A foamed ceramic that can be used at 1000 degrees celsius and a method of making the same

Abstract

The application relates to a foamed ceramic capable of serving at 1000 DEG C and a preparation method thereof, and belongs to the technical field of foamed ceramics. The preparation method of the foamed ceramic capable of serving at 1000 DEG C comprises the following steps: (1) mixing barium titanate, manganese oxide, iron oxide and fluorite to obtain a mixture; (2) ball milling the mixture into mixed powder I; (3) ball milling solid waste raw materials into mixed powder II; (4) mixing silicon nitride with the mixed powder I, the mixed powder II and water, stirring uniformly to prepare mixed powder III; (5) pressing the mixed powder III into a green body; and (6) sintering the green body to obtain the foamed ceramic. The physical and mechanical properties of the foamed ceramic prepared by the application are almost consistent with the initial state at room temperature after serving at 1000 DEG C for 100 hours, which indicates that the foamed ceramic has the characteristics of high high-temperature strength and stable comprehensive performance, and meets the application requirements of long-time service at 1000 DEG C.

Description

Technical Field

[0001] This invention relates to a foamed ceramic that can operate at 1000℃ and its preparation method, belonging to the field of foamed ceramic technology. Background Technology

[0002] Foamed ceramics are a functional material containing numerous pores, possessing many advantages such as lightweight, heat insulation, waterproofing, and fire resistance. They are widely used in many fields, especially in the construction industry. Using foamed ceramics as exterior wall insulation panels and interior partition panels aligns with the high-quality development needs of the construction industry, offering a broad market and considerable economic benefits. Furthermore, the production of foamed ceramics helps in the disposal of large quantities of solid waste tailings, providing significant environmental, ecological, and social benefits.

[0003] Currently, most foamed ceramics on the market use silicon carbide as a foaming agent and are fired in roller kilns at 1160–1220℃. Typically, the porous structure of foamed ceramics remains largely unchanged when the temperature is 300℃ below its preparation temperature, and its strength can be maintained at over 80% of its room temperature strength. Therefore, the maximum operating temperature of commercially available foamed ceramics is generally 860–920℃, which meets the requirements of most civilian applications.

[0004] With the widespread use of foamed ceramics in defense, military, and aerospace fields, these ceramics must withstand various harsh environments, especially when facing the application requirements of "high-temperature, long-term service," where they need to maintain high strength and a stable pore structure at 1000℃. Due to limitations in manufacturing temperature, commercially available foamed ceramics cannot be used at 1000℃, let alone serve at 1000℃ for extended periods. Summary of the Invention

[0005] The purpose of this invention is to provide a foamed ceramic that can operate at 1000°C and its preparation method to solve the technical problems existing in the prior art as described above.

[0006] The technical solution provided by this invention is as follows:

[0007] One objective of this invention is to provide a method for preparing foamed ceramics that can operate at 1000°C, comprising the following steps:

[0008] (1) Barium titanate, manganese oxide, iron oxide and fluorite are mixed in a weight ratio of 1.0:(0~0.8):(0~0.7):(0.3~0.6) to obtain a mixture;

[0009] (2) The mixture obtained in step (1) is ball-milled into mixed powder I;

[0010] (3) The solid waste raw materials are ball-milled into mixed powder II;

[0011] (4) Mix silicon nitride with mixed powder I, mixed powder II and water in a weight ratio of (0.8~1.5):(3.2~6.0):100:(7.3~9.1) and stir evenly to prepare mixed powder III;

[0012] (5) Press the mixed powder III into a blank;

[0013] (6) The green body obtained in step (5) is sintered to obtain the foamed ceramic.

[0014] The effects of adopting the above technical solution are as follows: silicon nitride acts as a foaming agent, generating gas through oxidation under high temperature conditions and forming pores in the molten ceramic matrix; manganese oxide and iron oxide act as oxygen-promoting agents, which can accelerate the oxidation of silicon nitride, shorten the firing time of foamed ceramics, and adjust the pore size; fluorite acts as a viscosity modifier, which is added to improve the high-temperature viscosity of the molten matrix, thereby adjusting the pore size of the foamed ceramics; barium titanate acts as a foam stabilizer, which can improve the roundness of the pores, thereby improving the uniformity of the pore structure and thus improving the compressive strength of the foamed ceramics.

