CN111508676A - Small-size distribution network annular zinc oxide resistance card and preparation method thereof - Google Patents
Small-size distribution network annular zinc oxide resistance card and preparation method thereof Download PDFInfo
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- CN111508676A CN111508676A CN202010333368.5A CN202010333368A CN111508676A CN 111508676 A CN111508676 A CN 111508676A CN 202010333368 A CN202010333368 A CN 202010333368A CN 111508676 A CN111508676 A CN 111508676A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/06—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base
- H01C17/065—Apparatus or processes specially adapted for manufacturing resistors adapted for coating resistive material on a base by thick film techniques, e.g. serigraphy
- H01C17/06506—Precursor compositions therefor, e.g. pastes, inks, glass frits
- H01C17/06513—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component
- H01C17/06533—Precursor compositions therefor, e.g. pastes, inks, glass frits characterised by the resistive component composed of oxides
- H01C17/06546—Oxides of zinc or cadmium
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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- H01C17/00—Apparatus or processes specially adapted for manufacturing resistors
- H01C17/30—Apparatus or processes specially adapted for manufacturing resistors adapted for baking
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Abstract
The invention relates to the technical field of high-voltage electrical sensitive ceramic materials, and particularly discloses a small-size distribution network annular zinc oxide resistance card and a preparation method thereof. The oxide powder is ground into fine particles, and then the metal salts are deposited on the surfaces of the oxide powder particles by a gradual deposition method to form a thin deposition layer. Through the deposition layer, the connection among oxide powder particles is tighter, the uniformity of the distribution of the grain components of the resistor disc is enhanced, the generation of tiny air gaps is reduced, and the potential gradient of the resistor disc is improved. Compared with the zinc oxide resistance card prepared by the conventional process, the small-size distribution network annular zinc oxide resistance card provided by the invention has the advantages that the density is higher, the distribution of all components is more uniform, and the defects in the resistance card are fewer, so that the through-current capacity is larger, the potential gradient is higher, and the comprehensive performance is better.
Description
Technical Field
The invention relates to the technical field of high-voltage electrical sensitive ceramic materials, in particular to a small-size distribution network annular zinc oxide resistance card and a preparation method thereof.
Background
The zinc oxide resistor disc is a core component of a metal oxide lightning arrester of power grid operation protection equipment, and is one of the most effective means for preventing lightning trip and damaging electrical equipment. The lightning protection principle of the zinc oxide resistance card is as follows: when the lightning overvoltage and the operation overvoltage are met, the resistance value of the zinc oxide resistance sheet can be instantly changed from high resistance to low resistance, so that strong instant overcurrent flows into the ground through the zinc oxide resistance sheet, and the electric equipment is prevented from being attacked by the overvoltage to influence the safe operation of a power grid.
At present, cake-shaped resistance discs are mostly adopted in the traditional zinc oxide lightning arrester, for example, in patents CN101383208 and CN100562951, and a cylindrical grinding tool is used for pressing to obtain the cake-shaped resistance discs. The lightning arrester prepared by the cake-shaped zinc oxide resistor disc needs to be installed in parallel with the insulator, the hanging point of the lightning arrester needs to be additionally increased during installation, and even the pole tower needs to be modified, so that the installation and construction difficulty is high, and the operability is poor. Meanwhile, when the lightning arresters installed in parallel are applied to a distribution network, the distribution network line is wide in points, the workload of tower transformation and lightning arrester installation is large, the cost is high, and the economical efficiency is poor. The lightning arrester and the insulator are connected into a whole, so that the installation is more convenient, the lightning arrester hanging points do not need to be increased, the operability is strong, and the economical efficiency is good. The lightning arrester and the insulator are installed in series, and an annular zinc oxide resistance card is required. CN206947082 discloses an annular zinc oxide resistance card which is prepared by a traditional solid phase method, wherein electrodes are designed on the top surface and the side surface, and the outside of the resistance card can be prevented from being oxidized. When zinc oxide resistance sheets are prepared by a traditional solid phase method (such as patents CN105884345, CN101950648, CN101503292 and CN110078494), zinc oxide, bismuth oxide, antimony oxide and other metal oxides are directly ground, granulated, tabletted and sintered to prepare finished resistance sheet products, and the preparation method has the characteristic of simple preparation process. However, because the center of the annular resistance card is a circular hole, when the resistance card is prepared by adopting a traditional solid phase method, the stress at each point of the resistance card is uneven when the resistance card is pressed, the phenomenon of uneven components in the resistance card is easy to occur, the through-current capacity of the resistance card is reduced, the mechanical strength is reduced, the stress is uneven, and the resistance card is easy to damage or even crack in the lightning protection process. Therefore, the formula and the preparation process of the high-performance annular resistance card with uniformly distributed internal components are urgently needed to be researched.
In addition, the requirement of the current distribution network line arrester standard (D L/T815-2012) on a 10kV resistor disc is low, namely the distribution network arrester with the impulse current resistance of only 65 kA. and the impulse current resistance of only 65kA is often damaged due to overlarge lightning current, so that the distribution network annular zinc oxide resistor disc with the impulse current resistance of more than 65kA needs to be developed.
