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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Materials design of perovskite solid solutions for thermochemical applications

Perovskites are excellent candidate materials as oxygen carriers in thermochemical processes. Due to their versatile composition, it is possible to fine-tune the perovskite's properties. Here, we present a method for the rational design of AMO 3– δ perovskite solid solutions with two different species on the Msite in order to tune their redox behavior. To account for the different ionic radii of different transition metal species M, two distinct ions are used in a solid solution on the A site, allowing tolerance-factor adjusted materials design. Using this methodology, we can create stable perovskites over a large range of different compositions. Leveraging the infrastructure of Materials Project, we calculate redox enthalpies for the reduction of over 240 of these $(\text {A}^{\prime}_x\text {A}^{\prime\prime}_{1-x})(\text {M}^{\prime}_y\text {M}^{\prime\prime}_{1-y})$O 3 perovskites to their brownmillerite phases based on density functional theory (DFT). We compare this data to experimentally measured data on thermodynamics of 24 of these materials to verify our theoretical framework. An empirical model is formulated for predicting the enthalpy and entropy changes as a function of the perovskites non-stoichiometry δ , which can be used to simulate the equilibrium composition as a function of temperature and oxygen partial pressure and to create a perovskite search engine based on an energetic analysis of the redox cycles. The data has been added as a contribution to MPContribs, which now includes publicly available user-controlled interactive graphs based on our theoretical and experimental data.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Local structure and controllable thermal expansion in the solid solution (Mn 1-x Ni x )ZrF 6

It is an interesting but challenge issue to prepare isotropic controllable thermal expansion materials with a wide coefficient of thermal expansion (CTE) range. Herein we report controllable thermal expansion in the double ReO 3 -type (Mn 1-x Ni x )ZrF 6 solid solutions, whose CTE varies from -4.4 to +15.5 × 10 -6 K -1 (300–700 K). In particular, zero thermal expansion has been obtained in the composition of (Mn 0.6 Ni 0.4 )ZrF 6 . (Mn 1-x Ni x )ZrF 6 exhibits full solid solution character. The thermal expansion of (Mn 1-x Ni x )ZrF 6 is adjusted by the flexibility of the atomic linkages, which is confirmed by the technique of temperature-dependent high-energy synchrotron X-ray pair distribution function.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Optimizing Blue Persistent Luminescence in (Sr 1-δ Ba δ ) 2 MgSi 2 O 7: Eu 2+ ,Dy 3+ via Solid Solution for Use in Point-of-Care Diagnostics

Inorganic persistent luminescent phosphors are an excellent class of optical reporters for enabling sensitive point-of-care diagnostics, particularly with smartphone-based biosensing devices in testing formats such as the lateral flow assay (LFA). Here, the development of persistent phosphors for this application is focused on the solid solution (Sr 1-δ Ba δ ) 2 MgSi 2 O 7 :Eu 2 +,Dy 3+ (δ = 0, 0.125, 0.25, 0.375), which is prepared using a high-temperature solid-state reaction as confirmed by synchrotron X-ray powder diffraction. The substitution of barium for strontium enables control over the Eu 2+ 5d-orbital crystal field splitting (CFS) as a tool for tuning the emission wavelength while maintaining luminescence lifetimes >9 min across the composition range. Thermoluminescence measurements of the solid solution provide evidence that trap states contribute to the persistent lifetimes with the trap depths also remaining constant as a function of composition. Time-gated luminescence images of these compounds are captured on a smartphone arranged in a layout to mimic a point-of-care test and demonstrate the viability of using these materials as optical reporters. Moreover, comparing the blue-emitting (Sr 0.625 Ba 0.375 ) 2 MgSi 2 O 7 :Eu 2+ ,Dy 3+ and the green-emitting SrAl 2 O 4: Eu 2+ ,Dy 3+ in a single LFA-type format shows these two compounds can be detected and resolved simultaneously, thereby permitting the development of a multiplexed LFA.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel to binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Investigating sluggish diffusion in a concentrated solid solution alloy using ion irradiation with in situ TEM

