An experimental investigation on the effect of nanopowder for micro-wire electro discharge machining of gold coated silicon

Micro Wire Electro Discharge Machining (μ-WEDM) is a type of electro-discharge machining (EDM) process where the wire is used instead of a rigid tool. It is a reliable and precise machining process, which is commonly used to produce various complex structural shapes for a wide range of industrial applications. However, to machine a semiconductor material of high resistivity like silicon (Si) requires more advanced processing to produce larger electrical sparks during the μ-WEDM operation. Current (μ-WEDM) technology is not enough to realize a stable machining environment for Si. In this research, a new type of μ-WEDM process for Si machining was investigated. At first, Si was temporarily coated with gold and then nanopowder mixed dielectric medium was used for the WEDMing process. The main purpose of this work is to investigate the effects of different nanopowder concentrations on two important response factors such as material removal rate (MRR) and spark gap (SG). In this regard, the μ-WEDMing of gold coated silicon was carried out in pure dielectric EDM oil and also in three different concentrations (0.1g/L,1g/L,2g/L) of nanopowder mixed dielectric oil to conduct an initial study with the aim to achieve better machining accuracy and stability. Based on the experimental investigations, the MRR were found to be increased on average minimum ∼ 1% to maximum ∼ 33% respectively for different carbon concentrations, as compared to machining in the pure dielectric medium. The spark gap was also observed to be increased by a significant margin on average of ∼ 2% to up to ∼ 159% than without using any nanopowder concentration, correspondingly

An enhanced distance-dependent electric field model for contact-separation triboelectric nanogenerator: Air-breakdown limit as a case study

Theoretical models have been proposed to bring an in-depth understanding of the working mechanisms of triboelectric nanogenerators (TENGs), aiming to enhance their output performance. This work proposes an enhanced distance-dependent electric field (EDDEF) model to predict triboelectric characteristics of TENGs more accurately. The model bridges the gap between the distance-dependent and distance-independent electric field models in terms of open-circuit (OC) voltage (VOC), short-circuit (SC) voltage (Vgap,SC), and SC surface charge density (σSC) at small separation distances by developing more accurate mathematical formulations of the electric potential. The EDDEF model was validated by finite element modeling (FEM) simulation. It introduced an accurate theoretical analysis of the air-breakdown boundary under the OC condition for the first time. The maximum surface charge density that can be obtained without air breakdown was predicted to be lateral sizedependent. It shows a monotonical decrease from 51.94 to 33.59 µC/m2 with a lateral size increase from 0.5 to 10 cm. Meanwhile, the corresponding separation distance increased from 0.915 to 12.48 mm, suggesting that improving CS-TENG’s performance by boosting the surface charge density is more effective at smaller lateral sizes and shorter separation distances. These findings serve as a guide towards the miniaturization of highly efficient CS-TENG technology. In addition, under SC condition, the EDDEF model showed great consistency with the distance-independent model in predicting the air-breakdown limit, supporting the distance-independent model applicability for predicting the air-breakdown under the CS conditionThis work was sponsored by Universiti Teknologi Malaysia under Professional Development Research University Fund R.J130000.7113.06E14 and UTM Fundamental Research Grant Q.J130000.3823.22H55 .Scopu