SEARCH · Engineering Papers

Results for “crystalline”

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.

SourceResearch connectionFrom yearThrough year

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

At least 19 records

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Crystallinity determination by curvefit procedure for a semi-crystalline polymer

Wide angle X-ray scattering (WAXS) data from poly(etheretherketone) (PEEK) was resolved into a crystalline contribution represented as four reflections and an amorphous contribution represented as a broad, smoothly varying curve. The crystalline scatter is described as a linear combination of Cauchy and Gaussian functions while that of the amorphous halo is expressed as a cubic polynomial. Statistical analysis of the measured scattered intensity from an amorphous specimen with that calculated from the cubic polynomial, as a function of the combination parameter (fraction of Cauchy and Gaussian functions), suggests that the crystalline fraction of the polymer specimen studied is about 0.39.

Wakelyn, N. T.↗

NASA NTRS2016

Soil Crystallinity As a Climate Indicator: Field Experiments on Earth and Mars

Soil crystallinity is largely determined by leaching rates, as high leaching rates favor the rapid precipitation of short order or poorly-crystalline phases like the aluminosilicate allophane. High leaching rates can occur due to high precipitation rates, seasonal monsoons, or weathering of glass, but are also caused by the rapid onset of seasonal melting of snow and ice in cold environments. Thus, cold climate soils are commonly dominated by poorly crystalline phases, which mature into kaolin minerals over time. Thus, we hypothesize that, in some contexts, soils with high abundances of poorly crystalline phases could indicate formation under cold climatic conditions. This model could be helpful in interpreting the poorly-constrained paleoclimate of ancient Mars, as the crystallinity of ancient soils and soil-derived sediments appears to be highly variable in time and space. While strong signatures of crystalline phyllosilicates have been identified in possible ancient paleosols on Mars, Mars Science Laboratory rover investigations of diverse ancient sediments at Gale Crater has shown that they can contain very high abundances (40-50 wt%) of poorly crystalline phases. We hypothesize that these poorly crystalline phases could be the result of weathering by ice/snow melt, perhaps providing support for sustained cold climates on early Mars punctuated by more limited warm climates. Furthermore, such poorly crystalline soils could be highly fertile growth media for future human exploration and colonization on Mars. To test this hypothesis, we are currently using rover-like instrumentation to investigate the mineralogy and chemistry of weathering products generated by snow and ice melt in a Mars analog alpine environment: the glaciated Three Sisters volcanic complex in central Oregon. Alteration in this glacial environment generates high abundances of poorly crystalline phases, many of which have compositions distinct from those identified in previous terrestrial investigations, and perhaps more similar to poorly crystalline phases identified on Mars.

Horgan, Briony↗

NASA NTRSDate not supplied

Evaluating Crystallinity in Thermoplastic Composites for Aerospace Applications

Polymer matrix composites (PMCs) offer many benefits for the aerospace industry due to their potential for weight reduction when compared to metal or ceramic based materials. Most PMCs currently in flight use thermoset matrices, however, thermoplastic resins are being explored as alternatives due to their ability to be remelted, which is of particular interest due to the potential for in-situ repair and faster production. Most thermoplastic resins are semicrystalline polymers. The properties of semicrystalline thermoplastics are directly influenced by their crystallinity, which can vary due to many factors including thermal treatments, environmental conditions, and mechanical deformation. Within thermoplastic PMC parts, crystallinity gradients can arise due to variations in part geometry, across part thicknesses, and along bonded joints. Monitoring the crystallinity of thermoplastic composites is key to ensuring these materials meet the high demands required for aerospace. Several different analytical techniques exist that can be used to characterize the bulk crystallinity of thermoplastic materials. However, many existing methods lack the specificity required to identify the subtle variations in crystallinity that may play a significant role in the performance and durability of PMC parts. Because of this, a significant amount of work is still required to fully characterize and understand the crystallinity profiles of thermoplastic PMCs and the resulting impact to material properties. This talk discusses the use of multiple techniques such as Differential Scanning Calorimetry, Polarized Light Optical Microscopy, and Fourier-Transform Infrared Spectroscopy to characterize the crystallinity in carbon fiber/thermoplastic composites. Samples of different crystallinity profiles were manufactured using various cooling procedures. This work aims to provide the fundamental data necessary to understand the effects of crystallinity on thermoplastic PMCs, which is key to advancing their use in aerospace applications.

