A nickel ferrite solid state reference electrode for concrete and a method of designing the same

Abstract

The application discloses a kind of nickel ferrite solid-state reference electrode for concrete and its design method, nickel ferrite solid-state reference electrode for concrete, including tube body and wire, cement paste layer, alkaline colloid layer, electrode material layer, conductive layer and packaging layer are sequentially arranged in tube body, one end of wire passes through packaging layer and is connected with conductive layer.Design method includes the following steps: the resistivity of cement paste layer, alkaline colloid layer, electrode material layer, conductive layer and packaging layer is calculated;Determine the target resistance and inner diameter size of nickel ferrite solid-state reference electrode;The thickness of cement paste layer, alkaline colloid layer, electrode material layer, conductive layer and packaging layer is calculated;Prepare nickel ferrite solid-state reference electrode for concrete.The general reference electrode is prepared in the application, the contact area of electrode layer and conductive layer increases, since the conductive performance of conductive layer is significantly better than electrode layer material, use the electrode material containing nickel ferrite, the potential stability and repeatability of prepared reference electrode are significantly improved.

Description

Technical Field

[0001] This invention pertains to solid-state reference electrodes and their design methods, specifically a nickel-ferrite solid-state reference electrode for concrete and its design method. Background Technology

[0002] Concrete durability refers to the ability of concrete to resist various destructive factors and maintain its strength and appearance integrity over a long period under working conditions. Monitoring the internal environment of concrete structures is of great significance for the study of concrete durability. Typically, reference electrodes, along with appropriate ion-selective sensors, temperature sensors, pH sensors, and oxygen sensors, are used to monitor the corresponding ion concentrations, temperature, pH, and oxygen content, thereby understanding the internal environment of the concrete. Providing data support for the durability assessment and remaining service life prediction of concrete structures is of great practical significance for developing scientific management and maintenance systems and ensuring the durability and service safety of concrete structures.

[0003] One of the key performance indicators of a reference electrode is its electrochemical performance, which is closely related to its charge transfer resistance and external circuit impedance. The external circuit impedance formed by the cement slurry layer, alkaline colloidal layer, and electrode material layer increases the high-frequency impedance of a solid reference electrode. Commercial products typically have certain requirements for the overall impedance of reference electrodes; for example, the external circuit impedance of the commercially available ERE20 reference electrode is 109.7 Ω·cm. 2 To meet the size requirements of sensors with different needs, there are requirements for the resistance of the sensor, and the size of the reference electrode also needs to be changed.

[0004] In general, there are many types of existing concrete monitoring sensors, which have many requirements for the size and resistivity of the reference electrode, and there is no universal reference electrode. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a nickel ferrite solid reference electrode for concrete that can meet the size requirements of different sensors. Another purpose of this invention is to provide a simple and convenient design method for a nickel ferrite solid reference electrode for concrete.

[0006] Technical solution: The present invention provides a nickel ferrite solid reference electrode for concrete, comprising a tube and a wire. The tube contains a cement slurry layer, an alkaline colloid layer, an electrode material layer, a conductive layer, and an encapsulation layer arranged sequentially. One end of the wire passes through the encapsulation layer and is connected to the conductive layer.

[0007] Furthermore, the thickness ratio of the cement slurry layer, the alkaline colloid layer, the electrode material layer, the conductive layer, and the encapsulation layer is 1:0.5~1.5:0.5~1.5:0.25~0.75:0.5~1.5.

[0008] Furthermore, the electrode material layer is made of nickel ferrite, cerium oxide, and graphite. Preferably, the mass ratio of nickel ferrite (NiFeO2), cerium oxide (CeO2), and graphite is 80:15:5.

[0009] Furthermore, the tube body is a hollow cylinder made of PVC, with a height of 3–9 cm and an inner diameter of 3–10 mm. Preferably, the height is 3–9 cm, the inner diameter is 3–10 mm, and the thickness is 1 mm.

