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AssigneeDirector-General of Agency of Industrial Science and Technology
InventorsKazuo Kobayashi, Ichitaro Ogawa, Hidemasa Honda, Yasuhiro Matsushita
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A process for the production of shaped articles of high density graphite ing excellent mold-releasing property which comprises incorporating amorphous carbon powder such as powdery coke or artificial graphite powder with about 3-20% by weight of boric acid or boron oxide as a sintering-promoting agent, and baking the mixture under a pressure of 150-500 kg/cm.sup.2 without the aid of a binding agent such as pitch. Shaped articles of high density graphite possessing excellent mechanical strength are obtained by this process.
A process for producing shaped articles of graphite having a density of at least about 2.0 comprising the steps of forming a generally uniform mixture of finely divided amorphous carbon or synthetic graphite and boric acid or boron oxide in an amount equal to about 3-30% by weight of the mixture, shaping said mixture into a given shape, and baking the mixture in the absence of a pitch binder to a temperature of at least about 2000.degree. C. while under a pressure of at least about 100 kg/cm.sup.2.
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Based on non-oxide ceramics: based on carbon, e.g. graphite
Based on carbon, e.g. graphite: obtained from carbonaceous particles with or without other non-organic components
Lime, magnesia
Term ended 6 Sep 1994 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates to a process for the production of shaped articles of high density graphite having excellent moldreleasing property which comprises incorporating amorphous carbon powder or artificial graphite powder with several percents by weight of boric acid or boron oxide as a sintering-promoting agent and baking the mixture under a pressure of several hundred kg/cm.sup.2 without the aid of any binding agent such as pitch.
At the present time, the production of shaped articles of high density graphite is an important research objective and is attacked by a variety of processes. Attempted hitherto are a process wherein a device is used for carbonaceous materials or binding agents such as pitch to be incorporated thereinto to increase the carbonization rate and contraction by graphitization is promoted to obtain high density products, a process wherein a carbonaceous material is sintered under pressure to increase the carbonization rate of a binding agent and contraction of the material is effected on sintering to obtain high density products, a process wherein a sintered material is impregnated with a liquid hydrocarbon and then the impregnated material is sintered to clog pores of the material for obtaining high density products, a process wherein a sintered material is permeated with a gaseous hydrocarbon and then the permeated material is heated to effect pyrolysis of the gaseous hydrocarbon in the internal pores of the material for clogging the pores, and a process wherein a sintered material is graphitized under mechanical pressure to effect collapse of pores in the material by creeping. In these processes, the products are produced from a starting material containing a binder. A process wherein a carbonaceous material is sintered under ultrasuperatmospheric pressure is also attempted as a process using no binder.
However, these prior art processes using a binder require complicated and/or costly operations. It is considerably difficult to produce products having a bulk density of at least 1.9 following to these processes and, when possible at all, the products will be expensive.
Other and further objects, features and advantages of the present invention will be apparent from the following description taken in connection with the accompanying drawing, wherein:
FIG. 1 is a graph showing the relation between the heating temperature and the loss in weight on oxidation in a test using the shaped articles of high density graphite of the present invention and commercially available shaped articles of high density graphite.
FIG. 2 is a graph showing the relation between the heating time and the loss in weight on oxidation in a test using the shaped articles of high density graphite of the present invention and commercially available shaped articles of high density graphite.
As a result of many studies made for developing a process for easily producing shaped articles of high density graphite without necessity of any binder such as pitch used in the prior art processes, it has now been found that the above mentioned purpose can be attained only by incorporating a carbonaceous material with several percent by weight of boric acid or boron oxide as a sintering-promoting agent. The present invention has been accomplished on the basis of the above finding.
In accordance with the present invention, there is provided a process for the production of shaped articles of high density which comprises incorporating amorphous carbon powder or artificial graphite powder with boric acid or boron oxide as a sintering-promoting agent and then baking the mixture under pressure.
In the prior art processes, carbonaceous products are generally manufactured by mixing and kneading an aggregate with a binder, shaping the mixture and then subjecting the shaped article to a heat treatment. Exclusion of a binder such as pitch or tar from the carbonaceous composition as contemplated in the present invention is not only effective for omission of the step for kneading the aggregate with the binder but also desirable from the viewpoint of environmental hygienics which is an especially sensitive problem in recent years. Thus, development of a process for producing carbonaceous products without the aid of any binder has long been demanded in the related fields of industry.