CN1230668C - Pressure, density and temperature performance test method for hydrogen storing alloy - Google Patents

Abstract

The present invention relates to a method for testing the performance of hydrogen storage alloy PCT. The total pressure value P<t> is measured by a pressure gauge or an ionization gauge; the mass spectrometry of all gas in a sample chamber is measured by a four-pole mass spectrometer; the subtle change of the mass of a thin film, namely the change of the hydrogen absorbing amount or the hydrogen releasing amount of a thin film is measured by a quartz oscillating micro balance weigher. Hydrogen partial pressure pH2 and hydrogen concentration C<H> are obtained according to a formula; consequently, a PC curve is drawn. In the present invention, hydrogen partial pressure is measured by mass spectroscopy, and a dynamic method of quartz oscillation micro balance is combined with the mass spectroscopy to measure hydrogen content; when the hydrogen partial pressure is measured, the hydrogen content of a hydrogen storage material is measured. Because the mass measuring method and the pressure measuring method are both high-accuracy measuring methods; therefore, the unprecedented precision of the measurement is obtained.

Description

A kind of low equilibrium pressure pressure, density and temperature performance test method for hydrogen storing alloy

Technical field:

The present invention provides a kind of mensuration to have the method that ultralow hydrogen ionic dissociation equilibrium is pressed the PCT curve of material especially, and higher measuring accuracy has been arranged for measuring a kind of method of hydrogen-storage alloy Pressure-concentration-temperature (PCT) (PCT) curve.

Background technology

The method of mensuration PCT curve commonly used has volumetric method and mass method.

The capacity ratio juris is to change the variation that (raising or reduction) calculates the hydrogen content of hydrogen storage material according to the Hydrogen Vapor Pressure in the constant volume that is connected with the hydrogen storage material sample chamber.Filling hydrogen or putting the hydrogen pressure variation and accumulate the interior hydrogen concentration of calculating hydrogen storage material in the METHOD FOR CONTINUOUS DETERMINATION constant volume changes, thereby obtains the PC curve.When volumetric determination fills hydrogen process PCT curve, fill hydrogen according to the hydrogen amount of filling of estimation.Owing to be to fill the hydrogen amount, test more convenient by the Hydrogen Vapor Pressure adjustment sample of adjusting in the constant volume.And measure when putting the PCT curve of hydrogen, put hydrogen pressure control hydrogen desorption capacity by adjusting in the constant volume, when low pressure and ultralow pressure because pressure survey is inaccurate, difficulty energy measurement not even comparatively when measuring the PCT curve of low equilibrium pressure.

Mass method is by the suction hydrogen of continuous recording hydrogen storage material or puts the hydrogen mass change and the variation of corresponding equilibrium hydrogen pressure, thereby obtains the PCT curve.The advantage of mass method is to the direct measurement of being measured as of hydrogen or hydrogen desorption capacity, can be dynamically or measure the PCT curve statically, fill hydrogen and put the hydrogen process all very convenient for mensuration.

Above-mentioned two kinds of methods all run into the mensuration difficulty that hydrogen balance is pressed when measuring the PCT curve of ultralow equilibrium pressure material, and inaccurate problem.Because under low air pressure condition, except the dividing potential drop of hydrogen, the adsorbed gas of vacuum chamber inside surface, bigger to the contribution of general pressure as the dividing potential drop of water vapor, nitrogen etc., the hydrogen dividing potential drop needs separating and measuring.In the PCT measuring technology, accurate mensuration low and ultralow equilibrium pressure (particularly ionic dissociation equilibrium pressure) is the technical barrier that needs to be resolved hurrily.Another difficult problem is under ultralow equilibrium pressure test condition, and the variable quantity of the suction of material, hydrogen desorption capacity and suction, hydrogen desorption capacity is at the very little order of magnitude, so the accurate measurement of hydrogen storage material hydrogen content also is a problem demanding prompt solution.

For obtaining the data of some low equilibrium pressure under the room temperature, practices well is the P-C curve of measuring under the high temperature, and extrapolation is calculated then.Computation process is as follows:

In charging and discharging H-H reaction, following relation is arranged according to thermodynamic argument:

$\ln P_{H_2}=\frac{\mathrm{\&Delta;}{H}^0}{\mathrm{RT}}-\frac{{\mathrm{\&Delta;S}}^0}{R}$

Δ H wherein ⁰Be the standard enthalpy change, Δ S ⁰Be standard entropy change, R is a gas law constant, Δ H ⁰And Δ S ⁰It is constant.So lnP _H2With Between have linear relationship.So, can obtain lnP by the data of middle high temperature _H2With

