201038473 六、發明說明： 【發明所屬之技術領域】 本發明係關於一種洋蔥狀碳及其製造方法。 【先前技術】 米尺寸正 富樂烯或 注目的材 ，形成內 在高溫下 性會受到 固體潤滑 品、燃料 ，一直以 用方面， ί言，以熱 3 000氣壓 的熱處理 洋菌狀碳，亦稱爲碳洋菌（Carbon Oni〇n)、奈 球形石墨、洋蔥狀石墨、洋蔥狀富樂烯等，係與 ' 奈米碳管爲同類物體，是作爲新型碳材料而受到 料。其形狀係同心球狀的碳構造，而且如洋蔥般 0 部收容有球狀碳構造而呈重叠。 洋蔥狀碳係質輕且安定，對放射線的耐性以及 . 的耐性優異。另外，由其形狀看來，認爲其高彈 期待，而可作爲在真空下或無潤滑環境下使用的 劑的應用。另外，還被認爲有作爲醫藥品、化妝 電池用氫貯藏碳材料的用途。 但是，洋蔥狀碳在其生產性方面有很大的問題 來有各式各樣的製造方法被提出，而在供應於實 〇 任一種方法都仍然有問題。 亦即，有文獻揭示出（1)就洋蔥狀碳的合成法iff 等靜壓加壓（hot isostatic pressing)法，在 1000 〜 下對由玻璃碳所構成之成形體實行2000〜3000 °C 而製造的方法（參照專利文獻1)。201038473 VI. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to an onion-like carbon and a method of producing the same. [Prior Art] The rice size is fullerene or the target material, which is formed by the solid lubricating oil and fuel under the inherent high temperature. It has been used for heat treatment. Carbon Oni〇n, Nai spherical graphite, onion-like graphite, onion-like fullerene, etc., are similar to the 'nano carbon tube, and are received as a new carbon material. The shape is a concentric spherical carbon structure, and the ingots have a spherical carbon structure and overlap. The onion-like carbon system is light and stable, and is excellent in radiation resistance and resistance. In addition, from the viewpoint of its shape, it is considered to be highly elastic and expected to be used as an agent for use under vacuum or in a non-lubricated environment. In addition, it is also considered to be used as a hydrogen storage carbon material for pharmaceuticals and cosmetic batteries. However, onion-like carbon has a great problem in terms of its productivity. A variety of manufacturing methods have been proposed, and any method of supply to the actual one is still problematic. That is, it has been revealed in the literature that (1) a method of synthesizing onion-like carbon iff iso isostatic pressing, applying 2000 to 3000 ° C to a molded body composed of glassy carbon at 1000 〜 Method of manufacturing (refer to Patent Document 1).
另外，有文獻揭示出（2)在惰性氣體環境中，以1 600〜 1800t加熱鑽石微粉末的方法（參照專利文獻2);以及（3) 在惰性氣體中，使用紅外線燈將鑽石微粉末加熱至1 7〇〇 °C 201038473 以上的方法（參照專利文獻3)。 另外’有文獻揭示出（4)藉由對多炔（polyyne)照射光 線、電子束或離子束，或實施加熱處理而製造洋蔥狀碳的 方法（參照專利文獻4)。進一步，有文獻揭示出（5)對聚四 氟乙烯、聚氯亞乙烯或聚氟亞乙烯照射光線、電子束或離 子束的方法（參照專利文獻5);以及（6)對煤狀碳照射電子 束、伽瑪射線、X射線、離子射線等高能量射線束，使其 轉換成洋蔥狀碳的方法（參照專利文獻6)。 Ο 有文獻揭示出（7)對具有雙鍵或參鍵的碳材料照射X射 線、微波及超音波之中的1種以上，製造出中空或將金屬 包在內部的洋蔥狀碳的方法（參照專利文獻7)。也有文獻揭 示出（8)對具有雙鍵或參鍵的材料照射光線、電子束或離子 束，製造出洋蔥狀碳的方法（參照專利文獻8)。 有文獻揭示出（9)以非平衡磁控濺鍍（Unbalanced Magnetron Sputtering)法製造出洋蔥狀碳膜的方法（參照專 利文獻9)。 〇 w 有文獻揭示出（10)對Sic粉末與Cu粉末的加壓成形體 施加35萬氣壓以上，2700°c以上的超高壓、超高溫的壓縮 衝撃，生成的方法（參照專利文獻10)。 進一步就使用放電現象的方法而言，有文獻揭示了在 (11)水中使碳電極間產生電弧放電而製造洋蔥狀碳的方法 (參照非專利文獻1)。 [先前技術文獻] [專利文獻] 201038473 [專利文獻1]日本特開平5-208805號公報 [專利文獻2]日本特開平udwws號公報 [專利文獻3]日本特開2〇〇2_8〇212號公報 [專利文獻4]日本特開平^-3^406號公報 [專利文獻5]日本特開平^-349307號公報 [專利文獻6]日本特開2001-48508號公報 [專利文獻7]日本特開2000-109310號公報 [專利文獻8]日本特開2000-16806號公報 [專利文獻9]日本特開2002-105623號公報 [專利文獻10]日本特開2003-137518號公報 [非專利文獻] [非專利文獻 l]Materials Research Bulletin 44 (2009) 324-327. 材料硏究學報第44期 2009年 324-327頁 【發明內容】 [發明所欲解決之課題] 認爲在（1)的方法中，須要相當於鑽石高壓合成的高價裝 置’製造價格亦與合成鑽石相當，而並非通用的方法。 在（2、3)的方法中，該等方法由於原料粉末高價，因此 會有洋蔥狀石墨變得比原料粉末更高價這樣的問題。 在（4、5、6、7、8)的方法，該等方法任一者，投予至對 象原料的能量皆受到限制，大量生產方面有極限。 在（9)的方法中，因爲是薄膜法的緣故，對於洋蔥狀碳粉 末的製造而言會有極限，生成速率也低，產量方面也有極 201038473 限。 在（ίο)的方法中，會有必要造出高溫、高壓這樣的極限 環境，不但裝置上難以對應，合成後的分離精製方面也還 殘留著課題。 在（11)的方法中，會有反應選擇率低、大量生成無定形 碳而難以分離的問題點。 因此，本發明之目的，在於提供一種能以工業規模安定 地製造洋蔥狀碳的方法。 