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

Patent · Tue Apr 07 00:00:00 EDT 1992

OSTI ID:7284173

Brown, J; Hirschfeld, D; Liu, D M; Yang, Y; Li, T; Swanson, R E; Van Aken, S; Kim, J M

Compositions, having the general formula (Ca[sub x]Mg[sub 1[minus]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 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 C to 1350 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. 7 figs.

• DOE Contract Number: AC05-84OR21400
• Assignee: Center for Innovative Technology, Herndon, VA (United States); Virginia Tech Intellectual Properties, Inc., Blacksburg, VA (United States); Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)
• Patent Number(s): US 5102836; A
• Application Number: PPN: US 7-533143
• OSTI ID: 7284173
• Resource Relation: Patent File Date: 6 Jun 1990
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM PHOSPHATES
THERMAL CONDUCTIVITY
THERMAL EXPANSION
CERAMICS
FABRICATION
MAGNESIUM PHOSPHATES
ZIRCONIUM PHOSPHATES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
EXPANSION
MAGNESIUM COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360204 - Ceramics
Cermets
& Refractories- Physical Properties