Modified barium titanate foam ceramic/thermosetting resin composites and preparation method thereof

Abstract

In a method of preparing a modified barium titanate foam ceramic/thermosetting resin composite material, an organic additive is used as an auxiliary; deionized water is used as a solvent; nanometer barium titanate is used as a ceramic raw material; and these components are mixed and grounded to form a slurry. A pre-treated polymer sponge is impregnated in the slurry for slurry coating treatment and a barium titanate foam ceramic is obtained after drying and sintering. Then, through dopamine modification, micrometer/nanometer silver is deposited in situ on a skeleton surface. A resin, which is in the molten state and is thermosettable, is immersed into pores of the modified barium titanate foam ceramic, and the modified barium titanate foam ceramic/thermosetting resin composite material is obtained after a thermosetting treatment.

Claims

1. A preparation method of modified barium titanate foam ceramic/thermosetting resin composites, comprising the following steps: (1) by weight, 100 parts of a nano barium titanate and 30 to 120 parts of an aqueous solution of an organic binder having a concentration of 1 to 15 wt % are ground to obtain a slurry (A); 10 to 80 parts of an aqueous solution of an organic rheological agent having a concentration of 0.5 to 3 wt % are added into the slurry (A) to form a first mixture, and the first mixture is ground to obtain a slurry (B); 20 to 80 parts of an aqueous solution of an organic dispersant having a concentration of 0.5 to 3 wt % are added into the slurry (B) to form a second mixture, and the second mixture is ground to obtain a slurry (C); said organic binder is one or more selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose and methyl cellulose; said organic rheological agent is one or more selected from the group consisting of carboxymethyl cellulose and hydroxyhexyl cellulose; said organic dispersant is one or more selected from the group consisting of polyacrylamide, polyethyleneimine and polyacrylic acid amine; (2) a polymer sponge having 15 to 35 pores per inch is soaked in an aqueous solution of sodium hydroxide having a concentration of 5 to 20 wt %, and then heated up to 50 to 75 C. and kept at that temperature for 2 to 6 h, the polymer sponge is taken out and washed with deionized water, followed by drying to obtain a polymer sponge (D); at room temperature, the polymer sponge (D) is soaked in an aqueous surfactant solution having a concentration of 0.5 to 3 wt % for 2 to 6 h, then taken out to remove an excess surfactant, after being dried at 40 to 80 C., a pretreated polymer sponge (E) is obtained; a polymer material of said polymer sponge is selected from the group consisting of polyurethane, polystyrene, and polyvinyl chloride; said surfactant is one or more selected from the group consisting of carboxymethyl cellulose and polyethyleneimine; (3) said pretreated polymer sponge (E) is soaked in the slurry (C) prepared in step (1) for 1 to 10 min at room temperature, after a draining process, an excess slurry in the pretreated polymer sponge (E) is removed by extrusion, and the pretreated polymer sponge (E) is dried at 40 to 80 C.; repeating the draining process and drying for 1 to 7 times, a green body of foam ceramics based on barium titanate is obtained; (4) said green body of foam ceramics based on barium titanate prepared in step (3) is heated from room temperature to 100-300 C. at a rate of 0.5-5 C./min, and then heated to 500-700 C. at a rate of 0.5-5 C./min and maintained at that temperature for 0.5-2 h, followed by continuously heating to 1000-1500 C. at a rate of 2-10 C./min and keeping at that temperature for 1-5 h, after cooling to room temperature, barium titanate foam ceramics are obtained; (5) using a buffering agent or a buffer, water and dopamine hydrochloride to prepare a dopamine aqueous solution having a concentration of 0.5-10 g/L; of which a pH value is adjusted to 8.3-8.8 with an alkali to obtain a solution (F); the barium titanate foam ceramics prepared in step (4) are soaked in the solution (F) and kept at room temperature for 1 to 24 h, followed by washing with deionized water and drying successively, to obtain dopamine-modified barium titanate foam ceramics; (6) by volume, 4 to 20 parts of a stabilizer aqueous solution having a concentration of 0.1-1 wt % are added into 100 parts of an ammoniacal silver solution having a concentration of 0.03-0.3 mol/L to form a third mixture, the third mixture is uniformly mixed to obtain a solution (G); the dopamine-modified barium titanate foam ceramics prepared in step (5) are soaked in the solution (G) and kept at room temperature for 0.5-24 h to obtain barium titanate foam ceramics loaded with nano silver, into which 50-300 parts of a reducing agent aqueous solution having a concentration of 1-30 g/L are added and kept at room temperature for 0.1-5 h, followed by washing with deionized water and drying successively, to obtain modified barium titanate foam ceramics; said stabilizer is one or more selected from the group consisting of polyvinylpyrrolidone and sodium alginate; said reducing agent is one or more selected from the group consisting of hydrazine hydrate, sodium citrate, sodium borohydride, glucose and ascorbic acid; (7) a molten and thermocurable resin is poured into the modified barium titanate foam ceramics prepared in step (6), after pores of the modified barium titanate foam ceramics are fully permeated with the resin, thermocuring and postprocessing are conducted, and the modified barium titanate foam ceramic/thermosetting resin composites are obtained.

2. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 1, wherein an average diameter of said nano barium titanate is less than or equal to 100 nm.

3. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 1, wherein said buffering agent or buffer is Tris-HCl, or disodium hydrogen phosphate-sodium dihydrogen phosphate buffer.

4. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 1, wherein said alkali is sodium hydroxide, or an aqueous ammonia solution.

5. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 1, wherein the process conditions of thermocuring and postprocessing are selected based on the thermocurable resin being used.

6. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 1, wherein said thermosetting resin is a resin which can be self-cured by heat, or a resin system consisting of a curing agent and a resin which cannot be self-cured by heat.

7. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 6, wherein said resin which can be self-cured by heat is one or more selected from the group consisting of bismaleimide resin and cyanate ester resin.

8. The preparation method of modified barium titanate foam ceramic/thermosetting resin composites according to claim 6, wherein said resin which cannot be self-cured by heat is an epoxy resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is X-ray diffraction patterns of barium titanate foam ceramic prepared in EMBODIMENT 1 of this invention, barium titanate foam ceramic loaded with nano silver prepared in EMBODIMENT 2, and barium titanate foam ceramic loaded with micro/nano silver prepared in EMBODIMENT 3.

(2) FIG. 2 is scanning electron microscope images (50,000) of barium titanate foam ceramic, dopamine-modified barium titanate foam ceramic and barium titanate foam ceramic loaded with nano silver prepared in EMBODIMENT 1 of this invention, barium titanate foam ceramic loaded with nano silver prepared in EMBODIMENT 2, and barium titanate foam ceramics loaded with micro/nano silver prepared in EMBODIMENTS 3 and 4.

(3) FIG. 3 is plots reflecting frequency dependence of dielectric constant of modified barium titanate foam ceramic/cyanate ester resin composites prepared in EMBODIMENTS 3 and 4 of this invention, and barium titanate foam ceramic/cyanate ester resin composite prepared in CONTROL EXAMPLE 1.

(4) FIG. 4 gives plots reflecting frequency dependence of dielectric loss of modified barium titanate foam ceramic/cyanate ester resin composites prepared in EMBODIMENTS 3 and 4, and barium titanate foam ceramic/cyanate ester resin composite prepared in CONTROL EXAMPLE 1.

(5) FIG. 5 is plots reflecting frequency dependence of AC conductivities of modified barium titanate foam ceramic/cyanate ester resin composites prepared in EMBODIMENTS 3 and 4, and barium titanate foam ceramic/cyanate ester resin composite prepared in CONTROL EXAMPLE 1.

DETAILED DESCRIPTION OF THE INVENTION

(6) The technical solution of this invention is further described by combining concrete drawings, embodiments and control examples as follows.

Embodiment 1

(7) 1) Preparation of Slurries

(8) 20 g of barium titanate (the average diameter is 100 nm) and 10 g of aqueous polyvinyl alcohol solution with a concentration of 10 wt % were sufficiently ground to obtain a slurry A; 5 g of aqueous carboxymethyl cellulose solution with a concentration of 2 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 10 g of aqueous polyacrylamide solution with a concentration of 1 wt % was added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(9) 2) Treatment of Polyurethane Sponge

(10) The polyurethane sponge having a specification of 25 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 15 wt %, and then heated up to 60 C. and keeping at that temperature for 3.5 h; the polyurethane sponge was taken out and washed with deionized water, followed by drying to obtain a polyurethane sponge D; at room temperature, the polyurethane sponge D was soaked in an aqueous carboxymethyl cellulose solution with a concentration of 1 wt % for 3 h; then took out and removed the excess carboxymethyl cellulose solution, after dried at 60 C., a pretreated polyurethane sponge E was obtained.

(11) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(12) The pretreated polyurethane sponge E was soaked in the slurry C prepared in step 1) and maintained for 5 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 40 C.; repeating processes of hanging pulp and drying for 4 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(13) 4) Preparation of Barium Titanate Foam Ceramics

(14) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 200 C. at a rate of 2 C./min, and then raised to 600 C. at a rate of 1 C./min and maintained at 600 C. for 1 h; followed by continuously heating to 1200 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained. Its X-ray diffraction pattern and scanning electron microscope image are shown in FIGS. 1 and 2, respectively.

(15) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(16) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 24 h, followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics. Its scanning electron microscope image is shown in FIG. 2.

(17) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(18) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 2 h to obtain barium titanate foam ceramics loaded with nano silver, its scanning electron microscope image is shown in FIG. 2; then, 100 mL of aqueous sodium borohydride solution with a concentration of 1 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(19) 7) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(20) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 160 C. in an oven; 2,2-bis(4-cyanatophenyl)propane (bisphenol A cyanate ester) was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 2

(21) 1) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(22) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) of EMBODIMENT 1 were soaked in solution G and kept at room temperature for 24 h to obtain barium titanate foam ceramics loaded with nano silver, its X-ray diffraction pattern and scanning electron microscope image are shown in FIGS. 1 and 2, respectively; then, 100 mL of aqueous glucose solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 0.1 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(23) 2) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(24) The modified barium titanate foam ceramics prepared in step 1) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 3

(25) 1) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(26) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) of EMBODIMENT 1 were soaked in solution G and kept at room temperature for 1 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous glucose solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 1.5 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics. Its X-ray diffraction pattern and scanning electron microscope image are shown in FIGS. 1 and 2, respectively.

