Surface graphitization analysis of cerium-polished HFCVD diamond films with micro-raman spectra

The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crystallinity and phase composition of diamond films was thoroughly investigated via the analysis of Raman spectra such as FWHM and ID/IG. Moreover, the issue on the graphitization of diamond after polishing with Ce was further researched through the detailed study of the depth distribution of Raman data including FWHM and ID/IG, and a result completely different from the hot-iron metal polished ones was obtained. The results showed that polished diamond films had considerably higher diamond content than those before polishing, and not a bit of graphitization was found in the polished ones, owing to a higher solubility of carbon in rare earth metal Ce than that in transition metals, and the original crystallinity of the films polished with Ce did not deteriorate.

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Surface Graphite Degeneration in Ductile Iron Castings for Resin Molds

The objective of this paper is to review the factors influencing the formation of degenerated graphite layers on the surfaces of ductile iron castings for chemical resins-acid molding and core-making systems and how to reduce this defect. In the resin mold technique the sulphur in the P-toluol sulphonic acid （PTSA）, usually used as the hardener, has been identified as one factor causing graphite degeneration at the metalmold interface. Less than 0.15% S in the mold （or even less than 0.07% S） can reduce the surface layer depth. Oxygen may also have an effect, especially for sulphur containing systems with turbulent flows in the mold, water-bearing no-bake binder systems, Mg-Silica reactions, or dross formation conditions. Despite the lower level of nitrogen in the iron melt after magnesium treatment （less than 90 ppm）, nitrogen bearing resins have a profound effect on the frequency and severity of surface pinholes, but a limited influence on surface graphite degeneration.

Molecular Dynamics Study of Ionic Liquid Film Based on [emim][Tf2N] and [emiml[TfO] Adsorbed on Highly Oriented Pyrolytic Graphite

Molecular dynamics simulation was used to study the ionic liquid（IL） crystalline film based on 1-ethyl-3-methylimidazolium bis[trifluoromethylsulfonyl]imide（[emim][Tf2N]） and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate（[emim][TfO]） on the graphite surface. Our results show that the cations are parallelly dis- tributed to the surface in the 1/2 monolayer（ML） crystalline film. The [Tf2N] anions are parallel to the surface with the oxygen atoms at the bottom, whereas the [TfO]- anions are perpendicularly distributed to the surface also with the oxygen atoms at the bottom in the 1/2 ML crystalline film. It has been found that the IL-vapor interface strongly in- fluences the arrangement of ions at the interface. The anions in the top layer with the oxygen atoms outmost turn over to make themselves with the F atoms outmost so as to form C--H...O hydrogen bonds with the cations. The calcu- lated orientational ordering shows that in the outmost layer at the IL-vapor interface, the cation rings present either oarallel or oernendicular to the surface at 350 K.

Effect of surface oxidation on the interfacial and mechanical properties in graphite/epoxy composites composite bipolar plates

Epoxy resin-reinforced graphite composites have found extensive application as bipolar plates in fuel cells for stationary power supplies,valued for their lightweight nature and exceptional durability.To enhance the interfacial properties between graphite and epoxy resin(EP),surface oxidation of graphite was carried out using diverse functional groups.Experimental assessments illustrated that the composites with graphite oxide resulted in heightened mechanical strength and toughness compared to pristine graphite,which could be attributed to the excellent interface connection.Moreover,these composites displayed remarkable conductivity while simultaneously retaining their mechanical attributes.Furthermore,molecular dynamics simulations outcomes unveiled that the inclusion of oxygen-containing functional groups on the graphite surface augmented the interfacial energy with EP,and the interface morphology between graphite and resin exhibited heightened stability throughout the stretching process.This simple and effective technique presents opportunities for improving composites interfaces,enabling high load transfer efficiency,and opens up a potential path for developing strong and tough composite bipolar plates for fuel cells.

Self-templated covalent functionalization of graphitic surfaces with a quasi-periodic pattern

Patterned covalent functionalization of graphitic surfaces(GSs)is of interest in the development of devices and nanocomposite materials.In contrast to the strategies using external templates or control for realizing patterned covalent functionalization of GSs,here,we present a self-templated strategy by exploiting the synergistic effects of chemical and physical functionalization of GSs.Therefore,a diazonium salt is reduced by potassium iodide(KI)in dimethyl sulfoxide while the solution is in contact with a GS,resulting in its spatially heterogeneous,that is,chemical and physical,functionalization.This heterogeneous functionalization leads to a quasiperiodic pattern of striped corrals with three equivalent orientations in the covalent layer.The formation of the striped corrals is ascribed to physisorbed domains formed by self-assembled N_(2),which is produced in situ during the reduction of the diazonium salt,preventing the covalent functionalization.