CN1082184C - Method for detecting metal oxidation kinetics - Google Patents

Abstract

The present invention relates to a method for detecting metal oxidation kinetics on the basis of a solid electrochemical principle. Oxidation kinetics curves are obtained by means that oxygen energy consumed in a metal oxygenizing process is converted into electric charge energy by an electrochemical process. A ZrO2 solid electrolyte pipe, an isolating valve and a quartz pipe form a closed system. Platinum electrodes are deposited or coated on an outer wall in the ZrO2 solid electrolyte pipe to form an electrochemical oxygen pump. An oxidation sample and the solid electrolyte electrochemical oxygen pump are respectively arranged at different temperature to realize that oxidizing temperature and oxygen pressure can be adjusted. Oxidation kinetics curves can be obtained by making graphs for the current integration of the oxygen pump and oxidation time and can be used for measuring metal and alloy oxidation kinetics and the kinetics of a volatile oxide generating system. The method of the present invention has the advantages of simple structure, simple operation, high precision of test data, low operating cost and control and data treatment by a computer.

Description

A kind of mensuration burning dynamics methods

The invention belongs to electrochemical method test metal material performance, particularly measure the metal material oxidation kinetics with electrochemistry of solids.

The test of oxidation kinetics is the important means of development high temperature oxidation resisting material.The test of oxidation kinetics will correctly demonstrate certain after all exactly can characterize parameter that oxidation reaction carries out degree rule over time.Traditional oxidation kinetics method of testing mainly is the consumption of directly measuring the sample weightening finish or measuring oxygen.The instrument of measuring weightening finish mainly contains the test macro and the high-precision electronics equality in hot day of analytical balance, precision spring formation.The test system structure that analytical balance or precision spring constitute is simple, operation is succinct, but the precision of data and reappearance are relatively poor; Electronics thermobalance measurement data precision height, favorable reproducibility, but therefore equipment complexity, operation inconvenience, equipment and operating cost costliness, high to the laboratory environment requirement still can not obtain widespread usage.The method of measuring zmount of oxygen consumption mainly is volumetric method and pressure application.The advantage of volumetric method is that under low pressure sensitivity is higher, but its limitation is to test in the pure oxygen of 13332.2～93325.4Pa, mixing of temperature variation, foreign gas or inert gas can bring measuring error, can not be used to generate the system of volatile products.The advantage of pressure application is that device is simple, and sensitivity is also higher, but shortcoming is difficult realization of accurate measurement of pressure, especially for low pressure, need calibratedly, the surface cleanliness of sample is had higher requirements, can not be used to produce the system of volatility corrosion product or secondary air.

Since the 1880s solid electrolyte was found, solid electrolyte had obtained in the thermodynamic study field using widely, and is incorporated into dynamic (dynamical) research gradually, studies comprising oxidation.Nineteen sixty-five, V.BTare and H.Schmolzried have reported the ZrO with the CaO stabilization ₂Solid electrolyte is used for the mensuration of iron oxidation reaction rate constant.Its principle is to utilize solid electrolyte in suitable operating temperature range, when its both sides partial pressure of oxygen there are differences, can constitute the characteristic of an oxygen concentration difference electrochemical cell.In the experiment test, the partial pressure of oxygen that makes solid electrolyte one side of creating conditions is controlled by the oxidation reaction speed of iron, it is constant that the partial pressure of oxygen of opposite side keeps, then electromotive force one time curve of oxygen concentration difference electrochemical cell by record can draw the oxidation reaction beginning and ending time, can calculate Oxidation Rate Constants of Antioxidants by correlation formula again.The limitation of the method is, requires high to specimen preparation; Can only under specific partial pressure of oxygen, test; Probe temperature is confined in the solid electrolyte operating temperature range.People such as C.Y.Yang then utilize ZrO ₂+ Y ₂O ₃The three-electrode system that solid electrolyte constitutes for the basis carries out the research of metal initial oxidation behavior.Its weak point is that solid electrolyte/metal interface is not equal to actual oxidizing atmosphere/metal interface, and partial pressure of oxygen can not be adjusted; The temperature range of research must be consistent with the operating temperature range of solid electrolyte; Can not arbitrarily change.Therefore, the electrochemistry of solids method does not obtain substantial application always as yet in the oxidation kinetics test.

