Inorganic high-resistance layer with low expansion coefficient and high insulating property and preparation method thereof

Abstract

The invention discloses an inorganic high-resistance layer with low expansion coefficient and high insulating property and a preparation method thereof, and the inorganic high-resistance layer with low expansion coefficient and high insulating property comprises the following components in molar percentage: 45-55% of zinc oxide, 25-35% of silicon oxide, 5-15% of antimony oxide, 1-10% of bismuth oxide, 1-4% of iron oxide and 1-10% of nickel oxide. The inorganic high-resistance layer is high in expansion coefficient and good in insulation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of resistor chips for lightning arresters, and specifically to an inorganic high-resistance layer with a low expansion coefficient and high insulation performance and a preparation method thereof. Background Art

[0002] Zinc oxide varistor is a polycrystalline semiconductor component, which is mainly made of zinc oxide and sintered with various oxides such as bismuth oxide, antimony oxide, cobalt oxide, manganese dioxide and nickel oxide as additives. Due to its very excellent non-linear coefficient and good energy tolerance ability, it has been widely used. However, after being impacted by a large current, the zinc oxide varistor usually shows damage phenomena such as side flashover and breakdown.

[0003] In order to improve the ability of the zinc oxide varistor to withstand large current impacts, a layer of inorganic high-resistance layer with good performance is usually coated on its side. The inorganic high-resistance layer is a slurry made by mixing inorganic insulating powder, organic binder and corresponding solvent. Since its composition is similar to that of the zinc oxide varistor body, after being coated on the side of the varistor and sintered together, a transition layer with good insulation performance can be formed on the side, thereby improving the ability of the zinc oxide varistor to withstand large current impacts. However, a performance inorganic high-resistance layer usually encounters two major problems. One is the expansion coefficient matching the zinc oxide varistor (the expansion coefficient of the resistor chip is 6.6 - 6.8×10 -6 / °C), and the other is excellent insulation performance.

[0004] At present, with the improvement of the performance requirements of the products required by the market, improving the ability of the zinc oxide varistor to withstand large current impacts has also become the main problem to be solved nowadays. Therefore, providing an inorganic high-resistance layer with a low expansion coefficient and high insulation performance and a preparation method thereof is already a problem worthy of research. Summary of the Invention

[0005] The purpose of the present invention is to provide an inorganic high-resistance layer with a low expansion coefficient and high insulation performance, which is matched with the zinc oxide varistor and has good insulation performance.

[0006] The purpose of the present invention is achieved as follows: An inorganic high-resistance layer with a low expansion coefficient and high insulation performance, comprising the following components, by mole percentage: 45 - 55% of zinc oxide, 25 - 35% of silicon oxide, 5 - 15% of antimony oxide, 1 - 10% of bismuth oxide, 1 - 4% of iron oxide and 1 - 10% of nickel oxide.

[0007] A preparation method of an inorganic high-resistance layer with a low expansion coefficient and high insulation performance, comprising the following steps: S1. Weighing: Weigh zinc oxide, silicon oxide, antimony oxide, bismuth oxide, iron oxide and nickel oxide and mix them to obtain a first mixture. Then weigh a polyvinyl alcohol solution with a mass fraction of 3% and add it to the first mixture to obtain a second mixture. The weight of the polyvinyl alcohol solution is equal to the weight of the first mixture. S2. Ball milling: Add the second mixture in S1 to a ball mill, use zirconia balls to ball mill the second mixture, stop stirring after 4 hours of ball milling to obtain a slurry, and measure the average particle size of the slurry. If the particle size after ball milling does not meet the requirements, the ball milling time and stirring speed can be appropriately increased. S3. Filtration: Use a 100-mesh sieve to separate the zirconia balls from the slurry, and put the filtered slurry into a spare container for standby. The filtered slurry is the inorganic high-resistance layer slurry with a low expansion coefficient and high insulation performance. S4. Coating: Pour the filtered slurry in S3 into a coater, and use the coater to evenly coat the slurry on the surface of the resistor chip to obtain a coated resistor chip. S5. Sintering: Place the resistor chip with the inorganic high-resistance layer coated in S4 in a high-temperature furnace for sintering. After sintering is completed, naturally cool it to room temperature to obtain a sintered resistor chip. Grind, ultrasonically clean, dry, heat-treat and coat the sintered resistor chip to obtain a resistor chip coated with an inorganic high-resistance layer with a low expansion coefficient and high insulation performance.

[0008] In the step S2, the diameter of the zirconia balls is 5 mm, and the mass ratio of the second mixture to the zirconia balls is 1:2.5.

[0009] In the step S2, an antifoaming agent is added during the ball milling process. The obtained slurry has no agglomerates, the powder is evenly dispersed in the polyvinyl alcohol solution, and should not contain foam.

