A novel processing approach for free-standing porous non-oxide ceramic supports from polycarbosilane and polysilazane precursors
In this contribution, a low-pressure/low-temperature casting technique for the preparation of novel free-standing macrocellular polymer-derived ceramic support structures is presented. Preceramic polymers (polycarbosilane and poly(vinyl)silazane) are combined with sacrificial porogens (ultra-high molecular weight polyethylene microbeads) to yield porous ceramic materials in the Si—C or Si—C—N systems, exhibiting well-defined pore structures after thermal conversion. The planar-disc-type specimens were found to exhibit biaxial flexural strengths of up to 60 MPa. In combination with their observed permeability characteristics, the prepared structures were found to be suitable for potential applications in filtration, catalysis, or membrane science.
Planar, Polysilazane‐Derived Porous Ceramic Supports for Membrane and Catalysis Applications
Porous, silicon carbonitride‐based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh‐molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizing both the composition as well as cross‐linking parameters, maximum characteristic biaxial flexural strengths of 65 MPa and porosities of 42% were achieved. The evolution of an interconnected, open‐pore network during thermal porogen removal and conversion of the preceramic polymer led to air permeabilities in the order of 10−14 m². The materials were further exposed to long‐term heat treatments to demonstrate the stability of properties after 100 h at 800°C in oxidizing, inert, and reducing environments. The determined performance, in combination with the versatile preparation method, illustrates the feasibility of this processing approach for the generation of porous ceramic support structures for applications at elevated temperatures in a variety of fields, including membrane and catalysis science.
Gross negligence ‘medical’ manslaughter in Ireland: Legal context and clinician concerns
In recent years, the prospect of the criminal prosecution of medical practitioners for patient safety incidents resulting in fatality which occur in the course of clinical practice has caused heightened anxiety among medical practitioners, particularly in England and Wales, where a number of high-profile cases have raised public consciousness of this issue. The full impact of this landscape on individual practitioners and the delivery of healthcare has yet to be ascertained, although research suggests that medical practice has been impacted. Of particular interest is the phenomenon of defensive medicine which occurs where physicians adopt assurance and/or avoidance behaviours in an attempt to minimise the risk of medical negligence litigation and/or to avoid complaints to regulatory bodies. While defensive medicine is traditionally conceived of in a civil context, the possibility of criminal prosecution for patient safety incidents resulting in fatality may also result in alterations to medical practice. Drawing on the findings of an empirical study (a survey), this research sought to explore the impact, if any, of the threat of criminal prosecution on surgical practice in the Republic of Ireland, including a potential rise in defensive practice.