Do 8 nm Co Nanocrystals in Long-Range-Ordered Face-Centered Cubic (fcc) Supracrystals Show Superspin Glass Behavior?

2010 ◽  
Vol 1 (7) ◽  
pp. 1139-1142 ◽  
Author(s):  
Dinah Parker ◽  
Isabelle Lisiecki ◽  
M. P. Pileni
Keyword(s):  
Long Range ◽  
Face Centered Cubic ◽  
Face Centered ◽  
Superspin Glass ◽  
Glass Behavior

Microstructure of aged Ni-Mo (Ni/Mo = 4) alloys containing Al

1996 ◽  
Vol 54 ◽  
pp. 1010-1011
Author(s):  
Elaine Shen ◽  
Charlie R. Brooks ◽  
E. A. Kenikt
Keyword(s):  
Solid Solution ◽  
Long Range ◽  
Short Range ◽  
Argon Atmosphere ◽  
Tetragonal Structure ◽  
Face Centered Cubic ◽  
Commercial Alloy ◽  
Arc Melting ◽  
Face Centered

Ni-rich Ni-Mo alloys containing around 20 at. % Mo exist as a face-centered cubic, short-range ordered (SRO), solid solution (α) above around 868 °C, and transform to a long-range ordered (LRO), body-centered tetragonal structure (β) upon cooling slowly to below this temperature. Upon quenching, the α is retained, which can then be converted to β upon aging below 868 °C. The formation of the β structure induces considerable strengthening (e.g.. the hardness doubles), but is accompanied by embrittlement.A commercial alloy based on this composition is Hastelloy B2, and precautions are exercised in its use to prevent ordering and hence embrittlement. In a continuing effort to develop Ni-Mo alloys strengthened by ordering but with usable toughness, we have been examining the addition of Al to the base Ni-25 at. % Mo composition. Specimens containing 2. 5, 7 and 9 at. % Al, with Ni/Mo = 4.0, were made by arc melting the appropriate amounts of a Hastelloy B2 alloy and Al. The buttons were melted several times under an argon atmosphere.

scholarly journals Diffraction Symmetry in Crystalline, Close-Packed C60

1990 ◽  
Vol 206 ◽  
Author(s):  
R. M. Fleming ◽  
T. Siegrist ◽  
P. M. Marsh ◽  
B. Hessen ◽  
A. R. Kortan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Long Range ◽  
Three Dimensional ◽  
Spherical Shape ◽  
Unit Cell ◽  
Face Centered Cubic ◽  
Long Range Order ◽  
Carbon Structure ◽  
Soccer Ball ◽  
Face Centered

ABSTRACTWe have grown crystals of the carbon structure C60 by sublimation. In contrast to solution-grown crystals, the sublimed crystals have long range order with no evidence of solvent inclusions. Sublimed C60 forms three dimensional, faceted crystals with a close-packed, face-centered cubic unit cell. We have refined a crystal structure using the “soccer ball” model of the C60 molecule. The results indicate that the C60 molecule has the expected spherical shape, however the data are not sufficiently accurate to unambiguously determine atomic positions.

Anti-Twinning in an Ni-Mo-Cr Alloy

2013 ◽  
Vol 203-204 ◽  
pp. 254-257
Author(s):  
Mirosław Wróbel ◽  
Elżbieta Stępniowska ◽  
Stanisław Dymek
Keyword(s):  
Long Range ◽  
The Body ◽  
Type I ◽  
Face Centered Cubic ◽  
The Matrix ◽  
The Face ◽  
Face Centered ◽  
Long Range Ordering ◽  
Mechanical Twins ◽  
Crystallographic Orientations

Two morphological types of mechanical twins occur in the microstructure of cold rolled Ni-Mo-Cr alloy: long – passing over whole grains and micro-twins – confined to individual long range ordered domains. Long mechanical twins were only formed in the disordered alloy. Such twins are typical for metals with the face centered cubic structure with relatively low stacking fault energy. They do not form in the grains with twinning prohibited crystallographic orientations, e.g. {110}. Both types of twins were found in an alloy subjected to prolong annealing at 650 °C. The annealing induces long range ordering reaction leading to the formation of ordered domains with the body centered orthorombic crystal structure (oI8). The twins were of type I, type II, compound twins or pseudo-twins, depending on the crystallographic orientation of the ordered phase in relation to the matrix. It was found that twins of such types were formed even in grains with the {110} orientation and result from the anti-twinning deformation. However, in this orientation they were confined to ordered domains rather than developed into the long form crossing entire grains. On the other hand, the long twins of various types were formed in grains with other twinning favoring crystallographic orientations.

