1‐Ethyl‐3‐methylimidazolium (EMIm+) and N‐butylpyridinium (BPy+) salts of the oxotetrafluorovanadate (VOF4–) and oxopentafluoromolybdate (MoOF5–) anions with low melting temperatures have been synthesized by the reactions of the corresponding fluorohydrogenate ionic liquids and metal oxide fluoride. Differential scanning calorimetry reveals that the melting points of EMImVOF4, BPyVOF4, and BPyMoOF5 are 348, 346, and 346 K, respectively, whereas the room‐temperature ionic liquid EMImMoOF5 only exhibits a glass transition at 190 K. Density, viscosity, and ionic conductivity of EMImMoOF5 are 1.76 g cm–1, 86 cP, and 5.1 mS cm–1 at 298 K, respectively. The cathode and anode limits of EMImMoOF5 are –0.3 and +1.4 V (vs. Ag+/Ag), respectively. The molecular geometries of the VOF4– and Mo2O4F62– anions have been determined by single‐crystal X‐ray diffraction, the latter being obtained by the hydrolysis of MoOF5–. The two VOF4– anions in EMImVOF4 interact with each other through two highly asymmetric V–F···V bridges with V–F and V···F distances of 1.8633(7) and 2.3786(7) Å, respectively. A dinuclear anion in (BPy)2Mo2O4F6 possesses two symmetric Mo–F–Mo bonds with Mo–F lengths of 2.1691(12) and 2.1829(11) Å.

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The first syntheses of a series of ionic liquids based on the hexafluorouranate(V) anion are described along with their physicochemical and electrochemical properties. The green room-temperature ionic liquid, 1-ethyl-3-methylimidazolium hexafluorouranate (EMImUF6), exhibits a conductivity of 7.9 mS cm−1, viscosity of 59 cP, and electrochemical window of 2.3 V at 298 K.

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Polycrystalline β-SiC and single-crystalline 4H-SiC surfaces were etched by reactive ion etching (RIE) using NF3 gas plasma. A smooth surface was obtained on the polycrystalline SiC after RIE at NF3 gas pressures of 2 and 10 Pa for 10 min, and neither spikes nor pillars were formed on it. On the other hand, some pillars were formed on the single-crystalline SiC surface by RIE at NF3 gas pressures of 2 and 10 Pa. Though the absence of carbon-rich regions and SiOx on the outermost surface before etching was confirmed by x-ray photoelectron spectroscopy and Raman analysis, x-ray diffraction analysis revealed that graphite crystallites were present in the single-crystalline SiC bulk. It was concluded that the graphite crystallites acted as masks and the pillars grew up from the graphite crystallites in the single crystalline SiC during RIE.