Molecular ceramic and method for preparing the same

Abstract

The application provides a kind of molecular ceramic and its preparation method.The preparation method comprises: at least using the secondary high pressure method to make the mixed reaction system containing polysiloxane, nano aluminum material and activation factor to react, to obtain precursor wet gel;After drying the precursor wet gel, low temperature calcination is carried out, the temperature of the low temperature calcination is 500-700 DEG C, to obtain molecular ceramic;Wherein, the activation factor includes one or more combinations of MgO, FeO, LiF, AIF3, TiO2, Fe2O3, BeO.The application adds activation factor in the synthesis process and cooperates secondary high pressure method, successfully reduces the calcination temperature of synthesizing mullite molecular ceramic, solves the high energy consumption problem existing in the high temperature calcination method in the prior art.The molecular ceramic provided by the application has excellent high temperature resistance, chemical stability, wear resistance and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation materials technology, specifically relating to a molecular ceramic and its preparation method. Background Technology

[0002] Mullite ceramics are widely used in refractory and thermal insulation materials and ceramic products due to their high hardness, high melting point, and low coefficient of thermal expansion. However, traditional methods for preparing mullite ceramics typically require extremely high-temperature treatment, leading to high energy consumption. For example, existing technology CN115974539B describes a method for preparing bulk high-temperature resistant mullite ceramic aerogel materials, which uses a sol-gel method combined with supercritical drying and heat treatment processes. This method utilizes inexpensive raw materials and a simple preparation process to produce bulk high-temperature resistant mullite ceramic aerogels, increasing the aerogel's temperature resistance in air to 1300℃, showing significant application potential in energy conservation, chemical engineering, and aerospace. However, this method still requires heat treatment at high temperatures of 1300–1500℃. Therefore, how to synthesize mullite molecular ceramics at lower temperatures is one of the urgent problems to be solved. Summary of the Invention

[0003] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0004] One objective of this invention is to provide a method for preparing molecular ceramics, comprising:

[0005] At least a sub-high pressure method is used to react a mixed reaction system containing polysiloxane, nano-aluminum materials and activating factors to obtain a precursor wet gel;

[0006] The precursor wet gel was dried and then calcined at a low temperature of 500-700°C to obtain molecular ceramics.

[0007] The activating factor includes one or more of MgO, FeO, LiF, AIF3, TiO2, Fe2O3, and BeO.

[0008] The molecular ceramics described in this invention refer to ceramic materials that are directly synthesized from monomers and possess abundant Al-O-Si bond structures and typical Mullai phase crystallization peaks without requiring high-temperature treatment above 700℃. These molecular ceramics exhibit excellent high-temperature stability, showing no crystal transformation even after treatment above 1300℃, and also demonstrate good chemical stability.

[0009] In some embodiments, the content of the activating factor in the mixed reaction system is 0.1-5 wt%. If the content of the activating factor is too low, the reaction rate will be too slow, the temperature reduction effect will be insignificant, and the product performance will be unstable; if the content of the activating factor is too high, it will lead to an excessively fast reaction rate, increased energy consumption, and increased impurity content.

[0010] In some embodiments, the pressure of the sub-high pressure method is 2 to 20 MPa. If the pressure is too low, the reaction may become slow or even fail to proceed effectively, and may also affect the crystal structure and properties of the product, preventing it from achieving the expected results; if the pressure is too high, the reaction will be too violent, the product structure will be unstable, and side reactions will easily occur. In addition, it may place an extra burden on the reaction equipment and increase the risk of equipment damage.

[0011] In some embodiments, the reaction temperature of the sub-high pressure method is room temperature to 150°C.

[0012] In some embodiments, the pH of the sub-high pressure method is 1 to 5.

[0013] In some embodiments, the reaction time of the sub-high pressure method is 1 hour to 30 days.

[0014] In some embodiments, the low-temperature calcination time is 1 to 10 hours.

[0015] In some embodiments, the polysiloxane has alkoxy bonds at its chain ends, including methoxy or ethoxy bonds.

[0016] In some embodiments, the number-average molecular weight of the polysiloxane is 100 to 1000.

[0017] In some embodiments, the monomers forming the polysiloxane include, but are not limited to, one or more of methyl orthosilicate, tetraethyl orthosilicate, or alkoxysilanes. The alkoxysilanes mentioned include, but are not limited to, methoxysilanes and ethoxysilanes.

[0018] In some embodiments, the nano-aluminum material includes one or a combination of nano-aluminum particles, aluminum salts, and organoaluminum.