[0015] Based on the above technical solution, the present invention can be further improved as follows:

[0016] Furthermore, the average particle size of the mixed powder I is 1-3 μm, the average particle size of the mixed powder II is 2-5 μm, and the particle size of the silicon nitride is 10-40 μm.

[0017] Furthermore, in step (3), the solid waste raw materials include one or more of the following: sea sand, river silt, metallurgical solid waste, mining solid waste, fuel ash, stone sawdust, and ceramic tile waste.

[0018] Further, in step (3), the total weight percentage of silicon oxide, aluminum oxide, sodium oxide and potassium oxide in the solid waste raw material is ≥92%, of which the weight percentage of silicon oxide is ≥66%, the weight percentage of aluminum oxide is ≥17%, the weight percentage of sodium oxide is ≥4%, and the weight percentage of potassium oxide is ≥5%.

[0019] Furthermore, the solid waste raw materials also include sodium feldspar and / or potassium feldspar.

[0020] Further, in step (5), the mixed powder III is pressed into a blank under a pressure of 0.6 to 0.9 MPa.

[0021] Furthermore, in step (6), the sintering temperature of the blank is 1320-1350℃ and the sintering time is 12-18min.

[0022] The second objective of this invention is to provide a foamed ceramic that can operate at 1000°C, which is made by the above-mentioned method for preparing a foamed ceramic that can operate at 1000°C.

[0023] The technical solution provided by this invention has the following advantages compared with the prior art:

[0024] (1) The preparation principle of the foamed ceramic of the present invention is as follows: at high temperature, the original solid green body becomes a molten state with a suitable viscosity. At the same time, the gas generated by the foaming agent gathers and grows in the molten matrix. After the ceramic matrix cools down and solidifies, it has a porous foam structure. The key to solving the problem of "low service temperature of foamed ceramic" is to "increase the sintering temperature of foamed ceramic". This requires increasing the melting temperature of the green body and using a foaming agent that can generate gas at a higher temperature. In the present invention, silicon nitride is used as the foaming agent. Silicon nitride has a higher oxidation temperature and a moderate oxidation rate in a wider high temperature range. Therefore, using silicon nitride as the foaming agent and using a green body with a higher melting temperature is the key to the successful preparation of the foamed ceramic of the present invention.

[0025] (2) In the preparation method of the foamed ceramic of the present invention, the proportion and particle size of silicon nitride have a significant impact on the overall performance of the foamed ceramic. Specifically, increasing the proportion of silicon nitride will simultaneously increase the foaming volume and pore size of the foamed ceramic, thereby reducing the density and compressive strength of the foamed ceramic; while increasing the particle size of silicon nitride will reduce the pore size of the foamed ceramic, which helps to improve the uniformity of the pore structure and the compressive strength of the foamed ceramic. Therefore, in preparing the foamed ceramic of the present invention, in order to improve the comprehensive performance of the foamed ceramic, the proportion and particle size of silicon nitride should be adjusted synergistically. For example, in order to reduce the density of the foamed ceramic, the proportion of silicon nitride must be increased, but at the same time, the particle size of silicon nitride should be increased to partially offset the decrease in the compressive strength of the foamed ceramic caused by the increase in the proportion of silicon nitride.

[0026] (3) In this invention, the solid waste raw material is prepared from solid waste tailings and accounts for a high proportion, which can dispose of a large amount of solid waste tailings and has good environmental, ecological and social benefits; the other raw materials are prepared from cheap and readily available commercial raw materials in proportion, and the preparation process is simple and has the advantage of low preparation cost.

[0027] (4) Compared with commercially available foamed ceramic products, the foamed ceramic prepared by this invention has the significant advantage of high operating temperature and excellent overall performance. By adjusting the raw material ratio, the foamed ceramic can have different densities and compressive strengths, thereby meeting the application needs of different fields.

[0028] (5) The density of the foamed ceramic prepared by this invention is 457-543 kg / m³. 3The compressive strength is 7.3–8.3 MPa, and the volume water absorption rate is 1.4%–1.8%. After being kept at 1000℃ for 100 hours, its compressive strength was measured to be 6.3–7.1 MPa, which is only 13.7%–15.8% lower than the initial compressive strength, and the decrease is stable. When cooled to room temperature, its density, compressive strength, pore size, and water absorption rate are almost the same as the initial state. This indicates that the foamed ceramic prepared by this invention has the characteristics of high high-temperature strength and stable comprehensive performance, which meets the application requirements of long-term service at 1000℃. Attached Figure Description

[0029] Figure 1 This is a flowchart of the preparation method of the foamed ceramic that can be used at 1000°C according to the present invention. Detailed Implementation

[0030] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0031] The flowchart of the preparation method of the foamed ceramic of the present invention, which can be used at 1000°C, is shown below. Figure 1 As shown.

