Differential REE uptake by sector growth of monazite

1999 ◽  
Vol 63 (6) ◽  
pp. 813-828 ◽  
Author(s):  
G. Cressey ◽  
F. Wall ◽  
B. A. Cressey
Keyword(s):  
Single Crystal ◽  
Microprobe Analysis ◽  
X Ray Diffraction ◽  
Backscattered Electron Imaging ◽  
X Ray ◽  
Backscattered Electron ◽  
Kink Site ◽  
Electron Imaging ◽  
The Relationship

AbstractMonazite-(Ce) from a dolomite carbonatite at Kangankunde, Malawi, is sector-zoned with variation in La2O3 of up to 6.0 wt.% and in Nd2O3 of up to 3.9 wt.% between sectors. Single crystal X-ray diffraction, backscattered electron imaging and microprobe analysis have been used to establish the relationship between the morphology and sector chemistry of this low-Th monazite, (Ce,La,Nd)PO4. Uptake of La by {011} sector surfaces is enhanced relative to that of and {100} sectors; Ce shows no partitioning differences; and uptake of Nd is more easily facilitated on and {100} surfaces relative to {011}. There appears to be a distinct relationship between the size of the REE ion and the probability of uptake via the different growth surfaces. Interpretation of this uptake behaviour, based on theories involving ‘protosites’, involves an investigation of the possible kink site geometries at edge-steps during growth. Part-formed kink sites with small entrance sizes are calculated to occur with higher frequency on relative to {011}, and this correlates with an increase in the smaller-sized REE (Nd) uptake by growth surfaces. The overall morphology and sector growth is suggested to be a function of uptake chemistry.

scholarly journals Permeable Nanomontmorillonite and Fibre Reinforced Cementitious Binders

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3245 ◽  
Author(s):  
Styliani Papatzani ◽  
Sotirios Grammatikos ◽  
Kevin Paine
Keyword(s):  
Mercury Intrusion Porosimetry ◽  
Pozzolanic Reaction ◽  
Particle Packing ◽  
X Ray Diffraction ◽  
Viable Option ◽  
Backscattered Electron Imaging ◽  
X Ray ◽  
Different Types ◽  
Backscattered Electron ◽  
Electron Imaging

Clinker reduction in cementitious binders is of paramount importance today, and nanotechnology has extended permissible limits. In the present study, a reference binder consisting of 60% Portland cement, 20% limestone, 20% fly ash, 3% polyvinyl alcohol (PVA) fibres and 2% superplasticizer is optimized with three different types of nano-montmorillonite (nMt) dispersions; two organomodified ones and an inorganic one at different proportions (0.5% to 4%). Flexural strength, measured on day 7, 28, 56 and 90, was improved after day 28 with the addition of inorganic nMt. Thermal gravimetric analyses carried out on day 7, 28, 56 and 90 coupled with x-ray diffraction (at day 28) showed a distinctively enhanced pozzolanic reaction. Backscattered electron imaging confirmed changes in the microstructure. Late age relative density measurements of the nMt cementitious nanocomposites showed higher values than these of the reference paste, which can be attributed to better particle packing. Mercury intrusion porosimetry measurements give support to the optimal nMt dosage, being 1% by total mass of binder and water impermeability tests (modified with BS EN 492:2012) suggest that inorganic nMt can be a viable option material where permeability constitutes a prerequisite. Suggestions for further activation of the nMt-fibre reinforced cementitious nanocomposites were also made.

The effect of Al/Si disorder on the bulk moduli of plagioclase feldspars

2010 ◽  
Vol 74 (6) ◽  
pp. 943-950 ◽  
Author(s):  
L. M. Sochalski-Kolbus ◽  
R. J. Angel ◽  
F. Nestola
Keyword(s):  
Bulk Modulus ◽  
Single Crystal ◽  
Equations Of State ◽  
X Ray Diffraction ◽  
Volume Increase ◽  
X Ray ◽  
Density Decrease ◽  
The Relationship

