Low-shrinkage lithium silicate heat accumulator and preparation method thereof
By optimizing the raw material particle size and gradient cooling process, a low-shrinkage lithium silicate thermal storage body was prepared, which solved the problem of cracking of traditional thermal storage bodies in high-temperature environments and achieved improvements in high-temperature stability and thermal energy storage performance.
Patent Information
- Application Number
- CN202510745901.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-05
- Publication Date
- 2025-09-16
AI Technical Summary
The traditional heat storage medium composed of spodumene, kaolin and quartz, which mainly contains spodumene phase, shrinks by more than 4% when fired under the ratio system, resulting in cracking or under-firing of the product when producing large-sized honeycomb ceramics.
Using raw materials such as lithium carbonate, silicon oxide, aluminum oxide, kaolin and binder, through specific particle size mixing and gradient cooling process, the sintering shrinkage rate is controlled to ≤2%, forming the main crystal phase of LiAlSi3O8, the thermal expansion coefficient is ≤1.3×10-6/℃, and it remains stable at high temperatures.
The preparation of low-shrinkage lithium silicate thermal storage body has been realized. The product has stable thermal expansion coefficient in the range of 30-1000℃, excellent thermal shock resistance, not easy to crack, and is suitable for heat energy storage and release in high temperature environment.
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Figure CN120647351A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of high-temperature ceramics, and in particular to a low-shrinkage lithium silicate thermal storage body and a preparation method thereof. Background Art
[0002] Thermal storage materials, as key materials for thermal energy storage and release, are widely used in industrial energy conservation. Traditional cordierite and mullite-based thermal storage materials suffer from high thermal expansion coefficients and poor thermal shock resistance, making them prone to cracking and failure during repeated thermal cycling. Lithium silicate materials, due to their extremely low thermal expansion coefficients and excellent high-temperature stability, have become a research hotspot for high-performance thermal storage materials.
[0003] Lithium silicate materials, due to their high thermal stability and chemical inertness, are often used for heat storage and release in high-temperature environments. Typically, spodumene, kaolin, and quartz are used to create thermal storage materials primarily containing a spodumene phase. However, this formulation often results in sintering shrinkage exceeding 4%, and the product's sintering temperature range is narrow. When producing large-scale honeycomb ceramics, this significant shrinkage can lead to cracking, or insufficient control of the sintering temperature gradient can result in underfiring. Summary of the Invention
[0004] Purpose of the invention: The purpose of the present invention is to provide a low-shrinkage lithium silicate thermal storage body and a preparation method thereof, so as to solve the problem that the existing technology uses spodumene, kaolin and quartz to generate a thermal storage body mainly containing spodumene phase, but the firing shrinkage under this ratio system is often greater than 4%, and the sintering temperature of the product is relatively narrow. When producing large-sized honeycomb ceramics, the large shrinkage may cause the product to crack, or the insufficient control of the sintering temperature difference may cause the product to be underfired.
[0005] Technical solution:
[0006] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 6-14 parts of lithium carbonate with a D50 particle size of 3-10 μm; 50-70 parts of silicon oxide with a D50 particle size of 5-30 μm; 8-25 parts of kaolin and calcined kaolin with a D50 particle size of 2-9 μm; 9-17 parts of aluminum oxide with a D50 particle size of 3-10 μm; 4-7 parts of a binder; 0.5-2 parts of a surfactant; and 0.5-2 parts of a lubricant.
[0007] The sintering shrinkage of the heat storage body is ≤2%, the thermal expansion coefficient at 30-1000°C is ≤1.3×10-6 / °C, the specific heat capacity at 1000°C is ≥2.2J / g / K, the main crystal phase is LiAlSi3O8, and contains residual α-Al2O3 and SiO2 phases.
[0008] Furthermore, the purity of lithium carbonate, silicon oxide and aluminum oxide is greater than or equal to 99%.
[0009] Furthermore, the amount of lithium carbonate is 7 to 10 parts.
[0010] Furthermore, the D50 particle size of the silicon oxide is 10 to 17 μm.
[0011] Furthermore, the binder is HPMC or CMC, the surfactant is GPE3000 or potassium laurate, and the lubricant is sodium stearate, zinc stearate or glycerol.
