Salt bath additive, preparation method thereof and strengthened salt

Abstract

The invention provides a salt bath additive, a preparation method thereof and reinforced salt. According to the salt bath additive disclosed by the embodiment of the invention, the salt bath additive comprises silicon oxide, sodium oxide, aluminum oxide and a fluorine element; in the salt bath additive, the mass fraction of silicon oxide is 20wt%-45wt%, the range of the mass ratio of sodium oxide to aluminum oxide is 1.16-5, and the mass fraction of fluorine element is 0.1 wt%-8wt%. The salt bath additive disclosed by the embodiment of the invention has relatively good water-resistant stability and adsorption efficiency.

Description

Technical Field

[0001] This application relates to the field of glass strengthening, specifically to a salt bath additive, its preparation method, and the strengthening salt. Background Technology

[0002] To achieve higher mechanical strength, glass is typically chemically strengthened. Chemical strengthening involves ion exchange of the glass with molten strengthening salts, thereby removing lithium ions (Li+) from the glass. + The process involves replacing lithium ions in the glass with sodium ions in the strengthening salt. The difference in radii between sodium and lithium ions creates high-pressure stress on the surface of the strengthened glass, effectively inhibiting crack propagation and ensuring its strength. However, as strengthening continues, the concentration of lithium ions in the strengthening salt increases. This concentration change affects the normal ion exchange process, resulting in a gradual decrease in surface compressive stress and expansion. When a certain level is reached, the low surface compressive stress severely reduces the glass's strength, rendering the strengthening salt unusable—a phenomenon known as "salt bath poisoning." In this case, strengthening can only be achieved by changing the salt bath, which increases production costs, reduces efficiency, and exacerbates environmental pollution. Summary of the Invention

[0003] This application provides a salt bath additive that has good water resistance stability and adsorption efficiency.

[0004] In a first aspect, embodiments of this application provide a salt bath additive, the salt bath additive comprising silicon oxide, sodium oxide, aluminum oxide and fluorine; wherein the mass fraction of silicon oxide in the salt bath additive is 20wt% to 45wt%, the mass ratio of sodium oxide to aluminum oxide is in the range of 1.16 to 5, and the mass fraction of fluorine is 0.1wt% to 8wt%.

[0005] Secondly, embodiments of this application also provide a method for preparing a salt bath additive, comprising:

[0006] Provide the raw material components for the salt bath additive and mix them evenly;

[0007] The raw material components of the salt bath additive are melted to obtain molten salt; and

[0008] Molten salt is shaped to obtain a salt bath additive, wherein the salt bath additive includes silicon dioxide, sodium oxide, aluminum oxide and fluorine; wherein the mass fraction of silicon dioxide in the salt bath additive is 20wt% to 45wt%, the mass ratio of sodium oxide to aluminum oxide is in the range of 1.16 to 5, and the mass fraction of fluorine is 0.1wt% to 8wt%.

[0009] Thirdly, embodiments of this application also provide a fortified salt, which is purified or impurity removed using the salt bath additives described in this application.

[0010] The salt bath additive described in this application includes silicon oxide, sodium oxide, aluminum oxide, and fluorine. In the salt bath additive, the mass fraction of silicon oxide is 20 wt% to 45 wt%, the mass ratio of sodium oxide to aluminum oxide ranges from 1.16 to 5, and the mass fraction of fluorine is 0.1 wt% to 8 wt%. This application introduces fluorine into the salt bath additive. Fluorine can partially replace oxygen in the silicon-oxygen network, forming Si-F covalent bonds. The bond energy of the Si-F covalent bond is higher than that of the Si-O-Si covalent bond, exhibiting higher chemical stability. This high bond energy makes the Si-F covalent bond more difficult to hydrolyze in an aqueous environment, improving the water resistance stability of the salt bath additive. The presence of fluoride ions can also change the coordination environment of aluminum in the salt bath additive. Aluminum ions (Al3+) usually exist in the additive in a tetracoordinate form ([AlO4]). After the introduction of fluorine, aluminum ions will transform into a higher coordination (e.g., hexacoordinate [AlO6]), forming Al-F covalent bonds. Highly coordinated (six-coordinate) aluminum ions are more stable in aqueous environments than four-coordinate aluminum ions, further improving the water resistance of salt bath additives. However, excessively high fluorine (F) content may lower the glass transition temperature (Tg) of the salt bath additive. A low Tg causes crystallization during molding, which can clog the discharge pipe and increase molding difficulty. This application designs the composition and content of silicon oxide, sodium oxide, aluminum oxide, and fluorine in the salt bath additive to achieve higher adsorption efficiency. When applied to enhanced salt purification, this improves purification efficiency and extends the service life of the enhanced salt. Furthermore, it also enhances the water resistance and stability of the salt bath additive, making it less prone to water absorption and deterioration. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic flowchart of a method for preparing a salt bath additive according to an embodiment of this application. Detailed Implementation

[0013] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0014] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0015] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0016] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0017] To achieve higher mechanical strength, glass is typically chemically strengthened. Chemical strengthening involves ion exchange of the glass with molten strengthening salts, thereby removing lithium ions (Li+) from the glass. + The process involves replacing lithium ions in the glass with sodium ions in the strengthening salt. The difference in radii between sodium and lithium ions creates high-pressure stress on the surface of the strengthened glass, effectively inhibiting crack propagation and ensuring its strength. However, as strengthening continues, the concentration of lithium ions in the strengthening salt increases. This concentration change affects the normal ion exchange process, resulting in a gradual decrease in surface compressive stress and expansion. When a certain level is reached, the low surface compressive stress severely reduces the glass's strength, rendering the strengthening salt unusable—a phenomenon known as "salt bath poisoning." In this case, strengthening can only be achieved by changing the salt bath, which increases production costs, reduces efficiency, and exacerbates environmental pollution.

