The Disorder-Order Transformation in Ni4Mo

1971 ◽  
Vol 15 ◽  
pp. 319-329 ◽  
Author(s):  
Fu-Wen Ling ◽  
E. A. Starke
Keyword(s):  
Order Parameter ◽  
Domain Size ◽  
Antiphase Domain ◽  
Domain Growth ◽  
Range Order Parameter ◽  
Line Broadening ◽  
Kcal Mole ◽  
X Ray ◽  
Isothermal Ageing ◽  
Internal Strains

The progressive ordering of a single crystal of Ni4Mo by isothermal ageing at 650°C (transformation temperature = 868°C) has been studied by x-ray line broadening techniques using the Warren- Averbach method employing computer techniques. The long-range-order parameter, antiphase domain size, and internal strains were measured as a function of ordering time and compared with those previously obtained at 700°C. The activation energies for domain growth and ordering were found to be 91 kcal/mole and 44.5 kcal/mole respectively. The rms strain developed during ordering was found to be dependent on the degree of tetragonality of the structure.

Antiphase Boundaries in Ordered Ni3FE Crystals

1969 ◽  
Vol 27 ◽  
pp. 62-63
Author(s):  
Y. H. Liu
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardening Mechanism ◽  
Superlattice Structure ◽  
Disordered Phase ◽  
Domain Boundaries ◽  
Atomic Scattering ◽  
The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

The Effect of Growth Temperature and Substrate Misorientation on Degree of Order and Antiphase Domain Size in Ga0.52In0.48P Epilayers Grown on GaAs (001) Substrates by Gs-Mbe

1998 ◽  
Vol 523 ◽  
Author(s):  
C. Meenakarn ◽  
A. E. Staton-bevan ◽  
S. P. Najda ◽  
G. Duggan ◽  
A. H. Kean
Keyword(s):  
Band Gap ◽  
Long Range ◽  
Growth Temperature ◽  
Order Parameter ◽  
Plate Thickness ◽  
Antiphase Domain ◽  
Range Order ◽  
Range Order Parameter ◽  
Long Range Order ◽  
Gaas Substrates

AbstractA Transmission Electron Microscopy (TEM), Photoluminescence (PL) and Photoluminescence Excitation Spectroscopy (PLE) investigation has been conducted on Ga0.52In0.48P epilayers grown on (001) GaAs substrates by Gas-Source Molecular Beam Epitaxy.For Ga0.52In0.48P epilayers grown on exact (001) GaAs substrates, increasing the growth temperature from 480°C to 535°C increased the antiphase domain plate thickness, t, from 7.3±0.4 to 17.4±0.9 Å, and decreased the long range order parameter, n, from 0.32 to 0.18±0.1. For epilayers grown at 530°C, on GaAs(001) substrates off-cut 0°, 7°, 10° and 15° towards [111]A, increasing the substrate misorientation from 0° to 15° decreased the antiphase domain plate thickness, from 12.3±0.6 to 6.0±0.3 Å. The long range order parameter also decreased from 0.19 to 0.10±0.01.The band gap energies of these samples, grown by GS-MBE, were close to those reported for fully disordered Ga0.52In0.48P epilayers grown by MOCVD at ∼760°C. This shows that GSMBE is also a good technique to grow GaInP for high band gap optical data storage applications and at lower growth temperatures. The optimum growth conditions in this study were at a growth temperature of 530°C on (001) GaAs substrate with 15° off-cut towards [111]A.

The investigation of the microstructure and mechanical properties of ordered alominide-iron (boron) nanostructures produced by mechanical alloying and sintering

2012 ◽  
Vol 05 ◽  
pp. 488-495 ◽  
Author(s):  
S. Izadi ◽  
Gh. Akbari ◽  
K. Janghorban ◽  
M. Ghaffari
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Order Parameter ◽  
Fracture Strain ◽  
Sintering Temperature ◽  
Range Order Parameter ◽  
Long Range Order ◽  
X Ray Diffraction ◽  
X Ray ◽  
Boron Nanostructures

In this study, mechanical alloying (MA) of Fe -50 Al , Fe -49.5 Al -1 B , and Fe -47.5 Al -5 B (at.%) alloy powders and mechanical properties of sintered products of the as-milled powders were investigated. X-ray diffraction (XRD) results showed the addition of B caused more crystallite refinement compared to the B -free powders. To consider the sintering and ordering behaviors of the parts produced from cold compaction of the powders milled for 80 h, sintering was conducted at various temperatures. It was found that the sintering temperature has no meaningful effect on the long-range order parameter. The transformation of the disordered solid solution developed by MA to ordered Fe - Al - ( B ) intermetallics was a consequence of sintering. Also, the nano-scale structure of the samples was retained even after sintering. The microhardness of pore-free zones of the nanostructured specimens decreased by increasing the sintering temperature. Moreover, the sintering temperature has no effect on the compressive yield stress. However, the fracture strain increased by increasing the sintering temperature. The samples containing 1 at.% B showed more strain to fracture compared with the B -free and 5 at.% B samples.

