CN104897508A - Method for testing thermodynamic parameters of functional material - Google Patents
Method for testing thermodynamic parameters of functional material Download PDFInfo
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- CN104897508A CN104897508A CN201410081084.6A CN201410081084A CN104897508A CN 104897508 A CN104897508 A CN 104897508A CN 201410081084 A CN201410081084 A CN 201410081084A CN 104897508 A CN104897508 A CN 104897508A
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Abstract
The invention relates to a method for testing the thermodynamic parameters of a functional material. The method comprises the following steps: using a resonant micro-cantilever as a micro-mass sensor, loading the functional material to the free end of the resonant micro-cantilever, testing the adsorption quantity of the functional material to different pressure gases at a specific temperature in real time to obtain the adsorption isotherm of the functional material, further calculating to obtain the thermodynamic parameters of the functional material, and carrying out characteristic assessment on the functional material according to the obtained thermodynamic parameters. The method is advanced, has practical application significance, and also has the characteristics of easy operation and low price.
Description
Technical field
The present invention relates to a kind of method of alternating temperature weight method test material thermodynamic parameter, be specifically related to resonant-type tiny cantilever beam in the test and calculating of functional material thermodynamic parameter, belong to the characterization of adsorption evaluation areas of functional material.
Background technology
Functional material, to the characteristic research such as absorption direction, mode, capacity of gas molecule, has important effect in various fields such as public safety, environmental protection, food securities.Such as, in order to reduce carbon dioxide (CO in air
2) content of isothermal chamber gas, be necessary that research is to CO
2there is super large adsorption capacity, and there is necessarily optionally novel absorption material; And for example, in order to increase the security of peasant in pesticide spraying process, be necessary that research has specific adsorption and the new material of cheapness to agricultural chemicals such as organophosphoruss; For another example, the high-performance sensors of specificly-response can be had to trace amount pesticide residue in the agricultural product such as vegetables to manufacture, needing badly and understanding sensitive material to the characterization of adsorption of pesticide molecule.Above-mentioned research field all needs the thermodynamic behaviour such as absorption direction, mode, capacity of evaluation function material for gaseous.
External bibliographical information has used thermodynamic parameter to assess new material (as metal organic framework compound) to CO
2characterization of adsorption (Nature, 2013,495,80-84).But this kind of research is all based on main equipments such as gas absorption instrument, Monte Carlo calculating simulation, quartzy balance and magnetic suspension balances, there is the shortcomings such as test value is high, material usage is many, the kind of test gas is single.
The present invention points out that resonant-type tiny cantilever beam as micro-mass sensor, at a constant temperature, can weigh material to the adsorbance of specified pressure gas, thus draw the characterisitic parameter such as absorption (or desorption) direction, mode, capacity of material in real time.The present invention has positive meaning to fields such as absorption (or desorption) characteristic evaluations of functional material, and has widened the application of resonant-type tiny cantilever beam.
Summary of the invention
The object of the invention is to the defect overcoming prior art, a kind of method of testing of functional material thermodynamic parameter is provided, for resonant-type tiny cantilever beam being applied to the specific evaluation areas of adsorption and desorption of functional material, the method is advanced, there is the application value of reality, and be easy to operation, cheap.
The present invention is achieved by the following technical solutions:
A kind of method of testing of functional material thermodynamic parameter, for using resonant-type tiny cantilever beam as micro-mass sensor, functional material is carried on the free end of resonant-type tiny cantilever beam, real-time testing functional material at a certain temperature, to the adsorbance of different pressures gas, obtain the adsorption isothermal of functional material, then calculate the thermodynamic parameter of described functional material further, and by the thermodynamic parameter obtained, characteristic evaluation is carried out to described functional material.
Described functional material is selected from mesoporous material, polymkeric substance, carbon nano-tube, Graphene etc.
Described resonant-type tiny cantilever beam is integrated piezoresistance type silicon-based micro-cantilevers.
The mass sensitivity of described resonant-type tiny cantilever beam is 1.53Hz/pg.Wherein, Hz is cps, 1pg=10
-12g.
Described thermodynamic parameter comprises enthalpy change, Entropy Changes, gibbs free energy change, absorption/desorption equilibrium constant and coverage.
The object of the characteristic evaluation of described functional material comprises absorption direction, desorption direction, suction type, adsorption capacity etc.
