A titanium dioxide filler for low thermal expansion ceramics and its preparation method

Abstract

This invention relates to the field of titanium dioxide. To address the problem that while titanium dioxide fillers improve the dielectric constant of ceramics, the coefficient of thermal expansion also increases simultaneously, a method for preparing low-thermal-expansion titanium dioxide fillers for ceramics is provided. The method includes: S100, under heating conditions, adding a doped ion solution to a titanium dioxide precursor solution to obtain a gel; the doped ion solution includes: Mo... 6+ and Sn 2+ Mo 6+ With Ti 4+ The molar ratio of Sn is (10-30):(1-2). 2+ With Ti 4+ The molar ratio is (10-20):(2-3); S200, the gel is calcined to obtain a preproduct; S300, the preproduct is coated with a film layer to obtain titanium dioxide filler; the film layer includes: a silica layer. This invention, by coating a film layer onto the outer surface of titanium dioxide, can utilize the film layer to limit the expansion of titanium dioxide at low temperatures, reducing the possibility of structural defects caused by differences in the thermal expansion of the raw materials; by coating titanium dioxide with a silica film layer, the expansion of titanium dioxide can be limited.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide, and more specifically, to a titanium dioxide filler for low thermal expansion ceramics and its preparation method. Background Technology

[0002] Dielectric ceramics are important electronic ceramics with excellent insulation and dielectric properties, and are widely used in electronics, communications, and other fields. Rutile titanium dioxide has a high dielectric constant, and when added to ceramic systems with low dielectric constants, it can improve the dielectric constant of the ceramic to a certain extent. However, the difference in the coefficients of thermal expansion between titanium dioxide and ceramic raw materials can easily lead to structural defects during the ceramic sintering process, thus affecting the overall dielectric properties of the ceramic. The dispersion and compatibility of titanium dioxide in the matrix also affect the dielectric properties of the final product.

[0003] While the applicant's improvement of titanium dioxide has increased the dielectric constant of ceramics, the final coefficient of thermal expansion of the ceramic product has also increased to some extent. Summary of the Invention

[0004] The purpose of this invention is to provide a titanium dioxide filler for low thermal expansion ceramics and its preparation method, thereby solving the problem that the coefficient of thermal expansion also increases simultaneously after the titanium dioxide filler improves the dielectric constant of the ceramic.

[0005] The embodiments of the present invention are achieved through the following technical solutions:

[0006] A method for preparing titanium dioxide filler for low thermal expansion ceramics, comprising:

[0007] S100. Under heating conditions, a doped ion solution is added to a titanium dioxide precursor solution to obtain a gel; the doped ion solution includes: Mo. 6+ and Sn 2+ ;The Mo 6+ With Ti 4+ The molar ratio of Sn is (10-30):(1-2). 2+ With Ti 4 + The molar ratio is (10-20):(2-3);

[0008] S200, The gel is prepared into a preproduct by a calcination process;

[0009] S300. After the preproduct is coated with a film layer through a coating process, titanium dioxide filler is obtained; the film layer includes: a silicon dioxide layer.

[0010] The concentration of the precursor solution can be selected from 18wt% to 25wt%; the solvent of the precursor solution can be deionized water or alcohol, such as ethanol or n-octanol.

[0011] The precursor solutions for titanium dioxide include one or more of the following: tetrabutyl titanate solution, titanium oxysulfate solution, tetraisopropyl titanate solution, and titanium tetrachloride solution.

[0012] High-dielectric ceramics play a crucial role in electronic components such as capacitors and filters. Utilizing their high dielectric constant, component size can be reduced, energy storage density increased, and response speed improved, meeting the miniaturization and integration requirements of modern electronic devices. High-dielectric ceramics also serve as potential energy storage materials, possessing advantages such as high energy storage density and fast charge / discharge speeds, and are expected to play a significant role in future energy storage systems. The sensitivity of high-dielectric ceramics to changes in electric fields makes them important materials for sensors, capable of detecting and converting changes in electric fields into measurable signals. However, the manufacturing cost of high-dielectric ceramics is relatively high. When the application scenario does not require an excessively high dielectric constant, or even does not need to reach the dielectric constant of rutile ceramics, a certain amount of high-dielectric functional filler can be added to relatively inexpensive raw materials to improve the dielectric constant to a certain extent, ensuring that production costs are not significantly increased.

