Neutron and X-Ray Scattering Studies of (FeF2) M (CoF2)n Multilayers

1993 ◽  
Vol 313 ◽  
Author(s):  
D. Lederman ◽  
D. P. Belanger ◽  
J. Wang ◽  
S-J. Han ◽  
C. Paduani ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Specific Heat ◽  
Temperature Anomaly ◽  
Magnetic Contribution ◽  
X Ray Diffraction ◽  
Neutron Data ◽  
Elastic Neutron ◽  
X Ray ◽  
X Ray Scattering ◽  
Higher Temperature

ABSTRACTWe have performed elastic neutron scattering measurements of the staggered magnetization in (FeF2) M (CoF2) n superlattices. Thermal expansion Measurements, which are proportional to the magnetic contribution to the specific heat, were also carried out using high resolution x-ray diffraction. One of the two measured samples has thicknesses of M = n = 4.5 and the other M = 26 and n = 28 Monolayers, as determined from high angle x-ray θ — 2θ scans. In the M = n = 4.5 sample, only one transition is observed at T/v = 62.9K. Analysis of the neutron data, including the rounding effects, indicates an effective β ≈ 0.42. This does not compare well with the 3D Ising exponent β = 0.325. The X-ray data also show the existence of only one specific heat anomaly at T = 62.8 K. For the M = 26, n = 28 sample, dips in the staggered magnetization and peaks in the thermal expansion were observed at T ≈ 40 K and 74 K. The higher temperature anomaly, associated primarily with the FeF2 layers, is sharper than the lower one, which is presumably rounded by the staggered ordering field imposed by the long range order in the FeF2 regions on the CoF2 regions.

X-ray Scattering Measurements of the Ag(111) Surface Thermal Expansion

2001 ◽  
Vol 678 ◽  
Author(s):  
Cristian E. Botez ◽  
William C. Elliott ◽  
Paul F. Miceli ◽  
Peter W. Stephens
Keyword(s):  
Molecular Dynamics ◽  
Thermal Expansion ◽  
Molecular Dynamics Simulations ◽  
Temperature Interval ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Measurements ◽  
The One ◽  
Dynamics Simulations

AbstractWe have used synchrotron X-ray diffraction to study the thermal expansion of the Ag(111) surface. Throughout the temperature interval between 300 and 1100K, we observed that the separation between the first and the second atomic layers at the surface, 12 d, differs from its bulk counterpart, d, by less than 1%, indicating that the thermal expansion at the surface is similar to the one in the bulk. This result represents the first experimental confirmation of the predictions from molecular dynamics simulations, which indicate a small enhancement of the anharmonic effects at this surface.

f-Element Influence on the Size of Nanophase Phosphate Inclusions in Silica

2003 ◽  
Vol 802 ◽  
Author(s):  
James V. Beitz ◽  
S. Skanthakumar ◽  
S. Seifert ◽  
P. Thiyagarajan
Keyword(s):  
Porous Silica ◽  
Vitreous Silica ◽  
Metal Phosphate ◽  
Uranyl Ions ◽  
Pore Collapse ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
X Ray Scattering ◽  
Higher Temperature

ABSTRACTInsight into the factors that control the formation and size of heavy metal phosphate nanophases in vitreous silica has been gained by combining conventional and anomalous small angle x-ray scattering studies with powder x-ray diffraction and laser-induced fluorescence investigations. Europium, thorium, and uranyl ions were sorbed from aqueous solutions into a chemically functionalized porous silica (termed Diphosil). Aliquots of those samples were heated to a series of temperatures that spanned the pore collapse point. Loading with trivalent europium ions resulted in production of nanophases whose size corresponded to the average number of metal ions per pore. Thorium or uranyl ions resulted in retention of porosity to higher temperature with eventual pore collapse that evidently resulted in formation of nanophases whose size exceeded that determinable under the experimental conditions.