[0010] Furthermore, the cement grout layer is composed of silicate cement and distilled water. Preferably, the water-cement ratio is 0.4 to 0.6, which is equivalent to 100 parts by weight of cement mixed with 40 to 60 parts by weight of distilled water.

[0011] Furthermore, the alkaline colloidal layer is prepared by heating a saturated Ca(OH)₂ solution to 80–90°C, adding sodium carboxymethyl cellulose, stirring, and then cooling to room temperature. Preferably, 0.5 g of sodium carboxymethyl cellulose is added to every 10 mL of saturated Ca(OH)₂ solution, and the mixture is heated to 85°C.

[0012] Furthermore, the conductive layer is made of graphite powder or graphite conductive adhesive.

[0013] Furthermore, the encapsulation layer is formed by curing a mixed epoxy resin. Preferably, the mixed epoxy resin is an AB mixed epoxy resin, where component A is an acrylic-modified epoxy or epoxy resin, or contains catalysts and other additives, and component B is a modified amine or other curing agent, or contains catalysts and other additives. The weight ratio of component A to component B is 3:1.

[0014] The design method for the above-mentioned nickel-ferrite solid reference electrode for concrete includes the following steps:

[0015] Step 1: Calculate the resistivity of the cement slurry layer, alkaline colloid layer, electrode material layer, conductive layer, and encapsulation layer;

[0016] Step 2: Determine the target resistance and inner diameter of the nickel ferrite solid reference electrode;

[0017] Step 3: Calculate the thickness of the cement slurry layer, alkaline colloid layer, electrode material layer, conductive layer, and encapsulation layer;

[0018] Step 4: Prepare a nickel ferrite solid reference electrode for concrete.

[0019] Furthermore,

[0020] Furthermore, in step three, by determining the thickness of any two of the cement slurry layer, alkaline colloid layer, and electrode material layer, the thickness of the other layer can be calculated. The calculation formula is as follows:

[0021]

[0022] Where r is the inner diameter of the reference electrode tube, R s Let ρ1 be the resistivity of the cement slurry layer, L1 be the thickness of the cement slurry layer, ρ2 be the resistivity of the alkaline colloid layer, L2 be the thickness of the alkaline colloid layer, ρ3 be the resistivity of the electrode material layer, and L3 be the thickness of the electrode material layer.

[0023] Furthermore, in step one, the resistance of the reference electrode wire and the conductive layer is very small and can be ignored. Beforehand, use a multimeter to measure the resistance of each layer of the reference electrode—the cement slurry layer, the alkaline colloid layer, and the electrode material layer—and calculate the resistivity. The calculation formula is shown below:

[0024]

[0025]

[0026] Where r is the inner diameter of the reference electrode tube, R s Let ρ1 be the resistivity of the cement slurry layer, L1 be the thickness of the cement slurry layer, ρ2 be the resistivity of the alkaline colloid layer, L2 be the thickness of the alkaline colloid layer, ρ3 be the resistivity of the electrode material layer, and L3 be the thickness of the electrode material layer.

[0027] Working principle: Cement mortar is used at the bottom of the electrode to provide ion diffusion channels, thereby reducing the internal resistance of the reference electrode. An alkaline colloidal layer is also added inside the reference electrode. This layer maintains a relatively stable internal pH, reducing the impact of pH changes on the electrode potential, and also mitigates the change in electrode potential caused by chloride ions intruding from the bottom cement mortar. Carboxymethyl cellulose is added, providing adhesive, water-retaining, and salt and acid-resistant properties.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0029] 1. A general-purpose reference electrode is obtained, with an increased contact area between the electrode layer and the conductive layer. At the same time, the conductivity of the conductive layer is significantly better than that of the electrode layer material. In addition, by using electrode materials containing nickel ferrite with specific composition and proportion, the potential stability and reproducibility of the obtained reference electrode are significantly improved.

