Electrochemical sensing device for in-situ detection of alloy Cr volatilization rate

Abstract

The invention provides an electrochemical sensing device for in-situ detection of alloy Cr volatilization rate, and relates to the technical field of stainless steel high-temperature oxidation and surface protection. Comprising a sensor connected with a to-be-tested sample and used for collecting an electric signal of the to-be-tested sample; the sensor fixing device is used for fixing the sensor and the sample to be detected; the heating device is connected with the sensor fixing device and is used for heating the sensor and the sample to be tested to a preset working temperature; and the signal collecting device is connected with the sensor and is used for collecting the electric signal. The invention solves the problems that the Cr volatilization rate determination method in the prior art causes errors due to alloy oxidation weight increment, the Cr recovery process is tedious, the in-situ monitoring capability is lacked, the deposition amount is difficult to accurately measure, the real working condition of the galvanic pile is difficult to simulate, and the overall accuracy and applicability are limited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature oxidation and surface protection of stainless steel, and particularly relates to an electrochemical sensing device for in-situ detection of Cr volatilization rate of an alloy. BACKGROUND

[0002] Energy crisis and global climate problems have prompted extensive research on efficient utilization technology of renewable and sustainable energy. As a clean and efficient energy conversion device, reversible solid oxide cell (RSOC) can convert chemical energy in fuel into electrical energy for power generation in fuel cell (SOFC) mode, and can convert electrical energy of renewable energy into chemical energy for storage in electrolytic cell (SOEC) mode. Due to the limited output power of single cell, in order to generate higher output power, multiple single cells are connected in series through a connecting body to form a high-power stack. Cr-containing alloy (such as ferritic stainless steel) is the first choice for high-temperature components of metal connecting body in the stack due to its excellent high-temperature oxidation resistance, good mechanical properties and matched thermal expansion coefficient. However, under the high-temperature and high-humidity service conditions of RSOC stack, Cr in the Cr-containing alloy will volatilize from the alloy surface according to the following reaction formula.

[0003] Cr2O3(s) + 3 / 2O2 → 2CrO3 (g) (1)

[0004] 1 / 2Cr2O3 (s) + H2O(g) +3 / 4O2 → 2CrO2(OH)2 (g) (2)

[0005] This phenomenon will cause Cr in the alloy matrix to continuously volatilize from the alloy surface, which will reduce the Cr content in the alloy and reduce the high-temperature oxidation resistance of the alloy; other elements in the matrix diffuse to the alloy surface to form non-protective oxides (such as Fe, Mn, etc.); the decrease of Cr content in the alloy will cause the abnormal thickening of the oxidation layer and the failure of the component, thereby affecting the safe operation of the entire device. In addition, under the working conditions of RSOC stack, the gaseous Cr volatilized from the metal connecting body will deposit on the surface of the cell electrode, thereby affecting the electrocatalytic property and long-term stability of the electrode, thereby limiting the commercial application of RSOC. Therefore, in-situ, rapid and accurate measurement of the Cr volatilization rate of the metal connecting body under high-temperature and high-humidity service environment is crucial for the protection of RSOC.

[0006] Currently, the measurement of alloy Cr evaporation rate mainly relies on the following methods: (1) gravimetric method, the weight loss after high temperature exposure is the weight loss of Cr evaporation; (2) condensation collection method, the method is to heat the alloy in a quartz tube, and the gaseous Cr is carried to the condenser by the gas flow and deposited, after a period of condensation, the condenser is washed with an acidic solution, and the content of Cr is determined by inductively coupled plasma mass spectrometry (ICP-MS); a variant of the traditional condensation method is the silicon wafer technology, in which a water-cooled silicon wafer is used as a condensation surface for volatile Cr species, and the amount of Cr condensed on the silicon wafer is evaluated by ion beam analysis; (3) ion conductance method, which works on the principle that the gas containing Cr volatile is introduced into deionized water, and Cr is dissolved to form ions to increase the conductivity of the solution, and the Cr evaporation is indirectly determined by monitoring the change of conductivity in real time; (4) Cr spectrum deposition method, the sample is placed between two alumina plates without contacting them. The Cr released from the sample is deposited on the surface of the collector. The amount of deposited Cr is determined by energy dispersive X-ray spectroscopy analysis.

