CN109231973B - Complex phase ceramic insulator and preparation method thereof - Google Patents
Complex phase ceramic insulator and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a complex phase ceramic insulating part and a preparation method thereof. The raw materials for preparing the complex-phase ceramic insulator comprise alpha-phase aluminum oxide, yttrium oxide and hexagonal boron nitride coated molybdenum composite powder, wherein the weight of the hexagonal boron nitride coated molybdenum composite powder accounts for 7.5-22.5% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum, and the weight of the yttrium oxide accounts for 3-8% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder. The complex phase ceramic insulator is formed by alpha-AL2O3Adding proper amount of h-BN coated Mo composite powder and Y as matrix material2O3Sintering to form a ceramic insulating part; the thermal shock resistance of the ceramic insulator is improved by Mo with good thermal conductivity, so that the ceramic insulator has better thermal shock resistance and higher mechanical strength.
Description
Technical Field
The invention relates to the power cable industry, in particular to a complex phase ceramic insulating part and a preparation method thereof.
Background
With the rapid development of national economy, the scale of power networks is continuously increasing. At the same time, the reliability of the power supply is also increasingly required, which requires all devices in the power network to operate reliably and stably for a long time. As an important electrical device, an insulator is defined in the national standard GB/t 2009.b-1995 "electrical term insulator" as: a device for electrical insulation and mechanical fixation of electrical equipment or conductors at different electrical potentials. The insulator is an insulating material with a certain shape provided with metal accessories. The electric porcelain material has the characteristics of certain mechanical strength, rapid cold and hot denaturation, excellent insulating property, extremely high chemical stability and capability of keeping the mechanical strength and the electrical strength unchanged after long-term operation, so that the electric porcelain material is the most extensive material for the insulator. The outer insulation of most high-voltage equipment adopts electroceramics. In addition, there are also tempered glass insulators and organic insulators. Although the mechanical strength and the electrical strength of the toughened glass insulator can exceed those of the electric porcelain, the toughened glass insulator is difficult to form a large and complex-shaped product, so that the dominant position of the electric porcelain insulator cannot be influenced. The organic insulator usually uses silicon rubber as an external insulating material, the silicon rubber is easy to form and has good electrical strength, but the silicon rubber does not have mechanical strength per se, and needs to form a composite insulating material with a resin material. In summary, the electric porcelain still has an irreplaceable position in the application of the power industry.
The insulator can be divided into: line insulators, substation insulators and sleeves. To date, no alternatives have emerged for porcelain bushings as structural members for high voltage cable terminations. However, electroceramics are brittle materials that break easily under tensile stress. In addition, the bending strength of the cable terminal porcelain bushing used in the current power grid is 150 Mpa-200 Mpa, the thermal shock resistance temperature difference is generally lower than 200 ℃, the problem of poor thermal shock resistance generally exists, the strength of the cable terminal porcelain bushing can be greatly reduced under the action of thermal shock, and the use reliability of structural parts is greatly reduced. Even in the case of a large temperature difference between the inside and the outside of the porcelain bushing, the porcelain bushing at the end of the cable may be cracked due to excessive thermal stress, thereby causing accidents and affecting the stability and reliability of power supply. The analysis and research of related accidents in the power grid also show that the power accidents related to the porcelain bushing are usually caused by the fact that the inside and the outside of the porcelain bushing generate large temperature difference due to factors such as severe external environment temperature change, line faults or misoperation, and the like, so that large thermal stress is generated in the porcelain bushing to cause the porcelain bushing to crack or generate visible cracks to cause subsequent faults.
In order to improve the properties of the electric porcelain, the research on improving the properties of the electric porcelain material by using a complex phase structure to form a special interface between two phases has been greatly advanced and the research work is deeper. However, the mechanical properties of the obtained electric porcelain are not satisfactory, and other properties, such as thermal shock resistance, are still to be improved.
Disclosure of Invention
In view of the above, there is a need for a complex phase ceramic insulator having both good thermal shock resistance and good mechanical properties.
