Thermal stability of the optical properties of plasma deposited diamond-like carbon thin films

In present paper we studied the optical constants of the diamond-like carbon (DLC) films and their changes with annealing. The multisample modification of combined variable angle spectroscopic ellipsometry and near normal spectroscopic reflectometry was used. The optical constants of the DLC films were simulated by our recently published six-parameter dispersion model employing a parameterization of the density of electronic states (DOS). Based on the dispersion model parameters the density of π and σ electrons were evaluated. We showed that from our model and the independently determined hydrogen atomic fraction of the films before and after annealing the ratio between momentum matrix elements of π → π* and σ → σ* transitions and the correct sp³-to-sp² carbon bonding configuration ratio can be calculated. It is worth to notice that the first quantity is usually assumed to be equal to unity but we showed that this assumption may cause a significant error in the determination of the sp³-to-sp² ratio. Therefore, our suggested method represents a novelty in this field.     

Interaction of transuranium elements with biologically relevant ligands. Synthesis,crystal structure,IR and electronic spectra of neptunium glycolate [NpO2(C2O3H3)(Bipy)] · 2.5H2O

As a result of Np(V) glycolate reaction with 2,2′-bipyridyl, the novel coordination polymer [NpO₂(C₂O₃H₃)(Bipy)] · 2.5H₂O was formed. The structure consists of infinite chains of [NpO₂(C₂O₃H₃)(Bipy)] and water molecules. The crystal structure is confirmed by IR and UV–vis spectroscopic data. This complex is the first example of An glycolate with neutral molecular ligand.     

Eu3+‐doped glass as a color rendering index enhancer in phosphor‐in‐glass

A new method for improving color rendering index (CRI) and low correlated color temperature (CCT) in high‐power white‐light‐emitting diodes (WLEDs) is proposed. We used a configuration of phosphor‐in‐glass (PIG) and studied light output changes with the increment in concentration of yellow‐emitting Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) phosphor. The PIG was coupled on the top of blue‐light‐emitting diodes (LED) chip (465 nm). To compensate the lack of red emission in the phosphor, Eu³⁺‐doped tellurium glass with different europium content was employed as a red emitter. The suitable contents of YAG:Ce³⁺ and Eu³⁺ were 7.5 weight percent (wt%) and 3 mol percent (mol%), respectively. The CRI value went from 72 to 82, whereas the CCT was reduced from 24 933 to 6434 K. The proposed structure can improve CCT as well as CRI of WLEDs just by placing a glass on top.     

Model for corrosion of metals covered with thin electrolyte layers: Pseudo-steady state diffusion of oxygen

A one-dimensional mathematical model is presented for the free corrosion of a bare metal surface (devoid of any oxide film) under a thin electrolyte layer using mixed potential theory where anodic metal dissolution is controlled by oxygen diffusion through the electrolyte layer and by the oxygen reduction at the metal surface. A pseudo-steady state is considered wherein the oxygen diffusion is at steady state while the metal and hydroxyl ions keep accumulating in the thin electrolyte layer due to a decoupling arising from the assumed Tafel laws for corrosion kinetics. Under free corrosion the oxygen diffusion is shown to depend on a non-linear boundary condition with a non-integer power on oxygen concentration at the metal surface which makes the model non-trivial. Analytical and numerical results for the oxygen concentration at the metal surface, corrosion potential, and corrosion current density are reported which depend on several kinetic, thermodynamic and transport parameters in the system. The model is applied to iron and zinc systems with input data taken from the literature. The experimental utility of the model for gathering thin-film corrosion parameters from a study of the corrosion current and potential as a function of the thickness of the electrolyte layer is discussed. Precipitation and passivity, though not the main object of study in this work, are briefly discussed.