Manufacturing method of titanium foil
The method addresses inefficiencies in titanium foil production by using controlled electrolysis conditions and cathode composition to produce thin titanium foil from titanium-based materials, enhancing efficiency and reducing costs.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOHO TITANIUM CO LTD
- Filing Date
- 2022-08-30
- Publication Date
- 2026-06-01
Smart Images
Figure 0007867925000003 
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Abstract
Description
[Technical Field]
[0001] This invention relates to a method for producing titanium foil by performing electrolysis in a molten salt bath using electrodes including an anode and a cathode, thereby depositing metallic titanium on the cathode. [Background technology]
[0002] Generally, titanium foil is manufactured by melting and casting sponge titanium obtained by the Chlor process to form titanium ingots or slabs, followed by rolling and other necessary processing. This method involves chlorination and reduction of titanium ore by the Chlor process, as well as the associated crushing of sponge titanium ingots and electrolysis of magnesium chloride. Because this method involves numerous steps, it cannot be said to be an efficient and low-cost way to manufacture titanium foil.
[0003] In contrast, as described in Patent Documents 1 to 3, for example, a method for producing titanium foil by electrolysis using a molten salt bath, so-called molten salt electrolysis, is being considered from the viewpoint of reducing energy consumption and costs in the manufacturing process.
[0004] Patent Document 1 proposes "a method for producing metallic titanium foil by molten salt electrolysis, characterized in that at least the titanium electrodeposition surface of the cathode electrode is metallic molybdenum or metallic silicon, and the molten salt bath is a molten salt bath in which titanium ions are dissolved in an alkali metal chloride or a mixed salt of chloride and iodide." Patent Document 1 states that "the titanium raw material supplied to the molten salt is titanium chloride."
[0005] Patent Document 2 discloses "a method for producing titanium foil or titanium plate by molten salt electrolysis using constant current pulses, wherein a titanium electrodeposited film is formed on the surface of a cathode electrode made of one or more selected from glassy carbon, graphite, Mo, and Ni, and then the titanium electrodeposited film is separated from the cathode electrode by performing one or both of the steps of applying an external force to the titanium electrodeposited film and removing at least a part of the cathode electrode." Patent Document 2 also states that "it is preferable that the raw material for titanium be mainly titanium chloride."
[0006] Patent Document 3 describes a method for producing metallic titanium by electrolysis using an anode and a cathode in a molten salt bath, comprising a titanium deposition step in which a titanium-containing anode is used as the anode and metallic titanium is deposited on the cathode, wherein the temperature of the molten salt bath is set to 250°C or higher and 600°C or lower, and the average current density of the cathode from the start of the titanium deposition step until 30 minutes have elapsed is 0.01 A / cm². 2 ~0.09 A / cm 2 The invention discloses a method for producing metallic titanium that maintains it within a certain range. Patent Document 3 states that "it is also possible to have titanium raw materials, such as titanium halides, in the molten salt bath beforehand, so that the molten salt bath contains titanium raw materials beforehand, and to have titanium raw materials present in the molten salt bath before starting electrolysis," and that "as mentioned above, if titanium raw materials such as titanium chloride are not mixed into the molten salt bath beforehand, an anodic dissolution step can be performed before the titanium deposition step, in which the anode is dissolved by electrolysis in the molten salt bath." [Prior art documents] [Patent Documents]
[0007] [Patent Document 1] Japanese Patent Publication No. 2017-137551 [Patent Document 2] International Publication No. 2018 / 159774 [Patent Document 3] International Publication No. 2020 / 044841 [Overview of the project] [Problems that the invention aims to solve]
[0008] Incidentally, by subjecting titanium ore to a specific treatment, titanium-based materials containing titanium, aluminum, and oxygen can sometimes be obtained. If titanium foil can be manufactured from such titanium-based materials, it may be possible to achieve a significant reduction in manufacturing time and cost compared to the methods described above. Furthermore, it may also be possible to manufacture titanium foil from titanium ore without going through sponge titanium.
[0009] Patent documents 1 to 3 use titanium chloride and metallic titanium as raw materials for molten salt electrolysis, but they do not describe anything about manufacturing titanium foil from the above-mentioned titanium-based materials.
