CN102618773B - Preparation method of Ag/La1-xSrxCoO3 electrical contact composite material - Google Patents

Abstract

The invention relates to the preparation of electrical contact composite materials, and aims to provide a preparation method of Ag/La _1-x Sr _x CoO ₃ electrical contact composite materials. The method comprises: preparing a La _1-x Sr _x CoO ₃ system conductive ceramic micro-nano powder by using a sol-gel method; mixing the above-mentioned La _1-x Sr _x CoO ₃ micro-nano powder and silver powder in a V-shaped powder mixer Mix evenly, the La _1-x Sr _x CoO ₃ powder accounts for 8% to 20% of the total mass of the mixed powder; the uniformly mixed powder is pressed into a green body by isostatic pressing, and then sintered, repressed, Re-firing process, and finally hot extrusion molding to obtain Ag/La _1-x Sr _x CoO ₃ electrical contact composite material. In the present invention, the reinforcing phase La _{1-x Sr x CoO 3 in the Ag/La 1-x Sr x CoO 3 electrical contact} composite material prepared by the sol-gel method is a nanoscale powder, and its high specific surface activity can improve the performance of the electric arc. The melt viscosity in the micro-melt pool on the surface of the electrical contact material comprehensively improves the electrical conductivity, mechanical strength, wear resistance, arc ablation resistance and other properties of the electrical contact material, and there is no problem of processing and molding difficulties.

Description

Preparation method of Ag/La1-xSrxCoO3 electrical contact composite material

technical field

The invention relates to a preparation method of a novel electrical contact composite material, specifically, a preparation method of an Ag/La _1-x Sr _x CoO ₃ electrical contact composite material.

Background technique

Electrical contact materials and components are the core components and key materials of electronic industrial equipment such as power switches, electrical appliances, instruments and meters, and are widely used in various fields such as civil, industrial, military, aerospace, aviation, and information. Electrical contact materials and components are mainly responsible for connecting and disconnecting circuits and load currents, and their performance directly affects the reliable operation and life of switching devices. At the same time, the electrical contact material is the key material in the switchgear. The main performance and life of the switchgear depend on the quality of the electrical contact material to a large extent. At present, my country's annual consumption of silver-based electrical contact materials has exceeded 10 billion yuan, and the market demand continues to grow rapidly.

So far, Ag/CdO material is still considered as the material of choice with the best electrical contact performance. However, Ag/CdO materials have serious environmental problems. In February 2003, the European Union promulgated the "Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment" (2002/95/EC-RoHS Directive), "Waste Electrical and Electronic Equipment" (2002/96/EC-WEEE directive) 2 important directives. Therefore, countries around the world are vigorously developing new systems of environmentally friendly electrical contact materials, the most representative of which are Ag/SnO ₂ materials, Ag/conductive ceramic materials, etc. There are many manufacturers of electrical contact materials in my country, but there is still a big gap between Ag/SnO2 electrical contact materials and foreign countries. In order to meet the needs of national economic development, a new system of environmentally friendly electrical contact materials with excellent comprehensive performance needs to be developed urgently.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a novel preparation method of Ag/La1-xSrxCoO3 electrical contact composite material.

For solving technical problem, solution of the present invention is:

A method for preparing an Ag/La _1-x Sr _x CoO ₃ electrical contact composite material is provided, specifically comprising the following steps:

(1) La _1-x Sr _x CoO ₃ system conductive ceramic micro-nano powder was prepared by sol-gel method;

(2) Mix the above-mentioned La _1-x Sr _x CoO ₃ micro-nano powder and silver powder in a V-shaped powder mixer, and the La _1-x Sr _x CoO ₃ powder accounts for 8% to 20% of the total mass of the mixed powder. %;

(3) The uniformly mixed powder is pressed into a green body by isostatic pressing, then sintered, repressed, and refired in sequence, and finally hot-extruded to obtain Ag/La _1-x Sr _x CoO ₃ electrical contact composite Material.

2. The preparation method of the Ag/La _1-x Sr _x CoO ₃ electrical contact composite material according to claim 1, characterized in that,

The sol-gel method used in step (1) to prepare La _1-x Sr _x CoO ₃ system conductive ceramic micro-nano powder is: La(NO ₃ ) ₃ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) Dissolve ₂ ·6H ₂ O in deionized water according to the stoichiometric ratio, add an appropriate amount of citric acid as a chelating agent under full stirring, and adjust the pH value of the solution to 6-10 with ammonia water or ethylenediamine, which is conducive to the formation of a sol. In the process of static aging, a wet gel is formed after a certain temperature of water bath is kept warm to evaporate excess solvent, and then dried at 120°C for 12 hours to obtain a dry gel, which is sintered at 600°C to 800°C in an air or oxygen atmosphere, and the temperature is raised The rate is 1-10° C./min, and the temperature is kept for 2-6 hours to obtain black La _1-x Sr _x CoO ₃ nanometer powder.

