scholarly journals Thermochemical characterization of polybenzimidazole with and without nano-ZrO2 for ablative materials application

2020 ◽  
Vol 142 (5) ◽  
pp. 2149-2161
Author(s):  
L. Paglia ◽  
V. Genova ◽  
M. P. Bracciale ◽  
C. Bartuli ◽  
F. Marra ◽  
...  
Keyword(s):  
High Performance ◽  
Phenolic Resin ◽  
Thermal Protection ◽  
Space Vehicle ◽  
Heat Fluxes ◽  
Heating Rates ◽  
Thermoplastic Material ◽  
Environmental Friendly ◽  
Very High

AbstractDuring the ballistic atmospheric re-entry, a space vehicle has to withstand huge thermo-mechanical solicitations because of its high velocity and the friction with the atmosphere. According to the kind of the re-entry mission, the heat fluxes can be very high (in the order of some MW m−2) ;thus, an adequate thermal protection system is mandatory in order to preserve the structure of the vehicle, the payload and, for manned mission, the crew. Carbon phenolic ablators have been chosen for several missions because they are able to dissipate the incident heat flux very efficiently. Phenolic resin presents satisfying performance but also environmental drawbacks. Thus, a more environmental-friendly solution was conceived: a high-performance thermoplastic material, polybenzimidazole (PBI), was employed instead of phenolic resin. In this work PBI-ablative material samples were manufactured with and without the addition of nano-ZrO2 and tested with an oxyacetylene flame. For comparison, some carbon-phenolic ablators with the same density were manufactured and tested too. Thermogravimetric analysis on PBI samples was carried out at different heating rates, and the obtained TG data were elaborated to evaluate the activation energy of PBI and nano-filled PBI. The thermokinetics results for PBI show an improvement in thermal stability due to the addition of nano-ZrO2, while the oxyacetylene flame test enlightens how PBI ablators are able to overcome the carbon phenolic ablators performance, in particular when modified by the addition of nano-ZrO2.

Plasma Sprayed Ultra High Temperature Ceramics for Thermal Protection Systems

2000 ◽  
Author(s):  
T. Valente ◽  
C. Bartuli ◽  
G. Visconti ◽  
M. Tului
Keyword(s):  
Plasma Spraying ◽  
High Performance ◽  
Thermal Protection ◽  
Electrical Discharge Machining ◽  
High Heat ◽  
Heat Fluxes ◽  
Space Vehicles ◽  
Ultra High Temperature Ceramics ◽  
Protection Systems ◽  
Plasma Sprayed

Abstract Reusable space vehicles, which must withstand re-entry into the Earth's atmosphere, require external protection systems (TPS) which are usually in the forms of rigid surface in areas of high or moderate working temperature. High heat fluxes and temperatures related to high performance hypervelocity flights also require the use of TPS materials having good oxidation and thermal shock resistance, dimensional stability, and ablation resistance. Components by these materials are usually fabricated, starting from either billets or plate stocks, by uniaxial hot pressing, and complex parts, such as low radius edges, are then obtained by electrical discharge machining technique. This article investigates an alternative fabrication technology, based on plasma spraying, to produce near net shape components. Results of experimental activities, such as optimization of plasma spraying parameters based on a DOE approach, are reported and discussed.

Design and Characterization of a Novel Upward Flow Reactor for the Study of High-Temperature Thermal Reduction for Solar-Driven Processes

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
H. Evan Bush ◽  
Karl-Philipp Schlichting ◽  
Robert J. Gill ◽  
Sheldon M. Jeter ◽  
Peter G. Loutzenhiser
Keyword(s):  
High Temperature ◽  
Flow Reactor ◽  
Thermal Reduction ◽  
Heat Fluxes ◽  
O2 Evolution ◽  
Transfer Model ◽  
Upward Flow ◽  
Heating Rates ◽  
Solar Simulator

