Rimantas Knizikevičius
Rimantas Knizikevičius
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The chemical etching of germanium in Br2 environment at elevated temperatures is described by the Michaelis–Menten equation. The validity limit of Michaelis–Menten kinetics is subjected to the detailed analysis. The steady-state etching rate requires synergy of two different process parameters. ...
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The chemical etching of germanium in Br2 environment at elevated temperatures is described by the Michaelis–Menten equation. The validity limit of Michaelis–Menten kinetics is subjected to the detailed analysis. The steady-state etching rate requires synergy of two different process parameters. High purity gas should be directed to the substrate on which intermediate reaction product does not accumulate. Theoretical calculations indicate that maximum etching rate is maintained when 99.89% of the germanium surface is covered by the reaction product, and 99.9999967% of the incident Br2 molecules are reflected from the substrate surface. Under these conditions, single GeBr2 molecule is formed after 30 million collisions of Br2 molecules with the germanium surface.
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2 days ago
Amelia Carolina Sparavigna
Amelia Carolina Sparavigna
Institution: Polytechnic University of Turin
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Vivianite is a hydrated iron phosphate mineral (Fe3(PO4)2·8H2O), crystallized in a monoclinic system. It is the endmember of a mineral series known as the vivianite group, where minerals have the general formula A3(XO4)2·8H2O, A is a divalent metal cation and X is phosphorus P or arsenic As. Today...
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Vivianite is a hydrated iron phosphate mineral (Fe3(PO4)2·8H2O), crystallized in a monoclinic system. It is the endmember of a mineral series known as the vivianite group, where minerals have the general formula A3(XO4)2·8H2O, A is a divalent metal cation and X is phosphorus P or arsenic As. Today, vivianite is attracting interest as a promising material for recovering phosphorous from wastewaters. In fact, the presence in wastewater sludges of soluble iron and phosphorus can lead to vivianite formation. As a crystal, it is a naturally occurring Van der Walls material. It can be easily characterized by means of Raman and infrared spectroscopies. Here we will consider the Raman spectroscopy, precisely that related to the hydroxyl-stretching region. We will propose the deconvolutions in q-Gaussian functions of spectra from RRUFF database, comparing the obtained results with those available from literature. Besides vivianite, we will consider also baricite and bobierrite for comparison (baricite and bobierrite are two other members of the vivianite group). About the hydroxyl-stretching region and the use of q-Gaussians, we take the chance to continue a discussion regarding the Raman spectroscopy of water, discussion that we started in March 2024.
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3 weeks ago
Arpita Biswas
Arpita Biswas
Institution: Department of Chemistry, Shibpur Dinobundhoo Institution (College),
Email: abiswas83@gmail.com
Synthesis of Zincoxide nanoparticles (ZnO NPs) with definite size and shape and their
morphological characterization rationally is really a challenging aspect at present due to the ongoing
demand of these nanosize particles for their divergent use in different field of science and technology.
...
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Synthesis of Zincoxide nanoparticles (ZnO NPs) with definite size and shape and their
morphological characterization rationally is really a challenging aspect at present due to the ongoing
demand of these nanosize particles for their divergent use in different field of science and technology.
Reduction of Zinc acetate dihydrate by sodium hydroxide was performed to produce ZnO NPs by
following precipitation method. Here the whole reaction was completed in aqueous medium in low
temperature. To characterize the synthesized ZnO NPs some recent techniques like X-ray diffraction
study (XRD), Ultra-violet Visible (UV-Vis) spectroscopy, Field emission scanning electron microscopy
(FESEM), Transmission electron microscopy (TEM), Selected area electron diffraction (SAED) and
Electron diffraction X-ray (EDX) were used systematically.
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2 years ago
Jacques Curely
Jacques Curely
Institution: Laboratoire Ondes et Matière d’Aquitaine, UMR 5798, University of Bordeaux,
Email: Jacques.curely@u-bordeaux.fr
:In earlier work, we previously established a formalism that allows to express the exchange
energy J vs. fundamental molecular integrals without crystal field, for a fragment A–X–B, where
A and B are 3d 1 ions and X is a closed-shell diamagnetic ligand. In this article, we recall this
formali...
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:In earlier work, we previously established a formalism that allows to express the exchange
energy J vs. fundamental molecular integrals without crystal field, for a fragment A–X–B, where
A and B are 3d 1 ions and X is a closed-shell diamagnetic ligand. In this article, we recall this
formalism and give a physical interpretation: we may rigorously predict the ferromagnetic (J < 0)
or antiferromagnetic (J > 0) character of the isotropic (Heisenberg) spin-spin exchange coupling.
We generalize our results to ndm ions (3 ≤ n ≤ 5, 1 ≤ m ≤ 10). By introducing a crystal field we
show that, starting from an isotropic (Heisenberg) exchange coupling when there is no crystal field,
the appearance of a crystal field induces an anisotropy of exchange coupling, thus leading to a z-z
(Ising-like) coupling or a x-y one. Finally, we discuss the effects of a weak crystal field magnitude
(3d ions) compared to a stronger (4d ions) and even stronger one (5d ions). In the last step, we are
then able to write the corresponding Hamiltonian exchange as a spin-spin one.
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2 years ago