(27) 2) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(28) The modified barium titanate foam ceramics prepared in step 1) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained. Its plots reflecting frequency dependence of dielectric constant, dielectric loss and AC conductivity are shown in FIGS. 3, 4 and 5, respectively.

(29) FIG. 1 displays X-ray diffraction patterns of barium titanate foam ceramic prepared in EMBODIMENT 1 of this invention, barium titanate foam ceramic loaded with nano silver prepared in EMBODIMENT 2 and barium titanate foam ceramic loaded with micro/nano silver prepared in EMBODIMENT 3. It can be seen that nano barium titanate exhibits significant diffraction peaks at 22.1, 31.6, 38.9, 45.2, 50.8, 56.1, 65.8, 70.2, 74.6 and 78.9, corresponding to crystal planes of (100), (110), (111), (002)/(200), (210), (211), (220), (221), (310) and (113) (JCPDS No. 5-0626), respectively. Whether 20 at 45.2 is split into two diffraction peaks or not is an effective evidence for judging the crystalline form of barium titanate. Since the barium titanate foam ceramics prepared in EMBODIMENT 1 exhibit a split peak at 45.2, it can be judged that the barium titanate foam ceramic prepared in EMBODIMENT 1 contains cubic and tetragonal phases. In addition, no other impurity peaks are found. Compared to barium titanate foam ceramics (EMBODIMENT 1), there are four significant diffraction peaks exhibiting at 38.1, 44.3, 64.5 and 77.4 after loaded with micro/nano silver, corresponding to crystal planes of (111), (200), (220) and (311) (JCPDS No. 04-0783), respectively. It can be judged that the particles loaded in EMBODIMENTS 2 and 3 are face-centered cubic silver. At the same time, the diffraction peak of barium titanate foam ceramics loaded with micro/nano silver is enhanced by further reduction using glucose solution.

Embodiment 4

(30) 1) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(31) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) of EMBODIMENT 1 were soaked in solution G and kept at room temperature for 1 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous glucose solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics. Its scanning electron microscope image is shown in FIG. 2.

(32) 2) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(33) The modified barium titanate foam ceramics prepared in step 1) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained. Its plots reflecting frequency dependence of dielectric constant, dielectric loss and AC conductivity are shown in FIGS. 3, 4 and 5, respectively.

(34) FIG. 2 gives scanning electron microscope images of barium titanate foam ceramic, dopamine-modified barium titanate foam ceramic and barium titanate foam ceramic loaded with nano silver prepared in EMBODIMENT 1 of this invention, barium titanate foam ceramic loaded with nano silver prepared in EMBODIMENT 2, and barium titanate foam ceramics loaded with micro/nano silver prepared in EMBODIMENTS 3 and 4. It can be seen that the barium titanate foam ceramic (EMBODIMENT 1) has a coating layer on the surface of barium titanate foam ceramic (EMBODIMENT 1) after treated with dopamine. After dopamine-modified barium titanate foam ceramic reacts with the ammoniacal silver solution, fine particles appear on the surface thereof, and the size and number of the particles on the surface increase with the extension of reaction time, that is the mass fraction of the deposition of silver increases (EMBODIMENT 1 and EMBODIMENT 2). After further reduction using glucose, the particle size of Ag particles translates from nanometer to micron, moreover, the silver particles become closer with the extension of reaction time (EMBODIMENT 3 and EMBODIMENT 4). At this time, by a careful observation, it can be found that the coating of sliver contains both nano and micron sizes, and these two sizes of silver particles are mosaic and accumulate with each other (EMBODIMENT 3).

(35) Based on above mentioned of FIGS. 1 and 2, barium titanate foam ceramic prepared in this invention is a kind of pure barium titanate foam ceramic with a single chemical composition, and there is no other impurity; after loaded with micro/nano silver, the skeleton of barium titanate foam ceramic is coated with Ag particles, this changes the skeleton structure of the original barium titanate foam ceramic.

(36) CONTROL EXAMPLE 1, preparation of barium titanate foam ceramic/cyanate ester resin composite: the barium titanate foam ceramic prepared in step 4) of EMBODIMENT 1 was placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, barium titanate foam ceramic/cyanate ester resin composite was obtained. Its plots reflecting frequency dependence of dielectric constant, dielectric loss and AC conductivity are shown in FIGS. 3, 4 and 5, respectively.

(37) FIG. 3 is plots reflecting frequency dependence of dielectric constant of modified barium titanate foam ceramic/cyanate ester resin composites prepared in EMBODIMENTS 3 and 4 of this invention, and barium titanate foam ceramic/cyanate ester resin composite prepared in CONTROL EXAMPLE 1. As can be seen, after barium titanate foam ceramic loaded with micro/nano silver, at 100 Hz, the dielectric constant of the resultant composite increases from 83.3 (CONTROL EXAMPLE 1) to 162.4 (EMBODIMENT 3), moreover, the dielectric constant of the composite shows excellent frequency stability; with continuous extension of the reduction time of silver, the dielectric constant of composite reaches 9618.1 (EMBODIMENT 4).