Linear relationship, this linear relationship is extrapolated to room temperature, calculating can obtain the equalized pressure of room temperature.Therefore this method is a kind of indirect method of testing, and precision depends on the high temperature test precision.When probe temperature during,, the precision of extrapolation is reduced greatly because extrapolation can be amplified error far above room temperature.If material undergoes phase transition being heated in the probe temperature process by room temperature, then the linear relationship of high temperature can not be extrapolated to room temperature.Such as for the Ti material, when being heated to 320 ℃, the β phase transformation takes place, the equilibrium pressure data of room temperature just can not be calculated with the extrapolation of the data more than 320 ℃.Therefore the method for extrapolation has certain limitation, promptly can only measure the low-pressure low-temperature PCT performance of some specific materials that do not undergo phase transition, and measuring accuracy is relatively poor.

Summary of the invention:

The invention provides a kind of low equilibrium pressure hydrogen-storage alloy PCT performance test methods, it is characterized in that:

(1) under a certain temperature T under the low equilibrium pressure test condition, film hydrogen storage material to be measured is filled hydrogen or puts hydrogen;

(2) filling hydrogen or putting a certain moment in the hydrogen process, measure total pressure value P with pressure gauge _t, record the mass spectrum of sample chamber all gas with quadrupole mass spectrometer,

Calculate the hydrogen dividing potential drop P in this moment _H2, formula is as follows:

$P_{H_2}=P_t\&CenterDot;\frac{S_{H_2}}{S}=P_t\&CenterDot;\frac{\underset{n_1}{\overset{n_2}{\&Integral;}}{I}_n\mathrm{dn}}{\underset{1}{\overset{N}{\&Integral;}}{I}_n\mathrm{dn}}$

In the formula: S _H2, S is respectively the area at hydrogen peak and the area at all gas peak; I _nBe the intensity of ion flow; N is the measurement upper limit mass number of mass spectrograph; n ₁, n ₂Be respectively certain gas peak initial mass number and end of a period mass number; N is a mass number, and its value is in the mass number scope that mass spectrograph is measured;

Subtle change with the little balance instrumentation of quartz oscillation amount film quality is the variation that film is inhaled hydrogen or hydrogen desorption capacity;

Calculate hydrogen concentration C in this moment film hydrogen storage material to be measured sample _H:

For filling the hydrogen process:

$C_n=\frac{{\mathrm{\&Delta;M}}_q}{M_{\mathrm{film}}}$

For putting the hydrogen process:

$C_n=\frac{M_0-\mathrm{\&Delta;}{M}_q}{M_{\mathrm{film}}}$

M wherein _FilmBe the quality of hydrogen-storage alloy film, g; M ₀For putting the initial hydrogen content in the sample before the hydrogen, g; Δ M _qBe the variation of film quality, g; Computing formula is as follows:

$\mathrm{\&Delta;}{M}_q=-A\&CenterDot;\mathrm{\&Delta;}{f}_q\left(\frac{{\mathrm{\&rho;}}_{\mathrm{\&Delta;t}}{V}_q}{2f_q^2}\right)$

In the formula: A is the area of hydrogen storage material film, cm ²Δ f _qBe the frequency shift amount, Hz; f _qBe the response frequency before filling hydrogen or putting hydrogen, Hz; ρ _MBe the density of oxygen-storaged alloy film, g/cm ³V _qIt is the acoustic velocity 3.336 * 10 in the quartz ⁵Cms ^-1

(3) record according to said method and fill hydrogen or put P in the hydrogen process _H2Hydrogen balance pressure and C _HHydrogen concentration during balance, thus draw out the PCT curve.

The present invention hangs down equilibrium pressure hydrogen-storage alloy PCT performance test methods, and described calculating can realize with computer software at an easy rate.

What the present invention adopted is mass method, i.e. suction hydrogen by the continuous recording hydrogen storage material or put the hydrogen mass change and corresponding hydrogen dividing potential drop obtains the PCT curve.Key problem in technology is to adopt quadrupole mass spectrometer, has realized in the hydrogen storage material PCT curve test process hanging down the accurate measurement of equilibrium pressure and ultralow equilibrium pressure.Usually when equilibrium pressure material PCT curve was hanged down in test, the force value that conventional method records was other all gas general pressure value in hydrogen and the container.Other is meant the gas leakage gas of the venting (as water vapor) of vessel surface and container and pipeline, valve etc., and when Hydrogen Vapor Pressure was higher, as the order of magnitude of hydrogen partial pressure more than Pa, the dividing potential drop of other gas in the container can be ignored.The present invention adopts quadrupole mass spectrometer, the measurements and calculations hydrogen partial pressure, and hydrogen disassociation dividing potential drop scope is 5 * 10 ^-2Pa～5 * 10 ^-9Pa.

