Evidence for a Cr metastable phase as a tracer in DLI-MOCVD chromium hard coatings usable in high temperature environment

On the key role of the surface of palygorskite nanofibers in the stabilization of hexagonal metastable β-Ag2CO3 phase in palygorskite-based nanocomposites

“…This issue would require further TEM investigations but me tastable phases are frequently difficult to observe by TEM due to their instability towards the electronic impact, which is more energetic than an X-ray beam. For instance, a metastable metallic S-Cr phase, ther mally stable up to about 400 "C, were identified by different techniques including XRD but was not observed directly by TEM using the same microscope and under similar conditions of this work (200 kV as beam energy) due to in situ phase transformation (Michau et al, 2017). This was also the case for the AgBr phase loaded on palygorskite (Yang and Zhang, 2012).…”

High-temperature oxidation resistance of chromium-based coatings deposited by DLI-MOCVD for enhanced protection of the inner surface of long tubes

“…Depending on the deposition temperature, the structure of the coating is amorphous (≤773 K) or polycrystalline (> 773 K) [31][32][33]. It is also possible to inhibit the incorporation of carbon into the coatings by adding a sulphur-containing (C 6 H 5 SH) or a chlorine-containing (C 6 Cl 6 ) inhibitor into the precursor solution, leading to the deposition of polycrystalline metal Cr coatings [24,32,[34][35][36]. Finally, low amounts of silicon can be introduced in the amorphous chromium carbide coatings by incorporating diphenylsilane ((C 6 H 5 ) 2 SiH 2 ) to the precursor solution.…”

“…DLI-MOCVD is indeed a suitable deposition process in order to homogeneously coat the inside of long and narrow tubes with a high shape factor (> 500). Moreover, with an adequately chosen chemical system, consisting of a liquid solution of bis(arene)chromium as molecular precursor in a hydrocarbon solvent, deposition can be performed at sufficiently low temperatures, around 673 K [24], to avoid any modification of the metallurgical state of the zirconium alloy. DLI-MOCVD is currently studied in order to protect the inner surface of long cladding tube segments (~1 m).…”

Chromium carbide growth at low temperature by a highly efficient DLI-MOCVD process in effluent recycling mode

“…The increasing use of metalorganic precursors is a way to reduce the cost of large-scale CVD process because this greatly lowers the deposition temperatures leading to substantial energy savings. This is evidenced for instance by the growth of metallic Cr at 673 K by DLI-MOCVD [1] in comparison with the industrial chromizing method of pack cementation which operates at about 1273 K.…”