Low-expansion radiation-proof glass ceramic and preparation method and application thereof

Abstract

The application discloses low-expansion radiation-proof glass ceramics and a preparation method and application thereof, and belongs to the technical field of lithium-aluminum-silicon glass ceramics. The raw materials of the low-expansion radiation-proof glass ceramics include the following components in terms of molar percentage: 50-83.5% of SiO2, 12-20% of Al2O3, 0-7% of B2O3, 2-5% of Li2O, 0-4% of Na2O, 0-2% of K2O, 0-8% of MgO, 0-6% of CaO, 0-2% of SrO, 0-1% of BaO, 1-3% of P2O5, 0-4% of ZnO, 0.5-0.7% of CeO2, 1-4% of ZrO2, 0-0.8% of TiO2 and 0-0.1% of a clarifying agent. The preparation method is as follows: the raw materials are mixed according to the components, and a base glass is obtained through melting; and the base glass is heated through two-step ceramming or one-step ceramming to obtain the glass ceramics.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium-aluminum-silicon glass ceramics, and particularly relates to a low-expansion radiation-proof glass ceramic and a preparation method and application thereof. BACKGROUND

[0002] Radiation is energy propagating to the surrounding medium in the form of wave or moving particles, and is a way of energy propagation. Radiation is divided into two categories: non-ionizing radiation and ionizing radiation. The non-ionizing radiation includes visible light, infrared light, ultraviolet light, etc. The ionizing radiation includes high-energy electromagnetic radiation and particle radiation. The high-energy electromagnetic radiation refers to non-charged particle radiation generated by X-rays and gamma rays. High-energy rays can destroy the network structure of glass, form a large number of free electrons, reduce the cations in the glass, cause the glass to be colored, and reduce the white light transmittance. At the same time, due to the destruction of the glass network structure, the loss of the optical fiber is increased. With the development of the aerospace, atomic energy industry and the field of radiation medicine, the contact with irradiation rays in production and life is increasing, and the protective glass capable of shielding rays has attracted widespread attention.

[0003] Ordinary glass has limited absorption capacity for irradiation rays, especially high-energy radiation. In order to reduce the damage caused by radiation, two ways are usually used to improve the shielding and protective capacity of the glass: one is to change the glass structure to reduce the glass density to improve the radiation-proof ability, and the other is to introduce a large amount of elements with high atomic number, such as lead, barium and bismuth, into the glass composition. Among them, heavy lead glass has been widely used in the field of radiation protection. For example, ZF7 lead glass has a glass density as high as 5.19 g / cm 3 , a lead equivalent of 0.33 per MM thickness, and a relatively high transmittance.

[0004] Foreign patent JP2008286787A describes a lightweight gamma radiation shielding laminate with improved radiation shielding performance. The improvements described in the application are achieved by adding a cover material with increased BaO and SrO content, compared to existing high-PbO monolithic glass containing 55-80% PbO. When the BaO and SrO content of the cover material matches that of the underlying high-PbO radiation shielding glass layer, it provides even higher radiation shielding capabilities. However, as the lead content in the glass composition increases, the density of the glass increases, and its radiation shielding performance has reached a bottleneck, making further improvement difficult. Foreign patent CN115836031A discloses radiation shielding glass products with thin glass panels and improved transmittance. The application describes glass with a high PbO content, whose network structure is easily destroyed by high-energy radiation, forming a large number of free electrons, which reduce cations in the glass, causing coloration and reducing the material's white light transmittance. However, lead, as a heavy metal, poses serious hazards to both humans and the environment. Existing patent CN101928103A discloses optical glass with a refractive index of 1.52-1.65. The PbO content in the glass is low, with a mass percentage of 25-50%, and it contains a large amount of SiO2. The glass contains at least three dopants among CeO2, MoO3, Bi2O3, WO3, Sb2O3 and As2O3. However, due to the addition of multiple variable valence ion dopants in this lead-containing radiation-resistant glass, metal elements may be precipitated after irradiation, causing the glass to be colored. In addition, the radiation resistance performance and mechanism are more complex, and the cost of glass preparation also increases accordingly.

[0005] The aerospace field has strict requirements for glass materials. In addition to the radiation resistance performance index, another important index is the thermal stability of the glass. Ordinary glass has average heat resistance and is difficult to meet the test of the harsh environment that aerospace has to face. The existing patent CN105948516B describes a window microcrystalline glass with radiation resistance, high transparency, high light transmittance, and strong impact resistance. CeO2 is introduced to replace high atomic number metal ions, and β-spodumene solid solution crystal phase is formed to improve the radiation resistance and thermal stability of the glass, providing a new idea for aerospace glass materials that can reduce the heavy metal content and improve the thermal expansion performance of the glass. However, the thermal expansion coefficient in this invention is in the range of 0-300℃, and the situation under lower temperature environment is not considered. Moreover, the thermal expansion coefficient in the range of 0-300℃ is (3~12)x10 -7 / K, zero inflation is not implemented.

