石墨烯增强铝基纳米复合材料

1、石墨烯增强铝基纳米复合材料（Graphene reinforced aluminananocomposites ）Graphene nanometers are two-dimensional materials of thethicknessof a singleatomic layermadeup of sp2 hybridcarbonatoms, showing a seriesof unusual physicalproperties.In 2004,Novoselov and other 1 used tape stripping method to preparegraphene

2、nano-chip samples and characterize theirmicrostructure and physical properties. Graphene nano piecebecause of its special two-dimensional structure, caused theacademic circles study physics, chemistry and materials thegreatinterestof scholars,the basicresearch and engineeringapplication research on

3、graphene become a research hotspot in recent years 2.Graphene isthe most tenacious, conductive and heat-conductingmaterial found to date. To make graphene meet engineeringapplication state as soon as possible, the European Union in2012 tostartthe graphene flagship technology project3, theUnited Stat

4、es also vigorously inputs, and in the applicationof graphene as a super capacitor and has made breakthroughprogress 3. The wet chemical reduction method is easy torealizethebulk preparation of graphene nanoparticles,and theobtained graphene has better hydrophilic and single dispersibility, which is

5、the ideal composite material nano-filler 4.Due to the high strength of graphene, its tensile strength can reach up to 1060GPa and how to use it to improve the strengthof composite materials becomes a research hotspot. There have been reports of graphene nanoparticles enhanced with 5 andthe ceramic m

6、aterial,6.The tensilestrengthof the graphenenano-chip with 0.7 % quality fraction in polyvinyl alcoholincreasedby 76%. The bending strengthof Al2O3 ceramic matrixwith 0.78% of the volume fractionwas increasedby 30.75% whilethe fracture strength increased by 27.20% 6. But no reports of graphene-enhan

7、ced metal matrix composites have been reported.Aluminum alloy has low density, high strength and goodductility. It has been widely used in aviation, aerospace andother fields. As a structural material, how to improve thestrength of aluminum alloy has been the main direction of itsresearchers. Now, u

8、se change alloy smelting method, controlcomponents, adjustment methods such as heat treatment and thedeformation process in further improving of aluminium alloyperformance is difficult to have a breakthrough, aluminummatrix composites arises at the historic moment. In thealuminum alloy with graphite

9、, silicon carbide, boron carbideand carbon nano-controlled preparation of aluminum matrixcomposite materials to improve the strength of alloy becomesthe research direction of the scholars. However, theenhancement effectwas not satisfactory,and the plasticityofthematerialdecreased significantly7-10.G

10、raphene nano hashighstrength,largespecificsurfacearea and good elongation,add it to thealuminum alloyaluminum matrixcomposites,whichwas formed in May is a good choice for improve the strength ofaluminum alloy problems.This work adopts the ball mill mixing powder, hot isostaticpressing (HIP) and hot

11、extrusion, the method of preparation of aluminum alloy material, the microstructure of aluminummaterial alloy structure and mechanical properties were characterized and analyzed graphene nano enhanced toughening mechanism.Experiment materials and methods1.1 preparation of aluminum alloy powderAlumin

12、um alloy powders (al-mg-cu) were prepared by tightly coupled aerosol, and the content of magnesium and copper was 1.5% and 3.9% respectively. Atomization medium for nitrogen(99.99%), atomizing chamber pressure is 800 pa, the temperature is 800 .1.2 preparation of graphene nanoparticlesGraphene nanop

13、articles were prepared from natural graphite with a purity of 99.9%.With the improved Hummersmethod preparationof graphene oxidenano powder, with hydrazine hydrate reduction of 24 h under95 , get a few pieces of graphene nano atomiclayer thickness,preparation method and the literature 11.1.3 prepara

14、tion process of aluminum alloy and aluminum base alloy(1) dispersing 3g graphene nanometer fragments into 3Lanhydrous ethanol, the ultrasonic oscillation 1h was obtained with a homogeneous black graphene solution; (2) will be 1 kg Al - Mg- Cu alloy powder were added to the 3 l graphene solutionconta

15、ining 0.3% (preparation of graphene aluminium matrixcomposites) and 3 l (compared to aluminum alloy) preparationof anhydrous ethanol, encapsulated in ball mill pot ball millfor 24 h; (3) the ball mill of the pulp into a beaker, movedto 80 water bath pot, dry processing under the mechanicalagitationt

16、o paste to dry state,moved tothevacuum dryingboxthoroughly dry processing; (4) the dry the powder intocylindrical aluminum coating, vacuum pressure and vacuum to 1x 10- 2 pa, afterheating to300 400 ,theheat preservation2 h,aftercoolingto room temperature weldingsealing; (5)willsealgood aluminum coat

17、ingon 480 / 150 mpa/ 2 h hot isostaticpressingprocess;(6) afterhotisostaticpressing block in400 480 in hot extrusion, extrusion ratio of 10:1, extrusion rate of 3 mm/s, extrusion pressure is 300 kn; (7) to the barfor 30 min solid solution treatment + 495 / 96 h naturalaging.1.4 microstructure charac

18、terization and mechanical property testingThe microstructure of materials was observed by optical microscope (Leica), field emission scanning electron microscope (FESEM, JEOL jsm-7001) and transmission electron microscope (TEM, FEI Tecnai G2 F20). The crystal structure ofthe materialwas characterize

