Microstructure of Liquid Co50Ni50 During Rapid Solidification

2020 ◽  
Vol 20 (12) ◽  
pp. 7593-7600 ◽  
Author(s):  
Min Li ◽  
Quan Xie ◽  
Shan Li
Keyword(s):  
Rapid Solidification ◽  
Cluster Structure ◽  
Solidification Process ◽  
Face Centered Cubic ◽  
Index Method ◽  
Bond Type ◽  
Bcc Structure ◽  
Hcp Structure ◽  
Face Centered ◽  
Fcc Structure

The rapid solidification process of Co50Ni50 alloy was simulated by molecular dynamics method, and the formation and evolution characteristics of cluster structure in the solidification process were analyzed by the pair distribution function, Honeycutt–Andersen bond type index method and the largest standard cluster. The results show that during the solidification process with a cooling rate of 1×1012 K·‐1, the probability of mutual bond formation between Co–Co atoms is always greater than that of Ni–Ni, and the formation of the 1421 bond type is dominant in the crystalline structure. The inflection point of the characteristic bond type 1421 varies with the crystalline transition temperature Tg of the system. The Co–Ni alloy is mainly composed of a face-centered cubic atomic group composed of the 1421 bond type. Meanwhile, there will also be a small amount of hcp structure and a smaller amount of bcc structure. Further analysis revealed that the formation of the fcc structure requires the fast decomposition of TCP structures (at 1450 K). That is to say, the TCP structure must be disassembled before the fcc structure is formed. These findings are useful to provide important guidance for the crystallization of Co50Ni50 alloy under rapid cooling in the experiment.

scholarly journals Ti-V-C-Based Alloy with a FCC Lattice Structure for Hydrogen Storage

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 552
Author(s):  
Bo Li ◽  
Liqing He ◽  
Jianding Li ◽  
Hai-Wen Li ◽  
Zhouguang Lu ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Room Temperature ◽  
Lattice Structure ◽  
Activation Process ◽  
Face Centered Cubic ◽  
Hydrogen Storage Materials ◽  
Fcc Lattice ◽  
Bcc Structure ◽  
Face Centered ◽  
Fcc Structure

Here we report a Ti50V50-10 wt.% C alloy with a unique lattice and microstructure for hydrogen storage development. Different from a traditionally synthesized Ti50V50 alloy prepared by a melting method and having a body-centered cubic (BCC) structure, this Ti50V50-C alloy synthesized by a mechanical alloying method is with a face-centered cubic (FCC) structure (space group: Fm-3m No. 225). The crystalline size is 60 nm. This alloy may directly absorb hydrogen near room temperature without any activation process. Mechanisms of the good kinetics from lattice and microstructure aspects were discussed. Findings reported here may indicate a new possibility in the development of future hydrogen storage materials.

Vapor phase dealloying-driven synthesis of bulk nanoporous cobalt with a face-centered cubic structure

CrystEngComm ◽  
2021 ◽  
Author(s):  
Yujun Shi ◽  
Yu Wang ◽  
Wanfeng Yang ◽  
Jingyu Qin ◽  
Qingguo Bai ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Vapor Phase ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Cubic Structure ◽  
Hcp Structure ◽  
Face Centered ◽  
Fcc Structure

Cobalt (Co) mainly exists in two allotropic forms: a low temperature hexagonal close-packed (HCP) structure and a high temperature face centered cubic (FCC) structure. However, annealing at high temperature only...

scholarly journals Effects of C Addition on the Microstructures of As-Cast Cu–Fe–P Alloys

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2772 ◽  
Author(s):  
Chen ◽  
Hu ◽  
Guo ◽  
Zou ◽  
Liu ◽  
...  
Keyword(s):  
Orientation Relationship ◽  
Supersaturated Solid Solution ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Matrix Microstructure ◽  
The Matrix ◽  
Bcc Structure ◽  
The Difference ◽  
Face Centered ◽  
Fcc Structure

Effects of C addition on the microstructures of as-cast Cu–Fe–P (mass fraction) alloys were systematically investigated. The results show that C addition can refine the matrix microstructure and make Fe particles finer. The Fe particles observed in both the non-C-alloyed and C-alloyed specimens are α-Fe particles, which possess a body-centered cubic (bcc) structure with a Nishiyama–Wassermann orientation relationship with the matrix. C is reported to be an γ-Fe stabilizer in the literature. The reason for the difference between the phases of Fe particles observed in this study, and that reported in the literature, are finally discussed. Additionally, C addition facilitates the decomposition of the supersaturated solid solution which occurs by the simultaneous precipitation of very fine Fe particles. Such initial decomposition product has an face-centered cubic (fcc) structure with a cube-on-cube orientation relationship with the matrix.

scholarly journals Potential high-Tc superconducting lanthanum and yttrium hydrides at high pressure

