Soda-lime-silica transparent ceramic and method for manufacturing the same
Sodium-calcium-silicon transparent ceramics were prepared by melt forming and atmospheric pressure heat treatment, which solved the problems of complex preparation and high porosity of transparent ceramics in the existing technology. This method achieved transparent ceramics with high transmittance and large size, and reduced costs and equipment requirements.
Patent Information
- Application Number
- CN202311185748.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-12
- Publication Date
- 2025-11-28
- Estimated Expiration
- 2043-09-12
AI Technical Summary
Existing methods for preparing transparent ceramics are complex, making it difficult to effectively reduce porosity and prepare large-size, low-cost polycrystalline materials containing alkali metals.
Sodium-calcium-silicon transparent ceramics were prepared by melt forming. Glass was transformed into transparent ceramics by heat treatment under normal pressure. The composition and heat treatment parameters, including the heating rate and temperature range, were controlled to suppress crystallization and pore formation.
This technology enables the production of transparent ceramics with high transmittance and high hardness, and allows for large-size forming, thereby reducing manufacturing costs and equipment requirements.
Smart Images
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of ceramic material preparation, and particularly relates to a sodium-calcium-silicon transparent ceramic and a preparation method thereof. BACKGROUND
[0002] Transparent ceramics have excellent mechanical properties and mechanical properties while ensuring good transmittance, and the crystal field environment of the polycrystalline material provides favorable conditions for electronic radiation transition. The transparent ceramics have important applications in the fields of military display windows, white light emitting diodes, X-ray detection scintillation materials, solid lasers, medical health, etc. However, the traditional transparent ceramic preparation method needs to go through a complex process of powder preparation, molding, sintering, etc., and has high requirements for powder, temperature, pressure and sintering time, etc., which need to be strictly controlled in the preparation process. The porosity is a key factor affecting the transmittance of transparent ceramics, and how to reduce the porosity of transparent ceramics has always been a hot and difficult point in the research of preparation technology. The transparent ceramic prepared by complete crystallization of glass can effectively eliminate pores, and the preparation process is simple, without the need for pressure and ultra-high temperature. In addition, the transparent ceramic with a metastable phase can be prepared, and it has important significance to prepare large-size low-cost transparent ceramics by using this route. SUMMARY
[0003] The application provides a sodium-calcium-silicon transparent ceramic and a preparation method thereof to solve the above technical problems. The transparent ceramic has high transmittance, low preparation cost and can be formed in a large size.
[0004] To achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows:
[0005] A sodium-calcium-silicon transparent ceramic, the sodium-calcium-silicon transparent ceramic comprises the following components in terms of molar percentage: SiO2: 45-50%; CaO: 30-35%; Na2O: 15-18%; ZrO2: 1-6%; B2O3: 0-6%.
[0006] Preferably, 1.8≤CaO / Na2O≤2.2, 2.8≤SiO2 / Na2O≤3.2, and 1≤ZrO2+B2O3≤8.
[0007] Preferably, the Vickers hardness of the transparent ceramic is greater than 5.5GPa, and the transmittance at a wavelength of 550nm is greater than 60% when the thickness is 1mm.
[0008] The preparation method of the sodium-calcium-silicon transparent ceramic is to prepare raw materials into glass by using a melt forming method, and then prepare the transparent ceramic by heat treatment under normal pressure.
[0009] Preferably, the preparation method specifically comprises the following steps:
[0010] The raw materials of the composition are melted at a temperature not less than 1500℃, and then the melted material is clarified and homogenized, and then cooled and shaped, and then annealed at a temperature range of 550-650℃ to obtain the transparent glass.
[0011] The annealed glass is heat treated to obtain the transparent ceramic.
[0012] Preferably, the heat treatment is one-step heat treatment or two-step heat treatment.
[0013] Preferably, the one-step heat treatment is at a temperature of 600-800℃, the holding time is not less than 1 hour, and the heating rate from room temperature to the heat treatment temperature is not higher than 20℃ / min, and further preferably, the heating rate is not higher than 10℃ / min.
