CN202676571U - Device for testing effective diffusion coefficient of weakly-adsorbed gas in large block nanoporous materials under low pressure - Google Patents

Device for testing effective diffusion coefficient of weakly-adsorbed gas in large block nanoporous materials under low pressure Download PDF

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CN202676571U
CN202676571U CN 201220293809 CN201220293809U CN202676571U CN 202676571 U CN202676571 U CN 202676571U CN 201220293809 CN201220293809 CN 201220293809 CN 201220293809 U CN201220293809 U CN 201220293809U CN 202676571 U CN202676571 U CN 202676571U
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air feed
pond
cell
valve
reference cell
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张睿
金鸣林
徐耀民
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Shanghai Institute of Technology
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Abstract

The utility model discloses a device for testing effective diffusion coefficient of weakly-adsorbed gas in large block nanoporous materials under a low pressure and application of the device. The device comprises a vacuum container system, a data acquiring system, a gas supplying bottle and the like, wherein the vacuum container system consists of a sample cell, a gas supplying cell, a reference cell, a calibration cell, a buffer tank and a vacuum pump; the sample cell is connected with the gas supplying cell through a valve and a pipeline; the gas supplying cell is connected with the reference cell through a valve and a pipeline arranged on the gas supplying cell, and is connected with the calibration cell, the buffer tank and the vacuum pump through valves and a pipeline which is arranged on the gas supplying cell and communicated with a four-way joint; the buffer tank is connected with the gas supplying bottle through a pipeline and a valve; the data acquiring system comprises a data collector and a computer connected with the data collector; and the data collector acquires data and transmits the data to the computer connected with the data collector. The device is simple in structure, and is applicable to the testing of the effective diffusion coefficient of weakly-adsorbed gas in the large block nanoporous materials under the low pressure.

Description

The determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar
Technical field
The utility model relates to the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar.
Background technology
When heat-barrier material was used for space industry and the heat insulation field of civilian movement, its volume and weight was the smaller the better, and the heat conductivility that therefore reduces heat-barrier material is most important.The superinsulation material is exactly a class material of the thermal conductivity thermal conductivity that is lower than still air under the same terms.In order to reduce the thermal conductivity of superinsulation material, the superinsulation material must be global formation or block materials, can reduce and eliminate like this gaseous exchange issuable hot short circuit of conducting heat, and the pore size of superinsulation material need to be less than the mean free path (70nm under room temperature and the normal pressure) of air molecule.And when superinsulation material nano hole during less than 70nm, gas coefficient of diffusion therein significantly reduces, mainly take Knudsen diffusion as main, and effective diffusion cofficient is less, it is more remarkable that gas heat-transfer suppresses, so the effective diffusion cofficient of gas in the superinsulation material is to weigh the important indicator whether gas heat-transfer is significantly suppressed.
In high temperature solid oxide fuel cell, require its electrode material both to have higher specific surface and improve its catalytic activity, require again it to have very high ionic conductivity, therefore its electrode material must be whole block, like this, ion just has very low conduction resistance on its continuous skeleton, simultaneously gaseous fuel and the supply of oxygen and the eliminating of gaseous product requires the effective diffusion cofficient of gas in the electrode material of this whole bulk to want large.Therefore the effective diffusion cofficient of gas in the high temperature solid oxide fuel cell electrode material of whole bulk is one of important indicator of weighing its performance.
Above-mentioned application requires assay method and the device of a kind of gas effective diffusion cofficient in large block material nano hole.
At present, be used for gas at the determinator of material effective diffusion cofficient, develop mainly for catalyst material and molecular sieve such as gravimetric method, volumetric method, chromatography, zero column length method etc., because the size of catalyst granules only has about 1mm, so these determinators are only applicable to the mensuration of the effective diffusion cofficient of powdered sample.
Such as the gravimetric method take the intelligent weight adsorption instrument of Britain Hiden company as representative, its sample is thin slice or the spherical granule of 0.5mm, and weight can not be greater than 150mg.Because the weight resolution of gravimetric method only is 10 -6G/g, and long 1-3.8s of response time are for the agglomerate body sample determination difficulty of weak absorption.
The volumetric method Pressure Sensor Precision is high, good stability, response time short (20-50ms).High 1 order of magnitude of weight resolution weight/power ratio method of sample.Yet the analytic solution of volumetric method diffusion equation are very complicated, can not get simply and intuitively separating.At present, this method only can be used for the good sample of symmetry, such as the mensuration of sheet and uniform-spherical particle.
