RU223126U1 - Solid State Electrochemical Sensor for Oxygen Detection - Google Patents

Abstract

The utility model can be used in applied electrochemistry, metallurgy, energy, automotive and other industries to determine the oxygen content in liquid and gaseous media, and this utility model can also be used in the presence of reducing gases such as sulfur dioxide. The sensor is suitable for measuring oxygen concentrations in many applications ranging from 5 parts per million (ppm) to 100%.

Solid-state electrochemical sensor for oxygen detection, containing a solid electrolyte cell made of zirconium dioxide, made in the form of a test tube, reference and comparative electrodes made of hydrogen tetrachlorodihydroxoplatinate (IV), deposited in a single layer with a 5 mm wide path along the entire length of the test tube from the inside and outside, respectively, current collectors installed at the base of the test tube in the form of clamping contacts, a thermocouple installed inside the test tube at a distance of 1 mm from the reference electrode, the base of the test tube with installed current collectors is connected to the metal body using a lock nut, a fitting and an o-ring, while the space between the nut and the o-ring is filled zirconium powder.

The technical result is an increase in the percentage of yield of suitable products (reduction in the percentage of defects) during production due to the use of not two, but one composition of zirconium dioxide.

Description

The utility model relates to analytical instrumentation and can be used in applied electrochemistry, metallurgy, energy, automotive and other industries to determine the oxygen content in liquid and gaseous media; this utility model can also be used in the presence of reducing gases such as sulfur dioxide. The sensor is suitable for measuring oxygen concentrations in many applications ranging from 5 parts per million (ppm) to 100%.

A hydrogen sensor with an electrochemical cell (ECC) is known, the sensitive element (SE) of which is a connection of a tubular insulator (ceramic tube based on Al ₂ O ₃ and MgO) with a hermetically mounted plug [ceramic solid electrolyte 2 composition (ZrO ₂ ) _0.9 ⋅( Y ₂ O ₃ ) _0.1 ] (patent RU 2334979, IPC G01N 27/417, published 09/27/2008). The ECC is placed in a sealed chamber and equipped with a heater and heat sink. The sealed chamber contains a working cavity located in the hot zone and an auxiliary cavity located in the cold zone. The working and auxiliary cavities are connected to each other by a pipeline. In the hot zone with the maximum temperature there is a hydrogen-permeable membrane in the form of a pipe plugged at one end, which is equipped with a displacer, a heater and a channel connecting it to the sensitive surface of the measuring electrode.

The disadvantage of the known technical solution is that there is a small percentage of yield of suitable ECC due to the lack of tightness of the plug-tube connection at the manufacturing stage. (Glass sealants for gas sealing of solid oxide fuel cells. V.V. Kuranov, S.P. Drovosekov, I.V. Popov. Russian Federal Nuclear Center - All-Russian Research Institute of Technical Physics named after Academician E.I. Zababakhin, Snezhinsk), that practically unrealistic for known materials used in ECC. In addition, it is known that the zirconium-yttrium solid solution is resistant to the action of Al ₂ O ₃ , which does not contribute to a tight tube-plug connection (A.A. Kortel, G.M. Sudilovskaya, T.M. Saraeva, S.A. Suvorov, V.I. Strakhov - Sinterability and technical properties of zirconium-spinel and zirconium-corundum refractories - Refractories. - 1997, - No. 4, - pp. 22-24).

The closest technical solution to the claimed utility model, which was selected as a prototype, is the sensitive element of an oxygen gas analyzer (RU 2339028, publ. November 20, 2008, IPC: G01N 27/417), containing a solid electrolyte cell, an electrical insulator, a metal shell, a current collector from the reference electrode, on the smaller base of the solid electrolyte cell and on the combined larger bases of the electrical insulator and solid electrolyte cell, two layers are applied sequentially, the first is from a mixture of noble metal powder and zirconium dioxide, the second is from noble metal powder, applied to the base of the current collector at the point of contact with the solid electrolyte cell foil made of the same noble metal, the gap between the mating surfaces of the metal shell and the electrical insulator is filled with amorphous foil made of an alloy containing 25-30% titanium, the rest is copper.

The disadvantage of this invention is the complex method of manufacturing the sensitive element. The complexity of manufacturing is due to the fact that in the process of manufacturing sensitive elements it is necessary to use two different ceramic compositions (Al ₂ O ₃ , MgO) and (ZrO ₂ , Y ₂ O ₃ ). This entails a low percentage of yield of suitable products due to the lack of tightness of the plug-tube connection at the manufacturing stage.

The second disadvantage of this invention is the process of applying platinum electrodes in 2 stages, which is energy- and labor-intensive.

The technical result achieved when using the claimed utility model is an increase in the percentage of yield of suitable products (reduction in the percentage of defects) in production due to the use of not two, but one composition of zirconium dioxide.

The technical result is achieved by the fact that the solid-state electrochemical sensor for detecting oxygen contains a reference and comparative electrode, a solid electrolyte cell made in the form of a test tube made of zirconium dioxide.

Reference and reference electrodes made of hydrogen tetrachlorodihydroxoplatinate (IV) are applied in one layer in a 5 mm wide path along the entire length of the tube from the inside and outside, respectively. The claimed sensor uses pyrolytic reduction hydrogen tetrachlorodihydroxoplatinate (IV) instead of platinum paste (patent 2807403, published 11/14/2023).

Current collectors are installed at the base of the test tube, made in the form of clamping contacts made of stainless steel alloy (for example, 12Х18Н9Т), or brass (for example, LAZH 60-1-1).

