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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Thermally evaporated methylammonium tin triiodide thin films for lead-free perovskite solar cell fabrication

Here, we report on the synthesis of methylammonium tin triiodide (MASnI 3 ) thin films at room temperature by a hybrid thermal evaporation method and their application in fabricating lead (Pb)-free perovskite solar cells. The as-deposited MASnI 3 thin films exhibit smooth surfaces, uniform coverage across the entire substrate, and strong crystallographic preferred orientation along the < 100 > direction. By incorporating this film with an inverted planar device architecture, our Pb-free perovskite solar cells are able to achieve an open-circuit voltage ( V oc ) up to 494 mV. The relatively high V oc is mainly ascribed to the excellent surface coverage, the compact morphology, the good stoichiometry control of the MASnI 3 thin films, and the effective passivation of the electron-blocking and hole-blocking layers. Finally, our results demonstrate the potential capability of the hybrid evaporation method to prepare high-quality Pb-free MASnI 3 perovskite thin films which can be used to fabricate efficient Pb-free perovskite solar cells.

14 SOLAR ENERGY↗
DOE OSTI2018

Evaporation-induced monolayer compression improves droplet interface bilayer formation using unsaturated lipids

In this paper, we report on a new experimental methodology to enable reliable formation of droplet interface bilayer (DIB) model membranes with two types of unsaturated lipids that have proven difficult for creating stable DIBs. Through the implementation of a simple evaporation technique to condition the spontaneously assembled lipid monolayer around each droplet, we increased the success rates of DIB formation for two distinct unsaturated lipids, namely 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), from less than 10% to near 100%. Separately, using a pendant drop tensiometer, we learned that: (a) DOPC and POPC monolayers do not spontaneously assemble into their tightest possible configurations at an oil-water interface, and (b) reducing the surface area of a water droplet coated with a partially packed monolayer leads to a more tightly packed monolayer with an interfacial tension lower than that achieved by spontaneous assembly alone. We also estimated from Langmuir compression isotherms obtained for both lipids that the brief droplet evaporation procedure prior to DIB formation resulted in a 6%–16% reduction in area per lipid for DOPC and POPC, respectively. Lastly, the increased success rates of formation for DOPC and POPC DIBs enabled quantitative characterization of unsaturated lipid membrane properties including electrical resistance, rupture potential, and specific capacitance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Evaporation and scattering of neon, methane, and water from a dodecane flat liquid jet

The evaporation and scattering of Ne, CD 4 , and D 2 O from a dodecane flat liquid jet are investigated in a molecular beam apparatus. The experiment yields translational energy distributions as a function of scattering angle by means of a rotatable mass spectrometer. In the evaporation experiments, one observes a Maxwell–Boltzmann distribution with a cos $θ$ angular distribution superimposed on a weak, isotropic background. The scattering experiments show contributions from impulsive scattering and thermal desorption. At select incident angles for the three systems, angular distributions show super-specular scattering for the impulsive scattering channel, an effect attributed to anisotropic momentum transfer to the liquid surface. The impulsive scattering channel is analyzed with a soft-sphere model to explore energy transfer between the scatterer and liquid as a function of deflection angle. In conclusion, compared to Ne scattering, the polyatomic gases exhibit more thermal desorption and, in the impulsive scattering channel, a higher degree of internal excitation.

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

NANO- AND MICROSTRUCTURES FOR THIN-FILM EVAPORATION-A REVIEW

Evaporation from thin films is a key feature of many processes, including energy conversion, microelectronics cooling, boiling, perspiration, and self-assembly operations. The phase change occurring in these systems is governed by transport processes at the contact line where liquid, vapor, and solid meet. Evidence suggests that altering the surface chemistry and surface topography on the micro-and the nanoscales can be used to dramatically enhance vaporization. The 2013 International Workshop on Micro- and Nanostructures for Phase-Change Heat Transfer brought together a group of experts to review the current state-of-the-art and discuss future research needs. This article is focused on the thin-film evaporation panel discussion and outlines some of the key principles and conclusions reached by that panel and the workshop attendees.

