Sökning: "quasicrystal"

Visar resultat 1 - 5 av 11 avhandlingar innehållade ordet quasicrystal.

1. 1. A structural investigation into the complexity of mesoporous silica crystals : From a view of curvature and micellar interaction to quasicrystallinity

   Författare :Changhong Xiao; Terasaki Osamu; Lidin Sven; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; electron microscopy; mesoporous silica; quasicrystal; minimal surface; Structural Chemistry; strukturkemi;

   Sammanfattning : Mesoporous silica crystals have a large variety of structures mainly due to the versatility of their structure template. The configuration and the chemical state of the templating micellar surfactants, together with the kinetic process of silica will determine the final outcome of the synthesis. LÄS MER

3. 2. Complexity of quasicrystal approximants —The RECd6 and RE13(Zn/Cd)~58 systems

   Författare :ShuYing Piao; Sven Lidin; Osamu Terasaki; Marc de Boissieu; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Rare-earth; Quasicrystal approximant; order and disorder; Chemistry; Kemi; oorganisk kemi; Inorganic Chemistry;

   Sammanfattning : This thesis is focused on the synthesis and structural determination of a series of quasicrystal approximants in the RE13Zn~58 (RE = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), Ce13Cd~58 and RECd6 (RE = Tb, Ho, Er, Tm and Lu) systems. Structural studies were performed by single crystal X-ray diffraction methods. LÄS MER

4. 3. Quasicrystal Approximants in the RE-Au-SM systems (RE = Gd, Tb, Ho, Yb; SM = Si, Ge) : Syntheses, structures and properties

   Författare :Girma Hailu Gebresenbut; Cesar Pay Gómez; Martin Sahlberg; Torbjörn Gustafsson; Alan I. Goldman; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Quasicrystal approximant; structure; physical property; Chemistry with specialization in Inorganic Chemistry; Kemi med inriktning mot oorganisk kemi; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

   Sammanfattning : In this study, new Tsai-type 1/1 quasicrystal approximants (ACs) in the RE-Au-SM systems (RE = Gd, Tb, Ho, Yb; SM = Si, Ge) were synthesized using high temperature synthesis techniques such as self-flux, arc-melting-annealing and novel arc-melting-self-flux methods. The syntheses not only provided appropriate samples for the intended structural and physical property measurements but could also be adapted to other systems, especially where crystal growth is a challenge. LÄS MER

5. 4. Syntheses, structure determination, magnetic and thermoelectric properties of quasicrystal approximants in RE-Au-SM systems (RE = Gd, Tb and Yb and SM = Si, Ge)

   Författare :Girma Hailu Gebresenbut; Cesar Gomez; Martin Sahlberg; Torbjörn Gustafsson; Lars Eriksson; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quasicrystals; quasicrystal approximants; thermoelectric properties; magnetic properties; Materialvetenskap; Materials Science;

   Sammanfattning : In this study, new compositions of Tsai-type 1/1 quasicrystal approximants Gd(14)Au(70)Si(16), Gd(14)Au(67)Ge(19), Tb(14)Au(70)Si(16) and Yb(16)Au(65)Ge(19)are synthesized using both self-flux and arc-melting-annealing techniques. Both syntheses routes resulted single phase samples. LÄS MER

7. 5. Electronic and magnetic properties of Tsai quasicrystals and their approximants under pressure

   Författare :Fernand Denoel; Roland Mathieu; Vassilios Kapaklis; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Tsai quasicrystal; high pressure; diamond anvil cell; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

   Sammanfattning : Quasicrystals constitute a special category of crystals exhibiting long-range order without periodicity. This strange feature allows them to exhibit rotational symmetries prohibited in regular crystals, such as 5-, 8-, 10- or 12-fold symmetry. Amongst them, icosahedral quasicrystals are the only type that is aperiodic along all 3 dimensions. LÄS MER