Vaporization of thermionic refractory materials fourteenth status report, 1 dec. 1964 - 28 feb. 1965
Sublimation rate of rhenium measured for determining source of contamination - vaporization of thermionic refractory materials
THERMIONICS↗
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Results for “Refractory material”
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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Atomic oxygen effects on refractory materials
Atomic oxygen in LEO may have undesirable effects on exposed refractory materials, such as are proposed for nuclear reactors in orbit, high temperature radiators, solar dynamic collectors, etc. Time-resolved measurement of the volatile efflux from such materials at high temperatures is being done in an ultrahigh vacuum atomic oxygen ion beam facility. Results of measurements of the efflux of volatile oxides of molybdenum and niobium-1 percent zirconium at temperatures as high as 1550 K are presented, along with a discussion of the roles of adsorption, desorption, and diffusion in atomic oxygen reactions on surfaces at high temperatures. The dependence of reaction rates for certain materials on the energy of the incident atomic oxygen beam will be emphasized.
Ferguson, Dale C.↗
Integrated Process and Materials Modeling for Development of Additive Manufacturing of Refractory Materials for Critical Applications
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36 MATERIALS SCIENCE↗
Investigations of the Deterioration of 22 Refractory Materials in a Mach Number 2 Jet at a Stagnation Temperature of 3,800 F
A limited investigation of the deterioration characteristics of 22 refractory materials was conducted by exposing them to a stagnation temperature of 3,800 F in a Mach number 2 ceramic-heated jet at the Langley Research Center. The materials tested were six materials whose major constituent was silicon carbide, five cermets whose major constituent was titanium carbide, six materials whose major constituents were metal borides, four cermets containing alumina, and one silicon nitride model. Tests consisted of obtaining weight change and appearance changes for 1/2-inch-diameter hemispherical-nose cylindrical models exposed to the air jet for 30 seconds at a time for a total of four runs or 2 minutes exposure. Curves of weight changes plotted against the number of 30-second tests in the jet were obtained. Estimates of average surface temperature near the stagnation point of the model were obtained by use of a special temperature-measuring camera. The models were examined before and after the completion of the tests for possible changes in microstructure; no significant changes were found. The data obtained were analyzed with the view that the oxidation characteristics of the materials were the main factor in deterioration of the materials under the conditions of the tests. It was concluded that only those materials which changed in weight the least could be recommended for further extensive application-oriented evaluations. The following materials fell in this category: silicon carbide - silicon, chromium - 28-percent alumina cermet, titanium boride - 5-percent boron carbide. The remainder of the materials tested had oxidation characteristics which appeared to be too severely limiting of their general applications to flight vehicles.
Lewis, B. W.↗
A Non-contact Measurement Technique for the Specific Heat and Total Hemispherical Emissivity of Undercooled Refractory Materials
This paper describes a non-contact measurement technique for (1) the constant pressure specific heat and (2) the total emissivity of undercooled refractory materials.
undercooled refactory materials↗
Stability of refractory materials in high temperature steam
The present invention relates, in part, to a discovery of a method for using atomic layer deposition (ALD) to improve the stability of refractory materials in high temperature steam, and compositions produced by the method.
Weimer, Alan W.↗
Novel Engineered Refractory Materials for Advanced Reactor Applications
This report summarizes the results of DOE-NEUP grant 10-853. The project spanned 48 months (36 months under the original grant plus a 12 month no cost extension). The overarching goal of this work was to fabricate and characterize refractory materials engineered at the atomic scale with emphasis on their tolerance to accumulated radiation damage. With an emphasis on nano-scale structure, this work included atomic scale simulation to study the underlying mechanisms for modified radiation tolerance at these atomic scales.
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
Compatibility Studies of Various Refractory Materials in Contact with Molten Silicon
The production of low cost, efficient solar cells for terrestrial electric power generation involves the manipulation of molten silicon with a present need for noncontaminating, high temperature refractories to be used as containment vessels, ribbon-production dies, and dip-coated substrates. Studies were conducted on the wetting behavior and chemical/physical interactions between molten silicon and various refractory materials.
Odonnell, T.↗
Non-Contact Measurements of Creep Properties of Refractory Materials
State-of-the-art technologies for hypersonic aircraft, nuclear electric/thermal propulsion for spacecraft, and more efficient jet engines are driving ever more demanding needs for high-temperature (>2000 C) materials. At such high temperatures, creep rises as one of the most important design factors to be considered. Since conventional measurement techniques for creep resistance are limited to about 17OO0C, a new technique is in demand for higher temperatures. This paper presents a non-contact method using electrostatic levitation (ESL) which is applicable to both metallic and non-metallic materials. The samples were rotated quickly enough to cause creep deformation by centrifugal acceleration. The deformation of the samples was captured with a high speed camera and then the images were analyzed to estimate creep resistance. Finite element analyses were performed and compared to the experiments to verify the new method. Results are presented for niobium and tungsten, representative refractory materials at 2300 C and 2700 C respectively.
