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At least 253 records · Page 14

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DOE OSTI2022

Orientation-controlled crystallization of γ-glycine films with enhanced piezoelectricity

Glycine, the simplest amino acid, is considered a promising functional biomaterial owing to its excellent biocompatibility and strong out-of-plane piezoelectricity. Practical applications require glycine films to be manufactured with their strong piezoelectric polar $\langle$001$\rangle$ direction aligned with the film thickness. Based on the recently-developed solidification approach of a polyvinyl alcohol (PVA) and glycine aqueous solution, in this work, we demonstrate that the crystal orientation of the as-synthesized film is determined by the orientation of glycine crystal nuclei. By controlling the local nucleation kinetics via surface curvature tuning, here we shifted the nucleation site from the edge to the middle of the liquid film, and thereby aligned the $\langle$001$\rangle$ direction vertically. As a result, the PVA–glycine–PVA sandwich film exhibits the highest average piezoelectric coefficient d 33 of 6.13 ± 1.13 pC N –1 . This work demonstrates a promising kinetic approach to achieve crystallization and property control in a scalable biocrystal manufacturing process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Spontaneous Strain Buffer Enables Superior Cycling Stability in Single-Crystal Nickel-Rich NCM Cathode

The capacity degredation in layered Ni-rich LiNixCoyMnzO2 (x >= 0.8) cathode largely originated from drastic surface reactions and intergranular cracks in polycrystalline particles. Herein, we report a highly stable single- crystal LiNi0.83Co0.12Mn0.05O2 cathode material, which can deliver a high specific capacity (similar to 209 mAh g(-1) at 0.1 C, 2.8-4.3 V) and meanwhile display excellent cycling stability (>96% retention for 100 cycles and >93% for 200 cycles). By a combination of in situ X-ray diffraction and in situ pair distribution function analysis, an intermediate monoclinic distortion and irregular H3 stack are revealed in the single crystals upon charging-discharging processes. These structural changes might be driven by unique Li-intercalation kinetics in single crystals, which enables an additional strain buffer to reduce the cracks and thereby ensure the high cycling stability.

in situ synchrotron characterization↗

DOE OSTI2025

Multistage nucleation pathway in LiF molten salt mirrors the crystal–melt interface structure

Despite over a century of studies, fundamental questions remain about the processes governing crystal nucleation from melts or solutions. Research over the past three decades has presented mounting evidence for kinetic pathways of crystal nucleation that are more complex than envisioned by the simplest forms of classical theory. Such observations have been presented for colloidal and elemental systems with covalent and metallic bonding. Despite the technological and geochemical importance of molten salts, similar studies for these ionically bonded systems are currently lacking. Here we develop a machine learning interatomic potential for a model ionic system: LiF. The potential features quantum-level accuracy for both liquid and multiple solid polymorphs over wide temperature and pressure ranges and accurately reproduces experimentally measured properties. Thanks to the efficiency of the potential, which enables microsecond-scale molecular dynamics simulations, induction times for nucleation of LiF solids from their melts are computed over a range of undercoolings. With the aid of a set of robust local order parameters established here, the simulations reveal that homogeneous crystal nucleation in undercooled melts preferentially initiates from liquid regions showing slow dynamics and high bond orientational order simultaneously, and the second-shell order of both precritical nuclei and the surface of postcritical nuclei is dominated by hexagonal close packing and body-centered cubic local structure, even though the nucleus core is dominated by face-centered cubic structure corresponding to the stable rocksalt crystal structure. Finally, we establish a connection between the crystallization pathway and the equilibrium crystal-melt interface structure.

Applied Physical Sciences↗

NASA NTRS2004

Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth: A Preliminary Atomic Force Microscopy Investigation

We examined particulars of crystal growth from measurements obtained at both microscopic and molecular levels. The crystal growth measurements performed at the microscopic level are well characterized by a model that balances the flux of macromolecules towards the crystal surface with the flux of the crystal surface. Numerical evaluation of model with measurements of crystal growth, in time, provided accurate estimates for the average growth velocities. Growth velocities thus obtained were also interpreted using well-established phenomenological theories. Moreover, we find that microscopic measurements of growth velocity measurements obtained as a function of temperature best characterizes changes in crystal growth modes, when present. We also examined the possibility of detecting a change in crystal growth modes at the molecular level using atomic force microscopy, AFM. From preliminary AFM measurements performed at various supersaturations, we find that magnitude of surface height fluctuations, h(x), increases with supersaturation. Further examination of surface height fluctuations using methods established for fluctuation spectroscopy also enabled the discovery of the existence of a characteristic length, c, which may possibly determine the mode of crystal growth. Although the results are preliminary, we establish the non- critical divergence of 5 and the root-mean-square (rms) magnitude of height-height fluctuations as the kinetic roughening transition temperatures are approached. Moreover, we also examine approximate models for interpreting the non-critical behavior of both 6 and rms magnitude of height-height fluctuations, as the solution supersaturation is increased towards the kinetic roughening supersaturation.