[0010] In the step S4, the coating thickness of the slurry is 0.1 - 0.15 mm.

[0011] In the step S5, pre-sinter at a temperature of 900 °C before sintering, keep the temperature for 2 hours for degumming, control the sintering temperature at 1150 °C, keep the temperature for 2 - 4 hours, and naturally cool it to room temperature.

[0012] The beneficial effects of the present invention are as follows: The zinc oxide resistor chip with a diameter of 42 mm prepared by using this inorganic high-resistance layer in the present invention does not show any adverse phenomena such as flashover on the side of the resistor chip after being impacted by a large current of 110 kA for 2 times at 4 / 10 μs, showing excellent insulation performance and improving the performance and quality of the product. This is mainly because iron-nickel can be further dissolved in the zinc oxide grains at high temperatures to form a synergistic effect, further reducing the expansion coefficient of the high-resistance layer and improving its insulation performance. Description of the Drawings

[0013] Figure 1This is the enlarged view of the product of Embodiment 3 of the present invention. Detailed implementation manners

[0014] The present invention will be further described below in conjunction with embodiments.

[0015] Comparative Example 1: An inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance is formulated according to the following molar percentages of raw materials: 50% zinc oxide, 25% silicon oxide, 10% antimony oxide, and 15% bismuth oxide, and a polyvinyl alcohol solution with a mass fraction of 3% equal to its weight is weighed; the above-mentioned weighed materials are added to a ball mill, and zirconia balls are used for ball milling to slowly stir the mixed materials, and an appropriate amount of defoaming agent is added to eliminate foam. After ball milling for 4 hours, stirring is stopped, and the average particle size of the slurry is measured. The average particle size of the slurry is required to be between 2.0 - 2.5 μm. If the particle size after ball milling does not meet the requirements, the ball milling time and stirring speed can be appropriately increased. The diameter of the zirconia balls used in the ball milling process is 5 mm, and the mass ratio of the materials to the zirconia balls is 1:2.5; after ball milling is completed, the zirconia balls are separated from the slurry using a 100-mesh sieve, and the filtered slurry is filled into a spare container for standby; the prepared inorganic high-resistance layer slurry is poured into a coater, and the coater is used to evenly coat the slurry on the surface of the resistor chip. The coating thickness of the inorganic high-resistance layer is required to be in the range of 0.1 - 0.15 mm; the coated resistor chip is placed in a high-temperature furnace for sintering. Before sintering, it is pre-sintered at a maximum temperature of 900 °C, degassed after holding for 2 hours, the sintering temperature is controlled at 1150 °C, and the holding time is 2 - 4 hours. Subsequently, it is naturally cooled to room temperature, and then grinding, ultrasonic cleaning, drying, heat treatment, and coating are carried out to obtain a resistor chip with good performance.

[0016] Comparative Example 2: An inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance is formulated according to the following molar percentages of raw materials: 50% zinc oxide, 25% silicon oxide, 10% antimony oxide, 10% bismuth oxide, and 5% nickel oxide. And a polyvinyl alcohol solution with a mass fraction of 3% equal to its weight is weighed; the above-mentioned weighed materials are added to a ball mill, and zirconia balls are used for ball milling. The mixed materials are stirred at a low speed, and an appropriate amount of defoaming agent is added to eliminate foam. After ball milling for 4 hours, the stirring is stopped, and the average particle size of the slurry is measured. The average particle size of the slurry is required to be between 2.0 - 2.5 μm. If the particle size after ball milling does not meet the requirements, the ball milling time and stirring speed can be appropriately increased. The diameter of the zirconia balls used in the ball milling process is 5 mm, and the mass ratio of the materials to the zirconia balls is 1:2.5; after ball milling is completed, the zirconia balls are separated from the slurry using a 100-mesh sieve, and the filtered slurry is filled into a spare container for standby; the prepared inorganic high-resistance layer slurry is poured into a coater, and the coater is used to evenly coat the slurry on the surface of the resistor chip. The coating thickness of the inorganic high-resistance layer is required to be in the range of 0.1 - 0.15 mm; the coated resistor chip is placed in a high-temperature furnace for sintering. Before sintering, it is pre-sintered at a maximum temperature of 900 °C, and degumming is carried out after holding for 2 hours. During sintering, the temperature is controlled at 1150 °C, and the holding time is 2 - 4 hours. Subsequently, it is naturally cooled to room temperature, and then grinding, ultrasonic cleaning, drying, heat treatment, and coating are carried out to obtain a resistor chip with good performance.