Among them, the value of X in La _1-x Sr _x CoO ₃ conductive ceramics is 0.1-0.9, and the ratio N/J of the amount of chelating agent citric acid to the total amount of metal ions in the sol is 1:1-2:1. The temperature of the water bath in the melting process is 30°C-90°C, and the finally obtained La _1-x Sr _x CoO ₃ powder is dispersed with a single particle size of 20-50nm and agglomerated large particles with a particle size of 50-500nm.

In the present invention, in the powder mixing process described in step (2) _, the particle size range of the La _1-x Sr _x CoO powder is 50-500 nm, the particle size range of the silver powder is 0.01-50 μm, and the powder mixing time is 1-50 nm. 6h;

In the present invention, the isostatic pressure range described in step (3) is 100-500MPa;

In the present invention, the sintering process described in step (3) refers to sintering under the protection of argon atmosphere, the sintering temperature is 700-900°C, and the sintering time is 2-10h;

In the present invention, the repressing process described in step (3) is to carry out hot pressing at 500-800°C, the pressure range is 300-800MPa, and the heat preservation (pressing) time is 10-90min;

In the present invention, the re-firing process described in step (3) refers to re-sintering under the protection of a hydrogen atmosphere, the sintering temperature is 700-900 ° C, and the sintering time is 2-10 hours;

In the present invention, in the hot extrusion molding process described in step (3), the mold preheating temperature is 300-800°C, the billet temperature is 300-800°C, the extrusion ratio range is 10-100, and the extrusion speed is 1-10cm /min.

Compared with the existing Ag/SnO _electric contact composite material, the beneficial effects of the present invention are:

Reinforcing phase La _1-x Sr _x CoO ₃ in Ag/La 1- _x Sr _x CoO ₃ electrical contact composite prepared by sol-gel method as nanoscale powder, its high specific surface activity can improve electrical contact under arc action The melt viscosity in the micro-melting pool on the surface of the material comprehensively improves the electrical conductivity, mechanical strength, wear resistance, arc ablation resistance and other properties of the electrical contact material, and at the same time there is no problem of difficult processing and molding.

La _1-x Sr _x CoO ₃ belongs to a series of high-temperature superconducting ceramics with a perovskite structure. The reported room temperature resistivity is as low as 10 ^-5 Ω·cm, and the resistivity of electrical contact materials (10 ^-6 Ω·cm cm level) is similar. The resistivity of SnO2 is 93Ω·cm. Through experiments, the electrical contact performance of Ag/La _1-x Sr _x CoO ₃ material is better than that of Ag/SnO ₂ .

The present invention pre-covers a silver layer on the surface of La _1-x Sr _x CoO ₃ through the surface silver loading technology, which improves the wettability of the reinforcement phase and the silver matrix; ensures that the Ag/La _1-x Sr _x CoO ₃ electrical contact material is protected After arc erosion, no serious segregation of La _1-x Sr _x CoO ₃ will appear on the surface, and more importantly, the reinforcement phase of La _1-x Sr _x CoO ₃ will decompose in advance near the melting point of Ag (960℃), so that the Ag/ The working performance of La _1-x Sr _x CoO ₃ is similar to that of Ag/CdO, and it has a significant arc blowing and arc extinguishing effect when an arc occurs, prolonging the service life of the material.

The invention not only increases the dosing amount of the reinforcing phase in the electrical contact composite material, but also extends the electrical life of the electrical contact material by selecting the reinforcing phase material La _1-x Sr _x CoO ₃ with excellent comprehensive performance. Generally speaking, compared with Ag/SnO ₂ material, Ag/La _1-x Sr _x CoO ₃ can save 3%-8% of silver.

Detailed ways

The present invention is further described by examples below.

The preparation method of the Ag/La1-xSrxCoO3 electrical contact composite material provided by the present invention specifically comprises the following steps:

(1) La _1-x Sr _x CoO ₃ system conductive ceramic micro-nano powder was prepared by sol-gel method;

(2) Mix the above-mentioned La _1-x Sr _x CoO ₃ micro-nano powder and silver powder in a V-shaped powder mixer, and the La _1-x Sr _x CoO ₃ powder accounts for 8% to 20% of the total mass of the mixed powder. %;

(3) The uniformly mixed powder is pressed into a green body by isostatic pressing, then sintered, repressed, and refired in sequence, and finally hot-extruded to obtain Ag/La _1-x Sr _x CoO ₃ electrical contact composite Material.