A method of testing for functional material thermodynamic parameter, specifically comprises the following steps:
(1) be coated with: utilize micromanipulation system by the free end of the dispersed liquid coating of functional material in resonant-type tiny cantilever beam, dry, for subsequent use;
(2) aging: being placed in by the resonant-type tiny cantilever beam being coated with functional material can the test pool of equilibrium temperature, stablizes aging under high pure nitrogen air-flow;
(3) baseline test is carried out: the flow fixedly passing into gas, passes into high pure nitrogen continuously, the frequency of record resonant-type tiny cantilever beam;
(4) sensitivity curve test: at a constant temperature, keep the gas flow identical with step (3), the combination gas of the adsorbed gas and nitrogen that pass into concentration known continuously adsorbs, the frequency of Real-time Collection resonant-type tiny cantilever beam, after remaining unchanged to frequency, the high pure nitrogen passing into same traffic continuously carries out purging desorption, and the frequency of Real-time Collection resonant-type tiny cantilever beam remains unchanged to frequency; Then change the concentration of the adsorbed gas in the mixed gas passed into, repeat above test process; Obtain at such a temperature, the frequency of resonant-type tiny cantilever beam is with the sensitivity curve of adsorbed gas concentration change;
(5) regulate the temperature of test pool to another steady temperature, repeat step (4), obtain frequency another sensitivity curve with adsorbed gas concentration change of resonant-type tiny cantilever beam at another temperature;
(6) according to the mass sensitivity of resonant-type tiny cantilever beam, the sensitivity curve that step (4) and (5) obtain is converted into adsorption isothermal curve: namely under steady temperature, the relation curve of gas absorption amount and pressure;
(7) according to adsorption isothermal curve, according to Clausius-Clapyron Equation, ask and calculate Adsorption en-thalpy Δ H °;
(8) appoint and get an adsorption isothermal curve, be deformed into the relation curve of p/V and p, obtain adsorption equilibrium costant K and standard equilibrium constant K ° by the intercept of this curve and slope;
(9) according to the numerical value of K, the coverage θ dividing pressure in concrete adsorbed gas is obtained by Lan Miaoer equation;
(10) probe temperature of the adsorption isothermal curve got according to K ° and step (8), obtains gibbs free energy change Δ G ° by van' t Hoff equation;
(11) according to the numerical value of gibbs free energy change Δ G ° with Adsorption en-thalpy Δ H °, Entropy Changes Δ S ° is obtained by the definition of gibbs free energy change.
Wherein,
Preferably, the solvent of the dispersion liquid of described functional material is selected from deionized water, ethanol, tetrahydrofuran etc.
Preferably, the middle functional material concentration of the dispersion liquid of described functional material is 1-50mg/mL; At the coating weight 0.01-1 microlitre of the free end of described resonant-type tiny cantilever beam.
Preferably, the temperature of drying described in step (1) is 60-100 DEG C, is more preferably 80 DEG C.
Preferably, in step (2), described to stablize the aging time be 1-5 days, is more preferably 3 days.
Preferably, the collection of described frequency uses commercial frequency meter, preferably adopts U.S. Agilent 5313A type frequency meter.
In step (7), the computing method of described Adsorption en-thalpy Δ H ° are be designated as T respectively from temperature
1and T
2two adsorption isothermals to take up an official post two numerical points got and there is same coverage θ, be designated as (p respectively
1, θ) and (p
2, θ), then calculate Δ H ° according to Clausius-Clapyron Equation.As nothing particularly points out, the T described in the present invention all refers to temperature, and the equal finger pressure of described p, described θ all refers to adsorption coverage.
Described Clausius-Clapyron Equation is as follows:
Or its integration type:
In step (8), the relation curve of described p/V and p is Lan Miaoer equation:
p/V=p/V
∞+(KV
∞)
-1（Ⅲ）
Wherein, K is adsorption equilibrium costant, and is calculated by the relational expression of K °=K × p ° and obtain standard equilibrium constant K °;
Wherein, p ° refers to normal pressure, and namely p °=101325 handkerchiefs, get its approximate value when actual computation
handkerchief.
When V refers to that adsorbed gas dividing potential drop is p, the adsorbance of functional material is converted into the volume under the status of criterion; V
∞finger functional material reaches capacity under adsorption conditions, and gas absorption amount is converted into the volume under the status of criterion, then coverage θ=V/V ∞.
The described status of criterion refers to the temperature state that to be 0 DEG C (273.15K) and pressure be 101.325 kPas (1 standard atmospheric pressure, 760 mm Hg).
