CN111665166B - Method for determining density of ceramic matrix composite substrate - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 71
- 239000011153 ceramic matrix composite Substances 0.000 title claims abstract description 53
- 239000000758 substrate Substances 0.000 title claims abstract description 25
- 239000000835 fiber Substances 0.000 claims abstract description 108
- 239000000843 powder Substances 0.000 claims abstract description 94
- 239000002131 composite material Substances 0.000 claims abstract description 92
- 239000000919 ceramic Substances 0.000 claims abstract description 73
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 64
- 239000011159 matrix material Substances 0.000 claims abstract description 51
- 238000000227 grinding Methods 0.000 claims abstract description 9
- 238000005259 measurement Methods 0.000 claims abstract description 9
- 239000000463 material Substances 0.000 claims description 26
- 230000005484 gravity Effects 0.000 claims description 21
- 238000005303 weighing Methods 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 9
- 239000012153 distilled water Substances 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 235000019441 ethanol Nutrition 0.000 claims description 6
- 238000011049 filling Methods 0.000 claims description 6
- 229920006395 saturated elastomer Polymers 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 2
- 238000002360 preparation method Methods 0.000 description 8
- 230000008595 infiltration Effects 0.000 description 4
- 238000001764 infiltration Methods 0.000 description 4
- 239000011204 carbon fibre-reinforced silicon carbide Substances 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001739 density measurement Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000002679 ablation Methods 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 239000002296 pyrolytic carbon Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/02—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by measuring weight of a known volume
- G01N9/04—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by measuring weight of a known volume of fluids
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Abstract
The invention discloses a method for determining the density of a ceramic matrix composite substrate, which comprises the following steps: step one, measuring and calculating the mass and the volume of the pycnometer; preparing a plurality of sections of ceramic-based fiber bundle composite materials, and measuring the total length and the total mass of the ceramic-based fiber bundle composite materials at the moment, wherein the ceramic-based fiber bundle composite materials are measurement samples prepared by adopting the same process as the ceramic-based composite materials to be detected; grinding the ceramic-based fiber bundle composite material into powder, pouring the powder into a pycnometer, and correcting and calculating to obtain the actual mass and length of the powder according to the mass of the pycnometer; adding absolute ethyl alcohol into the pycnometer, and measuring and calculating the volume of the ceramic-based fiber bundle composite powder in the pycnometer; step five, respectively calculating the volume and the mass of the fiber and the interface in the powder; and step six, calculating the mass and the volume of the matrix according to a mass conservation law, and finally obtaining the density of the matrix. The invention has the advantages of simplicity, easy application, high efficiency, accuracy and the like.
Description
Technical Field
The invention belongs to the field of materials, relates to a method for measuring component phase physical parameters of a composite material, and particularly relates to a method for determining the matrix density of a ceramic matrix composite material.
Background
The ceramic matrix composite material has the advantages of high temperature resistance, low density, high specific strength, high specific modulus, good oxidation resistance, ablation resistance and the like of the traditional ceramic material, and overcomes the defects of high brittleness and poor reliability of the traditional ceramic material by introducing the reinforcing phase. The density of the ceramic matrix composite material is only about one third of that of the high-temperature alloy material, and the material still has good mechanical property at high temperature. Therefore, the ceramic matrix composite material has wide application prospect in the field of aeroengines.
The volume fraction of the components of the ceramic matrix composite is an important basis for measuring the overall mechanical properties of the ceramic matrix composite. However, the microstructure of the ceramic matrix composite is complex, and it is difficult to directly obtain the volume fraction of the component phase. As the raw materials consumed in the preparation process of the ceramic matrix composite material can be determined, the mass and the mass fraction of the component phases in the material can be calculated, and then the volume fraction of the components can be obtained by the density of the component phases. Although this indirect method is feasible, it is often difficult to prepare pure matrix test blocks due to the particularity of the ceramic matrix composite preparation process, and the density data of the matrix is lacking. The ceramic matrix composite material has various main preparation processes, such as chemical vapor infiltration, chemical vapor deposition, precursor conversion, infiltration and the like, and the density of the matrix prepared by the processes is different, and the density of the matrix obtained by the same process with different parameters is also different.
