High dielectric constant composite material based on gel casting and preparation method thereof

Abstract

The invention relates to a high dielectric constant composite material based on gel casting and a preparation method thereof. The preparation method of the high-dielectric-constant composite material based on gel casting comprises the following steps: (1) carrying out primary mixing on Ca1-xLa2 / 3xTiO3 ceramic powder and water, then adding a binder and an isobutylene maleic anhydride copolymer, and carrying out secondary mixing to obtain ceramic slurry; wherein x is more than 0 and less than 0.3; (2) adding a surfactant into the obtained ceramic slurry, carrying out foaming treatment in a mechanical stirring manner, then pouring the ceramic slurry into a mold, and carrying out standing treatment so as to realize curing, so that a ceramic biscuit is obtained; (3) sintering the obtained ceramic biscuit at the temperature of 1300-1400 DEG C to obtain a porous ceramic skeleton; and (4) immersing the obtained porous ceramic skeleton in resin for vacuum impregnation, and then carrying out curing treatment to obtain the high dielectric constant composite material based on gel casting.

Description

Technical Field

[0001] The invention relates to a high dielectric constant composite material based on gel injection molding, a preparation method and an application thereof, and belongs to the technical field of microwave dielectric composite materials. Background Art

[0002] High-frequency composite dielectric materials refer to composite materials composed of resin and ceramic that have both the high reliability of resin and the excellent dielectric properties of ceramic. At present, high-frequency composite dielectric materials are widely used in aerospace, 5G / 6G communications and other fields by preparing them into substrates and various connectors. Since the size of electronic devices is inversely proportional to the square root of the dielectric constant of the material, high dielectric constant composite materials can achieve the miniaturization of electronic devices. Miniaturized devices will inevitably bring higher power density and more concentrated heat generation, so the material also needs to have a high thermal conductivity to reduce the thermal management burden of the device.

[0003] At present, the main method for preparing high dielectric constant and high thermal composite materials is to use high dielectric constant ceramics (BaTiO 3 、SrTiO 3 , Ca 3 Cu 4 TiO 12 etc.) and high thermal conductivity ceramics (h-BN, Al 2 O 3 , AlN, etc.) are compounded with a resin matrix. However, since the total filling amount of the ceramic phase in the resin matrix is ​​limited, it is often difficult for the material to have both a high dielectric constant and a high thermal conductivity. Summary of the invention

[0004] To this end, the present invention provides a high dielectric constant composite material based on gel casting and a preparation method thereof.

[0005] In one aspect, the present invention provides a method for preparing a high dielectric constant composite material based on gel casting, comprising: (1) Ca 1-x La 2 / 3x TiO 3 The ceramic powder and water are mixed once, and then a binder and an isobutylene maleic anhydride copolymer are added and mixed twice to obtain a ceramic slurry; wherein 0<x<0.3; (2) adding a surfactant to the obtained ceramic slurry, foaming the slurry by mechanical stirring, and then pouring the slurry into a mold and allowing it to stand for solidification to obtain a ceramic blank; (3) sintering the obtained ceramic blank at 1300° C. to 1400° C. to obtain a porous ceramic skeleton; (4) Immersing the obtained porous ceramic skeleton in a resin for vacuum impregnation, and then curing it to obtain the high dielectric constant composite material based on gel casting; preferably, the resin is selected from at least one of silicon-containing aryl acetylene, polydimethylsilane and epoxy resin.

[0006] In the present invention, firstly, Ca 1-x La 2 / 3x TiO 3 Ceramic powder is uniformly mixed with dispersant, water and binder in proportion to form a uniform slurry. Finally, a foaming agent is added and physical foaming is performed. Finally, the foamed slurry is allowed to stand for slow solidification of the isobutylene maleic anhydride copolymer to finally form a ceramic blank with pores. After the ceramic blank is sintered to be dense, it is vacuum impregnated with PSAE resin to obtain a composite material with a spherical pore structure. This composite material with a connected ceramic skeleton has a dielectric constant and thermal conductivity far higher than that of the 0-3 type composite material.

