Link between liquid structure and the nucleation barrier for icosahedral quasicrystal, polytetrahedral, and simple crystalline phases inTi−Zr−Nialloys: Verification of Frank’s hypothesis

2005 ◽  
Vol 72 (17) ◽  
Author(s):  
G. W. Lee ◽  
A. K. Gangopadhyay ◽  
T. K. Croat ◽  
T. J. Rathz ◽  
R. W. Hyers ◽  
...  
Keyword(s):  
Liquid Structure ◽  
Icosahedral Quasicrystal ◽  
Crystalline Phases ◽  
Nucleation Barrier

scholarly journals Maximum supercooling studies in Ti39.5Zr39.5Ni21, Ti40Zr30Ni30, and Zr80Pt20 liquids—Connecting liquid structure and the nucleation barrier

2019 ◽  
Vol 150 (20) ◽  
pp. 204510
Author(s):  
M. E. Sellers ◽  
D. C. Van Hoesen ◽  
A. K. Gangopadhyay ◽  
K. F. Kelton
Keyword(s):  
Liquid Structure ◽  
Nucleation Barrier

A Metastable Crystalline Phase Coexisted with the Decagonal Quasicrystals in Rapidly Solidified Al-Ir Al-Pd and Al-Pt Alloys

1990 ◽  
Vol 48 (1) ◽  
pp. 572-573
Author(s):  
Wang Rong ◽  
Ma Lina ◽  
K.H. Kuo
Keyword(s):  
Metastable Phase ◽  
Hexagonal Phase ◽  
Icosahedral Quasicrystal ◽  
Decagonal Quasicrystal ◽  
Decagonal Phase ◽  
Decagonal Quasicrystals ◽  
Pt Alloy ◽  
Pt Alloys ◽  
Diffraction Patterns ◽  
Rapidly Solidified

Up to now, decagonal quasicrystals have been found in the alloys of whole Al-Pt group metals [1,2]. The present paper is concerned with the TEM study of a hitherto unreported hexagonal phase in rapidly solidified Al-Ir, Al-Pd and Al-Pt alloys.The ribbons of Al5Ir, Al5Pd and Al5Pt were obtained by spun-quenching. Specimens cut from the ribbons were ion thinned and examined in a JEM 100CX electron microscope. In both rapidly solidified Al5Ir and Al5Pd alloys, the decagonal quasicrystal, with rosette or dendritic morphologies can be easily identified by its electron diffraction patterns(EDPs). The EDPs of the decagonal phase for the two alloys are quite similar. However, the existance of decagonal quasicrystal in the Al-Pt alloy has not been verified by our TEM study. It is probably for the reason that the cooling rate is not great enough for the Al5Pt alloy to form the decagonal phase. During the TEM study, a metastable hexagonal phase has been observed in the Al5Ir, Al5Pd and Al5Pt alloys. The lattic parameters calculated from the X-ray powder data of this phase are a=1.229 and c=2.647nm(Al-Pd) and a=1.231 and c=2.623nm(Al-Ir). The composition of this phase was determined by EDS analysis as Al4(Ir, Pd or Pt). It coexists with the decagonal phase in the alloys and transformed to other stable crystalline phases on heating to high temperature. A comparison between the EDPs of the hexagonal and the decagonal phase are shown in Fig.l. Fig. 1(a) is the EDPs of the decagonal phase in various orientions and the EDPs of the hexagonal phase are shown in Fig.1(b), in a similar arrangement as Fig.1(a). It can be clearly seen that the EDPs of the hexagonal phase, especially the distribution of strong spots, are quite similar to their partners of the decagonal quasicrystal in Fig.1(a). All the angles, shown in Fig.l, between two corresponding EDPs are very close to each other. All of these seem strongly to point out that a close structural relationshipexists between these two phases:[110]//d10 [001]//d2(D) //d2 (P)The structure of α-AlFeSi is well known [3] and the 54-atom Mackay icosahedron with double icosahedral shells in the α-AlFeSi structure [4] have been used to model the icosahedral quasicrystal structure. Fig.2(a) and (b) show, respectively, the [110] and [001] projections of the crystal structure of α- AlFeSi, and decagon-pentagons can easily be identified in the former and hexagons in the latter. In addition, the optical transforms of these projections show clearly decagons and hexagons of strong spots, quite similar to those in [110] and [001] EDPs in Fig.1(b). This not only proves the Al(Ir, Pt, Pd) metastable phase being icostructural with the α-AlFeSi phase but also explains the orientation relationship mentioned above.

