Improving the Phase Stability of the SLAC RF Driveline Network for SLC Operation
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Weaver, J.↗
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Phase stabilized and pulse shaped Ti: Sapphire oscillator-amplifier laser system for the LCLS rf photoinjector
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Kotseroglou, T.↗
Shape-stabilized phase change materials for energy storage based on hierarchically porous calcium magnesium carbonate
A composite phase-change material containing a hierarchically porous Ca 1-x Mg x CO 3 and having pores loaded with a phase change material is described. The heat storage material has a latent heat of melting 123 to 221 J/g, a latent heat of freezing of 107 to 201 J/g, and a thermal conductivity of 0.22 to 0.45 W·m −1 ·K −1 . The phase change material may be polyethylene glycol, and the polyethylene glycol does not leak from the pores of the hierarchically porous Ca 1-x Mg x CO 3 when heating or cooling over phase transitions.
25 ENERGY STORAGE↗
Cubic phases in phosphatidylethanolamine dispersions: Formation, stability and phase transitions
Not Available
Tenchov, Boris↗
Radio Science System Design and Measurement Results for the NASA Deep Space Network (DSN)
Radio science measurements have been performed using the NASA Deep Space Network (DSN) with many different spacecraft over several decades. Radio science has been used for the study of planetary atmospheres, the solar corona and the search for gravity waves, among other things. The majority of these measurements are made using the X and Ka-band deep space bands. Although the primary mission for the DSN is tracking, telemetry and command (TT&C) for NASA’s many deep-space spacecraft, radio science measurements continue to be an important secondary mission. The science requirements for these measurements have resulted in stringent performance requirements for both the spacecraft and ground system equipment. In particular, the requirements for amplitude stability, phase stability (Allen deviation) and phase noise are very demanding. The system Allen deviation requirement at Ka-band is < 2.4 E-15 over 1000 seconds, while the phase noise requirement is < -50 dBc/Hz for a 1 Hz offset. Various design techniques have been used for the DSN radio frequency (RF) electronics, high power transmitters and antenna structures to meet the stringent requirements for all 3 of these parameters. Some details for the design techniques will be described in the paper. Another important consideration for a radio science system is the verification approach for components, as well as for individual subsystems and then the overall system. Phase-locked oscillators (PLOs) are one of the key component types that determine overall phase noise and Allen deviation system performance. Measurement techniques used for PLOs, as well as for the overall ground system, will be discussed. Measurement results for the 2 new DSN antennas, recently built under the DSN Aperture Enhancement Project (DAEP) will also be shown. In addition, some recent radio science measurements from the Cassini and JUNO missions, using the new antennas, will be presented.
LaBelle, Remi C.↗
Thermal stability and phase transformation in fully indium oxide (InO{sub 1.5}) stabilized zirconia
Indium oxide (InO{sub 1.5}) stabilized zirconia (InSZ) is an attractive material as electrolyte, or electrode, in solid oxide fuel cells (SOFCs), and as corrosion resistant top coat in thermal barrier coatings. However, little is known about the phase stability of cubic InSZ at temperatures that simulate the conditions in an operating SOFC or turbine. This article provides an investigation of the phase stability and phase transformations in cubic InSZ after heat treatments at 800, 1000, and 1200 °C for periods up to 2000 h. The results revealed that cubic InSZ is not stable during annealing at 1000 and 1200 °C, owing to a fast destabilization of the initial cubic phase to tetragonal, and eventually to monoclinic (c → t → m). The c → t → m transition in InSZ is intimately associated with the indium volatilization. On the other hand, cubic InSZ remained stable for 2000 h at 800 °C, although the partial formation of the tetragonal phase was observed along with a 0.25% contraction in the unit cell volume of the cubic phase, caused by short-range ordering. These results demonstrate that technological applications of cubic InSZ are restricted to temperatures at which the volatilization of the InO{sub 1.5} stabilizer does not occur. - Highlights: •Phase stability of fully InO{sub 1.5} stabilized zirconia (cubic InSZ) was evaluated. •Cubic InSZ is instable at temperatures ≥ 1000 °C, owing to the cubic-to-tetragonal-to-monoclinic destabilization. •Cubic InSZ undergoes the cubic-to-tetragonal transformation at ~ 800 °C. •Owing to the low phase stability, applications of cubic InSZ in TBCs or SOFCs are restricted.
