Methods for forming nanotube fabrics with controlled surface roughness and degree of rafting
Methods for forming a nanotube fabric with a controlled surface roughness (or smoothness) and a selected degree of rafting are disclosed by adjusting the concentration levels of a selected ionic species within a nanotube formulation used to form the nanotube fabric. In one aspect, the present disclosure provides a nanotube formulation roughness curve (and methods for generating such a curve) that can be used to select a utilizable range of ionic species concentration levels that will provide a nanotube fabric with a desired surface roughness (or smoothness) and degree of rafting. In some aspects of the present disclosure, such a nanotube formulation roughness curve can be used adjust nanotube formulation prior to a nanotube formulation deposition process to provide nanotube fabrics that are relatively smooth with a low degree of rafting.
1. A method of forming a nanotube fabric, comprising:
suspending a volume of nanotubes within a liquid medium;
processing and purifying said suspension of nanotubes to realize a nanotube formulation;
selecting at least one ionic species to use within said nanotube formulation;
selecting at least one of a surface roughness threshold and a degree of rafting threshold for said nanotube fabric;
characterizing said nanotube formulation and using said nanotube formulation
characterization to select a target concentration level for said at least one ionic species within said nanotube formulation;
adjusting said nanotube formulation to form an adjusted nanotube formulation that includes said selected at least one ionic species at said target concentration level; and
depositing said adjusted nanotube formulation via a spin coating operation to form a nanotube fabric.
2. The method of claim 1 wherein said nanotubes within said volume of nanotubes have at least one preselected parameter.
3. The method of claim 2 wherein said at least one preselected parameter includes at least one of length, length distribution, degree of straightness, nanotube wall type, chirality, and functionalization.
4. The method of claim 3 wherein said nanotube wall type is one of singled walled, doublewalled, multi-walled, or a preselected mixture thereof.
5. The method of claim 1 wherein said nanotubes are carbon nanotubes.
6. The method of claim 1 wherein said nanotube formulation characterization includes defining a utilization range of concentration levels for said at least one selected ionic species.
7. The method of claim 6 wherein said utilization range corresponds to desired characteristics within said nanotube fabric.
8. The method of claim 7 wherein said desired characteristics include at least one of surface roughness and degree of rafting.
9. The method of claim 8 wherein said desired characteristics include a surface roughness less than a preselected threshold value.
10. The method of claim 8 wherein said desired characteristics include a degree of rafting less than a preselected threshold value.
11. The method of claim 1 wherein said at least one ionic species is selected from the list consisting of ammonium salts, nitrate salts, ammonium nitrate salts, ammonium formate, ammonium acetate, ammonium carbonate, ammonium bicarbonate, ionic organic species, ionic polymers, and inorganic salts.
12. The method of claim 1 where said at least one ionic species includes a cation component selected from the list consisting of ammonium, tetraalkylammoniums, acids of primary aliphatic amines, acids of secondary aliphatic amines, acids of tertiary aliphatic amines, acids of cylic amines, cylic aromatic quaternary amines, and phosphorus-based ions.
13. The method of claim 1 where said at least one ionic species includes an anion component selected from the list consisting of soluble organic acid bases, simple soluble aliphatic carboxylic acids, complex organic acids, nitrate, phosphate, sulfate, and carbonate.