In summary, at present, there is an urgent need to develop a small-size distribution network annular zinc oxide resistance card with impulse current resistance greater than 65kA and a preparation method thereof, which are applied to a lightning arrester installed in series with an insulator and improve the overall lightning protection level of a power transmission line in China. The method comprises the steps of gradually depositing a metal salt mixed solution on zinc oxide powder through a slow-release precipitator, and aging to obtain a prefabricated powder; the material composition in the grain boundary of the zinc oxide resistance card is adjusted through the two steps of gradual deposition and aging, and the small-size distribution network annular zinc oxide resistance card with higher density, better grain uniformity, fewer internal defects and higher flow capacity is prepared.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a small-size distribution network annular zinc oxide resistance card and a preparation method thereof.
In order to realize the purpose of the invention, the technical scheme of the invention is as follows:
in a first aspect, the invention provides a preparation method of a small-size distribution network annular zinc oxide resistance card, which comprises the following steps:
(1) mixing and grinding 85-93 parts by weight of zinc oxide, 1.5-4.0 parts by weight of bismuth oxide, 1-3 parts by weight of cobalt oxide, 0.5-1.2 parts by weight of nickel oxide, 0.2-1.0 part by weight of manganese oxide, 1.5-5.0 parts by weight of antimony oxide, 0.4-3.2 parts by weight of silicon oxide, 0.1-0.5 part by weight of zirconium oxide, 0.1-0.5 part by weight of gallium oxide, 0.1-0.5 part by weight of yttrium oxide and 0.1-0.3 part by weight of glass powder to obtain oxide solid powder;
(2) dissolving a slow-release precipitator in water to obtain a slow-release precipitator aqueous solution with the mass fraction of 10-80%, and then mixing the slow-release precipitator aqueous solution and the oxide solid powder obtained in the step (1) in a weight ratio of 2: 1-10: 1 under the condition of stirring to prepare a mixed solution to be deposited;
(3) dissolving metal salt in water to obtain a metal salt mixed solution with the mass fraction of 10-50%, dropwise adding the metal salt mixed solution into the mixed solution to be deposited obtained in the step (2) within 0.5-4 h under the conditions of stirring and heating, reacting and aging for 2-48 h after dropwise adding to obtain a deposit, filtering, washing and drying the deposit to obtain a prefabricated powder;
(4) placing the prefabricated powder obtained in the step (3) in a calcining furnace, pre-burning at a preset temperature, grinding a calcined product, and then washing and drying to obtain composite powder;
(5) adding a small amount of water into the composite powder obtained in the step (4), grinding to prepare mixed slurry, and drying and granulating through a granulation drying tower to obtain granules;
(6) adding the granulated material obtained in the step (5) into a tablet press and pressing into an annular coarse blank;
(7) and (4) sintering the annular rough blank obtained in the step (6) in a calcining furnace, and obtaining the large-through-flow high-gradient annular zinc oxide resistance card through processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface.
Furthermore, in the step (1), the zinc oxide, bismuth oxide, cobalt oxide, nickel oxide, manganese oxide, antimony oxide, silicon oxide, zirconium oxide, gallium oxide, yttrium oxide and glass powder are micron-sized or nano-sized powder, wherein nano-sized powder is preferred.
Furthermore, the preparation method of the nano-scale powder adopts one or more of a gas phase high-temperature oxidation method, an aqueous solution uniform precipitation method and a spray pyrolysis method.
More specifically, the gas phase high temperature oxidation method is a method in which a metal is heated to be converted into a metal vapor, and at the same time, the metal vapor is oxidized into a metal oxide powder by oxygen in the air. The homogeneous precipitation method of aqueous solution is to precipitate metal salts by using precipitation ions, and then to prepare metal oxide powder by heating treatment. The spray pyrolysis method is to spray a metal salt solution into a high-temperature atmosphere in a mist form, at the moment, evaporation of a solvent and thermal decomposition of the metal salt are immediately caused, and then a solid phase is precipitated due to supersaturation, so that the nano powder is directly obtained.
Further, in the step (2), the slow release precipitator is one or a combination of ammonium bicarbonate, ammonium carbonate and urea.
Further, the metal salt in the step (3) comprises 0-40 parts by weight of zinc salt, 0-30 parts by weight of bismuth salt, 15-45 parts by weight of cobalt salt, 15-30 parts by weight of nickel salt, 15-30 parts by weight of manganese salt, 15-30 parts by weight of zirconium salt, 15-30 parts by weight of gallium salt and 15-30 parts by weight of yttrium salt; the salt is one or more of nitrate, acetate, citrate, chloride and sulfate.
Further, in the step (3), the weight ratio of the mixed solution to be deposited to the mixed solution of metal salt is 5: 1-30: 1.
Further, in the step (3), the drying temperature is 80-150 ℃, and the drying time is 8-48 h.
Further, in the step (4), the pre-sintering temperature is 300-500 ℃, the heat preservation time is 1-4 h, and the temperature rise speed is 2-5 ℃/min; the drying temperature is 80-150 ℃, and the drying time is 8-48 h; the grinding mode adopts one of planetary ball milling and sand milling.
Further, in the step (7), the resistor disc is sintered by one of conventional heating sintering, spark plasma heating sintering, current-assisted heating sintering and microwave heating sintering.
Preferably, the current-assisted heating sintering is carried out by the following method: and in the process of sintering and heating the resistance card, applying direct current voltage with the voltage of 200V/mm-500V/mm at two ends, cooling to room temperature after sintering, and burning to obtain a finished zinc oxide resistance card product, wherein the voltage is reduced to 0.
Further, during sintering, the inner ring of the resistor disc is filled with granulated materials with the same formula as the prefabricated blank.
