Structure of pure metallic and semiconductor glasses

1990 ◽  
Vol 48 (4) ◽  
pp. 142-143
Author(s):  
Louis M. Holzman ◽  
Yeon-Wook Kim ◽  
Thomas F. Kelly
Keyword(s):  
Distribution Function ◽  
Radial Distribution Function ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Room Temperature ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Pure Element ◽  
Diffraction Patterns ◽  
Semiconductor Glasses

There has been a great deal of interest in amorphous materials as the advance of technology has enabled a greater variety of alloys and elements to be quenched into the amorphous state and as new uses for amorphous materials have been developed. Because the analysis of the structure of amorphous alloys is quite complicated, it is highly desirable to have specimens available of pure elements in the amorphous state in order to more easily study amorphous structure and for comparison with theory. However, very few pure elements have been quenched into the amorphous state and most of those that have been are only stable at temperatures close to absolute zero. This has limited the methods available for the study of their structure. We have produced room-temperature-stable amorphous samples of pure elements (V,Nb,Ta,Mo,W,Fe,Co,Ni,Si,Ge) from the melt using electrohydrodynamic (EHD) atomization. Diffraction patterns of these samples were obtained using a Vacuum Generators HB501 STEM and these patterns were analyzed to obtain the radial distribution function for the pure element specimens.

New method for the production of bulk amorphous materials of Nd–Fe–B alloys

2005 ◽  
Vol 20 (3) ◽  
pp. 563-566 ◽  
Author(s):  
Tetsuji Saito ◽  
Hiroyuku Takeishi ◽  
Noboru Nakayama
Keyword(s):  
Electron Microscopy ◽  
Amorphous Materials ◽  
Room Temperature ◽  
Amorphous Structure ◽  
X Ray Diffraction ◽  
Bulk Materials ◽  
X Ray ◽  
Transmission Electron ◽  
Melt Spun ◽  
Melt Spun Ribbons

We report a new compression shearing method for the production of bulk amorphous materials. In this study, amorphous Nd–Fe–B melt-spun ribbons were successfully consolidated into bulk form at room temperature by the compression shearing method. X-ray diffraction and transmission electron microscopy studies revealed that the amorphous structure was well maintained in the bulk materials. The resultant bulk materials exhibited the same magnetic properties as the original amorphous Nd–Fe–B materials.

Phase Decomposition in Cu-Ti Metallic Glass

1983 ◽  
Vol 28 ◽  
Author(s):  
R. D. Shull ◽  
S. P. Singhal ◽  
B. Mozer ◽  
A. Maeland
Keyword(s):  
Neutron Diffraction ◽  
Metallic Glass ◽  
Melt Spinning ◽  
Large Angle ◽  
Amorphous State ◽  
Glass Ribbon ◽  
Amorphous Structure ◽  
Phase Decomposition ◽  
X Ray ◽  
Diffraction Patterns

ABSTRACTA metallic glass ribbon of Cu55Ti45 prepared by melt spinning was examined by x-ray, neutron, and electron diffraction, by small angle neutron diffraction (SANS), transmission electron microscopy (TEM), and by differential thermal analysis (DTA). In the liquid quenched condition large angle diffraction data (both x-ray and neutron) show the broad banded structure typical of the amorphous state. The SANS data, however, exhibit highly anisotropic patterns arising from the phase decomposition during solidification. Ribbons annealed below the glass transition temperature (Tg ) produced neutron diffraction patterns of materials with the same amorphous structure combined with a new short range order; and the SANS patterns retained the asymmetry of the as-quenched material. Ribbons annealed above the crystallization temperature (Tc) show both isotropic and anisotropic contributions to the SANS patterns. Formation of the equilibrium TiCu phase occurs directly from the metallic glass at Tc. The equilibrium Ti3Cu4 phase, however, forms from the TiCu phase at slightly higher temperatures.

scholarly journals Facile Synthesis of Amorphous C3N4ZnxOy (x, y = 0.32–1.10) with High Photocatalytic Efficiency for Antibiotic Degradation

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 514
Author(s):  
Ran Zhang ◽  
Jing Xian Dong ◽  
Guo Liang Gao ◽  
Xue Lu Wang ◽  
Ye-Feng Yao
Keyword(s):  
Noble Metal ◽  
Amorphous Materials ◽  
High Efficiency ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Photocatalytic Efficiency ◽  
Metal Free ◽  
Synthetic Strategy ◽  
Photocatalytic Reactions ◽  
Antibiotic Degradation

