A method for preparing high temperature resistant zirconium silicate nanofiber

Abstract

The present invention relates to the technical field of zirconium silicate nanofiber preparation, and provides a method for preparing high temperature resistant zirconium silicate nanofiber, comprising the following steps: epoxy polysiloxane, methacrylic acid and triethylamine are mixed to prepare a silicon source solution; zirconium oxychloride octahydrate, acetic acid, ethylene glycol methacrylate acetoacetate and ethanol are mixed to prepare a zirconium source solution; the silicon source solution and the zirconium source solution are mixed, and a photoinitiator TPO-L is added, and ultraviolet cross-linking is performed to generate a zirconium silicate spinning solution; the zirconium silicate spinning solution is prepared into a zirconium silicate precursor fiber by an electrostatic spinning process, and after high temperature calcination, a zirconium silicate nanofiber is finally formed. The present invention successfully prepares a zirconium silicate precursor fiber in which Si atoms and Zr atoms are not directly connected and do not contain a spinning aid, thereby obtaining a zirconium silicate nanofiber with excellent temperature resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of zirconium silicate nanofiber preparation, and in particular relates to a method for preparing high-temperature resistant zirconium silicate nanofiber. Background Art

[0002] Zirconium silicate (ZrSiO4) is generally produced by solid-phase reaction of silicon oxide and zirconium oxide at high temperature. It has a high melting point (~2550℃), a high refractive index (1.78~2.01) and excellent chemical stability. These characteristics enable zirconium silicate to maintain stable performance in harsh environments such as high temperature and chemical corrosion. Zirconium silicate fiber has both the excellent performance of zirconium silicate and the high aspect ratio of the fiber itself. It is an excellent high-temperature thermal insulation material, high-temperature structural material and high-temperature catalyst carrier material. At present, the common preparation methods of zirconium silicate are sol-gel method, melting method, chemical vapor deposition method and electrospinning method. Among them, the electrospinning process has unique advantages in the preparation of nano-scale ceramic fibers and has been the focus of research in recent years.

[0003] The basic principle of preparing fibers by electrospinning is to use the electrostatic force generated by a high-voltage electrostatic field to make the spinning solution overcome the surface tension under the action of the electric field force to form a jet; the solvent of the jet evaporates or solidifies during the flight, and finally forms fibers on the receiving device. For the preparation of ceramic fibers, polymer fibers containing ceramic precursors are usually prepared first, and then the polymer is removed by high-temperature calcination to convert the ceramic precursor into a ceramic phase, thereby obtaining ceramic fibers. However, there are still the following difficulties in preparing zirconium silicate fibers by electrospinning. First, the sintering temperature of zirconium silicate ceramics is relatively high. Therefore, in order to promote the sintering and densification of zirconium silicate, the raw materials used are generally inorganic or organic silicon sources and zirconium sources in the form of ions, and the silicon source and the zirconium source are complexed together through various chemical reactions, such as hydrolysis-condensation, addition reaction, etc., to form a zirconium silicate precursor with Si-O-Zr as the main chain. This precursor has a high sintering activity and can form zirconium silicate at a relatively low temperature. However, it is precisely because of the low barrier to the formation of zirconium silicate that the zirconium silicate crystals formed at low temperatures will rapidly crystallize and grow at high temperatures. When the grain size is close to or larger than the fiber diameter, the entire zirconium silicate fiber will be pulverized. In addition, in order to increase the spinning properties of the zirconium silicate precursor, some polymer spinning aids, such as PVA, PVB, PVP, etc., are often added to the spinning solution. These spinning aids will pyrolyze into gas during high-temperature sintering, leaving holes inside the fiber. These holes also provide growth space for the growth of zirconium silicate crystals, which is not conducive to its temperature resistance. In summary, the temperature resistance of zirconium silicate prepared by electrospinning technology still needs to be improved. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing high-temperature resistant zirconium silicate nanofibers. Epoxy polysiloxane modified with methacrylic acid is used as a silicon source, and zirconium oxychloride modified with ethylene glycol methacrylate is used as a zirconium source. Under the auxiliary crosslinking of ultraviolet light, a zirconium silicate precursor is generated in which Si atoms and Zr atoms are not directly connected and does not contain a spinning aid. The precursor can overcome the problem of easy growth of zirconium silicate crystals in zirconium silicate nanofibers in the prior art.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing high temperature resistant zirconium silicate nanofibers comprises the following steps:

[0007] (1) mixing epoxy polysiloxane, methacrylic acid and triethylamine, heating and stirring to obtain a uniform silicon source solution; the mass ratio of the epoxy polysiloxane, methacrylic acid and triethylamine is 100: (15-45): (2-10);

