CN102175711B - Measuring method and device for coefficients of thermal expansion - Google Patents

Abstract

The invention discloses a measuring method and a measuring device for coefficients of thermal expansion. The measuring method comprises the following steps of: plating a layer of membrane which transmits light partially and reflects the light partially on upper and lower surfaces of a light transmission material to be measured respectively; heating the light transmission material; allowing a beam of monochromatic light to be incident to the light transmission material to be measured in the heating process, and reflecting the monochromatic light on the upper and lower surfaces of the light transmission material respectively, so that two beams of reflected light are interfered with each other; detecting the power of the interfered reflected light, finding a temperature value corresponding to the maximum value of the power of the reflected light, and determining the change period of the power of the reflected light in preset temperature intervals of the light transmission material; and calculating according to the change period to obtain the coefficients of thermal expansion of the light transmission material to be measured in the temperature intervals. By the measured method, the coefficients of thermal expansion of the light transmission material can be measured accurately, the test accuracy is relatively high, and system error caused by thermal expansion of sample frames and the like can be eliminated effectively; and due to the adoption of a single light source, a light path is simple, the cost is low, and the thermal expansion condition of each temperature interval can be reflected visually.

Description

A kind of measuring method of thermal expansivity and device

Technical field

The invention belongs to material thermal property technical field of measurement and test, be specifically related to a kind of measuring method of thermal expansivity of light transmissive material.

Background technology

Thermal expansivity is one of important parameter of exosyndrome material thermophysical property.For the material that is under the temperature variation condition, its thermal expansivity will determine the ability of material anti-thermal shock, the size of thermal stress and the degree of heat deformation.All can stand in various degree Aerodynamic Heating stage in operation and use procedure such as all aerospace flight vehicles, carrier rocket and bore etc., must adopt the less material of thermal expansivity, avoid the serious consequences such as the coating shedding that causes because of heat deformation even complete machine disintegration; In house building course, also should select as far as possible the building materials of low thermal coefficient of expansion, otherwise temperature Change will increase the building materials built-in thermal stress, the house is cracked even cave in.Therefore, the thermal expansivity of Measurement accuracy material has important realistic meaning.

Thermal expansivity measuring method commonly used mainly contains push rod plavini and michelson interferometry at present.Wherein the push rod plavini is a kind of non-absolute method of measurement, need to do further calibration work, and this is owned by France in contact type measurement, and the mechanical stress between bar and the sample can affect the accuracy of test result, thereby its measuring accuracy is relatively low; The two-beam of produce interfering in the michelson interferometry is respectively from the reflection of sample and standard specimen, the inevitable thermal expansion of the parts such as standard specimen and sample stage will affect measuring accuracy, and it can introduce stochastic error by the method for reading interference fringe quantity, test result is not directly perceived, can only measure the mean thermal expansion coefficients of certain warm area.Chinese invention patent " a kind of double light beam laser interferometry of material thermal expansion coefficient " (publication number CN101140249B, the measuring method of the thermal expansivity open day 2010.09.01) does not comprise the measuring method of light transmissive material thermal expansivity, and its use is two bundle incident lights, be difficult to guarantee fully the homogeneity of two bundle laser, the little deviation of light path all can produce larger error in the incident angle of this two-beam and the transmission course, thereby the method is to the selection of light source, the adjusting of light path and the preparation of sample require comparatively harsh, and equipment cost is higher.

Therefore, need urgently at present a kind of can be convenient and measure exactly the method for light transmissive material thermal expansivity.

Summary of the invention

The object of the present invention is to provide a kind of measuring method of thermal expansivity, the thermal expansivity of the method energy Measurement accuracy light transmissive material, its testing precision is higher, can effectively eliminate the systematic error that the thermal expansions such as specimen holder bring, light path is simple, with low cost, can intuitively react the thermal expansion situation of each temperature range.The present invention also provides the measurement mechanism of realizing said method.

A kind of measuring method of thermal expansivity, be specially: the reflective film in a layer segment light transmission part is plated respectively on the upper and lower surface of light transmissive material to be measured, light transmissive material is heated, adopt monochromic beam incident light transmissive material to be measured in the heating process, monochromatic light reflects respectively on the upper and lower surface of light transmissive material, two bundle reflected light interfere, detect the reflected optical power after interfering, obtain reflected optical power with the change curve of light transmissive material temperature, find out two different temperatures T corresponding to reflected optical power maximal value ₁And T ₂, and definite reflected optical power at light transmissive material from temperature T ₁Rise to temperature T ₂Interval period of change is counted N, calculates at last transparent material to be measured at temperature range T ₁To T ₂Between

Thermal expansivity

$\mathrm{\&sigma;}=N\&CenterDot;\frac{\sqrt{n^2-{\sin \mathrm{\&alpha;}}^2}}{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="110111143405.png,110111143407.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}\&CenterDot;\frac{\mathrm{\&lambda;}}{2d(T_2-T_1)}$

Wherein, λ is monochromatic wavelength, and n is the refraction coefficient of light transmissive material to be measured, and α is the angle of monochromatic light and light transmissive material surface normal to be measured, and d is the thickness before the light transmissive material plated film to be measured.