Further, in the step (7), sintering is carried out by adopting a multi-step curve sintering method, wherein the sintering temperature range is 900-1150 ℃, the heat preservation time range is 0.1-8 h, the temperature rise speed is 2-10 ℃/min, and finally, natural cooling is carried out to the normal temperature;
preferably, the sintering curve is specifically:
heating to 900-1150 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling to 750-1000 ℃ at a cooling rate of 2 ℃/min, and preserving heat for 6 h.
Furthermore, the processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface are all conventional processes, and are described as follows:
(1) grinding: polishing the end surface of the valve plate by using a double-end-surface grinding machine;
(2) cleaning: cleaning and drying the resistor disc by using tap water;
(3) aluminum spraying: spraying aluminum electrode materials on the upper and lower surfaces of the resistor disc to be sprayed by a full-automatic aluminum spraying machine, cleaning end face aluminum scraps of the resistor disc sprayed with aluminum by using a nylon brush, and then blowing the end face aluminum scraps by using gas;
(4) coating insulating glaze on the side: scrubbing floating ash on the side surface of the zinc oxide resistance chip coated with the electrode by using alcohol, and coating the side surface of the resistance chip by using glaze slurry which is uniformly stirred for multiple times by using a coating machine to ensure that the side glaze surface is uniform in thickness and the edge is flush with the two ends of the resistance chip. And drying the resistor disc coated with the insulating glaze.
In a second aspect, the invention provides a small-size distribution network annular zinc oxide resistance card which is prepared by the preparation method.
The small-size distribution network annular zinc oxide resistance card provided by the invention has the size of phi 30-phi 42.
The technical scheme principle of the invention is as follows:
according to the invention, through research, the electrical performance of the resistance card, particularly the current capacity, the potential gradient and the mechanical strength of the resistance card are closely related to the distribution of each component in the resistance card and the uniformity of the distribution of each component. When the component distribution uniformity of the resistance card is poor, on one hand, the density of the resistance card is low, a large number of air gap intervals exist in the resistance card, and when a large current passes through the resistance card, the air gap intervals have the effect of not conducting current, so that the through-current capacity of the whole resistance card is poor; on the other hand, a large number of defects exist among the resistor disc particles, and when a large current passes through the resistor disc, the stress borne by each part in the resistor disc is different, so that the mechanical performance of the resistor disc is obviously reduced.
Meanwhile, it has been found that when various metal oxides such as bismuth oxide, silicon oxide, bismuth oxide, nickel oxide, zirconium oxide and the like are added to a zinc oxide resistor chip, these metal oxides react with each other and with zinc oxide to produce various composite oxides, for example, the reaction of silicon oxide and zinc oxide to form Zn2SiO4Antimony oxide reacts with zinc oxide to form Zn7Sb2O12Reaction of bismuth oxide and antimony oxide to BiSb2O7And SbBiO4Formation of ZrSiO from zirconia and silica4. The composite oxides are distributed in grain boundaries, the growth and the average grain diameter of zinc oxide grains are controlled through a pinning effect, and the potential gradient of the resistance card is improved. The stronger the pinning effect, the smaller the particle size of the zinc oxide crystal particles in the resistance sheet, and the higher the potential gradient of the resistance sheet. However, Zn2SiO4The materials have poor conductive capacity, and when the materials are unevenly distributed and have large particles, the current capacity of the resistance card is obviously reduced. Therefore, the regulation of Zn is required2SiO4、Zn7Sb2O12、BiSb2O7、SbBiO4The uniformity and the grain size of the equal components, thereby improving the through-current capacity of the resistor disc.
The invention firstly grinds oxide powder into fine particles, and then deposits metal salts on the surfaces of the oxide powder particles by adopting a gradual deposition method to form a thin deposition layer. Through the deposition layer, the connection among oxide powder particles is tighter, the uniformity of the distribution of the grain components of the resistor disc is enhanced, the generation of tiny air gaps is reduced, and the potential gradient of the resistor disc is improved. Meanwhile, the deposits deposited on the surfaces of the zinc oxide crystal grains fully react to form various composite oxides, so that a strong pinning effect is formed, and the potential gradient of the resistance card is improved. In addition, it should be noted that, further, it was found that the composition, content and combination method of these composite oxide deposited layers can be controlled more precisely by hydrothermal reaction during aging. The invention realizes the repeated dissolution-crystallization of the composite oxide in the deposition layer by using the hydrothermal environment in the aging process, and the composite oxide is uniformly distributed in the grain gaps of the zinc oxide grains, thereby obtaining the annular zinc oxide resistance card with high density and high uniformity. Compared with the conventional resistance card, the resistance card has obviously stronger discharge current capability, potential gradient and mechanical property.
The bismuth oxide has four different crystal phases, namely α phase, β phase, gamma phase and phase, wherein the bismuth oxide of α phase has the best wettability on the boundary of oxide crystal particles, firstly, the bismuth oxide of α phase can improve the particle accumulation mode, so that the particles slide more easily, the grains are rearranged to ensure that the grains are distributed more uniformly, the microscopic uniformity of the resistance chip is improved, secondly, the bismuth oxide can ensure that the grains soaked in the bismuth oxide are generated more uniformly, abnormal growing particles are reduced, the flow capacity and the microscopic uniformity of the resistance chip are improved, and finally, the bismuth oxide can be better wrapped around the oxide crystals, the number of tiny air holes is reduced, and the flow capacity and the microscopic uniformity of the resistance chip are further improved.
