Structural and compositional evolution of PtNiMo octahedravia in situ gas and heating studies

2021 ◽  
Author(s):  
Katherine MacArthur ◽  
Keyword(s):  
Compositional Evolution

Surface faceting and compositional evolution of Pd@Au core–shell nanocrystals during in situ annealing

2019 ◽  
Vol 21 (6) ◽  
pp. 3134-3139 ◽  
Author(s):  
Zhemin Wu ◽  
Min Tang ◽  
Xiaoyan Li ◽  
Sai Luo ◽  
Wentao Yuan ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Transformation Process ◽  
Au Nanoparticle ◽  
Core Shell ◽  
Compositional Evolution

A step-wise transformation process of a Pd@Au nanoparticle both structurally and compositionally was observed. Monte Carlo simulation was used to explain the results.

scholarly journals Chemical Composition and Petrogenetic Implications of Apatite in the Khibiny Apatite-Nepheline Deposits (Kola Peninsula)

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 532 ◽  
Author(s):  
Lia Kogarko
Keyword(s):  
Vertical Section ◽  
Alkaline Complex ◽  
High Concentration ◽  
Magmatic Chamber ◽  
Alkaline Magma ◽  
Compositional Evolution ◽  
Eu Anomaly ◽  
Significant Enrichment ◽  
World Class

Khibiny, one of the largest of the world’s peralkaline intrusions, hosts gigantic apatite deposits. Apatite is represented by F-apatite and it contains exceptionally high concentration of SrO. (4.5 wt % on average) and increased amounts of rare earth elements (REEs; up to 8891 ppm). Such enrichment of apatite ores in REEs defined Khibiny deposit as world-class deposit with resources reaching several millions tons REE2O3. Apatite from the Khibina alkaline complex is characterized by the significant enrichment in light REEs relative to the heavy REEs (with average Ce/Yb ratio of 682) and the absence of a negative Eu anomaly. The obtained geochemical signature of apatite suggests a residual character of the Khibiny alkaline magma and it indicates that the differentiation of the primary olivine-melanephelinitic magma developed without fractionation of plagioclase which is the main mineral-concentrator of Sr and Eu in basaltic magmatic systems. The compositional evolution of the Khibiny apatite in the vertical section of the intrusion reflects primary fractionation processes in the alkaline magma that differentiated in situ. The main mechanism for the formation of the apatite-nepheline deposits was the gravitational settling of large nepheline crystals in the lower part of the magma chamber, while very small apatite crystals were suspended in a convective magma, and, together with the melt, were concentrated in its upper part of the magmatic chamber.

Compositional evolution and cryptic variation in pyroxenes of the peralkaline Lovozero intrusion, Kola Peninsula, Russia

2006 ◽  
Vol 70 (4) ◽  
pp. 347-359 ◽  
Author(s):  
L. N. Kogarko ◽  
C. T. Williams ◽  
A. R. Woolley
Keyword(s):  
Kola Peninsula ◽  
Temperature Interval ◽  
Magma Chamber ◽  
Vertical Section ◽  
Redox Conditions ◽  
Alkaline Magma ◽  
Compositional Evolution ◽  
Cryptic Variation ◽  
Alkaline Massif

AbstractThe Lovozero alkaline massif is the largest of the world's layered peralkaline intrusions (∼650 km2). We describe the evolution of clinopyroxene from the liquidus to the late residual stage throughout the whole vertical section (2.5 km thick) of the Lovozero Complex. Microprobe data (∼990 analyses) of the clinopyroxenes define a relatively continuous trend from diopside containing 15–20% hedenbergite and 10–12% aegirine components, to pure aegirine. The main substitutions during the evolution of the Lovozero pyroxenes are (Na,Fe3+,Ti) for (Ca,Mg,Fe2+). The composition of the pyroxene changes systematically upwards through the intrusion with an increase in Na, Fe3+ and Ti and decrease in Ca and Mg.The compositional evolution of the Lovozero pyroxene reflects primary fractionation processes in the alkaline magma that differentiated in situ from the bottom to the top of the magma chamber as a result of magmatic convection, coupled with the sedimentation of minerals with different settling velocities.The temperature interval of pyroxene crystallization is very wide and probably extends from 970 to 450°C. The redox conditions of pyroxene crystallization in the Lovozero intrusion were relatively low, approximating the QFM buffer.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

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