[0030] 2. A simple and convenient method for calculating the thickness of each layer of a solid reference electrode for concrete is provided to meet the resistance requirements of the solid reference electrode for concrete under different sensor size requirements, which is convenient and practical. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the present invention;

[0032] Figure 2 This is the equivalent circuit diagram of the present invention;

[0033] Figure 3 This is the open circuit potential diagram of the present invention in concrete. Detailed Implementation

[0034] In the following examples, all materials, reagents, and instruments used are commercially available unless otherwise specified. Experimental methods not specifically described in the examples are generally performed under standard conditions or as recommended by the manufacturer. The AB-mixed epoxy resin was purchased from Wenzhou Yinghuoban Technology Co., Ltd.

[0035] Example 1

[0036] like Figure 1 The tube 1 of the nickel-ferrite solid reference electrode for concrete is a hollow cylinder made of PVC material, with a height of 3-9 cm, an inner diameter of 3-10 mm, and a thickness of 1 mm. PVC material does not react with metals and metal oxides, is acid and alkali resistant, and has a certain strength. Inside the tube 1, from bottom to top, there are a cement slurry layer 2, an alkaline colloid layer 3, an electrode material layer 4, a conductive layer 5, and an encapsulation layer 6. One end of the wire 7 passes through the encapsulation layer 6 and connects to the conductive layer 5.

[0037] The cement slurry layer 2 is composed of P·O 42.5 type silicate cement and distilled water, with a water-cement ratio of 0.4–0.6, equivalent to 100 parts by weight of cement mixed with 40–60 parts by weight of distilled water. The alkaline colloidal layer 4 is prepared by heating a saturated Ca(OH)₂ solution to 85°C, then adding sodium carboxymethyl cellulose (0.5g) per 10mL of saturated Ca(OH)₂ solution, stirring, and then cooling to room temperature. The electrode material layer 4 is made of nickel ferrite (NiFeO₂) powder, cerium oxide (CeO₂) powder, and graphite, with a mass ratio of 80:15:5. The mixture is thoroughly mixed using a high-speed mixer and then pressed using a press. The conductive layer 5 is made of graphite powder or graphite conductive adhesive. The conductive layer 5 is in full contact with the electrode material layer 4, ensuring better electrical connection between the wire 7 and the electrode material layer 4, resulting in better potential stability and reproducibility of the prepared reference electrode. Encapsulation layer 6 is formed by curing an AB-mixed epoxy resin, in which the weight ratio of type A adhesive to type B adhesive is 3:1. Type A adhesive includes acrylic-modified epoxy or epoxy resin, or contains catalysts and other additives; type B adhesive includes modified amine or other curing agents, or contains catalysts and other additives.

[0038] Example 2

[0039] A design method for a nickel-ferrite solid reference electrode for concrete includes the following steps:

[0040] (1) Use a multimeter to measure the resistance of each layer and calculate the resistivity.

[0041] Table 1 Resistivity of each layer

[0042] Layering Resistance (kΩ) <![CDATA[Cross-sectional area (mm 2 )]]> Thickness (mm) Resistivity (Ω·mm) Cement grout layer 2 2.8 28 10 7840 Alkaline colloidal layer 3 1.4 28 10 3920 Electrode material layer 4 2.1 28 10 5880

[0043] Through the equivalent circuit diagram inside this invention, such as Figure 2 To meet the overall resistance requirements of this invention, the thickness of the third layer can be calculated by determining the thickness of any two of the reference electrode cement slurry layer 2, alkaline colloid layer 3, and electrode material layer 4. The calculation formula is as follows:

[0044] For example:

[0045] in,

[0046] r is the inner diameter of the reference electrode tube 1;

[0047] R s The resistance of the reference electrode;

[0048] ρ1, ρ2, and ρ3 are the resistivity of cement slurry layer 2, alkaline colloid layer 3, and electrode material layer 4, respectively.

[0049] R1, R2, and R3 are the resistances of the cement slurry layer 2, the alkaline colloid layer 3, and the electrode material layer 4, respectively.

[0050] L1, L2, and L3 represent the thicknesses of the cement slurry layer 2, the alkaline colloid layer 3, and the electrode material layer 4, respectively.

