CN106568681B - A kind of accurate measurement method of diamagnetic substance density - Google Patents
A kind of accurate measurement method of diamagnetic substance density Download PDFInfo
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- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/10—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by observing bodies wholly or partially immersed in fluid materials
- G01N9/12—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity by observing bodies wholly or partially immersed in fluid materials by observing the depth of immersion of the bodies, e.g. hydrometers
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Abstract
The invention discloses a kind of accurate measurement method of diamagnetic substance density, include the following steps: that (1) determines medium solution according to specimen material；(2) sample is placed in medium solution；(3) medium solution is placed in magnetic suspension detection device, that is, be placed among two opposed square magnets of homopolarity；The size of two square magnets is 50mm*50mm*25mm, mutual distance 60mm；(4) height that measurement sample floats；(5) sample rate is calculated.Compared with prior art, the beneficial effects of the present invention are: the required device of the present invention is easy to operate, low in cost, measurement result is easy to observe, and measurement accuracy is high, it is easy to accomplish automation.
Description
Technical field
The present invention relates to a kind of detection methods, and in particular to a kind of accurate measurement method of diamagnetic substance density.
Background technique
Density is most basic one of the important physical feature of substance, and the density of different material is generally different.Meanwhile it is different
Internal microstructure, substance, which are formed in, macroscopically can also be embodied in the variation of density.The measurement of density is in scientific research, production process
With important meaning is all had in life.The law of buoyancy that Archimedes has found before 2200 is the most widely used side of Density Detection
Method, deriving method include: infusion process, bottle method, method of drifting along, density gradient column method and densimeter method.In recent years, based on new
Technological development goes out gas differential pressure method, supercritical ultrasonics technology, Equation law of Ideal Gas State etc., for measuring the substance of different conditions
Density, precision highest can achieve 0.007g/cm3。
Magnetism is also one of basic physical features possessed by substance.Any substance can be magnetized in magnetic field.According to
Magnetize the complementary field direction generated, substance is divided into paramagnet and diamagnetic substance.The wherein additional magnetic of paramagnet
Field is identical as excitation field direction, conversely, the complementary field that diamagnetic substance generates is opposite with excitation field.Conjugate is magnetic
And magnetic-Archimedes's suspension that Archimedes principle proposes keeps floating condition of the object in magnetic field no longer harsh, Ke Yiqu
Obtain more application.
For Archimedes principle and its deriving method, it is existing that degree of precision is usually relatively inaccessible to the measurement of density
Density Detection method, to reach high-precision measurement, it usually needs use expensive measuring device.Also, it is based on A Ji meter
The measurement method of moral principle is not usually high to small sample sensitivity, be easy to cause biggish measurement error.And color density
Measurement method is then applied to newer technical method, and measuring device costly, and operates and calculation method is cumbersome, to small ruler
The application development of the density measure of very little sample compares limitation.
Summary of the invention
The present invention is theoretical based on magnetic suspension aiming at the problem that method of existing measurement density, propose it is a kind of based on magnetic-Ah
The accurate measurement method of the diamagnetic substance density of base Mead principle.
The measuring device of the method for the present invention is mainly identical having a size of 50mm × 50mm × 25mm by two pieces, and surface induction is strong
Spend it is identical, induction level be 0.425T square magnet homopolarity it is opposed at a distance of 60mm constitute.
The present invention be suitable for size it is lesser and for diamagnetism sample rate measure.
The principle of the invention is based on magnetic A-base Mead principle.Specific implementation step is as follows:
1) suitable medium solution is configured.
2) sample is placed in solution.
3) solution is placed in magnetic suspension detection device.
4) hoverheight of measurement sample in the solution.
5) sample rate is calculated.
The magnetic suspension detection method of above-mentioned density, calculation formula are as follows:
ρs=ρm-(660.739-48.232x+1.322x2-1.475×10-2x3)χm
In formula, ρsWith ρmRespectively sample density and medium solution density (g/cm3), χmFor medium solution magnetic susceptibility
(dimensionless).
Preferably, guaranteeing that sample floats distance in the solution is 10~50mm when collocating medium solution.
Preferably, medium solution is paramagnetic medium aqueous solution, further preferably MnCl2Aqueous solution.
Preferably, medium solution density is slightly less than sample rate when collocating medium solution.
Preferably, carrying out the calibration of the density and magnetic susceptibility of medium solution before collocating medium solution.
Preferably, the sample is that full-size is not more than 5mm.It is especially applicable to the lesser sample of size is close
Degree measurement, detection accuracy are higher.
Preferably, the sample is center symmetrical structure.
Preferably, the sample is circular sample.
The magnetic suspension measurement method of above-mentioned density should estimate the density of product, simultaneously according to product material before detection
Configure corresponding medium solution.It such as needs to accurately calculate solution magnetization rate, solution magnetization rate can be measured with Gu Aifa.
Compared with prior art, the beneficial effects of the present invention are: the present invention provides a kind of completely new detection material densities
Method, required device is easy to operate, and low in cost, measurement result is easy to observe, and measurement accuracy is high, it is easy to accomplish automatic
Change.