In step (10), described van' t Hoff equation is:
ΔG°=-RTlnK° （Ⅳ）
In step (11), the definition of described gibbs free energy change is:
ΔG°=ΔH°-TΔS° （Ⅴ）
Technical solutions according to the invention can also be:
The application of a kind of resonant-type tiny cantilever beam in the test of functional material thermodynamic parameter, for using resonant-type tiny cantilever beam as micro-mass sensor, functional material is carried on the free end of resonant-type tiny cantilever beam, real-time testing functional material at a certain temperature, to the adsorbance of different pressures gas, obtain the adsorption isothermal of functional material, then calculate the thermodynamic parameter of described functional material further; Then characteristic evaluation can be carried out by the thermodynamic parameter obtained to described functional material; Specifically comprise the following steps:
(1) be coated with: utilize micromanipulation system by the free end of the dispersed liquid coating of functional material in resonant-type tiny cantilever beam, dry, for subsequent use;
(2) aging: being placed in by the resonant-type tiny cantilever beam being coated with functional material can the test pool of equilibrium temperature, stablizes aging under high pure nitrogen air-flow;
(3) baseline test is carried out: the flow fixedly passing into gas, passes into high pure nitrogen continuously, the frequency of record resonant-type tiny cantilever beam;
(4) sensitivity curve test: at a constant temperature, keep the gas flow identical with step (3), the combination gas of the adsorbed gas and nitrogen that pass into concentration known continuously adsorbs, the frequency of Real-time Collection resonant-type tiny cantilever beam, after remaining unchanged to frequency, the high pure nitrogen passing into same traffic continuously carries out purging desorption, and the frequency of Real-time Collection resonant-type tiny cantilever beam remains unchanged to frequency; Then change the concentration of the adsorbed gas in the mixed gas passed into, repeat above test process; Obtain at such a temperature, the frequency of resonant-type tiny cantilever beam is with the sensitivity curve of adsorbed gas concentration change;
(5) regulate the temperature of test pool to another steady temperature, repeat step (4), obtain frequency another sensitivity curve with adsorbed gas concentration change of resonant-type tiny cantilever beam at another temperature;
(6) according to the mass sensitivity of resonant-type tiny cantilever beam, the sensitivity curve that step (4) and (5) obtain is converted into adsorption isothermal curve: namely under steady temperature, the relation curve of gas absorption amount and pressure;
(7) according to adsorption isothermal curve, according to Clausius-Clapyron Equation, ask and calculate Adsorption en-thalpy Δ H °;
(8) appoint and get an adsorption isothermal curve, be deformed into the relation curve of p/V and p, obtain adsorption equilibrium costant K and standard equilibrium constant K ° by the intercept of this curve and slope;
(9) according to the numerical value of K, the coverage θ dividing pressure in concrete adsorbed gas is obtained by Lan Miaoer equation;
(10) according to K ° and and step (8) described in the probe temperature of adsorption isothermal curve got, obtain gibbs free energy change Δ G ° by van' t Hoff equation;
(11) according to the numerical value of gibbs free energy change Δ G ° with Adsorption en-thalpy Δ H °, Entropy Changes Δ S ° is obtained by the definition of gibbs free energy change.
Assessment of the present invention, for theoretical according to the common Physicochemical of thing, the absolute value of Adsorption en-thalpy Δ H ° of value is less than 40kJ/mol and belongs to physisorption, be greater than 80kJ/mol and belong to chemisorption, marginal numerical value belongs to the acting force (as hydrogen bond etc.) being difficult to define, and judges thus to the adsorption form of material to special gas.
Technique effect of the present invention and advantage are: absorption (desorption) characteristic evaluation field resonant-type tiny cantilever beam being applied to functional material, and the method is advanced, the application value with reality, and are easy to operation, cheap.