[0010] The object of this invention is to provide a method for producing titanium foil, which can produce relatively thin titanium foil from a titanium-based material containing titanium, aluminum, and oxygen. [Means for solving the problem]
[0011] When electrolysis is performed in a molten salt bath using an anode containing a titanium-based material that also contains predetermined amounts of aluminum and oxygen, a thick layer of metallic titanium is often deposited on the cathode, preventing the formation of titanium foil. Through diligent research, the inventors have discovered that to deposit a thin layer of metallic titanium on the cathode, it is crucial to pre-add titanium ions to the molten salt bath before starting electrolysis, to keep the temperature of the molten salt bath low during electrolysis, and to reduce the current density. Furthermore, using a predetermined material for the cathode's electrolytic surface makes it easier to physically remove the foil-like metallic titanium deposited on the cathode's electrolytic surface. As a result, thin titanium foil can be manufactured.
[0012] The present invention provides a method for manufacturing titanium foil, comprising an electrodeposition step in which electrolysis is performed in a molten salt bath using electrodes including an anode and a cathode to deposit metallic titanium on the electrolytic surface of the cathode, wherein the anode is made of a titanium-based material containing titanium, with an aluminum content of 200 ppm by mass or more and 4500 ppm by mass or less, and an oxygen content of 8000 ppm by mass or more and 15000 ppm by mass or less, and is conductive, and the cathode is made of a cathode whose electrolytic surface contains 90% by mass or more of at least one selected from the group consisting of titanium, molybdenum, glassy carbon, and tungsten, the molten salt bath is pre-containing titanium ions, the temperature of the molten salt bath is maintained at 520°C or lower during the electrolysis, and the current density at the cathode is 0.2 A / cm². 2 The following will be implemented.
[0013] The molten salt bath used in the electrodeposition step preferably contains 80 ml or more of two or more substances selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride.
[0014] The molten salt bath used in the electrodeposition step preferably contains 1 ml or more of the titanium ions before the start of the electrolysis.
[0015] The above manufacturing method may include, after the electrodeposition step, a peeling step in which the metallic titanium deposited on the electrolytic surface of the cathode is physically peeled off from the cathode.
[0016] The above manufacturing method may include a purification step, prior to the electrodeposition step, in which electrolysis is performed using an electrode including an anode and a cathode containing a conductive crude titanium-based material containing titanium, aluminum, and oxygen in a molten salt bath, which is a chloride bath, to deposit a purified titanium-based material on the cathode. In this case, the purified titanium-based material obtained in the purification step can be used as the titanium-based material in the electrodeposition step.
[0017] In the purification step, the molten salt bath contains 75 mol% or more of magnesium chloride, the temperature of the molten salt bath is maintained at 750°C or higher during the electrolysis, and as the crude titanium-based material, a crude titanium-based material having a titanium content of 50% by mass or more and 80% by mass or less, an aluminum content of 3% by mass or more and 40% by mass or less, and an oxygen content of 0.2% by mass or more and 40% by mass or less is preferably used.
[0018] The above manufacturing method may include an extraction step of heating a mixture containing a titanium raw material containing titanium oxide, a reducing agent containing aluminum, and a separating agent before the purification step, and extracting the crude titanium-based material from the molten mixture.
Advantages of the Invention
[0019] According to the method for manufacturing a titanium foil of this invention, a relatively thin titanium foil can be manufactured from a titanium-based material containing titanium, aluminum, and oxygen.
Brief Description of the Drawings
[0020] [Figure 1] It is a flowchart showing a method for manufacturing a titanium foil according to an embodiment of this invention. [Figure 2] It is a cross-sectional view along the depth direction of a molten salt bath showing a purification step in the method for manufacturing a titanium foil according to an embodiment of this invention. [Figure 3] It is a similar cross-sectional view schematically showing a state in which the purified titanium-based material obtained on the cathode in the purification step of FIG. 2 is included in the anode used in the next electroplating step. [Figure 4] It is a similar cross-sectional view showing an electroplating step following the purification step of FIG. 2. [Figure 5] It is a cross-sectional view along the depth direction of a molten salt bath showing a purification step in the method for manufacturing a titanium foil according to another embodiment. [Figure 6] It is a similar cross-sectional view showing an electroplating step following the purification step of FIG. 5. [Figure 7]Furthermore, this is a cross-sectional view along the depth direction of the molten salt bath, showing the refining process in a titanium foil manufacturing method according to another embodiment. [Figure 8] This is a similar cross-sectional view showing the replacement of the anode in the purification process with the cathode for the subsequent electrodeposition process, as shown in Figure 7. [Figure 9] This is a similar cross-sectional view showing the electrodeposition process following the purification process, as shown in Figure 7. [Modes for carrying out the invention]
[0021] Embodiments of this invention will be described in detail below. A method for manufacturing titanium foil according to one embodiment of this invention includes an electrodeposition step in which electrodes, including an anode and a cathode, are immersed in a molten salt bath, electrolysis is performed by applying a voltage to the electrodes, and metallic titanium is deposited on the electrolytic surface of the cathode.
