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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

High-resolution characterization of ceramic-metal interface of TiN coating on ferritic-steels for nuclear application

Advanced fuel cladding is critical for fast reactors, offering sufficient thermal conductivity, mechanical and dimensional stability and radiation tolerance of the cladding base material. Additionally, it must provide corrosion resistance and high temperature coolant compatibility on the cladding outer surface, as well as chemical stability on the cladding inner wall against fuel cladding chemical interaction (FCCI). TiN ceramic coating has been considered an effective diffusion barrier for inner and outer cladding-walls for enhanced performance. The TiN-metal interface microstructure and chemistry play a critical role in coating bond strength and integrity under harsh conditions. High-resolution transmission electron microscopy characterization of ceramic-metal interface at atomic resolution in unirradiated, irradiated and thermal cycled conditions were performed. The interface remained intact after irradiation up to 200 dpa or thermal cycling five times up to 550 °C. In conclusion, this work discusses the potential impact of these results on coating performance and design for advanced claddings.

36 - MATERIALS SCIENCE↗
DOE OSTI2015

Characterization of TiN, TiC and Ti(C,N) in titanium-alloyed ferritic chromium steels focusing on the significance of different particle morphologies

Titanium-alloyed ferritic chromium steels are a competitive option to classical austenitic stainless steels owing to their similar corrosion resistance. The addition of titanium significantly influences their final steel cleanliness. The present contribution focuses on the detailed metallographic characterization of titanium nitrides, titanium carbides and titanium carbonitrides with regard to their size, morphology and composition. The methods used are manual and automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy as well as optical microscopy. Additional thermodynamic calculations are performed to explain the precipitation procedure of the analyzed titanium nitrides. The analyses showed that homogeneous nucleation is decisive at an early process stage after the addition of titanium. Heterogeneous nucleation gets crucial with ongoing process time and essentially influences the final inclusion size of titanium nitrides. A detailed investigation of the nuclei for heterogeneous nucleation with automated Scanning Electron Microscopy proved to be difficult due to their small size. Manual Scanning Electron Microscopy and optical microscopy have to be applied. Furthermore, it was found that during solidification an additional layer around an existing titanium nitride can be formed which changes the final inclusion morphology significantly. These layers are also characterized in detail. Based on these different inclusion morphologies, in combination with thermodynamic results, tendencies regarding the formation and modification time of titanium containing inclusions in ferritic chromium steels are derived. - Graphical abstract: Display Omitted - Highlights: • The formation and modification of TiN in the steel 1.4520 was examined. • Heterogeneous nucleation essentially influences the final steel cleanliness. • In most cases heterogeneous nuclei in TiN inclusions are magnesium based. • Particle morphology provides important information on inclusion formation.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Effect of TiN coating on suppressing Ce-Fe interaction under irradiation

Advanced cladding is critical for fast reactors with the adequate thermal conductivity, mechanical stability and radiation tolerance of the cladding base material, corrosion resistance and high temperature coolant compatibility of the cladding surface, and chemical stability of the cladding inner wall against fuel cladding chemical interaction (FCCI). The preliminary results of recent ion irradiation studies of two diffusion-couple samples of cerium (Ce)/oxide-dispersion strengthened steel (ODS) and Ce/TiN/ODS, irradiated with 80 MeV xenon (Xe) ions to 100 displacements per atom (dpa) at 500°C, are summarized. Significant Ce-Fe interaction occurred in the Ce/ODS sample, and no noticeable Ce-Fe interaction was found in the Ce/TiN/ODS sample. It shows the effectiveness of 1-µm TiN diffusion barrier coated by the pulsed laser deposition on suppressing Ce-Fe interaction, a major contributor to FCCI in cladding. Here, density function theory (DFT) calculations of the impurity diffusivities of Ce and Fe within the Ti sublattice of TiN were performed to assist a mechanistic understanding of the experimental results.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Genetic algorithm optimization of tin–copper graded shielding for improved plutonium safeguards measurements

