CN115196966B - Silicon carbide composite ceramic with constant temperature resistance and preparation method thereof - Google Patents
Silicon carbide composite ceramic with constant temperature resistance and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a silicon carbide composite ceramic with constant temperature resistance and a preparation method thereof. The main component of the silicon carbide composite ceramic comprises a SiC matrix material and TiC second phases uniformly dispersed at SiC grain boundaries; the mass fraction of the SiC is 75-85 wt%, and the mass fraction of the TiC is 9.2-15.8 wt%.
Description
Technical Field
The invention relates to silicon carbide composite ceramic with constant temperature resistance and a preparation method thereof, belonging to the field of silicon carbide ceramic.
Background
In all electronic components of the electronic product, the resistor has the largest consumption and the largest variety, and the voltage change in the circuit or the change of the working environment temperature can cause the change of the resistance value, so that the circuit state is unstable, and the situations such as: in electronic products used in special environments such as artificial satellites, radars, remote sensing, test instruments and meters and the like, the requirements on the precision, the temperature coefficient and the stability of resistance values are very high, and therefore, certain special materials are required to be manufactured into standard resistors.
Silicon carbide (SiC) materials have excellent oxidation resistance, high-temperature mechanical strength, high hardness, high thermal conductivity, and the like, and are important structural and electronic materials. By adding a proper kind and content of the second phase, the silicon carbide material with resistivity changing from an insulator to a conductor can be obtained, different use requirements can be met, and the silicon carbide material is a resistor material which is used under very promising severe environment conditions.
However, conventionally prepared silicon carbide ceramic materials have pressure-sensitive characteristics, exhibit nonlinear volt-ampere characteristics in a certain voltage range, and rapidly decrease in resistance with increasing voltage; in addition, silicon carbide ceramics are one of Negative Temperature Coefficient (NTC) thermosensitive ceramics, which are sensitive to temperature changes, and a grain boundary space charge layer of a silicon carbide material has a larger resistance to movement of carriers (electrons and holes) at a lower temperature, and as the temperature increases, the concentration of carriers increases, the movement capacity increases, the number of crossing grain boundaries also increases, and the resistance decreases significantly as the temperature increases. In the use process of the conventional silicon carbide ceramic as an electronic element, voltage change, working environment temperature change and self-heating temperature change can cause remarkable change of resistance values, so that the stability of a circuit is difficult to ensure, and the silicon carbide ceramic cannot be used as a standard element.
Disclosure of Invention
In order to ensure the stability of a circuit of the silicon carbide ceramic in use as an electronic element, the invention aims to provide the silicon carbide ceramic with constant temperature resistance and a preparation method thereof.
In a first aspect, the present invention provides a silicon carbide composite ceramic with constant temperature resistance, wherein the main component of the silicon carbide composite ceramic comprises a SiC matrix material and TiC second phases uniformly dispersed at SiC grain boundaries; the mass fraction of the SiC is 75-85 wt%, and the mass fraction of the TiC is 9.2-15.8 wt%.
SiC and TiC have opposite temperature sensitive properties. SiC is a Negative Temperature Coefficient (NTC) thermal sensitive ceramic, whose resistivity decreases significantly with increasing temperature, and the grain boundary space charge layer of the silicon carbide material has a greater resistance to movement of carriers (electrons, holes) at lower temperatures, and as the temperature increases, the concentration of carriers increases, the movement capacity increases, the number of crossing grain boundaries increases, the resistivity decreases significantly with increasing temperature, and the resistivity changes by more than two orders of magnitude in the use range of 20-300 ℃. Pure TiC is a type of well-conductive resistor with ohmic contact type (1.67×10 6 S·m -1 ) The metal-based Positive Temperature Coefficient (PTC) characteristic similar to metal resistance is provided, when the temperature is increased, the inside of the metal-based Positive Temperature Coefficient (PTC) is enhanced due to phonon vibration, the effect on electron scattering is more obvious, the directional movement of free electrons is blocked, and the resistance is increased. The positive temperature coefficient characteristic of the TiC resistor can be complemented with the negative temperature coefficient characteristic of the SiC resistor, so that the temperature sensitivity degree of the silicon carbide ceramic resistor is reduced, the resistivity is smaller along with the temperature change and is changed in the same order of magnitude, and a more constant state is maintained.
