The effect of annealing time on the structural and optical properties of ZnAl2O4:0.01% Cr3+ nanophosphor prepared via sol-gel method

Zinc aluminate (ZnAl2O4) host and 0.01% Cr3+ doped were successfully prepared using the sol–gel method. The annealing time (AT) was varied in the range of 0.5–19 h. The x-ray diffraction results showed that the AT does not affect the crystal structure of the prepared powders. Scanning electron microscopy (SEM) results showed that the morphology of the prepared nanophosphors was influenced by the AT. Energy dispersive x-ray spectroscopy (EDS) confirmed the homogeneous distribution of the constituent elements. Transmission electron microscopy (TEM) suggested that the average crystallites sizes of the ZnAl2O4 to be ~20 nm. Ultraviolet–visible (UV–Vis) spectroscopy results revealed that the bandgap (E g) of the prepared nanophosphor can be tuned by varying the AT. The emission peak at 390 nm is attributed to the intrinsic defects within the host material bandgap. The emission peak at 572 nm is attributed to both contribution from the host and Cr3+ (4T1 → 4A2) transition. The maximum PL intensity was observed from the samples annealed for 3 h. The International Commission on Illumination (CIE) chromaticity diagram showed a slight shift on the blue emission with an increase in AT.http://link.springer.com/journal/116642019-01-30hj2018Physic

Thermal Conductivity of Graphite-Based Polymer Composites

It is well known that polymers are insulators, which limit their usage in other applications where thermal conductivity is essential for heat to be efficiently dissipated or stored. In the past, the improvement in the thermal conductivity of polym.rs with conductive fillers has been investigated by researchers. Carbon-based materials such as graphite, graphene and carbon nanotube, which feature excellent properties such as a high mechanical strength, a high thermal conductivity and a tailorable electronic configuration, have been added to different polymer matrices to enhance their thermal conductivity. Amongst others, graphite more especially expanded graphite merits special interest because of its abundant availability at a relatively low cost and lightweight when compared to other carbon allotropes. Herein, we describe the thermal conductivity of polymer/graphite composites and their applications

Effects of annealing temperature on the structure and photoluminescence properties of the ZnO/ZnAl2O4/Ca5Al6O14/Ca3Al4ZnO10:0.1% Ce3+ mixed-phases nanophosphor prepared by citrate sol–gel process

Please read abstract in the article.The South African National Research Foundation (NRF) Thuthuka Programme and NRF incentive funding for rated researchers (IPRR).https://link.springer.com/journal/3392021-09-28hj2021Physic

Migration behaviour of Europium implanted into single crystalline 6H-SiC

Migration behaviour of Europium (Eu) implanted into 6H-SiC was investigated using Rutherford backscattering spectroscopy (RBS), RBS in a channelling mode (RBS-C) and scanning electron microscopy (SEM). Eu ions of 360 keV were implanted into 6H-SiC at 600 °C to a fluence of 1 × 1016 cm−2. The implanted samples were sequentially annealed at temperatures ranging from 1000 to 1400 °C, in steps of 100 °C for 5 h. RBS-C showed that implantation of Eu into 6H-SiC at 600 °C retained crystallinity with some radiation damage. Annealing of radiation damage retained after implantation already took place after annealing at 1000 °C. This annealing of radiation damage progressed with increasing annealing temperature up to 1400 °C. A shift of Eu towards the surface took place after annealing at 1000 °C. This shift became more pronounced and was accompanied by loss of Eu from the surface at annealing temperatures >1000 °C. This shift was accompanied by broadening of Eu peak/Fickian diffusion after annealing at temperatures >1100 °C. The migration of Eu occurring concurrently with the annealing of radiation damage was explained by trapping and de-trapping of Eu by radiation damage.The National Research Foundation (NRF) (grant no: 94104) of South Africahttp://www.journals.elsevier.com/vacuum2018-07-30hj2017Physic

Slow and swift heavy ions irradiation of zirconium nitride (ZrN) and the migration behaviour of implanted Eu

Please read abstract in the article.http://www.elsevier.com/locate/nimb2020-12-15hj2020Physic

Effects of annealing time on the structure and optical properties of ZnAl2O4/ZnO prepared via citrate sol-gel process