According to the invention, a multi-step sintering method is adopted, the crystal structure of bismuth oxide is adjusted by adjusting the temperature rise rate and the heat preservation time, the main crystal form of the bismuth oxide in the resistance chip is α phase, the boundary wettability of α phase bismuth oxide on oxide crystal particles is good, the uniformity of the size of oxide crystal grains in the resistance chip and the uniformity of crystal grain distribution are improved, and finally the improvement of the through-flow capacity of the resistance chip is realized on the premise of ensuring higher potential gradient and small leakage current.
Researches also find that the bismuth oxide has a low melting point, promotes liquid phase sintering in the sintering process and is beneficial to improving the stability of the resistance card. However, the volatilization temperature of bismuth oxide is lower than 900 ℃, so that bismuth oxide in the resistor disc volatilizes when the resistor disc is sintered at high temperature. The conventional sintering process at present adopts a common resistance wire for heating, and the resistance sheet is heated through the heat conduction of air. Therefore, the closer to the air part, the earlier the bismuth oxide is heated, and the faster the bismuth oxide is volatilized; the relative heating in the zinc oxide is delayed, and the volatilization of bismuth oxide is slower. This also results in some degree of uniformity of the grains within the resistive sheet. Compared with a cake-shaped resistor, the annular resistor has the advantages that two side faces of the annular resistor are in contact with the outside air, the volatilization speed of bismuth oxide is increased, the internal nonuniformity is increased, and through-flow tests also show that the through-flow performance of the annular resistor is reduced by more than 20% compared with that of the cake-shaped resistor in the resistor prepared by the conventional sintering process under the same through-flow area. Therefore, improvement on the production of the annular resistance card is also needed in the sintering process, and the uniformity and the through-flow performance of crystal grains inside the annular resistance card are improved.
The invention improves the internal uniformity of the annular zinc oxide resistance card through two aspects. Firstly, the inner ring is filled with materials, so that the inner ring is not directly contacted with the outside air, the heating form is similar to that of a cake-shaped sheet, and the uniformity of the inner part is improved. Secondly, voltage is applied to two ends of the resistance card, the resistance card is uniformly heated by internal current, the temperature rise of the furnace body is lower than 800 ℃, and the internal Bi is2O3The bismuth oxide in the green body of the zinc oxide resistance card is promoted to be fully diffused when the temperature of volatilization is not reached, so that the bismuth oxide is uniformly distributed in the resistance card, and the through-current capacity of the zinc oxide resistance card is further improved.
The raw materials or reagents involved in the invention are all common commercial products, and the operations involved are all routine operations in the field unless otherwise specified.
The above-described preferred conditions may be combined with each other to obtain a specific embodiment, in accordance with common knowledge in the art.
Compared with the prior art, the invention has the beneficial effects that:
compared with the zinc oxide resistance card prepared by the conventional process, the zinc oxide resistance card prepared by the preparation method has higher density, more uniform distribution of all components and fewer defects in the resistance card, so that the resistance card has higher through-current capacity, higher potential gradient and better comprehensive performance.
Drawings
FIG. 1 is a scanning electron micrograph of a zinc oxide electrical resistance sheet prepared by the method of example 1;
FIG. 2 is a scanning electron micrograph of a zinc oxide resistive sheet prepared using the conventional solid phase method of comparative example 1.
Detailed Description
Preferred embodiments of the present invention will be described in detail with reference to the following examples. It is to be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the present invention. Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the spirit and scope of this invention.
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
Example 1
The preparation process of the resistance card of the embodiment is as follows:
(1) 89.9Kg of zinc oxide, 3.0Kg of bismuth oxide, 1.5Kg of cobalt oxide, 1.0Kg of nickel oxide, 0.5Kg of manganese oxide, 1.8Kg of antimony oxide, 1.4Kg of silicon oxide, 0.2Kg of zirconium oxide, 0.2Kg of gallium oxide, 0.2Kg of yttrium oxide and 0.2Kg of glass powder are weighed, 1.5Kg of deionized water is added, a certain polyammonium acrylate dispersant is added, the rotating speed is set to 1800r/min in a sand mill, and the mixture is ground at a high speed for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 μm.
(2) Dissolving urea in water to obtain a slow-release precipitator aqueous solution with the mass fraction of 30%, then mixing the urea aqueous solution and the oxide solid powder in the step (1) in a weight ratio of 5:1 under the condition of stirring to prepare a mixed solution to be precipitated, and stirring for later use.
(3) Dissolving 4.5Kg of cobalt nitrate, 3Kg of nickel nitrate, 3Kg of manganese nitrate, 1.5Kg of zirconium nitrate, 1.5Kg of gallium nitrate and 1.5Kg of yttrium nitrate in a certain amount of water to obtain a metal salt mixed solution with the mass fraction of 30%, dropwise adding the metal salt mixed solution into the mixed solution to be deposited in the step (2) within 1h under the conditions of stirring and heating, reacting and aging for 8h to obtain a deposit, filtering, washing and drying the deposit at the drying temperature of 100 ℃ for 12h to obtain the prefabricated powder.
(4) Placing the prefabricated powder in the step (3) in a calcining furnace, and presintering at a preset temperature, wherein the presintering temperature is 400 ℃, the heat preservation time is 3 hours, and the heating speed is 2.5 ℃/min; and grinding the calcined product, and then washing and drying to obtain the composite powder. Wherein the drying temperature is 100 ℃, and the drying time is 12 h.