The development of novel, noble metal-free semiconductor catalysts with high efficiency is of great importance for the degradation of organic compounds. Among them, amorphous materials have been extensively studied for their unique and commercially useful properties. Here, a completely amorphous, noble metal-free photocatalyst C3N4ZnxOy (x, y = 0.32–1.10) was successfully synthesized from urea and ZnO by a simple high-temperature polymerization method. As the Zn content increased, the short-range ordered structures of the amorphous samples were still retained, as revealed by XPS, FTIR, and ssNMR. Meanwhile, the -CN3 structures were observed to be gradually destroyed, which may make the amorphous state more favorable for photocatalytic reactions. Compared with g-C3N4, the amorphous samples showed significantly reduced intensities in the photoluminescence spectra, indicating that the recombination rate of the photo-generated charge carriers was greatly reduced. It was confirmed that the optimized sample (C3N4Zn0.61O0.61) achieved a photocatalytic efficiency of 86.1% in the degradation of tetracycline hydrochloride under visible light irradiation within 1 h. This is about 2 times higher than that of both g-C3N4 and ZnO. This study emphasizes the importance of the amorphous structure in photocatalytic reactions, and this synthetic strategy may provide an effective model for designing other novel catalysts.

Atom Probe Analysis of a Zr-based Bulk Metallic Glass

2021 ◽  
pp. 1-11
Author(s):  
Huma Bilal ◽  
Keita Nomoto ◽  
Bernd Gludovatz ◽  
Jamie J. Kruzic ◽  
Anna V. Ceguerra ◽  
...  
Keyword(s):  
Amorphous Alloys ◽  
Mass Spectra ◽  
Amorphous Materials ◽  
Experimental Parameter ◽  
Atom Probe ◽  
Amorphous Structure ◽  
Systematic Evaluation ◽  
High Yield ◽  
Considerable Uncertainty ◽  
Surrounding Matrix

Zr-based bulk metallic glasses (BMGs) are amorphous alloys that can exhibit excellent mechanical properties, including high yield strength and fracture toughness. These properties are linked to local microstructural heterogeneities. Whether via microscopy-based techniques, synchrotron techniques, or calorimetric approaches, the amorphous structure of BMGs makes the characterisation of the details of these local structural and chemical heterogeneities extremely challenging. Our focus here is on atom probe tomography (APT), where considerable uncertainty remains in terms of how and when to apply this otherwise powerful technique to amorphous materials. This work reports a systematic evaluation of the experimental parameter space. We report results of BMG composition acquired against various APT operating parameters for Zr63.96Cu13.36Ni10.29Al11.04Nb1.25 (at. %). We demonstrate that a customised peak-based ranging approach yields satisfactory compositional accuracy with absolute errors of <1 at. %. Beyond composition, we have discussed the data quality in terms of attributes of the mass spectra: mass resolution, signal-to-thermal tail ratio, and overlapped peak ratio. We also assess the composition of the well-known clustered evaporation effects, common in APT data of BMGs. We conclude that these regions have negligible differences in composition from the surrounding “matrix” or bulk in these alloys.

scholarly journals Effect Of Low-Temperature Annealing On The Properties Of Ni-P Amorphous Alloys Deposited Via Electroless Plating

2015 ◽  
Vol 60 (2) ◽  
pp. 865-869 ◽  
Author(s):  
Guanlin Zhao ◽  
Yong Zou ◽  
Hui Zhang ◽  
Zengda Zou
Keyword(s):  
Low Temperature ◽  
Electroless Plating ◽  
Amorphous Alloys ◽  
Cluster Size ◽  
Amorphous Structure ◽  
X Ray Diffraction ◽  
Atomic Pair Distribution Function ◽  
Low Temperature Annealing ◽  
Atomic Pair ◽  
Diffraction Patterns

AbstractAmorphous Ni-P alloys were prepared via electroless plating and annealing at 200°C at different times to obtain different microstructures. The effects of low-temperature annealing on the properties of amorphous Ni-P alloys were studied. The local atomic structure of the annealed amorphous Ni-P alloys was analyzed by calculating the atomic pair distribution function from their X-ray diffraction patterns. The results indicate that the properties of the annealed amorphous Ni-P alloys are closely related to the order atomic cluster size. However, these annealed Ni-P alloys maintained their amorphous structure at different annealing times. The variation in microhardness is in agreement with the change in cluster size. By contrast, the corrosion resistance of the annealed alloys in 3.5 wt% NaCl solution increases with the decrease in order cluster size.

An investigation into the temperature phase transitions of synthesized lithium titanate materials doped with Al, Co, Ni and Mg by in situ powder X-ray diffraction

2020 ◽  
Vol 35 (4) ◽  
pp. 233-246
Author(s):  
X. van Niekerk ◽  
E. E. Ferg ◽  
C. Gelant ◽  
D. G. Billing
Keyword(s):  
Phase Transitions ◽  
Crystalline Phase ◽  
Room Temperature ◽  
Spinel Phase ◽  
Sol Gel ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Temperature Phase ◽  
Prolonged Heating