2017 ◽  
Vol 114 (27) ◽  
pp. 6990-6995 ◽  
Author(s):  
Hanyu Liu ◽  
Ivan I. Naumov ◽  
Roald Hoffmann ◽  
N. W. Ashcroft ◽  
Russell J. Hemley
Keyword(s):  
Group Structure ◽  
High Temperature Superconductors ◽  
Face Centered Cubic ◽  
Superconducting Transition ◽  
High Tc ◽  
Structure Search ◽  
Systematic Structure ◽  
Face Centered ◽  
Fcc Structure ◽  
Very High

A systematic structure search in the La–H and Y–H systems under pressure reveals some hydrogen-rich structures with intriguing electronic properties. For example, LaH10 is found to adopt a sodalite-like face-centered cubic (fcc) structure, stable above 200 GPa, and LaH8 a C2/m space group structure. Phonon calculations indicate both are dynamically stable; electron phonon calculations coupled to Bardeen–Cooper–Schrieffer (BCS) arguments indicate they might be high-Tc superconductors. In particular, the superconducting transition temperature Tc calculated for LaH10 is 274–286 K at 210 GPa. Similar calculations for the Y–H system predict stability of the sodalite-like fcc YH10 and a Tc above room temperature, reaching 305–326 K at 250 GPa. The study suggests that dense hydrides consisting of these and related hydrogen polyhedral networks may represent new classes of potential very high-temperature superconductors.

scholarly journals Generalization of the Unified Analytic Melt-Shear Model to Multi-Phase Materials: Molybdenum as an Example

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 86 ◽  
Author(s):  
Leonid Burakovsky ◽  
Darby Luscher ◽  
Dean Preston ◽  
Sky Sjue ◽  
Diane Vaughan
Keyword(s):  
Shear Modulus ◽  
Solid Phase ◽  
Model Parameters ◽  
Quantum Molecular Dynamics ◽  
Face Centered Cubic ◽  
Shear Model ◽  
Bcc Structure ◽  
Face Centered ◽  
Multi Phase ◽  
Theoretical Results

The unified analytic melt-shear model that we introduced a decade ago is generalized to multi-phase materials. A new scheme for calculating the values of the model parameters for both the cold ( T = 0 ) shear modulus ( G ) and the melting temperature at all densities ( ρ ) is developed. The generalized melt-shear model is applied to molybdenum, a multi-phase material with a body-centered cubic (bcc) structure at low ρ which loses its dynamical stability with increasing pressure (P) and is therefore replaced by another (dynamically stable) solid structure at high ρ . One of the candidates for the high- ρ structure of Mo is face-centered cubic (fcc). The model is compared to (i) our ab initio results on the cold shear modulus of both bcc-Mo and fcc-Mo as a function of ρ , and (ii) the available theoretical results on the melting of bcc-Mo and our own quantum molecular dynamics (QMD) simulations of one melting point of fcc-Mo. Our generalized model of G ( ρ , T ) is used to calculate the shear modulus of bcc-Mo along its principal Hugoniot. It predicts that G of bcc-Mo increases with P up to ∼240 GPa and then decreases at higher P. This behavior is intrinsic to bcc-Mo and does not require the introduction of another solid phase such as Phase II suggested by Errandonea et al. Generalized melt-shear models for Ta and W also predict an increase in G followed by a decrease along the principal Hugoniot, hence this behavior may be typical for transition metals with ambient bcc structure that dynamically destabilize at high P. Thus, we concur with the conclusion reached in several recent papers (Nguyen et al., Zhang et al., Wang et al.) that no solid-solid phase transition can be definitively inferred on the basis of sound velocity data from shock experiments on Mo. Finally, our QMD simulations support the validity of the phase diagram of Mo suggested by Zeng et al.

Formation of Face Centered Cubic Titanium Thin Films on MgO(111) Single Crystal Substrate

2018 ◽  
Vol 913 ◽  
pp. 264-269
Author(s):  
Lei Li ◽  
Yan Liu ◽  
Xiao Nan Mao ◽  
Vincent Ji
Keyword(s):  
Single Crystal ◽  
Single Crystal Substrate ◽  
Temperature Phase ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Crystal Substrate ◽  
Cubic Structure ◽  
Hcp Structure ◽  
Face Centered ◽  
Ti Films

High strength, low density, and excellent corrosion resistance are the main properties that make titanium attractive for a variety of applications. The phase structures and phase transitions of titanium, which are of tremendous scientific and technological interest, have attracted a great deal of attention for many years. In addition to hexagonal close packed α-Ti, high temperature phase β-Ti with body-centered cubic structure and ω-Ti with the hexagonal structure of high-pressure phase, the face-centered cubic structure, which is not in the P-T diagram of titanium, is observed in ultrathin films. In the present paper, the Ti films prepared by magnetron sputtering on MgO(111) single crystal substrate were investigated by means of X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscope (HRTEM). The results showed that the Ti films grow epitaxial with a face centered cubic (fcc) structure even the thickness is up to about 50nm. With the thickness increases, the Ti films transformed to hexagonal close packed (hcp) structure and showed an epitaxial growth along (002)hcp-Ti direction. The results show that the onset thickness of fcc-hcp structure transformation is 50-100nm. The temperature and power of sputter affect the formation of fcc-Ti.

