scholarly journals Quasi-Icosahedral Clusters in Zr-Based Metallic Glasses

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1135
Author(s):  
Guqing Guo
Keyword(s):  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Structural Parameters ◽  
Voronoi Tessellation ◽  
Building Blocks ◽  
Order Structure ◽  
Atomic Structures ◽  
Icosahedral Clusters ◽  
Almost All ◽  
Cluster Level

The icosahedral short-range order structure is one of the important local structural units in the field of metallic glasses. Based on the Voronoi tessellation method, the connection modes between shell atoms of Voronoi indexed clusters in ZrCu binary and ZrCuAl ternary metallic glasses were characterized systematically. It was revealed that Voronoi clusters with different connection modes can potentially have the same Voronoi index. By investigating the connection modes of clusters, three types of Voronoi indexed clusters can be defined as quasi-icosahedral clusters, which have the most similar five-fold environments to full icosahedral clusters. It was also found that the full icosahedral clusters and the quasi-icosahedral clusters had similar values for some structural parameters, and that these clusters contain almost all the atoms in these structural models, enhancing the space filling efficiency. Full icosahedral and quasi-icosahedral clusters should be regarded as the building blocks of atomic structures contributing to glass formation in amorphous alloys. This work is helpful for investigating and understanding the various macroscopic properties of metallic glasses at the atomic cluster level.

Crystallization Characteristic Study for Amorphous of Nd60Al10Cu20Ni10

2014 ◽  
Vol 556-562 ◽  
pp. 385-388
Author(s):  
Dong Man Yu ◽  
Yan Hui Hu ◽  
Di Wang ◽  
Xiao Jing Li
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Heating Temperature ◽  
Liquid Region ◽  
Ordinary Temperature ◽  
Thermal Features ◽  
High Cooling Rates ◽  
Almost All

Since the first synthesis of an amorphous phase in Au-Si system from liquid, a great number of amorphous alloys have been prepared by rapid solidification. Almost all amorphous alloys require high cooling rates and a lot of studies have been carried out for these metallic glasses. In this study, metallic glass of Nd60Al10Cu20Ni10 have been fabricated, and experimental research was carried out to reflect thermal features. It indicates that the Nd-based amorphous has shown a distinct glass transition and stable super-cooled liquid region. The research results show that the paramagnetic performance of Nd60Al10Cu20Ni10 metallic glass is different from other hard magnetic alloys at ordinary temperature. From the DSC experiment, it is found that the glass transition temperature is increasing with the heating temperature.

Local Atomic Structures in Amorphous and Quasicrystalline Zr70Ni10Pt20and Zr80Pt20Alloys by the Anomalous X-ray Scattering Method

2000 ◽  
Vol 644 ◽  
Author(s):  
Eiichiro Matsubara ◽  
Takahiro Nakamura ◽  
Masaki Sakurai ◽  
Muneyuki Imafuku ◽  
Shigeo Sato ◽  
...  
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Nearest Neighbor ◽  
Scattering Method ◽  
X Ray ◽  
Coordination Numbers ◽  
Atomic Structures ◽  
X Ray Scattering ◽  
Icosahedral Clusters ◽  
Ray Scattering

AbstractLocal atomic structures around Zr and Pt in a quasicrystalline Zr80Pt20alloy, and amorphous and quasicrystalline Zr70Ni10Pt20alloys have been determined by the anomalous x-ray scattering (AXS) method. A distinct prepeak observed in an intensity profile of the amorphous Zr70Ni10Pt20alloy indicates existence of strong chemical short-range order (CSRO) clusters in the amorphous phase. Total coordination numbers around Zr and Pt in a nearest neighbor region in both alloys have been evaluated. The values around Pt are almost equal to 12 in the amorphous and quasicrystalline states suggest formation of icosahedral clusters around Pt. Some of crystalline structures formed from the quasicrystalline phases by annealing consist of icosahedral clusters of Zr and Ni atoms, or polyhedral clusters of Zr and Pt atoms similar with icosahedral clusters. The present result appears to support that the phase transformation from the amorphous to the crystal through the quasicrystal is explained by the icosahedral CSRO clusters in the amorphous and quasicrystalline states.

