Minimizing crh defect formation in glass manufactured in precious metal systems

Abstract

A method is provided to minimize the formation of rhodium-platinum defects in a glass or glass-ceramic material or its melt. The method includes providing a container made of a platinum-rhodium alloy for use in a manufacturing process to obtain the material, with an interface between the container and the melt. The method may include providing sufficient hydrogen partial pressure outside and inside the container to control the oxygen partial pressure in the melt region adjacent to the interface. A method is also provided to minimize, or counteract, the formation of, localized thermal, electrical, or composite cells in a melt during a manufacturing process. This method may include adding a multivalent compound to the melt, adding a mixer to a refining tube, adding a mixing step to the manufacturing process, or expanding the mixing.

Description

Technical Field

[0001] This application claims priority to U.S. Provisional Application No. 63 / 069194, filed August 24, 2020, the entire contents of which are relied upon and incorporated herein by reference.

[0002] This disclosure relates to a method for minimizing the formation of glass defects in a manufacturing process involving precious metal systems, and more specifically, to a method for minimizing the formation of rhodium-rich defects in glass or glass-ceramic materials during a manufacturing process. Prior Technology

[0003] Many glass materials are manufactured in processes involving melting, refining, delivering, mixing, and / or forming containers made of platinum or platinum alloys. Platinum or platinum alloys are used in such containers for storing, transporting, and forming molten glass because they possess the necessary properties, such as high melting point, strength, and corrosion resistance, to withstand the extreme environments of molten glass (melt). While precious metals like platinum and platinum alloys are generally considered inert relative to glass at high temperatures, oxidation, reduction, or other reactions can occur at the melt-metal interface within the container, and these reactions can lead to defects in the melt and the resulting product.

[0004] Rhodium can be alloyed with platinum to increase strength and extend the life of manufactured containers. Rhodium defects have previously been found in some glasses; however, these defects are temporary rather than permanent, or their quantity is insufficient to warrant mitigation measures. For some glasses, removing rhodium from the system and using another suitable precious metal alloy may be an option, but this option is generally unacceptable for glasses with higher melting temperatures. Summary of the Invention

[0005] In various embodiments, a method is provided to minimize the formation of rhodium-platinum defects in a glass or glass-ceramic material. The method may include providing a container made of a platinum-rhodium alloy for a manufacturing process to obtain the material, wherein an interface exists between the container and the melt of the material. The method may include providing a hydrogen partial pressure outside the container relative to the hydrogen partial pressure inside the container in an amount sufficient to control the oxygen partial pressure in the melt region adjacent to the interface. In various embodiments, the rhodium-platinum defects may be rhodium-rich and the platinum-rhodium alloy in the container may be platinum-rich.

[0006] In some embodiments, the rhodium-platinum defect may include about 80% rhodium and about 20% platinum, and the platinum-rhodium alloy in the container may include about 80% platinum and about 20% rhodium.

[0007] In some embodiments, materials are provided that are produced by methods for minimizing rhodium-platinum defects. In such embodiments, the material may be substantially free of rhodium-platinum defects.

[0008] In various embodiments, a method is provided to minimize or counteract the formation of localized thermal, electrical, or composite batteries in a glass or glass-ceramic material. The method may include providing a container made of a platinum-rhodium alloy for a manufacturing process, wherein an interface exists between the container and a melt of the material. The method may include at least one step selected from: adding a multivalent compound to the melt, stirring the melt in a refining vessel during the manufacturing process, and stirring the melt immediately after it leaves the refining vessel.

[0009] In some embodiments, the formation of an electrical, thermal, or composite battery can lead to the formation of rhodium-platinum defects. In some embodiments, the defects may be rhodium-rich and the platinum-rhodium alloy in the container may be platinum-rich. In some embodiments, the defects may include about 80% rhodium and about 20% platinum, and the platinum-rhodium alloy in the container may include about 80% platinum and about 20% rhodium. In such embodiments, the material may be substantially free of rhodium-platinum defects.

[0010] In some embodiments, materials are provided that are produced by methods for minimizing the formation of localized thermal, electrical, or composite batteries, or for counteracting their effects. In some embodiments, the material comprises a multivalent substance. In some embodiments, the material may include greater than 0.1 wt% of tin oxide (SnO₂), iron oxide (Fe₂O₃), manganese oxide (MnO₂), cerium oxide (Ce₂O₃), or combinations thereof. In some embodiments, the material may include at least 0.05 wt% of a combination of antimony oxide (Sb₂O₃) and arsenic oxide (As₂O₃).