Concentrated solid solution alloys (CSAs) – including high entropy alloys – are known for their remarkable mechanical and corrosion resistances with superior tolerance against the deleterious effect of irradiation exposure when compared with pure metals and dilute alloys. To date, however, the mechanisms responsible for such improvements are still unclear and remain a subject of investigation. The present work reports in situ Transmission Electron Microscopy (TEM) study under simultaneous ion irradiation of the face-centred cubic (FCC) FeCrMnNi quaternary CSA, comparing with a non-equiatomic Fe-based alloy, the AISI-348 austenitic stainless steel that has Cr, Ni and Mn as alloying elements. The alloys were irradiated under the same conditions, with 6 keV He + and 134 keV Xe + ions at 298 K up to 1.7 x 10 17 ions·cm -2 (4 displacements-per-atom or dpa) and 2.7 x 10 15 ions·cm -2 (4 dpa), respectively. The nucleation of inert gas bubbles was tracked upon post-irradiation extended annealing up to 673 K. He and Xe bubbles were observed to grow at a rate slightly slower in the CSA. Trends from the bubble size analyses show that the nucleation and growth of inert gas bubbles may be suppressed or delayed in some conditions in the CSA.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Magnesian calcite solid solution thermodynamics inferred from authigenic deep-sea carbonate

Magnesian calcite is perhaps the most well studied solid solution in the geosciences due to the widespread use of marine carbonates to reconstruct paleoenvironment. Despite decades of research, the low temperature thermodynamic properties of magnesian calcite in seawater are poorly constrained, largely because very slow reaction kinetics prevent the direct measurement of equilibrium distribution coefficients ($K_d^{Mg}$) for anhydrous Mg-bearing minerals. In this study, we use the Mg content of authigenic calcite formed in deep-sea marine carbonate sediments to determine the dependence of $K_d^{Mg}$ on temperature and aqueous Mg/Ca between ~2 and 25 °C. We find that the solid activity coefficient of magnesite in Mg-calcite is strongly temperature dependent in this range, leading to predicted exsolution of Mg at low temperatures. At the temperatures typical of ocean bottom water, equilibrium Mg distribution coefficients are at least an order of magnitude lower than values inferred from inorganic calcite growth experiments. Moreover, the equilibrium temperature dependence of $K_d^{Mg}$ agrees well with field-based paleotemperature calibrations determined for low-Mg benthic and planktonic foraminifera at temperatures <20 °C. Partitioning of Mg in foraminiferal tests is expected to be highly dependent on the Mg/Ca ratio in the calcifying fluid, so ignoring secular variations in seawater Mg/Ca can lead to significant underestimation of paleotemperatures.

58 GEOSCIENCES↗
DOE OSTI2015

Mesoporous MnCeO x solid solutions for low temperature and selective oxidation of hydrocarbons

The development of noble-metal-free heterogeneous catalysts that can realize the aerobic oxidation of C–H bonds at low temperature is a profound challenge in the catalysis community. Here we report the synthesis of a mesoporous Mn 0.5 Ce 0.5 O x solid solution that is highly active for the selective oxidation of hydrocarbons under mild conditions (100–120 °C). Notably, the catalytic performance achieved in the oxidation of cyclohexane to cyclohexanone/cyclohexanol (100 °C, conversion: 17.7%) is superior to those by the state-of-art commercial catalysts (140–160 °C, conversion: 3-5%). Finally, the high activity can be attributed to the formation of a Mn 0.5 Ce 0.5 O x solid solution with an ultrahigh manganese doping concentration in the CeO 2 cubic fluorite lattice, leading to maximum active surface oxygens for the activation of C–H bonds and highly reducible Mn 4+ ions for the rapid migration of oxygen vacancies from the bulk to the surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Kinetic Properties of the Mn{sub 1–x}Gd{sub x}Se Solid Solutions

The results of kinetic study of the Mn{sub 1–x}Gd{sub x}Se chalcogenide solid solutions with different substitute concentrations (0 ≤ x ≤ 0.15) in the temperature range of 80–400 K are reported. The difference between the Hall constant and thermopower signs has been found. The electron-type conductivity determined from the Hall constant and hysteresis of the I–V characteristics have been explained by the existence of nanoareas with local electric polarizations. The sharp extrema observed in the temperature dependence of thermopower are explained by splitting of a narrow 4f subband by the crystal field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Synthesis and X-ray diffraction study of Cu{sub 2}ZnSn(S{sub x}Se{sub 1-x}){sub 4} solid solutions

Quaternary compounds Cu{sub 2}ZnSnS{sub 4} and Cu{sub 2}ZnSnSe{sub 4} and solid solutions on their basis have been fabricated by one-temperature synthesis from elementary components: Cu, Zn, Sn, S, and Se. Single crystals of these compounds have been grown by the method of chemical gas-transport reactions from polycrystalline samples. The compositional dependence of the unit-cell parameters of Cu{sub 2}ZnSn(S{sub x}Se{sub 1–x}){sub 4} has been investigated by X-ray diffraction. It is found that parameters a and c linearly decrease with an increase in sulfur concentration in accordance with Vegard’s law. The temperature dependences of parameters a and thermalexpansion coefficients α{sub a} of Cu{sub 2}ZnSnS{sub 4} and Cu{sub 2}ZnSnSe{sub 4} single crystals in the range of 100–300 K are determined.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of electronic energy dissipation on strain relaxation in irradiated concentrated solid solution alloys