36 MATERIALS SCIENCE↗
Influence of nanoscale interfaces on the dynamic deformation and spall failure of Cu–Fe alloy microstructures
Additively manufactured immiscible Cu–Fe alloys can exhibit a distribution of nanoscale interfaces due to the distribution of nanoscale clusters in the equilibrium and metastable phases. Molecular dynamics simulations investigate the role of such interfaces on the phase stability and transformation behavior during shock compression, as well as the mechanisms of damage nucleation during spall failure. The model multiphase Cu–Fe systems studied here comprise a distribution of Fe clusters in an FCC Cu matrix, as well as Cu clusters in a BCC Fe matrix. The length scales of the nanoscale clusters determine the energetics of the interfaces that can result in FCC/BCC (equilibrium) or FCC/FCC (metastable) interfaces in the Cu system matrix, and BCC/FCC (equilibrium) or BCC/BCC (metastable) interfaces in the Fe matrix. The MD simulations demonstrate that nanoscale metastable interface microstructures can induce plastic deformation and also stabilize phases or suppress phase transformations in metastable phase clusters. In contrast, equilibrium interfaces can influence phase transformation thresholds and serve as additional void nucleation sites during failure.
36 MATERIALS SCIENCE↗
Half-Metallic Ferromagnetism in V-Doped FmP Binary Monopnictide Compounds: an Ab Initio Calculations
The ab initio calculations of the structural phase stability, magnetic phase stability, and electronic and magnetic properties of the FmP binary monopnictides and the half-metallic ferromagnetic properties of their Fm{sub 1−x}V{sub x}P (for x = 0.25, 0.50, 0.75, and 1)-doped alloys have been assured through the spin-polarized density functional theory (DFT), and they are performed by employing the full-potential linearized augmented plane waves plus local orbitals (FP-L/APW + lo) method that is implemented in the WIEN2k package. The exchange and correlation potential is parameterized by the generated gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) scheme. According to the studies of the magnetic phase stability, the fermium monopnictides (FmP) have a paramagnetic regime, while the ferromagnetic behavior appears when we dope this compound with vanadium. Through the ferromagnetic character of all Fm{sub 1−x}V{sub x}P alloys, the spin-polarized band structures and densities of states exhibit a nearly half-metallic character of Fm{sub 0.75}V{sub 0.25}P alloy, whereas Fm{sub 0.50}V{sub 0.50}P, Fm{sub 0.25}V{sub 0.75}P, and VP compounds showed metallic character. Moreover, the total magnetic moment of the three ternary alloys is mainly contributed by Fm and V elements, where the p-d hybridization reduces the atomic magnetic moment of V element from its free space charge and produces feeble magnetic moments on the nonmagnetic P sites.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
From Cryogenic to High Temperatures: A Microstructural Evolution of δ-phase Pu-Ga Alloys Investigated by Time-of-Flight High-resolution Neutron Diffraction
Phase stability and phase transformations in binary Pu alloys are critical for multiple applications. Long-term phase stability affects mechanical properties, microstructure, corrosion behavior, and structural integrity. A clear and detailed understanding of phase transformations and phase stability mechanisms is necessary to assess the behavior and response to unexpected stimuli. Gaining advanced knowledge on the behavior of Pu and Pu alloys at a variety of temperatures, pressures, and time will ensure better predictions and control on evolution outside laboratory measurements.
36 MATERIALS SCIENCE↗
Defects, Entropy, and the Stabilization of Alternative Phase Boundary Orientations in Battery Electrode Particles
Using a novel statistical approach that efficiently explores the space of possible defect configurations, our present study investigates the chemomechanical coupling between interfacial structural defects and phase boundary alignments within phase-separating electrode particles. Applied to the battery cathode material Li X FePO 4 as an example, the theoretical analysis reveals that small, defect-induced deviations from an ideal interface can lead to dramatic shifts in the orientations of phase boundaries between Li-rich and Li-lean phases, stabilizing otherwise unfavorable orientations. Significantly, this stabilization arises predominantly from configurational entropic factors associated with the presence of the interfacial defects rather than from absolute energetic considerations. The specific entropic factors pertain to the diversity of defect configurations and their contributions to rotational/orientational rigidity of phase boundaries. Comparison of the predictions with experimental observations indicates that the additional entropy contributions indeed play a dominant role under actual cycling conditions, leading to the conclusion that interfacial defects must be considered when analyzing the stability and evolution kinetics of the internal phase microstructure of strongly phase-separating systems. Possible implications for tuning the kinetics of (de)lithiation based on selective defect incorporation are discussed. Ultimately, this understanding can be generalized to the chemomechanics of other defective solid phase boundaries.
