The magnesium (Mg) particle surface can be used to regulate fluorination or oxidation reactions depending on the applied heating rate and Mg particle size. Magnesium particles are surrounded by a complex hydroxide shell composed of an inner layer of magnesium oxide (MgO) and outer layer of magnesium hydroxide (Mg(OH)₂). As particles approach the nanoscale, the thick oxide shell (e.g., 22 nm) becomes an appreciable portion of the overall powder and can be exploited to regulate reactivity. In this study, the reactivity of 800 nm Mg particles (nMg) was compared to 44 µm Mg particles (µMg) when combined with Perfluoropolyethyer (PFPE), providing both fluorine and oxygen for Mg reactions. Experiments were performed at slow heating rates (10 °C/min) and separate experiments were performed at fast heating rates (6.0 × 10⁵ °C/min). The slow heating rate studies used a differential scanning calorimeter (DSC) and thermogravimetric (TG) analyzer to examine reaction kinetics. The faster heating rate experiments used a hot wire to ignite a thermal run-away reaction. Powder X-ray diffraction (XRD) analysis of recovered residue at various temperatures corresponding to exothermic events in the DSC revealed reaction pathways for nMg + PFPE favoring oxidation reactions. For nMg powders, the outer Mg(OH)₂ surface layer dehydrates at low temperatures (313 °C) creating highly reactive sites for surface oxidation reactions in the condensed phase leading to a higher conversion of Mg(OH)₂ to MgO and greater consumption of Mg through oxidation reactions. For µMg, higher Mg(OH)₂ dehydration temperatures (498 °C) stabilize µMg particles and the bulk of reactions occur at elevated temperatures and in the gas phase producing higher MgF₂ concentrations. Under high heating rate conditions, MgF₂ formation is favored over MgO formation for both particle sizes owing to the high reaction temperatures that promote gas phase reactions favoring MgF₂ formation. Theoretical analysis using density functional theory (DFT) through cluster models for Mg(OH)₂ and MgO surfaces further show that the Mg(OH)₂ surface is more reactive with fluorine species than MgO, especially at elevated temperatures. The DFT results help explain the high heating rate reaction pathway that favors fluorination reactions independent of Mg particle size.

取决于所施加的加热速率和Mg粒度，镁（Mg）颗粒表面可用于调节氟化或氧化反应。镁粒子被复合氢氧化物壳包围，该复合物由氧化镁（MgO）的内层和氢氧化镁（Mg（OH）₂）。随着颗粒接近纳米级，厚的氧化物壳（例如22 nm）成为整个粉末的相当一部分，可以用来调节反应性。在这项研究中，将800 nm Mg颗粒（nMg）与44 µm Mg颗粒（µMg）的反应性与全氟聚乙烯（PFPE）结合使用时，可以为Mg反应提供氟和氧。实验以缓慢的加热速率（10°C / min）进行，单独的实验以快速的加热速率（6.0×10 ^5）进行 °C / min）。慢升温速率研究使用差示扫描量热仪（DSC）和热重分析仪（TG）分析仪检查反应动力学。更快的加热速率实验使用热线点燃热失控反应。对应于DSC中放热事件的各种温度下回收残留物的粉末X射线衍射（XRD）分析揭示了nMg + PFPE有助于氧化反应的反应途径。对于nMg粉末，Mg（OH）₂的外表面层在低温（313°C）下脱水，从而在冷凝相中产生高活性的表面氧化反应位点，导致Mg（OH）₂转化为MgO的转化率更高，消耗量更大通过氧化反应生成镁。对于µMg，较高的Mg（OH）₂脱水温度（498°C）使µMg颗粒稳定，并且大量反应在高温下和气相中产生，并产生更高的MgF ₂浓度。在高加热速率的条件下，氟化镁₂形成是有利的MgO上形成为由于促进气相反应利于在氟化镁高的反应温度都粒径₂形成。使用密度泛函理论（DFT）通过Mg（OH）₂和MgO表面簇模型的理论分析进一步表明Mg（OH）₂与MgO相比，表面对氟的反应性更高，尤其是在高温下。DFT结果有助于说明高加热速率反应途径，该途径有利于与Mg粒径无关的氟化反应。