A PTC ceramic material and a method for producing the same
By combining barium titanate with modified silicon borate and using surface modification techniques, the shortcomings of traditional PTC ceramic materials in terms of thermal conductivity and mechanical strength have been overcome, enabling the preparation of high-performance PTC ceramic materials suitable for automotive electronics and industrial control.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIANTAO SHENGPENG NEW MATERIALS CO LTD
- Filing Date
- 2025-10-21
- Publication Date
- 2026-07-21
AI Technical Summary
Traditional PTC ceramic materials have shortcomings in thermal conductivity, mechanical strength, and process control, making it difficult to meet the high-performance requirements of modern electronic devices. In particular, existing modification technologies are not ideal in harsh environments such as automotive electronics and industrial control.
By employing a barium titanate matrix and functional fillers such as modified silicon boride, a nano-coating is constructed on the surface of silicon boride through dopamine polymerization and amidation reactions, forming a PTC ceramic material with high thermal conductivity and strong interfacial bonding. Combined with an optimized sintering process, the overall performance is improved.
It achieves a significant improvement in the high thermal conductivity, mechanical strength, and processing stability of PTC ceramic materials, making them suitable for high-end applications and possessing excellent PTC characteristics and good mechanical properties.
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Figure CN121248281B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of PTC technology, specifically to a PTC ceramic material and its preparation method. Background Technology
[0002] PTC (Positive Temperature Coefficient) ceramic materials are a class of functional ceramics exhibiting a positive temperature coefficient effect. Their resistivity increases sharply with increasing temperature within a specific temperature range, and they are widely used in overcurrent protection, isothermal heating, temperature sensing, and other fields. The physical mechanism of the PTC effect is based on the ferroelectric to paraelectric phase transition that occurs in perovskite ferroelectric ceramics near the Curie temperature, leading to a significant change in the grain boundary barrier, which in turn causes a jump in resistivity.
[0003] Currently, commercially available PTC ceramic materials mainly use barium titanate (BaTiO3) as the matrix, reducing room temperature resistivity by doping with rare earth elements (such as Y, La, Ce, etc.) and adding sintering aids (such as PbO, Bi2O3, etc.) to improve sintering performance and grain boundary characteristics. However, with the continuous increase in the power density of electronic devices and the increasingly harsh application environments, traditional PTC ceramic materials face many technical challenges.
[0004] The main problems with existing technologies include:
[0005] Insufficient thermal conductivity: The thermal conductivity of traditional barium titanate-based PTC ceramics is typically only 3-5 W / (m·K), far below the heat dissipation requirements of modern high-power electronic devices. Under high-current operating conditions, localized heat accumulation can easily lead to thermal runaway, affecting the safety and reliability of the device. Although existing technologies have attempted to add thermally conductive fillers such as alumina and silicon nitride, the improvement effect is limited due to problems such as poor interfacial compatibility and uneven dispersion.
[0006] Low mechanical strength: The flexural strength of pure barium titanate-based ceramics is typically between 50 and 70 MPa. They are brittle, have poor impact resistance, and are prone to microcracks under temperature cycling and mechanical stress, leading to degradation of electrical properties. This insufficient mechanical reliability is particularly prominent in harsh environments such as automotive electronics and industrial control systems.
[0007] Outdated filler modification technology: Existing inorganic filler modification mainly adopts traditional methods such as silane coupling agents, which result in unstable modification effects and easy decomposition and failure at high temperatures. For new high-performance fillers such as silicon boride, there is a lack of effective surface modification technology, leading to poor dispersibility and interfacial bonding performance in ceramic matrices, making it difficult to fully realize their excellent intrinsic properties.
[0008] Complex process control: In order to balance the contradiction between PTC characteristics, thermal conductivity and mechanical strength, existing technologies often require complex multi-step sintering processes or post-processing processes, resulting in high production costs, difficulty in controlling consistency, and hindering large-scale industrial applications.
[0009] In recent years, silicon boride (SiB6) has attracted attention as an emerging ultra-hard ceramic material due to its excellent thermal conductivity (>60 W / (m·K)), high-temperature stability (temperature resistance >2000℃), and moderate electrical conductivity. However, silicon boride is chemically inert and has poor compatibility with organic or inorganic matrices; direct addition often leads to interface defects and performance degradation. Existing silicon boride modification methods mainly focus on metal matrix composites, with limited research on its applicability to ceramic matrices, and the modification mechanisms are not sufficiently explored, resulting in less than ideal modification effects.