ZnAl2O4 nano-powders have been successfully prepared via citrate sol-gel technique. All powder samples were annealed at 600 °C for 1, 2, and 3 h. Thermogravimetric analysis (TGA) confirmed that the minimum annealing temperature of crystallization is ∼400 °C. Fourier Transform Infrared (FTIR) results showed a series of absorption peaks in the range of 810–4000 cm−1. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) results showed that the prepared nano-crystals consists of the mixture of both cubic (ZnAl2O4) and hexagonal (ZnO) structures. Ultra violet visible (UV–vis) spectroscopy revealed that the annealing time (AT) influences the band gap of the prepared phosphor materials. When the samples were excited at 275 nm, two emission peaks at 428 nm (violet) and 561 nm (green-yellow) were observed and they are attributed to the defects levels within the ZnO and ZnAl2O4 band gaps. The Commission Internationale de l’Elcairage (CIE) colour coordinates confirmed that all the prepared samples exhibit the violet emission and varying the AT does not influence the emission colour.The South African National Research Foundation (NRF) Thuthuka Programme (fund number: UID99266).https://www.elsevier.com/locate/mtcomm2019-03-01hj2018Physic

Effects of Ag and Sr dual ions implanted into SiC

Please read abstract in the article.National Research Foundation of South Africa, Knowledge Interchange and Collaboration Programme (KIC).http://www.elsevier.com/locate/nimbhj2021Physic

Intense pulsed neutron generation based on the principle of Plasma Immersion Ion Implantation (PI3) technique

Magister Scientiae - MScThe development of a deuterium-deuterium/ tritium-deuterium (D-D/ D-T) pulsed neutron generator based on the principle of the Plasma Immersion Ion Implantation (PI3) technique is presented, in terms of investigating development of a compact system to generate an ultra short burst of mono-energetic neutrons (of order 1010 per second) during a short period of time (< 20μs) at repetition rates up to 1 kHz. The system will facilitate neutron detection techniques, such as neutron back-scattering, neutron radiography and time-of-flight activation analysis. Aspects addressed in developing the system includes (a) characterizing the neutron spectra generated as a function of the target configuration/ design to ensure a sustained intense neutron flux for long periods of time, (b) the system was also characterised as a function of power supply operating conditions such as voltage, current, gas pressure and plasma density.South Afric

The effects of varying the annealing period on the structure, morphology and optical properties of MgAl2O4:0.1% Mn2+ nanophosphors

Please read abstract in the article.The South African National Research Foundation (NRF) Thuthuka programme and NRF incentive funding for rated researchers (IPRR).https://link.springer.com/journal/339hj2021Physic

The effects of varying the Eu3+ concentration on the structural and optical properties of Mg1.5Al2O4.5:x% Eu3+ (0 ≤ x ≤ 2) nanophosphors prepared by sol–gel method

Mg1.5Al2O4.5:x% Eu3þ (0 x 2) nanopowders were successfully synthesized via sol–gel method. The X-ray diffraction (XRD) spectrum revealed that the Mg1.5Al2O4.5:x% Eu3þ matches the single phase of face-centred cubic MgAl2O4. The estimated average crystallite sizes calculated using the XRD spectra were found to be in the order of 4 nm. The estimated crystal size was confirmed by the high-resolution transmission electron microscopy. The energy dispersive X-ray spectroscopy confirmed the presence of all expected elementary composition (Mg, Al, O and Eu). The field emission gun scanning electron microscope showed that varying the Eu3þ concentration influence the morphology of the prepared nanophosphor. The photoluminescence results showed that the host emits the violet colour at around 382 nm, which was attributed to the defects within the band gap (Eg) of host material. The Eu3þ-doped samples showed the emission at around 560, 580, 593, 618, 655 and 704 nm which are, respectively, attributed to the 5D1 ! 7F3, 5D0 ! 7F0, 5D0 ! 7F1, 5D0 ! 7F2, 5D0 ! 7F3 and 5D0 ! 7F4 characteristic transitions in Eu3þ. The International Commission on Illumination colour chromaticity showed that the Eu3þ doping influences the emission colour.The South African National Research Foundation (NRF) Thuthuka programme (fund number: UID99266) and NRF incentive funding for rated researchers (IPRR) (grant no: 114924).http://journals.sagepub.com/home/naxam2019Physic