Oxide Barrier Research Articles

Drone Delivery of Dehydro-Sulfurization Utilizing Doubly-Charged Negative Ions of Nanoscale Catalysts Inspired by the Biomimicry of Bee Species’ Bio-Catalysis of Pollen Conversion to Organic Honey

The sulfur dioxide (SO2) compound is a primary environmental pollutant worldwide, whereas elemental sulfur (S) is a global commodity possessing a variety of industrial as well as commercial functions. The chemical relationship between poisonous SO2 and commercially viable elemental S has motivated this investigation using the Density Functional Theory calculation of the relative transition state barriers for the two-step dehydro-sulfurization oxidation–reduction reaction. Additionally, doubly-charged nanoscale platelet molybdenum disulfide (MoS2), armchair (6,6) carbon nanotube, 28-atom graphene nanoflake (GR-28), and fullerene C-60 are utilized as catalysts. The optimal heterogeneous and homogeneous catalysis pathways of the two-step oxidation–reduction from SO2 to elemental S are further inspired by the biomimicry of the honeybee species’ multi-step bio-catalysis of pollen conversion to organic honey. Potential applications include environmental depollution, the mining of elemental sulfur, and the functionalization of novel technologies such as the recently patented aerial and amphibious LynchpinTM drones.

Metal oxide barrier layers for terrestrial and space perovskite photovoltaics

Metal oxide barrier layers for terrestrial and space perovskite photovoltaics

Two-Electron- and One-Electron-Transfer Pathways for TEMPO-Catalyzed Greener Electrochemical Dimerization of 3-Substituted-2-Oxindoles

Dimerized 3-substituted 2-oxindoles are essential building blocks for the total synthesis of alkaloids. Herein, three different types of 3-substituted-2-oxindoles were dimerized with a total of 41 examples employing TEMPO as a redox mediator and TEMPO+ as an in situ generated electrocatalyst using control potential electrolysis at an applied potential of only 0.8 V versus a Ag/Ag+ nonaqueous reference electrode. These reactions did not yield any product formation in the absence of TEMPO, keeping other experimental conditions the same. Two-electron- and one-electron-transfer pathways were operational depending on the oxidation potentials of 2-oxindoles. 3-Carboxylate-2-oxindoles having a lower oxidative energy barrier for a two-electron-transfer pathway followed a hydride-transfer mechanism to generate a carbocation, which thereafter reacted with the enol form of oxindole to produce dimerized 2-oxindoles. On the other hand, 3-alkyl-2-oxindoles and 3-alkylcarboxylate-2-oxindoles had significantly higher oxidative energy barrier compared to 3-carboxylate-2-oxindoles and followed the one-electron-transfer pathway to generate a radical species for dimerization. The two-electron transfer pathway was significantly faster compared to the one-electron transfer pathway, evident from reaction time (15 min vs 1 h 20 min or longer), which was due to a faster second-order rate constant for the two-electron transfer pathway (1.2 M–1 s–1) compared to the one-electron transfer pathway (0.29 M–1 s–1). Furthermore, four aspects of transforming greener electro-organic synthesis have been demonstrated. They are as follows: (a) electron-transfer rate measurement as an alternative method for synthesis optimization instead of lengthy product isolation, (b) prevention of electrode passivation employing electrocatalysis routes, (c) recovery of the electrolyte, and (d) mild reaction conditions employing control potential electrolysis. Finally, an efficient electrochemical oxidation strategy has been demonstrated for the total synthesis of a dimeric hexahydropyrrolo[2,3-b]indole alkaloids, (±)-chimonanthine (I) and (±)-folicanthine (II).

