Thermosensitive ceramic material based on 3D printing and preparation method and application thereof

Abstract

The application relates to the technical field of functional ceramic materials, in particular to a heat-sensitive ceramic material based on 3D printing and a preparation method and application thereof. Lead-based PTC ceramics with excellent performance and complex structures are obtained by using digital light processing (DLP) technology based on 3D printing technology and a vacuum impregnation (VI) process, the solidification depth of the PTC ceramic slurry can be improved by adding soluble starch, and the electrical performance, surface quality and preparation precision of the PTC ceramic are improved by combining the vacuum impregnation, degreasing and sintering processes, so that the 3D printing technology shows a broad application prospect in the preparation of PTC heaters with excellent performance and complex shapes.

Description

Technical Field

[0001] This invention relates to the field of functional ceramic materials technology, and in particular to a 3D-printed thermosensitive ceramic material, its preparation method, and its application. Background Technology

[0002] Barium titanate (BaTiO3)-based ceramics, due to their positive temperature coefficient of resistance (PTC) effect, are typical thermistor materials and have been widely used in self-regulating heating, temperature sensing, and battery safety protection. With the rapid development of new energy and electric vehicles, BaTiO3-based thermistors have found new applications in automotive air conditioning and battery thermal management systems. Therefore, the fabrication of high-performance and energy-saving BaTiO3-based thermistor ceramics is of great significance.

[0003] Typically, BaTiO3-based thermistors are obtained through traditional manufacturing processes such as dry pressing and tape casting. Furthermore, honeycomb structures with periodically arranged porous units are highly suitable for use as PTC heating elements due to their high efficiency, energy saving, uniform heating, durability, and safety. However, this complex geometry is limited by the mold design in traditional manufacturing methods, making it highly dependent on the mold used. This makes it difficult to obtain complex structures like honeycomb structures that offer high efficiency, energy saving, and uniform heating, and also requires long production cycles and high manufacturing costs. Therefore, there is an urgent need for an efficient and controllable manufacturing method to obtain BaTiO3-based thermistors with complex structures and excellent properties. Summary of the Invention

[0004] In view of this, the present invention proposes a 3D-printed thermosensitive ceramic material and its preparation method. By combining 3D printing technology with vacuum impregnation process, BaTiO3-based PTC ceramics with excellent electrical properties and complex shapes are obtained, and its application in PTC ceramic heaters is provided.

[0005] The technical solution of this invention is implemented as follows:

[0006] Lead-based PTC ceramics are considered ideal PTC ceramic materials due to their strong PTC effect, high Curie temperature, good thermal stability, and mature preparation process. However, lead-containing PTC ceramic powders often have high refractive index and ultraviolet absorption, resulting in a shallow curing depth of the PTC ceramic slurry under ultraviolet light irradiation in 3D printers, thus affecting the printing effect and forming accuracy. This invention improves the curing depth of the PTC ceramic slurry by adding soluble starch, solving the problems of high curing difficulty and poor printability in 3D printing lead-based PTC ceramics. Furthermore, vacuum impregnation (VI) of the 3D-printed PTC ceramic green body using nano-silica sol optimizes the grain boundary barrier and promotes sintering densification, further reducing the room temperature resistivity (ρ) and increasing the temperature coefficient of resistance (α).0-15 This process enhances the PTC effect of BaTiO3-based ceramics. Finally, a honeycomb structure with good surface quality and high fabrication precision was obtained through debinding and sintering processes, demonstrating the broad application of 3D printing technology in the fabrication of PTC heaters with excellent electrical properties and complex shapes.

[0007] On one hand, the present invention provides a method for preparing a thermosensitive ceramic material, comprising the following steps:

[0008] S1, under vacuum conditions, PTC powder, soluble starch, photocurable resin and additives are ball-milled to obtain PTC ceramic slurry;

[0009] S2, use 3D printing to solidify the PTC ceramic slurry obtained in step S1 into a single layer to obtain a PTC ceramic green body;

[0010] S3, Under vacuum conditions, the PTC ceramic green body obtained in step S2 is immersed in nano-silica sol for infiltration and then dried;

[0011] S4. The dried PTC ceramic blank is degreased and sintered to obtain PTC ceramic.