[0018] This application provides a salt bath additive, which includes silicon dioxide (SiO2), sodium oxide (Na2O), aluminum oxide (Al2O3), and fluorine (F). In the salt bath additive, the mass fraction of silicon dioxide is 20wt% to 45wt%, the mass ratio of sodium oxide to aluminum oxide is in the range of 1.16 to 5, and the mass fraction of fluorine is 0.1wt% to 8wt%.

[0019] The salt bath additive of this application can be used as an additive for strengthening salts in glass chemical strengthening. It is used to remove lithium ions from the strengthening salt, thereby purifying the strengthening salt, extending the service life of the strengthening salt, and reducing the cost of glass chemical strengthening.

[0020] In the embodiments of this application, when the numerical range a to b is involved, unless otherwise specified, the numerical value can be any value between a and b, including the endpoint value a and the endpoint value b.

[0021] It should be noted that the salt bath additive in this application is essentially a glassy compound.

[0022] Specifically, the mass fraction of silica in the salt bath additive can be, but is not limited to, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, and 45wt%. Silica can serve as the framework of the network structure of the salt bath additive, and its content directly affects the adsorption performance and stability of the salt bath additive's network framework. In salt bath additives, a low silica mass fraction reduces the stability of the additive's network framework and its chemical stability. Conversely, a high silica mass fraction results in insufficient content of other components, such as sodium oxide, which reduces the additive's adsorption efficiency and its ability to adsorb lithium ions. A silica mass fraction of 20wt% to 45wt% in the salt bath additive provides both better chemical stability and higher adsorption efficiency.

[0023] Specifically, the mass ratio of sodium oxide to alumina in the salt bath additive can be, but is not limited to, 1.16, 1.4, 1.6, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.3, 3.5, 3.8, 4, 4.3, 4.5, 4.8, and 5. If the mass ratio of sodium oxide to alumina in the salt bath additive is too low, the mass content of sodium oxide in the additive will be too low, and the mass content of alumina too high. Sodium oxide is mainly used to replace lithium ions in the fortified salt; if the sodium oxide content in the salt bath additive is too low, it will reduce the adsorption efficiency of the additive and increase the difficulty of melting. Alumina is beneficial for improving the stability of the network structure and chemical stability of the additive; however, if the alumina content is too high, it will make the additive difficult to form, requiring a higher melting temperature and increasing the production cost. If the mass ratio of sodium oxide to aluminum oxide in the salt bath additive is too high, the sodium oxide content will be too high and the aluminum oxide content too low. If the sodium oxide content is too high, the salt bath additive will easily absorb moisture. After absorbing water, the sodium oxide will react with the water to generate hydroxide ions (OH-). - When salt bath additives are used for strengthening salt purification, hydroxide ions can enter the strengthening salt, thus corroding the glass when it is used for glass strengthening, reducing the mechanical strength of the strengthened glass, and affecting its appearance. If the alumina content in the salt bath additive is too low, the stability of the additive's network structure will be reduced. Therefore, when the mass ratio of sodium oxide to alumina in the salt bath additive is too low, the adsorption efficiency of the salt bath additive is too low; when the mass ratio is too high, the water resistance stability of the salt bath additive is too low. A mass ratio of sodium oxide to alumina in the salt bath additive ranging from 1.16 to 5 allows the salt bath additive to have both high water resistance stability and high adsorption efficiency.

[0024] Furthermore, the mass ratio of sodium oxide to aluminum oxide in the salt bath additive ranges from 1.19 to 4.67. This allows the salt bath additive to possess both high water resistance and high impurity ion adsorption efficiency.

[0025] Optionally, the molar ratio of sodium oxide to aluminum oxide in the salt bath additive ranges from 1.8 to 3.5. Specifically, the molar ratio of sodium oxide to aluminum oxide in the salt bath additive can be, but is not limited to, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.3, 3.5, etc.

[0026] Specifically, the mass fraction of fluorine in the salt bath additive can be, but is not limited to, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 8.5 wt%, and 8 wt%. Introducing fluorine into the salt bath additive allows it to partially replace oxygen in the silicon-oxygen network, forming Si-F and Al-F covalent bonds. The bond energy of the Si-F covalent bond is higher than that of the Si-O-Si covalent bond, exhibiting higher chemical stability. This high bond energy makes the Si-F covalent bond more difficult to hydrolyze in an aqueous environment, improving the water resistance of the salt bath additive. The presence of fluoride ions can also alter the coordination environment of aluminum in the salt bath additive. Aluminum ions (Al3+) typically exist in additives in a tetracoordinate form ([AlO4]). Upon introduction of fluorine, these aluminum ions transform into higher-coordinate forms (e.g., hexacoordinate [AlO6]), forming Al-F covalent bonds. The higher-coordinate (hexacoordinate) aluminum ions are more stable in aqueous environments than the tetracoordinate forms, further improving the water resistance of the salt bath additive. Furthermore, fluorine can enhance the adsorption efficiency of the salt bath additive for impurity ions in the enhanced salt. However, excessively high fluorine content may lower the glass transition temperature (Tg) of the salt bath additive. A low Tg can cause crystallization during the molding process, which can clog the discharge pipe and increase molding difficulty. When the fluorine content in the salt bath additive is between 0.1 wt% and 8 wt%, it provides both good water resistance and adsorption efficiency.

[0027] Furthermore, the fluorine content in the salt bath additive is 1 wt% to 5 wt%. This gives the salt bath additive good water resistance and stability.

[0028] The salt bath additive described in this application embodiment includes silicon dioxide, sodium oxide, aluminum oxide, and fluorine. In the salt bath additive, the mass fraction of silicon dioxide is 20 wt% to 45 wt%, the mass ratio of sodium oxide to aluminum oxide ranges from 1.16 to 5, and the mass fraction of fluorine is 0.1 wt% to 8 wt%. Through the design of the composition and content of silicon dioxide, sodium oxide, aluminum oxide, and fluorine in the salt bath additive, the additive achieves high adsorption efficiency. When applied to enhanced salt purification, it can better improve purification efficiency and extend the service life of the enhanced salt. Furthermore, it also gives the salt bath additive higher water resistance and stability, making it less prone to water absorption and deterioration.

