One of the established limitations of metal additive manufacturing (AM) methods, such as selective laser melting (SLM), is the resulting rough surface finish. Laser polishing is one method that can be used to achieve an improved surface finish on AM printed parts. This study is focused on the laser surface polishing of AM parts using CO2 laser beam irradiation. Despite the fact that several researchers have investigated the traditional abrasive polishing method, there is still a lack of information reporting on the laser surface polishing of metal parts. In this study, AM 316L stainless steel cylindrical samples were polished using CO2 laser beam irradiation in continuous wave (CW) working mode. Two design of experiment models were developed for the optimization of the input processing parameters by statistical analysis of their effect on the resulting roughness. The processing parameters investigated were the laser beam power, the rotational speed of the sample, the number of laser scan passes, the laser beam focal position, and the percentage overlap of the laser tracks between consecutive passes. The characterization of the measured roughness and the modified layer microstructure was carried out using 3D optical and scanning electron microscopy (SEM). A maximum reduction of the roughness from 10.4 to 2.7 µm was achieved and no significant change in the microstructure phase type and micro-hardness was observed.
Screened field enhancement factor for the floating sphere model of a carbon nanotube array J. Appl. Phys. 110, 114311 (2011) Field-emission-assisted approach to dry micro-electro-discharge machining of carbon-nanotube forests J. Appl. Phys. 110, 103305 (2011) The hysteresis phenomenon of the field emission from the graphene film Appl. Phys. Lett. 99, 173104 (2011) Temperature dependence of the field emission from the few-layer graphene film Appl. Phys. Lett. 99, 163103 (2011) Additional information on J. Appl. Phys. A multistage chemical method based on nanosphere lithography was used to produce hexagonally patterned arrays of ZnO vertical nanowires, with 1 lm interspacing and aspect ratio $20, with a view to study the effects of emitter uniformity on the current emitted upon application of a dc voltage across a 250 lm vacuum gap. A new treatment, based on the use of analytical expressions for the image-potential correction functions, was applied to the linear region below 2000 V of the Fowler-Nordheim (FN) plot and showed the most suitable value of the work function / in the range 3.3-4.5 eV (conduction band emission) with a Schottky lowering parameter y $ 0.72 and a field enhancement factor c in the 700-1100 range. A modeled c value of $200 was calculated for an emitter shape of a prolate ellipsoid of revolution and also including the effect of nanowire screening, in fair agreement with the experimental value. The Fowler-Nordheim current densities and effective emission areas were derived as 10 11 Am À2 and 10 À17 m 2 , respectively, showing that field emission likely takes place in an area of atomic dimensions at the tip of the emitter. Possible causes for the observed departure from linear FN plot behavior above 2000 V were discussed.
Every year, the EU emits 13.4 Mt of CO2 solely from plastic production, with 99% of all plastics being produced from fossil fuel sources, while those that are produced from renewable sources use food products as feedstocks. In 2019, 29 Mt of plastic waste was collected in Europe. It is estimated that 32% was recycled, 43% was incinerated and 25% was sent to landfill. It has been estimated that life-sciences (biology, medicine, etc.) alone create plastic waste of approximately 5.5 Mt/yr, the majority being disposed of by incineration. The vast majority of this plastic waste is made from fossil fuel sources, though there is a growing interest in the possible use of bioplastics as a viable alternative for single-use lab consumables, such as petri dishes, pipette tips, etc. However, to-date only limited bioplastic replacement examples exist. In this review, common polymers used for labware are discussed, along with examining the possibility of replacing these materials with bioplastics, specifically polylactic acid (PLA). The material properties of PLA are described, along with possible functional improvements dure to additives. Finally, the standards and benchmarks needed for assessing bioplastics produced for labware components are reviewed.
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