Reinforced Epoxy Composites Modified with Functionalized Graphene Oxide

The possibility of using graphene oxide as a modifying additive for polymer fiber-reinforced composites based on epoxy resin and basalt roving has been studied. The content of graphene oxide in the system has been experimentally selected, which has the best effect on the physico-mechanical properties of the obtained polymer composite material. The efficiency of the modification of the graphene oxide surface with APTES finishing additives and aminoacetic acid, which provides chemical interaction at the polymer matrix–filler interface, has been considered. The influence of graphene oxide and functionalizing additives on the polymer curing process was investigated using the thermometric method and differential scanning calorimetry.

Influence of mechanochemical activation on dissolving model corrosion films formed on ion-exchange resins using Trilon B

Inorganic deposits formed during operation and intermediate storage contain radionuclides, whose removal during the chemical decontamination of spent ion-exchange resins used in filters for special water purification at nuclear power plants has proved to be a challenge. In such deposits, radionuclides of the corrosion group (58.60Co, 54Mn, 51Cr) are typically located in the crystal lattice of poorly soluble iron oxides. The present work discusses the possibility of using mechanochemical activation in the decontamination of spent ion-exchange resins polluted with deposits of activated corrosion products from structural materials. Samples of natural and synthesised on the surface of the KU-2-8 cation exchanger in the presence of the 57Co label magnetites were used as model deposits. It was shown that an increase in the duration of mechanochemical activation leads to an increase in the dissolution rate of magnetite in model decontamination solutions based on еthylenediaminetetraacetic acid disodium salt (Trilon B) and nitric acid. It was shown that, when using Trilon B, magnetite dissolves more efficiently, which is explained by the interaction between the oxide surface and organic complexing agents. It can be assumed that solid-phase reactions occur during the mechanochemical activation of magnetite in the presence of dry reagents (Trilon B, oxalic, ascorbic and citric acids). Therefore, a poorly soluble shell formed on the oxide surface hinders the dissolution at a low magnetite/solution ratio. Unlike the reagent-free activation, for magnetite activated in the presence of oxalic acid, an increase in the solution/magnetite ratio promotes the dissolution of iron oxides. Using the example of a model cation exchanger, it was shown that the rate and efficiency of decontamination of spent ion-exchange resins polluted with deposits containing activated corrosion products increase significantly after mechanochemical activation in the presence of oxalic acid.

A Two-Step Approach to Tune the Micro and Nanoscale Morphology of Porous Niobium Oxide to Promote Osteointegration

We present a two-step surface modification process to tailor the micro and nano morphology of niobium oxide layers. Niobium was firstly anodized in spark regime in a Ca- and P-containing solution and subsequently treated by acid etching. The effects of anodizing time and applied potential on the surface morphology is investigated with SEM and AFM, complemented by XPS compositional analysis. Anodizing with a limiting potential of 250 V results in the fast growth of oxide layers with a homogeneous distribution of micro-sized pores. Cracks are, however, observed on 250 V grown layers. Limiting the anodizing potential to 200 V slows down the oxide growth, increasing the anodizing time needed to achieve a uniform pore coverage but produces fracture-free oxide layers. The surface nano morphology is further tuned by a subsequent acid etching process that leads to the formation of nano-sized pits on the anodically grown oxide surface. In vitro tests show that the etching-induced nanostructure effectively promotes cell adhesion and spreading onto the niobium oxide surface.

Interaction of Graphene Oxide Modified with Linear and Branched PEG with Monocytes Isolated from Human Blood

