Ceramic electrothermal film heating tube

Abstract

The application relates to a ceramic electric heating film heating pipe which is made of a tubular structure of a ceramic base material, and an electric heating film layer is attached to the surface wall of the tubular structure, wherein the ceramic electric heating film heating pipe is composed of a ceramic base material layer, a rough transition layer and an electric heating film layer. The rough transition layer with good adhesion and good heat resistance is formed on the surface of the ceramic base material by adopting a high-temperature stamping sand blasting process and a metal electric heating film layer. The thermal expansion coefficients of the ceramic base material layer, the rough transition layer and the electric heating film layer are consistent through a formula, so that the electric heating film layer is not easy to be peeled off from the ceramic base material pipe, and the service life of the electric heating film heating pipe is prolonged.

Description

Technical Field

[0001] This invention relates to an electric heating film heating tube with ceramic as the substrate and its manufacturing method. Background Technology

[0002] Most existing heating film heating tubes use quartz heating tubes as their base material, whose main component is silicon dioxide. Quartz heating tubes are characterized by their transparency, good hydrophobicity, and high resistivity. However, quartz heating tubes themselves have four problems: First, they are brittle and easily break or even burst upon impact; second, quartz has poor thermal conductivity, resulting in low heat transfer efficiency when the heat from the heating film is transferred to the water inside the quartz heating tube. To meet the need for rapid heating of flowing water, the heating film itself generates significant heat, leading to substantial heat waste and potential burn-out during prolonged operation; third, quartz is susceptible to thermal runaway. Insufficient adhesion of the film can easily lead to a porous layer between the heating film and the quartz, or even bulging and cracking. A transition layer with adhesive properties needs to be added between the two to ensure that the heating film layer is effectively adsorbed on the surface of the quartz tube. Fourth, under repeated thermal shock, the expansion coefficients of the quartz and the heating film layer are inconsistent. Although the heating film is relatively thin, about 50 to 100 micrometers thick, its operating temperature is usually 300-500 degrees. Under repeated thermal shock, the contact layer will experience contact fatigue, and the heating film layer will deform with crazing, wrinkles and other phenomena.

[0003] Ceramic tubes, as a substitute for quartz heating tubes, possess certain hydrophobic and heat-resistant properties, as well as good insulation. However, traditional ceramic clays have complex compositions, including kaolin and clay, which are extracted and mixed with metal oxides, nitrides, borides, and carbides. The firing process is also complex; earthenware is fired at 800-1000 degrees Celsius, while porcelain is made from kaolin at 1300-1400 degrees Celsius. Ceramic products come in a wide variety, and their chemical composition, mineral composition, physical properties, color properties, and manufacturing methods often overlap and lack clear boundaries, yet their applications differ significantly.

[0004] Selecting suitable substrate materials for rapid heating tubes from numerous ceramic manufacturing options, and finding matching heating film materials and manufacturing processes to produce heating tube ceramic substrates and heating films with good thermal conductivity, high strength, resistance to physical and thermal shock, and similar expansion rates, is an important issue for the rapid heating industry. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a manufacturing process for a heating tube ceramic substrate and an electrothermal film that meets the performance requirements of rapid heating tubes.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: a ceramic electric heating film heating tube, which is a tubular structure made of ceramic substrate, and an electric heating film layer is attached to its surface wall. The ceramic substrate of the ceramic electric heating film heating tube is made of alumina powder with a purity ≥99.95%, particle size D50: 0.5μm, and specific surface area of ​​6.5g / cm2, with trace amounts of oxides such as yttrium oxide and lanthanum oxide added. The mass ratio is: 99.95% alumina / 100ppm yttrium oxide / 100ppm lanthanum oxide powder. The powder is sintered at a high temperature of 1800 to 2000°C under the protection of a reducing atmosphere (H2) to form a ceramic tube substrate.

[0007] After cleaning the surface of the above-mentioned substrate, the surface is roughened by sandblasting at an environment of 800-1000 degrees Celsius to form a rough transition layer. The sandblasting agent used is 65% boron nitride and 35% silicon dioxide, with a particle size of 100-120 mesh and a particle diameter of 120-150 micrometers.

[0008] Then, an electrothermal film layer is formed on the roughened substrate surface by thermal deposition. The electrothermal film layer is formed by dissolving powders of 80% to 85% tin chloride, 10% aluminum trichloride, 1% bismuth chloride, 1% to 1.5% antimony chloride, 2% cerium chloride, and 1% to 5% rare earth elements in a 50% alcohol solution, and then thermally depositing them onto the substrate surface after the roughening transition layer is completed at a temperature of 650 to 800 degrees Celsius and a pressure of 2 to 3 kPa.

[0009] The formulation ensures that the error in the coefficient of thermal expansion between the ceramic substrate layer and the electric heating film is within 5%.

[0010] The thickness of the rough layer formed after sandblasting is 150-200 micrometers.

[0011] The thickness of the aforementioned electrothermal film is 30-100 micrometers.

