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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Biodegradable High-Molecular-Weight Poly(pentylene adipate- co -terephthalate): Synthesis, Thermo-Mechanical Properties, Microstructures, and Biodegradation

Poly(pentylene adipate-co-terephthalate) (PPAT) is a promising biobased and biodegradable polymer that can replace polyethylene in flexible packaging films where biodegradability is desired. High-molecular-weight (100K–145 KDa) aliphatic–aromatic polyester PPAT was successfully synthesized, and the effects of reaction conditions on molecular weight were reported. PPAT polyesters were characterized for polymer compositions, number-average unit length, thermal transitions, and rheological properties. PPAT compression-molded films were characterized for crystallinity and tensile properties to correlate micro- and macroproperties. PPAT compression-molded films exhibited up to a 76% higher tensile modulus than compression-molded films from poly(butylene adipate-co-terephthalate) (PBAT), making PPAT films potentially comparable with compression-molded films from linear low-density polyethylene (LLDPE). Finally, PPAT is biodegradable in soil and freshwater environments with estimated 90% biodegradation times of 504–580 and 604–845 days, respectively, while PBAT takes 971 days in soil and 395 days in freshwater.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2004

Lunar Simulants: JSC-1 is Gone; The Need for New Standardized Root Simulants

A workshop was held in 1991 to evaluate the status of simulated lunar regolith material and to make recommendations on future requirements and production of such material. As an outgrowth of that workshop, a group centered at Johnson Space Center (JSC) teamed with James Carter of the University of Texas at Dallas and Walter Boles of Texas A&M University to produce and distribute a new standardized lunar regolith simulant termed JSC-1. Carter supervised the field collection, shipping, processing, and initial packaging and transportation of JSC-1. Boles stored and distributed JSC-1. About 25 tons were created and distributed to the lunar science and engineer community; none is left for distribution. JSC-1 served an important role in concepts and designs for lunar base and lunar materials processing. Its chemical and physical properties were described by McKay et al., with its geotechnical properties described by Klosky et al.. While other lunar regolith simulants were produced before JSC-1, they were not standardized, and results from tests performed on them were not necessarily equivalent to test results performed on JSC-1. JSC-1 was designed to be chemically, mineralogically, and texturally similar to a mature lunar mare regolith (low titanium). The glass-rich character of JSC-1 (approx. 50%) produced quite different properties compared to other simulants that were made entirely of comminuted crystalline rock, but properties similar to lunar mare near surface regolith.

Carter, James L.↗
DOE OSTI2021

Analysis of the Amorphous and Interphase Influence of Comononomer Loading on Polymer Properties toward Forwarding Bioadvantaged Copolyamides

In this paper we present an approach for selectively modifying the properties of semicrystalline polymers by introducing “bioadvantaged” counits. With this approach, the unique functionality of biomass can be leveraged to tailor the properties of the amorphous phase of semicrystalline polymers with minimal impact on crystallinity and thermomechanical properties. As a model case, PA 6,6 copolyamides were produced using the bioadvantaged monomer trans-3-hexenedioic acid (t3HDA). The analogous structure of t3HDA to adipic acid, a PA 6,6 monomer, allows for seamless integration. Screening over the entire composition range identified the t3HDA loading (20 mol%) beyond which properties deviate appreciably from Nylon 6,6. Once identified, copolyamides of suitable compositions were upgraded to commercial quality and fully characterized to assess the influence of counit loading and polymer structure on thermal and mechanical properties. Samples were characterized using gel permeation chromatography (GPC), proton nuclear magnetic resonance spectroscopy (1H NMR), heteronuclear single quantum coherence spectroscopy (HSQC), wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile testing, flexural testing, and water absorption testing. t3HDA units were shown to hydrate during the harsh polycondensation to 3-hydroxyhexanedioic acid (3HHDA) and fully incorporate into the polymer backbone. Loading levels up to 20% were shown to have comparable thermal and mechanical properties in the dry state, yet moisture absorption—a known method for improving the toughness, yield strain, and elongation of polyamides—was enhanced by over 100% at 20% loading. This case study on bioadvantaged copolymers elucidates the governing structure-function principles that can be leveraged to forward value-added renewable polymers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Liquid crystalline polymers

The remarkable mechanical properties and thermal stability of fibers fabricated from liquid crystalline polymers (LCPs) have led to the use of these materials in structural applications where weight savings are critical. Advances in processing of LCPs could permit the incorporation of these polymers into other than uniaxial designs and extend their utility into new areas such as nonlinear optical devices. However, the unique feature of LCPs (intrinsic orientation order) is itself problematic, and current understanding of processing with control of orientation falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial fibers). The current and desirable characteristics of LCPs are reviewed and specific problems are identified along with issues that must be addressed so that advances in the use of these unique polymers can be expedited.

