TWI395709B - 製作石墨物件之方法 - Google Patents

製作石墨物件之方法 Download PDF

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TWI395709B
TWI395709B TW095119849A TW95119849A TWI395709B TW I395709 B TWI395709 B TW I395709B TW 095119849 A TW095119849 A TW 095119849A TW 95119849 A TW95119849 A TW 95119849A TW I395709 B TWI395709 B TW I395709B
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coke
fibers
electrode
particle size
raw material
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TW200710032A (en
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James William Kortovich
Richard Liichang Shao
Dai Huang
Irwin C Lewis
Richard Thomas Lewis
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Ucar Carbon Co Inc
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Description

製作石墨物件之方法
本發明是關於石墨物件和其製造方法。更特別的是本發明之物件例如石墨電極或陰極之製造方法藉由混合(i)包含至少約35重量百分比之焙燒焦炭(calcined coke)之微粒份,和(ii)瀝青,其混合物進一步包括小尺寸微粒填充料,碳纖維,或其混合物。
石墨電極使用於鋼鐵工業中,主要在電熱熔爐中用來融化金屬和其他用來形成鋼鐵的原料。藉由通過電流於數個電極(通常是三個)所產生的熱量來融化金屬,且在電極和金屬之間形成電弧。通常使用電流超過100,000安培以上。所產生的高溫會融化金屬和其他成分。一般來說,使用於鋼鎔爐的電極各由電極柱組成,為一連串各別電極所形成的單一柱體,以此方式,當電極於加熱過程中耗損時,可使用可置換電極接合於柱體來維持延伸於鎔爐柱體的長度。
一般來說,電極是經由接腳(pin)(有時候表示為奶嘴狀突起)連接於柱體上,其接腳功能為連接鄰近電極之端。典型地,該接腳具有相對於公螺紋區域的形狀,讓至少一電極端包含母螺紋區域能為可與接腳之公螺紋區域配對。因此,當每個相對的接腳公螺紋區域穿進於兩電極端母螺紋區域之時,這些電極成為接合於電極柱體上。通常鄰接電極的接合端、和介於其間的接腳,在本項技藝中被稱為接頭(joint)。
給予電極和接頭經過熱壓處理(當然此處之電極柱為完整的),機械/熱因素像是強度、熱膨脹、和抗龜裂必須小心的評估以避免對電極柱或各個電極的傷害和破壞。例如,長方向(即沿著電極/電極柱的長方向)電極的熱膨脹,特別不同於接腳的熱膨脹比率會迫使接點分離,降低電極柱導電的效率。橫截面(即穿過電極/電極柱直徑)電極的熱膨脹超過接點的膨脹時會形成接腳與電極的緊密接合;然而,如果電極的橫截熱膨脹遠超過接腳的橫截熱膨脹時,會造成電極的傷害或是接腳的分離。再來還會造成電極柱的效力降低,或是電極柱的損害很嚴重讓電極柱在接腳部位失效。因此,電極熱膨脹的控制在長方向和橫截面方向是相當重要的。
