Modulated Structures in Ion Implanted Al-Fe System

1983 ◽  
Vol 27 ◽  
Author(s):  
K.V. Jata ◽  
D. Janoff ◽  
E.A. Starke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Purity ◽  
Annealing Treatment ◽  
Modulated Structure ◽  
Transmission Electron ◽  
Modulated Structures ◽  
Ion Energies ◽  
High Purity Aluminum ◽  
Al Matrix

ABSTRACTThe results of transmission electron microscopy studies of iron implantation into high purity aluminum foils are described. For both 50 and 100 + 50 keV incident ion energies, modulated structure has been detected in the as-implanted foils. Upon annealing at 793 K the modulated structure decomposes into the Al matrix and Al3Fe precipitates for the 50 keV implantation. A similar annealing treatment for the 100 + 50 keV implantation indicates that the modulated structure is more stable, although some Fe3Al precipitation occurs.

Transmission Electron Microscopy study of Bi-based superconducting phases

1990 ◽  
Vol 48 (4) ◽  
pp. 50-51
Author(s):  
J.G. Wen ◽  
K.K. Fung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Space Groups ◽  
Superconducting Phases ◽  
Ceramic Samples ◽  
Transmission Electron ◽  
Modulated Structures

Bi-based superconducting phases have been found to be members of a structural series represented by Bi2Sr2Can−1Cun−1On+4, n=1,2,3, and are referred to as 2201, 2212, 2223 phases. All these phases are incommensurate modulated structures. The super space groups are P2/b, NBbmb 2201, 2212 phases respectively. Pb-doped ceramic samples and single crystals and Y-doped single crystals have been studied by transmission electron microscopy.Modulated structures of all Bi-based superconducting phases are in b-c plane, therefore, it is the best way to determine modulated structure and c parameter in diffraction pattern. FIG. 1,2,3 show diffraction patterns of three kinds of modulations in Pb-doped ceramic samples. Energy dispersive X-ray analysis (EDAX) confirms the presence of Pb in the three modulated structures. Parameters c are 3 0.06, 38.29, 30.24Å, ie 2212, 2223, 2212 phases for FIG. 1,2,3 respectively. Their average space groups are all Bbmb.

scholarly journals Modulated Structure in Al65Cu20Fe15−XMnX Alloys, Studied by Transmission Electron Microscopy

1996 ◽  
Vol 37 (5) ◽  
pp. 1214-1218
Author(s):  
Chikai Sato ◽  
Tomoyuki Yokota ◽  
Katsuhiko Sato ◽  
Yasumasa Koyama
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Modulated Structure ◽  
Transmission Electron

scholarly journals Thickening of T1 Precipitates during Aging of a High Purity Al–4Cu–1Li–0.25Mn Alloy

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 30 ◽  
Author(s):  
Ines Häusler ◽  
Reza Kamachali ◽  
Walid Hetaba ◽  
Birgit Skrotzki
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Purity ◽  
External Load ◽  
Volume Fraction ◽  
Single Layer ◽  
Age Hardening ◽  
Defect Type ◽  
Transmission Electron

The age hardening response of a high-purity Al–4Cu–1Li–0.25Mn alloy (wt. %) during isothermal aging without and with an applied external load was investigated. Plate shaped nanometer size T1 (Al2CuLi) and θ′ (Al2Cu) hardening phases were formed. The precipitates were analyzed with respect to the development of their structure, size, number density, volume fraction and associated transformation strains by conducting transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) studies in combination with geometrical phase analysis (GPA). Special attention was paid to the thickening of T1 phase. Two elementary types of single-layer T1 precipitate, one with a Li-rich (Type 1) and another with an Al-rich (Defect Type 1) central layer, were identified. The results show that the Defect Type 1 structure can act as a precursor for the Type 1 structure. The thickening of T1 precipitates occurs by alternative stacking of these two elementary structures. The thickening mechanism was analyzed based on the magnitude of strain associated with the precipitation transformation normal to its habit plane. Long-term aging and aging under load resulted in thicker and structurally defected T1 precipitates. Several types of defected precipitates were characterized and discussed. For θ′ precipitates, a ledge mechanism of thickening was observed. Compared to the normal aging, an external load applied to the peak aged state leads to small variations in the average sizes and volume fractions of the precipitates.

scholarly journals The origin of striation in the metastable β phase of titanium alloys observed by transmission electron microscopy

2017 ◽  
Vol 50 (3) ◽  
pp. 795-804 ◽  
Author(s):  
Jiangkun Fan ◽  
Jinshan Li ◽  
Yudong Zhang ◽  
Hongchao Kou ◽  
Jaafar Ghanbaja ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dark Field ◽  
Atomic Scale ◽  
Intermediate Structure ◽  
Atomic Displacements ◽  
Β Phase ◽  
Transmission Electron ◽  
Modulated Structures ◽  
High Resolution Tem

For the β phase of Ti-5553-type metastable β-Ti alloys, striations in transmission electron microscopy (TEM) bright- and dark-field images have been frequently observed but their origin has not been sufficiently investigated. In the present work, this phenomenon is studied in depth from the macroscopic scale by neutron diffraction to the atomic scale by high-resolution TEM. The results reveal that the β phase contains homogeneously distributed modulated structures, intermediate between that of the β phase (cubic) and that of the α phase or the ω phase (hexagonal), giving rise to the appearance of additional diffraction spots at 1/2, 1/3 and 2/3 β diffraction positions. The intermediate structure between β and α is formed by the atomic displacements on each second {110}βplane in the \langle 1{\overline 1}0\rangle_{\beta} direction, whereas that between β and ω is formed by atomic displacements on each second and third {112}βplane in the opposite \langle 11{\overline 1}\rangle_{\beta } direction. Because of these atomic displacements, the {110}βand {112}βplanes become faulted, resulting in the streaking of β diffraction spots and the formation of extinction fringes in TEM bright- and dark-field images, the commonly observed striations. The present work reveals the origin of the striations and the intrinsic correlation with the additional electron reflections of the β phase.

