Synthesis and characterization of cyclotriphosphazenes containing silicon as single solid-state precursors for the formation of silicon/phosphorus nanostructured materials

The synthesis and characterization of new organosilicon derivatives of N3P3Cl6, N3P3[NH(CH2)3Si(OEt)3]6 (1), N3P3[NH(CH2)3Si(OEt)3]3[NCH3(CH2)3CN]3 (2), and N3P3[NH(CH2)3Si(OEt)3]3[HOC6H4(CH2)CN]3 (3) are reported. Pyrolysis of 1, 2, and 3 in air and at several temperatures results in nanostructured materials whose composition and morphology depend on the temperature of pyrolysis and the substituents of the phosphazenes ring. The products stem from the reaction of SiO2 with P2O5, leading to either crystalline Si5(PO4)6O, SiP2O7 or an amorphous phase as the glass Si5(PO4)6O/3SiO2·2P2O5, depending on the temperature and nature of the trimer precursors. From 1 at 800 °C, core−shell microspheres of SiO2 coated with Si5(PO4)6O are obtained, while in other cases, mesoporous or dense structures are observed. Atomic force microscopy examination after deposition of the materials on monocrystalline silicon wafers evidences morphology strongly dependent on the precursors. Isolated islands of size ∼9 nm are observed from 1, whereas dense nanostructures with a mean height of 13 nm are formed from 3. Brunauer−Emmett−Teller measurements show mesoporous materials with low surface areas. The proposed growth mechanism involves the formation of cross-linking structures and of vacancies by carbonization of the organic matter, where the silicon compounds nucleate. Thus, for the first time, unique silicon nanostructured materials are obtained from cyclic phosphazenes containing silicon.

Legends as music: new composition in the traditional Irish idiom

Engaging Ireland’s rich heritages of traditional music, story-telling, song, dance, and language, this doctoral composition project is a unique undertaking in the amalgamation of native art forms and the narrative realisation of Irish legends. The centrepiece of the project comprises of two collections of compositions inspired by the legends Oidhe Chloinne Lir (the tragic fate of the children of Lir) and Loinges Mac nUislenn (the exile of the sons of Uisliu). An interdisciplinary approach of traditional research and creative practice was employed in the development of this project, which informed and supported the formulation of personal and distinctive recensions of the chosen narratives, and the composition of over three hundred new works. Grounded in Irish traditional music, the compositional voice speaks in the familiar styles and structures of the idiom, and also resonates in contemporary and singular spaces. The Irish harping tradition is continued and extended in this research through the composition and recording of new music which is particularly suited to the instrument. Outputs include contextual, critical, and creative writings, recordings, video materials, musical scores, and storyboard and performance design artwork.