[0007] Preferably, the Ca 1-x La 2 / 3x TiO 3 The particle size of the ceramic powder is 1 to 2 μm; The Ca 1-x La 2 / 3x TiO 3 The preparation process of ceramic powder includes: 3 ,La 2 O 3 and TiO 2 Press Ca 1-x La 2 / 3x TiO 3 The stoichiometric ratio is weighed and mixed, and then calcined at 1100°C to 1200°C for 2 to 4 hours to obtain the Ca 1-x La 2 / 3x TiO 3 Ceramic powder. In the present invention, CaCO 3 ,La 2 O 3 and TiO 2 The high-performance calcium lanthanum titanium ceramic powder is obtained by mixing and calcining according to the stoichiometric ratio.

[0008] Preferably, Ca 1-x La 2 / 3x TiO 3 The ceramic powder is added with deionized water as a ball milling medium, and after secondary ball milling at 250-300 rpm for 2-4 hours, it is dried at 150°C.

[0009] Preferably, in step (1): the Ca 1-x La2 / 3x TiO 3 The volume ratio of ceramic powder to water is 10 vol% to 50 vol%: 100 vol%; The binder is polyvinyl alcohol, and the amount of polyvinyl alcohol added is Ca 1-x La 2 / 3x TiO 3 1-3wt% of the ceramic powder mass; The amount of the isobutylene maleic anhydride copolymer added is Ca 1-x La 2 / 3x TiO 3 0.2-0.4% of the mass of ceramic powder; The primary mixing method is ball milling mixing; The secondary mixing method is ultrasonic mixing and / or ball milling mixing.

[0010] Preferably, in step (2): the surfactant comprises at least one of triethanolamine dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and sodium oleate; The amount of surfactant added is Ca 1-x La 2 / 3x TiO 3 0.05wt% to 0.15wt% of the ceramic powder mass; The mechanical stirring speed is 200 to 300 rpm, and the time is 8 to 10 minutes; The standing temperature is 20-30° C. and the standing time is 48-72 hours.

[0011] Preferably, in step (3), the sintering time is 3 to 5 hours.

[0012] Preferably, in step (4), the parameters of the vacuum impregnation include: vacuum degree <100 Pa, impregnation temperature of 110-120° C., and vacuum impregnation time of 2-4 hours; The curing temperature is 110-200°C and the total time is 12-20 hours; Preferably, the curing treatment comprises: firstly keeping the temperature at 110-120° C. for 6-8 hours, then keeping the temperature at 140-150° C. for 4-6 hours, and finally keeping the temperature at 190-200° C. for 4-6 hours.

[0013] In another aspect, the present invention provides a high dielectric constant composite material based on gel casting prepared according to the above preparation method, comprising: a porous and interconnected Ca 1-x La 2 / 3x TiO 3 The ceramic skeleton serves as a matrix, and the resin is distributed in the matrix; the resin is silicon-containing aryl acetylene.

[0014] Preferably, the high dielectric constant composite material based on gel casting has a dielectric constant of 7.2 to 73 (e.g., 9.5 to 60) in the X / Y axis direction, a dielectric loss of 0.0001 to 0.0025, and a thermal conductivity of 0.450 to 1.342 W·m -1 ·K -1 .

[0015] Preferably, the dielectric constant of the high dielectric constant composite material based on gel casting in the Z-axis direction is 7.2 to 73 (for example, 9.5 to 60), the dielectric loss is 0.00045 to 0.0025, and the thermal conductivity is 0.44 to 1.34 W·m -1 ·K -1 .