The effectiveness of a hydrocolloid crusting method versus standard care in the treatment of incontinence-associated dermatitis among adult patients in an acute care setting: A randomised controlled trial

IntroductionIncontinence-associated dermatitis (IAD) is a type of irritant contact dermatitis due to prolonged exposure of the skin to moisture induced by urine or/and faeces. The main principles when treating IAD involves protecting the skin from further exposure to irritants, establishing a healing environment, and eradicating skin infections. This study aimed to evaluate the effectiveness of the hydrocolloid crusting method (HCM) versus the standard care method (SCM) in treating IAD. MethodA randomised controlled trial was conducted in an acute tertiary hospital in Singapore between August 2019 to September 2021. Using computer-generated numbers, patients were randomised into either HCM or SCM treatment groups. HCM treatment involved cleansing the affected area with a pH-neutral non-rinse moisturising cleanser, and the application of alternate layers of hydrocolloid powder, and non-sting film barrier spray (repeated three times during each use). Patients in the SCM treatment group received the same cleanser followed by a 30% zinc oxide barrier cream. IAD was assessed daily for up to seven days by the wound care nurses using the IAD severity tool. The primary outcome of the study was the mean difference in IAD score per day between both methods. ResultsForty-four patients were eligible and recruited (22 in HCM; 22 in SCM). Patients in both groups were comparable in age and gender. IAD Category 2 was more predominant in both methods. The most common location of IAD was at the perianal skin and diarrhea related to gastroenteritis was the most prevalent cause of IAD. More patients in the SCM group (n = 12; 54.5%) had their IAD healed within seven days compared to HCM, (n = 7; 31.8%) group. However, the average decrease in IAD scores per day for both methods were found to be similar. ConclusionHCM can be considered as a treatment of IAD along with the use of SCM. A skin care regimen should include effective cleansing, skin protection, and moisturization in IAD management.

Aluminum Particle Ignition Studies with Focus on Effect of Oxide Barrier

Aluminum particle ignition behavior in open atmosphere rocket propellants fires is of particular interest for preventing accidents for rockets carrying high-value payloads. For nominal motor pressures, aluminum particles oxidize to aluminum oxide in the gas phase and release significant combustion energy while minimizing motor instability. During rocket abort or launch pad malfunction which occur under atmospheric or low pressure, behavior of aluminum particle combustion becomes complex and aluminum appears to melt, agglomerate or form a skeletal structure. Furthermore, an oxide shell of alumina instantly forms on any fresh aluminum surface which is exposed to an oxidizing environment. Aluminum combustion then strongly depends on the oxide layer growth, which is influenced by causative factors, including particle size, environmental gas composition, and heating rate. This work focuses on the effect of the oxide barrier which forms on the surface of aluminum that is recognized to impede combustion of aluminum in solid rocket propellants. Understanding the mechanism for breach of this barrier is deemed to be an important consideration in the overall process. In this discussion, results of various experiments will be discussed which have a bearing on this process. Basically, a recognized criterion is the melting of the oxide layer at 2350 K is sufficient. However, in other situations, depending on the mechanism of oxide formation, there will occur defects in the oxide shell which provide for aluminum ignition at lower temperatures. For slow heating in an oxidizing environment, where the oxide layer can grow thick, then ignition is more difficult. Because there is no uniform model to establish an ignition criterion due to the unknown history of an aluminum particle, this paper reports experimental findings involving oxyacetylene torch, thermogravimetric analysis with differential scanning calorimeter, aluminum particle heating, electric ignition and aluminum powder heating, to address the influence of the oxide layer on the aluminum particle ignition.

Ultralow reaction barriers for CO oxidation in Cu-Au nanoclusters.

Systematic structure prediction of CunAum nanoclusters was carried out for a wide compositional area (n + m ≤ 15) using the evolutionary algorithm USPEX and DFT calculations. The obtained structural data allowed us to assess the local stability of clusters and their suitability for catalysis of CO oxidation. Using these two criteria, we selected several most promising clusters for an accurate study of their catalytic properties. The adsorption energies of reagents, reaction paths, and activation energies were calculated. We found several cases with low activation energies and explained these cases using the patterns of structural change at the moment of CO2 desorption. The unique case is the Cu7Au6 cluster, which has extremely low activation energies for all transition states (below 0.05 eV). We thus showed that higher flexibility due to the binary nature of nanoclusters makes it possible to achieve the maximum catalytic activity. Considering the lower price of copper, Cu-Au nanoparticles are a promising new family of catalysts.