結果,如果於電極/電極柱系統可排除接腳,就可以減低對於不同系統組合(即接腳和電極)平衡熱膨脹的需求。先前企圖排除該接腳已經被挑戰,其已經使用該種螺紋電極端或是其他電極配合方法。然而工業上接受性已落後,因為覺得石墨的強度若是無接腳的話,無法足夠支持電極柱的完整。不管接腳是否存在,增強電極強度和堅韌度(可定義成防止破裂度)和減低脆裂(可定義成破裂度的增加)是延長電極壽命所需的要件。
同樣的,增加強度和堅韌度將可使石墨陰極(使用於鋁熔煉工業)和其他人造石墨製品擁有較長的壽命和改善可用性。
已經有使用介晶相瀝青系碳纖維來改良主體石墨產品的特性,像是電極。例如,Singer在U.S.Pat.No.4,005,183中所描述介晶相瀝青系碳纖維產品,且說明因為其低電阻性,所以這些碳纖維可以使用作為在石墨電極產品中的填充劑。在British Patent 1,526,809中對於Lewis和Singer,重量百分比為50%至80%的碳纖維加入於重量百分比為20%至50%的瀝青黏合劑,然後經由擠壓形成石墨化的人造碳纖維製品。
在U.S.Pat.No.4,998,709中,Griffin et al.企圖對付由電極接腳過度長方向熱膨脹所產生的間題,藉由準備石墨突狀物(即接腳)具有介晶相瀝青系碳纖維於擠壓混合物中。Griffin et al.使用的碳纖維具有Young’s模數大於55x106 磅/平方英吋(psi),而在混合物中含有約8至20重量百分比。該混合物經由擠出、烘烤、接著石墨化大約5至14天的時間來製造出突狀物。雖然由Griffin et al.方法所製造的突狀物表現出在長方向熱膨脹係數(CTE)的遞減,其同樣表現出在在橫截面方向CTE之不欲的增加,電阻增加及破裂模數減少。另外,石墨化時間相的當拉長,將無益於商業上的製造。
在改善製造含纖維連接接腳的方法時,Shao et al.,在U.S.Pat.No.6,280,663中教授從在焙燒焦炭/瀝青混合物中的介晶相瀝青取得之碳纖維內含物。該產生之接腳表示出減少長方向CTE,而不需要商業上無益處的長時石墨化時間。然而,即使像是使用Shao et al.方法這樣改進的接腳仍然無法排除對於電極強度改善的需求;此外,如果可以全部排除接腳的話,對於節約和效率增加將會是相當大的效益。
所以所需要的是石墨元件在長方向相對於先前技術具有較小的CTE,而不需要犧牲橫截CTE或阻抗和破碎模數。此外,希望石墨物品具有增強的強度和堅韌度,特別是該增強的強度和堅韌度可充分允許電極間的相配而不需要使用接腳。同樣的也希望達到這些益處而不需要使用到高量的昂貴材料。
本發明之一態樣係提供一種製作石墨物品之方法。
本發明之另一態樣提供一種製作石墨物品之方法,像是石墨電極或石墨陰極,與先前技術比較起來具有減低長方向熱膨脹係數和增進抗碎裂性的優點。
本發明之再另一態樣提供一種製作石墨物品之方法,該物品具有與先前技術比較起來具有減低長方向熱膨脹係數,在同樣增加碎裂模數時,橫截面CTE或是抵抗力無實質上的犧牲。
本發明之更其它態樣為一種石墨物品,例如石墨電極或石墨陰極,與先前技術比較,具有減低長方向熱膨脹係數和改進對碎裂和斷裂的阻抗,當同樣增加碎裂模數時,沒有犧牲橫截面CTE或抵抗力。
鑑於下列說明此項技術者將顯而易見此等態樣和其他者可由提供製備石墨物品之方法而完成,該方法包括使用微粒份,此微粒份包含至少約35重量百分比,較佳為至少約50重量百分比,最佳為至少約70重量百分比,焦炭,煤或其聯合體具有粒徑可通過0.25mm至25mm之篩網。焙燒焦炭最常使用於微粒份中。該微粒份與液體或固體瀝青黏合劑混合以形成黏合劑原料;該黏合劑原料擠出形成生料;烘烤該生料形成碳化原料;在至少約2500℃下加熱且保持在這個溫度一定時間把碳化原料石墨化。該混合原料包括碳纖維在混合微粒份和瀝青後加入,和隨意地小尺寸填充物(有益地加入作為微粒份的部分)。