Yet, for superinsulation material or solid oxide fuel cell electrode material, the characteristics of its fragility are so that prepare laminar very difficult with the uniform-spherical particle, namely allow to prepare such sample, sample preparation so that its defective content significantly increase, and defective can cause the change of effective diffusion cofficient, therefore can not represent the original state of its sample.
Up to now, there is no both at home and abroad for weak adsorbed gas mensuration system of effective diffusion cofficient in the agglomerate body mano-porous material under the infrabar and relate to.
Summary of the invention
One of the purpose of this utility model is the determinator that weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar is provided in order to address the above problem.This device adopts the finite difference numerical evaluation, match pressure diffusion Solving Partial Differential Equations effective diffusion cofficient based on volumetric method, be applicable in theory the sample of any shape, therefore, the sample structure of having avoided sample preparation to cause destroys, and specimen has good representativeness.
The technical solution of the utility model
The determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar, its structural representation is measured system, data acquisition system (DAS) and air feed bottle 23 by vacuum tank system, temperature control and mensuration system, dynamic pressure and is formed as shown in Figure 1;
Described vacuum tank system by sample cell 1, air feed pond 2, reference cell 3, demarcate pond 4, surge tank 5 and vacuum pump 22 and form, air feed pond 2 is 2-3:1 with the volume ratio of sample cell 1;
Described sample cell 1 is connected with air feed pond 2 behind valve 15 by pipeline, air feed pond 2 is provided with one road device for cleaning pipeline and crosses valve 16 and be connected with reference cell 3, also be provided with on the air feed pond 3 behind one road device for cleaning pipeline four-way respectively through valve 19,18,17 with demarcate pond 4, surge tank 5 and vacuum pump 22 and link to each other;
Described surge tank 5 also is provided with a pipeline and links to each other with air feed bottle 23 through valve 21, in addition, also is provided with the valve 20 of a realization emptying on the surge tank;
Described dynamic pressure is measured system and is namely comprised absolute pressure meter 10,2 differential pressure gauges that are provided with 11 of reference cell 3 and air feed pond that reference cell 3 is provided with, 3 differential pressure gauges that are provided with 12 of sample cell 1 and reference cell;
Described temperature control and mensuration system comprise constant temperature oven 6, air feed pond 2 temperature probes 7 and sample cell 1 temperature probe 8 and sample cell constant temperature oven 9;
Above-mentioned air feed pond 2, reference cell 3 is demarcated pond 4, surge tank 5 and subsidiary pipeline, valve and and measurement instrument all be placed in the constant temperature oven 6;
Described data acquisition system (DAS) comprises data acquisition unit 13 and coupled computing machine 14 thereof, sends into coupled computing machine 14 after the data acquisition that data acquisition unit 13 sends differential pressure gauge 12, air feed pond temperature probe 7 and the sample cell temperature probe 8 of 1 of the differential pressure gauge 11 in 2 in the absolute pressure meter 10 on the reference cell 3, reference cell 3 and air feed pond, reference cell 3 and sample cell is come;
The maximum range of the differential pressure gauge 12 that the differential pressure gauge 11 that described reference cell 3 and air feed pond are 2 and reference cell 3 and sample cell are 1 is ± 10 torr, and precision is 0.15% of reading, and the response time is less than 50ms;
The picking rate that described data acquisition unit 13 gathers each parameter is 2-4/second;
Utilize the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under above-mentioned a kind of infrabar to the weak adsorbed gas method for measuring that effective diffusion cofficient carries out in the agglomerate body mano-porous material under the infrabar, comprise container demarcation, gas displacement, system balancing, mensuration process and data processing five steps, specific as follows:
(1), container is demarcated:
Measure to demarcate the volume in pond 4 with the water filling weight method, take the volume of demarcating pond 4 as benchmark, utilize the Ideal-Gas Equation, demarcate the volume of air feed pond 2 and sample cell 1, be recorded as respectively V1 and V;
