RU2129707C1 - Process registering mechanical waves in liquid media - Google Patents

Abstract

FIELD: physics of interphase phenomena. SUBSTANCE: process registering mechanical waves in liquid media is based on usage of physical phenomenon related to change of potential of electrode being in contact with liquid medium that depends on deformation. In given case any external action causing deformation of solid electrode leads to adequate change of electrode potential. This change of electrode potential is tested in process of registration of action of elastic waves on solid electrode placed into liquid medium. EFFECT: improved authenticity of method. 2 dwg

Description

 The invention relates to acoustics, physics of interfacial phenomena.

 Known methods for recording mechanical waves in a liquid medium [1, 2, 8]. In one of the methods, the registration principle is associated with tracking a light beam reflected from a liquid surface, fixing a spatial relief created by mechanical waves incident on its surface. Another method is based on the effect of the occurrence of electric polarization in the process of mechanical deformation when acoustic waves are exposed to the surface of a piezomaterial. On this basis, a detector was created for receiving acoustic waves in a liquid medium, known as a pressure gradient hydrophone [1, 2].

 These methods of recording mechanical waves have the following disadvantages: 1) the technological complexity of using piezoelectric transducers to create sensors of elastic vibrations at the solid / liquid interface; 2) the need to select for these purposes special materials that do not have a center of symmetry; 3) stringent requirements for the geometric dimensions of the selected piezocrystal; 4) the limited temperature range of the piezoelectric element, which is very important, for example, when working in molten media; 5) the deep dependence of the mode of operation of the hydrophone.

 The closest method of the same purpose to the claimed invention in terms of features is a method of converting acoustic vibrations of a liquid or gaseous medium, according to which two electrodes parallel to each other, at a distance less than half the wavelength, create nonequilibrium ionic conductivity of the medium, excite an electric field in it , the magnitude of the EMF induced on the electrodes by ionized particles moving in the front of the wave is recorded, its vibrations are used to judge medium vibrations, and with pour increase the sensitivity of the conversion, the electric field is excited in the traveling direction of the wave [8].

 The reasons that impede the achievement of the specified technical result when using the known method adopted for the prototype include: a) the limited choice of the spatial orientation of the electrodes due to the need to place the electrode in a plane parallel to the wave front; b) the need to create nonequilibrium ionic conductivity in the medium under study; c) the need for a constant power source that creates a voltage between the electrodes; d) the constant excitation of the electric field, which leads to the difficulty of converting acoustic vibrations in a large frequency range; d) the frequency range is limited by the distance between the electrodes, which should be less than half the wavelength, which leads to the limitation of the upper range of the recorded frequencies.

 The objective of the invention is the ability to record changes in electrode potential in an accessible way.

 The technical result is expressed in revealing the dependence of the electrode potential on the degree of deformation of the electrode under the influence of elastic waves.

 The essence of the invention is as follows: two solid-state electrodes are lowered into a liquid medium, one of them being in contact with the medium, and a change in the electrode potential is recorded, while mechanical waves are received by this electrode with the possibility of its surface deformation under their influence, and the other (the second ) the electrode is isolated from the medium and with its help, by changing the surface tension, a change in the electrode potential is recorded at the solid / liquid interface.

 We obtained experimental results confirming a change in the electrode potential when exposed to mechanical waves propagating in a liquid medium.

 The principle of wave registration is associated with the establishment of changes in the electrode potential on the degree of its deformation, which adequately depends on the parameters (frequency, amplitude) of the wave. Moreover, it was found that the magnitude of this change depends not only on the frequency and amplitude of the wave, but also on the distance between the source - receiver of the waves and on their relative orientation relative to each other.

 In essence, these phenomena are associated with electrocapillary phenomena due to the existence of a double electric layer (DEL) at the interface between a solid and liquid [3].

где F^S - удельная свободная поверхностная энергия (единицы площади поверхности);
U_ij - тензор поверхностной деформации;
I - единичный двухмерный тензор;
σ_ij - символ Кронекера;
q и φ - плотность заряда и электродный потенциал;
σ - коэффициент пограничного натяжения на межфазной границе ДЭС.In the general case, the electric field strength in a DEL is different from zero, which is due to the excess charge (from ions, electrons, and oriented dipoles) present in the layer. The presence of charges in this boundary layer affects the surface tension of the interfacial layer. At the same time, the work requiring to create a DEL on the interface, includes processes associated with surface stress (deformation), interfacial (boundary) tension, and with a change in electrode potential. Theoretically, the relationships between these parameters are given by the equations [3-7]

where F ^S is the specific free surface energy (units of surface area);
U _ij is the surface strain tensor;
I is the unit two-dimensional tensor;
σ _ij is the Kronecker symbol;
q and φ are the charge density and electrode potential;
σ is the coefficient of boundary tension at the interface of the DES.

