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

Abstract

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 themore » resulting macrostructures can be adjusted by varying the particle size of the polymeric powder used.

Inventors:
 [1];  [2];  [3];  [3];  [3];  [3];  [3];  [4]
+ Show Inventor Affiliations
  1. Christiansburg, VA
  2. Elliston, VA
  3. Blacksburg, VA
  4. Seoul, KR
Issue Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
OSTI Identifier:
868228
Patent Number(s):
5102836
Assignee:
Center for Innovative Technology (Herndon, VA); Virginia Tech Intellectual Properties, Inc. (Blacksburg, VA); Virginia Polytechnic and State University (Blacksburg, VA)
Patent Classifications (CPCs):
C - CHEMISTRY C01 - INORGANIC CHEMISTRY C01B - NON-METALLIC ELEMENTS
C - CHEMISTRY C04 - CEMENTS C04B - LIME, MAGNESIA
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DOE Contract Number:  
AC05-84OR21400
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
ceramic; materials; thermal; conductivity; coefficients; expansion; compositions; formula; mg; 1-x; zr; 99; produced; solid; sol-gel; processes; preferred; embodiment; mgczp; near-zero; mgczps; unusually; conductivities; stable; temperatures; macrostructures; formed; useful; wide; variety; high-temperature; applications; process; calcium; magnesium; zirconium; nitrate; solutions; ph; adjusted; addition; ammonium; dihydrogen; phosphate; dehydration; calcination; excess; 850; degree; approximately; 16; hours; single; phase; crystalline; powders; particle; sizes; ranging; 20; nm; 50; result; sintered; 1200; 1350; form; bulk; porous; combination; polymeric; powder; binding; agent; sintering; porosity; resulting; varying; size; structures formed; sol-gel process; nitrate solution; binding agent; temperature applications; ceramic material; thermal conductivity; thermal expansion; preferred embodiment; particle size; ceramic materials; wide variety; single phase; temperatures ranging; particle sizes; nitrate solutions; thermal conductivities; preferred process; sizes ranging; sol-gel processes; form solid; hydrogen ph; ceramic mater; temperature application; /501/264/

Citation Formats

Brown, Jesse, Hirschfeld, Deidre, Liu, Dean-Mo, Yang, Yaping, Li, Tingkai, Swanson, Robert E, Van Aken, Steven, and Kim, Jin-Min. Ceramic materials with low thermal conductivity and low coefficients of thermal expansion. United States: N. p., 1992. Web.
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Brown, Jesse, Hirschfeld, Deidre, Liu, Dean-Mo, Yang, Yaping, Li, Tingkai, Swanson, Robert E, Van Aken, Steven, & Kim, Jin-Min. Ceramic materials with low thermal conductivity and low coefficients of thermal expansion. United States.
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Brown, Jesse, Hirschfeld, Deidre, Liu, Dean-Mo, Yang, Yaping, Li, Tingkai, Swanson, Robert E, Van Aken, Steven, and Kim, Jin-Min. Wed . "Ceramic materials with low thermal conductivity and low coefficients of thermal expansion". United States. https://www.osti.gov/servlets/purl/868228.
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@article{osti_868228,
title = {Ceramic materials with low thermal conductivity and low coefficients of thermal expansion},
author = {Brown, Jesse and Hirschfeld, Deidre and Liu, Dean-Mo and Yang, Yaping and Li, Tingkai and Swanson, Robert E and Van Aken, Steven and Kim, Jin-Min},
abstractNote = {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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1992},
month = {Wed Jan 01 00:00:00 EST 1992}
}
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Works referenced in this record:

Synthesis, crystal data and thermal stability of magnesium zirconium phosphate [MgZr4(PO4)6]
journal, August 1988

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

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