A platinum coated singlemode-multimode (SM) structure is investigated in this paper as an optical fibre sensor (OFS) to monitor the phase transition of a phase change material (PCM). Paraffin wax has been used as an example to demonstrate the sensor's performance and operation. Most materials have the same temperature but different thermal energy levels during the phase change process, therefore, sole dependency on temperature measurement may lead to an incorrect estimation of the stored energy in PCM. The output spectrum of the reflected light from the OFS is very sensitive to the bend introduced by the PCM where both liquid and solid states exist during the phase transition. The measurement of strain experienced by the OFS during the phase change of the PCM is utilized for identifying the phase transition of paraffin wax between the solid and liquid states. The experimental results presented in this paper show that the OFS with a shorter multimode fibre section has better performance for monitoring the phase transition of paraffin wax with a measured phase transition temperature range of 41.5°C-57.7°C for the SM based OFS with a 5 mm long multimode fibre section.
Mn-doped Cu3N films were prepared by radio frequency reactive magnetron sputtering method under different manganese concentration. The deposits exhibit a satisfactory crystallinity and a preferred growth orientation along the (111) plane. The shapes of crystalline grains vary from pyramid-like to rugby-ball-like with the Mn-doping constituent in Cu3N film reaching 0.02%. The electrical resistivity of Mn-doped Cu3N films has dramatically increased from 0.102×103 Ω·cm to 0.495×103 Ω·cm at room temperature. Moreover, the reflectivity difference and ferromagnetic property have also been investigated.
Copper nitride thin films were deposited on glass substrates by reactive DC magnetron sputtering at various N2-gas flow rates and different substrate temperature. X-ray diffraction measurements show that the films are composed of Cu3N crystallites with anti-ReO3structure and exhibit preferential orientation to the [111] and [100]. The preferred crystalline orientation of the films changes with the N2-gas flow rate and substrate temperature. The N2-gas flow rate and the substrate temperature not only affect the crystal structure of films but also affect the deposition rate, the resistivity and the microhardness of the Cu3N films.
Ni-doped copper nitride films have been prepared by co-sputtering of Ni and Cu targets. The addition of Ni to Cu3N films reduced the intensity of the (111) diffraction peak, and lead a little angular shifts of the peaks. The films showed a large difference in reflectance in the infrared and visible before and after thermal decomposition, which is applicable to optical recording media. The films change from a semiconductor to a conductor with the increased ratio of Ni in Cu3N films.
Pure BiFeO3 (BFO), Ca-doped and Eu/Ca-codoped BFO nanoparticles were prepared by using a sol–gel method. The effects of Eu/Ca-codoped on the structural, magnetic and ferroelectric properties of the samples were studied. The X-ray diffraction (XRD) analysis reveals a structure transition in the codoped samples. Co-doped samples were obtained with the best ferromagnetic properties, with the largest remaining magnetization Mr = 0.20 emμ/g. The structure transition may be the main cause for the origin of improved magnetic properties, which destroys the space modulated spin structure of BFO and releases the locked magnetic. In addition, the doping of Eu into BFO can reduce the leakage current and enhance the ferroelectric properties.
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