Microstructural Stability of the CoCrFe2Ni2 High Entropy Alloys with Additions of Cu and Mo

New High Entropy Alloys based on the CoCrFe2Ni2 system have been developed by adding up to 10 at. % of Cu, Mo, and Cu + Mo in different amounts. These alloys showed a single face-centred cubic (FCC) structure after homogenization at 1200 °C. In order to evaluate their thermal stability, aging heat treatments at 500, 700, and 900 °C for 8 h were applied to study the possible precipitation phenomena. In the alloys where only Cu or Mo was added, we found the precipitation of an FCC Cu-rich phase or the µ phase rich in Mo, respectively, in agreement with some of the results previously shown in the literature. Nevertheless, we have observed that when both elements are present, Cu precipitation does not occur, and the formation of the Mo-rich phase is inhibited (or delayed). This is a surprising result as Cu and Mo have a positive enthalpy of mixing, being immiscible in a binary system, while added together they improve the stability of this system and maintain a single FCC crystal structure from medium to high temperatures

Modified Red Muds and Slag Based Hydraulic Binders for Zn Removal: A Matrix-Spiking Approach Applied on Clayey Sediments

Dredging sediments can be implemented as primary resources in several civil engineering applications, on the condition that the release of anthropogenic compounds meets environmental requirements. The remediation of sedimentary wastes constitutes therefore, a key step before valorization consideration in circular economy schemes. This study focused on Zn removal from clayey river sediments dredged in northern France (Lille, Saint-Omer and Aire-Sur-La Lys) using a Thermo-Evolved Red Mud (TERM) and a Slag Based Hydraulic Binder (SBHB). The first step consisted in investigating Zn-trapping mechanisms prior to TERM and SBHB application as Zn-stabilizers. Results underlined poorer metal retention within the most organic sediment (high fatty acids and polycyclic aromatic molecules concentrations), emphasizing the minor role of the organic fraction typology during Zn-trapping. The pollutant displayed its best binding yields within the sediment with the highest interstitial pH and specific areas, which stressed out the preponderant influence of alkalinization ability and particles size distribution. In a second step, the spiked sediments were treated with TERM and SBHB, which resulted in a substantial lowering of Zn release at 12% of stabilizer/sediment ratio. Even though the organic content role was not preeminent during the pollutant trapping, it appeared here influential as delays in removal efficiencies were observed for the most endowed sediment. Two preferential geochemical pathways were adopted during the remediation operations with significant promotive roles of basic background pH. Indeed, Zn removal with TERM consisted mainly in sorptive mechanisms involving exchanges with Ca and Mg ions, whereas binding onto SBHB was principally achieved through precipitation phenomena.

Cyclodextrins Allow the Combination of Incompatible Vancomycin and Ceftazidime into an Ophthalmic Formulation for the Treatment of Bacterial Keratitis

Ceftazidime (CZ) and vancomycin (VA) are two antibiotics used to treat bacterial keratitis. Due to their physical incompatibility (formation of a precipitate), it is not currently possible to associate both molecules in a single container for ophthalmic administration. We firstly characterized the incompatibility then investigated if 2-hydroxypropyl-beta (HPβCD) and 2-hydroxypropyl-gamma cyclodextrins (HPγCD) could prevent this incompatibility. The impact of pH on the precipitation phenomena was investigated by analysing the supernatant solution of the mixture using high performance liquid chromatography. A characterization of the inclusion of CZ with HPγCD using 1H nuclear magnetic resonance (NMR), and VA with HPβCD using 1H-NMR and a solubility diagram was performed. A design of experiment was built to determine the optimal conditions to obtain a formulation that had the lowest turbidity and particle count. Our results showed that VA and CZ form an equimolar precipitate below pH 7.3. The best formulation obtained underwent an in-vitro evaluation of its antibacterial activity. The impact of HPCDs on incompatibility has been demonstrated through the inclusion of antibiotics and especially VA. The formulation has been shown to be able to inhibit the incompatibility for pH higher than 7.3 and to possess unaltered antibacterial activity.

THE EFFICIENCY OF USING CAM MECHANISMS TO OPERATE THE EQUIPMENT FOR OPENING AND INTERRUPTING WATERING FURROWS

Due to climate change, there have been changes in temperature, distribution and precipitation, phenomena that have led to the development of technologies that increase the efficiency of precipitation water use and support the preservation of soil quality. The paper presents some theoretical considerations on the cam mechanisms for actuating the working parts the equipment for opening and interrupting watering furrows are provided with; setting the optimal dimensions of the blades of the equipment for furrow opening through the experiments performed is also made. By using the cam mechanisms in the equipment for opening and interrupting watering furrows both superior quality indices in the execution of the work but also a quiet operation of the equipment are obtained and by optimizing the size of the working part, the volume of water accumulated between furrows increases significantly.

Operando laser scattering: probing the evolution of local pH gradients on complex electrode architectures

Self-assembly, complexation, agglomeration and precipitation phenomena relevant to biological, electrocatalytic and technological processes are strongly influenced by changes of the local pH at the solid-liquid interfaces where they occur. Understanding proton dynamics in the diffusion layers generated by these processes is of prime importance to improve their diagnosis and enable modelling and better control over them. Here we introduce a non-invasive pH-sensing approach that is based on the Tyndall effect enhancement modulated by pH-controlled agglomeration events. Using metal electrodeposition for advanced semiconductor wiring technology as a test vehicle, we demonstrate that our proposed strategy simultaneously provides real-time visualization of the pH dynamics and pH-guided reactivity with high spatial resolution without physically or chemically influencing the investigated surfaces. We suggest that its applicability can be universally extended to other relevant nanoaggregation/decomplexation processes occurring at light-addressable interfaces provided the probed colloids are smaller than the wavelength of visible light.

Role of Small Addition of Sc and Zr in Clustering and Precipitation Phenomena Induced in AA7075

A detailed characterization of phase transformations in the heat-treated commercial 7075 aluminum alloys without/with low Sc–Zr addition was carried out. Mechanical and electrical properties, thermal and corrosion behavior were compared to the microstructure development. The eutectic phase consists of four parts: MgZn2 phase, Al2CuMg phase (S-phase), Al2Zn3Mg3 phase (T-phase), and primary λ-Al(Mn,Fe,Si) phase. Strengthening during non-isothermal (isochronal) annealing is caused by a combination of formation of the GP zones, η’-phase, T-phase and co-presence of the primary and secondary Al3(Sc,Zr)-phase particles. Positive influence on corrosion properties is owing to the addition of Sc–Zr. Positron annihilation showed an evolution of solute Zn,Mg-(co-)clusters into (precursors of) the GP zones in the course of natural ageing. The concentration of the (co-)clusters is slightly negatively affected by the low Sc–Zr addition. A combination of both precipitation sequences of the Al–Zn–Mg–Cu-based system was observed. The apparent activation energy values for dissolution/formation of the clusters/GP zones and for formation of the metastable η’-phase, stable T-phase and stable η-phase were calculated.