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Characterization of Glass Delamination


Table 1 : Comparison of SEM and TEM results for characterization of particulate from liquid samples suspected to contain glass delamination fl akes. SEM and TEM samples were simultaneously prepared on the same filter.


Sample A


B C D


Figure 2 : TEM/EDS spectrum from glass delamination fl ake on copper grid, clearly showing peaks for major, minor, and trace glass components.


and syringes [ 3 ]. Such samples are usually electron-transparent as isolated and require no further thinning, particularly when analysis is done in a 200–300 kV materials science TEM. A representative TEM spectrum acquired from a glass delami- nation fl ake displays major silicon and oxygen peaks, as well


Vial 1 SEM


No flakes observed


No flakes observed


13 glass flakes observed


No flakes observed


Vial 1 TEM


Two delamination flakes


Two delamination flakes


One large delamination flake


A few C-rich particles, two possibly graphite


as peaks for minor and trace elements that can aid in identifi - cation of specifi c glass formulations ( Figure 2 ). Though the TEM is ideal for characterization of these very thin samples, transfer of flakes and residues from filters to TEM grids can be challenging. A method has been developed whereby filtration of liquid products directly onto holey carbon-coated TEM grids captures a sufficient amount of representative material to identify particulate isolated from liquid products.


Figure 3 : (a) Holey carbon-coated TEM grid positioned on polycarbonate fi lter. (b) Dropwise application of liquid to TEM grid on fi lter. (c) Polycarbonate fi lter transferred to Petri dish and viewed with light microscope for removal of grid. (d) TEM grid and fi lter for SEM examination prepared from the same fi ltration.


38


Materials and Methods Filtrations were carried out in a hood in an ISO Class 5 cleanroom, which provided a particle-free environment for sample preparation. To prepare blank grids and samples from liquids suspected to contain glass delamination flakes, a holey carbon-coated 3 mm TEM grid was positioned off -center on a PC filter placed on a fritted surface on a standard filtration apparatus ( Figure 3a ). Liquid was applied drop- wise to the grid and to the center of the fi lter ( Figure 3b ). When fi ltration was complete, the PC filter was carefully liſt ed off of the fritted fi lter and placed in a disposable Petri dish. While observing under a light microscope, the grid was picked up from the fi lter using forceps and transferred to a storage capsule ( Figure 3c ). Using this procedure, samples suitable for both SEM and TEM analysis were prepared simultaneously ( Figure 3d ). Blank samples were prepared using particle-free water to ensure that no particulate observed on TEM grids prepared by this method had come from the cleanroom environment or any equipment used for the fi ltration. As-received grids were also examined for background particulate. TEM grids


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