The purpose of this invention is to provide a kind of test burning dynamics methods based on the electrochemistry of solids principle.Be converted to the quantity of electric charge by oxygen amount through electrochemical process and obtain the oxidation kinetics curve, realize that oxidizing temperature and oxygen presses adjustablely, can be used for producing the kinetic test of the system of volatility oxidation product the consumption of burning process.The test data of this method has high precision, control and data handling machineization.

Mensuration burning dynamics methods of the present invention is by ZrO ₂Solid electrolyte tube, vacuum isolating valve and quartz ampoule constitute a closed system, at ZrO ₂Deposition or coating platinum electrode constitute electrochemistry oxygen pump on the solid electrolyte tube inside and outside wall, oxygen are pumped or pumps into closed system by electrochemistry oxygen pump, and the oxygen that keeps being in setting in the closed system is pressed: ZrO ₂The coupling part of solid electrolyte tube and quartz ampoule is controlled at constant room temperature, ZrO ₂Two ends of solid electrolyte tube and quartz ampoule place the high-temperature heater of two independent temperature controls respectively, and are controlled at ZrO separately ₂The design temperature of 600-900 ℃ of work temperature of solid electrolyte and burning, sample is placed on quartz ampoule inner room warm area, treat that gas composition and pressure adjustment in the closed system are stable to the testing setup value, with the magnetic supplying system sample is pushed into the oxidation high-temperature region by the room temperature district, oxidation kinetics test beginning.Variation that oxygen is pressed during the oxidation of gaseous tension transmitter monitoring sample and output corresponding standard current signal; Control executive system control oxygen pump work by computing machine, digital-to-analogue, analog to digital converter, external control power supply etc. constitute pumps into oxygen to closed system, and it is in constant setting value that the oxygen in the maintenance system is pressed.Computer control system was gathered the gaseous tension signal every one second by mould one number converter when the oxygen pump work, the force value with acquired signal and setting compares simultaneously, the on off state of decision oxygen pump.When being in open mode, the oxygen pump pumps into oxygen to closed system with continuous current.Oxygen pump current integration is obtained flowing through the quantity of electric charge of oxygen pump, itself and between the oxygen amount that the oxygen pump transports, meet the Farady law, can obtain the oxygen increment of closed system thus, i.e. the oxidation increment of metal, oxidation increment and time relation are measured burning dynamics.

Fig. 1 is the brief configuration figure of burning kinetic test method of the present invention.

As shown in Figure 1, ZrO₂ Solid electrolyte tube 2 and quartz ampoule 1 pass through the vacuum seal rubber seal at openend Enter in the coupling flange 3, two flanges are coupled to each other again, one of them flange upper joint vacuum isolating valve 15, Vacuum isolating valve 15 directly and charge valve 16 join. Electrochemistry oxygen pump is by at ZrO₂Solid electrolyte tube 2 Inside and outside wall on deposition or apply two platinum electrodes 6, and the inside and outside platinum lead of corresponding connection consists of platinum in it Lead is drawn through connecting flange 3. Two blind ends of electrochemistry oxygen pump and quartz ampoule are equipped with high temperature separately Heating furnace 4,5. Inside and outside two permanent magnets 12 of parallel placement of quartz ampoule, permanent magnet and ceramic bar or stone in the pipe The push rod 13 that the FeCrAI silk of English silk or platinum filament or pre-oxidation is made connects push rod 13 another termination samples Product 14. Gas pressure transmitter 9 one ends and ZrO₂The attached method of solid electrolyte tube 2 and quartz ampoule 1 Blue 3 join, and the other end and mould one number converter 10 join. External control power supply potentiostat 7 one ends connect ZrO₂Two platinum electrodes 6 of solid electrolyte 2, the other end and digital-analog converter 8 while and computers Control system 11 is joined. Thermostatic control system is 17.

