Long-term Phase Stability Research Articles

Effects of Pr substitution in Y1-xPrxBaCo3ZnO7+δ (0 ≤ x ≤ 0.5) cathodes for intermediate temperature solid oxide fuel cells

In this investigation, we successfully synthesized a series of Swedenborgite-type Y1-xPrxBaCo3ZnO7+δ (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5, abbreviated as YPxBCZ) oxides by a solid-state reaction method. The results show that YPxBCZ (x = 0.0, 0.1, 0.2, and 0.3) are single-phase structures, but YP0.4BCZ and YP0.5BCZ show interesting self-assembled composite phases. After long-term phase stability testing, YP0.3BCZ showed the best thermal stability. All samples show good chemical and thermal compatibility with La0.9Sr0.1Ga0.8Mg0.2O3-δ electrolyte. The thermal expansion coefficients in the temperature range from 30 °C to 1000 °C are equal to 9.8-13.1 × 10−6 K−1, close to that of the LSGM electrolyte. It is also found that Pr doping improves high temperature conductivity of YPxBCZ. The conductivity of YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ reach 15.1, 18.5, and 22.5 S cm−1 at 800 °C. In addition, the area specific resistance (ASR) value decreases as the Pr content increases (0.038, 0.033, and 0.027 Ω cm2 at 800 °C for YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ), improving the catalytic activity of the material. Another interesting finding was that the ASR of samples subjected to high temperature thermal decomposition was not adversely affected by the presence of decomposition products. The maximum power densities of YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ in the single cells at 800 °C were 845, 930, and 1044 mW cm2, respectively. These results indicate that YP0.3BCZ, YP0.4BCZ, and YP0.5BCZ are promising cathode materials for intermediate-temperature solid oxide fuel cell.

Exploring the ambient metastability of yttrium substituted Bi2O3 electrolyte materials

The phase stability of (Bi1-xYx)2O3 (0.1 ≤ x ≤ 0.275) solid state electrolytes synthesized using the sol-gel method was investigated over prolonged periods under ambient conditions. The cubic polymorph was found to be metastable under ambient conditions, particularly for 0.1 ≤ x ≤ 0.15 where significant cubic-to-tetragonal transformation occurred. Spontaneous minor formation of both the rhombohedral polymorph and a bismuth subcarbonate phase was evident across the doping range but with varied reproducibility. Aging was significantly more prevalent for samples that had only been calcined (at 450 °C) as compared to those that were subsequently annealed (at 750 °C). The more highly substituted annealed materials (0.25 ≤ x ≤ 0.275) were initially phase pure cubic and far more stable, yet some rhombohedral and bismuth subcarbonate phase formation was also seen. Although the initial source of carbon which leads to the formation of the subcarbonate phase is not known at this stage, several suggestions are made. Pelletisation with additional sintering, as well as annealing powder samples under an inert atmosphere, was also shown to enhance the long-term phase stability characteristics of the cubic phase. This is the first longer term (over 2 years) ambient phase aging study of substituted bismuth oxides.

No evidence for synchronization of the solar cycle by a “clock”

The length of the solar activity cycle fluctuates considerably. The temporal evolution of the corresponding cycle phase, that is, the deviation of the epochs of activity minima or maxima from strict periodicity, provides relevant information concerning the physical mechanism underlying the cyclic magnetic activity. An underlying strictly periodic process (akin to a perfect “clock”), with the observer seeing a superposition of the perfect clock and a small random phase perturbation, leads to long-term phase stability in the observations. Such behavior would be expected if cycles were synchronized by tides caused by orbiting planets or by a hypothetical torsional oscillation in the solar radiative interior. Alternatively, in the absence of such synchronization, phase fluctuations accumulate and a random walk of the phase ensues, which is a typical property of randomly perturbed dynamo models. Based on the sunspot record and the reconstruction of solar cycles from cosmogenic 14C, we carried out rigorous statistical tests in order to decipher whether there exists phase synchronization or random walk. Synchronization is rejected at significance levels of between 95% (28 cycles from sunspot data) and beyond 99% (84 cycles reconstructed from 14C), while the existence of random walk in the phases is consistent with all data sets. This result strongly supports randomly perturbed dynamo models with little inter-cycle memory.