Plutonium nuclear material safeguards is essential to ensure that states do not divert plutonium to clandestine nuclear weapons programs. Traditional safeguards methods rely on correlated neutron measurements. Detection systems based on organic scintillators, which are sensitive to fast neutrons and photons, are gaining support for use in safeguards applications due to increased capabilities and shorter measurement times compared to the current state-of-the-art. A drawback of organic scintillators in plutonium measurements is data throughput limitations; 241 Am builds up in plutonium samples and emits 60-keV gamma rays with a high specific activity. In this work, a genetic algorithm is used to design graded shielding made of tin and copper to attenuate the 60-keV gamma rays. The shield is designed to limit the attenuation of the higher-energy, fission photons, because fission photons can be used as a signature. The genetic algorithm optimization takes days to run, while a complete search space exploration would take years. The genetic algorithm was run for different levels of 60-keV gamma-ray attenuation, and the thickness of the required shielding layers was determined at each level. Tin–copper shielding was placed in front of an array of organic scintillation detectors for a measurement of approximately 4.5 kg of alpha-phase, weapons-grade plutonium, an AmLi source, and a 252 Cf source. We show that the shield successfully attenuated low-energy, non-fission gamma rays, which significantly improved the organic scintillator performance.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Tin–Lead Alloying for Efficient and Stable All-Inorganic Perovskite Solar Cells

Cesium containing all-inorganic perovskites have received considerable interest in photovoltaics research because of their potential for improved stability compared to their organic-inorganic hybrid counterparts. However, the inorganic perovskites studied thus far still suffer from lower power conversion efficiency and long-term instability, due to an unfavorable bandgap and either phase instability or air-sensitivity. Herein, A strategy to mitigate these concerns is investigated by alloying tin and lead on the B site to form tin-lead alloyed low-bandgap (~1.34 eV) inorganic CsSn 0.3 Pb 0.7 I 3 perovskites. Solar cells made using this material in an inverted full-structured architecture with a PEDOT:PSS hole transport materials (HTM) attain power conversion efficiency (PCE) up to 9.41% (stabilized PCE 7.23%). Furthermore, a simple HTM-free device without PEDOT:PSS layer is demonstrated more stable than the full-structured device and exhibits a PCE of 7.60% (stabilized PCE 7.31%) – the highest efficiency to date for an inorganic perovskite with a bandgap below 1.40 eV. This simplified device structure shows good reproducibility and stability. Finally, this work provides a possible route for fabricating low-cost, high stability devices with competitive efficiencies.

14 SOLAR ENERGY↗
DOE OSTI2020

Electron Beam Infrared Nano-Ellipsometry of Individual Indium Tin Oxide Nanocrystals

Leveraging recent advances in electron energy monochromation and aberration correction, we record the spatially resolved infrared plasmon spectrum of individual tin-doped indium oxide nanocrystals using electron energy-loss spectroscopy (EELS). Both surface and bulk plasmon responses are measured as a function of tin doping concentration from 1–10 atomic percent. Furthermore, these results are compared to theoretical models, which elucidate the spectral detuning of the same surface plasmon resonance feature when measured from aloof and penetrating probe geometries. We additionally demonstrate a unique approach to retrieving the fundamental dielectric parameters of individual semiconductor nanocrystals via EELS. This method, devoid from ensemble averaging, illustrates the potential for electron-beam ellipsometry measurements on materials that cannot be prepared in bulk form or as thin films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Boosting Tin Perovskite Solar Cell Performance via Light-Induced Interface Doping

Continuous breakthroughs have been achieved in the photoelectric conversion efficiency (PCE) of tin-based perovskite solar cells (TPSCs) in recent years. Inspired by performance improvements observed during device storage, we identified beneficial light-induced interface doping (LIID) in the TPSCs. In situ analyses using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy reveal that ion migration and oxidation at the interface induce beneficial doping effects, enhancing carrier transport and significantly boosting device performance. By implementing specific illumination techniques or maximum power point tracking (MPPT) methods to achieve LIID, we increased the open-circuit voltage while maintaining a high short-circuit current, reaching a PCE of up to 14.91%. Furthermore, this efficiency was sustained at 70% of its maximum value after nearly 900 h of continuous operation. Our study introduces a novel approach to addressing energy band mismatch, paving the way for improved efficiency in tin-based perovskite solar cells.