〇 [用於解決課題之方法] 本發明人等，欲達成上述目的而潛心硏究反覆檢討，發 現藉由在溶劑中，在觸媒存在下使碳金屬電極間產生脈衝 電漿，可得到洋蔥狀碳，而完成本發明。 亦即，依據本發明，能提供以下所述之物。 [1] —種洋蔥狀碳之製造方法，其特徵爲在液體中，使碳 電極間發生脈衝電漿放電。 [2] —種洋蔥狀碳，係石墨層間距離係0.40nm以上。 ^ [發明之效果] 藉由本發明之製造方法，能夠以較低電壓、低電流，進 行脈衝放電等低能量製造洋蔥狀碳。另外，本發明的洋蔥 狀碳，石墨層間距離廣，在鋰離子2次電池的電極用途等 方面亦爲有用。 【實施方式】 本發明之洋蔥狀碳，其形狀呈同心球狀的碳構造，而特 徵爲石墨層間距離爲〇.40nm以上，更特定而言，爲0.50nm 201038473 以上。如此的具有廣石墨層間距離的洋蔥狀碳，無法以先 前技術的方法得到，而爲新穎的。在石墨層間可收容各 種離子，特別是有益於Li離子2次電池之電極用途等方 面。 本發明之洋蔥狀碳之製造方法，其特徵係於液體中使碳 電極間發生脈衝電漿放電，就碳電極而言，可使用石墨、 無定形碳、玻璃碳等任一種碳材料。 就電極的形態而言，爲棒狀、鐵絲狀、板狀等任一種形 〇 態皆無妨。關於兩極的大_小，兩者具有大小相異等的形狀 也都無妨。另外，兩極使用相同碳材料或相異材料皆可， 使用以單一種或多種碳材料成型之物亦無妨。 在本發明，係於液體中使洋蔥狀碳生成。就可使用的液 體（溶劑）而言，並未受到特別限定，只要是不會對反應造 成影響的物質，則並未特別受到限制。液體亦可爲兩種以 上化合物之混合物。亦可使用如己烷、辛烷、癸烷、環己 烷、環辛烷等飽和烴；如苯、甲苯、二甲苯、萘的芳香族 〇 烴；水、甲醇、乙醇、丙醇、丁醇、乙二醇、丙二醇、；1，4_ 丁二醇等醇類：醋酸甲酯、醋酸乙酯、醋酸丁酯、安息香 酸甲酯、苯二甲酸二甲酯等酯類；四氫呋喃、四氫吡喃、 二丙基醚、二丁醚、二乙二醇、四乙二醇等醚類。考慮到 所產生的碳生成物之分散、起火、氧化性，係以使用水、 飽和烴、芳香族烴及醇類爲佳，以及使用甲醇、乙醇爲 佳。 就液體之使用量而言，並未受到特別限制，兩電極只要 201038473 在液體中即可。較佳爲只要不會由電漿的發生造成液體飛 散、或者不會因爲生成物濃度造成液體擴散性消失的程度 即可。 就脈衝電漿放電的溫度而言，並未受到特別限制，也會 依隨所使用液體的種類而定。通常在室溫〜300。(：的範圍實 施。在溫度過高的時候，所使用溶劑的蒸氣壓上升，會有 因爲電漿造成起火的可能性，故爲不佳，在溫度過低的時 候，溶劑黏度上升，會損及生成物的擴散性，故爲不佳。 〇 在本發明，係藉由在液體中使碳電極間發生脈衝電漿放 電而產生洋蔥狀碳。就使電漿產生的電壓而言，並未受到 特別限制，20V〜5 00V之範圍，考慮到安全性、特殊裝置 的必要性，60V〜400V的範圍爲佳，80V〜300V的範圍爲 較佳。 就產生電漿的電流而言，並未受到特別限制，係在0.1 〜20A之範圍，如果考慮到能量效率，則以在0.2〜10A的 範圍實施爲佳。 ^ 關於施加脈衝電漿的間隔，並未受到特別限制，而以5 〜100毫秒爲佳，6〜50毫秒的循環爲較佳。施加電漿的間 隔若太短，則在電漿放電導致所產生的碳自由基消失前， 會誘發更多碳自由基的產生’因此除了成長爲洋蔥狀之 外，還牽涉到無定形碳的生成’故爲不佳。另外’在放電 間隔過長的時候，爲了引起電漿所使用的能量變得需要更 多，洋蔥狀碳的生成效率降低，故爲不佳。 脈衝電漿每次的持續時間’另外還會依照所施加的電壓 201038473 及電流而相異，而通常1〜50微秒，考慮到放電效率，宜 爲在2〜30微秒之範圍實施。電漿發生的時間若太長，則 由電漿放電所產生的碳自由基被大量誘發，因此除了成長 爲洋蔥狀碳之外，還牽涉到無定形碳的生成，選擇性降低， 故爲不佳。另外，在放電時間太短的時候，無法供給充分 的能量，爲了引起電漿需要使用更多能量，洋蔥狀碳的生 成效率降低，故爲不佳。 在本發明中，亦可對電極施加振動。藉著施加振動，在 〇 電極間析出的碳化合物沒有滯留，不僅可抑制反應性生物 附著在滯留物上，還能有效率地進行放電，故爲佳。就施 加振動的方法而言，並未受到特別限定，定期的施加振動 或者施加間歇性的振動的方法皆無妨。 就實施本發明的環境而言，並無特別限定，可在減壓 下、加壓下、常壓下任一種狀態實施，而通常考慮到安全、 操作性，可在氮、氬等惰性氣體下實施。 所生成的洋蔥狀碳，係堆積於液體中，因此藉由一般的 〇 方法，例如過濾，再以減壓等操作除去所使用的液體，可 得到洋蔥狀碳。 [實施例] 實施例1 取甲苯200g置於30 0ml燒杯，將兩根直徑6mm、長度 100mm之圓柱狀石墨電極（純度99%以上）插入該甲苯中， 使電極間固定爲1mm，爲了防止反應生成物堆積在電極表 面，提高反應效率，而施加振動。將各電極連接至交流電 201038473 源，以200V、2A使其產生脈衝放電。以脈衝電漿之間隔 爲20毫秒，脈衝電漿每次的持續時間爲實行10微秒。觀 測到放電開始的同時，黑色粉體會分散於液中，並且發生 反應。繼續反應30分鐘，將已沉降之物分離’並將黑色溶 液離心分離，加入適量甲苯，進行洗淨與分離。電極之消 耗量爲380mg。 在真空下，將所得到之黑色粉末加熱乾燥。所得到之黑 色粉末有254.6mg，將所得到之黑色粉末的TEM照片（倍 〇 率：1〇萬倍）表示於第1圖（第1圖的尺度爲20nm)’將TEM 照片（倍率：50萬倍）表示於第2圖（第2圖的尺度爲10nm， 在第2圖之中，層間距離係以2個箭號表示）。由照片可知， 所得到之黑色粉末，係層間距離0.62nm之洋蔥狀碳。產率 爲 6 7% 〇 實施例2 在實施例1中，除了使用水作爲溶劑以外，係以與實施 例1相同的方式進行。將所得到黑色粉末之TEM照片（倍 Ο 率：10萬倍）揭示於第3圖（第3圖的尺度爲l〇nm)，將TEM 照片（倍率：50萬倍）揭示於第4圖（第4圖的尺度爲5nm)。 電極的消耗量爲412mg，所得到之黑色粉末有271.9mg、 產率爲6 6%，由照片可知，係層間距離〇 . 5 5 nm之洋蔥狀碳。 比較例 在實施例1中，除了將電極連接至直流電源，以200V2A 連續放電以外，係以與實施例1相同的方式進行。所得到 之黑色粉末爲312mg，將所得到之黑色粉末的TEM照片（倍 -10- 201038473 率：20萬倍）表示於第5圖（第5圖的尺度爲5 nm)。同心球 狀之洋蔥狀碳並未被觀測到。 [產業上之可利用性] 根據本發明之製造方法，能夠以較低電壓、低電流來進 行脈衝放電等，以低能量即可製造洋蔥狀碳，產業上的有 用性大。 【圖式簡單說明】 第1圖係實施例1所得到黑色粉末之TEM照片（倍率： Ο 10萬倍）。 第2圖係實施例1所得到黑色粉末之TEM照片（倍率： 50萬倍）。 第3圖係實施例2所得到黑色粉末之TEM照片（倍率： 1 〇萬倍）。 第4圖係實施例2所得到黑色粉末之TEM照片（倍率： 5 0萬倍）。 第5圖係比較例所得到黑色粉末之TEM照片（倍率：2〇 〇萬倍）。 【主要元件符號說明】 無。 -11-In addition, there are literatures that disclose (2) a method of heating diamond fine powder at 1 600 to 1800 t in an inert gas atmosphere (refer to Patent Document 2); and (3) heating an infrared powder by using an infrared lamp in an inert gas Method up to 1 7 ° C 201038473 (refer to Patent Document 3). Further, it has been disclosed (4) a method of producing onion-like carbon by irradiating a polyyne with an optical line, an electron beam or an ion beam, or performing heat treatment (see Patent Document 4). Further, there is a literature revealing (5) a method of irradiating light, an electron beam or an ion beam to polytetrafluoroethylene, polyvinylidene chloride or polyfluoroethylene (see Patent Document 5); and (6) irradiating coal-like carbon A method of converting a high-energy ray beam such as an electron beam, a gamma ray, an X-ray, or an ion beam into onion-like carbon (see Patent Document 6). (7) A method of producing a hollow or metal-coated onion-like carbon by irradiating one or more of X-rays, microwaves, and ultrasonic waves to a carbon material having a double bond or a ginseng bond. Patent Document 7). There has also been disclosed (8) a method of producing light-emitting, electron beam or ion beam to a material having a double bond or a ginseng bond to produce onion-like carbon (see Patent Document 8). It is disclosed in the literature that (9) a method of producing an onion-like carbon film by the Unbalanced Magnetron Sputtering method (refer to Patent Document 9). 〇 有 有 有 10 10 10 10 10 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 Further, in the method of using the discharge phenomenon, a method of producing an onion-like carbon by causing an arc discharge between carbon electrodes in (11) water has been disclosed (see Non-Patent Document 1). [PATENT DOCUMENT] [Patent Document 1] Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. [Patent Document 5] Japanese Laid-Open Patent Publication No. Hei No. 2001-48508 (Patent Document No. JP-A-2001-48508) [Patent Document 7] JP-A-2000 Japanese Laid-Open Patent Publication No. 2002-105623 (Patent Document 10) Japanese Laid-Open Patent Publication No. 2003-137518 (Non-Patent Document) [Non- Patent Document 1] Materials Research Bulletin 44 (2009) 324-327. Journal of Materials Research, No. 44, 2009, 324-327 [Summary of the Invention] [Problems to be Solved by the Invention] In the method of (1), A high-priced device that requires the equivalent of high-pressure diamond synthesis' manufacturing price is also comparable to synthetic diamonds, and is not a universal method. In the methods (2, 3), since these raw materials are expensive, the onion-like graphite becomes more expensive than the raw material powder. In the method of (4, 5, 6, 7, and 8), the energy of any of the methods to be administered to the target material is limited, and there is a limit in mass production. In the method of (9), because of the film method, there is a limit to the production of onion-like carbon powder, and the production rate is also low, and the yield is also extremely limited to 201038473. In the method of (ίο), it is necessary to create an extreme environment such as high temperature and high pressure, which is difficult to cope with in the apparatus, and there is still a problem in separation and purification after synthesis. In the method of (11), there is a problem that the reaction selectivity is low and a large amount of amorphous carbon is formed and it is difficult to separate. Accordingly, it is an object of the present invention to provide a method for stably producing onion-like carbon on an industrial scale. 