Because TiC and SiC are directly used for compounding, compact complex-phase ceramic is difficult to sinter, and the obtained complex-phase ceramic has poor conductivity. The TiC second phase is composed of Ti 3 AlC 2 Decomposition results, the decomposition reaction equation is: ti (Ti) 3 AlC 2 →TiC+Ti 2 AlC，Ti 2 AlC→TiC+Al+Ti. During sintering process, ti 3 AlC 2 The decomposition produced TiC in the form of a second phase in the SiC matrix, and by scanning electron microscopy, it can be seen that TiC in the material exists as a separate phase, does not form a solid solution into the SiC lattice, and exists at SiC grain boundary sites. At the same time, al element enters SiC crystal lattice in solid solution state orIn the SiC matrix material in the form of alumina, ti reacts with C in SiC to form TiC, and in the preferential scheme, the reaction of Ti and SiC is carried out by 3 AlC 2 The mixed powder prepared from the powder is sintered at 1700-1900 ℃ to enable the TiC second phase to be formed at the SiC grain boundary.
Preferably, the silicon carbide composite ceramic further contains an Al element, wherein the Al element enters a SiC crystal lattice in a solid solution state or exists in a SiC matrix material in the form of aluminum oxide; the content of the Al element is 1.3-3.5 wt%.
During sintering process, ti 3 AlC 2 TiC generated by decomposition exists at the SiC grain boundary, so that the interface energy of SiC is reduced, the movement resistance of carriers is reduced, and the effect of adjusting the conductivity of SiC is achieved. Meanwhile, the positive temperature coefficient characteristic of the TiC resistor can be complemented with the negative temperature coefficient characteristic of the SiC resistor, so that the temperature sensitivity of the silicon carbide ceramic resistor is reduced.
Preferably, the silicon carbide composite ceramic further comprises a sintering aid with the mass percent of not more than 1 weight percent, wherein the sintering aid is B 4 C. B, C.
Preferably, the density of the silicon carbide composite ceramic is 3.13-3.31 g.cm -3 The relative density is 94.3-98.4% (due to the presence of Ti during sintering) 3 AlC 2 Al generated by decomposition is partially volatilized and partially reacted with oxygen on the surface of silicon carbide, and the specific content of each component is difficult to determine, so that when calculating the relative density, we use added Ti 3 AlC 2 Calculating the quantity); the silicon carbide composite ceramic has constant resistivity in the temperature change range of 20-300 ℃ and the resistivity fluctuates in the range of 4-68 omega cm.
In a second aspect, the invention provides a method for preparing the silicon carbide composite ceramic. The preparation method comprises the following steps: raw material powder (SiC powder and Ti) 3 AlC 2 Powder) is subjected to ball milling and mixing to obtain slurry with the solid content of 45-50wt%; drying, sieving or spray granulating the obtained slurry to obtain mixed powder; discharging plasma to burn the obtained mixed powderAnd (5) sintering (SPS) to obtain the silicon carbide complex-phase ceramic with constant temperature resistance.
Wherein the solid content of the slurry is limited to 45-50wt%, so that the slurry maintains good fluidity and dispersion uniformity. If the solid content of the slurry is too high, the uniformity of dispersion can be influenced due to the difficulty in mixing uniformly in the ball milling process; if the solid content of the slurry is too low, sedimentation and delamination can occur due to the density difference, and the uniform mixing of the powder is adversely affected. The SPS sintering, namely the spark plasma sintering, has the characteristics of high temperature rising speed, short sintering time and reduction of sintering temperature.
Preferably, the total mass of the raw material powder is 100wt%, the mass fraction of the SiC powder in the raw material powder is 75-85 wt%, and the Ti is 3 AlC 2 The mass fraction of the powder is 15-25 wt%; preferably, the raw material powder Ti 3 AlC 2 The mass fraction of the powder is 20-25 wt%.
When Ti is 3 AlC 2 When the addition amount of (C) is 15-25 wt%, the negative temperature resistance characteristics of the SiC ceramic are inhibited, and the resistivity is kept in a relatively constant state within a temperature variation range of 20-300 ℃.
