CN112924540B - Device and method for detecting uniformity of ceramic slurry based on ultrasonic waves - Google Patents

Device and method for detecting uniformity of ceramic slurry based on ultrasonic waves Download PDF

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CN112924540B
CN112924540B CN202110087726.3A CN202110087726A CN112924540B CN 112924540 B CN112924540 B CN 112924540B CN 202110087726 A CN202110087726 A CN 202110087726A CN 112924540 B CN112924540 B CN 112924540B
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CN112924540A (en
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张乐
陈俊羽
任海东
姚庆
曹秀华
李延彬
邵岑
康健
周伟
周天元
付振晓
陈浩
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    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
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Abstract

The invention discloses a device and a method for detecting the uniformity of ceramic slurry based on ultrasonic waves, which comprises a ceramic slurry volume container, three groups of ultrasonic transducers A1/A2, B1/B2 and C1/C2 and a hardware circuit, wherein the three groups of ultrasonic transducers are connected with the hardware circuit; probes of the ultrasonic transducers A1, B1 and C1 are respectively attached to the upper, middle and lower positions on the left side of the ceramic slurry volume container, and probes of the ultrasonic transducers A2, B2 and C2 are respectively attached to the right side of the ceramic slurry volume container and are respectively opposite to the positions of the ultrasonic transducers A1, B1 and C1. According to the invention, by utilizing the characteristic that the propagation speed of ultrasonic waves is influenced by the density of a medium when the ultrasonic waves propagate in the medium, the density of the ceramic slurry to be measured among three groups of ultrasonic transducers is calculated according to an impedance method, and the state of the ceramic slurry to be measured is obtained according to a relation method of the density ratio of the ceramic slurry to be measured at the upper position, the middle position and the lower position of a ceramic slurry volume container.

Description

Device and method for detecting uniformity of ceramic slurry based on ultrasonic waves
Technical Field
The invention relates to a device and a method for detecting the uniformity of ceramic slurry, in particular to a device and a method for detecting the uniformity of ceramic slurry based on ultrasonic waves, and belongs to the technical field of detection.
Background
Chip multilayer ceramic capacitors (MLCC) are one of the most widely used passive electronic components in the modern electronics industry. The data shows that MLCC global market size was about $ 105 billion in 2018, and by 2021 market size would exceed $ 120 billion, annual compound growth rate would reach 5%. As the largest consumer electronics manufacturing country in the world, the market scale of MLCC in 2018 reaches about 520 hundred million RMB, the MLCC in 2021 is estimated to reach 630 hundred million RMB, the annual composite growth rate reaches 7 percent and is far higher than the global average level. Therefore, the intensive development of the MLCC meets the strategic development requirement of China, and has great significance.
For the MLCC device, especially under the market environment where the information product is taught to be light, thin and small, and the application of the surface mount technology is increasingly popular, the technical competition direction is mainly focused on miniaturization, higher capacity of storing electricity, higher breakdown voltage and insulation resistance, etc. However, no matter which direction breaks through, the realization of the miniaturization of the MLCC device is the fulcrum of gaining competition and survival, and the core of the realization lies in the thin-layer design of the ceramic layer component in the MLCC device, and the practical and feasible industrialized approach of the thin-layer design of the ceramic can be realized, and only the casting molding is adopted. That is, the tape casting technique is an important technical support of the MLCC device.
In the flow of casting forming process, the control of the ceramic slurry performance is the most important, because the slurry performance determines the uniformity and microstructure of the casting biscuit, and further determines the quality of the electronic ceramic product, and the key index of the slurry performance evaluation is the uniformity. As is well known, ceramic slurries are composed primarily of solvent and powder particles, but the knowledge of slurry homogeneity focuses essentially only on the "micro-homogeneity" aspect, i.e., the agglomeration of powder particles. However, can the powder agglomeration of the slurry truly sufficiently reflect the uniformity of the slurry? The answer is one-sided, as the evaluation of the homogeneity of the slurry should be reflected more on its "macro-homogeneity" level.