〇 [Method for Solving the Problem] The present inventors have eagerly conducted a review in order to achieve the above object, and found that onion can be obtained by generating a pulsed plasma between the carbon metal electrodes in a solvent in the presence of a catalyst. The carbon is formed to complete the present invention. That is, according to the present invention, the following items can be provided. [1] A method for producing onion-like carbon, characterized in that a pulse plasma discharge occurs between carbon electrodes in a liquid. [2] An onion-like carbon having a graphite interlayer distance of 0.40 nm or more. [Effects of the Invention] According to the manufacturing method of the present invention, onion-like carbon can be produced at a low voltage and a low current with low energy such as pulse discharge. Further, the onion-like carbon of the present invention has a wide graphite layer distance and is also useful for electrode use of a lithium ion secondary battery. [Embodiment] The onion-like carbon of the present invention has a concentric spherical carbon structure and is characterized by a graphite interlayer distance of 〇40 nm or more, more specifically 0.50 nm 201038473 or more. Such onion-like carbon having a wide graphite interlayer distance cannot be obtained by a prior art method and is novel. Various ions can be accommodated between the graphite layers, particularly for the electrode use of Li ion secondary batteries. The method for producing onion-like carbon of the present invention is characterized in that a pulse plasma discharge is caused between the carbon electrodes in the liquid, and any carbon material such as graphite, amorphous carbon or glass carbon can be used for the carbon electrode. In the form of the electrode, it is possible to have any shape such as a rod shape, a wire shape, or a plate shape. Regarding the big _ small of the two poles, the two have different shapes and the like. In addition, the same carbon material or dissimilar material may be used for both poles, and it is also possible to use a material formed of a single or a plurality of carbon materials. In the present invention, onion-like carbon is formed in a liquid. The liquid (solvent) which can be used is not particularly limited, and is not particularly limited as long as it does not affect the reaction. The liquid may also be a mixture of two or more compounds. It is also possible to use saturated hydrocarbons such as hexane, octane, decane, cyclohexane, cyclooctane, etc.; aromatic anthracenes such as benzene, toluene, xylene, naphthalene; water, methanol, ethanol, propanol, butanol , ethylene glycol, propylene glycol, 1,4-butanediol and other alcohols: methyl acetate, ethyl acetate, butyl acetate, methyl benzoate, dimethyl phthalate and other esters; tetrahydrofuran, tetrahydropyridinium Ether, dipropyl ether, dibutyl ether, diethylene glycol, tetraethylene glycol and other ethers. In view of the dispersion, ignition, and oxidizing properties of the carbonaceous product produced, it is preferred to use water, a saturated hydrocarbon, an aromatic hydrocarbon, and an alcohol, and it is preferred to use methanol or ethanol. In terms of the amount of liquid used, it is not particularly limited, and the two electrodes may be in the liquid as long as 201038473. It is preferable that the liquid does not scatter due to the occurrence of plasma or that the liquid diffusibility