Detailed description of the invention
Fig. 1 is magnetic levitation system schematic diagram of the present invention.
Fig. 2 is that the present invention is 0.425T magnet to 50mm*50mm*25mm surface induction intensity, when distance is 60mm,XOy plane, component is parallel in the calculating cloud atlas of central cross-section.
Fig. 3 is fitting result of the present invention to standard density ball experimental result.
Specific embodiment
To be more clearly understood the present invention, below according to specific example and attached drawing of the invention, the present invention is carried out
Further instruction.
As shown in Figure 1, be magnetic levitation system schematic diagram of the invention, including magnet 1, magnet 4, medium solution 2, sample 3,
Medium solution container 5.Container 5 requires transparent to be easy to measure inner sample height.Distance is d between magnet 1, magnet 4.Detected sample
Hoverheight is Z to product 3 in the solution.
Magnet 1, magnet 4 are the square magnet of 50mm*50mm*25mm, the magnetic of center surface magnetic induction intensity 0.425T
Iron, the opposed composition of distance 60mm homopolarity.
Wherein, measurement method is as follows:
A kind of accurate measurement method of diamagnetic substance density, comprising:
(1) sample rate is estimated according to specimen material.
The medium solution of suitable concentration is configured, guarantees that sample can float more than 10mm in the solution.
Before the experiment, can density to medium solution and magnetic susceptibility demarcate, when calibration, configuration concentration is integer
Then mole every liter of solution carries out the calibration of density and magnetic susceptibility, referring to table 1.
When collocating medium solution, in suitable range, medium solution density is slightly less than sample rate.
(2) sample is placed in medium solution.
(3) medium solution is placed in magnetic suspension detection device, that is, be placed between magnet 1, magnet 4.
(4) height that measurement sample floats.
(5) sample rate is calculated.
Density measure is carried out to PV (vulcanized rubber) raw material (cylindrical pellet of full-size about 5mm) using this method,
The medium solution of selection is the MnCl of 2.5mol/L2Solution, various concentration MnCl2Density corresponding to solution and magnetic susceptibility such as table 1
It is shown:
Table 1 is various concentration MnCl2Density corresponding to solution and magnetic susceptibility.
| Concentration (mol/L) | Density (g/cm3) | Magnetic susceptibility |
| 1 | 1.099 | 1.774×10-4 |
| 1.5 | 1.148 | 2.771×10-4 |
| 2 | 1.196 | 3.724×10-4 |
| 2.5 | 1.244 | 4.650×10-4 |
| 3 | 1.292 | 5.438×10-4 |
Sample is placed in manganese chloride solution behind alcohol washes surface, is put into device.10 minutes are stood, to sample
Position is stablized, and measures hoverheight with milimeter scale.Altitude reading is 35.6mm, and the density by calculating available sample is
1.218g/cm3。
The magnetic suspension detection method of above-mentioned density, calculation formula are as follows:
ρs=ρm-(660.739-48.232x+1.322x2-1.475×10-2x3)χm
The magnetic suspension detection method of above-mentioned density, the principle is as follows:
For paramagnet in magnetic field, the complementary field of generation is identical as magnetic field, gravitation of the substance by magnetic field；
Conversely, diamagnetic substance will receive the repulsion in magnetic field:
In formula, χ is substance magnetic susceptibility, and paramagnet magnetic susceptibility is positive value, and diamagnetic substance magnetic susceptibility is negative；μ0=4 π
×10-7N/A2For space permeability；V is mass volume (m in magnetic field3)；For the magnetic induction intensity in substance position magnetic field
(T)；For vector gradient operator.
When there are when paramagnetic medium solution, magnetic field generates gravitation to medium solution in magnetic field, therefore can be to being immersed
Substance generates the additional buoyancy generated by magnetic field:
Diamagnetism sample will receive the comprehensive function of three gravity, buoyancy and magnetic force power in paramagnetism solution.
When three dynamic balances, sample, which suspends, reaches stable state:
In formula,For gravity,For buoyancy,The active force that sample is generated for magnetic field:
By above-mentioned several formulas it is found that if samples remained stable suspends,0 is necessary in x-axis and y-axis component.Work as sample
When product can keep stable suspersion, it can arrange to obtain:
In general, being suspended substance magnetic susceptibility several orders of magnitude numerically smaller than medium solution, can ignore:
When giving fixed-field and medium solution magnetic susceptibility, the hoverheight z of sample is only related to sample itself density.By upper
Formula can calculate sample rate according to sample hoverheight.
For device for detecting density proposed in this paper, two pieces of magnet intermediate regions, sample can be pulled to two magnetic blow out centre
On line, therefore, when substance can suspend in autocracy to get up, it can achieve to stablize on two magnetic blow out centre lines and hang
It is floating.