[0032] Example 1

[0033] A method for preparing foamed ceramics that can operate at 1000℃, comprising the following steps:

[0034] (1) Mix barium titanate, manganese oxide, iron oxide and fluorite in a weight ratio of 1.0:0.8:0:0.3;

[0035] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 3 μm;

[0036] (3) The solid waste raw material with a total weight ratio of 94.8% of silicon oxide, aluminum oxide, sodium oxide and potassium oxide, of which silicon oxide accounts for 67.1% of the weight, aluminum oxide accounts for 17.3% of the weight, sodium oxide accounts for 5.3% of the weight and potassium oxide accounts for 5.1% of the weight, is ball-milled into mixed powder II with an average particle size of 5μm.

[0037] (4) Mix silicon nitride with a particle size of 10 μm with mixed powder I, mixed powder II and water in a weight ratio of 0.8:3.2:100:7.3 and stir evenly to prepare mixed powder III;

[0038] (5) The mixed powder III is pressed into a blank under a pressure of 0.9 MPa;

[0039] (6) The green body obtained in step (5) is fired at 1320°C for 18 minutes to obtain the foamed ceramic.

[0040] Example 2

[0041] A method for preparing foamed ceramics that can operate at 1000℃, comprising the following steps:

[0042] (1) Mix barium titanate, manganese oxide, iron oxide and fluorite in a weight ratio of 1.0:0.5:0.2:0.4;

[0043] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 2 μm;

[0044] (3) The solid waste raw material with a total weight ratio of 96.4% of silicon oxide, aluminum oxide, sodium oxide and potassium oxide, of which silicon oxide accounts for 67.6% of the weight, aluminum oxide accounts for 17.5% of the weight, sodium oxide accounts for 5.7% of the weight and potassium oxide accounts for 5.6% of the weight, is ball-milled into mixed powder II with an average particle size of 4μm.

[0045] (4) Mix silicon nitride with a particle size of 20 μm with mixed powder I, mixed powder II and water in a weight ratio of 1.0:4.0:100:7.9 and stir evenly to prepare mixed powder III;

[0046] (5) The mixed powder III is pressed into a blank under a pressure of 0.8 MPa;

[0047] (6) The green body obtained in step (5) is fired at 1330°C for 16 minutes to obtain the foamed ceramic.

[0048] Example 3

[0049] A method for preparing foamed ceramics that can operate at 1000℃, comprising the following steps:

[0050] (1) Mix barium titanate, manganese oxide, iron oxide and fluorite in a weight ratio of 1.0:0.3:0.4:0.5;

[0051] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 1 μm;

[0052] (3) The solid waste raw material with a total weight ratio of 93.9% of silicon oxide, aluminum oxide, sodium oxide and potassium oxide, of which silicon oxide accounts for 66.4% of the weight, aluminum oxide accounts for 17.3% of the weight, sodium oxide accounts for 5.1% of the weight, and potassium oxide accounts for 5.1% of the weight, is ball-milled into mixed powder II with an average particle size of 3μm.

[0053] (4) Mix silicon nitride with a particle size of 30 μm with mixed powder I, mixed powder II and water in a weight ratio of 1.2:5.1:100:8.5 and stir evenly to prepare mixed powder III;

[0054] (5) The mixed powder III is pressed into a blank under a pressure of 0.7 MPa;

[0055] (6) The green body obtained in step (5) is fired at 1340°C for 14 minutes to obtain the foamed ceramic.

[0056] Example 4

[0057] A method for preparing foamed ceramics that can operate at 1000℃, comprising the following steps:

[0058] (1) Mix barium titanate, manganese oxide, iron oxide and fluorite in a weight ratio of 1.0:0:0.7:0.6;

[0059] (2) The mixture obtained in step (1) is ball-milled into mixed powder I with an average particle size of 2 μm;

[0060] (3) The solid waste raw material with a total weight ratio of 95.3% of silicon oxide, aluminum oxide, sodium oxide and potassium oxide, of which silicon oxide accounts for 66.7%, aluminum oxide accounts for 17.8%, sodium oxide accounts for 5.5% and potassium oxide accounts for 5.3% is ball-milled into mixed powder II with an average particle size of 2μm.