Gorti, Sridhar↗

NASA NTRS2004

Protein Crystals and their Growth

Recent results on binding between protein molecules in crystal lattice, crystal-solution surface energy, elastic properties and strength and spontaneous crystal cracking are reviewed and discussed in the first half of this paper (Sea 2-4). In the second par&, some basic approaches to solubility of proteins are followed by overview on crystal nucleation and growth (Sec 5). It is argued that variability of mixing in batch crystallization may be a source for scattering of crystal number ultimately appearing in the batch. Frequency at which new molecules join crystal lattice is measured by kinetic coefficient and related to the observable crystal growth rate. Numerical criteria to discriminate diffusion and kinetic limited growth are discussed on this basis in Sec 7. In Sec 8, creation of defects is discussed with the emphasis on the role of impurities and convection on macromolecular crystal I;erfection.

Chernov, A. A.↗

NASA NTRS1994

Convective flow effects on protein crystal growth

The long-term stability of the interferometric setup for the monitoring of protein morphologies has been improved. Growth or dissolution of a crystal on a 100 A scale can now be clearly distinguished from dimensional changes occurring within the optical path of the interferometer. This capability of simultaneously monitoring the local interfacial displacement at several widely-spaced positions on the crystal surface with high local depth resolution, has already yielded novel results. We found with lysozyme that (1) the normal growth rate is oscillatory, and (2) the mean growth step density is greater at the periphery of a facet than in its center. The repartitioning of Na(+) and Cl(-) ions between lysozyme solutions and crystals was studied for a wide range of crystallization conditions. A nucleation-growth-repartitioning model was developed to interpret the large body of data in a unified way. The results strongly suggests that (1) the ion to lysozyme ratio in the crystal depends mostly on kinetic rather than crystallographic parameters, and (2) lysozyme crystals possess a salt-rich core with a diameter on the order of 10 microns. The computational model for diffusive-convective transport in protein crystallization (see the First Report) has been applied to a realistic growth cell geometry, taking into account the findings of the above repartitioning studies. These results show that some elements of a moving boundary problem must be incorporated into the model in order to obtain a more realistic description. Our experimental setup for light scattering investigations of aggregation and nucleation in protein solutions has been extensively tested. Scattering intensity measurements with a true Rayleigh scatterer produced systematically increased forward scattering, indicating problems with glare. These have been resolved. Preliminary measurements with supersaturated lysozyme solutions revealed that the scatterers grow with time. Work has begun on a computer program for the unified evaluation of simultaneously obtained, multi-angle static and dynamic light scattering data.

Rosenberger, Franz↗

NASA NTRS1988

Two puzzling aspects of protein crystal growth

A study is presented of several mechanisms which may reduce crystal growth rates and or terminate crystal growth. It is found that salt gradients which change the local chemical potential of the protein are insufficient to account for the slow crystal growth rates which have been reported. Contaminants which adsorb protein from solution may reduce the effective protein concentration, but the impurity's concentration and its affinity for protein are unknown. Association of protein molecules in bulk solution can reduce the monomer concentration significantly, but extant theory and experiment are not sensitive enough to determine the actual concentration of aggregates in solution. For systems of interest, shear-induced effects were found to be too weak to interfere with normal binding of incoming protein molecules. Although we found that most crystal growth occurs in a regime where both interfacial kinetics and diffusion influence crystal growth, the role of mass transfer rates on the terminal size of crystals is unknown, primarily because no data exist which cover the size range of interest (0.1 mm to 1 mm in length).

Grant, M. L.↗

NASA NTRS1989

Novel polyimide compositions based on 4,4': Isophthaloyldiphthalic anaydride (IDPA)

A series of twelve high temperature, high performance polyimide compositions based on 4,4'-isophthaloyl diphthalic anhydride (IDPA) was prepared and characterized. Tough, film-forming, organic solvent-insoluble polyimides were obtained. Three materials were semicrystalline. Several gave excellent long-term thermooxidative stability by isothermal thermogravimetric analysis (ITGA) at 300 C and 350 C in air when compared to Kapton H film (duPont). One extensively studied material displayed different levels of semicrystallinity over a wide range of final cure time/temperatures. The polyimide from IDPA and 1,3-bis (4-aminophenoxy 4'-benzoyl) benzene exhibited multiple crystallization and melting behavior, implying the existence of two kinetic and two thermodynamic crystallization and melting transitions by differential scanning calorimetry (DSC).

