Temperature Dependent Structural Studies of K- and RB- Doped C60

1992 ◽  
Vol 270 ◽  
Author(s):  
Otto Zhou ◽  
Qing Zhu ◽  
Gavin B.M. Vaughan ◽  
John E. Fischer ◽  
Paul A. Heiney ◽  
...  
Keyword(s):  
Room Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Temperature Dependent ◽  
X Ray ◽  
Analysis Techniques ◽  
Temperature Range ◽  
Face Centered ◽  
Thermal Analysis Techniques ◽  
Bcc Phase

ABSTRACTThe temperature dependent structural evolutions of RbxC60 (x = 3, 5, 6) and K4C60 were studied using both in-house andsynchrotron x-ray powder diffraction and thermal analysis techniques over a temperature range of 10K - 673K. The superconducting face centered-cubic (fcc) Rb3C60 and the body centered-tetragonal (bct) M4C60(M = K, Rb) phases are found to be line compounds in this temperature range, while the body centered-cubic (bcc) phase forms a solid solution in which the solubility of vacant M sites increases with temperature. The orientation of the C60 molecules in the K4C60 phase was analyzed. A crystalline fcc Rb1C60 phase is stable only above room temperature.

Rotational Polymorphism of Methyl-Substituted Ammonium Perchlorates

1965 ◽  
Vol 9 ◽  
pp. 170-189 ◽  
Author(s):  
M. Stammler ◽  
R. Bruenner ◽  
W. Schmidt ◽  
D. Orcutt
Keyword(s):  
Phase Transition ◽  
Ammonium Perchlorate ◽  
Room Temperature ◽  
Decomposition Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Techniques ◽  
Cell Dimensions ◽  
Thermal Analysis Techniques ◽  
Space Requirements

AbstractThe thermal transformations which take place in solid methyl-substituted ammonium perchlorates have been studied using high-temperature X-ray diffraction and differential thermal analysis techniques. In the temperature range from 20°C to their decomposition temperature (above 300°C), ammonium perchlorate and tetramethyl ammonium perchlorate undergo only one enantiomorphic phase transition, namely at 240 and 340°C (with decomposition), respectively. This I—II transition is ascribed to the beginning of the free rotation of the ClO4− ions. The rotation of the cations, however, begins below room temperature. If the symmetry of the cation is lowered by having both methyl groups and hydrogens arranged around the nitrogen (as in monomethyl, dimethyl, and trimethyl ammonium perchlorates), there is an additional enantiomorphic phase transition. This I—II transformation is ascribed to the rotation of the cations which have, in the partially substituted ions, two sets of non-equivalent symmetry axes (different moments of inertia). The temperatures of transformation are discussed in terms of the space requirements for rotation. Symmetries and cell dimensions of some modifications were determined.

Epitaxial Growth of fee Fe and Cu Films on Diamond

1993 ◽  
Vol 313 ◽  
Author(s):  
D.P. Pappas ◽  
J.W. Glesener ◽  
V.G. Harris ◽  
J.J. Krebs ◽  
Y.U. Idzerda ◽  
...  
Keyword(s):  
Room Temperature ◽  
High Energy ◽  
Copper Films ◽  
Face Centered Cubic ◽  
Continuous Film ◽  
X Ray ◽  
Cu Films ◽  
Face Centered ◽  
X Ray Absorption ◽  
Oriented Single Crystal

ABSTRACTThe growth of iron and copper films and multilayers on the (100) face of diamond has been achieved and studied by reflection high energy electron diffraction (RHEED), extended x-ray absorption fine structure (EXAFS), ferromagnetic resonance (FMR), and SQUID Magnetometry. RHEED and AES studies show that 2–3 atomic layers (AL) of Fe on C (100) forms a continuous film. The films as deposited at room temperature are disordered, and after a 350° C anneal displays a face-centered cubic structure. Subsequent layers of Cu on this epitaxial Fe film grow as an oriented, single crystal fee film. FMR and SQUID signals have been observed from the Fe films, showing that they are ferromagnetic.

scholarly journals The Rolling Texture of Cu3Au

Texture ◽  
1974 ◽  
Vol 1 (3) ◽  
pp. 143-150 ◽  
Author(s):  
R. A. Vandermeer ◽  
J. C. Ogle
Keyword(s):  
Room Temperature ◽  
Pure Copper ◽  
Rolling Texture ◽  
Wire Drawing ◽  
Face Centered Cubic ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partial Dislocations ◽  
Face Centered

The rolling texture of Cu3Au has been investigated by X-ray diffraction. At room temperature, independently of the degree of long-range order, Cu3Au developed a mixed or “hybrid” texture; it consisted of elements of each of the prototype face-centered cubic textures characterized by pure copper and 70/30 brass. However, on rolling at 77 K the alloy in the disordered state was significantly more “brass-like” than when it was fully ordered. This result may be explained by a stacking fault energy texture reversal analogous to that observed in wire drawing at low SFE. The lack of twinning (or other deformation mechanism such as slip by partial dislocations) in the ordered alloy could be responsible for this reversal.

scholarly journals Cation Distribution in Natural Chromites from Oman

1996 ◽  
Vol 1 (1) ◽  
pp. 55
Author(s):  
Z. Al-Alawi ◽  
A.M. Gismelseed ◽  
A.A. Yousif ◽  
M.A. Worthing ◽  
H.H. Sutherland ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Atomic Concentration ◽  
X Ray ◽  
Diffraction Patterns ◽  
Face Centered ◽  
Mössbauer Analysis ◽  
Scanning Electron