As shown in fig. 2, in the initial stage, the powder particles of the slurry after ball milling and mixing are uniformly dispersed in the solvent, and the slurry is uniform. However, as time goes on, particles of the slurry settle down during aging, and the different powder particles inevitably have different settling rates due to the difference of parameters such as mass, volume, specific surface area and agglomeration degree, and finally the powder particles are not uniformly distributed in the solvent along the height direction, so that the slurry loses uniformity. It can be seen that the uniformity of the ceramic slurry is completely equivalent to the distribution of the density gradient of the powder in the solvent in the high direction, i.e. the macroscopic level uniformity of the slurry in the longitudinal dimension.
The slurry with poor uniformity inevitably causes density difference on different positions of the biscuit after casting, which not only causes inconsistent shrinkage in all directions during drying, leads the biscuit to deform and even crack, but also causes sintering shrinkage difference of the biscuit, causes uneven density distribution of sintered ceramics, and damages the performance of devices. At present, only by realizing the essential improvement of the good product rate of the MLCC device, the MLCC manufacturing industry can stand unabated in the fierce market competition, and the adoption of the casting slurry with good uniformity is a necessary premise for improving the good product rate of the MLCC device.
Currently, there are methods for studying the homogeneity of ceramic slurry, such as sedimentation observation, zeta potential, rheological measurement, multiple light scattering, gamma ray measurement, etc., and although these methods can obtain the homogeneity information of ceramic slurry to some extent, they all have a common problem in that they are difficult to obtain a numerical expression of the homogeneity of slurry as a whole while ensuring accurate measurement accuracy and satisfying time efficiency, and are expensive. Therefore, it is imperative to realize simple, accurate, rapid and comprehensive assessment of the uniformity of the ceramic slurry.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the device and the method for detecting the uniformity of the ceramic slurry based on the ultrasonic wave, which can realize the accurate measurement of the density of the ceramic slurry, simultaneously realize the one-time measurement of the density of the slurry at different heights, have high detection accuracy and high speed, and can meet the actual requirements of the development of the MLCC industry.
In order to achieve the purpose, the device for detecting the uniformity of the ceramic slurry based on the ultrasonic wave comprises a ceramic slurry volume container, three groups of ultrasonic transducers and a hardware circuit; the three groups of ultrasonic transducers are respectively an ultrasonic transducer A1/A2, a ultrasonic transducer B1/B2 and an ultrasonic transducer C1/C2, probes of the ultrasonic transducers A1, B1 and C1 are respectively and tightly attached to the upper, middle and lower positions on the left side of the ceramic slurry volume container, and probes of the ultrasonic transducers A2, B2 and C2 are tightly attached to the right side of the ceramic slurry volume container and are respectively opposite to the ultrasonic transducers A1, B1 and C1; the hardware circuit comprises an ARM processor, a field programmable gate array FPGA, a D/A converter, a driving circuit, a transmitting circuit of the ultrasonic transducer, a receiving circuit of the ultrasonic transducer, a signal amplifying circuit, a signal filtering circuit and an A/D converter;
the output end of the ARM processor is connected with the input end of the field programmable gate array FPGA, the output end of the field programmable gate array FPGA is connected with the input end of the D/A converter, the output end of the D/A converter is connected with the input end of a transmitting circuit of the ultrasonic transducer through a driving circuit, the ultrasonic transducers A1, B1 and C1 are connected with the transmitting circuit of the ultrasonic transducer, the ultrasonic transducers A2, B2 and C2 are connected with a receiving circuit of the transducer, and the output end of the receiving circuit is connected with the input end of the field programmable gate array FPGA through an amplifying circuit, a filter circuit and an A/D converter in sequence.
Preferably, the ultrasonic transducer is a piezoelectric ceramic transducer, the frequency of the piezoelectric ceramic transducer is 200kHz, and the direction angle of the ultrasonic transducer is 4 degrees.
