scholarly journals Tuning mechanical metastability in FeMnCo medium entropy alloys and a peek into deformable hexagonal close-packed martensite

2021 ◽  
Vol 119 (26) ◽  
pp. 261905
Author(s):  
Shaolou Wei ◽  
Michael Xu ◽  
James M. LeBeau ◽  
Cemal Cem Tasan
Keyword(s):  
Hexagonal Close Packed

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

scholarly journals Stability and equation of state of face-centered cubic and hexagonal close packed phases of argon under pressure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Agnès Dewaele ◽  
Angelika D. Rosa ◽  
Nicolas Guignot ◽  
Denis Andrault ◽  
João Elias F. S. Rodrigues ◽  
...  
Keyword(s):  
Equation Of State ◽  
Single Crystal ◽  
Single Crystal Sample ◽  
Moderate Pressure ◽  
Face Centered Cubic ◽  
Experimental Conditions ◽  
Crystal Sample ◽  
Hexagonal Close Packed ◽  
Face Centered ◽  
Fcc Phase

AbstractThe compression of argon is measured between 10 K and 296 K up to 20 GPa and and up to 114 GPa at 296 K in diamond anvil cells. Three samples conditioning are used: (1) single crystal sample directly compressed between the anvils, (2) powder sample directly compressed between the anvils, (3) single crystal sample compressed in a pressure medium. A partial transformation of the face-centered cubic (fcc) phase to a hexagonal close-packed (hcp) structure is observed above 4.2–13 GPa. Hcp phase forms through stacking faults in fcc-Ar and its amount depends on pressurizing conditions and starting fcc-Ar microstructure. The quasi-hydrostatic equation of state of the fcc phase is well described by a quasi-harmonic Mie–Grüneisen–Debye formalism, with the following 0 K parameters for Rydberg-Vinet equation: $$V_0$$ V 0 = 38.0 Å$$^3$$ 3 /at, $$K_0$$ K 0 = 2.65 GPa, $$K'_0$$ K 0 ′ = 7.423. Under the current experimental conditions, non-hydrostaticity affects measured P–V points mostly at moderate pressure ($$\le$$ ≤ 20 GPa).

scholarly journals Substrate wettability guided oriented self assembly of Janus particles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Meneka Banik ◽  
Shaili Sett ◽  
Chirodeep Bakli ◽  
Arup Kumar Raychaudhuri ◽  
Suman Chakraborty ◽  
...  
Keyword(s):  
Self Assembly ◽  
Janus Particles ◽  
Water Molecules ◽  
Functional Coatings ◽  
Hexagonal Close Packed ◽  
Local Densities ◽  
Inhomogeneous Properties ◽  
Metal Polymer ◽  
Specific Orientation

AbstractSelf-assembly of Janus particles with spatial inhomogeneous properties is of fundamental importance in diverse areas of sciences and has been extensively observed as a favorably functionalized fluidic interface or in a dilute solution. Interestingly, the unique and non-trivial role of surface wettability on oriented self-assembly of Janus particles has remained largely unexplored. Here, the exclusive role of substrate wettability in directing the orientation of amphiphilic metal-polymer Bifacial spherical Janus particles, obtained by topo-selective metal deposition on colloidal Polymestyere (PS) particles, is explored by drop casting a dilute dispersion of the Janus colloids. While all particles orient with their polymeric (hydrophobic) and metallic (hydrophilic) sides facing upwards on hydrophilic and hydrophobic substrates respectively, they exhibit random orientation on a neutral substrate. The substrate wettability guided orientation of the Janus particles is captured using molecular dynamic simulation, which highlights that the arrangement of water molecules and their local densities near the substrate guide the specific orientation. Finally, it is shown that by spin coating it becomes possible to create a hexagonal close-packed array of the Janus colloids with specific orientation on differential wettability substrates. The results reported here open up new possibilities of substrate-wettability driven functional coatings of Janus particles, which has hitherto remained unexplored.

scholarly journals Microstructure Refinement by Low-Temperature Ausforming in an Fe-Based Metastable High-Entropy Alloy

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 742
Author(s):  
Motomichi Koyama ◽  
Takeaki Gondo ◽  
Kaneaki Tsuzaki
Keyword(s):  
Low Temperature ◽  
Plastic Anisotropy ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Microstructure Refinement ◽  
Hexagonal Close Packed ◽  
Solution Treated Condition ◽  
Solution Treated ◽  
Face Centered

The effects of ausforming in an Fe30Mn10Cr10Co high-entropy alloy on the microstructure, hardness, and plastic anisotropy were investigated. The alloy showed a dual-phase microstructure consisting of face-centered cubic (FCC) austenite and hexagonal close-packed (HCP) martensite in the as-solution-treated condition, and the finish temperature for the reverse transformation was below 200 °C. Therefore, low-temperature ausforming at 200 °C was achieved, which resulted in microstructure refinement and significantly increased the hardness. Furthermore, plasticity anisotropy, a common problem in HCP structures, was suppressed by the ausforming treatment. This, in turn, reduced the scatter of the hardness.