[0029] Furthermore, the salt bath additive of this application is an energy-saving, environmentally friendly, easy-to-clean material that does not affect production efficiency. During use, it does not produce insoluble precipitates or weak acid radicals such as (PO4).3- (BO) 3- This process allows for precipitation, thereby minimizing damage to the surface quality of materials requiring ion exchange, such as glass.

[0030] In some embodiments, the sodium oxide content in the salt bath additive is 35 wt% to 60 wt%.

[0031] Specifically, the mass fraction of sodium oxide in the salt bath additive can be, but is not limited to, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, etc.

[0032] Sodium oxide is mainly used to replace lithium ions (Li) in enhanced salts. + The higher the sodium oxide content in the salt bath additive, the higher its adsorption efficiency and the higher its purification efficiency for enhanced salts. Furthermore, sodium oxide can reduce the difficulty of melting the salt bath additive. However, if the sodium oxide content is too high, the salt bath additive is prone to absorbing moisture. After absorbing water, the sodium oxide reacts with the water to generate hydroxide ions (OH-). - When salt bath additives are used for strengthening salt purification, hydroxide ions can enter the strengthening salt, thereby corroding the glass when it is used for glass strengthening, reducing the mechanical strength of the strengthened glass, and affecting its appearance. When the mass fraction of sodium oxide in the salt bath additive is 35wt% to 60wt%, the salt bath additive can have high adsorption efficiency and good water resistance stability.

[0033] Furthermore, the sodium oxide content in the salt bath additive is 38 wt% to 57 wt%. This allows the salt bath additive to have high adsorption efficiency while also exhibiting good water resistance stability.

[0034] In some embodiments, the mass fraction of alumina in the salt bath additive is 12 wt% to 30 wt%.

[0035] Specifically, the mass fraction of alumina in the salt bath additive can be, but is not limited to, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 25wt%, 26wt%, 28wt%, 30wt%, etc.

[0036] Alumina is beneficial for improving the stability of the network structure and chemical stability of salt bath additives. If the alumina content in the salt bath additive is too low, the stability of the network structure will decrease. As the alumina content increases, the stability of the network structure and the exchange rate of the salt bath additive improve. However, if the alumina content is too high, the salt bath additive becomes more difficult to form, requiring a higher melting temperature and increasing the production cost. When the mass fraction of alumina in the salt bath additive is between 12 wt% and 30 wt%, the salt bath additive exhibits good structural and chemical stability, a high exchange rate, and a low melting temperature.

[0037] Furthermore, the mass fraction of alumina in the salt bath additive is 12 wt% to 25 wt%. This allows the salt bath additive to have good structural and chemical stability, as well as a high exchange rate and a low melting temperature.

[0038] Understandably, in some embodiments, the salt bath additive comprises, by mass fraction: 20 wt% to 45 wt% SiO2; 35 wt% to 60 wt% Na2O; 12 wt% to 30 wt% Al2O3; and 0.1 wt% to 8 wt% fluorine.

[0039] In some embodiments, the salt bath additive comprises, by mass fraction:

[0040] 22wt% to 40wt% silicon dioxide;

[0041] 38 wt% to 57 wt% sodium oxide;

[0042] 12 wt% to 25 wt% alumina; and

[0043] Fluorine element from 1 wt% to 5 wt%.

[0044] Specifically, in the salt bath additive, the mass fraction of silicon dioxide can be, but is not limited to, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, and 40wt%; the mass fraction of sodium oxide can be, but is not limited to, 38wt%, 39wt%, 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, and 40wt%. The mass fractions of alumina can be, but are not limited to, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 25wt%, etc.; the mass fractions of fluorine can be, but are not limited to, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, etc.

[0045] When the salt bath additive adopts the components and proportions of this embodiment, it can achieve a higher adsorption efficiency, which can improve the purification efficiency when applied to enhanced salt purification. In addition, it can also make the salt bath additive more water-resistant and less prone to water absorption and deterioration.

[0046] In some embodiments, the salt bath additive further includes boron oxide (B2O3), wherein the molar content of sodium oxide in the salt bath additive is greater than or equal to the sum of the molar content of aluminum oxide and the molar content of boron oxide.

[0047] In other words, the sum of the molar content of alumina and the molar content of boron oxide is less than or equal to the molar content of sodium oxide. For example, if the molar content of alumina is M1, the molar content of boron oxide is M2, and the molar content of sodium oxide is M3, then M1 + M2 ≤ M3.

[0048] The network structure of the salt bath additive in this embodiment includes B-Si-O covalent bonds, Si-F covalent bonds, and Al-F covalent bonds. The salt bath additive, a covalently bond-based compound, has a larger structure than ceramics and exhibits higher efficiency in adsorbing impurity ions in enhanced salts.

[0049] Understandably, the sum of the molar content of aluminum oxide and the molar content of boron oxide is less than or equal to the molar content of sodium oxide.

[0050] Boron oxide is the network structure generator in salt bath additives. B₂O₃ can exist in the form of [BO₃]trigonal and [BO₄] tetrahedrons. Compared to the [BO₃] structure, the [BO₄] structure possesses higher geometric symmetry and structural integrity, exhibiting greater stability and stronger connectivity under alkaline and high-temperature / high-pressure conditions, thus better improving the stability of salt bath additives in high-temperature and alkaline environments. When the molar content of sodium oxide in the salt bath additive is greater than or equal to the sum of the molar content of aluminum oxide and boron oxide, boron (B) mostly exists in the network structure of the salt bath additive in the form of [BO₄] tetrahedrons, which can further improve the connectivity and stability of the network structure of the salt bath additive.