Polyethylenimine-CO2 adduct templated CaCO3 nanoparticles as anticancer drug carrier

BackgroundDue to their porous structure and capability to degrade under acidic conditions, CaCO3 nanoparticles in vaterite form can be used as carriers to effectively deliver drugs to low-pH sites such as tumors. The usually used intravenous administration requires long-term vaterite phase and colloidal stability for storage and blood circulation. While passive accumulation in tumors can be achieved via the enhanced permeation and retention effect, active accumulation requires reactive groups on vaterite nanoparticles to conjugate targeting molecules. Both requirements are hard to achieve in one simple and economical vaterite formulation. Herein, we used polyethylenimine (PEI)-based CO2 adduct as both a CO2 source and a template for vaterite mineralization to generate PEI-CO2@CaCO3 colloidal particles, with reactive amino groups from the PEI template.ResultsThe obtained nanoparticles with a hydrodynamic diameter of 200–300 nm have a vaterite phase and colloidal stability in an aqueous solution for over 8 months. These nanoparticles could effectively load anticancer drug doxorubicin via coprecipitation and be surface-modified with polyethylene glycol (PEG) and folic acid for long-term blood circulation and tumor targeting purposes, respectively. After being endocytosed, the PEI-CO2 adduct accelerates the dissolution of drug-loaded nanoparticles to generate CO2 bubbles to break the lysosomes, leading to rapid doxorubicin delivery inside tumor cells. The degradation of PEI-CO2 in the CaCO3 nanoparticles could also release PEI and CO2 and may contribute to the disruption of normal cellular functions. As a result, the drug-loaded PEI-CO2@CaCO3 nanoparticles strongly suppressed tumor growth in mice with HeLa tumor xenografts.ConclusionsA new and effective vaterite drug carrier for anticancer therapy has been developed using PEI-CO2 adduct as both a CO2 source and vaterite template for CaCO3 mineralization. This delivery system illustrates an application of CO2 generation materials in drug delivery and has the potential for further development.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment

Polyethylenimine-CO2 adduct-stabilized vaterite hydrocolloidal particles

We explore CaCO3 mineralization via the addition of a Ca(OH)2 solution to branched polyethylenimine–CO2 (PEI-CO2) adduct solutions. The alkylammonium carbamate zwitterions (i.e., CO2-adducted linkages) in PEI-CO2 adducts can hydrolyze to release bicarbonate ions to form CaCO3in situ; meanwhile, the zwitterions themselves transform into the polyamine structure of polyethylenimine (PEI). The PEI-CO2 polymer serves as both the CO2 source and template for vaterite CaCO3 nucleation and growth. A relatively low dosage of the Ca(OH)2 solution (e.g., at 9.2–37% stoichiometry) preserves enough CO2-adducted linkages in the templating PEI-based chains, allowing them to firmly adsorb onto the growing vaterite nanocrystallites, providing long-term vaterite phase and colloidal stability. The high molecular weight of the used PEIs (e.g., 10 k–25 k Da) strengthens the adsorption as well. The mesoporous structure, the dissolution in a weakly acidic environment (pH 6.5), the low cytotoxicity, the ease of endocytosis, and the presence of reactive PEI amino groups all make the obtained vaterite nanoparticles a versatile candidate for effective and acid-responsive drug delivery. This work highlights the multifunctionality of PEI-CO2 adducts for CaCO3 mineralization, serving as a CO2 source and vaterite template and providing the vaterite phase and colloid stability, as well as reactivity for further modification.

