SU1038869A1 - Method of producing solid-phase inner half-element for ion-selective glass electrode - Google Patents

Abstract

METHOD OF MANUFACTURING A SOLID STATE particles of 1-10 micron tungsten oxide bronze and electrode glass with a pressure of 250-300 kg / cm and a temperature below the softening temperature of glass by 50-70s, and the bronze and electrode glass contain the same alkali metal ion, and the ratio of components in mixtures of the following, wt.%; Tungsten oxidizing (L bronze 40-60 Electrode glass 40-60

Description

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(The invention relates to the technique of electrochemical measurements, in particular, to the technology of producing solid-phase ion-selective electrodes for analyzing liquid media and can be used in the manufacture of electrodes with ion-sensitive elements in the form of glass, mono- and polycrystalline membranes. A method of making completely solid-phase and ion-selective electrodes is known. / in which a layer of pure metal (Cu Hell, Pt, Pd, Sn, Pb, Ni, Co, Ta, C g, C d, V) is applied to the ion-exchange membrane, and then the organometallic Connections with its subsequent recovery of the U. The manufacture of the electrode and this method, firstly, is complex, in-btc, does not provide stable electrochemical characteristics also due to the absence of a reversible transition at the boundary of the inner semi-cell — the ion-sensing membrane. The proposed V is a method of manufacturing a solid-phase internal half-cell of an ion-selective glass electrode, involving the mixing of an ionically conductive material with an electrically conductive material. In the method, an ion-sensitive glass membrane is applied to a thin layer of glass enamel smeared to give it electronic conductivity with 3050% silver or other noble metal powder and deposited onto a metal substrate that has the form of a rod. According to this method, glass mass, mixed with metxlich ps, serves as an internal half-element of comparison, and the metal rod - tokovodsm. The method allows to obtain a fully PJ three-phase electrode. However, the electrode obtained by this method has a number of disadvantages, a mass service life, low metal strength and thermal stability, low stability and accuracy of readings. These deficiencies are due to the fact that the internal semi-element, consisting of a mixture of glass-gums and metshchalny powder, undergoes delamination by specific gravity when melted and applied to the substrate. The resulting chemical heterogeneity causes internal mechanical stresses, which can lead to cracking and breakdown of the electrical contact in the electrode as the temperature changes. In addition, such an internal half cell is not reversible to carrier ions of the charge in the membrane, since it does not contain the corresponding alkaline ion, which in turn reduces the stability of the electrode readings. Electrodes manufactured by this method have a low measurement accuracy of +0.1 pH, which makes their use very limited. The purpose of the invention is to increase the service life and improve the mechanical strength of the electrode. The goal is achieved by the method of manufacturing a solid-phase internal semi-element for an ion-selective glass electrode, which consists of mixing the material with ionic conductivity with an electrically conductive material 7, the internal semi-element is obtained by hot pressing a mixture of powders with a particle size of 1-10 microns of tungsten oxide bronze and an electrode stack with a pressure of 250-300 kg / cm and a temperature below the glass softening temperature of 50-70 ° С, bronze and electrode glass contain the same alkali ion About metal, and the ratio of components in the mixture is as follows, wt.%: Tungsten oxide bronze 40-60 Electrode glass At the indicated temperature conditions, the glass becomes plastic, but not liquid, as a result of which the mixture is easily molded and pressed, thereby completely eliminating stratification of the mixture components by specific the weight is usually in liquid media, leading to chemical heterogeneity and mechanical stresses and causing cracking of the electrodes, as in the prototype. The wired current output is fixed to the internally obtained half element by soldering or pressing, then the pop element is coupled to the ion-sensing membrane. The minimum pressing pressure is 250 kg / cm. With less pressure, the compressed half element does not have sufficient mechanical strength. At pressures greater than 300 kg / cm, repressing occurs, creating mechanical pressures. The temperature limits are determined with, as follows. If the temperature below the melting point of the glass is less than that, the glass becomes practically liquid and the components are stratified according to specific weight, resulting in chemical heterogeneity of the inner half element. If the temperature is taken below the melting point of the glass by more than one, the glass will be non-plastic and the mixture will not compress well. The permissible minimum amount of electrically conductive material in the mixture is 40 wt.%, As with a smaller quantity, the produced half cell has a low electrical conductivity. Maximum quantity of electrically conductive material is 60 wt.%. When the amount is greater, the strength of the composition decreases and the possibility of conjugation of the inner half-element to the membrane deteriorates. As an electrically conductive material, oxide bronze is preferably used, having electronic and ionic conductivity simultaneously and containing the same charge-carrier ions as in. As a result, a significant increase in the stability of the electrode's indicator with time is achieved compared with the prototype. 1. The powders used for the manufacture of the inner half cell are taken with a particle size of 1-10 microns. If you take a particle size of less than 1 micron, the mixture of powder compresses poorly and stratifies due to the release of air that is in the sorbed state on highly dispersed powders. With a particle size of pscc of more than 10 µm, the criticality of the mixture is not sufficient, which leads to poor sintering properties of the material, deterioration of its mechanical properties and changes in the electrical characteristics of the electrodes in the equestrian count. The proposed method for manufacturing the ion-selective electrode is as follows. Pre-finely powdered powders of electrically conductive material and electrode glass are thoroughly mixed. The resulting mixture in a vacuum or in an inert gas is pressed at a temperature below the temperature; melting electrode glass at 50-70 with a pressure of 250300 kg / cm. The compressed inner half-element mates with an ion-sensitive membrane. The metal collector is pressurized, coalesces into the inner half-metal during the pressing of the mixture or is soldered to the nickel layer deposited on the surface, half-body and 1-cent by elec- trical method. The resulting electrode is inserted into the housing and sealed. Example 1. For the manufacture of an ion-selective electrode having a pH function of a mixture containing 0.30 (60 wt.%) Lithium-lanthanum bronze (Lio, i5 Lao.ifWO) and 0.20 G (40 wt.%) PH-sensitive the glasses are preliminarily crushed, pressed under vacuum into a tablet (f 12 mm, h 2.5 mm) at a temperature below the glass melting point () and a pressure of 300 kg / cm. Electrochemically, a layer of nickel with a thickness of 20 µm is deposited onto one surface of the obtained half element, to which a current from copper wire is attached, and the other surface is matched with a membrane made of pH sensitive glass. The electrode is then glued into a glass electrically insulated canister case. the tube. The electrode is tested in buffer solutions with a pH of 4.01 and 6.86. The tests show that the electrode 1) function has an inclination close to the theoretical (55-57 mV / pH). Time establishing capacity 1 s. Measurement error not more than +0,0 pH. The period of stable operation of the electrode is more than 5000 hours. The mechanical strength of the electrode manufactured by the proposed method is high. The cracking of the sensitive element does not occur. Example 2. For the manufacture of an electrode, 1.2 g of a thoroughly ground mixture consisting of 0.48 g of 40 wt.% Of oxide sodium tungsten bronze (Nao, 7, WO5) and 0.72 g (60 wt.%) Are taken. Sodium-sensitive glass. The mixture is pressed into a tablet (f 12, h 2.5 mm) in vacuum at a temperature 70 ° C below the melting point of glass (melting point 690 ° C) at a pressure of 250 kg / cm, the pressing time is 30 min. The copper grid is pressed into the mixture for subsequent soldering current leads. The obtained half cell is conjugated by sintering with a sodium-sensitive glass membrane. Then the electrode is glued into the glass body tube. The pNa electrode obtained in this way is tested in Pctx NaCl solution with a concentration from IN. The tests show that the electrode function has a slope close to the theoretical 55-57 mV / pH, the sweat setting time is i s, the electrode stable operation time is more than 5000 hours. The mechanical strength of the electrode obtained by the proposed method is high, the cracking of the electrode does not occur . Example 3. A mixture of powders in the amount of 1.2 g with a particle size of 1-5 μm, consisting of O, 6 g of sodium-tungsten bronze of Nag-jWO composition and 0.6 g of electrode glass of composition 9Al2. SB Oj-eiSiO pressed into a tablet at. The temperature of softening of said glass) and a pressure of 300 kg / cm. On the basis of cooked such