[0012] Based on the above scheme, preferably, in step S1, the amount of soluble starch is 5 to 30 vol of the total amount of PTC powder and soluble starch; more preferably, the amount of soluble starch is 20 vol of the total amount of PTC powder and soluble starch.

[0013] Based on the above scheme, preferably, in step S3, the concentration of the nano silica sol is 1~30 wt%; more preferably, the concentration of the nano silica sol is 1~5 wt%.

[0014] Based on the above scheme, preferably, in step S1, the additives include ultrafine dispersant 41000, initiator TPO and anti-settling agent BYK410, and the photocurable resin is HDDA resin.

[0015] Based on the above scheme, preferably, in step S3, the impregnation time is 9~11 min, and the drying is carried out in an oven at 63~67 ℃ for 11~13 h.

[0016] Based on the above scheme, preferably, in step S4, the degreasing is carried out by first heating to 580~620 ℃ under argon gas at a rate of 0.18~0.22℃ / min for carbonization, then cooling, and then heating to 580~620 ℃ in air for degreasing.

[0017] Based on the above scheme, preferably, in step S4, the sintering is to heat the degreased PTC ceramic blank to 1230~1270 °C at a rate of 2.8~3.2 °C / min, hold it at that temperature for 1.8~2.2 h, and then cool it with the furnace.

[0018] Based on the above scheme, a further optimized method involves ball milling the raw material powder, photocurable resin, and other additives with 6 mm diameter zirconia balls at 2000 r / min for 15 min under room temperature vacuum conditions to obtain a PTC ceramic slurry with good flowability. A single-layer curing experiment is then conducted on the PTC ceramic slurry, with a layer thickness of 25 μm. By adjusting the exposure time and exposure power density, the single-layer curing depth is increased to more than twice the layer thickness (50 μm). The obtained PTC ceramic preform is then immersed in 1 wt% nano-silica sol for 10 min under vacuum conditions, followed by drying in a 65 ℃ oven for 12 h. Next, it is carbonized at 600 ℃ under argon at a rate of 0.2 ℃ / min, cooled, and then degreased at 600 ℃ in air. The degreased PTC ceramic preform is then heated to 1250 ℃ at a rate of 3 ℃ / min and held at that temperature for 2 hours. h, and then cooled with the furnace to obtain a PTC ceramic sample with excellent electrical properties.

[0019] Secondly, a thermistor ceramic material is provided, which is prepared by the preparation method of the thermistor ceramic material described above.

[0020] Thirdly, the application of the thermistor ceramic material as described above in the preparation of PTC heaters is provided.

[0021] The 3D-printed thermosensitive ceramic material and its preparation method of the present invention have the following advantages over the prior art:

[0022] (1) The present invention combines DLP technology in 3D printing with vacuum impregnation process (VI) to obtain BaTiO3-based PTC ceramic materials with excellent electrical properties, lower room temperature resistivity and higher temperature coefficient of resistance, and can also obtain a variety of complex shapes, thus realizing high-precision preparation of porous complex PTC ceramics.

[0023] (2) The introduction of soluble starch during 3D printing improves the curing performance and printability of PTC ceramic slurry and also achieves certain electrical properties;

[0024] (3) Combined with the vacuum impregnation process, the electrical properties of PTC ceramics are further improved to meet the application requirements of PTC heaters. The degreasing and sintering processes improve the surface quality and preparation precision of PTC ceramics, providing a new preparation process for thermistor ceramic materials required in the fields of self-controlled heating, temperature sensing and battery safety protection. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart of the preparation method of the present invention;

[0027] Figure 2 This diagram illustrates the effect of different soluble starch contents on the curing depth of PTC ceramics according to the present invention.

[0028] Figure 3 The XRD patterns of PTC ceramics with different soluble starch contents in Example 1 of the present invention are shown below.