Preferably, a sintering aid is also added into the raw material powder, wherein the sintering aid is B 4 C. B, C; the mass of the sintering aid is less than 1 weight percent of the total mass of the raw material powder.
Preferably, the purity of the SiC powder is more than or equal to 99 percent, and the grain size is less than or equal to 0.5 mu m; the Ti is 3 AlC 2 The purity of the powder is more than or equal to 99 percent, and the grain size is less than or equal to 10 mu m.
Preferably, the parameters of the SPS sintering are: under the vacuum condition, the temperature rising rate is 50-100 ℃/min, the sintering temperature is 1700-1900 ℃, the heat preservation time is 7-15 min, and the sintering pressure is 30-50 MPa. Preferably, the sintering temperature is 1850-1900 ℃, and the heat preservation time is 10-15 min.
In a third aspect, the application of the silicon carbide composite ceramic in a middle Wen Hengzu element provided by the invention, wherein the middle Wen Hengzu element can be used at a temperature of 20-300 ℃, and the resistivity fluctuates within the range of 53+/-15, 26+/-6 and 12+/-8 Ω & cm.
The beneficial effects are that:
1. the invention adopts SPS sintering, through Ti 3 AlC 2 The decomposed TiC and SiC are compounded to prepare the SiC-TiC complex-phase ceramic with higher density.
2. The prepared SiC-TiC complex-phase ceramic has better conductivity, improves the temperature sensitivity of the ceramic resistor and keeps a more constant state at the temperature of 20-300 ℃.
Drawings
FIG. 1 is 15wt% Ti 3 AlC 2 The volt-ampere characteristic curves of the silicon carbide ceramics at different temperatures of the added amount show that the material has better linear conductive characteristic and has little change degree in the whole temperature range.
FIG. 2 is 20wt% Ti 3 AlC 2 The volt-ampere characteristic curves of the silicon carbide ceramics at different temperatures of the added amount show that the material has better linear conductive characteristic and has little change degree in the whole temperature range.
FIG. 3 is 25wt% Ti 3 AlC 2 The volt-ampere characteristic curves of the silicon carbide ceramics at different temperatures of the added amount show that the material has better linear conductive characteristic and has little change degree in the whole temperature range.
FIG. 4 is a diagram of different Ti 3 AlC 2 And the resistivity change curves of the silicon carbide ceramics at different temperatures under the addition amount.
Detailed Description
The invention will be further described with reference to the accompanying drawings and the following embodiments, it being understood that the following embodiments are only illustrative of the invention and not limiting thereof.
The following illustrates the preparation and testing methods of the silicon carbide composite ceramic with constant temperature resistance characteristics.
Mixing ingredients and ball milling: weighing SiC and Ti according to a proportion 3 AlC 2 In a ball milling tank, the powder is ball milled and mixed by a planetary ball mill to prepare slurry with the solid content of 45-50wt%. Wherein the mass of the SiC can be 75 to 85 weight percent，Ti 3 AlC 2 The mass of (C) may be 15 to 25wt%. In a specific embodiment, a proper amount of sintering aid is also added to the formulation. The sintering aid is B 4 C. B, C. The addition amount of the sintering auxiliary agent is not more than SiC and Ti 3 AlC 2 1wt% of the total mass of the powder. The sintering aid mainly plays a role in promoting sintering densification, and the sintering aid can be added to form solid solution into SiC crystal lattice to enable the crystal lattice to be distorted and activated, so that the sintering temperature is reduced, and the sintering speed is increased.
Drying and sieving: and drying, sieving or spray granulating the obtained slurry to obtain mixed powder. Wherein the drying temperature is 60-70 ℃. The fineness of the powder is required to be 100-200 meshes, and the uniformity of the granularity of the obtained powder is maintained.