Preferably, the ARM processor is also connected with a keyboard, an LCD screen and an RS485 bus.
A method for detecting the uniformity of ceramic slurry based on ultrasonic waves comprises the following steps:
1) Coating an ultrasonic coupling agent on the contact surface of the ultrasonic transducer probe and the ceramic slurry volume container, and putting the ceramic slurry to be detected into the ceramic slurry volume container;
2) The ARM processor controls the field programmable gate array FPGA to output sine wave driving signals, and the signals convert digital signals into analog signals through a D/A converter; then sequentially passing through the driving circuit and the transmitting circuit, amplifying the power of the ultrasonic transducer, enabling the driving signal to reach the ultrasonic transducers A1, B1 and C1 on the left side, and enabling the ultrasonic transducers A1, B1 and C1 to convert the input signal into mechanical vibration to generate ultrasonic waves;
3) Ultrasonic waves generated by the ultrasonic transducers A1, B1 and C1 penetrate through the ceramic slurry to be detected in the ceramic slurry volume container, and then ultrasonic signals sent by the ultrasonic transducers A1, B1 and C1 on the left side are respectively received by the ultrasonic transducers A2, B2 and C2 on the right side of the ceramic slurry volume container and are converted into ultrasonic echo signals;
4) The receiving circuit transmits the ultrasonic echo signal to an amplifying circuit, the amplifying circuit 13 amplifies the ultrasonic echo signal, the filtering circuit 14 filters the ultrasonic echo signal, the A/D conversion circuit samples the ultrasonic echo signal, and the sampled data is stored in a field programmable gate array FPGA;
5) After sampling is finished, the ARM processor determines the moment corresponding to the starting point of the propagation time of the ultrasonic wave according to the data of the ultrasonic wave transmitted by the field programmable gate array FPGA; the ARM processor obtains the amplitude of an echo signal according to the sampling data of an A/D conversion circuit which reads the ultrasonic echo signal from the FPGA, obtains the time corresponding to the ultrasonic propagation time end point, determines the transmission time of the ultrasonic wave in the ceramic slurry to be detected between each group of ultrasonic transducers, and obtains the propagation speed v of the ultrasonic wave according to the relation between the distance and the time:
Figure GDA0003996198410000031
in the formula, s is the propagation distance of the ultrasonic wave, and t is the propagation time of the ultrasonic wave;
6) The ARM processor can precisely calculate the density rho of the ceramic slurry to be measured between the three groups of ultrasonic transducers according to an impedance method, displays the density rho on an LCD screen of the ARM processor, and adopts a ratio relation method of the density of the ceramic slurry to be measured at the positions of the upper part, the middle part and the lower part of the ceramic slurry volume container according to the density of the ceramic slurry to be measuredObtaining the state of the ceramic slurry to be measured, and setting the density of the ceramic slurry at the upper, middle and lower positions as rho a, rho b and rho c respectively, when the density is equal to the density of the ceramic slurry at the upper, middle and lower positions, obtaining the density of the ceramic slurry at the lower position
Figure GDA0003996198410000041
And is provided with
Figure GDA0003996198410000042
When the ceramic slurry to be measured is in a uniform state.