(5) Adding 1.5% of water into the composite powder in the step (4), grinding to prepare mixed slurry, and drying and granulating through a granulation drying tower to obtain granules; wherein the grinding mode is sand grinding, the rotating speed of the sand grinding machine is set to 1800r/min, and high-speed grinding is carried out for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 mu m.
(6) Adding the granulated material into a tablet press and pressing into an annular coarse blank.
(7) And (3) sintering the rough blank in a calcining furnace, and performing processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface. The resistor disc is sintered by adopting a traditional heating sintering method, and when the resistor disc is sintered, the inner ring of the resistor disc is filled with granulated materials with the same formula as the prefabricated blank; and sintering in a kiln by adopting a multi-step sintering curve method, heating to 1150 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling to 1000 ℃ at a cooling rate of 2 ℃/min, preserving heat for 6h, and finally naturally cooling to normal temperature to obtain the large-through-flow high-gradient annular zinc oxide resistance card.
Example 2
The preparation process of the resistance card of the embodiment is as follows:
(1) 89.9Kg of zinc oxide, 3.0Kg of bismuth oxide, 1.5Kg of cobalt oxide, 1.0Kg of nickel oxide, 0.5Kg of manganese oxide, 1.8Kg of antimony oxide, 1.4Kg of silicon oxide, 0.2Kg of zirconium oxide, 0.2Kg of gallium oxide, 0.2Kg of yttrium oxide and 0.2Kg of glass powder are weighed, 1.5Kg of deionized water is added, a polyammonium dispersant is added, the rotation speed is set to 1800r/min in a sand mill, and the mixture is ground at a high speed for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 μm.
(2) Dissolving ammonium carbonate in water to obtain a slow-release precipitator aqueous solution with the mass fraction of 30%, then mixing the ammonium carbonate aqueous solution and the oxide solid powder in the step (1) in a weight ratio of 5:1 under the condition of stirring to prepare a mixed solution to be precipitated, and stirring for later use.
(3) Dissolving 4.5Kg of cobalt nitrate, 3Kg of nickel nitrate, 3Kg of manganese nitrate, 1.5Kg of zirconium nitrate, 1.5Kg of gallium nitrate and 1.5Kg of yttrium nitrate in a certain amount of water to obtain a metal salt mixed solution with the mass fraction of 30%, dropwise adding the metal salt mixed solution into the mixed solution to be deposited in the step (2) within 1h under the conditions of stirring and heating, reacting and aging for 8h to obtain a deposit, filtering, washing and drying the deposit at the drying temperature of 100 ℃ for 12h to obtain the prefabricated powder.
(4) Placing the prefabricated powder in the step (3) in a calcining furnace, and presintering at a preset temperature, wherein the presintering temperature is 400 ℃, the heat preservation time is 3 hours, and the heating speed is 2.5 ℃/min; and grinding the calcined product, and then washing and drying to obtain the composite powder. Wherein the drying temperature is 100 ℃, and the drying time is 12 h.
(5) Adding 1.5% of water into the composite powder in the step (4), grinding to prepare mixed slurry, and drying and granulating through a granulation drying tower to obtain granules; wherein the grinding mode is sand grinding, the rotating speed of the sand grinding machine is set to 1800r/min, and high-speed grinding is carried out for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 mu m.
(6) Adding the granulated material into a tablet press and pressing into an annular coarse blank.
(7) And (3) sintering the annular rough blank in a calcining furnace, and performing processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface. The resistor disc is sintered by adopting a traditional heating sintering method, and when the resistor disc is sintered, the inner ring of the resistor disc is filled with granulated materials with the same formula as the prefabricated blank; and sintering in a kiln by adopting a multi-step sintering curve method, heating to 1150 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling to 1000 ℃ at a cooling rate of 2 ℃/min, preserving heat for 6h, and finally naturally cooling to normal temperature to obtain the large-through-flow high-gradient annular zinc oxide resistance card.
Example 3
The preparation process of the resistance card of the embodiment is as follows:
(1) 89.9Kg of zinc oxide, 3.0Kg of bismuth oxide, 1.5Kg of cobalt oxide, 1.0Kg of nickel oxide, 0.5Kg of manganese oxide, 1.8Kg of antimony oxide, 1.4Kg of silicon oxide, 0.2Kg of zirconium oxide, 0.2Kg of gallium oxide, 0.2Kg of yttrium oxide and 0.2Kg of glass powder are weighed, then a certain amount of deionized water is added, a polyacrylic acid ammonia dispersant is added, the rotating speed is set to 1800r/min in a sand mill, and the mixture is ground at a high speed for 2.0h to obtain the mixed slurry with the particle size of 0.5 to 2 mu m.
(2) Dissolving urea in water to obtain a slow-release precipitator aqueous solution with the mass fraction of 30%, then mixing the urea aqueous solution and the oxide solid powder in the step (1) in a weight ratio of 5:1 under the condition of stirring to prepare a mixed solution to be precipitated, and stirring for later use.
(3) Dissolving 1.5Kg of zinc nitrate, 1.5Kg of bismuth nitrate, 1.5Kg of cobalt nitrate, 3.0Kg of nickel nitrate, 3.0Kg of manganese nitrate, 1.5Kg of zirconium nitrate, 1.5Kg of gallium nitrate and 1.5Kg of yttrium nitrate in a certain amount of water to obtain a metal salt mixed solution with the mass fraction of 30%, dropwise adding the metal salt mixed solution into the mixed solution to be deposited in the step (2) within 1h under the conditions of stirring and heating, reacting and aging for 8h to obtain a deposit, filtering, washing and drying the deposit, wherein the drying temperature is 100 ℃, and the drying time is 12h to obtain the prefabricated powder.