(38) FIG. 4 gives plots reflecting frequency dependence of dielectric loss of modified barium titanate foam ceramic/cyanate ester resin composites prepared in EMBODIMENTS 3 and 4, and barium titanate foam ceramic/cyanate ester resin composite prepared in CONTROL EXAMPLE 1. As can be seen, loading micro/nano silver on barium titanate foam ceramic (EMBODIMENT 3) makes the composite has significantly reduced dielectric loss. For example, at 100 Hz, the dielectric loss of barium titanate foam ceramic/cyanate ester resin composite is 0.21 (EMBODIMENT 3), but that of modified barium titanate foam ceramic/cyanate ester resin composite is only 0.01 (EMBODIMENT 4). However, when the reduction time of the silver is extended, its dielectric loss reaches 5400 (EMBODIMENT 4).

(39) FIG. 5 is plots reflecting frequency dependence of AC conductivities of modified barium titanate foam ceramic/cyanate ester resin composites prepared in EMBODIMENTS 3 and 4, and barium titanate foam ceramic/cyanate ester resin composite prepared in CONTROL EXAMPLE 1. As can be seen in this figure, the AC conductivities of modified barium titanate foam ceramic/cyanate ester resin composites (EMBODIMENT 3 and EMBODIMENT 4) are higher than that of barium titanate foam ceramic/cyanate ester resin composite (CONTROL EXAMPLE 1), this should be attributed to the loading of micro/nano silver. In addition, the electric conductivity of the composite prepared in EMBODIMENT 4 has a typical conductor characteristic, which is mainly attributed to the various size and number of Ag loading. Therefore, compared with barium titanate foam ceramic/cyanate ester resin composite, modified barium titanate foam ceramic/cyanate ester resin composite has outstanding dielectric properties, which is originated from the change of composite structure induced by the loading with Ag.

(40) On the basis of FIGS. 3, 4 and 5, it can be seen that compared with barium titanate foam ceramic/cyanate ester resin composite, with the same content of barium titanate ceramic, the composite based on barium titanate foam ceramic loaded with micro/nano silver (before percolation threshold) shows excellent frequency stability, higher dielectric constant and low dielectric loss. This is because the skeleton of foam ceramics is coated with micro/nano silver, improving the interface between ceramic and resin; and because the sizes of coated silver contain nano (which is not conductive) and micron sizes, and these two sizes of silver particles are mosaic and accumulate with each other, this is helpful to reduce the contact between conductive particles and cause conduction loss, so a composite with low dielectric loss was obtained.

Embodiment 5

(41) 1) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(42) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) of EMBODIMENT 1 were soaked in solution G and kept at room temperature for 0.5 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous glucose solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 1 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(43) 2) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(44) The modified barium titanate foam ceramics prepared in step 1) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 6

(45) 1) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(46) 2 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % and 3 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % were added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.03 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) of EMBODIMENT 1 were soaked in solution G and kept at room temperature for 24 h to obtain barium titanate foam ceramics loaded with nano silver; then, 150 mL of aqueous sodium citrate solution with a concentration of 5 g/L was added into the solution G and kept at room temperature for 1 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(47) 2) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(48) The modified barium titanate foam ceramics prepared in step 1) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 7

(49) 1) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(50) 5 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % were added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) of EMBODIMENT 1 were soaked in solution G and kept at room temperature for 24 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous sodium borohydride solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(51) 2) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(52) The modified barium titanate foam ceramics prepared in step 1) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 8

(53) 1) Preparation of Barium Titanate Foam Ceramics

(54) The green body of barium titanate foam ceramics prepared in EMBODIMENT 1 was heated from room temperature to 200 C. at a rate of 2 C./min, and then raised to 600 C. at a rate of 1 C./min and maintained at 600 C. for 1 h; followed by continuously heating to 1300 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(55) 2) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(56) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 0.5 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 1) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(57) 3) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(58) 10 mL of aqueous sodium alginate solution with a concentration of 0.1 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.12 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 2) were soaked in solution G and kept at room temperature for 24 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous ascorbic acid solution with a concentration of 1 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(59) 4) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(60) The modified barium titanate foam ceramics prepared in step 3) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 9

(61) 1) Preparation of Green Body of Barium Titanate Foam Ceramics

(62) The pretreated polyurethane sponge E in EMBODIMENT 1 was soaked in the slurry C (EMBODIMENT 1) and maintained for 5 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 40 C.; repeating processes of hanging pulp and drying for 3 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(63) 2) Preparation of Barium Titanate Foam Ceramics

(64) The green body of barium titanate foam ceramics prepared in step 1) was heated from room temperature to 200 C. at a rate of 2 C./min, and then raised to 600 C. at a rate of 1 C./min and maintained at 600 C. for 1 h; followed by continuously heating to 1200 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(65) 3) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(66) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 2) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(67) 4) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(68) 10 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.1 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.3 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 3) were soaked in solution G and kept at room temperature for 0.5 h to obtain barium titanate foam ceramics loaded with nano silver; then, 25 mL of aqueous hydrazine hydrate solution with a concentration of 30 g/L was added into the solution G and kept at room temperature for 5 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(69) 5) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(70) The modified barium titanate foam ceramics prepared in step 4) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 10

(71) 1) Preparation of Green Body of Barium Titanate Foam Ceramics

(72) The pretreated polyurethane sponge E in EMBODIMENT 1 was soaked in the slurry C (EMBODIMENT 1) and maintained for 5 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 40 C.; repeating processes of hanging pulp and drying for 5 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(73) 2) Preparation of Barium Titanate Foam Ceramics