(2), gas displacement:
Agglomerate body mano-porous material sample
Figure 204404DEST_PATH_IMAGE001
Pack in the sample cell 1, Open valve 20,21 purges surge tank 5 with the weak adsorbed gas in the air feed bottle 23, and valve-off 20,21 afterwards;
Valve-off 18 is opened valve 15,16,17, starts 22 pairs of sample cells 1 of vacuum pump, air feed pond 2 and reference cell 3 and vacuumizes, and shows that pressure are 0 to the absolute pressure meter 10 of reference cell 3; Open valve 21, weak adsorbed gas from air feed bottle 23 is entered surge tank 5, valve-off 21 afterwards, open valve 18, allow the weak adsorbed gas of surge tank 5 enter sample cell 1, air feed pond 2 and reference cell 3, when the absolute pressure meter of reference cell 3 shows that pressure reaches pressure to be determined, valve-off 18;
(3), system balancing:
Valve-off 15 and 16, Open valve 18, allow the weak adsorbed gas of surge tank 5 enter air feed pond 2, the pressure differential of the differential pressure gauge 11 between air feed pond 2 and reference cell 3 is 7.5-9.5torr, valve-off 18 is waited for 1-3h, until test macro reaches equilibrium state, be sample cell 1, the temperature and pressure of air feed pond 2 and reference cell 3 is time to time change not substantially;
(4), mensuration process:
Moment is opened valve 15, i.e. t〉0, volume is V 1Air feed pond 2 in weak adsorbed gas enter the sample cell 1 that volume is V by valve 15, gaseous tension in the sample cell 1 rises, because weak adsorbed gas is to agglomerate body mano-porous material sample
Figure 665472DEST_PATH_IMAGE001
Interior scattering and permeating, the pressure in the sample cell 1 reaches after the maximal value, and prolongation in time descends gradually, before the mensuration, turn-on data collector 13 and data acquisition computer 14, every 500ms records a secondary data, and data comprise:
Differential pressure gauge 12 pressure P between the temperature T of sample cell 1 and sample cell 1 and the reference cell 3 d(t);
The temperature T in air feed pond 2 1And differential pressure gauge 11 pressure P between air feed pond 2 and the reference cell 3 d 1(t);
Absolute pressure meter 10 pressure P of reference cell 3 0(t);
Like this, the pressure P of sample cell 1 (t) is: P (t)=P d(t)+P 0(t); The pressure P 1 (t) in air feed pond 2 is: P 1(t)=P d 1(t)+P 0(t);
(5), data are processed:
According to pressure diffusion partial differential equation formula, agglomerate body mano-porous material sample in the sample cell 1
Figure 829737DEST_PATH_IMAGE001
Under satisfying, interior gaseous tension P establishes an equation (1):
Figure 2012202938094100002DEST_PATH_IMAGE002
（1）
Wherein, D is effective diffusion cofficient;
Φ is agglomerate body mano-porous material sample
Figure 507581DEST_PATH_IMAGE001
Porosity;
P0 is sample cell 1 at t=0 pressure constantly, and namely t=0 is constantly the time in the step (4), and the pressure P of sample cell 1 (0) is: P (0)=P d(0)+P 0(0);
Pc is agglomerate body mano-porous material sample
Figure 985967DEST_PATH_IMAGE001
At the terminal pressure of t=t during the moment, namely identical in the pressure P (t) of t=t during the moment with sample cell 1, x 0, y 0And z 0Be agglomerate body mano-porous material sample
Figure 363858DEST_PATH_IMAGE001
The size of three-dimensional, the in time variation of t of the pressure P in working sample pond 1 (t), i.e. the terminal pressure Pc(x of above-mentioned equation (1) 0, y 0, z 0, t);
Because the Ideal-Gas Equation is satisfied in the weak adsorbed gas in sample cell 1 and the air feed pond 2, that is:
Figure 902287DEST_PATH_IMAGE003
（2）
Wherein,
Figure DEST_PATH_IMAGE004
Gaseous tension;
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Gas volume;
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The amount of gaseous matter;
Figure 83925DEST_PATH_IMAGE007
Ideal gas constant;
Figure DEST_PATH_IMAGE008
Temperature;
T is constantly the time, the amount of substance of the weak adsorbed gas in the sample cell 1
Figure 316323DEST_PATH_IMAGE009
Can try to achieve by the mass balance of air feed pond 2 and sample cell 1, that is:
Figure DEST_PATH_IMAGE010
（3）
Wherein, Vs is agglomerate body mano-porous material sample
Figure 963336DEST_PATH_IMAGE001
Volume, calculate with the three-dimensional digital method of taking pictures;
Figure 913974DEST_PATH_IMAGE011
With Be respectively the middle sample cell 1 of step (4) at the t=0 moment and t=t pressure constantly,
Figure 734163DEST_PATH_IMAGE013
With
Figure DEST_PATH_IMAGE014