[0006] Under irradiation with high-energy radiation, defects inherent in the glass or those generated by the radiation capture free electrons or holes, forming color centers and reducing the glass's transmittance. Glass-ceramics are glasses with specific chemical compositions and strict melting requirements. After heat treatment at a certain temperature, they become composite materials with a uniform distribution of crystalline and glassy phases. Regarding glassy and crystalline materials of the same composition, the atoms in crystalline materials are arranged in an orderly manner, resulting in a relatively dense structure and higher bonding strength. Therefore, the structural strength of crystalline glass is generally higher than that of amorphous traditional glass. Therefore, there are two methods to improve the radiation resistance of glass materials: one is to capture free electrons and prevent them from falling into vacant structures within the material; the other is to allow ions with multiple valence states to react with electrons or holes to prevent them from being captured by defects. Therefore, variable-valence ions are often introduced into glass as radiation stabilizers. However, the variable valence ions of Fe, Mn, Cr, Co, Ni, Cu and other elements have absorption in the visible region, which affects the transmittance of the glass, while the short-wave absorption peak of Ce element is located in the ultraviolet band, which does not affect the transmittance of glass in the visible light band. It is generally believed that Ce in glass 4+ The higher the ratio of CeO2, the more stable the glass is when irradiated by high-energy rays. Therefore, CeO2 is the ideal and most common radiation stabilizer.

[0007] Existing radiation-resistant glass materials contain a large amount of high-atomic-number metal elements, but they are easily damaged in extreme environments with high- and low-temperature cycles and large temperature differences. Thermally stable glass materials are also susceptible to developing color centers when exposed to high-energy radiation, causing discoloration and altering their properties. Therefore, there is a need in the art to develop environmentally friendly glass-ceramics with a low coefficient of thermal expansion, excellent thermal stability, and radiation protection. Summary of the Invention

[0008] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a low-expansion radiation-proof glass ceramic and its preparation method and application. The provided glass ceramic has the advantages of being environmentally friendly, having a low thermal expansion coefficient, good thermal stability and providing radiation protection performance.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] The low-expansion radiation-proof glass ceramic comprises the following components in terms of mole percentage: 50-83.5% of SiO2, 12-20% of Al2O3, 0-7% of B2O3, 2-5% of Li2O, 0-4% of Na2O, 0-2% of K2O, 0-8% of MgO, 0-6% of CaO, 0-2% of SrO, 0-1% of BaO, 1-3% of P2O5, 0-4% of ZnO, 0.5-0.7% of CeO2, 1-4% of ZrO2, 0-0.8% of TiO2, and 0-0.1% of a clarifying agent.

[0011] The object and the technical problem of the present application can also be further achieved by the following technical measures.

[0012] The low-expansion radiation-proof glass ceramic comprises the following components in terms of mole percentage: 50-83.5% of SiO2, 12-20% of Al2O3, 0-7% of B2O3, 2-5% of Li2O, 0-4% of Na2O, 0-2% of K2O, 0-8% of MgO, 0-6% of CaO, 0-2% of SrO, 0-1% of BaO, 1-3% of P2O5, 0-4% of ZnO, 0.5-0.7% of CeO2, 1-4% of ZrO2, 0-0.8% of TiO2, and 0-0.1% of a clarifying agent.

[0013] The mass of the main crystal phase and the secondary crystal phase accounts for more than 70% of the mass of the glass ceramic; and the clarifying agent is one or more of Sb2O3, SnO2, As2O3, NaCl and CaF2.

[0014] The low-expansion radiation-proof glass ceramic comprises R2O composed of Li2O, Na2O and K2O, and RO composed of MgO, ZnO, CaO, SrO and BaO.

[0015] The mole percentage of R2O, RO and Al2O3 satisfies (R2O+RO) / Al2O3<1.

[0016] The low-expansion radiation-proof glass ceramic has a thermal expansion coefficient CTE of 0±1×10 -7 / K in the temperature range of -100℃ to 200℃; and an optical density increment per centimeter of thickness after being subjected to γ-ray irradiation with a total dose of 1×10 5 rad is less than or equal to 0.060.

[0017] The low-expansion radiation-proof glass ceramic has a transmittance of at least 70% for light in the wavelength range of 480-800 nm, a transmittance of at least 80% for light in the wavelength range of 500-800 nm, a transmittance of 0.01% to 3% for a wavelength of 200 nm, and a transmittance of at least 60% for a wavelength of 550 nm when the thickness of the glass ceramic is 6 mm.

[0018] The low-expansion radiation-proof glass ceramic has the following transmittance color coordinates in the CIELab color space: 15≤L*≤90, -3≤a*≤3 and -3≤b*≤20.

[0019] The application further provides a preparation method of the low-expansion radiation-proof glass ceramic, and specific steps are as follows:

[0020] S1: raw materials of the low-expansion radiation-proof glass ceramic are mixed according to components, and then the mixed raw materials are melted at a temperature of 1560-1680 DEG C to obtain base glass;

[0021] S2: the base glass is heated by two-step ceramming or one-step ceramming to obtain glass ceramic.

[0022] The two-step ceramming is as follows:

[0023] The base glass is heated from room temperature to 630-850 DEG C at a heating rate of 0.01 DEG C / min-10 DEG C / min, and then is kept at the temperature for 0.2-24 h to obtain crystallizable glass;

[0024] The crystallizable glass is heated to 850-1200 DEG C at a heating rate of 0.1 DEG C / min-10 DEG C / min, and then is kept at the temperature for 0.5-12 h to obtain glass ceramic.