[0007] The main problems of the above methods are: (1) the determination of Cr evaporation rate by weight change has a large error due to the slow weight gain of alloy oxidation at high temperature; (2) the Cr deposited on the quartz vessel needs to be washed with acid, and the collection of Cr is complex; (3) it cannot realize in-situ monitoring, and the determination of Cr evaporation rate needs to interrupt the experiment or disassemble the sample; (4) the analysis of Cr evaporation rate by alumina plate cannot accurately determine the amount of deposited Cr; (5) lack of working condition adaptability: the current change in the actual operation of the battery cannot be simulated. SUMMARY

[0008] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide an electrochemical sensing device for in-situ detection of alloy Cr evaporation rate, which solves the problems of error caused by alloy oxidation weight gain in the prior art Cr evaporation rate determination method, complex Cr recovery process, lack of in-situ monitoring capability, difficulty in accurate measurement of deposition amount and difficulty in simulating the real working condition of the battery, and the overall accuracy and applicability are limited.

[0009] To achieve the above purpose, the present application provides the following scheme:

[0010] An electrochemical sensing device for in-situ detection of alloy Cr evaporation rate, comprising:

[0011] A sensor connected to the sample to be measured for collecting the electrical signal of the sample to be measured;

[0012] A sensor fixing device for fixing the sensor and the sample to be measured;

[0013] A heating device is connected with the sensor fixing device, and is used for heating the sensor and the sample to be measured to a preset working temperature.

[0014] A signal collecting device is connected with the sensor, and is used for collecting the electric signal.

[0015] Preferably, the sensor is a double-sided symmetric laminated structure.

[0016] Preferably, the sensor comprises:

[0017] a first outer side and a second outer side;

[0018] The first outer side to the second outer side are sequentially a first sensitive electrode layer, a first barrier layer, an electrolyte layer, a second barrier layer and a second sensitive electrode layer.

[0019] The first sensitive electrode layer and the second sensitive electrode layer are both used for adsorbing gaseous Cr species volatilized from the sample to be measured; the first barrier layer is used for preventing Sr elements in the first sensitive electrode layer from diffusing to the electrolyte layer, forming an insulating phase and affecting the electric signal transmission; the second barrier layer is used for preventing Sr elements in the second sensitive electrode layer from diffusing to the electrolyte layer, forming an insulating phase and affecting the electric signal transmission; and the electrolyte layer is used for conducting O ions between the two sides of the first sensitive electrode layer and the second sensitive electrode layer.

[0020] Preferably, the electrolyte layer is prepared by a flow casting method.

[0021] Preferably, the first barrier layer and the second barrier layer are both prepared by a silk screen printing method.

[0022] Preferably, the sensor fixing device is a hollow cylindrical high-temperature-resistant alumina ceramic tube and is arranged in the heating device.

[0023] Preferably, the sensor fixing device is provided with an air inlet gas path and an air outlet gas path, wherein the air inlet gas path and the air outlet gas path control the flow rate and flow of the inlet and outlet gas through a flow meter.

[0024] The present application discloses the following technical effects:

[0025] The application provides an electrochemical sensing device for in-situ detection of alloy Cr volatility, comprising: a sensor connected with a sample to be detected, used for collecting an electric signal of the sample to be detected; a sensor fixing device used for fixing the sensor and the sample to be detected; a heating device connected with the sensor fixing device, used for heating the sensor and the sample to be detected to a preset working temperature; and a signal collecting device connected with the sensor, used for collecting the electric signal. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0027] Figure 1 A structural schematic diagram of an electrochemical sensing device for in-situ detection of alloy Cr volatility is provided for the embodiments of the present application.

[0028] Figure 2 A structural schematic diagram of a sensor is provided for the embodiments of the present application.

[0029] Figure 3 A test result schematic diagram of electrochemical impedance spectroscopy of the alloy to be detected with time is provided for the embodiments of the present application.

[0030] Figure 4 A weight gain curve schematic diagram of Cr volatility of the alloy to be detected with time is provided for the embodiments of the present application.

[0031] Figure 5 A quantitative corresponding curve schematic diagram of electrochemical impedance spectroscopy and Cr volatility of the alloy to be detected is provided for the embodiments of the present application.

[0032] Explanation of reference signs:

[0033] 1-wire; 2-gas inlet path; 3-sensor fixing device; 4-heating device; 5-sample to be detected; 6-sensor; 7-signal collecting device. DETAILED DESCRIPTION

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] like Figure 1 As shown, the present invention provides an electrochemical sensing device for in-situ detection of the Cr volatilization rate in alloys, comprising:

[0037] Sensor 6 is connected to the sample 5 to be tested and is used to collect the electrical signal of the sample 5 to be tested.