Thermoplastics↗

NASA NTRS1994

Characterization of the alpha-gamma and alpha-beta complex: evidence for an in vivo functional role of alpha-crystallin as a molecular chaperone

Previous studies have demonstrated that in vitro, alpha-crystallin can protect other lens proteins against extensive denaturation and aggregation. The mechanism of this protection involves preferential binding of the partially denatured protein to a central region of the native alpha-crystallin complex. To test whether a similar phenomenon might occur in vivo, a high molecular weight aggregate (HMWA) fraction was isolated from the aged bovine lens. Negative staining of this preparation revealed the presence of particles of 13-14 nm diameter, characteristic of alpha-crystallin. Immunolocalization of the same particles using antiserum specific for gamma- and beta-crystallins demonstrated preferential binding of these crystallins to the central region of the alpha-crystallin complex. Together, these results provide evidence that in the intact lens, the alpha-crystallins are functionally important molecular chaperones.

NASA Discipline Developmental Biology↗

NASA NTRS1993

The C-terminal region of alpha-crystallin: involvement in protection against heat-induced denaturation

Recent studies have demonstrated that the alpha-crystallins can protect other proteins against heat-induced denaturation and aggregation. To determine the possible involvement of the C-terminal region in this activity, the alpha-crystallins were subjected to limited tryptic digestion, and the amount of cleavage from the N-terminal and C-terminal regions of the alpha-A and alpha-B crystallin chains was assessed using antisera specific for these regions. Limited tryptic digestion resulted in cleavage only from the C-terminal region of alpha-A crystallin. This trypsin-treated alpha-A crystallin preparation showed a decreased ability to protect proteins from heat-induced aggregation using an in vitro assay. Together, these results demonstrate that the C-terminal region of alpha-A crystallin is important for its ability to protect against heat-induced aggregation, which is consistent with the hypothesis that post-translational changes that are known to occur at the C-terminal region may have significant effects on the ability of alpha-A crystallin to protect against protein denaturation in vivo.

NASA Discipline Cell Biology↗

NASA NTRS1992

The ability of lens alpha crystallin to protect against heat-induced aggregation is age-dependent

Alpha crystallin was prepared from newborn and aged bovine lenses. SDS-PAGE and tryptic peptide mapping demonstrated that both preparations contained only the alpha-A and alpha-B chains, with no significant contamination of other crystallins. Compared with alpha crystallin from the aged lens, alpha crystallin from the newborn lens was much more effective in the inhibition of beta L crystallin denaturation and precipitation induced in vitro by heat. Together, these results demonstrate that during the aging process, the alpha crystallins lose their ability to protect against protein denaturation, consistent with the hypothesis that the alpha crystallins play an important role in the maintenance of protein native structure in the intact lens.

NASA Discipline Cell Biology↗

NASA NTRS1991

Involvement of the N-terminal region in alpha-crystallin-lens membrane recognition

Previous studies have demonstrated that alpha-crystallin binds specifically, in a saturable manner, to lens membrane. To determine the region of the alpha-crystallin molecule that might be involved in this binding, native alpha-crystallin from the bovine lens has been treated by limited digestion with trypsin, to produce alpha-A molecules with an intact C-terminal region, and a nicked N-terminal region. Compared to intact alpha-crystallin, trypsin-treated alpha-crystallin binds less avidly to lens membrane, suggesting that the N-terminal region of the alpha-A molecule may play a key role in the recognition between lens membrane and crystallin.

Non-NASA Center↗

NASA NTRS2004

High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp

Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approx. 1000 K) in shocks in the 5-10 AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) > 1000 K at r(sub h) < 5 AU, 10(exp -6) - 10(exp -5) M(sub O)/yr, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-to-amorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

Wooden, D. H.↗

NASA NTRS2004

High Silicate Crystalline-to-Amorphous Ratios in Comets C/2001 Q4 (NEAT) and Hale-Bopp

Crystalline silicates, by their apparent absence in the ISM, are dust grains that experienced high temperatures in the solar nebula. Mg-rich crystalline silicates formed either by condensation from hot nebular gases (1450 K) or by the annealing of Mg-rich amorphous silicates (approximately 1000 K) in shocks in the 5-10AU region or by radial transport into and out of the hot inner zones, e.g., T(sub d) greater than 1000K at r(sub h) less than 5AU, 10(exp -6) -10(exp -5) solar mass per year, alpha = 10(exp -4) of the early solar nebula. Mg-rich crystalline silicates are found in interplanetary dust particles (IDPs) and produce IR spectral features in many Oort cloud comets. In May 2004, we discovered strong crystalline silicate features in the dynamically new Oort cloud comet C/2001 Q4 (NEAT). Thermal emission modeling of comets Q4 and C/1995 O1 (Hale-Bopp) demonstrate that both these comets have similar, high silicate crystalline-toamorphous ratios of 2.4 and 2.1, respectively, indicating that these icy planetesimals aggregated from similar reservoirs of material or that crystalline silicates were widely distributed within the comet-forming zone. This argues for efficient annealing mechanisms and radial mixing.