[0025] The one-step ceramming is as follows:

[0026] The base glass is heated from room temperature to 850-1200 DEG C at a heating rate of 0.005 DEG C / min-1 DEG C / min, and then is kept at the temperature for 0.5-48 h to obtain glass ceramic.

[0027] The application further provides application of the low-expansion radiation-proof glass ceramic in a radiation shielding protective window or a radiation transparent observation window.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] The present application provides a low-expansion radiation-proof glass ceramic. The first feature of the low-expansion radiation-proof glass ceramic is that LiO2 is introduced to reduce the thermal expansion coefficient and achieve zero expansion by the main crystal phase composed of a β-quartz solid solution crystal phase and a β-spodumene solid solution crystal phase. The β-quartz solid solution is a continuous solid solution formed by β-eucryptite (Li2O·Al2O3·2SiO2) and β-quartz (SiO2). The β-eucryptite and the β-quartz have the same hexagonal spiral structure, and the expansion coefficient in the direction indicated by the spiral (i.e., the c-axis direction) is negative, and the expansion coefficient in other directions is positive. The total expansion value of the material formed by the accumulation of the micro-crystals is also negative. The β-quartz solid solution can be precipitated in a crystalline state from a glass containing Li2O·Al2O3·SiO2. The glass ceramic obtained in this way contains a β-quartz solid solution and a residual glass phase, and the negative expansion of the former and the positive expansion of the latter offset each other, so that the glass ceramic has a zero or near-zero expansion coefficient. The β-spodumene belongs to the tetragonal system and is generally considered to be a filled derivative of quartz. The β-spodumene solid solution (Li2O·Al2O3·nSiO2) also has good thermodynamic properties. The thermal expansion properties are anisotropic, the expansion coefficient of the a-axis is negative, and the thermal expansion coefficient of the c-axis is positive. The cell parameters of the β-spodumene solid solution have a continuous change with the chemical composition (mainly the content of SiO2). As the value of n increases, the c-axis expansion amplitude becomes smaller and smaller, and the a-axis shrinkage amplitude becomes larger and larger. Therefore, after the same heat treatment system, the cell parameters of the β-spodumene solid solution formed tend to decrease with the increase of the SiO2 content, and the thermal expansion coefficient becomes smaller and smaller. Through further adjustment of the components, the high crystallinity of the glass ceramic and the thermal stability have a synergistic effect, that is, as the crystallinity of the glass ceramic increases, the molecular arrangement in the crystalline region is ordered, the structure is compact, the change of the structure is small when the temperature changes, and the thermal expansion coefficient decreases. The glass ceramic has a zero or near-zero expansion coefficient.

[0030] The second feature of the above low-expansion radiation-proof glass ceramic is that the thermal stability is good, and the zero expansion is 0±1×10 -7 / K.

[0031] The present application also provides the application of the above low-expansion radiation-proof glass ceramic in radiation shielding protective windows or radiation transparent observation windows. By reducing or not introducing TiO2 crystal nucleus agent to avoid the cerium-titanium effect coloring, the problem of reduced transmittance caused by excessive TiO2 in the glass ceramic is solved. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 X-ray diffraction patterns of the crystal phase of the glass ceramic of Example 1, Example 3, and Example 6 of the present application;

[0033] Figure 2 Pre-irradiation transmittance spectra of the glass-ceramics of Example 1, Example 3 and Example 6 of the present application;

[0034] Figure 3 Pre-irradiation transmittance spectra of the glass-ceramics of Example 4 of the present application after different total doses of 1 x 10 3 rad (Si), 1 x 10 4 rad (Si), 1 x 10 5 rad (Si) and 1 x 10 6 rad (Si) gamma-ray irradiation;

[0035] Figure 4 Thermal expansion CTE curves of the glass-ceramics of Example 3, Example 4 and Example 8 of the present application. DETAILED DESCRIPTION

[0036] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the present specification shall prevail.

[0037] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting on the scope of the present application, i.e. the present application can be practiced without regard to any particular theory or mechanism.

[0038] Herein, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, amounts, contents and concentrations, are for the sake of brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0039] Herein, unless otherwise specified, “comprise”, “include”, “contain”, “have” or similar words encompass the meaning of “consist of” and “consist essentially of”, e.g. “A comprises a” encompasses the meaning of “A comprises a and other” and “A comprises only a”.

[0040] Herein, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not contradict each other, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present specification.

[0041] The present application provides a low-expansion radiation-resistant glass-ceramic and a preparation method and application thereof.

[0042] The present application is further described in connection with the following embodiments. It should be understood, however, that the embodiments are set forth merely for illustration and that the scope of the present application is not limited to these embodiments. Furthermore, it should be understood that modifications and variations can be apparent to those of skill in the art upon reading this disclosure and that such modifications and variations are intended to fall within the scope of the appended claims.

