Metastable states in high carbon C–(Fe,Ni, Co) films obtained by three-electrode ion-plasma sputtering

Abstract

The effect of ion-plasma deposition on the structure of high-carbon films (at. %) Fe–(20–84) % С, Co–(5–52) % С, Ni–(7–61) % С was investigated. The lattice periods and crystallite sizes of nonequilibrium phases in the as-deposited state and after heating are determined. The temperatures of the beginning and end of the decay of metastable phases during heating at a constant speed are established. The transition from an amorphous to an equilibrium crystalline state in Fe–C films passes through the stage of formation and subsequent decomposition of an intermediate, metastable hcp phase of variable composition. The electrical and hysteretic magnetic properties of the films were measured in the as-deposited state and after heat treatment. The compositions and conditions for producing films with low values of the temperature coefficient of electrical resistance and high coercive force are established. Thus, high-carbon films of Ni–61% C in the as-depoteted state and Fe–69% C films after heating to 900?K are characterized by small TCR values (± 10^?6 К^?1) over a wide temperature range.     

Highly porous polymeric sponges for oil sorption

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Modified and environmentally friendly oxidation of phosphorane ylides to vicinal tricarbonyls using unsupported moist Oxone in dichloromethane

Abstract

Modified and eco-friendly oxidation of phosphorane ylides to the corresponding vicinal tricarbonyls (VTC) using unsupported moist Oxone in dichloromethane at room temperature is described. This green oxidation protocol is simple, mild, and highly efficient to operate, and allowing a chemoselective preparation of VTC from various phosphorane ylides without tedious workup procedures of extraction/drying process in excellent yields.     

A Bis-Chelating / Ligand for the Synthesis of Heterobimetallic Platinum(II)/Rhenium(I) Complexes: Tools for the Optimization of a New Class of Platinum(II) Anticancer Agents

The two independent and coordination sites of a newly synthesized bis[2-(hydroxyphenyl)-1,2,4-triazole] platform have been exploited to prepare four monometallic neutral ()Pt^II complexes carrying DMSO, pyridine, triphenylphosphine, or N-heterocyclic carbene as the fourth ligand. Then, the second coordination site was used to introduce an IR-active rhenium tricarbonyl entity, affording the four corresponding heterobimetallic neutral Pt^II/Re^I complexes, as well as a cationic Pt^II/Re^I derivative. X-ray crystallographic studies showed that distortion of the organic platform occurred to accommodate the coordination geometry of both metal centers. No ligand exchange or transchelation occurred upon incubation of the Pt^II complexes in aqueous environment or in the presence of Fe^III, respectively. The antiproliferative activity of the ligand and complexes was first screened on the triple-negative breast cancer cell line MDA-MB-231. Then, the IC₅₀ values of the most active candidates were determined on a wider panel of human cancer cells (MDA-MB-231, MCF-7, and A2780), as well as on a nontumorigenic cell line (MCF-10A). Low micromolar activities were reached for the complexes carrying a DMSO ligand, making them the first examples of highly active, but hydrolytically stable, Pt^II complexes. Finally, the characteristic mid-IR signature of the {Re(CO)₃} fragment in the Pt/Re heterobimetallic complexes was used to quantify their uptake in breast cancer cells.     

Predicting polycyclic aromatic hydrocarbon formation with an automatically generated mechanism for acetylene pyrolysis

Using Reaction Mechanism Generator (RMG), we have automatically constructed a detailed mechanism for acetylene pyrolysis, which predicts formation of polycyclic aromatic hydrocarbons (PAHs) up to pyrene. To improve the data available for formation pathways from naphthalene to pyrene, new high‐pressure limit reaction rate coefficients and species thermochemistry were calculated using a combination of electronic structure data from the literature and new quantum calculations. Pressure‐dependent kinetics for the CH potential energy surface calculated by Zádor et al. were incorporated to ensure accurate pathways for acetylene initiation reactions. After adding these new data into the RMG database, a pressure‐dependent mechanism was generated in a single RMG simulation which captures chemistry from C to C. In general, the RMG‐generated model accurately predicts major species profiles in comparison to plug‐flow reactor data from the literature. The primary shortcoming of the model is that formation of anthracene, phenanthrene, and pyrene are underpredicted, and PAHs beyond pyrene are not captured. Reaction path analysis was performed for the RMG model to identify key pathways. Notable conclusions include the importance of accounting for the acetone impurity in acetylene in accurately predicting formation of odd‐carbon species, the remarkably low contribution of acetylene dimerization to vinylacetylene or diacetylene, and the dominance of the hydrogen abstraction CH addition (HACA) mechanism in the formation pathways to all PAH species in the model. This work demonstrates the improved ability of RMG to model PAH formation, while highlighting the need for more kinetics data for elementary reaction pathways to larger PAHs.     

On the Statistical Calibration of Physical Models

We introduce a novel statistical calibration framework for physical models, relying on probabilistic embedding of model discrepancy error within the model. For clarity of illustration, we take the measurement errors out of consideration, calibrating a chemical model of interest with respect to a more detailed model, considered as “truth” for the present purpose. We employ Bayesian statistical methods for such model‐to‐model calibration and demonstrate their capabilities on simple synthetic models, leading to a well‐defined parameter estimation problem that employs approximate Bayesian computation. The method is then demonstrated on two case studies for calibration of kinetic rate parameters for methane air chemistry, where ignition time information from a detailed elementary‐step kinetic model is used to estimate rate coefficients of a simple chemical mechanism. We show that the calibrated model predictions fit the data and that uncertainty in these predictions is consistent in a mean‐square sense with the discrepancy from the detailed model data.