Plastic and nonmetallic article shaping or treating: processes – Carbonizing to form article
Patent
1995-06-26
1998-01-06
Speer, Timothy
Plastic and nonmetallic article shaping or treating: processes
Carbonizing to form article
264 292, 264 297, C01B 3100
Patent
active
057051062
DESCRIPTION:
BRIEF SUMMARY
SPECIFICATION
1. Field of Invention
The present invention relates to the field of production of refractory structural materials and can be useful in the production of heat insulation for a high-temperature technology, in metallurgy and aerospace engineering.
2. Description of Prior Art
The prior art in the field to which the present invention relates can be characterized by several conventional technical solutions in one or another way directed to obtaining porous (low-density) materials, insofar as porous carbon materials have thermal conductivity 10 to 15 times as low as that of compact carbon materials.
There is known in the art a process for producing porous heat-insulating carbon-based materials by introducing a sponging agent, in particular a this process, graphite powder is mixed with a binder (synthetic resin or petroleum pitch) and metal salt powder (NaCl). The resulting mixture is molded and upon cooking at a high temperature is subjected to leaching thereby dissolving the salt and forming pores.
The disadvantage of this process resides in obtaining a material having isotropic properties and a rather high thermal conductivity due to thermal radiation within the pores and a high thermal conductivity of graphite.
Also known in the art is a process for producing a porous carbon material based on short carbon fibers and a binder with an additive of a dissolvable granular substance which leads to the pore formation upon mixture consisting of short carbon fibers and a resin are milled, and to the resulting composition a dissolvable granular substance is added. Upon heating and molding under pressure the preform is placed into a solvent, and after dissolving the granular substance, is baked (carbonized).
This process makes it possible to obtain highly porous articles having a narrow small pores distribution and a reasonably high mechanical strength, yet low heat-insulating properties in spite of the porous structure and the presence of fibers, insofar as it does not prevent the radiation heat loss.
Heat transfer in a carbon composite is known to occur either as a heat flow across the structure compact part or via reradiation in the pores. The degree of heat transfer by the heat flow across the monolithic (compact) parts of the composite is defined by the heat flow proportionality to the volume fraction of the solid component in the low direction. Whereas the intensity of heat transfer via reradiation is proportional to the 4th power of the absolute temperature, i.e. it drastically increases with temperature. Therefore in case of a heat-insulating material working under high-temperature conditions with visible radiation being generated, the radiation effect can be reduced by putting shields such as transversely-oriented fibers, in the path thereof.
Further known in the art is a process for producing a low-density heat-insulating carbon material based on discrete fibers 250 to 750 .mu.m long and a carbon-containing binder with an additive of flake graphite binder (pitch), and milled natural graphite in a ratio of from 1.0:0.5:1.0 to 1.0:0.7:0.5 (% by weight) followed by carbonizing the binder.
The resulting material of 180 to 200 kg/m.sup.3 density exhibits thermal conductivity under vacuum of 0.18 to 0.20 W/(m*K) at 1300K and 0.6 to 0.8 W/(m*K) at 2500K, yet lacks an adequate load-carrying capacity required for structural materials, inasmuch as it is not rigid enough, thus being useful only for filling gaps or requiring additional strengthening means.
Still further known in the art is the most closely related to the presently claimed proposal a process for producing a heat-insulating carbon composite material based on carbon fibers and a carbonized thermosetting suspension of carbon fibers and a powdery thermosetting binder in a dispersive liquid such as water. The water is then removed by pouring the suspension into a tank with a perforated bottom, the resulting fibrous sediment, as intended, being oriented along the tank bottom while water removing. Thereupon the sediment is dried, the polymer thermos
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Demin Alexander Victorovich
Kolesnikov Sergey Anatoljevich
Kondratova Lyubov Semenovna
Kostikov Valery Ivanovich
Vasiljev Alexander Mikhailovich
Aerospatiale - Societe Nationale Industrielle
Niigrafit Research Institute
Speer Timothy
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