The study of the mechanical properties of thin films using piezoceramic acoustic resonators

Fedorov

et al. 2020

Novel bio-materials, like chitosan and its derivatives, appeal to finding a new niche in room temperature gas sensors, demonstrating not only a chemoresistive response, but also changes in mechanical impedance due to vapor adsorption. We determined the coefficients of elasticity and viscosity of chitosan acetate films in air, ammonia, and water vapors by acoustic spectroscopy. The measurements were carried out while using a resonator with a longitudinal electric field at the different concentrations of ammonia (100–1600 ppm) and air humidity (20–60%). It was established that, in the presence of ammonia, the longitudinal and shear elastic modules significantly decreased, whereas, in water vapor, they changed slightly. At that, the viscosity of the films increased greatly upon exposure to both vapors. We found that the film’s conductivity increased by two and one orders of magnitude, respectively, in ammonia and water vapors. The effect of analyzed vapors on the resonance properties of a piezoelectric resonator with a lateral electric field that was loaded by a chitosan film on its free side was also experimentally studied. In these vapors, the parallel resonance frequency and maximum value of the real part of the electrical impedance decreased, especially in ammonia. The results of a theoretical analysis of the resonance properties of such a sensor in the presence of vapors turned out to be in a good agreement with the experimental data. It has been also found that with a growth in the concentration of the studied vapors, a decrease in the elastic constants, and an increase in the viscosity factor and conductivity lead to reducing the parallel resonance frequency and the maximum value of the real part of the electric impedance of the piezoelectric resonator with a lateral electric field that was loaded with a chitosan film. This leads to an increase in the sensitivity of such a sensor during exposure to these gas vapors.

Section: Determination Of the Elastic And Viscosity Coefficients Of Chitosan Filmsmentioning

confidence: 99%

Evaluation of Elastic Properties and Conductivity of Chitosan Acetate Films in Ammonia and Water Vapors Using Acoustic Resonators

Fedorov

et al. 2020

“…It is also known that the mechanical and electrical properties of films can be determined using acoustic methods. For example, to determine the elastic modulus, viscosity coefficient, and density of thin films, piezoelectric resonators with a longitudinal electric field can be used [ 3 , 4 , 5 , 6 , 7 , 8 ]. This resonator represented a piezoelectric disk with electrodes on each side, and the film under study was deposited on one of these electrodes.…”

Section: Introductionmentioning

confidence: 99%

“…Then, by fitting the theoretical frequency dependencies of the impedance to the experimental ones, the modulus of elasticity, the viscosity coefficient, and the density of thin films were determined. This method was used to study the mechanical properties of silicon dioxide films [ 3 ], nanocomposite films based on low-pressure polyethylene [ 4 ], mycelial films [ 5 , 6 , 7 ], and chitosan films [ 8 , 9 ] in the presence of various gases. There is also an approach in which surface acoustic waves are used to determine the mechanical properties of films [ 10 ].…”

Section: Introductionmentioning

confidence: 99%

The Study of the Acoustic Characteristics of Chitosan Acetate Film Using a Radial Electric Field Excited Resonator

Semyonov

et al. 2023

Self Cite

Currently, the lateral electric field excited resonators are used for the creation of various sensors. We have recently proposed a new type of acoustic resonator called radial electric field excited disk acoustic resonator. The advantage of this type of resonator is its high sensitivity to mechanical and electrical boundary conditions on its free surface. This makes it possible to determine both the acoustic and electrical properties of a thin layer of material deposited on the free end of the resonator. In this work, we used a radial electric field excited disk acoustic resonator of Russian-made barium plumbum zirconate titanate (BPZT) piezoceramics. With the help of this resonator, the material constants for the piezoceramic sample were refined, and their temperature dependencies were determined. Then, this resonator was used to determine the elastic modulus, viscosity, and conductivity of the chitosan acetate film in air and ammonia vapors of various concentrations. It was shown that the chitosan acetate film under the influence of ammonia vapor significantly changes its mechanical properties and increases its electrical conductivity thousands of times, and then completely restores its properties.

“…At this stage, a finite element model of the resonator was created, and the characteristics of the material (elastic, piezoelectric and dielectric constants, density, and viscosity) of the resonator itself were refined [ 10 , 11 ]. This was done by the method of broadband acoustic resonance spectroscopy [ 10 , 11 , 12 ]. Then, these measurements were carried out in the same frequency range for the resonator, the free surface of which was in contact with the investigated medium.…”

Section: Introductionmentioning

confidence: 99%

“…This medium can be a viscoelastic film with finite conductivity or viscous conducting liquid. By changing the values of the resonance frequencies and the magnitude of the resonance peaks, one can estimate the properties of the medium under study [ 12 ]. In order to determine the mechanical and electrical properties of the medium, the electric field that accompanies acoustic oscillations must freely penetrate from the resonator into the medium.…”

Section: Introductionmentioning

confidence: 99%

The Radial Electric Field Excited Circular Disk Piezoceramic Acoustic Resonator and Its Properties

Semyonov

et al. 2021

Self Cite

A new type of piezoceramic acoustic resonator in the form of a circular disk with a radial exciting electric field is presented. The advantage of this type of resonator is the localization of the electrodes at one end of the disk, which leaves the second end free for the contact of the piezoelectric material with the surrounding medium. This makes it possible to use such a resonator as a sensor base for analyzing the properties of this medium. The problem of exciting such a resonator by an electric field of a given frequency is solved using a two-dimensional finite element method. The method for solving the inverse problem for determining the characteristics of a piezomaterial from the broadband frequency dependence of the electrical impedance of a single resonator is proposed. The acoustic and electric field inside the resonator is calculated, and it is shown that this location of electrodes makes it possible to excite radial, flexural, and thickness extensional modes of disk oscillations. The dependences of the frequencies of parallel and series resonances, the quality factor, and the electromechanical coupling coefficient on the size of the electrodes and the gap between them are calculated.