Background

Typical features of ZIRCAR Zirconia’s Type AL Alumina Ceramic Fibers and Textiles include:

· Excellent Thermal Shock Resistance

· 99% Pure Alumina

· Trace Level of Silica (0.09 wt%)

· Dimensional Stability in Hydrogen

· Low Thermal Conductivity

· No Outgassing

· Six Different Product Formats Offered

· Available ‘Off the Shelf’

AZoM - Metals, Ceramics, Polymer and Composites - Face of Alumina Knit Cloth Type ALK-15 at 6

Figure 1. Face of Alumina Knit Cloth Type ALK-15 at 6.
Product Overview

Alumina (Al2O3) has excellent thermal shock resistance, high dimensional stability and good chemical inertness, which makes our alumina fiber products ideal for fast firing cycles up to 1700°C. Our alumina fibers and textiles are made by the same unique Zircar process used for manufacturing yttria-stabilized zirconia cloths and felts. This process yields a high purity alumina fiber with only trace amounts of silica, making it more stable in hydrogen environments than the more commonly found sol-gel alumina fibers that have 3% silica. Our high purity alumina fiber and textiles are offered in six different standard product forms; bulk fiber Type ALBF, two felts Types ALF-50 and ALF-100 and three types of knit cloth Types ALK-15, ALW-15 and ALW-30.
Properties

Property


ALF-100


ALK-15

Nominal Composition wt%







Al2O3


99+


99+

ZrO2 + HfO2


0.42


0.42

SiO2


0.09


0.09

CaO


0.06


0.06

Melting Point °C (°F)


2015 (3630)


2015 (3630)

Bulk Porosity, %


97


88

Bulk Density, g/cc (pcf)


0.13 (8)


0.49 (31)

Tensile Strength, g/cm width (lb/inch width)


49 (0.28)


116 (0.65)

Loss on Ignition, 1hr @ 950°C (1742°F), wt %


3.8


1.4

Outgassing


Nil


Nil

% Shrinkage 1hr at 1650°C (3002°F)


15


7
Application Information

· Alumina fiber textiles are used as insulation for glass melting furnaces.

· Alumina bulk fiber, Type ALBF, is used as bulk fill insulation.

· Alumina fiber textiles are used as insulation for fiber optic furnaces.

· Alumina fiber textiles are used in SOFC and PEM type fuel cells as gaskets.

· Alumina fiber cloth is used as insulation in differential scanning calorimeters (DSC’s).
Microstructure of Zircar Zirconia’s Alumina Ceramic Fiber

Zircar’s Alumina Cloth Type ALK-15 has the unique advantage of being a knit structure. This structure allows irregular shapes to be cut that do not unravel or fray. The SEM photomicrograph to the in figure 2 shows the cut edge of Type ALK-15 and the individual filaments of the knit threads.

AZoM - Metals, Ceramics, Polymer and Composites - Micrograpgh of Alumina Cloth Type ALK-15

Figure 2. Micrograph of Alumina Cloth Type ALK-15

The SEM photomicrograph in figure 3 shows individual fibers arranged mostly parallel to each other in a thread. These filaments show the serrated nature of all “Zircar Process” fibers.

AZoM - Metals, Ceramics, Polymer and Composites - Micrograpgh showing the parallel nature of the alumina fibers.

Figure 3. Micrograpgh showing the parallel nature of the alumina fibers.

The SEM photomicrograph to the in figure 4 shows the end of an individual fiber in Type ALK-15. The individual submicron crystallites which make up the near theoretical density fiber can be seen clearly. Fiber diameter is approximately 6 microns.

AZoM - Metals, Ceramics, Polymer and Composites - SEM photomicrograph showing the end of an individual fiber in Type ALK-15.

Figure 4. SEM photomicrograph showing the end of an individual fiber in Type ALK-15.