[0010] Therefore, there is an urgent need to develop a new type of PTC ceramic material that can maintain the excellent properties of PTC while significantly improving thermal conductivity and mechanical strength, and also possess good processability and cost advantages to meet the needs of modern electronic technology development. In particular, it is necessary to overcome the bottleneck of surface modification technology for high-performance fillers to achieve strong interfacial bonding and synergistic performance optimization between the filler and the ceramic matrix. Summary of the Invention
[0011] To address the shortcomings of existing technologies, the present invention aims to provide a PTC ceramic material and its preparation method. This invention achieves a significant improvement in the comprehensive performance of PTC ceramic materials through the synergistic combination of barium titanate matrix and functional fillers such as modified silicon boride. This material possesses high PTC strength, excellent thermal conductivity, good mechanical properties, and stable process reproducibility, making it particularly suitable for high-end applications such as automotive electronics, industrial control, and high-power LED drivers.
[0012] To achieve the above objectives, the present invention adopts the following technical solution:
[0013] A PTC ceramic material, by weight, is composed of the following components: 50-65 parts barium titanate, 12-16 parts lead tetroxide, 0.1-0.3 parts yttrium oxide, 0.1-0.3 parts lanthanum oxide, 6-15 parts modified silicon boride, 4-10 parts alumina, 1-3 parts ammonium polyacrylate, and 3-6 parts polyvinyl alcohol.
[0014] Preferably, the modified silicon boride is prepared by the following method steps:
[0015] (1) Disperse silicon boride in ethanol, sonicate, dry and disperse in deionized water, add hydrogen peroxide, heat in a water bath, centrifuge, wash and dry the product to obtain activated silicon boride;
[0016] Surface hydroxylation: Hydrogen peroxide, acting as a strong oxidant, oxidizes the surface of silicon boride (SiB6) under heating conditions. Silicon and boron atoms are oxidized to form Si-OH (silanol) and B-OH (boronol) active groups. These hydroxyl groups not only increase the hydrophilicity of the material surface, but more importantly, provide the necessary nucleation sites and anchoring groups for the subsequent polymerization of dopamine.
[0017] Preferably, in step (1), the ratio of the amount of silicon boride, ethanol, deionized water and hydrogen peroxide is 10g: 100~200mL: 100~200mL: 100~150mL; and the concentration of hydrogen peroxide is 10~20wt%.
[0018] Preferably, in step (1), the ultrasonic treatment lasts for 30 to 60 minutes; the water bath heating conditions are 60 to 75°C and 300 to 500 r / min for 4 to 7 hours.
[0019] Preferably, in step (1), the silicon boride is SiB6 with a particle size of 50~150nm.
[0020] (2) Disperse activated silicon boride in Tris-HCl buffer, sonicate, slowly add dopamine hydrochloride while stirring, adjust the pH of the system, stir the reaction in the dark, centrifuge, wash and dry the product to obtain intermediate silicon boride;
[0021] In-situ polymerization coating of dopamine: Under weakly alkaline conditions, dopamine hydrochloride dissociates into free dopamine molecules, whose catechol structure is oxidized to a quinone structure, and then undergoes a self-polymerization reaction to form polydopamine (PDA). PDA preferentially nucleates and grows in situ under the action of hydroxyl groups on the activated silicon boride surface. It achieves strong adhesion by forming multiple hydrogen bonds and coordination bonds with surface Si-OH / B-OH through catechol groups, and finally forms a nano-coating rich in amino (-NH2) and hydroxyl (-OH) groups on the material surface.
[0022] Preferably, in step (2), the ratio of activated silicon boride, Tris-HCl buffer, and dopamine hydrochloride is 10g: 200~400mL: 2~5g.
[0023] Preferably, in step (2), the ultrasonic treatment is performed for 20-40 min; the pH of the system is adjusted to 8-9 and maintained; and the reaction is carried out under light-protected stirring conditions at room temperature for 12-24 h.
[0024] (3) Disperse intermediate silicon boride in anhydrous DMSO, then add triethylamine, sonicate, add docosic acid activation solution dropwise under nitrogen atmosphere, heat to react, centrifuge, wash and dry the product to obtain modified silicon boride.
[0025] Amide grafting: Docosic acid first reacts with EDC to form an active O-acylisourea intermediate (R-COO-EDC⁺). NHS then attacks this intermediate to generate a stable NHS ester (R-COO-NHS), while releasing EDU as a byproduct. Triethylamine acts as a basic catalyst to promote the reaction and neutralize the generated HCl. The primary amine group (-NH₂) on the PDA coating surface acts as a nucleophile to attack the carbonyl carbon of the NHS ester. After a tetrahedral intermediate transformation, the NHS group leaves, ultimately forming a stable amide bond (-NH-CO-) covalently linked, achieving covalent grafting modification of the long chain of docosic acid on the silicon boride surface.
