Glasses material removal mechanisms

Ultraprecision Grinding, Fig. 1 Material removal mechanism in grinding of glass... 

Material Removal Mechanisms in Grinding of Ceramics and Glasses... 

The material removal mechanism of the CMP process was relatively well explained by the previous scientists. The material removal mechanism of dielectric CMP is further well explained by Cook in his paper pubhshed in 1990 [7]. It was explained that the rate of mass transportation during glass pohshing is determined by five factors the rate of water diffusion into the glass surface, the dissolution of the glass under the applied load, the adsorption rate of the dissolved material onto the abrasive surface, the redeposition of the dissolved material onto the surface of the work piece, and the aqueous corrosion between particle impacts. Water diffuses into sUoxane bonding (Si—O—Si) and the diffusion rate is controlled by multiple process conditions such as pressure or temperature. This hydrated oxide surface is removed by an abrasion process. The indentation process by each abrasive was modeled by Hertzian contact and their contact stress was calculated from the theory of elasticity. 

The difference between this technique and GC or HPLC is that the separation process occurs on a flat essentially two-dimensional surface. The separated components are not usually eluted from the surface but are examined in situ. Alternatively, they can be removed mechanically for further analysis. In thin-layer chromatography (TLC), the stationary phase is usually a polar solid such as silica gel or alumina which is coated onto a sheet of glass, plastic, or aluminium. Although some moisture is retained by the stationary phase, the separation process is predominantly one of surface adsorption. Thin layers are sometimes made from ion-exchange or gelpermeation materials. In these cases the sorption process would be ion-exchange or exclusion. 

Powder blasting, or abrasive jet machining, is a technique in which a particle jet (typically A1203 particles of 3-30 lm) is directed towards a target for mechanical material removal. It is a fast (typically, 500 pm depth in 20 minutes), inexpensive, and accurate directional etch technique for brittle materials like glass, silicon, and ceramics. For complex and small structures a mask can be used. 

The shapes depicted in Fig. 5.8a-c are typical for microholes obtained by drilling at high depth or, more generally, when melting is the dominant mechanism for material removal. These effects are not restricted to glass but are also observed in other materials such as ceramics [104]. 

K. Allesu, A. Ghosh, M.K. Muju Preliminary qualitative approach of a proposed mechanism of material removal in electrical machining of glass. European Journal Mech. Eng. 36 (1992), p. 202. 

As conditioning is primarily considered as a mechanical process characterized by a two-body abrasive wear mechanism [8], the classical Preston equation [62], originally used to model polishing of glass, has been widely used to describe material removal (polishing) rate in [61]. Considering the similarity between wafer—pad interaction and pad—conditioner interaction, the Preston s equation has been adopted by many to model pad wear caused by conditioning. The Preston equation states that MRR is proportional to the applied pressure P and the relative velocity V between the wafer and the pad and Kp is a constant, called Preston s coefficient. 

For brittie materials such as glass, the surface removal mechanism is different. Impact by particles causes micro hractures in the surface and as ftnctures increase in numbers they grow together and produce chips, as shown in Fig. 2. 

To isolate the product, the tube is opened with a glass cutter and the material is mechanically removed from it and ground into powder using a mortar and pestle inside a nitrogen-filled glovebox. The air-sensitive black powder is stored in a vial with a screwcap and can be used in the same manner as for the following syntheses. This is PaSes in composition only. It is probably a mixture of various binary P/Se compounds, most of them amorphous. The actual phase composition is not important since it is used only as starting material. 

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