Described film thickness scope is 1～10nm.

Described film is metallic film or semiconductive thin film.

Described metallic film is Au or Ag or Cu or Al, and semiconductive thin film is Ge or Si or GeTe or Sb2Te3.

Realize the measurement mechanism of described thermal expansivity measuring method, comprise heating furnace, light transmissive material upper and lower surface to be measured is placed in the heating furnace by plated film; Be provided with in the heating furnace be used to the temperature thermocouple of measuring light transmissive material temperature to be measured, temperature thermocouple links by temperature data acquisition and connects data processor; The heating furnace top has light hole, the top of light hole is provided with laser instrument and photodetector, and the monochromatic light that laser instrument sends passes light hole incident light transmissive material to be measured, produces two bundle reflected light, two bundle reflected light interfere, and the reflected optical power after the interference is detected by photodetector; Photodetector sends reflected optical power to data processor by the power data capture card.

As further optimization, also between described light hole and described laser instrument, lay the semi-transparent semi-reflecting lens that is the miter angle inclination.

The thermal expansivity of the various light transmissive materials of measuring method energy Accurate Determining of the present invention.What the method was used is single lasing light emitter, and light path is simple, more easily realize, thereby with low cost; Because its two bundle laser of produce interfering are all from the reflection of testing sample, thereby can eliminate the systematic error that the thermal expansion such as specimen holder brings, testing precision is higher; Highly sensitive, even if adopt common red laser (wavelength 650nm) as light source, heating furnace temperature rise to 600 ℃, its minimum resolution still can reach 0.5nm; In addition, the method can also intuitively be reacted the thermal expansion situation of each temperature range.

Description of drawings

Fig. 1 is the synoptic diagram of method of testing of the present invention.

Fig. 2 is a kind of special case of method of testing of the present invention.

Fig. 3 is the structural drawing of test macro of the present invention.

Fig. 4 is that a kind of glass is through the test result synoptic diagram of this test macro.

1. light transmissive materials to be measured among the figure, 2. film, 3. incident light, 4. upper surface reflected light, 5. upper surface transmitted light, 6. lower surface reflected light, 7. lower surface reflection emergent light, 8. beam splitter, 9. upper surface secondary reflection light, 10. lower surface secondary reflection light, 11. heating furnace, 12. light holes, 13. specimen holders, 14. thermopair, 15. laser instruments, 16. photodetectors, 17. the power data capture card, 18. temperature data acquisition cards, 19. data processors

Embodiment

The invention will be further described below in conjunction with drawings and Examples.

Fig. 1 is the synoptic diagram of measuring method of the present invention.The upper and lower surface of light transmissive material 1 to be measured is parallel to each other, but uses vernier caliper Measurement accuracy upper and lower surface spacing d at normal temperatures, and generally speaking, spacing d should be greater than 1mm and less than 1000mm.

Plate respectively the reflective film 2 in a layer segment light transmission part in light transmissive material 1 upper and lower two parallel surfaces to be measured again, the major function of film 2 is to form two reflecting interfaces on the upper and lower surface of light transmissive material 1 to be measured, and its reflectivity should be greater than 10% to guarantee enough intensities of reflected light; For making incident light 3 can arrive lower surface, the transmissivity of film 2 also should be greater than 10%.The thickness of film 2 is generally 1nm to 100nm, be equivalent to survey light transmissive material 1 upper and lower surperficial d 1,000,000/, then the thermal expansion amount of film 2 in heating process also be about 1,000,000 of light transmissive material 1 to be measured/, can ignore on the impact of test result.

The method that generally can adopt sputter, extension or evaporation is at light transmissive material 1 upper and lower two parallel surfaces to be measured Au, Ag, the metallic film such as Cu, Al or Ge, Si, the semiconductive thin films such as GeTe, Sb2Te3 of 1nm to 10nm of growing respectively.These materials all can the reflective and part printing opacity of part when nano thickness, and its reflectivity and transmissivity can change by the thickness of regulating film 2.

