Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “functional properties”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Calcium-silicate-based porous particles, composition, method of making and use thereof

A method for synthesizing calcium-silicate-based porous particles (CSPPs) is described. Control over CSPP morphology and pore size is achieved through a refined solution-based synthesis, allowing loading of a variety of sealants. These particles, upon external stimuli, release the loaded sealant into the surrounding material. Methods of loading the CSPPs with loading sealant are described. The CSPPs may be used in pure form or mixed with another material to deliver self-healing, sealing and multi-functional properties to a physical structure. The composition of the CSPPs is described, along with methods of use of the CSPPs.

Shahsavari, Rouzbeh↗
DOE OSTI2023

Temperature Dependence of Band Gap Renormalization in High-T Sensor Materials via First-Principles and Experimental Corroboration

Understanding the temperature dependence of functional properties of high-T gas sensing materials is vital for their applications in combustion environments. The electron-phonon coupling that derives the electronic structure change with temperatures is a key property of interest as it affects other sensing responses. Herein, we assess the temperature dependence of band gap renormalization in metal oxides and perovskites by employing Allen-Heine-Cardona theory with first-principles simulations and corroborate with experimental observation. The calculated temperature-dependent band gap changes of these materials studied are in good agreement with in-house experimental data, proving that the theory can adequately predict renormalization on the band gap in the system of interest. The predicted and measured band gap variations are characterized using an analytical model, which can provide useful insights on the simulated zero-temperature band gaps. Based on the available data, a set of 53 metal oxides and perovskites were identified as potential high-T gas sensors. A machine learning model has been developed to predict the band-gap change by capturing the overall trend of the empirical parameters with respect to a reduced feature obtained by transforming the set of available physical features.

Park, Jongwoo↗
DOE OSTI2023

Selective thermal evolution of native oxide layer in Nb and Nb$_3$Sn-coated SRF grade Nb: An in-situ angular XPS study

This contribution discusses the results of an in-situ angular XPS study on the thermal evolution of the native oxide layer on Nb3Sn and pure Nb. XPS data were recorded with conventional spectrometers using an AlK(alpha) X-ray source for spectra collected up to 600 C, and an MgK(Alpha) X-rays source for temperatures above 600 C. The effect of the thickness, composition, and thermal stability of that oxide layer is relevant to understanding the functional properties of superconducting radiofrequency (SRF) cavities used in particle accelerators. There is a consensus that oxide plays a role in surface resistance (Rs). The focus of this study is Nb3Sn, which is a promising material that is used in the manufacturing of superconducting radiofrequency (SRF) cavities as well as in quantum sensing, and pure Nb, which was included in the study for comparison. The thermal evolution of the oxide layer in these two materials is found to be quite different, which is ascribed to the influence of the Sn atom on the reactivity of the Nb atom in Nb3Sn films. Nb and Sn atoms in this intermetallic solid have different electronegativity, and the Sn atom can reduce electron density around neighbouring Nb atoms in the solid, thus reducing their reactivity for oxygen. This is shown in the thickness, composition, and thermal stability of the oxide layer formed on Nb3Sn. The XPS spectra were complemented by grazing incident XRD patterns collected using the ESRF synchrotron radiation facility. The results discussed herein shed light on oxide evolution in the Nb3Sn compound and guide its processing for potential applications of the Nb3Sn-based SRF cavities in accelerators and other superconducting devices.

Cano, Arely↗
DOE OSTI2024

Electrospinner Upgrades for Nanofiber Production

Electrospinning is an inexpensive and flexible method for producing nanofibers. Nanofibers are highly adaptable with potential applications in accelerator target systems, air and water filtration, and biomedicine. This project aims to upgrade and test an existing roll-to-roll electrospinner that is more economical for industrial nanofiber production. Varying the diameter of nanofiber can change its functional properties. The current unit cannot adjust spinneret-collector separation, which determines nanofiber diameter. The electro-spinneret channel also does not have lateral adjustment capabilities for precise alignment. Lastly, the viscosities of our polymer solutions have not been quantified. Solution injection into the channel is presently inconsistent because of imperfect nozzle sizing, resulting in waste and decreased efficiency. Modeling was done with Siemens NX CAD software, and viscosity was measured using a Brookfield DVE-LV viscometer. A dual scissor lift design for channel displacement, powered by a dual-shaft DC motor coupled to precision lead screws, was approved and construction was started. Preliminary channel modifications also were initiated. Going forward, the scissor lift system will be integrated and evaluated with our electrospinner, along with further channel modifications. Viscosity measurements of polyvinyldimethylformamide (PVDF) were recorded with inconsistent results due to inadequate testing conditions. Future viscosity trials must be completed in accordance with testing requirements. The optimization and commercialization of roll-to-roll electrospinner units can make nanofiber production more feasible for many new industries and consumer products.

Black, Niko↗
NASA NTRS1971

Superconducting properties as a function of thickness in NbN films.

