# US 2014/0193323 A1 · Double Wall Carbon Nanotubes and Method for Manufacturing Same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0193323 A1 - Document ID: US20140193323A1 - Status: Published application - Kind: A1 - Application number: 14/238,234 - Filed: 2012-11-02 - Published: 2014-07-10 - Earliest claimed: 2011-11-04 - Assignees: Cheil Industries Inc. - Applicants: Cheil Industries Inc. - Inventors: Kyoung Tae Youm; Byeong Yeol Kim; Young Sil Lee; Bo Kyung Lim - Web page: https://patentgrep.com/patent/US20140193323A1 ## CPC - C01B 32/05: Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30 - B01J 23/8872: {Alkali or alkaline earth metals} - B01J 35/393: {Metal or metal oxide crystallite size} - B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites - C01B 32/158: Carbon nanotubes - C01B 32/16: Preparation - C01B 32/162: characterised by catalysts - B01J 21/185: {Carbon nanotubes (carbon nanotubes per se C01B32/15)} - B01J 35/80: characterised by their amorphous structures - B01J 37/031: {Precipitation} - B01J 2235/30: Scanning electron microscopy; Transmission electron microscopy - B82Y 40/00: Manufacture or treatment of nanostructures - C01B 2202/04: Nanotubes with a specific amount of walls - C01B 2202/30: Purity - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES ## Abstract The present invention relates to a method for manufacturing carbon nanotubes comprising: a preparatory step of a supported catalyst; a temperature-raising step of inserting the supported catalyst into a reactor, injecting hydrocarbon gas and hydrogen gas at the same time, and raising the temperature of the reactor to between 900 to 1000° C. to synthesize carbon nanotubes; and a temperature-lowering step of lowering the temperature of the reactor to between a room temperature to 200° C., injecting only hydrogen gas, and synthesizing carbon nanotubes. The carbon nanotubes manufactured by the above method have high purity, and excellent selectivity for double wall carbon nanotubes can be achieved. ## Claims ### Claim 1 A method for manufacturing double-wall carbon nanotubes comprising: a preparatory step of a supported catalyst; a temperature-raising step of inserting the supported catalyst into a reactor, injecting hydrocarbon gas and hydrogen gas at the same time, and raising the temperature of the reactor to between 900 to 1000° C. to synthesize carbon nanotubes; and a temperature-lowering step of lowering the temperature of the reactor to between a room temperature to 200° C., injecting only hydrogen gas, and synthesizing carbon nanotubes. ### Claim 2 (depends on 1) A method for manufacturing double-wall carbon nanotubes according to claim 1, wherein the supported catalyst is manufactured by calcining an aqueous catalyst solution which is a mixture of a metal catalyst and a support at a molar ratio as below, in a reactor at a temperature of 500 to 800° C.: Support [Mg]:Metal catalyst [Co]:Molybdenum-based activator [Mo]=0.99:x:0.025 wherein, 0.05≦x≦0.075]. ### Claim 3 (depends on 2) A method for manufacturing double-wall carbon nanotubes according to claim 2, wherein the supported catalyst is a metal catalyst supported in a porous amorphous support, and the size of the metal catalyst is less than or equal to 5 nm. ### Claim 4 (depends on 2) A method for manufacturing double-wall carbon nanotubes according to claim 2, wherein the double-wall carbon nanotubes are manufactured by calcining at the temperature of 500 to 800° C. for 20 to 60 minutes. ### Claim 5 (depends on 2) A method for manufacturing double-wall carbon nanotubes according to claim 2, further comprising a step of increasing the surface area of a catalyst by grinding the calcined supported catalyst. ### Claim 6 (depends on 1) A method for manufacturing double-wall carbon nanotubes according to claim 1, wherein the temperature of the reactor is raised between 900 to 1000° C., and is maintained for 30 to 90 minutes in the temperature-raising step. ### Claim 7 (depends on 1) A method for manufacturing double-wall carbon nanotubes according to claim 1, wherein the injection speed of hydrocarbon gas is 200 to 300 sccm in the temperature-raising step, and the injection speed of hydrogen gas is 700 to 900 sccm in the temperature-raising step and the temperature-lowering step. ### Claim 8 (depends on 1) A method for manufacturing double-wall carbon nanotubes according to claim 1, wherein the hydrocarbon is selected from a group consisting of methane, ethylene, acetylene, LPG, and a mixed gas thereof. ### Claim 9 (depends on 1) A method for manufacturing double-wall carbon nanotubes according to claim 1, wherein a yield per l g of the supported catalyst is more than or equal to 100%. ### Claim 10 (depends on 1) Double-wall carbon nanotubes manufactured by a method for manufacturing carbon nanotubes according to claim 1. ### Claim 11 (depends on 10) Double-wall carbon nanotubes according to claim 10, wherein a purity (C-purity) of carbon nanotubes is more than or equal to 50%. ### Claim 12 (depends on 10) Double-wall carbon nanotubes according to claim 10, wherein two peaks in a pair are appeared in an RBM mode area. ### Claim 13 (depends on 10) Double-wall carbon nanotubes according to claim 10, wherein an intensity of D band to G band (ID/IG) of the carbon nanotubes through the raman spectroscopy is less than 0.15. ### Claim 14 Double-wall carbon nanotubes, wherein the intensity of D band to G band (ID/IG) is less than 0.15 and two peaks in a pair is appeared in an RBM mode area through raman spectroscopy. ### Claim 15 (depends on 14) Double-wall carbon nanotubes according to claim 14, further comprising the supported catalyst as below: Support [Mg]:Metal catalyst [Co]:Molybdenum-based activator [Mo]=0.99:x:0.025 wherein, 0.05≦x≦0.075. ### Claim 16 (depends on 15) Double-wall carbon nanotubes according to claim 15, wherein the supported catalyst is a metal catalyst supported in a porous amorphous support, and the size of the metal catalyst is less than or equal to 5 nm. ### Claim 17 (depends on 14) Double-wall carbon nanotubes according to claim 14, wherein a purity (C-purity) of carbon nanotubes is more than or equal to 50%.