CNTs, online size characterization

To test this approach to online size characterization of CNTs, multi wall carbon nanotubes (MWNTs) ranging from 10 to 100 nanometers in diameter and 0.5 to 40 trm in length with a purity of 95% were aerosolized and the DMA was used to size-select CNTs by their electrical mobility. These CNTs were subsequently collected directly onto TIM grids using an electrostatic sampler. Transmission electron microscopy was used to determine the dimensions of the carbon nanotubes. These dimensions were then used to test the methodology, and the results are presented in Section 9.3.5. 

Experimental Results for Online Size Characterization of CNTs... 

As demonstrated above, the DMA is capable of online size classification of nanotubes and nanoflbers. Therefore, in addition to providing information about number concentration and catalyst impurities, the DMA can provide information about the physical size of the nanotubes. Once classification is achieved, online size characterization is possible using electrical mobility theory and the charge parameter, f, described above. To test the methodology, CNTs were classified by their electrical mobility with a DMA and the actual dimensions of the classified particles were measured by TEM. Table 9.1 lists the voltages used to collect the nanotube samples. Also listed are the corresponding spherical mobility diameters calculated using Eq. (30). 

To rapidly evaluate the effects of process variables, online characterization of size, number concentration, and purity of carbon nanotubes is needed, and in this section we describe such an approach, wherein a DMA is employed. As noted in Section 9.2.2, the DMA is capable of online classification of fibers [42,44,45]. In addition, Maynard et al. have classified nanotubes using the DMA, although a method for determining CNT size was not explicitly developed [67]. 

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