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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Stability Enhancement of Polymeric Sensing Films Using Fillers

Experiments have shown the stability enhancement of polymeric sensing films on mixing the polymer with colloidal filler particles (submicron-sized) of carbon black, silver, titanium dioxide, and fumed silicon dioxide. The polymer films are candidates for potential use as sensing media in micro/nano chemical sensor devices. The need for stability enhancement of polymer sensing films arises because such films have been found to exhibit unpredictable changes in sensing activity over time, which could result in a possible failure of the sensor device. The changes in the physical properties of a polymer sensing film caused by the sorption of a target molecule can be measured by any of several established transduction techniques: electrochemical, optical, calorimetric, or piezoelectric, for example. The transduction technique used in the current polymer stability experiments is based on piezoelectric principles using a quartz-crystal microbalance (QCM). The surface of the QCM is coated with the polymer, and the mass uptake by the polymer film causes a change in the oscillating frequency of the quartz crystal. The polymer used for the current study is ethyl cellulose. The polymer/ polymer composite solutions were prepared in 1,3 dioxolane solvent. The filler concentration was fixed at 10 weight percent for the composites. The polymer or polymer composite solutions were cast on the quartz crystal having a fundamental frequency of about 6 MHz. The coated crystal was subjected to a multistage drying process to remove all measurable traces of the solvent. In each experiment, the frequency of oscillation was measured while the QCM was exposed to clean, dry, flowing air for about 30 minutes, then to air containing a known concentration of isopropanol for about 30 minutes, then again to clean dry air for about 30 minutes, and so forth. This cycle of measurements for varying isopropanol concentrations was repeated at intervals for several months. The figure depicts some of the sensing film stability results for ethyl cellulose polymer, ethyl cellulose-carbon black, and ethyl cellulose-silicon dioxide composite systems. An ethyl cellulose film exhibited a marked decline in response in the first few months of study and settled to a steady average response after about four months. However, response varied widely around the average response for ethyl cellulose film. In contrast, ethyl cellulose- carbon black and ethyl cellulose-silicon dioxide composites also declined in the early months, but showed more repeatable sensing film activity after the initial decline. Similar trends were observed in experiments for ethyl cellulose-titanium dioxide and ethyl cellulose-silver composites.

Lin, Brian↗
NASA NTRS1978

Easy Meal

The woman pictured below is sitting down to a nutritious, easily-prepared meal similar to those consumed by Apollo astronauts. The appetizing dishes shown were created simply by adding water to the contents of a Mountain House* Easy Meal package of freeze dried food. The Easy Meal line is produced by Oregon Freeze Dry Foods, Inc., Albany, Oreaon, a pioneer in freeze drying technology and a company long associated with NASA in developing suitable preparations for use on manned spacecraft. Designed to provide nutritionally balanced, attractive hot meals for senior adults, Easy Meal is an offshoot of a 1975-77 demonstration project managed by Johnson Space Center and called Meal System for the Elderly. The project sought ways to help the estimated 3.5 million elderly Americans who are unable to take advantage of existing meal programs. Such services are provided by federal, state and local agencies, but they are not available to many who live in rural areas, or others who are handicapped, temporarily ill or homebound for other reasons. Oregon Freeze Dry Foods was a participant in that multi-agency cooperative project. With its Easy Meal assortment of convenience foods pictured above left, the company is making commercially available meal packages similar to those distributed in the Meal System for the Elderly program. In the freeze drying process, water is extracted from freshly-cooked foods by dehydration at very low temperatures, as low as 50 I degrees below zero. Flavor is locked in by packaging the dried food in pouches which block out moisture and oxygen, the principal causes of food deterioration; thus the food can be stored for long periods without refrigeration. Meals are reconstituted by adding hot or cold water, depending on the type of food, and they are table ready in five to 10 minutes. Oregon Freeze Dry Foods offers five different meal packages and plans to expand the line.