[0013] Titanium dioxide has a high dielectric constant, making it suitable as a functional filler in dielectric ceramics. Its addition also effectively improves the mechanical properties of ceramics. Ceramic raw materials generally consist of silicon dioxide, alumina, zirconium oxide, barium carbonate, magnesium oxide, and organic matrices. When adding inorganic fillers, the difference in thermal expansion coefficients between the filler and the other components must be considered to avoid surface quality defects during sintering and to prevent high dielectric losses due to low compatibility of the inorganic filler. Therefore, the amount of inorganic filler used is limited. Furthermore, ceramic firing is a densification process, involving not only changes in the volume of raw material particles but also the filling of pores in the ceramic body. During firing, the volume of ceramics typically shrinks. The sintering process generally includes a preheating stage, an oxidation stage, and a firing stage. The oxidation stage temperature is around 950℃, while the firing stage temperature for high-performance ceramics is generally above 1200℃, and can even reach above 2000℃. The coefficient of thermal expansion of silicon dioxide decreases with increasing temperature during firing, and becomes essentially stable above 1200℃. Commonly used titanium dioxide is primarily anatase and rutile, with rutile having a lower coefficient of thermal expansion than anatase. However, regardless of whether it is anatase or rutile, its coefficient of thermal expansion is higher than that of common raw materials such as silicon dioxide. Therefore, the applicant is considering how to reduce the difference in thermal expansion between titanium dioxide and other raw materials during ceramic firing, thereby reducing stress within the ceramic body.

[0014] Although rutile titanium dioxide has higher stability and dielectric constant than anatase titanium dioxide, and a smaller coefficient of thermal expansion, theoretically, incorporating rutile titanium dioxide into the raw materials during firing would be more advantageous for improving product performance and ensuring appearance quality. However, the applicant hopes to improve the ceramic sintering process by utilizing the shrinkage during the transformation of anatase titanium dioxide into rutile titanium dioxide. In the early stages of sintering, especially during the heating period, the ceramic volume expands to a certain extent. After reaching a sufficiently high temperature, the disappearance of pores and the filling of voids begin to cause significant volume shrinkage. The applicant hopes that titanium dioxide can undergo crystal transformation in the early stages of sintering, thereby compensating for the stress generated by spatial compression during expansion through titanium dioxide shrinkage. This could reduce the possibility of fine cracks in the ceramic, thus allowing for a certain increase in the amount of titanium dioxide used, thereby improving the dielectric constant of the ceramic. Furthermore, since titanium dioxide completes its crystal transformation in the early stages of sintering, the overall shrinkage rate of the ceramic volume will not be accelerated by titanium dioxide shrinkage in the later stages of sintering, thus reducing the possibility of cracks appearing in the later stages of sintering and expanding the range of process parameters. Currently, the volume shrinkage of most ceramics during sintering occurs after 1000℃. The temperature at which anatase titanium dioxide begins to transform into rutile is around 800℃. However, the time required to rise from 800℃ to 1000℃ during sintering is relatively short, making complete crystal transformation difficult at temperatures between 800℃ and 1000℃. Therefore, the applicant aims to lower the temperature at which anatase titanium dioxide transforms into rutile. The applicant has promoted this transformation through a doping process. Simultaneously, to control the transformation and prevent excessively rapid volume change during the heating phase, which could lead to microcracks, the applicant has experimentally controlled the doping amount. Furthermore, excessive doping can lead to uncontrolled grain growth and increased structural defects, affecting not only the dielectric constant but also the mechanical properties and chemical stability of the product.