Source record↗
NASA NTRS1977

Crystalline polyimides containing 4,4'-bis/3,4-dicarboxyphenoxy/diphenyl sulfide dianhydride

A high degree of crystallinity has been found in unoriented polymer films formed from 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride (BDSDA) and p-phenylenediamine (PDA). Partial crystallinity for a polymer containing BDSDA and benzidine is also reported. A study of the thermal properties of the crystalline polyimides shows crystalline melting points of 426 C and 483 C respectively for the BDSDA-PDA and the BDSDA-benzidine polymers.

Saint Clair, T. L.↗
DOE OSTI2024

Suppressed Lone Pair Electrons Explain Unconventional Rise of Lattice Thermal Conductivity in Defective Crystalline Solids

Manipulating thermal properties of materials can be interpreted as the control of how vibrations of atoms (known as phonons) scatter in a crystal lattice. Compared to a perfect crystal, crystalline solids with defects are expected to have shorter phonon mean free paths caused by point defect scattering, leading to lower lattice thermal conductivities than those without defects. While this is true in many cases, alloying can increase the phonon mean free path in the Cd-doped AgSnSbSe 3 system to increase the lattice thermal conductivity from 0.65 to 1.05 W m –1 K –1 by replacing 18% of the Sb sites with Cd. It is found that the presence of lone pair electrons leads to the off-centering of cations from the centrosymmetric position of a cubic lattice. X-ray pair distribution function analysis reveals that this structural distortion is relieved when the electronic configuration of the dopant element cannot produce lone pair electrons. Furthermore, a decrease in the Grüneisen parameter with doping is experimentally confirmed, establishing a relationship between the stereochemical activity of lone pair electrons and the lattice anharmonicity. The observed “harmonic” behavior with doping suggests that lone pair electrons must be preserved to effectively suppress phonon transport in these systems.

36 MATERIALS SCIENCE↗
NASA NTRS2020

Bonding to Bulk Metallic Glass using Aerospace-Grade Structural Adhesive

Bulk metallic glasses (BMGs) are non-crystalline metals with growing applications in aerospace. Due to their amorphous nature, BMGs generally exhibit stronger mechanical properties than most crystalline alloys and are more corrosion resistant. The limited reactivity of a corrosion resistant surface may explain the difficulty in establishing robust bonds to certain adhesives, especially commonly used structural adhesives for aerospace applications. Here, an amine cured aerospace adhesive was used for bonding an iron-nickel based BMG satellite component. Various types of processes were explored to avoid adhesive failure and increase bond strength. It was found that the BMG required specific chemical derivatization of the metal surface in order to achieve cohesive failure. Surface analysis was used to determine the mechanisms of adhesion enhancement. The process was optimized to maximize bond strength. This work helps explain the difficulties in bonding BMG materials and provides strategies for design of future bonded BMG components.

Roberts, Rose↗
DOE OSTI2020

Anisotropic Dynamics and Mechanics of Macromolecular Crystals Containing Lattice-Patterned Polymer Networks

The mechanical and functional properties of many crystalline materials depend on cooperative changes in lattice arrangements in response to external perturbations. However, the flexibility and adaptiveness of crystalline materials are limited. Additionally, the bottom-up, molecular-level design of crystals with desired dynamic and mechanical properties at the macroscopic level remains a considerable challenge. To address these challenges, we had previously integrated mesoporous, cubic ferritin crystals with hydrogel networks, resulting in hybrid materials (polymer integrated crystals or PIX) which could undergo dramatic structural changes while maintaining crystalline periodicity and display efficient self-healing. Here, the dynamics and mechanics of these ferritin-PIX were devoid of directionality, which is an important attribute of many molecular and macroscopic materials/devices. In this study, we report that such directionality can be achieved through the use of ferritin crystals with anisotropic symmetries (rhombohedral or trigonal), which enable the templated formation of patterned hydrogel networks in crystallo. The resulting PIX expand and contract anisotropically without losing crystallinity, undergo prompt bending motions in response to stimuli, and self-heal efficiently, capturing some of the essential features of sophisticated biological devices like skeletal muscles.