[0043] The following examples use conventional equipment in the art. Unless otherwise indicated, the experimental procedures in the following examples were conducted under conventional conditions, or under conditions recommended by the manufacturer. Specifically, the glass-ceramic liquidus temperature was measured using a Shanghai Linseis Scientific Instrument Co., Ltd. glass crystallization furnace (gradient furnace) (GTF-MD-16). The method includes placing crushed glass particles in a boat, placing the boat in a furnace with a gradient temperature zone, heating the boat at an appropriate temperature zone for 24-72 hours, and determining the highest temperature at which crystals appear inside the glass by detecting the crystals using a microscope. Specifically, the glass sample is completely removed from the boat, and then an optical microscope is used to determine the location and nature of the formed crystals. The liquidus viscosity is determined in poise (P) from the liquidus temperature and the Vogel-Fulcher-Tammann equation, etc.

[0044] The X-ray diffractometer (XRD) model D / MAX-RB from Japan RIGAKU Co. was used to determine the crystalline phase set, size, crystallinity, and weight percentage of the crystallized ceramic.

[0045] The ultraviolet-visible-near infrared spectrometer model (Cary 5000) from Varian, USA was used to measure the transmittance, and the internal transmittance curve of a 6 mm thick sample was obtained.

[0046] The thermal expansion coefficient CTE of the glass-ceramic from -100°C to 200°C was determined using the Netzsch TMA 402F3 instrument (-140°C to 1600°C) at 5°C / min.

[0047] Various raw materials were used in the following examples, and unless otherwise specified, conventional commercially available products were used, and the specifications were conventional specifications in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means mole percent.

[0048] As used herein, "glass-ceramic" is a solid obtained by controlled crystallization of a base glass, which has one or more crystalline phases and a residual glass phase.

[0049] As used herein, "first temperature Tl" is the temperature required to form a crystallizable glass, generally in the range of the transition temperature to 50°C above the transition temperature, and "second temperature T2" is the temperature required to form a glass-ceramic. "Crystallization" or "ceramming" is the process used to make a glass-ceramic by heating a crystallizable glass to a second temperature (T2) and maintaining the second temperature T2 for a predetermined period of time (t2) to form a glass-ceramic.

[0050] As used herein, "liquidus temperature" is the temperature at which the first crystal is observed in a standard gradient boat liquidus measurement (ASTM C829-81 and subsequent versions). "Visible light" means light within the 400 nm to 800 nm band of the electromagnetic spectrum. As used herein, "radiation" means light and rays within the electromagnetic spectrum, including but not limited to less than 200 nm, 200 nm to 400 nm, and greater than 800 nm.

[0051] As used herein, "transmittance" means the ratio of the light flux transmitted through a solid, liquid or gaseous medium to the light flux incident on the solid, liquid or gas; "X-ray resistance" means the stability of the optical glass to X-ray irradiation. The optical density of the glass increases after X-ray irradiation, and the stability to X-ray irradiation is characterized by the amount of increase in optical density; "optical density D" means the common logarithm of the reciprocal of the white light transmittance T. ΔD is the difference between the optical density after irradiation and the optical density before irradiation.

[0052] As a result of the production of the glass-ceramic, certain impurities or components that are not intentionally added can be present in the final glass-ceramic composition. Such materials are present in the glass or glass-ceramic in small amounts and are referred to herein as "unintentional materials."

[0053] A low-expansion radiation-shielding glass-ceramic according to a first aspect of the present application includes, in terms of mole percent, 50 to 83.5% SiO2, 12 to 20% Al2O3, 0 to 7% B2O3, 2 to 5% Li2O, 0 to 4% Na2O, 0 to 2% K2O, 0 to 8% MgO, 0 to 6% CaO, 0 to 2% SrO, 0 to 1% BaO, 1 to 3% P2O5, 0 to 4% ZnO, 0.5 to 0.7% CeO2, 1 to 4% ZrO2, 0 to 0.8% TiO2, and 0 to 0.1% fining agent.

[0054] The above-described glass-ceramics can be generally described as lithium-containing aluminosilicate glass-ceramics and comprise SiO2, AI2O3, and Li2O. In addition to SiO2, AI2O3, and Li2O, the above-described glasses and glass-ceramics can also comprise alkali salts such as Na2O, K2O, CaO or SrO, as well as P2O5, ZrO2, and a variety of other components as described below.

[0055] In one or more embodiments, the above-described low-expansion radiation-shielding glass-ceramics comprise a primary crystalline phase consisting of β-quartz solid solution crystalline phase and β-spodumene solid solution crystalline phase, but lithium phosphate, cristobalite, rutile, and the like, and residual glass phase can also exist as secondary crystalline phases; the amount of the resulting crystalline phase can be determined by the Rietveld method in X-ray diffraction. The crystalline portion generally accounts for at least 70%, preferably 80%, and more preferably 95% of the mass of the glass-ceramic.

[0056] The β-quartz solid solution is a continuous solid solution formed from β-eucryptite (Li2O AI2O3 2SiO2) and β-quartz (SiO2). β-eucryptite and β-quartz have the same hexagonal spiral structure, and their expansion coefficients in the direction of the spiral (i.e., the c-axis direction) are both negative, and their expansion coefficients in other directions are both positive, and the overall expansion of a material composed of small crystalline particles is also negative. The β-quartz solid solution can be crystallized from a glass containing Li2O AI2O3 SiO2, and the resulting glass-ceramic contains β-quartz solid solution and residual glass, and the negative expansion of the former and the positive expansion of the latter cancel each other out, resulting in a glass-ceramic with an expansion coefficient of zero or close to zero.

