Yttria Stabilized Zirconia
Characteristics of ZIRCAR Zirconia
Fiber Type ZYBF-2
Zirconia Cloth Battery
Molten Carbonate Fuel
Thermal Insulation in High
Temperature Crystal Growth Applications
Thermal Insulation Products
Microstructure of a Vacuum-Formed
Fibrous Ceramic Insulation.
The unique properties found in yttria-stabilized zirconia fiber products have
extended their usefulness into applications too corrosive and demanding for
other varieties of fibrous ceramic materials. Their characteristics, properties
and techniques utilized to make them, are discussed. The availability of these
highly stable ceramic fiber materials as well as certain corrosive and demanding
applications for them are reviewed.
Yttria Stabilized Zirconia
Characteristics and Properties
Products made of yttria-stabilized zirconia fiber have exceptional resistance
to most corrosive environments. They undergo little attack by molten alkali
metal chlorides and carbonates at temperatures as high as 700°C (1300°F) and to
aqueous solutions of alkali metal hydroxides at temperatures as high as 230°C
(450°F). In addition to being able to withstand short term exposure to mineral
acids at their boiling point fibrous yttria-stabilized zirconia has outstanding
resistance to oxidizing, reducing and vacuum atmospheres at high temperatures. A
high density vacuum formed product, ZIRCAR Zirconia
Insulation Type FBD can withstand oxidizing and reducing conditions to
temperatures as high as 2200°C (3992°F).
Characteristics of ZIRCAR Zirconia Fiber Type ZYBF-2
Length, mean mm (in)
Cubic + tetragonal
Yttria stabilizer content
Volatile content (0-1000°C)
Zirconia Fiber Type ZYBF-2 is manufactured using a unique precursor process
wherein an organic host is converted into an inorganic relic of the original
material. Woven and non-woven zirconia textiles are made using the same process.
Rigid insulating products are made by combining bulk fiber with various binders
into a slurry which is then consolidated by vacuum forming. ZIRCAR Zirconia
Fiber Type ZYBF-2 provides significant advantages over other ceramic fibers
due to its great refractoriness, resistance to chemical attack and low thermal
Figure 1. View of ends of ZIRCAR Zirconia Fiber Type
Zirconia Bulk fibers are relatively short, suitable for vacuum forming by
themselves, for ultrahigh temperature use or blending into lower temperature
fiber mixtures to increase their refractoriness.
Figure 2. ZIRCAR Zirconia Fiber Type
When blended into mixtures of lower temperature ceramic fibers, Zircar Zirconia
Bulk Fiber Type ZYBF-2 increases the refractoriness and chemical stability
of the fiber system.
Zirconia Cloth Battery Separators
Zirconia Cloth Type ZYK-15H , another unique material, has become the
product of choice for use as battery separators in aerospace nickel hydrogen and
nickel cadmium batteries. Zirconia fiber cloth products posses numerous unique
characteristics and properties which make them ideal for use in batteries. These
include their chemistry, thickness, porosity, physical strength, electrolyte
retention and resistance to attack by various electrolytes. Type ZYK-15H
exhibits virtually no loss in strength after prolonged exposure (1000+ hrs.) to
Figure 3. ZIRCAR Zirconia Cloth Battery Separators are
die cut in many shapes.
To date ZIRCAR Zirconia Cloth Battery Separators have logged millions
of hours of space time –without any failures.
Molten Carbonate Fuel Cells
Another application where fibrous zirconia’s chemical stability and
resistance to attack make it useful where other materials fall short include the
use of ZIRCAR
Zirconia Felt Type ZYF-100 in Molten Carbonate Fuel Cells. In this gasketing
application the mechanically interlocked zirconia fiber is exposed to high
concentrations of hot LiCO3 and shows no signs of degradation.
ZYF-100’s compressibility and flexibility enable it to conform to irregular
surfaces and to accommodate thermal expansion of various fuel cell
Zirconia Felt Type ZYF is also used as the burner mantle in diesel and
gasoline fueled heaters used in luxury automobiles and heavy trucks. In addition
to having the proper uniform porosity for even distribution of the fuel its
resistance to attack by lead oxide is what makes this material so useful in this
Thermal Insulation in High Temperature Crystal Growth
Zirconia Felt Type ZYF-100 is also utilized as thermal insulation in
numerous high temperature crystal growth applications. In these systems
corrosive salt vapors can attack other insulation materials making the desired
thermal gradient difficult to achieve.
A number of ZIRCAR fibrous zirconia materials were used as primary hot
face and load bearing components of a Crystal Growth Furnace (CGF) which flew on
two space shuttle missions. The chemical compatibility and resistance to
corrosion, low thermal conductivity, machineability, thermal shock
resistance and mechanical strength of rigid ZIRCAR fibrous
zirconia products all contribute to the reason NASA specified them for use
in the United States Microgravity Laboratory (USML). All of these fibrous
zirconia products with stood the vibration and G forces of take off and landing
- both very mechanically corrosive conditions.
Figure 4. ZIRCAR Zirconia Insulation - furnace components
used in CGF on two Space Shuttle Missions include Types FBD, ZYC and ZYZ-3
ranging in density from 30 pcf to 90 pcf.
USML-1 flew on the Space Shuttle Columbia (mission STS-50) June 25 to July 9,
1992. The CGF successfully performed experiments involving the growth of cadmium
zinc telluride, selenium doped gallium arsenide and mercury cadmium telluride
crystals. USML-2 flew on the Space Shuttle mission STS-73) from September 28 to
October 14, 1995. The CGF was used to conduct several directional solidification
and vapor crystal growth experiments.
Thermal Insulation Products
At elevated temperatures fibrous zirconia insulation products offer the
lowest thermal conductivity of all currently available ceramic fiber
materials. As with most ceramic fibers, the thermal conductivity of
fibrous zirconia is strongly dependent on their bulk density. At high
temperatures, where radiation is the primary mechanism of heat transfer, high
bulk densities of zirconia fiber provides the most effective insulation. At
1650°C to 1930°C minimal thermal conductivity is obtained at 30 pcf density.
Microstructure of a Vacuum-Formed Fibrous Ceramic
The tightly bonded structure which results from the uniform distribution of
the binder in these rigid products yields strong fibrous insulating bodies.
These products are available in flat boards, cylinders and custom
configurations. They can also be machined to exacting dimensional tolerances.
Tolerances of +/-.005” are obtainable with CNC equipment.
yttria-stabilized fibrous zirconia insulation products are useful in many
demanding applications too corrosive for other ceramic fiber products. These
zirconia products offer resistance to chemical attack, high refractoriness and
lower thermal conductivity at elevated temperatures than other fibrous ceramic
products. ZIRCAR’s alumina-bonded alumina fiber products are stable in
reducing conditions and are effective thermal insulators in many corrosive
environments to temperatures as high as 1800°C.
Source: Zircar Zirconia
For more information on this source please visit Zircar