Sun, Mulin↗
DOE OSTI2025

P-Type Doping of Mixed Tin–Lead Halide Perovskites Using Electron Transfer to Mo(tfd-COCF3) 3 and F 4 TCNQ

Mixed tin-lead halide perovskites are emerging as promising candidates to address the toxicity issues of lead-based perovskites and to provide additional bandgap tunability for optoelectronic applications. Electron-transfer doping offers a prospective pathway to modulate electronic properties of metal-halide perovskites, while not disturbing the underlying crystal structure. However, limited research exists comparing molecular dopants for these systems. Here, our study investigates the p-type electron-transfer doping of the mixed tin-lead halide perovskite MAPb 0.5 Sn 0.5 I 3 (MA = methylammonium) using a sequential deposition approach (perovskite film followed by dopant incorporation) and the molecular dopants F 4 TCNQ and Mo(tfd-COCF 3 ) 3 . Up to 3 orders of magnitude higher carrier density and up to 2 orders of magnitude greater conductivity are achieved relative to the undoped samples, with F 4 TCNQ and Mo(tfd-COCF 3 ) 3 demonstrating similar doping efficiencies (associated with the ratio of mobile charges added to the number of dopant molecules incorporated) of 0.031(3) % and 0.024(3) %, respectively. Differences in the doping effectiveness for a given molarity doping solution likely follow from variations in dopant incorporation within the film during the spin coating deposition step.

14 SOLAR ENERGY↗
DOE OSTI2024

Mixed Self-Assembled Monolayers for High-Photovoltage Tin Perovskite Solar Cells

Self-assembled monolayers (SAMs) are used as potent hole transport layers (HTLs) in lead-based perovskite solar cells, enabling large quasi-Fermi level splitting for high photovoltage (>1.1 V) with a deficit of <0.5 V. However, tin-based perovskite solar cells (TPSCs) with SAM HTLs suffer from low photovoltage (<0.65 V) with a deficit of >0.7 V. Herein we employ a holistic approach to tackle this significant challenge by designing a mixed SAM, engineering a compatible tin perovskite thin film, and leveraging an efficient electron transport layer. Consequently, high photovoltage of 0.829 V is achieved with an efficiency of 9.4%, which is a record to our knowledge among TPSCs using SAMs as sole HTLs. Finally, while SAMs have been little used in TPSCs thus far, our holistic approach should catalyze their future advancements toward outperformance.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Unraveling the Formation Mechanisms of Highly Oriented Tin Perovskite with a 3D-over-2D Heterostructure

Tin-based perovskites (TinPVKs) have become the most promising candidates for lead-free perovskite solar cells, owing to its low toxicity and improved photovoltaic performance. However, due to the absence of 4f shell, TinPVKs suffer from uncontrolled crystallization, limiting the power conversion efficiency (PCE) of tin perovskite solar cells (TinPSCs). Here, we systematically study the ligand regulated crystallization process of TinPVK. We find that with elongated spin time, TinPVK crystals undergo reorientation and lateral growth. 3D α-phase FASnI3 and 2D (n = 2) and 2D (n = 1) phases emerge sequentially to form a “3D-over-2D” heterostructure via a proposed “diffusion-propagation” mechanism. TinPSCs exhibit improved open circuit voltage (V OC ) due to favorable energy level alignment of the 3D-over-2D heterostructure, with a champion PCE value of 13.07% and T 80 value of over 1200 h. Furthermore, this work provides mechanistic insights on controlled crystallization and heterostructure formation of TinPVKs, paving the way toward high-efficiency TinPSCs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Performance Enhancement of Lead-Free Tin-Based Perovskite Solar Cells with Reducing Atmosphere-Assisted Dispersible Additive

