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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

gRASPA

GPU Monte Carlo Simulation Code with a taste of RASPA We present enhancements in Monte Carlo simulation speed and functionality within an open-source code, gRASPA, which uses graphical processing units (GPUs) to achieve significant performance improvements compared to serial, CPU implementations of Monte Carlo. The code supports a wide range of Monte Carlo simulations, including canonical ensemble (NVT), grand canonical, NVT Gibbs, Widom test particle insertions, and continuous-fractional component Monte Carlo. Implementation of grand canonical transition matrix Monte Carlo (GC-TMMC) and a novel feature to allow different moves for the different components of metal-organic framework (MOF) structures exemplify the capabilities of gRASPA for precise free energy calculations and enhanced adsorption studies, respectively. The introduction of a High-Throughput Computing (HTC) mode permits many Monte Carlo simulations on a single GPU device for accelerated materials discovery. The code can incorporate machine learning (ML) potentials. The open-source nature of gRASPA promotes reproducibility and openness in science, and users may add features to the code and optimize it for their own purposes. The code is written in CUDA/C++ and SYCL/C++ to support different GPU vendors. The gRASPA code is publicly available at https://github.com/snurr-group/gRASPA.

Li, Zhao [Purdue/Northwestern/Notre Dame Universit↗
NASA NTRS1985

Interaction of finite-amplitude sound with air-filled porous materials

The propagation of high intensity sound waves through an air-filled porus material was studied. The material is assumed: (1) to be rigid, incompressible, and homogeneous, and (2) to be adequately described by two properties: resistivity r and porosity. The resulting wave equation is still nonlinear, however, because of the u sgn(u) term in the resistivity. The equation is solved in the frequency domain as an infinite set of coupled inhomogeneous Helmholtz equations, one for each harmonic. An approximate but analytical solution leads to predictions of excess attenuation, saturation, and phase speed reduction for the fundamental component. A more general numerical solution is used to calculate the propagation curves for the higher harmonics. The u sgn(u) nonlinearity produces a cubic distortion pattern; when the input signal is a pure tone, only odd harmonic distortion products are generated.

Nelson, D. A.↗
NASA NTRS1994

Hydrophobic Porous Material Adsorbs Small Organic Molecules

Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

Sharma, Pramod K.↗
NASA NTRS1982

Oblique incidence sound absorption of porous materials covered by perforated metal and exposed to tangential airflow

The purpose of this study was to evaluate several acoustic linings that are candidate designs for the Ames 40- by 80-Foot Wind Tunnel test section. The acoustic treatment will be used to reduce wall reflections from aircraft model noise sources. The goal is not simply to attenuate sound propagating down the duct, but rather to create a semi-anechoic space in a windy environment by absorbing at least 80% of the incident acoustic energy over a wide frequency range, if possible.

Soderman, Paul T.↗
NASA NTRS2005

Crosslinking Amine-Modified Silica Aerogels with Epoxies: Mechanically Strong Lightweight Porous Materials

The mesoporous surfaces of TMOS-derived silica aerogels have been modified with amines by co-polymerization of TMOS with APTES. The amine sites have become anchors for crosslinking the nanoparticles of the skeletal backbone of the aerogel by attachment of di-, tri and tetra-functional epoxies. The resulting conformal coatings increase the density of the native aerogels by a factor of 2-3 but the strength of the resulting materials may increase by more than two orders of magnitude. Processing variables such as amount of APTES used to make the gels, the epoxy type and concentration used for crosslinking, as well as the crosslinking temperature and time were varied according to a multivariable design-of-experiments (DOE) model. It was found that while elastic modulus follows a similar trend with density, maximum strength is attained neither at the maximum density nor at the highest concentration of -NH2 groups, suggesting surface saturation effects. Aerogels crosslinked with the tri-functional epoxide always show improved strength compared with aerogels crosslinked with the other two epoxides under identical conditions. Solid C-13 NMR studies show residual unreacted epoxides, which condense with ne another by heating crosslinked aerogels at 150 C.

Meador, Mary Ann B.↗
NASA NTRS2005

Mechanically Strong, Lightweight Porous Materials Developed (X-Aerogels)

Aerogels are attractive materials for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other materials. Potential NASA applications for these materials include lightweight insulation for spacecraft, habitats, and extravehicular activity (EVA) suits; catalyst supports for fuel cell and in situ resource utilization; and sensors for air- and water-quality monitoring for vehicles, habitats, and EVA suits. Conventional aerogels are extremely fragile and require processing via supercritical fluid extraction, which adds cost to the production of an aerogel and limits the sizes and geometries of samples that can be produced from these materials. These issues have severely hampered the application of aerogels in NASA missions.

Leventis, Nicholas↗
NASA NTRS2005

Polymer Crosslinked 3-D Assemblies of Nanoparticles: Mechanically Strong Lightweight Porous Materials

In analogy to supramolecular assemblies, which are pursued because of properties above and beyond those of the individual molecules, self-standing monolithic three-dimensional assemblies of nanoparticles also have unique properties attributed to their structure. For example, ultra low-density 3-D assemblies of silica nanoparticles, known as silica aerogels, are characterized by large internal void space, high surface area and very low thermal conductivity. Aerogels, however, are also extremely fragile materials, limiting their application to a few specialized environments, e.g., in nuclear reactors as Cerenkov radiation detectors, in space (refer to NASA's Stardust Program) and aboard certain planetary vehicles (thermal insulators on Mars Rovers in 1997 and 2004). The fragility problem is traced to well-defined weak points in the aerogel skeletal framework, the interparticle necks. Using the surface functionality of the nanoparticle building blocks as a focal point, we have directed attachment of a conformal polymer coating over the entire framework, rendering all necks wider. Thus, although the bulk density may increase only by 3x, the mesoporosity (pores in the range 2-50 nm) remains unchanged, while the strength of the material increases by up to 300... Having addressed the fragility problem, aerogels are now robust materials, and a variety of applications, ranging from thermal/acoustic insulators to catalyst supports, to platform for sensors, and dielectrics are all within reach. Our approach employs molecular science to manipulate nanoscopic matter for achieving useful macroscopic properties, and in our view it resides at the core of what defines nanotechnology. In that spirit, this technology is expandable in three directions. Thus, we have already crosslinked successfully amine-modified silica, and we anticipate that more rich chemistry will be realized by been creative with the nanoparticle surface modifiers. On the other hand, although we do not expect orders-of-magnitude increase in strength, nevertheless, by varying the polymer we expect to impart other properties such as hydrophobicity, thermal stability and perhaps electrical conductivity. Besides polymers, crosslinkers will include metals and ceramics (e.g., through POSS precursors). Finally, network morphology directs load dissipation, and of approximately 30 different crosslinked oxide aerogels, vanadia, whose structure is fibrous rather than particulate, yields a much stronger (by 4..) material than silica of the same density. It seems imperative to implement control of network morphology, even through templating.

Leventis, Nicholas↗