Measurement of the superconducting properties of NbN films prepared by a high purity reactive sputtering process. The transition temperature was found to decrease with decreasing film thickness, while in contrast the critical current vs magnetic field was largely independent of film thickness and even slightly increased when the film thickness went down to 100 A. The average resistivity of the NbN films was 1000 microohm-cm.

Gavaler, J. R.↗
NASA NTRS1975

Hydrogen technology survey: Thermophysical properties

The thermodynamic functions, transport properties, and physical properties of both liquid and gaseous hydrogen are presented. The low temperature regime is emphasized. The tabulation of the properties of normal hydrogen in both Si and engineering units is given along with the tabulation of parahydrogen.

Mccarty, R. D.↗
DOE OSTI2020

Thermal Properties of Sodium Borosilicate Glasses as a Function of Sulfur Content

SO3 additions, up to 3.0 wt%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur-free composition of 50SiO2-10Al2O3-12B2O3-21Na2O-7CaO (wt%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.5 wt% SO3. It was found that sulfur (here as sulfate) in this glass increased the glass transition temperature, thermal diffusivity, heat capacity, and thermal conductivity, and decreased the mass density. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions, presumably due to Na2O being required to charge compensate the ionic SO42- additions, thus becoming unavailable to form non-bridging oxygen in the silicate network. It is postulated that this increased crosslinking of the borosilicate backbone lead to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.

Thermal properties, Borosilicate glass, Sulfur sol↗
NASA NTRS1995

Studies of radar backscatter as a function of wave properties and the winds in the turbulent marine atmosphere

The research on model functions for ADEOS and ERS-1 are summarized and an analysis of the differences between the three kinds of models is provided in this final report. The success of the AMI on ERS-1 obtained at GSFC and NMC is highlighted. The problem of wind stress description is reviewed within and the scatterometer model being developed for high winds monitoring for the AMI on ERS-1 and ERS-2 is described.

Pierson, Willard J., Jr.↗
DOE OSTI2020

Rethinking the magnetic properties of lepidocrocite: A density functional theory and cluster expansion study

The iron oxyhydroxide lepidocrocite (g-FeOOH) is an abundant mineral critical to a number of chemical and technological applications. Of particular interest is the ground state and nite temperature magnetic order, and the subsequent impact this has upon crystal properties. The magnetic properties, investigated in this work are governed primarily through superexchange interactions, and have been calculated using density functional theory and cluster expansion methods. Quantication of these exchange terms has facilitated the determination of the ground state magneto-crystalline structure and subsequent calculation of its lattice constants, elastic moduli, cohesive enthalpy, and electronic density of states. Further, using a collinear magnetic conguration model, the magnetic heat capacity versus temperature has been studied and the Neel temperature obtained.

Pope, Daniel J.↗
DOE OSTI2020

Real‐Time Optical Process Monitoring for Structure and Property Control of Aerosol Jet Printed Functional Materials

Abstract Aerosol jet printing is a popular digital additive manufacturing method for flexible and hybrid electronics, but it lacks sophisticated real‐time process control schemes that would enable more widespread adoption in manufacturing environments. Here, an optical measurement system is introduced to track the aerosol density upstream of the printhead. The measured optical extinction, combined with the aerosol flow rate, is directly related to deposition rate and accurately predicts functional materials properties such as the electrical resistance of printed graphene films. This real‐time system offers a compelling solution for process drift and batch‐to‐batch variability, rendering it a valuable tool for both real‐time control of aerosol jet printing and fundamental studies of the underlying process science.

Tafoya, Rebecca R.↗
NASA NTRS1972

Pattern Recognition and Linear Discriminant Function

The properties of a linear discriminant function are discussed for the case of arbitrary distributions with equal covariance matrices. Using two examples, a comparison is made showing how the difference of the means relates to the covariance matrices.

Finch, L. H.↗
DOE OSTI2024

Adsorption Properties of Au−Ni Surface Alloys with a Nonstoichiometric Moiré Structure: A Density Functional Theory Study

Due to the large lattice mismatch between gold and nickel, gold–nickel surface alloys can form unique nonstoichiometric overlayer structures characterized by a moiré pattern and subsurface defects. For this work, we performed density functional theory (DFT) calculations to study the adsorption of molecular oxygen, atomic hydrogen, and atomic carbon on a gold–nickel(111) surface alloy with 0.46 monolayer gold randomly distributed in the surface layer. We observed six distinct adsorption structures for molecular oxygen characterized by intramolecular stretching frequencies of <700, 729, 795, 857, 929, and 1004 cm –1 , which describe well the experimentally observed high-resolution electron energy-loss spectra. Surface atomic hydrogen adsorption is associated with adsorbate–surface modes in the ∼1000 cm –1 range, while subsurface hydrogen can have features as low as ∼400 cm –1 . We observed a unique adsorption structure for atomic carbon inside the surface dislocation loop defect, which explains the experimentally observed low carbon-surface mode at ∼340 cm –1 . Our study sheds light on the unique adsorption properties of the gold–nickel surface alloys and helps with rationalizing vibrational frequency experimental studies for this system.

adsorption↗