Two specimens or natural chromite from the Oman ophiolite were studied using Mossbauer Spectroscopy (MS), X-ray Diffraction (XRD). and Scanning Electron Microscopy (SEM). The diffraction patterns obtained at room temperature showed that the two specimens have a face-centered cubic spinal structure. Their Mossbauer spectra at 295 K. 160 K and 78 K have been fitted to three doublets. assigned to two Fe 2+ at the tetrahedral (A1+,A2) sites and one Fe1+ at the octahedral (B) site. The ferrous-ferric ratio obtained from the Mossbauer analysis together with the atomic concentration derived from the microprobe data are used to derive the chemical formulae for the two specimens. The data also supports also supports  a model of ordered caution distribution in the specimens examined.

scholarly journals Structural, Thermal, Optical, Electrical, and Adhesive Characteristics of FePdB Thin Films

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Yuan-Tsung Chen
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Room Temperature ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
Adhesive Properties ◽  
X Ray ◽  
Face Centered ◽  
Xrd Patterns

To study the structural, thermal, electrical, optical, and adhesive properties of magnetic FePdB thin films, 25–200-Å-thick Fe40Pd40B20and Fe60Pd20B20films were deposited on a glass substrate by direct current (DC) magnetron sputtering at room temperature (RT). X-ray diffraction (XRD) patterns indicated that the 25–75-Å-thick Fe40Pd40B20and Fe60Pd20B20films were amorphous, whereas the 100–200-Å-thick Fe40Pd40B20and Fe60Pd20B20films were crystalline, with a face-centered cubic (FCC) FePd (111) textured structure. The activation energy of the Fe40Pd40B20and Fe60Pd20B20thin films decreased as thickness was increased. The 25-Å-thick Fe40Pd40B20film exhibited the highest resistivity, whereas the 200-Å-thick Fe60Pd20B20film exhibited the lowest resistivity. Increasing the thickness and crystallization reduced transmission. The Fe40Pd40B20thin films exhibited higher surface energy and stronger adhesion than did Fe60Pd20B20thin films.

A compact, transportable, thermoelectrically cooled cold stage for reflection geometry X-ray powder diffraction

2012 ◽  
Vol 45 (3) ◽  
pp. 608-610 ◽  
Author(s):  
Ian G. Wood ◽  
N. J. Hughes ◽  
F. Browning ◽  
A. D. Fortes
Keyword(s):  
Low Temperature ◽  
Powder Diffraction ◽  
Room Temperature ◽  
The Body ◽  
Base Temperature ◽  
Thermoelectric Cooling ◽  
X Ray ◽  
Temperature Range ◽  
Cold Stage ◽  
Reflection Geometry

A cold stage for Bragg–Brentano geometry X-ray powder diffraction is described for use in the temperature range from about 250 to 300 K. The stage is constructed in such a way that it may be removed from the diffractometer and pre-cooled to its base temperature before the sample is loaded. After loading, thermoelectric cooling maintains the specimen at low temperature (ice free) whilst the body of the stage is allowed to return to room temperature prior to remounting on the diffractometer.

scholarly journals Microstructure, Texture, and Strength Development during High-Pressure Torsion of CrMnFeCoNi High-Entropy Alloy

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 336 ◽  
Author(s):  
Werner Skrotzki ◽  
Aurimas Pukenas ◽  
Eva Odor ◽  
Bertalan Joni ◽  
Tamas Ungar ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Strength Development ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
X Ray ◽  
High Entropy ◽  
Face Centered

The equiatomic face-centered cubic high-entropy alloy CrMnFeCoNi was severely deformed at room and liquid nitrogen temperature by high-pressure torsion up to shear strains of about 170. Its microstructure was analyzed by X-ray line profile analysis and transmission electron microscopy and its texture by X-ray microdiffraction. Microhardness measurements, after severe plastic deformation, were done at room temperature. It is shown that at a shear strain of about 20, a steady state grain size of 24 nm, and a dislocation density of the order of 1016 m−2 is reached. The dislocations are mainly screw-type with low dipole character. Mechanical twinning at room temperature is replaced by a martensitic phase transformation at 77 K. The texture developed at room temperature is typical for sheared face-centered cubic nanocrystalline metals, but it is extremely weak and becomes almost random after high-pressure torsion at 77 K. The strength of the nanocrystalline material produced by high-pressure torsion at 77 K is lower than that produced at room temperature. The results are discussed in terms of different mechanisms of deformation, including dislocation generation and propagation, twinning, grain boundary sliding, and phase transformation.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

Electron diffraction detection of ordliking in annealed PbTe thin film

1990 ◽  
Vol 48 (4) ◽  
pp. 1018-1019
Author(s):  
Karimat El-Sayed
Keyword(s):  
Thin Film ◽  
Electron Diffraction ◽  
Lead Telluride ◽  
Structural Basis ◽  
Face Centered Cubic ◽  
X Ray ◽  
Polycrystalline Thin Films ◽  
Stage Process ◽  
Diffraction Patterns ◽  
Face Centered

Lead telluride is an important semiconductor of many applications. Many Investigators showed that there are anamolous descripancies in most of the electrophysical properties of PbTe polycrystalline thin films on annealing. X-Ray and electron diffraction studies are being undertaken in the present work in order to explain the cause of this anamolous behaviour.Figures 1-3 show the electron diffraction of the unheated, heated in air at 100°C and heated in air at 250°C respectively of a 300°A polycrystalline PbTe thin film. It can be seen that Fig. 1 is a typical [100] projection of a face centered cubic with unmixed (hkl) indices. Fig. 2 shows the appearance of faint superlattice reflections having mixed (hkl) indices. Fig. 3 shows the disappearance of thf superlattice reflections and the appearance of polycrystalline PbO phase superimposed on the [l00] PbTe diffraction patterns. The mechanism of this three stage process can be explained on structural basis as follows :

Sign in / Sign up

Export Citation Format

Share Document