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

One Dimensional Topological Nanomaterials and Superconductivity (Final Technical Report)

The project synthesized and made transport properties of topological crystalline insulator tin telluride (SnTe) nanowires and other topological materials, such as MoTe 2 and WTe 2 . The transport properties of the nanowires were correlated with the diameter of the nanowire, in terms of the ferroelectric phase transition temperature, magnetoresistance response, and Josephson junction behaviors as a function of the nanowire diameter. The most important observation was the proximity-induced superconductivity in SnTe nanowires, which suggests time reversal symmetry breaking.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Enzymatic depolymerization of polyester: Foaming as a pretreatment to increase specific surface area

Abstract Poly(ethylene terephthalate) (PET) is widely used for its high strength‐to‐weight ratio, gas barrier properties, and chemical resistance. The growing PET use highlights the demand for a better recycling system. Enzymatic recycling, alongside mechanical and chemical methods, is eco‐friendly and yields properties similar to virgin PET. Substrate properties ( T g , crystallinity, and specific surface area [SSA]) and enzyme stability significantly impact conversion efficiency. Higher SSA and lower crystallinity tend to yield improved depolymerization when employing leaf compost‐cutinase (LCC‐ICCG) enzymes. This study explored melt extrusion and foaming as pretreatment techniques to modify PET structural properties, using a low‐cost chemical foaming agent (CFA). The monomer conversion rate and efficiency during depolymerization were measured and related to the processing, extrudate micro‐ and meso‐structure, and polyester type. Pretreated PET substrates showed reduced T g , crystallinity, density, and enhanced SSA, resulting in a 90% mass loss for foamed RPET and VPET substrates within 2 days. In contrast, PET with ~30% of cyclohexanedimethanol comonomer exhibited a nearly 50% lower depolymerization rate, with zero BHET production. It indicates that the combination of low crystallinity, low T g , and high SSA leads to improved monomer conversion. These findings emphasize the significance of amorphization and foaming in enhancing PET enzymatic depolymerization.

42 ENGINEERING↗
NASA NTRS1990

A database for solid-state laser, optical, and nonlinear materials

The database contains the physical properties of laser, optical, and nonlinear materials used by the laser models of a laser-modeling software system. The database is subdivided into two parts: spectra and tabulated data. The spectra are ASCII files of laser-material's absorption and emission spectra, and laser-diode's emission spectra. The tabulated data contains physical properties of laser, optical, and nonlinear materials, including crystalline, thermal, and mechanical properties. A menu-driven interface allows the execution from a personal directory where the user can store files containing input parameters for a specific model or the results of model's calculations.

Cross, P. L.↗
NASA NTRS1973

Friction and wear behavior of glasses and ceramics.

Adhesion, friction and wear behavior of glasses and ionic solids are reviewed. These materials are shown to behave in a manner similar to other solids with respect to adhesion. Their friction characteristics are shown to be sensitive to environmental constituents and surface films. This sensitivity can be related to a reduction in adhesive bonding and the changes in surficial mechanical behavior associated with Rehbinder and Joffe effects. Both friction and wear properties of ionic crystalline solids are highly anisotropic. With metals in contact with ionic solids, the fracture strength of the ionic solid, the shear strength in the metal, and those properties that determine these will dictate which of the materials undergoes adhesive wear.

Buckley, D. H.↗
DOE OSTI2023

Single crystal growth and thermoelectric properties of Nowotny chimney-ladder compound Fe 2 Ge 3

Fe 2 Ge 3 with an incommensurate Nowotny chimney-ladder (NCL) structure is a promising material for thermoelectric applications due to its low thermal conductivity. Previous experimental studies on Fe 2 Ge 3 have mainly focused on polycrystalline samples, resulting in a limited understanding of the material's intrinsic thermoelectric properties and the underlying causes of its low thermal conductivity. Here we report the synthesis and thermoelectric properties of single crystalline Fe 2 Ge 3 . Millimeter-sized Fe 2 Ge 3 single crystals grown by the chemical vapor transport method enable the study of the intrinsic thermoelectric properties. The Seebeck coefficient of Fe 2 Ge 3 is negative and its magnitude increases linearly with temperature, showing a degenerate n-type semiconductor behavior. Analysis of the electrical resistivity and specific heat data indicates the existence of an Einstein mode with a characteristic temperature of about 60 K, suggesting the presence of low-energy optical phonons. Further, the thermal conductivity of Fe 2 Ge 3 along the c axis is as low as 1.9Wm -1 K -1 at 300 K and exhibits a nearly temperature-independent characteristic, which is distinct from the previous theoretical calculations with a stronger temperature dependence. The low thermal conductivity may be attributed to the scattering of acoustic phonons by low-energy optical modes and the presence of non-extended diffuson modes, as reported in another NCL compound, MnSi 1.74 . This study provides valuable insights into the electrical and thermal properties of Fe 2 Ge 3 , which can open up possibilities for future advances in thermoelectric applications.

36 MATERIALS SCIENCE↗
NASA NTRS1973

Friction and wear behavior of glasses and ceramics

Adhesion, friction, and wear behavior of glasses and ionic solids are reviewed. These materials are shown to behave in a manner similar to other solids with respect to adhesion. Their friction characteristics are shown to be sensitive to environmental constituents and surface films. This sensitivity can be related to a reduction in adhesive bonding and the changes in surficial mechanical behavior associated with Rehbinder and Joffe effects. Both friction and wear properties of ionic crystalline solids are highly anisotropic. With metals in contact with ionic solids the fracture strength of the ionic solid and the shear strength in the metal and those properties that determine these will dictate which of the materials undergoes adhesive wear. The chemical activity of the metal plays an important role in the nature and strength of the adhesive interfacial bond that develops between the metal and a glass or ionic solid.