[0015] Although doping with specific ions can promote the transformation of anatase titanium dioxide to rutile, product testing revealed that the coefficient of thermal expansion (CTE) of the product generally increases at different temperatures. The applicant hypothesizes that structural defects introduced after crystal doping also increase the non-linearity of the CTE with temperature changes. The behavior of materials at different temperatures is difficult to predict; for example, the CTE of the matrix material increases almost linearly, but the CTE of the filler increases non-linearly, leading to poor thermal compatibility of ceramic products under temperature variations. The applicant aims to reduce the CTE of ceramic products using titanium dioxide fillers without significantly affecting their contribution to the dielectric properties of ceramics. Therefore, the applicant employs a coating technology to coat the titanium dioxide with a high-temperature resistant, low-thermal-expansion, and high-mechanical-property-strength thin film.

[0016] Preferably, the coating process includes: preparing the preproduct into a slurry, adding a dispersant, a silicon source, and PMMA microspheres to the slurry to obtain a first slurry; the first slurry is filtered, washed, dried, and ground to obtain titanium dioxide filler; the amount of the dispersant is 0.1wt%-0.2wt% of the preproduct; the amount of the silicon source, calculated as silicon dioxide, is 3wt%-5wt% of the preproduct; the amount of the PMMA microspheres is 0.1wt%-0.3wt% of the preproduct, and the particle size of the PMMA microspheres is 1μm-20μm.

[0017] This invention uses a silica film to restrict the expansion of titanium dioxide and the ceramic substrate, thereby reducing the overall coefficient of thermal expansion of the ceramic to a certain extent. PMMA microspheres give the silica film a porous structure, allowing stress to be more easily dispersed under pressure, resulting in better film stability and thus better confinement. The silica film also has a certain amount of pore space to compensate for the space required for expansion.

[0018] Preferably, the coating process further includes: adding a dispersant, 60wt%-70wt% of PMMA microspheres and all of the silicon source to a slurry at 80℃-90℃, stirring for 30min-60min, cooling the slurry to 50℃-70℃, adding the remaining PMMA microspheres, stirring for 45min-60min, and then letting it stand for 10min-15min to obtain the first slurry.

[0019] Preferably, the coating process further includes: adding 3-5 parts by weight of triethanolamine and 2-6 parts by weight of coupling agent to the first slurry for mixing and reaction to obtain a second slurry; drying the second slurry to obtain titanium dioxide filler; the first slurry is 100-120 parts by weight of the pre-product in the first slurry.

[0020] Because anatase titanium dioxide expands to a certain extent before transforming into rutile titanium dioxide, and its coefficient of expansion is greater than that of conventional ceramic raw materials, this can lead to structural defects in the product and ultimately affect its dielectric properties. Therefore, this invention coats titanium dioxide with a multilayer film. The film layers restrict the expansion of titanium dioxide, and the space created by the decomposition or volatilization of the triethanolamine film layer provides expansion space for the ceramic matrix. Thus, in this invention, the temperature at which the triethanolamine layer breaks down is lower than the crystal transformation temperature of anatase titanium dioxide.

[0021] In the early-stage ceramic forming process, to ensure morphological stability, the selection of film material can improve the dispersibility of titanium dioxide and enhance the bonding between titanium dioxide and organic binders during the forming process. Coupling agents can improve film stability, thereby increasing the decomposition temperature to 400℃-600℃. This invention utilizes PMMA microspheres, which not only improve the bonding between the triethanolamine film and the silica film but also increase the decomposition temperature of the triethanolamine film.

[0022] The coupling agent may be one or more of triisostearoyl titanate isopropyl ester, GR-501 and KH570.

[0023] Experiments showed that the product prepared using isopropyl triisostearoyl titanate has good performance.

[0024] Preferably, the temperature of the second slurry reaction system is 50℃-70℃, and the reaction time is 1.5h-3h.

[0025] By controlling the amount of raw materials, reaction temperature, and reaction time, the film thickness can be controlled, preventing the film from becoming too large and thus avoiding excessive porosity in the molded preform, excessive volume shrinkage after high-temperature sintering, and prolonged densification process time. Conversely, a film thickness that is too small is unsuitable for the expansion process before the transformation of anatase titanium dioxide. The applicant's experiments have shown that the product using the parameters of this invention exhibits superior performance.

