Breakdown Performance and Partial Discharge Development in Transformer Oil-Based Metal Carbide Nanofluids

In this work, the influence of semi-conductive SiC nanoparticles on the AC breakdown voltage and partial discharge development in natural ester oil FR3 is examined. Primarily, the dielectric constant and the electrical conductivity of the nanoparticles are measured following the broadband dielectric spectroscopy technique. The nanoparticles are added into the matrix following the ultrasonication process in three weight percentage ratios in order for their effect to be evaluated as a function of their concentration inside the base oil. The processing of the results reveals that the nanofluid containing SiC nanoparticles at 0.004% w/w demonstrates the highest AC dielectric strength improvement and shows the greatest resistance to the appearance of partial discharge activity. The mechanisms behind the aforementioned results are discussed in detail and confirmed by the broadband dielectric spectroscopy technique, which reveals that this particular nanofluid sample is characterized by lower dielectric constant and electrical conductivity than the one with double the weight percentage ratio.

Molecular laser-induced breakdown spectroscopy technique for the detection of nitrogen in waters

Nitrogen (N) content is a significant indicator for use in evaluating eutrophication. However, the conventional method, such as alkaline potassium persulfate digestion ultraviolet (UV) spectrophotometric or Kjeldahl method, always require...

Ionic-Liquid Gating in Two-Dimensional TMDs: The Operation Principles and Spectroscopic Capabilities

Ionic-liquid gating (ILG) is able to enhance carrier densities well above the achievable values in traditional field-effect transistors (FETs), revealing it to be a promising technique for exploring the electronic phases of materials in extreme doping regimes. Due to their chemical stability, transition metal dichalcogenides (TMDs) are ideal candidates to produce ionic-liquid-gated FETs. Furthermore, as recently discovered, ILG can be used to obtain the band gap of two-dimensional semiconductors directly from the simple transfer characteristics. In this work, we present an overview of the operation principles of ionic liquid gating in TMD-based transistors, establishing the importance of the reference voltage to obtain hysteresis-free transfer characteristics, and hence, precisely determine the band gap. We produced ILG-based bilayer WSe2 FETs and demonstrated their ambipolar behavior. We estimated the band gap directly from the transfer characteristics, demonstrating the potential of ILG as a spectroscopy technique.

Evolution of Free Volumes in Polycrystalline BaGa2O4 Ceramics Doped with Eu3+ Ions

BaGa2O4 ceramics doped with Eu3+ ions (1, 3 and 4 mol.%) were obtained by solid-phase sintering. The phase composition and microstructural features of ceramics were investigated using X-ray diffraction and scanning electron microscopy in comparison with energy-dispersive methods. Here, it is shown that undoped and Eu3+-doped BaGa2O4 ceramics are characterized by a developed structure of grains, grain boundaries and pores. Additional phases are mainly localized near grain boundaries creating additional defects. The evolution of defect-related extended free volumes in BaGa2O4 ceramics due to the increase in the content of Eu3+ ions was studied using the positron annihilation lifetime spectroscopy technique. It is established that the increase in the number of Eu3+ ions in the basic BaGa2O4 matrix leads to the agglomeration of free-volume defects with their subsequent fragmentation. The presence of Eu3+ ions results in the expansion of nanosized pores and an increase in their number with their future fragmentation.

Measuring of radioactive contamination by Gamma-ray Spectroscopy for many water projects in Baghdad City

The study aims to provide the effective monitoring of radioactive contents in refining water stations. Attempts were made to measure the radionuclide’s concentrations level which indicates to radioactive contamination in the samples of raw water taken from the Tigris River and samples of river sediments. The radionuclides contents have been obtained using the gamma-ray spectroscopy technique. Analysis system (HPGe) has been applied to measure the radioactivity concentration of Uranium, Radium, and Thorium in water and sediment samples. For solid samples (sediments), results have shown that the activity for238U the range was from (52±5.31Bq/kg)In S4 to(120±8)in S3, for 232Th the range was from(26±2.4Bq/kg)in S1to (48±3.1Bq/kg) in S3, for 40K, the range was from (247±17Bq/kg) in s4 to (453±18Bq/kg) in S3, for 137Cs the range was from(1.28±0.1Bq/kg) in S3 to (7.8±0.67) in S2. For liquid samples (water), the activity for 238U was from (10±1 Bq/l) in Kh1to(38±4.2Bq/l) in D1, for 232Th was from (1±0.35Bq/l) in kD1 to (1.8±0.60Bq/l) in D1, for 40K was from (10±0.3 Bq/l), in ka1to(48±5.7Bq/l) in KD1. In the final step (drinking water) showed only 40K isotope appeared at range(18±0.03 - 55±0.06Bq/l).

Characterization of In(Ga,Al)As/GaAs metamorphic heterostructures for mid-IR emitters by FTIR photoreflectance spectroscopy

Infrared photoreflectance (PR) spectra of In(Ga,Al)As/GaAs metamorphic heterostructures have been obtained using a novel photomodulation FTIR spectroscopy technique. An analysis of the PR spectra features allowed us to estimate the critical point energies corresponding to the direct interband transitions in various regions of the In(Ga,Al)As heterostructures, and distinguish the PR signals originating from Fabry-Perot interference. Observation of Franz-Keldysh oscillations originating from the InAlAs virtual substrate and an InGaAs waveguide layer has enabled determination of the built-in electric field intensities within the heterostructures. The obtained results open up possibilities for contactless control of free carrier concentration in In(Ga,Al)As/GaAs metamorphic heterostructures developed for growth of emitters of mid-IR spectral range.