Preferably, the impedance method comprises the steps of:
1) Let the amplitude of the ultrasonic signal source emitted by the ultrasonic transducers A1, B1, C1 be P1, and the amplitude of the ultrasonic echo signal received by the ultrasonic transducers A2, B2, C2 be P2, and make:
Figure GDA0003996198410000043
in the formula, Z1 is the acoustic impedance of the known ultrasonic transducers A1, B1 and C1, and Z2 is the acoustic impedance of the unknown ceramic slurry to be measured received by the ultrasonic transducers A2, B2 and C2;
meanwhile, the sound attenuation of the ultrasonic wave in the propagation of the ceramic slurry to be measured is set to be alpha, so that,
Figure GDA0003996198410000044
Figure GDA0003996198410000045
2) Dividing the amplitude P2 of ultrasonic echo signals received by the ultrasonic transducers A2, B2 and C2 into Pr and Px, dividing the unknown acoustic impedance Z2 of the ceramic slurry to be detected into Zr and Zx, and substituting the Zr and Zx into a formula (3) to obtain the ultrasonic wave-splitting ultrasonic wave-absorbing ceramic paste
Figure GDA0003996198410000046
3) Substituting equation Zx = Zr + δ ZPx = Pr + δ P into equation (4) to obtain
Figure GDA0003996198410000047
Neglecting δ Z 2 And δ Z δ P to obtain
Figure GDA0003996198410000048
4) It can be known from the formula (6) that the unknown acoustic impedance of the ceramic slurry to be measured is in direct proportion to the change of the measured amplitude, and because Zx = Zr + δ Z and Zx = ρ v, the density of the ceramic slurry to be measured between the three groups of upper, middle and lower ultrasonic transducers, that is, the density values of the ceramic slurry to be measured at the upper, middle and lower positions in the ceramic slurry volume container:
Figure GDA0003996198410000051
wherein, the first and the second end of the pipe are connected with each other,
Figure GDA0003996198410000052
s is the propagation speed of the ultrasonic wave, s is the propagation distance of the ultrasonic wave, and t is the propagation time of the ultrasonic wave.
Compared with the prior art, the method utilizes the characteristic that the propagation speed of ultrasonic waves is influenced by the density of the medium when the ultrasonic waves propagate in the medium, realizes the accurate measurement of the density of the ceramic slurry, and simultaneously realizes the one-time measurement of the density of the slurry at different heights. The invention ensures high measurement precision, ensures test timeliness, overcomes the defects of the traditional ceramic slurry detection method, realizes simple, accurate and rapid detection of the uniformity of the ceramic slurry, and meets the actual requirements of MLCC industrial development.
Drawings
FIG. 1 is a schematic view of the overall structure of the device for detecting the uniformity of ceramic slurry based on ultrasonic waves according to the present invention;
FIG. 2 is a schematic diagram of the uniformity of a ceramic slurry to be measured as a function of time;
fig. 3 is a top view of the ultrasonic transducer transmission and reception.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in FIG. 1, the device for detecting the uniformity of ceramic slurry based on ultrasonic waves comprises a ceramic slurry volume container, three groups of ultrasonic transducers and a hardware circuit; the three groups of ultrasonic transducers are respectively ultrasonic transducers A1 and A2, ultrasonic transducers B1 and B2 and ultrasonic transducers C1 and C2, probes of the ultrasonic transducers A1, B1 and C1 are respectively clung to the upper, middle and lower positions on the left side of the ceramic slurry volume container, and probes of the ultrasonic transducers A2, B2 and C2 are clung to the right side of the ceramic slurry volume container and are respectively opposite to the positions of the ultrasonic transducers A1, B1 and C1; the hardware circuit comprises an ARM processor, a field programmable gate array FPGA, a D/A converter, a driving circuit, a transmitting circuit of the ultrasonic transducer, a receiving circuit of the ultrasonic transducer, a signal amplifying circuit, a signal filtering circuit and an A/D converter;
the output end of the ARM processor is connected with the input end of the field programmable gate array FPGA, the output end of the field programmable gate array FPGA is connected with the input end of the D/A converter, the output end of the D/A converter is connected with the input end of a transmitting circuit of the ultrasonic transducer through a driving circuit, the ultrasonic transducers A1, B1 and C1 are connected with the transmitting circuit of the ultrasonic transducer, the ultrasonic transducers A2, B2 and C2 are connected with a receiving circuit of the ultrasonic transducer, and the output end of the receiving circuit is connected with the input end of the field programmable gate array FPGA through an amplifying circuit, a filter circuit and an A/D converter in sequence.
The ARM processor is also connected with a keyboard, an LCD screen and an RS485 bus; the FPGA comprises a high-speed data acquisition function, a channel switching logic control function and a sine signal generator.
