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  • 1
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    New Borothermal Reduction Route to Synthesize Submicrometric ZrB2 Powders with Low Oxygen Content (2011)
    Wiley
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    Publication Date: 2011-10-05
    Description: The ZrB 2 powders with submicrometric particle size and low oxygen content were synthesized by a new borothermal reduction route using ZrO 2 and excess boron as raw materials. The conventional process only contained the borothermal reduction of ZrO 2 with boron at 1550°C. By exploring the mechanism of ZrB 2 particle coarsening during conventional process, a new borothermal reduction route was proposed. This route included the borothermal reduction of ZrO 2 with boron at 1000°C, washing by hot water, and the removal of residual boron oxides at 1550°C, namely, two-step reduction plus intermediate water-washing (RWR). Using conventional process, the particle size and oxygen content of ZrB 2 powder were about 2–3 μm and 0.68 wt%, respectively. Based on the new route, the particle size and oxygen content of ZrB 2 powder were about 0.4–0.7 μm and 0.40 wt%, respectively.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 2
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    Pressureless Sintering of Zirconium Diboride Ceramics with Boron Additive (2012)
    Wiley
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    Publication Date: 2012-06-14
    Description: Influence of boron on densification and microstructure of zirconium diboride ( ZrB 2 ) ceramics using pressureless sintering has been studied. The ZrB 2 powders were synthesized by borothermal reduction of ZrO 2 with three different ZrO 2 / B ratios to produce powders nominally phase pure or that contained excess boron. The as-synthesized powders were then densified by heating to temperatures from 1800°C to 2200°C. The incorporation of 1.2 wt% excess boron increased relative density from ~54.3% to ~96.1% by reacting with and removing oxide impurities ( ZrO 2 and B 2 O 3 ) after sintering at 2000°C, whereas it also led to an exaggerated grain growth from 1–3 to 20–80 μm presumably due to high grain-boundary mobility. The faster grain growth resulted in the formation of intragranular pores and prevented the ZrB 2 ceramics from reaching full density. By the incorporation of 3 wt% excess boron, a fully dense ZrB 2 ceramics with relative density of ~99.7% and grain size of 5–10 μm was obtained at 2000°C. The full densification was attributed to the synergistic effects of boron through oxide impurities removal and grain- growth inhibition.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 3
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    TiB2 Powders Synthesis by Borothermal Reduction in TiO2 Under Vacuum (2014)
    Wiley
    Details
    Publication Date: 2014-03-27
    Description: TiB 2 powders were synthesized by borothermal reduction in nanoscale TiO 2 with boron under vacuum. Reaction processes were investigated, and the effect of by-product B 2 O 3 was evaluated. Results showed that TiO 2 was firstly reduced by boron to form TiBO 3 and Ti 2 O 3 , and then to produce TiB 2 and B 2 O 3 with increasing temperature. The reaction processes of TiB 2 powders synthesis included two-step reduction in TiO 2 by boron and the removal of B 2 O 3 . The presence of B 2 O 3 , which was previously reported as the most important factor in promoting the coarsening of ZrB 2 and HfB 2 powders by borothermal reduction, did not lead to significant coarsening of TiB 2 powders. Due to the minor effect of B 2 O 3 , TiB 2 powders with small particle size and low oxygen content could be prepared by direct heat treatment of TiO 2 and boron at 1550°C under vacuum for 1 h. The particle size and oxygen content of synthesized TiB 2 powders were ~0.9 μm and ~1.7 wt%, respectively.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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