Plawsky, JL↗
DOE OSTI2013

THE DISK EVAPORATION MODEL FOR THE SPECTRAL FEATURES OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

Observations show that the accretion flows in low-luminosity active galactic nuclei probably have a two-component structure with an inner, hot, optically thin, advection-dominated accretion flow (ADAF) and an outer, truncated, cool, optically thick accretion disk. As shown by Taam et al., the truncation radius as a function of mass accretion rate is strongly affected by including the magnetic field within the framework of disk evaporation model, i.e., an increase in the magnetic field results in a smaller truncation radius of the accretion disk. In this work, we calculate the emergent spectrum of an inner ADAF + an outer truncated accretion disk around a supermassive black hole based on the prediction by Taam et al.. It is found that an increase in the magnetic field from β = 0.8 to β = 0.5 (with magnetic pressure p{sub m} = B {sup 2}/8π = (1 – β)p{sub tot}, p{sub tot} = p{sub gas} + p{sub m}) results in a factor of ∼8.7 increase in the luminosity from the truncated accretion disk. Meanwhile, results of the peak emission of the truncated accretion disk shift toward a a factor of ∼5 higher frequency. We found that the equipartition of gas pressure to magnetic pressure, i.e., β = 0.5, failed to explain the observed anti-correlation between L{sub 2-10{sub keV}}/L{sub Edd} and the bolometric correction κ{sub 2-10{sub keV}} (with κ{sub 2-10{sub keV}} = L{sub bol}/L{sub 2-10{sub keV}}). The emergent spectra for larger values of β = 0.8 or β = 0.95 can explain the observed L{sub 2-10{sub keV}}/L{sub Edd}-κ{sub 2-10{sub keV}} correlation. We argue that in the disk evaporation model, the electrons in the corona are assumed to be heated only by a transfer of energy from the ions to electrons via Coulomb collisions, which is reasonable for accretion with a lower mass accretion rate. Coulomb heating is the dominated heating mechanism for the electrons only if the magnetic field is strongly sub-equipartition, which is roughly consistent with observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Updated constraints on primordial black hole evaporation

The Hawking evaporation process, leading to the production of detectable particle species, constrains the abundance of light black holes, presumably of primordial origin. Here, we reconsider and correct constraints from soft gamma-ray observations, including of the gamma-ray line, at 511 keV, produced by electron-positron pair-annihilation, where positrons originate from black hole evaporation. First, we point out that the INTEGRAL detection of the Large Magellanic Cloud provides one of the strongest bounds attainable with present observations; and that future MeV gamma-ray telescopes, such as GECCO, will greatly enhance such constraints. Second, we discuss issues with previous limits from the isotropic flux at 511 keV and we provide updated, robust constraints from recent measurements of the diffuse Galactic soft gamma-ray emission and from the isotropic soft gamma-ray background.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Primordial gravitational waves from black hole evaporation in standard and nonstandard cosmologies

Gravitons radiated from light, evaporating black holes contribute to the stochastic background of gravitational waves. The spectrum of such emission depends on both the mass and the spin of the black holes, as well as on the redshifting that occurs between the black hole formation and today. This, in turn, depends on the expansion history of the Universe, which is largely unknown and unconstrained at times prior to the synthesis of light elements. Here, we explore the features of the stochastic background of gravitational waves from black hole evaporation under a broad range of possible early cosmological histories. The resulting gravitational wave signals typically peak at very high frequencies, and offer opportunities for proposed ultrahigh-frequency gravitational wave detectors. Lower-frequency peaks are also possible, albeit with a suppressed intensity that is likely well below the threshold of detectability. We find that the largest intensity peaks correspond to cosmologies dominated by fluids with equations of state that have large pressure-to-density ratios. Such scenarios can be constrained on the basis of violation of Δ⁢N eff bounds.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Constraints on the maximal number of dark degrees of freedom from black hole evaporation, cosmic rays, colliders, and supernovae

A dark sector with a very large number of massive degrees of freedom is generically constrained by radiative corrections to Newton’s constant. However, there are caveats to this statement, especially if the degrees of freedom are light or massless. Here, we examine in detail and update a number of constraints on the possible number of dark degrees of freedom, including from black hole evaporation, from perturbations to systems including an evaporating black hole, from direct gravitational production at colliders, from high-energy cosmic rays, and from supernovae energy losses. Published by the American Physical Society 2025

Ewasiuk, Chris (ORCID:0009000253197890)↗
DOE OSTI2025

Fermionic sub-GeV dark matter from evaporating primordial black holes at DarkSide-50

We present a search for boosted dark matter from primordial black hole (PBH) evaporation using the DarkSide-50 ionization-signal-only dataset corresponding to the experiment’s ( 12202 ± 180 ) kg d exposure. We focus on evaporation of PBHs with masses in the range [ 10 14 , 10 16 ] g producing Dirac fermionic dark matter particles with sub-GeV kinetic energy. These relativistic particles, with energies up to hundreds of MeV, can generate detectable signals for masses below O ( 100 ) MeV . The absence of a signal enables setting complementary limits to those derived from cosmological observations and direct detection searches for cosmic-ray-boosted dark matter.