Preferred surface orientation for CO oxidation on SnO2 surfaces.

In the present study, we perform a comparative study on the oxidation mechanism of CO gas molecules on SnO2 (110), (101), and (100) surfaces. The optimized adsorption configurations show that the adsorption of CO molecules could occur similarly on the three SnO2 surfaces via two adsorption modes, physisorption of CO on the Sn5c site that is considered as the first step for CO oxidation, followed by CO chemisorption on the O2c site resulting in the formation of CO2 species. Based on the calculated adsorption energies and CO molecule diffusion on SnO2 surfaces, CO molecule adsorption on the (101) surface exhibits the highest adsorption energy and the lowest reaction barrier for CO oxidation compared to the widely considered (110) surface or the (100) surface. These findings are expected to have a major impact on improving sensing properties toward toxic gas by means of surface-orientation engineering.

Предельные параметры СИС-переходов в теории и технологические возможности их достижения

Tunneling Josephson junctions of the superconductor-insulator-superconductor (SIS) type have a history of more than 50 years, and theoretical estimates of the ultimate parameters of devices for receiving and processing signals based on them look very promising. In practice, in many cases, the actually achieved parameters turn out to be much worse than the theoretical ones, so for niobium SQUIDs the characteristic voltage Vc=IcRn at best reaches 200 µV, and according to theory it should be up to 2 mV. For Terahertz SIS mixers and oscillators, the main problems are a large specific capacitance, hysteresis, and leakage currents. These problems may be related to the morphology and crystal structure of superconductor films. In practice, films are granular, tunnel barriers are nonuniform, the effective area is about 10% of geometric area, leakage currents, parasitic capacitances occur. The crystal structure determines fundamentally different properties of the same elements, for example, for carbon it is diamond, graphite, fullerenes, nanotubes. Important components of a promising superconducting technology are: the use of single-crystal substrates matched in lattice constant and orientation with the grown films, optimization of growth temperature conditions, controlled formation of an oxide or nitride tunnel barrier. One option is to use a Schottky barrier for the semiconductor interlayer instead of a dielectric or normal metal one. This review presents the results of studying films by X-ray diffraction diagnostics, atomic force microscopy, and electron microscopy, showing the main bottlenecks of the existing technology with the deposition of niobium, niobium nitride, and aluminum films on oxidized standard silicon substrates, as well as the results of quasi-epitaxial growth of films on single-crystal substrates at various temperature conditions. Reproducible manufacturing of high-quality tunnel junctions can be achieved by implementing atomically smooth surfaces of tunnel contacts, which will improve the signal and noise characteristics of superconducting devices for receiving and processing information.

Maternal supplementation with glycerol monolaurate improves the intestinal health of suckling piglets by inhibiting the NF-κB/MAPK pathways and improving oxidative stability.

Glycerol monolaurate (GML) is a food safe emulsifier and a kind of MCFA monoglyceride that has been proven to confer positive benefits in improving animal health, production and feed digestibility as a feed additive. This study aims to evaluate whether supplementation of a sow diet with GML could affect the intestinal barrier function and antioxidant status of newborn piglets and to explore its regulatory mechanism. A total of 80 multiparous sows were divided into two groups, which were fed a basal diet or a basal diet supplemented with 0.1% GML. The results indicated that maternal supplementation with GML significantly increased fat, lactose and protein in sow colostrum, as well as fat and protein in sow 14-day milk (P < 0.05). The results showed that GML significantly reduced the concentrations of IL-12 in the duodenum, TNF-α, IL-1β and IL-12 in the jejunum, and IL-1β in the ileum of piglets (P < 0.05). Higher concentrations of T-AOC, T-SOD, GSH and GSH-Px and lower MDA in the intestine were observed in the GML group than in the control group. Correspondingly, the villi height, crypt depth and the ratio of villi height to crypt depth (V/C) in the jejunum and the V/C in the ileum in the GML group were significantly higher than those in the control group (P < 0.05). Moreover, the GML group displayed significantly increased protein abundance of zonula occludens (ZO)-1, occludin, and claudin-1 in the small intestine (P < 0.05), mRNA expression of mucins (MUCs) in the small intestine (MUC-1, MUC-3 and MUC-4), and mRNA expression of porcine beta defensins (pBDs) in the duodenum (pBD1 and pBD2), jejunum (pBD1, pBD2 and pBD129) (P < 0.05), and ileum (pBD2, pBD3 and pBD114) (P < 0.05). Further research showed that GML significantly reduced the phosphorylation of the NF-κB/MAPK pathways in the small intestine (P < 0.05). In addition, the results of 16S rDNA sequencing showed that maternal supplementation with GML altered the colonic microbiotic structure of piglets, and reduced the relative abundance of Escherichia shigella. In summary, a sow diet supplemented with GML enhanced the offspring's intestinal oxidative stability and barrier function and attenuated the offspring's intestinal inflammatory response, possibly by suppressing the activation of the NF-κB/MAPK pathways.