[0022] In the electrodeposition process, a titanium-based material is used as the anode. The titanium-based material contains titanium, as well as aluminum in an amount of 200 ppm to 4500 ppm by mass and oxygen in an amount of 8000 ppm to 15000 ppm by mass, and is electrically conductive. On the other hand, the electrolytic surface of the cathode contains 90% by mass or more of at least one material selected from the group consisting of titanium, molybdenum, glassy carbon, and tungsten, in order to allow the metallic titanium deposited thereon to be easily peeled off after the electrodeposition process.
[0023] In this process, to suppress the shortage of titanium ions in the molten salt bath at the start of electrolysis in the electrodeposition process and to deposit metallic titanium in a foil-like form on the cathode, titanium ions are pre-added to the molten salt bath before the start of electrolysis. Furthermore, during the electrolysis of the electrodeposition process, the temperature of the molten salt bath is kept below 520°C to maintain a relatively low temperature. In addition, the current density at the cathode during the electrodeposition process is set to 0.2 A / cm². 2 The following is observed. As a result, metallic titanium tends to deposit on the cathode in a foil-like form, making it easier to physically detach from the cathode.
[0024] To obtain the above-mentioned titanium-based material used in the electrodeposition process, as shown in Figure 1, a purification process can be performed before the electrodeposition process to convert the crude titanium-based material into a refined titanium-based material with a higher titanium purity by electrolytic refining. This refined titanium-based material can then be used as the titanium-based material in the electrodeposition process. Furthermore, to obtain the crude titanium-based material used in the refining process, an extraction process may be performed before the refining process to produce the above-mentioned crude titanium-based material from a titanium raw material containing titanium oxide, such as titanium ore. However, the extraction process, or the refining process and extraction process, may be omitted.
[0025] (extraction process) In the extraction process, a mixture containing titanium raw materials such as titanium ore containing titanium dioxide (TiO2) and other titanium oxides, a reducing agent containing aluminum (Al), and a separating agent is heated.
[0026] The heating temperature may be set to 1500°C to 1800°C. After the mixture melts due to heating, the crude titanium-based material (liquid or solid) separates from the slag due to density differences, allowing the crude titanium-based material to be extracted. The reaction in the extraction process is complex, but generally, it can be considered as 3TiO2 + 4Al → 3Ti + 2Al2O3. In this reaction equation, the Ti after the reaction has a considerable amount of Al and O dissolved in it, and corresponds to the crude titanium-based material.
[0027] The titanium raw material can be any material containing titanium oxide, for example, titanium ore that has undergone upgrading treatments such as leaching as needed. The titanium dioxide content in the titanium ore used as the titanium raw material may be, for example, 50% by mass or more, typically 80% by mass or more, and particularly 90% by mass or more.
[0028] The separating agent is used to facilitate the separation of crude titanium-based materials from the slag after heating. Specifically, it is preferable to use one or more of the following as the separating agent: calcium fluoride (CaF2), aluminum fluoride (AlF3), potassium fluoride (KF), magnesium fluoride (MgF2), calcium oxide (CaO), calcium chloride (CaCl2), and sodium fluoride (NaF). Among these, calcium fluoride is particularly preferred because it provides excellent separation of crude titanium-based materials from the mixture and has little effect on processes other than the separation itself.
[0029] The reducing agent may consist substantially of aluminum (Al) alone, or it may also contain calcium (Ca), sodium (Na), etc. For example, the mixture may be prepared by adjusting the molar ratio of TiO2:Al:CaF2 to 3:4 to 7:2 to 6.
[0030] The crude titanium-based material obtained in the extraction process contains titanium (Ti), aluminum (Al), and oxygen (O). For example, the titanium content may be 50% or more by mass and 80% or less by mass, the aluminum content 5% or more by mass and 30% or less by mass, and the oxygen content 8% or more by mass and 30% or less by mass. Alternatively, the crude titanium-based material may have a titanium content of 50% or more by mass and 85% or less by mass, an aluminum content of 3% or more by mass and 40% or less by mass, and an oxygen content of 0.2% or more by mass and 40% or less by mass. Typically, the titanium content of the crude titanium-based material may be 60% or more by mass, the aluminum content 20% or less by mass, and the oxygen content 20% or less by mass.
[0031] Such crude titanium-based materials are electrically conductive and can be used in molten salt electrolysis by incorporating them into the anode during the refining process described later. The resistivity of the crude titanium-based material measured at room temperature is, for example, 1 × 10⁻⁶. -8 Ω·m ~ 1 × 10 -4 Ω·m, typically 1 × 10⁻⁶ -7 Ω·m~5×10 -5 It is Ω·m.
