Strengthening Mechanism in Consolidated Amorphous Alloys

1986 ◽  
Vol 80 ◽  
Author(s):  
M. A. Otooni
Keyword(s):  
Amorphous Alloys ◽  
High Resolution Electron Microscopy ◽  
Strengthening Mechanism ◽  
Nucleation And Growth ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Resolution Electron ◽  
Major Factors ◽  
Microstructural Examination

AbstractSeveral samples of consolidated amorphous alloys have been studied by using High Resolution Electron Microscopy (HREM), Differential Scanning Calorimetry (DSC), Microdiffraction (MD), and Energy Dispersive X-Ray Diffraction Analysis (EDXD). The phenomenon of plastic deformation at consolidated particulate interfaces has been examined. Two simultaneous processes have been identified occurring at these boundaries, namely, accelerated nucleation and growth of the deformed zone and the the formation of dislocation microstructures (dislocation networks). It has been observed that both type and the density of microstructures depend on the mode of consolidation. Post consolidation processing, annealing, affects density and the directional distribution of defects in the plastic zone. Microstructural examination of the consolidated mass has revealed two major factors important in the strengthening mechanism: (1) presence of a plastically deformed and pressureinduced nucleated zone; (2) presence of a system of dislocation networks in the compacted particulates. Based on these observations, it has been concluded that the stored strain energies in the plastically deformed zones provides the necessary activation energy for dislocation motions from one particulate to the next. These observations have been employed in developing a quasi-quantative model to explain the strengthening mechanism in consolidated amorphous alloys.

The Composition Effect on the Nanocrystallization of Finemet Amorphous Alloys

1996 ◽  
Vol 457 ◽  
Author(s):  
J. Zhu ◽  
T. Pradell ◽  
N. Clavaguera ◽  
M. T. Clavaguera-Mora
Keyword(s):  
Amorphous Alloys ◽  
Nucleation And Growth ◽  
Secondary Crystallization ◽  
Composition Effect ◽  
Phase Precipitation ◽  
X Ray Diffraction ◽  
Initial Composition ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Diffusion Controlled

ABSTRACTDifferential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Neutron Diffraction (ND) and Mössbauer Spectroscopy (MS) were used to study the nanocrystallization process of Fe73.5Cu1Nb3Si22.5–xBx (x=5, 7, 8, 9 and 12) amorphous alloys. Both the temperature range and the activation energy of Fe(Si) phase precipitation from the amorphous martrix increase with the initial B composition. The initial Si composition influences the mechanism of the nanocrystallization: for the Si rich samples, the beginning of nucleation and growth processes is interface controlled, for the B rich samples it is diffusion controlled. Secondary crystallization from the remaining amorphous is mainly Fe3B and Fe2B, the ratio of Fe3B/Fe2B being dependent on the initial composition too.

Kinetic Study on the Formation of the Aragonite-Like Phase Ba(CuOx)1-Y(CO3)y

1995 ◽  
Vol 398 ◽  
Author(s):  
A. Tomasi ◽  
E. Galvanetto ◽  
F.C. Matacotta ◽  
P. Nozar ◽  
P. Scardi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Analysis ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
Formation Kinetics ◽  
Resolution Electron ◽  
Thermal Analysis Techniques ◽  
Kinetics Of

ABSTRACTA systematic study on phase formation and stabilisation in the Ba-Cu-C-O system in the temperature range 20-500°C, under various atmospheres, by traditional thermal analysis techniques, high temperature X-ray diffraction and high resolution electron microscopy, has permitted to identify and characterise the formation kinetics of a new copper containing phase isomorphic to γ-BaCO3.

A structural model for charoite

2009 ◽  
Vol 73 (5) ◽  
pp. 883-890 ◽  
Author(s):  
I. V. Rozhdestvenskaya ◽  
T. Kogure ◽  
E. Abe ◽  
V. A. Drits
Keyword(s):  
Structural Model ◽  
High Resolution Electron Microscopy ◽  
Tubular Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Xrd Patterns ◽  
Silicon Oxygen ◽  
Monoclinic Cell

AbstractThe crystal structure of charoite was investigated mainly by using selected-area electron diffraction (SAED), X-ray diffraction (XRD) and high-resolution electron microscopy (HREM). SAED and XRD patterns indicate that the structure has a monoclinic cell: a = 32.296, b = 19.651, c = 7.16 Å, β = 96.3° and V = 4517 Å3. The space group inferred from systematic absences and HREM images is P21/m. A model of the charoite structure is proposed that is based on the features of related Ca-alkaline silicate structures and HREM images. The structure of charoite consists of three different silicon-oxygen radicals (polymerized SiO4 tetrahedra) which are located between Ca polyhedra. Two of these radicals form continuous tubular structures comprising pectolite-like tetrahedral chains. Calcium polyhedra are joined to form blocks, each of which consists of four columns sharing edges and apices. Potassium and H2O molecules are probably located inside the tubular silicate radicals. From these results, a general formula is derived: K6-7(Ca,Na)18[(Si6O17)(Si12O30)(Si18O45)](OH,F)2.nH2O with two formula units in the unit cell (Z = 2).

