using diamond, silicon carbide, alumina, silica, or other abrasive media.

[0035] The samples are analyzed in Scanning Electron Microscopy (SE) and Electron Backscatter Diffraction (EBSD) modes. The average grain size of the final shaped product is measured by Orientation Imaging Microscopy (OIM) analysis in EBSD mode of the SEM. Briefly, the EBSD pattern is obtained by tilting the sample at about 70° and acquiring the diffraction pattern of the sample. The resulting Kikuchi pattern is analyzed to obtain the grain orientation information.

[0036] As discussed above, the final shaped product may have an average pore size. The average pore size and the volume percent of intergranular and intragranular porosity are measured on SEM micrographs based on a modified procedure of ASTM E112§13 (linear intercept method). Briefly, three lines are drawn on the SEM micrograph. The length of each pore intersecting each line is measured. OIM images are used to determine whether each measured pore is an intergranular or intragranular pore. The average of these lengths is calculated to obtain the average intergranular pore size and the average intragranular pore size. The lengths of the intergranular pores are added to calculate the total intergranular pores. The lengths of the intragranular pores are also added to obtain the total length of the intragranular pores. All measured pore lengths are then added to obtain the total of all pore lengths. The volume percent of intergranular and intragranular porosity is calculated from the above values. The total pore volume is calculated by dividing the sum of all pore lengths by the sum of the lengths of the three lines.

[0037] As used herein, "random grain orientation" means that there is no or limited preference for the grains to align in a particular direction; i.e., the crystallographic orientation of a grain is independent of the crystallographic orientation of its neighbors.

[0038] The distribution of crystal orientations within a sample of polycrystalline TiB2 can be determined from inverse pole figures, which are stereographic projections aligned with one of the known axes of the specified crystal structure of the sample.

[0039] Inverse pole figures are derived from electron backscatter patterns generated in a scanning electron microscope, where intersecting bands of diffracted electrons represent the crystallographic planes of a crystalline sample.

[0040] The diffracted beam produces a pattern of intersecting bands, called the electron backscattering pattern, which can be used to determine the orientation of the crystal lattice with respect to a particular crystallographic direction.

[0041] The measured intensity of a represented crystal orientation is typically normalized by calculating the amount of background or random intensity and comparing the background intensity to the intensity of the orientation present in the image.

[0042] Orientation imaging microscopy (OIM) uses electron backscattering patterns to analyze the orientation of each crystallite or grain that is imaged within a sample.

[0043] OIM analysis allows one to determine the background (random) intensity and use orientation distribution functions (ODFs) to generate relative ODF intensity values ​​for the population of imaged crystallites of a sample.

[0044] A series of ODF plots containing intensity (times random) representations can be generated for the imaged sample.

[0045] The ODF plot includes a maximum intensity rating on a predetermined scale and can be used as a quantitative measure of the degree of orientation in individual crystallites of a polycrystalline sample.

[0046] Higher ODF intensities indicate a higher degree of crystalline orientation between crystallites within a sample, while lower ODF intensities indicate a lower degree of orientation for a population of individual crystallites in a sample.

[0047] As noted above, the disclosed end-form products are in the form of electrodes and can be used in an aluminum electrolysis cell. As used herein, an "aluminum electrolysis cell" is a cell in which the cathode is at the bottom of the cell, the anode is at the top of the cell, and the aluminum produced migrates to the bottom of the cell. An example of an aluminum electrolysis cell is described in U.S. Patent Publication No. 2017 / 0283968, entitled "Apparatus and System for a Vertical Electrolysis Cell," which was filed by the applicant on March 30, 2017.

[0048] As noted above, the disclosed final form products are in the form of electrodes and can be used in an aluminum refining cell. As used herein, an "aluminum refining cell" is a cell in which a cathode is at the top of the cell, an anode is at the bottom of the cell, and refined aluminum travels to the top of the cell. An example of an aluminum refining cell is described in U.S. Patent No. 10,407,786, entitled "System and Method for Refining Aluminum," which was filed by the applicant on February 11, 2016.

[0049] The above examples are intended to illustrate the invention and should not be construed as limiting the invention.