Accompanying drawing explanation
Fig. 1 (a1) carboxyl-functional mesoporous nano-grain transmission electron microscope photo
(a2) the resonant-type tiny cantilever beam temporal frequency response curve (298K) of load carboxyl-functional mesoporous nano-grain
(a3) the resonant-type tiny cantilever beam temporal frequency response curve (318K) of load carboxyl-functional mesoporous nano-grain
(a4) carboxyl-functional mesoporous nano-grain is to the adsorption isothermal curve (298K, 318K) of trimethylamine gas
(b1) sulfonic acid funtionalized mesoporous nano-grain transmission electron microscope photo
(b2) the resonant-type tiny cantilever beam temporal frequency response curve (298K) of load sulfonic acid funtionalized mesoporous nano-grain
(b3) the resonant-type tiny cantilever beam temporal frequency response curve (318K) of load sulfonic acid funtionalized mesoporous nano-grain
(b4) sulfonic acid funtionalized mesoporous nano-grain is to the adsorption isothermal curve (298K, 318K) of trimethylamine gas
(c1) unmodified mesoporous nano-grain transmission electron microscope photo
(c2) the resonant-type tiny cantilever beam temporal frequency response curve (298K) of load unmodified mesoporous nano-grain
(c3) the resonant-type tiny cantilever beam temporal frequency response curve (318K) of load unmodified mesoporous nano-grain
(c4) unmodified mesoporous nano-grain is to the adsorption isothermal curve (298K, 318K) of trimethylamine gas
Functional hyperbranched polymer molecular structure figure described in Fig. 2 embodiment 2
The resonant-type tiny cantilever beam temporal frequency response curve (283K) of Fig. 3 (a) loading functional dissaving polymer
The resonant-type tiny cantilever beam temporal frequency response curve (298K) of (b) loading functional dissaving polymer
C () functional hyperbranched polymkeric substance is to DMMP(dimethyl methyl phosphonate) adsorption isothermal curve (283K, 298K)
Embodiment
Below by way of specific instantiation, technical scheme of the present invention is described.Should be understood that one or more method steps that the present invention mentions do not repel and before and after described combination step, also to there is additive method step or can also insert additive method step between these steps clearly mentioned; Should also be understood that these embodiments are only not used in for illustration of the present invention to limit the scope of the invention.And, except as otherwise noted, the numbering of various method steps is only the convenient tool differentiating various method steps, but not be ordering or the enforceable scope of restriction the present invention of restriction various method steps, the change of its relativeness or adjustment, when changing technology contents without essence, when being also considered as the enforceable category of the present invention.
Embodiment 1: three kind of mesoporous nano-grain is assessed the characterization of adsorption of trimethylamine
The synthesis of (1) three kind of mesoporous nano-grain sample
1. three kinds of mesoporous nano-grains refer to successively: a. carboxyl-functional mesoporous nano-grain; B. sulfonic acid funtionalized mesoporous nano-grain; C. unmodified mesoporous nano-grain
2. carboxyl-functional mesoporous nano-grain synthetic method is shown in patented claim: the manufacture method (number of patent application: 201210306247.7) with the carboxyl-functional mesoporous nano-grain of foraminous spiral tract.
3. the same file of the synthetic method of sulfonic acid funtionalized mesoporous nano-grain (number of patent application: 201210306247.7), but the silica-based aqueous sodium acetate solution of reagent trihydroxy replaces with 2-(4-chlorine sulfonyl-phenyl) ethyl trimethoxy silane, and [English name is 2-(4-Chlorosulfonylphenyl) ethyltrimethoxy silane, the dichloromethane solution of 50wt%], other reaction conditions is all same, can obtain sulfonic acid funtionalized mesoporous nano-grain.
4. the same file of the synthetic method of unmodified mesoporous nano-grain (number of patent application: 201210306247.7), but do not use the silica-based aqueous sodium acetate solution of reagent trihydroxy, other reaction conditions all with, unmodified mesoporous nano-grain can be obtained.
