An electric heating film substrate insulating ceramic material and a method for preparing the same

Abstract

This invention discloses an insulating ceramic material for an electric heating film substrate and its preparation method. Using corundum sand, talc, magnesium carbonate, clay, barium carbonate, etc., as raw materials, the process involves batching, ball milling, re-batching, ball milling and uniform mixing, adjusting the slurry, plaster mold casting, drying, and firing to obtain a high-temperature insulating composite ceramic material product with a resistivity negative temperature coefficient far less than cordierite. The material obtained by this invention achieves a room temperature resistivity of 10. 14 Order of magnitude, ≥1×10 at 1000℃ 5 Ωm, flexural strength ≥100MPa. Coefficient of thermal expansion approximately 2×10⁻⁶. ‑4 / ℃ (25℃~1000℃), the product can be used to prepare substrates for electric heating films and other products, with a maximum heating temperature of 1000℃.

Description

Technical Field

[0001] This invention belongs to the field of inorganic materials, specifically relating to an insulating ceramic material for an electric heating film substrate and its preparation method. Background Technology

[0002] With the rapid development of technology, various new types of film heating devices are constantly emerging. Electric heating films have many advantages such as rapid heating and high heating efficiency. They are classified according to their properties, including nickel-iron-copper electric heating films, carbon-based electric heating films, and semiconductor oxide electric heating films. Applications include rapid preheating in electric vehicle engines, oil pipelines, and water heaters. Electric heating films must be attached to a substrate, therefore the substrate material must have good thermal shock resistance, high insulation, and low NTC characteristics.

[0003] Therefore, some people have tried to use metal materials coated with an insulating layer as the base material for electric heating films. The advantage is that it can fully meet the need for rapid heating, but the insulating layer is easily broken down, causing short circuits and safety accidents.

[0004] Cordierite, with its excellent insulation and low coefficient of expansion, is the preferred material for products with superior thermal shock resistance, boasting a room temperature resistivity as high as 10 Ω·cm. 11 Its resistivity is on the order of Ωm. However, its NTC characteristics are also very pronounced; at 500℃, the resistivity rapidly drops to 10. 4 Ωm level. The substrate and the electrothermal film are generally connected in parallel, 10 4 The additional resistance created by resistivity in the Ωm range within the heating film circuit becomes non-negligible, significantly reducing the resistance value of the heating circuit. Actual measurements at 220V show that, under stable voltage conditions, once the temperature rises to 400℃, the power of the cordierite-based graphene film electric heating device increases rapidly. The fan struggles to dissipate the heat effectively, causing the heating element temperature to rise rapidly. Consequently, the resistance continues to decrease, the power continues to increase, and the temperature continues to rise, progressing in this manner until burnout.

[0005] Therefore, it is of great significance and essential to research and develop ceramic materials with low NTC characteristics and low coefficient of thermal expansion, especially those with high insulation at high temperatures, to fabricate electric heating film structure devices with stable and reliable power at high temperatures, and to meet the growing needs of rapid heating applications. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an insulating ceramic material for an electric heating film substrate that is inexpensive, easy to prepare, and has stable performance, as well as a method for preparing the same.

[0007] The present invention is achieved through the following technical solution: an insulating ceramic material for an electric heating film substrate, characterized in that: the weight percentage composition of the ceramic material blank is: 25-35% binder and 65-75% corundum sand.

[0008] The binder blank formulation has the following weight percentage composition: talc 15-22%, clay 68-72%, magnesium carbonate 5.5-17%, and barium carbonate 0-10%.

[0009] The method for preparing the above-mentioned insulating ceramic material for electric heating film substrate is characterized by the following steps:

[0010] Step 1: Weigh the materials according to the binder blank formula;

[0011] Step 2: Add the binder blank raw material, tap water, and ball milling pellets into the ball mill according to the proportion, and add water glass before ball milling for more than 48 hours, controlling D50≤5μm;

[0012] Step 3: Add corundum sand and tap water to the slurry from Step 2 according to the ratio and continue ball milling for 6-8 hours;

[0013] Step 4: Pass the slurry obtained in Step 3 through a 200-mesh sieve, with a residue of ≤0.5wt%. Then, pour it into a slurry tank or slurry pool equipped with a stirrer, add water and a desiccant, stir for more than 4 hours, and age for 48 hours to obtain the molding slurry.

[0014] Step 5: The molding slurry obtained in Step 4 is injected into the mold, and the product is obtained after demolding, drying and firing.

[0015] In step two, the weight ratio of material ball to water is 1:2:0.5, the diameter of the ball mill is 20mm, and the amount of water glass added is 0.3wt%.

[0016] The corundum sand in step three has a particle size of 150 mesh.

