title: Characterisation of nanovoiding in dental porcelain using small angle neutron scattering and transmission electron microscopy.
abstract: Recent studies of the yttria partially stabilised zirconia-porcelain interface have revealed the presence of near-interface porcelain nanovoiding which reduces toughness and leads to component failure. One potential explanation for these nanoscale features is thermal creep which is induced by the combination of the residual stresses at the interface and sintering temperatures applied during manufacture. The present study provides improved understanding of this important phenomenon.
  
  
  
  Transmission electron microscopy and small angle neutron scattering were applied to a sample which was crept at 750°C and 100MPa (sample C), a second which was exposed to an identical heat treatment schedule in the absence of applied stress (sample H), and a reference sample in the as-machined state (sample A).
  
  
  
  The complementary insights provided by the two techniques were in good agreement and log-normal void size distributions were found in all samples. The void number density was found to be 1.61μm-2, 25.4μm-2and 98.6μm-2in samples A, H and C respectively. The average void diameter in sample A (27.1nm) was found to be more than twice as large as in samples H (10.2nm) and C (11.6nm). The crept data showed the highest skewness parameter (2.35), indicating stress-induced growth of larger voids and void coalescence that has not been previously observed.
  
  
  
  The improved insight presented in this study can be integrated into existing models of dental prostheses in order to optimise manufacturing routes and thereby reduce the significant detrimental impact of this nanostructural phenomenon.
authors.affiliation: Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK. Electronic address: alexander.lunt@cern.ch.
authors.forename: Alexander
authors.initials: A
authors.lastname: Lunt
authors.affiliation: ISIS Pulsed Neutron and Muon Source, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Ann
authors.initials: A
authors.lastname: Terry
authors.affiliation: Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
authors.forename: Siqi
authors.initials: S
authors.lastname: Ying
authors.affiliation: Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Baimpas
authors.affiliation: Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
authors.forename: Tan
authors.initials: T
authors.lastname: Sui
authors.affiliation: ISIS Pulsed Neutron and Muon Source, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Kabra
authors.affiliation: ISIS Pulsed Neutron and Muon Source, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Joe
authors.initials: J
authors.lastname: Kelleher
authors.affiliation: ISIS Pulsed Neutron and Muon Source, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: King
authors.affiliation: Specialist Dental Group, Mount Elizabeth Orchard, #08-03/08-08/08-10, 228510, Singapore.
authors.forename: Neo Tee
authors.initials: NT
authors.lastname: Khin
authors.affiliation: Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Korsunsky
mesh_terms: D003776:Dental Porcelain; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D046529:Microscopy, Electron, Transmission; D053838:Scattering, Small Angle; D013696:Temperature; D015040:Zirconium
chemical_list: D003776:Dental Porcelain; D015040:Zirconium
keywords: Dental porcelain; Nanovoiding; Small angle neutron scattering; Transmission electron microscopy