TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Conditions: The heating is carried out in a furnace. The solution is expanded as it enters into the furnace. An intense light source is applied to the solution immediately before expansion.Preferred Catalyst: The transition metal catalyst precursor comprises methyl, cyclohexyl, carbonyl, cyclopentadienyl, cyclooctadiene, ethylene and/or benzene ligands.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: A transition metal catalyst precursor is used. The transition metal catalyst precursor comprises copper, chromium, molybdenum, tungsten, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, and/or metal of lanthanide or actinide series. The catalyst precursor comprises a 50/50 weight ratio of mixture of nickel and cobalt, iron and nickel, or iron and molybdenum. SPECIFIC COMPOUNDS - The carbon source and supercritical fluid are carbon monoxide, benzene, toluene, xylene, cumene, ethylbenzene, naphthalene, phenanthrene, anthracene, methane, ethane, propane, butane, pentane, hexane, cyclohexane, ethylene, propylene, acetylene, formaldehyde, acetaldehyde, acetone, methanol, and/or ethanol. Preferably, the supercritical fluid is carbon dioxide.    EXAMPLE - Iron pentacarbonyl beads were placed within a long tubular pressure vessel. Using a high-pressure pump, the tube was filled with carbon dioxide and maintained at 1000 psi at 40degreesC during operation, to form a supercritical carbon dioxide phase. Additional carbon dioxide was pumped along the tube and saturated with iron catalyst precursor. When the precursor was exhausted from one tube, flow was switched to the other while the first tube was recharged. The solution was passed from the active pressure reservoir into a chemical vapor deposition furnace held at 1000degreesC and 1.5 atm, by an expansion nozzle where it was mixed turbulently with methane separately introduced into the furnace and pre-heated to near furnace temperature. As the temperature of the iron pentacarbonyl was raised, it decomposed and reacted with the hydrocarbon to nucleate the growth of small diameter nanotubes. The nanotubes continued to grow as they passed along the furnace, and were collected by cyclonic separation and filtration after leaving the furnace.