In surface nuclear magnetic resonance, we use the geomagnetic field as the background field and excite hydrogen protons in groundwater by emitting an alternating current with a frequency equal to the Larmor frequency. However, in practical, inhomogeneous geomagnetic field (IGF) or magnetic anomaly caused by ferromagnetic materials will make the non-uniqueness of Larmor frequency, resulting in the simultaneous existence of on-resonance and off-resonance (we refer as composite resonance). If only the on-resonance or off-resonance model is used to interpret the composite resonance data, then the accuracy of the inversion results would be seriously affected. To solve the problem, we derived the expression of free induction decay (FID) signal of composite magnetic resonance based on the layered model. The influence of IGF on the characteristic parameters of the FID signal was analyzed through simulation models, which showed that with the increase of the frequency offset and gradient, the relaxation time decreased prominently. Furthermore, we proposed an iterative correction method based on a frequency-depth curve. Through the synthetic and measured data, this study proved that the water content and relaxation time are consistent with the truth after correction, and the data consistency is better than that before correction.

This study investigates how scanning speed influences the electrochemical performance and discharge behavior of aluminum–air (Al–air) batteries with CeO₂/Al6061 anodes fabricated through selective laser melting (SLM). Al–air batteries, celebrated for their exceptional energy density and eco-friendliness, encounter hurdles in their widespread application due to anode self-corrosion and the formation of passivation films. To address these challenges, this study integrates CeO₂-reinforcing phases into Al6061 alloys and leverages SLM technology to enhance anode performance. A comprehensive analysis was conducted on the effects of varying scanning speeds (800, 900, 1000, 1100, and 1200 mm/s) on the surface morphology, density, self-corrosion rate, electrochemical performance, and discharge behavior of the anodes. The findings reveal that a scanning speed of 1000 mm/s produces anodes with optimal density, minimal self-corrosion, and outstanding electrochemical and discharge performance. Specifically, this scanning speed leads to a high discharge voltage of 1.575 V and an anode utilization rate of 72.2%, which can be attributed to the complete melting of the powder and the formation of a uniform microstructure. These insights offer valuable guidance for the development of high-performance Al–air batteries, promising extended lifespans and enhanced efficiency.