does not disappear due to the concentration of the product. The temperature of the pulsed plasma discharge is not particularly limited and will depend on the type of liquid used. Usually at room temperature ~300. (The range of (:) is implemented. When the temperature is too high, the vapor pressure of the solvent used may increase due to the possibility of ignition due to the plasma, so it is not good. When the temperature is too low, the viscosity of the solvent rises and the damage increases. In the present invention, the onion-like carbon is generated by the pulse plasma discharge between the carbon electrodes in the liquid, so that the voltage generated by the plasma is not It is subject to special restrictions, ranging from 20V to 500V. Considering the safety and the necessity of special devices, the range of 60V~400V is better, and the range of 80V~300V is better. It is particularly limited to be in the range of 0.1 to 20 A. If energy efficiency is considered, it is preferably carried out in the range of 0.2 to 10 A. ^ Regarding the interval at which the pulse plasma is applied, it is not particularly limited, but is 5 to 100. The millisecond is better, and the cycle of 6 to 50 milliseconds is preferred. If the interval between the application of the plasma is too short, more carbon radicals are induced before the plasma radicals cause the disappearance of the generated carbon radicals. Growing into onion In addition, the formation of amorphous carbon is also considered to be poor. In addition, when the discharge interval is too long, the energy used to cause the plasma needs to be increased, and the production efficiency of onion-like carbon is lowered. Poor. The duration of the pulse plasma each time will vary according to the applied voltage 201038473 and the current, usually 1~50 microseconds, considering the discharge efficiency, preferably in the range of 2~30 microseconds. If the time of plasma generation is too long, the carbon radicals generated by the plasma discharge are greatly induced. Therefore, in addition to growing into onion-like carbon, the formation of amorphous carbon is involved, and the selectivity is lowered. In addition, when the discharge time is too short, sufficient energy cannot be supplied, and in order to cause the plasma to use more energy, the production efficiency of onion-like carbon is lowered, which is not preferable. Vibration is applied to the electrode. By applying vibration, the carbon compound deposited between the electrodes is not retained, and it is possible to prevent the reactive organism from adhering to the retentate and to discharge efficiently. The method of applying the vibration is not particularly limited, and a method of periodically applying vibration or applying intermittent vibration is not particularly limited. The environment for carrying out the present invention is not particularly limited, and may be under reduced pressure. It is carried out under any pressure or under normal pressure, and is usually carried out under an inert gas such as nitrogen or argon in consideration of safety and workability. The onion-like carbon formed is deposited in a liquid, so that it is generally The hydrazine method, for example, filtration, and removal of the liquid to be used under reduced pressure, etc., can obtain onion-like carbon. [Examples] Example 