US4252691A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Neutron absorber based on boron carbide and carbon and a process for their production
Assignee: Elektroschmelzwerk Kempten GmbH
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Filing: 1978-11-15
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Granted: 1981-02-24
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Expires: 1998-11-15
Abstract
Abstract The subject of the invention is thin large-area neutron-absorber plates having a volume composition of from 40 to 60% and preferably from 45 to 60% by volume of boron carbide, from 25 to 5% by volume and preferably 15 to 5% by volume of free carbon, the remainder being pores, a density of from 1.4 to 1.8 g/cm 3 , a flexural strength at room temperature of from 15 to 45 N/mm 2 , a compressive strength at room temperature of from 25 to 60 N/mm 2 , a modulus of elasticity at room temperature of from 10,000 to 20,000 N/mm 2 , and a resistance to ionizing radiation of at least 10 11 rad, which plates may be produced by mixing boron carbide powder, containing at least 75% by weight of boron and a proportion of boron oxide of less than 0.5% by weight, and having a particle size distribution of at least 95% finer than 50 μm and, optionally, graphite powder with a pulverulent organic resin binder and a wetting agent, shaping the mixture under pressure at room temperature, curing the resin binder at temperatures of up to 180° C., and then coking the shaped plates with the exclusion of air at temperatures of up to approximately 1000° C. with a controlled temperature increase.
Inventors
- 👤 Alfred Lipp
- 👤 Klaus Reinmuth
- 👤 Detlef von Struensee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:59
CPC Classifications
G; G21; G21F; G21F1/00; G21F1/02; G21F1/06
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
103 words
A neutron-absorber material having a volume composition of from 40 to 60% by volume of boron carbide and from 5 to 25% by volume of free carbon, the remainder being pores, said neutron-absorber material having the following properties: a density of from 1.4 to 1.8 g/cm 3 , a flexural strength at room temperature of from 15 to 45 N/mm 2 , a compressive strength at room temperature of from 25 to 60 N/mm 2 , a modulus of elasticity at room temperature of from 10,000 to 20,000 N/mm 2 , and a resistance to ionizing radiation of at least 10 11 rad.
Claim 2
Dependent Claim
103 words
A neutron-absorber material having a volume composition of from 40 to 60% by volume of boron carbide and from 5 to 25% by volume of free carbon, the remainder being pores, said neutron-absorber material having the following properties: a density of from 1.4 to 1.8 g/cm 3 , a flexural strength at room temperature of from 15 to 45 N/mm 2 , a compressive strength at room temperature of from 25 to 60 N/mm 2 , a modulus of elasticity at room temperature of from 10,000 to 20,000 N/mm 2 , and a resistance to ionizing radiation of at least 10 11 rad.
Claim 3
Dependent Claim
14 words
A neutron-absorber material according to claim 1 in the form of thin large plates.
Claim 4
Dependent Claim
178 words
A process for the production of a neutron-absorber material of claim 1, which comprises forming a mixture containing from about 50 to 85% by weight of boron carbide powder containing at least 75% by weight of boron and a proportion of B 2 O 3 of less then 0.5% by weight, and having a particle size distribution of at least 95% finer than 50 μm at least 90% finer than 30 μm at least 70% finer than 20 μm at least 50% finer than 10 μm at least 30% finer than 5 μm at least 10% finer than 2 μm, up to about 25% by weight graphite powder, from about 12 to 20% by weight of an organic resin binder and about 3 to 5% by weight of a wetting agent; shaping the mixture under pressure at room temperature; curing the resin binder at temperatures of up to 180° C.; and then coking the shaped mixture with the exclusion of air at temperatures of up to approximately 1000° C., with a controlled temperature increase not exceeding 120° C./hour.
Claim 5
Dependent Claim
147 words
A process according to claim 3, wherein 50 to 85% by weight of boron carbide powder 25 to 0% by weight graphite with a particle size finer than 40 μm 20 to 12% by weight of a powdered phenolformaldehyde condensation product as a resin binder and 5 to 3% by weight of furfural as a wetting agent, are mixed homogeneously, the powder mixture thus obtained is then molded into plates of about 5 to 10 mm thickness at room temperature and a pressure of 25 to 30 MPa, the plates thus formed are stacked between carrier plates of an inert material, heated to temperatures of up to 180° C. to harden the resin binder, then further heated up to about 1000° C. to cure the resin binder, with a temperature rise of not more than 120° C./hour and subsequently cooled over a period of about 24 hours.
Claim 6
Dependent Claim
24 words
A process according to claim 3, wherein graphite powder with a pulverulent organic resin and a wetting agent are included in the starting mixture.
Claim 7
Dependent Claim
22 words
A process according to claim 5, wherein the graphite powder is natural graphite having a particle size distribution finer than 40 μm.
Claim 8
Dependent Claim
28 words
A process according to claim 3, wherein the boron carbide has a particle size distribution in which 100% by weight of the particles are finer than 50 μm.
Claim 9
Dependent Claim
61 words
A process according to claim 7, wherein the boron carbide has a particle size distribution (by weight) of ______________________________________
100% finer than 50 μm,
at least 99% finer than 30 μm,
at least 97% finer than 20 μm,
at least 90% finer than 10 μm,
at least 75% finer than 5 μm, and
at least 50% finer than 2 μm.
______________________________________
Claim 10
Dependent Claim
15 words
A process according to claim 3, wherein the organic resin is pulverulent at room temperature.
Claim 11
Dependent Claim
13 words
A process according to claim 9, wherein the resin is a phenolic resin.
Claim 12
Dependent Claim
28 words
A process according to claim 10, wherein the phenolic resin is a phenol formaldehyde resin selected from the group consisting of novalak resins, resole resins and mixtures thereof.
References Cited (Backward Citations)
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Cited
US3133887A
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US3153636A
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US3810963A
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US3969124A
Cited
US4156147A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-24 | 1984-08-25 | 1985-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-24 | 1988-08-25 | 1989-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-24 | 1992-08-25 | 1993-02-24 | $7700.00 | Window Closed / Lapsed |