Scanning thermal microscopy (SThM) and infrared thermography are widely used for surface thermal characterization. However, the SThM technique is limited by measurement of the non-electrical conductive surfaces and the infrared thermography has insufficient spatial resolution for submicron localized thermal measurement. The “hot tip” Tribological Probe Microscope (TPM) has been designed to achieve better localized thermal analysis function in this paper. The schemes of system design are presented and the principle of the ‘hot-tip’ technique is explained by relating the signals to established thermal properties. After calibrating the lumped thermal resistances (LTR) of the probe and the ambient environment, the LTRs of 5 metal surfaces were measured and compared. In addition, the paper numerically studied the LTR of the indentation interfaces with defined thermal conductivity (TC) by Finite Element Method (FEM). Numerical linearity was observed and fitted between LTR and TC. Based on the measured LTR and the linearity, the deduced TCs of the 5 metal surfaces are agreed well with the reference values.
At ambient pressure, the effect of plasma discharge mode and reactor structure on ammonia decomposition to hydrogen was investigated. Dielectric barrier discharge (DBD) and alternating current (AC) arc discharge were produced upon adjusting the structure of the plasma reactor. By studying the discharge images, the voltage-current waveforms and the optical emission spectra in two discharge modes, we found that the AC arc discharge was a spatially partially stronger discharge compared with DBD. The AC arc discharge had a higher power efficiency and higher electron density than the dielectric barrier discharge. The ammonia molecules were mainly transformed into NH3 * in an electronic excited state, and the N-H bond ruptured upon collision with a high-energy electron in DBD. However, electrons with a high average electron energy upon AC arc discharge can rupture the N-H bond directly to form highly active NH2 and NH species, which can enhance the ammonia decomposition reaction. Results show that AC arc discharge had better performance toward ammonia decomposition than dielectric barrier discharge. The ability of different reactor structures to decompose ammonia under AC arc discharge increased in the following order: tube-tube>tube-flat>point-flat>flat-flat. The ammonia conversion can be as high as 60% under the tube-tube AC arc discharge with an input power of 30 W and a gap distance of 6 738 赵 越等: 非平衡等离子体放电模式及反应器结构对氨气分解制氢的影响 No.4 mm, while it was only 4% under the flat-flat dielectric barrier discharge.
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