[0057] β-spodumene belongs to the tetragonal system and is generally considered to be a filled derivative of quartz. The β-spodumene solid solution (Li2O AI2O3 nSiO2) also has good thermodynamic properties, and its thermal expansion properties are anisotropic, with a negative expansion coefficient in the a-axis direction and a positive expansion coefficient in the c-axis direction. The unit cell parameters of the β-spodumene solid solution continuously change with its chemical composition (mainly the content of SiO2), and as the value of n increases, the magnitude of the c-axis expansion decreases and the magnitude of the a-axis contraction increases as the temperature increases. Thus, the unit cell parameters of the β-spodumene solid solution formed by the same heat treatment regime tend to decrease with increasing SiO2 content, and the thermal expansion coefficient becomes smaller and smaller.

[0058] The above-described glass-ceramics contain β-quartz solid solution and β-spodumene solid solution grains, and the grains have a longest dimension of 80 nm or less, which is calculated by the Scherrer formula.

[0059] SiO2is mainly used as a glass network former to stabilize the structure of the glass-ceramic. It can reduce the coefficient of thermal expansion of the glass, increase the thermal stability, chemical stability, softening temperature, heat resistance, hardness and mechanical strength of the glass, and is an important component for forming the crystal phase. However, when the content of SiO2is too high, the high-temperature melting viscosity of the glass increases, and the melting temperature T 200P (200 poise temperature) can be controlled. In some embodiments, the glass-ceramic comprises about 50% to 83.5% SiO2, preferably 56% to 83.5%, and more preferably 61% to 83.5% SiO2.

[0060] Al2O3can stabilize the network structure of the glass-ceramic and improve its mechanical properties and chemical durability. However, when the content of Al2O3is low, the crystal formation rate is slow, the crystal content is low, and the application effect cannot be achieved. When the content of Al2O3is high, the melting viscosity of the glass increases, making it difficult to melt the glass. In some embodiments, the glass-ceramic comprises about 12% to 20% Al2O3, preferably 15% to 25%.

[0061] The divalent oxide RO (MgO, CaO, SrO, BaO, ZnO, etc.) can adjust the refractive index and thermal expansion coefficient of the glass, and improve the chemical stability and mechanical processing performance of the glass. CaO can adjust the properties of the glass, including adjusting the viscosity-temperature curve of the glass-ceramic, accelerating the melting and refining process of the glass, and improving the mechanical strength, hardness and chemical stability of the glass. In some embodiments, the glass-ceramic comprises about 0% to 6% CaO. An increase in the content of CaO makes the glass brittle and prone to wollastonite crystallization (CaO-SiO2), so adding an appropriate amount of MgO can reduce the high-temperature viscosity of the glass, reduce the tendency and speed of crystallization of the glass, and improve the mechanical strength, transmittance and chemical stability. In some embodiments, the glass-ceramic comprises about 0% to 8% MgO. The introduction of BaO can significantly increase the refractive index of the glass, and the dispersion increases slightly. However, when the content of BaO is too high, the high-temperature viscosity of the glass liquid becomes smaller, the glass flowability is large, but there are more small bubbles in the glass, which is not conducive to the control of the optical parameters of the glass. In addition, the high-temperature corrosion of BaO to corundum mullite ceramic crucibles and platinum crucibles increases when the content of BaO is too high, so the preferred range is 0% to 1% BaO. SrO and ZnO increase the stability of the glass, reduce the high-temperature viscosity of the glass, and improve the properties of the glass. In some embodiments, the glass-ceramic comprises about 0% to 2% SrO and 0% to 4% ZnO.

[0062] B2O3 and monovalent oxides (such as Li2O, Na2O, and K2O) act as fluxing agents, lowering the glass melting temperature and promoting melting and clarification of the molten glass. B2O3 can lower the glass melting temperature and improve the damage resistance of the glass-ceramic. When the boron in the residual glass is not charge-balanced by alkaline oxides or divalent cation oxides, it is in a tri-coordinated state, making the network structure around these tri-coordinated boron less rigid than that of tetra-coordinate boron. However, when its content is too high, it increases the tendency of the glass to crystallize and reduces its chemical stability. In some embodiments, the glass-ceramic contains approximately 0% to 7% B2O3. In the glass-ceramics described herein, Li2O is a key component in the formation of β-quartz and β-spodumene solid solutions. When its content is too low, glass nucleation and crystallization are difficult. When its content is too high, the crystal particles formed during the crystallization stage are large, the repulsive forces between the crystal particles are strong, and the optical and thermal properties of the glass are deteriorated. In some embodiments, the glass-ceramic contains approximately 2% to 5% Li2O.

[0063] ZrO2, P2O5 and TiO2 act as nucleating agents for glass to promote the crystallization of base glass, increase the nucleation and crystallization speed of glass, improve the crystallization quality, reduce the crystallization time, improve efficiency, reduce energy consumption and lower production costs.

[0064] One key aspect of the present invention is that TiO2, a component that helps lower the melting temperature of base glass and improve its chemical stability, is often used as a crystal nucleating agent. However, excessive TiO2 can cause discoloration and reduce transmittance in glass-ceramics. To avoid this reduction in transmittance, in some embodiments, the glass-ceramics contain approximately 0% to 0.8% TiO2.