Li4Ti5O12 (LTO) and its doped analogues Li4Ti4.95M0.05O12 (M = Al3+, Co3+, Ni2+, and Mg2+) were synthesized and characterized using in situ PXRD to monitor the phase transitions during the sol–gel synthesis of the spinel material. These results are complimented by thermogravimetric analysis, which illustrates the decomposition of the materials synthesized, where the final LTO products are seen to form at approximately 550 °C. The material has an amorphous structure from room temperature, coupled with a crystalline phase which is speculated to be H2Ti2O5·H2O. This crystalline phase disappears at 250 °C, with the material still in the amorphous state. The crystalline LTO phase starts at approximately 550 °C, with anatase co-crystallizing with the spinel phase. Rutile appears at 600 °C and co-crystallizes with the final product at 850 °C, where anatase is no longer seen. The rutile impurity remains present after cooling the material to room temperature, and results indicate that prolonged heating at 850 °C is required to reduce the rutile content. Rietveld refinement of diffraction patterns show that the unit-cell parameter increases with increasing temperature, coupled with a decrease when cooling the sample. The crystallite sizes follow the same trend, with a significant increase above temperatures of 750 °C.

The Influence of Temperature, the Pressure at Room Temperature, the Pressure at High Temperature on Structure and Heterogeneous Dynamics of Casio3 Bulk

2018 ◽  
Vol 7 (3.19) ◽  
pp. 140 ◽  
Author(s):  
Nguyen Trong Dung
Keyword(s):  
Molecular Dynamics ◽  
Boundary Condition ◽  
Distribution Function ◽  
High Temperature ◽  
Radial Distribution Function ◽  
Room Temperature ◽  
Angle Distribution ◽  
Structural Units ◽  
Influence Of Temperature ◽  
Heterogeneous Dynamics

This paper investigates the influence of temperature, the pressure at 300K, the pressure at 2000K on microstructure and heterogeneous dynamics of CaSiO3 bulk by molecular dynamics Born - Mayer, boundary condition. Samples analyzed by a radial distribution function, coordinate number, angle distribution, number of structural units, size, energy, heterogeneous dynamics showed the influence of factors on structure and heterogeneous dynamics of CaSiO3 bulk. In addition, at temperatures, the pressure at 300K and pressure at 2000K lead to Si-Si (Si2), Si-O (SiO), Si-Ca (SiCa), O-O (OO), O-Ca (OCa), Ca-Ca (Ca2), and CaOx, x = 3, 4, 5, 6, 7, 8, 9, 10, 11, 12; SiOy, y=4, 5, 6, significant changes  

Analysis and Interpretation of Diffraction Data from Amorphous Materials

1980 ◽  
Vol 24 ◽  
pp. 63-72
Author(s):  
J. H. Konnert ◽  
P. D'Antonio ◽  
J. Karle
Keyword(s):  
Distribution Function ◽  
Data Collection ◽  
Data Reduction ◽  
Interatomic Distance ◽  
Amorphous Materials ◽  
Structural Information ◽  
Structural Features ◽  
Polycrystalline Materials ◽  
Reduction Procedure ◽  
Diffraction Patterns

Amorphous materials give rise to rather diffuse diffraction patterns. In contrast to diffraction patterns from polycrystalline materials which are characterized by a large number of sharp diffraction rings, patterns from amorphous materials are composed of relatively few broadened features. Such a diffuse pattern, however, contains much structural information in the form of an interatomic distance distribution that may be computed directly from the measured diffraction pattern. This radial distribution function (RDF) provides information concerning bonded distances, the types of atomic groupings and the extent of ordering in the sample. Special care, however, must be taken during the analysis to avoid introducing spurious details into the RDF that may be confused with, or mask real structural features. Such false detail may arise both from data collection and data reduction procedures. The availability of modern computers has greatly facilitated the calculation of accurate RDF's by readily permitting the introduction of physical criteria into the data reduction procedure that must be satisfied by the RDF.

Crystallization of Amorphous Metastable Ceramic PVD-Coatings

1993 ◽  
Vol 321 ◽  
Author(s):  
O. Knotek ◽  
F. Löffler ◽  
L. Wolkers
Keyword(s):  
Amorphous Materials ◽  
Amorphous State ◽  
Amorphous Structure ◽  
Pvd Coatings ◽  
Additional Element ◽  
X Ray ◽  
High Temperature Wear ◽  
Wear Protection ◽  
New Applications ◽  
Thermal Stability Of

ABSTRACTCeramic PVD coatings have got very often an X-ray Amorphous structure. This is regarded for all classes of ceramics like covalent and ionic Materials. These Amorphous materials start to crystallize at temperatures about 800 °C, a quite low temperature for the practical use of such Materials. This prevents the propagation of this materials in applications like high temperature wear protection, oxidation resistivity etc.This paper describes several possible techniques to increase the thermal stability of the Amorphous state of ceramic PVD-coatings like A1203 and SiC up to 1200 °C. The best way is the incoporation of an additional element like nitrogen into the thin filmsl. The change of the mechanical properties of alumina leads to new applications like diffusion barriers.

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