The design and characterization of an upward flow reactor (UFR) coupled to a high flux solar simulator (HFSS) under vacuum is presented. The UFR was designed to rapidly heat solid samples with concentrated irradiation to temperatures greater than 1000 °C at heating rates in excess of 50 K/s. Such conditions are ideal for examining high-temperature thermal reduction kinetics of reduction/oxidation-active materials by temporally monitoring O2 evolution. A steady-state, computational fluid dynamics (CFD) model was employed in the design to minimize the formation of eddies and recirculation, and lag and dispersion were characterized through a suite of O2 tracer experiments using deconvolution and the continuously stirred tank reactors (CSTR) in series models. A transient, CFD and heat transfer model of the UFR was combined with Monte Carlo ray tracing (MCRT) to determine radiative heat fluxes on the sample from the HFSS to model spatial and temporal sample temperatures. The modeled temperatures were compared with those measured within the sample during an experiment in which Co3O4 was thermally reduced to CoO and O2. The measured temperatures within the bed were bounded by the average top and bottom modeled bed temperatures for the duration of the experiment. Small variances in the shape of the modeled versus experimental temperatures were due to contact resistance between the thermocouple and particles in the bed and changes in the spectral absorptivity and emissivity as the Co3O4 was reduced to CoO and O2.

Mbe Growth and Characterization of Hgcdte Heterostructures

1990 ◽  
Vol 198 ◽  
Author(s):  
R.J. Koestner ◽  
M.W. Goodwin ◽  
H.F. Schaake
Keyword(s):  
High Performance ◽  
Misfit Dislocations ◽  
Mbe Growth ◽  
Long Wavelength ◽  
Fine Control ◽  
Critical Materials ◽  
Long Wavelength Infrared ◽  
Growth Technology ◽  
Very High

ABSTRACTHgCdTe heterostructures consisting of a thin n-type widegap (250 meV or 5 μm cutoff) layer deposited on an n-type narrowgap (100-125 meV or 10-13 μm cutoff) layer offer the promise of very high performance metal-insulator-semiconductor (MIS) photocapacitors for long wavelength infrared (LWIR) detection. Molecular Beam Epitaxy (MBE) is a candidate growth technology for these two layer films due to its fine control in composition, thickness and doping concentration. The critical materials issues are reducing the defect content associated with twins in the grown layers, achieving low net donor concentrations in the widegap layer, and avoiding the formation of misfit dislocations at the HgCdTe heterointerface. This paper will report on our recent progress in these directions.

X-ray characterization of short-pulse laser illuminated hydrogen storage alloys having very high performance

2015 ◽  
Author(s):  
Hiroyuki Daido ◽  
Hiroshi Abe ◽  
Takahisa Shobu ◽  
Takuya Shimomura ◽  
Shinnosuke Tokuhira ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Pulse Laser ◽  
High Performance ◽  
Short Pulse ◽  
Hydrogen Storage Alloys ◽  
X Ray ◽  
Short Pulse Laser ◽  
Very High

Ceramic Composites and Thermal Protection Systems for Reusable Re-Entry Vehicles

2006 ◽  
Vol 45 ◽  
pp. 1505-1514 ◽  
Author(s):  
Teodoro Valente ◽  
Cecilia Bartuli ◽  
Giovanni Pulci
Keyword(s):  
High Temperature ◽  
Thermal Protection ◽  
Space Vehicle ◽  
Ceramic Composites ◽  
Heat Fluxes ◽  
Launch Vehicles ◽  
Processing Technologies ◽  
Reusable Launch Vehicles ◽  
Expected Benefits ◽  
The Right

Next generation of reusable launch vehicles and new hypersonic space vehicle concepts are currently under development, moving from traditional aerodynamic configuration towards slender profiles. Main expected benefits are reduction of drag, enhancement in lift-to-drag ratio and reduction of interferences with radio frequency transmissions during the re-entry. Flexibility in designing sharp profiles is strictly conditioned to the availability of suitable materials and processing technologies, required to fabricate components and surfaces able to withstand higher heat fluxes induced by the new profiles. Advances in the field of CMC's for high temperature structures and TPS are the basis for innovative approaches to the design of future RLV's. Beside baseline solutions, already available and well characterized, as for C/SiC CMC's, ultra high temperature ceramics seem to offer the right chance to fabricate hot structures having the required heat-resistant and load carrying capabilities. This paper deals with technologies based on the use of diboride based CMC's which can be considered promising candidate materials for the fabrication of hot structures of slender bodies, such as nose cap and wing leading edges. Recent experimental results will be presented and discussed.