[0014] Preferably, in the two-step heat treatment, the first step heat treatment temperature is in a range of 600-700℃, and the second step heat treatment temperature is in a range of 700-800℃. The interval between the first step heat treatment temperature and the second step heat treatment temperature is 10℃-120℃, and further preferably, the interval is 80-120℃; the holding time of the first step and the second step is not less than 1 hour. The heating rate from room temperature to the first step heat treatment temperature is not higher than 20℃ / min, and further preferably, the heating rate is not higher than 10℃ / min; the heating rate from the first step heat treatment temperature to the second step heat treatment temperature is not higher than 20℃ / min, and further preferably, the heating rate is not higher than 10℃ / min.
[0015] The sodium-calcium-silicon glass has good viscosity-temperature characteristics and good glass forming properties. After melting, clarifying and homogenizing, the glass can be shaped by pouring, flat plate shaping and other methods, and the glass of various shapes and large size can be conveniently shaped. Meanwhile, the sodium-calcium-silicon glass can be ceramized by heat treatment without additional forming pressure.
[0016] In the composition, the molar content ratio of Na2O:CaO:SiO2 is about 1:2:3, the crystal phase composition of the transparent ceramic obtained is close to Na2Ca2Si3O9, and the probability of formation of other crystal phases is reduced.
[0017] The ZrO2 is introduced in the present application, which has effects in two aspects. On the one hand, the content of Na2O in the glass composition is high, and the glass is easy to produce uncontrollable crystallization in the forming process; after the introduction of ZrO2, the glass forming ability is enhanced, the crystallization can be inhibited, and the glass forming is facilitated. On the other hand, in the crystallization (ceramization) process, due to the high temperature and strong diffusion ability of Na ions, the crystallization is easy to produce uncontrollable crystallization, and a variety of composition phases are easy to be generated, or the grain is excessively grown, which affects the transmittance of the ceramic. When the content of ZrO2 is low (especially lower than 1 mol.%), the above effects are not obvious; when the content of ZrO2 is high, ZrO2 related crystal phases are easy to be generated in the crystallization process, which affects the transmittance of the ceramic. When the content of ZrO2 is moderate, the Na + ions in the glass are distributed near the Zr-O polyhedron as charge neutralizers, and the diffusion and the like thereof are bound by the charge of the Zr-O polyhedron, which has a positive effect on inhibiting the diffusion of Na + ions and preventing uncontrollable crystallization of the glass in the heat treatment process.
[0018] In the present application, B2O3 can accelerate the clarification of the glass liquid, reduce the bubbles in the glass, and improve the transmittance of the ceramic obtained after heat treatment. However, the introduction of ZrO2 and B2O3 should not be too much to avoid the generation of related crystal phases in the heat treatment, so that a variety of crystal types are finally generated, and the difference in refractive index will seriously affect the transmittance of the transparent ceramic obtained.
[0019] In the heating process involved in the heat treatment in the present application, the heating rate should not be too high, and a too high heating rate is easy to cause the formation of pores in the ceramic, thereby reducing the transmittance of the ceramic.
[0020] Compared with the prior art, the present application has the following advantages and technical effects:
[0021] (1) The transparent ceramic is obtained under normal pressure based on the glass state-crystal state transition. Compared with the traditional transparent ceramic preparation technology, the preparation method of the transparent ceramic obtained by heat treatment of the precursor glass has mild preparation conditions, simple process, low requirement for equipment, and can realize large-size preparation.
[0022] (2) The transmittance of the transparent ceramic at 550 nm is greater than 60% (based on 1 mm thick ceramic), and the Vickers hardness is greater than 5.5 GPa.
[0023] (3) It is difficult to prepare an alkali metal-containing polycrystalline material by the traditional transparent ceramic preparation method, and the present application realizes the preparation of the alkali-containing transparent ceramic through composition design and heat treatment regulation. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 It is a real picture of the transparent ceramic obtained after two-step heat treatment of Example 1, and the transparent ceramic is 3 cm away from the background paper.