[0017] Example 1: An inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance is formulated according to the following molar percentages of raw materials: 50% zinc oxide, 25% silicon oxide, 10% antimony oxide, 8% bismuth oxide, 2% iron oxide, and 5% nickel oxide. And a polyvinyl alcohol solution with a mass fraction of 3% equal to its weight is weighed; the above-mentioned weighed materials are added to a ball mill, and zirconia balls are used for ball milling to stir the mixed materials at a low speed. An appropriate amount of defoaming agent is added to eliminate foam. After ball milling for 4 hours, the stirring is stopped, and the average particle size of the slurry is measured. The average particle size of the slurry is required to be between 2.0 - 2.5 μm. If the particle size after ball milling does not meet the requirements, the ball milling time and stirring speed can be appropriately increased. The diameter of the zirconia balls used in the ball milling process is 5 mm, and the mass ratio of the materials to the zirconia balls is 1:2.5; after ball milling is completed, the zirconia balls and the slurry are separated using a 100-mesh sieve, and the filtered slurry is filled into a spare container for standby; the prepared inorganic high-resistance layer slurry is poured into a coater, and the coater is used to evenly coat the slurry on the surface of the resistor chip. The coating thickness of the inorganic high-resistance layer is required to be in the range of 0.1 - 0.15 mm; the coated resistor chip is placed in a high-temperature furnace for sintering. It is pre-sintered at a maximum temperature of 900 °C before sintering, and degumming is carried out after holding for 2 hours. The temperature during sintering is controlled at 1150 °C, and the holding time is 2 - 4 hours. Subsequently, it is naturally cooled to room temperature, and then grinding, ultrasonic cleaning, drying, heat treatment, and coating are carried out to obtain a resistor chip with good performance.

[0018] Example 2: An inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance is formulated according to the following molar percentages of raw materials: zinc oxide 49%, silicon dioxide 25%, antimony oxide 10%, bismuth oxide 8%, iron oxide 3%, and nickel oxide 5%. Also, a polyvinyl alcohol solution with a mass fraction of 3% equal to its weight is weighed. The above-mentioned weighed materials are added to a ball mill, and zirconia balls are used for ball milling. The mixed materials are stirred at a low speed, and an appropriate amount of defoaming agent is added to eliminate foam. After ball milling for 4 hours, the stirring is stopped, and the average particle size of the slurry is measured. The average particle size of the slurry is required to be between 2.0 - 2.5 μm. If the particle size after ball milling does not meet the requirements, the ball milling time and stirring speed can be appropriately increased. The diameter of the zirconia balls used in the ball milling process is 5 mm, and the ratio of the material to the zirconia balls is 1:2.5. After ball milling, the zirconia balls are separated from the slurry using a 100-mesh sieve, and the filtered slurry is filled into a spare container for standby. The prepared inorganic high-resistance layer slurry is poured into a coater, and the coater is used to evenly coat the slurry on the surface of the resistor chip. The coating thickness of the inorganic high-resistance layer is required to be in the range of 0.1 - 0.15 mm. The coated resistor chip is placed in a high-temperature furnace for sintering. Before sintering, it is pre-sintered at a maximum temperature of 900 °C, and degumming is carried out after holding for 2 hours. During sintering, the temperature is controlled at 1150 °C, and the holding time is 2 - 4 hours. Subsequently, it is naturally cooled to room temperature, and then grinding, ultrasonic cleaning, drying, heat treatment, and coating are carried out to obtain a resistor chip with good performance.

[0019] Example 3: An inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance is formulated according to the following molar percentages of raw materials: zinc oxide 48%, silicon oxide 25%, antimony oxide 10%, bismuth oxide 8%, iron oxide 4%, and nickel oxide 5%. And a polyvinyl alcohol solution with a mass fraction of 3% equal to its weight is weighed. Add the above-mentioned weighed materials into a ball mill, use zirconia balls for ball milling, stir the mixed materials at a low speed, add an appropriate amount of defoaming agent to eliminate foam, stop stirring after 4 hours of ball milling, measure the average particle size of the slurry, and the average particle size of the slurry is required to be between 2.0 - 2.5 μm. If the particle size after ball milling does not meet the requirements, the ball milling time and stirring speed can be appropriately increased. The diameter of the zirconia balls used in the ball milling process is 5 mm, and the ratio of the material to the zirconia balls is 1:2.5. After ball milling, use a 100-mesh sieve to separate the zirconia balls from the slurry, and pour the filtered slurry into a spare container for standby. Pour the prepared inorganic high-resistance layer slurry into a coater, and use the coater to evenly coat the slurry on the surface of the resistor chip. The coating thickness range of the inorganic high-resistance layer is required to be 0.1 - 0.15 mm. Place the coated resistor chip in a high-temperature furnace for sintering. Pre-sinter at the highest temperature of 900 °C before sintering, degrease after holding for 2 hours, control the temperature at 1150 °C during sintering, and the holding time is 2 - 4 hours. Subsequently, cool naturally to room temperature, and then perform wafer grinding, ultrasonic cleaning, drying, heat treatment, and coating to obtain a resistor chip with good performance.