[0051] Optionally, the ratio of the molar content of sodium oxide M1 to the sum of the molar contents of aluminum oxide M2 ​​and boron oxide M3 ranges from 1.3 to 8.0. That is, 1.3 ≤ M1 / (M2+M3) ≤ 8.0.

[0052] Specifically, the ratio of the molar content of sodium oxide M1 to the sum of the molar content of aluminum oxide M2 ​​and the molar content of boron oxide M3 can be, but is not limited to, 1.3, 1.5, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.3, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, etc.

[0053] When the sodium oxide content is too low, Al 3+ Preferentially entering the network structure of salt bath additives as [AlO4], B 3+ The sodium oxide preferentially enters the network structure in the form of [BO3] rather than [BO4]. Therefore, if the sodium oxide content is too low, it will reduce the water resistance, high-temperature stability, and alkali resistance of the salt bath additive. If the sodium oxide content is too high, the excess oxygen atoms will exist in the form of non-bridging oxygen, thereby destroying the network structure connectivity and stability, which in turn reduces the stability of the network structure and water resistance of the salt bath additive. Therefore, when the ratio of the molar content of sodium oxide to the total molar content of aluminum oxide and boron oxide in the salt bath additive is in the range of 1.3 to 8.0, the salt bath additive can have higher water resistance, high-temperature stability, and alkali resistance.

[0054] Furthermore, the ratio of the molar content of sodium oxide to the total molar content of aluminum oxide and boron oxide in the salt bath additive ranges from 1.5 to 7. This allows the salt bath additive to possess higher water resistance, high-temperature stability, and alkali resistance.

[0055] Furthermore, the ratio of the molar content of sodium oxide to the total molar content of aluminum oxide and boron oxide in the salt bath additive ranges from 1.8 to 6. This allows the salt bath additive to possess higher water resistance, high-temperature stability, and alkali resistance.

[0056] In some embodiments, the total mass fraction of silicon oxide, boron oxide and aluminum oxide in the salt bath additive is 44 wt% to 55 wt%.

[0057] Specifically, the total mass fraction of silicon oxide, boron oxide and aluminum oxide in the salt bath additive can be, but is not limited to, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, 55wt%, etc.

[0058] Silica, boron oxide, and aluminum oxide are components of the network structure of salt bath additives. A higher total content of these three components contributes to the stability of the network structure, resulting in stronger resistance to decomposition at high temperatures. Therefore, a low total mass fraction of silica, boron oxide, and aluminum oxide in a salt bath additive reduces the stability of its network structure; conversely, a high total mass fraction results in a low sodium oxide content, reducing the additive's adsorption capacity (for absorbing impurities such as Li). + The ability to absorb heteroions such as Li) and the adsorption rate + (The rate). When the total mass fraction of silicon oxide, boron oxide and aluminum oxide in the salt bath additive is 44wt% to 55wt%, the salt bath additive can have a high heteroion adsorption capacity and adsorption rate, while the network structure of the salt bath additive has high stability.

[0059] In some embodiments, the mass fraction of boron oxide in the salt bath additive is less than or equal to 8 wt%.

[0060] Specifically, the mass fraction of boron oxide in the salt bath additive can be, but is not limited to, 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, etc.

[0061] Boron oxide is the network structure former of salt bath additives. B₂O₃ can exist in the form of [BO₃]trigonal and [BO₄]tetrahedral structures, especially the [BO₄]tetrahedral form, which forms a network structure with higher stability under high temperature and alkaline conditions. If the mass fraction of boron oxide in the salt bath additive is too low, it will not improve the thermal stability and alkali resistance of the additive, or its effect will be minimal; if the mass fraction of boron oxide in the salt bath additive is too high, it will reduce the Na₂O content, thus reducing the adsorption efficiency and adsorption rate of the salt bath additive. Therefore, when the mass fraction of boron oxide in the salt bath additive is between 0.1 wt% and 8 wt%, the salt bath additive can exhibit high water resistance and high adsorption efficiency.

[0062] Furthermore, the mass fraction of boron oxide in the salt bath additive is less than or equal to 5 wt%. This allows the salt bath additive to have higher adsorption efficiency and adsorption rate.

[0063] Furthermore, the mass fraction of boron oxide in the salt bath additive is 0.1 wt% to 5 wt%. This allows the salt bath additive to have higher adsorption efficiency and adsorption rate, and also improves its high-temperature stability and stability under alkaline conditions.

[0064] In some embodiments, the salt bath additive further includes oxides, the oxides including at least one of phosphorus pentoxide (P2O5), magnesium oxide (MgO), calcium oxide (CaO), and potassium oxide (K2O), wherein the mass fraction of the oxides in the salt bath additive is less than or equal to 5 wt%.

[0065] Specifically, the mass fraction of oxides in the salt bath additive can be, but is not limited to, 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, etc.

[0066] Phosphorus pentoxide can form a network structure in salt bath additives, thereby improving the stability of the network structure. Magnesium oxide and calcium oxide can improve the water resistance of salt bath additives, making them less prone to water absorption and deterioration. Potassium oxide (K₂O), as a functional component of salt bath additives, can adsorb impurity ions (Na₂O) in the ion exchange salt bath by introducing appropriate amounts. + If the mass fraction of oxides in the salt bath additive is too low, the improvement on the performance of the salt bath additive will be limited. If the mass fraction of oxides in the salt bath additive is too high, the content of other components such as sodium oxide, silicon oxide and aluminum oxide will be reduced, thereby reducing the adsorption capacity and adsorption rate of the salt bath additive, and also reducing the stability of the salt bath additive.

[0067] Furthermore, in the salt bath additive, the mass fraction of the oxide ranges from 0.1 wt% to 5 wt%. This allows the salt bath additive to possess higher network structure stability, water resistance stability, and better adsorption capacity and adsorption rate.

