From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Report appendix comparing the properties of a new ceramic insulating material, 'Sinterkorund', for sparking plugs.
| Identifier | ExFiles\Box 58\2\ Scan079 | |
| Date | 1st March 1932 | |
| Appendix to Report No.R.A.E/E&I.827. I.A.E. Research and Standardisation Committee. A New Insulating Material for Sparking Plugs. H.Kohl, D.Motor-Z., March, 1932, p.60. 'Sinterkorund', a new ceramic insulating material especially suitable for sparking plugs, is prepared by Siemens and Halske from pure aluminium oxide. It has the outward appearance of porcelain but is completely crystalline, its heat conductivity at 16 deg. C. being twenty times as high as that of porcelain. 'Sinterkorund' is unaffected by temperature: changes, and its electrical resistivity at 400 deg.C. is 100,000 times that of porcelain and, at 700 deg.C., is 100 times that of molten quartz. The following table gives the physical properties of 'Sinterkorund' compared with those of other insulating materials :- | Property | Mica. | Porcelain | Steatit | Sillimanit. | Sinter-korund. | |---|---|---|---|---|---| | Heat Conductivity in kg.cal.{Mr Calvert}/mh.{M. Huckerby} °C. | 0.3 | 0.87 | 1.25 | 1.45 | 16.8 | | Melting Point °C. | 1380 | 1670 | 1560 | 1816 | 2050 | | Insulating (Material) Properties up to °C | 600 decomposes | 450 Softening of the vitreous base. | 550 Softening of the vitreous base. | 650 Softening of the vitreous base. | above 800 crystalline | | Impact strength at 600°C. in cm. kg. | - | 45 | 50 | 120 | 180 | The impact strength of 'Sinterkorund' remains unimpaired even at the highest temperatures, and on account of its high hardness it is also a suitable material for cutting tool, grinding stones, etc. | ||