Compositional Engineering in α-CsPbI3 toward the Efficiency and Stability Enhancement of All Inorganic Perovskite Solar Cells

Fully inorganic CsPbI3 has emerged to be a promising light-harvesting material compared to the organic/hybrid perovskites because of its excellent absorption properties in the visible regime. However, the optically active pure α-CsPbI3 phase is unstable at room temperature. In this work, we have employed a partial replacement strategy at the B-site of α-CsPbI3 and achieved long-term phase stability. A controlled partial substitution of Pb2+ cations by Sn2+ in the host lattice has enhanced the carrier lifetime and film quality of α-CsPbI3. The alloying of Sn2+ decreases the band gap, which leads to an upsurge in the short circuit current of the solar cell. The device based on Sn2+ alloyed α-CsPbI3 with an active cell area of 18 mm2 has shown a colossal photoconversion efficiency than the device based on unalloyed δ-CsPbI3. The champion cell also maintained 78% of its primary efficiency after 15 days in a circumjacent atmosphere. This work brings out the optimal alloying amount of Sn for better stability and maximum device output.

3D Computational Welding Mechanics applied to IN625 Nickel-Base Alloy

Design for sustainability asks for higher and higher performance materials and enhanced techniques devoted to realizing their joints. For advanced applications, the emphasis is on high-temperature strength, long-term creep life, phase stability, oxidation resistance, and robust and flexible welding processes. In this scenario, Ni-based superalloy Inconel 625 is successfully used for mechanical components operating at high temperatures and stresses, conditions that however may cause surface cracks. In the frame of circular economy, fusion welding is therefore used as a convenient repairing technique, as well. However, correct process parameters avoiding metallurgical and mechanical defects need to be known for each case-study. Computational welding mechanics is a proper tool used to avoid expensive trials, provided that the used numerical model can capture the main phenomena involved in welding process. In this work, a 3D numerical model of Inconel 625 multi-pass welding process is developed and validated through residual stresses X-Ray diffraction measurements. The model showed a good accuracy and was therefore proved to be a powerful tool for welding process design of such alloy.

Significant phonon anharmonicity drives phase transitions in CsPbI3

Due to its high chemical stability and high power conversion efficiency as a solar cell absorber, the inorganic halide perovskite, CsPbI3, is considered one of the most promising competitors to its hybrid organic-inorganic counterpart, CH3NH3PbI3. However, the phase transition from the photoactive black phase to the inactive yellow phase is a remarkable limitation that harms long-term phase stability. In particular, the phase transitions follow different pathways as the temperature increases and/or decreases, a phenomenon that is anomalous and remains poorly understood. In this study, we systematically calculated the temperature-dependent free energy of CsPbI3 in different crystal phases (α, β, γ, δ) by considering the phonon contribution to the Gibbs free energy. It is found that the free energy results from calculations that include harmonic phonons cannot reproduce experimental observations. Alternatively, we utilized the renormalized phonon quasiparticle approach to derive the free energies of different CsPbI3 phases at finite temperatures. Based on these calculated free energies, whose derivations included the anharmonic effect, we observed phase-transition processes consistent with experimental results. The analysis of the temperature effect on the phonon frequencies further demonstrated that anharmonic effects in the CsPbI3 had a significant influence on its phase transitions.

Sagnac-type entangled photon source using only conventional polarization optics

We designed and implemented a novel combination of a Sagnac-interferometer with a Mach–Zehnder interferometer for a source of polarization-entangled photons. The new versatile configuration does not require multi-wavelength polarization optics, yet it performs with a good polarization quality and phase-stability over a wide wavelength range. We demonstrate the interferometer using only standard commercial optics to experimentally realize the pulsed generation of polarization-entangled photon-pairs at wavelengths of 764 nm and 1221 nm via type-I spontaneous four-wave mixing in a polarization-maintaining fiber. Polarization entanglement was verified by a polarization-correlation measurement with a visibility of 95.5% from raw coincidence counts and the violation of the Clauser–Horne–Shimony–Holt (CHSH) inequality with S = 2.70 ± 0.04. The long-term phase-stability was characterized by an Allan deviation of 8° over an integration time of about 1 h with no active phase-stabilization.

