简介:ZrO2-SnO2compositenanoparticleswerepreparedbyheatingthehydrateprecursorssynthesizedbythechemicalco-precipitationreactionofZrOCl2andSnCl4.Theprecursorswereexaminedbydifferentialthermalanalysis(DTA)andthermogravimetricanalysis(TGA).ThecompositepowderwascharacterizedusingX-raydiffraction(XRD),transmissionelectronmicroscopy(TEM)anddesorptionisotherm(Barrett-Joyner-Halendamethod).Theaveragecrystalsizeofthenanoparticlerangesfrom15to30nmforthesamplecontaining5%-25%ZrO2(massfraction).MostoftheporesintheZrO2-SnO2nanoparficlesareabout10-20nmindiameter.Thecompositepowderispromisingforchemicalsensors.
简介:ProblemsaboutsurfacemountingprocessforfinepitchdevicesandreasonsonsolderbridgingofLtypeleaddevicesweldedaredepicted.Bridgingmechanismandinfluencefactorsareanalyzedwithtwo-dimensionalgeometricmodel.Basedonthis,high-densitysurfacemounttechnology(SMT)forfinepitchLtypeleaddevicesheatedbyscan-ninglaserisraised.SurfacemountprocessforQFP208onprintedcircuitboard(PCB)isstudied.Theresultsoftestsarethatitisquitepossibletosolvethesolderbridgingofsurfacemountingforpitchdeviceswithscanninglaser-heat-ingmethod.
简介:Intheacceleratordrivensub-criticalsystem(ADS)cooledbyliquidPbBialloy,theausteniticstainlesssteel316Lisoneofthecandidatesofstructuralmaterials.However,thecorrosionandwearbehaviorof316Lsteelinthehigh-velocitystreamofliquidPbBiisthemostessentialissue,whichisurgenttobepaidcloseattention.Inordertoacquirethemorphologyandmechanicalpropertiesof316Lsteelintheconditionsofdifferentrelativeflowingvelocity(RFV),respectively2.62m/s,3.69m/s,4.77m/s,theexperimentwascarriedoutindynamicliquidPbBiat550℃,uptoabout1500h.Accordingtotheresults,thesurfaceof316LhasbeencorrodedbadlyandtheelementsofNi,Cr,etc.werefoundtodissolvealot.WiththeincreaseoftheRFV,thefeatureof316Lsurfacechangedfromthesurfacewithmuchdeeperpitsandlooserstructurestotherelativeplanarone,andthethicknessoftheouteroxidelayerdecreasedgraduallywhilethatoftheinneroxidelayerdiminishedalittle,andthemicrohardnessoftheoutermostsubstratealsodeclinedincreasingly,inaddition,thedomainofthepartialsubstratewithitsmicrohardnessbeingaltereddeepenedfurther.Theseexperimentaldatawouldoffertheoreticalbasisandpracticalvaluestostudycorrosionconditionof316LsteelinliquidPbBiwithhigh-velocity.
简介:采用化学抛光处理钛、阳极氧化和微弧氧化处理钛作为生物材料模型,研究成骨细胞MG-63在其表面的黏附和增殖机理。结果表明,阳极氧化和微弧氧化处理的钛表面通过促进MG-63细胞分泌纤维连接蛋白形成细胞外基质从而使其快速附着和伸展。另外,阳极氧化和微弧氧化处理的钛表面通过Outside-in信号传导通路,上调纤维连接蛋白及与其相关的整合素α5的转录水平,促进成骨细胞MG-63在其表面的增殖。
简介:采用纯Mg、Zn、Ca粉末和纳米羟基磷灰石(nHA)粉末,通过粉末冶金方法制备Mg-5Zn-0.3Ca/nHA生物复合材料,研究不同nHA增强相含量(1%、2.5%和5%,质量分数)对Mg-5Zn-0.3Ca合金腐蚀性能的影响。通过模拟体液浸泡试验和电化学技术测试其耐腐蚀性。结果显示,添加1%和2.5%的nHA提高镁合金的耐腐蚀性,这是因为生物活性nHA促进稳定的磷酸盐和碳酸盐表面沉积层的形成,从而提高纳米复合材料的耐蚀性。然而,在镁合金中添加更高含量的nHA作为增强相时,表面沉积层的密度增加,导致局部腐蚀产生的气体无法及时排出而聚集在沉积层下,减小层与基体的粘着力,导致耐腐蚀性能下降。对镁合金及其纳米复合材料的间接细胞毒性评价表明其浸提液无细胞毒性,添加1%nHA的纳米复合材料的测试结果与阴性对照组几乎相似。