(74) The green body of barium titanate foam ceramics prepared in step 1) was heated from room temperature to 200 C. at a rate of 2 C./min, and then raised to 600 C. at a rate of 1 C./min and maintained at 600 C. for 1 h; followed by continuously heating to 1200 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(75) 3) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(76) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 2) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(77) 4) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(78) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 3) were soaked in solution G and kept at room temperature for 12 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous glucose solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 1.5 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(79) 5) Preparation of Modified Barium Titanate Foam Ceramic/Bismaleimide/Cyanate Ester Resin Composite

(80) The modified barium titanate foam ceramics prepared in step 4) were placed in a mold and preheated at 140 C. in an oven; 2,2-diallyl bisphenol A, N, N-4,4-diphenylmethane bismaleimide and bisphenol A cyanate ester (mass ratio of 18:27:5) were blended with stirring at 140 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 140 C. for 0.5 h; followed by curing and postcuring using the procedures of 150 C./2 h+180 C./2 h+200 C./2 h, and 220 C./8 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/bismaleimide/cyanate ester resin composite was obtained.

Embodiment 11

(81) 1) Preparation of Barium Titanate Foam Ceramics

(82) The green body of barium titanate foam ceramics prepared in EMBODIMENT 1 was heated from room temperature to 200 C. at a rate of 0.5 C./min, and then raised to 600 C. at a rate of 1 C./min and maintained at 600 C. for 2 h; followed by continuously heating to 1200 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(83) 2) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(84) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with aqueous ammonia solution; barium titanate foam ceramics prepared in step 1) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(85) 3) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(86) 5 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.12 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 2) were soaked in solution G and kept at room temperature for 0.5 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous sodium borohydride solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(87) 4) Preparation of Modified Barium Titanate Foam Ceramic/Bismaleimide Resin Composite

(88) The modified barium titanate foam ceramics prepared in step 3) were placed in a mold and preheated at 130 C. in an oven; 2,2-diallyl bisphenol A and N, N-4,4-diphenylmethane bismaleimide (mass ratio of 3:7) were blended with stirring at 130 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 130 C. for 0.5 h; followed by curing and postcuring using the procedures of 150 C./2 h+180 C./2 h+200 C./2 h, and 220 C./8 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/bismaleimide resin composite was obtained.

Embodiment 12

(89) 1) Preparation of Slurries

(90) 20 g of barium titanate (the average diameter is 100 nm) and 6 g of aqueous methyl cellulose solution with a concentration of 15 wt % were sufficiently ground to obtain a slurry A; 16 g of aqueous carboxymethyl cellulose solution with a concentration of 0.5 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 10 g of aqueous polyacrylamide solution with a concentration of 0.5 wt % and 6 g of aqueous polyacrylic acid amine solution with a concentration of 0.5 wt % were added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(91) 2) Treatment of Polyurethane Sponge

(92) The polyurethane sponge having a specification of 25 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 10 wt %, and then heated up to 60 C. and keeping at that temperature for 3.5 h; the polyurethane sponge was taken out and washed with deionized water, followed by drying to obtain a polyurethane sponge D; at room temperature, the polyurethane sponge D was soaked in an aqueous polyethyleneimine solution with a concentration of 0.5 wt % for 3 h; then took out and removed the excess polyethyleneimine solution, after dried at 40 C., a pretreated polyurethane sponge E was obtained.

(93) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(94) The pretreated polyurethane sponge E was soaked in the slurry C prepared in step 1) and maintained for 5 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 80 C.; repeating processes of hanging pulp and drying for 4 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(95) 4) Preparation of Barium Titanate Foam Ceramics

(96) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 200 C. at a rate of 5 C./min, and then raised to 600 C. at a rate of 5 C./min and maintained at 600 C. for 0.5 h; followed by continuously heating to 1000 C. at a rate of 10 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(97) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(98) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 5 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(99) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(100) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 2 h to obtain barium titanate foam ceramics loaded with nano silver; then, 50 mL of aqueous sodium citrate solution with a concentration of 10 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(101) 7) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(102) The modified barium titanate foam ceramics prepared in step 7) were placed in a mold and preheated at 160 C. in an oven; bisphenol A cyanate ester was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 13

(103) 1) Preparation of Slurries

(104) 20 g of barium titanate (the average diameter is 30 nm) and 10 g of aqueous carboxymethyl cellulose solution with a concentration of 1 wt % and 10 g of aqueous methyl cellulose solution with a concentration of 1 wt % were sufficiently ground to obtain a slurry A; 2 g of aqueous carboxymethyl cellulose solution with a concentration of 2 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 10 g of aqueous polyacrylamide solution with a concentration of 1 wt % and 6 g of aqueous polyethyleneimine solution with a concentration of 1 wt % were added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(105) 2) Treatment of Polyurethane Sponge

(106) The polyurethane sponge having a specification of 35 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 15 wt %, and then heated up to 60 C. and keeping at that temperature for 3.5 h; the polyurethane sponge was taken out and washed with deionized water, followed by drying to obtain a polyurethane sponge D; at room temperature, the polyurethane sponge D was soaked in a mixed solution by equal volume of aqueous carboxymethyl cellulose solution with a concentration of 1 wt % and aqueous polyethyleneimine solution with a concentration of 1 wt % for 3 h; then took out and removed the excess mixed solution of carboxymethyl cellulose solution and polyethyleneimine solution, after dried at 60 C., a pretreated polyurethane sponge E was obtained.