[0026] Preferably, in step (3), the ratio of intermediate silicon boride, anhydrous DMSO, triethylamine, and docosinate activation solution is 10g: 150~200mL: 0.5~2mL: 150~300mL.
[0027] Preferably, in step (3), the preparation method of the docosinate activation solution is as follows: 10~20g of docosinate is added to 150~300mL of anhydrous DMSO, heated and stirred at 60~80℃ until completely dissolved, cooled and then 5~15g of EDC is added, stirred for 5~10min and then 3~10g of NHS is added, stirred and activated for 30~60min to obtain the docosinate activation solution.
[0028] Preferably, in step (3), the ultrasonic treatment is performed for 30-60 min; the heating reaction conditions are 50-65℃ and 300-500r / min stirring reaction for 18-24 h.
[0029] This invention also claims a method for preparing the PTC ceramic material, comprising the following steps: thoroughly mixing barium titanate, lead tetroxide, yttrium oxide, lanthanum oxide, modified silicon boride, and alumina in parts by weight to obtain a mixture; adding equal parts by weight of the mixture and deionized water to a ball mill and ball milling at 500-800 r / min for 6-9 h to obtain a slurry; allowing the slurry to stand for 4-8 h to remove impurities, then adding ammonium polyacrylate and polyvinyl alcohol, mixing thoroughly, spray granulating, and statically pressing at 50-70℃ and 20-30 MPa. Forming takes 150-300 seconds to produce a blank; the blank is heated to 600℃ at 2-4℃ / min and held for 0.5-1.5h; then heated to 800℃ at 2-4℃ / min and held for 0.5-1.5h; under a nitrogen atmosphere, the temperature is increased to 900-1200℃ at 8-12℃ / min and sintered at high temperature for 0.5-1.5h; then cooled to 800℃ at 4-8℃ / min and held for 0.5-1.5h, and then allowed to cool naturally to room temperature to complete the sintering of the blank; after grinding and polishing, the PTC ceramic material is obtained.
[0030] Compared with the prior art, the present invention has the following beneficial effects:
[0031] 1. The PTC ceramic material of this invention achieves excellent comprehensive performance through the synergistic combination of multiple components. Barium titanate, as the main material, possesses intrinsic ferroelectricity and a PTC effect due to its perovskite crystal structure (ABO3 type). Near the Curie temperature, it undergoes a phase transition from ferroelectric to paraelectric phase, leading to a sharp increase in resistivity, providing the fundamental physical basis for the PTC thermistor properties. Lead tetroxide, as a sintering aid, effectively lowers the sintering temperature, promotes grain growth, and forms a dense microstructure. Yttrium oxide and lanthanum oxide, as rare earth dopants, significantly improve the room temperature resistivity and PTC strength of the material by replacing Ba²⁺ sites in the barium titanate lattice, while also improving the stability at the Curie temperature. Modified silicon boride, as a high thermal conductivity filler, itself… With its high thermal conductivity, good electrical properties, and excellent thermal stability, PTC ceramics maintain structural stability during high-temperature sintering, constructing a three-dimensional thermally conductive network to effectively improve the heat dissipation performance of ceramic materials. Simultaneously, as a semiconductor filler, it moderately regulates the room-temperature resistivity of the material and optimizes the distribution of conductive pathways. Alumina, as a reinforcing phase, inhibits abnormal grain growth through grain boundary pinning, improving the material's flexural strength and thermal shock resistance. Ammonium polyacrylate and polyvinyl alcohol, as organic binders and dispersants, not only improve the rheological properties of the slurry and the uniformity of powder dispersion but also increase the forming density and strength of the green sheet. They completely decompose and volatilize during sintering, leaving no impurities that affect performance. Under precise control of the proportions and process, the components form a synergistic effect, enabling PTC ceramic materials to possess excellent PTC characteristics, high thermal conductivity, and good mechanical properties.