[0019] In some embodiments, the aluminum salt includes one or a combination of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum silicate, and aluminum sulfide.

[0020] In some embodiments, the organoaluminum comprises one or more of aluminum formate, aluminum oxalate, aluminum propionate, triethylaluminum, and triisobutylaluminum.

[0021] In some embodiments, the drying temperature is 50–150°C, and the drying time is 5–24 hours.

[0022] In some embodiments, the preparation method specifically includes:

[0023] A first mixture containing a silicon source, an acid, and a first solvent is provided, and the first mixture is heated at a temperature of room temperature to 200°C to obtain a molecular-level polysiloxane solution.

[0024] A second mixture containing nano-aluminum material and a second solvent is provided, and the second mixture is heated at a temperature of room temperature to 100°C to obtain a nano-sized aluminum solution;

[0025] The polysiloxane solution, aluminum solution, and activating factor are uniformly mixed to obtain the mixed reaction system.

[0026] In some embodiments, the acid includes one or more of hydrochloric acid, acetic acid, and formic acid, but is not limited thereto. The acid added to the first mixture can promote the transformation and curing process of the silica sol. The acid can react with the hydroxyl groups (-OH) in the silica sol to form silicon-oxygen bonds (Si-O-Si); and also plays a role in adjusting the pH.

[0027] In some embodiments, the first solvent and the second solvent include one or more of water, ethanol, methanol, acetone, isopropanol, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, n-hexane, and n-heptane, but are not limited thereto. The first solvent and the second solvent may be the same or different.

[0028] In some embodiments, the mass fraction of the silicon source in the polysiloxane solution is 1% to 50%.

[0029] In some embodiments, the mass fraction of nano-aluminum material in the aluminum solution is 10% to 40%.

[0030] In some embodiments, the volume ratio of the polysiloxane solution to the aluminum solution is 1:2 to 1:10.

[0031] The second objective of this invention is to provide molecular ceramics obtained by the preparation method described in any of the above technical solutions.

[0032] In some embodiments, the chemical structure of the molecular ceramic is dominated by Al-O-Si bonds and has a mullite phase.

[0033] In some embodiments, the density of the molecular ceramic is 0.1–2.5 g / cm³. 3 Its thermal conductivity is 0.05~2W / mK.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] (1) In the synthesis process of this invention, an activating factor is added and combined with a sub-high pressure synthesis method to successfully reduce the calcination temperature of the synthesized molecular ceramics. Specifically, the activating factor described in this invention can form a low eutectic mixture with the precursor solution containing polysiloxane and aluminum materials. In addition, this invention improves the reactivity and reaction rate of the mixed reaction system by adjusting the reaction pressure and temperature of the sub-high pressure method, and promotes full contact and reaction between polysiloxane, aluminum materials and activating factor. The use of activating factor combined with the sub-high pressure method reduces the formation temperature of mullite, and solves the problems of high energy consumption and high preparation cost of the high-temperature calcination method of mullite in the prior art.

[0036] (2) The synthesis method provided by the present invention is simple and efficient, and has broad application prospects and commercial value;

[0037] (3) The molecular ceramic provided by the present invention has a rich Al-O-Si bond structure without high temperature sintering above 700℃; it exhibits typical mullie phase crystallization peaks; and it has excellent high temperature stability, no crystal transformation occurs when treated at high temperature above 1300℃, and also has excellent chemical stability, wear resistance and corrosion resistance. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the process for synthesizing molecular ceramics in one embodiment of the present invention;

[0040] Figure 2 This is an XRD pattern of a molecular ceramic obtained according to an embodiment of the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0042] Unless otherwise specified, all raw materials and reagents used in this invention are commercially available.

[0043] Example 1

[0044] This embodiment provides a molecular ceramic and its low-temperature synthesis method. Figure 1 The synthesis process is illustrated below:

[0045] Methyl orthosilicate was used as the silicon source and dispersed in a mixed solvent to form a mixture with a mass fraction of 25%. The mixed solvent was formed by anhydrous ethanol and water with a volume ratio of 7:1. Hydrochloric acid with a content of 0.01 mol / L was added, and the mixture was heated under reflux at 130°C for 8 hours to obtain a molecular-level polysiloxane solution.

[0046] Nano-aluminum particles were dispersed in a mixed solvent to form a mixture, which was formed by anhydrous ethanol and water in a volume ratio of 1:2. The mixture was heated in a water bath at 50°C for 8 hours to obtain an aluminum solution with a mass fraction of 30%.