Therefore, to avoid the error introduced by unreasonable density data of the matrix, it is necessary to provide a simple and easy-to-apply method suitable for different ceramic matrix composite material preparation processes for determining the density of the ceramic matrix composite material.
Disclosure of Invention
The invention provides a method for determining the density of a ceramic matrix composite substrate, which aims to overcome the defects of the prior art.
In order to achieve the above object, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which has the following characteristics: the method comprises the following steps: step one, measuring and calculating the mass and the volume of the pycnometer; preparing a plurality of sections of ceramic-based fiber bundle composite materials, and measuring the total length and the total mass of the ceramic-based fiber bundle composite materials at the moment, wherein the ceramic-based fiber bundle composite materials are measurement samples prepared by adopting the same process as the ceramic-based composite materials to be detected; grinding the ceramic-based fiber bundle composite material into powder, pouring the powder into a pycnometer, and correcting and calculating the actual mass and length of the ceramic-based fiber bundle composite material powder in the pycnometer according to the mass of the pycnometer; adding absolute ethyl alcohol into the pycnometer, and measuring and calculating the volume of the ceramic-based fiber bundle composite powder in the pycnometer; step five, respectively calculating the volume and the mass of the fiber and the interface in the powder; and step six, calculating the mass and the volume of the matrix according to a mass conservation law, and finally obtaining the density of the matrix.
Further, the invention provides a method for determining the density of a ceramic matrix composite substrate,it is also possible to have the feature: the specific method of the first step comprises the following steps: s1.1, washing and drying a pycnometer, wherein the pycnometer in the application refers to an integral appliance comprising a pycnometer body, a bottle plug and a thermometer; s1.2, weighing mass M of air-containing pycnometerBottle and airRecording the ambient temperature T at the time of weighingWeighing machineRelative humidity of
And atmospheric pressure PairObtaining the saturated vapor pressure P of water vapor in the measuring environment by looking up the tablebCalculating the density ρ of air at that timewet：
S1.3, using a graduated dropper to fill distilled water into the pycnometer and measuring and calculating the volume V of the pycnometerMeasuringThen calculating the mass M of the air in the pycnometerAir (a)＝ρwetVMeasuring(ii) a S1.4, calculating the mass M of the pycnometerSpecific gravity bottle＝MBottle and air-MAir (a)。
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: wherein, step one still includes the correction of the heavy bottle volume: s1.5, pouring out and drying distilled water in the pycnometer, then filling absolute ethyl alcohol, weighing the mass M of the absolute ethyl alcoholPycnometer and absolute ethyl alcoholThe temperature M of the absolute ethanol at this time was measuredPycnometer and absolute ethyl alcoholThe temperature T of the absolute ethyl alcohol at this time was measuredAnhydrous ethanolObtaining the density rho of the absolute ethyl alcohol at the temperature by a table look-up methodAnhydrous ethanol(ii) a S1.6, correcting the volume V of the pycnometercalThe correction method comprises the following steps:
finally obtaining the mass M of the pycnometerSpecific gravity bottleAnd volume Vcal. Then pouring out the absolute ethyl alcohol in the pycnometer and drying for later use.