[0011] Additional features and advantages of the embodiments disclosed herein will be set forth in the following embodiments, and to some extent, those skilled in the art will readily understand such additional features and advantages from the embodiments described herein, or will recognize such additional features and advantages by practicing the embodiments described herein, including the following embodiments, the claims of the invention and the accompanying drawings.

[0012] The foregoing description and the following embodiments present examples intended to provide an overview or framework for understanding the nature and features of the embodiments disclosed herein. The accompanying drawings are included to provide further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the present disclosure and, together with the description, explain their principles and operation. Simple Explanation of the Diagram

[0013] Figure 1 (Prior Art) is a schematic diagram showing the structure of a glass delivery system in a pull-down melting process for preparing glass sheets;

[0014] Figure 2 is a cross-sectional view of an exemplary container according to embodiments of the present invention;

[0015] Figure 3 is an optical microscope image of a crystalline rhodium-platinum defect found in a glass or glass-ceramic material according to the embodiments described herein;

[0016] Figure 4 is an optical microscope image of a crystalline rhodium-platinum defect found in a glass or glass-ceramic material according to the embodiments described herein;

[0017] Figure 5 is a cross-sectional image of a crystalline rhodium-platinum defect found in glass or glass-ceramic materials, obtained using a scanning electron microscope according to the embodiments herein;

[0018] Figure 6 shows the spectra of crystallized rhodium-platinum defects obtained by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) according to the embodiments described herein.

[0019] Figure 7A is a schematic diagram and its inset, illustrating the steps involved in the formation of rhodium-platinum defects during crystallization as the melt passes through a manufacturing system, according to embodiments herein.

[0020] Figure 7B corresponds to Figure 7A and shows the temperature of the melt and the oxygen partial pressure as the melt passes through the manufacturing system according to the embodiments herein.

[0021] Figure 8A illustrates hydrogen exchange from the melt inside the container to the gas atmosphere surrounding the container through the platinum-rhodium wall of the container, according to an embodiment herein.

[0022] 8B illustrates hydrogen exchange through the platinum wall of the container from the gas atmosphere around the container to the melt inside the container, according to an embodiment herein;

[0023] Figure 9A illustrates the formation of a composition cell at the interface between the melt and the vessel wall in a manufacturing system, according to an embodiment herein;

[0024] Figure 9B illustrates the formation of an electric cell at the interface between the melt and the vessel wall in a manufacturing system, according to an embodiment herein;

[0025] Figure 9C illustrates the formation of a hot cell at the interface between the melt and the vessel wall in a manufacturing system according to an embodiment herein;

[0026] illustrates an experimental concentration difference cell according to an embodiment herein.

[0027] The accompanying drawings may not be drawn to scale, and for the sake of clarity and simplicity, certain features and certain views of the drawings may be enlarged or schematically displayed to scale. Implementation

[0028] The embodiments of the present elucidation case will now be referred to in detail, the examples of which are shown in the accompanying figures. Wherever possible the same component symbols will be used throughout the accompanying drawings to refer to the same or similar parts. However, the present exposé can be implemented in many different forms and should not be understood as limited to the embodiments articulated herein.

[0029] No methodology articulated herein is understood to require its steps to be performed in a particular order, nor is any device understood to require a particular orientation unless explicitly stated otherwise. Therefore, there is no intention to infer the order or orientation in any respect where the method claim does not actually describe the order in which its steps are intended to be followed, or any apparatus claim does not actually describe the order or orientation of the individual parts, or the scope or instructions for the patent application for the invention do not otherwise specifically state that the steps will be limited to a particular order or the particular order or orientation of the parts of the device is not stated. This applies to any possible non-explicit basis of interpretation, including: logical problems concerning the arrangement of steps, operating flows, part order, or part orientation; obvious meanings derived from self-syntax organization or punctuation; and the number or type of embodiments described in this specification.

[0030] As used herein, the term “about” means that the amount, size, formulation, parameters and other quantities or characteristics are not and need not be precise, but may be approximate and / or larger or smaller as required by: tolerances, conversion factors, rounding, measurement errors and other factors known to those skilled in the art.