(4) Placing the prefabricated powder in the step (3) in a calcining furnace, and presintering at a preset temperature, wherein the presintering temperature is 400 ℃, the heat preservation time is 3 hours, and the heating speed is 2.5 ℃/min; and grinding the calcined product, and then washing and drying to obtain the composite powder. Wherein the drying temperature is 100 ℃, and the drying time is 12 h.
(5) Adding 1.5% of water into the composite powder in the step (4), grinding to prepare mixed slurry, and drying and granulating through a granulation drying tower to obtain granules; wherein the grinding mode is sand grinding, the rotating speed of the sand grinding machine is set to 1800r/min, and high-speed grinding is carried out for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 mu m.
(6) Adding the granulated material into a tablet press and pressing into an annular coarse blank.
(7) And (3) sintering the annular rough blank in a calcining furnace, and performing processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface. The resistor disc is sintered by adopting a traditional heating sintering method, and when the resistor disc is sintered, the inner ring of the resistor disc is filled with granulated materials with the same formula as the prefabricated blank; and sintering in a kiln by adopting a multi-step sintering curve method, heating to 1150 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling to 1000 ℃ at a cooling rate of 2 ℃/min, preserving heat for 6h, and finally naturally cooling to normal temperature to obtain the large-through-flow high-gradient annular zinc oxide resistance card.
Example 4
The preparation process of the resistance card of the embodiment is as follows:
(1) 89.9Kg of zinc oxide, 3.0Kg of bismuth oxide, 1.5Kg of cobalt oxide, 1.0Kg of nickel oxide, 0.5Kg of manganese oxide, 1.8Kg of antimony oxide, 1.4Kg of silicon oxide, 0.2Kg of zirconium oxide, 0.2Kg of gallium oxide, 0.2Kg of yttrium oxide and 0.2Kg of glass powder are weighed, 1.5Kg of deionized water is added, a certain polyammonium acrylate dispersant is added, the rotating speed is set to 1800r/min in a sand mill, and the mixture is ground at a high speed for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 μm.
(2) Dissolving urea in water to obtain a slow-release precipitator aqueous solution with the mass fraction of 30%, then mixing the urea aqueous solution and the oxide solid powder in the step (1) in a weight ratio of 5:1 under the condition of stirring to prepare a mixed solution to be precipitated, and stirring for later use.
(3) Dissolving 4.5Kg of cobalt nitrate, 3Kg of nickel nitrate, 3Kg of manganese nitrate, 1.5Kg of zirconium nitrate, 1.5Kg of gallium nitrate and 1.5Kg of yttrium nitrate in a certain amount of water to obtain a metal salt mixed solution with the mass fraction of 30%, dropwise adding the metal salt mixed solution into the mixed solution to be deposited in the step (2) within 1h under the conditions of stirring and heating, reacting and aging for 8h to obtain a deposit, filtering, washing and drying the deposit at the drying temperature of 100 ℃ for 12h to obtain the prefabricated powder.
(4) Placing the prefabricated powder in the step (3) in a calcining furnace, and presintering at a preset temperature, wherein the presintering temperature is 400 ℃, the heat preservation time is 3 hours, and the heating speed is 2.5 ℃/min; and grinding the calcined product, and then washing and drying to obtain the composite powder. Wherein the drying temperature is 100 ℃, and the drying time is 12 h.
(5) Adding 1.5% of water into the composite powder in the step (4), grinding to prepare mixed slurry, and drying and granulating through a granulation drying tower to obtain granules; wherein the grinding mode is sand grinding, the rotating speed of the sand grinding machine is set to 1800r/min, and high-speed grinding is carried out for 2.0h to obtain the mixed slurry with the particle size of 0.5-2 mu m.
(6) Adding the granulated material into a tablet press and pressing into an annular coarse blank.
(7) And (3) sintering the rough blank in a calcining furnace, and performing processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface. The sintering method of the resistance card adopts current-assisted heating sintering, and comprises the following specific steps: sintering by adopting a multi-step sintering curve method, heating to 900 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling at a cooling rate of 2 ℃/min to 750 ℃, preserving heat for 6h, cooling to room temperature after the direct-current voltage with the voltage of 200V/mm-500V/mm at two ends is applied in the heating process, and reducing the voltage to 0 to obtain the finished zinc oxide resistance card.
Comparative example 1
The zinc oxide resistance card is prepared by adopting a traditional solid phase method, and by contrast, the preparation process of the resistance card is as follows:
1) 89.9Kg of zinc oxide, 3.0Kg of bismuth oxide, 1.5Kg of cobalt oxide, 1.0Kg of nickel oxide, 0.5Kg of manganese oxide, 1.8Kg of antimony oxide, 1.4Kg of silicon oxide, 0.2Kg of zirconium oxide, 0.2Kg of gallium oxide, 0.2Kg of yttrium oxide and 0.2Kg of glass powder are weighed, then a certain amount of deionized water is added, a polyacrylic acid ammonia dispersant is added, the rotating speed is set to 1800r/min in a sand mill, and the mixture is ground at a high speed for 2.0h to obtain the mixed slurry with the particle size of 0.5 to 2 mu m.
