CN100382205C - Preparation and Application of High Potential Gradient Zinc Oxide Varistor Material - Google Patents

Abstract

The invention relates to the preparation and application of a high potential gradient zinc oxide varistor material, belonging to the technical field of varistor material manufacture and application. Preparation of the material: mix the raw materials in a molar ratio of ZnO: Bi ₂ O ₃ : _Sb 2 O ₃ : Cr ₂ O ₃ : Co ₂ O ₃ : MnO ₂ is 96.5: 0.7: 1.0: 0.5: 0.8: 0.5, and pass The first high-energy fine grinding, low-temperature sintering, and the second high-energy fine grinding are three steps to obtain the product, a high-potential gradient zinc oxide varistor material. The application of the material, that is, the preparation of high-potential gradient zinc oxide varistors: using the material as raw material, through four steps of compression molding, low-temperature sintering, coating electrode silver paste and welding electrode leads, the product is obtained, and high-potential gradient oxidation Zinc Varistor. The invention has two high-energy ball mills to greatly refine the grain size of the metal oxide mixed powder; the sintering temperature is only 900°C, so that the grain size of the obtained high-potential gradient zinc oxide varistor is 1.5-3.5 μm; Conventional equipment, simple process, low production cost and other advantages.

Description

Preparation and Application of High Potential Gradient Zinc Oxide Varistor Material

technical field

The invention relates to the preparation and application of a high-potential gradient zinc oxide varistor material, to be precise, to a method for preparing a high-potential gradient zinc oxide varistor material by a low-temperature sintering process and the application of the material, which belongs to the varistor The technical field of fabrication and application of resistive materials.

Background technique

Zinc oxide varistors have excellent volt-ampere characteristics and are widely used in the manufacture of arrester valves. In order to realize the miniaturization and light weight of arrester valves and reduce manufacturing costs, it is a development trend to develop high potential gradients ^[1] . Viswanath ^[2] used ultrafine nano-powder obtained by gel suspension and centrifugal separation to prepare a zinc oxide varistor with a potential gradient as high as 3000V/mm at a sintering temperature of 750°C. Duran ^[3] also used chemical methods to prepare nano powders, and prepared zinc oxide varistors with a potential gradient of 2000V/mm at two-stage sintering temperatures of 900°C and 825°C. The above two methods all have the disadvantages of complicated process and high cost, and it is difficult to form large-scale production. Oh ^[4] adopts the method of sintering bismuth oxide-free powder for the first time, coating with bismuth oxide-containing slurry and then sintering the second time. The potential gradient of the developed zinc oxide varistor is 500-900V/mm, but the sintering temperature High, the first and second sintering temperatures are 1200-1350°C and 1000-1200°C respectively. Fah ^[5] used the high-energy ball milling method close to industrial technology to refine the powder to about 17nm, first uniaxial pressing and then isostatic pressing, and prepared a potential gradient of 440V/mm when the sintering temperature dropped below 1100°C. zinc oxide varistors. Alamdari ^[6] used high-energy ball milling with additives different from Fah, and the potential gradient of the zinc oxide varistor prepared at 1000 °C was 1550V/mm. However, the sintering temperature of the last two methods is still high, and the isostatic pressing technology increases the cost.

references:

[1] Li Shengtao. Basic research and technical development of ZnO varistors [J]. Electromagnetic arrester, 1998, (3): 42-48.

[2] R.N.Viswanath, S.Ramasamy, R.Ramamoorthy, et al.Preparation and characterization of nanocrystalline ZnO based materials for varistor applications[J].Nanostructured materials, 1995, 6: 993-996.

[3]P.Duran, F.Capel, J.Tartaj, C.Moure.Effects of low-temperature annealing on the microstructure and electrical properties of doped-ZnO varistors[J].KeyEngineering Materials, 2002, 206-213: 1389- 1392.

[4]Myung H.Oh, Kyung J, Lee, In J.Chung, etal.Fabrication method for highvoltage zinc oxide varistor[P].U.S.: 5004573, Apr.2, 1991.

[5] C.P.Fah, J.Wang.Effect of high-energy mechanical activation on the microstructure and electrical properties of ZnO-based varistors[J], Solid State Ionics, 2000, 132: 107-117.