High-temperature sintering: SPS sintering is adopted, and sintering temperature is 1700-1900 ℃ SPS sintering, namely discharge plasma sintering, and the sintering device has the characteristics of high temperature rising speed, short sintering time and reduction of sintering temperature. In a specific scheme, the temperature is increased to 1700-1900 ℃ under the vacuum condition at the heating rate of 50-100 ℃/min for sintering. The sintering temperature is preferably 1850 to 1900 ℃. The incubation time may be 7 to 15 minutes, preferably 10 to 15 minutes. The pressure is 30-50 Mpa, and the variable-temperature constant-resistivity silicon carbide complex-phase ceramic is obtained. The proper sintering temperature is favorable for sintering densification of the material, and the sintering temperature is lower, so that the material has more pores, is difficult to sinter and densify, and can cause the deterioration of the material performance due to the overhigh sintering temperature; the proper heat preservation time is favorable for the growth of crystal grains, thereby reducing the number of crystal boundaries and being favorable for the improvement of the conductivity of the material.
Density and relative Density testing: the density is measured by adopting an Archimedes drainage method, and the density of the obtained silicon carbide complex phase ceramic is 3.13-3.31 g.cm -3 The relative density of the obtained silicon carbide complex phase ceramic is 94.3-98.4%.
Temperature change resistivity test: grinding the outer circle of the obtained silicon carbide complex-phase ceramic grinding machine, processing into a wafer with the diameter of 20mm and the thickness of 2mm, uniformly coating normal-temperature conductive silver adhesive on two sides of the wafer to manufacture electrodes, and placing the electrodes in an oven to keep the temperature at 60 ℃ for 1h. And (3) placing the obtained silicon carbide composite ceramic wafer into a muffle furnace, heating the silicon carbide composite ceramic wafer from 20 ℃ to 400 ℃ at a heating rate of 3-5 ℃/min, and carrying out volt-ampere characteristic test on the silicon carbide composite ceramic wafer by using a Keithley2450 multi-channel test system in the heating process, so as to obtain the resistivity values obtained at different temperatures.
Through a variable-temperature resistivity test, the silicon carbide composite ceramic prepared by the method provided by the invention shows constant resistivity, and the resistivity fluctuates in a small range on the same order of magnitude along with the rise of temperature, so that the whole ceramic is in a constant state, and is expected to be used as a medium Wen Hengzu element.
The present invention will be described in more detail by way of examples. It is to be understood that the following examples are given by way of illustration of the present invention and are not to be construed as limiting the scope of the present invention, since various modifications and alterations of no particular nature will fall within the scope of the invention as defined by the appended claims. The specific process parameters and the like described below are also merely examples of suitable ranges, i.e., one skilled in the art can make a suitable selection from the description herein and are not intended to be limited to the specific values described below.
Example 1
Weighing 85g of SiC powder and Ti 3 AlC 2 15g of powder B 4 C powder 0.6g is put into a ball milling tank, 120ml of ethanol and 100g of SiC grinding balls are added, planetary ball milling is adopted, and the ball milling is carried out for 12 hours at the rotating speed of 300 r/min. The obtained slurry (solid content is 45 wt%) is put into a baking oven to be dried at 70 ℃, and the dried powder is sieved by a 100-mesh sieve. Loading the obtained powder into graphite mold, SPS sintering under vacuum atmosphere at 40MPa and 100 deg.C/min, sintering temperature 1850 deg.C, and maintaining for 10min to obtain ceramic with density of 3.13g cm -3 . Grinding the excircle of the obtained silicon carbide ceramic grinding machine, processing into a wafer with the diameter of 20mm and the thickness of 2mm, uniformly coating normal-temperature conductive silver paste on two sides of the wafer to prepare an electrode, and placing the electrode in an oven to be subjected to heat preservation at 60 ℃ for 1h. The obtained silicon carbide ceramic wafer is put into a muffle furnace, the temperature is raised from 20 ℃ to 300 ℃ with the temperature raising rate of 5 ℃/min, a Keithley2450 multichannel test system is used for carrying out volt-ampere characteristic test on the silicon carbide ceramic wafer in the temperature raising process, the SiC ceramic has linear conductive characteristic in the process,the resistivity was relatively constant with increasing temperature, and fluctuated in the range of 53.+ -.15. Omega. Cm.
