CN110981522B

CN110981522B - Resistivity-controllable high-power-density metal ceramic resistor material and preparation method thereof

Info

Publication number: CN110981522B
Application number: CN201911273112.3A
Authority: CN
Inventors: 张昊; 张雪萍; 魏剑; 李雪婷
Original assignee: Xian University of Architecture and Technology
Current assignee: Xian University of Architecture and Technology
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2022-03-18
Anticipated expiration: 2039-12-12
Also published as: CN110981522A

Abstract

The invention discloses a high-power density metal ceramic resistor material with controllable resistivity and a preparation method thereof, wherein the preparation method comprises the following steps: the components of 20-90% of alumina ceramic phase, 1-35% of metal phase, 1-50% of whisker precursor (1-35% of whisker is generated by reaction) and 5-10% of multi-element additive calcium oxide, mullite and spinel are stirred, ball-milled, granulated, pressed into tablets and sintered in an atmosphere furnace at 1400-1600 ℃. The metal phase component comprises one of molybdenum, nickel and the like. The whisker phase comprises one of titanium carbide, silicon carbide and the like. The metal ceramic resistor prepared by the invention has higher power density and lower seepage threshold, can resist high temperature and large current impact, and has simple operation and wide application value.

Description

Resistivity-controllable high-power-density metal ceramic resistor material and preparation method thereof

Technical Field

The invention belongs to the technical field of materials, relates to a resistance material, and particularly relates to a high-power-density metal ceramic resistance material with controllable resistivity and a preparation method thereof.

Background

The metal phase (such as molybdenum, copper, nickel and the like) is added into the ceramic material to reduce the resistivity to obtain the metal ceramic, so that the metal ceramic can obtain very low resistivity on the premise of keeping excellent mechanical properties, and can be widely applied to the fields of high-power resistance materials and the like. However, after the metal phase is added, the resistivity of the metal ceramic is difficult to control under the influence of a percolation threshold, and meanwhile, the bonding strength of the heterogeneous interface of the metal phase and the ceramic phase is poor, so that the mechanical property of the metal ceramic is reduced. The percolation threshold is generally defined as the volume resistivity of the composite material decreases significantly with the addition of the conductive filler, the volume or mass fraction of the conductive filler going from an insulator to a conductor.

For the preparation of materials with low percolation threshold, researchers have found that the percolation threshold of polymer materials can be significantly reduced by the bridging effect of different conductive phases. Relevant papers such as polydimethylsiloxane composite material using short carbon fiber and carbon nanotube as filler, a stable three-dimensional conductive network can be formed between the filler and the matrix, and low percolation threshold of 0.2% and high conductivity can be achieved (Fan Zhang, Shu y.wu, Chu h.peng, Chun h.wang, compound. sci.technol.165(2018) 131-. However, the preparation process of the polydimethylsiloxane polymer as a matrix material, mixing the filler and the matrix by using a three-high mill, and pressing the mixture into a blocky composite material is difficult to apply to the field of metal ceramic materials. Related patents, for example, CN110028734A, disclose a composite material with a three-dimensional network structure formed by conductive fillers of different shapes using 3D printing technology and using a polymer as a matrix. However, the technology relies on the polymer to perform extrusion molding at about 100 ℃, and the conductive filler is subjected to surface treatment and is arranged in a magnetic field, and the processes are difficult to be applied to a metal ceramic system.

In the field of metal ceramics, there are some related patents disclosing the technology of compounding metal or whisker with ceramic phase, for example, patent CN109824349A discloses a metal-plastic combined microcrystalline alumina ceramic, which improves the bending strength and toughness of the alumina ceramic by adding copper powder as metal phase, but the patent is only used for ceramic toughening and does not relate to the related content of copper powder for the seepage threshold and the resistivity control; patent CN109824365A discloses a titanium silicon carbon/alumina ceramic composite material, which has high strength and hardness of ceramic and good toughness of metal due to the specific crystal structure of titanium silicon carbon particles, further improving the comprehensive properties of the material. However, the titanium silicon carbon/alumina composite ceramic has very low conductivity and cannot be used as a metal ceramic resistor; patent CN108686524A discloses a method for preparing a silicon carbide ceramic hollow fiber membrane reinforced and toughened by silicon carbide whiskers, which utilizes silicon carbide whiskers to significantly improve the toughness of the ceramic, but does not relate to the influence of the silicon carbide whiskers on the percolation threshold and resistivity of the ceramic.

Disclosure of Invention

Based on the defects of the prior art, the invention aims to provide a high-power-density metal ceramic resistance material and a preparation method thereof, wherein the percolation threshold of alumina ceramic is reduced through the bridging action of whiskers and metal particles, and meanwhile, the mechanical property is improved, so that the high-power-density metal ceramic resistance material with controllable resistivity is finally obtained.