[0029] Figure 4 The images show SEM images and grain size distribution diagrams of the PTC ceramic in Example 1 of this invention.

[0030] Figure 5 The figures show the TG-DTA curves and debinding and sintering curves of the PTC ceramic green body of the present invention.

[0031] Figure 6 The diagram shows the electrical properties of the PTC ceramic in Example 1 of this invention.

[0032] Figure 7 The image shows the XRD patterns of PTC ceramics impregnated with silica sol of different SiO2 concentrations in Example 2 of the present invention.

[0033] Figure 8 The images show SEM images and grain size distribution diagrams of the PTC ceramic in Example 2 of this invention.

[0034] Figure 9 This is a diagram showing the electrical properties of the PTC ceramic in Example 2 of the present invention;

[0035] Figure 10 The images show the 3D-printed PTC ceramic preform and the sintered PTC ceramic sample of this invention. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] The PTC ceramic powder used in the PTC ceramic manufacturing raw materials of this invention was purchased from Foshan Nanhai Honeycomb Electronics Co., Ltd., China (average particle size 1.47 μm, purity >99%, made from titanium dioxide, lead tetroxide, barium carbonate, calcium carbonate, yttrium oxide, silicon dioxide, aluminum oxide and manganese dioxide in a specific ratio); the soluble starch powder was purchased from China National Pharmaceutical Group Chemical Reagent Co., Ltd. (average particle size 44.8 μm, purity >99.7%); the acrylate monomer 1,6-hexanediol diacrylate (HDDA resin) was purchased from Ryze Chemicals GmbH, Germany; the 41000 ultrafine dispersant was purchased from Lubrizol Advanced Materials GmbH, Spain; the anti-settling agent BYK-410 was purchased from BYK Chemicals GmbH, Germany; and the photopolymerization initiator 2,4,6-trimethylbenzoyl diphenyl oxide (TPO) was purchased from Shanghai Yinchang New Materials Co., Ltd., China.

[0038] Example 1: Preparation of PTC ceramic green body

[0039] The above-mentioned PTC ceramic powder and soluble starch were used as raw materials. HDDA resin accounted for 50-60 vol% of the PTC ceramic slurry, ultrafine dispersant 41000 accounted for 3 wt% of the PTC ceramic powder, initiator TPO accounted for 1 wt% of the HDDA resin, and anti-settling agent BYK410 accounted for 0.5 wt% of the total. The solid content of the PTC ceramic slurry was controlled at 40 vol%, and soluble starch was added to the above-mentioned PTC powder, photocurable resin, and additives at doping ratios of 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, and 30 vol% of the total PTC powder and soluble starch. Under room temperature vacuum conditions, the raw material powder, photocurable resin, and other additives were ball-milled with 6 mm diameter zirconia balls at 2000 r / min for 15 min to obtain a PTC ceramic slurry with good flowability. The curing performance of the PTC ceramic slurry was tested, and the results are as follows: Figure 2 As shown.

[0040] Figure 2 Figure (a) shows the curing depth of PTC ceramic slurries with different solid content. It can be found that when no substance is added, the optimal solid content of PTC ceramic slurry is 35 vol%. At this time, the curing depth of the slurry reaches more than 50 μm (twice the layer thickness), which meets the requirements of 3D printing. Figure 2 Figure (b) shows the curing depth of PTC ceramic slurries with different soluble starch contents. After adding soluble starch, the curing depth can meet the requirements of 3D printing by using appropriate process parameters. At the same time, the solid content of PTC ceramic slurry can be increased to 40 vol%, so that the obtained PTC ceramic has excellent electrical properties. Figure 2 Figure (c) shows the slurry with different soluble starch contents at 30 s. -1 The viscosity change under shear rate is shown in the figure. It can be seen that when the soluble starch content is 20 vo%, the viscosity of PTC ceramic slurry is the lowest, which has good fluidity and is conducive to the smooth progress of the 3D printing process. Figure 2 Figure (d) shows the viscosity change of PTC ceramic slurry with added soluble starch at different shear rates. It can be seen from the figure that as the shear rate increases, the viscosity of PTC ceramic slurry decreases continuously, showing obvious shear thinning characteristics.

