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Metal oxides (MOs) are of great importance in catalysts, sensor, capacitor and water treatment. Nano-sized MOs have attracted much more attention because of the unique properties, such as surface effect, small size effect and quantum size effect, etc. Hematite, an especially important additive as combustion catalysts, can greatly speed up the thermal decomposition process of energetic materials (EMs) and enhance the combustion performance of propellants. This review concludes the catalytic effect of hematite with different morphology on some EMs such as ammonium perchlorate (AP), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenete-tranitramine (HMX), etc. The method for enhancing the catalytic effect on EMs using hematite-based materials such as perovskite and spinel ferrite materials, making composites with different carbon materials and assembling super-thermite is concluded and their catalytic effects on EMs is also discussed. Therefore, the provided information is helpful for the design, preparation and application of catalysts for EMs.

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Phase-change insulation materials can effectively extend the holding time of submarine oil and gas pipelines. Shape-stable phase-change composites have good application prospects owing to their chemical stability and leakage resistance. In this study, a microencapsulated phase-change material (MPCM)-embedded polyurethane (PU) composite (PU–MPCM) was prepared as an insulation material for subsea pipelines. The unsteady heat transfer process of the PU–MPCM composite was simulated using COMSOL Multiphysics, and an insulation experiment was conducted on this composite. PU–MPCM exhibited a high thermal storage performance and favorable shape stability. The relative effective enthalpy coefficients of PU–MPCM composites with different MPCM contents were greater than 80%. The maximum MPCM content in the PU–MPCM composite was 24 wt% (PU–MPCM24). The melting enthalpy of PU–MPCM24 reached 35.95 J/g, and its effective thermal conductivity was as low as 0.16 W/(m∙K). The holding time of PU–MPCM24 could be increased by 229.79% compared with that of pure PU. The PU–MPCM composite exhibited good mechanical properties and low water absorption, making it suitable for underwater environments. Owing to its low-cost preparation process and excellent thermal properties, PU–MPCM24 can be considered a potential insulation material for practical applications in subsea pipelines.

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