Application of a drift compensation low-level radio frequency system based on time-multiplexing pick-up/reference signals.

The high accuracy, low drift low-level radio frequency (LLRF) system is essential for the long-term stability of the accelerator RF and the acquirement of low emittance, high intensity electron beams. A time-multiplexing pick-up/reference signal based LLRF system is proposed to deal with the component temperature related phase drift and has been deployed and applied at the Xi'an Gamma-ray Light Source (XGLS) injector. The long term dual-receiver out-of-loop stability experiments with a continuous wave laser based phase reference distribution system (PRDS) show that the LLRF system can achieve ∼40 fs Root-Mean-Square (rms) phase accuracy and 51 fs/52 fs peak-peak drift (in 7 days/17 h with the high power RF system, respectively) while the reference phase varies both ∼30 ps. An ∼4 h beam-based experiment has also been conducted to evaluate the overall performance of the whole XGLS timing and synchronization system, which shows that the PRDS, LLRF system, high power RF system, and laser oscillator laser-RF synchronization system can keep long-term phase stability.

Leveraging scatter in two-dimensional spectroscopy: passive phase drift correction enables a global phasing protocol.

Phase stability between pulse pairs defining Fourier-transform time delays can limit resolution and complicates development and adoption of multidimensional coherent spectroscopies. We demonstrate a data processing procedure to correct the long-term phase drift of the nonlinear signal during two-dimensional (2D) experiments based on the relative phase between scattered excitation pulses and a global phasing procedure to generate fully absorptive 2D electronic spectra of wafer-scale monolayer MoS2. Our correction results in a ∼30-fold increase in effective long-term signal phase stability, from ∼λ/2 to ∼λ/70 with negligible extra experimental time and no additional optical components. This scatter-based drift correction should be applicable to other interferometric techniques as well, significantly lowering the practical experimental requirements for this class of measurements.

Solving Recent Challenges for Wrought Ni-Base Superalloys

This paper reviews the status of technology in design and manufacture of new wrought polycrystalline Ni-base superalloys for critical engineering applications. There is a strong motivation to develop new alloys that are capable of operating at higher temperatures to realize improvements in thermal efficiency, which are necessary to achieve environmental targets for reduced emissions of harmful green-house gases. From the aerospace sector, the development of new powder metallurgy and ingot metallurgy alloys is discussed for disk rotor and static applications. New compositions for powder metallurgy contain about 50 to 55 pct of gamma prime (γ′) strengthening precipitates to ensure components operate successfully at temperatures up to 788 °C (1450 °F). In contrast, new compositions for ingot metallurgy aim to occupy a design space in temperature capability between Alloy 718 and current powder alloys that are in-service, and show levels of γ′ of about 30 to 44 pct. The focus in developing these alloys was design for manufacturability. To complement the aerospace developments, a review of work to understand the suitability of candidate alloys for multiple applications in Advanced-Ultra Supercritical (AUSC) power plants has been undertaken by Detrois, Jablonski, and Hawk from the National Energy Technology Laboratory. In these power plants, steam temperatures are required to reach 700 °C to 760 °C. The common thread is to develop alloys that demonstrate a combination of high-temperature properties, which are reliant on both the alloy composition and microstructure and can be produced readily at the right price. For the AUSC applications, the emphasis is on high-temperature strength, long-term creep life, phase stability, oxidation resistance, and robust welding for fabrications. Whereas for powder disk rotors in aircraft engines, the priority is enhanced resistance to time-dependent crack growth, phase stability, and resistance to environmental damage, while extending the current strength levels, which are shown by existing alloys, to higher temperatures.