Example 2
Weighing 80g of SiC powder and 80g of Ti 3 AlC 2 20g of powder B 4 C powder 0.6g is put into a ball milling tank, 120ml of ethanol and 100g of SiC grinding balls are added, planetary ball milling is adopted, and the ball milling is carried out for 12 hours at the rotating speed of 300 r/min. The obtained slurry (solid content is 45 wt%) is put into a baking oven to be dried at 70 ℃, and the dried powder is sieved by a 100-mesh sieve. Loading the obtained powder into graphite mold, SPS sintering under vacuum atmosphere at 40MPa and 100 deg.C/min, sintering temperature 1850 deg.C, and maintaining for 10min to obtain ceramic with density of 3.31g cm -3 . Grinding the outer circle of the obtained silicon carbide ceramic grinding machine, processing into a wafer with the diameter of 20mm and the thickness of 2mm, uniformly coating normal-temperature conductive silver paste on two sides of the wafer to manufacture electrodes, and placing the electrodes in an oven to keep the temperature at 60 ℃ for 1h. And (3) placing the obtained silicon carbide ceramic wafer into a muffle furnace, heating the wafer from 20 ℃ to 300 ℃ at a heating rate of 5 ℃/min, and carrying out volt-ampere characteristic test on the wafer by using a Keithley2450 multichannel test system in the heating process, wherein the SiC ceramic has linear conductive characteristic, and the resistivity is relatively constant and fluctuates within a range of 26+/-6 ohm cm along with the rising of the temperature.
Example 3
Weighing 75g of SiC powder and Ti 3 AlC 2 25g of powder B 4 C powder 0.6g is put into a ball milling tank, 120ml of ethanol and 100g of SiC grinding balls are added, planetary ball milling is adopted, and the ball milling is carried out for 12 hours at the rotating speed of 300 r/min. The obtained slurry (solid content is 45 wt%) is put into a baking oven to be dried at 70 ℃, and the dried powder is sieved by a 100-mesh sieve. Loading the obtained powder into graphite mold, SPS sintering under vacuum atmosphere at 40MPa and 100 deg.C/min, sintering temperature 1850 deg.C, and maintaining for 10min to obtain ceramic with density of 3.27g cm -3 . Grinding the outer circle of the obtained silicon carbide ceramic grinding machine, processing into a wafer with the diameter of 20mm and the thickness of 2mm, uniformly coating normal-temperature conductive silver paste on two sides of the wafer to manufacture electrodes, and placing the electrodes in an oven to keep the temperature at 60 ℃ for 1h. Putting the obtained silicon carbide ceramic wafer into a muffle furnace, heating from 20 ℃ to 300 ℃ at a heating rate of 5 ℃/min, and using Keith in the heating processThe ley2450 multichannel test system tests the volt-ampere characteristic, and the SiC ceramic in the process shows excellent linear conductive characteristic, and the resistivity change value is small along with the temperature rise and fluctuates within the range of 12+/-8 ohm cm.
Comparative example 1
Weighing 100g of SiC powder and B 4 C powder 0.6g is put into a ball milling tank, 120ml of ethanol and 100g of SiC grinding balls are added, planetary ball milling is adopted, and the ball milling is carried out for 12 hours at the rotating speed of 300 r/min. The obtained slurry (solid content is 45 wt%) is put into a baking oven to be dried at 70 ℃, and the dried powder is sieved by a 100-mesh sieve. Loading the obtained powder into graphite mold, SPS sintering under vacuum atmosphere at 40MPa and 100 deg.C/min, sintering temperature 1850 deg.C, and maintaining for 10min to obtain ceramic with density of 2.0g cm -3 . Grinding the outer circle of the obtained silicon carbide ceramic grinding machine, processing into a wafer with the diameter of 20mm and the thickness of 2mm, uniformly coating normal-temperature conductive silver paste on two sides of the wafer to manufacture electrodes, and placing the electrodes in an oven to keep the temperature at 60 ℃ for 1h. Putting the obtained silicon carbide ceramic wafer into a muffle furnace, heating the wafer from 20 ℃ to 300 ℃ at a heating rate of 5 ℃/min, and carrying out volt-ampere characteristic test on the wafer by using a Keithley2450 multichannel test system in the heating process, wherein the SiC ceramic shows obvious NTC characteristics, the resistivity is rapidly reduced along with the rising of the temperature, and the resistivity is 6.3 multiplied by 10 6 Omega cm to 1.9X10 4 Omega cm, the range of variation exceeds two orders of magnitude. Heat sensitivity index β:3279K (20-100 ℃), 2781K (100-200 ℃) and 4921K (200-300 ℃).