Sn-based halide perovskite materials have attracted tremendous attention and have been employed successfully in solar cells. However, their high conductivities resulting from the unstable divalent Sn state in the structure cause poor device performance and poor reproducibility. Herein, we used excess tin iodide (SnI 2 ) in Sn-based halide perovskite solar cells (ASnI 3 , A = Cs, methylammonium and formamidinium tin iodide as the representative light absorbers), combined with a reducing atmosphere to stabilize the Sn 2+ state. Excess SnI 2 can disperse uniformly into the perovskite films and functions as a compensator as well as a suppressor of Sn 2+ vacancies thereby effectively reducing the p-type conductivity. This process significantly improved the solar-cell performances of all the ASnI3 materials on mesoporous TiO 2 . Optimized CsSnI3 devices achieved a maximum power conversion efficiency of 4.81%, which is the highest among all inorganic Pb-free perovskite solar cells to date.

14 SOLAR ENERGY↗
DOE OSTI2020

Highly Distorted Chiral Two-Dimensional Tin Iodide Perovskites for Spin Polarized Charge Transport

Incorporating chiral organic molecules into organic/inorganic hybrid 2D-layered metal-halide perovskites results in a novel family of chiral hybrid semiconductors with unique spin-dependent properties. The embedded chiral organic moieties induce a chiroptical response from the inorganic metal-halide sublattice. However, the structural interplay between the chiral organic molecules and the inorganic sublattice, as well as their synergic effect on the resulting electronic band structure need to be explored in a broader material scope. Here we present three new layered tin iodide perovskites templated by chiral ( R/S -)methylbenzylammonium ( R/S -MBA), i.e. ( R-/S -MBA) 2 SnI 4 , and their racemic phase ( rac -MBA) 2 SnI 4 . These MBA 2 SnI 4 compounds exhibit the largest level of octahedral bond distortion compared to any other reported layered tin iodide perovskite. The incorporation of chiral MBA cations leads to circularly polarized absorption from the inorganic Sn–I sublattice, displaying chiroptical activity in the 300–500 nm wavelength range. The bandgap and chiroptical activity are modulated by alloying Sn with Pb, in the series of (MBA) 2 Pb 1-x Sn x I 4 . Finally, we show that vertical charge transport through oriented ( R-/S -MBA) 2 SnI 4 thin films is highly spin-dependent, arising from a chiral-induced spin selectivity (CISS) effect. We demonstrate a spin-polarization in the current-voltage characteristics as high as 94%. Our work shows the tremendous potential of these chiral hybrid semiconductors for controlling both spin and charge degrees of freedom.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Electrochemical Modification of Indium Tin Oxide Using Di(4-nitrophenyl) Iodonium Tetrafluoroborate

Optoelectronic applications typically rely on indium tin oxide (ITO) as a transparent electrode material. Improvements in the performance of such devices as photovoltaics and light-emitting diodes often requires robust, controllable modification of the ITO surface to enhance interfacial charge transfer properties. Here, modifier films were deposited onto ITO by the electrochemical reduction of di(4-nitrophenyl) iodonium tetrafluoroborate (DNP), allowing for control over surface functionalization. The surface coverage could be tuned from submonolayer to multilayer coverage by either varying the DNP concentration or the number of cyclic voltammetry (CV) grafting scans. Modification of ITO with 0.8 mM DNP resulted in near-monolayer surface coverage (4.95 × 10 14 molecules/cm 2 ). X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of 4-nitrophenyl (NO 2 Ph) moieties on the ITO surface through the detection of a NO 2 nitrogen signal at 405.6 eV after grafting. Further XPS evidence suggests that the NO 2 Ph radicals do not bond to the surface indium or tin sites, consistent with modification occurring either through bonding to surface hydroxyl groups or through strong physisorption on ITO. CV in the presence of an electroactive probe and electrochemical impedance spectroscopy (EIS) were used to explore the electronic effects that modification via DNP has on ITO. Even at submonolayer coverage, the insulating organic films can reduce the current response to ferrocene oxidation and reduction by more than 25% and increase the charge transfer resistance by a factor of 10.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Tin-graphene tubes as anodes for lithium-ion batteries with high volumetric and gravimetric energy densities