[0065] In addition to acting as a nucleating agent, ZrO2 can also improve the stability and elastic modulus of glass-ceramics. Adding ZrO2 can also reduce the grain size of crystals, forming transparent glass-ceramics. However, ZrO2 has low solubility in glass. Excessive ZrO2 content can increase the high-temperature viscosity of the glass, raise the liquidus temperature, and cause devitrification. In some embodiments, the glass-ceramics contain approximately 1% to 4% ZrO2.

[0066] P2O5 acts as a nucleating agent, enabling the base glass to nucleate under certain conditions. It also promotes the dissolution of ZrO2, aiding in glass clarification and ensuring that the expansion coefficient curve after crystallization approaches the zero line coordinate. If the P2O5 content is too low, the base glass will have low viscosity at higher temperatures and be prone to crystallization. If the P2O5 content is too high, the glass's tendency to separate phases increases, making it difficult to control devitrification after cooling during the base glass's formation, and reducing the glass's chemical stability. In some embodiments, the glass-ceramic contains approximately 1% to 3% P2O5.

[0067] Various defects exist in the glass network. When the rays are shot into the glass and hit the electrons, due to the strong ionizing radiation, a number of free electrons and holes are immediately formed in the glass material, i.e. the so-called photoelectric effect, and the rays lose part of their energy due to being scattered, i.e. the Compton effect. Then the electrons will concentrate together and combine with various defects in the glass to form "color centers" that absorb light. Since the free electrons or holes captured by the "color centers" have certain band structures, the energy level spacing thereof is equivalent to the photon energy of the visible spectrum, which causes them to produce absorption in the visible light region and thus result in glass coloring. The coloring degree is related to the glass composition and the radiation dose. However, in the presence of cerium in the glass, the free electrons or holes caused by radiation first react with the cerium ions. Due to the variable valence of the cerium ions (the absorption band caused by the change of the valence thereof is located in the ultraviolet region, so no coloring and influence on the transmittance occur), the electrons or holes can be captured or released, so that the electrons or holes recombine (Ce 4+ captures free electrons, Ce 3+ captures holes), which inhibits the formation of color centers in the visible light range, thereby preventing radiation coloring and improving the radiation stability of the glass. In some embodiments, the glass-ceramics contain about 0.5% to 0.7% CeO2.

[0068] In addition, one or more components of Sb2O3, SnO2, As2O3, NaCl and CaF2may be appropriately selected as the fining agent for the glass-ceramics during melting, so as to promote the removal of bubbles, reduce glass defects, and make the base glass transparent and uniform. However, when the content of the fining agent Sb2O3, SnO2or As2O3is too high, the glass will produce brown color under actinic radiation. In some embodiments, the glass-ceramics contain about up to 0.1% of the fining agent, preferably up to 0.05%, and more preferably contain no fining agent.

[0069] The above glass-ceramics satisfy the condition of (R2O + RO) / Al2O3 < 1, wherein the molar percentage of R2O is the sum of the molar percentages of Li2O, Na2O and K2O, and the molar percentage of RO is the sum of the molar percentages of MgO, ZnO, CaO, SrO and BaO.

[0070] The above glass-ceramics have the following properties:

[0071] ① Anti-radiation ability: the optical density increment per centimeter thickness △D / cm of the glass-ceramics after being subjected to a total dose of 1 x 10 5 rad (Si) γ-ray irradiation is ≤ 0.060. The material has a spatial radiation tolerance ability that meets the requirements of the radiation-resistant glass stipulated in "GB 903-87 Colorless Optical Glass".

[0072] ii. High optical quality: the glass-ceramic has a transmittance of at least 70%, more preferably at least 80%, in the wavelength range 480-800 nm at a thickness of 6 mm. It has the following transmitted color coordinates in the CIELab color space under the D65 light source: 15≤L*≤90, -3≤a*≤3 and -3≤b*≤20.

[0073] More particularly, the glass-ceramic has a transmittance of at least 80% for light in the wavelength range 500-800 nm at a thickness of 6 mm.

[0074] The glass-ceramic has a transmittance of 0.01% to 3% for a wavelength of 200 nm at a thickness of 6 mm.

[0075] The glass-ceramic has a transmittance of at least 60% for a wavelength of 550 nm at a thickness of 6 mm.

[0076] iii. Low thermal expansion coefficient: the glass-ceramic has a thermal expansion coefficient CTE of 0±1x10 -7 / K in the range -100°C to 200°C.

[0077] The present application further provides a more preferred component ratio, in terms of molar percentage, comprising the following composition: 61% to 83.5% SiO2, 12% to 20% Al2O3, 2% to 5% Li2O, 0% to 4% Na2O, 0% to 2% K2O, 0% to 8% MgO, 0% to 6% CaO, 0% to 2% SrO, 0% to 1% BaO, 1% to 3% P2O5, 0% to 4% ZnO, 0.5% to 0.7% CeO2, 0% to 0.8% TiO2, 1% to 4% ZrO2.

