Nanometric polishing of lutetium oxide by plasma-assisted etching

Plasma-assisted etching,in which the irradiation of hydrogen plasma and inorganic acid etching are integrated,is proposed as a novel polishing method for sesquioxide crystals.By means of this approach,low damage and even damage-free surfaces with a high material removal rate can be achieved in lutetium oxide surface finishing.Analysis of transmission electron microscopy and X-ray photoelectron spectroscopy reveal that plasma hydrogenation converts the sesquioxide into hydroxide,which leads a high efficient way to polish the surfaces.The influences of process conditions on the etching boundary and surface roughness are also qualitatively investigated using scanning electron microscope and white light interferometry.The newly developed process is verified by a systematic experiment.

In vitro evaluation of artificial joints: a comprehensive review

Development of artificial joints is a great progress for joint replacement operations of human being, but the short longevity of prostheses has concerned both industries and researchers since the advent of modem implants. Thus, continuous improvements have been made alongside the clinical applications. The methodologies to inspect the potential properties of new designs have also seen many advances. The test machines have evolved from easy pin-on-disk configuration to the modem joint simulator. Besides, various wear traces provided by testing machines are investigated greatly, and multi-directional files are recommended as motion profiles for in vitro testing. The typical testing parameters, like sliding speed or loading profile, are discussed in this article, and their working mechanisms are described in detail. Meanwhile, the calf or bovine serum has been regarded as the gold standard for testing lubricant, and the future trend of fluid will be focused on investigating the effects of lubricant composites on the tribological properties. Hard particles and proteins are discussed as well, and their effects on the wear mechanisms are the focus. Finally, various approaches to measure the wear rate, wear factor and the thickness of lubricant film are presented, and suggestions are given for the development in future.

Investigation of electropolishing characteristics of tungsten in ecofriendly sodium hydroxide aqueous solution

In this study,an eco-friendly electrolyte for electropolishing tungsten and the minimum material removal depth on the electropolished tungsten surface are investigated using an electrochemical etching method.Using a concentrated acid electrolyte,the polarization curve and current density transient are observed.For a NaOH electrolyte,the effects of interelectrode gap and electrolyte concentration on electropolishing are investigated.The differences in electropolishing characteristics are compared among different electrolyte types.Microholes are etched on the electropolished tungsten surface to determine the minimum material removal depth on the tungsten surface.Experimental results indicate the color effect due to a change in the thickness of the oxide film on the tungsten surface after electropolishing with a concentrated acid electrolyte.The surface roughness decreases with the interelectrode gap width owing to the increased current density when using the NaOH electrolyte.However,the electropolishing effect is less prominent with a significantly smaller gap because the generated bubbles are unable to escape from the narrow working gap in time.A material removal depth of less than 10 nm is achieved on the tungsten surface in an area of diameter 300 lm,using the electrochemical etching method.