In order to enable the sound energy density of the ultrasonic transducer to meet the requirement, the ultrasonic transducer is a piezoelectric ceramic transducer, the frequency of the piezoelectric ceramic transducer is 200kHz, the direction angle of the transducer is 4 degrees, the wave number is concentrated, and the sound energy density meets the requirement.
The invention discloses a method for detecting the uniformity of ceramic slurry based on ultrasonic waves, which comprises the following steps:
1) Selecting representative upper, middle and lower positions in a ceramic slurry volume container, respectively and tightly attaching ultrasonic probes to two sides of the upper, middle and lower positions, coating an ultrasonic coupling agent on the contact surface of the ultrasonic transducer probe and the ceramic slurry volume container, and putting the ceramic slurry to be detected into the ceramic slurry volume container;
the ceramic slurry to be tested is composed of ceramic powder, a solvent, a binder, a plasticizer, a dispersant and the like, is an organic substance with general cementing property, and can form a thick and plastic paste-like substance when dissolved or expanded in water or an organic solvent;
2) The ARM processor controls the field programmable gate array FPGA to output sine wave driving signals, and the signals are converted into analog signals through a D/A converter; then sequentially passing through the driving circuit and the transmitting circuit, amplifying the power of the ultrasonic transducer, enabling the driving signal to reach the ultrasonic transducers A1, B1 and C1 on the left side, and enabling the ultrasonic transducers A1, B1 and C1 to convert the input signal into mechanical vibration to generate ultrasonic waves;
3) Ultrasonic waves generated by the ultrasonic transducers A1, B1 and C1 penetrate through ceramic slurry to be detected in the ceramic slurry volume container, and then ultrasonic transducers A2, B2 and C2 on the right side of the ceramic slurry volume container respectively receive ultrasonic signals sent by the ultrasonic transducers A1, B1 and C1 on the left side and convert the ultrasonic signals into ultrasonic echo signals;
4) The receiving circuit transmits the ultrasonic echo signal to the amplifying circuit, the amplifying circuit amplifies the ultrasonic echo signal, the filtering circuit filters the ultrasonic echo signal, the A/D conversion circuit samples the ultrasonic echo signal, and the sampled data is stored in the FPGA;
5) After sampling is finished, the ARM processor determines the moment corresponding to the starting point of the propagation time of the ultrasonic wave according to the data of the ultrasonic wave transmitted by the field programmable gate array FPGA; the ARM processor obtains the amplitude of an echo signal according to the sampling data of an A/D conversion circuit which reads the ultrasonic echo signal from the FPGA, obtains the moment corresponding to the ultrasonic propagation time end point, determines the transmission time of the ultrasonic wave in the ceramic slurry to be detected between each group of ultrasonic transducers, and obtains the propagation speed v of the ultrasonic wave according to the relation between the distance and the time:
Figure GDA0003996198410000071
in the formula, s is the propagation distance of the ultrasonic wave, and t is the propagation time of the ultrasonic wave;
6) The ARM processor can precisely calculate the density rho of the ceramic slurry to be measured between the three groups of ultrasonic transducers according to an impedance method, the density rho is displayed on an LCD screen of the ARM processor, the state of the ceramic slurry to be measured is obtained according to a ratio relation method of the density of the ceramic slurry to be measured at the upper position, the middle position and the lower position of a ceramic slurry volume container, the density of the ceramic slurry at the upper position, the middle position and the lower position is respectively rho a, rho b and rho c, and when the density of the ceramic slurry at the upper position, the middle position and the lower position is respectively set as rho a, rho b and rho c, the ARM processor can precisely calculate the density rho of the ceramic slurry to be measured between the three groups of ultrasonic transducers according to the impedance method, and can obtain the state of the ceramic slurry to be measured
Figure GDA0003996198410000072
And is provided with
Figure GDA0003996198410000073
When the ceramic slurry to be measured is in a uniform state.