5. the transmission electron microscope photo of three kinds of mesoporous nano-grains is as shown in Fig. 1 (a1), (b1), (c1);
(2) sample preparation (mesoporous nano-grain is carried on the free end of integrated piezoresistance type silicon-based micro-cantilevers, forms micro-LOAD CELLS) and aging:
1. three kinds of mesoporous nano-grains (weight all about 10 milligrams) are scattered in 1 ml deionized water respectively in advance, respectively the dispersion liquid of obtained three kinds of mesoporous nano-grains;
2. utilize micromanipulation system, by the dispersed liquid coating of 1 microlitre mesoporous nano-grain in the free end of resonant-type tiny cantilever beam, dry at 80 DEG C, for subsequent use;
3. the resonant-type tiny cantilever beam being coated with mesoporous nano-grain material is placed in that have can the test pool of steady temperature function, stablize aging under high pure nitrogen air-flow, the time is 3 days;
(3) (for carboxyl-functional mesoporous nano-grain) is tested
1. baseline test: under high pure nitrogen air-flow, utilize the frequency of commercial frequency meter record resonant-type tiny cantilever beam (its free end load has carboxyl-functional mesoporous nano-grain);
2. temperature is 298K(25 DEG C) under sensitivity curve test: at 298K temperature, pass into 90ppb(ppb and refer to that volumetric concentration is part per billion) trimethylamine gas, the frequency of Real-time Collection resonant-type tiny cantilever beam, after remaining unchanged to frequency, pass into nitrogen stream, desorption is carried out to the carboxyl-functional mesoporous nano-grain being adsorbed with trimethylamine gas, after the frequency of resonant-type tiny cantilever beam remains unchanged, regulate the concentration of trimethylamine gas to 180ppb, repeated test, obtains the frequency data of micro-cantilever under this concentration gases atmosphere; Make in this way, then regulate the concentration of trimethylamine gas to 360ppb and 900ppb respectively, and test the frequency data of resonant-type tiny cantilever beam under these two concentration respectively.Thus obtain at 298K temperature, the real-time testing curve (as Suo Shi Fig. 1 (a2)) that the frequency of micro-cantilever changes with trimethylamine gas concentration;
3. regulate the temperature of test pool to 318K, according to step test process 2., another real-time testing curve (as Suo Shi Fig. 1 (a3)) that the frequency obtaining resonant-type tiny cantilever beam under 318K changes with trimethylamine gas concentration;
4. same method is adopted, the temperature of fixing test room is 298K and 318K respectively, and the real-time testing curve that the corresponding frequency obtaining the resonant-type tiny cantilever beam of sulfonic acid funtionalized mesoporous nano-grain load changes with trimethylamine gas concentration (as Suo Shi (b2) in Fig. 1 and (b3));
5. same method is adopted, the temperature of fixing test room is 298K and 318K respectively, and the real-time testing curve that the corresponding frequency obtaining the resonant-type tiny cantilever beam of unmodified mesoporous nano-grain load changes with trimethylamine gas concentration (as Suo Shi (c2) in accompanying drawing 1 and (c3));
(4) thermodynamic parameter calculates and assesses with characterization of adsorption
1. draw isothermal curve: according to the mass sensitivity of resonant-type tiny cantilever beam, test curve (in Fig. 1 shown in (a2) and (a3), (b2) and (b3), (c2) and (c3)) is converted into adsorption isothermal curve (respectively as shown in (a4), (b4) and (c4) in Fig. 1); Under described adsorption isothermal curve and steady temperature, the relation curve of trimethylamine gas absorption amount and pressure;
2. the calculating of enthalpy change (Δ H °): arbitrarily make a horizontal line and crossing with 2 adsorption isothermals, 2 intersection points are the partial pressure value of the trimethylamine under same coverage.As shown in (a4) in Fig. 1, the trimethylamine dividing potential drop under 298K is 18 milli handkerchiefs, and the trimethylamine dividing potential drop under 318K is 90 milli handkerchiefs, brings corresponding partial pressure value and temperature value into Clausius-Clapyron Equation
Can ask and calculate Adsorption en-thalpy Δ H ° of carboxyl-functional mesoporous nano-grain to trimethylamine is-63.4kJ/mol.Adopting same method, can be-149.6kJ/mol in the hope of calculating Adsorption en-thalpy Δ H ° of sulfonic acid funtionalized mesoporous nano-grain to trimethylamine; Adsorption en-thalpy Δ H ° of unmodified mesoporous nano-grain to trimethylamine is-23.0kJ/mol.