[6] H.D. Alamdari, S. Boily, M. Blouin, et al. High energy ball milled nanocrystalline ZnO varistors [J]. Materials Science Forum, 2000, 343-346: 909-917.

Contents of the invention

The first technical problem to be solved by the present invention is to provide a method for preparing a high potential gradient zinc oxide varistor material. The method has the advantages of simple process, easy operation, low requirement on equipment and low production cost.

The technical solution of the present invention to solve the above technical problems is to use commercially available micron-sized zinc oxide ZnO, bismuth trioxide Bi ₂ O ₃ , antimony trioxide Sb ₂ O ₃ , dichromium trioxide Cr ₂ O ₃ , dicobalt trioxide Co ₂ O ₃ and manganese dioxide MnO ₂ are used as raw materials, and the molar ratio of raw materials ZnO: _{Bi 2} O ₃ : Sb ₂ O ₃ : Cr ₂ O ₃ : _{Co 2} O _{3 :} MnO ₂ is 96.5: 0.7: 1.0: 0.5 : 0.8: 0.5, through the first three steps of high-energy fine grinding, low-temperature sintering, and second high-energy fine grinding, a high-potential gradient zinc oxide varistor material is obtained. The said material is the homogeneous mixed powder of the above-mentioned oxide nanoscale powder.

The above-mentioned technical solution is now described in detail.

A method for preparing a high-potential gradient zinc oxide varistor material, characterized in that, the specific operation steps:

The first step is the first high-energy fine grinding

Commercially available micron-sized zinc oxide ZnO, bismuth trioxide Bi ₂ O ₃ , antimony trioxide Sb ₂ O ₃ , chromium trioxide Cr ₂ O ₃ , cobalt trioxide Co ₂ O ₃ and manganese dioxide MnO ₂ The powder is used as the raw material, and the molar ratio of ZnO: Bi ₂ O ₃ : Sb ₂ O ₃ : Cr ₂ O ₃ : Co ₂ O ₃ : MnO ₂ is 96.5: 0.7: 1.0: 0.5: 0.8: 0.5 to form a metal oxide mixture powder, the mixed powder is put into a high-energy ball mill, under the conditions of high-energy ball milling with a rotating speed and a ball-to-powder ratio of 300-650rpm and 15-40:1, respectively, wet-milling in absolute ethanol for 2-10 hours, drying, and mixing The powder was then dry-milled for 0.5 hour under the same high-energy ball milling conditions to obtain dry metal oxide mixed powder;

Second step low temperature sintering

After pressing the dry metal oxide mixed powder obtained in the first step, sintering at a low temperature of 350-650° C. for 1.5-2.5 hours to obtain a sintered block;

The third step is the second high-energy fine grinding

High-energy ball milling conditions: the same as the first step, the sintered block obtained in the second step is pulverized, wet-milled in absolute ethanol for 3-6 hours, dried, and then dry-milled for 0.5 hours to obtain high-potential gradient zinc oxide Varistor material.

The further feature of the technical solution of the present invention is that the high-energy ball mill is a planetary high-energy ball mill using steel wear-resistant balls and nylon tanks.

The second technical problem to be solved by the present invention is to provide the application of high potential gradient zinc oxide varistor material, to be precise, to provide a method for preparing high potential gradient zinc oxide varistor using the above-mentioned prepared material as raw material.

The present invention adopts the following technical solutions to achieve the above technical problems. Using the above-mentioned prepared materials as raw materials, the high-potential gradient zinc oxide varistor is obtained through four steps of pressing, low-temperature sintering, coating electrode silver paste and welding electrode leads.

Now describe the described technical scheme in detail.

A method for preparing a high-potential gradient zinc oxide varistor, characterized in that, the specific operation steps:

The first step of compression molding

Press the high potential gradient zinc oxide varistor material into a columnar entity with a density of 5.50-5.57g/ ^cm3 ;

Second step low temperature sintering

Put the columnar entity obtained in the first step into a resistance furnace, and sinter at a low temperature of 900°C for 2-8 hours;

The third step is to apply electrode silver paste

Coat the electrode silver paste on both ends of the columnar entity fired in the second step, put it into a resistance furnace, keep it warm at 600°C for 10-30 minutes, and cool to room temperature with the furnace;

The fourth step is to weld the electrode leads

On the silver paste surface of the electrode fired in the third step, the electrode leads are welded by a brazing process to obtain a high potential gradient zinc oxide varistor.