New Structure of CTAB Templated Silica Films as revealed by GISAXS coupled to HRTEM

2000 ◽  
Vol 628 ◽  
Author(s):  
Sophie Besson ◽  
Catherine Jacquiod ◽  
Thierry Gacoin ◽  
André Naudon ◽  
Christian Ricolleau ◽  
...  
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Grazing Incidence ◽  
Hexagonal Structure ◽  
X Ray Diffraction ◽  
Electronic Microscopy ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Hexagonal Arrangement ◽  
Spherical Micelles

ABSTRACTA microstructural study on surfactant templated silica films is performed by coupling traditional X-Ray Diffraction (XRD) and Transmission Electronic Microscopy (TEM) to Grazing Incidence Small Angle X-Ray Scattering (GISAXS). By this method it is shown that spin-coating of silicate solutions with cationic surfactant cetyltrimethylammonium bromide (CTAB) as a templating agent provides 3D hexagonal structure (space group P63/mmc) that is no longer compatible with the often described hexagonal arrangement of tubular micelles but rather with an hexagonal arrangement of spherical micelles. The extent of the hexagonal ordering and the texture can be optimized in films by varying the composition of the solution.

scholarly journals X-ray and Neutron Study on the Structure of Hydrous SiO2 Glass up to 10 GPa

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 84 ◽  
Author(s):  
Satoru Urakawa ◽  
Toru Inoue ◽  
Takanori Hattori ◽  
Asami Sano-Furukawa ◽  
Shinji Kohara ◽  
...  
Keyword(s):  
Oxide Glasses ◽  
Void Space ◽  
X Ray Diffraction ◽  
Amorphous Sio2 ◽  
Sio2 Glass ◽  
X Ray ◽  
X Ray Scattering ◽  
Medium Range ◽  
Two Phases ◽  
A Minor

The structure of hydrous amorphous SiO2 is fundamental in order to investigate the effects of water on the physicochemical properties of oxide glasses and magma. The hydrous SiO2 glass with 13 wt.% D2O was synthesized under high-pressure and high-temperature conditions and its structure was investigated by small angle X-ray scattering, X-ray diffraction, and neutron diffraction experiments at pressures of up to 10 GPa and room temperature. This hydrous glass is separated into two phases: a major phase rich in SiO2 and a minor phase rich in D2O molecules distributed as small domains with dimensions of less than 100 Å. Medium-range order of the hydrous glass shrinks compared to the anhydrous SiO2 glass by disruption of SiO4 linkage due to the formation of Si–OD deuterioxyl, while the response of its structure to pressure is almost the same as that of the anhydrous SiO2 glass. Most of D2O molecules are in the small domains and hardly penetrate into the void space in the ring consisting of SiO4 tetrahedra.

scholarly journals Impact of high temperatures on aluminoceladonite studied by Mössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopy

2021 ◽  
Author(s):  
Mariola Kądziołka-Gaweł ◽  
Maria Czaja ◽  
Mateusz Dulski ◽  
Tomasz Krzykawski ◽  
Magdalena Szubka
Keyword(s):  
Photoelectron Spectroscopy ◽  
Integral Intensity ◽  
Photoelectron Spectra ◽  
X Ray Diffraction ◽  
Structural Reorganization ◽  
Oh Groups ◽  
X Ray ◽  
Al Content ◽  
Integral Intensity Ratio ◽  
Higher Temperature

