TITANIUM DIBORIDE (TiB2) THERMOCOUPLE PROTECTION TUBES
As a result of the presence of cryolite, an extremely corrosive atmosphere prevails in electrolysis cells for primary aluminum production. Until now it was not possible to use engineering ceramic products (e.g. thermocouple protection tubes) in this environment. As a result, fundamental process control parameters, such as temperatures, could only be determined periodically by immersing the instruments - if at all.
A titanium diboride (TiB2) material that has been newly developed and patented by ESK now, for the first time, allows permanent application of ceramic products in primary aluminum electrolysis cells. As a result, ESK can produce, e.g. thermocouple protection tubes for continuous measurements, from TiB2.
Properties
The titanium diboride material from ESK combines outstanding physical properties with extreme corrosion resistance. The physical properties include a Knoop hardness of almost 2600, flexural strength of 500 MPa, and a fracture toughness of 8. It is particularly important for the aluminum industry that this TiB2 is resistant to cryolite and aluminum.
Application
The high thermal conductivity of 54 W/mK permits the temperature variation in the cell to be tracked very accurately and with excellent time response. The optimization of the electricity supply to the cell that this permits results in a reduced energy consumption and higher productivity.
| Material properties | Norm | Symbol/Unit | Titanium Diboride |
| Density | DIN EN 623-2 | ρ [g/cm3] | >4.50 |
| Porosity | DIN EN 623-2 | P [%] | <1.5 |
| Knoop hardness | DIN EN 843-4 | HK 0.1 [GPa] | 25.6 |
| Young's modulus | DIN EN 843-2 | E [GPa] | 575 |
| Flexural strength, 4-pt bending | DIN EN 843-1 | σB [MPa] | 500 |
| Weibull modulus | DIN EN 843-5 | m | 16 |
| Poisson ratio | ν | 0.11 | |
| Klc (SENB) | Klc [MPa·m0,5] | 8.0 | |
| Coefficient of thermal expansion | DIN EN 821-1 | ||
| 20°C - 500°C | α [10-6/K] | 6.7 | |
| 500°C - 1000°C | α [10-6/K] | 8.2 | |
| Thermal conductivity | DIN EN 821-2 | ||
| at 50°C | λ [W/m K] | 54 | |
| Specific electrical resistance at 20°C |
ρ [Ω cm] | 2·10-5 |
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