Lee, Jonghyun↗
Modeling of Heat Transfer and Ablation of Refractory Material Due to Rocket Plume Impingement
CR Tech's Thermal Desktop-SINDA/FLUINT software was used in the thermal analysis of a flame deflector design for Launch Complex 39B at Kennedy Space Center, Florida. The analysis of the flame deflector takes into account heat transfer due to plume impingement from expected vehicles to be launched at KSC. The heat flux from the plume was computed using computational fluid dynamics provided by Ames Research Center in Moffet Field, California. The results from the CFD solutions were mapped onto a 3-D Thermal Desktop model of the flame deflector using the boundary condition mapping capabilities in Thermal Desktop. The ablation subroutine in SINDA/FLUINT was then used to model the ablation of the refractory material.
Harris, Michael F.↗
COMPATIBILITY OF MOLTEN URANIUM DIOXIDE WITH FIVE REFRACTORY MATERIALS
Compatibility of molten uranium dioxide with refractory metals
REFRACTORY METAL↗
New surface characterization tools for alumina based refractory material exposed to cavitation - Image analysis and pattern recognition approach
Highlights: • Surface degradation was monitored via mass loss measurement. • Observation of surface damage destruction was done using image analysis. • Shape parameters of surface defects change during cavitation. • Shape parameters changes are correlated to mass loss measurements. - Abstract: The aim of this study was to examine the influence of cavitation erosion on the morphology of defects formed on the surfaces of alumina-based materials. The alumina-based samples were exposed to cavitation erosion for 42 min. The damages that occurred were monitored at predefined time intervals by measuring the mass loss and observing the sample surfaces. Digital images of surfaces were processed using an image analysis software package to define morphological characteristics of the damages occurred. The calculated morphological parameters were subjected to analysis by pattern recognition techniques to correlate the appearance of particular morphological characteristics with the behavior of the material during cavitation erosion. The newly established method in describing cavitation erosion which uses pattern recognition approach for treatments of morphological parameters calculated for damages by image analysis tools gave the results efficient for material characterization as the traditional one.
36 MATERIALS SCIENCE↗
High voltage electrical insulation coating for refractory materials
Formula and process have been developed for coating refractory metal surfaces with high voltage electrical insulation for use at temperatures to 600 C. Coatings were specifically developed as an insulation for the surface of a perforated, molybdenum, ion-accelerator grid, but are not limited to this application.
Lent, W. E.↗
In-Operando Interactions of Refractory Materials with Ash/Slag from Mixed Feedstock Gasification: Interactions of Spruce Biomass with Alumina and Mullite-based Refractories upon Firing at 1200°C
TMS 2022, Virtual, February 27–March 3, 2022
Tippey, Kristin↗
Compatibility of refractory materials for nuclear reactor poison control systems
Metal-clad poison rods have been considered for the control system of an advanced space power reactor concept studied at the NASA Lewis Research Center. Such control rods may be required to operate at temperatures of about 140O C. Selected poison materials (including boron carbide and the diborides of zirconium, hafnium, and tantalum) were subjected to 1000-hour screening tests in contact with candidate refractory metal cladding materials (including tungsten and alloys of tantalum, niobium, and molybdenum) to assess the compatibility of these materials combinations at the temperatures of interest. Zirconium and hafnium diborides were compatible with refractory metals at 1400 C, but boron carbide and tantalum diboride reacted with the refractory metals at this temperature. Zirconium diboride also showed promise as a reaction barrier between boron carbide and tungsten.
Sinclair, J. H.↗
Floating zone process for drawing small diameter fibers of refractory materials
New process produces controlled purity, very high strength, single crystal fibers of materials with melting points to 4000 C. Process has been used to make single crystal fibers of highly refractory ceramics such as aluminum oxide, titanium carbide and yttrium oxide.
Westfall, L. J.↗
Computational synthesis of single-layer GaN on refractory materials
The synthesis of single-layer materials relies on suitable substrates. In this paper, we identify suitable substrates for the stabilization and growth of single-layer GaN and characterize the effect of the substrate on the electronic structure of single-layer GaN. We identify two classes of epitaxial substrates, refractory metal diborides and transition-metal dichalcogenides. We find that the refractory diborides provide epitaxial stabilization for the growth and functionalization of single layer GaN. We show that chemical interactions of single layer GaN with the diboride substrates result in n-type doping of the single-layer GaN. Transition-metal dichalcogenides, on the other hand, although epitaxially matched, cannot provide sufficient thermodynamic stabilization for the growth of single layer GaN. Nonetheless, energy band alignments of GaN/metal chalcogenides show that they make good candidates for heterostructures.
36 MATERIALS SCIENCE↗
Refractory Materials for Flame Deflector Protection System Corrosion Control: Coatings Systems Literature Survey
When space vehicles are launched, extreme heat, exhaust, and chemicals are produced and these form a very aggressive exposure environment at the launch complex. The facilities in the launch complex are exposed to this aggressive environment. The vehicle exhaust directly impacts the flame deflectors, making these systems very susceptible to high wear and potential failure. A project was formulated to develop or identify new materials or systems such that the wear and/or damage to the flame deflector system, as a result of the severe environmental exposure conditions during launches, can be mitigated. This report provides a survey of potential protective coatings for the refractory concrete lining on the steel base structure on the flame deflectors at Kennedy Space Center (KSC).
Calle, Luz M.↗