Low-Cost Hybrid Slurry Infiltration Synthesis and Characterization of VC/C-Fiber Composites with Nickel Catalyzed Carbon Nanostructures

Vanadium carbide (VC) is a material utilized commonly in catalysis and metallurgy, for its chemical activity and high hardness. VC is well suited for refractory and composite applications, due to its impressive high temperature performance metrics, making it useful in high temperature applications, such as aerospace. However, current syntheses are inefficient, as sintering techniques have energy and scalability concerns, and vapor deposition techniques require long hours on gas with low precursor usage/efficiency and a lack easily obtainable liquid or gaseous precursors to synthesize VC. In this work, three VC/carbon fiber composites embedded with nickel catalyzed carbon nanostructures were fabricated utilizing a hybrid slurry-salt synthetic methodology. This hybrid methodology uses a highly soluble salt in aqueous solution to introduce vanadium and nickel salts into carbon fiber bundles and subsequently carburize them at elevated temperatures with hydrogen and methane, to fabricate VC and Ni metal. These samples were characterized with various microscopy, diffraction, spectroscopy, and electrical resistivity methods. This study found that infiltration marks were sufficient, recording a porosity of only 7.8% and scanning electron microscopy micrographs displayed strong deposition. Nickel from both NiCl2 and NiO was shown to be metallic in the composite, showing that nickel is present in its catalytically active state upon synthesis. Transmission electron microscopy and Auger electron spectroscopy investigations revealed the presence of excess carbon, alongside VC deposition. Electrical resistivity values of fabricated composites reached as low as 0.118 Ω*cm. This study displays a facile and inexpensive way to fabricate dense VC/carbon fiber composites, when compared to commonly used methods such as chemical vapor infiltration or slurry infiltration. This method requires no dedicated vacuum equipment, which is typical for chemical vapor infiltration, and less to no polymeric dispersants, which is typical for slurry infiltration, while being able to easily incorporate catalytically grown carbon materials via introduction of secondary salts. Although this paper focuses on the addition of Ni, other salts could be utilized in different ratios to co-deposit other catalytic and structural materials. This technique can be offered as an alternative to slurry infiltration, sintering, and pure vapor deposition techniques which may present a greater financial obstacle.