In Vivo Voltammetric Imaging of Metal Nanoparticle-Catalyzed Single-Cell Electron Transfer by Fermi Level-Responsive Graphene.

Metal nanomaterials can facilitate microbial extracellular electron transfer (EET) in the electrochemically active biofilm. However, the role of nanomaterials/bacteria interaction in this process is still unclear. Here, we reported the single-cell voltammetric imaging of Shewanella oneidensis MR-1 at the single-cell level to elucidate the metal-enhanced EET mechanism in vivo by the Fermi level-responsive graphene electrode. Quantified oxidation currents of ~20 fA were observed from single native cells and gold nanoparticle (AuNP)-coated cells in linear sweep voltammetry analysis. On the contrary, the oxidation potential was reduced by up to 100 mV after AuNP modification. It revealed the mechanism of AuNP-catalyzed direct EET decreasing the oxidation barrier between the outer membrane cytochromes and the electrode. Our method offered a promising strategy to understand the nanomaterials/bacteria interaction and guide the rational construction of EET-related microbial fuel cells.

Immersion Corrosion Tests to Evaluate Polyaspartic Coatings on Steel

In this study, a waterproof polyaspartic coating used for concrete structures was modified into an anti-corrosion coating system to prevent steel assets from corroding. A micaceous iron oxide barrier, a zinc phosphate corrosion inhibitor and a novel resin hardener were added to the polyaspartic coating. Its corrosion performance was assessed through immersion corrosion tests in 3.5% NaCl solutions at room temperature (RT) and 35 °C for 30 days. The surface finish of the steel samples was milled and blasted (SA 2.5). The coating was applied directly to the metal substrate. The average thickness of the coating was 220 ±10 µm. The experimental results confirmed the successful enhancement of the control coating on steel that was previously applied to concrete by adding a zinc phosphate corrosion inhibitor and micaceous iron oxide barrier. However, defects in the coating and rust on the substrate of the control coating were hindered by applying the developed coating.

Study on characteristics of neutron-induced leakage current increase for SiC power devices