Buckley, D. H.↗
DOE OSTI2026

Web-accessible sorption database (Interim Progress Report)

This progress report (Level 4 Milestone Number M4SF-26LL010204053) summarizes research conducted at Lawrence Livermore National Laboratory (LLNL) within the Crystalline Host Rock Properties & Processes - LLNL Number SF-26LL01020405. This research is focused on the development of a web-accessible database of sorption data for minerals and rocks (bentonite backfill and crystalline host rock) that are likely to be present in a US hosted repository, including elevated temperature data that are expected in a DPC DGR scenario.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Chemistry and adhesive properties of poly(arylene ether)s containing heterocyclic units

Novel poly(arylene ether)s containing heterocyclic units were prepared, characterized, and evaluated as adhesives and composite matrices. The polymers were prepared by reacting a heterocyclic bisphenol with an activated aromatic dihalide in a polar aprotic solvent, using potassium carbonate. The polymerizations were generally carried out in N,N-dimethylacetamide at 155 C. In some cases, where the polymers were semicrystalline, higher temperatures and thus higher boiling solvents were necessary to keep the polymers in solution. Heterocyclic rings incorporated into the poly(arylene ether) backbone include phenylquinoxaline, phenylimidazole, benzimidazole, benzoxazole, 1,3,4-oxadiazole, and 1,2,4-triazole. The polymers were characterized by differential scanning calorimetry, solution viscosity, X-ray diffraction, thin film, and adhesive and (in some cases) composite properties. The glass transition temperatures, crystalline melt temperature, solubility, and mechanical properties varied depending upon the heterocyclic ring. The chemistry and properties of these materials are discussed.

Connell, John W.↗
DOE OSTI2023

Development of a scalar-based geometric parameterization approach for the crystal structure landscape of dithienylethene-based crystalline solids

Dithienylethenes (DTEs) are a promising class of organic photoswitches that can be used to create crystalline solids with properties controlled by light. However, the ability of DTEs to adopt multiple conformations, only one of which is photoactive, complicates the rational design of these materials. Herein, the synthesis and structural characterization of 19 crystalline solids containing a single DTE molecule are described. A novel D – D analysis of the molecular geometries obtained from rotational potential energy surface calculations and the ensemble of experimental structures were used to construct a crystal landscape for DTE. Of the 19 crystal structures, 17 contained photoinactive DTE rotamers and only 2 were photoactive. These results highlight the challenges associated with the design of these materials. Overall, the D – D analysis described herein provides rapid, effective and intuitive means of linking the molecular structure to photoactivity that could be applied more broadly to afford a general strategy for producing photoactive diarylethene-based crystalline solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Manipulation of amorphous precursors to enhance zeolite nucleation

Crystallization in media comprised of amorphous precursors is becoming a more common phenomenon for numerous synthetic, biological, and natural materials that grow by a combination of classical and nonclassical pathways. Amorphous phases can exhibit a wide range of physicochemical properties that may evolve during the course of nucleation and crystal growth. This creates challenges for establishing causal relationships between amorphous precursor properties and their effect(s) on the selection of mechanistic pathways of crystallization and ultimately the properties of the crystalline product. In this study, we examine ways to manipulate the composition and colloidal stability of amorphous (alumino)silicate precursors that are prevalent in nanoporous zeolite syntheses. Changes in the amorphous precursor properties are evaluated on the basis of their ability to enhance rates of crystal formation. Here, we use fumed silica as the primary silicon source and examine the effects of infusing the source or growth medium with additional alkali metal, which serves as an inorganic structure-directing agent to facilitate the formation of porous crystal structures. We also assess the impact of adding a polymer additive, which reduces the colloidal stability of precursors, wherein we posit that the confined pockets of solution within the interstitial spaces of the precursor aggregates play an important role in regulating the rate of zeolite crystallization. Three commercially relevant zeolites (mordenite, SSZ-13, and ZSM-5) were selected for this study based on their diverse frameworks and methods of preparation. Here our findings reveal that alkali infusion significantly reduces the crystallization times for mordenite and SSZ-13, but has little impact on ZSM-5 synthesis. Conversely, we find that polymer addition markedly enhanced the rates of crystallization among all three zeolites, suggesting that this method may be a general approach to reduce zeolite synthesis times. Given the relatively high costs associated with commercial zeolite production, identifying new methods to improve the efficiency of hydrothermal syntheses can have significant practical implications beyond the fundamental benefits of developing new routes to tailor nonclassical crystallization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