 From equations (1) and (2) it follows that any external action leading to deformation of the solid electrode should adequately change the electrode potential. This change in the electrode potential is recorded during the action of elastic waves on a solid-state electrode in a liquid medium.

 This was experimentally carried out as follows: a vibrator (source of mechanical waves) 2 connected to a generator 3 and a receiver of elastic waves 6 are lowered into a liquid medium 1, as shown in FIG. 1. The elastic wave receiver is an electrochemical cell with two metal electrodes of materials that are not corroded in a liquid medium and lowered into a weakly conducting liquid 7. One of the electrodes 4 is used to receive elastic waves, and the other electrode 5 is used as a reference electrode. The electronic device 8 registers the change in electrode potential observed during the experiment.

 The experimental results obtained for the first time in sea water are presented in FIG. 2, where the dependence of the electrode potential on frequency is shown. The relative changes in the electrode potential and the frequency of the vibrator are plotted on the coordinate axes. The graph shows that the magnitude of the received signal increases nonlinearly and is associated with the frequency of the elastic waves that deform the electrode.

 The electrode devices at our disposal for recording changes in the electrode potential versus frequency did not allow us to expand the frequency range above 100 kHz, although there are no fundamental limitations in such measurements in the higher frequency range.

 Thus, according to the obtained experimental results, one of the possible methods for recording (detecting) mechanical signals propagating in a liquid medium is proposed by a simpler, more affordable method than is realized using a hydrophone.

 The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information, and the identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find an analogue characterized by features identical to all the essential features of the claimed invention.

 Practical information on measuring the frequency dependence of the electrode potential during deformation was not found in the literature.

 The proposed method for recording mechanical waves has several advantages compared to the prototype: 1) allows you to create a device for recording mechanical (acoustic) waves without using piezoelectric materials, i.e. allows depending on the task to use a wide range of materials as solid-state electrodes; 2) the proposed method for recording mechanical waves can be implemented to study the physicochemical properties of the solid / liquid phase boundary in different modes, including in underground wells; 3) the design of the sensor allows you to change the shape and geometric dimensions of the used solid electrode; 4) the simplicity and low cost of the design of the sensor and the manufacturability of its manufacture; 5) the use of sensors for recording mechanical waves in solutions and melts.

 The possibility of implementing the proposed method for recording elastic waves is confirmed by experimental data.

 With regard to industrial applicability, the claimed method in its implementation is intended for use in hydroacoustics, geophysics, biomedicine and other fields associated with interfacial phenomena.

 Sources of information taken into account when compiling the description.

 1. Physical Acoustics, ed. U. Meson, 1966, - M .: Mir, 320 p.

 2. Bobber R. J. Hydroacoustic measurements, 1974, - M .: Mir, 362 p.

 3. Gokhshtein A.Ya. Electrochemistry, 1966, v. 2, c. 11, p. 1318.

 4. Benzon G., Yoon K. In the collection. Interphase boundaries gas / solid, 1970, - M .: Mir, 179 p.

 5. Frumkin A.N. Potentials of zero charge, 1979, M .: Science :, 259 p.

 6. Karpenko G.V., Zamostenik II, Babey Yu.I., Pakhmursky, V.I. Electrochemistry, 1971, v. 7, c. 2, p. 220.

 7. Kruglov V.I., Konorov P.P., Boykov Yu.A., Prilkin N.A. FTP, 1974, v. 8, c. 8, p. 1514.

 8. Copyright certificate, N 890074, G 01 H 3/06, 12.15.81., Bull. N 46.

Claims (1)

 A method of detecting mechanical waves in liquid media, according to which two solid-state electrodes are lowered into the liquid medium, the first of which is in contact with the medium, and a change in electrode potential is recorded, characterized in that the mechanical waves are received by the first electrode with the possibility of surface deformation under by their action, and the second electrode is isolated from the medium, and with its help, by changing the surface tension, the change in the electrode potential at the solid interface is recorded th body / liquid.

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