In order to achieve the purpose, the invention adopts the technical scheme that:

a high power density cermet resistive material having a controllable resistivity, the cermet consisting essentially of a ceramic phase, a metal phase and whisker phases dispersed between the cermet;

the ceramic phase is alumina-based ceramic and consists of alumina and a multi-element additive, wherein the multi-element additive is a mixture of calcium oxide, mullite and spinel;

the metal phase is low-resistivity metal particles;

the whisker phase is prepared by an in-situ growth method by using a whisker precursor, and is a whisker with low resistivity, wherein the resistivity is lower than that of a ceramic phase and higher than that of a metal phase.

The proportions of the alumina, the multi-element additive, the metal phase and the whisker precursor are respectively as follows by weight percent: 20-90%, 5-10%, 1-35% and 1-50%, based on the whisker phase generated by the reaction, the content of the whisker phase is 1-35%.

The calcium oxide: mullite: the mass ratio of the spinel is 1 (1-2) to 1-2.

The metal phase is molybdenum or nickel, and the particle size is 100 mu m.

The whisker phase is a silicon carbide whisker phase or a titanium carbide whisker phase, the diameter is 10 mu m, and the length is 20-50 mu m.

The invention also provides a preparation method of the high-power-density metal ceramic resistor material with controllable resistivity, which comprises the following steps:

1) mixing alumina, a multi-element additive, metal corresponding to the metal and a whisker precursor in proportion, putting the mixture into a ball mill, and wet-milling and uniformly mixing the mixture;

2) sieving the wet-milled raw materials to obtain powder, adding a binder into the powder, and then grinding and granulating to obtain granulated materials;

3) loading the granulated material into a die, and pressing the granulated material loaded into the die into a green body on a press;

4) and (3) demolding the blank, placing the demolded blank into a vacuum furnace, then preserving the heat for 1-3 hours at 1400-1600 ℃ in the atmosphere of nitrogen or argon, and cooling the blank along with the furnace after preserving the heat.

The metal corresponding to the metal is molybdenum or nickel.

The whisker precursor comprises the following raw materials in percentage by mass: nickel: titanium dioxide: carbon 1-20%: 1-10%: 1-50%: 1-60%, and preparing the titanium carbide whisker phase by an in-situ growth method; or nickel: silicon dioxide: carbon is 0.1-2%: 50-90%: 10-40%, and preparing the silicon carbide whisker phase by an in-situ growth method.

The ball mill is a barrel-rolling ball mill or a planetary ball mill, and the ball mill is sieved by a 100-mesh sieve in the step 2).

The multi-element additive is polyvinyl alcohol aqueous solution, the mass fraction is 5-10%, the adding amount is 5-10% of the weight of the powder, and the pressure adopted by the press when pressing the blank body is 100-200 MPa.

Compared with the prior art, the invention has the beneficial effects that:

1. the composite alumina ceramic resistance material prepared by the invention keeps the mechanical property and high temperature resistance of alumina ceramic, and simultaneously keeps the simplicity and integrity of the prior process.

2. The obtained metal ceramic resistor can resist thermal shock and large current shock, and the ceramic surface is easy to metalize due to the addition of the metal molybdenum (nickel) and can be welded with metal.

3. The invention overcomes the defects of low power density and poor thermal shock resistance of common high-power resistors such as carbon film ceramic resistors, zinc oxide linear ceramic resistors, cement resistors and the like, and can be widely applied to the fields of high-power resistor elements and the like.

4. The invention adds two fillers (metal phase and whisker phase) into the alumina ceramic at the same time, and can obtain the metal ceramic with low resistivity on the premise that the content of the metal phase is far lower than the seepage threshold of the common metal ceramic through the bridging action of the fillers.

5. Because the two fillers have different resistivities, the resistivity of the metal ceramic can be controlled within a certain range by adjusting the content and the appearance of the fillers, so that the defect that the resistivity of the original metal ceramic only has two states of insulation and complete conduction is overcome, and the application field of the metal ceramic resistor is expanded.

6. The addition of the whisker can obviously improve the mechanical property of the metal ceramic, thereby further improving the strength and the thermal shock resistance of the metal ceramic and being beneficial to improving the power density of the metal ceramic.

Drawings

FIG. 1 is a scanning electron micrograph of a cermet prepared with 10 wt.% molybdenum, 30 wt.% TiC whiskers, 55 wt.% alumina, and 5 wt.% of a multi-component additive (example 1, sample 9).

FIG. 2 is a spectrum of the cermet of FIG. 1.

