Producing dense zirconium diboride components by room-temperature injection molding of aqueous ceramic suspensions. Issue 2 (1st February 2016)

• Record Type: Journal Article
• Authors: Wiesner, Valerie L.; Rueschhoff, Lisa M.; Diaz-Cano, Andres I.; Trice, Rodney W.; Youngblood, Jeffrey P.
• Is Part Of: Ceramics international. Volume 42:Issue 2:Part A(2016)
• Page Start: 2750
• Page End: 2760
• Publication Date: 2016-02-01
• Subjects: Injection molding -- Borides -- Suspensions; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2015.11.005
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Aqueous suspensions of zirconium diboride (ZrB2 ), boron carbide (B4 C) and tungsten carbide (WC) with dispersant and water-soluble polyvinylpyrrolidone (PVP) were investigated for processing by room-temperature injection molding, a novel, environmentally benign ceramic processing method. B4 C and WC were used as sintering aids, and the as-received powders were attrition milled to reduce particle size to promote full densification of ZrB2 specimens by pressureless sintering. Zeta potential measurements of individual ZrB2, B4 C and WC powders and of powder mixtures revealed that maximum stability was achieved in aqueous solutions of attrition milled powder mixtures dispersed using an ammonium polyacrylate dispersant. A maximum powder loading of 49 vol% with ≤5 vol% PVP was attained for ZrB2 /B4 C/WC suspensions with dispersant. Although exhibiting a time-dependent rheological response determined by parallel-plate rheometry, suspensions containing 49 vol% powders and ≤3 vol% PVP, as well as suspensions of 46 vol% powders and ≤4 vol% PVP, were flowable under the conditions of the process. ZrB2 rings prepared by room-temperature injection molding were machinable prior to binder removal and exhibited maximum brown densities of 56% true density (TD). Sintered densities were >98%TD with ~20% linear shrinkage. Scanning electron microscopy revealed an average grain size of 7.3±2.8 µm, and chemical analysis confirmed that no undesirable oxide phases remained in the sintered ZrB2 specimens. Aqueous ZrB2 -based suspensions containing B4 C and WC sintering aids and PVP were effectively processed via room-temperature injection molding to yield dense ZrB2 rings after binder burnout and pressureless sintering.