Furthermore, the invention provides a method for determining the density of the ceramic matrix composite material matrixThe method may also have the following features: the third step is specifically as follows: s3.1, fully grinding the ceramic matrix fiber bundle composite into powder; s3.2, pouring the powder into a pycnometer and weighing the total mass M of the powderBottle for specific gravity, powder and air(ii) a S3.3, recording the ambient temperature T during the correctionCorrectionRelative humidity of
And atmospheric pressure Pair', then look-up the table to obtain the saturated vapor pressure P of the water vapor in the correction environmentb', calculating the density ρ of air at that timewet′：
Correcting to obtain the actual mass M of the ceramic-based fiber bundle composite powder in the pycnometerPractice ofAnd length LPractice ofThe correction method comprises the following steps:
Mpractice of＝MBottle for specific gravity, powder and air-MSpecific gravity bottle-Vcalρwet′；
In the formula, MSpecific gravity bottleAnd VcalThe weight of the pycnometer obtained in the step one and the volume, L, of the corrected pycnometerOriginalAnd MOriginalAnd D, measuring the total length and the total mass of the ceramic matrix fiber bundle composite materials in the plurality of sections in the second step.
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: wherein, in the fourth step, the pycnometer is filled with absolute ethyl alcohol and the absolute ethyl alcohol soaks the inside of the ceramic-based fiber bundle composite powder, and the mass M of the pycnometer containing the powder and the absolute ethyl alcohol is obtained by weighingPycnometer, powder and absolute ethyl alcoholRecording the actual test temperature TMixingLooking up the table to obtain the density rho of the absolute ethyl alcohol at the momentAnhydrous ethanol(ii) a Body for calculating ceramic-based fiber bundle composite material powder in pycnometerProduct VPowder of：
In the formula, MSpecific gravity bottleAnd VcalThe weight of the pycnometer obtained in the step one and the volume of the corrected pycnometer, MPractice ofAnd C, the actual mass of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: in the fourth step, the concrete method for filling absolute ethyl alcohol into the pycnometer and infiltrating the ceramic matrix fiber bundle composite powder comprises the following steps: adding sufficient absolute ethyl alcohol into the pycnometer until the ceramic matrix fiber bundle composite powder is completely submerged; connecting the pycnometer with a negative pressure generator, and discharging gas in the powder through the negative pressure generator to enable the anhydrous ethanol to infiltrate into the powder; then the pycnometer is filled with absolute ethyl alcohol.
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: wherein, in the fifth step, the mass M of the fiber in the powderfFiber volume VfInterface quality MiAnd the interfacial volume ViThe calculation method of (2) is as follows:
Mf＝Vfρf；
Mi＝Viρi；
in the formula, ρfIs the density of the fibres, dmfIs the diameter of the fiber filament, K is the number of the fiber filaments, tiIs an interfaceThickness, piIs the interface density, LPractice ofAnd C, the actual length of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: wherein, when the interface thickness and density parameters of the ceramic matrix composite material are unknown, the interface thickness t is calculated by the following methodiAnd interface density ρi: s5.1, preparing a composite material only with an interface and without a matrix by using the same fibers as the ceramic matrix fiber bundle composite material; s5.2, observing the cross section of the composite material prepared in the S5.1 under a scanning electron microscope, and measuring the thickness t of an interfacei(ii) a S5.3, taking a plurality of sections of the composite material prepared by the S5.1, and weighing the mass M of the composite materialf+iMeasuring its length Lf+i(ii) a S5.4, calculating the total mass M of the fibers in the composite material obtained in the S5.3f1And the total volume V of the interfacei1：
In the formula, ρfIs the density of the fibres, dmfIs the diameter of the fiber monofilament, K is the number of the fiber monofilament;
s5.5, calculating the interface density rhoi：
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: in the sixth step, the volume V of the matrix is calculated according to the conservation of massmAnd mass MmThe calculation method is as follows:
Vm＝Vpowder of-Vf-Vi；
Mm＝MPractice of-Mf-Mi；
In the formula, VPowder ofThe volume V of the ceramic-based fiber bundle composite material powder in the pycnometer obtained in the step fourf、Vi、MfAnd MiRespectively the fiber volume, the interface volume, the fiber mass and the interface mass, M, in the powder obtained in the step fivePractice ofAnd C, the actual mass of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
Further, the present invention provides a method for determining the density of a ceramic matrix composite substrate, which may further have the following characteristics: wherein, the matrix density rho of the ceramic matrix composite material is obtained by calculationm：
The invention has the beneficial effects that:
firstly, the method can realize the accurate measurement of the density of the ceramic matrix composite material in different processes, and avoid the error caused by the mixed use of the density data of the ceramic matrix composite material in different processes.
