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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

In situ characterization of metastable Pb3O5 and Pb2O3 phases during thermal decomposition of PbO2 to PbO

Nonstoichiometric lead oxides play a key role in the formation and cycling of the positive electrodes in a lead acid battery. These phases have been linked to the underutilization of the positive active material but also play a key role in the battery’s cycle life, providing inter-particle adhesion and the connection to the underlying lead grid. Similar phases have previously been identified by mass loss or color change during thermal annealing of PbO2 to PbO, suggesting that at least two intermediate PbOx phases exist. Using multiple in situ analysis techniques (powder diffraction, x-ray absorption, x-ray photoelectron spectroscopy) and ex situ nuclear magnetic resonance measurements, the structural conversion and changes in the lead oxidation states were identified during this process. Isolation of the PbOx phases enabled confirmation of Pb3O5 and Pb2O3 by diffraction and the first 207Pb NMR measurement of these intermediates.

Kinnibrugh, Tiffany L.↗
DOE OSTI2024

Low temperature atomic layer deposition of PbO 2 for electrochemical applications

A low temperature atomic layer deposition (ALD) process for PbO 2 was developed using bis(1-dimethylamino-2-methyl-2-propanolate)lead(II), Pb(DMAMP) 2 , and O 3 as the reactants, with a high growth rate of 2.6 Å/cycle. PbO 2 readily reduces under low oxygen partial pressures at moderate temperatures making it challenging to deposit ALD PbO 2 from Pb 2+ precursors. However, thin films deposited with this process showed small crystalline grains of α-PbO 2 and β-PbO 2 , without signs of reduced PbO x phases. The ALD PbO 2 thin films show the high electrical conductivity characteristic of bulk PbO 2 . In situ measurements of ALD PbO 2 film conductivity during growth suggest a reaction mechanism by which sub-surface oxygen mobility contributes to the growth of resistive PbO or PbO x during the Pb(DMAMP) 2 surface reaction step, which is only fully oxidized from Pb 2+ to Pb 4+ during the O 3 reaction step. These films were electrochemically reduced to PbSO 4 in H 2 SO 4 and then reoxidized to PbO 2 , demonstrating their suitability for use as an electrode material for fundamental battery research and other electrochemical applications.

atomic layer deposition↗
DOE OSTI2022

Spin–orbit configuration interaction study of spectral properties of PbO

Relativistic calculations of the structural and spectral properties of the PbO molecule can provide fundamental information about the importance of a proper treatment of angular momentum coupling among electrons in order to achieve accurate computational results for spectral properties. Specifically, the nature of these couplings in PbO is expected to be intermediate between the LS- and jj-coupling limits because of its light/heavy element composition. This article reports potential energy curves, transition energies, electric dipole transition moments, permanent dipole moments and spectroscopic constants of PbO calculated using a multireference single plus double excitations spin–orbit configuration interaction approach in the context of relativistic effective core potentials and their concomitant spin–orbit coupling operators. The calculated results are in general agreement with both available experimental results as well as earlier calculations. New values for properties of excited states are also reported. It is noteworthy that certain properties show larger deviations from previous calculations. Furthermore, these deviations are attributed to direct and indirect relativistic effects resulting from diatomic electron–electron angular momentum coupling effects, which are included consistently in the calculations reported herein.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on PbO by Materials Project

PbO is lead oxide structured and crystallizes in the tetragonal P4/nmm space group. The structure is two-dimensional and consists of one PbO sheet oriented in the (0, 0, 1) direction. Pb2+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Pb–O bond lengths are 2.35 Å. O2- is bonded to four equivalent Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PbO by Materials Project

PbO is TlF-II structured and crystallizes in the orthorhombic Pbcm space group. The structure is two-dimensional and consists of one PbO sheet oriented in the (0, 0, 1) direction. Pb2+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent O2- atoms. There are a spread of Pb–O bond distances ranging from 2.26–2.51 Å. O2- is bonded in a distorted see-saw-like geometry to four equivalent Pb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PbO by Materials Project

PbO is TlF-II structured and crystallizes in the orthorhombic Pca2_1 space group. The structure is two-dimensional and consists of one PbO sheet oriented in the (0, 0, 1) direction. Pb2+ is bonded in a distorted T-shaped geometry to three equivalent O2- atoms. There are one shorter (2.25 Å) and two longer (2.26 Å) Pb–O bond lengths. O2- is bonded in a trigonal planar geometry to three equivalent Pb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PbO by Materials Project

PbO crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. Pb2+ is bonded to four O2- atoms to form a mixture of distorted edge and corner-sharing PbO4 tetrahedra. All Pb–O bond lengths are 2.47 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a square co-planar geometry to four equivalent Pb2+ atoms. In the second O2- site, O2- is bonded in a square co-planar geometry to four equivalent Pb2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electrolyte-Induced Restructuring of Acid-Stable Oxygen Evolution Catalysts