an electrode with a membrane made of the same electrode glass was made by the internal half cell method. When tested, the electrode showed stable operation with nylon of the electrode function, which was close to theoretical for 5000 hours, while maintaining mechanical strength, no cracking.

Example 4. An internal popelement of the same composition and in the same mode as in example 1 was made from a mixture of powders with a particle size of 5-10 μm. Based on this half-cell, an electrode was made, when tested, showed the same characteristics as in example 1 .

M. As the electrically conductive material of the half-cell, tungsten bronze oxide is used with the general formula, where M is a metal of I, I, and III groups, O: X i 1. Bronze has both electronic and ionic conductivity on the same ion as the electrode glass. In addition, it has a thermal expansion coefficient close to the KTR of the electrode glass and equal. 910, which provides good sintering, mechanical strength of the half-cell, and high reliability of its welding with a glass membrane.

In the manufacture of internal flooring; The elements use tungsten bronze alloyed with lithium and sodium.

In accordance with the requirement of reversibility of the charge-carrying ion in the internal yuli element and the glass membrane sintered with it during the manufacture of the half-cell, the mixture is composed of electrode glass of the same composition as the glass membrane and tungsten bronze containing the same alkali metal ions as in the membrane.

For pH electrodes, glass of composition 271120-aiagOjj-2C rgO 69S I 0 and bronze ZlftggWOi are taken.

The proposed method of manufacture allows obtaining a solid-phase ion-selective electrode, having significant advantages: firstly, it has a homogeneous chemical and mechanical uniformity of the structure of the inner half-cell, which eliminates cracking during temperature fluctuations due to internal stresses, in-second, the inner half-cell contains the same ions - charge carriers, as well as the ion-sensitive membrane is conjugated with a half cell. This ensures that the system is reversible according to a specific ion, which in turn stabilizes the electrode reading. This greatly increases the stable operation of the electrode, which is not less than 5000 hours in (the prototype provides data for 3 days), and the measurement accuracy rises to +0.02 pH, whereas according to

5 given in the prototype, the measurement accuracy is only +0.1 pH.

Claims (1)

METHOD FOR PRODUCING A SOLID-PHASE INTERNAL SEMIELEMENT FOR THE ION-SELECTIVE GLASS ELECTRODE, which consists in mixing material with ionic conductivity with conductive material, characterized in that, in order to increase the service life and improve the mechanical strength of the electrodes, we use a hot metal . ' particles of 1-10 μm tungsten oxide bronze and electrode glass at a pressure of 250-300 kg / cm ² and a temperature below the glass softening temperature of 50-70 ° C, moreover, bronze and electrode glass contain the same alkali metal ion, and the ratio of components in the mixture the following, wt.%: Tungsten Oxide Bronze 40-60 Electrode glass 40-60 SU „„ 1038869