The SC-1 treatment prior to the O3/TEOS CVD was a very effective method for gapfilling the nanoscale trench of the high aspect ratio by improving the adsorption of TEOS precursors onto the wall oxide. It was found that the interval duration after the SC-1 cleaning was a critical parameter for the contact angle and the gapfill performance of the O3/TEOS CVD.
This paper reports a comprehensive overview of nonconventional machining (NCM) of fiber-reinforced polymers (FRPs), which are widely used in high-tech industries owing to their superior mechanical properties compared with conventional metallic materials. To achieve FRP applications, hole processing for bolting and milling is required to match the dimensional precision. However, the large cutting force induced in conventional machining (CM), such as drilling and milling, causes severe failures, such as delamination and thermal damage to FRPs. To replace CM, various NCM technologies with efficient and powerful processing have been introduced to reduce FRP damage during machining. However, the complex nature of FRPs makes it difficult to identify the material removal mechanism and predict the machining quality and degradation of material properties. Not only the quantification of the machining parameter and performance but also an analysis to determine their relation is necessary. However, unlike many previous CM reviews, there are only a few reviews on NCM for FRPs. This paper addresses three types of representative NCMs: laser beam machining, rotary ultrasonic machining, and abrasive water jet machining. Each NCM is classified and systematically reviewed using a parametric study, mechanistic model, and numerical simulation. In addition, further studies on the NCM of FRPs are suggested.
The application of polymer-based composite materials as bearing liner materials into eco-friendly water lubrication has received considerable attention owing to their superior tribological behaviors, corrosion resistance, and high damping characteristics, and its design flexibility can improve the bearing performances in response to the distribution of lubricant film pressure based on the regulation of elastic constants. However, the low viscosity and high density of water essentially cause thin-filmed lubrication accompanied by a low load-carrying capacity. Particularly, a high rotational speed enhancing the wedge effect induces turbulence and considerable inertial effect. Moreover, substantial elastic deformation of the composite bearing liners alters the formation of the lubricant film. In this study, we analyze a water-lubricated composite journal bearing system incorporating the turbulence, inertial effect, and elastic deformation of the bearing liner. Reynolds equation was modified considering the turbulence and inertial effect. The elastic deformation of the composite bearing liner was determined by solving the constitutive equation. The Reynolds equation and the constitutive equation were solved via the finite difference method and finite element method, respectively. In addition, the analytical relation for the elastic deformation was derived that suitably eliminated the requirement of solving the constitutive equation. With the introduction of the primary parameters, Sommerfeld number, Reynolds number, and deformation coefficient, the relation of the normalized minimum film thickness with respect to the parameters was modeled based on the Gaussian regression model. Accordingly, we proposed the new optimal maximum load-carrying capacity boundaries which narrowed down the operating region compared to conventional boundaries.
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