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FRG: M n+1 AX n Phase Solid Solutions: Unique Opportunities at Engineering Bulk and Surface Properties Micheal W. Barsoum, Drexel University, DMR 0503711.
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FRG: Mn+1AXn Phase Solid Solutions: Unique Opportunities at Engineering Bulk and Surface PropertiesMicheal W. Barsoum, Drexel University, DMR 0503711 Graduate student T. Scabarozi of Drexel, undergraduate students C. Gennaoui, J. Roche, P. Hann, T. Fleming, and A. Rosenfeld and faculty members J. Hettinger and S. Lofland of Rowan have synthesized thin films of Ti2AlC, Nb2AlC, V2AlC and Cr2AlC, as well as, solid solutions of (TixNb1-x)2AlC. These materials are candidates for application as thin film protective coatings. We found that Ti2AlC requires a seed layer of TiC to grow epitaxially on sapphire, while Nb2AlC will grow directly on the substrate. Both materials require substrate temperature in excess of 850ºC to form. However, V2AlC and Cr2AlC both appear to be more versatile since they form on either bare substrates or with seed layers. Single-phase films (see Fig. 1) can be synthesized at substrate temperature as low as 500ºC. Graduate student O. Leaffer at Drexel use density functional theoretical simulations of the lattice dynamics to predict the Raman active mode energies in MAX-phases. Close agreement between experiment and prediction was shown (Fig. 2). Raman should thus become an effective means of identifying the MAX phases. Graduate student, S. Amini, fabricated and characterized both Ti2SCand Cr2GeC in bulk form for the first time ever. The micrographs, shown on this page, exhibit the nanolaminate structure of these compounds and their unique deformation by kinking mechanism. Fig. 2 Fig. 1
FRG: Mn+1AXn Phase Solid Solutions: Unique Opportunities at Engineering Bulk and Surface Properties Micheal W. Barsoum, Drexel University, DMR 0503711Broader Impact Two groups were formed, the part-time students (< 16 h/wk) synthesized binary carbides to act as an interface layer between substrate and MAX and to investigate possible diffusion of Al from the substrate (Al2O3) into the carbide. The findings of this group were relayed to the full-time students who then used them to synthesize the more complex MAX-phase counter parts (e.g. VC results were used to synthesize V2AlC). It is during this time the research team was able to synthesize 6 MAX-phases for the first time ever. Included among the educational activities were weekly research presentations given by one student to the entire group. Each student was identified as the group “custodian” for a single instrument. This included the student writing a standard operating procedure and training their colleagues in use of the equipment. By the end of the program all students were proficient in performing measurements using x-ray diffraction, scanning electron microscopy, atomic force microscopy, profilometry, electrical conductivity measurements, and the sputtering system. This type of training is an invaluable experience that prepares them for graduate school or industry. Synthesis of New Materials: As a result of their layered structure, elastic properties and high conductivities, MAX-phase materials are candidates for protective coating and electronic applications. These require their synthesis in the form of thin film. We have successfully synthesized 6 textured films: Cr2AlC, V2AlC, V3AlC2, V4AlC3, (Ti1-xNbx)2AlC, and (Ti1-xNbx)4AlC3.The latter 4 are totally new materials synthesized in thin film form for the first time ever. Preparation of Future Scientists- Accelerated Research Effort During the 2007 summer a group of 6 Rowan undergraduate students participated in an 11-week accelerated research effort. The group consisted of students funded by the grant, as well as some taking research for course/program credit. Each student had their own ternary system to investigate, from synthetic requirements to material characterization.