[0032] 2. This invention provides a modified silicon boride. The first step, hydrogen peroxide oxidation, introduces a large number of Si-OH and B-OH hydroxyl groups onto the silicon boride surface. These active hydroxyl groups not only improve surface energy and hydrophilicity, enabling good dispersion in water-based slurry systems, but more importantly, provide chemical reaction sites for subsequent modification, avoiding the defects of easy detachment from physical coatings. The second step, in-situ polymerization of dopamine, constructs a polydopamine (PDA) transition layer on the surface. PDA achieves super-strong adhesion through chemical adsorption. The abundant amino (-NH2) and hydroxyl (-OH) groups in PDA endow the surface with amphoteric characteristics and high reactivity. Simultaneously, PDA molecules can penetrate into the microporous structure of the silicon boride surface. During subsequent high-temperature sintering, PDA, as a nitrogen-containing organic compound, undergoes thermal decomposition, and some nitrogen elements can enter the grain boundary region of the ceramic matrix. By moderately influencing the interfacial electron transport characteristics through grain boundary regulation, it helps optimize the PTC material. Electrical response characteristics and sensitivity; In the third step, the long chain of docosic acid is covalently grafted onto the amino group of the PDA layer through an EDC / NHS-mediated amidation reaction, forming a stable CN amide bond. The alkyl chain with up to 22 carbon atoms constructs a dense hydrophobic layer and a significant steric hindrance effect on the silicon boride surface, effectively preventing the aggregation of particles by van der Waals forces and significantly reducing the surface energy. This surface hydrophobic modification forms a synergistic dispersion mechanism with the PDA intermediate layer, enabling the modified silicon boride to maintain excellent dispersion stability in various process steps such as ceramic slurry preparation, ball milling dispersion, and spray granulation. It greatly improves the interfacial wettability and compatibility between silicon boride and the ceramic matrix, reduces interfacial defects, pores, and agglomerates. At the same time, the flexible molecular structure of the long carbon chain can effectively absorb and buffer thermal stress concentration, improve the interface's resistance to crack propagation, and maximize the high thermal conductivity, high toughness, thermal shock resistance, and corrosion resistance of the modified silicon boride. Attached Figure Description
[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 The resistance-temperature characteristic curves of Example 1, Comparative Example 1, and Comparative Example 2 are shown. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.
[0036] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.
[0037] Barium titanate: purchased from Hubei Baidu Chemical Co., Ltd.;
[0038] Lead tetroxide: purchased from Wuhan Jiyesheng Chemical Co., Ltd.;
[0039] Yttrium oxide: purchased from Shanghai Maclean Biochemical Technology Co., Ltd., product number: Y835830;
[0040] Lanthanum oxide: Purchased from Shanghai Maclean Biochemical Technology Co., Ltd., product number: L812319.
[0041] Alumina: purchased from Condis Chemical (Hubei) Co., Ltd.;
[0042] Polyvinyl alcohol: purchased from Shanghai Maclean Biochemical Technology Co., Ltd., product number: P875285.
[0043] A method for preparing a PTC ceramic material includes the following steps:
[0044] (1) Disperse 10g of silicon boride in 100-200mL of ethanol, sonicate for 30-60min, dry and disperse in 100-200mL of deionized water, add 100-150mL of 10-20wt% hydrogen peroxide, react in a water bath at 60-75℃ and 300-500r / min for 4-7h, centrifuge, wash and dry the product to obtain activated silicon boride;
[0045] (2) Disperse 10g of activated silicon boride in 200-400mL Tris-HCl buffer, sonicate for 20-40min, slowly add 2-5g of dopamine hydrochloride while stirring, adjust the pH of the system to 8-9 and maintain it, stir and react at room temperature in the dark for 12-24h, centrifuge, wash and dry the product to obtain intermediate silicon boride.
[0046] (3) Disperse 10g of intermediate silicon boride into 150-200mL of anhydrous DMSO, then add 0.5-2mL of triethylamine, sonicate for 30-60min, and add 150-300mL of docosic acid activation solution dropwise under nitrogen atmosphere (add 10-20g of docosic acid to 150-300mL of anhydrous DMSO, heat and stir at 60-80℃ until completely dissolved, cool and add 5-15g of EDC, stir for 5-10min and then add 3-10g of NHS, stir and activate for 30-60min to obtain), stir at 50-65℃ and 300-500r / min for 18-24h, centrifuge, wash and dry the product to obtain modified silicon boride;
[0047] (4) By weight, 50-65 parts of barium titanate, 12-16 parts of lead tetroxide, 0.1-0.3 parts of yttrium oxide, 0.1-0.3 parts of lanthanum oxide, 6-15 parts of modified silicon boride, and 4-10 parts of alumina are thoroughly mixed to obtain a mixture; equal parts by weight of the mixture and deionized water are added to a ball mill and ball-milled at 500-800 r / min for 6-9 h to obtain a slurry; the slurry is allowed to stand for 4-8 h to remove impurities, and then 1-3 parts of ammonium polyacrylate and 3-6 parts of polyvinyl alcohol are added, mixed evenly, and spray-granulated at 50-70℃ and 20-3 The blank is formed by static pressure treatment at 0 MPa for 150-300s; the blank is heated to 600℃ at 2-4℃ / min and held for 0.5-1.5h; then heated to 800℃ at 2-4℃ / min and held for 0.5-1.5h; under a nitrogen atmosphere, the temperature is increased to 900-1200℃ at 8-12℃ / min and sintered at high temperature for 0.5-1.5h; then cooled to 800℃ at 4-8℃ / min and held for 0.5-1.5h, and then allowed to cool naturally to room temperature to complete the sintering of the blank; after grinding and polishing, the PTC ceramic material is obtained.