Secondly, the ceramic matrix fiber bundle composite prepared by the same process as the ceramic matrix composite of the detection object is used as the measurement sample, and the preparation method is simple, low in preparation cost and short in preparation period. More importantly, the ceramic matrix fiber bundle composite material can be prepared in the same furnace (same process) with any ceramic matrix composite material with a complex preform structure, so that accurate data of the matrix density of the complex preform ceramic matrix composite material can be obtained.
The method is simple and easy to implement, does not need complex process equipment, and has low measurement cost, high measurement efficiency and wide application range.
Drawings
FIG. 1 is a schematic view of a powder assisted infiltration and density measurement apparatus;
reference numerals: 1-pycnometer body, 2-thermometer, 3-ceramic-based fiber bundle composite material powder, 4-absolute ethyl alcohol, 5-negative pressure generator, 6-gas discharged from powder, 7-bottle stopper and 8-gas discharge path.
Detailed Description
The present invention is further illustrated by the following specific examples.
The embodiment provides a method for determining the density of a ceramic matrix composite substrate, wherein a detection object is the ceramic matrix composite material with the fiber of C and the substrate of SiC, and the method comprises the following steps:
step one, measuring and calculating the mass and the volume of the pycnometer. The specific method comprises the following steps:
s1.1, washing the pycnometer by using distilled water and absolute ethyl alcohol in sequence, and drying the pycnometer after washing. The pycnometer is an integral appliance comprising a pycnometer body, a bottle plug and a thermometer.
S1.2, weighing the mass M of the air-containing pycnometer using an analytical balanceBottle and air31.0698g, recording the ambient temperature T at the time of weighingWeighing machine288.15K relative humidity
And atmospheric pressure Pair102.0KPa, obtaining saturated vapor pressure P of water vapor in measuring environment by table look-upbAt 1.704KPa, the density ρ of air at that time was calculatedwet：
Calculating to obtain the density rho of the air at the momentwet＝1.2289×10-3g/cm3。
S1.3, using a graduated dropper to fill distilled water into the pycnometer and measuring and calculating the volume V of the pycnometerMeasuring＝27.00cm3Then calculating the mass M of the air in the pycnometerAir (a)＝ρwetVMeasuring＝3.3180×10-2g。
S1.4, calculating the mass M of the pycnometerSpecific gravity bottle＝MBottle and air-MAir (a)＝31.0366g。
S1.5, pouring out distilled water in the pycnometer, drying the distilled water, and then filling absolute ethyl alcohol. Weighing its mass M using an analytical balancePycnometer and absolute ethyl alcoholThe temperature T of absolute ethanol at this time was measured using a thermometer at 52.6255gAnhydrous ethanolDensity ρ of absolute ethanol at this temperature was obtained by a table lookup method as 289.15KAnhydrous ethanol＝0.7949g/cm3。
S1.6, correcting the volume V of the pycnometercalThe correction method comprises the following steps:
finally obtaining the mass M of the pycnometerSpecific gravity bottleAnd volume Vcal. Then pouring out the absolute ethyl alcohol in the pycnometer and drying for later use.
Step two, preparing a plurality of sections of ceramic-based fiber bundle composite materials, and measuring the total length L of the ceramic-based fiber bundle composite materials at the momentOriginal1437mm and total mass MOriginal＝2.9034g。
The ceramic-based fiber bundle composite material is a measurement sample prepared by adopting the same process as the ceramic-based composite material to be detected, even the same furnace. The two composite materials are prepared by the same process, so that the matrix densities of the two composite materials are the same, and the matrix density of the ceramic matrix fiber bundle composite material (measurement sample) determined by the method is the matrix density of the ceramic matrix composite material to be detected.