Pratt, J. Richard↗

NASA NTRS1967

Kinetics of oxide film growth on metal crystals - Electron tunneling and ionic diffusion.

Growth rate of oxide and other dielectric contact films on metal crystals computed for ionic diffusion and electron tunneling

GROWTH↗

NASA NTRSDate not supplied

Investigation of the Reactivity of Calcium Minerals Under Simulated Venus Conditions

The temperature and pressure at the modal radius on Venus is approximately 740K-95.6 bar, while the atmosphere is composed of various volcanic gases such as SO2, OCS, and H2S. Experiments and modeling completed by past researchers have found that these gases can be highly reactive with minerals at Venus conditions. However, the kinetics for many of these reactions have yet to be constrained by experiments. In this project we will research the effects of simulated Venus conditions on the stability of calcium minerals. In particular, we will focus on experiments with exposure to SO2 due to its reactivity with calcium. Additionally, we have selected several minerals that form under different geologic processes to investigate the effects of crystal lattice on kinetics.

S T Port↗

NASA NTRSDate not supplied

Investigation of the Reactivity of Calcium Minerals Under Simulated Venus Conditions

S T Port↗

NASA NTRS1985

Bulk Formation of Metallic Glasses and Amorphous Silicon from the Melt

By using metallic glass compositions with a high relative glass transition temperature, such as Pd40Ni40P20, homogeneous nucleation also becomes negligible. Large (5g) masses of this alloys were obtained using a molten B2O3 flux. Presently, bulk glass formation in iron based glasses is being investigated. It is expected that if an undercooling of about 250K can be achieved in a Ge or Si melt, formation of the amorphous semiconductor phase (rather than the crystal) may be kinetically favored. The volumetric behavior of undercooled liquid Ga droplet dispersion is investigated by dilatometry. A theoretical model (both analytical and numerical) was developed for transient nucleation in glass forming melts. The model, originally designed for isothermal conditions, was extended to continuous quenching. It is being applied to glass formation in various metallic and oxide systems. A further refinement will be the inclusion of diffusion controlled interfacial rearrangements governing the growth of the crystal embryos.

Spaepen, F.↗

DOE OSTI2024

Halide Perovskites Breathe Too: The Iodide–Iodine Equilibrium and Self-Doping in Cs 2 SnI 6

The response of an oxide crystal to the atmosphere can be personified as breathing-a dynamic equilibrium between O 2 gas and O 2– anions in the solid. We characterize the analogous defect reaction in an iodide double-perovskite semiconductor, Cs 2 SnI 6 . Here, I 2 gas is released from the crystal at room temperature, forming iodine vacancies. The iodine vacancy defect is a shallow electron donor and is therefore ionized at room temperature; thus, the loss of I2 is accompanied by spontaneous n-type self-doping. Conversely, at high I 2 pressures, I 2 gas is resorbed by the perovskite, consuming excess electrons as I 2 is converted to 2I – . Halide mobility and irreversible halide loss or exchange reactions have been studied extensively in halide perovskites. However, the reversible exchange equilibrium between iodide and iodine [2I – (s) ↔ I 2(g) + 2e – ] described here has often been overlooked in prior studies, though it is likely general to halide perovskites and operative near room temperature, even in the dark. An analysis of the 2I – (s) /I 2(g) equilibrium thermodynamics and related transport kinetics in single crystals of Cs 2 SnI 6 therefore provides insight toward achieving stable composition and electronic properties in the large family of iodide perovskite semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Sr(Ag 1− x Li x ) 2 Se 2 and [Sr 3 Se 2 ][(Ag 1− x Li x ) 2 Se 2 ] Tunable Direct Band Gap Semiconductors

Abstract Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid‐state reactions, leading to crystal formation of kinetically stable compounds. In this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two‐dimensional Sr(Ag 1− x Li x ) 2 Se 2 layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag 1− x Li x ) 2 Se 2 with x up to 0.45. In addition, a new type of intergrowth compound [Sr 3 Se 2 ][(Ag 1− x Li x ) 2 Se 2 ] was synthesized upon further reaction of Sr(Ag 1− x Li x ) 2 Se 2 with SrSe. Both Sr(Ag 1− x Li x ) 2 Se 2 and [Sr 3 Se 2 ][(Ag 1− x Li x ) 2 Se 2 ] exhibit a direct band gap, which increases with increasing Li substitution ( x ). Therefore, the band gap of Sr(Ag 1− x Li x ) 2 Se 2 can be precisely tuned via fine‐tuning x that is controlled by only the flux ratio and temperature.