In this paper, the displacement damage degradation characteristics of silicon carbide (SiC) Schottky barrier diode (SBD) and metal oxide semiconductor field effect transistor (MOSFET) are studied under 14-MeV neutron irradiation. The experimental results show that the neutron irradiation with a total fluence of 1.18×10&lt;sup&gt;11&lt;/sup&gt; cm&lt;sup&gt;–2&lt;/sup&gt; will not cause notable degradation of the forward &lt;i&gt;I-V&lt;/i&gt; characteristics of the diode, but will lead to a significant increase in the reverse leakage current. A defect with energy level position of &lt;inline-formula&gt;&lt;tex-math id="Z-20230916130504"&gt;\begin{document}$ E_{\rm{C}} - 1.034 $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20230976_Z-20230916130504.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20230976_Z-20230916130504.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; eV is observed after irradiation by deep level transient spectroscopy (DLTS) testing, which is corresponding to the neutron-induced defect cluster in SiC. This deep level defect may cause the Fermi level of n-type doping drift region to move toward the mid-gap level. It ultimately results in the decrease of the Schottky barrier and the increase of the reverse leakage current. In addition, neutron-induced gate leakage increase is also observed for SiC MOSFET. The gate current corresponding to &lt;i&gt;V&lt;/i&gt;&lt;sub&gt;gs&lt;/sub&gt; = 15 V after irradiation increases nearly 3.3 times that before irradiation. The donor-type defects introduced by neutron irradiation in the oxide layer result in the difference in the conductivity mechanism of gate oxygen between before and after irradiation. The defects have an auxiliary effect on carrier crossing the gate oxide barrier, which leads to the increase of gate leakage current. The defects introduced by neutron irradiation are neutral after capturing electrons. The trapped electrons can cross a lower potential well and enter the conduction band to participate in conduction when the gate is positively biased, thus causing the gate current to increase with the electric field increasing. After electrons captured by donor-type defects enter the conduction band, positively charged defects are left from the gate oxide, leading to the negative shift of the transfer characteristics of SiC MOSFET. The results of DLTS testing indicate that the neutron irradiation can not only cause the intrinsic defect state of SiC material to change near the channel of MOSFET, but also give rise to new silicon vacancy defects. However, these defects are not the main cause of device performance degradation due to their low density relative to the intrinsic defect’s.

Facile Synthesis of Gram-Scale Mesoporous Ag/TiO2 Photocatalysts for Pharmaceutical Water Pollutant Removal and Green Hydrogen Generation.

This work demonstrates a two-step gram-scale synthesis of presynthesized silver (Ag) nanoparticles impregnated with mesoporous TiO2 and evaluates their feasibility for wastewater treatment and hydrogen gas generation under natural sunlight. Paracetamol was chosen as the model pharmaceutical pollutant for evaluating photocatalytic performance. A systematic material analysis (morphology, chemical environment, optical bandgap energy) of the Ag/TiO2 photocatalyst powder was carried out, and the influence of material properties on the performance is discussed in detail. The experimental results showed that the decoration of anatase TiO2 nanoparticles (size between 80 and 100 nm) with 5 nm Ag nanoparticles (1 wt %) induced visible-light absorption and enhanced charge carrier separation. As a result, 0.01 g/L Ag/TiO2 effectively removed 99% of 0.01 g/L paracetamol in 120 min and exhibited 60% higher photocatalytic removal than pristine TiO2. Alongside paracetamol degradation, Ag/TiO2 led to the generation of 1729 μmol H2 g-1 h-1. This proof-of-concept approach for tandem pollutant degradation and hydrogen generation was further evaluated with rare earth metal (lanthanum)- and nonmetal (nitrogen)-doped TiO2, which also showed a positive response. Using a combination of ab initio calculations and our new theory model, we revealed that the enhanced photocatalytic performance of Ag/TiO2 was due to the surface Fermi-level change of TiO2 and lowered surface reaction energy barrier for water pollutant oxidation. This work opens new opportunities for exploiting tandem photocatalytic routes beyond water splitting and understanding the simultaneous reactions in metal-doped metal oxide photocatalyst systems under natural sunlight.

Behavior of Control and Inhibitive Polyaspartic Coatings Using Alkylammonium and Zinc Phosphate Corrosion Inhibitors in Soil

This study is part of an anti-corrosion coating development project at CHEMSYSTEMS. The corrosion performance was assessed through erosion, immersion and soil corrosion experiments. The erosion results have previously been published. This article discusses the impact of soil on control polyaspartic coatings used to protect concrete and the modified polyaspartic coating intended to protect underground steel substrates. The modified polyaspartic coating was boosted with a micaceous iron oxide barrier, a liquid alkylammonium corrosion inhibitor, a powdered zinc phosphate corrosion inhibitor and a novel hardener. The surface finish of the steel samples was of a milled and blasted nature (SA 2.5). The coating was applied directly to the metal without the application of a primer or second layer of coating. The average thickness of the coating was 220±10 µm as a direct-to-metal protection system. The experiments were conducted in soil at room temperature (RT) and 35°C over 30 days. The experimental results of the control polyaspartic coating loaded on steel substrates exhibited severe blistering. The polyaspartic coating dispersed with a liquid alkylammonium inhibitor also exhibited blistering, whereas the modified polyaspartic coating with a zinc phosphate corrosion inhibitor showed an adequate degree of resistance to the impact of soil under the evaluated conditions. The results confirmed that the presence of a zinc phosphate corrosion inhibitor in combination with a micaceous iron oxide barrier improved the resistance of the coating to the evaluated soils in which it was positioned and at the investigated temperatures.