[0025] Figure 2 SEM micrograph of the transparent ceramic obtained after heat treatment by two-step method for Example 1.
[0026] Figure 3 XRD curve and Na4Ca4Si6O 18 XRD comparison chart of standard card.
[0027] Figure 4 Transmittance curve of the transparent ceramic obtained after heat treatment by two-step method for Example 1, Example 2, Example 3, with thickness of 1mm.
[0028] Figure 5 Transmittance curve of the transparent ceramic obtained after heat treatment by two-step method for Example 4, Example 5, Example 6, with thickness of 1mm.
[0029] Figure 6 SEM micrograph of the sample obtained after heat treatment by two-step method for Comparative Example 8.
[0030] Figure 7 XRD curve and Na4Ca4Si6O 18 XRD comparison chart of standard card, ZrSiO4 standard card.
[0031] Figure 8 XRD chart of the sample obtained after heat treatment by two-step method for Comparative Example 10.
[0032] Figure 9 Cross-section SEM of the sample in Comparative Example 11.
[0033] Figure 10 CT imaging chart of the voids in the sample in Comparative Example 11. DETAILED DESCRIPTION
[0034] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.
[0035] The present application provides a sodium-calcium-silicon transparent ceramic, which comprises the following components in terms of mole percentage: SiO2: 45-50%; CaO: 30-35%; Na2O: 15-18%; ZrO2: 1-6%; B2O3: 0-6%.
[0036] The present application also provides a preparation method of the calcium-silicon transparent ceramic,
[0037] The raw materials with the above composition are melted at a temperature of not less than 1500°C, homogenized and then cooled and formed, and then annealed at a temperature of 550-650°C to obtain transparent glass.
[0038] The annealed glass is heat treated to obtain transparent ceramic.
[0039] The melting temperature is 1550-1650°C.
[0040] The following will be illustrated by specific examples. As shown in Table 1, the composition, heat treatment schedule and parameters, transmittance and hardness of Example 1 to Example 6 are shown. The heating rate (including one-step and two-step heat treatment) in Table 1 is 8°C / min.
[0041] Table 1
[0042]
[0043]
[0044] Figure 1 The photograph of the transparent ceramic obtained after two-step heat treatment of Example 1 is shown, and the heat treatment conditions are shown in Table 1. Figure 1 The transparent ceramic is 3 cm away from the background paper. It can be found that the obtained ceramic has high transmittance, and the letters on the background paper can be clearly observed.
[0045] Figure 2 The scanning electron microscope micrograph of the transparent ceramic obtained after two-step heat treatment of Example 1 is shown, and the heat treatment conditions are shown in Table 1. The transparent ceramic shown in the figure is composed of densely packed grains, and the average grain size is less than 50 microns.
[0046] Figure 3 The X-ray diffraction curve of the transparent ceramic obtained after two-step heat treatment of Example 1 is shown, and the X-ray diffraction comparison chart of the standard card is shown. The heat treatment conditions of the sample are shown in Table 1. As shown in the figure, the diffraction curve of the transparent ceramic clearly shows the diffraction peak of the crystal, and no diffraction peak of the glass is observed, which indicates that the content of ceramic crystal phase in the transparent ceramic is basically 100%. 18
[0047] Figure 4 The transmittance curve of the transparent ceramic obtained after two-step heat treatment of Example 1, Example 2 and Example 3 with a thickness of 1 mm is shown. The heat treatment conditions of the above samples are shown in Table 1. The transmittance of the above example samples at a wavelength of 550 nm is obviously higher than 60%.
[0048] Figure 5 Transmittance curves of the transparent ceramics with thickness of 1 mm after heat treatment by two-step method for Example 4, Example 5, Example 6. The heat treatment conditions of the above samples are shown in Table 1. The transmittance of the above samples at 550 nm is all higher than 60%.
[0049] Comparative Example 1
[0050] SiO2: 50%, CaO: 28%, Na2O: 16%, ZrO2: 4%, B2O3: 2%;
[0051] The CaO / Na2O in the component is <1.8, and the CaO molar content is less than 30%. The composition is prone to crack after heat treatment at 650°C for 20h / 750°C for 20h.
