• M Guedes

      Articles written in Bulletin of Materials Science

    • Processing and characterization of alumina/LAS bioceramics for dental applications

      M Guedes V Costa T Silva A Teles X Yang A C Ferro

      More Details Abstract Fulltext PDF

      Alumina allows to recreate the functionality and aesthetics of natural teeth. However, its low fracture toughness rises concern regarding use in dental restoration. Structural reliability is addressed here by formulating a material containing alumina and a glass–ceramic from LAS system. The presence of LAS in the mixtures result in formation of glass phase during sintering, promoting densification at lower temperature and enhanced surface finishing. A composite microstructure with increased toughness can thus be produced. Powder mixtures containing 0, 20, 50, 80 and 100 wt\%-LAS were prepared by planetary milling and uniaxial pressing and sintered. The compositions were investigated regarding their processability, mechanical performance and biological behaviour. Aesthetics was evaluated by comparison with a commercial dental matching guide. Variations on hardness and fracture toughness with starting LAS fraction were assessed by indentation. Interaction with biological medium was evaluated by immersion in a simulated body fluid. Resulting microstructures were characterised by FEG–SEM, EDS and XRD.

    • Characterization of titanium–hydroxyapatite biocomposites processed by dip coating

      R Baptista D Gadelha M Bandeira D Arteiro M I Delgado A C Ferro M Guedes

      More Details Abstract Fulltext PDF

      Ti orthopaedic implants are commonly coated with hydroxyapatite (HA) to achieve increased biocompatibility and osseointegration with natural bone. In this work the dip-coating technique was used to apply HA films on Ti foil. A gel was used as the support vehicle for commercial HA particles. The experimental parameters like surface roughness of the metallic substrate and immersion time were studied. All coated substrates were heat treated and sintered under vacuum atmosphere. The produced coatings were characterized by field-emission gun scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, microhardness, scratch test and profilometry. Additionally, the apatite-forming ability of the produced material was tested by exposure to a simulated body fluid. Higher substrate surface roughness and longer immersion time produce thicker, denser films, with higher surface roughness. Lower film porosity is accompanied by higher hardness values. However, thicker coating promotes differential shrinkage and crack formation during sintering. Both coating thickness and coating roughness increase with coating time. HA films $\sim$30–40 $\mu$m thick with 45–50% HA theoretical density produced on Ti substrates with surface roughness of $R_z\sim 1.0–1.7$ $\mu$m, display an attractive combination of high hardness and resistance to spallation. Attained results are encouraging regarding the possibility of straightforward production of biocompatible and bioactive prosthetic coatings for orthopaedic applications using commercial HA.

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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