Process for producing humic acid-derived conductive foams

1. A process for producing a humic acid-derived foam, said process comprising:

(a) preparing a humic acid dispersion having multiple humic acid molecules or sheets dispersed in a liquid medium, wherein said humic acid is selected from a group consisting of fluorinated humic acid, chlorinated humic acid, brominated humic acid, iodized humic acid, and a combination thereof and wherein said humic acid has a content of non-carbon elements no less than 5% by weight and said dispersion contains a blowing agent having a blowing agent-to-humic acid weight ratio from 0/1.0 to 1.0/1.0;

(b) dispensing and depositing said humic acid dispersion onto a surface of a supporting substrate to form a wet layer of humic acid;

(c) partially or completely removing said liquid medium from the wet layer of humic acid to form a dried layer of humic acid; and

(d) heat treating the dried layer of humic acid at a first heat treatment temperature from 80° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from said non-carbon elements or to activate said blowing agent for producing said humic acid-derived foam which is composed of multiple pores and pore walls and has a physical density from 0.005 to 1.7 g/cm 3 and a specific surface area from 50 to 3,200 m 2 /g, wherein said pore walls contain single-layer or few-layer humic acid-derived hexagonal carbon atomic planes or sheets merged together in an edge-to-edge manner, said few-layer hexagonal carbon atomic planes or sheets have 2-10 layers of stacked hexagonal carbon atomic planes having an inter-plane spacing d 002 from 0.3354 nm to 0.60 nm as measured by X-ray diffraction, and said single-layer or few-layer hexagonal carbon atomic planes contain 0.01% to 25% by weight of non-carbon elements.

2. The process of claim 1 , wherein said dispensing and depositing procedure includes subjecting said humic acid dispersion to an orientation-inducing stress.

3. The process of claim 1 , further including a step of heat-treating the humic acid-derived foam at a second heat treatment temperature higher than said first heat treatment temperature for a length of time sufficient for obtaining a graphitic foam wherein said pore walls contain stacked hexagonal carbon atomic planes having an inter-planar spacing d 002 from 0.3354 nm to 0.36 nm and a content of non-carbon elements less than 2% by weight.

4. The process of claim 1 , wherein said blowing agent is a physical blowing agent, a chemical blowing agent, a mixture thereof, a dissolution-and-leaching agent, or a mechanically introduced blowing agent.

5. The process of claim 1 , which is a roll-to-roll process wherein said steps (b) and (c) include feeding said supporting substrate from a feeder roller to a deposition zone, continuously or intermittently depositing said humic acid dispersion onto said surface of said supporting substrate to form said wet layer of humic acid thereon, drying said wet layer of humic acid to form the dried layer of humic acid, and collecting said dried layer of humic acid deposited on said supporting substrate on a collector roller.

6. The process of claim 1 , wherein said first heat treatment temperature is from 100° C. to 1,500° C.

7. The process of claim 3 , wherein said second heat treatment temperature includes at least a temperature selected from the group consisting of (A) 300-1,500° C., (B) 1,500-2,100° C., and (C) 2,100-3,200° C.

8. The process of claim 3 , wherein said second heat treatment temperature includes a temperature in the range of 300-1,500° C. for at least 1 hour and then a temperature in the range of 1,500-3,200° C. for at least 1 hour.

9. The process of claim 3 , wherein said non-carbon elements include an element selected from the group consisting of oxygen, fluorine, chlorine, bromine, iodine, nitrogen, hydrogen, and boron.

10. The process of claim 3 , wherein said a step of heat treating the dried layer of humic acid at said first heat treatment temperature is conducted under a compressive stress.

11. The process of claim 1 , further comprising a compression step to reduce a thickness, a pore size, or a porosity level of said foam.

12. The process of claim 3 , wherein said first and/or second heat treatment temperature contains a temperature in the range of 300° C.-1,500° C. and the foam has an oxygen content or non-carbon content less than 1%, and pore walls having an inter-planar spacing less than 0.35 nm, a thermal conductivity of at least 250 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 2,500 S/cm per unit of specific gravity.

13. The process of claim 3 , wherein said first and/or second heat treatment temperature contains a temperature in the range of 1,500° C.-2,100° C. and the foam has an oxygen content or non-carbon content less than 0.01%, pore walls having an inter-planar spacing less than 0.34 nm, a thermal conductivity of at least 300 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 3,000 S/cm per unit of specific gravity.

14. The process of claim 3 , wherein said first and/or second heat treatment temperature contains a temperature greater than 2,100° C. and the foam has an oxygen content or non-carbon content no greater than 0.001%, pore walls having an inter-planar spacing less than 0.336 nm, a mosaic spread value no greater than 0.7, a thermal conductivity of at least 350 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 3,500 S/cm per unit of specific gravity.

15. The process of claim 3 , wherein said first and/or second heat treatment temperature contains a temperature no less than 2,500° C. and the foam has pore walls containing stacked hexagonal carbon planes having an inter-planar spacing less than 0.336 nm, a mosaic spread value no greater than 0.4, a thermal conductivity greater than 400 W/mK per unit of specific gravity, and/or an electrical conductivity greater than 4,000 S/cm per unit of specific gravity.

16. The process of claim 1 , wherein said humic acid-derived foam has a density from 0.005 to 1.7 g/cm 3 , a specific surface area from 50 to 3,200 m 2 /g, a thermal conductivity of at least 100 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 500 S/cm per unit of specific gravity.

17. The process of claim 3 , wherein said humic acid-derived foam has a density from 0.005 to 1.7 g/cm 3 , a specific surface area from 50 to 3,200 m 2 /g, a thermal conductivity of at least 100 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 500 S/cm per unit of specific gravity.

18. A process for producing a fluorinated humic acid-derived foam, said process comprising:

(a) preparing a humic acid dispersion having multiple fluorinated humic acid molecules or sheets dispersed in a liquid medium, and wherein said dispersion contains an optional blowing agent having a blowing agent-to-fluorinated humic acid weight ratio from 0/1.0 o 1.0/1.0;

(b) dispensing and depositing said fluorinated humic acid dispersion onto a surface of a supporting substrate to form a wet layer of fluorinated humic acid;

(c) partially or completely removing said liquid medium from the wet layer of humic acid to form a dried layer of fluorinated humic acid; and

(d) heat treating the dried layer of fluorinated humic acid at a first heat treatment temperature from 80° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from non-carbon elements or to activate said blowing agent for producing said fluorinated humic acid-derived foam, which is composed of multiple pores and pore walls, wherein said pore walls contain single-layer or few-layer fluorinated humic acid-derived hexagonal carbon atomic planes or sheets merged together in an edge-to-edge manner, said few-layer hexagonal carbon atomic planes or sheets have 2-10 layers of stacked hexagonal carbon atomic planes having an inter-plane spacing d 002 from 0.3354 nm to 0.60 nm as measured by X-ray diffraction, and said single-layer or few-layer hexagonal carbon atomic planes contain 0.01% to 25% by weight of non-carbon elements.