[0032] (Purification process and electrodeposition process) While various electrolytic cells can be used for the purification and electrodeposition processes, here we will explain using electrolytic cell 1 shown in Figure 2 as an example. Note that Figure 2 is a schematic representation of electrolytic cell 1, and the dimensions and arrangement of each component may be changed as appropriate in actual implementation. The same applies to Figures 3 to 9 described later.
[0033] The illustrated electrolytic cell 1 comprises a container-shaped tank body 2 for storing molten salt inside to form a molten salt bath Bm, and a power supply (not shown) to which electrodes 3 are connected. The tank body 2 may have an openable and closable lid (not shown), and a gas passage for supplying an inert gas such as argon gas or for discharging gas may be connected inside. The electrolytic cell 1 can be heated internally by heaters (not shown) arranged around the tank body 2, or by a temperature controller arranged inside.
[0034] The molten salt bath Bm used in the refining process is primarily a chloride bath containing metal chlorides, preferably containing 75 mol% or more, more preferably 85 mol% or more, and especially 90 mol% or more, of magnesium chloride (MgCl2). Using a molten salt bath with a high concentration of magnesium chloride allows for the production of refined titanium-based materials with significantly reduced oxygen and aluminum content. Furthermore, the molten salt bath Bm may optionally contain lower titanium chlorides with a lower Ti valence than titanium tetrachloride, specifically TiCl2 (titanium dichloride) or TiCl3 (titanium trichloride). The titanium ion content in the molten salt bath Bm is, for example, 1 mol% to 25 mol%, and may be 4 mol% to 10 mol%. The inclusion of titanium ions increases the amount of refined titanium-based material precipitated per unit time, improving productivity. The molten salt bath Bm may consist of magnesium chloride and lower titanium chloride. The content of metal chlorides and metal ions in the molten salt bath Bm can be measured by ICP emission spectrometry or atomic absorption spectrometry. The titanium ion content is determined as a percentage of the total metal ion content in the molten salt bath Bm.
[0035] As the anode 3a used in the purification process, for example, those containing the crude titanium-based material obtained in the above-described extraction process are used. As an example, the anode 3a has a cage-shaped container made of a metal such as Ni, Ni-based alloy, Hastelloy, etc. which has a smaller ionization tendency than Ti, and has a number of through-holes. In this case, as shown in Fig. 2, a granular or powdery crude titanium-based material can be arranged in the cage-shaped container such as a cylindrical shape. The external shape of the above cage-shaped container may be cylindrical or plate-shaped, etc. Regardless of the external shape of the cage-shaped container, as described above, the crude titanium-based material is arranged inside it. However, the form of the anode 3a is not limited to this. For example, although not shown, it may be in the form of a rod, column, plate, or cylindrical shape such as a cylinder or other arbitrary shape produced by melting and casting from the crude titanium-based material. The cathode 3b used in the purification process can be made of Ti, and its shape is not particularly limited and can be appropriately determined according to the shape of the anode 3a, for example. Note that the electrode 3 may further have a bipolar electrode arranged between the anode 3a and the cathode 3b in addition to the anode 3a and the cathode 3b.
[0036] During the electrolysis in the purification process, the temperature of the molten salt bath Bm is maintained at 750 °C or higher, and may be 800 °C or higher. The temperature of the molten salt bath is often 850 °C or lower. By performing electrolysis in such a relatively high-temperature molten salt bath Bm, most of the aluminum contained in the crude titanium-based material is removed, and a purified titanium-based material with a sufficiently low aluminum content can be obtained.
[0037] In the purification process, the current density at the cathode 3b is 0.01 A / cm 2 ~5 A / cm 2 It may be set as such. The current density is calculated by the formula: current density (A / cm 2 ) = current (A) ÷ electrolysis area (cm 2This can be calculated by ( ). Electrode 3 can be used to continuously supply current, or it may be used to supply pulsed current such as ON / OFF control, where periods of current supply and periods of current supply are alternately repeated, with a current supply period set to zero. The maximum voltage between electrodes 3 may be, for example, 0.2V to 3.5V. During the purification process, it is preferable to maintain an inert atmosphere such as argon inside the electrolytic cell 1.
[0038] In the purification process, current is supplied from the power supply to the anode 3a and cathode 3b of electrode 3, and a voltage is applied between the electrodes 3. As a result, titanium ions are eluted from the crude titanium-based material contained in anode 3a into the molten salt bath Bm, and as shown in Figure 2, the titanium ions are deposited on cathode 3b as purified titanium-based material. In Figure 2, since the cylindrical anode 3a is arranged around the cylindrical cathode 3b, the purified titanium-based material is deposited on the electrolytic surface around cathode 3b.