And step three, grinding the ceramic-based fiber bundle composite material into powder and pouring the powder into a pycnometer. Taking the loss of the ceramic matrix fiber bundle composite material in the grinding and transferring processes into consideration, and linearly correcting the actual quality and length of the material powder in the heavy bottle: and (4) correcting and calculating the actual mass and length of the ceramic-based fiber bundle composite powder in the pycnometer according to the mass of the pycnometer. The specific method comprises the following steps:
and S3.1, fully grinding the ceramic matrix fiber bundle composite into powder.
S3.2, mixingPouring the powder into a pycnometer and weighing the total mass MBottle for specific gravity, powder and air＝33.8689g。
And S3.3, considering the loss of the ceramic-based fiber bundle composite material in the grinding and transferring processes, and performing linear correction on the actual quality and length of the ceramic-based fiber bundle composite material powder in the heavy bottle. Record the ambient temperature T at this correctionCorrection288.15K relative humidity
And atmospheric pressure Pair' -102.3 KPa, and looking up the table to obtain the saturated vapor pressure P of water vapor in the correcting environmentb' 1.7062KPa, and the density ρ of the air at that time was calculatedwet′：
Calculating to obtain the density rho of the air at the momentwet′＝1.2310×10-3g/cm3，
Correcting to obtain the actual mass M of the ceramic-based fiber bundle composite powder in the pycnometerPractice ofAnd length LPractice ofThe correction method comprises the following steps:
Mpractice of＝MBottle for specific gravity, powder and air-MSpecific gravity bottle-Vcalρwet′；
In the formula, MSpecific gravity bottleAnd VcalThe weight of the pycnometer obtained in the step one and the volume, L, of the corrected pycnometerOriginalAnd MOriginalAnd D, measuring the total length and the total mass of the ceramic matrix fiber bundle composite materials in the plurality of sections in the second step. Calculating to obtain the actual mass M of the ceramic-based fiber bundle composite powder in the pycnometerPractice of2.7989g and length LPractice of＝1385.28mm。
And step four, adding absolute ethyl alcohol into the pycnometer, and measuring and calculating the volume of the ceramic matrix fiber bundle composite powder in the pycnometer. The specific method comprises the following steps:
adding enough absolute ethyl alcohol into the pycnometer until the ceramic matrix fiber bundle composite powder is completely submerged. As shown in fig. 1, a powder-assisted infiltration and density measurement apparatus was used to connect a pycnometer 1 to a negative pressure generator 5, and gas 6 inside the powder 3 was discharged by the negative pressure generated by the negative pressure generator 5, so that the powder 3 was infiltrated with absolute ethanol 4. Then opening the pycnometer, filling absolute ethyl alcohol into the pycnometer body, then inserting the thermometer and the bottle plug, wiping the bottle body, and standing until the temperature indication number is not changed.