[0050] The accompanying drawings are intended to at least partially illustrate various relevant features of the technology disclosed herein. The drawings are not necessarily to scale, with emphasis instead generally being placed on illustrating the principles of the present invention. Furthermore, some features may be exaggerated to show details of certain components. Furthermore, dimensions, specifications, etc. shown in the drawings are for illustrative purposes and not limiting. Therefore, specific structural and functional details disclosed herein should not be construed as limiting, but should be understood as a representative basis for those skilled in the art in various applications of the present invention.

[0051] Advantages and improvements of the present invention are disclosed, while other objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. Although detailed embodiments of the present invention are disclosed, it should be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. Furthermore, the examples given in connection with the various embodiments of the present invention are presented for purposes of illustration and not limitation.

[0052] Throughout the specification and claims, the following terms take the meanings expressly associated therewith, unless the context clearly dictates otherwise. As used herein, the terms "in one embodiment" and "in some embodiments" do not necessarily refer to the same embodiment, although they may. Additionally, as used herein, the terms "in another embodiment" and "in some other embodiments" do not necessarily refer to different embodiments, although they may. Thus, various embodiments of the invention can be readily combined without departing from the scope or spirit of the invention.

[0053] Additionally, as used herein, the term "or" is an inclusive "or" modifier and is equivalent to the term "and / or" unless the context clearly dictates otherwise. The term "based on" is not exclusive and may be based on additional unrecited elements unless the context clearly dictates otherwise. Additionally, throughout this specification, "a," "an," and "the" include the plural meaning unless the context clearly dictates otherwise. "In" includes the meanings "in" and "on" unless the context clearly dictates otherwise.

[0054] These and other aspects, advantages, and novel features of this new technology will be 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 the practice of one or more embodiments of the technology provided by this disclosure.

[0055] Although the present disclosure is generally directed to methods of manufacturing articles (e.g., electrodes) for use in aluminum electrochemical cells (e.g., aluminum electrolysis cells or aluminum refining cells), the articles and methods described herein are also applicable to other electrochemical cells, such as magnesium electrolysis cells or magnesium refining cells. [Brief description of the drawings]

[0056] The patent or application file contains at least one color drawing. 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.

[0057] [Figure 1] FIG. 1 is a flow chart illustrating one embodiment of a method for producing 130 a final shaped product.

[0058] [Diagram 2] FIG. 2 is a flow chart illustrating one embodiment of forming 110 the TiB2 feedstock into a shaped article.

[0059] [Figure 3a] FIG. 3a is a flow chart illustrating one embodiment of final shape product characteristics (132).

[0060] [Figure 3b] FIG. 3b is a flow chart illustrating one embodiment of final shape product characteristics (133-136).

[0061] [Figure 3c] FIG. 3c is a flow chart illustrating one embodiment of a method for heating 140, 144 a shaped product.

[0062] [Figure 4] FIG. 4 is a flow chart illustrating one embodiment of a method for producing 130 a final shaped product.

[0063] [Figure 5a] FIG. 5a is a flow chart illustrating one embodiment of a method for preparing (90) a TiB2 feedstock.

[0064] [Figure 5b] FIG. 5b is a flow chart showing one embodiment of the raw material properties (93-97) of TiB2 granules.

[0065] [Figure 6] FIG. 6 is a flow chart illustrating one embodiment of a method for producing 130 a final shaped product.

[0066] [Figure 7] FIG. 7 is a flow chart illustrating one embodiment of a method for producing (130) a final shaped product, showing the components of the slurry used in preparing the TiB2 feedstock (82, 84, 86) and the properties of the deagglomerated TiB2 powder (52).

[0067] [Figure 8] FIG. 8 is an SEM micrograph of an exemplary embodiment of a TiB2 electrode made in accordance with the present disclosure.

[0068] [Figure 9a] FIG. 9a is a SEM micrograph of an exemplary embodiment of a TiB2 electrode fabricated in accordance with the present disclosure and analyzed using OIM analysis.

[0069] [Figure 9b] FIG. 9b shows the corresponding grain size analysis results obtained from the OIM analysis of FIG. 9a.