Agnes, P. [Gran Sasso; GSSI, Aquila]↗
DOE OSTI2014

Fabrication and characterization of silver- and copper-coated Nylon 6 forcespun nanofibers by thermal evaporation

Silver and copper nanoparticles were deposited as thin films onto substrates consisting of Nylon 6 nanofibers manufactured using forcespinning{sup ®} equipment. Different rotational speeds were used to obtain continuous nanofibers of various diameters arranged as nonwoven mats. The Nylon 6 nanofibers were collected as successive layers on frames, and a high-vacuum thermal evaporation method was used to deposit the silver and copper thin films on the nanofibers. The structures were investigated using scanning electron microscopy–scanning transmission electron microscopy, atomic force microscopy, x-ray diffraction, and electrical resistance measurements. The results indicate that evaporated silver and copper nanoparticles were successfully deposited on Nylon 6 nanofibers as thin films that adhered well to the polymer substrate while the native morphology of the nanofibers were preserved, and electrically conductive nanostructures were achieved.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Electron-beam-evaporated thin films of hafnium dioxide for fabricating electronic devices

Thin films of hafnium dioxide (HfO 2 ) are widely used as the gate oxide in fabricating integrated circuits because of their high dielectric constants. In this paper, the authors report the growth of thin films of HfO 2 using e-beam evaporation, and the fabrication of complementary metal-oxide semiconductor (CMOS) integrated circuits using this HfO 2 thin film as the gate oxide. The authors analyzed the thin films using high-resolution transmission electron microscopy and electron diffraction, thereby demonstrating that the e-beam-evaporation-grown HfO 2 film has a polycrystalline structure and forms an excellent interface with silicon. Accordingly, we fabricated 31-stage CMOS ring oscillator to test the quality of the HfO 2 thin film as the gate oxide, and obtained excellent rail-to-rail oscillation waveforms from it, denoting that the HfO 2 thin film functioned very well as the gate oxide.

42 ENGINEERING↗
DOE OSTI2025

Thermal evaporation of thin Li films

Thermal evaporation of lithium is considered a promising technique for the fabrication of clean lithium thin films for solid-state batteries. Here, in this study, we present a practical investigation of nanometer scale lithium films prepared by evaporation on different substrates. These substrates include Li-alloying and nonalloying metals as well as different classes of solid-state lithium-ion conductors. The deposition rate was also varied. For films less than 100 nm thick, the data show that the deposition rate has the biggest impact on the surface coverage. At 50 Å/s, Li forms small particles <1 μm in diameter while higher deposition rate of 150 Å/s resulted in more uniform film morphology on all the substrates. At the lower deposition rates, the wetting of Li to the substrate will impact the particle morphology. We also used the particles to estimate a contact angle between Li and the substrate to qualitatively compare the adhesion from substrate to substrate. The smallest contact angle was observed from lithium films on Li 7 La 3 Zr 2 O 12 and LiPON (nominal Li 2.94 PO 3.5 N 0.31 ) solid-state electrolytes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Structure of the surface microrelief of a droplet evaporating from a rough substrate as a possible cause of contact angle hysteresis

Based on the refraction images of a droplet evaporating on a rough substrate, we simultaneously observed the dynamics of its surface microrelief, contact angle, and contact line deformations along the entire perimeter of the contact line. This has led us conclude that the microrelief structure is directly related to the phenomenon of contact angle hysteresis and the jump-like pattern of contact line deformation. We suggest a possible mechanism for the occurrence of contact angle hysteresis during droplet evaporation and derive the relations that specify the range of possible contact angles at known microrelief parameters.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

New Nanosized Luminophores Obtained via Evaporation of REE Silicates and Germanates

