Test method for normal spectral emittance of metals and nonmetallic materials
Some standard content:
National Standard of the People's Republic of China
Spectral method for metals and nonmetallic materials
Test method for normal spectral emittalceof metals aod nonmetallic Hic meterials UDC 666.764:620
.193.6
GB 7286.2—87
This standard applies to the precise determination of the spectral normal emissivity of metal and nonmetallic material samples. The test wavelength range is not less than 2.5-25.0m, and the temperature range is 700～1300. 1 Terms
1.1 Radiant brightness "L"
It is defined in accordance with GB3102.6--82 "Light and related electromagnetic radiation symbols and units" 1+6-12.1. 1.2 Emissivity "ε", spectral emissivity "(a)" Spectral directional emissivity "(,,)" is defined in accordance with 6-18.1 ~ 18.3 of GH 3102.6-821. 1.s Full normal emissivity "&n (T)"
Definition: The ratio of the normal radiant brightness of the surface of the thermal radiator to the normal radiant brightness of the black body at the same temperature within the wavelength range of 0 ~ α.
1.4 Spectral normal emissivity "e. (, T)" is defined as the spectral directional emissivity when = 0". The spectral directional emissivity measured within the 5" angular range can be called spectral normal emissivity in this standard. 1.5 The relationship between the total normal emissivity and the spectral normal emissivity can be calculated according to the following equation:
Wherein: La
en (T)=a Jmen(A, T)Lhda/aT
Blackbody spectral radiance, W/sr-m·um wavelength,
Steffan-Boltzmann constant, 5.67×10aW/m.KT Sample and blackbody temperature, K.
2. Test Principle
2.1 This standard adopts the separation blackbody test method with higher test accuracy. Under the conditions of a clean and dry atmosphere and the same geometric optics, the spectral normal radiance of the sample is taken as the ratio of the spectral normal radiance of the sample to the spectral normal radiance of the black body at the same temperature, that is, the spectral normal emissivity of the sample is obtained. Figure 1 is a schematic diagram of the test equipment.
2.2 The characteristics of this standard are the use of a precise double-beam automatic recording infrared spectrophotometer, which has the function of recording the ratio of the spectral radiance of the sample to the spectral radiance of the black body, and the scanning range is not less than 12.5 ~ 25.0um. A precise temperature controller is used to control and maintain the same temperature on the sample surface and the black body. Approved by the National Bureau of Standards on February 21, 1987
1987 -12-01 Implementation
3 Sample
3.1 Sample shape and size
3.1.1 The sample is in the shape of a disc.
Thermoelectric
Detector
GB7288.2—87
Detector
Mountain pass makeup
Enter! Get seam
M5 optical wedge
Cheng reducer
Cold and water inlet 1
Cold water
Long cold light cake
Figure 1 Infrared spectrum emissivity test equipment Schematic diagram 3.1.2 The diameter of the gold sample is 20.0mm and the thickness is 2.0mm. There is a temperature measuring hole with a diameter of 1.2mm and a depth of 1.5~1.8mm in the center of the back.
The diameter of the non-metallic sample is 20.0mm and the thickness is 2.51m. There is a temperature measuring hole with a diameter of 1.2mm and a depth of 2.0~2.3mm in the center of the back.
3.2 Sample preparation
Process and treat the surface of the wafer according to the actual surface state; or sample the surface of the actual object to be tested. The surface of the sample should not be damaged during the L process. 3.8 Buried Thermoelectric
Thermocouples are fixed to the temperature measuring holes on the back of the sample by riveting or high-temperature adhesive bonding. The thermocouples fixed to the temperature measuring holes of the sample should withstand at least 1N of tensile force without falling off.
Test equipment
, 1 required body
4.1.1 The structure of the black body furnace recommended in this standard is shown in Figure 2. The furnace core made of stainless steel is a finite cylindrical cavity closed at one end, with a threaded groove on the inner surface. It is oxidized at 1273K for 3h, and the inner surface emissivity can be above 0.86. GB7286.2-87||tt| |Figure 2 Schematic diagram of the structure of the black body furnace
1—furnace cover 2—stone and metal bottle, 3—black body cavity core, 4—temperature measurement and temperature control thermocouple, —furnace shell: 6—oxide ceramic, 7—resistance wire: 8—aluminum silicate refractory red quartz Dewar bottle cover 41.2 This standard requires that the effective emissivity of the black body cavity is greater than 0.99. When the temperature difference from the bottom of the black body cavity to the cavity mouth is maintained below 3K, it can be approximated as an isothermal cavity. The effective emissivity of the black body cavity can be calculated by referring to the Gouffe equation or the DeVos equation. Gauffe calculation equation l is as follows: e[1 +(1-e)(
I Where:
black body cavity effective emissivity;
black body cavity internal surface emissivity;
black body cavity parallel port area, mm\:
S—total surface area of the black body cavity, mm2, [distance from cavity mouth to cavity bottom, mm.