Hydrothermal Synthesis and Solid-State Laser Refrigeration of Ytterbium-Doped Potassium Lutetium Fluoride (KLF) Microcrystals

2020 ◽  
Author(s):  
Xiaojing Xia ◽  
Anupum Pant ◽  
Xuezhe Zhou ◽  
Elena Dobretsova ◽  
Alex Bard ◽  
...  
Keyword(s):  
Hydrothermal Synthesis ◽  
Solid State ◽  
Information Science ◽  
Point Group ◽  
Solid State Laser ◽  
Lanthanide Ions ◽  
Group Symmetry ◽  
Luminescence Spectra ◽  
Crystalline Phases ◽  
State Laser

Fluoride crystals, due to their low phonon energies, are attractive hosts of trivalent lanthanide ions for applications in upconverting phosphors, quantum information science, and solid-state laser refrigeration. In this article, we report the rapid, low-cost hydrothermal synthesis of potassium lutetium fluoride (KLF) microcrystals for applications in solid-state laser refrigeration. Four crystalline phases were synthesized, namely orthorhombic K<sub>2</sub>LuF<sub>5</sub> (Pnma), trigonal KLuF<sub>4</sub> (P3<sub>1</sub>21), orthorhombic KLu<sub>2</sub>F<sub>7</sub> (Pna2<sub>1</sub>), and cubic KLu<sub>3</sub>F<sub>10</sub> (Fm3m), with each phase exhibiting unique microcrystalline morphologies. Luminescence spectra and emission lifetimes of the four crystalline phases were characterized based on the point-group symmetry of trivalent cations. Laser refrigeration was measured by observing both the optomechanical eigenfrequencies of microcrystals on cantilevers in vacuum, and also the Brownian dynamics of optically trapped microcrystals in water. Among all four crystalline phases, the most significant cooling was observed for 10%Yb:KLuF<sub>4</sub> with cooling of 8.6 $\pm$ 2.1 K below room temperature. Reduced heating was observed with 10%Yb:K<sub>2</sub>LuF<sub>5</sub>

Probing the Small-Scale Plasticity of an Icosahedral Quasicrystal I-Al-Pd-Mn at Elevated Temperatures

2020 ◽  
Author(s):  
Changjun Cheng ◽  
Yuan Xiao ◽  
Michel J.R. Haché ◽  
Zhiying Liu ◽  
Alla S. Sologubenko ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Small Scale ◽  
Icosahedral Quasicrystal

The model rotator phase

1988 ◽  
Vol 53 (5) ◽  
pp. 889-902
Author(s):  
Josef Šebek
Keyword(s):  
High Temperature ◽  
Partition Function ◽  
Conformational Flexibility ◽  
Small Probability ◽  
Crystalline Phases ◽  
Rotator Phase

It is shown that the formation of the so-called rotator phase of alkanes (one of the high temperature crystalline phases) might be connected with a partial increase of the conformational flexibility of chains. The conformations with higher number of kinks per chain, which have been neglected till now, are shown to contribute effectively to the conformational partition function. Small probability of these states given by the Boltzmann exponent is compensated by a large number of ways in which they can be distributed along the chain. The deduced features of the rotator phase seem to be in agreement with the experimentally observed properties.

Other topics

2018 ◽  
Author(s):  
Ted Janssen ◽  
Gervais Chapuis ◽  
Marc de Boissieu
Keyword(s):  
Photonic Crystals ◽  
Crystal Morphology ◽  
Three Dimensional ◽  
Icosahedral Quasicrystal ◽  
Crystal Surfaces ◽  
Decagonal Quasicrystal ◽  
System A ◽  
Fundamental Law ◽  
Quasiperiodic Systems ◽  
Aperiodic Crystals

The law of rational indices to describe crystal faces was one of the most fundamental law of crystallography and is strongly linked to the three-dimensional periodicity of solids. This chapter describes how this fundamental law has to be revised and generalized in order to include the structures of aperiodic crystals. The generalization consists in using for each face a number of integers, with the number corresponding to the rank of the structure, that is, the number of integer indices necessary to characterize each of the diffracted intensities generated by the aperiodic system. A series of examples including incommensurate multiferroics, icosahedral crystals, and decagonal quaiscrystals illustrates this topic. Aperiodicity is also encountered in surfaces where the same generalization can be applied. The chapter discusses aperiodic crystal morphology, including icosahedral quasicrystal morphology, decagonal quasicrystal morphology, and aperiodic crystal surfaces; magnetic quasiperiodic systems; aperiodic photonic crystals; mesoscopic quasicrystals, and the mineral calaverite.

scholarly journals Crystalline Phases Relating to Stable Al–Cu–Fe Quasicrystal

1990 ◽  
Vol 31 (12) ◽  
pp. 1033-1040 ◽  
Author(s):  
V. S. Raghunathan ◽  
D. Sundararaman ◽  
R. Divakar
Keyword(s):  
Crystalline Phases

scholarly journals Impact of Baffle on Liquid Structure Connection in Fuel Tank Sloshing

2020 ◽  
Vol 995 ◽  
pp. 012044
Author(s):  
D Rohini ◽  
R Abinaya ◽  
D Lokesharun ◽  
K Karthik ◽  
V Sovishnuchringth ◽  
...  
Keyword(s):  
Liquid Structure ◽  
Fuel Tank ◽  
Tank Sloshing
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