The raw materials for preparing the complex-phase ceramic insulator comprise alpha-phase aluminum oxide and yttrium oxide hexagonal boron nitride coated molybdenum composite powder, wherein the weight of the hexagonal boron nitride coated molybdenum composite powder accounts for 7.5-22.5% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder, and the weight of the yttrium oxide accounts for 3-8% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder.
The complex phase ceramic insulator of the invention is prepared from alpha phase alumina (alpha-Al) with the characteristics of high melting point, high hardness, chemical corrosion resistance, excellent dielectric property and the like2O3) As a matrix material, by adding alpha-Al2O3Adding proper amount of hexagonal boron nitride (h-BN) coated molybdenum (Mo) composite powder in the matrix, and adding sintering aid yttrium oxide (Y)2O3) Formed into ceramic insulation by sinteringA member; the metal molybdenum has good thermal conductivity and can improve the thermal shock resistance of the ceramic insulator, and the hexagonal boron nitride coated metal molybdenum can avoid the influence of metal on the insulating property of the ceramic insulator, so that a proper amount of hexagonal boron nitride coated molybdenum composite powder is added into the alpha-phase matrix material, the thermal shock resistance of the ceramic insulator can be well improved, and the insulating property of the ceramic insulator cannot be influenced, so that the ceramic insulator has good thermal shock resistance and higher mechanical strength, the operation stability and reliability of a cable terminal can be greatly improved, and the reliable and stable operation of a power system can be strongly guaranteed.
It is understood that the weight of the hexagonal boron nitride coated molybdenum composite powder is 7.5% to 22.5% of the sum of the weight of the alpha phase alumina and the weight of the hexagonal boron nitride coated molybdenum composite powder, and the weight of the alpha phase alumina is 77.5% to 92.5% of the sum of the weight of the alpha phase alumina and the weight of the hexagonal boron nitride.
In one embodiment, the weight of the hexagonal boron nitride coated molybdenum composite powder is 10% to 18% of the sum of the weight of the alpha phase alumina and the hexagonal boron nitride coated molybdenum composite powder.
In one embodiment, the weight ratio of the hexagonal boron nitride to the molybdenum in the hexagonal boron nitride-coated molybdenum composite powder is (1.8-2): 1. Therefore, the hexagonal boron nitride can be well coated on the molybdenum to ensure that the molybdenum loses the conductive property, so that the insulating property of the ceramic insulating part cannot be reduced; the hexagonal boron nitride has low modulus, anisotropic expansion coefficient and matrix material alpha-Al2O3The modulus and the expansion system of the ceramic insulator have larger difference, and microcracks can be formed in the sintering process, so that the thermal shock resistance of the ceramic insulator is further improved.
In one embodiment, the hexagonal boron nitride coated molybdenum composite powder is on the nanometer scale.
Preferably, the particle size of the hexagonal boron nitride-coated molybdenum composite powder is 50 nm-200 nm.
Further, in the hexagonal boron nitride-coated molybdenum composite powder, the particle size of the hexagonal boron nitride coated on the surface of the molybdenum powder is 20nm to 30 nm.
Adopts nano-level h-BN to coat Mo composite powder to be introduced into a ceramic matrix, and the h-BN and the alpha-Al2O3The surface has better chemical compatibility and fusion property of the crystal surface, can well play a role in toughening the material, and improves the thermal shock resistance of the material.
In one embodiment, the composite ceramic insulator may be a cable termination insulator.
The invention also aims to provide a preparation method of the complex phase ceramic insulating part.
A preparation method of a complex phase ceramic insulating part comprises the following steps:
providing ceramic powder, wherein the ceramic powder comprises alpha-phase aluminum oxide, yttrium oxide and hexagonal boron nitride coated molybdenum composite powder, the weight of the hexagonal boron nitride coated molybdenum composite powder accounts for 7.5-22.5% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder, and the weight of the yttrium oxide accounts for 3-8% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder;
pressing the ceramic powder into a ceramic insulating part green body;
and sintering the ceramic insulating part blank for 5-12 hours under the conditions of hydrogen atmosphere and temperature of 1650-1800 ℃ to obtain the complex phase ceramic insulating part.