The effect of energy deposition by energetic particles on Ni and two single-phase concentrated solid solution alloys (NiFe and NiCoCrFe) is explored through combined experimental and modelling efforts. Damage evolution as a function of increasing ion fluence is monitored via elastic strain developed in the irradiated crystals. We show that damage produced from displacement collision cascades is sensitive to subsequent highly ionizing irradiation that the strain generated by elastic nuclear collisions undergoes partial relaxation upon high-energy irradiation. This result suggests a change in the damage structure upon electronic energy deposition due to both predominant defect annealing and growth of small defect clusters. Strain relaxation, more pronounced in the alloys than in Ni, is ascribed to both higher thermal conductivity and weaker electron-phonon coupling in Ni.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structure Transformation and Cerium-Substituted Optical Response across the Carbonitridosilicate Solid Solution (La δ Y 1–δ ) 2 Si 4 N 6 C(δ = 0–0.5)

Following an investigation proving La 2 Si 4 N 6 C crystallizes in a monoclinic space group, isostructural to Y 2 Si 4 N 6 C, the reportedly hexagonal (La 0.5 Y 0.5 ) 2 Si 4 N 6 C was reinvestigated to examine the apparent crystal structure change across the solid solution. Initially, calculating the electronic structure and phonon density of states of (La 0.5 Y 0.5 ) 2 Si 4 N 6 C in the P6 3 mc space group revealed an imaginary phonon mode, which is indicative of a structural instability. Displacing the atoms along the pathway of the imaginary vibration led to a previously unreported space group for carbonitridosilicates, trigonal P31c. The assignment of the trigonal space group was subsequently confirmed by synthesizing (La 0.5 Y 0.5 ) 2 Si 4 N 6 C using high-temperature, solid state synthesis and analyzing the crystal structure with high-resolution synchrotron X-ray powder diffraction. Preparing the solid solution, (La δ Y 1–δ ) 1.98 Ce 0.02 Si 4 N 6 C (δ = 0–0.5), showed that the crystal structure changes from the monoclinic to the trigonal space group at δ ≈ 0.25. Finally, substituting Ce 3+ in the crystal structure to investigate the optical response via steady-state luminescent and photoluminescent quantum yield measurements reveals severe luminescent quenching with increasing La 3+ content, due to a combination of absorption of luminescence by the host structure and thermal quenching. Here, these results display the virtue of combining computational and experimental techniques to solve inorganic crystal structures and assess potential phosphor hosts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Novel ferroelectric single crystals of Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} ternary solid solution

Ferroelectric single crystals of a new lead-reduced Bi(Zn{sub 1/2}Ti{sub 1/2})O{sub 3}-PbZrO{sub 3}-PbTiO{sub 3} (BZT-PZ-PT) ternary solid solution system have been grown for the first time by three different methods, namely high temperature solution growth (HTSG, or flux method), top-cooled solution growth (TCSG), and top-seeded solution growth (TSSG). The chemical and thermodynamic parameters, including the flux concentration, the soaking temperature and the cooling rate, have been optimized, leading to the growth of good quality BZT-PZ-PT crystals of pseudo-cubic morphology. A large size crystal of the dimensions of 2 × 2 × 0.5 cm{sup 3} has been obtained by the TSSG technique. The crystal structure is analyzed by means of X-ray powder diffraction. The highest ferroelectric Curie temperature T{sub C} of the grown crystals is found to be 320 °C by means of dielectric measurements. A remnant polarization of 32 μC/cm{sup 2} is displayed with a coercive field of 15.4 kV/cm. The high T{sub C} and large coercive field of the BZT-PZ-PT single crystal make this material a promising candidate for applications in high power electromechanical transducers that can operate in a wider temperature range and at high fields.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

A comparative characterization of defect structure in NiCo and NiFe equimolar solid solution alloys under in situ electron irradiation

Dislocation loops in NiCo and NiFe, both being single-phase, equimolar solid solution alloys, are generated by in situ high-voltage electron irradiation and characterized inside a transmission electron microscope. In addition to the different defect growth rates, the two alloys present dislocation loops with distinct shape evolution and element segregation, which reflect the element-sensitive, intrinsic properties (e.g., defect energetics, lattice distortion, and local ordering) of the alloys. These results provide evidence that the structure and dynamics of radiation-induced defects in concentrated alloys depend on not only the number but also the species of alloying elements.

36 MATERIALS SCIENCE↗