Preparation And Ferromagnetism Of Few-layer Graphene,Phosphorene And Graphene-phosphorene Hybrid Materials

In 2004,the discovery of graphene sparked an upsurge of research on two-dimensional(2D)materials in the scientific community.Nevertheless,there are few reports on the study of 2D materials synthesis through sealed high-pressure technology.In 2010,Zhao et al.used the ball-milling method,through dynamic high-pressure technology,and prepared mono-layer and few-layer graphene.This is the first time that high-pressure technology combined with two-dimensional carbon materials synthesis.In 2014,phosphorene was founded and was widely studied by the scientific community,due to its unique layer-dependent band gap.Black phosphorus,as a raw material of phosphorene,is a high-pressure phase of phosphorus.Therefore,the synthesized method of phosphorene appeared using high-pressure technique.In2015,Du et al.used the RP thin film was converted to BP thin films at 10 GPa and room temperature in a multi-anvil high-pressure cell.This is the first time that directly synthesis of phosphorene by high-pressure route.The two-dimensional material like graphene and phosphorene has many fascinating properties in many fields.However,compared to the researches in the field of electrical and optical,the studies on magnetism are very few.Graphene and phosphene as d~0 element,the study of its magnetic properties will become an important subject in the scientific research.Furthermore,due to the excellent flexibility,graphene and phosphorene will be expected widely using as magnetic coatings and magnetic devices.Two theoretical models have been proposed to explain the source of ferromagnetism in graphene and phosphorene.One is the localized electron model and the other is the band model.Base on the two theoretical models,in this paper,we have prepared few-layer graphene,hydrogenated graphene,mono-layer and few-layer phosphorene and graphene-phosphorene hybrid materials by planetary ball mill,Quickpress 3.0 pistons-cylinder high pressure devices and HR-1B-2 type LECO high-temperature and high-pressure hydrothermal reaction devices,and investigated their ferromagnetism.(1)We have prepared few-layer graphene and hydrogenated graphene with high-pressure method by planetary ball mill and Quickpress 3.0 piston-cylinder high-pressure device,and the best synthesis conditions was gained through a lot of experiment.Moreover,the samples’structure,morphology and ferromagnetic were carefully investigated.Both gas-phase hydrogenation and liquid-phase hydrogenation method were employed in hydrogenation experiments,and the magnetic moment was measured by superconducting quantum interference device(SQUID).The mechanism of ferromagnetism was discussed and the band model seems contributed more than localized electron model.(2)We proposed and applied a new method called“pressure quenching”to investigate and explain the mechanism of phase transition between red phosphorus and black phosphorous by the HR-1B-2 type LECO high-temperature and high-pressure hydrothermal reaction device.As a comparative experiment,Quickpress 3.0piston-cylinder high pressure device was used to synthesize black phosphorus through traditional high temperature and high pressure method.The two samples were characterized by XRD,Raman spectroscopy,TEM and AFM,the result confirmed that the phase transition between red phosphorous and black phosphorus was occurred below 0.5 GPa.And the pressure quenching phase diagram was drawn.Meanwhile,the thickness of the sample which synthesized by pressure quenching was characterized by AFM.Through the analysis,the few-layer phosphorene could be synthesized in one step by quenching method.(3)We have prepared mono-layer and few-layer phosphorene with ball milling method though a planetary ball mill.The morphology and structure were determined by Raman spectroscopy,SEM,TEM and AFM.The degree of oxidation dependent on the number of layers was explained preliminarily by XPS analysis.Meanwhile,red phosphrous might recrystallization during the process of overmilling in our experiment.(4)The HR-1B-2 type LECO high-temperature and high-pressure hydrothermal reaction device was used to synthesize graphene-phosphorene composite material by quenching pressure.XRD,Raman spectrum,FI-IR and XPS were used to characterize the structure,morphology and bond information.The magnetic moment of mono-layer phosphorene,few-layer phosphorene and graphene-phosphorene hybrid material was measured by SQUID.The ferromagnetism of the black phosphonene caused by P-O bond,P-C bond and P-O-C bond is analyzed,and the results showed that the ferromagnetism of the phosphorene is mainly caused by the strong polarization of spin electron caused by P-O bond.