Structure of Molten Mn74Si26 and Molten Mn33.5Si66.5 by Neutron Diffraction

1997 ◽  
Vol 52 (8-9) ◽  
pp. 645-649
Author(s):  
B. Sedelmeyer ◽  
P. Lamparter ◽  
S. Steeb
Keyword(s):  
Correlation Function ◽  
Neutron Diffraction ◽  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Pair Correlation ◽  
Range Order Parameter ◽  
Compound Formation ◽  
X Ray ◽  
Coordination Numbers

Abstract Molten Mn74Si26 and molten Mn33.5Si66.5 were investigated by neutron diffraction. The pair correlation function yielded, together with the X-ray results from a former paper, the partial coordination numbers, atomic distances, and the short range order parameter with the result that the atomic distribution in molten Mn33.5Si66.5 is statistical while the structure factor of molten Mn74Si26 , as obtained with neutrons, shows a strong prepeak which means rather strong compound formation.

Nahordnung in binären Schmelzen und Mischkristallen / Short Range Order in Binary Melts and Binary Solid Solubilities

1977 ◽  
Vol 32 (11) ◽  
pp. 1222-1228 ◽  
Author(s):  
Alfred Boos ◽  
Peter Lamparter ◽  
Siegfried Steeb
Keyword(s):  
Solid Solution ◽  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Range Order ◽  
Range Order Parameter ◽  
Refined Model ◽  
Binary Solid Solution ◽  
X Ray ◽  
Angle Scattering

AbstractThe X-Ray or neutron-intensity scattered from binary melts can be described in a similar way as that from a binary solid solution, namely as a sum of three contributions. One of these contributions describes the short range order scattering which consists of small angle scattering for segregated melts and which leads to premaxima for melts containing compound-like agglomerates. A method is shown to reveal the short range order parameter for the so-called simple model of the melts. A second method leads to the evaluation of the concentration of the agglomerates existing in com­ pound-forming melts for the so-called refined model of the melts.

Effects of Antiphase Domain Size and Twin Platelet Width on the Hardness of an Ordered CuAu Alloy

1994 ◽  
Vol 362 ◽  
Author(s):  
Takanobu Shiraishi ◽  
Michio Ohta ◽  
Masaharu Nakagawa
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
Continuous Growth ◽  
X Ray ◽  
Structure Changes ◽  
Transmission Electron ◽  
Three Stages ◽  
Twin Spacing ◽  
Coherency Strains ◽  
Disordered Alloy

AbstractEffects of antiphase domain (APD) size and inter-twin spacing on the hardness of CuAu I-phase in the overaging stage were investigated by hardness testing, transmission electron microscopy, and X-ray powder diffraction. Overaging in CuAu I-phase upon progressive ordering at 300°C was found to proceed through three stages: stages I through III. In the stage I, twinning actively occurred, and most of the coherency strains were removed. Average inter-twin spacing slightly increased. These microstructural evolutions slightly decreased the hardness of the alloy. In the stage II, both APD size and average inter-twin spacing grew larger with time, leading to a continuous decrease in hardness. In the stage III, the APD size markedly grew larger, while the growth rate of average inter-twin spacing markedly slowed down. The continuous growth of APD size apparently contributed to the further decrease in hardness. Although the crystal structure changes during the CuAu I ordering, a perfectly ordered alloy with no planar defects was suggested to be not so strong as the corresponding disordered alloy.

Nondestructive Inspection of Thin, Low-Z Samples using Multiplexed Compton Scatter Tomography

1997 ◽  
Vol 503 ◽  
Author(s):  
B. L. Evans ◽  
J. B. Martin ◽  
L. W. Burggraf
Keyword(s):  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Filtered Backprojection ◽  
Line Broadening ◽  
Compton Scatter ◽  
X Ray ◽  
Tomography System ◽  
Transmission Computed Tomography ◽  
High Purity Germanium ◽  
Scattered Energy

ABSTRACTThe viability of a Compton scattering tomography system for nondestructively inspecting thin, low Z samples for corrosion is examined. This technique differs from conventional x-ray backscatter NDI because it does not rely on narrow collimation of source and detectors to examine small volumes in the sample. Instead, photons of a single energy are backscattered from the sample and their scattered energy spectra are measured at multiple detector locations, and these spectra are then used to reconstruct an image of the object. This multiplexed Compton scatter tomography technique interrogates multiple volume elements simultaneously. Thin samples less than 1 cm thick and made of low Z materials are best imaged with gamma rays at or below 100 keV energy. At this energy, Compton line broadening becomes an important resolution limitation. An analytical model has been developed to simulate the signals collected in a demonstration system consisting of an array of planar high-purity germanium detectors. A technique for deconvolving the effects of Compton broadening and detector energy resolution from signals with additive noise is also presented. A filtered backprojection image reconstruction algorithm with similarities to that used in conventional transmission computed tomography is developed. A simulation of a 360–degree inspection gives distortion-free results. In a simulation of a single-sided inspection, a 5 mm × 5 mm corrosion flaw with 50% density is readily identified in 1-cm thick aluminum phantom when the signal to noise ratio in the data exceeds 28.