Be respectively the middle air feed pond 2 of step (4) at the t=0 moment and t=t pressure constantly;
With Be respectively the temperature in the middle sample cell 1 of step (4) and air feed pond 2;
V and V 1Be respectively the air feed pond 2 of demarcation in the step (1) and the volume of sample cell 1;
Because , then during t=t, diffuse into agglomerate body mano-porous material sample
Figure 784573DEST_PATH_IMAGE001
In the amount of gaseous matter
Figure 408453DEST_PATH_IMAGE009
Can be calculated by following formula (3);
At agglomerate body mano-porous material sample
Figure 615443DEST_PATH_IMAGE001
Inside since particle between have nano-pore, externally under the gas pressure, weak adsorption gas molecule can penetrate in the nano-pore, at this little space (d
Figure DEST_PATH_IMAGE018
) in, satisfy the ideal gas formula, obtain:
Φ
Figure 165111DEST_PATH_IMAGE019
d
Figure DEST_PATH_IMAGE020
=
Figure 28025DEST_PATH_IMAGE021
d
Figure DEST_PATH_IMAGE022
Figure 190016DEST_PATH_IMAGE023
Φ
Figure DEST_PATH_IMAGE024
d
Figure 454775DEST_PATH_IMAGE020
=d
Figure 909765DEST_PATH_IMAGE022
（4）
At agglomerate body mano-porous material sample
Figure 322292DEST_PATH_IMAGE001
Interior integration obtains t=t during the moment, penetrates into agglomerate body mano-porous material sample Interior total weak adsorbed gas amount of substance:
Figure 469556DEST_PATH_IMAGE025
d
Figure 924808DEST_PATH_IMAGE020
=
Figure DEST_PATH_IMAGE026
=
Figure 496735DEST_PATH_IMAGE027
（5）
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Can be according to agglomerate body mano-porous material sample
Figure 738415DEST_PATH_IMAGE001
The three-dimensional digital terminal pressure Pc(x that takes pictures image, above-mentioned pressure diffusion partial differential equation (1) and measure 0, y 0, z 0, t), obtain with the method for finite difference numerical evaluation;
Because in practical problems,
Figure 364569DEST_PATH_IMAGE027
Measurement error is arranged,
Figure 423792DEST_PATH_IMAGE027
Measured value and calculated value constantly has error.Therefore,
Figure DEST_PATH_IMAGE029
Measured value can only be identical with calculated value approx, namely
Figure 731276DEST_PATH_IMAGE025
d
Figure 887451DEST_PATH_IMAGE020
Figure DEST_PATH_IMAGE030
Figure 622189DEST_PATH_IMAGE029
, the error of the two can be expressed as:
Error
Figure 684821DEST_PATH_IMAGE031
(6)
Make error Hour, this Be required effective diffusion cofficient;
Because the pressure gauge range is larger, the error when measuring pressure near lower bound is larger.For the error of the piezometry that reduces air feed pond 2 and sample cell 1, adopt the differential pressure gauge 11 and 12 of small-range come the pressure in working sample pond 1 and air feed pond 2, its absolute pressure be the force value of reference cell absolute pressure meter 10 and two differential pressure gauges 11 and 12 measure pressure and;
In order to reduce temperature fluctuation to the impact of piezometry, air feed pond 2, reference cell 3, surge tank 5 and attached pipeline, valve and measurement instrument thereof all are placed in the constant temperature oven 6, the temperature of constant temperature oven 6 is controlled at 40 ℃, and temperature fluctuation and uniformity coefficient are less than ± 0.5 ℃.Like this, the pressure surge that produces owing to temperature fluctuation is less than ± 0.15%;
The above-mentioned determinator that utilizes weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar carries out the mensuration of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under the infrabar, is that pressure is 50-100000Pa under the described infrabar;
Described weak adsorbed gas is nitrogen, argon gas, helium;
Described agglomerate body mano-porous material is aerogel material or mano-porous material, and its specification is preferably (10-30) * (10-40) * (50-60) mm.
The beneficial effects of the utility model
The determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar of the present utility model, find the solution effective diffusion cofficient owing to adopting the match of finite difference numerical computation method, this numerical computation method is not subjected to the symmetric restriction of sample, do not need sample preparation, prototype structure feature that can representative sample, therefore the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material is the mensuration that is applicable to be difficult to be prepared into the effective diffusion cofficient of the superinsulation material of laminar and uniform-spherical particle or solid oxide fuel cell electrode material under a kind of infrabar of the present utility model.