The heat shock resistance of the ceramic insulator can be improved due to the higher heat conductivity of the metal Mo, the influence of the metal Mo on the insulativity of the ceramic insulator can be avoided by coating the Mo with the h-BN, and the h-BN and the alpha-AL2O3Has a large difference in expansion coefficient, and therefore alpha-AL2O3The proper amount of hexagonal boron nitride coated molybdenum composite powder is added into the matrix material, and the ceramic insulating part can generate a proper amount of microcrack effect in the sintering and subsequent cooling processes, so that the thermal shock resistance of the ceramic insulating part is further improved; on the one hand, the yttrium oxide is used as the sintering aid to reduce the temperature required by calcination and on the other hand, the yttrium oxide is favorable for improving the strength of the ceramic material, so the method of the invention uses alpha-AL2O3Adding proper amount of h-BN coated Mo composite powder and Y as matrix material2O3The pressing and sintering processes are combined, so that the ceramic insulating part has good thermal shock resistance and high mechanical strength on the premise of ensuring that the insulating property of the ceramic insulating part is not reduced, the operation stability and reliability of a cable terminal can be greatly improved, and the reliable and stable operation of a power system can be powerfully guaranteed.
In one embodiment, the weight of the hexagonal boron nitride coated molybdenum composite powder is 10% to 18% of the sum of the weight of the alpha phase alumina and the hexagonal boron nitride coated molybdenum composite powder.
In one embodiment, the preparation method of the complex phase ceramic insulator further comprises the steps of preparing the hexagonal boron nitride coated molybdenum composite powder:
mixing molybdenum powder with boric acid and urea, ball-milling for 24-50 hours by taking ethanol as a medium, ultrasonically dispersing, removing the ethanol, and drying to obtain a mixture;
and calcining the mixture in air or hydrogen for the first time at 500-700 ℃, and then calcining for the second time at 800-1000 ℃ in nitrogen atmosphere.
Boric acid and urea are used as boron nitride sources, and the nano-scale h-BN is generated by controlling the dosage of each raw material and the calcining condition and uniformly coated on the surface of the metal molybdenum particles to form a compact coating layer. Therefore, a uniform nano-scale h-BN coating layer with proper thickness is formed on the surfaces of the metal molybdenum powder particles, so that the toughness and mechanical strength of the ceramic insulating part can be further improved, and the metal molybdenum powder loses the conductivity in a certain range.
Further, the molar ratio of the urea to the boric acid to the molybdenum powder is (30-40): (18-20): 1. In the process of coating the hexagonal boron nitride-coated molybdenum composite powder, the weight ratio of h-BN to Mo in the obtained nano h-BN coated molybdenum composite powder is 1.8-2.2 by controlling the addition amount of each raw material.
Specifically, the step of removing ethanol and drying is to remove the ethanol by using a rotary evaporator and then place the ethanol in a vacuum oven at the temperature of 98-102 ℃ for drying for 10-12 hours.
In one embodiment, the first calcining step is: and heating the mixture to 500-700 ℃ in air or hydrogen at a fixed heating rate to calcine the mixture.
In one embodiment, the fixed heating rate is 1 ℃/min to 3 ℃/min.
Further, the first calcination time is 20-25 hours, and the second calcination time is 5-10 hours. And performing twice calcination reactions to generate hexagonal boron nitride, and tightly coating the hexagonal boron nitride on the surface of the metal molybdenum powder to obtain the nano hexagonal boron nitride-coated molybdenum composite powder.
In one embodiment, the method further comprises the step of preparing the ceramic powder:
mixing the components of the ceramic powder with ethanol, performing ultrasonic dispersion, performing ball milling for 24-48 hours, removing the ethanol, grinding for 60-120 minutes, sieving, and performing spray drying.