Wooden, D. H.↗

NASA NTRS1999

Detection of Crystalline Hematite Mineralization on Mars by the Thermal Emission Spectrometer: Evidence for Near-surface Water

The Thermal Emission Spectrometer (TES) instrument on the Mars Global Surveyor (MGS) mission has discovered a remarkable accumulation of crystalline hematite ((alpha-Fe2O3) that covers an area with very sharp boundaries approximately 350 by 350-750 km in size centered near 2 S latitude between 0 and 5 W longitude (Sinus Meridiani). Crystalline hematite is uniquely identified by the presence of fundamental vibrational absorption features centered near 300, 450, and >525/cm, and by the absence of silicate fundamentals in the 1000/cm region. Spectral features resulting from atmospheric CO2, dust, and water ice were removed using a radiative transfer model. The spectral properties unique to Sinus Meridiani were emphasized by removing the average spectrum of the surrounding region. The depth and shape of the hematite fundamental bands show that the hematite is crystalline and relatively coarse grained (>5-10 micron). Diameters up to and greater than 100s of micrometers are permitted within the instrumental noise and natural variability of hematite spectra. Hematite particles <5-10 micron in diameter (either as an unpacked or hard-packed powders) fail to match the TES spectra. The spectrally-derived areal abundance of hematite varies with particle size from approximately 10% for particles >30 micron in diameter to 40-60% for unpacked 10 micron powders. The hematite in Sinus Meridiani is thus distinct from the fine-grained (diameter <5-10 micron), red, crystalline hematite considered, on the basis of visible, near-IR data, to be a minor spectral component in Martian bright regions like Olympus-Amazonis. Sinus Meridiani hematite is closely associated with a smooth, layered, friable surface that is interpreted to be sedimentary in origin. This material may be the uppermost surface in the region, indicating that it could be a late-stage sedimentary unit, or it could be a layered portion of the heavily cratered plains units. We consider five possible mechanisms for the formation of coarse-grained, crystalline hematite. These processes fall into two classes depending on whether they require a significant amount of near-surface water: (1) chemical precipitation that includes origin by (a) precipitation from oxygenated, Fe-rich water (iron formations), (b) hydrothermal extraction and crystal growth.

Christensen, P. R.↗

NASA NTRS2002

Rotationally Molded Liquid Crystalline Polymers

Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers advantages of low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semi-rigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers.

Rogers, Martin↗

NASA NTRS2002

Rotationally Molded Liquid Crystalline Polymers

Rotational molding is a unique process for producing hollow plastic parts. Rotational molding offers low cost tooling and can produce very large parts with complicated shapes. Products made by rotational molding include water tanks with capacities up to 20,000 gallons, truck bed liners, playground equipment, air ducts, Nylon fuel tanks, pipes, toys, stretchers, kayaks, pallets, and many others. Thermotropic liquid crystalline polymers are an important class of engineering resins employed in a wide variety of applications. Thermotropic liquid crystalline polymers resins are composed of semirigid, nearly linear polymeric chains resulting in an ordered mesomorphic phase between the crystalline solid and the isotropic liquid. Ordering of the rigid rod-like polymers in the melt phase yields microfibrous, self-reinforcing polymer structures with outstanding mechanical and thermal properties. Rotational molding of liquid crystalline polymer resins results in high strength and high temperature hollow structures useful in a variety of applications. Various fillers and reinforcements can potentially be added to improve properties of the hollow structures. This paper focuses on the process and properties of rotationally molded liquid crystalline polymers. This paper will also highlight the interactions between academia and small businesses in developing new products and processes.