Elastic and nanostructural properties of Cu/Pd superlattices

1992 ◽  
Vol 7 (6) ◽  
pp. 1356-1369 ◽  
Author(s):  
B.M. Davis ◽  
D.X. Li ◽  
D.N. Seidman ◽  
J.B. Ketterson ◽  
R. Bhadra ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Brillouin Scattering ◽  
High Resolution Electron Microscopy ◽  
Anomalous Behavior ◽  
Electron Beam Evaporation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Composition Modulation ◽  
Tension Tests ◽  
Resolution Electron

A series of Cu/Pd superlattices with composition modulation wavelengths (Λ's) ranging from 1.6 to 3.5 nm and a strong [111] growth texture were prepared by electron beam evaporation. The elastic properties of the films were examined using the methods of uniaxial tension tests [a Young's modulus (1/s11), where sij is an elastic compliance] with the applied load parallel to the plane of the Cu/Pd interface and Brillouin scattering [a shear modulus (1/s44) with the shear waves parallel to the plane of the Cu/Pd interface]. Also, the films were characterized using both x-ray diffraction and high-resolution electron microscopy; this was done to assess the effect of the nanostructure on a possible “supermodulus effect.” The films are nanostructurally very similar to the superlattice films employed in previous studies at Northwestern in which a supermodulus effect was reported. But, contrary to previous studies, no anomalous behavior was observed for the measured elastic properties of the thin films. Therefore the present results negate the earlier results and cast a serious doubt on the existence of a supermodulus effect.

Electron optical studies of the formation of vanadium pentoxide catalyst

1987 ◽  
Vol 45 ◽  
pp. 354-355
Author(s):  
A. Legrouri
Keyword(s):  
Electron Microscopy ◽  
Vanadium Pentoxide ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
Optical Studies ◽  
X Ray ◽  
Physicochemical Changes ◽  
Structural Correlation ◽  
Resolution Electron ◽  
Xrd Techniques

The oxides of vanadium, especially vanadium pentoxide, have been extensively studied because of their interesting physical properties particularly in catalysis. Vanadium pentoxide is generally used in the oxidation and ammoxidation of hydrocarbons.This catalyst has been prepared via the thermal decomposition of ammonium metavanadate (AMV) in air. Thermogravimetric analysis (TGA), infrared spectroscopy (IRS) and x-ray diffraction (XRD) techniques together with high resolution electron microscopy (HREM) and scanning electron microscopy (SEM) have enabled us to elucidate the physicochemical changes occurring during the decomposition process.According to TGA results, the decomposition of AMV commences at 150°C and is complete by 320°C leading to vanadium pentoxide by loss of ammonia and water with the formation of two intermediate compounds, namely at 190°C, ammonium bivanadate: (NH4)2V4 O11, and at 230°C, ammonium hexavanadate AHV: (NH4)2V6O16 . Samples for structural correlation studies were prepared by heating AMV in a stream of air for 2 hours at selected temperatures of 140, 190, 230, 320 and 400°C.

High Resolution Electron Microscopy of a Novel Zeolite

1997 ◽  
Vol 3 (S2) ◽  
pp. 441-442
Author(s):  
P.A. Crozier ◽  
I.Y. Chan ◽  
C.Y. Chen ◽  
L.W. Finger ◽  
R.C. Medrud ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Low Dose ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
High Adsorption ◽  
Structural Units ◽  
X Ray ◽  
Resolution Electron ◽  
Crystal Structural

Low-dose high resolution electron microscopy (HREM) is a useful technique for elucidating the structure of zeolites. In recent years a number of zeolite structures have been solved using combinations of different characterization techniques including adsorption measurements, powder x-ray diffraction and low-dose high resolution electron microscopy (for example see ref. 2). We have used these techniques to study the structure of a novel zeolite material. However, great care must be exercised when interpreting data from these techniques in terms of crystal structural units. In this particular case, the structure was recently determined using single crystal x-ray diffraction and showed some surprises.Details of the synthesis of this zeolite are given elsewhere. The high adsorption capacity suggested that this zeolite possessed two interpenetrating channels (either a 10 and a 12 ring or two 12 ring channels). X-ray powder diffraction showed the material to be monoclinic with a= 18.5Å, b= 13.4 Å, c= 7.6 Å β = 101.5°).

Sign in / Sign up

Export Citation Format

Share Document