[0017] In step four, the degumming agent is sodium humate, and the density of the molding slurry is 1.70–1.80 g / cm³. 3 The slurry flow rate is approximately 14 m / s, and the thickness is 1.05.

[0018] The grouting process in step five is either atmospheric pressure grouting or high pressure grouting.

[0019] The highest firing temperature in step five is 1380–1460°C, and the high-temperature holding time is ≥2 hours.

[0020] The product in step five has a flexural strength ≥100MPa and a volume resistivity of ≥6×10⁻⁵℃. 14 Ωm, ≥1×10 at 1000℃5 Ωm; coefficient of thermal expansion ≥2×10 -4 / ℃ (25~1000℃); Thermal shock resistance: No cracking after 50 cycles of heating to 600℃ in 5 minutes; Maximum operating temperature of the product is 1000℃.

[0021] The product from step five can be used to produce insulating substrates for electric heating films.

[0022] This invention uses 150-mesh corundum with high thermal conductivity and high insulation strength as aggregate to prepare magnesium aluminum silicate / corundum composite ceramics with low resistivity negative temperature coefficient (NTC) characteristics, excellent high-temperature insulation, and a maximum heating temperature of 1000℃. The substrate has no additional impact on the circuit at high temperatures, and the electric heating film has stable and reliable power.

[0023] Magnesium aluminum silicate with a low coefficient of thermal expansion is used as a high-temperature binder and sintered at high temperature. The aggregate and binder are firmly bonded, and the resulting magnesium aluminum silicate / corundum composite porous ceramic has a micron-sized pore size with uniform distribution. The material or product has a small coefficient of thermal expansion, high strength, and excellent thermal shock resistance, which meets the requirements for rapid heating of membrane heating devices.

[0024] This material possesses excellent comprehensive electrical, mechanical, and thermal properties, making it a typical structural and functional integrated ceramic material. The raw material has a small particle size, making it suitable for slip casting. The resulting material has a delicate and smooth surface, which is conducive to coating a high-quality electric heating film. It is mainly made of natural mineral raw materials, with chemical raw materials as auxiliary materials. The process is simple, easy to implement, and low in cost. Detailed Implementation

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the present invention will be described in detail below with reference to preferred embodiments: Example 1

[0026] An insulating ceramic material for an electric heating film substrate, wherein the ceramic material blank formulation comprises, by weight percentage: 35% binder and 65% corundum sand.

[0027] The binder blank formulation has the following weight percentage composition: talc 15%, clay 69%, magnesium carbonate 16%, and barium carbonate 0%.

[0028] The method for preparing the insulating ceramic material for the electric heating film substrate includes the following steps:

[0029] Step 1: Weigh the materials according to the binder blank formula;

[0030] Step 2: Add the binder blank raw material, tap water, and ball milling pellets into the ball mill according to the proportion, and add water glass before ball milling for 48 hours, controlling D50≤5μm;

[0031] Step 3: Add corundum sand and tap water to the slurry from Step 2 according to the ratio and continue ball milling for 7 hours;

[0032] Step 4: Pass the slurry obtained in Step 3 through a 200-mesh sieve, with a residue of ≤0.5wt%. Then, pour it into a slurry tank or slurry pool equipped with a stirrer, add water and a desiccant, stir for 4 hours, and age for 48 hours to obtain the molding slurry.

[0033] Step 5: The molding slurry obtained in Step 4 is injected into the mold, and after demolding, drying and firing, a 120mm×120mm×6mm square substrate product is obtained.

[0034] In step two, the weight ratio of material ball to water is 1:2:0.5, the diameter of the ball mill is 20mm, and the amount of water glass added is 0.3wt%.

[0035] The corundum sand in step three has a particle size of 150 mesh.

[0036] In step four, the degumming agent is sodium humate, and the density of the molding slurry is 1.76 g / cm³. 3 The slurry flow rate is approximately 14 m / s, and the thickness is 1.05.

[0037] In step five, the grouting process is either atmospheric pressure grouting or high pressure grouting, and the drying method is natural ventilation drying.

[0038] The highest firing temperature in step five is 1380℃, and the high-temperature holding time is 3 hours.

[0039] The flexural strength of the product in step five is 110.3 MPa; the volume resistivity is 6 × 10⁻⁶ at 25°C. 14 Ωm, 1.5×10 at 600℃ 9 Ωm, 1.3×10 at 1000℃ 5 Ωm; Coefficient of thermal expansion: 2×10 -4 / ℃ (25~1000℃); Thermal shock resistance: No cracking after 50 cycles of heating to 600℃ in 5 minutes; Maximum operating temperature of the product is 1000℃. Example 2

[0040] An insulating ceramic material for an electric heating film substrate, wherein the ceramic material blank formulation comprises, by weight percentage: 25% binder and 75% corundum sand.

