Microstructure and Wear Behavior of Plasma‐Sprayed Nanostructured WC–Co Coatings

Atmospheric plasma spraying of WC–Co particles with standard gas mixtures (Ar–H₂) typically results in largely decarburized coatings with relatively low wear resistance. To fabricate cermet coatings with enhanced tribological properties, nanostructured WC–Co coatings were plasma sprayed using two different process gas mixtures. Phase composition and microstructure were investigated by X‐ray diffraction and scanning electron microscopy, respectively. Microhardness increased by increasing the amount of retained WC grains in coating microstructure. Friction and wear properties, measured under dry sliding conditions, strongly depended on the degree of decarburization. They were comparable to those of conventional coatings produced using identical conditions.     

Effects of Two Sublethal Concentrations of Mercury Chloride on the Morphology and Metallothionein Activity in the Liver of Zebrafish (Danio rerio)

Mercury (Hg) is a highly hazardous pollutant widely used in industrial, pharmaceutical and agricultural fields. Mercury is found in the environment in several forms, elemental, inorganic (iHg) and organic, all of which are toxic. Considering that the liver is the organ primarily involved in the regulation of metabolic pathways, homeostasis and detoxification we investigated the morphological and ultrastructural effects in Danio rerio liver after 96 h exposure to two low HgCl₂ concentrations (7.7 and 38.5 μg/L). We showed that a short-term exposure to very low concentrations of iHg severely affects liver morphology and ultrastructure. The main effects recorded in this work were: cytoplasm vacuolization, decrease in both lipid droplets and glycogen granules, increase in number of mitochondria, increase of rough endoplasmic reticulum and pyknotic nuclei. Pathological alterations observed were dose dependent. Trough immunohistochemistry, in situ hybridization and real-time PCR analysis, the induction of metallothionein (MT) under stressor conditions was also evaluated. Some of observed alterations could be considered as a general response of tissue to heavy metals, whereas others (such as increased number of mitochondria and increase of RER) may be considered as an adaptive response to mercury.     

Comparison of the electrochemical properties of intermediate temperature solid oxide fuel cells based on protonic and anionic electrolytes

The physico-chemical properties of two protonic electrolytes BaCe_0.8Y_0.2O_3-δ and BaCe_0.9Y_0.1O_3-δ were investigated. The BaCe_0.8Y_0.2O_3-δ electrolyte showed better crystallographic purity and lower amount of carbonate phase on the surface. A comparison between the BaCe_0.8Y_0.2O_3-δ protonic electrolyte supported cell and an anionic (Ce_0.8Gd_0.2O_1.95) one was made. The maximum power densities (IR-free) of 183 mW cm⁻² and 400 mW cm⁻² were obtained in H₂ (R.H. 3%) at 700 °C, for the protonic and anionic electrolyte based cells, respectively.     

Conductivity studies of sol-gel prepared BaCe0.85−xZrxY0.15O3−δ solid electrolytes using impedance spectroscopy

A systematic investigation on doped barium cerate perovskites on conductivity was performed by means of ac electrochemical impedance spectroscopy technique. BaCe_0.85?xZr_xY_0.15O_3?δ powders (x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by a modified sol-gel Pechini method and sintered at 1,250 °C–1,450 °C, depending on Zr content, to obtain good densities (93–97% of the theoretical ones). The measured total conductivities for these solid solutions in three different atmospheres were reported: in dry oxygen, in dry nitrogen and wet (0.5 bar H₂O) hydrogen (5%H₂/Ar) atmospheres. Arrhenius plots recorded in dry oxygen as well as in dry nitrogen showed some residual hydration which remained in the specimens upon initial heating. The compositions with x = 0.3 and 0.4 gave conductivities close to 10^?2 S/cm in 5%H₂/Ar/H₂O atmosphere at 600 °C. The isothermal conductivities values showed a little variation for x from 0.2 to 0.4 between 500 and 800 °C.