在該發明方法中,碳纖維可表示在每100部份焙燒焦炭重量中具有大約0.5至大約6重量份,或是大約0.4重量%至大約5.5重量%之全部混合組成物(除了黏合劑之外)。該纖維較佳具有平均直徑約6至約15微米,且長度較佳為大約4mm至大約25mm之間,而最佳為小於32mm。使用於發明方法的碳纖維應最好具有至少約150,000psi的張力強度。最有益地是碳纖維呈束加入原料混合,而每一束包括大約2000至20,000條纖維。
如上所述,在開始混合微粒份和瀝青後加入碳纖維。在混合開始後加入纖維可以幫助維持纖維的長度(纖維長度可能在混合過程中縮短)而因此有益的碳纖維內含物的作用,將會影響纖維的長度。為了達到有益的結果,該纖維應該要加入在大至少約15%混合過程完成時後加入此纖維為較佳,以在大約30%混合過程完成後加入為更佳。當然,再更具體化,該纖維至少在混合過程一半後加入,最有益的是在混合過程的3/4後加入。例如,如果微粒份和瀝青的混合需要兩個小時(即混合過程需兩小時),則該纖維需要在混合過程開始至少18分鐘後加入(即兩小時混合過程的15%)。
如上所述,該微粒份可包含小尺寸顆粒填充劑(此處的小是與焙燒焦炭的顆粒來比較,其一般尺寸粒徑為可通過25mm篩網但不可通過0.25mm篩網)。更特別的是該小尺寸填充劑包括至少約75%煤粉未,表示煤具有直徑至少約70%而以達到約90%為佳,可通過200Tyler篩網,相當於74微米。
該小尺寸填充劑可進一步包括至少約0.5%至多至約25%的其他添加劑,像是膨脹抑制劑,例如氧化鐵。添加劑亦應可使用在微粒尺寸小於慣常使用上。例如當氧化鐵作為填充料時,氧化鐵微粒的平均粒徑應該小於約10微米。其他額外的添加劑可使用石油焦粉末,該石油焦粉末具有平均粒徑小於約10微米,加入於多孔物件然後讓瀝青黏合劑數量的控制能夠更好。該小尺寸的填充料應該包括至少約30%,高如約50%、甚至65%的微粒份。
烘烤生料的溫度較佳發生於多至約700℃至約1000℃,於非氧化還原的環境中,而石墨化溫度較佳於約2500℃至約3400℃之間。
如上所述,石墨物件(此處所使用的石墨物件至少包含石墨電極、用於石墨電極的接腳、和陰極)可藉由合併微粒份來製造,該微粒份包括了焙燒焦炭(當製作石墨電極為石墨製品時)、瀝青和介晶相瀝青或PAN系碳纖維於混合原料中。更具體而言,壓碎、分粒和加工過的鍛石油焦與煤焦油瀝青黏合劑混合形成混合物。該焙燒焦炭的粒徑根據物件的用途來選擇大小,且為在該領域中之技術。一般來說使用於加工鋼鐵之石墨電極,其微粒直徑大小平均多至約25毫米(mm)。該微粒份較佳包括小微粒尺寸的包含煤粉末之填充劑。其它添加劑可混入小微粒尺寸的包括氧化鐵之填充劑,用來防止膨脹(由於在煤微粒中硫從與碳的鍵結中釋放出來所造成),煤粉末和焦油或其他用來促進擠壓混合料的潤滑劑。
該微粒份可包括除焙燒焦炭之外的”大的”顆粒份微粒份。例如,當物件為石墨(包括半石墨)陰極,所使用的煤可為焙燒焦炭,或石油焦,焦衍生之煤,和這些焦之組合物。該陰極的製造也可包括無煙煤焙燒焦炭取代焦或與焦一起使用。
在混合原料中也包括了介晶相碳纖維或PAN(聚丙烯晴)衍生之纖維,於混合原料開始後加入。也可使用石墨化纖維。該纖維應該具有Young’s模數(在碳化之後)大約15x106 psi至40x106 psi之間。較佳具有平均粒徑為大約6至約15微米,抗拉強度為約200x103 psi至約400x103 psi之間,且平均長度為約4mm至約32mm之間。合適的纖維長度可為約為6mm或以下,約為12mm或以下,約為18mm或以下,約為25mm或以下。該碳纖維的長度最好不要超過最大的煤微粒。最有益的是纖維呈束加入於混合料中,根據使用的尺寸,纖維束每束包括約2000至約20,000條纖維。