The four-electrode spectrum method is according to ion flow and the mass number curve measured, and deduction carries out integration with all peak shapes and obtains area after carrying on the back the end, the area of the gas of surveying (as the hydrogen) ratio that accounts for the total area promptly be the partial pressure mark of this gas.For specific element, as hydrogen, mass number is 2, obtains mass number and be the area at 2 peak, again divided by the total area at all peaks, multiply by total pressure after, obtain the partial pressure of hydrogen.Being calculated as follows shown in the formula of partial pressure.

$p_i=p_i\&CenterDot;\frac{s_i}{s}=p_i\&CenterDot;\frac{\underset{n_1}{\overset{n_2}{\&Integral;}}{I}_n\mathrm{dn}}{\underset{1}{\overset{N}{\&Integral;}}{I}_n\mathrm{dn}}$

P in the formula _iBeing the partial pressure of certain gas, is pressure values to be determined, singly refers to the partial pressure value of hydrogen in the PCT test; S _i, S is respectively the area at this gas peak and the area at all gas peak; I _nBe the intensity of ion flow; N is the measurement upper limit mass number of mass spectrograph; n ₁, n ₂Be respectively certain gas peak initial mass number and end of a period mass number; N is a mass number, and its value is in the mass number scope that mass spectrograph is measured.

Therefore the four-electrode spectrum method has solved the problems of measurement in low pressure condition therapeutic method to keep the adverse qi flowing downward body dividing potential drop.

In addition, the present invention fills in measurement, in the process of hydrogen desorption capacity, adopt the variation of the direct MEASUREMENTS OF THIN hydrogen storage material of the little balance of quartz oscillation (QCM) method hydrogen content.It is one of the highest method of present resolution that little day quadratic method of quartz oscillation measured mass change, its principle is the subtle change according to film quality, cause the change of quartz vibrator frequency,, calculate the change of film quality according to quartz vibrator frequency and frequency shift situation.The film quality variable quantity is shown below:

${\mathrm{\&Delta;M}}_q=-A\&CenterDot;\mathrm{\&Delta;}{f}_q\left(\frac{{\mathrm{\&rho;}}_M{V}_q}{2f_q^2}\right)$

Wherein, Δ M _qBe the mass change amount, g; A is the area of hydrogen storage material film, cm ²Δ f _qBe the frequency shift amount, Hz; f _qBe the response frequency before filling hydrogen or putting hydrogen, Hz; ρ _MBe the density of oxygen-storaged alloy film, g/cm ³V _qBe the acoustic velocity in the quartz, 3.336 * 10 ⁵Cms ^-1Therefore the change of quartz vibrator resonant frequency can reflect the variation of suction, hydrogen desorption capacity, has solved suction thus, has put the problems of measurement of the small quality change of the hydrogen storage material in the hydrogen process, thereby can measure suction hydrogen or hydrogen desorption capacity.

In sum, the present invention measures the hydrogen dividing potential drop with mass spectroscopy and measures hydrogen content in conjunction with little day quadratic method of dynamic quartz oscillation, measures the hydrogen content of hydrogen storage material when measuring the hydrogen dividing potential drop; Because mass measuring method and pressure measurement method all are high-precision measuring methods, therefore measurement reaches unprecedented precision.

Description of drawings:

Fig. 1 forms (P-C) curve with the room temperature pressure one of the titanium of the inventive method acquisition.

Embodiment:

Choose the quartz vibrator of selling on the electronic market, remove, use the piezoid that has plated the Au film in the oscillator and connect the oscillator that lead is made the little balance of quartz oscillation with the sealing shroud of machining process with oscillator.Then this piezoid is put into magnetron sputtering coater, single face plates the Ti film on piezoid.Obtain about 10 microns of Ti film thickness with the method for weighing, its diameter is 4 millimeters.The position of titanium film is to be plated on the golden film, and the scope that covers less than golden film.

Piezoid behind the plated film and connection electric wire thereof are moved in the PCT sample chamber.Be about to contain leaded oscillator and be plugged on the good binding post of insulation, and thermopair is fixed on the surface of hydrogen-storage alloy film.Sealed sample chamber then, and the sample chamber is evacuated to 10 ^-5The Pa magnitude.Begin the heated sample chamber then, insulation was 30 minutes after the temperature for the treatment of piezoid arrived 250 ℃.Then reduce temperature to 25 ℃ of room temperatures.Mensuration is filled the oscillator frequency f before the hydrogen ₀In the sample chamber, charge into the 50kPa high-purity hydrogen then, be heated to 250 ℃ simultaneously, be incubated and be cooled to room temperature after 30 minutes.Measure the oscillator frequency f ₁According to f ₀And f ₁Calculate the Ti film and inhale the hydrogen total amount.