4.1.3 The temperature of the blackbody cavity is measured by a calibrated thermocouple. The thermocouple contact is riveted to the inner wall of the cavity bottom from the back of the cavity bottom, and the thermocouple lead wire is insulated by an alumina sleeve. The temperature of the blackbody cavity is controlled by a precision temperature controller. The test process is small, and the change of the cavity temperature should be small.
4.1.4 When the required temperature measurement range is 500~1000K and meets the test requirements of this test method, the blackbody furnace that meets the first-level standard technical conditions as specified in J3G 309-3 "500~1000KT Industrial Blackbody Radiation Source" can be applied to this standard. 4.1.5 In order to calibrate the 100-frequency line of the tester, this standard requires the preparation of two blackbody furnaces. 4.2 Sample Heating Furnace
4.2.1 The structure of the sample heating furnace recommended by this standard is shown in Figure 3. 4.2.2 In order to ensure the uniform surface temperature of the sample, a uniform heating plate is installed on the back of the sample. The temperature difference of the sample surface in the test area should be less than 1K. 4.2. The sample temperature is measured by a thermocouple embedded in the sample from the back. The thermocouple of metal samples is riveted, and the thermocouple of non-metallic samples is bonded with a high-temperature adhesive. In order to ensure reliable contact between the thermocouple and the sample, the thermocouple should be able to withstand at least 1N of tension without falling off the sample.
GB 72B6.2—87
Figure 3 Schematic diagram of the sample heating furnace structure
1—quartz Dewar cover: 2—furnace shell cover 3—furnace shell: 4—alumina sample hook heating rack, 5-temperature control thermocouple, 6—Shimei glass Dewar, 7—alumina ceramic tube, 8—silicic acid pot refractory red fiber, 9—resistance wire, 10—stainless steel furnace core, 11—sample, 12—alumina ceramic gasket, 13—washer: 14 temperature measuring thermocouple
4.2.4 The temperature control thermocouple of the sample heating furnace is riveted to the furnace core from the back of the bottom of the furnace core and insulated with an alumina sleeve. The temperature is controlled by a precision temperature controller. During the test, the temperature change of the sample surface should be less than 1K. 4.2.5 The projected radiation from the furnace mouth to the sample surface should be minimized. In this test method, the surface of the quartz Dewar cover at the furnace mouth is evaporated with gold. 4.3 Infrared spectrophotometer
4.3.1 Use a double-beam automatic scanning and recording spectrophotometer. 4.3.2 The scanning wavelength range of the spectrophotometer shall not be less than 2.5-25.0μm. 4.3.8 The accuracy of the instrument shall be better than 1%.
4.4 Temperature measurement and temperature control
The thermocouple used for temperature measurement shall be calibrated, and the thermocouples of the same batch shall be selected as much as possible. 4.4.2 The temperature measuring instrument shall not be lower than Class 0.5. 4.4.3 The temperature control accuracy of the precision temperature controller shall be better than 1K. 4.5 Water-cooled light barrier
4.5.1 A single-circulation water-cooled light barrier shall be placed in front of the furnace mouth of the black body furnace and the sample heating furnace to reduce the stray radiation entering the infrared spectrophotometer. The water-cooled light barrier shall be able to maintain the temperature of the cooling water without being affected by the furnace temperature. The surface of the water-cooled light barrier shall be painted with matte black paint. 4.5.2 The size of the effective aperture of the water-cooled light barrier is related to the black body cavity and the detector. Figure 4 shows the geometric arrangement of the two. The effective aperture of the water-cooled light barrier should satisfy the equation:
GB72B6.2—87
Figure 4 Determination of the effective aperture of the water-cooled light barrier
dD,-(S/ (DD)
Wu: d-effective aperture of the water-cooled light barrier, mm; D,——diameter of the bottom of the black body cavity, mml
0,-—opening aperture of the black body cavity, mm;
1-—length of the black body cavity, mm,wwW.bzxz.Net
S is the distance from the bottom of the black body cavity to the effective light barrier, mm. In addition, the distance L from the detector to the water-cooled light barrier satisfies the equation L[(H+d)/ (D,-d)JS
—
The maximum line length of the effective receiving area of the detector. 4.6 Optical adjustment frame
The black body furnace and the sample heating oven are placed on the optical adjustment frame respectively, and the optical path is adjusted to meet the same geometric optical conditions of the sample light beam and the reference beam, so that the bottom of the black body cavity and the sample fill the entire observation angle. 5 Test conditions
5.1 This test method is carried out in a large atmosphere. In order to reduce the absorption effect of water vapor and carbon dioxide in the atmosphere and allow infrared absorption in the range of 15 to 25u㎡, the test equipment should be placed in a dry and clean environment, and the relative humidity should meet the working requirements of infrared spectrophotometry.
