skip to main content

Title: Lattice strain and texture analysis of superhard Mo 0.9 W 1.1 BC and ReWC 0.8 via diamond anvil cell deformation
Mo 0.9 W 1.1 BC and ReWC 0.8 compositions have recently been identified to have exceptional hardness and incompressibility. In this work, these compositions are analyzed via in situ radial X-ray diffraction experiments to comparatively assess lattice strain and texture development. Traditionally, Earth scientists have employed these experiments to enhance understanding of dynamic activity within the deep Earth. However, nonhydrostatic compression experiments provide insight into materials with exceptional mechanical properties, as they help elucidate correlations between structural, elastic, and mechanical properties. Here, analysis of differential strain ( t / G ) and lattice preferred orientation in Mo 0.9 W 1.1 BC suggests that dislocation glide occurs along the (010) plane in orthorhombic Mo 0.9 W 1.1 BC. The (200) and (002) planes support the highest differential strain, while planes which bisect two or three axes, such as the (110) or (191), exhibit relatively lower differential strain. In ReWC 0.8 , which crystallizes in a cubic NaCl-type structure, planar density is correlated to orientation-dependent lattice strain as the low-density (311) plane elastically supports more differential strain than the denser (111), (200), and (220) planes. Furthermore, results indicate that ReWC 0.8 likely supports a higher differential stress t than Mo 0.9 W more » 1.1 BC and, based on a lack of texture development, bulk plastic yielding is not observed in ReWC 0.8 upon compression to ∼60 GPa. « less
Authors:
; ; ; ; ; ;
Award ID(s):
1654687
Publication Date:
NSF-PAR ID:
10161386
Journal Name:
Journal of Materials Chemistry A
Volume:
7
Issue:
41
Page Range or eLocation-ID:
24012 to 24018
ISSN:
2050-7488
Sponsoring Org:
National Science Foundation
More Like this
  1. Two new alkali vanadate carbonates with divalent transition metals have been synthesized as large single crystals via a high-temperature (600 °C) hydrothermal technique. Compound I , Rb 2 Mn 3 (VO 4 ) 2 CO 3 , crystallizes in the trigonal crystal system in the space group P 3̄1 c , and compound II , K 2 Co 3 (VO 4 ) 2 CO 3 , crystallizes in the hexagonal space group P 6 3 / m . Both structures contain honeycomb layers and triangular lattices made from edge-sharing MO 6 octahedra and MO 5 trigonal bipyramids, respectively. The honeycomb and triangular layers are connected along the c -axis through tetrahedral [VO 4 ] groups. The MO 5 units are connected with each other by carbonate groups in the ab -plane by forming a triangular magnetic lattice. The difference in space groups between I and II was also investigated with Density Functional Theory (DFT) calculations. Single crystal magnetic characterization of I indicates three magnetic transitions at 77 K, 2.3 K, and 1.5 K. The corresponding magnetic structures for each magnetic transition of I were determined using single crystal neutron diffraction. At 77 K the compound orders in the MnO 6more »-honeycomb layer in a Néel-type antiferromagnetic orientation while the MnO 5 triangular lattice ordered below 2.3 K in a colinear ‘up–up–down’ fashion, followed by a planar ‘Y’ type magnetic structure. K 2 Co 3 (VO 4 ) 2 CO 3 ( II ) exhibits a canted antiferromagnetic ordering below T N = 8 K. The Curie–Weiss fit (200–350 K) gives a Curie–Weiss temperature of −42 K suggesting a dominant antiferromagnetic coupling in the Co 2+ magnetic sublattices.« less
  2. Multiphase materials are widely applied in engineering due to desirable mechanical properties and are of interest to geoscience as rocks are multiphase. High-pressure mechanical behavior is important for understanding the deep Earth where rocks deform at extreme pressure and temperature. In order to systematically study the underlying physics of multiphase deformation at high pressure, we perform diamond anvil cell deformation experiments on MgO + NaCl aggregates with varying phase proportions. Lattice strain and texture evolution are recorded using in-situ synchrotron x-ray diffraction and are modeled using two-phase elasto-viscoplastic self-consistent (EVPSC) simulations to deduce stress, strain, and deformation mechanisms in individual phases and the aggregate. Texture development of MgO and NaCl are affected by phase proportions. In NaCl, a (100) compression texture is observed when small amounts of MgO are present. In contrast, when deformed as a single phase or when large amounts of MgO are present, NaCl develops a (110) texture. Stress and strain evolution in MgO and NaCl also show different trends with varying phase proportions. Based on the results from this study, we construct a general scheme of stress evolution as a function of phase proportion for individual phases and the aggregate.