FIG. 3 shows the effect of Mo and TiC whisker content on the electrical resistivity of the cermet.

Detailed Description

The embodiments of the present invention will be described in detail below with reference to the drawings and examples.

A high power density cermet resistance material with controllable resistivity and its preparation, according to the different parameters selected, provides several embodiments, its preparation method includes the following steps:

(1) the raw material patterns with the following components were prepared according to the raw material ratios, and the pattern numbers and ratios are shown in table 1. Wherein, the metal phase is molybdenum, the whisker phase is titanium carbide whisker, the raw materials of the whisker precursor and the mass ratio of sodium chloride are as follows: nickel: titanium dioxide: carbon 20%: 5%: 50%: 25 percent;

(2) the raw materials are put into a ball milling tank, and the weight percentages are as follows: 1: 2, adding alumina balls into the ball milling tank according to the mass ratio, taking absolute ethyl alcohol as a ball milling medium, and carrying out wet milling on a planetary ball mill at the rotating speed of 600r/min for 8 hours;

(3) taking out the ball-milled raw materials, drying, and sieving with a 100-mesh sieve to obtain powder. Adding a PVA (polyvinyl alcohol) aqueous solution (the mass fraction of which is 5%) of which the weight is 5% of the powder into the powder, and grinding and granulating to obtain granules;

(4) loading the granulated material into a die, and pressing the die into a disc-shaped blank on a press with the pressure of 150 MPa;

(5) and (3) demolding the blank, raising the temperature to 1550 ℃ at the speed of 700 ℃/h in the nitrogen atmosphere, preserving the temperature for 2h, and then cooling along with the furnace to obtain the composite alumina ceramic.

The resistivity results are shown in Table 1. As can be seen from table 1, when the molybdenum is added in an amount of less than 10%, the ceramic is an insulator. When the amount of Mo added is more than 30%, the resistivity of the ceramic is drastically lowered to be a conductor, and the composite ceramic of example 1 has a percolation threshold of Mo of 30%. By increasing TiC and reducing Mo dosage, the resistivity is 3.3X 10 when Mo content is 10% and TiC content is 30%^-3Ω·cm^-1The cermet of (2). As can be seen from FIGS. 1 and 2, the TiC whiskers and the Mo particles form a bridging structure, and the energy spectrum analysis shows that the main elements are Ti, Al and Mo.

It can be seen from FIG. 3 that when the molybdenum content is 10%, the electrical resistivity of the ceramic material decreases by 3.3X 10 due to the bridging effect at a whisker content of 30%^-3Ω·cm^-1It is believed that the percolation threshold of the cermet is significantly reduced from 30% when it is doped with molybdenum alone.

TABLE 1 test sample composition and Performance test

Claims

1. The metal ceramic resistor material with controllable resistivity and high power density is characterized in that the metal ceramic mainly comprises a ceramic phase, a metal phase and a whisker phase dispersed among the metal ceramic;

the metal phase is low-resistivity metal particles;

the whisker phase is prepared by an in-situ growth method by using a whisker precursor, is a whisker with low resistivity, and has the resistivity lower than that of a ceramic phase and higher than that of a metal phase;

2. The controlled resistivity high power density cermet resistive material of claim 1 wherein the calcium oxide: mullite: the mass ratio of the spinel is 1 (1-2) to 1-2.

3. The controlled resistivity high power density cermet resistance material of claim 1 wherein the metal phase is molybdenum or nickel with a 100 μm grain size.

4. The controlled resistivity high power density cermet resistive material of claim 1, wherein the whisker phase is a silicon carbide whisker phase or a titanium carbide whisker phase with a diameter of 10 μm and a length of 20-50 μm.

5. The method for preparing a high power density cermet resistance material with controllable resistivity of claim 1 comprising the steps of:

6. The method according to claim 5, wherein the metal corresponding to the metal is molybdenum or nickel.

7. The preparation method according to claim 5, wherein the raw materials of the whisker precursor are sodium chloride: nickel: titanium dioxide: carbon = 1-20%: 1-10%: 1-50%: 1-60%, and preparing the titanium carbide whisker phase by an in-situ growth method; or nickel: silicon dioxide: carbon = 0.1-2%: 50-90%: 10-40%, and preparing the silicon carbide whisker phase by an in-situ growth method.

8. The method for preparing a porous material according to claim 5, wherein the ball mill is a barrel ball mill or a planetary ball mill, and the step 2) is carried out by sieving with a 100-mesh sieve.

9. The preparation method according to claim 5, wherein the binder is an aqueous solution of polyvinyl alcohol with a mass fraction of 5-10% and is added in an amount of 5-10% of the weight of the powder, and the pressure applied by the press when pressing the green body is 100-200 MPa.