scholarly journals Evidence for a Phase Transition in Silicate Melt at Extreme Pressure and Temperature Conditions

2012 ◽  
Vol 108 (6) ◽  
Author(s):  
D. K. Spaulding ◽  
R. S. McWilliams ◽  
R. Jeanloz ◽  
J. H. Eggert ◽  
P. M. Celliers ◽  
...  
2017 ◽  
Vol 119 (13) ◽  
Author(s):  
D. K. Spaulding ◽  
R. S. McWilliams ◽  
R. Jeanloz ◽  
J. H. Eggert ◽  
P. M. Celliers ◽  
...  

2019 ◽  
Vol 47 (3) ◽  
pp. 1641-1647 ◽  
Author(s):  
Giacomo Galli ◽  
Hassen Hamrita ◽  
C. Jammes ◽  
Michael J. Kirkpatrick ◽  
Emmanuel Odic ◽  
...  

2014 ◽  
Author(s):  
J. Huang ◽  
P. Guraieb ◽  
C. Yan ◽  
E. Contreras ◽  
M. Tomson ◽  
...  

2016 ◽  
Vol 71 (5) ◽  
pp. 439-445 ◽  
Author(s):  
Sebastian J. Metzger ◽  
Florian Ledderboge ◽  
Gunter Heymann ◽  
Hubert Huppertz ◽  
Thomas Schleid

AbstractTransparent single crystals of the scheelite-type Ln[AsO4] phases with Ln = La–Nd are obtained by the pressure-induced monazite-to-scheelite type phase transition in a Walker-type module under high-pressure and high-temperature conditions of 11 GPa at 1100–1300 °C. Coinciding with this transition, there is an increase in density and a reduction in molar volume of about 4.5 % for the scheelite-type phases (tetragonal, I41/a) for La[AsO4] (a = 516.92(4), c = 1186.1(9) pm), Ce[AsO4] (a = 514.60(1), c = 1175.44(2) pm), Pr[AsO4] (a = 512.63(4), c = 1168.25(9) pm), and Nd[AsO4] (a = 510.46(4), c = 1160.32(11) pm) as compared to the well-known monazite-type phases (monoclinic, P21/n). Surprisingly enough, the scheelite-type oxoarsenates(V) exhibit a lower coordination number for the Ln3+ cations (CN = 8 versus CN = 8 + 1), whereas the isolated tetrahedral [AsO4]3– anions (d(As–O) = 168.9–169.3 pm for the scheelites as compared to d(As–O) = 167.1–169.9 pm for the monazites) remain almost unchanged. So the densification must occur because of the loss of two edge-connections of the involved [LnO8+1]15– polyhedra with the [AsO4]3– tetrahedra in the monazite- resulting in exclusively vertex connected [LnO8]13– and [AsO4]3– units in the scheelite-type structure.


2014 ◽  
Vol 70 (a1) ◽  
pp. C193-C193
Author(s):  
Vladimir Solozhenko

Nanomaterials in the form of zero-, one- and two-dimensional nanostructures make a high-impact background for both science and technology. At the same time, the synthesis of bulk nanostructured materials remains the least-explored but challenging domain that allows combining the desired physical, chemical and mechanical properties and gives rise to nanoelectronics, nanomechanics, band-gap engineering, etc. The common methods of soft chemistry allow obtaining nanoparticles whose direct sintering unavoidably leads to the grain growth and lost of nanostructure. The extreme pressure is a parameter of choice to suppress the self-diffusion responsible for high-temperature recrystallization. The bulk nanostructured materials shows the superior fracture toughness and extremely high hardness as compared to corresponding microcrystalline bulks. The remarkable changes in physical and mechanical properties, however, do not affect the original thermal and chemical stability of the phase(s). All this opens unique opportunities for high-temperature superabrasive and electronic applications of such materials. Finally, the extreme pressure-temperature conditions are powerful and promising tool for grain-size control during direct solid-state phase transformations. The simultaneous variation of pressure and temperature makes possible to combine different nucleation, growth and aggregation regimes with high flexibility, and, therefore, to go deep into nanoscale engineering.


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