[0016] The present invention includes the following beneficial effects: 1. The existing ice template method uses the principle of directional crystallization of ice crystals to prepare ceramic skeletons, and the prepared composite materials are anisotropic, which is not conducive to practical application. This time, through the gel injection molding method, the holes constructed are spherical holes, which have an isotropic skeleton structure, and the preparation of uniform composite materials is achieved, which greatly improves the practicality; 2. The PSAE / CLT composite material prepared by the present invention realizes a significant improvement in omnidirectional thermal conductivity and dielectric constant through the constructed isotropic skeleton. Under the same ceramic filling ratio, the composite material obtained by the structure constructed by gel injection molding has a higher dielectric constant. Therefore, in the application scenario of the same dielectric constant, the composite material constructed by gel injection molding has a lower ceramic solid content and a lower density of the composite material, which is of great significance for the lightweight of the device. DETAILED DESCRIPTION

[0017] The present invention is further described below by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0018] In the present disclosure, the high dielectric constant composite material based on gel casting comprises: a porous and interconnected Ca 1- x La 2 / 3x TiO 3 The ceramic skeleton is used as a matrix, and the resin distributed in the matrix; the resin is polydimethylsilane, epoxy resin or silicon-containing aromatic acetylene. 1-x La 2 / 3x TiO 3 The porosity of the ceramic skeleton may be 50 to 90%.

[0019] The method for preparing the composite material based on the combined method of gel casting and resin vacuum infusion is exemplified.

[0020] CaCO 3 ,La 2 O 3 and TiO 2 Press Ca 1-x La 2 / 3x TiO 3 The mixture is mixed in a stoichiometric ratio of (0<x<0.3), deionized water is added as a ball milling medium, and the mixture is ball milled at 250 rpm for 4 hours (12 hours), dried at 150° C. (e.g., 150° C.), and then the powder is calcined at 1100° C. to 1200° C. for 4 hours (e.g., 4 hours) to obtain Ca 1-x La 2 / 3x TiO 3 Ceramic powder.

[0021] The calcined Ca 1-x La 2 / 3x TiO 3 The ceramic powder was added with deionized water as a ball milling medium, and after secondary ball milling at 250 rpm for 3 hours, it was dried at 150°C.

[0022] Ca 1-x La 2 / 3x TiO 3 The ceramic powder is mixed with water at a volume ratio of 10 vol% to 50 vol%, and 2 wt% of polyvinyl alcohol and 0.3 wt% of isobutylene maleic anhydride copolymer are added. After ultrasonic dispersion for 1 hour, the mixture is ball-milled at 250 rpm for 2 hours to obtain a uniformly dispersed ceramic slurry.

[0023] 0.05 wt% to 0.15 wt% of triethanolamine dodecyl sulfate (surfactant) is added to the ceramic slurry, and foaming is performed by mechanical stirring (250 rpm, 10 minutes). The foamed sample is poured into a PTFE mold and allowed to stand for at least 48 hours (e.g., 46 hours) to form a ceramic blank after slow solidification.

[0024] The ceramic blank is sintered at 1300°C to 1400°C. The sintered ceramic skeleton is immersed in silicon-containing aromatic acetylene (PSAE), placed in a vacuum oven, heated to 120°C, and then negative pressure is applied, the vacuum degree is less than 100Pa, and the negative pressure is maintained for 4 hours before returning to normal pressure.

[0025] The resin was cured by keeping the temperature at 140°C for 4 hours, 180°C for 4 hours, and 210°C for 4 hours, and finally cooled to obtain a composite material.

[0026] In the present invention, a network analyzer and a broadband dielectric spectrometer are used to test the dielectric constant and dielectric loss of the high dielectric constant composite material based on gel casting in the X / Y axis direction or the Z axis direction.

[0027] In the present invention, a laser thermal conductivity meter is used to test the thermal conductivity of the high dielectric constant composite material based on gel casting in the X / Y axis direction or the Z axis direction.