(107) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(108) The pretreated polyurethane sponge E was soaked in the slurry C prepared in step 1) and maintained for 10 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 50 C.; repeating processes of hanging pulp and drying for 4 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(109) 4) Preparation of Barium Titanate Foam Ceramics

(110) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 200 C. at a rate of 2 C./min, and then raised to 600 C. at a rate of 1 C./min and maintained at 600 C. for 1 h; followed by continuously heating to 1000 C. at a rate of 2 C./min and keeping at that temperature for 1 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(111) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(112) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(113) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(114) 5 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.12 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 2 h to obtain barium titanate foam ceramics loaded with nano silver; then, 50 mL of aqueous sodium citrate solution with a concentration of 10 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(115) 7) Preparation of Modified Barium Titanate Foam Ceramic/Bismaleimide Resin Composite

(116) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 130 C. in an oven; 2,2-diallyl bisphenol A and N, N-4,4-diphenylmethane bismaleimide (mass ratio of 3:7) were blended with stirring at 130 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 130 C. for 0.5 h; followed by curing and postcuring using the procedures of 150 C./2 h+180 C./2 h+200 C./2 h, and 220 C./8 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/bismaleimide resin composite was obtained.

Embodiment 14

(117) 1) Preparation of Slurries

(118) 20 g of barium titanate (the average diameter is 50 nm) and 6 g of aqueous polyvinyl alcohol solution with a concentration of 10 wt % and 10 g of aqueous carboxymethyl cellulose solution with a concentration of 1 wt % were sufficiently ground to obtain a slurry A; 5 g of aqueous carboxymethyl cellulose solution with a concentration of 2 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 5 g of aqueous polyacrylamide solution with a concentration of 1 wt % and 5 g of aqueous polyethyleneimine solution with a concentration of 1 wt % were added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(119) 2) Treatment of Polyvinyl Chloride Sponge

(120) The polyvinyl chloride sponge having a specification of 15 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 20 wt %, and then heated up to 60 C. and keeping at that temperature for 2 h; the polyvinyl chloride sponge was taken out and washed with deionized water, followed by drying to obtain a polyvinyl chloride D; at room temperature, the polyvinyl chloride D was soaked in an aqueous carboxymethyl cellulose solution with a concentration of 0.5 wt % for 3 h; then took out and removed the excess carboxymethyl cellulose solution, after dried at 60 C., the pretreated polyvinyl chloride sponge E was obtained.

(121) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(122) The pretreated polyvinyl chloride sponge E was soaked in the slurry C prepared in step 1) and maintained for 5 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 40 C.; repeating processes of hanging pulp and drying for 4 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(123) 4) Preparation of Barium Titanate Foam Ceramics

(124) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 200 C. at a rate of 0.5 C./min, and then raised to 600 C. at a rate of 5 C./min and maintained at 600 C. for 2 h; followed by continuously heating to 1200 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(125) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(126) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 0.5 g/L, and then solution F was obtained by adjusting pH to 8.5 with aqueous ammonia solution; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 12 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(127) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(128) 10 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.1 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.3 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 0.5 h to obtain barium titanate foam ceramics loaded with nano silver; then, 25 mL of aqueous hydrazine hydrate solution with a concentration of 30 g/L was added into the solution G and kept at room temperature for 5 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(129) 7) Preparation of Modified Barium Titanate Foam Ceramic/Bismaleimide/Cyanate Ester Resin Composite

(130) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 140 C. in an oven; 2,2-diallyl bisphenol A, N, N-4,4-diphenylmethane bismaleimide and bisphenol A cyanate ester (mass ratio of 18:27:5) were blended with stirring at 140 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 140 C. for 0.5 h; followed by curing and postcuring using the procedures of 150 C./2 h+180 C./2 h+200 C./2 h, and 220 C./8 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/bismaleimide/cyanate ester resin composite was obtained.

Embodiment 15

(131) 1) Preparation of Slurries

(132) 20 g of barium titanate (the average diameter is 30 nm) and 24 g of aqueous methyl cellulose solution with a concentration of 1 wt % were sufficiently ground to obtain a slurry A; 4 g of aqueous hydroxyhexyl cellulose solution with a concentration of 3 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 16 g of aqueous polyethyleneimine solution with a concentration of 0.5 wt % was added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(133) 2) Treatment of Polystyrene Sponge

(134) The polystyrene sponge having a specification of 25 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 5 wt %, and then heated up to 75 C. and keeping at that temperature for 6 h; the polystyrene sponge was taken out and washed with deionized water, followed by drying to obtain a polystyrene sponge D; at room temperature, the polystyrene sponge D was soaked in an aqueous polyethyleneimine solution with a concentration of 3 wt % for 2 h; then took out and removed the excess polyethyleneimine solution, after dried at 60 C., the pretreated polystyrene sponge E was obtained.