Ethanol is added in the ball milling process, so that the surface energy of the surface of the raw material powder can be reduced, and the powder is prevented from agglomerating; and the ethanol is easy to volatilize, so that the subsequent removal is convenient, the moisture content of the raw material powder cannot be increased, and the cooling effect can be realized to a certain extent.
Further, the time of ultrasonic dispersion is 15-30 minutes.
In one embodiment, the step of sieving controls the particle size of the ceramic powder to be less than 360 mesh.
In one embodiment, the step of pressing the ceramic powder into a ceramic insulator green body comprises: and carrying out cold isostatic pressing on the ceramic powder under the condition of 230-250 MPa to obtain the ceramic insulating part blank.
In one embodiment, the preparation method of the complex phase ceramic insulator further comprises the step of obtaining alpha phase alumina:
and calcining the alumina powder for 10-15 hours at 1500-1650 ℃ in the air atmosphere.
Specifically, the particle diameter is set to be 1 to 5 μm highHigh purity industrial alumina powder (Al content over 99.5%)2O3) Calcining the mixture for 10 to 15 hours at 1500 to 1650 ℃ in the air atmosphere, and fully grinding the mixture to obtain the catalyst.
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
At present, although the cable terminal porcelain bushing is formed by adding a complex phase material, the cable terminal porcelain bushing has poor thermal shock resistance and is easy to generate stress concentration and release under severe temperature difference, so that the porcelain bushing is cracked or generates visible cracks, and the stable operation of a power system is influenced.
The thermal shock resistance refers to the ability of a material to withstand a large change in temperature, which is a comprehensive reaction of the mechanical and thermal properties of the material on the heating conditions. The thermal shock resistance of the ceramic material depends on the thermal stress in the material, and the magnitude of the thermal stress depends on the influence of factors such as the mechanical property and the thermal property of the ceramic material, so the thermal shock resistance of the ceramic material is a comprehensive expression that the mechanical property and the thermal property of the ceramic material correspond to various heating conditions. The thermal shock damage of the ceramic material can be divided into instantaneous fracture under the thermal shock effect and cracking and stripping under the thermal shock cycle effect until the ceramic material is damaged integrally. In view of the different ways of thermal shock damage of ceramic materials, there are two types of thermal shock evaluation theories generally accepted by people at present: one is a critical stress fracture theory based on a thermoelastic theory, and the other is a thermal shock damage theory based on fracture mechanics.
Wherein the critical stress rupture theory is thermal stress sigmaHAnd the intrinsic strength σ of the materialfThe balance therebetween is taken as a basis for resistance to thermal shock damage, and it is considered that thermal stress caused in the material when thermal shock is applied exceeds the inherent strength of the material, i.e., σH≥σfThe theory of thermal shock fracture resistance is based on strength-stress, the material cracks after the thermal stress in the material reaches the tensile strength limit, and the material is completely destroyed once the crack nucleates. According to the thermal shock damage theory, the relation between thermoelastic strain energy W and fracture energy U is used as a criterion of thermal shock damage, and the dynamic processes of crack nucleation, expansion and inhibition of the material under the condition of temperature change are analyzed. When the strain energy W stored in the material exceeds the energy U required for the fracture of the material, namely W is more than or equal to U, cracks begin to generate and propagate, and the thermal shock damage of the material is caused.
Thus, the present application is in alpha-Al2O3The molybdenum with high thermal conductivity is introduced to improve the thermal shock resistance of the ceramic insulator. As metal is a conductor, the insulating property of the ceramic insulating part can be reduced, so that the insulating property of the ceramic insulating part can not meet the requirement of the insulating property, the hexagonal boron nitride is adopted to coat the metal molybdenum powder, so that the introduced metal molybdenum directly loses the electric conductivity in a microscopic range with a certain size, the hexagonal boron nitride also has the characteristics of good heat conductivity and good thermal shock resistance, the thermal shock resistance of the ceramic material is obviously improved through the conditions of the dosage collocation of various raw material components, the subsequent pressing and sintering process and the like, and the thermal shock resistance of the ceramic material is improved while the other physical properties, such as mechanical strength and the like, are realized.