[0028] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0029] Embodiment 1: Step (1): CaCO 3 ,La 2 O 3 and TiO 2 By CaTiO 3 The mixture was mixed in a stoichiometric ratio, deionized water was added as a ball milling medium, and after ball milling for 12 hours, the mixture was dried at 150°C, and then the powder was calcined at 1100°C for 4 hours; Step (2): adding deionized water to the calcined powder as a ball milling medium, ball milling for 2 hours, and drying at 150° C. Step (3): the powder was mixed with water at a volume ratio of 10 vol%, and 2 wt % of polyvinyl alcohol and 0.3 wt % of isobutylene maleic anhydride copolymer were added, and ultrasonic dispersion was performed for 1 hour, and ball milling was performed for 2 hours to obtain a uniformly dispersed slurry; Step (4): Add 0.05 wt% of triethanolamine dodecyl sulfate (surfactant) to the slurry and foam it for 10 minutes by mechanical stirring. Pour the foamed sample into a PTFE mold and let it stand for 46 hours to form a green blank after it slowly solidifies; Step (5): sintering the obtained ceramic blank at 1300° C., immersing the sintered ceramic skeleton in silicon-containing aromatic acetylene (PSAE), placing it in a vacuum oven, heating it to 120° C., and then applying negative pressure, with a vacuum degree of less than 100 Pa, and then returning to normal pressure after maintaining the negative pressure for 4 hours; Step (6): curing the resin by keeping the temperature at 140° C. for 4 hours, 180° C. for 4 hours, and 210° C. for 4 hours, and finally cooling to obtain a composite material.

[0030] Embodiment 2: The steps are the same as those in Example 1, except that the volume ratio of the ceramic powder is 20 vol%.

[0031] Embodiment 3: The steps are the same as those in Example 1, except that the volume ratio of the ceramic powder is 30 vol%.

[0032] Embodiment 4: The steps are the same as those in Example 1, except that the volume ratio of the ceramic powder is 40 vol%.

[0033] Embodiment 5: The steps are the same as those in Example 1, except that the volume ratio of the ceramic powder is 50 vol%.

[0034] Embodiment 6: The steps are the same as in Example 1, and the ceramic component is Ca 0.9 La 0.067 TiO 3 , the calcination temperature is 1150℃, the secondary ball milling time is 2h, the volume ratio of ceramic powder is 10vol%, the addition amount of triethanolamine dodecyl sulfate is 0.1wt%, and the green body sintering temperature is 1350℃.

[0035] Embodiment 7: The steps are the same as those of Example 6, except that the volume ratio of the ceramic powder is 20 vol%.

[0036] Embodiment 8: The steps are the same as those of Example 6, except that the volume ratio of the ceramic powder is 30 vol%.

[0037] Embodiment 9: The steps are the same as those of Example 6, except that the volume ratio of the ceramic powder is 40 vol%.

[0038] Embodiment 10: The steps are the same as those of Example 6, except that the volume ratio of the ceramic powder is 50 vol%.

[0039] Embodiment 11: The steps are the same as in Example 1, and the ceramic component is Ca 0.8 La 0.133 TiO 3 , the calcination temperature is 1200℃, the secondary ball milling time is 3h, the volume ratio of ceramic powder is 10vol%, the addition amount of triethanolamine dodecyl sulfate is 0.15wt%, and the green body sintering temperature is 1400℃.

[0040] Embodiment 12: The steps are the same as those of Example 11, except that the volume ratio of the ceramic powder is 20 vol%.

[0041] Embodiment 13: The steps are the same as those of Example 11, except that the volume ratio of the ceramic powder is 30 vol%.

[0042] Embodiment 14: The steps are the same as those of Example 11, except that the volume ratio of the ceramic powder is 40 vol%.

[0043] Embodiment 15: The steps are the same as those of Example 11, except that the volume ratio of the ceramic powder is 50 vol%.

[0044] Embodiment 16: The steps are the same as those in Example 10, except that the ceramic composition is CaTiO 3 .

[0045] Embodiment 17: The steps are the same as those in Example 10, except that the ceramic component is Ca 0.8 La 0.133 TiO 3 .

[0046] Embodiment 18: The steps are the same as those of Example 10, except that the amount of triethanolamine dodecyl sulfate added is 0 wt %.

[0047] Embodiment 19: The steps are the same as those of Example 10, except that the amount of triethanolamine dodecyl sulfate added is 0.05 wt %.

[0048] Embodiment 20: The steps are the same as those of Example 10, except that the amount of triethanolamine dodecyl sulfate added is 0.15 wt %.