[0068] Furthermore, in the salt bath additive, the mass fraction of the oxide ranges from 0.5 wt% to 4 wt%. This allows the salt bath additive to possess higher network structure stability, water resistance stability, and better adsorption capacity and adsorption rate.

[0069] In some embodiments, the raw material components of the salt bath additive include SiO2 source, Na2O source, Al2O3 source and fluoride.

[0070] Optionally, the SiO2 introduction source includes at least one of quartz sand, Na2SiO3, and Na2SiF6.

[0071] Optionally, the source of Na2O introduction includes at least one of Na2CO3, NaOH, NaCl, NaHCO3, Na2SiO3, NaNO3, NaF, and Na2SiF6.

[0072] Optionally, the Al2O3 introduction source includes at least one of aluminum oxide, aluminum hydroxide, aluminum nitrate, and aluminum fluoride.

[0073] Optionally, the fluoride includes at least one of NaF, AlF, and Na2SiF6.

[0074] In this embodiment, the use of these raw material components to prepare salt bath additives can result in salt bath additives with higher structural stability, higher water resistance, and higher adsorption efficiency.

[0075] In some embodiments, the raw material components of the salt bath additive further include a B2O3 introducing source, which includes at least one selected from borax and sodium-containing boron oxides. In this embodiment, using these B2O3 introducing sources for the preparation of the salt bath additive can result in the salt bath additive exhibiting higher structural stability, higher water resistance, and higher adsorption efficiency.

[0076] Figure 1 This is a schematic flowchart of a method for preparing a salt bath additive according to an embodiment of this application.

[0077] Please see Figure 1 This application also provides a method for preparing a salt bath additive, comprising:

[0078] S101 provides the raw material components for the salt bath additive and mixes them uniformly;

[0079] Optionally, the raw material components of the salt bath additive are placed into a mixer in a preset ratio and mixed evenly to obtain a mixture.

[0080] In some embodiments, the raw material components of the salt bath additive include SiO2 source, Na2O source, Al2O3 source and fluoride.

[0081] In other embodiments, the raw material components of the salt bath additive include SiO2 introducing sources, Na2O introducing sources, Al2O3 introducing sources, fluorides, and B2O3 introducing sources.

[0082] S102, melting the raw material components of the salt bath additive to obtain molten salt; and

[0083] Optionally, the raw material components of the salt bath additive are placed in a platinum crucible and melted at a melting temperature of 1300°C to 1600°C, and held at that temperature for 0.5 h to 5 h to homogenize the components.

[0084] Specifically, the melting temperature can be, but is not limited to, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, etc. If the melting temperature is too low, some raw material components in the salt bath additive may not be completely dissolved, resulting in unmelted particles remaining in the molten salt, thus affecting the performance of the prepared salt bath additive. If the melting temperature is too high, the sodium oxide source is prone to decomposition and volatilization, resulting in a significant difference between the sodium oxide content in the prepared salt bath additive and the designed content, making it difficult to control the composition of the salt bath additive and thus affecting its performance.

[0085] Specifically, the holding time can be, but is not limited to, 0.5h, 1h, 2h, 3h, 4h, 5h, etc. If the holding time is too short, some raw material components in the salt bath additive may not be completely dissolved, resulting in unmelted particles remaining in the molten salt, thus affecting the performance of the prepared salt bath additive. If the holding time is too long, the sodium oxide source is prone to decomposition and volatilization, resulting in a significant difference between the sodium oxide content in the prepared salt bath additive and the designed content. This makes it difficult to control the composition of the salt bath additive, thus affecting its performance. In addition, a long holding time increases the preparation cost of the salt bath additive.

[0086] This application achieves a smooth surface by forming a borosilicate compound above its melting point, thereby enabling the salt bath additive to be applied to the enhanced salt. When the enhanced salt bath (salt bath) is removed, the amount of salt bath material adhering to the surface of the salt bath additive is greatly reduced, thus reducing the waste of salt bath material.

[0087] S103, the molten salt is shaped to obtain a salt bath additive, wherein the salt bath additive includes silicon dioxide, sodium oxide, aluminum oxide and fluorine; in the salt bath additive, the mass fraction of silicon dioxide is 20wt% to 45wt%, the mass ratio of sodium oxide to aluminum oxide is in the range of 1.16 to 5, and the mass fraction of fluorine is 0.1wt% to 8wt%.

[0088] In some embodiments, molten salt is cooled to 500°C to 1100°C and extruded or stretched to obtain sheet-like salt bath additives.

[0089] Specifically, the molding temperature can be, but is not limited to, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, etc. If the extrusion molding or stretching temperature is too low, crystallization is likely to occur, causing the salt bath additive to turn white locally and affecting the adsorption performance of the salt bath additive; if the extrusion molding or stretching temperature is too high, the viscosity of the molten salt will be too low, increasing the difficulty of extrusion molding or stretching.

[0090] Optionally, the thickness of the sheet-like salt bath additive is less than or equal to 1.5 mm. Specifically, the thickness of the sheet-like salt bath additive can be, but is not limited to, less than or equal to 1.5 mm, less than or equal to 1.2 mm, less than or equal to 1.0 mm, less than or equal to 0.8 mm, less than or equal to 0.5 mm, etc. The thinner the salt bath additive, the larger the contact area between the salt bath additive and the enhanced salt when it is used for impurity removal or purification of enhanced salt, and the faster the adsorption rate of impurity ions. However, the thinner the salt bath additive, the more difficult it is to prepare.

[0091] In other embodiments, molten salt can be directly water-quenched to obtain granular salt bath additives.