[0039] The purified titanium-based material deposited on the cathode 3b during the purification process can be physically removed from the cathode 3b using a cutting tool or the like, as shown in Figure 3, after the electrolysis is complete, and can be placed, for example, into the cage-like container of the anode 13a in the subsequent electrodeposition process. The purified titanium-based material may be subjected to acid washing and / or water washing to remove molten salts, either together with the cathode 3b on which it is electrodeposited, or after being removed from the cathode 3b. Vacuum drying may then be performed as needed. Alternatively, instead of the washing and drying described above, vacuum separation may be performed to remove molten salts under high temperature and reduced pressure conditions.
[0040] In the refining process, the refined titanium-based material described above may be used as the crude titanium-based material and subjected to repeated electrolysis multiple times. Repeated electrolysis reduces the aluminum and oxygen content of the refined titanium-based material, resulting in a refined titanium-based material with high titanium purity.
[0041] Subsequently, the purified titanium-based material obtained in the above purification process is used as the titanium-based material for anode 13a, and the electrodeposition process is carried out as shown in Figure 4.
[0042] In the electrodeposition process, the titanium-based material in the cage-like container of the anode 13a (the refined titanium-based material obtained in the refining process) has an aluminum content of 200 ppm or more and 4500 ppm or less, an oxygen content of 8000 ppm or more and 15000 ppm or less, and the remainder is substantially titanium. The titanium-based material may also contain impurities. Preferably, the aluminum content of the titanium-based material is 200 ppm to 3000 ppm and the oxygen content is 8000 ppm to 12000 ppm. If the aluminum content of the titanium-based material is too high, the metallic titanium deposited on the cathode 13b will contain a considerable amount of aluminum, forming a titanium alloy, which may lead to a decrease in strength. Also, if the oxygen content is too high, the metallic titanium deposited on the cathode 13b will contain a relatively large amount of oxygen, which may affect its ductility and make it prone to fracture. Therefore, it is desirable to obtain a refined titanium-based material in which the aluminum and oxygen content has been sufficiently reduced in the aforementioned refining process.
[0043] The cathode 13b used in the electrodeposition process has an electrolytic surface that contains at least 90% by mass or more of at least one material selected from the group consisting of titanium, molybdenum, glassy carbon, and tungsten, preferably substantially composed of at least one of the above materials. With a cathode 13b having an electrolytic surface of such material, in many cases it becomes possible to physically peel off the foil-like metallic titanium deposited on the electrolytic surface after the electrodeposition process. The cathode 13b may be made of the above material not only in its electrolytic surface but throughout its entirety.
[0044] The molten salt bath Bm used in the electrodeposition process shall contain titanium ions beforehand. At the start of electrolysis in the electrodeposition process, the titanium ions in the molten salt bath Bm may be depleted, in which case metallic titanium may not form a foil on the cathode 13b, for example, by depositing in the form of dendrites or powder. This is to suppress that. In addition, the inclusion of titanium ions increases the amount of metallic titanium deposited per unit time on the cathode 13b, improving productivity. The titanium ion content in the molten salt bath Bm before the start of electrolysis is preferably 1 mole or more, more preferably 4 mole or more, and may be 20 mole or less, or 10 mole or less. If a purification process is performed before the electrodeposition process and the same molten salt bath Bm is used in the electrodeposition process, the molten salt bath Bm may contain titanium ions generated in the purification process. If necessary, a titanium source may be added to the molten salt bath Bm before the start of electrolysis to include titanium ions. Examples of titanium sources include titanium chloride, titanium scrap, and titanium sponge. When using titanium scrap or titanium sponge as a titanium source, these can be brought into contact with titanium tetrachloride (TiCl4) to produce lower titanium chlorides such as titanium dichloride (TiCl2) and / or titanium trichloride (TiCl3), which can then be dissolved to form a molten salt bath Bm containing titanium ions.
[0045] Furthermore, the molten salt bath Bm is preferably a chloride bath mainly containing metal chlorides. It is preferable that it does not contain fluoride ions. This is because when washing, such as rinsing with water, is performed after the electrodeposition process to remove the components of the molten salt bath Bm from the metal titanium on the cathode 13b, the presence of fluoride may generate harmful hydrogen fluoride or hydrofluoric acid upon contact with water. The molten salt bath Bm preferably contains 80 mol% or more, preferably 85 mol% to 95 mol%, and more preferably 90 mol% to 95 mol%, of two or more selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride. By making the molten salt bath Bm contain multiple types of metal chlorides in this way, the molten state can be maintained at a relatively low temperature. It is preferable that one of the two or more above be magnesium chloride, and the magnesium chloride content is preferably 20 mol% or more.