2) And adding the obtained mixed slurry into a polyvinyl alcohol adhesive, carrying out spray drying, and sieving the dried powder with a 80-mesh sieve to obtain the granulated material.
3) And further drying and pre-sintering the prepared prefabricated blank, heating the prefabricated blank from room temperature to 400 ℃ at the speed of 2.5 ℃/min in an open air atmosphere, and keeping the temperature for 3 hours to obtain a semi-finished product of the resistance card.
4) Coating aluminum spraying or electrode slurry on the upper and lower surfaces of the semi-finished product of the zinc oxide resistance card, coating insulating glaze on the side surface, and sintering by adopting a traditional heating sintering method, wherein during sintering, the inner ring of the resistance card is filled with granulated materials with the same formula as the prefabricated blank; and (3) sintering in a kiln by adopting a multi-step sintering curve method, heating to 1150 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling to 1000 ℃ at a cooling rate of 2 ℃/min, preserving heat for 6h, and finally naturally cooling to normal temperature to obtain the finished product of the resistor disc.
Comparative example 2
The zinc oxide resistance card is prepared by adopting a traditional solid phase method, and by contrast, the preparation process of the resistance card is as follows:
1) 89.9Kg of zinc oxide, 3.0Kg of bismuth oxide, 1.5Kg of cobalt oxide, 1.0Kg of nickel oxide, 0.5Kg of manganese oxide, 1.8Kg of antimony oxide, 1.4Kg of silicon oxide, 0.2Kg of zirconium oxide, 0.2Kg of gallium oxide, 0.2Kg of yttrium oxide and 0.2Kg of glass powder are weighed, then a certain amount of deionized water is added, a polyacrylic acid ammonia dispersant is added, the rotating speed is set to 1800r/min in a sand mill, and the mixture is ground at a high speed for 2.0h to obtain the mixed slurry with the particle size of 0.5 to 2 mu m.
2) And adding the obtained mixed slurry into a polyvinyl alcohol adhesive, carrying out spray drying, and sieving the dried powder with a 80-mesh sieve to obtain the granulated material.
3) And further drying and pre-sintering the prepared prefabricated blank, heating the prefabricated blank from room temperature to 400 ℃ at the speed of 2.5 ℃/min in an open air atmosphere, and keeping the temperature for 3 hours to obtain a semi-finished product of the resistance card.
4) Coating aluminum spraying or electrode slurry on the upper and lower surfaces of the semi-finished product of the zinc oxide resistance chip, coating insulating glaze on the side surface, and further sintering by adopting a traditional heating sintering method, wherein during sintering, the inner ring of the resistance chip is filled with granulated materials with the same formula as the prefabricated blank; sintering in a kiln, adopting a traditional one-step sintering curve method to sinter, heating to 1000 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 6h, naturally cooling to normal temperature, and sintering to obtain a finished product of the zinc oxide resistance card
The size of the produced resistor disc is phi 42. The voltage gradient, the current capacity and the large current impact resistance of the obtained resistance chip were measured, as shown in table 1.
TABLE 1 comparison of the comprehensive Properties of the resistive sheets
As can be seen from Table 1, compared with the zinc oxide resistance card obtained by the conventional process, the zinc oxide resistance card synthesized by the process has the advantages that the potential gradient, the current capacity and the large-current impact resistance capability are remarkably improved. Example 1 differs from example 2 in that example 1 uses urea as the slow release precipitant and example 2 uses ammonium carbonate as the slow release precipitant. Example 1 is different from example 3 in that the metal salt composition in the metal salt mixed solution used in example 3 is different from that in example 1. Example 1 differs from example 4 in that example 4 employs a sintering process of current-assisted heat sintering. From the test results, the performance of the resistance cards in the embodiments 1 to 4 is better within the protection range of the invention. The resistance card of example 4 has the best performance, which is related to the sintering process of example 4 which adopts current-assisted heating sintering. The current-assisted heating sintering is beneficial to improving the uniformity and the relative density of the internal microstructure of the resistance card, and further improving the comprehensive performance of the resistance card.
The difference between the comparative example 1 and the example 1 is that the comparative example 1 adopts the traditional solid phase grinding and sintering method to prepare the zinc oxide resistance chip, and the test result shows that the performance of the zinc oxide resistance chip prepared by the preparation method of the invention is obviously stronger than that of the resistance chip prepared by the traditional solid phase grinding and sintering method, which is attributed to the fact that the resistance chip prepared by the preparation method provided by the invention has higher density, more uniform distribution of components and fewer defects in the resistance chip, so the through-current capacity is higher, and the potential gradient is higher, the comparative example 2 is different from the comparative example 1 in that the comparative example 2 adopts the traditional one-step sintering method to sinter, and the experimental result shows that the through-current capacity of the comparative example 2 is poorer than that of the comparative example 1, the potential gradient is smaller, and the leakage current is larger, because of the multi-step sintering method, the bismuth oxide crystal structure can be adjusted by adjusting the temperature rise rate and the heat preservation time, so that the bismuth oxide crystal form of the bismuth oxide in the resistance chip is the α phase, the α phase bismuth oxide crystal has better wettability to oxide crystal grain boundary of the oxide crystal particles, the uniformity of the oxide crystal form of the resistance chip is improved, the zinc oxide crystal form of the resistance chip prepared by the traditional scanning electron microscope, and the zinc oxide resistance chip prepared by the method is also the zinc oxide scanning method, the zinc oxide resistance chip prepared by adopting the electron microscope 1, the zinc oxide scanning method, the zinc oxide resistance chip with the zinc oxide material with the high current scanning method, the high zinc oxide resistance chip, and the zinc oxide resistance chip prepared by the high current scanning method.