[0031] A range may be expressed herein as from “about” a particular value and / or to “about” another particular value. When expressing such a range, another embodiment includes from the one particular value to the other particular value. Similarly, when a value is expressed as an approximation by using the antecedent “about,” it should be understood that the particular value forms another embodiment. It should also be understood that the endpoints of each range are meaningful both in relation to and independently of the other endpoint. In some embodiments, “about” means values ​​within 10% of each other, such as within 5% of each other, or within 2% of each other.

[0032] As used herein, the terms "substantial," "substantively," and their variations are intended to indicate that the described feature is equal to or approximately equal to a value or description. For example, a "substantively planar" surface is intended to mean a planar or nearly planar surface. Furthermore, "substantively" is intended to mean that two values ​​are equal or approximately equal. In some embodiments, "substantively" means that the values ​​are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0033] As used herein, "container" includes components used in an apparatus or system for manufacturing glass or glass-ceramic materials, including melting chambers, refining tubes, forming chambers, or any connecting tubes between such containers. Typical components of a glass manufacturing system are described in U.S. Patent No. 7,032,412, the entire contents of which are hereby incorporated by reference. As shown in Figure 1 (prior art), the apparatus (10) includes a melting chamber (12) (through which a batch is introduced, as indicated by arrow (14)), a refining tube (16), a stirring chamber (18), a refining tube-to-stirring chamber connection (20), a drum (22), a stirring chamber-to-drum connection (24), a lower conduit (26), an inlet (28), and a melting tube (30). Many containers are made of refractory materials such as platinum or platinum-containing alloys (e.g., platinum-rhodium).

[0034] As used herein, “higher temperature” refers to a temperature in the range of approximately 1400°C to approximately 1600°C, and “lower temperature” refers to a temperature in the range of approximately 1000°C to approximately 1350°C.

[0035] In various embodiments, a process for manufacturing high-alkali glass is disclosed. In some embodiments, the process includes the manufacture of other glass materials, glass ceramics, and / or ceramic materials. In such processes, persistent and novel defects have been found in the material. These defects are highly reflective and, although typically less than 100 micrometers in diameter, are visible in polished glass with diameters as low as 2 µm. Glass with these defects is unacceptable for many applications, including, for example, the use of the material in displays, protective cover glass, or as a substrate.

[0036] In some embodiments, the defect is a thin sheet of crystalline rhodium-platinum (Rh / Pt) (also referred to herein as "cRh"). The cRh defect has a regular geometry (e.g., triangular, hexagonal) and a thin, substantially planar cross-sectional thickness. Figures 3 and 4 are optical microscopic images of typical cRh defects found in glass or glass-ceramic materials. The defect in Figure 3 has a triangular shape with approximately three equal sides of about 46.50 µm between its vertices, and the defect in Figure 4 has a hexagonal shape with a transverse face length of about 27.45 µm from one side to the opposite parallel side. Figure 5 is a cross-sectional image of an exemplary cRh defect obtained using a scanning electron microscope (SEM). Figure 5 shows a cRh defect (200) with a flat shape and a width (the thickness of the defect) of less than 1 µm.

[0037] In some embodiments, a combination of SEM and energy-scattered X-ray spectroscopy (EDS) is used to determine the composition of cRh defects. Figure 6 shows typical results for cRh defects. The SEM-EDS spectra in Figure 6 show that the cRh defects are rhodium-rich, rather than platinum-rich as is common in noble metal defects in other materials. As used herein, "rhodium-rich" means that the concentration of rhodium contained in the defect is higher than the concentration of the other component. Specifically, the composition was determined to be about 80% rhodium and about 20% platinum (80Rh / 20Pt). This result is contrary to typical platinum-rhodium defects having about 80% platinum and about 20% rhodium (80Pt / 20Rh), which have the same composition as platinum-rhodium containers. The different chemical characteristics of cRh defects are an important distinction between these cRh defects and the typical metallic defects discussed above.

[0038] Unbound by any particular scientific theory, cRh defects are believed to be generated in the melt through a three-step process, as shown in Figures 2 and 7a. Figure 2 shows a cross-sectional view of an exemplary container (100) used in the glass manufacturing process (e.g., a cross-section of the refining tube (16) taken along line 2-2 of Figure 1). In Figure 2, the container (100) is enclosed within a shell (180) containing a gas atmosphere (160). The interior of the container wall (140) contains the bulk melt (150) and a local melt (170) adjacent to the container wall (140).