Semi-Empirical Fitting of Partial Pair Correlation Functions of Amorphous Alloys

1995 ◽  
Vol 50 (12) ◽  
pp. 1205-1218
Author(s):  
E. Sváb ◽  
F. Hajdu ◽  
Gy. Mészáros
Keyword(s):  
Amorphous Alloys ◽  
Structural Parameters ◽  
Pair Correlation ◽  
Analytical Formula ◽  
Partial Structure ◽  
Fitting Procedure ◽  
Atomic Pair ◽  
Structure Factors ◽  
Characteristic Features ◽  
Semi Empirical

Abstract A semi-empirical fitting procedure has been developed and used in analysing the characteristic features of the partial structure factors of binary amorphous alloys. An analytical formula is given to fit the experimental atomic pair correlation function as a sum of Gaussians. The inverse Fourier transform of the fitted terms reproduces all features of the experimental structure function. In addition to the structural parameters, the modelling gives a quantitative explanation for the complex origin of characteristic features in the diffraction pattern such as pre-peak, pre-minimum, and split peaks in the partial structure factor.

scholarly journals Local Atomic Structures of Zr70Ga10Ni20 Amorphous Alloys by the Anomalous X-ray Scattering Method

1995 ◽  
Vol 36 (9) ◽  
pp. 1093-1096 ◽  
Author(s):  
Teruyuki Ikeda ◽  
Eiichiro Matsubara ◽  
Yoshio Waseda ◽  
Akihisa Inoue ◽  
Tao Chang ◽  
...  
Keyword(s):  
Amorphous Alloys ◽  
Scattering Method ◽  
X Ray ◽  
Atomic Structures ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Specific Features of Structure Transformation and Properties of Amorphous-Nanocrystalline Alloys

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 358 ◽  
Author(s):  
Alexandr Aronin ◽  
Galina Abrosimova
Keyword(s):  
Amorphous Phase ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Structural Changes ◽  
Shear Bands ◽  
Component Composition ◽  
Amorphous Structure ◽  
Structure Evolution ◽  
Current State ◽  
Heterogeneous Phase

This work is devoted to a brief overview of the structure and properties of amorphous-nanocrystalline metallic alloys. It presents the current state of studies of the structure evolution of amorphous alloys and the formation of nanoglasses and nanocrystals in metallic glasses. Structural changes occurring during heating and deformation are considered. The transformation of a homogeneous amorphous phase into a heterogeneous phase, the dependence of the scale of inhomogeneities on the component composition, and the conditions of external influences are considered. The crystallization processes of the amorphous phase, such as the homogeneous and heterogeneous nucleation of crystals, are considered. Particular attention is paid to a volume mismatch compensation on the crystallization processes. The effect of changes in the amorphous structure on the forming crystalline structure is shown. The mechanical properties in the structure in and around shear bands are discussed. The possibility of controlling the structure of fully or partially crystallized samples is analyzed for creating new materials with the required physical properties.

scholarly journals Self-standing and flexible covalent organic framework (COF) membranes for molecular separation

2020 ◽  
Vol 6 (41) ◽  
pp. eabb1110
Author(s):  
Jiangtao Liu ◽  
Gang Han ◽  
Dieling Zhao ◽  
Kangjia Lu ◽  
Jie Gao ◽  
...  
Keyword(s):  
Building Blocks ◽  
Shape Selectivity ◽  
Honeycomb Lattice ◽  
Free Standing ◽  
Covalent Bonds ◽  
Separation Science ◽  
Covalent Organic Framework ◽  
Molecular Building Blocks ◽  
Almost All ◽  
Organic Framework

Almost all covalent organic framework (COF) materials conventionally fabricated by solvothermal method at high temperatures and pressures are insoluble and unprocessable powders, which severely hinder their widespread applications. This work develops an effective and facile strategy to construct flexible and free-standing pure COF membranes via the liquid-liquid interface-confined reaction at room temperature and atmospheric pressure. The aperture size and channel chemistry of COF membranes can be rationally designed by bridging various molecular building blocks via strong covalent bonds. Benefiting from the highly-ordered honeycomb lattice, high solvent permeances are successfully obtained and follow the trend of acetonitrile > acetone > methanol > ethanol > isopropanol. Interestingly, the imine-linked COF membrane shows higher nonpolar solvent permeances than b-ketoenamine-linked COF due to their difference in pore polarity. Both kinds of COF membranes exhibit high solvent permeances, precise molecular sieving, excellent shape selectivity, and sufficient flexibility for membrane-based separation science and technology.

scholarly journals Brain structural correlates of schizotypal signs and subclinical schizophrenia nuclear symptoms in healthy individuals

2020 ◽  
pp. 1-10
Author(s):  
Tina Meller ◽  
Simon Schmitt ◽  
Ulrich Ettinger ◽  
Phillip Grant ◽  
Frederike Stein ◽  
...  
Keyword(s):  
Negative Correlation ◽  
Psychotic Disorders ◽  
Structural Parameters ◽  
Brain Structures ◽  
Precentral Gyrus ◽  
Healthy Individuals ◽  
Positive Correlation ◽  
Temporal Pole ◽  
The Right ◽  
Cluster Level

