Controlling the formation of sodium/black phosphorus intercalated compounds towards high sodium content

The solid-state synthesis of pure sodium-black phosphorus intercalation compounds (Na-BPICs) has been optimized in bulk for two stoichiometric ratios. Specifically, in-situ X-Ray diffraction (XRD) allowed the precise identification of the optimal temperature range for the formation of Na-BPICs: 94 °C–96 °C. Moreover, as the undesired formation of Na3P takes place at this very same range, we succeeded in introducing a new synthetic route based on a fast-thermal ball milling implementation that results in the bulk production of BPIC without Na3P in 9 out of 10 cases. Finally, by combining XRD, Raman spectroscopy, and DFT calculations we developed a new structural model for Na-based BPICs showing an increase of BP's unit cell with Na atoms incorporated in every second layer. These results will pave the way for the large-scale synthesis and application of pure BPICs, which are of great interest in fields such as optoelectronics or energy storage.PNICTOCHEM 804110 (G.A.)PID2019-111742-GA-I00CIDEGENT/2018/00

Effect of Tantalum Solid Solution Additions on the Mechanical Behavior of ZrB₂

Mechanical properties and microstructure were compared for zirconium diboride and two zirconium diboride solid solutions containing 3 and 6 at% tantalum diboride. X-ray diffraction indicated that the ceramics were nearly phase-pure and that tantalum dissolved into the ZrB2 lattice to form (Zr,Ta)B2 solid solutions. Microstructural analysis indicated that samples achieved nearly full relative density with average grain sizes that ranged from 3-5 μm. The three compositions had similar values of Young\u27s modulus (510-531 GPa), shear modulus (225-228 GPa), Vickers hardness (15.2-16.4 GPa), and flexural strength (391-452 MPa). Fracture toughness ranged from 2.6 to 3.7 MPa m1/2 and with increasing tantalum content, the fracture mode changed from predominantly intergranular to predominantly transgranular. Diboride solid solution materials had comparable properties to the single metal diboride, but differences in microstructure, secondary phases, and strain state among the three ceramics partially obscured the actual effects of the solid solution on fracture behavior

A Revised Relationship Between Fracture Toughness and Y2O3 Content in Modern Dental Zirconias

The relationship between fracture toughness and Yttria content in modern zirconia ceramics was revised. For that purpose, we evaluated here 10 modern Y2O3-stabilized zirconia (YSZ) materials currently used in biomedical applications, namely prosthetic and implant dentistry. The most relevant range between 2-5 mol% Y2O3 was addressed by selecting from conventional opaque 3 mol% YSZ up to more translucent compositions (4-5 mol% YSZs). A technical 2YSZ was used to extend the range of our evaluation. The bulk mol% Y2O3 concentration was measured by X-Ray Fluorescence Spectroscopy. Phase quantification by Rietveld refinement are supplied by considering only two tetragonal phases or an additional improbable cubic phase. A first-account of the fracture toughness (KIc) of the partly-sintered materials is given, which amounted to 0.4 – 0.7 MPaÖm. In the fully-densified state, an inverse power-law behavior was obtained between KIc and bulk mol% Y2O3 content, whether using only our measurements or including literature data, challenging some established relationships.</p

Cover. Carbon Nano-onions: Potassium Intercalation and Reductive Covalent Functionalization

This cover illustrates how carbon nano-onions can be intercalated with potassium atoms through surface defects by means of thermal heating. This reductive route allows the efficient covalent functionalization with electrophiles such as alkyl iodides.PNICTOCHEM 804110 (G.A.)CIDEGENT/2018/001PID2019-111742-GA-I0