Zhou, Xiuquan↗

DOE OSTI2023

Sr(Ag 1-x Li x ) 2 Se 2 and [Sr 3 Se 2 ][(Ag 1-x Li x ) 2 Se 2 ] Tunable Direct Band Gap Semiconductors

Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid-state reactions, leading to crystal formation of kinetically stable compounds. Here, in this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two-dimensional Sr(Ag 1-x Li x ) 2 Se 2 layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag 1-x Li x ) 2 Se 2 with x up to 0.45. In addition, a new type of intergrowth compound [Sr 3 Se 2 ][(Ag 1-x Li x ) 2 Se 2 ] was synthesized upon further reaction of Sr(Ag 1-x Li x ) 2 Se 2 with SrSe. Both Sr(Ag 1-x Li x ) 2 Se 2 and [Sr 3 Se 2 ][(Ag 1-x Li x ) 2 Se 2 ] exhibit a direct band gap, which increases with increasing Li substitution (x). Therefore, the band gap of Sr(Ag 1-x Li x ) 2 Se 2 can be precisely tuned via fine-tuning x that is controlled by only the flux ratio and temperature.

2D materials↗

DOE OSTI2024

In Situ Alloying Enabled by Active Liquid Metal Filler for Self‐Healing Composite Polymer Electrolytes

Abstract Solid inorganics, known for kinetically inhibiting polymer crystallization and enhancing ionic conductivity, have attracted significant attention in solid polymer electrolytes. However, current composite polymer electrolytes (CPEs) are still facing challenges in Li metal batteries, falling short of inhibiting severe dendritic growth and resulting in very limited cycling life. This study introduces Ga 62.5 In 21.5 Sn 16 (Galinstan) liquid metal (LM) as an active liquid alternative to conventional passive solid fillers, aiming at realizing self‐healing protection against dendrite problems. Compared to solid inorganics, for example silica, LM droplets could more significantly reduce polymer crystallinity and enhance Li‐ion conductivity due to their liquid nature, especially at temperatures below the polymer melting point. More importantly, LMs are unraveled as dynamic chemical traps, which are capable of blocking and consuming lithium dendrites upon contact via in situ alloying during battery operation and further inhibiting dendritic growth due to the lower deposition energy barrier of the formed Li‐LM alloy. As a proof of concept, by strategically designing an asymmetric CPE with the active LM filling, a solid‐state Li/LiFePO 4 battery achieves promising full‐cell functionality with notable rate performance and stable cycle life. This active filler‐mediated self‐healing approach could bring new insights into the battery design in versatile solid‐state systems.

Wu, Kai↗

DOE OSTI2020

Factors Defining the Intercalation Electrochemistry of CaFe 2 O 4 -Type Manganese Oxides

Oxides with the CaFe 2 O 4 -type structure have been predicted as being suitable hosts for reactions of intercalation of light cations such as Li and Mg because of their favorable cationic diffusion. Although Li has been shown to intercalate into the Mn 2 O 4 variant, the key structure property correlations determining function are not fully ascertained. This basic information is needed before attempting the intercalation of divalent cations, which face comparably higher migration barriers. For this purpose, here the electrode function of CaFe 2 O 4 -type Li 0.8 Mn 2 O 4 was compared for materials made by a direct high-pressure route or through cation exchange from NaMn 2 O 4 . X-ray diffraction and absorption spectroscopy revealed that, despite having largely the same bulk structure, the presence of surface defects blocked Li + transfer in Li 0.8 Mn 2 O 4 made at high pressure. These defects were not present in the cation-exchanged material, which resulted in highly reversible Li intercalation with very fast kinetics in micrometric crystals. Delithiated electrodes from the cation-exchange synthesis were subsequently reduced in an ionic liquid electrolyte containing Mg 2+ . The process induced topotactic changes in the bulk, strongly suggesting the existence of intercalation, but it is accompanied by severe reactivity with the electrolyte that impedes reversibility. This study uncovers that defects affect the fundamentals of cation intercalation in this novel class of materials. The ability of the cation-exchanged material to conduct fast reactions with Li is consistent with calculated activation energy barriers and creates promise for their use as Mg hosts, provided that novel electrolytes enhanced stability at high potential can be realized.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Isotope effects on the structural transformation and relaxation of deeply supercooled water

Herein, we have examined the structure of supercooled liquid D 2 O as a function of temperature between 185 and 255 K using pulsed laser heating to rapidly heat and cool the sample on a nanosecond timescale. The liquid structure can be represented as a linear combination of two structural motifs, with a transition between them described by a logistic function centered at 218 K with a width of 10 K. The relaxation to a metastable state, which occurred prior to crystallization, exhibited nonexponential kinetics with a rate that was dependent on the initial structural configuration. When the temperature is scaled by the temperature of maximum density, which is an isostructural point of the isotopologues, the structural transition and the non-equilibrium relaxation kinetics of D 2 O agree remarkably well with those for H 2 O.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