The following are some specific examples:
α-Al2O3the powder can be obtained commercially or by self-production.
Example 1
The preparation method of the cable terminal porcelain bushing comprises the following specific steps:
1) high-purity industrial alumina (the purity is more than 99.5 percent) with the grain diameter of 1-5 mu m is calcined for 12 hours at 1600 ℃ in the air atmosphere to be fully converted into alpha-Al2O3Then subjecting the obtained alpha-Al2O3The powder is fully ground.
2) Fully grinding metal Mo powder with the particle size of 20-130 nm, and mixing the Mo powder with (NH)2)2CO、H3BO3In a molar ratio of 1:38:19, the milled Mo powder and urea ((NH)2)2CO) and boric acid (H)3BO3) Mixing, adding absolute ethyl alcohol and a proper amount of deionized water, ball-milling in a ball mill for 48 hours, fully dispersing by ultrasonic waves, evaporating the solvent on a rotary evaporator, and drying in a vacuum oven at 100 ℃ for 12 hours to obtain a dried mixture.
3) Heating the mixture obtained in the step 2) in air at a heating rate of 2 ℃/min to 600 ℃ for calcining for 20-25 hours, and then calcining in N2Calcining for 8 hours at 950 ℃ in the atmosphere to obtain the nano h-BN coated Mo composite powder. The obtained nano h-BN coated Mo composite powder is detected, the weight of h-BN accounts for 67.2 percent of the weight of the composite powder, and the particle size of h-BN is 20nm to 50 nm.
4) Coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O385 wt% of powder and 15 wt% of nano h-BN coated Mo composite powder.
5) According to Y2O3The addition amount of the nano-h-BN coating Mo composite powder and the alpha-Al2O35% of the total weight of the powder, mixing the powder obtained in step 4) with Y2O3Mixing and fully grinding, wherein the yttrium oxide is analytically pure; then placing the ground raw materials into absolute ethyl alcohol to be stirred, and dispersing for 30min by using ultrasonic waves; then placing the mixture into a ball mill for ball milling for 36 hours, placing the mixture into a rotary evaporator for drying the solvent by distillation at 100 ℃, and then placing the mixture into a constant-temperature oven at 100 ℃ for drying for 12 hours; then grinding for 100min, sieving by a 360-mesh sieve to obtain mixed ceramic powder, and drying the ceramic powder by a spray drying method.
6) And (3) carrying out cold isostatic pressing on the dried ceramic powder under the condition of 230-250 MPa to obtain a cable terminal porcelain bushing blank.
7) Sintering for 12 hours in a flowing hydrogen atmosphere at 1750 ℃, and naturally cooling to room temperature to obtain a sample of the cable terminal porcelain bushing.
Preparing at least three samples according to the method, and detecting the performances of the samples:
the average density of the cable terminal porcelain bushing sample is 4.01g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 390 MPa; the temperature cycle test adopts a heating and rapid cooling method, the operation is repeated for 10 times, then the thermal shock resistance of the material is obtained by measuring the residual bending strength, and finally the bending strength loss rate is 5% when the thermal shock resistance temperature difference is 750 ℃.
Example 2
Example 2 is essentially the same as example 1, except that: step 4) coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O389.5 wt% of powder and 10.5% of nano h-BN coated Mo composite powder.
And (3) detecting the sample of the obtained cable terminal porcelain bushing:
the average density of the cable terminal porcelain bushing sample is 3.98g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 395 MPa; the temperature cycle test adopts a heating and rapid cooling method, the operation is repeated for 10 times, then the thermal shock resistance of the material is obtained by measuring the residual bending strength, and finally the bending strength loss rate is 5% when the thermal shock resistance temperature difference is 723 ℃.
Example 3
Example 3 is essentially the same as example 1, except that: step 4) coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O3The powder accounts for 83.5 wt%, and the nano h-BN coated Mo composite powder accounts for 16.5 wt%.