The thermocouple is installed inside the test tube at a distance of 1 mm from the reference electrode.

The geometric dimensions of the cell are chosen to minimize the electrical resistance of the electrolyte. This is achieved through the use of a platinum coating composition. Patent for invention No. 2807403.

The reference electrode detects constant atmospheric air, and the reference electrode detects exhaust or flue gas. As a result, the mV output voltage changes, which is converted into concentration.

Also, the proposed design takes into account the separation of two gas volumes (the first reference is the determined atmospheric air, the second comparative is the exhaust or flue gas), without which the sensor is not viable. Separation of gas volumes is ensured by pressing the sensor into a pre-prepared metal case, made in the form of a locking nut and a fitting with zirconium powder. When tightening the fitting, the o-ring compresses the zirconium powder and is pressed against the nut.

The essence of the claimed utility model is illustrated by the figure, which shows a general view of the electrochemical sensor, where

1 - reference electrode;

2 - comparative electrode;

3 - solid electrolyte cell;

4 - fitting;

5 - sealing ring;

6 - zirconium powder;

7 - locking nut;

8 - thermocouple;

9 - current collector;

10 - metal case.

Solid-state electrochemical sensor for oxygen detection, containing reference 1 and comparative 2 electrodes, a solid electrolyte cell 3 made of zirconium dioxide, while the solid electrolyte cell is made in the form of a test tube, the reference and comparative electrodes are made of hydrogen tetrachlorodihydroxoplatinate (IV), applied in one layer with a track 5 wide mm along the entire length of the test tube from the inside and outside, respectively, current collectors 9 are installed at the base of the test tube in the form of clamping contacts made of stainless steel alloy (12Х18Н9Т) or brass (LAZH 60-1-1), and thermocouple 8 is installed inside the test tube at a distance of 1 mm from the reference electrode, this entire structure is assembled into a housing using a nut 7, an o-ring 5 and a fitting 4. After this, the assembly of parts 3, 4, 5, 7 is filled with zirconium powder 6, after which it is attached to an adapter for a metal housing using a locking nut 7 10.

The assembly of a solid-state electrochemical sensor is carried out as follows. A solid electrolyte cell 3 (SEC) is made in the form of a test tube from zirconium dioxide stabilized in the cubic phase, for example, by slip casting.

The geometric dimensions of the cell are chosen to minimize the electrical resistance of the electrolyte and optimize the effective area of the electrode. As a result of this approach, the optimal cell geometry can be found, which will ensure the highest performance and efficiency of the electrolytic system.

Next, they proceed to the creation of reference 1 and comparative 2 electrodes.

To do this, the composition of hydrogen tetrachlorodihydroxoplatinate (IV) is applied inside and outside in one layer with a path 5 mm wide along the entire length of the test tube, then by pyrolytic reduction, reference 1 and comparative 2 electrodes are obtained by heating in air to 700 ° C with the condition that, after heating occurs no faster than 3.5°C per minute.

Then, a thermocouple 8 is inserted into the resulting test tube with applied electrodes and current-collecting contacts 9 are installed, then the entire assembly is inserted by pressing into a pre-prepared metal body 10 containing a locking nut 7, an o-ring 5 and a fitting 4 with zirconium powder 6. When the fitting is tightened 4, the sealing ring 5 compresses the zirconium powder 6 and is pressed against the locking nut 7, thereby sealing the separation of two gas volumes.

The metal body is made of steel 14X17H2 with a thermal expansion coefficient of 10.8×10 ^-6 , coinciding with the thermal expansion coefficient of zirconium dioxide, from which the solid electrolyte cell (SEC) is made.

A solid-state electrochemical sensor works as follows.

A solid electrolyte cell with electrodes deposited on its surface is “washed” by the analyzed and reference gases and is hermetically divided into two gas volumes (reference and comparative). With a difference in concentrations (partial pressures), as a result of electrochemical reactions on the electrodes, the output voltage mV changes, and the cell generates an electromotive force (EMF), which, for a given oxygen content of the reference gas on the reference electrode and at a fixed temperature of the electrochemical cell, allows one to calculate the oxygen content on a comparative electrode in accordance with the Nernst equation.

E=(RT/4F)⋅Ln(Pl/P2),

where R is the gas constant;

F - Faraday's constant;

T - cell temperature, °C;

P1 and P2 are the partial pressures of the reference and comparative (controlled) gas, respectively;

E - electromotive force (EMF), Ln natural logarithm.

Claims (3)

1. Solid-state electrochemical sensor for oxygen detection, containing a solid electrolyte cell made of zirconium dioxide, made in the form of a test tube, reference and comparative electrodes made of hydrogen tetrachlorodihydroxoplatinate (IV), deposited in one layer with a 5 mm wide path along the entire length of the test tube from the inside and outside, respectively, current collectors , installed at the base of the test tube in the form of clamping contacts, a thermocouple installed inside the test tube at a distance of 1 mm from the reference electrode, the base of the test tube with installed current collectors, connected to the metal body using a lock nut, a fitting and an O-ring, with the space between the nut and The sealing ring is filled with zirconium powder. 2. Solid-state electrochemical sensor according to claim 1, characterized in that the current collectors are made of stainless steel alloy 12Х18Н9Т or brass LAZH 60-1-1. 3. Solid-state electrochemical sensor according to claim 1, characterized in that the solid electrolyte cell is made of stabilized zirconium dioxide.