[0052] Comparative Example 2
[0053] SiO2: 46%, CaO: 36%, Na2O: 16%, ZrO2: 2%, B2O3: 0%;
[0054] The CaO / Na2O in the component is >2.2, and the CaO molar content is more than 35%. The composition is severely devitrified after heat treatment at 610°C for 20h / 710°C for 20h.
[0055] Comparative Example 3
[0056] SiO2: 52%, CaO: 30%, Na2O: 16%, ZrO2: 2%, B2O3: 0%;
[0057] The SiO2 / Na2O in the component is >3.2, and the SiO2 molar content is more than 50%. The composition is severely devitrified after heat treatment at 660°C for 20h / 760°C for 20h.
[0058] Comparative Example 4
[0059] SiO2: 44%, CaO: 34%, Na2O: 16%, ZrO2: 4%, B2O3: 2%;
[0060] The SiO2 / Na2O in the component is <2.8, and the SiO2 molar content is less than 45%. The composition is severely devitrified after heat treatment at 600°C for 20h / 700°C for 20h.
[0061] Comparative Example 5
[0062] SiO2: 47%, CaO: 33%, Na2O: 14%, ZrO2: 4%, B2O3: 2%;
[0063] The Na2O content in the component is less than 15%. The composition appears surface crystallization after heat treatment at 670°C for 20h / 770°C for 20h.
[0064] Comparative Example 6
[0065] SiO2: 49%, CaO: 31.5%, Na2O: 18.5%, ZrO2: 1%, B2O3: 0%;
[0066] The Na2O content in the component is more than 18%. The composition appears devitrification after heat treatment at 610°C for 2h.
[0067] Comparative Example 7
[0068] SiO2: 50%, CaO: 33.3%, Na2O: 16.7%, ZrO2: 0%, B2O3: 0%;
[0069] The component does not contain ZrO2. The glass is partially devitrified when the composition is glass-cast into a block, and the glass-forming ability is poor. Meanwhile, the glass is prone to uncontrollable crystallization after heat treatment, resulting in low transmittance of the sample.
[0070] Comparative Example 8
[0071] SiO2: 46%, CaO: 30%, Na2O: 16%, ZrO2: 8%, B2O3: 0%;
[0072] The ZrO2 content in the component is too high. The composition appears a large amount of zirconium-related crystalline phases in addition to the Na4Ca4Si6O 18 crystalline phase after heat treatment at 680°C for 20h / 780°C for 20h, and a large amount of zirconium-related crystalline phases are generated, resulting in low transmittance.
[0073] Figure 6 The scanning electron microscope micrograph of the sample after two-step heat treatment of Comparative Example 8. Due to the high ZrO2 content of the composition, zirconium-containing crystalline phases are easily formed after heat treatment, resulting in coarse grains. Meanwhile, the composition of the zirconium-containing crystalline phase is quite different from that of other sodium-calcium-silicon crystalline phases, and the refractive index difference is large, resulting in low transmittance of the obtained ceramic.
[0074] Figure 7 The X-ray diffraction curve of the sample after two-step heat treatment of Comparative Example 8 and the X-ray diffraction comparison chart of the Na4Ca4Si6O 18 standard card, and the X-ray diffraction comparison chart of the ZrSiO4 standard card. The results show that when the ZrO2 content in the original glass is high, zirconium silicate is formed after heat treatment.
[0075] Comparative Example 9
[0076] SiO2: 50%, CaO: 33.2%, Na2O: 16.7%, ZrO2: 0.1%, B2O3: 0%;
[0077] The component has slightly improved glass forming ability compared to Comparative Example 7 due to the introduction of trace ZrO2; however, the crystallization after heat treatment is uncontrollable, and devitrification easily occurs.