AbstractMössbauer, Raman, X-ray diffraction and X-ray photoelectron spectroscopies were used to examine the effects of temperature on the structure of two aluminoceladonite samples. The process of oxidation of Fe2+ to Fe3+ ions started at about 350 °C for the sample richer in Al and at 300 °C for the sample somewhat lower Al-content. Mössbauer results show that this process may be associated with dehydroxylation or even initiate it. The first stage of dehydroxylation takes place at a temperature > 350 °C when the adjacent OH groups are replaced with a single residual oxygen atom. Up to ~500 °C, Fe ions do not migrate from cis-octahedra to trans-octahedra sites, but the coordination number of polyhedra changes from six to five. This temperature can be treated as the second stage of dehydroxylation. The temperature dependence on the integral intensity ratio between bands centered at ~590 and 705 cm−1 (I590/I705) clearly reflects the temperature at which six-coordinated polyhedra are transformed into five-coordinated polyhedra. X-ray photoelectron spectra obtained in the region of the Si2p, Al2p, Fe2p, K2p and O1s core levels, highlighted a route to identify the position of Si, Al, K and Fe cations in a structure of layered silicates with temperature. All the measurements show that the sample with a higher aluminum content and a lower iron content in octahedral sites starts to undergo a structural reorganization at a relatively higher temperature than the less aluminum-rich sample does. This suggests that iron may perform an important role in the initiation of the dehydroxylation of aluminoceladonites.

Study of Low-Grade Nickel Laterite Processing Using Palm Shell Charcoal as Reductant

2020 ◽  
Vol 1000 ◽  
pp. 436-446
Author(s):  
Bambang Suharno ◽  
Nolzha Primadha Ilman ◽  
Achmad Shofi ◽  
Deni Ferdian ◽  
Fajar Nurjaman
Keyword(s):  
Sodium Sulfate ◽  
Selective Reduction ◽  
Reduction Process ◽  
Low Grade ◽  
X Ray Diffraction ◽  
X Ray ◽  
Palm Shell ◽  
Higher Temperature ◽  
Nickel Grade

This study was conducted to investigate the effect of palm shell charcoal reductant in the selective reduction of nickel ore with the addition of additive at various temperatures and times. In this present work, 10 wt. % of sodium sulfate as additive and 5, 10, 15 wt. % of palm shell charcoal as reductants were used. The reduction of nickel ore was performed at 950oC, 1050oC, and 1150oC for 60, 90, and 120 minutes. A wet magnetic separation method was then carried out to separate the concentrates and tailings. Characterization of reduced ore was performed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), while the composition of ferronickel in concentrate was identified by X-Ray Fluorescence (XRF). The result showed that the higher temperature reduction, the higher of nickel grade, and its recovery at the concentrate. Nevertheless, the longer reduction time and the more reductant in nickel ore lowering the nickel grade and its recovery in the concentrate. The optimum condition in this selective reduction process was obtained with the addition of 5 wt. % of reductant and 10 wt. % of sodium sulfate in nickel ore, which was reduced at 1150oC for 60 minutes. It resulted in 4.60% and 73.23% for nickel grade and its recovery, respectively.

Comparative Studies of Ultra Low-κ Porous Silica Films with 2-D Hexagonal and Disordered Pore Structures

2004 ◽  
Vol 812 ◽  
Author(s):  
Nobutoshi Fujii ◽  
Kazuhiro Yamada ◽  
Yoshiaki Oku ◽  
Nobuhiro Hata ◽  
Yutaka Seino ◽  
...  
Keyword(s):  
Pore Structure ◽  
Nonionic Surfactants ◽  
Porous Silica ◽  
Silica Film ◽  
X Ray Diffraction ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Porous Silica Film ◽  
Diffraction Peaks

AbstractPeriodic 2-dimensional (2-D) hexagonal and the disordered pore structure silica films have been developed using nonionic surfactants as the templates. The pore structure was controlled by the static electrical interaction between the micelle of the surfactant and the silica oligomer. No X-ray diffraction peaks were observed for the disordered mesoporous silica films, while the pore diameters of 2.0-4.0 nm could be measured by small angle X-ray scattering spectroscopy. By comparing the properties of the 2-D hexagonal and the disordered porous silica films which have the same porosity, it is found that the disordered porous silica film has advantages in terms of the dielectric constant and Young's modulus as well as the hardness. The disordered porous silica film is more suitable for the interlayer dielectrics for ULSI.

Sign in / Sign up

Export Citation Format

Share Document