The foregoing are merely exemplary embodiments of the present disclosure, which enable those skilled in the art to understand or practice the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A preparation method of a small-size distribution network annular zinc oxide resistance card is characterized by comprising the following steps:
(1) mixing and grinding 85-93 parts by weight of zinc oxide, 1.5-4.0 parts by weight of bismuth oxide, 1-3 parts by weight of cobalt oxide, 0.5-1.2 parts by weight of nickel oxide, 0.2-1.0 part by weight of manganese oxide, 1.5-5.0 parts by weight of antimony oxide, 0.4-3.2 parts by weight of silicon oxide, 0.1-0.5 part by weight of zirconium oxide, 0.1-0.5 part by weight of gallium oxide, 0.1-0.5 part by weight of yttrium oxide and 0.1-0.3 part by weight of glass powder to obtain oxide solid powder;
(2) dissolving a slow-release precipitator in water to obtain a slow-release precipitator aqueous solution with the mass fraction of 10-80%, and then mixing the slow-release precipitator aqueous solution and the oxide solid powder obtained in the step (1) in a weight ratio of 2: 1-10: 1 under the condition of stirring to prepare a mixed solution to be deposited;
(3) dissolving metal salt in water to obtain a metal salt mixed solution with the mass fraction of 10-50%, dropwise adding the metal salt mixed solution into the mixed solution to be deposited obtained in the step (2) within 0.5-4 h under the conditions of stirring and heating, reacting and aging for 2-48 h after dropwise adding to obtain a deposit, filtering, washing and drying the deposit to obtain a prefabricated powder;
(4) placing the prefabricated powder obtained in the step (3) in a calcining furnace, pre-burning at a preset temperature, grinding a calcined product, and then washing and drying to obtain composite powder;
(5) adding a small amount of water into the composite powder obtained in the step (4), grinding to prepare mixed slurry, and drying and granulating through a granulation drying tower to obtain granules;
(6) adding the granulated material obtained in the step (5) into a tablet press and pressing into an annular coarse blank;
(7) and (4) sintering the annular rough blank obtained in the step (6) in a calcining furnace, and obtaining the large-through-flow high-gradient annular zinc oxide resistance card through processes of grinding, cleaning, spraying aluminum and coating insulating glaze on the side surface.
2. The method according to claim 1, wherein in the step (3), the metal salt comprises 0 to 40 parts by weight of a zinc salt, 0 to 30 parts by weight of a bismuth salt, 15 to 45 parts by weight of a cobalt salt, 15 to 30 parts by weight of a nickel salt, 15 to 30 parts by weight of a manganese salt, 15 to 30 parts by weight of a zirconium salt, 15 to 30 parts by weight of a gallium salt, and 15 to 30 parts by weight of an yttrium salt; the metal salt is one or a combination of more of nitrate, acetate, citrate, chloride and sulfate.
3. The preparation method according to claim 2, wherein in the step (3), the weight ratio of the mixed solution to be deposited to the mixed solution of metal salt is 5: 1-30: 1.
4. The preparation method according to claim 3, wherein in the step (3), the drying temperature is 80-150 ℃ and the drying time is 8-48 h.
5. The preparation method according to any one of claims 1 to 4, wherein in the step (2), the slow-release precipitator is one or more of ammonium bicarbonate, ammonium carbonate and urea.
6. The preparation method according to any one of claims 1 to 4, wherein in the step (4), the pre-sintering temperature is 300 to 500 ℃, the heat preservation time is 1 to 4 hours, and the temperature rise speed is 2 to 5 ℃/min; the drying temperature is 80-150 ℃, and the drying time is 8-48 h.
7. The preparation method according to any one of claims 1 to 4, wherein in the step (7), the resistor sheet is sintered by one of conventional heating sintering, spark plasma heating sintering, current-assisted heating sintering and microwave heating sintering;
preferably, the resistance card is sintered by current-assisted heating, a direct-current voltage of 200V/mm-500V/mm is applied to two ends in the sintering and temperature rising process of the resistance card, the resistance card is cooled to room temperature after sintering, the voltage is reduced to 0, and the finished zinc oxide resistance card is sintered.
8. The preparation method according to any one of claims 1 to 4, wherein in the step (7), during sintering, the inner ring of the resistor disc is filled with the granulated material which has the same formula as the prefabricated blank.
9. The preparation method according to any one of claims 1 to 4, characterized in that in the step (7), a multi-step curve sintering method is adopted for sintering, the sintering temperature ranges from 900 ℃ to 1150 ℃, the heat preservation time ranges from 0.1 hour to 8 hours, the temperature rise speed ranges from 2 ℃/min to 10 ℃/min, and finally the mixture is naturally cooled to the normal temperature;
preferably, the sintering curve is specifically:
heating to 900-1150 ℃ at a heating rate of 5 ℃/min, preserving heat for 10min, then cooling to 750-1000 ℃ at a cooling rate of 2 ℃/min, and preserving heat for 6 h.
10. A small-size distribution network annular zinc oxide resistance card is characterized by being prepared by the preparation method of any one of claims 1-9.
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