[0046] During the electrolysis process of the electrodeposition step, the temperature of the molten salt bath Bm is maintained at 520°C or lower. If the temperature of the molten salt bath Bm is too high, the crystal grains of the titanium metal deposited on the cathode 13b tend to coarseen, and dendrite growth may progress, potentially impairing the smoothness of the deposited titanium metal. In addition, at high temperatures, it may be difficult to physically remove the titanium metal deposited on the cathode 13b. However, if the molten state of the molten salt constituting the molten salt bath Bm can be maintained and electrolysis using the molten salt bath Bm is possible, the temperature of the molten salt bath Bm can be kept sufficiently low. The temperature of the molten salt bath Bm is set taking into consideration the bath composition, and may be, for example, 420°C or higher and 520°C or lower, or 450°C or higher and 520°C or lower.
[0047] In the electrodeposition process, the current density at cathode 13b is set to 0.2 A / cm². 2 The following is preferably 0.15 A / cm 2 The following applies. The current density is 0.01 A / cm². 2The above may be applied. If the current density is too high, it may become difficult to easily detach the metallic titanium from the cathode 13b. Here, either a constant current, which flows continuously at a constant current value, or a pulsed current such as ON / OFF control, which intermittently changes the current value, may be used. With a pulsed current, diffusion of titanium ions may occur in the molten salt bath Bm when the current is stopped. Taking such effects into consideration, it is desirable to adjust the current density so that the physical detachment of metallic titanium from the cathode 13b after the electrodeposition process is easy. If the current value changes during electrolysis, the above current density should be such that the maximum value from the start to the end of electrolysis satisfies the above upper limit, lower limit, or range conditions. During the electrodeposition process, the inside of the electrolytic cell 1 may be maintained in an inert atmosphere such as argon.
[0048] In the electrodeposition process, under the above conditions, when a voltage is applied to the electrode 13 to perform electrolysis, the titanium-based material of the anode 13a dissolves, and as shown in Figure 4, metallic titanium is deposited on the electrolytic surface of the cathode 13b in a relatively thin foil-like form. During electrolysis, if the titanium ion concentration around the cathode 13b decreases, the metallic titanium deposited on the cathode 13b may become difficult to peel off. To suppress this, it is preferable to place a pump (not shown) inside the electrolytic cell 1 in the molten salt bath Bm and stir the molten salt bath Bm with the pump so that the concentration becomes as uniform as possible.
[0049] Incidentally, the cathode 3b used in the refining process may be used as the anode 13a in the electrodeposition process. For example, in Figure 5, the refining process is carried out in the same manner as in Figure 2, except that the anode 3a and cathode 3b are both plate-shaped in appearance. As a result, the refined titanium-based material is deposited on one side of the electrolytic surface of the cathode 3b. After that, the anode 3a is removed from the electrolytic cell 1, and as shown in Figure 6, the cathode 13b is placed there, and the electrodeposition process is carried out using the cathode 3b from the refining process as the anode 13a. As a result, foil-like metallic titanium is deposited on the electrolytic surface of the cathode 13b on the anode 13a side, and titanium foil is obtained. Here, the same molten salt bath Bm is used in both the refining process and the electrodeposition process, and it is not necessary to perform any processing such as cutting, peeling, washing, or drying of the refined titanium-based material on the cathode 3b between the refining process and the electrodeposition process.
[0050] The purification and electrodeposition processes shown in Figures 5 and 6 are preferably carried out by providing electrode exchange chambers 11 and 12 on the electrolytic cell 1, which allow for adjustment of the internal atmosphere, as shown in Figures 7 to 9. In this example, first, the purification process is carried out in the same manner as in Figure 5, as shown in Figure 7. Next, the anode 3a from the purification process is lifted from the electrolytic cell 1 to one of the electrode exchange chambers 11 located on the left side of Figure 8, as indicated by the arrow in the same figure, and there it is replaced with the cathode 13b from the electrodeposition process. The cathode 13b is then placed inside the electrolytic cell 1 for the next electrodeposition process. After that, the electrodeposition process is carried out in the same manner as in Figure 6, as shown in Figure 9. The other electrode exchange chamber 12 can be used when replacing the cathode 3b or anode 13a located directly below it.
[0051] (Peeling process) After the electrodeposition process, the metallic titanium deposited on the cathode 13b can be removed by leaching or other methods, but it is preferable to physically remove it from the cathode 13b in a delamination process.