Extended Gibbs Free Energy and Laplace Pressure of Ordered Hexagonal Close-Packed Spherical Particles: A Wettability Study

Langmuir ◽  
2021 ◽  
Author(s):  
Amir Bayat ◽  
Mahdi Ebrahimi ◽  
Saeed Rahemi Ardekani ◽  
Esmaiel Saievar Iranizad ◽  
Alireza Zaker Moshfegh
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Laplace Pressure ◽  
Spherical Particles ◽  
Hexagonal Close Packed

Three-Dimensional Hexagonal Close-Packed Superlattices of Passivated Ag Nanocrystals

1997 ◽  
Vol 3 (S2) ◽  
pp. 431-432
Author(s):  
S. A. Harfenist ◽  
Z. L. Wang ◽  
R. L. Whetten ◽  
I. Vezmar ◽  
M. M. Alvarez ◽  
...  
Keyword(s):  
Carbon Film ◽  
Three Dimensional ◽  
Structure Characterization ◽  
Self Assembled Monolayers ◽  
Hexagonal Close Packed ◽  
Self Assembling ◽  
Transmission Electron ◽  
Assembled Monolayers ◽  
High Resolution Tem ◽  
Nanocrystal Superlattices

Silver nanocrystals passivated by dodecanethiol self-assembled monolayers were produced using an aerosol technique described in detail elsewhere [1]. Self-assembling passivated nanocrystal-superlattices (NCS's) involve self-organization into monolayers, thin films, and superlattices of size-selected nanoclusters encapsulated in a protective compact coating [2,3,4,5,6,7]. We report the preparation and structure characterization of three-dimensional (3-D) hexagonal close-packed Ag nanocrystal supercrystals from Ag nanocrystals of ˜4.5 nm in diameters. The crystallography of the superlattice and atomic core lattices were determined using transmission electron microscopy (TEM) and high-resolution TEM.SEM was used to image the nanocrystal superlattices formed on an amorphous carbon film of an TEM specimen grid (fig. la). The superlattice films show well shaped, sharply faceted, triangular shaped sheets. Figure lb depicts numerous Ag nanocrystal aggregates uniformly distributed over the imaging region. Inset in this figure is an enlargement of the boxed region at the edge of a supercrystal typifying the ordered nanocrystal packing.

Observation of the Formation Processes of Hexagonal Close-packed and Face-centered Cubic Ru Nanoparticles

2019 ◽  
Vol 48 (9) ◽  
pp. 1062-1064 ◽  
Author(s):  
Naoki Araki ◽  
Kohei Kusada ◽  
Satoru Yoshioka ◽  
Takeharu Sugiyama ◽  
Toshiaki Ina ◽  
...  
Keyword(s):  
Face Centered Cubic ◽  
Formation Processes ◽  
Hexagonal Close Packed ◽  
Ru Nanoparticles ◽  
Face Centered

Über einige Beziehungen zwischhen Kristallstrukturen

1956 ◽  
Vol 11 (11) ◽  
pp. 920-934b
Author(s):  
Konrad Schubert
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Spatial Correlation ◽  
Chemical Elements ◽  
Electron Gas ◽  
Lattice Constants ◽  
Hexagonal Close Packed ◽  
Binary Compounds ◽  
Atomic Radii ◽  
Insight Into

In determining structures we use physical propositions in order to find a likely crystal structure. The same propositions are of value for the ordering of known structures into a natural system. The atomic radii form such a proposition. Another proposition is contained in the spatial correlation of electrons in the electron gas. The question is, whether this correlation is of influence on the crystal structure or not. To gain a first insight into this question, it is useful to know whether the crystal structures are physically compatible with a certain spatial correlation of electrons. Some qualitative rules are given to assess the physical possibility of a spatial correlation of electrons in a crystal structure. For the crystal structures of some chemical elements proposals for electron correlation are given. These proposals account for rationalities existing between some lattice constants, e. g. the axial ratios of the hexagonal close packed structures of Co and Zn. The proposals are also applicable to some binary compounds. With regard to these commensurabilities, it seems possible that the examination of the spatial correlation of electrons may lead to a better understanding of the crystal-chemical empiry.

Stacking faults in double hexagonal close-packed crystals

1969 ◽  
Vol 4 (5) ◽  
pp. 262-270 ◽  
Author(s):  
S Lele ◽  
B Prasad ◽  
P Rama Rao
Keyword(s):  
Stacking Faults ◽  
Hexagonal Close Packed
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