[0020] The inorganic high-resistance layer slurry prepared by using the formulas and processes described in the above Comparative Examples 1 and 2 and Examples 1, 2, and 3 is coated on the surface of a resistor chip blank with a diameter of 42 mm through a coater, and then after pre-sintering, sintering, wafer grinding, ultrasonic cleaning, drying, heat treatment, and coating, the zinc oxide resistor chips obtained have the following test parameters: 4 / 10 μs high-current impulse withstand test: 8 / 20 μs repetitive charge transfer test: Comparative Example 1 is the high-resistance layer before improvement. When testing the repeated transfer of charges, the high-resistance layer peeled off, indicating that the expansion coefficients of the high-resistance layer body and the high-resistance layer are inconsistent. Comparative Example 2 is a sample with 5% nickel oxide added. Side flashover occurred during the high-current test, indicating that the expansion coefficient was improved, but the total insulation energy was insufficient. The zinc oxide resistor chips with a diameter of 42 mm prepared from the inorganic high-resistance layers used in Examples 1 - 3 passed the 4 / 10 μs high-current 110 kA impact withstand test 2 times, and no flashover or other adverse phenomena occurred on the side of the resistor chips. Compared with the conventional (Comparative Example 1, Comparative Example 2) inorganic high-resistance layers, the current-carrying capacity and insulation performance were improved, and the product quality was improved. This is mainly because iron-nickel can be further dissolved in zinc oxide grains at high temperatures to form a synergistic effect, further reducing the expansion coefficient of the high-resistance layer and improving its insulation performance. The enlarged view of Example 3 is as shown in Figure 1 shown, and it can be seen from Figure 1 that the contact between the resistor chip body and the high-resistance layer is good, and the expansion coefficients are basically the same.

Claims

1. An inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance, characterized in that It comprises the following components by mole percentage: 45-55% of zinc oxide, 25-35% of silicon oxide, 5-15% of antimony oxide, 1-10% of bismuth oxide, 1-4% of iron oxide and 1-10% of nickel oxide.

2. A method for preparing an inorganic high-resistance layer with a low coefficient of thermal expansion and high insulation performance as described in claim 1, characterized in that, It comprises the following steps: S1. Weighing: Weigh zinc oxide, silicon oxide, antimony oxide, bismuth oxide, iron oxide and nickel oxide and mix them to obtain a first mixture. Then weigh a polyvinyl alcohol solution with a mass fraction of 3% and add it to the first mixture to obtain a second mixture. The weight of the polyvinyl alcohol solution is equal to that of the first mixture. S2. Ball milling: Add the second mixture in S1 to a ball mill, and use zirconia balls to ball mill the second mixture. Stop stirring after 4 hours of ball milling to obtain a slurry. S3. Filtration: Use a 100-mesh sieve to separate the zirconia balls from the slurry, and put the filtered slurry into a spare container for standby. The filtered slurry is the inorganic high-resistance layer slurry with a low expansion coefficient and high insulation performance. S4. Coating: Pour the filtered slurry in S3 into a coater, and use the coater to evenly coat the slurry on the surface of the resistor chip to obtain a coated resistor chip. S5. Sintering: Place the resistor chip with the inorganic high-resistance layer coated in S4 in a high-temperature furnace for sintering. After sintering is completed, naturally cool it to room temperature to obtain a sintered resistor chip. Grind, ultrasonically clean, dry, heat-treat and coat the sintered resistor chip to obtain a resistor chip coated with an inorganic high-resistance layer with a low expansion coefficient and high insulation performance.

3. The preparation method of the inorganic high-resistance layer with low expansion coefficient and high insulation performance according to claim 2, characterized in that, In the step S2, the diameter of the zirconia balls is 5 mm, and the mass ratio of the second mixture to the zirconia balls is 1:2.

5.

4. The preparation method of the inorganic high-resistance layer with low coefficient of thermal expansion and high insulation performance according to claim 2, characterized in that, In the step S2, an antifoaming agent is added during the ball milling process, and the obtained slurry has no agglomerates, and the powder is evenly dispersed in the polyvinyl alcohol solution.

5. The preparation method of the inorganic high-resistance layer with low expansion coefficient and high insulation performance according to claim 2, characterized in that, In the step S4, the coating thickness of the slurry is 0.1-0.15 mm.

6. The preparation method of the inorganic high-resistance layer with low coefficient of thermal expansion and high insulation performance according to claim 2, characterized in that, In the step S5, pre-sinter at 900 °C before sintering, keep the temperature for 2 hours for degumming, control the sintering temperature at 1150 °C, keep the temperature for 2-4 hours, and naturally cool it to room temperature.

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