[0038] The sensor fixing device 3 is used to fix the sensor 6 and the sample 5 to be tested;

[0039] Heating device 4, connected to sensor fixing device 3, is used to heat sensor 6 and sample 5 to a preset working temperature;

[0040] The signal collection device 7 is connected to the sensor 6 and is used to collect the electrical signal.

[0041] Furthermore, the sensor 6 has a double-sided symmetrical stacked structure.

[0042] Furthermore, the sensor 6 includes:

[0043] First outer side and second outer side;

[0044] The first outermost layer to the second outermost layer are, in sequence, a first sensitive electrode layer, a first barrier layer, an electrolyte layer, a second barrier layer, and a second sensitive electrode layer;

[0045] Both the first and second sensitive electrode layers are used to adsorb gaseous Cr species volatilized from the test sample 5. The first barrier layer prevents Sr elements in the first sensitive electrode layer from diffusing into the electrolyte layer, forming an insulating phase and affecting electrical signal transmission. The second barrier layer prevents Sr elements in the second sensitive electrode layer from diffusing into the electrolyte layer, forming an insulating phase and affecting electrical signal transmission. The electrolyte layer is used to conduct O ions between the first and second sensitive electrode layers.

[0046] Specifically, the sample 5 to be tested is placed on one side of the sensor 6, the air inlet channel 2 and the lead wire 1 are arranged in the fixing device, and the lead wire 1 is connected with the signal collection device 7. The sensor 6 is arranged in the heating device 4. In this embodiment, the heating device 4 is a small open-tube furnace available on the market, such as the OTF-1200X-S-Ⅱ tube furnace of Hefei Kejing Company, which can be heated to a maximum of 1100°C, meeting the requirement for simulating the high-temperature working environment of different alloy materials. The fixing device is a hollow ceramic tube arranged in the heating device 4 and used for fixing the sensor 6. The air inlet channel 2 is used for conveying air to the surface of the sensor 6 through the air inlet channel 2.

[0047] The surface of the sensor 6 is coated with platinum slurry, the lead wire 1 is a platinum wire and is in contact with the platinum slurry, the signal collection device 7 collects the electrical signal of the sample 5 to be tested through the lead wire 1, and the signal collection device 7 is an analyser Gamry Interface 5000E available on the market.

[0048] In the test, the sample 5 to be tested is first placed on one side of the sensor 6, then the sample 5 to be tested and the sensor 6 are placed between the fixing device, the fixing device is arranged in the heating device 4, a flow meter is arranged to convey air to the surface of the sensor 6 through the air inlet channel 2, and the heating device 4 is arranged to reach the service temperature of the sample 5 to be tested. At this temperature, the surface of the sample 5 to be tested will emit gaseous Cr species, the gaseous Cr species will diffuse to the sensitive electrode and be adsorbed and react, the active sites of the sensitive electrode will be occupied by the gaseous Cr species, the impedance of the sensitive electrode will change, the change of the impedance of the sensor 6 in contact with the sample 5 to be tested with time is recorded, the change of the electrical signal is recorded and associated with the calibration curve, and the Cr volatilization rate of the sample 5 to be tested is obtained.

[0049] In this embodiment, the test results of the 310S alloy are shown as follows. Figure 3 As shown in the figure, the impedance of the sensor 6 increases with the increase of the test time. In addition, the pre-calibrated Cr volatilization rate is shown as follows. Figure 4 As shown in the figure, the Cr volatilization rate increases with the increase of the test time. In combination with the pre-calibrated electrical signal-Cr volatilization rate, the following is obtained. Figure 5 The mathematical model is as follows.

[0050]

[0051] Among them, is the impedance, is the initial impedance increment, is the maximum impedance increment, is the Cr volatilization rate, is the critical volatilization rate, is the Cr poisoning response width.

[0052] The sensor 6 device for in-situ detection of Cr evaporation rate of alloy in the embodiment. The Cr evaporation rate of sample can be directly measured in real time in-situ without interrupting the experiment or sampling, which greatly reduces the difficulty of detecting the Cr evaporation rate of alloy.

[0053] Further, the electrolyte layer is prepared by a flow casting method.

[0054] Further, the first barrier layer and the second barrier layer are both prepared by a screen printing method.

[0055] Further, the sensor fixing device 3 is a hollow cylindrical high-temperature-resistant alumina ceramic tube and is arranged inside the heating device 4.