Abstract Background Subclinical psychotic-like experiences (PLE), resembling key symptoms of psychotic disorders, are common throughout the general population and possibly associated with psychosis risk. There is evidence that such symptoms are also associated with structural brain changes. Methods In 672 healthy individuals, we assessed PLE and associated distress with the symptom-checklist-90R (SCL-90R) scales ‘schizotypal signs’ (STS) and ‘schizophrenia nuclear symptoms’ (SNS) and analysed associations with voxel- and surfaced-based brain structural parameters derived from structural magnetic resonance imaging at 3 T with CAT12. Results For SNS, we found a positive correlation with the volume in the left superior parietal lobule and the precuneus, and a negative correlation with the volume in the right inferior temporal gyrus [p < 0.05 cluster-level Family Wise Error (FWE-corrected]. For STS, we found a negative correlation with the volume of the left and right precentral gyrus (p < 0.05 cluster-level FWE-corrected). Surface-based analyses did not detect any significant clusters with the chosen statistical threshold of p < 0.05. However, in exploratory analyses (p < 0.001, uncorrected), we found a positive correlation of SNS with gyrification in the left insula and rostral middle frontal gyrus and of STS with the left precuneus and insula, as well as a negative correlation of STS with gyrification in the left temporal pole. Conclusions Our results show that brain structures in areas implicated in schizophrenia are also related to PLE and its associated distress in healthy individuals. This pattern supports a dimensional model of the neural correlates of symptoms of the psychotic spectrum.

Comparative study of local atomic structures in Zr2CuxNi1−x (x = 0, 0.5, 1) metallic glasses

2015 ◽  
Vol 118 (19) ◽  
pp. 195902 ◽  
Author(s):  
Yuxiang Huang ◽  
Li Huang ◽  
C. Z. Wang ◽  
M. J. Kramer ◽  
K. M. Ho
Keyword(s):  
Comparative Study ◽  
Metallic Glasses ◽  
Atomic Structures

Bulk Metallic Glasses

2008 ◽  
Vol 604-605 ◽  
pp. 229-238
Author(s):  
Marcello Baricco ◽  
Tanya A. Başer ◽  
Gianluca Fiore ◽  
Rafael Piccin ◽  
Marta Satta ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Shear Bands ◽  
Bulk Metallic Glasses ◽  
Rapid Quenching ◽  
Second Phase ◽  
Research Activity ◽  
Long Time ◽  
Geometrical Constraints

Rapid quenching techniques have been successfully applied since long time for the preparation of metallic glasses in ribbon form. Only in the recent years, the research activity addressed towards the synthesis of bulk metallic glasses (BMG), in form of ingots with a few millimetres in thickness. These materials can be obtained by casting techniques only for selected alloy compositions, characterised by a particularly high glass-forming tendency. Bulk amorphous alloys are characterised by a low modulus of elasticity and high yielding stress. The usual idea is that amorphous alloys undergo work softening and that deformation is concentrated in shear bands, which might be subjected to geometrical constraints, resulting in a substantial increase in hardness and wear resistance. The mechanical properties can be further improved by crystallisation. In fact, shear bands movement can be contrasted by incorporating a second phase in the material, which may be produced directly by controlled crystallisation. Soft magnetic properties have been obtained in Fe-based systems and they are strongly related to small variations in the microstructure, ranging from a fully amorphous phase to nanocrystalline phases with different crystal size. The high thermal stability of bulk metallic glasses makes possible the compression and shaping processes in the temperature range between glass transition and crystallisation. Aim of this paper is to present recent results on glass formation and properties of bulk metallic glasses with various compositions. Examples will be reported on Zr, Fe, Mg and Pd-based materials, focussing on mechanical and magnetic properties.

BULK AMORPHOUS AND NANOSTRUCTURED MATERIALS BY HIGH ENERGY BALL MILLING

2008 ◽  
Vol 22 (18n19) ◽  
pp. 2905-2913 ◽  
Author(s):  
CONSTANTIN POLITIS
Keyword(s):  
Ball Milling ◽  
Nanostructured Materials ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Glassy State ◽  
High Strength ◽  
Supercooled Liquid ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Energy Ball

Mechanical alloying by high energy ball milling is a promising method for the production of bulk metallic glasses, amorphous alloys and nanostructured materials. Amorphous alloys reinforced by nanocrystals represent a big step in the optimization of new ultra high strength materials. Nano-scale W-Y solid solutions were synthesized by high energy ball milling. Only 1 at. % oxygen can stabilize the bulk metallic glassy state of Zr 54 Cu 19 Ni 8 Al 8 Si 5 Ti 5 O 1 to higher T x and to large supercooled liquid range Δ T xg .

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