[0048] The present invention will be further described below through specific embodiments.
[0049] Example 1
[0050] A method for preparing a PTC ceramic material includes the following steps:
[0051] (1) Disperse 10g of silicon boride in 150mL of ethanol, sonicate for 45min, dry and disperse in 150mL of deionized water, add 120mL of 15wt% hydrogen peroxide, react in a water bath at 75℃ and 400r / min for 4h, centrifuge, wash and dry the product to obtain activated silicon boride.
[0052] (2) Disperse 10g of activated silicon boride in 300mL Tris-HCl buffer, sonicate for 30min, slowly add 5g of dopamine hydrochloride while stirring, adjust the pH of the system to 8.5 and maintain it, stir and react at room temperature in the dark for 12h, centrifuge, wash and dry the product to obtain intermediate silicon boride;
[0053] (3) Disperse 10g of intermediate silicon boride into 180mL of anhydrous DMSO, then add 2mL of triethylamine, sonicate for 45min, and add 300mL of docosic acid activation solution dropwise under nitrogen atmosphere (add 20g of docosic acid to 200mL of anhydrous DMSO, heat and stir at 70℃ until completely dissolved, cool and add 15g of EDC, stir for 5min and then add 10g of NHS, stir and activate for 45min to obtain), stir at 65℃ and 400r / min for 18h, centrifuge, wash and dry the product to obtain modified silicon boride;
[0054] (4) According to the weight proportions, 6500g barium titanate, 1600g lead tetroxide, 30g yttrium oxide, 30g lanthanum oxide, 1500g modified silicon boride, and 1000g alumina are thoroughly mixed to obtain a mixture; the same weight proportions of the mixture and deionized water are added to a ball mill and ball-milled at 600r / min for 8h to obtain a slurry; the slurry is allowed to stand for 6h to remove impurities, and then 300g ammonium polyacrylate and 600g polyvinyl alcohol are added, mixed evenly, and spray-granulated. The blank was formed by static pressing at 60℃ and 25MPa for 200s; the blank was heated to 600℃ at 3℃ / min and held for 1h; then heated to 800℃ at 2℃ / min and held for 1h; under a nitrogen atmosphere, the temperature was increased to 1100℃ at 10℃ / min and sintered at high temperature for 1h; then cooled to 800℃ at 6℃ / min and held for 1h, and then allowed to cool naturally to room temperature to complete the sintering of the blank; after grinding and polishing, the PTC ceramic material was obtained.
[0055] Example 2
[0056] A method for preparing a PTC ceramic material includes the following steps:
[0057] (1) Disperse 10g of silicon boride in 150mL of ethanol, sonicate for 45min, dry and disperse in 150mL of deionized water, add 120mL of 15wt% hydrogen peroxide, react in a water bath at 70℃ and 400r / min for 5h, centrifuge, wash and dry the product to obtain activated silicon boride.
[0058] (2) Disperse 10g of activated silicon boride in 300mL Tris-HCl buffer, sonicate for 30min, slowly add 4g of dopamine hydrochloride while stirring, adjust the pH of the system to 8.5 and maintain it, stir and react at room temperature in the dark for 16h, centrifuge, wash and dry the product to obtain intermediate silicon boride;
[0059] (3) Disperse 10g of intermediate silicon boride into 180mL of anhydrous DMSO, then add 1.5mL of triethylamine, sonicate for 45min, and add 250mL of docosic acid activation solution dropwise under nitrogen atmosphere (add 16g of docosic acid to 200mL of anhydrous DMSO, heat and stir at 70℃ until completely dissolved, cool and add 12g of EDC, stir for 5min and then add 8g of NHS, stir and activate for 45min to obtain), stir at 60℃ and 400r / min for 20h, centrifuge, wash and dry the product to obtain modified silicon boride;
[0060] (4) According to the weight proportions, 6000g of barium titanate, 1500g of lead tetroxide, 25g of yttrium oxide, 25g of lanthanum oxide, 1200g of modified silicon boride, and 800g of alumina are thoroughly mixed to obtain a mixture; the same weight proportions of the mixture and deionized water are added to a ball mill and ball-milled at 600r / min for 8h to obtain a slurry; the slurry is allowed to stand for 6h to remove impurities, and then 250g of ammonium polyacrylate and 500g of polyvinyl alcohol are added, mixed evenly, and spray-granulated. The blank was formed by static pressing at 60℃ and 25MPa for 200s; the blank was heated to 600℃ at 3℃ / min and held for 1h; then heated to 800℃ at 2℃ / min and held for 1h; under a nitrogen atmosphere, the temperature was increased to 1100℃ at 10℃ / min and sintered at high temperature for 1h; then cooled to 800℃ at 6℃ / min and held for 1h, and then allowed to cool naturally to room temperature to complete the sintering of the blank; after grinding and polishing, the PTC ceramic material was obtained.
