Механические свойства композитного покрытия SiC на графите, полученного методом замещения атомов

The mechanical properties of composite coatings made of silicon carbide on graphite are studied for the first time. For the deposition of coatings, a new method of annealing the initial graphite was used, which was in contact with a silicon melt in an atmosphere of carbon monoxide.The samples were studied by nanoindentation and scanning electron microscopy. It is shown that the formed coating consists of a continuous film of monocrystalline silicon carbide lying on the surface, dendrites and crystalline druses, with roots going deep into the sample through a system of pores. It is shown that the coating significantly increases the mechanical characteristics of the graphite surface, including the microhardness.

Intercalation of lithium into disordered graphite in a working battery

The structural transformations occurring during the intercalation of lithium into disordered graphite in a working battery were studied in detail by operando X-ray powder diffraction (XRPD). By using a capillary-based micro-battery cell, it was possible to study the stacking disorder in the initial graphite as well as in lithiated graphites. The micro-battery cell was assembled in its charged state with graphite as positive electrode and metallic lithium as counter electrode. The battery was discharged until a stage II compound (LiC12) was formed. The operando XRPD data reveal that the graphitic electrode material retains a disordered nature during the intercalation process. A DIFFaX+ refinement based on the initial operando XRPD pattern shows that the initial graphite generally has an intergrown structure with domains of graphite 2H and graphite 3R. However, the average stacking sequence of the initial graphite also contains a significant concentration of AA-type stacking of the graphene sheets. DIFFaX+ was further used to refine structure models of a stage III type compound and the final stage II compound. The refinement of the stage II compound showed that it is dominated by AαAAαA-type stacking, but that it also contains a significant concentration of AαABβB-type slabs in the average stacking sequence.

Fe3O4/Reduced Graphene Oxide Nanocomposite: Synthesis and Its Application for Toxic Metal Ion Removal

The synthesis of reduced graphene oxide modified by magnetic iron oxide (Fe3O4/rGO) and its application for heavy metals removal were demonstrated. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and magnetic measurement. The results showed that the obtained graphene oxide (GO) contains a small part of initial graphite as well as reduced oxide graphene. GO exhibits very high surface area in comparison with initial graphite. The morphology of Fe3O4/rGO consists of very fine spherical iron nanooxide particles in nanoscale. The formal kinetics and adsorption isotherms of As(V), Ni(II), and Pb(II) over obtained Fe3O4/rGO have been investigated. Fe3O4/rGO exhibits excellent heavy metal ions adsorption indicating that it is a potential adsorbent for water sources contaminated by heavy metals.

Thermal Analysis of Solidification Process and Mechanical Properties in Heavy Section Ductile Iron Casting

A heavy section ductile casting (HSDIC) with dimensions of Φ590 mm×800 mm was prepared. Cooling curves at the center, at 85 mm from the center, at 170 mm from the center and at 255 mm from the center of the casting were recorded and analyzed. The results show that the precipitation of initial graphite, nucleation of eutectic cell and mass eutectic reaction at 255 mm from the center were all earlier than the other three locations. Moreover, it takes the longest time of 53 minutes of recalescence at 170 mm from the center with the highest temperature rise of 7 °C, though the cooling rate at this location is not the lowest in the casting, the mechanical properties are the worst. In addition, the largest amount of chunky graphite appears at 170 mm from the center.

Synthesis of cubic diamond in the graphite-magnesium carbonate and graphite-K2Mg(CO3)2 systems at high pressure of 9–10 GPa region

Cubic diamond was synthesized with two systems, (1) graphite with pure magnesium carbonate (magnesite) and (2) graphite with mixed potassium and magnesium carbonate at pressures and temperatures above 9.5 GPa, 1600 °C and 9 GPa, 1650 °C, respectively. At these conditions (1) the pure magnesite is solid, whereas (2) the mixed carbonate exists as a melt. In this pressure range, graphite seems to be partially transformed into hexagonal diamond. Measured carbon isotope δ13C values for all the materials suggest that the origin of the carbon source to form cubic diamond was the initial graphite powder, and not the carbonates.