[0078] Comparative Example 10
[0079] SiO2: 50%, CaO: 33%, Na2O: 16.7%, ZrO2: 0.3%, B2O3: 0%;
[0080] The component further improves ZrO2 compared to Comparative Example 9, and transparent glass can be cast; however, the crystallization after heat treatment is uncontrollable, and devitrification easily occurs. Figure 8 The XRD pattern of the glass cast from Comparative Example 10 and the sample after heat treatment is shown. After heat treatment, the glass phase still exists in the glass, the crystallization degree is low, and phase separation occurs, resulting in low transmittance of the sample.
[0081] Comparative Example 11
[0082] SiO2: 46%, CaO: 32%, Na2O: 16%, ZrO2: 4%, B2O3: 2%;
[0083] The component is the same as that of Example 2; heat treatment at 770°C for 2h with a heating rate of 25°C / min. Due to the excessively large heating rate, nucleation is insufficient, resulting in the growth of some grains being too large, pores are formed between the grains, and the transmittance is reduced. Figure 9 The cross-section scanning electron microscope of Comparative Example 11 after heat treatment shows that pores are formed after heat treatment at a heating rate of 25°C / min. Figure 9 The left SEM image of the pores has a size of more than 100μm; the right image is a morphology image at a low magnification, and the pores easily form a connected structure.
[0084] Figure 10 The CT imaging image of the sample of Comparative Example 11 is shown. The image further shows that the pore structure formed in the ceramic after heat treatment presents a large-area connected structure.
[0085] The various raw materials listed in the present application, as well as the upper and lower limits of the raw materials, the upper and lower limits of the process parameters, and the interval values can all achieve the present application, and examples are not listed one by one; any simple modification, equivalent change or modification made according to the technical essence of the present application to the above examples still belongs to the scope of the technical solutions of the present application.
Claims
1. A sodium calcium silicon transparent ceramic, characterized in that, The main crystal phase of the transparent ceramic is Na4Ca4Si6O 18 , the space group is , and the sodium calcium silicon transparent ceramic comprises the following components in terms of molar percentage: SiO2: 45-50%; CaO: 30-35%; Na2O: 15-18%; ZrO2: 1-6%; B2O3: 0-6%.
2. The sodium calcium silicate transparent ceramic of claim 1, wherein, Wherein 1.8≤CaO / Na2O≤2.2, 2.8≤SiO2 / Na2O≤3.2, 1≤ZrO2+B2O3≤8.
3. The sodium calcium silicate transparent ceramic of claim 1, wherein, The transparent ceramic has a Vickers hardness greater than 5.5 GPa and a transmittance greater than 60% at a thickness of 1 mm and a wavelength of 550 nm.
4. The method of claim 1, wherein the sodium calcium silica transparent ceramic is prepared by a method comprising: preparing a mixture of a sodium source, a calcium source, and a silica source; and sintering the mixture to form the sodium calcium silica transparent ceramic. The preparation method comprises the following steps:
5. The production method according to claim 4, wherein The raw materials are melted at a temperature not lower than 1500 ℃, and then cooled and formed after clarification and homogenization, and annealed at a temperature ranging from 550 to 650 ℃ to obtain a transparent glass. The glass is heat treated to obtain a transparent ceramic. The heat treatment is a one-step heat treatment or a two-step heat treatment.
6. The production method according to claim 4 or 5, characterized by, The one-step heat treatment is performed at a temperature ranging from 600 to 800 ℃, and the holding time is not less than 1 hour, and the heating rate from room temperature to the heat treatment temperature is not higher than 20 ℃ / min.
7. The production method according to claim 6, wherein The first-step heat treatment in the two-step heat treatment is performed at a temperature ranging from 600 to 700 ℃, and the second-step heat treatment is performed at a temperature ranging from 700 to 800 ℃.
8. The production method according to claim 6, wherein The interval between the first-step heat treatment temperature and the second-step heat treatment temperature ranges from 10 ℃ to 120 ℃, and the heat treatment time of the first step and the second step is not less than 1 hour.
9. The production method according to claim 7, wherein The heating rate from room temperature to the first-step heat treatment temperature is not higher than 20 ℃ / min, and the heating rate from the first-step heat treatment temperature to the second-step heat treatment temperature is not higher than 20 ℃ / min.
10. The production method according to claim 7, wherein