[0041] Single-layer curing experiments were conducted on PTC ceramic slurries with different soluble starch contents. The layer thickness was set to 25 μm, the exposure time to 32 s, and the exposure power density to 32 mW / cm³. 2 This allows the solidification depth of a single layer to reach more than twice the layer thickness (50 μm) to meet the requirements of 3D printing. The phase composition, microstructure, and grain size distribution of the obtained PTC ceramic were tested and analyzed, and the results are as follows: Figure 3 and Figure 4 As shown:

[0042] Figure 3 The XRD patterns of PTC ceramics with different soluble starch contents reveal their phase composition. As shown in the figure, all PTC ceramic samples possess a pure perovskite structure, with barium titanate (BaTiO3) and lead titanate (PbTiO3) as the main phases, indicating that the introduction of soluble starch has virtually no impact on the crystal structure of PTC ceramics. The diffraction peak intensity of the PTC ceramics gradually decreases as the soluble starch content increases from 5 vol% to 30 vol%. This is because the increase in soluble starch content leads to a gradual decrease in the bulk density of the PTC ceramics, hindering solid-phase diffusion between grains and delaying the densification process, thereby continuously reducing the crystallinity of the PTC ceramics.

[0043] Figure 4The images show SEM images and grain size distributions of PTC ceramics with different amounts of soluble starch. Images (a) to (d) represent SEM images of PTC ceramics with 10 vol%, 15 vol%, 20 vol%, and 30 vol% soluble starch, respectively. It can be seen that the number and size of pores in the PTC ceramics increase with increasing soluble starch content. The introduced soluble starch hinders the direct contact between ceramic particles, and the pores formed during heat treatment interfere with mass transfer between ceramic grains, thus inhibiting the sintering and densification process of the PTC ceramics. Simultaneously, it can be found that when the soluble starch content is 10 vol%, 15 vol%, 20 vol%, and 30 vol%, the average grain sizes of the PTC ceramics are 5.67 μm, 3.89 μm, 3.31 μm, and 4.87 μm, respectively (as shown in Figures 1-3). Figure 4 (As shown in Figures (e) to (h)). Soluble starch forms numerous pores after heat treatment, which can interfere with the mass transfer process between grains, thereby inhibiting the growth of PTC ceramic grains.

[0044] Through the TG-DTA curve, such as Figure 5 Figure (a) shows the degreasing curves for PTC ceramic green bodies with different soluble starch contents. The degreasing process mainly consists of six stages: 0-100 ℃, 100-200 ℃, 200-300 ℃, 300-420 ℃, 420-500 ℃, and 500-600 ℃, which correspond to the weight loss stages in the TG curve. At around 600 ℃, the organic matter in the PTC ceramic green body can be basically removed. To obtain highly densified PTC ceramics, such as... Figure 5 As shown in (b), the degreased PTC ceramic preform was heated to 1250 °C at a rate of 3 °C / min and held at that temperature for 2 h. Through the degreasing and sintering process, PTC ceramics with good surface quality and excellent electrical properties were obtained.

[0045] After sintering the PTC ceramic obtained above, its electrical properties were tested and analyzed, and the results are as follows: Figure 6 As shown, Figure 6 These are the resistance-temperature (RT) characteristic curves of 3D-printed PTC ceramics with different soluble starch contents. Figure (a) shows the relationship between resistance and temperature, and Figure (b) shows the room temperature resistivity and the temperature coefficient of resistance (α). 0-15 The relationship between soluble starch content and soluble starch content. Figure 6 Figure (a) shows that all PTC ceramic samples exhibit a significant PTC effect at around 220 °C. The Curie temperature of PTC ceramics is approximately 220 °C, indicating that the introduction of soluble starch does not change the Curie temperature of 3D-printed PTC ceramics. Figure 6As shown in Figure (b), when the soluble starch content is 20 vol%, ρ reaches its minimum value of 238 Ω·cm, and α 0-15 The maximum value of 23.53% / ℃ was reached. The pores formed by soluble starch after heat treatment can refine ceramic grains and reduce grain boundary barriers, thereby improving carrier mobility and reducing room temperature resistivity. At the same time, the pores generated by soluble starch can optimize the grain boundary structure of PTC ceramics, improve the uniformity of grain boundary barrier height, and thus enhance the temperature sensitivity of PTC ceramics.

