scholarly journals Calcite Nanocrystals Investigated Using X-ray Absorption Spectroscopy

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 490
Author(s):  
Varsha Singh ◽  
Anil Kumar Paidi ◽  
Cheol-Hwee Shim ◽  
So Hee Kim ◽  
Sung Ok Won ◽  
...  

For the present work, calcite nanocrystals were grown by annealing precursors at 500 °C. These precursors were obtained by three different thermal schemes. Among these schemes, two involve heating at 100 °C for 16 h and 16 + 24 h, respectively. In the third scheme, heating was performed at 100 °C for 16 h, followed by annealing at 300 °C for 24 h. X-ray diffraction studies, followed by Fourier transform infrared and Raman spectroscopic studies, exhibited the formation of calcite phase of calcium carbonate. Transmission electron microscopy showed that particle sizes of synthesized calcite nanocrystals were in the range of 25–40 nm. Onsets of shape change were also observed with different thermal schemes, using these measurements. X-ray absorption spectroscopy envisaged that the coordination numbers of Ca-O and Ca-Ca shell were not influenced by the thermal schemes; however, bond lengths of these shells were modified. This study in the near edge region evidenced the manifestation of a local electronic structure of calcite when kept in an open environment, depending upon different thermal schemes.

Author(s):  
С.С. Подсухина ◽  
А.В. Козинкин ◽  
В.Г. Власенко ◽  
Г.Ю. Юрков ◽  
О.В. Попков

The composition, electronic and atomic structure of palladium nanoparticles stabilized in high pressure polyethylene (with palladium concentrations of 10 and 20 mass%) were studied by transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. It was found that nanoparticles consist of metal (Pd) and oxide (Pd2O3) components, and their average size and coordination numbers for first Pd coordination sphere decrease(from 7 to 6 nm and from 7 to 5.7, respectively) with a decrease in metal concentration.


2009 ◽  
Vol 1193 ◽  
Author(s):  
B. L. Metcalfe ◽  
S. K. Fong ◽  
L. A. Gerrard ◽  
I. W. Donald ◽  
E. S. Welch ◽  
...  

AbstractThe choice of surrogate for plutonium oxide for use during the initial stages of research into the immobilization of intermediate level pyrochemical wastes containing plutonium andamericium oxides in a calcium phosphate host has been investigated by powder X-ray diffraction and X-ray absorption spectroscopy. Two non-radioactive surrogates, hafnium oxide and cerium oxide, together with radioactive thorium oxide were compared. Similarities in behaviour were observed for all three surrogates when calcined at the lowest temperature, 750°C but differences became more pronounced as the calcination temperature was increased to 950°C. Although some reaction occurred between all the surrogates and the host to form a substituted whitlockite phase, increasing the temperature led to a significant increase in the cerium reaction and the formation of an additional phase, monazite. Additionally it was observed that the cerium became increasingly trivalent at higher temperatures.


Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.


2020 ◽  
Vol 153 (6) ◽  
pp. 064501
Author(s):  
Emiliano Fonda ◽  
Alain Polian ◽  
Toru Shinmei ◽  
Tetsuo Irifune ◽  
Jean-Paul Itié

2015 ◽  
Vol 54 (23) ◽  
pp. 11127-11135 ◽  
Author(s):  
Martina Vrankić ◽  
Biserka Gržeta ◽  
Dirk Lützenkirchen-Hecht ◽  
Sanja Bosnar ◽  
Ankica Šarić

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