Impact pressure induces synthesis of nanocrystalline olivine Co2SiO4.
Understanding changes in material properties through external stimuli is critical to validating the expected performance of materials as well as engineering material properties in a controlled manner. Here, we investigate a change in the c-axis electrical properties of graphite nanoflakes (GnFs) induced by gamma-ray irradiation, using conductive probe atomic force microscopy (CP-AFM). The fundamentals behind the change in their electrical properties are elucidated by analyzing the interlayer spacing, graphitization, and morphology. An increase in gamma-ray irradiation dose for GnFs leads to an exponential increase in the electrical conductance and a gradual decrease in the interlayer spacing, while accompanying indistinguishable changes in their morphology. Our experimental results suggest that the c-axis electrical conductance enhancement of GnFs with gamma-ray irradiation might be attributed to a reduction in interlayer spacing, though the created defects may also play a role. This study demonstrates that gamma-ray irradiation can be a promising route to tailor the electrical properties of GnFs.
Nanocrystalline olivine-structured Mg2SiO4 and MgCoSiO4, with an average particle size of 27 nm and 31 nm, respectively, were successfully synthesized from oxide precursors via mechanochemical methods. The two nanocrystalline products were obtained after milling for 360 min and displayed high concentrations of Mg2SiO4 (>94%) and MgCoSiO4 (>95%), together with minor amounts of WC (~3%) contaminant originating as debris abraded off milling balls and chambers. The macroscopic temperature monitoring of the grinding jars during milling trials recorded a peak temperature of 75 °C. A combination of analytical techniques that included XRD, TEM, SAED, and EDS were employed for the characterization of the synthesized products.
The past few decades have witnessed mechanochemistry emerging at the forefront of solid-state chemical synthesis, driven by the search of new and cleaner synthetic methodologies. Mechanochemical synthesis utilizes high energy impact phenomenon to initiate chemical reactions. The peak impact pressures, which the individual sample particles experience, vary depending on the type of mill, milling speed, as well as size, shape, and density of the milling components, but can often exceed 10 GPa, while the temperature remains below 100 o C. Evolving beyond simply a solvent-free alternative, mechanochemistry offers significant sample quantities (grams) processed over a short period of time (minutes to hours). The design of the mill (e.g. tumbler, oscillatory, planetary) can also control the relative contributions of friction and impact during the milling process. In an effort to introduce mechanochemistry further into geoscience, the current presentation wishes to showcase the successful mechanochemical synthesis of compounds in the Mg-Co olivine solid solution series (e.g. Mg2SiO4, MgCoSiO4, Co2SiO4) starting from simple oxide precursors such as MgO, CoO, and SiO2 utilizing oscillating mill equipped with tungsten carbide (WC) jars/ balls as reaction vessels [1,2]. We further address on the contamination issue of the final synthesized product with debris shaved off from milling media (e.g. stainless steel, WC) and report on a successful development of method for converting WC to a water-soluble form [3]. Lastly, we report our investigations into pressureinduced phase transformation of anatase TiO2 to rutile TiO2, quartz-type α-GeO2 to rutile GeO2, and cubic Dy2O3 to monoclinic Dy2O3, processes that require pressure up to 7.7 GPa in a typical diamond anvil cell experiment [4]. Powder X-Ray Diffraction was employed as the main process characterization, with complete Rietveld refinements of the powder patterns of end products, where applicable.
We synthesized and characterized a novel iron(II) aceto EMIM coordination compound, which has a simplified empirical formula Fe 4 (OAc) 10 [EMIM] 2 , in two different hydration forms: as anhydrous monoclinic compound and triclinic dihydrate Fe 4 (OAc) 10 [EMIM] 2 •2H 2 O. The dihydrate compound is isostructural with recently reported Mn 4 (OAc) 10 [EMIM] 2 • 2H 2 O, while the anhydrate is a superstructure of the Mn counterpart, suggesting the existence of solid solutions. Both new Fe compounds contain chains of Fe 2+ octahedrally coordinated exclusively by acetate groups. The EMIM moieties do not interact directly with the Fe 2+ and contribute to the structural framework of the compound through van der Waals forces and C−H•••O hydrogen bonds with the acetate anions. The compounds have a melting temperature of ∼94 °C; therefore, they can be considered metal-containing ionic liquids. Differential thermal analysis indicates three endothermic transitions associated with melting, structural rearrangement in the molten state at about 157 °C, and finally, thermal decomposition of the Fe 4 (OAc) 10 [EMIM] 2 . Thermogravimetric analyses indicate an ∼72 wt % mass loss during the decomposition at 280−325 °C. The Fe 4 (OAc) 10 [EMIM] 2 compounds have higher thermal stability than their Mn counterparts and [EMIM][OAc] but lower compared to iron(II) acetate. Temperature-programmed desorption coupled with mass spectrometry shows that the decomposition pathway of the Fe 4 (OAc) 10 [EMIM] 2 involves four distinct regimes with peak temperatures at 88, 200, 267, and 345 °C. The main species observed in the decomposition of the compound are CH 3 , H 2 O, N 2 , CO, OC−CH 3 , OH−CO, H 3 C−CO−CH 3 , and H 3 C−O− CO−CH 3 . Variable-temperature infrared vibrational spectroscopy indicates that the phase transition at 160−180 °C is associated with a reorientation of the acetate ions, which may lead to a lower interaction with the [EMIM] + before the decomposition of the Fe 4 (OAc) 10 [EMIM] 2 upon further heating. The Fe 4 (OAc) 10 [EMIM] 2 compounds are porous, plausibly capable of accommodating other types of molecules.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.