Comparative example 2
Weighing 95g of SiC powder and Ti 3 AlC 2 5g of powder B 4 C powder 0.6g is put into a ball milling tank, 120ml of ethanol and 100g of SiC grinding balls are added, planetary ball milling is adopted, and the ball milling is carried out for 12 hours at the rotating speed of 300 r/min. The obtained slurry (solid content is 45 wt%) is put into a baking oven to be dried at 70 ℃, and the dried powder is sieved by a 100-mesh sieve. Loading the obtained powder into graphite mold, SPS sintering under vacuum atmosphere at 40MPa and 100 deg.C/min, sintering temperature 1850 deg.C, and maintaining for 10min to obtain ceramic with density of 2.26g cm -3 . Grinding the outer circle of the obtained silicon carbide ceramic grinding machine to obtain a wafer with the diameter of 20mm and the thickness of 2mmAnd then uniformly coating normal-temperature conductive silver adhesive on both sides of the wafer to manufacture electrodes, and placing the electrodes in an oven to keep the temperature at 60 ℃ for 1h. Putting the obtained silicon carbide ceramic wafer into a muffle furnace, heating the wafer from 20 ℃ to 300 ℃ at a heating rate of 5 ℃/min, and carrying out volt-ampere characteristic test on the wafer by using a Keithley2450 multichannel test system in the heating process, wherein the SiC ceramic shows NTC characteristics, the heat sensitivity index beta (50-150 ℃) is 1985K, the resistivity is reduced along with the increase of the temperature, and the resistivity is increased by 1.4x10 6 Omega cm to 6.8X10 4 Omega cm. Heat sensitivity index β:2049K (20-100 ℃), 1563K (100-200 ℃), 1803K (200-300 ℃).
Comparative example 3
88g of SiC powder and Ti are weighed 3 AlC 2 12g of powder B 4 C powder 0.6g is put into a ball milling tank, 120ml of ethanol and 100g of SiC grinding balls are added, planetary ball milling is adopted, and the ball milling is carried out for 12 hours at the rotating speed of 300 r/min. The obtained slurry (solid content is 45 wt%) is put into a baking oven to be dried at 70 ℃, and the dried powder is sieved by a 100-mesh sieve. Loading the obtained powder into graphite mold, SPS sintering under vacuum atmosphere at 40MPa and 100 deg.C/min, sintering temperature 1850 deg.C, and maintaining for 10min to obtain ceramic with density of 2.86g cm -3 . Grinding the outer circle of the obtained silicon carbide ceramic grinding machine, processing into a wafer with the diameter of 20mm and the thickness of 2mm, uniformly coating normal-temperature conductive silver paste on two sides of the wafer to manufacture electrodes, and placing the electrodes in an oven to keep the temperature at 60 ℃ for 1h. Putting the obtained silicon carbide ceramic wafer into a muffle furnace, heating from 20 ℃ to 300 ℃ at a heating rate of 5 ℃/min, and carrying out volt-ampere characteristic test on the silicon carbide ceramic wafer by using a Keithley2450 multichannel test system in the heating process, wherein the SiC ceramic shows NTC characteristics, the resistivity is reduced along with the increase of the temperature, and the resistivity is increased from 2.4x10 4 Omega cm to 2.7X10 3 Omega cm. Heat sensitivity index β:1064K (20-100 ℃), 1467K (100-200 ℃), 1570K (200-300 ℃).
Comparative example 4
The silicon carbide composite ceramic of this comparative example 4 was prepared by referring to example 2, except that: weighing 60g of SiC powder, 40g of TiC powder and B 4 0.6g of C powder is placed in a ball milling pot. The obtained silicon carbide ceramic wafer is put into a muffle furnace,the temperature is increased from 20 ℃ to 300 ℃ at a rate of 5 ℃/min, and during the temperature increasing process, the Keithley2450 multichannel test system is used for carrying out volt-ampere characteristic test, so that the SiC ceramic shows PTC characteristics, and the resistivity is increased from 11.87 Ω & cm to 16.06 Ω & cm along with the temperature increase.