[0012] The present invention also discloses a method for preparing a low-shrinkage lithium silicate thermal storage body, comprising the following steps:
[0013] S1. Raw material mixing: lithium carbonate, silicon oxide, kaolin, aluminum oxide, binder, surfactant, and lubricant are mixed according to the formula, and water is added to form a uniform slurry;
[0014] S2, green body forming: extruding the slurry into a honeycomb green body, and obtaining an initial green body after drying;
[0015] S3, pre-calcination treatment: pre-calculate at 600-800°C for 2-4 hours to remove organic matter and decompose lithium carbonate;
[0016] S4. Sintering: heating to 1320-1400°C at 1-5°C / min and keeping at this temperature for 3-8h to form the main crystal phase of LiAlSi3O8;
[0017] S5. Gradient cooling: cooling from the sintering completion temperature to 1200°C at a rate of 5-10°C / min; 1200°C to room temperature: cooling at a rate of 10-20°C / min to obtain the final product.
[0018] Furthermore, in step S5, the gradient cooling rate from the sintering temperature to 1200°C is controlled at 7-9°C / min to form a uniformly distributed microcrack network.
[0019] Beneficial effect: lithium carbonate, kaolin, calcined kaolin, process silicon oxide, process aluminum oxide are used, and the temperature is kept at 1320-1400℃ for 3-8h to obtain a lithium silicate thermal storage body with a sintering shrinkage of less than 2%. The thermal expansion coefficient of the product is less than 1.3*10 at 30-1000℃. -6 / ℃, it does not crack under thermal shock at 700℃, and has a large specific heat capacity. The specific heat at 1000℃ is 2.28J / g / K, and can be used as a heat storage body for RTO devices with high thermal performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 is an XDR image of Example 1 of the present invention;
[0021] Figure 2 2 is a graph showing the specific heat capacity data of Example 1 of the present invention. DETAILED DESCRIPTION
[0022] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0023] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 6-14 parts of lithium carbonate with a D50 particle size of 3-10 μm; 50-70 parts of silicon oxide with a D50 particle size of 5-30 μm; 8-25 parts of kaolin and calcined kaolin with a D50 particle size of 2-9 μm; 9-17 parts of aluminum oxide with a D50 particle size of 3-10 μm; 4-7 parts of a binder; 0.5-2 parts of a surfactant; and 0.5-2 parts of a lubricant.
[0024] The sintering shrinkage of the heat storage body is ≤2%, the thermal expansion coefficient at 30-1000°C is ≤1.3×10-6 / °C, the specific heat capacity at 1000°C is ≥2.2J / g / K, the main crystal phase is LiAlSi3O8, and contains residual α-Al2O3 and SiO2 phases.
[0025] Furthermore, the purity of lithium carbonate, silicon oxide and aluminum oxide is greater than or equal to 99%.
[0026] Furthermore, the amount of lithium carbonate is 7 to 10 parts.
[0027] Furthermore, the D50 particle size of the silicon oxide is 10 to 17 μm.
[0028] Furthermore, the binder is HPMC or CMC, the surfactant is GPE3000 or potassium laurate, and the lubricant is sodium stearate, zinc stearate or glycerol.
[0029] The present invention also discloses a method for preparing a low-shrinkage lithium silicate thermal storage body, comprising the following steps:
[0030] S1. Raw material mixing: lithium carbonate, silicon oxide, kaolin, aluminum oxide, binder, surfactant, and lubricant are mixed according to the formula, and water is added to form a uniform slurry;
[0031] S2, green body forming: extruding the slurry into a honeycomb green body, and obtaining an initial green body after drying;
[0032] S3, pre-calcination treatment: pre-calculate at 600-800°C for 2-4 hours to remove organic matter and decompose lithium carbonate;
[0033] S4. Sintering: heating to 1320-1400°C at 1-5°C / min and keeping at this temperature for 3-8h to form the main crystal phase of LiAlSi3O8;
[0034] S5. Gradient cooling: cooling from the sintering completion temperature to 1200°C at a rate of 5-10°C / min; 1200°C to room temperature: cooling at a rate of 10-20°C / min to obtain the final product.