Crystalline metal oxide catalysts operating under oxygen evolution reaction (OER) conditions invariably restructure, resulting in active sites with hydroxo/oxo species in an amorphous environment. An increase in the population of terminal hydroxo/oxo species (i.e., edge sites) facilitates proton-coupled electron-transfer (PCET) kinetics for oxygen generation and thus improves catalyst competency. While amorphous films benefit from a greater density of active sites, they suffer from diminished charge transport as compared to that of extended crystalline lattices. Managing this amorphous–crystalline dichotomy is essential when designing OER catalysts, which we highlight with the examination of electrodeposited PbO x materials, which historically are very poor OER catalysts. Along these lines, the presence of phosphate during PbO x electrodeposition truncates the growth of an extended lattice owing to its strong bonding to oxide surfaces to afford an amorphous catalyst film (A-PbO x ) with significant charge-transfer resistance (138 ± 42 Ω) and poor OER kinetics (420 ± 105 mV dec –1 Tafel slope). Conversely, electrodeposition of Pb 2+ in the presence of less coordinating electrolytes such as nitrate affords crystalline β-PbO2 with improved charge-transfer resistance (42.6 ± 1.1 Ω), though still poor OER kinetics (134 ± 36 mV dec –1 Tafel slope). By operating amorphous A-PbOx in less coordinating electrolytes, however, a new partially crystalline material can be generated (μc-PbO x ) with further reduced charge-transfer resistance (33.0 ± 1.4 Ω) and improved OER kinetics (70 ± 15 mV dec –1 Tafel slope). The enhanced OER activity of μc-PbO x is the result of coupling the high edge-site population of an amorphous PbOx phase with crystalline-like charge transport properties. Finally, the ability to use an electrolyte to induce OER activity in an inactive amorphous form of PbO x highlights the benefits of optimizing the amorphous–crystalline phase compositions in the design of active OER catalysts.

catalysts↗
DOE OSTI2022

High-pressure phase transitions and melt structure of Pb O 2 : An analog for silica

In situ x-ray diffraction measurements and inverse Monte Carlo simulations of pair distribution functions were used to study the structural response of PbO 2 under pressure and to characterize the local structure of liquid PbO 2 . Two phase transitions are observed upon room-temperature compression of crystalline PbO 2 up to ~65 GPa. Here, the starting mixture of rutile structured β– PbO 2 and orthorhombic α– PbO 2 undergoes a transition to a ZrO 2 -type orthorhombic phase with space group Pbca at ~21 GPa. Above 42 GPa, the Pbca phase transforms to a cotunnite-type phase with space group Pnam. In this paper, we also report short-range order in liquid PbO 2 , showing ~8–9-fold and 4–5-fold coordination around Pb and O atoms, respectively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Do Piperonyl Butoxide Long-Lasting Insecticide Treated Nets Provide Additional Protection Against Malaria Infections Compared with Conventional Nets in an Operational Setting in Western Kenya?

Malaria control in sub-Saharan Africa has stagnated despite widespread adoption of control measures such as long-lasting insecticidal nets (LLINs). Progress has stalled, in part, because of pyrethroid insecticide resistance, driving the need for retooling to increase the effectiveness of bed nets. Consequently, LLINs have been treated with the chemical synergist piperonyl butoxide (PBO). Piperonyl butoxide LLINs have been shown to be efficacious in controlled settings; however, their effectiveness in real-world settings warrants investigation. In Bungoma County, Western Kenya, a cohort of 768 participants was followed from June 2017 to December 2023 via active and passive surveillance. Household visits were conducted monthly, during which LLIN use for nets distributed in 2017 and 2021 was recorded, and symptomatic malaria cases were identified using rapid diagnostic tests (RDTs). The comparative effectiveness of PBO versus conventional LLINs was assessed in terms of malaria infections. A multilevel logistic regression model was fit with monthly RDT results as the dependent variable. The study results indicate that PBO LLINs provide greater protection against malaria at the individual level than conventional LLINs (odds ratio: 0.70; 95% CI: 0.47–1.03), although the findings were not statistically significant. The added protection against malaria infections provided by PBO LLINs compared with conventional LLINs observed in the current study aligns with findings from most previous studies, although this finding was not statistically significant. In areas with documented pyrethroid resistance, the use of LLINs with an added synergist, such as PBO, can provide additional protection against malaria infections (compared with pyrethroid-only LLINs) and should be considered for scaled-up scenarios despite the additional cost.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Excellent antioxidizing, thermally insulating and flame resistance silica‐polybenzoxazine aerogels for aircraft ablative materials

Abstract High‐performance thermal protective composites with lightweight, micro‐ ablation and high‐efficient thermal insulation are urgently required for thermal protection systems in advanced hypersonic speed vehicles. However, the practical applications of thermal protective composites have long been hampered by the main issues such as low mass residual rate and poor long‐term antioxidation of the matrix in high‐temperature aerobic environments. Here, we report a novel silica‐polybenz oxazine (SiO 2 ‐PBO) aerogels with interpenetrated networks, possessing the ability to antioxidation, thermal insulation, and flame‐retardant properties. The resulting SiO 2 ‐PBO aerogels exhibit low density (0.25 g/cm 3 ), low thermal conductivity (0.035 W/(m·K)), and superior peak heat release rate value (15.3 W/g). Moreover, the mass residual rate is up to 70.46 wt% in the N 2 atmosphere and remains 57.83 wt% despite existing in the air atmosphere and experiencing the highest temperature of 800°C. Briefly, SiO 2 ‐PBO aerogels as‐prepared could be a potential matrix for a new gene ration of high‐performance thermal protective composites in the future.