Incident light 3 is preferably monochromatic light of coherence, its wavelength is λ, to become the direction at α angle to be incident to light transmissive material 1 upper surface to be measured with light transmissive material 1 surface normal to be measured, wherein a part of light obtains upper surface reflected light 4 through film 2 reflections, part light obtains upper surface transmitted light 5 through film 2 transmissions, transmitted light 5 is the refract light of incident light 3, and the refraction coefficient of light transmissive material 1 to be measured is n, and transmitted light 5 satisfies following refraction condition with the angle β of light transmissive material 1 surface normal to be measured:

sinα＝n sinβ (1)

Transmitted light 5 obtains lower surface reflected light 6 in light transmissive material 1 lower surface reflection to be measured, lower surface reflected light 6 obtains lower surface reflection emergent light 7 through 2 transmissions of upper surface film, lower surface reflection emergent light 7 is parallel with upper surface reflected light 4 directions as can be known by the refraction condition, and two-beam is from same incident light 3, frequency is identical, thereby lower surface reflects emergent light 7 and upper surface reflected light 4 will interfere.Detector is placed reflected optical power after this two bundle can detect interference on the catoptrical emitting light path, and reflected optical power will be with the variation of the phase differential generating period of this two-beam.

Can be got by geometric relationship, the optical path difference Δ s of lower surface reflection emergent light 7 and upper surface reflected light 4 is

Δs＝2d/cosβ (2)

By coherent condition as can be known, the optical path difference Δ s of surface reflection emergent light 7 and upper surface reflected light 4 is even-multiple (2N, N=0,1,2 of half wavelength lambda/2 instantly ...) time, two row light coherent phases are long, and reflected optical power is maximum; Instantly the optical path difference Δ s of surface reflection emergent light 7 and upper surface reflected light 4 is odd-multiple (2N+1, N=0,1,2 of half wavelength lambda/2 ...) time, two row light coherent subtractions, reflected optical power is minimum.In the process of heating transparent material 1 to be measured, its upper and lower surface spacing changes because of thermal expansion, and reflected optical power is with the variation of generating period.If when transparent material to be measured 1 is respectively T in temperature ₁And T ₂The time, its upper and lower surface spacing is respectively d ₁And d ₂, peak-peak all appears in reflected optical power, and temperature T ₁, T ₂The N of the corresponding reflected optical power of difference ₁, N ₂Individual peak value is then had by formula (1), formula (2) and coherent condition:

${\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="110111143405.png,110111143407.png"\; state="\{\{state\}\}">d</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="110111143405.png,110111143407.png"\; state="\{\{state\}\}">N</figure-callout>}}_1\&CenterDot;\frac{\sqrt{n^2-{\sin \mathrm{\&alpha;}}^2}}{n}\&CenterDot;\frac{\mathrm{\&lambda;}}{2}$

${\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="110111143405.png,110111143407.png"\; state="\{\{state\}\}">d</figure-callout>}}_2={\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="110111143405.png,110111143407.png"\; state="\{\{state\}\}">N</figure-callout>}}_2\&CenterDot;\frac{\sqrt{n^2-{\sin \mathrm{\&alpha;}}^2}}{n}\&CenterDot;\frac{\mathrm{\&lambda;}}{2}$

N wherein ₁, N ₂Be positive integer.

Then transparent material 1 to be measured is at temperature range T ₁And T ₂Between thermal expansivity σ be:

$\mathrm{\&sigma;}=\frac{d_2-d_1}{d\&CenterDot;(T_2-T_1)}=N\&CenterDot;\frac{\sqrt{n^2-\sin {\mathrm{\&alpha;}}^2}}{n}\&CenterDot;\frac{\mathrm{\&lambda;}}{2d(T_2-T_1)}---\left(3\right)$

In the formula (3), N=N ₂-N ₁, expression temperature range T ₁And T ₂Between the periodicity that changes of reflected optical power, can directly count by reflected optical power variation with temperature graph of a relation, incident light 3 and angle α, the refraction coefficient n of light transmissive material to be measured 1 of light transmissive material 1 surface normal to be measured, upper and lower surface spacing d and the wavelength X of incident light 3 at normal temperatures is all known, just can try to achieve transparent material 1 to be measured at temperature range T ₁And T ₂Between thermal expansivity σ.

Especially, when incident light 3 vertical incidence light transmissive material to be measured 1 surface, the angle α of incident light 3 and light transmissive material 1 surface normal to be measured=0, formula (3) can be write as:

$\mathrm{\&sigma;}=N\&CenterDot;\frac{\mathrm{\&lambda;}}{2d(T_2-T_1)}---\left(4\right)$

Can record the refraction coefficient n of light transmissive material 1 to be measured thermal expansivity when unknown with this method.