[0041] The binder blank formulation has the following weight percentage composition: talc 22%, clay 68%, magnesium carbonate 10%, and barium carbonate 0%.

[0042] The method for preparing the insulating ceramic material for the electric heating film substrate includes the following steps:

[0043] Step 1: Weigh the materials according to the binder blank formula;

[0044] Step 2: Add the binder blank raw material, tap water, and ball milling pellets into the ball mill according to the proportion, and add water glass before ball milling for 60 hours, controlling D50≤5μm;

[0045] Step 3: Add corundum sand and tap water to the slurry from Step 2 according to the ratio and continue ball milling for 6 hours;

[0046] Step 4: Pass the slurry obtained in Step 3 through a 200-mesh sieve, with a residue of ≤0.5wt%. Then, pour it into a slurry tank or slurry pool equipped with a stirrer, add water and a desiccant, stir for 6 hours, and age for 48 hours to obtain the molding slurry.

[0047] Step 5: The molding slurry obtained in Step 4 is injected into the mold, and after demolding, drying and firing, a 120mm×120mm×6mm square substrate product is obtained.

[0048] In step two, the weight ratio of material ball to water is 1:2:0.5, the diameter of the ball mill is 20mm, and the amount of water glass added is 0.3wt%.

[0049] The corundum sand in step three has a particle size of 150 mesh.

[0050] In step four, the degumming agent is sodium humate, and the density of the molding slurry is 1.77 g / cm³. 3 The slurry flow rate is approximately 14 m / s, and the thickness is 1.05.

[0051] In step five, the grouting process is either atmospheric pressure grouting or high pressure grouting, and the drying method is natural ventilation drying.

[0052] The highest firing temperature in step five is 1460℃, and the high-temperature holding time is 2 hours.

[0053] The product in step five has a flexural strength of 102.8 MPa and a volume resistivity of 6.3 × 10⁻⁶ at 25°C. 14 Ωm, 1.8 × 10 at 600℃ 9 Ωm, 1.6 × 10 at 1000℃ 5 Ωm; coefficient of thermal expansion 2.2×10 -4 / ℃ (25~1000℃); Thermal shock resistance: No cracking after 50 cycles of heating to 600℃ in 5 minutes; Maximum operating temperature of the product is 1000℃. Example 3

[0054] An insulating ceramic material for an electric heating film substrate, wherein the ceramic material blank formulation comprises, by weight percentage: 25% binder and 75% corundum sand.

[0055] The binder blank formulation has the following weight percentage composition: talc 18%, clay 70%, magnesium carbonate 6%, and barium carbonate 6%.

[0056] The method for preparing the insulating ceramic material for the electric heating film substrate includes the following steps:

[0057] Step 1: Weigh the materials according to the binder blank formula;

[0058] Step 2: Add the binder blank raw material, tap water, and ball milling pellets into the ball mill according to the proportion, and add water glass before ball milling for 72 hours, controlling D50≤5μm;

[0059] Step 3: Add corundum sand and tap water to the slurry from Step 2 according to the ratio and continue ball milling for 8 hours;

[0060] Step 4: Pass the slurry obtained in Step 3 through a 200-mesh sieve, with a residue of ≤0.5wt%. Then, pour it into a slurry tank or slurry pool equipped with a stirrer, add water and a desiccant, stir for 6 hours, and age for 48 hours to obtain the molding slurry.

[0061] Step 5: The molding slurry obtained in Step 4 is injected into the mold, and after demolding, drying and firing, a 120mm×120mm×6mm square substrate product is obtained.

[0062] In step two, the weight ratio of material ball to water is 1:2:0.5, the diameter of the ball mill is 20mm, and the amount of water glass added is 0.3wt%.

[0063] The corundum sand in step three has a particle size of 150 mesh.

[0064] In step four, the degumming agent is sodium humate, and the density of the molding slurry is 1.77 g / cm³. 3 The slurry flow rate is approximately 14 m / s, and the thickness is 1.05.

[0065] In step five, the grouting process is either atmospheric pressure grouting or high pressure grouting, and the drying method is natural ventilation drying.

[0066] The highest firing temperature in step five is 1450℃, and the high-temperature holding time is 2.5h.

[0067] The product in step five has a flexural strength of 113.10 MPa and a volume resistivity of 7.2 × 10⁻⁶ at 25°C. 14 Ωm, 3.3×10 at 600℃ 9 Ωm, 2.1×10 at 1000℃ 5 Ωm; coefficient of thermal expansion 2.5×10 -4 / ℃ (25~1000℃); Thermal shock resistance: No cracking after 50 cycles of heating to 600℃ in 5 minutes; Maximum operating temperature of the product is 1000℃. Example 4

[0068] An insulating ceramic material for an electric heating film substrate, wherein the ceramic material blank has the following weight percentage composition: 30% binder and 70% corundum sand.