[0070] [Figure 10a] FIG. 10a is an SEM micrograph of a comparative example of a non-invention TiB2 electrode made according to the present disclosure and analyzed using OIM analysis.

[0071] [Figure 10b] FIG. 10b shows the corresponding grain size analysis results obtained from the OIM analysis of FIG. 10a.

[0072] [Figure 11a] FIG. 11a is an SEM micrograph of an exemplary embodiment of the major face of a TiB2 electrode fabricated in accordance with the present disclosure and analyzed using OIM analysis.

[0073] [Figure 11b]FIG. 11b is an SEM micrograph of an exemplary embodiment of a second surface perpendicular (orthogonal) to the primary surface of a TiB2 electrode fabricated in accordance with the present disclosure and analyzed using OIM analysis.

[0074] [Figure 12a] FIG. 12a is an inverse pole figure generated from OIM analysis of an exemplary embodiment of a major surface of a TiB2 electrode made in accordance with the present disclosure.

[0075] [Figure 12b] FIG. 12b is an inverse pole figure generated from OIM analysis of an embodiment of a second surface perpendicular (orthogonal) to the primary surface of a TiB2 electrode made according to the present disclosure.

[0076] [Figure 13a] FIG. 13a is a comparative example SEM micrograph of a major surface of a non-invention TiB2 electrode made in accordance with the present disclosure and analyzed using OIM analysis.

[0077] [Figure 13b] FIG. 13b is a comparative example SEM micrograph of a second surface perpendicular (orthogonal) to the primary surface of a non-invention TiB2 electrode made according to the present disclosure and analyzed using OIM analysis.

[0078] [Figure 14a] FIG. 14a is an inverse pole figure generated from a comparative example OIM analysis of a major surface of a non-invention TiB2 electrode made according to the present disclosure.

[0079] [Figure 14b] FIG. 14b is an inverse pole figure generated from a comparative example OIM analysis of a second surface perpendicular (orthogonal) to the major surface of a non-invention TiB2 electrode made according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0080] Two plates were made, one inventive and one non-inventive. The inventive plate is described in more detail below. A first powder with TiB2 particles was deagglomerated to produce a second powder with TiB2 particles. Deagglomeration was performed by jet milling. The properties of the second powder were measured. The results are as follows: Median particle size: 1.8~2.6μm Surface area is 1.5~2.5m 2 / g Oxygen content is 1.25% by weight or less Carbon content is 1.0% by weight or less Irregular particle morphology

[0081] The deagglomerated TiB2 powder was then mixed with water, a dispersant, and a binder to form a slurry, which was then spray dried to form TiB2 granules having the following properties: D90 is less than 200μm D10 is at least 20μm Bulk density is 1.0~1.8g / cc Moisture content less than 0.5% by weight Flow rate of at least 0.2g / s

[0082] Approximately 10 kg of spray dried TiB2 granules were transferred to a 26.5" x 14.5" die. A pressure of 7500 psi was then applied to the die at room temperature to form a green electrode (e.g., a shaped product). The density of the green electrode was approximately 60% of the theoretical density of TiB2.

[0083] The green electrode was then sintered to produce the final TiB2 plate (e.g., final shaped product) by first heating to 500°C at a rate of 5°C / min, holding at 500°C for 1 hour, then heating to 1825°C at a rate of 5°C / min, and then holding at 1825°C for 12 hours (130). After holding at 1825°C, the final TiB2 plate was cooled in the furnace until it reached ambient temperature. The measured density of the final TiB2 plate was 4.10 g / cc (90.7% of the theoretical density of TiB2).