The impedance method comprises the following specific steps:
1) As shown in fig. 3, assuming that the amplitude of the ultrasonic signal source emitted by the ultrasonic transducers A1, B1, and C1 is P1, and the amplitude of the ultrasonic echo signal received by the ultrasonic transducers A2, B2, and C2 is P2, the following steps are performed:
Figure GDA0003996198410000074
in the formula, Z1 is the acoustic impedance of the known ultrasonic transducers A1, B1 and C1, and Z2 is the acoustic impedance of the unknown ceramic slurry to be measured received by the ultrasonic transducers A2, B2 and C2;
meanwhile, the sound attenuation of the ultrasonic wave in the propagation of the ceramic slurry to be measured is set to be alpha, so that,
Figure GDA0003996198410000075
Figure GDA0003996198410000076
2) Dividing the amplitude P2 of the received ultrasonic echo signal into Pr and Px, dividing the unknown acoustic impedance Z2 of the ceramic slurry to be detected into Zr and Zx, and substituting the Zr and Zx into a formula (1) to obtain the ultrasonic echo signal
Figure GDA0003996198410000077
3) Substituting equation Zx = Zr + δ ZPx = Pr + δ P into equation (2) to obtain
Figure GDA0003996198410000081
Due to delta Z 2 The value of the sum δ Z δ P is very small and thus, can be ignored
Figure GDA0003996198410000082
4) It can be known from the formula (4) that the unknown acoustic impedance of the ceramic slurry to be measured is proportional to the change of the measured amplitude, and because Zx = Zr + δ Z and Zx = ρ v, the acoustic impedance of the ceramic slurry to be measured is proportional to the change of the measured amplitude
Figure GDA0003996198410000083
And because the A/D sampling data of the ultrasonic echo signals are read in the FPGA to obtain the time corresponding to the ultrasonic propagation time end point, the transmission time of the ultrasonic waves in the ceramic slurry to be measured among the three groups of ultrasonic transducers A1/A2, B1/B2 and C1/C2 is determined, and the transmission speed of the ultrasonic waves is determined according to the ultrasonic propagation speed
Figure GDA0003996198410000084
The density of the ceramic slurry to be measured of the three groups of upper, middle and lower ultrasonic transducers can be precisely calculated by combining the formula (5):
Figure GDA0003996198410000085
in the formula: s is the propagation distance of the ultrasonic wave, and t is the propagation time of the ultrasonic wave.
Particle sedimentation occurs in the ceramic slurry to be measured which is uniform just after the lapse of time in the aging process, for example, as shown in fig. 2, the sedimentation rate difference is caused by the inconsistency of the distribution of parameters such as mass, volume, specific surface area and agglomeration degree among different powder particles, so that the density of the powder particles in the solvent along the height direction is inconsistent, a slurry density gradient is generated, the density values of the ceramic slurry to be measured at the upper, middle and lower positions in the ceramic slurry volume container from high to low can be clearly known through the LCD screen of the ARM processor, and the density values of the ceramic slurry to be measured at the upper, middle and lower positions are obtained, the density of the ceramic slurry at the upper, middle and lower positions are respectively designated as rho, rho b and rho c, when the density of the ceramic slurry at the upper, middle and lower positions is respectively designated as rho, rho b and rho c, the particle sedimentation rate difference occurs in the aging process of the ceramic slurry to be measured at the upper, middle and lower positions is obtained
Figure GDA0003996198410000086
And is
Figure GDA0003996198410000087
In the process, the ceramic slurry to be measured is in a uniform state.