[0049] Comparative Example 1: Step (1): CaCO 3 ,La 2 O 3 and TiO 2 By CaTiO 3 The mixture was mixed in a stoichiometric ratio, deionized water was added as a ball milling medium, ball milled for 12 hours, dried at 150°C, and then calcined at 1150°C for 4 hours; Step (2): Add deionized water to the calcined powder as a ball milling medium, perform secondary ball milling for 2 hours, and then dry at 150°C. Step (3): sinter the powder at 1350°C and grind the sintered ceramic powder to D 50 ~5μm. Step (4): compounding the above powder with silicon-containing aromatic acetylene (PSAE) at a volume ratio of 50 vol%, placing it in a vacuum oven, heating it to 120° C., and then applying negative pressure, with a vacuum degree of less than 100 Pa, and maintaining the negative pressure for 4 hours before returning to normal pressure; Step (5): curing the resin by keeping the temperature at 140° C. for 4 hours, 180° C. for 4 hours, and 210° C. for 4 hours, and finally cooling to obtain a composite material.

[0050] Table 1 shows the preparation parameters of the materials in the examples:

[0051] According to Examples 1-15, as the proportion of ceramic powder increases, the dielectric constant and thermal conductivity of the composite material are significantly improved because the dielectric constant and thermal conductivity of the ceramic are higher than those of the resin. Since the dielectric loss of the ceramic itself is lower than that of the resin, the dielectric loss of the composite material increases with the increase of the ceramic filling ratio. When the ceramic filling ratio reaches 50 vol%, the dielectric constant and thermal conductivity of the composite material are the highest, and the dielectric loss is the lowest. Therefore, Examples 5, 10, and 15 have achieved relatively good electrical and thermal properties.

[0052] The foaming agent is mainly used to reduce the surface energy of the bubble so that it can exist relatively stably. Comparative Example 5, Example 10, Example 15 and Example 18, Example 19 and Example 20, as the amount of foaming agent increases, the surface number of bubbles that can exist stably increases, the porosity of the ceramic skeleton formed increases, the resin content increases after impregnation, and the dielectric constant of the composite material is on a downward trend. Therefore, it is necessary to reduce the amount of foaming agent used to prepare a composite material with a high dielectric constant, but too low an amount of use will cause the number of bubbles to decrease, produce closed pores, hinder the filling of resin, and reduce the density of the composite material. Therefore, although Example 5 obtains a higher dielectric constant, its dielectric loss is significantly increased, and the thermal conductivity is low due to the scattering of the cavity. In contrast, Example 10 obtains the best dielectric and thermal conductivity.

[0053] Comparing the data of the X / Y axis direction and the Z axis direction of all the examples, it can be seen that there is no obvious difference in the performance of the material in each direction, and the surface of the material is homogeneous. Compared with the 0-3 type composite material (Comparative Example 1), under the same ceramic filling ratio (Example 10), the dielectric constant of the composite material prepared by the present invention is increased by about 3 times, and the thermal conductivity is increased by more than 40%.

[0054] Comparing Example 10, Example 16 and Example 17, as the La content in the ceramic component increases, on the one hand, the dielectric constant and dielectric loss of the ceramic itself gradually decrease, so that the dielectric constant and dielectric loss of the composite material show a downward trend. 0.9 La 0.067 TiO 3 When the dielectric constant is relatively high, the composite material achieves relatively high dielectric constant and low dielectric loss.

[0055] Table 2 shows the performance parameters of the materials prepared by the present invention:

Claims

1. A method for preparing a high dielectric constant composite material based on gel casting, It is characterized in that include: (1) Ca 1-x La 2 / 3x TiO 3 The ceramic powder and water are mixed once, and then a binder and an isobutylene maleic anhydride copolymer are added and mixed twice to obtain a ceramic slurry; wherein 0<x<0.3; (2) adding a surfactant to the obtained ceramic slurry, foaming the slurry by mechanical stirring, and then pouring the slurry into a mold and allowing it to stand for solidification to obtain a ceramic blank; (3) sintering the obtained ceramic blank at 1300° C. to 1400° C. to obtain a porous ceramic skeleton; (4) Immersing the obtained porous ceramic skeleton in a resin for vacuum impregnation, and then curing it to obtain the high dielectric constant composite material based on gel casting; preferably, the resin is selected from at least one of silicon-containing aryl acetylene, polydimethylsilane and epoxy resin.