[0026] Preferably, S100 includes:

[0027] Dissolve phosphomolybdic acid in ethanol to obtain solution A;

[0028] Solution B is obtained by dissolving tin tetrachloride in ethanol;

[0029] Under heating conditions, solutions A and B were added to the titanium dioxide precursor solution and mixed under ultrasonic conditions for 10-30 minutes. The mixture was then allowed to stand at room temperature for 8-12 hours to obtain a gel. The ultrasonic frequency was 20-30 kHz.

[0030] Preferably, solution B is added to the titanium dioxide precursor solution all at once, and then solution A is added gradually.

[0031] During the doping experiment, the applicant discovered that when both solution A and solution B were added to the precursor solution simultaneously or gradually, Sn... 4+ The applicant hypothesizes that the limited doping amount is due to competition between the two types of ions during the doping process.

[0032] Preferably, the temperature of the reaction system in S100 is 60℃-80℃, and the pH value is 7.5-9.

[0033] pH can be adjusted using ammonia. Appropriate system temperature and pH are beneficial for the entry of metal ions into the titanium dioxide lattice, the completion of precursor solution hydrolysis, and the stability of hydrolysis products.

[0034] Preferably, the silicon source includes one or more of sodium silicate, potassium silicate, and tetraethyl orthosilicate.

[0035] A titanium dioxide filler prepared by the aforementioned method.

[0036] The present invention has at least the following beneficial effects:

[0037] This invention utilizes the crystal form change of anatase titanium dioxide in the early stage of sintering to reduce the possibility of microcracks in ceramics. Anatase titanium dioxide can complete its transformation to rutile form before high-temperature sintering, avoiding further shrinkage under the already high volume shrinkage rate of high-temperature sintering, which would increase the possibility of structural defects in ceramics under the same process conditions. Titanium dioxide powder prepared through a doping process can promote its transformation to rutile titanium dioxide. After coating the outer surface of titanium dioxide with a film layer through a coating process, the film layer can limit the expansion of titanium dioxide at low temperatures, reducing structural defects caused by differences in thermal expansion of raw materials. The possibility of triethanolamine film volatilization or decomposition before the crystal transformation of titanium dioxide allows the released film space to be used for the expansion of the surrounding substrate, reducing internal stress; the presence of the film can also increase the dispersibility of titanium dioxide and its compatibility with the substrate, thereby increasing the dielectric properties of the product; by coating titanium dioxide with a silica film, the thermal expansion of titanium dioxide during the use of ceramic products can be limited; the use of porous silica film allows the film to have a certain lateral expansion space under pressure, reducing stress concentration; the use of PMMA microspheres not only provides pore-forming function, but also improves the bonding between silica film and triethanolamine film. Detailed Implementation

[0038] To make the objectives, methods, and advantages of the embodiments of the present invention clearer, the methods in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0039] Example 1: A method for preparing titanium dioxide filler for low thermal expansion ceramics, comprising:

[0040] S100. Dissolve phosphomolybdic acid in ethanol to obtain solution A; dissolve tin tetrachloride in ethanol to obtain solution B;

[0041] Under heating conditions, solutions A and B were added to the titanium dioxide precursor solution and mixed under ultrasonic conditions for 10 min. The mixture was then allowed to stand at room temperature for 8 h to obtain a gel; the ultrasonic frequency was 20 kHz. The doped ion solution included: Mo. 6+and Sn 4 + ;The Mo 6+ With Ti 4+ The molar ratio is 10:2, and the Sn 2+ With Ti 4+ The molar ratio is 10:3;

[0042] S200, The gel is prepared by a calcination process to obtain a preproduct;

[0043] S300. After the preproduct is coated with a film layer through a coating process, titanium dioxide filler is obtained; the film layer includes: a silicon dioxide layer.

[0044] The coating process includes: mixing the preproduct with deionized water to form a slurry; adding a dispersant, 60 wt% PMMA microspheres, and all of the silicon source to the slurry at 80°C; stirring for 30 min; cooling the slurry to 50°C; adding the remaining PMMA microspheres; stirring for 45 min; and then letting it stand for 10 min to obtain a first slurry; adding 3 parts by weight of triethanolamine and 2 parts by weight of triisostearoyl titanate to the first slurry and mixing to obtain a second slurry; filtering, washing, drying, and grinding the second slurry to obtain titanium dioxide filler; the first slurry contains 100 parts by weight of the preproduct.

