SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
TiI crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Ti is bonded in a 4-coordinate geometry to four equivalent I atoms. There are three shorter (2.76 Å) and one longer (2.80 Å) Ti–I bond lengths. I is bonded in a 4-coordinate geometry to four equivalent Ti atoms.
A previously unreported layered spin ½ triangular lattice polymorph of TiI 3 is described, synthesized under 6 GPa of applied pressure at 900 °C, but stable at atmospheric pressure. This air-sensitive material has a CdI 2 -type layered structure (P-3m1 (no. 164), a = 4.012 Å and c = 6.641 Å at 120 K, Z = 1 of Ti 0.667 I 2 ) with an in-plane triangular lattice, related to that of TiI 4 (Ti 0.5 I 2 ). Although the TiI 3 formula is consistent with expectations for a layered honeycomb lattice of spin ½ Ti(III), there appears to be disorder in the crystal structure. Magnetic susceptibility and heat capacity measurements suggest that the material undergoes several low temperature phase transitions.
The Space Shuttle program has a unique propellant purity requirement for determination of nonvolatile residue (NVR) in monomethylhydrazine (MMH). TIis requirement differs from the Military Specification procurement specification by requiring a NVR analysis with a limit of less than or equal to 10 milligrams per liter. In June 2008, a routine MMH replenishment delivery was transferred into a NASA KSC owned tanker for future delivery to the Space Shuffle pad MMH storage tank. Per Shuffle standard operating procedure, the receiving tanker was sampled and analyzed for purity and surprisingly it failed the Shuttle use NVR specification limit. Detailed examination of the NVR revealed that it was fundamentally different than the typical MMH NVR. This paper will examine various aspects of NVR determination in MMH and the analytical characterization processes used to identify the NVR.