5.2 In order to eliminate the different atmospheric absorption effects of the dual light paths, the optical path lengths of the dual beams should be as similar as possible. The observation apertures of the dual beams should be equal to ensure that the dual paths have the same viewing angle and equivalent radiation source area. 5.3 During the test, the temperature difference between the sample surface and the bottom of the blackbody cavity should be less than 1K. 5.4 The wavelength resolution of the monochromator of the spectrophotometer should be less than the width of any emission or absorption band of the test spectrum. The response characteristics of the detector amplifier system should test the radiation spectrum or linearity. 6 Test steps
6 .1 Load the sample into the sample heating furnace. Heat and maintain the sample heating furnace and two blackbody furnaces to the required temperature. 6.2 After the relative condensation of the environment reaches the requirement, preheat the infrared spectrophotometer and put it into working state. 6.3 Put two blackbody furnaces with the same temperature into the dual optical path of the infrared spectrophotometer, adjust the optical path, calibrate and plot the [% line and the zero line according to the test requirements. The unevenness of the obtained curve is less than 5%. During the test, the temperature difference between the two blackbody furnaces should be less than 1K, and appropriate parameters such as slit program, time, and amplifier gain should be selected. GB7286.2—87
6.4 Replace the blackbody furnace in the sample optical path with the sample heating furnace, and maintain the temperature difference between the sample surface and the bottom of the blackbody cavity within 1K, and then perform the infrared scanning test.
Calculation results
7.1 Measure the height of the obtained curve at each wavelength and calculate the spectral normal emissivity at each wavelength. The calculation equation is as follows: En(A, T) - (SA-Z-)/ (Ha-ZA)
Where: S: — height of the sample curve on the same length, mm; Z: — height of the piano wire on the same length, mm; H: — height of the 100% line at the same wavelength, mm. (5)
7.2 When measuring, if the zero line height is adjusted to the zero line position of the recording paper, and then the 100% line is adjusted to coincide with the 100% line of the recording paper, and then the sample is scanned, the value of each point on the measured curve is the spectral normal emissivity of the sample at each wavelength. 8 Calibration of test equipment
8.1 When initially building the test equipment or when necessary, the test equipment should be calibrated with standard samples. 8.2 Due to the deviation caused by differences between standard samples and random errors in the test, the maximum deviation of the measured curve from the standard value The deviation should not exceed 5%.
8.3 The maximum deviation between repeated tests of the same sample under the same conditions should be less than 3%. When the spectral normal emissivity is less than 0.20, the allowable deviation is within 5-10%. 9 Test report
The spectral normal emissivity of the sample is affected by the material, wavelength, temperature and surface state. The test report should indicate: 9.1 Name of the sample sending unit,
9.2 Name of the sample material, surface state, sampling product batch number and sampling date: 9.3 Test temperature, K,
9.4 Test wavelength range, ums
Test value, attached (,) curve chart,
Test date:
Signature and seal of the tester and the test unit.
Additional instructions:
This standard was proposed by the National Bureau of Standards and is under the jurisdiction of the Hubei Provincial Bureau of Standards. This standard was drafted by the Institute of Industrial Silicates, Chinese Academy of Sciences and the Chinese Academy of Sciences. The main drafters of this standard are Xu Qintang, Ge Xinshi and Fu Ruihua.
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