[0045] The mass ratio of deionized water to preproduct is 100:90;

[0046] The amount of the dispersant is 0.1 wt% of the preproduct; the dispersant is polyethylene glycol.

[0047] The amount of silicon source used, calculated as silicon dioxide, is 3 wt% of the preproduct; the silicon source is sodium silicate.

[0048] The amount of PMMA microspheres used is 0.1 wt% of the preproduct, and the particle size of the PMMA microspheres is 1 μm.

[0049] The temperature of the second slurry reaction system is 50℃, and the reaction time is 1.5h.

[0050] The reaction system in S100 has a temperature of 60°C and a pH of 7.5.

[0051] Example 2: A method for preparing titanium dioxide filler for low thermal expansion ceramics, comprising:

[0052] S100. Dissolve phosphomolybdic acid in ethanol to obtain solution A; dissolve tin tetrachloride in ethanol to obtain solution B;

[0053] Under heating conditions, solutions A and B were added to the titanium dioxide precursor solution and mixed under ultrasonic conditions for 30 min. The mixture was then allowed to stand at room temperature for 12 h to obtain a gel; the ultrasonic frequency was 30 kHz. The doped ion solution included: Mo. 6+ and Sn 4+ ;The Mo 6+ With Ti 4+ The molar ratio is 30:1, and the Sn 2+ With Ti 4+ The molar ratio is 20:2;

[0054] S200, The gel is prepared by a calcination process to obtain a preproduct;

[0055] S300. After the preproduct is coated with a film layer through a coating process, titanium dioxide filler is obtained; the film layer includes: a silicon dioxide layer.

[0056] The coating process includes: mixing the preproduct with deionized water to form a slurry; adding a dispersant, 70 wt% PMMA microspheres, and all of the silicon source to the slurry at 90°C; stirring for 60 min; cooling the slurry to 70°C; adding the remaining PMMA microspheres; stirring for 60 min; and then allowing it to stand for 15 min to obtain a first slurry; adding 5 parts by weight of triethanolamine and 6 parts by weight of triisostearoyl titanate to the first slurry and mixing to obtain a second slurry; and filtering, washing, drying, and grinding the second slurry to obtain titanium dioxide filler.

[0057] The mass ratio of deionized water to preproduct is 120:90;

[0058] The amount of the dispersant is 0.2 wt% of the preproduct; the dispersant is polyethylene glycol.

[0059] The amount of silicon source used, calculated as silicon dioxide, is 5 wt% of the preproduct; the silicon source is sodium silicate.

[0060] The amount of PMMA microspheres used is 0.3 wt% of the preproduct, and the particle size of the PMMA microspheres is 20 μm.

[0061] The temperature of the second slurry reaction system is 70℃, and the reaction time is 3h.

[0062] The reaction system in S100 has a temperature of 80℃ and a pH value of 9.

[0063] Example 3: A method for preparing titanium dioxide filler for low thermal expansion ceramics, comprising:

[0064] S100. Dissolve phosphomolybdic acid in ethanol to obtain solution A; dissolve tin tetrachloride in ethanol to obtain solution B;

[0065] Under heating conditions, solutions A and B were added to the titanium dioxide precursor solution and mixed under ultrasonic conditions for 20 min. The mixture was then allowed to stand at room temperature for 10 h to obtain a gel; the ultrasonic frequency was 25 kHz. The doped ion solution included: Mo. 6+ and Sn 4+ ;The Mo 6+ With Ti 4+ The molar ratio is 20:1.5, and the Sn 2+ With Ti 4+ The molar ratio is 1.5:2.5;

[0066] S200, The gel is prepared by a calcination process to obtain a preproduct;

[0067] S300. After the preproduct is coated with a film layer through a coating process, titanium dioxide filler is obtained; the film layer includes: a silicon dioxide layer.