Source record↗
NASA NTRS1989

Improved silicon carbide for advanced heat engines. I - Process development for injection molding

Alternate processing methods have been investigated as a means of improving the mechanical properties of injection-molded SiC. Various mixing processes (dry, high-sheer, and fluid) were evaluated along with the morphology and particle size of the starting beta-SiC powder. Statistically-designed experiments were used to determine significant effects and interactions of variables in the mixing, injection molding, and binder removal process steps. Improvements in mechanical strength can be correlated with the reduction in flaw size observed in the injection molded green bodies obtained with improved processing methods.

Whalen, Thomas J.↗
NASA NTRS1981

A unique approach to fabricating precision space structures elements

A procedure of fabricating graphite epoxy columns used in the assembly of large space platforms is described. The requirement for precise dimensional control led to a unique hot resin injection process. Dry, high modulus fiber is wound over a vertically mounted steam-heated mandrel. A steam-heated sleeve or caul is slipped over the wound mandrel and resin is injected and cured in place. Approximately 200 column elements have been fabricated using this efficient process.

Cohan, H.↗
NASA NTRS1979

High density circuit technology

Polyimide dielectric materials were acquired for comparative and evaluative studies in double layer metal processes. Preliminary experiments were performed. Also, the literature indicates that sputtered aluminum films may be successfully patterned using the left-off technique provided the substrate temperature remains low and the argon pressure in the chamber is relatively high at the time of sputtering. Vendors associated with dry processing equipment are identified. A literature search relative to future trends in VLSI fabrication techniques is described.

Wade, T. E.↗
NASA NTRS1985

Response of cumulus clouds to large-scale forcing and cumulus parameterization

Using the cumulus ensemble model (Soong and Ogura, 1980), statistical properties of cumulus clouds that occur in response to the imposed large scale forcing were investigated both in the tropical and midlatitude situtations. A strong drying process was found to occur in the boundary layer in association with deep convection in a midlatitude case. The Arakawa-Schubert (1974) cumulus parameterization scheme was tested semi-prognostically against both the model result and the observation in a tropical rain event that occurred in GATE. The Cloud heating and drying effects predicted by the Arakawa-Schubert scheme were found to agree well both with the observation and the model result. However, it was also found that the Arakawa-Schuber scheme underestimates both condensation and evaporation rates substantially. An inclusion of the downdraft effect, as formulated by Johnson (1976), appears to alleviate this deficiency. This downdraft effect may be important in predicting the behavior of the boundary accurately.

Ogura, Y.↗
NASA NTRSDate not supplied

Layered Electrode Architectures Enabled by Holey Graphene Hosts

Battery electrodes are typically prepared using a slurry-based method, where high boiling point organic solvents are typically used with a polymer binder to disperse active electrode materials and conductive carbon additives followed by casting into current collector sheets. In this process, the use of organic solvents are environmentally hazardous, energy intensive, and time-consuming, while polymeric binders add weight and can undergo parasitic reactions during battery cycling. Here we discuss the use of a unique conductive carbon nanomaterial, namely holey graphene, as a multifunctional host that can be processed via a facile, solvent-free, binder-free, cold pressing method to prepare electrodes with unique architectures. This approach can accommodate a broad range of battery chemistries, such as lithium oxygen/carbon dioxide (Li-O2/CO2), lithium sulfur/selenium (Li-S/Se), and various lithium ion chemistries. The successful use of dry, cold compression allows the convenient modification of electrode mass loading with unique architectures containing active materials randomly mixed or layered with single or multiple layers of one or more active materials. In the conventional slurry-based electrode fabrication method, it is difficult, if not impossible, to achieve such layered architectures. In particular, the layered electrode architectures from the dry, cold press approach are easy to fabricate without significantly sacrificing device performance, and are amenable to continuous roll-to-roll dry processing. In addition, these architectures offer unprecedented perspectives on the battery material loading vs. utilization efficiency, as well as enabling unique characterization opportunities to advance mechanistic understanding of various battery chemistries. Potential applications of this unique electrode fabrication approach for solid-state batteries will also be discussed.

