Process and apparatus for carbon nanotube formation

A process for forming carbon nanotubes, the process comprising:

• introducing a first aqueous solution to a pressure-controlled system, the pressure-controlled system comprising a silanated glass element, a porous membrane, and a container;
• applying a pressure to the pressure-controlled system to draw the first aqueous solution from the silanated glass element, through the porous membrane, and to the container at a flow rate to form a filtrate disposed within the container and a retentate disposed above the porous membrane, the retentate comprising carbon nanotubes;
• changing the pressure of the pressure-controlled system, comprising:
• optically detecting a position of a meniscus of the first aqueous solution in the silanated glass element with an optical device;
• measuring the flow rate, a height of the meniscus, or both;
• and
• determining a pressure based on the measured flow rate, the position of the meniscus, or both;
• and
• forming carbon nanotubes on the porous membrane.

An apparatus, comprising:

• a membrane defining a retentate side and a filtrate side;
• a container on the filtrate side of the membrane;
• a pressure source coupled to the container;
• and
• a silanated glass element coupled to the container, wherein at least a portion of the silanated glass element is on the filtrate side of the membrane, and wherein the silanated glass element has a meniscus-to-glass contact angle of about 80° to about 100°.