Danny T. Xiao

Deposition of thermal barrier coatings using the solution precursor plasma spray process

The solution-precursor plasma-spray (SPPS) process is capable of producing highly durable thermal barrier coatings. In an effort to improve the understanding of the deposition mechanisms in this novel process, a series of specific experiments, where the substrate is held stationary and the plasma torch is programmed to scan a single pass across the substrate, were conducted and the resulting deposits were carefully characterized. In addition to the deposition mechanisms identified previously in the stationary torch experiments, the deposition mechanisms of two other types of deposits, thin film and fine spherical particles, were identified in this study. The melting of inflight formed 7YSZ particles and their rapid solidification to form ultra-fine splats on the substrate was found to be the dominant deposition mechanism. The characterization of actual SPPS coatings confirmed that the various coating-deposition mechanisms identified in the model experiments occur in concert during the actual coating process. Adherent deposits (ultra-fine splats, deposits from gel-like precursor and film formed via chemical vapor deposition), unmelted particles (spherical particles, deposits from non-decomposed precursor) and porosity were estimated to constitute ∼65, ∼19 and ∼16 vol%, of the coating, respectively.

Reducing dissolution of MnO2 nanofibers by doping with ferric ion

Abstract MnO2 nanofiber was found to possess high adsorption capacities for heavy metal ions such as, arsenic and lead, in water due to its high specific surface area (SSA) and high surface activity. However, a significant amount of manganese was found to leach from MnO2 nanofibers. Reducing MnO2 dissolution is very important for improving its applications in drinking water treatment. In this study, MnO2 nanofiber was doped with Fe3+ to reduce its dissolution in water. Dissolution tests were conducted on un-doped and Fe-doped MnO2 nanofibers. The results revealed that doping with Fe3+ significantly reduced MnO2 dissolution. SSA and defects of MnO2 materials were analyzed by BET and XRD methods. The effects of Fe3+ on MnO2 dissolution were discussed and the optimal dopant amount was identified.

Nanostructured cathode materials for alkaline and lithium rechargeable batteries

US Nanocorp, Inc. is pioneering the synthesis of nanostructured active battery materials by a novel aqueous solution reaction (ASR) process that is inherently low cost and scalable to volume production. Strategies for the production of high energy content battery electrodes are discussed. Focus areas include Ni(OH)/sub 2/, both pure and Al-doped and /spl gamma/-MnO/sub 2/ for rechargeable alkaline batteries as well as the hollandite form of /spl alpha/-MnO/sub 2/ for intercalation of lithium. The synthesis of nanostructured pyrite as a feedstock powder for thermal spray to rapidly deposit FeS/sub 2/ thin film electrodes for thermal batteries is also discussed.