混合原料中包含的碳纖維為以介晶相瀝青或PAN為基底。介晶相瀝青纖維由具有至少部分轉變成液晶或所謂的介晶相之瀝青所製成。介晶相瀝青可由像是芳香石油氣、乙烯裂解焦油、煤衍生物、石油熱焦油、液體裂解殘渣和壓力芳香蒸餾液具有沸點由340℃至約525℃之間之原料。例如介晶相瀝青的製法可參見U.S.Pat.No.4,017,327,Lewis et al.中所描述。介晶相瀝青藉由在化學惰性氣氛(例如氮氣、氬氣、氦氣或其類似氣體)中以大約350℃至500℃加熱原料。化學惰性氣體可在加熱時發泡通過原料,促進介晶相瀝青的形成。碳纖維的準備上,介晶相瀝青應該具有軟化點,軟化點為介晶相瀝青開始變形之溫度,其溫度小於約400℃且通常小於約350℃。如果瀝青軟化點的溫度較高的話,會使得要達成碳纖維結構具有所需物理特性的會變得困難。
一旦介晶相瀝青被製備,以其所需的直徑吐出細絲,藉由所知的方法例如融化旋轉法、離心旋轉法、吹氣旋轉法或其他熟習於該技術領域者使用之方法。旋轉生產碳纖維適合使用製備本發明之電極。細絲保持在不高於瀝青軟化點的溫度(但通常大於250℃)大約5至60分鐘,然後再以高溫處理,依序多至約1000℃和更高溫,而在一些案例中可高達約3000℃,更典型的溫度約1500℃至1700℃之間,來將纖維碳化。碳化製程於惰性氣氛中實行至少0.5分鐘,惰性氣體像是氬氣。碳化最常使用的停留時間為大約1至25分鐘之間。然後將纖維截斷,且形成束狀。這裡所說的束狀纖維例如可由Cytec Industries Inc.of West Paterson,New Jersey和Mitsubishi Chemical Functional Products Inc.of Tokyo,Japan所取得。
用於製造PAN纖維的方法包括從聚丙烯晴溶液中精紡出纖維。該纖維接著用與介晶相瀝青系纖維相同的方式來穩定。例如PAN纖維產品可由Dan D.Edie和John J.McHugh在”High Performance Carbon Fibers”p.119-138之Carbon Material for Advanced Technologies,1s t Ed,Elsevier Science Ltd.1999,其揭示以參考文獻併入本文。
混合原料中的碳纖維在每100重量份焙燒焦炭中較佳具有大約0.5至約6重量份。以具有纖維在大約1.25至約6重量份為最佳。就混合物而言(除黏合劑之外),碳纖維以大約1%至5.5%的重量百分比組合,以大約1.5%至5.5%的重量百分比為較佳,而以約5.0%或以下為更佳。
製備微粒份、瀝青黏合劑、碳纖維...等等的混合物之後,經由擠壓通過沖模或在一般模具成模形成所謂的生料。製作的方法不論是經由擠壓成型或是用模子製造,必須在接近瀝青軟化溫度處理,通常為約100℃或更高溫度。雖然沖模或是模子所形成的物件大致上為最後的形狀與大小,但通常會需要物件的機械加工,至少提供像是螺紋的結構。生料的尺寸可以改變;用於電極的直徑可介於大約220mm至700mm之間。關於陰極,則可使用矩形橫截面。
擠壓過程後,將生料施予熱處理,在大約700℃至約1100℃之間烘烤,而以約800℃至約1000℃之間為較佳,將瀝青黏合劑碳化為固態瀝青焦,讓物件形狀不變形,具有高機械強度、優異熱傳導性,和較低的電阻性,然後形成碳化材料。該生料在相對缺乏空氣下烘烤。烘烤溫度應該為每小時大約1℃至約5℃的速率來升溫到所需的溫度。烘烤完之後,注入一或兩次煤焦或石油瀝青於碳化原料,或是注入其他種瀝青形式或工業上所知的樹脂,鍍覆額外的焦碳於原料打開之氣孔中。每個注入過程根據額外烘烤步驟來完成。
