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Spatial resolution is one of the key factors in orientation microscopy, as it determines the accuracy of grain size investigation and phase identification. We determined the spatial resolutions of on-axis and off-axis transmission Kikuchi diffraction (TKD) methods by calculating correlation coefficients using only the effective parts of on-axis and off-axis transmission Kikuchi patterns. During the calculation, we used average filtering to evaluate the spatial resolution more accurately. The spatial resolutions of both on-axis and off-axis TKD methods were determined in the same scanning electron microscope at different accelerating voltages and specimen thicknesses. The spatial resolution of the on-axis TKD was higher than that of the off-axis TKD at the same parameters. Furthermore, with an increase in accelerating voltage or a decrease in specimen thickness, the spatial resolutions of the two configurations could be significantly improved, from tens of nanometers to below 10 nm. At a voltage of 30 kV and sample thickness of 74 nm, both on-axis and off-axis TKD methods exhibited the highest resolutions of 6.2 and 9.7 nm, respectively.

The explosion is one of the most serious safety incidents occurring in the application of the gas methane in industrial process. The new developments in attenuating the destruction and environmental hazard of this explosion are conducted using the combined inert gas and ABC dry powder. The explosive characteristic parameters including flame configuration, velocity of flame propagation, explosion pressure, and pressure rising rate are quantified and revealed. The difference of explosion mitigation effect of ordinary and ultra‐fine ABC dry powders are examined based upon the specific surface area and the settling velocity. As the concentration of ordinary or ultra‐fine ABC dry powder increases, the explosion pressure initially increases and decreases afterwards, indicating that there is an optimal mass concentration of explosion mitigation for both powders. The effect of ignition delay time on the explosion mitigation of ultra‐fine ABC dry powder is characterized on the basis of the turbulent lever and the dry powder particle settling state. Moreover, the mechanisms of explosion mitigation with CO2 and the ultra‐fine ABC dry powder are fully revealed both on the physical and chemical properties. The present research provides basic data and theoretical guidance for prevention and controlling of gas explosion accidents.

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