The indicators of the above products: density is 5.50-5.57g/cm ³ , varistor potential (V _1mA ) gradient is 820-900V/mm, nonlinear index is 31-40, leakage current (0.75V _1mA ) is 6.27-9.60 μA.

Compared with the background technology, the present invention has the following outstanding advantages:

(1) X-ray diffraction (XRD) analysis shows that after two times of high-energy ball milling, the grain size of the metal oxide mixed powder is reduced to about 22nm, and the grain size is greatly refined, ensuring good low-temperature sintering performance.

(2) The low-temperature sintering process in the second step causes a certain solid-state reaction between the components of the metal oxide mixed powder, and the dispersion uniformity of each component is greatly improved. The sintering performance has a great promotion effect on obtaining a uniform metal oxide mixed powder sintered body.

(3) The sintering temperature is greatly reduced, only 900°C. Fracture analysis of the scanning electron microscope shows that the crystal grain size of the high potential gradient zinc oxide varistor prepared by the method of the invention is 1.5-3.5 μm.

(4) Conventional equipment is adopted, the process is simple, and the production cost is low.

The performance comparison between the high potential gradient zinc oxide varistor prepared by the method of the present invention and similar resistors at home and abroad is listed in Table 1.

Table 1

Varistor Compare objects Density (g/cm³) Varistor potential gradient (V/mm) nonlinear index Sintering temperature (℃) Zinc Oxide Varistor Fah high energy ball milling method 5.51-5.59 420-440 greater than 50 1100 Zinc Oxide Varistor Domestic doping rare earth method —— 583 36 1100-1200 Zinc Oxide Varistor this invention 5.50-5.57 820-900 31-40 900

Description of drawings

Figure 1 is the X-ray diffraction pattern of metal oxide mixed powder after high energy ball milling: 5 hours of wet milling and 1 hour of dry milling.

Figure 2 is the SEM fracture morphology of metal oxide mixed powder after high energy ball milling: wet milling for 5 hours and dry milling for 1 hour, sintering at 900°C and heat preservation for 2 hours.

Detailed ways

All the embodiments are completely operated according to the above-mentioned preparation method of the high-potential gradient zinc oxide varistor material and the above-mentioned preparation method of the high-potential gradient zinc oxide varistor.

Example 1

(1) Preparation of high potential gradient zinc oxide varistor materials

In the first step, commercially available micron-sized zinc oxide ZnO, bismuth trioxide Bi ₂ O ₃ , antimony trioxide Sb ₂ O ₃ , chromium trioxide Cr ₂ O ₃ , cobalt trioxide Co ₂ O ₃ and Manganese dioxide MnO ₂ powder is used as raw material, and the molar ratio of ZnO: _{Bi 2} O ₃ : Sb ₂ O ₃ : Cr ₂ O ₃ : Co ₂ O _{3 :} MnO ₂ is 96.5: 0.7: 1.0: 0.5: 0.8: 0.5 mixed into metal oxide mixed powder. The high-energy ball mill is a planetary high-energy ball mill, which uses steel wear-resistant balls and nylon tanks. High-energy ball milling conditions: rotating speed 620rpm, ball-to-powder ratio 16:1. Wet mill in absolute ethanol for 2 hours, dry and dry mill for 0.5 hour. In the second step, a 10-ton universal hydraulic press is pressed into blocks, and sintered at a low temperature of 380°C for 1.5 hours in a resistance furnace. In the third step, the sintered mass is pulverized. High energy ball milling conditions: the same as the first step. wet grinding in absolute ethanol for 3 hours, drying, and dry grinding for 0.5 hour to obtain a high potential gradient zinc oxide varistor material.