Rogers, Martin↗

NASA NTRS1992

An assay for intermolecular exchange of alpha crystallin

An affinity column of alpha crystallin linked to cyanogen bromide-activated Sepharose was developed to study the exchange of alpha subunits. Alpha crystallin bound to the Sepharose-alpha complex was dissociated with 8 mol/l urea, followed by quantitation using high-performance reverse-phase liquid chromatography. The time course of binding at 37 degrees C showed a hyperbolic binding pattern reaching equilibrium between 6-18 hr. Under these conditions, binding of beta and gamma crystallins to the same matrix was less than 10% of the alpha values, as was binding of alpha to glycine-coupled Sepharose. This assay was used to demonstrate changes in the subunit exchange of alpha crystallins present in high molecular weight versus lower molecular weight aggregates of the human lens. These results show that this binding procedure was a specific reproducible assay that might be used to study intermolecular interactions of the alpha crystallins.

NASA Discipline Cell Biology↗

NASA NTRS2009

Radiation-Induced Amorphization of Crystalline Ice

We study radiation-induced amorphization of crystalline ice, ana lyzing the resu lts of three decades of experiments with a variety of projectiles, irradiation energy, and ice temperature, finding a similar trend of increasing resistance of amorphization with temperature and inconsistencies in results from different laboratories. We discuss the temperature dependence of amorphization in terms of the 'thermal spike' model. We then discuss the common use of the 1.65 micrometer infrared absorption band of water as a measure of degree of crystallinity, an increasingly common procedure to analyze remote sensing data of astronomical icy bodies. The discussion is based on new, high quality near-infrared refl ectance absorption spectra measured between 1.4 and 2.2 micrometers for amorphous and crystalline ices irradiated with 225 keV protons at 80 K. We found that, after irradiation with 10(exp 15) protons per square centimeter, crystalline ice films thinner than the ion range become fully amorphous, and that the infrared absorption spectra show no significant changes upon further irradiation. The complete amorphization suggests that crystalline ice observed in the outer Solar System, including trans-neptunian objects, may results from heat from internal sources or from the impact of icy meteorites or comets.

Fama, M.↗

NASA NTRS2014

Amorphous and Crystalline H20 Ice at Rhea's Inktomi Crater

We present the analysis of Cassini spectral data from spectral mapping of Saturnian icy moons Dione and Rhea, to investigate possible effects of impact crater formation on the relative abundances of crystalline and amorphous water ice in the moons' ice crusts. Both moons display morphologically young ray craters as well as older craters. Possible changes in ice properties due to crater formation are conjectured to be more visible in younger craters, and as such Rhea's well imaged ray crater Inktomi is analysed, as are older craters for comparison. We used data from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). For each pixel in the VIMS maps, spectral data were extracted in the near-infrared range (1.75 micrometers less than lambda less than 2.45 micrometers). Analysis was begun by fitting a single Gaussian to the peak in absorption at 2.0 micrometers, which was then subtracted from the data, leaving residuals with a minimum on either side of the original 2.0-micrometers band. The spectra of the individual spatial pixels were then clustered by the differences between these minima, which are sensitive to changes in both ice grain size and crystallinity. This yielded preliminary maps which approximated the physical characteristics of the landscape and were used to identify candidates for further analysis. Spectra were then clustered by the properties of the 1.5-micrometers band, to divide the map into regions based on inferred grain size. For each region, the predicted differences in minima from the Gaussian residuals, over a range of crystallinities, were calculated based on the found grain sizes. This model was used to find the crystallinity of each pixel via grain size and characteristics of the residual function. Preliminary results show a greater degree of crystallization of young crater interiors, particularly in Rhea's ray crater Inktomi, where ice showed crystalline ice abundances between 33 percent and 61 percent. These patterns in ice crystallization are possibly attributable to increased heat generated during crater formation.

Saturn Satellites↗

NASA NTRSDate not supplied

Evaluating Crystallinity in Thermoplastic composites

Thermoplastics↗

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.↗

NASA NTRS1985

Study of the physical properties of crystalline rocks in the southeast Voronezh anteclise

The physical properties of rocks, in the crystalline mass of the Voronezh anteclise, were studied. The study of the physical properties of rocks is important for the improvement of geophysical methods for mapping crystalline rocks in the foundation and exploration of different geological objects which are associated with the crystalline foundation, covered by the sedimentary mantle. It is found that: (1) rocks in the crystalline foundation are very different in physical properties; (2) the physical properties are closely related to their substance composition and genesis; (3) petrographic properties give clues of rock afficiation to certain complexes; and (4) physical and magnetic properties should be examined by petrography, chemical and X-ray analysis.

Dmitriyevskiy, V. S.↗