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Abstract: A low‐permittivity dielectric ceramic Li2GeO3 was prepared by the solid‐state reaction route. Single‐phase Li2GeO3 crystallized in an orthorhombic structure. Dense ceramics with high relative density and homogeneous microstructure were obtained as sintered at 1000‐1100°C. The optimum microwave dielectric properties were achieved in the sample sintered at 1080°C with a high relative density ~ 96%, a relative permittivity εr ~ 6.36, a quality factor Q × f ~ 29 000 GHz (at 14.5 GHz), and a temperature coefficient of resonance frequency τf ~ −72 ppm/°C. The sintering temperature of Li2GeO3 was successfully lowered via the appropriate addition of B2O3. Only 2 wt.% B2O3 addition contributed to a 21.2% decrease in sintering temperature to 850°C without deteriorating the dielectric properties. The temperature dependence of the resonance frequency was successfully suppressed by the addition of TiO2 to form Li2TiO3 with a positive τf value. These results demonstrate potential applications of Li2GeO3 in low‐temperature cofiring ceramics technology. [ABSTRACT FROM AUTHOR]

Well dispersed silica-graphene nanoplatelet (GNP) and silica-graphene oxide nanoplatelet (GONP) composites were fabricated by optimising their processing conditions. Different processing methods, including colloidal and powder processing, were investigated using different solvents. High temperature and inert environment during SPS resulted in the reduction of the GONP during sintering. The in situ reduction of GONP in the SPS was investigated for various sintering times and temperatures, and characterised using Raman spectroscopy and XRD analysis. The composite sintered at 1200°C, 50MPa pressure and 15min dwell time confirmed the recovery of the crystalline graphitic phase of GNP after reduction without crystallising the silica matrix. GONP was found to inhibit the crystallisation of the silica matrix at higher sintering times and temperatures possibly due to increased viscosity and reduced mobility of the silica particles bound to GNP. [ABSTRACT FROM AUTHOR]

Abstract: 45S5 Bioglass® powder has been densified at low temperatures using Spark Plasma Sintering (SPS). By employing SPS with pressures ranging from 70 to 300MPa, it was possible to achieve fully dense and completely amorphous 45S5 Bioglass® samples at temperatures as low as 500–550°C. By increasing the sintering temperature up to 600°C the dense samples crystallized to Na2CaSi2O6 phase rather than Na2Ca2Si3O9 which is usually achieved at higher temperature. Acellular in vitro test results in Simulated Body Fluid (SBF) revealed that SPSed samples sintered at 600°C resulted in faster formation of hydroxyapatite compared to pressureless sintered ones (1050°C), which were highly crystallized. Amorphous Bioglass® and/or Na2CaSi2O6 phase prepared by SPS could potentially produce Bioglass® composites with increased bioactivity. [Copyright &y& Elsevier]