[0046] Example 2:

[0047] Based on Example 1, the electrical properties of PTC ceramics are further improved by combining the vacuum impregnation (VI) process.

[0048] A vacuum infiltration (VI) process was used to infiltrate PTC ceramic green bodies containing 20 vol% soluble starch into nano-silica sols with different silica concentrations (1 wt%, 5 wt%, 10 wt%, and 30 wt%) for 10 min under vacuum. The infiltrated PTC ceramic green bodies were then dried in an oven at 65 ℃ for 12 h. After drying, the PTC ceramic green bodies underwent debinding and sintering. Specifically, carbonization was first performed at 600 ℃ under argon atmosphere at a rate of 0.2 ℃ / min, followed by cooling. Then, debinding was performed by heating to 600 ℃ in air. The debinded PTC ceramic green bodies were heated to 1250 ℃ at a rate of 3 ℃ / min and held for 2 h, followed by furnace cooling to obtain PTC ceramics. The main phase composition, SEM images, grain size distribution, and electrical properties of the obtained PTC ceramics were analyzed and tested. The results are as follows: Figure 7 , Figure 8 and Figure 9 As shown;

[0049] Figure 7 The XRD patterns of PTC ceramics infiltrated with silica sol at different SiO2 concentrations are shown. The figures reveal that the main phase composition of the PTC ceramics is BaTiO3, PbTiO3, mullite, and cristobalite. Low concentrations of SiO2 nanoparticles can fill the pores between PTC ceramic grains, reducing scattering effects at grain boundaries and increasing the intensity of diffraction peaks by enhancing densification. However, excessive SiO2 nanoparticles can easily disrupt the main phase structure, forming heterogeneous phases of mullite and cristobalite, and may induce microcracks and dislocations, leading to a decrease in the intensity of the diffraction peaks in the PTC ceramics.

[0050] Figure 8SEM images and grain size distributions of PTC ceramics impregnated with silica sol of different SiO2 concentrations are shown. It can be observed that with increasing SiO2 concentration, the number and size of pores in the PTC ceramics gradually decrease (e.g., ...). Figure 8 (As shown in Figures (a) to (d)). SiO2 nanoparticles in the silica sol enter the interstices of the PTC ceramic. The glassy phase generated at high temperatures enhances the bonding force between ceramic particles, thereby reducing the number and size of pores. Furthermore, the formation of mullite leads to internal volume expansion in the ceramic, which contributes to the densification of the PTC ceramic. During high-temperature sintering, SiO2 nanoparticles may form a liquid phase, promoting material transport between grains and increasing the grain size of the PTC ceramic. Therefore, the average grain sizes of PTC ceramics impregnated with silica sol at SiO2 concentrations of 1 wt%, 5 wt%, 10 wt%, and 30 wt% are 3.50 μm, 3.78 μm, 4.25 μm, and 4.39 μm, respectively (as shown in Figures (a) to (d)). Figure 8 (As shown in Figures (e) to (h)).

[0051] Figure 9 Figure (a) shows the resistance-temperature (RT) characteristics of 3D-printed PTC ceramics impregnated with silica sol of different SiO2 concentrations. All obtained PTC ceramic samples exhibited a significant PTC effect at approximately 220 °C. The Curie temperature of PTC ceramics impregnated with silica sol of different SiO2 concentrations was approximately 220 °C, indicating that the impregnation process does not affect the Curie temperature of 3D-printed PTC ceramics. Figure 9 Figure (b) in the figure provides the room temperature resistivity (ρ) and temperature coefficient of resistance (α) of PTC ceramics impregnated with silica sol of different SiO2 concentrations. 0-15 When the SiO2 concentration is 1 wt%, ρ reaches its minimum value of 207 Ω·cm, and α 0-15 The maximum value was reached at 25.14% / ℃. Silica nanoparticles in silica sol can improve the electrical conductivity of PTC ceramics by filling internal pores, optimizing grain boundary barriers, and enhancing atomic diffusion. Simultaneously, silica can also maintain the purity of the main phase and, through synergistic densification effects, lead to a more concentrated temperature-sensitive response to resistivity changes at grain boundaries.

