Study on surface integrity and ductile cutting of PV polycrystalline silicon and wear mechanisms of electroplated diamond wire

Abstract

This study aimed to evaluate and better understand the mechanical and crystalline responses of polycrystalline silicon sawn by diamond wire sawing. To simplify the multi-wire sawing kinematic, an endless wire saw with a single looped diamond wire was used. The wire cutting speed and feed rate of the sawing process were varied in order to evaluate the characteristics of sawn surface morphology, surface roughness and subsurface damage. The analysis of brittle-ductile transition and residual stress of the sawn surface and silicon chips were performed with Raman spectroscopy. The wear and failure mechanism of the diamond wire were analyzed. The results show that sawn surface is composed of brittle and ductile regions and the predominance of one of these directly affected the surface roughness R a . The ductile cutting mode induced the predominance of microgrooves and ploughing over the sawn surface and led to formation of an amorphous layer with residual compressive stress of up to -192.3 MPa. Micro-cracks in subsurface were identi ed and it reached a minimum depth of 7.2±1.6 µm.Chip fragments and elongated chips were observed and Raman spectra showed that the latter are amorphous. The wire wear analysis indicated that during the cutting there is deformation of the Ni-layer, exposed grits and grit pullout. The main wear mechanisms are Ni-matrix removal and abrasive wear of the diamond grit. A better surface quality of polycrystalline silicon was obtained on increasing wire cutting speed and decreasing feed rate. The results found in this study can help to reach a high quality surface of silicon wafer for photovoltaic application. HighlightsAnisotropy of poly-Si induces to sawn surface composed of brittle and ductile regions and it affected the surface roughness Ductile cutting leads to surface formation with amorphous phases and residual compressive stress On increasing wire cutting speed and decreasing feed rate was obtained a minimum micro-crack depth Chip fragments and elongated chips were observed and Raman spectra showed that the latter are amorphous Wear mechanisms of the diamond wire were Ni-matrix deformation and removal, abrasive wear and grits pullout

Influence of Diamond Wire Saw Processing Parameters on the Sawn Surface Characteristics of Silicon Nitride Ceramics

“…Qiu et al [ 18 , 19 ] found that increasing the saw wire speed and decreasing the feed rate are beneficial for improving the sawing performance and reducing the surface roughness of photovoltaic silicon wafers in multi-wire cutting. Costa et al [ 20 ] found a similar pattern of effects when cutting polysilicon. Huang et al [ 21 ] found that increasing the wire speed can increase the proportion of material ductile domain removal on the slice surface and reduced the slice surface waviness period.…”

“…The materials processed are mainly focused on silicon crystals. It was found that wire saw cutting parameters have a significant effect on as-sawn slice surface properties [ 16 , 17 , 18 , 19 , 20 , 21 ]. Yin et al [ 16 ] and Liu et al [ 17 ] found that high wire speeds and low workpiece feed speeds resulted in a better slice-surface quality in their experiments of cutting polysilicon using diamond saw wires with different diameters.…”

Meso-scale energy harvester: a comparison between MEMS and micromachined designs

“…The MEMS device was fabricated using the PiezoMUMPs 22 process. Whereas, the MM prototype was made with STEMINC's SMBA4510T05M bimorph and cut using an endless diamond wire saw 23,24 with a costume-made fixture to hold the bimorph. Two steel seismic masses were machined to match the natural frequency of the prototype that used a tungsten mass because no other dense material was available during the period of the fabrication.…”

Experimental research on the non-uniform wear of the carbon strip of the metro pantograph

“…In general, electric locomotives exhibit environmental protection, high efficiency, and energy conservation, which are beneficial for urban rail transit development. [1][2][3] In terms of power supply, the pantograph catenary system is widely used at this stage to provide electric energy for vehicles-a high-voltage catenary system is established, the pantograph above the vehicle contacts the catenary, and the electric energy is transmitted from the catenary to the pantograph and finally to the metro vehicle motor to convert electric energy to kinetic energy. 4 The normal operation of vehicles is strongly dependent on the current collection quality of the pantograph given its key role as functional equipment of metro vehicles.…”