[0052] In the delamination process, various methods can be employed to delaminate the titanium metal. For example, a method can be employed in which a portion of the titanium metal is grasped and physically delaminated from the cathode (mechanical delamination). Here, physical delamination means separating the titanium metal from the cathode 13b by applying an external force in a direction that causes them to separate, without using chemicals or electricity. One specific example of such physical delamination is peeling.
[0053] By performing the electrodeposition process under the conditions described above, it becomes possible to relatively easily and physically remove the titanium metal deposited in a foil-like manner on the cathode 13b.
[0054] The titanium foil produced in this manner is substantially composed of titanium, with aluminum and oxygen sufficiently removed. The total content of impurities other than titanium in the titanium foil is preferably 5000 ppm by mass or less, more preferably 3000 ppm by mass or less. The aluminum content of the titanium foil may be 5 ppm to 1000 ppm by mass, and the oxygen content may be 4400 ppm by mass or less, or 50 ppm to 500 ppm by mass.
[0055] Titanium foil may contain impurities derived from ore or chloride baths. Specifically, such impurities in titanium foil may include nitrogen content of 0.03% by mass or less, carbon content of 0.01% by mass or less, iron content of 0.010% by mass or less, magnesium content of 0.05% by mass or less, nickel content of 0.01% by mass or less, chromium content of 0.03% by mass or less, silicon content of 0.005% by mass or less, manganese content of 0.05% by mass or less, and tin content of 0.01% by mass or less.
[0056] Furthermore, according to the above embodiment, for example, the thickness is about 20 μm to 1000 μm and the surface area is 100 mm². 2 ~10000mm 2It is sometimes possible to manufacture titanium foil in areas of a certain size, or even larger. [Examples]
[0057] Next, the titanium foil manufacturing method of this invention was experimentally implemented, and its effects were confirmed, which are described below. However, this description is for illustrative purposes only and is not intended to be an exhaustive limit.
[0058] A mixture containing titanium ore with 95% by mass of titanium dioxide, aluminum as a reducing agent, and calcium fluoride as a separating agent, in a molar ratio of TiO2:Al:CaF2 within the range of 3:4 to 7:2 to 6, was heated under an argon atmosphere at 1500°C to 1800°C to extract crude titanium-based material.
[0059] The content of components other than titanium in the crude titanium-based material is shown in Table 1. The metal components were measured by ICP emission spectrometry (PS3520UVDDII, Hitachi Corporation), oxygen by inert gas fusion-infrared absorption spectrometry (TC-436AR, LECO Corporation), nitrogen by inert gas fusion-thermal conductivity spectrometry (TC-436AR, LECO Corporation), carbon by combustion-infrared absorption spectrometry (EMIA-920V2, Horiba, Ltd.), and chlorine by silver nitrate titration (GT-200, Nitto Seiko Analytech Co., Ltd.).
[0060] [Table 1]
[0061] Furthermore, when the resistivity of a sample taken from crude titanium-based material was measured at room temperature using a two-terminal measurement method (low resistance meter 3566-RY, manufactured by Tsuruga Electric Co., Ltd.), the resistivity was found to be 5 × 10⁻⁶. -5 It was Ω·m.
[0062] Using the crude titanium-based material described above, electrolytic refining was performed using a molten salt bath in an electrolytic cell as shown in Figure 2. The main body of the electrolytic cell had dimensions of 300 mmΦ × 570 mm depth for the section that holds the molten salt bath. The molten salt bath consisted of 96 ml of magnesium chloride and 4 ml of lower titanium chloride. The anode was constructed by placing the crude titanium-based material inside a cylindrical cage-like container, and the cathode was a cylindrical titanium electrode. During electrolytic refining, the temperature of the molten salt bath was set to approximately 800°C, and the current density at the cathode was set to 1.0 A / cm². 2 Electrolysis was performed as a result, and refined titanium-based material was deposited on the cathode.
[0063] Next, the cathode used in the electrolytic refining process described above, along with the purified titanium-based material electrodeposited thereon, was removed from the electrolytic cell, washed with dilute hydrochloric acid, and then dried under a reduced pressure atmosphere to remove the purified titanium-based material from the cathode. The purified titanium-based material had a titanium content of 98% by mass, an aluminum content of 2000 ppm by mass, and an oxygen content of 10000 ppm by mass.
[0064] Subsequently, the purified titanium-based material obtained as described above was placed in a cylindrical cage-like container and electrolytic emission was performed using this as the anode. Table 2 shows the conditions for each step. The cathode was cylindrical and made of titanium, nickel, or molybdenum. The molten salt bath used for electrolytic emission contained 35 ml of magnesium chloride, 35 ml of sodium chloride, 20 ml of potassium chloride, and 10 ml of titanium ions. The molten salt bath used in Comparative Example 4 was the same as in the other examples except that it did not contain titanium ions. The molar ratio of the molten salt bath used in Comparative Example 4 was magnesium chloride:sodium chloride:potassium chloride = 35:35:20.