Xiao, Yunyun↗
DOE OSTI2022

Study of alkaline carbonate cooling to mitigate Ex-Vessel molten corium accidents

To mitigate adverse effects from molten corium following a reactor pressure vessel failure (RPVF), some new reactor designs employ a core catcher and a sacrificial material (SM), such as ceramic or concrete, to stabilize the molten corium and avoid containment breach. Existing reactors cannot easily be modified to include these SMs but could be modified to allow injectable cooling materials. Current reactor designs are limited to using water to stabilize the corium, but this can create other issues such as reaction of water with the concrete forming hydrogen gas. Here the novel SM proposed is a granular carbonate mineral that can be used in existing light water reactor plants. The granular carbonate will decompose when exposed to heat, inducing an endothermic reaction to quickly solidify the corium in place and producing a mineral oxide and carbon dioxide. Corium spreading is a complex process strongly influenced by coupled chemical reactions, including decay heat from the corium, phase change, and reactions between the concrete containment and available water. A recently completed Sandia National Laboratories laboratory directed research and development (LDRD) project focused on two research areas: experiments to demonstrate the feasibility of the novel SM concept, and modeling activities to determine the potential applications of the concept to actual nuclear plants. Small-scale experiments using lead oxide (PbO) as a surrogate for molten corium demonstrate that the reaction of the SM with molten PbO results in a fast solidification of the melt due to the endothermic carbonate decomposition reaction and the formation of open pore structures in the solidified PbO from CO 2 released during the decomposition. A simplified carbonate decomposition model was developed to predict thermal decomposition of carbonate mineral in contact with corium. This model was incorporated into MELCOR, a severe accident nuclear reactor code. A full-plant MELCOR simulation suggests that by the introduction of SM to the reactor cavity prior to RPVF ex-vessel accident progression, e.g., core-concrete interaction and core spreading on the containment floor, could be delayed by at least 15 h; this may be enough for additional accident management to be implemented to alleviate the situation.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2020

Materials Data on Pb2ClO2 by Materials Project

(PbO)4Cl2 crystallizes in the tetragonal I4/mmm space group. The structure is two-dimensional and consists of two hydrochloric acid molecules and two PbO sheets oriented in the (0, 0, 1) direction. In each PbO sheet, Pb is bonded in a 4-coordinate geometry to four equivalent O atoms. All Pb–O bond lengths are 2.35 Å. O is bonded to four equivalent Pb atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H2Pb4SO8 by Materials Project

(H(PbO)2)2SO4 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of two sulfuric acid molecules and one H(PbO)2 ribbon oriented in the (0, 1, 0) direction. In the H(PbO)2 ribbon, there are four inequivalent Pb4+ sites. In the first Pb4+ site, Pb4+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Pb–O bond distances ranging from 2.33–2.37 Å. In the second Pb4+ site, Pb4+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.30–2.71 Å. In the third Pb4+ site, Pb4+ is bonded in a 5-coordinate geometry to three O2- atoms. There are a spread of Pb–O bond distances ranging from 2.28–2.43 Å. In the fourth Pb4+ site, Pb4+ is bonded in a 3-coordinate geometry to three O2- atoms. There are one shorter (2.34 Å) and two longer (2.40 Å) Pb–O bond lengths. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three Pb4+ and one H1+ atom. In the second O2- site, O2- is bonded to four Pb4+ atoms to form a mixture of corner and edge-sharing OPb4 tetrahedra. In the third O2- site, O2- is bonded in a single-bond geometry to two Pb4+ and one H1+ atom. In the fourth O2- site, O2- is bonded to four Pb4+ atoms to form a mixture of corner and edge-sharing OPb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HPb3ClO3 by Materials Project

(H(PbO)3)2Cl2 crystallizes in the orthorhombic Pmc2_1 space group. The structure is two-dimensional and consists of four hydrochloric acid molecules and one H(PbO)3 sheet oriented in the (0, 1, 0) direction. In the H(PbO)3 sheet, there are six inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.22 Å) and one longer (2.45 Å) Pb–O bond lengths. In the second Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to four O2- atoms. There are two shorter (2.43 Å) and two longer (2.45 Å) Pb–O bond lengths. In the third Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.30 Å) and one longer (2.41 Å) Pb–O bond lengths. In the fourth Pb2+ site, Pb2+ is bonded in a 7-coordinate geometry to four O2- atoms. There are two shorter (2.42 Å) and two longer (2.43 Å) Pb–O bond lengths. In the fifth Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.25 Å) and one longer (2.38 Å) Pb–O bond lengths. In the sixth Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.30 Å) and one longer (2.37 Å) Pb–O bond lengths. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of corner and edge-sharing OPb4 tetrahedra. In the second O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of corner and edge-sharing OPb4 tetrahedra. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two Pb2+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two Pb2+ and one H1+ atom.

36 MATERIALS SCIENCE↗