At this time, the pycnometer is filled with absolute ethyl alcohol, and the absolute ethyl alcohol infiltrates the inside of the ceramic matrix fiber bundle composite powder. Putting the pycnometer filled with the ceramic-based fiber bundle composite material powder and the absolute ethyl alcohol into an analytical balance for weighing to obtain the mass M of the pycnometer containing the powder and the absolute ethyl alcoholPycnometer, powder and absolute ethyl alcoholRecord the actual test temperature T as 54.4180gMixingWhen the density ρ of the absolute ethanol is found by looking up the table at 289.15KAnhydrous ethanol＝0.7949g/cm3。
Calculating the volume V of the ceramic-based fiber bundle composite powder in the pycnometerPowder of：
In the formula, MSpecific gravity bottleAnd VcalThe weight of the pycnometer obtained in the step one and the volume of the corrected pycnometer, MPractice ofAnd C, the actual mass of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained. Calculating to obtain the volume V of the ceramic-based fiber bundle composite material powder in the pycnometerPowder of＝1.2647cm3。
And step five, respectively calculating the volume and the mass of the fiber and the interface in the powder. Mass of fibres in powder MfFiber volume VfInterface quality MiAnd the interfacial volume ViThe calculation method of (2) is as follows:
Mf＝Vfρf；
Mi＝Viρi；
in the formula, ρfIs the density of the fibres, dmfIs the diameter of the fiber filament, K is the number of the fiber filaments, tiIs the interface thickness, piIs the interface density, LPractice ofAnd C, the actual length of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
The fibers in the ceramic matrix fiber bundle composite material used in the embodiment are Dongli T700-12K fiber bundles, and the density rho of the fibersf＝1.80g·cm-3Diameter d of the filament of the fiber mf7 μm, number of filaments K12000, pyrolytic carbon at the interface, and thickness ti0.551 μm, density ρi＝1.50g·cm-3. Calculating to obtain the mass M of the fibers in the powderf1.1509g, fiber volume Vf＝0.6394cm3Interface quality Mi0.3259g and interfacial volume Vi＝0.2173cm3。
Because the thickness and density of the interface in the ceramic matrix composite material have great relationship with the preparation process thereof, when the interface thickness and density parameters of the ceramic matrix composite material are unknown, the interface thickness t is calculated by the following methodiAnd interface density ρi：
S5.1, preparing a composite material only with an interface and no matrix by using the same fibers as the ceramic matrix fiber bundle composite material.
S5.2, observing the cross section of the composite material prepared in the S5.1 under a scanning electron microscope, and measuring the thickness t of an interfacei。
S5.3, taking several sections S5.1 instituteThe composite material thus prepared was weighed to obtain a mass Mf+iMeasuring its length Lf+i。
S5.4, calculating the total mass M of the fibers in the composite material obtained in the S5.3f1And the total volume V of the interfacei1：
In the formula, ρfIs the density of the fibres, dmfIs the diameter of the fiber filament, K is the number of fiber filaments.
S5.5, calculating the interface density rhoi：
And step six, calculating the mass and the volume of the matrix according to a mass conservation law, and finally obtaining the density of the matrix.
First, the volume of the matrix VmAnd mass MmThe calculation method of (2) is as follows:
Vm＝Vpowder of-Vf-Vi；
Mm＝MPractice of-Mf-Mi；
In the formula, VPowder ofThe volume V of the ceramic-based fiber bundle composite material powder in the pycnometer obtained in the step fourf、Vi、MfAnd MiRespectively the fiber volume, the interface volume, the fiber mass and the interface mass, M, in the powder obtained in the step fivePractice ofAnd C, the actual mass of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained. Calculating to obtain Vm＝0.4080cm-3And mass Mm＝1.3220g。
Then, the ceramic matrix composite is obtained by calculationMatrix density of material ρm：
Finally, the density rho of the matrix is obtained through calculationm＝3.24g·cm-3。
The density of the matrix of the ceramic matrix composite determined by the method falls within the density range of the matrix disclosed in 'the relation between the porosity and the performance of the 3D C/SiC composite (Yan symphony, Zhouwu, Song Maili, et al.3 3D C/SiC composite [ J ] carbon technology, 1999(S1):11-13 >)', and the matrix density of the ceramic matrix composite can be accurately determined by the surface method.
