Extended Data Fig. 5: Interior temperature measurements of the graded-pore pyrolysis reactor using SFBGs.
From: Selective electrified polyethylene upcycling by pore-modulated pyrolysis
The internal temperature of the pyrolysis reactor was measured using Femtosecond laser-inscribed single crystal sapphire fiber Bragg gratings (SFBGs). These precise temperature sensors were inscribed on a 4-inch sapphire optical fiber using a Femtosecond laser microfabrication system and placed in the reactor to monitor temperature during pulsed heating in an argon-controlled environment. The setup included a supercontinuum light source, multimode scrambler, Bayspec interrogator, and a glass-to-sapphire splice for light transmission. The SFBGs responded to temperature fluctuations by altering their refractive index, and the resulting wavelength shifts were detected and converted to temperature readings. Measurements across three reactor zones showed a clear temperature gradient: Zone 1 ranged from 630 °C to 530 °C, Zone 2 from 530 °C to 470 °C, and Zone 3 from 490 °C to 420 °C, as illustrated in Fig. 2d.