Analysis of the Aerodynamic Heating for a Re-Entrant Space Vehicle

1959 ◽  
Vol 81 (3) ◽  
pp. 223-229 ◽  
Author(s):  
M. J. Brunner
Keyword(s):  
Pressure Distribution ◽  
Wall Temperature ◽  
Space Vehicle ◽  
Heat Fluxes ◽  
Aerodynamic Heating ◽  
Heating Rates ◽  
Local Pressure ◽  
High Lift ◽  
Maximum Heating ◽  
Vehicle Bodies

An analysis of the aerodynamic heating is presented through the trajectory and over the surface of a re-entrant hypersonic space vehicle. Bodies exhibiting zero and high lift over drag ratios are considered. The turbulent and laminar convective heat inputs are specified as functions of the trajectory and space vehicle parameters. The maximum heating rates and time integrated heat fluxes are given as functions of the local pressure distribution, body geometry, and wall temperature. Examples are presented to illustrate the application of this analysis.

Preparation and Characterization of NH2-Terminal Fibrinogen Bβ Fragments from N-DSK of Human Fibrinogen

1984 ◽  
Vol 51 (01) ◽  
pp. 016-021 ◽  
Author(s):  
S Birken ◽  
G Agosto ◽  
B Lahiri ◽  
R Canfield
Keyword(s):  
High Performance ◽  
Gel Filtration ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Reverse Phase ◽  
Human Fibrinogen ◽  
Human Volunteers ◽  
Cnbr Cleavage ◽  
Two Peaks

SummaryIn order to investigate the early release of NH2-terminal plasmic fragments from the Bβ chain of fibrinogen, substantial quantities of Bβ 1-42 and Bβ 1-21 are required as immunogens, as radioimmunoassay standards and for infusion into human volunteers to determine the half-lives of these peptides. Towards this end methods that employ selective proteolytic cleavage of these fragments from fibrinogen have been developed. Both the N-DSK fragment, produced by CNBr cleavage of fibrinogen, and Bβ 1-118 were employed as substrates for plasmin with the finding of higher yields from N-DSK. Bβ 1-42 and Bβ 1-21 were purified by gel filtration and ion-exchange chromatography on SP-Sephadex using volatile buffers. When the purified preparation of Bβ 1-42 was chromatographed on reverse-phase high performance liquid chromatography, two peaks of identical amino acid composition were separated, presumably due either to pyroglutamate or to amide differences.

Production of Asbestos-free Brake Pad Using Groundnut Shell as Filler Material

2018 ◽  
Vol 4 (12) ◽  
Author(s):  
W. C. Solomon ◽  
M. T. Lilly ◽  
J. I. Sodiki
Keyword(s):  
Phenolic Resin ◽  
Cost Effective ◽  
Filler Material ◽  
Particle Sizes ◽  
Brake Pad ◽  
Brake Pads ◽  
Environmental Friendly ◽  
Sieve Size ◽  
Groundnut Shell ◽  
The Cost

The development and evaluation of brake pads using groundnut shell (GS) particles as substitute material for asbestos were carried out in this study. This was with a view to harnessing the properties of GS, which is largely deposited as waste, and in replacing asbestos which is carcinogenic in nature despite its good tribological and mechanical properties. Two sets of composite material were developed using varying particle sizes of GS as filler material, with phenolic resin as binder with percentage compositions of 45% and 50% respectively. Results obtained indicate that the compressive strength and density increase as the sieve size of the filler material decreases, while water and oil absorption rates increase with an increase in sieve size of GS particle. This study also indicates that the cost of producing brake pad can be reduced by 19.14 percent if GS is use as filler material in producing brake pad. The results when compared with those of asbestos and industrial waste showed that GS particle can be used as an effective replacement for asbestos in producing automobile brake pad. Unlike asbestos, GS-based brake pads are environmental friendly, biodegradable and cost effective.

KEMPER C688

Alloy Digest ◽  
2017 ◽  
Vol 66 (12) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Copper Alloy ◽  
High Performance ◽  
High Conductivity ◽  
Bend Strength ◽  
Very High

Abstract Alloy C688 is a high-performance copper alloy with very high conductivity. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming and joining. Filing Code: Cu-867. Producer or source: Gebr. Kemper GmbH + Company KG Metallwerke.

KEMPER KHP7025

Alloy Digest ◽  
2017 ◽  
Vol 66 (10) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Tensile Properties ◽  
Copper Alloy ◽  
High Performance ◽  
High Conductivity ◽  
Bend Strength ◽  
Very High

Abstract Alloy KHP 7025 (UNS C70250) is a high-performance copper alloy with very high conductivity. Uses include connector springs, tabs, contact springs, switches, relays, and leadframes. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming, machining, and joining. Filing Code: Cu-865. Producer or source: Gebr. Kemper GmbH + Company KG Metallwerke.

Sign in / Sign up

Export Citation Format

Share Document