Ali Abdelaziem

The objective of this study is to explore how the replacement of barium oxide (BaO) by bismuth oxide (Bi2O3) affects the optical, structural and gamma rays shield ability of borate glasses. To accomplish this, a series of borate-based glasses was fabricated according the chemical formula 60B2O3 + (40-x) BaO + xBi2O3, where 0 < x < 10 wt.%. X-ray diffraction confirmed that an amorphous phase was present at all fabricated glasses. Thermal analysis indicated that Bi2O3 could serve as a glass modifier for all values of x greater than zero. Furthermore, the optical absorption profile showed that the samples had a greater absorption rate as x increased within the 1–4 eV photon energy range, with only minor fluctuations beyond 4 eV. Monte Carlo simulation demonstrated that increasing the concentration of Bi2O3 led to an increased radiation-absorbing capacity, where the linear attenuation coefficient of the fabricated glasses enhanced by 26% from 74.48 to 94.17 cm−1 at gamma ray energy of 0.015 MeV. Simultaneously, the half value thickness for the fabricated glasses reduced from 3.99 to 3.73 cm, raising the Bi2O3 concentration between 0 and 10 wt.%, respectively. These results indicate that adding Bi2O3 to boron oxides can significantly improve shielding the ability of the material to against gamma rays, alter the glass samples, and potentially be cost-effective. This study could lead to faster synthesis processes for glass modifiers, with important implications for designing and producing materials to shield against harmful gamma rays in industrial and medical applications.

2D transition-metal dichalcogenides of chromium are technologically important due to their diverse electrical and magnetic properties. Herein this study, 1T-CrS2 nanosheets as thin as 2?nm are successfully synthesized by an atmospheric pressure space-confined chemical vapor deposition method. The prepared CrS2 nanosheets are stable at room temperature. Electrical measurement shows a quasi n-type semiconductor behavior. In addition, terahertz characterizations on 1T-CrS2 reveal its potential to integrate with the ultrathin infrared sensor platforms.

Terahertz (THz) spectroscopy technique has been applied in ex vivo biomechanical properties analysis of human corneas. Upon the application of light pressure on the cornea, the photo elastic birefringent effect, anisotropic deformation, thickness changes and hydration levels will contribute to the sudden phase changes of terahertz time domain signal. The shelf lifetime study shows that the phase shift is reduced and cornea loose the biomechanical properties with the increase of hydration level. Mechanical behaviors have been further studied based on the “fresh” cut corneas with the similar hydration levels. THz signal was collected by focusing inside of the cornea to avoid the phase shift due to light stress caused movement of the corneal surface. By this way, the amount of THz signal refractive index variation is correlated to the elastic property of the corneas. The correlation between the THz signal phase shift and refractive index shift due to the corneal strain can be used to derive the elastic Young’s modulus. Our results demonstrated the THz spectroscopy, as a non-contact and non-invasive detection method, could be potential for understanding the mechanism of corneal deformation under the action of intraocular pressure in the physiological environment in future.

Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D FexGeTe2 ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown FexGeTe2. As a result, high-quality Fe3GeTe2 and Fe5GeTe2 flakes have been grown selectively using the CS-CVD technique. Curie temperature (TC) of the as-grown FexGeTe2 can be up to ∼ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe5GeTe2 reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe5GeTe2 display the highest conductivity among other FexGeTe2 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.

A novel scalable approach combining Monte Carlo Simulation (MS) and the Phy-X/PDS (Phy-X) software program have been developed to investigate the radiation shielding properties of the well-known (CBS-1, 2, and 3) family of glass-ceramics (CaO, B2O3, and SiO2). The linear attenuation coefficient (LAC), half-value layer (HVL), mean free path (MFP) and transmission factor (TF) were identified as important parameters controlling the behavior of the CBS shielding family by MS. Phy-X, on the other hand, explored the effective (Zeff) and equivalent (Zeq) atomic numbers, as well as the build-up factors. It was discovered that (CBS-1) and (CBS-3) shielding could be comparable to commercially manufactured glass shielding, and even higher in some cases. Furthermore, CBS-3 demonstrated the greatest shielding ability among the CBS family members, with a maximum LAC value of ~ 38.77 cm-1 at a gamma energy of ~ 0.015 MeV. Our findings pave the way for future research based on the CBS glass family to accelerate the development of shielding materials for high-energy electromagnetic waves.

Abstract A Novel scalable approach using Terahertz (THz) waves together with the electromagnetic field simulation was applied to investigate four rabbits of eight rabbit corneas in vivo. One eye of each rabbits? corneas was edema induced; the other eye of the corneas served as the control. The simulation revealed the propagation of THz waves at a certain distance along the sub-surface of the cornea. THz spectra have been collected close to the corneal surface by deviating the direct reflection of the THz beam for the edema cornea, the reflected wave intensity for edema corneas is generally larger compared with the control cornea. Upon edema becomes severe at the end of the observation, the reflected wave intensities obtained by detector corresponding to the corneal deep stroma layer approach to the same value for all observed corneas. Good correlation is observed between central corneal thickness measurements and THz wave reflection signal intensities. Our results demonstrated that THz spectroscopy technique could obtain the information from different corneal sublayers.

La 0.8 Sr0.2MnO3 (LSM) polycrystalline powder was synthesized using hydrothermal method at 900 °C. High Resolution Transmission Electron Microscope (HR-TEM) showed that the particles were uniform with average particle size of 657 nm. X-ray Diffraction (XRD) and lattice fringes indicated rhombohedral structure of LSM particles. Thin LSM films were successfully grown on cleaned Si (100) substrate by pulsed laser deposition (PLD). Annealing of LSM films in air affected structure, morphology and electrical properties that films where crystallization of the LSM films was started at 600 °C and enhanced by further annealing as indicated by XRD. Field Emission Scanning Electron Microscope (FESEM) revealed that the grain size increases by increasing annealing temperature and at temperature of 1000 °C cracks were seen. Average roughness and root mean square roughness decreased with further annealing (up to 800 °C) then increased at 1000 °C that were verified by atomic force microscope (AFM). Moreover, Raman scattering was enhanced and all major bands were revealed at 800 °C. Resistivity of LSM films decreases with increasing temperature (from 25 °C to 200 °C) and all films underwent a semiconductor behavior in the most of applied temperatures. The lowest resistivity of LSM films was reached at annealing temperature of 800 °C with low activation energy value (Ea) of about 0.1 eV.