In this astonishing picture it seems like part of the wires are molten, but in fact it is what grains look like after major slipping. Platinum appears to have a high adherence to aluminium-oxide, so sometimes the friction between these materials calls for major engineering experience, skills and clever constructions.
A limited number of molecules affect platinum. One of them is silicon, and even as silicon-carbide or other silicides, physical contact between the two should be avoided. Molecules such as phosphorous and sulphur aren’t really Kryptonite-like, but need to be taken into account. Hydrogen, by means of hydrogen induced cracking (or SOHIC, its stress oriented version), can be detrimental. In case of any performer chemical analysis, for example with the SEM-analysis we supply, you may notice a presence of potassium or calcium. Some of these however may be residues from the cleaning agent or the use of wrong glove-material during handling of the noble metal.
Most of the sensors we manufacture with noble metal thermocouples have a ceramic protection sleeve, often fused silica, silicon-nitride or silicon-carbide. Sometimes however customers need a mineral insulated type thermocouple with a metal alloy sheath. In this case care needs to be taken not to expose the instrument to higher temperatures, or allow for some additional uncertainty in the measurement over time, as some of the components of the alloy tend to migrate through the isolating ceramic towards the thermocouple conductors.
The application of type B thermocouple pairs has shown increased interest: the price of the costly component rhodium has dropped, while the more recent transmitters can cope with the lower output at lower temperatures, providing us with an extended range and other mechanical bonuses.
Please do not hesitate to contact us via info@te-instrumentation.com for more information, to study this topic more in detail or when you request a proposal from Thermo Electric Instrumentation, based on our experience in:
- solar industry (e.g. furnaces for the production of the cells themselves);
- semiconductor industry;
- other CVD and epitaxy (EPI) applications;
- desulphurisation furnaces;
- liquid metal applications;
- calibration / reference standards;
- thermowells for extreme/hot acids or erosive wear solutions.