Silicon carbide, with single‐edge precracked beam (SEPB) toughness greater than 7 MPa·m1/2, was made by hot‐pressing using Al–B–C (ABC) or Al–Y2O3 (YAG) as additives. The hardness of SiC processed with a liquid phase was always less than SiC densified without a liquid phase despite having a similar or finer grain size. With increasing Al content, the ABC system changed from trans‐ to intergranular fracture with a drop in hardness and a two‐ to threefold increase in SEPB toughness. Strength and Weibull modulus for materials processed with a liquid phase were higher than those of solid‐state densified SiC. Ballistic testing, however, did not show any improvement over SiC densified with B and C additives. Depth of penetration was controlled by hardness of the SiC‐based materials, while V50 values for 14.5 mm WC–Co cored projectiles were in the range of 720–750 m/s for all materials tested.

Perioperative and latent infections are leading causes of revision surgery for orthopaedic devices resulting in significant increased patient care, comorbidities, and attendant costs. Identifying biomaterial surfaces that inherently resist biofilm adhesion and bacterial expression is an important emerging strategy in addressing implant-related infections. This in vitro study was designed to compare biofilm formation on three biomaterials commonly employed in spinal fusion surgery-silicon nitride (Si N ), polyetheretherketone (PEEK), and a titanium alloy (Ti6Al4V-ELI) -using one gram-positive and one gram-negative bacterial species. Disc samples from various surface treated Si N , PEEK, and Ti6Al4V were inoculated with 10 CFU/mm Staphylococcus epidermidis (ATCC®14990™) or Escherichia coli (ATCC 25922™) and cultured in PBS, 7% glucose, and 10% human plasma for 24 and 48 h, followed by retrieval and rinsing. Vortexed solutions were diluted, plated, and incubated at 37 °C for 24 to 48 h. Colony forming units (CFU/mm ) were determined using applicable dilution factors and surface areas. A two-tailed, heteroscedastic Student's t-test (95% confidence) was used to determine statistical significance. The various Si N samples showed the most favorable bacterial resistance for both bacilli tested. The mechanisms for the bacteriostatic behavior of Si N are likely due to multivariate surface effects including submicron-topography, negative charging, and chemical interactions which form peroxynitrite (an oxidative agent). Si N is a new biomaterial with the apparent potential to inhibit biofilm formation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1521-1534, 2017.

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Processing additives and conditions allow a wide variation in microstructures and mechanical properties for Sic-based ceramics prepared by hot pressing. Five experimental materials with a wide variety of microstructures and mechanical properties were fabricated and compared with SIC-N, a commercially available material. Quasi-static fracture modes varied from predominantly transgranular to primarily intergranular, leading to a twofold increase in the single-edged precracked beam (SEPB) fracture toughness. Hardness varied due to an order of magnitude change in grain size, while porosity varied by less than one percent. Ballistic v 5 0 performance was measured using 14.5 mm projectiles shot at ceramic/composite targets. The relative ranking of ballistic performance is discussed in terms of microstructure and mechanical properties.The data indicate that a wide variety of Sic-based materials can give good ballistic results, contradicting some of the theories about what is important to improve ceramics for armor. Several materials were as good or better than Sic-N in these tests. The relative ballistic ranking was not predictable based solely on hardness, toughness, strength, grain size, elastic modulus, or fracture mode. Although Weibull modulus correlated with ballistic performance, this is likely coincidental since strength values extrapolated to a low failure probability based on the respective Weibull distributions could not rank the ballistic results. INTRODUCTIONSic is the ceramic armor of choice for moderate to heavy threats due to the likely amorphitization of BhC at high pressures. The key to making improved armor is to understand what controls the ballistic performance of the armor system. This paper focuses only on the ceramic portion of the ballistic package realizing that the performance is tied to the system. In previous work' using 7.62 mm diameter by 51 mm long WC-Co cored ammunition, it was