National Institute of Standards

The solid electrolyte interphase (SEI) critically governs the reversibility of sodium metal batteries, through dynamically mediating ion transport and interfacial reactions. However, its kinetic evolution under operating conditions, and how it influences interfacial stability, remains poorly understood. Here, we reveal that the SEI undergoes coupled chemical and mechanical changes during sodium plating and stripping, leading to spatial and temporal heterogeneity that drives interfacial degradation. Synchrotron operando grazing-incidence wide-angle X-ray scattering and soft X-ray absorption spectroscopy capture the sequential formation and dissolution of inorganic SEI phases (NaF, NaH, NaOH, Na2PO3F), accompanied by depth-dependent alterations in organic SEI components. Mesoscale modeling connects this evolving SEI heterogeneity to localized current density fluctuations and stress accumulation at the Na interface, identifying pathways to electrically isolated sodium formation. These findings show that SEI instability fundamentally limits reversibility in sodium metal batteries, and that controlling SEI chemistry–mechanics coupling is essential to achieving its durability.

Abstract Broadband and low-loss superconducting switches can facilitate large-scale quantum information processors and cryogenic detectors by dynamically reconfiguring the connectivity of their circuits. The time dependent connectivity is enabled by the nonlinearity of lossless Josephson junctions, which are often wired into superconducting loops to be controlled by magnetic flux. However, this approach needs a power-consuming constant flux bias and dynamic flux actuation, both of which are hard to isolate from other switches or flux sensitive elements, limiting their integration density. Here, we design and characterize a microwave switch that implements a persistent current bias and direct current actuation to reduce static power consumption, actuation energy and potential crosstalk to other devices. We show that persistent current associated with tens of flux quanta is stable and long-lived, reducing the need for on-the-fly tuning. We further demonstrate that our switch has desirable performance for superconducting-circuit-based quantum information processing, including an off mode with more than 20 dB isolation comparable to commercial ferrite isolators, power handling larger than 100 pW sufficient for resonator readout tones and amplifier pumps, and modulation bandwidth broader than 600 MHz useful for multiplexing schemes.

Yb2O3-doped aluminum–lead alkali phosphate glasses with the nominal composition 47P2O5–23Na2O–(24 − x)PbO–6Al2O3–xYb2O3 (x = 0.0, 0.1, 0.5, 1.0, and 3.0 mol%) were fabricated by melt-quenching and investigated using FTIR spectroscopy, ultrasonic pulse-echo measurements, and radiation-shielding calculations. The density slightly decreased from 4235 to 4182 kg·m− 3, while the molar volume increased from 33.21 × 10− 6 to 34.86 × 10− 6 m3·mol− 1 as x increased from 0.0 to 3.0 mol%. The ultrasonic velocities increased with Yb2O3 addition, where the longitudinal velocity rose from 3567 to 3663 m·s− 1 and the shear velocity increased from 2021 to 2089 m·s− 1, indicating a composition-dependent enhancement in elastic response. The Debye temperature increased from 296 to 302 K at the highest Yb2O3 content (3.0 mol%), supporting the observed stiffening trend. FTIR analysis, including band deconvolution, suggests that the phosphate network rearranges upon Yb addition and that modifier-related linkages form. This is in line with the changes in measured ultrasonic parameters that were reported to be caused by changes in composition. Radiation-shielding descriptors tested between 15 keV and 15 MeV show that the glasses we made have a lower half-value layer (HVL) than standard concrete and commercial RS-360 shielding glass. This shows that they could be good materials for shielding gamma rays in a small space.

Desalination membranes are essential for global freshwater production, yet the performance of conventionally synthesized membranes is limited by the lack of synthetic control over the selective film. Solvent-based polymerization methods result in inhomogeneous density, nodular morphology, and the presence of nanoscale defects that hinder salt and boron selectivities. By employing a vapor-phase synthesis strategy, we circumvent the reliance on solvent interfaces to create compositionally homogeneous, defect-free thin-film composite polyamide membranes with Angstrom-level control over thickness. With a structure and thickness defined with nanoscale precision, we measure previously inaccessible properties of membrane selective layers, including intrinsic water and salt permeabilities, and explore the limits of thickness on membrane performance. Membranes with a 12 nm, vapor-synthesized, selective layer exhibit a two-order-of-magnitude reduction in both salt ions and uncharged boron molecules permeabilities, and a twofold improvement in NaCl selectivity relative to commercial desalination membranes. Mechanistic analysis, supported by theoretical modeling and molecular dynamics simulations, demonstrates that salt permeability increases sharply for films thinner than the Bjerrum length, revealing a physical lower bound on selective-layer thickness. These results establish a high-precision platform for probing and optimizing molecular transport in thin-film composite membranes.

Molecular branching, an important characteristic of both synthetic and natural polymers, plays a crucial role in determining the physical properties of polymeric materials. Nevertheless, the mechanisms of how branching affects polymer glass formation are not fully understood. Here, the generalized entropy theory (GET) is extended to study the glass formation of graft polymer melts having variable grafting density. Our theoretical calculations indicate that polymers with a flexible backbone and rigid side chains exhibit opposite trends in the characteristic properties of glass formation compared to other classes of polymers when grafting density is varied, supporting the previous finding that the relative rigidities of backbone and side chains serve as a key factor governing the glass formation of graft polymers. The predictions from the GET are shown to be consistent with molecular dynamics simulation results of a coarse-grained graft polymer melt. Moreover, the GET framework allows us to offer insights into the grafting density dependence of the glass transition temperature (Tg) and fragility (m) from a perspective of packing frustration. Remarkably, the GET predicts universal relations between the change in the extent of collective motion at Tg relative to the polymer fluid in the Arrhenius regime and both Tg and m.

The National Institute of Standards and Technology (NIST) Standard Reference Material® (SRM®)2921a Human Cardiac Troponin Complex delivers a certified value for the concentration of human cardiac troponin I in a solution of the human cardiac troponin complex and the associated uncertainty of the certified value. The material is intended for 1) use in validating measurement procedures and 2) use in qualifying control materials produced in-house and analyzed using measurement methods for the determination of the concentration of human cardiac troponin Iin human blood samples. A unit of SRM 2921a consists of three (3) vials of a frozen aqueous solution of human cardiac troponin complex. This publication documents the production, measurement processes, results, and statistical evaluations involved in the production and certification of SRM 2921a

The National Institute of Standards and Technology (NIST) Standard Reference Material (SRM ) 3666 Albumin and Creatinine in Frozen Human Urine is a secondary measurement standard for albumin and creatinine in human urine.The material is intended for use in a calibration hierarchy, in the validation of measurement procedures, or as quality control material for the determination of albumin, creatinine, or the albumin to creatinine ratio (ACR) in human urine.A unit of SRM 3666 consists of four (4) vials of frozen pooled human urine with four (4) different levels (Level I to Level IV) of endogenous albumin determined using the NIST reference measurement procedure (RMP) for albumin in urine, and creatinine determined using a modification of the NIST RMP for creatinine in serum.The certified values and associated uncertainties for albumin and creatinine were used to calculate the ACR for each level (Level I to Level IV).This publication documents the production, measurement processes, results, and statistical evaluations involved in the production and certification of SRM 3666.