holey graphene, batteries, electrode architecture,↗
NASA NTRS1991

RTM: Cost-effective processing of composite structures

Resin transfer molding (RTM) is a promising method for cost effective fabrication of high strength, low weight composite structures from textile preforms. In this process, dry fibers are placed in a mold, resin is introduced either by vacuum infusion or pressure, and the part is cured. RTM has been used in many industries, including automotive, recreation, and aerospace. Each of the industries has different requirements of material strength, weight, reliability, environmental resistance, cost, and production rate. These requirements drive the selection of fibers and resins, fiber volume fractions, fiber orientations, mold design, and processing equipment. Research is made into applying RTM to primary aircraft structures which require high strength and stiffness at low density. The material requirements are discussed of various industries, along with methods of orienting and distributing fibers, mold configurations, and processing parameters. Processing and material parameters such as resin viscosity, perform compaction and permeability, and tool design concepts are discussed. Experimental methods to measure preform compaction and permeability are presented.

Hasko, Greg↗
NASA NTRS2014

Insights on TTL Dehydration Mechanisms from Microphysical Modelling of Aircraft Observations

The Tropical Tropopause Layer (TTL), a transition layer between the upper troposphere and lower stratosphere in the tropics, serves as the entryway of various trace gases into the stratosphere. Of particular interest is the transport of water vapor through the TTL, as WV is an important greenhouse gas and also plays a significant role in stratospheric chemistry by affecting polar stratospheric cloud formation and the ozone budget. While the dominant control of stratospheric water vapor by tropical cold point temperatures via the "freeze-drying" process is generally well understood, the details of the TTL dehydration mechanisms, including the relative roles of deep convection, atmospheric waves and cloud microphysical processes, remain an active area of research. The dynamical and microphysical processes that influence TTL water vapor concentrations are investigated in simulations of cloud formation and dehydration along air parcel trajectories. We first confirm the validity of our Lagrangian models in a case study involving measurements from the Airborne Tropical TRopopause EXperiment (ATTREX) flights over the central and eastern tropical Pacific in Oct-Nov 2011 and Jan-Feb 2013. ERA-Interim winds and seasonal mean heating rates from Yang et al. (2010) are used to advance parcels back in time from the flight tracks, and time-varying vertical profiles of water vapor along the diabatic trajectories are calculated in a one-dimensional cloud model as in Jensen and Pfister (2004) but with more reliable temperature field, wave and convection schemes. The simulated water vapor profiles demonstrate a significant improvement over estimates based on the Lagrangian Dry Point, agreeing well with aircraft observations when the effects of cloud microphysics, subgrid-scale gravity waves and convection are included. Following this approach, we examine the dynamical and microphysical control of TTL water vapor in the 30ºS-30ºN latitudinal belt and elucidate the dominant processes in the winter and summer seasons. Implications of the TTL dehydration processes for the regulation of global stratospheric humidity will be discussed.

stratosphere↗
NASA NTRS1970

Progress in research on chlorate candle technology

Research and development program improves sodium chlorate candle formulation, production method, and igniter design. Cobalt is used as the fuel, dry processing methods are used to lower the water content, and a device based on pyrotechnic heater concepts is used as the igniter.

Littman, J.↗
NASA NTRS1974

Influence of moisture content on the velocity of ultrasounds in black poplar wood

Correlations among the longitudinal, radial and tangential velocities of ultrasounds in black poplar on the one hand and among these magnitudes and the wood's moisture content on the other hand are presented. Mathematical equations approximating these correlations are given, and the influence of moisture content on the elastic constants of wood is discussed. The possibility of using ultrasonic methods in automating the wood drying process and in testing the quality and homogeneity of wood is pointed out.