Nanophosphors in the amorphous state are first obtained via pulsed electron beam evaporation of targets made of polycrystalline phosphors with the compositions Ca{sub 2}M{sub 8}(SiO{sub 4}){sub 6}O{sub 2}:Eu (M = Y and Gd) and Ca{sub 2}La{sub 8}(GeO{sub 4}){sub 6}O{sub 2}:Eu with the structure of oxyapatite. Reduction of ions Eu{sup 3+} → Eu{sup 2+} in the electron beam is found. Modification of the Raman scattering (RS) spectra of the samples in the case of a decrease in the size of the particles from bulk to a nanosized state is found. The change in the forbidden band width E{sub g} of the samples in the case of transition from a bulk powder to an NP is considered. The spectral and luminescence characteristics of the samples in the polycrystalline and nanoamorphous states are studied. It is shown that, in the case of transition to nanosamples, the ligand field around Eu{sup 2+} changes. This may be due to the violation of the translational symmetry in the NP. The bond between the 4f and 5d electrons weakens. Degeneracy of the {sup 2}e{sub g} level appears. Presumably, the reduction of ions Eu{sup 3+} → Eu{sup 2+} in the electron beam due to the breaking of the Si(Ge)–O bond in the process of evaporation of the samples and capture of the released electron by the Eu{sup 3+} ions is found.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic and Luminescent Properties of Barium Fluoride Nanopowder Obtained by Electron-Beam Evaporation in Low-Pressure Gas

Mesoporous amorphous-crystalline nanopowders of BaF{sub 2} with the specific surface area up to 34.8 m{sup 2}/g were obtained using evaporation by a pulsed electron beam in vacuum. Influence of the thermal annealing of the BaF{sub 2} nanoparticles in air at the temperatures from 200 to 900°C on the size and morphology of the particles and changes in their magnetic and luminescent properties was studied. The paramagnetic response of the BaF{sub 2} nanopowder was found to transform to the ferromagnetic response after annealing at 900°C. The appearance and transformation of the magnetic response in nanopowders made of BaF{sub 2}, which is diamagnetic as the bulk material, are ascribed to the appearance of radiation-induced and structural defects during the synthesis process by pulsed electron-beam evaporation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

SolVap_StarTer (Solvent Evaporation Graphical User Interface) [SWR-26-029]

SolVap_StarTer is an open-source solvent evaporation GUI. The software combines previously published (peer-reviewed scientific journals) evaporation and crystallization physics into an easy-to-use graphical interface. The software will allow the user to specify a coating composition and drying environment, and then predict the evolution of the film as it dries. Potential applications include tracking the change in multi-solvent composition and solute concentration in solution-processed perovskites films, predicting the point of crystallization, and calculating equivalent processing parameters for transferring a process between different coating and drying methods. Github repo: https://github.com/NatLabRockies/SolVap Streamlit app: https://solvap.streamlit.app/

Starger, Jesse [National Laboratory of the Rockies↗
DOE OSTI2021

An evaluation of size-resolved cloud microphysics scheme numerics for use with radar observations Part II: Condensation and evaporation

Accurate numerical modeling of clouds and precipitation is essential for weather forecasting and climate change research. While size-resolved (bin) cloud microphysics models predict particle size distributions without imposing shapes, results are subject to artificial size distribution broadening owing to numerical diffusion associated with various processes. Whereas Part I of this study addressed collision–coalescence, here we investigate numerical diffusion that occurs in solving condensation and evaporation. In a parcel model framework, all of the numerical schemes examined converge to one solution of condensation and evaporation as the mass grid is refined, and the advection-based schemes are recommended over the reassigning schemes. Including Eulerian vertical advection in a column limits the convergence to some extent, but that limitation occurs at a sufficiently fine mass grid, and the number of iterations in solving vertical advection should be minimized to reduce numerical diffusion. Insubstantial numerical diffusion in solving condensation can be amplified if collision–coalescence is also active, which in turn can be substantially diminished if turbulence effects on collision are incorporated. Here, large-eddy simulations of a drizzling stratocumulus field reveal that changes in moments of Doppler spectra obtained using different mass grids are consistent with those obtained from the simplified framework, and that spectral moments obtained using a mass grid designed to effectively reduce numerical diffusion are generally closer to observations. Notable differences between the simulations and observations still exist, and our results suggest a need to consider whether factors other than numerical diffusion in the fundamental process schemes employed can cause such differences.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Platform-agnostic waveguide integration of high-speed photodetectors with evaporated tellurium thin films

Many attractive photonics platforms still lack integrated photodetectors due to inherent material incompatibilities and lack of process scalability, preventing their widespread deployment. Here, we address the problem of scalably integrating photodetectors in a photonics-platform-independent manner. Using a thermal evaporation and deposition technique developed for nanoelectronics, we show that tellurium, a quasi-2D semi-conductive element, can be evaporated at low temperatures directly onto photonic chips to form air-stable, high-speed, ultrawide-band photodetectors. We demonstrate detection from visible (520 nm) to short-wave infrared (2.4 µm), a bandwidth of more than 40 GHz, and platform-independent scalable integration with photonic structures in silicon, silicon nitride, and lithium niobate.

42 ENGINEERING↗