Investigating the optical properties of polycrystalline AgCl(1-x)Br(x) (0≤x≤1) and Ag(0.95)Tl(0.05)Br(0.95)I(0.05) for IR engineering.
Using the Michelson technique we measured the refractive indices for the plane-parallel thin plates made of AgCl1-xBrx(0≤x≤1) and, to the best of our knowledge, for the first time for the Ag0.95Tl0.05Br0.95I0.05 plate, manufactured by hot embossing, at 632.8 nm. We recorded their absorption spectra within the range of 0.19-41.67 μm using UV-Vis spectrophotometry and Fourier transform infrared spectroscopy, which demonstrated that the increase of substituent silver bromide or thallium monoiodide mole fraction in the corresponding solid solution causes the optical density to grow. As the result it moves the transmission edges toward longer wavelengths, while slightly reducing the transmission peak.
Refractive index dispersion of AgCl 1-x Br x (0≤x≤1) and Ag 1-x Tl x Br 1-x I x (0≤x≤0.05)
Abstract For polycrystalline AgCl 1- x Br x (0 ≤  x  ≤ 1) and Ag 1- x Tl x Br 1- x I x (0 ≤  x  ≤ 0.05) thin plates manufactured by hot embossing, we recorded the ultraviolet (UV) to near-infrared (NIR) transmission spectra in order to reveal the absorption edge and to measure the refractive index at short wavelengths. The former moves towards longer wavelengths and the latter increases significantly, when the substituting agent content in the solid solution ( x ) is being increased. Using mid-infrared (MIR) spectra, recorded by Fourier-transform infrared spectroscopy (FTIR), we determined both real ( n ) and imaginary ( k ) parts of the refractive index at 4.5, 5.0, 8.0, 12.0, 14.0 μm. These data, together with the ones collected earlier with He-Ne laser and at 10.6 μm via FTIR, allow observing that the introduction of a heavy substituting agent into a host lattice forces the refractive index to grow gradually at a fixed wavelength and to fall considerably within each composition (vice versa for the extinction coefficient), especially in the NIR. Fresnel reflection ( R ) and absorption coefficients ( K ) were also calculated, and several error-calculation equations for n, k, K, and R were proposed concerning all contributions of each approach used.
Effect of superficial gas velocity on the particle temperature distribution in a fluidized bed with heat production
The heat transfer behavior of particles and gas in an olefin polymerization fluidized bed was numerically analyzed using an in-house developed 3-D computational fluid dynamics discrete element model (CFD-DEM). First the implementation of the model was verified by comparing simulation results with analytical results. A constant volumetric heat production rate was implemented in the particle energy equation to mimic the heat production due to the polymerization reaction. It was found that the probability density function (PDF) of the particle temperature becomes more homogeneous with increasing superficial gas velocity. Furthermore, instantaneous snapshots of the thermal driving force (the difference between the single particle temperature and bed-average gas temperature, Tp− ) for different heat production rates provide detailed insight in the particle temperature distribution inside the fluidized bed. The time- and bed-averaged particle convective heat transfer coefficient, which was calculated by Gunn׳s correlation, was found to be independent of the superficial gas velocity. This is explained by the fact that the relative velocity of gas and particles in the emulsion phase, where most of the particles and gas interact, is hardly influenced when increasing the gas superficial velocity. From the spatial distribution of Nusselt number, it becomes apparent that the high heat transfer regions are found in the wake of rising bubbles, whereas low heat transfer rates are found in the clouds of the bubbles.