[0051] The resistivity of cement slurry layer 2, alkaline colloid layer 3, and electrode material layer 4 were calculated to be 7840, 3920, and 5880 Ω·mm, respectively.

[0052] (2) The sensor requires an electrode diameter of 6mm and a reference electrode internal resistance of no more than 8kΩ.

[0053] (3) The thickness of electrode material layer 4 is calculated to be 15 mm and the thickness of alkaline colloid layer 3 is 10 mm. It can be concluded that the thickness of cement slurry layer 2 is no more than 12.6 mm.

[0054] (4) Fix one end of the tube 1 (6 mm in diameter) to the fixed platform, fill the other end of the tube 1 with cement slurry and let it solidify to form a cement slurry layer 2 with a thickness of 10 mm; introduce a mixture of calcium hydroxide, water and sodium carboxymethyl cellulose into the tube 1 through the other end to form a calcium hydroxide colloidal layer 3 with a thickness of 10 mm; put electrode material into the tube 1 through the other end to form an electrode material layer 4 with a thickness of 15 mm; introduce graphite powder or graphite conductive adhesive into the tube 1 through the other end to form a conductive layer 5 with a thickness of 5 mm; insert the wire 7 into the conductive layer 5 through the other end; then introduce epoxy resin into the tube 1 and let it solidify to form an encapsulation layer 6 with a thickness of 10 mm.

[0055] Example 3

[0056] A design method for a nickel-ferrite solid reference electrode for concrete includes the following steps:

[0057] (1) Use a multimeter to measure the resistance of each layer and calculate the resistivity. The resistivity of cement slurry layer 2, alkaline colloid layer 3, and electrode material layer 4 is calculated to be 7840, 3920, and 5880 Ω·mm, respectively.

[0058] (2) The sensor requires an electrode diameter of 3mm and a reference electrode internal resistance of no more than 8kΩ.

[0059] (3) The thickness of electrode material layer 4 is determined to be 3 mm, the thickness of alkaline colloid layer 3 is determined to be 3 mm, and the thickness of cement slurry layer 2 is determined to be no more than 3.6 mm.

[0060] (4) Fix one end of the tube 1 (6 mm in diameter) to the fixed platform, fill the other end of the tube 1 with cement slurry and let it solidify to form a cement slurry layer 2 with a thickness of 3 mm; introduce a mixture of calcium hydroxide, water and sodium carboxymethyl cellulose into the tube 1 through the other end to form a calcium hydroxide colloidal layer 3 with a thickness of 3 mm; put electrode material into the tube 1 through the other end to form an electrode material layer 4 with a thickness of 3 mm; introduce graphite powder or graphite conductive adhesive into the tube 1 through the other end to form a conductive layer 5 with a thickness of 3 mm; insert the wire 7 into the conductive layer 5 through the other end; then introduce epoxy resin into the tube 1 and let it solidify to form an encapsulation layer 6 with a thickness of 3 mm.

[0061] Example 4

[0062] A design method for a nickel-ferrite solid reference electrode for concrete includes the following steps:

[0063] (1) Use a multimeter to measure the resistance of each layer and calculate the resistivity. The resistivity of cement slurry layer 2, alkaline colloid layer 3, and electrode material layer 4 is calculated to be 7840, 3920, and 5880 Ω·mm, respectively.

[0064] (2) The sensor requires an electrode diameter of 10mm and a reference electrode internal resistance of no more than 5kΩ.

[0065] (3) The thickness of electrode material layer 4 is determined to be 20 mm, and the thickness of alkaline colloid layer 3 is determined to be 20 mm. Therefore, the thickness of cement slurry layer 2 is no more than 30 mm.