(135) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(136) The pretreated polystyrene sponge E was soaked in the slurry C prepared in step 1) and maintained for 10 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 50 C.; repeating processes of hanging pulp and drying for 7 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(137) 4) Preparation of Barium Titanate Foam Ceramics

(138) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 200 C. at a rate of 0.5 C./min, and then raised to 600 C. at a rate of 5 C./min and maintained at 600 C. for 2 h; followed by continuously heating to 1000 C. at a rate of 10 C./min and keeping at that temperature for 5 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(139) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(140) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 12 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(141) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(142) 5 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 24 h to obtain barium titanate foam ceramics loaded with nano silver; then, 100 mL of aqueous sodium borohydride solution with a concentration of 20 g/L was added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(143) 7) Preparation of Modified Barium Titanate Foam Ceramic/Epoxy/Cyanate Ester Resin Composite

(144) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 150 C. in an oven; epoxy (commercial name: E-51) and bisphenol A cyanate ester (mass ratio of 1:9) were blended with siring at 150 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 150 C. for 0.5 h, followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h, and 220 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/epoxy/cyanate ester resin composite was obtained.

Embodiment 16

(145) 1) Preparation of Slurries

(146) 20 g of barium titanate (the average diameter is 50 nm) and 6 g of aqueous polyvinyl alcohol solution with a concentration of 15 wt % were sufficiently ground to obtain a slurry A; 16 g of aqueous hydroxyhexyl cellulose solution with a concentration of 0.5 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 8 g of aqueous polyacrylic acid amine solution with a concentration of 3 wt % was added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(147) 2) Treatment of Polyvinyl Chloride Sponge

(148) The polyvinyl chloride sponge having a specification of 25 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 20 wt %, and then heated up to 50 C. and keeping at that temperature for 2 h; the polyvinyl chloride sponge was taken out and washed with deionized water, followed by drying to obtain a polyvinyl chloride sponge D; at room temperature, the polyvinyl chloride sponge D was soaked in an aqueous polyethyleneimine solution with a concentration of 0.5 wt % for 2 h; then took out and removed the excess polyethyleneimine solution, after dried at 70 C., the pretreated polyvinyl chloride sponge E was obtained.

(149) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(150) The pretreated polyvinyl chloride sponge E was soaked in the slurry C prepared in step 1) and maintained for 1 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 70 C.; repeating processes of hanging pulp and drying for 1 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(151) 4) Preparation of Barium Titanate Foam Ceramics

(152) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 200 C. at a rate of 5 C./min, and then raised to 600 C. at a rate of 0.5 C./min and maintained at 600 C. for 0.5 h; followed by continuously heating to 1500 C. at a rate of 10 C./min and keeping at that temperature for 3 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(153) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(154) Dopamine hydrochloride was dissolved in 10 mmol/L buffer solution of Tris-HCl to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.5 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(155) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(156) 5 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 12 h to obtain barium titanate foam ceramics loaded with nano silver; then, 50 mL of aqueous hydrazine hydrate solution with a concentration of 30 g/L and 50 mL of aqueous sodium borohydride solution with a concentration of 10 g/L were added into the solution G and kept at room temperature for 1 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(157) 7) Preparation of Modified Barium Titanate Foam Ceramic/Epoxy Resin Composite

(158) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 60 C. in an oven; epoxy (commercial name: E-51) and 2-ethyl-4-methylimidazole (mass ratio of 25:1) were blended with siring at 60 C. for 0.5 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 60 C. for 0.5 h, followed by curing and postcuring using the procedures of 80 C./2 h+100 C./2 h+120 C./2 h, and 140 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/epoxy resin composite was obtained.

Embodiment 17

(159) 1) Preparation of Slurries

(160) 20 g of barium titanate (the average diameter is 100 nm) and 15 g of aqueous polyvinyl alcohol solution with a concentration of 10 wt % were sufficiently ground to obtain a slurry A; 10 g of aqueous carboxymethyl cellulose solution with a concentration of 1 wt % was added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 5 g of aqueous polyacrylic acid amine solution with a concentration of 2 wt % was added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(161) 2) Treatment of Polyurethane Sponge

(162) The polyurethane sponge having a specification of 25 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 15 wt %, after heated up to 65 C., and keeping at that temperature for 3 h; the polyurethane sponge was taken out and washed with deionized water, followed by drying to obtain a polyurethane sponge D; at room temperature, the polyurethane sponge D was soaked in an aqueous polyethyleneimine solution with a concentration of 0.5 wt % for 6 h; then took out and removed the excess polyethyleneimine solution, after dried at 60 C., a pretreated polyurethane sponge E was obtained.

(163) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(164) The pretreated polyurethane sponge E was soaked in the slurry C prepared in step 1) and maintained for 3 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 40 C.; repeating processes of hanging pulp and drying for 7 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(165) 4) Preparation of Barium Titanate Foam Ceramics

(166) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 100 C. at a rate of 2 C./min, and then raised to 500 C. at a rate of 2 C./min and maintained at 500 C. for 2 h; followed by continuously heating to 1200 C. at a rate of 8 C./min and keeping at that temperature for 3 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(167) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(168) Dopamine hydrochloride was dissolved in 12.5 mmol/L buffer solution of disodium hydrogen phosphate-sodium dihydrogen phosphate to prepare aqueous dopamine solution with a concentration of 2 g/L, and then solution F was obtained by adjusting pH to 8.3 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(169) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(170) 5 mL of aqueous sodium alginate solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.12 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 0.5 h to obtain barium titanate foam ceramics loaded with nano silver; then, 50 mL of aqueous ascorbic acid solution with a concentration of 1 g/L and 50 mL of aqueous sodium citrate solution with a concentration of 10 g/L were added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(171) 7) Preparation of Modified Barium Titanate Foam Ceramic/Cyanate Ester Resin Composite

(172) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 160 C. in an oven; 2,2-bis(4-cyanatophenyl)propane (bisphenol A cyanate ester) was melted at 160 C. for 1 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 160 C. for 0.5 h; followed by curing and postcuring using the procedures of 160 C./2 h+180 C./2 h+200 C./2 h+220 C./2 h, and 240 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/cyanate ester resin composite was obtained.