Claims (4)

1. The method for detecting the uniformity of the ceramic slurry based on ultrasonic waves is characterized by comprising a device for detecting the uniformity of the ceramic slurry, wherein the device comprises a ceramic slurry volume container, three groups of ultrasonic transducers and a hardware circuit; wherein, the three groups of ultrasonic transducers are respectively an ultrasonic transducer A1/A2, a ultrasonic transducer B1/B2 and an ultrasonic transducer C1/C2, probes of the ultrasonic transducers A1, B1 and C1 are respectively clung to the upper, middle and lower positions on the left side of the ceramic slurry volume container, and probes of the ultrasonic transducers A2, B2 and C2 are clung to the right side of the ceramic slurry volume container and are respectively opposite to the positions of the ultrasonic transducers A1, B1 and C1; the hardware circuit comprises an ARM processor, a field programmable gate array FPGA, a D/A converter, a driving circuit, a transmitting circuit of the ultrasonic transducer, a receiving circuit of the ultrasonic transducer, a signal amplifying circuit, a signal filtering circuit and an A/D converter;
the output end of the ARM processor is connected with the input end of the field programmable gate array FPGA, the output end of the field programmable gate array FPGA is connected with the input end of the D/A converter, the output end of the D/A converter is connected with the input end of a transmitting circuit of the ultrasonic transducer through a driving circuit, the ultrasonic transducers A1, B1 and C1 are connected with the transmitting circuit of the ultrasonic transducer, the ultrasonic transducers A2, B2 and C2 are connected with a receiving circuit of the ultrasonic transducer, and the output end of the receiving circuit is connected with the input end of the field programmable gate array FPGA through an amplifying circuit, a filter circuit and an A/D converter in sequence; the specific method comprises the following steps:
1) Coating an ultrasonic coupling agent on the contact surface of the ultrasonic transducer probe and the ceramic slurry volume container, and putting the ceramic slurry to be detected into the ceramic slurry volume container;
2) The ARM processor controls the FPGA to output sine wave driving signals, and the signals convert digital signals into analog signals through a D/A converter; then sequentially passing through the driving circuit and the transmitting circuit, amplifying the power of the ultrasonic transducer, enabling the driving signal to reach the ultrasonic transducers A1, B1 and C1 on the left side, and enabling the ultrasonic transducers A1, B1 and C1 to convert the input signal into mechanical vibration to generate ultrasonic waves;
3) Ultrasonic waves generated by the ultrasonic transducers A1, B1 and C1 penetrate through the ceramic slurry to be detected in the ceramic slurry volume container, and then ultrasonic signals sent by the ultrasonic transducers A1, B1 and C1 on the left side are respectively received by the ultrasonic transducers A2, B2 and C2 on the right side of the ceramic slurry volume container and are converted into ultrasonic echo signals;
4) The receiving circuit transmits the ultrasonic echo signal to the amplifying circuit, the amplifying circuit amplifies the ultrasonic echo signal, the filtering circuit filters the ultrasonic echo signal, the A/D conversion circuit samples the ultrasonic echo signal, and the sampled data is stored in the FPGA;
5) After sampling is finished, the ARM processor determines the time corresponding to the starting point of the propagation time of the ultrasonic wave according to the data of the ultrasonic wave transmitted by the field programmable gate array FPGA; the ARM processor obtains the amplitude of an echo signal according to the sampling data of an A/D conversion circuit which reads the ultrasonic echo signal from the FPGA, obtains the moment corresponding to the ultrasonic propagation time end point, determines the transmission time of the ultrasonic wave in the ceramic slurry to be detected between each group of ultrasonic transducers, and obtains the propagation speed v of the ultrasonic wave according to the relation between the distance and the time:
Figure FDA0004040946800000021
in the formula, s is the propagation distance of the ultrasonic wave, and t is the propagation time of the ultrasonic wave;
6) The ARM processor calculates the density rho of the ceramic slurry to be measured among the three groups of ultrasonic transducers according to an impedance method, displays the density rho on an LCD screen of the ARM processor, obtains the state of the ceramic slurry to be measured according to a ratio relation method of the density of the ceramic slurry to be measured at the upper position, the middle position and the lower position of a ceramic slurry volume container, sets the density of the ceramic slurry at the upper position, the middle position and the lower position as rho a, rho b and rho c respectively, and when the density of the ceramic slurry at the upper position, the middle position and the lower position is equal to rho a, rho b and rho c respectively
Figure FDA0004040946800000022
And is provided with
Figure FDA0004040946800000023
When the ceramic slurry to be measured is in a uniform state.