Bucar, V.↗
NASA NTRS1979

A study of trends and techniques for space base electronics

The use of dry processing and alternate dielectrics for processing wafers is reported. A two dimensional modeling program was written for the simulation of short channel MOSFETs with nonuniform substrate doping. A key simplifying assumption used is that the majority carriers can be represented by a sheet charge at the silicon dioxide-silicon interface. In solving current continuity equation, the program does not converge. However, solving the two dimensional Poisson equation for the potential distribution was achieved. The status of other 2D MOSFET simulation programs are summarized.

Trotter, J. D.↗
NASA NTRS1980

High density circuit technology

Acquisition of polyimide materials for inter-metal dielectrics was obtained from three vendors, with considerable evaluation conducted on the Dupont PI2550 material. Experimental results indicate this material can be patterned using contact printing to line width far below 0.1 mils. Optimum line width is acquired using plasma etch equipment. Metal lift-off experiments on thermal evaporated films were optimized for application to sputtered deposited films. Alternate metal-lift-off experiments are proposed for future investigation. Dry processing equipment studies and future trends in VLSI fabrication techniques are on-going.

Wade, T. E.↗
NASA NTRS1983

A technique for thick polymer coating of inertial-confinement-fusion targets

A technique to coat a stalk-mounted inertial-confinement fusion (ICF) target with a thick polymer layer has been successfully demonstrated. The polymer solution is first atomized, allowed to coalesce into a droplet, and positioned in a stable acoustic levitating field. The stalk-mounted ICF target is then moved into the acoustic field by manipulating a 3-D positioner to penetrate the surface membrane of the droplet, thus immersing the target in the levitated coating solution. The target inside the droplet is maintained at the center of the levitated liquid using the 3-D positional information provided by two orthogonally placed TV cameras until the drying process is completed. The basic components of the experimental apparatus, including an acoustic levitator, liquid sample deployment device, image acquisition instrumentation, and 3-D positioner, are briefly described.

Lee, M. C.↗
NASA NTRS1987

Making Highly Porous Ceramics

Rigid, lightweight insulation withstands temperatures greater than 1,400 degrees C made by cryogenic freeze-drying process. New insulation expected to have solid content as low as 1 percent by volume and to be mechanically isotropic.

Green, David J.↗
NASA NTRS1988

Microgravity particle reduction system

The Controlled Ecological Life Support System (CELSS) project, sponsored by NASA, is assembling the knowledge required to design, construct, and operate a system which will grow and process higher plants in space for the consumption by crew members of a space station on a long term space mission. The problem of processing dry granular organic materials in microgravity is discussed. For the purpose of research and testing, wheat was chosen as the granular material to be ground into flour. Possible systems which were devised to transport wheat grains into the food processor, mill the wheat into flour, and transport the flour to the food preparation system are described. The systems were analyzed and compared and two satisfactory systems were chosen. Prototypes of the two preferred systems are to be fabricated next semester. They will be tested under simulated microgravity conditions and revised for maximum effectiveness.

Brandon, Vanessa↗
NASA NTRS1991

Freeze-drying for morphological control of high performance semi-interpenetrating polymer networks. III

The feasibility of using a freeze-drying (solvent removal by sublimation) approach for controlling the morphology of a high-performance semi-IPN is assessed. A high-performance thermoplastic polyimide and commercially available 4,4'-bismaleimide diphenylenemethane were dissolved in a solvent, 1,3,5-trioxane. The solvent was removed from the constituents by freeze-drying. For purposes of comparison, the constituents were dissolved in a high-boiling-point solvent, N,N-dimethylformamide. The solvent was removed from the solution by evaporation. The physical and mechanical properties and phase morphology of the neat resins and composites prepared by freeze-drying and traditional solution methods are presented and compared. It is concluded that the TG is higher and that the magnitude of minor constituent separation is less in the freeze-dry processed materials than for the processed solution.

Hsiung, H. J.↗