[0047] The above-mentioned polysiloxane solution and aluminum solution were mixed at a volume ratio of 1:5, and 0.6 wt% MgO activator was added to obtain a mixed reaction system with a pH of 3. This mixed reaction system was subjected to a sub-high-pressure reaction at room temperature and a pressure of 2 MPa for 1 hour to obtain a precursor wet gel. The precursor wet gel was dried at 50°C to form a precursor dry gel. The precursor dry gel was then ground and sintered at 500°C for 1 hour to obtain a mullite molecular ceramic with Al-O-Si bonds as the main structure. Figure 2 The image shows the XRD pattern of this mullite molecular ceramic.

[0048] Example 2

[0049] Tetraethyl orthosilicate was used as the silicon source and dispersed in a mixed solvent to form a 1% mass fraction mixture. The mixed solvent was formed by anhydrous ethanol and water in a volume ratio of 8:1. Acetic acid with a content of 0.01 mol / L was added, and the mixture was heated under reflux at 130°C for 8 hours to obtain a molecular-level polysiloxane solution.

[0050] Aluminum chloride was dispersed in a mixed solvent to form a mixture, which was formed by anhydrous ethanol and water in a volume ratio of 3:5. The mixture was heated in a water bath at 50°C for 8 hours to obtain an aluminum solution with a mass fraction of 10%.

[0051] The above-mentioned polysiloxane solution and aluminum solution were mixed at a volume ratio of 1:2, and 0.8 wt% of activating factor FeO was added to obtain a mixed reaction system with a pH of 3. The mixed reaction system was subjected to a sub-high pressure reaction at room temperature and a pressure of 10 MPa for 10 days to obtain a precursor wet gel. The precursor wet gel was dried at 100℃ to form a precursor dry gel. The precursor dry gel was ground and sintered at 600℃ for 5 hours to obtain a mullite molecular ceramic with Al-O-Si bonds as the main body.

[0052] Example 3

[0053] Alkoxysilane was used as a silicon source and dispersed in a mixed solvent to form a mixture with a mass fraction of 50%. The mixed solvent was formed by anhydrous ethanol and water with a volume ratio of 9:1. Formic acid with a content of 0.01 mol / L was added. The mixture was heated under reflux at 130°C for 8 hours to obtain a molecular-level polysiloxane solution.

[0054] Triethylaluminum was dispersed in a mixed solvent to form a mixture, which was formed by anhydrous ethanol and water in a volume ratio of 7:10. The mixture was heated in a water bath at 50°C for 8 hours to obtain an aluminum solution with a mass fraction of 40%.

[0055] The above-mentioned polysiloxane solution and aluminum solution were mixed at a volume ratio of 1:10, and 1 wt% of activating factor LiF was added to obtain a mixed reaction system with a pH of 3. The mixed reaction system was subjected to a sub-high pressure reaction at room temperature and a pressure of 20 MPa for 30 days to obtain a precursor wet gel. The precursor wet gel was dried at 150°C to form a precursor dry gel. The precursor dry gel was ground and sintered at 700°C for 10 hours to obtain a mullite molecular ceramic with Al-O-Si bonds as the main body.

[0056] Example 4

[0057] The only difference between Example 4 and Example 1 is that Example 4 uses 0.1 wt% AIF3 as the activating factor, while the rest is the same as Example 1.

[0058] Example 5

[0059] The only difference between Example 5 and Example 1 is that the activating factor used in Example 5 is 5 wt% TiO2, and the rest is the same as in Example 1.

[0060] Example 6

[0061] The only difference between Example 6 and Example 1 is that the activating factor used in Example 6 is Fe2O3, and the rest is the same as in Example 1.

[0062] Example 7

[0063] The only difference between Example 7 and Example 1 is that the activating factor used in Example 7 is BeO, and the rest is the same as in Example 1.

[0064] Example 8

[0065] The only difference between Example 8 and Example 1 is that the content of the activating factor added in Example 8 is 0.01 wt%, and the rest is the same as in Example 1.

[0066] Example 9

[0067] The only difference between Example 9 and Example 1 is that the content of the activating factor added in Example 9 is 10wt, and the rest is the same as in Example 1.

[0068] Comparative Example 1

[0069] The only difference between Comparative Example 1 and Example 1 is that the mixed reaction system of Comparative Example 1 does not contain the activating factor MgO.

