The structural, electronic, dynamical, and optical properties of a group of 2D germanium-based compounds, including GeC, GeN, GeO, GeSi, GeS, GeSe, and germanene, are investigated by employing first-principles calculations. The most stable structure of each of these systems is identified after considering the most probable configurations and performing accurate phonon calculations. We introduce a new phase of germanene, which we name the tile germanene, which is significantly more stable than the known hexagonal germanene. We apply the modern modified Becke–Johnson and DFT1/2 schemes to obtain an accurate band structure for the selected 2D materials. It is seen that GeO and GeC exhibit the highest bandgaps of >3 eV in this group of nanomaterials. Moreover, we argue that, in contrast to the semi-metallic nature of hexagonal germanene, tile germanene is a very good conductor. The band edges of our semiconducting 2D materials are accurately aligned to the vacuum level to address the potential photocatalytic application of these systems for water splitting and carbon dioxide reduction. The optical properties, including dielectric functions, refractive index, reflectivity, and loss function of the samples, in the presence of excitonic effects, are investigated in the framework of the Bethe–Salpeter approach.
In this paper MgAl 2 O 4 spinel powder with average particle size of 90 nm, purity of 99.99%, with stoichiometric ratio α-Al 2 O 3 and MgO and only 0.8 %wt. LiF add-on was solid-state synthesized at a temperature of 1300˚C and used in gel suspension with 83% solid load. Using the optimal value of ISOBAM (0.9 %wt.) as both dispersion and gelation factors led to a significant increase in the relative density of green body from 48.5% to 62.2%. Relative density increased after sintering at 1550˚C for 1h from 78% to 99.6% and pore size (40 nm) reduced to half the size of powder particles. Also, it resulted in appropriate pore distribution, because of the low number and value of the add-on in the gel system, and also optimization and preparation of nanopowders, as well as preparation and manufacture of suspension. XRD, BET, ICP, FESEM, FTIR analyses were done for synthesis and preparation of powder. Viscometery, Rheometery, Porosimetery, TG-DSC, Zeta potential, and sediment deposition analyses were done in order to optimize the parameters of the casting.
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