[0035] Furthermore, in step S5, the gradient cooling rate from the sintering temperature to 1200°C is controlled at 7-9°C / min to form a uniformly distributed microcrack network.
[0036] Example 1
[0037] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 8 parts of lithium carbonate with a D50 particle size of 3 to 10 μm; 64 parts of silicon oxide with a D50 particle size of 10 to 17 μm; 11.6 parts of kaolin with a D50 particle size of 2 to 9 μm; 16.4 parts of aluminum oxide with a D50 particle size of 3 to 10 μm; 4 to 7 parts of a binder; 0.5 to 2 parts of a surfactant; and 0.5 to 2 parts of a lubricant.
[0038] The sintering temperature is 1380℃, the sintering expansion rate is -1.89%, and the thermal expansion coefficient of the product at 30~1000℃ is 0.977*10 -6 / ℃, no cracking after thermal shock at 800℃.
[0039] Example 2
[0040] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 14 parts of lithium carbonate with a D50 particle size of 3 to 10 μm; 68 parts of silicon oxide with a D50 particle size of 10 to 17 μm; 8 parts of kaolin with a D50 particle size of 2 to 9 μm; 10 parts of aluminum oxide with a D50 particle size of 3 to 10 μm; 4 to 7 parts of a binder; 0.5 to 2 parts of a surfactant; and 0.5 to 2 parts of a lubricant.
[0041] The sintering temperature is 1400℃, the sintering expansion rate is -2.00%, and the thermal expansion coefficient of the product at 30~1000℃ is 0.421*10 -6 / ℃, no cracking after thermal shock at 800℃.
[0042] Example 3
[0043] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 11 parts of lithium carbonate with a D50 particle size of 3 to 10 μm; 64 parts of silicon oxide with a D50 particle size of 10 to 17 μm; 11.6 parts of kaolin with a D50 particle size of 2 to 9 μm; 13.4 parts of aluminum oxide with a D50 particle size of 3 to 10 μm; 4 to 7 parts of a binder; 0.5 to 2 parts of a surfactant; and 0.5 to 2 parts of a lubricant.
[0044] The sintering temperature is 1390℃, the sintering expansion rate is -0.92%, and the thermal expansion coefficient of the product at 30~1000℃ is 0.769*10 -6 / ℃, no cracking under thermal shock of 750℃.
[0045] Example 4
[0046] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 8 parts of lithium carbonate with a D50 particle size of 3 to 10 μm; 58.5 parts of silicon oxide with a D50 particle size of 10 to 17 μm; 11.6 parts of kaolin, 10 parts of calcined kaolin with a D50 particle size of 2 to 9 μm; 11.88 parts of aluminum oxide with a D50 particle size of 3 to 10 μm; 4 to 7 parts of a binder; 0.5 to 2 parts of a surfactant; and 0.5 to 2 parts of a lubricant.
[0047] The sintering temperature is 1340℃, the sintering expansion rate is -0.70%, and the thermal expansion coefficient of the product at 30-1000℃ is 1.132*10 -6 / ℃, no cracking under thermal shock of 750℃.
[0048] Example 5
[0049] A low-shrinkage lithium silicate thermal accumulator comprises, by weight, 8 parts of lithium carbonate with a D50 particle size of 3 to 10 μm; 56 parts of silicon oxide with a D50 particle size of 10 to 17 μm; 11.6 parts of kaolin, 15 parts of calcined kaolin with a D50 particle size of 2 to 9 μm; 9.42 parts of aluminum oxide with a D50 particle size of 3 to 10 μm; 4 to 7 parts of a binder; 0.5 to 2 parts of a surfactant; and 0.5 to 2 parts of a lubricant.
[0050] The sintering temperature is 1320℃, the sintering expansion rate is -1.50%, and the thermal expansion coefficient of the product at 30~1000℃ is 1.156*10 -6 / ℃, no cracking under thermal shock of 750℃.
