Track etch ratio

The requirement for use of these membranes as templates is to have high track etch ratios. For PC, track etch ratios above ten thousand have been observed. At the other extreme, addition of solvents, such as methanol, ethanol or propanol can dramatically decrease the track etch ratio, down to 2 to 4 in the case of PET. Although they accelerate the etching process, polymers like PMMA are generally etched with an acidic medium leading to very low etch track ratios 1-10. In a recent study on the polymer polyallyl diglycol carbonate (PADC) [9] it was found that etch-rate values of the PADC increase nearly fourfold if the polymer is irradiated with 100 Mrad dose of electrons at 2 MeV prior to the heavy ion irradiation. The etch tracks were created by 140 MeV Si ions. 

Some of the reported ISP-MS applications to radionuclide determination are presented next. Kim et al. (1989a) measured the Pu/ Pu ratio in two soils and an estuary silt after performing radiochemistry. They also measured this ratio in these soils by the fission track-etch technique and found that ICP-MS gave better precision. They... 

Two types of track-etch monitor occur, open and closed types. In the open type, the SSNTD is not contained in a volume and is exposed to the air as a bare foil. This detector will register the alpha radiation from the Rn and RnD in the air, and the track density on the foil represents the sum of these activities. However, the Rn signal will be much larger than the signal from the RnD, except at very high levels of RnD (high F factor), and the track density has to be interpreted in terms of this ratio, which is typically unknown. In close monitors the SSNTD is enclosed in a closed container into which Rn diffuses through a filter. This prevents the entry of RnD and dust particles into the chamber, and the foil is then sensitive only to the alpha radiation from Rn and RnD formed in the container. There is a repeatable equilibrium between the isotopes in the container, and calibration provides the relationship between the Rn concentration and the track density on the foil. A typical track-etch radon monitor of the closed type is shown in Fig. 9.27. 

The fact that ALD is based on a self-terminating gas-solid reaction yielding excellent deposition conformality aliows to coat high aspect ratio nanostructures, including colloidal arrays, anodized alumina and track etched poly(carbonate) membranes [19, 20]. 

Fig. 31 Comparison of the swelling ratio of poly(allylamine hydrochloride)/poly(sodium-4-styrenesulfbnate) multilayers a on a planar Si substrate (determined by in-situ ellip-sometry) and b in the cylindrical pores of a 800 nm pore track-etched PC membrane. The filled circles and open diamonds represent data generated after a pH 10.5 pretreatment and after a pH 2.5 pretreatment, respectively. Reproduced from [252]. (2006) American Chemical Society...

Track-etched polymer membranes, which have straight cylindrical pores that are oriented normal to the plane of the membrane, provide a promising platform to design membranes with nano-domains with high aspect ratios oriented in the desired direction. Presently, track-etched membranes are commercially available in polyester and polycarbonate with various thicknesses (6 pm or above), pore sizes (10 nm to microns), and porosities ( 0.05% to... 

Swift heavy ion beams with extremely high LETs are used to degrade strongly polymer chains within tracks over a range of a few tens of micrometers. After irradiation, the top surface of bulk thermoplastics such as polyethyleneterephtalate, polycarbonate, polyvinylidene fluoride or polyimide materials as well as thin films made of the same material are subsequently etched by a wet chemical treatment that reveals pores of which the shape, surface density and dimensions can be controlled by choosing appropriate conditions. High aspect ratio cylindrical or conical traces of diameter ranging from a few nanometers to some... 

From the standpoint of nanostructuring, ion track membranes are unique in that every track can be seen as an individual nanostructure with an extreme aspect ratio The length of the channel is usually in the 10- to lOO-pm range and spans the whole thickness of the exposed film. The width of the channels, typically in the range of 100 nm to several micrometers, is defined by the ion and its energy as well as the etching parameters after ion bombardment. Furthermore, the polymer and the process parameters influence the exact shape of the channel formed [38]. 

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