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Ceramic materials with low thermal conductivity and low coefficients of thermal expansion

Patent ·
OSTI ID:868228
 [1];  [2];  [3];  [3];  [3];  [3];  [3];  [4]
  1. Christiansburg, VA
  2. Elliston, VA
  3. Blacksburg, VA
  4. Seoul, KR
+ Show Author Affiliations

Compositions having the general formula (Ca.sub.x Mg.sub.1-x)Zr.sub.4 (PO.sub.4).sub.6 where x is between 0.5 and 0.99 are produced by solid state and sol-gel processes. In a preferred embodiment, when x is between 0.5 and 0.8, the MgCZP materials have near-zero coefficients of thermal expansion. The MgCZPs of the present invention also show unusually low thermal conductivities, and are stable at high temperatures. Macrostructures formed from MgCZP are useful in a wide variety of high-temperature applications. In a preferred process, calcium, magnesium, and zirconium nitrate solutions have their pH adjusted to between 7 and 9 either before or after the addition of ammonium dihydrogen phosphate. After dehydration to a gel, and calcination at temperatures in excess of 850.degree. C. for approximately 16 hours, single phase crystalline MgCZP powders with particle sizes ranging from approximately 20 nm to 50 nm result. The MgCZP powders are then sintered at temperatures ranging from 1200.degree. C. to 1350.degree. C. to form solid macrostructures with near-zero bulk coefficients of thermal expansion and low thermal conductivities. Porous macrostructures of the MgCZP powders of the present invention are also formed by combination with a polymeric powder and a binding agent, and sintering at high temperatures. The porosity of the resulting macrostructures can be adjusted by varying the particle size of the polymeric powder used.

Research Organization:
LOCKHEED MARTIN ENRGY SYST INC
DOE Contract Number:
AC05-84OR21400
Assignee:
Center for Innovative Technology (Herndon, VA); Virginia Tech Intellectual Properties, Inc. (Blacksburg, VA); Virginia Polytechnic and State University (Blacksburg, VA)
Patent Number(s):
US 5102836
OSTI ID:
868228
Country of Publication:
United States
Language:
English

References (3)

Open-Cell, Low-Density Ceramics Fabricated from Reticulated Polymer Substrates journal October 1987
Hydrothermal preparation of the low-expansion NZP family of materials journal January 1988
Synthesis, crystal data and thermal stability of magnesium zirconium phosphate [MgZr4(PO4)6] journal August 1988

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/501/264/
1-x
1200
1350
16
20
50
850
99
addition
adjusted
agent
ammonium
applications
approximately
binding
binding agent
bulk
calcination
calcium
ceramic
ceramic mater
ceramic material
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coefficients
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compositions
conductivities
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crystalline
degree
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dihydrogen
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hydrogen ph
macrostructures
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nitrate
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nitrate solutions
nm
particle
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ph
phase
phosphate
polymeric
porosity
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preferred
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produced
ranging
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single
single phase
sintered
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size
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sol-gel
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sol-gel processes
solid
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stable
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temperature application
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temperatures
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thermal
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unusually
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variety
varying
wide
wide variety
zirconium
zr