The sol-gel method used in step (1) to prepare La _1-x Sr _x CoO ₃ system conductive ceramic micro-nano powder is: La(NO ₃ ) ₃ , Sr(NO ₃ ) ₂ , Co(NO ₃ ) Dissolve ₂ ·6H ₂ O in deionized water according to the stoichiometric ratio, add an appropriate amount of citric acid as a chelating agent under full stirring, and adjust the pH value of the solution to 6-10 with ammonia water or ethylenediamine, which is conducive to the formation of a sol. In the process of static aging, a wet gel is formed after a certain temperature of water bath is kept warm to evaporate excess solvent, and then dried at 120°C for 12 hours to obtain a dry gel, which is sintered at 600°C to 800°C in an air or oxygen atmosphere, and the temperature is raised The rate is 1-10° C./min, and the temperature is kept for 2-6 hours to obtain black La _1-x Sr _x CoO ₃ nanometer powder. Among them, the value of X in La _1-x Sr _x CoO ₃ conductive ceramics is 0.1-0.9, and the ratio N/J of the amount of chelating agent citric acid to the total amount of metal ions in the sol is 1:1-2:1. The temperature of the water bath in the melting process is 30°C-90°C, and the finally obtained La _1-x Sr _x CoO ₃ powder is dispersed with a single particle size of 20-50nm and agglomerated large particles with a particle size of 50-500nm.

The test data in each embodiment sees the following table:

Finally, it should also be noted that what is listed above are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All deformations that can be directly derived or associated by those skilled in the art from the content disclosed in the present invention should be considered as the protection scope of the present invention.

Claims (3)

1. Ag/La _1-xSr _xCoO ₃The preparation method of electric contact composite material specifically comprises the steps:

(1) adopt sol-gel method to prepare La _1-xSr _xCoO ₃System conductivity ceramics micro nano powder;

(2) with above-mentioned La _1-xSr _xCoO ₃Micro nano powder and silver powder mix in the V-type meal mixer, La _1-xSr _xCoO ₃Powder accounts for 8%～20% of mixed powder total mass;

(3) powder after mixing is by waiting static pressure to be pressed into base substrate, then successively through oversintering, press again, resintering technique, last hot extrusion molding obtains Ag/La _1-xSr _xCoO ₃Electric contact composite material;

The concrete steps of step (1) are: with La (NO ₃) ₃, Sr (NO ₃) ₂, Co (NO ₃) ₂6H ₂O dissolves in deionized water by stoichiometric ratio, adds citric acid to make sequestrant under fully stirring, and with ammoniacal liquor or quadrol regulator solution pH value to 6～10, is conducive to form colloidal sol; Water bath heat preservation by 30 ℃～90 ℃ in still aging process, form wet gel after evaporating unnecessary solvent, then obtain xerogel at 120 ℃ of dry 12h, 600 ℃～800 ℃ sintering in air or oxygen atmosphere, 1～10 ℃/min of temperature rise rate, insulation 2～6h can obtain black La _1-xSr _xCoO ₃Nano-powder;

Wherein, La _1-xSr _xCoO ₃In conductivity ceramics, the value of X is 0.1～0.9, and in sequestrant Citric Acid Dosage and colloidal sol, the ratio N/J of the total amount of metal ion is 1: 1 ~ 2: 1;

In step (3), the described static pressure pressure range 100～500MPa that waits; Sintering process refers to sintering under the argon gas atmosphere protection, 700～900 ℃ of sintering temperatures, sintering time 2～10h; Multiple compression technology is to carry out hot pressing under 500～800 ℃, pressure range 300～800MPa, soaking time 10～90min; Resintering technique refers under hydrogen atmosphere protection sintering again, 700～900 ℃ of sintering temperatures, sintering time 2～10h; In hot extrusion molding technique, 300～800 ℃ of mold preheating temperatures, 300～800 ℃ of blank temperatures, the extrusion ratio scope is 10～100, extrusion speed is 1～10cm/min.

2. Ag/La according to claim 1 _1-xSr _xCoO ₃The preparation method of electric contact composite material is characterized in that, the La that obtains at last _1-xSr _xCoO ₃Single particle diameter after powder disperses is 20～50nm, and the macrobead particle diameter of reunion is 50 ~ 500nm.

3. Ag/La according to claim 1 _1-xSr _xCoO ₃The preparation method of electric contact composite material is characterized in that, described in step (2) in blending processes of powders, and La _1-xSr _xCoO ₃The particle size range of powder is 50 ~ 500nm, and the particle size range of silver powder is 0.01～50 μ m, mixed powder time 1～6h.