Embodiment 18

(173) 1) Preparation of Slurries

(174) 20 g of barium titanate (the average diameter is 100 nm) and 10 g of aqueous polyvinyl alcohol solution with a concentration of 10 wt % were sufficiently ground to obtain a slurry A; 5 g of aqueous carboxymethyl cellulose solution with a concentration of 1 wt % and 5 g of aqueous hydroxyhexyl cellulose solution with a concentration of 1 wt % were added into the slurry A, and the mixture was sufficiently ground to obtain a slurry B; 10 g of aqueous polyacrylamide solution with a concentration of 1 wt % was added into the slurry B, and the mixture was sufficiently ground to obtain a slurry C.

(175) 2) Treatment of Polyurethane Sponge

(176) The polyurethane sponge having a specification of 25 PPI was soaked in an aqueous sodium hydroxide solution with a concentration of 20 wt %, and then heated up to 60 C. and keeping at that temperature for 3.5 h; the polyurethane sponge was taken out and washed with deionized water, followed by drying to obtain a polyurethane sponge D; at room temperature, the polyurethane sponge D was soaked in an aqueous carboxymethyl cellulose solution with a concentration of 1 wt % for 2 h; then took out and removed the excess carboxymethyl cellulose solution, after dried at 60 C., a pretreated polyurethane sponge E was obtained.

(177) 3) Preparation of Green Body of Barium Titanate Foam Ceramics

(178) The pretreated polyurethane sponge E was soaked in the slurry C prepared in step 1) and maintained for 5 min at room temperature; after hanging pulp, the excess slurry in the sponge was removed by extrusion, and the sponge was dried at 50 C.; repeating processes of hanging pulp and drying for 4 times, a green body of foam ceramics based on barium titanate with even coating and no blocks was obtained.

(179) 4) Preparation of Barium Titanate Foam Ceramics

(180) The green body of barium titanate foam ceramics prepared in step 3) was heated from room temperature to 300 C. at a rate of 2 C./min, and then raised to 700 C. at a rate of 1 C./min and maintained at 700 C. for 0.5 h; followed by continuously heating to 1300 C. at a rate of 5 C./min and keeping at that temperature for 2 h; after the furnace was cooled to room temperature, barium titanate foam ceramics were obtained.

(181) 5) Preparation of Dopamine-Modified Barium Titanate Foam Ceramics

(182) Dopamine hydrochloride was dissolved in 15 mmol/L buffer solution of disodium hydrogen phosphate-sodium dihydrogen phosphate to prepare aqueous dopamine solution with a concentration of 5 g/L, and then solution F was obtained by adjusting pH to 8.8 with sodium hydroxide; barium titanate foam ceramics prepared in step 4) were soaked in solution F and kept at room temperature for 24 h; followed by washing with deionized water for several times and drying, successively, to obtain dopamine-modified barium titanate foam ceramics.

(183) 6) Preparation of Barium Titanate Foam Ceramics Loaded with Micro/Nano Silver

(184) 5 mL of aqueous polyvinylpyrrolidone solution with a concentration of 0.2 wt % was added into 50 mL of a fresh ammoniacal silver solution with a concentration of 0.06 mol/L, the mixture was uniformly mixed to obtain solution G; the dopamine-modified barium titanate foam ceramics prepared in step 5) were soaked in solution G and kept at room temperature for 0.5 h to obtain barium titanate foam ceramics loaded with nano silver; then, 50 mL of aqueous sodium citrate solution with a concentration of 10 g/L, 50 mL of aqueous ascorbic acid solution with a concentration of 1 g/L and 50 mL of aqueous glucose solution with a concentration of 10 g/L were added into the solution G and kept at room temperature for 2 h; followed by washing with deionized water and drying, successively, to obtain barium titanate foam ceramics loaded with micro/nano silver, that is modified barium titanate foam ceramics.

(185) 7) Preparation of Modified Barium Titanate Foam Ceramic/Epoxy Resin Composite

(186) The modified barium titanate foam ceramics prepared in step 6) were placed in a mold and preheated at 60 C. in an oven; epoxy (commercial name: E-51) and 2-ethyl-4-methylimidazole (mass ratio of 25:1) were blended with siring at 60 C. for 0.5 h to obtain an solution, which was poured into the preheated modified barium titanate foam ceramics and degassed under vacuum at 60 C. for 0.5 h, followed by curing and postcuring using the procedures of 80 C./2 h+100 C./2 h+120 C./2 h, and 140 C./4 h, successively; after slowly cooled to room temperature, modified barium titanate foam ceramic/epoxy resin composite was obtained.