[0092] Optionally, the particle size of the granular salt bath additive ranges from 3 mm to 10 mm. Specifically, the particle size of the granular salt bath additive can be, but is not limited to, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc. When salt bath additives are used for enhanced salt purification, the granular salt bath additives are usually placed in a stainless steel box with a porous structure. If the particle size of the salt bath additive is too small, it increases the processing difficulty of the stainless steel box; if the particle size of the salt bath additive is too large, the surface area of ​​the salt bath additive is small, which reduces the impurity adsorption rate of the salt bath additive.

[0093] Furthermore, the particle size of the granular salt bath additive ranges from 3mm to 5mm. This allows the salt bath additive to have high adsorption efficiency while also making the stainless steel box easy to process.

[0094] For a detailed description of other aspects of the salt bath additive, please refer to the description in the corresponding section of the above embodiments, which will not be repeated here.

[0095] The salt bath additive prepared by the method described in this application includes silicon dioxide, sodium oxide, aluminum oxide, and fluorine. In the salt bath additive, the mass fraction of silicon dioxide is 20 wt% to 45 wt%, the mass ratio of sodium oxide to aluminum oxide ranges from 1.16 to 5, and the mass fraction of fluorine is 0.1 wt% to 8 wt%. Through the design of the composition and content of silicon dioxide, sodium oxide, aluminum oxide, and fluorine in the salt bath additive, the salt bath additive exhibits high adsorption efficiency. When applied to enhanced salt purification, it can better improve purification efficiency and extend the service life of enhanced salt. Furthermore, it can also give the salt bath additive higher water resistance and stability, making it less prone to water absorption and deterioration.

[0096] This application also provides a fortified salt, which is purified or impurity removed using the salt bath additive described in this application.

[0097] When the salt bath additive of this application embodiment is used for the purification or removal of impurities in enhanced salt, the salt bath additive is placed in a stainless steel box with a porous structure, and then the stainless steel box containing the salt bath additive is placed in molten enhanced salt containing at least one of sodium nitrate (NaNO3) and potassium nitrate (KNO3), so that the salt bath additive adsorbs impurity ions (such as lithium ions) in the enhanced salt, thereby purifying or removing impurities from the enhanced salt.

[0098] Understandably, the fortified salt includes at least one of sodium nitrate and potassium nitrate.

[0099] In some embodiments, the fortified salt comprises, by mass fraction, 5 wt% to 100 wt% sodium nitrate and 0 wt% to 95 wt% potassium nitrate. Specifically, the mass fraction of sodium nitrate in the fortified salt may be, but is not limited to, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 100 wt%, etc. The mass fraction of potassium nitrate in the fortified salt may be, but is not limited to, 0 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, etc.

[0100] Optionally, the temperature for strengthening the salt is between 350°C and 540°C. Specifically, it can be, but is not limited to, 350°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, 520°C, 540°C, etc.

[0101] Understandably, salt bath additives can be added to the strengthening salt along with the glass during glass strengthening, or they can be added to the strengthening salt after glass strengthening is completed. The specific method can be determined according to the actual situation, and this application does not make any specific limitations.

[0102] For a detailed description of other aspects of the salt bath additive, please refer to the corresponding sections of the above embodiments, which will not be repeated here.

[0103] The salt bath additive of this application includes silicon dioxide, sodium oxide, aluminum oxide, and fluorine. In the salt bath additive, the mass fraction of silicon dioxide is 20 wt% to 45 wt%, the mass ratio of sodium oxide to aluminum oxide ranges from 1.16 to 5, and the mass fraction of fluorine is 0.1 wt% to 8 wt%. This application introduces fluorine into the salt bath additive. Fluorine can partially replace oxygen in the silicon-oxygen network, forming Si-F covalent bonds. The bond energy of the Si-F covalent bond is higher than that of the Si-O-Si covalent bond, exhibiting higher chemical stability. This high bond energy makes the Si-F covalent bond more difficult to hydrolyze in an aqueous environment, improving the water resistance stability of the salt bath additive. The presence of fluoride ions can also change the coordination environment of aluminum in the salt bath additive. Aluminum ions (Al3+) usually exist in the additive in a tetracoordinate form ([AlO4]). After the introduction of fluorine, aluminum ions will transform into a higher coordination (e.g., hexacoordinate [AlO6]), forming Al-F covalent bonds. Highly coordinated (six-coordinate) aluminum ions are more stable in aqueous environments than four-coordinate aluminum ions, further improving the water resistance of salt bath additives. However, excessively high fluorine (F) content may lower the glass transition temperature (Tg) of the salt bath additive. A low Tg causes crystallization during molding, which can clog the discharge pipe and increase molding difficulty. This application designs the composition and content of silicon oxide, sodium oxide, aluminum oxide, and fluorine in the salt bath additive to achieve higher adsorption efficiency, thus improving purification efficiency when used in enhanced salt purification. Furthermore, it also enhances the water resistance and stability of the salt bath additive, making it less prone to water absorption and deterioration.

[0104] Therefore, the salt bath additive of this application embodiment has high water resistance stability and adsorption efficiency. By using the salt bath additive of this application embodiment to purify or remove impurities from the strengthening salt, the service life of the strengthening salt can be extended and the cost of chemical strengthening of glass can be reduced.

[0105] This application also provides a tempered glass, which is strengthened using the strengthening salt described in this application. The strengthening salt is purified or impurity-removing using the salt bath additive described in this application.

[0106] The salt bath additive of this application will be further described below through specific embodiments.

[0107] Examples 1 to 26, Comparative Examples 1 to 7

[0108] The salt bath additives in each embodiment are prepared by the following steps:

[0109] (1) Weigh out the SiO2 source, Na2O source, Al2O3 source, fluoride, and B2O3 source according to the preset ratio. Among them, the SiO2 source is Na2SiO3, the Na2O source is Na2CO3, the Al2O3 source is alumina, the B2O3 source is borax, and the fluoride is NaF. Put each source into a mixer for mixing.