Start mechanical pump and molecular pump then, when the vacuum tightness for the treatment of the sample chamber is better than 0.1Pa, start quadrupole mass spectrometer and oscillation power.Under the data that quadrupole mass spectrometer the records cooperation by the software of above-mentioned formula customization on computers, calculate the hydrogen partial pressure P of sample chamber in real time.The resonant frequency of piezoid is measured by oscillation power simultaneously, goes out the quality reduction according to real-time frequency computation part.Variation C according to hydrogen concentration in the Mass Calculation membrane of film suction hydrogen total amount, piezoid quality reduction, hydrogen-storage alloy film.Thereby obtain the PC curve of room temperature, see Fig. 1.According to curve, as seen in the platform midpoint, it is 4 * 10 that the ionic dissociation equilibrium of hydrogen is pressed ^-5Pa.

Existing equipment is most to be that volumetric method is tested.Because the restriction of measuring principle and technical conditions, energy measurement does not hang down equilibrium pressure, and the ionic dissociation equilibrium that more energy measurement is not low is pressed.Indivedual import equipments can realize the mass method measurement, and the test problem for low equilibrium pressure still can not carry out.Use method of the present invention to measure and be up to 5 * 10 ^-9The ionic dissociation equilibrium of Pa is pressed.In addition, in PCT low pressure and ultralow pressure test, yet there are no the report that uses little day quadratic method of quartz oscillation.

Claims (1)

1, a kind of low equilibrium pressure pressure, density and temperature performance test method for hydrogen storing alloy is characterized in that:

(1) under a certain temperature T under the low equilibrium pressure test condition, film hydrogen storage material to be measured is filled hydrogen or puts hydrogen;

(2) filling hydrogen or putting a certain moment in the hydrogen process, measure total pressure value P with pressure gauge _t, record the mass spectrum of sample chamber all gas with quadrupole mass spectrometer,

Calculate the hydrogen dividing potential drop p in this moment _H2, formula is as follows:

$p_{H_2}=p_t\&CenterDot;\frac{S_{H_2}}{S}=p_t{\&CenterDot;}_{\underset{1}{\overset{N}{\&Integral;}}{I}_n\mathrm{dn}}^{\underset{n_1}{\overset{n_2}{\&Integral;}}{I}_n\mathrm{dn}}$

In the formula: S _H2, _SBe respectively the area at hydrogen peak and the area at all gas peak; I _nBe the intensity of ion flow; N is the measurement upper limit mass number of mass spectrograph; n ₁, n ₂Be respectively certain gas peak initial mass number and end of a period mass number; N is a mass number, and its value is in the mass number scope that mass spectrograph is measured;

Subtle change with the little balance instrumentation of quartz oscillation amount film quality is the variation that film is inhaled hydrogen or hydrogen desorption capacity;

Calculate hydrogen concentration C in this moment film hydrogen storage material to be measured sample _H:

For filling the hydrogen process:

$C_H=\frac{{\mathrm{\&Delta;M}}_q}{M_{\mathrm{film}}}$

For putting the hydrogen process:

$C_H=\frac{M_0-{\mathrm{\&Delta;M}}_q}{M_{\mathrm{film}}}$

M wherein _FilmBe the quality of hydrogen-storage alloy film, g; M ₀For putting the initial hydrogen content in the sample before the hydrogen,

G; Δ M _qBe the variation of film quality, g; Computing formula is as follows:

${\mathrm{\&Delta;M}}_q=-A{\&CenterDot;\mathrm{\&Delta;f}}_q\left(\frac{{\mathrm{\&rho;}}_M{V}_q}{{2f}_q^2}\right)$

In the formula: A is the area of hydrogen storage material film, cm ²Δ f _qBe the frequency shift amount, Hz; f _qBe the response frequency before filling hydrogen or putting hydrogen, Hz; ρ _MBe the density of oxygen-storaged alloy film, g/cm ³V _qIt is the acoustic velocity 3.336 * 10 in the quartz ⁵Cm s ^-1

(3) record according to said method and fill hydrogen or put p in the hydrogen process _H2Hydrogen balance pressure and C _HHydrogen concentration during balance, thus draw out the PCT curve.

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