[0065] After the electrolytic emission described above, the cathode, along with the foil-like titanium metal electrodeposited onto it, was removed from the electrolytic cell and washed with dilute hydrochloric acid. Subsequently, an attempt was made to physically remove the titanium metal from the cathode.
[0066] In Examples 1 and 2, metallic titanium could be peeled off the cathode using either a titanium or molybdenum cathode, thereby producing titanium foil. Furthermore, these titanium foils had reduced aluminum and oxygen content compared to the refined titanium-based material described above, as shown in Table 1.
[0067] In Comparative Example 1, the high temperature of the molten salt bath made it difficult to physically peel off the metallic titanium from the cathode. Furthermore, after electrolysis in Comparative Example 1, a sample was taken from the metallic titanium deposited on the cathode, and component analysis of the sample revealed an aluminum content of 50 ppm by mass and an oxygen content of 5000 ppm by mass.
[0068] In Comparative Example 2, the high current density made it difficult to physically remove the metallic titanium from the cathode. In Comparative Example 3, since the cathode material was nickel, it was difficult to physically remove the metallic titanium from the cathode, and the metallic titanium deposited on the cathode alloyed with nickel. In Comparative Example 4, the molten salt bath did not contain titanium ions before the start of electrolysis, so the overvoltage increased and the metallic titanium turned into powder.
[0069] [Table 2]
[0070] From the above, it has been found that, according to this invention, a relatively thin titanium foil can be manufactured from a titanium-based material containing titanium, aluminum, and oxygen. [Explanation of Symbols]
[0071] 1 electrolytic cell 2 Tank body 3, 13 electrodes 3a, 13a anode 3b, 13b cathode 11, 12 Electrode exchange room Bm molten salt bath
Claims
1. A method for manufacturing titanium foil, The process includes an electrodeposition step in which electrolysis is performed using electrodes, including an anode and a cathode, in a molten salt bath, and metallic titanium is deposited on the electrolytic surface of the cathode. In the electrodeposition step, As the anode, an anode is used that contains titanium and has an aluminum content of 200 ppm by mass or more and 4500 ppm by mass or less, and an oxygen content of 8000 ppm by mass or more and 15000 ppm by mass or less, and is conductive and titanium-based; as the cathode, a cathode is used in which the electrolytic surface contains 90% by mass or more of at least one selected from the group consisting of titanium, molybdenum, glassy carbon, and tungsten. The molten salt bath is pre-soaked with titanium ions, and the temperature of the molten salt bath is maintained at 520°C or below during the electrolysis. The current density at the cathode is 0.2 A / cm². 2 The following is a method for manufacturing titanium foil.
2. The method for producing titanium foil according to claim 1, wherein the molten salt bath used in the electrodeposition step contains 80 mol or more of two or more selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride.
3. The method for producing titanium foil according to claim 1, wherein the molten salt bath used in the electrodeposition step contains 1 mol% or more of the titanium ions before the start of the electrolysis.
4. A method for manufacturing titanium foil according to claim 1, further comprising a peeling step of physically peeling off the metallic titanium deposited on the electrolytic surface of the cathode after the electrodeposition step.
5. Prior to the electrodeposition step, the process includes a purification step in which electrolysis is performed in a molten salt bath, which is a chloride bath, using electrodes including an anode and a cathode containing a conductive crude titanium-based material containing titanium, aluminum, and oxygen, thereby depositing the purified titanium-based material on the cathode. A method for producing titanium foil according to any one of claims 1 to 4, wherein the purified titanium-based material obtained in the purification step is used as the titanium-based material in the electrodeposition step.
6. In the aforementioned purification process, The molten salt bath contains 75 mol% or more of magnesium chloride, and the temperature of the molten salt bath is maintained at 750°C or higher during the electrolysis. The method for producing titanium foil according to claim 5, wherein the crude titanium-based material used has a titanium content of 50% by mass or more and 80% by mass or less, an aluminum content of 3% by mass or more and 40% by mass or less, and an oxygen content of 0.2% by mass or more and 40% by mass or less.
7. A method for producing titanium foil according to claim 5, comprising an extraction step of heating a mixture containing a titanium raw material containing titanium oxide, a reducing agent containing aluminum, and a separating agent before the aforementioned refining step, and extracting the crude titanium-based material from the molten mixture.