CN104121873A - Liquid molecule radius measurement method based on microwave frequency sweeping - Google Patents

Abstract

Disclosed is a liquid molecule radius measurement method based on microwave frequency sweeping. The liquid molecule radius measurement method based on the microwave frequency sweeping includes: step one, using a vector network analyzer and a broadband antenna to sweep frequency of liquid based on a transmission method, and confirming an optimum absorption frequency point f of the liquid; step two, obtaining polarization relaxation time tau of the liquid to be detected by using the corresponding condition that omega*tau=1 if dielectric loss of an electromagnetic wave of certain frequency reaches the maximum value when the electromagnetic wave of the certain frequency passes through the liquid to be detected according to Debye theory; step 3, obtaining the radius of each liquid molecule by using a computational formula of the polarization relaxation time, which meets the equation that tau=4*pi*eta* alpha*3/kT, wherein the eta value is viscosity value of the liquid to be detected at specified temperature. The liquid molecule radius measurement method based on the microwave frequency sweeping effectively improves accuracy of data.

Description

A kind of liquid molecular radius measuring method based on microwave frequency sweep

Technical field

The invention belongs to thermometrically field, be specifically related to a kind of liquid molecular radius measuring method based on microwave frequency sweep.

Background technology

The order of magnitude of a molecular size is a very small size, can find a kind of simple and effective method to measure bulk of molecule, thus to the order of magnitude of molecule have one clearly understanding be highly significant.

At present, the relevant method of measuring molecular radius mainly contains two kinds both at home and abroad: the first is the common oil film method of Middle School Physics; The second is according to Einstein's, utilizes the size of solute molecule in solution and the relation of the coefficient of interal friction in solution and neat solvent to try to achieve the size of liquid molecular radius.First method requires higher to details of operation, as the preparation of solution, the measurement of a liquor capacity, the assurance of the thickness of dusting and degree of uniformity etc., working specification step is numerous, difficulty is large, thereby success ratio is lower.Second method is because the coefficient of interal friction of liquid is subject to the impact of temperature larger, but its accurately to the relation of temperature not how explanation.

Summary of the invention

The present invention is intended to solve liquid molecular radius in existing measuring method and measures complex operation step, problem that measuring accuracy is low, and a kind of liquid molecular radius measuring method based on microwave frequency sweep that can effectively improve measuring accuracy is provided.

The liquid molecular radius measuring method based on microwave frequency sweep that the present invention proposes obtains according to Debye theory, from Debye theory, specific inductive capacity has plural form, its imaginary part is called dissipation factor, when when the electromagnetic wave of certain frequency sees through testing liquid, its dielectric loss is maximum, corresponding condition is ω τ=1, the polarization relaxation time that wherein τ is liquid.Accordingly, the method based on microwave frequency sweep is determined the polarization relaxation time that just can obtain liquid after the optimal absorption Frequency point of testing liquid.Finally, according to the relation between the relaxation time of liquid and fluid molecule radius, can obtain the molecular radius of testing liquid.

The molecular radius of trying to achieve liquid according to Debye theory is a kind of more novel method, is not found at present this similar method.

Compared with prior art, the present invention has the following advantages:

The present invention determines the optimal absorption Frequency point of testing liquid by the method for microwave frequency sweep, and according to Debye theory, obtains the polarization relaxation time of testing liquid, and then draws the molecular radius of testing liquid.Solved the problem that in prior art, complex operation, difficulty are greatly, precision is not high.

Specific embodiments

The embodiment that describes this measuring method below in detail, comprises the steps:

Step 1, utilizes vector network analyzer, Broadband Transmitting Antenna Under and receiving antenna to build microwave scanning system, utilizes this apparatus system liquid towards material to carry out frequency sweep, determines the optimal absorption Frequency point f of this material;

Step 2, determines polarization relaxation time of testing liquid according to Debye theory

Debye relaxation equation is shown below:

${\mathrm{\ϵ}}_r^{\′}\left(\mathrm{\ω}\right)={\mathrm{\ϵ}}_{\∞}+({\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_{\∞})\frac{1}{1+{\mathrm{\ω}}^2{\mathrm{\τ}}^2}$

${\mathrm{\ϵ}}_r^{\′\′}\left(\mathrm{\ω}\right)=({\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_{\∞})\frac{\mathrm{\ω\τ}}{1+{\mathrm{\ω}}^2{\mathrm{\τ}}^2}$

ε ' _r(ω) with ε " _r(ω) be respectively real part and the imaginary part of specific inductive capacity.Wherein, ε _sfor quiet specific inductive capacity, ε _∞for optical dielectric constant.ε " _r(ω) with the relation of frequency change, reflected the loss of medium, while seeing through testing liquid by the electromagnetic wave of the known certain frequency of Debye equation, the maximum corresponding condition of its dielectric loss is ω τ=1, in the polarization relaxation time that wherein τ is liquid, finally can obtain the relaxation time τ=1/2 π f of testing liquid.

Step 3, determines the radius of liquid molecule to be measured

The computing formula in relaxation time is as follows:

τ＝4πηa ³/kT

In formula, the viscosity number that η is testing liquid, k is Boltzmann constant, T is temperature, the molecular radius that a is testing liquid.The relaxation time of the testing liquid obtaining according to step 2, and bring the molecular radius that the viscosity number of testing liquid under specified temp T can obtain testing liquid into.

Claims (1)

1. the liquid molecular radius measuring method based on microwave frequency sweep, is characterized in that, said method comprising the steps of:

Step 1, utilizes vector network analyzer and all channel antenna liquid towards material to carry out frequency sweep, determines the optimal absorption Frequency point f of this material;

Step 2, determines polarization relaxation time of testing liquid according to Debye theory

Debye relaxation equation is shown below:

${\mathrm{\ϵ}}_r^{\′}\left(\mathrm{\ω}\right)={\mathrm{\ϵ}}_{\∞}+({\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_{\∞})\frac{1}{1+{\mathrm{\ω}}^2{\mathrm{\τ}}^2}$

${\mathrm{\ϵ}}_r^{\′\′}\left(\mathrm{\ω}\right)=({\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_{\∞})\frac{\mathrm{\ω\τ}}{1+{\mathrm{\ω}}^2{\mathrm{\τ}}^2}$

ε ' _r(ω) with ε " _r(ω) be respectively real part and the imaginary part of specific inductive capacity.Wherein, ε _sfor quiet specific inductive capacity, ε _∞for optical dielectric constant.ε " _r(ω) with the relation of frequency change, reflected the loss of medium, when while seeing through testing liquid by the electromagnetic wave of the known certain frequency of Debye equation, its dielectric loss is maximum, corresponding condition is ω τ=1, in the polarization relaxation time that wherein τ is liquid, finally can obtain the relaxation time τ=1/2 π f of testing liquid.

Step 3, determines the radius of testing liquid molecule

The computing formula in relaxation time is as follows:

τ＝4πηa ³/kT

In formula, the coefficient of viscosity that η is fluent meterial to be measured, k is Boltzmann constant, T is temperature, the molecular radius that a is testing liquid.The relaxation time of the testing liquid obtaining according to step 2, and bring the molecular radius that the coefficient of viscosity of testing liquid under specified temp T can obtain testing liquid into.