[0061] Example 3
[0062] A method for preparing a PTC ceramic material includes the following steps:
[0063] (1) Disperse 10g of silicon boride in 150mL of ethanol, sonicate for 45min, dry and disperse in 150mL of deionized water, add 120mL of 15wt% hydrogen peroxide, react in a water bath at 65℃ and 400r / min for 6h, centrifuge, wash and dry the product to obtain activated silicon boride.
[0064] (2) Disperse 10g of activated silicon boride in 300mL Tris-HCl buffer, sonicate for 30min, slowly add 4g of dopamine hydrochloride while stirring, adjust the pH of the system to 8.5 and maintain it, stir and react at room temperature in the dark for 20h, centrifuge, wash and dry the product to obtain intermediate silicon boride;
[0065] (3) Disperse 10g of intermediate silicon boride into 180mL of anhydrous DMSO, then add 1mL of triethylamine, sonicate for 45min, and add 200mL of docosic acid activation solution dropwise under nitrogen atmosphere (add 10~20g of docosic acid to 200mL of anhydrous DMSO, heat and stir at 70℃ until completely dissolved, cool and add 8g of EDC, stir for 5min and then add 5g of NHS, stir and activate for 45min to obtain), stir at 55℃ and 400r / min for 22h, centrifuge, wash and dry the product to obtain modified silicon boride;
[0066] (4) According to the weight proportions, 5500g of barium titanate, 1300g of lead tetroxide, 15g of yttrium oxide, 15g of lanthanum oxide, 900g of modified silicon boride, and 600g of alumina are thoroughly mixed to obtain a mixture; the same weight proportions of the mixture and deionized water are added to a ball mill and ball-milled at 600r / min for 8h to obtain a slurry; the slurry is allowed to stand for 6h to remove impurities, and then 150g of ammonium polyacrylate and 400g of polyvinyl alcohol are added, mixed evenly, and spray-granulated. The blank was formed by static pressing at 60℃ and 25MPa for 200s; the blank was heated to 600℃ at 3℃ / min and held for 1h; then heated to 800℃ at 2℃ / min and held for 1h; under a nitrogen atmosphere, the temperature was increased to 1100℃ at 10℃ / min and sintered at high temperature for 1h; then cooled to 800℃ at 6℃ / min and held for 1h, and then allowed to cool naturally to room temperature to complete the sintering of the blank; after grinding and polishing, the PTC ceramic material was obtained.
[0067] Example 4
[0068] A method for preparing a PTC ceramic material includes the following steps:
[0069] (1) Disperse 10g of silicon boride in 150mL of ethanol, sonicate for 45min, dry and disperse in 150mL of deionized water, add 120mL of 15wt% hydrogen peroxide, react in a water bath at 60℃ and 400r / min for 7h, centrifuge, wash and dry the product to obtain activated silicon boride.
[0070] (2) Disperse 10g of activated silicon boride in 300mL Tris-HCl buffer, sonicate for 30min, slowly add 2g of dopamine hydrochloride while stirring, adjust the pH of the system to 8.5 and maintain it, stir and react at room temperature in the dark for 24h, centrifuge, wash and dry the product to obtain intermediate silicon boride;
[0071] (3) Disperse 10g of intermediate silicon boride into 180mL of anhydrous DMSO, then add 0.5mL of triethylamine, sonicate for 45min, and add 150mL of docosic acid activation solution dropwise under nitrogen atmosphere (add 10g of docosic acid to 200mL of anhydrous DMSO, heat and stir at 70℃ until completely dissolved, cool and add 5g of EDC, stir for 5min and then add 3g of NHS, stir and activate for 45min to obtain), stir at 50℃ and 400r / min for 24h, centrifuge, wash and dry the product to obtain modified silicon boride;
[0072] (4) According to the weight proportions, 5000g barium titanate, 1200g lead tetroxide, 10g yttrium oxide, 10g lanthanum oxide, 600g modified silicon boride, and 400g alumina are thoroughly mixed to obtain a mixture; the same weight proportions of the mixture and deionized water are added to a ball mill and ball-milled at 600r / min for 8h to obtain a slurry; the slurry is allowed to stand for 6h to remove impurities, and then 100g ammonium polyacrylate and 300g polyvinyl alcohol are added, mixed evenly, and spray-granulated. The blank was formed by static pressing at 60℃ and 25MPa for 200s; the blank was heated to 600℃ at 3℃ / min and held for 1h; then heated to 800℃ at 2℃ / min and held for 1h; under a nitrogen atmosphere, the temperature was increased to 1100℃ at 10℃ / min and sintered at high temperature for 1h; then cooled to 800℃ at 6℃ / min and held for 1h, and then allowed to cool naturally to room temperature to complete the sintering of the blank; after grinding and polishing, the PTC ceramic material was obtained.