1 200 g of toluene was placed in a 30 ml beaker, and two cylinders having a diameter of 6 mm and a length of 100 mm were obtained. A graphite electrode (purity of 99% or more) was inserted into the toluene to fix the electrode between the electrodes to 1 mm. In order to prevent the reaction product from accumulating on the surface of the electrode, the reaction efficiency was increased and vibration was applied. Connect each electrode to the AC 201038473 source to generate a pulse discharge at 200V, 2A. The interval between the pulsed plasmas is 20 milliseconds, and the duration of the pulsed plasma is 10 microseconds. When the discharge is detected, the black powder is dispersed in the liquid and reacts. The reaction was continued for 30 minutes, the settled material was separated, and the black solution was centrifuged, and an appropriate amount of toluene was added to wash and separate. The consumption of the electrode was 380 mg. The obtained black powder was dried by heating under vacuum. The black powder obtained was 254.6 mg, and the TEM photograph (twist rate: 1 million times) of the obtained black powder was shown in Fig. 1 (the scale of Fig. 1 was 20 nm) 'The TEM photograph (magnification: 50) 10,000 times) is shown in Fig. 2 (the scale of Fig. 2 is 10 nm, and in Fig. 2, the distance between layers is indicated by two arrows). As can be seen from the photograph, the obtained black powder was an onion-like carbon having a distance of 0.62 nm between layers. The yield was 6 7%. Example 2 In Example 1, except that water was used as the solvent, the same procedure as in Example 1 was carried out. The TEM photograph (double magnification: 100,000 times) of the obtained black powder is disclosed in Fig. 3 (the scale of Fig. 3 is l〇nm), and the TEM photograph (magnification: 500,000 times) is disclosed in Fig. 4 ( The scale of Figure 4 is 5 nm). The electrode consumption was 412 mg, and the obtained black powder had 271.9 mg and a yield of 6 6%. It can be seen from the photograph that the inter-layer distance is 洋葱 5 5 nm of onion-like carbon. Comparative Example In Example 1, the same procedure as in Example 1 was carried out except that the electrode was connected to a DC power source and continuously discharged at 200 V2A. The obtained black powder was 312 mg, and the TEM photograph (time -10-201038473 rate: 200,000 times) of the obtained black powder is shown in Fig. 5 (the scale of Fig. 5 is 5 nm). Concentric globular onion-like carbon was not observed. [Industrial Applicability] According to the production method of the present invention, it is possible to produce onion-like carbon with a low voltage and a low current, and to produce onion-like carbon with low energy, which is industrially useful. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a TEM photograph of a black powder obtained in Example 1 (magnification: 100,000 times). Fig. 2 is a TEM photograph (magnification: 500,000 times) of the black powder obtained in Example 1. Fig. 3 is a TEM photograph of the black powder obtained in Example 2 (magnification: 1 million times). Fig. 4 is a TEM photograph (magnification: 50,000 times) of the black powder obtained in Example 2. Fig. 5 is a TEM photograph of the black powder obtained in the comparative example (magnification: 2 10,000 times). [Main component symbol description] None. -11-