[0008] (2) adding zirconium oxychloride octahydrate, acetic acid, and ethylene glycol methacrylate acetoacetate to ethanol, heating and stirring to obtain a uniform zirconium source solution; the mass ratio of zirconium oxychloride octahydrate, acetic acid, ethylene glycol methacrylate acetoacetate, and ethanol is 100: (3-15): (10-35): (10-35);

[0009] (3) mixing the prepared silicon source solution and zirconium source solution at a molar ratio of silicon element to zirconium element of 1:1 to obtain a silicon-zirconium mixed solution;

[0010] (4) adding a photoinitiator TPO-L to the silicon-zirconium mixed solution, and performing ultraviolet crosslinking treatment under magnetic stirring to obtain a zirconium silicate spinning solution;

[0011] (5) The zirconium silicate spinning solution is prepared into zirconium silicate precursor fibers by an electrospinning process, and after calcination, zirconium silicate nanofibers are finally formed.

[0012] Furthermore, the mass ratio of the epoxy polysiloxane, methacrylic acid and triethylamine is 100:(20-40):(3-5).

[0013] Furthermore, the heating temperature in step (1) is 100-120° C., and the stirring time is 4-6 hours.

[0014] Furthermore, the mass ratio of zirconium oxychloride octahydrate, acetic acid, ethylene glycol methacrylate acetoacetate, and ethanol is 100: (5-10): (15-30): (15-30).

[0015] Furthermore, the heating temperature in step (2) is 40-60° C., and the stirring time is 4-6 hours.

[0016] Furthermore, the mass ratio of the silicon-zirconium mixed solution to the photoinitiator TPO-L is 100:(0.5~1).

[0017] Furthermore, the UV intensity used for the UV crosslinking treatment is 0.05-0.2 mW / cm 2 , the processing time is 5~10s.

[0018] Furthermore, in the electrospinning process, the spinning voltage is 10-20 kV, the spinning rate is 0.5-2.0 mL / h, and the spinning distance is 10-20 cm.

[0019] Furthermore, the calcination temperature is 1100-1300° C., the heating rate is 2-10° C. / min, and the holding time is 1-3 h.

[0020] The electrospinning zirconium silicate precursors reported so far all adopt inorganic or organic silicon sources and aluminum sources in the form of ions, and through various chemical reactions, such as hydrolysis-polycondensation, addition reaction, etc., the silicon source and the zirconium source are complexed together to form a zirconium silicate precursor with Si-O-Zr as the main chain. During the sintering process, this precursor will directly form zirconium silicate with Si-O-Zr as the main structure. Therefore, the zirconium silicate prepared by the above-mentioned precursor is easy to crystallize and grow at high temperatures, thereby affecting its heat resistance. In view of the above problems, the present application proposes to first use epoxy polysiloxane as the silicon source, and through the ring-opening reaction of the epoxy group, methacrylic acid is embedded in the epoxy polysiloxane, thereby forming methacrylic acid modified epoxy polysiloxane. Subsequently, zirconium oxychloride octahydrate is used as the zirconium source, and the zirconium source modified by acetoacetic acid ethylene glycol methacrylate is generated by its hydrolysis and reaction with acetoacetic acid ethylene glycol methacrylate. Since the reaction mechanisms of silicon source and zirconium source are different, when the two solutions are mixed together, only physical mixing will occur, and no chemical reaction will occur. However, both silicon source and zirconium source contain acryloyloxy groups that can undergo cross-linking reactions under ultraviolet light. Therefore, under the action of ultraviolet light, the silicon source and zirconium source will be cross-linked together through carbon-carbon double bonds to form zirconium silicate precursor fibers with longer molecular chains. This zirconium silicate precursor fiber formed with carbon chains as connecting points allows the silicon in the entire precursor fiber to still exist in the form of Si-O-Si, and zirconium also exists in the form of Zr-O-Zr. Therefore, during the high-temperature sintering process, the zirconium silicate precursor fiber will first form silicon oxide and zirconium oxide, and then generate zirconium silicate nanofibers through solid-phase reaction. This ensures that its crystallization barrier at high temperature is high, and no obvious crystallization growth will occur at high temperature. In addition, in order to increase the spinning properties of the zirconium silicate precursor, some polymer spinning aids, such as PVA, PVB, PVP, etc., are often added to it. These spinning aids will volatilize at high temperatures, thereby providing growth space for zirconium silicate crystals, which is also not conducive to its temperature resistance. However, the present application increases the polymerization degree of the precursor through ultraviolet cross-linking reaction. Therefore, the zirconium silicate spinning precursor fiber prepared by the present application does not contain organic matter, which can effectively prevent the growth of zirconium silicate crystals inside the zirconium silicate nanofibers.