In addition, the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar of the present utility model, because used piezometry system response time is fast, response time is 50ms, therefore can collect abundant data point and be used for numerical evaluation, because the measuring accuracy of piezometry system is high, and precision is 0.15% of reading, the resolution of gas dosing is up to 10 simultaneously -8G/g, therefore, the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material is suitable for the mensuration of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar of the present utility model.
Description of drawings
The structural representation of weak adsorbed gas determinator of effective diffusion cofficient in the agglomerate body mano-porous material under Fig. 1, the infrabar; Wherein: 1 is sample cell, and 2 is the air feed pond, and 3 is reference cell, and 4 for demarcating the pond, 5 is surge tank, and 6 is constant temperature oven, and 7 is air feed pond temperature probe, and 8 is the sample cell temperature probe, 9 is the sample cell heating furnace, and 10 is reference cell absolute pressure meter, and 11 is differential pressure gauge between air feed pond and reference cell, and 12 is differential pressure gauge between sample cell and reference cell, 13 is data acquisition unit, and 14 is data acquisition computer, 15,16,17,18,19,20,21 are respectively vacuum valve, and 22 is vacuum pump, and 23 is air feed bottle;
Fig. 2, the structural representation of weak adsorbed gas determinator of effective diffusion cofficient in the agglomerate body mano-porous material under the infrabar among the embodiment 1, wherein: 1 is sample cell, and 2 is the air feed pond, 3 is reference cell, and 4 for demarcating the pond, and 5 is surge tank, 6 is constant temperature oven, and 7 is air feed pond temperature probe, and 8 is the sample cell temperature probe, 9 is the sample cell heating furnace, and 10 is reference cell absolute pressure meter, and 11 is differential pressure gauge between air feed pond and reference cell, 12 is differential pressure gauge between sample cell and reference cell, and 13 is data acquisition unit, and 14 is data acquisition computer, 15,16,171,172,173,181,182,183,19,20,21 are respectively vacuum valve, and 22 is vacuum pump, and 23 is air feed bottle.
Embodiment
Below by embodiment also by reference to the accompanying drawings, the utility model is described in further detail, but do not limit the utility model.
The fundamental property of the brick shape particle dispersion nano-pore superinsulation block sample of 2 kinds of described powder compacting of embodiment sees Table 1:
Figure DEST_PATH_IMAGE034
Embodiment 1
The determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar, its structural representation is measured system, data acquisition system (DAS) and air feed bottle 23 by vacuum tank system, temperature control and mensuration system, dynamic pressure and is formed as shown in Figure 2;
Wherein said vacuum tank system by sample cell 1, air feed pond 2, reference cell 3, demarcate pond 4, surge tank 5 and vacuum pump 22 and form, air feed pond 2 is 2-3:1 with the volume ratio of sample cell 1;
Described sample cell 1 is connected with air feed pond 2 behind valve 15 by pipeline, air feed pond 2 is provided with one road device for cleaning pipeline and crosses valve 16 and be connected with reference cell 3, also be provided with on the air feed pond 2 behind one road device for cleaning pipeline four-way respectively through valve 19 with demarcate pond 4, through the valve 181,182 of three grades of series connection, 183 with surge tank 5, link to each other with vacuum pump 22 through the valve 171,172,173 of three grades of series connection;
Above-mentioned mainly is that air inlet is very large when opening owing to present fine tuning valve, can not realize the fine setting of the pressure of each vacuum tank.For this reason, the valve that links to each other with surge tank 5 and vacuum pump 22 adopts three grades of series connection, namely adopts gradually the method for balance that the pressure of each vacuum tank is finely tuned;
Described surge tank 5 also is provided with a pipeline and links to each other with air feed bottle 23 through valve 21, in addition, also is provided with the valve 20 of a realization emptying on the surge tank 5;
Described dynamic pressure is measured system and is namely comprised absolute pressure meter 10,2 differential pressure gauges that are provided with 11 of reference cell 3 and air feed pond that reference cell 3 is provided with, 3 differential pressure gauges that are provided with 12 of sample cell 1 and reference cell;
Described temperature control and mensuration system comprise temperature probe 8 and the temperature probe 7 of sample cell 2 and the constant temperature oven 9 of sample cell 2 in constant temperature oven 6, air feed pond 1;
Above-mentioned air feed pond 1, reference cell 3 is demarcated pond 4, and surge tank 5 and coupled pipeline, valve and measurement instrument all are placed in the constant temperature oven 6;
Described data acquisition system (DAS) comprises data acquisition unit 13 and coupled computing machine 14 thereof, sends into coupled computing machine 14 after the data acquisition that data acquisition unit 13 sends the temperature probe 7 of the temperature probe 8 in the differential pressure gauge 12 of 2 of the differential pressure gauge 11 in 2 in the absolute pressure meter 10 on the reference cell 3, reference cell 3 and air feed pond, reference cell 3 and sample cells, air feed pond 1 and sample cell 2 is come.
