Stochastic Metallic-Glass Cellular Structures Exhibiting Benchmark Strength

By identifying the key characteristic “structural scales” that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date

High porosity metallic glass foam: A powder metallurgy route

A powder metallurgy route to the fabrication of metallic glass foam is introduced. The method involves consolidating metallic glass powder blended with blowing agent particulates to produce expandable precursors, capable of yielding foams with porosities as high as 86%. The foams are found to inherit the strength of the parent metallic glass and to be able to deform heavily toward full densification absorbing high amounts of energy

Synthesis method for amorphous metallic foam

A synthesis method for the production of amorphous metallic foam is introduced. This method utilizes the thermodynamic stability and thermoplastic formability of the supercooled liquid state to produce low-density amorphous metallic foams in dimensions that are not limited to the critical casting thickness. The method consists of three stages: the prefoaming stage, in which a large number of small bubbles are created in the equilibrium liquid under pressure; the quenching stage, in which the liquid prefoam is quenched to its amorphous state; the foam expansion stage, in which the amorphous prefoam is reheated to the supercooled liquid region and is processed under pressures substantially lower than those applied in the prefoaming step. Results from a dynamic model suggest that the foam expansion process is feasible, as the kinetics of bubble expansion in the supercooled liquid region are faster than the kinetics of crystallization. Within the proposed synthesis method, bulk amorphous foam products characterized by bubble volume fractions of as high as 85% are successfully produced

Thermo-plastic expansion of amorphous metallic foam

Amorphous Pd_(43)Ni_(10)Cu_(27)P_(20) foam is produced at 38%, 49%, and 70% porosity by isothermally expanding a 25%-porosity amorphous precursor in the supercooled liquid state for varying durations. The foam morphologies exhibit good spatial homogeneity as well as good size uniformity of bubbles, which is a consequence of the high viscosity of the supercooled liquid state which inhibits floatation and dampens the growth kinetics. The expansion capability of amorphous metals into high-porosity foam demonstrated in this study is attributed to the plastic deformability of the supercooled liquid state, which enables large plastic membrane elongations during foaming

Expansion evolution during foaming of amorphous metals

Amorphous Pd_(43)Ni_(10)Cu_(27)P_(20) foam of 38, 49, and 70% porosity is produced by expanding a 25% porosity amorphous precursor in the supercooled liquid state in three isothermal stages of varying durations. Metallographic examination suggests that expansion evolves by bubble growth towards a limit at which bubbles become critically packed. This limit is found to be close to the limit of random close packing of spheres of 63.7%. Beyond this critical limit, bubbles tend to impinge and coalesce and expansion progresses by growth of bubble clusters via stretching of intracellular membranes. The expansion evolution is modeled by means of a dynamic treatment of over-damped growth of individual bubbles. The model captures the expansion evolution reasonably well up to porosities between 50–70%, hence verifying that a transition from a bubble growth mechanism to a cluster growth mechanism takes place at some intermediate porosity

Exploring the safety and quality of mobile X-ray imaging in a new infectious disease biocontainment unit: an in situ simulation and video-reflexive study

Objectives During a precommissioning inspection of a new biocontainment centre, radiographers noted structural features of quarantine rooms that could compromise staff and patient safety and the X-ray image quality, even after significant modifications had been made to an earlier radiography protocol. The aim of this study was to explore the safety and effectiveness of the modified protocol, in the new space, and identify improvements, if required.Design A qualitative study using in situ simulation and video-reflexive methods.Setting A newly built biocontainment centre, prior to its commissioning in 2021, in a large, tertiary hospital in Sydney, Australia.Participants Five radiographers, and a nurse and a physician from the biocontainment centre, consented to participate. All completed the study.Interventions Two simulated mobile X-ray examinations were conducted in the unit prior to its commissioning; simulations were videoed. Participants and other stakeholders analysed video footage, collaboratively, and sessions were audio recorded, transcribed and analysed thematically. Problems and potential solutions identified were collated and communicated to the hospital executive, for endorsement and actioning, if possible.Results Four themes were identified from the data: infection exposure risks, occupational health and exposure risks, communication and X-ray image quality. Facilitated group reviews of video footage identified several important issues, across these four areas of risk, which had not been identified previously.Conclusions In situ simulation is used, increasingly, to evaluate and improve healthcare practices. This study confirmed the added value of video-reflexive methods, which provided experienced participants with a richer view of a familiar protocol, in a new setting. Video footage can be examined immediately, or later if required, by a broader group of stakeholders, with diverse experience or expertise. Using video reflexivity, clinicians identified potential safety risks, which were collated and reported to the hospital executive, who agreed to implement modifications