Comparative example 5
The silicon carbide composite ceramic of this comparative example 5 was prepared by referring to example 2, with the only difference that: weighing 50g of SiC powder and 50g of Ti 3 AlC 2 50g of powder B 4 0.6g of C powder is placed in a ball milling pot. The obtained silicon carbide ceramic wafer is placed in a muffle furnace, the temperature is increased from 20 ℃ to 300 ℃, the temperature increasing rate is 5 ℃/min, and in the temperature increasing process, a Keithley2450 multichannel test system is used for carrying out volt-ampere characteristic test on the silicon carbide ceramic wafer, at the moment, the SiC ceramic shows PTC characteristics, and the resistivity is increased from 5.28 Ω & cm to 6.38 Ω & cm along with the temperature increase.
Claims (7)
1. A silicon carbide composite ceramic with constant temperature resistance is characterized in that the main components of the silicon carbide composite ceramic comprise SiC matrix material, tiC second phase uniformly dispersed at SiC crystal boundary, and sintering aid B 4 C, and Al element, wherein Al element is incorporated into SiC lattice in a solid solution state or is present in SiC matrix material in the form of alumina; the mass fraction of the SiC is 75-85 wt%, the mass fraction of the TiC is 9.2-15.8 wt% and the sintering aid B is calculated according to the mass fraction 4 The mass fraction of C is not more than 1wt%, and the content of the Al element is 1.3-3.5 wt%; the TiC second phase is composed of Ti 3 AlC 2 Decomposition occurs, the Ti is 3 AlC 2 The addition amount of (2) is 15-25 wt%; the silicon carbide complex phase ceramic fluctuates in resistivity within the range of 4-68Ω cm within the temperature variation range of 20-300 ℃;
the preparation method of the silicon carbide composite ceramic comprises the following steps:
SiC powder and Ti 3 AlC 2 The powder is used as raw material powder and is ball-milled and mixed to obtain slurry with the solid content of 45-50wt%;
drying and sieving the obtained slurry to obtain mixed powder;
carrying out spark plasma sintering on the obtained mixed powder to obtain the silicon carbide composite ceramic with constant temperature resistance characteristics;
the parameters of the spark plasma sintering include: under the vacuum condition, the temperature rising rate is 50-100 ℃/min, the sintering temperature is 1700-1900 ℃, the heat preservation time is 7-15 min, and the sintering pressure is 30-50 MPa.
2. The silicon carbide composite ceramic with constant temperature resistance according to claim 1, wherein the density of the silicon carbide composite ceramic is 3.13-3.31 g cm -3 The relative density is 94.3-98.4%.
3. The silicon carbide composite ceramic having a constant temperature resistance according to claim 1, wherein the mass fraction of the SiC powder in the raw material powder is 75 to 85wt%, based on the total mass of the raw material powder, of Ti 3 AlC 2 The mass fraction of the powder is 15-25 wt%.
4. The silicon carbide composite ceramic having a constant temperature resistance according to claim 3, wherein Ti in the raw material powder 3 AlC 2 The mass fraction of the powder is 20-25 wt%.
5. The silicon carbide composite ceramic with constant temperature resistance according to claim 1, wherein a sintering aid B is added into the raw material powder 4 C, performing operation; the sintering aid B 4 The mass of C is less than 1wt% of the total mass of the raw material powder.
6. The silicon carbide composite ceramic with constant temperature resistance according to claim 1, wherein the purity of the SiC powder is more than or equal to 99 percent, and the grain size is less than or equal to 0.5 μm; the Ti is 3 AlC 2 The purity of the powder is more than or equal to 99 percent, and the grain size is less than or equal to 10 mu m.
7. Use of a silicon carbide composite ceramic having constant temperature resistance properties according to any of claims 1-6 in a medium Wen Hengzu element, wherein said medium Wen Hengzu element is capable of being used at a temperature of 20-300 ℃ and has a resistivity that fluctuates in the range of 53±15, 26±6, 12±8 Ω -cm.
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