[0039] In Figure 7A, the first step involves the oxidation of platinum and rhodium at the interface between the melt (150) and the container wall (140) (e.g., the refining tube wall), producing platinum oxide (PtO₂) and rhodium oxide (RhO₂), both of which dissolve in the melt. The matrix of dots and shaded areas indicates the relative concentrations of platinum oxide and rhodium oxide in localized melts (170). Figure 7A shows that the concentrations of oxides are highest in the melt adjacent to the container wall (140) and in the melt upstream of the process, where temperatures are higher. The second step involves the transport of dissolved platinum oxide and rhodium oxide to other locations in the melt via diffusion and / or convection. The third step involves the reduction of platinum oxide and rhodium oxide to reduced platinum and rhodium compounds. When the melt containing these oxides reaches a location where the melt is sufficiently supersaturated with platinum and rhodium compounds (which have lower solubility than their corresponding oxides), the reduction reaction can lead to the precipitation of crystalline rhodium-platinum (cRh). The inset in Figure 7A shows that the relative concentrations of platinum oxide and rhodium oxide in the melt are depleted in the region surrounding the newly precipitated cRh defects.

[0040] Figure 7B shows the temperature (temp) and oxygen partial pressure (pO2(melt)) (y-axis) of a localized melt (170) varying with its position (x-axis) in the manufacturing process. Specifically, pO2 decreases at lower temperatures, typically after the melt has passed through the refining tube. Therefore, the first oxidation reaction may occur upstream in the manufacturing process where the localized melt temperature and pO2 are both higher, which also increases the solubility of platinum oxide and rhodium oxide in the melt. In contrast, the third step may occur downstream in the process where the localized melt temperature and pO2 are both lower, which also decreases the solubility of platinum oxide and rhodium oxide in the melt. However, the first and third steps may also occur close to each other. For example, when an electrochemical cell is established in a localized region of oxidized and / or reduced melt adjacent to the PtRh wall. Figures 9A-9C illustrate that electrochemical cells can be established using unintended composite cells, electro-cells, or thermal cells during the manufacturing process.

[0041] The cRh defects formed by the aforementioned three-step process are rhodium-rich because the solubility of rhodium in the local melt (170) is much higher than that of platinum. For example, when an 80Pt / 20Rh alloy is exposed to various glass melts at high temperatures, the melt can absorb 2 to 10 times more rhodium oxide than platinum oxide. Therefore, when this glass is subsequently cooled and / or subjected to a lower oxygen partial pressure (pO2) and becomes supersaturated with platinum and rhodium, the resulting defects are rhodium-rich. In some embodiments, the rhodium concentration in the defects is in the range of about 60% to about 90%, or about 65% to about 85%, or about 70% to about 80%, including any combination of neutron ranges. This is in contrast to defects formed via a gaseous route. For example, when an 80Pt / 20Rh alloy is exposed to oxygen-containing gas at high temperatures, the gas absorbs rhodium and platinum in proportions similar to its concentration in the source alloy. Therefore, when the gas is subsequently cooled and / or experiences a lower oxygen partial pressure (pO 2) and becomes supersaturated, the resulting defects are as platinum-rich as the source alloy.

[0042] In various embodiments, a process is provided to minimize the formation of cRh defects in high-alkali glass. In some embodiments, the process includes one or more steps that can be used alone or in combination during the manufacturing process to prevent, eliminate, or minimize the formation of cRh defects in the melt.

[0043] In some embodiments, for example, the process includes minimizing or maximizing the oxygen partial pressure (pO2) in a localized melt. In some embodiments, cRh defects are minimized by limiting the oxidation reaction in the first step of a three-step process for forming PtRh. In some embodiments, cRh defects are minimized by limiting the reduction reaction and / or precipitation of cRh defects in the melt in the third step. In some embodiments, the process includes limiting the oxidation reaction in the first step and the reduction reaction and / or precipitation in the third step. In such embodiments, the process includes minimizing the pO2 of a localized melt in the first step and maximizing the pO2 of a localized melt in the third step.