Figure 2 shows that a kind of special case of measuring method of the present invention when incident light 3 vertical incidence light transmissive material to be measured 1 surface.Because incident light 3 and lower surface reflection emergent light 7 and upper surface reflected light 4 must arrange in the input path of incident light 3 semi-transparent semi-reflecting lens 8 on the same light path.With semi-transparent semi-reflecting lens 8 and incident light transmissive material 1 surperficial placement at 45 ° to be measured, incident light 3 sees through semi-transparent semi-reflecting lens 8 vertical incidence light transmissive material to be measured 1 surface, upper and lower surface reflection through light transmissive material 1 to be measured obtains upper surface reflected light 4 and lower surface reflection emergent light 7 respectively, upper surface reflected light 4 and lower surface reflection emergent light 7 are back to semi-transparent semi-reflecting lens 8 along original optical path, after semi-transparent semi-reflecting lens 8 reflections, be parallel to light transmissive material to be measured 1 surface and penetrate, obtain respectively upper surface secondary reflection light 9 and lower surface secondary reflection light 10.Upper surface secondary reflection light 9 and lower surface secondary reflection light 10 interfere, detect this two bundles reflected optical power, and describe reflected optical power variation with temperature curve, from curve map, read temperature corresponding to reflected optical power peak value and during the periodicity that changes of reflected optical power, just can be obtained the thermal expansivity of transparent material 1 to be measured by formula (4).

Fig. 3 is a kind of structural drawing of realizing the test macro of measuring method of the present invention.Have light hole 12 on the cover plate of heating furnace 11, be provided with furnace chamber in the heating furnace 11, specimen holder 13 is positioned at the furnace chamber of heating furnace 11, and be positioned at light hole 12 under, temperature thermocouple 14 is positioned at specimen holder 13 bottoms, is placed with laser instrument 15 and photodetector 16 above light hole 12.Light transmissive material to be measured 1 upper and lower surface is parallel, and be coated with respectively the reflective film 2 in a layer segment light transmission part, light transmissive material 1 to be measured is placed horizontally on the specimen holder 13, and is positioned on laser instrument 15 emitting light paths, and photodetector is positioned on the reflected light path of 1 pair of incident light 3 of light transmissive material to be measured.Temperature thermocouple 14 links to each other with data processor 19 by temperature data acquisition card 18, and photodetector 16 links to each other with data processor 19 by power data capture card 17.

If during incident light 3 vertical incidence light transmissive material to be measured 1 surface, then a semi-transparent semi-reflecting lens 8 must be set in the input path of incident light 3, and semi-transparent semi-reflecting lens 8 and incident light transmissive material 1 surperficial placement at 45 ° to be measured.

During use, the incident light 3 of laser instrument 15 emissions incides on the light transmissive material 1 to be measured through light hole 12, photodetector 16 is used for receiving by light transmissive material 1 to be measured, the upper surface reflected light 4 that lower surface reflects respectively and lower surface reflection emergent light 7, export power data capture card 17 to after converting reflected optical power to electric signal, power data capture card 17 comprises integrated operational amplifier, A/D modular converter and connectivity port, signal by photodetector 11 outputs is sent to the A/D modular converter after integrated operational amplifier is amplified to suitable scope, the A/D modular converter links to each other with data processor 19 by the connectivity port, the A/D modular converter provides clock by data processor 19, and by beginning and end that data processor 19 provides enable signal control to gather, so just photodetector 16 received optical power signals are sent to data processor 19.After starting heating furnace 12, thermopair 14 is for detection of real time temperature, and temperature signal is changed into the electric signal number go out to temperature data acquisition card 18, temperature data acquisition card 18 links to each other with data processor 19 by the connectivity port, so just with temperature over time relation data be sent to data processor 19.Data processor 19 will carry out related with the reflected optical power data of being obtained by power data capture card 17 by the temperature data that temperature data acquisition card 18 obtains, realize the coordination of the sample frequency of temperature data and reflected optical power data by interpolation processing, and the calibration of passing through system time realizes the consistent of sampling start time, be convenient to like this to realize the corresponding one by one of temperature data and reflected optical power data, can obtain reflected optical power-temperature curve thus.From curve map, read temperature corresponding to reflected optical power peak value and during the periodicity that changes of reflected optical power, just can be obtained the thermal expansivity of transparent material 1 to be measured by formula (3).

Because the two row light that interfere (upper surface reflected light 4 and lower surface reflection emergent light 7) are all from the reflection of light transmissive material to be measured, thermal expansion from specimen holder 13 and relevant retaining element affects two row light with equal extent ground, and cancel out each other in asking the process of path difference, thereby it can eliminate the systematic error of being brought by thermal expansions such as specimen holders 13.