Due toCalculation formula complexity it is cumbersome, therefore by being fitted to experimental result, obtain density
Approximate formula.Selection standard density ball is tested in the MnCl of 2.0mol/L2One group of experiment of middle progress, standard density ball are selected
1.07~1.30g/cm3, it is divided into 0.01g/cm324 samples suspend in measuring device, record hoverheight, such as
Table 2.
Table 2
| Standard density ball density (g/cm3) | Hoverheight (mm) |
| 1.07 | 51.3 |
| 1.08 | 50.2 |
| 1.09 | 49.2 |
| 1.1 | 48.2 |
| 1.11 | 46.9 |
| 1.12 | 45.7 |
| 1.13 | 44.3 |
| 1.14 | 42.6 |
| 1.15 | 41 |
| 1.16 | 39.3 |
| 1.17 | 36.9 |
| 1.18 | 34.3 |
| 1.19 | 31.1 |
| 1.2 | 28.1 |
| 1.21 | 25.2 |
| 1.22 | 22.9 |
| 1.23 | 20.5 |
| 1.24 | 18.7 |
| 1.25 | 17 |
| 1.26 | 15.4 |
| 1.27 | 14.1 |
| 1.28 | 12.7 |
| 1.29 | 11.5 |
| 1.3 | 10.4 |
By the fitting to these experimental results, the available MnCl in 2.0mol/L2In medium solution, the meter of density
Calculate formula are as follows:
ρs=1.4428-0.01828z2+5.00887×10-4z2-5.59201×10-6z3
Fitting result and experimental result have very high degree of fitting, curve R2=0.99991.
In conjunction with the MnCl of 2.0mol/L2The density and magnetic susceptibility of solution, can derive the in office of the method for the present invention device
Density calculation formula under the conditions of meaning medium solution are as follows:
ρs=ρm-(660.739-48.232x+1.322x2-1.475×10-2x3)χm
The accurate measurement method of above-mentioned diamagnetic substance density should estimate the close of product according to product material before detection
Degree, while configuring corresponding medium solution.It such as needs to accurately calculate solution magnetization rate, solution magnetization can be measured with Gu Aifa
Rate.
The foregoing is merely an application example of the invention, the not restrictions to sample range is applicable in.It can apply
The material that the present invention measures, there is no need and unable to exhaustive one by one, it is all within spirit of that invention and principle, done any repair
Change, equivalent replacement, improve etc., it should be included within the scope of the present invention.
Claims (6)
1. a kind of accurate measurement method of diamagnetic substance density, which comprises the steps of:
(1) medium solution is determined according to specimen material；When collocating medium solution, medium solution density is slightly less than sample rate, protects
Demonstrate,prove sample in the solution hoverheight between 10~50mm；
(2) sample is placed in medium solution, the sample is that full-size is not more than 5mm；
(3) medium solution is placed in magnetic suspension detection device, that is, be placed among two opposed square magnets of homopolarity；Two sides
The size of shape magnet is 50mm*50mm*25mm, mutual distance 60mm；
(4) height that measurement sample floats；
(5) sample rate is calculated；
Wherein:
ρs=ρm-(660.739-48.232x+1.322x2-1.475×10-2x3)χm；
ρsFor sample density, g/cm3；ρmFor medium solution density, g/cm3；χmFor medium solution magnetic susceptibility.
2. the accurate measurement method of diamagnetic substance density according to claim 1, which is characterized in that two square magnets
The magnet for being 0.425T for center surface induction intensity.
3. the accurate measurement method of diamagnetic substance density according to claim 1, which is characterized in that medium solution is suitable
Magnetic medium aqueous solution.
4. the accurate measurement method of diamagnetic substance density according to claim 1, which is characterized in that collocating medium solution
Before, carry out the calibration of the density and magnetic susceptibility of medium solution.
5. the accurate measurement method of diamagnetic substance density according to claim 1, which is characterized in that during the sample is
Heart symmetrical structure.
6. the accurate measurement method of diamagnetic substance density according to claim 5, which is characterized in that the sample is circle
Shape sample.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108872007B (en) * | 2017-05-15 | 2020-11-03 | 浙江大学 | Double-block ring magnet magnetic suspension detection method for detecting density |
| CN107478543B (en) * | 2017-07-08 | 2019-07-05 | 上海交通大学 | Centrifugal density measuring equipment and method based on diamagnetic suspension theory |
| CN108120660B (en) * | 2017-12-04 | 2019-09-24 | 浙江大学 | A kind of magnetic method of operating based on magnetic Archimedes |
| CN109916771B (en) * | 2019-03-18 | 2021-11-05 | 北京工业大学 | Powder bed density calibration and measurement device for powder type 3D printer |
| CN110376274B (en) * | 2019-06-26 | 2021-06-04 | 浙江大学 | Magnetic suspension detection method and device for shrinkage cavity defect of aluminum alloy part |
| CN111426599B (en) * | 2020-04-20 | 2021-07-30 | 上海交通大学 | Dynamic diamagnetic suspension multi-dimensional density measuring device and method |
| CN113203657A (en) * | 2021-04-28 | 2021-08-03 | 浙江大学 | Large magnetic suspension detection method and device based on magnet array |
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