2. The method for detecting the uniformity of ceramic slurry based on ultrasonic waves as claimed in claim 1, wherein the ARM processor is further connected with a keyboard, an LCD screen and an RS485 bus.
3. The method for ultrasonically testing the uniformity of ceramic slurry according to claim 1 or 2, wherein the ultrasonic transducer is a piezoelectric ceramic transducer with a frequency of 200kHz and a transducer direction angle of 4 °.
4. The method for detecting the uniformity of ceramic slurry based on ultrasonic waves as claimed in claim 3, wherein the impedance method in the step (6) comprises the following steps:
1) Setting the amplitude of the ultrasonic signal source emitted by the ultrasonic transducers A1, B1 and C1 as P1 and the amplitude of the ultrasonic echo signal received by the ultrasonic transducers A2, B2 and C2 as P2, and making:
Figure FDA0004040946800000024
in the formula, Z1 is the acoustic impedance of the known ultrasonic transducers A1, B1 and C1, and Z2 is the acoustic impedance of the unknown ceramic slurry to be measured received by the ultrasonic transducers A2, B2 and C2;
meanwhile, the sound attenuation of the ultrasonic wave in the propagation of the ceramic slurry to be measured is set to be alpha, so that,
Figure FDA0004040946800000025
Figure FDA0004040946800000031
2) Dividing the amplitude P2 of ultrasonic echo signals received by the ultrasonic transducers A2, B2 and C2 into Pr and Px, dividing the unknown acoustic impedance Z2 of the ceramic slurry to be tested into Zr and Zx, and substituting the Zr and Zx into a formula (3) to obtain the ultrasonic wave-sensitive material
Figure FDA0004040946800000032
3) Substituting equation Zx = Zr + δ Z Px = Pr + δ P into equation (4) to obtain
Figure FDA0004040946800000033
Neglecting δ Z 2 And δ Z δ P to
Figure FDA0004040946800000034
In the formula: δ Z is Zx imaginary component, δ P is Pr imaginary component;
4) It can be known from the formula (6) that the unknown acoustic impedance of the ceramic slurry to be measured is in direct proportion to the change of the measured amplitude, and because Zx = Zr + δ Z and Zx = ρ v, the density of the ceramic slurry to be measured between the three groups of upper, middle and lower ultrasonic transducers, that is, the density values of the ceramic slurry to be measured at the upper, middle and lower positions in the ceramic slurry volume container are:
Figure FDA0004040946800000035
in the formula (I), the compound is shown in the specification,
Figure FDA0004040946800000036
s is the propagation speed of the ultrasonic wave, s is the propagation distance of the ultrasonic wave, and t is the propagation time of the ultrasonic wave.
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CN203519458U (en) * 2013-11-01 2014-04-02 重庆理工大学 Multichannel high-precision densimeter
CN105424810A (en) * 2015-11-11 2016-03-23 南昌航空大学 Evaluation method for uniformity of fiber reinforcement ceramic matrix composite
CN209745322U (en) * 2019-04-26 2019-12-06 重庆理工大学 multi-parameter measuring instrument for fluid
CN110702794A (en) * 2019-11-12 2020-01-17 南通赛洋电子有限公司 Method for rapidly identifying substance based on ultrasonic waves

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101813515A (en) * 2010-04-30 2010-08-25 重庆理工大学 Method and device for precisely measuring ultrasonic wave transmission time
CN203519458U (en) * 2013-11-01 2014-04-02 重庆理工大学 Multichannel high-precision densimeter
CN105424810A (en) * 2015-11-11 2016-03-23 南昌航空大学 Evaluation method for uniformity of fiber reinforcement ceramic matrix composite
CN209745322U (en) * 2019-04-26 2019-12-06 重庆理工大学 multi-parameter measuring instrument for fluid
CN110702794A (en) * 2019-11-12 2020-01-17 南通赛洋电子有限公司 Method for rapidly identifying substance based on ultrasonic waves

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