[0073] Comparative Example 1
[0074] A method for preparing a PTC ceramic material includes the following steps:
[0075] (1) Disperse 10g of silicon boride in 150mL of ethanol, sonicate for 45min, dry and disperse in 150mL of deionized water, add 120mL of 15wt% hydrogen peroxide, react in a water bath at 75℃ and 400r / min for 4h, centrifuge, wash and dry the product to obtain activated silicon boride.
[0076] (2) Disperse 10g of activated silicon boride in 300mL Tris-HCl buffer, sonicate for 30min, slowly add 5g of dopamine hydrochloride while stirring, adjust the pH of the system to 8.5 and maintain it, stir and react at room temperature in the dark for 12h, centrifuge, wash and dry the product to obtain intermediate silicon boride;
[0077] (3) According to the weight proportions, 6500g barium titanate, 1600g lead tetroxide, 30g yttrium oxide, 30g lanthanum oxide, 1200g intermediate silicon boride, 300g icosanoic acid, and 1000g alumina are thoroughly mixed to obtain a mixture; the same weight proportions of the mixture and deionized water are added to a ball mill and ball-milled at 600r / min for 8h to obtain a slurry; the slurry is allowed to stand for 6h to remove impurities, and then 300g ammonium polyacrylate and 600g polyvinyl alcohol are added and mixed evenly. The material is spray-granulated and statically pressed at 60℃ and 25MPa for 200s to form a blank. The blank is then heated to 600℃ at 3℃ / min and held for 1 hour. It is then heated to 800℃ at 2℃ / min and held for 1 hour. Under a nitrogen atmosphere, the temperature is increased to 1100℃ at 10℃ / min and sintered at high temperature for 1 hour. The temperature is then decreased to 800℃ at 6℃ / min and held for 1 hour. Finally, the blank is allowed to cool naturally to room temperature to complete the sintering process. After grinding and polishing, the PTC ceramic material is obtained.
[0078] Comparative Example 2
[0079] A method for preparing a PTC ceramic material includes the following steps:
[0080] (1) Disperse 10g of silicon boride in 150mL of ethanol, sonicate for 45min, dry and disperse in 150mL of deionized water, add 120mL of 15wt% hydrogen peroxide, react in a water bath at 75℃ and 400r / min for 4h, centrifuge, wash and dry the product to obtain activated silicon boride.
[0081] (2) According to the weight proportions, 6500g barium titanate, 1600g lead tetroxide, 30g yttrium oxide, 30g lanthanum oxide, 1200g activated silicon boride, 300g dopamine hydrochloride, and 1000g alumina are thoroughly mixed to obtain a mixture; the same weight proportions of the mixture and deionized water are added to a ball mill and ball milled at 600r / min for 8h to obtain a slurry; the slurry is allowed to stand for 6h to remove impurities, and then 300g ammonium polyacrylate and 600g polyvinyl alcohol are added and mixed evenly. The material is spray-granulated and statically pressed at 60℃ and 25MPa for 200s to form a blank. The blank is then heated to 600℃ at 3℃ / min and held for 1 hour. It is then heated to 800℃ at 2℃ / min and held for 1 hour. Under a nitrogen atmosphere, the temperature is increased to 1100℃ at 10℃ / min and sintered at high temperature for 1 hour. The temperature is then decreased to 800℃ at 6℃ / min and held for 1 hour. Finally, the blank is allowed to cool naturally to room temperature to complete the sintering process. After grinding and polishing, the PTC ceramic material is obtained.
[0082] The PTC ceramic materials prepared in the examples and comparative examples were ground to 24mm×15mm×2.42mm, chamfered, cleaned and dried, and then aluminum electrodes were sprayed on both sides to form finished products for performance testing. Impedance: A Wenke Precision Impedance Analyzer, model 6510B, was used, with a test frequency of 20Hz~10MHz; Room temperature resistance: Tested at room temperature using a multimeter; Curie temperature: The temperature corresponding to the steepest rise in resistivity was measured using a multimeter; Resistance-to-resistance ratio: lg(Curie point resistance / room temperature resistance); Withstand voltage: The breakdown voltage was tested using a BYD-GN-02 withstand voltage tester; the test results are shown in Table 1.
