If, as achievable with the present nanocarbon, the percolation limit is low with respect of the amount of filler to be tolerated in the composite, heat and electrical conductivity can be significantly enhanced over present materials. The carbon black-nanocarbon (CNT/CNF) composites provide fillers with much higher specific conductivity.
Monday, May 3, 2010
1:00 AM Alton Parrish No comments
Sud-Chemie AG (Munich, DE) inventors Robert Schlogl, O A Abd Bee Binti and Sharifah Hamid disclose carbon-carbon composite material comprising a carbonaceous carrier and nanosize carbon structures (e.g. carbon nanotubes (CNT) or carbon nanofibers (CNF)) which can be used for oil spill remediation in U.S. Patent Application 20090220767 published in September 2009.
The process for the manufacture of a carbon-carbon-composite material comprises the steps of treating a carbonaceous carrier material with a metal-containing catalyst material. The metal is capable of forming nanosize carbon structures, and growing nanosize carbon structures by means of a CVD (chemical vapor deposition) method on the treated carrier in a gas atmosphere comprising a carbon-containing gas, followed by an optional surface modification step. This process allows optimizing porosity, hydrodynamical properties and surface chemistry independently from each other, which is particularly beneficial in respect of the use of the composite for water purification. Carbon black-based composites are particularly useful for filler applications.
The shortcomings of conventional filler (percolation limit up to 50 wt. %) can be avoided. The macro-, meso-, micro or nano-sized carbon support breaks the linear anisotropy in part and prevents thereby the agglomeration to bundles. The fact that one support particle carries many nanocarbons like tentacles of an octopus makes these supports into nodes of an automatically forming 3-dimensional network. Both factors and the additional intrinsic mechanical strength plus thermal/electrical conductivity reduce the filling needed for percolation to a small fraction of conventional carbon fillers. Depending on the length of the nanocarbon elements that can be tailored to modify strength (short) or elasticity (long) of the network, percolation limits as low as 5 to 10 wt % can be reached.
The application area or preparation of different qualities of water using nanocarbons is a preferred target of the present invention. This is motivated by the traditional strong position of carbon products, the great demand for improved technological solutions and by the general relevance of water as biological and technical resource. The applications listed can occur in all branches of water treatment including waste water purification, drinking water preparation, utility water generation and ultra-high purity water production.
FIG. 1 shows the SEM images of a) activated carbon obtained from palm kernel shells, b) said activated carbon after calcination and mild oxidation at 400.degree. C. (AC-400), c) the calcined activated carbon after impregnation with iron, "catalytic drilling" of further pores into the activated carbon structure and reduction of catalyst particles, d) carbon nanofibers (CNFs) grown on the calcined activated
TABLE 3 Profile for the focus application "Adsorption"