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.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

Microstructure of Electro-Eroded Cemented Carbide Surfaces

1968 ◽  
Vol 26 ◽  
pp. 284-285
Author(s):  
V. N. Filimonenko ◽  
M. H. Richman ◽  
J. Gurland
Keyword(s):  
Surface Layer ◽  
Cobalt Content ◽  
Cemented Carbides ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Standard Procedures ◽  
Face Centered ◽  
Diamond Paste ◽  
Plastic Carbon

The high temperatures and pressures that are found in a spark gap during electrical discharging lead to a sharp phase transition and structural transformation in the surface layer of cemented carbides containing WC and cobalt. By means of X-ray diffraction both W2C and a high-temperature monocarbide of tungsten (face-centered cubic) were detected after electro-erosion. The W2C forms as a result of the peritectic reaction, WC → W2C+C. The existence and amount of the phases depend on both the energy of the electro-spark discharge and the cobalt content. In the case of a low-energy discharge (i.e. C=0.01μF, V = 300v), WC(f.c.c.) is generally formed in the surface layer. However, at high energies, (e.g. C=30μF, V = 300v), W2C is formed at the surface in preference to the monocarbide. The phase transformations in the surface layer are retarded by the presence of larger percentages of cobalt.Metallographic examination of the electro-eroded surfaces of cemented carbides was carried out on samples with 5-30% cobalt content. The specimens were first metallographically polished using diamond paste and standard procedures and then subjected to various electrical discharges on a Servomet spark machining device. The samples were then repolished and etched in a 3% NH4OH electrolyte at -0.5 amp/cm2. Two stage plastic-carbon replicas were then made and shadowed with chromium at 27°.

Faceted antiphase boundaries in GaAs grown on Ge

1987 ◽  
Vol 45 ◽  
pp. 314-315
Author(s):  
N.-H. Cho ◽  
S. McKernan ◽  
C.B. Carter ◽  
K. Wagner
Keyword(s):  
Cross Section ◽  
Atomic Resolution ◽  
Face Centered Cubic ◽  
Electrical Behavior ◽  
Sphalerite Structure ◽  
Antiphase Boundaries ◽  
Transmission Electron ◽  
Face Centered ◽  
Quality Material ◽  
Simulated Images

Interest has recently increased in the possibility of growing III-V compounds epitactically on non-polar substrates to produce device quality material. Antiphase boundaries (APBs) may then develop in the GaAs epilayer because it has sphalerite structure (face-centered cubic with a two-atom basis). This planar defect may then influence the electrical behavior of the GaAs epilayer. The orientation of APBs and their propagation into GaAs epilayers have been investigated experimentally using both flat-on and cross-section transmission electron microscope techniques. APBs parallel to (110) plane have been viewed at the atomic resolution and compared to simulated images.Antiphase boundaries were observed in GaAs epilayers grown on (001) Ge substrates. In the image shown in Fig.1, which was obtained from a flat-on sample, the (110) APB planes can be seen end-on; the faceted APB is visible because of the stacking fault-like fringes arising from a lattice translation at this interface.

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 :

NICROFER 5923 HMo-ALLOY 59

Alloy Digest ◽  
1993 ◽  
Vol 42 (5) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Heat Treating ◽  
Face Centered Cubic ◽  
Low Carbon ◽  
High Alloy ◽  
Temperature Performance ◽  
Cubic Structure ◽  
Face Centered

Abstract NICROFER 5923 hMo, often called Alloy 59, was developed with extra low carbon and silicon contents and with a high alloy level of molybdenum to optimize its corrosion resistance. Nicrofer 5923hMo has a face-centered cubic structure. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance as well as forming, heat treating, and joining. Filing Code: Ni-430. Producer or source: VDM Technologies Corporation.

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