Limited by the size of microelectronics, as well as the space of electrical vehicles, there are tremendous demands for lithium-ion batteries with high volumetric energy densities. Current lithium-ion batteries, however, adopt graphite-based anodes with low tap density and gravimetric capacity, resulting in poor volumetric performance metric. Here, by encapsulating nanoparticles of metallic tin in mechanically robust graphene tubes, we show tin anodes with high volumetric and gravimetric capacities, high rate performance, and long cycling life. Pairing with a commercial cathode material LiNi0.6Mn0.2Co0.2O2, full cells exhibit a gravimetric and volumetric energy density of 590 W h Kg-1 and 1,252 W h L-1 , respectively, the latter of which doubles that of the cell based on graphite anodes. This work provides an effective route towards lithium-ion batteries with high energy density for a broad range of applications.

25 ENERGY STORAGE↗
DOE OSTI2020

Low-bandgap mixed tin–lead iodide perovskites with reduced methylammonium for simultaneous enhancement of solar cell efficiency and stability

High-performance perovskite/perovskite tandem solar cells require high-efficiency and stable low-bandgap perovskite subcells. State-of-the-art low-bandgap mixed tin–lead iodide perovskite solar cells exhibit either a high power-conversion efficiency or improved stability, but not both. In this article we report a two-step bilayer interdiffusion growth process to simultaneously meet both requirements for formamidinium-based low-bandgap mixed tin–lead iodide perovskite solar cells. The bilayer interdiffusion growth process allows for the formation of high-quality and large-grained perovskite films with only 10 mol% volatile methylammonium. Additionally, one-dimensional pyrrolidinium perovskite was applied to passivate the perovskite film and improve the junction quality, which resulted in a carrier lifetime of 1.1 µs and an open circuit voltage of 0.865 V for our perovskite film and device with a bandgap of 1.28 eV. Our strategies enabled a power-conversion efficiency of 20.4% for low-bandgap perovskite solar cells under AM 1.5G illumination. More importantly, an encapsulated device can retain 92% of its initial efficiency after 450 h of continuous 1 sun illumination.

14 SOLAR ENERGY↗
DOE OSTI2020

Structural trends in atomic nuclei from laser spectroscopy of tin

Tin is the chemical element with the largest number of stable isotopes. Its complete proton shell, comparable with the closed electron shells in the chemically inert noble gases, is not a mere precursor to extended stability; since the protons carry the nuclear charge, their spatial arrangement also drives the nuclear electromagnetism. We report high-precision measurements of the electromagnetic moments and isomeric differences in charge radii between the lowest 1/2 + , 3/2 + , and 11/2 - states in 117–131 Sn, obtained by collinear laser spectroscopy. Supported by state-of-the-art atomic-structure calculations, the data accurately show a considerable attenuation of the quadrupole moments in the closed-shell tin isotopes relative to those of cadmium, with two protons less. Linear and quadratic mass-dependent trends are observed. While microscopic density functional theory explains the global behaviour of the measured quantities, interpretation of the local patterns demands higher-fidelity modelling.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Purely electronic mechanism of electrolyte gating of indium tin oxide thin films

Epitaxial indium tin oxide films have been grown on both LaAlO 3 and yttria-stabilized zirconia substrates using RF magnetron sputtering. Electrolyte gating causes a large change in the film resistance that occurs immediately after the gate voltage is applied, and shows no hysteresis during the charging/discharging processes. When two devices are patterned next to one another and the first one gated through an electrolyte, the second one shows no changes in conductance, in contrast to what happens in materials (like tungsten oxide) susceptible to ionic electromigration and intercalation. These findings indicate that electrolyte gating in indium tin oxide triggers a pure electronic process (electron depletion or accumulation, depending on the polarity of the gate voltage), with no electrochemical reactions involved. Electron accumulation occurs in a very thin layer near the film surface, which becomes highly conductive. These results contribute to our understanding of the electrolyte gating mechanism in complex oxides and may be relevant for applications of electric double layer transistor devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