[0068] The coating process includes: mixing the preproduct with deionized water to form a slurry; adding a dispersant, 65 wt% PMMA microspheres, and all of the silicon source to the slurry at 85°C; stirring for 45 min; cooling the slurry to 60°C; adding the remaining PMMA microspheres; stirring for 50 min; and then allowing it to stand for 12 min to obtain a first slurry; adding 4 parts by weight of triethanolamine and 4 parts by weight of triisostearoyl titanate to the first slurry and mixing to obtain a second slurry; and filtering, washing, drying, and grinding the second slurry to obtain titanium dioxide filler.

[0069] The mass ratio of deionized water to preproduct is 110:90;

[0070] The amount of the dispersant used is 0.15 wt% of the preproduct; the dispersant is polyethylene glycol;

[0071] The amount of silicon source used, calculated as silicon dioxide, is 4 wt% of the preproduct; the silicon source is sodium silicate.

[0072] The amount of PMMA microspheres used is 0.2 wt% of the preproduct, and the particle size of the PMMA microspheres is 8 μm.

[0073] The temperature of the second slurry reaction system is 60℃, and the reaction time is 2h.

[0074] The reaction system in S100 has a temperature of 70°C and a pH of 8.

[0075] Example 4: A method for preparing titanium dioxide filler for low thermal expansion ceramics, comprising:

[0076] S100. Dissolve phosphomolybdic acid in ethanol to obtain solution A; dissolve tin tetrachloride in ethanol to obtain solution B;

[0077] Under heating conditions, solution B was added once to the titanium dioxide precursor solution, followed by the addition of 25 wt% solution A every 5 minutes. During this period, the system was subjected to ultrasonication. After 20 minutes, the mixture was allowed to stand at room temperature for 10 hours to obtain a gel. The ultrasonic frequency was 25 kHz. The doped ion solution included: Mo. 6+ and Sn 4+ ;The Mo 6+ With Ti 4+ The molar ratio is 20:1.5, and the Sn 2+ With Ti 4+ The molar ratio is 1.5:2.5;

[0078] S200, The gel is prepared by a calcination process to obtain a preproduct;

[0079] S300. After the preproduct is coated with a film layer through a coating process, titanium dioxide filler is obtained; the film layer includes: a silicon dioxide layer.

[0080] The coating process includes: mixing the preproduct with deionized water to form a slurry; adding a dispersant, 65 wt% PMMA microspheres, and all of the silicon source to the slurry at 85°C; stirring for 45 min; cooling the slurry to 60°C; adding the remaining PMMA microspheres; stirring for 50 min; and then allowing it to stand for 12 min to obtain a first slurry; adding 4 parts by weight of triethanolamine and 4 parts by weight of triisostearoyl titanate to the first slurry and mixing to obtain a second slurry; and filtering, washing, drying, and grinding the second slurry to obtain titanium dioxide filler.

[0081] The mass ratio of deionized water to preproduct is 110:90;

[0082] The amount of the dispersant used is 0.15 wt% of the preproduct; the dispersant is polyethylene glycol;

[0083] The amount of silicon source used, calculated as silicon dioxide, is 4 wt% of the preproduct; the silicon source is sodium silicate.

[0084] The amount of PMMA microspheres used is 0.2 wt% of the preproduct, and the particle size of the PMMA microspheres is 8 μm.

[0085] The temperature of the second slurry reaction system is 60℃, and the reaction time is 2h.

[0086] The reaction system in S100 has a temperature of 70°C and a pH of 8.

[0087] Comparative Example 1: A method for preparing titanium dioxide filler for low thermal expansion ceramics, comprising:

[0088] S100. Dissolve phosphomolybdic acid in ethanol to obtain solution A; dissolve tin tetrachloride in ethanol to obtain solution B;

[0089] Under heating conditions, solution B was added once to the titanium dioxide precursor solution, followed by the addition of 25 wt% solution A every 5 minutes. During this period, the system was subjected to ultrasonication. After 20 minutes, the mixture was allowed to stand at room temperature for 10 hours to obtain a gel. The ultrasonic frequency was 25 kHz. The doped ion solution included: Mo. 6+ and Sn 4+ ;The Mo 6+ With Ti 4+ The molar ratio is 20:1.5, and the Sn 2+ With Ti 4+ The molar ratio is 1.5:2.5;

[0090] S200, The gel is prepared by a calcination process to obtain a preproduct;

[0091] S300. After the preproduct is coated with a film layer through a coating process, titanium dioxide filler is obtained.