3. other thermodynamic parameter of carboxyl-functional mesoporous nano-grain (calculating of Entropy Changes, gibbs free curve (can become, absorption/desorption equilibrium constant and coverage): it is deformed into the relation of p/V and p wherein by an adsorption isothermal, p is the dividing potential drop of gas, V is that under corresponding dividing potential drop p, adsorbate amount is converted into the volume under the status of criterion), according to Lan Miaoer equation
p/V=p/V
∞+(KV
∞)
-1，
Adsorption equilibrium costant K=63Pa is obtained by the intercept of this curve and slope
-1.(refer in particular to a kind of gaseous material because the present invention only relates to gas-particle two-phase adsorption reaction and be adsorbed in a kind of solid matter surface, produce another kind and have gas absorption at the solid matter on its surface) in, so standard equilibrium constant K °=° (p ° refers to normal pressure to K × p, namely p °=101325 handkerchiefs, get its approximate value when actual computation
handkerchief), namely K °=63 × 10
5=6.3 × 10
6.Due to before the absorption that reaches capacity, gas with various divides pressure, and the coverage of material surface is different, therefore, needs to calculate coverage in an appointment point pressure.According to absorption/desorption equilibrium constant K=63Pa
-1with appointment dividing potential drop (such as p=9 × 10
-3pa) under, then by another form of Lan Miaoer equation
θ=Kp/(1+Kp)，
Obtain coverage θ=0.36.According to van' t Hoff equation Δ G °=-RTlnK °, wherein temperature T gets the temperature value 298K of Fig. 1 (a4) isothermal curve, by K °=6.3 × 10
6substitute into, can in the hope of calculating the gibbs free energy change Δ G °=-38.8kJmol of this adsorption process
-1.Finally, by gibbs free energy change definition Δ G °=Δ H ° of-T Δ S °, Entropy Changes Δ S °=-82.6JK can be obtained
-1.
4. characterization of adsorption assessment: physico-chemical theories it has been generally acknowledged that, the absolute value of Adsorption en-thalpy Δ H ° of value is less than 40kJ/mol and belongs to physisorption, be greater than 80kJ/mol and belong to chemisorption, marginal numerical value belongs to the acting force (as hydrogen bond etc.) being difficult to define.Therefore, known according to the Adsorption en-thalpy Δ H ° value calculating gained, trimethylamine molecule is adsorbed in the surface of carboxyl-functional mesoporous nano-grain in hydrogen bond mode, be adsorbed in the surface of sulfonic acid mesoporous nano-grain in chemisorption mode, be adsorbed in unmodified mesoporous nano-grain surface with physical adsorption way.Wherein, carboxyl-functional mesoporous nano-grain has certain selective adsorption to trimethylamine, can desorption, is suitable for use as the sensitive material of amine class gas; Sulfonic acid funtionalized mesoporous nano-grain has stronger suction-operated to trimethylamine, and is difficult to desorption after absorption, is suitable for use as the adsorbent of amine gas.
Embodiment 2: (its synthetic method is with document Chem.Mater.2004 for functional hyperbranched polymkeric substance, 16,5357-5364, described functional hyperbranched polymer molecular structure figure are as shown in Figure 2) to organophosphorus simulant DMMP(dimethyl methyl phosphonate) characterization of adsorption assessment:
(1) sample preparation (by the free end of functional hyperbranched Polymer-supported in resonant-type tiny cantilever beam, forming micro-LOAD CELLS) and aging
1. about 10 milligrams of functional hyperbranched polymkeric substance are scattered in 1 milliliter of tetrahydrofuran in advance;
2. utilize micromanipulation system, by the tetrahydrofuran dispersed liquid coating of 1 microlitre dissaving polymer in the free end of resonant-type tiny cantilever beam, dry at 80 DEG C, for subsequent use;
3. the resonant-type tiny cantilever beam being coated with functional material is placed in that have can the test pool of steady temperature function, stablize aging under high pure nitrogen air-flow, the time is 3 days.
(2) test
1. baseline test: under high pure nitrogen air-flow, utilize the frequency of commercial frequency meter record resonant-type tiny cantilever beam;
2. temperature is 283K(10 DEG C) under sensitivity curve test: at 283K temperature, pass into 80ppb(ppb and refer to that volumetric concentration is part per billion) DMMP gas, the frequency of Real-time Collection resonant-type tiny cantilever beam, after remaining unchanged to frequency, pass into nitrogen stream and desorption is carried out to the sensor of adsorbed gas; After the frequency of micro-cantilever remains unchanged, regulate the concentration of DMMP gas to 160ppb, repeated test, obtains the frequency data of micro-cantilever under this concentration gases atmosphere; Make in this way, then regulate the concentration of DMMP gas to 270ppb and test the frequency data of resonant-type tiny cantilever beam under this concentration.Thus obtain at 283K temperature, the real-time testing curve (as Suo Shi Fig. 3 (a)) that the frequency of micro-cantilever changes with DMMP gas concentration.
3. regulate the temperature of test pool to 298K, according to step 2., another real-time testing curve (as shown in Figure 3 (b)) that the frequency obtaining micro-cantilever at such a temperature changes with DMMP gas concentration.
