Search results for "Compres"
showing 10 items of 1107 documents
Mapping and holistic design of natural hydraulic lime mortars
2020
Supplementary data to this article can be found online at https://doi.org/10.1016/j.cemconres.2020.106167.
Shear capacity in concrete beams reinforced by stirrups with two different inclinations
2014
Abstract A model for the estimation of shear capacity in Reinforced Concrete (RC) beams with web reinforcement is provided by introducing a generalization of classical plastic Nielsen’s model, which is based on the variable-inclination stress-field approach. The proposed model is able to predict the shear capacity in RC beams reinforced by means of stirrups having two different inclinations and longitudinal web bars. A numerical comparison with the results of experimental tests and those provided by a Finite Element Model (FEM) based on the well known theory of Modified Compression Field Theory (MCFT) is carried out for validating the robustness of the proposed model. Finally, a set of para…
High-pressure crystal structure, lattice vibrations, and band structure of BiSbO4
2016
The high-pressure crystal structure, lattice-vibrations HP crystal structure, lattice vibrations, and band , and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressur…
Compressibility Systematics of Calcite-Type Borates: An Experimental and Theoretical Structural Study on ABO(3) (A = Al, Sc, Fe, and In)
2014
The structural properties of calcite-type orthoborates ABO(3) (A = Al, Fe, Sc, and In) have been investigated at high pressures up to 32 GPa. They were studied experimentally using synchrotron powder X-ray diffraction and theoretically by means of ab initio total-energy calculations. We found that the calcite-type structure remains stable up to the highest pressure explored in the four studied compounds. Experimental and calculated static geometries (unit-cell parameters and internal coordinates), bulk moduli, and their pressure derivatives are in good agreement. The compressibility along the c axis is roughly three times that along the a axis. Our data clearly indicate that the compressibi…
Crystal structure of BaCa(CO3)2 alstonite carbonate and its phase stability upon compression
2021
Authors thank the financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN) and the Agencia Estatal de Investigación under projects MALTA Consolider Ingenio 2010 network (MAT2015-71070- REDC) and PGC2018-097520-A-I00 (cofinanced by EU FEDER funds) and from the Generalitat Valenciana under project PROMETEO/2018/123. D.S.-P. and A.O.R. acknowledge the financial support of the Spanish MINECO for RyC-2014-15643 and RyC-2016-20301 Ramón y Cajal grants, respectively. C.P. acknowledges the financial support from the Spanish Ministerio de Economia y Competitividad (MINECO project FIS2017-83295-P). Authors also thank Dr. Nicolescu and the Mineralogy and Meteoritic…
Comment on “High-pressure x-ray diffraction study of YBO3/Eu3+, GdBO3, and EuBO3: Pressure-induced amorphization in GdBO3” [J. Appl. Phys. 115, 04350…
2014
High-pressure x-ray diffraction studies on vaterite-type borates were reported on the above paper and their room-temperature P-V equation of state (EOS) determined. YBO3/Eu3+ and GdBO3 were found to have bulk moduli around 320 GPa, 90% larger than the bulk modulus obtained for EuBO3. Consequently, it was stated that vaterite-type borates are as incompressible as cubic BN. Such a different compressional behavior of isomorphic borates contradicts the known systematic of related borates. Here, we show that the conclusions reported on the above article could be hindered by experimental errors and artifacts. Ab initio calculations support our criticism giving similar bulk moduli (130–141 GPa) in…
In situ high-pressure synchrotron X-ray diffraction study of the structural stability in NdVO4 and LaVO4
2014
Abstract Room-temperature angle-dispersive X-ray diffraction measurements on zircon-type NdVO 4 and monazite-type LaVO 4 were performed in a diamond-anvil cell up to 12 GPa. In NdVO 4 , we found evidence for a non-reversible pressure-induced structural phase transition from zircon to a monazite-type structure at 6.5 GPa. Monazite-type LaVO 4 also exhibits a phase transition but at 8.6 GPa. In this case the transition is reversible and isomorphic. In both compounds the pressure induced transitions involve a large volume collapse. Finally, the equations of state and axial compressibilities for the low-pressure phases are also determined.
An Ultrahigh CO2-Loaded Silicalite-1 Zeolite: Structural Stability and Physical Properties at High Pressures and Temperatures
2018
[EN] We report the formation of an ultrahigh CO2-loaded pure-SiO2, silicalite-1 structure at high pressure (0.7 GPa) from the interaction of empty zeolite and fluid CO, medium. The CO2-filled structure was characterized in situ by means of synchrotron powder X-ray diffraction. Rietveld refinements and Fourier recycling allowed the location of 16 guest carbon dioxide molecules per unit cell within the straight and sinusoidal channels of the porous framework to be analyzed. The complete filling of pores by CO, molecules favors structural stability under compression, avoiding pressure-induced amorphization below 20 GPa, and significantly reduces the compressibility of the system compared to th…
High-pressure phase transitions and compressibility of wolframite-type tungstates
2010
This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. The diffraction experiments show that monoclinic wolframite-type MgWO4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO4 and FeMoO4-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO4 the onset of the monoclinic-triclinic transition has been also found at 15.1 GPa. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transiti…
High-pressure x-ray diffraction study of CdMoO4 and EuMoO4
2011
International audience; We studied the effects of high pressure on the crystalline structure of scheelite-type CdMoO4 and EuMoO4. We found that the compressibility of the materials is highly nonisotropic, with the c-axis being the most compressible one. We also observed clear evidence of a structural phase transition at 12 GPa (CdMoO4) and 8.8 GPa (EuMoO4). The high-pressure phase has a monoclinic structure similar to M-fergusonite. The transition is reversible, and no volume change is detected between the low- and high-pressure phases. The results contradict early x-ray diffraction studies carried out in CdMoO4 and are compared with those obtained previously in isomorphic molybdates. Final…