[0092] The coating process includes: mixing the preproduct with deionized water to prepare a first slurry, and then adding 4 parts by weight of triethanolamine and 4 parts by weight of triisostearoyl titanate isopropyl ester to the first slurry for mixing and reaction to obtain a second slurry; the second slurry is then filtered, washed, dried and ground to obtain titanium dioxide filler.

[0093] The mass ratio of deionized water to preproduct is 110:90;

[0094] The temperature of the second slurry reaction system is 60℃, and the reaction time is 2h.

[0095] The reaction system in S100 has a temperature of 70°C and a pH of 8.

[0096] Comparative Example 2: The difference from Example 4 is that PMMA microspheres were not added.

[0097] Comparative Example 3: The difference from Example 4 is that after the preproduct was mixed with deionized water to form a slurry, the dispersant, all PMMA microspheres and all silicon source were added to the slurry at 85°C. After stirring for 45 minutes, the temperature was lowered to 60°C, stirred for 50 minutes and then allowed to stand for 12 minutes to obtain the first slurry.

[0098] experiment:

[0099] Preparation method of experimental samples: Ceramic powder and binder PVA were mixed by wet ball milling for 30 hours to obtain a slurry. The amount of binder was 4% of the powder. After pressing the slurry into a blank, sintering was started. The sintering process was as follows: preheating at 300℃ for 1 hour, then heating to 1000℃ at a rate of 80℃ / h and holding for 1 hour, then heating to 1300℃ at a rate of 60℃ / h and holding for 5 hours. The ceramic powder consisted of 70wt% alumina powder, 10wt% magnesium oxide powder, 1wt% silica, and the balance titanium dioxide filler.

[0100] Experiment 1: Titanium dioxide fillers prepared according to the methods provided in Examples 1-4 and Comparative Examples 1-3 were used to prepare experimental samples. The dielectric constant of the prepared samples was then tested according to GB / T5594.4-2015 standard. The test conditions were: 1MHz, 25℃, and 5mm thickness. The average value was taken after 5 tests for each group. The test results are shown in Table 1.

[0101] Table 1

[0102] Example 1 Example 2 Example 3 Example 4 Dielectric constant 31.6 28.3 32.8 33.5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Dielectric constant 33.7 29.1 31.9

[0103] As can be seen from the experimental results of Examples 1-4, the titanium dioxide filler prepared by the preparation method provided by the present invention still has a significant effect on improving the dielectric constant of ceramics.

[0104] A comparison of the experimental results of Comparative Example 1 and Example 4 shows that, compared with only the triethanolamine layer, the titanium dioxide filler obtained by coating titanium dioxide with both silicon dioxide and triethanolamine layers in this invention has almost no decrease in the improvement of the ceramic dielectric constant.

[0105] A comparison of the experimental results from Comparative Examples 2-3 and Example 4 shows that the addition of PMMA microspheres and the method of addition both affect the promoting effect of titanium dioxide filler on the dielectric constant of ceramics. The applicant hypothesizes that the reason is that the stability and uniformity of the silica film structure affect the compatibility between titanium dioxide and the ceramic matrix, as well as the film's limiting effect on titanium dioxide expansion.

[0106] Experiment 2: Titanium dioxide fillers prepared according to the methods provided in Examples 1-4 and Comparative Examples 1-3 were used to prepare experimental samples. The coefficients of thermal expansion (×10⁻⁶) of the prepared samples were then measured using the linear expansion method. -6 The thickness of the sample was measured at 25℃ ( / ℃). The test conditions were 25℃ and 5mm. Each group was tested 5 times and the average value was taken. The test results are shown in Table 2.