Ozone-Based Atomic Layer Deposition of HfO2 and HfxSi1-xO2 and Film Characterization

2004 ◽  
Vol 811 ◽  
Author(s):  
Yoshihide Senzaki ◽  
Seung Park ◽  
Douglas Tweet ◽  
John F. Conley ◽  
Yoshi Ono
Keyword(s):  
Atomic Layer ◽  
Optical Measurements ◽  
Face Centered Cubic ◽  
Hafnium Silicate ◽  
X Ray ◽  
Layer Deposition ◽  
Face Centered ◽  
Fcc Phase ◽  
20 Nm ◽  
Fcc Structure

Abstract:New ALD processes for hafnium silicate films have been developed at Aviza Technology by co-injection of tetrakis(ethylmethylamino)hafnium and tetrakis(ethylmethylamino)silicon precursors. Alternating pulses of the Hf/Si precursor vapor mixture and ozone allow process temperatures below 400°C to grow HfxSi1-xO2 films. Film characterization, including film density, crystallinity, and thermal anneal effect, was performed on five 20 nm thick HfxSi1-xO2 films where x = 0.2, 0.4, 0.6, 0.8, 1.0. X-ray measurements revealed the film densities and thicknesses for the as-deposited and 1000°C annealed samples. The densification with anneals seen in the optical measurements were confirmed. The as-deposited amorphous HfO2 and Hf0.8Si0.2O2 were crystallized after a 600°C anneal. The HfO2 formed the well known monoclinic phase while the silicate formed a face-centered-cubic (fcc) structure. This fcc phase has only recently been mentioned in the literature [1].

Critical factors that determine face-centered cubic to body-centered cubic phase transformation in sputter-deposited austenitic stainless steel films

2004 ◽  
Vol 19 (6) ◽  
pp. 1696-1702 ◽  
Author(s):  
X. Zhang ◽  
A. Misra ◽  
R.K. Schulze ◽  
C.J. Wetteland ◽  
H. Wang ◽  
...  
Keyword(s):  
Thin Films ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Phase Stability ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Bcc Structure ◽  
Face Centered ◽  
Sputter Deposited

Bulk austenitic stainless steels (SS) have a face-centered cubic (fcc) structure. However, sputter deposited films synthesized using austenitic stainless steel targets usually exhibit body-centered cubic (bcc) structure or a mixture of fcc and bcc phases. This paper presents studies on the effect of processing parameters on the phase stability of 304 and 330 SS thin films. The 304 SS thin films with in-plane, biaxial residual stresses in the range of approximately 1 GPa (tensile) to approximately 300 MPa (compressive) exhibited only bcc structure. The retention of bcc 304 SS after high-temperature annealing followed by slow furnace cooling indicates depletion of Ni in as-sputtered 304 SS films. The 330 SS films sputtered at room temperature possess pure fcc phase. The Ni content and the substrate temperature during deposition are crucial factors in determining the phase stability in sputter deposited austenitic SS films.

Structure of Self-Assembled Fe and FePt Nanoparticle Arrays

2000 ◽  
Vol 636 ◽  
Author(s):  
S. Yamamuro ◽  
D. Farrell ◽  
K. D. Humfeld ◽  
S. A. Majetich
Keyword(s):  
Phase Contrast ◽  
Face Centered Cubic ◽  
Nanoparticle Arrays ◽  
Hexagonal Close Packed ◽  
Transmission Electron ◽  
Self Assembled ◽  
Hcp Structure ◽  
Face Centered ◽  
Contrast Image ◽  
Image Simulations

AbstractArrays were self-assembled by evaporating suspensions of 4 nm FePt or 8 nm Fe nanoparticles. The monolayers had a hexagonal close packed (hcp) structure, but the multilayer structure varied. To identify the multilayer structures, transmission electron microscopy (TEM) images were compared with phase contrast image simulations. The results showed that Fe could be grown as both hcp and face-centered cubic (fcc), or fcc-like, structures. The results of image analysis of the FePt arrays were consistent with fcc structures.

scholarly journals Simple Metal and Binary Alloy Phases Based on the fcc Structure: Electronic Origin of Distortions, Superlattices and Vacancies

2017 ◽  
Author(s):  
Valentina F. Degtyareva ◽  
Nataliya S. Afonikova
Keyword(s):  
Binary Alloy ◽  
Complex Structures ◽  
Face Centered Cubic ◽  
Energy Contribution ◽  
Simple Metal ◽  
Fermi Sphere ◽  
The Face ◽  
Face Centered ◽  
The Stability ◽  
Fcc Structure

Crystal structures of simple metals and binary alloy phases based on the face-centered cubic (fcc) structure are analyzed within the model of Fermi sphere – Brillouin zone interactions to understand the stability of original cubic structure and derivative structures with distortions, superlattices and vacancies. Examination of the Brillouin-Jones configuration in relation to the nearly-free electron Fermi sphere for several representative phases reveals significance of the electron energy contribution to the phase stability. Representation of complex structures in the reciprocal space clarifies their relationship to the basic cubic cell.

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