Ashraf Fathy El Sherif

Enhanced emission from nano coated titanium target over than that from normal solid one was measured. The plasma was induced from both targets by the interaction of Nd: YAG laser source at a wavelength of 1064 nm. The enhanced signal emission was monitored using the Ti I- spectral lines at 453.32 and 498.17 nm. Another experiment was conducted after addition of a thin layer of 20 nm gold nanoparticles to the surface of bulk titanium. Enhancement factors were found up to twenty folds. The plasma-enhanced emission was attributed to the strong reduction in the plasma ignition threshold by a factor of 40 after adding the layer ofgold nanoparticles. Modeling to explain the origin of the strong reduction to the ignition threshold and enhanced emission is in advance which recommended that there a strong reduction of the thermal diffusion length of the bulk material to the limits of nanomaterial diameter size.

In the pages that follow,the structure of the crystal, unit cell dimension and complete structure information will be shown by single crystal x-ray diffraction and measuring some physical properties of 1D propylene diammonium pentachloro bismuthate [(NH₃)₂(CH₂)₃]BiCl₅ organic-inorganic hybrid perovskites (OIHs).Slow evaporation method is used to prepared the synthesis. The process of preparation occurred by mixing ethanolic solution of equimolar ratios (1:1) of its basic components (organic / inorganic). The Bi hybrid crystallized in orthorhombic non centro-symetric Pca21 structure with 8 molecules per unit cell.The unit cell parameters are a = 19.8403 (7) Å, b = 6.3303 (2) Å, c = 19.0314 (7) Å. The average C-C bond lengths are 1.50Å. The average N-C bond lengths are 1.47Å. The connection between organic parts to inorganic part is via hydrogen bond (H. Bond). Raman spectroscopy and also Fourier transform infrared spectroscopy (FTIR) have been used to study the vibrational spectra that shows the main diffraction peaks and their assignment. Diffuse reflectance spectra (DRS) method is used to study the optical properties and show that there is a strong absorption in the UV region for Bi hybrid. Kubelka–Munk equation has been used to calculate the band gap energy and indicates that the band gap for the present investigated hybrid is equals 3.15 eV.

In this work, we discuss a new technique for measuring the linear thermal expansion of refractory metals and alloys over their entire temperature range from room to near melting. The technique is based on generating multi-wavelength laser shadowgraphs for filament wire samples under gradual heating, and measuring the dimensional changes from its shadowgraphs using digital camera. The samples are clamped from both ends and joule heated by direct current under vacuum. The measurements are non-contact and accurate, enabling low cost dilatometric measurements that help in future synthesis and test of new grade of refractory materials, used as plasma facing material in nuclear fusion reactor, or special super alloys for high temperature applications were thermal structural stability are required.

This paper introduces both optical and mechanical design and simulation of large static deflection MOEMS actuator. The designed device is in the form of an adjustable optical wedge (AOW) laser scanner. The AOW is formed of 1.5-mm-diameter plano-convex lens separated by air gap from plano-concave fixed lens. The convex lens is actuated by staggered vertical comb drive and suspended by rectangular cross-section torsion beam. An optical analysis and simulation of air separated AOW as well as detailed design, analysis, and static simulation of comb -drive are introduced. The dynamic step response of the full system is also introduced. The analytical solution showed a good agreement with the simulation results. A general global minimum optimization algorithm is applied to the comb-drive design to minimize driving voltage. A maximum comb-drive mechanical deflection angle of 12 deg in each direction was obtained under DC actuation voltage of 32 V with a settling time of 90 ms, leading to 1-mm one-dimensional (1-D) steering of laser beam with continuous optical scan angle of 5 deg in each direction. This optimization process provided a design of larger deflection actuator with smaller driving voltage compared with other conventional devices. This enhancement could lead to better performance of MOEMS-based laser beam scanners for imaging and low-speed applications.