碳化原料在烘烤之後石墨化。石墨化是藉由以大約2500℃至約3400℃的溫度來處理碳化原料,讓碳化原料可以造成位於煤焦和瀝青焦黏合劑的碳原子從無序列態變成石墨結晶結構。石墨化的形成最好溫度保持在至少大約2700℃,而以大約2700℃至約3200℃之間為較佳。在這樣的高溫下,碳之外的元素都氣化為蒸汽。該製程石墨化溫度所需的時間不超過大約18小時,甚至不超過大約12小時。更佳地石墨化時間大約1.5小時至約8小時。
注意到當石墨化完成時,最後的物件可切割為所需大小然後機械加工或其他方式形成最後的結構。本發明製備之物件與習知技術製備之物件相比較,本發明製備之物件表示出實質上在CTE長方向的減小。該物件在彎曲強度的增加(即破裂模數)和Young’s模數的增加,沒有附隨象徵在橫截面CTE上或特別電阻增加,以及沒有商業上無益的石墨化時間的要求。此外,該物件藉由減小脆裂性和增加堅韌性來阻抗碎裂或斷裂亦可以觀察得知。
下面實施例用來進一步解釋說明本發明內容,但不限定於任何一項之中。全部的部份和百分比都是以重量來計算,且是建立在在產品微粒時期製程的重量的基礎上。
實施例1
石墨電極的試驗是由纖維添加物處理,纖維來自Mitsubishi Chemical(介晶相瀝青纖維,18mm長的管束),Cytec(介晶相瀝青纖維,6mm和25mm長的管束),和Zoltek(PAN系纖維,25mm長的管束)。
纖維束的濃度在混合(除黏合劑之外)時是介於大約2.5至約5重量百分比之間。該原料可經由攪拌臂、滾筒混合設備、冷卻、且擠壓成為大約150mmx約330mm長的電極。該電極經過上述之處理。該具有纖維之電極的物理性質與其它沒有纖維的電極之比較如下所示:
實施例2
第二石墨電極試驗由纖維添加物處理,纖維獲自Mitsubishi Chemical(介晶相瀝青纖維,30mm長的管束),Zoltek(PAN系纖維,51mm長的管束),Cytec(介晶相瀝青纖維,6mm和25mm長的管束),和ConocoPhillips(介晶相瀝青纖維,25mm長的管束)取得。
纖維束的濃度是介於大約1.5至約3重量百分比之間。該原料可經由雙攪拌臂、Sigma葉片混合器、冷卻、且擠壓成為大約150mmx約330mm長的電極。該電極經過上述之處理。該具有纖維之電極的物理性質與其它沒有纖維的電極之比較如下所示:
實施例3
第三石墨電極試驗是由纖維添加物處理,只使用Mitsubishi Chemical(介晶相瀝青纖維,6mm長的管束)的纖維,U.S.Pat.No.6,280,663中使用相同的纖維。添加物的量為2、4、和6重量百分比。該原料可經由攪拌臂、滾筒混合設備、冷卻、且擠壓成為150mmx330mm長的電極。該電極經過上述之處理。該具有纖維之電極的物理性質與其它沒有纖維的電極之比較如下所示:
實施例4
第四石墨電極試驗是由纖維添加物處理,從Mitsubishi Chemical(介晶相瀝青纖維,6mm和25mm長的管束)取得纖維。添加量為5%。該原料可經由Sigma混合器、冷卻、再擠壓成為150mmx330mm長的電極。該填充劑的尺寸(煤粉末和氧化鐵)不是標準就是細緻(煤粉55%細於74微米,或是90%細於74微米,氧化鐵5微米而非74微米,額外煤細粉(1-10微米)加入於投料中)。而這些投料其中一些為在加熱/混合過程70分鐘製程中的第50分鐘後加入纖維而非於開始時加入。該電極經過上述之處理。該具有纖維之電極的物理性質與其它沒有纖維的電極之比較如下所示:
全部被引用的專利揭露和在本申請案所提及的刊物,併入本文之參考文獻。
