TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The metallorganic precursor/organic hydrocarbon liquid mixture is injected as a mist of droplets at room temperature into a first portion of a reactor tube at room temperature. The droplets are transported by a carrier gas from the room temperature portion of the reactor tube to at least one of the first and second temperature regions of the reactor tube, where the first and second temperature regions are above room temperature. The temperature of the first temperature region is sufficiently high to vaporize the solvent without vaporizing the metallorganic precursor. The remaining molecules of the metallorganic precursor are transported to the second temperature region of the reactor tube, where the second temperature region is at a temperature higher than room temperature. The thermal decomposition produces at least individual metal atoms, individual carbon atoms and remaining molecules. The deposited metal atoms form clusters of metal particles on the additional surfaces. The carbon atoms from the thermally decomposed precursor chemically attach to the clusters of metal particles. The additional carbon atoms chemically attach to the carbon atoms from the thermally decomposed precursor. The carbon nanotubes comprise one or more multi-walled carbon nanotubes (MWNT) and metal impurities, and the method further comprises controlling a wt.% of the metal impurities by controlling the concentration of the precursor in the mixture. The method further comprises controlling the precursor concentration of the mixture to have a molarity in the vicinity of 0.1, where the vicinity contains molarity values either slightly less than or greater than 0.1, so as to produce one or more MWNT having a metal impurity less than 5 wt.%. The method further comprises controlling the precursor concentration of the mixture to have a molarity greater than or less than 0.1 so as to produce MWNT having a metal impurity of less than 5 wt.%. The step of chemically attaching carbon atoms to the metal atoms of the clusters so as to form carbon nanotubes comprises accreting to and chemically attaching additional carbon atoms to carbon atoms attached to the metal atom cluster. In part (e), the metallorganic precursor molecules are thermally decomposed into at least metal atoms and carbon atoms and remainder molecules, and further comprise transporting the remainder molecules away from the surface within the second temperature region. Preferred Components: The metallorganic precursor comprises iron. The metallorganic precursor and the organic hydrocarbon solvent are liquids at room temperature. The additional surfaces are made from one or more: fused silica (quartz), alumina, stainless steel, tungsten, or tantalum. The metallorganic precursor is of formulae (Fe2(C5H5)2(CO)4), (Fe2(C5H5)(C5HnR5-n)(CO)4), (Fe2(C5HnR5n)2-m(CO)4), (FeW(CO)4(C5H5)2-m(C5HnR5-n)m), (FeW(CO)4(C5H5)2-m(C5HnR5-n)m), (FeMn(CO)7(C5H5)1-m(C5HnR5-n)m), (FeRe(CO)7(C5H5)1-m(C5HnR5-n)m), (FeCo(CO)6(C5H5)1-m(C5HnR5-n)m), (FeCo(CO)6(C5H5)1-m(C5HnR5-n)m), (FeNi(CO)3(C5H5)1-m(C5HnR5-n)m), (Fe(CxH8)(CO)3), (M(CxHx)(CO)3), ((C8H8)Fe(CO)3), (FeW(Z)(C5H5)2-m(C5HnR5-n)m), (FeMn(Z)(C5H5)1-m(C5HnR5-n)m), (FeRe(Z)(C5H5)1-m(C5HnR5-n)m), (FeCo(Z)(C5H5)1-m(C5HnR5-n)m), (FeNi(Z)(C5H5)1-m(C5HnR5-n)m), (Fe(CxH8)(Z)) or (M(CxHx)(Z)).n = 0-5;R = CH3, C2H5, C3H7 or C4H9;m = 0-2;x = 6 or 8, where x is 6 for M being Cr, Mo, or W, and x is 5 for M being Mn;Z = one or two phosphine ligands of formula (PX3), (P(Ar1)3) or (P(OX)3);X = CH3, C2H5, C3H7, C4H9, C5H9, or C6H11; andAr1 = C6H5, C6H4Cl or C6H4CH3.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The second temperature region of the reactor tube contains surfaces in addition to those of the reactor tube. The temperature of the second temperature region is high enough to thermally decompose the molecules of the metallorganic precursor. The second temperature region of the reactor tube includes surfaces in addition to the reactor tube surfaces, where the additional surfaces make intimate thermal contact with the interior of the reactor tube. The additional surfaces comprise one or more baffles (2).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The ring group comprises an aromatic ring. The organic hydrocarbon solvent comprises an aromatic compound, preferably toluene. EXAMPLE - Bis-carbonyl(cyclopentadienyl)iron (0.115 g) was dissolved in toluene (5 ml). The solution was injected into the first zone of the 2-zone furnace, at a rate of 2 ml/hour. The solution was injected using a syringe, syringe needle and syringe pump. The temperature of the first zone of the furnace was maintained at 200 degrees C. The vaporized bis-carbonyl(cyclopentadienyl)iron catalyst and solvent were swept into the second zone of the furnace by a 4% hydrogen/96% argon carrier gas with a flow rate of 1.5 liters/minute. In the second zone of the furnace, the carbon nanotubes grew on the walls of the furnace at 685-750 degrees C. The temperature of the second zone was maintained at 775 degrees C to give multi-walled carbon nanotubes.