Search

The objective of this study was to develop a replica method for producing zirconia-reinforced bioactive glass (ZRBG) porous structures for bone repair. Four different types of porous structures were produced: zirconia (G1), 58S BG-coated zirconia (G2), zirconia-reinforced BG (G3) and 58S BG-coated zirconia-reinforced BG (G4). A complete characterization of the specimens was performed via SEM-EDS, Archimedes method, 3D X-ray micro-tomography, micro-indentation, compressive strength tests and SBF immersion tests. G3 and G4 specimens presented a BG matrix (~ 33% glassy phase) with dispersed zirconia particles. The porosity of the specimens ranged from 86% up to 93%. BG58S-zirconia groups G3 and G4) exhibited lower YM (38.76 ± 11.20 GPa and 43.49 ± 2.16 GPa) than that of G1 monolithic zirconia specimens (94.39 ± 12.62 GPa), which were more compatible to that of the bone. No significant difference in compressive strength between BG58S-zirconia (G3: 0.41 ± 0.20 MPa; G4: 0.45 ± 0.11 MPa) and zirconia (G1: 0.32 ± 0.11 MPa) was detected observed (p > 0.05). In vitro SBF tests showed a potential bioactivity for ZRBG porous structures.

Grinding wheel content characterization is still mainly based on empirical tests, lacking the necessary scientific approach. To further develop the current existing methodology, this study introduces a method to characterize the grinding wheel structure and content, using microscale X-ray tomography allied with image processing techniques. An X-ray tomography characterization was performed on four different conventional grinding wheels, each containing a specific mixture of electro-fused and sol-gel aluminum oxide abrasives as grits. The grinding wheels were evaluated in terms of volumetric phase fraction, representative elementary volume, phase, and pore size distribution. The results showcased that even though the grinding wheels presented the same manufacturing label (in terms of mechanical properties), the volumetric phase fraction between the grinding wheels was significantly different. This study aggregates the empirical knowledge used to characterize grinding wheels, opening possibilities for academic and industrial research.

In this work, ceramic shell foams produced by direct foaming and gelcasting of proteins containing 35 vol.% of solids were efficiently tailored through the optimization of suspension parameters, foaming and also according to the gelling temperature. These were key parameters employed for controlling the foamability and foam stability, and hence the foam porosity and pore characteristics after the sintering process. The potential of using microtomography in characterizing the morphometric parameters of foams was explored. Airflow permeability measurements (∼24 °C to 727 °C) were performed in order to investigate the applicability of such materials in the fluid flow field. The samples exhibited a wide range of pore sizes (60 ± 5–1700 ± 90 μm), porosity values higher than 80 %, Darcian (k1) and non-Darcian (k2) permeability coefficients values in the ranges of 1.32–1.83 x 10−9 m2 and 8.34–22.46 x 10-5 m, respectively.

The Earth, Moon and Mars samples have been investigated in terms of gamma ray energy absorption buildup factors ( EABF ) depending on penetration depth, weight fraction of constituent elements and photon energy. The five parameter geometric progression (G-P) fitting approximation has been used to compute the buildup factors in the energy region 0.015–15 MeV up to a penetration depth of 40 mean free paths (mfp). The maximum values of EABF have been observed for the Earth, Mars and Moon samples at 0.2, 0.3 and 0.2 MeV, respectively. At the corresponding energies where maximum EABF occur, the Earth samples have the highest and the Mars samples have the lowest EABF values. There is no significant variation in EABF for the Earth, Moon and Mars samples beyond 1 MeV, hence the values of EABF remain constant with the variation in chemical composition for all the given materials. Finally, the buildup factors so obtained have been discussed in function of the penetration depth, weight fraction of constituent elements and photon energy.

Abstract Two nuclear methodologies were used for porosity and pore size distribution determination of SiC ceramic foams. Thirty samples were analysed, six of each one of the following pore densities: 30, 45, 60, 80 and 100 pores per inch (ppi). The two nuclear techniques employed were X-ray microtomography and gamma ray transmission. For the microtomography technique, the spatial resolution of the images was 32 μm. For the gamma ray transmission methodology, a NaI (Tl) scintillation detector and Am-241 radioactive source were used. The gamma transmission technique was precise for porosity determination in relationship to the nominal values supplied for the sample manufacturer. The 30 and 45 ppi samples analysed by the microtomography technique present average porosities equivalent to the nominal porosity, and the other samples present an average of 4·6% smaller values. The 30 and 45 ppi sample two-dimensional images show voids inside the structural solid material of the ceramic.