Raman Mapping of the Indentation‐Induced Densification of a Soda‐Lime‐Silicate Glass

Abstract

Micro-Raman spectroscopy was used to map the Vickers indentation-induced densification on a window glass (soda-lime silicate glass), from the correlation between Raman spectrum and density. Both top surface and cross-section of the residual imprints were investigated. It is shown that the sample preparation needed for the investigation of the in-depth densification does not alter the results. The maximum densification ratio measured is about 3.8%, which is 60% of the maximum densification measured after a high-pressure hydrostatic loading. Within the experimental errors, densification maps are self-similar for the two indentation loads used 10 N and 20 N. A comparison with finite element results based on a constitutive model developed for silica is discussed.

A Raman-spectroscopic study of indentation-induced structural changes in technical alkali-borosilicate glasses with varying silicate network connectivity

“…increasing number of NBOs at silicate sites in the order KBS b NABS b NBS1 b NCS, glass deformation by densification becomes progressively less pronounced as shear-driven deformation evolves as the dominant mechanism and becomes mostly pronounced for glass NCS. Silicate glasses with a composition similar to NCS have a higher packing density than SiO 2 glass [7,[59][60][61], a fact contributing also to the smaller tendency toward deformation by densification, which is in good agreement with the present results.…”

“…According to the literature glasses similar to NCS are expected to show no microcracks under 100 mN, and in some cases also 500 mN [4,60], and shear flow is the prime cause of deformation [58,73]. This seems to be also the dominating mechanism at low pressures, whereas at higher loads (N10 N) shearing and densification compete with each other [7,59,73]. The main reason for this response is that the high NBO content creates an open network with weak points which favor shear flow under pressure, while the network modifiers at the same time decrease the compressibility in comparison to silica glass [74,75].…”

“…SiO 2 , soda-lime silicate and borosilicate glasses have been studied by several groups to establish calibration curves between applied pressure and the Raman spectra in order to quantify the local densification in glasses after indentation [7][8][9][60][61][62][63][64][65][66][67]. For silica glass, for example, the shift of the 430-490 cm −1 peak was correlated directly to glass densification caused by structural rearrangements as revealed by both, in-situ and ex-situ Raman measurements.…”

“…However, the prediction of the material response to deformation is a key factor in designing new compositions with improved properties. In this context, studies of vitreous silica and soda-limesilicate glasses by spectroscopic and numerical methods revealed significant structural changes under hydrostatic pressure as well as under indentation [4][5][6][7][8][9][10][11]. Structural studies on the indentation response of the important group of borosilicate glasses concentrated so far on technical low-alkaline borosilicate glasses such as the "Pyrex" or "Duran"-type glasses [12][13][14][15][16][17].…”

Competing Indentation Deformation Mechanisms in Glass Using Different Strengthening Methods

“…Emerging demand for stronger and lighter car windshields and other novel transparent structural materials further stimulates a need for deeper understanding and improvement of glass strengthening techniques. Studies of contact cracking (Lawn and Wilshaw, 1975;Ostojic and McPherson, 1987;Cook and Pharr, 1990) date back at least one century (Johnson, 1985;Lawn, 1998) and tremendous progress has been achieved to understand the shear flow, densification, and cracking under indentation in brittle solids (Lawn and Swain, 1975;Lawn and Wilshaw, 1975;Marshall and Lawn, 1978;Hagan, 1979;Lawn et al, 1983;Johnson, 1985;Ostojic and McPherson, 1987;Cook and Pharr, 1990;Lawn, 1998Lawn, , 2004Perriot et al, 2006;Gross and Tomozawa, 2008a,b,c;Gross et al, 2009;Kato et al, 2010;Gross, 2012a;Kassir-Bodon et al, 2012;Niu et al, 2012;Tran et al, 2012;Kjeldsen et al, 2013;Smedskjaer et al, 2013;Striepe et al, 2013b;Aakermann et al, 2015;Rouxel and Yokoyama, 2015). It is commonly believed that the surface strengthening against contact cracking comes from the linear superposition of a compressive stress (CS) profile onto the surface of the glass (Marshall and Lawn, 1978;Lawn and Fuller, 1984).…”