[0069] The binder blank formulation has the following weight percentage composition: talc 15%, clay 68%, magnesium carbonate 8%, and barium carbonate 9%.

[0070] The method for preparing the insulating ceramic material for the electric heating film substrate includes the following steps:

[0071] Step 1: Weigh the materials according to the binder blank formula;

[0072] Step 2: Add the binder blank raw material, tap water, and ball milling pellets into the ball mill according to the proportion, and add water glass before ball milling for 72 hours, controlling D50≤5μm;

[0073] Step 3: Add corundum sand and tap water to the slurry from Step 2 according to the ratio and continue ball milling for 7 hours;

[0074] Step 4: Pass the slurry obtained in Step 3 through a 200-mesh sieve, with a residue of ≤0.5wt%. Then, pour it into a slurry tank or slurry pool equipped with a stirrer, add water and a desiccant, stir for 4 hours, and age for 48 hours to obtain the molding slurry.

[0075] Step 5: The molding slurry obtained in Step 4 is injected into the mold, and after demolding, drying and firing, a 120mm×120mm×6mm square substrate product is obtained.

[0076] In step two, the weight ratio of material ball to water is 1:2:0.5, the diameter of the ball mill is 20mm, and the amount of water glass added is 0.3wt%.

[0077] The corundum sand in step three has a particle size of 150 mesh.

[0078] In step four, the degumming agent is sodium humate, and the density of the molding slurry is 1.77 g / cm³. 3 The slurry flow rate is 14 m / s and the thickness is 1.05.

[0079] In step five, the grouting process is either atmospheric pressure grouting or high pressure grouting, and the drying method is natural ventilation drying.

[0080] The highest firing temperature in step five is 1380℃, and the high-temperature holding time is 3 hours.

[0081] The product in step five has a flexural strength of 115.9 MPa and a volume resistivity of 6.8 × 10⁻⁶ at 25°C. 14 Ωm, 5.5 × 10 at 600℃ 9 Ωm, 1.8 × 10 at 1000℃ 5 Ωm; coefficient of thermal expansion 2.4×10 -4 / ℃ (25~1000℃); Thermal shock resistance: No cracking after 50 cycles of heating to 600℃ in 5 minutes; Maximum operating temperature of the product is 1000℃.

Claims

1. An insulating ceramic material for an electric heating film substrate, characterized in that: The ceramic material formulation consists of the following weight percentages: 25-35% binder and 65-75% corundum sand. The binder has the following weight percentage composition: talc 15-22%, clay 68-72%, magnesium carbonate 5.5-17%, and barium carbonate 0-10%. The preparation method of the insulating ceramic material for the electric heating film substrate specifically includes the following steps: Step 1: Weigh the materials according to the adhesive formula; Step 2: Add the binder raw material, tap water, and ball milling pellets to the ball mill according to the specified ratio, and add water glass before ball milling for more than 48 hours, controlling D50≤5μm; Step 3: Add corundum sand and tap water to the slurry from Step 2 according to the ratio and continue ball milling for 6-8 hours; Step 4: Pass the slurry obtained in Step 3 through a 200-mesh sieve, with a residue of ≤0.5wt%. Then, pour it into a slurry tank or slurry pool equipped with a stirrer, add water and a desiccant, stir for more than 4 hours, and age for 48 hours to obtain the molding slurry. Step 5: The molding slurry obtained in Step 4 is poured into molds, and the product is obtained after demolding, drying, and firing. The product in step five has a flexural strength ≥100MPa and a volume resistivity of ≥6×10⁻⁵℃. 14 Ωm, ≥1×10 at 1000℃ 5 Ωm; Thermal shock resistance: No cracking after 5 minutes of heating to 600℃ and 50 cycles; Maximum operating temperature of the product is 1000℃; The product in step five is used to produce an insulating substrate for electric heating films. The corundum sand in step three has a particle size of 150 mesh.

2. The insulating ceramic material for the electric heating film substrate according to claim 1, characterized in that: In step two, the weight ratio of material ball to water is 1:2:0.5, the diameter of the ball mill is 20mm, and the amount of water glass added is 0.3wt%.

3. The insulating ceramic material for the electric heating film substrate according to claim 1, characterized in that: In step four, the degumming agent is sodium humate, and the density of the molding slurry is 1.70–1.80 g / cm³. 3 The slurry flow rate is 14 m / s and the thickness is 1.

05.

4. The insulating ceramic material for the electric heating film substrate according to claim 1, characterized in that: The grouting process in step five is either atmospheric pressure grouting or high pressure grouting.

5. The insulating ceramic material for the electric heating film substrate according to claim 1, characterized in that: The highest firing temperature in step five is 1380–1460°C, and the high-temperature holding time is ≥2 hours.