Metal particles size influence on graded structure in composite Al2O3-Ni

The aim of this study was to investigate the effect of the nickel particle size on the changes in metallic phase content in the graded structure in the Al2O3-Ni composites.Centrifugal slip casting was chosen as the method of composite fabrication.This method allows the creation of a graded distribution of Ni particles in the hollow cylinder composite sample.Functional graded materials were prepared in the vertical rotation axis.In the experiments the following powders were used: a-Al2O3 TM-DAR from Taimei Chemicals (Japan) of an average particle size 0.133 μm and density 3.96 g/cm 3 and Ni powders from Sigma-Aldrich of average particle sizes 3 μm and 8.5 μm.Aqueous slurries containing alumina (50 % of volume fractions of solid phase volume content) and nickel powders (10 % of volume fractions) were tested.Deflocculates diammonium citrate (p.a., Aldrich) and citric acid (p.a., POCH Gliwice) were also added.Final sintering was conducted on all the specimens at 1400 °C in a reducing atmosphere (N2/H2).The obtained samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).In addition, quantitative analyses of the Ni particles distribution were made.In the fabricated samples the graded structure were characterized by zones with different Ni particles concentration.The size of the Ni particles influences the width of these zones.Vickers indentation was used to determine the hardness of the materials.Keywords: functionally graded material (FGM), centrifugal slip casting (CSC), Al 2 O 3 -Ni system Namen {tudije je bil preiskati vpliv velikosti delcev niklja na spreminjanje vsebnosti kovinske faze v gradientni strukturi kompozita Al2O3-Ni.Centrifugalno oblikovalno ulivanje je bilo izbrano kot metoda za izdelavo kompozita.Ta metoda omogo~a stopenjsko razporeditev delcev Ni v votlem cilindri~nem kompozitnem vzorcu.Funkcionalno razporejen material je bil izdelan na vertikalni rotacijski osi.Za preizkuse so bili uporabljeni naslednji prahovi: a-Al2O3 TM-DAR iz Taimei Chemicals (Japan) s povpre~no velikostjo delcev 0.133 μm in gostoto 3.96 g/cm 3 ter prah Ni iz Sigma-Aldrich, s povpre~no velikostjo delcev 3 μm in 8.5 μm.Preizku{ena je bila na vodi osnovana me{anica (z vsebnostjo 50 % volumenskega dele`a trdne faze), ki je vsebovala prah glinice in niklja (10 % volumenskega dele`a).Uporabljeni deflokulant je bil sestavljen iz diamonium citrata (p.a., Aldrich) in citronske kisline (p.a., POCH Gliwice).Kon~no sintranje je bilo pri vseh vzorcih na 1400 °C, v reduktivni atmosferi (N2/H2).Dobljeni vzorci so bili pregledani z rentgensko difrakcijo (XRD) in vrsti~no elektronsko mikroskopijo (SEM).Poleg tega je bila izvedena tudi kvantitativna analiza razporeditve Ni delcev.V vzorcih je bila analizirana gradientna struktura po podro~jih z razli~no koncentracijo Ni delcev.Velikost Ni delcev vpliva na {irino teh podro~ij.Dolo~ena je bila trdota materiala po Vickersu.