And (3) detecting the sample of the obtained cable terminal porcelain bushing:
the average density of the cable terminal porcelain bushing sample is 4.02g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 380 MPa; the temperature cycle test adopts a heating and rapid cooling method, the operation is repeated for 10 times, then the thermal shock resistance of the material is obtained by measuring the residual bending strength, and finally the bending strength loss rate is 5% when the thermal shock resistance temperature difference is 762 ℃.
Example 4
Example 4 is essentially the same as example 1, except that: step 4) coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O3The powder accounts for 90 wt%, and the nano h-BN coated Mo composite powder accounts for 7.5%.
And (3) detecting the sample of the obtained cable terminal porcelain bushing:
the average density of the cable termination porcelain bushing sample was 3.95g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 385 MPa; the temperature cycle test adopts a heating and rapid cooling method, the operation is repeated for 10 times, then the thermal shock resistance of the material is obtained by measuring the residual bending strength, and finally the bending strength loss rate is 5% when the thermal shock resistance temperature difference is 705 ℃.
Example 5
Example 5 is essentially the same as example 1, except that: step 4) coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O377.5 wt% of powder and 22.5% of nano h-BN coated Mo composite powder.
And (3) detecting the sample of the obtained cable terminal porcelain bushing:
the average density of the cable terminal porcelain bushing sample is 4.00g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 350 MPa; the temperature cycle test adopts a heating and rapid cooling method,repeating the steps for 10 times, measuring the residual bending strength to obtain the thermal shock resistance of the material, and finally obtaining the material with the bending strength loss rate of 5% when the thermal shock resistance temperature difference is 770 ℃.
Comparative example 1
Example 1 is substantially the same as example 1 except that: step 4) coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O3The powder accounts for 95 wt%, and the nano h-BN coated Mo composite powder accounts for 5 wt%.
And (3) detecting the sample of the obtained cable terminal porcelain bushing:
the average density of the cable terminal porcelain bushing sample is 4.02g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 424 MPa; the temperature cycle test adopts a heating and rapid cooling method, the heating and rapid cooling is repeated for 8 times, then the thermal shock resistance of the material is obtained by measuring the residual bending strength, and finally the bending strength loss rate is 5% when the thermal shock resistance temperature difference is 280 ℃.
Comparative example 2
Comparative example 2 is substantially the same as example 1 except that: step 4) coating the nano h-BN with Mo composite powder and alpha-Al2O3Mixing the powders to obtain a mixed powder, wherein, the alpha-Al2O385 wt% of powder and 25 wt% of nano h-BN coated Mo composite powder.
And (3) detecting the sample of the obtained cable terminal porcelain bushing:
the average density of the cable termination porcelain bushing sample was 3.96g/cm3(ii) a A three-point method is adopted to carry out a four-way bending test, and the average bending strength (room temperature) of a cable terminal porcelain bushing sample is 450 MPa; the temperature cycle test adopts a heating and rapid cooling method, the heating and rapid cooling is repeated for 8 times, then the thermal shock resistance of the material is obtained by measuring the residual bending strength, and finally the bending strength loss rate is 5% when the thermal shock resistance temperature difference is 270 ℃.