[0021] The advantages and positive effects of the present invention are:

[0022] The invention uses methacrylic acid-modified epoxy polysiloxane as a silicon source and acetoacetic acid methacrylate-modified ethylene glycol zirconium oxychloride octahydrate as a zirconium source, and generates a zirconium silicate precursor in which Si atoms and Zr atoms are not directly connected and do not contain a spinning aid under the auxiliary crosslinking of ultraviolet light. The zirconium silicate nanofiber prepared after calcination has excellent temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1The SEM image of the zirconium silicate nanofibers prepared in Example 1 was magnified 10,000 times;

[0024] Figure 2 The SEM image of zirconium silicate nanofibers prepared in Example 2 was magnified 8000 times;

[0025] Figure 3 The SEM image of zirconium silicate nanofibers prepared in Comparative Example 1 was magnified 10,000 times;

[0026] Figure 4 This is a SEM image of the zirconium silicate nanofibers prepared in Comparative Example 2, magnified 10,000 times. DETAILED DESCRIPTION

[0027] In order to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings. In the case of no conflict, the features in the case can be combined with each other. The raw materials used in the following examples are all commercially available analytically pure raw materials. Example 1

[0028] A method for preparing high temperature resistant zirconium silicate nanofibers comprises the following steps:

[0029] (1) Mix 100 g epoxy polysiloxane, 25 g methacrylic acid and 3 g triethylamine and o C and stirred for 4 h to obtain a uniform silicon source solution;

[0030] (2) adding 100 g of zirconium oxychloride octahydrate, 5 g of acetic acid, and 20 g of ethylene glycol acetoacetate methacrylate to 20 g of ethanol, and stirring at 40° C. for 6 h to obtain a uniform zirconium source solution;

[0031] (3) mixing the prepared silicon source solution and zirconium source solution at a molar ratio of silicon element to zirconium element of 1:1 to obtain a silicon-zirconium mixed solution;

[0032] (4) Weigh 100g of silicon-zirconium mixed solution, add 1g of photoinitiator TPO-L, and under magnetic stirring, place the mixture under ultraviolet light with an intensity of 0.1 mW / cm 2 The zirconium silicate spinning solution was obtained by treating the solution under the above conditions for 10 seconds.

[0033] (5) Electrospinning was performed according to the spinning parameters of spinning voltage of 12 kV, spinning rate of 0.7 mL / h, and spinning distance of 15 cm to prepare zirconium silicate precursor fibers. The zirconium silicate precursor fibers were then heated to 1300 °C at a rate of 3 °C / min and kept warm for 2 h to finally obtain zirconium silicate nanofibers with uniform morphology.

[0034] The scanning electron microscope image of the zirconium silicate nanofibers prepared in Example 1 is Figure 1 . Example 2

[0035] A method for preparing high temperature resistant zirconium silicate nanofibers comprises the following steps:

[0036] (1) Mix 100 g epoxy polysiloxane, 40 g methacrylic acid and 5 g triethylamine and heat at 110 °C. o C and stirred for 6 h to obtain a uniform silicon source solution;

[0037] (2) adding 100 g of zirconium oxychloride octahydrate, 7 g of acetic acid, and 25 g of ethylene glycol acetoacetate methacrylate to 30 g of ethanol, and stirring at 60° C. for 4 h to obtain a uniform zirconium source solution;

[0038] (3) mixing the prepared silicon source solution and zirconium source solution at a molar ratio of silicon element to zirconium element of 1:1 to obtain a silicon-zirconium mixed solution;

[0039] (4) Weigh 100 g of the silicon-zirconium mixed solution, add 0.7 g of the photoinitiator TPO-L, and under magnetic stirring, place the mixture under ultraviolet light with an intensity of 0.15 mW / cm 2 The zirconium silicate spinning solution was obtained by treating the solution under the above conditions for 8 seconds.

[0040] (5) Electrospinning was performed according to the spinning parameters of spinning voltage of 18 kV, spinning rate of 1.0 mL / h, and spinning distance of 18 cm to prepare zirconium silicate precursor fibers. The zirconium silicate precursor fibers were then heated to 1200 °C at a rate of 5 °C / min and kept warm for 2 h to finally obtain zirconium silicate nanofibers with uniform morphology.

[0041] The scanning electron microscope image of the zirconium silicate nanofibers prepared in Example 2 is Figure 2 .

[0042] Comparative Example 1

[0043] A method for preparing high temperature resistant zirconium silicate nanofibers. The preparation method is the same as that of Example 1, except that step (1) is to mix 100 g of ethyl orthosilicate, 40 g of methacrylic acid, 5 g of water and 5 g of ethanol, and stir at 60° C. for 6 h to obtain a uniform silicon source solution.

[0044] The scanning electron microscope image of the zirconium silicate nanofiber prepared in Comparative Example 1 is Figure 3 .

