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dashan_612木虫 (正式写手)
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[求助]
求一张纯Si的红外扫描图
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| 样品在Si上面作的，首先要做的就是把Si放在那里扫描一下背底的光谱，然后在测试样品的光谱。现在我就是想要一张标准的Si的红外光谱，谢谢 |
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We then began to investigate the reliability of the supplied IR measurements. One of the authors, G. Forster, noted the transparency of the silicon crystal to IR radiation. Then, we surmised that the experimental technique and the data obtained might be suspect. Our suspicion was further reinforced when we reviewed the literature on the radiative properties of silicon crystals in the infrared region of the spectrum (see Figures 2 and 3). The steep variations in these properties, particularly in the infrared region, and the corrections needed to account for the transmittance and reflectance of silicon seem to preclude unaided and direct thermometric measurement of the silicon crystal. Another author, A. Khounsary, suggested that the silicon crystal be coated with a layer of a material opaque to infrared. Figure 2: Normal Spectral Reflectance of Silicon [6].  Figure 3: Normal Spectral Transmittance of Silicon [6].  The IR scanner (Inframetrics model 525) used at Cornell is an "8-12" unit. This means that it is most sensitive to and suitable for (blackbody) temperature measurements in the 20-100°C range. Unfortunately, it is in this very range that a silicon crystal exhibits steep variations in its radiative properties. Therefore, if the crystal is not coated, the row data taken by the infrared scanner must be processed and interpreted to infer the actual temperatures, a laborious (and unnecessary) task in view of the strong frequency dependence of the radiative properties of silicon crystals in the spectral range of interest. On the basis of these considerations, it was then decided to run some temperature measurement tests at the ANL/Bldg. 223 laboratory. Experimental apparatus consisting of a piece of spare silicon crystal with a Peltier-effect back was set up. A thermocouple was also contact-mounted on the frontal surface of the crystal to independently measure the surface temperature at that location. Inframetrics, Inc., was contacted to seek advice on possible opaque coatings. They suggested black vinyl electrician's tape, spray foot powder, and dye penetrant developer powder; in addition, we also considered carbon black and candle soot as acceptable candidates. These materials are all opaque to infrared radiation, have emissivities in excess of 0.9 and are readily available. The black electrician's tape and the dye penetrant developer powder (in patches) were used in our experiment. Both were equally practical, but the tape would lose its adhesiveness and peel off at higher operating temperatures. The thermocouple itself was also coated so that its temperature would also be monitored to assure proper surface contact, and thus accurate reading of the surface temperature. Our preliminary experimental data indicated a linear correlation between the IR scanner readings and the thermocouple measurements. As a result of these experiments, therefore, we believe that the source of the three-fold difference between our thermal-hydraulic modeling results and the Cornell IR temperature measurements are due to erroneous interpretation of the IR readings. The actual temperature rise along the surface of the three-channel crystal is about three times the values presented at the March 11 meeting. Thus, the correct value is in the 40-45°C range (assuming that the flow rate, channel and footprint dimensions, power level, etc. that are provided are accurate). Follow-up IR calibration studies in the laboratory and accompanying analytical work verified the above conclusions. This follow-up work is detailed below. |
2楼2008-03-08 12:54:26
dashan_612
木虫 (正式写手)
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3楼2008-03-08 21:50:18
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