[0084] FIG. 8 shows a SEM micrograph of a typical TiB2 plate produced by the above process. As can be seen, the pores (820) are uniformly distributed throughout the plate area (810). In the plate shown in FIG. 8, the pores occupy about 10% of the total area of ​​the plate. The plate also contains a non-TiB2 secondary phase (830) that is non-reactive with aluminum, which occupies about 2% by volume of the TiB2 plate. The pore size shown in the SEM was calculated by the linear intercept method, and the results are shown in Table 1 below. [Table 1]

[0085] FIG. 9a shows a SEM micrograph analyzed using OIM analysis. As can be seen, there is a uniform distribution of pores (920) throughout the plate. OIM analysis was used to determine whether the pores are intergranular or intragranular. This analysis shows that 96.4% of the pores are intergranular and 3.6% of the pores are intragranular. FIG. 9a also shows that the plate is composed of TiB2 grains (940). The average grain size was determined using OIM analysis and is shown in FIG. 9b. The average grain size of this plate was measured to be 2.86 μm ± 1.46. The pore size vs. grain size results show that the average pore size is smaller than the average grain size of this plate.

[0086] Figures 11a and 11b show the grain orientation determined by OIM analysis for the primary face and the secondary face perpendicular (orthogonal) to the primary face, respectively. In this exemplary embodiment, the primary face is perpendicular to the pressing direction. Figures 12a and 12b show the inverse pole figures generated from the OIM analysis of the primary face and the secondary face, respectively. As can be seen, the grains in both faces, the primary face and the secondary face, are randomly oriented in the same way.

[0087] The non-invention plates were made by conventional methods, such as uniaxial hot pressing. TiB2 powder was loaded between two graphite plates in a graphite die. Uniaxial pressure was applied to the major surfaces of the graphite plates while the graphite die was heated to a temperature higher than 1800°C. The TiB2 powder was densified to a near net shape product, and then the surface reaction layer was removed by machining. The density of the comparative plate was measured to be 4.335g / cc (95.9% of the theoretical density of TiB2).

[0088] Figure 10a shows a SEM micrograph of a non-invention plate analyzed using OIM analysis. As can be seen, the plate is composed of TiB2 grains (1040) that are, on average, larger than the inventive plate. As also shown in Figure 10a, the pores (1020) of the non-invention plate are, in part, much larger than the inventive plate. The average grain size was determined by OIM analysis and is shown in Figure 10b.

[0089] Figures 13a and 13b show the grain orientations determined by OIM analysis of the primary face and the secondary face perpendicular (orthogonal) to the primary face, respectively, for a non-invention plate. In this comparative example, the primary face is perpendicular to the hot pressing direction. The grains on the primary face show a preferred orientation in the 0001 direction. The grains on the secondary face show a preferred orientation in the 21 10 direction.

[0090] Figures 14a and 14b show inverse pole figures generated by OIM analysis of the primary and secondary sides, respectively, for a non-invention plate. Applying ODF to this data set shows that the exemplary embodiment sample along the 0001 direction has less than 3 times the random ODF intensity, while the comparative sample has more than 5 times the random ODF intensity. This is shown in Figures 13a and 13b. This relative difference in ODF intensity between the samples can be used to quantify the degree of orientation present in the samples. The comparative sample has 2.5 times more orientation than the exemplary embodiment sample.

[0091] Ceramic manufacturing techniques other than dry pressing can be used to form the green electrode, including, but not limited to, pressing TiB2 granules in an isostatic press, roll forming TiB2 granules, extruding TiB2 powder, and casting TiB2 powder into a desired shape.

Claims

1. (a) TiB ２ A step of forming a predetermined shape product from raw materials, wherein the predetermined shape product is pure TiB ２ TiB achieves a density of 40% to 70% of the theoretical density. ２ A step of forming the raw material into a product of a predetermined shape, (b) A method comprising the step of producing a final-shaped product having an average pore size of 120% or less of the average grain size from the predetermined-shaped product, A method comprising the manufacturing step of exposing the predetermined shaped product to a high temperature, wherein the exposure causes the final shaped product to have a plurality of pores.

2. The aforementioned TiB ２ The raw material is TiB ２ Particles, TiB ２ The method according to claim 1, comprising granules and combinations thereof.

3. Step (a) described above is to form the predetermined shaped product, the TiB ２ The method according to claim 1, comprising performing one or more of the following on the raw material: press working, roll compression, casting, and extrusion.

4. The method according to claim 1, wherein the forming step (a) includes applying a pressure of at least 5,000 psi, or at least 6,000 psi, or at least 7,000 psi, or at least 7,500 psi.

