Comparative study of reactive and nonreactive spark plasma sintering routes for the production of TaB2‐TaC composites

Melis Kaplan Akarsu,Gultekin Goller,Filiz Sahin,Ipek Akin

doi:10.1111/ijac.13900

Melis Kaplan Akarsu, Gultekin Goller + Show 2 more

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https://doi.org/10.1111/ijac.13900

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Abstract

AbstractThe influence of two different spark plasma sintering (SPS)‐based processing routes (i.e., reactive SPS [RSPS] and nonreactive SPS) on the properties of TaB2‐TaC composites was investigated. Ta2O5 and B4C powders were used as starting materials in the RSPS method, and synthesis and densification of TaB2‐TaC composites were accomplished in a facile single step. The effect of sintering temperature and time on the microstructure and densification of the in‐situ RSPS were investigated. The obtained results were compared with nonreactive spark plasma sintered TaB2‐TaC composites. The highest densification (∼99.5%) was achieved for the TaB2‐TaC composite with 6.64 vol.% TaC after reactive sintering at 1550°C under 40 MPa with a 5 min holding time. Although lower SPS temperature was used in the RSPS method, better densification and higher Vickers hardness were obtained compared to the nonreactive SPS. While platelet‐shaped TaC formation was observed in both processes, the average grain size was smaller in the RSPS method. On the other hand, no significant difference was detected in the oxidation behavior of the composites produced by RSPS and nonreactive SPS.

Highlights

Transition metal borides in groups IVB and VB are members of a family known as ultra-hightemperature ceramics (UHTCs) [1]
It was approached to the densification process of RSPSed composites in three stages: formation of TaB2 and TaC phases, densification, and elimination of pores
According to Eq (3), reaction products are TaB2(s), TaC(s), and B2O3(l), and enthalpy of mixing of the compounds can be sorted as B2O3(l)< TaC(s)< TaB2(s)

Summary

Introduction

Transition metal borides in groups IVB and VB are members of a family known as ultra-hightemperature ceramics (UHTCs) [1]. According to Peshev et al [5], several methods have been described for the preparation of diborides, including the direct interaction between elements, electrolysis of molten oxides and salts, reducing a mixture of metal oxide and B2O3 with carbon, reducing metal oxides with boron carbide under vacuum, and the borothermic reduction of the pure-metal oxides under vacuum. You et al [6] synthesized sub-micrometric TaB2 powders via the reduction of Ta2O5 using B4C in a mild vacuum (~15 Pa) with starting molar ratios of 1.57 and 1.90 for B4C/Ta2O5. Guo et al [7] investigated the borothermal reduction process for Ta2O5 with boron under vacuum where the various borides obtained depended on the molar ratio of boron/Ta2O5 and the temperature. Zhang et al [8] synthesized pure TaB2 powder by reducing Ta2O5 with B4C and graphite at 1600 C under an argon atmosphere, and hot pressed with a relative density of ~98% at 2100 C

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