Study of modulated structures by transmission electron microscopy

1985 ◽  
Vol 18 (1-4) ◽  
pp. 97-110 ◽  
Author(s):  
J.W. Steeds ◽  
D.M. Bird ◽  
D.J. Eaglesham ◽  
S. McKernan ◽  
R. Vincent ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Modulated Structures

Characterization of the Ni/NiO, Interface Region in Oxidized High Purity Nickel by Transmission Electron Microscopy

1985 ◽  
Vol 48 ◽  
Author(s):  
Howard T. Sawhill ◽  
Linn W. Hobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Purity ◽  
Structure Factor ◽  
Dihedral Angles ◽  
Interfacial Energies ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Interface Structures

ABSTRACTNi/NiO interface structures were investigated using TEM, and the observed structures were compared with current heterophase interface models. Relative magnitudes of Ni/NiO interfacial energies were obtained from measurements of dihedral angles at triple grain junctions between Ni and NiO grains. Extra reflections in diffraction patterns from oxide grains adjacent to the Ni/NiO interface were compared with kinematical structure factor calculations for several proposed structures.

Microstructure and dielectric properties of Ba(Cd1/3Ta2/3)O3 microwave ceramics synthesized with a boron oxide sintering aid

2004 ◽  
Vol 19 (12) ◽  
pp. 3526-3533 ◽  
Author(s):  
Shaojun Liu ◽  
Jian Sun ◽  
Richard Taylor ◽  
David J. Smith ◽  
N. Newman
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Treatment ◽  
Hexagonal Structure ◽  
Microwave Properties ◽  
Microwave Ceramics ◽  
Sintering Aid ◽  
Boron Doped ◽  
Transmission Electron ◽  
Liquid Sintering

The use of boron as a sintering aid reduces the sintering temperature, enhances the sintering density, and improves the microwave properties of Ba(Cd1/3Ta2/3)O3 ceramic dielectrics. Observations by transmission electron microscopy indicate that the liquid sintering mechanism contributes to the improvement in sintering density for boron concentrations exceeding 0.5 wt%. The introduction of as small as 0.01% boron also results in the production of high-density samples (∼95%), presumably indicating that a point defect mechanism may also play an important role in the sintering process. X-ray diffraction data combined with high-resolution transmission electron microscopy images show that boron-doped Ba(Cd1/3Ta2/3)O3 ceramic material has a well-ordered hexagonal structure. Annealing treatment is found to improve the microwave properties. The best sample has a dielectric constant of 32, a temperature coefficient of resonant frequency of 80 ± 15 ppm/°C, and a quality factor of >25,000 at 2 GHz.

scholarly journals Unravelling the characteristics of Al-alloy corrosion at the atomic to nanometre scale by transmission electron microscopy

2020 ◽  
Vol 326 ◽  
pp. 01007
Author(s):  
Shravan K. Kairy ◽  
Nick Birbilis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Al Alloy ◽  
Second Phase ◽  
Clear Understanding ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Al Matrix

The localised corrosion associated with Mg2Si in the Al-matrix of an Al-Mg-Si alloy was studied in 0.1 M NaCl at pH 6 by quasi in-situ transmission electron microscopy. Herein, physical imaging of corrosion at the atomic to nanometre scale was performed. Phase transformation and subsequent chemical composition variations associated with the localised corrosion of Mg2Si were studied. It was observed that corrosion initiated upon Mg2Si, often preferentially at the interface with the Al-matrix, and propagated until Mg2Si was completely dealloyed by Mg-dissolution, resulting in an amorphous SiO-rich phase remnant. The SiO-rich remnant became electrochemically inert and did not initiate corrosion in the Al-matrix. This study provides a clear understanding on the localised corrosion of Al-alloys associated with Mg2Si. In addition, the methodology followed in this study can also be applied to understand the role of precipitates and second phase particles in the localised corrosion of Al-alloy systems.

Evaporated Titanium Films on Rocksalt

1967 ◽  
Vol 25 ◽  
pp. 296-297
Author(s):  
Frank E. Wawner ◽  
Kenneth R. Lawless
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Single Crystal ◽  
High Purity ◽  
Early Stages ◽  
Transmission Electron ◽  
Single Crystal Films ◽  
Crystal Films ◽  
Purity Titanium

Thin single crystal films of high purity titanium were needed in our laboratory for investigations of the early stages of the oxidation of titanium. Experiments were carried out to determine the feasibility of preparing single crystal titanium films of different orientations by evaporation onto the (100), (110) and (111) surfaces of rocksalt. The structures of these films were investigated by transmission electron microscopy and electron diffraction.

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