[0107] Table 2

[0108] Example 1 Example 2 Example 3 Example 4 coefficient of thermal expansion 6.72 7.03 6.58 6.42 Comparative Example 1 Comparative Example 2 Comparative Example 3 coefficient of thermal expansion 8.40 7.11 6.78

[0109] As can be seen from the test results of Examples 1-4, ceramics using the titanium dioxide filler provided by the present invention not only improve the dielectric constant but also have the advantage of low thermal expansion.

[0110] As can be seen from the comparison between Comparative Example 1 and Example 4, adding the silicon dioxide film layer provided by the present invention to the triethanolamine layer can reduce the coefficient of thermal expansion of titanium dioxide.

[0111] As can be seen from the comparison between Comparative Examples 2-3 and Example 4, the addition of PMMA microspheres and the method of addition both affect the effect of titanium dioxide filler on reducing the coefficient of thermal expansion of ceramics.

[0112] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a low thermal expansion ceramic titanium white filler, characterized by, The application relates to a preparation method of a titanium white powder filler. S100, adding a doping ion solution into a precursor solution of titanium dioxide under heating conditions to obtain a gel; The doped ion solution comprises: Mo 6+ and Sn 4+ ; the molar ratio of Mo 6+ to Ti 4+ is (10-30):(1-2), and the molar ratio of Sn 4+ to Ti 4+ is (10-20):(2-3); S200, preparing a pre-product through a calcination process; S300, obtaining the titanium white powder filler after coating a film layer on the pre-product through a coating process; the film layer comprises a silica layer; The coating process comprises the following steps: after the pre-product is configured into slurry, a dispersing agent, a silicon source and PMMA microspheres are added into the slurry to obtain a first slurry; after the first slurry is filtered, washed, dried and ground, the titanium white powder filler is obtained; The amount of the dispersing agent is 0.1wt%-0.2wt% of the pre-product; The amount of the silicon source is 3wt%-5wt% of the pre-product in terms of silicon dioxide; The amount of the PMMA microspheres is 0.1wt%-0.3wt% of the pre-product, and the particle size of the PMMA microspheres is 1-20mu.

2. The production method according to claim 1, characterized by, The coating process further comprises the following steps: the dispersing agent, 60wt%-70wt% of the PMMA microspheres and all the silicon source are added into the slurry at 80-90 DEG C, the slurry is cooled to 50-70 DEG C after stirring for 30-60 minutes, the remaining PMMA microspheres are added, and the slurry is stirred for 45-60 minutes and then is left to stand for 10-15 minutes to obtain the first slurry.

3. The preparation method according to claim 1, characterized in that, The coating process further comprises the following steps: 3-5 parts of triethanolamine and 2-6 parts of a coupling agent are added into the first slurry to react, and the second slurry is obtained; the second slurry is dried to obtain the titanium white powder filler; the amount of the first slurry is 100-120 parts in terms of the weight of the pre-product in the first slurry.

4. The preparation method according to claim 3, characterized in that, The temperature of the second slurry reaction system is 50-70 DEG C, and the reaction time is 1.5-3 hours.

5. The method of any one of claims 1-4, wherein the method further comprises, The S100 comprises the following steps: Phosphomolybdic acid is dissolved in ethanol to obtain solution A; Tin tetrachloride is dissolved in ethanol to obtain solution B; Under heating conditions, solution A and solution B are added into a precursor solution of titanium dioxide, and are mixed under ultrasonic environment for 10-30 minutes, and then are left to stand at normal temperature for 8-12 hours to obtain a gel; the ultrasonic frequency is 20-30 KHz.

6. The preparation method according to claim 5, characterized in that, Solution B is added into the precursor solution of titanium dioxide at one time, and then solution A is gradually added.

7. The preparation method according to claim 5, characterized in that, The temperature of the reaction system in the S100 is 60-80 DEG C, and the pH value is 7.5-9.

8. The preparation method according to claim 5, characterized in that, The silicon source comprises one or more of sodium silicate, potassium silicate and tetraethyl orthosilicate.

9. A titanium white powder filler prepared by the preparation method in any one of claims 1-8.