[0044] In such embodiments, the pO2 of the local melt (170) (relative to the pO2 of the bulk melt (150)) refers to the pO2 of the melt adjacent to the PtRh container wall (140). The local melt (170) is the relevant region because the PtRh container wall (140) is the source of platinum oxide and rhodium oxide, and due to the laminar flow of the melt in the manufacturing system, the dissolved oxides are still most concentrated in the melt (170) near the PtRh container wall (140). In this context, "adjacent" includes the melt in direct contact with the PtRh container wall (140) and a portion of the melt affected by oxygen (O2) enrichment or depletion. For example, the local melt (170) region adjacent to the container wall (140) includes the melt within a distance of approximately 2 mm, approximately 1 mm, or approximately 0.1 mm from the container wall, or any combination thereof. In some embodiments, the local melt (170) adjacent to the container wall is a radial ring extending from direct contact with the container wall to a distance of approximately 2 mm from the container wall. As those skilled in the art will recognize, the size of the local melt (170) region adjacent to the container wall depends on many factors, including the geometry of the melt, its flow, and its temperature.

[0045] In various embodiments, hydrogen permeation exacerbates the first and / or third steps of the process that generate cRh defects by affecting the pO2 of the melt adjacent to the PtRh wall. The PtRh wall is permeable to hydrogen, so hydrogen can be exchanged between the local melt (170) and the gas atmosphere (160) surrounding the PtRh wall (140). In various embodiments, the direction and extent of hydrogen exchange, and therefore the degree of change in pO2 of the melt adjacent to the PtRh wall (140), can be controlled by adjusting the relative values ​​of the hydrogen partial pressure pH2 (gas) (160) in the gas atmosphere and the hydrogen partial pressure pH2 (melt) (170) in the local melt. Therefore, in some embodiments, a mismatch between pH2 in the local melt (170) and pH2 in the gas atmosphere (160) surrounding the container causes hydrogen to leave the local melt or enter the local melt from the surrounding gas atmosphere. In such embodiments, the local melt (170) adjacent to the PtRh wall enriches or depletes O2, as determined by the following water reaction: H2O ↔ 2H + 0.5O2. For example, when a high local pH 2 (melt) is present at the interface between the melt and the container, hydrogen will permeate out of the melt into the gaseous atmosphere, thereby depleting the hydrogen in the local melt (170). Based on the water reaction, for every mole of hydrogen leaving the local melt, half a mole of oxygen is left at the interface.

[0046] Figure 8A shows that when pH 2 (gas) is less than pH 2 (melt), hydrogen will transfer from the local melt (170) to the gaseous atmosphere (160), resulting in an increase in the local pO 2 of the local melt due to the rightward shift of the water reaction. However, Figure 8B shows that when pH 2 (gas) is greater than pH 2 (melt), hydrogen will transfer from the gaseous atmosphere (160) to the local melt (170), resulting in a decrease in the local pO 2 of the local melt due to the leftward shift of the water reaction. When pH 2 (gas) is equal to pH 2 (melt), there is essentially no hydrogen transfer, and the pO 2 of the local melt (170) will be substantially equal to the pO 2 of the bulk melt (150).

[0047] In some embodiments, hydrogen exchange between the local melt (170) and the surrounding gas atmosphere (160) can be controlled by changing the water content (β-OH) in the melt. As used herein, "β-OH" is a measure of the hydroxyl content in the glass as determined by IR spectroscopy. Specifically, β-OH is the linear absorption coefficient of the material and is calculated from the IR transmission spectrum of the material using the following formula: β-OH = (1 / X) LOG 10(T 1 / T 2), where X is the sample thickness in millimeters, T 1 is the sample transmittance at a reference wavelength (nm), and T 2 is the minimum sample transmittance at the hydroxyl absorption wavelength (nm). In some embodiments, for example, increasing pH 2 (the melt) can be achieved by increasing the water content (β-OH) in the glass. In such embodiments, the water content can be increased by various process modifications, including, for example, adding raw materials or batches with high water content (such as those described in U.S. Patent No. 8,623,776, the entire contents of which are hereby incorporated by reference), and / or bubbling a wet gas into the bulk melt (150). As used herein, "wet gas" means a gas containing some amount of water vapor. Such modifications provide a means of directly injecting water into the melt and are suitable at different stages of the manufacturing process, such as in the early pre-melt or in the later refining tube.

[0048] In some embodiments, the pH 2 (gas) can be set to any desired value by controlling the %O 2 and the dew point of the gas atmosphere (160). In some embodiments, a higher pH 2 (gas) (e.g., nitrogen (N 2) containing 1% oxygen (O 2) with a dew point of 65°C) can be used in the upstream section at a higher temperature (e.g., before and including the refining tube (16) in Figure 1), while a lower pH 2 (gas) (e.g., nitrogen (N 2) containing 1% O 2 with a dew point of -30°C to -10°C) can be used in the downstream section at a lower temperature (e.g., after the refining tube (16) in Figure 1). In some embodiments, the formation of cRh defects is minimized when a gas atmosphere with a high pH 2 is replaced with a gas atmosphere with a low pH 2 (such as ambient air or N 2 containing 1% O 2 with a dew point of around -20°C).