Effect of phosphorus content and grain size on the long-term phase stability of Ni-base superalloys

The effect of grain size on the phase stability of two nominally identical high refractory content powder-processed Ni-base superalloy with varying levels of P additions (0.013 wt% for alloy P1 and 0.026 wt% for alloy P3) was studied. Solutioning of the alloys at either sub-solvus or super-solvus temperatures were used to vary the grain size of the starting microstructure prior to long-term thermal exposures at 800 °C for up to 1000 h. EBSD analyses revealed that the sub-solvus solutioned samples had an average grain size of 10 μm and possessed a high angle grain boundary length density that was approximately 2.5 times greater than that found in the super-solvus solutioned samples with an average grain size of 16 μm. Differences in both the initial grain boundary character distribution and P content present in these alloys resulted in varying behavior with respect to the grain boundary precipitation of Laves and sigma phase during aging. Since P additions to Ni-base superalloys are known to promote the formation of Laves phases and segregate predominately to grain boundaries, sub-solvus heat treated samples exhibited a lower susceptibility of Laves phase precipitation compared with super-solvus heat treated samples for both P1 and P3 alloys. Sub-solvus heat treated P1 samples were found to be resistant to the formation of Laves phase after 1000 h exposure while the coarser grained super-solvus heat treated P3 samples exhibited extensive formation of intertwined Sigma-Laves along the grain boundaries just after 100 h exposure. The improvement in phase stability could be attributed to the reduced concentration of P along the grain boundary as increasing the length density of random high-angle grain boundary resulted in a more dilute spatial distribution of segregated P atoms.

A Ka-Band Scalable Hybrid Phased Array Based on Four-Element ICs

In this article, a scalable hybrid phased-array system is presented through synchronization, analog complex weighting, and digital beamforming of numerous fully integrated Ka-band four-receiver (RX)/four-transmitter (TX) phased-array transceiver integrated circuits (ICs). A 1.09-GHz clock synchronizes the local oscillator (LO) and a 50-MHz clock synchronizes analog-to-digital (A/D)/digital-to-analog (D/A) converters for all array elements. Phase shifting is first accomplished in the analog domain using optimal intermediate frequency (IF)/LO complex weighting and signal summing in the 4RX/4TX IC to reduce the number of signals by a factor of four, followed by A/D sampling and digital beamforming in field-programmable gate arrays (FPGAs) and central processing units (CPUs). Phase-shifting properties, programmable gain variations, and antenna patterns of each RTX channel are measured and tabulated to calculate the optimal channel weights. The long-term phase stability is enhanced through temperature control by monitoring all ICs’ temperatures in real time and adaptively adjusting the duty cycle of the TX mode of each IC to limit instantaneous temperature variations to ±0.5 °C over each calibration session. This reduces random phase errors from 13.3° to 4.8° in the TX mode. After each Vivaldi antenna is located on a 2-D rectangular grid, an $8 \times 4$ subarray module with synchronized digital output is demonstrated. With the boresight pointing along the $\hat {x}$ -axis, the eight-element dimension pointing along the $\hat {y}$ -axis, and the four-element dimension pointing along the $\hat {z}$ -axis, this subarray steers radiation patterns with the $\overrightarrow {E}$ -field polarized to the $\hat {y}$ -axis between ±40° in both azimuth and elevation with 13.4° and 26.4° measured 3-dB beamwidths, respectively.

A novel microwave switch-based LLRF system for long-term system phase drift calibration

Long-term phase stability is a significant issue for Low-level RF systems. Crosstalk and temperature effect on the RF field detectors would significantly limit the performance of phase detecting and phase locking. A novel microwave switch-based LLRF system has been developed in Tsinghua Accelerator Lab. Microwave switches are applied in the chopper circuit to turn continuous waves into pulse waves in the time domain to avoid mutual interference of signals. In this paper, the LLRF sys-tem based on microwave switches is presented. The result of preliminary long-term experiments shows the phase stability can achieve about 50fs RMS slow drift. The peak-to-peak value of the slow drift was ~100fs (~2 °C p-p) in 4 days.