The below demonstrates the process that this measuring method and test macro are measured material thermal expansion coefficient as an example of a kind of transparent glass material example:

Get the common microslide of a slice, recording its upper and lower surface spacing d with vernier caliper is 1.52mm, adopts the method for sputter to plate respectively the thick Sb2Te3 film of 5nm on the upper and lower surface of microslide, and the microslide behind the plated film is placed on the specimen holder in the heating furnace.Produce the laser that a branch of wavelength is 650nm by semiconductor laser, vertical incidence slide surface after the semi-transparent semi-reflecting lens transmission, reflected light is received by photodetector, and reflected optical power reaches data processor through the power data capture card.Start the heating furnace heating, real time temperature is surveyed by thermopair, and is sent to data processor through the temperature data acquisition card.Data processor is made reflected optical power after with the reflected optical power that obtains and temperature data correspondence---temperature curve.

Reflected optical power---the temperature curve from 20 ℃ to 250 ℃ of room temperatures that Fig. 4 obtains through this test macro for this microslide, as can be seen from the figure, respectively at 41.9 ℃, 74.3 ℃, 98.7 ℃, 121.8 ℃, 144.7 ℃, 168 ℃, 191.5 ℃, 214.3 ℃, the peak value of reflected optical power appears in 237.1 ℃ of temperature places, it is interval to choose two adjacent peak value corresponding temperatures, then N in the formula (4) ₂-N ₁=1, and calculate this microslide at each temperature range thermal expansivity, result such as following table by formula (4):

Table 1 glass sample is in heat bang the swollen coefficient test result of each temperature range

The simple glass thermal expansivity is 4～11.5 * 10 in " mechanical design handbook " ^-6/ ℃, comparatively identical with it with the result that measuring method of the present invention records.Measuring method of the present invention can also Measurement accuracy different temperatures interval thermal expansivity, measurement result can intuitively show from figure.

The above is preferred embodiment of the present invention, but the present invention should not be confined to the disclosed content of this embodiment and accompanying drawing.So everyly do not break away from the equivalence of finishing under the spirit disclosed in this invention or revise, all fall into the scope of protection of the invention.

Claims (6)

1. the measuring method of a thermal expansivity, be specially: the reflective film in a layer segment light transmission part is plated respectively on the upper and lower surface of light transmissive material to be measured, light transmissive material is heated, adopt monochromic beam incident light transmissive material to be measured in the heating process, monochromatic light reflects respectively on the upper and lower surface of light transmissive material, two bundle reflected light interfere, detect the reflected optical power after interfering, obtain reflected optical power with the change curve of light transmissive material temperature, find out two different temperatures T corresponding to reflected optical power maximal value ₁And T ₂, and definite reflected optical power at light transmissive material from temperature T ₁Rise to temperature T ₂Interval period of change is counted N, calculates at last transparent material to be measured at temperature range T ₁To T ₂Between

Thermal expansivity

Wherein, λ is monochromatic wavelength, and n is the refraction coefficient of light transmissive material to be measured, and α is the angle of monochromatic light and light transmissive material surface normal to be measured, and d is the thickness before the light transmissive material plated film to be measured.

2. the measuring method of thermal expansivity according to claim 1 is characterized in that, described film thickness scope is 1～10nm.

3. the measuring method of thermal expansivity according to claim 1 is characterized in that, described film is metallic film or semiconductive thin film.

4. the measuring method of thermal expansivity according to claim 3 is characterized in that, described metallic film is Au or Ag or Cu or Al, and semiconductive thin film is Ge or Si or GeTe or Sb2Te3.

5. realize the measurement mechanism of one of claim 1 to 4 described thermal expansivity measuring method, comprise heating furnace, light transmissive material upper and lower surface to be measured is placed in the heating furnace by plated film; Be provided with in the heating furnace be used to the temperature thermocouple of measuring light transmissive material temperature to be measured, temperature thermocouple links by temperature data acquisition and connects data processor; The heating furnace top has light hole, the top of light hole is provided with laser instrument and photodetector, and the monochromatic light that laser instrument sends passes light hole incident light transmissive material to be measured, produces two bundle reflected light, two bundle reflected light interfere, and the reflected optical power after the interference is detected by photodetector; Photodetector sends reflected optical power to data processor by the power data capture card.

6. measurement mechanism according to claim 5 is characterized in that, also lays to be the semi-transparent semi-reflecting lens that miter angle tilts between described light hole and described laser instrument.

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