[0049] In some embodiments, the gas atmosphere surrounding the platinum-rhodium containers is controlled by providing a housing around each platinum-rhodium container (e.g., 180 in Figures 2, 8A, and 8B) or by providing a housing around the entire manufacturing process or a portion thereof. In some embodiments, a single gas atmosphere is delivered to the entire PtRh system. In such embodiments, a lower hydrogen partial pressure pH 2 (gas) in the gas atmosphere (160) is preferred. In some embodiments, different gas atmospheres are delivered to specific platinum-rhodium containers or portions thereof. For example, containers with different gas atmospheres or segments are configured to operate at a higher pH 2 (gas) in the upstream section of the process at higher temperatures to reduce local pO 2 of the local melt (170) and minimize oxidation of platinum and rhodium to platinum oxide and rhodium oxide; and to operate at a lower pH 2 (gas) in the downstream section of the process at lower temperatures to increase local pO 2 of the local melt (170) and minimize reduction of platinum oxide and rhodium oxide and / or precipitation of cRh defects.

[0050] In some embodiments, the process includes controlling the formation of electrical, thermal, and composite cells in the PtRh system. As shown in Figures 9A, 9B, and 9C, electrical, thermal, and composite cells can establish higher and lower pO2 regions in a localized melt (170) adjacent to the platinum-rhodium alloy container wall (140). The higher and lower pO2 regions in the localized melt (170) exacerbate cRh defect problems.

[0051] In some embodiments, for example, the composition battery is a sludge layer in the refining tube. As used herein, "sludge layer" refers to a layer of glass with a different composition from the bulk melt and is typically enriched with oxides of refractory material from the container walls and electrodes. In some embodiments, the sludge layer is formed in the premelt by the continuous dissolution of refractory bricks and / or electrodes in the melt, followed by its downstream transport to the refining tube and other downstream sections before the stirring chamber. For example, Figure 9A shows a melt region on the left (glass A) that differs from the melt region on the right (glass B). Each melt composition is in contact with the PtRh container wall, and the different melt compositions in contact with the container wall establish localized anodes and cathodes. This results in a localized increase in pO2 at the anode and a localized decrease in pO2 at the cathode. In such embodiments, the sludge layer can establish a composition battery.

[0052] Referring to Figure 9B, an unintended grounding loop can form an electric cell, creating localized anodes and cathodes along the PtRh container wall. At the localized anode, there is a localized increase in pO₂, and at the cathode, a localized decrease in pO₂, which can lead to the formation of platinum-rhodium precipitates. Figure 9C illustrates the formation of a thermal cell when a steep temperature gradient is present. As indicated by the different thermometer symbols, the temperature gradient can create localized anodes and cathodes along the PtRh container wall, resulting in a localized increase in pO₂ at the anode and a localized decrease in pO₂ at the cathode. Similar to composite cells, unintended electric and thermal cells can exacerbate cRh defect problems and should be minimized during the manufacturing process.

[0053] In some embodiments, it is important to agitate the melt (150) using a mixing device that minimizes composition gradients before the melt enters the cooling section. In some embodiments, for example, agitation devices (e.g., bubblers or static mixers) are added before and / or immediately after the refining tube to minimize the development of sludge layers and concentration cells in the higher and lower temperature sections of the glass manufacturing process.

[0054] In some embodiments, adding a multivalent substance (such as tin, iron, etc.) to the melt can minimize the effects of any compositional, electrical, or thermal cell effects that cannot be eliminated by changes in the mechanical process. In such embodiments, the multivalent substance counteracts any local pO2 (melt) gradient and minimizes the formation of subsequent cRh defects. For example, in some embodiments, the multivalent substance can mitigate negatively charged oxygen ions in the melt, which are formed by the decomposition of water or hydroxyl substances in the melt and can be converted into molecular oxygen.

