WorldWideScience

Sample records for allotropy

  1. Clathrates and beyond: Low-density allotropy in crystalline silicon

    Science.gov (United States)

    Beekman, Matt; Wei, Kaya; Nolas, George S.

    2016-12-01

    In its common, thermodynamically stable state, silicon adopts the same crystal structure as diamond. Although only a few alternative allotropic structures have been discovered and studied over the past six decades, advanced methods for structure prediction have recently suggested a remarkably rich low-density phase space that has only begun to be explored. The electronic properties of these low-density allotropes of silicon, predicted by first-principles calculations, indicate that these materials could offer a pathway to improving performance and reducing cost in a variety of electronic and energy-related applications. In this focus review, we provide an introduction and overview of recent theoretical and experimental results related to low-density allotropes of silicon, highlighting the significant potential these materials may have for technological applications, provided substantial challenges to their experimental preparation can be overcome.

  2. Sull’origine di armeno k‘oweay ‘dado’

    Directory of Open Access Journals (Sweden)

    Andrea Scala

    2016-07-01

    Full Text Available Il lessema armeno k‘oweay ‘dado’, registrato nei lessici per lo più con questa forma, conosce almeno due altri allotropi: k‘owē e k‘oway. Il rapporto tra le forme k‘oweay e k‘owē è chiaro: la flessione dei sostantivi in -eay e di quelli in -ē coincide in tutti i casi indiretti (cfr. a titolo di esempio hreay ‘ebreo’ con origine remota in sir. īhūdāyā e mediazione iranica, gen.-dat. sing. hrēi plur. hrēic‘, strum. sing. hrēiw plur. hrēiwk‘ e hiwłē ‘materia, atomo’ < gr. ὕλη, gen.-dat. sing. hiwłēi plur. hiwłēic‘, strum. sing. hiwłēiw plur. hiwłēiwk‘, mentre è distinta nei casi retti (cfr. nom. hreay plur. hreayk‘, acc. hreay plur. hreays contro nom. hiwłē plur. hiwłēk‘, acc. hiwłē plur. hiwłēs e non sono rari i casi di conguaglio analogico tra i due schemi flessionali, con creazione di allotropi al nominativo e all’accusativo; cfr. anche ašteay/aštē ‘lancia’, bazeay/bazē ‘falcone, sparviero’.

  3. Oana Salişteanu Cristea, Prestito latino - Elemento ereditario nel lessico della lingua italiana - Doppioni e varianti, Istituto di Studi Romanzi, Facoltà di Lettere, Università Carolina Praga; Praga 2000, pp. 199

    Directory of Open Access Journals (Sweden)

    Pavao Tekavčić

    2000-12-01

    Full Text Available La ricchezza del lessico italiano dall'antichità ad oggi e la sua complicata stratificazione sono oggetto dell'interesse dei linguisti da più di un secolo e mezzo; eppure, c'è una serie di problemi non studiati a fondo, tuttora aperti e promettenti. Uno di tali temi è la coesistenza di due (o più riflessi di una sola base latina, cioè gli allotropi e doppioni (franc. doublets. Dai tempi di Ugo Angelo Canello (anni 70 dell'Ottocento questo settore del vocabolario non cessa di preoccupare gli studiosi ed il più recente contributo -- importantissimo, diciamolo subito-- che riassume, discute, sistematizza e in gran parte completa quanto fatto finora, è il recentissimo volume della professoressa Oana Sălişteanu Cristea, docente di linguistica italiana (storia della lingua, filologia e dialettologia all'Università di Bucarest. Questo libro è l'oggetto della presente recensione.

  4. Effect of Recrystallization and Phase Transitions on the Mechanical Properties of Semihard Magnetic FeCo-7.15V Alloy During the Thermomechanical Process

    Science.gov (United States)

    Hasani, Saeed; Shamanian, Morteza; Shafyei, Ali; Nezakat, Majid; Mostaan, Hossein; Szpunar, Jerzy A.

    2017-01-01

    FeCo alloys (with 7 to 14 wt pct V) are industrially key engineering materials that play an outstanding role in applications requiring semihard magnetic materials. In this study, the effects of recrystallization and phase transitions on the mechanical properties of FeCo-7.15 wt pct V alloy, in the cold-rolled and annealed conditions, were investigated. Hence, cold-rolled Fe-Co-7.15V alloy (with 90 pct reduction in thickness) was annealed at different temperatures. The microstructural evolutions were observed by scanning electron microscopes, and mechanical properties were examined using microhardness and tensile tests. Experimental results showed that the mechanical properties of the alloy depend on several phase transitions, including recrystallization, allotropy, and ordering. It was found that this alloy is too brittle and difficult to fabricate in ordered condition, and depending on the annealing temperature, the order/disorder transition is responsible for the mechanical properties. Also, after annealing at temperatures higher than 723 K (450 °C) and up to 1023 K (750 °C), the γ phase was observed in the structure, so that by annealing at 973 K (700 °C), the microstructural observation showed a duplex structure consisting of α + γ phases. In this condition, elongation was increased by an increase in the volume fraction of γ phase. Furthermore, the Young's modulus of this alloy changed at various annealing temperatures as a function of texture evolutions.