  3. Na-ion conducting solid electrolytes can enable both the enhanced safety profile of all-solid-state-batteries and the transition to an earth-abundant charge-carrier for large-scale stationary storage. In this work, we developed new perovskite-structured Na-ion conductors from the analogous fast Li-ion conducting Li 3 x La 2/3− x TiO 3 (LLTO), testing strategies of chemo-mechanical and defect engineering. Na x La 2/3−1/3 x ZrO 3 (NLZ) and Na x La 1/3−1/3 x Ba 0.5 ZrO 3 (NLBZ) were prepared using a modified Pechini method with varying initial stoichiometries and sintering temperatures. With the substitution of larger framework cations Zr 4+ and Ba 2+ on B- and A-sites respectively, NLZ and NLBZ both had larger lattice parameters compared to LLTO, in order to accommodate and potentially enhance the transport of larger Na ions. Additionally, we sought to introduce Na vacancies through (a) sub-stoichiometric Na : La ratios, (b) Na loss during sintering, and (c) donor doping with Nb. AC impedance spectroscopy and DC polarization experiments were performed on both Na 0.5 La 0.5 ZrO 3 and Na 0.25 La 0.25 Ba 0.5 ZrO 3 in controlled gas environments (variable oxygen partial pressure, humidity) at elevated temperatures to quantify the contributions of various possible charge carriers (sodiummore »ions, holes, electrons, oxygen ions, protons). Our results showed that the lattice-enlarged NLZ and NLBZ exhibited ∼19× (conventional sintering)/49× (spark plasma sintering) and ∼7× higher Na-ion conductivities, respectively, compared to unexpanded Na 0.42 La 0.525 TiO 3 . Moreover, the Na-ion conductivity of Na 0.5 La 0.5 ZrO 3 is comparable with that of NaNbO 3 , despite having half the carrier concentration. Additionally, more than 96% of the total conductivity in dry conditions was contributed by sodium ions for both compositions, with negligible electronic conductivity and little oxygen ion conductivity. We also identified factors that limited Na-ion transport: NLZ and NLBZ were both challenging to densify using conventional sintering without the loss of Na because of its volatility. With spark plasma sintering, higher density can be achieved. In addition, the NLZ perovskite phase appeared unable to accommodate significant Na deficiency, whereas NLBZ allowed some. Density functional theory calculations supported a thermodynamic limitation to creation of Na-deficient NLZ in favor of a pyrochlore-type phase. Humid environments generated different behavior: in Na 0.25 La 0.25 Ba 0.5 ZrO 3 , incorporated protons raised total conductivity, whereas in Na 0.5 La 0.5 ZrO 3 , they lowered total conductivity. Ultimately, this systematic approach revealed both effective approaches and limitations to achieving super-ionic Na-ion conductivity, which may eventually be overcome through alternative processing routes.« less
  4. null (Ed.)
    Garnet is an important mineral phase in the upper mantle as it is both a key component in bulk mantle rocks, and a primary phase at high-pressure within subducted basalt. Here, we focus on the strength of garnet and the texture that develops within garnet during accommodation of differential deformational strain. We use X-ray diffraction in a radial geometry to analyze texture development in situ in three garnet compositions under pressure at 300 K: a natural garnet (Prp60Alm37) to 30 GPa, and two synthetic majorite-bearing compositions (Prp59Maj41 and Prp42Maj58) to 44 GPa. All three garnets develop a modest (100) texture at elevated pressure under axial compression. Elasto-viscoplastic self-consistent (EVPSC) modeling suggests that two slip systems are active in the three garnet compositions at all pressures studied: {110}<1-21 11> and {001}<110>. We determine a flow strength of ~5 GPa at pressures between 10 to 15 GPa for all three garnets; these values are higher than previously measured yield strengths measured on natural and majoritic garnets. Strengths calculated using the experimental lattice strain differ from the strength generated from those calculated using EVPSC. Prp67Alm33, Prp59Maj41 and Prp42Maj58 are of comparable strength to each other at room temperature, which indicates that majorite substitutionmore »does not greatly affect the strength of garnets. Additionally, all three garnets are of similar strength as lower mantle phases such as bridgmanite and ferropericlase, suggesting that garnet may not be notably stronger than the surrounding lower mantle/deep upper mantle phases at the base of the upper mantle.« less
  5. We present exact results that give insight into how interactions lead to transport and superconductivity in a flat band where the electrons have no kinetic energy. We obtain bounds for the optical spectral weight for flat-band superconductors that lead to upper bounds for the superfluid stiffness and the two-dimensional (2D)Tc. We focus on on-site attraction|U|on the Lieb lattice with trivial flat bands and on the π-flux model with topological flat bands. For trivial flat bands, the low-energy optical spectral weightD̃lowñ|U|Ω/2withñ=minn,2n, where n is the flat-band density and Ω is the Marzari–Vanderbilt spread of the Wannier functions (WFs). We also obtain a lower bound involving the quantum metric. For topological flat bands, with an obstruction to localized WFs respecting all symmetries, we again obtain an upper bound forD̃lowlinear in|U|. We discuss the insights obtained from our bounds by comparing them with mean-field and quantum Monte Carlo results.