[0078] The present application further provides a more preferred component ratio, in terms of molar percentage, comprising the following composition: 61% to 83.5% SiO2, 12% to 20% Al2O3, 2% to 5% Li2O, 0% to 4% Na2O, 0% to 2% K2O, 0% to 8% MgO, 0% to 6% CaO, 0% to 2% SrO, 0% to 1% BaO, 1% to 3% P2O5, 0% to 4% ZnO, 0.5% to 0.7% CeO2, 0% to 0.8% TiO2, 1% to 4% ZrO2.

[0079] S1: mixing the raw materials of the low-expansion radiation-protective glass-ceramic according to the components, and melting the mixture at a temperature of 1560-1680°C to obtain a base glass;

[0080] S2: heating the base glass by two-step ceramming or one-step ceramming to obtain a glass-ceramic.

[0081] The two-step ceramming heating process is as follows:

[0082] heating the base glass from room temperature to a first temperature T1 of 630-850°C at a first heating rate v1 of 0.01°C / min to 10°C / min, and holding the temperature for a predetermined period t1 of 0.2-24 h to obtain a crystallizable glass;

[0083] The crystallizable glass is heated to a second temperature T2 of 850-1200℃ at a second heating rate v2 of 0.1-10℃ / min and then kept at the second temperature for a predetermined time period t2 of 0.5-12h to obtain the glass ceramic.

[0084] The one-step ceramicizing heating process is as follows:

[0085] The base glass is heated from room temperature to a temperature T8 of 850-1200℃ at a heating rate of 0.005-1℃ / min and then kept at the temperature for a predetermined time period t of 0.5-48h to obtain the glass ceramic.

[0086] The components of the specific embodiments 1-13 are shown in Table 1 below.

[0087] Table 1

[0088]

[0089]

[0090] Table 1 (continued)

[0091] Example 6 Example 7 Example 8 Example 9 Example 10 SiO2 52.67 83.05 68.66 50.67 68.63 Al2O3 18.49 12.14 14.39 19.54 15.12 B2O3 6.64 / 2.37 6.74 0.14 Li2O 3.12 2.01 4.73 3.16 2.03 Na2O 3.28 / 1.2 0.35 / [K2O] / / 1.95 0.12 1.27 MgO 5.53 / / 7.52 1.58 CaO 3.36 / / 5.43 5.14 SrO 1.37 / / 1.78 0.84 BaO 0.38 / / 0.18 / P2O5 1.35 1.21 2.78 2.09 1.13 ZnO / / 1.32 / 1.4 ZrO2 2.31 1.06 1.9 1.85 2.11 TiO2 0.8 / / / / CeO2 0.7 0.53 0.7 0.57 0.56 Fining agent / / / / 0.05 T 200P (°C) 1585 1600 1605 1580 1610 Liquidus temperature (°C) 1300 1400 1350 1350 1400 Liquidus viscosity (P) 7863 2231 7116 3562 2306 Annealing temperature (°C) 688 681 680 692 685

[0092]

[0093]

[0094] The technical solutions of the present application and the test results are described in detail below in combination with specific embodiments:

[0095] Table 2 below shows the process parameters of the glass ceramics prepared in the above embodiments 1-13 and the corresponding test results.

[0096] Table 2

[0097]

[0098]

[0099] Table 2 (continued)

[0100]

[0101]

[0102]

[0103] According to the standard "GB / T7962.12-2010 Test Methods for Colorless Optical Glass Part 12: Spectral Internal Transmittance", the transmittance of the radiation-proof low expansion glass-ceramic sample was measured using an ultraviolet-visible-near infrared spectrophotometer, and the internal transmittance curves of the sample at 200nm, 550nm, and 780nm were obtained. Figure 1 As shown, the samples of Examples 1, 3, and 6 exhibit low transmittance in the ultraviolet and near-ultraviolet bands, demonstrating UV shielding capabilities. The tristimulus values ​​(X, Y, Z), chromaticity coordinates (x, y, z), and color space L*, a*, and b* values ​​in the CIE standard colorimetry system were measured in accordance with the standard "GB / T3977-2008 Color Representation Methods."

[0104] According to GBT903-2019 Colorless Optical Glass and GB139-89 Ferrous Sulfate Dosimeter Standard, Co 60 The gamma ray source is calibrated for the dose field, the glass samples are marked and inspected before irradiation, and the transmittance curve of the sample before irradiation is tested, such as Figure 2 As shown in the figure, find the given dose rate line according to the calibration, place the axis of the sample on the dose rate line, and perform irradiation test on the sample at the given dose rate; according to irradiation dose = irradiation dose rate × irradiation time, determine the irradiation time corresponding to the total dose of the test plan; accumulate the irradiation dose (or time), and when the sample irradiation dose reaches the total dose or dose point of the test plan, remove the sample and immediately test the transmittance curve after irradiation with a spectrophotometer; irradiation test dose rate: 5×10 3 rad(Si) / h, the total dose reaches: 1×10 3 rad(Si),1×10 4 rad(Si),1×10 5 rad(Si),1×10 6 rad(Si). Example 4 was treated with different total doses of 1×10 3 rad(Si),1×10 4 rad(Si),1×10 5 rad(Si) and 1×10 6 The transmittance curve after rad(Si)γ-ray irradiation is as follows Figure 3 As shown, compared with the unirradiated glass material, the optical density increment ΔD corresponding to 550 nm per centimeter thickness is 0.035, 0.043, 0.051 and 0.060 respectively.