5. The aforementioned predetermined shaped product is TiB ２ The method according to claim 1, which achieves a density of at least 45%, or at least 50%, or at least 55%, or at least 58%, or at least 60% of the theoretical density.

6. The product of the predetermined shape is TiB ２ The method according to claim 5, which realizes a density of 68% or less of the theoretical density of

7. The manufacturing step (b) is: The predetermined shaped product is subjected to a first heating process at a first temperature for a first time. The method according to claim 1, comprising: performing a second heating of the predetermined shaped product at a second temperature higher than the first temperature for a second time.

8. The method according to claim 7, wherein the first temperature is at least 200°C, or at least 300°C, or at least 400°C, or at least 500°C.

9. The method according to claim 7, wherein the first time is 1 minute or more and 48 hours or less.

10. The method according to claim 7, wherein the second time is 1 minute or more and 96 hours or less.

11. The method according to claim 7, wherein the first heating comprises heating from an initial temperature to the first temperature at a first heating rate, the first heating rate being 10°C / min or less, or 8°C / min or less, or 6°C / min or less, or 5°C / min or less.

12. The method according to claim 11, wherein the second heating comprises heating from the first temperature to the second temperature at a second heating rate, the second heating rate being 8°C / min or less, or 7°C / min or less, or 6°C / min or less, or 5°C / min or less.

13. The TiB used in step (a) of forming ２ The process includes a step of preparing raw materials, wherein the preparation step involves spray-drying the slurry before the forming step (a) to TiB ２ The method according to claim 1, comprising generating granules.

14. The slurry comprises a liquid medium, and the TiB ２ The granules are formed by at least a dispersant and a binder. (i) D of 200 micrometers or less ９０ , (ii) D of at least 10 micrometers １０ , (iii) 1.0-1.8g / cm ３ bulk density, (iv) Liquid media content of 0.5% by weight or less, and (v) A flow rate of at least 0.2 g / s, The method according to claim 13, comprising at least one of the following.

15. The above preparation step involves the first TiB ２ The powder is deaggregated to form a second TiB ２ The process includes generating a powder, and the second TiB ２ The powder (i) D of 0.5 to 4.0 micrometers ５０ , (ii) 1.0-3.0m ２ / g surface area, (iii) 5.0% by weight or less of O, or 4% by weight or less of O, or 3% by weight or less of O, or 2.5% by weight or less of O, or 2.0% by weight or less of O, or 1.5% by weight or less of O, or 1% by weight or less of O (iv) C in amounts of 5.0% by weight or less, or 4% by weight or less, or 3% by weight or less, or 2.5% by weight or less, or 2.0% by weight or less, or 1.5% by weight or less, or 1% by weight or less, and (v) Irregular particle morphology, The method according to claim 13, which achieves at least one of the following.

16. The aforementioned final product shape is (i) TiB ２ Densities of 85% to 98% of the theoretical density, (ii) Average grain size of 15 micrometers or less, (iii) Intergranular porosity of 1 to 15 volume%, and (iv) Random grain orientation, A method according to any one of claims 1 to 15, which achieves at least one of the above.

17. (a) at least 50 volume% TiB ２ , and (b) Average pore size less than or equal to 120% of the average grain size Includes monolithic titanium diboride (TiB ２ )product.

18. The aforementioned monolithic titanium diboride (TiB ２ ) The product, (i) TiB ２ Densities of 85% to 98% of the theoretical density, (ii) Average grain size of 15 micrometers or less, (iii) Intergranular porosity of 1 to 15 volume%, and (iv) Random grain orientation, The monolithic titanium diboride (TiB) according to claim 17, which achieves at least two of the above. ２ )product.

19. The aforementioned monolithic titanium diboride (TiB ２ The product is a monolithic titanium diboride (TiB) as described in claim 17, configured for use in an electrochemical cell. ２ )product.

20. The aforementioned monolithic titanium diboride (TiB ２ The product comprises a first surface and a second surface, the second surface being adjacent to or perpendicular to the first surface, and is titanium diboride (TiB) according to any one of claims 17 to 19. ２ )product.

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