(Color online) Example of an uncoated nylon nanofiber sample mounted on a cardstock frame using double sided Kapton tape prior to stress–strain testing.
(Color online) Schematic of the home built hot-wall viscous flow reactor used to coat the nylon nanofibers.
(Color online) Film thickness vs ALD cycle number for the silicon wafer monitors coated at a deposition temperature of (a) 105 °C and (b) 50 °C. Thewafers were placed in the reactor while the nanofibers were being coated to monitor film growth.
Representative SEM images showing the morphology of (a) uncoated nylon nanofibers, approximately 200 nm in diameter with smaller nanofibrils dispersed throughout the mat. The morphology of the nanofibers was not changed after coating with either 100 cycles of (b) Al2O3, (c) ZnO, (d) TiO2 using TiCl4/H2O, or (e) TiO2 using TIP/H2O. The nanofibrils are more apparent after Al2O3 and TiO2 via TiCl4/H2O.
Cross-sectional TEM images of nylon nanofibers that were (a) and (b) uncoated, (c) and (d) coated using 200 cycles of TiCl4/H2O, and (e) and (f) coated using 200 cycles of TIP/H2O. All coatings were performed at 50 °C. The uncoated nanofibers show little TEM contrast relative to the epoxy, whereas there is a clearly defined shell around the titania coated nanofibers. The film is very uniform on the TiCl4/H2O coated fibers, but coating is thinner and less well-defined for the TIP/H2O process.
(Color online) FTIR difference spectra of the titanium dioxide coated nylon nanofibers for coating using (a), (c) TiCl4/H2O and (b), (d) TIP/H2O. Spectra in (a) show TiO2 modes after ∼100 TiCl4/H2O cycles, whereas spectra in (b) show minimal TiO2 features after 400 cycles of TIP/H2O. Under a more magnified absorbance scale in (c) and (d), TiO2 features become apparent for TIP/H2O samples.
(Color online) (a) XPS survey scan for uncoated nylon shows oxygen, nitrogen, and carbon signals. After 100 cycles of TiCl4/H2O, only trace amount of nitrogen are detected, whereas a nitrogen peak is still visible for the TIP/H2O sample. (b) and (c) show the atomic percentages based on film thickness for titanium and oxygen for TiCl4/H2O and TIP/H2O samples, respectively.
(Color online) Stress–strain data from one representative nylon nanofiber sample coated with titanium dioxide using (a) TiCl4/H2O, (b) TIP/H2O, (c)aluminum oxide, and (d) zinc oxide. The initial slope of the stress–strain curves increase with increasing cycle numbers for the samples coated with either (a) TiCl4/H2O or (c) aluminum oxide, indicating more ceramic behavior. The (b) TIP/H2O and (d) zinc oxide coated samples show properties similar to the uncoated nylon nanofibers even at higher cycle number.
(a) Ultimate strain and (b) Young's Modulus vs cycle number for nylon nanofibers coated with TiCl4/H2O and TIP/H2O ALD at 105 °C (solid symbols) and 50 °C (open symbols), as well as results from nylon coated with ALD Al2O3 and ZnO at 105 °C. As the number of ALD cycles increases, the ultimate strain decreases and Young's Modulus increases for the aluminum oxide and TiCl4/H2O coated samples, consistent with increased brittleness. The TIP/H2O and zinc oxide samples show trends similar to the uncoated nylon nanofibers.
Dosing and purging times used to coat the nylon nanofibers samples for aluminum oxide, zinc oxide, and titanium dioxide coatings.
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