The maximum range of the differential pressure gauge 12 that the differential pressure gauge 11 that described reference cell 3 and air feed pond are 1 and reference cell 3 and sample cell are 2 is ± 10 torr, and precision is 0.15% of reading, and the response time is less than 50ms.
The picking rate that described data acquisition unit gathers each parameter is 2-4/second, described data acquisition unit gathers each parameter, namely is spaced apart 250-500ms the writing time of the differential pressure between differential pressure, reference cell and the sample cell between reference cell absolute pressure, reference cell and air feed pond, air feed pond temperature and sample cell temperature.
Embodiment 2
Determinator with weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under embodiment 1 described a kind of infrabar is being measured weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under the infrabar, refer under the infrabar described in the present embodiment that pressure is 50-100000Pa, described weak adsorbed gas is respectively nitrogen, argon gas and helium, the brick shape particle dispersion nano-pore superinsulation block that described agglomerate body mano-porous material is powder compacting, concrete mensuration process comprises the steps:
(1), device normalization
Measured the volume of demarcating pond 4 with the water filling weight method first, then with demarcating pond 4, utilize argon gas that sample cell 1 and air feed pond 2 are demarcated, suppose that helium obeys the Ideal-Gas Equation under room temperature and normal pressure, timing signal demarcate pond 4 pressure selection four, namely 101.4,235.3,432.3 and 676.5torr, the each repetition 3 times demarcated 12 times altogether, averages, relative deviation is within ± 0.25%, and final calibration result sees Table 2.
Table 2 effective diffusion cofficient device normalization result
Demarcate pond 4(ml) Sample cell 1, V(ml) Air feed pond 2, V 1（ml）
172.14 189.09 511.25
(2), gas displacement
Before the test brick shape particle dispersion nano-pore superinsulation block sample of powder compacting is put into sample cell 1, valve-off 183,20,21, Open valve 15,16,171,172,173,19,181,182, open vacuum pump 22, test macro is vacuumized 6h, until the demonstration pressure of absolute pressure meter 10 is 0, valve-off 171,172,173.
Open valve 20 and 21 with the gas in the weak adsorbed gas purging displacement surge tank 5 of air feed bottle 23, is closed emptying valve 20;
Open valve 183, to the test macro gas injection, until the pressure of absolute pressure meter 10 reaches mensuration pressure, valve-off 19,181,182,183, system leaves standstill, balance 1 hour;
(3), system balancing
Valve- off 15,16, valve-off 182 is opened valve 183, to pipeline gas injection between valve 182 and 183, then, valve-off 183, open valve 182, allow valve 182 and 183 ducted gases enter air feed pond 2, until the pressure reduction of 3 of air feed pond 2 and reference cells is at 7.5-9.5 torr; If the pressure reduction that air feed pond 2 and reference cell are 3 is greater than 9.5 torr, Open valve 173, allow the gas in air feed pond 2 and the pipeline space balance between valve 172 and 173, valve-off 173 is opened valve 172 and 171, takes gas between valve 172 and 173 away with vacuum pump 22, so repeatedly, until the pressure reduction of 3 of air feed pond 2 and reference cells is at 7.5-9.5 torr, system leaves standstill, balance 1 hour;
(4), mensuration process
Moment is opened valve 15, the weak adsorbed gas in air feed pond 2 enters the space outside the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting in the sample cell 1, because the pressure outside the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting is greater than the pressure of the brick shape particle dispersion nano-pore superinsulation block sample hole of powder compacting, weak adsorbed gas in the process of the brick shape particle dispersion nano-pore superinsulation block sample interior diffusion of powder compacting, the terminal pressure Pc(x of the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting 0, y 0, z 0T) t reduces gradually in time, when gaseous tension reached balance in the brick shape particle dispersion nano-pore superinsulation block sample of gaseous tension and powder compacting outside the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting, this terminal pressure is temporal evolution no longer;