[0066] (4) Fix one end of the tube 1 (10 mm in diameter) to the fixed platform, fill the other end of the tube 1 with cement slurry and let it solidify to form a cement slurry layer 2 with a thickness of 20 mm; introduce a mixture of calcium hydroxide, water and sodium carboxymethyl cellulose into the tube 1 through the other end to form a calcium hydroxide colloidal layer 3 with a thickness of 20 mm; put electrode material into the tube 1 through the other end to form an electrode material layer 4 with a thickness of 20 mm; introduce graphite powder or graphite conductive adhesive into the tube 1 through the other end to form a conductive layer 5 with a thickness of 5 mm; insert the wire 7 into the conductive layer 5 through the other end; then introduce epoxy resin into the tube 1 and let it solidify to form an encapsulation layer 6 with a thickness of 10 mm.

[0067] Comparative Example

[0068] The remaining structures of this comparative example are identical to those in Example 1, except that the electrode material layer is replaced with graphene. Results showed a significant decrease in stability and reproducibility. Figure 3 .

[0069] The electrode potential of this invention, when embedded in mortar, reaches a relatively stable stage after approximately 30 days. After entering the stable period, the potential fluctuations are small. Within 25 to 45 days, the maximum potential fluctuation of this invention is 20 mV, with a potential fluctuation variance of 7.25 mV. In contrast, simply changing the material to graphene results in large potential fluctuations, with a maximum fluctuation of 150 mV. Therefore, in practical concrete systems, the stability and reproducibility of this invention are significantly improved.

Claims

1. A ferronickel ferrite solid state reference electrode for concrete, characterized in that: It includes a tube body (1) and a wire (7). The tube body (1) is provided with a cement slurry layer (2), an alkaline colloid layer (3), an electrode material layer (4), a conductive layer (5) and an encapsulation layer (6) in sequence. One end of the wire (7) passes through the encapsulation layer (6) and is connected to the conductive layer (5). The electrode material layer (4) is made of nickel ferrite, cerium oxide and graphite, and the mass ratio of nickel ferrite, cerium oxide and graphite is 80:15:

5.

2. The ferronickel solid state reference electrode for concrete according to claim 1, characterized in that: The thickness ratio of the cement slurry layer (2), alkaline colloid layer (3), electrode material layer (4), conductive layer (5) and encapsulation layer (6) is 1:0.5~1.5:0.5~1.5:0.25~0.75:0.5~1.

5.

3. The nickel-ferrite solid reference electrode for concrete according to claim 1, characterized in that: The tube (1) is a hollow cylinder made of PVC, with a height of 3~9cm and an inner diameter of 3~10mm.

4. The ferronickel solid state reference electrode for concrete according to claim 1, characterized in that: The cement grout layer (2) is made of silicate cement and distilled water.

5. The ferronickel solid state reference electrode for concrete according to claim 1, characterized in that: The alkaline colloidal layer (3) is prepared by heating a saturated Ca(OH)2 solution to 80~90℃, adding sodium carboxymethyl cellulose, stirring, and then cooling to room temperature.

6. The solid state reference electrode of claim 1, wherein: the nickel ferrite is a nickel ferrite having a formula of NiFe204. The conductive layer (5) is made of graphite powder or graphite conductive adhesive.

7. The nickel-ferrite solid reference electrode for concrete according to claim 1, characterized in that: The encapsulation layer (6) is formed by curing a mixed epoxy resin.

8. The method for designing a ferronickelic solid state reference electrode for concrete according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Calculate the resistivity of the cement slurry layer (2), alkaline colloid layer (3), electrode material layer (4), conductive layer (5), and encapsulation layer (6); Step 2: Determine the target resistance and inner diameter of the nickel ferrite solid reference electrode; Step 3: Calculate the thickness of the cement slurry layer (2), alkaline colloid layer (3), electrode material layer (4), conductive layer (5), and encapsulation layer (6); Step 4: Prepare a nickel ferrite solid reference electrode for concrete.

9. The method of designing a solid state reference electrode of a nickel ferrite for concrete according to claim 8, characterized in that: In step three, the thickness of any two of the cement slurry layer (2), alkaline colloid layer (3), and electrode material layer (4) can be determined to calculate the thickness of the other layer.

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