The realization of purpose of the present invention specifically describes as follows in conjunction with the brief configuration figure of oxidation kinetics method of testing:

Before the test beginning, intrasystem gas composition of closed test and pressure are transferred to the testing setup value by vacuum isolating valve 15 and gas filling valve 16.Gaseous tension is measured and is exported with the normalized current signal by gaseous tension transmitter 9.During the test beginning, sample is pushed the high-temperature oxydation district rapidly by the room temperature district by the sample supplying system.After the test beginning, computer control system 11 was passed through analog-digital converter 10 acquisition system gaseous tension signals every one second, and itself and force value of setting compared: if the collection value is less than setting value, show that oxidation causes the consumption of oxygen, then computer control system is exported the external control voltage working signals according to the pump oxygen current value of program setting and through D-A converter 8 to external control power supply potentiostat 7.External control power supply potentiostat is exported constant voltage in view of the above and is converted to continuous current by oxygen pump two electrodes through transfer resistance.Direction of current flow makes oxygen be transported in the pipe by pipe is outer for to flow to external electrode by the oxygen inner pump electrode through solid electrolyte.In oxygen pump work process, computer control system per second acquisition system internal pressure signal.If the collection value equals setting value, show that the oxygen of oxidation consumption is replenished.Computer control system instruction external control power supply potentiostat output no-voltage, the oxygen pump stops the work of going up, and is in off state; If the collection value is less than setting value, then the oxygen pump works on, and is in out state.Judge the on off state of oxygen pump before the operation of computer control system per second earlier, so that can correctly carry out pump oxygen current integration.Can adjust the size of pump oxygen electric current at any time, keep the pressure surge minimum in the test macro.Because the oxygen amount that enters in the closed system by the oxygen pump in a certain period equals the used up oxygen amount of the burning same period, this oxygen amount and flow through between the quantity of electric charge of oxygen pump and meet the Farady relational expression, so just can calculate the oxidation increment of the unit area of a certain section time build-in test sample behind the current integration.In the oxidation test process, the size of pump oxygen electric current can be adjusted at any time, so that the pressure in the test macro keeps minimal ripple.Pressing time interval that control program sets obtains the oxidation increment of unit area of sample and the relation curve of oxidization time, promptly obtains the oxidation kinetics curve of sample.The oxidation kinetics curve can screen display, and data (oxidation increment-time) can the document form data deposit, can select coordinate to be figure on demand through the drawing subsystem.

In the present invention, owing to adopt solid electrolyte tube, quartz ampoule and vacuum isolating valve to constitute the closed test system, guaranteed to keep in the closed system in the test process constant oxygen to press, the oxygen that burning consumes only replenishes by the oxygen that electrochemistry oxygen pump pumps into.The working temperature of electrochemistry oxygen pump and the temperature of burning are provided by the heating furnaces of two independent controls, have therefore overcome traditional solid electrolyte limitation that probe temperature must be consistent with the solid electrolyte working temperature in oxidation research.Thermostatic control system has guaranteed that test macro keeps steady temperature in whole test process, and the fluctuation of gaseous tension in the system that has avoided causing because of environmental temperature fluctuation has guaranteed the normal operation of test macro.Partial pressure of oxygen is set easily, and oxygen is pressed wide ranges 5066Pa-101325Pa.Specimen preparation and oxidation product situation are not had specific (special) requirements, can be used for generating the oxidation kinetics test of volatile products system.By the switch of computer control system control oxygen-generating pump, the oxygen amount that oxidation consumption falls is obtained by the integral and calculating of the electric current that flows through the oxygen pump to the oxygen pump work time.The measuring accuracy height has been realized test data collection, the computerize of handling and analyzing, and has greatly overcome the personal error of introducing in the conventional oxidation kinetic test; Whole test system is simple in structure, control operation is succinct.

Adopt the present invention that five kinds of metals such as pure iron, zirconium, titanium, nickel, copper are carried out the oxidation kinetics test, operation steps is as follows:

1. will treat that oxidation sample is connected with push rod, place the interior room temperature district of quartz ampoule of proving installation.

2. with ZrO ₂Flange on solid electrolyte tube and the quartz ampoule connects (between two flanges cushioning fluororubber vaccum seal ring and apply high vacuum seal fat) by bolt.

3. the intrasystem total gas pressure of closed test is transferred to a little less than the test desired level, close vacuum isolating valve and gas filling valve.

4. the pressure changing in the continuous monitor system then can not carried out subsequent operation if seepage takes place.