[0055] Figure 10 illustrates the system (200) used in experiments where a multivalent substance (220) was added to a composite cell provided by adding a small amount of SnO₂ powder to the bottom of a small 80Pt-20Rh foil crucible (240), followed by covering it with a melt (250) containing various levels of different multivalent substances. Different glass material compositions were included in this study, and the multivalent substances contained in each composition are shown in Table 1. Each sample was heated to 1550°C for 48 hours, cooled to 1250°C and held for 24 hours, and then quenched in air. The cRh defects of the glass were then examined.

[0056] Table 1. Moer% Ex1 Ex2 Ex3 Ex4 Ex5 Ex6 Ex7 Ex8 Ex9 Ex.10 SiO 2 70.9 70.9 70.9 70.9 70.9 70.9 70.9 70.9 70.9 70.9 Al₂O₃ 4.3 4.3 4.3 4.3 4.3 4.3 4.3 4.3 4.3 4.3 Li 2O twenty two twenty two twenty two twenty two twenty two 22 22 22 22 22 ZrO2 2 2 2 8 2 2 2 2 2 2 P 2O 5 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 SnO2 0 1 0 0 0.5 0 0 0 0 0 Fe2O3 0 0 0.25 0 0 0.125 0 0 0 0 CeO2 0 0 0 0 0 0 0.1 0.5 0 0 MnO 2 0 0 0 0 0 0 0 0 0.1 0.5 cRh many none none ZrO2 defects none none Some Some Some Some

[0057] As shown in Table 1, the sample with the lowest concentration of multivalent substances (Ex.1) produced the most metallic defects, samples with cerium or manganese additives (Ex.8, Ex.10) produced some defects, and samples with tin or iron additives (Ex.2, Ex.5, Ex.3, Ex.6) produced no defects. Therefore, tin and iron additives are very effective in minimizing the local pO2 gradient (formed by the composite cell established by the SnO2 powder at the bottom of the crucible) and the subsequent formation of cRh defects, while cerium and manganese additives are somewhat effective. In these examples, due to the relatively large amount of tin oxide powder added, the resulting concentration cells may be more severe than any cells observed in the glass manufacturing process. Therefore, in larger production vessels, with appropriate heat and atmosphere control, small amounts of multivalent additives may be sufficient.

[0058] In some embodiments, the glass or glass-ceramic material comprises more than 0.1 wt% of one or more multivalent substances. In some embodiments, for example, the material comprises more than 0.1 wt% of SnO2. In some embodiments, the material comprises more than 0.1 wt% of Fe2O3. In some embodiments, the material comprises more than 0.2 wt% of a combination of SnO2, Fe2O3, MnO2, and Ce2O3. In some embodiments, the material comprises at least 0.05 wt% of a combination of Sb2O3 and As2O3. In some embodiments, the melt comprises more than a molar amount of Li2O in Al2O3.

[0059] In some embodiments, a method is provided for minimizing cRh defects in a process of manufacturing glass or glass-ceramic materials using one or more containers (e.g., melting chambers, refining tubes) or all containers in a manufacturing system, the containers being made of a rhodium-free precious metal or metal alloy. In such embodiments, the elimination of rhodium from the system and the use of a suitable Rh-free precious metal alloy provide glass with a higher melting temperature. In some embodiments, the dissolution of rhodium in the melt (150) is minimized or eliminated by changing the container from 80Pt / 20Rh to 100Pt. In some embodiments, the dissolution of rhodium in the melt (150) is minimized or eliminated by changing the container from 80Pt / 20Rh to a platinum alloy containing another precious metal (e.g., molybdenum). In such embodiments, the formation of cRh defects in the melt is avoided.

[0060] In various embodiments, processes for manufacturing glass or glass-ceramic materials are provided. In some embodiments, the material comprises SiO2, Al2O3, Li2O, P2O5, ZrO2, K2O, and Na2O. In various embodiments, the formation of cRh defects is minimized or eliminated by: penetration control, including providing pH2 (gas) relative to pH2 (melt) at an amount sufficient to control the oxygen partial pressure in the melt region adjacent to the interface between the melt and the container wall; and / or minimizing the formation of localized thermal, electrical, or composite cells in the melt. In various embodiments, the material comprises less than 15 cRh defects per pound, or less than 10 cRh defects per pound, or less than 5 cRh defects per pound, or less than 1 cRh defect per pound.

[0061] It will be apparent to those skilled in the art that various modifications and alterations can be made to the embodiments of this disclosure without departing from the spirit and scope of this disclosure. Therefore, this disclosure is intended to cover such modifications and alterations that fall within the scope of the appended patent applications and their equivalents.