Claims (10)
1. A method for determining the density of a ceramic matrix composite substrate is characterized in that:
the method comprises the following steps:
step one, measuring and calculating the mass and the volume of the pycnometer;
preparing a plurality of sections of ceramic-based fiber bundle composite materials, and measuring the total length and the total mass of the ceramic-based fiber bundle composite materials at the moment, wherein the ceramic-based fiber bundle composite materials are measurement samples prepared by adopting the same process as the ceramic-based composite materials to be detected;
grinding the ceramic-based fiber bundle composite material into powder, pouring the powder into a pycnometer, and correcting and calculating the actual mass and length of the ceramic-based fiber bundle composite material powder in the pycnometer according to the mass of the pycnometer;
adding absolute ethyl alcohol into the pycnometer, and measuring and calculating the volume of the ceramic-based fiber bundle composite powder in the pycnometer;
step five, respectively calculating the volume and the mass of the fiber and the interface in the powder;
and step six, calculating the mass and the volume of the matrix according to a mass conservation law, and finally obtaining the density of the matrix.
2. The method for determining the density of a ceramic matrix composite substrate according to claim 1, wherein:
the specific method of the first step comprises the following steps:
s1.1, washing and drying a pycnometer;
s1.2, weighing mass M of air-containing pycnometerBottle and airRecording the ambient temperature T at the time of weighingWeighing machineRelative humidity of
And atmospheric pressure PairObtaining the saturated vapor pressure P of water vapor in the measuring environment by looking up the tablebCalculating the density ρ of air at that timewet：
S1.3, using a graduated dropper to fill distilled water into the pycnometer and measuring and calculating the volume V of the pycnometerMeasuringThen calculating the mass M of the air in the pycnometerAir (a)＝ρwetVMeasuring；
S1.4, calculating the mass M of the pycnometerSpecific gravity bottle＝MBottle and air-MAir (a)。
3. The method for determining the density of a ceramic matrix composite substrate according to claim 2, wherein:
wherein, step one still includes the correction of the heavy bottle volume:
s1.5, pouring out and drying distilled water in the pycnometer, then filling absolute ethyl alcohol, weighing the mass M of the absolute ethyl alcoholPycnometer and absolute ethyl alcoholAt this time, the temperature ρ of the absolute ethanol was measuredAnhydrous ethanolObtaining the density rho of the absolute ethyl alcohol at the temperature by a table look-up methodAnhydrous ethanol；
S1.6, correcting the volume V of the pycnometercalThe correction method comprises the following steps:
finally obtaining the mass M of the pycnometerSpecific gravity bottleAnd volume Vcal。
4. The method for determining the density of a ceramic matrix composite substrate according to claim 3, wherein:
the third step is specifically as follows:
s3.1, fully grinding the ceramic matrix fiber bundle composite into powder;
s3.2, pouring the powder into a pycnometer and weighing the total mass M of the powderBottle for specific gravity, powder and air；
S3.3, recording the ambient temperature T during the correctionCorrectionRelative humidity of
And atmospheric pressure Pair', then look-up the table to obtain the saturated vapor pressure P of the water vapor in the correction environmentb', calculating the density ρ of air at that timewet′：
Correcting to obtain the actual mass M of the ceramic-based fiber bundle composite powder in the pycnometerPractice ofAnd length LPractice ofThe correction method comprises the following steps:
Mpractice of＝MBottle for specific gravity, powder and air-MSpecific gravity bottle-Vcalρwet′；
In the formula, MSpecific gravity bottleAnd VcalThe weight of the pycnometer obtained in the step one and the volume, L, of the corrected pycnometerOriginalAnd MOriginalIs the step ofAnd measuring the total length and the total mass of the ceramic matrix fiber bundle composite materials.
