Vario macri cube

Carbon and nitrogen content of the lab made nitrogen doped CNTs was determined by elemental analysis using a CHNS (Carbon-Hydrogen-Nitrogen-Sulphur) macro analyzer vario MACRI cube (Elementar, Langenselbold, Germany).
Scanning electron microscopy images for samples were acquired using a Supra 55 VP FEG (Carl Zeiss AG, Oberkochen, Germany) scanning electron microscope (SEM) at 5 kV acceleration voltage. The samples had been broken and sputtered with a thin gold film.
The CNT content in the composites was been determined by wet chemical methods. An acid digestion was carried out for this purpose DIN EN 2564.
The thermoelectric characterization was carried out in a Seebeck measuring device developed at IPF Dresden (Figure 8a). More details are given in following references [12 (link),18 (link),27 (link)]. The measuring temperature was set to 313.15 K (40 °C), with a temperature variation range around this temperature of ±8 K in which the slope was used as the measure for the Seebeck coefficient at 40 °C. The measurements of the electrical volume resistivity were done using the same equipment applying the 2-wire technique. The free sample length between the silver coated ends was 10 mm.

Carbon and nitrogen contents were determined by elemental analysis using a gas chromatograph coupled with a thermal conductivity detector CHNS macro analyzer vario MACRI cube (Elementar, Langenselbold, Germany). Iron content was determined by immersion of the samples in aqua regia and subsequent investigation using an inductively coupled plasma optical emission spectrometer. Thermogravimetric analysis (TGA) was carried out on a TGA Q500 (TA Instruments, New Castle, DE, USA) at 10 °C min⁻¹ heating ramp under 60 mL min⁻¹ gas flow of synthetic air (20% O₂, 80% N₂). Raman spectra were acquired using a Jobin Yvon HR800 (Horiba, Bensheim, Germany) quipped with a He-Ne laser (633 nm) and grid (600 mm⁻¹) at 30 mW and 30 s integration time. Each sample was measured 5 times at different positions to provide average values. Electron microscopy images were acquired using either a Supra 55 VP FEG (Zeiss, Oberkochen, Germany) scanning electron microscope (SEM) at 5 kV or at a FEI Talos F200X (Thermo Fischer, Waltham, MA, USA) transmission electron microscope (TEM) at 200 kV acceleration voltage.