[0110] (2) Place the mixed source into a platinum crucible, heat it to 1400℃ to melt it, and keep it at that temperature for 2 hours;

[0111] (3) The molten salt is cooled to 800°C and drawn into a sheet to obtain a salt bath additive with a thickness of 0.6 mm. The components and contents of each component of the salt bath additives prepared in each embodiment and comparative example are shown in Table 1 below.

[0112] The following performance tests were conducted on the salt bath additives of each embodiment and comparative example:

[0113] (1) Water resistance stability test: Approximately 10g of salt bath additive was dried in an oven at 150℃. After drying, the weight was recorded as m1. Then, the dried salt bath additive was boiled in 100mL of deionized water at 100℃ for 10 minutes. After removal, it was dried in an oven at 150℃ and weighed again, recorded as m2. 100%×(m1-m2) / m1 was used as the evaluation standard for water resistance stability. The larger the 100%×(m1-m2) / m1, the higher the mass loss rate, indicating that the water resistance of the salt bath additive is worse.

[0114] (2) Adsorption efficiency: 99.7 wt% NaNO3 and 0.3 wt% LiNO3 (Li concentration 300 ppm) were added to a chemical strengthening furnace, and then the temperature was raised to 470℃ for melting. 1 wt% salt bath additive was added to the molten strengthening salt bath. Samples were taken from the strengthening salt bath at strengthening times of 5 h and 10 h. The Li in the strengthening salt bath was tested using atomic absorption spectrometry (AAS). + The greater the decrease in Li concentration over the same period of time, the better the adsorption efficiency of the salt bath additive.

[0115] The test results of the water resistance stability of the salt bath additives in each embodiment and comparative example are shown in Table 1 below.

[0116] Table 1. Composition and water resistance stability test data of salt bath additives in each embodiment and comparative example.

[0117]

[0118]

[0119] Table 2 shows the adsorption efficiency test data of the salt bath additives in each embodiment and comparative example.

[0120]

[0121] The test results of Examples 1 to 5 and Comparative Examples 1 to 2 show that, compared to Comparative Example 1, the salt bath additives of Examples 1 to 5 exhibited lower mass loss rates in the water resistance stability test. This indicates that adding fluorine to the salt bath additive can improve its water resistance stability. The test results of Examples 1 to 5 show that the water resistance stability of the salt bath additive gradually increases with increasing fluorine content. When the mass fraction of fluorine in the salt bath additive is low, the adsorption efficiency of the salt bath additive for impurity ions decreases slightly. However, with increasing fluorine content, the adsorption efficiency of the salt bath additive for impurity ions gradually increases. The test results of Comparative Example 2 show that when the fluorine content in the salt bath additive is high, although the water resistance stability of the salt bath additive further increases, the adsorption efficiency decreases. Therefore, when the mass fraction of fluorine in the salt bath additive is between 0.1 wt% and 8 wt%, the salt bath additive can exhibit both high water resistance stability and high adsorption efficiency.

[0122] The test results from Examples 7 to 11 and Comparative Examples 3 to 4 show that as the mass ratio of sodium oxide to aluminum oxide in the salt bath additive increases, the water resistance of the salt bath additive gradually decreases, while its adsorption efficiency gradually increases. The tests and results from Comparative Example 3 show that when the mass ratio of sodium oxide to aluminum oxide in the salt bath additive is too low, although the salt bath additive exhibits good water resistance, its adsorption efficiency is significantly reduced. Similarly, the tests and results from Comparative Example 4 show that when the mass ratio of sodium oxide to aluminum oxide in the salt bath additive is too high, although the salt bath additive exhibits good water resistance, its adsorption efficiency is significantly reduced. Therefore, when the mass ratio of sodium oxide to aluminum oxide in the salt bath additive is in the range of 1.16 to 5, the salt bath additive can possess both high water resistance and high adsorption efficiency.

[0123] The test results from Examples 12 to 17 and Comparative Examples 5 to 6 show that the ratio of sodium oxide to aluminum oxide in the salt bath additive remains constant (approximately 2:1), and the mass fraction of fluorine also remains constant. As the mass fraction of silica in the salt bath additive increases, the water resistance of the additive gradually increases. However, as the mass fraction of silica in the salt bath additive increases, the adsorption efficiency of the additive gradually decreases. Therefore, when the mass fraction of silica in the salt bath additive is between 20 wt% and 45 wt%, the additive can exhibit both high water resistance and high adsorption efficiency.

[0124] The test results from Examples 4 and 18 show that adding boron oxide to the salt bath additive in Example 18 improves its water resistance, indicating that the addition of boron oxide can enhance the water resistance of the salt bath additive. Furthermore, the adsorption efficiency of the boron-added salt bath additive for impurity ions slightly decreased after 5 hours of purification, but improved after 10 hours of purification.

[0125] The test results from Examples 18 to 21 show that the water resistance of the salt bath additive gradually increases with the increase of the boron oxide mass fraction. Furthermore, the adsorption efficiency of the salt bath additive for impurity ions gradually increases with the increase of the boron oxide mass fraction. However, the test results from Comparative Example 7 show that when the boron oxide mass fraction in the salt bath additive is too high, the adsorption efficiency of the salt bath additive for impurity ions actually decreases.

[0126] The test results of Examples 22 and 23 show that the addition of phosphorus pentoxide (P2O5) to the salt bath additive of Example 23 slightly reduced the water resistance stability of the salt bath additive of Example 23. However, the adsorption efficiency of the salt bath additive of Example 23 for impurity ions was significantly increased.

[0127] The test results of Examples 22 and 24 show that the addition of magnesium oxide (MgO) to the salt bath additive in Example 24 increases the water resistance of the salt bath additive in Example 24, and also increases the adsorption efficiency of the salt bath additive in Example 24 for impurity ions.