Multiple graphene-based therapeutics have recently been developed, however potential risks related to the interaction between nanomaterials and immune cells are still poorly understood. Therefore, studying the impact of graphene oxide on various populations of immune cells is of importance. In this work, we aimed to investigate the effects of PEGylated graphene oxide on monocytes isolated from human peripheral blood. Graphene oxide nanoparticles with lateral sizes of 100–200 nm and 1–5 μm were modified with linear and branched PEG (GO-PEG). Size, elemental composition, and structure of the resulting nanoparticles were characterized. We confirmed that PEG was successfully attached to the graphene oxide surface. The influence of GO-PEG on the production of reactive oxygen species (ROS), cytokines, phagocytosis, and viability of monocytes was studied. Uptake of GO-PEG by monocytes depends on PEG structure (linear or branched). Branched PEG decreased the number of GO-PEG nanoparticles per monocyte. The viability of monocytes was not altered by co-cultivation with GO-PEG. GO-PEG decreased the phagocytosis of Escherichia coli in a concentration-dependent manner. ROS formation by monocytes was determined by measuring luminol-, lucigenin-, and dichlorodihydrofluorescein-dependent luminescence. GO-PEG decreased luminescent signal probably due to inactivation of ROS, such as hydroxyl and superoxide radicals. Some types of GO-PEG stimulated secretion of IL-10 by monocytes, but this effect did not correlate with their size or PEG structure.

Atomic Scale Insight into Corrosion Inhibition: DFT Study of 2-Mercaptobenzimidazole on Locally De-Passivated Copper Surfaces

A key factor for effective inhibition by organic molecules of the initiation of localized corrosion by pitting is their ability to form a protective organic film in locally de-passivated zones exposing the bare metal next to the oxide-covered surface. Herein, based on quantum chemical DFT calculations, we study the chemistry of the interface between 2-mercaptobenzimidazole (MBI) and a copper surface partially covered by a Cu2O passive oxide film. The results show the adaptability of the molecule to adsorb strongly on the different zones, oxide or metal, of a locally de-passivated surface. However, differences in the local adsorption configurations, involving covalent bonding with H-bonding depending on oxide or metal and on conformer, thione or thiolate, lead to the formation of an inhomogeneous organic film. Increasing order of local adsorption strength is oxide walls < metal surface < oxide surface < oxide edges for the thione species, whereas there is no significant difference of local adsorption strength for the thiolate species. Our results suggest that both species of MBI can heal the oxygen and copper low coordinated sites as well as can protect the exposed metal surface, thus enhancing the barrier properties of the passivated surface even when locally defective.

Origin of Enhanced Thermal Atomic Layer Etching of Amorphous HfO2

HfO2 is a high-k material that is used in semiconductor devices. Atomic-level control of material processing is required for the fabrication of thin films of high-k materials at nanoscale device sizes. Thermal atomic layer etching (ALE) of metal oxides, in which up to one monolayer of material can be removed, can be achieved by sequential self-limiting (SL) fluorination and ligand-exchange reactions at elevated temperatures. First-principles based atomic-level simulations using density functional theory (DFT) can give deep insights into the precursor chemistry and the reactions that drive the etch of metal oxides. A previous study examined the hydrogen fluoride (HF) pulse in the first step in the thermal ALE process of crystalline HfO2 and ZrO2. This study examines the HF pulse on amorphous HfO2 using first-principles simulations. The Natarajan-Elliott analysis, a thermodynamic methodology is used to compare reaction models representing the self-limiting and spontaneous etch processes taking place during an ALE pulse. For the HF pulse on amorphous HfO2, we found that thermodynamic barriers impeding spontaneous etching are present at ALE relevant temperatures. HF adsorption calculations on the amorphous oxide surface is studied to understand the mechanistic details of the HF pulse. A HF molecule adsorbs dissociatively by forming Hf-F and O-H bonds. HF coverages ranging from 1.1 ± 0.3 to 18.0 ± 0.3 HF/nm2 are investigated and a mixture of molecularly and dissociatively adsorbed HF molecules is present at higher coverages. A theoretical etch rate of -0.82 ± 0.02 Å/cycle for amorphous HfO2 was calculated using a maximum coverage of 9.0 ± 0.3 Hf-F/nm2. This theoretical etch rate is greater than the theoretical etch rate for crystalline HfO2 that we previously calculated at -0.61 ± 0.02 Å/cycle. Undercoordinated atoms and void regions in amorphous HfO2 allows for more binding sites during fluorination whereas crystalline HfO2 has a limited number of adsorption sites.