Partha P. Paul

Carbon materials obtained from organometallic modification of pitch and its oxidation resistance properties

Although carbon fiber reinforced carbon matrix (C/C) composites are used in the aerospace and utility industries, carbon materials oxidize readily at temperatures above 425 °C. A variety of coatings have been used to protect C/C composites from oxidation. The thermal expansion mismatch creates microcracks that could result in catastrophic failure. To alleviate these difficulties, we have used the approach of modifying the carbon precursor molecule with organometallic functions, which results in uniform and nanosize mixing of antioxidants in the carbon matrix. Mesophase pitch, which is a carbon precursor, was grafted with silicon and aluminum preceramic functions by using organometallic chemistry to produce Compounds 1, 2, 3 and 4. These organometallic pitches produce Chars A, B, C and D upon carbonization. Char C exhibits oxidation resistance superior to that of commercial carbon fiber.

Lean-NOx reduction catalysis by metal-complex impregnated molecular sieves – Effect of ligands and metals

Abstract We have developed lean-NOx catalysts using modified mesoporous molecular sieves which operate under very low hydrocarbon concentrations. Transition metal (copper and iron)-complex impregnated mesoporous molecular sieves have been synthesized. Cryptand type ligands (L1 and L2) have been used for complex formation. The ligand plays a crucial role in the complex formation and catalytic activity. These metal-complex impregnated molecular sieves are further treated with [Pd(NH3)4] Cl2. Fe–L2 and Cu–L2-based catalysts are active towards NOx reduction under oxygen rich (lean-NOx) conditions. The catalytic activity towards NOx, CO and HC was studied using simulated exhaust gas, as well as engine exhaust gas from a lean burning gasoline engine. Using engine exhaust gas at an air/fuel ratio of 16.10, test results showed a reduction of NOx up to 10% at inlet temperatures ranging from 260°C to 285°C and HC/NOx=2/1.

Chemical synthesis and characterization of nanosized titanium aluminide

Abstract Titanium aluminides are among the more promising intermetallics for use in aerospace and automotive applications; however, their acceptance has been hampered by their lack of ductility. Significant improvement in ductility may be obtained from nanostructured intermetallics. Reaction of Ti[N(SiMe 3 ) 2 ] 3 with excess alane produces a precursor (Compound 1) to titanium aluminide. We propose compound 1 to be a loose cluster (or family of clusters) in which titanium and aluminum atoms are both bonded directly and bridged by imidosilanes. This chemically synthesized precursor, when heated to 1000 °C, produces nanosized particles of TiAl 3 . Nanosized TiAl 3 has been characterized by chemical analysis, solid-state NMR, X-ray diffraction, energy dispersive spectroscopy, and high-resolution electron microscopy.

Chemical Synthesis and Characterization of Nanostructured Titanium Aluminide

Although plagued by a lack of ductility, titanium aluminides are among the most promising intermetallics under development. Significant improvements in ductility may be obtained from nanostructured intermetallics. Nanosize particles of TiAl 3 have been prepared by heat-treatment of chemically synthesized precursor (compound 1). Nanosized TiAl 3 has been characterized by chemical analysis, XRD, EDS, NMR, and HREM.