[0045] Comparative Example 2

[0046] A method for preparing high temperature resistant zirconium silicate nanofibers. The preparation method is the same as that of Example 1, except for step (4): weighing 100 g of a zirconium-silicon mixed solution, adding 8 g of PVP, and obtaining a zirconium silicate spinning solution under magnetic stirring.

[0047] The scanning electron microscope image of the zirconium silicate nanofiber prepared in Comparative Example 2 is Figure 4 .

[0048] Evaluation and characterization

[0049] Figure 1 This is a SEM image of the zirconium silicate nanofibers prepared in Example 1 magnified 10,000 times; Figure 2 This is a SEM image of the zirconium silicate nanofibers prepared in Example 2 magnified 8000 times; it can be seen that the obtained zirconium silicate nanofibers have uniform morphology, high sintering densification degree, and no obvious crystallization phenomenon on the fiber surface.

[0050] Figure 3 The SEM image of the zirconium silicate nanofiber prepared in Comparative Example 1, which is magnified 10,000 times, shows that the entire zirconium silicate fiber has been completely deformed and the crystallization is particularly serious. The silicon source selected in Comparative Example 1 is ethyl orthosilicate, which will first be hydrolyzed to generate a large amount of Si-OH. This mechanism is similar to the hydrolysis mechanism of zirconium oxychloride octahydrate. Therefore, when the silicon source solution and the zirconium source solution are mixed together, the Si-OH bond in the silicon source will react with the Zr-OH bond in the zirconium source to form a Si-O-Zr bond. This results in a large amount of Si-O-Zr bonds inside the formed zirconium silicate precursor, which can directly form zirconium silicate after sintering. Therefore, the grains inside the zirconium silicate nanofiber prepared using this precursor are very easy to grow, affecting its temperature resistance.

[0051] Figure 4 The SEM image of the zirconium silicate nanofibers prepared in Comparative Example 2 is magnified 10,000 times. It can be seen that the crystallization of the entire zirconium silicate fiber is also particularly serious. Compared with Example 1, Comparative Example 2 does not use the UV cross-linking method to increase the viscosity of the entire zirconium silicate precursor, but instead uses PVP to increase the viscosity of the spinning solution. During the high-temperature sintering process, PVP will leave a large number of holes inside the fiber after pyrolysis. These holes will provide growth space for zirconium silicate crystals, thereby causing the zirconium silicate crystals inside the fiber to grow rapidly, affecting its temperature resistance.

[0052] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high temperature resistant zirconium silicate nanofibers, characterized in that: The steps include: (1) mixing epoxy polysiloxane, methacrylic acid and triethylamine, heating and stirring to obtain a uniform silicon source solution; the mass ratio of the epoxy polysiloxane, methacrylic acid and triethylamine is 100: (15-45): (2-10); (2) adding zirconium oxychloride octahydrate, acetic acid, and ethylene glycol methacrylate acetoacetate to ethanol, heating and stirring to obtain a uniform zirconium source solution; the mass ratio of zirconium oxychloride octahydrate, acetic acid, ethylene glycol methacrylate acetoacetate, and ethanol is 100: (3-15): (10-35): (10-35); (3) mixing the prepared silicon source solution and zirconium source solution in a molar ratio of silicon element to zirconium element of 1:1 to obtain a silicon-zirconium mixed solution; (4) adding a photoinitiator TPO-L to the silicon-zirconium mixed solution, and performing ultraviolet crosslinking treatment under magnetic stirring to obtain a zirconium silicate spinning solution; (5) The zirconium silicate spinning solution is prepared into zirconium silicate precursor fibers by an electrospinning process, and after calcination, zirconium silicate nanofibers are finally formed.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the epoxy polysiloxane, methacrylic acid and triethylamine is 100:(20-40):(3-5).

3. The preparation method according to claim 1, characterized in that: The heating temperature in step (1) is 100-120° C., and the stirring time is 4-6 hours.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the zirconium oxychloride octahydrate, acetic acid, ethylene glycol methacrylate acetoacetate, and ethanol is 100: (5-10): (15-30): (15-30).

5. The preparation method according to claim 1, characterized in that: The heating temperature in step (2) is 40-60° C. and the stirring time is 4-6 hours.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the silicon-zirconium mixed solution to the photoinitiator TPO-L is 100:(0.5-1).

7. The preparation method according to claim 1, characterized in that: The UV intensity used for the UV crosslinking treatment is 0.05-0.2 mW / cm 2 , the processing time is 5~10s.

8. The preparation method according to claim 1, characterized in that: The spinning voltage in the electrospinning process is 10-20 kV, the spinning rate is 0.5-2.0 mL / h, and the spinning distance is 10-20 cm.

9. The preparation method according to claim 1, characterized in that: The calcination temperature is 1100-1300° C., the heating rate is 2-10° C. / min, and the heat preservation time is 1-3 hours.

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