In this study, gallium oxide hydroxide (GaOOH) nanorods were synthesized using a hydrothermal method, which was followed by a high-temperature nitriding process to synthesize gallium nitride (GaN) nanorods. Then, potassium chloride (KCl)-modified GaN nanorod composite materials were prepared using the physical mixing method. The analysis of the humidity sensitivity test demonstrated that the KCl/GaN nanorods with a KCl loading of 2.5 wt% exhibited the best humidity sensitivity, with a resistance change response of 36589.59 under 97% relative humidity (RH), which was 2.51 times that of pure GaN nanorods without KCl doping. The response and recovery times of the KCl/GaN-2.5- wt% nanorod humidity sensor in a 97%-RH environment were 3 s and 80 s, respectively. The response time did not exhibit considerable fluctuations compared with the undoped GaN nanorods, and the recovery time increased. The hierarchical morphology of the GaN nanorods created abundant adsorption sites for water molecules, while the incorporation of KCl enhanced the electrical conductivity of the composite material, thereby resulting in an increase in the magnitude of the resistance changes of the sensor in environments with different humidity conditions. The sensor also demonstrated excellent repeatability and long-term stability, making it suitable for applications in respiratory monitoring.
A modified structured dry water (SCDW) was prepared by introducing sodium alginate (SA) and calcium L-lactate (CL) into conventional dry water (DW) to mitigate the risks associated with methane–air explosions. The preparation parameters were optimized, yielding uniformly distributed and structurally stable particles. The results demonstrate that SCDW exhibits superior mechanical stability and water retention compared to DW. Pipeline explosion experiments evaluated the suppression performance of six sodium- and potassium-modified SCDWs. At spraying concentrations of 25–100 g/m 3 , all modified SCDWs significantly reduced the maximum explosion pressure and flame propagation distance, outperforming DW. Specifically, 5 wt% KCl-SCDW at 100 g/m 3 reduced the maximum explosion pressure and flame propagation distance by 38.75 % and 24.10 %, respectively, compared to DW. When the spraying concentration exceeded 200 g/m 3 , both parameters stabilized. A quantitative analysis of five explosion-related parameters confirmed that salt-modified SCDWs provided superior suppression performance compared to DW, with potassium-modified SCDWs exhibiting stronger effects than sodium-modified ones, and KCl-SCDW demonstrating the best suppression performance. HSC and Chemkin simulations revealed that SCDW exerts both physical and chemical suppression effects. Physically, DW particles suppress combustion through evaporative cooling, oxygen dilution, energy absorption from particle collisions, and thermal radiation blocking. Chemically, gaseous active species capture and consume H and OH free radicals, interrupting chain reactions through catalytic cycles and generating stable compounds, thereby reducing the maximum explosion pressure and flame propagation speed. Modified SCDWs offer an environmentally friendly, stable, and efficient approach to methane-air explosion suppression.
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