Microwave Synthesis for the PTB Cesium Fountain Clocks

Microwave synthesizers that are used to generate microwave signals for the CSF1 and CSF2 fountain clocks at the Physikalisch-Technische Bundesanstalt (PTB) are described. The synthesizers are based on a divider chain and a digital frequency synthesis and have been designed for use with an optically stabilized microwave oscillator. They have been designed in a modular fashion to assure long-term operation and low down times. The results of an in-depth examination of spectral purity, phase noise, and long-term phase stability are presented. Also, the implications of measured parameters on the fountain timing are assessed. Two methods of suppressing the frequency-shifting effect of microwave leakage fields are implemented, with one method in each synthesizer. The first method uses an interferometric switch, and the second uses a phase-coherent and phase-preserving frequency detuning scheme; their contribution to the systematic uncertainty of the fountains is assessed. The overall systematic uncertainty contribution associated with the fountain electronics is below $1 \times 10^{-17}$ for both fountain clocks.

Development of vacuum impregnation equipment and preparation of mass/uniform shape-stabilized phase change materials

Various industries require production equipment for uniform mass-production short periods of time, such as in the construction industry. This study presents vacuum impregnation equipment that is capable of mass-producing uniform, shape-stabilized PCM (MUSPCM). The vacuum impregnation equipment can manufacture MUSPCM of various diameters without additional filtering and crushing process because the mixing ratio of the SSPCM was analyzed beforehand through a TGA analysis. As the result, MUSPCM using vacuum impregnation equipment can save 32.5 times based on production of 15.0 kg compared to conventional vacuum impregnation. In addition, the analysis of the thermo-physical properties and long-term stability of the MUSPCM were characterized via DSC and TGA analysis. The results indicate that a large amount of uniform MUSPCM were produced, and the long-term phase stability was excellent. Therefore, the developed vacuum impregnation equipment is expected to be useful in various industries, including construction.

Direct Laser Writing of δ- to α-Phase Transformation in Formamidinium Lead Iodide

Organolead halide perovskites are increasingly considered for applications well beyond photovoltaics, for example, as the active regions within photonic devices. Herein, we report the direct laser writing (DLW: 458 nm cw-laser) of the formamidinium lead iodide (FAPbI3) yellow δ-phase into its high-temperature luminescent black α-phase, a remarkably easy and scalable approach that takes advantage of the material’s susceptibility to transition under ambient conditions. Through the DLW of α-FAPbI3 tracks on δ-FAPbI3 single-crystal surfaces, the controlled and rapid microfabrication of highly luminescent structures exhibiting long-term phase stability is detailed, offering an avenue toward the prototyping of complex perovskite-based optical devices. The dynamics and kinetics of laser-induced δ- to α-phase transformations are investigated in situ by Raman microprobe analysis, as a function of irradiation power, time, temperature, and atmospheric conditions, revealing an interesting connection between oxygen intercalation at the surface and the δ- to α-phase transformation dynamics, an insight that will find application within the wider context of FAPbI3 thermal phase relations.

Long-Term Gamma Prime Phase Stability after Various Heat Treatment Conditions with Temperature Dropping during Solution Treatment in Cast Nickel Base Superalloy, Grade Inconel-738

Cast nickel based superalloy, Grade Inconel 738, is a material for turbine blades. Its rejuvenation heat treatment usually consist of solution treatment condition with temperature range of 1125-1205 oC for 2-6 hours. Then it is following with double aging process including primary aging at 1055oC for 1 hour and secondary aging at 845oC for 24 hours. However, the various selected temperature dropping program were performed during solution treatment to simulate the possible error of heating furnace. The maximum number of temperature dropping during solution treatment is varied from 1-3 times From all obtained results, the various temperature dropping during solution treatment conditions showed extremely the significant effect on the final rejuvenated microstructures and long-term gamma prime stability after heating at temperature of 900oC for 200 hours.