AbstractThe volumes of a disordered An20 (Qod = 0.15), a disordered An78 (Qod = 0.55) and an ordered An78 (Qod = 0.81) were determined up to 9.569(10) GPa, 8.693(5) GPa and 9.765(10) GPa, respectively, using single-crystal X-ray diffraction. The volume variations with pressure for these samples are described with 4th-order Birch Murnaghan equations of state with V0 = 669.88(7) Å3, K0 = 59.7(7) GPa. K′ = 5.7(5), K″ = −0.8(2) GPa−1 for disordered An20, V0 = 1340.48(10) Å3, K0 = 77.6(5) GPa, K0′ = 4.0(3), K″ = -0.59(9) GPa−1 for disordered An78 and V0 = 1339.62(6) A3, K0 = 77.4(6) GPa, K′ = 4.2(4), and K″ = −0.7(1) GPa−1 for ordered An78. Along with data from previous studies (An0 ordered, An0 disordered and An2o ordered), the volumes for the disordered samples were found to be up to ∼0.3% larger than the ordered samples of the same composition. The disordered samples are softer than the ordered samples of the same composition by 4(1)% for An0, 2.5(9)% for An20 and essentially zero for An78. The relationship between volume increase, density decrease, and decreasing bulk modulus with increasing disorder is in accordance with Birch's Law.

Phase equilibria and solidification behavior in the PbF2−AlF3 system

1991 ◽  
Vol 6 (10) ◽  
pp. 2188-2192 ◽  
Author(s):  
Linda V. Moulton ◽  
Robert S. Feigelson
Keyword(s):  
Solid Solution ◽  
Phase Equilibria ◽  
Directional Solidification ◽  
Microprobe Analysis ◽  
Binary Phase Diagram ◽  
Peritectoid Reaction ◽  
Solidification Behavior ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Relationship

The relationship between phase equilibria in the PbF2−AlF3 system and the solidification behavior of several ternary lead aluminum fluoride compounds was explored. A partial binary phase diagram for the PbF2−AlF3 system was determined from differential thermal analysis, annealing and directional solidification studies. The compounds AlF3, Pb3Al2F12, Pb9Al2F24, and a PbF2 solid solution were identified by x-ray diffraction, energy dispersive and microprobe analysis. The previously reported phases PbAlF5 and PbAl2F8 were not observed. Directional solidification studies showed that it is possible to grow crystals of AlF3, Pb3Al2F12, and the PbF2 solid solution from nonstoichiometric PbF2−AlF3 melts. The compound Pb9Al2F24 was found to decompose on heating by a peritectoid reaction (forming two other solids) and thus could not be solidified directly from a PbF2−AlF3 melt.

Monoclinic structure and nonstoichiometry of `KAlSiO4-O1'

2013 ◽  
Vol 69 (4) ◽  
pp. 334-336 ◽  
Author(s):  
Aleksandar Kremenović ◽  
Biljana Lazic ◽  
Hannes Krüger ◽  
Martina Tribus ◽  
Predrag Vulić
Keyword(s):  
Single Crystal ◽  
Electron Microprobe ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Monoclinic Structure ◽  
X Ray Diffraction ◽  
Flux Method ◽  
X Ray ◽  
Derivatives Of ◽  
Aluminium Silicate

Crystals of KAlSiO4-O1(potassium aluminium silicate) were synthesized using a flux method and analysed utilizing single-crystal X-ray diffraction and electron microprobe analysis. Both methods confirm that the crystals are nonstoichiometric according to K1−xAl1−xSi1+xO4withx= 0.04 (1). KAlSiO4-O1is closely related to the stuffed derivatives of tridymite, although the topology of the Si/Al-ordered framework is different. Six-membered rings of UUDDUD and UUUDDD (U = up and D = down; ratio 2:1) configurations are present in layers parallel to theabplane. In contrast, the framework of tridymite exhibits UDUDUD rings. The crystals are affected by inversion, pseudo-orthorhombic and pseudo-hexagonal twinning.

scholarly journals Phase relationships in the Al-rich region of the Al-Y-Zr system

2017 ◽  
Vol 53 (1) ◽  
pp. 9-12 ◽  
Author(s):  
X. Bao ◽  
L. Liu ◽  
S. Huang ◽  
Y. Jiang ◽  
X. Wang ◽  
...  
Keyword(s):  
First Principle ◽  
Rich Region ◽  
Backscattered Electron Imaging ◽  
X Ray ◽  
First Principle Calculations ◽  
Three Phase ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
Scanning Electron ◽  
Phase Relationships

The phase relations in the Al-Y-Zr ternary system at 873 K have been investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) in backscattered electron imaging (BSE) modes. Six three-phase equilibria are determined and no ternary compound is observed. In the meantime, first principle calculations are used to provide theoretical guidance to understand the experimental results.

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