Effect of Starting Particle Size and Oxygen Content on Densification of ZrB2

Zirconium diboride (ZrB 2 ) ceramics were densified by pressureless sintering (PS), hot pressing, or spark plasma sintering (SPS) of powders with a range of starting particle sizes and oxygen contents. Microstructural analysis of the ZrB 2 ceramics revealed a wide range of final grain sizes. SPS resulted in an average grain size as small as 1.6 μm after densification at 1900°C, while the largest grains, 31 μm, were produced by PS at 2100°C. Oxygen impurities in boride ceramics caused grain coarsening in all densification techniques, but inhibited full densification only for PS. Carbon was added to react with and remove oxygen impurities, which promoted densification, reduced ZrB 2 grain size, and led to increased room-temperature flexure strengths. The highest strength was 527 MPa for SPS ZrB 2 , while the lowest strength was measured for pressurelessly sintered ZrB 2 , 300 MPa. Overall, SPS was the superior technique for providing the highest strength and greatest ability to remove oxygen.

[1]  T. Goto,et al.  Microstructure and densification of ZrB2–SiC composites prepared by spark plasma sintering , 2009 .

[2]  R. Rapp,et al.  Effects of Phase Change and Oxygen Permeability in Oxide Scales on Oxidation Kinetics of ZrB2 and HfB2 , 2009 .

[3]  Bikramjit Basu,et al.  Simulation of thermal and electric field evolution during spark plasma sintering , 2009 .

[4]  Yutaka Kagawa,et al.  Spark Plasma Sintering of Zirconium Diborides , 2008 .

[5]  D. Shetty,et al.  Effect of Additives on the Activation Energy for Sintering of Silicon Carbide , 2008 .

[6]  R. Telle,et al.  Boride‐Based Hard Materials , 2008 .

[7]  D. Fang,et al.  Processing and Mechanical Properties of Zirconium Diboride‐Based Ceramics Prepared by Spark Plasma Sintering , 2007 .

[8]  D. Sciti,et al.  Effects of MoSi2 additions on the properties of Hf-and Zr-B2 composites produced by pressureless sintering , 2007 .

[9]  G. Hilmas,et al.  Pressureless sintering of carbon-coated zirconium diboride powders , 2007 .

[10]  William G. Fahrenholtz,et al.  Refractory Diborides of Zirconium and Hafnium , 2007 .

[11]  T. Grande,et al.  Preferential Grain Orientation in Hot Pressed TiB2 , 2007 .

[12]  Mark M. Opeka,et al.  A Model for the Oxidation of ZrB2, HfB2 and TiB2 (Postprint) , 2007 .

[13]  G. Hilmas,et al.  Pressureless Densification of Zirconium Diboride with Boron Carbide Additions , 2006 .

[14]  G. Hilmas,et al.  Pressureless Sintering of Zirconium Diboride , 2006 .

[15]  Doh-Yeon Kim,et al.  Densification and properties of transition metal borides-based cermets via spark plasma sintering , 2006 .

[16]  P. Becher,et al.  Effect of oxygen contamination on densification of TiB2 , 1987 .

[17]  D. Kalish,et al.  Densification Mechanisms in High‐pressure Hot‐Pressing of HfB2 , 1969 .