(3) thermodynamic parameter calculates and assesses with characterization of adsorption
1. draw isothermal curve: according to the mass sensitivity of resonant-type tiny cantilever beam, test curve (Fig. 3 (a) and (b)) is converted into adsorption isothermal curve (namely under steady temperature, the relation curve of DMMP gas absorption amount and pressure, as shown in Figure 3 (c));
2. the calculating of enthalpy change (Δ H °): arbitrarily make a horizontal line and crossing with 2 adsorption isothermals, 2 intersection points are the partial pressure value of the DMMP under same coverage (as shown in Figure 3 (c), DMMP dividing potential drop under 283K is 8 milli handkerchiefs, DMMP dividing potential drop under 298K is 19.5 milli handkerchiefs), bring corresponding partial pressure value and temperature value into Clausius-Clapyron Equation, asking and calculating Adsorption en-thalpy Δ H ° is-41.6kJ/mol;
3. characterization of adsorption assessment: physico-chemical theories it has been generally acknowledged that, the absolute value of Adsorption en-thalpy Δ H ° of value is less than 40kJ/mol and belongs to physisorption, be greater than 80kJ/mol and belong to chemisorption, marginal numerical value belongs to the acting force (as hydrogen bond etc.) being difficult to define.Therefore, known according to Adsorption en-thalpy Δ H ° value (-41.6kJ/mol) calculating gained, DMMP molecule is the surface being adsorbed in functional hyperbranched polymkeric substance in the mode of hydrogen bond, has certain selectivity, and can desorption, be suitable for use as the sensitive material of organic phosphates gas.
Claims (10)
1. the method for testing of a functional material thermodynamic parameter, for using resonant-type tiny cantilever beam as micro-mass sensor, functional material is carried on the free end of resonant-type tiny cantilever beam, real-time testing functional material at a certain temperature, to the adsorbance of variable concentrations gas, obtain the adsorption isothermal of functional material, then calculate the thermodynamic parameter of described functional material further, and by the thermodynamic parameter obtained, characteristic evaluation is carried out to described functional material.。
2. the method for testing of a kind of functional material thermodynamic parameter as claimed in claim 1, it is characterized in that, described functional material is selected from mesoporous material, polymkeric substance, carbon nano-tube and Graphene.
3. the method for testing of a kind of functional material thermodynamic parameter as claimed in claim 1, is characterized in that, described resonant-type tiny cantilever beam is integrated piezoresistance type silicon-based micro-cantilevers.
4. the method for testing of a kind of functional material thermodynamic parameter as claimed in claim 1, is characterized in that, the mass sensitivity of described resonant-type tiny cantilever beam is 1.53Hz/pg.
5. the method for testing of a kind of functional material thermodynamic parameter as claimed in claim 1, is characterized in that, specifically comprise the following steps:
(1) be coated with: utilize micromanipulation system by the free end of the dispersed liquid coating of functional material in resonant-type tiny cantilever beam, dry, for subsequent use;
(2) aging: being placed in by the resonant-type tiny cantilever beam being coated with functional material can the test pool of equilibrium temperature, stablizes aging under high pure nitrogen air-flow;
(3) baseline test is carried out: the flow fixedly passing into gas, passes into high pure nitrogen continuously, the frequency of record resonant-type tiny cantilever beam;
(4) sensitivity curve test: at a constant temperature, keep the gas flow identical with step (3), the combination gas of the adsorbed gas and nitrogen that pass into concentration known continuously adsorbs, the frequency of Real-time Collection resonant-type tiny cantilever beam, after remaining unchanged to frequency, the high pure nitrogen passing into same traffic continuously carries out purging desorption, and the frequency of Real-time Collection resonant-type tiny cantilever beam remains unchanged to frequency; Then change the concentration of the adsorbed gas in the mixed gas passed into, repeat above test process; Obtain at such a temperature, the frequency of resonant-type tiny cantilever beam is with the sensitivity curve of adsorbed gas concentration change;
(5) regulate the temperature of test pool to another steady temperature, repeat step (4), obtain frequency another sensitivity curve with adsorbed gas concentration change of resonant-type tiny cantilever beam at another temperature;
(6) according to the mass sensitivity of resonant-type tiny cantilever beam, the sensitivity curve that step (4) and (5) obtain is converted into adsorption isothermal curve: namely under steady temperature, the relation curve of gas absorption amount and pressure;
(7) according to adsorption isothermal curve, according to Clausius-Clapyron Equation, ask and calculate Adsorption en-thalpy Δ H °;
(8) appoint and get an adsorption isothermal, be deformed into the relation curve of P/V and P, obtain adsorption equilibrium costant K and standard equilibrium constant K ° by the intercept of this curve and slope;
(9) according to the numerical value of K, the coverage θ dividing pressure in concrete adsorbed gas is obtained by Lan Miaoer equation;
(10) probe temperature of the isothermal curve got according to K ° and step (8), obtains gibbs free energy change Δ G ° by van' t Hoff equation;
(11) according to the numerical value of gibbs free energy change Δ G ° with Adsorption en-thalpy Δ H °, Entropy Changes Δ S ° is obtained by the definition of gibbs free energy change.