(2) Preparation of high potential gradient zinc oxide varistors

In the first step, the dry high-potential gradient zinc oxide varistor material is pressed into a columnar entity with a density of 5.50g/ ^cm3 under a 10-ton universal hydraulic press, such as a cylindrical standard sample of Φ10×2.0mm. In the second step, the standard sample was placed in a resistance furnace and sintered at a low temperature of 900°C for 2 hours. In the third step, evenly coat the electrode silver paste on the two end surfaces of the fired standard sample, put it into a resistance furnace, keep it warm at 600°C for 10 minutes, and cool down to room temperature with the furnace. In the fourth step, on the surface of the fired electrode silver paste, the electrode leads are welded by a brazing process to obtain a high potential gradient zinc oxide varistor.

The technical indicators of the above-mentioned products, high-potential gradient zinc oxide varistor: the density is 5.50g/cm ³ , the varistor potential (V _1mA ) gradient is 875.44V/mm, the nonlinear index is 31.5, the leakage current (0.75V _1mA) ) is 9.60μA.

Example 2

(1) Preparation of high potential gradient zinc oxide varistor materials

In the first step, commercially available micron-sized zinc oxide ZnO, bismuth trioxide Bi ₂ O ₃ , antimony trioxide Sb ₂ O ₃ , chromium trioxide Cr ₂ O ₃ , cobalt trioxide Co ₂ O ₃ and Manganese dioxide MnO ₂ powder is used as raw material, and the molar ratio of ZnO: _{Bi 2} O ₃ : Sb ₂ O ₃ : Cr ₂ O ₃ : Co ₂ O _{3 :} MnO ₂ is 96.5: 0.7: 1.0: 0.5: 0.8: 0.5 mixed into metal oxide mixed powder. The high-energy ball mill is a planetary high-energy ball mill, which uses steel wear-resistant balls and nylon tanks. High-energy ball milling conditions: rotating speed 460rpm, ball-to-powder ratio 20:1. Wet mill in absolute ethanol for 2 hours, dry and dry mill for 0.5 hour. In the second step, a 15-ton universal hydraulic press is pressed into blocks, and sintered at a low temperature of 550 ° C for 2 hours in a resistance furnace. In the third step, the sintered mass is pulverized. High energy ball milling conditions: the same as the first step. wet grinding in absolute ethanol for 3 hours, drying, and dry grinding for 0.5 hour to obtain a high potential gradient zinc oxide varistor material.

(2) Preparation of high potential gradient zinc oxide varistors

In the first step, the dry high-potential gradient zinc oxide varistor material is pressed into a columnar entity with a density of 5.56g/ ^cm3 under a 15-ton universal hydraulic press, such as a cylindrical standard sample of Φ10×2.0mm. In the second step, the standard sample was placed in a resistance furnace and sintered at a low temperature of 900°C for 4 hours. In the third step, evenly coat the electrode silver paste on the two end surfaces of the fired standard sample, put it into a resistance furnace, keep it at 600°C for 20 minutes, and cool down to room temperature with the furnace. In the fourth step, on the surface of the fired electrode silver paste, the electrode leads are welded by a brazing process to obtain a high potential gradient zinc oxide varistor.

The technical indicators of the above products, high potential gradient zinc oxide varistor: density is 5.56g/cm ³ , varistor potential (V _1mA ) gradient is 819.77V/mm, nonlinear index is 36, leakage current (0.75V _1mA ) is 6.27μA.

Example 3.

(1) Preparation of high potential gradient zinc oxide varistor materials

In the first step, commercially available micron-sized zinc oxide ZnO, bismuth trioxide Bi ₂ O ₃ , antimony trioxide Sb ₂ O ₃ , chromium trioxide Cr ₂ O ₃ , cobalt trioxide Co ₂ O ₃ and Manganese dioxide MnO ₂ powder is used as raw material, and the molar ratio of ZnO: _{Bi 2} O ₃ : Sb ₂ O ₃ : Cr ₂ O ₃ : Co ₂ O _{3 :} MnO ₂ is 96.5: 0.7: 1.0: 0.5: 0.8: 0.5 mixed into metal oxide mixed powder. The high-energy ball mill is a planetary high-energy ball mill, which uses steel wear-resistant balls and nylon tanks. High-energy ball milling conditions: rotating speed 320rpm, ball-to-powder ratio 40:1. Wet grinding in absolute ethanol for 8 hours, drying, and dry grinding for 0.5 hours. In the second step, a 25-ton universal hydraulic press is pressed into blocks, and sintered at a low temperature of 630°C for 2.5 hours in a resistance furnace. In the third step, the sintered mass is pulverized. High energy ball milling conditions: the same as the first step. Wet grinding in absolute ethanol for 6 hours, drying, and dry grinding for 0.5 hours to obtain a high potential gradient zinc oxide varistor material.