5. two high temperature furnaces are controlled to oxygen pump and sample oxidation probe temperature respectively, start thermostatic control system simultaneously.

6. treat that two high temperature furnaces rise to the temperature of regulation, the pressure changing in the continuous monitor system.If intrasystem pressure causes that the pressure unit variation of output signals is no more than ± 1mV, can think that then system pressure reaches stable.By vacuum isolating valve, gas filling valve, outer source of the gas, oil-sealed rotary pump or oxygen pump system's internal pressure and gas composition are transferred to the test desirable value.

7. computing machine and control system are ready, and sample is pushed into the high-temperature oxydation district by the room temperature district, and computing machine and control system bring into operation, oxidation test beginning.

8. in the test process, poor according to actual pressure value in the system and experiment initial set value, (generally speaking, when the test beginning, the electric current of oxygen pump is bigger, and the later stage is less to adjust the electric current of oxygen pump.)。

9. during end of test (EOT), close the oxygen pump, sample is retreated to the room temperature district by the high-temperature oxydation district, open ring flange after the cooling, take out sample.

10. the data of computer acquisition are handled on demand, obtained the oxidation kinetics curve map.

Fig. 2 is that pure iron is at 673 ℃ of airborne oxidation kinetics curves of pressure 1atm.

Fig. 3 is the oxidation kinetics curve of zirconium in 800 ℃ of pressure 1atm pure oxygens.

Fig. 4 is that titanium is at 800 ℃ of airborne oxidation kinetics curves of pressure 1atm.

Fig. 5 is that nickel is at 900 ℃ of (airborne oxidation kinetics curves of pressure 1atm.

Fig. 6 is respectively 0.06,0.21 and oxidation kinetics curve during 1atm for copper 673 ℃ of air pressures.

Can see that from above-mentioned oxidation kinetics curve the oxidation kinetics curve smoothing of the present invention's actual measurement does not have Significantly disturb sudden change, reflected exactly the oxidation kinetics behavior of different metal under different condition.

Claims (5)

1, a kind of mensuration burning dynamics methods is used solid electrolyte, it is characterized in that, by ZrO ₂Solid electrolyte tube, quartz ampoule and vacuum isolating valve constitute a closed system, keep required oxygen to press; ZrO ₂The coupling part of solid electrolyte tube and quartz ampoule is controlled at constant room temperature, ZrO ₂Other two closed ends of solid electrolyte tube and quartz ampoule place the high-temperature heater of two independent temperature controls respectively, and they are heated to ZrO ₂The design temperature of the working temperature 600-900 of solid electrolyte ℃ and burning; ZrO ₂Solid electrolyte tube inside and outside wall deposition or coating platinum electrode constitute electrochemistry oxygen pump, oxygen are pumped or pumps into closed system by electrochemistry oxygen pump, and the oxygen that keeps setting in the closed system is pressed; Sample is placed on the interior room temperature district of quartz ampoule, treats that gas composition and the pressure adjustment in the closed system stablized to the testing setup value, with the magnetic supplying system sample is pushed into the oxidation high-temperature region by the room temperature district, oxidation kinetics test beginning; The variation that gaseous tension transmitter monitoring oxygen is pressed is also exported corresponding electric signal, and computer control system pumps into oxygen according to this signal controlling oxygen pump work to closed system, makes the oxygen in the system press the value that remains on setting; Measure and calculate oxidation kinetics data and the automatic oxidation kinetics curve of drawing that oxygen pump electric current obtains sample.

2, method according to claim 1, it is characterized in that, computer control system is when the oxygen pump work, gathered the gaseous tension signal every one second by analog-digital converter, force value with acquired signal and setting compares simultaneously, the on off state of decision oxygen pump pumps into oxygen with continuous current to closed system when the oxygen pump is in open mode.

3, method according to claim 1 and 2 is characterized in that, the gaseous tension in the closed system is by pressure transmitter measurement, and exports with the normalized current signal.

4, method according to claim 1 and 2 is characterized in that, in the oxidation test process, the size of pump oxygen electric current can be adjusted at any time, keeps the pressure surge in the test macro to be in minimum state.

5, method according to claim 1 and 2 is characterized in that, the oxidation kinetics data are calculated by oxygen pump current integration and obtained.

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