19、d byX-ray diffractometer(XRD).Test the tensile properties on the universal stretching machine, the test temperature is room temperature, the loading directionis in line with the direction of hot extrusion, and the size of the tensile sample workspace is phi 5mm x 2.5mm.2 results and discussion2.1 st

20、ructure of micronano powderThe aluminum alloy powder is a spherical or ellipsoidalparticlewitha diameter of d < 40 mu m. Graphene nanoparticlesare feathery, translucent and thin, and radial dimensions aremicrometers, with typical corrugated structurecharacteristics.The aluminum alloy powder isthe

21、 surfacecorecubic crystalstructure,and no impurities likeAl4N3 or Al2O3have been seen, indicating that the aluminum alloy has notreacted with O and N elements in the process of atomization.Graphene nano piece ofXRDspectrum has a wide of the near 26 °diffractionpeak, thatgraphene nano powder isv

22、ery small,thereports and literature 12 the high quality of graphene nanoresults are same. Ball mill, aluminum alloy by sphericalparticles into flake structure, chip is not more than 100microns in diameter, the thickness of a few microns, graphenesheet attached to the aluminum alloy nanoparticles sur

23、face,make thealuminum alloyparticles with graphene nano piecehasgreat interface, and fold structure of graphene nano piece be well preserved.2.2 microstructure of alkylene alloyAfterthe heat treatmentof aluminum alloy,the microstructureof the microstructure was uniform and fine, the metallurgicalqua

24、litywas good, and the defectsof metallurgywere not obvious.The aluminum alloyhas a lamellarstructure,and the thicknessof the laminar is about 3 8 micrometers. The diameter of the laminar is about 20 40 microns.HIP + hot extrusion process does not destroythe flaky structureof aluminum alloypowder. Th

25、e axial microstructureretainsthecharacteristics of extrusion deformation. The tissue iselongated toover100 mu m in thedirectionof deformation,andthe thicknessisa few microns.The authorsfirstobservedthemorphology of graphene nanoparticles in graphene reinforcedmetalnanocomposites inTEM. Graphene nano

26、 malleablealuminumalloysubstrate withthegood, thetwo had a greatcombinationof interface,clearlysee the graphene nano 2 d thinfilm shapeand fold structure characteristics,observed areaofgraphenenano size than 2 microns, that graphene nano piece withoutrupture in the aluminum alloy material alloy subs

27、trate. Theball mill, hot isostatic pressing, hot extrusion and aftersolution heattreatmentand so on a series of crafts,graphenenano retains the original organizational structure characteristics, presumably it still maintained the original high tensile strength.The mechanical propertiesof aluminum al

28、loyand aluminum alloyAdd graphene nano piece can improve the aluminum materialyieldstrength and tensile strength of alloy, and the elongation isimproved, the increasein the second phase in the study of metalmatrix composites is found for the first time. The tensilestrength of graphene nanoparticles

29、increased from 364MPa to455MPa and increased by 25%. At the same time, the yieldstrengthof the alloyis increasedsharply,from 204 mpato 322mpa, increase up to 58%, the increase of the amplitude is superior to other materials reinforced aluminum matrix composites enhanced effect 13. At the same time,

30、it can be seen in graphene nano film, not like SiC 7, 8 or 10 carbonnanotubes reinforced aluminum matrix composites plasticity declined significantly, aluminum alloy elongation did not decline, also slightly increases, increased to 11.80% from11.03% alloy. Add graphene nano piece of little effects o

31、n the elastic modulus of the aluminum alloy, compared with the experimental data for particles or carbon fiber reinforced,graphene nano piece of the action mechanism of the metal substrate are different from ordinary carbon fiber or particles.2.4 analysis of toughening mechanism of graphene nano-chi

32、pThe microstructureof the tensilefracture ofthealuminum basealloyrod istypicalofthe ductilefracture,thetoughnessandtearing edges are even and small,thesurfaceofthe ridgescanbe clearlyobservedwith graphene nanoparticles.Comparedwithother reinforcing materials, graphene nanoparticles havedifferent tou

33、ghening mechanisms for aluminum alloy matrix.Firstofall,by TEMobservationshows graphene nano pieceandthe combination of the aluminum alloy matrix formed a goodinterface, and graphene nano has * * specific surface area,which effectively prevents the heat treatment process ofaluminum alloy grain grew

34、up, at the same time the graphenenano/aluminum alloycombined interfacecan effectivelypreventthe dislocation movement in the process of deformation andcrack propagation. Second, the thickness of the graphene areonlya few nanometers,the spacing between aluminum alloy grainsize is very small, it is mor

35、e advantageous to the externalforce from the aluminum substrate is transferred to thegraphene nano film,so the ultra-highstrengthofgraphene nanopiececouldbe directlyused, so as to realizethehighstrengthof materials. Finally, because the graphene nano large specific surface area, easy to form a great

36、 combination of excellent performance of aluminum alloy matrix interface, and graphene nano piece of fold structure, make the aluminum alloy in the process of stress,Graphene nanoparticles have a process of flattening andrefracture, and the graphene nanometer itself has goodplasticity,so the plastic

37、ityof the materialis very good. Thisgives a wide application prospect for the alkylene alloymaterial. However,the structureof graphenefoldsdeterminesthe good plasticity of alkylene alloy. Although graphene nano reinforced aluminum alloy, the mechanical properties of nanocomposite increase significantly, but there are manyunknown need further explorati