25 ENERGY STORAGE↗
Formation of As–As Interlayer Bonding in the cT Phase of EuFe{sub 2}As{sub 2} and CeFeAsO Under Pressure from First Principle
The electronic band structure and structural phase stability of EuFe{sub 2}As{sub 2} and CeFeAsO compounds were studied using the full-potential linearized augmented plane wave (FP-LAPW) method implemented using WIEN2k. To calculate the structural stability and phase transition of these compounds, the total energies have been computed as a function of reduced volumes and fitted with the Birch–Murnaghan equation. The calculated lattice parameters are found to be in agreement with the available experimental data. The present results show that EuFe{sub 2}As{sub 2} and CeFeAsO compounds undergo structural phase transition from body-centered tetragonal (BCT) into collapsed tetragonal (cT) and tetragonal (T) into cT phase under pressure. The calculated phase transition pressures are in agreement with recent experimental data. The calculated valence charge density of collapsed tetragonal phase reveals that As–As interactions found to be stronger under pressure.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films
The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110) orientation leads to a lower symmetry and more complicated phase transition than the (111) orientation in BaTiO{sub 3} films. The increase of compressive strain will dramatically enhance the Curie temperature T{sub C} of (110)-oriented BaTiO{sub 3} films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110)- and (111)-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.
36 MATERIALS SCIENCE↗
Stability of the 1144 phase in iron pnictides
A series of iron arsenides (e.g., CaRbFe 4 As 4 , SrCsFe 4 As 4 ) have been discovered recently, and have provoked a rise in superconductor searches in a different phase, known as the 1144 phase. For the presence of various chemical substitutions, it is believed that more 1144 compounds remain to be discovered. Here in this work, we perform general model analysis as well as scenario calculation on a basis of density functional theory to investigate phase stability in a variety of compounds. We predict that the 1144-type phase could be stabilized in EuKFe 4 As 4 , EuRbFe 4 As 4 , EuCsFe 4 As 4 , CaCsFe 4 P 4 , SrCsFe 4 P 4 , BaCsFe 4 P 4 , InCaFe 4 As 4 , InSrFe 4 As 4 , etc. Remarkably, it involves rare earths, trivalence elements (e.g., indium) and iron phosphides, which greatly expands the range of its existence and suggests a promising prospect for experimental synthesis. In addition, we find that the formation of many random doping compounds (e.g., Ba 0.5 Cs 0.5 Fe 2 As 2 , Ba 0.5 Rb 0.5 Fe 2 As 2 ) is driven by entropy and could be annealed to a 1144-type phase. Eventually, we plot a phase diagram about two structural factors Δa and Δc, giving a bird's-eye view of stability of various 1144 compounds.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Phase transformations in body-centered cubic NbxHfZrTi high-entropy alloys
Highlights: • BCC phase stability and phase transformations of NbxHfZrTi HEAs were investigated. • Three types of phase transformations: β → ω, β → α″ and β → α′ in HEAs were observed. • The athermal ω phase in Nb{sub 0.2}HfZrTi HEA leads to a much higher yield strength. • The reversible β → α″ in Nb{sub 0.4}HfZrTi HEA results in a narrow cyclic hysteresis loop. • A sluggish effect of martensitic transformations in complex HEAs is revealed. - Abstract: The stability of body-centered cubic (β) phases and phase transformations of NbxHfZrTi (x = 1, 0.6, 0.4 and 0.2) high-entropy alloys (HEAs) were investigated. Three types of transformations were observed: the β → ω transformation during cooling in Nb0.2 HEA, the deformation-induced β → α″ and β → α′ transformations in Nb0.4 and Nb0.2 HEAs, respectively. This implies that the phonon anomalies, T{sub 1}1/2(110) and L2/3(111), as the origins of phase transformations in simple Ti, Zr and Hf alloys, also exist in composition-complex TiZrHf-based HEAs. However, the very small fraction of deformation-induced α′/α″ martensite in fractured Nb0.4 and Nb0.2 suggests a sluggish effect of transformation as compared with simple β-Ti alloys.
36 MATERIALS SCIENCE↗
Aeroservoelastic stabilization technique refinement for hypersonic flight vehicles
Conventional gain-stabilization techniques introduce low frequency effective time delays which can be troublesome from the viewpoint of SSTOV vehicles' flying qualities. These time delays can be alleviated through a blending of gain-stabilization and phase-stabilization techniques; the resulting hybrid phase stabilization (HPS) for the low-frequency structural modes has been noted to have greater residual response than a conventional gain-stabilizer design. HPS design procedures are presently refined, and residual response metrics are developed.
Cheng, Peter Y.↗
Stability of Phase Transformation Temperatures During Cycling of Ti-15.8Nb-4.94Al-0.06Sc Shape Memory Alloy
The active ω phase formation decreases the martensitic transformation temperatures sharply and can even suppress the martensitic transformation during thermal cycling in Ti-Nb-based alloys. No ω phase is observed in the present Ti-15.8Nb-4.94Al-0.06Sc alloy when it is annealed at 650 °C for 4 h or subsequently aged at 200 and 250 °C for 2 h. The exclusion of ω phase remarkably improves the stability of phase transformation temperatures during thermal cycling. The martensitic transformation start temperature of the present alloy decreases by 30 °C but tends to be stable gradually during the 20 thermal cycles, owing to the saturation of lattice defects.
36 MATERIALS SCIENCE↗