[0070] Comparative Example 2

[0071] The only difference between Comparative Example 2 and Example 1 is that the mixed reaction system of Comparative Example 2 is carried out under normal pressure, while the rest is the same as Example 1.

[0072] Comparative Example 3

[0073] The only difference between Comparative Example 3 and Example 1 is that the calcination temperature is 1000°C, and the rest of the procedures are the same as those in Example 1.

[0074] Table 1. Relevant properties of mullite molecular ceramics in the examples and comparative examples.

[0075]

[0076] In summary, this invention utilizes an activating factor combined with a sub-high pressure synthesis method to synthesize mullite molecular ceramics at relatively low calcination temperatures. This invention introduces a novel concept of molecular ceramics, overcoming the bottleneck of low-temperature mullite ceramization. The prepared molecular ceramics possess a mullite phase, excellent high-temperature resistance, chemical stability, and superior wear resistance and corrosion resistance. This preparation method lowers the sintering temperature of mullite ceramics, significantly reducing preparation costs and energy consumption.

[0077] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0078] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0079] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for preparing molecular ceramics, characterized in that, include: At least a sub-high pressure method is used to react a mixed reaction system containing polysiloxane, nano-aluminum materials and activating factors to obtain a precursor wet gel; The reaction conditions for the sub-high pressure method include: a reaction temperature of room temperature to 150°C, a pH value of 1 to 5 in the reaction system, a pressure of 2 to 20 MPa, and a reaction time of 1 hour to 30 days. The precursor wet gel was dried and then calcined at a low temperature of 500~700℃ to obtain a molecular ceramic with an Al-O-Si bond structure and a mullie phase crystallization peak. The activating factor includes one or more of MgO, FeO, LiF, AIF3, TiO2, Fe2O3, and BeO.

2. The method for preparing molecular ceramics according to claim 1, characterized in that: In the mixed reaction system, the content of the activating factor is 0.1~5wt%.

3. The method for preparing molecular ceramics according to claim 1, characterized in that, The low-temperature calcination time is 1~10h.

4. The method for preparing molecular ceramics according to claim 1, characterized in that: The polysiloxane has alkoxy bonds at its chain ends, including methoxy or ethoxy bonds.

5. The method for preparing molecular ceramics according to claim 1, characterized in that: The number average molecular weight of the polysiloxane is 100~1000.

6. The method for preparing molecular ceramics according to claim 1, characterized in that: The nano-aluminum material includes one or more of the following: nano-aluminum particles, aluminum salts, and organoaluminum.

7. The method for preparing molecular ceramics according to claim 4 or 5, characterized in that: The monomers forming the polysiloxane include one or more of methyl orthosilicate, tetraethyl orthosilicate, or alkoxysilane.

8. The method for preparing molecular ceramics according to claim 6, characterized in that: The aluminum salt includes one or a combination of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum silicate, and aluminum sulfide.

9. The method for preparing molecular ceramics according to claim 6, characterized in that: The organoaluminum compounds include one or more of aluminum formate, aluminum oxalate, aluminum propionate, triethylaluminum, and triisobutylaluminum.

10. The method for preparing molecular ceramics according to claim 1, characterized in that: The drying temperature is 50~150℃, and the drying time is 5~24h.

11. The method for preparing molecular ceramics according to claim 1, characterized in that, Specifically, it includes: A first mixture containing a silicon source, an acid, and a first solvent is provided, and the first mixture is heated at a temperature of room temperature to 200°C to obtain a polysiloxane solution; A second mixture containing nano-aluminum material and a second solvent is provided, and the second mixture is heated at a temperature of room temperature to 100°C to obtain an aluminum solution. The polysiloxane solution, aluminum solution, and activating factor are uniformly mixed to obtain the mixed reaction system.

12. The method for preparing molecular ceramics according to claim 11, characterized in that: The first solvent and the second solvent include one or a combination of multiple of the following: water, ethanol, methanol, acetone, isopropanol, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, n-hexane, and n-heptane.

13. The method for preparing molecular ceramics according to claim 11, characterized in that: The polysiloxane solution contains 1% to 50% silicon source by mass, the aluminum solution contains 10% to 40% nano-aluminum material by mass, and the volume ratio of the polysiloxane solution to the aluminum solution is 1:2 to 1:

10.

14. Molecular ceramics obtained by the preparation method of molecular ceramics according to any one of claims 1 to 13.

15. The molecular ceramic according to claim 14, characterized in that: The density of the molecular ceramic is 0.1~2.5 g / cm³. 3 Its thermal conductivity is 0.05~2 W / m·K.

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