Compared with the cable terminal porcelain bushing (the bending strength is 150 Mpa-200 Mpa, the thermal shock resistance temperature difference is generally lower than 200 ℃) on the common market and the cable terminal porcelain bushing of the comparative examples 1-2, the cable terminal porcelain bushing of the embodiments 1-5 of the invention has better bending strength and thermal shock resistance temperature difference. Further, as can be seen from examples 1 to 5 and comparative examples 1 to 2 in which the mass percentage of the nano h-BN coated Mo composite powder in the raw material is changed, the mass percentage of the nano h-BN coated Mo composite powder in the raw material is changed within the range of 7.5% to 22.5%, the obtained cable terminal porcelain bushing has good mechanical strength and thermal shock resistance, and when the mass percentage of the nano h-BN coated Mo composite powder is 10.5% to 16.5%, the obtained cable porcelain bushing has the best terminal performance under the condition that the mechanical strength and the thermal shock resistance are comprehensively considered.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The multiphase ceramic insulating part is characterized in that raw materials for preparing the multiphase ceramic insulating part are as follows: the composite powder comprises alpha-phase aluminum oxide, yttrium oxide and hexagonal boron nitride coated molybdenum, wherein the weight of the hexagonal boron nitride coated molybdenum composite powder accounts for 10.5-15% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder, and the weight of the yttrium oxide accounts for 5% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder;
the weight ratio of the hexagonal boron nitride to the molybdenum in the hexagonal boron nitride coated molybdenum composite powder is (1.8-2.2): 1.
2. The composite phase ceramic insulator as claimed in claim 1, wherein the weight of the hexagonal boron nitride clad molybdenum composite powder is 15% of the sum of the weight of the alpha phase alumina and the hexagonal boron nitride clad molybdenum composite powder.
3. The composite phase ceramic insulator as claimed in claim 1, wherein the weight of the hexagonal boron nitride clad molybdenum composite powder is 10.5% of the sum of the weight of the alpha phase alumina and the hexagonal boron nitride clad molybdenum composite powder.
4. The composite ceramic insulator as claimed in claim 1, wherein the hexagonal boron nitride coated molybdenum composite powder has a particle size of 50nm to 200 nm.
5. The preparation method of the complex phase ceramic insulating part is characterized by comprising the following steps of:
providing ceramic powder, wherein the ceramic powder consists of alpha-phase aluminum oxide, hexagonal boron nitride coated molybdenum composite powder and yttrium oxide, the weight of the hexagonal boron nitride coated molybdenum composite powder accounts for 10.5-15% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder, and the weight of the yttrium oxide accounts for 5% of the sum of the weight of the alpha-phase aluminum oxide and the weight of the hexagonal boron nitride coated molybdenum composite powder;
the weight ratio of the hexagonal boron nitride to the molybdenum in the hexagonal boron nitride coated molybdenum composite powder is (1.8-2.2): 1;
pressing the ceramic powder into a ceramic insulating part green body;
and sintering the ceramic insulating part blank for 5-12 hours under the conditions of hydrogen atmosphere and temperature of 1650-1800 ℃ to obtain the complex phase ceramic insulating part.
6. The method of making a composite ceramic insulator of claim 5, further comprising the step of making the hexagonal boron nitride coated molybdenum composite powder:
mixing molybdenum powder with boric acid and urea, ball-milling for 24-50 hours by taking ethanol as a medium, ultrasonically dispersing, removing the ethanol, and drying to obtain a mixture; the molar ratio of the urea to the boric acid to the molybdenum powder is (30-40): (18-20): 1;
and calcining the mixture in air or hydrogen for the first time at 500-700 ℃, and then calcining for the second time at 800-1000 ℃ in nitrogen atmosphere.
7. The method of making a composite ceramic insulator as claimed in claim 5, further comprising the step of making the alpha phase alumina:
and calcining the alumina powder at 1500-1650 ℃ for 10-15 hours in the air atmosphere to obtain the alpha-phase alumina.
8. The method of manufacturing a complex phase ceramic insulator as claimed in claim 5, further comprising the step of preparing the ceramic powder:
mixing the components of the ceramic powder with ethanol, performing ultrasonic dispersion, performing ball milling for 24-48 hours, removing the ethanol, grinding for 60-120 minutes, sieving, and performing spray drying.
9. The method of claim 8, wherein the sieving step controls the particle size of the ceramic powder to be less than 360 mesh.
10. The method for preparing the complex phase ceramic insulator as claimed in any one of claims 5 to 9, wherein the step of pressing the ceramic powder into a ceramic insulator green body comprises: and carrying out cold isostatic pressing on the ceramic powder under the condition of 230-250 MPa to obtain the ceramic insulating part blank.
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