[0012] Compared with existing technologies, the advantages of this invention are: it is made of a high-temperature ceramic substrate with excellent impact resistance, near-zero water absorption, dielectric constant greater than 10MHz, and volume resistivity of 4.5×10¹⁵ Ω·cm³, with a thermal expansion coefficient of 8x10⁻⁶ 1 / K, and the error between the substrate and the heating film is within 5%. The substrate has an electric heating element with good insulation and excellent thermal shock resistance.

[0013] Its 1.5mm thick heating element has a thermal conductivity of 25ω / mK (20℃), which is more than 4 times that of ordinary tempered glass (6.2). Therefore, it can better transfer heat and transfer the heat generated by the heating film to the water.

[0014] Actual testing revealed that, without any other auxiliary heat dissipation conditions, when water at room temperature (20°C) is heated to 100°C, a quartz heating tube with the same wall thickness and specifications operating at the same heating power reaches a surface temperature of 350-400°C, while the heating tube of this invention only reaches a temperature of 150-170°C. The temperature is reduced by half, and the energy efficiency increases from 92% to 95%. The performance is exceptionally superior. Attached Figure Description

[0015] Figure 1 This is a structural diagram of an electric heating film heating tube with a ceramic substrate.

[0016] 1 is a ceramic substrate, 2 is a rough transition layer, and 3 is an electrothermal film layer. Detailed Implementation

[0017] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0018] The ceramic electric heating film heating tube of this invention is a ceramic crystal formed by high-temperature firing under a reducing atmosphere (H2) after the substrate is mainly composed of alumina and doped with other auxiliary materials. The surface roughness is increased by sandblasting, and a metal oxide electric heating film layer is formed by thermal deposition. Compared with the more common quartz heating tubes on the market, its heat conduction efficiency is increased by nearly 4 times, the operating temperature is reduced by nearly half, and the expansion coefficients of the substrate and the electric heating film layer are nearly identical, with an error within 5%.

[0019] The manufacturing process is as follows: 1. Alumina powder with a purity ≥99.95%, particle size D50: 0.5μm, and specific surface area of ​​6.5g / cm2 is used, and trace amounts of oxides such as yttrium oxide and lanthanum oxide are added. The mass ratio is: 99.95% alumina / 100ppm yttrium oxide / 100ppm lanthanum oxide. The resulting powder is sintered at a high temperature of 1800 to 2000°C under a reducing atmosphere (H2) to form a ceramic tube substrate.

[0020] 2. After the above-mentioned substrate has cooled to room temperature, surface cleaning is performed.

[0021] 3. Using boron nitride (65%) and silicon dioxide (35%), with a particle size of 100-120 mesh and a particle diameter of 120-150 micrometers, the surface of the substrate is roughened by sandblasting at an environment of 800-1000 degrees Celsius to form a rough transition layer with a thickness of 150-200 micrometers.

[0022] 4. Dissolve 80% to 85% tin chloride, 10% aluminum trichloride, 1% bismuth chloride, 1% to 1.5% antimony chloride, 2% cerium chloride, and 1% to 5% rare earth elements in a 50% alcohol solution to prepare a spray. Spray the spray onto the surface of the rough transition layer at a temperature of 650 to 800 degrees Celsius and a pressure of 2 to 3 kPa. Then, form an electrothermal film layer by thermal deposition.

[0023] The ceramic-metal film electric heating tube produced by the above process has the following properties in its substrate:

[0024] (Pipe diameter 6mm-20mm, length 70mm-200mm, wall thickness 0.5mm-1.5mm)

[0025]

Claims

1. A ceramic electric heating film heating tube, comprising a tubular structure made of a ceramic substrate, wherein an electric heating film layer is attached to its surface wall, characterized in that: The ceramic substrate of the ceramic electric heating film heating tube has a purity of ≥99.95%, a particle size D50 of 0.5μm, and a specific surface area of ​​6.5g / cm². 2 Alumina powder with trace amounts of yttrium oxide and lanthanum oxide powder is sintered at 1700-1800℃ under a reducing atmosphere (H2) to form a ceramic tube substrate; the mass ratio of alumina powder, yttrium oxide and lanthanum oxide is: alumina 99.95% / yttrium 100ppm / lanthanum oxide 100ppm. After surface cleaning, the surface of the above-mentioned substrate is roughened by sandblasting to form a rough transition layer with a roughness level between 1.5 and 2.

5. The sandblasting agent used is 65% boron nitride and 35% silicon dioxide, with a particle size of 100-120 mesh and a particle diameter of 120-150 micrometers. Then, an electrothermal film layer is formed on the roughened substrate surface by thermal vapor deposition. The electrothermal film layer is formed by dissolving powders of 80% to 85% tin chloride, 10% ferric chloride, 1% bismuth chloride, 1% to 1.5% antimony chloride, 2% cerium chloride, and 1% to 5% rare earth elements in a 50% alcohol solution, and then atomizing the solution and spraying it onto the substrate surface after the roughening transition layer at a temperature of 650 to 800 degrees Celsius and a pressure of 2 to 5 kPa. The formula ensures that the error in the coefficient of thermal expansion between the ceramic substrate layer and the electric heating film is within 5%. The thickness of the aforementioned electrothermal film is 30-100 micrometers.

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