The equilibration time of ignoring the outer gas of brick shape particle dispersion nano-pore superinsulation block sample of powder compacting, then P (t)=Pc(x 0, y 0, z 0, t); And P (t)=P d(t)+P 0(t), wherein, P d(t) and P 0(t) be respectively the reading pressure of differential pressure gauge 12 and the reading pressure of pressure gauge 10.The two over time curve send into computing machine 14 records after by data acquisition system (DAS) 13 that this data acquisition is complete;
Because the pressure P in air feed pond 2 1(t)=P d 1(t)+P 0(t), wherein, P d 1(t) and P 0(t) be respectively the reading pressure of differential pressure gauge 11 and the reading pressure of pressure gauge 10, the two over time curve send into computing machine 14 records after by data acquisition system (DAS) 13 that this data acquisition is complete;
The temperature in sample cell 1 and air feed pond 2, T and T 1Measure with temperature sensor 8 and 7 respectively, and send into computing machine 14 records after by data acquisition system (DAS) 13 that this data acquisition is complete;
(5), data are processed
Owing to reaching balance between the brick shape particle dispersion nano-pore superinsulation block sample of sample cell 1 and powder compacting, the weak adsorbed gas of sample cell 1 is 0 in 0 amount that enters the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting constantly, therefore, the n(0 of equation (3))=0.Like this, utilize the sample cell 1 of step (1) demarcation and volume V and the V in air feed pond 2 1, the T that step (4) is measured, T 1, P(t) and P 1(t), and the porosity Φ of the brick shape particle dispersion nano-pore superinsulation block sample of table 1 powder compacting, volume Vs, long, wide and thick, x 0, y 0And z 0, can calculate the constantly amount of gaseous matter in the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting of t according to equation (3)
Figure 478782DEST_PATH_IMAGE009
Suppose an effective diffusion cofficient D, then according to terminal pressure Pc(x 0, y 0, z 0, t), the brick shape particle dispersion nano-pore superinsulation block sample physical dimension (x of powder compacting 0, y 0And z 0) and equation (5), adopt the finite difference numerical evaluation, can calculate one
Error function J (D) can be calculated by equation (6) like this.
Change effective diffusion cofficient D, then error function J(D) also change thereupon, work as J(D) for hour, with respect to effective diffusion cofficient D* be the match value of finding the solution.This effective diffusion cofficient D* is under this temperature and pressure, and the weak adsorbed gas of studying is at the effective diffusion cofficient of the brick shape particle dispersion nano-pore superinsulation block inside of powder compacting.
In the said determination process:
Experiment original pressure P 0For: 0.1,3.8,22.5,41.3,60.0,78.8,97.5,116.3,135.0,153.8,210.0,266.3,322.5,397.5,472.5,547.5,622.6,716.3 torr (totally 18 points);
Experimental temperature: 30 ℃;
Experimental gas medium: nitrogen, argon gas and helium (purity: 99.999%);
The pressure differential of air feed pond 2 and sample cell 1: 7.5-9.5 torr;
Pressure samples interval time: 2/second;
According to this condition, be total to get 54 groups of experimental datas, obtaining different weak adsorbed gases is 54 of nitrogen, argon gas and the helium effective diffusion cofficients in the brick shape particle dispersion nano-pore superinsulation block in powder compacting under different temperatures and the pressure, error function J(D under all experiment conditions) can restrain well, the effective diffusion cofficient of trying to achieve sees Table 3.
Figure 480553DEST_PATH_IMAGE035
As can be seen from Table 3, weak adsorbed gas helium, nitrogen and the effective diffusion cofficient of argon gas in the brick shape particle dispersion nano-pore superinsulation block sample of powder compacting are all than little 1 order of magnitude of self-diffusion coefficient of the gas under uniform temp and the pressure, weak adsorbed gas helium, nitrogen and the diffusion of argon gas in the brick shape particle dispersion nano-pore superinsulation block of powder compacting are take Knudsen diffusion as main, and namely weak adsorbed gas helium, nitrogen and argon gas and the collision of nanometer hole wall are the main resistances of diffusion.