[0061] (4) Mix silicon nitride with a particle size of 40 μm with mixed powder I, mixed powder II and water in a weight ratio of 1.5:6.0:100:9.1 and stir evenly to prepare mixed powder III;

[0062] (5) The mixed powder III is pressed into a blank under a pressure of 0.6 MPa;

[0063] (6) The green body obtained in step (5) is fired at 1350°C for 12 minutes to obtain the foamed ceramic.

[0064] The density, compressive strength, and water absorption of the foam ceramics prepared in Examples 1-4 were tested.

[0065] The test method was carried out in accordance with the national standard "Test Methods for Inorganic Rigid Thermal Insulation Products, GB / T5486-2008".

[0066] The compressive strength was tested using a thermal simulation testing machine (model Gleeble-3500) from Dynamic Systems Inc. (DSI), USA; the average pore size was obtained by photographing the samples and then analyzing the photos using ImageJ software.

[0067] The test results are shown in Table 1:

[0068] Table 1. Test results of the physical and mechanical properties of the foam ceramics prepared in Examples 1-4

[0069]

[0070]

[0071] As can be seen from Table 1, the density of the foamed ceramics prepared in Examples 1-4 is 457-543 kg / m³. 3 The compressive strength was 7.3–8.3 MPa, and the volumetric water absorption rate was 1.4%–1.8%. After being maintained at 1000℃ for 100 hours, the compressive strength was measured to be 6.3–7.1 MPa, only 13.7%–15.8% lower than the initial compressive strength, and the decrease was stable. Excluding the influence of testing errors, the foamed ceramics prepared in Examples 1-4, after being serviced at 1000℃ for 100 hours, showed consistent density, compressive strength, pore size, and water absorption rate at room temperature, indicating that the foamed ceramics prepared in this invention possess high high-temperature strength and stable comprehensive performance, meeting the application requirements for long-term service at 1000℃.

[0072] In addition, from Example 1 to Example 4, while increasing the proportion of silicon nitride, the particle size of silicon nitride was also increased. Although the density of the prepared foam ceramic decreased significantly in turn, the pore size and water absorption rate remained basically unchanged, maintaining the integrity of the pore structure. Therefore, the decrease in compressive strength was not significant.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing foamed ceramics capable of operating at 1000℃, characterized in that, Includes the following steps: (1) Barium titanate, manganese oxide, iron oxide and fluorite are mixed in a weight ratio of 1.0:(0.3~0.8):(0.2~0.7):(0.3~0.6) to obtain a mixture; (2) The mixture obtained in step (1) is ball-milled into mixed powder I, wherein the average particle size of mixed powder I is 1~3μm; (3) The solid waste raw material is ball-milled into mixed powder II, wherein the average particle size of mixed powder II is 2~5μm; wherein the total weight percentage of silicon oxide, aluminum oxide, sodium oxide and potassium oxide in the solid waste raw material is ≥92%, wherein the weight percentage of silicon oxide is ≥66%, the weight percentage of aluminum oxide is ≥17%, the weight percentage of sodium oxide is ≥4%, and the weight percentage of potassium oxide is ≥5%; (4) Mix silicon nitride with mixed powder I, mixed powder II and water in a weight ratio of (0.8~1.5):(3.2~6.0):100:(7.3~9.1) and stir evenly to prepare mixed powder III; the particle size of the silicon nitride is 10~40μm; (5) Press the mixed powder III into a blank; (6) The green body obtained in step (5) is sintered at a temperature of 1320~1350℃ for 12~18min to obtain foamed ceramic.

2. The method for preparing foamed ceramics capable of operating at 1000℃ according to claim 1, characterized in that, In step (3), the solid waste raw materials include one or more of the following: sea sand, river silt, metallurgical solid waste, mining solid waste, fuel ash, stone sawdust, and ceramic tile waste.

3. The method for preparing foamed ceramics capable of operating at 1000℃ according to claim 2, characterized in that, The solid waste raw materials also include sodium feldspar and / or potassium feldspar.

4. The method for preparing foamed ceramics capable of operating at 1000℃ according to claim 1, characterized in that, In step (5), the mixed powder III is pressed into a blank under a pressure of 0.6~0.9MPa.

5. A foamed ceramic that can operate at 1000℃, characterized in that, It is made by the method for preparing foamed ceramics that can operate at 1000°C as described in any one of claims 1-4.

Images