2. The preparation method according to claim 1, It is characterized in that The Ca 1-x La 2 / 3x TiO 3 The particle size of the ceramic powder is 1 to 2 μm; The Ca 1-x La 2 / 3x TiO 3 The preparation process of ceramic powder includes: 3 ,La 2 O 3 and TiO 2 Press Ca 1-x La 2 / 3x TiO 3 The stoichiometric ratio is weighed and mixed, and then calcined at 1100°C to 1200°C for 2 to 4 hours to obtain the Ca 1-x La 2 / 3x TiO 3 Ceramic powder.

3. The preparation method according to claim 2, It is characterized in that Ca 1-x La 2 / 3x TiO 3 The ceramic powder is added with deionized water as a ball milling medium, and after secondary ball milling at 250-300 rpm for 2-4 hours, it is dried at 150°C.

4. The preparation method according to claim 1, It is characterized in that In step (1): the Ca 1-x La 2 / 3x TiO 3 The volume ratio of ceramic powder to water is 10 vol% to 50 vol%: 100 vol%; The binder is polyvinyl alcohol, and the amount of polyvinyl alcohol added is Ca 1-x La 2 / 3x TiO 3 1-3wt% of the ceramic powder mass; The amount of the isobutylene maleic anhydride copolymer added is Ca 1-x La 2 / 3x TiO 3 0.2-0.4% of the mass of ceramic powder; The primary mixing method is ball milling mixing; The secondary mixing method is ultrasonic mixing and / or ball milling mixing.

5. The preparation method according to claim 1, It is characterized in that In step (2): the surfactant comprises at least one of triethanolamine dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and sodium oleate; The amount of surfactant added is Ca 1-x La 2 / 3x TiO 3 0.05wt% to 0.15wt% of the ceramic powder mass; The mechanical stirring speed is 200 to 300 rpm, and the time is 8 to 10 minutes; The standing temperature is 20-30° C. and the standing time is 48-72 hours.

6. The preparation method according to claim 1, It is characterized in that In step (3): the sintering time is 3 to 5 hours.

7. The preparation method according to claim 1, It is characterized in that In step (4), the parameters of the vacuum impregnation include: vacuum degree <100 Pa, impregnation temperature of 110-120° C., and vacuum impregnation time of 2-4 hours; The curing temperature is 110-200°C and the total time is 12-20 hours; Preferably, the curing treatment comprises: firstly keeping the temperature at 110-120° C. for 6-8 hours, then keeping the temperature at 140-150° C. for 4-6 hours, and finally keeping the temperature at 190-200° C. for 4-6 hours.

8. A high dielectric constant composite material based on gel casting prepared according to the preparation method according to any one of claims 1 to 8, It is characterized in that include: Porous and interconnected Ca 1-x La 2 / 3x TiO 3 The ceramic skeleton is used as a matrix, and the resin is distributed in the matrix; the resin is selected from at least one of silicon-containing aryl acetylene, polydimethylsilane and epoxy resin.

9. The high dielectric constant composite material based on gel casting according to claim 8, It is characterized in that The high dielectric constant composite material based on gel casting has a dielectric constant of 7.2 to 73 in the X / Y axis direction, a dielectric loss of 0.0001 to 0.0025, and a thermal conductivity of 0.450 to 1.342 W·m -1 ·K -1 ; The high dielectric constant composite material based on gel casting has a dielectric constant of 7.2 to 73 in the Z-axis direction, a dielectric loss of 0.00045 to 0.0025, and a thermal conductivity of 0.44 to 1.34 W·m -1 ·K -1 .

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