(2) Preparation of high potential gradient zinc oxide varistors

In the first step, the dry high-potential gradient zinc oxide varistor material is pressed into a columnar entity with a density of 5.57g/ ^cm3 under a 25-ton universal hydraulic press, such as a cylindrical standard sample of Φ10×2.0mm. In the second step, the standard sample was placed in a resistance furnace and sintered at a low temperature of 900°C for 4 hours. In the third step, after evenly coating the electrode silver paste on the two end surfaces of the fired standard sample, put it into a resistance furnace, keep it warm at 600°C for 30 minutes, and cool down to room temperature with the furnace. In the fourth step, on the surface of the fired electrode silver paste, the electrode leads are welded by a brazing process to obtain a high potential gradient zinc oxide varistor.

The technical indicators of the above products, high-potential gradient zinc oxide varistor: density is 5.57g/cm ³ , varistor potential varistor potential (V _1mA ) gradient is 870.00V/mm, nonlinear index is 40, leakage current (0.75 V at _1mA ) is 8.37µA.

Claims (3)

1. the preparation method of a high-potential gradient zinc oxide piezoresistive material is characterized in that, the concrete operations step:

The first step is the high energy fine grinding for the first time

To be purchased micron order zinc oxide ZnO, bismuth oxide Bi ₂O ₃, antimonous oxide Sb ₂O ₃, chrome green Cr ₂O ₃, cobalt sesquioxide Co ₂O ₃With manganese dioxide MnO ₂Powder is raw material, ZnO in molar ratio: Bi ₂O ₃: Sb ₂O ₃: Cr ₂O ₃: Co ₂O ₃: MnO ₂It is 96.5: 0.7: 1.0: be mixed into the metal oxide mixed powder at 0.5: 0.8: 0.5, this mixed powder is put into high energy ball mill, be respectively 300-650rpm and 15-40 at rotating speed and ball powder ratio: under 1 the high-energy ball milling condition, in absolute ethyl alcohol wet-milling 2-10 hour, oven dry, this mixed powder under identical high-energy ball milling condition, was dry grinded 0.5 hour again, got dry metal oxide mixed powder;

The second step low-temperature sintering

After the dry metal oxide mixed powder compacting that the first step is obtained, at 350-650 ℃ of following low-temperature sintering 1.5-2.5 hour, the sintering block;

The high energy fine grinding for the second time of the 3rd step

The high-energy ball milling condition: identical with the first step, after the sintering block that second step was obtained was pulverized, in absolute ethyl alcohol wet-milling 3-6 hour, oven dry was dry grinded 0.5 hour again, high-potential gradient zinc oxide piezoresistive material.

2. the preparation method of high-potential gradient zinc oxide piezoresistive material according to claim 1 is characterized in that, high energy ball mill is the planetary high-energy ball mill that adopts wear-resisting ball of steel and nylon jar.

3. one kind is raw material with the described high-potential gradient zinc oxide piezoresistive material of claim 1, prepares the method for high-potential gradient zinc oxide piezoresistive, it is characterized in that the concrete operations step:

First step compression moulding

It is 5.50-5.57g/cm that high-potential gradient zinc oxide piezoresistive material is pressed into density ³The cylindricality entity;

The second step low-temperature sintering

The cylindricality entity that the first step obtains is put into resistance furnace, 900 ℃ following low-temperature sintering 2-8 hour;

The 3rd step was coated with electrode silver plasm

Go on foot on two end faces of the cylindricality entity that burns till second, coat electrode silver plasm, put into resistance furnace, 600 ℃ are incubated 10-30 minute down, cool to room temperature with the furnace;

The 4th step welding electrode lead-in wire

Go on foot on the electrode silver plasm face that burns till the 3rd, adopt soldering processes welding electrode lead-in wire, get high-potential gradient zinc oxide piezoresistive.

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