Radar wave absorption

The powders produced from the above method are very fine. TEM observation in Figure 3.29 shows that the typical powder is composed of equiaxed particles and has a size in the range of 50 to 80 nm. Experimental results reveal that the chemical composition of the powders depends weakly on processing conditions. The main chemical compositions of the powders are 50% wt of Si, 28% wt of C, 16% wt of N, while there is a small amount of O and H, 4% wt and 2% wt respectively. Selected area electron diffraction (SAED) also reveals the existence of a partial crystalline phase in the amorphous structure, this being a unique material feature which cannot normally be obtained using other manufacturing techniques. This feature makes it possible for the powders to be used as good functional materials, such as radar wave absorption materials. 

Surface acoustic wave Semiconductor Target Radiation Radar Surface acoustic wave Electrophoresis Electrochemical Paramagnetic Chemi/bioluminescence Tunable diode laser absorption... 

The absorption of radiation (for NMR, in the radio wave range, 10-80 MHz, or in the radar range, up to 1 GHz for EPR, in the microwave range, 3-100 GHz) depends on the relative population of the ground, or lower (1) state and first excited, or upper (u) state, that is, it depends on a Boltzmann factor of the type Nu/N exp (—AE/kBT), where AE is the relevant energy difference. 

Rotational transitions correspond to photon wavelengths in the microwave region. The radiation sources in microwave spectrometers are klystron tubes, which were originally developed for radar apparatuses in World War II. Hollow metal wave guides carry the radiation to the sample cell, which is a hollow metal cavity, and the resonant radiation in the cavity is sampled to detect absorption. Microwave spectroscopy has played an important role in identifying molecules in interstellar space, but it is not a common tool in many chemical laboratories. 

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