S.V. Motloung

The Effects of Cd2+ Concentration on the Structure, Optical and Luminescence Properties of MgAl2O4:x% Cd2+ (0 < x ≤ 1.75) Nanophosphor Prepared by Sol–Gel Method

Cadmium-doped magnesium aluminate (MgAl2O4:x% Cd2+) powders with different cadmium concentrations (0 < x ≤ 1.75) were prepared by the sol–gel method. Energy dispersive x-ray spectroscopy (EDS) analysis confirmed the presence of the expected elements (Mg, Al, O, and Cd). The x-ray diffraction (XRD) analysis revealed that the powders crystallized into the cubic spinel structure. Cd2+ doping influenced crystallinity of the powder samples. The crystallite size and particle morphology were not affected by variation in the Cd2+ concentration. Ultraviolet–visible spectroscopy (UV–vis) measurements revealed that the band gap of the MgAl2O4 was influenced by Cd2+ doping. Un-doped and Cd2+-doped MgAl2O4 nanophosphors exhibited violet emission at 392 nm. There was no evidence of the emission peak shift, which suggested that all emissions originated from the defects within the host material. Increasing the Cd2+ concentration up-to 0.88 mol.% lead to luminescence intensity enhancement, while further increase of Cd2+ concentration lead to concentration quenching. The critical energy transfer distance (Rc) between the neighbouring donors and acceptors was found to be 5.21 Å, suggesting that the multipole–multipole interaction (M-MI) is the major cause of concentration quenching. Commission Internationale de l’Elcairage (CIE) colour coordinates confirmed non-tuneable violet emission with intensity dependent on the Cd2+ concentration.

The effect of boehmite alumina nanoparticles on the properties of polylactide/polypropylene blend composites

The effect of boehmite alumina nanofiller on properties of polylactide/polypropylene blend compatibilized with 3% maleic anhydride grafted polypropylene was investigated. Boehmite alumina nanoparticles were finely dispersed in polylactide/polypropylene/boehmite alumina blend up to 7 wt.% to form blend nanocomposites which were prepared by twin-screw melt compounding. The morphology, thermal, mechanical, heat distortion temperature, thermomechanical and degradation characteristics were investigated. Scanning electron microscopy indicated a tubular morphology with increasing boehmite alumina in the blend matrix particularly at 5 and 7 wt.% of boehmite alumina loadings with few agglomerates. Transmission electron microscopy indicated a highly dispersed boehmite alumina in the blend nanocomposites. Boehmite alumina nanoparticles significantly influenced the thermal properties and a nucleation of the blend matrix. A significant improvement in the tensile modulus and tensile strength upon addition of boehmite alumina in the blend nanocomposites was obtained. However, beyond 3 wt.% of boehmite alumina addition, there was a clear deterioration in mechanical properties.

Effect of sodium dodecylbenzene sulphonate modifier and PP-g-MA on the morphology and thermal conductivity of PP/EG composites

ABSTRACT This study investigates the influence of expanded graphite (EG) and sodium dodecylbenzene sulfonate (SDBS) treated EG (SDBS/EG) on the structure, thermal stability and thermal conductivity of polypropylene (PP) and polypropylene/maleic anhydride-grafted polypropylene (PP/MAPP) blend. The dispersion of EG and SDBS/EG was characterized by scanning electron microscopy (SEM). The SDBS-EG showed a crushed and randomly deformed structure. There was an improved interfacial adhesion between the polymer and the SBDS-EG particles. The graphite dispersed much better with less restacking for PP/MAPP/SDBS/EG system. The better dispersion also contributed towards the improved compatibility between the PP or PP/MAPP and SBDS/EG. The SDBS functionalised EG composites showed better thermal stability than the non-functionalized SDBS composites. It was further shown that the functionalized graphite significantly improved the thermal conductivity of the PP and PP/MAPP. This is because the functionalized SDBS/EG seemed to improve the interfacial heat transfer between the conductive filler (EG) and PP matrix.