Tham khảo tài liệu 'nanofibers part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 290 Nanofibers Time 5min 30min 1hr 2 hr 4hr 8hr 24hr 48 hr 96 hr Low q Rg bm P G 106 B High q Rg bm P G 108 B Table 4. Guinier radii and exponents as a function of time for plasma-treated carbon nanofibers. Fig. 22. Evolution of the light scattering profile of plasma-treated nanofibers in water for four days following dispersion by sonication. The suspensions were sonicated at 10W for five minutes before the observations began. The measurements were taken in the batch mode. The scattering curves consist of two power-law regimes and two Guinier regimes that define two length scales . Each Guinier regime is followed by a quasi power-law regime. The curves were fit using Beaucage s Unified Model to extract Rg the power-law exponents P and the Guinier prefactors G and power-law prefactor B associated with each length scale. Morphology and Dispersion of Pristine and Modified Carbon Nanofibers in Water 291 These parameters are displayed in Table 4 for the two structural levels. The high q data share similarity with that for the untreated sample. These data imply minimal change in morphology with time on length scales below 1 pm. The decrease in the scattered intensity at low q up to 10 hours is pronounced and ascribed to precipitation. After 10 hr however the large-scale agglomerates gradually form. Figure 23 compares the scattering profile for plasma-treated and as-purchased carbon nanofibers PR19HT at 10 hr after sonication. Compared to the untreated sample the intensity at low q G for the treated sample is much smaller indicating small entities in the suspension. The extracted length scale Rg at 10 hr pm .