Si-SiC oxidation barrier coating on 3D printed Si-SiC strut-based architectures deposited by electrophoretic deposition

This work reports on the production and oxidation behavior at 1500 °C of SiC coated Si-SiC tetrakaidekahedron periodic structures. C-SiC lattices were first produced by 3D printing of polymers templates followed by the replica technique and pyrolysis. They were then coated by electrophoretic deposition (EPD) with submicron SiC particles. SiC particles were dispersed in water and deposited successfully on C–SiC structures by optimising voltage, frequency and duty cycle to minimize water electrolysis in the aqueous system. Different coating thicknesses were deposited on the substrates by varying the deposition time. Samples were infiltered with molten silicon, oxidized at 1500 °C and characterized.

Химический состав, структура и микротвердость многослойных высокотемпературных покрытий

Introduction. Plasma spraying is one of the modern and effective methods for coatings application for various purposes and compositions. With the help of thermal plasma flows, it is possible to spray almost any powder materials (ceramic, metal, metal-ceramic). Plasma spraying of multilayer protective coatings can be successfully used to increase the durability of pierced mandrels, which are the main tool in the production of hollow billets. The purpose of this work is to study the chemical composition, structure, and microhardness of multilayer high-temperature coatings of two different compositions deposited by plasma spraying, which are supposed to be used to increase the durability of pierced mandrels. Materials and research methods. The deposition of multilayer coatings of two compositions was carried out on a plasma-powder spraying unit with contact excitation of an arc discharge UPN-60KM TSP2017. Coatings were obtained by sequential deposition of three layers with different powder compositions. After deposition of all three coating layers, oxidative annealing was carried out at a temperature of 900°C to form a dense scale layer of FeO + Fe2O3 + Fe3O4 on the surface. The chemical composition of the coatings was studied by X-ray microanalysis using a TESCAN scanning electron microscope with an OXFORD attachment. The microstructure of the coatings was studied using a NEOPHOT metallographic microscope. Phase X-ray diffraction analysis was performed on a SHIMADZU diffractometer in Kα chromium radiation. Microhardness was measured on a LEICA hardness tester at a load of 50 g. Results and discussion. The nature of the distribution of chemical elements over the thickness of the coating, consisting of four layers, is established: an inner metal layer that provides protection against high-temperature corrosion; a transitional metal layer designed to equalize the thermal properties between the layers; α-Fe metal oxide layer and iron oxides and external thermal barrier oxide layer FeO + Fe2O3 + Fe3O4. Coatings are characterized by a non-uniform distribution of structural components and microhardness over its thickness. The microhardness of the inner layer reaches 1,400 HV0.05, the transition layer is 800 HV0.05, and the metal oxide layer is 300 HV0.05.

A comparative study on the optical and structural degradation behaviors and enhanced stability of CsPbBr3 embedded in oxide barriers

A series of experiments were conducted to investigate the optical and structural degradation behavior and enhanced stability of CsPbBr3 quantum dots (CPB QDs) embedded in oxide barrier materials such as SiOx, AlOx, and SiOx–AlOx by monitoring photoluminescence (PL) intensity, morphology, and phase under various environmental conditions such as UV exposure and ambient temperatures. Pristine CPB QDs showed a significant reduction in PL intensity under all environmental conditions even in the dark. The CPB QDs embedded in oxide materials showed relatively enhanced stabilities in general. The use of mixed-oxide SiOx–AlOx embedment for CPB QDs demonstrated better stability than the use of single-oxide embedment (SiOx and AlOx). The enhanced stability could be attributed to the reduced number of defects such as pinholes and voids by the synergistic effect of mixed oxides as barrier layers. These results offer an avenue and better understanding to improve the stability of CPB QDs for diverse applications.