[0062] 10: Device 12: Melting Chamber 14: Arrow 16: Refining tube 18: Mixing Chamber 20: Connection pipe from refining pipe to mixing chamber 22: Drum 24: Connecting pipe from the mixing chamber to the drum 26: Lowering the catheter 28: Entrance 30: Fusible Link 100: Container 140: Container wall 150: Bulk Melt 160: Gas Atmosphere 170: Localized melt 180: Casing 200:cRh Defect / System 200a:cRh defect 200b:cRh defect 220: Multivalent substance 240: Crucible 250: Melt

[0063] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A method for minimizing the formation of a rhodium-platinum defect in a glass or glass-ceramic material, comprising the steps of: providing a container made of a platinum-rhodium alloy for a manufacturing process of obtaining the material, wherein an interface exists between the container and a melt of the material; providing a hydrogen partial pressure outside the container relative to a hydrogen partial pressure inside the container, sufficient to control the amount of oxygen partial pressure in a melt region adjacent to the interface, comprising: adjusting the hydrogen partial pressure outside the container to be greater than the hydrogen partial pressure inside the container when the melt is at a first temperature to reduce the oxygen partial pressure in the melt region adjacent to the interface, and then adjusting the hydrogen partial pressure outside the container to be less than the hydrogen partial pressure inside the container when the melt is at a second temperature below the first temperature to increase the oxygen partial pressure in the melt region adjacent to the interface; wherein the rhodium-platinum defect is rhodium-rich and the platinum-rhodium alloy in the container is platinum-rich.

2. The method as claimed in claim 1, wherein the rhodium-platinum defect comprises a substantially planar geometry having a cross-sectional thickness of less than 3 µm and a diameter of 2 µm to 150 µm.

3. The method as described in claim 2, wherein the rhodium-platinum defect comprises 80% rhodium and 20% platinum, and the platinum-rhodium alloy in the container comprises 80% platinum and 20% rhodium.

4. The method as described in claim 3, wherein the material contains the rhodium-platinum defect when a step is missing in which the amount of oxygen partial pressure in the melt region adjacent to the interface is sufficient to control the amount of hydrogen partial pressure outside the container relative to the hydrogen partial pressure inside the container.

5. The method as described in claim 1, wherein the first temperature is in the range of 1400°C to 1600°C.

6. The method as described in claim 1, wherein the second temperature is in the range of 1000°C to 1300°C.

7. The method as described in claim 1, comprising the step of adding water or a hydroxide-containing compound to the melt to increase the hydrogen partial pressure inside the container.

8. The method as described in claim 1, comprising the step of: bubbling a wet gas into the melt to increase the hydrogen partial pressure inside the container.

9. A method for minimizing the formation of a rhodium-platinum defect in a glass or glass-ceramic material during a manufacturing process, wherein a platinum-rhodium (PtRh) alloy is used in a container of the manufacturing process, wherein an interface exists between the container and a melt of the material, the method comprising the steps of: providing a hydrogen partial pressure outside the container relative to a hydrogen partial pressure inside the container, sufficient to control the amount of oxygen partial pressure in a melt region adjacent to the interface, comprising: adjusting the hydrogen partial pressure outside the container to be greater than the hydrogen partial pressure inside the container when the melt is at a first temperature, thereby reducing the oxygen partial pressure in the melt region adjacent to the interface; and then adjusting the hydrogen partial pressure outside the container to be less than the hydrogen partial pressure inside the container when the melt is at a second temperature below the first temperature, thereby increasing the oxygen partial pressure in the melt region adjacent to the interface; wherein the rhodium-platinum defect is rhodium-rich and the platinum-rhodium alloy in the container is platinum-rich.

10. The method as claimed in claim 9, wherein the rhodium-platinum defect comprises a substantially planar geometry having a cross-sectional thickness of less than 3 µm and a diameter of 2 µm to 150 µm.

11. The method as described in claim 10, wherein the rhodium-platinum defect comprises 80% rhodium and 20% platinum, and the platinum-rhodium alloy in the container comprises 80% platinum and 20% rhodium.

12. The method as claimed in claim 11, wherein the material contains the rhodium-platinum defect when a step is missing in which the amount of oxygen partial pressure in the melt region adjacent to the interface is sufficient to control the amount of hydrogen partial pressure outside the container relative to the hydrogen partial pressure inside the container.

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