A fast and versatile method for spectral emissivity measurement at high temperatures

International audienceIn this paper, the development of a new device for high temperature emissivity measurement is described. This device aims at measuring both spectral and total emissivity for a thermal range of 600–1000 °C. The main targeted properties of this device are versatility and simplicity. To achieve this, a rigorous selection of components such as heating systems, heat sources, sample holders, and measuring devices was made. Sample dimensions and the corresponding sample holder were optimized through a ray tracing model computation. Selection of sensors to compute the total emissivity was also discussed. A near-infrared (NIR) spectrometer and two mid-infrared (MIR) cameras equipped with optical filters covering the bandwidth of 3–5 and 7.5–13 μm were chosen for spectral measurements. The major impediment was the separation of the sample signal and various spurious signals emitted by the environment. A specific measurement methodology was then made for each bandwidth to resolve this issue. Platinum was chosen as the reference material for the device validation. Spectral emissivity measurements were then compared to values from a commercial spectrometer. A good agreement was found between NIR and MIR band I measurements, and a higher error rate was seen in MIR band II which is explained by a less favorable signal to noise ratio. Integrated emissivity is then calculated and compared to values found in the literature. A good agreement between these values is found, and similar trends with temperature are observed. The device is then validated for spectral and total emissivity measurements. Device versatility and simplicity allow for an easy adaptation to a large area of applications

Lyotropic and interfacial behaviour of an anionic gemini surfactant

The sodium salt of N,N′-hexane-bis (1-dodecen-1-ylsuccinamic acid) is an anionic dimeric (gemini) surfactant. A flooding penetration scan of this surfactant in water demonstrates a sequence of lyotropic phases at room temperature (20 °C). Preparation of surfactant–water mixtures has resulted in a phase diagram which shows that the same sequence of phases exists up to 100 °C. These phases are tentatively assigned to the sequence: micellar to normal hexagonal (H1) to cubic (V1) to lamellar (Lα). The interfacial tension at the n-heptane/water interface has been determined in the presence of this surfactant. The surfactant head group area at the interface is large (2.8±0.3 nm2 at 298 K) and the interfacial tension above the critical micelle concentration is low (7 mN m−1), but considerably higher than the ultra-low values that have been reported for cationic dimeric surfactants at various hydrocarbon–water interfaces