5. The method for determining the density of a ceramic matrix composite substrate according to claim 3, wherein:
wherein, in the fourth step, the pycnometer is filled with absolute ethyl alcohol and the absolute ethyl alcohol soaks the inside of the ceramic-based fiber bundle composite powder, and the mass M of the pycnometer containing the powder and the absolute ethyl alcohol is obtained by weighingPycnometer, powder and absolute ethyl alcoholRecording the actual test temperature TMixingLooking up the table to obtain the density rho of the absolute ethyl alcohol at the momentAnhydrous ethanol；
Calculating the volume V of the ceramic-based fiber bundle composite powder in the pycnometerPowder of：
In the formula, MSpecific gravity bottleAnd VcalThe weight of the pycnometer obtained in the step one and the volume of the corrected pycnometer, MPractice ofAnd C, the actual mass of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
6. The method for determining the density of a ceramic matrix composite substrate according to claim 5, wherein:
in the fourth step, the concrete method for filling absolute ethyl alcohol into the pycnometer and infiltrating the ceramic matrix fiber bundle composite powder comprises the following steps:
adding sufficient absolute ethyl alcohol into the pycnometer until the ceramic matrix fiber bundle composite powder is completely submerged;
connecting the pycnometer with a negative pressure generator, and discharging gas in the powder through the negative pressure generator to enable the anhydrous ethanol to infiltrate into the powder;
then the pycnometer is filled with absolute ethyl alcohol.
7. The method for determining the density of a ceramic matrix composite substrate according to claim 1, wherein:
wherein, in the fifth step, the mass M of the fiber in the powderfFiber volume VfInterface quality MiAnd the interfacial volume ViThe calculation method of (2) is as follows:
Mf＝Vfρf；
Mi＝Viρi；
in the formula, ρfIs the density of the fibres, dmfIs the diameter of the fiber filament, K is the number of the fiber filaments, tiIs the interface thickness, piIs the interface density, LPractice ofAnd C, the actual length of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
8. The method for determining the density of a ceramic matrix composite substrate according to claim 7, wherein:
wherein, when the interface thickness and density parameters of the ceramic matrix composite material are unknown, the interface thickness t is calculated by the following methodiAnd interface density ρi：
S5.1, preparing a composite material only with an interface and without a matrix by using the same fibers as the ceramic matrix fiber bundle composite material;
s5.2, observing the cross section of the composite material prepared in the S5.1 under a scanning electron microscope, and measuring the thickness t of an interfacei；
S5.3, taking a plurality of sections of the composite material prepared by the S5.1, and weighing the mass M of the composite materialf+iMeasuring its length Lf+i；
S5.4, calculating the total fiber in the composite material obtained in S5.3Mass Mf1And the total volume V of the interfacei1：
In the formula, ρfIs the density of the fibres, dmfIs the diameter of the fiber monofilament, K is the number of the fiber monofilament;
s5.5, calculating the interface density rhoi：
9. The method for determining the density of a ceramic matrix composite substrate according to claim 1, wherein:
in the sixth step, the volume V of the matrix is calculated according to the conservation of massmAnd mass MmThe calculation method is as follows:
Vm＝Vpowder of-Vf-Vi；
Mm＝MPractice of-Mf-Mi；
In the formula, VPowder ofThe volume V of the ceramic-based fiber bundle composite material powder in the pycnometer obtained in the step fourf、Vi、MfAnd MiRespectively the fiber volume, the interface volume, the fiber mass and the interface mass, M, in the powder obtained in the step fivePractice ofAnd C, the actual mass of the ceramic-based fiber bundle composite powder in the pycnometer obtained in the step three is obtained.
10. The method for determining the density of a ceramic matrix composite substrate according to claim 9, wherein:
wherein, the matrix density rho of the ceramic matrix composite material is obtained by calculationm：
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| CN104458495A (en) * | 2014-11-28 | 2015-03-25 | 中国科学院金属研究所 | Method for measuring particle volume fraction of reinforced body in particle-reinforced metal-based composite material |
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| CN103558119A (en) * | 2013-10-15 | 2014-02-05 | 北京星航机电装备有限公司 | Method for detecting density of continuous fiber ceramic-based composite material |
| CN103630463A (en) * | 2013-11-29 | 2014-03-12 | 成都成工工程机械井研铸造有限责任公司 | Detection method for degree of graphitization of cast iron |
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