C(spn)−X (n=1–3) Bond Activation by Iron

AbstractThe iron‐catalyzed oxidative addition of C(spn)−X bonds (n=1–3 and X=H, CH3, Cl) in archetypal model substrates H3C−CH2−X, H2C=CH−X and HC≡C−X to Fe(CO)4was investigated using relativistic density functional theory at ZORA‐OPBE/TZ2P. The C(spn)−X bonds become substantially stronger going from C(sp3)−X to C(sp2)−X to C(sp)−X, whereas the oxidative addition reaction barrier decreases along this series. Our activation strain and energy decomposition analyses expose that the decreased reaction barrier for the oxidative addition going fromsp3tosp2tospstems from a relief of the destabilizing (steric) Pauli repulsion between the catalyst and substrate. This originates from the decreasing coordination number of the carbon atom that goes from four in C(sp3)−X to three in C(sp2)−X to two in C(sp)−X. In analogy with our previous results on palladium‐catalyzed oxidative additions, this enhances the stabilizing catalyst–substrate interaction, which is able to overcome the more destabilizing strain associated with the stronger C(spn)−X bonds. This work again demonstrates that iron‐based catalysts can resemble the behavior of their well‐known palladium analogs in the oxidative addition step of cross‐coupling reactions.

Suppression of pyrite oxidation by co-depositing bio-inspired PropS-SH-tannic acid coatings for the source control acid mine drainage

In previous works, both tannic acid (TA) and organosilane-based passivators have been proven to possess good inhibition effects on pyrite oxidation, which could effectively prevent acid mine drainage (AMD) generation at the source. However, the hydrophilicity of TA passivation film and the complex coating process of organosilane-based passivators (high temperature conditions were required during the process carried out) may limit their further practical use. Therefore, to achieve the purpose of better coating treatment of pyrite under mild conditions, TA and γ-mercaptopropyltrimethoxysilane (PropS-SH) were introduced to synergistically passivate pyrite in this work. Electrochemistry tests and chemical leaching experiments both confirmed that PropS-SH-TA coated pyrite had better oxidation resistance than raw pyrite and single PropS-SH or TA coated pyrite. Additionally, the analyses of scanning electron microscopy (SEM) measurements and static water contact angle tests demonstrated that a scaly coating was formed on PropS-SH-TA coated pyrite surface, which may be the reason for the significant improvement of its surface hydrophobicity. Finally, the study on the film-forming mechanism of PropS-SH-TA composite passivator displayed that the benzoquinone derivatives formed by TA could copolymerize with PropS-SH through Michael addition or Schiff base reaction, which constructed a dense hydrophobic film on pyrite surface. The newly formed composite film could provide a better oxidation barrier for pyrite based on TA passivation film.

PECVD barrier coating systems on post-consumer recyclates for food contact applications

ABSTRACT As using recyclates in the food sector is currently severely restricted due to the risk of harmful contamination, the reuse of PCR (Post-Consumer Recyclates) could be greatly increased through the development of migration barriers. However, the deposition of functional barrier coatings in PECVD processes (Plasma-Enhanced Chemical Vapour Deposition) on thermoformed PCR polypropylene cups is non-trivial due to complex geometries and difficult surface properties (high roughness, non-polarity, fluctuation of recycylate properties). To develop barriers in this system, material properties of recyclate and virgin material were compared by rheometric and thermal analysis and surface properties of PCR and virgin material cups were analysed morphologically in order to define specific coating challenges. Subsequently, coatings were deposited by PECVD consisting of both, silicon organic intermediate layers (SiOCH) and silicon oxide barrier layers (SiOx). The barrier, measured by the oxygen transmission rate, could be improved by a factor of about 60 compared to uncoated cups.