[0052] Example 3

[0053] PTC ceramics were prepared using both the conventional pressing method and the DLP-VI process described in this invention.

[0054] Using the same batch of BaTiO3-based PTC ceramic powder, PTC ceramics prepared by combining DLP technology and vacuum infiltration (VI) in 3D printing were compared with those prepared by the traditional pressing method. The electrical properties of the PTC ceramics were tested and analyzed, and the results are shown in Table 1. It can be found that the PTC ceramics prepared by the two processes have similar Curie temperatures. However, the PTC ceramics prepared by the DLP-VI process have lower room temperature resistivity and a higher temperature coefficient of resistance, exhibiting superior electrical properties.

[0055] Table 1 Electrical properties of PTC ceramics prepared by DLP-VI and tableting processes

[0056]

[0057] The morphology of PTC ceramic preforms and PTC ceramic samples prepared using the DLP-VI process is as follows: Figure 10 As shown, Figure 10 Figure (a) shows a PTC ceramic preform prepared by 3D printing. Figure 10 Figure (b) shows the PTC ceramic sample obtained by sintering. It can be observed that both the PTC ceramic green body and the sintered sample with complex structure have good surface quality and high preparation accuracy, which proves the broad application prospects of DLP technology in the preparation of complex ceramic shapes.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a thermosensitive ceramic material, characterized in that, Includes the following steps: S1, Under vacuum conditions, PTC powder, soluble starch, photocurable resin, and additives are ball-milled to obtain PTC ceramic slurry; the amount of soluble starch is 5-30 vol% of the total amount of PTC powder and soluble starch; the raw material components of PTC powder include titanium dioxide, lead tetroxide, barium carbonate, calcium carbonate, yttrium oxide, silicon dioxide, aluminum oxide, and manganese dioxide; S2, use 3D printing to solidify the PTC ceramic slurry obtained in step S1 into a single layer to obtain a PTC ceramic green body; S3, Under vacuum conditions, the PTC ceramic green body obtained in step S2 is immersed in nano-silica sol for impregnation, and then dried; the concentration of the nano-silica sol is 1~5 wt%. S4, the dried PTC ceramic blank is degreased and sintered to obtain PTC ceramic; the phase composition of the PTC ceramic includes BaTiO3, PbTiO3, mullite and cristobalite.

2. The method for preparing the thermosensitive ceramic material as described in claim 1, characterized in that: In step S1, the additives include ultrafine dispersant 41000, initiator TPO, and anti-settling agent BYK410.

3. The method for preparing the thermosensitive ceramic material as described in claim 1, characterized in that: In step S3, the impregnation time is 9-11 min, and the drying is carried out in an oven at 63-67 ℃ for 11-13 h.

4. The method for preparing the thermosensitive ceramic material as described in claim 1, characterized in that: In step S4, the degreasing is carried out by first heating the gas to 580-620 ℃ under argon atmosphere at a rate of 0.18-0.22 ℃ / min for carbonization, then cooling, and then heating the gas to 580-620 ℃ in air for degreasing.

5. The method for preparing the thermosensitive ceramic material as described in claim 1, characterized in that: In step S4, the sintering involves heating the degreased PTC ceramic blank to 1230-1270 °C at a rate of 2.8-3.2 °C / min, holding it at that temperature for 1.8-2.2 h, and then cooling it in the furnace.

6. A thermosensitive ceramic material, characterized in that, It is prepared by the method for preparing the thermosensitive ceramic material according to any one of claims 1 to 5.

7. The application of the thermistor ceramic material as described in claim 6 in the preparation of PTC heaters.

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