上述說明書提及之內容能夠讓熟悉該項習知技術者能實行該項發明。這並不意謂詳述全部讓熟習該項技術在閱讀說明書時可以顯而易懂其內容的可能變化和修改。然而其意謂這樣之修改與變化包含於本發明所述申請專利範圍之中。本專利範圍意謂包含了指名的元件和步驟之任何影響滿足本發明之目標的先後順序,除非該內文具體地指出相反之事物。

Claims (12)

  1. 一種製造石墨物件的方法,該方法包括(a)混合(i)一微粒份,其包括至少約35重量百分比之焦炭,煤或其混合物,其主要份粒徑可通過25mm篩網,但通不過0.25mm篩網,(ii)一瀝青黏合劑和(iii)碳纖維,以形成一混合原料;(b)壓該混合原料形成一生料;(c)烘烤該生料形成一碳化材料;且(d)將碳化材料保持於溫度至少約2500℃以上,將該碳化材料石墨化;其中在混合開始後,且在至少完成混合周期的約15%後,將纖維加入該微粒份及該瀝青黏合劑中;其中每100重量份中焙燒焦炭具有約0.5至約6重量份之碳纖維。
  2. 如申請專利範圍第1項之方法,其中纖維具有不超過約32mm之平均長度。
  3. 如申請專利範圍第1項之方法,其中在至少在完成混合周期的約50%後將纖維加入混合原料中。
  4. 如申請專利範圍第1項之方法,其中碳纖維具有至少約150,000psi以上之張力強度。
  5. 如申請專利範圍第1項之方法,其中碳纖維約具有楊氏係 數約15x106 psi。
  6. 如申請專利範圍第1項之方法,其中碳纖維具有平均直徑約6μm至約15μm之間。
  7. 如申請專利範圍第1項之方法,其中微粒份包括選自焙燒焦炭、石油焦、煤衍生之焦炭、焙燒無煙煤焦炭或者其混合物組成的材料。
  8. 如申請專利範圍第1項之方法,其中微粒份具有多至約65%的填充劑,該填充劑至少包含約75%的焦炭,該焦炭粒徑至少約70%可通過一200Tyler篩網。
  9. 如申請專利範圍第8項之方法,其中於填充劑中之焦炭粒徑至少約90%可通過一200Tyler篩網。
  10. 如申請專利範圍第8項之方法,其中該填充劑包括介於約0.5%至約25%之間的添加劑。
  11. 如申請專利範圍第10項之方法,該添加劑包括具有一平均粒徑小於約10μm的氧化鐵,一平均粒徑小於約10μm的石油焦,和其組合物。
  12. 如申請專利範圍第1項之方法,該微粒份包括至少約50重量百分比的焦炭,煤或其混合物,其具有的主要份粒徑可通過一25mm篩網,但不能通過0.25mm篩網。
TW095119849A 2005-06-08 2006-06-05 製作石墨物件之方法 TWI395709B (zh)

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JP5367218B2 (ja) 2006-11-24 2013-12-11 シャープ株式会社 蛍光体の製造方法および発光装置の製造方法
US8466660B2 (en) 2009-11-06 2013-06-18 Toyota Motor Engg. & Mfg. North America, Inc. Wireless energy transfer antennas and energy charging systems
CN102117912B (zh) * 2010-01-06 2014-12-10 顾向宏 掺杂复合碳锂离子电池活性负极材料的制备方法
CN108751993A (zh) * 2018-06-05 2018-11-06 大同新成新材料股份有限公司 一种uhp石墨电极的制造工艺

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