[0056] Further, the sensor fixing device 3 is provided with an air inlet gas path 2 and an air outlet gas path, wherein the air inlet gas path 2 and the air outlet gas path control the flow rate and flow of the inlet and outlet gas through a flow meter.

[0057] Specifically, the structure of the sensor 6 includes an electrolyte YSZ, a barrier layer GDC and a sensitive electrode LSCF, and the structure is LSCF|GDC|YSZ|GDC|LSCF, wherein the solid-state electrolyte YSZ is prepared by a flow casting process, and after being degreased at 240°C for 8 hours and then sintered at 1400°C for 4 hours, a dense YSZ substrate with certain mechanical strength is obtained. The barrier layer is prepared by mixing GDC powder and a binder at a mass ratio of 3:2 to prepare a slurry, and then the slurry is printed on both sides of the electrolyte substrate by screen printing and sintered at 1250°C for 2 hours. The sensitive electrode is prepared by mixing LSCF powder and a binder at a mass ratio of 1:1 to prepare a slurry, and then the slurry is printed on both sides of the electrolyte substrate by screen printing and sintered at 1050°C for 2 hours, to obtain the required sensor 6 for testing, as shown in Figure 2 .

[0058] The device detects the change of Cr evaporation rate of alloy in real time in-situ by recording the change of electric signal of the sensor 6. When the Cr-containing alloy is in a high-temperature and high-humidity environment, gaseous Cr species (CrO3, CrO2(OH)2) are volatilized, and when the gaseous Cr species diffuse to the surface of the sensitive electrode, adsorption and chemical reaction occur, and the gaseous Cr species that are adsorbed occupy the active potential of the sensitive electrode, causing the impedance of the sensitive electrode to change. In addition, the gaseous Cr species reacts with the LSCF sensitive electrode as follows:

[0059] La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3 + xCrO3(g) → La 0.6 Sr 0.4-x Co 0.2 Fe 0.8O3+xSrCrO4;

[0060] This process generates SrCrO4, which occupies the active potential of the sensitive electrode and causes a change in the electrode's impedance. By recording the changes in the electrical signal and correlating them with a calibration curve, real-time in-situ quantitative detection of the Cr volatilization rate in the alloy can be achieved.

[0061] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0062] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An electrochemical sensing device for in-situ detection of the chromium volatilization rate in alloys, characterized in that, include: A sensor, connected to the sample to be tested, is used to collect the electrical signals of the sample. A sensor fixing device is used to fix the sensor and the sample to be tested; A heating device, connected to the sensor fixing device, is used to heat the sensor and the sample to be tested to a preset working temperature; A signal collection device, connected to the sensor, is used to collect the electrical signal.

2. The electrochemical sensing device for in-situ detection of Cr volatilization rate in alloys according to claim 1, characterized in that, The sensor has a double-sided symmetrical stacked structure.

3. The electrochemical sensing device for in-situ detection of Cr volatilization rate in alloys according to claim 2, characterized in that, The sensor includes: First outer side and second outer side; The first outermost layer to the second outermost layer are, in sequence, a first sensitive electrode layer, a first barrier layer, an electrolyte layer, a second barrier layer, and a second sensitive electrode layer; Both the first and second sensitive electrode layers are used to adsorb gaseous Cr species volatilized from the sample to be tested; the first barrier layer is used to prevent Sr elements in the first sensitive electrode layer from diffusing into the electrolyte layer, and the second barrier layer is used to prevent Sr elements in the second sensitive electrode layer from diffusing into the electrolyte layer. The electrolyte layer is used to conduct O ions between the two sides of the first and second sensitive electrode layers.

4. The electrochemical sensing device for in-situ detection of Cr volatilization rate in alloys according to claim 2, characterized in that, The electrolyte layer is prepared by a casting method.

5. An electrochemical sensing device for in-situ detection of the Cr volatilization rate in alloys according to claim 2, characterized in that, Both the first barrier layer and the second barrier layer are prepared by screen printing.

6. The electrochemical sensing device for in-situ detection of Cr volatilization rate in alloys according to claim 1, characterized in that, The sensor fixing device is a hollow cylindrical high-temperature resistant alumina ceramic tube and is located inside the heating device.

7. An electrochemical sensing device for in-situ detection of the Cr volatilization rate in alloys according to claim 6, characterized in that, The sensor fixing device is provided with an air inlet path and an air outlet path, wherein the flow rate and flow volume of the incoming and outgoing gas are controlled by a flow meter.

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