Quantification of Starch Order in Physically Modified Rice Flours Using Small-Angle X-ray Scattering (SAXS) and Fourier Transform Infrared (FT-IR) Spectroscopy

2021 ◽  
pp. 000370282110282
Author(s):  
Daitaro Ishikawa ◽  
Jiamin Yang ◽  
Tomoyuki Fujii
Keyword(s):  
Infrared Spectroscopy ◽  
Small Angle ◽  
Water Sorption ◽  
Order Parameter ◽  
Rice Flour ◽  
Ordered Structure ◽  
X Ray ◽  
Glucose Unit ◽  
X Ray Scattering ◽  
Ray Scattering

The purpose of this study was to understand the ordered structure of starch in rice flour based on a physical modification with non-heating, milling, and water sorption through the structural evaluation of rice flour using small-angle X-ray scattering (SAXS) and infrared spectroscopy within the 4000–100 cm−1 region. The SAXS pattern of the samples with low moisture contents subjected to milling yield a band within the 0.4–0.9 nm−1 of the q range owing to a lamellar repeat of starch with an ordered structure in rice flour. We proposed an order parameter using the intensity of the SAXS band to quantify the order structure of starch in rice flour, and the true density was negatively correlated with the order parameter. Infrared band at 990 cm−1 in COH bending mode applied to the hydroxyl group of C6 shifted to a low wavenumber corresponding to the order parameter. A linear correlation was found between the order parameter and the 990 cm−1 and band at 861 cm−1 owing to COC symmetrical stretching of glycoside bond and CH2 deformation of the glucose unit of starch, 572, 472, and 436 cm−1, owing to the pyranose ring in the glucose unit of starch. The identified infrared bands are effective for quantifying the ordered structure of starch at the lamellar level. When subjected to water sorption, the band position at 990 cm−1 shifted to a higher wavenumber above a water activity of 0.7. This result revealed that the water-induced transition of glass to rubber of starch in rice flour can be clearly evaluated through infrared spectroscopy using the band at 990 cm−1. In addition, the band at 861 cm−1 also shifted to a higher wavenumber, whereas those at 572 and 436 cm−1 did not show a significant shift. These results indicate that water sorption slightly affects the internal structure and may mainly affect the surface of starch.

Temperature-induced structural phase transitions in RERhSn (RE = Y, Gd-Tm, Lu)

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Simon Engelbert ◽  
Rolf-Dieter Hoffmann ◽  
Jutta Kösters ◽  
Steffen Klenner ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Phase Transitions ◽  
Driving Force ◽  
Room Temperature ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray

Abstract The structures of the equiatomic stannides RERhSn with the smaller rare earth elements Y, Gd-Tm and Lu were reinvestigated on the basis of temperature-dependent single crystal X-ray diffraction data. GdRhSn crystallizes with the aristotype ZrNiAl at 293 and 90 K. For RE = Y, Tb, Ho and Er the HP-CeRuSn type (approximant with space group R3m) is already formed at room temperature, while DyRhSn adopts the HP-CeRuSn type below 280 K. TmRhSn and LuRhSn show incommensurate modulated variants with superspace groups P31m(1/3; 1/3; γ) 000 (No. 157.1.23.1) (γ = 3/8 for TmRhSn and γ = 2/5 for LuRhSn). The driving force for superstructure formation (modulation) is a strengthening of Rh–Sn bonding. The modulation is expressed in a 119Sn Mössbauer spectrum of DyRhSn at 78 K through line broadening.

X-Ray Diffraction Study of Hep Metals. I. Line Broadening in Polycrystalline Cd Powder

1974 ◽  
Vol 29 (12) ◽  
pp. 1771-1777 ◽  
Author(s):  
N. C. Haider ◽  
S. H. Hunter
Keyword(s):  
Room Temperature ◽  
Small Deformation ◽  
Correction Factors ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Fault Probability ◽  
Large Particle Size ◽  
X Ray ◽  
Melting Temperatures ◽  
Diffraction Patterns

Powder Cd of 99.999% purity was prepared at room temperature (25 °C) and x-ray diffraction patterns were obtained using CuKaα radiation with Ni-filter. The line broadening was analyzed after incorporating the appropriate correction factors. At room temperature Cd was found to have large particle size (653 A), small root mean square strain (.001), small deformation fault probability a (.003). and negligible growth fault probability β(0). Compared to other hep metals which have been studied earlier and which have higher melting temperatures, metal Cd is much less affected by mechanical deformation at room temperature.

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