[0083] Table 1. Performance test results of PTC ceramic materials
[0084] Room temperature resistivity (Ω·cm) Curie temperature (°C) Rise-to-drag ratio Withstand pressure (V) Example 1 59 213 7.1 1343 Example 2 63 208 6.8 1337 Example 3 68 205 6.7 1331 Example 4 74 201 6.3 1327 Comparative Example 1 97 189 5.2 1256 Comparative Example 2 112 176 4.6 1219
[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A PTC ceramic material, characterized in that, It is made of the following components by weight: 50-65 parts barium titanate, 12-16 parts lead tetroxide, 0.1-0.3 parts yttrium oxide, 0.1-0.3 parts lanthanum oxide, 6-15 parts modified silicon boride, 4-10 parts aluminum oxide, 1-3 parts ammonium polyacrylate, and 3-6 parts polyvinyl alcohol; The modified silicon boride is prepared by the following steps: (1) Disperse silicon boride in ethanol, sonicate, dry and disperse in deionized water, add hydrogen peroxide, heat in a water bath, centrifuge, wash and dry the product to obtain activated silicon boride; (2) Disperse activated silicon boride in Tris-HCl buffer, sonicate, slowly add dopamine hydrochloride while stirring, adjust the pH of the system, stir the reaction in the dark, centrifuge, wash and dry the product to obtain intermediate silicon boride; (3) Disperse intermediate silicon boride in anhydrous DMSO, then add triethylamine, sonicate, add docosic acid activation solution dropwise under nitrogen atmosphere, heat to react, centrifuge, wash and dry the product to obtain modified silicon boride.
2. The PTC ceramic material according to claim 1, characterized in that, In step (1), the ratio of the amounts of silicon boride, ethanol, deionized water and hydrogen peroxide is 10g: 100~200mL: 100~200mL: 100~150mL; the concentration of hydrogen peroxide is 10~20wt%.
3. The PTC ceramic material according to claim 1, characterized in that, In step (1), ultrasonic treatment is performed for 30-60 minutes; the water bath heating conditions are 60-75℃, 300-500r / min, and the water bath reaction is performed for 4-7 hours.
4. The PTC ceramic material according to claim 1, characterized in that, In step (2), the ratio of activated silicon boride, Tris-HCl buffer, and dopamine hydrochloride is 10g: 200~400mL: 2~5g.
5. The PTC ceramic material according to claim 1, characterized in that, In step (2), the ultrasonic treatment lasts for 20-40 minutes; the pH of the system is adjusted to 8-9 and maintained; the reaction is carried out under light-protected stirring conditions at room temperature for 12-24 hours.
6. The PTC ceramic material according to claim 1, characterized in that, In step (3), the ratio of intermediate silicon boride, anhydrous DMSO, triethylamine, and docosinate activation solution is 10g: 150~200mL: 0.5~2mL: 150~300mL.
7. The PTC ceramic material according to claim 1, characterized in that, In step (3), the preparation method of the tichoic acid activation solution is as follows: 10~20g of tichoic acid is added to 150~300mL of anhydrous DMSO, heated and stirred at 60~80℃ until completely dissolved, cooled and then 5~15g of EDC is added. After stirring for 5~10min, 3~10g of NHS is added and stirred for 30~60min to obtain the tichoic acid activation solution.
8. The PTC ceramic material according to claim 1, characterized in that, In step (3), the ultrasonic treatment lasts for 30-60 minutes; the heating reaction conditions are 50-65℃ and 300-500r / min stirring reaction for 18-24 hours.
9. A method for preparing the PTC ceramic material according to any one of claims 1 to 8, characterized in that, The process includes the following steps: Barium titanate, lead tetroxide, yttrium oxide, lanthanum oxide, modified silicon boride, and alumina are thoroughly mixed in parts by weight to obtain a mixture; equal parts by weight of the mixture and deionized water are added to a ball mill and ball-milled at 500-800 r / min for 6-9 hours to obtain a slurry; the slurry is allowed to stand for 4-8 hours to remove impurities, then ammonium polyacrylate and polyvinyl alcohol are added, mixed thoroughly, spray-granulated, and statically pressed at 50-70℃ and 20-30 MPa for 150-300 seconds to form the final product. The blanks are formed; the blanks are heated to 600℃ at a rate of 2-4℃ / min and held for 0.5-1.5h; then heated to 800℃ at a rate of 2-4℃ / min and held for 0.5-1.5h; under a nitrogen atmosphere, the temperature is increased to 900-1200℃ at a rate of 8-12℃ / min and sintered at high temperature for 0.5-1.5h; then cooled to 800℃ at a rate of 4-8℃ / min and held for 0.5-1.5h, and then allowed to cool naturally to room temperature to complete the sintering of the blanks; after grinding and polishing, the PTC ceramic material is obtained.