[0051]
[0052] All five examples demonstrate that this technical solution successfully produces low-shrinkage lithium silicate thermal accumulators: the raw materials are 6-14 parts of lithium carbonate with a D50 particle size of 3-10 μm; 50-70 parts of silicon oxide with a D50 particle size of 5-30 μm; 8-25 parts of kaolin and calcined kaolin with a D50 particle size of 2-9 μm; and 9-17 parts of aluminum oxide with a D50 particle size of 3-10 μm, combined with binders and other additives. The sintering shrinkage of all samples is strictly ≤2% (measured sintering expansion is -0.70% to -2.00%), and the thermal expansion coefficient is stable at ≤1.3×10-1 at 30-1000°C. -6 / ℃(0.421-1.156×10 -6 / °C), and all passed the 750-800°C thermal shock test without cracking. The sintering temperature ranges from 1320-1400°C, with a holding time of 3-8 hours, and gradient cooling to ensure the formation of the main crystalline phase LiAlSi3O8.
[0053] The key rules are as follows: Increasing the content of lithium carbonate can significantly reduce the thermal expansion coefficient (0.421×10 -6 / ℃), but the silicon oxide ratio needs to be increased simultaneously (68%); low temperature sintering at 1320-1340℃ can still achieve ≤1.5% shrinkage (Examples 4-5). The thermal expansion coefficient of the whole system is <1.3×10 -6 / ℃ verified the correctness of the formula. Its core innovation lies in the raw material particle size control (D50≤30μm), element molar ratio optimization and gradient process coordination, breaking through the traditional spodumene system's >4% shrinkage bottleneck.
[0054] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.
Claims
1. A low shrinkage lithium silicate thermal storage body, characterized in that: The raw materials include, by weight, 6 to 14 parts of lithium carbonate with a D50 particle size of 3 to 10 μm; 50 to 70 parts of silicon oxide with a D50 particle size of 5 to 30 μm; 8 to 25 parts of kaolin and calcined kaolin with a D50 particle size of 2 to 9 μm; 9 to 17 parts of aluminum oxide with a D50 particle size of 3 to 10 μm; 4 to 7 parts of a binder; 0.5 to 2 parts of a surfactant; and 0.5 to 2 parts of a lubricant.
2. The low shrinkage lithium silicate thermal storage body according to claim 1, characterized in that: The sintering shrinkage of the heat storage body is ≤2%, and the thermal expansion coefficient at 30-1000℃ is ≤1.3×10 -6 / ℃, specific heat capacity at 1000℃ ≥2.2J / g / K, the main crystalline phase is LiAlSi3O8, containing residual α-Al2O3 and SiO2 phases.
3. The low shrinkage lithium silicate thermal storage body according to claim 1, characterized in that: The purity of lithium carbonate, silicon oxide and aluminum oxide is greater than or equal to 99%.
4. The low shrinkage lithium silicate thermal storage body according to claim 1, characterized in that: The amount of lithium carbonate is 7 to 10 parts.
5. The low shrinkage lithium silicate thermal storage body according to claim 1, characterized in that: The D50 particle size of silicon oxide is 10 to 17 μm.
6. The low shrinkage lithium silicate thermal storage body according to claim 1, characterized in that: The binder is HPMC or CMC, the surfactant is GPE3000 or potassium laurate, and the lubricant is sodium stearate, zinc stearate or glycerol.
7. A method for preparing a low-shrinkage lithium silicate thermal storage body according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Raw material mixing: lithium carbonate, silicon oxide, kaolin, aluminum oxide, binder, surfactant, and lubricant are mixed according to the formula, and water is added to form a uniform slurry; S2, green body forming: extruding the slurry into a honeycomb green body, and obtaining an initial green body after drying; S3, pre-calcination treatment: pre-calculate at 600-800°C for 2-4 hours to remove organic matter and decompose lithium carbonate; S4. Sintering: heating to 1320-1400°C at 1-5°C / min and keeping at this temperature for 3-8h to form the main crystal phase of LiAlSi3O8; S5. Gradient cooling: cooling from the sintering completion temperature to 1200°C at a rate of 5-10°C / min; 1200°C to room temperature: cooling at a rate of 10-20°C / min to obtain the final product.
8. The method for preparing a low-shrinkage lithium silicate thermal storage body according to claim 7, characterized in that: In step S5, the gradient cooling rate from the sintering temperature to 1200°C is controlled at 7-9°C / min to form a uniformly distributed microcrack network.