[0128] As can be seen from the test results of Examples 22 and 25, the addition of calcium oxide (CaO) to the salt bath additive in Example 25 has little effect on the water resistance stability of the salt bath additive, but it can increase the adsorption efficiency of the salt bath additive for impurity ions.

[0129] As can be seen from the test results of Examples 22 and 26, the addition of potassium oxide (K2O) to the salt bath additive in Example 26 reduced the water resistance stability of the salt bath additive, but greatly increased the adsorption efficiency of the salt bath additive for impurity ions.

[0130] Tests showed that the mass loss rate of the salt bath additive of this application embodiment after boiling in deionized water at 100°C for 10 minutes was 0.04% to 0.64%. Specifically, the mass loss rate of the salt bath additive of this application embodiment after boiling in deionized water at 100°C for 10 minutes can be, but is not limited to, 0.04%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, and 0.64%. The salt bath additive of this application embodiment has good water resistance and stability, and is not easily degraded by absorbing water. When applied to the purification of fortified salts, it can better avoid the contamination of fortified salts by surface hydroxide ions, and better avoid the corrosion of glass cups during glass strengthening.

[0131] Tests have shown that the salt bath additive of this application has high adsorption efficiency when used to purify enhanced salt. When the amount of salt bath additive added is 1 wt%, after purifying enhanced salt at 470°C for 5 hours, the impurity ions in the enhanced salt can be reduced by 30.3% to 52% (i.e., the removal rate is 30.3% to 52%, specifically, it can be, but is not limited to, 30.3%, 35%, 40%, 45%, 50%, 52%, etc.); after purifying enhanced salt for 10 hours, the impurity ions in the enhanced salt can be reduced by 35.7% to 57.7% (i.e., the removal rate is 35.7% to 57.7%, specifically, it can be, but is not limited to, 35.7%, 40%, 45%, 50%, 52%, 55%, 57.7%, etc.).

[0132] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form yet another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A salt bath additive, characterized in that, The salt bath additive includes silicon dioxide, sodium oxide, aluminum oxide, and fluorine. In the salt bath additive, the mass fraction of silicon dioxide is 20 wt% to 45 wt%, the mass ratio of sodium oxide to aluminum oxide is in the range of 1.16 to 5, and the mass fraction of fluorine is 0.1 wt% to 8 wt%.

2. The salt bath additive according to claim 1, characterized in that, In the salt bath additive, the mass fraction of sodium oxide is 35 wt% to 60 wt%.

3. The salt bath additive according to claim 1, characterized in that, In the salt bath additive, the mass fraction of alumina is 12 wt% to 30 wt%.

4. The salt bath additive according to claim 1, characterized in that, The salt bath additive comprises, by mass fraction: 22wt% to 40wt% silicon dioxide; 38 wt% to 57 wt% sodium oxide; 12 wt% to 25 wt% alumina; and Fluorine element from 1 wt% to 5 wt%.

5. The salt bath additive according to claim 1, characterized in that, The salt bath additive also includes boron oxide, wherein the sum of the molar content of aluminum oxide and the molar content of boron oxide in the salt bath additive is less than or equal to the molar content of sodium oxide.

6. The salt bath additive according to claim 5, characterized in that, In the salt bath additive, the total mass fraction of silicon oxide, boron oxide and aluminum oxide is 44 wt% to 55 wt%.

7. The salt bath additive according to claim 5, characterized in that, In the salt bath additive, the mass fraction of boron oxide is less than or equal to 8 wt%.

8. The salt bath additive according to claim 5, characterized in that, In the salt bath additive, the mass fraction of boron oxide is less than or equal to 5 wt%.

9. The salt bath additive according to claim 1, characterized in that, The salt bath additive further includes oxides, which include at least one of phosphorus pentoxide, magnesium oxide, calcium oxide, and potassium oxide. The mass fraction of the oxides in the salt bath additive is less than or equal to 5 wt%.

10. The salt bath additive according to claim 1, characterized in that, The raw material components of the salt bath additive include a SiO2 source, a Na2O source, an Al2O3 source, and a fluoride; the SiO2 source includes at least one of quartz sand, Na2SiO3, and Na2SiF6; the Na2O source includes at least one of Na2CO3, NaOH, NaCl, NaHCO3, Na2SiO3, NaNO3, NaF, and Na2SiF6; the Al2O3 source includes at least one of alumina, aluminum hydroxide, aluminum nitrate, and aluminum fluoride; and the fluoride includes at least one of NaF, AlF, and Na2SiF6.

11. The salt bath additive according to claim 10, characterized in that, The raw material components of the salt bath additive also include a B2O3 introduction source, which includes at least one of borax and sodium-containing boron oxides.

12. A method for preparing a salt bath additive, characterized in that, include: Provide the raw material components for the salt bath additive and mix them evenly; The raw material components of the salt bath additive are melted to obtain molten salt; as well as The molten salt is shaped to obtain a salt bath additive, wherein the salt bath additive includes silicon dioxide, sodium oxide, aluminum oxide and fluorine; in the salt bath additive, the mass fraction of silicon dioxide is 20wt% to 45wt%, the mass ratio of sodium oxide to aluminum oxide is in the range of 1.16 to 5, and the mass fraction of fluorine is 0.1wt% to 8wt%.

13. The method for preparing the salt bath additive according to claim 12, characterized in that, The raw material components of the salt bath additive are melted to obtain molten salt, including: melting the raw material components of the salt bath additive at a temperature of 1300℃ to 1600℃ to obtain molten salt; The process of molding the molten salt to obtain a salt bath additive includes: cooling the molten salt to 500°C to 1100°C and extruding or stretching it to obtain a sheet-like salt bath additive; or quenching the molten salt in water to obtain a granular salt bath additive.

14. A fortified salt, characterized in that, The enhanced salt is purified or impurity removed using the salt bath additive described in any one of claims 1-11, or the enhanced salt is purified or impurity removed using the salt bath additive prepared by the method described in claim 12 or 13.

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