6. the method for testing of a kind of functional material thermodynamic parameter as described in right 5, is characterized in that, in the dispersion liquid of described functional material, functional material concentration is 1-50mg/mL; Be 0.01-1 microlitre in the coating weight of the free end of described resonant-type tiny cantilever beam; The solvent of the dispersion liquid of described functional material is selected from deionized water, ethanol and tetrahydrofuran.
7. the method for testing of a kind of functional material thermodynamic parameter as described in right 5, is characterized in that, in step (2), described to stablize the aging time be 1-5 days.
8. the method for testing of a kind of functional material thermodynamic parameter as described in right 5, is characterized in that, the collection of described frequency uses U.S. Agilent 5313A type frequency meter.
9. the application of resonant-type tiny cantilever beam in the test of functional material thermodynamic parameter, for using resonant-type tiny cantilever beam as micro-mass sensor, functional material is carried on the free end of resonant-type tiny cantilever beam, real-time testing functional material at a certain temperature, to the adsorbance of different pressures gas, obtain the adsorption isothermal of functional material, then calculate the thermodynamic parameter of described functional material further; Then characteristic evaluation can be carried out by the thermodynamic parameter obtained to described functional material.
10. the application of a kind of resonant-type tiny cantilever beam as claimed in claim 8 in the test of functional material thermodynamic parameter, is characterized in that, specifically comprise the following steps:
(1) be coated with: utilize micromanipulation system by the free end of the dispersed liquid coating of functional material in resonant-type tiny cantilever beam, dry, for subsequent use;
(2) aging: being placed in by the resonant-type tiny cantilever beam being coated with functional material can the test pool of equilibrium temperature, stablizes aging under high pure nitrogen air-flow;
(3) baseline test is carried out: the flow fixedly passing into gas, passes into high pure nitrogen continuously, the frequency of record resonant-type tiny cantilever beam;
(4) sensitivity curve test: at a constant temperature, keep the gas flow identical with step (3), the combination gas of the adsorbed gas and nitrogen that pass into concentration known continuously adsorbs, the frequency of Real-time Collection resonant-type tiny cantilever beam, after remaining unchanged to frequency, the high pure nitrogen passing into same traffic continuously carries out purging desorption, and the frequency of Real-time Collection resonant-type tiny cantilever beam remains unchanged to frequency; Then change the concentration of the adsorbed gas in the mixed gas passed into, repeat above test process; Obtain at such a temperature, the frequency of resonant-type tiny cantilever beam is with the sensitivity curve of adsorbed gas concentration change;
(5) regulate the temperature of test pool to another steady temperature, repeat step (4), obtain frequency another sensitivity curve with adsorbed gas concentration change of resonant-type tiny cantilever beam at another temperature;
(6) according to the mass sensitivity of resonant-type tiny cantilever beam, the sensitivity curve that step (4) and (5) obtain is converted into adsorption isothermal curve: namely under steady temperature, the relation curve of gas absorption amount and pressure;
(7) according to adsorption isothermal curve, according to Clausius-Clapyron Equation, ask and calculate Adsorption en-thalpy Δ H °;
(8) appoint and get an adsorption isothermal curve, be deformed into the relation curve of p/V and p, obtain adsorption equilibrium costant K and standard equilibrium constant K ° by the intercept of this curve and slope;
(9) according to the numerical value of K, the coverage θ dividing pressure in concrete adsorbed gas is obtained by Lan Miaoer equation;
(10) probe temperature of the adsorption isothermal curve got according to K ° and step (8), obtains gibbs free energy change Δ G ° by van' t Hoff equation;
(11) according to the numerical value of gibbs free energy change Δ G ° with Adsorption en-thalpy Δ H °, Entropy Changes Δ S ° is obtained by the definition of gibbs free energy change.
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