Nitrogen-rich Ca-α-SiAlON ceramics were synthesized using nanosized precursors via spark plasma s... more Nitrogen-rich Ca-α-SiAlON ceramics were synthesized using nanosized precursors via spark plasma sintering process for various holding times (10, 20, 30 min) at relatively low temperatures of 1500 °C and 1600 °C. The effects of the experimental conditions, namely sintering time and temperature, on the densification and mechanical properties of the processed α-SiAlON were investigated. All of the conditions yielded nearly completely densified ceramics. A remarkable combination of hardness and toughness was obtained for the samples at either sintering temperature; and these values were greatest after 30 min sintering time, with Vickers hardness values of 21.6 GPa and 20.5 GPa and fracture toughness values of 7.3 MPa√m and 9.7 MPa√m for sintering temperatures of 1500 °C and 1600 °C, respectively. The differences in the mechanical properties of these samples were related to differences in the phases formed during the sintering process.
This paper focuses on activity and stability studies of metal-nitride-carbide nanocomposites as P... more This paper focuses on activity and stability studies of metal-nitride-carbide nanocomposites as Pt-free catalyst for PEMFCs cathode. In one example, iron based catalyst (denoted as Fe-N-C/C) demonstrated good activity and stability; after 20,000 cycles between 0.6 and 1V/RHE, the catalyst retained 50% of its initial activity. Moreover, the catalyst has good selectivity; it does not show any activity towards methanol oxidation, which makes it an excellent candidate for direct methanol fuel cell (DMFC) cathode.
Nitrogen-rich Ca-α-SiAlON ceramics were synthesized using nanosized precursors via spark plasma s... more Nitrogen-rich Ca-α-SiAlON ceramics were synthesized using nanosized precursors via spark plasma sintering process for various holding times (10, 20, 30 min) at relatively low temperatures of 1500 °C and 1600 °C. The effects of the experimental conditions, namely sintering time and temperature, on the densification and mechanical properties of the processed α-SiAlON were investigated. All of the conditions yielded nearly completely densified ceramics. A remarkable combination of hardness and toughness was obtained for the samples at either sintering temperature; and these values were greatest after 30 min sintering time, with Vickers hardness values of 21.6 GPa and 20.5 GPa and fracture toughness values of 7.3 MPa√m and 9.7 MPa√m for sintering temperatures of 1500 °C and 1600 °C, respectively. The differences in the mechanical properties of these samples were related to differences in the phases formed during the sintering process.
This paper focuses on activity and stability studies of metal-nitride-carbide nanocomposites as P... more This paper focuses on activity and stability studies of metal-nitride-carbide nanocomposites as Pt-free catalyst for PEMFCs cathode. In one example, iron based catalyst (denoted as Fe-N-C/C) demonstrated good activity and stability; after 20,000 cycles between 0.6 and 1V/RHE, the catalyst retained 50% of its initial activity. Moreover, the catalyst has good selectivity; it does not show any activity towards methanol oxidation, which makes it an excellent candidate for direct methanol fuel cell (DMFC) cathode.
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Papers by Abbas Hakeem