Error at measurment to effective diffusion cofficient measurement result in the above embodiments 2 is analyzed:
Select helium as measuring medium, be respectively 0.1,37.7 with pressure, 147.5 and 727.9torr under Pc(x 0, y 0, z 0, t)-and the t curve is benchmark, analyzes according to each parameter maximum error of following measuring, the maximum error of each influence factor is listed in the table below 4:
Table 4, error analysis result
Each parameter V V 1 V s x 0 y 0 z 0 Φ P 1(t) P(t)
Each parametric measurement value (± %) 0.25 0.25 0.15 0.039 0.065 0.05 0.25～1 0.15 0.15
Effective diffusion cofficient D error amount (%) 1.82 1.79 0.42 0.018 0.051 0.038 0.58～1.71 2.78 2.93
As shown in Table 4, the error of piezometry is the main contributions of effective diffusion cofficient error.And P because the P(0 of equation (3))-P(t) 1(0)-P 1(t) be the pressure reduction of differential pressure gauge 12 and differential pressure gauge 11, the piezometry error of absolute pressure meter 10 is for not contribution of actual error.The range of differential pressure gauge is little, and error is that 0.15%, two differential pressure gauge of reading all places constant temperature oven, and temperature coefficient can be ignored.Therefore, the method that this experiment takes error of measurement to press has reduced experimental error effectively.
Above said content only is the basic explanation under the utility model design, and according to any equivalent transformation that the technical solution of the utility model is done, all should belong to protection domain of the present utility model.

Claims (5)

1. the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under the infrabar, the determinator that it is characterized in that weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under the described infrabar is measured system, data acquisition system (DAS) and air feed bottle by vacuum tank system, temperature control and mensuration system, dynamic pressure and is formed;
Described vacuum tank system is comprised of sample cell, air feed pond, reference cell, demarcation pond, surge tank and vacuum pump, and the volume ratio of air feed pond and sample cell is 2-3:1;
Described sample cell is connected with the air feed pond behind valve by pipeline, and the air feed pond is provided with one road device for cleaning pipeline and crosses valve and be connected with reference cell, also be provided with on the air feed pond one road pipeline behind four-way respectively through valve with demarcate pond, surge tank and vacuum pump and link to each other;
Also be provided with a pipeline on the described surge tank and link to each other with air feed bottle through valve, in addition, also be provided with the valve of a realization emptying on the surge tank pond;
Described dynamic pressure is measured the differential pressure that is provided with between absolute pressure meter, reference cell and the air feed pond that system comprises that namely reference cell is provided with and is taken into account the differential pressure gauge that is provided with between sample cell and reference cell;
Described temperature control and mensuration system comprise constant temperature oven, air feed pond temperature probe and sample cell temperature probe and sample cell constant temperature oven;
Above-mentioned air feed pond, reference cell is demarcated the pond, surge tank and subsidiary pipeline, valve and and measurement instrument all be placed in the constant temperature oven;
Described data acquisition system (DAS) comprises data acquisition unit and coupled computing machine, sends into coupled computing machine after the data acquisition that data acquisition unit sends the differential pressure gauge between differential pressure gauge, reference cell and sample cell between the absolute pressure meter on the reference cell, reference cell and air feed pond, air feed pond temperature probe and sample cell temperature probe is come.
2. the determinator of adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material a little less than under a kind of infrabar as claimed in claim 1, it is characterized in that differential pressure gauge between described reference cell and air feed pond and the maximum range of the differential pressure gauge between reference cell and sample cell are ± 10 torr, precision is 0.15% of reading, and the response time is less than 50ms.
3. the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under a kind of infrabar as claimed in claim 2 is characterized in that the picking rate that described data acquisition unit gathers each parameter is 2-4/second.
4. the determinator of adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material a little less than under a kind of infrabar as claimed in claim 3, it is characterized in that described data acquisition unit gathers each parameter, namely be spaced apart 250-500ms the writing time of the differential pressure between differential pressure, reference cell and the sample cell between reference cell absolute pressure, reference cell and air feed pond, air feed pond temperature and sample cell temperature.
5. such as the determinator of weak adsorbed gas effective diffusion cofficient in the agglomerate body mano-porous material under claim 1,2, the 3 or 4 described a kind of infrabar, it is characterized in that the road pipeline that described air feed pond is provided with links to each other with demarcation pond, surge tank and vacuum pump through valve respectively behind four-way;
The wherein said valve that links to each other with surge tank and vacuum pump is respectively the continuous valve of 3 tandems.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102706778A (en) * 2012-06-21 2012-10-03 上海应用技术学院 Measuring device of effective diffusion coefficient of weak adsorption gas in bulk nano-porous material under low pressure

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102706778A (en) * 2012-06-21 2012-10-03 上海应用技术学院 Measuring device of effective diffusion coefficient of weak adsorption gas in bulk nano-porous material under low pressure

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