[0105] Dilatometry (DIL) is a method for measuring the change in length of a sample in a test direction with respect to temperature or time under the control of a certain temperature program (ramp, soak, and combination thereof) and negligible load. The test system places the material to be tested in a furnace, and as the temperature rises, the material expands. The amount of expansion is transmitted to a displacement sensor through a top rod, thereby obtaining the displacement amount of the material thermal expansion. As the furnace temperature rises, the system transmits the temperature signal and the displacement signal to a computer in real time through data acquisition and processing, and the thermal expansion coefficient of the material is calculated through the thermal expansion formula. Figure 4 The thermal expansion CTE curves of the glass-ceramics of Example 3, Example 4, and Example 8 are shown in FIG. 1, and the thermal expansion coefficients in the range of -100°C to 200°C are -0.442, -0.693, and -0.732, respectively.

[0106] The glass-ceramics prepared from the above data were tested, and the results are shown in Table 2 above and FIGS. 2 and 3. Figure 1 Figure 2 Figure 3 Figure 4 The glass-ceramics have a grain size mainly distributed in the range of 80 nm, and the optical density increment per centimeter thickness ΔD / cm after irradiation with a total dose of 1×10 5 rad (Si) γ-rays is ≤0.060. The glass-ceramics have a thermal expansion coefficient of 0±1×10 -7 / K in the range of -100°C to 200°C. The glass-ceramics have transmission color coordinates L*, a*, and b* in the color space as follows: 15≤L*≤90, -3≤a*≤3, and -3≤b*≤20. The glass-ceramics have the characteristics of low thermal expansion coefficient, good thermal stability, and radiation resistance, and can meet the actual application requirements of products.

[0107] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the present application.​​​

Claims

1. A low-expansion radiation-shielding glass ceramic, characterized by, The raw materials of the low-expansion radiation-proof glass ceramic include the following components in terms of mole percentage: 50-83.5% SiO2, 12-20% Al2O3, 0-7% B2O3, 2-5% Li2O, 0-4% Na2O, 0-2% K2O, 0-8% MgO, 0-6% CaO, 0-2% SrO, 0-1% BaO, 1-3% P2O5, 0-4% ZnO, 0.5-0.7% CeO2, 1-4% ZrO2, 0-0.8% TiO2, and 0-0.1% fining agent; The low-expansion radiation-proof glass ceramic includes a main crystal phase composed of a β-quartz solid solution crystal phase and a β-spodumene solid solution crystal phase, a secondary crystal phase, and a residual glass phase; The mass of the main crystal phase and the secondary crystal phase accounts for more than 70% of the mass of the glass ceramic; The low-expansion radiation-proof glass ceramic includes R2O composed of Li2O, Na2O, and K2O, and RO composed of MgO, ZnO, CaO, SrO, and BaO; The mole percentage of R2O, RO, and Al2O3 satisfies (R2O+RO) / Al2O3<1; The low-expansion radiation-proof glass ceramic has a thermal expansion coefficient CTE of 0±1×10 -7 -6 / K in a temperature range of -100°C to 200°C; the low-expansion radiation-proof glass ceramic has an optical density increment per centimeter thickness after being subjected to γ-ray irradiation with a total dose of 1×10 5 rad of less than or equal to 0.

060. The low-expansion radiation-proof glass ceramic has a transmittance of at least 70% for light in the wavelength range of 480-800 nm, a transmittance of at least 80% for light in the wavelength range of 500-800 nm, a transmittance of 0.01-3% for a wavelength of 200 nm, and a transmittance of at least 60% for a wavelength of 550 nm when the thickness of the glass ceramic is 6 mm; The low-expansion radiation-shielding glass-ceramic has the following transmission color coordinates in the CIELab color space: 15≤L ≤90, -3≤a ≤3 and -3≤b ≤20.

2. The low expansion radiation shielding glass ceramic according to claim 1, characterized in that, The fining agent is one or more of Sb2O3, SnO2, As2O3, NaCl, and CaF2.

3. A method of producing the low expansion radiation shielding glass ceramic according to any one of claims 1 to 2, characterized by, The method includes the following steps: S1: mixing the raw materials of the low-expansion radiation-proof glass ceramic according to the components, and melting the mixture at a temperature of 1560-1680°C to obtain a base glass; S2: heating the base glass by two-step ceramming or one-step ceramming to obtain a glass ceramic.

4. The method for preparing the low expansion radiation-proof glass ceramic according to claim 3, characterized in that: The two-step ceramming is as follows: heating the base glass from room temperature to 630-850°C at a heating rate of 0.01°C / min-10°C / min, and holding the temperature for 0.2-24 h to obtain a crystallizable glass; heating the crystallizable glass to 850-1200°C at a heating rate of 0.1°C / min-10°C / min, and holding the temperature for 0.5-12 h to obtain a glass ceramic; The one-step ceramming is as follows: heating the base glass from room temperature to 850-1200°C at a heating rate of 0.005°C / min-1°C / min, and holding the temperature for 0.5-48 h to obtain a glass ceramic.

5. Use of the low-expansion radiation-proof glass ceramic according to any one of claims 1-2 in a radiation shielding protective window or a radiation transparent observation window.

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